REESE LIBRARY OF THE UNIVERSITY OF CALIFORNIA. ,190 . Accession No. 82892- Class No. THE R. BAUMEISTER, PROFESSOR AT THE TECHNICAL INSTITUTE OF CAKLSRUHE. ADAPTED FROM THE GERMAN, WITH PERMISSION OF THE AUTHOR. J. M. GOODELL, C. E, SECOND EDITION, REVISED AND CORRECTED, TOGETHER WITH AN ADDITIONAL APPENDIX. NEW YORK : ENGINEERING NEWS PUBLISHING CO., Copyright, 1895. BY THE ENGINEERING NEWS PUBLISHING COMPANY. INTRODUCTORY. THE literature on sewerage and allied subjects is quite exten- sive. Even in America numerous publications have appeared, covering more or less thoroughly certain special systems or ques- tions which have arisen from time to time. Much of our litera- ture is in the form of reports or is contained in periodicals and in the proceedings of societies ; but no general and comprehensive treatise on sewerage has yet appeared in this country. The pub- lishers of the present volume have therefore done a good service in preparing for American readers a translation of Prof. BAU- MEISTER'S recent work. The author, whose name is already familiar to a number of American engineers, is well versed in the subject, though not a practising engineer. His object has been to present in a compact form the elementary principles which govern ail the essential parts of a design, and to confine himself to the usual practical questions, rather than to dilate on the more intricate problems which occasionally arise. His impartiality, characteristic thoroughness, and judicial temper have fitted him to present the subject-matter^ concerning which all controversy has not yet ceased, in a more balanced and scientific form than I have seen in any other book. We can therefore credit this work with the additional merit of tending to restrain any reader from plunging headlong into theories and practices which, both in Europe and America, are occasionally advocated by parties who fail to see all sides of the subject, or who are biased in the direction of their personal interests. In using this book for practical purposes, the American reader should realize that it was written primarily for German engineers, and for conditions prevalent in the German Empire. Although the collection, treatment, and disposal of sewage must accomplish the same object in every civilized community, we must remember i V IS TROD C/o 2 OR Y. the fact that social customs, domestic appliances, climate, and rainfall are in some respects different from what they are in our own country, which will modify some features of the works. The- data and recommendations which are suitable for Germany should therefore not necessarily be accepted and applied here without intelligent examination and scrutiny. I shall endeavor to point out below some cases where American conditions require a differ- ent practice. The first part of Prof. BAUMEISTER'S book here omitted concerns plans for the extension of cities, for pavements, and street railways. This omission is justified by the existence of publica- tions or these subjects which are well adapted to American wants. The second part forming the present volume concerns the de- sign and construction of sewerage works, the purification of sewage, street cleaning, and refuse removal. After stating the general principles governing grades, depth,, outlets, and alignments, the author, in Chapters 2 and 3, enters- upon the question of the quantities of sewage and rain-water to be- provided for. It is asserted that the German practice in design- ing water- works is to allow 40 galls, per head per day. In America the water consumption is much greater and also varies in different cities, reaching in some instances more than three times the- above amount. The character of the sewage, its chemical composition and dilu- tion will vary correspondingly. Likewise, the data concerning" rainfalls and the amount reaching sewers are not entirely suitable for American conditions. We have heavier downpours and they are more frequent than in Europe. The author, moreover, credit* us very truly with being " less willing to put up with the incon- venience of overflowed streets and cellars." When we apply the deductions of Prof. BAUMEISTER to works in America, we must therefore modify his figures and conclusions accordingly. The methods, however, according to which these data are to- be weighed and applied are well presented, and their description, thus furnishes information which is of course equally applicable to our own conditions. The chapter on the shape of sewers describes more completely than I believe is found in any single publication the characteris- tic forms for various conditions occurring in practice. The INTRODUCTORY. v chapter pertaining to the methods for the calculation of sizes embodies the latest and best formulas and convenient diagrams to facilitate the necessary computations. The details of construction, such as manholes, lampholes, junctions, overflows, siphons, and outlets, are quite fully treated and well illustrated, with a view to showing the proper variation in the designs for different conditions. These details are appli- cable and many will be equally serviceable in American practice. The remarks on relief outlets or storm water overflows are par- ticularly useful. The chapter on catch-basins and street- water inlets describes some devices which are not suitable for general use in this country. The great care given to the cleaning of sewers in Europe frequently permits the use 'of the more simple and direct inlets without either catch-basin or trap. In America such would, as a rule, be objectionable, though occasionally their use might be satisfactory. Flushing and ventilation are subjects which as yet have re- ceived insufficient attention in America, particularly in those of cur cities having combined systems of sewerage ; the many sug- gestions of Prof. BAUMEISTER will therefore be of special value. Begarding>the automatic flushing appliances, the American reader will observe several curious statements, some slight confusion of names, and the omission of some of our best appliances. The advantages and applicability of the separate system of sewerage are stated in a manner which plainly indicates the author's broad and impartial views. The chapter on cost is, again, one which cannot be applied to American conditions without caution and without a knowledge of the difference in prices and methods of working. It will be noticed that in many instances the cost is not far from, our own, sometimes exceeding what we think is an average price in this country. Any one who observes the practical operations of build- ing in both countries will, I think, find the explanation in the circumstance that, while the average American mechanic and la- borer are paid higher wages, their work is generally done with greater energy, and they are assisted by a greater number of labor- saving appliances. The second part of the work before us pertains to the purifi- cation of sewage. At the present day there is published prob- T i INTRODUCTORY. ably nowhere else, within the same short space here devoted to it, a more complete and rational account of this subject. The con- clusions, as far as they are given, may generally be followed un- der ordinary conditions prevailing in this country. The questions of pollution and self-purification of rivers receive due considera- tion. The chapters on chemical precipitation contain a good deal of matter with which American readers have not as yet been made familiar, particularly in regard to the smaller plants as used in Germany. The annual cost of precipitation ranges from 11 to 24 cts. per capita, but it is not safe to estimate on these figures in this country. The purification of sewage by aeration, filtration, and irriga- tion are each given a careful consideration. The information pertains more to results and cost than to methods and details of design ; but there are a number of suggestions regarding the lat- ter which will be found valuable. The volume closes with a part devoted to the questions of gen- eral municipal sanitation, street cleaning, garbage and excrement removal, and disinfection. While we might consider some of the contrivances mentioned as unsuitable here, the general recom- mendations are sound, and if faithfully followed would much im- prove the condition of our cities. RUDOLPH HEKING, March, 1891. CONTENTS. PAGE. INTRODUCTORY "i PART I. SEWERAGE. CHAPTER I. General Principles ' 1 CHAPTER II. Carrying or Waste Water CHAPTER III.-Rain Water 12 CHAPTER IV. Character of Waste and Rain Water and Sewage 20 CHAPTER V. Shape and Material of Sewers 23 CHAPTER VI. Calculation of Sewers 34 CHAPTER VII. Special Details of Construction 41 CHAPTER VIII. Catch-Basins i . 57 CHAPTER IX. Flushing . . . '. ( CHAPTER X. Ventilation 80 CHAPTER XL Effects of Subsoil Water J CHAPTER XII. The Separate System ! CHAPTER XIII. Cost of Work 106 PART II. THE PURIFICATION OF SEWAGE. CHAPTER I. Pollution of Rivers 112 CHAPTER II. Chemical Precipitation 123 CHAPTER III. Precipitating Tanks 127 CHAPTER IV. Results and Cost of Purification 142 CHAPTER V. Aeration 150 CHAPTER VI. Filtration 152 CHAPTER VII. Irrigation 158 CHAPTER VIII. Results and Cost of Irrigation 163 PART III. GENERAL MUNICIPAL AND DOMESTIC SANITATION. CHAPTER I. The Sanitary Problem 169 CHAPTER II.- -General Principles 173 CHAPTER III. The Use of Gutters 175 CHAPTER IV. Quantity and Character of Refuse 177 CHAPTER V. Implements for Street Cleaning 181 CHAPTER VI. Removal of the Rubbish 184 CHAPTER VII. Miscellaneous Regulations Concerning Streets 190 CHAPTER VIII. Quantity and Characteristics of Excrement . . 196 CHAPTER IX. Removal of Excrement 198 CHAPTER X. Removal through Pneumatic Tubes 209 CHAPTER XL Financial Considerations 214 HAPTER XII. Special Treatment of Excremental Matter 218 CHAPTER XIII. Separation of Excremental Matter 221 CHAPTER XIV. Disinfection . . 224 AMERICAN PRACTICE IN STREET CLEANING AND SEWERAGE 232 APPENDIX. Diagrams of Hydraulic Formulas 275 APPENDIX to Revised Edi r ion 279 INDEX . 289 PART L-SEWERAGE, CHAPTER I. GENERAL PRINCIPLES. On account of the great diversity in local surroundings, it is impossible to give fixed rules to be followed in designing sewers, but only a statement of the general principles underlying all such work. These principles and the details of construction are essen- tially independent of the character of the sewage and the system of sewerage designed to remove it. We may take as a type the complete water-carriage or combined plan. 1. Grade of Sewers. It is usual to assume, as a result of Eng- lish investigation, that a velocity of the water of from 2 to 2.6 ft. per second is sufficient to carry off all solid matter which may enter the sewers. In smaller lines, where the current is often checked, from 3.3 to 3.9 ft. per second may be necessary. Since the velocity varies with the depth of water, the question arises as to what quantity of water is to be specified in determining the minimum velocity a question which is rarely clearly stated or answered. Of course the maximum amount of water (rain and carrying) must be able to pass at that rate, also the maximum flpw of carrying water per hour in dry weather and, if possible, the average hourly flow, should have this velocity in' order that the solids may be kept in suspension. By carrying water is meant that part of the water supply which reaches the sewerage system after employment for various domestic purposes. It is easier, as a rule, to prevent a deposit in sewers by maintaining a reason- able velocity than to flush out such matter after it has settled. Practical experiments show that sewers of the usual sections will remain clean with the following minimum grades : Separate house connections, 2 per cent. ; extreme cases, 1 per cent. See note, page 279. 2 GRADE OF SEWERS. Small street sewers, 1 per cent.; extreme cases, 0.7 per cent. Main sewers, 0.7 percent.; extreme cases, 0.5 per cent. The extreme cases are for sewers carrying only rain or quite pure water. The following empirical formula will give the minimum grade for a sewer of a clear diameter equal to d inches, and either cir- cular or oval in section. 100 Minimum grade, in per cent. = 5 d + 50 In Wiesbaden, the least grade was calculated on theassumpcioii that with 0.8 ins. depth of water, the velocity would be 1.83 ft. per second. KXAUFF advocates a velocity of 2.3 ft. per second in house connections running with a depth of water equal to one- fourth their diameter. This would correspond to a velocity of 3.28 ft. when the pipes are full. Where it is impossible from local or financial causes to main- tarn clean sewers by giving them a proper grade, flushing or mechanical cleaning becomes necessary. But flushing tanks are desirable and usual in systems with grades above the minimum, since their use renders the removal of deposits fairly certain. Experience shows that sewers cleaned in this way always have better air than others, even when the latter are self-cleansing. As the lowest limit of grades which can be flushed, 0.1 to 0.2 percent, may be assumed for sewers which are sometimes dry, while 0.03 per cent, is allowable for the trunk sewers in cities like London, Hamburg, Mannheim, Dusseldorf, and Brussels. Exceptions to these rules can always be made in places on the sea-coast or tidal rivers, such as Westham and Hamburg, where the flow is main- tained by gates opened and closed at the proper stages of the tide or by other means. Although the slope " should preferably be steep, in order to economize in material and cost, yet there are maximum limits beyond which the velocities generated would cause the water to wear away the sewers or would carry off the water so quickly that the solid matter would partly remain. The water should not flow away too fast, as the early formation of a tolerably constant cur- rent in the entire system would thus be prevented. The sewers should be dry as rarely as possible. On this account it is not usual to exceed a velocity of 5.9 ft. in England ; the street sewers GENERAL PRINCIPLES. 3 '9. - of Berlin have a maximum grade of 2.0 per cent., in Lubeck of 4 per cent. In steep streets in Stuttgart and Mainz grades of 8 per cent, still occur, and in necessary cases almost perpendicular descents of a few feet are made. The maximum grade of house connections is fixed at 5 per cent, in many places, but it would seem better to specify a uniform grade in the pipes and thus avoid the use of knees, as these drains run dry under all circumstances. Since any checking of the current causes a deposit of the sus- pended solids, it is desirable to maintain the same velocity throughout the entire sewerage system, especially with low water in the pipes. Hence the grades in sewers of the same class should be everywhere equal. For the same purpose, lines which carry but little water should receive more of a slope than the others of similar sections. The grades of the entire net-work should be de- termined in this way, provided the points mentioned in the next section do not modify the plan. 2. Setver Depth below Street Surface. Economical con- struction calls for sewers as near the surface of the streets as pos- sible. The least depth is determined by the position of the house connections and by the frost line, which is never less than 4ft. be- low the surface. Moreover, it is desirable to have the sewers so low that the bottom of the cellars can be drained and the water in the soil curried off. For this purpose, from 10 to 13 ft. can be assumed as a minimum depth, while 7 to 10 are sufficient when cellar drainage is neglected. The usualdepth of sewers in Frankfurt varies from 13 to 20 ft.; the average is 17 ft. In city extensions, it is often necessary to decide between raising a street level or lowering a sewer, and a further complication occurs when it is necessary to form connections with a flushing reservoir at a fixed elevation. When the street grade is often changed, a fixed position of the sewer, relatively to the road bed, cannot be maintained ; some- times a d^pth of over 30 ft. occurs and tunneling is necessary in construction. In very steep streets, the sewers are laid like a flight of steps, with a shaft at every step, down which the sewage falls. The large trunk sewers are constructed with little refer- ence to the lay of the land, since they receive tributary lines at but few points. At Paris and Hamburg large tunnels have been driven for these sewers, but it is sometimes possible to avoid the cost of such works by using siphons on a large scale. 4 OUTLETS. 3. Outlets. The ocean, lakes, rivers, canals and moats have all been used as receivers of sewage. It is often very important to determine if the sewers can lawfully discharge their contents in the intended manner ; it sometimes happens that only storm sewers or the drains from good chemical, irrigation or nitration plants are allowed to empty into rivers or canals. Small brooks, industrial canals and similar streams often receive sewage and become drains of the worst character. In order to clean and adapt them for carrying such matter, they should be turned into trunk sewers, provided their position allows of this and their occasional open stretches are few and short, as in Karlsruhe, Vienna, Worms and Essen. When this is not possible, it is the duty of the authori- ties to block up all the places at which the offensive matter enters and parallel the canal or brook with a trunk sewer to receive the sewage, 'as has been extensively done in Brussels, Stuttgart, Wiesbaden, Basle and Vienna. The same measures apply to ditches and navigable basins that are used in many towns as dumping- places for all kinds of refuse. Sometimes a canal can be closed at both ends of the part used for traffic and the sewage carried under or around it by a special sewer, as is done in Hamburg. Where, however, canals must be used for traffic and as receptacles for sewage, adequate means for diluting the latter must be pro- vided. In Amsterdam there are facilities for adding to the canals each day an amount equal to their own volume of water, arid at the Hague an amount equal to half the contents can be supplied. In general, the outlets of a sewerage system should be placed so high that the effluent can escape at all stages of the water into which it flows. This does not exclude a quick fall in the outlet sewers, for the purpose of keeping the mouths of the drains generallv or alwavs un- Fio. 1 OUTLET AT MUNICH. der water and out of sight. The last sections thus remain continually full of water, which does not, however, interfere with their working. The out- let in Munich is arranged as shown in Fig. 1. The main sewer empties above the low water level, but a smaller iron pipe leads down to a point always submerged. In this way, the foul parts of the sewage are always discharged below the surface of the GENERAL PRINCIPLES. 5 river, while the rain water, which is of large volume, is some- times seen during low water to flow from the mouth of the trunk sewer. Rivers which carry much sediment and have shifting beds must be carefully examined before locating the outlets, or the lat- ter may become stopped with sand. Where the sewage is discharged below the high water level and the sewer grades are very flat, the outlets must be closed part oi the time. In Dresden- Altstadt there are 15, in Crefeld 16, in Co- logne (proposed plan) 20 days in the year when more or less set- ting back of the sewage occurs in the sewers, as is the case at every flood tide in Hamburg, Bremerhafen, Emden and also many English towns on the coast. In such cases, the water from the re- ceiving basins, rivers or sea either enters the sewers, or the out- lets are closed and the sewage retained in the system, which thug becomes a sort of a reservoir and must be designed accordingly. At Hamburg, the sewage is discharged into canals while the outlets are closed, and at Emden large reservoirs, containing 8 days' ef- fluent, have been formed by earth dams. .See note, page 279. Where high' water lasts during the greater part of the time, or where the sewage must be raised for irrigating or other purposes, recourse must be had to pumps. When these are not continually in use, they are an expensive investment and it is wise, in making the first designs, to see if the most economical expenditure of the capital at hand would not be attained by a general raising of the streets and sewers. The economical working of the pumps can be sometimes increased by building receiving basins to hold the large quantities of water that occasionally are discharged. In London, masonry reservoirs with flushing appliances are used for this purpose, while in Mannheim large ditches are employed. 4. Relief Outlets. In many cities there are opportunities foi building relief outlets, openings in the sewers at a certain height through which the sewage can escape when rain has increased the depth of the contents so that their level is above the bottom of these outlets. The section (wetted perimeter) of the sewers below these outlets need not be so great as would be the case without them, and every outlet diminishes the expense of construction. When the rain water begins to enter the system at a number of points, the carrying water will be diluted and dis- charged more rapidly. Since the reliefs first act when it has rained for some time and the street refuse has been swept away, 6 CLASSIFICATION OF SEWERAGE SYSTEMS. the discharge from these side outlets is fairly pure water, which may be allowed to run off in small pipes. The height of the out- lets is determined by the degree of dilution which the sewage shall have before being discharged. The effluent from these openings may be carried off through old sewers or in any suitable manner. It is generally better to distribute a considerable num- ber of them over the whole sewerage system rather than concen- trate a few in a limited district, since the action of the sewers is more uniform, and the river, or other receptacle of the overflow, does not receive a large mass of water at a single point. There- fore the old sewers and brooks should be utilized whenever possible, and the construction of new drains to the more remote districts never be omitted when they may be of advantage. 5. Systems of Sewers. Five different methods of dividing a town into collecting districts and laying out the main sewers can be recognized. (a) Perpendicular System. Where a city is divided by a water- course of some kind, or is bounded on one side by such a body, it is usual to divide the area into a number of districts with entirely distinct systems. Each district has its trunk sewer and branches, and is approximately at right angles to the body into which its sewage flows. Halle, Salzburg, Vienna, Ulm, Eostock, Bern, and Saegedin are arranged in this way. The advantages are due to the short length and small section of the sewers. The disadvan- tages are a possible overflow in the lower parts of 'the city due to heavy discharges, in rainy seasons in the upper districts, and the pollution of the river, or other body, within the city limits. These evils are avoided in the (b) Intercepting System. Intercepting sewers are run along the banks of the river and receive the sewage of the several dis- tricts, discharging it below the city or on suitable filtration beds. This plan is sometimes adopted after the disadvantages of a have been felt, as at Brighton, Dresden, Kassel, and Strassburg. The first system may be so designed that it can be easily changed into this when necessary, and the small deposits that may occur in the river at first can be removed by dredging. An intercepting sewer is usually expensive on account of its large size ; moreover, it is so low that relief outlets are sometimes impossible. On the other hand, when pumps are necessary, this system enables them to be concentrated at a single station. In Pest, where the first system GENERAL PRINCIPLES. 7 with 6 separate steam pumping stations was formerly used, this plan was adopted, and the pumps all concentrated in a single station, operated by water power. (c) Fan System. 1\\ this plan, from a single main outlet a number of radiating trunk sewers lead off in different directions and thus, through their branches, drain the whole city. One of the districts, that comprising the center of the city, is usually much larger than the others. Karlsruhe, Wiesbaden, Emden, Breslau, Dortmund, Bremen, and Brussels offer examples of this plan. (d) Zone System. In this construction, the district to be drained is divided by con tour, planes ; the zones usually have separate receiving sewers and are connected for flushing purposes only. The advantages are due to the diminished difficulties at the outlets (in pumping, closing gates, etc.), the lack of large quantities of water in the lower parts of the city, and the small section that may be given the receiving sewers if a modification of the intercepting system is used. It is also advantageous at times to have a number of filtration beds, and this plan enables them to be easily located at different heights. The fan system is usually employed in the different zones, although the intercepting system often offers some advantages. Frankfurt, Mainz, Dussel- dorf, Stuttgart, Heidelberg, Paris, Munich, and London are types. (e) Radial System. In this system, the city is divided into a number of sectors and each of these drained from the center outward. A number of filtration beds with the necessary pumps are often located around the city. The great advantage of the plan lies in the fact that the small sewers are in the center of the city and the sections grow in size as the distance from this center is increased. In this way, the lines already laid are fairly certain to remain the proper size for some time. In the intercepting and fan systems, the trunk sewers are designed for an assumed popu- lation which may be exceeded and new and expensive lines made necessary; moreover, the growth of the city is continually adding to the number of small sewers on the outskirts, and the sewage thus added must be provided for by the old lines, which were de- signed without reference to any possible annexed territory in the future. The greater the city, the more advantageous does this radial plan become. Berlin is an excellent type. Of course, there are many combinations of these systems that 8 BRANCHES. can be made ; the sewer nets of Hamburg, Liverpool and Cologne offer interesting examples of this. 6. Branches. Each street sewer and its house connections forms a miniature system and should be carefully planned. It may be generally assumed that for each drop of water to be car- ried off there is one shortest path by which it can go. The pres- ence of steep grades, however, often makes the use of winding drains necessary in order that a sudden change of velocity where the drain and sewer join may not cause a deposit of solid matter. Great care is necessary in designing the flushing system. In flat districts, the flushing water must be furnished through pipes relatively high as compared with the sewers. When a line with a flat grade is joined by others which are steeper, the latter may be utilized as flushing drains for the former by giving proper bends to the connections. In general, the question of a system of complicated sewers is not solved by laying a number of equally important lines, but by leading the drains to a common center. It is cheaper to build a single system of n x capacity than n systems of x capacity. But it is sometimes more economical to lay a main sewer of a size only sufficient for present needs, and afterward lay a parallel line when greater sections are necessary. Dead ends are to be avoided; two parallel sewers should be con- nected at their ends, and in such a manner that the contents of one will flush the other. Moreover, the ventilation is much superior if the system is a continuous one. In some cities, Ber- lin, Dusseldorf, Mannheim, Pest, Innsbruck, Paris, two sewers, one on each side of the street, are used instead of a single one in the center. This plui reduces the length of the house connec- tions and betters their grades. The cost of the system is much greater than with a single sewer, however, and it is more difficult to keep them clean. CHAPTEE II. CARRYING OR WASTE WATER. From tables prepared by GRAHN and THIEM, it is certain that the consumption of water in German cities has an average daily value for the year of from 4 to 58 galls, a person, generally from 6.6 to 37 galls. Household purposes do not call for more than 10.5 to 12 galls. The larger figures that are sometimes found, especially in America, are due to wasteful habits. The presence or absence of water-closets makes no essential difference. Their future use should be provided for, however, in the pro- visions for flushing and cleaning the sewers. In designing water- works, the present German practice is to allow 40 galls, per day per person ; in England 28 Imperial, or 34 United States galls, are taken as a basis in designing water-carriage sewer systems. In manufacturing districts, special provisions must be sometimes made for carrying off exceptionally large volumes.* The radial system used in Berlin offers special advantanges for the determination of the difference in water consumption among different classes of people. The sewage pumped from a thickly populated, but poor district, averaged, according to the 1887-88 report of the Commissioners, 21.1 galls, per day per cap- ita ; in districts with a larger street surface and somewhat higher class of residents, 26.4 galls. ; in manufacturing districts, 37 galls. ; in the most fashionable districts, 44.9 galls. The average con- sumption of all the districts was a little over 26 galls. The city water-works supply 16.9 galls, daily to each person, and private sources add some 13.2 more, making a total average supply of 30.1. This amount is in excess 01 the sewage pumped away from the city, and shows conclusively that in designing the sewers for large areas it is not necessary to regard the entire water supply as flowing away through the system. The difference between the supply and effluent is probably due to the quantities used in sprinkling, cleaning and such operations, which result in con- siderable water soaking into the ground. The sewers must be able to dispose of the maximum quanti- ties furnished by a fluctuating source of supply. On the days of greatest consumption, the averages given above will be 1| times 10 FLUCTUATION OF WASTE WATER as large. Moreover, the hour-maximum in the day varies from 1 J to If, average 1, times the hourly mean. Hence the capacity of a sewer must be designed to remove hourly H x ij ^ 24 " """ of the average daily quantity or about twice the amount calcu- lated on the supposition that the same quantity of sewage was supplied each hour of the year. In the ffandbuch des Wasser- baues by FRANZIUS and SONNE, the daily maximum is fixed at 1, and the hourly at If, making the relation between the latter and the daily average 1J x If 24 - L = TT approx. American engineers assume the daily maximum as 1, and the hourly as 1, making the relation between the latter and the daily average. Another method of investigation is based directly on the aver- age daily sewage, since it does not necessarily follow that the maximum daily effluent will be coincident with heavy rains. On this supposition it is usually assumed that half the discharge takes places in from 4 to 9 hours of the morning. This gives a maximum hourly flow of from to -fa of the average daily amount, and the mean is again about -fy. In order to apply these results to the system of any place it is necessary to know the density of the population. In German cities this varies from 49 to 202 persons per acre, but in single districts it is sometimes still greater. In American sewerage de- sign it is customary to calculate on from 30 to 60 per acre, but in some places these figures are exceeded. The future popula- tion must be estimated by a careful study of local surround- ings, and is usually taken at from 10 to 50 per cent, larger than the present. Or the greatest density in any one district can be assumed as the future density in all. In this way the maximum number of people per acre in great cities may probably be fixed at 325. In designing trunk sewers, provision must also be made for the annexation of new districts to the present city limits, pro- vided that the cost of such an enlarged sewer is not greater than that of a subsequent parallel one. CARRYING OR WASTE WATER. 11 From such data the proper capacity of a sewer can be calcu- lated for disposing of the necessary number of cubic feet per acre per second, the usual compound unit used in such computations. As an aid in beginning such a calculation, the following table of the estimates used in designing a number of systems, some not yet completed, is given. Where it was possible to obtain the numbers for the sewerage estimates of the separate districts, these have been given. The numbers for entire cities give the average density of population over the entire area and are used for the outlet trunk sewer de- signs. The density of single wards and the capacity of single sewers may be far different. Where no figures have been given for future densities, it is assumed that the increase in population will be in districts at present thinly populated. TABLE I. ESTIMATES OF THE AMOUNT OF CARRYING WATER. CITY. Mode of estimating. Gallons a day per capita. Hour max. Inhabitants per acre. Cu. ft. an acre a second. Present. Future. Berlin... Average population Suburbs 33.5 33.5 33.5 32.8 26.1 f 23 8 \23.8 33 33 33.5 33.5 21.1 39.6 37 37 37 39.6 39.6 37 42.3 26.4 39.6 23 8 41.7 Vl8 i YM 1 Vl8 i 1 Vs Vn #: Vie Vs 6 f 81- t 202 324 162 270 101 214 146 0.022 0.011 0.019 0.008 0.006- 0.012 012 008 Oil 0.003 0.028 0.012 0.006 0.010 008 0.019 0.012 0.029 031 OJ05- 0.020 0.015 0.006 0.004- 0.039 0.012 0.016 0.009 0.006 0.002 o.oio 0.012 Berlin Berlin Breslau Chemnitz ... Danzig. . Average of five sectors. Separate districts Separate districts 137 j 101 1 202 194 73 135 28 243 f 61- 1 101 81 Right bank ) *? <. i Danzig Dortmund . . . Dortmund. Dusseldorf. . Dusseldorf . . Emden Frankfurt... Hamburg Cologne Cologne Koenigsberg . Karlsruhe. .. London Mannheim . . . Mannheim... Munich Nuremburg.. Pest Wiesbaden.. Wiesbaden... Wiesbaden. . Vienna Witten Left bank } of Vistula. Inner town Entire city Old city 38 405 162 Other parts Separate districts Entire city 81 101 Suburbs Old city 162 101 222 / 32- 1 162 j 40- 1 174 121 New citv Entire city 307 162 ...X Separate districts Separate districts Isner city 162 J 109 32 283 219 202 162 101 30 Neckar suburb Separate districts / 22 \ 190 Separate districts Separate districts Thickly peopled districts Thinly peopled districts. Suburban districts Separate districts 26.4 26 4 26.4 v" $ Separate districts 31.7 Via 67 121 CHAPTER III. RAIN WATER. In designing water-works, it is necessary to know the maximum precipitation for one day, one month and one year, and especially the average fall during continued storms. These data, however, are only useful in sewerage design in determining the dimensions of the outlet basins, when such are used. At Emden, for example, the basins are calculated to hold J- of the maximum monthly rain- fall plus of the amount of waste water flowing in a month. Moreover, the design of sewers depends somewhat for its data upon the short heav;y storms over a small area which result in .large quantities of water quickly finding their way into the catch basins. It is not sufficient to know the rainfall per hour ; the severity of a storm often reaches a maximum during from 10 to 20 minutes only, and this maximum should be determined if possi- ble. The following record, made during a long storm at Zurich,, on June 3, 1878, illustrates this point : Average precipitation, 11 hrs 0.37 cu. ft. per sec. per acre. Maximum 30 min 2.04 " " 10 " 3.03 Exact observations of these phenomena require self-registering instruments, and are therefore very scarce. The subjoined table gives a number of measurements in different cities and shows the great precipitation that must be provided for. The compound unit adopted, cubic feet per second per acre, is better adapted to engineering purposes than the usual meteorological one of cubic inches per hour per square inch. The lack of careful measurements in the past renders it a matter of some doubt as to how high the maximum rainfall must be assumed. Wherever the maximum of a city is considerably below that of places similarly situated as regards meteorological conditions, it is safe to assume that the maximum registered in the past will be exceeded in the future, especially if the region is liable to cloud-bursts. The influence of neighboring mount- ains is evident from the table. HELLMANN recommends from 2.43 to 2.86 cu. ft. per second per acre for the level plains of RAIN WATER. 13 Germany, while in the Alpine regions, nu'merous cases of over 4.28 cu. ft. have been observed. TABLE II. MAXIMUM INTENSITY OF RAINFALL. PLACE. Time. Duration, minutes. Cu. ft., per sec. per acre. Authority. Albany July 10 1876 10 7.32 Weather Rev Annaberg Berlin* ... Sept. 10, 1867 . , Oct 6, 1883 15 15 3.81 2 63 } Hellmann. Meteorological Berlin* May 15 1889 20 2 69 j Society Bern June 19 1877 45 3.49 Blirkli Boston July 20, 1880 12 4 30 Eng. News. Budapest* June 26 1875 60 2.61 Biirkli -Chemnitz T June 3. 1886 . 15 4.37 Deutsch. Bauz "Czernowitz Aug 21 1869 20 3.37 Dresden June 17 1885 12 4 17 Deutscb. Bauz 'Galveston . ... June 4, 1871 ! 14 16.9U Weather Rev Giitersloh July 29, 1838 7 4.87 Hellmann. TCsvrlsrnhp* June 29. 1885 . . . 60 3.89 Kassel May 21 1872 30 2 70 Kiel Oct. 3, 1879 20 2.81 Hellmann Klausthal July 21, 1864. .. 25 3.43 Hellmann. Kcenigsberg London* June 16,1864.... Aug. 1, 1846 Sept 8 1873 45 60 36 2.90 3.96 514 Wiebe. Biirkli. Blirkli Mannheim . July 21 1888 20 2.61 Munich Aug. 12, 1873 30 4.04 Gordon. Paris ... Spot. 20 1837 20 4.89 Burkli, Philadelphia July 26, 1887. 7 5.31 Weather Rev. Posen.. June 26 1863 20 2 86 Hellmann Providence* Rochester. . . Aug. 6,1878 June 24 1888 36 20 5.83 2.60 Shedd. Kuichling St Gallen June 25 1888 20 5 00 Schw Bauz St. Louis Stuttgart* Trier Aug. 15,1848.... July 23, 1883 June 17 1856 75 3 60 4.04 5.93 2.90 Weather Rev. Dobel. Hellmann ^Washington July 29 1877 28 309 Wermsdorf May 9 1867 15 4.99 Hellmann Zurich Sept. 9, 1876 10 5.04 Burkli. t Doubtful. It is not absolutely essential to determine these extreme cases of rainfall, since sewer sections are usually proportioned without regard to them ; in fact, sewers corresponding to these quantities would be expensive, and the difficulties of keeping them in good condition would be great. On the other hand, too small sections result in a backing up of the water in the streets and catch - basins. In some respects this would be advantageous (the veloc- ity on the surface of the water is greater than at the bottom, and lience a full sewer will discharge quicker than under other condi- tions), but the pressure against the walls will be so great that there is a constant danger of rupture. The sanitary effects of full sewers are very bad; the ground becomes wet and the sewage backs up in the house drains. Although this condition of affairs is usually of short duration, in those storms noted in the foregoing table by an asterisk the overflow proved highly deleterious, both 14 RAINFALL DIAGRAMS. to health and comfort. Neglect to provide drains large enough to carry off the usual rains results in a decline in the value of the land in question, and causes the tenants in the neighborhood to- move. On this account, BURKLI recommends for Swiss cities, a sewer capacity corresponding to a fall of from 1.79 to 2.86 cu. ft. per second per acre. In Germany, from 1 to 2.14 cu. ft. would probably be a fair allowance. English and American engineers usually assume 1 cu. ft,, although in America heavier rainfalls occur in periods ranging from 1 to 4 years. It is probable that the practice in the United States will tend toward a larger figure, as the people become less willing to put up with the inconvenience of overflowed streets and cellars. Wherever records of the rainfall have been kept in a scien- tific manner, it is very easy to come to a decision regarding the capacity necessary to carry away the storm water. In such a case the records should be examined, and all notes of precipitations exceeding, say 0.70 cu. ft., plotted to scale, using the duration in minutes of the maximum fall as an abscissa and the fall itself as an ordinate.* In this way a collection of points is formed, the upper limit of which gives the relation between maximum rate of precipi- tation and its duration for the place in question. Prof. NIPHER found that this upper boundary for St. Louis was an hyperbola. KUICHLING found that in Eochester the locus was formed by two in- tersecting straight lines, the one at the left of the diagram being much inclined, the other less so. Such results are of doubtful value unless the observations are very numerous. The best plan is ta draw a horizontal line between the mass of the points and those more scattered, and take this line as the basis of calculation. The rain water is disposed of in three ways: part evaporates, part percolates through the soil, .and part flows away over the surface. For sewerage purposes, it is very desirable to know the relation between the first two and the last, but data are usually wanting on this point. In order to determine the amount of water reaching the sewers it is necessary to have self-registering rain gauges and water-meters of some kind in the drains. The apparatus should be distributed over the city so that the amount of discharge from each district can be determined. The first scientific work of this sort was probably done by KUICHLING, at * The fall itself may be used if stated as cu. ft. per sec. per acre, otherwise the rate or fall as inches per hour should be used. A rate of 1 inch per hour corresponds to very nearly 1 cu. ft. per sec. per acre. RAIN WATER. 15 Rochester, N. Y. At other places the estimates are to be re- garded as of a more or less approximate nature. The conditions influencing the division of the rainfall into the above-mentioned three parts are as follows : a. The amount of moisture in the air and ground. If at the beginning of a storm the air and ground are already saturated from previous rains, the amount of evaporation and absorp- tion will be small while the surface discharge will be large. The same holds true for continued rains ; the percentage of surface water compared with the total fall will gradually increase for some time. The sand and gravel walks in gardens and parks illustrate this point, since these materials absorb the water rapidly at first, but soon become thoroughly soaked. b. The relation between the impervious area (roofs, paved: streets and courts) and the more porous surfaces (gardens and parks). For drainage purposes, the ratio of the storm sewage to the total precipitation can be assumed as the same as that existing be- tween the impervious and the total area. In this connection it is of interest to note that KUICHLI^G has demonstrated that the per- centage of precipitation reaching the sewers is a constant with all variations of rainfall. c. Size and slope of the area under consideration. The greater the area and the more level its surface, the greater will be the time necessary for the rain to reach the sewers, and the greater the opportunities for evaporation and absorption. Hence the per- centage of water reaching the sewers will gradually increase during protracted storms until the farthest areas begin to discharge their precipitations into the system. If the rain is of short duration, such as those given above, it is probable that the storm will cease before the outer districts begin to discharge, unless the total area is small. In large districts it is usually true that the flow in sewers first begins to increase with any rapidity when the storm has begun to abate in intensity. Numerical data concerning the amount of water conducted away in drains are as follows : In England from to 70 per cent, of the fall reaches the drains, averaging about 50. In different districts of London from 53 to 94 per cent, has been registered. It required from 3 to 4 times the duration of the rain to carry off the water, and the maximum flow per second in the sewers rose as high as 2.4 times the average obtained by dividing the total effluent due 16 VOLUME OF STORM SEWAGE. to the storms by the number of seconds of flowing. Hence it will 05x24 be seen that the necessary capacity will be ' ' = 1 of the o. rainfall per second. In general, it is customary to assume the greatest quantity of storm water at ^ to ^ of the total fall, according to the nature and extent of the area drained and its configuration. BURKLI fixes the greatest necessary capacity at 0.86 cu. ft. per second per acre, but this is a mere approximation, obtained by using but one coefficient for the conditions expressed under a, b and c above. In more exact calculations, although it is difficult to obtain a sat- isfactory reducing factor for a, a coefficient should be given for b and c, so that the form of the equation for the maximum flow becomes A = xy R F where A is the quantity of effluent, R the precipitation per acre, both in cubic feet per second, F the drainage area, in acres, x a coefficient expressing the ratio discussed in b, and y a coefficient discussed under c. As regards x, it is simply the ratio of impervious surfaces to the whole area. When this is difficult to determine, especially in districts not yet developed, various expedients are adopted. This ratio is from 0.25 to 0.5 in villages, from 0.5 to 0.7 in towns and 0.7 to 1 in cities. The means of these sets of values, 0.4, 0.6, and 0.8, are probably accurate enough in designing sections for future as well as present conditions. But it is to be noticed that the use of a single coefficient for a whole city would make many sewers unnecessarily large and expensive. For American conditions, KUICHLING gives the following re- lations for heavy and impervious ground, in places having a vari- able density of population : Population per Population per Heavy Impervious acre. sq mile. ground. ground. 2* 16,001) 21.5 percent. 25 per cent. 32 20,700 250 " " 33 " " 40 25,600 27.5 " 43 " 50 32,000 28.0 " " 55 " " The sand and gravel walks are assumed to be semi-heavy, while roofs and paving is regarded as impervious. Only the last column of figures is of use in determining x. RAIN WATER. 17 A number of different plans have been proposed for deter- mining the value of ?/.* The three leading German formulas are graphically given in Fig. 2, which represents the curves /.Ot C6\ Gt 0.1 O2\ Drainabi At res SOO 200 300 40O 500 6OO 700 FIG. 2 -DIAGRAM SHOWING VALUES OF THE COEFFICIENT OF RETARDATION. of BURKLI, MANK and BRIX for determining the coefficient y with approximate accuracy at a glance. According to KNAUFF, the maximum quantity of storm efflu- ent from impervious surfaces is from 40 to 80 per cent, of the rainfall ; from 50 to 70 per cent, in courts and squares, from 40 to 50 per cent, on flat, and 60 to 80 per cent, on steep roofs. In general, these figures must be regarded as rather low for small areas, since the point of saturation is soon reached. The following table gives the figures used in calculating the sewerage systems of a number of European cities. 1 1t will be no- ticed that a distinction is drawn between sewers without or above relief outlets and those in which such openings occur. The differ- ence between these sets of figures gives the capacity of the out- lets. * The remainder of this chapter is considerably condensed from the original German text, to which the reader is referred for a more complete discussion of the subject. See page 280 et seq. 2 18 ESTIMATES OF STORM SEWAGE IN EUROPE. TABLE III. ESTIMATED RAINFALL AND EFFLUENT IN EUROPEAN CITIES. CUBIC FEET PER SECOND PER ACRE CITY. Mode of esti- mating. Above outlets. Effluenc. Below outlets. Rain fall. Coefficient. Rain fall. Coefficient Effluent. Berlin Average pop- ulation Districts with parks Average of 5 districts 0.91 0.91 ^ 1-6 0.30 0.15 0.28 0.41 0.09 0.04 Brunswick. . . Breslau Chemnitz Danzig. 0.039* H 0.015* Outlying dis- tricts.... 0.83 0.26 0.13 1 lateral sewers Main Outlet Varies with population and surface inclination.. Thickly inhab- ited districts Thinly inhab- ited districts Small sewers.. Average " Outlet Average 0.021* ( 0.029 \ 050 0.011* 0.007* 1.00 0.51 0.51 0.36 0.36 0.36 1.61 Mank's curve. X f 0.2t \ 0.71 0.26 0.17 0.24 0.18 0.12 0.54 0.27 0.021* 0.021* ^ H Dortmund.... Dusseldorf ... Enid en 0.048 ^ 0.024 0.012 Flood area (roof drain - Railway sta- 14 jateral sewers Uain Hany cities. .. Varies with siz 0.91 M 0.30 England Frankfurt.. . Freiburg Hamburg 0.040 1.00 i* 0.50 o 17 Slopes & pop. In tercepting sewers 0.43 0.040 Thickly peo pled distr's.. Thinly peopled districts New designs. . 0.57-0 71 0.29 2.57 1.11 51 1.00 1.00 1.00 1.00 2.90 Mank's curve. ^ 35 about H 4-5 about ^ yXl.54 055 0.26 060 0.36 0.80 0.49 0.73 79 0.040 % 0.027 Karlsruhe Cologne Main sewers, old city Main sewers, new city Lateral sewers old city 0.040 0.040 Koenigsberg . Linz Lateral sewers new city Main sewers.. 0.514 V* 0.129 London Varies with size and den- sity of popu- lation 1.00 0.87 1.59 1.79 1.79 1.79 : Burkli's curve. 0.330.50 0.29 0.79 V X 1.2 y X 0.9 y X 0.6 Mainz Mannheim .. Center of city Suburbs Very open suburbs RAIN WATER. TABLE III. CONTINUED. CITY. Mode of esti- mating. Above outlets. 4* Below outlets. Rain fall. Coefficient. '^ 1 Coefficient Effluent. Munich Suburbs Trunk sewers. Varies with size of dist.. . Trunk sewers. Trunk sewers. 0.64 0.64 0.51 1.79 1.00 0.51 15-^ about Jjj * 15-0.3 K 0.130.32 0.21 0.17-0.25 0.60 0.16- 0.3 0.26 0.170 24 Nuremburg Paris 05-O.Ht Pest Stettin Stuttgart .... Yienna Wiesbaden. . . Main sewers.. Trunk Single sewers, old system.. Trunk sewers, new system.. Cultiva'd land Dense popula- tion Thin popula- tion 0.179 0.27 0.049 1.00 0.78 0.78 1.39 1 39 % & Brix's curve. , 0.38 0.26 0.13 y X 1.04 I/ X 0.77 y XO 51 0.040 0.037 0.023 0.009 Suburbs . 1.39 .... NOTE. These figures were used in designing the several systems noted, and must not be taken as giving the actual rainfall or effluent. The figures marked with an asterisk were used in calculating the pumping plant. of [A complete translation of what Prof. Baumeister has to say on the subject run-off " will be found in the appendix. ED. ] CHAPTER IV. CHARACTER OF WASTE AND RAIN WATER AND SEWAGE. The waste water is in part pure, such portions as are sup- plied from baths, wells, boilers, etc., and .in part polluted with sand,* soap, kitchen refuse, and the waste products of manufact- uring establishments. Rain water which falls after a period of dry weather washes more or less matter from the streets into the sewers, and the amount of impurities depends largely on the manner of cleaning 'the roads and highways, and the extent of the traffic. That such impurities are quite considerable is at once evident to the senses when an old sewer is being cleaned. Careful and extended researches by EMMERICH show that even the waste water from sinks and that used in cleaning floors or sprinkling streets, will become poisonous if allowed to stand for some days. Examinations of waste and rain water as it flows into the sewers are of little value on account of the great variations in its character. As an extreme case, Parisian sewers are interesting ; it has been found that at the beginning of a heavy rain or a thorough street cleaning the water in the gutters had a much higher quantity of organic matter suspended and dissolved in it than the sewage. Analyses of sewage from different cities in which the relative proportions of excrement, waste and rain water vary con- siderably, are of much greater interest, since a comparison of the data will give the influence of each component. But the propor- tions in which the different parts of the sewage are added are known in but few cities ; especially lacking are data concerning the disposal of excrement. The following table is very instructive on account of its accuracy in this respect. The figures in the first column give the proportion of excre- ment which passes into the sewers. In London, Berlin and Danzig nearly all the matter is so carried away, about 70 per > i I o 231.5 246.9 'ios!' 185.2 77.2 324.1 324.1 694.5 169.8 108. 123.5 308!(5 266! 6 Inorganic. Organic. .8 C .2 O Average 'f 16 Eng- lish cities with water closets. .... London, average. . . London, sudden storms 1 1 1 1 1 0.7 0.7 0.7 0.8 0.4 0.3 0.2 0.2 6.36* 7.06* 105.75 154.7 798.84 94. 83 94.39 33.21 348.29 164.75 15.73 77.79 458.85 17.48 17.48 249 45.89 43.7 874. 262.2 89.59 112.75 224.62 197.96 165.62 31.46 88.71 401.6 40.23 93.08 225.06 14.86 34.96 53 93.08 43.7 611 8 218.5 31* 28] 27f 221.12 218.06 250 4 105.01 158.07 130.23 36i 249.96 777.86 157.76 44* 267 88 305.9 1573.2 524.4 5.51 1.86 ..75 108.81 74.73 124.55 109.25 253.9 79.53 ).09 112 75 406.41 83.03 5.63 100.51 131 1 568.1 305.9 510.85 549.31 1299.21 622.72 552.80 439.62 651.26 978.32 265.72 530.96 1046.62 1216.61 293.23 698.16 507.36 524.4 3627.1 1311. 37.15 34.96 32.34 30.59 28.41 20.54 29.28 50.26 49.82 31.9 19.67 10.05 26 .'22 46.32 26.22 $84.05 61.18 Berlin, average JJanzig 3.53* 6.36* 3.53 11.30 6.36* 14.13 5.30* 5 30* 12.18 16.42 Frankfurt, dry weather Frankfurt, moist weather Frankfurt, settling basins Zurich, average Average of 15 Eng- lish cities with mixed sanitary arrangements Paris, average Wiesbaden Munich Bremen E^sen 6.71* Halle, minimum.. maximum., average 3.18 NOTE. One gramme per cubic meter is equivalent to 0.437 grains per cubic foot. The number of micro-organisms varies between 30 and 100 millions per cubic meter of sewage. considerably different now from the tabulated quantities, which are accurate for the condition of the sewage existing a short time ago. In the second column are the quantities of sewage per day per person, those marked with an asterisk being the average for the year. The examinations were made at the outlets and generally at different hours of the day in order to eliminate the local and hourly variations as much.as possible. To show the variation that sometimes exists, the maximum, minimum and average figures are 22 CHARACTER OF SEWAGE. given for Halle. The figures for London were calculated from 21 observations extending over several months ; those for Berlin are the average of three years' examinations ; the Danzig data are the means of tests made during one rainy and six dry days, while the Paris figures are taken from records made during the years 1868- 77 inclusive. The figures for the other cities are for dry weather, but they are fairly true for the annual average. The influence of rains, taken annually, is not particularly great as a rule, and it is very seldom that the annual precipitation equals or exceeds the amount of waste water. Where the excess of rain in the sewers passes off through overflows, it is certainly safe to assume that the carrying water and sewage are of the same character. Examina- tions in London show that an increase in the amount of sewage by rains, instead of diluting renders it still more impure by the addi- tion of sand and other street refuse. It is the usual practice in England to consider this street water of the same degree of im- purity as the sewage in dry weather. It must be noticed, however, that ground and flushing water are relatively free from organic matter and nitrogen. About a third of the sewage in Zurich and a half in Munich is ground and flushing water. The analyses for Wiesbaden are based upon a mixture of 2 parts brook water and 1 part sewage. The actual amount of organic matter is, therefore, about three times that given in the table. The large amount of inorganic matter is due to the mineral character of the carrying water. The figures in the last column are of especial value as proving the statement sometimes met with that the actual effect of excre- ment in sewage is less than that determined on theoretical grounds. Both the Prussian and English government engineers have long held this view. The table shows that the character of the sewage depends not only on the amount of dilution, but also on the habits of the peo- ple, the manufacturing establishments and the plan of the sew- erage system, whether the effluent flows away directly or is some time in the sewers, whether or not deposits are formed, and, if they are formed, on the frequency of their removal. CHAPTER V.. SHAPE AND MATERIAL OF SEWERS. r* -V' / /'. The minimum height of a sewer that will permit the passage of a laborer is usually taken at from 3 ft. 3 ins. to 3 ft. 6 ins., although Hamburg, Frankfurt, Stuttgart and Munich allow 3 ft. In many cities the accepted practice calls for all sewers to be large enough for a man to enter and clean them ; Hamburg, Linz, London, Magdeburg and Wurzburg have such regulations. Formerly Budapest, Prague, Paris and Vienna required even the house connections to fulfill these conditions, but the rules are not enforced. From another point of view it will be seen that there is little advantage to be derived from increasing the dimensions of a small drain above the hydraulic requirements, unless the increase will be inexpensive. But when a certain size has been reached it will be found that the excavation forms the chief item of cost, and it makes comparatively little financial difference whether the section is 1 ft. 6 ins. or 3 ft. high, while the advantages of increased capacity and better circulation with the latter size 'are consider- able. This limit for very small sections is 2.08 ft. in Berlin and Danzig, 1.64 in Dusseldorf, 1.54 in Breslau, 1.48 in Munich, Stuttgart and Karlsbad, 1.31 in Liege and 1.26 in the very low sewers of Frankfurt. Sewers between these limits and a height allowing the passage of a man are very rare. This view of the matter is all the more allowable from the fact that such quite small sections are self -flushing and can be laid with little expense, so that the cost of laying a similar parallel line, if the amount of sewage should ever call for an increased capacity, would be small. The cross section should always give the greatest possible hydraulic mean radius (the hydraulic mean depth of Rankine), and hence the greatest possible velocity. The mean radius is the quotient of the section of the water divided by the wetted peri- meter. Where the sewage varies considerably in volume the egg- shaped section is the most advantageous. Fig. 3 is a diagram of 24 EGG-SHAPED SEWERS. this form ; the figures are the multiples of the width, which is taken as unity. The section designed by PHILIPPE, and given in Fig. 4, is better adapted for very small quantities of water, while Fig. 5 represents a shape also adapted for small quantities, and at the same time very easy of access for cleaning. In Linz the height is taken at twice the width, except for the largest sewers. A very good form as regards the comfort of the laborers is shown in Figs. 6 and 7. The sections for trunk sewers where the depth of water is fairly constant are sometimes designed as in Figs. 8 and 9, which show a very flat curve for the sole.* Occasionally the shapes given in Figs. 10 and 11 are employed where a con- FIG. 4. SEWER SECTIONS AT LIEOE. FIG. 3. stant flow allows the use of a broad sole and a considerable height is desired. Although the egg section is especially adapted to secondary sewers on account of the ease with which it can be built from any material and its peculiar fitness lor the variable quantities of water which flow through such sewers, nevertheless the German engineers usually prefer the circular section in such cases on ac- count of the ease with which it can be cleaned by brushes. More- over, in large trunk sewers which never run dry, the egg-shape is of little advantage and the gain in wet section at the same height of water by using a circular form of equal area is considerable. On this account the egg section is usually restricted to heights * Sole = Invert. SHAPE AND MATERIAL OF SEWERS. between 1.6 and 5.2 ft., although all sewers in Dresden, Mainz, Oologne, and Wiesbaden are of this shape. Where large quantities of water must be carried and a low sec- tion is desired, the sewers shown in Figs. 12 and 13 are satisfac- tory. The forms shown in Fig. 14 are used in England. But if allowance must also be made for carrying small bodies of water, a secondary section must be added. This is particularly the case where small brooks are utilized in the sewerage system. The torook shown in Fig. 15 was at one time partly arched, and -=1.63 to 1.75 , especially at the lower end ; arrangements for flushing with sewage or fresh water, all are useful in keeping the siphon clean. All these devices are united in the arrangement shown in Fig. 54. The 27J-in. siphon is formed of riv- eted plates, the catch basin is cov- er e d with a screen, and there is a flushing valve at the beginning of the invert proper. The re- lief outlet is so ar- ranged that water may be taken Fia 57. SIPHON IN BRESLAU. from the river through it for flushing purposes, if it is so desired. A still more complete arrangement, shown in Fig. 55, was de- signed by WIEBE. In this figure, d is placed at the fork of the 56 INVERTED SIPHONS. sewer, where it divides into two branches, for there are two separ- ate pits into which the sewage is alternately admitted. This du- plication of the plant enables the system to be easily and rapidly cleaned. At e is a gate for use in flushing, at f is a relief out- let, at g is a removable screen, h is a flap for closing the siphon during cleaning, k is a valve to prevent sewage from entering the siphon when it is desired to clean it with water admitted by the yalve I. A similar arrangement was designed for Breslau, Fig. 56. Here there are two chambers, a and J, into which the sewage is alternately pumped. Each chamber is quite deep, in order to check the current and precipitate the greater part of the solids. At c is a pipe which serves both as a relief and an intake from the river when the siphon is to be flushed. It is sometimes possible to use a regular siphon in place of these inverts. Fig. 57 represents such a siphon in use in Breslau. The sewage flows into a catch basin, through a screen and is then carried through a6-in. pipe attached to a bridge to a second catch basin. There is a difference in elevation of 10 ins. between the ends of the siphon. An air lock is placed over the second catch basin, as shown in the cut, and the air thus collected is automati- cally released whenever the level of the water in the lock sinks to a certain point. The pipes are covered with a thick wrapping to guard against the frost. The upright siphon is much less liable to be stopped by sediment than the inverted type, and is less expen- sive, both in first cost and subsequent repairs. CHAPTER VIII. CATCH BASINS. 1. Street Catch Basins. The inlets of these may be entirely open and cut in the curb stone, as in Fig. 65, or partly closed,, either by a stone cap as in Fig. 58, or by a cast-iron hood as in Figs. 62 and 67. Their height is from 4 to 6 ins. and the width varies from 1 to 4 ft. When the inlet is horizontal, the old custom was to have a stone slab for a cover, but the present prac- tice is to use an iron casting, either funnel-shaped or flat, Figs. 63-69. These castings are commonly from 1 to 2 ft. long. Oc- casionally they are formed of wrought iron bars 0.8 to 1 in. thick, 2 to 4 ins. deep, and spaced so that the openings are from 0.8 to 1.6 ins. wide. The covers are either hinged, as in Figs. 60 and 61, or loose in their beds, as in Figs. 67-69. Of the two posi- tions, the upright is to be preferred as out of the way of wheels and less liable to be stopped, but has been found to allow a greater amount of solids to enter the sewers. This can be partly remedied by using a coarse screen as is done in Brussels, Fig. 62. In the markets of Paris iron baskets are hung below the inlets in order to catch the refuse. In some of the older sewer systems all the street water and refuse is carried into the sewers directly from the inlets, Figs. 58-60. Such a plan is uneconomical, as the cost of removing the deposits is then quite high. In a good sewerage system deposits should be formed but rarely. Even if heavy rains carry a large amount of fine sand into the sewers, the unusual quantity of water will be sufficient to carry off all but the largest solids, which should, indeed, be prevented from entering the system. This is done by silt pits, Figs. 61, 63-69. It is sometimes desirable to incline the silt pits in narrow streets toward the center of the roadway and lead away the sewage by side sewers, as is done in Munich. The dimensions of a catch basin depend upon the area of hard surface which it drains, usually from 480 to 960 sq. yds. ; additions to this area from lawns arid gardens may increase the ,58 STREET INLETS. surface to 1,200 sq. yds. The cross section of the shaft is usually square or round measuring from 1.3 to 2.6 ft. on a side or in diameter. A German empirical rule is to allow as many milli- meters diameter as there are square meters of drainage surface. Those basins which receive the water and refuse of steep streets should have much larger dimensions. The water level in these street catch basins should be from '2 to 3 ft. lower than the street surface, as a protection against frost. The total depth of the basin should be from to 8 ft., as when a less depth is chosen there is danger of freezing. Masonry has given way to cement, clay, or iron pipes as a material for this work. These pipes are usually 2-3, 1-1 J- and 0.8-1 in. in thickness for the different kinds mentioned. Cast-iron is least adapted on ac- FIG. 58. STREET INLET, PARIS. count of its liability to rust. The shaft usually consists of two or three pieces, and carries the inlet at its upper end, as shown in Fig. 69, although this is occasionally supported, as shown in Fig. 67, in order to make future adjustments to grade as easy as possible. Formerly no provision was made against the escape of sewer air, Figs. 58 and 59. Now it is necessary to use more care in building the catch basins near sidewalks. In Hamburg a small flap valve, shown in Fig. 60, has been adopted. This is opened by the escaping water and is very simple in all respects, but by no means tight in dry weather. . The use of valves in any part of the inlet is of little value, as has been shown in the older sewers at Munich and Linz. A better and more simple connection is made by a common water trap, 4 to 8 ins. deep. This may be formed by a tongue, as shown in Figs. 63 and 64, by an inverted outlet, as in Figs. 65, 66, 68 and 69, or CATCH BASINS. 59 by some special arrangement similar to that shown in Fig. 67. The 'outlet shown in Fig. 63 is cleaned by folding back the hinged flap. Those shown in Figs. 65 and 66 are cleaned by simply re- moving the short curved outlet, while the other forms illustrated oan only be cleaned by flushing. At x, Fig. 67, is shown a water- trap, which offers the great advantage over the form represented in place in the cut, of being easily cleaned withour, breaking into the pipe, as must be done at x in Fig. 68. In all such designs care must be taken to expose as small a surface as possible to the action of rust. In the arrangement shown in Fig. 67, solids 1:50 FIG. 60. STREET INLET, HAMBURG. FIG. 59. STREET INLET, HAMBURG. 1:50 FIG. 61. -STREET INLET, MUNICH. may be easily caught in the invert, as might also happen in Figs. 63 and 64. Generally water traps and silt pits are found in the same basin, but this construction is not always adopted. At Brussels a water trap is placed immediately below the inlet. Fig. 62, and the flushing done by means of a connection from the water mains. The opposite of this arrangement is employed in the open suburbs of Munich, where a small catch basin discharges directly into the sewer connection, Fig. 61. The pipe leading to the sewer is from 5 to 6 ins. in diameter when silt pits are employed, and may be increased to 20 ins. where these are not used. The pipes are best curved or placed at an angle at the intersection with the sewers, except in cases simir 60 STREET ISLETS. lar to that shown in Fig. 63, where the sewer lies directly under the catch basin. The mud is removed from these basins by shovels or by buckets, as shown in Figs. 66, 68 and 69. The diameter of the- latter is from 2 to 4 ins. less than that of the shaft in which they are placed and their height is to be determined by the posi- tion of the outlet pipe. Holes should be made in the lower part of the bucket in order that the water can drain out as the mud is lifted up to be removed. In order that all the material may en- FIG. 62. STREET INLETS, BRUSSELS. FIG. 63. STREET INLET, BERLIN. FIG. 64. STREET INLET, KARLSRUHE. ter the buckets, it is usual to place small hoppers or funnels un- der the grating at the inlet, Figs. 67-69. Sand is very apt to- settle around the buckets, making their removal somewhat difficult, and it . requires considerable labor to empty the mud into the- carts which carry it away. In order to diminish this labor, the- apparatus shown in Fig. 70 was proposed by GEIGER. The- bucket is held in position by an iron ring and receives all the mat- CATCH BASINS. 61 ter entering the inlet above. Equal atmospheric or hydrostatic pressure above and below the ring is maintained by the small pipe a 1), so that only the weight of the bucket and its contents has to be lifted. The bottom of the bucket is hinged and held in position by a catch c. In replacing the bucket in the shaft, the valve d opens when the water level is reached and allows the water to enter until the whole is again in position. Whether the apparatus would work well in muddy places is open to ques- tion. The mud in the basins is always foul, and should be kept cov- ered with water in order that no disagreeable gases may be given off. It is often desirable in prolonged dry weather to occasionally admit water from the service mains. In no case ought the water FIG. 65. STREET INLET AT HEIDELBERG. FIG. 66. STREET INLET AT WIESBADEN. traps or siphons be placed under the mud buckets, as is done in Budapest, for this construction causes the mud to dry up very ^quickly. 2. House Inlets and Connections. That all house connections should be separated from the sewers by some kind of water trap is now universally admitted and generally demanded in the speci- fications for such work. The depth of these traps varies from 2 to 4, or even 6 ins. where there is much grease in the drainings. The means of holding back the impurities are often very scanty. Not only do the usual impurities of street sewage occur in these connections, but also fats, soap and other kitchen and washroom drainings. The fat gradually solidifies in the pipes and forms a tough coating which collects the other matter. For connections in courts, where sand and leaves form the leading solids swept into the sewers, any of the catch basins STREET INLETS. shown in Figs. 63-69 will serve, while in very large courts that represented in Fig. 62 could be employed by omitting the water pipe. They are usually made as small as possible in order to hav& a good fall to the sewer. The diameter of the basin may be re- duced to 10 ins., the depth to 3 ft., or less, in places not ex- posed to frost, and the outlet to the sewer need not greatly exceed 3 ins. Small cast-iron basins of several forms are shown in Figs. FIG. t>7. FRANKFURT. FIG. 68. KARLSRUHE. 71-74. The dotted lines in Fig. 72 indicate the form to be used in places exposed to frost. Rain water from roofs, which is apt to carry with it dust, ashes, pieces of slate or tile and similar substances, is usually conducted by suitable drains to a small mud pit at the rear of the house. When this is not possible, special arrangements are made for re- ceiving the water at the front or street side of the house. For this purpose, in Dresden and Cologne a small basin or pit, pro- vided with a cover at the sidewalk level, receives the water from the roofs and discharges it into the sewers through properly fitted outlets. The devices in Figs. 75-77 are much more simple and CATCH BASINS. 63 as efficacious. In the form shown in Fig. 75 the pipe from- the eaves trough is enlarged at the base and fitted with a screen and opening for cleaning, while in Fig. 76 the same arrangement has been adopted but placed underground. The device shown in Fig. 77, and employed in Erfurt and Stuttgart, has the advantage of being well protected from the frost. In Berlin, such arrange- ments are used only in houses with roofs of earthy material, or in bad condition. Since, however, there is no doubt as to the value of these screens, and their cost is quite low, it seems better to call for their general adoption. Some cities call for merely a FIG. 69. STUTTGART. knee or bend in the pipe, with an opening for cleaning. In Breslau, the only precaution taken is to place a grating over the top of the eaves 4 pipe, which, however, is stopped more often than would be thought probable, and is difficult to clean. In Wies- baden, a small basket to keep back the leaves and other objects is placed at the top of the eaves pipe, and a small box or pail at the lower end receives the mud, Fig. 78. Wherever an eaves-pipe opens above in the neighborhood of a roof window, and there is danger of sewer air escaping, it is required in Munich to place a water trap at such a point as to prevent this. At Freiburg and Basle these traps are required for every pipe carrying water from roofs. The house sewage is often screened by passage through a grate and siphon, many cities having expressly ordered each house con- nection to be provided with a grating and a water trap. For 64 GREASE TRAPS. purifying the drainings from kitchens several forms of grease traps have been used. These cause the fatty matter to he separated by cooling, the grease being retained floating on the water in the trap. An American form, made of stoneware, is shown in Fig. 79. They are usually placed below the sinks, and intercept not only the grease but also all the heavy substances which enter them. In order that the layer of fat on the top of the water may not be agitated too greatly, the drain from the sink should enter from the side and not the top. A pail is some- FIG. 71. Fia. 72. Fia. 73. times provided for removing the solids, Fig. 80, but it must be provided with tight bearings or all the matter will not be inter- cepted. If this condition is fulfilled an ordinary catch pit will serve as a fat or grease trap by placing the outlet sufficiently low, Fig. 81. Such an arrangement is often employed for a general catch pit in a court or cellar in case no traps are used in connec- tion with the sinks. It is desirable to have all the pipes nearly vertical, in order that they may remain clean, and to have suitable arrangements for ventilating the drains, thus avoiding any tend- ency to create a partial vacuum in any part of the connections. Catch basins with movable partitions or tongues, like those shown in Fig. 63, are not adapted for intercepting floating sub- CATCH BASINS. 65 stances, for it has been found in practice that during the process of cleaning, a large proportion of the matter floating on the sur- face of the water is carried into the sewer. Hence no movable tongues or siphons, Fig. 65, are allowed in private basins in Karls- ruhe. Where large quantities of water must be handled, it is usual to double the dimensions of the traps or basins, Fig. 82. Where the outflow from manufacturing establishments is large, it should run into precipitating tanks or even receive chemical treatment, before entering the sewers. The preceding devices for screening house sewage are by no means everywhere used in the same manner, and there are a great FIG. 74. FIG. 75. GRATINGS IN RAIN PIPES. FIG. 76. RAIN PIPE IN- LET, KARLSRUHE. number of regulations concerning water carrying grease and sand. In many cities, as, Hamburg, Frankfurt and Basle, only bends are required under the sinks, and the pipes discharge directly into the sewers, being kept clean by flushing alone. This arrange- ment has been found to work badly with water containing much fatty matter, and grease traps are often employed although not officially required. In several other cities, as Berlin, Cologne and Freiburg, kitchens and laundries are generally allowed to discharge directly into the sewers, but where fat and soap are discharged "in un- usually large quantities," a grease trap must be connected to the outfall from laundries, restaurants, soap works, abattoirs and 5 6*5 TRAPS IN HOUSES. such establishments. In Berlin a very large amount of sand must be taken from the sewers annually, which could be equally well and more cheaply intercepted by house traps, as the greater part of it comes from dwellings where it has been used in cleaning. Exactly the opposite plan has been adopted in Stuttgart, Karlsruhe, Mainz, Wiesbaden, Goattingen and Halle. Here all FIG. 77. RAIN PIPE IN- LET AT ERFURT. Gasket. Fia. 81. FIG. 82. water containing fats or sand must pass through traps before leaving the premises. In small houses this may be done in a single pit, to which all the pipes run, and from which the sewer connection is laid. In larger establishments several pits are usu- ally employed, partly on account of ease in laying the pipes and partly to reduce the number of flat grades, and thus diminish the deposits. On the latter account a regulation has been adopted in.Weisbaden prohibiting the use of grease traps at a greater dis- tance than 7 ft. from the foot of the house pipe. Since the dis- CA TCH BASINS. Q 7 charge from courts also requires to be screened before entering the sewers, it will often be found possible to make one pit serve for both the house and court connections, and even for roof water in some cases. Such a combination should not be made without care, or the pit or basin will overflow at times. In Wiesbaden, one pit may only receive the entire discharge from an area less than 54 sq. yds. in extent. In the majority of cities it is not necessary to pass water that is reasonably pure, such as that from baths, through intercepting traps. The rules in use ut Karlsruhe read as follows : Rainfall pipes may discharge into the sewer or house drain without a water trap ; kitchen pipes must be connected with the sewer by a bend or knee under the inlet, and a catch pit ; other discharge pipes to be provided with a siphon or catch pit, or, in cases where unusually large quantities of grease occur, with an easily cleaned grease trap. The extent to which preliminary purification is to be carried depends entirely on local circumstances. Where the quantity of sand used in the household is small, and the flow of water in the discharge pipes is so rapid as to flush away the sediment that col- lects, catch pits may be omittedi Since all the domestic sewage must be swept away, it will not do to pass any part through a catch pit, and hence a separate connection ought to be laid to the sewer when the kitchen drainings pass through such a pit. On sanitary grounds, all deposits in the vicinity of a house are to be avoided, and the expense and annoyance attending their removal is considerable. When such are unavoidable, they should be con- centrated as much as possible to facilitate removal, and the pipes should be arranged to give the greatest amount of ventilation. The preceding remarks are based on the supposition that water-closets are used. This is by no means universal, however. In some old cities it is customary to have a dry connection from the privies to the sewers, and even when better sanitary arrange- ments may be had, to retain such arrangements on econo.mical grounds, or through lack of water for flushing, as in Aachen, Bonn, Linz, Salzburg, and Wurzburg. The evil results of such a practice are many, such as the escape of sewer air into the houses and the formation of offensive deposits in the connecting pipes, which cannot be entirely obviated. The best results are attained by an oft repeated flushing of such connections, by means of hose lines, as in Salzburg, Liverpool, andr Danzig. CHAPTER IX. FLUSHING. For flushing purposes, water may be classified under the fol- lowing heads : a. Flowing or standing water at the higher ends of the sewers to be flushed, which can be admitted without previous collection and allowed to drain off from the lower ends of the system into other channels. In Bern, Wurzburg and Innsbruck brooks are used in this manner, while in Freiburg industrial canals are utilized for the purpose. b. Rivers with a rapid fall, from which water may be taken .above the city, and to which it is returned after passing through the sewers, as is done in Breslau, Danzig, Liege, Munich, Reichenhall, Zurich and Strassburg. c. In places on tidal waters the variation in the sea level is utilized for flushing. In Bremerhafen, for example, water is ad- mitted to the basins during high tide, and allowed to flow from them into the sewers as soon as the water level has fallen suf- ficiently to cause a scouring action. At Brighton water is ad- mitted at high tide at one end of a sewer running along the shore, and escapes at low tide from the other end. At Emden water is admitted at several points during high tide. d. Water collected by pumps or pipes at the upper end of the system, either in ditches, reservoirs, or sections of sewers cut off for the purpose. The latter plan is much used where there are several lines of sewers to be flushed and the water for the purpose must be supplied through a single line, as in Danzig and Karls- ruhe. Reservoirs fed by brooks are employed in Mainz, Munich, Diisseldorf, Cologne and Wiesbaden. It is necessary to pass the water of the brooks through catch basins in order to remove all the sand before admitting it into the sewers. In Bremen, water is pumped from the Weser River into the moat surrounding the city and then flows into the sewer to be flushed. e. Rain, spring, and ground water is often collected in reser- voirs, usually underground galleries through the walls of which it is admitted. Frankfurt, Stuttgart and Gcettingen have such FLUSHING. 6& I reservoirs. In Frankfurt, the gallery is 984 ft. long, 4.6 ft. wide and 5.6 ft. high, and is filled every day except in rainy weather, when it is sometimes filled three times daily. f. The public water supply is often used. The water is generally admitted to flushing tanks from which it is discharged into the sewers. g. Water from shops of various kinds is used when it can be had in sufficient quantities. In Dortmund water is taken from the city baths, in Liege from mining establishments, in Linz from a large brewery, and in Pest the water of condensation from large flouring mills is employed. h. Where free water is lacking, and that from the waterworks is too dear, the sewage itself may be used for flushing. Generally, however, water is also added from the mains to the upper end of the sewer to be cleaned, because there the quantity of sewage is small. In Berlin the addition of water for this purpose averages about 11 cu. ft. a year per capita. The quiet flow of water in a sewer will only have a cleansing- power when large quantities can IDC used for several hours. This is rarely possible, even where hose connections can be made with hydrants, and in such cases temporary shields are usually placed in the sewers, enough water being thus collected to cause a strong flushing action when the shield is suddenly removed. The sewers are divided into stretches by movable partitions, and each length then separately cleaned. It is customary to begin at the upper end and wash the sand and mud down toward the lower points, although occasionally flushing begins in several points, simultaneously, in order to avoid clogging the system in any place. The length of the section that can be flushed with one setting of the partitions varies greatly, being governed by the grade and size of the sections. Care must be taken that the backwater from the lower part of the sewer does not cause incon- venience to the residents along the line, and that the extra pressure does, not fracture the pipes or masonry. The partitions employed sometimes occupy the entire cross section of the sewer and sometimes only a portion of it. When the effect of flushing cannot be well calculated while Designing the system, it is best to leave several points in the masonry so arranged that flushing tanks can be placed in position later if found necessary. 70 HAND FLUSHING. The interval between successive flushings varies greatly. Some of the sewers in Hamburg are cleaned in this way every few days ; in Berlin every twelve, in Frankfurt and Danzig every three weeks, while in England the interval is from one to three months. The flushing devices may be divided into four classes as follows : 1. Hand Apparatus. In Fig. 83 a y the water is kept back by a cover held in place by a small brace. At b the cover is held by the hydro- static pressure alone, while in c the cover is also partly Fl - *& supported by a frame in which it slides, and in d there is a hinged flap over the outlet. The forms shown at a and #*may be moved from manhole to man- hole, but do not adapt themselves to a well-designed base, like that illustrated in Fig^ 89. In order to discharge the water it is necessary in all cases for a laborer to enter the manhole and pull the rod or chain connected with the cover. In case he should forget to do this, an overflow pipe is sometimes provided, as at J, or a float, as at d. The over- flow pipe is specially adapted to a manhole in which the inlet pipe has a marked bend, as in Fig. 84, for in such cases there is little backing in the inlet until the over- flow begins to act. Where there are no manholes in the proper place for flushing, small pipes can be used for casing in the rods of the covers (Fig. 85). Figs. 86, Fia ^.-FLUSHING SHAFT AT WIESBADEN. 87 represent forms of plate covers adapted to larger sewers. 2. Flushing Gates, revolving on an upright or slightly inclined axis. The two hinges are attached to a cast-iron frame FLUSHING. 71 in Fig. 88, and the gate itself stiffened with braces. While the sewage is held back the gate is braced by an arm which rests against a corner of the masonry. In order to allow the water to escape, this arm must be withdrawn, usually by an attached rod, Fig. 89. The gate must be closed by hand. A more convenient attachment is shown in Fig. 90. The arm is easily thrown from the position shown by solid lines to that indicated by the FIG. 85. FIG. 86. FIG 87. dotted outline, by turning an eccentric bolt, not shown in the cut, when the rush of the water will throw the gate open as indicated by the dotted outline in th6 section on d. The hinges are slightly out of perpendicular in order that the gate will fall back as soon as the water has returned to its normal level. When it is desired to retain the sewage for flushing, the end of the arm holding the gate is fixed to a shoe which is then driven forward by the crank and gearing until it can be turned on the eccentric bolt before mentioned, bringing the whole 72 SLIDING VALVES. apparatus into the position indicated in the figure. The work- men stand in the niche containing the gears. Another apparatus quite widely used is shown in Fig. 91. The arm a is here attached to a movable rack, driven by the pinion c, which is turned by a key d, a pawl holding the pinion in position* When the pawl is released the pressure of the water will open the gate. Sometimes the sewer is closed by means of a pinion gear- ing into a quadrant-shaped rack attached to the frame of the door. But the use of teeth should be avoided as much as possible in such devices on account of the quickness with which they are attacked FIG. 88. FLUSHING GATE AT HAMBURG. FIG. 89. by rust. In very wide sewers it is sometimes necessary to use a gate with two wings. 3. Sliding Valves, with mechanical lifting appliances. The form used in a great number of cities is shown in Fig. 92 for small, and Fig. 93 for large sewers. In the latter modification a gear is keyed to the top of the worm shaft and counterweights maintain an approximate equilibrium. Several defects, which have been noticed in this arrangement of parts, have been overcome in the apparatus, Fig 94, made under the GEIGER patents. The worm is protected from dirt and is easily oiled. The guides are faced with bronze and the cover is beveled below, so that a tight joint is- formed. In the street cover is an indicating apparatus showing; the exact amount of opening. These gates have given good re- sults in Karlsruhe, where they are used on sewers from to 6-Jft.. FLUSHING. 73 in diameter. In all valves of this class, the opening is done more slowly than when gates are employed. They are, therefore, best adapted for use with large quantities of water, where a small loss is of no consequence, and have the advantage of delivering the FIG. 90. FLUSHING GATES, FRANKFURT, DUESSELDORF AND STUTTGART. water in a fairly steady flow, which carries off the impurities in a satisfactory manner. 4. Automatic flushing appliances reduce the expenditure for labor, especially in cleaning house connections. They operate after the manner of intermittent springs. A reservoir is slowly filled with water and sewage, which is suddenly discharged into the sewer, thus causing a flushing wave. The amount of water and period of flushing should be so chosen that the sewer will run 74 FIELD FLUSHING TANKS. full. The wave will become flatter as it proceeds and the length of sewer that can be cleaned by each reservoir is limited. The whole process is automatic and recurs at regular intervals. a. The ROGERS FIELD system,, Fig. 95, much used in Eng- land and America, is usually employed at the dead ends of sewers. The reservoir is fed from the water mains with a valve for admitting water adjusted to give the proper quantity for regu- 1:25 FIG. 91. FLUSHING GATES, DANZIG. FIG. lar action. When the water level reaches the mouth of the de- livery pipe the reservoir is emptied through the siphon formed by the inner and outer tubes, the discharge being quite rapid. A small quantity of water remains and acts as a water seal against sewer air. In Memphis, Tenn., the cistern holds 53 cu. ft., and is emptied every 24 hours, the discharge lasting 40 seconds and cleaning about 1,000 ft. of sewer. b. The improved FIELD system is shown in Fig. 96, which represents the apparatus manufactured by Booking & Co. It was noticed in the older Field apparatus that the thin edges at the FLUSHING. 75 top of the inner tube at times prevented the discharge of the water by a siphon action, the overflow taking place very slowly and only equaling the discharge of .the water pipe in amount. Therefore, a small funnel was placed at the top of the inner tube, and the outer tube bent down, as shown in the cut. This ar- rangement insures a proper discharge by causing the parts to act like an injector. In apparatus of this kind in Rome, placed every 722 ft. on a FIG. 93. FLUSHING PENSTOCK. sewer previously subject to large deposits, it was found that the discharge of 88 cu. ft. of water twice a day was sufficient to keep the system in good condition. In one district of Paris a number of these reservoirs are used which discharge from 14 to 25 cu. ft. three times a day, while about 600 larger cisterns are used at the dead ends and on the dirtier streets throughout the city, likewise discharging three times daily, or more often if managed by a laborer. c. The CUNTZ system, Fig. 97. In order to make certain 76 VAN VEANKEN FLUSHING. that the siphon acts properly, the water passes through an injec- tor, 1}, before it passes into the reservoir through the pipe f. In. this way air is constantly sucked from the space a, but is also ad- mitted through c until the end of that pipe is closed by the water. Then the air in a is removed by the injector and the siphon be- gins to work. When the reservoir is to be filled more quickly than can be done by the injector alone, the cock d is opened. In Karlsbad 140 cu. ft. are discharged in four minutes. d. System of VAN VRAXKEN", Fig. 98. In this construction a box is placed under the siphon. This slowly fills with water FIG. 94. FLUSHING GATE, GEIGJZR SYSTEM. and seals the end of the discharge pipe. When the box is filled it tips on its supports into the position indicated by the dotted lines, and thus sets the siphon in action. Afterward it falls back into its original position. Unfortunately, it is difficult to ex- amine the box while in place, and on that account the end of the siphon is sometimes carried through the wall of the reservoir into- another chamber, as at Regensburg. e The FRUHLING system, Fig. 99. The discharge pipe is closed by a valve which is connected by a rod with a float, b. The upper end of the float is connected with one end of a lever, bear- ing at its other end a box and weight, c. W T hile the water is ris- ing ~b and c are in equilibrium. Finally, however, the water pours FLUSHING. 77 into the box causing it to sink, and thus opening tlie valve. The .great velocity of the discharge, 13 ft. a second, causes eddies in the reservoir which sweep away all solids. Hence sewage may be used for flushing, which is not possible in the CUNTZ system, This plan is followed at Koenigsberg and Magdeburg. f. The American system, Fig. 100. In this apparatus an un- symmetrical box is slowly filled until its equilibrium is destroyed 1:50 FIG. 95. FLUSHING TANK, FIELD SYSTEM. FIG. 96. FLUSHING TANK, SYSTEM BOECKING. FIG. 97. FLUSHING TANKS, CUNTZ SYSTEM. FIG. 98. VAN VRANKEN FLUSH TANKS. and it tips on its supports, discharging its contents. The size of the box and quantity of water discharged cannot be very large, thus restricting its use to house connections. With properly constructed inlets and flushing apparatus, the- water carriage system of sewerage ought to prevent the formation of deposits, so that only with very long intervals between flushing will mechanical cleaning be necessary. When water for flushing cannot be had, or is too expensive, other methods must be em- ployed. See note, page 282. SPECIAL METHODS OF CLEANING. In small sewers or drains a large chain can be pulled back and forth, but a brush is much better, using first one of small diameter and a larger one afterward. Sometimes spherical metallic floats slightly smaller than the section of the sewer are allowed to pass through it. These floats are caught by each deposit and hold back the sewage until a sufficient head is obtained to sweep away the obstacle. Manholes are built in the streets for the pur- FIG. 99. FLUSHING TANKS, SYSTEM FRUEHLING. Frp. 100. FIG. 10L pose of employing these various means. In private grounds it is usually sufficient to form connections like that shown in Fig. 101, where the upper cut represents the form of connection for use outside and the other for use inside a house. In Berlin, Mann- heim, Wiesbaden and other places, a covered opening, 1 ft. long, must be provided in every house connection within the limit of the private property, for purposes of inspection. In case this opening is under ground a pit must be built in order to reach it FLUSHING. 79 This is usually done in cellars, see Fig. 116, which represents such an opening in connection with a hinged gate for flushing. In large sewers the deposits are collected with wooden shov- els, and the walls then swept with brush brooms. In Berlin, the gangs for this work consist of three labor- ers, and each sewer is cleaned every 20 days. In the larger sewers of Brussels and Paris, carts with hanging metal plates are used, Fig. 102. The plates are lowered by the screw rod on the cart until the sewage begins to back up behind, which causes a strong cur- rent to pass under the plates and wash away the sediment. The cart is moved along to a great extent by the pressure of the sew- age. The deposits are usually collected in dump carts running on the same rails used by the cleaning cart. A somewhat similar plan is followed in Berlin, where a frame is carried by a rolling platform from manhole to manhole. In Cologne, the frames are hung after use on tackles in chambers leading to the sewers. FIG. 102. CLEANING CART, PARIS. CHAPTER X. VENTILATION. Like water, the air in sewers should never be stagnant, but rather constantly in motion, escaping at some points of the sys- tem and being renewed at others. In this manner all the im- purities, both suspended and solid, will be more or less oxidized instead of collecting in putrefying masses, as they were at one time believed to do, and the air will not differ materially from that outside. It will contain no injurious gases, only a some- what larger amount of carbon dioxide (1 to 5 permille compared with 0.5 in the open). Moreover, in the circulation of the air, alterations in its press- ure will be caused by the inrush of water from houses and adjoin- ing sewers, and equilibrium must be restored as soon as possible, in order that water in the traps may not be blown out or the sewer air escape at unsuitable points. It has, indeed, not yet been proved that disease germs are carried through sewers properly constructed, and the weight of evidence is in favor of the view -that the spread of epidemics is entirely independent of sewer air. This may result from the adherence of the germs to the coating on the sewers, and the great dilution of the sewer air when it enters the open. The question is extremely complicated, and, on aftiy account, the formation of deposits in the neighborhood of houses is to be avoided, from their unpleasant odors, if for no other reason. And it is to be remembered that the odors from the regular outlets will become less marked as the circulation in the sewers is more rapid. Here, as in all hygienic matters, prevention is better than cure. The causes of the circulation of air in the sewers are the dif- ferences in temperature and moisture within and without the sys- tem. In summer the interior air is cooler and heavier, and hence flows downward toward the outlets. In the cooler seasons it is warmed by the surrounding earth and tends to rise. In conse- quence of the action of the sun on the various inlets and outlets the heat communicated to the house pipes from chimneys and hot- VENTILATION. SI water pipes, and the different depths at which the sewers are laid, the resulting flow of air is constantly varying, and a system with its numerous branches and openings has no single main current. Minor influences are the temperature of the sewage, the nature of the sewer walls (affecting the coefficient of friction), and the winds blowing over the different openings. In view of all these influences, which together determine the currents,, it is not sur- prising that the direct observations made in sewers do not always agree. In general a downward flow of air toward the outlet is desirable, as the tendency is then to draw the gases from the houses, with the sewage. Such a motion has been found to pre- vail in Munich in the street sewers during the summer,, while in the house drains the currents are upward, through the escape pipes to the roofs. See note, page 2-84. Practically these currents consist of two columns of air of different temperatures and therefore weight, which imperceptibly mingle within the sewers. The outer air enters at several points, its temperature and amount of moisture are altered, and it then leaves as sewer air. That this motion should always be in one direction is of course desirable, but not to be expected. Usually the direction changes fre- quently, especially when the grades of the sewers are steep. On this account it has been sug- FIG. 103.- AIR VALVE, gested that the sewerage system be divided into zones by contours from 25 to 35 ft. apart, and the air be prevented from rising from one zone to the next above by air valves similar to those shown in Fig. 103. These valves are much like the traps in mines and afford a ready passage to the sewage, but are com- paratively air-tight. Such devices do not act as well in practice as in theory, and it appears advisable to confine the attempts at ventilation to preventing the sewer air from entering houses. The various systems of ventilation for this purpose are shown in diagram in Fig. 104. 1. In the first system, the sewers and the air communicate by means of manholes, ventilation shafts, street inlets, and rain pipes, while the inside connections are all made by water traps. These means of ventilation are rarely all present at the same place ; gen- erally the house drains are cut off by a running trap. Sometimes the man-holes are also closed to prevent the escape of possibly injurious 6 82 HOUSE CONNECTIONS. gases, and in such cases the only ventilation obtainable is through the rain pipes. An objection to this system is the unreliability of these pipes. The difference in temperature at their ends may be FIG. 104. DIAGRAMS OF HOUSE CONNECTIONS. so little that no current will be created ; and, moreover, during a heavy rainfall the water in them will act as a piston for com- pressing the air and, in place of giving a means of ventilation, will rather tend to cause stagnation. On this account the rain water is often led into -the sewers by entirely separate pipes, emptying into the crown, as shown in the third sketch. The worst feature VENTILATION. 83 t of this system is the liability of the water in the traps to be blown out by the compressed air in the mains. 2. An improvement is introduced in the second system by pro- longing the house pipes up ward through the roofs, thus affording a means of equalizing every change in pressure of the sewer air. Since this air would be apt to enter the water of the traps by the inclined connections, it is well to join the highest point of the trap by a suitable pipe with this ventilator, or with a secondary pipe opening either into the higher part of the first or into the open air, as shown by the dotted lines in the second sketch. This plan is the simplest method of preventing the escape of the water in traps, which is often caused by the suction or press- ure of a large quantity of water suddenly falling through the main soil drain. It also serves to remove the gases from grease traps and to prevent the slow absorption of sewer air by the water in little-used con- nections. The pipes should be of such a size that the friction of the air in passing through Fia 1U5 - them will be quite small. On this account the ventilating pipes should be as large as the soil pipe of which it is an extension, and the connecting pipes should be at least 2 ins. in diameter. A number of mechanical devices have been tried for prevent- ing the escape of water from traps, but they all fail as soon as dirt collects about them. The best of these is the rubber ball of GERHARD, Fig. 105, which is pressed against an upper seat when there is danger of a blow-out, and drawn against a lower seat when there is any tendency to suck out the water from a trap. As before mentioned, in the normal circulation of the air, it enters at the street connection and rises through the soil pipes. This current is more certainly maintained when the house drains are specially warmed or placed in the vicinity of chimneys, al- though the latter method is not always reliable in dwellings. When there are quite a number of trap- ventilating pipes in a house it is often well to connect them to a secondary ventilator built into a special flue in the chimney, as is required in Munich. In many dwellings the situation of the rooms will permit of two secondary ventilators, one for water closets and one for kitch- en and other connections. Sometimes the kitchen drains are $4 HOUSE CONNECTIONS. .supplied with traps before they join the sewer connection. In this way the closet gases are prevented from entering the kitchen pipes. Such construction, however, does not appear necessary if the designs are suitably made, and the flushing action of the kitchen wastes is lost. But foul gases should never be allowed to come in contact with traps in which the water is liable to evapor- ate from disuse. These ought to be separately connected with a trap surely filled, such as those used in kitchens. When it happens that a kitchen drain terminates in a grease trap the latter must have a connection of some kind with the air, in order that proper ventilation may be maintained in that drain. In such a case the circulation in the street sewers is obtained through the soil pipes alone, as in Wiesbaden. Where the closets are not connected with the sewers, the latter have no air connection whatever with the houses and must depend on other means for ventilation. In a number of German cities the sewerage system is connected with the air by the threefold means of manholes, rain pipes and soil drains. The house pipes are ventilated in this way, as well as the sewers, although the number of dead ends in buildings tends to decrease the actual length of pipe through which the air circu- lates. In most cases the householder should be required to afford a good ventilation, either by soil pipes without catch pits at the bottom, rain pipes connected directly to the sewers, yard or court inlets without traps, or special ventilating pipes. The latter might be partly paid for by the city, as they directly aid the municipal system. As already remarked under (1), the rain pipes are unreliable and the soil pipes cease to act as ventilators as soon as their out- lets into the sewers are closed. On this account special ventilat- ing pipes are attached to the houses of several cities, as shown by the dotted line in diagram 2. These pipes take the place of the rain and soil connections in rainy weather, and in very narrow streets they occasionally replace ventilating shafts in the streets. They are especially to be recommended for dead ends, and are extensively employed in Wiesbaden, Basel and Danzig. In the latter city over 100 are used, together with some 300 ventilating shafts. They have proved especially valuable in Ernden, where the manholes are tightly closed, ventilating extensions not required or used over the soil pipes, and the rain pipes lead to cisterns VENTILATION. g& where the water is collected for household purposes^ Therefore an air pipe was taken from each manhole, under the pavement, and carried up the front of a neighboring building. 3. From the third diagram on, the public and private drains are separated by disconnecting traps in order to prevent sewer air from entering the dwellings. In diagram 3, the rain pipe is not disconnected, as it is designed to aid in the street sewer ven- tilation. This complete separation of the houses, generally adopt- ed in England and America, is certainly excellent on account of the sanitary protection it affords, but appears somewhat unneces- sary when all the details shown by dotted and full lines in diagram 2 are properly designed and constructed, and, moreover, compli- cates the ventilating arrangements. In diagram 3 it will be seen that the circulation of air in the sewers depends entirely on the unreliable rain pipes, while the soil pipe has only one outlet into the air, that at the upper end. 4. In the fourth system there are two house pipes one for the kitchens and sinks and the other of the closets. One of these is located near a chimney, so that its temperature is sufficiently above that of the other to maintain a good current of air through both. Dead ends are to be carefully avoided in this .system. In the diagram the rain pipe is disconnected by a trap, as should be always done when its upper end is near a roof window. 5. In this system the rain pipe serves as an air inlet to the house pipes, and a special ventilator is attached to the front of the houses, as indicated by the dotted lines. 6. Since the rain pipe is unreliable in its action, the last men- tioned system is frequently replaced by the construction shown in diagram 6, in which a special pipe, opening into a court or under a flight of steps, furnishes a constant supply of air. The points x and y should be some distance apart, the farther the bet- ter. When the direction of the current is contrary to that indi- cated by the arrows, z must be some distance from the house, and the uncertainty as to the direction of this current has led to the introduction of the next system. 7. Here the ventilating pipe is carried up through the house to the roof and a fairly constant circulation is assured by placing one of the pipes near a chimney. This plan has' the advantage of removing the gases of a house in the quickest way. In the dia- gram it will be noticed that the same plan is followed outside the ' ' o 86 HOUSE CONNECTIONS. house as inside, and the ventilation of the whole system is certain, as no reliance is placed on the action of the rain pipe. This sys- tem, or the last one, is required in Cologne, with the addition of a secondary ventilating pipe, similar to that shown in diagram 2, when the soil pipe connects with more than two stories. From the preceding paragraphs it will be noticed that the disconnecting system leads to considerable multiplication of pipes when it is desired to secure as perfect a ventilation as can be ob- tained by the second system outlined above. The additional security against sewer air is costly, too costly according to German ideas. In America much stress is laid on the interception thus obtained of " unsuitable " bodies before they reach the sewers, FIG. 106. FIG. 107. but the retention of such bodies near or in a house is more apt to be disagreeable than otherwise. If it is not desirable to attach the long pipe shown in diagram 7 to the front of a building, there is always a danger of the water seal between the house, and the sewer being blown out and the effect of the disconnecting trap thus lost. This has led to the following system: 8. In diagram 8 it will be seen that a large pipe is placed just beyond the disconnecting trap. This is shown on a larger scale in Fig. 106, and consists of either a masonry or pipe shaft. If the water seal is blown out, the sewer air will escape rather through this shaft than by the narrow soil pipes. In this way, also, a constant supply of air enters the soil pipes and aids the circula- tion in the house. This plan is adopted in Linz, where the shafts are of masonry and the sewer pipe sealed by a flap which can be turned back for cleaning, as shown in Fig. 106 a. These shafts are usually located in courts. 9 and 10. In still another system, shown in diagram 9, Fig, VENTILATION. 87 104, there are two disconnecting traps near each jother, with a ventilator between the two, which allows the gases to escape when either seal is broken, usually the outer. If the two traps are placed outside a house the construction shown in Fig. 107 may be employed, which also serves for collecting surface rain water. The short open stretch through which the sewage flows is unim- portant if there is no tendency to form deposits in the shaft. A FIG. 109. FIG. 111. modification of the same arrangement may be adopted within a building, as shown in diagram 10, and then necessitates two ventilating pipes, as in the seventh system. The two adjacent traps can be formed by a single casting, as shown in Fig. 108. The tongue on the side next the street is not so long as the other, in order that the seal beneath it may be the first to give away. In general it may be claimed that the last systems are too re- fined for the purposes to which they are adapted, and even if all the seals are destroyed the results would not be so extremely bad, 88 SEWER VENTILATION. for the traps for each individual house connection would still re- main intact, and could not be injured if the inside piping is ar- ranged as in the second diagram. As regards the details of the water traps before mentioned, it will be seen from Fig. 109 that the angular form a causes deposits- which leave a curved channel for the sewage. This curved chan- nel is usually followed in making the bends or knees shown in I c, Fig. 109. It is always best to leave an opening in the pipe for cleaning, as in c, d, and e. The forms d and e are especially suited for systems 4-10, in which a vertical pipe for either water or air i& connected just behind the water seal. In e there are two openings- for cleaning the adjacent connections. The ventilating shafts already mentioned as being located over the street sewers are placed every 100 to 350 ft. They are espe- cially suited for dead ends and for the- arched construction shown in Figs. 32 and 37. Manholes and lampholes are adapted for this use ; and where they are not properly spaced for the purpose, special ventilating" shafts similar to those shown in Fig. 36 are necessary. The construction shown in Figs. 28 and 31 allows all the dirt from the- streets to fall into the sewers and should be modified in some manner so that the sewage may be kept fairly free from sand and leaves. In the Berlin manholes, Fig. 30, the cover is pierced with holes near the circumference, and a plate, with a hole in the center, is. fixed a short distance below this cover. In America the arrange- ment shown in Figs. 29 and 98 is employed. Here the holes are- in the center of the cover, and a pan is suspended in the center of the shaft. It is sometimes the practice to close the manhole tightly and rely for ventilation on a special ventilating chamber constructed as shown in Fig. 110. In this chamber the sand and leaves are retained while the water drains away unchecked. Where small pipe ventilators are used, the same results are ob- tained by the arrangement's shown in Figs. Ill and 112, the first being a German and the second an American model. In the lat- ter form, the water entering through the grating is allowed to set- tle into the ground. It is occasionally deemed necessary to disinfect the sewer air FIG. 112. VENTILATION. gg t before allowing it to escape. This is usually done by passing it through charcoal. The best device of this nature is that em- ployed by KAWLINSOX and shown in Fig. 110. It consists of a layer of charcoal held between two wire screens. The water entering the ventilator, filters through a layer of sand, and then runs into the shaft through a drain indicated by dotted lines. Generally such screens are little used, not only on account of the check they produce in the ventilation, but als.o from the fact that the great dilution of the sewer air as it enters the open air prac- tically removes all danger. There are two other peculiar methods of producing currents which require notice. One is the building of tall chimneys at the highest points of a system, through which the sewer air may escape. There are two such in Frankfurt. They are not heated, and on that account their action is of ten doubtful. Their dimen- sions are difficult to calculate so that the currents will be of proper velocity and the chimneys of manufacturing establishments would produce a much stronger current. In every case their influence will only extend to the nearest opening in the system, and their value is therefore much restricted. Mechanical ventilation has been tried with good results in London. The sewer to be ventilated is open to the air at one end, and is furnished with a suction device driven by the wind. The other end may be low or high, provided only that there is free access to the air. The direction in which the current moves is immaterial. A large sewerage net must be subdivided into a number of small sections where this system is used. In this way the air in the London sewers is renewed 46 times daily. Such a device could be used to increase the circulation in houses cut off by a disconnecting trap, as in systems 4-10, Fig. 104. See note, page 284. CHAPTER XL EFFECTS OF SUBSOIL WATER. Where the regulator relief outlets of a sewerage system lie be- low the high-water level of the receiver of the sewage, some sort of a gate or valve must be used. The outlets can be left open and the water allowed to back up in the sewers only in places where the system is placed so far below the surface that the effects of the back water are limited to a small area, for otherwise extensive de- FIG. 113. OUTLET AT DANZIG. posits, difficult to remove, would be formed. A common con- struction is an automatic door or gate, Fig. 113, so balanced that a, slight excess of pressure on either side is sufficient to move it. For larger sections the flap should be suspended by links, Fig. 114, and provided with a chain for opening the sewer in case of an accident. The great defect of these gates is their imperfect contact with their seats, allowing a constant leakage and prevent- ing the sewage, when it does escape, from doing so with enough velocity to sweep away the sediment. Hence in large sewerage systems, where a slight increase in the labor expenses is com- paratively unimportant, it is much better practice to employ slid- ing gates, similiar to those illustrated in Chapter IX. Occasionally both swinging and sliding gates are employed, the latter being used in case the former fail to work. Those relief outlets of the Ham- EFFECTS OF SUBSOIL WATER. 91 FIG. 114. burg system that discharge into navigable waters* are protected from inflowing water by swinging gates, Fig. 114#, which open automatically as soon as the sewage has attained a sufficient depth. Moreover, many of these out- lets are provided with sliding gates, as shown in the cut, which are useful in flushing. Such a plan has been followed in designing the outlet of the trunk sewer in Hamburg, Fig. 115. While a short length of the outfall remains open to high water, some distance from the outlet two sets of gates effectually shut off the system from the inrush of water during unusually high tides. One set of gates is arranged on the same plan as canal locks, the others are sliding gates. All are operated by hand. Moreover, needle weirs can be used if necessary, somewhat after the plan shown in Fig. 45. Cut-off valves are also necessary for house connections to sewers liable to be filled during floods, which serve as reservoirs a part of the time, or are so small in section that adequate provision has not been made for unusually large rainfalls, or are so near the sur- face of the ground that the house connections must enter at the side and not the crown. The valves are usually placed in cellars, but sometimes outside of the houses. They are gener- ally automatic, because it is not possible to trust the watchfulness of the householders. The devices are either hinged doors or balls. The first are illustrated in Fig. 116, showing an easily moved flap, opened by the outflowing sewage Fm ' 1U -- RELIBF UTLKT AT HAMBURG. but closed by any back water. A cover is provided for clean- ing purposes. Another somewhat similar valve, Fig. 117, is MAIN OUTLET AT HAMBURG. EFFECTS OF SUBSOIL WATER. 93 used in Breslau. It is provided with a tongue, e, f cts _ _ 9 Concrete sewers made in place cost, exclusive of excavation, from $7.50 to $9.60 per cu. yd. in Mannheim, $6.90 to $8.40 in Stutt- gart ; in Zurich the average cost was $8.60, and in Bern $9.20. The excavation and filling comes to from 47 to 75 cents per cu. yd. 3. Cost per lineal foot of completed sewers, including ex- cavation and similar work, but excluding manholes and inlets : TABLE V. COST OF SEWER CONSTRUCTION. o5 Clay pipe or Eggshaped brick sewers. Cement or concrete. C | , G 1 . S-, i tc f \ i 3 d 5 Ja s ej ~ bj) 1 a & \ = Emden. XS B I J3 1 ,d o a h S y 1 P 2 jj ^ e8 C ffl M z : > << ^ H 5 N ( 8 9 1 06 83 1.29 1.14 .45- .61 1.82 1.52 3 "3 OD > fc, . -, S 3 J " *|S *.$ || 1 g , Q 3*1 ! 1 fc fi o ^ Basel Rhine.. 70000 08 13600 18754 3 54 fifi ^SQ Brunswick. . .. Ocker... 84,000 0.2 03 35 35 Breslau Oder 300000 1 03 706 212 2 30 '. AA Budapest Danube... 420,000 1 008 24,730 5 085 3 28 16 679 Dresden Elbe >5, both provided with outlets. The total quantity then passes Longitudinal Section. 1,500 1.500 Transverse Sections. FIG. 134. SECTIONS OP THE CLEARING BASINS. through a sand pit with a velocity of 2 ins. a second, then under a plank projecting into the sewage to a sufficient depth to inter- cept all floating matter, and finally passes through gratings into the mixing channel, where it receives its proper charge of lime and alumina from pipes leading to the machine-house. From the mixing channel the sewage passes into the delivery channel, where the velocity sinks to 1.2 in., and large quantities of sludge collect, which are removed by traveling bucket dredges, without interfering with the working of the tanks. The sewage enters the tanks proper through 2 submerged openings. The depth of water 134 FRANKFURT PRECIPITATING TANKS. at the entrance is 6J ft., and 10 ft. at the outlet ; the velocity of the current is from | to of an inch. The currents are very sensitive to changes in temperature at different depths, and on that account the sewage is drawn off from the lower layers in summer and the upper in winter. In this way the sewage that has remained the longest in the tanks is first drawn off, an im- mersion plate being used to regulate the depth from which the discharge takes place. There is only 1.3 in. of water over the weirs which separate the tanks from the outfall chamber, which dis- charges into the main river. During high water in the river the outfall sewer is closed, and the purified effluent removed by pumps. The 4 tanks shown in the cuts were calculated to dis- pose of a normal dry-weather sewage of about 4,760,000 gals, daily, or 31.7 gals, per capita. Each tank has a capacity of 291, 000 gals., about a fourth of the quantity which passes through it daily. The average amount of sewage treated daily is 7,136,000 gals ; the maximum amount is 9,515,000 gals. When such quantities of sewage pass through the works, the velocity is natu- rally greater than when the dry- weather flow is taking place. The relief outlets prevent the precipitation process from being hurried too much. The tanks are cleaned by drawing off the water to the level of the bottom of the outfall chamber, through gates at different depths (see Fig. 134, Z), which empty into a drain below the chamber. Whenever the effluent is at all turbid the gates are closed, and in this manner all the sludge is collected in the tanks, from which it is pumped. It is sometimes necessary to shove? the heavier parts away. There are also a number of openings in the arches over the tanks, through which .the sludge may be removed by bucket dredges. The plant at Wiesbaden, Fig. 135, is a transition type between the system just described and the upright tanks to be explained later on. It was designed on tne basis of a dry-weather sewage of about 1.718,000 gals, daily, and has 3 settling basins of 178,400 gals, capacity each, 2 of which are generally in use and the other being cleaned. Hence, the duration of the water in the settling tanks is 2 x 178,400 x 24 -~ 1,718,000 = 5 hours, corre- sponding to a velocity of only a sixth of an inch a second. At present the velocity is generally greater, since the sewerage system still contains a number of brooks, and the amount of discharge to PRECIPITATING TANKS. be treated is about 6,343,000 gals. The sewage 9 first passes under immersion plates and through gratings into a delivery channel, from which it flows into the preliminary tanks, through mixing channels where the chemicals are added in the manner shown in Fig. 127. In these preliminary tanks the sewage is obliged to rise twice (see Fig. 135), and is thus freed from much of the sludge present. Finally it passes through 3 submerged gates into the tanks, from which it flows over 2 small weirs into the outfall channel. The sludge is pumped from the preliminary tanks without shutting them off. This is done by means of a suction hose leading to a stationary pumping plant. The main 138 UPRIGHT PRECIPITATING TAXKS. tanks are cleaned by draining the water into a special outfall sewer for the purpose, and then removing the sludge by a suction pipe from the pumps. All flat basins are open to the objection that the sludge may ferment and the gases thus given off will rise and prevent the desired precipitation, even infecting the air at times. This ac- tion would also diminish the effect of the chemicals added ; and it is therefore best to remove the sludge soon after its precipita- tion, without interrupting the flow of the sewage, if possible. Moreover, the extensive area of the tanks should be covered, to- FIG. 136. PRECIPITATION TANKS IN HALLE, MUELLER NAHN SEN SYSTEM. FIG. 137. UPRIGHT TANKS, ROECKNER- ROTHE SYSTEM. prevent the injurious effects of changes in the weather. This is expensive, however, as is also the removal of a large stratum of sludge ; and on that ground the following system is to be preferred : 3. Upright Precipitating Tanks. One of the leading systems using these tanks is the MUELLER-NAHNSEN, operated in Halle. The plant in this town is designed to treat a daily sewage of 800,000 gals., although at present the quantity is less than a third of this amount. It consists of 2 tanks, Fig. J36, shaped like wells, and provided with a by-pass to be used during repairs or ex- PRECIPITATING TANKS. 137 ceptionally heavy storms. The sewage passes through a sand pit and mixing channel into the tanks by an opening embracing a third of the circumference. It then rises and finally escapes through a number of separate channels into the outfall. During the rise of 9| ft. the sludge is precipitated and collected in the bot- tom, whence it is removed by suction pipes. The same process is then gone through with in the second tank, and the finer parts of the precipitate collected, although a single larger tank would probably suffice for the whole operation. In another MUELLER- NAHNSEN plant in Ottensen the bottoms of the tanks are conical, as shown by the dotted lines in Fig. 136, in order to better collect the sludge about the suction pipe. In this plant the inlet and outlet are simply 2 openings diametrically opposite, although not on the same level. This arrangement did not give a good circula- tion, and in a recent plant in Halle the effluent escapes from around the whole upper rim. The RoECKXER-RoTHE system was tested experimentally in Essen, and finally permanently adopted. The apparatus, Fig. 137, consists of a conical well, in which the bottom of an iron chamber, or bell, is held by means of suitable beams. The sewage flows into the well through an iron pipe after being mixed with the charge of chemicals. A skeleton frame of iron rods, arranged like an umbrella, causes the sewage to become thoroughly mixed with chemicals before it rises to the top of the bell, whence it flows into an iron outfall pipe leading to an open drain. The motion of the sewage in the bell and outfall pipe is entirely automatic, being due to the slight difference in elevation between the water level in the inlet and outlet drains caused by the friction of the apparatus. In order to start the siphon, a small tube is attached to a pipe at the top of the bell and the air above the water removed by a small air pump. This pump is also operated a short time each day, in order to remove the gas that collects. The particles of sludge are precipitated on the iron frame and at the bottom of the well, where they enter a suction pipe and are thus removed. A small pipe leads from the upper level of the water in the bell to a waste channel, and is used to remove the globules of fatty matter which collect on the surface. The plan of the Essen plant is shown in Fig. 138, from which it will be seen that the sewage passes through a grating, sand pit, and salmonway before entering the precipitating tanks, 4 138 ROECKXER-ROTHE SYSTEM. in number. The spaces marked y receive the effluent from the grease drains, and the chemicals are added at x. With a maximum daily sewage of 636,000 cu. ft., and all the tanks in operation, the sewage will pass upward through the bells at a velocity of about 0.16 in. a second, and will remain in the tanks about 40 minutes. The average daily flow is only about 459,- 000 cu. ft., while the sewage takes 55 minutes to pass through the tanks and has a velocity of only 0. 12 in. a second. Experi- vT FIG (J ,. 139. p\ - T\ f \ f \ mm f _d f i t 1 1 FIG. 138. PLAN OF PURIFICATION WORKS AT ESSEN. FIG. 140. ments show that a velocity of 0.23 in. is allowable. On clear days, when the sewage may sink to 423,000 cu. ft., one of the tanks can be cut off and repaired if necessary. A similar plant is in use in Brunswick, where 2 tanks like those shown in Fig. 137 are employed to treat daily 17,650 cu. ft. of sewage containing excrement. The appliances are of sufficient size to treat 158,900 cu. ft., which will be eventually supplied by the sewerage system under construction. Cologne is also experiment- PRECIPITATING TANKS. 139 Ing with a similar plant. The good results so far attained by the .apparatus are to be ascribed to the very slow velocity of the cur- rent in the tanks and bells. A siphon may be started by pouring in water, as well as by drawing out air, at its highest point. Advantage has been taken of this fact by SAGAS- SER in designing tank shown in Fig. 139. This consists of 2 concentric cylinders .and 2 pipes. The ap- paratus is filled with water by closing the cocks, y, v, and z, and opening x. After- ward, when y and z are again opened, a con- stant stream flows from the inlet chan- nel, at y, to the out- fall drain, at z. In order to remove the sludge or clean the tanks, y and z are closed and x and v opened. Although the SECTION ON a-b. SECTION 'Marl FIG. 141. PRECIPITATION TANKS, DORTMUND. apparatus is quite compact, it is possible that with large dimen- sions the circulation would not be perfectly satisfactory. 'In this 140 PRECIPITATING TASKS. respect an improved form invented by PICHLER and SEDLACECK T Fig. 140, would probably be more satisfactory, since there are a large number of ascending and descending currents,, caused by a series of concentric cylinders closed below by conical bottoms, as shown. The sewage enters and leaves the tank at the top while the sludge escapes through a pipe at the bottom. The last 2 devices are possibly not suited for the large quantities of sewage which are furnished by cities, but their con- struction is interesting as containing many points of similarity with one of the latest German precipitation plants, that at Dort- mund. This is calculated for a daily maximum of 706,000 cu. ft. during storms, 264,000 cu. ft. during dry weather, and a maxi- mum discharge of 4.6 cu. ft. per second. The average annual flow per second may be assumed to be about 7 cu. ft. Four tanks similar to those shown in Fig. 141 are employed ; they are shaped like wells, with a conical bottom, and are driven through quick- sand to a firm stratum of marl. The circulation is kept up by hy- drostatic pressure alone. The suction sludge pipe passes through an axis of the wheel, as shown. It is surmounted by the inlet pipe and reaches down to the base of the conical portion. The sewage flows from the bottom of this inlet pipe through a set of radiating channels open at the bottom, which insure a good circulation in the tank. Experiments are still being made to determine the most suitable form for these arms. A filter is placed just below the outlet drains, and in this way the light, floating particles are retained. The calculated maximum velocity in the tank is 0.08 in. per second, while the average is fixed at about 0.06 in. As com- pared with the MUELLER-N^AHXSEX system, it is more compact, and there will probably be a more uniform circulation ; compared with the RoECKXER-RoTHE system it is less expensive and more simple, although the removal of the sludge offers greater difficul- ties. The intention is to remove this sludge by means of tight vessels from which the air has been exhausted. On connecting the sludge pipe with one of these, it is hoped that the sludge will be forced into the vessel by atmospheric pressure. A combination of this system with some of the features of the ROECKNER-ROTHE plan has been proposed but not yet tested. In general, it is safe to say that with our present knowledge the nature of the ground on which the plant is to be built will largely determine the nature of the system to be adopted. PRECIPITATING TANKS. 141 t The 3 classes of precipitation works described have not as yet furnished any large amount of data by which their respect- ive merits may be judged. In each of them a suitable quantity of chemicals will produce satisfactory results. In order to compare the cost of treating by the different systems, extensive experiments on equal quantities of the same sewage must be conducted for some time. Theoretically and experimentally, intermittent pre- cipitation offers many advantages 011 account of the complete rest of sewage in the tanks. Experiments seem to show that this method is preferable to the continuous treatment, however slow it may be. In Bradford it has been noticed that particles settled at the rate of about 2 .36 ins. a minute in the intermittent tanks. If there had been the usual current of upright or continuous tanks, little settlement could have taken place. Upright tanks are undoubtedly the most unsuitable in this respect, since the current directly opposes the falling matter, and the tanks themselves are of comparatively small size. Complete quiet and plenty of time are necessary for complete chemical precipitation, and the intermittent treatment seems best adapted to these requirements, especially on financial grounds. Since the proper method of disposal is to be settled, not only on chemical grounds, but also with reference to local conditions and cost of plant, the following facts must be borne in rnind: 1. Level tanks for intermittent precipitation require much space and a considerable difference in elevation between inlet and out- let channels. 2. Level tanks, with continuous precipitation, also occupy considerable space, but do not require any grade within the plant. 3. Upright tanks require little room or grade. The latter are therefore to be preferred within city limits, where the cost of the land is considerable. The first class are unsuited for cities with a level surface, since the pumping that would be nec- essary is expensive. The regular and practically continuous removal of the sludge in the upright tanks necessitates but little space in which it may collect, and insures a freedom from the injurious effects upon the effluent which long-standing deposits may cause. The sludge is also better adapted for handling while in a fresh condition. The intermittent tanks come next in this respect, especially if they are cleaned every day. The continuous tanks rank last as regards the treatment of the sludge, which, in them, is liable to decay, become offensive, and injure the purity of the effluent. CHAPTER IV. RESULTS AXD COST OF PURIFICATION. The results of purification are to be determined by the appear- ance of the effluent, by chemical analyses, and by examinations of the bacteria; all three methods are necessary to arrive at a correct decision, and any one, by itself, may lead to wrong conclusions. The effluent may be clear and free from disease germs, but con- tain dissolved matter which is subject to change as soon as new bacteria are absorbed from the air. On the other hand, a turbid effluent may be harmless so long as none of the matter decays, and a chemically pure water swarming with bacteria may have no bad properties as long as the animalculas are 'of an innocuous character. A great number of chemical and microscopical investigations have been made of both ordinary and purified river water in the English and German places where purification has been tested or adopted. The mass of data thus given is of little value in obtain- ing a clear idea of the actual advantages of the different methods and apparatus for purification, since climatic, local, and other attendant influences are so varied. On that account only a gen- eral summary of the results will be given. English experiments show that in simple mechanical precipi- tation, from 60 to 80 per cent, of the suspended matter, organic and inorganic, is thrown down. Where a preliminary purification is conducted by gratings and the sewage remains some time in large basins, as in Frankfurt, the results are better and even equal to those obtained by chemical means. There may be some quite light organic matter in the sewage, and this will oniy be pre- cipitated by adding chemicals. In general, from 75 to 100 per cent, of the suspended matter may be precipitated by both pro- cesses; where this is not the case, either the time of settling or the chemical action is too weak. Of dissolved matter, from 30 to 60 per cent., both organic and inorganic, may be precipitated by chemical treatment. But it is not unusual to meet with an increase of both classes, and the RKSULTS AND COST OF PURIFICATION. 143 sewage will sometimes contain, after the addition dt chemicals, 25 per cent, more matter liable to decay than originally. This may be partly owing to the excess of lime in the charge having caused some of the suspended matter to become dissolved, and partly to the decay of the precipitated sludge. An increase in the amount of dissolved inorganic matter is of little consequence, and indeed is welcome, up to a certain degree, when due to lime, which is a disinfectant. The clarifying material used up to the present time is not able to work surely on all the dissolved matter. A reagent for ammonia is specially needed, for the best methods now in vogue will only act upon about 20 per cent, of the quan- tity present. The dissolved potash also remains unaffected, which is not of consequence so long as the water- course itself, into which the effluent flows, contains mineral matter. Phosphoric acid is almost entirely removed, and the nitrogen is reduced about a third in quantity, occasionally as much as 60 per cent. The experiments in Frankfurt apparently show that by using large settling tanks, especially long ones, almost as good results may be obtained by mechanical means as by chemical treatment in smaller tanks. The bacteria are naturally only affected by chemical precipita- tion.* In this way the greater part may be removed; in Wiesbaden 70 per cent., in other places as high as 90 per cent., and there is no doubt that all can be eliminated with a sufficient charge of chemicals and enough time for complete precipitation. Accord- ing to KOCH and investigations in Cologne, lime is the only disin- fectant; while in other places this material has not given so good results. Experiment shows that both sludge and effluent are purified, and both remain free from germs .so long as free lime is present. It is a question, however, how long the development of bacteria is hindered by this means, since the lime absorbs carbonic dioxide from the air and changes to calcium carbonate. More- over, the combinations of lime and fatty acids are not stable, and the lime in them also changes into a carbonate. The organic mat- ter set free is liable to subsequent fermentation, both in the water and in the sludge, by absorbing bacteria from the air. If this could be prevented until the effluent enters the water-course, all requirements would be fulfilled, since the dilution then brought about would reduce the action of the bacteria, and the resulting products would be widely scattered. * Simple sedimentation will undoubtedly carry down mary bacteria. 144 RESULTS OF PURIFICATION. If a charge of chemicals sufficient to kill all bacteria were added, then the purpose of sewage purification, i. e., the preserva- tion of the harmless character of water-courses, would not be ful- filled, since the chemicals added would, practically poison the water, besides greatly increasing the expense of the treatment. On this account the addition of strong disinfectants, such as carbolic acid, zinc chloride, copper sulphate, or large quantities of quicklime, is by no means to be recommended. In short, it is only a best possible, not ideal best, method which should be sought out. Looking at the matter from this standpoint, which is that of the German Association for Public Sanitation, many persons claim that sewage is sufficiently purified when it appears clear to the eye, at the outside, when the bacteria are destroyed, and main- tain that the precipitation of dissolved matter is not necessary, since it is never complete and is less important. The clarification, which insures subsequent freedom from sediment, hardly requires the use of chemicals for ordinary sewage, but may usually be ob- tained by careful mechanical treatment. Chemicals are necessary to destroy the bacteria. Among those now in use, the cheapest, lime, is fortunately the best and possibly the only substance. Since the mechanical and chemical treatments are carried out in the same way, it is possible to use the former during the ordinary condition of the sewage and water-course, reserving the latter for unusual occasions, such as low water or epidemics. The presence of factory sewage, or some similar outside addition to domestic sewage, may render the constant use of chemicals necessary, and the sludge may also require such an addition. The sludge in settling tanks must be sufficiently wet to be re- moved by suction pipes", since a firmer consistency greatly increases the cost of handling. Generally, in flat basins about 90 percent, of water and 10 per cent, of solids will be a good proportion, while in upright tanks sludge with only 65 to 80 per cent, of water can be pumped away. From the quantity of chemicals and suspended matter it is easy to calculate the theoretical amount of sludge which will be precipitated, but such calculations are not sure. English investigations show that from every gallon of sewage con- taining excrement about 2.3 cu. ins. of sludge will be deposited in the above liquid condition, while in Essen only 0.9 cu. in. is precipitated from the sewage without excrement. The proper RESULTS AND COST OF PURIFICATION. 145 size of intermittent settling tanks can be easily calculated. Sup- pose, for instance, the tank shown in Fig. 128 requires 3 hours to be filled, and 3 days elapse between the successive removals of the sludge. Let there be a capacity of 8,829 cu. ft. above the outlet. Then the sludge basin must have a capacity of 24 x 8,829 x 00.01 = 2,119 cu. ft. if the sewage deposits 1 per cent, of solid matter. The sludge may or may not have a disagreeable odor, depending largely on the nature of the process used. It is certainly possible by suitable chemicals to have a practically odorless sediment, as the RoECKNEii-RoTHE process has shown, but it is not always best to go to extra expense for such a purpose. Generally the sludge has an extremely offensive odor, which is dissipated but slowly. The sludge is disposed of by numerous methods, and a choice between them is to be made according to local circumstances. They may be divided as follows . 1. Removal from the settling or receiving tanks by pumps or pneumatic methods to vats in which the sludge is carried to the fields for fertilizing purposes. 2. Deposition in sludge basins 1 to 5 ft. deep, formed by puddled or masonry walls, arid suitably drained. The sludge flows into these generally through open channels, and loses by evaporation and drainage in 1 week 30 per cent., in 3 weeks 50 per cent, of its water, becomes firm, and has only a slight odor Finally it is removed to fields. 3. Drying on loose soil, and then plowing, as soon as possible, iuto the ground where it lies. 4. .Removal of the water either mechanically or by a gravel filter. 5. Concentration by a filter-press until 50 per cent, of the water has escaped ; the product used as a fertilizer. 6. Removal of 80 to 90 per cent, of the water by a vacuum process or by evaporation, leaving a powder. 7. Reduction to a powdei*, as in 6, but with the addition of ground bone> ammonium sulphate, or a similar substance, in order to obtain a better fertilizer. 8. Burning in a suitable furnace after a preliminary drying. The ashes are fertilizing in character. 9. Mixing the sludge of the lime process with clay to form cement ; the Scott process. 10. Mixing with clay to form bricks, which are of very ordinary quality when lime precipitation has been employed. 10 146 DISPOSAL OF SLUDGE. 11. Mixing with combustible, and if possible disinfecting- substances to form briquettes for burning. Peat, tan bark, and tar are suitable additions. 12. Mixing the partially dried sludge with earth and rubbish to form compost heaps. Vegetable mold, marl, gypsum, and sweepings may be used. Since the house and street sweepings have a greater bulk than the sludge from sewage, the treatment of the latter is a subordinate and easy matter as long as there are- suitable regulations governing the disposal of the rubbish of a city. In this process the presence of lime in the sludge is advanta- geous. The simple agricultural disposal of the sludge by methods l r 2, 3, and 12 offers many advantages. The third method is espe- cially economical on account of the absence of transporation ex- penses, since the sludge runs directly to the fields and into a ditch, which will subsequently be coverod by the earth taken from a parallel one during its excavation. The land may receive in thia way a deposit of sludge sufficient to raise it 1 \ ft. After it has stood a year it may be used for raising crops, which will be bene- fited by the fertilizing sludge. The number of years that must elapse before a second layer may be added depends upon the agricultural use of the land; generally 3 will suffice. The gradual increase in elevation of the land is an unavoidable evil, and may be insurmountable in a flat locality. The method mentioned under 1 requires no special plant, while 2 and 3 require but a moderate area. The methods 1 and 12 are commendable on account of the decrease in odor, the great nuisance of sludge disposal. Although a continuous removal of sludge is greatly to be de- sired, it is opposed by the fact that the fields require fertilizing, or are even fit to receive the matter during certain seasons only. Hence a very undesirable accumulation of sludge is formed, which may be avoided by the fifth method, and several secondary advantages obtained at the same time. A filter-press will require but little space, and produces a marketable briquette, possessing little odor and easily handled. The theoretical value of sewage sludge as a fertilizer is not great, since only a part of the organic matter is precipitated. The following table gives a summary of .series of determinations of sewage sludge containing excrement from several English cities RESULTS AND COST OF PURIFICATION. 147 and from Frankfurt. The sludge from English cities was ob- tained by the lime process, while that of Frankfurt was taken from the settling basins already described : COMPOSITION OF SEWAGE, IN PER CENT. England. Frankfurt. Dry. Fluid. Dry. Fluid. Water 7-15 20-40 0.5-1.5 90 2.2-4 0.05-0.16 45-57 3.3 91-94 3.7-4.2 0.2-0.3 Nitrogen The sludge from other German purification works, into which a part of the excrement enters, has been repeatedly analyzed. In a dry condition it contains from 17 to 37 per cent, organic matter, 0.7-1.5 per cent, nitrogen, and 0.8-2.5 per cent, phosphoric acid. The presence of lime is unnecessary, except where the soil to be fertilized is very poor. Theoretical calculations of the value of the sludge are of no sig- nificance, since the relations of supply and demand decide that subject, and the actual net proceeds are very different in the various plants. In several purification works the accumulation of heaps of sludge has caused much trouble, and in the majority of cases the directors are usually glad to have the sludge itself, or even the products made from it, removed without cost to- themselves. In Wiesbaden, Essen, and Frankfurt the municipal authorities have begun to use it on the public property, in order to encourage private parties. In Dortmund the sludge, treated by the second method and containing some lime, is sold at from 12 to 19 cts. per cu. yd., being valuable as a fertilizer on account of the extremely poor soil in the vicinity. In Halle, where the fifth method of treatment is employed, the sludge con- taining about 50 per cent, of water, is worth about 50 cts. a ton at the works. In chemical clarification the precipitants form the chief item of expense. Since the amount of these varies considerably and is not to be determined beforehand with any accuracy, it is best to base the calculations on the quantity of carrying water and a cer- tain fraction of the annual rainfall, which under favorable circum- 148 COST OF CHEMICAL PRECIPITATION. stances, such as concentrated rains and numerous relief outlets, may reduce to almost nothing. From data running back for several years, obtained by examining the records of 7 English plants, it is possible to form some idea of the operating expenses of such works. It has been found that it costs from 47 cts.' to $1.70 to treat 100,000 galls, of the total sewage, some of which is not, however, actually passed through the works. This corresponds to from 10 to 35 cts. per cap- ita annually. If these figures are increased by an amount corre- sponding to the interest and depreciation on the plant, they become 94 cts. to $2. 35, 1 7 to 45 cts., respectively. The Coventry process has been the most expensive. TABLE VIII. APPROXIMATE COST OP CHEMICAL PRECIPITATION IN GERMANY. Frankfurt. Wiesbaden. Halle. Essen. No. of residents which the plants serve 150 COO 60 000 10 000 68 000 Cost of plant, total i 187,500 50,000 8 700 57 000 Ditto, per capita ..$ 1.25 083 088 83 Annual running expenses. . . $ 35,000 8,250 1 650 7 250 Ditto, per capita .. $ 024 14 1*5 11 Ditto including interest . $ 031 19 22 16 Average daily sewage cu. ft. 950.000 22,900 31.700 457,0'JO Ditto, per capita cu. ft. 6.3 3.9 0.3 6.7 Running expenses.per 100 cu. ft., cts 1.0 1.0 1.4 0.4 Ditto, including interest ...cts. 1.3 1.3 1.8 0.6 Some of the experimental results obtained in German cities are interesting. In the ROECKNER-ROTHE apparatus tested at Essen the separate .items of cost for treating 100 cu. ft. of sewage were : Chemicals, 0. 7 ct. ; labor and power, 0. 5 ct. ; interest and repairs, 0.2 ct.; total, 1.4 cts. The operating expenses of the MUELLER-NAHNSEN system in Halle were variously stated to be from 1.8 to 3.8 cts. per 100 cu. ft, of which amount about 2.1 cts. represent the cost of the chemicals. The price received from the sludge, 0.1 or 0.2 ct., must be deducted, and 0.4 ct. added for interest. In the comparative table above, it is to be noted that $20,000 of the Frankfurt expenditure was paid for land, and $35,000 in Wiesbaden went for a mill for supplying power. The small expense for operating in Essen is due to the extremely diluted condition of the sewage and the absence of excrement, found in the sewage of the other three cities. In other cases, the ROECKNER-ROTHE system may be dearer; in Bruns- RESULTS AND COST OF PURIFICATION. 149 wick,, for example, the annual operating expenses for each resident are 40 cts. and 3 cts. per 100 cu. ft. Since German experiments in this direction are still very few, it is to be hoped that more extended data will be found to give diminished expenses. The experiments so far made public give no means for deciding upon the relative value of the different systems now in the market. CHAPTER V. AERATION. Since it is not possible to remove by precipitation more than a small part of the organic matter dissolved in water, a process by which ne'arly all could be removed after the water was otherwise purified would be welcome. This may be accomplished by forc- ing currents of air into the stream. The more oxygen there is present in the water the greater will be the reduction of the organic substances to carbonic dioxide and other compounds by the bacteria, as already explained in the chapter on the self-purifi- cation of rivers. This aeration may be accomplished in several ways. Merely forcing currents of air against the surface of water has not been successful. Better results are obtained by agitating the water by hand, or with revolving wheels provided with floats or arms, but such methods are not possible with large quantities. The air may be blown into the water through a number of openings in a pipe, either by a blowing engine or an injector, Fig. 127. KOERTING has proposed an automatic aerator through which the water flows and absorbs air by its own motion; compare Fig. 184. The best plan with large quantities would probably be to separate the whole mass into as fine subdivisions as possible. In several English cities the effluent from the purification works flows in extremely shallow streams over weirs; in Sheffield the surface of the effluent spillway is 904 sq. ft. The same end can be accomplished by large sieves, which have been used in the precipitation works designed by Professor KoENiGat the starch-factories in Salzuflen, where the average daily effluent is 52,900 cu. ft. The apparatus has been installed for experimental purposes, and its continued use or improvement will depend upon the results attained. The water is allowed to escape along the entire length of a wooden channel to a wire sieve having an undulating surface. Professor KOEXIG'S investigations with this apparatus show that the decaying and other organic matter is oxidized, especially the sulphurous acid into sulphuric acid, and the sewage is mixed with a large AERATION. amount of oxygen, which may rise to eight times the original contents, and continue the reduction after the effluent enters the river. Other investigations have shown that the oxygen in the water gradually disappears, while the carbonic acid proportionally increases. It is said that ammonia will sometimes be directly oxidized without the presence of bacteria in certain cases. It is important to remember that the aeration of turbid water will only have a temporary deodorizing effect, and the process should there- fore be only used after the sewage has been clarified. It has been already noted that, in sludge precipitated with an excess of lime, carbonate of lime will be found. An increase in the quantity of inorganic sludge will also tend to increase the organic deposits. Hence the addition of carbon dioxide would be advantageous in some cases. KOENIG has employed furnace smoke for this purpose, and the experiment has been successful in the main in precipitating both lime and organic matter. The smoke -contains not only carbon dioxide, but also small quantities of oxygen and distillation products containing creosote compounds, which check decay. The aeration of sewage by sieves requires a difference in eleva- tion that may necessitate pumping, which is necessary in all the other processes for the same purpose. Whether the resulting ex- penditure is warranted is still undecided. CHAPTER VI. FILTRATION. The sewage of a city is often purified by the process of inter- mittent filtration, in which it is distributed over the upper surface of the ground, passes through from 4 to 6 ft. of filtering mate- rial, and finally flows away through a network of subsoil drains. The filter-bed may consist of earth, sand, clay, pieces of brick, coke, or fine quarry chips. The beds may be only 2 ft. thick in some cases, and the sewage may be forced upward or horizontally through the material. The action of a filter is due partly to a simple mechanical retention of the floating matter, and partly to the oxidation of organic matter by oxygen contained in the interstices of the material, aided by bacteria. The results of the process, especially with earth filters, are very variable. Beside the climatic conditions, the following influences are to be noted : Permeability to Air, preventing decay, insuring oxidation, and allowing carbonic dioxide, a disassociation product from the or- ganic matter, to escape. AVith plenty of air the proper bacteria will be found, while without it those attending putrefaction will be present. According to old English experiments a quantity of sewage not exceeding 2 to 6J per cent, of the volume of the filter bed should pass through it in 24 hours ; FRANKLAND, after com- paring results from a large number of plants, says 2 to 4 per cent. The beds should rest about 3 hours for every 1 of filtration, in order to absorb oxygen from the air. They should also be occa- sionally cleaned and the upper layers renewed. , Permeability to Water. The filtering material must be in- soluble, easily dried, and allow a good circulation of the water. The filtration may be too quick, however, to permit the removal of any appreciable amount of the dissolved organic matter, as during heavy rains or through coarse gravel. The duration of the process in heavy ground may be fifty times that in more porous soil. Absorbing Power. The beds should retain the dissolved organic matter, especially ammonia, but allow the nitrates, resulting from FILTRATION. 153 the oxidation of such compounds, to be washed away.* This process is at the basis of water purification by filtration, especially by charcoal filtration. Pressure on Filter-bed. If a deep body of water covers the filter-bed, the effluent will be diminished by the choking of the interstices with sludge, in spite of the advantage of a large hydro- static pressure. Experiments with a sand-filter in Berlin showed that the effluent under a pressure of 3.27 ft. was from 0.23 to (i. 65 cu. ft. per day per square foot of filtering area. Under a pressure of 1 ft. the effluent was from 1.35 to 3.05 cu. ft. Subsoil Water. Its presence, either from the low position of the land or by capillary action, prevents aeration, and tends to breed the bad species of bacteria. The drainage of a filter-bed should be directed, therefore, to subsoil water as well as sewage. With proper management, all of the suspended and from 70 to 90 per cent, of the dissolved organic matter may be removed. The inorganic matter, on the contrary, will be increased by various carbonates and nitrates. Chlorine passes unchanged through the filter, while from 50 to 90 per cent, of the nitrogen will be re- moved. The animalculge disappear with the organic matter on which they subsist. From the above data it is easy to calculate the dimensions of a iiltration plant, but it is generally more safe to make direct ex- periments in each case. In seven English cities an acre of filter- ing area is allowed for from 400 to 2,800 inhabitants; in other words, 1 acre will suffice for from 2,150,000 to 3,580,000 cu. ft. annually. If an attempt is made to diminish the area of such beds by in- creasing the amount of sewage passing through them, the result is bad, owing to the fact that only the suspended matter will be removed, while the dissolved passes through unaltered or partly converted into ammonia. If the periods of rest are not long enough the same results follow. Other difficulties attending filtra- tion consist of the depreciation in value of the sewage as a fer- tilizer, and the trouble of disposing of the saturated layers of the beds when removed after long use. The use of the land for raising crops only partly remedies these evils. For the above reasons the filtration process has been often given up after trial, especially in England, where it has been much favored. It is now employed in few places, only where an excel- ]54 FILTRATION. lent porous soil can be found which is not of sufficient area fcr irrigation. In a few such plants, other lands in the neighborhood are occasionally allowed to be used as filter beds, while in still other places the beds are used as adjuncts to irrigation fields, in order to be able to treat unusually large quantities of sewage if required. The area considered necessary for intermittent filtra- tion is gradually increasing, and it will soon be somewhat difficult to draw a line of demarcation between filtration and irrigation. The leading English advocate of the system now recommends 1 acre of filter beds for 1,010 inhabitants with the best, and 210 inhabi- tants with the worst, class of ground. BUERKLI bases his calcula- tions on 1,400,000 cu. ft. of sewage per acre annually, and designs his plant in such a manner that each bed is used every third year for intermittent filtration, and is worked as an irrigation field during the other years. The difficulties mentioned above have often led to a prelimi- nary chemical treatment of the crude sewage before it is run through the filters. When the greater part of the suspended matter has been removed, the pores of the ground become less frequently choked, the odor is not so offensive, and the filter beds may be of reduced extent. Their thickness is sometimes only from 1.9 to 3.3 ft., but generally from 4.9 to 5.9 ft., and an English empirical rule for their size is to make them equal to half the volume of crude sewage treated. Intermittent filtra- tion, with 3 hours rest to 1 of action, is the process employed in such cases. In several places river water is filtered through sand for the purpose of obtaining a water supply. In such cases the beds are from 3J- to 6 ft. thick and deliver from 0.33 to 0.59 cu. ft. daily from each square foot of area. The period of rest is generally short. Since sewage is Hot so pure as river water, and the pores of a sewage filter must contain a greater amount of oxygen than a water filter in order that the necessary chemical changes may take place, it may be approximately assumed that the .area of the- former class should be from two to three times that of the latter. The results of combined precipitation and filtration depend naturally upon the duration of the process and size of the plant. Since the latter is usually as small as possible in order to reduce* the expenditure for land, it is not surprising that the effluent is. generally inferior to that from filtration proper alone. In Birming- FILTRATION. ham about 30 per cent, of dissolved organic matter was removed by lime precipitation and 34 per cent, by a subsequent filtration, while 'direct filtration, properly conducted, removes from 80 to 90 per cent., as already stated. A considerable area is always necessary to obtain good results, and the relative cost of land, chemicals, and other items of expenditure govern the employment of preliminary precipitation. The sewage might be made to first pass through filters and afterward be treated chemically, a more rational order, since the mechanical process would remove the greater part of the sus- pended matter, and the charge of chemicals necessary to precipi- tate the dissolved substances would be diminished. The removal of the sludge would be easier, although the filter would collect a relatively greater amount of matter. Fortunately the latter draw- back can be diminished by using horizontal filters, such as have been employed for some years in English cities. Fig. 142 shows the arrangement adopted at Coventry, where masses of sand, held by boards, are used. Dr. PETRI has employed this principle in the purification plant of the prison at Ploetzensee, near Berlin, where 3,500 cu. ft. of FIG. 112. -FILTERS AT domestic sewage are treated daily. The results cannot be definitely stated as yet. A peculiarity of this plant is the use of peat as a filter, which acts not only mechanically, but also as an antiseptic, reducing the amount of chemicals necessary in the charge. The operation of the plant can be easily understood from the diagram shown in Fig. 143. The sewage flows from the channel a into a series of tanks, b, where the preliminary filters of peat are placed. The peat is arranged between walls in such a manner that sections of it may be replaced without interrupting the pro- cess. The sewage flows from these chambers into a collecting channel, c, which empties into a mixing tank, d, where the charge of chemicals is added. PETRI has recommended various chemi- cals, the latest being a mixture of 20 grains of lime and 3 grains of magnesium sulphate to each gallon of sewage. The precipitation or settling basin is at e, through which the sewage constantly flows. Water weeds are allowed to grow here in order to aid in oxidation, as mentioned in the chapter on the self- 156 COMBINED FILTRATION AND PRECIPITATION. purification of rivers. The sewage then passes through a channel, /*, filter, g, and channel, li, arranged like a, 1), and c, into a final filter, t, composed of gravel or coke. The peat in g contains lumps of limestone for absorbing the sulphate of alumina, which might otherwise enter and poison the river. The effluent is thus actually clarified. A grating is placed over the filters, as shown by the dotted line at b. On this rests a thin layer of peat sprinkled with carbolic acid, to counteract the offensive vapors given off by the matter retained in the filters. WJhether such an arrangement is necessary depends naturally on the local circumstances. The dimensions of the plant at Ploetzensee, the only one now in use, are as follows: Average depth of water in a, 1.2 ft. ; length of filter from slope to wall, 10.5 ft ; rate of filtration, horizontally, c d FIG. 113. PRECIPITATION TANKS, PETRI SYSTEM. from 0.13 to 0.22 in. a second. Hence each square foot of ver- tical cross-section delivers about 6 cu. ft. of effluent an hour, much more, owing to the porous peat, than the results with an ordinary sand filter and river water. Moreover, the peat becomes choked less rapidly and requires less aeration. In actual practice the surface is occasionally raked over during the day, and the slope of the filter renewed. Otherwise there is no labor necessary, except a renewal of the peat every 20 or 30 days, when the effluent begins to be turbid. The maximum flow of sewage only occurs a short time each day, and the peat is sufficiently ventilated dur- ing the remainder of the 24 hours. The second filter has only three-fourths the sectional area of the first, and remains in good condition three times as long. The quantity of chemicals employed for each gallon of sewage may be reduced from that already given in the chapter on chemical pre- cipitation on account of the diminished duty demanded in this part of the process. Chemical analyses show that not only the suspended, but also F1LTRA T10N. 1 57 the dissolved, organic matter is almost entirely removed, and of the inorganic matter only 20 per cent., mainly lime and chlorine compounds, remains in the effluent. Extensive experiments must be made before the best dimensions and methods of working are determined. The cost of operating still remains to be ascertained. KNAUFF estimates it at about from 10 to 18 cts. per capita annu- ally, or from 0.7 to 1.4ct. per 100 cu.ft. of domestic sewage, depend- ing largely on the ease with which peat can be obtained. This esti- mate assumes that the filtering material and sludge may be easily removed and the former employed as a fertilizer or fuel. The ability of such a process to treat large quantities of sewage still remains to be demonstrated, as well as its financial relation to other methods. CHAPTER VII. IRRIGATION. Irrigation with sewage on a large scale is a comparatively new branch of agriculture, not yet adapted for all places, and with defects which may be overcome later on. The term " irrigation," when used in connection with sewage, covers a much wider range of problems than the simple watering of a meadow or plain, which is its usual signification. The different plans for disposing of the sewage are as follows : 1. Surface Irrigation. This plan consists in leading the sewage to a long channel, having a square cross-section of about 1 ft., and running along a ridge from which the land slopes away at a grade of one or more per cent. The sewage flows over the dge of this channel along its whole length, and is prevented from collecting in little streams on the slope by a series of shallow ditches running parallel to the main channel and from 35 to 50 ft. apart. Where there are extensive fields to be irrigated in this way, the land is subdivided into areas from 650 to 1,160 ft. long and 200 to 230 ft. wide, down the center of which runs a channel from which the sewage escapes on both sides. 2. Bed Irrigation. In this system the land is subdivided into a number of beds 3 ft, wide and 65 to 100 ft. long by ditches ftbout a foot wide. The sewage passes through the network of ditches and is absorbed by the beds. The sludge that collects in the ditches is occasionally removed and dug into the lands. Before planting it is possible to overflow the beds according to the next method. 3. System of Flooding. In this method of irrigation it is cus- tomary to flood the land with from 10 to 20 ins. of sewage by means of earth walls about 3 ft. high. The liquid part of the sewage percolates through the ground and escapes, leaving the fertilizing portions on the surface. Sometimes the water is allowed to flow away over' the surface, while at other times, espe- cially in winter, the process is repeated until a deposit of sludge as thick as 8 ins. may be formed. Low plants are started after the IRRIGA Tl ON. 159 flooding, while shrubs and trees may be set out at any time, since the presence of the sewage has little effect upon them. It is best to give fields managed in this way for cereal crops a considerable urea ; from 5 to 22 acres have been thus treated in single fields in Berlin. 4. Gerson's System. GERSO^ conducts the sewage to the fields in cast-iron pipes placed below the frost line and about 1,300 ft. apart. These pipes have hydrants every 650 ft. or so, from which the sewage can be discharged, through a galvanized- iron pipe line 4 to 7 ins. in diameter, over the surrounding land. By means of a plow a series of low, temporary walls can be easily formed, between which the sewage is allowed to settle. Various modifications of the general plan are made to suit the require- ments of the different seasons and crops. The advantage of the system lies in the fact that the land is not divided by fixed boundaries. 5. Subsoil Irrigation. This plan consists in conducting the sewage through a brick or cement delivery sewer, from which it passes into a network of tile pipes underlying the whole field. The sewage escapes from the joints of the pipes, usually of 2-in. tile, from 8 to 16 ins. below the surface and 3 to 6 ft. apart. Semi -cylindrical covers over the top of the pipes will prevent their clogging by dirt. The grades should not exceed one per cent., in order that the sewage may be uniformly distributed over the entire area. In all cases it is necessary to provide two sets of pipes, one for the sewage and one for the effluent. Each is a separate network, and may be partly on the surface and partly below it. The sew- age pipes must be higher than the others, and it is therefore occasionally necessary to make artificial slopes. The distance between the sewage and effluent systems should be so chosen that the sewage flows evenly and with sufficient velocity to prevent any accumulations detrimental to the crops. In general the greater the slope the greater may be the distance between the delivery and discharge ditches. Starting out from the pipe lines through which the sewage .is pumped to the irrigation fields, as in Danzig, Berlin, Breslau, and other places, or the simple gravity ditches, similar to those employed in Freiburg, are the series of underground or surface pipes which lead to all parts of the field, gradually decreasing in size toward 160 IRRIGATION. the outer ends. Suitable arrangements of flash boards and gate? control the distribution of the sewage, and facilities for regulating the total quantity delivered to a field should always be provided. In addition to a telegraphic communication with the pumping stations, it is often customary to erect small stand-pipes at the end of the pipe line or highest point of the ditches. These stand- pipes are usually about 20 ins. in diameter and 33 ft. high, pro- vided with a float carrying a flag or other signal by which the condition of the supply can be easily seen at a glance. The tops of these stand-pipes end or connect with a small reservoir, where any overflow may be collected. The effluent is collected by ditches or pipe drains, the choice being governed primarily by the nature of the soil, and in a less degree by the relative cost of construction of the two systems. The drains are from 4 to 6 ft. below the surface, although in the very sandy soil of Berlin they are only a trifle over 3 ft. deep. The action of an irrigation field is threefold : a. The sewage- is mechanically filtered and the suspended matter thus separated. b. The dissolved organic matter is also removed by oxidation in the presence of bacteria, and ammonia and minute quantities of nitric and sulphuric acids given off. c. The plants absorb the fertilizing substances, especially the dissolved organic matter, and, in a lesser degree, the products of disassociation of the preceding processes. The first and second methods of action are similar to those of filtration beds. They are more complex, however, and more subject to the influence of changes in the weather. In order that the whole process may be successful, certain conditions must b3 fulfilled. They relate to the following matters : 1. Nature of the Ground. The same rules govern the selec- tion of fields for irrigation as for filtration. A fairly sandy soil is the best. With such ground the sewage should flow in small quantities, but at frequent 'intervals. With heavy loam the sewage is rapidly absorbed, but given off very slowly. In order to have considerable absorbing capacity, it is desirable that there be a quantity of vegetable mold in the earth. The heavier the ground the greater the extent of land neces- sary, since the oxidation will cease nearer the surface. With a too loose soil the sewage flows off before giving up all its fertilizing matter, and on that account the land should be terraced and the effluent from one level run over the next lower one. Where thi# IRRIGATION. is not possible, gates may be placed in the main efflitent channel and the sewage held back at different places until it has a sufficient head to be discharged over the land in the vicinity. 2. Nature of Plants. It is desirable that the plants raised on irrigation fields should take up all the matter deposited from the sewage directly, if possible, and after disassociation in any case. This is an ideal condition, however, and it remains to choose such plants as most nearly conform with v the composition of the depos- ited substances. Some ingredients, especially when the sewage contains the waste products from industrial establishments, will always remain unchanged in the soil and be gradually washed away. The variable quantity of sewage and the different agricul- tural demands during the year render any exact adaptation of crops to the sewage impossible. About 1 per cent, of ammonia, 0.4 of potash, and 0.4 of phos- phoric acid are present in manure, arid the same relation between the three substances is also found in sewage. These proportions are not adapted for plants on account of the large quantity of nitrogen in the ammonia. The leaves of a plant demand the nitrogen, the fruit the other ingredients. Hence grass, " greens," turnips, shrubs, and the like give the best crops. Only 15 to 25 per cent, of the fertilizing value of the sewage can be used, accord- ing to KNAUPF. A change of crops is advisable in order that as many as possible of the substances added by the sewage to the fields may be absorbed. The plants should also be so selected that they will allow the air and sunlight to act readily on the earth. 3. CKaracter of the Sewage. The suspended matter has no special fertilizing value in a crude state, and is useful only after disassociation into soluble substances, while it may form an inju- rious slime on the fields or stop the drains. Whether this disad- vantage outweighs its fertilizing value depends upon the method of irrigation. Where drains may be clogged or the level of the ground raised to an extent that hinders the process, the suspended matter is usually removed by a sand-pit, occasionally by a settling; tank on the fields. Chemical precipitation has been occasionally adopted, its -cost being met by the saving in the labor necessary to- remove the sludge or slirne from the fields and keep the drains open. Since the dissolved matter is valuable, it is only necessary to employ chemicals enough to precipitate the suspended sub- 11 162 DISTRIBUTING TANK. stances. Where all the organic matter is used and is plowed into the land, it is sometimes well to employ mechanical agitators to prevent any settlement in the tanks and ditches. Such a plan has been pursued at Ploetzensee. Care must be taken that the sewage is not too concentrated, for if a large amount of soluble matter is present the chemical processes of disassociation and combination are rendered difficult and all the substances will not be removed from the effluent. The necessary dilution may be affected by the addition of water from neighboring brooks or ponds, or by running the effluent over the fields a second time. The same means may be employed to furnish the fields with suf- ficient water during dry seasons. 4. Management. With every irrigation field a good aeration of the ground is a fundamental necessity, and in this respect the different methods outlined above vary consid- erably. With overflowed fields there is of course no circulation of the air either with slow or rapid percolation. In such cases simply mechanical filtration takes place, the chemical action is in- complete, and it is important to subject the effluent from these fields to a further purification in other places. With under- ground irrigation, the purification is also incomplete, since the air necessary for oxidation must penetrate a stratum of earth before coming in contact with the sewage. Bed irrigation is more favorable, but the best plan is surface irrigation worked intermittently. Small areas may be easily cul- tivated by the distributing and settling tank shown in Fig. 144, in which the sewage is collected, settled, and delivered, either by hand or automatically by a float, when the water-level in the tank has risen to a proper height. FIG. CHAPTER VIII. RESULTS AND COST OF IRRIGATION. There is an immense amount of data to be had regarding irri- gation, and on that account only general results will be given in this chapter. With the usual methods, the suspended matter is completely removed or reduced to a few traces and the effluent is clear. In favorable cases the dissolved matter is reduced 90 per cent. ; in the most unfavorable cases there may be a slight increase in the total amount. The total quantity of nitrogen may be nearly all removed or only a third or half withdrawn, according to cir- cumstances. These differences are due to the different conditions of weather and crops during the year. With a proper plant and treatment, the irrigation process will furnish a purer effluent, both chemically and microscopically, than is found in many wells and brooks ; and on that account it is possible that this process is the most successful method of sewage disposal. On the other hand, very unsatisfactory results are sometimes obtained. Analyses of the effluent from beds and fields in Berlin showed that it some- times contained 30 per cent, of the amount of ammonia in the crude sewage, while 36 per cent, was found in the effluent from overflowed areas. In every case careful adaptation of the drains to the subsoil water is necessary. See note, page 287. Under some circumstances it would be better to run the crude or partly purified sewage into a river, than to allow it to mingle with subsoil water and thus enter wells or spring^. The irrigation process in Paris is stopped when high water in the river hinders the free discharg;e of the effluent, and the crude sewage is emptied directly into the Seine. The effects of evaporation from fields treated in the first and second methods, outlined in the previous chapter, are compara- tively without any drawbacks, but the evaporation from fields managed by the third and fourth plans is very bad, since the sewage remains stagnant over a coating of decomposing sludge.* In winter many receiving basins are necessary, but in summer the * See note, page 287. 164 RESULTS OF IRRIGATION. sewage should not stand more than a few days at most. In the comparatively warm climate of .England the process may be con- tinuous, although in other places the addition of the sewage to the plants during the cold weather is regarded as injurious. At such times simple nitration may be employed, as is done on the sandy soil at Danzig. Complaints against the process have gen- erally proved unfounded. The crops may be too rank under bad management, but usually make excellent fodder. The results and cost of irrigation are to a great extent depend- ent upon jthe relation between the quantity of sewage and the extent of the fields. In order that the fertilizing value of the sewage may be utilized to its utmost extent, large areas are neces- sary, over which the water is repeatedly turned. 'Where the land must be of less extent, the agricultural aspect of the process is neglected, and the aim is to simply furnish a pure effluent. The latter case occurs more frequently. The best system is to have private parties control the sewage during irrigation, as is extensively done in Paris and, recently, in Berlin. Freiburg offers an in- teresting case of this sort. In this city a large meadow along an industrial canal had been common property for years, and was used for sewage farms. When the sewerage system with water closets was introduced, difficulties arose. In spite of the exten- sive area of the meadow, the sewage was not always purified, and polluted the brooks below the place more than heretofore. A regular and uniform treatment was no longer possible, and the sewage was used in a number of ways, so that, by an alternation of processes, the effluent was maintained in a good condition. Naturally private parties could not be allowed to choose their own methods of treatment in such a case, and the whole process was placed under municipal supervision. The data upon 'which an irrigation field may be calculated are of two classes relating either to the quantity of sewage or the amount of fertilizing ingredients contained in it. The quantity of sewage used on an acre annually depends upon the volume of the voids in the earth, but is not equal to it, since allowance must be made for aeration. About one- third the volume of sand is taken up by the voids, and of this amount one-half at the most should be filled with sew- age at one time. With 6J ft. depth of drainage an acre of sandy ground will therefore take up about 47,000 cu. ft. of RESULTS AND COST OF IRRIGATION. 160 sewage at each flow; and if the land is treated 6 tinfes a year, the total quantity that may be disposed of in this way annually is about 282,000 cu. ft. Looking at the matter from the second point of view, there are certain species of grass that will assimi- late 291 Ibs. of nitrogen per acre annually. The city sewage contains nearly 9 Ibs. of nitrogen for each inhabitant annually ; hence an acre must be allowed for each 33 persons, in order to obtain the best agricultural results. A larger extent of land is desirable for raising other crops, since sugar-beets require only 219 Ibs. of nitrogen per acre annually, carrots 125, and other plants still less. On the other hand, greatly diluted sewage must be used at times, and a less amount of land will be then fertilized with the same quantity of sewage. Hence in England an "agri- cultural standard " of an acre for each 20 to 40 persons, according to the kind of ground, has been adopted. From a purely sanitary point of view an acre might be allowed to more than this number of persons, since the purification can be effected by the soil as well as by plants. The surplus nitrogen will then be combined to form soluble nitrates, which will be washed away. As a " sanitary standard," therefore, the English have adopted an acre for each 80 to 120 persons, with surface ir- rigation and grass crops. The bed system allows a somewhat greater quantity of water to be used. A recent French regulation requires an acre for each 580,000 cu. ft. of sewage annually, and the irrigation fields for the annexed districts of Pans have been designed on this basis. A rough approximation is to have the fields as large as the city itself, and this rule is fairly good for a population of from 60 to 120 per acre. When the farmers have more generally adopted irrigation the municipal land for the pur- pose need not be so extensive. Another method of estimating sewage irrigation is based upon the annual rainfall. An acre of land receives annually from 58,000 to 132,000 cu. ft. of storm water, although much greater quantities have been recorded. On account of the fertilizing in- gredients of sewage, the latter should never equal the amount of pure water which can be removed from a field by drainage, and which may amount to 2,280,000 cu. ft. per acre annually. It is doubtful if the quantity of sewage that may be treated varies in proportion to its ingredients, since there is a limit to which even pure water can be applied to land. 166 COST OF IRRIGATION. TABLE EX. APPROXIMATE DATA REGARDING SEWAGE FOB IRRIGATION FIELDS, Pifv Pop. per Sewage, cu. Sewage per capita gals. per day, acre. per year. Dry days. Rainy days. Average. Twelve English cities . . . | Berlin 61 283 133 73,000 583,000 / 175,000 \ 18 40 18 77 26 Breslau .... 178 \ 219,000 f 350.000 23 53 40 Danzig 203 482,000 40 61 48 Freiburg 49 1,167,000 Paris 267 526 000 26 66 40 Brussels projected 40 131,000 40 79 66 Munich, " 162 40 106 Zurich " 162 848,000 58 106 The relation between ordinary and storm sewage depends up- on- the number of relief outlets. The figures for dry-weather sewage do not agree with those given in the preceding tables, since the latter are based upon the assumed quantities, while this table gives the actual amounts at present treated. In Breslau, Danzig, and Zurich the subsoil and flushing water is included in the carrying water and the duty of the irrigation fields corre- spondingly raised. The cost of preparing the surface of an irrigation field, in- cluding grading, ditching, etc., averages from $40 to $160 an acre, and the drainage comes to from $20 to $60. The total cost per acre in Berlin was $190, in Breslau only $83. The proceeds of management is the difference between the entire outlay for labor and material and the receipts from the products sold. The work is generally , managed by contractors, and the rent forms the proceeds. In a number of English, cities, the proceeds may be $200 an acre, and from that figure dwindle to nothing, or even show a loss. The average is about $50. In Df FIG. 159. FIG. 161. used. The thin film of salt retains dust and moisture, and thus reduces the amount of work to be done. Care must be taken that no injurious chemical results follow this practice. Several Eng- lish cities have special pumps and mains for distributing salt water for this purpos v e. 2. Removal of Snow. The demands of traffic, more imperative as the fall of snow grows larger, require the removal of part, at least, of the accumulation by private parties. The householders are everywhere required to keep the sidewalk clear, but where this is very wide (over 13 ft. in Paris), or where the number of pedestrians is small, only a part of walk need be cleared by them. The snow is thrown into the street, and must then be removed by the city. It is hardly possible in the majority of large cities to let the snow be compacted into a surface fit for runners, because MISCELLANEOUS REGULATIONS CONCERNING STREETS. 193 the irregular masses between the roadway and the sidewalks would prevent easy passing from the carriages or wagons to shops and houses, and the thawing of the snow would result in an unbearable nuisance on account of the closed gutters. The principal objec- tions would come from the street railways, which require their tracks to be free from snow, and would therefore render any use of runners out of place on streets where their cars run. There- fore the street should be cleaned from house line to house line as soon as possible. But this is expensive, and it may be well to simply clear off only a part of the entire width sufficient for one or two wagons in addition to the street cars. This results in an accumulation of walls of snow along the curbing, and requires FIG. 162 - SNOW PLOW. numerous passages from the street to the sidewalk. Such a plan is followed in many cities, and the snow is allowed to melt away slowly. Where the streets are narrow they must be completely cleared in order to permit of traffic. On account of the great diversity of local conditions, no rules for the work are possible, and the methods to be employed are those which will apparently give the best condition of the streets. The snow is of course removed most easily soon after falling and before it has had an opportunity to become firm, but this is often impossible. The necessary tools are shovels, picks, pushers, Figs. 147 and 159, and revolving sweepers, Fig. 150, so long as the snow is not more than 4 ins. deep. Eevolving brushes have been mounted on cars for the street railways, as shown in Fig. 160, where two brushes are so geared to the axles that either may be lowered across one rail, and thus be made to keep that part of the line free. By running such a car over a line in both directions, a 6-ft. strip of the street can generally be kept open all the time. When the snow is somewhat high, plows must be used. They 13 19 A REMOVAL OF SAW. are usually made of wood, in the shape shown in Fig. 161, and are loaded with stones and the attendant laborers. One horse is suffi- cient up to a depth of 6 ins., when two become necessary. This plow has many disadvantages; it does not adapt itself to inequali- ties of the surface, requires considerable power to use it, and is easily worn out. On this account DURKOOP has patented the plow shown in Fig. 162. It consists of an iron frame carried by two wheels, and a runner on the pole. The frame, which is at an angle of 45 with the pole, bears a number of curved iron shovels,, each movable about a common axis or bar. These shovels cut away the snow, both moist and frozen, and force it to the side of the street. By going over the street a sufficient number of times, or by using a number of plows, the whole surface will finally be cleaned, except near the gutters. Two horses and two laborers are necessary with each plow. The snow is usually removed in dump-carts, drawn by one or two horses. The cost, including transportation to the dumping places, is from 19 to 29 cts. per cu. yd. in Berlin and Hamburg, and is less in places, such as St. Petersburg, where the snow can be disposed of within the city limits. If the snow can be melted at a slight expense and thus allowed to enter the sewers, the cost of removal will be reduced. No appliances for this purpose have as yet been tested on a large scale with unexpected and great quantities of snow. Heated air, steam, water, and salt have been employed. An apparatus invented by CLARKE and tested in London, melts the snow by gas flames in special pits or ditches, about 260 cu. yds. of loose snow being melted in a day in one such ditch at a cost of 5 cts. per cu. yd. HEKTSCHEL has invented a warm-water machine, consisting of a boiler, reservoir, and revolving brush mounted on trucks, and. managed like an ordinary machine sweeper. The snow is simply melted and brushed away. Salt is often sprinkled over the snow, which it melts on account of the temperature of the brine which is formed, namely 15 Cent. In Paris about 0.9 ounce of crushed salt is allowed for each inch of depth on a square yard of surface, and this amount is scattered before the snow has a chance to pack. After a few hours the slush can be easily swept into the sewer inlets and the streets cleaned with water from the mains. The economy by a systematic use of such a plan is said to be considerable, but the presence of the brine MISCELLANEOUS REGULATIONS CONCERNING STREETS. 195 and slush is certainly disagreeable, and is liable to cause colds and similar complaints. On this account the work is generally done at night in Paris and Liverpool; in Berlin the use of salt on sidewalks is forbidden. 3. Regulations Concerning Slipperiness. Ice and mud are principally open to objections under this head. Sidewalks must generally be kept passable by the householders, since thov alono can do the work with sufficient celerity. Asphalt is kept in condition by the city, and the tramways by the street-railway companies. Slippery pavements are usually reme- died by scattering sand or ashes, generally by hand. Wagons have been invented for FlG< i- SALT SPRINKLER. the purpose, but their value is not great. One cubic yard of sand will suffice for about 3,500 sq. yds. of pavement. Since salt will melt the ice, a mixture of sand and salt may be found to work well in places, although the resulting slush is exceedingly unpleasant. On this account the use of salt is usually restricted to street rail- way tracks, where it is distributed from specially constructed cars, Fig. 163. These feed the material by means of a hopper, with revolving arms, through pipes directly to the rails. The amount used is governed by the speed of the arms or by cocks placed in the pipes. CHAPTER VIII. QUANTITY AND CHARACTERISTICS OF EXCREMENT. Different authorities estimate the amount of faeces per capita daily from a mixed population of all ages and both sexes at from 2.82 to 458 ounces avoirdupois. The greater part of the figures given in the literature on the subject are based on males alone, and must be reduced by a third for a mixed population. The average composition is 75 per cent, water and 25 per cent, solids, and of the latter class 20 per cent, are of organic origin. Nitrogen is the most characteristic and important constituent, and makes up from 0.6 to 2 per cent, of the total weight. The amount of urine per capita daily is variously estimated at from 31.8 to 45.8 ounces. From 4 to 7 per cent, of this quantity {average, 5 per cent.) is solid matter, and from 1.8 to 2.5 per cent, {average, 2) is of organic origin. The amount of nitrogen varies from 0.8 to 3 per cent., averaging about 1. The approximate composition of all excrement per capita daily, reckoned in ounces avoirdupois, is as follows: Total. Water. Inorganic. Organic. Nitrogen (grains). Faeces 3.53 2.64 0.18 0.71 15.4 Urine 38.84 369 1.16 0.78 169.8 Total.. 42.37 39^54 IH 1.49 185.2 Hence about 970 Ibs. of excrement must be assumed per capita annually. The theoretical value of excrement as a fertilizer is estimated even more variously than its quantity, since local conditions of supply and demand must be largely influential in such compari- sons. Generally its yalue is stated at from $1 to $3.75 per capita annually; the German Agricultural Commission gives $2.82 as an approximate average. Such estimates are comparatively worth- less, however, since the large amount of water present renders the use of excrement practically impossible, except near the cities and Tillages. A certain percentage of the urine will always be removed in other than the prescribed ways, depending largely on the habits QUANTITY AND CHARACTERISTICS OF EXCREMENT. 197 of the people, and on that account the annual amount of excre- ment per capita which passes through the sewerage system or is otherwise disposed of may be estimated at 750 Ibs., an amount which is nearly that actually measured in Heidelberg, where the excrement is removed by the cask system. In this connection it must also be noted that a part of the- waste water will become mixed with the excrement. Where water closets are employed, the water used in them per capita daily varies from 1.3 to 5.3 galls., according to a report of a committee of the German Gas and Hydraulic Engineers' Society. Investiga- tions in Stuttgart, Karlsruhe, and Wiesbaden show that the actual amount of excrement and water to be removed annually is- from 1,000 to 1,100 Ibs. per capita, and similar investigations at Strassburg have indicated that this amount may equal 1,300 Ibs. In this way the amount of nitrogen becomes 0. 7 rather than 1 per cent. Analyses of the fresh contents of casks and pneumatic tubes show that with from 5 to 9 per cent, of solids there will be from 0.4 to 0.84 per cent, of nitrogen. The character of human excrement changes quickly. Within 24 hours dangerous gases, carbonic acid and ammonia, will have- been given off amounting to 0.1 per cent, of the total weight of the- mass. The liquids in cesspools and retaining basins show quite different results on being examined chemically, according to the- decomposition that has taken place. The limiting values of solid matter are 2 and 6 per cent.; of nitrogen, 0.24 and 0.66 per cent.;, the average being 0.4 per cent. The character and influence of excrement has been well shown by Dr. EMMERICH by experiments with animals. On injecting- fresh urine containing no bacteria into the blood, no evil conse- quence could be noticed ; while faeces, which are partly decom- posed on leaving the system, had to be diluted 20,000 times in order to become harmless. Every kind of excrement was fatal after standing a few days and had taken up bacteria. The different conditions under which excrement occurs in- sanitary engineering practice are as follows, reckoned for each inhabitant per year: PnnrtiHnn Quantity, Solids. x Nitrogen.--^ Condition. * lbg J per cent> Per cent . Lbs . Fresh, total amount 970 7 9.7 For removal in sewers , 880 7 For separate removal, fresh 1,100 6 0.7 7.7 decomposed 1,100 4 0.4 4.* CHAPTER IX. REMOVAL OF EXCREMENT. There are three ways in which privy vaults are cleaned by manual labor direct, by pumps, and by pneumatic apparatus. 1. Manual Labor. In this plan laborers either descend into the vaults and remove the contents by handing up buckets, or the removal is effected by buckets on long handles, with which the contents are scooped out of the vault without entering it. The first method may be dangerous in badly ventilated places, and various remedies have been proposed, such as pumping in air or disinfecting several hours before the work begins. The pres- ence of dangerous gases can be detected by lowering a light, which should not go out. In spite of its cheapness the profits often exceed the expenses since the peasants do the work themselves, and the lack of responsibility thrown upon the town authorities, hand removal is not adapted to cities, on account of the time con- sumed, the uncleanliness, and the odor attending it. 2. Pumps. A combined suction and force pump, driven by cranks, is mounted on wheels and connected by pipes with the vault on one side and the receptacle on the other side. The lat- ter is usually a cask of wood, or, better, iron, mounted on wheels, holding from 320 to 790 galls., and provided with a glass water- gage, air valve, manhole, and cocks for connection with the pipes. Where the pumps must be stationed some distance from the vaults, the connections are formed with thin iron pipes and rubber hose. The suction pipe ends in a sieve to hold back the solid matter, which would injure the machinery. For a like purpose the con- tents of the vault are sometimes diluted with water or stirred, although the more simple plan would be to remove the solid por- tions subsequently. Under any system, the pumps will be quickly worn out. To this defect must also be added the long time required and the vile odor. Hence this method has been replaced in many cities by the following : 3. Pneumatic Method. In this plan the cask by which the REMOVAL OF EXCREMENT. 199 excrement is removed is first exhausted of air and the*n connected by a pipe with the vault,, the contents of which will be then trans- ferred by pneumatic pressure without passing through valves or similar appliances. A 4-in. pipe is usually employed. The fol- lowing apparatus have been employed to create the necessary vacuum : 200 CESSPOOL PUMPS. a. Portable pumps operated by one to four men. Fig. 16-1 represents a form driven by cranks, and Fig. 105 one operated by levers. The air is sucked from the cask, forced by the pumps under a coal fire, and escapes in a fairly pure condition from the- chimney. The time necessary for this process is considerable, being from 4 to 10 minutes for each cask, and the vacuum is not sufficient to remove the semi-fluid sediment in the bottom of the vaults. 1). Portable Steam Pumps. The fires are usually fed with coke, since it gives oh* little smoke. The pumps are usually of 2 or FIG. 16.=). CESSPOOL PUMP. 3 horse-power, worked with 30 to GO Ibs. pressure, and require from 110 to 154 Ibs. of coke daily. It requires only about 2 min- ut3s to create a vacuum of ^ to J of an atmosphere in an iron cask of 660 galls. or88 cu. ft. capacity. This reduction of pressure is sufficient to drain a vault of nearly all its contents, even when they are quite thick, and any further reduction is a waste of fuel and time. Five men will fill from 50 to 70 casks with this machine daily. The air that is pumped from the casks is forced through the fire, causing an artificial draught that is highly bene- ficial. By properly adjusting the valve gear all noise from the escaping steam is avoided. This apparatus is extensively employed in Strassburg, Metz, Karlsruhe, Munich, Hannover, and several other places. REMOVAL OF EXCREMENT. 201 $ c. In the LENOIR and SNEITLER system, an iron reservoir is mounted on the same frame with the pumps. It is filled with the contents of a vault by being exhausted of air in the manner just indicated. The valves of the pumps are then changed for press- ure service, and the reservoir is emptied into the casks for removal by forcing air into it again. The advantage gained lies in the fact that casks in which the matter is removed need not be air- tight as in the TALARD system, described under b. The double duty required of the pumps and the consequent loss of time are decided drawbacks. d. Steam Ejectors, KELLER-PHILIPPOT system. In this system the steam consumption is so great that the boilers must work under a pressure of 100 to 130 Ibs., in order that the ejector may have the 45 Ibs. pressure necessary to fill a series of casks continuously. This requires about 330 Ibs. of coke daily. The air absorbed by the ejector from the casks is forced through a reducing valve into the fire-box, or else returned to the vault through a second pipe, where it serves to agitate the contents, Although the apparatus, arranged like a steam injector, is more simple thair an ordinary pump, and has no moving parts, never- theless it possesses disadvantages, such as a dangerous boiler press- ure to be carried in streets, and a large fuel consumption for the work done. The system is employed in Strassburg,and Muelhausen. e. The casks are exhausted of air outside the city at the dump- ing places after the contents of the previous trip have been dis- charged. This may be done by stationary pumps, but usually one of the two following methods is employed: The casks may be filled with live steam, which will cause a partial vacuum on condensa- tion, as is done in Muenster and Bremen ; or the casks may be filled with water and then placed in a chamber where a vacuum is maintained. On allowing the water to run out, the casks will be free from air. If the air inlet of a cask is connected with a 33-ft. pipe closed at the upper end and the water is then allowed to run out, a vacuum can also be obtained. This system is employed in Turin and Milan. The empty casks are then taken back to the city. The advantages of this process lie in the short time required for the work done within the city, and the escape of the foul air only outside the city limits. On the other hand, absolutely air- tight casks are necessary. /. A Frankonthal company (KLEIX, SCHANZLIX & BECKE c T 1 7' TT -R Q 202 COST OF REMOVAL. has introduced a system in which each cask is supplied with a small pump. The motive power is furnished by the horses in drawing the casks between the city and dumping places. For this purpose one of the cart wheels is keyed to its axle, which in turn is geared to the pump. While the wagon is in motion the pump is also moving, unless thrown out of gear purposely. Beside the advantages mentioned under e, this system has a special claim for preference from the fact that the casks are emptied of air without manual labor or delay. The cost, however, is somewhat high. The cost of the removal varies greatly. The exact figures can only be determined when all the work is done by municipal labor- ers; Stuttgart is the only large city where this is the case. Hence the comparison is usually restricted to the taxes which the house- holders pay for the work, which range from to 61 cts. per 100 galls. The removal is gratis in Krefeld, Wiesbaden, and Strass- burg; in the majority of small German cities it is from 5 to 19 cts., and in the larger places it may rise to 43 cts.; 61 cts., the maxi- mum, is paid in Paris. In the majority of cities the tax is the same for all houses a simple plan for the authorities, but only right where the style of architecture is uniform. The charges should be graded according to the difficulty of the work, as is done in some cities. Vaults which are easily accessible are more quickly emptied than others that require a long line of pipe to the pumps and casks. In Dres- den the charges are divided into 5 grades, and range from 30 to 48 cts. per 100 galls., according to the length of pipe necessary. The average in that city is 37 cts. Such a regulation tends to have the vaults in new buildings located in places that are easily reached, which is a desirable sanitary precaution, and has led to the introduction of fixed pipes leading from the vaults into courts, or even to the street, by which the excrement is removed without uncovering the pits. Such fixed pipes may lead, to a number of vaults. In some places an additional tax is levied where water closets are connected with the vaults, since the excrement then has a smaller commercial value. In Leipzig the regular prices are doubled, and in Wiesbaden the tariff is raised 9J cts. per 100 galls. There is no material save iron, which is expensive, that will prevent the escape of the contents of privy vaults and cess-pools. Ml other materials are subject to change, owing to their alternat- REMOVAL OF EXCREMENT. ing contact with air, water, and in some cases acids. The vitia- tion of the air is a still worse feature of vaults, and their contents have a smaller value after standing for a short time than when fresh. Both facts call far as frequent cleaning of such places as possible, while the disagreeable features of the work tend to cause delays. Stuttgart has passed a regulation requiring the cleaning to be done once in four weeks in ordinary houses, and more often in large establishments. In all other cities the work is done on application of the householder, the contractor being allowed from one to two weeks, within which time the vault must be cleaned. A systematic cleaning by streets is much more economical than this plan, and is in force in Stuttgart, where the cost of the work when done in regular order is 35 cts. per 100 galls., or 46 cts. when done on ap- plication. The Prussian Commission- ers recommend a more frequent clean- ing when water closets discharge into the vaults than when the closets are all dry, on the ground that in such cases there is more leaking through the walls into the surrounding soil. All of these drawbacks have led to the use of small, movable receptacles, which can be easily and quickly emptied. Small open pails holding from 5 to FlG ' 166< 10 galls, and placed directly under the privy seats are extensively employed in Bremen, Groningen, and other places. Such a sys- tem is directly opposed to all sanitary demands, and the appear- ance of the pails standing on the sidewalks before the carts arrive is extremely offensive. A slight improvement is made in Kiel, Eostock, Emden, and Amsterdam, where the pails are provided with tightly fitting covers. But they remain as unpleasant in the house and are as bad, from a hygienic point of view, as the vaults. The system is satisfactory only when soil pipes lead from the closets to the pails, and the gases from the latter are prevented from escaping in the houses and on the streets. Wood is a less suitable material than iron for these pipes, being harder to clean and less durable. The Heidelberg pails, Fig. 166, are from 15 to 18 ins. in diameter, 31 to 35 ins. high, 23 to 29 galls, capacity, 204 HOUSE CONNECTIONS. and weigh from 75 to 100 Ibs. when empty and 290 to 330 Ibs. when full. They are painted or galvanized annually. The largest pails are used in Augsburg, where they are made of beech wood, and hold from 47 galls, in small houses to 79 in large. The connection between soil pipe and drain is often only loose, pimply a funnel or similar contrivance. This would be sufficient if the pail chamber was thoroughly ventilated by a continually warm ventilating pipe, as required in Goerlitz. Where this is not FIG. 167. the case the system has few advantages over open pails, although extensively employed, especially in the country. An air-tight connection which can be quickly removed, usually held by a bayonet catch 2 to 4 ins. long, is to be preferred, and may be regarded as the present standard. The escape of gases is pre- vented in .four ways, as follows : a. The soil pipe is directly connected with the lid of the pail, and prolonged upward through the roof as a ventilator. This method may suffice where the pails are removed every other day and decomposition is not allowed to take place to any great extent within the building. 1). The soil pipe is arranged as in a, but has a water- trap con- REMOVAL OF EXCREMENT. 205 jf nection with each closet in order to prevent the escape of gases from the pails into the house. c. The soil pipe has a water-trap connection with the pails, as shown in Fig. 167. A prolongation of the soil pipe as a ventilator is desirable, but not so necessary as in the above cases. In Heidel- berg, where the closets are all on the ground floor, no extension is provided. In order to clean the trap and protect it from frost various plans have been adopted, such as a movable lid in the LIPOWSKY system, shown at x, used in Heidelberg, or a movable tongue, shown at y, and employed in Weimar in the SCHMIDT system. The heating appliances used as a preventative measure against freezing do not cause any ventilation. The FRIEDRICH system, employed in Leipzig, is shown at z. d. The soil pipe is closed above the upper closet and is con- nected directly with the pail. A special ventilation pipe, see Fig. 168, leads from the soil pipe just above the pail to the roof, and is warmed by its proximity to a chimney or by a special gas jet at its foot. The best systems, especially as regards the gases in the soil pipe, are those falling under b and d, yet the others have proved satisfactory where the pails are frequently changed. The employ- ment of water flushing also influences the choice. This is gene- rally practicable, but increases the cost of removing the excre- ment ; when it is not done the methods Z and c are questionable. Everything considered, the last system is probably the best. As a safeguard against overflow, a small drip pipe should be provided, as shown in Fig. 166. It should be guarded by a sieve within the pail and empty into a small bucket or a second pail. The second plan would be better as preventing evaporation, but might lead to the destruction of the water seals, owing to the sud- den escape of a large amount of air from the pails to the soil pipe. Where a standard pail is not of sufficient size, several might be coupled, as shown in Fig. 168, the last being provided with an open drip pipe. The pail chamber should be constructed with solid walls and a water-tight floor ; water taps and good drainage are desirable, as well as a means of heating. The pails should stand upon wooden platforms to prevent rust and decay. The chamber should be designed only after thoroughly considering the probable effect of the heat of summer and the cold of winter, and be so situated that 206 METHODS OF TRANSPORTATION. the pails can be easily removed. Generally they are in the base- ment, when suitable means of removal must be supplied. Some- times the pails are rolled up a skid, as shown in Fig. 168, and sometimes pulled up by a tackle, as in Fig. 169. Oftentimes they are carried out by two men by bars run througlrthe handles, Fig. 173, when the distance is not great. The further transport to the gardens or fields may be done in shoulder pails, Fig. 170, holding only a small quantity, or in larger receptacles mounted on wheels, Figs. 171, 172. When the latter method is employed the pails should be supported near their center FIG. 170. FIG FIG. 172. of gravity, thereby allowing the contents to be poured out easily. In cities, wagons carrying a number of pails are necessary. Ordi- nary trucks are not suitable for the purpose, since they must be loaded by skids. Low bodies, on which the pails can be easily lifted, are much better. One horse will draw from 10 to 1 standard pails, but larger loads are easily handled by the wagons- used in Heidelberg, shown in Fig. 173. These are provided with curtains, which hide the load from the sight. The Manchester wagons also carry a receptacle for the dry pails, a great conven- ience for the residents. In large buildings, where the quantity of excrement is great, casks mounted on wheels or even special wagons are used in place- of pails. The receptacles shown in Figs. 174 and 175 hold from REMOVAL OF EXCREMENT. 207 50 to 100 galls.,, and have inlets and outlets controlled by valves and a glass water gage. Where still greater capacity is required, a large iron tank mounted on 4 wheels is usually employed. These sometimes hold as much as 775 to 800 galls., and are pro- vided with two or more inlets and a manhole, as shown in Fig. FIG. 175. FIG. 176. 176. By giving the tank a slightly conical form all its contents will readily flow from the outlet. In removing a pail, it is of course necessary to have another to take its place. They should be thoroughly cleaned after being emptied, and disinfectants may be sometimes used advantageously in this work. The interval between successive removals varies greatly in dif- ferent places. Where small pails are employed they should be changed every third day at least. In Kiel, Rostock, and Emden 2u8 FREQUENCY OF REMOVAL. the removal takes place twice every week. In Heidelberg, where the service is exemplary, the pails in houses containing from 15 to 20 persons are changed every 2 or 3 days, with fewer persons every 3 or 4 days, and in crowded dwellings daily. The average time is 3 days; in Goerlitz, 5 ; in Angsburg, Weimar, and Rochdale, 7; in Bergen, 14 ; although frequent disinfection occurs in the interim. The cost of pail removal is met everywhere by taxes or fees. In many places the contractor receives a bonus from the city in addition to the usual fees, x m order to make up for the somewhat greater labor required by the system. The fee for removing each small pail once is 2 cts. in Koenigsberg. 3| cts. in Kiel, 7{ cts. in Rostock ; standard pails, 5 cts. in Heidelberg and Weimar. The total cost of the system, including the bonus from the city, averages between 37 and 63 cts. per capita annually. Although the work can be carried out more easily with a large than a small number of pails, yet there is a limit beyond which the system will give rise to heavy transportation expenses to the dumping grounds, and to an interference with ordinary traffic. Hence it is best adapted to places of moderate size, and is unsuited for large cities. The English cities Manchester and Rochdale are so arranged that the removal takes place from the rear of the houses through small streets and alleys, and does not occur very frequently. In the German cities mentioned as using the pail system, only a part of the houses are fitted in this manner. Gratz is the only place where its use is universal, and there the service is by no means commendable. Nuremberg adopted it only to be again abandoned. CHAPTER X. REMOVAL THROUGH PNEUMATIC TUBES. The disadvantages attending the storage of excremental matter in houses and the cumbrous appliances employed in the pail system led LIER^UR to invent a network of underground tubes through which this matter is removed by pneumatic methods. At a suitable place, as low as possible, without the city, is a central reservoir, from which a system of main pipes lead to a number of district reservoirs. The latter are scattered over the whole city, and are entirely separate from one another. From these district reservoirs a series of street pipes radiate in every direction, and to these are connected the house pipes. The size of the dis- tricts is such that the longest street pipe will be about 1,000 ft., and connect with 60 houses, while the district reservoir must be large enough to contain all the excremental matter of a day from its district, which usually is from 37 to 50 acres in extent, and contains from 2,000 to 3,000 inhabitants. Each house pipe must be of sufficient capacity to contain the daily matter of the house to which it is connected, see Fig. 177, or at least the greater part of it, the remainder passing into the street pipe. All pipes and reservoirs are constructed of iron, must be air- tight, and lie below the frost line. Each district reservoir must be connected with the main and street drains by valves, the stems of which run to the surface and are operated like water hydrants. The pipes are generally 5} ins. in diameter. The air pump at the central reservoir, calculated by assuming 0.25 horse-power for each acre, according to the inventor, main* tains a vacuum of 11 Ibs. per sq. in., or three-fourths of an atmos- phere at this point during the entire period of operation. This diminution of pressure also occurs in the district reservoirs as soon as the valves are opened, and the same thing also occurs when the street pipes are connected. This reduction of pressure causes the matter in the house pipes to be sucked through the street pipes to the district reservoir. The work is performed by empty- ing one street pipe at a time, the vacuum in the reservoir being 14 210 THE L1ERNUR SYSTEM. renewed after each discharge. The district reservoirs are emptied into the central basin in the same manner, either directly or through each other. The entire manipulation of a street pipe- requires only 2 or 3 minutes; and a district reservoir can be- emptied in 10 to 20 minutes, so that the entire excremental matter can be removed daily, although in Holland from 1 to 3 days elapse between successive removals. All the house pipes connecting with the same street pipe become empty simultaneously, as otherwise air would enter the network through the first empty tube, and hinder or prevent the removal of the remainder of the matter. This danger was formerly met by a rubber ball floating on the top of the liquid in a chamber above the siphon, as shown in Fig. 105. After the matter has been sucked away, the ball is pressed down against the lower seat and prevents any air from entering the vacuum pipes. This theoretically correct action was only imperfectly obtained in practice ; the exclusion of the air was imperfect, and occa- sionally the ball stuck to the lower 16 f seat and failed to rise. Hence its FlG< 177< use was discontinued, and the ar- rangement shown diagramatically in Fig. 178 has been adopted, It is essentially a large water-trap, with an inclined arm from 20 to 50' times as large as the upright section. From a very full trap or sack the discharge is quicker than from one con- taining a smaller amount of matter, but the difference is not sufficient to cause all the pipes to become empty simultane- ously, and the LIERXUB system never completely removes all the contents of the pipes. A complete discharge can only be obtained by connecting each house pipe with the street by a valve, and opening and closing these valves one after the other down the whole length of a street. Each closet must have a water trap connection with the soil pipe, which should be prolonged to the roof as a ventilator, as a safeguard against the matter remaining in the house pipe. A less suitable plan is to have a water trap at the foot of the soil pipe or at its entrance to the house, and thus keep the gases shut in the pneumatic tubes. The objection is that the gases from the soil pipe are allowed to enter the dwelling-rooms unchecked. LIER- REMOVAL THROUGH PNEUMATIC TUBES. 211 NUB proposes, as the most satisfactory plan, the arrangement out- lined in Fig. 177. There are three siphon traps one at a at the foot of the soil pipe, one at b at the house wall, one at c at the connection with the street pipe ; a valve at d is provided for the purpose of shutting off the house for repairs. In large plants the main pipes might consist of two tubes laid side by side, one being a suction pipe for producing the vacuum and the other a transporting pipe through which the matter is removed. The latter should not have a uniform grade in large plants, since the pressure of the air in such a case might separate the "piston" of excremental matter in front of it and result in only a portion of the total quantity being drawn to the central reservoir. Hence the transporting pipe should have several abrupt descents of 3 ft. or so, at the foot of which the matter is again united and the air concentrated, /sstreet Pipe. .The same result may be obtained by employing a number of small sec- ondary reservoirs, from which the FlG - 178 - flow begins anew. If a central reservoir is dispensed with, each district reservoir, or even each house, can be connected with portable pumps, and its contents thus removed. Main pipes are entirely wanting in such a case. As compared with privy vaults, the system offer? the advantage of daily removal, and the house is entirely free from disagreeable operations, but there is then need of a large number of carts. In places where only a few districts would be needed, the system may deserve consideration. It was employed in Amsterdam until 1884, where some 30,000 residents were divided into 6 districts, and 30,000 more were served in a house to house manner. Since then the system has been more cen- tralized. The LIEENUR system has been adopted in a barrack at Prague and in parts of Amsterdam, Leyden, and Dordrecht. From the first installation on, the connection between the closets and the pipes was by means of a so-called excrement seal, the last discharge forming the seal, and giving rise to highly offensive odors as well as tending to stop the pipes. In the barracks this would give rise to no great difficulties, but in the Dutch cities large quantities of water are discharged into the pipes, partly to keep them clean and partly to be easily rid of the waste water. In some places as 212 THE BERL1ER SYSTEM. much as 1.3 galls, per capita come from the closets daily, although the average is only 0.37 gall., as already noted ; the mean of all the Dutch LIER^UR systams is 0.63 to 0.74 gall. Hence the num- ber of water closets should be taken as a basis of calculation,, and the consumption of water be limited to from 1 to 1.3 galls, daily per capita or even 1.6 galls, in order to allow for a future increase of the numbers using the closets. The removal of excrement by pneumatic tubes insures great safety against pollution of the air and contamination of the soil. The iron construction prevents serious leakage, arid disease FIG. 179. germs are carried along the pipes to the reservoirs, from which all the air is discharged under the grate of a furnace or boiler, and the germs are therefore burned. However excellent the system ap- pears in theory, in large plants it fails practically on account of the complicated apparatus. In Amsterdam the removal costs 20 cts. per capita annually in districts with fixed pumps ; where house to house service prevails, the cost is 43 cts. The pneumatic principle has been experimentally employed by BERLIER in one of the Paris barracks. The excrement passes from the closets to a receiver, Fig. 179, placed in the base- ment and containing a cylinder of wire with large meshes, which retain the large substances that should not enter the closets. The matter then passes through a pipe to a discharger, with which several receivers can be connected. An india-rubber ball, REMOVAL THROUGH PNEUMATIC TUBES. K, closes the lower conical part from the pneumatic tube, A. The ball is connected to a float, S. When the liquid has reached a certain level, the float and ball are lifted and the contents of the chamber escape, the current bearing with it the matter clinging to the basket, D. The process is re- peated automatically and may be continuous if the liquids are present in sufficient quantities to keep the discharge always nearly full. The network of the pipes can be laid in the same manner as in LIERNUR'S system. Although this plan offers the advantages of separate house con- nections and an automatic regula- tion, it has the following serious defects : 1. The wire basket must be re- volved several times a week, in or- der to keep the meshes open. 2. The basket must be removed and cleaned inside the house. 3. Considerable basement room is required, and the house must be visited by laborers. 4. Evaporation will take place through the hole in the lid of the discharger, which is necessary for a proper working of the apparatus. 5. The ball and float may become fixed by deposits of solid matter. Experiments still require to be made to show the force of these objections with large plants ; they have been partly met in the new apparatus of BERLIER, in which the receiver and discharger are in the same chamber. The former is horizontal and discharges through a grating, as shown in Fig. 180, CHAPTER XI. FINANCIAL CONSIDERATIONS. The excremental matter of a city is generally the property of the city, or the contractor who removes it, where public removal is obligatory. But it is often desirable to allow the owner of a vault to form a private agreement with the contractor to have the contents of the vault removed to land belonging to its owner. In Karlsruhe this work is paid for at the rate of 21 cts. per 100 galls. and haul of 1.243 miles. Some return should be received for the very considerable amount of fertilizing matter in the excrement. The land necessary for utilizing these fertilizers maybe calculated from the fact that from 25 to 70 Ibs. of nitrogen per acre are required annually. These amounts correspond to from 4 to 9 persons in case the matter is fresh, as is the case with the pail system, or from 6 to 16 persons when it reaches the fields in a partly decomposed condition. In some places an agreement has been made with the farmers by the terms of which they receive the pails on their fields in regular turn or store the contents in private reservoirs or in tank wagons. The transfer to the latter can be most easily made by running the city carts upon a raised platform below which the private wagons are placed; iron pipes and funnels make the trans- fer a very easy and quick operation. Since the advent of winter puts a stop to the use of fertilizers, the sewage must be stored during this season in private or public reservoirs. Those employed in Strassburg and Karlsruhe are large enough to contain the excremental matter of three months. It is advantageous to have several reservoirs at different points outside the city limits ; they should be located so that the offensive odors which arise will not create a nuisance, and should be constructed of water-tight masonry with a wooden or arched top, through openings in which the pails from the city may be emptied. The use of carts is only economical up to a certain length of haul, beyond which steam tramways are more suitable. Stuttgart has developed the latter system most completely of any German FINANCIAL CONSIDERATIONS. 215 - city, being compelled to do so by the rapid growth of the place and the hilly character of the surrounding country. The tank carts are emptied by tubes at a special station into cars carry- ing 3 wooden tanks, holding, in all, 790 galls. At the country stations the private parties may receive the matter in their carts or it may be run off into reservoirs and stored. The repeated transfer is cheaper under such topographical conditions than the long transportation in wagons would be. In level places it might be better to remove the matter in the same tank from the city to the reservoir. The steam tramways in Munich, Dresden, and Leipzig are ar- ranged on a somewhat different plan. In order to diminish the weight as much as possible, large tank cars holding 2,640 galls, are employed. The city tanks are emptied by the same pneu- matic apparatus used previously to fill them. In these cities the tramways are already from 40 to 56 miles long. In Stuttgart more than half the excremental matter is removed in this manner. The proceeds from direct sale of the matter depend upon the amount of dilution it has received and the time it has stood, upon the distance it must be hauled, and upon the competition of other fertilizers and the general demand for them. Hence it is not strange that the price of excremental matter at the reservoirs varies from 13 to 57 cts. per 100 galls., the latter amount being sometimes paid in Strassburg and Stuttgart. When the peasant receives the matter within the city he naturally pays less 38 cts. in Strassburg, 27 cts. in Mainz as is also the case when his carts are filled directly from the railway cars, as in a number of Baden country places, where the price ranges from 28 to 44 cts. In Mainz the price for delivery at the fields is 67 cts. The proceeds from the pail system are generally not greater than the above figures, being largest in Goerlitz, 48 cts., and Ros- tock, 56 cts., although the fresher condition of the matter makes it really more valuable. But it cannot always be immediately applied, and in such cases decomposition soon reduces its original value. The pneumatic tubes deliver the matter in a very fresh condition but greatly diluted. In Holland, from 14 to 48 cts. per 100 galls, is paid, the average being about a half of the proceeds from the pail system. German prices cannot be given, but such matter is sometimes refused by the peasants. 216 FINANCIAL CONSIDERATIONS. The sale is always attended with risks, and in some places, when no persons apply for the matter, it is thrown into the water, as in Graz, Amsterdam, and Paris. Purchase of land for cultivation with excremental matter is not advisable for cities, on account of the extent of the work. But land belonging to the city might be leased with the understanding that a certain amount of the ex- crement is to be used upon it by the tenant. In order to relieve the municipal authorities of all the difficul- ties attending the disposal and sale of ' faecal substances the whole work is usually let to a contractor. Hence the net earnings are difficult to determine. When the work is done by the city, the figures are easily obtained, although even then part of the labor, such as pumping or carting, may be done by con- tract. The account for Stuttgart for the financial year of 1885-86 showed that the total expenses per capita were 62 cts., and the total proceeds 37 cts., leaving 25 cts. to be paid by taxation. The city called for 45 cts. per capita as a tax, so that the accounts showed a nominal profit of 20 cts. as far as the disposal accounts went, although the householders were not able to show any such profit. In Manheim, the entire outfit belongs to the city ; in 1887 the proceeds there were 57 cts. and the expenses 71 cts., the difference being partly met by a tax of 11 cts., which has since been raised. . . From 1871 to 1889 the pail system in Heidelberg was man- aged by an association of the householders ; since then by the city. From 1881 to 1886 both expenses and proceeds averaged 61 cts. per capita annually, the latter consisting of 20 cts. for the matter and 41 cts. paid by each person (the latter sum being the cost of the system to members of the association). The city gave a bonus for covering the additional expenses caused by certain municipal regulations regarding the dumping places. The Baden barracks present the only example of places actually receiving a profit from the excrement, which is .partly due in their case to the fact that the matter is carried in a fresh condition directly to the fields. The peasants sometimes pay for it a sum corresponding to 62 cts. per capita annually. When the entire work is done by contract the expense to the householders is simply the fee they are required to pay. The city loses the interest on the sum invested in the appliances and build- ings lent to the contractors. Sometimes, but rarely, the removal is FINANCIAL CONSIDERATIONS. 9 done gratuitously. Some contractors apparently make large profits, such as the Dresden Removal Co., which pays 9 per cent, dividends, while others apparently work at a loss. The city might give out short contracts and supply all the tools and ap- pliances, or require the contractors to pay into its treasury all profits exceeding a certain percentage. Under such conditions the municipal authorities would be sure of receiving some returns if the disposal was very profitable. CHAPTER XII. SPECIAL TREATMENT OF EXCREMENTAL MATTER. The drawbacks attending the sale of excremental matter are eliminated when the portions which are of value to farmers are separated and reduced to a form adapted for transportation and use. The poudrette, the usual product of the concentration, should be delivered in such a condition that it can enter into competition with existing fertilizers. Numberless inventions for this concentration have been brought forward from time to time, all of them based on one or more of the following processes : Evaporation, concentration in a filter-press, chemical treatment, or mixing with other fertilizers. No description of these pro- cesses will be given, as they have all proved impracticable or too expensive. RAWLINSON* and READ stated in one of their works that no method of preparing fertilizers from city refuse, either with or without the addition of chemicals, has paid for the cost of the process. Since this opinion was given three new methods, described below, have been introduced ; 1. PODEWILS treats the excrement with sulphuric acid to fix the ammonia, and then saturates it in an agitator with smoke from a fire, whereby it is partly evaporated and deodorized. The mass is then completely evaporated in shallow pans, placed eight deep, one above the other, in a chamber through which circulate the heated air and flames from a fire at the bottonii Recently vacuum chambers have been employed in which boiling takes place at from 150 to 185 degrees Fahrenheit. The faeces come in contact with the air at no stage of the treatment, and the gases developed are all burned. Such a plant is employed in Augsburg. 2. LIERXUR has invented a process in which the excremental matter is first neutralized with about 1 per cent, of sulphuric acid, to fix the ammonia, and then boiled in a vacuum chamber. The latter corresponds closely to a three-chambered evaporator used in the preparation of sugar, in which the gases from one division aid in warming the next. The exhaust steam from the engine is used in the first chamber, after it has been superheated and thoroughly dried. The thick fluid thus produce^ is spread SPECIAL TREATMENT OF EXCREMENTAL MATTER. 219 thinly over the surface of highly heated revolving cylinders. The dry crust is scraped off by means of a second cylinder carrying a number of projections, and falls down as a fine powder. The process was tried in Dordrecht, and given up in order to install & more complete plant, it is said. In Amsterdam the process was .adopted to prepare a thick fluid, which was said to be better suited for a fertilizer than the powder. Recently the process was given up on account of the great dilution of the faecal matter, as men- tioned in the preceding chapter. 3. BUHL and KELLER have adopted a process founded on dis- coveries by HEJSTNEBUTTE and VAUREAL. The excrement is mixed in an agitator with from 0.4 to 1.6 galls, of a 5 per cent, solution of zinc sulphate and 0.6 to 1.2 Ibs. of quicklime for every 100 galls, of the matter. The liquid is then run into large tanks where from one-fourth to one-third of its volume is precipitated, the precipitate containing all the solid and the greater part of the dissolved faecal matter. This precipitate is compressed in a filter- press, and the cakes dried and powdered. The liquid remaining in the tank is treated with sulphuric acid to form ammonium sul- phate. The process prepares, therefore, two substances the pou- drette, or dried night-soil and the ammonium sulphate, about 42 Ibs. of the former and 6}^ of the latter from each 100 galls, of ex- crement. The final effluent is practically pure water. A plant of this kind was tried in Freiburg, but was recently given up. Analyses of the poudrette from the three methods give the following relative proportions, in per cent., of the important constituents. Organic Process. Water, matter. Nitrogen. 1. PODEWILS , 9 59-70 7.0-10.7 2. LIERNUR 15-22 50-58 6.7-8.1 3. BUHL and KELLER 11-14 36-50 2.3- 3.6* *This comparatively small amount is due to the fact that much of the nitrogen is changed into ammonium sulphate. The first and second methods are preferable, since all the solid matter enters into the powder, while in the last the. potash is largely dissolved in the effluent. Salts of potash are cheap and easily obtained, and the above objection is counterbalanced by the fact that one of the products, ammonium sulphate, commands a good price. The relatively large amount of water in the LIERNUR process is due to the difficulty of completely drying any thick semi-fluid 220 MANUFACTURE OF POUDRETTE. mass. PODEWILS uses shallow pans and adds earthy matter to remedy this. In the third process there is no heating of any but perfect liquids, with which the heat is fully used. The above difficulty also causes a difference in the amount of fuel employed, the most expensive item in poudrette manufacture. LIERNUR claims that his system will evaporate 16 Ibs. of water with 1 pound of coal, a result theoretically doubtful and not yet practically shown. Theoretically the BUHL and KELLER system requires but a third of the heat necessary in the other processes. All of them must be regarded as in the experimental stage. Other methods are employed in Paris, Manchester, and else- where, generally at a loss. The plants should be designed with a due regard to hygienic requirements. The 24 establish- ments in the neighborhood of Paris are notoriously bad, and were- recently compelled to conduct their operations in metal-lined chambers with proper ventilation. They were also required to dispose of the matter within 4 days of its collection. CHAPTER XIII SEPARATION OF Exc REMEDIAL MATTER. It is sometimes considered desirable to separate excremental matter into solid and fluid portions, the latter passing away through the Sewerage system and the former being removed separately. Such a plan offers the advantages, as compared with the separate removal of all such matter, of less cost and the un- restricted use of water-closets. As compared with the discharge of all the matter into the sewerage system, it results in cleaner sewers and purer rivers, since a certain quantity of more or less sticky solids is kept out of them. It is true that there is no certain line of demarcation between fluids and solids in such oases, but there are a number of processes which accomplish a partial separation. The division takes place in the soil pipe, at the outfall of the vault, or through sand filters or perforated partitions in vaults or special pails. 1. Separation by overflow connections of cesspools and vaults with the sewers is much employed in Amsterdam, Wiesbaden, Baden, and numerous English cities in consequence of the intro- duction of water-closets ; it is allowed in some other places. The interval between the successive removals of the solids is greatly extended by such separation, but it should be noted that the resi- due is in no sense an actual solid, but rather consists of a more or less semi-liquid mass, easily removed by pneumatic means. If the vault is used by 20 persons and cleaned once a year, then the outlet will discharge 365 x 20 x 0.25 = 1,825 cu. ft. if it is assumed that 0.035 cu. ft. of excrement and 0.211 cu. ft. of flushing water are furnished per capita daily. The contents of the vault are insignificant compared with this volume of discharge, and it will be easily seen that nearly all the excrement must pass into the sewers. The character of the discharge is certainly no longer that of the original excrement. After the cleaning of the vault, it will Jbe several days before the overflow begins to discharge, and the 2^2 SEPARATING PAILS. 1:30 FIG. 181. accumulated contents will have already begun to putrefy. The soil pipe and outfall are usually at opposite ends of the vault, and gases and certain soluble substances formed during putrefaction will check the desired precipitation during the flow from one opening to the other. Since the specific gravity of faeces is somewhat less than that of urine, it is un- doubtedly true that a part of the former passes into the sewers with the latter, even when screens are used. Hence the effluent is probably between the original discharge from the closets and the ordinary contents of cess-pools in character, approaching the latter as the vault is increased in size and the inter- vals between successive cleanings prolonged. Overflow vaults are of as doubtful value in houses as those of ordinary construction, and are worse for the sewers than a complete discharge of all the excrement, since- the quality of the effluent is more dangerous and the quantity is not materially decreased. The faeces, however, are usually finely divided, which is something of an advantage, but would be still greater if the effluent was passed through a gravel filter, such a has been patented by NESSLEE and is shown in Fig. 182. It gives an increased opportunity for settlement and is easily cleaned, yet its use seems an over-refinement if a grating is employed and the sewers are properly constructed. 2. Separating pails, Fig. 181, con- nected with the sewers are used oc- casionally, especially in Paris and Zurich. The results of the separation depend naturally upon the size of the holes in the partition. Theoretically these should be small enough to retain all the faeces, but in this case they are soon stopped, especially in the bottom of the pail, and simple overflow results. In this respect a Paris report states that the only demonstrated result of the use of these pails is that the faeces and urine enter the sewers at somewhat different times. Experience shows that about a fifth of the excrement is removed. Thorough flushing of closets and soil pipes without increased FIG. 182. SEPARATION OF EXCREMENTAL MATTER. 223 expense, and a protection from gases by a water-seal, are advan- tages not so easily obtained with ordinary as with separating pails. Moreover, the latter may be changed at longer intervals, 1 to 2 weeks, since they are not so quickly filled. BUERKLI esti- mates the costs as equal to those of the usual cess-pool system ; in Zurich the proceeds from the residue cover the expense. The character of the effluent from separating pails is not so bad as that of the discharge from overflow vaults, since it gener- ally passes through the partition to the sewers in a fresh state. Any quantitative gain from holding back only a fifth of the ex- crement is hardly to be expected. The residue will always give off some gases, necessitating good ventilation ; and a frequent change of pails is desirable. On these grounds, the use of separating pails is apparently advantageous only when it is desired to remove solid matter from the effluent passing into sewers with deficient flushing facilities. 3. In Stockholm and several other Swedish cities where the use of pails is obligatory, frequent use is made of closets in which the urine is immediately separated, in the closet, from the faeces and conducted to the sewers, the solids remaining in the pails. The use of such arrangements has reduced the amount of matter separately removed in Stockholm to only 220 Ibs. per capita annually. If the pails are removed tit long intervals, the nuisance in the house is great, and has led to the substitution of small vessels of 12 galls, capacity for the casks holding 34 galls, that were formerly used. Moreover, the period of removal has been shortened to 2 weeks, and a regular service adopted in place of the system of removal on application, that was once in vogue. 4. Mention must be made of the high-pressure gas system of BREYER. From a vault below the house, receiving not only do- mestic sewage but also waste water and even refuse, the liquid mat- ter is filtered away and discharged into the sewers, the solids being from time to time forced into a cask by a pressure of 45 to 60 Ibs. per sq. in., and again filtered. The solid matter thus col- lected is heated to kill the bacilli and reduced to poudrette. A portable apparatus passes from house to house and furnishes the necessary pressure to compress the matter and remove it. The technical possibility and hygienic value of the system are indis- putable, though it has not been actually tried. The principal objection lies in the cost both of appliances and management. CHAPTER XIV. DISINFECTION. By disinfection, micro-organisms are killed and putrefaction retarded, both while the excremental matter is standing and after it has passed away. Deodorization is partial disinfection, suf- ficient to prevent or destroy offensive gases, but not able to kill the bacteria. Various materials have been employed for disinfect- ing on a large scale earth, peat, sawdust, ashes, carbolic acid, tar, charcoal, copper and iron sulphates, quicklime, and other substances. The earthy materials work mechanically, absorbing water and excrement, fixing the gases, especially ammonia, and retaining the bacteria. Moreover, a chemical action between the oxygen they contain and the organic matter also takes place. The chemical substances change the excrement, precipitating some portions of it. Their influence on bacteria depends upon the kind of chemicals employed. Investigations by ERISMANN on the character of thegases given off from vaults in 24 hours and the oxygen absorbed in the same time resulted as follows, the figures representing grains per gal- lon : Carbonic acid. Ammonia. Methane. Oxygen. Without disinfection 36 6.6 24 45 With iron sulphate 23 ... 9 20 " garden loam 48 2.2 9 53 powdered charcoal 55 6.4 11 52 It will be seen that the chemical action of the iron sulphate is more powerful than the mechanical action of the earthy materials. The latter absorbed more oxygen and gave off more carbonic acid, showing that oxidation rather than putrefaction was taking place. The generation of ammonia does not stop, and possibly the gas carries with it the bacteria which the earthy matter in no way destroys. The cost of disinfection (for materials, appliances, and inspec- tion) must be considered, as well as its actually incomplete work- ing; and on both these grounds a thorough ventilation of a house may be more satisfactory. The process is generally restricted to buildings requiring specially complete sanitation. DISINFECTION. 225 1. Disinfection ivitli Ear tliy Materials. Since the object of such disinfectants is to substitute oxidation for putrefaction, they should be adapted to receive oxygen from the air arid are prefer- ably dry and finely divided. In respect to the absorption of gases, especially ammonia, the fineness of the particles, giving increased surface, and the composition of the substances employed, act in a manner hardly explicable. Investigations by OKTH show that a cubic yard of sand will fix, or retain, 4,100 grains of nitrogen in the form of ammonia. On adding loam and humus the absorb- ing capacity is increased until it reaches 5.5 Ibs. with very rich clay. Hence sand is not adapted for such purposes, while humus, loam, and clay are. This variation gives rise to the diverse require- ments in different places. In England, 4>^ Ibs. of earth per capita are generally used, while in other places as much as 11 Ibs. are employed. The oxidizing power of earth remains constant so long that finally all the excremental matter will be changed to gaseous or soluble bodies. After drying, the earth may be used again and is occasionally employed 5 or 6 times. After satura- tion it is especially adapted for fertilizing purposes, since it con- tains many substances that can be directly assimilated by plants. Ashes act much like earth, both as disinfectants and as fertil- izers, and are more adapted for economical use from the neces- sity of their removal in any case. In many towns they are removed from the house refuse by sieves, which, at the same time, reduce the matter to the desired size. The requisite amount, twice the quantity of excrement, is rarely furnished by the house, Man- chester being apparently the only place where a sufficient quan- tity is obtained. The sifted ashes are stowed away and used in " ash pails " as required. The quantity of material necessary is greatly diminished by the use of some of the special preparations of peat that have recently been introduced. The peat is cut up and sifted, about 80 per cent, of the product being a coarse, fibrous mass, and the remainder a fine powder. Both forms are capable of absorbing liquids and reducing them to various gases, the powder being more efficient than the other portion. The latter, the coarse fibers, will take up 4 to 6 times its weight of water, while the powder absorbs from 6 to 12 times its weight of water and 1.5 to 2 per cent, of its weight of ammonia. Hence, if the annual ex- crement per capita be assumed as 970 Ibs., an eighth of that 15 22Q PEAT DISINFECl'ANTS. weight, 121 Ibs., of powdered turf will be sufficient to absorb the matter, although not enough to take up all the ammonia. In general, the requisite amount for dwellings varies from 66 to 154 Ibs. per capita annually, although sometimes only 33 Ibs. is needed in schools and factories. The bacteria in the saturated peat were found by GAFFKY and SOYKA to be of the harmless species. No injurious bacilli can exist, on account of the tendency of the material to develop acid characteristics. The saturated peat is an almost odorless fertilizer, easily handled and employed. Its value naturally depends upon the amount of water in the excremental matter and upon the soil ; for some kinds it is better adapted than compost earth, and for other kinds it is not so good. The best results are obtained with a light soil, and in any case the ingredients lacking can be easily supplied by adding small quantities of the usual commercial fertilizers. The principal advantage of the peat lies in the ease with which it can be transported. The average results of analyses of this material, after one saturation, give 80 to 88 per cent, of water, 10 to 17 per cent, of organic matter, chiefly vegetable fiber, and 0.4 to 0.8 per cent, of nitrogen. The latter is not greater than the amount present in the contents of cess-pools, but may be raised to perhaps 2 per cent, by repeated saturation. The earthy disinfectants are applied in the closets, vaults, or receiving stations. In the first method the earth is placed in a pail or pan, either when the receptacle is cleaned or automatically by dropping the lid of the seat or moving the door of the closet. The removal is generally by the pail system, although occasion- ally the matter passes through soil pipes to vaults or casks. In the latter case the vaults must be emptied by hand, which is not such disagreeable labor as with the usual class of cess-pools, and takes more time. The preparation and transportation of the disinfectant naturally increases the cost of such systems of treatment and re- moval of excrement, which ranges from $1.50 to $2.50 per capita annually when earth is employed. The proceeds from the sale of the saturated contents of the pails or vaults are sometimes quite large, especially when the earth is used more than once. But earth closets require a constant municipal control, which is ex- pensive, since the householders cannot be trusted to keep the ap- DISINFECTION. 227 plitinces in proper condition. Hence the system has only a limited use, as in Lancaster, where the urine is separately re- moved before disinfection and the amount of earth employed is- only } Ib. per capita daily, and in Manchester and Rochdale, where the house ashes are sifted and the finer parts placed in the closet pails. It is better to use the preparations of peat, already mentioned, as is now largely done in Brunswick, Hannover, Olden- burg, and other places. The cost of 110 Ibs. per capita annually is 40 cts. ; labor and expense of removal, 55 cts. ; total annual cost per capita, 95 cts. In Brunswick the saturated peat is sold at from $1 to $1.75 per ton. In Warsaw, on the contrary, the introduction of peat closets was unsatisfactory. Disinfection in the privy vaults rather than in the separate closets appears to be commendable only where the work of con- trol and removal is easily done, as in the country or in buildings- like the Lyceum at Strassburg, where the vault is easily entered from the side instead of from above. The system is extensively employed in Christiana, where the excrement from each house runs into a shallow pit and there receives the peat and lime used for disinfecting. The thick mass contains 0.7 per cent, of nitro- gen, and is highly valued as a fertilizer, bringing $4.25 a ton. Those portions that cannot be used at once are worked into com- post heaps. This process avoids the use of disinfectants in the closets, and is possibly less expensive than that system. It has, however, the disadvantage of not reaching the small particles of matter that cling to the sides of the soil pipe. Both methods possess the advantage of not contaminating the soil, even with porous or otherwise defective vaults. On the other hand, it is a matter of serious consideration whether or not the earth and its- contents should be allowed to dry and be again used within a house ; an objection that has led to the introduction of the follow- ing system : In many cities the excremental matter is disinfected at re- ceiving stations. This is done partly to preserve the fertilizing portions for future agricultural use and partly to make a mercan- tile product of the dry parts of the street refuse. The latter is an excellent disinfectant, and also adds to the resulting mass from 0.2 to 0.5 per cent, of its weight of nitrogen. The compost is prepared in ditches from 1 to 1-j- ft. deep, and contains from 0.3 to 0.8 per cent, of nitrogen according to the amount of water 228 DISINFECTION BY CHEMICALS. present ; so that the addition of the refuse to the excrement results in a compound containing as high a percentage of nitrogen as the latter of its two ingredients. The faecal compost has considerable value in some places from 48 cts. to $1.24 per cu. yd. in Holland, 57 cts. in Glasgow, 67 cts. in Emden. In some cases the cost of removal is more than covered by the proceeds. In Emdeu the contractors do the work gratis ; in Glasgow and Groningen a profit of 20 to 50 cts. per capita an- nually is made. On the other hand, in Bergen and Stockholm, there is a loss of 42 and 18 cts. , respectively, per capita annually. Where the compost must be carted any distance in wagons its value is considerably re- duced, as in Cologne, where it is worth only 19 cts. per cu. yd. delivered at the fields. In this connection, it should be noted that in Amsterdam the excre- mental matter from 40,000 per- sons is delivered, by the pneu- matic system at a central station, as already described, and is there worked into compost with the street sweepings. Sometimes the faeces are mixed with the semi-fluid matter removed from overflow vaults, in order to "freshen" it. 2. Disinfection by Chemicals. Chemicals are extensively used in the " separation" system of handling excremental matter, in order that the urine passing into the sewers and the faeces re- maining in the pails or vaults may be rendered harmless and odorless. The chemicals are always added in a liquid form and mixed with the excrement as thoroughly as possible. GERLOCZY recommends the use of copper sulphate and carbolic acid, as giv- ing the best results at a small expense. A number of compound disinfectants are now in the market, but the principal ones are sold by ROBBER, in Dresden; MAXFRIEDRICH & Co., in Leipzig,and ZEITLER, in Berlin. The FRIEDRICH disinfectant contains carbolic acid, hydrate of alumina, oxide of iron, and lime. The leading sys- tems of domestic disinfection are those of FRIEDRICH and ZEITLER. FIG. 183. DISINFECTION. The closets are arranged as shown in Fig. 183, and usually nave a "mixer," Fig. 184, in the top story, which acts much like an ordinary flush tank, being connected at one place with the water mains and at a second place with the flushing pipe of the closets and urinals. A perforated zinc box contains the disin- fectant, the flushing water is taken from the tank arid a fresh supply is admitted from the mains. In the FRIEDKICH sys- tem, Fig. 184, the inflowing supply passes through an in- jector, which forces air into the water through a perforated tube at the bottom of the tank and causes the water to circulate through and around the box of disinfecting material. In the ZEITLER system, Fig. 184#, the water has to pass through two conical FIG. 184a. FIG. 181&. orifices, and in this way a series of little waves is caused, which effectually send the water through the box. The closets are thus flushed with disinfecting water, which also passes through the soil pipe into the vault, and there precipitates the solids by the sulphate of alumina and lime it contains. The first vault is usually connected by an overflow opening with another, called the settling tank, where the re- maining suspended matter is removed and a fairly pure effluent enters the sewers. The sewer connection can generally be closed by a valve, in order that the contents of the vaults may stand a sufficient time to separate into solid ^ and liquid portions. Various modifications of this gen- FIG. i84e. eral process have been proposed from time to time. The follow* ing are the most important : a. The mixer is sometimes placed below the closets, Fig. 184c, in order to save piping and diminish the probability of freezing. The whole apparatus is then tightly closed, and the 230 DIS1NFECITON BY CHEMICALS. pipe to the closets is somewhat larger than that to the mains, in order that the flushing water may contain a portion of the con- tents of the mixer. A check valve prevents the passage of water in the wrong direction. Z. A mixer is sometimes employed for each closet, in order that the existing piping need -be altered as little as possible. In such cases a small apparatus is placed below each seat. * A mixer is occasionally placed near the vault, into which the disinfecting solution is discharged once or twice weekly in houses, and more often in large buildings. Special attendance is neces- sary in this case, and the closets and soil pipe no longer receive any benefit from the process, which has led to its official prohibi- tion in Berlin. It has the ad- vantage of requiring no altera- tion in existing piping, and was recently recommended by FRIEDRICH. It is now the standard system in Karlsruhe. d. Where there are no suit- able water pipes, the excrement itself is used to dissolve the dis- infectant, which is contained in a small tank, as shown in Fig. 185. The results of such an arrangement are uncertain. The thoroughness with which the process is conducted is tested by chemical analyses of the contents of the second vault. The liquid must have an alkaline reaction when the disinfectants are properly added, usually once a week. The standard effluent contains, besides carbolic acid, 35 grains of quicklime per gallon, which have been found sufficient to prevent putrefaction. Since it also contains nearly all the nitrogen of the excrement, the de- posits in the vaults have little agricultural value, and the inter- ception makes no material change in the hygienic character of the sewers and rivers, serving chiefly to prevent deposits in the sewerage system. In this respect, the chemical separation is more efficient than the mechanical. This system of simultaneous disinfection and separation is permitted in Leipzig, Dresden, Chemnitz, Hannover, and Karls- ruhe, and is extensively used in the cities of Saxony, where the separation of faeces is regarded as of fundamental importance. FIG. 185. DISINFECTION. In the still unsewered districts of Berlin, where there is a water service, the system is employed, and the purified effluent allowed to flow off in the street gutters. The cost of disinfection is stated by FRIEDRICH to be %2% cts. per capita annually for small dwellings and less for larger houses. The removal of the sludge in the tanks may be estimated at 10 to 18 cts. Since the sludge has no commercial value, the cost of the system averages from 25 to 38 ccs., sometimes rising to 50 cts. per capita annually. In addition to this sum is the expense of public supervision, without which the process might not be properly conducted. The frequent presence of these officials in a house is certainly unwelcome, and an official report of a Prussian committee declares such supervision to be " impossible and hate- ful. " On this account the plan is not suited for large cities, and will probably be restricted to public buildings and the better class of private houses. The cost of the FRIEDRICH system, as well as alleged choking of the pipes, have led to its rejection in favor of simply manual addition of the disinfectant, either in the vault, as in theSuEVERX- ROEBER system, or else in the closet. The latter plan is plainly the better, since the closets and soil pipes are then disinfected. But official inspection is then absolutely essential in order to in- sure that the additions of disinfectant are made at the proper interval, and the system is best adapted for places where it is sure to be properly conducted, as in hospitals and railway stations. Waste water is also disinfected in some places, either by flush- ing the kitchen and other connections with disinfecting water from the mixer or by conducting the waste to the vault, which must then contain a somewhat increased amount of the disin- fectant. PETRI has proposed to dispose of the sludge in the vaults by mixing it with peat and pressing the mass into bricks, which will burn cleanly and without odor. 232 AMERICAN STREET MAINTENANCE AND SEWERAGE. FIG. 187. PROVIDENCE CATCH-BASIN. Weights, 167 and 177 Ibs. ***>*:{> ,^jv'-** **,' Weight, 80 Ibs. Fia. 189,-MoDiFiED CROES TRAP. FIG. 190. CATCH-BASIN COVER. NOTES ON AMERICAN PRACTICE IN STREET MAINTENANCE AND SEWERAGE. The following matter relating to sewers, street maintenance, and the disposal of refuse is chiefly taken from a series of ar- ticles on municipal engineering, published in ENGINEERING NEWS in- 1886. These articles were prepared by engineers con- nected usually with the departments described, and give the actual practice at that date in the several localities mentioned. The illustrations were prepared from standard drawings furnished by the departments. CATCH-BASINS AND TRAPS. Fig. 186 illustrates the Boston standard design for a catch-basin. These basins are usually located about 250 ft. apart, with the Fro. 186. STANDARD CATCH-BASINS, BOSTON, MASS. manhole in the sidewalk, as shown. When this basin is on a grade in the street the entrance-stone is so shaped as to divert the water into the curb opening, as indicated. The trap here illustrated is- open to the objection that, if the water in the basin has to be passed out of the 10-in. pipe, or if this pipe is in any 234 AMERICAN STREET MAINTENANCE AND SEWERAGE. way obstructed, the cement seal about the hinged trap must be broken and then renewed. The usual practice, however, in emptying this basin is to dam the gutter entrance and then hoist the water out of the manhole in buckets. Figs. 187 and 188 illustrate the Providence standard catch- basin with a modified form of the CROES trap. The bottom of this basin is formed of North River flagstone, and the brick walls are 8 ins. thick and lined on the inside with cement mortar up to the water line. Fig. 189 shows plans and sections of different Horizontal Sec. A B Plan. FIG. 191. CATCH BASIN, WASHINGTON, D. C. types of " extra inlets" to catch-basins, by the use of which the number of such basins is reduced, the water is more easily disposed ' of, and the amount of water flowing over the crossings is reduced. The style of catch-basin cover is shown in Fig. 190. The standard catch-basin used in the city of Washington, D. C., is shown in Fig. 191. These basins are built of brickwork, made perfectly water-tight by an interior coating of neat hydraulic CATCH-BASINS. 235 cement | in. in thickness. The cover of the basin is usually 4-in. flagstone ; the manhole opening is 2 ft. in diameter, and is closed with a cast-iron cover ; the throat-stone and side-stones are of granite. The usual dimensions of this basin are as follows : Gutter opening, 3 ft. 5 ins. long by 8 ins. high ; the interior of the receiving basin is 2 ft. by 4 ft. and 6 ft. deep ; the " stench - box" is 1 ft. 3 ins. square, and the bottom of the discharge pipe is located 6 ins. above the top of the opening connecting the receiv- ing chamber and the stench-box. Fig. 192 shows an alley and gutter basin of the same general construction as the one described above, but smaller and covered with an iron grating. This drop is used in alleys, street gutters, and at public hydrants to carry off waste water. The Philadelphia standard catch-basin is illustrated by Fig. 193. While the general design is somewhat similar to the Wash- ington catch-basin, just described, the detail is more elabo- rate, and the parts subject to wear in cleaning are faced with flagstone. The arched cover to the stench-box is also less liable to permit the escape of nox- ious gases than the -single cemented stone used in the former case. Fig. 194 shows a cast iron catch-basin used to some extent in Philadelphia. The trap here is an initial part of the casting. A form of catch -basin used in the city of Louisville, Ky., by E. T. SCOWDEN, City Engineer, is shown in Fig. 193. This basin is constructed of brick laid in hydraulic cement. Ac- cording to the specifications provided, the bottom of the excavated pit is first covered with a 2-in. layer of concrete, and on this is laid a course of brick flatwise, thoroughly imbedded in cement mortar. Over the brick is a 1^-iri. course of cement mortar, and on this is laid another of brick flatwise. On this upper course of FIG. 192. ALLEY AND GUTTER DROP. 236 AMERICAN STREET MAINTENANCE AND SEWERAGE. brick is laid a flooring of 2-in. oak boards, to prevent disturb- ance of the brick, or wear in removing the contents of the basin. The side walls are carried on the brick and concrete only ; though one or two brick courses are allowed to project inside over Sectional Elevation. FIG 192a. LOUISVILLE CATCH-BA&INS^ FIG. 193. STANDARD CATCH-BASIN, PHILADELPHIA. the boards to keep them in position. In carrying up the walls a space 1|- ins. wide, is left between the inner and outer rows of SEWER SECTIONS. 237 brick, which space is thoroughly fitted with cement mortar as the bricks are laid. The space between the outside of the brickwork and the sides of the pit, about 2 ins., is also well filled with cement mortar. The trap shown is made of stoneware, and is provided with a tight iron cover. 238 AMERICAN STREET MAINTENANCE AND SEWERAGE. SEWER SECTIONS. The following sketches illustrate various American types of sections adopted for sewer construction. Fig. 195 is reduced from an illustration in "Main Drainage Works of the City of Boston, Mass./' by ELIOT C. CLARKE, C. E., engineer in charge. Taking the figures found upon this plate, Figs. 1 and 2 show the 10 ft. 6 in. main sewer, with rubble side walls ; Fig. 3 is the bond used in the spandril ; Figs. 5 and 6 are the manholes- and their connections, with the wrought- iron step shown at Fig. 7. These manholes are usually located 400 ft. apart. Fig. 9 shows the sewer in conglomerate rock and coarse sand. Fig. 10 represents a portion of this sewer where it is car- ried over a bed of marsh mud from 2O to 86 ft. deep. In this case the intend- ed street was first filled in and the- Fl S- 8 S ewer then built with a wooden shell, formed of 4-in. spruce plank 10 ins, wide. Every fourth plank was wedge- shaped on the radial line, and the whole structure was se- curely spiked and treenailed together. It was finally lined with 4 ins. of brickwork, and the average cost complete of a sewer 10 ft. 6 ins. m inside diameter was $56 per lineal foot. In the course of about two years this section settled in a long curve 18 ins. below the original grade line, but without any apparent damage. SIDE ENTRANCE AND BOW CHAMBER FIG. 195. SEWER SECTIONS. 239 Fig. 11 in tliis plate shows a portion of this* sewer passing within 35 ft. of a large gasholder. Sheet-piling was used here as a precaution, and the trench was back-filled with concrete to the level of the crown of the arch. Figs. 12 and 16 show side en- trances arid a boat chamber, the opening to the street being rect- angular, 11 ft. by 4 ft., large enough to permit a boat to be passed down to the sewer for inspection purposes. Fig. 13 illus- trates a pile foundation ; and Figs. 14 and 15. tunnel sections. The total cost, in 1878, of 3.2 miles of this main sewer, 10 ft. 6 in. diameter, was $606,031, or about $36 per lineal foot. The standard section for oval sewers in the city of Providence, R. I., is shown in Fig. 196, together with a table of elements used by the city engineering depart- ment in figuring upon sew- ers of this type. These ele- ments are all given in parts of the smaller or horizontal inside diameter, D, and are self-explanatory. The standard type for Washington, D. C., is given in Fig. 197. The present practice in this city is to make all sewers above a 24- in. pipe in size egg-shaped up to a maximum size of 10 x 15ft. No pipe sewers less than 8 ins. in diameter are put down, and these are laid in concrete, as shown at the base of the cut. This con- - rw'ie" ~ COVER crete is 6 ins. thick on the FIG. i95a. sides and bottom, and the joints are covered by a band laid in hy- draulic cement. T-branches for 6-in. house connections are put in when the sewer is being constructed, and a record kept of the distance of these connections from the nearest manhole. 240 AMERICAN STREET MAINTENANCE AND SEWERAGE. In egg-shaped brick sewers varying in size from 2x3 ft. to and including 4 x 6 f t. the invert is made of the half of a terra- cotta pipe laid in Portland cement. For the invert of all sewers larger than this a paving of trap or granite blocks is set in Port- land cement. In the brick sewers terra-cotta junction blocks are set in for house connections just above the springing line of the arch. The minimum radius for turning angles is 50 ft. in all cases. EGG SHAPC. TABLE OF ELEMENTS FOX/H : CE NTfO?UJJ?f! t. Name. Egg Shape. Four-Cen. Ell. Area 1.1485321 Z>* 1.1728072 Z> 2 Periphery 3.9649467 D 3.9649519 D Mean hydraulic radius, when full f 0.289671 D 0.295794 D Approx. value of D in terms of the dia. 6 of a circular sewer of equal capacity of discharge 0.8388 <* 0.8272 rf FIG. 196. SECTIONS OF OVAL SEWERS, PROVIDENCE, R. I. In the upper corner of Fig. 197 a drop for dry-weather flow is shown, to be used in cases where it is undesirable to discharge into a stream, unless the sewage flow is very much diluted by the rain- fall. As will be seen, the ordinary flow runs over the stone sill into a square receiving basin below, and is carried in a pipe sewer to a proper sewage outlet. In the case of a storrn, the in- creased velocity dne to the greater volume causes this diluted flow to leap the drop opening and to pass to the storm outlet. In Philadelphia, Pa., both circular and oval sewers are used, as is shown in Fig. 198, both being maximum sizes of their class. DETAILS OF SEWERS. 241 No special explanation of these sketches is necessary. The house connections are G ins. in diameter and are located 15 ft. apart. They are inserted about 45 above the springing line and at an angle of 45 with the sewage current. Fig. 198 shows the pipe sewers and their concrete beds, as constructed in this city. SEWER DETAILS. Manhole Covers. Figs. 199 and 200 illustrate the ventilated manhole cover and its catch-bucket used in the improved sewer- JVC i. FIG. 197. STANDARD SEWERS, WASHINGTON. age of Boston, Mass. This studded cover has been carefully de- signed and well tested ; and the bucket suspended under it, as shown in Fig. 8 of Fig. 195&, is intended to catch any dirt from the roadway, or miscellaneous rubbish that might pass through the 16 242 AMERICAN STREET MAINTENANCE AND SEWERAGE. openings in the cover. The bucket is made of galvanized iron, well - coated with tar, and is lifted out and emptied as occasion requires. Fig. 201, page 245, shows a similar manhole cover and bucket in use in Philadelphia, Pa. The- standard frame and cover as used in Providence, R. I., is given. in Fig. 202,. page 246. Sewer Con- nections. The standard con- nections for sewers as print- Red on the back of drain permits issued by the- city of Boston are shown in Natural foundation. Fig. 203. The- connections for pipe and brick sewers are of the usual type ; but the third illustration is made necessary by the old wooden sewers still in existence in that city. Beveled connec- tion pipes of 6, 8, and 12 in. diameter are given in Fig. 204, as used in Providence, E. I. Manholes to Sewers. In ad- dition to the form of manhole used in the Boston improved sewerage work (Fig. 195), we- have in Figs. 205 and 206 the standard type used in Providence, Type of Maximum Section on Artificial foundation. FIG. 198. STANDARD SEWERS, PHILADELPHIA. Fia. 198a. PIPE SEWERS. R. I., for deep and pipe sewers. The standpipe shown with Fig. CLEANING SEWERS. 205 is located with its top 11 ft. below the general surface of the- street ; it is put in when the sewer is built and equalizes the FIG. 199. -VENTILATED MANHOLE COVER. depth of cutting for future house connections, regardless of the- depth of the sewer proper. The method of building manholes on 244 AMERICAN STREET MAINTENANCE A\D SEWERAGE. FIG. 200. CATCH-BUCKET UNDER VENTILATED COVER. large sewers in Philadel- phia is shown in Fig. 207. Wrought and cast iron steps for manholes are illustrated in Figs. 206 and 207. Invert Blocks. Where the work of lay- ing sewers has to be conduct- ed in wet ground, in- vert blocks are employed Cotftrecr/o/f trrrn Bfif Cotftficr/ott N/TH ftboa tfei FIG. 203. SEWER CONNECTIONS, BOSTON, MASS. for the bottom por- tion. Those used in Providence, R. I. (Fig 208), are made of good clay, well burned and salt-glazed, similar in these respects to sewer pipe. These blocks are hollow and are made in two sizes, to conform to 8-in. and H FIG. 204. BEVELED CONNECTIONS. CLEANING SEWERS. 245 4-in. brickwork, and eacrh block is 2 ft. long. I*n Philadelphia, blocks of concrete and a combination of concrete and brick are used for the same purpose. (See Figs. 209, 210.) Flushing Small Sewers. A device introduced in Boston some years ago and successfully used for flushing small sewers is shown in Fig. 211. The cut illustrates the general arrangement adopted for a 3-f t. circular sewer, though it is understood that the same method was applied with success to an oval sewer 5 ft. high by 2 ft. 8 ins. wide. For convenience in passing it down the sewer manholes, the " kite " or scraper is made in two parts, as shown. The bottom brace and roller keeps the rope from being cut by the brickwork 246 AMERICAN STREET MAINTENANCE AND SEWERAGE. fairly in the axis of the tunnel, and a couple of turns of the rope around the top frame enables the attendant to control the forward movement of the scraper. Weight of Frame alone Zoo. Ibs. FIG. 202. KNOBBED MANHOLE COVER. 22 20 FIG. 202a. PLAIN MANHOLE COVER. In practice, the trailing wheel was found to be a necessary adjunct to counteract the backward tip of the frame resulting; OF THK UNIVERSITY CLEANING SEWERS. 247 from the weight of a long rope. In using this scraper it is put together as shown, and is then held stationary just below the man- hole until a sufficient volume of water has accumulated behind it. The scraper being somewhat smaller than the sewer sections, the water escapes through the annular space in the form of a thin sheet or jet, and with a velocity due to the head secured, some- Cross Section. Longitudinal Section. FIG. 205. MANHOLE ON DEEP SEWER. Horizontal Section. FIG. 206. MANHOLES o.v PIPE SEWERS, PROVIDENCE, R. I. times equaling 16 ft. per second. As the rope is slowly paid out the scraper advances and pushes before it a bed of sand and gravel, some- times 8 ins. deep and 100 ft. long in the Bos- ton practice. When the debris becomes too heavy the scraper is 248 AMERICAN STREET MAINTENANCE AND SEWERAGE. stopped at a manhole, the water is allowed to resume its usual low level, and the rubbish is hoisted out. Sewer Cleaning. F. FLOYD WELD, City Engineer of Water- bury, Conn., in 1885, describes the following appliance for cleaning out small sewers. In the city named there are about 10,000 lin. ft. of sewers, 1 ft. 6 in. by 2 ft. 3 in. These sewers carry storm water from catch -basins, and those having a light grade were found to retain sand and mud carried in from un- paved streets. PRIVATE DRAINS. 249 As men cannot enter these sewers, the engineering depart- ment devised the apparatus shown in Fig. 21la. This was a three- leg derrick, a scraping bucket, and a pulley set in a frame, as shown in the cuts. The derrick stood about 8 ft. high, and attached to two of the logs was a winding-drum operated by two ordinary carriage wheels. The bucket, or scraper, was made of galvanized iron, strength- ened by iron bands around the two ends. It was 8 ins. in dia- meter, about 2 ft. long, and provided with a flaring collar or mouth. To the in- side of the mouth an iron bail was riveted. The pulley shown was 6 ins. in diameter, and a band of iron 2x4 FIG. 207a. MANHOLE STEP. FIG. 209. FIG. 208. INVERT BLOCK. FIG. 210. ins. connected the two ends of the IJ-in. iron shaft. This curve conformed to the crown of the sewer. A turn-buckle on the shaft served to press it out and hold it in position against the sides of the sewer. In operating this apparatus the derrick is set up over the man- 250 AMERICAN STREET MAINTENANCE AND SEWERAGE. hole where the material is to be removed ; the pulley and frame are put in place, and a small line is then floated down from the manhole above. This line is caught at the manhole and used to FIG. 211. SMALL SEWER FLUSHING. draw the hauling rope to the upper manhole; one end of this rope is then attached to the ring in the end of the bucket bail, and the other end to the drum on the derrick. Another rope is also tied to the ring on the scraper and let out as this advances, and is used to pull it back for a fresh load. When the sand is cleaned out from one section, the third leg of the derrick is folded down upon the drum, the ropes, bucket, and pulley loaded FIG. 2iia. PRIVATE DRAINS. 251 on the derrick, and the whole is then trundled off to the next point of use on the two wheels which do other duty in operating the drum. It has been successfully used in pipe sewers, and Mr. WELD said that they have had no difficulty in passing around -curves. The Hitchcock Sewer Inlet Trap. The purpose of the trap shown in Fig. 211b is to prevent the escape of gases from the sewer through an in- let in the cooler sea- sons, when the air in the sewer is usually warmer than the air in the streets. The device explains itself. The lid, A, opens and permits the discharge of water en- FIQ. 2ii6. tering the inlet ; but at other times it remains tightly closed. by its own weight against the fixed spout D. This trap is made of cast iron, and has been -successfully used in Springfield, Mass., for about 15 years. It is manufactured by the Springfield Foundry Co., of that city. A diagram illustrating the standard system of drainage in Providence, E. I., is given in Fig. 212. This is a cross-section FIG. 212. SECTION ILLUSTRATING DRAINAGE. of a typical street, showing the location of the catchbasin, sewer and storm sewer, house connections, and water and gas pipes. The diagram is self-explanatory. It should be mentioned that in this city the ruling depth of sewers from street grade to the inside crown of the sewer has been fixed at 11 ft., and over 30 252 AMERICAN STREET MAINTENANCE AND SEWERAGE. miles of sewers have been built in accordance with this rule. The 11 ft was adopted because it permitted the private drain, laid at the minimum slope permitted (see rules and regulations for private drains), to reach a point 100 ft. from the street line and still be below the level of the curb. MISCELLANEOUS TABLES ASTD RULES, FOR SEAVERS A:N~D DRAINS. TABLE SHOWING SIZE, RELATIVE CAPACITY, AND MATERIAL REQUIRED FOR VARIOUS SIZES OF SEWERS, WASHINGTON, D. C. f , *> S. A 1 . Size. 2^. |.S 1| o ^c^ 55 w fi P.'"". "lo? ^1 - 2 o o u o 2 ro *pH Is? W^ K| ffl E-i 12" 0.78 0.25 1.00 1.69 12 1.0 15" 1.23 0.31 1.84 2.33 15 ' 1.0 18" 1.77 0.375 3.05 2.40 18 1.0 i 21" 2.40 0.438 4.65 3.^0 21 1 24" 3.14 0.500 6.68 3.35 24 1.0 2.0' X 3.0' 4.64 0.567 10.81 3.88 4.680 12 5 2.25' X 3.37' 5.92 0.649 15.17 4.225 5.128 15 0.5 2.50' X 3.75' 7.23 0.700 19.40 4.165 5.521 15 0.5 i 2.75' X 4.12' 8 71 0.787 25 51 4.643 6.099 15 0.5 ! 3 0' X 4.50' 10.41 0.857 32.46 5.360 6.620 15 0.5 i 3.25' X 4.87' 12.13 0.937 40.15 5.393 7.134 18 0.5 3.50' X 5.25' 14.10 1. 010 49.26 5.622 7.683 18 0.5 3.75' X 5.62' 16.19 1.090 59.30 6.270 8.213 18 0.5 4.0' X 6.0' 18 54 1.150 70.69 6.347 8.624 21 0.5 4.5' X 6.75' 23.26 1.300 95.75 6.040 8.660 4.550 5.0' X7.50' 28.71 1.450 126.44 7.330 8.650 5.310 5.25' X 7.87' 31.67 1.521 144.84 7.800 9.860 5.310- 5.50' X 8.25' 34.74 1.590 163.13 8.138 10.135 5.938 6.0' X 9.0' 41.61 1.738 205.89 12.830 15.000 6.080 *6.5' XSi.75' 48.53 1.882 254.60 15.612 16.832 6.768 t6.5' X 9.75' 48.53 1.882 254.60 26.350 7.270 6.768 7.0' X10.50' 56.27 2.027 309.25 14.730 17.160 7.770 *10.0 circ. 78.54 2.oOO 493.03 17.378 27.598 10.470 t20.0 " 314.16 5.000 3016.73 130.421 28.512 15.908 * Brick arch, t Concrete arch. Rules and Regulations for Private Drains Adopted by the Board of Public Works of Providence, R. /., May 27, 1882. 1. Applications for permits to connect with any sewer must be made in writing to the Board of Public Works by the owners of the property to be drained, or by their duly authorized attorneys, and must be accompanied by a clear description of the premises to be drained and of the drains required, and also by certain agreements, all as provided in the printed form of application issued by said Board. 2. No one but a drain layer duly licensed by the Board 01 Public Works will be allowed to make connection with the sewers,. PRIVATE DRAINS. 253 nor lay any drains in connection therewith; and any person so li- oensed shall give personal attention to any work done under his li- oense. He shall also employ none but competent persons to -do said work. 3. Notice must be given at the office of said Board 24 hours, if required, before any street or public way can be opened for the purpose of laying a private drain, or before any drain pipe can be extended from work previously done and accepted, or new connec- tions of any kind be made with such work, unless otherwise per- mitted by the City Engineer. 4. No work of laying drains can be commenced or continued unless the permit is on the ground, in the hands of the drain- layer or some one employed by him. Rules for Laying Drains. 1. In opening any street or public way, all materials for paving or ballasting must be removed with the least possible injury or loss of the same, and, together with the excavated materials from the trenches, must be placed where they will cause the least practicable inconvenience to the public. As little as possible of the trench must be dug until the junction piece into the sewer is found, unless it is first determined to make a new opening into the sewer. 2. Whenever, in the opinion of the City Engineer or author- ized inspector, the sides of the trenches will cave, sheeting and braces must be used to prevent caving. 3. The Board of Public Works, the City Engineer, and their authorized agent are to have at all times facilities for inspecting the work and materials while under the charge of the drain layer ; and, if required, no pipe or other materials for the drains can be used till they have been examined and approved. 4. The least inclination that can be allowed for water closet, "kitchen, and all other drains of not over 6 ins. diameter, liable to receive solid substances, is i an in. in 2 ft.; and for cellar or other drains, to receive water only, of an in. in 2 ft. The depth of the crown of a drain at the curb line shall be deter- mined by a rise of J- of an in. per foot from the crown of the sewer directly opposite. 5. The ends of all pipes not to be immediately connected with are to be securely stopped by brick and cement or other \vater tight and imperishable materials. 6. All pipes that must be left open to drain cellars, areas, 254 AMERICAN STREET MAINTENANCE AND SEWERAGE. yards, or gardens must be connected with suitable catch -basins, the bottoms of which must not be less than 2? ft. below the bot- tom of the outlet pipe, the size, form, and construction of which are to be prescribed by the officers named in the second rule.. When meat-packing houses, slaughter-houses, lard-rendering es- tablishments, hotels, or eating-houses are connected with the- sewers, the dimensions of the catch-basins will be required to be of a size according to the circumstances of the case. When the end of the drain pipe is connected with a temporary wooden catch- basin for draining foundations during the erection of buildings,, the drain layer will be held responsible for dirt or sand getting into the drain or sewer from such temporary catch-basin. 7. No private catch-basin can be built in the public street, but must be placed inside of the line of the lot to be drained, ex- cept when the sidewalks are excavated and used as cellars. 8. Unless special permit shall be granted by the Board of Public Works, no privy vaults can be connected with the sewers ex- cept through an intervening catch-basin, and the discharge pipe of the vault must be high enough above its bottom to effectually prevent anything but the liquid contents of the vault from pass- ing into the drain; 9. The inside of every drain, after it is laid, must be left smooth and perfectly clean throughout its entire length ; and to insure the same a scraper of suitable material, of the shape of the pipe and slightly less in diameter, shall be drawn through each length of pipe after the same has been laid. 10. In case it shall be necessary to connect a drain pipe with a public* sewer where no junction is left in such sewer, the new connection with such sewer can only be made either by one of the employes of the Board of Public Works or when an officer r named in rule two, is present to see the work done. 11. Whenever it is necessary to disturb a drain in actual use, it must in no case be obstructed without the special direction of one of the officers named in rule two. 12. The back-filling over drains, after they are laid, must be puddled or solidly rammed, and together with the replacing of ballast and paving must be done within 48 hours after the completion of that part of the drain lying within the public way, and done so as to make them at least as good as they were before they were disturbed, and to the satisfaction of the Board PR JVATE DRAINS. 255 of Public Works and the officers mentioned in second rule ; and the owner will be held responsible for any settlement of the ground which occurs within one year on account of laying said drain. All water and gas pipes must be protected from injury or settling, to the satisfaction of the Engineer. 13. Every drain layer must inclose any opening which he may make, in the public streets or ways, with sufficient barriers, and must maintain red lights at the same at night, and must take all other necessary precautions to guard the public effectually against all accidents from the beginning to the end of the work, and can only lay drains on condition that he shall use every precaution against accidents to persons, horses, vehicles, or property of any kind. 14. In case a water or gas pipe should come in the way of a drain, the question of passing over or under the water or gas pipe, or of raising or lowering it, must be determined by one of the officers named in rule two. 15. All exhausts from steam engines and all blow-offs from steam boilers must be first connected with a catch-basin of such dimensions as the officers mentioned in second rule may prescribe ; and in no case will they be allowed to connect directly with the private or public sewers without special permission from the Board of Public Works or the City Engineer. 16. Such information as the City Engineer has with regard to the position of junctions will be furnished to drain layers, but at their risk as to the accuracy of the same. 17. When any change of direction is made in the pipe, either in a horizontal or vertical direction, curves must be used. No pipe can be clipped contrary to the direction of officers mentioned in rule two. 18. All persons are required to place an effectual trap in the line of drain just before it leaves the premises, and to make an open connection with a down-spout back of the trap ; also, when possible, to make an open connection with the highest part of the soil-pipe within the premises through a large pipe or flue, to a point above the roof of the building, unless special permit to vary from the same shall be granted by the Board of Public Works. 19. The drain layer shall faithfully observe all the rules for laying drains as adopted by the Board of Public Works, and, if so directed, shall not cover any of his work until it has been ex- amined and accepted by the proper officer. 256 AMERICAN STREET MAINTENANCE AND SEWERAGE. 20. No drain laver or person employed by him will be allowed to rest any planking or other material upon any gas or water pipe. Violations of this rule will be sufficient cause for the revocation of license. 21. The drain-layer who obtains the permit shall carefully fill out the blank return provided, whether for new work or for alterations or additions, and return the same within 48 hours after the completion of said work. 22. All work shall be done in such manner and at such times as to interfere as little as possible with the public travel and con- venience ; and the drain-layer shall conduct his work for this object as the Engineer may from time to time direct. 23. Every person violating any of the provisions of the fore- going rules shall be liable to pay a fine of not less than twenty nor more than fifty dollars, and shall be subjected to a forfeiture of his license. Rules for Finding Number of Bricks in Circular and Egg- SJiaped Sewers. Mr. MEADOWS, of the Canadian Society of Civil Engineers, gives the following rules for the above, with brick 8-J- x 2 x 4 ins., and J-in. joints: For circular sewers, multiply the internal diameter of sewer in inches by 1.1421 to find the number of bricks in first ring. Then add 10.28 inches to the internal diameter for each addi- tional ring. For circular sewers j (d/' x 1.1421) + [(d 2 " + 10.28) x 1.1421] I x length in ft. x 1.37144 = number of bricks in sewer. For egg-shaped sewers, multiply the internal transverse diameter of the sewer in inches by 1.4418 for the first ring, and add 10.28 inches to the internal diameter, as before, for each additional ring. NOTE. The most usual way is to calculate the number of cubic feet of masonry in the sewer . See Washington, D . C . , p . 252 . 258 AMERICAN STREET MAINTENANCE AXD SEWERAGE. STREET CLEANING. SWEEPING MACHINES. At the time this series of articles on " Municipal Engineering" was prepared (1885) the sweeping machine in use in Boston was that known as the STACKPOLE (Fig. 213). While the illustration shows a one-horse sweeper, other machines in use by the depart- ment were fitted with a pair of front wheels and a pole, and were pulled by two horses. The reason given for the greater economy of the latter machine was that two horses can work in such a machine all day, while in the smaller sweeper one horse can enly work one-half day, and time is lost in the change. Rattan is used in the broom instead of the usual " bass " : and while this rattan is more expensive, it is found to be much more- efficient in handling slush in winter, in sweeping gravel from the railway tracks, cleaning crossings, etc. The rattan (in 1885) cost 30 cts. per pound, as compared with " coir grass," or "bass," at 12 cts. per pound. The sweepers used in Providence, R. I. (Fig. 214), are made by the ABBOTT DOWNING Co., of Concord, N. H. But in this case a third wheeLand a pole is added, adapting them to use with two horses. Figs. 215 and 215 show the '' Capital" sweeping machine, invented by L. P. WEIGHT, of Washington, D. 0., and was used by him when he had the contract for cleaning that city. This machine is made entirely of iron, except the wheels, and is made heavy so as to remove all dirt from the depressions in the pave- ment, car tracks, etc. It is pulled by four horses and sweeps from the center of the street, to the right, into the gutter. 260 AMERICAN STREET MAINTENANCE AND SEWERAGE. FIG. 215. STREET SWEEPER, WASHINGTON, D. C. THE CAPITAL SWEEPING MACHINE. 261 262 AMERICAN STREET MAINTENANCE AND SEWERAGE. The broom, which makes an angle of 45 with the axis of the machine, is 12 ft. long, and sweeps a path 9 ft. wide. When new this broom is 5 ft. in diameter, and, with the broom shaft, it weighs 650 Ibs. The broom is made of 96 bunches of white birch twigs, and is worn down to 2 ft. in diameter before it is renewed. The whole broom is hung at the center so that it can readily ad- just itself to any un- even surfaces or in crossing a street. This machine sweeps 125,000 sq. yds. in 10 hours. The city of London uses about 2,000 of the sweeping machines shown in Fig. 216, page 258. This is the so-called BARNARD- CASTLE machine. The frame is built almost entirely of wrought iron, and it is durable, light and handy. Sev- eral sizes are built; one, to be used with one or two horses, will sweep a path 6 ft. wide ; and the other is a heavier machine requiring t\Vo horses and sweeps 7J ft. wide. The cut illustrates the latest form of the machine, which sweeps 7 1 feet wide. The broom in this machine has a universal joint in the center to compensate for inequalities in the pavements. In his treatise on the scavenging and cleaning of towns, Mr. H. PERCY BOUL^OIS, M. Inst. C. E., says that a 6-ft. machine will sweep from 8,000 to 10,000 sq. yds. per hour in fair work. He fur- ther says that it costs little for repairs, and that one set of brushes (costing about $10) will last during 180 hours of constant work. This machine is now sold in the United States by W. C. OASTLER, 43 Exchange Place, New York, the American repre- sentative of the makers. FIG. 213. STACKPOLE STREET SWEEPER. STREET SPRINKLING. 263 STKEET SPRINKLING. What may be called a very common form of street sprinkling machine in American cities is shown in Fig. 217, page 266, in longitudinal section, rear cross-section, and front view. This is the so-called ".Monitor" type of sprinkler, made by the ABBOTT DOWNING Co., of Concord, N. H. A street-scraping machine made by L. P. WRIGHT & SON, of Washington, D. C., is shown in Fig. 217. It is used for collecting FIG. 214. STREET SWEEPER, PROVIDENCE, R. I. snow or mud from the streets, in cases where this mud is too deep and heavy for a sweeping machine. The machine has an iron frame with 12 steel shovels beneath the body, arranged diagon- ally, and pressed down against the pavement by strong springs. With 4 or 5 horses to pull it, the claim is made that this machine will do the work of 200 men with hoes. In a thaw the plows can be re- FIG. 2i7a. versed and the machine used to scrape snow irom the gutters toward the middle of the street, so as to allow the water to run off. Sea Water for Street Sprinkling. A paper upon this sub- ject was read in 1889 before the Civil and Mechanical Engineers' 264 AMERICAN STREET MAINTENANCE AND SEWERAGE. Society of England by Mr. S. H. TERRY. Inquiries were sent out to the engineers of 35 coast towns in England that had used sea water for sprinkling the streets. The answers showed that 23 of these towns had abandoned its use, for various reasons. The Ramsgate and Folkestone engineers said that it destroyed all kinds of road material except wood. Some towns advised its- use in sewer-flushing, but others thought it produced obnoxious gases when brought into contact with sewage. On roads of flint and gravel the application of sea water doubtless pre- vents dust, and Berwick- on-Tweed highly com- mends it for this purpose. The engineer of that town found that one cart 4Jj of seawater was equal to " two of fresh water for & this purpose. The town of Bourne- mouth, Eng., found salt water particularly advan- tageous for macadamized roads, as "it seemed to make the im mediate sur- face more compact." It was found there that the surface held the moisture almost three times as long' with salt as with fresh water. STREET CLEANING METHODS. As the writer of the article on the municipal engineering of Boston, Mass., describes the method of street cleaning at con- siderable length and from observation of actual practice, this matter is practically reprinted here, as follows : STREET CLEANING. 265 Taking a street of average width as an example, and few of the old Boston .streets are wide, work commences at such an hour in the morning in the business portion of the city that the streets are cleaned and the dirt removed by 7 A. M. In the operation of. cleaning, a city watering-cart first passes over the ground. This cart differs from that ordinarily used in street sprinkling in hav- ing finer jets or openings to the sprinkler. After this cart usu- ally follow two one-horse sweeping machines, moving in echelon in the narrower streets, so as not to obstruct travel. Commencing in the middle of the streets, these two machines sweep the dirt toward the gutters, making several turns over the block if the width of the street requires it. The dirt thus collected in long rows is then roughly gathered into piles by two men, one on 266 AMERICAN STREET CLEANING AND SEWERAGE. each side of the street, with a distance between piles regulated by the quantity of dirt swept up. Two other men follow in each gutter, and, with ordinary birch brooms, sweep clean the inter- vals between the piles and clean out such angles as the sweeping machine itself cannot reach. Finally come one-horse carts, with two men to each. One of these men shovels the dirt into the cart and the other assists him in filling his shovel by handling the special carter's broom shown in Fig. 218. In Boston (in 1885) all street clean- ing was done by the city with its own men, horses, and machines. The work- ing force consisted of 181 men (87 being sweepers). 34 carts, 10 sweeping - ma- chines, and 6 water- ing-carts. With this force an average of 185 miles of streets were cleaned each week. All principal streets were swept daily, and the others twice a week. The quantity of street dirt removed in ths year mentioned was 92,180 cu. yds., and the amount paid out in the year for labor was $97,280.10. The wages paid per day in 1885 were as follows : Teamsters, $2.10 ; teamsters' helpers, $2.02 ; drivers of sweeping-machines, $2.10 ; sweepers and their helpers, $2 each. The men employed were selected for their fitness only, young married men having the Fia. 217. MONITOR SPRINKLER. FIG. 218. TEAMSTER'S BROOM. STREET CLEANING. 267 preference. At the time this Boston article was prepared, the Superintendent in charge of this department had been in office over 20 years, and the permanency of employment for good men, inaugurated by him, had made positions in the department so de- sirable that, having many to select from and being free to choose for himself, only the best of the applicants received appointments. This method of handling a city office is so rare at the present day that the Boston method, here described, is worthy of especial note. Whether that city conducts its work now on similar lines is not known. The daily cost in 1885, without a driver, was $2 for watering- averaging the load at 60 cu. ft., a total of 63,400 cu. yds. of swill. The sum of $87,691.93 was ex- pended for labor, and the amount realized from the sale of swill was $36,420.52. For the collection of ashes and house dirt Boston is divided into 76 fixed routes, to each of which is assigned one one-horse cart, a driver, and a helper. This class of refuse is removed from hotels, tenement-houses, and stores twice a week and from dwelling- houses once a week. The ash carts have a capacity of about 44 cu. ft., and they must be covered with canvas while passing through the streets.. The city employee must remove these, ashes, etc., from the re- ceptacle in the yard, but is not required to go up stairs for it. The usual practice is that, while the driver is taking a load to the city dump, his helper remains on the route and transfers the- BARNEY DUMPING SCOW. 271 ash tubs to the street ready for the next, load. Each cart makes from to 8 trips per day. "Whereas this refuse was for years utilized in filling in the low lands about Boston, these places of deposit are fast decreasing in area and number. Of late years the Barney dumping-scow (Fig. 220) has been used for taking this rubbish out to sea. This is the same scow employed by the Xew York authorities in the removal of city refuse. The price of one of these scows (in 1885) was $12,000, and $1,500 annually as a royalty. This patent dumping-boat is 110 ft. long, 28 ft. wide, and 12 ft. deep. Its carrying capacity is about 500 tons, and when 4. Knd View while Pumping. Fia. 220. BARNEY DUMPING Scow. loaded it draws about 9 ft. of water. It is thoroughly seaworthy in construction,, and two men will dump the load, wash out and close the boat, and be ready to return to port in from 5 to 10 minutes. The illustration shows two strong half-hulls, or pontoons, se- cured together at each end and in the middle by heavy bridges hinged to its outboard shell. The storage hold is V-shaped. The fastenings at the three bridges are operated from one center wheel ; and as soon as these are released the load forces the pontoons 272 AMERICAN STREET CLEANING AND SEWERAGE. apart and escapes at the bottom, and the empty pontoons auto- matically close, the movement being about one-eighth of a circle. An official report of the Boston Board of Health stated that between June 1, 1884, and April 1, 1885, one of these scows had carried to sea and dumped 14,823 " loads/' The board estimated that the saving to the city in horses, carts, and labor due to this change in method of disposal was $25.000 for the period named. Catch-basins are cleaned by this same department as before mentioned. In this service a wagon is used, built in every re- .spect like the swill-wagon before described. With each wagon are three men, one of whom fills the bucket (Fig. 221) at the bottom of the basin ; another hoists the bucket by the hook, shown in the same cut, and the third empties contents of the bucket into the wagon. The material thus removed is -usually hauled to one of the city dumps and covered with ashes. In Washington, D. C., garbage removal is performed by contract- daily from hotels, etc., and from dwellings three times a week in summer and twice in winter. The contractor is required to collect the swill or house refuse in bar- rels having a tight-fitting cover, and these are carried away on a low-hung wagon. VAULT CLEANING. The cleaning of vaults in the majority of American cities is performed by the so-called "OTis odorless excavator," built un- der patents controlled by KEYSER & PAINTER, No. 44 Holiday St., Baltimore, Md. This company makes yearly contracts with a city and usually performs its work under the control of the Board of Health. The regulations for the city of Boston will sufficiently outline the terms and conditions under which this service is performed. These are as follows : The contracting company has the exclusive right for the con- tract period of removing the contents of all vaults in the city. The city receives and forwards .all applications for cleaning, and VAULT CLEANING. 273 the contractor may demand from the owner of the premises the sum of $5 for every load of 80 cu. ft. removed, and the same sum if the vault contains less than 80 cu. ft. The contractor may demand a deposit of money from the citizen to secure his fee. This work is now most generally carried on in the daytime, without any offense whatever. The " excavator " is simply a very strong, air-tight, cylindrical tank mounted on wheels, with a capacity of about 80 cu. ft. This tank is connected with the 18 274 AMERICAN STREET CLEANING AXD SEWERAGE. vault by a substantial suction hose admitting of a range of 150ft. An air-pump on the tank provides the vacuum necessary for trans- ferring the contents of the vault to the tank, and the gases are- rendered inoffensive by passing them through a chemical com- pound, of which carbolic acid is the base. Stout barrels, with lids fitting tight, with screw-clamps and a gasket, are used in handling the more solid matter. A modified form of apparatus made by the same company is shown in Fig. 222. This is a profitable machine used in connec- tion with barrels. The chief novelty in this device lies in the- form of the valves, which may be called upon to pass all manner of rubbish. This valve is made of soft, elastic, vulcanized rubber, with two flat pieces placed face to face and riveted along the two* opposite edges. Its length is equal to about three diameters when open. One end of this valve is distended by and is securely fastened to the collar shown, by clamps and bolts. The straps or braces at the mouth of the valve are intended to directly guard the post, and to prevent the elastic pipe from being forced into the post by external pressure. The pump itself is cylindrical and single-act- ing, with one fixed and one movable valve, the latter being oper- ated by the two .side stems shown, passing through stuffing- boxes. As this valve is essentially a collapsible tube of greater length than diameter, and with one end permanently distended, any ob- ject that can pass through the induction opening must eitherpass through the inboard end of the valve or be held tightly on the valve (as shown in one of the cuts) until the inner end opens on the next stroke. The manufacturers state that in one case a large rope about 40 ft. in length was " pumped through with the greatest facility." APPENDIX. DIAGRAMS OF HYDRAULIC FORMULAS. The hydraulic diagrams in the present edition were constructed by- Messrs. Adams and Gemmell, and, with several others, appeared as an inset in ENGINEERING NEWS of April 27, 1893. They are intended to take the place of the diagram compiled by J. Leland Fitzgerald, M. Am, Soc. C. E., which was reproduced in the first edition, but which necessitated the insertion of a large folding plate. These diagrams will not serve for all sewerage calculations which may be necessary, but should be taken by the engineer as a guide or indication of the manner in which other diagrams may be constructed to meet various conditions. For instance, diagrams for an elliptical section, or four-center ellipse, are often required. Then again, in practice it is desir- able to have such diagrams on a larger scale than could be conveniently shown here. The engineer may also have some preference for the manner of indicating the slope ; an extremely useful way is to show it as a per- centage of the length, i. e., a fall of a certain number of feet per hundred. The discharge is given by these diagrams in cubic feet per minute, but it might perhaps have been better to have given it in cubic feet per second , which is the method generally adopted. It must be borne in mind that although these diagrams are only in- tended to give " approximate" results, yet in practice no serious inaccu- racy can be caused by their use, as any slight errors in plotting or draw- ing are well within the limit of error in the formula itself. The following references to hydraulic diagrams which have appeared in ENGINEERING NEWS may prove useful to the engineer: " Diagrams of Vari- ous Hydraulic Formulas for Approximate Use," compiled by J. Leland Fitzgerald, M. Am. Soc. C. E., Sept. 6, and (correction) Sept. 13, 1890; " Flume and Ditch Diagrams," by A. L. Adams (of Adams and Gemmell), Feb. 13, 1892; " Diagrams for Flow in Pipe Sewers," by Prof. A. N. Tal- bot, M. Am. Soc. C. E., Aug. 11, 1892. Reference may also be made to the sewer diagrams designed by Rudolph Hering, M. Am. Soc. C. E., given in his paper, " The Flow of Water in Small Channels," which may be found in Vol. VIII , Trans. Am. Soc. C. E., 1879. 276 DIAGRAMS OF HYDRAULIC FORMULAS. Plate I. Discharge and Velocity of Flow in Pipe Sewers from 6 Inches to 24 Inches in Diameter. Tnere ar four different plottings on this plite, numbered for reference as Diagrams 1, 2, 3 and 4. All have b?en computed by Kutter's formula, using the coefficient of roughness " N "= 013. In Diagram 1 the inclination or slope, expressed as oie in 200, 300, etc., hiving been taktm on the left-hand vertical scale, the discharge in cubic fest per minute may be found on the top horizontal srale. In Diagram 2, the Inclination being taken on the left-hand vertical scale, the discharge in cubic feet per minute may be found on the bottom horizontal scale. In Diagrams 3 and 4, the discharge in cubic feet per minute having been taken on the right band vertical scales, the velocit/m feet per minute may be found on the horizontal r cale. If it be desired to use the coefficient " N " = 0.012, then 10# should b> added to the results obtained by the diagrams. Plate 2. Discharge and Velocity in Circular Sewers Flowing Full. There are two plottings on this plate: Diagram 1 for discharge, and Diagram 2 for velocity. They have been computed by Kutter's formula, using " N " = 0.013. In Diagram 1 ROD 1C JO Cub.Ff.per Min. Discharqe for Di'aq.l. 100 150 200 250 300 550 IZOO 600 150 150 ' - 350 .,450 _. 550, 650 750 Cub. ft. per Mm. Discharge for Diag.Z.. PLATE 1. DISCHARGK AND VELOCITY OF FLOW IN 6 TO 24 IN. PIPE SEWERS. the inclination being taken on the right hand vertical scale, the discharge, in cubic feet per minute, may be found on the bottom horizontal scale. Diagram 2: the dis- charge, in cubic feet per minute, being taken on the left-hand vertical scale, the v- locity, in feet per minute, may be found on the top horizontal scale. If it is desired to use the coefficient " N " = 0.015, then 18* should be deducted from the results obtained from the diagrams. Plate 3. Discharge ani. Velocity in Eya-shaped Sewers FJowino Full. There are two plottings on this plate: Diagram 1 for discharge, and Diagram 2 fo^ velo- city. They have also been computed from Kutter's formula, using "N" = 0.013. In Diagram I the inclination being taken on tne right-hand vertical scale, the discharge in cubic feet per minute may be found on the bottom horizontal scale. In Diagram 2, the di-charge, in cubic feet per minute, being taken on the left-hand vertical scale the velocity, in feet per minute, may be found on the top horizontal scale. If it is desired to use the coefficient " N " = 0.015, then 18% should be deducted from the re suits obtained by the diagrams. DIAGRAMS OF HYDRAULIC FORMULAS. 277 VetocitYfnFr.perMfrt., Di'aq. Z. S S | van 3500 3000 2500 2000 1500 Discharge in Cub.ff.perMin.fo ( r Diag.U o PLATE 2. DISCHARGE AND VELOCITY IN CIRCULAR SEWERS FLOWING FULL. Velocrtv in Ft. per MI'M . for Diag '. 2 6500 4500 4000 3500 3000 3500 2000 Discharqe in Cub.ft. per Min.for Diaq. I . PLATE 3. DISCHARGE AND VELOCITY IN EGG-SHAPED SEWERS FLOWING FULL. 278 DIAGRAMS OF HYDRAULIC FORMULAS. Plate i. Ratios of Velocity and Volume of Sewers Partially Full to the Same When full. The full lines on this Diagram refer to circular sewers, and the dotted lines to egg-shaped sewers. The curves have been computed by Kutter's later for- mula, which allows for the decrease of the f rictional coefficient as the mean radius 0.9 ~x~^; I M iiiiyijjijjjijljjiipij bo.7 Ml Mi ]\ 1 ?==:: = *o.e :::::::::::::::i:::::::i^s|!j :::t::jjj|jj;;!:: | | | 1 | | | | || | | | | | | | | | | |J'j/i | JT^TJt ::::::::::::-=:jj!S3| dffi ::J3j3!!(ii!|:;:::E:::?:::: *| g; : : :i:: HS ^jH C : i : : : : : ^ pi, ^_ ^ E^j];;. i^ j;:?;!?: tH 1 Urn H 11 | l:EEEE;:EEEEEEEi!EEjij5fc o., jjjjijjjjjipjijjjjjjjj!; JilMMwlii ::::: : ;JS: "tt" l^^T fe^ll 1 xv-&t%r"" " : M ! . ' : O.I O.Z 03 0.4 0.5 0.6 0.7 0.8 0.9 1.0 'I. I . Ratio of Velocity and Volume for partial Depths to the same with full Sewer. PLATE 4. RATIOS OF VELOCITY AND VOLUME OF SEWERS PARTIALLY FULL TO THE SAME WHEN FULL. increases. The vertical diameter of the sewer and the volume of discharge ard velocity of flow with the sewer running full are all taken as unity. If the ratio of the depth of flow to the sewer diameter be found on the vertical scale, then on the horizontal scale may be found the ratio of velocity and also of volume at that depth to the same when the sewer is flowing full. APPENDIX TO REVISED EDITION. SEWER GRADES. PAGE 1, SECOND PARAGRAPH. The proper grades of sewers and house connections given on pages 1 and 2 are subject to considerable modifica- tion in many places, owing to local conditions. For instance, in the main drainage system of London, the high level sewer on the north side of the Thames, varying from 4 ft. to 9 by 12 ft. in size, has a quite rapid fall, ranging from 1 in 71 to 1 in 376 at its upper end and from 1 in 1,320 to 1 in 1,056 at its lower end. One of the stormwater sewers of Duluth, illustrated in ENGINEERING NEWS of Oct. 25, 1890, has a fall of from 7- to 12| per cent. This sewer is from 40 to 48 ins. in width, with an invert of granite blocks laid in Portland cement mortar, and was reported by HERING and ROSEWATER to be an excellently planned and executed piece of work. The same engineers recommended that the minimum fall of house drains be restricted to 1 in 48 in that city, while the plumbing and drainage regulations of Brooklyn, N. Y., require a fall of at least one-half inch to the foot. As regards drains, it may be assumed that a 4-in. pipe laid at a grade of 1 in 24 will safely carry off the wastes and rain water of about 2,000 sq. ft. of roof area. SEWAGE PUMPS. In the second paragraph on page 5, the subject of pumps for use during high water in the river or other recipient of the sewage, when the outfall sewer would be choked, is briefly noticed. An interesting installation for such a purpose was recently made at Winona, Minn., by URBAN H. BROUGHTON, Assoc. M. Inst. C. E. This city is situated on the right bank of the Mississippi River and has a population of about 18,500. During 6 or 8 months of the year the sewage flows readily from the outfall sewer, but during the remaining months, the river rises and the discharge is checked. Instead of putting in steam or gas pumps for use at such sea- sons, Mr. BROUGHTON used two Shone ejectors, illustrated on page 104, operated by an air compressor in the pumphouse of the water-works de- partment, which is located about 1.000 ft. from the ejector station. About 4 miles of sewers, principal!}' 8-in., were laid to drain an area of 220 acres. In this manner the expense of an independent pumping plant and the necessary attendance was much reduced. 280 CLEANING AND SEWERAGE OF CITIES. CONSUMPTION OF WATER IN AMERICA. The remarks on the consumption of water in American cities, given on page 9, require a little explanation. From the "Manual of American Water- Works,'' it appears that the consumption in a number of Ameri- can cities is as follows : Allegheny, 238 gallons per capita ; Baltimore. 94; Boston, 80 ; Buffalo, 186; Cambridge, 64; Camden, 131; Chicago, 140; Cincinnati, 112; Cleveland, 103: Columbus, 78; Dayton, 47; Detroit. 161; Fall River, 29; Indianapolis, 71; Jersey City, 97; Kansas City, 71; Lowell, 66; Louisville, 74: Memphis, 124; Milwaukee, 110; Minneapolis, 75; Newark, 76; New Orleans, 37; Omaha, 94 ; Paterson, 128 ; Philadel- phia, 132; Pittsburg company, 153; public, 144; Providence, 48; Read- ing, 75; Richmond, 167; Rochester, 66; St. Paul, 60; St. Louis, 72; San Francisco, 61; Syracuse, 68; Toledo, 72; Trenton, 62; Troy, 125; Wash- ington, 158; Wilmington, 113; Worcester, 59. With such a wide varia- tion as this, the necessity for carefully investigating the consumption of each city is self-evident. S:>me of the cities are reducing their per capita consumption. Detroit, for example, introduced meters in 1888 and 1889, and has decreased its total pumpage although over 7,000 additional families have been supplied from the mains. RAINFALL. The table at the bottom of page 16 is condensed from an interesting essay on the relation between the density of population and the amount of impervious surface in cities, appended to a report made in 1889 by Mr. EMIL KUICHLING on a proposed trunk sewer for Rochester, N. Y. En- gineers interested in the subject are referred to the paper, which is too long to reproduce here. The conclusions are that with a population of 25 per acre, 25 per cent, of the ground may be assumed as impervious and the discharge from the remaining 75 per cent, neglected ; with 32 persons per acre, 33 per cent. ; with 40 persons, 43 per cent. ; and with 50 persons, 53 per cent. These results were obtained by measuring the discharge from different classes of surface, such as roofs, pavements, roads and highways, and thea determining the amount of each class of surface with the different densities of population. Finally the equivalent in imper- vious surface of each of these classes was computed and the results added. A rather common rule in the New England States is to assume the maximum rainfall as 1 in. per hour and design the sewers to carry off the rain falling on one : seventh of the area under consideration, without taking into account the considerations elaborated in paragraph c, page 15, and shown graphically on page 17. RUN OFF. Several inquiries having been made as to the original treatment by Prof. Baumeister of the subject of run-off, which was given in a consid- erably condensed form in the first edition of this book, the following translation is printed here. The condensed statement is retained in the body of the book, however, as it is sufficiently clear for the purposes of the engineer; it will be found on pages 17 et seq. : APPENDIX. 281 " Buerkli has worked backward from an empirical formula employed by English engineers for determining the size of sewers and finds the following relation between the rainfall, R, and the volume of run-off, A: Here F is tbe drainage area in hectares, G is the grade of the sewer per mille, and 0.5 corresponds provisionally to the coefficient x [see page 16]. This expression is open to the objection that the grade of the sewer has nothing to do with the occur- rences outside it, and the grade of the drainage area corresponds more with the proper value of G. In American formulas, assuming G to designate the average inclination of the drainage area, the following forms occur as the value of the re- lation: G7~~ 3 Af \/G / and / = / /R / VF These appear to have been deduced experimentally in order to give "practical" widths to the sewers. From the point of view taken as a basis of the BUEHKLI for- mula, the relation between the rainfall and the run-off, that is to say the relation between the retardation of flow from tracts of different areas, is " In order to investigate the matter theoretically, we start with the interval of time wbicu it will take a material point to run down a straight line of length ^in- clined at an angle of a degrees. Leaving out of consideration the influence of fric- tion and demoting the acceleration of gravity by g, this interval of time is 4$~Z -*- sin a. If now under I is understood the length which a raindrop must pass in moving from the limit of the drainage area to the sewer, it is evident that the time which it will take to reach tbe sewer from the limit of a drainage area of any size is proportional to the square root of I. By the geometrical properties of similar figures, this length I is proportional to the square root of the drainage area, F. Hence the retardation is really inversely proportional to the fourth root of the drainage area. This corre- sponds fairly well with most of the observations, although for the cloudburst noted in the table on page 13 as occurring at Budapest the form *=!/. /Y*' is more accurate. This ratio was adopted by BRIX in the preparation of plans for the sewerage of Wiesbaden, where the drainage area, like that on the left bank of the Danube at Budapest, has a hevy grade. For areas of less extent than 1 ha. the value of y should always be 1. "From the heavy rainfall at Dresden, noted in +he table on page 13, MANK has deduced an empirical value of y. Since tbe run-off from an area of infinitely small extent will equal the raintall, he assumed that for .F 7 equal to O, y equals 1. It was found by direct measurement that for an area of 80 ha. y equaled 0.22. 1 hese two values were plotted and the assumption was made that the run-off from areas of more than 80 hectares would be governed bv the same coefficient, y, as that from an area of hO ha. A flexible rule was then made to pass through the two plotted points and be tangent to the straight line passing through the coefficient for 80 ha. on the diagram. The curve thus drawn is manifestly an arbitrary settlement of tbe problem, of questionable value. This is clearly shown in Fig. 2, where the curve is plotted with others. The ordinates stand for the values of y. " The curve of BUKRKLI certainly is most to be trusted. It was used recently in Mannheim, while in Chemnitz and Freiburg tbe MANK curve is used. It will be readily seen from Fig. 2 that there is an error made when it is assumed th^t the same coefficient of retardation may be used for every district of a city. A distinc- tion should at least be drawn between sewers for small areas and large trunk sewers. Evidently in the case of the latter tbe most accurate course is to compute the flow and time of flow in the branch sewers, and then add them in proper order. Such a process is, however, tedious and inaccurate for branch sewers. " From observations in Rochester, KUICHLTNG has proposed to regard the coef- ficient ynot as dependent on the area F, but as a function of the duration of the rain, t; he places y equal to at, where a is a constant. This formula is said to apply to all cases where the time of the rainfall is shorter than the time it requires for the ground to become saturated and the rain to reach the sewer from all parts of the 282 CLEANING AND SEWERAGE OF CITIES. drainage area. For rains lasting not more than one hour, 't has been found that in Rochester R equals [b ct], where 6 and c are constants. Hence in this case A = This expression reaches its maximum value for t equal to [b 2c]. From the obser- vations in Rochester of all rains lasting less than one hour, the constants are such that a rainfall lasting 51 minutes gives the greatest run-off and is therefore the most important in sewerage calculations. "Experiments are still wanting which will show what is the influence of the slope of the drainage area on the quantity of storm water reaching the sewers. It may be taken into account by a suitable selection of the rate of rainfall and by a reduction of the amount of run-off from level ground. The rates of precipitation selected by BUERKLI show that the maximum run-off from steep ground may be twice that from flat areas. Moreover, it depends in a high degree upon the general form of the drainage area and on the direction of the streets." CLAY AND CEMENT PIPE. PAGE 29, SECOND PARAGRAPH. The remarks of Prof. Baumeister con- cerning clay and cement pipes require some comment. Their use is so extensive in this country that the following table of sizes and weights, furnished by BLACKMER & POST, will be more in accordance with Ameri- can practice : STANDARD SEWER PIPE. Diameter, ins... . 3 5 8 1C 12 15 18 24 30 Weight per ft., Ibs ...... '. 7 12 24 33 42 58 80 125 220 DOUBLE STRENGTH CULVERT PIPE. Diameter, ins ............ 12 15 18 20 22 24 26 28 30 Depth of socket, ins ..... 333 3^ 3% 4 4^ 4% 5 Thickness, ins ............ U4 1*4 IV* 1% We 2 2V. % 2^ Weight per ft., Ib3 ........ 48J4 68 100 125 148 180 210 250 300 This pipe is all made in sections 2i ft. long, and this length, as well as the depths of the sockets, was only adopted after a number of engineers had advised these dimensions rather than the smaller ones formerly in use. The thickness of the standard sewer pipe is uniformly about one- sixteenth the diameter. See ENGINEERING NEWS for Feb. 6, 1892. SIZE OF SEWERS. PAGE 40. A series of valuable diagrams for use in determining the proper size of sewers will be found in a paper by RUDOLPH HERING in Vol. 8 of the Transactions of the American Society of Civil Engineers, while a voluminous collection of tables is given in P. J. FLYNN'S volume entitled "Flow of Water in Irrigation Canals, Ditches, Flumes. Pipes, Sewers. Conduits, etc." Both diagrams and tables are based on KUTTER'S formula. FLUSH TASKS. PAGE 77. The use of flush tanks is becoming so general in the United States that the descriptions of PROFESSOR BAUMEISTER require supple- menting. The RHO ADS- WILLIAMS s'phon, design d by the late WILLIAM G. RHOADS, of Philadelphia, and BENEZETTE WILLIAMS, of Chicago, jointly, consists of an annular intaking limb and a discharging limb terminating hi a deep trap below the level of the sewer. As will be seen from the cut, below the permanent water line in the discharging limb, is connected one end of a small blow-off, or relief trap, having a less depth of seal than the main trap, the other end of which joins the main trap on the opposite side, at its entrance to the sewer and above the water line of APPENDIX. 283 the trap. At the same point is connected an upright v"ent pipe which rises through the tank to a point above the high water line, and is turned down through the top of and into the intaking limb of the siphon, termi- nating at a given point above its bottom. As the tank fills (the main and blow-off traps being full) the water rises in the intaking limb even with m&$(8$Bffl RHOADS-WILLIAMS SIPHON. the level of the water in the tank, until reaching the end of the vent pipe, a volume of air is confined in the two limbs of the siphon between the water in the intaking limb and the water in the main trap. As the water rises higher in the tank the confined volume of air is compressed 264 CLEANING AND SEWERAGE OF CITIES. and' the water is depressed in the main and in the blow-off trap. This goes on until the water in the tank reaches its highest level above the top of the intaking limb, at which time the water is depressed in the blow-off trap to the lowest point and the confined air breaks through the seal carrying the water with it out of the trap and releasing the compressed air. In this manner the siphon is put in action, which continues until the water in the tank reaches the level of the intaking limb, and air is admitted through the vent pipe. The walls of the tanks should be at least 8 ins thick, and the surround- ing earth and concrete thoroughly consolidated about the parts of the siphon. The discharging end of the siphon should be set at least one-half the diameter of the sewer higher than the grade of the sewer. The siphons can be made of any desired size, but the fallowing are most usually em- ployed: x-; Sewer. Capacity of 100 Diameter Discharging Discharge, Diameter of ft. of sewer, of, ins. limb. cubic feet. tank, feet. cubic feet. 6 5 27 4 2' 8 6 40 4V 35 10 8 59 5 55 12 10 85 6 79 15 12 128 7 122 The ROGERS FIELD siphon illustrated by PROF. BAUMEISTER has been materially changed by COL. GEORGE E. WARING, Jr., and its form, as now extensively used, is shown in the accompanying cut. The discharg- ing limb terminates in a weir chamber, which, when full to its overflow point, just seals the limb. Over the crest of the weir is a small siphon whose function is to draw the water from the weir chamber and thus un- seal the main siphon, performing the same work as the vent pipe in the RHOADS-WILLIAMS type. The siphon designed by ANDREW ROSEWATER and described in ENGI- NEERING NEWS of July 17, 1 8 36, is also in extensive use. The VAN VRANKEN tank, described by PROF. BAUMEISTER, has been employed quite widely by STALEY and PIERSON in the separate sewerage systems designed by them. HOUSE PLUMBING. PAGE 80. The portions of Chapter X referring to house plumbing oy no means accord with standard American and English practice, concern- ing which HELLYER'S "Lectures on the Science and Art of Sanitary Plumbing " may be safely consulted. VENTILATION. PAGE 80, LAST PARAGRAPH. Recent investigations apparently indicate that the direction of the wind at the openings of a sewerage system has a greater influence on the circulation of the sewer air than would be in- ferred from PROF. BAUMEIS TKR'S words. PAGE 89. A vpntilating device known as the ''Keeling Sewer Gas Ex- hauster and Destructor " was introduced in England in 1886, and has since been used in several places in that country. It will be made clear from the following description written by City Engineer H. PERCY APPENDIX. 285 BOULNOIS, of Liverpool: " The apparatus consists of a hollow column surmounted by an ordinary street gas lantern, the column being perfor- ated with slots just below the lantern. The base of this column is con- nected with the sewer by ordinary 6-in. drain pipe. The destructor is placed in the base of the column, and consists of an atmospheric gas burn- er. The gas is admitted from below, and just at the point where the gas pipe joins the jet of the burner is inserted an ordinary No. 6 Bray's gas jet. This is not lighted, but it acts as a regulator, as not more than 6 ft. pt r hour will pass through and be consumed under ordinary pressures. Above the atmospheric burner is an inverted fluted cone of cast-iron, ROGERS FIELD SIPHON. which becomes intensely heated when the gas is lighted. This cone is encased in an iron cover to prevent the loss of heat. Above this are other cones and fluted passages, all of which present a large area of heated surface. The sewer gas enters from below and passes up through and around the burner; while some of it is immediately burned, the whole of the remainder must come into contact with the hot iron cones, and be- fore it passes away into the upper part of the shaft is deprived of all vital particle, injurious to health." The cost of gas for this device is stated to be from $25 to $30 a year, and this f aci!, coupled with the generally innoc- uous character of air in well designed and built sewerage systems (see 286 CLEANING AND SEWERAGE OF CITIES. page 80). leads the editor to doubt the value of the apparatus except in cer- tain special places; for example, over the underground public conven- iences in use in many European cities. With regard to the ventilating fans mentioned on page 89, they were tried in Liverpool, proved a failure and are now discarded. For further information on this point see the article in ENGINEERING NEWS of Oct. 25, 1890, on the sewerage of Liverpool. POLLUTION AND SKLF-PURIFICATION OF RIVERS. PAGE 113. NOTE TO SECOND PARAGRAPH. The pollution and self-puri- fication of rivers are debatable questions and will probably remain unde- cided for many years to come. One important fact, however, must not be lost sight of in these discussions, viz. : it is the amount of impurities iu the sewage of a town, rather than its total volume, which should be made the basis of calculations. This view of the matter, prominently advocated fty RUDOLPH HERING and recently recommended by PROF. BAtJMEiSTER, makes the population the starting point in investigating the pollution of a river, instead of the more usual assumptions based on the total quantity of sewage. CHEMICAL PRECIPITATION. NOTE TO LAST PARAGRAPH, PAGE 125. Too much importance cannot be attached to the proper adjustment of chemicals to sewage. This is plainly shown at the precipitatiop works at Worcester, Mass., fully de- scribed in ENGINEERING NEWS of Nov. 15, 1890. Here the sewage is ex- tremely acid owing to the waste sulphuric and hydrochloric acids from large wire works discharged into it. This acid appears at the precipita- tion station once every six hours, and in sufficient quantity to render the sulphate of alumina, at first used, unnecessary. When the flow of acid is detected, a sufficient quantity of lime is added to the sewage to make it alkaline and it is then run into two of the precipitating basins, through which all the crude sewage during the remainder of the period of six hours is forced to flow. This process has resulted in a large saving of lime and alumina and has been found to give a better effluent than when the chemicals were added at regular intervals, in unvarying amounts. Two methods of treatment have recently been brought into prominence in England since PROFESSOR BAUMEISTER published his work. In one of these the sewage is mixed with a precipitant called ferozone, composed of 24.64 parts of ferrous sulphate, 2.19 parts of aluminum sulphate, 3.3 parts of calcium sulphate, 5.17 parts of magnesium sulphate, 11.35 parts of silica, 19.01 parts of magnetic oxide of iron and 32.34 parts of water. The sewage thus treated is then filtered thrpugh a mixture of sand and polarite, the latter consisting of 53.85 parts of magnetic oxide of iron, 5.68 parts of alumina, 7.55 parts of magnesia, 25.5 parts of silica, 2.01 parts of lime and 5.41 parts of water. At Acton this process has given great satisfaction and several other places have since adopted it. The other process is the invention of HERR WOLLHEIM, and is known as the Amines process. The precipitant employed is a mixture of from APPENDIX. SO to 50 grains of lime and 3 grains of herring brine to each Imperial gallon of sewage. The process is especially intended to produce a com- pletely sterilized effluent and is said to be very rapid and complete. It has been used at Wimbledon for some time. The WEBSTER electric process, which has been in use at Crossness for some time, cannot yet be said to have proved commercially successful ; at least it is impossible to obtain authoritative statements of the cost of complete purification by this means, and until this is known it is unfair to draw any definite conclusions. Full particulars of the process will be found in ENGINEERING NEWS of April 13, 1889. BERLIN SEWAGE FARMS. PAGE 163, 14 LINES FROM BOTTOM. By overflowed areas are meant the beds treated by intermittent filtration. In 1889-90 there were 5 334 acrts at Berlin so operated, against 2,080 acres treated by broad irrigation. The total amount of ammonia abstracted by broad irrigation, which is only employed on grass plots, averages 98.87 per cent, during the year, while that abstracted from the sewage by filtration averages 97.82 per cent., or about one per cent. less. PAGE 163, 2 LINES FROM BOTTOM. The receiving basins of Berlin have an area of 410 acres and vary in size from 5 to 22 acres. They are formed by embankments about 3 ft. high and 13 to 20 ft. wide on top. TOP OF PAGE 167. The great extent of the Berlin sewage farms and the favorable character of their soil make the operating expenses compara- tively small when contrasted with some other places. In 1889-90 there were four farms with a total area of 1 1 ,016 acres, which received sewage, while several others were under preparation for such purposes. Of these 11,016 acres, 2,080 were used for broad irrigation. - r ,334 for intermittent filtration; 410 for settling basins or reservoirs for sewage during the winter, and the remainder of the land was used for dwellings, roads and gardens with the usual methods of cultivation. The total income during the year was $340,770 and the total expenditures for maintenance and wages were $287,092. The average cost of the farms per acre has been $356 and the interest on this sum and the repayment of loans called for $241,386, which must be increased by $6,988 for loss in valuation. Kence the net loss was $194,686, or something over $16 per million gallons of sewage received. INDEX. Aeration 150 Alumina, sulphate of 124 Ammonia in sewage 143 Ashes as disinfectant 227 Storage and disposal 178 Assessments for sewers 108 Bacteria 142. 226 Effect of lime on 124 Nature of 169 Removal by chemical precip. 143 Branch sewers 8 Brick sewers 29 Brooms 181 Canals as receptacles of sewage . . 4 Casks, connected with closets 206 Catch-basins 57, 233 Cleaning 60 Cast iron sewers 28 Cellars, drainage of 96 Chemical precipitation. Chemicals employed 122, 286 Cost of 148 Coventry process. 124 Effects of 142 Filtration combined with . . 155 Methods of mixing the charge 125 Mueller- Nahnsen system. .125, 198 Principles involved 123. 286 Roeckner-Hothe system.. ,125, 148 Clay drains and sewers 29, 282 Cleaning streets, se&Sireet cleaning. Closets 203, 206, 222 Concrete sewers 30 Crematories for garbage 188 Dampness, results of 172 Depth of sewer below street sur- face 3 Diagrams. Coefficient of retardation of rainfall entering sewers 17 Hydraulic 275 Relation between quantity and velocity of water, and area of web section in cir- cular and egg shaped sew- ers 39 Size of egg-shaped sewers . . 3S Size of circular sewers 37 Values of c in formula for flow of water." 36 Disease, influence of sewers on. .. 80 Spread of, by bacteria 171 Disinfection 224 Drainage. Subsoil 95 Surface 176 Systems of 159 Drains, house 61 Rules for laying, Providence. 25^ Size of 26 Systems of house 81 Earth as disinfectant 225 Effluent from purifying plants. . . 142 Aeration of 150 Composition ... 142 Ejector, Shone 104, 279 Steam 201 Evaporation from irrigation fields 162 Excrement. Analysis and character of . .'. . 196 Berlier system of removal. . . 212 Cost of pail removal 208 Disposal of 214 Liernur system of removal of. 209 Pneumatic removal of 209 Poudrette manufacture 218 Removal 198 Separation of 221 Special treatment of 218 Filter beds. Peat 155 Requisites of 152 Size of 154 Filtration 152 And precipitation 154 Results of 153 Flow of water. 34,275 Flushing. Automatic 68, 282 Gates 73 Manholes 70 Small sewers . 70 Tanks, see T inks, flushing .. 245 Formulas, hydraulic 275 Kutter's 34 Garbage. Removal 184, 269 Storage ' 178 Wagons 186 Gases from vaults 224 Grades of sewers 1, 279 Effect, on commingling of sew- age and river water 117 Grease traps 64 Gutters 175 Hydro pneumatic system of sew- erage 103 Inlet, street 251 In submerged districts. ..*... 93 See Catch-basins. Irrigation, cost of 166, 287 Nature of process 160 Results of 162, 287 290 INDEX. Irrigation fields, management of. 162 Requisites for 160 Sizeof 164, 287 Intersection of sewers 43 With water mains 53 Lime, as a precipitant 122 Lampholes 43 Magnesia as precipitant 125 Manholes 41, 247 Organic matter in rivers 114 In street gutters 20 In street sweepings 177 Precipitated in tanks 142 Removed by filtration 153 Osmosis 96 Outlets 4, 117 Relief, see Relief outlets. Oxidation. Of organic matter in rivers. . . 117 Pails, for closets 203 222 Peat as disinfectant 225 Penstocks. . . 72, 75, 76 Pipes. Cement 31 Rain, see Rain pipes. Plants for irrigation fields 161 Pneumatic removal of excrement 209 Pollution of rivers 112, 286 Official reports on 190 Poudrette 218 Precipitating tanks, see Tanks, precipitating. Precipitation,chemical, see Chem- ical precipitation. And filtration, combined rate of, in tanks 154 Pumps 50, 279 For emptying vaults 199, 273 Purification of sewage, see Chem- ical precipitation; Filtra- tion; Irrigation. Petri system 155 Results and cost of 142 Putrefaction 170 Rainfall. Diagrams of maximum 14 Disposal of 14 Estimates of 18 Maximum intensity of 12, 280 Part reaching sewers ..... 15, 280 Rain pipes 62 Traps for 65 Refuse, street and domestic 178 See Garbage. Relief outlets 5, 47, 122 Construction of 90 Reservoirs for sewage 5 Rivers, pollution of 112, 286 Reports on 120 Self-purification of 115 Salt for removing snow 194 Sandpits 130 Sanitation, results of municipal.. 172 Scow, Barney dumping 271 Scrapers, for streets 182 Sediment, In sewage carrying rivers 117 Separate system 98 Separation of excremental mat- ter 221 Sewage, Analyses of 21, 147 Character of 112 Dilution of 113 Discharge into Dutch canals.. 119 Discharge into gutters 175 Discharge into rivers ... .47, 113 Effluent after purification. See Effluent. Fertilizing value of. See also Sludge 160 Objections to discharging into rivers . 118 Purification. See Purification. Purification by dilution ...... 120 Purification before discharg- ing into rivers 119 Retention in sewers 5 Sewers. Arrangement in Providence . . 251 Cleaning 68,245,248 See Flunking. Cost of 100, 106 Distance below surface 3 Influence of rainfall on size. . . 13 Intersection of, see Intersection*. Materials for 28 Number of brick in 256 Size 40, 282 Sewer sections 23, 238 Sewerage systems 6 Cost of 107 Liernur.... 105 Shone. 104 Shpne system of sewerage 103, 279 Silicic acids as precipitants 125 Silt pits 57 Siphons 54 Slag as precipitant 125 Sludge. Agricultural value of 146 Disposal of 144 Effect of standing in tanks. . . 141 Removal 128, 133, 137 Snow. Removal 192, 268 Sprinkling streets 190, 263 Stone sewers 30 Street cleaning 185, 264 Costof 189, 267 Implements for 181, 259 Sweeping machines 182, 259 Sweepings from streets 177, 259 Quantity of 180 Removal 184 See Street cleaning. Systems of sewers, classification. 6 Tables; chemical precipitation in in Germany, cost 148 Elements of standard sewer sections in Washington.. 252 Garbage, quantity of street domestic 179 INDEX. 291 Tables; irrigation fields, data con- cerning 166 Rainfall 18 Max. intensity of 13, 280 Rivers, pollution of 114 Sewage, analyses of 21 Roofing over 127 Sand pits 129 Sagasser system 139 Tun bridge Wells 131 Upright 136 Weisbadt len 134 Composition of 147 j Taxes for sewer construction 108 Sewerage systems, cost of .... 107 j Traps, g/ease 64 Sewers, cost of 106 1 Disconnecting for house Street cleaning, cost of 267 drains 86 Water, estimates of waste... 11 For pail closets.'.'.'.'.'. '.'.'.'!'..;.' 205 Tanks, precipitating. Ventilated 88 Advantages of d i ffe r e n t ^ J Valves, disconnecting 71, 91, 95 Classes of . . ' '. ' '. '. '. '. .' .' .' .'. I'.!!"".! 127 | Vau ^ s ' , Continuous . . .129 }eamne 198 > 272 Cross walls in 131 Current in 133 Materials for. Separating ... 221 Dortmund 131, 140 Ventilation of sewers 80, 284 Essen 137 ! Y branches 45 Frankfurt 133 ! Water. Halle 136 j Consumption per capita 9, 280 Intermittent 128 | Flow of ..... 35, 275 Muller-Nahnsen 136 j For flushing 68 Ottensen . . 137; For street sprinkling 191 Parje system 129 j Requirements for potability.. 114 Petri system 156 j Subsoil 90 Pichler and Sedlaceck system 140 Rate of precipitation in 141 Roeckner-Rothe system 137 Waste, estimated quantity. . 11 Waste, maximum quantity per hour 10 INDEX OF PRINCIPAL ILLUSTRATIONS. (Only the principal illustrations are indexed below; all others may be found by consulting the preceding index under the proper head.) Catch-basins. Berlin 60 Boston 233 Cast iron 237 Frankfurt 62 Heidelberg...'. 61 Karlsruhe ....60, 62 Louisville 236 Paris 58 Providence 232 Stuttgart . 63 Washington 234 Covers for manholes, 190, 243, 244, 245, 246 Filter Beds. Coventry 155 Flushing, gates for. Danzier 74 Dusseldorf 73 Frankfurt 73 Hamburg 72 Stuttgart 73 Garbage wagons 186 Pails 269, 272 Inlets, street 232 Brussels 60 Hamburg . 59 Munich 59 Wiesbaden 61 Intersection of sewers. Berlin 47, 50 Boston 24 Frankfurt 43, 51 Invert blocks ..249 Manholes. Berlin 41 Frankfurt 4^ Heidelberg 41 Philadelphia 248 Providence 247 Stuttgart 4z Outlets, see also Relief outlets. Hamburg 92 Munich 4 Pumps for cleaning vaults. .197, 200, 273 Rain pipes, traps for. Erfurt 66 Karlsruhe. 65 Wiesbaden 56 Relief outlets. Berlin 49 Danzig 90 Relief Outlets. Hamburg 91 London 46 Scow, Barney dumping 271 Sewer sections. Altenberg 28 Berlin 27 Boston 238 Bremen 26 Cologne 25 Dresden 30 England 27 Karlsruhe 27 Liege 24 Mainz 25 Maulbronn 28 Munich 32 Paris 28 Philadelphia 242 Providence 240 Stuttgart 25 Vienna 26 Washington 241, 252 Wiesbaden 52 Siphons. Breslau , 55 Danzig 53 Wiesbaden 52 Snowplow 193 Sprinklers 190. 266 Sweepers, street 192, 258, 260, 261, 262, 263, 264, 265 Tanks, flushing. American 78 Boecking, Cuntz, Field 77 Fruehling 78 Rhoads-Williams 283 Rogers-Field 285 Van Vranken 77 TanlvS, precipitating. Dortmund 131, 139 Essen 138 Frantfurt, 132 Mueller-Nahnsen 136 Parje 129 Petri 156 Roeckner-Rothe 137 Tunbridge Wells 131 Wiesbaden 135 Trap. Gerhard bail 83 Valve, air. Munich 81 14 DAY USE RETURN TO DESK FROM WHICH BORROWED LOAN DEPT. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. -- .- - , , - ; . .- ^ . rttt FEB f 2003 ^flil U. C. BERKELEY Qi^j^fUtjLA^ C^r-t