E ACTIVATED SLUDGE PROCESS OF SEWAGE TREATMENT A Bibliography of the Subject With Brief Abstracts, Patents, News Items, Etc., Compiled Mainly from Current Literature. Second Edition, 1921 -JFORNIA ;VIL ENGINEER! N- F CALIFORNIA NT OF CIVIL ENGINEE :KELEV 41* By J. EDWARD PORTER Consulting Chemical Engineer General Filtration Co., Inc. ROCHESTER, N. Y. Copyright 1921 by General Filtration Co., Inc. PRICE $1.00 THE ACTIVATED SLUDGE PROCESS OF SEWAGE TREATMENT '- : - A Bibliography of the Subject With Brief Abstracts, Patents, News Items, Etc., Compiled Mainly from Current Literature. Second Edition, 1921 By J. EDWARD PORTER Consulting Chemical Engineer General Filtration Co., Inc. ROCHESTER, N. Y. >?*/ ': ': G" : ii ..; .FOREWORD IN compiling this bibliography, an attempt has been made to arrange the matter in chronological order. The first periodical reference for each abstract is supposed to indicate the first appearance of the article in print, though not necessarily the full pa- per, as proceedings, transactions, annual re- ports, etc., which contain it are often issued many months later. The subsequent period- ical references under the same abstract may be either the original article, a reprint or an abstract of it. Publications appearing monthly are credited with issue on the first of the month, annual reports, transactions, etc., are placed at the end of the year in which the document is dated. The periodical index at the end gives the date of publication cor- responding to the volume and page number. While there are doubtless some omissions, an effort has been made to make this revision of the bibliography complete from the be- ginning to the end of 1920, the compiler not attempting to define "the beginning" of the activated sludge process proper, further than to insert as the first reference the earliest article relating to the subject which has come to his attention. At all events it is believed that the compilation will be found useful to Sanitary Engineers and others interested in sewage disposal. Indebtedness is acknowledged to Prof. Ed- ward Bartow, Professor of Chemistry and Head of the Department of Chemistry, State University of Iowa; to Dr. F. W. Mohlman, Chief Chemist for the Chicago Sanitary Dis- trict, and to Mr. T. Chalkley Hatton, Chief Engineer, Milwaukee Sewerage Commission, for valuable assistance given. January, 1921. d =*" Nomenclature and Definitions NOMENCLATURE CONCERNING THE ACTIVATED SLUDGE PROCESS OF SEWAGE DISPOSAL AS SUGGESTED BY F. A. DALLYN, GEO. T. HAMMOND AND T. CHALKLEY HATTON, A COMMITTEE APPOINTED FOR SUCH PURPOSE AT AN INFORMAL MEETING OF MEMBERS OF THE AM. SOC. C. E. AND OTHERS INTERESTED IN SEWAGE DISPOSAL, HELD AT PITTSBURGH, JUNE, 1916. (Revised December, 1920) DEFINITIONS 1. Activated sludge treatment miay be defined as a biochemical process by which the purification of sewage is accomplished by passing it through tanks, in which sewage sludge is artificially agitated and intimately mixed with sewage and is supplied with the requisite oxygen for the optimum develop- ment of countless numbers of nitrifying organisms incorporated in and ad- hering to the sludge, the final settlement of which causes a distinct clarifica- tion of the oxidized sewage. 2. Activated sludge may be defined as a flocculent sludge of medium brown color enveloped by masses of aerobic organisms possessing the power of rapidly oxidizing and nitrifying sewage, and which, though of low specific gravity, settles rapidly. 3. The process may be divided into the following treatments: (a) Economic screening. (b) Preliminary rapid sedimentation in properly designed grit chambers where combined flow of sewage and storm water must be treated. It being quite essential to prevent detritus of heavy specific grav- ity, such as sand and gravel, from reaching the treatments which follow. (c) Thorough mixing in aerating the sewage with activated sludge, which may be effected by means of air, by mechanical mixers, or a com- bination of both. In any case sufficient air for oxidation must be applied to the admixture. (d) Sedimentation of the sludge contained in the admixture as it passes from the aerating tank. This may be accomplished by either horizontal or vertical flow sedimentation tanks. (e) The return of a portion of the settled activated sludge to the raw sewage before, or at the time, it enters the aerating tank. (f) Reaerating the sludge which is returned to the raw sewage in sep- arate aerating tanks. This may or may not be necessary, depend- ing upon the character of the sewage treated and effluent required. (g) Secondary sedimentation for partially dewatering the separated sludge not returned to the raw sewage. 447714 The Activated Sludge Process (h) Sludge disposal. This may be effected in several ways. Where the climatic conditions are favorable, it may be dried in beds or lagoons in the open air or under cover, and the residue used for filling in low ground, or for fertilizer, or burned. Under un- favorable climatic conditions it may be pressed or centrifuged and burned, or dried by artificial heat and the residue used as fertilizer. The terms used in connection with the process may be defined as follows: 4. Screening. Such as may be the most economical under the existing conditions. Probably through from one-eighth to one-sixteenth inch screen. 5. Grit. That portion of the mineral solids carried in the sewage liquor which will settle out under a velocity of one foot per second. The grit chamber should be so designed, and the removal of the grit so performed, that a fairly uniform velocity through the chamber may be maintained. Probably from 0.75 to 1.25 feet per second. Grit in the aerating tank seriously affects the process. 6. Air. To be obtained by means of a low pressure compressor or blower, and must be kept free of oil, grease or dust. The latter may be removed effec- tively by means of a standard type of air washer. (a) Volume of air used should be expressed as "Air Factor," obtained by multiplying the volume-of-f ree-air-per-volume-of -sewage- treated by the feet-of-air-submergence, or the cubic-feet-of-air- per-gallon-of-sewage by the pounds-of-pressure. (b) Area of air diffusers, where porous plates are used, to be expressed as a ratio between effective square feet of air diffusers and square feet of water surface in tank. Where grills or grids of pipes are used, size of pipe, size and spacing of perforations, spacing of pipes and grids, to be expressed in feet and inches. Feet-of-air- submergence should be noted in this connection. (c) Time of aeration of raw sewage should be expressed in hours and minutes, computed from the average period required for the mix- ture of sewage and activated sludge to pass through the aerating tank. (d) Where the activated sludge is reaerated after removal from the sedi- mentation tank, and before being returned to aerating tank, the air used for this purpose should be separately measured and expressed in cubic feet of air per gallon of sewage treated and added to the volume of air used in the aerating tanks to determine the full quantity of air used in the process, assuming air is used for reaerating at same pressure as for aerating. (e) Where the sludge deposited in the sedimentation tank is removed by an air lift, the quantity used should be separately measured and expressed in cubic feet of free air per gallon of sewage treated. Pressure being considered. (f ) Power used. 7. Activated sludge. Must be of such a flocculent character as to absorb the colloidal matter in raw sewage within a contact period of two hours, and be of a golden brown color. (a) It is to be introduced into the raw sewage as it passes into the aerating tanks, the air effecting the mixing as both pass through the tanks, in such proportions as may be necessary to secure the required effluent in each case. Probably from 15% to 25%. Nomenclature and Definitions (b) The proportion of the admixture shall be expressed in percentage of volume determined by settlement for one-half hour in a gradu- ated one-liter glass cylinder approximately fifteen inches in height and two and one-quarter inches in diameter. It is also recom- mended that such percentage be determined as parts per million of total dry solids where facilities for making such determina- tions are available. (c) The volume of sludge removed and recovered by the process should be expressed in pounds per million gallons of sewage treated, based upon the weight of the sludge free from moisture. It is also handy to express the sludge removed in gallons per million gallons of sewage treated, noting the percentage of moisture in the sludge. 8. Sedimentation. This may be accomplished in either of two ways: Up- ward or horizontal flow. If upward flow is used the velocity should be ex- pressed in feet per hour. If horizontal flow, express the velocity in feet per minute. Average velocities being used. Probably the most certain method of expressing rate of sedimentation is by gallons of sewage passing through per square foot of tank surface. (a) The ratio between the area of sedimentation tank and aerating tank should be stated; also the ratio of the volumes of the two. 9. Effluent. Character of effluent should be expressed in plain biological chemical and physical terms. (a) Biologically, in total bacteria per c. c. growing for 48 hours in nutrient agar at 20 C., and percentage of removal. Also bacteria at 37 C. (b) Chemically, in oxygen consumed, dissolved oxygen, organic nitrogen and free ammonia as determined by the standard methods recom- mended by the American Public Health Association. Stability in hours Trith methylene blue without dilution at 70 P. (c) Physically, in suspended matter in parts per million and in percentage of removal from raw sewage. Clarification in terms of turbidity determined by the standard methods recommended by the Ameri- can Public Health Association. 10. Capacity. (a) Capacity for areation should be expressed in gallons per acre of tank surface per 24 hours, stating effective depth of tanks and average contact period. (b) Capacity for sedimentation should be expressed in gallons per square foot of tank surface per 24 hours, stating effective depth of tank. 11. Costs. To be expressed in million gallons of sewage treated and divided) as follows: (a) Population served. (b) Character of sewage, whether purely domestic, or domestic and manufacturing, or combined with storm water. (c) Total volume of sewage treated per year. (d) Average daily volume of sewage treated, with low and peak rates. 5 The Activated Sludge Process (e) Average daily suspended matters in raw sewage. (f ) High, low and average temperatures of sewage and atmosphere. (g) Method of sludge disposal. (h) Pounds of sludge produced per year on dry basis. (i) Pounds of sludge produced (on dry basis) per million gallons treated (average). (j) Cost of sludge disposal per dry ton produced, including overheads. (k) Cost of sludge disposal per million gallons of sewage treated, includ- ing overheads. (1) Cost of sewage treatment, including sludge disposal per million gal- lons of sewage treated, including overheads. (m) Total! cost of plant and when built. (n) Fixed annual charges, including interest and depreciation. (o) Total operating charges including ordinary repairs. (p) Total cost of sewage treatment, including overhead and fixed charges, per million gallons of sewage treated. Note: Where possible, operating charges should be subdivided into cost of air furnished, plant labor, sludge disposal labor, and other charges in connection with disposing of sludge. F. A. DALLYN, GEORGE T. HAMMOND, T. OHALKLEY HATTON, Committee. ABSTRACT BIBLIOGRAPHY 1912 1 Experiments upon the purification of sewage and water at the Lawrence Experiment Station. H. W. CLARK and S. DEM. GAGE. 44th Annual Re- port State Board of Health of Mass. 1912. 275-367. In the sub-chapter on the aeration of sewage as an aid to nitration (pp. 290-2), it is noted that the aera- tion of sewage perceptibly clarified it, and that when green growths occurred in the aerated sewage, it became saturated with 0. These observations led to a series of experiments begun in April, 1912, to test the efficiency of aeration combined with these growths, in which three small sand filters were used; the first receiving raw sewage; the siecond, sewage aerated for twenty-four hours by drawing or blowing air through it and the third containing aerated sewage with green growths. It was found, after the experiments had been under way for several months, that nitrification was occurring in the aerated sewage containing the growths, over 1.5 parts of nitrate per 100,000 being found. Later an aerating tank containing slabs of slate was put into operation, in which it was observd that the slate and sides of the tank became covered with a compact brown growth, and that this growth collected not only the suspended matters, but also a large portion of the colloids, so that after a few hours treatment the sewage became free from both. Tables of analytical data show- ing free and albuminoid ammonia, nitrates, nitrites, and consumed in the raw and treated sewage are given. 1913 2 Preliminary note on the bacterial clarification of sewage. G. J. FOWLER and E. M. MUMFORD. Jour. Royal Sanit. Inst. 34, 497-500. Surveyor 44, 287-8. Chem. Abst. 7, 3632. Laboratory experiments on quantities up to 4 liters indicate the possibility of removing the colloidal matter from sewage by adding 1 grain of iron salt per gallon, inoculating with the iron bacterium "M7" (*) and passing air through the liquid for 6 hours. A precipitate of ferric hydrate is obtained which settles out in 6 hours leaving a clear, color- less liquid. The coarser suspended matter must first be removed. * (Further reference to the iron bacterium "M7" can be found in Jour. Chem. Soc. 103, 645-50. Jour. Royal Sanit. Inst. Nov., 1913. Surveyor 42, 497; 45, 504-6. Can. Engr. 26, 598-60. Chem. Abst. 7, 2770; 8, 2016. See also Book "Iron Bacteria"; D. Ellis, pp. 179, Metheun & Co., Lt'd., London. 1919.) 3 Aeration of sewage and other foul liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 22,952, Oct. 11, 1913. Jour. Soc. Chem. Ind. 34, 244. Chem. Abst. 9, 831. A series of diff users spaced apart and each formed of a porous earthenware plate, on the under side of which compressed air is admitted, are arranged transversely across' the bottom of each section of the tank holding the sewage to be aerated. The sewage is transferred from one section of the tank to the next by a circulator consisting of an uptake pipe at the bottom of which compressed air is admitted; the mix- ture of air and sewage rises and is delivered onto the covered top of a down- take pipe, into which air is also admitted below the water level. The lower end of the downtake pipe is enlarged to form a foot chamber, where the excess of air escapes and is passed on to supply the diffusers, while the sewage passes into the bottom of the next section of the tank. (Cf. U. S. Patent 1,247,540. Ref. No. 341.) ' **i r 'T&e- Actiwatttd Sludge Process 4 Work of the Lawrence Experiment Station for 1913 The Purification of sewage and water and investigations on allied subjects. H. W. CLARK and S. DE M. GAGE. 45th Annual Report State Board of Health of Mass. 265- 368. Respecting the aeration of sewage, the studies begun in 1912 were con- tinued with various modifications and a new aerating tank put into operation on Jan. 2nd. Aerating periods varying from 24 to 5 hours, and air volumes ranging from 200,000 to 25,000 cu. ft. per hour per million gallons of sewage were tried, the results of the various changes in the methods of operating producing far less differences in the efficiency of the process than might be expected. The effect of the gelatinous growths in reducing the Kjeldahl N was clearly established, as was also the clarifying effect of aerating with sludge. Effluent stability was more pronounced when the sewage was aerated 10 hours or more. A brief historical review of sewage aeration work is given, as well as several tables of analytical data. 1914 5 Purification of sewage or other impure waters. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 729, Jan. 10, 1914. Jour. Soc. Chem. Ind. 34, 197. Chem. Abst. 9, 1814. The sewage is purified in presence of air and cultivated sludge in an annular tank. Transverse depres- sions are formed in the floor of the tank at intervals and in each depression a plate is suspended so that the circulating sewage has to pass underneath the plate in each depression. Circulation is brought about by admitting com- pressed air at the bottom of each depression in such a way as to mix with the sewage on one side of the plate only. The upper part of the plate is so formed as to deflect the rising current horizontally towards the next depression. 6 Sewage treatment by aeration and contact in tanks containing layers of slate. H. W. CLARK and G. O. ADAMS. Eng. Record 69, 158-9. Chem. Abst. 8, 1319. Sewage treated with air in tanks with vertical slate walls one inch apart, gave 87% removal of suspended matter with 5 hours aeration. 7 Experimental plant for treating sewage at Brooklyn, N. Y. G. T. HAM- MOND. Munic. Jour. 36, 233-9. Munic. Eng'rg. 47, 427-36. Equipment in- cludes various tanks and apparatus for the investigation of sewage treatment by forced aeration. Plant not operating long enough to justify publishing results. 8 The present position of the sewage disposal problem. G. J. FOWLER. Surveyor 45, 504-6. Engineer 117, 272. Wasser u. Abwasser 8, 417-8. Trans. Liverpool Engr. Soc. 35, 213-23. Sanit. Record 53, 294. Expt. Sta. Record 32, 88. The sanitary aspects of sewage disposal are discussed with reference to conditions permitting use of the sludge as fertilizer. The author anticipates the time when it will be possible to purify sewage completely in a tank, with production of inoffensive sludge which can be disposed of as fer- tilizer. The forced aeration experiments at Lawrence, Mass., and those in progress at Davyhulme (Manchester, Eng.) are referred to. 9 Experiments on the oxidation of sewage without the aid of niters, I. E. ARDERN and W. T. LOCKETT. Jour. Soc. Chem. Ind. 33, 523-39. Sur- veyor 45, 610. Chem. Abst. 8, 2207. Expt. Sta. Record 32, 387. The solid matter obtained by prolonged aeration of sewage which for reference pur- poses and the want of a better name has been designated "activated sludge" has the power of enormously increasing the purification of sewage by simple aeration, its effect depending upon intimate contact with, and its proportion in the raw sewage. Unoxidized solids should not be allowed to accumulate. Tem- perature exerts considerable influence. Laboratory experiments indicate that purification of average strength Manchester sewage can be accomplished in 6 to 9 hours, using 25% sludge. DR. J. GROSSMANN, F. R. O'SHAUGHNESSY, S. E. MELLING, P. GAUNT, J. T. THOMPSON and DR. G. J. FOWLER participated in the discussion, covering mainly the composition of the sludge, operating 8 Abstract Bibliography 1914 costs and possible revenues from the process. Several tables of analytical data are given. 10 Apparatus for the purification of sewage and analagous liquids. W. JONES and JONES & ATTWOOD, LT'D., Amblecote, Worcestershire, Eng. British Patent 19,915, April 11, 1914. Jour. Soc. Chem. Ind. 33, 1170. Chem. Abst. 10, 655. A pipe, reaching nearly to the bottom of a tank containing the sewage, extends over a partition to the bottom of a second tank; com- pressed air is delivered into the end of the pipe in the first tank, thus causing a mixture of liquid and air to pass over into the second tank; the lower end of the pipe in this tank has a perforated chamber which distributes the air into the liqud. A supplementary volume of air is introduced into the descend- ing pipe in the second tank. 11 Apparatus for the purification of sewage and analogous liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 19,916, April 11, 1914. Jour. Soc. Chem. Ind. 34, 632. Chem. Abst. 10, 655. In an aerating tank for the treatment of sewage, the floor of the tank is divided into a number of saucer-like depressions, in the center of which is a porous plate. Compressed air is admitted to chambers below the porous plates, and fine bubbles rise from their upper surface; currents of liquid upwards over the porous plates and downwards between the depressions are thus produced, carrying with them the suspended solids and bacteria. The bottom of the tank being curved or inclined downwards to the diifusers from points between the same, cause the deposited solids falling to the bottom of the tank between the diffusers to pass under the influence of the air currents from the latter. The sewage is admitted at the bottom of one end of the tank and flows over a wall at the other end. After aeration is completed, the liquid is allowed to stand till clear, when the clarified liquid is run off and the solids allowed to remain. Fresh sewage is then admitted at once and the aeration recommenced. fCf. U. S. Patent 1,282,587, Ref. No. 428.) 12 Sewage purification by aeration: Manchester experiments. EDITORIAL. Surveyor 46, 113-4. Experimental results promising. Costs still in doubt. Tank capacity should be 1.5 times dry weather flow, based on 12 hour period. Preliminary calculations, from meager data, give approximately 1 cu. ft. of air per gallon of sewage. Cautions with regard to cost of such large volumes of air. 13 Apparatus for purifying sewage. G. W. & J. F. NAYLOR, Denby Dale, Yorks, Eng. British Patent 20,259, Sept. 28, 1914. Jour. Soc. Chem. Ind. 34, 814. Chem. Abst. 10, 655. A tank has a false bottom of porous tiles, so supported that the air space below each row of tiles is separate from the adjoining air space. Air under pressure is admitted through horizontal pipes laid below each row of tiles. The tiles may be supported directly on the floor of the tank or may fit in trays. The air pipes may support the trays or the tiles, or may have short upright branches supporting them. The pipes and branches have perforations for the passage of the air to the under side of the tiles. 14 Apparatus for purifying sewage. G. W. & J. F. NAYLOR, Denby Dale, Yorks, Eng. British Patent 20,579, Oct. 6, 1914. Jour. Soc. Chem. Ind. 34, 978. Chem. Abst. 10, 945. In the purification of sewage by aeration in a tank with a false bottom of porous material, the false bottom is made of a pliable material, such as filter-cloth, felt, canvas, or perforated metal, supported if desired on wire netting, through which the air supply diffuses into the sewage in the tank. The porous floor may be laid on the air pipes placed horizontally along the bottom of the tank, or on the framework covering each line of pipes and dividing the air space into separate compart- ments. The floor may also be supported on boxes with porous sides, the air pipes coming through the bottom of the tank and being in a vertical position in the center of each box. 9 The Activated Sludge Process 15 Purification of sewage and analogous liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 21,976, Nov. 4, 1914. Jour. Soc. Chem. Ind. 35, 272. Chem. Abst. 10, 1068. Active bacterial sludge is prepared by forcing air in small bubbles through raw sewage, keeping the latter in circulation. After a time the sludge is allowed to deposit, the liquid run off, a fresh quantity of sewage run in, and the process repeated. Sufficient active sludge is prepared to fill the treatment tank one-fifth to one-third full. The tank is then filled up with raw sewage. The tank is formed of one or more long endless channels of rectangular form, the bottom of the tank sloping to one end. The dividing wall between the two portions of the channel has vertical slits in it so as to permit the free passage of sludge and water and the maintenance of level throughout the channel. Air is supplied in small bubbles transversely across the channel at several points, and just in front of these points a baffle plate is hung. In this way the rising mixture of air and sewage causes a current of sewage under the baffle, and the current is kept up throughout the channel, inducing a continuous circulation of the sewage. Aeration is conducted for one to five hours and then stopped for one or two hours, the clear liquid then drawn off down to as low a level as desired, and the tank then filled up with fresh sewage. The sludge formed from each charge is drawn off from time to time. Closed tanks may also be used, the air liberated at the surface of the first channel being led to the bot- tom of the adjoining one and so on, the last channel being open or the air led away by a shaft. The pressure of the air over the liquid may also be used for emptying the channels. When the sewage is below 46 F. (8 C.) it is warmed to this temperature in order that nitrification of the sludge may not be hindered. Aerating sewage in the presence of humus obtained from fil- ter beds is also claimed. The aeration is carried out by forcing air through porous bodies, such as porous earthenware, textile fabrics, cocoanut fiber or lead wool. A suitable apparatus is shown. 16 Means of and methods for treating sewage. W. M. BECKETT, Manchester, Eng. British Patent 21,985, Nov. 4, 1914. Jour. Soc. Chem. Ind. 34, 1269. Chem. Abst. 10, 1068. The sewage enters a closed tank having a floor pervious to air. Compressed air rising through the floor agitates and aerates the sew- age and sludge, and the gases given off are passed with the air to a destructor or other combustion furnace. The purified liquid is discharged from the tank by a floating arm, down to a certain level, below which the sludge is allowed to collect, a portion being run out from time to time. Porous tiles, perforated pipes, etc., may be used for the pervious floor. 17 Purification of sewage and analogous liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 22,736, Nov. 19, 1914. Jour. Soc. Chem. Ind. 35, 195. Chem. Abst. 10, 1241. Sewage is admitted gradually to a tank containing a residuum of activated sludge from a pre- ceding operation, and air is blown through it from the bottom of the tank at the same time, the operation taking one to six hours. When the tank is full aeration is stopped, the sewage allowed to remain quiescent for one or two hours, the clear liquid being then drawn off from the top down to the level of the sludge layer in about half an hour. If through any cause the sludge should get less active, it may be drawn off into side tanks for aeration, and afterwards returned to the main tank. Cultures of organisms may be added to the tank to assist in the purification process. Several tanks ma} be worked in combination, in which case the valves for supplying air and sewage and for discharging the liquid are operated in sequence by automatic means, such as float valves, or a water-clock, or other time-piece operating pneumatic or electrical devices, so that the operation is continuous. (Cf. U. S. Patent 1,247,543, Ref. No. 344.) 18 Purification of sewage and analogous liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 22,737, Nov. 19, 1914. Jour. Soc. Chem. Ind. 35, 195. Chem. Abst. 10, 1241. A tank of continuous 10 Abstract Bibliography 1914 channel form with semi-circular ends is used, the space enclosed by the inner wall of the channel forming an inner tank. Air diffusers are placed along the bottom of the tank, and just behind these, baffle plates are let down from the surface. The mixture of sewage and air passes under the bottom and rises up the side of the baffle, and thus produces a forward movement of the sewage along the tank. A weir leads from one part of the channel into the inner tank, and some distance in front of this weir the introduction of air is stopped, so that there is time for some sedimentation of the sludge to take place before the sewage passes into the inner tank, which constitutes a settling tank and from the upper part of which the purified sewage is con- tinuously drawn off. The sludge deposited in the inner tank is lifted back by an air-lift into the treatment tank. An annular treatment tank or one in the form of a zig-zag channel may also be used. (Cf. U. S. Patent 1,247,542, Ref. No. 343.) 19 The complete bacterial treatment of sewage without filters. W. NAYLOR. Surveyor 46, 592-4. Chem. Abst. 9, 229. In discussion of the paper by ARDERN and LOCKETT, (Ref. No. 9), mention is made of isolated instances of purification without filters on sewage farms where the sewage was al- lowed to stand in pools. This purification required considerable time. It is noted that one volume of sludge to 4 or 5 of sewage used in the experiments of A. and L. is almost too solid to deal with, as ordinary precipitation methods give one part of sludge to 110 of sewage and require 6 hours for settling. The air used for aerating may require after-treatment on account of odors taken up from the sewage. Sludge disposal should be made easier because the material is non-putr^scezit and it should be pressed more easily, as it would be leas slimy than ordinary sludge. 20 Tank for the purification of sewage. G. W. & J. F. NAYLOR, Denby Dale, Yorks, Eng. British Patent 23,146, Nov. 27, 1914. Jour. Soc. Chem .Ind. 34, 1269. Chem. Abst. 10, 1389. The tank has a level floor and is divided into several compartments by baffle plates reaching from the top nearly to the bottom, and which may be inclined in the direction of the flow of sewage. Porous tiles are fitted in the floor behind each baffle plate and air is forced through the tiles. Air may also be blown over the surface of the sewage by pipes attached to the top of the baffle plates. The circulation of the sewage is assisted by the upward current of air and the sludge is kept in suspension. The exit pipe of the tank is provided with a float discharge, arranged to empty three-fourths of the contents, leaving the remainder to activate the succeeding supply of sewage. The baffle plates may also be arranged to reach the bottom of the tank, and pipes provided passing through each plate. The tank may be divided longitudinally into two sections to economize space. 21 Sewage treatment by aeration. EDITORIAL. Surveyor 46, 674. Comment on paper by W. H. DUCKWORTH. (Ref. No. 22). Caution recommended with regard to cost data. 22 Aeration experiments with activated sludge. W. H. DUCKWORTH. Sur- veyor 46, 681-2. Chem. Abst. 9, 679. Experiments at the Salford sewage works showed successful treatment of sewage by the process of ARDERN and LOCKETT. In tanks of 34,500 gallons capacity with 25% sludge, 75,000 gallons could be treated in 21 hours. One hour to fill, 3 hours of aerating, 2 hours to settle and one hour to empty; 7 hours for complete treatment of one tankfull. Purification was 90% on the oxygen absorption and 76% on the albuminoid ammonia. The sludge contained only half the fat of ordinary sewage sludge, while the phosphoric acid was twice and the nitrogen about 3 times the amount in ordinary sludge. As the experiments were made with apparatus at hand, and in connection with the regular work of the plant, no accurate cost figures could be given. 23 Oxidation of sewage without the aid of filters, II. E. ARDERN and W. T. LOCKETT. Jour. Soc. Chem. Ind. 33, 1122-4. Chem. Abst. 9, 679. Expt. 11 The Activated Sludge Process Sta. Record 34, 888. Continuous flow experiments with a tank of 35 gallons capacity were satisfactory though the tank was not designed for best results. Perforated pipes distributed the air. Sludge was re-aerated. Fill and draw experiments in 50 gallon casks, using porous tiles for air diffusers also gave satisfactory results, 4 hours aeration with 25% sludge showing a purification by perforated pipes. Comparative results are given in tabular form. Experi- ence shows the necessity for adequate scientific control. Experiments using a tank of 20,000 gallons capacity, 400 sq. ft. area, are being made. This should handle 60,000 gallons of sewage daily. 24 The purification of Salford sewage along the lines of the Manchester experiments. S. E. MELLING. Jour. Soc. Chem. Ind. 33, 1124-30. Chem. Abst. 9, 679. Refers to the same work as described under reference 22. It is an established fact that it is possible to clarify and purify crude sewage in bulk in 3 hours, the effluent produced satisfying any local or international standard. Several tables of analytical data accompany the article. In the discussion, MR. J. P. WAKEFORD referred to the promising tests of the acti- vated sludge process at Wakefield, Eng., (Cf. Ref. No. 63), where various trade wastes were encountered. The dry sludge there contained 43.99% organic matter, 56.01% mineral water; total N, 4.59%, phosphates, 2.74%, iron, 9.67%. The possibility of the iron acting: as a catalyst in flocculating the colloids was suggested. MR. W. H. DUCKWORTH stated that 80,000 gallons per day were being treated at Salford on the fill and draw plan. A 12,000 gallon continuous flow tank is contemplated. Some difficulty had been experienced through the stopping up of the holes in the perforated pipes. DR. G. J. FOWLER said that the idea which started these particular researches really originated at Lawrence, Mass. In his opinion, the iron bacterium "M7" probably played some part in the process. MR. J. H. LESTER, MR. W. THOMPSON, DR. J. GROSSMANN and DR. E. ARDERN also participated in the discussion, the latter emphasizing the importance of complete admixture and intimate contact of the activated sludge with the sewage, describing as use- ful for this purpose, a specially prepared porous tile air diffuser. 25 Sewage treatment by aeration. EDITORIAL. Surveyor 46, 701. Analogy drawn between the Lawrence, Mass, slate tank experiments and ARDERN and LOCKETT'S experiments. Filters become choked and the amount of air supplied cannot be controlled as in the activated sludge process. Cost data again asked for. 26 A recent development of the sewage problem. E. ARDERN. Surveyor 46, 714-7. Sanitary Record 54, 401, 413; 55, 5-6. Chem. Abst. 9, 679. A report of the bottle and cask experiments at Davyhulme, Manchester, (Ref. No. 9) and a summary of the Salford work. (Ref. Nos. 22, 24.) Grit should be re- moved. Proportions of sludge to sewage should be 1 to 4. Purification is seri- ously diminished below 10 C., and trade wastes may have inhibitory action. Costs discussed briefly. 27 Purification of sewage. G. W. & J. F. NAYLOR. Denby Dale, Yorks, Eng. British Patent 24,386, Dec. 21, 1914. Jour. Soc. Chem. Ind. 35, 195. Chem. Abst. 10, 1567. A tank is divided into compartments by vertical baffles and is provided with an air supply from tubes entering the pipes by which the sewage flowing over the baffles is led to the lower portion of the next compart- ment. In an alternative form, air is supplied to rows of boxes with perforated or permeable faces fixed to one or each side of the baffles; the boxes may be arranged checker- wise, with the permeable faces delivering horizontally; or obliquely overlapping, with inclined permeable faces alternately directed up- wards and downwards. Agitators may be used to mix the sludge at the bottom of the tank with the incoming sewage, and may also deliver air into the sewage. 12 Abstract Bibliography 1915 28 Apparatus for the purification of sewage and analogous liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 24,630, Dec. 24, 1914. Jour. Soc. Chem. Ind. 35, 195. Chem. Abst. 10, 1686. A tank has a discharge pipe practically flush with the bottom, and over the pipe, and fitting on it, is a superposed series of rings or cylinders reaching above the surface of the liquid in the tank, all the joints being water-tight. When all the rings are in position the series forms a closed tube. Each ring is con- nected with the one below it by sliding links which permit of the rings being lifted in succession from the top and which leave a considerable space between the lifted ring and the one below it. As each ring is lifted, liquid flows into the mouth of the next lower ring, and in this way the tank is emptied in suc- cessive layers from the surface. The rings are lifted by means of a pulley chain connected with a bucket which is filled from a cistern through a regulated tap, the cistern being filled with liquid from the tank by a pipe near the surface with a regulating tap. When all the rings have been lifted a percussion valve in the bottom of the pulley bucket is opened automatically and the bucket emptied; the empty bucket being raised again by the rings in the tank subsiding into their places. In an alternative form of the apparatus, part of the discharge end of the tank is formed of wooden slats working in grooves, the top slat being connected at each end to a pair of pulley chains and lifting those below it by links, the discharge in this case taking place through the end of the tank. The pulley bucket works inside of the tank. Another method of effecting the dis- charge is by a float carrying a siphon discharge pipe which empties into the tank discharge pipe, the float being counterbalanced by a weight acting over a pulley. The short legs of the siphon are trapped by cups just below the surface of the liquid. Sludge is discharged from the tank when desired, by valves in the bottom. The discharge apparatus may be arranged to open and close the sewage inlet valves of the tank and to actuate the air supply valve. 29 A recent development of the sewage problem. DISCUSSION. Surveyor 46, 754. In the discussion of the paper by E. ARDERN (Ref. No. 26), DR. G. J. FOWLER describes how previous work led up to activated sludge experiments. W. H. DUCKWORTH discusses the Salford work. DR. ARDERN claims the sludge is granular and can be handled easily by simple straining filters. Hopes that the length of the accumulation period may be cut down. 30 Experiments upon the purification of sewage and water at the Lawrence experiment station during the year 1914. H. W. CLARK and G. O. ADAMS. 46th Annual Report Mass. State Dept. Health. 295-346. Chem. Abst. 11, 177. Expt. Sta. Record 35, 887. In the chapter on the purification of sewage by aeration and growths, (pp 301-9) are reports on the aerating tank put into operation in January, 1913, and of three others which were started to determine the effect of this treatment on raw, settled, and septic sewage. The effect of aeration in a secondary tank was also studied. Calculated on capacity, all of these tanks contained 5 to 15% of slate. Air was supplied through jets in the tank bottom, with deflecting baffles to cause circulation of the sewage. With a 5 hour aeration period, and air supplied at the rate of 25,000 and 50,000 cu. ft. per hour per million gallons of sewage, all the effluents were well clarified and 20 to 50% of the samples taken were stable. 5 hours re-aeration increased the proportion to 90%. Tabulated analytical data showing free and albuminoid ammonia, organic and inorganic N, O con- sumed, and bacterial removal are given. 1915 31 Sewage treatment by aeration. G. B. KERSHAW. Surveyor 47, 8. The treatment of storm water, up to three times the dry weather flow, will be expensive. Refers to the Brooklyn aeration experiments where the cost of air was considered high with 2 hours aeration. 32 Sanitary engineering in 1914. The activated sludge system. ANON. Engineer 119, 32. A brief outline of the activated sludge process is 13 The Activated Sludge Process given, with particular reference to the production of the active sludge. The bearing of the organism "M7" on the process is considered, as are the experi- ments of DR. FOWLER, ARDERN & LOCKETT, W. H. DUCKWORTH, S. E. MELLING, and J. P. WAKEFORD. 33 Purification of sewage and other liquids. W. JONES and JONES & ATTWOOD, LT'D., Stourbridge, Eng. British Patent 1,141, Jan. 23, 1915. Jour. Soc. Chem. Ind. 35, 326. Chem. Abst. 10, 2017. Air is supplied to the sewage mixed with the sludge, not uniformly as is usual, but intermittently, or in varying volumes or at varying pressures, or both, during the period of aeration. By employing a relatively small volume of air over a long period, the aeration of the sewage may be effected, and by increasing the volume or pressure for a short period, the sludge and sewage are thoroughly mixed. In this way a smaller quantity of air is used than for a uniform supply. An automatic valvular apparatus is provided which consists of a bucket-wheel in a tank of water, to which compressed air is supplied, causing the wheel to rotate. The spindle of the wheel carries a cam which operates a valve in piston form in connection with an air chest; when the piston is raised air passes from the chest to a pipe leading to a main air valve which it actuates. The valve passes compressed air either directly to the diffusing pipes in the sewage tank, in which case a pulsating effect is produced in the sewage, or first to an air receiver which after being filled is allowed to empty into the dif- fusing pipes, in which case a gradually decreasng volume of air is supplied to the sewage. Other methods of varying the air supply are also described. (Cf. U. S. Patent 1,247,541, Ref. No. 342 and Can, Patent 183,586, Ref. No. 402.) 34 Apparatus for introducing gases into intimate contact with liquid sewage. G. W. MOTTRAM, Deepcar, Yorks, Eng. British Patent 2,421, Feb. 16, 1915. Jour. Soc. Chem. Ind. 35, 434. In a vertical cylindrical sewage tank, the apparatus takes the form of a vertical rotating shaft carrying a pair of arms at its lower end. The shaft is hollow and compressed air is supplied through it to the arms, which are made of perforated pipes or of plain metal pipes carrying earthenware pipes. These earthenware pipes are arranged concentrically around the metal pipes and spaced from them by distance pieces to provide an air passage. The earthenware pipe is porous prefer- ably along one section of its length only. In a rectangular tank the air diffusing pipes are supported at each end on wheels running along rails on the bottom of the tank, or are suspended from arms supported on wheels on rails on the top of the walls of the tank. The air supply is brought by flexible piping to one of the supporting arms which takes it to the air diffusing pipes. (Cf. U. S. Patent 1,195,067, Ref. No. 177.) 35 Observations on some European water purification plants and sewage disposal works. E. BARTOW. Jour. Am. Waterworks Assoc. 2, 213-24. Chem. Abst. 9, 1521. Univ. III. Bull. 13, 162-72. (Water Survey Series No. 12, 1915.) Reference is made to the experiments on the aeration of sewage in the presence of activated sludge in progress at Manchester, Eng., and to similar work which is being carried on by the Water Survey Station at the Univ. of 111. at Urbana. 36 English experiments on sewage aeration revived as preliminary to the Baltimore tests. L. C. FRANK. Eng. Record 71, 288-9. Chem. Abst. 9, 1645. Enumerates some features of the activated sludge process at Manches- ter and Salford as described by ARDERN and LOCKETT, and others. (Ref. Nos. 9, 22, 23, 24.) A continuous flow tank will supercede the fill and draw methods. 37 Treatment of sewage. C. H. COOPER, Wimbleton, Surrey, Eng. British Patent 3,831, March 10, 1915. Jour. Soc. Chem. Ind. 35, 326. Chem. Abst. 10, 2116. A portion of sewage which has been activated is mixed with raw sewage in an enlargement of the mouth of a vertical pipe up which the raw 14 DIVERSITY OF CALIFORNIA ^ = NT OF CIVIL ENGINEERING Abstract Bibliography 1915 sewage is conveyed . The mixture passes out through a nozzle in the side of the enlargement and below the surface of the sewage; at the same time com- pressed air is blown through the nozzle with the sewage mixture. In this way the sewage mixture is atomized as it leaves the nozzle, and afterwards is mixed further with air drawn in through louvres against the lower sides of which the atomized sewage impinges. 38 The purification of sewage by aeration. R. O. WYNNE-ROBERTS. Can. Engr. 28, 335-6. Contract Record 29, 647-9. Chem. Abst. 9, 1210. The aeration of sewage is reviewed, particularly the work of CLARK and GAGE at Lawrence, Mass., and that of FOWLER and MUMFORD, in which the iron bac- terium played a part. The activated sludge work of ARDERN and LOCKETT at the Davyhulme works, Manchester, Eng., DR. E. BARTOW at Urbana, DUCK- WORTH and MELLING at Salford, and of J. P. WAKEFORD at Wakefield are also noted and some of their results given, including cost estimates. The proposed activated sludge experiments at Milwaukee, Baltimore and Regina, Sask., Canada, the latter in some detail, are also referred to. 39 Apparatus for introducing gases into intimate contact with liquids. G. W. MOTTRAM, Sheffield, Eng. British Patent 4,240, March 18, 1915. Jour. Soc. Chem. Ind. 35, 521. The gas is passed into a pipe of porous material or a conduit formed of porous tiles or blocks immersed in the liquid. The porous tubes, tiles or blocks are formed of coarse materials, and are provided with a surface facing of much finer material, so that while the gas passes easily through the coarser layers, it is very finely divided by the finer material before it comes in contact with the liquid. 40 Sewage aeration at Lawrence and Manchester compared. H. W. CLARK. Eng. Record 71, 367-8. Chem. Abst. 9, 1521. Mr. Clark states that the heavy, brownish gray, gelatinous and other growths upon the slate beds at Lawrence which clarify the circulating sewage are probably the same bodies as those developed by FOWLER and ARDERN & LOCKETT in the Manchester tank and called "activated sludge." 41 Can sewage sludge be made valuable as a fertilizer? EDITORIAL. Eng. News 73, 593. Expt. Sta. Record 33, 423. Refers to a paper presented by DR. E. BARTOW and to a sample of dried activated sludge exhibited by him at the meeting of the Lake Mich. Water Com. held at Milwaukee on March 19, 1915. Sample contained 6% N in a form available for plant food, and the estimated value of the sludge in N, P, and K compounds was $15 to $20 per ton. 42 Sewage aeration experiments in the United States. EDITORIAL. Surveyor 47, 449. Refers to the continuous flow activated sludge experiments to be started by the U. S. Public Health Service at Baltimore, Md., using a modified Imhoff tank. 43 Purification of sewage by aeration in the presence of activated sludge. E. BARTOW and F. W. MOHLMAN. Jour. Ind. Eng. Chem. 7, 318-20. Eng. News 73, 647-8. Eng. Record 71, 421-2. Eng. & Contg. 43, 310-1. Munic. Jour. 38, 504-5. Jour. Soc. Chem. Ind. 34, 508. Surveyor 47, 642. Chem. Abst. 9, 1521. Expt. Sta. Record 33, 423, 786; 38, 490. Univ. III. Bull. 14, 325-35. (Water Survey Series No. 13.) Experiments at Urbana, 111., with fresh sewage of domestic origin, showed that nitrate was formed in 15 days by blowing 4830 cu. ft. of air. By siphoning off the supernatant liquid and re- filling, sludge was accumulated. On the 31st treatment 3 cu. ft. of air per gallon of sewage was required in 5 hours. Nitrification was complete. One hour aeration seemed practically sufficient. Worm life was active. (Aeolosoma hemprichi). The sludge contained on a dry basis, 6.3% N, 4.0% fat, 1.44% phosphoric acid and 75% volatile matter. UNIVERSITY OF CALIFORNIA DEPARTMENT OF CIVIL ENGINEERING The Activated Sludge Process 44 The Milwaukee, Wis., sewage tests. NEWS ITEM. Eng. News. 73, 650. Briefly reviews the methods tried and states that "large scale studies of activated sludge are to be made under the direction of DR. GILBERT J. FOWLER of Manchester, Eng." 45 An exceptionally promising method of sewage treatment. EDITORIAL. Eng. & Contg. 43, 306. Commenting on the work of BARTOW and MOHL- MAN, (Ref. No. 43), it is noted that their activated sludge experiments indi- cate a stable effluent, a commercially valuable residual sludge, and that the process is free from nuisance. The cost question is of chief consideration, though the effects of low temperatures, amount of air necessary, and flexi- bility of the process are points yet to be tleared up. 46 Activated sludge in sewage oxidation. EDITORIAL. Munic. Jour. 38, 509. Refers to English experiments; discusses the question of practicability; the possible necessity of keeping the air at certain temperatures; and expresses the hope that some way may be found to operate continuous flow tanks rather than the intermittent type. 47 Co-operation sought in conducting activated sludge experiments at Balti- more. L. C. FRANK and C. W, HENDRICK. Eng. Record 71, 521-2. Chem. Abst. 9, 1521. Discussion of design and operation of continuous flow aero tanks is accompanied by request for suggestions and criticisms. 48 Process of purifying sewage or other wastes, and apparatus therefor. L. C. FRANK, Washington, D. C. U. S. Patent 1,139,024, May 11, 1915. (Application filed April 2, 1915. 10 claims.) Off. Gaz. 214, 498. Jour. Soc. Chem. Ind. 34, 680. Chem. Abst. 9, 1647. Purifying sewage by agitating and oxidizing a flowing stream at one point in its path by injection of jets of air, allowing the sediment to settle at another point in the path of flow, and return- ing the sediment to the point of oxidation for further treatment. The sewage is led down by a pipe to the bottom of a central chamber of the tank and flows upwards. Air is admitted, also, at the bottom, and oxidizes the sewage which overflows at the top of the chamber into two V-shaped side chambers where settling takes place; the deposited solids fall through openings at the bottom of the side chambers into the central chamber, while the clear liquid passes to the effluent channel. (This patent dedicated to the public.) 49 Aeration method of purifying sewage. J. P. WAKEFORD. Inst. Munic. and County Engrs. June, 1915. Can. Engr. 29, 249-51. Chem. Abst. 9, 2785. Experiments on activated sludge are described. Barrel and bottle tests showed complete oxidation of the ammonia by aeration for two hours. A porous tile diffuser was used. In a large tank holding 11,000 gallons exclusive of 25% sludge, operated on the fill and draw plan, a cycle of half -hour fill, two hours blow, two hours settlement and half-hour empty, worked well. 90 cu. ft. of air per minute was used under a pressure of 5 Ibs. per sq. in. The sludge con- tained 4.59% nitrogen. Analyses of sludge and sewage are given. 50 Activated sludge experiments at Baltimore. L. C. FRANK and C. W. HEN- DRICK. Surveyor 47, 693. Chem. Abst. 9, 2786. Continuous flow neces- sary for economical operation. Oxidation promoted by fineness of bubbles. Aeration may be effected by (a) impact of inflowing sewage, (b) aeration, (c) mechanical devices. Sludge must be returned from settling to aeration tank. 51 Fertilizers. G. J. FOWLER and G. MUMFORD. British Patent 8,397, June 7, 1915. Jour. Soc. Chem. Ind. 35, 1074. Chem. Abst. 10, 2948. A fer- tilizer is produced by sterilizing any form of sewage sludge by heat and re- storing bacterial activity by the addition of fresh active residue or sludge produced by the aeration of sewage or like liqiud in the presence of bacteria. The temperature of sterilization is preferably not higher than the boiling point of water, and the proportion of the active sludge added is from 5 to 10% 16 Abstract Bibliography 1915 of the bulk. In a modification, the fertilizer is produced by a partial steriliza- tion of the active residue or sludge at a temperature of about 60 or 70 C. (Cf. Danish Patent 22,389, Ref. No. 309: U. S. Patent 1,294,080, Ref. No. 454: Can. Patent 189,921, Ref. No. 467.) 52 Treatment of sewage sludge. ANON. Trans. Can. Soc. C. E. 28, part 2. Can. Engr. 28, 697-9. A discussion of P. GILLESPIE'S paper by R. O. WYNNE-ROBERTS in which the activated sludge experiments of DR. FOWLER and ARDERN & LOCKETT at Manchester, Eng., and of W. H. DUCKWORTH at Salford are briefly described. 53 Activated sludge and the Baltimore experiments. W. S. COULTER. Eng. Record 71, 784. In a letter to the editor a continuous flow activated sludge tank is suggested, which comprises an aerating and settling tank, the latter having a hopper bottom with very steep sides, communicating through a bottom outlet with a chamber from which the deposited sludge can be raised and de- livered as desired by an air lift. 54 Activated sludge experiments in Canada. R. O. WYNNE-ROBERTS. Can. Engr. 29, 112. Munic. Eng'rg. 49, 68-9. Surveyor 48, 211. Chem. Abst. 9, 2787. Refers to experiments at Regina, Can., in which two galvamzed-iron tanks 4 ft. 7.5 in. diam., by 24 ft. deep, with glass windows in the side were used. About 577 gallons of sewage was treated in each tank, that in tank one by straight blowing, perforated pipes distributing the air, while in the other tank aeration was produced by injecting air by means of a centrifugal pump. The air was intended to be supplied at the rate of 15 cu. ft. per sq. ft. of tank area per hour, but was not closely controlled in the second tank. Absence of objectionable odors were noted, but no results or conclusions are given. 55 Activated sludge and the Baltimore sewage experiments. G. J. REQUARDT. Eng. Record. 72, 23. In a letter to the editor Mr. Requardt refers to the use of converted Imhoff tanks for activated sludge experiments and suggests that better oxidation may be obtained by having the flow perpendicular to the direction of the agitating air bubbles. Sketch of a suggested horizontal con- tinuous flow tank is also included. 56 Tanks for the purification of sewage. G. W. & J. F. NAYLOR. British Patent 9,870, July 7, 1915. Jour. Soc. Chem. Ind. 35, 615. In tanks for the purification of sewage wherein air is forced through porous tiles, the latter are arranged at the bottom of the tank in continuous rows, curves or circles, in such a manner as to enclose areas which are available for the deposition of the sludge. 57 Purification of sewage. G. W. & J. F. NAYLOR. Denby Dale, Yorks, Eng. British Patent 9,989, July 9, 1915. Jour. Soc. Chem. Ind. 35, 434. A tank is used with a porous floor under which pipes are laid for diffusing air through the floor to aerate the sewage. The floor of the tank is divided into sections, either zones, quadrants, parallel strips or squares. The pipes under the floor are placed parallel or crossing each other, and have alternate perforated and blank lengths, so as to supply air to alternate sections of the floor. The air is sup- plied under a low pressure through valves controlled by a clockwork arrange- ment which is worked so as to supply air to the various sections alternately or in any desired combination. 58 Activated sludge experiments at Milwaukee, Wis. T. C. HATTON. Eng. News, 74, 134-7. Surveyor 48, 258-61. Chem Abst. 9, 2412. Tests of the activated sludge method of sewage treatment are described. A large fill and draw tank, a continuous flow tank of the same size, and two small tanks pro- vided with glass windows are included in the studies being made. Methods of air diffusion, volume and time of air application, and cost records are given. 17 The Activated Sludge Process 59 The sludge problem: standards for effluents recommended by the Royal Commission on Sewage Disposal, and sewage purification by aeration in the presence of activated sludge. H. M. WILSON. Surveyor 48, 74-6. Chem. Abst. 10, 793. A short account of the development of the activated sludge method and the results of its use leads to the conclusion that the process pro- duces satisfactory purification, but the cost of operation has not yet been fully worked out. 60 Activated sludge in America. W. N. BAKER. Eng. News 74, 164-71. Chem. Abst. 9, 2412. Exp. Sta. Record 34, 332. Notes on the new process of sewage treatment gathered by Mr. Baker on visits to several experimental plants. Sewage is aerated in the presence of an accumulation of aerated sludge. There is reason to hope that a high degree of clarification and perhaps bac- terial reduction when necessary with a stable effluent and a quick drying sludge, high in fertilizing value, can be produced by this process. 61 Brooklyn sewage aeration and activated sludge experiments. E. J. FORT. Eng. News 74, 214-7. Chem. Abst. 9, 2682. Studies have been made of sewage aeration by compressed air passed upwards from a pipe grid and shal- low gravel bed through sewage passing downwards, in a deep tank containing 9 horizontal disk deflectors. The first experiments with plain aeration of the sewage in this tank were not very encouraging, an air supply of 0.75 volume per volume of sewage with two hours retention, being insufficient to produce any marked improvement on crude sewage. The second experiment was carried out in an aerated contact bed. The improvement was very marked, the 24 hour samples being almost of drinking water quality. The third experiment dealt with the activated sludge process and was carried out in the same tank as the first experiment. The continuous flow and fill and draw plan was tried alter- natively. 24 hours aeration resulted in 100% relative stability. 62 Sewage purification by forced aeration. EDITORIAL. Surveyor 48, 129. Comment on paper by J. P. WAKEFORD. (Ref. No. 63.) High moisture content of sludge is undesirable. Odors and costs questioned. Careful control necessary. J. D. WATSON'S caution against trade wastes cited, also E. B. MARTIN'S remark that he was unable to find a satisfactory air diffuser at Sal- ford. 63 Brief notes of experiments in sewage purification by forced aeration. J. P. WAKEFORD; Surveyor 48, 132-3. Can. Engr. 29, 429. Chem. Abst. 10, 793. Expt. Sta. Record 34, 488. At Wakefield, Eng., experiments were carried out in a tank 30 by 12 by 6.5 ft. on the fill and draw plan, allowing 0.5 hour for filling, 2 hours for blowing, 2 hours for settling and 0.5 hour for emptying. Results were satisfactory, but several engineering difficulties must be overcome before the process can be worked on a large scale. When this is done it is safe to assume that the treatment will be less offensive, more rapid, will require less area, and be less expensive to maintain than present processes, on account of the omission of chemicals, greater fertilizing value of the sludge, and less expense for attendance. 64 The activated sludge process. EDITORIAL. Can. Engr. 29, 239. Refers to articles by ARDERN & LOCKETT, (Ref. Nos. 9 and 23), and by S. E. MEL- LING (Ref. No. 24) on the Manchester and Salford work, and notes that ex- periments are under way in several places in the United States and Canada, with concordant results in general considering the variety of the experiments. The Canadian authorities can be depended upon to take an important part in these investigations. The principles of the process are discussed. 65 Experiments in sewage purification by forced aeration. DISCUSSION. Sur- veyor 48, 143-6. Discussion of J. P. WAKEFORD'S paper. (Ref. No. 63.) Large tank volumes considered necessary. J. D. WATSON criticises complexity 18 Abstract Bibliography 1915 of the process and is sceptical regarding its practicability. E. B. MARTIN discusses undesirability of tarry matters in sewage and the difficulties in handling variations in flow. A. T. GOOSEMAN, R. BROWN, E. H. CRUMP, C. H. COOPER and E. J. SILCOCK also participated in the discussion. 66 Activated sludge sewage treatment. EDITORIAL. Munic. Jour. 39, 257. Refers to the several experimental plants in the United States and to the encouraging results obtained. Discusses the plant at Milwaukee and concludes that the process promises extremely well, though many practical points are yet to be studied. 67 Experiments on separate digestion of activated sludge needed. W. L. STEVENSON. Eng. Record 72, 238. In a letter to the editor, the author suggests the desirability of experimentation on the separate digestion of acti- vated sludge in order to obtain a sludge of less bulk, and freedom from odor. 68 Sewage disposal by aeration. EDITORIAL. Surveyor 48, 253. The results of experiments on sewage aeration are inconclusive as yet. The most difficult questions to be settled are, the best method of air diffusion and the adoption of the process to the continuous method of treatment. Varying the depth of the tanks, or properly baffling the tank to obtain maximum contact with the air, may be a solution of the first question. 69 Activated sludge progress at Cleveland. R. W. PRATT. Eng. News 74, 571. Chem. Abst. 9, 2957. A unit to handle one million gallons of sewage is to be built. The experimental tank gave good results with 3 hours aeration and 10 to 15 minutes' sedimentation. 70 Milwaukee's activated sludge plant; the pioneer large-scale installation. T. C. HATTON. Eng. News 74, 667-8. Eng. Record 72, 481-4. Surveyor 48, 564-7. Engineer 121, 58-9. Chem. Abst. 10, 77. The plant consists of 11 cir- cular reinforced concrete tanks, 30 ft. inside diam. by 13 ft. max. depth. Tanks 1 to 8 inclusive are the aerating tanks in which the sewage mixed with acti- vated sludge is aerated. Tank 9 is used as the sedimentation tank and tanks 10 and 11 are the activated sludge tanks. Drawings are given showing the curved baffles and the manner of sloping the bottom of the running-through channels of the aerating tanks. The sewage enters tank 1 and is aerated with the sludge, then passes to tank 2 and is again aerated, and so on through the other tanks to tank 9, where it is settled. The sludge from this tank is dis- charged by gravity into tanks 10 and 11, where it is aerated to maintain the nitrogen cycle. From these tanks the sludge is pumped to the inlet chamber of tank 1. Activated sludge which is in excess of that needed is dried and used for fertilizer. The plant is designed to treat 1,600,000 gallons of sewage per day with a four-hour period of aeration and with 25% activated sludge. It is estimated that the cost will be $5.30 per million gallons, exclusive of engine room and plant labor, and the cost of disposal of the sludge. 71 Oxidation of sewage without the aid of niters, III. E. ARDERN and W. T. LOCKETT. Jour. Soc. Chem. Ind. 34, 937-43. Surveyor 48, 450-4. Chem. Abst. 10, 502, 794. Expt. Sta. Record 34, 888. Manchester sewage was aerated in 50-gal. casks, but not to complete nitrification. In 4 weeks enough sludge was obtained to give satisfactory results with 8 hours aeration. Data as to amount of sludge produced were not conclusive. Mineral precipitates were added to the sludge, but no advantage ensued ; a deflocculating action was fre- quently observed. Experiments in gallon bottles indicate that the volume of air necessary may be as low as 6 cu. ft. per hour per sq. ft. of tank area. The best proportion of sludge to sewage is given as 2:3 for Manchester sewage. Estimated cost of air per million gal. of sewage: Min. $1.98, Max. $4.92, with electricity at one cent per kw. hour. 19 The Activated Sludge Process 72 American Sewerage Practice. METCALF & EDDY. (Book) Vol. Ill, First Edition, 1915. pp. 222, 386-94. A brief general review of the activated sludge process is given, with mention of the work done at Lawrence, Milwaukee, 111. State Water Survey at Urbana, and Manchester, Eng. 73 Activated sludge progress at Houston, Texas. ANON. Eng. News 74, 717. Can. Engr. 29, 503. Chem Abst. 10, 240. In a communication from the city engineer, Mr. E. E. SANDS, statement is made that a 14,000 gallon tank has just begun operating and is expected to be running normal in a few weeks. The small 12 in. square, 8 ft. deep tank is also operating. 74 Purification of sewage by the utilization of activated sludge. E. LONG, Manchester, Eng. British Patent 14,733, Oct. 19, 1915. Jour. Soc. Chem. Ind. 35, 1129. Chem. Abst. 11, 1229. Screened sewage is passed downward through a pipe containing a form of injector nozzle, and means are provided for admitting air to this part of the pipe, or compressed air may be introduced. The mixture of sewage and air passes into a widened portion of the pipe which contains a rotary agitator, and thence through a rotary pump into the bottom of a tank. A pipe connects the top of the tank with the pipe above the injector nozzle, and the apparatus may be worked so as to circulate the contents of the tank until a sludge is obtained so altered in character as to justify the term "activated sludge." The apparatus may also be employed for circulating a mixture of activated sludge and sewage or waste water. 75 The world's first full-scale plant for the treatment of sewage by the activated sludge process. T. C. HATTON. Eng. & Contg. 44, 322-7. Can. Engr. 29, 517-9, 549-50. Proc. Am. Soc. Munic. Improv. 22, (1915). Engineer 121, 58-9. Chem. Abst. 10, 78. Tests on the plant at Milwaukee are described, showing bacteria removals of 99% and cost data indicating a partial cost of $4.43 per million gallons of sewage when 1.77 cu. ft. of air per gallon are used. A stable effluent is produced with city sewage containing 250 p.p.m. of suspended matter. The sludge contained 5.45% of ammonia. 76 Has the activated sludge process of sewage treatment made good? EDI- TORIAL. Eng. & Contg. 44, 322. Commenting on the work at Milwaukee, it is noted that the activated sludge process is exceedingly flexible, free from nuisance, and provides a high degree of bacterial removal and clarification. Winter conditions of operating are yet to be studied. 77 Sewage treatment by aeration. EDITORIAL. Surveyor 48, 445. Continuous flow desirable. Air costs not so great as thought at first. Investigation of effect of tanks of various depths is urged. 78 Choosing air compressors for activated sludge tanks. C. H. NORDELL. Eng. News 74, 904-6. Chem. Abst. 10, 238. Reciprocating and hydraulic air compressors, turbo-blowers, and positive pressure blowers are discussed. Positive pressure blowers are useful in small installations while turbo-blowers are best for large plants. 79 Sewage treatment and the war. EDITORIAL. Eng. News 74, 899. Com- ments on the passing of the Royal Commission on Sewage Disposal and the improbability of Imhoff tank installations in England for some time, sug- gesting that when the war is over there may be some surprising realignment of sewage treatment and that the activated sludge process, if its possibilities and economies are then shown, may find its way to all parts of the world. 80 British Engineer submits an activated sludge query. O. J. WILKINSON. Eng. News 74, 948. Chem. Abst. 10, 238. Attention is called to the simi- larity of sprinkling filters and activated sludge, in that both depend upon the passage of sewage in thin films over active sludge. Grit should be removed. Uniform contact and distribution are requisite. The cost is not yet definitely known. 20 Abstract Bibliography 1915 81 Activated sludge at Milwaukee, Wis. ANON. Munic. Jour. 39, 776. Re- cent information concerning tests being made. Effect of low temperatures. Plant for continuous operation. Results and cost of treatment. ; I : 82 Activated sludge and the Baltimore sewage experiments. O. J. WILKINSON. Eng. Record 72, 640. In a letter to the editor Mr. Wilkinson refers to his experience with the activated sludge process and to proposals for tanks of vari- ous designs, the general difficulty being to keep the particles of activated sludge uniformly distributed and at the same time in intimate contact with the whole of the flow, without excessive use of air. 83 Recent results of experiments on the purification of sewage by aeration in the presence of activated sludge, at the University of Illinois. E. BARTOW and F. W. MOHLMAN. Eng. & Contg. 44, 433-4. Eng. News 74, 1096-7, Jour. Ind. Eng. Chem. 8, 15. Jour. Soc. Chem. Ind. 35, 555. Chem. Abst. 10, 362. Expt. Sta. Record 34, 591. Univ. III. Bull. 14, 325-35. (Water Sur- vey Series No. 13.) A test plant of 4 tanks, each 3 ft. 2 in. square by 8 ft. 5 in. deep, has been operated on domestic sewage on the fill and draw plan. The sludge was accumulated on a 6-hour cycle. Results show that one sq. ft. of filtros in 10 sq. ft. tank area is not sufficient, but that 3 in 10 gives the best results. About one cu. ft. of air per gallon of sewage was used, though more was required for strong sewage. The free ammonia and presence of nitrates was used as indicators. 84 The fertilizer value of activated sludge. E. BARTOW AND W. D. HATFIELD. Eng. & Contg. 44, 434-6. Jour. Ind. Eng. Chem. 8, 17-20. Jour. Soc. Chem. Ind. 35, 552. Am. City 14, 282-5. Chem. Abst. 10, 365. Pot studies and gar- dening experiments show that the N in activated sludge is in a very avail- able form and that this sludge is a valuable fertilizer, being comparable with dried blood. (Cf. Ref. No's. 118 and 444.) 85 The treatment of sewage by aeration in the presence of activated sludge. E. BARTOW. Metal. & Chem. Eng'rg. 13, 901-4. Trans. Am. Inst. Chem. Eng. 8, 119-29: (1915). Chem. Abst. 10, 794. Expt. Sta. Record 34, 591; 37, 87. Status of the activated sludge process of sewage treatment in America, with details of the work done at the State Water Survey station, Univ. of Illinois, Urbana, 111. (Cf. Ref. No. 83.) 86 Activated sludge plants for packinghouse wastes. NEWS ITEM. Eng. News, 74, 1101. Experimental activated sludge plants are being built in Chicago by SULZBERGER & SONS Co. and by ARMOUR & Co. It is stated that at a recent conference of engineers and chemists representing the Chicago packinghouse interests, much enthusiasm was shown for the activated sludge process, and that some even went so far as to declare that it was the only process of sewage treatment brought to their attention which gives promise of satisfactorily treating the liquid wastes from the packinghouses, and at the same time recovering the valuable material which they contain. 87 Sewage disposal by aeration. EDITORIAL. Surveyor 48, 562. Comment on the Milwaukee experiments. (Ref. No. 70.) Questions if tanks are deep enough. Cost data very interesting. 88 A year of activated sludge. W. T. CARPENTER. Annual Report N. J. Sanit. Assoc. (1915). Following a brief historical review of the process, the Brooklyn experiments on the fill and draw plan are described. For this work a 16,000 gallon tank was used, perforated pipes diffusing the air at the rate of about 1.17 volumes per volume of sewage per hour. The experi- ments on the continuous flow plan utilized a tank of 4 ft. diam. by 8 ft. deep of about 900 gallons capacity, the air being diffused through carborundum discs. Both experiments were promising from a chemical and bacteriological standpoint. The work of DR. BARTOW at Urbana, 111., and of MR. T. C. 21 The Activated Sludge Process HATTON at Milwaukee is referred to, the advantages and disadvantages of the process being summed up in closing. 89 A year of activated sludge at Milwaukee, Wis. G. W. FULLER. Eng. News 74, 1146-7. Surveyor 49, 233-4. Chem. Abst. 10, 239. The author accepts the theory of activated sludge as correct but comments on practice. At Milwaukee 2 to 3 hours aeration removes 96 to 99% of the bacteria and nitrifies the effluent according to the amount of air used. Odors are removed ; the sludge dries readily; though the process may fail through excessive or insufficient aeration or the presence of mineral grit. 90 Activated sludge treatment for packinghouse wastes. NEWS ITEM. Eng. News 74, 1148. Chem. Abst. 10, 238. At the Chicago stockyards ARMOUR & Co. after successful experiments with small tanks, now have an experi- mental plant with a tank of 20,000 gallons capacity working on the continuous flow plan with excellent results since early in Nov. 1915. MORRIS & Co. and SWIFT & Co. have plants of the same general character, and the latter is said to be building a 500,000 gallon plant. SULZBERGER & SONS Co. are re- ported to be experimenting with both the activated sludge and the electroly- tic processes. The above are independent but relate to the investigations carried on by the Sanitary District of Chicago respecting the utility of the activated sludge process for treating the trade wastes from the stockyards. The latter is building a plant to handle 150,000 gallons of sewage daily. 91 Activated sludge system of sewage purification. G. J. FOWLER. Surveyor 48, 604. In a letter to the editor DR. FOWLER reports that JONES & ATT- WOOD have installed a fill and draw plant at the Baguley Sanatorium of the Manchester Corporation, and that they have also started continuous flow ex- periments at Stamford and Worcester (Eng.) The latter plant is to treat 2 million g. p. d. The first tank used at Milwaukee was designed by J. & A., who claim all patent rights. 92 Method of and apparatus for the treatment and purification of sewage. E. B. MARTIN, Eccles, Lancastershire, Eng. British Patent 17,463, Dec. 14, 1915. Jour. Soc. Chem. Ind. 36, 160. The apparatus consists of a cylin- drical tank divided into segments, each segment forming a treatment unit. The apparatus may be worked on the continuous flow or the quiescent system, or on a combination of both. The sewage enters any one segment where it meets with activated sludge, and the mixture is agitated by air blown in from the bottom and evenly distributed by baffle plates. The treated sewage overflows into a radial trough in which any sludge settles put and which is run back into the segment, while the liquid flows over a weir and is led into to the next segment for further treatment. One or more of the last segments is used for a settling tank before the completely purified liquid is discharged. One segment is always being emptied and cleaned in the cycle of working. The activated sludge is run out from each segment into a central well. The volume of air supplied to any segment can be varied at will by adjustable valves. 93 The activated sludge experiments at Salford, Eng. W. H. DUCKWORTH. Biggs & Sons' Contractors Record 15. (Dec. 15, 1915). Surveyor 48, 648-52. Engineer 120, 620-1. Munic. Jour. 40, 199-200. Chem. Abst. 10, 1064. Continuation of the Salford experiments (Ref. No. 24) has given satisfactory purification of sewage with 2 hours blowing of air, even in winter, and part of the time with only one hour aeration. The presence of trade wastes of a sterilizing nature at times necessitates longer periods of blowing to restore the activity of the sludge. Success, with some of the air jets clogged up, leads to the conclusion that a smaller amount of air might be used. In continuous treatment 60,000 gallons per day are treated in an aeration tank of 12,000 gallons capacity, with 4 tanks of 1,500 gallons capacity in series for recovery of sludge carried from aeration tank. From each of the first two settling 22 Abstract Bibliography 1915 tanks, sludge is pumped back to the inlet of the aeration tank for about 5 minutes in every half-hour, while the other two require pumping back only about 2 minutes per week. Conclusions have not been reached in regard to cost of operation or disposal of excess sludge. 94 Activated sludge is capturing the popular fancy. EDITORIAL. Eng. & Contg. 44, 453. Advises engineers to stick to the old methods of sewage treatment until the activated sludge process has definitely made good. "Ac- tivated sludge will need to be active indeed if it accomplishes all that the public expects it to do." 95 The work done at Salford by the activated sludge process. DISCUSSION. Surveyor 48, 629-30. Sanitary Record 56, 466-7. Discussion of W. H. DUCKWORTH'S paper. (Ref. No. 93). Waste of air and utilization of oxygen considered. S. RIDEAL claims the rate of aeration is too rapid for efficient absorption of the oxygen. Costs are paramount. S. BARWISE, J. B. BARFORD, W. D. SCOTT-MONCRIEFF, W. H. MAKEPEACE, P. GAUNT and J. LAMB also participated in the discussion. 96 Sewage purification by forced aeration. EDITORIAL. Sanitary Record 56, 463-4. Comment on the salient points in W. H. DUCKWORTH'S paper. (Ref. No. 93). The paper was especially directed towards establishing the reliability of sewage purification by forced aeration, and also to indicate from results obtained in the experiments: (1) The minimum time of aeration required to obtain a satisfactory effluent. (2) Whether the method is liable to be affected by weather conditions. (3) Whether the air jets would become clogged and in what period of time. (4) The minimum amount of air necessary. (5) Whether the "continuous flow" method was possible and preferable to the "fill-and-draw" plan. (6) If the process as a whole was an economic possibility. 97 Chicago activated sludge experiments. NEWS ITEM. Eng. Record 72, 768. Activated sludge experiments will soon be carried on intensively by the Sanitary District of Chicago with the stockyards sewage, $10,000 having recently been appropriated by the trustees for that purpose. 98 Sewage disposal by aeration. EDITORIAL. Surveyor 48, 645. American results are reported more promptly than English. Air jets can be used but need frequent cleaning. Proper depth of tanks still an unknown factor. 99 Activated sludge. W. N. BAKER. Sanitary Record 56, 487-8. A survey of the activated sludge experiments conducted at various places in the United States. This method of sewage treatment involves the forced aera- tion of sewage in the presence of accumulated sludge, and appears to be adapt- ed to changes of season, flood, drought, and other conditions. (Cf. Ref. No. 60). 100 Second Annual Report of the Milwaukee Sewerage Commission. T. C. HATTON and W. R. COPELAND. Pamphlet pp. 188. (Dec. 31, 1915). Data from reports of Chief Engineer HATTON and Chief Chemist COPELAND, respect- ing the activated sludge experiments at the Jones island sewage testing sta- tion, for the year ending Dec. 31, 1915. The experiments began in the labora- tory using a glass tube 6 ft. long by 1.5 in. diam.; next, two tanks 5 ft. by 1 ft. by 10 ft. deep with glass windows in the sides were tried; then a tank 32 ft. by 10.5 ft. by 9 ft. deep on the fill and draw plan; later another tank of the same size on the continuous flow plan, this being the first continuous flow operation of the activated sludge process. The numerous experiments made with these tanks were so encouraging that a plant to handle 2 million gallons per day was decided upon. This comprised 11 circular reinforced concrete tanks 30 ft. diam.; 8 designed for aeration, 1 for sedimentation, and 2 for sludge re-aeration. The aerating tanks were so baffled that a channel 114 ft. long was provided in each, 78 filtros plates in the sloping 23 The Activated Sludge Process bottom of each channel being used as air diffusers: ratio 1 to 8.5. The settlement tank had a hopper bottom terminating in a 4 ft. diam. cast-iron pipe 24 ft. below the bottom of the tank, with an air lift for removing the sludge. The raw sewage passed through a conduit to No. 1 aerating tank, activated sludge in the desired proportion being added to it enroute, the mixture then passing through each of the 8 aerating tanks in rotation, flowing a total of 912 lineal feet. With a 4 hour aeration period, the estimated ca- pacity of the plant was 1,620,000 gallons per day; with a 3 hour aeration period, 2,160,000 gallons per day. Different means of air diffusion, volumes of air, volumes of sludge, etc., are but a few of the great number of experi- ments made, the summarized results of which are shown in a mass of analyti- cal and other data occupying about 100 pages of the report. Numerous illustrations, diagrams, and inserts of plans also accompany the report. 101 Experiments upon the purification of sewage and water at the Lawrence Experiment station during the year 1915. H. W. CLARK. First Annual Report Mass. State Dept. Health. 377-429. Engineering 104, 99-100. Expt. Sta. Record 37, 787. The sewage aeration work from 1912 to date is briefly reviewed, with particular reference to its relation to the activated sludge process. Investigations begun in 1913-14 have been continued with modifi- cations, the results being shown in tabulated data. An activated sludge tank without slate was started early in the year and operated with 3, 5, 8, and 24 hour aeration periods. 80% of the 3-hour samples and all of the others were stable on incubation. Sludge investigations showing the increase in N and the decrease in fats, with comment on its fertilizer value are also given. 102 Worcester (Eng.) sewage works. ANON. Pamphlet 1915. 16 pages. Describes a visit of the water and sewerage commission to the Salford fill and draw activated sludge plant, where 80,000 gallons of sewage was being treated daily. Perforated pipes with holes at 9 inch intervals distrib- uted the air. About 25% of sludge was carried, with the following cycle of operations: 1 hour fill, 3 hour aeration, 2 hour settlement, 1 hour emptying. 1916 103 Activated sludge sewage treatment. EDITORIAL. Eng. Record 73, 5-6. A review of the subject covering the work to date at Manchester, Eng., Milwaukee, Wis., Brooklyn, N. Y., and the Chicago stockyards. The articles of the past year contributed by DR. FOWLER, ARDERN & LOCKETT, DR. BARTOW, and MR. T. C. HATTON are discussed, the editor summing up the apparent advantages of the process as (1) the ability to control the quality of the effluent, (2) freedom from offensive odors, (3) small plant area required, (4) low first cost. 104 Sewage disposal by the activated sludge process. W. B. FULLER. Am. City 14, 78-81. A brief resume of the process with illustrations of the Brooklyn experimental plant for sewage disposal. 105 The activated sludge method of sewage treatment. ANON. Munic. Engr. 50, 6-8. A brief history of the rapid development of the activated sludge method of sewage treatment, abstracted from the results of the research of PROF. EDWARD BARTOW, of the Univ. of Illinois. It shows that there is much promise in this latest attempt to solve the great problem of the disposal of the sludge resulting from this method of sewage treatment, in part by destroying some of it in the treatment process, in part by making it innocuous and practically inoffensive, and in part by giving it some value as a fertilizer not too low in grade for practical use. 106 Sanitary engineering in 1915. The activated sludge method of sewage disposal. ANON. Engineer 121, 30-1. A general review of the activated sludge work during the year, in which reference is made to the plants at 24 Abstract Bibliography 1916 Manchester, Eng., Salford, Eng., Milwaukee, Wis., and Cleveland, 0. The 1915 articles on the subject by ARDERN & LOCKETT and by T. C. HATTON are discussed. 107 Activated sludge process at Wimbledon, (Eng.) EDITORIAL. Surveyor 49, 51. Discussion of paper by C. H. COOPER. (Ref. No. 108). Doubtful about his plan of mixing aerated effluent with raw sewage, returning only a small amount of sludge, but agrees with him that it is not so much intimate contact of air with sewage as thorough mixing of activated sludge with sewage. 108 Activated sludge. C. H. COOPER. Surveyor 49, 55-6. Aeration experi- ments are to be undertaken at Wimbledon using atomizers. Anticipates cost of air will not exceed $5.50 per million gallons. (Imp.) Proposes to eliminate sludge, using instead the purified effluent. Statements are rather vague. 109 Brooklyn's fill-and-draw tank not a small one. W. T. CARPENTER. Eng. Record 73, 121. A letter to the editor to correct an impression in a recent editorial. (Ref. No. 103). The size of the tank in question being of 16,000 gallons capacity. 110 British and American patents on activated sludge. T. C. HATTON. Eng. News 75, 189-90. Chem. Abst. 10, 1064. U. S. Patent 1,139,024, issued to L. C. FRANK (Ref. No. 48) and four British patents issued to JONES & ATTWOOD, (Ref. No's. 3, 5, 10, 11), have identical process and apparatus claims. Americans have developed the continuous flow apparatus. (Cf. Ref. No. 129). 111 Sewage disposal appliances. JONES & ATWOOD, LT'D. Surveyor 49, 126. The first permanent activated sludge plant was installed at the Baguley Sanatorium, Manchester, Eng., being of 20,000 gallons capacity. The next plants were at Stamford and Worcester, Eng., where half the flow was first treated, then all. Worcester's total is 6 million gallons per day. 112 Pioneer activated sludge plant in service. NEWS ITEM. Eng. Record 73, 160. The Milwaukee plant when operating with 25% sludge in the aerating tanks and with a 4 hour running-through period, has a capacity of 1,620,000 gallons per day. The sedimentation period is 27 minutes and the velocity of flow through the 8 aerating tanks, covering 912 ft. direct travel, is 3.8 ft. per minute. Decreasing the running-through period to 3 hours increases the capacity to 2,160,000 gallons per day and the velocity to 5 ft. per minute. Costs of pumps, meters and tanks are given. 113 Purification of sewage by aeration in the presence of activated sludge. II. E. BARTOW. Trans. Am. Inst. Chem. Engrs. 9, 161-8. Jour. Bad. 1, 111. Chew,. Abst. 10, 2115. A continuation of the experiments in the concrete tanks previously referred to, (Ref. No. 83) dealing particularly with the building up of the active sludge, and the diffusion area required. The compo- sition of the effluent air, the N in the sludge and results of pot tests with the latter as fertilizer are also given. Mechanical, chemical, and bacterio- logical features of the process are considered, the future of which is very bright, though much depends upon whether the sludge can be economically recovered as fertilizer material. 114 First annual report of the city engineer on sewage disposal, City olj Houston, Texas. E. E. SANDS. Feb. 1, 1916. Chem. Abst. 10, 2015. 5,000,000 gallons of untreated sewage cause a nuisance at White Oak Bayou, one-quarter mile from the business section. Experimental work with two- story settling tanks, aerated contact beds, the electrolytic process and the 25 The Activated Sludge Process activated sludge method of sewage treatment showed the superiority of the latter method. On the fill and draw plan, 4 hours aeration with 0.437 cu. ft. of free air per gallon of sewage treated per hour, secured an average re- moval of 67% total organic nitrogen, 95% free ammonia, 44% total organic matter, 90% oxygen consumed, 98% dissolved oxygen consumed, 98% sus- pended matter and 95.8% bacteria. A continuous flow tank appeared best adapted to local conditions. A 2-unit and a 4-unit activated sludge plant have been designed. Each unit is expected to handle the sewage from 37,100 persons or an average flow of 2,190 gallons per minute. The aeration deten- tion period of the sewage will be 1 hour 50 minutes and the sludge will be aerated for 3 hours. The tank will be supplied with 0.26 cu. ft. of free air per minute per sq. ft. of tank surface. Surplus sludge will be handled on drying beds and sold to market gardeners. The estimated construction cost is $378,000. The estimated cost for disposal is $4.20 per million gallons when the plants operate at full capacity and serve 280,000 people. 115 Activated sludge experiments at Brooklyn, N. Y. ANON. Munic. Eng'rg. 50, 73. Refers to a paper by G. T. HAMMOND presented at a meeting of the Am. Assoc. Adv. Science in which the experiments conducted during 1915 are described. The work done does not justify a very positive conclusion, though it offers considerable promise. 116 Success of the activated sludge process seems assured. EDITORIAL. Eng. & Contg. 45, 97-8. The critical period has been safely passed, both at Milwaukee and Urbana, these plants operating well through the cold weather. The process appears to be practical for cities having excess of 2 million gallons daily flow of sewage. Early conclusions subject to modification and many wrinkles yet to iron out. 117 Summary and latest results on experimental work on activated sludge at Milwaukee, Wis. T. C. HATTON. Eng. & Contg. 45, 104-8. Contract Record 30, 382-5. Surveyor 49, 308-9. Expt. Sta. Record 35, 188. A paper before the Joint Annual Convention of 111. Section, Am. W. W. Assoc. and 111. Soc. of Eng'rs. and Surveyors, Urbana, 111., Jan. 27, 1916, which covers the early experiments, data on air diffusers, functions of activated sludge, effects of cold weather and volume of air, data on unit quantities, and gen- eral conclusions. 118 The value of activated sludge as a fertilizer. W. D. HATFIELD and E. BARTOW. Univ. III. Bull. 14, 336-47. (Water Survey Series No. 13). Chem. Abst. 11, 1711. Activated sludge was analyzed and found to contain greater quantities of N and P than other sewage sludges. The best evidence of its value was the greater growth of wheat, lettuce and radishes when the sludge was used as a fertilizer. (Cf. Ref. No's. 84 and 444.) 119 Sewage purification by the activated sludge process. EDITORIAL. Surveyor 49, 143. Comment on paper by DR. G. J. FOWLER. (Ref. No. 120.) Draws analogy between the activated sludge process and sprinkling filters. Conserva- tion of nitrogen an attractive feature of the activated sludge process. 120 The activated sludge process of sewage purification. G. J. FOWLER. Sur- veyor 49, 148-51. Expt. Sta. Record 35, 188. A summary of the present knowledge of both the scientific and practical phases of the activated sludge process of sewage purification. It has been shown by DR. BARTOW and DR. ARDERN that it is not necessary to nitrify sewage while building up sludge. Activated sludge contains no algae. Refers to American results by DR. BARTOW, T. C. HATTON, et al. JONES & ATTWOOD first developed air lifts which did not give sufficient aeration; then nozzles, which clogged; finally, porous stone diffusers, which proved satisfactory. The results being obtained in the Davyhulme and the author's laboratories indicate a possible fixation of atmos- pheric nitrogen. Sludge drying is a problem for the engineers. A list of 23 references to the subject is given. 26 Abstract Bibliography 1916 121 The activated sludge process of sewage treatment. G. J. FOWLER. Can. Engr. 30, 227-8. Surveyor 49, 405-6. Jour. Bact. 1, 251. Chem. Abst. 10, 1064. In a written discussion of the paper by RUDOLPH HERING on the "Dis- posal of Suspended Matter in Sewage," DR. FOWLER sketches the historical de- velopment of the activated sludge process and dwells on the effect of adding "M7" bacterial cultures in the presence of iron in solution. Much research is still required. The work of MR. HATTON at Milwaukee, and DR. BARTOW at Urbana is referred to. 122 Activated sludge experiments at Milwaukee, Wis. T. C. HATTON. Eng. News 75, 262-3, 306-8. A number of activated sludge tanks of different designs have been operated by different methods with such promising results that a start has been made on the construction of a 100,000,000 gallon plant. Filtros was the air diffuser used in some of the tanks, the ratio of plate area to tank area being 1 to 6.6. Varied and extended studies of the activated sludge process of sewage treatment conducted during the past year are summarized and conclusions drawn as to general results and costs. With a continuous flow tank an effluent stable for 5 days, 90% reduction of suspended matter and 95% removal of bacteria at 20 C., has been obtained by using 1.75 cu. ft. of air per gallon of sewage, with a 4 hour aeration in the presence of 20% activated sludge. Basing the results upon the operation of a 50,000,000 gallon plant, the estimated cost will be $4.38 per million gallons including all overhead and boiler-room charges, but excluding engine-room and plant attendance and the disposal of the sludge. Plant construction costs are estimated at $18,000 per million gallons. 123 News item. Eng. News 75, 293. A 150,000 gallon activated sludge plant to treat packing-house sewage was put into operation the latter part of January by the Sanitary District of Chicago, under the direction of LANGDON PEARSE, Division Eng., and DR. ARTHUR J. LEDERER, Chemist. 124 The oxidation of sewage without the aid of filters. E. ARDERN and W. T. LOCKETT. Jour. Soc. Chem. 2nd. 35, 153-5. Chem. Abst. 10, 2015. Dis- cussion of a previous paper (Ref. No. 71) in which DR. G. J. FOWLER, MR. HALLIWELL, MR. P. GAUNT and MR. W. THOMPSON participated. Mr. Ardern in response, said, among other things: "With regard to the adoption of wire meshes as air diffusers, this was possibly a feasible proposition. It was a question of durability. Other suggestions had been the adopton of porous metal, cocoanut matting and asbestos fiber, but up to the present nothing better had been found than a porous mineral septum. Most of the tiles used up to the present in the course of the experiments under consideration, had been made of silica which was dried and burned." 125 Sewage treatment by the activated sludge process. HENRY TRAXLER. Iowa Eng. Soc. Proc. 28, 80-5. (1916). Chem. Abst. 11, 509. In a brief review of the history of the process, the author states that "In this country BLACK and PHELPHS in New York; CLARK, GAGE, and ADAMS at the Mass. State Board of Health experiment station at Lawrence, were the first to obtain promising results." DR. FOWLER'S visit to Lawrence is referred to and the subsequent work of ARDERN & LOCKETT at Manchester, Eng., whose first ex- periments made use of 5-pint bottles. DR. BARTOW'S work at the Univ. of 111. in 1914, and MR. T. C. HATTON'S at Milwaukee in 1915 followed. Brief con- siderations of the results obtained to date (Feb. 1916) are given. 126 Air diffusers tested at Milwaukee sewage plant. T. C. HATTON. Eng. Record 73, 255. Chem. Abst. 11, 80. Results of experiments on activated sludge. Tabulated data obtained with open air jets, Monel metal cloth, filtros and kieselguhr are given. Filtros plates, composed of quartz sand baked, of uniform porosity, have given the most satisfactory results. 27 The Activated Sludge Process 127 Apparatus for aerating sewage and other foul liquids. R. AMES, Brighton, Eng. British Patent 104,361, Feb. 25, 1916. Jour. Soc. Chem. Ind. 36, 519. The apparatus consists of a circular tank in which there is a central standpipe supporting a chamber carrying horizontal radial arms, capable of being revolved above the level of the liquid in the tank. The sewage enters by a pipe, in which it is mixed with compressed air, along the bottom of the tank to the central standpipe, from openings in the bottom of which the sewage passes into the body of the tank. Air is supplied to the chamber carrying the radial arms, and pipes depend from these arms nearly to the floor of the tank, with atomizers attached to their ends. The atomizers consist either of a metal casing containing a porous block, or layers of wire gauze, or of a hollow metal block with narrow slots. The radial arms are rotated by the pressure of the escaping air on the liquid, or by mechanical means. The purified liquid is drawn off intermittently or continuously. (Cf. Brit. pat. 110,197, Ref. No. 194). 128 Activated sludge treatment of packinghouse wastes. EDITORIAL. Sur- veyor 49, 234. ARMOUR & Co. have a 20,000 gallon continuous flow plant, while that of the Sanitary District of Chicago will treat 150,000 g. p. d. 129 Is the activated sludge process of sewage treatment to be patented again? ANON. Eng. & Contg. 45, 208-9. In a recent paper by MR. T. C. HATTON before the Indiana Engrs. Soc., it was stated that DR. G. J. FOWLER of England was the real discoverer of the process if it can be considered a discovery rather than a combination of well known principles and that his interests were turned over to JONES & ATTWOOD who secured British patents on the art. In the meantime, MR. L. C. FRANK of Washington, D. C., was granted a U. S. patent on the process covering particularly the continuous flow principle. With so much similarity between this patent and JONES & ATTWOOD'S pending applications for U. S. patents, it would appear as though the U. S. would not be warranted in granting the latter. Statement is also made that the majority of the apparatus patented in England by JONES & ATTWOOD is not essential to the proper operation of the process (Cf. Ref. No. 110). 130 The aeration or activation of sewage. G. T. HAMMOND. Surveyor 49, 255-7. A history of sewage aeration processes including BLACK and PHELPS' work at Brooklyn. Following these experiments, activated sludge tests were begun at Brooklyn in a tank of 16,000 gallon scapacity. Pipe grids with 1-16 in. holes, overlaid with 7.5 in. of broken stone served as air diffusers. Fill and draw tests with 5 hours aeration and 7 volumes of air per volume of sewage, gave a stability of 62 and nitrates 1.2 p. p. m. Next experiments were on the continuous flow plan using a tank 4.5 ft. diam. by 8 ft. deep, of about 1,000 gallons capacity, with a lower chamber for aeration and an upper one for settling, the latter occupying about 1-10 the tank. Using carborundum discs for air diffusers, air at the rate of 0.7 cu. ft. per minute, 8 hours aeration and 45 minutes settlement, the stability was low and no nitrates formed. With 4 hours aeration and 23 minutes settlement, results were unsatisfactory. 131 The fundamental principles of the activated sludge process of sewage treatment. T. C. HATTON. Eng. and Contg. 45, 235-6. Eng. News 75, 503. Jour. Bact. 1, 250. Chem. Abst. 10, 1064, 3122. Ind. Sanit. and Water Supply Assoc. 1916. In a paper before the Indiana Engineers Soc., Mr. Hatton points out that the activated sludge process should not be confused with the kind of artificial aeration of sewage, attempted from time to time in the past, which made no use of the sludge as an aid to oxidation. He thinks that the activated sludge process depends on the presence of biologic life in the sludge under aerobic conditions and that the definition given by MR. W. R. COPELAND is the best one, viz.: "The sludge embodied in sewage and consisting of sus- pended organic solids, including those of a colloidal nature, when agitated with air for a sufficient period, assumes a flocculent appearance very similar to small pieces of sponge. Aerobic and facultative aerobic bacteria gather in these flocculi in immense numbers from 12,000,000 to 14,000,000 per c. c. 28 Abstract Bibliography 1916 some having been strained from the sewage and others developed by natural growth. Among the latter are species which possess power to decompose organic matter, especially of an albuminoid or nitrogenous nature, setting this nitrogen free; and others, absorbing this nitrogen, convert it into nitrites and nitrates. These biological processes require time, air and favorable environ- ment, such as suitable temperature, food supply and sufficient agitation to distribute them throughout all parts of the sewage." 132 Report of the board of engineers on sewage disposal, to the cities of Pasadena, South Pasadena, and Alhambra, Calif. R. V. ORBISON, C. E. HEWES and JOHN MACMILLAN. Pamphlet, pp. 54. (March 27, 1916.) The activated sludge process is described, and an account of the early experi- ments given. Sludge disposal and cost problems are discussed in connection with the possibility of a trial of the process. 133 Some observations on the treatment of sewage by activated sludge. W. H. DUCKWORTH. Surveyor 49, 352-4. Chem. Abst. 10, 3122. A review of results at other places and reference to the Salford experiments. Air was not measured. Jets clogged rapidly. Sludge recovered quickly from inhibitory effect of trade wastes. The author considers the activated sludge process sim- ilar to an "intensified contact bed." The Salford plant treating 55,000 g. p. d., gave satisfactory results in winter. Over-aeration is possible. As much sludge is produced as from chemical precipitation. Discussion followed in which there participated, A. R. BLEAZARD, R. J. McKENN, W. M. JONES, ARTHUR BOWES and TOM FOGG. 134 The activated sludge process of sewage purification. G. J. FOWLER. Jour. Inst. Sanit. Engrs. 20, 29-38. DISCUSSION, (Same journal) 20, 39-49. "The activated sludge process of sewage purification may be described as a process of intensive bacterial oxidation and would appear to consist broadly of three operations: a clotting or clarifying action; a rapid carbon oxidation process, and finally, nitrification." The scientific researches of ARDERN & LOCKETT and of DR. BARTOW and his associates are referred to, as well as the engineering developments at Davyhulme, Salford, Worcester and Stamford in England, and Milwaukee, Baltimore, Cleveland, Houston and Chicago in the United States, and Regina in Canada. Quotations from the reports of the several engineers in charge of the various plants are numerous. Of the future "Much work remains to be done on both the scientific and tech- nical sides * * *" MR. A. P. I. COTTERELL, DR. McGowAN, DR. E. ARDERN, MR. G. B. KERSHAW, MR. C. SMITH and MR. H. A. ROECHLING participated in the discussion, bringing up questions of costs, effects of varying amounts of air, supervision of the process, sludge treatment and revenues therefrom, and the effects of trade wastes on the process. 135 The latest method of sewage treatment. E. BARTOW. Jour. Boston Soc. C. E. 3, 153-70. Jour. Am. Waterworks Assoc. 3, 327-44, 869-70. Chem. Abst. 10, 3122. Expt. Sta. Record 35, 787. Relates to the activated sludge process and the experiments made at Urbana, 111. Sludge could be built up by frequently changing the sewage rather than waiting for complete nitrifica- tion before making a change. The fertilizer value of the sludge has been shown by experiments with wheat. Discussion by W. F. WILCOX relates to the adaptation of a septic tank by dividing it into 16 chambers, each one the inverted frustum of a pyramid, so that 5 to 7 million gallons per day were satisfactorily treated. 136 The extent to which sewage can be purified by practical methods of artificial treatment now in use. H. P. EDDY. Proc. Eng. Soc. West. Penn. 32, 226-70. Surveyor 50, 238-41. With respect to the activated sludge process, the following features are considered: theory of action; method of operation; aeration; sedimentation; sludge handling; character of effluent; application to trade wastes; and costs. A brief description of the Milwaukee 29 The Activated Sludge Process experiments are given. The method produces a clear, sparkling, well-oxidized effluent and its bacterial efficiency and power to oxidize and remove organic matter, apparently approaches that of the sand filter. 137 Trial activated sludge unit at Cleveland, O. R. W. PRATT. Eng. News 75, 671-2. Description of a million gallon plant operated on the contin- uous flow principle, 4 hour aeration period, half-hour settlement. The tank is 60 ft. long, 30 ft. wide and 15 ft. deep, divided into 6 compartments each 9.5 ft. by 30 ft. Four compartments are used for aerating, one for maintaining activity of the sludge and one for sedimentation. Filtros is used as the air diffuser, covering 25% of the tank bottom area. 138 Give conclusions on activated sludge tests. T. C. HATTON and W. R. COPELAND. Eng. Record 73, 489. Surveyor 49, 486. Chem. Abst. 10, 3122. Notes from an elaborate report of the findings at the Milwaukee Sewage Testing Station in the report of the Milwaukee Sewerage Commission for 1915. (Cf. Ref. No. 100.) 139 Purification of sewage by compressed air. . . BOWES. Jour. Soc. Chem. Ind. 35, suppl. 30. British Patent Application 5,215, April 10, 1916. 140 Plans prepared for Houston, Texas, sewage disposal plant. NEWS ITEM. Eng. Record 73, 561. The north side plant has been designed to accommo- date an average daily flow of 12,600,000 gallons and the south side plant 6,300,000 gallons. The estimated cost of disposal plants and pipe lines is $639,000 and the operating cost is given as $61,939 per annum. 141 Purification of sewage by activated sludge in winter at the sewage test- ing station, Milwaukee, Wis. W. R. COPELAND. Eng. and Contr. 45, 386-7. Jour. Ind. Eng. Chem. 8, 642-3. Jour. Bact. 1, 457. Jour. Soc. Chem. Ind. 35, 904. Chem. Abst. 10, 2260. The winter temperature of Milwaukee sewage averages about 51 F. (10.5 C.) and occasionally falls to 40 F. (4.5 C.) or lower. By increasing the air supply from 1.6 to 2.3 cu. ft. per gallon of sewage, it has been possible to remove about 90% of the bacteria and suspended matter by the continuous flow activated sludge process. The sludge contains about 98% of water, but this can be reduced to 75% by pressing, without the addition of lime, and the sludge press-cake is easily handled and can be converted into fertilizer. On a 10% moisture basis the sludge contains about 5% of nitrogen calculated as ammonia, 1.75% of available phosphoric acid, and 0.4% of potash. It is estimated that one million gallons of Milwaukee sewage, containing from 260 to 440 parts per million of suspended matter, will yield 3,000 to 4,000 gallons of sludge containing 98% water, which is equivalent to about half a ton on a 10% moisture basis. The sludge is being dewatered in a WORTHINGTON press. It is estimated that it will cost $5 to $6 to dry and deliver to the customer a sludge worth $10 to $12. With the out- side temperature at times as low as -15 F. (-26.1 C.) and the temperature of the sewage on a few occasions reaching 34 F. (1.1 C.), good bacterial removal and clarification was maintained. 142 Chemical observations on the activated sludge process as applied to stockyard sewage. A. LEDERER. Eng. and Contr. 45, 388. Jour. Ind. Eng. Chem. 8, 652. Jour. Bact. 1, 457. Chem. Abst. 10, 2260. The stock- yards waste lends itself readily to the process, though the free oxygen demand is approximately 8 to 10 times greater than the domestic sewage of Chicago. Temperatures vary between 60 and 90 F. throughout the year at the Center Ave. outlet, and even in the coldest winter weather the fall of temperature in the plant is only a few degrees. The removal of colloidal matter was the only immediate indication of accomplished oxidation. With turbidities of 10 parts per million or less the effluent is stable. The quantity of settling suspended matter in the effluent merely indicated the efficiency of the settling process and has nothing to do with the activated sludge process proper. 30 Abstract Bibliography 1916 143 Status of activated sludge sewage treatment. G. T. HAMMOND. Eng. News 75, 798-800. Chem. Abst. 10, 2115. Expt. Sta. Record 35, 490. After visits to five working-scale plants, the author, who has been in engi- neering charge of the activated sludge experiments at Brooklyn, draws some noteworthy conclusions regarding the probable desirability of preliminary screening, the apparent advantages of pipe-grid as against porous plate dif- fusers, the uncertainty, but great importance of sludge recovery for fertilizer base and of sludge dewatering. He considers the activated sludge process, while promising, as still in the early experimental stage, but fortunately the experiments are on a large scale and in charge of able men. Illustrations of plants at Brooklyn, Cleveland, Milwaukee, Chicago and Baltimore accompany the article. 144 Activated sludge Problems. EDITORIAL. Eng. News 75, 809-10. Com- menting on the article by GEO. T. HAMMOND (Ref. No. 143), it is noted that the activated sludge process combines clarification, oxidation, and bac- terial reduction in a single tank or series of them. The great question is that of costs, though that of air supply seems to be a critical matter. There may be various difficulties besides that of final sludge disposal. 145 Milwaukee's activated sludge investigations. R. 0. WYNNE-ROBERTS. Can. Engr. 30, 473-6, 561-5. Chem. Abst. 10, 3123. A resume of results of experiments carried on during the year 1915 by the Milwaukee Sewerage Commission. Analyses are given. (Cf. Ref. No. 100.) 146 Activated sludge at Houston, Tex. ANON. Munic. Jour. 40, 585-8. Ex. periments on this method, together with Imhoff tanks, aerated contact beds and electrolytic tanks. Methods and results with activated sludge. Plans adopted for permanent plant. 147 Sewage disposal by the activated sludge process. EDITORIAL. Surveyor 49, 480. Comment on the Milwaukee results as noted in ref. No. 138 . A valuable feature of the activated sludge process is the possibility of varying the degree of purification by altering the volume of air applied or the aeration period. The degree of purification should first be fixed and the plant built to give this purification. 148 Activated sludge process on stockyards sewage. A. LEDERER. Eng. News 75. 932. The object of this short paper is -to elaborate certain facts of a chemical and biologic nature which have presented themselves in the course of operations, and not to furnish any prescription for the treatment of stock- yards waste. The work indicates that the temperature of the liquid treated will be a controlling factor. 149 Tanks for the purification of sewage. T. CAINK. Worcester, Eng. British Patent 105,654, May 20, 1916. Jour. Soc. Chem. Ind. 36, 611. Chem Abst. 11, 2248. The apparatus is designed to be used in the purification of sewage by the activated sludge process and consists of a tank divided into several bays in series and covered with an air-tight roof which prevents the air injected by the diffusers from escaping directly into the atmosphere, but deflects it horizontally to an exit, whereby circulation of the sewage in the tank is set up to effect more efficient aeration. The tank is filled to the roof with sewage. Air is admitted along the bottom of one side of each bay and imparts to the sewage a vertical circulatory motion, which is aided by suitable guiding baffles arranged so as to prevent deposition of the solids on the floor of the bays. In another form, the tank is divided into a number of parallel bays and air is supplied along the side of the first bay only, parallel to the direction of the flow of the sewage. The dividing walls between the bays have openings at the top and bottom to permit of the passage of air to and fro at right angles to the flow of the sewage. This imparts a spiral motion to the sewage in the tank. 31 The Activated Sludge Process 150 Activated sludge. EDITORIAL. Can. Engr. 30, 581. Briefly reviews the introduction of the process by DR. FOWLER, (suggested to him by DR. MACLEAN WILSON) and ARDERN & LOCKETT, concluding with this paragraph: "The comprehensive experiments made at Milwaukee have so fully confirmed the statements made by ARDERN & LOCKETT, that there remains but little doubt in the minds of sanitarians generally, that we are to witness a great revolu- tion in the methods of sewage treatment, and in the standards of purification which will in the future be attainable in ordinary everyday practice." 151 Sewage disposal by the activated sludge process. T. C. HATTON. Can. Engr. 30, 590-3. Chem. Abst. 10, 3123. The activated sludge process is compared with sprinkling filters, contact beds, etc., from a biological point of view and from the standpoint of relative areas required. The effect of varying volumes of air, plant design, and sludge handling are discussed, and the results of some of the Milwaukee experiments are given. 152 Manurial value of sewage sludge. G. MUMFORD. Jour. Bd. Agric. 23, 129-35. Jour. Soc. Chem. Ind. 35, 647. A sample of activated sludge obtained at Manchester from domestic sewage lost 69.8% on ignition, and contained 4.3% phosphoric acid and 5.5% nitrogen. Some samples contained as much as 6 or 7% nitrogen, the high nitrogen content being accounted for by assuming that the solid particles of sludge assimilate nitrogen from the liquid portion, the effluent holding very little matter in suspension. The nitro- gen of the sludge is in a readily available condition. 153 Activated sludge at Milwaukee. T. C. HATTON. Munic. Jour. 40, 785-7, 824-5, 830. Chem. Abst. 10, 2491. In a paper before the N. Y. State Conference of Mayors and other City Officials, Mr. Hatton stated that the Milwaukee sewage could be treated with 1.75 cu. ft. of free air per gallon of sewage, with 4 hours contact in the presence of 20% activated sludge. Filter-pressing of the sludge is probably feasible, followed by drying. The results obtained at Milwaukee are outlined. MR. G. D. HOLMES in discussion adds that the great problem yet to be solved is the disposal of the watery sludge without offense. 154 Activated sludge sewage disposal. EDITORIAL. Munic. Jour. 40, 833. Comments on MR. T. C. HATTON'S paper. (Ref. No. 153.) Intimates that offensive odors may arise on drying the sludge and that at present the process is too expensive for small cities. Considers plant costs as compared with other processes and suggests caution in adopting the method, notwith- standing the promising nature of it. 155 Artificial means of sewage treatment. ANON. Eng. & Contg. 45, 581-6. Chem. Abst. 10, 2489. From a paper by MR. H. P. EDDY presented at a meeting of the Eng. Soc. of West. Penn., which discusses the general principles of sewage treatment. The activated sludge method is still in the experimental stage, with possibility of high cost of power and the commercial possibilities yet to be demonstrated. The results of the different methods of sewage treatment are compared briefly. (Cf. Ref. No. 136.) 156 Aeration of sewage in the presence of activated sludge. E. J. FORT. Jour. Ind. Eng. Chem. 8, 643. Chem. Abst. 10, 2260. Reviews the experiments at Brooklyn with the 16,000 gallon aerator tank in the fall of 1915, this tank supporting 7% inches of broken stone on a grid, and operated both on the continuous-flow and the fill-and-draw plan. Tabulated results with and with- out activated sludge are given. The author believes that the engineer is not yet warranted in recommending the activated sludge process for general adoption. 157 Activated sludge experiments at the sewage disposal plant, Baltimore. C. W. HENDRICK. Jour. Ind. Eng. Chem. 8, 645. Chem. Abst. 10, 2260. Reviews the laboratory and the larger experiments and gives some tabulated 32 Abstract Bibliography 1916 results. Air diffuser troubles are cited with special reference to that caused by the oil which is carried along from the compressor. The possibility of purifying sewage by the activated sludge method is shown, but additional experiments are recommended. 158 Composition of the effluent air from an activated sludge tank. F. N. CRAWFORD and E. BARTOW. Jour. Ind. Eng. Chem. 8, 646-7. Chem. Abst. 10, 2260. The carbon dioxide increases from 4.3 parts per 10,000 in the influent air to 36 to 40 in the effluent air. The oxygen decreases from 20.5% to 19.3%. About 5% of the oxygen in the air is therefore used in the process. (Cf. Ref. No. 335.) 159 Sewage disposal experiments at Brockton, Mass. R. S. WESTON. Jour. Ind. Eng. Chem. 8, 647-8. Jour. Soc. Chem. Ind. 35. 904. Science, N. S. 44. 322. Chem. Abst. 10, 2261. The activated sludge process promises relief for over- worked filter beds; it does not seem to be practical to use it alone. Fill and draw activated sludge tank, followed by sand bed at 500,000 gallon rate gave excellent results. Continuous process now being tried for clarifica- tion alone with good results. Aeration period at least 4 hours. The experi- ments are being continued. 160 The activated sludge process in the treatment of tannery wastes. H. P. EDDY and A. L. FALES. Jour. Ind. Eng. Chem. 8, 648. Jour. Am. Leather Chem. Assoc. 11, 441-9. Jour. Soc. Chem. Ind. 35, 905. Surveyor 50, 282-4. Chem. Abst. 10, 3123. Wastes are from the manufacture of sheep, calf and kid leather and pulled wools. Average analyses are given of raw wastes and of activated sludge influents and effluents. A 1,000 gallon tank is operated on the fill and draw plan and the method of building up the activated sludge is described. Temperature of waste was kept between 65 and 75 F. by live steam. Aeration for 11 days with 20% sludge, based on 2 hours sedimentation, gave a stable effluent and reduced the ammonia nitrogen 97% and the albumi- noid nitrogen 63%. Nitrite and nitrate nitrogen was increased in 17 days from to 35 parts per million. This was mostly nitrite and was not changed to nitrate by 11 days more aeration. Volume of sludge decreased in 28 days from 20 to 7.6%. When tank was filled once a day and air was supplied at the rate of 0.5 cu. ft. per gallon per hour, the effluents were clear and stable. Tables are given showing composition of the sludge and the effects of different periods of sedimentation on the volume of the sludge and the turbidity of the effluents. 161 Treatment of packing-house sewage by aeration in the presence of activated sludge. PAUL RUDNICK and G. L. NOBLE. Jour. Ind. Eng. Chem. 8, 651-2. Jour. Am. Leather Chem. Assoc. 11, 450-3. Jour. Soc. Chem. Ind. 35, 904. Science, N. S. 44. 323. Chem. Eng. and Manuf. 24, 86. Chem. Abst. 10, 3123. The sewage treated is a mixture of wastes from all depart- ments of the packing-house and of domestic sewage. It contains about 4 times as much suspended solids as domestic sewage. The tank is operated on the continuous flow plan with a 10 hour aeration using 3 cu. ft. of air per gallon of sewage. The sludge is allowed to settle 40 to 60 minutes, and the effluent is clear and stable for at least 4 days. Typical analyses of effluent give the following nitrogen percents: Albuminoid 2.4 to 7.4, ammonia 16.2 to 31.2, nitrite 0.07 to 0.60, nitrate 0. Albuminoid, ammonia and total organic nitro- gen, total organic matter, and the suspended solids are reduced 66 to 95%. The average analysis of the sludge on a 10% moisture basis is 4.59% nitrogen, 2% phosphoric acid. No sludge drying method satisfactory in all respects has been developed. Purification seems to be independent of depth of aerating chamber. 162 Development of the purification of sewage by aeration and growths at Lawrence, Mass. H. W. CLARK. Jour. Ind. Eng. Chem. 8, 653-4. Jour. Soc. Chem. Ind. 35, 904. Science, N. S. 44, 322. Chem. Abst. 10, 3116. This 33 The Activated Sludge Process paper describes the discovery and development, at the Lawrence Experiment Station of the Mass. State Dept. of Health, of the method of purifying sewage by aeration and growths, a method quite generally known as the activated sludge method. The paper shows that the method was developed there in 1911 and 1912, that it was shown to DR. GILBERT FOWLER of Manchester, Eng., in the fall of 1912, and that the English work was largely a repetition of the Lawrence work. It quotes from FOWLER and from ARDERN and LOCKETT, his colleagues, to prove that their activated sludge work was based upon the Law- rence work. The paper gives the statement of DR. MACLEAN WILSON of Eng- land, made in his presidential address to the Assoc. of Sewage Works Man- agers, to the effect that the efficiency of growths in the purification of sewage by aeration, was discovered at Lawrence. The paper further describes the Lawrence work during the past 4 years and gives the results of much of this work, with the conclusions that the governing factors of the success of this process of sewage treatment are, (1) the cost of power for supplying the large volumes of air necessary; (2) a sewage that readily yields itself to this method of treatment. 163 London sewage experiments. NEWS ITEM. Eng. News 76, 37. Activated sludge experiments on London sewage are being conducted by the County Council of London, Eng., according to the last annual report of the Council. 164 Sewage treatment recommended for Lima, Ohio. NEWS ITEM. Eng. News 76, 46. Riensch-Wurl screens and activated sludge tanks have been recommended to treat the sewage of Lima, O., by MR. G. W. FULLER. The plan is to operate the screens the year round, but at the outset to run the activated sludge tanks about 7 months in the year when the flow of the Ottawa river is relatively small. 165 Purification of sewage and other liquids. W. JONES and JONES & ATT- WOOD, L'TD., Stourbridge, Eng. British Patent 104,187, July 11, 1916. Jour. Soc. Chem. Ind. 36, 471. Chem. Abst. 11, 1868. In treating sewage and other impure liquids by aeration in the presence of bacterial sludge, the sewage enters at the end of a long tank divided lengthwise down the middle and having a bottom of ridge and furrow form, with air diff users in the bottom of the furrows. The flow is directed by baffles and submerged walls to the opposite end, where the sewage turns at right angles into the other division of the tank, along which it flows in the reverse direction. Before being discharged from the tank, the sludge is deposited in settling chambers having bottoms sloping towards the dividing wall of the tank. At these points part of the wall is cut away to allow connection with the other division of the tank. At the foot of the wall on the first division side is an air diffuser, and a low wall is built around the diffuser and both sides of the opening in the wall so as to form a well. When the air supply is turned on, an upward current of sludge and sewage is produced on that side of the wall, and a current of sludge and sewage is induced to flow through the opening from the other side. In this way the sludge can be transferred from the exit to the entry end of the tank. At intervals along the base of the dividing wall there are openings similar to the foregoing; in this way sludge can be transferred from one side to the other along the whole length of the tank. In another form of apparatus, instead of one long tank, there are a number of short tanks arranged side by side and connected in series; in this form the tanks have a flat bottom and the air diffusers are placed at each end of the short tanks. 166 The sewage problem. SIDNEY BARWISE. Surveyor 50, 29-30. A history of sewage filtration, contact beds, etc. The activated sludge treatment is preferable if the sewage must be pumped. Mechanical processes of intro- ducing air are hopeful. Research should be encouraged. 167 Activated sludge experiments at Sheffield. (Eng.) DISCUSSION. Sur- veyor 50, 33-4. In the discussion of J. HAWORTH'S paper (Ref. No. 168) 34 Abstract Bibliography 1916 C. H. BALL claimed that acid wastes were very detrimental to the process. J. H. KERSHAW said that sulphocyanides in gas liquors could be eliminated by aeration. J. HAWORTH said that a fungus growth had been noted inside the porous tiles used at Sheffield. Filtros plates were found to give the best air distribution. 168 Experimental work with regard to the purification of sewage by activated sludge. JOHN HAWORTH. Surveyor 50, 40-2. Can. Engr. 31, 167-9. Con- tract Record 30, 959-62. Water and Water Eng. 18, 265-7. Chem. Abst. 10, 3123, 11, 177. Experiments at Sheffield, Eng., extending over a period of 4 years are reported in a paper before the Assoc. of Managers of Sewage Dis- posal Works. Effluents from contact beds were subjected to (1) aeration by jets of air, (2) aeration through land tiles and silica brick, (3) aeration by allowing the liquid to fall in sprays, (4) aeration on percolating filters of various depths, (5) sand nitration and (6) precipitation by chemicals. Acti- vated sludge experiments were carried out on tank effluents, on mixtures of tank effluents and settled sewage, on settled sewage and on crude sewage. With porous diffusers well clarified effluents were usually obtained which were within the limits of allowed impurity. Acid trade wastes unless neutralized, temporarily destroyed the activity of the sludge. Unequal porosity caused uneven aeration. Porous tiles became choked after a few months due to dust and grease in the compressed air and by bacterial growths in the pores of the plates. Cracking of the tiles caused shut-downs for repairs. An apparatus designed in 1880 for the oxidation of oils gave satisfactory results in aerating sewage. It consisted of a vertical cylindrical tube fitted with a spindle carry- ing an Archimedean screw or propeller blades which sucked sewage and air to the bottom of the cylinder upon being revolved. Clarified npn-putrescible effluents were obtained from settled sewage after 5 hours aeration in a tank equipped with a series of perforated steam pipes covered with 2 feet of clinker broken into % inch cubes. Crude sewage was satisfactorily treated for 6 months in a small iron tank equipped with a horizontal shaft to which were attached hollow paddles that trapped small volumes of air when rotated above the surface of the contained sewage. It was concluded that (1) a normal sewage may be clarified by the activated sludge method, (2) that mechanical circulation with minimum aeration is efficient, (3) that trade wastes may interfere seriously with the process, (4) that further investigation is needed with respect to modes of application of the sludge to the sewage, periodical removal of the surplus sludge and the effect of such removal on the process, and the costs of plant and upkeep before older plants and methods can be abandoned, (5) that skilled control of the process will be essential, (6) that, while the resulting sludge is undoubtedly richer in nitrogenous organic matter than ordinary sewage sludge, it remains to be proved by actual agricultural trials that such nitrogen is in a form suitable for ready assimilation by plant life, and that the sludge will be a valuable fertilizer. 169 Appoint committee on the activated sludge process. NEWS ITEM. Eng. Record 74, 91. At an informal meeting of members of the Am. Soc. of Civil Eng. held at Pittsburgh on June 28, 1916, F. A. DALLYN, Toronto; G. T. HAMMOND, Brooklyn, and T. C. HATTON, Milwaukee, were appointed a com- mittee to prepare standard definitions and other terms relating to the activated sludge process of sewage treatment. They will also tabulate and distribute a summary of the work now being done or contemplated, and suggest such correlation of current work as may be desirable. The question of submitting to the Commissioner of Patents information relating to priority of knowledge of the activated sludge process, was left with PROF. EARLE B. PHELPS, H. W. CLARK and DR. EDWARD BARTOW. 170 Air diffuser experiences with activated sludge tanks. ANON. Eng. News 76, 106-10. Surveyor 50, 160-3. Chem. Abst. 10, 2779. Differences of experiences and opinions as to the use of porous block and perforated pipe diffusers for intimately mixing air and agitating sewage in activated sludge 35 The Activated Sludge Process tanks are expressed by engineers in charge of tests and working plants at Milwaukee (MR. HATTON), Baltimore (MB. HENDRICK, MR. FRANK), Brooklyn (MR. HAMMOND), Cleveland (MR. PRATT), Urbana, 111., (DR. BARTOW), Chi- cago (MR. PEARSE, MR. NOBLE), and Houston, Texas, (MR. SANDS). The majority find filtros satisfactory. Two prefer perforated grids. 171 Sewage plans for Matawan, N. J. NEWS ITEM. Eng. News 76, 140i Plans for an activated sludge plant to treat the sewage of Matawan, N. J., drawn by G. A. JOHNSON, N. Y. City, have been approved by the State Board of Health. 172 The activated sludge process. Results at Worcester, Eng. EDITORIAL. Surveyor 50, 83. JONES & ATTWOOD are conducting tests at Worcester, treating half the flow. The tests are to continue for one year under agree- ment that 750,000 g. p. d. are to be treated with an effluent containing not more than 40 p. p. m. of suspended solids and which shall not be capable of putrefaction. Thus far five samples show better than these limits. 173 Tests show activated sludge process adapted to treatment of stock-yards wastes. M. D. HARDING, G. L. NOBLE and P. RUDNICK. Eng. Record 74, 137-8. Chem. Abst. 10, 3123. The sewage of ARMOUR & Co., Chicago, averages 700 p. p. m. suspended matter and is of a complex nature. Using 15% by volume of activated sludge with beef-slaughtering sewage, a stable effluent was obtained after two days aeration; long before clarification. Experiments are being conducted in a 30,000 gallon tank on the continuous flow plan, the air being distributed by means of one inch galvanized-iron pipes, perforated with one-twenty-fifth inch holes spaced two inches apart. Processes for de- watering the sludge are being studied. The estimated cost of treatment per million gallons of sewage is $3, exclusive of interest, depreciation and repairs. 174 Progress in the treatment of sewage. EDITORIAL. Surveyor 50, 93. Com- ment on the article of S. BARWISE, (Ref. No. 166) and reference to J. HAWORTH'S method of mechanical agitation at Worcester. Expresses the belief that further investigations should be directed along this line. 175 Stockyard wastes can be treated by activated sludge process. ANON. Contract Record 30, 788-90. Digest of the article by HARDING, NOBLE and RUDNICK appearing in the Eng. Record. (Cf. Ref. No. 173.) 176 Baltimore activated sludge air diffusers. L. C. FRANK. Eng. News 76, 267. Chem. Abst. 10, 3123. It was found that some of the old filtros disks showed evidence of disintegration upon removal from the umbrella- shaped diffuser grid. 177 Apparatus for introducing gases into intimate contact with liquid sewage. G. W. MOTTRAM, Deepcar, near Sheffield, Eng. U. S. Patent 1,195,067, Aug. 15, 1916. (Application filed Feb. 17, 1916. 3 claims.) Off. Gaz. 229, 872. Chem. Abst. 10, 2493. Claim 3: The combination, with a tank of sew- age, of a vertical air supply pipe provided with laterally projecting branch pipes arranged in the lower part of the tank and provided with outlet holes, tubular casings of porous material through which air can pass inclosing the said branch pipes, and means for revolving same. (Cf. British pat. 2,421. Ref. No. 34.) 178 Activated sludge progress. EDITORIAL. Eng. News 76, 366. Refers to several plants in the United States and England, cites the need of caution in adopting the method because of the many details yet to be worked put, and suggests that engineers should give it careful consideration because it would fall little short of revolutionizing sewage disposal should its highest promises be realized. Abstract Bibliography 1916 179 Activated sludge plant for Hermosa Beach, Calif. NEWS ITEM. Eng. News 76, 380. Munic. Engr. 51, 105. The first Pacific coast city to pro- ject an activated sludge plant has authorized the construction of a "BROSIUS system of activated and aerated sludge treatment." The plant will consist of 8 concrete tanks each 12.5 ft. in diameter by 13 ft. deep. 180 Activated sludge treatment in America. ANON. Engineer 122, 170. Re- fers to the Milwaukee plant and the recent papers by T. C. HATTON; the Baltimore and Brooklyn experimental plants, and to G. T. HAMMOND'S recent investigation of the subject. This article deals especially with the various air diffusing means employed, filtros being fully described. 181 Apparatus for aerating sewage. GRIFFITHS and HARTLEY. British Pat- ent Application No. 12,084, Aug. 26, 1916. Jour. Soc. Chem. Ind. 35, Suppl. 55. 182 How other cities in the United States are disposing of their sewage. R. V. ORBISON and T. D. ALLIN. Pamphlet (Sept. 1916) Proc. 19th Ann. Conv. Pacific Munic. 61-77. The activated sludge process referred to as in Ref. No's. 210, 223 and 250. 183 The activated sludge process. An American Committee. ANON. Sur- veyor 50, 247. On Sept. 15, 1916, members of the Am. Soc. C. E. met at Pittsburgh and appointed F. A. DALLYN, G. T. HAMMOND and T. C. HATTON a committee to prepare standard definitions of the activated sludge process and to tabulate and distribute a summary of the work in progress. A pat- ent committee was also appointed consisting of E. B. PHELPS, H. W. CLARK and DR. E. BARTOW to present evidence of priority of knowledge of the activated sludge process to the Commissioner of Patents. 184 Activated sludge in India. NEWS ITEM. Eng. News 76, 624. Activated sludge studies at three points in India, with particular attention to fertilizer possibiltes, are to be made by DR. G. J. FOWLER, formerly of Man- chester, Eng. 185 Present status of activated sludge. EDITORIAL. Munic. Jour. 41, 383-4. Chem. Abst. 10, 3122. The editor indicates that the process is still in the experimental stage and that the cost of handling the sludge is very uncertain. 186 Bacteriological study of sewage purification by aeration. R. RUSSEL and DR. E. BARTOW. Univ. Ill Bull. 14, 348-58. (Water Survey Series No. 13) Chem. Abst. 11, 1707. Expt. Sta. Record 38, 490. The investigation has shown the following bacteriological features of the activated sludge process of sewage purification: (1) There is a large and consistent reduction of the total number of bacteria in the sewage; (2) the actual stabilization process is due to a typical aerobic bacterial flora which gains almost complete ascend- ency, the other inhabitants being largely incidental; (3) the actual nitrifi- cation is accomplished by two typical known nitrifiers "Nitrosomonas" and "Nitrobacter." 187 Nitrogen in activated sludge. EDITORIAL. Eng. News 76, 663. Refers to a paper by MR. COPELAND (Ref. No. 188) and the difficulties of de- watering activated sludge. "If a process of sewage disposal could be per- fected that would yield a sludge convertible into fertilizing material at less than capital charges and operating expenses, and without causing a nuisance, one of the most baffling municipal problems of the last half century would be solved." 188 Nitrogen from sewage sludge, plain and activated. W. R. COPELAND. Eng. News 76, 665-6. Can. Engr. 31, 340. Munic. Jour. 41, 446. Chem. Abst. 10, 3124; 11, 509. The practicability of recovering nitrogen from sewage 37 The Activated Sludge Process depends upon (1) the amount present, (2) the cost of recovering and dis- posing of it, and (3) its market value. Nitrogen is largely recovered from suspended matter. Sludge from best known processes ranges from 1.2 to 3% nitrogen, whereas activated sludge at Milwaukee contains 5 to 9% wet, and 4 to 4.5% when dry. Estimated cost of recovery is $10 to $12 per ton with 10% moisture, with market value from $9 to $15. 189 Discussion of Mr. Gopeland's paper on nitrogen recovery. G. W. FULLER. Eng. News 76, 667. Eng. Record 74, 445. Chem. Abst, 11, 80. Mr. Fuller points out that while the activated sludge process saves loss of nitrogen, the real problem is to economically dewater the sludge. Possible use of the DICKSON yeast fermentation process is suggested, with the final reduction of water content by means of heat dryers. 190 Commercial possibilities with activated sludge. EDITORIAL. Eng. Record 74, 428. Commenting on MR. COPELAND'S paper (Ref. No. 191) it is the opinion that if sewage treatment plants can produce valuable fertilizer material, their usefulness will increase, and the reduced operating costs will also stimulate plant construction, especially where present sewage disposal methods create a nuisance. 191 Nitrogen recovery from sewage sludge reaches a commercially practicable stage. W. R. COPELAND. Eng. Record 74, 444-5. Chem. Abst. 11, 273. Parallel experiments on Milwaukee sewage showed that most of the nitrogen in the sewage passed out in the suspended and colloidal matters in the effluent when treated by the Imhoff tank, but in the activated sludge method it was stored up in the sludge. As secured in the settling tank activated sludge contained 98-9% of water which has been difficult to remove. Latest information favors a combination of settling and decantation to reduce to 96%, filter-pressing to bring down to 75%, and dewatering of the press-cake in a drier to 10% or less. Lime in filter-pressing was shown to be unnecessary. Little or no nitrogen was lost in drying. Data indicates that Milwaukee sew- age will contain 4.6 to 5% nitrogen as ammonia, 0.6 to 0.7% available phos- phoric acid, 0.25 to 0.50% potash and 3 to 4% fat. Tables give analyses of sewage and of effluents and sludges obtained by both Imhoff and activated sludge processes. 192 Aeration suggested for sludge disposal. G. T. HAMMOND. Eng. Record 74, 448-9. Surveyor 50, 400-1. Chem. Abst. 11, 375. Two to four thousand gallons of sludge containing 96 to 99% of water result from each million gallons of sewage treated by the activated sludge process. Many cities would not install expensive dewatering plants, and for these fine screening, partial drying by pressing or prolonged aeration of the sludge offer possibilities for minimization of the amount of sludge produced. Long contnued aeration reduces activated sludge to 10% or less of its original volume. Experimentation would be necessary to produce properly designed plants for removing excess water as the cost of aerating large volumes would be prohibitive. 193 Large activated sludge plant at Milwaukee, Wis. ANON. Eng. News 76 686-8. Chem. Abst. 11, 510. A two million gallon daily capacity plant costing $61,536 is described. Operating data is given. Steeper slopes of 60 degrees from the horizontal are recommended for hopper of settling tank. Air pressure required is increasing with use, and larger amounts in cold weather. Immediate settling following aeration is necessary, with constant removal of the sludge. 194 Apparatus for aerating sewage and other foul liquids. R. AMES, Brigh- ton, Eng. British Patent 110,197, Oct. 13, 1916. (Addition to British Patent 104,361. Ref. No. 127). Jour. Soc. Chem. Ind. 36, 1247. The original apparatus is improved by providing above the tank a rotary chamber, to 38 A bstract Bibliography 1 91 6 which the incoming sewage is supplied. From this chamber the sewage flows into troughs, fixed to the chamber on either side, from which depend open- topped vertical pipes with bell-mouth bottoms reaching to within a few inches of the bottom of the tank. The compressed air supply comes from an air chamber on the top of the sewage chamber, the air being conveyed by pipes which pass down the inside of the vertical sewage pipes and end in atomizers located in the bell-mouths of the sewage pipes. 195 Sewage treatment by aeration and activation. G. T. HAMMOND. Can. Engr. 31, 305-11. Surveyor 50, 453-5; 479-80. Proc. Am. Soc. Munic. Impvts. 23, 327-403. Chem. Abst. 11, 1867. (Also in pamphlet form, reprinted from the Proc. Am. Soc. Munic. Impvts., 1916, with discussion of all activated sludge papers presented at that meeting, pp. 101). A very complete and critical review of the activated sludge process. Refers to sewage aeration experiments from 1884 to the present time, and as a result of personal visits to the several plants, or by correspondence with those in charge, the author has collected in this article all the important data of the plants at Balti- more, Brooklyn, Champaign, 111., Chicago, (Armour and Sanit. Dist. plants) Cleveland, Edmonton, Can., Fort Worth, Tex., (Armour plant), Houston, Tex., Lawrence, Mass., Milwaukee, Regina, Can., San Marcos, Tex., and Urbana, 111. No forecast of the value of the activated sludge process can be made at this time, but it is noted that methods of air distribution and sludge treatment still require study. The apparent advantages are a clear and stable effluent from a plant requiring small area, and freedom from odor. 196 Activated sludge sewage treatment. ANON. Munic. Jour. 41, 480-3; 510-13. A review of the experiments being conducted and results ob- tained at 11 plants, with an outline of the provisions for co-operation of ex- perimenters. Abstracts of several papers presented at the 1916 meeting Am. Soc. Munic. Impvts. 197 Present status of activated sludge. ANON. Water and Water Eng. 18, 257-8. Chem. Abst. 11, 178. While the activated sludge process has been more thoroughly and promptly investigated than any other method of sewage disposal, yet the plant at San Marcos, Texas, treating about 150,000 gallons of sewage per day, is the only plant in actual operation and not under experimental conditions. The work at Milwaukee is reviewed. Engi- neers are cautioned against hasty copying of experimental plants. 198 The activated sludge process. EDITORIAL. Surveyor 50, 373-4. Com- ment on the interesting results at Manchester, Eng. Experiments on sedimentation are needed. The process can be adjusted to the character of the sewage and the quality of effluent desired. Desirable to purify to a greater degree when stream flow is at a minimum, and to vary air supply accordingly. 199 The activated sludge process. Manchester research work. ANON. Sur- veyor 50, 379-80. Chem. Abst. 11, 2517. A digest of the annual report of the Manchester Rivers Committee. With a weak domestic sewage tried at the Withington works, satisfactory purification was not dependent on the stage to which nitrification was carried, nor was the question of temperature as serious as with sewage containing trade wastes, satisfactory purification being maintained with air temperatures below zero, and sewage tempera- tures from 5 to 10. 200 Some remarks on activated sludge. W. T. CARPENTER and M. P. HORO- WITZ. Am. Jour. Public Health 6, 1218-23. Chem. Abst. 11, 1224. An aerated contact bed was fitted up in a 50 gallon barrel. After 5 hours aera- tion the liquid drawn from the barrel was practically devoid of suspended matter and purified. Purification was complete after 20 hours. A table of results is given from which it is seen that the rate of fall of demand for 39 The Activated Sludge Process oxygen diminishes throughout the cycle, thus showing that the action pro- ceeds rapidly at first and that a definite amount of air would be most advantageously used by blowing it rapidly in the beginning and more slowly later. It is claimed that while a short period of retention will suffice to settle the sludge which has been aerated 20 hours without any addition of fresh sewage, a longer period is necessary when operation is continuous during a shorter aeration period. Short-circuiting the sewage can be mini- mized by dividing the retention among several smaller tanks in series or by using one tank with a length great in proportion to its breadth and height. 201 Mechanical agitation of sewage proved unsuccessful. C. H. NORDELL, Eng. News 76, 856. Chem. Abst. 11, 509. Description of some experi- ments made with screw propellers and stirrers of various forms, from which evidence is deduced that agitation itself plays a minor part, liberal aera- tion being essential for the efficient and economical working of the activated sludge process. 202 Definitions of sewerage and sewage disposal terms. ANON. Eng. News 76, 858. Am. Jour. Public Health 7, 847. The committee on the sewer- age and sewage disposal of the sanitary section of the Am. Public Health Assoc., with the co-operation of eminent engineers, suggests the following def- inition for the activated sludge process: "Activated-Sludge Process consists in the agitation of a mixture of sewage with about 15% or more of its volume of bacterially active liquid sludge in the presence of ample atmospheric oxygen, for a sufficient period of time to at least coagulate a large proportion of the collodial substances, followed by sedimentation adequate for the subsidence of the sludge flocculi; the activated sludge having been previously produced by aeration of successive portions of sewage and maintained in its active condition by adequate aeration by itself or in contact with sewage." 203 Digestion of activated sludge. H. P. EDDY. Proc. Am. Soc. Munic. Impvts. 23, 429-39. Can. Engr. 31, 353-5. Surveyor 50, 504-6. Details are given of the operation of an experimental activated sludge plant on tan- nery wastes, including analytical data, sludge accumulation period, sludge ac- tivation period, period of operation on one filling per day, with increased proportion of sludge, on two fillings per day, with and without sludge re- moval, quantity of sludge produced, sludge digestion, digestion of fats, in- creasing the volume of sludge by its partial removal. About 10 cu. ft. of air per gallon of sewage were used with 12 hours aeration on the fill and draw plan. Sludge volume will not exceed 10,000 gallons per million gallons of sewage. 88.7% of the fats were digested and the mineral matter in the sludge decreased 77.8%. 204 Comparative costs of construction and operation of the activated sludge and Imhoff trickling-filter process of sewage treatment. ANON. Eng. Record 74, 557. Eng. & Contg. 47, 154-7. From a paper by H. P. EDDY pre- sented to the West. Soc. of Engs., covering an engineering study of the two processes based on comparative designs for Fitchburg, Mass., in which the total estimated cost of the Imhoff plant is $431,170 and of the activated sludge plant $313,880, engineering and administration charges included. Both plants designed for 5.5 million gallons daily capacity. Estimated annual costs are $17,080 for the Imhoff and $40,140 for the activated sludge. Advantages and disadvantages of both methods are discussed. (Cf. Ref. No. 217). 205 The pioneer activated sludge plant. ANON. Contract Record 30, 1066-8. A description of the new 1,600,000 g. p. d. installation at Milwaukee, (Ref. No. 70) covering the general scheme, air diffuser experiments, and some results of operation. 206 Disposal of sludge from activated process. ANON. Contract Record 30, 1074. Review of a paper by G. T. HAMMOND in which the work of 40 Abstract Bibliography 1916 FOWLER and others, and the experiments at Brooklyn, Lawrence, Milwaukee and ARMOUR & Co., Chicago, are referred to. The SCHAEFER-TER-MEER centri- fugal sludge drier, the WORTHINGTON press and the DICKSON yeast process are considered in connection with sludge dewatering. The long continued aeration of the sludge is also suggested as a means of minimizing the surplus sludge. 207 Results and conclusions from a year's operation of the activated sludge sewage treatment plant at Milwaukee. ANON. Eng. & Contg. 46, 407-9. Chem. Abst. 11, 510. Expt. Sta. Record 36, 489. Digest of a paper by T. C. HATTON before the Am. Soc. Munic. Impvts., 1916 meeting, covering work more fully described in the annual report of the testing station. (Cf. Ref. No. 227). 208 Activated sludge novelties at Hermosa Beach, Calif. A. M. BROSIUS. Eng. News 76, 890-2. Chem. Abst. 11, 510. This plant handles 400,000 gallons of sewage per day with an aeration period of 3 hours. 60 kw. hours are required per 100,000 gallons treated. A submerged propeller or dif- fuser wheel in the bottom of a circular tank draws air and sewage down through a central foam chamber to the bottom of the tank, from which both pass upwards. Air under one pound pressure will also be admitted to each central pipe. 209 Terms used in sewerage and sewage disposal. An American Committee's definitions. ANON. Surveyor 50, 430-2. From a report of the com- mittee of the Am. Pub. Health Assoc., referring to activated sludge as in Ref. No. 202. 210 Activated sludge given preference. T. D. ALLIN and R. V. ORBISON. Eng. Record 74, 628. Chem. Abst. 11, 375. After visiting several sew- age treatment plants throughout this country in behalf of the city t)f Pasadena, Calif., the committee reports that the activated sludge process occupies less space, costs less for construction, gives a better effluent and is absolutely odorless, as compared to Imhoff tank and the sprinkling filter process. The cost of operation is higher but the greater fertilizing value of activated sludge will reduce the difference. (Cf. Ref. Nos. 182, 223, and 250). 211 Activated sludge experiments at the University of Illinois. E. BARTOW, F. W. MOHLMAN and J. F. SCHNELLBACH. Eng. News 76, 972-3. Sur- veyor 51, 6. Am. Jour. Public Health 7, 679. Chem. Abst. 11, 509. The plant handles about 150,000 gallons daily of domestic sewage, using 2 cu. ft. of air per gallon. Stable effluents have usually been obtained. The settling cham- ber 24 to 37 minute period has proved too small. 212 Recommends isolated sewage treatment plants for lake cities north of Chicago. J. W. ALVORD, H. P. EDDY and G. W. FULLER. Eng. Record 74, 656-8. Chem. Abst. 11, 679. The activated sludge process is too expensive for local conditions. 213 Bottom of pipe perforated for air distribution. ANON. Eng. Record 74, 660. Air distribution in the activated sludge plant at Edmonton, Can., is accomplished by pipes perforated on the under side with %-inch holes, 3- inch centers. Provision is made for lifting each air line independently. 214 Chicago sewage treatment and dilution. NEWS ITEM. Eng. News 76, 1056. Eng. Record 74, 695. Munic. Jour. 41, 677. Chem. Abst. 11, 510. Among the important improvements in the sewage disposal system of Chicago, there is a recommendation by the Board of Trustees of the Sanitary District for the treatment of domestic sewage centering at the 39th street pumping station from an area of about 22 square miles by settling basins or an activated sludge plant in the vicinity of this station. 41 The Activated Sludge Process 215 Mechanical agitation and aeration and trade wastes in the activated sludge process. ANON. Munic. Eng'rg. 51, 234-5. From a paper by JOHN HAWORTH presented at a meeting of the Assoc. of Mgrs. of Sewage Disposal Works held at Sheffield, Eng., dealing with the activated sludge work in that city. (Cf. Ref. No. 168). 216 A new type of trickling filter. G. G. NASMITH. Jour. Royal Sanit. Inst. 37, (Dec. 1916). Surveyor 51, 4-5. Expt. Sta. Record 37, 488. The author states that the principles of the trickling filter and the activated sludge process are identical. In the first, the sewage trickles over the bac- terial mass in the air; in the activated sludge process air is passed into the sewage in contact with the bacterial mass; the end results being exactly the same. 217 A comparison of the activated sludge and the Imhoff tank-trickling; filter processes of sewage treatment. H. P. EDDY. Jour. West. Soc. Engs. 21, 816-52. Engineering 104, 288-90, 319-20. Surveyor 51, 370-2. Expt. Sta. Record 37, 694. A detailed specific comparison of the two methods from which the author concludes that, "At the present time it appears that the Imhoff tank-trickling filter process is a less expensive means of oxidizing the organic matter of sewage and industrial wastes than the activated sludge process, where oxidation alone is considered. If the areas of land required for isolation, the loss of head in the plant, the danger of objectionable odors and of fly annoyance, and other disadvantages of the trickling filter process are of marked importance in any specific case, the balance may be decidedly in favor of the activated sludge process, even in its present state of develop- ment." Comparative cost estimates are included. (Cf. Ref. No. 204). 218 Recovery of fats and nitrogen compounds from sewage. S. RIDEAL. Chem. Trade Jour. 59, 571-2. Jour. Soc. Chem. Ind. 36, 44. Can. Engr. 32, 82, 157. Chem. Abst. 11, 859, 1225. Expt. Sta. Record 38, 625. Dried active sludge with 10% moisture, contains 5 to 9% N and if retorted should give higher yields of ammoniaca! liquor than are obtained from coal in gas works. To recover nitrates from effluents it is suggested that a filter bed with no effluent drain, protected from rainfall, might be irrigated with the effluent so that nitrates would become gradually concentrated by evaporation. "If all the nitrogen in sewage could be recovered, it is estimated that the military camps would yield 11,640 tons and the civil population 116,400 tons per annum." 219 Activated sludge results at Cleveland. R. W. PRATT and G. B. GASCOIGNE. Eng. News 76, 1061-6, 1124-8. Chem. Abst. 11, 509. The conditions require only a low degree of purification for the sewage from 75% of the population. To remove iron from the sewage requires % hour more aera- tion than clarification. The sewage treated contains in parts per million: Suspended matter 250, organic nitrogen 8.5, free ammonia 12.1, iron 21, occasionally up to 350. Filtros plates were used for air distribution, in ratio of plate surface to tank area, 1 to 5. Some clogging has been noted. The tanks are 15 feet 1 inch deep, requiring 0.75 cu. ft. free air per gallon of sewage for clarification. With equal aeration for liquid and solid, a 3 hour period is required. In the horizontal flow settling basin a 30 minute period is ample with a velocity of 1 foot per minute. Steep bottom slopes are required. 25% of the sewage treated is pumped back. Very careful operation is required. Minimum cost for labor and power per million gallons is $4.50 with power at 0.75 cent per kw. hour. Analytical results are given. Re-aeration of the sludge with 20 to 25 cu. ft. of air per gallon improves its drying and keeping qualities. Separate sludge digestion is possible. Unless the unit quantities of sludge produced are materally lessened, the use of sand beds for dewatering is financially prohibitive. Centrifugals have re- duced sludge moisture to 85%. Available data indicate that presses are suit- able for primary dewatering, irrespective of whether or not the sludge war- 42 Abstract Bibliography 1916 rants further drying for fertilizers. Present data are insufficient to estimate the cost of sludge disposal. The nitrogen value in Cleveland sludge may be about $5.50 per million gallons of sewage. 220 The attractiveness of the activated sludge process to sanitary engineers. EDITORIAL. Can. Engr. 31, 475. "Probably there has never been an innovation which ever took so firm a hold of sanitary engineers and has engaged the attention of so many students of sewage disposal as the acti- vated sludge process. A surprisingly large number of municipalities and industrial plants throughout the continent are either conducting experimental plants or are laying plans to do so. Out of all this the science of sanitary engineering should emerge the richer." 221 Tanks for the purification of sewage. G. W. and J. F. NAYLOR, Denby Dale, Yorks, Eng. British Patent 111,548, Dec. 7, 1916. Jour. Soc. Chem. Ind. 37, 72A. The air diffusing means along the bottom of the tank for the treatment of sewage by diffusion of air in small bubbles, may consist of non- porous tubes with small perforations on their under side, covered by strips of cloth tightly encircling the tubes. The whole length of the tube is en- closed by a cloth casing kept from touching the under side of the tube by de- pending stays. The air from the perforations in the tube diffuses through the cloth casing, mainly at the sides. The tubes may also be made of porous earthenware, the upper surfaces being painted over so that air escapes from the sides only. 222 Purification of sewage and other impure liquids. W. JONES, Stourbridge, and JONES & ATTWOOD, LT'D., Amblecote, Eng. British Patent 111,720, Dec. 9, 1916. Jour. Soc. Chem. Ind. 37, 72 A. Chem. Abst. 12, 597. Crude sewage enters a treatment tank through a hydropneumatic appliance whereby a mixture of sewage and air is delivered well below the surface into the body of the liquid in the tank. The bottom of the tank is of inverted conical shape with a sump at the apex, and the dilute sludge passes out by the sump into a separate tank with ridged bottom provided with air diffusers, whereby it is aerated and circulated. This invigorated sludge is then returned by an air lift to the top of the liquid in the sewage tank. In another form of the tank, the mixture of sewage and air is delivered into radial arms at the level of the conical portion of the tank, and as it issues from these through a series of holes along one side, it causes them to revolve and bring about a perfect distribution. The process may be carried out also in several tanks connected in series. 223 Sewage disposal methods of 16 cities. ANON. Eng. & Contg. 46, 534-6. Pacific Municipalities, March, 1917. From a report by T. D. ALLIN and R. V. ORBISON referring to the activated sludge plants at Baltimore, Chicago, Cleveland, Milwaukee, and the contemplated plant at Worcester, Mass. (Cf. Ref. Nos. 182, 210 and 250). 224 Activated sludge process. ANON. Can. Engr. 31, 489-90. Ann. Report Manchester Rivers Com. (1916) Experiment has demonstrated that the air supply should be filtered and the sewage screened from detritus. Abnor- mal amounts of trade wastes interfere with the process. The process can be operated in cold weather. Clarification is independent of nitrification. 225 Aerating apparatus. C. H. NORDELL, Milwaukee, Wis. U. S. Patent 1,208,821, Dec. 19, 1916. (Application filed March 23, 1916. 1 claim.) Off. Gaz. 233, 800. Jour. Soc. Chem. Ind. 36, 201. A container for sludge having a bottom composed of wooden slabs cut transversely of the grain to form minute elastic air passages for air, a casing below the wood slab bottom forming an air chamber, and a means for introducing air under pressure into the chamber whereby it is forced through the fibrous passages of the wood 43 The Activated Sludge Process slabs to form minute bubbles for uniformly aerating the body of sludge that is supported by the fibrous bottom. (Cf. U. S. Patent 1,281,816. Ref No 427). 226 Community activated sludge plant for Chicago stockyards. NEWS ITEM. Eng. Record 74, 784. Engineers of the stockyards interests and the Sanitary District of Chicago, after making a joint study of the proper dis- posal system, agree that the activated sludge method will handle the sewage and conclude that a community plant to take care of all the wastes from all the packing industries is better than the disposal by each company of its own wastes. 227 Third Annual Report of the Milwaukee Sewerage Commission. T. C. HATTON and W. R. COPELAND. Pamphlet pp. 127. (Dec. 31, 1916) An elaborate report on the activated sludge work for the year ending Dec. 31, 1916, at the sewage testing station. Of all the processes experimented with, the activated sludge process appears to be the only one which fits the exist- ing conditions in Milwaukee. The maximum volume of air required to pro- duce a stable effluent from which 95% bacteria and 98% suspended solids have been removed, is 2 cu. ft. per gallon of sewage, based on 10 ft. depth of sewage in the aerating tank. Maximum aeration period, 4 hours, and the percentage of sludge carried may vary from 15 to 25 without materially effecting the results. Sedimentation period required is from 40 to 50 min- utes, with a maximum horizontal velocity of 3 ft., and a vertical velocity of about 8 inches per minute. Slopes for successfully removing settled sludge should be from 1 to 2, to 1 to 3. Breaking up the air into small bubbles increases the O absorbed, but sufficient air must be used to manitain the solids in suspension. Filtros plates are satisfactory air diffusers, but all oil and dust should be excluded from the air lines. Wood plates give smaller bubbles than filtros at less loss of pressure, but insufficient experience does not warrant their adoption. Sewage can be clarified in from 1 to 1.5 hours aeration in the presence of well activated sludge, by using 0.5 to 1 cu. ft. of air per gallon of sewage in a 10 ft. deep tank, but the activity of the sludge cannot be maintained without additional aeration. Storm flow can be taken care of by increasing the volume of air and sludge, but extra settlement capacity must be provided if a standard effluent is to be main- tained. Conduits should not be used as the sludge settles too quickly. Re- covered sludge contains 99% of water, which may be reduced to 96% by additional settlement of 1 to 3 hours. Over-aeration reduces its volume and also its coagulating properties. Sludge can be dewatered from 96 to 75% by presses without the use of lime, and from 75 to 10% by either indirect steam, or direct heat dryers, without appreciable loss of ammonia. Milwau- kee sludge, on a dry basis, contains 4.5 to 5% ammonia. With 4 hours aera- tion and 2 hours settlement, 8 million gallons of sewage can be treated upon 1 acre. About 80 pages of analytical and other data, and several illustra- tions accompany the report. 228 A few figures on the building and operation of the Baltimore disposal plant and notes on the activated sludge experiments. G. J. REQUARDT. Proc. Am. Soc. Munic. Impvts. 23, 416-28. Refers to the activated sludge experiments made in the converted Imhoff tank with the umbrella-like dif- fuser grids. 229 A year's progress in activated sludge sewage treatment. T. C. HATTON. Proc. Am. Soc. Munic. Impvts. 23, 404-15. Covers operation, the secur- ing of the activated sludge, aeration, the effects of low temperatures, sedi- mentation, sludge disposal, and general notes on the Milwaukee experimental work. More fully abstracted from the annual reports, Ref. Nos. 100 and 227. 230 Discussion of papers on activated sludge. Proc. Am. Soc. Munic. Impvts. 23, 439-43. Covers oral and written discussion of the papers mentioned in references 195, 203, 228 and 229. Participated in by Messrs. HATTON, 44 Abstract Bibliography 1917 COPELAND and NORDELL of Milwaukee; Messrs. FOLWELL, FULLER and POTTER of N. Y. City; MR. E. B. PHELPS of the U. S. Public Health Service; MR. J. R. ELLIS of Regina, Canada; (whose letter describes quite fully the activated sludge experiments in that city) ; MR. G. L. NOBLE of Chicago; MR. W. T. CARPENTER of Brooklyn; and MR. W. L. STEVENSON of Philadelphia, Pa. 231 Report of the Committee on Sewage and Sanitation. G. A. CARPENTER. Proc. Am. Soc. Munic. Impvts. 23, 324-6. "It is very generally recog- nized that the activated sludge method is yet in the process of development, and should not be adopted except under expert advise. Thus far the con- ditions necessary for success have not been sufficiently standardized to jus- tify the adoption of this method by small communities and the great prob- lem with reference to it today is the question of cost." 232 Water purification and sanitation. F. R. O'SHAUGNESSY. Ann. Report of the Soc. Chem. Ind. of the Progress of Appl. Chem. 1, 265-7. (1916). A brief general review of the activated sludge process for the year 1916. English plants mentioned are those at Manchester, Worcester, Salford, Stam- ford and Sheffield. Milwaukee experiments and the work at the Univ. of 111., Urbana, are the only American plants considered. 233 Experiments upon the purification of sewage and water at the Lawrence experiment station during the year 1916. H. W. CLARK. 2nd. Ann. Report Mass. State Dept. Health. 123-57. Continuation of some of the earlier experiments are recorded, with generally favorable results as shown by the removal of suspended matter, stability, and the tabulated data. A new and larger activated sludge tank was put into operation on the fill and draw plan, allowing 2.5 and 3.5 hours for aeration, 1.5 hours for settlement, and with air supplied at the rate of 0.4 cu. ft. per gallon of sewage, through filtros diffusers, Investigations have shown that the N of the colloids is from 2 to 3 times as great as the N of the coarser solids of the sludge, which fact increases the N content of the sludge about 33%, except in the case of tannery sewage. Investigations of paper mill and tannery trade wastes by the activated sludge process, and several tables of chemical and bacteriological data are included. 234 Sewerage. A. P. FOLWELL. (Book) Seventh Edition, 468-70. (1916). A brief history and present status of sewage treatment by aeration and the activated sludge process. Refers to experiments at Manchester, Eng., and Milwaukee, Wis. 1917 235 A new method of purifying tannery and other effluents. Y. H. GONONIAN. Leather Manuf. 28, 45-9. Chem. Abst. 11, 1506. A preliminary report in which the author discusses briefly the subject of purification, and then gives a general description of his treatment which involves oxidation, chem- ical precipitation, and filtration. The crude sewage, screened from coarse ma- terals, is mixed with activated sludge, slowly passed through a septic tank and gravity tank, and fed through a perforated pipe into the top of the filtration and oxidation device. The latter is composed of a series of 5 large superimposed tanks fitted with false bottoms. Under each tank except the last, there passes an endless belt of filter cloth, furnished with scrubbing brushes and washing boxes, which are in turn connected to the settling tanks. Tanks for chemicals are arranged to feed automatically on to the first three filter cloths. The large tanks are partly filled with stones and gravel, the fourth one in the series having a perforated pipe connected to a compressed air or ozone generator for extra aeration when necessary. The first filter cloth is supplied from one of the chemical tanks with a layer of coal ashes, coal, or charcoal; the second with hydrated lime; the third with aluminum sulphate. The effluent in passing through the lime is made alkaline, which 45 The Activated Sludge Process favors the coagulation by the aluminum sulphate on the following cloth. Further aeration in the fourth tank tends to complete the oxidation and pre- cipitation. Diagrams are given. 236 The activated sludge method of sewage disposal. E. E. SANDS. Texas Municipalities (Jan. 1917) pp. 16-21. A paper presented at the 4th Ann. Conv., League of Texas Munic. held on Oct. 26, 1916, giving a general description of the activated sludge process, and account of the experiments at Houston, Texas, with outline of the proposed plant for that city. 237 Activated sludge power costs. G. J. REQUARDT. Eng. News 77, 18. Ghent. Abst. 11, 2517. Curves are given with an explanation of their use for computing the cost of the compressed air which may be required under varying conditions. 238 Air diffusers for activated sludge. EDITORIAL. Munic. Jour. 42, 11-2. Comments on the merits of filtros plates for that purpose, and con- siders their proper handling and installation. 239 Activated sludge process of sewage disposal firmly established. T. C\ HATTON. Eng. Record 75, 16-9. Chem. Abst. 11, 679. Refers to the several plants in various parts of the country, considers types of sedimenta- tion tanks, air requirements per gallon of sewage treated and its cost, de- watering and drying of the sludge, its costs and value, and emphasizes the importance of complete supervision over the process. 240 Water supply and sanitary engineering in 1916. ANON. Engineer 123, 32-3. A general review of the progress of activated sludge work during the year. Refers to the Milwaukee plant and the extensive experiments there carried on; to the Salford, Stamford, and Worcester plants in England, and to DR. RIDEAI/S paper on the recovery of N from sewage. 241 Engineers guide sewage disposal inspection trip. P. T. HICKS and ED- WARD BARTOW. Eng. Record 75, 95-7. Chem. Abst. 11, 679. Covers the results of an inspection trip by a party from Decatur, 111., refers to the acti- vated sludge plants at Brooklyn and Cleveland, and comments on the dis- posal of surplus sludge. 242 Sewerage and sewage disposal. The activated sludge process. EDITORIAL. Surveyor 51, 80-2. Although few reports on activated sludge work have been published, it is known that the process is operating in about 6 places in England. Reference is made to the plant at Worcester treating 800,000 gallons per day, and belief is expressed that after the war the activated sludge process will be adopted in many places. Utilization of the sludge is also discussed. 243 Activated sludge progress. TRADE NOTE. Surveyor 51, 108. In col- laboration with DR. FOWLER'S staff at Manchester Univ., the engineering staff of JONES & ATTWOOD have been able to make great progress along scien- tific lines in the activated sludge process. Five large plants have been in- stalled and two are under construction. Diffusers, aeration, sludge settle- ment and treatment, are being satisfactorily solved. 244 The activated sludge process of sewage purification. E. ARDERN. Jour. Soc. Chem. Ind. 36, 65-8. Surveyor 51, 298-9. Jour. Am. Leather. Chem. Assoc. 12, 128-35. Chem. Abst. 11, 2517. Expt. Sta. Record 37, 286. For the purpose of comparing the effect of trade wastes, the experimental activated sludge plant previously employed on the Manchester sewage a strong trade sewage was transferred to the Withington sewage works where a purely domestic sewage is dealt with. The plant consisted of wooden casks of 200 liters capacity. Floating matter and grit was removed from the sewage by adequate detritus tank treatment. Porous tile was used for the air diffusers. 46 Abstract Bibliography 1917 The investigation extended over a period of 15 months with the following summary of results. (1) The activated sludge produced from the Withington sewage has an appreciably higher nitrogen content than either the Manchester or Salford sludge, due to some extent to the fact that the percenage of mineral matter is considerably less. (2) That, contrary to the opinion formed as the result of earlier experiments when working with a strong trade waste, the maintenance of the activity of the sludge is not dependent on the stage to which nitrification is carried. (3) That when dealing with a sewage free from inhibitory trade effluents, no appreciable loss of efficiency need be an- ticipated in this country (England) during the winter months. (4) That while the problem of sludge disposal remains to be fully developed, it ap- pears from known data that the cost of dewatering and drying will be more than repaid by the value of the resultant dried sludge. Tabulated data and analyses of the dried sludge are given. 245 Modern sewage treatment. T. C. HATTON. Jour. West. Soc. Engrs. 22, 87-100. A general review of sewage treatment work with special ref- erence to the activated sludge process. Many of the Milwaukee experiments are described, particularly those relating to different methods of aeration, sedimentation and sludge treatment, and a general summary of the results obtained are given. The practical or experimental activated sludge plants in several cities are referred to and their plans or results discussed. The author concludes by expressing his entire confidence in the process because it gives greater promise of satisfactorily solving a complex problem than any other so far introduced. 246 The purification of sewage in the presence of activated sludge, Illinois. E. BARTOW, F. W. MOHLMAN and J. F. SCHNELLBACH. Jour. West Soc. Engrs. 22, 101-9. (Discussion 109-15). The activated sludge plant at Cham- paign, 111., is described. Details are given with special reference to the settling chamber and retention period test, the amount of sewage treated daily during the different periods ranging from 61,100 g. p. d. to 177,600 g. p. d. The authors conclude that 75,000 g. p. d. could be satisfactorily treated with the present aerating and settling capacity, though double this amount could be handled in the aerating tank if additional sedimentation were provided. Sludge dewatering devices are considered. In the discussion following, which included also the paper of MR. HATTON, (Ref. 245) PROF. BARTOW, LANGDON PEARSE, PAUL RUDNICK, and others participated. 247 The Worcester (Eng.) activated sludge experiments. T. CAINK. Surveyor 51, 144. A letter to the editor to correct a misstatement in a previous article that air was delivered intermittently to the sewage through pulsating valves. This was not the case, the air being delivered continuously through- out the whole period of the experiments. 248 Brushwood as a medium for sewage filters. GEO. PHELPS. Can. Engr. 32, 117-21. Eng. Record 75, 376. Surveyor 51, 254-5. Engineer 123 337-8. Am. City 16, 604-7. Chem. Abst. 11, 2517. Expt. Sta. Record, 37, 489. A description of the North Toronto, Can., brushwood filter experiments, citing the similarity between the conditions here and those of the activated sludge process. (Cf. Ref. No. 272). 249 Notes on experiments with activated sludge at Regina, Can. J. RUSSEL ELLIS. Can. Engr. 32, 124-6. Two galvanized-iron tanks 4.5 ft. in diam. by 5 ft. 10 in. deep were used with perforated pipe covered with a loose fitting sleeve of canvas for air diffusion. The plant was operated on the fill and draw plan with cycles of 6 to 12 hours and the results indicate that the process is adapted to local conditions. The size of the plant did not warrant an attempt to determine the cost of operation. 47 The Activated Sludge Process 250 How sewage plants are operating. ANON. Munic. Jour. 42, 196-7. Re- sume of an inspection trip by officials of Pasadena, Calif., on which sev- eral cities were visited where the activated sludge process is in use. The ex- cellent results obtained by this process led them to believe that it will even- tually supersede all others where a high degree of purification is necessary. They also find that it occupies less space, costs less for construction, is abso- lutely odorless, and gives a better effluent than the Imhoff tank and sprinkling filter process. The cost of operation is greater, however, but revenue from the sale of sludge should reduce this difference in costs. They express hope that the sludge may be dried on open beds in a warm climate like southern California. (Cf. Ref. Nos. 210 and 223). 251 Activated Sludge plants at Houston, Texas. C. L. WILLIFORD. Eng. News. 77, 236-8. Two activated sludge plants with a combined capacity of 19,000,000 gallons a day, with continuous flow aeration tanks, vertical flow settling tanks, and sludge re-aeration tanks are described in considerable detail. One plant consists of four units, the other of two units, each unit having a rectangular aerating tank 280 by 18 feet with a net depth of 9 ft. 9 in., a battery of 10 vertical flow settling tanks and one sludge re-aerating tank. 627 filtros plates are contained in each aerating tank in 112 frames of 6 plates each. The ratio of aeration surface to tank surface is 1 to 7.5. Costs of construction and operation are given. 252 Activated sludge at San Marcos, Texas. H. E. ELROD. Eng. News 77, 249. Description of a plant having a capacity for treating 150,000 gal- lons of sewage daily. It consists of an aerating tank 40 by 16 by 8^ ft. deep with four rows of filtros plates in the bottom, and a settling tank 25 ft. long, 10 ft. wide, 25 ft. deep with walls having a vertical batter of 1 to 2. Effluents have a relative stability of 99% and bacterial reduction amounts to 98%. Total cost in round figures was $3,500. 253 Sink concrete cofferdam in sand for activated sludge plant. ANON. Eng. Record 75, 228-9. Description of work on the activated sludge plant at Escanaba, Mich., which will treat approximately one million gallons of sew- age daily on the continuous flow plan. Filtros plates in the ratio of 1 sq. ft. aerating surface to 8.3 sq. ft. tank surface are to be used for air diffusers. 254 Definitions of terms used in sewerage and sewage disposal practice. ANON. Eng. & Contg. 47, 168-9. Can. Engr. 32, 214-6. A report of a committee of the Am. Public Health Assoc., referring to the activated sludge process as in reference No. 202. 255 Apparatus for aerating sewage and other foul liquids. R. AMES, Bright- on, Eng. British Patent 107,937, Feb. 24, 1917. Jour. Soc. Chem. Ind. 36, 977. The sewage is treated in a rectangular tank over which is a traveling carriage running on side rails and bearing a drum with a coil of flexible piping. One end of the piping is connected to an air compressor at the end of the tank, and the end of the drum is connected to a horizontal pipe from which vertical pipes depend nearly to the bottom of the tank. Air diffusers, consisting of porous clay blocks in metal casings, are affixed to the ends of the vertical pipes. The sewage enters at the bottom of the tank through an inverted U-shaped pipe. An air pipe connected to the compressor enters the upward limb of the U-shaped pipe; thus air can be passed into the sewage entering the tank, as well as into the sewage in the tank from the diffusers. 256 Purification of sewage and other liquids. W. JONES, Stourbridge, and JONES & ATTWOOD, LT'D., Amblecote, Eng. British Patent 113,333, Feb. 26, 1917. Jour. Soc. Chem. Ind. 37, 193A. An improved form of tank for use in the activated sludge process consists of a long channel arranged as the outer coil of a spiral, with air diffusers placed along its length, either in the 48 Abstract Bibliography 1917 middle of the channel or at one or both sides. The floor is made to slope towards the air diffusers. The channel may be restricted in width at each end or at the position of the air diffusers by baffles projecting from the side walls. The channel terminates at the center in a round tank with a conical bottom, not furnished with air diffusers, in which the sludge settles at the bottom and is returned by an air lift or other means to the crude sewage inlet of the channel. Another form of the channel consists of a to and fro rectangular arrangement, with the sludge deposit tank at one end. 257 Activated sludge tests at Pasadena, Calif. NEWS ITEM. Eng. News 77, 373. The aerating chamber has a capacity of 50,000 gallons per day with a 4 hour aerating period. There are two settling tanks, a sludge pump and a sludge aerating tank. The tests are in charge of MR. R. V. ORBISON who reports gratifying results and that a plant to handle 3 to 6 million gallons is under consideration. 258 Worcester's 35-year grapple with sewage disposal problems. W. L. BUTCHER. Eng. News 77, 384-5. Chem. Abst. 11, 2517. Reviews the history of sewage disposal at Worcester (Mass.) and refers to the contem- plated activated sludge experiments. 259 San Marcos, Texas, activated sludge plant. G. B. ZIMMELE, Munic. Jour. 42, 333-5. Chem. Abst. 11, 1225. This is believed to be the first acti- vated sludge plant to go into regular operation treating the entire volume of sewage of a city. Operations were commenced April 27, 1916. The raw sewage is settled in a tank 40 ft. diam. by 9 ft. deep, with inflow and outflow at different points, which serves to remove the gross material. From this it flows to the aerating tanks, 4 in number, 39 ft. by 4 ft. by 8 ft. extreme depth, and connected in series. Air is diffused through filtros plates set in concrete with special provision for draining the air chamber beneath. Aerating period 2.5 to 5 hours. The sedimentation chamber is 20 ft. by 10 ft. and has a depth of about 25 ft. with bottom slopes of 2 to 1, a period of 1 to 2 hours being allowed for settling. Baffles are also provided in this tank. About 150,000 gallons of sewage are treated daily, from a population of about 5,000. The blower has a capacity of 230 cu. ft. per minute. 260 Worcester sewage treatment history. EDITORIAL. Eng. News 77, 406. It is to be hoped that Worcester (Mass.) will give the activated sludge process as full a test as may be needed to determine its suitability for local conditions. The Brockton (Mass.) activated sludge experiments are also referred to. 261 Operate continuous flow activated sludge plant. ANON. Eng. Record 75, 380-1. Abstract of article by BARTOW, MOHLMAN and SCHNELLBACH, covered by references 211, 246. 262 Activated sludge plant for Chicago packinghouse district. NEWS ITEM. Eng. News. 77, 454. An activated sludge plant for treating the sewage and industrial wastes from the Chicago packinghouse district has been recommended by the committee appointed to consider the question. The cost is estimated at $3,500,000 with an annual operating expense of $800,000. The committee was composed of LANGDON PEARSE, Division Eng. of the Sanitary District of Chicago, and DR. W. D. RICHARDSON, chemist for the packinghouse companies. 263 Experiments relating to the activated sludge process of sewage purifi- cation. W. T. LOCKETT. Jour. Soc. Chem. Ind. 36, 264-9. Jour. Am. Leather Chem. Assoc. 12, 199. Chem. Abst. 11, 2128. Some small scale ex- periments were made with sewage of "average" strength, which contained a variety of trade wastes, some of them of inimical character. Special atten- tion was given to (1) the volume of air required for the efficient working of 49 The Activated Sludge Process the process, (2) possible means of effecting economy of air, (3) experi- ments relating to the maintenance of sludge activity and (4) the bacterio- logical nature of the effluent. The conclusions reached were (1) air in ex- cess of that required for adequate mixture and circulation of the sewage and sludge is of no material advantage. (2) Sludge and sewage in the pro- portions of 1 : 4 required more air for equivalent results than when the proportion was 2 : 3. Intermittent aeration suggested by MR. W. MAKEPEACE was tried and the fact definitely established that sewage can be purified with reduced expenditure of air by this method, but the time necessary is materi- ally increased and larger tank capacity would be required. The evidence thus far accumulated does not warrant a general recommendation of this method but further experiments are in progress which may eventually have practical importance. (3) Activity of the sludge can be recovered by pro- longed aeration, even after standing for several days. (4) Although bac- terial removals of 99% and upwards were obtained, and effluents of excep- tional clarity and eminently satisfactory from a chemical point of view also obtained, B. coli above 1,000 per c. c. were present when the raw sewage was correspondingly high in these organisms. 264 The activated sludge process. EDITORIAL. Surveyor 51, 297. Comment- ing upon the paper of DR. E. ARDERN (Ref. No. 244) it is noted that the process adapts itself to the needs of particular cases. Domestic sewage, trade wastes, storm flow, etc., can be handled and the extent to which purification is carried can be adjusted to a nicety. Such conditions indicate the possibility of bringing down operating costs and increasing the application of the process. 265 The activated sludge process of sewage purification. E. ARDERN. Sur- veyor 51, 299-300. In the discussion of this paper MR. J. H. HOSEASON, MR. S. E. MELLING, MR. W. THOMPSON and MR. P. GAUNT brought up ques- tions of sludge digestion, possible recovery of the N as sulphate of ammonia, of using peat as a dilutent for the sludge, and the question of more or less complete nitrification on the saving of time in the process. 266 Activated sludge plant at Edmonton, Canada. ANON. Can. Engr. 32, 265. An account of the plant and the experimental work done at Edmonton, taken from a pamphlet on activated sludge by G. T. HAMMOND. Details of aerating chambers, motor equipment, and air plant are given. 267 Is the recovery of nitrogen in sewage sludge practicable? W. R. COPE- LAND. Jour. Ind. Eng. Chem. 9, 374-6. Jour. Soc. Chem. Ind. 36, 517-8. Chem. Abst. 11, 2008. Expt. Sta. Record 37, 425. Summing up the whole situation, dried sludge has a market value of $9 to $15 per ton of material (present figures) with 10% moisture. The total cost of production and placing it on the market will be $8 to $12 per ton, depending on local con- ditions. Large plants may reduce this cost as a result of further experience. 268 Biochemical treatment of sewage with special reference to the acti- vated sludge method. G. T. HAMMOND. Jour. Ind. Eng. Chem. 9, 399-403. Chem. Abst. 11, 2008. A very concise and complete historical sketch is given on the biochemical treatment of sewage and its newest application in the activated sludge process. Though it is yet in the experimental stage, this method seems very promising. Many problems are yet to be solved, par- ticularly methods of aeration, sludge disposal, and biological control. 269 Sewage treatment units. J. W. ALVORD, H. P. EDDY, and G. W. FULLER. Munic. Jour. 42, 526. In a report to the North Shore Sanitary District the authors give the following basic data used by them in preparing plans for sewage treatments considered in the report. "Activated sludge Minimum period of aeration (during maximum rate of flow), 3 hours, 1 2-3 cu. ft. of air per gallon of sewage treated in aerating tanks 15 ft. deep. Sedimentation j 50 Abstract Bibliography 1917 tank providing one hour's sedimentation at maximum rate. Sludge storage tank, capacity for 10 days output. Sludge drying bed 3 1-3 sq. ft. per capita; or sludge presses for % to 1 ton of dry sludge per 10,000 people." 270 Activated sludge vs. tanks and filters. EDITORIAL. 'Surveyor 51, 359. Comment on paper by H. P. EDDY. (Ref. No. 217). Relative areas of land necessary will govern choice in most cases. Small loss of head in the activated sludge process will be in its favor, as well as the superior quality of the effluent. 271 The activated sludge process for handling packingtown trade wastes. LANGDON PEARSE and W. D. RICHARDSON. Report to the Board of Trustees of the Sanitary District of Chicago, pp. 36. (April 16, 1917). Suggestions or recommendations include grit chamber, with additional fa- cilities for skimming grease; coarse bar followed by fine screens; aerating tanks in 32 units, each 160 ft. by 38.333 ft. by 16.5 ft. deep, divided longitud- inally and of 1.5 million gallons daily capacity; air diffusion through filtros plates, the area of which to the superficial area of the tank is about 1 to 6; air washers to be installed ahead of compressors; continuous flow system with 8 hour contact period and 4 cu. ft. of air per gallon of sewage; settling tanks of the circular Dortmund type, 30 ft. inside diam. with hopper bottom on a slope of 60 degrees, and with a water depth of 33.5 ft.; settling period, 1 hour; sludge handling open to various expedients but from the standpoint of the recovery of values, filter pressing and heat drying only have been demonstrated. Plant cost estimated at $3,751,535, with an annual operating cost of $821,947, of which $270,000 is for power. Revenues expected per mil- lion gallons of sewage are: 600 to 1,000 Ibs. dry screenings; 47 Ibs. grease, and 1,500 to 2,500 Ibs. dry sludge. Tables, maps, analytical and other data are given. 272 The North Toronto brushwood filters. S. H. ADAMS. Engineer 123, 375. Surveyor 51, 458. Reference is made to the experiments with brush- wood filters and some fundamental differences between this method of sewage purification and the activated sludge process are pointed out. The principal reason for their success in Canada is that their domestic sewage is only about half the strength of that in England. (Cf. Ref. No. 248). 273 Air diffusion in activated sludge. W. S. COULTER. Eng. News-Record 78, 255-6. Surveyor 51, 506-7. Chem. Abst. 11, 2008. Experiments indicate the possibility of prolonging the air and sewage contact period by a downward jet entraining air. 274 Separation and settlement of solids and semi-solids from sewage and analogous liquids. W. CLIFFORD, Wolverhampton, and JONES & ATTWOOD, L'TD., Amblecote, Eng. Brtish Patent 115,872, May 17, 1917. Jour. Soc. Chem. Ind 37, 440A. A tank in the form of an inverted cone is used, into which the sewage is brought by a horizontal pipe, the mouth of which directs the current into a wide bucket suspended in the upper part of the tank. This has the effect of breaking up the currents and causing eddies which pass upwards and out of the bucket. These eddies are prevented from spread- ing by a guard wall of much larger diameter, surrounding the bucket and carried upwards above the level of the liquid in the tank. The guard wall is open at the bottom, and the liquid passes from it at a low velocity and without any disturbing effect on the deposited sludge in the bottom of the tank. The liquid finally passes out of the tank over a weir at the circum- ference. The sludge is withdrawn through a pipe in the apex of the cone. 275 Decanting and settling chemcal and other liquids. W. CLIFFORD, Wolver- hampton, and JONES & ATTWOOD, LT'D., Amblecote, Eng. British Patent 117,472, May 24, 1917. Jour. Soc. Chem. Ind. 38, 497A. Chem. Abst. IS, 502. In the separation and settlment of suspended matters from chemical and 51 The Activated Sludge Process like manufacturing liquids, providing at or near the top of the settlement tank a bucket or like vessel by which the liquid from the inlet is directed upwardly into a relatively large body of liquid within an open-bottomed guard chamber or well, which directs the slowly moving liquid downward into the body of the liquid in the tank. In a modification, the bucket or like vessel is replaced by a funnel-shaped vessel carried at the end of the inlet pipe, and adapted to direct the flow upwards. (Cf. U. S. Patent 1,343,764. Ref. No. 565). 276 Marked advance in treating sewage from packinghouses. G. B. ZIMMELE. Eng. News-Record 78, 436-7. Surveyor 52, 252. Chem. Abst. 11, 2246. Expt. Sta. Record 37, 694. An experimental activated sludge plant at Fort Worth, Tex., is equipped with revolving screen and settling tanks, treating packinghouse wastes containing 3000 to 6000 p. p. m. suspended matter. Even when screened and settled, this sewage is too strong for the activated sludge process, and must be diluted with either 4 parts of water or 1 part of treated effluent. 35% sludge during aeration is better than 25%, and separate aera- tion of the sludge is advisable. The effluent is stable and can be re-used in the packinghouse. The dewatering of the sludge by acidulation and heat has given great promise; this method reducing the water content from 99 to 85%, and increasing the ammonia content from 8 to 11%. (Cf. Ref. No. 291). 277 The operation of the activated sludge type of sewage plants. G. B. GAS- COIGNE. Ohio Eng. Soc. Proc. (1917) pp. 79-86. A general description of the process, the necessary plant, its operation, the sludge dewatering problem, estimated costs, and the method of recording results are given. 278 Sewage treatment: activated sludge system. JONES & ATTWOOD, L'TD. Booklet No. 52, pp. 18. (June, 1917.) A detailed description of the acti- vated sludge plant at Worcester, (Eng.) covering structural features; air compression, distribution, and diff users ; operating data ; degree of purification obtained and running costs. The pulsating gear for supplying air intermit- tently is described, and some data on the fertilizing properties of activated sludge given. 279 Report of the city engineer upon an experiment with the activated sludge process of sewage purification. THOS. CAINK. Pamphlet pp. 12. (June 13, 1917.) Deals particularly with the terms between the contractors and the city of Worcester (Eng.), and compares costs of the activated sludge process with that of the old system. 280 Activated sludge experimental work at Milwaukee. T. C. HATTON. Can. Engr. 32, 491-4. Chem. Abst. 11, 3074. Data from the 3rd. Ann. Report of the Milwaukee Sewerage Com. Results of the work are given with details of the sludge pressing experiments. It is concluded that for Milwaukee sewage, the activated sludge process will work with 2 cu. ft. of air per gallon of sewage. With a 4 hour aeration period and 15 to 20% sludge present, 40 to 50 minutes sedimentation is required and a maximum horizontal velocity of 3 ft. per min- ute, and vertical velocity under 8 inches per minute. Dried sludge contains 4.5 to 5% ammonia. 281 Activated sludge in India. NEWS ITEM. Eng. News-Record 78, 535. DR. G. J. FOWLER has reported on the possibility of dealing with the sewage of Sakchi, India, a settlement of the Tanta Steel Works with a future popula- tion of 150,000, by the activated sludge process. 282 The activated sludge process at Worcester, (Eng.) THOS. CAINK. Sur- veyor 51, 546-8. The tests undertaken by JONES & ATTWOOD (Ref. Nos. 172 and 284) were started April 25, 1916. The sewage is screened and grit removed before entering the aerating tanks, which are 18 ft. deep, baffled, and 52 Abstract Bibliography 1917 provided with porous tile diffusers. Aeration period 8 hours, using 0.8 cu. ft. of air per gallon of sewage. Two settling tanks have hopper bottoms with 60 degree slopes, where the sludge is detained for 2.25 hours, being then returned by air lifts. The sludge may be dried on land if applied in layers of one inch, without development of odors. Conditions of tests were fully met. Plant and results are more completely described in a pamphlet issued by JONES & ATT- WOOD. (Ref. No. 278.) 283 The activated sludge process at Worcester, (Eng.) EDITORIAL. Surveyor 51, 544-5. Comment on the paper by T. CAINK (Ref. No. 282), who was responsible for the activated sludge installation. Cost data should be given in detail. Porous plate diffusers are most successful in England. 284 Activated sludge plant at Worcester, (Eng.) JONES & ATTWOOD. Sur- veyor 51, 549. Chem. Abst. 11, 3074. Complete results of the experi- mental work at Worcester are given. The tank used was 80 ft. long by 72 ft. wide, divided into 9 longitudinal sections of which 5 were used for aeration and 4 for settling. Air was diffused through porous tiles and no trouble through clogging has been encountered with clean air. The amount of sewage treated on the continuous flow plan varied from 600,000 to 1 million gallons per day. An interesting temperature chart is given, showing sewage, effluent and air temperatures during the winter months. 285 Apparatus for aerating sewage and other foul liquids. R. AMES, Brighton, Eng. British Patent 115,933, June 19, 1917. Jour. Soc. Chem. Ind. 37, 440A. The sewage enters a channel located alongside a treatment tank, from which it is siphoned into a trough which travels over the tank. The sewage flows into the tank through vertical pipes with bell-mouths, which depend from the trough to the bottom of the tank. Other pipes pass down the centers of the vertical pipes and carry horizontal fans at their lower ends, adapted to revolve inside the bell-mouths, whereby vortices are created and air drawn down the pipes. The blades of the fans are hinged in order to permit of the fans being drawn up the pipes when they require cleaning. A further supply of air is obtained through a pair of tubes extending from the surface to the inside of each bell-mouth. 286 Recommend 50,000,000 gallon activated sludge plant. ANON. Eng. News- Record 78, 594-6. Eng. & Contg. 48, 28-30. Chem. Abst. 11, 3074. Joint committee representing the Chicago Sanitary District and the packers recom- mend a 50 million gallon per day activated sludge plant for treating stockyards sewage, but advise a six months trial of a 1.5 million gallon unit. Digest of the report of PEARSE and RICHARDSON, Ref. No. 271. 287 Activated sludge bibliography. NEW LITERATURE NOTE. Eng. News- Record 78, 604. Eng. & Contg. 49, 354. Chem. Abst. 11, 3076. Expt. Sta. Record 38, 691. Refers to the first edition of this bibliography. 288 Milwaukee air-diffusion studies in activated sludge. C. H. NORDELL. Eng. News-Record 78, 628-9. Chem. Abst. 11, 2517. The problem is to pro- long contact with sewage by subdividing the air into small enough bubbles so that their speed of ascent is lessened. From 25 to 50% of the tank area must be diffusing area or the bubbles will coalesce rapidly. This fact eliminates the use of nozzles and mechanical beaters. Further studies are being made to perfect fine-bubble diffuser plates. 289 Purification of tannery wastes. H. B. HOMMON. Jour. Am. Leather Chem. Assoc. 12, 320. In discussion of this paper, V. KADISH stated that the activated sludge process had been tried at a chrome tannery in Milwaukee. It worked well with soak liquors and also sulphide liquors if not too concen- trated. 53 The Activated Sludge Process 290 Buffalo Meeting of the Am. Inst. Chem. Engrs. ANON. Met. & Chem. Eng'rg. 17, 6. Abstract of a paper on the activated sludge process by DB. E. BARTOW. (Cf. Ref. No. 310.) 291 Treating packinghouse sewage. G. L. NOBLE. Eng. News-Record 79, 33. A letter to the editor to correct an article by G. B. ZIMMELE, (Ref. No. 276) refuting the statement that the effluent from the activated sludge sewage plant is re-used in the packinghouse like ordinary water. It is also suggested that the statement respecting acid treatment of the sludge, be con- fined to Fort Worth conditions only. 292 Sewage aeration and activated sludge. ANON. Engineering 104, 16-17. A general review of the origin and development of the activated sludge process. Refers to the work of BLACK and PHELPS at Brooklyn; CLARK at Lawrence; FOWLER and ARDERN & LOCKETT at Manchester; DUCKWORTH and MELLING at Salford; BARTOW and MOHLMAN at Urbana; HATTON at Milwau- kee; NOBLE and RUDNICK at the Chicago stockyards; the plants at Baltimore, Houston, Brockton; and the trial of the process on tannery wastes at Norwood, Mass. 293 Worcester (Eng.) activated sludge plant. NEWS ITEM. Surveyor 52, 10. The Worcester City Council accepts recommendations made by the water and sewage committee to purchase the activated sludge plant installed by JONES & ATTWOOD for experimental purposes. 294 Air lifts for activated sewage sludge. T. CAINK, Worcester, Eng. British Patent 116,580, July 7, 1917. Jour. Soc. Chem. Ind. 37, 484A. A vertical pipe is arranged with its lower openings near the floor of the settling chamber, and its upper end surrounded by an annular chamber having a weir at one side over which the sewage flows to another chamber, and thence to the aerating tank. Air is supplied through a small concentric vertical pipe having its lower end terminating in a porous air diffuser, through which the air rises into the lift pipe, carrying the sludge with it. A gage-tube is provided on the annular chamber, so that the height of the liquid over the weir, and consequently the rate of flow, is indicated. The proportion of sludge is indicated by the amount of solid matter settling in the gage-tube. 295 Activated sludge process of sewage purification at Worcester, Eng. T. CAINK. Engineering 104, 49-51. Surveyor 52, 51-5. Jour. Soc. Chem. Ind. 36, 938. Can. Engr. 33, 30; 38-40. Chem. Abst. 11, 3358. A paper pre- sented at the annual meeting of the Assoc. of Mgrs. of Sewage Disposal Wks., July 7, 1917, in which a detailed account of the plant is given, accompanied by designs which show the lay-out and construction. The tank used has a ca- pacity of 626,000 gallons and is divided into 28 rectangular bays, 20 for aera- tion and 8 for settling. The floor is on the ridge-and-furrow principle with porous tile diffusers in the furrows. These diffusers are placed 5 ft. apart in the first bays of the tank receiving the raw sewage, and 10 ft. apart in the other bays. The floors of the settling bays are in the form of inverted pyra- mids, in the apices of which are air lifts whereby the sludge is raised to a main which conveys it back to the sewage inlet channel. Excess sludge is drawn off to a sand filter for drying. The purified effluent is decanted from the settling tank. The volume of sewage treated on the continuous flow plan is 750,000 gallons per day, with 8 hours aeration and 2.5 hours settling. The area of the diffusers is about 1-10 the area of the aeration bays, and the vol- ume of air used is 0.8 cu. ft. per gallon of sewage. The sludge when drained, contains 95% water. The analyses of the sewage and effluent are respectively as follows in p. p. m.: Solids in suspension, 104, trace; solids in solution, 1510, 1430; NaCl, 689, 677; free ammonia, 20, 26; albuminoid ammonia, 5.7, 1.7; O absorbed in 4 hours, 21, 5.6; nitrates and nitrites, none, none. Dissolved O absorbed by the effluent in 5 days, 6.3 ; stable for 5 days by the incubation test. The standard to which it must conform is that it must be incapable of putrifica- 54 Abstract Bibliography 1917 tion and shall not contain more than 40 p. p. m. suspended solids. This has been met in dry weather, but not with a wet weather flow. 296 A resume of the present position of the activated sludge process of sew- age purification. E. ARDERN. Jour. Soc. Chem. Ind. 36, 822-30. Engi- neering 104, 134. Engineer 124, 94. Surveyor 52, 140-2. Chem. Abst. 11, 3357. The paper deals more particularly with typical installations with which the author is familiar, or respecting which authentic information is available. The English plants considered are those at Manchester, Salford, Worcester, and Stamford, while the following American plants are mentioned: Mil- waukee, Houston, and the 111. State Water Survey. A summary of the progress of the method is given, together with intimations of what may be expected in the future. 297 The activated sludge process. S. BARWISE. Surveyor 52, 40. Describes the principles involved in this method of sewage treatment, and specu- lates as to the various methods of applying these in the future; for example, in the form of a new percolating filter. 298 Activated sludge treatment at Worcester. (Eng.) EDITORIAL. Surveyor 52, 45-6. Remarks on the paper of MR. T. CAINK (Ref. No. 295) with the intimation that further investigation of the effect of tarry liquids which upset the plant at Worceser and elsewhere would be interesting. 299 Assoc. of Mgrs. of Sewage Disposal Works Meeting. Discussion of papers. Surveyor 52, 67. Referring to the Worcester activated sludge experi- ments, MR. T. CAINK describes the incident of large quantities of tarry matter entering the tanks, and interfering seriously with the purification. The O absorption in the sewage rose from 30 or 40 p. p. m. to 140, and in the effluent from 8 p. p. m. to 84. The latter contained only 28 p. p. m. of suspended matter, however, and was stable for 5 days. Antiseptics of this or any other kind should be kept from the sewers, as they operate injuriously against any system of bacterial purification. MR. W. H. DUCKWORTH said that personally he believed there was a great future for the activated sludge process from several points of view, and agreed with Mr. Caink that it was probably not equalled, certainly not surpassed. 300 Activated sludge process of sewage disposal. T. CAINK. Surveyor 52, 87-8. Replies to questions raised in connection with the author's paper on the Worcester activated sludge experiments. (Ref. No. 295.) Refers to air requirements, quantity of trade waste in the sewage, contains an estimate of construction and operating charges for a new plant, suggestions for the design of aerating tanks so as to get an efficient flow, and means for removing the sludge. 301 Activated sludge sewage purification plant near Worcester. (Eng.) Engineering 104, 118-9. Chem. Abst. 12, 1224. A plant for an Admiralty Airship Station with a population of 400 is described and illustrated. Plans and some tabulated data are given. 302 Dewatering sludge at Urbana Sewage Station. ANON. Eng. News- Record 79, 269. Abstract from a portion of a paper on the activated sludge process by DR. E. BARTOW. (Cf. Ref. No. 310.) 303 Filtros plates made best showing in air diffuser tests. ANON. Eng. News-Record 79, 269-70. Abstract from a portion of a paper on the activated sludge process by DR. E. BARTOW. Competitors were basswood plates and perforated pipes. (Cf. Ref. No. 310 and 367.) 304 Apparatus for purifying sewage, etc. LOCKETT and HERRING- SHAW. Brit- ish patent applications 11,561; 11,562, Aug. 11, 1917. Jour. Soc. Chem. Ind. 36, Suppl. 79. 55 The Activated Sludge Process 305 Changes in Cleveland sewage plans. ANON. Eng. News-Record 79, 308-12. Surveyor 52, 342. Chem. Abst. 11, 3358. The activated sludge process is not recommended because of lack of funds, because sufficient treat- ment for some time to come should be afforded by screening, chlorination, and dispersion of the sewage into the lake through the new submerged multiple outlet pipe, and because valuable local data on sludge handling may be expected in the near future. At some future date the indications are that the activated sludge process should be considered for lake shore sites. 306 Fine screens or Imhoff tanks? EDITORIAL. Eng. News-Record 79, 290. A consideration of the different recommendations made for sewage dis- posal at Cleveland, O. The activated sludge experiments and the high hopes expressed for this process are referred to. 307 The activated sludge process. EDITORIAL. Surveyor 52, 137-8. Comment on the paper by DR. E. ARDERN (Ref. No. 296) in which attention is called to the fact that sewage in most American cities is very weak, the dry weather flow in some cases amounting to 60 to 120 gallons per head, while in English cities it may run from 20 to 50 gallons per head. Therefore, figures given as to cost of air per million gallons of sewage treated in the two countries are very apt to be misleading, and the suggestion is made that a safer method of comparison would be to express such figures in terms of popu- lation, say per thousand people. 308 Purification of sewage and other liquids. W. JONES, Stourbridge, and JONES & ATTWOOD, L'TD., Amblecote, Eng. British Patent 122,428, Aug. 24, 1917. Jour. Soc. Chem. Ind. 38, 197 A. Chem. Abst. 13, 1734. Sewage is treated with bacterial (activated) sludge and the mixture agitated by the injection of air. The sludge is separated continuously or intermittently from the liquid, and passed to another tank where its activity is intensified by the injection of air, and the active sludge is returned to the treating tank. The separation of the sludge is effected in a series of tanks so arranged that the mixture flows through them at varying rates, and sludges of varying specific gravity are separated and deposited in separate sludge pits connected with the settling tanks. All the operations form a continuous cycle. 309 Fertilizer. G. J. FOWLER. Danish Patent 22,389, Aug. 27, 1917. Chem. Abst. 12, 512. Air is blown through masses obtained in the purification of sewage in the presence of bacteria. The product is then heated and dried, and then mixed with small quantities of a solid containing bacteria beneficial to plant life, so that the final product contains bacteria favorable to plant growth in addition to large quantities of nitrogen. (Cf. Brit. Pat. 8,397, Ref. No. 51; U. S. Pat. 1,294,080, Ref. No. 454; Can. Pat. 189,921, Ref. No. 467.) 310 Purification of sewage by aeration in the presence of activated sludge, III. E. BARTOW. Jour. Ind. Eng. Chem. 9, 845-50. Jour. Soc. Chem. Ind. 36, 1146. Jour. Am. Leather Chem. Assoc. 12, 563. Trans. Am. Inst. Chem. Engrs. 10, 159-75. Chem. Abst. 11, 3357. Gives further results obtained at the sew- age experiment station of the 111. State Water Survey. A septic tank was reconstructed into an activated sludge tank to handle about 200,000 gallons per day on the continuous flow plan. A bar screen with % in. openings and a two-compartment grit chamber 34 ft. long was provided. The aerating tank is 36 l /2 ft. by 17 ft. by 9% ft. deep, divided by 3 baffles into 4 compartments, thus giving the sewage a flow of about 140 ft. The settling chamber is 10 Ms ft. by 6 ft. by 11 ft. deep with sloping walls, and provided with an air lift. Filtros plates supported on T-bars embedded in concrete, in sets of 6, serve as air diffusers. Aerating periods of 6, 5, and 4 hours, treating 144,000, 170,000, and 216,000 gallons respectively, with settling periods of 24, 31, and 37 minutes were tried. About 2 cu. ft. of air per gallon of sewage was necessary to pro- duce a stable effluent. Various modifications of the operating details were tried and the results given in the tabulated data. For comparing different air 56 Abstract Bibliography 1917 diffusers the 3 ft. 2 in. square by 8 ft. deep concrete tanks used in former experiments were employed. (Ref. No. 83.) "A" tank was fitted with per- forated pipes having 1-25 in. holes spaced 2 in. apart, and staggered at an angle of 45 degrees from the top of the pipe. "B" tank contained basswood blocks covering an area of 1 ft. 3 9-16 in. by 2 ft. 3 in. "C" tank contained 3 sq. ft. of filtros designated as "fine," and "D" tank 3 sq. ft. designated as "coarse." These tanks were operated during three periods of 15, 20, and 35 days, all conditions being maintained as nearly identical as possible. The re- sults obtained from these comparative tests indicate the superiority of filtros, with little if any difference between the two grades. In the sludge dewatering experiments drying on sand beds was not satisfactory, nor did filter pressing give a good cake even with a fairly concentrated sludge. The Koering rotary pressure drum filter gave unsatisfactory results on the first trial, further tests being prevented by an accident. Experiments with a modified basket type of centrifuge and a cream separator were encouraging, but a specially con- structed centrifuge, designed by the Tolhurst Machine Works, gave the best results and indicated that a large machine would reduce the water content of the sludge to about 88%. Drying tests pointed to a practical way of dewater- ing further. 311 Some characteristics of the activated sludge process of sewage treatment. A. L. FALES. Munic. Engrg. 53, 108. Can. Engr. 33, 230. A general dis- cussion of the process giving the following requisites as essential for the suc- cessful treatment of sewage by this process. (1) Correct amount of bacterially active sludge; about 25%. (2) Supply of oxygen to promote growth; about 1.75 cu. ft. of air per gallon of sewage. (3) Proper aeration period; about 4 hours for ordinary sewage. (4) Optimum temperature for bacterial action. 312 Comparative tests of air diffusers and devices for dewatering activated sludge. ANON. Eng. & Contg. 48, 217-20. Can. Engr. 33, 339-41. Chem. Abst. 11, 3074. Abstract of a paper by DR. E. BARTOW presented at the Buffalo meeting of the Am. Inst. Chem. Engrs. Filtros plates, perforated pipes and wood blocks were tried, filtros proving most satisfactory. Centri- fuges reduced the moisture content of the sludge to 85-88%. (Cf. Ref. Nos. 310 and 367.) 313 Jersey City water supply clean-up proposed. NEWS ITEM. Eng. News- Record 79, 522. Diversion of sewage below Boonton dam with activated sludge plant and chlorination recommended. 314 Apparatus for aerating sewage. GRIFFITHS & HARTLEY. British Patent Application 13,374, Sept. 18, 1917. Jour. Soc. Chem. Ind. 36, Suppl. 95. 315 Activated sludge plant proposed. NEWS ITEM. Munic. Jour. 43, 291. To treat the sewage discharged into the Rockaway river, the activated sludge process is recommended for the reasons stated by G. A. JOHNSON, that the effluent obtained will be highly satisfactory as far as physical and chemical characteristics are concerned. Low electric power cost and the possibility of disposing of the sludge at a profit, justifies its adoption on economic grounds. 316 Brockton (Mass.) activated sludge plans. NEWS ITEM. Eng. News- Record 79, 551. Plans for the proposed activated sludge plant are being made by H. S. CROCKER, city engineer, but will probably not be sufficiently advanced for bids until 1918. Plant will have a capacity of 3 million gallons daily, with a 4 hour running-through period. 317 Fifty million gallon plant recommended for Chicago stockyards. EDITOR- IAL. Surveyor 52, 253. Abstract of a pamphlet issued by the Sanitary District of Chicago (Ref. No. 271) containing the report and recommendations of RICHARDSON and PEARSE for a 50 million g. p. d. activated sludge plant for Packingtown. 57 The Activated Sludge Process 318 The treatment of trade wastes. EDITORIAL. Surveyor 52, 246. Mentions successful experiments for treating very strong packinghouse wastes at Fort Worth, Texas, by the activated sludge process, and comments on the proposed 50 million plant at the Chicago stockyards. 319 Various methods of de watering activated sludge. DR. E. BARTOW. Munic. Eng'rg. 53, 148-9. Sand beds, filter presses, the Koering rotary drum, and centrifuges were considered. (Cf. Ref. No. 310.) 320 Experiments on sewage purification by the activated sludge process, A. CRONIN. Austral Pharm. Notes (Oct. 1, 1917) 18-20. Jour. Soc. Chem. Ind. 37, 106A. Chem. Abst. 12, 2033. The first trial was made at Sydney, Aust., in 1916, the plant consisting of 3 wooden tanks of 500 gallons capacity each, air being supplied through perforated pipes covered with broken stone. Two of the tanks were seeded with sludge from contact beds, but this method proved a failure. In the third tank raw sewage was treated in the usual way, 3 days aeration being followed by 15 hours settling. An- alyses made after 2, 3, and 4 months working gave practically concordant results, the purification being about 99% in suspended solids, 92% in organic N, and 84% in O absorption. All the effluents were stable by the methylene blue test and no odor was given off during treatment. A larger tank of 10,000 gallons capacity was then constructed of concrete, and has been in continuous operation since Nov., 1916, on the fill and draw plan. The aera- tion period at starting was 4 days, then 3 days, then 20, 10, 7, 6, and 5 hours. After 8 weeks the accumulated sludge occupied 20-25% of the capacity of the tank. 5 hours aeration did not give good results, so after 6 months operation the aerating period was fixed at 6 hours with 2 hours settling. Purification was 96% in suspended solids, 87.7% in organic N, and 86.3% in O absorption. The effluent was odorless but had a faint "peaty color," and was stable after the first three weeks working. Air used was 4.8 cu. ft. per gallon of sewage. The sludge contained 66% (?) of moisture and dried readily on sand. An analysis calculated to 10% moisture showed total N, 3.2%; phosphoric acid, 2.7%; potash, 0.35%. 321 Comparative tests of air diffusers. ANON. Surveyor 52, 528. The re- sults of competitive tests of wood blocks, perforated pipes and filtros plates, indicated the superiority of the latter. From DR. E. BARTOW'S paper, reference No. 310. 322 Activated sludge process for the Stockyards. ANON. Munic. Jour. 43, 377-9. Digest of the report of PEARSE and RICHARDSON on the proposed activated sludge plant for treating packinghouse wastes. (Cf. Ref. No. 271). 323 Machinery in sewage treatment. EDITORIAL. Munic. Jour. 43, 381. Com- ments on the report of PEARSE and RICHARDSON on the 50 million gallon plant proposed at Chicago, and points out the large amount of machinery required in the activated sludge process as compared with other methods, as well as the skill required for its operation. 324 Removal of activated sludge. T. C. HATTON. Munic. Jour. 43, 382. Sur- veyor 52, 445. A Dorr thickener was used in a 13 ft. diam. tank, re- moving the sludge continuously to a central draw-off, and promises to be successful. The sludge is prevented fiom settling on the slopes of the hopper bottom and becoming septic. 325 Preliminary treatment of sewage: fine screens. EDITORIAL. Surveyor 52, 333. It is mentioned that the activated sludge process was given due consideration at Cleveland, O., but was rejected as not suitable under present existing conditions. 58 Abstract Bibliography 1917 326 Notes on activated sludge with particular reference to the treatment of packinghouse wastes. LANGDON PEARSE. Can. Engr. 33, 358-9. A paper presented at the meeting of the Am. Pub. Health Assoc. on Oct. 18, 1917. The sewage testing station of the Chicago Sanitary District is described, and the results obtained up to March, 1917, show that the sewage should be screened through 30 mesh, as it will then by 8 hours aeration produce a stable effluent in summer with 4 cu. ft. of air per gallon, in tanks 16.5 ft. deep. 6 cu. ft. of air or more, may be required in cold weather to produce equivalent stability. Air distribution was through filtros plates set in cast-iron boxes; ratio, 1 to 6. Recoveries per million gallons of sewage were as follows: Grease as scum, 360 Ibs.; as grease, 47 Ibs.; screenings, dry basis, 600-1000 Ibs.; sludge, dry basis, 2000-3000 Ibs. Requirements for Fort Worth, Texas, packinghouse sewage plants are compared with those for Chicago. The ar- rangement and design of the tanks; methods of baffling, agitation, and air distribution; sludge settling and treatment, touching on the effect of acid on activated sludge from different sources; and stability of effluent are consid- ered. The plants herein referred to have been remarkably free from odor. Typical analyses of sewage, screenings, and sludge are given, and the author expresses the opinion that the activated sludge process offers the best promise of treating packinghouse wastes, and recommends a unit plant of 1.5 million gallons daily capacity, so as to obtain large-scale working results. (Cf. Ref. Nos. 271, 327, 337 and 371). 327 Activated sludge to solve packinghouse wastes problem. LANGDON PEARSE. Eng. News-Record 79, 777-8. Chem. Abst. 12, 75. At Chicago, 4 cu. ft of air per gallon of sewage in summer, and 6 cu. ft. in winter, is sufficient to stabilize the effluent. Filtros plates appears to be the best material for air diffusion, though perforated pipes were tried but they required more air. The ratio of gross area of filtros plates to tank area at Chicago was 1 to 6.3 ; net area 1 to 8. At Fort Worth, Texas, 1 to 7 has been used. Settling period may be 0.5 to 1 hour, and bottom slopes should be 60 degrees from the horizontal. Velocities should be low. For 9 months, with screened sewage, about 46,500 gallons of liquid sludge having 99.2% water, was obtained per mil- lion gallons of sewage, which is equivalent to 2,420 Ibs. of dry solids. The screenings, on 30 mesh, varied from 500 to 1,200 Ibs. of dry material. Plain sedi- mentation reduces considerably the moisture content of the sludge, which contains on a dry basis from 5 to 6% N, with an estimated value of $12 to $18 per ton. (Cf. Ref. Nos. 271, 326, 337 and 371). 328 The treatment of sewage by aeration and activated sludge. ANON. Engin- eering 104, 444. Chem. Abst. 12, 1224. Comments on efficient air dif- fusion and aeration; the progress of the activated sludge work in America, with special reference to Milwaukee; the work at Sheffield, Eng.; and on DR. E. ARDERN'S paper. (Ref. No. 296). Operating costs and sludge treat- ment are discussed, including the DICKSON yeast process of dewatering. 329 New Haven (Conn.) tests five processes of sewage treatment. F. W. MOHLMAN. Eng. News-Record 79, 829-30. Engineer 125, 97. Respect- ing the activated sludge process, the experiments were carried out on the continuous flow plan in tanks 16 ft. by 4 ft. by 8 ft. deep, with filtros plates set in cast-iron frames as the air diffusers. 17,000 gallons are treated daily, allowing 3 hours for aeration and 66 minutes for settling. (Cf. Ref. No. 338). 330 Sewage purification. L. G. B. requirements and other data. S. H. ADAMS. Pamphlet pp. 6. (Nov. 1917). A brief general description of the acti- vated sludge process, and some data from the Milwaukee experiments, occupy one page. 331 How the activated sludge process of sewage disposal is working in Pas- adena. R. V. ORBISON. Pacific Municipalities (Nov. 1917) 594-606. A description of the testing station, the process, and a brief summary of the results obtained. Treatment cost estimates and a consideration of the pos- sible revenues from the process are given. (Cf. Ref. 349). 59 The Activated Sludge Process 332 Clearing house summary on activated sludge. EDITORIAL. Eng. News- Record 79, 817. Comment on T. C. HATTON'S paper. (Ref. No. 333). "In a large sense, Milwaukee has been a clearing house for activated sludge data and opinion, for nearly everyone interested in the process has visited the Milwaukee testing station or at least has corresponded with Mr. Hatton. The initial work at Lawrence and its elaboration by DR. GILBERT J. FOWLER and his followers in England, should never be lost sight of by those who desire to give credit where credit is due." 333 Conclusions on the activated sludge process at Milwaukee, Wis. T. C. HATTON. Eng. News-Record 79, 840-4. Surveyor 53, 232-3, 254-5. Chem. Abst. 12, 75. Mr. Hatton's paper before the Am. Public Health Association in October, 1917. When sewage is treated 1 hour with 0.5 cu. ft. of air per gallon in an aerating tank of 15 ft. effective depth, a 98% removal of sus- pended matter is obtained, but for complete nitrification 0.75 to 1.1 cu. ft. of air per gallon must be applied 4 to 6 hours. To prevent clogging of the air diffusing plates, grit chamber treatment is necessary when storm water is mixed with the sewage, and preliminary treatment with fine screens is recommended for sewage from industrial communities, while for purely do- mestic sewage, 3-16 in. slotted screen is sufficient. About 20% of well activated sludge is necessary for satisfactory treatment. The sludge as withdrawn from the aerating tanks contains 99 to 99.5% water, which is reduced to 96% by 5 to 6 hours settling. Presses and driers can be used to lower the water content to 10%. Typical analysis of dried sludge shows 5.1% ammonia, 5.3% fat, 0.5% soluble phosphorus pentoxide, and 0.25% potas- sium oxide. Flies, insects, and worms do not infest the treatment plant, nor is any offensive odor connected with the process. 334 The activated sludge method of sewage treatment. F. W. MOHLMAN. Univ. Ill Bull 15, 75-113. (Water Survey Series No. 14). Abst. Bact. 2, 149. Pamphlet pp. 43. "1. In the aeration of sewage there is almost quan- titative oxidation of ammonia N to nitrite N, followed by oxidation to nitrate N. From 10 to 20 days are required. In the aeration of sewage in contact with activated sludge, ammonia N is oxidized to nitrate N in from 4 to 5 hours. Nitrite N is evidently oxidized to nitrate N almost as rapidly as it is formed. 2. Satisfactory activated sludge can be obtained with 6 hour aera- tion periods without complete nitrification from the beginning of the opera- tion. 3. In a small tank the equivalent of 1,300 Ibs. of dry sludge per million gallons of strong sewage was obtained. In larger tanks 740 to 1,150 Ibs. of dry sludge per million gallons of average sewage were obtained. 4. In the presence of 25% sludge, weak sewage was well nitrified in 4 hours with 1 cu. ft. of air per gallon of sewage. Normal sewage required 4-5 hours aeration and 1.3 cu. ft. of air per gallon of sewage. Strong sewage required more than 5 hours aeration and more than 1.5 cu. ft. of air per gallon of sewage. 5. Better results were obtained when 1-3 the floor surface was covered with porous plates, than when all or 1-9 of the floor surface was covered. 6. The N in the sludge increases by from 0.5 to 1.5% per day until an average of 5.1% N is obtained. 7. The content of phosphoric pentoxide varies in the same way as the N, reaching an average of about 3%. 8. Dewatering the sludge is a problem which has not yet reached a satisfactory solution, although small scale experiments with centrifuges have given promising results. It has been practically impossible to obtain a solid cake by filter-pressing the acti- vated sludge and experiments with precipitants and filtros-plate filters also gave unsatisfactory results." The above is the author's summary of the article. 335 Decomposition products of sewage disposal. F. N. CRAWFORD. Univ. III. Bull. 15, 162-8. (Water Survey Series No. 14). Abst. Bact. 2, 149. A study of the effluent gases in the activated sludge process. Author's con- clusions: "Aeration of tap water, of sewage, and of sewage in the presence of activated sludge, yield quantities of carbon dioxide and of O which are 60 Abstract Bibliography 1917 greatly at variance. (1) Tap water containing bicarbonates, when aerated undergoes a loss of carbon dioxide, the partial conversion of bicarbonates to normal carbonates, and the establishment of dissolved at the normal for water saturated with atmospheric gases. (2) Sewage alone undergoes similar changes; the extinction of free carbon dioxide; partial conversion of bicarbonates to normal carbonates, and dissolved O slightly less than the nor- mal for air-saturated water. (3) Sewage with activated sludge similarly aerated yields increasing quantities of carbon dioxide as the sludge builds up, while the bicarbonate alkalinity remains unchanged. The increment of carbon dioxide appearing in the effluent gases collected during aeration of the sew- age with activated sludge is derived from biological fermentation of car- bonaceous matter." (Cf. Ref. 158). 336 Bacterial purification of sewage. W. F. KAMM. Univ. III. Bull. 15, 146-61. (Water Survey Series No. 14). Chem. Abst. 12, 1674. Abst. Bact. 2, 149. Conclusions: "(a) Denitrifying bacteria reduce the nitrate and nitrite in sewage, (b) They are constantly present in sewage, but their action is often overlooked because of the greater amount of nitrification, (c) In all the aeration experiments a large amount of N (as ammonia) is lost, (d) The denitrifying action (under certain conditions) predominates over the nitrifying action and may be the cause of the failure to nitrify the sewage in some aeration tanks, (e) Denitrifying organisms play an essential role in the purification of sewage by aeration in the presence of activated sludge." Numerous diagrams accompany the article. 337 The treatment of packinghouse wastes by the activated sludge process. ANON. Eng. & Contg. 48, 386-8. Practically the full paper presented by LANGDON PEARSE at the meeting of the Am. Public Health Assoc. on Oct. 18, 1917. (Cf. Ref. Nos. 271, 326, 327 and 371). 338 The sewage experiment station at New Haven, Conn. ANON. Eng. & Contg. 48, 390-1. The activated sludge experiments were on the con- tinuous flow plan in an aerating tank 16 by 4 by 8 ft. deep, with a bottom sloping at 45 degrees to a trough 1 ft. wide, in which were placed 15 filtros plates as air diffusers. The settling tank is 4 by 4 by 12 ft. deep to the bottom of the hopper. Aerating tank has a capacity of 3,100 gallons and is treating 17,000 gallons of sewage daily with a 3 hour aeration period. Settling tank has a capacity of 1,150 gallons, and the settling period is 66 minutes. (Cf. Ref. 329). 339 Papers on activated sludge. NEWS ITEM. Eng. News-Record 79, 940. Refers to reprints of papers by DR. E. ARDERN which are available. These reprints cover articles noted in Ref. Nos. 244 and 296. 340 Nature of activated sludge. F. DIENERT. Comptes rend. 165, 1116-7. Jour. Soc. Chem. Ind. 37, 71 A. Chem. Abst. 12, 1224. To prepare acti- vated sludge from Paris sewage it was found necessary to aerate the sewage for 30 hours to effect nitrification of the 10 mgrs. of ammonia per liter which it contained. The liquid was then decanted, a further volume of sewage admitted to the residual sludge, and aeration continued. These operations were repeated for 15 to 20 days, when the time required for nitrification had been reduced to 1.5 hours, and the volume of the sludge had much increased. During the aeration the dissolved carbon dioxide is expelled and the calcium bicarbonate precipitated as carbonate; at the same time the precipitate re- moves some of the suspended and dissolved organic matter by absorption. It was found that the alkalinity of the sewage was reduced from 180 to 60 parts of lime per million, by 1.5 hours aeration. The activated sludge con- tained 50% mineral matter, chiefly calcium carbonate; 20% of albuminoid matter, and 30% of non-albuminoid matter. In tests in which the sewage took 2 hours to travel along the sewers, it was found that in consequence of the aeration which took place during that time, that about three-quarters of the albuminoid and ammoniacal matter was absorbed by the precipitated cal- cium carbonate, and was found in the deposits of same along the sewers. 61 The Activated Sludge Process 341 Purification of sewage and analogous liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,247,540, Nov. 20, 1917. (Application filed Oct. 9, 1914. 16 claims). Off. Gaz. 244, 774. Jour. Soc. Chem. Ind. 37, 38A. Chem. Abst. 12, 397. Claim 3 : The process of treating sewage or the like, consisting in causing a local upflow in the liquid, and supplying air locally into the liquid in its flow; causing the sludge and solid matters to pass to a point of the part of the flow which is being supplied with air; and removing the clarified liquid from the body. Claim 5: The process of treating sewage or the like, consisting in causing an up and down flow, and a lateral flow in the liquid, the lateral flow being from the upper part of the upflowing part of the liquid, and supplying air into the liquid in its flow. (Cf. Brit. Pat. 22,952. Ref. No. 3). 342 Purification of sewage and other liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,247,541, Nov. 20, 1917. (Application filed Sept. 13, 1915. 6 claims). Off. Gaz. 244, 774. Jour. Soc. Chem. Ind. 37, 38A. Chem. Abst. 12, 397. Claim 1: The process of purifying sewage or other impure liquid by supplying the sewage or impure liquid to a tank, supplying or de- livering air in small bubbles periodically a plurality of times at different points to the liquid in the tank during its treatment, until it is purified, and run- ning off the purified liquid. (Cf. Brit. Pat. 1,141, Ref. No. 33 and Can. Pat. 183,586, Ref. No. 402). 343 Purification of sewage and analogous liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,247,542, Nov. 20, 1917. (Application filed Oct. 18, 1915. 9 claims). Off. Gaz. 244, 774. Jour. Soc. Chem. Ind. 37, 38A. Chem. Abst. 12, 397. Claim 4: The process of purifying sewage or analogous liquids, consisting in supplying crude sewage or liquid, causing it to flow while being treated, delivering air into the liquid in the presence of bacterial sludge or solid matter, depositing the sludge at a point of its flow removed from that where the aeration or oxidation is taking place, and transferring the deposited sludge or solid matters to the sewage or liquid in the aerating or oxidizing portion. (Cf. Brit. Pat. 22,737, Ref. No. 18). 344 Purification of sewage and analogous liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,247,543, Nov. 20, 1917. (Application filed Oct. 18, 1915. 6 claims). Off. Gaz. 244, 775. Jour. Soc. Chem. Ind. 37, 38A. Chem. Abst. 12, 397. Claim 5: The process of purifying sewage or analogous liquids, which consists in aerating or oxidizing a plurality of quantities of liquid in the presence of bacterial sludge, depositing sludge or solid matters therefrom, transferring the sludge in which the bacteria have deteriorated or weakened to tanks, aerating or oxidizing the removed and debilitated sludge and so recuperating it, and transferring the recuperated sludge to one or more of the bodies of the liquid being treated. (Cf. Brit. Pat. 22,736. Ref. No. 17). 345 Handling sludge from activated plants. ANON. Munic. Jour. 43, 508. Conclusions from operation of the test plants at Chicago and Fort Worth, Texas. Acid acts differently on the two sludges. Plain settling has considerable value in reducing moisture content, but effectiveness varies with the condition of the sludge. Improvements in settling tanks, other devices as the Dorr tank, the use of coagulents, filter pressing, etc., should be studied with a view of more effectively reducing the water content of acti- vated sludge. 346 Sewage disposal for Indianapolis, Ind. ANON. Munic. Jour. 43, 510. A report on the application of modern methods of sewage treatment to the conditions at Indianapolis, made by G. W. FULLER to the sanitary com- mission of that city, considers in some detail the Imhoff tank, the activated sludge, and the fine screen methods of treatment, concluding in favor of 62 Abstract Bibliography 1917 the last. The report refers to the large installations of Imhoff tanks and their difficulties, and to the large experimental activated sludge plants, but is not encouraging as to the efficiency of either. (Cf. Ref. No. 347). 347 Screens, filters and humus tanks for Indianapolis, Ind. ANON. Eng. News-Record 79, 972-4. Chem. Abst. 12, 395. This method of sewage treatment has been recommended by G. W. FULLER after considering also, Imhoff tanks with sprinkling filter, and the activated sludge process. It is stated, however, that the activated sludge process is the cheapest one to install and that it would produce the most complete purification, but in com- paring its status at Indianapolis with its suitability elsewhere, recognition should be given to the fact that there would be no saving in the purchase of site or in construction of intercepting or outfall sewers by locating this compact type of plant nearer the city. (Cf. Ref. No. 346). 348 Many activated sludge plants. NEWS ITEM. Eng. News-Record 79, 987. About 25 experimental activated sludge plants have been built in vari- ous parts of the world, according to a paper read recently by MR. T. C. HAT- TON before the Am. Pub. Health Assoc. Of these one was in India, 7 in England, and 14 in the United States. Seven treatment plants have been built in the United States, and 4 more of considerable magnitude are pro- posed. 349 Activated sludge tests made by California cities. ANON. Eng. News- Record 79, 1009-10. Chem. Abst. 12, 395. Description of experimental plant and result of tests made at Pasadena, Calif., under the direction of R. V. ORBISON. The aerating tank is 20 by 9 by 10 ft. deep, with two length- wise partitions giving a 60 ft. continuous channel, in which 21 filtros plates are located. Ratio 1 to 8.5. Two settling tanks were built but only one used. A sludge reaerating tank 12 by 6 at the top, 12 by 2 at the bottom, and 10 ft. deep, equipped with 4 filtros plates is in use. 4 hours aeration using 1 cu. ft. of air per gallon of sewage, with 10-20% activated sludge, followed by 30 minutes settling, gives a non-putrescible effluent, containing nitrates, and a bacterial reduction of 96 to 99.6%. Other aeration periods and air volumes were tried. Sludge drying in open beds gives rise to odors that make this means impossible. The daily flow from the 3 cities interested (Pasadena, South Pasadena and Alhambra) is about 3 million gallons, nor- mal; 7.5 million gallons, maximum. Testing plant handles 50,000 gallons daily on an area of 267 sq. ft., or the equivalent of 8 million gallons per acre on a 4 hour aeration basis. It is estimated that the activated sludge process would save at least 50% on the construction cost of Imhoff tanks with neces- sary accessories. (Cf. Ref. No. 331). 350 Activated sludge. THOS. CAINK. Surveyor 52, 471. In a communi- cation to the editor it is stated that because of its buoyant nature, the sludge will not flow down sloping sides. Scrapers on flat-bottom tanks were first recommended by the author in his paper in The Surveyor 52, 51-2. July 20, 1917. (Ref. No. 295). 351 Worcester, (Mass.) activated sludge experiments. M. GAULT. Ann. Re- port. Supt. Sewers for year ending Nov. 30, 1917. 697-731. Refers to the 100,000 gallons experimental activated sludge plant which begun opera- tions July 7, 1917. Results to be reported when experiments are completed. (Cf. Ref. No. 487 and 540). 352 Sewage disposal in Kansas. F. M. VEATCH, H. P. EVANS and L. E. JACKSON. Bull. Univ. of Kansas, 18, 30. A brief general description of the activated sludge process is given. 353 Some conclusions reached at Milwaukee on the treatment of sewage by the activated sludge process. ANON. Munic. Eng'rg. 53, 243-6. Results 63 The Activated Sludge Process of observations and studies of operation of the sewage testing station. From a paper by T. C. HATTON presented at a meeting of the Am. Public Health Assoc. (Cf. Ref. No. 333). 354 Copper in sewage at New Haven Experiment Station. F. W. MOHLMAN. Jour. Ind. Eng. Chem. 9, 1093-6. Refers to the activated sludge plant and experiments as in references Nos. 329 and 338. 355 Pressing sewage sludge. ANON. Can. Engr. 33, 473-4. Munic. Jour. 44, 14-6. Eng. & Contg. 49, 165-8. Chem. Abst. 12, 842. Abridgement of a paper by KENNETH ALLEN read at the 1917 meeting of the Am. Soc. Munic. Impvts., in which activated sludge is referred to only as in reference No. 365. 356 Are fine screens needed for the activated sludge process? G. B. GASCOIGNE and T. C. HATTON. Eng. News-Record 79, 1072-3. Letters to the editor in which the first author questions the necessity for fine screens as prelimin- ary to the activated sludge process: answered by the second author to the effect that they insure a more satisfactory operation of the plant. Essentially a discussion as to the merits of coarse and fine screens at Cleveland and Milwaukee respectively. 357 Cleveland sewage screen plans withdrawn from State Dept. of Health. ANON Eng. News-Record 79, 1128. City will submit plans for screens and activated sludge plant, and request that construction of the latter be postponed until screens have been operated for one year. 358 California sewage plants are neglected. ANON. Eng. News-Record 79, 1127. Refers to sewage plants in general but notes that the new acti- vated sludge plant at the Folsom state prison has recently been put into opera- tion to handle the sewage produced by 1,500 inmates. Ordinary objections to power costs do not pertain here as the prison generates its own power. (Cf. Ref. No. 567.) 359 The real issue as to sewage plans at Cleveland. EDITORIAL. Eng. News- Record 79, 1085. Intimates that the local conditions may compel the city to treat its sewage by activated sludge process. 360 Activated sludge system of sewage purification at Worcester, Eng. ANON. Sanitary Record 59, 393. Chem. Abst. 11, 3357. The cost of power for aerating sewage and sludge is 32s per million gallons, when the rate is 750,000 gallons per day. Average analyses of 12 samples of effluent, cover- ing a 12-month period was: Suspended matter 7.2; albuminoid ammonia, 1.4; O absorbed in 4 hours, 5.6 p. p. m. Porous tile seems to diffuse the air better than mechanical diffusers. A reduction of 50% of the air used is obtained by the use of a patent pulsating gear (Ref. No. 33) which supplies the air in ?uffs, resulting in better circulation. Experiments with activated sludge as ertilizer showed an increased yield of potatoes of 100% over those to which barnyard manure was applied. 361 The activated sludge process. EDITORIAL. Surveyor 52, 527. Comment on DR. E. BARTOW'S article on air diffusers (Ref. No. 321) in which it is noted that porous tile diffusers are more satisfactory in America as well as in England. 362 Investigations in regard to purification of sewage and water at the Lawrence experiment station during the year 1917. H. W. CLARK. 3rd. Ann. Report State Dept. of Health, Mass. 122-72. Munic. Jour. Pub. Works 47, 345-6. Chem. Abst. 14, 1174. During 1917 the tanks containing layers of slate remained in operation, and new and larger activated sludge tanks were started. Briefly summarizing the extensive studies, it may be noted that sewage of different characters and strengths require very different aerating 64 A bstract Bibliography 1 91 7 periods and air volumes for satisfactory results, and unless these are employed in excess, a modified, rather than a purified sewage results. The quality of the sludge, physically and chemically, appears to be of vital importance, and too much can be used. In certain experiments the amount of O required for sewage oxidation was found to be 350 pounds per million gallons, whereas- activated sludge at 2 cu. ft. of air per gallon, required 100 times this amount to stability. Studies on the destruction of organic matter by oxidation; the effect of sterilizing chemicals on activated sludge; (mercuric chloride stops its action completely) and of the progressive flow through activated sludge and other tanks (Ref. No. 434) are noted in this report, as well as numerous tables of analytical data. 363 Syracuse, N. Y., tests two methods of sewage treatment. ANON. Eng. News-Record 79, 1201-2. Chem. Abst. 12, 730. The activated sludge in- stallation embraces an aerating tank 12 by 4 by 10 ft. deep, and 1 inch pipes with 1-16 inch perforations 3 inches center to center, distributes the air. Set- tling tank is 4 ft. square, maximum dentil 15 ft., with 4 to 1 sloping bottom. From this tank an air lift delivers the sludge back to the aerating tank or to a sludge re-aerating tank, also 4 ft. square. (Cf. Ref. No. 378.) 364 The disposal of sludge. DISCUSSION. Surveyor 52, 552-3. Various prac- tices are discussed at the annual meeting of Mgrs. of Sewage Disposal Works. Mention is made of the fine screens used successfully at the Milwaukee activated sludge plant. 365 The pressing of sewage sludge. K. ALLEN. Trans. Am. Soc. Munic. Impvts. 24, 1-25. A tabulation of the properties and quantities p. m. g. of the various sludges is given, including activated sludge. The Berrigan or Worthington press at Milwaukee, with activated sludge, reaches an ultimate pressure of 60 Ibs. per sq. in., and produces 5 tons of cake per 24 hours, having a moisture content of 75%. Estimated cost of operation is $3.46 per ton of cake. MR. G. W. FULLER estimates the cost of pressing activated sludge at about $3.00 per ton of dry solids, or $2.70 per ton with 10% moisture. PEARSE and RICHARDSON (Ref. No. 271) estimate the cost of pressing sludge from stockyards sewage at $5.72, based on 96 tons of dry material daily. In the discussion following, (pp. 57-62, 81-96) reference was made to sludge from the activated process by C. E. A. WINSLOW, R. S. WESTON, G. B. KERSHAW, and F. A. DALLYN. 366 Water purification and sanitation. S. RIDEAL. Ann. Reports Soc. Chem. Ind. on the Progress of Appl. Chem. 2, 461-3. A brief general review of the activated sludge process is given for the year 1917. English plants referred to are: Manchester, (Withington works) Salford, Worcester, Stam- ford, Lincoln, and Sheffield. American plants mentioned are: Milwaukee, Houston, Fort Worth, and Chicago. 367 Tests of air diffusers for the activated sludge process. E. BARTOW and F. L. MICKLE. Eng. & Contg. 52, 41-2. III. State Water Survey Bull 15, 116-20.. Engineer 128, 146. Chem. Abst. 13, 2406. Authors' conclusions: (1) Filtros plates proved the most efficient of the three types of air diffusers, as evidenced by the analytical data. They gave a sludge that settled rapidly leaving clear and stable effluents. (2) The degree of porosity of the filtros plates made no apparent difference, for the coarse and fine grades of plates gave practically the same results. (3) The wood block diffusers gave un- stable effluents in the majority of samples. With these effluents the chemical results were not as satisfactory as with those from filtros plates. (4) The wooden blocks were very difficult to install, and even in the short time they were in service they showed evidence of marked deterioration. Until these defects can be remedied their installation in working-scale plants is impractica- ble. (5) The perforated pipes gave the least satisfactory chemical results. The majority of the effluents were unstable. (6) Clogging of the diffusers during the period covered by these experiments was not sufficient to have practical significance. 65 The Activated Sludge Process 368 Experimental study of the extraction of grease from dried activated sludge. D. F. MCFARLAND. III. State Water Survey Bull 15, 108-15, (1917). Eng. & Contg. 52, 196-7. Chem. Abst. 13, 2406. Using petroleum ether as a solvent, 4.16 to 6% grease was extracted from dried, untreated sludge produced in the experimental activated sludge plant. On treating with acid, the yield of grease was 5.81 to 8.10%. 1918 369 Notes on the activated sludge tests at Cleveland, O. R. W. PRATT. Am. Jour. Public Health 8, 55-7. Gives results of recent experiments. A clear effluent stable for 36 hours may be produced with 0.75 cu. ft. of air per gallon in 2 hours, using 25% activated sludge. The sewage treated is high in iron and 1.75 hours more aeration is necessary to remove the iron color. A hydroturbine compresses the air which is diffused through filtros plates. Dry- ing the sludge on sand beds required too large an area, and 7 days were re- quired to reduce the moisture to 75%. Centrifuging has given the best results. Sludge averaged 4% ammonia, half of which is in available form. Estimated treatment cost is given for a 500,000 gallon plant. 370 The treatment of sewage by the activated sludge process. ANON. Am. City 18, 1-4; 114-9; 199-203. An installment article from a paper by MR. T. C. HATTON read before the war convention of the Am. Pub. Health Assoc., in which the following subjects are considered. Principles of the process; character of the sewage to be treated; character of the effluent re- quired; type of aerating and sedimentation tanks; extended studies of sedi- mentation; types of air diff users and their ratio to tank surface area; period of aeration and sedimentation; volume of air required; percentage of activated sludge and volume to handle; removing sludge from sedimentation tanks and dewatering same; and special studies of dehydrating apparatus. Illustrations of the Milwaukee plant accompany the article. 371 Activated sludge and the treatment of packinghouse wastes. LANGDON PEARSE. Am. Jour. Public Health 8, 47-54. Jour. Am. Leather Chem. Assoc. 13, 145-55. Jour. Soc. Chem. Ind. 37, 348A. Results and conclusions of experiments carried on at the Chicago stockyards. More fully covered in references 326 and 327. 372 Activated sludge in the treatment of sewage. M. YOUNG and S. E. MELLING. Sanitary Record 61, 38, 68, 90, 122. Surveyor 53, 42-4. Jour. Royal Sanit. Inst. 39, 10-25. Chem. Abst. 12, 1325. Abst. Bact. 3, 41. General principles and bacterial actions involved are explained. Diffusers for air dis- tribution are practicable for economic reasons. Experiments at the Davyhulme works (Manch., Eng.) show that a pulsating air supply is advantageous and minimizes the clogging of the diff users. At Salford (Eng.) about 22% sludge by volume is used with good results, with a sewage containing considerable trade waste which at times has a very inhibitory character. Perforated pipes were used in these experiments for diffusing air, and although irregular clog- ging of the air jets occurred, the sludge remained active and was distributed satisfactorily in the various chambers. Results were obtained which met the dissolved O and suspended solids limits of the Royal Commis. Cost of treat- ment depends largely on power costs. Claims are made by the inventors of the pulsating apparatus (Ref. No. 33) that a 50% saving in power can be effected by its use. Aside from this saving two desirable effects are ensured: (1) That all the sludge is carried to the surface periodically, and (2) that the evenness of distribution is improved. The authors also point out the following as constituting decided advantages of the process: (1) A very satisfactory effluent is obtainable. (2) Plant can be built nearer to cities, avoiding long outfall sewers. (3) Fly nuisance is avoided as activated sludge has no offensive odors. (4) The recovery of the N and its fertilizer value. Precau- tions to be observed in order to obtain satisfactory results, are enumerated. Abstract Bibliography 1918 373 Sewage treatment at Manchester. (Eng.) Activated sludge research work. ANON. Surveyor 53, 4-5. Chem. Abst. 13, 354. Work has been carried on in 50-gallon casks with mixed domestic sewage and an acid trade waste from chemical plants. Experimental runs indicate that the activated sludge process is successful in the presence of wastes from the manufacture of sulphate of ammonia, products from benzene and aniline, and from a dye works, but more time is required for aeration. absorption and ammonia figures are given. 374 The activated sludge experiments at Pasadena, Calif. ANON. Eng. & Contg. 49, 36-7. Chem. Abst. 12, 842. Covers results obtains from Jan. 29, to Sept. 1, 1917, at the experimental plant. (Ref. No. 349.) A grit cham- ber, diverting box and rag-picker was installed ahead of the aerating tank. The plant was operated on both the fill and draw and continuous plans, and filtros plates set in individual cast-iron holders diffused the air. With a 4-hour aeration period and an air consumption of 1 cu. ft. per gallon of sewage, "ex- ceedingly fine" results were obtained. 375 Definitions of terms used in sewerage and sewage disposal practice. ANON. Eng. & Contg. 49, 38-9. Surveyor 53, 46-8. Amended report of the committee on sewerage and sewage disposal of the Am. Pub. Health Assoc. Definition for activated sludge same as in Ref. No. 202. 376 Bacterial treatment of sewage. ANON. Engineering 105, 40-1. Sci. Am. Suppl. 85, 167. Chem. Abst. 12, 1224. Briefly refers to the slate beds hydrolytic tanks as forerunners of the activated sludge process, and to the suggestions of DR. G. J. FOWLER, made in 1914, that sewage could be purified in tanks without the aid of filters. 377 Fourth Annual Report of the Milwaukee Sewerage Commission. T. C. HATTON and W. R. COPELAND. Pamphlet pp. 70. (Jan. 15, 1918.) Covers the following activated sludge investigations made during the year ending 1917 at the testing station. Aeration of sewage in tanks 10 and 15 ft. deep, with tabulated results; aeration periods of 2.4 to 11 hours using 0.6 to 2.8 cu. ft. of air per gallon with tabulated results and discussion of the ad- vantages and disadvantages of various combinations from an economic point of view. Comparison of perforated pipes, wood blocks, and filtros plates as air diffusers, with the merits and demerits of each considered. But, "* * * all questions in regard to air diffusers, size of bubbles, etc., sink into insig- nificance when compared to the importance of furnishing clean air * *." Sludge settlement experiments with rectangular tanks having flat bottoms, steep coned bottoms, and flat coned bottoms; and with Dorr thickeners of different depths, show that when the sludge has been well aerated the volume returned by the 15 ft. deep Dorr thickener was reduced to 20% of the raw sewage flow, and to a moisture content of less than 98%. Concentration of sludge by treatment with sulphuric acid, shows that settled sludge containing about 98% of water, can be dewatered by the acid to 91% in 2.25 hours, but that at 1 cent per Ib. for 60 degree Be. acid, the cost of acid alone would be about $1.00 per million gallons of sewage, to which another dollar should be added for heating the sludge, handling acid, etc. Sludge pressing with the Worthington and Simplex plate presses, showed in both cases press cakes carrying 72 to 83% moisture. A Smith direct heat dryer reduced a press cake of 75-80% moisture to 4-10%, and a Buckeye semi-direct heat dryer reduced the moisture from 61-83% to 4-18%. Several tables of analytical and other data accompany the report. 378 Sewage tests at Syracuse, N. Y. NEWS ITEM. Mimic. Jour. 44, 59. The city is awaiting the results of tests now being made by Chief Eng. G. D. HOLMES to determine whether the activated sludge or aerated filter systems is best suited for treatment of the city sewage. At the testing station, crude sewage is pumped to a grit chamber 30 ft. long, and then passed through a 67 The Activated Sludge Process bar screen with 0.75 inch spacing. Part of it then enters the activated sludge tank, the rest going to two Dortmund tanks, one with a horizontal flow filter, the other with a vertical flow aerated gravel filter. (Cf. Ref. 363.) 379 Activated sludge in the treatment of sewage. DISCUSSION. Surveyor 53, 117-9. Discussion of YOUNG and MELLING'S paper (Ref. No. 372) in which MR. T. CAINK, by letter, stated that atmospheric temperatures as low as 21F., sewage temperature 43F., had no appreciable effect on the purifica- tion at Worcester. (Eng.) He had, however, observed that the activated sludge process was very sensitive to sudden increases in the rate of flow through the aeration tank, the effluent being inferior ; but if the same increased rate was reached gradually, it was without effect on the degree of purification. DR. E. ARDERN related some experiences at the Withington works, (Manchester, Eng.), where 400,000 gallons of sewage was being treated daily with satis- factory effluent, and with about 75% of the volume of air originally estimated on. In his opinion sludge dewatering and drying remained one of the most important problems to solve. MR. P. GAUNT, MR. W. CLIFFORD, DR. S. RIDEAL, MR. G. P. MILN, MR. W. D. SCOULLER, MR. J. A. COOMBES, and MR. G. W. LACEY brought up questions of sludge disposal and utilization, the relative merits of perforated pipes and porous tiles as air diffusers, the matter of costs, and the possibilities of converting existing plants into activated sludge plants. 380 Sewerage and sewage disposal. The activated sludge process. EDITORIAL. Surveyor 53, 71-3. Reviews the progress of the process in England and America; suggests standard units for measuring sewage, air, etc., so as to get comparable figures on volumes used; notes that porous plates have been found most satisfactory for air diffusion; and comments on the experiments on packinghouse wastes made at Fort Worth, Texas, and the proposed plant for the Chicago stockyards. 381 Activated sludge equipment. NEWS ITEM. Surveyor 53, 106. The CLIFFORD patent tank equipment (Ref. No. 275) for securing rapid settlement of activated sludge has proved a great success at the Withington works and at Stamford. JONES & ATTWOOD air diffusers have been in use over two years and showed no signs of deterioration. 382 Sludge disposal. ANON. Surveyor 53, 114-5. Abstract from the paper by K. ALLEN before the Am. Soc. Munic. Impvts. (Cf. Ref. 365.) 383 Activated sludge treatment. W. C. MOOR, Fort Worth, Tex. U. S. Patent 1,254,833, Jan. 29, 1918. (Assigned to ARMOUR & Co., Chicago. Applica- tion filed July 9, 1917. 6 claims.) Off. Gaz. 246, 1097. Jour. Soc. Chem. Ind. 37, 193A. Chem. Abst. 12, 731. Claim 5: The method of dehydrating acti- vated sludge which consists in heating the same to above 30 C., then subjecting the same to the action of sulphuric acid whereby coagulation takes place ac- companied by the generation of gas therein and the coagulated sludge is caused to float, and then separating the coagulated floating sludge from the liquid and drying. 384 Activated sludge treatment. G. B. MULLOY, Chicago, 111. U. S. Patent 1,254,836, Jan. 29, 1918. (Assigned to ARMOUR & Co., Chicago. Applica- tion filed July 9, 1917. 1 claim.) Off. Gaz. 246, 1097. Jour. Soc. Chem. Ind. 37, 193 A. Chem. Abst. 12, 731. The improvement in the activated sludge method of treatment as applied to industrial sewage, which consists in pre- liminary diluting the raw sewage with effluent from previously treated sewage. 385 Activated sludge treatment. G. L. NOBLE, Chicago, 111. U. S. Patent 1,254,841, Jan. 29, 1918. (Assigned to Armour & Co., Chicago. Appli- cation filed July 9, 1917. 2 claims.) Off. Gaz. 246, 1099. Jour. Soc. Chem. Ind. 37, 193A. Chem. Abst. 12, 731. Claim 2: The improvement in the activated sludge method of treatment as applied to sewage, which consists in drawing off 68 Abstract Bibliography 1918 the activated sludge from previously treated sewage, aerating such sludge for a period of about 3 hours after its withdrawal to enhance the virility of the aerobic organisms therein, and then inoculating the raw sewage with such re-vitalized sludge. 386 Activated sludge defined. ANON. Eng. News-Record 80, 205. Can. Engr. 34, 144. Definition as given in Ref. No. 202. 387 Filtros air diffusing plates used in the activated sludge process of sewage treatment. ANON. Munic. Eng'rg. 54, 78-9. A general description of filtros, noting the advantages of its physical properties as an air diffusion medium, and names of several localities where it is in use in activated sludge plants. 388 Activated sludge treatment. EDITORIAL. Surveyor 53, 125. Refers to YOUNG and MELLING'S paper (Ref. No. 372) and comments on the useful discussion that followed its presentation, especially that in regard to handling of the sludge. 389 Costs of sewage screens at Milwaukee. T. C. HATTON. Eng. News- Record 80, 272. In a letter to the editor MR. HATTON corrects an error in his reply to G. B. GASCOIGNE'S letter (Ref. No. 356) pertaining to the Operating costs of the screens at the activated sludge plant in Milwaukee, which should be $0.46 per million gallons or a total of approximately $14,000 annually, and not half of those figures as erroneously stated. 390 Cleveland may use fine screens for sewage. ANON. Eng. News-Record 80, 382. Refers to the activated sludge process only as in Ref. No. 357. 391 Sewage treatment and disposal. G. B. KERSHAW. Can. Engr. 34, 243-5. Surveyor 53, 197. Eng. & Contg. 49, 595-7. Chem. Abst. 12, 1491. At the conclusion of an article on various methods of sewage purification, the author expresses the belief that the activated sludge process has a promising future, and that economical methods of dewatering the sludge and its value as a fertilizer, will determine the net cost of the process. 392 Activated sludge disposal at Houston, Texas. NEWS ITEM. Oil, Paint and Dru.g Rep. 93, 27. The city of Houston will erect an addition at the north side disposal plant which will be used for the manufacture of fertilizer from dried activated sludge. Estimated cost $70,000. 393 Activated sludge process. EDITORIAL. Surveyor 53, 229. Comment on a paper by T. C. HATTON, (Ref. No. 333) in which the editor notes that Mr. Hatton confirms the stand long held by the Surveyor that the quality of effluent should be suited to local needs, and controlled by varying the amount of air according to conditions of dilution. 394 Purification of sewage by aeration in the presence of activated sludge. R. G. TYLER. Proc. Texas Assoc. Am. Soc. C. E. 5, 7-13. A general description of the process, covering preliminary treatment, aeration, settle- ment, sludge dewatering, etc., with reference to the work done at Chicago, Cleveland, Fort Worth, Houston, Milwaukee, San Marcos and Urbana. Skilled supervision is important. Power costs must be low and at least one million g. p. d. handled to be economical for small cities. Each proposition must be worked out on its own merits. An experimental plant is under construction at Austin by the Univ. of Texas in conjunction with the city. 395 Sewage terms recommended for adoption as a standard by a committee of the Am. Public Health Assoc. ANON. Munic. Jour. 44, 223-5. An amended report which refers to the activated sludge process as in reference No. 202. 69 The Activated Sludge Process 396 Appaartus for purifying sewage. GRIFFITHS & HARTLEY. British Patent Application No. 4,726, March 18, 1918. Jour. Soc. Chem. Ind. 37, 196A. 397 Activated sludge developments. ANON. Can. Engr. 34, 294. Chem. Abst. 12, 1674. A large settling tank at the Davyhulme works (Manchester, Eng.) is to be converted into an activated sludge tank capable of treating one million gallons of sewage per day. The Withington works, designed to treat 250,000 g. p. d. has had new features introduced which has increased its capacity to 400,000 g. p. d. The Worcester (Eng.) activated sludge plant has fulfilled the city engineer's expectations in every respect. 398 Activated sewage sludge. ANON. Engineer 125, 297-8. Considers the several methods of sludge dewatering and drying, with particular ref- erence to the tests at Milwaukee. The commercial value of the dried sludge and methods of marketing same are also discussed. 399 Sewage sludge as fertilizer. ANON. Surveyor 53, 314. Gives value of sewage sludges on the basis of their nitrogen and phosphoric acid con- tent, as fixed by the British Government order, and mentions a patent sludge drier using waste steam which can handle from 20 to 30 tons of sludge daily, and requires but two men to operate. 400 Considerations leading to the recommendations for fine screens, sprinkling filters, humus tanks and sludge recovery, as the sewage disposal method for Indianapolis, Ind. ANON. Eng. & Contg. 49, 368-72. From a paper by G. W. FULLER presented at a meeting of the Ind. Sanit. and Water Supply Assoc. on March 28, 1918. The activated sludge process is incidentally re- ferred to as in references Nos. 346 and 347. 401 Small activated sludge plant proposed at Chicago. NEWS ITEM. Eng. News-Record 80, 734. Plans for an intercepting sewer and an activated sludge plant are proposed by the Sanitary District of Chicago to treat the sewage from Melrose Park, Maywood, River Forest and other villages having a total population of about 30,000. Estimated cost $750,000. (Cf. Ref. No. 598.) 402 Purification of sewage. W. JONES. Canadian Patent 183,586, April 16, 1918. Chem. Abst. 12, 1326. Air is supplied to the sewage under treat- ment at different points periodically, to stimulate the bacteria in the sewage. (Cf. Brit. Patent 1,141, Ref. No. 33; U. S. Pat. 1,247,541, Ref. No. 342.) 403 Rockaway Valley sewage plans approved. NEWS ITEM. Eng. News- Record 80, 839. Plans for the diversion of sewage of Rockaway Valley towns to a point below the Boonton dam of the Jersey City water supply, and treatment of the sewage there by the activated sludge process, were approved by the N. J. State Dept. of Health on April 9, 1918. 404 Purification of sewage and other liquids. W. JONES, Stourbridge, and JONES & ATTWOOD, L/TD., Amblecote, Eng. British Patent 132,826, April 27, 1918. Jour. Soc. Chem. Ind. 38, 876A. In the activated sludge process of sewage treatment, the aeration tank is constructed in longitudinal sections with the angles between the walls and floor rounded off, and also with the top of the walls made to overhang, so as to partly cover the top of the tank, the overhanging portions being curved on their under surface to the same radius as the bottom of the wall. Air diffusers are placed in the side walls near the bottom, and the combined action of the air and the rounded portions is to give a circular motion to the sewage in a transverse direction to the flow, and also to cause the air to circulate in the outer layers of the sewage. The general direction of flow is down one longitudinal section and back by another, and so on. The tank is also divided into sections by transverse walls, with the com- municating openings between sections placed near the source of air supply. 70 Abstract Bibliography 1918 By this means all the sewage is made to pass several times near the sources of air supply in its passage through the tank. Various modifications in the position of the air supply and in the wall structure are described. (Cf. U. S. Pat. 1,341,561, Ref. No. 561.) 405 The fertilizing value of activated sludge. G. G. NASMITH and G. P. McKAY. Jour. Ind. Eng. Chem. 10, 339-44. Can. Engr. 34, 377-82. Eng. News-Record 80, 1193. Eng. & Contg. 50, 31-2. Jour. Soc. Chem. Ind. 37, 384A. Chem. Abst. 12, 1229. An extended study of the subject including a report of plot experiments with activated sludge. It appears to be especially valuable to root crops. Compared with a standard barnyard manure used by farmers, the increase in yields due to activated sludge was: with beets, 138%; radishes, 40%; late radishes, 316%; lettuce, 103.3% beans, 77.3%; tomatoes, 291%; onions, 3 varieties, 81.1, 191, and 554%. No increase was obtained with carrots. The drying and handling of the sludge is also discussed. 406 Note on the fertilizing value of activated sludge. PAUL RUDNICK. Jour. Ind. Eng. Chem. 10, 400. Chem. Abst. 12, 1329. In a letter to the editor, the author claims that the experimental work of NASMITH and McKAY (Ref. No. 405) and of BARTOW and HATFIELD (Ref. Nos. 84 and 118) does not rep- resent conditions which will prevail in practice. The good results of the latter two are probably due to the fact that their experiments were made with sterilized soil, in which the nitrifying organisms in the activated sludge will work as well as in unsterile soil, though this is not the case with dried blood. In actual practice sterile soil is not used. 407 Aeration of sewage and other impure liquids. O. STOTT, Birmingham, and E. R. JONES, Stourbridge, Eng. British Patent 133,722, May 14, 1918. Jour. Soc. Chem. Ind. 38, 961A. In the activated sludge process of sewage purification, the treatment tank is provided with a propeller disposed longi- tudinally on the surface of the sewage. The propeller blades, which are of the feathering type, introduce air into the surface layer of the liquid and induce a surface current transversely to the direction of flow. Guides are placed in the tank to facilitate the continuation of the current at the sides and across the bottom of the tank. The propeller may be submerged in the sewage, in which case air is introduced into the surface by a blower or other means. (Cf. U. S. Pat. 1,343,797, Ref. No. 566.) 408 The development of sewage treatment. K. ALLEN. Munic. Eng'rg. 54, 244-9. Chem. Abst. 13, 49. Development of the activated sludge process has been hindered by the war, but valuable data has been secured at Milwaukee, Urbana, and Chicago. Removal of the coarser particles by screens has reduced the volume of air required. Tank details, types of diffusers, etc., are yet to be standardized. The advantages of the activated sludge process are the small space required and the recovery of values from the sludge. Brief reference is made to methods of sludge handling. 409 Purification of sewage by aeration. Activated sludge tanks at Lawrence Experiment Station. EDITORIAL. Surveyor 53, 457. Extracts from the 1916 Report of the Mass. Experiment Station. (Ref. No. 233.) 410 Apparatus for pressing activated sludge. WM. BUCKLEY, Chicago, III. U. S. Patent 1,271,425, July 2, 1918. (Application filed July 20, 1916. 4 claims.) Off. Gaz. 252, 187. Jour. Soc. Chem. Ind. 37, 604A. Claim 1: In an apparatus of the class described, a container for sludge liquid, automatic- ally operating mechanism including means adapted to receive a charge thereof from said container, and to close communication with said container there- after, and a sludge press, said mechanism operating to force the received charge of sludge liquid into said press for the recovery of the sludge there- from, the frequency of said operation being dependent upon the rate of filtra- tion of the sludge through the press. (Also Brit. Pat. 130,146, Ref. No. 413.) 71 The Activated Sludge Process 411 Water-purifier. (So titled in patent.) GEO. MOORE, Joplin, Mo. U. S. Patent 1,271,925, July 9, 1918. (Assigned to THE CHEMICAL PROCESS Co., N. Y. City. Application filed Oct. 31, 1914. 10 claims.) Off. Gaz. 252, 360. Jour. Soc. Chem. Ind. 37, 603A. Chem. Abst. 12, 1905. Claim 3: In com- bination, a container, means for agitating sewage therein, a container com- municating with the first container and adapted to allow settling of solids entering from the first container, means for discharging thickened materials from the lower portion of the second container, directly back to the first con- tainer; a third container communicating with the upper portion of the second container and adapted to receive fluid and solids in suspension therefrom, and means for separately treating products discharged from the upper and lower portions of the third container. (Cf. following abst.) 412 Sewage treatment. GEO. MOORE, Joplin, Mo: U. S. Patent 1,271,926, July 9, 1918. (Assigned to THE CHEMICAL PROCESS Co., N. Y. City. Application filed Oct. 31, 1914. 14 claims.) Off. Gaz. 252, 360. Jour. Soc. Chem. Ind. 37, 603A. Chem. Abst. 12, 1905. Claim 5: In a process of the class described, as a continuous operation, maintaining agitation of a mass of sewage, previously coagulated sewage-solids and foreign solids, (charcoal, coal dust, peat, etc.) continuously supplying thereto original sewage, drawing off therefrom fluid portions of the mass, returning to the mass solids from the drawn off portion, and filtering the remaining drawn off portion. (Cf. previous abst.) 413 Apparatus for pressing activated sludge. WM. BUCKLEY, Chicago, 111. British Patent 130,146, July 24, 1918. Jour. Soc. Chem. Ind. 38, 694A. (Cf. U. S. Patent 1,271,425, Ref. No. 410.) 414 Sewage disposal at Houston, Texas. NEWS ITEM. Munic. Jour. 45, 84. At the Sixth Annual Convention of the League of Texas Municipalities, held at San Antonio on June 19-20, 1918, an illustrated address on sewage disposal was delivered by E. E. SANDS, city engineer of Houston, dealing with the activated sludge plant in that city. 415 The Worcester (Eng.) experiments with the activated sludge process. ANON. Eng. & Contg. 50, 122-3. Chem. Abst. 13, 49. An existing tank 86 by 78 by 18 ft. deep was baffled into 36 bays, each 21 by 8 ft., of which 28 are used for aerating and 8 for settlement. Perforated pipes are used with holes 12 inches apart, over which are placed porous tiles forming the bottom of the valleys. Settling tanks have 60 degree bottoms with 6 inch air lifts. Sludge contains 96% of water. Aeration period is 6 hours, with a flow rate of one million gallons per 24 hours. 20% sludge carried. Settling period is one hour and 40 minutes. 750,000 gallons per 24 hours are actually treated. Analyses are given of the screened sewage and of the effluent. 416 Sprinkling-filter system and auxiliaries vs. the activated sludge process. T. C. HATTON. Munic. County Eng'rg. 55, 67-70. Engineer 124, 561. Chem. Abst. 12, 2643. A consideration of the relative advantages of each sys- tem. On one acre the sprinkling-filter system should handle 2.5 million gal- lons, the activated sludge process 10 to 15 million gallons, with respective head losses of 12 ft. as against 2 to 3 ft. Low temperatures do not materially effect the activated sludge process; it gives a clarified effluent with freedom from odor; and offers a satisfactory method of sludge disposal. The cost per million gallons for the sprinkling-filter system is estimated much higher than for the activated sludge process. 417 Sewage engineering and sewage disposal. J. E. WILCOX. Munic. Eng'rg. & Sanit. Record 62, 74, 84, 124. Can. Engr. 35, 224-5. Chem. Abst. 12, 2642. Abstract of presidential address British Assoc. of Managers of Sew. Disp. Works. The most remarkable work which has been done during the past year has been in connection with the activated sludge process, and in addition 72 Abstract Bibliography 1918 to the installations in operation at Worcester, Stamford and Salford, a large plant has recently been installed at the Withington works, Manchester. For the past year or two most of the investigation and research work has been done in the United States, the Milwaukee experiments being especially worthy of note. The paper discusses the principal points arising in connection with the process. 418 Means for supplying air or gas in a more or less finely divided state., W. JONES, Stourbridge, and JONES & ATTWOOD, LT'D., Amblecote, Eng. British Patent 131,158, Aug. 17, 1918. Jour. Soc. Chem. Ind. 38, 790A. A layer of cement, concrete, or the like, is suppored on a perforated metal or other plate extending along the upper part of a trough, channel, or box. The top of the channel is narrower than the lower part so as to retain the porous layer. Air under pressure admitted to the channel passes through the porous cement and escapes from its surface in a finely divided state. 419 Purification of sewage and other liquids. W. JONES, Stourbridge, and JONES & ATTWOOD, LT'D., Amblecote, Eng. British Patent 132,581, Aug. 17, 1918. Jour. Soc. Chem. Ind. 38, 843A. In the activated sludge method of purifying sewage, the aerating tank is discharged during times of normal flow through an opening near the bottom. The opening is made of a size proportionate to the capacity of the tank, or it is provided with a regulator or valve, either method permitting of a continuous regulated outflow, carrying the heavier particles of sludge to a settling chamber. The top of the aerating tank is provided with a weir which comes into operation at times of abnor- mally increased flow of sewage, and the overflow from which joins the regu- lated flow passing to the settling chamber. 420 Sewage treatment policies as influenced by war-time conditions. G. W. FULLER. Munic. County Eng'rg. 55, 106-8. With respect to activated sludge, the inference is that high prices and shortage of farm labor will mean that more attention will be paid to fertilizers, and consequently stimulate investigations, not only as to activated sludge, but to sludges from other sources. 421 Brockton postpones building its activated sludge plant. NEWS ITEM. Eng. News-Record 81, 514. The State Board of Health having advised further sewage experiments, Brockton, Mass., has postponed until after the war, the building of its proposed activated sludge plant. 422 The activated sludge process. J. EADE. Surveyor 54, 131. Description of a small experimental plant at St. Albans, Eng. Aerating tank is 57 ft. 3 in. long, with a width varying from 5 ft. to 7 ft. 2 in., of 5 ft. depth, and with a capacity of 7,375 gallons. 46 diffusers having an effective area of 32 sq. ft. are located in a channel running the full length of the tank. Ratio 1 to 10. Three settlement tanks of 612, 844, and 2,125 gallons capacity, with hopper bottoms and air lifts are provided, as is also a sludge re-aerating tank of 2,194 gallons capacity, with 17 air diffusers. Air con- sumption averaged 12.5 cu. ft. per cu. ft. of sewage, (about 1.67 cu. ft. per U. S. gal.) treating 30,000 gallons of sewage per day, and giving a good effluent. Trade wastes from the breweries, bleaching works, gas works, a straw hat factory and a tallow factory, have not caused serious trouble with the plant. 423 Fertilizer experiments at Toronto. NEWS ITEM. Surveyor 54, 139. Fer- tilizer experiments with activated sludge at the Toronto sewage works produced 37 bushels of wheat per acre, as against 13 bushels when the equivalent amount of N had been added to the land in the form of dried blood. 424 Sewage purification by the activated sludge process. W. R. COPELAND. Can. Engr. 35, 302, 315-7. Chem. Abst. 12, 2643. Consideration in de- 73 The Activated Sludge Process tail of sewage aeration from the standpoint of the volume of air, period of contact, kind of diffusers, and depth of tanks. Air was tried in amounts ranging from 0.6 to 2.8 cu. ft. per gallon of sewage, and contact periods ranging from 2.4 to 11 hours. Filtros plates proved the best diffusers. Clean air is essential. Sedimentation is important to remove sludge. (Cf. Ref. 377). 425 Manchester (Eng.) activated sludge plant. NEWS ITEM. Surveyor 54, 166. Refers to a visit to the Withington works by members of the Assoc. of Mgrs. of Sewage Disposal works on Oct. 5, 1918, at which time DR. E. ARDERN related his recent experiences with the activated sludge process. 426 Four methods of sewage treatment studied at New Haven testing station. C. E. A. WINSLOW and F. W. MOHLMAN. Munic. Jour. 45, 280-2, 297-9, 321-2. Eng. News-Record 82, 32. Chem. Abst. 13, 626. Fine screens, Imhoff, and activated sludge, all with subsequent chlorine disinfection, and Miles' acid precipitation with sulphur dioxide were tried. The activated sludge process was studied less as an oxidizing than as a clarfying process. Trials were made with aerating periods ranging from 2.5 to 10 hours; air volume 1.1 to 2 cu. ft. per gallon; sludge volumes (very dilute sjudge) 50 to 73; and sedimentation periods of 30 to 78 minutes. Satisfactory results were not obtained, partly because of faulty design of settling tank, the small size of the sludge pipes, and the lack of a re-aerating tank, but principally because of antiseptic trade wastes in the sewage, mainly copper salts from munition works. 427 Air diffusing apparatus. C. H. NORDELL, Milwaukee, Wise. U. S. Patent 1,281,816, Oct. 15, 1918. (Application filed May 12, 1917. 2 claims). Off. Gaz. 255, 524. Jour. Soc. Chem. Ind. 38, 53A. Claim 1: A liquid con- tainer having means for aerating the liquid therein, said means comprising a member having a recess provided with a concave bottom, a plurality of diffusing blocks disposed edge to edge and positioned to form an arch, said blocks being disposed in said recess in the member, the curvature of said arch conforming to the curvature of the bottom of said recess, curved spacing ribs disposed between the plurality of blocks and the bottom of said recess, and means for admitting air between the blocks and the bottom of the said recess. (Cf. U. S. Pat. 1,208,821, Ref. No. 225). 428 Apparatus for the purification of sewage and analogous liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,282,587, Oct. 22, 1918. (Orig- inal application filed Oct. 9, 1914; divided, and this application filed Nov. 7, 1916. 8 claims). Off. Gaz. 255, 772. Jour. Soc. Chem. Ind. 38, 116A. Chem. Abst. 13, 151. Claim 1: In an apparatus for purifying sewage, comprising a tank, means for introducing air or oxygen at the lower part of the tank, said tank being of a size above the air-introducing means to provide a ma- terial-receiving area above and laterially of such means, and beyond the direct influence of the air from such means. (Cf. Brit. Pat. 19,916, Ref. No. 11). 429 Two sludge problems. A. J. MARTIN. Surveyor 54, 195-6. Chem. Abst. 13, 354. Sewage treated by the activated sludge process requires from 20 to 70 times the amount of air necessary to furnish the O needed to combine with the organic matter. This excess is required to perform the mixing and because the air passes rapidly through the sewage. The author proposes the use of long horizontal cylindrical tanks, the contents of which are maintained in a state of rapid rotation, combined with a slow longitudinal flow. The rotation may be produced by jets of sewage or air. For the removal of a considerable part of the water or sludge, it is suggested that the sludge be allowed to settle in tall shafts, where its own weight would consolidate the material and force it out through doors at the base of the shaft. With activated sludge it might be necessary to blow air through the shaft to prevent de-aeration. 74 Abstract Bibliography 1918 430 All reports should be published. EDITORIAL. Eng. News-Record 81, 785. Comment on the reports of the several engineers respecting the sewage disposal problems in Cleveland, O., the activated sludge process being one of the methods that has been considered. 431 Sewage sedimentation advised for Cleveland, O. ANON. Eng. News- Record 81, 806-8. From a report by H. P. EDDY in which the activated sludge process and fine screens are not recommended as a solution of the westerly district problem, because of excess cost over Imhoff tanks with disinfection, and because the activated sludge process as proposed, was to operate only during the bathing season. 432 The recovery of grease from city sewage. C. E. A. WINSLOW and F. W. MOHLMAN. Munic. County Eng'rg. 55, 173-5. Proc. Am. Soc. Munic. Impvts. 25, 203-22. Makes brief reference to the activated sludge process as one among a number of sewage purification processes tried at New Haven, Conn. 433 Consolidation of sludge as a dewatering method. ANON. Eng. & Contg. 50, 467. From a paper by A. J. MARTIN (Ref. No. 429) in which tall shafts are suggested. The author is not certain that this method will apply to ac- tivated sludge. 434 Sewage mixes progressively in its passage through tanks. H. W. CLARK. Eng. News-Record 81, 930-1. Surveyor 55, 143. Chem. Abst. 13, 1610. Experiments with actviated sludge and settling tanks show that the time of passage of liquid through a tank is not equal to the number of hours it would take to fill the tank as a given rate of flow. NaCl or AmCl was used to determine the time of passage. With a rate of 10.5 hours, sewage appeared at the outlet of the tank in 1 hour; 50% in 7.5 hours, while the remaining 50% lagged for 35 hours. The effluent therefore, was always a mixture of applied and held sewage. Other similar experiments are described. 435 Purification of sewage and analogous liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,286,017, Nov. 26, 1918. (Application filed Oct. 18, 1915. 4 claims). Off. Gaz. 256, 766. Jour. Soc. Chem. Ind. 38, 116A. Chem. Abst. 13> 244. Claim 1: The process of purifying sewage or the like, con- sisting in delivering air into the sewage to activate same, permitting such activated sewage to settle, drawing off the liquid, and utilizng the accumu- lated activated sludge in the subsequent treatment of raw sewage. Claim 4: The process of purifying sewage or analogous liquid, consisting in delivering air into the liquid in the presence of bacterial sludge, collecting the air liber- ated from the sewage or one body of same, and delivering it into and passing it through sewage or liquid in another tank or body. 436 Shanghai's sewage disposal and water supply problems. ANON. Surveyor 54, 255. From a report on the situation by DR. G. J. FOWLER, in which it is stated that the city must look forward to the ultimate inoffensive dis- position of at least 50 million gallons of sewage, and he suggests that the activated sludge process would serve both the sanitary and economic re- quirements. 437 Worcester (Mass.) activated sludge experiments. M. GAULT. Ann. report Supt. Sewers. (For year ending Nov. 30, 1918). Experiments at the 100,000 gallon activated sludge plant begun in July, 1917, were suspended on account of the war on Aug. 20, 1918. Report on the 13 months operation to be issued later. (Cf. Ref. 487 and 540). 438 Apparatus for aerating sewage. A. M. BROSIUS, Pasadena, Calif. U. S. Patent 1,286,520, Dec. 3, 1918. (Application filed Aug. 28, 1916. 3 claims). 75 The Activated Sludge Process Off. Gaz. 257, 83. Jour. Soc. Chem. Ind. 38, 157 A. Chem. Abst. 13, 355. Claim 1: In an apparatus for treating sewage, a foam chamber, means for introducing sewage into said chamber, and paddle means in said chamber for churning said sewage to form a foam. Claim 2: In an apparatus for treating sewage, a tank, pipe means for passing air into the sewage in said tank, and a power driven mixing means for finely subdividing said air to form a foam. Claim 3: In an apparatus for treating sewage, a tank, a down-flow pipe for passing a mixture of sewage and air to the bottom of said tank, and a power driven impeller for breaking up said mixture of sewage and air to form a foam, and for expelling said foam into said tank. 439 Device for activating sludge. LESTER E. REIN and JAS. W. Cox, Chicago, 111. U. S. Patent 1,286,775, Dec. 3, 1918. (Assignors to PACIFIC FLUSH TANK Co., Chicago, 111. Application filed Oct. 6, 1916. 6 claims). Off. Gaz. 257, 140. Jour. Soc. Chem. Ind. 38, 157A. Chem. Abst. 13, 255. Claim 6: In a device of the class described, a sewage tank having an inlet and an overflow outlet, a pump having an inlet member adapted to extend into said tank, a return pipe connected to the exhaust of the pump, an injector con- nected to the return pipe and adapted to inject air into the contents thereof, and a deflector guide arranged at the outlet of the return pipe and adapted to deflect the discharge therefrom into the body of the material in the tank. 440 Activated sludge research in India. ANON. Appendix 9th Ann. Report Council Indian Inst. Science. (Bangalore, India, 1918) Jour. Soc. Chem. Ind. 38, 4R. Research on activated sludge has been carried out since Nov., 1917, at a small experimental plant erected outside the applied chemistry de- partment. Data have been obtained for the construction of the larger instal- lation at Sakchi and also valuable information concerning the character of the sludge under different conditions, with a view of its use as a fertilizer. 441 Sewage pollution. DISCUSSION. Proc. Am. Soc. Munic. Impvts. 25, 176-93. Mr. G. B. KERSHAW (by letter) comments on the activated sludge process, stating that he would like to see an activated sludge plant run side by side with say, a percolating filter installation, both designed with the latest improvements and treating the same sewage. 442 Water purification and sanitation. E. ARDERN. Ann. Reports Soc. Chem. Ind. on progress Appl. Chem. 3, 421-7. An interesting review of the activated sludge process for the year 1918. English plants mentioned are those at Manchester, Worcester and St. Albans. American plants referred to are at Milwaukee and Houston. 443 Report of the provincial sanitary engineer. F. A. DALLYN. Ann. Report Provincial Board of Health of Ontario. 37, 58-65. Chem. Abst. 14, 1722. Work was undertaken with satisfactory results, to determine the fertilizer value of activated sludge. 444 Activated sludge as a fertilizer. W. D. HATFIELD and E. BARTOW. Proc. Am. Soc. Munic. Impvts. 25, 225-57. Covers historical development of sewage sludges as fertilizers; theoretical discussion of organic nitrogenous material and its decomposition products as fertilizers; expermental results with wheat, lettuce, radishes, corn, beets, onions and tomatoes, the chemical constitution of the organic nitrogenous compounds in activated sludge, which laboratory tests have shown to be principally in the form of nucleoprotein and its decomposition products; and a statement to the effect that garden experiments in 1917 proved that both wet and dry activated sludge were valuable as fertilizers, the wet sludge giving the better results. Some data on dewatering activated sludge by coagulation and by centrifugals, are also given. (Cf. Ref. Nos. 84 and 118). 76 Abstract Bibliography 1919 445 Notes on main drainage and its relation to river and harbor front im- provements. MORRIS KNOWLES and JOHN M. RICE. Proc. Am. Soc. Munic. Impvts. 25, 138-70. In the chapter on "Methods of sewage treatment," a brief general review of the activated sludge process is given. 446 Investigations upon the purification of sewage and water at the Law- rence experiment station during the year 1918. H. W. CLARK. 4th. Ann. Report Mass. State Dept. Health. 117-49. A continuous flow activated sludge tank was put into operation early in the year, the average aeration period being 5.38 hours, the air supply ranging from 1.78 to 2.80 cu. ft. per gallon of sewage, diffusion being through hollow perforated brass discs. Approxi- mately 20% of sludge was carried, the surplus being removed at intervals. The latter amounted to the equivalent of 770 Ibs. of dry sludge per million gallons of sewage treated, and averaged 6.15% N, 5% fats. Investigations to learn the best volume of air for efficient aeration, and studies in regard to the effect of varying volumes of sludge are also noted. Several tables of analytical data are included. 447 Report of the Bureau of Sanitary Engineering. V. M. EHLERS. Ann. Report Texas State Board of Health, pp. 34. (1918) Refers to the activated sludge process as being received with a great deal of favor through- out the entire state, 8 cities using it in the treatment of domestic sewage, and 2 experimental plants treating packinghouse wastes. The first cost of acti- vated sludge plants is less than that of any other type giving the same results, but several features must be first considered before adopting the process. 448 Report on the sewage disposal problem of New Haven, Conn. C. E. A. WINSLOW and F. W. MOHLMAN. Pamphlet pp. 97. (1918) The acti- vated sludge plant is described and the results obtained from it given. (Cf. Ref. Nos. 329, 338, 354, 426 and 432). 1919 449 Sewage disposal at Manchester (Eng.) ANON. Surveyor 55, 17-8. Can. Engr. 36, 222-3. Chem. Abst. 13, 1889. From the annual report, Man- chester Rivers Dept., for the year ending March, 1918, the following data on the activated sludge investigations are summarized. Withington works : aerat- ing tank 100 by 20 by 6 ft. deep, of 55,000 gallons capacity, is divided into 5 channels with bottom on the ridge and furrow plan, air diffusers in the furrows. Area of net diffusion area to tank area is 1 to 10. Settlement tank 23.5 by 26.5 by 23.5 ft. deep to bottom of hopper, 27,000 gallons capacity, and equipped with CLIFFORD'S patent arrangement. (Ref. No. 274). Sludge is discharged from apex of the tank to a re-aerating tank, from which it may be returned to the aerating tank by air lifts. Plant designed to treat 250,000 gallons daily, with an average aerating period of 4 hours, and began opera- tions in Sept., 1917. Detritus chamber and screens preceed the aeration tank. Volume of sludge carried varied from 15 to 25%. Tabular analytical data showing results of daily treatment of 250,000 gallons with a 4 hour aeration period and 1.8 cu. ft. of air; 375,000 gallons with a 3 hour aeration period and 1.2 cu. ft. of air; 500,000 gallons with a 2 hour aeration period and 0.9 cu. ft. of air are given. If nitrification is not essential, satisfactory effluents can be obtained when working at double the capacity the plant was designed for. 375,000 gallons can be handled easily. Bacterial removal was 98-99%, and the effluents were highly clarified. Sludge, on a dry basis, amounts to somewhat more than 0.5 ton per million gallons of sewage, and showed on analysis: Loss on ignition, 75.2%, mineral matter, 24.8%. Nitrogen, 6.4%; phosphorus pentoxide, 3.8%. As removed from the settlement tank it contains 98.5% water. Davyhulme: aerating tank 25 by 16 by 9 ft. deep, operated from July, 1917, to March, 1918, on the fill and draw plan, averaging 0.5 hour to fill, 5.25 hours aeration, 1 hour, 50 min. settlement, and 0.5 hour discharging. 77 The Activated Sludge Process 45,000 gallons were treated daily with an air consumption of 1 to 1.5 cu. ft. per gallon. The contemplated million gallon continuous flow plant is re- ferred to. 450 Purification of sewage. HARTLEY & HARTLEY. British Patent Applica- tion 1,604, Jan. 22, 1919. Jour. Soc. Chem. Ind. 38, 96 A. 451 Sewerage and sewage disposal. The activated sludge process. EDITORIAL. Surveyor 55, 66-9. The possibility of draining the sludge on coarse filters protected from rain is discussed, the fertilizer value of it as disclosed in the paper of NASMITH & McKAY is commented upon, as is the paper by MR. T. C. HATTON presented before the Am. Pub. Health Assoc. (Ref. No. 370). 452 English activated sludge plants. TRADE NOTE. Surveyor 55, 105. JONES & ATTWOOD refer to the plants of their construction at Manchester, (Davyhulme works) one million gallons per day; at Tunstall, 250,000 gallons per day; at St. Albans, at the Am. Red Cross Hospital near Sarisbury Court; at a Royal Airship Station near Worcester; and to the plants at Harpenden and Worcester. 453 Fifth annual report of the Milwaukee Sewerage Commission. T. C. HATTON and W. R. COPELAND. Pamphlet pp. 51. (Jan. 31, 1919). The reports of Ch. Eng. Hatton and Ch. Chem. Copeland for the year ending Dec. 31, 1918, gives detailed results of the operation of the chain belt fine screen at head losses of from 2 to 6.7 in., collecting 441 to 953 Ibs. of screen- ings of 88.1 to 89.0% moisture. Analysis of these screenings show an average of 5.94% N on a dry basis. Two aerating tanks 15 ft. deep with filtros plates in the ratios of 1 to 4.4 and 1 to 6.0, treat the equivalent of 16 million gallons of sewage per acre per day, and two tanks of 10 ft. depth with the filtros plates in the same ratios, treat the equivalent of 10 million gallons per acre per day. All 4 tanks have a liquid area of 284 sq. ft. All tests showed better than 99% removal of suspended matter, 95% bacterial removal, and effluent stability of 95 to 120 hours. The standard aimed at for these factors are 95%, 90% and 72 hours. The importance of supplying clean air to the diffusers is emphasized. The lines should be of non-corrosive material so as to prevent scales of iron rust from clogging the diffusers. Dorr thickeners in the sludge settling tanks gave good service, the discharged sludge ranging from 97 to 99.5% moisture, with the overflow effluent carrying less than 5 p. p. m. of suspended solids on the average. Several tables of analytical data accompany the report. 454 Improved fertilizer. G. J. FOWLER and G. MUMFORD. U. S. Patent 1,294,080, Feb. 11, 1919. (Application filed June 1, 1916. 7 claims). Off. Gaz. 259, 289. Chem. Abst. 13, 1121. Claim 6: The herein described improved fertilizer, consisting of bacterially active dry sewage sludge of granular character. (Cf. Brit. Pat. 8,397, Ref. No. 51; Dan. Pat. 22,389, Ref. No. 309; Can. Pat. 189,921, Ref. No. 467). 455 Improvements in or relating to apparatus for use in the treatment of sewage and other effluents. L. WHYTE, Wilmslow, and H. FOTHERGILL, Cheadle Hulme, Eng. British Patent 104,189, February 28, 1919. Jour. Soc. Chem. Ind. 39, 347A. The object of the invention is to provide means for thoroughly mixing together the sewage and activated sludge, and assuring that the whole of the mixture shall be brought into contact with the atmosphere. Stationary mixing devices in the form of an archimedean screw or spiral are disposed at selected points in the channels, each being of appropriate axial length and with the screw-like vanes shaped to fit closely to the bottom and side walls of the channels, which may be of rectangular or circular form, so that the whole of the mixture is effected, there being no clear flow through the channels. The mixing devices may be made of metal, earthenware, or other 78 Abstract Bibliography 1919 material. As the mixture of sewage and sludge flows through the channels a rotary motion is imparted to it and fresh surfaces brought into contact with the atmosphere. Adapted to be used in either continuous flow or intermittant treatment tanks. 456 Analyses of sewage and sewage sludges. ANON. Water and Water Eng'rg. (Mar. 20, 1919). Eng. & Contg. 51, 465. Chem. Abst. 13, 1733. A typical sewage and 8 sludge analyses are given. Activated sludge shows the most N, 7.5% on dry weight. 457 Texas activated sludge plants. ANON. Munic. Jour. 46, 225. From a report of the bureau of sanitary engineering, Texas State Board of Health, in which the statement is made that "Texas is pecularly the home of the acti- vated sludge process, there being 10 such plants in operation there, one of them being the first city in the world to treat the entire sewage of a city." 458 City of Sheffield sewage disposal department. J. HAWORTH. Report of Highway and Sewerage Com. (For 2 years ending March, 1919), pp. 10. Sanit. Record 63, 228-9. Chem. Abst. 13, 1609. Expt. Sta. Record 42, 188. Activated sludge experiments have been continued and developed, and two new tanks added treating 50,000 and 60,000 gallons of trade sewage per day. These tanks are 30 by 14 by 4 ft. deep, with level floors, and divided into channels about 3.25 ft. wide. Mechanical agitation is furnished by 2 vertical pistons of the Root's blower type which also circulate the sewage with a velocity of 1.5 to 2 ft. per second which is sufficient to prevent sludge settlement. 10 days were required to produce a well activated sludge, the tanks then being worked on the fill and draw plan, 3 fillings per day, continuously and satisfactorily for the past 3 months, the only air the sewage received being by contact at the surface. 20 HP. per million gallons is required. (In a private communication to the compiler, Mr. Haworth states that a plant capable of treating not less than one million gallons is being constructed, the operation of which is expected in Sept., 1920.) 459 Results of experiments with Miles acid process of sewage treatment. E. S. DORR and R. S. WESTON. Jour. Boston Soc. C. E. 6, (April, 1919). Can. Engr. 36, 455-60. Eng. & Contg. 51, 510-3. Surveyor 55, 419-21. The activated sludge process is mentioned only by way of comparison. Sludge from the acid process amounts to only one-seventh as much as from the acti- vated sludge process and contains less moisture; 90% as against 98.5%. (Abst. of a paper on this subject by WINSLOW and MOHLMAN in Eng. News-Record 81, 1034-6, Am. City 20, 467-9. (Cf. Ref. No. 426.) 460 Operating experiences with activated sludge process for factory wastes. G. W. FULLER. Can. Eng. 38, 367-8. Munic. County Eng'rg. 57, 123-5. Chem. Abst. 13, 3263. Describes experiments on the wastes of a plant handling cocoanut oil, making edible oil, margarine, etc. 150,000 gallons per 24 hours with a temperature of 40 C. are treated by a plant comprising preliminary grease trap, aerating tanks, re-aerating tank, and final settling tank. Milk of lime may be added at the inlet to aerating chamber. Perforated pipes are used for air distribution. Tests showed need for organic matter, hence cow manure is added at the rate of 8 cu. ft. per 24 hours for the 150,000 gallons of waste. Air is supplied at the rate of 1.5 cu. ft. per gallon; 3 hour period of contact. 3 grains of lime per gallon are added at inlet of final sedimentation tank, pro- ducing a clear and stable effluent. 461 Reading (Eng.) and the activated sludge process. NEWS ITEM. Surveyor 55, 282. The town clerk of Reading has been instructed to ascertain the names of places in which activated sludge installations are in operation, either experimental or otherwise, and whether the process has proved successful. 79 The Activated Sludge Process 462 Chlorination of sewage. ANON. Munic. Jour. Pub. Works 46, 266. Can. Engr. 36, 404. Chem. Abst. 13, 1733. At New Haven, Conn., the follow- ing p. p. m. of chlorine were required: Crude sewage 7 to 8; activated sludge effluent, 3; Imhoff effluent, 6; screened sewage, 5. With the activated sludge effluent, 2 p. p. m. of chlorine reduced the total bacteria 78%. In the samples containing- 3 p. p. m. of chlorine, the activated sludge process had already reduced the number of B. Coli 73%, and no further reduction was effected by chlorine. 463 Activated sludge process at Worcester (Eng.). NEWS ITEM. Surveyor 55, 298. Relates to financing the completion of the activated sludge plant. Large economies in the working of the system should be assured be- fore going further. 464 Milwaukee sewage pumping station. T. C. HATTON. Fire and Water Eng'rg. 65, (April 23, 1919). A description of the pumping equipment for the new activated sludge plant. 465 Report on the activities of the Bureau of Sanitary Engineering of the Texas State Board of Health. R. G. UPTON. Proc. Texas Assoc. Am. Soc. C. E. 6, 57-8. 1919.) Over 168 sewage systems are in operation in Texas towns and all have disposal plants except a few on tide water and elsewhere. The 10 or 12 activated sludge plants are producing excellent effluents and the process is referred to as the only odorless sewage disposal method known. 466 Apparatus for aerating sewage and other foul liquids. R. AMES, Brigh- ton, Eng. British Patent 143,369, April 28, 1919. Jour. Soc. Chem. Ind. 39, 52 5 A. In aerating tanks, a movable device for raising the sludge to the surface, comprising a series of vertical pipes fixed in a carriage, the lower ends of the pipes being bell-mouthed, and the upper ends being provided with mush- room-shaped flanges. By means of an internal concentric pipe, and an air lift consisting of a conical box with apex below and slotted to allow air to escape upwards, or other suitable device, the sludge is raised to the surface through the bell-mouthed pipes, and then flows in a cascade over the mushroom flanges back into the tank, becoming aerated in the process. 467 Fertilizer. G. J. FOWLER. Canadian Patent 189,921, April 29, 1919. Chem. Abst. 13, 1121. Consisting of bacterially active non-colloidal sewage sludge rich in nitrogen, in a state available for plant food, made by forcing air through sewage in the presence of bacteria, thus forming an active sludge which is heated to sterilize and dry it. It is then inoculated with a portion of fresh active sludge. (Cf. Brit. Pat. 8,397, Ref. No. 51; Dan. Pat. 22,389, Ref. No. 309; U. S. Pat. 1,294,080, Ref. No. 454.) 468 Mechanical agitation for activated sludge. EDITORIAL. Munic. Jour. Pub. Works 46, 349. The experiments at Sheffield, Eng., (Ref. No. 458) ap- parently demonstrate that not even for oxidation purposes was applied air necessary, as sufficient is absorbed at the surface if the sewage is kept agitated. Considered by the editor a very promising discovery. 469 Activated sludge without compressed air. ANON. Munic. Jour. Pub. Works 46, 356. Chem. Abst. 13, 2248. Descriptive of the experiments at Sheffield, Eng., with mechanical agitators which indicate the possible substi- tution of them for compressed air, surface absorption of the O being depended upon for oxidizing purposes. (Cf. Ref. No. 458.) 470 Activated sewage process extension. NEWS ITEM. Surveyor 55, 470. The Worcester (Eng.) City Council has resolved to carry out the scheme proposed by MR. T. CAINK, city engineer, for applying the activated sludge process to the whole of the remainder of the city's sewage not already so treated. The scheme proposes to treat 1.5 million gallons of dry weather flow daily at an estimated cost of 5,550 pounds. 80 Abstract Bibliography 1919 471 Toronto will investigate the activated sludge process. NEWS ITEM. Can. Engr. 37, 46. "Officials of the City of Toronto will visit Milwaukee at an early date to investigate the activated sludge process. If satisfied with the progress made at Milwaukee the Toronto City Council will allow $50,000 for an experimental unit; which if successful will result in the construction of a large plant to handle all of Toronto's sewage." 472 Reading (Eng.) and the activated sludge process. ANON. Surveyor 56, 49. It is recommended that the sedimentation tanks be reconstructed for use in the activated sludge process, which because of local conditions, can be adopted to advantage as it will create no nuisance and produce an effluent that would meet all requirements. 473 Separation of sludge and scum from sewage and other liquids. S. H. ADAMS. British Patent 145,291, Aug. 1, 1919. Jour. Soc. Chem. Ind. 39, 581A. A sedimentation tank is provided with an apron roof, sloping longi- tudinally from near one wall to near the bottom of the opposite wall, and suspended on pivots. The floor of the tank slopes in the opposite direction to the roof, and at its lower side terminates in a sludge channel. Sewage enters at one end of the tank and flows over the roof towards the exit pipe at the opposite end. Solids settling out of the sewage slide down the roof into the lower portion of the tank to the sludge channel. Scum rising from the floor of the tank is directed by the under side of the roof into a scum space at the surface between the top of the roof and the side wall of the tank, from which it is removed over a weir into a scum channel. When used for activated sludge the tank is made preferably of circular form, the air inlets being so placed as to impart a revolving motion to the liquid. In this case the exit pipe is placed axially and receives the liquid through perforations along its length. 474 Problems of sewage disposal at Shanghai, (China). C. H. GODFREY. Munic. Gaz. (Shanghai) 12, 291-6. Surveyor 56, 225-6. Water & Water Engr. 21, 318-20. Chem. Abst. 14, 583. Extracts from a preliminary report covering the author's observations after visiting several activated sludge plants in the United States. An experimental activated sludge plant is rec- ommended for Shanghai. 475 Salford (Eng.) and the activated sludge process. NEWS ITEM. Surveyor 56, 146. The Salford Town Council Rivers Committee recommend the adoption of the activated sludge process, successful experiments having been carried out for some time. 476 Activated sludge plant for Chicago stockyards. NEWS ITEM. Eng. & Contg. 52, 310. "The committee of the trustees of the Sanitary Dist. of Chicago voted Sept. 3, 1919, to construct an activated sludge plant for the treatment of the trade wastes from the stockyards. It also voted to request the packers to pay two-thirds of the cost of installation and operation." 477 A sewage-treatment experiment. ANON. Munic. Jour. Pub. Works 47, 199-200. Chem. Abst. 13, 3263. Describes an experimental plant of 50,000 gallons capacity at Mt. Vernon, N. Y., comprising a rotary driven screen, 24 mesh, with flow from the outside in, a special tank containing both aeration and sedimentation compartments, and Dorr thickeners, which treat the sewage with about one-third the usual amount of air. The plant was designed and is operated by the Dorr Co., the object being to develop a more efficient applica- tion of the activated sludge process. (Cf. Ref. Nos. 579 and 581.) 478 Activated sludge sewage treating plant to require much power. ANON. Elect. Review 75, 529-30. At the Chicago meeting of the West. Soc. Eng., MR. LANGDON PEARSE stated that electric power was proposed for the stock- yards' new activated sludge plant, involving a connected load of about 12,000 H.P., and using approximately 38,500,000 kw-hr. annually. Assuming a power rate of 0.7 cent per kw-hr. the power cost for a year would be about $270,000. 81 The Activated Sludge Process 479 The utilization of sewage sludge. J. D. WATSON. Munic. Jour. Pub. Works 47, 210-3; 226-7. Can. Engr. 37, 420-2; 427-9. Deals principally with other than activated sludge, referring to it only in a quotation from the report of a joint English Committee as follows: "We have not specifically inquired into the results to be obtained from sewage treated by the activated process, but as a result of visits made by the Committee to the Manchester and Sheffield sewage disposal works where the activation by aeration and activation by agitation processes respectively are under investigation, it would appear that the residual sludge from such processes contained a higher percentage of nitrogen, and consequently as a fertilizer would be of greater value than sludge produced in the ordinary way. Experiments have been commenced to ascertain its fertilizing value, but further investigation is necessary to find out the best method of dewatering and drying." 480 Utilization of sewage sludge. EDITORIAL. Munic. Jour. Pub. Works 47, 219. Refers to sewage sludges in general, but concludes with the hope that the activated sludge process now operating in so many places, will furnish valuable information on the subject of their use. 481 Bingley municipal works. Activated sludge experiments. H. BOTTOMLEY. Surveyor 56, 258. Experiments have been carried out for about 15 months, successfully treating 300,000 gallons of sewage on the fill and draw plan, in a tank 8 ft. diam. by 4 ft. deep, of 1000 gallons capacity. 14 porous tiles were used as air diff users. After the 7th filling satisfactory results were obtained with 4 hours aeration. Two fillings per day treating 750 gallons at each fill was the procedure for about 3 months. After some alterations to plant, experiments were resumed and continued for about 12 months with successful results. Aeration period varied from 2 to 9 hours. In the discus- sion, MR. J. P. WAKEFORD referred to the mechanical agitation experiments at the Tinsley works, Sheffield, where two tanks were being equipped to handle 200,000 gallons daily, agitation being produced by two small propellers work- ing horizontally. 482 Agreement reached for packingtown sewage disposal. ANON. Eng. World (Nov. 1, 1919). Exerpt from a paper by LANGDON PEARSE pre- sented at the Chicago meeting West. Eng. Soc. in Sept. Material covered by Ref. No. 533. 483 Purification of sewage. HARTLEY & HARTLEY. British Patent Applica- tion No. 27,205, Nov. 5, 1919. Jour. Soc. Chem. Ind. 38, 884 A. 484 Economic values in sewage sludge. R. WELLS. Munic. Jour. Pub. Works 47, 278-80. Eng. News-Record 83, 948-52. Can. Engr. 37, 563-6. Proc. Am. Soc. Munic. Impvts. 26, 55-97. The following data and remarks pertaining to activated sludge are noted in this paper. Chicago Sanit. Dist. fresh activated sludge contained 5.10% ammonia; 14.70% grease. When 9 months old it contained 4.40% ammonia and 5.0% grease. Syracuse, N. Y., fresh activated sludge contained 5.06% ammonia, and 17.7% grease. In the discussion, MR. H. T. CALVERT and DR. H. MACLEAN WILSON, of Wakefield, Eng., write that activated sludge apparently contains less grease than fresh sludge, but the larger amount of N increases its value as a fertilizer. DR. F. Wi MOHLMAN writes that grease extraction from activated sludge is unprofitable as the amount is greatly reduced, probably by bacterial action, a condition which does not detract from the value of activated sludge as fertilizer. When grease extraction is considered, other processes than activated sludge are advisable. 485 The activated sludge plants at Manchester. (Eng.) EDITORIAL. Munic. Eng'rg. & Sanit. Record 64, 342-3. Comments on that part of the report of the Manchester Rivers Committee for the year ending March 31, 1919, which deals with the experimental activated sludge plants installed at the Withington and Davyhulme sewage works. The Committee report that "the 82 Abstract Bibliography 1919 satisfactory results previously obtained by the treatment of the Withington sewage by the activated sludge process have been well maintained." (Cf. Ref. No. 499.) 486 The activated sludge system. A hospital installation. ANON. Surveyor 56, 293. Illustration without detail description, of an activated sludge plant installed at the American Red Cross Hospital at Sarisbury Court, Eng., to care for the sewage of 2,000 patients and the staff. 487 Report on the experimental treatment of sewage by the activated sludge process. M. GAULT. Ann. Report Supt. Sewers, City of Worcester, Mass. For year ending Nov. 30, 1919. 473-549. An elaborate and detailed report covering structual features of the plant, operating data, and sludge dewatering experiments. Plant consisted of a bar screen, grit chamber, sew- age aerating tank, sludge re-aerating tank, sedimentation tank, and sludge concentrating tank. Aerating tank was 26.25 by 14 by 10 ft. deep, divided into three channels each 4 ft. 8 in. wide, with filtros plates set in 7 rows of 4 plates each across each channel at 3 ft. 9 in. centers. A total of 84 filtros plates, and a diffuser area of 1 to 5.2. Capacity of the tank, 25,283 gallons. Sludge re-aerating tank was 12 by 5 ft. 4 in. by 10 ft. deep, divided into two channels with 4 rows of 2 filtros plates each spaced at 3 ft. clear in each row. Capacity of this tank, 4,386 gallons. Sedimentation tank was 14 ft. diam. by 9 ft. deep, with a hopper bottom tapering to 2 ft. diam. Sludge concentration tank was 3 ft. diam. by 20 ft. deep, of wood, concrete lined, with a hopper bottom sloping to 14 in. diam. Sewage treated varied from 75,000 to 125,000 gallons rr day, aeration period from 4 to 6 hours, sludge re-aeration period from to 6.5 hours, sedimentation period from 1.7 to 2.9 hours, air flow 1.7 to 5.0 cu. ft. per gallon of sewage, and volume of sludge carried 16 to 30%. Com- plete analyses of the air from the sewage and sludge re-aerating tanks are given, as well as of the sludge which averaged 1.94% solids, and contained on a dry basis, 51.12 to 71.10% organic matter, 8.37 to 17.88% iron, 3.16 to 7.35% N, and 1.86 to 9.02% fats. Numerous other tables of data accompany the report, as well as illustrations. (Cf. Ref. No. 540.) 488 A new process of sewage purification: oxidation of sewage without a bacterial bed. E. ROLANTS. Rev. Hyg. et Police Sanit. 41, 459-78. Exp. Sta. Record 42, 188. Chem. Abst. 14, 2671. A review of the work on sewage purification by the activated sludge process. 489 The activated sludge process at Tunstall. (Eng.) ANON. Surveyor 56, 366. Illustration without detailed description of the converted aerating tanks which are treating 300,000 gallons of sewage per day by the activated sludge process. 490 Treatment of sewage sludge. G. MUMFORD. British Patent Application 30,579, Dec. 6, 1919. Jour. Soc. Chem. Ind. 38, 968A. 491 Results of 1918 operations of the testing station of the Milwaukee Sewer- age Commission. ANON. Eng. & Contg. 52, 669. Chem. Abst. 14, 1175. It is concluded from the report of MR. W. R. COPELAND, Chief Chemist, that endless belt plate screen with slots 1-8 by 2 in., with a 2 in. loss of head, will handle 3 million gallons of sewage per 24 hours upon 27 sq. ft. of wetted area, and remove 150 Ibs. of dry solids per million gallons. Aerating tanks 15 ft. deep treated the equivalent of 16.5 million gallons of sewage per acre per day. Tanks 10 and 15 ft. deep were tried, all equipped with filtros plates as air diffusers. Sludge and rust filled the holes in perforated pipes so quickly that it was necessary to empty tanks and clean the pipes after 2 days run. Air must be thoroughly cleaned. Dorr thickeners proved successful in concen- trating the sludge in the settling tanks. Tables of analytical data are given. 492 Present status of the sew.age disposal problem. G. G. NASMITH. Con- tract Record 33, 1137-40. Can. Engr. 37, 519-22. Surveyor 57, 19-21. Chem. Abst. 14, 1173. General problems are discussed, chiefly the nuisance 83 The Activated Sludge Process of sludge treatment. Numerous features of the activated sludge process are referred to, the author stating that the principles underlying this process and trickling filters are identical, and that the complete solution of the sewage disposal problem will eventually come through a combination of one of these processes with sludge digestion. Efforts to recover soluble nitrogenous values in sludge are made difficult by their collodial nature, and it may be better to dissolve and oxidize as much organic material as possible, turn out a smaller quantity of stable residue, and make no attempt at conservation. 493 Activated sludge plants in Texas. ANON. Eng. News-Record 83, 920. Besides the two large plants at Houston, smaller plants have been put in at Coleman, Gainesville, San Angelo, San Marcos and Quanah. (Also at Sherman, Paris, and Fort Worth. J. E. P.) 494 Sewage purification problems. EDITORIAL. Surveyor 56, 398. Comment on the paper of MR. A. J. MARTIN (Ref. No. 495) in which approval is given the suggestion that a central testing station be established, in order that all new methods of sewage disposal may be judged on their merits. 495 Sewage purification problems. A. J. MARTIN. Surveyor 56, 401-2; 419. Eng. & Contg. 53, 364-5. Chem. Abst. 14, 2389. The activated sludge process is referred to as the most promising novelty for the purification of sewage which we have had, and that a way will be found to very materially reduce the power now required so that the process will become valuable. Sludge dewatering and its use as a fertilizer is discussed. 496 Progress in sludge dewatering tests. EDITORIAL. Eng. News-Record 83, 973. The work at Houston, Texas, is referred to (Ref. No. 497) but is considered as still in the experimental stage. If sludge dewatering can be done practically and economically, it may assure the success of the activated sludge process which produces a sludge of high N content. 497 Notes on the activated sludge plants at Houston, Texas. ANON. Eng. News-Record 83, 1003-4. Chem. Abst. 14, 440. City engineer J. C. McVEA and principal assistant G. L. FUGATE supply the following data. The north side plant, started in May, 1917, rated at 10 million gallons per day, is now treating 5.5 million gallons daily. Plant cost $254,671. South side plant, started in August, 1918, rated at 5 million gallons per day, cost $115,085. The filtros plates when first installed were held by cast-iron holders, the rust from which clogged the plates so they were removed and set in concrete. Washing with hot HC1 restored their porosity to nearly the original capacity. Sludge presses in operation two Simplex presses of 120 plates each indicate that 18,000 Ibs. of sludge of 98.25% moisture, can be reduced to 80% moisture in 8 hours. Addition of 0.65 gallon of 66 Be. sulphuric acid per 1000 gallons of sludge aids dewatering and increases the N content of the sludge from 5.47 to 6.93%. Cost of treatment by the activated sludge process is about $12 per million gallons, and it is expected that the revenue from the sludge will pay the cost of dewatering and drying same, as well as interest and depreciation on the $85,000 invested. 0.5 ton of sludge per million gallons of sewage, and a profit of $4 to $10 per ton of sludge is estimated. 10% moisture basis. Sta- bility of effluent is obtained as long as 1 p. p. m. of nitrate is present in the treated sewage. The free ammonia results are an index of the condition of the effluent, ranging from 22 p. p. m. in the crude sewage to 2 p. p. m. in the effluent. The latter is remarkably clear. Removal of suspended matter is about 95%. 498 $6,000,000 sewage scheme recommended for the western part of York Township, Ontario, Canada. Can. Engr. 37, 559-60. Abstract from the report of engineers FRANK BARBER and R. O. WYNNE-ROBERTS. The method of treatment will be either by means of tanks and filters or by the activated sludge process. 84 Abstract Bibliography 1919 499 Development of the activated sludge process at Manchester. (Eng.) ANON. Surveyor 56, 417-8. Can. Engr. 38, 245-7. Chem. Abst. 14, 1400. Excerpts from the annual report of the Manchester Rivers Dept. for the year ending March 31, 1919. At the Withington works 172,000 gallons per day were handled, with air varying from 0.8 to 1.7 cu. ft. per gallon of sewage, and sludge varying from 15 to 30%. Nitrification varied from 0.10 to 0.65 grain per gallon, the nitrite and nitrate N being calculated as am- monia. The tanks are 6 ft. deep, and the diif users therein have been used for 2 years with a replacement of 6 out of 300. In wet weather 0.8 cu. ft. of air maintains a good effluent. The plant works well on varying rates. 0.5 ton of dry sludge is produced per million gallons: as discharged it contains 98.8% moisture. Centrifugal dewatering has not been encouraging. At Davyhulme the fill and draw plant has handled 45,000 gallons per day. A large plant is under construction, comprising a grit chamber, aerating tanks, sludge reaction channel, and settling tanks of circular type cleaned by a scraper, and also a hopper bottom type. This plant will handle 1 million gallons per day with 6 hours aeration, and with 2 to 4 hours re-aeration. Diffusers are one-eighteenth tank area. 500 Milwaukee sewage-testing station: experimental data. ANON. Eng. News-Record 83, 1063. Surveyor 57, 244. Chem. Abst. 14, 439. Data from the 1918 reports of Ch. Eng. T. C. HATTON and Ch. Chem. W. R. COPELAND. Sewage was screened through Hamburg type screens with 1-8 in. wide slots, which protects the aeration tanks from coarse debris and enable the equiva- lent of 16.5 millions gallons of sewage per acre per day to be treated, as against 7 million gallons without screening. Suspended matter removed 99% ; bacteria removed 95% ; stability over 100% on their standard. The air at the plant is sooty and clogged the filtros plates, hence it was filtered through a layer of 12-oz. duck and then through canton flannel, which improved it. Galvanized iron pipes are preferred for air distribution, as black iron pipes soon rust and the rust clogs the air passages. 501 The Sanitary District of Chicago. Stockyards (sewage) treatment plant. COMMITTEE REPORT. Pamphlet pp. 32. (Dec. 1919.) Reports of the committee on engineering, the chief engineer, and the attorneys, respecting the treatment of sewage from the stockyards district, and the relations be- tween the Sanit. Dist., the packers, and others, concerning the construction, maintenance, operation, and income from a treatment plant suitable for the purpose. The activated sludge process is favored. 502 Water and sewage purification. A. C. HOUSTON. Ann. Reports Soc. Chem. Ind. on the Progress of Appl. Chem. 4, 482-5. The review of the activated sludge process for the year 1919, is confined almost exclusively to the work at the Sheffield (Eng.) plant. 503 Brooklyn, N. Y., sewage treatments experiments. G. T. HAMMOND. Trans. Am. Soc. Munic. Impvts. 26, 98-198. Eng. & Contg. 53, 39. Fire and Water Eng'rg. 66, 1278-82. Refers in passing to the activated sludge and aeration experiments, but an account of this work is reserved for a separate paper. 504 Bureau of Sanitary Engineering. Municipal Sanitation. C. W. GODDARD and V. M. EHLERS. Texas State Board of Health, publication No. 3. pp. 18. (1919.) The activated sludge process should be considered by the smaller towns only when very cheap power is available and objections are made to other methods of sewage treatment. For larger cities where a revenue can be obtained from the sludge, the method may prove to be the most econom- ical one. More efficient handling of the sludge is desirable. Comparative initial costs of activated sludge plants are approximated at about one-half that of a "Scresetfildis" plant. (Screens, settling, filtration, disinfection.) 85 The Activated Sludge Process 505 English activated sludge plants. ACTIVATED SLUDGE, L'TD. Trade Cir- cular (undated). Illustrates and refers to the following plants: Man- chester; Davyhulme works; the fill and draw installation of 1914, and the later continuous flow plant; Withington works; plant treating 250,000 g. p. d. with 4 hours aeration and 82% purification, or 375,000 g. p. d. with 3 hours aeration and 81% purification. The Worcester works, in operation continu- ously since 1916, purifying 750,000 g. p. d. The plant at Stamford treating 100,00 g. p. d. of strong sewage containing much abattoir refuse, with an average purification of 90% by the O absorption test, and of 86% by the albuminoid ammonia test. A plant at the National Filling Factory at Aintree, operating since 1916 on the wastes of 2000 workers. A plant for the Ad- miralty Airship Station at Moreton; population 400. The experimental plant at Harpenden for H. M. Bd. of Agr., for producing activated sludge for fer- tilizer tests. A plant for the Am. Red Cross Hospital near Southampton; population 2000. A plant for a Gov. cartridge factory at Blackpole, completed in 1917 and treating the sewage from 4000 workers. A plant at Tunstall, treating 300,000 g. p. d. 506 Sewage disposal. Book. L. P. KINNICUTT, C. E. A. WINSLOW and R. W. PRATT. Second Edition, 1919. Chapter XII, pp. 381-405, deals with the activated sludge process from an historical, experimental and practical point of view, discusses the results obtained at several places, and gives a list of references to the subject. 192O 507 Activated sludge process of sewage purification. E. ARDERN. Munic. Eng'rg. & Sanit. Record 65, 11-2, 26. Surveyor 57, 8-9. Chem. Abst. 14, 583. A review of the experiments in England as presented in an address at the meeting of the Assoc. of Mgrs. of Sewage Disp. Works. At the Withing- ton works (Manchester) there is a tank of 20,000 gallons capacity, capable of treating 45,000 gallons of sewage daily, also a 250,000 gallon plant with aerating chamber 100 ft. long, divided by baffles into 5 channels each 4 ft. wide. This plant could handle 350,000 g. p. d. Effluents were satisfactory, purification quite good and air consumption less than 1 cu. ft. per gallon. 300 diffusers have been in use for two years and only 8 removed for cleaning. Air pressure is 3.1 Ibs. Fertilizer experiments with activated sludge at the Harpenden plant are referred to, and mention made of the activated sludge plants at Tunstall, Bury, for the army, and some institutions. MR. J. KERSHAW, P. LAMB, J. BOULTON, W. H. MAKEPEACE and A. J. MARTIN participated in the discussion which included such matters as elasticity of plant, effect of gas liquors on the purification, mechanical agitation, sludge treatment and costs of air compression. 508 British Sanitary Engineering developments in 1919. EDITORIAL. Engineer 129, 10-2. Eng. & Contg. 53, 357-9. Chem. Abst. 14, 2524. Concerning the activated sludge process, it is noted that despite the fact that it has had adverse conditions to contend with during practically the whole of its existance, it has made a wonderful amount of headway. Refers to the new experimental million gallon plant at the Davyhulme works (Manchester) and a small plant at Harpenden. Reading has decided to treat the whole of its sewage by the activated sludge process. The results of producing fer- tilizer material from activated sludge are also noted. 509 Bacterial flora of sewage purified by the activated sludge process. P. COURMONT and A. ROCHAIX. Compt. rend. 170, 75-8. Jour. Soc. Chem. Ind. 39, 171A. Chem. Abst. 14, 1400. The bacterial flora of samples of sew- age before and after treatment by the activated sludge process were studied. Aeration was carried out in a small laboratory apparatus. The total bac- terial reduction was considerable; in one sample the number of organisms 86 Abstract Bibliography 1920 was reduced from 202 million per cc. to 67,000. The bacterial species found in the purified sewage were few in number and all aerobic, chromogenic species predominating. No B coli were found. 510 Record forms for activated sludge plants, Houston, Texas. G. L. FUGATE. Eng. News-Record 84, 75. Chem. Abst. 14, 790. Daily report sheets as used at Houston are reproduced. 511 Proposed activated sludge plant at Burnley (Eng.) NEWS ITEM. Surveyor 57, 27. A committee after visiting the Sheffield activated sludge plant, suggest to the Council that the process be tried at Burnley. 512 Sixth Annual Report of the Milwaukee Sewerage Commission. T. C. HATTON. Pamphlet pp. 49, with inserts. (Jan. 15, 1920). The report of Ch. Eng. Hatton for the year ending Dec. 31, 1919, states that the Com- mission unanimously and formally adopted the activated sludge process. The work at the testing station may be summarized as follows: Grit chamber; little information was obtained owing to weather and sewage conditions. Screens: chain belt screens with 1-8 in. and with 3-32 in. slots, sewage with 274 to 350 p. p. m. suspended solids, head on screens 2 to 4 in., passed 128,435 to 246,000 gallons per sq. ft. of wet screen area, from which 472 to 1,017 Ibs. of screenings of 85 to 87.2% moisture were collected per million gallons of sewage. Aerating tanks: there was a slight difference in favor of the 15 ft. depth of tank, not taking into consideration the extra cost of compressing air for a 15 ft. dept of liquor over that for a 10 ft. depth. Indications pointed to easily treating 12 millions g. p. d. per acre in 10 ft. deep tanks, and 20 million g. p. d. per acre in 15 ft. deep tanks. 155,000 gallons of sludge of 97.4% moisture were returned to the aerating tanks p. m. g. of sewage treated. Excess sludge was 12,100 gallons of 97.5% moisture p. m. g. of sewage treated. Ratio of diffusion plates of 1 to 4.4 was more favorable than 1 to 6. Contact period ranged from 4 to 6 hours. Volume of air per gallon of sewage was 1.25 cu. ft. though less could be used but for the agi- tating effect desired. Experiments showed that owing to the fluctuation in the character of the sewage, and to prevent the light floculent sludge from rising to the surface, that a 15 ft. deep sedimentation tank was necessary, and that with this depth of tank, 1,600 to 2,000 gallons of mixed liquor per sq. ft. of tank area, could be satisfactorily clarified. Sludge re-areation tests do not appear to justify the additional tankage and air required for the purpose. After one year's run there was no evidence that the filtros plates had in any way been reduced in porosity or stability. Aif was filtered through 10 oz. duck, then through canton flannel, and washed by the hydro-turbo blower. Sludge pressing and drying investigations are still in progress. Thus far, filter press experiments indicate about 3 Ibs. of sludge cake of 80% moisture per sq. ft. of filter cloth in 4.5 hours, from a sludge containing initially 97.5% moisture. The report of the Ch. Chem. for the year is issued as a separate document. 513 Treatment and disposal of sewage. H. B. HOMMON, J. K. HOSKINS, H. W. STREETER, R. E. TARBETT and H. H. WAGENHALS. U. S. Public Health Reports 35, 101-31. Chem. Abst. 14, 1721. The description of the activated sludge process is very brief, covering in short paragraphs; theory, outline of plant, process, advantages and disadvantages, and general. Under the latter head reference is made to the proposed or existing plants at Milwaukee, Chicago and Houston, Texas. A bibliography of 30 references concludes the article. 514 Sewerage and sewage disposal. The activated sludge process. EDITORIAL. Surveyor 57, 75-7. Reviewing the activated sludge work for the year 1919, reference is made to the plant at Manchester (Withington works) where 172,000 gallons of sewage has been treated daily on an average, throughout the year, with an effluent of uniformly high purity, and with 1 87 The Activated Sludge Process cu. ft. of air per gallon, except when a high degree of nitrification was re- quired. Sludge averaged 0.5 ton of dry matter p. m. g. sewage. Reference is also made to the mechanical agitation experiments conducted by MR. J. HAWORTH at Sheffield, Eng., and to methods of sludge treatment. 515 Studies of methods for the treatment and disposal of sewage. L. C. FRANK and C. P. RHYNUS. U. S. Pub. Health Bull 101. Expt. Sta. Record 43, 189. Incidentally refers to the activated sludge method as among those studied at one time. 516 The activated sludge process. TRADE NOTE. Surveyor 57, 119. " in July last (1919) a limited company (Activated Sludge Lt'd.) was formed to acquire the full control of all patents held by Messrs. JONES & ATT- WOOD, Limited, of Stourbridge, and others relating to this process." AMES- CROSTA apparatus. "For several years past the company (Ames-Crosta Sani- tary Engineering Co., Lt'd.) has devoted close attention to the treatment of sewage by activated sludge and it is hoped that an installation on a large scale of machinery of a distinctly novel character, will be ready for in- spection in a very short time." 517 Sewage disposal in small cities and towns. M. F. STEIN. Munic. County Eng'rg. 58, 71-5. Refers to the activated sludge process as offering a substitute for the Imhoff tank-trickling filter plant, but is more compact and probably produces an effluent of greater purity. It is largely on an ex- perimental basis at present. The difficulties of the process are those of operating under the limitations of practical conditions as against experi- mental, and the disposal of the sludge. 518 Modern sewage disposal plant at San Angelo /Texas. ANON. Am. City 22, 147-8. An activated sludge plant located less than 1,000 ft. from the main street of the city, adjoining a public park, and operating only in the day time. Two old septic tanks 110 by 20 by 8 ft. deep, and 60 by 20 by 8 ft. deep, were utilized, half of the larger tank being converted into an aerat- ing chamber, in which the air is distributed through perforated pipes. The other half receives the raw sewage where it is detained for about 3 hours for plain sedimentation. The smaller tank receives the night flow of sewage from which it is injected to the aeration tank during the following day. A sludge settling tank 20 by 18 by 25 ft. deep adjoins the aerating tank. Plant has a capacity of 400,000 g. p. d. but is treating only 225,000 g. p. d. at present. Effluent is clear and sparkling with a slight musty but not offensive odor, and is discharged into a nearby river. Stability tests with methylene blue have shown it to be well within the requirements of the law. 519 The origin of the activated sludge process. EDITORIAL. Surveyor 57, 199. Eng. & Contg. 53, 726. Chem. Abst. 14, 2524. A consideration of the claim of the Lawrence, Mass., and Manchester, Eng. workers, in which the editor concludes that " it is not too much to say that the credit for the development of the laboratory observations and deductions, and their trans- lation into practice, is due entirely to the Manchester workers." 520 The activated sludge process. ANON. Surveyor 57, 201-2. Refers to the report of the Lawrence, Mass., experiment station for the year 1917, (Ref. No. 362) quoting therefrom on the activated sludge experiments recorded, and taking exception to the "remarkable American claim" that it is "essentially a Lawrence process." 521 Sewage disposal methods of London, Eng. ANON. Surveyor 57, 205. Eng. & Contg. 53, 762. Chem. Abst. 14, 2524. Statement that the laboratory activated sludge experiments after many failures and adjustments gave sufficiently successful results to justify investigation on a practical scale. These experiments, undertaken prior to the war and suspended on account of it, are to be revived. 88 Abstract Bibliography 1920 522 Glasgow and the acivated sludge process. NEWS ITEM. Surveyor 57, 208 "An exhaustive investigation has strongly convinced a deputation of the Glasgow Corporation sewage committee of the value of the activated sludge process." The advantages of the process over all other methods, especially as to the values recovered from the sludge, will result in a recom- mendation for an activated sludge plant at Shieldhall. 523 The origin of the activated sludge process. EDITORIAL. Surveyor 57, 216. Refers to the opinions of the American experts, (Ref. No. 524) and notes that they agree with those of the editor. 524 The origin of the activated sludge process. ANON. Surveyor 57, 222. Quotations from the second edition of "Sewage Disposal," pages 282-3, by Kinnicutt, Winslow and Pratt, from which it may be noted that DR. G. J. FOWLER " ' to whom is due the actual discovery of the activated sludge process ' " admitted that " ' the illuminating idea which originated the work was due to the visit he had paid while in the United States to the Mecca of sewage purification namely, the experiment station at Lawrence in the State of Massachusetts.' " " 'Nevertheless, American engineers should reciprocate Dr. Fowler's graceful acknowledgement by recognizing that none of the investigations on this side of the water had really brought sewage aeration to a state of practical usefulness. It was the Manchester studies, and particularly the discovery of the effectiveness of previously aerated or 'activated' sludge in promoting oxidisation, which really gave us this im- portant method of sewage purification.' " 525 Experience with the activated sludge process at Manchester (Eng.) ANON. Eng. & Contg. 53, 280-2. Data from the last annual report of the Manchester Rivers Dept. on the fill and draw plant at the Davyhulme works, and description of the large continuous flow plant there under con- struction, also on the plant at the Wellington works. (Cf. Ref. No. 499). 526 Fine screen specifications for the activated sludge plant at Milwaukee. T. C. HATTON. Eng. News-Record 84, 511. Chem. Abst. 14, 1400. The specifications call for screen plates not less than 3-16 in. thick with slots 3-32 in. minimum width, by 2 to 2.5 in. long. These screens are for a plant to treat 130 million g. p. d. normal flow, and 190 million g. p. d. storm flow. 527 The activated sludge process of sewage purification large-scale opera- tion. E. ARDERN. Jour. Soc. Chem. Ind. 39, 60-4T. Surveyor 58, 427-8. Chem. Abst. 14, 1865. A large-scale continuous flow plant, to replace the experimental plant was installed for the treatment of Withington sewage late in 1917. A description of the installation and a general account of the results are given. 528 Purification of sewage with activated sludge. R. CAMBIER. Compt. rend. 170, 681-4. Jour. Soc. Chem. Ind. 39, 347 A. Chem. Abst. 14, 2388. Chem. & Met. Eng'rg. 23, 440. During the first few minutes of contact of raw sewage with activated sludge, there is a considerable reduction in am- monia without a corresponding increase in nitrate N, which shows a marked increase only after one hour. The phenomenon is less appreciable if old sludge is used, and in this case, if aeration is prolonged excessively, there results a decomposition of the sludge with production of nitrate. The effects of aerating ammonia-free water in the presence of washed activated sludge for a period of several days, was to reduce its volume from 500 to 50 cc., and to produce in the liquid 360 mg. nitrogen trioxide. The sludge was found to be entirely inactivated. In the presence of activated sludge nitrification is most rapid between 20 and 25 C. Aeration for 2 hours are required as compared with 15 hours at C. and 4 hours at 5 C. Above 30 C. nitrate is produced in very slight amounts, and at 37 C. (optimum temperature for nitrification in pure culture) only a trace of nitrate is formed and there is The Activated Sludge Process no clarification of the sewage. If a mixture of activated sludge and sewage after nitrification is decanted after 3 hours, the liquid in the interstices of the sludge is found to be considerably denitrified. The nitrifying capacity of the sludge, however, is not effected thereby. Both the ammonia and col- liodal matter of the sewage are for the most part absorbed by the sludge at the moment of contact. 529 Development of sewage purification. S. H. ADAMS. Can. Engr. 38, 314-5. In a letter to the editor, reference is first made to certain technical journals raising the question as to who invented the so-called activated sludge process, followed by a brief review of the progressive development of sew- age purification for the past 30 or 40 years, noting the "air-activation" work of DR. CLARK at Lawrence and DR. FOWLER at Manchester, and the "mechan- ical-activation" work of MR. J. HAWORTH at Sheffield, the concluding para- graph containing the statement that " these changes from land irrigation, chemical precipitation, contact beds and sprinkling filters to activated and mechanically agitated sludge, are but simple evolutionary stages in the solution of a difficult problem ." 530 Formation of activated sludge. F. DIENERT. Compt. rend. 170, 762-3. Jour. Soc. Chem. Ind. 39, 347 A. Chem. Abst. 14, 2229. In the prepara- tion of activated sludge, air is bubbled for a certain time through sewage, which is allowed to settle, the water drawn off, fresh sewage added, air again bubbled through, this being repeated until during a period of bubbling for 5 consecutive hours, 20 mg. of ammoniacal N per liter of sewage is con- verted into nitrous or nitric N. Experiments with various samples of sewage and water showed that the time required to produce activated sludge depends upon the water employed, its temperature, and the quantity of air used. Before being activated the sludge of sewage has little if any action upon the water in which it was formed. Analysis of water made 5 days before activation of the sludge gave 3.0 mg. per liter of N as nitrates before aera- tion, and 3.7 mg. after 4 hours aeration; the figures for ammoniacal N were 14.9 and 14.0 respectively. The day the sludge became active the figures were 2.4 and 12.0 mg. nitrate N before and after 4 hours aeration, and the ammoniacal N 16.2 and 1.0 mg. respectively. Analysis of the sludge gave as follows: after an aeratoin period of 58 days, but 5 days before it became active, the total nitrate N was 36.4 mg. per gram of dry sludge, and the ammoniacal N 1.3 mg. On the day the sludge became active, after an aera- tion period of 63 days, the figures were 31.5 and 1.5 respectively. The condition of activation is reached abruptly. In experiments with water from the tanks of the Pasteur Inst., it was proved that a nitrous fermentation took place after the period of activation, nitrate N only appearing after several weeks. During an activation period of 11 days, each time after 24 hours aeration, all the ammonia introduced (20 mg.) was recovered, but on the 12th day all the ammonia was transformed into nitrites. 531 Activated sludge process considered at London, Eng. ANON. Eng. News- Record 84, 616. Authority to visit some of the English activated sludge plants has been requested by a committee, apparently to study the process with a view of its adoption in London. The volume of sewage discharged from the two London outfalls is 348,000,000 g. p. d., and about 2,000,000 tons of sludge are dumped into the sea annually. 532 Canada's first successful activated sludge sewage system at Brampton, Ont. G. G. REID. Contract Record 34, 292-7. Chem. Abst. 14, 2042. In 1908 Brampton built a pair of reinforced concrete tanks, each about 13 ft. wide by 100 ft. long, with covers. In 1918-19 the old tanks were con- verted into aeration chambers and a two-chamber settling tank was added, 30 by 16 by 22 ft. deep with two pockets at the bottom. Filtros air diffusing plates are used. The plant is operated 15 hours per day, aerating at night. (Cf. Ref. No. 548). 90 Abstract Bibliography 1920 533 Treating the waste of Packingtown, Chicago. LANGDON PEARSE. Jour. West. Soc. Eng'rs. 25, 365-73. Public Works 49, 251-3. Chem. Abst. 14, 3489. A brief review of the packinghouse industrial waste problem in Chi- cago. The packers have agreed to pay 60% of the cost. The results of the testing station are briefly reviewed. The activated sludge process proved most practicable, offering a possible recovery of fertilizer material and grease. The plans recommended included intersepting sewers, fine screens, aeration for 8 hours using 4 cu. ft. of air per gallon of sewage, settling, handling the sludge with acid, filter pressing and rotary driers. A stability of 80 to 90% in summer and 30 to 60% in winter, was obtained in the tests. 534 Origin of the activated sludge process. H. W. CLARK. Surveyor 57, 308. In a letter to the editor Dr. Clark quotes from published articles by DR. FOWLER, DR. H. MACLEAN WILSON, ARDERN & LOCKETT, and from the reports of the Lawrence Expt. Sta., also from correspondence of Dr. Fowler, in support of the author's contention that the process originated at Lawrence. "There is no intention on our part to belittle or depreciate the further de- velopment of this process by English workers, but in its essentials it is a Lawrence process; and if, in 1912, we had not shown the work then being carried on to Dr. Fowler, the process would not have been taken up in England for further study. The gallon bottles and carboys in which this process was being carried on by us in 1912, and which were shown to him, were operated in all essential details exactly as activated sludge tanks are today, and producing equally good results, although we had not at that time given the process the very attractive name afterwards attached to it by the English workers." 535 Action of activated sludges on the ammonia of sewage and of ordinary water. F. DIENERT and GIRAULT. Comptes rend. 170, 899-901. Jour. Soc. Chem. Ind. 39, 382-3 A. Chem. Abst. 14, 2670. The activated sludge pre- pared as previously described (Ref. No. 530) causes the disappearance of ammoniacal N from sewage and from ordinary water in an almost identical manner, the ammoniacal N content of the water having been made equal to that of the sewage. The experiments were made by means of allonges in a water bath at 25 C., in each of which was placed 450 c. c. of activated sludge containing about 12 grams of dry matter at 120 C., and 1500 c. c. of sewage or ordinary water, the ammonia content of each being known. The same amount of air was made to bubble through the mixture until the ammonia had passed out, when the time required for its disappearance was noted and the nitrates and nitrites then determined. On each day the liquid in the two allonges was decanted and replaced by other samples of the same nature containing known amounts of ammonia, and the determinations re- peated. This was continued for 9 months, the average figures for each month being given. As the sludge gets older the ratio of ammonia oxidized to time of disappearance, at first diminishes, then increases. Nitrous N only appears after the sludge has been used for several months. 536 Filtros plates successfully cleaned. G. L. FUGATE. Eng. News-Record 84, 754. Chem. Abst. 14, 1865. The removal of iron rust from filtros plates in the activated sludge plant at Houston, Tex., was accomplished success- fully by immersing them in HC1 (strength not given) at 98 C. 537 The origin of the activated sludge process. W. CLIFFORD. Surveyor 57, 328. A letter to the editor referring to the letter of H. W. CLARK (Ref. No. 534) in which the author contends that "Sufficient surface of slate or other material upon which abundant growths may occur is not an essential condi- tion of the activated sludge process." 538 The fertilizing value of sewage sludges. W. E. BRENCHLEY and E. H. RICHARDS. Chem. Age. (Lond.) 2, 404. Jour. Soc. Chem. Ind. 39, 145R, 177-82T. Chem Abst. 14, 3743. Results of experiments (pot) with activated and slate- 91 The Activated Sludge Process bed sludges are given. With 1 and 6 units of activated sludge, barley showed 65 and 92% increase in the weight of the crops over that of the control sample. After barley had been cropped, mustard was sown in the soil left in the pots, the 6-unit pot showing an increase of 940% over that of the control sample, from which the authors conclude that activated sludge may be of considerable utility because of the high residual value. 539 Action of the bacteria of sewage purified by the activated sludge process on albuminoid material, urea, and nitrates. P. COURMONT and A. ROCHAIX. Comptes rend. 170, 967-70. Jour. Soc. Chem. Ind. 39, 423 A. Chem. Abst. 14, 2671. The proteolytic properties of the 7 species of bacteria found in the effluent from sewage purified by the activated sludge process are either absent or much reduced, according to the reactions of these species towards coagulated serum, gelatin, egg albumin, milk casein, and the production of indole. Five of the 7 gave indole following action on peptone, but not upon the other albuminoid material studied. B. subtilis attacks each of the albuminoid sub- stances yielding albumoses, peptones, leucine and tyrosine. It secretes a rennin but not casease, and it slowly attacks urea. Three of the 7 are active in the fermentation of urea and three entirely without action. Two of the species were without action upon nitrates in bouillon or peptone ; the other 5 were direct denitrifying bacteria, as shown by their action on potassium nitrate, some of which were very active. 540 Activated sludge experiments at Worcester, Mass. RAY S. LANPHEAR. Eng. News-Record 84, 819-23. Chem. Abst. 14, 1865. The experimental activated sludge plant consisted of a bar screen, grit chamber, sewage aeration tank, sludge aeration tank, sludge concentrating tank, and a shallow tank for measuring excess sludge previous to disposal. The bar screen, 0.5" openings, removed 11.4 cu. ft. screenings p. m. g. of sewage treated. At least 2 cu. ft. of air per gallon and 4 hours aeration was required for weak sewage and 3 cu. ft. of air and 6 hours aeration for strong sewage. Filtros air diffusers were used. Albuminoid ammonia must be below 2 p. p. m. if a stability of 75% is desired. The effluent was clear but contained considerable suspended matter. Dissolved oxygen was low in the effluent and nitrification was absent. On account of the presence of industrial wastes and the strength of the Worcester sewage, the process is considered unsatisfactory. The sludge analyzed: total N, 4.06%, available N, 1.39%; total phosphorus pentoxide 2.26%; citrate soluble 1.76%. 541 Sewage treatment plans for the Chicago Sanitary District. ANON. Eng. News-Record 84, 873. Chem. Abst. 14, 1865. The plans comprise the following program: Construction of an activated sludge plant at Maywood to abate the nuisance in the Des Plaines River; negotiations for a large activated sludge plant for the stockyards district costing $9.5 million; also negotiations for treatment plants at Corn Products Co. and chrome tannery of Greiss- Pfleger Co., and the treatment of the sewage from the Calumet region. 542 By-products from sewage sludge. R. S. WESTON. Am. Jour. Public Health 10, 405-7. Chem. Abst. 14, 2041. Interest in fat and fertilizer recovery from sludge is renewed because of the shortage of fats and fertilizers during the war, and the discovery of the activated sludge and Miles processes for sewage treatment. Both of these processes are briefly described. 543 St. Louis Meeting Am. Chem. Soc. Water, Sewage and Sanitation division. ANON. Jour Ind. Eng. Chem. 12, 419. Activated sludge and other methods proposed for the treatment of sewage, especially those applicable to the wastes from industrial plants, was discussed at this meeting. 544 Modern methods of sewage disposal. E. S. CHASE. Am. City 22, 485-9. A popular article on the subject, referring to the activated sludge process as one with a low first cost, requiring careful operation, comparatively small 92 Abstract Bibliography 1920 area, but somewhat more elaborate machinery than the older processes. It produces a clear, sparkling, colorless effluent and the bacterial removal is high. The sludge, if handled rapidly, is inoffensive and has a value as fertilizer material. 545 Action of activated sewage sludges. F. DIENERT, F. WANDENBULKE and M. LAUNEY. Comptes rend. 170, 1089-92. Jour. Chem. Ind. 39, 424A. Chem. Abst. 14, 2670-1. Experiments were made to determine the influence of varying amounts of activated sludge upon the rate of nitrification of Seine water containing increasing quantities of ammonia. To 1 liter samples of this water there was added 400, 200, lOOi, and 50 c. c. of activated sludge, correspond- ing to 12, 6, 3, 1.5 grams of dry matter at 1001 C. Air was bubbled through at the rate of about 50 liters per hour. Points determined' were the amount of ammonia driven off and of nitric and nitrous N formed. Tests were made with the following amounts of ammonia per liter: 20 mg. for 1 hour; 40 mg. for 1 hour; 40 mg. for 2 hours; 60 mig. for 2 hours; and 60 mg. for 3 hours. By thus varying the amounts of activated sludge and ammonia it was found that the ratio of ammonia destroyed to the dry weight of the sludge introduced, dimin- ishes as the amount of sludge used increases. The results of this process of sewage purification were checked by bacterial counts upon different samples. It rapidly gives an effluent free from ammonia and non-putrescible, but on ac- count of the great difference in the composition of the various waters, the reduction in the number of bacteria was very variable. 546 The nitrogen in sewage. G. M'GowAN. Surveyor 57, 405-7. Eng. & Contg. 53, 736-8. Chem. Abst. 14, 3735. Referring to the activated sludge pro- cess, the author notes that the conservation in this sludge of the more readily assimilable N of the sewage colloids and solids* N which hitherto has been in great part lost should prove a marked asset in its favor. Pot cultures and field plot experiments made with it are mentioned. 547 Action of the bacteria of the flora of sewage purified by the activated sludge process on carbohydrates. P. COURMONT and A. ROCHAIX. Comptes rend. 170, 1134-5. Jour. Soc. Chem. Ind. 39, 465 A. Chem. Abst. 14, 3440. The bacteria of the flora of sewage purified by the activated sludge process exert a marked fermenting action on carbohydrates. Varies with the species. 548 Reconstructed septic tanks serve as activated sludge plant. ANON. Eng. & Contg. 53, 543. Because of the nuisance, the town of Brampton, Ont., Can., remodeled a septic tank 100 ft. long by carrying down one longitudinal wall about 6 ft. to a horizontal bottom about 3 ft. wide, a 1 to 1 slope being carried to the opposite wall. The tank was also divided into 6 sections by cross walls. Filtros plates in the horizontal bottom diffused the air. A settling tank 30 by 16 by 22 ft. deep was built with 2 chambers which slope to hoppers 4 by 4 ft. Surplus sludge is dried on outside beds. Plant operates 15 hours per day with one attendant and has received the approval of the Provincial Board of Health. (Cf. Ref. No. 532.) 549 The work of the water and sewage laboratory of the Mass. State Board of Health. ANON. Eng. & Contg. 53, 552^3. At the present time the principal sewage studies at the station are in regard to the activated sludge process, which is stated to have had its inception at Lawrence in 1912, in the purification of sewage by aeration and growths. 550 Results of activated sludge experiments at Milwaukee. ANON. Eng. & Contg. 53, 554. Chem. Abst. 14, 2388. Abstract of the Sixth Annual Re- port of the Milwaukee Sewerage Commission. (Cf. Ref. No. 512.) 551 Separation of suspended matters from sewage. ACTIVATED SLUDGE LT'D. and COOMBS. Jour. Soc. Chem. Ind. 39, 434A. British patent application No. 13,202, of May 13, 1920. 93 The Activated Sludge Process 552 Sewage purification plants. ACTIVATED SLUDGE LT'D. and COOMBS. Jour. Soc. Chem. Ind. 39, 434A. British patent application No. 13,203, of May 13, 1920. 553 The nitrogen in sewage. DISCUSSION. Surveyor 57, 426-7. In discussion of DR. M'GowAN's paper (Ref. No. 546), A. P. I. COTTERELL referred to the mechanical agitation experiments at Sheffield, and to the activated sludge fertilizer tests at Harpenden. A. J. MARTIN suggested means for aeratnig sewage at less cost and J. FIELDHOUSE related a case where T. N. T. and chemical wastes had injuriously interfered with the activated sludge process. 554 Activated sludge moves forward. EDITORIAL. Eng. News-Record 84, 989. Comment on T. C. HATTON'S paper (Ref. No. 555), considering some fea- tures from the practical point of view that apply especially to Milwaukee. The activated sludge process is very promising and it is hoped that it may eventually take a leading place among the several methods of sewage treatment. 555 Activated sludge plant for the city of Milwaukee. T. C. HATTON. Eng. News-Recond 84, 990-6. Public Works 48, 536-8. Surveyor 58, 21-3, 48-9. Chem. Abst. 14, 2229. Plans are for treating 85 million g.p.d. in 1930 and 130 million g.p.d. in 1950. The plant will comprise bar screens, grit chambers, revolving slotted fine screens 3-32", and activated sludge treatment. The bar screens will be spaced 3 11-16" apart. A velocity in the grit chambers of from 0.64 to 1.0 second feet is provided. The aeration tanks (2) are 340 ft. long, 22 ft. wide and 15 ft. effective depth, with filtros plates set at right angles to the direction of flow and 4.5 ft. between centers. The sedimentation tanks are 72 ft. square and are provided with Dorr thickeners. The treated sewage will be discharged into Lake Michigan at 14 ft. depth. Air required is 1.5 cu. ft. per gallon of sewage. Tanks 15 ft. deep are more effective than those 10 ft. deep. Sulphuric acid-^4.5 c. c. per gallon of sludge assists in dehydrating it. The sludge and screenings are to be pressed and then dried in revolving driers. Coarse screenings are estimated at 40 Ibs. p. m. g.; grit 2.3 cu. ft.; fine screen- ings at 618 Ibs. with 87. 2% moisture, and excess sludge at 12,100 gallons p.m.g. of sewage treated. Contact in the aeration tanks is based on a 6 hour period. The cost of the plant is estimated at $5,000,000. 556 Activated sludge experiments at Champaign-Urbana, 111. NEWS ITEM. Eng. News-Record 84, 1034. It is proposed to install at first a 100,000 g.p.d. activated sludge plant complete in every particular. Experiments will be directed particularly to the reduction of the amount of air used and to drying the sludge. The old plant at Champaign will be utilized in part. DR. EDWARD BARTOW, Chief 111. State Water Survey, will direct the work. 557 The activated sludge process: Reading's 148,000 scheme. ANON. Sur- veyor 57, 440. The activated sludge process is recommended by M. TAYLOR as particularly suitable for Reading, the sedimentation tank scheme held up by the war, being abandoned. 558 The progress of sewage disposal. A. J. MARTIN. Surveyor 57, 446. A popular lecture on the subject, in which the activated sludge process is briefly described. This new process has been very favorably received, its chief drawback being the great bulk of the resultant sludge and the difficulty of drying it. 559 "Forced Aeration" sewage treatment. ANON. Public Works 48, 446. Can. Engr. 38, 522. As the result of a prize offered by Munic. Eng'rg. & Sanit. Record (London) for a new name for the activated sludge process, no less than 20 were submitted from which "Forced Aeration" was chosen. 560 New Name for activated sludge. EDITORIAL. Public Works 48, 447. The editor considers "forced aeration" less descriptive of the activated sludge process than the name it would replace, and questions its adoption. 94 Abstract Bibliography 1920 561 Purification of sewage and other liquids. W. JONES, Stourbridge, Eng. U. S. Patent 1,341,561, May 25, 1920. (Application filed Aug. 8, 1919. 4 claims.) Off. Gaz. 274, 755. Jour. Soc. Chem. Ind. 39, 526 A. Claim 1: In a purification system, a tank divided into a plurality of communicating open chambers, and an air supply for each chamber, the walls of the chamber being formed to direct the flow of the liquid under the pressure of the air supply in a circulatory path within the chambers. (Cf. Brit. Pat. 132,826, Ref. No. 404.) 562 Tunstall activated sludge plant. NEWS ITEM. Surveyor 57, 469. At a meeting of the Midland District of the Assoc. of Mgrs. of Sewage Dis- posal Works, held at Tunstall, the activated sludge plant was inspected, the process being explained in detail by the sewage engineer, W. H. MAKEPEACE. 563 Purification of sewage by activated sludge. R. CAMBIER. Comptes rend. 170, 1417-9. Jour. Soc. Chem. Ind. 39, 525A. A very slight trace of chloroform in the air bubbled through the sewage during treatment by the activated sludge process is sufficient to inhibit the formation of nitrates. Sim- ilarly, if air saturated with chloroform is bubbled through the sewage for one hour, and then pure air for four hours to remove the chloroform, on the introduction of the sludge and the subsequent bubbling of air, the ammonia disappears, but no nitrates are formed. Further, attempts to isolate nitrifying organisms from activated sludges were not successful. These results are opposed to the view that nitrification takes place during the purification of sewage by the activated sludge process. 564 Sewage effluents for disposal with and without dilution. ANON. Eng. News-Record 84, 1161-2. Chem. Abst. 14, 2960. From a report on sewage works operation submitted to the Sanit. Eng. Sec., Am. Pub. Health Assoc. in Oct., 1919. The normal characteristics of activated sludge effluents as produced experimentally are as follows: "(1) Low total suspended solid matter. (2) A practical absence of settleable suspended matter. (3) Presence of oxidized nitrogen as nitrites or nitrates in amounts equivalent to or better than in sprinkling filter effluents. (4) A low oxygen demand. (5) A high re- duction in total bacteria content." The importance of skilled supervision for practical activated sludge plants is emphasized. 565 Separation and settlement of solid matters from sewage and other liquids. WM. CLIFFORD, Oxley, Wlolverhampton, Eng. U. S. Patent 1,343,764 June 15, 1920. (Application filed March 27, 1918. 2 claims. Assigned to JONES & ATTWOOD, L'TD., Amblecote, Eng.) Off Gaz. 275, 539. Chem. Abst. 14, 2388. Claim 1: A settling tank, an inflow pipe, a guard about the delivery end of said pipe and comprising a cylindrical casing of uniform diameter throughout with open ends above and below said inflow pipe, and a vessel closed at the bottom and open at the top arranged centrally within and wholly above the lower end of the guard, the inflow pipe directing the material into the open end of said vessel. (Cf. Brit. Pat. 117,472, Ref. 275.) 566 Aeration of sewage and other impure liquids. OSWALD STOTT, Birming- ham, Eng., and ERNEST R. JONES, Stourbridge, Eng. U. S. Patent 1,343,- 797, June 15, 1920. (Application filed June 21, 1919. 6 claims.) Off. Gaz. 275, 546.. Jour. Soc. Chem. Ind. 39, 557 A. Chem. Abst. 14, 2388. Claim 1: In a process of purifying sewage and other impure liquids in which the purification is effected by bacterial sludge and air, artificially crculating the sewage or liquid, and at the same time ruffling or agitating the surface, so as to cause the introduction of air into the liquid by said ruffling or agitation. (Cf. Brit. Pat. 133,722, Ref. No. 407.) 567 Activated sludge plant at California State Prison. ANON. Eng. News- Record 84, 1260. The activated sludge plant at the Folsom State Prison has served a population of about 1500 for two years with excellent results, 95 The Activated Sludge Process though operated by convict labor that is very unreliable. Air diffusion through perforated pipes has given almost no trouble. The activated sludge plant proposed for Hermosa Beach has never been constructed, hence the Fol- som plant is the only activated sludge plant in California. 568 The treatment of sewage activated sludge system, Folly Point, Sydney. ANON. Commonwealth Eng. 7, 330-2. Chem. Abst. 14, 2833. Because increased volume of sewage made plant additions necessary, the activated sludge system was adopted instead of installing additional septic tanks. Both septic tanks and the activated sludge system are in use at the present time. 569 Stream pollution in Illinois. LANGDON PEARSE. Jour. Am. Waterworks Assoc. 7, 549-52. Chem. Abst. 14, 2833. Refers to the proposed activated sludge plant for treating packinghouse wastes in Chicago, the experiments on tannery and corn-products wastes, and to the ultimate treatment of all sewage in the entire Sanitary District of Chicago. 570 Purification of sewage by activated sludge. R. CAMBIER. Comptes rend. 171, 57-60. Chem. Age (Lond.) 3, 76. Jour. Soc. Chem. Ind. 39, 556-7 A. The ferrous sulphide normally present, or artificially introduced, into sludges, appears to be an important factor in the purifying and nitrifying action of these sludges on sewage. It is frequently noticed that when such sludges lose their activity a reddish color due to ferric hydroxide is apparent. All the causes which tend to destroy the ferrous sulphide, or modify its physical state, equally tend to destroy the activity of the sludge. It was found that sludges which had become practically inactive could be re-activated by the addition of either ferrous sulphide or of equimolecular proportions of solu- tions of ferrous sulphate and ammonium sulphide. 571 London County Council's large-scale experimental works. ANON. Sur- veyor 58, 23. Chem. Abst. 14, 3735. At the southern outfall works, lime-water tanks at present out of use, are to be equipped for activated sludge experiments capable of treating 250,000 g. p. d. One tank is to be equipped on the principle adopted at Manchester and Worcester, air agitation and one on the plan adopted at Sheffield, mechanical agitation. 572 A sewage farming possibility. EDITORIAL. Eng. News-Record 85, 145-6. Refers to possible use of Los Angeles, Calif., sewage for land irrigation, and suggests that the activated sludge process as a preliminary treatment might be worth looking into. The Pasadena activated sludge experiments are referred to as a near-by source of information. 573 Activated sludge exhibit. NEWS ITEM. Surveyor 58, 64. Chem. Age (Lond.) 3, 133. At the Health exhibition of the Royal Sanitary Institute Congress held at Birmingham (Eng.) in July, 1920, an exhibit of the activated sludge process attracted much attention. 574 Some points to observe in the design of sewerage systems and disposal works. THEO. HORTON. Munic. & County Eng.rg. 59, 58-9. While conceding the activated sludge process to be practical, it seems to have some inherent features which are difficult to control, and it is therefore not being very generally adopted. 575 Proposed sewerage and water supply scheme for Port Colborne, Ont., Canada. ANON. Can. Engr. 39, 269. For this town of 4,000 population R. O. WYNNE-ROBERTS recommends the activated sludge process of sewage treatment. 576 The design of Cleveland's sewage treatment works. G. B. GASCOIGNE. Eng. News-Record 85, 344-9. Chem. Abst. 14, 3488. A consideration of the different plants proposed and reference to the activated sludge investiga- tions made. 96 Abstract Bibliography 1920 577 Sewerage and water developments at Decatur, 111. ANON. Eng. News- Record 85, 457-8. Chem. Abst. 14, 3487. During 1917 small scale tests were made with the activated sludge process on mixed industrial and domestic sewage, and in 1919 the activated sludge process was tried on crude starch waste alone. The process was found applicable in the first case but not in the latter. The normal city sewage consists of a mixture of about 4,250,000 gal- lons of domestic and 1,250,000 gallons of industrial sewage daily. Decision has not been made as to the type of treatment plant. 578 Sewage disposal. C. H. GODFREY. Munic. Gaz. (Shanghai), 13, 317-8. Surveyor 58, 292. A report of the author's visit to India and Burmah. When treating sewage by the activated sludge process it is important to break up the solids or remove as much of them as possible by screens. The mechanical agitations experiments at the Sheffield activated sludge plant are referred to. 579 Relation of chemical engineering to sewage and trade waste treatment. R. H. EAGLES. Chem. & Met. Eng'rg. 23, 438-40. The activated sludge process is briefly described, with special reference to the various means of air diffusion. Attention is directed to the common use of air far in excess of theoretical requirements. The use of the Dorr thickener for sludge concen- tration and problems in connection with its dewatering and drying are also discussed. The Dorr company's activated sludge plant at Mt. Vernon, N. Y., is mentioned. 580 A novel laboratory for industrial research. ANON. Chem. & Met. Eng'rg. 23, 496-8. Refers to the Westport mill of the Dorr Co. Their modifica- tion of the activated sludge process is very briefly described. After passing a revolving screen the sewage is aerated in a specially designed thickener which affects distribution and circulation of the air bubbles in one chamber, and causes sedimentation in another chamber. The indications are that aeration may thus be accomplished in less time and at less cost than by other means, as less air is used. Research work on biological sludge treatment is in progress. 581 Activated sludge experiments at Mt. Vernon, N. Y. R. H. EAGLES. Eng. News-Record 85, 490-2. Chem. Abst. 14, 3488. 45,000 gallons of rather strong domestic sewage are treated daily, first passing a 0.75" bar screen. The plant proper consists of a "Dorrco" rotary screen and two combination aeration- sedimentation tanks in series, each 12 ft. in diameter by 11 ft. deep, with a total capacity of 17,600 gallons. Aeration occurs in the lower compartment where the liquid depth is 6.5 ft., air being diffused through filtros plates. Ap- proximately 75% of the air used is introduced into the first unit and 25% in the second. Sedimentation takes place in the upper compartment. Purifica- tion is effected by 0.6 cu. ft.' of air per gallon of sewage, with an aerating period of 8 to 10 hours. Effluent is clear, colorless, contains less than 20 p. p. m. of suspended solids (initially 245 p. p. m.), up to 1 p. p. m. nitrate and nitrite N, and is stable at least 4 days by the methylene blue test. 90% of the bacteria is removed and the O consumption reduced 79.6% (initially 154 p. p. m.) The dry sludge has 7 to 9% N as ammonia. Some tabulated data are given. 582 Sewage disposal research work. NEWS ITEM. Surveyor 58, 188. The Ministry of Health have investigated the results of the activated sludge process at various locations and is continuing the work. The use of sewage sludge as fertilizer has also been investigated in co-operation with the Min- istry of Agriculture and Fisheries. 583 Reading (Eng.) sewage disposal. NEWS ITEM. Surveyor 58, 221. Eng. News-Record 85, 833. Authority to borrow the necessary funds for the building of an activated sludge plant capable of treating the entire sewage of the city has been given. The plans have been prepared by G. M. TAYLOR. 97 The Activated Sludge Process 584 Disposal of waste. F. W. PARSONS. Saturday Eve. Post. 193, 36-8. A popular article on sewage disposal practice, with particular reference to the Milwaukee activated sludge plant, illustrating the 2 million g. p. d. plant built in 1917. 585 Peterboro favors Imhoff tanks, Municipal Board orders activated sludge. NEWS ITEM. Can. Engr. 39, 410. Because the Ontario Board of Health refuses to permit the discharge of Imhoff tank effluent into a river, the Munici- pal Board says an activated sludge plant must be installed, notwithstanding a favorable report on the Imhoff tank process by the city council. 586 The activated sludge process. EDITORIAL. Surveyor 58, 225. Can. Engr. 39, 627-8. Refers to the approval of the Reading (Eng.) activated sludge scheme by the Ministry of Health as an official endorsement of the process, and briefly summarizes the progress which the process has made since 1914. It is concluded that the activated sludge process has now definitely emerged from the experimental stage. 587 North Shore Sanitary District's sewage disposal problem. W. J. ALLEN. Fire & Water Eng'rg. 68, (Oct. 13, 1920). Aeration strongly advised, with thickening machines suggested as a method of separating the sludge from the liquid. 588 Activated sludge process at Sydney, Australia. J. W. SMAIL. Ann. Report Met. Board of Water Supply and Sewage. (1919-20.) Jour. Inst. Munic. & County Engrs. ? Eng. News-Record 85, 780. Six activated sludge tanks displace septic tanks, three of which are in operation treating 900,000 g. p. d. on the fill and draw plan, 12 hour cycle. 7 hours aeration, 2 hours settling, 1 hour decanting, 2 hours sludge re-aeration. Centrifugal sludge dewatering experiments are in progress. 589 Am. Soc. Munic. Impvts. St. Louis Meeting, 1920. ANON. Eng. News- Record 85, 815. Public Works 49, 385-7, 461-3. The advances in the activated sludge process were brought out by the papers of LANGDON PEARSE and PROF. E. BARTOW, and in the discussion following. A description of the Argo, 111. plant, of the Chicago stockyards plant, and a brief history of the activated sludge work of the Chicago Sanit. Dist. was given by Mr. Pearse. Prof. Bartow's paper on the present status of the activated sludge process reviewed recent work and described the new experimental plant at Urbana, 111. T. C. HATTON reported the total cost of operating the Milwaukee plant as $35 p. m. g., with credit for sludge values of $18, or a net cost of $17 p. m. g. of sewage treated. J. C. McVEA stated that the cost of operating the Houston activated sludge plant was $14 p. m. g., exclusive of overhead and sludge treatment. Sludge handling methods were discussed. The process as yet is applicable only in special cases. 590 Ter Meer sludge dewaterer at Milwaukee. ANON. Eng. News-Record 85, 889. This is a centrifugal machine of German make under trial at the activated sludge plant. Preliminary tests gave a 4 inch cake and thus far the machine is giving a satisfactory product. Because the sludge varies greatly between winter and summer as to colloid content, filter press operation seems uncertain. 591 Activated sludge in England. EDITORIAL. Eng. News-Record 85, 1018. Comment on the approval of the activated sludge plant for Reading (Eng.) by the Ministry of Health. "* * * the adoption of the activated sludge process for all the sewage of so large a British town (nearly 100,000 pop.) is something that may well be noted by American engineers." 592 The disposal of trade wastes. R. S. WESTON. Public Works 49, 504-6. A general description of the nature and origin of various trade wastes 98 Abstract Bibliography 1920 and their effects in sewage, referring to the activated sludge process only in connection with its failure to successfully purify the sewage at New Haven, because of the poisonous nature of the copper salts present. 593 Activated sludge. EDITORIAL. Surveyor 58, 374. Comment on the report of W. H. MAKEPEACE on the Tunstall activated sludge plant. (Ref. No. 595.) The process is shown to be entirely satisfactory from every point of view, including both construction and maintenance costs. The suggested re- quirements for a complete scheme of activated sludge treatment should be useful to other engineers. 594 Sewage disposal at Manchester, (Eng.) ANON. Surveyor 58, 375. Ex- tracts from the annual report of the Rivers Dept. for the year ending March 31, 1920. The fill and draw activated sludge plant at Davyhulme has operated throughout the year, receiving 3 or 4 fillings per day with an aerating period of 4 to 5 hours. The large continuous flow plant has been completed but is not yet in service because of delays in obtaining operating equipment. Research during the year has been confined almost exclusively to activated sludge investigations, including experiments on the acceleration of sludge settlement by means of tank design, acid and various electrolytes; dewatering the sludge by filter pressing and centrifuges, the latter being the most promis- ing; tests relating to aerating tank design, from which it appears that the length of travel through the tank is not as important as first thought, pro- vided thorough admixture of sludge and sewage is effected, and a prolonged investigation of the N content of the sludge in relation to that of the sewage treated, the results of which should be available for publication shortly. 595 Activated sludge experiments at Tunstall. ANON. Surveyor 58, 380. Extracts from the report of W. H. MAKEPEACE, sewage engineer, which is summarized as follows : "* * * it marks a distinct advance in the meth- ods of treating sewage and possesses many possibilities over the other types. It is reliable when once established. It is not likely to be interfered with by trade wastes of our district. It is considerably less costly to construct. It certainly would be less costly to maintain than our existing plants. It causes no aerial nuisance under the worst conditions. It is controlled by a much smaller though more skilled staff. It can often be applied without a pumping scheme. The resultant sludge possesses higher fertilizing value than the sludge from existing plants. The sludge is not offensive. Portions of our existing plants can be readily adapted to the fill and draw method. It com- plies easily with all the requirements of the Royal Com. recommendations." 596 Large activated sludge installation at Reading, Eng. ANON. Eng. News- Record 85, 1125. Plant designed to ultimately handle 4,200,000 g. p. d. and will be the largest activated sludge plant in England. Will comprise screens, detritus chambers, 4 aeration tanks with a total capacity of 2,100,000 gallons, 2 settling tanks, total capacity 540,000 gallons, sludge storage tanks of 180,000 gallons, and a re-aeration tank of 312,000 gallons. (All U. S. gal- lons.) 597 Houston activated sludge plant results. ANON. Eng. News-Record, 85, 1128. As given by J. C. McVEA, city engineer, at the St. Louis meeting, Am. Soc. Munic. Impvts. One plant is handling a little more than 6 million g. p. d., the other about 1 million. Total air used is 1.44 cu. ft. per gal. of sewage treated, divided 0.94 cu. ft. in the aerating tanks, 0.44 cu. ft. in the re-aerating channels and 0.06 cu. ft. for the air lifts. Average aerating period is 2.25 hours. Re-aerating sludge 4 hours 40 min. Suspended solids are reduced 96-98%, O consumed 50 to 84%, relative stability about 98%. The effluent is clear and unoffensive. 598 The Des Plaines River activated sludge plant. LANGDON PEARSE. Eng. News-Record 85, 1134-8. This plant is under construction at Riverside, The Activated Sludge Process 111., by the Sanit. Dist. of Chicago. It is designed to care for the sewage from a population of over 30,000 and with a wide flexibility for practical and experi- mental purposes. Coarse bar screens are followed by a two-compartment grit chamber, each compartment being 47 by 3.5 by 3 ft., and this by a Riench-Wurl screen 14 ft. in diameter. Four aerating tanks are provided, all 126 ft. long inside. One, 21 ft. wide by 15 ft. deep, and one, 30 ft. 4 in. wide by 10 ft. deep, both baffled once longitudinally, will be used as straight flow tanks. One, 10 ft. deep, divided by baffles into 4 longitudinal channels each 7 ft. 7 in. wide, will treat sludge re-aerated during its return, and another of the same dimen- sions and design will be run with sludge re-aerated and settled before re-use. All aerating tanks have ridge and furrow bottoms with filtros plates in con- crete containers in the furrows. Ratio, 1 to 5.7, to 1 to 5.9. Settling tanks with hopper bottoms and others with Dorr thickeners are provided, with air lifts for handling the sludge. For sludge concentration or storage 6 tanks 15 ft. square by 11.5 ft. deep are provided. Filter presses, a centrifuge of the Ter Meer type and a direct-indirect dryer are to be used for sludge handling. Cloth screens and a hydroturbine blower will supply clean air. 599 Tunstall activated sludge experiments. W. H. MAKEPEACE. Surveyor 58, 397-8. The plant comprises a detritus tank 21 by 9 by 5.5 ft. deep of 6,700 gallons capacity, aerating tanks (converted filter plant) 75 by 42 ft. 9 in. with semi-circular ends and average depth of 7 ft. 9 in., of 156,875 gallons capacity, divided into 10 chambers; sedimentation tank 25 ft. diam. by 13 ft. 10.5 in. deep of 42,500 gallons capacity. Aerating tank floor is on the ridge and furrow plan with porous tile diffusers at the bottom of the furrows. 300,000 g. p. d. are treated on the continuous flow plan. The plant was sub- jected to abuses likely to arise in practice and stood all the tests satisfactorily. "* * * it is a vast improvement and advance on any known method, not only for its thoroughness, but for its more hygenic methods during treatment." 600 Notes on sludge disposal. J. E. FARMER. Surveyor 58, 412. With re- spect to activated sludge, it is suggested that the liquid sludge be pumped directly onto the land to be fertilized. Laboratory experiments show that the odor of ordinary sewage sludge is changed to an earthy smell if treated by aeration as in the activated sludge process, and that there is no loss of N. In the discussion, (p. 430) C. H. BALL stated that a "drying tank" to deal with 5,000 tons of activated sludge per annum was being installed at Manchester. 601 Assoc. of Managers of sewage disposal works. General meeting in London. ANON. Surveyor 58, 413-4. Excerpts from the presidential address of A. J. MARTIN, in which reference is made to the Worcester and London acti- vated sludge experiments, to the proposed plant at Milwaukee, and that of the Chicago Sanit. Dist. in the stockyards. Also to DR. G. McGowAN's paper on the nitrogen in sewage. "The outstanding feature of the year has undoubt- edly been the continued progress of activated sludge." 602 Activated sludge experiments in England. ANON. Munic. Eng. and Sanit. Record 66, ? Public Works 49, 567-9. From a report of W. H. MAKEPEACE on the Tunstall sewage works. Essentially the same material as covered by reference No. 599. Air consumption was from 0.624 to 1.108 cu. ft. per gallon of sewage treated. Suggestions for a new plant are given. 603 The New Orleans Meeting, Am. Inst. Chem. Engrs. ANON. Chem. & Met. Engrg. 23, 1198rl202. A brief review of the papers presented in- cluding that on activated sludge by DR. E. BARTOW. In the author's opinion the greatest problem requiring solution appears to be an economical method of drying the sludge. Experiments at Milwaukee are referred to. 604 Nitrogen in sewage. ANON. Chem. Age (Lond.) 3, 709. Refers to the activated sludge fertilizer experiments at Harpenden. According to the report of the Developments Commission, the total amount of N contained in 100 A bstract Bibliography -1 9W, , the sewage of the United Kingdom is estimated at 230,000 tons, equivalent to 1,150,000 tons of sulphate of ammonia, most of which is wasted. With the general adoption of the activated sludge process considerable would be added to the supply of organic manures. 605 Test of Trent activated sludge devices at Pasadena. R. V. ORBISON. Eng. News-Record 85, 1286-8. The Trent device consists of revolving perforated arms of the Barker mill type, submerged in the aerating tanks. The experiments were carried on for six months and the general conclusion reached was that it was not as satisfactory as the old aeration method through filtros plates, it requiring twice the time and costing more to operate. Removal of suspended solids and bacteria, reduction of O consumed and stability, were all inferior to the old method. Plant consisted of four tanks designed to treat 50,000 g. p. d. 606 The conservation of nitrogen with special reference to activated sludge. G. J. FOWLER. Jour. Ind. Inst. Science. 3, (Part VIII) 227-79. (Decem- ber, 1920.) An elaborate and detailed account of the sources, production and consumption of N, with particular reference to the possibility of recovering the greater portion of the N in sewage. The activated sludge and other methods of sewage treatment are described, the following data indicating the extent to which first method is considered. Activated sludge as manure, giving a summary of the results obtained and conclusions reached by several workers. The nitrogen in activated sludge, showing its several combinations as revealed by the experiments at the Frankland laboratory, Univ. of Manchester, by the experiments of MRS. MUMFORD, the Rothamsted experiments and those at the Indian Inst. of Science under the author's direction, the latter pointing to a fixation of atmospheric N by activated sludge and the suggestion made that by the proper choice of carbohydrate food, the necessary symbiotic organisms, and proper temperature control, that it may be possible to build up a special activated sludge which will fix N in quantity and at such a rate that it might compete with commercial processes. Paragraphs are devoted to "The selec- tion of plants responsive to activated sludge"; "Effect of activated sludge on special Indian crops"; "Condition of availability of nitrogen in activated sludge"; "Intensive cultivation by means of activated sludge"; and "The dry- ing of activated sludge for transport." In the latter connection, electroend os- mose is suggested as an attractive line of attack. "The treatment of concen- trated latrine sewage by activated sludge" with reference to conditions in Shanghai, China, is considered and several illustrations of present methods of nightsoil collection given. A brief summary of the literature concludes the article. 101 The Activated Sludge Process A.SX-: >:*.' : ' '' INDEX OF LOCATIONS WITH SOME PLANT DATA. Aintree, Eng. 1916 on. Regular plant at National Filling Factory. Popula- tion 2,000. Porous tile air diffusers. Ref . 505. Alhambra, Calif. See Pasadena. America. Ref. 60, 85, 180, 328, 380. Argo, 111. See Chicago, Sanitary District. Austin, Tex. 1918. Experimental plant at the Univ. of Texas in conjunction with the city. Ref. 394. Baltimore, Md. 1915-6. Municipal experimental plant. City sewage. Aerat- ing tank capacity 200,000 gallons. Continuous flow plan. Disks of FIL- TROS, carborundum and perforated brass tried as air diffusers. Ref. 36, 38, 42, 47, 50, 53, 55, 82, 134, 143, 157, 170, 176, 180, 195, 223, 228, 292. Bangalore, India. 1917. Experimental plant at the Indian Institute of Science, for research purposes. Ref. 440, 606. Bingley, Eng. 1918 on. Municipal experimental plant. City sewage. Treat- ment capacity 300,000 g. p. d. on the fill and draw plan. Porous tile air diffusers. Ref. 481. Blackpole, Eng. 1917. Regular plant at Government cartridge factory. Popu- lation 4,000. Porous tile air diffusers. Ref. 505. Boonton, N. J. 1918. Plant proposed and plans approved. Ref. 313, 315, 403. Brampton, Ont., Can. 1918. Regular municipal plant. City sewage. FIL- TROS air diffusers. Ref. 532, 548. Brockton, Mass. 1915 on. Municipal experimental plant. City sewage. Aerating tank capacity approx. 4,500' gallons, fill and draw plan. 1916, continuous flow plan. 1917, plans preparing for a 3 million g. p. d. plant. 1918, postponed on account of the war. Ref. 159, 260, 292, 316, 421. Brooklyn, N. Y. 1915 on. Municipal experimental plant. City sewage. Aerating tank capacity on fill and draw plan, 16,000 gal., on continuous flow plan, 900 gal. Air diffusion through perforated pipes, carborundum and other porous material. Ref. 7, 31, 61, 88, 103, 104, 109, 115, 130, 143, 156, 170, 180, 195, 206, 241, 292, 503. Burnley, Eng. 1920. Plant proposed. Ref. 511. Bury, Eng. 1920. Plant referred to in Ref. 507. Canada. Ref. 54. Champaign, 111. 1915 on. Municipal experimental? plant in connection with the 111. State Water Survey. (See Urbana.) Aerating tank ca- capacity 36,000 gal. City sewage. Continuous flow plan. FILTROS air diffusers. 1920, a complete experimental plant of 100,000 g. p. d. proposed. Ref. 195, 246, 310, 556. Chicago, 111. Armour & Co., stockyards. 1915 on. Private experimental plant. Packinghouse wastes. Aerating tank capacity 30,000 gal. Con- tinuous flow plan. Perforated pipe air diffusers. Ref. 86, 90, 128, 173, 175, 195, 206, 292. Chicago, 111. Sanit. Dist. Argo, 111. 1920 on. Experimental plant. Corn products refining wastes. Continuous flow plan. Treatment capacity about 50,000 g. p. d. FILTROS air diffusers. Other methods being tried. (Private advice.) Ref. 541, 589. Chicago, 111. Sanit. Dist. Calumet region. 1920 on. Regular plant under construction. Aerating capacity 3.5 million g. p. d. Continuous flow plan. FILTROS air diffusers. (Private advice.) Ref. 541. Chicago, 111. Sanit. Dist. DesPlaines river plant. 1920 on. Regular and semi-experimental plant under construction. Domestic sewage. Contin- uous flow plan. Aerating capacity 4.5 million g. p. d. FILTROS air dif- fusers. Ref. 401, 541, 598. 102 Indexes Chicago, 111. Sanit. Dist. Griess-Pfleger testing station. 1920 on. Experi- mental plant. Tannery wastes. Continuous flow plan. Aerating capacity 100,000 g. p. d. FILTROS air diffusers. (Private advice.) Ref. 541. Chicago, 111. Sanit. Dist. Stockyards. 1915 on. Experimental plant. Mixed packinghouse (75%) and domestic (25%) sewage. Aerating tanks, four of 35,000 gal. capacity each . Continuous flow plan. Perforated pipes and FILTROS air diffusers used. 1917, 50 million g. p. d. plant recommended, FILTROS air diffusers specified. Ref. 90, 97, 103, 123, 128, 134, 142, 143, 147, 148, 170, 195, 223, 226, 262, 271, 286, 317, 318, 322, 323, 326, 327, 337, 345, 365, 366, 380, 394, 408, 476, 478, 482, 484, 501, 513, 533, 541, 569, 589, 601. Chicago, 111. Sanit. Dist. 39th St. Center. 1916. Plant considered. Ref. 214. Chicago, 111. Swift & Co., Morris & Co., Sulzberger & Sons Co. 1915. Pri- vate experimental plants. Packinghouse wastes. Ref. 86, 90. Cleveland, O. 1915 on. Municipal experimental plant. City sewage. De- signed to treat 1 million g. p. d. Continuous flow plan. FILTROS air diffusers. Ref. 69, 106, 134, 137, 143, 170, 195, 219, 223, 241, 305, 306, 325, 356, 357, 359, 369, 390, 394, 430, 431, 576. Coleman, Tex. 1919. Regular plant and septic tanks treat entire sewage of city. Ref. 493. Columbus, O. 1920. Small experimental plant. City sewage. FILTROS air diffusers, (Private advice). Decatur, 111. 1917. Municipal experimental plant. City sewage. Ref. 241, 577. Decatur, 111. 1919. Private experimental plant. Starch factory wastes. FILTROS air diffusers. (Private advice). East Walpole, Mass. 1916. Private experimental plant. Paper mill wastes. (See Jour. Ind. Eng. Chem. 8, 648.) Edmonton, Alberta, Can. 1915 on. Part of regular municipal plant. City sewage. Six aerating tanks of about 25,000 gal, capacity each. Fill and draw plan. Perforated pipe diffusers, Ref. 195, 213, 266. El Dorado, Kans. 1920. Municipal experimental plant under construction. FILTROS air diffusers. (Private advice). England Ref. 79, 178, 195, 242, 332, 348, 380, 507, 534. Escanaba, Mich. 1917. Regular municipal plant. City sewage. Aerating capacity, approx. 1 million g. p. d. Continuous flow plan. FILTROS air diffusers. Ref. 253. Folsom, Calif. 1917. Regular plant. Institutional sewage. Perforated pipe air diffusers. Ref. 358, 567. Fort Worth, Tex. 1916-7. Armour & Co. Private experimental plant. Pack- inghouse wastes. Aerating capacity about 86,400 g. p. d. Perforated pipes and FILTROS air diffusers used. Ref. 195, 276, 291, 318, 326, 327, 345, 366, 380, 394, 493. Fremont, Mich. 1919. Private experimental plant. Tannery wastes. FILTROS air diffusers. (Private advice). Gainesville, Tex. 1919. Ref. 493. Gastonia, N. C. 1920. Municipal plant. City sewage. FILTROS air diffusers. (Private advice). Glasgow, Scot. 1920. Experimental plant to be recommended. Ref. 522. Grand Rapids, Mich. 1918. Private experimental plant. Tannery wastes. FILTROS air diffusers. (Private advice). Harpenden, Eng. 1918. Experimental plant for H. M. Bd. of Agr. for pro- ducing activated sludge for fertilizer tests. Ref. 452, 505, 507, 508, 553, 604. 108 The Activated Sludge Process Hermosa Beach, Calif. 1916. Regular municipal plant proposed. City sew- age. Treatment capacity, 400,000 g. p. d. Mechanical agitation. Ref. 179, 208, 567. Houston, Tex. 1915 on. Municipal experimental plant, later, two regular pants. City sewage. Total treatment capacity about 15 million g. p. d. Continuous flow plan. FILTROS air diffusers. Ref. 73, 114, 134, 140, 146, 170, 195, 236, 251, 292, 296, 366, 392, 394, 414, 442, 493, 496, 497, 510, 513, 536, 589, 597. India. Ref. 184, 281, 348, 440. Indianapolis, Ind. 1917. Activated sludge process considered but rejected as unsuited to local conditions. Ref. 346, 347, 400. Jersey City, N. J. See Boonton, N. J. Kansas. Ref. 352. Lawrence, Mass. 1912 on. State experiment station. Numerous studies: various size tanks. Perforated brass disks and FILTROS air diffusers tried. Ref. 1, 4, 8, 25, 30, 38, 40, 72, 101, 125, 162, 195, 206, 233, 292, 332, 362, 409, 446, 519, 520, 524, 529, 534, 549. Lima, Ohio. 1916. Activated sludge plant recommended. Ref. 164. Lincoln, Eng. 1917. Experimental plant referred to in ref. 366. London, Eng. 1916 on. Laboratory experiments and Municipal experimental plant. Ref. 163, 521, 531, 571, 601. Manchester, Eng. Bagulay Sanatorium. 1914. First regular plant in Eng- land. Fill and draw plan. Capacity 20,000 g. p. d. Porous tile dif- fusers. Ref. 91, 111. Manchester, Eng. Davyhulme works. 1913 on. Municipal experimental plant. City sewage. Numerous experiments. 1918-9. 1 million g. p. d. plant under construction. Continuous flow plan. Ref. 8, 26, 38, 120, 134, 372, 397, 449, 452, 485, 499, 505, 508, 525, 594. Manchester, Eng. Withington works. 1913 on. Municipal experimental plant. City sewage. Numerous experiments. 1918. Continuous flow tanks treating up to 375,000 g. p. d. Ref. 199, 244, 366, 379, 381, 397, 417, 420, 425, 449, 485, 499, 505, 507, 514, 525, 527. Manchester, Eng. Works not stated. Ref. 9, 12, 24, 35, 36, 40, 64, 71, 72, 103, 106, 125, 152, 162, 198, 224, 232, 234, 292, 296, 373, 442, 479, 519, 524, 529, 600. Matawan, N. J. 1916. Plans for plant approved. Ref. 171. Maynard, Mass. 1916. Private experimental plant. Woolen mill wastes. (See Jour. Ind. Eng. Chem. 8, 648.) Milwaukee, Wis. 1914 on. Municipal experimental plant. City sewage, numerous experiments with aerating tanks of various sizes on both fill and draw and continuous flow plans. Perforated pipes, wood blocks and FILTROS air diffusers tried. 1920. 85 million g. p. d. regular plant under construction, FILTROS air diffusers specified. Ref. 38, 44, 58, 66, 70, 72, 75, 76, 81, 87, 88, 89, 91, 100, 103, 106, 112, 116, 117, 121, 122, 125, 126, 134, 136, 138, 141, 143, 145, 147, 150, 151, 153, 170, 180, 188, 191, 193, 195, 197, 205, 206, 207, 223, 227, 229, 232, 234, 240, 245, 280, 288, 292, 296, 328, 330, 332, 333, 353, 356, 364, 365, 366, 370, 377, 389, 394, 398, 408, 417, 442, 453, 464, 471, 491, 500, 512, 513, 526, 550, 554, 555, 584, 589, 590, 601, 603. Milwaukee, Wis. 1915. Private experimental plant. Tannery wastes. FILTROS air diffusers. (Private advice). Ref. 289. Moreton, Eng. (Near Worcester). 191 ? Regular plant for Admiralty Air- ship Station. Population, 400. Porous tile diffusers. Ref. 301, 452, 505. Moscow, Russia. 1917. Experimental plant. Fill and draw plan. Capacity 135,000 g. p. d. Perforated pipe diffusers. (Noted in K. W. & P. Book. Ref. 506). 104 Indexes Mt. Vernon, N. Y. 1919. Experimental plant, privately conducted. City sewage. Treatment capacity, 45,000 g. p. d. Mechanical agitation and FILTROS air diffusers. Ref. 477, 579, 581. New Britain, Conn. 1920. Municipal experimental plant. City sewage. FILTROS air diffusers. (Private advice). New Haven, Conn. 1917 on. Experiment station. City sewage. Treatment capacity, 17,000 g. p. d. Continuous flow plan. FILTROS air diffusers used. Ref. 329, 338, 354, 426, 432, 448, 462, 592. North Toronto, Can. Ref. 248, 272. Norwood, Mass. 1916. Private experimental plant. Tannery and wool scouring wastes. Aerating tank, 1,000 gal. capacity. Fill and draw plan. FILTROS air diffusers. Ref. 203, 292. Paris, France. 1917. Laboratory experiments. Ref. 340. Paris, Texas. 1916. Regular municipal plant. City sewage. FILTROS air diffusers used. Ref. 493. Pasadena, Calif. 1916 on. Experimental municipal plant. City sewage of South Pasadena and Alhambra included. Treatment capacity 50,000 g. p. d. FILTROS air diffusers. 1919-20. Trent agitating devices tried. Ref. 132, 210, 250, 257, 331, 349, 374, 572, 605. Peterboro, Ont., Can. 1920. Activated sludge plant considered. Ref. 585. Pittsfield, Mass. 1920. Private experimental plant. Industrial wastes. FILTROS air diffusers. (Private advice). Port Colborne, Ont., Can. 1917. Private regular plant. Metallurgical and domestic wastes. FILTROS air diffusers. (Private advice). Port Colborne, Ont., Can. 1920. Regular municipal plant considered. Ref. 575. Providence, R. I. 1917. Municipal experimental plant. City sewage. FILTROS air diffusers. (Private advice). Quanah, Texas. 1918. Regular municipal plant. Ref. 493. Reading, Eng. 1919. Activated sludge process adopted to treat entire city sewage. Ref. 461, 472, 508, 557, 583, 586, 591, 596. Regina, Sask., Can. 1915. Municipal experimental plant. City sewage. Aerating tanks, two of 577.8 Imp. gallons each. Fill and draw plan. Air diffused through perforated pipes covered with canvas. Ref. 38, 54, 134, 195, 230, 249. Sakchi, India. 191? Plant considered to care for future population of 150,000. Ref. 281, 440. Salford, Eng. 1914 on. Municipal experimental plant. City sewage. Treat- ment capacity, 75,000 gal. in 21 hours on fill and draw plan; 60,000 g. p. d. on continuous flow plan. Perforated pipe air diffusers. 1919. Adoption recommended for regular plant. Ref. 22, 24, 26, 29, 36, 38, 62, 64, 93, 95, 102, 106, 133, 134, 232, 240, 244, 292, 296, 366, 372, 417, 475. San Angelo, Tex. 1919. Regular municipal plant. City sewage. Treatment capacity, 400,000 g. p. d. Perforated pipe air diffusers. Ref. 493, 518. San Marcos, Tex. 1916. Regular municipal plant; beieved to be the first in the U. S. treating the entire sewage of a city. Treatment capacity, 150,000 g. p. d. FILTROS air diffusers. Ref. 195, 197, 252, 259, 394, 493. Sarisbury Court, Eng. (Near Southampton). 1918. Hospital installation for 200 patients and staff. Porous tile air diffusers. Ref. 452, 486, 505. Shanghai, China. 1919. Experimental municipal plant recommended. FILTROS air diffusers. Ref. 436, 474, 578, 606. Sheffield, Eng. 1915 on. Experimental municipal plant. City sewage. Nu- merous experiments. 1919: aerating tanks treating 110,000 g. p. d. using mechanical agitation. 1920: 1 million g. p. d. plant building. Ref. 167, 168, 215, 232, 328, 366, 458, 468, 469, 479, 481, 502, 511, 514, 529, 553, 578. 105 The Activated Sludge Process Sherman, Tex. 1918. Regular municipal plant. City sewage. FILTROS air diffusers. Ref. 493. Shieldhall, Scot. See Glasgow. South Pasadena, Calif. See Pasadena. St. Albans, Eng. 1918. Experimental municipal plant. City sewage. Treat- ment capacity 30,000 g. p. d. Continuous flow plan. Porous tile diffusers. Ref. 422, 442, 452. Stamford, Eng. 1915 on. Experimental municipal plant. City sewage. Treating 100,000 g. p. d. Porous tile air diffusers. Ref. 91, 111, 134, 232, 240, 296, 366, 381, 417, 505. Sydney, Australia. 1916 on. Experimental municipal plant. Aerating tanks, 500 and 10,000 gal. capacity. Fill and draw plan. Perforated pipes covered with broken stone for air diffusion. 1919-20. Treating 900,000 g. p. d. Ref. 320, 568, 588. Syracuse, N. Y. 1917 on. Municipal experimental plant. City sewage. Aerating tank approximately 3,000 gal. capacity. Continuous flow plan. Perforated pipe air diffusers. Ref. 363, 378, 484. Texas. Ref. 447, 457, 465, 493, 504. Toronto, Can. 1920. Small experimental plant. FILTROS air diffusers. (Pri- vate advice). Tunstall, Eng. 1918. Municipal experimental plant. City sewage. Treat- ing 300,000 g. p. d. on continuous flow plan. Porous tile air diffusers. Ref. 452, 489, 505, 507, 562, 593, 595, 599, 602. United States. Ref. 36, 66, 178, 348, 420. Urbana, 111. 1914 on. Experiment station 111. State Water Survey at the Univ. of 111. Numerous investigations. Believed to be the first ex- clusive activated sludge plant in the U. S. First to use FILTROS air diffusers. Ref. 35, 38, 43, 72, 88, 113, 116, 121, 135, 170, 195, 210, 232, 292, 296, 302, 310, 394, 408, 556, 589. Wakefield, Eng. 1915 on. Municpial experimental plant. City sewage. Ca- pacity of aerating tank approximately 13,500 gal. on fill and draw plan. Porous tile air diffusers. Ref. 20, 38, 63. Wimbledon, Eng. 1916. Aeration experiments contemplated, using atomizers. Ref. 107, 108. Woodstock, Ont., Can. 1920. Regular municipal plant building. FILTROS air diffusers. (Private advice). Worcester, Eng. 1915 on. Municipal experimental plant. City sewage. Nu- merous experiments. 1916: treating 750,000 g. p. d. on continuous flow plan. Porous tile air diffusers. Ref. 91, 102, 111, 134, 172, 174, 232, 240, 242, 247, 278, 279, 282, 283, 284, 293, 295, 296, 298, 299, 300, 360, 366, 379, 397, 415, 417, 442, 452, 463, 470, 505, 601. Worcester, Mass. 1917-8. Municipal experimental plant. City sewage. Treatment capacity, 100,000 g. p. d. Continuous flow plan. FILTROS air diffusers. Ref. 223, 258, 260, 351, 437, 487, 540. York Township, Ont., Can. 1919. Activated sludge process considered. Ref. 498. 106 Indexes INDEX OF NAMES Ref. Activated Sludge Lt'd. 505-516-551-552 Adams, G. O. 6-30-125 Adams, S. H. 272-330-473-529 Allen, K. 355-365-382-408 Allen, W. J. 587 Allin, T. D. 182-210-223 Alvord, J. W. 212-269 Ames, R. 127-194-255-285-466 Ames-Crosta Sanit. Eng. Co. 516 Adern, E. 9-19-22-23-24-25-26-29 -32-36-38-40-52-64-71-103 -106-120-124-125-134-150-162 -244-264-265-292-296-307-328 -339-379-425-442-507-527-534 Armour & Co. 86-90-128-173 195-383-384-385 Baker, W. N. 60-99 Ball, C. H 167-600 Barber, F. 498 Barford, J. B. 95 Bartow, E. 35-38-41-43-45-83-84 -85-88-103-105-113-118-120 -121-125-134-135-158-169-170 -183-186-211-241-246-261-290 -292-302-303-310-312-319-321 -361-367-406-444-556-589-603 Barwise, S. 95-166-174-297 Beckett, W. M. 16 Black, Gen. Wm. M 125-130-292 Bleazard, A. R. 133 Bottomly, H. 481 Boulton, J. 507 Bowes, ?. ?. 139 Bowes, A. 133 Brenchley, W. E. 538 Brosius, A. M. 179-208-438 Brown, R. 65 Buckley, Wm 410-413 Butcher, W. L. 258 Caink, T_. 149-247-279-282-283 -294-295-298-299-300-350-379-470 Calvert, H. T. 484 Cambier, R. 528-563-570 Carpenter, Geo. A. 231 Carpenter, W. T 88-109-200-230 Chase, E. S 544 Chemical Process Co. 411-412 Clark, H. W. 1-4-6-30-38-40-101 -125-162-169-183-233-292 -362-434-446-529-534-537 Clifford, Wm. 274-275-379 -381-449-537-565 Coombs, J. A. 379-551-552 Cooper, C. H. 37-65-107-108 Copeland, W. R. 100-131-138 -141-187-188-189-190-191-227 -230-267-377-424-453-491-500 Cotterell, A. P. I. 134-553 Ref. Coulter, W. S. 53-273 Courmont, P. 509-539-547 Cox, J. W 439 Crawford, F. N. 158-335 Crocker, H. S. 316 Cronin, A. 320 Crump, E. H. 65 Dallyn, F. A. 169-183-365-443 Dickson, A. 189-206-328 Dienert, F. 340-530-535-545 Dorr Co. 324-345-377-477-491 -555-579-580-581-598 Dorr, E. S. _459 Duckworth, W. H. 21-22-24-29-32 -38-52-93-95-96-133-292-299 Eade, J. 422 Eagles, R. H. 579-581 Eddy, H. P. 136-155-160-203-204 -212-217-269-270-431 Ehlers, V. M. 447-504 Ellis, J. R. 230-249 Elrod, H. E. 252 Evans, H. P. 352 Fales, A. L. 160-311 Farmer, J. E. 600 Fieldhouse, J. 553 Fogg, Tom 133 Folwell, A. P. 230-234 Fort, E. J. 61-156 Fothergill, H. 455 Fowler, G. J. 2-8-9-24-29-32-38-40 -44-51-52-91-103-119-120-121 -124-125-129-134-150-162-184 -206-243-281-292-309-332-376 -436-454-467-524-529-534-606 Frank, L. C. 36-47-48-50 -110-129-170-176-515 Fugate, G. L. 497-510-536 Fuller, G. W. 89-164-189-212-230 -269-346-347-365-400-420-460 Fuller, W. B. 104 Gage, S. DeM. 1-4-38-125 Gascoigne, G. B._ .219-277-356-389-576 Gault, M 351-437-487 Gaunt, P. 9-95-124-265-379 Gillespie, P. 52 Girault, ?. ? 535 Goddard, C. W. 504 Godfrey, C. H. 474-578 Gononian, Y. H. 235 Gooseman, A. T. 65 Griffiths & Hartley 181-314-396 Grossmann, J. 9-24 Halliwell, ?. ?. 124 Hammond, Geo. T._ .7-115-130-143-144 -169-170-180-183-192 -195-206-266-268-503 Harding, M. D 173-175 107 The Activated Sludge Process INDEX OF NAMES (Cont.) Ref. Hartley & Hartley 450-483 Hatfield, W. D. 84-118-406-444 Hatton, T. C. 58-70-75-88 -100-103-106-110-117-120^121 -122-125-126-129-131-138-151 -153-154-169-170-180-183-207 -227-229-230-239-245-246-280 -292-324-332-333-348-353-356 -370-377-389-393-416-451-453 -464-500-512-526-554-555-589 Haworth, J. 167-168-174 -215-458-514-529 Hendrick, C. W. 47-50-157-170 Hering, R 121 Hewes, C. E. __132 Hicks, P. T 241 Holmes, G. D. 153-378 Hommon, H. B. 289-513 Horowitz, M. P. 200 Horton, Theo. 574 Hoseason, J. H. 265 Hoskins, J. K 513 Houston, A. C. 502 Jackson, L. E. 352 Johnson, G. A. 171-315 Jones, E. R 407-566 Jones, W. 3-5-10-11-15 -17-18-28-33-165-222-256 -308-341-342-343-344-402 -404-418-419-428-435-561 Jones, W. M. 133 Jones & Attwood, L'td. 3-5-10-11 -15-17-18-28-33-91-110-111 -120-129-165-172-222-243-256 -274-275-278-282-284-293-308 -381-404-418-419-452-516-565 Radish, V 289 Kamm, W. F. 336 Kershaw, G. B 31-134-365-391-441 Kershaw, J. H. 167-507 Kinnicutt, Winslow & Pratt. _. 506-524 Knowles, M. 445 Lacey, G. W. 379 Lamb, J. 95-507 Lanphear, R. S. 540 Launey, M. 545 Lederer, A. J 123-142-148 Lester, J. H 24 Lockett, W. T 9-19-22-23-25-32-36 -38-40-52-64-71-103-106-124 -125-134-150-162-263-292-534 Lockett & Herring-Shaw 304 Long, E. 74 MacMillan, J. _ __132 Makepeace, W. H. 95-263-507-562 -594-595-599-602 Martin, A. J. 429-433-494-495 -507-553-558-601 Ref. Martin, E. B 62-65-92 McFarland, D. F. 368 McGowan, Dr. G. 134-546-553-601 McKay, G. P. 405-406-451 McKenn, R. J. 133 McVea, J. C. 497-589-597 Melling, S. E. 9-24-32-38-64 -265-292-372-379-388 Metcalf & Eddy 72 Mickle, F. L. 367 Miln, G. P. 379 Mohlman, F. W. 43-45-83 -211-246-261-292-329-334 -354-426-432-448-459-484 Moor, W C. 383 Moore, George 411-412 Morris & Co. 90 Mottram, G. W. 34-39-177 Mulloy, G. B. 384 Mumford, E. M. 2-38 Mumford, G. 51-152-454-490 Nasmith, G. G.216-405-406-451-492 Naylor, G. W. & J. F 13-14-20 -27-56-57-221 Naylor, W. 19 Noble, G. L. 161-170-173-175 -230-291-292-385 Nordell, C. H._ .78-201-225-230-288-427 Orbison, R. V. 132-182-210-223 -257-331-349-605 O'Shaugnessy, F. R 9-232 Pacific Flush Tank Co 439 Parsons, F. W. 584 Pearse, L 123-170-246-262-271-286 -317-322-323-326-327-337-365 -371-478-482-533-569-589-598 Phelps, E. B.__125-130-169-183-230-292 Phelps, Geo. 248 Potter, Alex. 230 Pratt, R. W.69-137-170-219-369-506 Reid, G. G. 532 Rein, L. E. 439 Requardt, G. J. 55-228-237 Rhynus, C. P. 515 Rice, J. M 445 Richards, E. H. 538 Richardson, W. D 262-271-286 -317-322-323-365 Rideal, S. 95-218-240-366-379 Rochaix, A. 509-539-547 Roechling, H. A. 134 Rolants, E. 488 Rudnick, P. __ 161-173-175-246-292-406 Russel, R. 186 Sands, E. E. 73-114-170-236-414 Schnellbach, J. F 211-246-261 Scott-Moncrieff, W. D 95 Scouller, W. D. 379 108 Indexes INDEX OF NAMES (Cont.) Ref. Silcock, E. J. _. __65 Smail, J. W. 588 Smith, C 134 Stein, M. F. 517 Stevenson, W. L. 67-230 Stott, O. 407-566 Streeter, H. W. 513 Sulzberger & Sons Co. 86-90 Swift & Co. 90 Tarbett, R. E. 513 Taylor, G. M. 557-583 Thompson, J. T. 9 Thompson, W 24-124-265 Traxler, H. 125 Tyler, R. G 394 Upton, R. G. 465 Veatch, F. M. 352 Wagenhals, H. H. 513 Ref. Wakeford, J. P 24-32-38-49 -62-63-65-481 Wandenbulke, F. 545 Watson, J. D. 62-65-479 Wells, R 484 Weston, R. S 159-365-459-542-592 Whyte, L. 455 Wilcox, J. E. 417 Wilcox, W. F. 135 Wilkinson, O. J. 80-82 Williford, C. L. 251 Wilson, H. M 59-150-162-484-534 Winslow, C. E. A 365-426-432 -448-459-506 Wynne-Roberts, R. O 38-52-54 -145-498-575 Young, M. 372-379-388 Zimmele, G. B 259-276-291 Oct. 11. Brit. INDEX OF PATENTS 1913. Ref. Ref. 22,952 (J & A) 3 Dec. 19. U.S. 1,208,821 (Nordell) ___225 Jan. 10. Apr. 11. Apr. 11. Sep. 28. Oct. 6. Nov. 4. Nov. 4. Nov. 19. Nov. 19. Nov. 27. Dec. 21. Dec. 24. Brit. Brit. Brit. Brit. Brit. Brit. Brit. Brit. Brit. Brit. Brit. Brit. Jan. 23. Feb. 16. Mar. 10. Mar. 18. May 11. June 7. June 7. July 9. Oct. 19. Dec. 14. Feb. 25. Apr. 10. May 20. July 11. Aug. 15. Aug. 26. Oct. 13. Dec. 7. Dec. 9. Brit. Brit. Brit. Brit. U. S. Brit. Brit. Brit. Brit. Brit. 1914. 729 19,915 19,916 20,259 20,579 21,976 21,985 22,736 22,737 23,146 24,386 24,630 1915. 1,141 2,421 3,831 4,240 1,139,024 8,397 9,870 1917. (J & A). (J & A). (J & A). (Naylor) (Naylor) (J & A). (Beckett) (J & A). (J & A). (Naylor) (Naylor) (J & A). ._ 5 ._ 10 ._ 11 ._ 13 ._ 14 ._ 15 ._ 16 ._ 17 ._ 18 ._ 20 _ 27 _ 28 14,733 17,463 1916. Brit. 104,361 Britap. 5,215 Brit. 105,654 Brit. 104,187 U.S. 1,195,067 Brit. ap. 12,084 Brit. 110,197 Brit. 111,548 Brit. 111,720 (J & A) 33 (Mottram) _ 34 (Cooper) ___ 37 (Mottram) __ 39 (Frank) .48,110 (Fowler) ___ 51 (Naylor) ___ 56 (Naylor) ___ 57 (Long) 74 (Martin) ___ 92 (Ames) 127 (Bowes) 139 (Caink) 149 (Jones) 165 (Mottram) 177 (Griffith) ___181 (Ames) 194 (Naylor) 221 (J & A) 222 Feb. 24. Feb. 26. May 17. May 24. June 19. July 7. Aug. 11. Aug. 11. Aug.24. Aug. 27. Sep. 18. Nov. 20. Nov. 20. Nov. 20. Nov. 20. Jan. 29. Jan. 29. Jan. 29. Mar. 18. Apr. 16. Apr. 27. May 14. July 2. July 9. July 9. July 24. Aug. 17. Aug. 17. Oct. 15. Oct. 22. Nov. 26. Dec. 3. Dec. 3. 107,937 113,333 115,872 117,472 115,933 116,580 Brit. Brit. Brit. Brit. Brit. Brit. Brt. ap. 11,561 Brt. ap. 11,562 Brit. 122,428 Dan. 22,389 Brt. ap. 13,374 U.S. 1,247,540 U.S. 1,247,541 U.S. 1,247,542 U.S. 1,247,543 1918. U.S. U.S. U.S. Brit. Can. Brit. Brit. U.S. U.S. U.S. Brit. Brit. Brit. U.S. U.S. U.S. U.S. U.S. 1,254,833 1,254,836 1,254,841 ap. 4,276 183,586 132,826 133,722 1,271,425 1,271,925 1,271,926 130,146 131,158 132,581 1,281,816 1,282,587 1,286,017 1,286,520 1,286,775 (Ames) (J & A)___. (Clifford) _. (Clifford) __. (Ames) (Caink) ___. (H-S & L)_ (H-S & L)_ (Jones) (Fowler) __. (Griffith) __. (Jones) (Jones) (Jones) (Jones) (Moor) _ (Mulloy) (Noble) (Griffith) __. (Jones) (Jones) (Stott & J)_. (Buckley) _. (Moore) (Moore) (Buckley) _. (Jones) (Jones) (Nordell) __. (Jones) (Jones) (Brosius) __. (Rein, et aL). .255 .256 .274 .275 .285 .294 .304 .304 .314 .341 .342 .343 .344 .383 .384 .385 .396 .402 .404 .407 .410 .411 .412 .413 .418 .419 .427 .428 .435 109 The Activated Sludge Process INDEX OF PATENTS (Cont.) 1919. Ref. Jan. 22. Brit.ap. 1,604 (Hartley) 450 Feb. 11. U. S. 1,294,080 (Fowler) ___454 Feb. 28. Brit. 104,189 (Whyte & F.)455 Apr. 28. Brit. 143,369 (Ames) 466 Apr. 29 Can. 189,921 (Fowler) ___467 Aug. 1. Brit. 145,291 (Adams) ___473 Nov. 5. Britap. 27,205 (Hartley) 483 Ref. Dec. 6. Brit.ap. 30,579 (Mumford) _490 1920. May 13. Brit. ap. 13,202 (A. S. Lt'd)._551 May 13. Brit. ap. 13,203 (A. S. Lt'd)__552 May 25. U. S. 1,341,561 (Jones) 561 June 15. U. S. 1,343,764 (Clifford) ___565 June 15. U. S. 1,343,797 (Stott & J.)__566 INDEX OF PERIODICALS. (Though more than 50 regularly issued periodicals are mentioned in this bibliography, only those most frequently referred to and which contain substantially complete articles are here indexed. Indexes of abstract journals, annual reports, pamphlets, etc., are omitted.) THE AMERICAN CITY. Volume 14, 1916. Ref. Jan. pp. 78-81 (Fuller) 103 Mar. pp. 282-5 (Bartow, et al.)___ 84 Volume 16, 1917. June pp. 804-7 (Phelps) 248 Volume 18, 1918. Jan. pp. 1-4 (Anon.) 370 Feby. pp. 114-9 (Anon.) 370 Mar. pp. 199-208 (Anon.) 370 Volume 20, 1919. June pp. 467-9 (Winslow, et al.)__459 Volume 22. 1920. Feby. pp. 147-8 (Anon.) 518 May pp. 485-9 (Chase) 544 AMERICAN JOURNAL OF PUBLIC HEALTH Volume 6, 1916. Ref. Nov. pp. 1218-23 (Carpenter, et al.)_200 Volume 7, 1917. Aug. p. 679 (Bartow, et al.)___211 Oct. p. 847 (Anon.) 202 Volume 8, 1918. Jan. pp. 47-54 (Pearse) 371 Jan. pp. 55-7 (Pratt) 369 Volume 10, 1920. May pp. 405-7 (Weston) 542 CANADIAN ENGINEER Volume 28, 1915. Ref. Mar. 11, pp. 335-6 (Wynne-Roberts) 38 June 24, pp. 697-9 (Wynne-Roberts) 52 Volume 29, 1915. July 1, p. 112 (Wynne-Roberts) 54 Aug. 5, p. 239 (Edit.) 64 Aug. 12, pp. 249-51 (Wakeford) 49 Sep. 30, p. 429 (Wakeford) 63 CANADIAN ENGINEER (Contd.) Volume 29, 1915 (Cont.) Ref. Oct. 21, p. 503 (Sands) 73 Oct. 28, pp. 517-9 (Hatton) 75 Nov. 4, pp. 549-50 (Hatton) 75 Volume 30, 1916. Feb. 10, pp. 227-8 (Fowler) 121 Apr. 27, pp. 473-6 ( Wynne-Roberts )__145 May 25, pp. 561-5 ( Wynne-Roberts )__145 May 25, p. 581 (Edit.) 150 June 1, pp. 590-2 (Hatton) 151 Volume 31, 1916. Aug. 31, pp. 167-9 (Haworth) 168 Oct. 19, pp. 305-11 (Hammond) 195 Oct. 26, p. 340 (Copeland) 188 Nov. 2, pp. 353-5 (Eddy)____ 203 Dec. 7, p. 475 (Edit.) 220 Dec. 14, pp. 489-90 (Anon.) 224 Volume 32, 1917. Feb. 1, p. 82 (Rideal) 218 Feb. 8, pp. 117-21 (Phelps) 248 Feb. 8, pp. 124-6 (Ellis) 249 Feb. 15, p. 157 (Rideal) 218 Mar. 8, pp. 214-6 (Anon.) 254 Mar. 29, p. 265 (Anon.) 266 June 14, pp. 491-4 (Hatton) 280 Volume 33, 1917. July 12, pp. 30, 38-40 (Anon.) 295 Sept. 13, p. 230 (Fales) 311 Oct. 18, pp. 339-41 (Bartow) 312 Oct. 25, pp. 358-9 (Pearse) 326 Dec. 6, pp. 473-4 (Allen) 355 Volume 34, 1918. Feb. 14, p. 144 (Anon.) 386 Mar. 21, pp. 243-5 (Kershaw) 391 Apr. 4, p. 294 (Anon.) 397 May 2, pp. 377-82 (Nasmith, et al.)_405 Volume 35, 1918. Sep. 5, pp. 224-5 (Wilcox) 417 Oct. 3, pp. 302, 315-7 (Copeland) 424 110 Indexes INDEX OF PERIODICALS (Cont.) CANADIAN ENGINEER (Cont.) Volume 36, 1919. Ref. Feb. 13, pp. 222-3 (Anon.) 449 Apr. 24, p. 404 (Anon.) 462 May 15, pp. 455-60 (Dorr et al.) 459 Volume 37, 1919. July 3, p. 46 (News item) 471 Oct. 30, pp. 420-2, 427-9 (Watson)__479 Dec. 11, pp. 519-22 (Nasmith) 492 Dec. 25, pp. 559-60 (Anon.) 498 Dec. 25, pp. 563-6 (Wells) 484 Volume 38, 1920. Feb. 26, pp. 245-7 (Anon.) 499 Mar. 18, pp. 314-5 (Adams) 529 Apr. 8, pp. 367-8 (Fuller) 460 June 3, p. 522 (Anon.) 559 Volume 39, 1920. Aug. 19, p. 269 (Anon.) 575 Oct. 7, p. 410 (News item) 585 Dec. 23, pp. 627-8 (Anon.) 586 COMPTES RENDUS (Acd. Sci.) Volume 165, 1917. Ref. Nov. ?, pp. 1116-7 (Dienert) 340 Volume 170, 1920. Jan. 5, pp. 75-8 (Courmont) 509 Mar. 15, pp. 681-4 (Cambier) 528 Mar. 22, pp. 762-3 (Dienert) ____530 Apr. 12, pp. 899-901 (Dienert) 535 Apr. 19, pp. 967-70 (Courmont) 539 May 3, pp. 1089-92 (Dienert) 545 May 17, pp. 1134-5 (Courmont) 547 June 7, pp. 1417-9 (Cambier) 563 Volume 171, 1920. July 5, pp. 57-60 (Cambier) 570 CONTRACT RECORD Volume 29, 1915. Ref. June 23, pp. 647-9 (Wynne-Roberts) 38 Volume 30, 1916. Apr. 19, pp. 382-5 (Hatton) 117 Aug. 9, pp. 788-90 (Anon.) 175 Oct. 4, pp. 959-62 (Haworth) 168 Nov. 8, pp. 1066-8 (Anon.) 205 Nov. 8, p. 1074 (Anon.) 206 Volume 33, 1919. Dec. 10, pp. 1137-40 (Nasmith) 492 Volume 34, 1920. Mar. 31, pp. 292-7 (Reid) 532 THE ENGINEER Volume 117, 1914. Ref. Mar. 6, p. 272 (Fowler) 8 Volume 119, 1915. Jan, 8, p. 32 (Anon.) 32 THE ENGINEER (Cont.) Volume 120, 1915. Ref. Dec. 31, pp. 620-1 (Duckworth) 93 Volume 121, 1916. Jan. 14, pp. 30-1 (Anon.) 106 Jan. 21, pp. 58-9 (Hatton) 70, 75 Volume 122, 1916. Aug. 25, p. 170 (Anon.) 180 Volume 123, 1917. Jan, 12, pp. 32-3 (Anon.) 240 Apr. 13, pp. 337-8 (Phelps) 248 Apr. 27, p. 375 (Adams) 272 Volume 124, 1917. Aug. 3, p. 94 (Ardern) 296 Dec. 28, p. 561 (Hatton) 416 Volume 125, 1918. Feb. 1, p. 97 (Mohlman) 329 Apr. 5, pp. 297-8 (Anon.) 398 Volume 128, 1919. Aug. 8, p. 146 (Mickle) 367 Volume 129, 1920. Jan. 2, pp. 10-2 (Anon.) 508 ENGINEERING. Volume 104, 1917. Ref. July 6, pp. 16-7 (Anon.) 292 July 13, pp. 49-51 (Caink) 295 July 27, pp. 99-100 (Anon.) 101 Aug. 3, pp. 118-9 (Anon.) 301 Aug. 3, p. 134 (Ardern) 296 Sep. 14, pp, 288-90 (Eddy) 217 Sep. 28, pp. 319-20 (Eddy) 217 Oct. 26, p. 444 (Anon.) 328 Volume 105, 1918. Jan. 11, pp. 40-1 (Anon.) 376 ENGINEERING NEWS. Volume 73, 1915. Ref. Mar. 25, p. 593 (Edit.) __ 41 Apr. 1, pp. 647-8 (Bartow et al.)___ 43 Apr. 1, p. 650 (News item) 44 Volume 74, 1915. July 15, pp. 134-7 (Hatton) 58 July 22, pp. 164-71 (Baker) 60 July 29, pp. 214-7 (Fort) 61 Sep. 16, p. 571 (Pratt) 69 Sep. 30, pp. 667-8 (Hatton) 70 Oct. 7, p. 717 (Sands) _ 73 Nov. 4, p. 899 (Edit.) 79 Nov. 4, pp. 904-6 (Nordell) 78 Nov. 11, p. 948 (Wilkinson) 80 Dec. 2, pp. 1096-7 (Bartow et al.)___ 83 Dec. 2, p. 1101 (New,s item) 86 Dec. 9, pp. 1146-7 (Fuller) 89 Dec. 9, p. 1148 (News item) 90 111 The Activated Sludge Process INDEX OF PERIODICALS (Cont.) ENGINEERING NEWS (Cont.) Volume 75, 1916. Ref. Jan. 27, pp. 189-90 (Hatton) 110 Feb. 10, pp. 262-3 (Hatton) 122 Feb. 10, p. 293 (News item) 123 Feb. 17, pp. 306-8 (Hatton) 122 Mar. 16, p. 503 (Hatton) 131 Apr. 6, pp. 671-2 (Pratt) 137 Apr. 27, pp. 798-800 (Hammond) 143 Apr. 27, pp. 809-10 (Edit.) 144 May 18, p. 932 (Lederer) 148 Volume 76, 1916. July 6, p. 37 (News item) 163 July 6, p. 46 (News item) 164 July 20, pp. 106-10 (Anon.) 170 July 20, p. 140 (News item) 171 Aug. 10, p. 267 (Frank) 176 Aug. 24, p. 366 (Edit.) 178 Aug. 24, p. 380 (News item) 179 Sep. 28, p. 624 (News item) 184 Oct. 5, p. 663 (Edit.) 187 Oct. 5, pp. 665-6 (Copeland) 188 Oct. 5, p. 667 (Fuller) 189 Oct. 12, pp. 686-8 (Anon.) 193 Nov. 2, p. 856 (Nordell) 201 Nov. 2, p. 858 (Anon.) 202 Nov. 9, pp. 890-2 (Brosius) 208 Nov. 23, pp. 972-3 (Bartow et al.)__211 Nov. 30, p. 1056 (News item) 214 Dec. 7, pp. 1061-6 (Pratt et al.) 219 Dec. 14, pp. 1124-8 (Pratt et al.) 219 Volume 77, 1917. Jan. 4, p. 18 (Requardt) 237 Feb. 8, pp. 236-8 (WilMford) 251 Feb. 8, p. 249 (Elrod) 252 Mar. 1, p. 373 (News item) 257 Mar. 1, pp. 384-5 (Butcher) 258 Mar. 8, p. 406 (Edit.) 260 Mar. 15, p. 454 (News item) 262 ENGINEERING NEWS-RECORD. Volume 78, 1917. Ref. May 3, pp. 255-6 (Coulter) 273 May 31, pp. 436-7 (Zimmele) 276 June 14, p. 535 (News item) 281 June 21, pp, 594-6 (Anon.) 286 June 21, p. 604 (Literature note) 287 June 28, pp. 628-9 (Nordell) 288 Volume 79, 1917. July 5, p. 33 (Noble) 291 Aug. 9, p. 269 (Anon.) 302 Aug. 9, pp. 269-70 (Anon.) 303 Aug. 16, p. 290 (Edit.) 306 Aug. 16, pp. 308-12 (Anon.) 305 Sep. 13, p. 522 (News item) 313 Sep. 20, p. 551 (News item) 316 Oct. 25, pp. 777-8 (Pearse) 327 ENGINEERING NEWS-RECORD (Cont.) Volume 79, 1917 (Cont.) Ref. Nov. 1, p. 817 (Edit.) 332 Nov. 1, pp. 829-30 (Mohlman) 329 Nov. 1, pp. 840-4 (Anon.) 333 Nov. 15, p. 940 (News item) 339 Nov. 22, pp. 972-4 (Anon.) 347 Nov. 22, p. 987 (News item) 348 Nov. 29, pp. 1009-10 (Anon.) 349 Dec. 6, pp. 1072-3 (Hatton et al.) 356 Dec. 13, p. 1085 (Edit.) 359 Dec. 13, p. 1127 (Anon.) 358 Dec. 13, p. 1128 (Anon.) 357 Dec. 27, pp. 1201-2 (Anon.) 363 Volume 80, 1918. Jan. 31, p. 205 (Anon.) __386 Feb. 7, p. 272 (Hatton) 389 Feb. 21, p. 382 (Anon.) 390 Apr. 11, p. 734 (News item) 401 Apr. 25, p. 839 (News item) 403 June 20, p. 1193 (Nasmith et al.) 405 Volume 81, 1918. Sep. 12, p. 514 (News item) 421 Oct. 31, p. 785 (Edit.) 430 Oct. 31, pp. 806-8 (Anon.) 431 Nov. 21, pp. 930-1 (Clark) 434 Dec. 5, pp. 1034-6 (Winslow et al.)__459 Volume 82, 1919. Jan. 2, pp. 32-6 (Winslow et al.) 426 Volume 83, 1919. Dec. 4, pp. 948-52 (Wells) 484 Dec. 16, p. 920 (Anon.) 493 Dec. 20, p. 973 (Edit.) 496 Dec. 20, pp. 1003-4 (Anon.) 497 Dec. 29, p. 1063 (Anon.) 500 Volume 84, 1920. Jan. 8, p. 75 (Fugate) 510 Mar. 11, p. 511 (Hatton) 526 Mar. 25, p. 616 (Anon.) 531 Apr. 15, p. 754 (Fugate) 536 Apr. 22, pp. 819-23 (Lanphear) 540 Apr. 29, p. 873 (Anon.) 541 May 20, p. 989 (Edit.) 554 May 20, pp. 990-6 (Hatton) 555 May 20, p. 1034 (News item) 556 June 10, pp. 1161-2 (Anon) 564 June 24, p. 1260 (Anon.) 567 Volume 85, 1920. July 22, pp. 145-6 (Edit.) 572 Aug. 19, pp. 344-9 (Gascoigne) 576 Sep. 2, pp. 457-8 (Anon.) 577 Sep. 9, pp. 490-2 (Eagles) 581 Oct. 21, p. 780 (Anon.) 588 Oct. 21, p. 815 (Anon.) 589 Oct. 28, p. 833 (News item) 583 112 Indexes INDEX OF PERIODICALS (Cont.) ENGINEERING NEWS-RECORD (Cont.) Volume 85, 1920 (Cont.) Ref. Nov. 4, p. 889 (Anon.) 590 Nov. 25, p. 1018 (Edit.) 591 Dec. 9, p. 1125 (Anon.) 596 Dec. 9, p. 1128 (Anon.) 597 Dec. 9, pp. 1134-8 (Pearse) 598 Dec. 30, pp. 1286-8 (Orbison) 605 ENGINEERING RECORD. Volume 69, 1914. Ref. Feb. 7, p. 158 (Clark et al.) 6 Volume 71, 1915. Mar. 6, pp. 288-9 (Frank) 36 Mar. 20, pp. 367-8 (Clark) 40 Apr. 3, pp. 421-2 (Bartow et al.) 43 Apr. 24, pp. 521-2 (Frank et al.) 47 June 19, p. 784 (Coulter) 53 Volume 72, 1915. July 3, p. 23 (Requardt) 55 Aug. 21, p. 238 (Stevenson) 67 Oct. 16, pp. 481-4 (Hatton) 70 Nov. 20, p. 640 (Wilkinson) 82 Dec. 18, p. 768 (News item) 97 Volume 73, 1916. Jan. 1, pp. 5-6 (Edit.) 103 Jan. 22, p. 121 (Carpenter) 109 Jan. 29, p. 160 (News item) 112 Feb. 19, p. 255 (Hatton) 126 Apr. 8, p. 489 (Hatton et al.) 138 Apr. 22, p. 561 (News item) 140 Volume 74, 1916. July 15, p. 91 (News item) 169 July 29, pp. 137-8 (Harding et al.)_._173 Oct. 7, p. 428 (Edit.) 190 Oct. 7, pp. 444-5 (Copeland) 191 Oct. 7, p. 445 (Fuller) 189 Oct. 7, pp. 448-9 (Hammond) 192 Nov. 4, p. 557 (Anon.) 204 Nov. 18, p. 628 (Allin et al.) 210 Nov. 25, pp. 656-8 (Alvord et al.)___212 Nov. 25, p. 660 (Anon.) 213 Dec. 2, p. 695 (News item) 214 Dec. 23, p. 784 (News item) 226 Volume 75, 1917. Jan. 6, pp. 16-9 (Hatton) 239 Jan. 20, pp. 95-7 (Bartow et al.) 241 Feb. 10, pp. 228-9 (Anon.) 253 Mar. 10, p. 376 (Phelps) 248 Mar. 10, pp. 380-1 (Anon.) 261 ENGINEERING & CONTRACTING. Volume 43, 1915. Ref. Apr. 7, p. 306 (Edit.) 45 Apr. 7, pp. 310-1 (Bartow et al.) 43 ENGINEERING & CONTRACTING. (Cont.) Volume 44, 1915. Ref. Oct. 27, pp. 322-7 (Hatton) 75 Oct. 27, p. 322 (Edit.) 76 Dec. 1, pp. 433-4 (Bartow et al.) 83 Dec. 1, pp. 434-6 (Bartow et al.) 84 Dec. 15, p. 453 (Edit.) 94 Volume 45, 1916. Feb. 2, pp. 97-8 (Edit.) 116 Feb. 2, pp. 104-8 (Hatton) 117 Mar. 1, pp. 208-9 (Anon.) 129 Mar. 15, pp. 235-6 (Hatton) 131 Apr. 26, pp. 386-7 (Copeland) 141 Apr. 26, p. 388 (Lederer) 142 June 28, pp. 581-6 (Anon.) 155 Volume 46, 1916. Nov. 8, pp. 407-9 (Anon.) 207 Dec. 13, pp. 534-6 (Orbison et al.)__223 Volume 47, 1917. Feb. 14, pp. 154-7 (Anon.) 204 Feb. 14, -pp. 168-9 (Anon.) 254 Volume 48, 1917. July 11, pp. 28-30 (Anon.) 286 Sep. 12, pp. 217-20 (Anon.) 312 Nov. 14, pp. 386-8 (Anon.) 337 Nov. 14, pp. 390-1 (Anon.) 338 Volume 49, 1918. Jan. 9, pp. 36-7 (Anon.) 374 Jan. 9, pp. 38-9 (Anon.) 375 Feb. 13, pp. 165-8 (Anon.) 355 Apr. 10, p. 354 (Literature note) 287 Apr. 10, pp. 368-72 (Anon.) 400 June 12, pp. 595-7 (Kershaw) 391 Volume 50, 1918. July 10, pp. 31-2 (Anon.) 406 July 31, pp. 122-3 (Anon.) 415 Nov. 13, p. 467 (Anon.) 433 Volume 51, 1919. Apr. 30, p. 465 (Anon.) 456 May 14, pp. 510-3 (Dorr et al.) 459 Volume 52, 1919. July 9, pp. 41-2 (Bartow et al.) 367 Aug. 13, pp. 196-7 (McFarland) 368 Sep. 10, p. 310 (News item) 476 Dec. 10, p. 669 (Anon.) 491 Volume 53, 1920. Jan. 14, p. 39 (Hammond) 503 Mar. 10, pp. 280-3 (Anon.) 525 Mar. 31, pp. 357-9 (Ed reprint) 508 Mar. 31, pp. 364-5 (Martin) 495 May 12, p. 543 (Anon.) 548 May 12, pp. 552-3 (Anon.) 549 May 12, p. 554 (Anon.) 550 June 30, p. 726 (Ed. reprint) 519 June 30, pp. 736-8 (McGowan) 546 June 30, p. 762 (Anon.) 521 113 The Activated Sludge Process INDEX OF PERIODICALS (Cont.) JOUR. AM. LEATHER CHEM. ASSOC. Volume 11, 1916. Ref. August, pp. 441-9 (Eddy et al.) 160 August, pp. 450-3 (Rudnick et al) 161 Volume 12, 1917. April, pp. 128-35 (Ardern) 244 May, p. 199 (Lockett) 263 July, p. 320 (Hommon) 289 October, p. 563 (Bartow) 310 Volume 13, 1918. April, pp. 145-55 (Pearse) 371 JOUR. INDUS. & ENG. CHEM. Volume 7, 1915. Ref. April, pp. 318-20 (Bartow et al.) 43 Volume 8, 1916. January, p. 15 (Bartow et al.) 83 January, pp. 17-20 (Bartow et al.) 84 July, pp. 642-3 (Copeland) 141 July, p. 643 (Fort) 156 July, p. 645 (Hendrick) 157 July, pp. 646-7 (Bartow et al.) 158 July, pp. 647-8 (Weston) 159 July, p. 648 (Eddy et al.) 160 July, pp. 651-2 (Rudnick et al.) 161 July, p. 652 (Lederer) 142 July, pp. 653-4 (Clark) 162 Volume 9, 1917. April, pp. 374-6 (Copeland) 267 April, pp. 399-400 (Hammond) 268 September, pp. 845-50 (Bartow) 310 December, pp. 1093-5 (Mohlman) 354 Volume 10, 1918. May, pp. 339-44 (Nasmith et al.) 405 May, p. 400 (Rudnick) 406 Volume 12, 1920. May, p. 419 (Anon.) 543 JOUR. SOC. CHEMICAL INDUSTRY. Volume 33, 1914. Ref. May 3Q, pp. 523-39 (Ardern et al.)___ 9 Dec. 15, pp. 1122-4 (Ardern et al.)__ 23 Dec. 15, pp. 1124-30 (Melling) 24 Dec. 15, p. 1170 (J. & A. pat.) 10 Volume 34, 1915. Feb. 27, p. 197 (J & A pat.) 5 Mar. 15, p. 244 (J & A pat.) 3 May 15, p. 508 (Bartow et al.) 43 June 15, p. 632 (J & A pat.) 11 June 30, p. 680 (Frank pat.) 48 July 31, p. 814 (Naylor pat.) 13 Sep. 30, pp. 937-43 (Ardern et al.)__ 71 Sep. 30, p. 978 (Naylor pat.) 14 Dec. 31, p. 1269 (Beckett pat.)___.__ 16 Dec. 31, p. 1269 (Naylor pat.) 20 JOUR. SOC. CHEMICAL INDUSTRY. (Cont.) Volume 35, 1916. Ref. Feb. 15, pp. 153-5 (Ardern et al.)___124 Feb. 15, p. 195 (J & A pat.)__17, 18, 28 Feb. 15, p. 195 (Naylor pat.) 27 Feb. 29, p. 272 (J & A pat.) 15 Mar. 15, p. 326 (J & A pat.) 33 Mar. 15, p. 326 (Cooper pat.) 37 Apr. 15, p. 434 (Mottram pat.) 34 Apr. 15, p. 434 (Naylor pat.) 57 Apr. 29, p. 30 Sup. (Bowes pat. Ap.)_139 May 15, p. 521 (Mottram pat.) 39 May 15, p. 552 (Bartow et al.) 84 May 15, p. 555 (Bartow et al.) 83 May 31, p. 615 (Naylor pat.) 56 June 15, p. 647 (Mumford) 152 Aug. 31, p. 904 (Copeland) 141 Aug. 31, p. 904 (Weston) 159 Aug. 31, p. 904 (Rudnick et al.) 161 Aug. 31, p. 904 (Clark) 162 Aug. 31, p. 905 (Eddy et al.) 160 Sep. 15, p. 55 Sup. (G & H pat. Ap.)181 Oct. 31, p. 1074 (Fowler & M. pat.)__ 51 Nov. 15, p. 1129 (Long pat.) 74 Volume 36, 1917. Jan. 15, p. 44 (Rideal) 218 Jan. 31, pp. 65-8 (Ardern et al.) 244 Feb. 15, p. 160 (Martin pat.) 92 Feb. 28, p. 201 (Nordell pat.) 225 Mar. 15, pp. 264-9 (Lockett) 263 Apr. 30, p. 471 (J & A pat.) 165 May 15, pp. 517-8 (Copeland) 267 May 15, p. 519 (Ames pat.) 127 June 15, p. 611 (Caink pat.) 149 July 31, pp. 822-30 (Ardern) 296 Aug. 31, p. 938 (Caink) 295 Aug. 31, p. 79 Sup. (L & H-S pat. Ap.)304 Sep. 15, pip. 977-8 (Ames pat.) 255 Oct. 15, p. 95 Sup. (G & H pat. Ap.)_314 Nov. 15, p. 1146 (Bartow) 310 Dec. 15, p. 1247 (Ames pat.) 194 Volume 37, 1918. Jan. 31, pp. 38A (Jones pat.) 343, 344 Feb. 15, p. 71A (Dienert) 340 Feb. 15, p. 72A (Naylor pat.) 221 Feb. 15, p. 72A (J & A pat.) 222 Feb. 28, p. 106A (Cronin) 320 Apr. 15, p. 193A (J & A pat.) 256 Apr. 15, p. 193A (Moor pat.) 383 Apr. 15, p. 193A (Mulloy pat.) 384 Apr. 15, p. 193A (Noble pat.) 385 Apr. 15, p. 196A (G & H pat. Ap.)__396 June 29, p. 348A (Pearse) 371 July 15, p. 384A (Nasmith et al.)___405 Aug. 15, p. 440A (Clifford pat.)_____274 Aug. 15, p. 440A (Ames pat.) 285 Aug. 31, p. 484A (Caink pat.)- 294 Oct. 15, p. 603A (Moore pat.) 411, 412 Oct. 15, p. 604A (Buckley pat.) 410 114 Indexes INDEX OF PERIODICALS (Cont.) JOUR. SOC. CHEMICAL INDUSTRY. (Cont.) Volume 38, 1919. Ref. Jan. 15, p. 4R (Anon.) 440 Jan, 31, p. 53A (Nordell pat.) 427 Feb. 15, p. 96A (H & H pat. Ap.) 450 Feb. 28, p. 116A (Jones pat.) 428, 435 Mar. 15, p. 157A (Brosius pat.) 438 Mar. 15, p. 157 A (Rein et al. pat.)___439 Mar. 31, p. 197A (J & A pat.) 308 Sep. 16, p. 497A (Clifford pat.) 275 S0p. 30, p. 694 A (Buckley pat.) 413 Oct. 31, p. 790A (J & A pat.) 418 Nov. 15, p. 843A (J & A pat.) 419 Nov. 30, p. 876A (J & A pat.) 404 Nov. 30, p. 884 A (H & H pat. Ap.)__483 Dec. 31, p. 961A (Stott & J. pat.)___407 Dec. 31, p. 968A (Mumford pat.) 490 Volume 39, 1920. Feb. 28, p. 171A (Courmont) 509 Mar. 15, pp. 60-4T (Ardern) 527 Apr. 30, p. 145R (Brenehley et al.)__538 May 15, p. 347 A (Whyte et al. pat.)_455 May 15, p. 347A (Gambler) 528 May 15, p. 347A (Dienert) 530 May 31, pp. 382-3A (Dienert) 535 June 15, p. 423A (Courmont) 539 June 15, p. 424A (Dienert) 545 June 15, p. 434 A (A. S. Lt'd. pat.) 551, 552 June 30, p. 465A (Courmont) 547 July 15, pp. 177-82T (Brenchley et al.) 538 July 31, p. 525A (Ames pat.) 466 July 31, p. 525A (Cambier) 563 July 31, p. 526A (Jones pat.) 561 Aug. 16, pp. 556-7A (Cambier) 570 Aug. 16, p. 557 A (Stott & J. pat.)___566 Aug. 31, p. 581A (Adams) 473 MUNICIPAL ENGINEERING. Volume 47, 1914. Ref. December, pp. 427-36 (Hammond) 7 Volume 49, 1915. August, pp. 68-9 (Wynne-Roberts)-- 54 Volume 50, 1916. January, pp. 6-8 (Anon.) 105 February, p. 73 (Anon.) 115 Volume 51, 1916. September, p. 105 (News item) 179 December, pp. 234-5 (Anon.) 215 Volume 53, 1917. September, p. 108 (Fales) 311 October, pp. 148-9 (Bartow) 319 December, pp. 243-6 (Anon.) 353 Volume 54, 1918. February, pp. 78-9 (Anon.) 387 June, pp. 244-9 (Allen) 408 MUNICIPAL & COUNTY ENG'RG. Volume 55, 1918. Ref. August, pp. 67-70 (Hatton) 416 September, pp. 106-8 (Fuller) 420 November, pp. 173-5 (Winslow et al.)432 Volume 57, 1919. September, pp. 123-5 (Fuller) 460 Volume 58, 1920. February, pp. 71-5 (Stein) 517 Volume 59, 1920. August, pp. 58-9 (Horton) 574 MUNICIPAL JOURNAL. Volume 36, 1914. Ref. Feb. 19, pp. 233-9 (Hammond) 7 Volume 38, 1915. Apr. 15, pp. 504-5 (Bartow et al.)__ 43 Apr. 15, p. 509 (Edit.) 46 Volume 39, 1915. Aug. 19, p. 257 (Edit.) 66 Nov. 18, p. 776 (Anon.) 81 Volume 40, 1916. Feb. 10, pp. 199-200 (Duckworth) 93 Apr. 27, pp. 585-8 (Anon.) 146 June 8, pp. 785-7 (Hatton) 153 June 15, pp. 824-5, 830 ( Hatton) ___153 June 15, p. 833 (Edit.) 154 Volume 41, 1916. Sep. 28, pp. 383-4 (Edit.).. __185 Oct. 12, p. 446 (Copeland) 188 Oct. 19, pp. 480-3 (Anon.) 196 Oct. 26, pp. 510-3 (Anon.) 196 Nov. 30, p. 677 (News item) 214 Volume 42, 1917. Jan. 4, pp. 11-2 (Edit.) 238 Feb. 8, pp. 196-7 (Anon.) 250 Mar. 8, pp. 333-5 (Zimmele) 259 Apr. 12, p. 526 (Alvord et al.) 269 Volume 43, 1917. Sep. 20, p. 291 (News item) 315 Oct. 18, pp. 377-9 (Anon.) 322 Oct. 18. p. 381 (Edit.) 323 Oct. 18, p. 382 (Hatton) 324 Nov. 22, p. 508 (Anon) 345 Nov. 22, p. 510 (Anon.) 346 Volume 44, 1918. Jan. 5, pp. 14-6 (Anon.) 355 Jan, 19, p. 59 (News item) 378 Mar. 16, pp. 223-5 (Anon.) 395 Volume 45, 1918. July 29, p 84 (News item)__ __414 __426 __426 -426 Oct. 12, pp. 280-2 (Winslow et al. Oct. 19, pp. 297-9 (Winslow et al. Oct. 26, p.p 321-2 (Winslow et al. 115 The Activated Sludge Process INDEX OF PERIODICALS (Cont.) MUNIC. JOURNAL PUBLIC WORKS. Volume 46, 1919. Ref. Mar. 29, p. 225 (Anon.) 457 Apr. 12, p. 266 (Anon.) 462 May. 17, p. 349 (Edit.) 468 May 17, p. 356 (Anon.) 469 Volume 47, 1919. Sep. 27, pp. 199-200 (Anon.) 477 Oct. 4, pp. 210-3 (Anon.) 479 Oct. 11, p. 219 (Edit.) 480 Oct. 11, pp. 226-7 (Anon.) 479 Nov. 8, pp. 278-80 (Wells) 484 Dec. 6, pp. 345-6 (Clark) 362 PUBLIC WORKS. Volume 48, 1920. Ref. May 22, p. 446 (Anon.) 559 May 22, p. 447 (Edit.) ___560 June 29, pp. 536-8 (Hatton) 555 Volume 49, 1920. Sep. 18, pp. 251-3 (Pearse) 533 Oct. 23, pp. 385-7 (Anon.) 589 Nov. 13, pp. 461-3 (Anon.) 589 Nov. 27, pp. 504-6 (Weston) 592 Dec. 18, pp. 567-9 (Anon) 602 THE SURVEYOR. Volume 45, 1914. Ref. Mar. 20, pp. 504-6 (Fowler) 8 Apr. 10, p. 610 (Ardern) 9 Volume 46, 1914. July 24, pp. 113-4 (Edit.) 12 Nov. 22, pp. 592-4 (Naylor) 19 Dec. 11, p. 674 (Edit.) 21 Dec. 11, pp. 581-2 (Duckworth) 22 Dec. 18, p. 701 (Edit.) 25 Dec. 18, pp. 714-7 (Ardern) 26 Dec. 25, p. 754 (Discussion) 29 Volume 47, 1915. Jan. 1, p. 8 (Kersihaw) 31 Mar. 26, p. 449 (Edit.) 42 May 21, p. 642 (Bartow et al.) 43 June 4, p. 693 (Frank et al.) 50 Volume 48, 1915. July 16, pp. 74-6 (Wilson) 59 July 30, p. 129 (Edit.) 62 July 30, pp. 132-3 (Wakeford) 63 Aug. 6, pp. 143-6 (Discussion) 65 Aug. 20, p. 211 (Wynne-Roberts) 54 Sep. 3, p. 253 (Edit.) 68 Sep. 3, pp. 258-61 (Hatton) 58 Oct. 29, p. 445 (Edit.) 77 Oct. 29, pp. 450-4 (Ardern et al.) 71 Dec. 3, p. 562 (Edit.) 87 Dec. 3, pp. 564-7 (Hatton) 90 Dec. 10, p. 604 (Fowler) 91 Dec. 17, pp. 629-30 (Discussion) 95 Dec. 24, p. 645 (Edit.) 98 Dec. 24, pp. 648-52 (Duckworth) 93 THE SURVEYOR (Cont.) Volume 49, 1916. Ref. Jan. 21, p. 51 (Edit.) 107 Jan. 21, pp. 55-6 (Cooper) 108 Jan. 28, p. 126 (Jones & Attwood)__lll Feb. 4, p. 143 (Edit.) 119 Feb. 4, pp. 148-51 (Fowler) 120 Feb. 25, pp. 233-4 (Fuller) 89 Feb. 25, p. 234 (Edit.) 128 Mar. 3, pp. 255-7 (Hammond) 130 Mar. 17, pp. 308-9 (Hatton) 117 Mar. 31, pp. 352-4 (Duckworth) 133 Apr. 14, pp. 405-6 (Fowler) 121 May 12, p. 480 (Edit.) 147 May 12, p. 486 (Hatton et al.) 138 Volume 50, 1916. July 14, pp. 29-30 (Barwise) 166 July 14, pp. 33-4 (Discussion) 167 July 14, pp. 40-2 (Haworth) 168 July 28, p. 83 (Edit.) 172 Aug. 4, p. 93 (Edit.) 174 Aug. 25, pp. 160-3 (Anon.) 170 Sep. 15, pp. 238-41 (Eddy) 136 Sep. 15, p. 247 (Edit.) 183 Sep. 29, pp. 282-4 (Eddy et al.) 160 Oct. 27, pp. 373-4 (Edit.) 198 Oct. 27, pp. 379-80 (Anon.) 199 Nov. 3, pp. 400-1 (Hammond) 192 Nov. 10, pp. 430-2 (Edit.) 209 Nov. 17, pp. 453-5 (Hammond) 195 Nov. 24, pp. 479-80 (Hammond) 195 Dec. 1, pp. 504-6 (Eddy) 203 Volume 51, 1917. Jan. 5, pp. 4-5 (Nasmith) __216 Jan. 5, p. 6 (Anon.) 211 Jan. 26, pp. 80-2 (Edit.) 242 Jan. 26, p. 108 (News item) 243 Feb. 2, p. 144 (Caink) 247 Mar. 9, pp. 254-5 (Phelps) 248 Mar. 23, p. 297 (Edit.) 264 Mar. 23, pp. 298-9 (Ardern) 244 Mar. 23, pp. 299-300 ( Discussion) ___265 Apr. 13, p. 359 (Edit.) 270 Apr. 13, pp. 370-2 (Eddy) 217 May 18, p. 458 (Adams) 272 June 1, pp. 506-7 (Coulter)___ 273 June 15, pp. 544-5 (Edit.) 283 June 15, pp. 546-8 (Caink) 282 June 15, p. 549 (Jones & Attwood) 284 Volume 52, 1917. July 6, p. 10 (News item) 293 July 13, p. 40 (Barwise) 297 July 20, pp. 45-6 (Edit.) 298 July 20, pp. 51-5 (Caink) 295 July 20, p. 67 (Discussion). 299 July 27, pp. 87-8 (Caink) 300 Aug. 17, pp. 137-8 (Edit.) 307 Aug. 17, pp. 140-2 (Ardern) 296 116 Indexes INDEX OF PERIODICALS (Cont.) THE SURVEYOR (Cont.) Volume 52, 1917 (Cont.) Sep. 21, p. 246 (Edit.) 318 Sep. 21, p. 252 (Zimmele) 276 Sep. 21, p. 253 (Edit.) 317 Oct. 19, p. 333 (Edit.) 325 Oct. 19, p. 342 (Anon.) 305 Nov. 23, p. 445 (Hatton) 324 Nov. 30, p. 471 (Caink) 350 Dec. 21, p. 527 (Edit.) 361 Dec. 21, p. 528 (Anon.) 321 Dec. 28, p. 552 (Discussion) 364 Volume 53, 1918. Jan. 4, pp. 4-5 (Anon.) 373 Jan. 18, pp. 42-4 (Young et al.) 372 Jan. 18, pp. 46-8 (Anon.) 375 Jan. 25, pp. 71-3 (Edit.) 380 Jan. 25, p. 106 (News item) 381 Jan. 25, pp. 114-5 (Anon.) 382 Jan. 25, pp. 117-9 (Discussion) 379 Feb. 1, p. 125 (Edit.) 388 Feb. 22, p. 197 (Kershaw) 391 Mar. 8, p. 229 (Edit.) 393 Mar. 8, pp. 232-3 (Hatton) 333 Mar. 15, pp. 254-5 (Hatton) 333 Apr. 5, p. 314 (Anon.) 399 June 28, p. 457 (Edit.) 409 Volume 54, 1918. Sep. 13, p. 131 (Bade) 422 Sep. 20, p. 139 (News item) 423 Oct. 4, p. 166 (News item) 425 Oct. 25, pp. 195-6 (Martin) 429 Nov. 29, p. 255 (Anon.) 436 Volume 55, 1919. Jan. 10, pp. 17-8 (Anon.) 449 Jan. 31, pp. 66-9 (Edit.) 451 Jan. 31, p. 105 (Trade note) 452 Feb. 14, p. 143 (Clark) 434 Apr. 11, p. 282 (News item) 461 Apr. 18, p. 298 (News, item) 463 June 6, pp. 419-21 (Dorr et al.) 459 June 20, p. 470 (News item) 470 Volume 56, 1919. July 18, p. 49 (Anon.) 472 Sep. 5, p. 146 (News item) 475 Oct. 17, pp. 225-6 (Godfrey) 474 THE SURVEYOR (Cont.) Volume 56, 1919 (Cont.) Oct. 31, p. 258 (Bottomly) 481 Nov. 14, p. 293 (Anon.) 486 Dec. 5, p. 366 (Anon.)__ 489 Dec. 19, p. 398 (Edit.) 494 Dec. 19, pp. 401-2 (Martin) 495 Dec. 26, pp. 417-8 (Anon.) 499 Dec. 26, p. 419 (Martin) 495 Volume 57, 1920. Jan. 2, pp. 8-9 (Anon.) 507 Jan. 9, pp. 19-21 (Nasmith) 492 Jan. 9, p. 27 (News item) 511 Jan. 30, pp. 75-7 (Edit.) 514 Jan. 30, p. 119 (Trade note) 516 Feb. 27, p. 199 (Edit.) 519 Feb. 27, pp. 201-2 (Anon.)_. 520 Feb. 27, p. 205 (Anon.) 521 Feb. 27, p. 208 (News item) 522 Mar. 5, p. 216 (Edit.) 523 Mar. 5, p. 222 (Anon.) 524 Mar. 12, p. 244 (Hatton) 500 Apr. 9, p. 308 (Clark) 534 Apr. 16, p. 328 (Clifford) 537 May 7, pp. 405-7 (McGowan) 546 May 14, pp. 426-7 (Discussion) 553 ,May 21, p. 440 (Anon.) 557 May 21, p. 446 (Martin) 558 May 28, p. 469 (News item) 562 Volume 58, 1920. July 9, pp. 21-3 (Hatton) 555 July 9, p. 23 (Anon.) 571 July 16, pp. 48-9 (Hatton) 555 July 23, p. 64 (News item) 573 Sep. 17, p. 188 (News item) 582 Oct. 1, p. 221 (News item) 583 Oct. 8, p. 225 (Edit.) 586 Oct. 29, p. 292 (Godfrey) 578 Dec. 3, p. 374 (Edit.) 593 Dec. 3, p. 375 (Anon.) 594 Dec. 3, p. 380 (Anon.) 595 Dec. 10, pp. 397-8 (Makepeace) 599 Dec. 17, p. 412 (Farmer) 600 Dec. 17, pp. 413-4 (Anon.) 601 Dec. 24 pp. 427-8 (Ardern) 527 Dec. 24, p. 430 (Discussion) 600 UNIVERSITY OF CALIFORNIA DEPARTMENT OF CIVIL ENGINEERING PHRKELEY. CALIFORNIA 117 GENERAL FILTRATION COMPANY, INC. GENERAL OFFICES - ROCHESTER, N. Y. 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