REESE LIBRARY 
 
 OF THE 
 
 UNIVERSITY OF CALIFORNIA. 
 
 APR 21 1893 
 
 Accessions No, -S~ ^^- z -/ . C/j$s Nn. 
 
SEWAGE TREATMENT, PURIFICATION, 
 AND UTILIZATION. 
 
THE SPECIALISTS' SERIES. 
 
 Crown 8vo, } cloth, With many Illustrations, 
 
 Magneto and Dynamo-Electric Machines. By W. B. ESSON. 7s. 6d. 
 Gas Engines. By W. MACGREGOR. 8s. 6d. 
 Ballooning. By G. MAY. 2s. 6d. 
 
 Electric Transmission of Energy. By G. KAPP. 7s. 6d. 
 Arc and Glow Lamps. By J. MAIER. 75. 6d. 
 On the Conversion of Heat into Work. By WM. ANDERSON. 6s. 
 Sewage : Treatment, Purification and Utilisation. By J. W. 
 SLATER. 6s. 
 
 In Preparation, 
 
 The Telephone and its Practical Applications. By W. H. PREECE, 
 
 F.R.S., and J. MAIER, Ph. D. (Ready shortly.) 
 Galvanic Batteries. By Professor GEORGE FORBES, M.A., F.R.S. 
 Induction Coils. By Professor A. J. FLEMING, M.A., D.Sc. 
 Manures. By Dr. A. B. GRIFFITHS, F.R.S. Ed., F.C.S., Principal and 
 
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 (Others to follow.) 
 
SEWAGE TREATMENT, PURIFICATION, 
 AND UTILIZATION. 
 
 A 
 PRACTICAL MANUAL FOR THE USE OF CORPORATIONS, 
 
 LOCAL BOARDS, MEDICAL OFFICERS OF HEALTH, 
 
 INSPECTORS OF NUISANCES, CHEMISTS, 
 
 MANUFACTURERS, RIPARIAN OWNERS, 
 
 ENGINEERS AND RATEPAYERS. 
 
 BY 
 
 J. W. SLATER, F.E.S. 
 
 LATE EDITOR OF "JOURNAL OF SCIENCE." AUTHOR OF " MANUAL OF COLOURS 
 AND DYE WARES." 
 
 Of THE 
 
 UNIVERSITY 
 
 OF 
 
 LONDON: 
 
 WHITTAKER & CO., PATERNOSTER SQUARE. 
 
 GEORGE BELL & SONS, YORK STREET, COVENT GARDEN. 
 
 1888. 
 
 (The right of 2'ranslation is reterved.) 
 
A' 
 
PREFACE. 
 
 THE importance of the Sewage question may, perhaps, 
 be fairly gauged by the number of patents of which it 
 has been the subject, and its still unsettled state may be 
 concluded from their varied and contradictory character. 
 
 Freezing and heating, concentration and dilution, 
 electrisation and magnetising, the addition of oxidisers 
 and deoxidisers, of ferments and preventives of fermenta- 
 tion recommended, if not actually tried, show the want 
 of any distinct and generally recognised principle. 
 
 I have, therefore, thought it my duty to lay before the 
 public in plain language and in a concise form the 
 result of my experience in treating sewage and waste 
 waters. That experience dates back to the year 1868, 
 and except in 1870 my attention has during the whole 
 of that time been almost exclusively directed to this 
 question. I have worked with sewage in every quantity, 
 from a few ounces in a beaker or a hydrometer-jar to a 
 daily flow of ten million gallons. I have had oppor- 
 tunities for examining almost every known process, 
 irrigation, filtration, aeration as well as precipitation in 
 its many variations. I have studied sewage in droughts 
 and in storms, in hot weather and in cold, by day and by 
 
vi PREFACE. 
 
 night, in residential towns and in industrial centres. 
 My conclusion is that there is no one process universally 
 applicable. 
 
 Unfortunately there is no subject, outside the range 
 of party politics, on which so much envy, hatred, malice, 
 and all uncharitableness prevail as on the treatment of 
 sewage. But I ask people to judge by the evidence of 
 their own senses. Do not read about this or that process, 
 but go and look. I know instances where bitter enemies 
 of chemical processes have been convinced of their error 
 by just one unexpected and unprepared for visit of 
 inspection. 
 
 A few supplementary remarks and explanations are 
 needful : 
 
 The list of patents is not by any means as complete 
 as the author could have wished. Under the existing 
 state of the Patent law nearly twelve months may 
 elapse from the date of application to that of the 
 acceptation of the complete specification, and more time 
 elapses before such " complete " is printed and is to be 
 found in its place in the Patent Office Library. In the 
 meantime no one can tell whether a patent has been 
 abandoned or not. The difficulty is increased by the 
 circumstance that provisional specifications, if not 
 proceeded with, are now not printed, as heretofore. 
 This renders it difficult to obtain a correct list of the 
 patents for any given year until about eighteen months 
 have elapsed from its termination. When opposite the 
 number of a patent there appear the words " not 
 published," or a blank space, the reader will understand 
 that the " complete " was not to be found at the dates 
 when the author made his searches. 
 
 The specification M.L.G.G, Daudinart (A.D. 1886), 
 
PREFACE. vii 
 
 No. 4,203, was misunderstood. The zinc precipitate is 
 not applied as a manure. 
 
 It should be noted that, if we may judge from the 
 local papers, the process adopted at Hendon (p. 91) 
 gives but a very limited degree of satisfaction to the 
 ratepayers. 
 
 As regards " germs " or morbific ferments, it is now 
 generally held that these tiny organisms when introduced 
 into the system are not the direct causes of disease and 
 death, but that they generate within the body they 
 invade certain most intense poisons, which do the deadly 
 work. Practically speaking this is not a matter of 
 importance. If we can prevent the entrance of these 
 "germs" into our system, or if we can destroy them 
 after entering, they can have no opportunity to develop 
 poisons. 
 
 Here comes up another point: In addition to the 
 disease-germs, "pathogenic organisms," as they are 
 technically called, there exist in sewage and in other 
 waters germs of a very different class. These latter it 
 would seem, according to the researches of Dr. Dupre, 
 play a very important part in the purification of waters. 
 If, therefore, we remove all germs, whether by filtration, 
 precipitation, disinfection, or any other process, we may 
 in some cases do more harm than good. Can we, 
 therefore, devise some discriminating means which 
 shall destroy the evil germs and leave the useful 
 ones untouched ? If we can do this we may hope 
 to render sewage potable. Here, then, is scope for 
 the inventor. 
 
 The action of electric currents upon polluted waters 
 remains to be studied. Laboratory experiments hold out 
 hopes, but on the large scale they may prove too costly. 
 
viii PREFACE. 
 
 The shape, size, and general construction of tanks, 
 (p. in) likewise require further study. I may 
 here record my conviction that, wherever practicable, 
 intermittent working is preferable to continuous treat- 
 ment. The sewage is better dealt with at a less outlay 
 for power, chemicals, and labour. 
 
 There is surely room and need for that fair co- 
 operation of experts which Dr. DupnS asks for, as quoted 
 on p. 267. 
 
 Journal of Science Office, 
 Ludgate Hill, B.C. 
 
CONTENTS. 
 
 INTRODUCTION. 
 
 CHAPTER I. 
 
 Nature and Composition of Sewage Sewage of Residential 
 Towns of Manufacturing Towns Day and Night Sewage- 
 Sunday Sewage Water Supply Single or Double Sewer- 
 age Pages i6 
 
 CHAPTER II. 
 
 How, When and Where is Sewage Injurious Definition of 
 " Nuisance " Microbia in Sewage Sewage Detrimental to 
 Fish Organic Nitrogen in Sewage Urea, Ammonia, Nitrogen 
 Acids Phosphoric Acid Potash, Common Salt Putrescent 
 Vegetable Matter Sulphur Compounds " Hardness " of 
 Sewage its Temperature Sewer Ventilators Matters Hurt- 
 ful to Fish Hurtful to Plants 924 
 
 CHAPTER III. 
 
 Disposal and Treatment of Sewage The Cesspool The Dry 
 Closet Pneumatic Systems . ... 24 30 
 
 CHAPTER IV. 
 
 Water-carriage in General First use of Water-closet Sewer Gas 
 Dangers of Escape into Houses Proposals for dealing with 
 Sewer Gas by P. Spence and W. A. Gibbs The Dust 
 Bin ... . 30 37 
 
x CONTENTS. 
 
 CHAPTER V. 
 The Bazalgette System a Failure in London . Pages 3743 
 
 CHAPTER VI. 
 
 Irrigation, its Principle and Conditions Quality of Soil and 
 Climate Italian Rye-Grass convertible into Hay Irrigation at 
 Gennevilliers Soil Water-proofed Manurial Matter in Sewage 
 only Partially Utilised Irrigation does not remove " Germs" 
 Encourages Flies Flies convey Disease-GermsExperiments 
 of Mr. Smee, Jun. 43 67 
 
 CHAPTER VII. 
 
 Modifications of Irrigation Settling-pits Introduction of 
 Disinfectants Irrigation as Supplement to Precipi- 
 tation 67 71 
 
 CHAPTER VIII. 
 
 Filtration Structure of Filter-beds Filtering-materials Spongy 
 Iron Professor H. Robinson's Process Intermittent Down- 
 wards Filtration 71 82 
 
 CHAPTER IX. 
 
 Precipitation " Clarify and Purify " Occlusion or Absorption 
 Organic matters eliminated by Chemical Processes Properties 
 required for Precipitants Lead Condemned Iron Alkaline 
 Effluents Lime condemned Sulphates not Desirable 
 Gypsum condemned Sulphates, Hypochlorites, Salts of 
 Barium condemned Useless Agents Phosphate Pro- 
 cesses Salts of Aluminium Alum not Suitable Sodium 
 Aluminate Salts of Manganese Salts of Zinc and Copper 
 Absorbents, Fatty Clays, Coke, Peat, Charcoals, Gelatinous 
 Silica Joint action of Precipitants and Absorbents Inverse 
 Irrigation Intermittent or Continuous Working Treatment of 
 Sewage Sludge Knostropp Works Clean Tanks Supple- 
 mentary Filtration General Arrangements of Works Bogus 
 Patents and Bogus Working 83113 
 
CONTENTS. xi 
 
 CHAPTER X. 
 
 D eodorising Chloride of Lime Manganates Aeration of Effluents 
 and of Sewage Gases patented for Treatment of 
 Sewage Pages 118124 
 
 CHAPTER XI. 
 Destruction The Scott Process Sewage Cement . 124126 
 
 CHAPTER XII. 
 
 Promiscuous Methods Distillation Freezing Elec- 
 tricity 127133 
 
 CHAPTER XIII. 
 
 Self-Purification Cellular Chemical Treatment Rivers Self- 
 purifying The Vesle, the Calder and Hebble Navigation The 
 Passaic, the Oder, the Seine 134142 
 
 CHAPTER XIV. ]/ 
 
 Detection of Sewage Pollution in Rivers -Watercress in Polluted 
 Waters Experiments Sewage Fungus Professor Koch on 
 Microbia in Water Dr. Link on the Microscopic examination 
 of Water Pollution of Wells The "Recommendations" 
 Their Shortcomings Rational Scale . . . 143 163 
 
 CHAPTER XV. 
 
 Recognition of Purification in Sewage Tanks Underground 
 Pollution Sampling ... . 164 171 
 
 CHAPTER XVI. 
 
 Precipitation Mud, methods of Drying Stanks Filter Presses- 
 Press Liquor Drying Cylinders .... 178187 
 
 CHAPTER XVII. 
 Sewage Manures Errors regarding .... 172 178 
 
xii CONTENTS. 
 
 CHAPTER XVIII. 
 
 Sewage Legislation The Act of 1876 Its Defects Proposed 
 Measure of 1885 Pages 186190 
 
 CHAPTER XIX. 
 Sewage Patents 191256 
 
 CHAPTER XX. 
 
 Discussion on Dr. Tidy's Paper, read before the Society of Arts 
 May 5th, 1886 . 257267 
 
SEWAGE TREATMENT, PURIFICATION, 
 AND UTILISATION. 
 
 CHAPTER I. 
 
 NATURE AND COMPOSITION OF SEWAGE. 
 
 STRANGE to say, even professed sanitarians, municipal 
 authorities, and the like not to speak of educated and 
 intelligent people in general have often very vague 
 notions concerning the nature of sewage. They know 
 that it is nasty, and that it contains sundry matters 
 unsightly and offensive. But they are little aware of its 
 complexity, and of its liability to vary according to the 
 locality, the season, the weather, and even the hour of 
 the day. Were these points better understood many 
 futile processes for sewage treatment would never have 
 been proposed ; or, if proposed, would never have been 
 entertained. 
 
 We will take, first, the simplest case, that of a " resi- 
 dential " town. By this term sanitarians mean a town 
 where few, if any, manufacturing operations are carried 
 
 B 
 
2 SEWAGE TREATMENT. 
 
 on, and where the liquid refuse is mainly of domestic 
 origin. As examples, we may mention Oxford, Win- 
 chester, Bury St. Edmunds, Keswick, Leamington, and 
 Aylesbury. The sewage of such towns is generally of a 
 concentrated character, and the matters which it holds in 
 solution are, for the most part, of an organic and readily 
 putrescible nature. It contains the solid and liquid excre- 
 tions of the inhabitants, the urine of horses and cattle 
 discharged in the streets, the drainage of stables and 
 piggeries, the blood (more or less) of cattle slaughtered 
 in the town, and the washings of the slaughter-houses. 
 Another important constituent is the water which has 
 served for washing the persons of the inhabitants, their 
 clothing, and their cooking utensils, etc. These " slops," 
 as they are called, are very offensive ; they hold in suspen- 
 sion and solution soap, fatty acids, the juices of meat 
 and vegetables, and the exudations from the human skin. 
 Almost every one must have observed that if a bowl of 
 suds from " washing-day " has been allowed to stand, it 
 gives off in the course of a few hours a most unpleasant 
 odour. There are also certain organic substances not 
 offensive nor readily capable of putrefaction, out which, 
 nevertheless, play a most important part as far as the 
 treatment of sewage is concerned. Thus a very large 
 quantity of waste paper finds its way into the sewers, and 
 is there subdivided into particles, which quite escape 
 the notice of an inexperienced observer. To these are 
 added fine filaments derived from washing linen and 
 cotton articles, and, to a less extent, from woollens. I 
 say to a less extent, not because woollens when washed 
 give off a smaller quantity of fibre, but because the total 
 amount of woollens washed in a residential town is much 
 smaller than that of cotton and linen fabrics. These 
 
NATURE AND COMPOSITION OP SEWAGE. 3 
 
 filaments of textile materials and of paper are scarcely 
 perceptible on a hasty examination. A glass of sewage 
 held up to the light, if not rendered turbid by suspended 
 clay, road-silt, etc., appears almost as limpid as ordinary 
 river or pond water. But if we try to filter it through 
 the filter-paper used by chemists, we find that the flow, 
 though tolerably rapid at first, quickly slackens, and soon 
 comes practically to an end. If the liquid is then poured 
 carefully away from the filter-paper, and if a small 
 portion of the latter is examined with the microscope, 
 it will be found coated with the above mentioned fila- 
 ments of textile matters, which effectually choke up its 
 pores. If we attempt to filter unprepared sewage through 
 coke, gravel, sand, peat, asbestos, or ordinary arable soil, 
 we encounter the same difficulty, the rapid flow observed 
 at first becoming sooner or later obstructed. Hence, as 
 I shall endeavour to explain more fully below, filtration 
 is not practically successful even for freeing sewage from 
 its suspended impurities. 
 
 There is another constituent of sewage harmless in 
 itself, but which seriously interferes with most processes 
 of treatment. I mean the sand, gravel, and pulverized 
 stone which are washed into the sewers by every heavy 
 shower, to the greatest extent in towns, where the streets 
 are "metalled" or macadamized. We shall show else- 
 where how this silt, by keeping bad company, acquires 
 offensive properties. Its inconvenience in the various 
 forms of sewage treatment will be duly noticed. 
 
 In a manufacturing town or district the sewage is of 
 a much more complicated character, and is more un- 
 sightly, though not necessarily more dangerous to public 
 health often, indeed, less so. Its purification is some- 
 times easier than that of the sewage of residential towns. 
 
4 SEWAGE TREATMENT. 
 
 The pollution reaches its greatest height in places 
 where the textile, tinctorial, and chemical arts are carried 
 on. Here we find in the sewage, in addition to the 
 normal excrementitious matters, sulphuric, hydrochloric, 
 and nitric acids ; alkalies, soap-lyes, solutions of iron, zinc, 
 tin, alum, copper, chrome, antimony, and arsenic ; waste 
 dye liquors, spent dye wares, glue, sizes, dressings, waste 
 tan solutions, etc. It must not be supposed that all these 
 substances will be found in the sewage of a manufactur- 
 ing town at one and the same moment. Many of them, 
 indeed, neutralise and precipitate each other a circum- 
 stance on which is founded a simple process for dealing 
 with liquid industrial refuse. But if we watch the flow 
 of such sewage, we shall find striking changes both in its 
 colour and its odour, according to the kind of waste 
 just emitted from one or other manufacturing establish- 
 ment. I have repeatedly seen some agent proposed for 
 sewage purification fulfill all requirements for several 
 hours in succession, but on the sudden discharge of a 
 new kind of impurity into the sewage it has been found 
 not merely useless, but injurious., actually intensifying the 
 evil. 
 
 The sewage of such towns, though containing a larger 
 proportion of solid matter, both suspended and dissolved, 
 than that of a residential town, is of far lower agricul- 
 tural value a point to be had in remembrance in select- 
 ing a method for its purification. Some of its possible 
 ingredients, indeed, such as salts of zinc, proto-salts of 
 iron (ferrous salts), are not merely useless, but positively 
 injurious to the land. 
 
 The sewage of districts engaged in the metallurgical 
 arts, the manufacture of hardware, etc., contains little 
 extra organic impurity. On the other hand, it often 
 
ATURE AND COMPOSITION OF SEWAGE. 5 
 
 holds in solution iron in considerable amount, derived, 
 e.g.) from " pickling " iron wire. Copper and tin are 
 rarely present, the value of their solutions being a 
 guarantee that they will not be knowingly or wilfully 
 run into the sewer. But certain salts of iron, as ferrous 
 chloride, formerly known as muriate of iron, produced 
 whenever metallic iron is scoured or cleaned from rust 
 by means of hydrochloric acid (muriatic acid, spirit of 
 salt), are abundant in certain kinds of sewage, and are 
 not merely hurtful to crops for the time being, but 
 permanently deteriorate the soil. 
 
 The sketch of the sewage of manufacturing towns just 
 given is, of course, very general. Each such town, in fact, 
 turns out a special type of sewage, the nature, effects, 
 and treatment of which can be understood only after 
 careful observation and experiment. 
 
 In all towns there is generally a well-marked diffe- 
 rence between the day and the night sewage. In a 
 residential town the sewage, from midnight till five or 
 six in the morning, is very much reduced in strength, 
 as well as in quantity. Often it consists of little more 
 than the surface-water from the streets and roofs, and of 
 the ground springs, which find their way into the sewers 
 to a- considerable extent. As the day advances the 
 flow of sewage becomes more copious and more offen- 
 sive, and is at its worst from two to eight p.m. In 
 manufacturing towns the difference between the day 
 and the night sewage is often less marked, since certain 
 kinds of waste waters are discharged in the night, if 
 requisite, and refuse which should not rightfully be run 
 into the sewers at all, is often introduced when there is 
 least chance of detection. Hence it is a serious mistake 
 to imagine that the night sewage may be safely neglected 
 
6 SEWAGE TREATMENT. 
 
 and be allowed to pass into the rivers unwatched and 
 untreated. 
 
 On Sundays, in a residential town > the sewage differs 
 little from its condition during the rest of the week. 
 In manufacturing towns it is on Sundays more purely 
 excremental in its character, the industrial waste waters 
 being in great part absent. The same holds good with 
 respect to public holidays. In small agricultural centres 
 the sewage on market days is perceptibly stronger than 
 on other days, and requires an extra share of attention. 
 
 The question has often been raised whether there 
 is any marked difference between the sewage of a 
 " closetted " town and one where a proportion, larger 
 or smaller, of the inhabitants make use of the old- 
 fashioned cesspools or of dry closets and kindred 
 appliances. Certain authorities, on the faith of their 
 analyses, have maintained that there is little or no diffe- 
 rence in the strength of the sewage. Careful considera- 
 tion will show that this is scarcely possible. It may be 
 at once admitted that the liquid excretions of man, and 
 of all analogous animals, contain a larger proportion of 
 nitrogenous matter than do the solid excreta But in a 
 closetted town the whole of the excrements of the popu- 
 lation, liquid and solid, find their way into the sewers. 
 In an unclosetted town, not merely the solid, but the 
 great bulk of the liquid excretions are discharged into 
 the cesspools and dry closets. Very frequently also, 
 in small, straggling towns, public urinals, if they exist 
 at all, are not connected with the sewers. Thus the 
 water running in the latter consists, to a great extent, of 
 soap-suds, the washings of pots and pans, and, in short, 
 what is technically known as " slops." I do not see 
 therefore, how it is possible, all " dilution " notwithstand- 
 
NATURE AND COMPOSITION OF SEWAGE. 7. 
 
 ing, for the sewage of an unclosetted town to contain 
 the same matters as those of a closetted town. 
 
 A very important consideration is the water supply, 
 known and unknown. By the " known " supply is meant 
 the average quantity per head of the population served 
 out from the water-works. By the " unknown " is meant 
 the quantity which leaks into the sewers from other 
 sources, as well as the surface drainage. Where the 
 sewerage system lies in a wet sub-soil, full of ground 
 springs, and where the sewers themselves are not water- 
 tight, the flow of sewage in dry weather may rise to one 
 hundred gallons per head of the population per twenty- 
 four hours ; whilst in towns where the water supply is 
 scanty, and the sewers well made, it may fall as low as 
 twenty gallons. 
 
 Another capital distinction is the space covered by a 
 town in respect to its population. Where the streets 
 are wide, where there are few persons to a house, and 
 where there are many gardens, paddocks, vacant spots 
 of building ground, etc., the sewage, especially in wet 
 weather, loses many of its distinguishing properties. 
 
 This brings us to the question of single or double 
 sewerage. It is suggested by certain engineers that the 
 water-closets, the domestic sinks, the public urinals, etc., 
 should discharge their contents into one set of sewers, 
 whilst the surface drainage is carried off by a distinct 
 system. It must be admitted that this double arrange- 
 ment has some striking advantages : the sewage, pro- 
 perly so-called, would be at all times much more nearly 
 alike in strength and quantity, which would facilitate its 
 treatment, whether by irrigation or precipitation ; its 
 value would also be much greater. On the other hand, 
 the expense of double drainage is a very serious con- 
 
8 SEWAGE TREATMENT. 
 
 sideration. The water from the street gutters, though 
 receiving nothing from the urinals and closets, will be 
 far from clean, and its admission into the rivers, despite 
 the catch-word " the sewage to the land, and the water 
 to the river," will be a very doubtful question. In manu- 
 facturing towns there are waste liquids such as the 
 rinsing waters from dye-works which, if run into the 
 sewage, will much dilute it ; but if allowed to pass into 
 the rivers will greatly spoil their appearance. 
 
 Lastly, it is sometimes found, even where the common 
 single system prevails, that the sewers require flushing 
 to prevent solid matter from being deposited in parts 
 where the gradient is insufficient. It is reasonable to 
 suppose that this. will be much more frequently the case 
 in a sewer which carries faecal matters only, undiluted 
 with surface water. Here, then, we should get back, 
 occasionally at least, to that dilution of the sewage 
 which was to be avoided by the double system. 
 
HOW IS SEWAGE INJURIOUS 
 
 CHAPTER II. 
 
 HOW, WHEN, AND WHERE IS SEWAGE INJURIOUS? 
 
 BEFORE entering upon these questions I may, perhaps, 
 be asked what is here meant by " injury," or " nuisance " ? 
 In my opinion these terms may fairly be taken in a wider 
 sense than it is usually done. Judge McCarter, in try- 
 ing the Newark case of river pollution, ruled that it was 
 not necessary for the offensive matter complained of to 
 be present in actually poisonous quantity in order to 
 constitute a punishable nuisance. " It is sufficient if it 
 render the water offensive or disagreeable to the taste 
 or smell." Whether this decision be sound law I 
 cannot presume to say, but it is assuredly sound common 
 sense. It is not enough to contend that some particular 
 matter poured into the streams, allowed to diffuse itself 
 into the air, or to soak into the ground, does not directly 
 and palpably cause some definite form of disease, or 
 formally prevent the successful carrying on of some trade 
 or calling. If it occasions discomfort to persons living 
 near if it offends their senses of sight or smell the 
 public have surely a full right to complain, and to demand 
 judicial or, if necessary, legislative interference. My 
 definition of " nuisance " is, therefore, wider than that 
 too commonly accepted. I should include under this 
 head any matter, whether solid, liquid, or gaseous, which 
 
io SEWAGE TREATMENT. 
 
 is in itself injurious to health, or which may become so 
 in contact with other substances, whether the latter may 
 be in themselves hurtful or not ; further, any matter 
 which, though not demonstrably poisonous, is offensive 
 to the senses. 
 
 There are, of course, certain limitations to be kept in 
 view. Solid, non-volatile matter, on private premises, 
 cannot be regarded as a nuisance so long as it can 
 neither contaminate the air, nor be washed into water- 
 courses, nor out on to public roads, or the lands of other 
 persons. 
 
 Sewage contains, or rather consists of, in a large 
 proportion liquid, or, at least, soluble matters, which, 
 being liable to rapid chemical changes, give off volatile 
 products vapours and gases in abundance. These 
 vapours and gases are highly offensive to the sense of 
 smell, and, if not directly poisonous, as it is still often 
 maintained, they lower the vital tone of persons who 
 habitually breathe air with which they are mixed. The 
 greatest danger of sewage, and of water to which it has 
 been added, is that it generally, if not always, contains 
 minute living beings, bacteria, bacilli, etc., some of which 
 are found to be casually connected with infectious 
 diseases. These tiny organisms, named collectively 
 microbia, or micro-organisms, are liable to increase and 
 multiply in the water of rivers, wells, or pools into 
 which sewage finds its way. Such water is thus ren- 
 dered unfit for consumption by human beings, probably 
 also by cattle. It may occasion sickness and death if 
 used; e.g., for rinsing out milk-pails, washing cooking 
 utensils, not to speak of watering milk. 
 
 It may be urged, in opposition, that there are places, 
 many of which I know, where the only water available 
 
HOW IS SEWAGE INJURIOUS! 11 
 
 for domestic consumption is drawn from shallow wells, 
 separated from cesspools only by a few yards of chalk, 
 gravel, or other open, porous subsoil ; yet the general 
 standard of health in the district remains good. 
 
 To this it must be replied that the residents of 
 such neighbourhoods have, by a process of "natural 
 selection/' become inured to the effects of polluted waters; 
 whilst a stranger coming to live in such localities is 
 often seriously affected. But, above all, the health of 
 a population using polluted waters depends on what is 
 commonly called accident. If a simple case of typhoid 
 fever, dysentery, or cholera, is introduced into such a 
 district, the disease spreads on all sides, and commits 
 sad havoc. Thus persons who drink impure waters 
 hold their health or their lives at the mercy of chance. 
 
 But the microbia of contaminated waters find their 
 way also into the air, and may be inhaled with it. In 
 every highly polluted river fermentation is constantly 
 going on. If anyone carefully watches the Aire at 
 Leeds, the Kelvin Water at Glasgow, the Irwell, Irk, 
 and Medlock at Manchester, he will see, especially if 
 the day is warm and the barometer low, bubbles rising 
 to 'the surface and bursting. These bubbles contain 
 sewage gas, a mixture of compounds of carbon, hydro- 
 gen, and, to a less extent, of sulphur. In bursting they 
 carry up with them the microbia, or disease germs, above 
 mentioned, which thus become diffused in the air; whether 
 these microbia are also carried up into the air when 
 polluted waters evaporate quietly, without the escape 
 of bubbles, has been disputed, but it may now be 
 regarded as experimentally demonstrated. 
 
 There are, of course, cases where the volume of the 
 sewage poured into a river may be very trifling com- 
 
12 SEWAGE TREATMENT. 
 
 pared with that of the river itself. Even London itself 
 could not suffice to pollute the Amazon. But most of 
 the great cities of the modern world discharge their 
 refuse into comparatively small streams. 
 
 Seeing, then, that sewage is in the wrong place if 
 poured into waters, we have to ask how does it behave 
 on the land ? Better, perhaps, but not quite free from 
 reproach. It is then spread out over a larger surface 
 than when it flows in a sewer or in a river, and it neces- 
 sarily exposes a larger surface to evaporation in any one 
 locality. However porous the soil, and however com- 
 plete the drainage, a quantity of the evil-smelling liquid 
 rises up into the air, carrying with it disease germs, if 
 such be present. It will be found that if water is allowed 
 to flow, however gently, over the surface of dry soil, 
 bubbles are formed and burst. Thus, whenever sewage 
 is turned on to land which has not been kept constantly 
 damp, disease germs will be carried into the air, just as 
 in the case of the bubbles which form on a polluted 
 river. Further, the putrescent matter and the disease 
 germs will be absorbed by two-winged flies (diptera), 
 and distributed over the food and the persons of human 
 beings. 
 
 Summing up this part of the subject, it may be safely 
 asserted that sewage is harmful and offensive by its 
 odour and its appearance, and especially by its afford- 
 ing a pabulum and breeding ground for disease germs- 
 It is offensive in the water-courses and rivers by 
 rendering the water unfit, not merely for human con- 
 sumption, but for all delicate manufacturing processes. 
 This last point is often overlooked. It may seem a 
 convenience to the manufacturer to discharge his waste 
 waters into the river, but by so doing he renders it of 
 
110 If 7 IS SE WA GE INJURfO US? 13 
 
 little use, save as a sewer, to all establishments lower 
 down stream. 
 
 The sewage even of a residential town, except in 
 very small proportions, unfits a river for the use of 
 bleach, dye, print, or colour works. 
 
 The question has been raised by a pseudonymous 
 writer in Ashore or Afloat whether sewage is truly 
 detrimental to fish. We must here remember that 
 there are fish, and fish. Not all species are alike in the 
 conditions under which they can flourish, or even 
 subsist. But one point, at least, is analytically proved. 
 The greater the proportion of organic pollution in a 
 stream, the smaller is the percentage of free oxygen 
 held in solution, such oxygen serving to oxidise in 
 other words, to burn up the impurities, and proving 
 insufficient. Again, we know that certain fish e.g., the 
 trout can live only in well aerated, highly oxygenised 
 waters. Putting these two considerations together, we 
 can have little hesitation in pronouncing sewage pollu- 
 tion to be at least one of the causes which have tended 
 to reduce the fish in our rivers. That in many cases, 
 such as the Thames and the Clyde, other causes are at 
 work, especially steam navigation, is highly probable. 
 
 We have now to consider what are the compounds or 
 principles which make sewage water unfit for domestic 
 purposes drinking, cooking, washing, bathing, etc., and 
 for the use of cattle. 
 
 Foremost come the compounds of nitrogen. These 
 are of four kinds. There is nitrogen in organic com- 
 bination, spoken of by chemists as " organic nitrogen " 
 or " albumenoid ammonia." It is contained in albumen, 
 gelatine, and, in general, in all the complex liquid or 
 semi-liquid bodies of animal origin. These substances 
 
14 SEWAGE TREATMENT. 
 
 are introduced into sewage in the shape of blood, urine, 
 pus, mucus, half-digested animal food, as well as by 
 certain vegetable products. All such substances pass 
 very readily into intense putrefaction, and are not only 
 exceedingly offensive, but serve as nutriment for those 
 low forms of animal and vegetable life which have been 
 already mentioned as especially dangerous. 
 
 The second state is urea, which foims a very large 
 part of the solids held in solution in urine. Urea is not 
 dangerous in itself, and, in contact with a ferment which 
 is never absent in sewage, it is quickly resolved into 
 ammonium carbonate. It may therefore be regarded 
 as a mere transition compound. 
 
 The third and fourth states in which nitrogen occurs 
 in sewage are as ammonia and as nitric and nitrous 
 acids, the two latter, in combination either with the 
 ammonia or with potash or soda, forming nitrates and 
 nitrites. 
 
 Ammonia, with its salts, and the nitrates and nitrites, 
 even in the largest proportions in which they are ever 
 met with in sewage, are harmless in themselves, though, 
 like organic nitrogen, they may afford nourishment 
 for microbia. Moreover, these forms organic nitrogen, 
 ammonia, and the nitrates are constantly passing and 
 repassing into each other. Growing fungi, and other 
 plants, convert ammonia and the nitrates into organic 
 compounds of nitrogen. The only way to render any 
 water absolutely incapable of nourishing low forms of 
 life is to keep it free from combined nitrogen in every 
 shape and state. But, with waters exposed to the air, 
 this, in any absolute sense of the words, is impractic- 
 able. 
 
 Phosphoric acid is another ingredient introduced into 
 
HO W IS SE WA GE INJURIO US? 15 
 
 water by contamination with the excrements of animals, 
 or with any other decomposing organic matter. It is 
 no absolute proof of the presence of such pollution, 
 since many natural waters, on careful examination, may 
 be found to contain it in very small quantity. 
 
 It is, in itself, not merely harmless, but doubtless in 
 most cases beneficial. Yet it may be an indirect source 
 of danger by favouring the multiplication of microbia. 
 
 Much the same may be said of potash. It is note- 
 worthy that the three constituents combined nitrogen, 
 phosphoric acid, and potash which are most valuable 
 on the land, as being necessary to the growth of our 
 food-crops, should be most dangerous in the water as 
 fostering the growth of disease germs. One and the 
 same kind of matter, accordingly as it is in the right 
 or the wrong place, becomes the source of life or 
 death. 
 
 Common salt (sodium chloride) is more largely 
 present in sewage than in ordinary natural waters. It 
 is, as every one knows, harmless to human life, even in 
 greater proportions than it is ever known to occur in 
 sewage. In water from a pump in London, now dis- 
 used, it has been found to the extent of 60 grains per 
 gallon. But it tells a tale of animal pollution. If in 
 water there is more than I grain of chlorine per gallon 
 (=nearly if grain common salt), we have good primoi 
 facie reason to suspect that sewage, or at least the 
 blood or the urine of animals, must have found its way 
 in quantity into the river or the well. 
 
 There are, of course, exceptions, where salt springs 
 and beds of saliferous minerals occur in the district, or 
 if aluminium, iron, tin, etc., chlorides have been intro- 
 duced by industrial waste waters. These latter, how- 
 
1 6 SEWAGE TREATMENT. 
 
 ever, rarely find their way into a stream unaccompanied 
 by sewage in the stricter sense of the term. 
 
 Waters containing merely putrefying vegetable matter, 
 such as the drainage of rice-fields, may be positively 
 poisonous. Mr. L. d'Aguilar Jackson, C.E., observed, 
 when in Venezuela, that the result of getting wet in 
 some rivers there, without subsequently rubbing dry, 
 is malignant fever. 
 
 Thus the absence of chlorine (common salt), save in 
 very trifling proportions, may be accepted as proof 
 that a stream is free from animal pollution but not 
 necessarily that it is a safe drinking water. 
 
 Soluble compounds of sulphur, especially hydrogen 
 sulphide (commonly known as sulphuretted hydrogen), 
 ammonium sulphide, etc., are very generally present in 
 sewage if at all stale, and are a main cause of its evil 
 odour, though not necessarily of its worst effects. 
 
 We must here note that, though putrefaction is in 
 certain of its phases accompanied by a disgusting smell, 
 we must not venture on the inverse conclusion that the 
 absence of such a smell is any proof of the absence of 
 the products of putrefaction. 
 
 The sulphur compounds are in great part derived 
 from the solid excrements of men and cattle, who feed 
 largely upon cabbages, turnips, and other cruciferous 
 vegetables, and from water in which such vegetables 
 have been boiled. 
 
 Sulphuretted hydrogen is also found in abundance 
 when organic matter undergoes decomposition in pre- 
 sence of sulphates, such as gypsum. This reaction, as 
 we may remark in passing, is a reason against the use 
 of gypsum (sulphate of lime, calcium sulphate) in any 
 form in the treatment of sewage. 
 
HO IV IS SE WA GE INJURIO US? 1 7 
 
 I once met with an instance of gypsum having been 
 added to sewage mud to aid in solidifying it. Sulphu- 
 retted hydrogen was given off in such plenty that the 
 men employed suffered from temporary blindness, a 
 well-known effect of this offensive gas. 
 
 Volatile compounds of phosphorus (hydrogen phos- 
 phide, phosphuretted hydrogen) have been popularly 
 supposed to be given off by sewage and sewage deposits, 
 I know of no analytical evidence in proof of this notion, 
 and consider it a pure freak of imagination. 
 
 Marsh gas (light carburetted hydrogen or methane) 
 is found in abundance in stale sewage, as also in sewers 
 with too small a gradient, in ill-managed subsidence 
 tanks, and in accumulations of sewage mud where de- 
 composition is not checked by proper chemical agents. 
 If such deposits are stirred up, and if a light is held over 
 them, the bubbles of gas ignite and burn with a very 
 pale flame. Marsh gas has no especially injurious action 
 on the animal system. 
 
 Carbonic acid (carbon dinoxide) is another gaseous 
 product of the decomposition of sewage, and is given off 
 mingled with methane. Workmen have been suffocated 
 by this mixture in ill-ventilated sewers and other under- 
 ground passages. 
 
 A gas invariably present in natural waters, but prac- 
 tically absent in sewage, and found only in exceptionally 
 small proportions in polluted rivers, is free and uncom- 
 bined oxygen. In sewage it is spent or consumed by 
 acting upon the organic pollution. This negative feature 
 of sewage and of impure streams accounts for a part of 
 their injurious action upon the higher aquatic plants and 
 upon animals. 
 
 As regards "hardness" (i.e., the presence of the salts 
 
18 SEWAGE TREATMENT. 
 
 of lime and magnesia), sewage differs little from the 
 ordinary water supply of the district. If anything, it 
 will be softer on account of the introduction of soap and 
 washing soda, and of a considerable proportion of rain 
 water. 
 
 The sewage of a residential town has generally an 
 alkaline reaction ; that of a manufacturing town may be 
 at times slightly acid, owing to various kinds of indus- 
 trial refuse. 
 
 It will be at once seen, on considering the extreme 
 complexity of sewage and the unstable character of most 
 of its components, that as it flows it must be continually 
 changing its character ; that a sample taken in the heart 
 of a town will differ in its chemical properties and in 
 its physiological action from another sample which has 
 travelled along the sewers for the distance, say, of two 
 miles. These changes are most decisive where, as in 
 certain manufacturing towns, the sewage has a tempera- 
 ture of 60 to 70 Fahr. It is needless to say that 
 organic matters suspended or dissolved in water at 
 such temperatures must undergo very rapid fermenta- 
 tions. Wherever the sewers are open, as at the grids 
 and ventilation holes, clouds of steam rise up, carrying 
 with them a very sickening odour. 
 
 Here, I may remark, is a serious flaw in the water 
 carriage of excrementitious matters as at present con- 
 ducted. If there are no ventilators the sewage gas 
 is liable, under certain very possible contingencies, to 
 be forced back into the houses, overcoming the traps 
 of the sinks and water-closets. If there are ventilators 
 of the ordinary kind, i.e., gratings or trap-doors along 
 the streets, all the passers-by are forced to inhale the 
 fumes. In some towns, e.g., in many parts of London, 
 
HO IV IS SE WA GE INJURIO US ? 1 9 
 
 these trap-doors are constructed in the foot ways, and 
 are opened for a certain time daily to reduce the pressure 
 within. At such times it is a common sight to see a 
 small crowd collect round the opening, craning out their 
 necks as if to lose no chance of inhaling the vile fumes. 
 
 So far I have been speaking of the ingredients of 
 sewage found to be harmful to men or other animals 
 living near them. But, as far as fish and other animals 
 living in the waters are concerned, several other impuri- 
 ties found in sewage and in polluted rivers must not be 
 forgotten. Foremost must come, perhaps, solutions of 
 free chlorine and of the hypochlorites, such as bleaching 
 lime and bleaching soda. When these liquids find their 
 way into a river the fish are destroyed far and wide. 
 The surface of the Medway, at Maidstone, is sometimes 
 covered with their dead bodies to such an extent that an 
 exceedingly offensive smell is given off. H. H. Saare 
 and Schwab (Archiv fur Hygiene, vol. III., part I, page 
 8 1) have observed that liquids containing 0*04 to 0*005 
 per cent, are rapidly fatal to tench, while solutions of 
 0*0008 per cent, are directly deadly to trout. A change 
 into fresh water did not restore fishes after they had 
 fallen on one side. As the lowest limit of this destruc- 
 tive action may be taken a proportion of 0^0005 per 
 cent, of chlorine acting for two and a half hours. The 
 presence of acids increases the action of the chlorine. 
 
 Of sulphur compounds I have already made some 
 mention. Sodium sulphide (sulphuret) is, like not a 
 few other substances, the more harmful the higher the 
 temperature. Tench could bear for half an hour the 
 proportion of O.I per cent. ; and for two hours twenty- 
 six minutes the proportion of 0*05 per cent. Their 
 natural colour was, to a great extent, removed by the 
 
20 SEWAGE TREATMENT. 
 
 experiment, and did not return even on prolonged 
 sojourn in pure water. Sulphuretted hydrogen was 
 regarded fatal in proportion of O'Oi and 0*00 1 per cent, 
 and proved deadly also to tench. 
 
 Lime in its caustic state, whether introduced into the 
 stream as quick-lime, slacked lime, or lime-water, is well 
 known as a fish destroyer, and has for ages been com- 
 monly employed by poachers. Its application in the 
 treatment of sewage is common, and the attendant 
 dangers are too often overlooked even by professed 
 experts. I should advise riparian owners, lessees of 
 fisheries, etc., to protest against its introduction into 
 their waters. One manner in which lime present in 
 waters destroys fish is by entering their gills, and, being 
 there precipitated by the carbonic acid exhaled, it forms 
 deposits of carbonate of lime, which interfere with 
 respiration. 
 
 Common salt, even in the proportion of 10 per cent, 
 was found harmless at temperatures ranging from 43" 
 to 68 Fahr. Ten per cent, of chloride of calcium 
 (formerly known as muriate of lime, and by no means to 
 be confounded with chloride of lime) is harmless at 43 
 Fahr., but becomes hurtful, and even deadly, about 68 
 Fahr. Sulphate of soda, accidentally escaping into a 
 river in unknown quantity, has proved very widely 
 destructive to fish. 
 
 Ammonia and ammonium carbonate are inactive in 
 any proportion likely to be met with in rivers. 
 
 Sulphurous acid, especially if accompanied by another 
 acid, is even more deadly than chlorine. But its normal 
 salts are harmless, and salts of lime diminish its injurious 
 action. Hence the introduction of sulphurous acid is 
 less pernicious in hard than in soft waters. Carbonic 
 
HO W IS SE WA GE TNJURIO US? 21 
 
 acid at o'l per cent, kills in a few minutes, while at 0*075 
 per cent, it has no permanent action. 
 
 Hydrochloric, sulphuric, and nitric acids are injurious. 
 The first-mentioned at I per cent, is invariably fatal 
 both to trout and tench. Sulphuric acid at 0*1 per 
 cent, is fatal to trout in two to six hours ; whilst tench 
 are not seriously affected in eighteen hours. From the 
 duration of the resistance against these three acids, 
 Saare and Schwab infer that the higher the molecular 
 weight of an acid, the less rapid is its action. Oxalic acid 
 ato'i per cent, had no action on a trout in thirty minutes. 
 Tannic acid at 0*1 per cent, is harmless even to trout. 
 
 Soda at I per cent, is fatal to trout on prolonged 
 exposure. Its occurrence in streams to this extent is 
 exceedingly improbable. 
 
 At 46 degs. Fahr. a tench remained for twenty-two 
 hours without injury in a 5 per cent, solution of man- 
 ganese chloride, and a trout endured a I per cent, 
 solution for five hours. 
 
 Iron is a specific poison for fishes, both as a ferrous 
 (proto) and a ferric (per or sesqui) salt ; 0*02 to o'Oi of 
 ferric oxide in a solution is injurious. Ammonia and 
 potash-alum have as acute an action as the salts of iron, 
 the limit of endurance falling between o* I and 0*05 per 
 cent. As the poisonous action is said to depend on the 
 proportion of alumina, it is probable that the simple 
 salts of aluminium will be poisonous also. 
 
 It must here be remembered that the proportion of 
 aluminium and iron compounds used in the treatment of 
 sewage can be, and practically is, much more completely 
 regulated than that of lime. It is very rare to see an 
 excess of a sulphate or chloride of aluminium passing 
 out into a river. 
 
22 SEWAGE TREATMENT. 
 
 Arsenious acid in the proportion of OT per cent., 
 whether free or combined with soda, is not poisonous 
 to trout and tench. 
 
 Mercuric chloride (corrosive sublimate) is at once 
 fatal in proportions of 0*1 to 0*05 per cent. Copper 
 sulphate in O'l and i.o per cent, kills trout in a few 
 minutes if they cannot escape into pure water. Potas- 
 sium cyanide, 0*01 and 0*005 per cent, is also deadly. 
 Ammonium sulpho-cyanide and potassium ferro-cyanide 
 have no effect at I per cent. 
 
 Carbolic acid is poisonous to trout in proportions 
 between o'Oi and 0*005 P er cent. 
 
 H. H. Saare and Schwab, in summing up their results, 
 declare every substance soluble in water to be more or 
 less injurious to fishes. Proportions which do not 
 induce acute disease will probably be found hurtful on 
 more prolonged action, and will especially interfere with 
 the multiplication of fish. 
 
 Many of the results of these authors stand in need of 
 verification, and their experiments have not extended to 
 various substances, such as salts of lead, zinc and tin, 
 chromates, etc., which may easily find their way into 
 industrial waste waters, and which have even been 
 recommended for the treatment of sewage. 
 
 We have next to consider what constituents of sewage,- 
 if any, are hurtful to plants. In the recent sewage of a 
 residential town there is nothing in the least hurtful to 
 any of our cultivated plants, unless it is either supplied 
 in too large a quantity, or that it is too strong. Very 
 few plants can bear repeated waterings with undiluted 
 urine. 
 
 But in the sewage of manufacturing towns there are 
 abundance of constituents which destroy or injure trees, 
 
HO W IS SE WA GE INJURIO US ? 23 
 
 crops, etc., and have, further, even a sterilising effect 
 upon the soil. As such may be mentioned waste 
 bleaching liquors, most sulphur compounds, including 
 the waste of the alkali manufacture, sulphuric and 
 hydrochloric acids, solutions of alumina, iron, tin, lead, 
 zinc, chrome, etc. Further, waters containing tannin, 
 gallic acid, starch, glucose, and many coal-tar products. 
 Thus objection must be taken to the waste waters of 
 paper-mills, bleach-, dye-, print-, and chemical works, 
 electro-plating establishments, and works where wire is 
 " pickled," where the manufacture of tin and tern plates 
 is carried on. On the other hand, the waste waters of 
 soaperies, glue arid gelatine works, and some other 
 establishments are not to be feared. It will be at once 
 seen that the useful disposal of waters injurious to 
 vegetation is an exceedingly difficult task, and that 
 some of the best methods are at once excluded. 
 
24 SEWAGE TREATMENT, 
 
 CHAPTER III. 
 
 THE DISPOSAL AND TREATMENT OF SEWAGE. 
 
 IN the primitive condition of mankind population was 
 necessarily scanty, and, above all, it was nowhere con- 
 gested into dense masses. Hence the offensive products 
 necessarily resulting from animal life in whatsoever 
 form occasioned no trouble. Sewage, as we understand 
 it, was not produced, and consequently no question 
 concerning its dangers and its treatment could arise. 
 Both the liquid and the solid excreta were voided on 
 the ground, and, never accumulating in large quantities, 
 they were easily absorbed by the soil, or were in part 
 consumed by certain insects. Even to the present day 
 there are places in England, not to speak of less 
 populous countries, where this system, if I may so call 
 it, still prevails. So long as the population remains 
 thin, and as no epidemic is present, there is no mani- 
 fest harm. Epidemics, indeed, are the rarer and the 
 less formidable in proportion as a country is sparsely 
 peopled. But so soon as it becomes at all numerously 
 or densely inhabited, excrementitious matter ac- 
 cumulates in the neighbourhood of dwellings and is 
 liable to be washed by heavy rains into wells and other 
 waters used for drinking. Hence in times of any 
 common sickness serious consequences may ensue. 
 
THE DISPOSAL AND TREATMENT OF SEWAGE. 25 
 
 It is interesting to note how, in so ancient a document 
 as the Pentateuch, it was especially enjoined upon the 
 Israelites that excrements should not be left to lie upon 
 the surface of the soil, but should be covered with earth 
 (Deuteronomy xxiii. 13.) This command evidently 
 implies a knowledge of the sanitary efficacy of the soil 
 possibly also of the danger of exposing faecal matter 
 to be washed into the rivers, or to be the pabulum of 
 flies, which then settle upon human beings and their 
 food, and thus propagate disease. The possession of 
 such knowledge at so early a date is a very remarkable 
 circumstance, if we suppose it to be a dictate of Egyptian 
 civilization. 
 
 The next step, unavoidable as soon as large villages 
 and towns took their rise, was the cess-pool. This was, 
 and often still is, a mere pit in the soil, not in any way 
 rendered water-tight to prevent the contents from 
 soaking into the earth at the bottom or sides. Nor 
 was it generally covered in so as to minimise the escape 
 of offensive odours. In most places the contents were 
 dug or scooped out from time to time, and conveyed 
 into the gardens or the fields. Here, at any rate, was 
 an attempt to restore to the soil what had been taken 
 from it. 
 
 But this method is open to very serious objections. 
 Unless the cess-pit is made water-tight with masonry 
 or cement, the liquid portions of the excrement its 
 most valuable part soaked into the earth and were 
 lost. Worse than lost, they not uncommonly found, 
 and still find, their way into chinks and crevices in the 
 sub-soil, especially in chalky districts, or drained through 
 porous formations (gravel, etc.) into wells and water- 
 courses. 
 
25 SEWAGE TREATMENT. 
 
 A further objection is that the emptying such cess- 
 pools is a very loathsome process, and under certain 
 circumstances it may prove highly dangerous both to 
 the workmen employed and to all persons living in the 
 immediate neighbourhood. 
 
 To lessen this drawback it became, from a very early 
 age, customary to add to the contents of the cess-pits 
 matters which, it was supposed, might to some extent 
 absorb and neutralise the evil odours. Among such 
 substances the ashes of wood, peat, coal, etc., took a 
 prominent place. The cess-pool became also the 
 general receptacle for all the refuse of the household, 
 some of which was far from tending to render it less 
 offensive or less dangerous. Such is the village cess- 
 pool in our days, tolerable only where it is lined with 
 slabs of slate or flag-stones well cemented together, so 
 as to prevent infiltration into the sub-soil. 
 
 But in many districts, where room was plentiful and 
 where the soil is, as commonly termed, " light," the 
 cess-pools were not emptied periodically, or indeed at 
 all. 
 
 When full, they were covered in, not by any means 
 in an air-tight manner, whilst a fresh pit was excavated 
 near at hand and brought into use instead. There are 
 towns where this process has been carried on so long and 
 so generally though now put an end to that the 
 entire subsoil is polluted to an unknown depth, and its 
 sanitation becomes scarcely possible. It is, or was until 
 very lately, common to find in castles and other large 
 mansions old cess-pools, the very existence of which 
 had been quite forgotten. I understand that sub- 
 sequent to the death of Prince Albert not a few such 
 abominations were detected in Windsor Castle. The 
 
THE DISPOSAL AND TREATMENT OF SEWAGE. 27 
 
 same evil was not wanting in dwellings of much less 
 pretentions. It often happens in country places, when 
 a row of old cottages is demolished to make room for 
 some new buildings, the cess-pits are not cleared out, 
 but simply filled up with any kind of available rubbish, 
 and new houses or manufacturing premises are built 
 over the spot, the occupants being in happy ignorance 
 of what lies beneath their feet. 
 
 To sum up this part of the subject, it may be said 
 that cess-pools are utterly out of the question in towns. 
 They are permissible, nay, sometimes they may be the 
 best expedient, in the case of villages and detached 
 houses in the country. But the following conditions 
 must be observed : 
 
 1. The pit must be lined in a water-tight manner with 
 masonry, flag-stones, etc., so that nothing can leak out 
 into the soil. 
 
 2. It must be situate so that a clear current of air can 
 play between it and any dwelling or workshop, etc., 
 and it should be covered in from rain. 
 
 3. It must be regularly cleared out and the contents 
 dug into the soil not in the immediate neighbourhood of 
 any well or water-course. 
 
 4. Garden mould or fine ashes should be added to 
 the faecal matter liberally. 
 
 5. At the time of thus emptying out, it is well to add 
 some active disinfectant. The like should be done if 
 any infectious disease occurs among the persons making 
 use of the convenience, or indeed in the neighbourhood. 
 The emptying should, if possible, never be performed 
 in warm, calm, moist weather. Frost, or, in its absence, 
 drying winds afford the best opportunity. 
 
 We turn now to various improvements on the cess- 
 
28 SEWAGE TREATMENT. 
 
 pool system. Foremost among these stands the earth- 
 closet or dry-closet, first proposed by Mr. Goux, and 
 since variously modified. Its principle is that a quantity 
 of dry earth, peat-mould, charcoal, etc., is stored up be- 
 hind and above the seat of a closet much resembling 
 that of an ordinary water-closet. After this has been 
 used a handle is pulled, and a quantity of the dry mate- 
 rial just mentioned falls down so as to cover the excreta 
 and prevent the escape of any offensive fumes. Daily 
 or oftener, the box, pail, or other receptacle, is emptied 
 out either by the inmates of the house or by public 
 servants. 
 
 This system has very great advantages from a sani- 
 tary point of view. There is, with ordinary care, no 
 nuisance, no danger to health, no generation and escape 
 of sewer gas either in-doors or in the streets and roads ; 
 no pollution of rivers, whilst the liquid and solid excre- 
 ments are restored to the soil undiluted, and before they 
 have had time to enter into fermentation. 
 
 But, on the other hand, there is considerable trouble 
 and expense in preparing the absorbent material, which 
 must be dry, conveying it into the closet, and emptying 
 the pail or receiving-box. This system, too, like the 
 water-closet scheme, fails to make provision for vege- 
 table refuse, and not only so, but for soap-suds and wash- 
 ing waters, which have still to flow into the sewers, and 
 may easily be the carriers of disease germs. 
 
 In some cases the dry absorbent matter is omitted, 
 and the excrements are received into tubs or cans 
 capable of being closed air-tight after use. This system 
 has been adopted in some small towns, where carts go 
 round daily to receive the full pails and leave empty 
 ones in their stead. It is, of course, essential that these 
 
THE DISPOSAL AND TREATMENT OF SEWAGE. 29 
 
 vessels, of whatever shape and material, should be 
 thoroughly cleaned when emptied, or the nuisance 
 would be serious. Hence the working cost is consider- 
 able. Thus, though this system has given satisfaction 
 in some small towns, it is out of the question in larger 
 cities, where the distances to be traversed would require 
 the employment of a ruinous number of carts, horses, 
 and men. 
 
 In another form, there is in each house a fixed recep- 
 tacle into which all excreta are voided, and which is 
 fitted after use with a (supposed) air-tight cover. From 
 the bottom of this receptacle runs a pipe, which passes 
 through the outer wall of the house, and is closed at its 
 end with a plug. In the night, carts go round to each 
 house. The plug is withdrawn, and a pump is attached 
 to the pipe, which draws the contents of the receptacle 
 into the cart. This operation is not unattended with 
 nuisance, and it is practically impossible for the recep- 
 tacle ever to be thoroughly cleansed from putrescent 
 faecal matter. 
 
 This is, perhaps, the place to mention the system of 
 Liernur who, unlike prophets, finds honour in his native 
 country, if nowhere else. Here, also, there is no water 
 of dilution. The movable pails and the collecting carts 
 are suppressed, and the excreta are aspirated by power- 
 ful pneumatic machinery out of the recipients through a 
 system of pipes. That either the recipient or the in- 
 terior of the pipes can be entirely sucked clean in this 
 manner, even if a perfect vacuum could be instantly 
 created at the outer extremity of the system, is not to 
 be expected or believed. 
 
 We thus come to the end of the systems which do not 
 call in the aid of water, but which deal with the excreta 
 
30 SEWAGE TREATMENT. 
 
 of human beings as a whole, not first forming sewage, 
 in the conventional sense of the word, and then striving 
 to extract some of its constituents for useful purposes. 
 
 All these dry systems, except the primitive cess-pool, 
 require the dust-bin as an accessory. All of them, as I 
 have briefly hinted, fail to provide for household " slops." 
 Still more completely they are out of the question for 
 industrial waste waters, and even for the washings of 
 slaughter-houses, and the drainage of piggeries and 
 stables. 
 
 Hence in all towns a system of sewage becomes 
 essential, and the notion of disposing of human excreta 
 also in this manner naturally suggests itself. To this 
 we therefore proceed. 
 
WATER CARRIAGE IN GENERAL. 31 
 
 CHAPTER IV. 
 
 WATER CARRIAGE IN GENERAL. 
 
 THE use of rivers, arms of the sea, and canals as the 
 recipients of faecal matter is not of modern origin. 
 Certain antiquarians consider that the water-closet, as 
 we now have it, was known in ancient Rome, and even 
 that the " summer-parlour " of Eglon, King of Moab 
 (Judges iii. 20), w r as a convenience of this kind. But in 
 modern times it has been common, wherever dwelling- 
 houses or factories stood on the brink of a stream, to 
 have out-shot closets jutting over it, so that the faecal 
 matters might fall at once into the water. The margins 
 of the Fleet Ditch, in London, so long as it remained 
 open, are said to have been lined with such arrange- 
 ments. In the East of Germany they existed about 
 the year 1830. In the North of England they were not 
 uncommon twenty years ago, even on the brink of 
 rivers which were nearly dry in summer, thus occasioning 
 a grievous nuisance. I have seen in a Midland district 
 a contrivance, if possible, still more offensive. A row of 
 cottages stood on a high ground, separated by a public 
 road from a brook, or rather, ditch. Each cottage had a 
 kind of cess-pool, from the bottom of which there ran 
 an ill-made drain under the road. Whenever there was 
 a fall of rain part of the contents of these cess-pools 
 were washed through the drains, down the bank, and 
 
32 SEWAGE TREATMENT. 
 
 into the tiny brook, which was thus converted into an 
 open sewer. 
 
 In Melbourne, with an average temperature higher by 
 10 Fahr. than that of London, cess-pools in houses 
 were allowed to overflow into the surface-water gutters 
 at the sides of the streets. 
 
 The first systematic use of the water-closet and of the 
 water-carriage of faecal matters began with the suppres- 
 sion of cess-pools in London and other large cities. The 
 excreta of the population were thus compulsorily and 
 by authority diverted into the rivers, no attempt at 
 purification being thought of. Before proceeding to 
 describe the various modifications of, and improvements 
 on, this crude and nasty procedure, I must point out 
 certain initial disadvantages which attend water-car- 
 riage, however the sewage matters may be ultimately 
 disposed of. 
 
 There is, in the first place, a very serious consumption 
 of water, over and above what would otherwise be 
 necessary for domestic purposes. This increase may, 
 perhaps, be roughly taken as 20 per cent. Thus if a 
 residential town without water-closets requires 100,000 
 gallons of water daily, if these conveniences are 
 generally introduced the daily demand will rise to 
 120,000 gallons. This increase may easily mean more 
 than an addition of 20 per cent, to the cost of the water- 
 supply. It is recognised on all hands that the water 
 furnished to a town must be good in quality. But such 
 water is not everywhere t be obtained in sufficient 
 quantity within a reasonable distance. It might happen 
 that a source fully adequate for a town in other respects 
 might not leave a sufficient margin for the water carriage 
 of excreta. 
 
WATER CARRIAGE IN GENERAL. 33 
 
 It may be contended that a second-rate water is quite 
 good enough for working water-closets and flushing 
 sewers. So it is ; but we are then driven to the trouble- 
 some and costly expedient of a double water supply 
 a good quality for drinking, cooking, etc., and an inferior 
 sort for the closets. This would prove a heavy addition 
 to local taxation a sphere where no one thinks of 
 retrenchment. 
 
 Another disadvantage is the generation of " sewer 
 gas." This term includes all the volatile products 
 gases or vapours arising from excreta in various stages 
 of decomposition. Such sewage gas may or may not 
 be capable of directly occasioning disease. But few 
 very few competent medical authorities will deny that 
 if persistently inhaled it lowers the tone of the con- 
 stitution, and renders the inroads of fevers, etc., more 
 probable. Above all, this same sewage gas is liable to 
 convey disease germs into our dwellings and into our 
 bodies. It is a serious consideration that we have now 
 this gas " laid on," so to speak, in every house. Not 
 only our water-closets, but our bath-rooms and our very 
 sleeping apartments, are placed, potentially at least, in 
 connection with the sewer. If there is a chink in the 
 piping, a defect in the soldering, or if the valves are out 
 of order, this potential connection becomes actual. 
 Hence, in addition to good plumbing at the beginning 
 and careful management and watching afterwards, the 
 water-closet requires precautions in its position. It may 
 be a luxury or a convenience to have water-closets in 
 the interior of a house, separated, perhaps, from the 
 bed rooms merely by ill-fitting doors. It is very agree- 
 able, doubtless, to have the wash-stand in a dressing- 
 room fitted with a fixed basin from which the water can 
 
 D 
 
34 SEWAGE TREATMENT. 
 
 be discharged into the sewer by lifting a plug. But this 
 convenience has to be paid for in the shape of risk. 
 The true situation of the water-closet in a house is in an 
 out-shot annex with two windows on opposite sides, so 
 that it may be ventilated not into the house, but into 
 the air outside. 
 
 It must also be remembered that water forms no ab- 
 solute barrier between the air of the sewer and the air 
 inside the house. Through the water there is a constant, 
 though slow, interchange of gases going on. 
 
 As for the plugged wash-basins in bed-rooms and 
 dressing-rooms, despite their convenience, they had better 
 be given up. This change, I understand, has been 
 carried out in many of the principal hotels in America. 
 
 Another drawback on the water carriage system is 
 that the sewers, if not absolutely water-tight which is 
 scarcely possible allow more or less of their contents 
 to ooze out and saturate the surrounding soil, thus grad- 
 ually forming a bed of poisonous matter. This bed 
 alters the character of the "ground -water," which has 
 been so thoroughly investigated by Professor von Petten- 
 kofer, of Munich, and renders it more harmful. The 
 vapours given off from this polluted "ground-water " will 
 escape in the direction of least resistance, and that 
 direction, in the case of streets paved, flagged, and 
 especially asphalted, will be into the cellars or the sunk 
 ground-floors of the adjoining houses. 
 
 If a momentary digression is permissible, I would 
 add my protest against the custom, all but universal, of 
 carrying the soil-pipes of water-closets under the floor 
 of the house to join the sewer outside in the street. If 
 the connections are imperfect, or have never been 
 made at all as is sometimes the case -ill-health and 
 
WATER CARRIAGE IN GENERAL. 35 
 
 death will be the lot of the occupiers of the house. A 
 sewer should never be permitted to pass under any 
 human habitation unless there is a clear, open air-way 
 left between the top of such sewer and the foundations 
 of the house. 
 
 Another point is the ventilation of the sewers an 
 absolute necessity. If we suppose a system of sewerage 
 perfectly air-tight, and having no inlets, save the trapped 
 openings through which the liquids from sinks, water- 
 closets, etc., find entrance, it would very often happen, 
 from the fermentation of the faecal matters, that the 
 pressure inside the sewer would be greater than the 
 pressure of the external atmosphere. In such cases the 
 sewer gas would force its way through the ordinary sink- 
 traps, and escape in bubbles into the houses. To 
 prevent such a grave inconvenience it is usual in most 
 towns to provide the sewers with trap-doors, which, 
 when opened, act as ventilators, and allow the condensed 
 gases, if any, to come to an equilibrium. But these 
 ventilating trap-doors are placed too often in the foot- 
 ways, with the bad results which I have already pointed 
 out. Surely situations might be found for ventilating 
 traps not open to this objection. 
 
 It will be perceived that the sewer retains its 
 unpleasant character up to the very point where it 
 discharges its contents for treatment. No system of 
 purification adopted at this point can obviate the 
 nuisance arising from every grid on the way. Disin- 
 fectants of various kinds are sometimes poured into the 
 sewers in an intermittent manner, in the hope of 
 preventing the formation of sewer gas. It sometimes 
 happens that conterminous sanitary authorities use 
 substances which are mutually incompatible, one, for 
 
36 SEWAGE TREATMENT. 
 
 instance, employing chloride of lime or a permanganate, 
 whilst his neighbour is using some de-oxidising agent, 
 such as carbolic acid or an alkaline sulphite. 
 
 I can here merely refer to two projects for dealing 
 with sewage gases and the sewer ventilation question. 
 The late Peter Spence, of the Pendleton Alum Works, 
 proposed to connect all chimneys, whether of houses or 
 factories, with the sewers, whilst these, again, were made 
 to vent into one huge central stalk, actuated by a mighty 
 furnace. In this manner all the sewage gases would be 
 aspirated into the central chimney, and, being already to 
 some extent disinfected by the smoke and other products 
 of combustion drawn into them, would be finally dealt 
 with in passing through the furnace and discharged in 
 a harmless state from the central chimney. Thus smoke 
 and sewage gas would be done away with at once. 
 
 Mr. W. A. Gibbs, of Gillwell Park, Essex, proposes a 
 different scheme for towns situate on the banks of tidal 
 rivers. Huge fans, worked by tidal power, would be 
 erected at the outfalls, say at Barking Creek and 
 Crossness. The air in the streets of London would 
 rush into the sewers, removing fog, sewage gas, and all 
 evil vapours. Whether it would be possible by any 
 power applied at the outfalls to create an in-draught into 
 the sewers at the most remote parts of the metropolis, I 
 am not prepared to decide. But I could wish that both 
 of these schemes might have a fair trial in some town, 
 smaller than London, and conveniently situate. 
 
 Not the smallest of the defects of the water carriage 
 of excreta is that the excessive dilution reduces their 
 agricultural value, and renders any method of treatment 
 that may be adopted less remunerative, if not less easy. 
 
 Lastly, we must remember that where water carriage 
 
WATER CARRIAGE IN GENERAL. 37 
 
 is adopted the dust-bin is indispensable. The solid 
 refuse, household ashes, the bones, skins and shells of 
 fish, the parings and stalks of fruit and vegetables, etc., 
 cannot be passed down the soil-pipe, and hence they 
 find a temporary home in the dust-bin. This receptacle 
 is supposed to be from time to time cleared out by the 
 servants of the local authority, or by contractors an 
 unpleasant operation, in which smells, offensive, if not 
 positively harmful, are diffused. The nuisance is the 
 greater the longer the refuse is allowed to accumulate. 
 Such time may be somewhat long, especially if the 
 householder is not willing to give the men employed a 
 liberal backsheesh. But the worst evil is the subsequent 
 destination of the matter. It is sold by the contractors 
 to building speculators, who use it for all manner of 
 unsanitary purposes, such as filling up hollows, laying 
 out streets, mixing mortar, etc. I have even seen it 
 employed in mending old-established streets, long since 
 in the hands of the local authorities. The unpleasant 
 smells, and the flocks of blow-flies hovering round, 
 proved but too plainly that the "dust" was utterly unfit 
 to be used in street repairing or in building operations. 
 The contractor is supremely indifferent about complaints 
 inserted in the Press, or addressed to the local sanitary 
 department. He has duly " squared " the surveyor, 
 who will, as in duty bound, " make it all right." But in 
 spite of its shortcomings, and of its needful adjunct 
 the dust-bin, the water carriage system is in all large 
 cities simply Hobson's choice. No one has yet suggested 
 any practicable method by which it might be superseded. 
 Our inventors are too busily employed in devising 
 " aerostats," submarine boats, and other devices for 
 taking human life, to turn their attention in this direction. 
 
38 SEWAGE TREATMENT. 
 
 CHAPTER V. 
 
 THE BAZALGETTE SYSTEM. 
 
 CONCERNING the direct discharge of sewage and other 
 waste waters into rivers, nothing further need be said. 
 It has no advocates, and offers no advantages save a 
 fallacious cheapness. The whole vexed question of river 
 pollution is the outcome of this mistake. 
 
 The first method that we shall discuss is very simple, 
 very costly, and very unsatisfactory. The original 
 responsibility for this process seems to fall upon F. 
 Lipscombe, who proposed it in a patent, A.D. 1857, No. 
 2168. E. Strangman (A.D. 1861, No. 1040) obtained a 
 patent for a somewhat similar scheme. 
 
 It may, however, be conveniently called Bazalgettism, 
 from the distinguished engineer to the Metropolitan 
 Board of Works, who has carried it out on a gigantic 
 scale as a means of disposing of the sewage of London. 
 Its essential principle is discharge either directly into 
 an arm of the sea, or into a tidal river, at the time of 
 ebb. 
 
 In the latter case, the sewage must be received, in the 
 first place, in large reservoirs or store-tanks, in which it 
 is allowed to accumulate during the flow of the tide, and 
 is let out as soon as the ebb commences. The theory 
 of the process is that before the tide again flows, all the 
 
THE BAZALGETTE SYSTEM. 3 9 
 
 offensive matter will have passed out at the mouth of 
 the river and have been diffused into the sea. 
 
 It is manifest that this method is available only in a 
 limited class of places. If a city lies on the banks of a 
 river, so far from the sea that the sewage would not 
 have time to reach its mouth whilst the tide is running 
 out, it is met by the next flood tide and carried back 
 again. Thus the lower part of the river becomes a sink 
 of pollution, intensified by constant recruits of filth. 
 
 Even on the sea-shore this system cannot be safely 
 applied in the case of land-locked harbours, and narrow 
 deep bays. In few situations is sewage pollution more 
 formidable than in the harbours of Marseilles, Bombay, 
 Rio Janeiro, Bahia, etc. Those of Sydney and Mel- 
 bourne will, doubtless, in due time reach the same 
 undesirable condition. 
 
 The expense of Bazalgettism is exceedingly serious. 
 The construction of the tanks to store up the sewage 
 whilst the tide is running up involves an outlay which 
 for many communities is simply prohibitive. Such 
 tanks cannot, for obvious reasons, be situate in or very 
 near to the city or town in question. They must lie at 
 a lower level than such city, or the sewage cannot be 
 conveyed into them by gravitation. Yet they must be 
 so high that their contents can be run out to the very 
 bottom at low water. These two conditions will 
 generally be found mutually incompatible. Thus, at 
 the two London sewage outfalls, Barking Creek and 
 Crossness, the sewage is first pumped up into the storage 
 tanks. I have seen a calculation what every stroke of 
 the powerful and ornate machinery effecting this task 
 extracts out of the pockets of the ratepayers. 
 
 It will be at once seen that this system offers not the 
 
40 SEWAGE TREATMENT. 
 
 slightest set-off against the expenditure. It is all out- 
 lay, with no returns. 
 
 Nor is the prevention of nuisance by any means com- 
 plete. I will suppose, for argument's sake, that every 
 drop of the discharged sewage is carried out to sea be- 
 fore it can be forced back by the returning flood tide. 
 Yet the lower part of the river is of necessity polluted 
 to the annoyance and danger of persons navigating it or 
 dwelling near its banks. A portion of the finely divided 
 mineral matter which invariably enters into the sewage 
 of a town, especially where the lamentable custom of 
 macadamising or " metalling " the roads is tolerated, 
 is gradually deposited in the bed of the stream, and 
 must, all assertion to the contrary notwithstanding, take 
 rank as one of the agencies which silt up the channel. 
 Each such particle of sand or clay or ground-stone 
 becomes, by surface attraction, coated with a thin layer 
 of the offensive organic matters present in the sewage. 
 Any one who doubts this may soon be convinced to the 
 contrary if he will take a pound of such sewage silt, dry 
 it, and then heat it strongly, when a powerful faecal 
 odour will be given off. 
 
 Even in those few localities where the outflow can 
 take place directly into the sea, there is still an opening 
 for mischief. The suspended particles of excrementi- 
 tious matter "hug the shore," just as corks or chips 
 floating in a tub of water make their way by attraction 
 to the side. Among the unpleasant results of this 
 phenomenon I may mention that shrimps feed upon the 
 unclean matter, and are then caught and consumed by 
 men before it can be completely assimilated. It has 
 been lately established that mussels found in the open 
 sea are harmless, but if deposited in harbours they be- 
 
THE BAZALGETTE SYSTEM. 41 
 
 come poisonous, and lose anew their malignant proper- 
 ties on being taken back to the open. It is exceedingly 
 probable that the poisonous properties developed are 
 due to the consumption of sewage matters. Two of the 
 poisons detected in mussels by Dr. Brieger are ptomaines. 
 
 Where sewers open into the sea without the inter- 
 position of a storage tank, the case is still worse. When 
 the tide rises and covers the mouth of the drain pipes 
 the sewage gas, holding possibly disease germs in sus- 
 pension, is driven back into the town, and into the very 
 houses, overcoming the traps. 
 
 In the rare cases where a manufacturing establish- 
 ment is situate on an open coast not a tide-way or 
 harbour its liquid refuse may find vent direct into the 
 sea, if no more useful mode of disposal can be devised. 
 
 But the admission which we made above, for argu- 
 ment's sake, is found, in the case of London, to be quite 
 incorrect. Sewage matters discharged into the river at 
 Barking and Crossness are not pushed out to sea by 
 the combined action of the ebbing tide and of the cur- 
 rent They mingle with the water, and work their way 
 back to points far above the outfalls, thus effecting that 
 pollution which the intercepting sewers and the costly 
 channels running parallel to the river were to have 
 averted. 
 
 The Bazalgette process, as applied to London, is a 
 total failure. It involves the utter waste of all the 
 manurial matters in the sewage ; it aids in silting up the 
 bed of the Thames ; it occasions a nuisance much com- 
 plained of by the inhabitants of the country below the 
 outfalls on both banks ; its cost is exceedingly serious ; 
 and it does not even guarantee to the inhabitants of 
 London an unpolluted river. Some persons might 
 
42 SEWAGE TREATMENT. 
 
 think that all these charges against the system being 
 admitted, the Metropolitan Board of Works would 
 hasten to abandon the scheme altogether, and cry 
 peccavimus with the best grace possible. Whoever 
 should form such an expectation would betray a very 
 imperfect knowledge of the official mind. Instead of 
 renouncing the whole scheme as a failure, they seek its 
 extension. It is proposed to convey the sewage down 
 to Thames Haven in a vaulted culvert, that from the 
 south side of the Thames being carried under the river 
 by a tunnel and then pumped up into the culvert on 
 the northern shore. The cost of this gigantic sewer, 
 twenty miles in length, is estimated by Sir Joseph 
 Bazalgette at 4,000,000. Those who have had some 
 experience in engineering estimates will expect this 
 sum to be largely exceeded should the scheme unfor- 
 tunately be carried into execution. The working cost 
 with which the ratepayers of the metropolis are threat- 
 ened is 3 1 7,000 yearly, in addition to interest on the 
 four millions borrowed and the expense of paying off 
 the loan. 
 
 At Thames Haven the entire sewage will be dis- 
 charged. 
 
 We will now examine the probable result of this 
 scheme. The annual charges for dealing with the 
 sewage of London, already quite heavy enough, will 
 be seriously increased. The faecal matters of the sewage 
 will still, as at present, be wasted. The dwellers on 
 the shore near the point of outflow will complain of a 
 nuisance, just as now do their neighbours a little higher 
 up stream. Sewage matters will scarcely find their way, 
 as at present, to points above London Bridge, and the 
 silting up process will be suspended. But, on the other 
 
THE BAZALGETTE SYSTEM. 43 
 
 hand, the Thames will be deprived of a tribute of 120 
 million gallons of water which are now poured into it 
 daily, at a time when its level is lowest owing to the 
 ebb. Surely it would be far better to pour this volume 
 of water into the river in a purified condition, which, as 
 we shall see, might be effected more cheaply, and with 
 at least a partial utilisation of the manurial matters 
 contained in the sewage. 
 
 It is well known on the west coast of Africa and in 
 Mauritius that the contact of polluted land waters with 
 the sea is greatly to be dreaded, as far as public health 
 is concerned. 
 
44 SEWAGE TREATMENT. 
 
 CHAPTER VI. 
 
 IRRIGATION. 
 
 THE second method of sewage treatment is irrigation ; 
 a system which has contrived to secure advocates, many, 
 influential and enthusiastic. Its essential principle is 
 the application of the sewage to cultivated land, under 
 the impression that the excrementitious and other 
 offensive and putrescent matters held in solution or 
 suspension will be absorbed by the soil, and utilised 
 by the growing crops ; whilst the water, sufficiently 
 purified, will pass away into the drains, and may be 
 permitted to enter the rivers without fear of pollution. 
 
 The action is supposed to be two-fold ; on the one 
 hand, the soil itself has an absorbent power. As the 
 sewage soaks down into the ground, it carries with it 
 air, by which certain of its organic impurities are 
 oxidised and destroyed. That such a purifying process 
 really takes place, whatever its theory, may be proved 
 by the simple experiment of rilling a flower-pot with 
 soil, and pouring a little sewage, etc., upon it. The 
 water which oozes out below will, unless the quantity 
 is too great, be to a very considerable extent deprived 
 of its offensive smell. 
 
 On the other hand, the growing vegetation is supposed 
 to absorb and assimilate a proportion of the organic 
 matter present, just as it does any other manure. The 
 
IRRIGA TION. 45 
 
 mere filtering action of the soil is thus reinforced, and 
 the impurities are not merely removed, but turned to 
 account 
 
 Hence, irrigation is, under favourable circumstances, 
 very efficacious. It requires, however, certain con- 
 ditions, which are not everywhere to be met with in 
 combination. The first essential is, of course, a large 
 plot of land, which should be at some distance from the 
 town supplying the sewage, and should not border upon 
 any populous district. The irrigation farm, as such a 
 plot is called, should also be situate at a lower level 
 than the town, as, if the sewage has to be raised to a 
 higher level by pumping, both the first outlay and 
 the annual working cost are necessarily and heavily 
 increased. 
 
 Now, as nearly all our inland towns lie on the banks 
 of some river, the only ground to which the sewage can 
 flow by gravitation will generally be found at some point 
 lower down the river valley. But in the more populous 
 parts of England and Scotland the river valleys are 
 generally occupied by a string of towns, villages, and 
 factories. Hence, land in such situations is very valu- 
 able, and to acquire a plot suitable for an irrigation farm, 
 if practicable at all, is, necessarily, a costly undertaking. 
 When such a plot has been found, a further outlay is 
 incurred in laying it out, and in conveying the sewage 
 thither. The latter point may be very serious : the 
 authorities of a town in Lancashire, having conveyed 
 their sewage to a plot of land at a certain distance, were 
 sued for heavy damages by the owner of some subjacent 
 coal deposits, on the plea that the working of such 
 deposits would be interfered with by the sewage 
 channel. 
 
46 SEWAGE TREATMENT. 
 
 Another consideration is that if the sewage has to be 
 conveyed to some distance before it can be applied to 
 the land, the river of the district must be, for a part of 
 the course at least, robbed of no small share of the 
 waters which it would otherwise receive. This point 
 is the more serious, as many streams in the manufac- 
 turing districts are very low in a dry season. 
 
 Again, the quality of the soil is no less important 
 than the situation. If it is too open and porous in its 
 texture the sewage passes rapidly through it, and 
 emerges, scarcely, if at all, purified. This is especially 
 the case with shallow, sandy, or gravelly soils over- 
 lying rocks. If, on the other hand, it is too compact 
 and retentive, the water cannot escape readily enough, 
 and the soil is rendered swampy. Perhaps the worst 
 case is when the soil, as is not uncommon in chalky 
 districts, is intersected by cracks or crevices which 
 extend far away underneath the surface. Into these 
 the sewage may pass unpurified, and may thus find 
 its way into wells, water-courses, etc., at a very con- 
 siderable distance, thus leading to unsuspected mis- 
 chief. 
 
 It must next be remembered that not all kinds of 
 sewage are fit and proper to be applied to cultivated 
 land. If there is a notable proportion of industrial 
 refuse, such as acids, metallic salts, dye and tan liquors, 
 etc., it will injure or even destroy the crops, and may 
 sterilize the land for a considerable time. 
 
 Another point too often overlooked is that a given 
 plot of land cannot go on for ever deodorising and 
 disinfecting an unlimited supply of putrescent or 
 putrescible organic matter. On referring to the chapter 
 on sewage it will be seen that certain of its constituents 
 
IRRIGATION. 47 
 
 gradually choke" up any porous material, as was shown 
 by an easy experiment. In addition, the soil, as in the 
 case of an old and crowded graveyard becomes ultimately 
 saturated, and would have to be left unused for a con- 
 siderable time probably many years before it could 
 again become capable of disinfecting putrescent matter. 
 Hence in selecting a plot for an irrigation farm the 
 possibility of extension, if needful, has to be taken into 
 account. 
 
 I must here point out an erroneous assumption in an 
 official document which appeared a few years ago. In 
 speaking of the various towns which have adopted the 
 irrigation process as a means of disposing of their 
 sewage, and of the sums expended and the rates per 
 pound required for paying off the first outlay and 
 defraying the working expenses, it is invariably added, 
 "the cost of acquiring the land will be paid off in so 
 and so many years, and the rate per pound will then 
 be reduced to such-and-such a figure," or words to 
 that effect. But this flattering prospect is based entirely 
 upon the assumption that a given plot of soil will go 
 on for ever absorbing and disinfecting the excretions 
 of an increasing population. This assumption is so 
 contrary to experience in all analogous cases e.g., that 
 of graveyards that until it shall have been demon- 
 strated by actual observation under the strictest test 
 conditions it cannot for a moment be entertained. 
 
 The next point is that of climate. In some countries 
 the rain fall is too small, either positively, or in relation 
 to the degree of evaporation from the surface of the 
 ground. Or, if not insufficient, it is intermittent, and 
 falls in torrents after long intervals of drought. In all 
 such climates, especially if their average yearly tern- 
 
48 SEWAGE TREATMENT. 
 
 perature, or even that during the season when vegetation 
 is active, is high, irrigation is the one thing necessary 
 to convert a desert into a garden. Instances may be 
 seen in Italy, Spain, Algeria, Syria, Persia, India, etc. 
 Hence we often find Indian officers enthusiasts in 
 irrigation. 
 
 But, on calm consideration, we shall find the climate 
 of England differing from that of the countries above 
 mentioned in almost every essential particular. Our 
 average yearly temperature is only about 49 deg. Fahr., 
 and even this small allowance of heat is made up rather 
 by the usual absence of severe frost in winter, than by 
 solar activity in summer. Our rainfall though abso- 
 lutely small as compared with that of some countries, 
 is large if we take into consideration our low tem- 
 perature, our cloudy skies, and frequent fogs, which 
 intercept the direct rays of the sun, and thus check 
 evaporation. Besides, with us, rain descends not in few 
 and violent gushes, but in a very frequent drizzle. So 
 that, in short, with us, moisture is not the one thing 
 needed for agriculture, but the great enemy of our 
 farmers. 
 
 In a document which appeared some years ago, under 
 the auspices of the Local Government Board, it was 
 admitted that sewage irrigation is not well adapted to 
 white crops and to potatoes, and that even to the ordinary 
 root crops it must be applied with caution. 
 
 The fact is that, as was brought into distinct pro- 
 minence by H. Lefeldt, a Prussian engineer sent over 
 by his government to examine and report on the 
 various systems of sewage treatment in use in England, 
 sewage can be (to a certain extent) purified by passing 
 through the soil, and it can also serve as a manure. But 
 
IRRIGATION. 49 
 
 it cannot, under ordinary conditions, combine these two 
 functions. The farmer could, even in England, often 
 use sewage to advantage if he could have it now and 
 again for a few hours in unusually dry weather. But 
 if the sewage of a town is to be purified in this manner, 
 it must flow upon the land day and night, summer and 
 winter, seed-time and harvest, in wet weather and in 
 dry. Nay, just when rain is most plentiful, and is con- 
 sequently least needed, the sewers pour out an increased 
 volume, which must be admitted upon the land. Hence 
 the interests of the farmer and of the sanitary authority 
 are in full opposition. 
 
 One plant, and, I believe, only one Italian rye-grass 
 answers the conditions of both parties. Its appetite for 
 moisture seems insatiable. Hitherto its cultivation has 
 been checked by the great practical difficulty of convert- 
 ing it into hay, portable, and capable of being reserved 
 for sale when the market was favourable. 
 
 At Whitley Manor Farm, near Reading, the rye-grass, 
 the produce of ninety-four acres of land irrigated with 
 sewage, has been successfully converted into hay by 
 means of the " Harvest Saver " of Mr. W. A. Gibbs, of 
 Gillwell Park, Essex. 
 
 This is a very decided advantage for irrigation, and, 
 where that system is otherwise practicable, may render 
 the treatment of sewage self-supporting, even if not 
 positively remunerative ! 
 
 As regards other crops, the benefits of irrigation are 
 very doubtful from an agricultural or a horticultural 
 point of view. At the celebrated irrigation farm of 
 Gennevilliers, near Paris, where, by the way, all the 
 circumstances are exceptionally favourable, the produc- 
 tion of vegetables and strawberries is very large. But 
 
50 SEWAGE TREATMENT. 
 
 there is this important drawback these crops come in 
 late in the season, when the market is already glutted, 
 and fetch in consequence the lowest prices. The object 
 of the farmer and the gardener being to bring forward 
 their produce as early as possible, sewage farming is, 
 at least in cold climates, like that of Britain, placed at 
 a disadvantage. 
 
 The question may be raised, " Why should irrigation, 
 or the application of liquid manure retard a crop ? " I 
 reply, because it lowers the temperature of the soil and 
 of the stratum of air immediately over the soil. Water 
 cannot evaporate without abstracting a portion of heat 
 from any neighbouring bodies. Irrigation, therefore, 
 chills the soil just as a wet coat chills the wearer, or a 
 damp house the inhabitants. But if irrigation is kept 
 up, day by day, the effect is the same as if the field 
 were altogether removed into a colder climate. Few 
 persons will, I think, admit that the soils of England 
 are likely to be benefited by chilling. 
 
 The next question must be, What is the influence of 
 continuous irrigation upon the texture and condition of 
 a soil ? Have we improvement or deterioration ? 
 
 The action exerted is twofold. Suppose a quantity 
 of porous soil or of potting-mould is placed in a flower- 
 pot, filled with every appliance to facilitate drainage, 
 and is then continually drenched with pure water. It 
 will soon be found that the soil loses its open, porous 
 character, and becomes compact and sodden, and any 
 ordinary plants which may have been growing therein 
 begin to show marks of declining health. In a sewage 
 irrigation field the same process, of course, takes place. 
 If, for any reason, the supply of water is interrupted, as, 
 e.g. whilst gathering in the crops, the soil bakes together 
 
IRRIGATION. 51 
 
 into a hard mass, which is afterwards not easily made 
 permeable to air and water. This result may be very 
 well shown in the flower-pot above-mentioned. If the 
 surface, after receiving for some time a superfluity of 
 water is allowed to go dry, such soil becomes most 
 intractable. 
 
 But when soil is constantly drenched, not with pure 
 water, but with sewage, the action is complicated. 
 
 As the reader may find on reference to a former 
 chapter, and as, indeed, his own common sense must tell 
 him, sewage holds in suspension finely-divided fila- 
 ments of paper, cotton, linen, etc. These are gradually 
 deposited in the interstices or tiny channels between the 
 granules of the soil, and fill them up with what may 
 be called a kind of papier machk. In fact, the upper 
 layer of such a soil is water-proofed ; the sewage in con- 
 sequence penetrates into it less and less readily, and 
 begins to stagnate upon the surface in small pools. 
 
 Sewage, further, contains no small amount of fatty 
 matter derived from soap. This also is deposited upon 
 the soil and helps to render it less easily pervious to 
 water. I have heard, on excellent authority, of an instance 
 of a plot of good, dry meadow-land, perfectly free from 
 any tendency to swampiness, which became part and 
 parcel of an irrigation farm. Everything was done 
 according to the rules of art, to promote drainage, and 
 to prevent stagnation. Nevertheless, within a few years 
 the character of the soil was so changed that it became 
 a haunt of snipe. Surely every naturalist, and every 
 sportsman must see the meaning of this fact 
 
 Industrial waste waters may become especially in- 
 jurious to the land if they contain large proportions of 
 carbo-hydrates, that is of sugary, starchy, an gummy 
 
52 SEWAGE TREATMENT. 
 
 matters ; such as the drainage of sugar-works, starch- 
 works, distilleries, breweries, and kindred establishments. 
 Such waters ferment and render the soil " sour." Before 
 irrigating with such liquids, the compounds in question 
 should be eliminated or destroyed. 
 
 A sewage irrigation farm, therefore, if the soil is not 
 to suffer deterioration, must be ample in size so that 
 each field, after being dosed with sewage for a year, may 
 be disconnected from the pipes, ploughed over, and 
 treated in the ordinary manner of farming for at least 
 the next year, or, perhaps, for the next two or more 
 years, whilst the sewage is made to flow over other 
 plots. By such alternate treatment, the land may be 
 kept from swampiness. But it must be admitted that 
 such a farm would, from its size, be very costly, both to 
 acquire and to lay out, and would compel the urban 
 authorities to become farmers on a very large scale. 
 
 I come now to the question, In how far does sewage 
 irrigation turn to good account the manunal matters ; in 
 other words, the plant-food contained in the sewage ? 
 The great objection to the old custom of running sewage 
 at haphazard into the streams and rivers, as well as 
 to Sir J. Bazalgette's modification, is the waste in- 
 volved. The available and accessible supplies of phos- 
 phoric acid, potash, and combined nitrogen in the world 
 are by no means infinite. If we go on year by year, and 
 century by century, pouring them into the sea, a time 
 must ultimately come when these essentials, if not ex- 
 hausted, must become scarce. For lack of them the 
 yield of the soil will decrease, and human food must in 
 necessary consequence grow scanty. Hence one of the 
 strongest recommendations of any system of sewage 
 treatment would be that it utilises the whole, or prac- 
 
IRR1GA TlOtf. 53 
 
 tically the whole of the plant-food present in the sewage. 
 This is the more important, since the very kinds of 
 matter which are the most precious when applied to 
 the soil, are the most dangerous and noisome if allowed 
 to find their way into the water. 
 
 Now Dr. Maercker (Zeitschrift fur Spiritus Indus- 
 trie, vi., p. 371) has recently been making some careful 
 experiments on the waste waters of starch works. These 
 waters are fully as offensive as town sewage,often, indeed, 
 more so, and contain the very same ma nu rial matters, 
 viz., combined nitrogen, potash, and phosphoric acid. 
 Hence their introduction into the rivers, without due pre- 
 vious purification, is in most countries prohibited by law. 
 One of the ways in which their purification has been 
 attempted is by irrigation, applied chiefly to grass-lands. 
 
 Dr. Maercker, it appears, found the total flow of 
 waste water from a starch works, and by analysing 
 average samples ascertained its composition. He then, 
 in like manner, analysed the grass of the meadows and 
 found its quantity. From these two sets of figures it 
 appeared that of the total plant-food conveyed to the 
 meadows only 2 per cent, of the potash, 3*2 per cent, 
 of the nitrogen, and of the phosphoric acid only 2*9 
 per cent, were retained and utilized. The residual 
 majority of these three valuable ingredients was there- 
 fore wasted ! 
 
 This case may, indeed, be considered exceptional ; 
 but even Dr. Frankland, who is certainly not likely to 
 undervalue the good effects of irrigation or to magnify 
 its shortcomings, admits that of the total combined 
 nitrogen distributed upon an irrigation field in the form 
 of sewage, from one-third to one-half may make its 
 escape in the effluent water, and be lost in the rivers. 
 
54 SEWAGE TREATMENT. 
 
 But there is a further consideration : Is manuria* 
 matter, when dissolved in a large quantity of water, as 
 is the case with sewage, presented to plants in a favour- 
 able form ? I have already shown that irrigation, by 
 lowering the temperature of the soil, delays the maturity 
 of crops. But we may go further. Mr. E. Manson, 
 C.E., in a work entitled Sewage no Value ; the Sewage 
 Difficulty Exploded (E. and F. R. Spon), makes the fol- 
 lowing admission : " Sewage, like water, retards the 
 ripening of the fruit and grain, and develops the leaf. 
 Sewage cannot supersede manure, for it cakes the 
 ground, seals up its pores, and prevents the air from 
 getting at the roots of the crops. It has been found at 
 all times, and in all climates, that irrigation develops 
 the growth of the leaves at the expense of the fruit or 
 grain." These statements, which are fully in harmony 
 with my own experience, are of the greater weight as 
 coming from one who apparently favours sewage irriga- 
 tion, and is no friend of chemical treatment. 
 
 Entering now upon the sanitary phase of the subject, 
 we have to ask, Does irrigation render sewage, or 
 water contaminated with sewage, sufficiently pure to be 
 introduced without danger into any ordinary river? 
 Does it, in effecting purification, give rise to any 
 nuisance or injury to persons living near the irrigation 
 plots ? Are the vegetables grown on such irrigation 
 plots fit for human consumption and for the food of 
 animals whose flesh or milk may form a part of our 
 diet? 
 
 To the first question an answer cannot be given in a 
 couple of words. It may be at once granted that, pro- 
 viding always that an irrigation field is properly laid out, 
 that the soil and subsoil are suitable, and have not be- 
 
IRRIGATION. 55 
 
 come choked by too prolonged and continuous use, and 
 that the sewage is not swept away into the drains and 
 the streams by floods, the effluent water will, on analysis, 
 show but a very small proportion of organic putrescible 
 matter. In colour, transparency, and odour, it will pro- 
 bably not remind the spectator at all of sewage. 
 
 But it is now contended, on very good grounds, that 
 the chief danger of the introduction of sewage into 
 streams, wells, etc., lies not in dead organic matter, but 
 in living organised matter. In other words, what we 
 have to keep out of our drinking waters is not so much 
 the decomposing residues of plants and animals and 
 the excretions and secretions of the latter, as those 
 minute living beings known scientifically as bacteria, 
 bacilli, micrococci, etc., and called popularly " disease 
 germs," from the fact that certain of them at least, when 
 introduced into the body of a living animal, have the 
 power of setting up morbid changes which may prove 
 fatal. 
 
 We have, therefore, to ask whether irrigation or any 
 kind of filtration can be depended upon to remove these 
 disease germs ? The answer must be in the negative. 
 Dr. Percy Frankland, though a friend by right of here- 
 dity of sewage irrigation, made the following honest 
 admission in a paper read before the Society of Arts 
 on March I3th, 1884: "There is absolutely no evidence 
 that morbific matter, if present, would be removed," 
 either by irrigation, or by " downward intermittent filtra- 
 tion," of which in a subsequent chapter. " On the con- 
 trary," he proceeded, " there is very strong reason to 
 believe that these processes of purification offer no sort of 
 guarantee that noxious organised matters present in the 
 
 wage may not pass through into the effluent. For the 
 
56 SEWAGE TREATMENT. 
 
 removal of organic matter by means either of irrigation or 
 intermittent filtration depends upon the oxidising action 
 which a porous soil exerts upon such matter, and it is 
 quite analogous to the purification of water percolating 
 through a few feet of soil into shallow wells. Now, the 
 instances on record of the percolation of sewage into 
 shallow wells becoming the means of infection are so 
 numerous and so well authenticated, that it is unneces- 
 sary for me to refer to them here At Stuttgart, in 
 
 Germany, and Winterthur, in Switzerland, some years 
 ago, epidemics of typhoid fever were proved most con- 
 clusively to have been caused by the contamination of 
 the water supply with the effluent from irrigation 
 meadows," 
 
 At the same meeting, Dr. Jabez Hogg, F.R.M.S., the 
 distinguished microscopist, cited the well-known case of 
 a stream in Switzerland which soaked through an entire 
 mountain of oolitic rocks, yet, on emerging into another 
 valley, was found to have brought with it the infection 
 of typhoid fever. 
 
 I have seen flocks of sewage fungus (Beggiatoa alba) 
 in the effluent from a large, well-managed irrigation 
 farm on a deep soil. The spores of this fungus must, 
 therefore, have traversed the soil. 
 
 In passing, I may here mention that this fungus is 
 not, as many persons suppose, a certain indication of the 
 presence of organic pollution. It flourishes where and 
 only where sulphur is present. It is found in streams, 
 into which fall sulphuretted mineral waters, as in the 
 Pyrenees ; it has been observed in the drainage from 
 heaps of " tank-waste," the residue of the Leblanc 
 alkali process, as well as in sewage, and sewage-polluted 
 waters. Nor is its presence in sewage at all universal 
 
IRRIGATION. 57 
 
 or apparently connected with the degree of pollution. 
 It is sometimes abundant in the sewage of a town in one 
 season, but in the next it may be almost or altogether 
 absent, though no change can be traced in the character 
 of the sewage. Instances of this have been noted in 
 the sewage of Aylesbury as it arrives at the Sewage 
 Works. Hence the presence, the quantity, or the absence 
 of sewage fungus cannot, as it is popularly supposed, 
 be taken as an index of the greater or less degree of 
 impurity of the water. 
 
 Returning from this digression, we must conclude that 
 if the living microscopic organisms in sewage are its 
 most dangerous feature, and if irrigation is unable to 
 remove such organisms, then the effluent from irrigation 
 fields cannot safely be allowed to escape into wells or 
 streams which supply water for human consumption. It 
 seems not improbable that the chief mischief of excre- 
 mentitious matters, etc., in water, is that they give scope 
 for the multiplication of the " disease germs " in ques- 
 tion. 
 
 It has next to be asked : Does irrigation effect its 
 object without occasioning annoyance or injury to the 
 inhabitants of the district ? 
 
 I have never happened to visit or to pass near an 
 irrigation field in warm, still weather without detecting 
 an unpleasant smell. At Gennevilliers, near Paris, the 
 odour, on calm, autumnal evenings may, without exag- 
 geration, be described as abominable. The Prussian 
 Commissioner, Lefeldt, when visiting Romford, found 
 the smells emitted to be " mephitic in the most fearful 
 sense of the word." Now, if I am right in my concep- 
 tion of what constitutes a nuisance, a loathsome odour, 
 even though no definite disease can be traced in those 
 
58 SEWAGE TREATMENT. 
 
 who inhale it, is something against which the surround- 
 ing population has the clearest right to protest. 
 
 As regards the production of actual disease in the 
 neighbourhood, diarrhoea, dysentry, typhoid fever, etc., 
 the evidence is somewhat conflicting. In England, 
 enthusiastic irrigationists maintain that e.g., at Croydon 
 no increase of disease or of mortality in districts 
 bordering on an irrigation farm has been observed. 
 But against such negative instances (which somewhat 
 remind us of the thief who brought witnesses to swear 
 that they had never seen him steal a horse) there is to 
 be placed direct, positive evidence. 
 
 It is well-known that in India irrigation with ordinary 
 river-water is needful in dry seasons ; it is therefore 
 practised on a very large scale. But, according to Mark- 
 ham, it has been found that the health of the irrigated 
 districts is deteriorated, so that a committee appointed 
 to re-consider the question proposed that a double belt 
 of trees should be interposed between the irrigated fields 
 and any adjacent villages. 
 
 Now, if irrigation is thus recognized as anti-sanitary 
 in India, where ordinary river-water is employed, and 
 where the fields are flooded or moistened only in time 
 of drought, may we not expect at least as great injury 
 from sewage irrigation in England, where the water 
 applied is seriously polluted, containing sometimes 
 disease germs, and where the fields are to be drenched 
 from January to December? 
 
 It has been all along contended by sanitary authorities 
 that a river polluted with sewage is productive of ill- 
 health, not merely to persons who drink of it, but to 
 those who inhale air which has swept over it. Be it so : 
 I then ask why a plot of sewage-irrigated land, exposing 
 
I R RIG A TION. 59 
 
 as great as, or perhaps a greater surface than does the 
 river in any one part, and giving evil odours, distinctly 
 recognisable, should not be equally noisome ? However 
 rapidly the sewage may sink into the earth, a certain 
 portion must escape by evaporation, and must rise into 
 the air before it has had the opportunity to be disin- 
 fected. 
 
 To meet this difficulty, a clever hypothesis has been 
 devised, the only flaw in which is that it lacks founda- 
 tion. We are told that so long as a sheet of water or a 
 stream, however full of disease germs, remains quiet, 
 these germs will not rise up into the atmosphere. But 
 if, as is usually the case in foul ponds or streams, fer- 
 mentation is going on and bubbles of gas are rising to 
 the surface and bursting, these microscopic organisms are 
 flung upwards into the air and are carried away by the 
 wind. But from the surface of a plot of land, wet with 
 sewage, such bubbles do not arise, and consequently the 
 disease germs present do not escape into the air ! 
 
 In reply to this supposition, I must remind the reader 
 that if we pour any liquid upon a portion of earth 
 somewhat dry for instance, the soil in a flower-pot 
 we see bubbles arise and force their way through the 
 film of liquid, until all the air existing in the interstices 
 or pores of the soil is completely expelled. These 
 bubbles must, of course, on bursting, project any germs 
 present into the air, just as do the bubbles bursting on 
 the surface of a polluted river. 
 
 But the assertion that germs are not thrown off from 
 the surface of still water without the action of bubbles 
 is denied on the faith of direct experiment. 
 
 Portions of liquid containing organisms of known 
 kinds, and not undergoing any fermentation, have been 
 
60 SEWAGE TREATMENT. 
 
 placed in dishes under glass bells. On standing over- 
 night, organisms of the same kind as those present in 
 the liquids have been found in plenty upon glass plates 
 suspended over the dishes, but under the bells. Hence, 
 in accordance with our present state of knowledge, the 
 action of a polluted river, and of a plot of land, frequently 
 or constantly moistened with sewage, must be very 
 similar substantially alike. 
 
 I must now invite the reader to make a very easy 
 experiment. If he has a garden, let him select a plot 
 of ground, say a square yard, free from vegetation, 
 and, if possible, of a fairly open texture. Let him then 
 pour over this plot a quart of sewage, or, in default 
 of that liquid, a similar quantity of the mixture of 
 urine and soap-water from the chambermaid's slop- 
 pail. Let him then watch the result. If the weather 
 is at all genial a number of two-winged flies (dipterd) 
 of different species will soon settle upon the wet earth, 
 and may be seen sucking up the moisture. As the first 
 comers fly away they will be succeeded by others, and 
 for some hours the damp plot will be a source of 
 attraction to these unclean insects. A similar plot of 
 ground, moistened with clear water by way of a 
 counter-check, will, on the contrary, have very few 
 visitants. This experiment proves that, its admitted 
 deodorising' and disinfecting powers notwithstanding, 
 earth does not immediately absorb and destroy the 
 offensive matters of sewage. Secondly, we learn that 
 soil thus moistened, and, a fortiori, any sewage irrigation 
 field, is an attraction and an encouragement to flies. 
 Let us take the case of a farm receiving the sewage 
 of a town. All the summer long it will be haunted 
 by numbers of blow-flies, dung-flies, house-flies, gnats, 
 
IRRIGATION. 6 1 
 
 blood-suckers (Stomoxys calcitrans\ and many others. 
 All these will become saturated with the putrescent 
 matter. If the sewage contains, as it conceivably may, 
 the excretions of a cholera or a typhoid patient, the 
 flies imbibe the " germs " of such diseases. 
 
 Some of the insects will then enter our houses, and 
 crawl over articles of food. Others settle upon our 
 persons and inflict malignant wounds. Fatal illness 
 has not unfrequently been traced to the bite of flies 
 which feed on sewage or carrion. These flies being 
 now recognised as among the greatest agents for 
 carrying putrid poisons and disease germs to the 
 healthy, it is important that all places where they can 
 increase and multiply, and all matters upon which 
 they may feed, should be made offensive to them or 
 destroyed, as the case may admit. Thus, we bury the 
 dead bodies of birds, beasts, and fishes, which are 
 either uneatable or which have perished from disease, 
 as well as all putrid and putrescible solid matter. We 
 do not, if we are prudent, allow blood especially the 
 blood of animals slaughtered by way of stamping out 
 the cattle-plague to stagnate or to soak into the earth. 
 To collections of excrementitious matters, such as the 
 contents of cess-pools, we add such disinfectants as 
 may make them unfit for the habitation of maggots. 
 We do not throw the dejecta of cholera patients, etc., 
 into the gardens and the fields, but treat them with 
 corrosive sublimate. Thus, in all cases where we have 
 to deal with offensive animal matter, especially such as 
 has been the seat of virulent disease, we withdraw it 
 from the reach of dipterous insects by fire, by chemical 
 agents, or by burial. But if we practice sewage 
 irrigation we spread out excrementitious matter, 
 
62 SEWAGE TREATMENT. 
 
 possibly containing disease germs, over a large extent 
 of surface, and thus throw it fully open to unclean 
 insects. 
 
 Lest anyone should think that the views above given 
 are exaggerated, we may refer to a recent communi- 
 cation by Dr. Maddox, in a late number of the Journal 
 of the Royal Microscopical Society. This gentleman has 
 proved that the "comma bacillus," now known to be 
 the agent producing cholera, " can pass in a living state 
 through the digestive organs of flies, which may in this 
 manner become carriers of contagion." Dr, Grassi, of 
 Rovellarca, studied this question two years ago. His 
 experiments point to the conclusion that flies may be 
 regarded as veritable promoters of epidemics, and 
 agents in the propagation of other infectious maladies. 
 To prove this, he placed upon a plate in his laboratory 
 some ova of the Trichocephalus, and in a short time 
 these were removed by the flies, and deposited in 
 another place some little distance away. He caught 
 some of the flies, and found that their digestive tubes 
 were full of feculent matter, and of the ova. He also 
 put segments of the tape-worm (Taenia solium) into 
 water. Some of their eggs remained suspended in the 
 water ; the flies drank of the fluid, and in less than an 
 hour he found the eggs of the tape-worm in their 
 intestines, and in their excrements. Flies, he further 
 found, will also transmit the eggs of the small thread- 
 worm Oxyuris, 
 
 He likewise fed flies on mildewed cream, and after- 
 wards found within them, Oidium lactis. Other flies 
 fed on the "muscardine" of the silkworm voided 
 spores of that pest in their excretions still capable of 
 development. 
 
IK RIGA TION. 63 
 
 Hence Grassi inferred that these organisms are 
 not destroyed when swallowed by insects, since the 
 germs of mildews and of Schizomycetes pass through 
 their bodies uninjured. Flies are also certain to carry 
 about with them living organisms on their feet and 
 trunk. 
 
 M. Daraine shows that by feeding flies with infected 
 blood they can be made to convey infection. 
 
 Dr. Manson has likewise shown that mosquitoes are 
 carriers of the germs of Filaria sanguinis kominis, and 
 that it is quite possible for the dreaded " Tsetse fly " 
 of Central Africa to transmit infections to the animals 
 which it attacks. 
 
 After many and varied experiments, Dr. Maddox 
 found that the cholera-bacillus can pass through the 
 intestines of a fly in a living state. 
 
 Hence, surely anything which encourages flies and 
 supplies them with putrid and frequently diseased nutri- 
 ment ought to be carefully avoided. 
 
 We now come to the third and last question concern- 
 ing the sanitary value of sewage irrigation : Are the 
 vegetables grown on sewage farms fit for human con- 
 sumption or for the food of cattle ? 
 
 On this subject very conflicting opinions prevail. I 
 must remark that the question probably turns on a 
 point commonly left quite out of consideration. We 
 know that from time immemorial night-soil, the material 
 from cess-pools, including all the constituents to be 
 found in the sewage of a residential town, has been 
 applied to gardens without the production of any 
 known evil effects. At least, if mischief has arisen it 
 has not been recognised. But such night-soil, as far as 
 I am aware, was either dug into the earth some time 
 
64 SEWAGE TREATMENT 
 
 before the intended crop was planted or else was 
 trenched in between the rows, say, of potatoes, apple- 
 trees, gooseberry-bushes, etc. It was never applied in 
 a fresh state to strawberries, celery, salad-herbs, and 
 the like. Thus the faecal matter never came in im- 
 mediate contact with the roots of plants, nor was the 
 application repeated in the same season. In farming, 
 night-soil was, and doubtless still is, applied to stubble- 
 fields, to be ploughed in, and scattered over pastures 
 and meadows in the late autumn. But I have observed 
 that cattle turned into such pastures next spring would 
 avoid those parts where the night-soil had been applied, 
 and keep, in preference, to any part which had been 
 dressed with farm-yard manure. Now, as regards 
 sewage irrigation all the circumstances of the case are 
 altered. Excrementitious matters suspended or dis- 
 solved in water are passed into the fields not merely 
 during the absence of crops or between the rows of 
 plants, but, practically speaking, throughout the season 
 and in all parts of the land. Suspended excrement, 
 healthy or diseased, as the case may be, comes in direct 
 and constantly renewed contact with the roots and the 
 stems of grasses and other plants, and no matter how 
 close upon perfection the drainage of the field may have 
 been carried, there it will adhere. Of this any 
 candid person may convince himself by observation in 
 such fields, or even by direct experiment. Let him, for 
 instance, fit up a funnel loosely with a grass root and 
 pour sewage upon it. However well the filter acts, he 
 will soon find . the stems and the roots coated with an 
 adhesive matter, concerning the nature of which no 
 doubt can be entertained. 
 
 If, then, such grass is cut from time to time, without 
 
IRRIGATION. 65 
 
 any intermission of irrigation, and is given to cows, the 
 faecal matters in question are conveyed into the stomachs 
 of these animals, and their tissues and their secretions 
 may become poisoned. That disease germs may pass 
 into milk and thus reach fresh victims is an established 
 fact. 
 
 But we have to do not merely with sewage matters 
 clinging to the outer surfaces of plants. The impurities 
 penetrate also into the interior. Herr Lefeldt, to whom 
 I have already referred, in his report on the various 
 systems of sewage treatment as pursued in this country, 
 notices stems of grass from irrigation meadows, full of 
 unassimilated sewage matters (Kloaken-Stoffe). Were 
 the irrigation suspended for a sufficient time these matters 
 would doubtless be assimilated by the plants, which would 
 then be perfectly harmless. But if the sewage flows on 
 day by day, fresh excrementitious matter is absorbed as 
 fast as perhaps faster than the former doses can be 
 assimilated. Surely such grasses or other plants placed 
 in similar conditions must be of very doubtful value as 
 food, whether for man or beast. 
 
 I now come to the experiments carried out by Mr. 
 Smee, Jun., and published by him in a work entitled, 
 " Milk in Health and Disease." These experiments and 
 their results have been met, I am compelled to say, 
 with something very like the "conspiracy of silence." 
 Certainly, so far as I can learn, no attempt has been 
 made to prove them inaccurate, or to refute the author's 
 conclusions. Two cows were set aside for experiment. 
 The one, which we may call A, was fed on sewage 
 irrigation grass, and the other, B, on grass from an 
 ordinary meadow. The milk obtained from each cow 
 was kept separate, and examined. It was found that 
 
66 SEWAGE TREATMENT. 
 
 the milk of A became not merely sour, but it putrefied 
 and stank much sooner than that of B. It was noticed 
 that a favourite cat, exceedingly dainty in its tastes* 
 entirely refused to lap the milk of A. The butter from 
 A's milk became rapidly rancid as compared with butter 
 obtained from cows fed on ordinary pasturage. Cream 
 from the milk of A required, in three successive lots, \\ 
 hour, i^ hour, and 2\ hours to churn, and the butter was 
 soft and smeary. Check samples of cream from cows 
 fed on normal food required only thirty-five minutes, i^ 
 hour, and f hour to churn, and the butter was firm. 
 
 So far, of course, this experiment is open to the 
 objection that the bad quality of the milk and butter 
 from A was due to some morbid condition in herself, 
 rather than in her food. To meet this doubt, Mr. Smee 
 reversed the experiment, feeding B on sewage grass and 
 A on normal herbage. He also tried other cows. Still 
 the results reached were practically the same, the milk 
 from every cow fed on sewage grass was notably more 
 prone to putrescence than that from cows fed on common 
 meadow grass. 
 
 Mr. Smee made further experiments on the grass 
 itself. He found that the juice of sewage grass became 
 more quickly and more offensively putrid than that of 
 common grass. Hay made from sewage-grass, if kept 
 in a vessel of water in a warm place, quickly set up a 
 putrid fermentation, whilst hay from ordinary grass, 
 treated in the same manner, behaved quite differently. 
 
 It will, of course, be granted that the application of 
 sewage to fruits and vegetables which are ordinarily 
 eaten raw, such as celery, lettuce, watercress, radishes, 
 strawberries, etc., requires the greatest degree of caution. 
 In connection with this subject it should be remembered 
 
IRRIGA TION. 67 
 
 that when it not long ago seemed probable that the 
 cholera might visit Paris, the inhabitants were formally 
 warned by the sanitary authorities against consuming 
 vegetables from the sewage irrigation farm at Genne- 
 villiers ! 
 
 I should suggest that where sewage irrigation is 
 practiced, it should be suspended for the very least a 
 fortnight before the crop is reaped or gathered. Thus, 
 in case of strawberries, it might be well to shut off the 
 sewage from the appearance of the blossoms until the 
 plants have ceased fruiting. 
 
 I cannot help expressing my regret that the warm 
 friends of irrigation should have shown so little dis- 
 position to investigate this part of the question more 
 closely. Have they a secret misgiving that the truth, if 
 ascertained, may be of an unpleasant character ? 
 
 In conclusion, I would submit that irrigation, though 
 an excellent method of disposing of, and at the same 
 time utilising, sewage, where suitable land is available, 
 where the climate is warm, and the rainfall scanty or 
 intermittent, is not applicable where these conditions 
 are absent. Any attempt to represent it as the only 
 means of dealing with the sewage difficulty, and to force 
 it upon reluctant communities, is a grave error in fact 
 a crime, the motives for which are in most cases hard 
 to trace. 
 
68 SEWAGE TREATMENT. 
 
 CHAPTER VII. 
 MODIFICATIONS OF IRRIGATION. 
 
 IN the last chapter I have understood irrigation as 
 consisting in the direct application to the land of 
 sewage as it flows from the town without any previous 
 preparation. There are, however, modified processes, 
 some of which obviate more or less completely certain 
 of the inconveniences attending upon irrigation " pure 
 and simple." 
 
 One of these is the introduction of settling-pits, into 
 which the sewage first flows and collects before being 
 passed upon the land. These pits serve, in the first 
 place, to average the sewage. It has been already 
 shown that the sewage of any town varies considerably 
 both in strength and general characters at different 
 parts of the day and night. By averaging the whole, 
 its treatment, on what system soever, is made more 
 convenient. 
 
 But the settling-pits have a more important task 
 to perform. I have already mentioned, in passing, as 
 among the ingredients of sewage, grit and silt derived 
 from the streets and roads, and I have pronounced this 
 silt as a formidable difficulty in any and every method 
 of sewage treatment. It is, of course, most abundant 
 after heavy rain, but it is also much affected by the 
 character of the streets. If these are asphalted, paved 
 
MOD I PICA TIONS OF I R RIG A TION. 69 
 
 with wood, or even with stone, the quantity of such 
 silt is relatively trifling. But where the abomination 
 devised by Macadam prevails, as in all parts of London 
 except the City, its quantity is something frightful. 
 
 Sewage, if allowed to stand even for a few hours in 
 a settling-pit deposits the greater part of this grit. But 
 unfortunately, each grain, by sojourning in the sewer 
 in company with noisome matter, acquires an organic 
 coating of most offensive odour. Hence such settlings 
 cannot be used in mending roads, in making mortar, 
 or in filling up hollows in the ground. The only 
 legitimate use to which they can be put is the improve- 
 ment of heavy clay soils, and if such are not close at 
 hand their disposal is not easy. On the other hand, 
 if sewage is allowed to flow upon the land without 
 having first deposited its silt and grit, the channels are 
 being continually choked up, and the entire level of the 
 ground will be gradually raised. In filtration and pre- 
 cipitation processes the silt is equally an inconvenience. 
 
 Hence there is a strong temptation to use settling- 
 pits, even when the disposal of their contents is difficult. 
 Their odour is not pleasant, and has, indeed, been 
 described by a foreign authority as being " mephitic, 
 in the most fearful meaning of the term." Still, this 
 difficulty may be got over by the use of some suitable 
 disinfectant. 
 
 Another modification of the sewage irrigation process 
 is the introduction of some such disinfectant prior to 
 its being allowed to flow over or through the land. 
 This plan has been adopted at Carlisle, the material 
 used being a combination of carbolic and sulphurous 
 acids. By this expedient certain of the objections to 
 crude irrigation are got rid of. Thus the disagreeable 
 
70 SEWAGE TREATMENT. 
 
 smell often given off by irrigated land is done away 
 with ; the plague of flies is greatly reduced ; and cattle 
 eat the grass with a better relish. Whether the dairy 
 produce obtained from cows fed on such disinfected 
 sewage grass is equal to that of cows pastured on 
 ordinary grass has not, so far as I can learn, been 
 experimentally tested. 
 
 It is remarkable that attempts in the disinfection, or 
 at least de-odorizing, of sewage prior to use on land 
 have not been more numerous and more varied. It 
 must be remembered that the choice of disinfectants 
 for this purpose is limited. Some are too costly, some 
 poisonous. The use of carbolic acid is not quite free 
 from objections, as fish in rivers into which it is 
 introduced seem to be rendered more liable to parasitic 
 diseases. Experiments on this subject are needed. I 
 should gladly have undertaken this inquiry, but I have 
 been advised that it would be legally unsafe in England 
 without a licence under the " Vivisection Act " ! 
 
 Irrigation has been occasionally tried as a supplement 
 to some of the precipitation processes to be discussed in 
 a succeeding chapter. Such a combined method is, or 
 was recently, in operation at Coventry. The notion 
 which underlies such schemes is that of a smaller outlay 
 for chemicals and plant than would be required for a 
 thorough precipitation process ; and, on the other hand, 
 that a smaller plot of land would suffice to receive the 
 sewage. Whether there is any real economy in this 
 double working is, however, at least open to question. 
 Just in proportion as a sewage is purified by precipitation, 
 its manurial value for irrigation will decrease down to 
 that of plain water. A certain chemist, now no longer 
 living, did, indeed, once try to argue that the effluent 
 
MODIFICA TIONS OF IRRIGA TION. 71 
 
 from a precipitation process which he had pronounced 
 well purified was yet better suited and more valuable for 
 irrigation than the original sewage. This attempt at 
 running with the hare and holding with the hounds met 
 with little approval. 
 
 Sewage freed by some precipitation process from its 
 suspended impurities will, however, have the advantage 
 of not choking up the pores of the land, and thus 
 rendering it liable to become water-logged and ultimately 
 swampy. 
 
72 SEWAGE TREATMENT. 
 
 CHAPTER VIII. 
 FILTRATION. 
 
 FILTRATION differs in principle but little from irrigation. 
 During the winter an irrigation field is, in fact, merely an 
 extensive earth-filter. In summer, the difference is 
 greater, as in the irrigation field the growing plants take 
 a certain share in the work, and absorb a part of the 
 impurities existing in the sewage. 
 
 The duties of a filter are firstly, to remove me- 
 chanically all matters, organic or inorganic, suspended 
 in the sewage. This work is often known as " clarification.'' 
 Secondly, the water, in descending into the pores of the 
 filter bed, draws along with it a certain quantity of 
 atmospheric air, which oxidises, or, in plain language, 
 burns up the animal or vegetable matter present, 
 converting it into substances which are no longer 
 injurious to health. Thirdly, the process of filtration 
 decomposes a number of organic compounds quite 
 irrespective of any oxidation. Lastly, it is supposed, or 
 at least hoped, to withdraw from the liquid to be filtered 
 any disease germs which may be present. These tasks 
 are performed in very varying degrees, according to the 
 kind of material used, to the time the filter has been kept 
 in action, and to the rate at which it is intended to work. 
 
 Whatever be the material chosen, there are two 
 different kinds of filtration : downwards and upwards ; or 
 
FILTRATION. 73 
 
 as they are also named, descending and ascending. In 
 downward filtration, which is by far the most common, 
 the liquid to be purified flows upon the surface of the 
 filter bed, passes down through its mass, and is delivered 
 at the bottom. In upward filtration, which is practicable 
 only under peculiar circumstances, the liquid is forced up 
 through the filter bed, and flows out at the top. Down- 
 ward filtration is not only the simplest and oldest kind of 
 filtration, but it is generally the most efficient. In it only 
 is the liquid purified in the second method above- 
 mentioned, that is, by means of atmospheric air drawn 
 down along with it into the pores of the filter. But to 
 this end it is necessary that there should not be any 
 considerable depth of water standing above the level of 
 the filter bed, as otherwise the aeration cannot fully take 
 place. The upper surface should be kept only just wet, 
 a layer of a quarter inch in depth being quite enough. 
 
 The manner in which the filter is made up is very 
 important ; if the bed is too thin and irregularly thrown 
 together, the water is apt to force its way through in 
 some few places, and thus to escape unfiltered. In 
 building up the filter, the coarsest materials are spread out 
 at the bottom ; over these are placed, regularly and evenly, 
 layers of finer and finer materials, the finest being near 
 the top. But lest the inrush of the water should disturb 
 this fine upper layer, a few large, flattish stones, pieces of 
 slate, or large lumps of coke are laid on the top of all in 
 order to receive the stream at its entrance, and distribute 
 it in thin layers over the surface. It is further desirable 
 that the liquid to be filtered should enter in a shallow sheet 
 over a wide lip. Roughly speaking, for a filter of given 
 size and material, the less rapidly the liquid passes 
 through it, the more thoroughly will- it be purified. 
 
74 SEWAGE TREATMENT. 
 
 The chief materials used for forming filter beds are 
 gravel, sand, moor-earth, burnt clay, pumice, coke, animal 
 charcoal, wood charcoal, peat (raw or carbonized), seaweed 
 charcoal, spent oil shales, Kimmeridge carbon as obtained 
 from the so-called Kimmeridge blackstone, lignite, spent 
 dye woods and sawdust, especially if slightly carbonised 
 by fire or by the application of acids ; shavings, rushes, 
 faggots, straw, and other hard vegetable matters exposing 
 considerable surface. Further, I must mention spongy 
 iron, magnetic iron ore, black oxide of manganese, scrap 
 iron, and cylinders of unglazed porcelain. These materials 
 are used sometimes alone, sometimes in combinations, 
 which may be varied almost indefinitely. 
 
 It will be easily seen that for the treatment of sewage 
 many of these materials are out of the question. As it 
 has been already pointed out, the filtration of sewage is 
 far more difficult than that of spring, river, or lake 
 waters for domestic or manufacturing purposes. I lately 
 found that half a litre (about i;i fluid ounces) of the 
 effluent from a certain sewage works took exactly two 
 hours in passing through a 5 -inch paper filter. The same 
 measure of the untreated sewage from the same works 
 took exactly seventy-two hours to pass through a filter of 
 the same size and quality. This simple experiment shows 
 the relative difficulty of filtering sewage. The large 
 quantity of paper pulp and of the fibres from textile 
 goods always present in sewage, even such as appears 
 almost transparent, quickly clogs up the filter beds. The 
 fatty matter derived from soap and from culinary 
 operations combines with these fibrous matters in as it 
 might be called waterproofing the filter, forming an 
 impervious, water-repelling layer not only over the 
 surface, but even within the interstices of the mass. This 
 
FILTRATION. 75 
 
 choking and clogging process is quite independent of the 
 nature of the materials used, or rather, we may say, that 
 the better the filter was originally, the more thoroughly 
 and quickly it will become choked ; whilst one which 
 allowed the water to run through rapidly will remain in 
 full activity much longer. Hence filters for sewage must 
 be relatively larger than those for river water, etc., and 
 they will require more frequently cleaning or changing. 
 Cleaning a filter bed when it has become dirty is in many 
 cases a most troublesome operation, as the faecal matters 
 which adhere to the sand, coke, etc., will have become 
 very offensively putrid. It is commonly said : take out 
 the soiled and clogged materials, and spread them out to 
 the air. But for this the necessary room is not always to 
 be had, and the smell of the mass thus exposed is liable 
 to raise objections. If we wash the soiled matter, where 
 are we to turn the washings ? If into the river, we occa- 
 sion a pollution nearly as great as if we had all along 
 allowed the sewage to flow in unfiltered ; if we turn it 
 back into the sewage, we have the work to do over again 
 under greater difficulties than at first. Purification by 
 fire is with some materials impossible, and in most cases 
 it requires special kilns or furnaces. 
 
 A change of filters, to be used alternately, is recom- 
 mended where the room is sufficient. When one filter 
 shows signs of clogging, or allows the sewage to pass 
 through in a foul condition, it is shut off, and the liquid 
 is turned into the other. 
 
 Sand and gravel, however deep in mass, and however 
 well spread, do little more than remove the suspended, 
 or, I might say, the coarser suspended impurities. But 
 they are relatively cheap, procurable almost everywhere, 
 and when foul they may be easily dealt with. The sand 
 
76 SEWAGE TREATMENT. 
 
 may serve to improve clay soils, whilst gravel, after due 
 airing, can be used for mending field paths ; but never 
 for filling up hollows upon which houses may subse- 
 quently be built. 
 
 Moor-earth a mixture of sand and peat where pro- 
 curable, acts better than sand or gravel. When spent, 
 it may be used for farming and gardening purposes. 
 Burnt clay ranks about with gravel. Pumice is toler- 
 ably efficient, but it is too expensive. Animal charcoal, 
 otherwise known as bone-black and as spodium, is also 
 far too costly. This is the less to be regretted since, 
 whilst it purifies polluted waters well at first, it after- 
 wards becomes charged with offensive matter in such a 
 manner that it contaminates water instead of improv- 
 ing. Wood charcoal, if thoroughly burnt, so as to be 
 quite free from oily and tarry matters, acts fairly well 
 in combination with sand, etc. Peat was applied to the 
 filtration of town sewage by the Peat Engineering 
 Company, Limited. It acts well for a time, but when 
 clogged it is difficult to deal with. Peat-charcoal is a 
 promising material, as seaweed charcoal would be also, 
 could it be procured at a lower figure. Mr. S. K. Page, 
 manager of the Aylesbury Sewage Works, has made a 
 series of careful experiments upon the Kimmeridge 
 carbon. Here the results were at first all that could be 
 desired, but the bed soon choked up, and the first cost 
 of the material would not permit it to be frequently 
 exchanged. Unglazed porcelain filters, as proposed by 
 Pasteur and Chambeland, may be considered perfect, as 
 they remove even microscopic organisms. But for 
 dealing with the sewage of a town they are utterly out 
 of the question. 
 
 Spongy iron bears deservedly a very high character, 
 
FILTRATION. 77 
 
 and is even said by some authorities to remove bacteria, 
 though this is denied by Mr. Jabez Hogg, M.R.C.S., 
 F.R.M.S., one of our most competent microscopists, and, 
 in this special department, perhaps the most eminent. 
 Be this as it may, spongy iron, like all metallic sub- 
 stances, is inapplicable to the sewage of manufacturing 
 towns, as it would be acted upon and injured by the 
 acids and acid salts rarely absent. It would also, like 
 manganese, soon become mixed with the silt and grit 
 brought down by the current. To separate this refuse 
 matter when the filter-beds require cleaning would be no 
 easy matter without wasting a considerable proportion 
 of the active material. 
 
 There are two methods, or processes, of filtration 
 which have been especially recommended for dealing 
 with sewage. One is that of Professor Henry Robinson, 
 first made public at the Dublin meeting of the Sanitary 
 Institute, and reported in the Sanitary Record fo r 
 October, 1884. This gentleman an engineer, if I 
 mistake not proposes to adapt clay lands for a some- 
 thing midway between filtration and irrigation by 
 digging ou t the soil to the depth of six feet, burning ib 
 and arranging it in layers interspersed with a stratum of 
 open, alluvial soil, of course unburnt. Such a bed, six 
 feet in depth, will, we are told, continuously clarify it 
 is not said purify the sewage of 1,500 persons per acre. 
 The cost of preparation however, reaches, according to 
 Mr. Robinson's own estimate, the modest sum of ,750 
 to ,1,000 per acre. Every one knows that such 
 estimates fall far short of the actual cost of these 
 schemeswhen reduced to practice. An observant friendtells 
 me that every 1,000 in an estimate means in reality 
 about ^2,500. But let us accept the estimate, and take 
 
78 SEWAGE TREATMENT. 
 
 a town with a population of 300,000 persons say, Leeds. 
 At 1,500 persons per acre we should require 200 acres 
 of land, to be prepared at a first cost of .200,000 ! 
 Or, for London, 2,666 acres, costing .2,666,000. I do 
 not find whether in this estimate is included the pur- 
 chase of the land, which anywhere within a moderate 
 distance from a large town must be a heavy item. But 
 this is not all ; Professor Robinson is of opinion that 
 before running the sewage upon this bed the coarser 
 suspended impurities should first be removed by a 
 process of ascending filtration, of course through a 
 separate set of beds, the materials of which, when 
 sufficiently polluted, are to be taken away, and " dug 
 into low-lying land," whilst fresh ascending filters must 
 be brought into action. These ascending filters and the 
 land for digging in the coarser sewage matters will 
 occupy a considerable space ! Even if we are bold 
 enough to assume that the acres stated will go on for 
 ever purifying the flow of sewage, we must admit that 
 the yearly working of this most singular scheme will 
 be no trifle. Nor must it be forgotten that the plots of 
 land thus prepared will be thereby converted into 
 deserts, which neither art nor nature will henceforth be 
 able to reclaim. 
 
 We come now to the process, designated officially as 
 "intermittent downward filtration," and recommended 
 officially and officiously as the alternative to irrigation, 
 to be used when land of a quality and in a situation 
 suitable for a sewage farm is not to be had. That the 
 term in question is novel must be admitted, but that 
 there is any novelty in the thing itself it might be hard 
 to show. The reader has been already reminded that 
 all ordinary filtration is " downward/' and the term 
 
FILTRATION. 79 
 
 intermittent merely implies that the filter beds are to be 
 made in duplicate or in triplicate, the one to be in use 
 whilst the others are being cleansed. 
 
 It may be well to state Professor Frankland's original 
 plan in full. A plot of ground is to be procured, say 
 three times larger than is necessary to receive the en- 
 tire sewage of the town. The soil of this plot, to begin 
 with, must be of suitable quality, and it is prepared 
 (presumably dug up, drained, and rendered uniformly 
 light and open), to the depth of six feet. It is then 
 divided into three plots. Upon one of these the entire 
 sewage is run for eight hours. It is then turned upon 
 the second plot for the next eight hours, and finally 
 upon the third plot for the last eight hours. Thus 
 each plot will have eight hours' action and sixteen 
 hours' rest. I am not aware that there is any sacred- 
 ness in these exact numbers. It would, perhaps, 
 be permissible to divide the plot of land into four parts 
 instead of three, thus giving each part only six hours' 
 action and eighteen hours' rest. From certain labora- 
 tory experiments the distinguished author of this scheme 
 calculated that each acre of land would in this manner 
 purify the sewage of 3,300 persons in saecula saeculorum. 
 In a recent letter to the Times he has reduced his esti- 
 mate to 2,000 persons per acre, and some of his dis- 
 ciples have further varied the figure. Another point of 
 difference is regarding the possible utilisation of the 
 land laid out as filtration beds. Professor Frankland, 
 unless I misunderstand him, holds that it involves the 
 sacrifice of the land from an agricultural point of view, 
 and, of course, of the fertilising matters contained in the 
 sewage. Mr. Bailey Denton who seems to be to Pro- 
 fessor Frankland what AH was to Mahomed and Mr. 
 
So SEWAGE TREATMENT. 
 
 Grant Allen to Charles Darwin thinks that this pecu- 
 liar kind of filtration is the best means of getting a good 
 crop. Now I would ask any practical farmer what crop 
 save, perchance, rye-grass would be the better for hav- 
 ing turned upon it, in addition to the natural rainfall, the 
 sewage of 3,300 persons ; that is, on the average 99,000 
 gallons of water per acre every day from year end to 
 year end ? 
 
 Professor Frankland has now essentially modified his 
 views, and recommends that the earth for a " downward 
 intermittent filtration " bed should be prepared to the 
 depth of two feet only, thus tacitly admitting that the 
 lower four feet are of little use, and that his former ex- 
 periments, or at least the conclusions based upon them, 
 were fallacious. It would be a grave error to cavil at 
 a man of science for retracting and modifying opinions 
 which, upon further experiments and observations, are 
 found no longer tenable. But surely a savant who thus 
 openly and honourably confesses his own fallibility 
 might be led to inquire whether some of his other 
 utterances are not quite as much in need of revision ? 
 
 We have now to ask whether a daily rest of sixteen, 
 or even of eighteen hours will keep the land up to its 
 original degree of permeability ? We have already seen 
 how the soil is waterproofed by the deposit on its sur- 
 face and in its pores of the fibres of paper, linen, cotton, 
 etc. Now these fibres, if exposed to air and moisture, 
 would doubtless in time become disintegrated and 
 oxidised, save for one circumstance. That is, they are 
 coated with greasy matter, as it has been mentioned 
 above, and are thus protected in a very great measure 
 from the action of water and of atmospheric oxygen. 
 Even ordinary clean water applied to soil in such pro- 
 
FILTRATION. Si 
 
 portions as it is recommended for " intermittent down- 
 ward filtration " will ruin its texture. Let any one take 
 a box of soil of one foot square, set in it any kind 
 of plants other than swamp vegetation, and then 
 pour upon it, day by day, two gallons of water 
 (= 90,000 gallons per acre), he will find that its poro- 
 sity will be destroyed, and that the plants will not thrive. 
 How much more must this mischief occur when we have 
 superadded to the water the waterproofing materials 
 above mentioned, and when we have, in addition, the 
 yearly rainfall to contend with ? In proportion as the 
 soil becomes waterlogged (which must ultimately be 
 the case), little pools will begin to stagnate upon the 
 surface, and a larger and larger proportion of the 
 moisture will have to be got rid of by evaporation a 
 result injurious both agriculturally, as chilling the soil, 
 and from a sanitary point of view, as favouring the 
 diffusion of sewage vapours and probably of disease 
 germs. " Digging in " the deposit cannot well be 
 executed whilst any crop is on the ground, and can at 
 most only defer the evil. 
 
 It must never be forgotten that, whilst irrigation and 
 precipitation present at least the possibility of some 
 return, all the outlay in filtration, as in the Bazalgette 
 system, is pure waste. The object is not utilization but 
 destruction. 
 
 It must not, however, be supposed that filtration, even 
 as applied to crude sewage, is in all cases to be con- 
 demned. Let us suppose a town or village which is not 
 closetted, and where, consequently, little excrementitious 
 matter finds its way into the sewers. But let there be 
 instead some large manufacturing establishment, emit- 
 ting much liquid refuse, acids, solutions of metals, drain- 
 
82 SEWAGE TREATMENT. 
 
 age from tank-waste, residual liquors from dye-works, 
 tanneries, paper-mills, etc. If we irrigate with such 
 liquids we kill, instead of nourishing, the crops. 
 If we precipitate we may obtain a clear, colourless, 
 inodorous effluent, but the precipitate will be fit 
 " neither for the land nor for the dunghill." In such 
 cases filtration may prove the least objectionable 
 method of treatment. 
 
 Further, filtration may often be usefully applied as 
 finale to a precipitation process where extreme purity 
 of effluent is desired. 
 
PRECIPITA TION. 83 
 
 CHAPTER IX. 
 PRECIPITATION. 
 
 THE processes for the chemical treatment of sewage are 
 so numerous, so different in their principles, and so 
 varied in their grades of efficiency, that a complete dis- 
 cussion of each is purely impossible. Fortunately, many 
 of them are merely changes rung upon comparatively 
 few agencies, so that they may be dealt with in groups. 
 Before considering the substances used to effect pre- 
 cipitation, we must prepare to meet a cavil which has 
 been uttered with great confidence, not to say rashness, 
 though its first author, like many inventors, is unknown, 
 blushing, perhaps, at the fame which might be his mede. 
 It is said that " chemical agents, though they may clarify 
 i.e., withdraw suspended impurities cannot purify, 
 i.e., they are unable to remove dissolved impurities." It 
 is difficult to understand how any chemist can make such 
 an assertion without placing himself in a very unpleasant 
 dilemma. To begin, it is well known that suspension 
 and solution fade away into each other by scarcely 
 perceptible gradations. 
 
 It is further evident that suspended organic matters 
 under which head we must include living organisms, 
 the germs of disease, and putrefaction must, in the 
 strictest sense of the word, rank as impurities. If we 
 remove them we/r0 tanto purify the water. 
 
84 SEWAGE TREATMENT. 
 
 It is also known that there are two methods, if not 
 more, in which dissolved substances can be separated 
 from the solvent liquid : precipitation in the strict sense 
 of the word, and occlusion or aborption. In a well- 
 planned precipitation process these two modes of action 
 are systematically combined. In precipitation proper 
 the dissolved body enters into a definite and more or 
 less stable chemical combination with some other sub- 
 stance introduced, forming a compound which is in- 
 soluble in the liquid, and which then subsides to the 
 bottom. This occurs with organic as well as with in- 
 organic bodies. Thus, if we dissolve a little white of 
 egg (albumen) in water, and add a solution of sugar of 
 lead, the albumen combines with the lead to form an 
 insoluble mass. Or if we take a solution of gelatine in 
 water and add to it a solution of tannin, the gelatine 
 coagulates, and is deposited in combination with the 
 tannin. Everyone acquainted with the arts of dyeing 
 and tissue-printing will know instances where dissolved 
 organic substances are rendered insoluble by contact 
 with metallic salts. 
 
 These facts are here mentioned, not as in any way 
 novel, but merely to prove the general proposition that 
 dissolved organic compounds are capable of being pre- 
 cipitated. Before passing to instances proving that 
 sewage matters in particular are capable of being thus 
 thrown down, it is proper to refer to occlusion. Here a 
 dissolved substance is withdrawn from solution, not by 
 forming a definite chemical compound with some other 
 body introduced, but by becoming entangled in its 
 pores. Gelatinous silica and hydrated alumina, when 
 freshly precipitated, are capable of thus entangling dis- 
 solved organic matters. 
 
PRECIPITATION. 85 
 
 We may now pass to an experiment showing the pre- 
 cipitability of dissolved sewage matters. Take a pint 
 of sewage and filter it through the finest filter-paper, 
 which will prove a work of time. The liquid running 
 through may be almost as bright and clear as spring- 
 water. But if there be then added to this liquid a few 
 drops of a solution of alum, or of hydrated aluminium 
 chloride, commonly spoken of as muriate of alumina, or 
 of sugar of lead (all which must be free from any excess 
 of acid), there will soon form a white cloud in the liquid, 
 which will then, before long, settle to the bottom. This 
 is a compound of alumina (or respectively of lead) with 
 the organic matter which was previously in a state of 
 solution. If some of the filtered liquid is analysed 
 before and after the addition of the alum or other pre- 
 cipitant, it will be found that a large proportion of the 
 organic matter previously dissolved in the sewage has 
 been removed. Thus, Professor Dewar, F.R.S., and Dr. 
 Tidy, in the report of their recent prolonged investiga- 
 tion of the sewage of Aylesbury, and its treatment by 
 the "A. B. C. process," state that they found about 
 60 per cent, of the dissolved organic matter in the 
 sewage was removed, and, further, that the portion not 
 thus removed was precisely that least likely to enter 
 into offensive or dangerous decomposition. 
 
 Lastly, pure water is a thing which does not occur in 
 nature, and which the majority of those who utter the 
 above-quoted cavil have certainly never seen. If they 
 mean to say that sewage cannot be brought to this state 
 by chemical means or, indeed, by any other they 
 merely utter a gratuitous truism. If under cover of this 
 truism they insinuate that sewage cannot, by precipita- 
 tion processes be so far purified as to be safely admis- 
 
86 SEWAGE TREATMENT. 
 
 sible into the rivers of a populous and cultivated country, 
 they state at best an opinion which they would find it 
 hard to prove. 
 
 It is, therefore, sincerely to be hoped that we may 
 have heard the last of the cavil that organic impurities 
 dissolved in water cannot be got rid of by chemical 
 treatment. 
 
 I find, however, that when I wrote the above para- 
 graph I was paying an undeserved compliment to public 
 intelligence and candour. A few days ago there fell 
 into my hands the prospectus of a new sewage process 
 by aeration. The inventor goes somewhat out of his 
 way to attack precipitation, and writes that the Royal 
 Commission on the Metropolitan Sewage (1883) 
 " admits " note this term ! that the best precipitation 
 processes only clarify, but do not purify ! It is lament- 
 able when a Royal Commission "admits" something 
 very far from the truth. That Commission refused, or 
 neglected and in such a case, these two terms are 
 nearly equivalent to examine fully and fairly into the 
 merits of precipitation. It overlooked the fact that 
 many chemists, engineers, and other experts, who a few 
 years ago were decidedly hostile to chemical treatment, 
 have latterly seen reasons for changing their views. It 
 would not, or at least did not, visit Aylesbury. It was 
 satisfied to condemn precipitation on the faith of the 
 archaic reports of the Royal Rivers Pollution Commis- 
 sion, reports which, if true at the date when written 
 and this is a fairly strong concession are demonstrably 
 false if applied, e.g., to the process now in operation at 
 Aylesbury. 
 
 It must now be asked, What organic matters are 
 
PRECIPITA TION. 87 
 
 capable of being eliminated by so-called chemical 
 processes ? We may say that this is the case with 
 albumen and analogous compounds ; with gelatine, 
 mucus, and with peptones. The same holds good with 
 pyin, the albuminoid constituent of pus. Thus we see 
 that the most important portions i.e. t those most 
 likely to occasion mischief on decomposition of blood, 
 urine, and of the soluble part of solid excrements, are 
 amenable to precipitation. That suspended matters 
 can be precipitated has never, probably, been seriously 
 disputed, though some of them, such as fatty particles, 
 are much more difficult to deal with than the bulk of 
 the dissolved impurities. Phosphoric acid is invariably 
 present in sewage, being introduced by urine and by 
 blood. Though not to be called an organic impurity, 
 it is highly objectionable, as it is necessary to the 
 growth and multiplication of disease germs and other 
 microbia. It is satisfactory to know that it may be 
 almost absolutely removed by precipitation. 
 
 In the waste liquors of industrial establishments 
 there are a vast number of impurities capable of being 
 removed by chemical treatment. Such are the salts of 
 the heavy metals, colouring and tanning matters, etc. 
 
 Among the substances which resist precipitation are 
 oils and fats, essences, waste products of gas-works, 
 and refuse resulting from the manufacture of india- 
 rubber articles ; ammoniacal salts, salts of the alkalis, 
 especially nitrates, nitrites, and common salt. Con- 
 cerning these various bodies it is to be noticed that 
 gas-works refuse cannot be lawfully run into the 
 sewers at all, and that where soapsuds are abundant 
 they are generally kept back by the manufacturers, and 
 separately treated for the recovery of the fatty matter. 
 
88 SEWAGE TREATMENT. 
 
 One of the principal animal products which hitherto 
 has not been found practically precipitable is urea. 
 This substance, in contact with a ferment which is 
 never absent in urine, is quickly converted into 
 ammonium carbonate, and never reaches the sewage 
 tanks. 
 
 The ammoniacal salts and the alkaline nitrates and 
 nitrites are never found either in polluted rivers, or 
 in sewage in such a proportion as to be in themselves 
 a nuisance. At the same time we must regret that 
 they are not precipitable, because : 
 
 1. If they could be thus arrested, they would greatly 
 increase the manurial value of the deposit obtained. 
 
 2. Though in themselves inodorous, incapable of 
 putrescence, and, in fact, harmless, the nitrogen which 
 they contain may be brought into putrescible conditions 
 by the action of living organisms, and because they will 
 doubtless favour the multiplication of microbia. It 
 must be remembered that in irrigation and filtration 
 nitrites and nitrates occur in abundance in the effluent 
 water. 
 
 I have now to point out what are the properties, 
 positive and negative, which a precipitating agent 
 ought to have over and above mere efficiency. In 
 the first place it must be cheap cheap, not merely 
 by reason of present small demand, but of abundant, 
 or, rather, unlimited supply. 
 
 It must not be actively or cumulatively poisonous. 
 Certain salts of lead are well adapted for throwing 
 down organic matter from suspension and from 
 solution. But, on the one hand, the deposit would 
 be unsafe as a manure ; and, on the other, the slightest 
 excess remaining in the effluent water would be deadly 
 
PRE CIP1 7 'A T10N. 89 
 
 to vegetation, to fish, and to cattle, which might drink 
 of the stream. Antimony is excluded on the same 
 grounds, as are also tin and bismuth, which are, in 
 addition, too costly. 
 
 The precipitating agent must not have in itself any 
 distinct colour, or generate a colour with substances 
 which it may probably have to encounter. 
 
 This condition condemns, under most circumstances y 
 compounds of iron. Many of these are in other respects 
 well adapted for precipitation. But waters to which 
 they have been added take a greenish-yellow colour on 
 prolonged exposure to the air, and a yellow, ochreous 
 deposit is formed on stones, brick-work, piles, etc. 
 Though these deposits may be perfectly harmless, yet 
 to the public they convey the notion of an excremen- 
 titious origin, and the process is at once condemned. 
 Iron sediments, if containing sulphur, or if coming in 
 contact with sulphur compounds (mineral or organic), 
 turn intensely black, and have an unpleasant appear- 
 ance. 
 
 All substances are objectionable which yield an 
 alkaline effluent. This principle, strange as it may 
 sound, at once excludes the commonest agent lime. 
 The reason is that putrefaction is more active in alka- 
 line solutions than in such as are neutral or acid. In 
 all experiments on the culture of the microscopic 
 organisms, to which we have referred so often, and 
 in all attempts to generate life from dead matter, alka- 
 linity is a condition insisted upon. Now lime, if used 
 not merely to neutralise some acid or acid salt, but, 
 as a substantive precipitant, invariably renders the 
 effluent water alkaline, and thus favours decomposi- 
 tion. Whether the lime is applied in a powder, as 
 
90 SEWAGE TREATMENT. 
 
 cream of lime, or as clear lime water, is merely a 
 question of convenience and cost. 
 
 According to some recent investigations of Professor 
 Konig and Dr. Boehmer (Landwirth Jahrbiicher, 1885, 
 vol. xiv., part 2, pp. 228-238), lime reduces the total 
 organic matters suspended and dissolved in sewage 
 by 33 per cent, in the tanks, and if the effluent be then 
 allowed to flow over grass-land, by about 25 per cent. 
 more, making thus a total of 58 per cent. But salts of 
 alumina, with the aid of proper absorbents, are found 
 capable of reducing the total organic impurities sus- 
 pended and dissolved by 83 per cent, in the tanks alone, 
 without flowing over grass at all. 
 
 A lime effluent is well known to be injurious to fish 
 in any stream into which it penetrates. Of course, it 
 will be said that the caustic lime present will soon be 
 rendered inert, and be precipitated by the carbonic acid 
 of the atmosphere. But if the supply of lime is con- 
 tinuous, a considerable tract of water may easily remain 
 deadly to fish. 
 
 It will have been generally noticed that lime effluents 
 and lime sewage deposits give off a very peculiar and 
 most unpleasant odour. This, I suspect, is due to the 
 volatilisation of some ptomaine (putrefaction alkaloid) 
 present in the sewage. 
 
 The action of lime upon colouring matters in sewage 
 and in industrial waste waters, discharged, e.g., from 
 tanneries and dye works, is very unsatisfactory. I have 
 seen such waters easy to treat by other agents, but 
 which, if mixed with lime water, were turned from a 
 pale yellow to a dark and very permanent mahogany 
 colour. 
 
 It is interesting to find that Professor E. Frankland, 
 
PRE C I PIT A TION. 9 1 
 
 in conjunction with Dr. Stevenson, has recently recom- 
 mended lime as a precipitating agent for the Hendon 
 sewage. The better to appreciate this advice, we turn 
 to vol. i. of the first report of the " Royal Rivers Pollu- 
 tion Commission" of 1868, of which body Professor 
 Frankland was the most active arid prominent member. 
 
 In this document, published in 1870, we read : 
 
 "(a). Treatment with Lime. This process was, doubt- 
 less, first suggested by the ingenious operation devised 
 by the late Dr. Clark, of Aberdeen, for softening certain 
 hard waters. 
 
 " It has been applied to sewage upon an extensive 
 scale at Tottenham, for the manufacture of Tottenham 
 sewage guano ; at Blackburn, and especially at Leicester, 
 in the production of the so-called ' Leicester Bricks ' 
 (the name under which the manure was sold). 
 
 " In all these places the plan has been a conspicuous 
 failure, whether as regards the manufacture of valuable 
 manure, or the purification of the offensive liquid. 
 
 " We have witnessed the process at Blackburn, and 
 on two occasions at Leicester, where it is still used, 
 the machinery employed at the latter place being very 
 perfect and efficient. 
 
 " At both places the method obviously failed in the 
 purification of the sewage to such an extent as to render 
 it admissible into a river. At Blackburn especially, the 
 river below the outlet of the limed sewage was in a most 
 offensive condition of putrefaction, our note, made at 
 the time of our visit, being as follows : ' Horribly offen- 
 sive, turbid, blackish stream, disengaging most offensive 
 gases, with black masses of putrid mud floating on the 
 surface.' " 
 
 A committee of most eminent chemists, not, perhaps, 
 
92 SEWAGE TREATMENT. 
 
 remarkable for their special experience in the treatment 
 of sewage, have recently devised and published a palliative 
 process for the London sewage until the culminating 
 extravagance of conveying it down to Thames Haven 
 has been completed. These savants recommend the use 
 per gallon of 37 grains of lime with one grain of copperas. 
 It need scarcely be said that the effluent after the 
 addition of this mixture will possess the defect of being 
 alkaline. It may, indeed, to some extend " clarify," but 
 it cannot " purify," the foul odour not being removed. In 
 hot weather, therefore, it is recommended to add from 
 '5 to I 5 g r ain of manganate of soda, with half its weight 
 of sulphuric acid. This formula will still leave the water 
 alkaline, and in a good condition for the multiplication 
 of micro-organisms. 
 
 It has been recently alleged by Dr. Percy Frankland 
 that treatment with caustic lime (as in the Clarke process) 
 removes bacteria from water to a considerable extent. 
 The same authority has subsequently materially qualified 
 this statement, informing us that after a few days the 
 micro-organisms become more numerous than ever. 
 
 Lime is admitted to have a decomposing action upon 
 the suspended organic impurities, in virtue of which the)/ 
 are in part rendered soluble. 
 
 Among the substances to be as far as possible avoided 
 are further sulphates compounds of sulphuric acid with 
 various metals. The reason is that if brought into con- 
 tact with moist carboniferous matter, such as sewage 
 deposits, they may be gradually reduced to sulphides 
 (sulphurets), which, in turn, if they meet with even the 
 feeblest acids, liberate sulphuretted hydrogen. This 
 result is easily noticed when copperas (ferrous sulphate, 
 protosulphate of iron, or green vitriol) is used as a 
 
PRECIPITA TION. 93 
 
 precipitating agent. The change is shown in this case 
 by the intense black colour of the mass, which has been 
 mentioned above. 
 
 Sulphate of lime (gypsum), or any mixture or com- 
 bination by which sulphate of lime can be produced, is 
 exceedingly objectionable. Although there is here no 
 blackening, yet hydrogen sulphide (sulphuretted hydro- 
 gen) is given off in plenty. Instances are on record 
 where men employed in mixing sewage deposits with 
 gypsum to promote solidification have been rendered 
 seriously ill. 
 
 Even sulphate of alumina of which below is probably 
 one of the least desirable forms in which alumina can be 
 introduced in the treatment of sewage. 
 
 Sulphurets (sulphides) are very rarely admissible. On 
 no account should any soluble sulphide, or anything 
 which may form such a sulphide, be allowed to pass into 
 a river. 
 
 Hypochlorites, such as bleaching lime (commonly 
 called chloride of lime), and the corresponding magnesia 
 and soda compounds, must also be excluded. The late 
 Royal Rivers Pollution Commission was fully justified in 
 its protest against these substances as unfitting the water 
 of rivers for almost every conceivable purpose, and 
 especially rendering it deadly to fish. Mr. A. Anthony 
 Nesbit, F.C.S., has shown within what narrow limits this 
 deadly action takes place. 
 
 Salts of barium, such as barium chloride and baryta 
 water, have been proposed for the treatment of sewage, 
 and even for the improvement of drinking waters. They 
 will, of course, remove from a water any sulphuric acid, 
 free or combined, which may be present in solution, and 
 will also precipitate carbonic and phosphoric acids. But 
 
94 SEWAGE TREATMENT. 
 
 they are more expensive than lime, the lowest figure for 
 the native carbonate (Witherite) being 505. per ton. 
 Above all, they are very poisonous, and any portion 
 passing out in the effluent or remaining in the deposit in 
 a soluble state may work mischief both to animal and 
 vegetable life. Salts of strontium, if they become 
 cheaper, might be used with more safety. 
 
 Free acids, at least the hydrochloric (muriatic) and 
 sulphuric, have been proposed. They are first to be run 
 into the sewage, and then neutralised by the addition of 
 an alkali or an alkaline earth, lime as the cheapest 
 having probably been used. It is hard to see what good 
 end can be reached in this manner, the alkali or alkaline 
 earth undoing anything that the acid might have effected, 
 and the final result being merely an 'addition of calcium 
 sulphate or chloride (in older language, sulphate or 
 muriate of lime) to the sewage. 
 
 Common salt has been used with no definite advantage. 
 This result might be expected if we remember that this 
 same salt, derived from urine, is one of the characteristic 
 features of sewage, and that, if found in any water, it is 
 considered primd facie evidence of contamination with 
 the excreta of animals. 
 
 Petroleum, coal tar, and similar products have also 
 been recommended. They do not well mix with water ; 
 and> though they may at times mask an offensive smell, 
 they cannot remove putrescent or putrescible matter. 
 Being in themselves a nuisance in water, the Bill intro- 
 duced last year by Mr. Walrond and Earl Percy very 
 rightly proposed to make their emission into streams 
 penal. 
 
 One of the strangest mixtures ever suggested is ground 
 sulphur and turpentine ! Being insoluble in water, and 
 
PRECIPITATION. 95 
 
 incapable of mixing with it, the action of this composition 
 would be nil. 
 
 We come next to a class of systems which cannot 
 fairly be condemned, but which are still not by any 
 means free from objections. Here belong all the many 
 processes which turn on the introduction of phosphates 
 into the sewage. It is highly important that all the 
 phosphoric acid originally existing in sewage should be 
 removed, because such phosphoric acid remaining in the 
 effluent water favours the multiplication of disease germs, 
 and is, in addition, so much loss or waste withdrawn from 
 the manure. 
 
 The phosphate processes are somewhat varied, the 
 agent selected being either aluminium, iron, calcium 
 (phosphate of lime), or magnesium phosphate. Of these 
 the two first mentioned are generally dissolved in sul- 
 phuric or muriatic acid, avoiding excess. The solution 
 is then run into the sewage and allowed to mix with 
 it in a uniform manner. Lastly, milk of lime, or clear 
 lime-water, is added, so as to neutralise the acid and 
 cause the phosphate of alumina, or of iron, as the case 
 may be, to be reprecipitated, occluding, as it goes down, 
 more or less of the suspended and dissolved impurities. 
 When phosphate of lime is the agent, it has been recom- 
 mended to add to the sewage ordinary superphosphate, 
 and then to precipitate with lime-water as above. Not 
 a few inventors have proposed to remove at once phos- 
 phoric acid and ammonia from the sewage in the form 
 of ammonium-magnesium phosphate, better known as 
 the double phosphate of ammonia and magnesia. 
 
 All these processes are more suitable for the labora- 
 tory than for actual practice on the large scale. The 
 large quantity of phosphoric acid added must be again 
 
96 SEWAGE TREATMENT. 
 
 removed, or there occurs not merely loss, but the 
 multiplication of microscopic organisms is promoted. 
 Gelatinous phosphate of lime, in the state in which it 
 exists when freshly precipitated, decidedly promotes 
 decomposition of an unsafe character. If superphos- 
 phate is introduced into the sewage sulphate of lime 
 accompanies it, and if phosphates of alumina and of 
 iron are used dissolved in sulphuric acid, sulphate of 
 lime is thereby formed in the tanks. The objectionable 
 character of this compound in sewage or in sewage 
 mud needs no further demonstration. Further, in all 
 these phosphatic processes the effluent must be kept on 
 the alkaline side. This, except in the magnesia modi- 
 fication, is effected by means of lime. Consequently, 
 all the objections against lime processes come here into 
 force. 
 
 Further, a per cent, of phosphate of alumina rendered 
 soluble by means of sulphuric acid, and a per cent, of 
 soluble phosphate of lime, costs more than a per cent, of 
 soluble alumina in sulphate of alumina, or in hydrated 
 aluminium chloride. As for the phosphate of magnesia 
 processes, it must be remembered that the double phos- 
 phate of magnesia and ammonia (ammonium-magnesium 
 phosphate) is not a gelatinous mass like hydrated alu- 
 mina, but has a granular texture, and is consequently 
 much less adapted for occluding and entangling the 
 organic impurities of sewage. Every chemist who has 
 used the " magnesia process " for determining phos- 
 phoric acid must be aware that the conditions under 
 which this acid can be entirely removed from a liquid 
 are not such as can be produced in a sewage tank. 
 
 These considerations, combined with careful and pro- 
 longed experimentation on different scales, have driven 
 
PRECIPITATION. 97 
 
 me to the very unwelcome conclusion that the phosphate 
 processes are not to be recommended for the treatment 
 of sewage. 
 
 Having thus glanced at the principal agents which 
 should not be used, we come to those which are more 
 or less free from objection, and which may, therefore, be 
 generally applied. 
 
 Foremost come the salts of aluminium. They are 
 relatively cheap, inexhaustible, colourless, and harmless 
 in any moderate proportion. As may be seen from their 
 use as mordants, they have what is called a great 
 " affinity " for organic matter. This holds good as well 
 for sewage pollution, dissolved or suspended, as it does 
 for the ordinary colours used by the dyer and the 
 printer. If a solution of a salt of aluminium, say com- 
 mon alum or cake alum (sulphate of alumina), is thrown 
 into a large quantity of water, it is decomposed. A 
 basic sulphate, or as some call it, a subsulphate, is de- 
 posited, and combines with the major part of the impuri- 
 ties present in the water. This action is the more 
 energetic if the water is slightly alkaline, as is usually the 
 case with town sewage when free from industrial waste 
 waters. The decomposition of the salt of aluminium 
 and the precipitation of the impurities is also accelerated 
 if it be added to the sewage hot, as proposed by Mr. 
 W. C. Sillar. 
 
 It must now be asked, Which is the most suitable salt 
 of aluminium to be applied in the treatment of sewage ? 
 Alum, though used in some of the earlier sewage pro- 
 cesses, such as the original "ABC" process, is not to 
 be recommended. In addition to its high price, it con- 
 tains a considerable proportion of an alkaline sulphate 
 (potassium or ammonium sulphates) which, without 
 
98 SEWAGE TREATMENT. 
 
 contributing in any degree or shape either to the 
 purification of the sewage or to the agricultural value 
 of the deposit obtained, make the effluent water " analyse 
 worse." This is especially the case with ammonia-alum 
 (double ammonium and aluminium sulphate), which 
 causes the quantity of ammoniacal salts in sewage to 
 be apparently increased by treatment. This fact (the 
 apparent increase of ammonium salts) has been duly 
 noted by certain official opponents of sewage precipita- 
 tion, who have, at the same time, taken good care not to 
 explain its cause. 
 
 Aluminium acetate, used by dyers and tissue-printers 
 under the name of " red liquor," is a powerful precipi- 
 tant, but its cost is prohibitive. 
 
 Much the same may be said of the nitrate, which, in 
 addition, increases the proportion of nitrates in the 
 water. The sulphate (cake alum, concentrated alum, 
 or patent alum) is cheaper than alum, more rapidly 
 soluble, and contains 15 per cent, of actual alumina, 
 whilst potash alum contains only 10 and ammonia alum 
 II. If it contains a little iron, as in Spence's "alumino- 
 ferric cake," no disadvantage is occasioned, but, if any- 
 thing, rather an improvement. 
 
 Basic aluminium sulphates, where easily procurable, 
 are, price for price, preferable to the ordinary sulphate, 
 as they contain a larger amount of alumina, and are more 
 readily decomposed in contact with the dissolved and 
 suspended organic bodies ; but, as it has been already 
 remarked, sulphates are not to be selected except as a 
 matter of necessity. 
 
 The best of the aluminium salts is the hydrated 
 chloride, familiarly spoken of as muriate of alumina. 
 Until recently this salt could not be prepared at a 
 
PRECIPITATION. 99 
 
 cost sufficiently moderate to admit of its being used in 
 sewage treatment. Of late, however, a series of pro- 
 cesses have been devised, suitable to different localities, 
 by which a muriate of alumina, sufficiently pure for 
 sewage purposes, can be produced at a very low price. 
 
 The aluminate of soda was proposed and patented 
 as an agent for sewage treatment by A. J. Vassard, 
 in 1871. More recently it has been patented, in a 
 different combination, by F. Maxwell Lyte. Its pre- 
 cipitating power is indisputable, but the question of 
 relative cost is somewhat doubtful. When used it 
 must be accompanied by some acid salt, otherwise the 
 effluent would, in ordinary cases, be rendered alkaline. 
 
 The aluminium salts have not merely the property 
 of throwing down dead organic matter (dissolved or 
 suspended) present in water, but they can, to a 
 very great extent, remove disease germs. From time 
 immemorial the Chinese, before using the very ques- 
 tionable water of their rivers for culinary purposes, 
 have been in the habit of adding a pinch of alum to 
 a tub of the water, and allowing it to subside. The 
 French troops in Tonkin have adopted the same 
 expedient, arid have by this simple means almost 
 entirely got rid of the endemic dysentery from which 
 they previously were great sufferers. 
 
 Dr. Brautlecht has even proposed the use of alum 
 as a means of detecting the microscopic germs present 
 in water. He adds a few drops of a solution of alum 
 to some of the suspected water contained in a test- 
 tube, allows the precipitate to subside, decants off the 
 clear, redissolves the sediment in a few drops of acetic 
 acid, and searches for the organisms in the solution 
 thus obtained. 
 
ioo SEWAGE TREATMENT. 
 
 It should, therefore, appear that the effluent water 
 from any sewage process in which a salt of aluminium 
 is the precipitatingagent should be to a great extent 
 freed from the disease germs in question. 
 
 An insoluble compound, or alleged compound, of 
 alumina, has recently been recommended for sewage 
 precipitation. This is the so-called carbonate of 
 alumina. The chief authorities, such as Gmelin 
 (" Handbook of Chemistry ") and Watts (" Dictionary 
 of Chemistry") do not admit the existence of such a 
 body, though Mu sprat t (Journal of Chemical Society, 
 ii., p. 210) alleges that he has obtained a true aluminium 
 carbonate by precipitating a solution of alum with 
 ammonium carbonate. The patentee precipitates, it 
 would seem, solutions of cake alum with chalk (or 
 soda-ash ?), obtaining thus a mixture which, at any rate, 
 contains sulphate of lime, undecomposed chalk, and 
 either hydrated alumina (aluminium hydroxide), or the 
 alleged carbonate, or possibly both. However this 
 may be, I have been unable to find this mixture or 
 compound at all more efficacious in purifying sewage, 
 if the same is neutral or alkaline, than the quantity of 
 cake alum from which it was originally obtained. In 
 case of a strongly acid sewage it enables the use of 
 lime water, etc., for neutralising the water to be dis- 
 pensed with. This, however, is a distinction of little 
 moment : if we add sulphate of alumina to acid 
 sewage and neutralise with lime, the final result is the 
 same as if chalk had been added to the sulphate of 
 alumina before putting it into the sewage. The cost 
 of the " carbonate of alumina " is, of course, somewhat 
 higher than that of the cake alum from which it is 
 made. 
 
PREC1PITA TION. 101 
 
 Carbonates of any kind, or indeed substances which 
 can continue to give off gases after having been mixed 
 with the sewage, are to be condemned. The bubbles 
 of gas disturb the sediment, and cause minute particles 
 to remain in suspension. 
 
 It is, of course, well known that freshly precipitated 
 hydrated alumina, if well shaken up with the solutions 
 of certain substances e.g., colouring matters is capable 
 of withdrawing them from solution. As far as the 
 mere principle is concerned, this method would be 
 applicable in sewage treatment, but in practice it is 
 scarcely admissible, as the action is not sufficiently 
 rapid and energetic, and the mechanical arrangements 
 would prove too costly. 
 
 Soluble salts of manganese are excellent precipitants. 
 Not only do they carry down organic substances, dis- 
 solved as well as suspended, but they destroy certain 
 impurities by transferring to them a continual supply 
 of oxygen from the atmosphere, and from the air 
 dissolved in the water. This property is found more 
 or less well marked in the salts of all metals which 
 have two grades of oxidation. Any salt of a higher 
 oxide in contact with organic matter is reduced to 
 the lower oxide, and the oxygen which it gives off 
 oxidises, or, in other words burns up, the organic 
 impurities, whether dissolved or suspended. The lower 
 oxide then takes up fresh oxygen from the air, is 
 reconverted into a salt of the higher oxide, and repeats 
 the former process. It is devoutly to be hoped that 
 the opponents of the chemical treatment of sewage 
 will not seek to deny that in such cases purification 
 and clarification go hand in hand. Oxygen thus trans- 
 ferred to the particles of organic matter in sewage 
 
102 SEWAGE TREATMENT. 
 
 has a far more energetic action than the oxygen of air 
 driven in by a pump. 
 
 A manganese process is at present in action in the 
 town of Freiberg. Whether the manurial value of the 
 deposit is reduced by the oxidising action just men- 
 tioned the writer has not been able to learn, though 
 such a result seems likely. 
 
 Prior to the introduction of the Weldon process, the 
 refuse of the chlorine stills at manufactories of bleach- 
 ing powder was an admirable material for precipitation, 
 either used alone or as an addition to the other precipi- 
 tants. It was, in fact, patented in 1854, by J. A. Man- 
 ning (No. 61). It is now no longer available, save in 
 exceptional cases. 
 
 This may serve as an instance of the risks of basing 
 an industrial process upon the employ of some waste 
 product ; either an improvement in the primary manu- 
 facture or its decline may render such waste product 
 no longer available. 
 
 Sulphate of manganese, formed by heating black 
 manganese ore with sulphuric acid, is too expensive an 
 article for sewage purposes. But there has been 
 recently proposed an interesting process by which 
 this difficulty is got over. The inventor designs also 
 to make a joint sulphate of manganese and iron. 
 
 Zinc, on account of its highly poisonous nature, can- 
 not be applied in the treatment of sewage, though it 
 has been repeatedly claimed. 
 
 Copper is costly, and is also poisonous, but, according 
 to recent researches, so slightly so in small proportions 
 that it is capable of being used along with other agents 
 as a transferrer of oxygen. 
 
 Having thus glanced at the principal agents which 
 
PRECIPITATION. 103 
 
 form combinations with organic impurities and carry 
 them down, we come to a class of substances which act 
 in a different manner, and may be very advantageously 
 combined with the former. The bodies in question act 
 upon impurities by absorption or occlusion. The 
 substances of this kind are for the most part the same 
 as those which are used in irrigation and filtration, but 
 they are applied in an inverse manner. Instead of 
 passing the sewage to be purified through clays, arable 
 soils, grass-roots, etc., or through filter-beds made up of 
 charcoals, coke, sand, peat, lignite, etc., we agitate these 
 bodies in the sewage. Here is the advantage that fresh 
 portions of the purifying material are continually 
 brought into play, so that the annoyance of clogging or 
 saturation never can arise. 
 
 As the best of these materials may be mentioned 
 fatty clays, as free as possible from sand, grit, and 
 especially from carbonates and sulphates of lime and 
 magnesia. Such clay, in addition to its absorbing, puri- 
 fying action, serves as ballast ; it enables the sediment 
 more readily to subside, and prevents it from being 
 easily buoyed up again to the surface by any escape of 
 gases. 
 
 Burnt clay, ground clinkers, etc., subside to the bottom, 
 and, like sand, they occlude mere traces of the dissolved 
 impurities. Their presence in the manure is objected 
 to on good grounds. 
 
 Arable soil is as efficacious in precipitation as in 
 irrigation. But a supply sufficient for use with the 
 sewage of a town even of moderate size is not ordinarily 
 to be procured. 
 
 This will at once appear if we reflect that such soil 
 is rarely above a foot in depth, and that after its removal 
 
io 4 SEWAGE TREATMENT. 
 
 the land is rendered worthless for the farmer and the 
 gardener for a time practically unlimited. It might, of 
 course, after it has taken its part in a precipitation 
 process, be brought back and spread upon the fields 
 again. All chalky, lime or marl-soils are out of the 
 question, on account of the carbonate of lime they 
 present, which decomposes and wastes the metallic salts 
 used in precipitation. 
 
 Coke has some absorbent powers, and it has been 
 found by Dr. Percy Frankland very effectual in re- 
 moving microscopic organisms from impure waters. It 
 has been tried in a powdered state in precipitation pro- 
 cesses, but, as it does not improve the resulting manure, 
 the quantity in which it can be used is very limited. 
 
 Coal ashes have also been applied, but they have 
 little to recommend them. They contain finely- divided 
 silica no better than sand ; alkalies, which impair the 
 effluent, lime, magnesia and sulphur compounds, etc., 
 none of which are desirable. 
 
 Peat, which in many parts of the United Kingdom is 
 to be had without limit, is an excellent absorbing or 
 occluding agent. It has also, as it is well known, a 
 certain antiseptic action. It must, however, never be 
 used in sewage or waste waters containing compounds 
 of iron, or, of course, where iron is introduced in any 
 shape into the precipitating mixture. 
 
 We come now to the various kinds of carbon : lignite, 
 peat, and sea-weed charcoal, wood-charcoal, bone-black 
 sawdust, charred by moistening with sulphuric or muriatic 
 acid, the residual carbon from the manufacture of 
 prussiate of potash, as also soot. In selecting any 
 kind of carbon for sewage treatment certain points 
 must be attended to. The carbon must be neither t 
 
PRECIPITA TION. 105 
 
 dense nor too light. In the former case it settles at 
 once to the bottom without having the time to act upon 
 the dissolved impurities. If too light, it floats on the 
 surface without coming properly into action, and giving 
 the effluent water a very unsightly appearance. Sus- 
 pended charcoal powder may be justly objected to in 
 a stream, whether it is used for industrial or domestic 
 purposes. 
 
 All charcoals employed must be thoroughly well 
 burnt. If this is not the case they retain fatty and 
 tarry matters, which repel the water and prevent it 
 from penetrating into the pores of the charcoal. 
 
 On this account soot is very objectionable ; it 
 contains so much fatty matter as to float upon the 
 surface of water without becoming wetted. It contains 
 also a fair proportion of ammonia (r65 per cent), 
 which, without aiding at all in the purification, causes 
 the effluent to contain more ammonia, and, conse- 
 quently, to analyze worse. 
 
 A very powerful absorbing agent is gelatinous silica. 
 Without forming definite or permanent chemical com- 
 binations with the organic impurities, it entangles them, 
 and carries them down. Its use in various combinations 
 has been repeatedly patented. 
 
 Cement, Portland or Roman, has been repeatedly 
 proposed as an agent for sewage precipitation. If it 
 has any action at all (which is by no means demon- 
 strated), it will be most likely as an absorbing and 
 occluding substance. I am not aware that it has ever 
 been even tried on a practical scale. That a material 
 which sets or hardens in water can form the basis of 
 a manure seems highly doubtful. 
 
 In addition to precipitants and absorbents, certain 
 
io6 SEWAGE TREATMENT. 
 
 substances are also occasionally used, which have, or 
 are supposed to have, disinfecting, or, at least, deodo- 
 rising, powers. Among these rank certain gases, such 
 as chlorine, nitric oxide, sulphurous acid, atmospheric 
 air, carbonic acid ; further, carbolic and cresylic acids, 
 carbolic sulphite, creosote, oils of coal and wood-tar, 
 oil of turpentine, ethers, chloroform (!) ; also, chlorides 
 of lime, magnesia and soda, sulphites and bisulphites, 
 manganates and permanganates. Some of these bodies 
 may be applied beneficially ; others are utterly im- 
 practicable, being, e.g., not capable of mixing with 
 water. Some are mutually incompatible, the one 
 undoing what the other has done. Of others, it may 
 be strongly suspected that their chief effect is merely 
 to mask or hide an evil odour, rather than to prevent 
 or destroy it. 
 
 But of these substances generally it will be more 
 convenient to speak in the chapter on deodoration. 
 
 If anything approaching to a thorough purification 
 is intended, no one substance will effect the purpose. 
 It is generally requisite to employ conjointly some 
 absorbent body or bodies and a precipitating agent. 
 The absorbents, which are best added to the sewage 
 first, have the task of occluding and entangling in 
 their pores offensive gases and noisome products 
 existing in solution in the sewage. When these 
 materials have become thoroughly incorporated with 
 the sewage, and are saturated with the various 
 nuisances, the precipitant, in the strict sense of the 
 term, is then added. It forms insoluble compounds 
 with much of the remaining dissolved matter, and 
 coagulates both the suspended impurities and the fine 
 particles of the absorbents (now charged with filth), 
 
PRECIPITA TION. 107 
 
 and carries all to the bottom together. It is generally 
 found that the offensive smell of the sewage is removed 
 as soon as it has been properly mixed up with the 
 absorbents, but that the liquid remains dull and turbid. 
 On the other hand, the precipitant, if added alone, 
 renders the sewage clear and bright, but does not in 
 all cases entirely remove odours and colours. Both 
 conjointly share the task of removing microscopic 
 organisms, "germs," etc., from the sewage. 
 
 It will be then seen that the systematic conjoint 
 action of precipitants and absorbents or occluders is 
 needed, and that only those sewage processes can be 
 trustworthy in which this co-operation is recognised. 
 
 It cannot be too clearly impressed upon the mind 
 that a properly managed precipitation process is, or, 
 at least, includes, inverse irrigation, and that this 
 inversion gets rid of almost all the objections which 
 can be raised against irrigation direct. 
 
 We must come now to the manner in which the 
 chemical agents are brought to bear upon the sewage. 
 The materials, dissolved, if soluble, or, if insoluble, 
 ground to a pulp with water which may be a portion 
 of the sewage are allowed to flow into and become 
 incorporated with the sewage in a channel. This 
 channel should be of such dimensions and construction 
 that every drop of the sewage should have the oppor- 
 tunity to come in contact with the agents used. The 
 channel then delivers the mixture into tanks, where 
 the process of deposition or settlement takes place, 
 whilst the clear water or effluent remains above. 
 
 This part of the process may be either intermittent 
 or continuous. In the intermittent system we require 
 a number of tanks, arranged side by side, each uncon- 
 
io 8 SEWAGE TREATMENT. 
 
 nected with, and independent of, the remaining. The 
 treated sewage is first let flow into one of these tanks. 
 When that one is full, the current is cut off and turned 
 into the next tank, and so on, tank after tank being 
 filled. As soon as the first tank is found to have 
 settled, the clear liquid is allowed to run off by 
 gravitation, if there is a sufficient fall, or is otherwise 
 pumped off, with due precautions to prevent the mud 
 at the bottom from being disturbed. The mud is then 
 run off through distinct channels, or, if necessary, is 
 pumped into a collecting reservoir, whence it is 
 forwarded to the filter-presses, drying-floors, or other 
 drying apparatus. 
 
 In the continuous process the treated sewage flows 
 into the first of a series of tanks, all connected together, 
 and from the last of which it passes constantly into the 
 outfall channel. When any one of the tanks is found 
 or judged to contain as much mud as is proper, it is 
 cut off from the series, and pumped or run off, as in 
 the intermittent system, whilst the sewage is let pass 
 through the remainder of the set. 
 
 It is therefore necessary to have tank room enough to 
 receive and deal with the day's flow even if one tank is 
 temporarily disconnected. In this manner every tank 
 is successively cleaned out. It will be, of course, evident 
 that the tank into which the treated sewage first falls 
 will require emptying much oftener than the rest of the 
 set. Superabundant tank room is essential, as the bulk 
 of the sewage varies greatly according to the weather. 
 The construction of the tanks is a point of capital im- 
 portance. The arrangement shown in the accompany- 
 ing plan has been in use at the Aylesbury Sewage 
 Works for some years, and, except as regards its size, 
 
*/U. 
 
 Z f 
 
 < 
 
 H 
 
 \\ 
 
 
 c 
 
 1L 
 
 s 
 
 
 o 
 
 CO 
 
 fe 
 
 o 
 
PRECIPITATION. 109 
 
 has given general satisfaction. It is adapted for con- 
 tinuous working. The sewage of the town flows down 
 to the works by gravitation, and is delivered from the 
 sewer at the point marked A, where there is a grating to 
 arrest rags, etc. Here it receives from the trough B a 
 proper proportion of the purifying (absorbent or occlu- 
 sive) mixture, which at once removes all offensive 
 odour, an<i after flowing a few feet further, the precipi- 
 tating agent (in the strict sense of the word) enters 
 from the trough c. Where space is ample the distance 
 between A and B might be increased with advantage. 
 The sewage, having now received all the materials neces- 
 sary for its purification, flows along the channel D to 
 tank No. I, entering it at the point marked E, and 
 thence through the tank, passing round the partition- 
 board F, through the outlet G, into the channel H. The 
 water next passes into tank No. 2, at the inlet I, round 
 the partition-board K, through the outlet L, into the 
 channel M. It next passes through the three inlets N, 
 N, N, into the tank No. 3, and, passing slowly through 
 it, discharges at the outlet o, into the channel P, flowing 
 thence round the partition Q, into the outer channel R, 
 to the outfall S. Here it enters an open cutting about 
 a quarter of a mile in length, and lined with concrete, 
 finally venting into the river. 
 
 The mud, when it requires removal, is pumped out 
 through pipes which pass from the front end of each 
 tank beneath the channel D, and which can be con- 
 nected as required with a powerful steam-pump. Any 
 one of the tanks may be shut out of circuit if needed 
 whilst the mud is being cleared away. 
 
 A specimen of well-arranged tanks for continuous 
 working, but upon a much larger scale, may be seen at 
 
no SEWAGE TREATMENT. 
 
 Knostrop, Leeds. Here the level of the ground allows 
 of the tanks being emptied by gravitation without any 
 pumping, which is not possible at Aylesbury. The flow 
 in sewage tanks must be as gentle as possible, so as not 
 to hinder the subsidence of the precipitate, or disturb 
 that which has already settled. To this end the fall 
 from B to S, and especially from E to s, should be mini- 
 mized. In the arrangements for passing the sewage 
 from tank to tank, or from tank to channel, eddies or 
 whirlpools should be most carefully guarded against ; 
 they bore the mud from the bottom up to the surface. 
 
 Speaking within compass, I venture to say that ill- 
 planned tanks, which require an extra allowance of 
 chemicals to force precipitation, may lead to a waste of 
 20 per cent. } and then not give a satisfactory result. 
 
 The proportions of the ingredients to each other, and 
 to the impurities to be dealt with, cannot be usefully 
 modified beyond a certain point. 
 
 For a large town, where the number of tanks must neces- 
 sarily be considerable, they are best placed in a double 
 row. If arranged in a single file, a long narrow slip of 
 land is needed, which is not always easily to be had. 
 There is also trouble at least where gravitation is not 
 available with the appliances pumping out the mud ; 
 these must, of course, be capable of acting in every tank. 
 As it has been already said, ample, superabundant 
 tank room is desirable. In all towns where a double 
 system of sewerage is not in action, we have to keep in 
 view the possibility of storm-water. The sewage of a 
 town, which in fair weather averages 250,000 gallons 
 daily, may by a sudden heavy thunder-storm be swelled 
 to a million gallons or upwards. If such a flood is 
 allowed to force its way into a set of small tanks, the 
 
PRECIPITATION. in 
 
 deposit is washed up again, and swept down into the 
 river, giving rise to not unjustifiable complaints. On 
 the other hand, it is not advisable to let the excess of 
 water sweep by untreated. The sewers, after prolonged 
 dry weather, will be found coated with dry faecal matters 
 in very foul states of putrefaction. All this is brought 
 down by a sudden storm, and is certainly harder to treat 
 than normal sewage. 
 
 Some engineers, in laying out sewage works, have 
 proposed to roof the tanks over. This is a capital 
 mistake. The treater cannot know whether the process 
 is working satisfactorily or not without he can walk 
 round the tanks and see them in different lights. 
 Further, the free contact with the air and the access of 
 light assist no little in purifying the sewage. If the 
 tanks are found to give off a bad smell, it is proof that 
 the process is not being satisfactorily worked, or that it 
 is essentially deficient, and needs to be superseded. 
 
 The tanks shown in the plan are considerably deeper 
 at the inlet end than at the outlet end. In some works 
 the depth is alike at both ends, and in others again, the 
 inflow end is made the shallowest. Decisive experi- 
 ments on the comparative results of these three arrange- 
 ments, all other circumstances being kept the same, are 
 still wanting. 
 
 It is also to be regretted that engineers to whom it 
 evidently belongs have never fully solved the following 
 problem : For a given flow of treated sewage, what 
 should be the shape, size, and arrangement of tanks, so 
 that settlement may take place the most quickly and 
 completely ? 
 
 The importance of this question has on several occa- 
 sions painfully forced itself upon the writer's attention. 
 
H2 SEWAGE TREATMENT. 
 
 A great mistake is, as it has been proposed by some 
 inventors, to have two or more successive precipitations, 
 the sewage being treated in one tank with some given 
 material, and in another with a second agent, etc. Such 
 systems of necessity lead to a duplication not merely 
 of tanks and channels, but of grinding and mixing 
 machinery, of mud-pumps, ducts and reservoirs for 
 different kinds of sediments, as well as to an increase of 
 the mechanical power and of the labour needed. Now, 
 is there any set-off against all this extra outlay ? 
 
 Whatever process be adopted, and whether the 
 working be continuous or intermittent, among the 
 most essential requisites are CLEAN TANKS. In their 
 default the best process in the most skilful hands will in 
 a great measure fail. The reason for this is not far to 
 seek. The deposit formed at the bottom of the tanks, 
 if left for many days in contact with water, begins to 
 undergo change. Matter which had been rendered 
 insoluble tends to decompose, and fouls the water above. 
 Bubbles of gas chiefly hydro-carbons are liberated, 
 and buoy up lumps of the mud to the surface. Here 
 they burst, and diffuse the finely divided mud through 
 the water. These changes take place especially if the 
 barometer is low and the temperature high. It is to be 
 remarked that the sewage mud from a proper pre- 
 cipitation process, when freed from water, does not give 
 off any bad odour, or appear to undergo any rapid 
 changes. 
 
 Where a very high grade of purification is aimed at, 
 the water, as it passes away from the last tank, may be 
 aerated. This can be effected in various ways : where 
 space allows, it may be permitted to flow in an open* 
 shallow channel for some distance before being dis- 
 
PR EC I PIT A TION. 1 1 3 
 
 charged into a stream. Or along the outflow channel 
 there may be laid, below the water level, pipes perforated 
 with a number of fine holes, through which air is forced 
 by any available power. Or the water may be made, if 
 the ground allows, to form a series of cascades or rapids. 
 Or, before being discharged, it may be filtered over a bed 
 of coke, lignite, peat, blackstone carbon, or other suitable 
 material. Or, lastly, it may be utilised for irrigating any 
 plot of land which may be the better for an increased 
 supply of moisture. 
 
 It has been already mentioned that where there is 
 scope for such an arrangement it is advisable to let the 
 sewage average itself before treatment in a collecting 
 tank. 
 
 At some sewage works the liquid before treatment 
 passes through revolving wire screens of different grades 
 of fineness, no less than 4-horse power being in one place 
 consumed in setting this machinery in motion. This 
 seems a costly and a needless complication. If the 
 sewage, before entering the channel where the treatment 
 takes place, is allowed to pass through a grating of iron 
 rods, laid in a direction sloping away from the current, 
 all coarse suspended matters, corks, rags, dead rats, 
 lumps of solid excreta, etc., are arrested, and may 
 be easily cleared away with the stroke of a rake and 
 thrown into a wheelbarrow for removal. With this 
 grating and the occasional attention of a labourer, this 
 object is as well effected as with costly machinery and a 
 considerable amount of steam power. 
 
 It is desirable that the grinding mills and the mixing 
 pits in which the ground materials are kept ready for use 
 should be close over the sewer mouth. Thus the fore- 
 man who conducts the treatment can watch the character 
 
 i 
 
114 SEWAGE TREATMENT. 
 
 of the sewage as it enters the channel, and on the 
 appearance of any change in its quantity or quality can, 
 without stirring a step, by simply reaching his hand to a 
 cock or a valve, make the corresponding change in the 
 quantities and proportions of the mixture used. 
 
 To control the process the following very simple 
 method may be employed : Suppose that we are using 
 two ingredients, a and b. We take four small hydro- 
 meter glasses and fill them to a known height with the 
 sewage after it has received the mixture. No. I glass 
 we leave as it is. To No. 2 we add a little more of a (a 
 solution of which is kept ready at hand for the purpose) ; 
 to No. 3 a little more of b, which is also kept ready ; 
 and to No. 4 a little more raw sewage. We then 
 observe which of the four glasses is the best, i.e., which 
 goes down with the cleanest, boldest flakes, leaving clear, 
 colourless, inodorous water above and between. If No. I 
 is the best, the treatment is continued as it was ; if No. 2 
 is seen to be an improvement, we increase the proportion 
 of a added ; if No. 3 has the advantage, we increase in 
 like manner the dose of b. And if No. 4, to which more 
 raw sewage has been added, is the best, we see that we 
 have been using too much material, and we reduce the 
 quantity accordingly. 
 
 It is easy to sneer at this method as a " rule of thumb" 
 procedure, an expression often used in a very " rule of 
 thumb "-like manner. But considering that in many 
 towns the character of the sewage may, and often actually 
 does, undergo a decisive change within a few minutes, we 
 shall see that no process of chemical analysis is suffi- 
 ciently rapid. There are other methods by which the 
 treater may be guided. He may from time to time dip 
 up a hydrometer glass full of the treated sewage from 
 
PRECIPITA TION. 1 1 5 
 
 different points of the channel D (see plan), and set them 
 aside in a good light to observe how they settle. He 
 should occasionally walk round his tanks and inspect 
 them from different points of view as regards the light. 
 If any process is acting well, the effluent water, when in 
 bulk, appears of a peculiar bluish tinge. This indicates 
 not merely " clarification," but " purification," since this 
 blue tint, according to the researches of Mr. W. Crookes^ 
 F.R.S., is the more decided the freer a water is from 
 dissolved organic matter. 
 
 The treater must learn, by careful, intelligent obser- 
 vation, what modifications the sewage he has to deal 
 with generally undergoes ; at what hours, on what days, 
 or under what conditions of weather, etc., these changes 
 come on, and how they are all to be met. 
 
 It must be remarked that the specific gravity of a 
 sample of sewage gives no clue to the quantity or quality 
 of the treatment it will require. Mineral substances in 
 solution, which raise the specific gravity of a sewage, may 
 cause it to require less absorbing and precipitating matter 
 than a sample specifically lighter, because richer in 
 organic matter. 
 
 Sewage is more readily precipitated if warm than 
 when cold. There is also a decided advantage in using 
 the precipitating agents hot, as proposed in a recent 
 patent. 
 
 It has been suggested, by way of economy, to use the 
 deposit over again as an occluding or absorbing agent 
 with a fresh dose of a metallic salt, and with or without a 
 recruit of carbonaceous or earthy matters. The experi- 
 ments made in this direction have not been remarkably 
 successful. The first time of re-using, the effluent was 
 found, perhaps, nearly as good as one obtained with 
 
ii6 SEWAGE TREATMENT. 
 
 fresh materials ; the second and third times gave 
 decidedly worse results, and on trying a fourth and fifth 
 re-usal the effluent was bad in colour and odour, and 
 showed on analysis little improvement if compared 
 with raw sewage. This result cannot be termed un- 
 expected. The occluding power of carbon, in its various 
 forms, and that of clay, arable soils, etc., cannot be 
 supposed infinite, and when saturated they cannot take 
 up more. If they are then again and again brought into 
 contact with fresh portions of polluted liquids, the pro- 
 bability is that, instead of taking up any more putrescent 
 matter, they may part with some that they had already 
 absorbed. 
 
 Nor is the prospect of economy very clear even if it 
 were found possible to re-use the deposit once or twice. 
 In that case, to work systematically, and to know what 
 is being done, it will be necessary to keep distinct a, 
 the deposit obtained with fresh materials; b, the deposit 
 obtained on once re-using ; and c, the deposit obtained 
 on twice re-using. To do this on a practical scale 
 requires considerable trouble and expense, since each 
 kind of mud, on cleansing out the tanks, requires to be 
 drawn off into a separate receptacle, and the lots which 
 are to be re-used have to be pumped back into the 
 mixing pits. 
 
 It may not be useless to consider some of the causes 
 which have raised so strong a feeling against the chemi- 
 cal treatment of sewage a prejudice which, though 
 abandoned by the majority of observers in deference 
 to facts, still lingers in official quarters. 
 
 In the first place, we must admit that a multitude of 
 sewage processes have been devised without the lights 
 either of theory or of practice. Instead of selecting 
 
PRE C I PIT A TION. 1 1 7 
 
 materials which might mutually support and supplement 
 each other, inventors seem mainly to have looked out for 
 articles which were cheap, or entirely worthless, and 
 heaped them together without any definite notion of 
 the part which they were separately and collectively to 
 play. This alone can account for the recommendation 
 of such bodies as coal-ashes, soot, salt, gypsum, etc., 
 which in almost every case would do more harm than 
 good. Very often we see, especially in the older speci- 
 fications, materials given as alternatives whose action, if 
 any, must be evidently quite dissimilar the one to the other. 
 
 Not uncommonly, to furnish the basis for a patent, 
 some well-known and often-used agent was proposed, 
 and with it, to give an air of novelty, some useless or 
 even mischievous matter. 
 
 In addition to " bogus " patents there was " bogus " 
 working. A municipal authority, or a company, or a 
 contractor it does not matter which might be nomi- 
 nally and ostensibly working according to some process 
 which has much to be said in its favour. But in daily 
 practice the most important agent would be left out 
 entirely, or else used merely in quantities sufficient to 
 swear to. If some important personage or deputation 
 was expected, then the omitted article was brought into 
 use, and the good result produced was triumphantly 
 exhibited as that of the ordinary, normal working* 
 Further, there is no obligation on a man who contracts 
 to purify sewage to work under any patent at all. He 
 may legally and equitably make use of any patent 
 which has expired and become public property. Or 
 he may make a combination of such methods. Or he 
 may have a secret process of his own. But if a man 
 thus acting professes to be working under a patent 
 
iiS SEWAGE TREATMENT. 
 
 which has expired, or which has never existed, he is 
 sailing under false colours. 
 
 Another great misfortune has been the exaggerated ex- 
 pectations entertained and fostered by the earlier sewage 
 purifiers concerning the commercial value of sewage. 
 From calculations, perfectly correct in themselves, of 
 the waste incurred day by day in the form of ammonia 
 and phosphoric acid poured down the sewers, the in- 
 ference was drawn that the whole of this value was 
 recoverable. Hence, certain municipalities claimed 
 payment for their sewage, and individuals, syndicates, 
 and companies were found sanguine enough to offer 
 such payments, and still hope to cover all the working 
 expenses, and secure a fair profit on the capital invested. 
 
 From this error, which, be it remarked, was merely 
 one of the delusions common in the early days of any 
 new undertaking e.g., electric lighting all persons 
 concerned have now recovered. Whilst insisting, as 
 will be explained in a future chapter, that a very con- 
 siderable amount of plant food i.e., manurial matter 
 can be obtained from sewage, either by irrigation or by 
 judicious chemical treatment, we must clearly admit 
 that the value thus realised is not sufficient to pay 
 working expenses, and leave such a margin as will 
 remunerate capitalists who take the matter in hand. 
 If a firm or a company undertake to guarantee the 
 treatment of the sewage of any town, and furnish 
 security for the due execution of the undertaking, the 
 town must expect to pay a reasonable subsidy. 
 
 Concerning opinions which are the mere result of 
 prejudice, and which their authors dare not retract for 
 fear of owning themselves in the wrong, there is no 
 need to enlarge. 
 
DEODORISING. 119 
 
 CHAPTER X. 
 
 DEODORISING. 
 
 THE title which, for want of a better, is given to this 
 chapter, is not, perhaps, as intelligible as might be 
 desired. In irrigation and precipitation processes one 
 of the main objects kept in view is to deodorise the 
 sewage. But the processes about to be here discussed 
 do not seek to remove the impurities from sewage or 
 other foul waters, but merely to prevent them from 
 being immediately offensive. They are, in short, pallia- 
 tive rather than either preventive or curative. They 
 derive at present an exceptional and transitory im- 
 portance from the attempts made by the Metropolitan 
 Board of Works to deal with the present state of the 
 Thames, as arising from the practical failure of the 
 Bazalgette system, without having been compelled to 
 own themselves mistaken. 
 
 In order to form an opinion concerning the promise 
 and potency which are in deodorising processes, let us 
 take one which was actually used by the Metropolitan 
 Board of Works. Chloride of lime (bleaching powder) 
 was, as it is said, put into the sewage not in any suitable 
 precipitation tanks, but into the river itself, after it had 
 been polluted by the discharge of sewage at Barking 
 Creek and Crossness. The deodorisation, if it was any- 
 thing more than mere masking, could but be temporary. 
 
::o SEWAGE TREATMENT. 
 
 The active chlorine must soon escape, and the organic 
 matters present could not be destroyed or rendered per- 
 manently inactive by any proportion of the bleaching 
 agent that could possibly be applied. Were this point 
 actually reached the crews of vessels on the river, and 
 even all persons living or working near the margin, 
 would be subject to great inconvenience, if not to actual 
 danger. Many kinds of cargoes and all the metal fit- 
 tings of ships would be injured or corroded. Fish, if 
 present, would be at once destroyed. The precipitation 
 of the various pollutions could not be notably greater 
 than that of a lime process, and the matter precipitated, 
 be it more or less, would be deposited at the bottom 
 of the river. Here it could not be regularly removed, 
 as would be done in a precipitation tank. Nor would 
 matters be greatly improved if chloride of lime were 
 applied to the sewage in tanks. To treat only a part 
 of the sewage in this manner, leaving the rest in its 
 original nastiness, could only be regarded as playing 
 with the question. And if we suppose the whole of the 
 sewage of London, say 170 million gallons, daily collected 
 in tanks and there treated with chloride of lime, a 
 nuisance would be generated far greater than any of 
 those which the Alkali Act was intended to combat. 
 
 But chloride of lime soon departed, though not in the 
 odour of sanctity, and was succeeded by manganate of 
 soda. The alkaline manganates and permanganates, 
 and, indeed, various other compounds of manganese, 
 have long been used for transferring oxygen to organic 
 matters in solution, or, in other words, for burning them 
 up. Thus, W. C. Sillar, G. R. Sillar,and G. W. Wigner, 
 in a patent, No. 1,954, of 1868, claim manganate of potash 
 as one of the ingredients in the original "ABC" mix- 
 
DEODORISING. 121 
 
 ture. Whether it was actually used in this combination 
 I am unable to say ; but the manganates and perman- 
 ganates have some serious drawbacks as sanitary agents. 
 They do not actually destroy the organic matters dis- 
 solved in water unless introduced in relatively large 
 quantities and assisted by heat. Chemists who have 
 been accustomed to determine organic matter in drink- 
 ing waters by the aid of the permanganate process in 
 any of its modifications, will be slow to believe that, in 
 the proportions introduced by the Metropolitan Board 
 of Works in their operations at Crossness, it can have 
 had any marked effect. The permanganate has cer- 
 tainly not been added to the entire volume of polluted 
 waters, and anything less is trifling. Experiments ? 
 But what is the use of experimenting on points already 
 decided ? That permanganates, unless accompanied 
 by a quantity of sulphuric or other acid sufficient to 
 neutralise all the alkali, must leave the sewage in an 
 alkaline state, needs no demonstration. Their inability to 
 destroy micro-organisms is well known. I have seen 
 animalculae large enough to be distinguished with the 
 naked eye surviving for an entire day in water to which 
 potassium permanganate had been added in excess. 
 How long they would have survived I am unable to say, 
 as a laboratory boy took it upon himself to empty out 
 the contents of the vessel. 
 
 This is, perhaps, the proper place to notice certain 
 attempts, or at least proposals, to deal with sewage by 
 forcing into it common air or antiseptic gases. Aera- 
 tion, as supplemental to precipitation, has already been 
 noticed, and where a very high degree of excellence is 
 required, it is at least worthy of trial. But aeration has 
 also been proposed as a substantive process for grappling 
 
 UNIVERSITY 
 
122 SEWAGE TREATMENT. 
 
 either with the crude sewage or with the sewage merely 
 freed from its solid impurities. Thus James Bannehr 
 (No. 2,918, A.D. 1867) treats the liquid portion of sewage 
 with an acid to fix the ammonia, passes through the 
 chamber containing the mass under treatment a current 
 of air, which may be warmed and " charged with a cur- 
 rent of electricity or of carbonic acid. v Ferrar Fenton 
 (No. 1,897, A.D. 1871) passes through the sewage "a 
 blast of atmospheric air." E. Hills and B. Biggs (No. 
 3,464, A.D. 1872), after having run the sewage into 
 an air-tight tank and added sufficient lime to set free 
 the ammonia, force atmospheric air through such sewage 
 into another tank, where it encounters sulphurous acid 
 to arrest ammonia and decompose sulphuretted hydro- 
 gen. R. S. Symington (No. 912, A.D. 1873), after filter- 
 ing the sewage upwards through ashes, exposes it to the 
 action of the atmosphere " by falling in a broken manner 
 through a sufficient height before passing through the 
 last filtering tank." G. Rydill (No. 399, A.D. 1875), after 
 filtering foul water and treating it with caustic soda or 
 lime, " forces air into it from perforated pipes arranged 
 in a tank and connected to a blower." Lastly, a Mr. 
 James, of Tottenham, recently patented an arrangement 
 for the treatment of sewage by aeration, and has called 
 attention to his system in a circular which contains some 
 rather hazardous assertions. He proposes to run raw 
 sewage into an air-tight tank, at the bottom of which 
 lie a number of perforated iron pipes, into which air is 
 forced by some suitable mechanical arrangement. The 
 air, after having bubbled through the sewage, escapes 
 through two pipes, one of which is supposed to convey 
 the sewage gases, and the other the air deprived of its 
 oxygen, into a chimney 150 feet in height, whence it 
 
DEODORISING. 123 
 
 escapes into the atmosphere. The circular makes no 
 mention of any arrangement for forcing the sewage 
 gases, possibly charged with microbia, through a furnace. 
 
 How long this treatment has to be continued before 
 a tankful of sewage is purified, the inventor does not 
 say. This is to be regretted, since without this point 
 is ascertained, approximately at least, neither the first 
 cost of the plant for a given flow nor the subsequent 
 working expenses can be calculated. I must avow my 
 suspicions that the time required for thus purifying 
 raw, undiluted sewage by the mere contact of air will 
 prove very long. In rivers which are to some extent 
 polluted with sewage there are, as it is shown in the 
 chapter on self-purification, certain agencies at work 
 which in the treatment of undiluted sewage in an 
 air-tight tank are out of the question. Nor is the high 
 chimney a satisfactory arrangement. High chimneys 
 have been found to do little towards mitigating the 
 nuisance from the discharge of sulphurous or hydro- 
 chloric acid gases, chlorine, coal-smoke, etc., into the 
 air. The sulphuretted hydrogen, and the liquid and 
 solid impurities which must be mechanically carried 
 aloft by the ascending current, will be brought down 
 again to the earth by rain, and will be introduced where 
 they are not wanted. 
 
 Nor must it be forgotten that in this process, as in 
 Bazalgettism and " intermittent downward filtration " 
 but unlike irrigation and precipitation the entire cost 
 is incurred in pure waste. No fraction of the plant- 
 food contained in the sewage is returned to the soil, 
 but all is hurried out to the sea. Hence this process, 
 surely, is greatly to be deprecated. 
 
 It must be remembered that Mr. James proposes to 
 
124 SEWAGE TREATMENT. 
 
 lay his perforated air-pipes, not merely in special tanks, 
 but also along the course of the sewer. Here, we 
 presume, the sewage gases will have to escape, not 
 by way of a chimney into the upper regions of the 
 atmosphere, but through the sewer-grids and ventilation 
 holes into the streets. 
 
 Some inventors have proposed carbonic acid, either 
 as an auxiliary or as a sole agent, in the treatment of 
 sewage. There is nothing intrinsically absurd in this 
 idea. Carbonic acid has a certain antiseptic power, as 
 it has been lately re-discovered, and as a sequel to a 
 lime process it might be useful. 
 
 Nitrous oxide, chlorine, sulphurous acid, and hydro- 
 chloric acid, have been patented as agents sole or 
 merely adjunct in the purification of sewage. In very 
 rich animal liquids containing little but urine, and 
 especially blood, like the drainage from slaughter-houses, 
 treatment with chlorine is advantageous. With blood 
 its behaviour is remarkable ; the blood quickly sets 
 into a loose, dry, granular mass, incapable of offensive 
 changes, and well adapted for distant transport For 
 ordinary town sewage agents of this class are incon- 
 venient, and far too costly and troublesome in their 
 application. 
 
DESTRUCTION. 125 
 
 CHAPTER XL 
 
 DESTRUCTION. 
 
 THE organic matter contained in sewage is essentially 
 manurial, including, as it does, all the nitrogen 
 eliminated from the bodies of men and other animals, 
 as well as the phosphoric acid and potash. Hence 
 every process by which this manurial matter is applied, 
 or sought to be applied, not to the fields and gardens 
 where it may serve as plant-food, but to any other 
 purpose, or is, in conventional language, destroyed, 
 wasted, may be termed "destructive." Some of the 
 processes already discussed might fairly share this 
 name, such as the Bazalgette system, the aeration 
 process of Mr. James, and, indeed, " intermittent down- 
 ward filtration " itself. 
 
 But, as types of destruction, we may take the pro- 
 cesses patented by the late General Scott (Nos. 849, 
 A.D. 1872, and 296, A.D. 1873). It is commonly said 
 that by these processes he converts the sewage matters 
 into cement. This is not a correct way of looking at 
 the matter. He adds to the sewage certain substances 
 from which cement can be made in the absence of 
 sewage. By these added substances the impurities 
 present are precipitated and entangled (in part, at least), 
 and when the deposit is calcined the organic portion 
 of such impurities is destroyed. But that the sewage 
 
126 SEWAGE TREATMENT. 
 
 matters contribute anything to the value of the cement, 
 or that the cement is in any way improved by sewage 
 having been implicated in its formation, is not proven. 
 The case is like the far-famed " pebble-soup " of the 
 mendicant friar, or the petroleum soap of the American 
 " crank." 
 
 Concerning the quality of the cement thus obtained 
 practical men have given their opinions, and, so far as 
 the writer learns, these are not flattering. 
 
 The charge of destruction brought against this pro- 
 cess, and every other where it is sought to convert 
 sewage matters into cement, ballast, bricks, or other 
 non-manurial products, is based upon the following facts : 
 The free ammonia, and that present in ammoniacal 
 salts, will be expelled by the excess of lime added, and 
 will escape in the gaseous form ; or, if in part entangled 
 in the precipitate, it must be driven off in waste during 
 calcination. The organic nitrogen will, in part, be pre- 
 cipitated, and will also be destroyed during calcination. 
 The phosphoric acid, in as far as it is rendered insoluble 
 by the excess of lime, will also be withdrawn from 
 circulation, being not indeed destroyed, but rendered 
 useless. Now, the supply of phosphoric acid and of 
 combined nitrogen in the world is not unlimited, and 
 as these substances are the scarcest items of plant-food, 
 their destruction or misapplication is a serious crime 
 against humanity in general, and ought in every way to 
 be discountenanced. 
 
PROMISCUOUS METHODS. 127 
 
 CHAPTER XII. 
 
 PROMISCUOUS METHODS. 
 
 WE consider here a number of systems of sewage treat- 
 ment which cannot be placed under any general head. 
 Foremost may come distillation. It has been repeatedly 
 proposed in patents, to collect the sewage in suitable 
 stills, with or without the previous addition of agents 
 to promote the liberation of ammonia, and to distil. 
 The ammonia, driven off by the heat is to be passed 
 into suitable vessels charged with sulphuric acid, and 
 thus absorbed and rendered marketable as sulphate of 
 ammonia. The methods for carrying out this process 
 vary in minor details. In some cases the raw sewage 
 is to be distilled ; in others the effluent from some pre- 
 cipitation process; and in others, again, the sewage-mud, 
 if from any cause it is not applicable as manure, is to be 
 submitted to destructive distillation. One circumstance 
 first pointed out by Professor J. A. Wanklyn is much 
 in favour of these distillation processes. That is, the 
 ammonia is given off almost entirely at an early stage 
 of the distillation. In some of these processes the 
 separation of the ammonia from the sewage is promoted 
 by driving through it a current of hot air, or steam. 
 
 The great difficulties in the way of these distillation 
 processes are I. The enormous size, or number, of the stills 
 needed for treating the sewage of a large town, and the 
 
128 SEWAGE TREATMENT. 
 
 question : 2. What is to be done with the residual 
 liquor? For the ammoniacal salts in the sewage, which 
 alone are extracted by this process, if perhaps the most 
 saleable, are not the most dangerous or noisome con- 
 stituents of sewage. The residual liquor will contain 
 the organic carbon and organic nitrogen, the nitrates, 
 nitrites and phosphates, and must be disposed of either 
 by irrigation, filtration, or by a precipitation-absorption 
 process. 
 
 One system of distillation escapes some of these ob- 
 jections, by means of extreme complication. The sewage 
 as it enters the works passes through a series of revolving 
 gratings, becoming successively finer and finer. In this 
 manner are arrested corks, lumps of soap, fatty matters, 
 hair, rags, etc., and these materials are said to be capable 
 of profitable utilization. Whether they can ever be 
 cleansed and disinfected so as to make them again fit 
 for coming in contact with the human person or with 
 articles of human consumption, is, perhaps, open to 
 doubt. 
 
 After escaping from the revolving screens the sewage 
 runs into tanks, where it is precipitated by the lime 
 process. 
 
 The operations now become twofold : a. The sewage 
 mud or sediment is collected, dried, and submitted to 
 destructive distillation in retorts similar to those used 
 in the gas manufacture. The nitrogen present in organic 
 combination will be driven off, chiefly as ammonia, and 
 may be collected by means of an acid scrubber, yielding 
 sulphate of ammonia. 
 
 The residue in the retorts, which will retain the phos- 
 phoric acid, may be sold as manure, provided that any- 
 one will buy it. 
 
PROMISCUOUS METHODS. 129 
 
 b. We return now to the effluent from the lime pre- 
 cipitation. This liquid is passed into large receivers, 
 from which the air can be almost entirely exhausted. 
 The effluent gives off its ammonia, which is pumped 
 into sulphuric acid, thus forming a second lot of sulphate 
 of ammonia. It is evident that this process must require 
 a costly plant. It is not evident that the lime effluent, 
 after the removal of its ammonia will be fit for admission 
 into a river without further outlay in the way of filtration 
 or irrigation. It will, of course, be alkaline. 
 
 Freezing by means of artificial cold has been pro- 
 posed for sewage treatment. There still prevails a notion 
 in some quarters that water, in freezing, rejects its im- 
 purities. Hence the idea was conceived that by applying 
 cold to sewage its pollutions might be concentrated in 
 the portion remaining liquid, whilst the ice formed 
 would be pure, and might either be thrown into any 
 river, or even sold for any purposes to which ice is 
 applicable. This entire process is founded on a mistake. 
 The suspended pollutions in foul waters are entangled 
 in ice during freezing just as are leaves, straw, etc., in 
 a pond. Nor is it very different with soluble impurities, 
 Ice from impure water has been found to contain 
 organic nitrogen and carbon, and has been recognised 
 as dangerous to health. Lastly, microscopic organisms 
 are not killed by freezing, nor even by much lower 
 temperatures, and resume their activity when the ice 
 thaws. 
 
 It must further be borne in mind that freezing sewage 
 on the large scale would be a very expensive process. 
 
 One inventor (No. 2,997, A - D - I 8/i) proposes to 
 reduce the temperature of the air above the tank " by 
 allowing liquid carbonic acid to evaporate into it." 
 
130 . SEWAGE TREATMENT. 
 
 Cheaper methods of obtaining cold are now available, 
 but even by the most economical process the partial 
 freezing of the sewage of a town of moderate size would 
 be a most costly undertaking. Some advocates of 
 freezing recommend that precipitating agents should 
 be added to the sewage before or after refrigeration, a 
 step which would improve the result, but, at the same 
 time, swell the working cost. 
 
 Another agent recommended is electricity, generally 
 in combination with other processes or agencies. Thus 
 C. F. Kirkman (No. 2,653, A.D. 1870) proposes a filtration 
 process, but suggests that on its way to the filters the 
 liquid should pass through a receptacle in which are a 
 number of zinc and copper plates, by which arrange- 
 ment " a continuous current of electricity is made to 
 pass through the sewage water, and will materially aid 
 in freeing it from its manurial properties." 
 
 F. H. Atkins (No. 556, A.D. 1873) also proposes to 
 apply " galvanic, magnetic, or electrical action to 
 filtering apparatus, reservoirs, or tanks, for the purpose 
 of precipitating organic and inorganic matters or im- 
 purities held in suspension or solution in the water or 
 other liquids." He arranges plates in the tanks, and 
 passes magnetic or electric currents through the liquid 
 by using such plates as electrodes. 
 
 E. H. C. Monckton (No 265, A.D. 1874) proposes to 
 use " electrified channels " for purifying sewage, or to 
 drive ozonised water (ozonised, it would seem, by 
 electric action) into sewage. He likewise proposes to 
 employ windmills to generate electricity, which may be 
 used for purifying sewage. 
 
 On these and other similar processes it may be re- 
 marked that magnetism has not been found to have any 
 
PROMISCUOUS METHODS. 131 
 
 distinct power of occasioning chemical decomposition, 
 and that special experiments have yielded no definite 
 results. With electric currents the case is different 
 From experiments on a small scale, the writer is disposed 
 to conclude that imperfect effluents from any kind of 
 process might thus be brought up to a high degree of 
 purity. On the question of working cost it is difficult 
 to decide, but probably where there exists a fall of water, 
 or other inexpensive means of turning a dynamo-electric 
 machine, the process might be practicable. 
 
 Contact with bundles of iron wire has been suggested. 
 I am not aware that it has ever been actually tried, nor 
 does its manner of action seem intelligible. It is not 
 said that the wire is to be formed into a filter or strainer. 
 
 It may seem surprising that desiccation, in other 
 words, simple drying up, has been recommended as a 
 method of dealing with sewage. The writer is not aware 
 that this process has been tried or even suggested for 
 raw sewage. But it has been proposed to get rid of the 
 (< solids," to expel the ammonia by the addition of lime, 
 and then receive it in sulphuric acid. The water, after 
 being thus deprived of its suspended matter and am- 
 monia, was to be evaporated to dryness in covered 
 vessels, so arranged that the fumes should be carried 
 through a furnace and up a chimney. The great ex- 
 pense of treating sewage by any process in closed tanks 
 makes it unnecessary for us to examine this proposal 
 any further. 
 
 Here also must be mentioned a system in which 
 cement is used as a precipitating or absorbing agent 
 W. H. Hughan (No. 2,883, A.D. 1868) adds powdered 
 cement to sewage in the sewers, and then delivers it into 
 a tank " where precipitation takes place." The sludge 
 
132 SEWAGE TREATMENT. 
 
 is then mixed with more cement, until the required 
 degree of consistency is obtained. Here it would seem 
 that the cement is to be added until the whole is brought 
 to the consistency of ordinary mortar. Portland or 
 Roman cement is used, but along with it I part of 
 copperas to 6 parts of cement, or the material may be 
 calcined. How such a deposit can serve as a manure is 
 not easily understood, if we consider that the cements 
 above-mentioned contain from 54 to 56 per cent, of 
 lime, from 21 to 36 of alumina, and from 8 to 15 per 
 cent, of oxide of iron, and that they further quickly 
 " set " to a hard mass with water. 
 
 " Screening," as distinct from filtration, has had its 
 defenders, especially in the earlier days of the sewage 
 question. Certain inventors arranged very elaborate 
 screens of gratings, wire gauze, etc., and were evidently 
 of opinion that when the visible suspended impurities 
 were removed the water might be safely admitted into a 
 river. It is plain that the purification thus effected, un- 
 like that of an earth or a carbon filter, could be merely 
 mechanical, and that the more dangerous part of the 
 impurities remain. 
 
 A peculiar method of treating, or rather of partially 
 utilizing, sewage has been proposed by A. M. Graham 
 (No. 4,791, A.D. 1876). This inventor precipitates the 
 sewage, first rendering it alkaline, by any suitable pro- 
 cess, preferably by the use of a salt of alumina, iron, 
 or manganese. The sediment thrown down is treated 
 with sulphuric or hydrochloric acid, and heated in a 
 retort until the fatty acids, water, etc., are driven off. 
 The fatty acids are then collected from the water. 
 
 It is a fact that a certain quantity of fatty acids can 
 thus be recovered, but it is very doubtful whether the 
 
PROMISCUOUS METHODS. 133 
 
 product recovered could cover the expense of the pro- 
 cess. Large consumers of soaps generally collect the 
 waste lyes separately and recover the fatty matter. 
 
 Perhaps this is the place to notice the so-called 
 " Metropolitan system," that, to wit, which the Metro- 
 politan Board of Works seem about to apply to the 
 sewage of London. The first stage is precipitation with 
 a small quantity of lime (3^ grs. per gallon) and copperas. 
 The effluent is then to be dosed with a mixture of 
 the permanganate of soda and sulphuric acid. Next 
 follows aeration, air being forced through the water in a 
 multitude of fine bubbles. Lastly, the deposit is to be 
 put on board ship, carried out and sunk in the North 
 Sea ! This will doubtless remind the reader of Dr. 
 Abernethy's celebrated receipt for dressing cucumbers. 
 It need only be pointed out that in this process the 
 entire expenditure is incurred in pure waste, no value 
 being recovered from the sewage. 
 
134 SEWAGE TREATMENT. 
 
 CHAPTER XIII. 
 
 SELF-PURIFICATION CELLULAR CHEMICAL 
 TREATMENT. 
 
 THIS subject must be viewed in two different lights, 
 according as we refer to tanks filled with sewage, or to 
 rivers more or less polluted with the sewage of towns and 
 with industrial waste waters, That sewage left to itself 
 in tanks or pools will become spontaneously purified 
 must, practically speaking, be denied. If it be allowed 
 to stand exposed to air and light for a time longer or 
 shorter according as its quantity is larger or smaller, 
 and its foulness more or less intense, and if the access 
 of fresh supplies of putrescible matter is completely 
 excluded, there comes, indeed, a point when the most 
 palpably offensive phases of putrefaction are at end. 
 Bubbles of gas are given off rarely or not at all, and 
 fetid matter is no longer deposited. The water may 
 even have become limpid and colourless, but it would 
 be very hazardous to regard it as pure. The pool will 
 have become a nursery for micro-organisms, possibly 
 including disease germs, and a sediment of foul mud 
 will remain at the bottom. Moreover, during the whole 
 time of exposure the pool or tank will have been a 
 serious nuisance to all persons living near or even pass- 
 ing by it. On these grounds, and also because the time 
 and the space required for this imperfect self-purifica- 
 
SELF-PURIFICA TION. 135 
 
 tion are both excessive, I am not aware that anyone 
 now in Britain, at least, seriously proposes to deal 
 with the sewage of a town on this principle. A 
 number of patents were at one time taken out for dealing 
 with sewage by simple subsidence without the aid of any 
 agent, occluding, precipitating, or deodorising. The 
 clear liquid was then to be let off into a river or into the 
 sea, and the deposit was to be dealt with in various 
 manners, as if it were either the most valuable or the 
 most dangerous portion of the sewage. Some of the 
 patentees had, indeed, the discretion to suggest that the 
 gases and fumes given off from the subsidence tanks 
 should be passed through a furnace or up a high 
 chimney-stalk. 
 
 Treatment of sewage by simple subsidence was once 
 tried at Knostrop, near Leeds, at the suggestion of an 
 official. When, a few days afterwards, the Sanitary 
 Committee of the Town Council went to see or smell 
 not one of them, it is said, ventured within some 
 yards of the tank. But all experiments made formerly 
 in this direction, and all opinions expressed as to the 
 practicability of subsidence, may be passed over in 
 charitable silence. 
 
 For waste waters, not containing any sewage, in the 
 strict sense of the term, but rich in carbo-hydrates, 
 fermentation is much employed on the Continent. 
 Urine, and sometimes lime, or any other agent deemed 
 suitable, may be added to quicken fermentation. Thus 
 refuse waters from sugar works have first been allowed 
 to subside so as to remove the coarser suspended matters. 
 Then followed treatment with precipitating agents 
 (sometimes spoken of abroad as molecular chemical 
 treatment), and the effluent was next brought into fer- 
 
136 SEWAGE TREATMENT. 
 
 mentation in separate tanks. Lastly, the water was used 
 for irrigation. Concerning this very circumstantial and 
 necessarily costly process, it must be remarked that pre- 
 cipitating agents, so far as it is at present known, take 
 very little effect upon sugar existing in solution. But 
 the preliminary subsidence process, prior to the addition 
 of the precipitants, is utterly needless, a mere waste 
 of time and of plant. It will be at once understood 
 that the fermentation process (cellular treatment) cannot 
 be carried out in the same tanks as precipitation. For 
 fermentation it is desirable that the water should be 
 slightly alkaline. Hence the effluent from the precipita- 
 tion tanks must receive a small dose of lime, of urine, 
 or of wood ashes. 
 
 As regards the self-purification of rivers more or less 
 polluted with sewage, with the drainage of manured and 
 cultivated lands, and with the waste waters of factories, 
 we find eminent authorities expressing the most con- 
 flicting views. Perhaps, indeed, these differences are 
 more seeming than real. Different chemists and micro- 
 scopists may not attach precisely the same meaning to 
 the terms " pollution " and " purification." Further 
 must be considered the relative proportions of the 
 volumes of sewage, and of the river into which it falls. 
 If a large, pure, and tolerably rapid stream, receives at 
 some one point sewage to the extent of, say, one 
 twentieth of its own volume, we have evidently one set 
 of conditions. But if a small, sluggish stream, receives 
 foul waters all along its course, and that, moreover, in 
 large volumes, the case is essentially different. What is 
 true in the one instance may be utterly untrue in the 
 other. 
 
 It cannot be denied that, unless the pollution of a 
 
SELF-PURIFICA TION. 137 
 
 stream has reached a very great height, there are certain 
 natural agencies which very much reduce the extent of 
 its impurity. Some years ago, an eminent French 
 chemist, Gerardin, proposed to estimate the relative 
 purity of waters by the proportion of free oxygen, which 
 they were found to contain in solution, and which he 
 proposed to determine by the method of Schutzen- 
 berger and De Lalande. The details of this method 
 need not occupy us here. Among other waters which he 
 examined were those of the river Vesle, above and below 
 Reims. As this town is the seat of thriving woollen 
 manufactures, the Vesle is polluted in a very similar 
 manner to the Aire at Leeds, with refuse of the most 
 varied kinds, organic and inorganic. The investigator 
 found that at a few miles above the town the water con- 
 tained a normal proportion of free oxygen. Approaching 
 to Reims, and receiving the waste waters of the woollen 
 mills, it showed a smaller and smaller percentage of free 
 oxygen and a minimum in this respect, with a corre- 
 sponding maximum of organic pollution was reached a 
 little below the town. Afterwards, as the stream con- 
 tinued its course through an open agricultural country, 
 the proportion of oxygen again increased, and at the 
 distance of about 20 miles below Reims it showed the 
 same percentage of dissolved oxygen as had been 
 observed above the town. At the same time there were 
 observed a series of changes in the organic forms inhabit- 
 ing the river, which seemed to proceed step by step 
 with the decrease and then with the increase of oxygen 
 dissolved in the water. To these changes I must beg 
 to call special attention elsewhere. Our present concern 
 is merely with the fact that the river Vesle became pol- 
 luted by the filth of a manufacturing city, and afterwards, 
 
138 SEWAGE TREATMENT. 
 
 from a chemical point of view, at least, returned to its 
 former condition without having been submitted to any 
 artificial process of purification. 
 
 We may take another case nearer home. In the year 
 1868, with a view of throwing light upon a scheme in 
 contemplation for purifying the waste waters of some 
 extensive dye-works, the present writer visited a branch 
 of the Calder and Hebble navigation, which extends 
 from the lower end of the town of Halifax down to the 
 village of Salter Hebble, about i mile off, where it 
 joins the main trunk of the Calder. The descent is so 
 steep that the canal is merely a series of pools separated 
 by locks, and at its origin in the town it is fed not 
 with water, in the ordinary sense of the word, but with 
 sewage from the shallow river Hebble, which receives 
 the refuse, domestic and manufacturing, of the town. 
 Having inspected the canal basin, where the water was 
 very foul and turbid, and emitted an offensive smell, I 
 walked along the towing-path, carefully noting the 
 phenomena manifested. For the first two or three 
 locks there was no material change ; no animal life 
 could be detected in the water, and no plants were 
 seen except sewage fungus, which had here and there 
 attached itself to stonework, piles, etc. When about 
 half the length had been traversed water weeds began 
 to make their appearance at first few and by no means 
 flourishing. They quickly became more numerous, 
 both in individuals and species, as well as more healthy 
 looking. The water exhibited a corresponding change 
 both in colour and smell. The canal, it must be added, 
 was very sparingly used, and its successive pools might 
 be regarded as a series of subsidence tanks. Hence it 
 appears that subsidence and exposure to air alone will 
 
SELF-PURIFICA TION. 1 39 
 
 bring impure water in the absence, at least, of certain 
 mineral poisons to a state which permits of the exist- 
 ence of aquatic plants and of insect life. This point 
 being once reached, a further and considerable im- 
 provement is effected by these natural agencies. 
 
 Another case of self-purification, effected on a far 
 larger scale, though in a water probably much less pol- 
 luted than that of the Hebble, as just mentioned, is 
 described by Prof. A. R. Leeds, Ph. D., in his report on 
 the water supply of Wilmington (Wilmington, Dela- 
 ware: James & Webb). This eminent and experienced 
 chemist goes further than I should venture, since he 
 pronounces that " there is no foundation in fact for 
 the oft-repeated statement that water once polluted 
 by sewage can never again become safe for drinking 
 purposes." He relies on the various natural purifying 
 agencies constantly at work, giving especial promi- 
 nence to the action of aquatic plants, and to that 
 of the finely-divided earth washed into rivers by 
 the rains, the former influence oxidising in other 
 words, burning up and the latter occluding and pre- 
 cipitating the organic impurities. In proof of the effi- 
 cacy of these natural agencies, he refers to the River 
 Passaic, pure above the town of Paterson, but polluted 
 by the sewage and the manufacturing refuse of that 
 town. He writes : " The river immediately below the 
 town is black with dye-wares, the fish carried over the 
 great falls are immediately poisoned, and I have seen 
 the foul-smelling and disgusting water covered with 
 their floating carcases." Yet samples of water taken at 
 intervals of a mile apart down the river show a regular 
 decrease in the organic pollution, and an improvement 
 in the quality, until at a point 16 miles below Paterson 
 
140 SEWAGE TREATMENT. 
 
 the river has returned to a condition of purity not much 
 inferior to that which it exhibited above Paterson, and 
 at this point it is used as a water supply for the 300,000 
 inhabitants of Jersey City and Newark. 
 
 Another case of self-purification in a river is reported 
 by Dr. F. Hulwa, in the Gesundheits Ingenieur. He 
 has found experimentally that the water of the Oder, 
 after receiving the sewage and other liquid refuse of 
 Breslau, is purified by the oxygen of the atmosphere, 
 and by the action of vegetation. Fourteen kilometres 
 (about 8 miles) below Breslau the sewage matters can 
 neither be detected microscopically nor chemically, and 
 the water of the river was of the same quality as above 
 the town. 
 
 An excellent illustrative case is supplied by the Seine 
 below Paris. Immediately below Paris, say at St. Ouen, 
 the water is very filthy ; at Epinay and Argenteuil fish 
 reappear. At Beyon water plants grow luxuriantly, 
 whilst at Meulon and Vernon pollution may be said to 
 have disappeared, and the water is actually purer than it 
 is at some distance above Paris. The total nitrogen 
 in the water at Agnieres above Paris (not to be con- 
 founded with Asni^res below the city) is 1*5 gramme 
 per litre; at Clichy and St. Denis 4*0 to 7*0 
 grammes ; at Meulon and Vernon respectively 2 '2 and 
 I '4 gramme. 
 
 Further instances of this kind might be brought 
 forward were it at all necessary. But those already 
 given may be fairly held to prove that, under certain 
 favourable conditions, polluted river waters may be 
 purified by natural agencies without any special human 
 intervention. It may be well to fix the degree to 
 which such purification may extend. I have seen no 
 
SELF-rURIFICA TION. \ 4 1 
 
 instance where a river when once polluted with sewage 
 has become spontaneously fit for drinking and cookery. 
 But I should be very reluctant to drink the effluent 
 from the most successful precipitation process, passed, 
 for additional security, over a new irrigation field. Yet 
 self-purified rivers may reach such a relative point of 
 purity that they no longer offend the eyes and the 
 nose, and that their proximity has no perceptible effect 
 upon public health. Such a stage is, perhaps, the 
 utmost that can be demanded from rivers, even in 
 uninhabited countries. 
 
 But the relative purity in question is reached only 
 under certain special conditions not everywhere met 
 with. The volume of polluting liquid must be small 
 compared with that of the river itself, and, above all, 
 fresh supplies of sewage must not be introduced every 
 couple of miles. These conditions are plainly wanting 
 in the case of English rivers in the manufacturing dis- 
 tricts. They are, comparatively speaking, small, their 
 flow is, in the summer, often scanty ; and even when 
 they do not pass through towns their banks are gar- 
 nished with a succession of cotton and woollen factories, 
 chemical works, dye and print works, etc. Thus the 
 natural purifying agencies, whatever their efficiency, 
 have no opportunity to come into play. Further, so 
 much of the matter poured into these streams is of a 
 poisonous character that water weeds, the great oxidising 
 agents, cannot grow. Even the dreaded sewage fungus 
 (Beggiatoia alba) may be unable to flourish. 
 
 But the great reason why we cannot trust to self-puri- 
 fication in the case of rivers is that it requires prolonged 
 exposure to the air, during which time the water is 
 unfit for almost every imaginable use, domestic or 
 
I 4 2 SEWAGE TREATMENT. 
 
 industrial, and the vapours given off are offensive, if 
 not positively dangerous to health. We want a much 
 more speedy system of treatment, and which shall not 
 in the meantime create nuisances as great as, or 
 possibly greater than, those which it is intended to 
 correct. 
 
DETECTION OF SEWAGE POLLUTION, 143 
 
 CHAPTER XIV. 
 
 DETECTION OF SEWAGE POLLUTION IN RIVERS 
 AND WELLS. 
 
 WHERE the degree of pollution in a stream is excessive 
 whether caused by town sewage in the ordinary sense 
 of the term, or by industrial waste waters no special 
 methods of investigation are needed. An ordinary pair 
 of eyes, an ordinary nose, with the will to use them, and 
 to tell truthfully what has been observed, is fully suffi- 
 cient. If the water of a river, viewed in bulk, looks 
 blackish and opaque ; if bubbles of gas are seen ascend- 
 ing to the surface and bursting, occasionally, perhaps, 
 bringing up with them lumps of filth, and if in calm 
 weather the smell is decidedly offensive, no further in- 
 quiry is needed. As instances may be mentioned the 
 Irwell, Irk, and Medlock at Manchester, the Clyde be- 
 low Glasgow, the Mersey at Widnes, the Soar at Lei- 
 cester, the Calder at Brighouse and Mirfield, the Aire 
 at Leeds, and, generally speaking, the rivers below any of 
 our manufacturing towns. But there are many cases 
 where the degree of pollution, though less excessive, is 
 yet enough to render the water unfit for all domestic 
 and for most manufacturing purposes. To judge of 
 these, attention must be specially directed to certain 
 points which may easily escape the attention of the 
 general public. I must, therefore, invite my readers to 
 
1^4 SEWAGE TREATMENT. 
 
 form themselves into a volunteer " Rivers' Pollution 
 Commission," unpaid, but honest, and not mainly in 
 search of evidence to support pre-conceived notions. 
 Let them then kindly accompany me in an imaginary 
 stroll along the banks of a stream. 
 
 We will first take the river as it flows through a rural 
 district. We do not, of course, find here the transparency 
 of the Leven where it issues from Loch Lomond, of 
 the Dudden, or the Derwent. But we see fishes darting 
 through the waters, the whirligig-bettle is spinning 
 merrily round, singly and in little groups ; Dytisci 
 plunge to the bottom on our approach, water-boatmen 
 and water-scorpions are searching for prey, whilst bril- 
 liant dragon-flies are wheeling on high over the stream. 
 The shallows are lined with arrow-heads, reeds, flags, 
 and the water-iris. In quiet pools the water-lilies lie at 
 anchor, spreading out their broad leaves, and, if we 
 have come at the right season, their beautiful flowers. 
 In short, animal and plant-life, adapted to the water, 
 are to be seen in all their variety and luxuriance. 
 
 We dip up a small glass jar of the water and hold it 
 up to the light. We might not, perhaps, select it as a 
 beverage, or like our food to be cooked in it. It receives, 
 undeniably, the drainage from ditches which traverse 
 manured fields. Here and there, too, we may have 
 seen a cottage near the banks, which may have contri- 
 buted its driblet of animal and vegetable contamination. 
 May, we say, because the night soil, the soap-suds, and 
 other impurities from such cottages are more apt to 
 find their way into the garden plot than into the stream. 
 But, in spite of all such possible pollutions, the water 
 looks fairly clean, and gives off no smell, and as we throw 
 it away, we must admit that numbers of our country- 
 
DE TECTION OF SE WA GE POLL UTION. 145 
 
 men of all ranks are drinking worse water, did they but 
 know it. 
 
 Now let us suppose that the stream, in accordance 
 with that " beneficent arrangement of Providence " which 
 has moved a modern rhetorician to an eloquent out- 
 burst, approaches a small town, free from manufactures 
 and unharrassed by " injunctions " concerning river 
 pollution. Here it will be found that every householder 
 uses the stream as a general receptacle for liquid refuse, 
 and too often for solids also. If we now carefully ex- 
 amine the river below the town, where the banks are no 
 longer interfered with by buildings, we shall see that a 
 change has taken place. The water has become dis- 
 tinctly duller, more opaque, less free from colour, and 
 gives out a smell, not yet exactly to be called a stench, 
 but tending in that direction. If we stir up the mud 
 at the bottom with a stick, we shall generally see bubbles 
 of gas arising. Most especially a change comes over 
 the character of the vegetation. Some species will have 
 disappeared altogether ; others exist, but they do not 
 flourish. 
 
 Here, however, we must point out an error into which 
 not a few authorities have fallen. It has been believed 
 that watercress, growing along the margin of a stream, 
 or in ditches communicating with it, is a proof of the 
 absence of sewage pollution. This assertion at once 
 struck me as being little in harmony with my own ob- 
 servations and those of my friends. Mr. C. Cresswell, 
 Q.C., of Isleworth, a gentleman well-known for his in- 
 telligent zeal in the cause of sanitary reform, came upon 
 a ditch which received the entire sewage and household 
 slops from a row of about a dozen cottages. Yet it was 
 filled with the most luxuriant watercress, which, sad to 
 
 L 
 
146 SEWAGE TREATMENT. 
 
 say, appeared to be regularly cut for sale. To decide 
 the matter, I performed a somewhat extensive series of 
 experiments at Aylesbury in the summer and autumn 
 of the year 1878. Earth was placed at the bottom of 
 four small movable tanks, and in each were planted 
 healthy roots of watercress. The tanks were then filled 
 respectively with town sewage, undiluted, and taken 
 directly from the sewer mouth ; with similar sewage after 
 treatment with clay, carbon, and aluminium sulphate ; 
 with water from a feeder of the river Thame, which 
 flows past the town, receiving the drainage of manured 
 and cultivated lands, and, I believe, sewage from scat- 
 tered cottages along the upper part of its course, and 
 with the excellent drinking water supplied by the Chil- 
 tern HillsjCompany. The loss by evaporation or leak- 
 age in each tank was made up by the regular addition 
 of the same kind of water as had been taken at first. 
 The result did not admit of a moment's doubt ; the 
 watercress planted in sewage not merely lived and grew, 
 but far surpassed the other three lots in luxuriance and 
 vigour, and continued so to do until the experiment was 
 broken off by the frosts in the beginning of winter. 
 
 Hence it may surely be concluded that the presence 
 of watercress in any stream or pond affords no proof 
 of the purity of the water. It must be understood, 
 however, that the sewage made use of, though unusually 
 rich in faecal matters, blood from slaughter-houses, and 
 other animal pollutions, was perfectly free from manu- 
 facturing refuse. I have never come upon or heard 
 of any case of watercress found growing in a stream 
 which receives the waste waters of chemical works, dye 
 works, woollen factories, etc. ; but as the sewage in 
 question contained very much less free oxygen in 
 
DETECTION OF SEWAGE POLLUTION. 147 
 
 solution than the Chiltern Hills' water, or even the river 
 water, it is plain that the growth of the higher vegetation, 
 i.e., green plants as distinguished from grey fungi, does 
 not follow, step by step, the rising or falling proportion 
 of such oxygen in the water. We may, indeed, ask why 
 should it? It can scarcely be needful to remind the 
 reader that all green plants in other words, all plants 
 which develop chlorophyll in their tissues give off 
 oxygen on exposure to the sun, or even to diffused day- 
 light. Hence water plants are not so much the effect as 
 the cause or at least one great cause of the presence 
 of free oxygen in water. Their absence in highly 
 polluted streams is due not so much to a deficiency of 
 oxygen, as to some positive injurious agency, whether 
 acids, alkalies, or metallic compounds. In the absence 
 of such plant-destroyers, green vegetation is very 
 efficient in freeing water from excrementitious pollution. 
 There are, of course here, certain limits ; solutions of 
 putrescent animal matter may be too concentrated to 
 admit of vegetable life, just as liquid manures may be 
 applied in too strong a dose. This is a point rarely 
 reached in any stream, and when green plants are absent, 
 we may generally seek the cause in the waste waters of 
 some manufacturing establishment. Town sewage, when 
 treated by any process which leaves in it a large pro- 
 portion of any compound of lime, is also unfriendly to 
 aquatic vegetation. The sanitary authorities of a large 
 manufacturing town were advised by the late Mr. Smee 
 to plant Elodea Canadensis in the outer tank of their 
 sewage works, and to attempt the growth of reeds and 
 sedges around the margin. The advice was in itself 
 excellent, inasmuch as such vegetation would have 
 completed the purification of the sewage. But, as the 
 
148 SEWAGE TREATMENT. 
 
 process adopted involved the daily consumption of about 
 fifteen tons of lime, we can scarcely wonder if the plants 
 failed to survive. As far as the writer has observed, 
 natural streams of very hard water are not rich in 
 aquatic vegetation. 
 
 We have now to turn to the animal world, and ask 
 whether the presence or absence of fishes can be said, in 
 general terms, to be solely or mainly dependent upon 
 the greater or smaller proportion of free oxygen in the 
 water ? Or to put the same thing in a slightly modified 
 form, upon the smaller or larger proportion of decom- 
 posing organic matter in the stream, since we have 
 already noted that where such organic matter is most 
 abundant, there free oxygen must exist in the smallest 
 proportion or be entirely wanting. That free oxygen, 
 or, as it is commonly called, a " good aeration " of the 
 water, is necessary for fishes must be known to even the 
 most careless proprietor of an aquarium. We may, 
 therefore, safely say that if free oxygen is wanting, fishes 
 will be wanting likewise. But can we draw the converse 
 inference, that if fish are wanting oxygen must be 
 deficient ? By no means. There are various substances 
 which occasionally find their way into rivers, and prove 
 very widely fatal to fish, but which are not calculated 
 to effect any decrease in the proportion of dissolved 
 oxygen. We may take an instance given on very 
 good authority, and briefly recorded in fat Journal of 
 Science for 1880 (p. 213). Dr. Auerbach during an 
 entire summer observed certain water-beetles from his 
 description evidently Gyrimis natator living in tanks 
 full of a saturated solution of sodium sulphate (Glauber's 
 salt). When alarmed, these little beetles dived down, 
 and hid themselves among the crystals that were 
 
DE TECTION OF SE WA GE POLL UTION. 149 
 
 forming, just as they would do among the plants in 
 a pool. But a little of this liquid, thus harmless to 
 certain insects, happened to escape from the tanks by 
 leakage, and found its way along a ditch into a river at 
 some distance, where it proved fatal to a multitude 
 of fish. It can certainly not be contended that a small 
 quantity of a solution of sodium sulphate added to the 
 water of a river would either appropriate or expel the 
 free oxygen, yet we see that it turned the scale between 
 life and death. 
 
 Cream of lime thrown into a stream will, as it is 
 universally known, seize upon carbonic acid, leaving 
 any oxygen it may encounter unaffected. 
 
 The presence of fish is certainly no proof of the 
 absence of faecal matter. At Kingston, just where the 
 sewage of the town entered the Thames, in the spring 
 of 1875 it may possibly have since been diverted I 
 have seen fish darting about in numbers, and I learnt 
 that the sewer mouth was a favourite spot for anglers. 
 But where the volume of sewage is small as compared 
 with the volume of the river into which it flows, such 
 pollution by no means necessarily involves a deficiency 
 of free oxygen. In recent sewage there are also various 
 matters which certain fishes will eat greedily, though 
 with doubtful benefit to their health. At least it is 
 asserted that fish caught in polluted waters enter into 
 decomposition with exceptional rapidity, a probable 
 indication that their entire system is in a bad condition. 
 
 Among amphibious creatures frogs are found in pure 
 waters, and in those but slightly polluted, and the same 
 may be said of newts. If either excrementitious or 
 manufacturing refuse is introduced in appreciable 
 quantity, they withdraw. 
 
ISO SEWAGE TREATMENT. 
 
 The presence of aquatic insects is not a character 
 from which any definite conclusion can be drawn, though 
 where industrial waste waters are to be found in 
 quantity they are generally wanting. Thus I have 
 never seen either larvae or adult insects in the Bridge- 
 water Canal, or the Irwell below Manchester ; in the 
 notorious Sanky Brook, in the Aire below Leeds, the 
 Kelvin Water, or similarly polluted streams. But in 
 rivers fouled with putrescent vegetable refuse or faecal 
 matter they often abound. On the contrary, in the very 
 purest water they are necessarily absent, as finding there 
 no food. It would be interesting to find what is the 
 minimum of impurity at which the larvae of gnats and 
 bloodworms (Cheironomus plumosus) are able to exist, 
 and what is, if any, their maximum limit. 
 
 These larvae are frequently found in water-butts and 
 cisterns, which have no other source of contamination 
 but the organic matter of dust. Still, I would suggest 
 that no water, in which these larvae are present, should 
 ever be used for domestic purposes, since their excre- 
 tions, as far as the writer has been able to observe, set 
 up in organic matter decomposition of an exceedingly 
 offensive and probably dangerous type. This character 
 of their juices may possibly explain the irritating and, 
 in some cases, even dangerous effect of the bite of sand- 
 flies, mosquitoes, and pollution-fed diptera in general. 
 
 Water beetles, such as A cilius sulcatus, Colymbetes of 
 various species, etc., and also certain Hemiptera, may be 
 found in water, which, from the absence of known 
 sources of pollution, and from chemical and microscopi- 
 cal examination, may be pronounced potable. But they 
 are also met with in pools fed by the surface drainage of 
 manured fields and pasture lands. As a rule, it may be 
 
DE TECTION OF SE WA GE POLL UTION. 1 5 1 
 
 said that animals which prey upon living animals or 
 upon growing plants are not, in themselves, a bad symp- 
 tom. All such as consume comminuted or putrescent 
 matters, animal or vegetable, must be considered ques- 
 tionable, as proving the presence of the matter upon 
 which they subsist. 
 
 But we must now return to our river, once fairly pure, 
 but now polluted by its wanderings among the dwellings 
 of man. Let us suppose the contaminations increase to 
 such a degree that the green water plants become per- 
 ceptibly less plentiful and less flourishing. If we now 
 look carefully into the water at the margin of the stream 
 and examine piles, piers of bridges, the roots of trees 
 projecting under water, we shall see a growth, which is 
 considered most characteristic of polluted waters. This 
 is so-called sewage fungus (Beggiatoa alba), a plant 
 which is much talked about, but which many redoubted 
 sanitary reformers and patentees of processes for the 
 purification of sewage appear never to have seen. They 
 often seem to suppose that it must have something of 
 the appearance of a mushroom or toadstool. This is a 
 complete error ; in form and colour it is not unlike a 
 bundle of tow, with the fibres running parallel to each 
 other and ending in loose tufts. Suppose such a bundle 
 fixed at one end to a stick, or a stone, or to the earth at 
 some little depth under water, and swaying to and fro 
 in the current, and you have a fair resemblance of 
 sewage fungus. The chief difference is that this unholy 
 and unlovely plant has a greater specific gravity than 
 hemp and flax, and tends to sink rather than rise if not 
 kept in a horizontal position by the current. The colour, 
 too, is modified by the particles of dirt which get en- 
 tangled in the fibres. What concerns us is neither the 
 
152 SEWAGE TREATMENT. 
 
 structure, nor the affinities, nor the chemical composition 
 of this fungus, but the conditions under which it exists, 
 and its consequent value as a sign of water pollution. 
 
 In the first place, contrary to the common notion, it 
 is not peculiar to sewage. It has been found in the 
 North of England in streams quite free from animal 
 pollution, but which receive the drainage from the heaps 
 of vat-waste^-the unpleasant residuary product of the 
 alkali manufacture on Leblanc's principle. It is found 
 in the escape waters of the medicinal sulphur springs of 
 the Western Alps and the Pyrenees. In short, what it 
 indicates is not necessarily animal pollution, but sulphur. 
 Without sulphur it cannot live ; and where it thrives, 
 sulphur in some form is certainly present. 
 
 It is almost, without exception, peculiar to running 
 water. Only once have I seen it formed under my eyes 
 in a jar of impure water. I have never seen it at the 
 sides of any pond or reservoir, whether of pure or of 
 polluted water, nor at the bottom of such pools, if 
 emptied. If planted in an aquarium for experimental 
 purposes, it hangs straight downwards from the stick 
 or root to which it has been found attached, and whether 
 kept in the light or in the dark, it shows no disposition 
 to spread. Moving water seems, therefore, essential to 
 its growth. If preserved in the dark it undergoes no 
 change for months, and seems unaffected by the most 
 powerful chemical agents, except in enormous propor- 
 tions certainly by no quantity which could be added 
 to the waters of a river. Chromic acid is not reduced 
 by it, even on prolonged contact. If, however, sewage 
 fungus is placed in still water and exposed to a strong 
 light, green confervae fix themselves upon it, overspread 
 it, and seem gradually to effect its destruction. Similar 
 
DE TECTION OF SE WA GE POLL UTION. 1 53 
 
 cases may be observed in shallow trenches, in which 
 partially purified sewage is flowing ; but where water is 
 still strongly charged with animal matter the fungus 
 appears to hold its own, especially if the depth and tur- 
 bidity of the stream interfere with the free action of 
 light. It need scarcely be said that sewage fungus is 
 never found in pure mountain streams, and but very 
 rarely in the brooks and ditches of rural districts which 
 receive the drainage of cultivated lands, except where 
 they are connected with some sewer. But if portions of 
 the plant are swept down out of a sewer e.g., by a 
 violent storm of rain they are able to live in running 
 water where the amount of pollution is exceedingly 
 small ; smaller, indeed, than the proportion specified as 
 to be tolerated in the far-famed " recommendations " of 
 the late " Rivers' Pollution Commission." If it be asked 
 how this is ascertained, I reply that I know a small 
 stream, which, down to a certain point, is absolutely free 
 from sewage fungus, as I have satisfied myself by care- 
 ful and repeated examination. At that point it receives 
 a stream of sewage effluent about the one-sixth part of 
 its own volume, and purified to such a degree that one of 
 the highest authorities on water analysis, after repeat- 
 edly examining samples taken at haphazard, has pro- 
 nounced it to fall well within the limits of the recom- 
 mendations just referred to. Yet the stream, after 
 receiving this infinitesimal dose of faecal matter, dis- 
 plays here and there a tuft of sewage fungus along with 
 a most luxuriant growth of green water plants. It must 
 further be noticed that, on following the stream down- 
 wards for a few hundred yards, the fungus disappears, 
 its pabulum having, without doubt, been burnt up by 
 the oxygen evolved by the higher plants. 
 
154 SEWAGE TREATMENT. 
 
 But whilst water may thus be too pure to supply the 
 sulphur and the other nourishment required by sewage 
 fungus, it may also be found, if not too impure, at least, 
 not to possess the right kind of impurity. I have made 
 frequent and most minute examination of the sewage of 
 Leeds, and of the results of the various processes which 
 have been adopted for its purification. But I have never 
 seen a trace of sewage fungus, either brought down the 
 sewers from the town or floating in the tanks, or in the 
 outflow channel, or where the latter vents into the filthy 
 river Aire. This absence was always distinct, what- 
 ever was the nature and the success of the process 
 adopted. 
 
 Again, the London sewage at the southern outfall has 
 never, in so far as I have had the opportunity of observ- 
 ing, contained a trace of sewage fungus. 
 
 The same may be said of the sewage of Paris, which 
 I have studied daily for some weeks at Gennevilliers. 
 On the other hand, a ditch at Wimbledon, which re- 
 ceived the sewage of the district, some of it treated and 
 some of it untreated, contained in the autumn of 1875, 
 some beautifully characteristic specimens. At Ayles- 
 bury, some years ago, it was swept down the sewers 
 from the town after heavy rains, and arrived at the 
 sewage works in quantity. For the last few years it has 
 almost totally disappeared. At Hertford, it has been 
 seen in great perfection in the outflow channel. 
 
 Hence we may probably conclude that sewage fungus 
 grows by preference in the rich sewage of residential 
 towns rather than in the waste waters, unless sulphuretted, 
 of the great manufacturing centres, or in the very dilute 
 sewage of London or Paris. When once fairly esta- 
 blished, it is, however, able to live on in relatively pure 
 
DETECTION OF SEWAGE POLLUTION. 155 
 
 water, It need scarcely be said that this fungus, con- 
 taining no chlorophyll, gives off no oxygen on exposure 
 to light, and, consequently, does not contribute, as does 
 green vegetation, to the purification of the water which 
 it inhabits. Of course it withdraws a certain quantity 
 of organic matter from the water so as to form its own 
 tissues, but this, on its ultimate decomposition will be 
 returned to the stream. 
 
 It does not appear to form the food of any animal, 
 certainly not of fishes, insects, the higher crustaceans-- 
 such as Astacus fluviatilis and mollusca. Infusoria 
 swarm among its fibres, probably as a place of shelter. 
 Nor can I learn that it has ever been tried as an article 
 of human diet. It might not here be impertinent to 
 express the wish that a certain person, who, some years 
 ago, wrote to the papers suggesting rats (sic /) foci of 
 Trichinae as food for the destitute, would kindly make 
 an experiment with sewage fungus in corpore suo vilis- 
 simo. It is certainly nitrogenous, possibly nutritious 
 and delicate, and just as possible poisonous. 
 
 Summing up the foregoing, we may fairly conclude 
 that neither vegetable nor animal life varies in any simple 
 relation with the quantity of free oxygen found in the 
 stream ; that all grey or whitish plant growths, when 
 existing alone indicate great pollution ; but where they 
 occur along with green plants, the impurities may be very 
 trifling. Yet, even vegetation of a relatively higher 
 grade, such as the watercress, gives no positive proof that 
 a stream is potable and wholesome. Perhaps the worst 
 sign of all is the total absence of all vegetation, except 
 its existence is rendered impossible by the rapidity of 
 the current, or by the nature of the banks. Lastly, it is 
 impossible to argue from ordinary town sewage, to 
 
156 SEWAGE TREATMENT. 
 
 industrial waste waters, or to a mixture of the two. 
 The influence of the former upon animal and vegetable 
 life is indeed distinct from that of the latter. 
 
 I have purposely avoided any attempt at giving in- 
 structions for the chemical or the microscopic examina- 
 tion of waters. The due performance of such operations 
 can be learnt only by actual practice in the laboratory. 
 Without such training, the experimentalist will find his 
 results utterly untrustworthy, and misleading. It some- 
 times even happens that experts of undoubted skill and 
 wide experience, arrive at results which are far from 
 accordant. I have heard of three identical samples of a 
 water being sent to three analytical chemists who have 
 made such investigations their speciality. One of the 
 three authorities declared the water quite unfit for drink- 
 ing, but fit for washing. The second pronounced it 
 admissible for drinking, but not suited for washing ; 
 whilst the third expert, taking higher ground, condemned 
 it for both purposes. 
 
 Considerable weight has of late been laid on a micro- 
 scopic determination of the number of living organisms 
 present in water as a clue to its quality. Thus, Profes- 
 sor Koch, in a recent publication, declares that " an 
 abundance of microbia in a water is proof that it must 
 have received an influx of liquids rich in decomposing 
 matter, and containing, among many minute organisms, 
 which may be innocent, possibly others which may be 
 pathogenetic, i.e., which may constitute the infection of 
 diseases." He continues : " As far as present know- 
 ledge extends, the number of micro-organisms in good 
 waters varies from 10 to 150 per cubic centimetre. If 
 the number exceed this limit, the water must be sus- 
 pected as contaminated. If it reaches 1,000, the water 
 
DE TECTION OF SE WA GE POLL UTION. 1 57 
 
 should be at once condemned, especially in times of 
 cholera epidemics." 
 
 Dr. Link, on the contrary, informs us in the ArcJiiv 
 der Pharmacie, and in the Chemiker Zeitung, that he has 
 examined a number of the well waters of Danzig, both 
 chemically and microscopically, the results being not in 
 accord with the opinion of Koch as above quoted. 
 On the contrary it became manifest that there prevailed 
 no regular relation between the results of the chemical 
 analysis and the number of bacteria as recognised by 
 the microscope. Many good well waters not directly 
 or indirectly exposed to animal contaminations con- 
 tained great numbers of micro-organisms. On the con- 
 trary, others, which had been found bad on chemical 
 examination, and had been undoubtedly polluted with 
 sewage, contained only very insignificant numbers of 
 bacteria undergoing development. We also consider 
 that the great majority, if not the totality, of bacteria 
 in a well water are probably of a harmless character, 
 and that even if a water is contaminated with patho- 
 genic germs, these will not generally find in well waters 
 the conditions necessary for their multiplication, espe- 
 cially in default of a temperature bordering on that of the 
 human body, and a due concentration of nutritive matter. 
 Hence it follows that the number of the micro-orga- 
 nisms present does not warrant us in pronouncing on 
 the character of the water, and may lead us to conclu- 
 sions in opposition to the results of chemical analysis. 
 The attempt to put forward microscopic examination as 
 a decisive means of ascertaining the quality of a water, 
 is for the present devoid of an adequate foundation. 
 
 To this criticism it may, however, be replied that 
 chemical analysis of waters in like manner fails to show 
 
158 SEWAGE TREATMENT. 
 
 whether their carbon and nitrogen are in the state of 
 harmless or pernicious compounds. 
 
 One very simple test which may be applied to any 
 apparently pure water, is to put a few ounces of the 
 sample in a perfectly clean bottle, close it with a glass 
 stopper, or with a new clean cork, and let it stand for 
 some days at a temperature of 60 to 70 Fahrenheit. 
 If on unstoppering the bottle it is found to give off an 
 unpleasant smell the water must be condemned. 
 
 This test applies as much to the water of wells and 
 springs as to that of streams. 
 
 In wells we are deprived of the help of certain signs 
 which in a stream indicate impurity. There is, or should 
 be, no visible life, vegetable or animal. The water 
 must be rejected for a domestic supply if it contain the 
 larvae of gnats, or the so-called blood worms. A very 
 bad sign is, if the water after having been undisturbed 
 for some time, e.g., early in the morning, displays an 
 oily scum on its surface. Minute bubbles of gases, ad- 
 hering to the sides of a glass in which the water has 
 been allowed to stand, are always to be regarded with 
 suspicion, since they may be due to the putrefaction of 
 organic matter. Some of the most deadly waters are 
 the most bright and sparkling. Wells in porous soils 
 such as chalks, sands, and gravels, are unsafe if there 
 are any cesspools in the neighbourhood. There is at 
 present no legal remedy for the pollution of a well by 
 impurities which leak into it underground. I am sorry 
 to say that the Bill brought into Parliament during the 
 session of 1885 by Earl Percy and others, did not pro- 
 pose to remedy this capital defect. 
 
 This is, perhaps, the place to touch upon proposed 
 regulations as to the quality of the waters which should 
 
DETECTION OF SEWAGE POLLUTION. 159 
 
 b'j allowed to pass into a river. This is a subject which 
 has been abundantly discussed. Every man and woman 
 in the kingdom, almost every child, must have heard of 
 the "Recommendations" of the late Royal Rivers' 
 Pollution Commission which have been so persistently 
 obtruded upon the public for about sixteen years, and 
 which, if last year's Sewage Bill had unfortunately been 
 passed, would have acquired legal sanction. 
 
 For convenience sake I must here reproduce them. 
 The Commissioners proposed to exclude : 
 
 a. Any liquid containing, in suspension, more than 
 three parts by weight of dry mineral matter, and one 
 part by weight of dry organic matter, in 100,000 parts by 
 weight of the liquid. 
 
 b. Any liquid containing, in solution-, more than two 
 parts by weight of organic carbon, and 0*3 part by weight 
 of organic nitrogen, in 100,000 parts by weight of the 
 liquid. 
 
 c. Any liquid which shall exhibit by daylight a dis- 
 tinct colour, when a solution of it, one inch deep, is placed 
 in a white porcelain or earthenware vessel. 
 
 d. Any liquid which contains, in solution, in 100,000 
 parts by weight, more than two parts by weight of any 
 metal except calcium, magnesium, potassium, and 
 sodium. 
 
 e. Any liquid which in 100,000 parts by weight con- 
 tains, whether in solution or suspension, in chemical com- 
 bination or otherwise, more than 0*05 parts by weight of 
 metallic arsenic. 
 
 /. Any liquid which after acidification with sulphuric 
 acid, contains in 100,000 parts by weight, more than one 
 part by weight of free chlorine. 
 
 g. Any liquid which contains in ioo,ocoparts by weight, 
 
160 SEWAGE TREATMENT. 
 
 more than one part by weight of sulphur, in the condition 
 either of sulphuretted hydrogen or of a soluble sulphuret. 
 
 h. Any liquid possessing an acidity greater than that 
 which is produced by adding two parts by weight of 
 real muriatic acid to 1,000 parts by weight of distilled 
 water. 
 
 L Any liquid possessing an alkalimity greater than 
 that produced by adding one part of dry caustic soda 
 to 1,000 parts of distilled water. 
 
 To these recommendations a most judicious addendum 
 has been proposed, viz., the total exclusion of petroleum 
 and gas tar products, and the refuse of gas-works in 
 general, and of that of india-rubber works. 
 
 I must now beg my readers not to be dazzled by the 
 scientific reputation of the late Commissioners, or, at 
 least of one of them but to take these recommendations 
 on their own merits, and to weigh them calmly and 
 impartially. 
 
 It will at once strike the critic that these recom- 
 mendations ignore the volume and the condition of the 
 river, and attend solely to the quality of the waters 
 poured into it from manufactories, town sewers, etc. 
 without any regard to their quantity. 
 
 Now, suppose a number of establishments emitting 
 abundance of water just within the proposed standards 
 into a small river ; will it not speedily be brought into 
 a condition like that of the Kelvin Water, the Aire, or 
 the Irwell? But again, suppose a manufacturer on 
 the banks of a river wishes to get rid daily of 
 100,000 gallons of a liquid containing an alkalinity 
 equal to 2\ " parts by weight of dry caustic soda in 
 1,000 parts of distilled water," and therefore exceeding 
 the standard. What can he do to extricate himself 
 
DE TE C TION OF SE WA GE POLL UTION. 1 6i 
 
 from the difficulty ? He simply pumps up 100,000 
 gallons of water from the river, mixes it with his waste 
 water, and lets the whole 200,000 gallons flow into the 
 river triumphantly ! On analysis it will be found within 
 the standard, containing alkalinity equal only to IT part 
 of dry caustic soda to 1,000 parts of water. He has 
 therefore, obeyed the law, and yet he has put into the 
 river, to a grain, the same quantity of matter as if he 
 had run his 100,000 gallons directly into the river. 
 Indeed, the purer the river, the easier do such evasions 
 become. 
 
 I therefore submit that all t( standards " based on 
 the principle of so or so many grains or fractions of 
 a grain being permissible in a gallon, or in 100,000 gallons 
 of water, and anything beyond that limit being con- 
 traband, are fundamentally and essentially absurd, as 
 simply courting evasion. 
 
 If we come to details, the recommendations do not 
 improve. They are not so much stringent, as grossly 
 inconsistent. Nor, as far as I have been able to learn, 
 have the Commissioners ever attempted to justify the 
 precise limits which they laid down in each particular 
 case. The exclusion of free chlorine and of sulphuretted 
 hydrogen, and the soluble sulphides, might have ration- 
 ally been carried somewhat further. Nor can we object 
 that the disposal of arsenic is rigidly restricted. But 
 why are the neutral salts of potash, soda, lime, and 
 magnesia to be admitted in any proportion ? These 
 salts in certain quantities those especially of magnesia 
 are injurious if habitually introduced into the animal 
 economy. And why are all the other metals and their 
 solutions placed upon one dead level 2 parts by 
 weight in 100,000? Some of these, such as aluminium, 
 
 II 
 
162 SEWAGE TREATMENT. 
 
 strontium, and iron, are harmless to animal life in even 
 larger proportions. On the other hand, chromium, zinc, 
 and lead, are formidable poisons, and in manufacturing 
 districts are not unlikely to find their way into rivers. 
 Surely 1-4 grains of metallic lead per gallon in a water 
 supply would be amply enough to occasion lead poisoning. 
 
 With organic pollutions there is the same inconsist- 
 ency. One part of suspended organic matter is allowed 
 per 100,000, but only 0*3 part of "organic nitrogen " in 
 solution. Yet " organic carbon " in solution is allowed 
 up to 2 parts per 100,000. How is this ? " Organic 
 nitrogen " in solution is, therefore, in the judgment of 
 the late Commissioners, more dangerous than " organic 
 matter" in suspension. Yet "organic carbon" in solution 
 is less dangerous than " organic matter " in suspension. 
 Dissolve organic matter, and it becomes less dangerous 
 as regards its carbon, but more dangerous as touching 
 its nitrogen ! Surely this is a hard saying. 
 
 Again, all sorts of organic matter are not equally 
 prone to decomposition, or equally dangerous when 
 decomposing. The suspended organic matter in a water 
 might consist of stearic acid or of woody fibre, or it 
 might be composed of solidified albumen or of the 
 fibrous matter of blood. Would the danger to public 
 health in these two sets of cases be equal ? Yet of such 
 differences, and of numbers of others, the Recommen- 
 dations take no cognisance. 
 
 It is, therefore, I submit, the duty of the public to 
 dismiss them as impracticable, unpractical, and even 
 dangerous, and to propose some simpler standards, less 
 elaborate, and turning less on disputable analyses. 
 
 Not a few chemists of merit incline to something like 
 the following scale : 
 
DETECTION OF SEWAGE POLLUTION. 163 
 
 (a) The effluent or any water turned into a river 
 shall be clear and colourless if examined in a cylindrical 
 pint bottle of white glass. 
 
 (b) It must not be alkaline to test-paper. 
 Alkalinity is more dangerous in waters than acidity, 
 
 as it favours putrefaction. 
 
 (c) If to a pint of the water there is added I grain 
 of sulphate of alumina or of alum, previously dissolved 
 in 100 grains of water, there shall not beany perceptible 
 turbidity produced within half-an-hour. 
 
 (d) If a pint bottle is half-filled with the water in 
 question and well shaken up after standing for 10 
 minutes, no foam shall appear. 
 
1 64 SEWAGE TREATMENT. 
 
 CHAPTER XV. 
 
 RECOGNITION OF THE DEGREE OF PURIFICATION 
 REACHED IN SEWAGE TANKS. 
 
 IT is often important to judge in how far the effluent 
 water contained in a sewage tank or in the outflow 
 channels has been purified. The chemical tests proposed 
 by Professor Frankland, Professor Wanklyn, Dr. Tidy, 
 and others, whatever may be their respective values, do 
 not permit of an immediate decision on the spot. We 
 have, therefore, to take recourse to a variety of indica- 
 tions, which require careful observation. 
 
 In the first place must come the colour of the water. 
 The purer water is, the more its colour inclines, when 
 seen in large masses, to a transparent blue. If, on the 
 other hand, it is rich in dissolved impurities, it verges 
 upon a brown. This distinction has been very clearly 
 brought out in the joint investigation of the London 
 water supplies, undertaken by Mr. Crookes and Drs. 
 Odling and Tidy. 
 
 The blue tint of a pure water is something peculiar ; 
 it is not whitish-blue or milky, but borders slightly upon 
 a green, and is combined with a very high degree of 
 transparency. To observe the colour, it is well to make 
 the complete circuit of the tank, so as to view the water 
 in all directions with reference to the light. If there are 
 brick buildings near at hand, dark clouds overhead, or if 
 
PUR I PICA TION IN SE WA GE TANKS. 1 65 
 
 the wind is very strong, an erroneous impression may be 
 made. 
 
 In addition to examining the water in bulk as it stands 
 or flows in the tanks, a portion should be dipped up in a 
 clean glass and inspected both by reflected and trans- 
 mitted light. The presence or absence of scum, 9f 
 floating particles, and of any colour or opacity, should be 
 carefully noted. 
 
 The next point is the odour. Of all man's senses, that 
 of smell is generally the vaguest in its impressions. 
 Many people smell, or profess to smell, not the odours 
 which actually exist, but those which they think might, 
 could, would, or should, be perceptible. It has been 
 said that a scent which would pass unnoticed in a 
 drawing-room, will at once excite hostile comments at 
 sewage works. The present writer once met with an 
 instance of this kind. A very strong east wind was 
 blowing, and carried to and over a certain sewage works 
 the smell of a factory locally known as " Honey-pots' 
 Hall," where animal offal of various kinds was treated for 
 grease, glue, manure, etc. A visitor who had no faith in 
 precipitation processes, and who maintained, con strepitu, 
 that " even the best of them do not purify but only 
 clarify," complained that the smell came from the effluent! 
 He was prevailed on to walk on until he was more than 
 a hundred yards to the windward of the tanks and the 
 effluent channel, and was asked whether the stench 
 could possibly travel such a distance in the teeth of a 
 strong wind ? His reply was characteristic : " I still 
 adhere to my opinion." Such a man was by nature 
 qualified for a " Royal Commissioner," who can never 
 admit that either himself or any of his predecessors can 
 have been mistaken. 
 
iC6 SEWAGE TREATMENT. 
 
 If any person wishes to form an honest opinion as to 
 the presence or absence of smell from effluent, I should 
 recommend him to walk carefully round the tanks and 
 along the channels. The fairest judgment can be formed 
 when the mouth of the sewer is to the leeward of the 
 observer, so that he may not ascribe to the effluent the 
 offensive smell of the raw sewage. It is sometimes 
 the practice to bottle samples of the effluent, stopper 
 them and set them aside for future examination. In 
 such cases it is well to take, on the same day, accom- 
 panying samples of water from some ordinary river or 
 pool which does not receive excremental pollution, and 
 compare the smell of the two ! The proportion of fair 
 average drinking waters, which, when thus preserved for 
 a time in closed bottles, do not give off a disagreeable 
 smell is smaller than might be either desired or 
 expected. 
 
 Another point to be observed is the vegetation which 
 may be found clinging to the wood or stone work of the 
 tanks and the outfall channels ; if these are fringed with 
 sewage fungus it is a sign that the purification of the 
 sewage still leaves something to be desired. But if stone 
 work just about the level of the water or below it in 
 shallow places is covered with green confervae, the pro- 
 cess in action may be considered good. The confervae 
 will carry on the good work by means of the nascent 
 oxygen, which they give off under the action of light, and 
 which burns up, or in technical language, oxidises the 
 remaining organic impurities. Hence persons in charge 
 of sewage works should never sweep away such green 
 growths. By so doing they merely destroy a useful 
 fellow servant. 
 
 It is always desirable to watch the behaviour of the 
 
PURIFICATION IN SEWAGE TANKS. 167 
 
 water where it flows over a lip, down a steep incline, or 
 passes any obstacle which causes the formation of 
 bubbles or froth. If such bubbles break immediately, 
 the effluent may be regarded as well freed from dis- 
 solved organic impurities, or, in other words, as being 
 not merely " clarified but purified," But if the froth is 
 persistent and may be traced a considerable distance 
 down the channel, much soluble organic matter is still 
 present. This test, however, gives very little clue to 
 the nature of the impurity. Thus a spent lye from 
 soap works, containing glycerine, favours frothing as 
 much as does gelatine, mucus, albumen, or other 
 putrescible nitrogenous matter. 
 
 If practicable, it is well to follow the outfall channel 
 down to the stream into which it discharges, examining 
 both the appearances along its course and its effect, if 
 any, upon the water of the river. The points to be more 
 particularly considered are the occurrence of a secondary 
 precipitation in the channel. This, if it takes place, is 
 a sign that the tanks are too small, or the incline too 
 steep, so that the water after treatment has not sufficient 
 time to settle. A defect of this nature is no evidence 
 against the process in itself, though it affords proof of 
 defective arrangements. 
 
 But if a fresh precipitation takes place where the 
 effluent water mingles with that of the river, we may 
 generally infer that some precipitating agent used for 
 the sewage has been added in excess, so that it goes on 
 precipitating the suspended and dissolved solids in the 
 stream, which action will not take place if the water of 
 the river is very pure, containing practically no solids. 
 Nor will it be noticeable in the case of a very foul river con- 
 taining much manufacturing refuse. But in the streams 
 
168 SEWAGE TREATMENT. 
 
 of lowland rural districts it may be very striking, and 
 may give rise to complaints that the effluent water from 
 the sewage works is polluting the river. I have seen a 
 case of this kind, where the sewage of a large suburban 
 village and district was first treated with lime in pre- 
 cipitation tanks of the ordinary structure, and the 
 effluent was then used for irrigation on a large plot of 
 land. Yet the outflowing water on mingling with that 
 of the little river which received it, occasioned a decided 
 increase of turbidity, and there was an outcry accord- 
 ingly. But the river was full of vegetable pollution, 
 the drainage of extensive woodlands, and of a large 
 stretch of fields, pastures, and market gardens, and the 
 effluent from the sewage works merely rendered these 
 impurities more conspicuous. 
 
 Another point of no small importance is the action 
 of the effluent upon fish. Do they, if the level allows, 
 ascend the outfall channel without suffering any appa- 
 rent inconvenience ? Are they to be found in the river 
 below, as well as above, the point of outfall, or do they 
 carefully avoid coming in contact with the effluent? 
 These are questions of great importance. If the effluent 
 is fatal to fish, or if it at least is evidently an annoyance 
 to them, we may conclude that the sewage is insuffi- 
 ciently purified, or that some improper agent is used in 
 its purification. 
 
 A few hints may here be given about sampling 
 effluents for analysis, or for preservation. I write here 
 mainly for the guidance of officials left in charge of 
 sewage works, that they may know what tricks may be 
 attempted. It is commonly said " that any stick is good 
 enough to beat a dog with," and, on a similar principle, 
 any unfair, dishonourable stratagem is held legitimate 
 
PURIFICATION IN SEWAGE TANKS. 169 
 
 to bring discredit on a process for the chemical treat- 
 ment of sewage. 
 
 I must first speak of the construction of the works 
 Everything should be so arranged that it should be 
 impossible to take a sample surreptitiously. The 
 manager should always be able to state upon oath, 
 if required, whether any given person did on some 
 specified day receive a sample or not. I have known 
 samples of water fraudulently concocted and then 
 analysed with all due solemnity, whilst all the while no 
 such water was at the time running in the stream from 
 which they were said to have been taken. A certain 
 very astute contractor for treating sewage, always takes 
 good care that the effluents on leaving the enclosure of 
 the works, flow in a covered channel, and issue into the 
 river below the surface. Thus the surreptitious procuring 
 of a sample is rendered impossible. 
 
 Another needful precaution is to admit no visitors, 
 and allow no sampling at times of flood, unless the 
 tanks and other arrangements are fully capable of deal- 
 ing with the unusual quantity of storm-water. To pay 
 visits of inspection at such times, and omit in sub- 
 sequent reports, all mention of the abnormal state of 
 things, is a device not quite strange to the official 
 mind. We believe a person once paid a visit of 
 this kind to the whilome Leamington Sewage Works, 
 and sat in a cab, which was not quite lifted off the 
 ground by the flood, watching the working of the pro- 
 cess through the window. No visitors should be allowed 
 who have not the opportunity to examine closely and 
 carefully, and at the same time have not the candour 
 to confess under what anomalous circumstances their 
 inspection has been made. 
 
170 SEWAGE TREATMENT. 
 
 Another necessary precaution relates to sampling. 
 If any visitor asks for a sample, it should be given him 
 solely on the condition that he takes and seals up at 
 the same time a check sample, to be left at the works 
 for analysis by some independent chemist. Without this 
 precaution he may, for instance, add to his sample a 
 little urine or blood, or a culture solution, and still 
 represent it as a normal sample. 
 
 The bottles used must be perfectly clean, by prefer- 
 ence new, and fitted with glass stoppers. They should 
 have been well washed out with plenty of a fairly good 
 drinking water, and be then rinsed out twice or thrice 
 with the effluent to be sampled. No one should be 
 permitted to take a sample in a bottle which has con- 
 tained wine, beer, or any organic liquid whatever. 
 
 It must not be thought that these precautions are 
 dictated by an imputative jealousy ; they are the fruits 
 of experience. I have seen a man come to a sewage 
 works for a sample of the effluent, bringing with him 
 a bottle most palpably dirty. One of the workmen 
 shattered it with a crow-bar, and on examining some 
 of the fragments I found them thickly coated within 
 with organic matter. As the man refused a sample in 
 a clean bottle, I can only conclude that his dirty bottle 
 must have been specially selected or prepared, in order 
 to admit of a false and condemnatory analysis. This 
 is by no means the only case where bottles brought by 
 strangers have been found to be exceptionally dirty. 
 
 The act of taking the samples should be done in 
 presence of both parties. If bottles are filled from a 
 channel lined with stone, brick, or concrete, there is no 
 possibility of any jugglery. But I have known in- 
 stances where it was desired to take a sample at the 
 
PURIFICATION IN SEWAGE TANKS. 
 
 171 
 
 point of junction where the effluent was discharged into 
 a dirty brook. In two such cases, the person who had 
 come for the sample showed an evident desire to scrape 
 up a portion of the dirt at the bottom of the stream, 
 which would have seriously swelled the sum of " total 
 matter in suspension," the more so as prior to the 
 adoption of the process of treatment a large portion 
 of the sewage of the town had been discharged at the 
 very spot in its raw condition. 
 
172 SEWAGE TREATMENT. 
 
 CHAPTER XVI. 
 
 PRECIPITATION MUD. 
 
 WITH the production of an effluent, clear and pure as 
 practicable, the difficulties of sewage treatment are not 
 exhausted. The water and the deposit have to be 
 separated from each other, so that, according to a 
 favourite phrase, " the water may go to the river, and 
 the manure to the land." This must be done frequently. 
 If not, the tanks begin to choke, the sediment ferments 
 and rises up, spoiling the water, and the result is one 
 to gladden the heart, and for once justify the repre- 
 sentations of ex- Royal Rivers' Pollution Commissioners. 
 Further, the effluent must be drawn off very quietly, 
 without disturbing the mud. Where the slope of the 
 ground allows, this is effected by gravitation. The tank 
 to be emptied is shut out of connection with the 
 remainder, and allowed to rest for a few hours, so as 
 to ensure perfect settlement, and the water is then run 
 off as nearly as possible to the level of the deposit. 
 The pipe through which this is effected ends in several 
 feet of flexible hose (more or less, according to the 
 depth of the tank), and is capped with a funnel opening 
 upwards. This funnel is at first placed near the surface 
 of the liquid, and as the process goes on it is gradually 
 
PRECIPITA TION MUD. 173 
 
 and carefully lowered by means of ropes or chains, until 
 the mouth of the funnel, still kept upwards, is only just 
 above the level of the mud. Where there is not a 
 sufficient fall, the water is drawn off by means of a 
 pump, but the flexible hose and funnel are still 
 necessary. 
 
 When the effluent water is thus disposed of, the mud 
 is run off, or pumped off, into suitable receptacles for 
 further treatment and conversion into a portable 
 manure. The mud is a thin paste, containing, on an 
 average, 90 per cent, of water. If a good process for 
 precipitation has been used it is, practically speaking, 
 inodorous ; it does not, when separated from the water, 
 pass readily into fermentation, and it has but little 
 attraction for flies. 
 
 It may be dried by a variety of methods. Where 
 there is a sandy or otherwise porous soil, and where the 
 climate is dry, the mud may be run into a stank, i.e., a 
 large, shallow reservoir, with an earth bottom and sides. 
 Here it forms a layer about 6 to 9 inches in depth. 
 The moisture is given off, partly by evaporation, but 
 chiefly by absorption into the soil below. Under 
 favourable circumstances it may, in this manner, be 
 reduced to 20 per cent. Such a result cannot always 
 be reached in Britain, at least in any ordinary season, 
 and as the process requires considerable space, a long 
 time and much labour, it cannot be generally recom- 
 mended. The mud-stanks, further, though free from 
 nuisance, if a proper system of treatment has been 
 employed, have an unsightly appearance. 
 
 The best method of dealing with the mud is, gene- 
 rally speaking, to run it into a filter-press, such as that 
 of Needham and Kite, of Johnstone, or of Manlove, 
 
174 SEWAGE TREATMENT. 
 
 Alliatt & Co. The accompanying figures, 2 and 3, 
 represent the filter-presses of the last-mentioned firm. 
 
 Here the moisture present is reduced down to 50-40 
 per cent, according to the pressure put on and the time 
 allowed. The mud comes out on opening the presses 
 
 FIG. 2. 
 
 FIG. 3. 
 
 in flat cakes, circular or rectangular, according to the 
 make of the press, sufficiently coherent for handling. 
 
 At many sewage works it is, strange to say, customary 
 to add some substance to the mud before running it into 
 the presses, for the purpose of facilitating the drying 
 process. 
 
PRECIPITATION MUD. 175 
 
 Among the materials so used are 
 
 a. Finely-ground basic slag, coprolite, apatite, or other 
 phosphatic mineral. This substance has, of course, an 
 intrinsic manurial value and cannot be supposed to 
 deteriorate the properties of the sewage mud. But it 
 has little solidifying power, and scarcely facilitates dry- 
 ing. When finely ground it is also somewhat expensive, 
 and cannot well, in the resulting manure, be sold for 
 more than it has cost, so that the whole transaction is 
 like giving change for a shilling. 
 
 b. Gypsum, or plaster of Paris. Everyone knows 
 that this mineral, at least in the burnt state, readily 
 takes up water, and solidifies it, so that if a sufficient 
 quantity were added to the mud, neither pressing nor 
 any other drying process would be needed. But in con- 
 tact with carbonaceous matter, gypsum is decomposed 
 with a plentiful escape of sulphuretted hydrogen. This, 
 if occurring at all on a large scale in the neighbourhood 
 of human habitations, may rightly be viewed as a public 
 nuisance, and in any case, it will greatly endanger the 
 health of the workmen. Besides, gypsum may be safely 
 pronounced to have no manurial value, our ablest agri- 
 cultural chemists regarding it as a " mere diluent." 
 
 c. Carbonate of lime, in the state of chalk, or other 
 convenient form. 
 
 Here we have certainly no production of a nuisance, 
 as in the case of gypsum. But we have, firstly, a direct 
 deterioration of the manure by the loss of one of its 
 most valuable constituents. The nitrogen existing in 
 the state of ammoniacal salts is liable to be driven off. 
 Mr. T. Brown, writing recently in the Chemical News, 
 on " The Failure of Sulphate of Ammonia in Manuring 
 Experiments," points out that ammonia is volatilised 
 
i;6 SEWAGE TREATMENT. 
 
 even by chalky soils. Of course, if quicklime, or slaked 
 lime, is used, the loss is greater and more rapid. 
 
 But even if we suppose that no ammonia were 
 directly expelled by these additions, we must not forget 
 how greatly the value of sewage mud is diminished by 
 the addition of any worthless material for the purpose 
 of drying up. Let us suppose a mud containing 90 per 
 cent, of water, and consequently, only 10 per cent, of 
 solids, more or less manurial. If we add to such a mud 
 10 per cent, of chalk, we divide the nitrogen present, the 
 phosphoric acid, etc. in a given weight, by 2. If we use 
 20 per cent, of chalk or other carbonate of lime pro- 
 portions which, I believe, are not merely reached, but 
 actually exceeded in practice we reduce the nitrogen 
 and the phosphates present to one-third their original 
 percentage. Can we then wonder if sewage manures thus 
 treated, are pronounced not worth the cost of carriage, 
 and of the labour involved in applying them to the soil ? 
 
 Gypsum, if burnt, at least, behaves still worse, since it 
 seizes on and retains one-fifth its weight of the moisture 
 present in the mud. Thus, if we add 20 per cent, of 
 gypsum to sewage mud, we shall have 24 per cent, of 
 rubbish. 
 
 Additions of lime, chalk or gypsum, to sewage mud, 
 are, therefore, a complete mistake, as well as being quite 
 needless. 
 
 The greatest drawback in the use of the filter press is 
 the exuding water. This is in quantity no trifle. One 
 hundred tons of mud contain 20,000 gallons of water, 
 of which about 9,000 are squeezed out by the press. 
 The disposal of this liquid is a matter of some difficulty. 
 In some places it is passed back into the sewage or into 
 the tanks, and is treated over again. This is by no 
 
CJ 
 
 o 
 
PRECIPITATION MUD. 177 
 
 means judicious ; the press liquor is far harder to treat 
 than fresh sewage, requiring an extra dose of chemicals, 
 and even then, giving but a doubtful result. Press 
 liquor, in fact, behaves very much like stale, putrid 
 sewage. Hence it should either be run into distinct 
 tanks and treated especially, without being allowed to 
 mix with the fresh sewage which involves extra ex- 
 pense or it must be let flow over a portion of land. 
 Above all things, it must not be allowed to escape into 
 the river, as I have seen done. 
 
 The press cakes, coming from the filter press, and 
 containing about 50 per cent, of water, may be further 
 dried in various manners. They may be loosely stacked 
 on racks in a shed, freely open to the wind, but secure 
 from rain. In this manner the moisture may be brought 
 down in time to 20 per cent. ; or the cakes may be shot 
 upon drying floors, heated by suitable furnaces below, 
 or by means of steam pipes, or hot-air pipes. 
 
 I have seen the press stuff moulded into a kind of 
 brick, a little larger than an ordinary brick. These are 
 then exposed to air and sun, just as are bricks before 
 being placed in the kiln; or they may be dried at 
 temperatures not exceeding 80 R, by means of waste 
 heat. I have seen sewage deposit dried in this manner 
 down to 13^ per cent., without the addition of lime, 
 gypsum, ashes, or rubbish of any kind. 
 
 Perhaps the best arrangement for drying, generally 
 speaking, is the drying cylinder, patented in 1872 (No. 
 314), byGibbs and Berwick, a section of which is shown 
 in the accompanying figure. The cake stuff is mechani- 
 cally agitated in an iron cylinder, whilst a current of 
 hot air passes over it, at the same time. The fumes 
 given off, which, though not hurtful, are unpleasant, 
 
 N 
 
1 78 SEWAGE TREATMENT. 
 
 may be passed through a scrubber or a coke tower, and 
 finally into the chimney of the engine furnace. 
 
 After its passage through the drying cylinders the 
 manure retains from 30 to 35 per cent, of water. But 
 if allowed to lie in heaps in a shed, it loses the greater 
 portion of this moisture, down to about 15 per cent., in 
 which condition it is usually sold. 
 
 As a matter of course, if the sewage deposit is to be 
 applied close at hand, so that the extra weight carried is 
 little object, or where there is direct water carriage to 
 the place of consumption, the stuff from the cylinders, or 
 even the press cakes, may be dispatched at once. 
 
SEWAGE MANURES. 179 
 
 CHAPTER XVII. 
 
 SEWAGE MANURES. 
 
 THE question of sewage manures and their value, is one 
 which has been very needlessly complicated by ex- 
 traneous considerations. We know now that plants 
 require food, just as do animals ; they cannot create this 
 food, but can merely appropriate such matters as are 
 necessary for their growth. These matters they take up, 
 partly from the air, partly from the rain, but chiefly 
 from the soil. 
 
 Now the supply of plant food in the soil is by no 
 means infinite. If we plant crops and reap them year 
 after year without returning anything to the soil, it will 
 ultimately become exhausted. Plants will grow in it 
 less and less luxuriantly than they did at first, and by- 
 and-by they will cease to grow at all, and the land will 
 be rendered barren. Millions of acres in the countries 
 bordering on the Mediterranean have been brought into 
 this state. Abundance of land in the United States, 
 once exuberantly fertile, can now be scarcely cultivated 
 at a profit. We said, " Without returning anything to 
 the soil." But if we do make a full and due return, if we 
 give back to the land all the residues and waste of the 
 crops which have grown upon it and all the excre- 
 ments, liquid and solid, of the animals which have 
 directly or indirectly been fed upon such crops, the 
 
i8o SEWAGE TREATMENT. 
 
 land will remain substantially at its original point of 
 fertility. 
 
 This has been attempted more or less successfully 
 in all old peopled countries, where land is scarce. In 
 China and Japan the attempt has been successful, 
 because the whole of the excretions have been returned 
 to the soil. In most European countries, and especially 
 in England, the restitution has been very incomplete, 
 because the excretions of the human inhabitants have 
 not been brought back to the soil, but, especially since 
 the introduction of water closets have been run into the 
 rivers, thence into the sea, and thus wasted. Hence, 
 the deficiency has had to be made good, either by the 
 aid of mineral matters mined in this country coprolites 
 or by means of matters imported from abroad, such 
 as guano, apatites, kainite, bone ashes, etc. 
 
 Now it is very plain that if a country, in addition to 
 sending abroad its agricultural produce, exports manures 
 also, such especially as bones, bone charcoal, bone ash, 
 and dried blood, its own soils must before long become 
 exhausted. Hence we find that countries which 
 formerly exported such products to England have now 
 ceased so to do, the home demand having so far raised 
 the price that the transaction is no longer profitable. 
 
 Other and more distant regions will gradually, as their 
 population becomes denser, follow in the same track. 
 Ultimately, they will even cease to export agricultural 
 produce, and will compete with us for a supply of 
 mineral plant foods, nitrate of soda, apatite, phosphorite, 
 and the like. Thus, ultimately, every country will be 
 driven back upon the produce of its own soil for 
 support. The bearing of this truth upon the sewage 
 question is most evident. Will it in the coming time 
 
SEWAGE MANURES. 181 
 
 be at all practicable to go on wasting the excreta of 
 our urban population as we are now in most cases still 
 doing ? Shall we not want it to keep up the fertility 
 of our own lands against the time when the foreign 
 supply, both of food and manures, begins to show a 
 marked decline ? 
 
 By many of our present systems, viz., Bazal- 
 gettism, intermittent downward filtration, the per- 
 manganate process, the Scott cement processes, etc., 
 we are exhausting the food producing capacity of any 
 and every part of the earth which supplies us with 
 food. 
 
 Suppose that London is fed on Indian wheat, 
 Australian mutton, and Argentine beef. Be it so : we 
 are then busy sterilising India, Australia, etc., and let 
 this game be carried on long enough, and generally 
 enough, and the whole world will become comparatively 
 barren. Surely, therefore, we should be wise in time, 
 and desist from our profligate waste. 
 
 There is a further consideration ; it is commonly said 
 that the money spent in making sewage manures is not 
 well laid out, and that plant food might be had at a less 
 cost from other sources. For the present this may be 
 true. But on sanitary grounds we are compelled to 
 purify the sewage ; and the question is therefore whether 
 we shall do this in pure waste, or whether we shall not 
 recover, at least, a part of our outlay in the form of 
 manure? To a practical mind there can be here no 
 room for doubt. 
 
 Sewage manures, it must further be remembered, are 
 by no means so deficient in the most essential con- 
 stituents of plant food as some would-be authorities 
 wish the public to suppose. Average samples of the 
 
182 SEWAGE TREATMENT. 
 
 Aylesbury sewage manure, taken absolutely at dis- 
 cretion, have been lately analysed by Professor Dewar 
 and Dr. Tidy, and found to contain 3 per cent, of 
 available ammonia and phosphoric acid equal to about 
 5 per cent, of tricalcic phosphate of lime. If we 
 remember that farmyard manure in its ordinary con- 
 dition contains only about 0*5 per cent, of available 
 ammonia, we shall see that sewage manures are not 
 necessarily to be despised, even from a mere analytical 
 point of view. If we look at the results obtained in 
 agricultural and horticultural practice, results obtained 
 from so many and so different quarters as to eliminate 
 all possibility of bribery, corruption, or mistake, we 
 shall find them much better than the mere percentage 
 composition of the manure would lead us to expect. 
 Hence, we are pointed to the truth that the condition, 
 as readily assimilable or otherwise, of a manure, may be 
 of as great importance as the mere percentage of its 
 constituents. 
 
 There are, however, many different grades of sewage 
 manures. If the sewage of a town consists largely of 
 industrial waste waters, the matter precipitated or 
 absorbed from it may have but a very low agricultural 
 value, acting worse in practice than its analytical value 
 would lead us to expect, Such sewages, it must be 
 remembered, are sure to give unsatisfactory results if 
 applied in irrigation, certain of their constituents being 
 more or less poisonous to plants. But when the sewage 
 of a town brings with it the entire excreta of its human 
 and animal inhabitants, plus the blood from the 
 slaughter-houses, &c., and all this dissolved or suspended 
 in a volume of water, not greatly exceeding 30 gallons 
 daily per head of the population, and with little or no 
 
SEWAGE MANURES. 183 
 
 dye or tan liquors, solutions of metals, etc., such sewage, 
 if properly treated, will yield a manure of approximately 
 the strength above mentioned. 
 
 The manner of treatment, of course, greatly affects 
 the result. The lime processes not merely throw down 
 from the sewage a smaller proportion of the dissolved 
 organic impurities than do, e.g. y the salts of alumina, but 
 the lime goes on exerting a decomposing action upon 
 the sediment, expelling gradually the ammonia, and 
 thus constantly reducing its manurial value. Other 
 changes take place simultaneously, as may be judged 
 from the peculiar sickly smell which lime deposits give 
 off for a very considerable time. 
 
 Further, though lime, in the caustic state, or as 
 carbonate, is very commonly applied as a dressing to 
 land, and often with good results, yet it is never used 
 along with any organic manurial matter, whether farm- 
 yard manure, night-soil, guano, refuse fish, etc. On the 
 contrary, the lime is applied by itself, generally in the 
 autumn, after the crops have been gathered, and the 
 nitrogenous manure is used some months later, in the 
 beginning of spring. But if the deposit from a lime 
 sewage process is applied, we have the very mixture 
 which practice has taught the farmer to avoid. These 
 remarks will hold good whether the sewage has been 
 precipitated with lime by itself, with magnesian lime, 
 or with lime in conjunction with phosphates, with 
 copperas or other salts of iron, salts of alumina, etc. In 
 short, we may say that no precipitate from an alkaline 
 effluent is likely to prove very satisfactory as a manure. 
 
 It need scarcely be said that sewage deposits thrown 
 down by any poisonous agent, such as gas lime, salts of 
 baryta, zinc or lead, are quite inadmissible as manures. 
 
1 84 SEWAGE TREATMENT. 
 
 Gas lime and alkali waste precipitates may, however, 
 be usefully applied to kill weeds, heath, etc., on waste 
 lands which it is desired to bring under cultivation. 
 Even in such cases, it might be simpler to apply the gas 
 lime, etc., at once, without first passing it through sewage. 
 
 Very powerful oxidising agents, such as the manga- 
 nates, the permanganates, and the chromates (if the 
 latter should ever come into use), must, pro tanto, lessen 
 the value of the manure. 
 
 The deposit from sewage left to itself in a settling 
 tank, without chemical treatment, is worthless. It con- 
 tains very little of the dissolved organic matters of the 
 sewage, which during the settling process have taken to 
 themselves wings and flown away in the form of noisome 
 gases, often conveying putrefactive and disease engender- 
 ing organisms. It consists chiefly of the sand, gravel, 
 comminuted stones, etc., which the sewage sweeps along, 
 especially in towns where the streets have been dealt 
 with according to the iniquity of Macadam. 
 
 At a certain sea-coast town a curious mistake led 
 to the production of a sewage precipitate supposed 
 very similar in character and value to the spontaneous 
 deposit just mentioned. The precipitation tanks were 
 so situate that the effluent water could at low tide be 
 run off into the sea. The manager of the works, instead 
 of adding the precipitating and occluding agents to the 
 sewage, conceived the original but most unhappy thought 
 of allowing the sewage to subside spontaneously, run- 
 ning the liquid off into the sea and adding the precipi- 
 tating mixture to the deposit. No good end was effected 
 by this strange process ; the organic impurities which 
 should have re-appeared in the manure, passed out to 
 sea. To make the matter worse, the town in question 
 
SEWAGE MANURES. 185 
 
 lies, in part, on a very steep declivity, so that in time of 
 heavy rain the surface water rushes furiously down to 
 the lower levels charged with little but silt. This mate- 
 rial, after settling in the sewage tanks, and being sprinkled 
 over with the precipitating mixture, was sold as manure 
 to a very considerable extent before the fatal blunder 
 was detected. The consequence is that in the districts 
 around the town in question, comprising some of the 
 most highly cultivated land in all England, sewage 
 manure, no matter from what source or of what quality, 
 has been brought into utter disrepute and would scarcely 
 be accepted as a gift. I had the opportunity of obser- 
 ving a large tract of meadow land, one half of which had 
 received a heavy dressing of this supposed sewage 
 manure, whilst the other had received no manure at all. 
 On examining the land carefully I was unable to per- 
 ceive any difference between the manured and the un- 
 manured portion, and this in the beginning of June. 
 
 I cannot help noticing that a part of the unmerited 
 contempt and neglect with which sewage manures are 
 greeted is due to the efforts of the manufacturers of 
 super-phosphates, dissolved guano, and other chemical 
 fertilisers. These gentlemen very naturally wish to 
 keep the market to themselves, and of course object 
 to an increased supply, and an improved quality of 
 sewage manures, as an unwelcome competition. Thus 
 we find one of the most eminent manure manufacturers 
 as above noticed, arguing in favour of Bazalgettism, and 
 pronouncing it good policy to run our sewage into the 
 sea to feed the fishes. Of all men, super-phosphate 
 makers are the very last who should be consulted on 
 sewage treatment, since their own interests lead them to 
 favour the waste and the destruction of excreta. 
 
1 86 SEWAGE TREATMENT. 
 
 CHAPTER XVIII. 
 
 SEWAGE LEGISLATION. 
 
 UNDER this head we may briefly consider the laws 
 relating to the pollution of rivers, water-courses, wells, and 
 springs by household sewage, and of the waste waters of 
 manufacturing establishments, or of any other source of 
 pollution. Previous to 1876, there was no special statute 
 bearing upon the subject. A riparian proprietor, ag- 
 grieved by the fouling of a stream passing by or through 
 his estate, might apply to the Chancery Division of the 
 High Court of Justice for an injunction restraining the 
 offenders from continuing the pollution. Such applica- 
 tions were frequently successful, and they appear to have 
 been among the first causes which led to attempts for 
 the purification of sewage and waste waters. 
 
 But the right to turn refuse, solid and liquid, into a 
 river in other words, to pollute such river seems in 
 some cases to have become included by prescription 
 among the easements of an estate situate on the banks. 
 At least, at a meeting on the pollution of rivers, one of 
 the most eminent calico printers in Great Britain, stated 
 that some years previously he had begun experiment- 
 ing on the purification of the waste waters turned out 
 from his works. To his great surprise he soon received 
 a formal letter from the ground landlord, warning him 
 that by so doing he was imperilling one of the prescrip- 
 
SEWAGE LEGISLATION. 187 
 
 live rights of the estate, and consequently violating one 
 of the covenants of his lease ! Thus in certain cases 
 river pollution was not only facultative, but was even a 
 duty. 
 
 Then came the Act of 1876, a mild measure, which 
 has been a failure because it has not been duly put in 
 force. It did not contain any fixed standards for the 
 quality of the waters which might and might not be 
 legally allowed to flow into rivers. It ignored the well- 
 known " Recommendations " which have been discussed 
 in a previous chapter. Nor was there any attempt to 
 force some particular method of sewage treatment upon 
 the nation. Whatever defects the Act might possess- 
 and to two of them we are about to turn our attention 
 its framers were thoroughly aware of the delicacy and 
 difficulty of the task. Whilst acting in the spirit of the 
 grand maxim, " sanitas sanitatum et omnia sanitas" they 
 were careful not needlessly to harass municipalities 
 and manufacturers. They wished to effect the desired 
 reforms gradually, not laying down at once hard and 
 fast lines, which could only be enforced by an offensive 
 espionage, by continual fines, and by strengthening the 
 hand of an aggressive bureaucracy. 
 
 But the Act did not even attempt to codify the law 
 on the pollution of rivers. It is what, I believe, is 
 called in the language of the law a " cumulative " 
 measure, that is, a statute which provides new pro- 
 cedures and new penalties for certain omissions and 
 commissions, but leaves all old precedents, customs 
 and statutes, bearing upon the particular subject, still 
 perfectly valid. A riparian proprietor who knows or 
 fancies that some manufacturer or municipal authority 
 is polluting a river has under that Act still a choice 
 
1 88 SEWAGE TREATMENT. 
 
 of procedures. He may take action under the statute, 
 or he may, I suppose, still apply to the Chancery 
 Division for an injunction, just as if the Act had never 
 been passed. 
 
 Now, this power of option, with all the uncertainty 
 hanging over the subject, may be very convenient for 
 a litigious person, who, from whatever motive, wishes 
 to harass a neighbour. But it is, I submit, grossly 
 unfair to municipalities and to manufacturers. Both 
 are surely, in common fairness, entitled to have open 
 to them a clear, definite, comprehensive statement of 
 what is legal, and what is illegal, as regards the disposal 
 of sewage and waste waters, so that they may know 
 when they are obeying the law, and may feel assured 
 that when so doing they are not open to any proceedings 
 whatever. 
 
 On the other hand a riparian owner, a municipality, 
 or manufacturer, situate down stream, and feeling 
 aggrieved by the actions or omissions of a neighbour 
 up stream, might surely be satisfied if one sufficient and 
 efficient remedy is placed at his disposal. 
 
 Another shortcoming of the Act of 1876 and of all 
 existing law on the subject has been brought to light 
 very lately. The law provides remedies in case of the 
 pollution of any river, brook, lake, or other piece of 
 water open to the air and light. But concerning under- 
 ground waters it is silent. An explanatory instance 
 is here necessary. A. B. had within the limits of his 
 property a well which supplied his household with 
 potable water. On the property of his neighbour, C. D., 
 there was also a well, disused as a water supply. 
 C. D. took upon himself to turn the sewage of his house 
 into the abandoned well. Before long the various kinds 
 
SEWAGE LEGISLATION. 189 
 
 of polluting matter found their way through the inter- 
 vening subsoil and contaminated A. B.'s well. The latter 
 thereupon took proceedings for the abatement of so 
 grave a nuisance ; but the judges, finding neither statute 
 nor precedent bearing upon the question, were compelled 
 to decide in favour of the defendant, or offender. 
 
 In 1885, we had an attempt, though an unsuccessful 
 one, to improve the law of river pollution. Earl Percy, 
 Colonel Walrond, and Mr. Hastings brought in a Bill 
 of a decidedly more drastic character than the Act of 
 1876. As a prominent feature it embodied the very 
 objectionable " Recommendations " of the late Royal 
 Rivers' Pollution Commissioners, which we have already 
 discussed. It adopted also their cardinal errors, of 
 enforcing one standard for all the rivers in the kingdom, 
 of paying no regard to the river itself, and of looking 
 merely at the quality, neglecting the quantity of any 
 polluting influx. 
 
 The Bill also made no attempt to remedy those 
 serious defects in the Act of 1876 which have just been 
 pointed out. There is assuredly no provision against 
 the pollution of underground waters. Codification 
 further, is distinctly repudiated. It is laid down that : 
 " The powers given by this Act shall not be deemed 
 to prejudice or affect any other rights or powers now 
 existing or vesting in any person or persons by Act of 
 Parliament, law or custom ; and such right or power 
 may be exercised in the same manner as if the Act had 
 not passed, and nothing in this Act shall legalise any 
 act or default which would, but for the Act, be deemed 
 a nuisance." This is one of those " saving clauses " to 
 which an irreverent friend of the writer's applies an 
 exactly opposite epithet. 
 
ipo SEWAGE TREATMENT. 
 
 Not having enjoyed a legal training I cannot presume 
 to form an opinion as to whether, in virtue of this clause, 
 any person who had enjoyed by prescription the right 
 of polluting some river, would have been justified in 
 continuing the pollution. 
 
 Several most mischievous clauses disfigured the Bill. 
 There may be, and probably will be found, cases where 
 the river is worse than the sewage or waste waters 
 discharged into it. For such cases the Bill provided 
 that : " It shall be no defence to any offence against 
 this Act, to prove that, after any offence against the 
 Act has been committed, the water of the stream is less 
 polluted than is defined by the standard of purity here- 
 inafter mentioned." Had this Bill unhappily become 
 the law of the land, a manufacturer might have incurred 
 heavy penalties 50 per day for turning into a 
 stream water purer than the stream itself, if only such 
 water transgressed the standards in any one point. Yet 
 such a manufacturer, instead of polluting the river 
 would be improving it. Further still : if a stream is in 
 any one point less pure than required by the standards 
 it would have been an offence to take out a quantity of 
 such water for any purpose, and let it flow back in its 
 original condition. 
 
SEWAGE PATENTS. 191 
 
 CHAPTER XIX. 
 
 SEWAGE PATENTS. 
 
 Abstracts of Specifications for the Chemical Treatment 
 of Sewage. 
 
 1. W.Higgs. 1846. No. 11,181. 
 
 Precipitates with slaked lime, and brings the sewage 
 gases evolved in contact with chlorine or hydrochloric 
 acid gas. 
 
 2. /. H. Browne. 1850. No. 13,280, 
 
 Precipitates with basic salts, such as subsulphate of 
 peroxide of iron, or any neutral metallic salt, or metallic 
 salts mixed with cheap oleaginous matter. Or chloride 
 of calcium. 
 
 3. T. Wicksteed. 1851. No. 13,526. 
 
 Uses milk of lime. 
 
 4. R. Dover. 1851. -^.13,775. 
 
 Treats with hydrochloric acid or other mineral acid, 
 iron filings, oxide of iron, chloride of sodium or proto- 
 sulphate of iron. He then filters' effluent through 
 charcoal, clay, gypsum or peat. 
 
 5. H. Stothert. 1852. No. 14,073. 
 
 Precipitates with caustic lime, sulphate of alumina, 
 sulphate of zinc, compound animal and vegetable 
 charcoal (obtained by distilling the precipitated matters 
 of sewage waters, or by distilling night-soil, creosote 
 or oil of peat), peat mould, tanner's spent bark, burnt 
 
I 9 2 SEWAGE TREATMENT. 
 
 clay, old mortar or mixture of such matters or other 
 matters. 
 
 6. A. W. Gilbee. New Act, 1852. No. 250. 
 
 Applies to drains and sewers a deodorising powder, 
 obtained by burning lignites, or any ligneous sub- 
 stance, etc. 
 
 7. W. Bardwell. 1853. No. 29. 
 
 Filters within a close chamber, and receives the 
 gases in suspended trays of sawdust moistened with 
 sulphuric acid. 
 
 8. / F. Pinel. 1853. No. 581. 
 
 Adds to sewage sulphate of zinc, potash, alum, 
 common salt and sand (!) 
 
 9. /. T. Herapath. 1853. No. 643. 
 
 Precipitates the phosphoric acid and ammonia of 
 sewage by the addition of magnesian compounds at or 
 about the same time as the addition of some chemical 
 agent which will not decompose ammonia or its salts, 
 but will combine with or absorb hydrosulphuric acid, 
 such as metallic sulphates or metallic chlorides, or 
 animal or vegetable carbon. 
 
 10. T. T. Dimsdale. 1853. No. 1,252. 
 
 Adds to the sewage a peculiar kind of peat-earth 
 containing a salt or salts of iron or oxide of iron. 
 n. A. Macpherson. 1853. No. 1,511. 
 
 Mixes with the sewage peat charcoal, mixed with 
 common salt. 
 
 12. /. A. Manning. 1853. No. 2,780. 
 
 Treats sewage with animal charcoal, alum, carbonate 
 of soda and gypsum. 
 
 13. A. MacpJierson. 1853. No. 2,876. 
 
 Uses peats dried or charred, charred saw dust, sulphuric 
 acid, common salt, hydrate of lime, quicklime, brick- 
 dust, or dry clay as a filter bed. 
 
SEWAGE PATENTS. 193 
 
 14. A. R. Smith and A. Macdougall. 1854. No. 142. 
 
 Treat sewage with magnesia and lime, combined 
 with sulphurous acid or carbolic acid. 
 
 15. T. Wicksteed. 1854. No. 193. 
 
 Precipitates with lime and finely divided charcoal, 
 preferably prussiate carbon. 
 
 1 6. T. J. Herapath. 1 854. No. 
 
 Uses coke of Boghead coal for drying ? deodorising, or 
 absorbing sewage. 
 
 17. J. A. Manning. 1854. No. 709. 
 
 Treats sewage with " soft sludge " from alum works. 
 
 1 8. J.Littleton. 1854. Afa. 2,532. 
 
 Separates gases from sewage by the action of a vacuum, 
 and absorbs them in charcoal or other matter. 
 
 19. J. A. Manning. 1855. 7V0. 1,786. 
 
 Treats sewage with alum-slate, alum-shale, alum- 
 schist, alum-stone, alum-ore, and other aluminous 
 minerals. He uses also powdered lime and animal 
 charcoal. 
 
 20. T. Wicksteed. 1856. No. 1,815. 
 
 A mere nitration arrangement. 
 
 21. J. T. Victor. 1856. No. 2,273. 
 
 Uses as an "anti-putrefactive," sulphate of zinc and 
 copper and water. 
 
 22. G. Vertue. 1856. No. 2,842. 
 
 Deodorises sewage with quicklime, taken hot from 
 the kiln, slaked close to the sewers and passed into 
 them. 
 
 23. F. H. Maberley. 1857. No. 49. 
 
 Mechanical arrangements for separating the solid 
 from the liquid portions of sewage. 
 
 24. Sir James Murray. 1857. j\fo. 114. 
 
 Appears to treat sewage with carbonic acid, generated 
 and applied in various manners, 
 o 
 
194 SEWAGE TREATMENT. 
 
 25. H. Medlock. 1857. No. 186. 
 
 Purifies water by contact with bundles of iron wire, and 
 afterwards filtering. 
 
 26. J. W. Rogers. 1857. No. 992. 
 
 Filters through peat-charcoal. 
 
 27. /. Lloyd. 1857. No. 1,793. 
 
 Treats sewage with ashes and cinders, mixed with 
 lime, and occasionally with chloride of lime. 
 
 28. F. Lipscombe. 1857. No. 2,168. 
 
 This patent is mentioned here merely as containing 
 the germ of the Bazalgette process. The sewage is to 
 be run through iron culverts into the sea. 
 
 29. W. T. Manning. 1857. No. 2,949. 
 
 A filtration process. 
 
 30. /. A. Manning. 1858. No. 61. 
 
 Treats sewage with refuse from chlorine stills, *'.<?., 
 manganese chloride. 
 
 31. G. Niellon. 1858. No. 171, 
 
 Sewage is led into reservoirs and is assumed to be 
 precipitated, though no agents are mentioned. The 
 effluent is filtered through vegetable matter. 
 31. /. A. Manning. 1858. No. 179. 
 
 Collects sewage in tanks, and precipitates the solids 
 with alum-sludge, or its chemical equivalents (see Spe- 
 cification No. 1,786, 1855), an d combined, if necessary, 
 with refuse charcoal, lime, or chloroform (sic) \ 
 
 We can only hope, in common charity, that " chlo- 
 roform " is a clerical or typographical error. 
 33. G. L. Blyth. 1858. No. 287. 
 
 Employs a soluble phosphate to neutralise and fix any 
 ammonia or nitrogenous matter in sewage, or other 
 fluids, such as gas, or dye, or other waste liquors, and 
 also to neutralise the excess of acid by lime, or other 
 alkali, or alkaline earth, or magnesia, or magnesian 
 
SEWAGE PATENTS. 195 
 
 limestone, or aluminium, so as to precipitate the whole 
 of the phosphate from the liquid. Instructions are 
 given for preparing soluble phosphates, and in place of 
 phosphate of lime, phosphate of magnesia, alumina, 
 iron, or copper may be used, as these, except phosphate 
 of magnesia, which does not require the addition, can 
 be brought to the soluble form, and by double decom- 
 position with a soluble salt of magnesia converted 
 into superphosphate of magnesia. 
 
 In most dye-liquors nitrogenous matter is not 
 abundant. 
 
 34. /. Hadfield. 1868. No. 400. 
 
 Filters sewage through a bed, the first layer of which 
 is spent tanner's bark, saturated with solution of cop- 
 peras ; the second is of chalk ; the third again of veget- 
 able matter, saturated with copperas. The liquid is 
 then again filtered through chalk, or a mixture of chalk 
 and sulphate of baryta. 
 
 35. T. Spencer. 1858. No. 1,415. 
 
 Filters foul waters through a bed of magnetic iron 
 carbide. 
 
 36. B. Young and P . Brown. 1,858. No. 1,460. 
 
 Let sewage settle in tanks, pass gases through fur- 
 naces, and after some days allow supernatant water to 
 flow into river or sea, and apply the solids usefully. 
 
 37. /. Chisholme. 1858. No. 1,499. 
 
 Treats sewage by electricity, for doing which he 
 describes eight processes. 
 
 38. A. R. Broonan. 1858. No. 1,616. 
 
 Precipitates the solids of sewage with lime water or 
 soluble salts of lime. Mixes solids with gypsum recently 
 baked to plaster. 
 
 39. /. B. A. Duglere. 1858. No. 2,073. 
 
 Separates solids from liquids for disinfecting purposes, 
 by employing magnesia, salts, metallic precipitants arid 
 
196 SEWAGE TREATMENT. 
 
 phosphoric and ammoniac acids. What 
 acid " may be is doubtful. 
 
 40. H. Moule. 1859. No. 539. 
 
 Treats sewage by evaporation. 
 
 41. Bridge Standon. 1859. No. 1,567. 
 
 Treats sewage and excrement with mineral oil, 
 paraffin, gallipoli or rape oil ; common salt may also 
 be applied. Sulphuric acid is used to neutralise 
 ammonia. 
 
 42. N. Hereford. 1859. No. 2,107. 
 
 Proposes to purify polluted rivers by forcing sea water 
 up them, and applying it also to cesspools. 
 
 The inventor was probably not aware that the con- 
 tact of polluted streams with sea water is exceed- 
 ingly dangerous to health. 
 
 43. John Dales. 1859. No. 2,157. 
 
 Treats sewage with magnetic-chloride of iron, " pre- 
 pared by dissolving in muriatic acid magnetic oxide of 
 iron, or any of those ferruginous products from various 
 metallurgical processes and manufactures which are 
 magnetic." He uses also chloride of manganese. 
 
 This approaches very closely to a solution of iron 
 recently sold in France and Italy as a disinfectant, 
 under the name of " Smorbo." 
 
 44. R. Smith. 1859. No. 2,359. 
 
 Treats sewage with a mixture of powdered sulphur 
 and turpentine, " with any of the ordinary agents 
 employed to animal or vegetable matter in a state of 
 decomposition." 
 
 45. A. McDougall. 1859. No. 2,958. 
 
 Treats sewage with a heavy oil of tar, dissolved in 
 water, by the use of alkali, or alkaline earths ; and 
 secondly, treats the oil of tar with an acid previously, 
 to increase its solubility. If the sewage is already putrid 
 
SEWAGE PATENTS. 197 
 
 a small quantity of a metallic salt may be added to the 
 oil, after treatment with the acid. 
 
 46. M. Mangles. 1860. No. 655. 
 
 Forces chlorine, or sulphurous, nitrous, hydrochloric 
 gases through sewage, &c. 
 
 47. /. A. Manning. 1860. No. 1,343. 
 
 Alum-sludge again ; but the sewage is allowed to settle 
 first for some time, and only the clear water is to be 
 treated. 
 
 48. F. Durand. 1860. No. 1,612. 
 
 Constructs a canal to the sea, with gates to be open 
 or closed, according to the state of the tide. 
 
 49. /. Harrop. 1863. No. 132. 
 
 Treats faecal and urinous matter with chloride of 
 sodium alone, dissolved in water, or mixed with suitable 
 resinous, bituminous, earthy, vegetable, metallic, or 
 alkaline matters. 
 
 50. W. Clark. 1863. No. 761. 
 
 Filters through a layer of " crotels " sulphate of mag- 
 nesia in powder, on other layers of " crotels," saturated 
 with free phosphoric acid, and phosphate of lime. As 
 other filtering materials are mentioned " faeces and 
 paunches of animals " (!). 
 
 51. R. C. Clapham. 1860. No. 976. 
 
 Treats sewage with chlorides of manganese and iron. 
 
 52. W.Clark. 1863. No. 1,362. 
 
 Passes urine, &c., upon beds of quick-lime. 
 
 53. H. Martin. 1863. No. 1,435. 
 
 Mixes sewage or night soil with charred tan, or other 
 charred vegetable material. 
 
 54. T. H. Baker and G. Friend. 1863. No. 2,208. 
 
 Filter through sand, shingle, waste tan, gravel, 
 charred tan, &c. 
 
I9 SEWAGE TREATMENT. 
 
 55. F. Maynes. 1863. No. 3,264. 
 
 Freezes sewage, &c., to effect separation of the 
 solids. 
 
 Even if this process were practicable it would not 
 fully remove either dissolved or suspended impurities. 
 
 56. W. E. Weston. 1864. No. 1,688. 
 
 Treats sewage with neutral sulphate of peroxide of 
 iron (ferric sulphate). 
 
 57. W. Bardwell. 1864. .#0.3,115. 
 
 Precipitates the solids of sewage with sulphate of 
 lime. 
 
 58. H.Bird. 1864. No. 3,160. 
 
 Mixes sewage waters with sulphated clay, i.e., crude 
 aluminium sulphate. 
 
 59. R. Smith. 1 865 . No. 45 1 . 
 
 Introduces into the sewers peat, saw-dust, or other 
 ligneous matter saturated with sulphurous acid, or 
 superphosphate of lime. 
 
 60. C. G. Lenk. 1865. No. 1,242. 
 
 Adds to foul water, a mixture of permanganate of 
 potash, carbonate of soda, alum and neutralised 
 aluminite. 
 
 6 1. A. Bird. 1865. No* 2 >4i5- 
 
 Precipitates with sulphate of alumina. 
 
 62. /. Linton. 1865. No. 2,626. 
 
 Adds to sewage solids ground clay, or other 
 
 suitable refuse, with a small quantity of gypsum (!) 
 as a deodoriser. 
 
 63. C. G. Lenk. 1865. No. 2,674. 
 
 Adds to foul waters alum, "alumnite" neutralised 
 or not, two parts carbonate of soda and solution of 
 iron, or of permanganate of potash. 
 
 This border very closely upon No. 1,242 of the 
 same year. 
 
SEWAGE PATENTS. 199 
 
 64. H. Y. D. Scott. 1865. No. 2,808. 
 
 Deodorises sewage with lime and metallic salts, is 
 chiefly perchloride or persulphate of iron, the former 
 to neutralise the phosphoric and carbonic acid 
 contained in sewage, and the latter to seize upon the 
 sulphuretted hydrogen. The patentee admits that 
 these substances have been already used, but not in 
 the right way ! He causes the lime to act upon the 
 sewage in a separate reservoir and then runs off the 
 effluent into another tank, where it is treated with 
 the solution of iron. 
 
 It is only necessary to remark ,'that the neutral- 
 isation of carbonic acid is a point of no importance, 
 and that in recent sewage sulphuretted hydrogen is 
 not necessarily present. The patentee adds also some- 
 times sulphate of lime, common salt, and carbolic 
 acid. 
 
 65. F. Sutton. 1866. Nc. 101. 
 
 Treats sewage with sulphate of alumina, alone 
 or in conjunction with clay, sulphate of magnesia, or 
 peroxide of iron. 
 
 66. G. E. Moone. 1866. No. 1,163. 
 
 Treats with lime and distils off the ammonia 
 which is received in hydrochloric acid, forming sal- 
 ammoniac. 
 fy.A.Kithne. 1866. No. 2,107. 
 
 Treats foul water with chlorine or alkaline perman- 
 ganates, with or without sulphate of iron or other 
 metallic salts ; if excess of permanganate has been used, 
 the inventor neutralises it with hypo-sulphite of soda. 
 68. R. Irvine. 1866. No. 2,218. 
 
 Treats sewage with mineral charcoal obtained from 
 the residuum left by the distillation of paraffin oil from 
 shale, and containing silicate of alumina, with lime, mag- 
 
200 SEWAGE TREATMENT. 
 
 nesia, oxides of iron and carbon in a finely divided 
 state. 
 
 This specification should be carefully compared with 
 that of Mr. Coleman, of Glasgow, No. 1,954, of 1875. 
 
 69. A. H. Bonseville. 1866. No. 2,926. 
 
 Treats foul waters with lignite coke, charcoal, sul- 
 phate of iron, potter's clay, and slaked lime. 
 
 70. Ernst Silvern. 1867. No. 119. 
 
 Treats sewage, &c., with a mixture of burnt lime, with 
 5 per cent, of coal tar, and about ten times as much 
 water as lime, with the addition, when necessary, of 10 
 to 25 per cent, chloride of magnesium. The reader is 
 requested to compare this specification with the subse- 
 quent ones, 1870, No. 3,167 ; and 1876, No. 1,355. 
 
 71. W. Parry and J. Fr ear son. 1867. No. 417. 
 
 Mix with the sewage clay, clay iron ore or manganesic 
 earths, and allow it to settle. 
 
 72. A. H. Hart and W. Parry. 1867. No. 788. 
 
 Use the same materials. 
 
 73. E. Guenin. 1867. No. 1,229. 
 
 Uses waste manganese chloride from the chlorine 
 stills, neutralising acid if needful with dolomite, or other 
 calcareous magnesian substance, or lime / or zinc or 
 iron scrap, or oxidised ores of the same. He also adds 
 2 or 3 per cent, of raw salts of alumina from the 
 washing of aluminous schists, or a certain quantity of 
 the schists themselves in a natural state. 
 
 74. F. Tolhausen. 1867. No. 2,549. 
 
 Treats urine with plaster, peat, and ashes. 
 
 75. T. H. Baker and T. Woodroffe. 1867. No. 2,894. 
 
 No purifying agent is mentioned beyond baked earth . 
 
 76. A. M. Clark. 1867. No. 3,566. 
 
 Treats sewage with neutral phosphate of magnesia, 
 in order to precipitate ammoniaco-magnesian phos- 
 phate. 
 
SEWAGE PATENTS. 201 
 
 77- W. C. Sillar, R. G. Sillar, and G. W. Wigner. 1868. 
 No. 1,954. 
 
 Treat sewage with 4lbs. per 1,000 gals, of the 
 following mixture : 
 
 Parts, 
 
 Alum .... 
 Blood .... 
 Clay 
 
 600 
 i 
 
 
 c 
 
 Manganate of potash 
 Burnt clay 
 Chloride of sodium 
 Animal charcoal 
 Vegetable charcoal 
 Magnesian limestone 
 
 10 
 
 . . 25 
 
 10 
 
 15 
 
 20 
 2 
 
 2,588 
 
 This is the original ABC process. It may be 
 sufficient here to remark that the chloride of sodium 
 is certainly injurious, whilst the magnesian limestone, 
 the burnt clay, and the magnesia are, under most circum- 
 stances, inert. 
 
 78. W. H. Hughan. 1868. No. 2,883. 
 
 Mixes the sewage with cement to the consistency of 
 mortar. Acids or salts may be added, e.g. I part of 
 copperas to 6 parts of cement. Describes a special 
 cement made of 4 parts alum and I part of clay or 
 sulphate or phosphate of lime in solution ; a little caustic 
 lime or phosphates may be added, as also charcoal or 
 salt, also bone ash. 
 
 It is difficult to conceive the quantity of cement which 
 would be needed to solidify the sewage of London. 
 
 79. E. H. Prentice. 1868. No. 2,919. 
 
 Adds to sewage phosphoric acid, or any soluble phos- 
 phate, in the proportion of 12 or 15 Ibs. to 1,000 gals. 
 
202 SEWAGE TREATMENT. 
 
 sewage, and then precipitates with 20 to 30 Ibs. lime to 
 4,000 gals, sewage. 
 
 This is a favourable specimen of the phosphate 
 process. 
 
 80. G. Chapman. 1868. No. 3,203. 
 
 Lets the sewage decompose in large tanks (!) at a 
 temperature of 70 to 80 degs. Fahr. ; then adds caustic 
 lime in a precipitating tank, and passes through the 
 clear liquor steam to extract the ammonia. 
 
 The first part of this process would be a fearful 
 nuisance. A part of the ammonia would be lost on 
 addition of the lime, if not before. 
 
 81. C.Jones. 1868. ^7.3,457. 
 
 Precipitates sewage with slaked lime and petroleum, 
 or, instead of petroleum, the acid tar obtained in the 
 manufacture of liquid hydro-carbons. To improve the 
 manure, chloride of zinc, or sulphuric acid, or burnt 
 clay, or magnesia may be added. 
 
 What is to precipitate the petroleum ? Chloride of 
 zinc is a poison to vegetation. 
 
 82. T. Smith and J. van Nor den Bazalgette. 1868. 
 No. 3,562. 
 
 Treat sewage with a mixture of marl, clay, mould, 
 schists, refuse products, ashes, treated by mineral acids. 
 
 The term refuse products includes substances some of 
 which would be useless, and others positively injurious. 
 
 83. A.M. Clark. 1868. No. 3,714. 
 
 Treats sewage with a double phosphate of magnesia 
 and iron. 
 
 84. M.J.Anderson. 1869. No. 3,550. 
 
 Precipitates with sulphate of alumina (lib. to 100 gals.) 
 followed up by 5 Ibs. slaked lime. 
 
 This patent became the property of the " Rivers 
 Purification Association," and has been worked for some 
 years at Coventry and Nuneaton, followed up, however, 
 
SEWAGE PATENTS. 203 
 
 by irrigation. It will be observed that the lime is much 
 more than sufficient to neutralise any acids likely to be 
 present in the sewage, and will therefore act as a 
 substantive precipitant. 
 
 85. W. H. Hughan. 1870. No. 67. 
 
 Uses to sewage natural phosphates, treated with 
 dilute acids, diluted with urine and mixed with night- 
 soil, along with the cement indicated in his former 
 patent, 1,868, No. 2883. 
 
 86. D.Forbes and A. J. Price. 1870. No. 607. 
 
 Add to the sewage phosphate of alumina, previously 
 dissolved in sulphuric acid, and follow up with lime. 
 The proportion of phosphate preferred is 2 Ibs. to 1 ,000 
 Ibs. of sewage. 
 
 This process, like the two following, came into the 
 hands of the Phosphate Sewage Company, and was 
 worked at Hertford. 
 
 87. D. Forbes and A. P. Price. 1870. No. 1,137. 
 
 This specification differs very little from that of 1870, 
 No. 607. The inventors now propose to heat the 
 phosphate of alumina in hydrochloric acid or in a 
 mixture of that and sulphuric acid, and they also add 
 deodorising agents, such as animal or vegetable char- 
 coal. 
 
 88. A. P. Price. 1870. No. 1,314. 
 
 This invention, again, borders very closely upon 
 Nos. 607 and 1,137 of the same year. The inventor 
 uses "natural phosphates of iron, lime, and alumina." 
 
 89. G. W. Wigner. 1870. No. 1,354. 
 
 This is an improvement upon No. 1,954 of 1868. 
 The inventor uses : 
 
 Parts. 
 
 Alum .... 600 
 
 Blood ... i 
 
 Clay .... 1,900 
 
 Magnesia ... 5 
 
204 SEWAGE TREATMENT. 
 
 Parts 
 
 Manganate of potash . 10 
 
 Burnt clay . . .25 
 
 Chloride of sodium . . 10 
 
 Animal charcoal . . 15 
 
 Vegetable charcoal . . 20 
 
 Magnesian limestone . 2 
 
 Sulphate of alumina . .169 
 
 Sulphate of iron . . 3 
 
 Sulphate of lime . . 66 
 
 Alumina . . .94 
 
 2,920 
 
 There is added the proviso that, instead of the last four 
 substances, 488 parts of crude alum may be used, 
 making the entire quantity of alum to be used 1,088 
 parts. 
 
 It is certainly strange to find alum and sulphate of 
 alumina combined in the same formula. Alum is not 
 only much more costly and less readily soluble, but has 
 the serious disadvantage of introducing into the effluent 
 water, in pure waste, sulphate of potash or sulphate of 
 ammonia. The useless ingredients of the patent 
 No. 1,954 f J 868 (magnesia, burnt clay, chloride of 
 sodium, and magnesian limestone), are re f ained, and 
 two new ones, sulphate of lime and alumina (unless 
 the hydrate be meant), are introduced. This patent 
 came into the possession of the Native Guano Company, 
 but it has long been abandoned in favour of simpler and 
 more rational processes. 
 
 90. B. G. Sloper. 1870. No. 1,706. 
 
 Mixes fresh sewage with stale sewage to promote 
 fermentation. Then draws off the supernatant water (!), 
 and mixes with the sediment a salt of magnesia and 
 phosphate of soda or lime. To deodorise the sewage 
 he uses sulphate of alumina, sulphate of iron, sulphate 
 of lime, and chloride of lime. 
 
SEWAGE PATENTS. 205 
 
 To the fermentation process there is a strong objec- 
 tion, mentioned under No. 3,203, A.D. 1868. Sulphates 
 of alumina and iron precipitate, but they have little 
 deodorising power. Sulphate of lime is altogether out 
 of place in sewage treatment, and chloride of lime, if 
 used in sufficient quantity to deodorise sewage, will 
 destroy fish in any river into which the effluent may 
 make its way. 
 gi.J.J.Hays. 1870. No. 2,297. 
 
 Treats sewage with " ground peat, peat charcoal, 
 or other suitable material." Lets settle, and filters 
 effluent. 
 
 92. G. Bischof. 1870. No. 2,516. 
 
 Passes sewage upwards or downwards through a 
 layer of spongy iron, about a foot thick, at the bottom 
 of a tank or filtering bed. The solids are to be pre- 
 viously filtered out. 
 
 This process, which involves double filtration is, of 
 course, inapplicable when the sewage contains any sub- 
 stance capable of acting on iron. 
 
 93. F. Fenton and S. Hollins. 1870. No. 2,534. 
 
 Treat sewage with a combination of gypsum, sulphate 
 of lime, bisulphate of iron, soot, chalk, salt, cinder 
 breeze or ashes, or a combination of the bind, clay 
 shale, alum shale, or barren shale of the coal measures, 
 or alum clay or alum shale, either raw or roasted with 
 any or all of the above. 
 
 For acid waters they use any of the above ingredients, 
 or salt and lime, or salt, lime, gypsum, and chalk, or 
 plaster of Paris, or calcined gypsum, hydrated together 
 or separately, and afterwards mixed. The product may 
 be used " as a substitute for coprolites " (!). 
 
 The error of using soot, sulphate of lime, chalk, and 
 salt in sewage treatment has been already explained. 
 Most clay shales, raw or roasted, are quite inert. 
 
206 SEWAGE TREATMENT. 
 
 94. C. F. Kirkman. 1870. No. 2,653. 
 
 Seeks to disinfect sewage by treatment with carbonic 
 acid, and by passing through a receptacle in which are 
 a number of zinc and copper plates, by which " a con- 
 tinuous current of electricity is made to pass through 
 the sewage." 
 
 95. /. /. Hays. 1870. No. 2,838. 
 
 Treats sewage with peat charcoal, and filters through 
 a bed of peat charcoal, and afterwards through carbonate 
 or hydrate of lime and sand. (See 1870, No. 2,297.) 
 
 It is necessary to remark that the actions of carbonate 
 of lime and of hydrate of lime upon sewage are not alike. 
 
 96. A . Bryant and S . H. Culley. 1870. No. 3,107. 
 
 Let sewage deposit in settling tanks, after the addition 
 of deodorising materials, such as carbolic acid, and then 
 filter through sawdust, dried or charred. 
 
 97. F. Hille. 1870. No. 3,167. 
 
 Uses as a disinfectant for sewage, chloride of zinc, 
 calcium and magnesium, lime and gas-tar. (See 
 specification of E. Siivern, 1867, No. 119, in which the 
 use of chloride of magnesium, in combination with lime 
 and coal tar is already mentioned.) 
 
 98. H. Y. Darracott Scott. 1870. No. 3,169. 
 
 Treats sewage with lime, preferably gas-lime (!), to- 
 gether with certain metallic salts, suitable for preci- 
 pitating sulphuretted hydrogen. These agents are to be 
 introduced at different parts in the course of the sewers. 
 
 This system is objectionable since the deposits 
 produced may accumulate and putrefy in the sewer. 
 The metallic salts best fitted for removing sulphuretted 
 hydrogen are poisonous, and too expensive. 
 
 99. C. Rawson y P. Ovenden, James Wylde, W. McCree, 
 andH. Hill. 1870. No. 3,399. 
 
 Improvements on No. 1,954, A.D. 1868, and on No. 
 1,354, A.D. 1870. The inventors substitute for blood, 
 
SEWAGE PATENTS. 207 
 
 <( albuminous, albumenoid, or gelatinous substances." 
 They also propose an alkaline mixture to be added if 
 necessary to the sewage, either before or after the 
 ingredients mentioned in the two former patents. 
 
 100. 5. Proctor and J. M. Sutton. 1871. No. 297. 
 
 Remove large; solids from the sewage by mechanical 
 arrangements ; add then disinfectants such as carbolic 
 acid, and filter. 
 
 101. G. B. SloperandF.J.J. Washer. 1871. No. 329. 
 
 Treat sewage first with an alkali, to decompose nitro- 
 genous matters and convert them into ammonia ; then 
 add salts of magnesia and soluble phosphates to pre- 
 cipitate ammoniacal magnesium phosphate, and complete 
 the 'process by adding " small quantities of lime with 
 sulphate of alumina, or chloride of lime, or protosulphate 
 of iron." 
 
 Treatment with an alkali fails to decompose some 
 possible nitrogenous compounds altogether, and acts 
 upon others only at very high temperatures. 
 
 102. C. Baly. 1871. No. 351. 
 
 Treats sewage with charcoal from the manufacture of 
 acetic acid and slaked lime ; one part charcoal, two 
 lime to five sewage. 
 
 103. A. P. Vassard. 1871. No. 1,211. 
 
 Treats sewage first with a solution of superphosphate 
 and phosphate of soda, then with sulphate of magnesia, 
 sulphate of alumina and sulphate of ammonia (!). A 
 little lime may also be added. 
 
 104. F. Fenton. 1871. No. 1,897. 
 
 In addition to the processes given in No. 2,534, A - D - 
 1870, the inventor forces atmospheric air through the 
 sewage. 
 
 105. E. Taylor. 1871. No. 1,969. 
 
 Treats the solids separated from the liquid sewage with 
 
208 SEWAGE TREATMENT. 
 
 a mixture of chloride of lime, sugar (!) and alum. The 
 same ingredients are apparently to be used also for 
 urine and blood. 
 
 1 06. /. T. Lupton. 1871. No. 2,140. 
 
 Treats sewage with 20 to 40 per cent of carbon, it 
 may be ashes, with a small amount of phosphate of lime. 
 
 107. H. Y. Darracott Scott. 1871. No. 2,243. 
 
 Precipitates sewage with quicklime, dries precipitate 
 and calcines it. Uses the calcined precipitate as manure, 
 or as mortar, or as cement. If used as manure, " super- 
 phosphate may be manufactured therefrom." 
 
 A substance containing so much lime and so little 
 phosphoric acid cannot prove a very profitable material. 
 
 108. /. Banks and W. Walker. 1871. No. 2,495. 
 
 Filter after settling, and mix sediment with sawdust, 
 straw, etc. 
 
 109. /. Hiirrow. 1871. No. 2,659. 
 
 Treats with an iron, salt and an alkali. 
 HO. /. B.Pow. 1871. No. 2,760. 
 
 Treats in first tank with copperas ; then filters through 
 i, gypsum, magnesian limestone and charcoal ; 2, 
 aluminium shale from the lias containing sulphates ol 
 aluminium and potassium, with a portion of sulphate 
 of iron combined with vegetable charcoal ; 3, spongy 
 iron, and 4, cocoa-nut fibre or peat charcoal. 
 in. F.L. Hahn Danchell. 1 87 1 . No. 2,903. 
 
 Treats sewage with a mixture of clay or lime, or both 
 with peat, the mass being charred. 
 112. A. P. Vassard. 1871. No. 2,926. 
 
 Treats sewage first with lime ; then adds to the liquid 
 oxide of barium and biphosphate of lime ; then with 
 chloride of lime and aluminate of soda. Instead of 
 oxide of barium, the sulphide or other soluble salt may 
 be used j instead of biphosphate of lime ordinary 
 superphosphate or other phosphate. Also other salts of 
 
SE WA GE PA TENTS. 209 
 
 magnesia (!) may be used instead of the chloride, and 
 various alkaline re-agents instead of aluminate of soda. 
 
 The objectionable character of barium compounds has 
 been already noticed ; the sulphide (sulphuret) as giving 
 off sulphuretted hydrogen is the worst. 
 
 113. /. Cole and W.Abbott. 1871. No. 2,975. 
 
 Precipitate the sewage in a tank, but do not state 
 what is the agent employed. 
 
 114. H. Smith. 1871. No. 2,997. 
 
 Reduces the temperature of the sewage and of the air 
 above the tanks, the latter by allowing liquid carbonic 
 acid to evaporate into it. 
 
 Even if this process could be carried out on the large 
 scale it would be useless, as water, if freezing, is not 
 freed from either its suspended or dissolved impurities. 
 
 115. /. F. Fahlman. 1871. No. 3,233. 
 
 A new mechanical arrangement, where no particular 
 method of disinfecting the sewage is claimed. 
 
 116. /. A. Wanklyn. 1871. ^0.3,436. 
 
 Obtains ammonia from sewage, driving it off either 
 by heat, or by " a current of air of a suitable temperature," 
 and condenses the ammonia by means of acid in a coke 
 tower. 
 
 117. H. Y. D. Scott. 1871. No. 3,515. 
 
 Brings the effluent from, it would seem, any pre- 
 cipitation process in contact with charcoal. When the 
 charcoal is saturated with ammonia it is dried at a 
 gentle heat so as not to expel the ammonia, then heated 
 to redness and the ammonia collected by any suitable 
 means. 
 
 The power of wet charcoal to absorb and retain 
 ammonia from liquids is not strikingly great. 
 
 1 1 8. F. G. Prange and W. Whitthread. 1872. No. 379. 
 
 Treat sewage with a solution of dicalcic phosphate in 
 an aqueous solution of mono-calcic phosphate, with an 
 p 
 
210 SEWAGE TREATMENT. 
 
 alkaline earth or alkali, such as lime. If there is an 
 excess of free ammonia, magnesium salts may also be 
 added. 
 
 119. A. M. Clark. 1872. No. 388. 
 
 Fixes the ammonia in sewage by means of bi-magnesian 
 phosphate or calcic magnesian phosphate. 
 
 1 20. /. Robey. 1872. ^7.435. 
 
 Mixes peat and clay, burns the mixture, and uses it 
 in treating sewage. 
 
 121. Silvester Fulda. 1872. No. 448. 
 
 Treats sewage with unslaked lime, sulphate of soda, 
 and, if required, of nitrate of soda, borax, and silica. 
 
 The uses of sulphate of soda in sewage treatment are 
 almost as hard to imagine as the circumstances under 
 which nitrate of soda and borax can be requisite. 
 Except the original sewage is strongly acid, the effluent 
 from this treatment must be alkaline. 
 
 122. F. Hille. 1872. No. 484. 
 
 Mixes sewage with chloride of magnesium, then passes 
 it into another tank, where it is treated with milk of 
 lime, forces carbonic acid gas into it, or adds instead a 
 small quantity of perchloride of iron, and filters over 
 charcoal. In hot weather, a mixture of lime and tar may 
 be added in a subsequent tank, or in the mixing-tank. 
 It is hard to see the precise novelty in this process. See 
 the inventor's previous patent, No. 3,167 of 1870. 
 
 123. 5. W. Rick. 1872. No. 547. 
 
 Lixiviates aluminous schists, adds to the liquor 
 chloride of sodium and evaporates down. In this 
 manner is obtained a crude chloride of aluminium, fit 
 for treating sewage. 
 
 124. W.E.Gedge. 1872. No. 626. 
 
 Treats sewage and other ammoniacal liquids in a 
 succession of boilers and passes the ammonia into dilute 
 sulphuric acid. 
 
SEWAGE PATENTS. 211 
 
 125. R.Blackburn. 1872. No. 671. 
 
 Screens and strains sewage, and treats the liquid 
 portions chemically (how, it is not stated), or uses them 
 for irrigation, or allows them to run into a water-course, 
 
 As in several patents, the fact that the " liquid 
 portions " of sewage are at once the most valuable, and, 
 if run direct into a watercourse, the most dangerous, is 
 here overlooked. 
 
 126. H. Y. D. Scott. 1872. No. 849. 
 
 Precipitates the suspended impurities with lime, prefer- 
 ably dolomitic ; treats the effluent from first precipita- 
 ting tank with phosphoric acid or a phosphate to preci- 
 pitate lime ; treats then the effluent from the second 
 tank may be treated with phosphate of magnesia to 
 extract the ammonia. Various things are also mentioned 
 which a may " be done. 
 
 127. Dugald Campbell. 1872. No. 944. 
 
 Treats sewage with acid, phosphate of lime, and then 
 adds milk of lime. 
 
 128. 5. W.Rich. 1872. No. 1,243. 
 
 Converts the alumina and peroxide of iron in burnt 
 shales into sulphates by treatment with sulphurous acid. 
 The process is carried on continuously in a kiln, in 
 which the shale is burnt while sulphurous acid gas (from 
 burning pyrites) are introduced below. The product 
 formed is lixiviated, and the liquor used for treating 
 sewage. 
 
 129. T. Christy. 1872. No. 1,257. 
 
 Disinfects foul waters with heavy oils, and then treats 
 them with silica to form a mixture which the inventor 
 terms " silicoid." 
 
 130. F.L.H. Danchell. 1872. No. 1,394. 
 
 Treats sewage with animal or vegetable refuse, mixed 
 with loam, clay, phosphate of alumina, lime, carbonate 
 of lime, or phosphate of lime, and charred. 
 
212 SEWAGE TREATMENT. 
 
 131. James Robey. 1872. No. 1,421 
 
 Chars arable soil in retorts, and uses the product for 
 treating sewage. 
 
 132. James Robey. 1872. No. 2,181. 
 
 Chars sewage sludge from processes No. 1,954 of 1,868, 
 or No. 1,354 f I ^7o, and uses it for treating sewage. 
 
 133. IsaacBrown. 1872. No. 2,279. 
 
 A mere mechanical arrangement which aims at puri- 
 fying sewage by settling, screening and straining. 
 
 134. H. Y.D. Scott. 1872. No. 2,538. 
 
 Precipitates the sewage with lime, treats the effluent 
 with the " phosphatic precipitants " mentioned in No. 
 849 of 1872, with or without charcoal. It is very diffi- 
 cult to find any essential difference between the process 
 here described, and that given in No. 849 of 1872. 
 
 135. B. W. Gerland and E.Johnson. 1872. No. 2,569. 
 
 Char fresh turf, and sawdust, spent tan, mixed with 
 loam, and use the product for filtration, with or with- 
 out the addition of phosphoric acid. They divide the 
 sewage into two branches ; to the one is added phos- 
 phoric acid, with or without the charcoal dust, and to 
 the other, milk of lime. The precipitate is let settle, 
 and the effluent filtered through the charcoal above- 
 mentioned. 
 
 136. W. Astrop. 1872. No. 2,991. 
 
 A mechanical method of separating the solids from 
 the liquid portions of sewage. 
 
 137. H. Y.D.Scott. 1872. No. 3,028. 
 
 A method of adding lime to sewage, and a process for 
 drying sewage sludge. 
 
 138. /. A. Manning. 1872. No. 3,356. 
 
 Evaporates sewage to dryness, passing the fumes given 
 off into a furnace (!). The cost of this in the case of a 
 large city ? 
 
SEWAGE PATENTS. 213 
 
 139. G. Alsing. 1872. No. 3,412. 
 
 Converts sewage and night-soil into manure by mix- 
 ing with sulphate of lime. 
 
 140. C . Hills and B . Biggs . 1872. No. 3,464. 
 
 Mix sewage in an air-tight tank with lime to liberate 
 ammonia. Force air through the sewage into a second 
 tank containing sulphurous acid. Or they force sul- 
 phurous acid into the sewage instead of air. 
 
 141. D. Curran and James Dewar. 1872. No. 3,533. 
 
 Use peat, either alone or along with chalk, lime, earth, 
 etc., for filtering, disinfecting and absorbing foul waters. 
 
 142. H. Y.D.Scott. 1872. -Afo. 3,755. 
 
 Uses the effluent from a lime-process for working 
 water-closets. 
 
 143. H. Y. D. Scott. 1873. No. 154. 
 
 Treats sewage with lime in excess, and adds to the efflu- 
 ent " soluble salts of cheap metallic oxides." After this, 
 the effluent may be filtered through charcoal, or may 
 be run at once into a stream. 
 
 144. /. L. D. Target. 1873. No. 168. 
 
 Chars sewage solids mixed with sawdust, tar, etc., and 
 uses them as fuel. Boils the sewage along with lime 
 and catches the ammonia. 
 
 145. E. C. Hamilton, W. R. Preston, and H. Jones. 
 1873. No. 187. 
 
 Mix shoddy with sewage. 
 
 146. James Robey. 1873. ^7.230. 
 
 Chars the sludge obtained under No. 1,954 of 1868, 
 and No. 1,354 of 1870, with or without an admixture of 
 clay, and uses it for treating sewage. 
 
 As the inventor claimed the use of the same sewage 
 sludge charred, for the same purpose, in patent No. 2,181 
 of 1872, but abandoned the idea without proceeding to 
 the great seal, the question might be raised, whether he 
 did not, by so doing, anticipate the present patent ? 
 
2i 4 SEWAGE TREATMENT. 
 
 147. J.Jacobsen. 1873. No. 266. 
 
 Treats sewage with phosphate of lime and sulphuric 
 acid, diluted with the liquid sewage itself. 
 
 148. H. Y. D. Scott. 1873. No. 296. 
 
 Precipitates the suspended matters in sewage by lime- 
 water in excess. Treats the effluent with acid solution 
 of phosphatic substances. If this is added in excess, 
 the effluent is again treated with lime. Here we recog- 
 nise a strong family likeness to the inventor's previous 
 processes. 
 
 149. Baldwin Latham. 1873. No. 331. 
 
 Treats the deposits from various sewage processes 
 preferably that from No. 3,650 of 1869 with sulphuric 
 acid to obtain fresh material for treating further portions 
 of sewage. 
 
 The economy of this process, and of similar processes, 
 is very doubtful, since a portion of sulphuric acid 
 (the expensive article in making sulphate of alu- 
 mina) is wasted by the organic matter and the lime 
 present in the deposit. 
 
 150. F.H. Atkins. 1873. No. 556. 
 
 Filters sewage through ground coke or cinders con- 
 verted by pressure into slabs. He also applies "galvanic, 
 . magnetic, or electric action to filtering apparatus, 
 reservoirs, or tanks, for the purpose of precipitating 
 organic and inorganic matters in suspension or solution." 
 
 151. R. S. Symington. 1873. No. 912. 
 
 An improvement on No. 2,667 of 1868. The effluent 
 water is to be purified by " falling in a broken manner 
 through a sufficient height before passing through the 
 last filtering tank." 
 
 152. G. Alsing. 1873. No. 1,319. 
 
 Mixes sewage sludge with dry gypsum. 
 
 153. H. Y. D. Scott. 1873. No. 1,445. 
 
 The sewage deposit, of course from a lime process, is 
 
SEWAGE PATENTS. 215 
 
 treated with more lime, and mixed with some material 
 wetted with sulphuric or hydrochloric acid. The com- 
 pound obtained is used for deodorising pail-stuff, and 
 finally employed as manure. Chloride of lime, or chloride 
 of zinc or iron, or sulphates of those metals, may also be 
 added to the compound. 
 
 Salts of zinc are injurious to vegetation, and cannot, 
 therefore, be safely added to any kind of manure. 
 
 154. H. Y. D. Scott. 1873. No. 1,509. 
 
 Dries sewage deposits from lime processes ; are dried in 
 retorts and used along with lime, chloride of lime and 
 charcoal. 
 
 155. Walter Brown. 1873. .Afo. 1,555. 
 
 Calcines shaly minerals with exclusion of air, 
 quenches them with water, and uses the pieces for mak- 
 ing a filter-bed, or for treating sewage in other ways. 
 
 It must be remembered that many " shaly minerals " 
 contain nothing capable of yielding a soluble salt of 
 alumina after ignition. 
 
 156. E.Moriarty. 1873. No. 1,686. 
 
 Treats sewage with, per 28 Ibs. : 12 ozs. acid phos- 
 phate of magnesia, 6 ozs. sulphate of iron, 4 ozs. 
 sulphur (!), 4 ozs. ammonia, 4 ozs. phosphoric acid, 4 ozs. 
 nitrate of soda, 3 ozs. nitrate of potash, 4 Ibs. gas tar, 
 6 Ibs. wood charcoal, and sulphate of lime to bring the 
 whole to a solid state. 
 
 This process does not aim at producing an effluent, 
 and is intended for cesspool matters rather than for 
 town sewage. 
 \tf.B.Green. 1873. Afo. 1,885. 
 
 Draws sewage gases through a fire, lets solids deposit 
 as manure, and runs the liquid into a river. 
 158. Jos. Townsend. 1873. No. 1,967. 
 
 Treats sewage with any of the three following mix- 
 tures : i. 100 Ibs. of a phosphate containing 40 per cent. 
 
216 SEWAGE TREATMENT. 
 
 phosphoric acid and 20 per cent, alumina is mixed 
 with 50 Ibs. of lime, and by preference 2 to 5 per cent, of 
 soda or potash, or an equivalent quantity of carbonate, 
 sulphate, or sulphite of soda or potash, " with sufficient 
 lime to set free the alkali." The resulting products are 
 " principally phosphate and aluminate of lime." For 
 the lime may be substituted 36 Ibs. magnesia, or 47 Ibs. 
 lime and 8 Ibs. magnesia. 2. A mixture of alumina with 
 lime or magnesia, or both lime and magnesia. 3. A 
 " substance containing alumina associated with silica " 
 is mixed with lime or magnesia and alkali, or u substances 
 yielding alkali " are added. 
 1 59- Jo/m Leigh. 1 873 . No. 2,07 1 . 
 
 Adds a solution of an earthy salt, followed by a 
 solution of silicate of soda or potash. As earthy salt 
 chloride of lime may be used (!). If much gelatinous 
 or aluminous matter is present tannin is also added. 
 
 For " aluminous " the correct reading is probably 
 " albuminous." 
 
 1 60. Jeremiah Marsden and J. Collins. 1873. .#0.2,317. 
 
 Treat sewage per 200,000 gallons with 12 cwt. lime, 
 4ocwt. coal ashes, i6cwt. charcoal, "and a small 
 quantity of an acid salt of soda, potash, iron, manganese, 
 or the like." 
 
 This process is, or has been, at use at Bolton. How 
 manganese can be called " the like " of soda or potash 
 is not apparent. Coal ashes are of very doubtful value. 
 
 161. Robert Knott. 1873. .#0.2,442. 
 
 Treats sewage with a mixture of quicklime and soda 
 .introduced into the sewage in a boiling state. 
 
 162. F.Jacobsen. 1873. -#0.2,454. 
 
 Precipitates sewage with the refuse " obtained after 
 the lye-water of paper-mills has undergone the soda- 
 recovering process." To facilitate precipitation he 
 further adds common salt, sulphate of zinc, chloride of 
 
SEWAGE PATENTS. 217 
 
 iron, alum, slaked lime, and " the water from electric 
 batteries." 
 
 Sulphate of zinc is fatal, common salt useless, and 
 the water from batteries very doubtful. 
 
 163. F.Jacobsen. 1873. No. 2,455. 
 
 Treats the waste water from paper-mills and other 
 works with lime. To assist the process he adds 
 " common salt, sulphate of zinc, chloride of iron, and 
 perchloride of iron." 
 
 164. William White. 1873. No. 2,532. 
 
 Neutralises sewage with lime if necessary, and treats 
 with sufficient chloride of calcium to precipitate sulphates, 
 carbonates, and phosphates along with albuminous and 
 other matters. The solution is then treated with 
 sulphate of iron to convert the excess of chloride of 
 calcium into sulphate, setting free chloride of iron, 
 which may be precipitated as oxide by the addition of 
 lime. 
 
 The final effluent will therefore be alkaline after these 
 four successive treatments. In the deposit there will be 
 sulphate of lime, which, as already explained, is not to 
 be desired. 
 
 165. James Robey. 1873. No. 2,534. 
 
 Treats sewage with raw peat, and adds any suitable 
 precipitating agent. 
 
 166. C.Rawson, W. C. Sillar,J. W. Slater, and T. S. 
 Wilson. 1873. No. 2,662. 
 
 Pass sulphurous acid, chlorine, or other disinfecting 
 gases through sewage, and then precipitate with sul- 
 phate of alumina, etc., if needful. 
 
 This process was mainly intended for blood. For 
 sewage it is too costly and circumstantial. 
 
 167. R. Goodall. 1873. No. 2,791. 
 
 Adds per i ,000 gallons 2 bushels of fine ashes and 
 
2i 8 SEWAGE TREATMENT. 
 
 23lbs. slaked lime. After agitation, I pint sulphate of 
 iron and 7 pints of solution of sulphate of magnesia. 
 
 168. W. Whitthread. 1873. No. 3,169. 
 
 Treats sewage with manganese tetra-chloride. Other 
 haloid salts of manganese may be used. Finally, an 
 alkali is added. 
 
 169. A. C. Fraser and W. Watson. 1873. No. 3,632. 
 
 Treat sewage with calcined schist, which may be 
 saturated with dilute sulphuric acid, and mixed with 
 clay and sulphate of lime. The outflow from the last 
 tank passes into a filter charged with lime, calcined 
 schist, charcoal and sand. 
 
 170. H. Y.D. Scott. 1873. No. 3,742. 
 
 Sewage is precipitated in the " ordinary " manner 
 with lime, and the effluent is treated with "an impure 
 sulphate or chloride of lime and alumina," prepared by 
 " digesting prussiate of potash charcoal with dilute 
 sulphuric or hydrochloric acid." 
 
 Chloride of lime cannot be obtained at all in the way 
 described. Alumina is present in the charcoal merely 
 as an impurity present in the carbonate of potash used 
 in prussiate-making. The product really obtained will 
 consist mainly of sulphate or chloride of iron, which 
 can be more conveniently or cheaply obtained in other 
 manners. 
 
 171. W. White. 1873. No. 3,781. 
 
 Precipitates sewage with lime-charcoal, a calcined 
 mixture of chalk, peat, and sawdust. Soluble phosphate 
 may be added to the sewage before the treatment with 
 lime-charcoal. " Lime-coke" may also be used, made by 
 burning a mixture of small coal and lime. Ground 
 mineral phosphates may be mixed with peat, or other 
 form of carbon, and used as above. Industrial waste 
 waters unfit for manure may be treated with " lime- 
 
SEWAGE PATENTS. 219 
 
 clay-charcoal," a calcined mixture of lime and clay with 
 or without carbon. 
 
 172. W. White. 1873. No. 3,781. 
 
 Disclaims the method of preparing the precipitating 
 agents mentioned in the last specification. 
 
 173. B. Green. 1873. No. 3,833. 
 
 Lets the sewage settle in pits, carrying the gases into 
 a furnace, and letting the liquid run into " a river, the 
 sea, or elsewhere." 
 
 This patent, like certain others, is based on the 
 mistaken notion that sewage, after spontaneously de- 
 positing its " sludge," is harmless, and may be safely 
 run off into rivers. 
 
 174. Paul Curie. 1873. ^0.4,181. 
 
 Treats the sewage with a " disinfectant," sulphate of 
 iron, clay, chalk, etc. The products of combustion from 
 a furnace, mixed with air, are driven through the 
 sewage, which is then apparently evaporated to 
 dryness. 
 
 175. A. E. Schmersahl. 1874. No. 160. 
 
 Treats sewage with a mixture of 2 parts sulphuric 
 acid and I part hydrochloric acid, and then with lime. 
 
 The result of such treatment will be the formation of 
 sulphate of lime art evil and chloride of calcium. 
 
 176. H. M. Synge. 1874. No. 255. 
 
 A complicated filtration process through successive 
 tanks charged with materials of increasing fineness. 
 
 177. E. H. C. Monckton. 1874. No. 265. 
 
 Purifies sewage by passage through electrified channels, 
 or drives ozonised water into sewage for the purpose of 
 purifying it. Recovers metals in solution from the 
 sewage of manufacturing towns by an electric process. 
 Uses windmills as a power to generate electricity for 
 purifying sewage. 
 
 Ozone would doubtless prove a powerful deodorising 
 
220 SEWAGE TREATMENT. 
 
 agent for sewage if its price permitted. It might be 
 interesting to try the action of electricity on sewage 
 where power for driving dynamos could be had free of 
 cost. 
 
 178. H. Y. D. Scott. 1874. No. 283. 
 
 Precipitates sewage by lime, or removes the solids by 
 other means. Passes liquid through filters charged 
 with " phosphate of iron salts," or adds such salts to the 
 liquid. Runs effluent through filters of lime and char- 
 coal. Gives methods for making the phosphate of iron 
 salts, to which, before use, lime refuse from soda or gas- 
 works may be added. 
 
 The effluent here will apparently be alkaline. It is 
 interesting to note how many changes, capable of being 
 patented, have been rung on the old lime process, in 
 which its cardinal faults are retained, whilst its cheap- 
 ness and simplicity are lost. 
 
 179. H. Y.D. Scott. 1874. No. 653. 
 
 Precipitates sewage by lime mixed with soluble 
 phosphate, or phosphoric acid, or soluble metallic salts. 
 
 Lime mixed with " soluble metallic salts " will pre- 
 cipitate those most likely to be used for sewage 
 purposes, and render them comparatively inert. It will 
 also render the soluble phosphate or the phosphoric 
 acid insoluble. Phosphoric acid is, further, an agent 
 far too costly to be used in sewage treatment, 
 
 1 80. Rupert Goodall. 1874. No. 848. 
 
 The author places in one vessel a " mixture of calcium 
 and carbon," in another slaked lime and carbon, or 
 slaked lime alone, and in a third vessel a solution of 
 sesqui-persulphate of iron, and delivers these into the 
 sewage. 
 
 181. W.R.Lake. 1874. M?. 1,415. 
 
 Boils the sewage, and receives the volatile matters 
 in a series of Woolf's bottles containing sulphate of 
 
SEWAGE PATENTS. 221 
 
 iron, lime, sulphuric acid, etc., to fix the ammonia. The 
 residue left in the boilers is cooled and used as manure. 
 How the residue is to be rendered inoffensive we are 
 not informed. Quaere How many boilers would be 
 required to receive the sewage of London ? 
 
 182. /. Towle. 1874. No. 1,426. 
 
 Delivers sewage into pits into which town refuse is 
 also cast. Spent hops and cut straw are also placed in 
 the pits. 
 
 183. /. H. Kidd. 1874. No. 1,764. 
 
 Allows the sewage solids to settle in tanks and runs 
 off the effluent water. Adds, apparently to the deposit, 
 salt or lime and carbonised shale. 
 
 184. Rupert Goodall. 1874. No. 1,826. 
 
 Treats sewage per 1 ,000 gallons with i quart of sesqui- 
 persulphate of iron, and I pint thereof, and I pint 
 of nitrate of iron. There may also be added along 
 with the iron liquors saturated solutions of lead salts, or 
 of ferro-cyanide of potassium. 
 
 Or a mixture of gas-lime I or 2 parts, slaked lime 
 I or 2 parts, and animal carbon 2 to 4 parts may be 
 added in the proportion of 27 Ibs. per 1,000 gallons. 
 After agitation, iron salts as above are added, or a 
 mixture of 10 parts animal carbon, 2 or 3 brown oil of 
 vitriol, or 3 or 4 nitrosulphuric acid, after which the 
 whole is again agitated. 
 
 This patent, it is believed, was assigned to the Rivers 
 Clarification Company, Limited, of Leeds. 
 
 185. W. H. Hughan. 1874. No. 1,959. 
 
 Treats the sewage with an "antiseptic" made of 
 Portland cement, sulphates of soda, magnesia and 
 potash mixed in oil, preferably mineral oil, and then 
 precipitates with a mixture of Portland cement, fluor- 
 spar and oil. The effluent is filtered, and the pre- 
 cipitate with the residue from the filtration is mixed 
 
222 SEWAGE TREATMENT. 
 
 with hot superphosphate. The " antiseptic " may also 
 be made from seaweed, clay and soda -waste treated with 
 sulphuric acid. 
 
 1 86. S. Hallsworth and R. Bailes. 1874. No. 2,408. 
 
 Agitate sewage in a tank with either persulphate of 
 iron made from iron pyrites, or a mixed solution of 
 sulphuric acid and iron from the beds of coal and iron 
 pyrites, or sulphuric acid mixed with the mother- 
 liquor left after crystallisation of copperas, or a mixture 
 of sulphuric acid with other equivalent or suitable 
 solution of iron, or of a solution of copperas and sul- 
 phuric acid. 
 
 187. A. E. Schmersakl. 1874. No. 2,439. 
 
 Treats sewage with a mixture of 2 parts dilute sul- 
 phuric acid and I part hydrochloric acid, enough to 
 make the sewage acid. Or the acids may be added 
 separately, or phospho-muriate of lime, commonly 
 called bone-liquor, may be employed, or chloride of 
 manganese. Sufficient milk of lime is then added to 
 neutralise the acid. See the inventor's previous patent 
 (No 1 60, of 1874). 
 
 1 88. W.A.Lyttle. 1874. ^7.2,446. 
 
 Gives directions for deodorising sludge ; how it is to 
 be precipitated the inventor does not state. 
 
 189. H. Y.D.Scott. 1874. No. 2,450. 
 
 The object of this patent is the recovery of carbonate 
 of ammonia from sewage. If a manure is to be made, 
 magnesia and phosphate of magnesia are agitated with 
 the liquid to be treated. 
 
 190. W. Spence. 1874. ^0.2,461. 
 
 Treats sewage in lead-lined tanks having false bottoms 
 of copper. U A coil of pipes is inserted in such a 
 manner that the half of the pipes are above and the 
 other half below the false bottom." To the first tank 
 acid is added in quantity sufficient to fix the ammonia 
 
SEWAGE PATENTS. 223 
 
 and dissolve the phosphates of lime. Steam is then 
 admitted into the coils. 
 
 There is no mention of any phosphate of lime having 
 been added. 
 
 191. G. Willett, R. J. Harris, and James Lund. 1874. 
 No. 2,567. 
 
 Filter through tanks of coal-ashes or coke. 
 
 192. H. Y. D. Scott. 1874. No. 2,568. 
 
 Treats phosphates with acids, adds magnesia, and uses 
 the product to fix the ammonia of urinous or other 
 ammoniacal liquids. 
 
 193. /. H. Kidd. 1874. No. 3,199. 
 
 Lets sewage settle, runs off effluent and dries the 
 solids. 
 
 194. JamesMcIntyre. 1874. No. 3,225. 
 
 Depositing tanks without the use of any precipitant 
 or deodorant. 
 
 195. 5. HallsworthandR.Bailes. 1874. No. 3,459. 
 
 The inventors take per 5,000 gallons of sewage, i| 
 gallons of pyrites liquor and 50 Ibs. of slaked lime, or 
 100 Ibs. of gas lime. 
 
 196. A. F. Paget. 1874. No. 3,613. 
 
 Treats waste waters with a mixture of sesqui-chloride 
 of iron and aluminium chloride, and afterwards with 
 lime-water. The chloride solution is obtained by dis- 
 solving any argillaceous iron ore containing phosphoric 
 acid in hydrochloric acid. Carbolic acid, permanganate, 
 or other disinfectants may be added as the water leaves 
 the mixing tanks. 
 
 197. G. Mackay. 1874. No. 3,751. 
 
 Treats waste waters with per-salts of iron, preferably 
 the perch loride or persulphate, and thej^ wjrth lime 
 or other suitable alkali. 
 
 F* Of THt 
 
 UNIVERSITY 
 
224 SEWAGE TREATMENT. 
 
 198. V. B. Halle. 1874. No. 3,784. 
 
 A mere process of precipitation with lime followed by 
 filtration. 
 
 199. F. T. Bond. 1874. ^0.3,799. 
 
 Uses for disinfection sulphates of iron, aluminium and 
 copper, carbolic acid, terebene potassium, bichromate 
 and permanganate. 
 
 200. Rupert Goodall. 1874. No. 4,158. 
 
 Mixes ashes and gas lime or waste lime from ammonia 
 works with sulphuric acid till effervescence ceases ; adds 
 water and uses one to two gallons of this to 1,000 gal- 
 lons of sewage. 
 
 The sewage is first treated with slaked lime, or with a 
 mixture of six parts slaked lime and one part animal 
 carbon. Five pounds of lime or 20 Ibs. of the com- 
 pound may be used for every 1,000 gallons of sewage 
 and \ to i gallon of the first described mixture is then 
 stirred in. 
 
 20 1. J. C. Morrell. 1874. No. 4,247. 
 
 Treats sewage with alum, quicklime, or a crystallised 
 chemical substance, which does not appear to be named 
 or described. 
 
 202. H. Y. D. Scott. 1874. No. 4,305. 
 
 Lets sewage deposit in a tank. To the emuent from this 
 he adds milk of lime in a second tank. The lime 
 emuent is then treated in another tank with an acid 
 solution of phosphate of iron, lime, and alumina. 
 
 Successive precipitations with different agents are bad 
 on account of the great outlay for plant and labour which 
 they involve. 
 
 203. W.J.Pughsley. 1,874. A 7 ^ 4,373- 
 
 Treats .refuse liquor from tin-plate works by filtering 
 first through limestone, then through charcoal, and then 
 through bone-ash. The two latter are separated from 
 each other by a perforated board, and the bones are 
 
SEWAGE PATENTS. 225 
 
 supported upon an iron plate. The bones are removed 
 from time to time and used as manure. 
 
 204. G. Mackay. 1875. No. 91. 
 
 Treats sewage with mixed solutions of perchloride 
 and persulphate of iron. Salts obtained from alum, 
 alkali, and galvanising works may be mixed with the 
 solution. Lime or other alkali is then added. 
 
 205. G.Rydill. 1875. No. 150. 
 
 Filters through a bed of ashes. 
 
 206. /. Box,E. Aubertin, L. Boblique, and H. Leplay. 
 1875. No. 214. 
 
 Treat sewage first with a ferruginous phosphate of 
 soda or potash and then with a salt of magnesium. 
 
 207. G. Rydill. 1875. No. 399. 
 
 Treats sewage, etc., with caustic soda or lime. Filters 
 through ashes, and forces air through it from perforated 
 pipes. 
 
 208. /. Hallsworth and R. Bailes. 1875. No. 573. 
 
 Treat sewage with two clarifying mixtures. I. Spent 
 residues of iron pyrites or other ores containing iron 
 as peroxide are ground and mixed with an equal weight 
 of any of the following : Copperas, dry copperas, cop- 
 peras bottoms, copperas sediment, or sediment from the 
 manufacture of nitrate of iron. The mixture is cal- 
 cined and allowed to cool. 2. The pyrites residue or 
 iron ore is saturated with liquor from the pyrite beds 
 at copperas works, or with dilute sulphuric or hydro- 
 chloric acid. The sewage is first treated with slaked 
 lime or with calcium (?) in the proportion of 78 Ibs. of 
 the former or 156 Ibs. of the latter to 5,000 gallons of 
 liquid, and mixed together ; 23 Ibs. of mixture No. I 
 or 46 Ibs. of No. 2 is then mixed with a portion of 
 sewage and then added to the lime sewage. 
 
 209. W. M. Brown. 1875. No. 1,335. 
 
 A kind of filtration process. 
 Q 
 
226 SEWAGE TREATMENT. 
 
 210. T. Page. 1875. No. 1,625. 
 
 A screening arrangement, the deodorising agent is 
 named. 
 
 211. P. Spence and F. M. Spence. 1875. No. i ,704. 
 
 Manufacture of alumino-ferric cake, used in sewage 
 treatment. 
 
 212. /. Hill. 1875. No. 1,745. 
 
 A contrivance for expressing moisture which the 
 inventor applies to separating the solid from the liquid 
 portions of sewage. 
 
 213. John Yule. 1875. No. 1,759. 
 
 A barge for conveying sewage. 
 
 214. M.F.Anderson. 1875. No. 1,845. 
 
 Treats sewage sludge with coprolite, phosphorite, or 
 ground bone, together with sulphuric acid. 
 
 215. J. J. Coleman. 1875. No. 1,954. 
 
 Filters sewage through spent shale from the mineral 
 oil works, or the shale may be added in the sewers and 
 the sewage allowed to settle in tanks. The effluent is 
 passed through beds of shale. See Specification of R. 
 Irvine, 1886, No. 2,218. 
 
 216. P. Spence and F. M. Spence. 1875. No. 1,961. 
 
 Improvements in alumino-ferric cake, rendering it 
 more basic and better adapted for treating sewage. 
 
 217. D. Wilks. 1875. No. 1,972. 
 
 Treats sewage in tanks with powder obtained by car- 
 bonising town refuse. The effluent is filtered. 
 
 2 1 8 . /. Odams and R. Blackburn . 1875. ^0.2,358. 
 
 Revolving screens for separating the solids from 
 sewage. 
 
 219. /. Hanson. 1875. No. 2,675. 
 
 Precipitates sewage with, per 100,000 gallons, slaked 
 lime 20 to 23 Ibs., soot or flue dust J lb., black-ash (by 
 which the inventor means oat waste from the alkali 
 works) 30 Ibs. 
 
SEWAGE PATENTS. 227 
 
 220. T. Stevens. 1875. No. 2,829. 
 
 Adds sulphate of lime and common salt to the sewage 
 on its way to the settling tank. Adds milk of lime as 
 it enters the tank, and finally filters. 
 
 221. A.M. Clark. 1875. No. 3,162. 
 
 Treats sewage, according to circumstances, with i. 
 Aluminate of soda, alone or in conjunction with soluble 
 alkaline or earthy phosphates. 2. The same phosphates 
 mixed or combined with oxide or phosphate of iron 
 along with a soluble salt of magnesia. 3. Oxides of 
 nitrogen higher than nitrous oxide but lower than nitric 
 acid. 
 
 In consequence of this patent, no general claim to 
 the use of aluminate of soda can be maintained by 
 subsequent inventors. 
 
 222. /. W. Slater. 1875. No. 3,368. 
 
 Ignites sewage sludge in retorts, obtaining a carbon 
 which may be used in treating gas. The volatile pro- 
 ducts are condensed and yield ammonia and illuminating 
 gas. 
 
 The gas thus obtained is of " 8 candle " power. 
 
 223. C. Rawson and J. W. Slater. 1875. No. 3,703. 
 
 Use in place of alum aluminous shales, such as those 
 of Campsie, either in their raw state or artificially 
 weathered by treatment with super-heated steam, or 
 steam and atmospheric air, or hot air charged with 
 moisture, or sulphurous acid gas along with air or 
 steam. 
 
 224. A. Le Tellier. 1875. No. 4,061. 
 
 A mechanical arrangement for treating sewage. 
 
 225. James Bannehr. 1875. No. 4,122. 
 
 A mechanical arrangement. The effluent is filtered 
 and treated with electric currents. 
 
 226. H.M.Ramsay. 1875. No. 4,420. 
 
 Filters sewage first over loose charcoal and scrap metals 
 
228 SEWAGE TREATMENT. 
 
 and then over " porous-plastic carbon." These filters may 
 be cleansed by reburning or by forcing clean water 
 through them. 
 Where, in the latter case, is this water to go ? 
 
 227. John Hanson. 1876. No. 225. 
 
 Improvement on No. 2,675, f I ^7S- Blast-furnace 
 slag and "Paris white" (i.e., whiting), with or without 
 the addition of sulphuric or hydro-chloric acid, are 
 used to precipitate sewage, either alone or mixed with 
 the ingredients named in the former specification. 
 
 If the slag is added without acid, it is inert. If acid 
 is used it will be neutralised by the " Paris white." 
 
 228. H. Y. D.Scott. 1876. No.$22. 
 
 A complicated process for treating solid excreta and 
 pail-stuff. 
 
 229. F. Hille. 1876. No. 1,355. 
 
 Slakes lime with sea-water, or with solutions of 
 magnesian salts, or with the refuse liquor from salt 
 works, dried, calcined and re-dissolved in water, with 
 5 Ibs. gas tar to every 100 Ibs. of lime. This paste is 
 mixed with water, and applied to sewage in tanks. The 
 effluent from this process may be treated with iron- 
 perchloride or with carbonic acid gas. 
 
 230. /. Bannehr and S. A. Varley, 1876. No. 1,739. 
 
 A mechanical arrangement for intercepting solids. 
 Air is then forced through the liquid ; such air may be 
 ozonised by means of electric currents. 
 
 231. C. Raw son and J.W. Slater. 1876. No. 1,893. 
 
 Treat sewage with double fluorides and silico-fluorides. 
 Make an artifical animal charcoal by treating phosphates 
 with carboniferous and nitrogenous matters. 
 
 232. W. Clark. 1876. No. 1,930. 
 
 Mixes sewage with an acid to fix ammonia, draws off 
 clear liquid and evaporates. Or treats sewage with 
 lime, and drives off the ammonia in a " triple effect 
 
SE WA GE PA TENTS. 229 
 
 evaporator." The ammonia is condensed, and the sludge 
 filtered and pressed. 
 233 G. Bischof. 1876. No. 2,080. 
 
 Purifies sewage either by means of spongy iron or 
 manganic dioxide, employed either as filtering media, 
 or added in powder to the sewage. 
 
 234. W. Webb. 1876. No. 2,124. 
 
 A mechanical arrangement for separating the liquid 
 from the solid portions of sewage. 
 
 235. Thomas Lovell. 1876. No. 2,387. 
 
 Merely arrangements for irrigation. 
 
 236. F. W. F.Reinhold Goedicke. 1876. No. 2,526. 
 
 Separation of solids from liquids, the latter being 
 applied for irrigation or other purposes. 
 
 237. /. W. Slater. 1876. No. 3,095. 
 
 Treats sewage with alkaline, alkaline earthy, earthy 
 or metallic salts of hypo-sulphurous, sulphurous and 
 thionic acids. These are obtained by exposing tank-waste 
 to air. They may be used along with aluminium sul- 
 phate or chloride. Claims also infusorial earth in com- 
 bination with salts of alumina, hydrated silica, and clay, 
 or as a filter bed. 
 
 238. James Miller. 1876. No. 3,107. 
 
 Passes sewage through tanks with perforated sides 
 filled alternately with gravel and sand, or lime and 
 sand. 
 
 239. Henry Staples. 1876. No. 3,307. 
 
 Treats natural sulphates of alumina, Campsie shale, 
 etc., with hydrochloric acid in heat, and uses the pro- 
 duct for treating sewage. Adds to the com pound alkali 
 waste to take up moisture, but not to decompose salts of 
 alumina or iron, or to give the mixture on alkaline 
 reaction. 
 
 240. Joe Frost. 1876. No. 3,365. 
 
 Precipitates sewage with sulphides and hydrate of 
 
230 SEWAGE TREATMENT. , 
 
 barium, hydrates/precipitated hydrates, sulphydrates and 
 sulphides of the same metal, sulphides of soda, slaked 
 lime, carbonate of lime and sulphuric acid. 
 
 The poisonous character of the salts of barium is well 
 known. 
 
 241. W. White. 1876. No. 3,576. 
 
 Treats sewage with oxychloride or chloroxide of 
 calcium, obtained by boiling lime in a strong solution 
 of calcium chloride, or quicklime may be slaked with 
 dilute hydrochloric acid. Sulphates of aluminium, iron 
 or zinc may be used in connection, as also charcoal and 
 chloride of lime. 
 
 The poisonous nature of the sulphate of zinc, and the 
 inadmissibility of chloride of lime have been already 
 explained. 
 
 242. A. Greenwood, G. E. Davis, and J. J. Speakman. 
 1876. No. 3,673. 
 
 Place liquid sewage in a tank, and allow it to remain 
 until the nitrogen has been transformed into ammonia 
 (a great nuisance !), which is then driven off and 
 fixed. 
 
 243. J.Watson. 1876. 7V0. 4,203. 
 
 Treats sewage with hydrochloric acid in a tank, and 
 uses the precipitated sludge for manure. 
 
 244. C.D.Abel. 1846. -Afo. 4.516. 
 
 A complicated system of settling and filtration. 
 
 245. G.Rydill. 1876. No. 4,848. 
 
 Precipitates sewage with waste liquors from the treat- 
 ment of woollen, silk, and other manufactures, also 
 waste acid liquors which have been used for separat- 
 ing animal and vegetable fibres. Treats sewage in a 
 filter-bed made of " extracted vegetable substances, dust 
 and foreign matter," or "vegetable substances con- 
 taining acid ; chemicals are used as a disinfectant, with 
 
SEWAGE PATENTS. 231 
 
 earth alum, shale, clay refuse, animal carbon, ashes, lime, 
 or salt, the same being strongly impregnated with 
 sulphuric, hydrochloric or nitric acid, or alum along 
 with clay or other chemical agents." 
 
 In other words, the inventor claims things in 
 general, useful or useless, compatible or incompa- 
 tible. 
 
 246. H. D. Y. Scott. 1877. No. 103. 
 
 Treats pail-stuff and gas liquor for manures. 
 
 247. Houzeau and others. 1877. No. 263. 
 
 Use for sewage, coal-ashes of all kinds from dwell- 
 ings and manufactories ; pyritous, ligneous, or sulphurous 
 ashes, sulphatized or not ; ashes and residues from 
 manufactories of soda, sulphuric acid, sulphate of iron, 
 and waste products from polishing glass; all refuse of 
 products having been used for industrial purposes (!) ; 
 gas from the crystallization of alums, sulphate of 
 alumina, sulphate of iron, and all crystalline salts. 
 These bodies are lixiviated, with or without the aid of 
 an acid, and added to the sewage along with (in most 
 cases) milk of lime. 
 
 This is, perhaps, the most singular specification ever 
 drawn up as far as sewage treatment is concerned. 
 Among the substances claimed under the head " All 
 refuse of products having been used for industrial pur- 
 poses," there are not a few totally unsuitable, and 
 others which have been used and claimed before. Among 
 the former may be mentioned the highly poisonous re- 
 fuse of the manufacture of magenta, and among the 
 latter a variety of aluminous products. French in- 
 ventors seem, as a rule, utterly to ignore the fact that, 
 according to English law, a bad claim imperils the 
 entire patent, and they re-invent with great calmness 
 processes which are already public property. 
 
232 SEWAGE TREATMENT. 
 
 248. /. H. Johnson (Emile Barrault). 1877. No. 488. 
 
 Claims manufacture of sulphate of alumina by the 
 action of sulphuric acid upon dried or powdered shales, 
 and uses the sulphate thus obtained in treating 
 sewage (! !). 
 
 249. G. Lunge. 1877. No. 638. 
 
 Purifies the drainage from alkali waste. 
 
 250. R. Turnbull. 1877. No. 824. 
 
 Mechanical arrangements only. 
 
 251. G. Alsing. 1877. 7V0. 835. 
 
 Filters through a screen, and treats with a solution 
 of hydrate and sulphide of calcium and gibbside (sic] 
 and filters effluent again. 
 
 252. John Hanson. 1877. No. 860. 
 
 Treats sewage with waste haematite, sulphurous gas, 
 a mixture of alum, soda, and " black ash refuse," i.e., 
 tank waste. 
 
 Softens water with carbonate of potash and some- 
 times nitre-cake. 
 25 3. S. Hallsworth and R. Bailes. 1877. No. 952. 
 
 Treat sewage with (i) 1,000 gallons of liquor from 
 beds of iron pyrites (50 Tw.), mixed with 250 Ibs. sul- 
 phuric acid at 144 Tw. (2) 1,000 gallons of dissolved 
 copperas, or copperas bottoms, or other liquor from 
 copperas at 40 Tw. with 370 Ibs. sulphuric acid at 
 144 Tw. (3) 1,000 Ibs. solution of iron at 40 Tw. from 
 pickling iron at wire and sheet iron works, along with 
 250 Ibs. sulphuric acid at 144 Tw. (4) A liquor from iron 
 byrites and sulphuric aci d and water neutralized with 
 scrap iron, set at 75 Twaddle, adding to each 1,000 
 gallons 250 Ibs. sulphuric acid at 154 Tw. ... (6) tap- 
 cinder from puddling-furnaces, or other slags containing 
 protoxide of iron and dissolved in sulphuric acid. (7) 
 nitrate of iron at 4 Tw. To 10,000 gallons of the 
 
SEWAGE PATENTS. 233 
 
 sewage they add any of the aforesaid mixtures, followed, 
 or, in some cases, preceded, by milk of lime. 
 
 This specification might be advantageously studied 
 by inventors who propose copperas and lime as a novelty 
 in sewage-treatment. 
 
 254. M. H. Singe. No. 1,619. 
 
 Filtering and purifying apparatus. 
 
 255. H. Y. D. Scott. No. 1,772. 
 
 A magnesian lime-process. 
 
 256. /. Fenton. No. 1,982. 
 
 A filtering arrangement. 
 
 257. W. R. Lake. No. 2,661. 
 
 Prepares an artificial bone black. 
 
 258. /. Hanson. No. 2,725. 
 
 Treats sewage with six liquids, viz., muriate or 
 nitro-muriate of tin at 50 Tw. ; silicate of soda dis- 
 solved in 7 parts of water ; borax dissolved in 9 parts of 
 water ; " litchen " or Iceland moss boiled in water ; a 
 mixture of the tin solution and of the decoction of 
 Iceland moss, and peracetate of iron in 4 parts of 
 water. In conjunction with the above may be used 
 carbonates or hydrated oxides of iron deposited by water 
 draining from mines and dissolved in sulphuric acid, 
 asbestos ground in water, slaked lime, tank-waste, and 
 sulphurous acid gas. 
 
 Salts of tin are doubtless good precipitating agents, 
 but they are too costly and too poisonous. Sulphurous 
 acid gas has been already noticed. 
 
 259. C.J. Wollaston. ^7.2,841. 
 
 Uses sulphurous acid or chlorine, or both (!) in con- 
 junction with lime and magnesia. 
 
 The fact that the actions of sulphurous acid and of 
 chlorine are antagonistic, the former being a de-oxidis- 
 ing and the latter an oxidising agent, is here over- 
 looked. 
 
234 SEWAGE TREATMENT. 
 
 260. B. B. Standen. 1877. No. 3,395. 
 
 No agents for treating sewage are here proposed. 
 
 261. H. Y.D. Scott. 1877. No. 3,977. 
 
 Proposes no means of treating sewage. 
 
 262. /. Gray. 1877. No. 3,571. 
 
 Merely a lime process. The lime is slaked with boiling 
 water, or alum water, and is then used for treating. 
 The alum is, of course, decomposed ! 
 
 263. H. Robinson andj. C. Melliss. 1878. No. 12. 
 
 Treat sewage with the joint addition of copperas and 
 sulphate of alumina, or, if necessary, lime. Quaere, the 
 novelty ? 
 
 264. /. Foulis and}, A . Carrick. 1878. No. 75. 
 
 Treat waste waters with sulphate or chloride of 
 zinc, waste bleach, and soda-limes (?) separately or in 
 conjunction. 
 
 265. Walter East. 1878. No. 92. 
 
 Adds putrescent sewage to hasten fermentation. Con- 
 veys away noxious gases in pipes. Adds iron oxide to 
 remove sulphuretted hydrogen. 
 
 266. R. U. Etzensberger. 1878. No. 264. 
 
 Does not bear upon sewage. 
 
 267. /. Adamson and H. Booth. 1878. No. 2,937. 
 
 A lime process. 
 
 268. W. Pochin. 1878. No. 4,270. 
 
 Treats iron slag with sulphuric acid. No mention 
 of sewage. 
 
 269. W. R. Lake. 1879. No. 179. 
 
 Enriching phosphate of lime. No reference to 
 sewage. 
 
 270. W.H.Denham. 1879. No. 437. 
 
 Burns household refuse and precipitates sewage with 
 the ashes. 
 
SEWAGE PATENTS. 235 
 
 271. H. Chamberlain. 1879. No. 2,599. 
 
 A straining process. 
 
 272. 1879. Afo. 2,345. 
 
 Irrelevant. 
 
 273. W. L. Wise (Loewig}. 1879. No. 3,195. 
 
 Prepares " carbonic alkali of alumina." 
 
 274. T.H.Cobley. 1879. .#"0.3,312. 
 
 No reference to sewage. 
 
 275. R. Wild. 1879. No. 3,373. 
 
 Treats with lime and alum and " other suitable pre- 
 cipitant," and filters. 
 
 276. R. Wild and H. Ledger. 1879. No. 3,980. 
 
 Mechanical arrangements. 
 
 277. W. F. Mast. 1879. No. 4,402. 
 
 Method of extracting ammonia from excrement and 
 urine. 
 
 278. H. C. Bull. 1879. No. 5,324. 
 
 No reference to sewage. 
 
 279. /. C. Mewbari. 1880. No. 243." 
 
 Purifies wool-washings with caustic lime, epsoms and 
 copperas, forming insoluble soaps. 
 
 280. /. G. Tongue. 1880. No. 742. 
 
 Destroys organic matter in waste waters by heating 
 them and applying lime white, chloride of magnesium, 
 and other " suitable chemicals." Special mechanical 
 arrangements. 
 
 281. /. Duke. 1880. No. 748. 
 
 Filters through silicates of lime, potash, soda or 
 alumina separately or combined, peat charcoal, and 
 superphosphates. 
 
 282. C. Dickinson. 1880. No. 3,898. 
 
 Proposes mechanical arrangements. Uses for sewage 
 treatment salt-cake, alum and potash, and, if necessary, 
 " well-known deodorising means." 
 
236 SEWAGE TREATMENT. 
 
 Salt-cake is, of course, useless, and potash, if it 
 answers any good end, is very expensive. 
 
 283. E. Parry andT. H. Cobley. 1880. No. 3,554. 
 
 Prepare earthy silicates, and make no reference to 
 sewage. 
 
 284. /. Duke. 1880. No. 2,994. 
 
 Manufactures soluble silicates by treating Roman 
 and Portland cement, or suitable natural silicates, or 
 kainite, with sulphuric or hydrochloric acid. The re- 
 sulting product is applied to manures, but not to the 
 treatment of sewage. 
 
 The part which kainite can play in the preparation 
 of silicates is very questionable. 
 
 285. /. H. Johnson. 1880. No. 4,603. 
 
 Treats lavas with sulphuric acid or hydrochloric acid, 
 and uses the resulting mixture, " lava-syrup," as a dis- 
 infectant or for treating sewage. Uses also alumnite 
 calcined in presence of potassium chloride. 
 
 286. VV. H. Denkam. 1881. <Afo. 1,413. 
 
 Mechanical arrangements. 
 
 287. W.R.Lake. 1881. No. 1,448. 
 
 A process for recovering muriatic acid used in treat- 
 ing bones. No reference to sewage. 
 
 288. R. Wild and H. Ledger. 1881. No. 1,564. 
 
 Claim treatment of sewage with alumino-ferric cake 
 and soap water, or in combination with ammonia. Two- 
 fold precipitation. 
 
 Soap water is one of the impurities which have to be 
 removed from sewage. The addition of ammonia to 
 sewage is an unhappy idea. Alumino-ferric cake has 
 been used for sewage treatment ever since it appeared 
 in commerce. 
 
 289. /. Storr. 1 88 1. No. 1,716. 
 
 Proposes a process for obtaining ammonia from 
 sewage, etc. Provisional protection was not granted. 
 
SEWAGE PATENTS. 237 
 
 290. H. Collett. 1 88 1. No. 2,004. 
 
 Treats sewage with " vitriolic powder," which is, as 
 he says, u a special substance prepared from pyrites," 
 and with or without the addition of crude zinc sulphate 
 and sulphuric acid. Further, he adds, or may add, to the 
 " separated liquid" probably to the effluent water from 
 this first precipitation chalk, limestone or other matter 
 containing carbonate of lime, slaked lime, carbonate 
 or sulphate of soda. Instead of " vitriolic powder " may 
 be used silicates of soda or potash, zinc or iron sulphates, 
 fluorides of silicon or boron, or hydrofluosilicic acid, 
 bark, sumac, peat, charcoal powder. 
 
 In this strange specification the preparation of 
 " vitriolic powder " is nowhere described a serious 
 omission, since there is no article known in commerce 
 under that name. Salts of zinc are, from their poisonous 
 nature, quite out of the question. Sulphate of soda is 
 useless, and carbonate of soda is not only too costly, but 
 injurious. I do not suppose that this process has ever 
 been worked upon a practical scale. 
 
 291. Baron Adelbert von Podewils. 1881. ^0.2,295. 
 
 Proposes arrangements for disinfecting faecal matters 
 by fumigation. 
 
 292. W. R.Lake(F.Petri}. 1881. ^0.2,345. 
 
 Uses as a disinfectant peat- waste, etc., moistened with 
 carbolic acid and chloroform ; a powdered mixture of 
 copperas and coke, with a solution of nitro-benzol in 
 alcohol. To stale faecal matters he adds chloride of 
 lime and alcohol ! ! ! 
 
 This most extraordinary process is apparently in- 
 tended not so much for sewage as for night-soil, pail- 
 stuff, the contents of cess-pools, etc. 
 293. G. W. von Nawrocki. 1881. No. 2,790. 
 
 Proposes an arrangement for evaporating and drying 
 sewage. 
 
238 SEWAGE TREATMENT. 
 
 294. H. E. Newton. 1881. Afo. 4,088. 
 
 Adds to sewage first an astringent, then milk of lime, 
 sulphates of iron or manganese, or powdered gypsum. 
 The faecal matters are then distilled with alkali so as 
 to liberate ammonia. 
 
 295. A. M. Clark. 1881. No. 5,199. 
 
 Treats sewage with chlorides and fluorides, e.g., 
 chloride of zinc, potash and phosphate of lime, or 
 chloride of manganese potash, silicate of potash and 
 alumina in the form of phosphate or carbonate. 
 
 Chloride of manganese was an excellent precipitant, 
 but it is no longer obtainable as a waste product. 
 Chloride of zinc from its poisonous nature is inadmissible. 
 Potash and silicate of potash are much dearer than 
 soda and silicate of soda, without having any advan- 
 tages. Carbonate of alumina is a body whose existence 
 is doubtful. Carbonates as a class are injurious in 
 sewage precipitation, since the carbonic gas which they 
 give off in contact with acids or acid salts stirs up the 
 deposit. 
 
 296. F. Petri. 1881. No. 5,390. 
 
 Proposes a filtration process. Disinfects with 
 carbolic or salicylic acid, ethylic or triethylic chlorides, 
 or other chlorides of alcohol. 
 
 297. Peter Lowe. 1882. No. 268. 
 
 Proposes arrangements for straining sewage. 
 
 298. H. Y. D. Scott. 1882. No. 311. 
 
 A process for the manufacture of manure. 
 
 299. John Brock. 1882. No. 473. 
 
 Manufactures manure from alkali waste ! 
 
 300. G. J. Andrews andF. H. Parker. 1882. No. 1,396. 
 
 Treat sewage with muriatic acid and " alkaline soda," 
 They then add sulphate of iron. 
 
 What " alkaline soda" may be can only be guessed. 
 
SEWAGE PATENTS. 239 
 
 As chlorine gas is said to be evolved by the meeting of 
 these chemicals, it must probably be chloride of soda, 
 otherwise known as bleaching soda, or sodium hypo- 
 chlorite, which is not a very cheap article. 
 
 301. E.Edwards. 1882. No. 2,970. 
 
 Proposes a scheme for treating sewage in closed 
 receptacles. 
 
 302.7. C. W. Stanley. 1882. No. 3,091. 
 
 Makes paints from river mud. There is no mention 
 of the purification of sewage. 
 
 303. T. H. Cobley. 1882. No. 3,497. 
 
 Treats sewage with chlorides of aluminium, calcium, 
 iron and magnesium, alone or in combination with 
 carbonaceous matter. These substances are principally 
 obtained from basic clay, cinder and scoriae, " shale-ash 
 clay " and bauxite, treated with hydrochloride acid. 
 
 " Shale ash clay " is a doubtful substance. The above- 
 mentioned chlorides have all been previously claimed or 
 mentioned in patents for the treatment of sewage. 
 
 304. James Young. 1882. No. 3,562. 
 
 Treats sewage by distillation, with or without the 
 addition of lime, and collects the ammonia given off. 
 
 305. R. Nicholls. 1882. No. 3,863. 
 
 Proposes a scheme for enabling each house to treat 
 its own excreta. No novel chemicals are claimed. 
 
 306. James Young. 1882. No. 4,659. 
 
 Expels ammonia from sewage by passing into it 
 steam or steam and air. The sewage passes through a 
 tower in one direction, whilst the steam and air 
 travel in the opposite direction. 
 
 307. 5. Walter. 1882. No. 5,285. 
 
 Treats sewage with waste lime and lime-water, and 
 filters. 
 
 Waste lime is not a very abundant article, and brine 
 of any kind is an undesirable addition to sewage. 
 
240 SEWAGE TREATMENT. 
 
 308. F. Petri. 1882. No. 5,303. 
 
 Treats with sulphate of alumina, milk of lime, and 
 organic chlorides. The organic chlorides to be used 
 are not named, but they are said to be derived from 
 chloride of lime, muriatic acid and raw spirit, which 
 appear to be added to the sewage. The inventor then 
 filters over peat. 
 
 In England the use of " raw spirit '' in sewage 
 treatment is inadmissible on financial grounds, whatever 
 may be the deodorising powers of the organic chlorides 
 thus generated. It must not be forgotten that alcohol 
 is rarely absent in sewage. 
 
 309. Peter Jensen. 1882. No. 5,536, 
 
 Uses sulphate of alumina, and then irrigates or filters. 
 
 310. R. Nichols. 1882. No. 5,981. 
 
 Lets the sewage settle ; adds slaked lime, and, if 
 extreme purity is required, sulphate of alumina. 
 
 311. James Young. 1883. ^0.332. 
 
 Obtains a partial vacuum, so as to enable sewage to be 
 boiled at a low temperature for the distillation of 
 ammonia. 
 
 312. James Young. 1883. No. 434. 
 
 Further improvements in the separation of ammonia 
 from sewage by distillation. 
 
 313. W. C. SillarandJ. W. Slater. 1883. No.. 1,144. 
 
 Prepare crude muriate of alumina or muriates of 
 alumina and iron by bringing solutions of sulphate of 
 alumina (natural or artificial), and either alone or in 
 conjunction with sulphate of iron, into contact with 
 solutions of chloride of calcium. The clear liquid, 
 muriate of alumina or muriate of alumina and iron, is 
 drawn off from the deposit of sulphate of lime and 
 used in the treatment of sewage, either alone or in con- 
 junction with carbonaceous matter, clay, etc. 
 
SEWAGE PATENTS. 241 
 
 314. /. H. Kidd and T.J. Barnard. 1883. No. 1,522. 
 
 Propose mechanical arrangements for dealing with 
 sewage. 
 
 315. /. Bock. 1883. No. 3,255. 
 
 Treats sewage with fibrous matter, salts of iron and 
 magnesia, and effects precipitation with milk of lime. 
 The fibrous matter employed is " wood-pulp, or paper 
 fibre," or " fibriferous mud." There is no mention of 
 peat. 
 
 This patent is rational in so far as precipitants and 
 absorbents are here brought into conjoint action. But 
 wood-pulp and paper fibre are too costly for sewage 
 treatment. The former, containing 50 per cent, mois- 
 ture, is quoted at present at 6 ics. in Hull. 
 
 316. A. Goldthorpe. 1883. No. 3,914. 
 
 Treats impure waters with phosphate of soda. 
 
 It would seem that Mr. Goldthorpe is in possession 
 of a much more efficient method of purifying waters for 
 industrial uses, e.g., for dyeing. This process he works 
 as a secret. The above quoted patent was never com- 
 pleted. 
 
 317. John Young and Peter Fyfe. 1883. No. 4, 5 7 1 . 
 
 Propose arrangements for separating solid and liquid 
 matter in sewage, street slops, and smiliar material. 
 
 318. G.Epstein. 1883. ^0.5,436. 
 
 Does not refer to sewage. 
 
 319. /. H. Kidd. 1883. No. 5, 5 50. 
 
 Takes dried sewage-sludge or dried excrement, adds to 
 it as much sulphuric acid as it will absorb, and u places 
 it in trays in a purifier " so as to allow the gas which is 
 generated in the retorts after cooling to be passed 
 through such purifying materials for the purpose of 
 fixing any free ammonia that might otherwise pass 
 away with the gas and be lost. 
 
242 SEWAGE TREATMENT. 
 
 The " purifier " here mentioned is a gas-purifier, and 
 the gas generated in the retorts is coal-gas, which is 
 passed after cooling over the sludge or excreta, 
 
 320. T. D. Harries. 1883. No. 5,147. 
 
 Mechanical arrangements for preventing the pollution 
 of rivers. 
 
 321. F.Herbert. 1883. No. 5,850. 
 
 Proposes an electrolytic process for the treatment of 
 sewage. Dispenses with chemicals, filter-beds, etc. 
 
 322. 5. C. Dean. 1884. No. 93. 
 
 Filters sewage and foul waters through a mixture 
 of 500 Ibs, coal (not anthracite), 56 Ibs. clay, 20 Ibs. tar, 
 5 Ibs. marine shells, i Ib. borax, or 4 Ibs, soda, coarsely 
 ground together and carbonized in a gas-retort or coak- 
 ing-oven. When used as filters to aerate or to force 
 a purifying gas through foul waters, the bottom to be 
 laid with perforated pipes, and air, steam, or a gas 
 forced by any known means through the filter. 
 
 He also provides receiving tanks and precipitates the 
 solid matter by a simple process, saving the ammonia and 
 the phosphoric acid in a semi-soluble state, suitable for 
 the food of plants, and passes the supernatant water 
 through the filters. The u simple process " is unfortun- 
 ately not given. 
 
 323. F.Hille. 1884. No. 1,279. 
 
 Intercepts floating matter by means of screens, and 
 treats with chloride of magnesium, chloride of calcium, 
 chlor oxide of calcium or oxychloride of calcium, or 
 per chloride of iron, or other chlorides or alum, followed 
 by lime-water. 
 
 The application for this patent was successfully 
 opposed. 
 
 324. James Nuttall, F. Nuttall, and J . Rouse. 1884. 
 
 No. 3,417. 
 An arrangement to purify noxious or gaseous 
 
SEWAGE PATENTS. 243 
 
 vapours (!) arising from heated liquids or other 
 materials, applicable chiefly to cooking stoves. 
 
 325. /. Foulis. 1884. No. 4,202. 
 
 Proposes certain mechanical arrangements. 
 
 326. S. K. Page, C.E. Robinson, and W. Stevens. 1884. 
 
 No. 7,198. 
 
 Propose improvements in apparatus for use in the 
 treatment of sewage, and in other operations in which 
 solids have to be added to fluids in definite proportions. 
 
 327. /. F.Joknstone and J. B. Alliott. 1884. No. 7,387. 
 
 Arrangements for drying animal refuse and for con- 
 centrating liquids. 
 
 328. C.Waite. 1884. No.f4.Si. 
 
 A process for upward and lateral filtration ; no special 
 filtering materials proposed ; lime is applied to the 
 deposit. 
 
 329. W. Anderson. 1884. No. 7,665. 
 
 Upward filtration through spongy iron or finely 
 divided iron. 
 3 30- John Hanson. 1 884. No. 9, 5 87, 
 
 Claims treatment of solid and liquid impurities 
 or foul matters with black ash waste or a liquor or 
 decoction resulting or prepared therefrom. 
 
 This patent was successfully opposed, 
 
 331. W. Lloyd Wise. 1884. No. 9,768. 
 This patent does not refer to sewage, 
 
 332. D. Nicoll. 1884. No. 10,275. 
 
 Proposes certain mechanical arrangements for the 
 treatment of sewage. 
 
 333. /. C. Stephenson. 1884. No. 10,648. 
 
 Ignites mixtures of clay and carbon and uses the 
 product for deodorising purposes. 
 
 334. E.J. Leveson and J. W. Slater. 1884. No. 11,641. 
 
 Dissolve Kimmeridge blackstone shale or blackstone 
 
244 SEWAGE TREATMENT. 
 
 carbon, or other shales containing alumina soluble in 
 muriatic acid, and a considerable quantity of carbon in 
 muriatic acid, and use the solution or mixture for the 
 treatment of sewage along with a small proportion (i 
 per cent, calculated on the solids) of chloride of copper, 
 clay and carbon, and use the mixture in the treatment 
 of sewage. 
 
 335. W.Astrop. 1884. No. 11,901. 
 
 Precipitates sewage with "calcium sulphate and 
 carbonate of alumina together or mixed with other in- 
 gredients." Among these ingredients there may be, 
 it appears, alkaline sulphates, also ground cinders and 
 ashes. There are also arrangements for drying and 
 pulverising the deposit. 
 
 On this process it must be remarked that calcium 
 sulphate (sulphate of lime) is not desirable, that the 
 alkaline sulphates and ashes are at best useless, and 
 that the existence of carbonate of alumina is not proven. 
 
 336. G.Jones and J. C. Bromfield. 1884. No. 11,971. 
 
 Treat sewage with slate-waste ground in water to an 
 inpalpable powder. 
 
 337. Curzon and Jones. 1884. No. 12,054. 
 
 Calcine slate-waste, grind to powder and treat with 
 sulphuric acid in heat, thus obtaining a crude sulphate 
 of alumina, which is, of course, applicable in the treat- 
 ment of sewage. 
 
 The inventors seem to forget that the cost-price of 
 sulphate of alumina turns on the sulphuric acid. Slate- 
 refuse is doubtless cheap and abundant, but so are 
 many other materials containing alumina, so that there 
 is here no distinct advantage. 
 
 338. W. Donaldson, Isaac Shone, and E. Ault. 1884. 
 
 No. 12,643. 
 
 Propose to purify sewage by forcing through it at- 
 mospheric air or sulphurous acid gas or chlorine. 
 
SEWAGE PATENTS. 245 
 
 Similar proposals will be found in the earlier portion 
 of this list. 
 
 339. W. G. Gard. 1884. No. 12,713. 
 
 Proposes to disinfect and precipitate sewage with a 
 mixture of alum, sulphate of iron and sulphate of 
 copper. 
 
 340. /. W. Slater. 1884. No. 12,830. 
 
 Treats sewage with dense and compact peat, ground 
 up with clay and water to a thin paste, and further 
 with slags or slag-wool treated with muriatic acid, so 
 as to form hydrated aluminium chloride. Adds, under 
 certain circumstances, chloride of copper or waste 
 manganese from chlorine stills. 
 
 341. W. D. Cur zon and G. Jones. 1884. No. 13,327. 
 
 Treat sewage with a double sulphate of alumina and 
 iron obtained from " impure silicate of alumina con- 
 taining iron, such as slate debris, shales, schists, and 
 such like substances." Such minerals are roasted at a 
 low red heat, ground, boiled in sulphuric acid, the mass 
 lixiviated with water, the liquid run off and evaporated 
 to a cake. This cake is mixed with \ its weight of 
 slaked lime, made into a liquid of creamy consistence 
 with water and used in the treatment of sewage. 
 
 The following questions here arise : How does the 
 cake above described differ from Spence's " alumino- 
 ferric cake," well known in commerce ? What is the 
 advantage of the above described process of making a 
 double sulphate of alumina and iron over that com- 
 monly followed for making crude sulphate of alumina 
 from shales and schists, and how indeed do they differ ? 
 Will not the addition of slaked lime to the cake 
 decompose pro tanto the sulphates of alumina and 
 iron ? 
 
 342. A. Angel. 1884. No. 13,818. 
 
 Calcines together a mixture of clay and carbonaceous 
 
246 SEWAGE TREATMENT. 
 
 material, and uses the product along with lime as a 
 filtering mass. 
 
 343. /. Y.Johnson. 1884. No. 14,822. 
 
 Purifies water by saturating it under pressure and 
 whilst in motion with compressed air, oxygen or ozonised 
 oxygen. 
 
 344. /. W. Slater and W. Stevens. 1884. No. 15,810. 
 
 Prepare muriate of alumina for use in sewage preci- 
 pitation by treating with muriatic acid minerals con- 
 taining terhydrate of alumina. The muriate of alumina 
 is used along with refuse carbon, carbonised peat, 
 lignite and clay. 
 
 345. /. W. Slater and W. Stevens. 1884. No. 16,592. 
 
 Claim the use of fresh blood along with the ingre- 
 dients named in No. 15,810. 
 
 346. H. Wagner. 1885. No. 629. 
 
 Precipitates with slaked lime, and proposes certain 
 mechanical arrangements in which the novelty of the 
 patent must lie. 
 
 347. F.M.Lyte. 1885. No. 900. 
 
 Uses in the treatment of sewage a soluble aluminate, 
 preferably that of soda, followed up, if necessary, by 
 some acid, such as sulphuric or hydrochloric, or by an 
 acid salt. Adds further, for producing a purer water, 
 charcoal from seaweed or peat, or shale ground together. 
 
 This is a good process. Its practical applicability 
 turns on the price at which aluminate of soda is pro- 
 curable. 
 
 348. Y. W. Barton. 1885. No. 1,345. 
 
 Proposes vehicles for conveying away town refuse. 
 
 349. 1885. No. 1,421. 
 
 No final specification has been filed. In this case, 
 under the existing law, the provisional is not published. 
 
 350. J. Richmond and T. Birtwistle. 1885. No. 1,891. 
 
 Furnaces for consuming town refuse. 
 
SEWAGE PATENTS. 247 
 
 351. C. Price and H. Cleave. 1885. No. 2,728. 
 
 Propose mechanical arrangements for treating sewage. 
 
 352. W. S. Page. 1885. No. 2,804. 
 
 A device for lighters to convey away sewage-sludge. 
 353- W. F. B. Massey-Mainwaring and J. Edmunds. 
 1885. No. 2,885. 
 
 Force into sewage water supercharged with oxygen, 
 and thus effect the oxidation, or, in fact, combustion of 
 the organic impurities. 
 354. 1885. No. 2,913. 
 
 Not published. 
 35$. 1885. No. 3,172. 
 Not published. 
 
 356. 1885. No. 3,682. 
 
 Not published. 
 
 357. A. Engle. 1885. No. 4,046. 
 
 Submits night-soil to destructive distillation, and 
 utilizes the gases given off during the process. 
 
 358. 1885. No. 4,207. 
 
 Strains sewage through graduated screens, precipitates 
 the clear liquid with lime, and extracts the oily and 
 fatty matters by treatment with carbon disulphide 
 (sulphuret of carbon). 
 
 359. T.M.Lownds. 1885. No. 4,502. 
 
 To prevent nuisance covers the liquid in urinals with 
 a layer of oil, to which is added some disinfecting 
 matter, such as carbolic acid. 
 
 360. /. W. Slater. 1885. No. 4,532. 
 
 Precipitates sewage with natural waters containing 
 sulphate of alumina or other aluminous salt. If such 
 waters are too weak, adds to them salts of iron or 
 alumina. 
 
 Or adds sulphate of alumina to ferruginous waters. 
 Uses along with any of these waters clay, refuse 
 carbon, etc. 
 
?4 SEWAGE TREATMENT. 
 
 361. /. Homes. 1885. No. 5,153. 
 
 Incinerates night-soil in a special furnace (cremator), 
 and uses the product as a precipitant, along with lime, 
 salts of protoxide and peroxide of iron, or " acid extract 
 of indigo, cudbear, sulphuric acid, sodium sulphate, 
 hydrochloric acid, bichromate of potash, picric acid and 
 logwood chips." 
 
 Bichromate of potash, as poisonous to man and beast 
 and as harmful to vegetation, is quite inadmissible in 
 the treatment of sewage. The advantages to be derived 
 from the use of such bodies as extract of indigo, cud- 
 bear, picric acid, and logwood chips is exceedingly pro- 
 blematical, especially if we consider their prices, 
 
 362. C.Lehoffer. 1885. No. 5,227. 
 
 Proposes mechanical arrangements. 
 
 363. M. Maehnsen. 1885. No. 5,348. 
 
 Precipitates with phosphoric (basic) slags. 
 
 364. 1885. No. 5,448. 
 
 Not published. 
 
 365. E. Burton. 1885. No. 6,053. 
 
 Proposes furnaces for destroying excreta and refuse. 
 
 366. F. M. Lyte. 1885. No. 6,054. 
 
 Referring to former specification (A. D. 1885, No. 900), 
 claims certain neutral salts such as calcium, chloride 
 and sulphate, salts of magnesia, zinc, etc., instead of 
 acids and acid salts for following up aluminate of soda. 
 
 367. W. B. G. Bennett. 1885. No. 6,055. 
 
 Mixes " carbonised clay," or " carbonised earthy 
 deposit containing iron, and alumina," grinds to fine 
 powder, treats with oil of vitriol, and afterwards adds 
 water at from 150 to 212 Fahr., and uses it in 
 sewage treatment. 
 
 368. W. Grimsh&w. 1885. No. 6,453. 
 
 Dries pail-stuff, passing the fumes through current of 
 sulphurous acid. 
 
SEWAGE PATENTS. 249 
 
 369. 1885. No. 6,559. 
 
 Not published. 
 3/O. 1885. No. 6,692. 
 
 Not published. 
 
 371. 1885, No. 7, 1 86, 
 
 Not published. 
 
 372. B. D. Healey. 1885. No. 7,703. 
 
 Furnaces for burning up refuse. 
 
 373. P. Smith. 1885. No. 7,714. 
 
 Arrangements for separating solids and semi-solids 
 from sewage, 
 
 374. /. M. H. Munro, S. H. Johnson, and C. C. 
 
 Hutchinson. 1885. No. 7,759- 
 
 Treat sewage with basic cinder, followed up with milk 
 of lime. 
 
 Without special provision to the contrary, the effluent 
 from this process will be alkaline. 
 
 375. 1885. No. 8,058. 
 
 Not published . 
 
 376. H. H. James. 1885. No. 8,084. 
 
 Forces air and steam into sewage. 
 
 377. /. B. Alliott. 1885. Afa. 8,183. 
 
 Arrangements for dealing with mud, slops and road 
 sweepings. 
 
 378. 1885. No. 8,690. 
 
 Destructors for town refuse. Burns gases given off. 
 
 379. /. Berger Spence. 1885. No. 8,912. 
 
 Passes sulphurous acid gas through or over the 
 sewage in the sewers. 
 
 380. 1885. No. 9,268. 
 
 Not published. 
 
 381. 1885. No. 9,392. 
 
 Not published. 
 
250 SEWAGE TREATMENT. 
 
 382. 1885. No. 9,992. 
 
 Not published. 
 
 383. 1885. No. 10,107. 
 
 Not published. 
 
 384. 1885. No. 10,832. 
 
 Not published. 
 
 385. 1885. No. 10,879. 
 
 If precipitation is not to be followed by filtration or 
 irrigation uses per gallon of sewage a mixture of 5 to 10 
 grains of coke, 2 to 5 grains of clay, 2 to 5 grains of lime, 
 and 2 to 5 grains of sulphate of alumina or of copperas. 
 If the effluent is to be filtered or passed over land the 
 formula used is merely 5 to 20 grains of coke and 
 i to 10 grains of clay per gallon. 
 
 These mixtures will each give an alkaline effluent. 
 
 386. 1885. No. 11,155. 
 
 Not published. 
 
 387. 1885. No. 11,436. 
 
 Treats sewage with a mixture of soot 5 to 10 grains 
 soot, 2 to 5 grains clay, and 2 to 5 grains lime, along 
 with the deposit from the mineral spring of South- 
 bourne-on-Sea or with a quantity of the water. Such 
 water, or the sediment, containsa considerable proportion 
 of sulphates of iron and alumina. 
 
 This patent was objected to on the ground of want 
 of novelty. 
 
 388. 1885. No. 11,491. 
 
 389. 1885. No. 11,542. 
 
 Uses for sewage treatment a so-called u vitriolised 
 ash." He forms a chloro-sulphate or sulphite ofalumina 
 and iron by heating " sulphury material, "which may be 
 ashes, spent pyrites, etc., with common salt and sulphuric 
 acid (chamber acid) to a temperature of about 200 
 Fahr. This mixture is used in sewage treatment along 
 with lime. 
 
SE WA GE PA TENTS. 25 1 
 
 390. 1885. No. 11,750. 
 
 Not published. 
 
 391. /. Hanson. 1885. No. 12,261. 
 
 Uses vat-waste or gas lime oxidised naturally or 
 artificially, along with lime. 
 
 This patent was objected to on the ground of want 
 of novelty, 
 
 392. /. Webster. 1885. No. 12,344. 
 
 Treats the drainage from tank-waste, but makes no 
 reference to sewage, 
 
 393. 1885. No. 12,674. 
 
 Not published. 
 
 394. 1885. No. 13,281. 
 
 Not published. 
 
 395. 1885. No. 13,587- 
 
 Not published. 
 
 396. W. G. Sillar. 1885. 13,749. 
 
 In treating sewage uses hot solutions of salts of 
 alumina, etc,, with or without other suitable agents. 
 397- / W. Slater and the Native Guano Company, 
 
 Limited. 1885. No. 13,750. 
 
 Treat sewage with a muriatic solution of copper 
 slag in conjunction with a solution of iron slag in 
 muriatic acid, or of hydrated aluminium chloride or 
 manganese chloride, with or without carbonaceous matter 
 and clay or earth. 
 398. 1885. 13,761. 
 
 Treats sewage alternately with an alkaline and an acid 
 extract of Redonda, Alta-Vela or other natural phosphate 
 of alumina. The alkaline extract is obtained by fusing 
 the ground phosphate with caustic alkali, and the acid 
 extract by treating the ground mineral with sulphuric 
 or hydrochloric acid or a mixture of both. 
 
252 SEWAGE TREATMENT. 
 
 399- /. Carey. 1885. No. 13,866. 
 
 Barges for conveying away sewage mud, 
 
 400. J.Carey. 1885. ^0.16,025. 
 
 Ships for conveying sewage, 
 
 401. Miller. 1886. No. 10. 
 
 Dries sewage by propelling air through it by atmo- 
 spheric pressure into a partial vacuum. 
 
 402. Botham. 1886. No. 530. 
 
 Proposes an apparatus for extracting sewage sludge 
 out of tanks. 
 
 403. Hardley. 1886. No. 572. 
 
 404. G.H.Leane. 1886. No. 1,053. 
 
 Filters sewage through burnt Kimmeridge shale ; 
 claims certain arrangements of plant. 
 
 405. Cox and Cox. 1886. No. 1,259. 
 
 406. Jeyes. 1886. No. 1,261. 
 
 407. Hartland. 1886. No. 1,727. 
 
 408. F. Candy. 1886. No. 1,792. 
 
 Ignites in closed vessels a mixture of quicklime and 
 tar or tarry oils, resins and bitumens or other liquid 
 or semi-liquid carbonaceous matters, and uses the 
 product in the treatment of sewage. This mixture 
 is an attempt to combine the purifying agency of carbon 
 with lime as a precipitant. 
 
 409. Davis. 1886. No. 1,840. 
 
 410. F. H. Danchell. 1886. No. 2,439. 
 
 Chars sewage mud or deposits, which he then calls 
 charcoaline, and niters sewage through it. 
 
 411. Cobley. 1886. No. 2,752. 
 
 412. /. B. H annoy. 1886. No. 3,217. 
 
 Precipitates sewage with a mixture of lime or carbon- 
 nate of lime and clay and makes cement of the deposit. 
 
 Here, of course, as in the Scott processes the plant- 
 food present in the sewage is wasted. 
 
SEWAGE PATENTS. 253 
 
 413.7. W. Slater, S. K. Page, W. Stevens, and the 
 Native Guano Company, Limited. 1 886. No. 3 ,973 . 
 Prepare a sulphate of manganese by gently igniting 
 in a crucible a layer of sulphur over which is placed a 
 layer of the black oxide or peroxide of manganese. Or 
 they prepare mixed sulphates of manganese and alumina 
 by treating in a similar manner a mixture of peroxide 
 of manganese and Eglington clay, bauxite or other 
 hydrates of alumina. Or they prepare chloride of 
 manganese or of manganese and aluminium by adding to 
 the aforesaid mixtures common salt. The products are 
 used in the treatment of sewage alone or in combina- 
 tion. 
 
 414. L, G. G.Daudinart. 1886. ^7.4,203. 
 
 Treats sewage first with lime and then with a 
 mixture of sulphate of alumina and chloride of zinc. 
 
 The well-known poisonous character of the salts of 
 zinc renders them very undesirable in the treatment of 
 sewage. If the zinc is precipitated the sludge will be 
 unsafe as manure for plants, and if any of it remains 
 in solution the effluent cannot be fit for admission into 
 streams. 
 
 415. F. Petri. 1886. .#0.4,512. 
 
 Precipitates first with lime, and then with epsoms or 
 other salts of magnesium or barium, and filters the 
 effluent finally through matters containing tannin. 
 
 Great care will be here necessary to prevent barium 
 remaining in solution. Nor will its presence in the 
 sludge be advantageous for manurial purposes, since 
 it is not a plant food. Matter containing tannin, if 
 used as a filter, is well suited for removing certain 
 impurities from the effluent water. 
 
 416. T. Reid. 1886. No. 4,544. 
 
 Mechanical arrangements for filtering. 
 
254 SEWAGE TREATMENT. 
 
 417. W. F. B. Massey-Maimvaring. 1886. No. 4,878. 
 
 Proposes improvements in filter presses for drying 
 sewage sludge, &c. 
 
 418. G.R.Redgrave. 1886. 7V0. 6,520. 
 
 A lime process for the conversion of sewage matters 
 into cement. 
 
 419. T.H.Cobley. 1886. No. 6,732. 
 
 Uses the ash of sewage deposits in place of lime as an 
 addition to sludge for pressing. 
 
 Long experience has shown that there is not the least 
 occasion for an addition of lime to sewage mud before 
 pressing. 
 
 420. /. Fenton. 1886. No. 7,333. 
 
 Passes sewage through a tank containing alum, and 
 then into strainers. 
 
 421. Alsing. 1886. No. 7,730. 
 
 422. H.R. Newton. 1886. No. 8,144. 
 
 Proposes certain mechanical arrangements. 
 
 423. Georgi. 1886. No. 8,411. 
 
 424. F. H. Danchell. 1886. No. 8,469. 
 
 425. James Bannehr. 1886. No. 8,874. 
 
 Claims certain mechanical arrangements. 
 
 426. Bohlig andHayne. 1886. No. 9,276. 
 
 Produce " carbon magnesia " from chlorate of magnesia. 
 Chlorates as waste products are not very abundant. 
 
 427. H. W.Lafferty. 1886. M?. 9,431. 
 
 Propose to utilise the refuse of breweries and dis- 
 tilleries. 
 
 428. W. Burns. 1886. No. 9,569. 
 
 Mixes animal dung (is there any other than animal 
 dung ?) with sawdust, peat, coal dust, chalk, blood and 
 iron to form a "depurating carbon," and distils the 
 mixture in retorts. 
 429. H. Cobley. 1886. No. 9,847. 
 
SEWAGE PATENTS. 255 
 
 430. W. Astrop. 1886. No. 10,047. 
 
 Proposes drying arrangements for sewage sludge. 
 
 431. Johnstone. 1886. No. 11,068. 
 
 432. Hannay. 1886. No. 11,165. 
 
 433. W. P. Thompson. 1886. No. 11,366. 
 
 Proposes apparatus for drying " offal." There is no 
 direct reference to sewage. 
 
 434. A. Forrest and W. Welsh. 1886. No. 11,409. 
 
 Propose apparatus for drying up blood, sewage, &c., 
 so as to be available for manure. 
 
 435. Miller. 1886. No. 11,461. 
 
 436. G.H.Leane. 1886. 7V0. 11,820. 
 
 Uses Kimmeridge carbon in place of lime, as an addi- 
 tion to sewage mud for pressing. 
 
 Kimmeridge carbon is undoubtedly much preferable 
 to lime, but no addition at all is necessary. 
 
 437. Gerson. 1886. No. 11,830. 
 
 438. /. H. Barry. 1886. No. 11,833. 
 
 Strains off the liquid portion of sewage from the 
 deposits, concentrates the liquid by distillation, returns 
 the residue to the deposit, and treats it by precipitation 
 and nitration. 
 
 No novel precipitant is claimed. Without doubt a 
 very good effluent can be obtained in this manner, pro- 
 vided a good precipitant is selected. The ammonia 
 given off during the distillation may be collected, and 
 either added to the precipitate, or may be otherwise 
 utilised at pleasure. But the process must prove expen- 
 sive, as the straining and the distillation are superadded 
 to the ordinary operations of precipitation treatment. 
 
 439. Soldenhoff. 1886. No. 12,259. 
 
 440. Hallett. 1886. No. 12,382. 
 
 441. Bremner. 1886. No. 12,981. 
 
 442. Perkins. 1886. No. 12,850. 
 
256 SEWAGE TREATMENT. 
 
 443. Butterfield and Mason. 1886. No. 13,007. 
 444- Abel. 1886. No. 13,470. 
 
 445. Ames. 1886. No. 13,791. 
 
 446. F. Candy. 1886. .M?. 13,829. 
 
 Prepares a compound which he names " magnetic 
 precipitant," and which he uses in the treatment of 
 sewage. He ignites in a closed vessel argillaceous iron 
 stone or iron ores (which should contain either lime or 
 magnesia, or both of them) and either with or without 
 the addition of carbonaceous matter. The temperature 
 must not be high enough to vitrify the matter, which is 
 afterwards treated with sulphuric and hydrochloric acid. 
 
 The final product is, of course, a mixture of carbon 
 with sulphates of alumina, iron, lime, and magnesia, or 
 with the corresponding chlorides. No one can deny 
 that the combination of salts of iron and alumina with 
 carbon form an efficient precipitating mixture. But 
 whether there is any advantage in preparing such mix- 
 ture in the manner specified, is an open question. 
 
 447. Donnithorne. 1886. No. 14,221. 
 
 448. Burns. 1886. No. 15,222. 
 
 449. Mayes. 1886. No. 15,341. 
 
 450. W.F.Mast. 1886. No. 15,887. 
 
 Adds to sewage matters an alkaline base, such as lime 
 and common salt, or some equivalent chloride. He 
 then heats to high temperatures in a suitable vessel, and 
 collects the ammonia. 
 
 The novelty and the value of this process turn on 
 the alleged effects of the addition of an alkaline chloride, 
 such as common salt, in expelling ammonia from organic 
 matter. 
 
 451. Hartland. 1886. No. 16,039. 
 
 452. Wilson. 1886. No. 16,244. 
 
 453. Brown. 1886. No. 16,461. 
 
 454. Barry. 1886. No. 16,866. 
 
DR. TIDY'S PAPER. 
 
 257 
 
 CHAPTER XX. 
 THE DISCUSSION ON DR. TIDY'S PAPER, HELD MAY 5TH, 
 
 l886, BEFORE THE SOCIETY OF ARTS. 
 
 I AM prevailed upon to notice this discussion, not because 
 it brought to light anything at once novel and true con- 
 sisting, indeed, as it did, in no small part, of matter possessing 
 neither of these attributes but because it affords good speci- 
 mens of the views still current in official circles. I regret 
 having to put on record the fact that two, perhaps more, of 
 the speakers who took part in the debate were apparently 
 reading prepared and, to some extent, independent papers 
 on sewage treatment, rather than simply criticising Dr. Tidy. 
 This is a defect not readily avoidable in the case of an 
 adjourned discussion. 
 
 It will be remembered that Dr. Tidy did not, in his 
 original paper, pose as the advocate of any one exclusive 
 system. But this lack of an Athanasian Creed has left him 
 open to criticism from all sides. The exceptions taken to his 
 views, and his arguments in the discussion in question, came 
 mainly from irrigationists and filtrationists. But room is left 
 for the friends of precipitation, as rationally conducted with 
 the aid of absorbents, to say a word. 
 
 The learned doctor was not seen to draw a sufficiently broad 
 distinction between precipitation pure and simple, z'.e., the 
 treatment of sewage by means of salts of alumina, iron, 
 magnesia, etc., separately or jointly, with or without the 
 addition of lime ; and, on the other hand, precipitation plus 
 absorption, the absorbent materials being added first, and 
 
 s 
 
258 SEWAGE TREATMENT. 
 
 the true precipitants afterwards. Those who advocate and 
 practice this double method have the advantage over the 
 irrigationist, inasmuch as, like him, they absorb the soluble 
 matter of the sewage in earth or clay, etc., but are able con- 
 stantly to bring fresh material into play, so that no choking 
 or supersaturation can ever arise. They have the advantage 
 over the precipitationist " pure and simple," inasmuch as all 
 the doubts and queries and quibbles about "clarification, but 
 not purification," pass by them like very idle wind. With 
 the addition of the absorbent materials to the sewage the 
 bad smell disappears, and on the subsequent introduction of 
 the precipitant the suspended sewage matters, as well as the 
 particles of the absorbent, now saturated with the soluble and 
 gaseous impurities^ are thrown down together. In short, we 
 have first purification and then clarification. 
 
 When Dr. Tidy's paper was read there was to be seen a 
 press-cake of sewage deposit. Any person acquainted with 
 sewage treatment would have known at once by the smell 
 that this cake was the result of some modification of the lime 
 process. But, so far as I can remember, the lecturer said no 
 word to that effect ; no more did any of his critics during the 
 subsequent discussion. Hence, it was left open for any person 
 so disposed to insinuate, or actually to believe, that this cake 
 was a product (say) of the " A B C " process, or of some other 
 of those processes combining absorption and precipitation. 
 That the full truth should come to light in this matter is the 
 more urgent in view of the somewhat strong language used 
 in the discussion by Dr. Dupre, F.R.S. 
 
 This gentleman is reported to have said : " It was a well- 
 known trick of counsel* in sewage cases to have a large cake 
 
 * That counsel have certainly their " tricks " in sewage cases, as well 
 as in others, is perfectly true. But 
 
 "For ways that are dark, and for tricks that are vain, 
 
 The Royal Commissioner is peculiar, 
 Which the same I am free to maintain." 
 
DR. TIDY'S PAPER. 259 
 
 of this pressed sludge brought into court to point out how 
 inodorous it was, and to almost advise persons to take it home 
 and place it on the mantelpiece ; but it was not said that that 
 was generally especially pressed cake, very carefully dried by 
 exposure to the air. If you took that cake and moistened it 
 and bottled it up, and then smelt it again a week after, no 
 one would think of recommending it to be kept in a dining- 
 room. They had all heard Dr. Tidy's story about walking 
 about amongst thousands of tons of this which really smelt 
 rather nice ; * but he (Dr. Dupre) had had the misfortune also 
 to go about this heap of thousands of tons, having visited it 
 on a cold May morning, when there had been a frost during 
 the night a very unfavourable time for producing smells. 
 He visited the heap with the engineer, who told them that 
 he could not smell anything ; but, after going some distance 
 in the direction of the wind, they found it really very 
 offensive. The engineer said he never smelt it so strong 
 before, although il was a cold morning ; they went as far 
 as they could, and measured the distance, and found it was 
 six hundred yards, and there the smell was most powerful 
 and offensive." 
 
 Now, I do not for one moment believe and I should 
 gravely deplore having to believe that Dr. Dupre in the 
 above remarks was knowingly and intentionally misleading 
 his hearers. But it is, I think, to be regretted that he did 
 not say plainly by what process the " thousands of tons " 
 had been obtained. We must remember that : 
 
 1. There is cake and cake. 
 
 2. That the sample on view on the occasion of Dr. Tidy's 
 paper was a lime-process cake, and that its smell was decidedly 
 offensive. 
 
 3. That the cake from lime processes is well known to be, 
 in quantity, a manifest nuisance, whilst the same charge 
 
 * Dr, Tidy said, "and really smelt very little" a very different 
 proposition. 
 
260 SEWAGE TREATMENT. 
 
 cannot be brought against the cake or mud produced by a 
 combined absorption-precipitation process, or even by a 
 simple precipitation process, where lime plays no part 
 except that of removing any excess of acid. 
 
 Dr. Dupre might, I fear, when speaking of this pressed 
 sludge, that cake, etc., be understood to mean any and every 
 kind of sewage-sludge or cake. Hence I am compelled to 
 mention, lest his " story " of going about this heap of thou- 
 sands of tons should be misconstrued, that Dr. Dupre has 
 never visited the Aylesbury Sewage Works. This I have 
 ascertained by special and very careful inquiry. Had he 
 so done, he would have found neither a " most powerful and 
 offensive smell," nor a heap of thousands of tons of sludge 
 or cake. Nor, so far as I .can learn, is there any other place 
 in the kingdom where a true absorption-precipitation pro- 
 cess is at work where a nuisance is experienced, or where 
 "thousands of tons " of sludge or cake could be met with. 
 Hence it follows that when Dr. Dupre went a-Maying it 
 must have been to some lime-process works, and the de- 
 fenders of such processes may refute his charges if they 
 can. 
 
 Taking in order of time the speakers who bore part in 
 the discussion, I am glad to note the fact that Lieut.-Col. 
 A. S. Jones, V.C., evinced in his remarks more candour 
 and breadth than is usually to be found among irrigationists. 
 He seems to me to raise a question interesting and legitimate 
 enough in itself, but which has already been practically 
 decided. He thinks that in judging the effect produced by 
 any given precipitant, we should compare the effluent, not 
 with -the raw sewage, but with the liquid obtained by simple 
 subsidence without the aid of any chemicals. But the amount 
 of spontaneous subsidence from sewages of identical composi- 
 tion is by no means a constant quantity. It varies with 
 temperature, atmospheric pressure, and time allowed. Thus 
 the liquid obtained from such natural subsidence would 
 
DR. TIDY'S PAPER. 261 
 
 furnish no term of comparison with the effluent obtained by 
 any rational precipitation process. 
 
 Further, the deposit obtained by subsidence is different, both 
 in quantity and quality, from that produced by precipitation. 
 The spontaneous deposit is decidedly and invariably smaller 
 in weight, and contains a much lower proportion of organic 
 matter. It consists principally of silt, sand, road dust, and 
 other heavy and insoluble mineral bodies. I have repeatedly 
 allowed quantites of sewage to subside for different lengths 
 of time, ranging from six to twenty-four hours. When all 
 subsidence was at an end, I have carefully decanted off the 
 clear liquor, and on adding to it a suitable precipitant say 
 hydrated aluminium chloride or aluminium acetate I have 
 obtained a very copious precipitate. Hence the dictum that 
 a precipitation process is little better or more efficient than 
 a subsidence process can have sprung only from inob- 
 servance or from prejudice. 
 
 It is highly probable that if we allow sewage to settle 
 spontaneously, and then add to the clear liquid some pre- 
 cipitating agent, the two deposits added together would not be 
 equal in amount to that obtained by at once adding the pre- 
 cipitant to the sewage. The reasons for taking this view are : 
 
 1 . Recent sewage is more easily precipitated than such 
 as is stale. 
 
 2. During spontaneous subsidence, which is a much slower 
 process than precipitation, fermentation sets in. Solids are 
 converted into liquids, and both solids and liquids into gases. 
 Simple subsidence has been proposed by not a few inventors 
 as one step in systems of dealing with sewage, followed up 
 in most cases by treatment with chemicals, by irrigation or 
 by some kind of filtration. But the patentees appear to 
 have been fully aware of the character of the fumes given 
 off. They recommend that the tanks should be covered 
 in, and connected with a tall chimney or with a furnace to 
 convey away or to destroy such fumes. 
 
262 SEWAGE TREATMENT. 
 
 In a further paragraph of his speech (or may we say 
 paper ?), Col. Jones goes, I submit, beyond the legitimate 
 boundaries of a discussion on Dr. Tidy's paper. The learned 
 doctor had certainly not expressed any opinion on much 
 less defended the policy of the Native Guano Company. 
 To have done so would have been on his part a departure 
 from his subject, and a breach of method. But Colonel Jones, 
 strangely enough, intercalates an examination of the policy 
 of the Native Guano Company in his critique of Dr. Tidy's 
 paper ! 
 
 Of the u two serious mistakes" which Col. Jones con- 
 siders that the Native Guano Company has committed, the 
 second, as he admitted almost in the same breath, was 
 scarcely under its control, viz., that u the Stock Exchange 
 afforded opportunities for gambling in 'Natives.'' 1 The 
 shares of all limited companies are exposed to "bull and 
 bear " manipulations, which neither the Legislature, nor the 
 Courts, nor Boards of Directors can hinder or control. 
 
 Col. Jones's remarks on the scheme adopted by the Metro- 
 politan Board of Works are judicious. He considers the efflu- 
 ent from such an imperfect precipitation-process " inadmis- 
 sible into the estuary even at Thames Haven.' 1 Besides show- 
 ing the inefficiency of the prescribed dose, he further, with 
 perfect correctness, reminded his hearers that the deodorisa- 
 tion produced by the application of permanganate is transi- 
 tory in effect. <4 This," he truly said, " anybody might ascer- 
 tain by keeping a bottle of effluent deodorised by perman- 
 ganate for a few days, and as the sewage is not supposed to 
 reach the Nore for some six weeks after its discharge at 
 Barking, it would seem hardly worth the expense of deo- 
 dorising it for about one-twentieth part of that period." 
 
 Certainly, if permanganate is to be used to advantage, as 
 much as possible of the organic matter ought to be pre- 
 viously removed from the sewage. Further, if the perman- 
 ganate is to oxidise, in other words burn up the residual 
 
DR. TIDY'S PAPER. 263 
 
 organic matter, it must be used in much greater quantity 
 than the Metropolitan Board have proposed. Permanganate 
 entirely fails in removing the microbia which are now so 
 much dreaded. 
 
 Neither Col. Jones nor any following speaker succeeded 
 in showing how sewage irrigation could be other than an 
 evil when the amount of rainfall is in itself more than is 
 good for the land. 
 
 Mr. Baldwin Latham considered that sewage farms were 
 rather favourable than otherwise to public health. This 
 statement differs greatly from the results obtained in India, 
 as recorded by Markham. There, irrigation with ordinary 
 river water, and applied only in dry weather, is recorded as 
 having had an unfavourable effect on public health. 
 
 Mr. Peregrine Birch endeavoured, very unsuccessfully, to 
 explain and justify the statement of Professor Frankland, 
 that the sewage of midden towns was practically as foul as 
 the sewage of closeted towns. The additional water thrown 
 into the sewers of the latter does not remove or destroy the 
 excrementitious matters. In a midden town all the solid 
 excreta, and, to a very large extent, the urine also, are kept 
 out of the sewers. That the quantity of water introduced 
 can compensate for this pollution is a delusion. 
 
 Mr. Birch thinks that the cracks in clay lands can be got 
 rid of by putting on more sewage, irrespective, of course, 
 of its action on the crops. But what of the cracks and 
 crevices in subjacent chalk and other strata ? These, it is to 
 be feared, no excess of sewage will fill up. From the con- 
 flicting statements of Way, that a light soil is best for 
 irrigation, and of Liebig that a stiff soil is best, Mr. Birch 
 draws the singular inference that "there was scarcely any 
 soil in the world that would not do for the purpose." If 
 nothing more was known on the subject than the dicta just 
 quoted, it would be quite as legitimate to infer that " scarcely 
 any soil in the world would do for the purpose." 
 
264 SEWAGE TREATMENT. 
 
 Mr. Birch agrees with Dr. Tidy, and differs from Col . Jones, 
 in thinking that "sewage, spread over the land, forms papier 
 mac he" 
 
 But his grand coup, delivered over his own knuckles, was 
 an attempt to show ll the absurdity of the assertion that 
 native guano is worth $ los. a ton." As Dr. Tidy had 
 not made any such assertion, nor discussed the value of 
 native guano at all in his paper, Mr. Peregrine Birch was 
 clearly out of order in introducing the subject. But let us 
 examine if what he said could in any manner justify his 
 departure from the question before the society. He took up 
 a table, showing the composition and value (?) of the weekly 
 out-put at Aylesbury, giving the following figures for 
 sixteen tons : 
 
 s. d. 
 
 Charcoal 4 tons 14 cwt. at . . o i o 
 Clay 6 tons 10 cwt. at . . . . o i o 
 Alum i ton 17 cwt. at ....200 
 
 and consequently he finds, by way of difference, that there 
 are in sixteen tons of native guano only two tons eighteen 
 cwt. of sewage matter ! 
 
 Here he evidently forgets or ignores the fact that the 
 charcoal used contains at least 50, often 60, per cent, of water, 
 which passes out in the effluent. The clay, in like man- 
 ner, contains 40 per cent, of moisture, whilst of the alum 
 only the alumina, 13 to 14 per cent, enters into the precipi- 
 tate. So that instead of the 13 tons i cwt. of non-manu- 
 rial matter which Mr. Peregrine Birch estimates as present 
 in native guano, -there are only about 6^ tons, and the 
 proportion of matter derived from the sewage, in place of 
 2 tons 1 8 cwt., is about 9 tons 9 cwt. in a dry sample, or in 
 one containing 14 per cent, of moisture 8 tons 2 cwt. ! 
 
 But we must follow Mr. Peregrine Birch two steps further. 
 He seems to forget that most common clays contain a con- 
 siderable proportion of coarse sand, gravel, and pebbles, which 
 
DR. TIDYS PAPER. 265 
 
 remains in the grinding pans, mixing pits and shoots con- 
 veying the ABC mixture, and never reaches the preci- 
 pitating tanks at all ! Hence a further deduction must be 
 made from the estimate of non-manurial matter, and a 
 corresponding increase of the sewage matters. 
 
 It may further be asked, what conceivable bearing the 
 cost of the alum (alum-cake), here given as 2 per ton, has 
 upon the value of the native guano ? Alum has no manu- 
 rial value at all, and the alumina which it contains acts 
 merely by forming, with the nitrogenous matters of the 
 sewage, a lake-like compound. But here we may very well 
 afford to take leave of Mr. Peregrine Birch. 
 
 Next followed Dr. Percy Frankland, who considered that 
 the strength of the sewage in midden towns, as compared 
 with water-closet towns, is simply a question of water sup- 
 ply. I have already shown that faecal matter, even plus a 
 somewhat large supply of water, must give a sewage fouler 
 than one in which such matter is absent. Says Dr. Frank- 
 land : " The average for the water-closet towns was largely 
 obtained from London itself, and the midden towns were 
 principally taken from Lancashire, where the water supply per 
 head was much smaller than in London." But, on the other 
 hand, it should be remembered that the average rainfall of 
 Lancashire is notably greater than that of London. The 
 comparison is further complicated by the fact that in Lanca- 
 shire it is difficult to find a town where the sewage does 
 not receive much industrial waste waters. If the late Rivers 
 Pollution Commissioners had wished to make a really useful 
 comparison they should have selected two groups of purely 
 residential towns, the one closeted, and the other provided 
 with middens. If the contention is true, that the pollution of 
 the sewers is simply <( a question of water supply/' it is 
 hard to see the value or the relevance of the fact. 
 
 The next speaker was Dr. Dupr^, a chemist of unques- 
 tionable eminence and authority. We find him venturing 
 
266 SEWAGE TREATMENT. 
 
 on the conclusion that " no precipitation process which had 
 been at present brought forward did sensibly more than 
 clarify the sewage." Strange to say, he added, that " in this 
 opinion he was borne out by experiments which had been 
 made by Dr. Tidy and Professor Dewar." Now, as Pro- 
 fessor Dewar subsequently pointed out, u three-fourths of 
 the readily oxidisable matter was removed " from sewage 
 by the process in use at Aylesbury, including dissolved as 
 well as suspended impurities ! ! 
 
 Dr. Dupre further falls into error, when speaking of the 
 ABC process, by ignoring, like Mr. Peregrine Birch, the 
 moisture present in the materials used. Hence his statements 
 that the pressed cake is chiefly formed of the materials 
 which had been added, and that no real benefit was produced 
 require to be taken with a very large grain of salt. Whence 
 come the three per cent, of ammonia and the phosphoric 
 acid, equal to five per cent, tricalcic phosphate, which 
 recent analysis shows in the native guano ? 
 
 Mr. Dibdin spoke of the " common mistake " that 
 because a glass of effluent water was clear, therefore it 
 was pure. Clear waters, not merely effluents, are certainly 
 not necessarily pure a point of which the public have been 
 by this time informed to satiety. But if the suspended matter 
 is, as Colonel Jones remarks, u the foulest of town sewage;" 
 if it is, as Lord Bramwell's Commission called it, the " crux " 
 of the question, even clarification is not to be despised. 
 There is a "common mistake" about " pure water" and 
 11 purification." Pure water, in the strictest sense of the word 
 and no other is legitimate is almost as much an abstraction 
 as the lines and points of the mathematician. It has never 
 been obtained on a practical scale. If, therefore, we are told 
 that " precipitation does not purify sewage," the remark 
 is a mere truism. Nor does any one contend that sewage 
 can be rendered fit or safe to drink, except by natural pro- 
 cesses. But the assertion that sewage cannot be rendered 
 
DR. TIDYS PAPER. 267 
 
 by any precipitation process, safe and fit to be admitted 
 into "any river," must be pronounced exceedingly rash. 
 
 There is very little novelty in the information that an 
 excess of precipitants, beyond a certain limit, does not 
 necessarily improve an effluent. I could find working men 
 who have been aware of this truth a dozen years ago. 
 Especially does this rule hold good if lime is concerned. 
 Mr. Dibdin says, truly enough, that " this large quantity of 
 lime (700 grains per gallon) dissolved some of the suspended 
 matters, and brought them into solution. This is, in fact, 
 one of the grave objections to the use of lime as a preci- 
 pitant. 
 
 We find here a very curious report on a sample of effluent 
 which had been examined by Dr. Bell, of the Excise Labo- 
 ratory, Somerset House. It is said that u after careful 
 examination more organic matter was found in the effluent 
 than there was in the sewage.'' Whence had it come, if 
 only lime had been added ? 
 
 This critique had best close with the words of Dr. 
 Dupre : " Let everybody fairly co-operate in the question ; 
 and, above all, let every one give to those opposed to him 
 credit for being actuated by the same honourable motives as 
 he was himself." Very rarely indeed have the advocates of 
 chemical processes received hitherto such credit, especially 
 from official bodies. 
 
INDEX. 
 
 A B C Process, 85, 97, 258 
 
 Absorbents in sewage treatment, 
 103 
 
 Aeration necessary for fish, 148 
 
 of effluents, 112, 121 
 
 Aire River, n, 160 
 
 Alkaline effluents injurious, 89 
 
 Alum not good for sewage treat- 
 ment, 97 
 
 Alumina acetate too costly, 88 
 
 Carbonate, 100 
 
 Muriate, 99 
 
 Aluminate of soda, 99 
 
 Aluminium, basic sulphates of, 98 
 
 Hydrated chloride of, 98 
 
 Salts of, 97 
 
 Alumino-ferric cake, 98 
 
 Ammonia in waters, 20 
 
 Volatilised by chalky soils, 
 
 Ammonium, salts of, 88 
 
 Amphibia in streams, 149 
 
 Antimony in manufacturing sew- 
 age, 4 
 
 Arable soil an absorbent, 103 
 
 Archiv fuer Hygtene, 19 
 
 der Pharmacie, 157 
 
 Arsenic in manufacturing sewage, 4 
 
 Asbestos a filtering medium, 3 
 
 Auerbach, Dr., 148 
 
 Aylesbury, sewage-manure of, 182 
 
 Sewage Works, 57, 85, 86, 
 
 108, 146, 260 
 
 a rium, salts of, unfit for sewage 
 
 treatment, 93 
 Barking Creek, sewer outfall at, 36 
 
 Bazalgette system, 38, 185 
 
 Beggiato a alba, 144, 151 
 
 Bell, Dr., 267 
 
 Birch, Mr. Peregrine, 263 
 
 Blackburn, lime process at, 91 
 
 Bleaching liquors kill fish, 19, 93 
 
 Boehmer, Dr., action of lime on 
 
 sewage, 90 
 
 Bottles for sampling, 170 
 Brautlecht, Dr., precipitates germs 
 
 with alum, 99 
 
 Cake alum, 98 
 
 Cake, sewage, 258 
 
 Calderand Hebble Navigation, 138 
 
 Carbolic acid unsafe in waters, 76 
 
 Carbonates unfit for sewage treat- 
 ment, 101 
 
 Carbons, waste, 105 
 
 Cement, cf doubtful value, 105 
 
 Cement processes, Gen. Scott's, 125 
 
 Cesspools, defects of, 25 
 
 Charcoals, 104 
 
 Chemical News, 175 
 
 Chemiker Zeitung, 157 
 
 Chiltern Hills water, 146 
 
 Chinese method of purifying water, 
 99 
 
 Adopted by French in 
 
 Tonkin, 99 
 
 Cholera, germs of, distributed by 
 flies, 62 
 
 Clay, fatty, an absorbent, 103 
 
 Climate, its bearing on irrigation, 
 47 
 
 Coal-ashes of little use, 104 
 
 Coal-tar proposed, 94 
 
 Coke said to remove microbia, 104 
 
INDEX. 
 
 269 
 
 Commission, Royal, on Metropo- 
 litan Sewage, 86 
 
 Refuses evidence, 86 
 
 On Rivers Pollution, 86, 
 
 0.3, 160, 161 
 
 Commissioners on Rivers Pollution, 
 their Recommendations, 159 
 
 Confervas improve effluents, 166 
 
 Copper, use of, 102 
 
 Coventry, sewage treatment at, 70 
 
 Cresswell, Mr. C., 145 
 
 Crooskes, Mr. W., F.R.S., 115,164 
 
 Crosness, sewage outfall at, 41 
 
 Cylinders for drying sludge, 177 
 
 Danzig, well waters of, 157 
 Denton, Mr. Bailey, 79 
 Deodorising sewage, 119 
 Dewar, Professor,' 85, 266 
 Dibdin, Mr., 266 
 
 Disinfection applied to sewage, 70 
 Dupr6, Dr., F.R.S., 258, 264, 265, 
 
 266 
 
 Dust-bins, evils of, 37 
 Drying cylinders, 177 
 
 Effluents, alkaline, bad, 89 
 
 Examination of, 164, 166 
 
 Improved by green vegeta- 
 tion, 166 
 Elodea Canadenszs, 147 
 
 Filters, cleaning, 75 
 
 Construction of, 73 
 
 Duties of, 72 
 
 Materials for, 74 
 
 Filtration, how differing from irri- 
 gation, 72 
 
 Intermittent, 78 
 
 Upwards and downwards, 
 
 72 
 
 Fish, substances hurtful to, 19 
 Flies, carriers of infection, 37, 60 
 Frankland, Professor E., 53, 79, 
 80,90 
 
 Dr. Percy, 55, 92, 104 
 
 Froth in tanks and channels, 167 
 
 Gasworks, refuse may not be put 
 in sewers, 87 
 
 Gennevilliers, bad smell at, 57 
 
 Irrigation farm at, 49 
 
 Sewage at, 154 
 
 Gerardin, M., 137 
 Germs not removed by irrigation 
 or filtration, 55 
 
 Thrown up from still waters, 
 
 59 
 
 Gesundheits Ingenieur, 140 
 
 Gibbs, Mr. W. A., on sewer gas, 
 36 
 
 Harvest saver, 49 
 
 and Berwick, drying 
 
 cylinder, 177 
 
 Gnats, larvae of, in water, 150 
 
 Grassi, on flies as carriers of disease, 
 62,63 
 
 Ground water, 34 
 
 Gypsum useless in sewage treat- 
 ment, 93 
 
 Hendon, use of lime recommended 
 
 at, 91 
 
 Hertford, sewage treatment at, 203 
 Hogg, Mr. Jabez, M.R.C.S., 
 
 F.R.M.S., 56, 77 
 Hulwa, Dr. F., 140 
 Hypochlorites not fit for use in 
 
 treatment, 93 
 
 India, irrigation in, 58, 263 
 Intermittent treatment, 107 
 Irk, River, n 
 Irrigation efficacious, 45 
 
 Inverse, 107 
 
 Modifications of, 68 
 
 Quality of soil for, 46 
 
 Retards crops, 50 
 
 Made self-supporting, 49 
 
 Suitable climate for, 47 
 
 Irwell, River, II 
 
 Jackson, Mr. L. d'Aguilar, C.E., 16 
 Jones, Colonel, V.C., 260 
 
 Kelvin Water, 160 
 
 Kimmeridge carbon andblackstone, 
 
 74 
 
 Kingston, fish at sewer-mouth 149 
 Knostrop Sewage Works, no 
 Koch, Dr., 156 
 
20 7 
 
 INDEX. 
 
 Konig, Prof., action of lime on 
 sewage, 90 
 
 Land waters polluted, action with 
 
 sea water, 43 
 
 LandwirthschaftlicheJahrbucJier^ 90 
 Latham, Mr. Baldwin, 263 
 Lead unfit for treating sewage, 88 
 Leeds, Dr. A. R., 139 
 Leeds, sewage of, 154 
 Lefeldt, Herr, opinion on irrigation, 
 
 48 
 
 On smells at Romford, 57 
 
 On unassimilated sewage in 
 
 grass, 65 
 
 Leicester, lime process at, 91 
 Liebig, on soils fit for irrigation, 
 
 263 
 
 Liernur, Captain, 29 
 Lignite, absorbent and filter 
 
 material, 113 
 Lime, its action on dyes in sewage, 
 
 90 
 
 Effluents and muds, 90 
 
 Hurtful to fish, 20, 90 
 
 Lime process at Blackburn and 
 
 Leicester, Prof. Frankland, on, 
 
 91 
 
 London, sewage of, 154 
 Lyte, Mr. F. Maxwell, 99 
 
 Macadamized roads deteriorate 
 
 sewage, 3 
 
 McCarter, Judge, on nuisances, 9 
 Maddox, Dr. , flies conveying comma 
 
 bacillus, 62, 63 
 Maercker, Dr., on nitrogen in 
 
 waste waters, 53 
 
 Manganese a good precipitant, 101 
 Manson, Dr., on mosquitoes as 
 
 carriers of germs, 63 
 
 Mr. E., C.E., 54 
 
 Markham, Mr., on irrigation in 
 
 India, 58, 263 
 Marsh-gas, in sewers, 17 
 Melbourne, sanitary state of, 32 
 Microbia, 10, n 
 Micro-organisms, IO, II 
 "Milk in Health and Disease," 65 
 Moor-earth, as filtering medium, 76 
 
 Mud from sewage, drying, 173 
 Mussels rendered poisonous by 
 sewage, 41 
 
 Native Guano Company, 262 
 Nesbit, Mr. A. Anthony, on bleach 
 
 liquors in rivers, 93 
 Night-soil applied to fields, 63 
 Nuisance, definition of, 9, 57 
 Nuneaton, sewage treatment at, 202 
 
 Oder, River, 140 
 
 Odling, Professor, 164 
 
 Officials at sewage works, hints to, 
 
 168 
 
 Outfall channels, 167 
 Oxygen, free, generally absent in 
 
 sewage, 17 
 Ozone as purifying agent, 219 
 
 Page, Mr. S. K., 76 
 
 Paris, sewage of, 154 
 
 Passaic River, 139 
 
 Pasteur and Chamberland, their 
 
 filter, 76 
 
 Patents, " bogus," 116 
 Peat as absorbent, 104 
 Peat Engineering Company, 76 
 Percy, Earl, his Sewage Bill of 
 
 1885, 158, 189 
 Petroleum proposed for treating 
 
 sewage, 94 
 
 Pettenkofer, Prof, vcn, 34 
 Phosphate processes, 95 
 Phosphate Sewage Company, 203 
 Pollution, subterranean, 158 
 Purification, indicated by blue tint 
 
 "5 
 
 Precipitants, use of hot, 97 , 
 
 Used in excess, 167 
 
 Precipitation //#.$ absorption, 257 
 
 Control of, 114 
 
 Re-treatment in, 115 
 
 Press-cake, limed, 258 
 Ptomaines, 41, 94 
 
 " Recommendations' of Rivers 
 Pollution Commission, 159 
 Criticised, 160 
 
 Rivers Clarification Company of 
 Leeds, 221 
 
INDEX. 
 
 271 
 
 River Purification Association, 
 
 203 
 
 Robinson, Prof. H. (of Dublin), 77 
 Rye-grass converted into hay, 49 
 
 Saare and Schwab, observations on 
 substances deadly to fish, 19 
 
 Salt, common, in waters, 15 
 
 Sampling effluents, precautions in, 
 170 
 
 Sanitary Institute, 77 
 
 Sanitary Record ', 77 
 
 Schutzenberger and De Lalande, 
 
 137 
 
 Scum, oily on waters, 158 
 Seine, River, 138 
 Settling pits, 68 
 Sewage, discharge of into sea, 40 
 
 Filtration of, difficult, 3 
 
 Flow of, in dry weather, 7 
 
 Fungus, 151, 153 
 
 Of manufacturing towns, 2 
 
 Nature and composition of, I 
 
 Of Residential towns, 3 
 
 Alkaline, 18 
 
 Specific gravity of, 115 
 
 Where injurious, 9 
 
 Sewerage, single and double, 7 
 
 Sewer-gas, 33 
 
 Sewers, ventilation of, 18 
 
 Silica, gelatinous, absorbent, 105 
 
 Sillar, Mr. W. C., 97 
 
 Silt and road-dirt, 3 
 
 Slag, basic, added to mud, 175 
 
 Smee, jun., Mr., his experiments, 65 
 
 Smell, offensive, not always found 
 
 in putrid matter, 1 6 
 Smell, sense of, 165 
 Smorbo, 196 
 Soap in sewage, 51 
 Soil, its sanitary efficacy, 28 
 Soot of little value, 105 
 Spence, P. (the late), his alumino- 
 
 ferric cake, 98 
 
 his central chimney for 
 
 sewer-gas, 36 
 
 Spongy iron as filter material, 74 
 
 Stevenson, Dr., 91 
 Storm-water, no 
 Streams, pure, insects in, 150 
 Strontium, salts of, admissible, 94 
 Sulphur proposed for use, 94 
 Sulphurets rarely admissible, 93 
 
 Tanks, construction of, 1 1 1 
 
 Covered, a mistake, in 
 
 Foul, 112 
 
 Room, ample, no 
 
 Thames Haven, proposed out-fall, 
 
 42 
 
 Tidy, Dr., 85, 257 
 Tonkin, French troops in, 99 
 Towns, closeted, sewage of, 6 
 
 Residential, sewage of, 2 
 
 Turpentine proposed for use, 94 
 
 Urea, its presence transitory, 14 
 
 Vesle, River, 137 
 
 Visitors at sewage works, 169 
 
 Wanklyn, Prof. J. A., 127 
 
 Water, consumption of by closets, 
 
 32 
 Pure, does not occur in 
 
 nature, 85 
 
 Purification, Chinese 
 
 method, 99 
 
 Samples of, fraudulent, 169 
 
 Softening, Clark process, 81 
 
 Sparkling, 158 
 
 Supply, effect on sewage, 7 
 
 Waters, chemical analysis of, 157 
 Impure, why sometimes 
 
 harmless, 10 
 
 Dangerous externally, 16 
 
 Microscopic examination of 
 
 157 
 Way, T., on soils fit for irrigation, 
 
 263 
 Well-waters, 157 
 
 Zinc, salts of condemned, 102 
 
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