STATE OF ILLINOIS DEPARTMENT OJ REGISTRATION AND EDUCATION. DIVISION OF THE STATE WATER SURVEY A. M. BOSWELL, Chief. BULLETIN NO. 18 Activated Sludge Studies 1920-1922 (Printed by authority of the State of Illinois URBANA, ILLINOIS PUBLICATIONS OF THE STATE WATER SURVEY. No. 1. Chemical survey of the waters of Illinois. Preliminary Report. 98 pp., 3 pi., 1 map. 1897. (Out of print.) No. 2. Chemical survey of the waters of Illinois. Report for the years 1897-1903. XVI+254 pp., 55 pi. 1905. (Out of print J No. 3. Chemical and biological survey of the waters of Illinois. Report for year ending August 31, 1906. 30 pp., 5 cuts. 1906. No. 4. Mineral content of Illinois waters. VIII-f-192 pp. 1908. No. 5. Municipal water supplies of Illinois. VIII-f-123 pp. Map. 1907. (Out of print.) No. 6. Chemical and biological survey of the waters of Illinois. Report, September 1, 1906, to December 31, 1907. 88 pp., 3 cuts, 9 pi. 1908. No. 7. Chemical and biological survey of the waters of Illinois. Report for 1908. 204 pp., 4 cuts. 1909. (Out of print.) No. 8. Chemical and biological survey of the waters of Illinois. Report for 1909 and 1910. 150 pp., 28 cuts. 1911. No. 9. Chemical and biological survey of the waters of Illinois. Report for 1911. 171 pp., 20 cuts. 1913. No. 10. Chemical and biological survey of the waters of Illinois. Report for 1912. 198 pp., 19 cuts. 1914. No. 11. Chemical and biological survey of the waters of Illinois. Report for 1913. 473 pp., 106 cuts. No. 12. Chemical and biological survey of the waters of Illinois. Report for 1914. 261 pp., 32 cuts. No. 13. Chemical and biological survey of the waters of Illinois. Report for 1915. 381 pp., 36 cuts. No. 14. Chemical and biological survey of the waters of Illinois. Report for 1916. 192 pp., 40 cuts. No. 15. Chemical and biological survey of the waters of Illinois. Report for 1917. 136 pp., 8 cuts. No. 16. Chemical and biological survey of the waters of Illinois. Report for 1918 and 1919. 280 pp., 36 cuts. No. 17. Index to Bulletins 1-16. No. 18. Activated Sludge Studies 1920-1922. For copies of these reports or for other information, address Chief, State Water Survey Division, Department of Registration and Education, Urbana’ 111. STATE OF ILLINOIS. DEPARTMENT OF REGISTRATION AND EDUCATION. DIVISION OF THE STATE WATER SURVEY A. M. BUSWELL, Chief. BULLETIN NO. 18 Activated Sludge Studies 1920-1922 (Printed by authority of the State of Illinois' URBANA, ILLINOIS Springfield, III.: Illinois State Register Printers- 19 2 3 81873—2700 CONTENTS. Pasre Introduction 9 Recent progress 11 Review of experiments with aerators and automatic sludge return... 11 CHAPTER I. Summary 17 Description of testing station... 18 General character of sewage 19 Nitrogen balance 20 Reversal of nitrogen cycle and “fixation” of nitrates and ammonia... 22 Wet burning of solids 24 Character of sludge 24 Relation between volume and weight of sludge 24 Microbiology of activated sludge 26 Mechanical operation of the plant 27 Purification results 28 General operation '. 28 Sludge drying 30 CHAPTER II. Description of Sewage Experiment Station 1920-21 33 Grit chamber 33 Dorrco screen 34 Pump pit 36 Dorr-Peck tanks 36 Blower and pumping equipment 44 Sludge dewatering equipment 47 CHAPTER III. Champaign Sewage 48 General characteristics 48 Volume of flow 48 CHAPTER IV. Operation of Activated Sludge Plant 54 Operation periods 54 Notes on operation 54 Operating records 55 Sampling points 56 Collection of samples 56 Physical characteristics of sludge 58 Rate of subsidence 58 Effect of reaeration 60 Effect of sewage on rate of subsidence 62 Diurnal variations 62 Weight and volume of settleable solids 64 Grit chamber 65 Dorrco screen results 65 CHAPTER V. Bio-chemistry of the Process 68 Nitrogen cycle 68 Ammonification 69 CONTENTS—Concluded. Page Nitrification 70 Loss of Gaseous nitrogen 70 Nitrogen fixation 71 Denitrification 72 Nitrogen cycle in activated sludge tanks 73 Summary 81 CHAPTER VI. Microbiology and Theory of Activated Sludge 82 Experimental 86 Summary of microscopic observations, May 3-17, 1921 86 Discussion of data 87 Minute ciliates and flagellates.... 87 INFUSORIA 90 Peritrichs 90 Hypotrichia 90 Holotrichia and Heterotrichia 90 Suctoria 91 THE WHEEL ANIMALECULES 91 Rotatoria 91 ROUND WORMS 91 Nematoda 91 ZOOGLEAL MASSES 91 BACTERIAL SURFACE 92 SUMMARY 92 CHAPTER VII. Sludge Drying Experiments 93 pH control of acidification 93 Effect of acidification and heat 93 Acid-heat-flotation process 98 Conclusions 103 Bayley drier 103 Summary 108 Filter press experiments 108 Preparation of sludge for press 109 Conditions of operation 109 Observation , 110 Remarks 110 Oliver filter Ill Centrifuge 112 BIBLIOGRAPHY 113 APPENDIX 116 ILLUSTRATIONS. TABLES AND FIGURES. Introduction. Page Fig. 1 Sewage aerators 12 Fig. 2 Manchester type tank; Woodstock, Canada 15 CHAPTER I. Fig. 3 A general view of experimental plant 19 Table I Raw sewage turbidity 20 Table II Screened sewage analyses; weekly averages 21 Table III Nitrogen balance Dec. 14, 1920 to Feb. 18, 1921 22 Fig. 4 Air and nitrogen curves 23 Table IV Sludge analyses (64 samples) 24 Fig. 5 Relation between volume and weight of settleable solids... 25 Table V Average analyses from May 3 to Sept. 3, 1921 28 Fig. 6 General operation curves 29 CHAPTER II. Fig. 7 General plat of entire plant...." 32 Fig. 8 Flow sheet through Dorr-Peck tanks 34 Fig. 9 Picture of Dorrco-Screen .- 35 Fig. 10 Circulation in the Dorr-Peck tank 37 Fig. 11 Plan and Section of Filtros plates 38 Fig. 12 Plan and section of Mechanism and Superstructure 40 Fig. 13 Overflow weir 41 Fig. 14 Photograph of weir in operation 41 Fig. 15 Measuring return air and sludge thru down-cast well 43 Fig. 16 Improved method for regulating flow 44 Fig. 17 Plan of pump house 45 CHAPTER III. Table VI Champaign Sewage mean, maximum and minimum daily flow 49 Table VII Champaign sewage average hourly variation for 12 selected weeks 52 Table VIII Champaign sewage hourly variation for typical daily flows.. 53 CHAPTER IV. Fig. 18 Samples of daily data sheets 57 Fig. 19 Theoretical curves of sludge settling 59 Page Fig. 20 Effect of aeration on settling rate of sludge 60 Fig. 21 Variation in settling rates of sludges 61 Fig. 22 Diurnal variation of settleable solids 63 Fig. 23 Daily variation from May 5 to June 20, 1921 63 Table IX Dorrco Screen Result 67 CHAPTER V. Fig. 24 Marshals Nitrogen Cycle 68 Fig. 25 Reversible Nitrogen Reactions 69 Table X NJialance 5/3 to end of run 75 Table XI Nitrate Reduction 5/3-9/1 1 78 Table XII Nitrate Reduction Winter 1920-21 79 Table XIII Nitrate Reduction at Lawrence, Mass 79 CHAPTER VI. Table XIV Organism Count Tank 1 88 Table XV Organism Count Tank 2 , 89 CHAPTER VII. Table XVI Effect of acid and heat (5 experiments) 94 Table XVII Effect of acid 96 Fig. 26 Effect of acid and heat Fig. 27 Effect of acid alone Fig. 28 Flotation unit 99 Fig. 29 Bayley Drier ...104 Table XVIII Readings on Bayley Drier 1/19 and 1/20 106 Fig. 30 Patterson press 109 Table XIX Patterson press experiments •. ...110 Fig. 31 Oliver filter Ill ILLUSTRATIONS—Continued. STATE OF ILLINOIS. DEPARTMENT OF REGISTRATION AND EDUCATION BOARD OF NATURAL RESOURCES AND CONSERVATION ADVISORS. A. M. Shelton, Chairman. William A. Noyes, Chemistry, Secretary. John W. Alvord, Engineering. Edson S. Bastin, Geology. John M. Coulter, Forestry. William Trelease, Biology. Bayard Holmes, Physician. Kendric C. Babcock, Repre- senting the President of the University of Illinois. MEMBERS OF WATER SURVEY DIVISION SUB- COMMITTEES. A. M. Shelton. Kendric C. Babcock. William A. Noyes. John W. Alvord, LETTER OF TRANSMITTAL. State of Illinois, Department of Registration and Education, State AVater Survey Division. Urbana, Illinois, May 1, 1920. A. M. Shelton, Chairman, and Members of the Board of Natural Resources and Conservation Advisors; Gentlemen—Herewith I submit report of the investigations of the activated sludge process of sewage disposal carried on by this Division during 1920-21 and 22 and request that it be printed as Bulletin No. 18. • Since the Directors’ report includes a statement of the general activities of all Divisions, it has seemed advisable to discontinue the publication of an annual report of this Division and to prepare instead summaries of our various investigations as they are completed. Acknowledgment should be made to Professor Edward Bartow, Chief of the State AVater Survey to September 1, 1920, who was retained as consultant until February, 1921; to Mr. C. Lee Peck, who supervised the final stages of installation and early operation of the Dorr-Peck tanks; and to Mr. G. C. Ilabermeyer, engineer, and Dr. R. E. Greenfield, chemist of the staff of this Division, who took active part in the conferences on the more important problems encountered. We are indebted to the Dorr Company for the loan of the Dorr thickener mechanisms used in these experiments, and for the license to build tanks after the Dorr-Peck design. The blower wras loaned by the Nash Engineering Company, and the air meter by the Rotary Meter Company. The Staley Manufacturing Company of Decatur furnished the two large cypress tanks in which the Dorr-Peck appa- ratus was installed. The many courtesies extended to the State Water Survey by the cities of Champaign and Urbana greatly assisted the prosecution of the work. Extensive use has been made of the Bibliography of Activated Sludge, prepared by J. Edward Porter of the General Filtration Company, Rochester, NewT York. Respectfully submitted, A. M. Buswell, Chief. INTRODUCTION. It is our purpose in the present bulletin to offer first a brief historical survey of progress in the development of the activated sludge process of sewage disposal, and second, with this historical view as a background, to present the chemical and biological data which have been collected during the past year’s experimentation with low air operation of an activated sludge plant treating 75,000 gallons per day. For the sake of completeness a historical sketch printed in a previous bulletin will he quoted here d “The earliest attempts to oxidize sewrnge by aeration were made by Dupre and Dibdin2 on the sewage of London, and by Dr. Drown3 on the sewage of Lawrence, Massachusetts. They found that oxida- tion accomplished in this way was a very slow process, and accordingly not at all practicable. In 1892 Mason4 and Hine conducted experiments on the oxidation of sewage by means of aeration. They concluded that air had but little oxidizing effect on sewage. In 1894 Waring5 attempted to apply air on a working scale at New Port, R. I., but his project was unsuccessful. In 1897 Fowler6 aerated the effluent from the chemical precipi- tation tanks at Manchester, England, but without accomplishing any considerable degree of purification. In 1911 aeration was again attempted. Black7 and Phelps studied the possibility of aerating the sewage of New York City. They used tanks filled with inclined wooden gratings for varying periods up to twenty-four hours. The oxidation was so slight that determinations of nitrogen showed prac- tically no purification, although some measure of improvement was indicated by the incubation tests. Black arid Phelps recommended the process for a large-scale installation but it was not adopted. Clark, Gage and Adams8 had tried aeration of sewage at the Lawrence Experimental Station, but had been unable to obtain satis- factory results until 1912. In that year, however, they -were able to nitrify sewage successfully by aeration for twenty-four hours in a tank containing vertical slabs of slate placed about one inch apart, and covered with a zoogleal mass of colloidal matter deposited from the sewage. They submitted the effluent to further treatment for they did not claim that the aeration would entirely obviate filtration. 10 Gilbert J. Fowler,9 of Manchester, England, had tried aeration with some modification on English sewages, but had obtained only indifferent results. Upon his return to England after a visit to Law- rence in 1912, he suggested work on aeration to Edward Ardern and W. T. Lockett,10 resident chemist and assistant chemist, respectively, at the Davyhulme Sewage Works of Manchester. On April 3, 1911, they reported the remarkable results which they had obtained in their preliminary investigations. In their first experiment, Ardern and Lockett aerated samples of Manchester sewage in gallon bottles, until complete nitrification was accomplished the aeration was affected by drawing air through the sewage with an ordinary filter pump. Aeration for about five weeks was required to obtain complete nitrification. The clear oxidized liquid was then removed by decanta- tion, raw sewage added to the deposited sludge, and aeration con- tinued until the sewage was again completely nitrified in six to nine hours. The sludge which induced such active nitrification was called “activated sludge” by Ardern and Lockett. In August, 1914, Edward Bartow11 ,saw the work in progress at Manchester, and upon his return to this country, suggested that experiments with activated sludge be started at the University of Illinois.” Experiments on the purification of sewage by aeration in the presence of activated sludge were begun at the laboratories of the Illinois State Water Survey in November, 1914, and have been con- tinued to the present date. The first series carried out by Bartow and Mohlman included experiments in three gallon bottles, a small tank with glass sides five feet deep, and later concrete tanks of ten square feet area, and eight feet five inches deep. This series demonstrated the effect of activated sludge on the rate of nitrification, the superiority of filtros plates as air diffusers over wood diffusers, and furnished data on the ratio of diffuser area to tank area. These experiments are completely reported in Bulletin 13. During this series of experiments such problems arose as the required area for air diffusion, the nitrogen cycle, the time of aeration, the fertilizing value of the sludge, the required sludge for purification. The fill and draw method proved inadequate and attention was given to the construction of a new plant. In the summer and fall of 1916, the septic tank designed by Professor A. N. Talbot in 1897 for the city of Champaign was re- 11 constructed into a continuous-flow plant where the second series of experiments on the activated sludge process was conducted. The reconstructed plant was designed to treat 200,000 gallons of domestic sewage daily, and consisted of a combined screen chamber and pump, a two-compartment grit chamber, separate aeration and settling tanks, the necessary machinery and accessories for furnishing and measuring the air and sewage. Other parts of the plant con- sisted of sludge drying beds and a pond, into which the effluent was discharged. A full description of the plant, results and conclusions are given in an article by Professor Edward Bartow.12 Recent Progress. In the meantime a relatively enormous amount of experimental work has been in progress throughout the world. Porter’s bibliography lists over eighty experimental plants and seven- teen municipal activated sludge plants completed or in process of construction at the present date. In this country a most extensive series of experiments has been carried on at Milwaukee, Wisconsin,13 leading to the design and con- struction of an activated sludge disposal' plant for the entire city of Milwaukee. A plant has been in operation in Houston, Texas, since 1917. The most recent report on operating results will be found in Eng. News Record, 85. 1128. San Marcos, Texas, with a sewage flow of 150,000 gallons per day, is believed to be the first town in the United States to use activated sludge treatment for its entire sewage. Considerable progress in the treatment of trade wastes by the activated sludge process has been made by the Sanitary District of Chicago. The British experiments have been along somewhat different lines from the American, and will be described under special headings. Review of Experiments with Aerators and Automatic Sludge Return. One of the most extensively investigated problems is that of reducing the amount of air necessary for maintenance of the proper operation of the activated sludge process. Unless the cost of operation can be very materially reduced or considerable return realized on the sludge the process will be of very limited application. We have found in going through the technical and patent litera- ture some thirty articles or patents describing either methods of intro- ducing air into sewage other than by blowing through porous tile, or methods for increasing the period of contact and efficiency of air when once blown into the sewage. A few of the methods which have been employed with more or less success for the introduction of air into sewage other than by blowing through porous plates will be discussed. Fig. 1 shows illus- trations of nine such methods. 12 Fig. la 13 Fig. lb 14 Coulter14 describes experiments in which he forced water under considerable pressure through a nozzle, allowing it to strike upon the surface of the liquid in the tank. The force of the stream carried a considerable amount of air down into the liquid. In fact, by using a large diameter pipe directly beneath the point where the stream struck the liquid in the tank, thereby producing a sort of suction pump, it was found possible to carry air bubbles several feet beneath the surface of the liquid. This method has not to our knowledge been employed on a large scale in purifying sewage. A second method which was employed by Brosius15 and Trent10 independently, produces a mixture of air and liquid by drawing or forcing the liquid rapidly down a vertical pipe at such a rate that air is mechanically carried down with the water. In the Trent appa- ratus a series of small pipes inside the large vertical downtake pipe facilitated the introduction of air. In neither of these machines were the conditions produced satisfactory for the maintenance of activated sludge. A third method for introducing air, and one which has been fre- quently attempted, is that of surface aeration. Haworth17 appears to have successfully operated an activated sludge plant by surface aera- tion at Sheffield, England. He causes the sewage and activated sludge to circulate through long channels. These channels are approximately four feet wide and four feet deep. The rate of flow is just sufficient to maintain the sludge in suspension and amounts to one and a half feet per second. Housings cover paddle wheels which force the liquid along the channels. This plant has a capacity of 500,000 gallons of sewage per day and has been in successful operation for over a year. The capacity is equivalent to 1.3 million gallons per acre per day and the power equals 50 h.p. per million gallons. One point which should be mentioned in connection with the success of this particular experiment is that there is a considerable amount of iron or pickle liquor waste in the raw sewage. It will be remembered that Mumford in describing her M7 called attention to the importance of iron. Another mechanical process which seems to have found practical application is the “Simplex”18 installed by the Ames Crosta Sanitary Engineering Company, Ltd., at Bury, England, and elsewhere. “The tank is arranged with a conical bottom, and a central tube coned at the lower end is fixed a few inches from the bottom of. the tank, the top portion terminating in a dish, the outer edge of which is raised about half an inch above the top water level. Inside the dish a revolving cone with suitably formed vanes is suspended by means of a vertical 15 shaft running on ball bearings rotated by shafting and bevel wheels. When the cone is in motion the liquid is thrown out in the form of a film wave, and the liquid and sludge then rise in the central tube to replace the liquid thrown out by the revolving cone. The vanes of the cone are arranged to throw the liquid off so as to strike the surface of the main volume of liquid in the tank in such a manner as to induce a circular motion which causes the liquid to sink in the form of a spiral to the bottom of the tank to be re-circulated. To obtain the necessary amount of agitation and aeration the contents of the tank are circu- lated once in twenty minutes or three times an hour, the horsepower absorbed being about 12 h.p. per twenty-four hours, run per million gallons. The aeration period ranges from eight to sixteen hours, depending upon the strength of the sewage.” The circulating tank like that described by Hurd19 has given very good results with about one-half the air required by ordinary aeration tanks. These tanks are built with the diffusers along one side Fig. 2 and a single baffle through the center. The air life effect pumps the liquor over this baffle and returns it underneath. In this way a vigorous circulation is set up. The ratio of diffuser to floor area is from 1:10 to 1:16. Ure20 has described a similar aerating chamber at Woodstock, Ont. (Fig. 2). 16 Of the various methods of economizing on air we should like to call attention to the intermittent aeration proposed by G. A. H. Burn.21 This author suggests cutting off the air during the peak of the power load. If the peak does not last more than three or four hours, satisfactory results might be obtained. A number of attempts have been made to build activated sludge tanks so that settled sludge could be returned automatically or with- out pumping to the aeration chamber. Among the previous investi- gators who have designed such apparatus might be mentioned the following: Prank22 describes a tank with a central aerating chamber, and two elevated side chambers with a V cross section, the aeration taking place in the central chamber from which the aerated sewage over- flows into the side chambers where sedimentation takes place. The bottoms of these chambers are open so that the settled sludge drops back into the aerating chamber. Martin23 describes a cylindrical tank divided into segments. A radial trough is provided for sedimentation, from the bottom of which the settled sludge may be returned to the aerating segment. G. T. Hammond’s24 tank had an upper and lower chamber, the lower chamber being used for aeration and the upper chamber for sedimentation. The settled sludge could be returned by gravity. George Moore25 describes a two-chamber tank with means for discharging the thickened sludge from the lower portion of the second tank directly back to the first. S. H. Adam’s26 sedimentation tank had an apron roof in which sedimentation took place in the upper portion of the tank on the apron, the settled sludge slipping through a slot into the lower portion of the chamber. Other means for accomplishing these results have no doubt been employed. The above are mentioned simply as examples of progress in this direction. The Dorr-Peck tank used in our experiments combined the cir- culating features of Hurd’s tanks with automatic sludge return simi- lar to Prank’s svstem. 17 CHAPTER I. Summary. By A. M. Buswell. State Water Survey’s Third Series of Experiments. Since the present series of experiments involved the use of a novel apparatus previously constructed by a private concern; since, furthermore, a change occurred in the administration of the State Water Survey after the equipment had been ordered and construction of the experi- mental plant was well under way—but before operation was started— it seems best to insert at this point a brief statement of events pre- liminary to the third series of investigations. On his return from the war in July, 1919, Col. Bartow, then Chief of the Water Survey, began plans for an extension of the sewage experiment station with the purpose of continuing investiga- tions into methods of sewage purification. Construction of the experi- mental plant was commenced in April, 1920. In a previous paper Col. Bartow described the plant as follows: “A small appropriation had been made for the biennium 1917-19, which was not used and had been reappropriated for the biennium 1919-21. With this as a nucleus the testing station is being revived. The Division funds have been supplemented by contributions of loans of instruments, apparatus, and machinery. The several sanitary dis- tricts in the State have promised their cooperation and support. Several manufacturing concerns have loaned apparatus for the work. Tanks, machinery, a blower, a filter press, a continuous filter, and a drier have been obtained in this way. “It is not proposed to confine the experimental work to the acti- vated sludge process, but to try other methods of sewage treatment as time and funds permit. Many cities in Illinois are located on large streams into which a partly purified sewage can be emptied. “Owing to the limited amount of funds, all of the schemes can- not be tried at once, and it has been decided to make a study first of the Dorr-Peck modification of the activated sludge process, with addi- tions so that the process will be complete from the raw sewage to the clarified and purified effluent, and the dried sludge ready to be used as a fertilizer.” The following extract from a statement by the Dorr Company published in the Journal of the Boston Society of Engineers, v. 7, 18 p. 255, gives briefly the history of the Dorr-Peck process referred to above. “The experimental work which led to the development of this process was undertaken with the idea of evolving an apparatus which would secure high efficiency from the air, in order to reduce the operating costs of this desirable system to a figure comparable to that of other systems in general use. ‘ ‘ The idea was conceived that an aeration unit could be designed to effect self-contained sludge circulation and prolonged contact by utilizing the full mechanical efficiency of the escaping air bubbles in the form of an air lift. “An experimental station was established at Mount Vernon, N. Y., early in 1919, by courtesy of the city authorities, and duplicate aeration units were installed to treat a flow of 45,000 gallons per day of fresh sewage drawn from the lower side of the city bar-screen chamber, containing % inch racks. “The work was directed by Mr. C. Lee Peck, director of research and development of our Sanitary Engineering Department. Mr. Peck was responsible for the inception and successful development of the experimental work. “Other vital features affecting the successful aerobic treatment of sewage were developed, which have warranted the adoption of a distinct name for the modification, which has been designated the ‘ ‘ Dorr-Peck Process. ’ ’ “A close study of the biologic control and stimulation has indi- cated the probability of high nitrogen values being recovered in the sludge, by the use of this system. It is our hope that the time is not far distant when municipal sewage may be treated at a profit. These experiments extended over a period of six months. ’ ’ After visiting the Mt. Vernon plant Col. Bartow suggested to the Dorr Company that it furnish an apparatus for experimental pur- poses at Champaign. The Dorr Company, appreciating the advantage of having the apparatus tried out at the State Water Survey, agreed to design the tanks and furnish a considerable amount of equipment for the experiment. The purpose of the experiment was two-fold. First, to investigate further the performance of the Dorr-Peck tank, and second, to determine the effect of various methods of dehydrating and drying upon the sludge produced. Description of Testing Station. The plant at which the ex- periments described in this paper were carried out is shown in 19 Fig. 3. At the left in the foreground is a steam boiler; further back Fig. 3 and a little to the right, is a Barley drier, while at the extreme right of the picture are seen the two Dorr-Peck tanks which were operated in series. The small tank was used for drawing and concentrating sludge. In the background is seen the housing over the old Talbot septic tank of historic interest. This tank is also known as the orig- inal Champaign septic tank. At the left of and a little behind the drier can be seen the Patterson filter press. A Foxhoro gauge makes a continuous permanent record of the amount of the effluent. At the left of the tanks may he seen a portion of the housing covering the motors, pumps and blower. The white collars about the upper portion of the tank are canvas wind breaks provided to prevent disturbance of the sedimentation chamber. General Character of Sewage. Analyses of the sewage were made on samples of the screened sewage collected hourly and com- posited into three shift samples for each day. The manner of collec- tion and compositing of samples and the analytical procedure is given on page 116. The determinations were made in accordance with the standard methods of A. P. H. A. Table III in the appendix gives the analyses and flow of the raw sewage for the entire City of Champaign, as well as for the influent and effluent of the treatment plant. The mean flow was 1.24 million gallons per day. During the period of high flow, i. e., from 132 to 171 per cent 20 of the mean flow, large amounts of nitrate, from 2.9 to 6.4 p.p.m. were present. The chlorides and alkalinity were lower than the average in such periods. The largest amount of organic nitrogen, 21.6 p.p.m. was present in the period of minimum flow from August 16-21, 1921. The turbidity of the raw sewage during the three shift periods of each day was determined separately. Weekly averages from Feb- ruary 22 to September 17, 1921, are tabulated in Table I. Excepting RAW SEWAGE: TURBIDITY OF SHIFT SAMPLES. TABLE I. TIME OF DAY. For Week of— 8:30 A.M.-4:30 P.M. 4:30 P.M.-12:30 A.M. 12:30 A.M.-8:30 A.M. Feb. 22-28, 1921.... 290 220 85 March 1-7, 1921... 350 320 90 “ 8-14, 1921.. 260 220 100 “ 15-21 175 140 70 “ 22-28 160 120 70 March 29-Apr. 4.. .. 130 110 55 May 6-13 220 180 85 “ 14-21 200 150 60 “ 22-28 170 150 60 May 29-June 4 165 140 55 June 5-11 180 170 50 “ 12-18 200 170 65 “ 19-25 220 180 65 “ 26-July 2 250 165 55 July 3-9 240 130 45 “ 10-16 240 140 50 “ 17-23 230 170 75 “ 24-30 240 170 75 Aug. 1-6 240 175 50 “ 7-13 250 200 50 “ 14-20 250 150 45 “ 21-27 250 180 55 Aug. 28-Sept. 3... 260 265 50 “ 4-10 220 110 ' 35 • “ 11-17 260 170 . 50 for the periods of high rain-falls, the turbidity roughly indicates the difference in the strength of the sewage during each day. The tur- bidity of the night flow was fairly constant while turbidity of the day samples increased from May to September. Table II gives the weekly averages of the screened sewage analyses for the day and night flow. The periods extend from February 22 to September 17, 1921. Nitrogen Balance. Previous experiments carried on by the Dorr Company with the cooperation of Professor D. D. Jackson of Columbia University, had indicated that the activated sludge process as carried out in this apparatus did not result in the loss of nitrogen. Accord- ingly, one of our first experiments was to determine whether or not nitrogen was lost in this process. 21 Day Night 8:30 A.M.—12:30 A.M. 12:30 A.M.— 8:30 A.M. HrH m O Si > > O O 3 > 3 3 > O 2 * 3 ® 1 C+ -J '*< 3; r+- •p » xygen sumed p o O ft ►r- c <<■3 p s *b to x c *< a trc 3 0) <» a & M c? o O ft O o . Cl 3 . o . 3 3 . o . 3 Feb. 22-28 101 91 65 24.0 24.0 16.0 7.8 R 2 .60 .89 2.46 .26 19 445 91 115 41.00 15. 1.77 2.44 .28 376 59 Mar. 1-7 456 106 105 44.80 13.6 1.54 2.05 .28 369 62 “ 8-14 2.86 .25 363 97 125 35.00 8.6 1.11 4.22 .21 308 54 “ 15-21 53 14.5 2.85 2.05 .52 370 97 85 26.0 5.4 1.31 4.34 .38 303 58 “ 22-28 230 52 10.5 2.86 4.68 .60 319 85 110 25.0 4.9 1.15 6.63 .33 224 51 Mar. 29-Apr. 4 190 47 10.9 2.40 6.71 .94 328 74 75 28.0 4.9 1.14 10.0 .56 266 53 May 7-13 280 60 16.2 4.11 1.30 .43 410 81 130 28.7 12.0 2.20 5.3 .43 326 61 “ 14-20 290 69 18.3 5.82 1.02 .28 447 103 90 30.6 9.8 1.65 4.42 .45 365 70 “ 21-27 280 38 14.6 3.36 5.52 .39 364 113 70 28.6 12.6 1.12 8.50 .50 284 72 May 28-Jun. 3 230 49 9.0 2.40 2.97 .96 384 95 90 31.6 4.4 .80 8.57 .68 304 70 Jun. 4-10 241 14.2 5.10 1.0 .02 423 126 60 32.1 6.2 1.28 4.78 .34 323 64 “ 11-17 330 73 18.2 6.51 .64 .04 448 1 33 80 32.6 8.4 1.40 2.75 .25 384 86 “ 18-24 76 19.4 6.00 .60 .01 471 127 110 37.4 9.6 1.54 1.97 .18 402 105 Jun. 25-July 1 300 80 16.6 4.85 .07 .01 474 128 75 40.4 11.2 2.08 .92 .18 402 102 July .2-8 • 340 68 5.50 .29 .01 465 148 80 39.0 10.9 1.66 1.30 .18 370 110 “ 9-15 265 71 16.1 4.68 .30 .00 467 143 70 42.6 13.5 1.93 .40 .06 425 106 “ 16-22 310 65 23.7 4.57 .04 .00 470 128 95 35.5 12.3 1.71 .85 .24 400 88 “ 23-29 300 64 23.4 4.17 .44 .03 467 130 95 39.0 14.0 2.22 .74 .20 346 92 July 29-Aug. 5 320 76 22.0 6.40 .30 .01 454 123 70 39.0 12.6 1.82 .91 .15 355 87 Aug. 6-12 330 83 23.4 6.85 .53 .08 454 130 70 37.8 13.0 1.71 1.22 .16 352 88 “ 12-19 370 98 29.1 7.88 .91 .00 476 143 80 49.8 14.6 1.60 1.18 .11 420 103 “ 20-26 370 70 20.4 7.97 1.07 .00 466 153 105 36.7 10.9 1.82 .72 .07 337 96 Aug. 27-Sept. 2 370 61 19.5 4.11 .55 .00 464 161 90 36.1 11.7 1.10 .40 .10 392 90 Sept. 3-9 290 59 17.8 3.71 1.11 .25 421 115 90 33.0 8.7 1.65 3.0 .29 353 77 10-16 340 68 26.0 4.80 .69 .10 476 118 85 44.0 16.3 2.62 1.1 .09 427 93 TABLE II. 22 For this purpose, hourly samples of the effluent and influent were taken and composited for analysis. The sludge drawn from the apparatus was carefully measured and samples taken. The analyses included determination of free and albuminoid ammonia, nitrates, nitrites, and total organic nitrogen by the Kjeldahl method. The ammonia, nitrate and nitrite, and organic nitrogen all expressed as nitrogen, were added together, converted into pounds per 1,000 gallons and multiplied by the flow for each day. These sums were tabulated for the entire period from December 14, 1920, to February 18, 1921, and are presented in Table III. TABLE III. Nitrogen Balance Dec. 14, 1920—Feb. 18, 1921. Total gallon influent 5,556,310.00 Total gallon effluent 5,468,810.00 Total gallon sludge 87,500.00 Total nitrogen influent, lbs 1,423.83 Total nitrogen effluent, lbs 1,332.15 Total nitrogen sludge, lbs 85.66 Net loss nitrogen, lbs 6.02 Net loss .43% From this table it will be observed that during a run extending over sixty-three days there was a net loss of .43 per cent of nitrogen. Since this amount is within the limits of experimental error, we would conclude that our methods of sampling and analyzing have been sufficiently accurate to keep track of all of the nitrogen, and that in this process there is no volatilization of free ammonia and no reaction taking place whereby gaseous nitrogen is formed. Nor is there any fixation of atmospheric nitrogen. At least if these two reactions occur they neutralize each other in net effect. Data on the nitrogen balance were collected throughout the experi- ment and will be found in the body of the report. These results are interesting when compared with results of nitrogen recovery experi- ments on activated sludge made by other workers with different types of activated sludge tanks, and using much larger quantities of air. For instance, Pearce and Mohlman27 state that in the summer there is a 41 per cent loss of nitrogen and in the winter a 23 per cent loss of nitrogen. In the Packingtown experiments of these authors it might be noted that to 4 cubic feet per gallon of air was used. There is, of course, danger of being misled when comparing results obtained on different sewage. Reversal of Nitrogen Cycle and “Fixation” of Nitrates and Ammonia. In the earlier experiments of the activated sludge process considerable attention was paid to the amount of nitrification, that is, of oxidation of organic nitrogen and ammonia to nitrates. 23 Metcalf and Eddy,28 quoting Hatton and Copeland’s29 work, report that in experiments at Milwaukee using as little as .67 cubic feet of air per gallon, clarification was obtained but no marked stabilization of the sewage. Reference to the table of data in the article cited above shows that using that amount of air, there was a complete reduction of nitrites and a 50 per cent reduction of nitrates. By using enough air so that decided nitrate formation was produced, these workers obtained a clear and stable effluent. Fig. 4 In Fig. 4 we have plotted the amount of air used in our experi- ments, the amounts of free and albuminoid ammonia in the effluent and influent, and the amounts of nitrates plus the nitrites in the effluent over the period from May 13 to September 28. From this diagram it is seen that there is an appreciable decrease in both free and albuminoid ammonia as well as in the nitrates in the effluent. It is interesting to note, however, that when the air amounts to 1% cubic feet per gallon, the effluent and influent curves for nitrates cross. In other words, at this point nitrification takes place. Again, on reducing the air to one cubic foot per gallon there is a reduction of nitrates. This data leads to the conclusion that in the experiments reported in this paper, the nitrification phase of the activated sludge process is entirely absent, and that nitrification is not essential to the success of the process. It is apparently possible under some conditions to produce a clarification and reasonable stabilization of sewage oper- ating with so little air that nitrate oxygen in the raw sewage is actually 24 consumed by the micro-organisms of the sludge. Attention should be called, however, to the fact that one maximum in the stability curve occurs simultaneously with the maximum influent nitrate and the other with the maximum air. If it is assumed that the free ammonia and nitrates and nitrites are essential as food for the micro-organisms composing the sludge, this may explain why there is no very apparent loss of nitrogen. These compounds are undoubtedly synthesized into microbial protein instead of being reduced to gaseous nitrogen. I Wet Burning of Solids. At the suggestion of Mr. Gr. W. Fuller, we made a calculation from our data to determine the amount of solids “wet burned.” From this calculation it was seen that the total amount of solids in the influent from May 3 to September 3 was 78,300 pounds, while the effluent contained 65,400 pounds and the sludge 8,070 pounds of solids. Adding the sludge solids to those of the effluent and subtracting from the total solids in the influent, we see that there is a loss of approximately 5,000 pounds of solids. In other words, approximately only two-thirds of the solids removed are obtained as sludge. The sludge yield amounts to a little less than one-half ton per 1,000,000 gallons. Character of Sludge. From the analyses of the sludge given in Table IV its extremely light character can be observed. The average analysis of sixty-four samples of sludge shows 99.74 per cent moisture. The nitrogen in the dry sludge calculated from analyses of wet samples amounted to 5.63 per cent. This, it will be noted, is calculated as nitrogen and not as ammonia. SLUDGE ANALYSES. TABLE IV. (Average of 64 samples) Moisture 99.74% Total solids 2622. p. p. m. Total nitrogen Nitrogen in dry sludge 5.63% Relation Between Volume and Weight of Sludge. It has gen- erally been the practice30 to control the amount of sludge in the aerating chamber bv withdrawing a sample from time to time and reading the volume to which it settles in a given length of time. Our experience led to the observation that where the sludge was exceed- ingly light and feathery in appearance, it did not have the same purifying effect as when a denser sludge was employed. In order to determine whether there was any distinct relation between the volume and weight of these settleable solids, we have plotted in the diagram (Fig. 5) the volume against the weight. These points indicate that 25 /P 3 X S3 § G a g 1 ; w X pj v \ d £3 G a 1 a a i « C '1 £ * C _J a a i a «. 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 221 23 24| 25 261 27 28 29 301 311 1315 1017 1148 1110 1096 1121 1 1131 I 1093 980 1030 1058 1009 956 1010 1040 | 910 | 1002 | 983 | 1002 | 982 | 1130 1 1174 | 1026 | 1127 1 1100 f 1064 ! 1022 ! 1052 I 1138 1 1173 | 1268 1810 1270 1376 1480 1480 1410 1407 1473 1330 1340 1510 1336 1410 1340 1343 1191 1282 1315 1350 1300 1382 1530 1398 1502 1468 1432 1255 1397 1537 1257 1537 ' ' 83o| .02 7101 6801 650 j 600| 710' 650| .17 593| 596] 600 596 575 550 .12 575 6031 .01 516| 528| 524| 500| 450| .02 717! .28 692! .20 670| 612| 697! .02 637! .10 587! 613 f 78l[ .10 9071 .55 867| .01 1 1 1 1170| 1537| 817 1164| 14671 817 11201 13971 657 11291 13971 817 12631 14671 817 1114| 1397| 904 1301| 1687| 867 1344i 16871 937 13671 17571 867 12781 16171' 817 12211 16871 817 11971 15001 815 1112| 14671 757 1194| 14671 757 1281! 14671 757 11491 1502] 697 10811 14671 637 11001 1467| 697 1114| 15371 697 10381 14321 697 1151| 1577] 697 1162! 15371 697 11381 1502| 670 1113] 1502! 697 11041 13971 697 10961 1502| 697 991| 1327| 697 1084| 1432| 637 ! ! ! 1 1 1 1 • .15 .28 . 05 * .01 1249 1110 1100 1123 1127 1134 1358 1719 1616 1600 1723 2164 2112 2068 2041 1911 1716 1801 1833 1728 1650 1663 1630 1989 2031 2025 2071 1847 1907 1901 1948 1447 1577 1400 1400 1420 1455 1540 2110 1900 2080 2200 2300 2190 2240 2240 2225 2020 2080 2120 2040 1960 2020 2080 2040 2040 2080 2150 2000 2000 1960 1920 910] 665| .35 650| 763| 763] 7631 .08 9371 .42 1190| .41 1180| .41 1180| 1300| 1900| .90 1900! .10 18301 1590] 15401 1290| 1540| 13301 1420| 12001 .55 1200! .02 13301 19001 .79 19001 .22 17501 .34 17501 .62 17801 .70 19001 16001 16001 l 1802 1841 1881 1930 1924 1883 1920 1920 1920 1960 1960 1980 G o "5 Sh 0) ft o .5 o G G aj s i 11401 1390| 18301 18501 1780| 1780| .23 rH Jan. 16-17 Jan. 31 Feb. 20-21 Mar. 6 Mar. 29 May 20-21 May 26-27 June! 7-8 June 29-3C Period of Winter Wet Wet-—but No rain Rain Commenc- Maximum Effect Flow Weather no rain 3 days 5 days ing to rain of get dry 9 A.M 31.5 63.5 34.0 previous 35.4 previous 72.5 dry 66.5 for year 103.5 May rain 72.5 weather 43.5 10 * 36.0 60.5 40.5 48.5 71.0 69.5 103.5 79.5 48.5 11 43.5 60.5 56.0 51.5 78.0 63.5 110.0- 76.0 46.0 12 P.M 40.5 60.5 53.0 51.5 80.0 63.5 110.0 74.5 46.0 1 46.0 . 59.0 54.5 51.5 80.0 63.5 103.5 74.5 50.0 2T 54.5 50.0 54.5 80.0 60.5 103.5 69.5 40.5 3 43.5 60.5 47.5 54.5 78.0 63.5 103.0 69.5 40.5 4 57.5 46.0 51.5 78.0 63.5 107.0 71.0 43.5 5 57.5 43.5 51.5 78.0 65.0 103.5 71.0 43.5 6 43.5 56.0 40.5 51.5 78.0 65.0 106.5 69.5 43.5 7 56.0 40.5 51.5 78.0 65.0 106.5 66.5 42.0 8 38.0 51.5 40.5 47.5 76.0 66.5 106.5 62.0 35.5 9 38.0 51.5 40.5 47.5 76.0 68.0 106.5 60.5 33.0 10 38.0 47.5 40.5 46.0 76.0 65.0 106.5 56.0 42.0 11 38.0 46.0 39.0 44.5 76.0 43.5 97.5 56.0 30.5 12 A.M 31.5 46.0 38.0 43.5 74.5 42.0 97.5 54.5 28.0 1 29.0 42.0 38.0 42.0 74.5 40.5 95.5 53.0 25.5 28.5 39.0 33.0 38.0 73.0 35.5 95.5 51.5 20.5 3 21.0 35.5 30.5 33.0 73.0 32.0 97.5 48.5 20.5 4 18.0 35.5 28.0 30.5 73.0 28.0 97.5 47.5 22.0 5 18,0 35.5 25.5 28.0 73.0 27.0 97.5 47.5 22.0 6 18.0 34.0 25.5 28.0 76.0 27.0 103.5 46.0 21.0 7 20.0 33.0 30.5 30.0 74.5 28.0 97.5 46.0 24.0 8 28.5 38.0 38.0 36.5 76.0 34.0 97.5 60.5 25.5 820.5 1,181.0 953.5 1,048.4 1,823.0 1,246.0 2,457.0 1,483.5 837.5 Corrected Mean ... 910.0 1,268.0 1,038.0 1,135.0 1,907.0 1,330.0 2,544.0 1,580.0 925.0 Max . . 1,191.0 1,537.0 1,432.0 1,455.0 2,000. 1,750.0 2.700.0 1,910. 1,300.0 Min ... 516.0 867.0 697. 763 1,900 725. 2,350.0 1.110 570. HOURLY RATE OF FLOW IN THE CHAMPAIGN SEWER FOR SELECTED DAYS. Rate given in G.p.hr. TABLE VIII. 54 CHAPTER IV. OPERATION OF ACTIVATED SLUDGE PLANT. A. A. Brensky and S. L. Neave. Operation Periods. Operation of the activated sludge plant covered a total number of three hundred and fifty-five days, which may be divided into three periods, the first extending from December 15, 1920, to April 6, 1921; the second from May 4, 1921, to October 31, 1921, and the third from November 16, 1921, to January 7, 1922. Previous to December 15, 1920, tank No. 1 had been in operation for about three weeks for a trial run. Notes on Operation. The mechanical operation of the activated sludge tanks and machinery was on the whole satisfactory. Most of the repairs and changes were made during operation. The only shut- down for repairs was made on April 6, 1921, due to the wearing of the armature ring of the motor which operated the blower. Opera- tion would have commenced again in a few days but during the month of April infiltration of ground water into the city sewers produced a weak sewage, and it was decided to postpone operation until the period of wet weather had passed. From July 11 to 14, 1921, each tank was examined while the other was in operation. The mechanism in tank No. 1 was found to have been striking the tray at one place and was repaired. The mechanism in tank No. 2 was in fair shape. Only a few leaks in the filtros system of the tanks needed repairing. The plant was closed down from October 31 to November 16 for the purpose of examining and cleaning the tanks preparatory to iron dosing. During the time the first tank was • in operation, previous to December 15, 1921. some changes were made in the second tank. First, it was found necessary to place concrete over the tray to fill in the irregularities of the surface. In some places, the rakes would scarcely pass the trav, while in other places the clearance was as great as six inches. The concrete shell greatly improved this defect. This difficulty was due to the quality of the material chosen for the con- struction of the trays. Since sludge collected and became septic in the peripheral downcast wells, it was thought that the peripheral wells were too large for the quantity of returning sludge. They were 55 made smaller in cross-section in the second tank by nailing two inch by four inch planks longitudinally to the staves. Another difficulty in the operation of the second tank was due to air bubbles escaping from the aeration chamber to the settling chambers. These bubbles found their way up between the wooden shelf upon which the tray was nailed and the staves of the tank, and caused local disturbances in the sedimentation chamber. Asphalt was poured several inches thick between the concrete and wood staves which greatly improved conditions. Air bubbles, nevertheless, found their way through the asphalt joint at various places throughout the operation. The disturbances were minimized by trapping the air below the surface and localizing it to small areas. An outburst of escaping bubbles was noted in the daily data sheets as an ‘ ‘ air leak. ’ ’ Such an occurrence effected the turbidity of the effluent. The laying of the filtros tile in the second tank was found defect- ive. Air was observed to escape through cracks in the concrete at various places some distance from the plates. Apparently this air must have made its way from the air channels between the concrete and the wood floor to the cracks. (See Fig. 11.) This condition was corrected by placing new concrete reinforced with nails partly driven into the wood around both sides of the system of filtros plates. This repair was apparently successful, for but very few leaks were found when the places were examined. A number of minor changes in construction were made early in the operation of the plant. On January 3, 1921, a wind break con- sisting of a canvas collar two feet in height was placed around the top of each tank to prevent eddy currents and ripples of the surface liquid. Go-devils which were attached to the ends of each set of upper rakes were removed. Unfortunately one of the go-devils became wedged in the top of a peripheral well and did not allow enough clearance for the rake. It resulted in twisting one arm of the thick- ener, but did not impair its effectiveness. The tanks were always cleaned before starting a new run. The two-inch outlets in the sand hutches were too small for rapid dis- charge, and much trouble was encountered during the cleaning of a tank. The blower required attention from time to time but did not necessitate a complete shut-down. Two men could overhaul, clean, and put the blower in running order in less than three hours. Operating Records. The daily operation of the activated sludge plant was divided into three shifts of eight hours each, with an attendant for each shift. The routine measurements were re- 56 corded on daily data sheets by the attendants. Fig. 18 shows the blank forms that were used during the latter part of the second period of operation. These sheets were modified from time to time in order to take care of additional data or changes. Each reading was taken on the hour and is an average of the previous and follow- ing half-hours. The day was arbitrarily taken from 8 :30 a.m. of one day to 8:30 a.m. of the following day. This arrangement made it possible to transport all the samples of a day’s operation to the labo- ratory in one trip. Some of the readings on Sheet B were taken every two hours and others as often as was deemed necessary. The remarks on the general operation and observation were also recorded on this sheet. Sheet C of Fig. 18 is a form of the computation sheet made from the original data collected at the plant. Summaries of the daily mechanical results were prepared to cover the periods cor- responding to the various experimental runs. Sampling Points. The general plan in sampling was to collect representative portions of the raw sewage, the screened sewage, which constituted the influent to tank No. 1, the liquor flowing from tank No. 1 to tank No. 2, “overflow,” the final effluent, and the sludge, at sufficiently frequent intervals to furnish average samples when composited for analysis. Samples were generally collected by the attendants in charge. Schedules of the samples and methods of col- lection were posted from time to time. A summary of the schedule of sampling and chemical determinations are given under the dis- cussion of chemical data. Samples for microscopic examination were taken from May 4 to 18 and from September 21 to December 28. From June 6 to August 18 a daily sample of the screenings from the Dorrco screen was sent to the laboratory for moisture determination. Various other samples were taken and many special tests were conducted which are not enumerated above. Tests on the settleable solids in the aeration chamber and on the peripheral downcast wells of both tanks were made from May 3 to December 30, 1921. Four samples were taken daily at 7 a.m., 1 p.m., 6 p.m. and 12 a.m. The settleable solids were expressed as the per cent of the volume of sludge in a liter cylinder (70 c.c. to the inch) after settling for one hour. These tests were performed at the plant by the operators. Collection of Samples. As a rule it is difficult to secure rep- resentative samples of unscreened and raw sewage. Samples of the unscreened sewage were collected at the inlet to the Dorrco screen by quickly submerging a wide-mouthed bottle of about 500 c.c. 57 Fig. 18 .State Water Survey Division— “Sewage Experiment Station — TESTS SHOWING PERCENT OF SETTlEABlE SOLIDS AFTER ONE HOUR'S SETTLING IN A LITER CYLINDER —State Water Survey Division— '-Sewage Experiment Station — —State Water Survey Division — —Sewage Experiment Station — '—State Water Survey Division — —Sewage Experiment Station — 58 capacity. Samples of the screened sewage were obtained as it passed the 12-inch weir. The stirring and mixing in the screen assisted greatly in securing a representative sample of the screened sewage. The effluent from tank No. 2 was collected as it flowed into the efflu- ent weir box. During the winter of 1920 and 1921 a small portion of the effluent was by-passed through the pump building for sampling. The overflow sample from tank No. 1 was collected as it entered the six-inch overflow pipe leading to tank No. 2. Samples of the aeration chamber sludge were collected at the upcast wells, and were called sludge from upcast well No. 1 or No. 2. Tray samples collected at the sludge removal pipes were designated as Tray 1 or Tray 2 samples. Physical Characteristics of Sludge. The process of activated sludge purification is primarily a problem in clarification of sewage by aeration, which involves the study of the physical characteristics of the sludge, and particularly, the rate of subsidence. The degree of clarification of the supernatant liquid and the density of the settled sludge, other conditions being equal, are directly dependent upon the rate of subsidence and the nature of the sludge. Furthermore, in a Dorr-Peck tank the study becomes more important and more compli- cated because the mechanical features are so closely related. One condition cannot be changed without a variation of several conditions. The naturfe and the color of the activated sludge changed with the seasons and with the conditions of operation. During winter and spring a dark gray sludge predominated; the floes were large and distinct. During summer and fall, the unsettled sludge was of a light gray color, much thinner and lighter in texture. With few exceptions the floes were not as well formed as those of the winter and spring. During the last period of operation, when iron sulphate was added to the sewage, a very characteristic reddish-brown sludge was obtained. The coarser and finer floes seemed to settle evenly. A line of demarcation between sludge and supernatant liquid was evi- dent the first minutes of subsidence. Some very light floes, however, remained in suspension for many hours, and were discharged with the effluent which greatly effected its stability. Rate of Subsidence. The settling rate of activated sludge samples was determined in liter, cylinders 170 c.c. equivalent to one inch height,). Fig. 19 shows theoretical rates of subsidence curves of sludge collected in the aeration chamber and on the tray. It gives the figures for relative volumes of solids settling in a liter cylinder of sludge during the first hour. For example, after the first ten minutes of settling the line of demarcation between the settleable 59 b-c part shomny "free settling ‘zone C-d port shornny ’compression’zone ‘d-f’ port Shewing effect of stirring Theoretical 6ett/my fates Typical of Upcast & Tray JJudges Fig. 19 solids and the liquids was at 730—in other words, the sludge occupied 73 per cent of the original volume. The settling curves of the sludge as drawn from the aerating chamber are divided into two distinct parts. The first part, b-c, is a straight line and is known as the period of free settling, that is, each particle or floe falls unhindered by the presence of others. The rate of subsidence is constant during this period. The steeper this line the greater becomes the rate of free settling. The second part of the curve is known as the compression zone of the sludge settling curve. It commences just where the floes and particles of sludge interfere with each other and continue to settle collectively at an increasingly retarded rate. During this period the floes are partly supported by each other, and some of the accompanying moisture is expelled by the pressure of the particles exerted upon each other. From the point “d” the rate is practically nil and little decrease in volume will occur with continued detention. The dotted line d-f shows how gentle stirring with a glass rod affects the sludge volume. The settling action in a liter cylinder is in a way characteristic of that occurring in the settling chambers. The effect of the Dorr thickeners is likewise similar to that produced by stirring with a glass rod. The curve of subsidence of the tray sludge in Fig. 18 shows no free settling rate and very little decrease in volume. It has been thickened sufficiently on the tray so that further settling will not decrease the volume materially. Under these conditions the sludge is at the best stage to be returned to the aeration chamber, or to be dis- charged from the tank. 60 There occurred, however, many variations from these ideal sub- sidence rates. Several factors, such as the state of activation, charac- ter of the sewage, temperature, and dilution, all independent of the Dorr-Peck tanks as well as the mechanical features of design influ- enced the nature and character of the sludge. The effects of some of these factors are discussed below. Effect of Reaeration.33’ 34 Much trouble was experienced in securing a sludge with a good consistent settling rate, especially dur- ing the summer months. On August 8 and September 13 some experi- ments upon samples. taken from the aeration chamber were made on a small scale in order to study the effect of aeration only. Twelve gallon samples of each were aerated separately in vitrified tiles equipped with filtros plates. Fig. 20 shows the effect of continued Curve A - <2s taken from dC 0*2 I Carve, A L/aht s/udgo UC t Curve 3 Offer 20 hoars AcraboA Carte B Offer /Chrs Aenrf/on Curve’D after 44 hrs Aewt/on vJurveO Offer 40Ora Aeration Curve after 43hr$ Aeration A, B/C p.pm fetal solids 3500 Curves f4Q- CO * 93l7ry Aeration Fig. 20 aeration upon the rate of subsidence. The condition of operation previous to the time of sampling, and the effect of aeration are tabu- lated below. Aug. 1921 gept 13 Test plant flow for previous days1 (5), gallons 70,000 67,000 Air used per gallon 0.84 1.47 Total Champaign sewage flow (1000 gal.) 780 934 Average nitrates in influent (p. p. m.) 0.4 0.7 Ratio test plant to total flow 9.0% 7.2 % Maximum free settling rate, feet per hour 1.36 1.2 Theoretical capacity of settling chamber, gal. per hr. 2,200 1,920 Effect of aeration only (time), hours 44 16 Free settling rate, feet per hour 3.0 3.6 Capacity of settling chamber, gallons per hour 4,800 5,800 Con’d aeration, hours 48 40 Settling rate, feet per hour 4.3 3.9 Capacity, gallons per hour 6,900 6,200 . 61 Fig. 21 62 Comparing the results it is seen that in the case of the first sample a marked change in the settling property of the sludge required forty-four hours aeration while the second sample required but six- teen hours. This is partly due to the condition of the sludge at the time of sampling. The first sample was taken at a time when the sewage was weaker and when less air per gallon was used than at the period of taking the second santple. After forty-eight hours of aeration, the free settling rates approached each other and increased very little. The volume of the settleable solids, however, continued to decrease after forty-eight hours aeration. Effect of Sewage on Rate of Subsidence. Another factor, the character of the sewage, had a marked effect upon the rate of sub- sidence. Fig. 21 shows an average settling curve for samples of sludge taken from the aeration chamber of the second tank during February 1 to 15, 1921, a comparatively wet period, and also several curves for samples taken from the same tank from August 20 to Sep- tember 7. 1921, a dry period in which there were occasional heavy showers. The storm water entering the sewer, increased the free set- tling rate of the sludge by producing a weaker sewage and by dilut- ing the sludge itself. Dilution of the sludge content in the tanks assisted good operation. The diurnal variation in the settling rate noted below is probably due to dilution. In the mornings the sludge blanket, i. e., the division between the settleable solids and the clear liquid, was comparatively lower than in the afternoon. In the early morning a dilute sewage was pumped into the tanks while the period of the strongest sewage was from 9 a.m. to 12 p.m. Temperature changes in the tank during the day were slight, not varying over 2° centigrade. A maximum temperature of 26° C in the summer and a minimum of 10° C in the coldest weather was experienced. The effect of other factors on the sludge was much greater than the effect of temperature variations. A sudden change in the barometric pressure not infrequently affected the height of the sludge blanket. Diurnal Variations. Fig. 22 represents the diurnal variations of the volume of settleable solids in the aeration and settling chamber of both tanks. These curves are averages of the settleable solids deter- mined in a liter cylinder after one hour’s settling. They were taken four times per day from May 4 to August 1, 1921. From this figure it is seen that the maximum volume on the trays occurs in the morn- ing about 7 a.m. 63 Fig. 22 The daily variations were independent of the removal of sludge from the system. This can be seen in Fig. 23. The volume of sludge drawn is represented by the areas of the blocks on the lower line. Fig. 23 This figure shows many deviations from the ideal represented by the averaged figures in the diurnal variations. The large number of variations may to some extent be attributed to the variations of the 64 sewage from day to day, and others to the mechanical features of the Dorr-Peck tank. These curves are of general interest since they show the variations from day to day and week to week in the volume of settleablo solids. Weight and Volume of Settleable Solids. On account of the wide variation in sludge by volume it was thought advisable to direct attention to the control of the of the sludge. For this purpose the total solids were determined. Sometimes the sludge was exceed- ingly light and feathery in appearance and did not purify as effect- ively as denser sludge. Fig. 5 shows an attempt to determine some relation between the total solids and the volume occupied after one hour’s settling. These points show that many more factors effect this relation. With as wide and irregular variations as these it is apparent that in our case at least it was impossible to judge the effective amount of sludge by sedimentation. If the variations were only slight it might still be possible to operate using settleable solids as a control. Two conditions of operation in the mechanical design of the tanks which affected the rate of subsidence were the overflowing of sludge from the first tank, and the ratio of the sewage flow to the inflow into the settling chamber. In normal operation the sludge was allowed to overflow from the first tank into the second. Overflowing sludge was caused by overloading the capacity of the settling cham- ber. This may also occur when the sludge is not in proper condition and fails to thicken properly. The effect frequently extended to the second tank, and sometimes caused particles of light sludge to over- flow with the effluent. Overflowing sludge was employed as a guide in drawing excess sludge, although as is shown above this was not a satisfactory means of judging the amount of sludge. It is possible even with uniform conditions of the sewage, temperature and activa- tion, to have a large daily variation in the settleable solids in the aeration chamber and on the tray. The factor effecting this was the inflow to the settling chamber. For example, if twice the normal flow passed into the settling chamber for one hour an equal increase would go through the peripheral wells carrying the densest sludge back into the aeration chamber. Probably the feature hardest of control was the relative capacity of the volume of settling to that, of the area. Sometimes it was impossible to thicken the sludge properly although allowed to accumulate to a rather large volume. Under these conditions sludge would overflow with the effluent. It has been shown that dilution assisted the rate of settling. 65 Attempts were made to.control the total solids to a given weight, but it was found that it limited the total solids of the trav sludge. In summarizing the importance of sludge settling it may be said that the Dorr-Peek tank limited the variation of control to a much smaller range than the physical characteristics of the sludge allowed. Grit Chamber. The amount of grit retained by the grit cham- ber was little—in fact, no experiments were conducted, due to the low amount of grit in the sewage. For this reason this step in the process could have been omitted. The bar screen was removed as only paper pulp was collected by it. A heavy scum collected over the surface of the chamber. The velocity through the channel varied from .8 to 1.2 feet per second. In former experiments here, similar results were found with a grit chamber one foot wide and thirty-four feet long. Materials which would ordinarily roll along the invert of the sewer passed by the grit chamber. Most of the grit that would collect was mineral matter with varying amounts of organic matter. At times grit of the appearance of coffee grounds was collected. The grit chamber was cleaned out three or four times during the year, which was done by increasing the sewage flow through the grit cham- ber, by passing the screen, and returning the flow to the main sewer. By means of a shovel or stiff brush the contents in the grit chamber were stirred up and washed out. The scum which collected upon the surface became putrescent during the summer weather and was covered to prevent fly breeding. During the rainy seasons greater amounts of dirt and sand were present in the sewage than in an ordi- nary flow. Dorrco Screen Results. The Dorrco screen was primarily oper- ated to provide screened sewage for the activated sludge experiments. Extensive tests were being conducted at the time by the Connecticut State Board of Health on an improved type of the Dorrco screen and so no attempt was made to carry on similar experiments. Some work, however, was done with the screen, and is given below. The screen is described in Chapter II, page 34. The volume of sewage entering the screen chamber was regulated by a gate placed in the inlet channel; and the rate of flow was measured after passing the screen drum. The solids were collected on the screening surface and discharged into the pit. The operator with the aid of a per- forated dipper collected the screenings regularly during the day from the pit and placed them in perforated cans. The screenings were weighed daily after twenty-four hours of draining and samples were sent to the laboratory for moisture content determinations. The 66 screen drum was used at Mt. Vernon, N. Y.„ by the Dorr Company. It was originally designed for a life of six months, but with more or less repairs it continued to operate during the activated sludge experiments. Three different screen mediums were used, namely, one-half inch by one-sixteenth of an inch slots parallel with the axis of rotation, one-half inch by one-sixteenth of an inch slots parallel to the direction of rotation, and one-sixteenth of an inch circular perforations. The net screen width was six inches, and with the slot screens, 26 to 28 per cent of the total effective screen area were openings. The screen was submerged from 44 to 48 per cent of its diameter, depending upon the rate of flow through the screen. The rotation produced a head from two to three inches inside the screen and established a flow outwardly through the screen. This kept the solids washing into the pump pit. The best speed of rotation was from twenty-two to twenty-six revolutions per minute, or an average peripheral velocity of 300 feet per minute. The fin assisted in dislodging the solids from the screen surface. During the winter a lime soap froze to the screening surface, and it was necessary to clean the screen as well as to keep it entirely covered. Cleaning was done by a jet of steam playing against the drum. In the summer some material would occasionally remain col- lected in the slots and partly blind the openings. With the use of a wire brush and kerosene the screen was cleaned in a few minutes as it revolved. Table IX gives a summary of the removal of solids by weight. The latter tests extended from June 7 to October 29. Better results could have been obtained if changes in design could be made, but the location limited modifications. The size of the screen pit (one and one-half square feet area) was far too small for the rest of the screen and many solids would find their way through the screen. In the latter part of August the area of the screen pit was increased to about four square feet and a circulating flow from the screen pit to the inlet of the screen was allowed; the level in the screen pit was about two inches higher than the sewage level in the inlet to the screen. This was due to the rotation of the screen. Some measurements on the loss of head through the drum were made. These can be summarized by saying that with the rate of flow of 200,000 gallons per day, three inch difference between the inlet and outlet sewage level was measured; and with the rate of flow of 50,000 gallons per day the loss of head was from one to one and a half inches. These experiments were made with the screen medium having slots parallel to the direction of rotation. 67 Scr’nga Plow Total Ratio Period No. of as Moist Wt. of Thru Champ. Sc. flow Removal Prom—to Daya Weighed of Dry Screen Plow to p.p.m. Remarks Lbs. Scr’ngs 1,000 Gal. M.G.D. Total .Turn! 7-30 24 85.2 5.4 159 1.10 14.5 4.1 Screen worn out. July 18-28 11 76.5 82.0 14.0 164 .89 18.5 10.0 New screen— July 29-Aug. 8 11 62.0 84.0 10.4 135 .84 16.0 9.3 slots parallel. Aug. 18-23 6 77.0 84.8 11.7 To direction 120 .76 15.7 •11.7 of rotation. Sept. 13-23 11 76.0 84.0 12.3 123 1.05 11.7 12.0 Oct. 3-15 12 79.0 85.0 11.9 137 1.14 12.0 10.4 Oct. 15-29 15 91.0 85.0 13.7 135 1.20 11.2 12.2 Weighted Average 66 79.0 12.5 136.0 1.01 13.0 10.0 TABLE IX. DORRCO SCREEN OPERATION. 68 CHAPTER V. BIO CHEMISTRY OF THE PROCESS. A. M. Buswell and S. L. Neave. Nitrogen Cycle. Before proceeding to the discussion of the experimental data bearing on the chemical reactions of the nitro- genous compounds we shall review briefly the current opinions on the subject.35 The conventional nitrogen cycle36 (Fig. 24) used in most text Fig. 24 books on sanitary subjects emphasizes certain distinctions which are not of particular importance when applied to the reactions in sewage disposal. For instance, the change from vegetable to animal protein does not materially affect the final decomposition reactions although it is represented by a large arc of the circle. The probable chemical course of some of the oxidation and reduction reactions is not brought out clearly by the diagram, nor is the reversibility of these reactions emphasized sufficiently for the purposes of the present discussions. Denitrification is represented as the direct reduction of ammonia to nitrogen, while undoubtedly nitrite is formed as an intermediate 69 product. Nitrate is also represented as being formed directly into plant protein while chemical evidence requires its preliminary reduc- tion to ammonia. By including death in the circle the reactions are made to appear to take place in one direction only, i. e., clockwise, while as shown below all of the reactions are reversible and must be so regarded in interpreting the bio-chemistry of sewage disposal. We suggest, therefore, representing the chemical reactions of the nitrogen cycle as shown in Fig. 25. Fig. 25 Ammonification. If we begin with proteins at the top of the figure, we note first that these may be decomposed by means of hydrolysis to form ammonia. The intermediate steps have been worked out by Robinson."57 Apparently amino acids are first formed 70 and these may then be further broken down to ammonia, organic acids and C02 according to one or more of the following reactions: r-ch-nh2-cooh + h2 = r-ch2cooh + nh/8 R-CH-NH/COOH + 02 = RCOOH + C02 + NH3 R-CH*NH2-COOH + H20 = RCH'OH'COOH + NH» R-CH-NH/COOH + H20 = RCH2'OH + C02 + NH3 The reactions are undoubtedly the result of microbial activity. Marchal40 attributed ammonification in the soil to the activity of the B Mycoides group and B fluorescens liq. while Conn41 claims that the Mycoides organisms are relatively poor ammonifiers and that two organisms Ps. fluorescens and Ps. caudatus which multiply rapidly in freshly manured soils are the important ammonifiers. Waks- man42 43 has shown that fungi, especially actinomycetes, are good ammonifiers. Doryland’s44 investigation of these reactions from the standpoint of energy requirement of the bacteria indicate that am- monia formation is incidental. The bacteria attack compounds from which they can obtain energy; if suitable non nitrogenous compounds are present proteins will be attacked but slightly, or not at all, and consequently little or no ammonia will be formed. Nitrification. The fact that NH3 may be oxidized to nitrite and then to nitrate by Nitrosomonas and Nitrobacter, respectively, is so thoroughly discussed in texts both on soil chemistry and on the chemistry of sewage disposal, that it requires but passing mention here. In the soil CaC03 or MgC03 and C02 seem to be essential to the reaction. Since these organisms are sensitive to changes in acidity it seems probable that the buffer effect of these carbonates may explain their beneficial action. No intermediate chemical products between NII3 and nitrite have been detected so that this step of the reaction is not definitely known. Loss of Gaseous Nitrogen. The data on this phase of the nitrogen cycle are in many cases of a negative character. Experi- menters have failed to show a balance of nitrogen, and where the difference was greater than could be otherwise accounted for, it was attributed to evolution of gaseous nitrogen. Russel refers to the works of Chick45, Adeney46, and Muntze and Laine47 for evidence of the occurrence of this specific reaction in sewage disposal. A review of the references, however, raises a question as to whether this reaction occurs to any such extent as is generally 'supposed. Chick, in her wTork on trickling filters (Table II, loc.cit.), does not take account of the nitrogen in the microbial growth on the filters. This is also true of the work of Frankland quoted by Adeney and Letts, loc.cit., and of that of Muntz and Laine. In the experiments 71 of Adeney and Letts septic tank effluent was incubated with the addi- tion of KN03. The incubation took place in tightly stoppered bottles. At the conclusion of the experiment the various forms of nitrogen, with the exception of the Kjeldahl Nitrogen, were de- termined and the dissolved gases were analyzed; non-nitrated blanks were similarly treated and analyzed. In the experiments in which KNO3 wras added, the nitrate was assumed to be completely reduced and an excess of dissolved nitrogen over that in the blank was found. The excess was practically equivalent to the nitrates reduced. Thife experiment when finished gave six sets of results, three of which were discarded on account of errors due to the difficulties of the analytical procedure. On the basis of the three remaining experiments the authors apparently assume that when nitrate is reduced it is con- verted quantitatively into nitrogen, for in subsequent experiments by these authors nitrate reduction is referred to as “ loss of nitrogen. ’ ’ This, as will be shown later, is contrary to our experience. From purely chemical considerations there appear to be two ways in which the formation of nitrogen may be brought about. First, by the direct oxidation of ammonia, with the formation of N2 and HoO. This occurs when ammonia is burned in pure oxygen. A similar oxidation takes place when ammonia reacts with chlorine or bromine, in which case halogen acid and nitrogen are formed. Second, by the reduction of nitrates and nitrites by organic matter with the formation of nitrogen and Co2. "When nitrates are reduced in the course of inorganic reactions, considerable amounts of ammonia as w*ell as various oxides of nitrogen are formed. There is evidence in favor of both of these courses of reaction. In the sewage beds studied by Chick (loc.cit) and Muntz and Laine (loc.cit.) loss of nitrogen was said to have occurred under ample aera- tion, while in the experiments of Adeney and Letts, (loc.cit.) the re- action was undoubtedly one of reduction. When nitrites and ammonia are both present “auto-oxidation reduction” may occur, one nitrogen atom oxidizing the other and itself being reduced according to the well known reaction NH.t N02—N2+2 H20. K. Scheringa48 claims that with a concentration of 4 mg. of NH4+ and 2 mg. NOt per liter the last reaction did not take place. From the references cited we must conclude that there is no data in the literature showing that nitrogen gas is formed to any great extent during the reactions of sewage purification. The forms of nitrogen left undetermined by the earlier experimenters would, probably have accounted for most of the “loss.” Nitrogen Fixation. By purely chemical reactions nitrogen may 72 be caused to combine in two well known ways. Oxidation may be brought about by means of electrical discharge, which reaction occurs to a slight extent in nature during thunder storms. Reduction or combination of N with hydrogen can be brought about under proper conditions with the aid of catalysts. One can hardly imagine that this reaction could occur in nature. These reactions have little more than theoretical importance in the present connection. Nitrogen fixation is brought about in nature by means of the nitrogen fixing organisms, Clostridium pasterianum, aztobacter, and the symbiotic form»s, all of which with other less known members of the group will be found described in any text on general bac- teriology. The course of the reaction by which these organisms effect the fixation of nitrogen is entirely unknown. To avoid complicating the diagram (Fig. 25) it is represented by a broken arrow passing through ammonia to protein. Since in general the reactions go on under anaerobic conditions there is some reason for the path chosen. Ex- perimental results point to the fact that carbon compounds such as sugars are among the substances which stimulate these organisms, while soil biologists seem unanimous in the opinion that large amounts of nitrogenous organic matter, such as are met with in sewage, would be unfavorable if not strictly inhibitory to these organisms. Denitrification. This process, the reduction of nitrates and nitrites, while brought about by bacteria, is not specific. A variety of organisms can effect the reaction, the presence of nitrates and easily oxidizable organic matter being the only essentials. The products of the reaction include nitrogen, oxides of nitrogen, ammonia and protein. The production of the first three has been discussed above. The production of protein from nitrates as well as from ammonia has been noted by a large number of workers (Koch, A.,49 Pettit, H., Doryland, C.,50 and others). It should be noted that the term denitrification in its strictest sense is used to indicate reduction of nitrates and nitrites with the loss of nitrogen. In a broader sense it may include the assimilation of nitrates referred to above. Assimilation of nitrates and ammonia to form insoluble bacterial protein is sometimes referred to as nitrogen fixation, since the leaching out of nitrogen is thus prevented. In summarizing the nitrogen cycle shown in the diagram (Fig. 25) we note first that all the changes are brought about by reversible chemical reactions which in practically all cases are catalyzed by bacteria. The usual course of mineralization is indicated by the arrows pointing straight downward from “protein” and under cer- 73 tain conditions, or, when desired, the process may be interrupted at any one of the indicated steps. (For the sake of simplicity the inter- mediate steps in ammonification have been omitted.) The steps from ammonia to nitrate are peculiar in that they are brought about by specific organisms. At the nitrite stage the reverse action may be split into two paths, one of which gives nitrogen by reduction, and the other, ammonia and protein by assimilation. The downward reactions result in the formation of nitrogen or its compounds which may ultimately be lost, while the upward reactions tend toward the reten- tion of nitrogen as protein. If we classify the reactions under the two main headings, loss of nitrogen, and formation of protein, they may be grouped as follows: Reduction of NOs 6 & 7 Oxidation of NH3 9 Auto oxidation and reduction 9 & 7 As N2 Loss of Nitrogen I As Compounds Soluble NH>4, 11; NO-„ 14; NO-,, 15. Volatile oxides 13 i Fixation Bacterial 12 Oxidation 8 Reduction 10 Formation of Protein N0„ 6, 4, 2 N02, 4, 2 NH3, 2 Assimilation Nitrogen Cycle in Activated Sludge Tanks. Previous experi- ments carried on by the Dorr Company with the co-operation of Professor D. D. Jackson of Columbia University had indicated that the activated sludge process as carried out in this apparatus did not result in the loss of nitrogen. Accordingly, one of our first experi- ments was to determine whether or not nitrogen was lost in this process. Although the operation of the plant had not been sufficiently standardized to completely prevent appreciable quantities of sludge overflowing with the effluent, thereby making the stability results uncertain, it was decided to run a careful nitrogen control to deter- mine whether or not nitrogen was lost in the process. For this purpose hourly samples (for details of sampling and analytical procedure see page 116) of the effluent and influent were taken and composited for analysis. The sludge drawn from the ap- paratus was carefully measured and a sample taken for analysis. The analyses included determinations of free and albuminoid ammonia, nitrates, nitrites and total organic nitrogen by the Kjeldahl method. The ammonia, nitrate and nitrite, and organic nitrogen, all expressed 74 as nitrogen, were added together, converted into pounds per 1.00C gallons and multiplied by the flow for each day. These sums were tabulated for the entire period from December 14, 1920 to February 18, 1921, and are presented in a preceding table (Table III). From this table it will be observed that during a run extending over sixty- three days there was a net loss of .43 per cent of nitrogen. Since this amount is within the limits of experimental error we would conclude that our methods of sampling and analyzing have been sufficiently accurate to keep track of all of the nitrogen, and that in this process there is no volatilization of free ammonia and no reaction taking place whereby gaseous nitrogen is formed. Some of the determinations necessary to keep track of the nitrogen balance had to be discontinued at the end of the above run in order to allow other tests to be made. They were resumed, however, on the third day of May and the tabulation of the results separated into ten to fifteen day periods, extending up to the end of the run, is shown in Table X. The data is presented in this form in order to point out the danger of drawing conclusions from short periods of operation. For instance, it appears that from the 14th to the 21st of May, approxi- mately 11 per cent of the entering nitrogen was lost, while from the 2nd to the 15th of June there was an apparent gain of 25.7 per cent. Such a result as this last would lead one to infer that there must be considerable fixation of atmospheric nitrogen, while as a matter of fact, there was undoubtedly an accumulation of sludge from the preceding period which wTas drawn during the first two weeks of June. Averaging the results for the entire period we note the ap- parent gain of one and a half per cent of nitrogen. When the difficulties involved in obtaining an average sample are considered as well as the limits of accuracy of the analytical procedure, we regard this value of one and a half per cent as being within the limits of experimental error, and checking reasonably well with our loss of .4 of a per cent, the result of the previous run. It has been claimed that in the presence of iron and crenothrix like organisms there was marked fixation of atmospheric nitrogen. From November 17 to December 27, FeS04 was added to the screened sewage to the extent of 9.6 p.p.m. of Fe++ for the purpose of stimulating these organisms. Table X, however, indicates no fixation. These results are interesting when compared with results of nitrogen recovery experiments on activated sludge made by other workers with different types of activated sludge tanks, and using much larger quantities of air. For instance, Pearse and Mohlman32 (in 75 Duration of Run Influent Effluent Sludge Average Total lbs. Total lbs. Total gals. Total lbs. Loss or Gain Date Days Gals/24 Ni in Gals/24 Nj in drawn dur- Ns in of Nitrogen hrs. Inf. hrs. Eff. ing run sludge (Per cent) May 3-13 . 11 88,200* 200.3 84,100 184.3 none! — 7.9 “ 14-21 8 86,700 163.9 85,600 122.2 9,050 23.68 —10.9 44 22- 1 . 11 88,500 152.0 86,600 118.7 17,100 43.07 + 6.4 June 2-15 . 14 91,400 273.0 85,200 176.1 87,150 166.85 +25.7 44 16-30 . 15 87,700 338.9 85,800 277.3 26,840 25.04 —10.8 July 1-10 . 10 84,800 216.1 81,100 210.2 3,700 3.08 — 1.3 44 15-31 . 17 78,600 343.9 73,500 268.4 88,100 100.40 + 7.2 Aug-. 1-15 . 15 70.500 293.2 62,800 187.4 92,450 101.50 — 0.1 16-21 6 62.000 132.6 57,000 65.9 30,100 83.60 + 12.7 “ 22- 1 . 11 64,600 207.6 62,800 143.3 19,630 51.40 — 6.2 Sept. 2-20 . 19 66,500 345.3 64,900 248.4 4,460 129.20 + 9.3 “ 20-28 8 66,600 147.0 59,500 102.8 8,070 63.60 + 13.2 44 29- 6 8 63,800 151.7 54.600 134.2 9.200 101.47 +55.3 Oct. 7-16 . 10 102,300 320.6 99,200 264.3 5.300 67.30 + 3.4 44 17-31 . 15 93,800 486.2 89.100 374.1 4,900 117.20 + 1.0 Nov. 16-30 . 15 80,500 273.1 80,500 240.7 none —11.8 Dec. 1- 7 7 75,200 150.9 75.200 98.5 none —34.7 44 8-28 . 21 77,800 508.6 75,300 316.8 3,800 172.18 — 3.8 Total . 221 1,429,500 4,704.9 1,362,800 3,533.6 409.850 1,252.57 Average 79,400 75,700 27,300 + 1.8 NITROGEN BALANCE. TABLE X. * Includes filling the tanks. 76 their report to the Board of Trustees of the Sanitary District of Chicago on the industrial wastes from the stockyards and Packing- town, dated January, 1921, pages 29 and 150) state that in the summer there is a 41 per cent loss of nitrogen, and in the winter a 23 per cent loss of nitrogen. In the Packingtown experiments it might be noted that three and a half to eleven cubic feet per gallon of air was used. There is, of course, danger of being misled when com- paring results obtained on different sewage. Fowler31, in an extensive review of the conservation of nitrogen with special reference to activated sludge, states that “there is little doubt that not only does the activated sludge process recover the nitrogen present in the foecal matter of sewage but through fixation from the air an actual increase takes place over what can be recovered from the sewage.” He bases this assertion on various experiments carried out by himself and co-workers. These experiments which are described in some detail in the reference cited, we have summarized below. (1) Experiments in which 50 cc. portions of activated sludge were aerated with and without the addition of 1 per cent glucose showed 3.3 per cent of combined nitrogen in the sludge to which no glucose had been added, and 7.51 per cent in the sludge to which glucose had been added. This experiment is interpreted by Fowler as indicating fixation of nitrogen. The result may, however, be due to the inhibition of denitrification by carbohydrates mentioned by Doryland (loe.eit.). No data is cited to show the total amount of combined nitrogen at the start and finish of the experiment. (2) An experiment was carried out with activated sludge in a closed flask in which there was evidence of the absorption of gaseous nitrogen. The authors state, however, that the experiment should be repeated with an improved form of apparatus. (3) In a small scale experiment with activated sludge, operated on the fill and draw plan, Fowler reports a 32.6 per cent gain in nitrogen. He states, however, that “it should be mentioned that the Kjeldahl nitrogen was only determined in the initial and final sludge. Only the ammoniacal and the albuminoid nitrogen were determined in the sewage added and in the effluent. It is possible, therefore, that the value given for the gain in nitrogen may in consequence be somewhat too high, a greater proportion of Kjeldahl nitrogen being present in the sewage added than in the effluent passing away.” (4) In another experiment in which complete analyses of in- fluent and effluent nitrogen were made, the apparent gain or fixation was only 4 per cent. 77 (5) Experiments in which a substrate designed to favor nitrogen fixing organisms was inoculated with dried activated sludge and aerated, showed 15 per cent to 25 per cent fixation. On account of the small scale on which the experiments were carried out, the amount of nitrogen fixed was from .004 to .007 gms. The analytical methods are not given. Fowler interprets Ardern’s data as indicating nitrogen fixation. Ardern, however, does not mention such an interpretation of his results. The evidence that there is fixation of nitrogen in the acti- vated sludge process as presented by Fowler seems to be open to question. Our results and those of Richards and Sawyer32 fail to give evidence to that effect. Certainly further investigation of the question is needed. That fixation of nitrate and ammonia nitrogen by means of their synthesis into the insoluble microbial protein of the floe, occur- ring in the activated sludge process seems to be pretty well demon- strated, however. In the earlier experiments of the activated sludge process con- siderable attention was paid to the amount of nitrification, that is, of oxidation of organic nitrogen and ammonia to nitrates. Under such conditions protein synthesis could not, of course, be detected. Metcalf and Eddy28, quoting Hatton and Copeland’s20 work, report that in experiments at Milwaukee using as little as .67 cubic feet of air per gallon, clarification was obtained but no marked stabilization of the sewage. Reference to the table of data in the article cited above shows that using so small an amount of air there was a com- plete reduction of nitrites and a 50 per cent reduction of nitrates. By using enough air so that decided nitrate formation was produced these workers obtained a clear and stable effluent. Their data does not, however, indicate the fate of the nitrates. Our experience53 with low quantities of air using sewage much higher in nitrates than the average, has shown that this nitrite oxygen may be utilized as a source of oxygen by the micro-organisms in the sludge, while at the same time an effluent of reasonable stabil- ity is obtained. Table XI gives the amounts of nitrate and nitrite reduced during the successive periods of operation. As a matter of interest we have recalculated this oxygen in terms of cubic feet of oxygen and free air per 1,000,000 gallons. While this represents only a very minute fraction of the air used in maintaining the activated sludge process, it will be seen that it represents a much larger portion of the air actually required for oxidation of sewage as calculated by Bartow34, 78 N03 + N02 Equivalent in Equiv. Duration of Run Nitrates and Nitrites Nitrites (asN2> oxygen supplied in free Date Days Inf. Eff. Removal Inf. Eff. Removal lbs/ cu. ft/ air p.p.m. p.p.m. p.p.m. 7o p.p.m. p.p.m. p.p.m. 70 per m.g. m.g. m.g. m.g.' May 3-13 ...11 2.90 1.60 1.30 44.8 0.47 0.36 0.11 23.4 0.1560 0.5351* 5.9° 28.1 “ 14-21 ... 8 2.10 0.22 1.88 89.5 0.32 0.05 0.27 84.3 0.2257 0.7741 8.7 41.4 22- 1 ...11 6.40 3.92 2.48 38.8 0.24 0.35 0.2977 1.0211 11.4 54.3 June 2-15 ...14 2.20 0.20 2.00 90.9 0.20 0.26 0.2401 0.8235 9.2 43.8 “ 16-30 ...15 1.00 0.20 0.80 80.0 0.07 0.00 6.07 100.6 0.0960 0.3293 3.7 17.6 July 1-10 ...10 0.60 0.27 0.33 55.0 0.05 0.00 0.05 100.0 0.0396 0.1358 1.5 7.1 15-31 ...17 0.49 0.12 0.37 75.7 0.04 0.002 0.038 95.0 0.0444 0.1523 1.7 8.1 Aug. 1-15 ...15 0.80 0.20 0.60 75.0 .06 0.00 .06 100.0 0.0720 0.2469 2.7 12.8 16-21 ... 6 0.80 0.10 0.70 87.5 0.02 0.00 0.02 100.0 0.0840 0.2880 3.2 15.2 22- 1 ...11 0.70 0.10 0.60 87.5 0.04 0.00 0.04 100.0 0.0720 0.2469 2.7 12.8 Sept. 2-20 ...19 1.14 1.61 0.12 0.76 21-28 ... 8 0.70 0.70 6.66 6.6 0.04 0.23 <« 29- 6 ... 8 0.60 0.60 0.00 0.0 0.05 0.02 6.03 60.0 . . • Oct 7-16 ... 10 1.00 0.40 0.60 60.0 0.09 0.06 0.03 33.3 0.0720 0.2466 2.7 12.8 17-31 ...15 0.90 0.10 0.80 88.9 0.06 0.00 0.06 100.0 0.0960 0.3289 3.7 17.6 16-30 ...15 6.50 7.00 0.79 0.90 1- 7 ... 7 3.50 1.70 . i.80 6i .4 0.53 0.19 6.34 64. i 0.2161 0.7403 8.3 39.5 8-28 ...21 4.50 2.00 2.50 55.6 0.43 0.13 0.30 69.8 0.3001 1.0282 11.5 54.7 REDUCTION OF NITRATES AND NITRITES. TABLE XI. *14.01 parts of N2 gives 48 parts of Ch. "At 0°C, 760 mm. Hg., 1 cu. ft. O2-40.482 gms.-0.08936 lbs. 79 TABLE XII. REDUCTION OF NITRATES. Dec. 14/20 to Fe’b. 18/21. 63 days. Illinois Water Survey. INP. av. EFF aV. Flow M. g.p.d. Air cu. ft. per gal. NO2NO. 1.56 .787 12/18 to 1/15 100 12/18 to 1/22 1 NH2 19.6 15.9 1/15 to 1/22 75 1/22 to 2/7 .8 TON 9.95 11.7 1/22 to 2/18 87 2/7 to 2/18 .7 namely, .05 cubic feet per gallon. Table XII gives the summarized figures for nitrates and nitrites during an earlier period. From this table it will be seen that approximately one-half of the nitrite oxygen is utilized in the process. For the purpose of furnishing another example of the reduction of nitrates by sewage sludge, we have reproduced at this point (Table XIII) a portion of the results carried on at the Lawrence Experi- TABLE XIII. DEODORIZING SLUDGE BY MEANS OF EFFLUENT FROM TRICKLING FILTERS. Lawrence Experiment Station. Effluent applied to Sludge: Parts in 100,000. 1919. Ammonia Kjeldahl Nitrogen Nitrogen as Oxygen Con- sumed Fred Albuminoid Total In Solution Nitrates Nitrites 3.00 .45 .26 .81 2.16 .1255 2.76 Overflow from Sludge 3.51 .35 .25 I .64 0.41 .0940 2.38 - Effluent applied to Sludge: Parts in 100,000 1920 2.87 .54 1 .28 1.00 1.36 .0841 2.94 2.92 .36 .24 0.68 0.31 .0603 2.23 Overflow from Sludge ment Station for deodorizing septic sludge by means of nitrified effluent from trickling filters. In this experiment nitrified effluent was 80 run into a tank containing septic sludge. The comparison of the analyses of the liquors added with those of the overflow from the tank shows that about 75 per cent of the nitrate oxygen is used in stabilizing the sludge. In the Dorr-Peck tank a somewhat similar condition exists on the tray or floor of the sedimentation chamber. It will be recalled that the sludge settles out from this tray, but is in contact with the freshly aerated liquor from the aerating chamber. The sludge on the tray consumes the nitrate oxygen. (For further references see Porter’s Bibliography, Nos. 160, 224, 244, 384, 528, 530, 535). From the ammonia data in the upper table it will be noted that there is an appreciable reduction of free ammonia. As may be seen from Fig. 4 there is an appreciable decrease in both free and albuminoid ammonia in the effluent, which is practi- cally independent of the amount of air used. It is interesting to note, however, that when the air amounts to one and a half cubic feet per gallon the effluent and influent curves for nitrates cross— in other words, at this point nitrification takes place. Again, on reducing the air to one cubic foot per gallon there is a reduction of nitrates. This data leads to the conclusion that in the experiments reported in this paper the nitrification phase of the activated sludge process is entirely absent, and that nitrification is not essential to the success of the process. It is apparently possible under some condi- tions to produce clarification and reasonable stabilization of sewage operating with so little air that nitrate oxygen in the raw sewage is actually consumed by the micro-organisms of the sludge. Attention should, however, be called to the fact that one maximum in the stability curve occurs simultaneously with the maximum influent nitrate and the other with the maximum air. From the discussion of denitrification we see that there is abundant evidence that nitrates and ammonia are taken up by the organisms of the sludge and synthesized into protein rather than being lost as gaseous nitrogen. Protein formation must have oc- curred in our experiments, otherwise our nitrogen balance sheet would have shown a loss. In the article by Richards and Sawyer cited above the conclusion is also reached that the biochemical reactions in this phase of the nitrogen cycle result in protein formation. Their summary is quoted: ‘‘1. If activated sludge is aerated for a short period in an am- moniacal solution the recovery of nitrogen is quantitative. The nitrogen not found as ammonia or nitrate in the effluent is recovered in the sludge. 81 2. If aeration is continued loss of nitrogen occurs. The loss is roughly inversely proportional to the volume of sludge present. 3. The same effects are observed with sewage. The ammonia falls while the sludge gains nitrogen with a loss of nitrogen on the whole balance after sixteen days operation. 4. There is considerable evidence that the extra nitrogen in activated sludge, over and above that found in the old type sludges, is derived from the ammonia of the sewage. There is no evidence of fixation of atmospheric nitrogen.” The straw filter for sewage purification used by Richards and Weeks55 takes advantage of this reaction. They state that: “Labor- atory experiments have shown that about 72 per cent of the nitrogen content of sewage can be recovered by filtration through wheat straw at the rate of 250 gallons per cubic yard of straw per day. The best results were obtained after twenty days when the straw had become activated by bacteria present in the sewage. Operations on a larger scale showed a recovery of 65 per cent of the nitrogen content of the sewage, the resulting manure being odorless and containing 2.06 per cent of nitrogen.” Summary. 1. An effluent of reasonable stability can be ob- tained without using air sufficient to produce nitrification. 2. Denitrification results in protein formation rather than in loss of nitrogen. 3. There is apparently no loss of nitrogen when using a mini- mum amount of air for aeration. 4. There is no evidence of nitrogen fixation even when treating wfith FeS04 to stimulate crenothrix like organisms. 82 CHAPTER VI. MICROBIOLOGY AND THEORY OF ACTIVATED SLUDGE. A. M. Buswell and H. L. Long In reviewing the opinions of experimenters with regard to the theory underlying the activated sludge process of sewage disposal one soon comes to the conclusion that two main lines of action are held responsible for the results obtained. That the mechanism of the reaction is sometimes described as that of adsorption of the colloidally dispersed matter by sludge already present in the sewage is evident from the following statement quoted from well known authorities :3(i “The sludge embodied in sewage and consisting of suspended 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, some having been strained from the sewage and others developed by natural growth.” In other words, the usual suspended particles in sewage grow by the accretion of material colloidally dispersed, thus producing activated sludge. Other writers refer to the “scrubbing action” of suspended particles, and compare the action of activated sludge to that of coagulated alum.57 The process is often referred to as one of oxida- tion, assuming that oxidation is a principal step in the purification of sewage. Another definition states that activated sludge must be of “a character to absorb colloidal matter,” and another author refers to the “clotting”38 of the colloids in the sewage. Such expressions seem to indicate what might be called a colloidal or mechanical theory for the mechanism of the'action of activated sludge, similar in many respects to the Hampton doctrine of the action of sewage filters. Ardern59 summarizes the latter as follows: According to this theory the purification process is primarily and essentially a desolution ef- fect brought about purely by physical causes; any bacterial or bio- logical action is definitely ancillary. Another theory which in reality seems to have been the first to be prepared, is what might be called the biological theory and re- sembles Dunbar’s theory of sewage filters. Those00 emphasizing this viewpoint of the action of activated sludge call attention to the 83 analogy between the action of slate beds, contact beds, and sprinkling filters and the action of activated sludge. The sludge is referred to by these writers, not as a clotted, agglomerated or coagulated sludge produced by the mechanical growth of suspended particles in the sludge, but as biological growths arising from the germination and propagation of micro-organisms whose “spores” are always present in sewage. The term “cultivated sludge”01 used by one author, con- trasts perhaps as strongly as any with the term “coagulated” or “agglomerated” sludge, used by those favoring the colloidal theory. Of the authors who favor the biological theory, we find that some62 refer to nitrification and nitrifying organisms as requisites for the success of this method of sewage treatment, while others refer to the sludge as being composed of a variety of micro-organisms. Mum- ford’s63 M7 seems to have been the only specific organism mentioned as having power to produce the purification of sewage. This organism, it will be remembered, required for its best activity appreciable amounts of iron. If one examines particles of activated sludge under the micros- cope he is immediately impressed with the fact that there is practi- cally no absorbed, precipitated or coagulated amorphous matter in these sludge particles, but that they are composed entirely of active- growing microscopic organisms of varieties ranging from true bacteria up through the giant bacteria, with occasional molds and yeasts, and also a variety of free swimming and attached protozoa64. These communities of micro-organisms must obtain food and this food must be supplied from the colloidal and dissolved matter and salts in the sewage. From what we know of the metabolism of micro-organ- isms it is probable that the unicellular forms absorb through their membrane such soluble forms of organic matter as are able to pass through this membrane, and that they also secrete enzymes which are capable of peptizing or liquifying colloidal particles too large to be directly absorbed. Protozoa, on the other hand, can easily be seen to approach and ingest visible particles of organic matter. This biological theory of the action of activated sludge may be summarized and emphasized by proposing what seems to be a rather striking analogy, namely, that the purification of sewage effected by micros- copic communities appearing as floes is entirely similar to that of disposal of garbage by feeding it to hogs. It does not seem probable that adsorption of colloids or mechanical precipitation plays any greater part in the metabolism of micro-organisms than they do in the digestion of the larger animals. One serious objection to the colloidal theory of coagulation is that the colloidal particles in sewage 84 and the activated sludge particles are, so far as we are able to deter- mine, both negatively charged. Since adsorption of colloids is most effective between oppositely charged particles it should not be applied to the conditions of the activated sludge particles without reservation. Furthermore, adsorption is an almost instantaneous action, while considerable time is required for the activated sludge reaction. Discussion of the theory at this time may seem academic and impractical. Since, however, these two theories would suggest rather different lines of attack on the general problem we have chosen to review and compare them. If the action is largely colloidal and mechanical, then we shall need to study particularly the colloid chemistry of the sewage. If, on the other hand, it is biological, we should study the biology of the sludge so that we may obtain complete knowledge of the desirable and undesirable members of these microbial communities upon which we are to rely for the purification of sewage. The biological theory suggests a somewhat different notion of the importance of oxidation in sewage purification than that ordinarily expressed. When garbage is disposed of by feeding to hogs, only as much oxidation takes place as is required to furnish energy for the life processes of the hogs. Final oxidation does not take place until the pork chops are eaten and burned up in the body to furnish human energy. If the analogy of this process to sewage disposal is ad- mitted, oxidation appears as an incidental reaction. Clark,65 in 1912, called attention to this viewpoint in the following manner: “In experiments upon aeration of sewage tried during the past twenty- five years by various investigators, as described by Drown, Dupre and Dibdin, Mason and Hine, Black and Phelps, etc., the chief object of each study has been to learn the oxidation changes induced by such treatment. The collection of suspended and colloidal matters, as here described, is an entirely new feature of aeration work.” Comparatively little has been published on the organisms of activated sludge. Earlier writers make special mention of nitrifying bacteria; Bartow and Smith66 noticed at times in the sludge large numbers of worms (Aeolosoms Hemprichii) as well as Vorticella and Rotifera. Purdy64 counted the various protozoa in strawboard waste activated in a three inch glass tube and fed by the fill and draw method. More recently Dienert67 and Cambier68 have debated the role of bacteria in the activated sludge process. Dienert maintains that bacteria are essential since nitrification did not take place in the presence of phenol. Cambier on the other hand maintains that the 85 activated sludge process is an example of ordinary chemical catalysis. His conslusions appear to be based on three experiments; one in which chloroform was introduced with the air used for aeration, apparently on the assumption that the chloroform would be a germicide; one carried out at low temperature (0°-12° C) on the assumption that nitrifying bacteria are not active at these tempera- tures; and one in which iron sulfide was added. That nitrification and purification were accomplished under these conditions, Cambier interprets as proof of the catalytic theory of the reaction. He pre- sents, however, no definite data to show sterility of his solutions. In the same journal Courmont69 reports a study of the bacterial flora of activated sludge effluent. He found seven species, one of which was B. Subtilis. No obligatory anerobes were found, and in some cases B. Coli was absent. Richards and Sawyer52 have recently presented data including chemical analyses, bacteria counts and microscopic determinations of the number of protozoa. A relation was established between the number of protozoa and bacteria, and the high nitrogen in the acti- vated sludge was attributed to synthetic living protein of the bodies of bacteria and protozoa. Under certain conditions of aeration free ammonia and nitrates were synthesized into proteins, as contrasted with the formation of free ammonia and nitrates which is ordinarily observed in the activated sludge process. Of the various investigations which have been made, that of Purdy64 furnishes the most complete data on the various organisms present in the sludge. Purdy followed the usual Sedgwick-Rafter method of enumerating the microscopic organisms, reporting the zoogleal floes in standard units of 0.004 mm. sq. Purdy used a 500 cc. aerating vessel operated with an unmeasured excess of air on the fill and draw system with twenty-four hour aeration periods. This system served admirably the purposes of the particular investiga- tion which showed the presence of relatively large numbers of pro- tozoa, especially of Peritrichs. Some work of the present authors on a similar scale and with excess of air and twenty-four hour fillings gave similar results. They do not seem to correspond to results ob- tained when smaller amounts of air are used, nor with the results on larger experimental units. The analytical data herewith reported refer to samples taken from the aeration chambers of a two tank Dorr-Peck activated sludge unit fully described elsewhere.53 For the purpose of the present article it will be sufficient to state that the apparatus was treating about 65.000 gallons per day in two aeration chambers having capae- 86 ities of 14,400 and 12,700 gallons respectively and operated in series. Approximately 0.75 cubic feet of air was used per gallon, of which two-thirds was used in the first tank and one-third in the second. A good degree of clarification and an average methylene blue stability of three days were obtained during the run. Experimental. Microscopic observation made during the winter of 1920-21 indicated that some sort of a relation existed between the amount of air used, the strength of the sewage, the settling rate of the sludge and the types of organisms composing the sludge. When after a shutdown for repairs, the plant was started up in the spring without any activated sludge as a “starter,” daily microscopic ob- servations were made to follow the changes in microbial life as the sludge built up. The daily records, which on account of the unex- pected pressure of the other work, had to be limited to brief observa- tions, are given below. In general it is to be noted that the Holot- richs were the first to appear in noticeable numbers, but that they gave way in time to other forms. The Peritrichs (Carchesium and Vorticella) appeared only after several days of aeration. The matured sludge seemed to be composed largely of zoogleal masses with frequent colonies of Peritrichs and occasional Hypotrichs (generally Euplotes). May 3. Plant started operation. May 4. I. A few Paramecium, paper fibres and miscellaneous vegetable cells. II. Same as under I (May 4.) May 5. I. Paramecium, paper fibres and miscellaneous vegetable cells. II. Zoogleal masses of fine bacterial filaments beginning to form. May 6. I. Large floes of zoogleal mass of fine bacterial filaments. II. Zooglea, Paramecium, Colpidium. May 7. I. Branching zoogleal masses of fine bacterial filaments Para- mecium, Spyrogyra. II. Paper fibres with much attached zooglea. Many Paramecium, few Peritrichs (Vorticellidae), branched zoogleal masses of fine filaments. May 8. I. Branched zoogleal masses of fine bacterial filaments, Para- mecium, Colpidium, 1 filament of Spyrogyra. II. Branched zoogleal masses of fine bacterial filaments, few Holotrichs, mould hyphae and paper fibers. May 9. I. First appearance of Peritrichs in I. One filament of Spyrogyra, zoogleal masses of filamentous bacteria. II. Increase in Peritrichs. May 10. I. Few ciliates, 80% of field consists of zoogleal masses. II. Many Peritrichs. May 11. I. Largely zoogleal masses of filamentous bacteria, some Hypo- trichs and Peritrichs. II. Largely zoogleal masses of filamentous bacteria, fewer Peri- trichs. May 12. No change in character. May 13. Increase in Peritrichs. May 15,16,17 No change in character. Summary of Microscopic Observations May 3-17, 1921. 87 In September the daily qualitative study of the sludge was re- sumed and a careful investigation was made of the forms in the zoogleal masses. In November an interruption in the operation of the plant offered another opportunity to study the forms appearing during the building up of sludge. In this series of examinations, which dates from November 17, qualitative estimates were made, using, as Purdy did, the Sedgwuck-Rafter method of enumeration. Be- ginning with the 9th of December, FeSO4, equivalent to 10 mg. per liter of Fe, was added to the influent sewage for the purpose of determining its effect on the nitrogen cycle. It appeared to have no effect on the character of the organisms found. The results of these examinations are given in Tables XIV and XV. Discussion of Data. A study of the microbiology of activated sludge in its development from raw sewage shows a definite succes- sion or addition of forms. Beginning with the characteristic micro- ■ of raw sewage as it is taken into the aeration chamber, there is a predominance of the minute flagellates and ciliates, with occasional Peritrichs and Holotrichs. In a few days the minute forms diminish in number until they become a negligible quantity, while Peritrichs, Holotrichs, and Heterotrichs increase in number, the Peritrichs predominating throughout. As the minute forms be- come insignificant, there appear zoogleal masses of the teriacae and Nematodes, to be followed in a few days by the sudden appearance of Peritrichs. This point then brings us to the character- istic fauna and flora of the matured activated sludge, under the particular conditions of operation employed. Observations on the occurrence of the various group of organisms have been summarized as follows: Minute Ciliates and Flagellates. The fauna of the samples taken November 17, two days after the beginning with raw sewage, was characteristic of the crude sewage. The minute ciliates and flagellates constituted practically the entire of animal life. These forms continued to predominate in decreasing numbers until the 7th to 8th day when with the gradual formation of the sludge there was a marked decrease, with a predominance of larger forms. From November 22 on through the period of observation, minute forms were present but not in sufficient abundance to enumerate. Perhaps there were more of such forms present throughout the period, but were hidden from observation by the heavy sludge. Of the typical forms present, the minute free-swimming individuals predominated. 88 TABLE XIV. TANK 1. ORGANISMS AND SOLIDS. CO CO ro CO CO to to to to M M 0 CO to to LO tO CO to IO CO Date 00 -4 © OX 4*. CO to © © 00 © Ot CO LO H4 © © 00 © at 44 CO CO Q © © 00 -1 © at CO LO M © © 00 to 00 Minute ciliates + + + + + + + + + + + + 1 + + : + -j- + + + + i + + I + + © © at 00 at and Flagellates at • © © © (Thousands per c.c.) M M M M . M I-1 CO o Ot CO © 44. OX © M OX CO ot to © 44 © at CO 44 44 -4 00 to © 44 ?° CO © CO • Peritrichia o 00 o o o o 44 © © OO © to © © © © © © © © © © © © © © 00 © © © ox © © © © © © © • © 44 44 © 0 © 00 at at © • © © © —4 © “■4 © 09 30 10 (Thousands per c.c.) * 4s- * to to • at * * Holotrichia and © © M to • 44 Heterotrichia 09 00 50 © 40 40 © LO © TO © © © © © © © 60 • © 44 © © 44 © © © © • © • © © © 4^ © © © 44 . © • © © 44 © 30 (Thousands per c.c.) M CO M CO M CO CO 44. CO M M ro to CO • 44 CO CO CO M CO • M M Hypotrichia (Thousands per c.c.) 00 © Ot 05 44 © 44 © © OX © © © to © © © at -I OO • at © CO 44 OO 00 to o o o o © © © © © © © © O 0 © © © © © © . © © © © © © • O © ox © 44. ai at © Larger Flagellates © © © © © (Thousands per c.c.) M M to 1-4 M M CO . to CO M M M Nematoda 40 20 80 © © at © © © © © © © at © at © at © CO © © © 44 • © 44 © OO © © © © © 70 50 10 20 20 10 (Thousands per c.c.) Beggiatoa CO r1 44 CO OX at CO i* CO 44 CO r1 : Filaments 40 50 80 © © © © lO © © lO © 80 OX © © © © © at © 00 © CO © © © © © to © 40 • at • © 90 09 40 80 40 33 30 60 30 10 30 20 (Thousands per c.c.) Standard Units CO M to to 44 M .54 M .37 CO OO Zooglea Masses © © to M © to CO 1-4 CO Ot £ © 44 © 44 © © *-* © © © £ 44 © 00 © -4 00 . 44 (Millions per c.c.) CO CO to ro CO to CO CO CO 44. CO 4*. 44 44 4^ 44. at • © ~1 © .r- Total Solids 00 © 00 © 4-*- © © © © -1 iO to 4- /) CO © CO ul 44 00 CO • © at © CO © • -4 to o © © © © © © © © © © © © © © © © © © © © © 3 5 © • © © © © © • © © Mg/1 81 61 70 05 CO 67 54 54 62 56 54 © © 55 OX OO 59 ox -4 an -a 56 64 52 74 74 75 78 84 82 00 76 89 48 37 18 29 15 13 11 © 00 -4 —4 at Per cent Solids Vol. 1 hr. sed. * Colony or cluster of peritrichs present. + The! standard unit is used here as a measure of surface only and =0.0004 mm.sq. 89 TABLE XV. TANK II. CO M h-i M 0 CO CO to to CO to to to CO to CO M M 00 05 OX 4* CO CO o CD oo -a 05 ox CO to © 00 -4 © cn 4*. co to M CD a © 00 -4 © cn 4*- CO LO M © © 00 -jo Date <1 Minute ciliates + + + :++++++ :++++++ : + : : : + + + + + + + M to CJl -1 cn © © CO © CO © © and Flagellates (Thousands per c.c.) M M i to © 4-. CO • 4*. o ZJX CO to 05 -3 CD CD © © CO 4^ CO 00 OX M I-1 to l“4 Peritrichia 4* o OO © OO o • 00 • o 4*. o © o 4* o 4* O o 05 • O o o CJl © CJl © © © to © 00 . © © oo © © © © . . • M . . • o © © cn © CJl © to © © © M © M © © © cn © © © (Thousands per c.c.) Holotrichia and M Heterotrichia 80 00 o to o CD © 4^ O © 4^ O CJl © CM © CJl © 4*. © . © —4 © © © © © . . . 4^. . . . o © CO © © © OX © 00 © © 4^ © 00 © -4 © cn © CO © (Thousands per c.c.) to to - CO CO cn CJl to cn CO M to Hvpotrichia 80 4*- o o o • o OO o to o © © o 05 O O © © © 4- © . © © CO © 4^ © © © LO © to © © (Thousands per c.c.) M to to CO to - Nematoda. to o CD o 4* O o • 00 • o OX © at © © © © 4» © . © © © © LO © © © . . . O © M © M © © CO © © (Thousands per c.c.) • to to CO to CO CO CO CO Baggiatoa ro to 00 05 o ox CJl CJl . CJl CO 4*. i-1 CO cn Filaments c.c.) o o o • o o o o o o • o © © © © © © © © © © © © © © © (Thousands per M M M CO to u M M M to CO CO M Units Zoogloe- 4* M © • 05 00 H-* CO CJl I—1 • cn CD © 4^ © . CO cn © to • • * o b M © H-1 to to M to © © Masses (Millions per c.c.) Cn o cn • OX © CO o o o o LO N. © © • M © CO © cn . . . « * © Si cn cn cn to * 00 CO CO CO . to CO CO CO CO CO CO 4*- 4^ 4» 4*. 4^ CO I—1 CO oi ox • 05 © to CJl 05 05 4^ © CD Ol © 4s*. . —4 cn © H* • “9-4 00 © © to t-4 CO 4— CO CO CO Mg/l o © • o © o © O o • O © © © © © . © © © © © • © © © © © © © © © © © © © CD CD i 00 00 -4 © -41 © © © to Per cent. Solids Vol. -4 00 o . LO CO to OO 05 CO CO Ol © CM CJl © © 4*. LO 4*- © -4 4*- • • • o M to to to to -O to CO to to to 1—* 1 hr. sed. ORGANISMS AND SOLIDS. 90 INFUSORIA. Peritrichs. As indicated in the table, the Peritrichs were the most abundant forms throughout the entire period of observation. Beginning with a very low count they reached the point of predomi- nance in eight days, with a count of 14,000 in eleven days, and con- tinued to be the predominating type. In many cases the extremely high count was due to the presence of colonial forms or to clusters of individuals not colonial. From December 5 to 16 the Peritrichia were more or less quiescent or encysted. From the 5th to the 10th only very few individuals showed signs of activity; other individuals were largely either quiescent or encysted. From the 12th to the 16th quiescent and active individuals were about equal in prominence. The predominating type of Peritrichia were Vorticella. Indi- viduals of the Pyxidium type were quite common on November 29, December 5, 8, and 13; occasional individuals were recorded at other times. A few colonies of Carchesium were observed. A stalk of Zoethamnium, with its characteristic continuous muscle, while never observed in the unstained sludge, was found on a prepared slide stained with fuchsin. Colonies and individuals were invariably attached to the amorphous particles of the sludge by means of the more or less long stalk. There were present also occasional free-swimming stalkless individuals resulting from division. Hypotrichia. After ten days of operation hypotrichs of the Euplotes type suddenly became abundant. No Hypotrichs had been observed up to November 23. On the 25th, the 24th being Sunday, the calculated count was 1200 per cubic centimeter. The count remained in the thousands the remainder of the period, reaching the highest count of 4500 on December 3 and next highest on the 31st. In habits the characteristic Euplotes type was generally asso- ciated with the zoogleal masses of sludge where it apparently found its best forage. The Holotrichia and Heterotrichia. Organisms of this class principally Frontonia were observed in the first sample taken, though in very limited numbers. With the evolution of the sludge they increased to a count of 6400 after fifteen days but showed a marked decrease from this point on, with a total absence in many observations. There is a similar curve in the unit mass content of the sludge, but the drop is not as sharp as in the case of the IIolo and Hetero- trichous forms 91 of the type Genus Podophyra occurred very rarely, while individuals of the type Genus Acineta were quite common. One or two were observed in the field on the following days, November 20, 21, 23, 24, and December 1, 3, 5, 6, 19, 21 and 28. Suctoria. Suctoria of two types were observed. Individuals THE WHEEL ANIMALECULES. Rotatoria. The Rotifers were so rarely observed during the forty-six days that they hardly deserve mention. As the concentra- tion of the sludge increased from the beginning of formation to the climax, apparently the conditions were not suitable for the life and multiplication of the Rotifers. In the small scale experiment, how- ever, carried on with large amounts of air in the laboratory and at the plant Rotifers became more abundant as the sludge became heavier and more concentrated. In the small scale sludge experiment a much heavier sludge developed because only the effluent was removed. This condition seemed to be favorable to the Rotifers. The forms most common were representative of the Genus Notom- mata, while individuals of the type Genus Brachionus were also observed. ROUND WORMS. Nematoda. The Nematodes were of common occurrence in the experimental sludge after eleven days of operation. In the observa- tions made in the large plant Nematodes were observed on the fourth day and gradually increased to 2400 per c.c. on the eighteenth day, to a maximum of 3300 on the twenty-first day and then a gradual decrease that was comparable to the decrease in the Rotifers. Zoogleal Masses. Having briefly reviewed the fauna of the sludge, we shall now turn our attention to the sludge proper. On November 17, after two days’ operation with raw sewage, units of zoogleal mass numbered 115,000; by November 25, 1,089,500; by December 1, 2,062,500. The count continued ranging between one and two million units throughout the period, a count typical of a climax sludge maintained at the given dilution. The animal inclusions of the sludge made up a very small part of the entire mass. The base of the sludge was composed of zoogleal masses intermixed largely with filamentous bacteria and occasional zoogleal ramigera. It appears that the filamentous forms overwhelmingly predomi- nate in the sludge. The literature on filamentous forms is scattered and rather uncertain taxonomicallv. Therefore a more extended 92 study of these inclusions and the literature on the subject is being made, which will determine the species of the forms present. Creno- thrix polyspora, Sphaerotilus dichotomus and zooglea ramigera were, however, undoubtedly present in large numbers. Bacterial Surface. Herring31 long ago pointed out the import- ance of bacterial surface in sewage purification, though little definite data has been compiled since his paper on the subject. From the table we may obtain a notion of the order of magnitude at least of the sludge surface of the activated sludge process. Let us take a case where two million standard units of zoogleal masses was found per cubic centimeter in the aeration chamber. Each floe must have a lower surface, equal at least to the upper surface, so that leaving out the side surfaces we would have four million standard units of 0.0004 mm. sq. each, or 16.0 cm. sq. of surface per cubic centimeter of vol- ume. This figure does not include the surface of the protozoa or the free-swimming bacteria. If increased by fifty or one hundred per cent it would probably approach more closely the correct value. This would mean a surface of approximately 500.0 square feet of sludge surface in one cubic foot of the aeration chamber. Summary. In view of previous work of other authors cited and the data of the present article we wish to propose the following statement of the theory of the activated sludge process. Activated sludge floes are composed of a synthetic gelatinous matrix similar to that of Nostoc, or Merismopedia, in which filamentous and unicel- lular bacteria are imbedded and on which various protozoa crawl and feed. The purification is accomplished by ingestion and assimilation, by assimilation by organisms of the organic matter in the sewage and its re-synthesis into the living material of the floes. This process changes organic matter from colloidal and dissolved states of disper- sion to a state in which it will settle out. A calculation from data given indicates approximately 500.0 square feet of sludge surface per cubic foot of aeration tank volume. 93 CHAPTER VII. SLUDGE DRYING EXPERIMENTS. pH Control of Acidification. (By A. M. Buswell and C. C. Larson.)10 Bartow and co-workers, especially Hatfield71 and Molil- man,72 have tried the effect of the addition of a variety of chem- icals on the rate of sedimentation, filtration, or separation by centrifuging, of activated sludge. They report that acidification was especially beneficial and Hatfield further states that when the acid added is sufficient to pass the Methyl Orange end point the acidified sludge contracts to one-third the volume to which the un- acidified sludge will" settle in the same length of time, and that the acidified sludge floats on the liquid from which it is separated. The above mentioned investigators also observed that the acidified sludge did not become septic in a short time as did the untreated sludge. The increased filterability of acidified activated sludge had also been observed by Copeland and chemists of the Sanitary District of Chi- cago. The same difficulties which are encountered at times when one tries to adjust the reaction of bacteriological culture media by adding the amount of acid calculated from titration have been met with in controlling the acidification of activated sludge. Experiments showed that in one ease one-third the amount of acid calculated from titration was the right amount to produce the desired result. The work of Clark and Lubs73 on the determination of H+ con- centrations in culture media suggested to the authors that a method which would measure the intensity rather than the capacity factor of acidity would be a proper one to employ in controlling such a reaction. Furthermore, the work of Loeb74 on gelatin led us to expect that activated sludge which behaves in many respects as a gel, might have a point of minimum swelling or maximum contraction, the so-called isoelectric point. To test the applicability of Clark and Lubs’ results and those of Loeb to the problem of dewatering activated sludge, the work here reported was undertaken. Effect of Acidification and Heat. In these experiments the following procedure was used: Activated sludge was taken as it came from the tanks, allowed to settle for an hour, and the super- na.tent liquid siphoned off. This gave a sludge with a moisture content 94 After thirty minutes the cylinders were removed and the volume occu- pied by the sludge read as accurately as possible. With the aid of a pair of draftsman’s dividers a fairly accurate estimate of the volume occupied by the sludge was obtained. The sludge in each case rose to the top of the cylinders, leaving a comparatively clear liquid below. A pipette was thrust down through the floating sludge and 10 c.c. of the subnatent liquor removed for determination of the hydrogeD ion concentration. The ten c.c. portion was placed in a test tube, five drops of indicator added and the color matched with that of freshly prepared standards. It was assumed that the supernatent or subnatent liquor from the sludge was in equilibrium with the sludge itself. The liquor usually contained some suspended matter, but this did not interfere seriously with the colorimetric comparison. The results of five of the experiments are given in Table XVI. TABLE XVI. EFFECT OF ACIDIFICATION AND HEAT. Temperature 50° Time x/i hour Number c.c.N/1 H-SCh pH Per cent vol. sludge 1 0 6.8 37 2 5 6.5 27 3 1.0 6.1 20 4 2.0 4.5 16 5 3.0 3.0 16 6 4.0 2.7 16 7 5.0 2.3 16 8 6.0 2.0 17 9 7.0 1.7 16 10 8.0 1.4 16 The raw sludge had a pH value of 7.0. Experiment i. Experiment II. Samples of the sludge from the following run were removed and the moisture content determined by evaporating on a steam bath and drying at 105° C. for 24 hours. Temperature 50° C Per cent Time % hour Per cent Number c.c.N/1 HsSCR pH vol. sludge moisture 1 0 7.4 26 98.23 2 .5 6.4 18 97.13 3 1.0 6.1 15 96.23 4 1.2 5.8 13.5 95.73 5 1.4 5.4 13 95.43 6 1.6 4.8 12.5 95.39 7 1.8 3.3 12 94.85 8 2.0 3.0 12 95.42 9 2.2 2,5 13 95.18 10 2.4 2.5 12.5 95.70 11 5 Raw sludge 1.9 11 95.15 99.49 95 Temperature 50° Number C c.c.N/1 H2SO4 pH Time % hour Per cent vol. s.udge 1 0 7.0 53 2 .2 6.6 43 3 .4 6.4 39 7 1.2 6.0 30 8 1.4 5.8 27 9 1.6 5.6 26 10 1.8 5.3 25 Experiment III. Temperature 50° C Per cent Time y2 hour Per cent Number c.c.N/1 H2SO* pH vol. sludge moisture 1 0 6.9 41 98.13 2 .5 6.4 33 3 1.0 6.0 27 4 1.2 6.0 24 96.86 5 1.4 5.8 23 6 1.4 5.5 23 7 1.8 5.3 22 8 Raw sludge 2.0 5.1 20 99.23 Experiment IV. Experiment V. The following run was made in 500 c.c. graduated cylinders and the subnatenf liquor siphoned off and turbidity determinations made. It will be noticed that the turbidity of the subnatent liquor reached a minimum at a pH value approximately the same as that of maximum shrinkage, indicating a minimum of dissolution or dispersion of the gel at that point. Number c.c.N/1 H2S04 pH Per cent vol. sludge Per cent moisture Turbidity 1 0 6.7 17 97.16 220 2 2.5 6.2 13 195 3 5.0 5.9 11 95.91 195 4 7.5 3.5 10 95.42 95 5 1.0 2.5 10 95 6 12.5 2.3 10 96.23 110 7 15.0 2.2 10 115 8 17.5 2.1 11 95.50 110 9 20 1.9 10 130 of approximately 99 per cent. Equal amounts of the sludge were placed in 100 c.c. graduated cylinders and amounts of normal sul- furic acid varying from 0 to 10 c.c. were added. The contents of the cylinders were thoroughly mixed and cylinders placed in a water bath at 50° C. equipped with a mechanical stirrer to insure uniform temperature. The cylinders were heated to hasten the equilibrium. When the experiments were carried on in the cold the sludge in the cylinders containing the least acid settled to the bottom, whereas with the higher acid concentration the sludge floated. The change occurred in each case at a pH value of approximately 5.0. Further- more, there was a marked color change of the sludge itself in both the hot and cold runs. There was a graduation of color from deep black in the tube to which no acid had been added to a light gray in the tubes with the most acid. A sharp change occurred between a pH of 5.0 and 6.0. (Table XVII.) 96 EFFECT OF ACIDIFICATION. TABLE XVII. A similar series of experiments were made without heating but allowing the cylinders to stand in the cold for a longer period of time. Experiment I. Number c.c.N/1 IHSCb pH Per cent 1 0 7.3 61 2 .5 6.8 74 3 1.0 6.2 55 4 1.5 5.7 36 5 2.0 5.0 27 6 2.5 3.2 26 7 3.0 2.6 25 8 3.5 2.4 24 9 4.0 2.3 24 Time 3 hours The sludge in tubes numbers 1, 2, and 3 settled to the bottom. That in num- ber 4 separated, but one-sixth settled and the remainder floated to the surface. The sludge came to the surface in all the remaining tubes. Experiment II. Time 3 hours Number c.c.N/1 HsSOi pH Per cent vol. sludge 1 0 7.3 52 3 1.0 te 6.1 35 4 1.2 5.7 31 5 1.4 5.2 27 6 1.6 4.8 23 7 ] .8 4.0 22 8 2.0 3.2 22 9 2.5 3.0 20 10 3.0 2.7 22 The sludge in tube number 1 settled; that in tubes numbers 3, 4, and 5 sepa- rated, in each case that going to the bottom was about one-sixth of the total. In tubes numbers 6, 7, 8, 9 and 10 the sludge floated to the surface. Fig. 26 Fig. 27 97 From the curves (Figs. 26 and 27) it is evident that the volume shrinkage of the sludge is a function of the hydrogen ion concentra- tion, and that a maximum shrinkage occurs at a pH value of approxi- mately 5.0. The addition of more acid does not materially affect its shrinkage, although there is some evidence that an expansion occurs as the concentration of acid is increased beyond a pH value of 4.5. The phenomenon of floating to the surface is probably due to the action of the acid on carbonates in the sludge and mother liquors liberating minute bubbles of carbon dioxide which buoy up the sludge particles. The specific gravity of activated sludge is about the same as that of the liquid in which it is suspended, as evidenced by its low rate of settling under plain sedimentation. Furthermore, activated sludge after its vigorous aeration in the tanks is thoroughly saturated with air and when the temperature is raised, the dissolved air is driven out of solution, and is trapped in the particles of sludge exert- ing a buoyant effect. The observations of Hatfield with regard to the sterilizing action of the acid were confirmed. Untreated sludge usually became septic in a few hours, whereas the acidified sludge remained sweet for a much longer period of time. At first inspection, a reduction of the water content from 99.5 per cent to 95 per cent does not appear very great, and yet if we consider the per cent of dry solids, the actual amount of water elimi- nated becomes very significant. For the basis of calculation we will consider one ton of dry sludge. As it comes from the tanks this ton of solids will be mixed with water in ratio of about one to two hun- dred. Upon reduction to 95 per cent sludge the ratio will be one part of solids to approximately twenty parts of water, or, in other words, about 180 tons or nine-tenths of the total water will have been re- moved. One ton of coal will evaporate approximately six tons of water; in order to effect this reduction by means of heat alone it would require some thirty tons of coal. The acid necessary to effect the same reduction by the method herein described would cost from fifty cents to one dollar. 98 Acid-heat-flotation Process. (A. A. Brensky and S. L. Neave.) Experiments carried on in this laboratory in November, 1920, by Mr. C. Lee Peck, showed that treatment with acid and heat cause activated sludge to shrink to a comparatively small volume, and that under certain conditions the separated sludge floated to the top of the ves- sel, forming a fairly compact cake. A small continuous unit for treating sludge by this process was constructed at the Experimental Plant and operated with the co-operation of the State Water Survey. The results obtained were promising, and Mr. Peck obtained a patent upon the method, assigning same to the Dorr Company, by whom he was employed. The “flotation process,” as the acid-heat treatment was called, was further used in experimental work carried on by the Dorr Company at New Britain, Conn.,75 resulting in some improve- ments in design. With the permission of the Dorr Company a flotation or frother unit was constructed at our Experimental Plant in November, 1921, and operated from December 16, 1921, to January 6, 1922, to secure partly dewatered sludge (85% moisture) for experiments on further dehydration, especially for experiments with the Bayley sludge drier. Previous experiments in dewatering sludge were tried by pressing, filtering and centrifuging. A Patterson filter press and Oliver con- tinuous filter had proven unsuccessful, and the capacity of our Tol- hurst centrifuge was too small to furnish sufficient sludge for the Bayley drier. The flotation unit was in actual operation for a total number of approximately one hundred hours and furnished an abundant supply of sludge for heat drying experiments. This process of dewatering sludge may be called the acid-heat- flotation process. It consists of heating a suitable mixture of sludge and acid to such a temperature as to cause the agglomeration of sludge particles to a cake, floating upon an effluent liquor, comparatively low in turbidity. The flotation is assisted by heat since the buoyancy of the cake depends upon numerous minute bubbles of gas liberated in the acidification of the alkaline sludge. Fig. 28 shows diagrammatically the final arrangement of the flotation unit which consists of a flotation tank, a reaction chamber, a heating system, and flow measurement device. The flotation tank is two feet in diameter and eight feet four inches in depth, the lower part of which is made of concrete and the upper part of twenty-four inch vitrified pipe. The tank is four feet six inches below the ground 99 surface. In the bottom of the flotation tank and concentric with it is the reaction chamber, one foot in diameter and three feet three inches in depth, made of galvanized iron. Around the reaction cham- ber, forty feet of half inch pipe forms a heating coil. A small boiler supplies steam for heating. The inlet to the unit is through a one inch cast iron pipe in the bottom of the reaction chamber and the outlet is through a one inch pipe, extending from the bottom of the flotation tank to the effluent control at the top. The lower part of this pipe is outside of the reaction chamber and the upper part is outside of the flotation tank. (Fig. 28.) The sludge and acid rates of flow were measured by constant head orifices. The head in the half inch orifice box for sludge measurement was regulated by a hand operated valve. Activated sludge for the experiments with the acicl-heat-flotation process was obtained from both trays of the Dorr-Peck tanks. Sludge Fig. 28 100 was drawn continuously during tlie operation of tlie dotation unit at the rate of from, four to eight gallons per minute and allowed to settle in a circular wooden tank of 2300 gallons capacity. The super- natant liquor from this tank overdowed the periphery at the top, and the settled sludge for dotation was drawn from the bottom. When the frother unit was not in operation, the sludge was kept fresh by air diffused through a dltros tile set in the bottom of the tank. Acid for the experiments was prepared in the laboratory. Com- mercial sulphuric acid (94%-96% strength) was diluted to a ten per cent strength, and was carried to the plant in dve gallon carboys. The handling and regulating of the acid was very satisfactory. The settled sludge and sulphuric acid do wed separately to a point dve to six feet from the inlet to the reaction chamber, where they mixed. The mixture entered the bottom of the reaction chamber and was heated by the surrounding coil as it dowed upward through the chamber. Here the reaction which effected the coagulation and agglomeration occurred. As the contents left the reaction chamber the sludge particles rose and joined the doating cake or natant sludge. When the level of the sludge cake reached the top of the dotation tank, the subnatant liquor was discharged through the one inch efflu- ent control pipe. The height of natant sludge depends upon the sub- natant liquor level, which is regulated by raising or lowering the effluent control pipe. When the sludge cake became from twelve to eighteen inches in thickness part of it was skimmed off, or the entire cake was allowed to build up in the tank until the turbidity in the effluent indicated excess accumulation of sludge particles. By removing part of the sludge cake, a clear effluent was again produced with continued opera- tion. When continuing a run from the previous day all but about twelve to eighteen inches of the sludge was scooped out. The top part of the sludge cake was drier than sludge continuously skimmed. Most of the sludge cake was spread on a wooden platform covered with burlap sacks, and drained for twenty-four hours or more. Water amounting to one-fourth to one-third of the original weight of freshly floated sludge was lost by drainage. In an experiment on sludge draining the entire content of one day’s flotation was spread eight inches thick on a cinder bed covered with burlap sacks. After forty-eight hours the sludge depth was less than six inches. The increasing demand for securing sludge to operate the Bayley drier limited experimentation with the unit to a few days. Some attention was given to securing a more buoyant natant sludge so as to obtain a drier cake from the flotation unit. A central heater placed 101 inside of the reaction chamber was tried, but no better results were observed. Large bubbles caused the cake to break at the surface and allowed the minute bubbles to escape. A truncated cone made of galvanized metal was placed in the top of the frother tank, so as to secure the entire buoyant effect on a smaller area. No noticeable improvement resulted and the cone was removed. As nearly as could be determined with the limited time of experi- mentation, and with the assistance of former experiments, the best conditions of operation for securing the maximum quantity of de- watered sludge were: (1) Rate of feeding settled sludge was from 1.6 to 2.0 gallons per minute. (2) Rate of feeding sulphuric acid was from 100 to 120 c.c. per minute. This rate gave a pH of the effluent between 4.6 and 5.0 (colorimetric tests). (3) The tempera- ture of the effluent liquor was maintained between 48° and 52° C. These conditions were maintained for the remaining period of operation. When feeding more than 2.0 gallons per minute of sludge to the flotation unit the separation of the natant sludge particles and subnatant liquor wms not complete. A sample of the effluent after remaining quiescent for a minute or two, would have a clear sub- natant liquor and a thin layer of floating sludge. Effluents with tur- bidities varying from 20 to 50 parts per million were obtained under good operating conditions and with the rate of feed less than 1.8 gallons per minute. The desirable hydrogen ion concentration of the effluent was found by previous experiments to be from 4.6 to 5.0. Some interest- ing observations with other pH values were made. On the first test, with the pH about 6.0, heavy sludge particles discharged with the effluent. Apparently, the acidification was not sufficient for complete flotation. During the last test an excess of sulphuric acid was added. (Pet-cock was opened accidently during the changing of bottles.) The excess acidity caused the breaking up of the sludge cake by comparatively large gas bubbles. In an effort to secure the necessary drainage of floated sludge before discharging, the effect of variation of temperature was ob- served. The temperature varied from 40° C to 65° C. The best separation occurred at approximately from 48° C to 55° C. Tem- perature of 65° C to 70° C caused a very characteristic puncture through the center of the cake. The temperature of the cake below the surface was always a few degrees higher than the effluent. 102 Sludge Feed Sludge Cake Effluent Moisture 99.2 92.9 (freshly floated) Total Solids' . 1160 p. p. m. Total Organic Nitrogen—472.1 p. p. m 2.8 p. p. m. Chemical results of a run on December 16, 1922, are as follows: The physical characteristics of sludge obtained from acid-heat- flotation process changed with time and with the manner of treat- ment. The freshly floated cake was very loose and wet. Clear water was visible in the fibrous mass quite separate from the sludge par- ticles themselves. The sludge was amenable to drying by drainage and required about three days. With the appearance of dehydration cracks on a bed of sludge within a day or so, the physical character- istics changed from a loose mass to a gummy and putty consistency, stiff and gritless. On December 17, 1921, samples of freshly floated sludge were left on a cinder bed in the open under all weather conditions. A sample examined a week later resembled a fine sponge. On com- pressing the mass clear water was expelled. A sample from the same bed examined in February was loose, soft and very spongy. When the material was pressed no free water was expelled and it expanded again to almost its original volume. The entire process of flotation and drying on beds was free from offensive odors. The material did not deteriorate at a time when the temperature was higher than normal room temperature most of the day for over a week. At present. March, 1922, sludge stored in wooden boxes, a vitrified pipe, and a steel tank, is in practically the same condition as when first stored. Winter conditions have been favorable to good results in the storage of the sludge. The need of large quantities of dewatered sludge for the Bayley drier, and the uncertainty of the duration of such experiments, made it necessary to store the maximum amount of sludge. Considerable wet sludge with a moisture content of from 96 to 98 per cent was poured on a cinder bed indoors, and drained to about 85 per cent moisture. Freshly floated sludge had a moisture content of about 88 to 92 per cent, which readily drained to about 85 per cent. During the 100 hours of actual operation of the flotation unit, all floated sludge produced was drained and weighed. When stored, the sludge weighed about two tons and had a moisture content of approximately 85 per cent. A sample of sludge taken to the laboratory January 23, 1922, during the operation of the drier, was found to contain 80 per cent moisture. Some calculations on quantities of coal and acid required for the 103 flotation unit are made for such conditions of operation as are likely to be met with. With the following conditions, viz., (1) A sludge feed of 98.8 per cent moisture or one-tenth pound of dry solids for every gallon of sludge. (During September 5 to 10, 1921, sludge of 98.8 per cent moisture was drawn from tray No. 2 of the Dorr-Peck tank.) (2) An increase in temperature of sludge from 12° C to 50° C (a difference of 100° Fahrenheit). (3) An effluent with hydrogen ion concentration of from 4.6 to 4.8. (4) A maximum rate of feed of 120 gallons per hour (40 gallons per hour per square foot) a sludge cake of 88 per cent moisture may be floated, which after twenty-four to forty-eight hours drainage would reduce to 83 per cent moisture. Coal with 10,000 B.t.u. per pound available for heating would produce approximately eight pounds of 85 per cent moisture sludge from feed sludge of 98.8 per cent moisture. (One pound of good coal contained 14,000 B.t.u.) This may be stated as follows: It would require five-sixths pound of coal to float one pound of sludge, on the basis of dry sludge. Using 60 c.c. of ten per cent sulphuric acid per gallon of sludge feed, it would require 0.14 pounds of acid per pound of dry solids produced. Summing up the relations on the basis of one ton of dry solids, it would require 1,660 pounds of coal and 280 pounds of sulphuric acid for flotation. With coal at $6.00 per ton and sulphuric acid of 94 to 96 per cent strength at $17.00 per ton, the cost to produce sludge by flotation on the basis of a ton of dry solids is estimated to be (a) $5.00 for coal plus (b) $2.50 for acid, or a total of $7.50. Soon after the conditions of operation were determined, unskilled labor was left at times to operate the entire unit. One man was capable of operating the boiler, changing the acid bottles and observ- ing the temperature and rates of flow. Conclusions. (1) Experience at Urbana and New Britain has shown that the acid-heat-flotation process works from a mechanical standpoint so smoothly that further experimentation for reducing the cost would he justifiable. (2) Floated sludge is amenable to drying on beds and probably in mechanical filters and presses. (3) Alkaline carbonates in the sludge are apparently necessary for flotation. BAYLEY DRIER. (By G. C. Habermeyer and A.\A. Brensky.) Experiments in drying sludge containing 80 per cent moisture were run with a dryer shown in Fig. 29 which was manufactured especially for these tests by the Bayley Manufacturing Company of Milwaukee. 104 Fis. 29 In this drier the sludge was carried along the upper sides of three endless woven wire belts arranged one above the other, drop- ping from one end of the upper belt to the middle belt and from that to the bottom belt. At one end" of the apparatus the top belt passes through a compartment into which the sludge was shoveled. In this compartment the upper side of the belt, which traveled upward, is inclined at an angle of two and a half vertical to one horizontal. Except for this incline and the turns the belts traveled horizontally. Air drawn from outside or from the drying compartment was forced by a fan through Chinook steam coils and passed to the lo.wer part of the drying compartment in which it circulated in direction oppo- site to the travel of the sludge. Steam coils were also placed between the top and the bottom of each belt, so that the temperature on any belt could be regulated. Baffles, or partitions, below the two upper belts prevented a direct flow of the hot air upward. Exhaust air not drawn to the blower passed out at the top of the apparatus. Pulleys, gears, chain drives, belt tighteners, counterweights, canvas flaps to reduce loss of heat at openings, and details are not shown in the figure. Power was furnished by two electric motors, one to drive the belts, and the other of one horsepower to drive the blower. A one horsepower motor to drive the belts was exchanged 105 for a three horsepower motor on the evening of January 17, after sprockets had been exchanged to increase the speed of the belts. The larger motor did not pull the load and the sprockets were changed back. The trouble was later found to have been due to loose driving gear and unequal tension on two sides of the upper belt. These were adjusted before the run on January 18. Steam for heating was supplied by a twenty horsepower vertical boiler. This was placed on low ground sixty feet distant from the drier in order to secure circulation without using an injector, but during the experiments returned steam passed through traps to a barrel on a platform scale, and was then returned to the boiler through an. injector. Wet and dry bulb thermometers were placed at the air inlet and air outlet of the drier. Holes were drilled for thermometers in front of the steam coils, beyond the steam coils and above each of the three belts near the center of the apparatus. All temperature readings were centigrade. Readings of inlet air temperatures were of little use as the temperature varied greatly with slight changes in the posi- tion of thermometers placed inside of the fresh air intake. The sludge used in these experiments had been floated, using sulphuric acid and heat as described in an earlier section, and had then been stored in boxes. At the time of tests the moisture content was 80 per cent (the sludge used on January 16 and 17 probably had a moisture content of 80 to 85 per cent.) On January 16 sludge was placed in the sludge tank and a small amount caught on the belt. The fan operated 660 revolutions a minute. An excellent dried product was secured but in small quan- tities. From measurements made later it is probable that the rate of feed of wet sludge was less than 10 pounds per hour. On January 17 the speed of the upper two belts was increased to a little more than one foot a minute, and the speed of the lower belt adjusted to about six-tenths of a foot a minute by exchanging sprockets on the drive and by adjusting gear. The speed of the fan was reduced to 450 revolutions a minute in an attempt to increase temperatures. At the inlet and outlet sides of the fan the pressures were —.15 and -f- .38 inches respectively. A sag in the belt affected the feed. At times certain parts would pick up a layer of sludge, and more would adhere to the sides and rivet-heads than to the center. Sludge was carried upward a few inches by the belt and rolled off, with the appearance of a solid roller placed close to the belt. Some sludge was fed by rubbing a stick back and forth close to the belt to prevent this rolling away of sludge. At 106 other times the sludge was placed on the belt with a small trowel. Results secured were of little value, principally due to poor operat- ing conditions, slipping of belt, breaks, poor adjustment, and conse- quently over-loading of motor. On January 18 the gear was adjusted to give a speed to the upper two belts of 1.4 feet a minute and to the lower belt a speed of .82 feet a minute. Adjustments were made to give good operation except for feed of sludge onto the belt. Sludge was thrown into the sludge tank to be caught on the belt on its travel downward and around the sprockets in the tank, but without success. Some sludge was spread on the belt with a broom, but the rate of feed was low. During a considerable part of the test the gage on the boiler registered 80 pounds, the air leaving the heating coils was at a tem- perature of 104° and wet and dry bulb thermometers in the exhaust registered 89° and 40° respectively. On January 19 the speed of the fan was changed back to 660 revolutions a minute, and the pressures varied from —.33 to —.42 inches at the fan inlet, and from .76 to .68 at the fan outlet. Wet and bulb thermometers were placed between the fan and heating coils, and a pressure gage was attached to the heating coils. The boiler pressure could not be held uniform. At times very little water circulated and at other times water was returned from the coils at a rate of 400 pounds an hour. The range of operating conditions is shown by the readings in Table XVIII. TABLE XVIII. January 19 January 20 Time 12:20 4:00 5:20 3:25 4:10 4:30 4:40 p.m. p.m. p.m. p.m. p.m. p.m. p.m. Pressure at boiler 75 60 64 48 75 72 60 Pressure at coils 56 55 46 69 46 52 Temperature °F—• Inlet, dry bulb 60° 63 51 51 48 43 46 Inlet, wet bulb 31 38 28 27 25 27 Past coils Ill 103 100 96 90 88 92 Bottom belt 102 101 Center belt 104 104 95 95 Top belt 98 98 Outlet, dry bulb 99 96 96 92 87 84 Outlet, wet bulb 44 39 38 36 35 36 Water was added to sludge containing 80 per cent moisture, and a small amount of water was found to be of advantage in causing sludge to adhere to the belt, but the amount which adhered was so small that no measurements were made and the experiment was dis- continued. An excellent dried product was secured, but in small quantity, as during the first day of the tests. Sludge was then spread on the belt with a broom, but the rate of 107 feed was not high and a large part of the sludge adhered to the top belt during more than one complete revolution. The brush placed below the belt near the discharge end was adjusted to give various pressure against the belt, but without success. The small amount of sludge discharged from the machine was very well dried. Sludge was then spread on the belt with a trowel at a rate of 50 pounds of wet sludge an hour, which was considerably higher than any previous rate of feed. This increased rate was partly due to better adjustment, tighter belt, and a more uniform speed, which was 1.15 feet a minute for the two upper belts, and .68 of a foot for the lower belt. A large part of the sludge adhered to the top belt without falling off, and some large masses accumulated on the brush and then fell to the belt below. Masses one-fourth of an inch thick and more were not satisfactorily dried, and but a small quantity of well dried sludge was secured. On January 20 the speed of the belts was maintained as on the previous day. As the air at the exhaust was dry and as it was diffi- cult to keep a high boiler pressure, as much air as possible was returned to the fan. Various methods of feeding the sludge were tried. A box with a slot in the bottom was placed above the top roller at the inlet end of the top belt. Sludge was placed in this box and an attempt was made to regulate the rate of feed with a board held close to the belt to act as a dam, but this was not successful. An opening was then made in the side of the box and sludge was forced through the opening with a wood block, but the sludge was then fed in too thick a layer. Feeding through a slot might have been a little more successful with wetter sludge. Sludge was placed on the upper belt with a trowel at a rate of 30 pounds an hour. A considerable amount was held on the upper belt for more than one complete revolution. Wet sludge mixed with dried sludge in the proportion of twenty- five pounds of wet sludge to eight pounds of dried sludge, was fed at a rate of thirty pounds an hour, and the brush was adjusted tightly against the bottom of the top belt. A large quantity of very well dried sludge was secured. The experiment lasted an hour, feeding from 3 to 4 p.m. A large part of the dried material secured was material unloaded from the upper belt, which at the beginning of the test was coated with material adhering to it. During this experi- ment boiler troubles were at a maximum. Operating conditions are given in Table XVIII. Mixing 50 pounds of wet sludge with 20 pounds of ashes was 108 tried. This formed a more uniform and less granular mixture than the wet and dried sludge and apparently was not as successful. It is not directly comparable as the feed was much more rapid in an attempt to secure greater efficiency from the machine. The rate of feed of the mixture was 100 pounds an hour. Temperature condi- tions during a considerable part of the test are shown above. The drop in temperature in the air (4.40 p.p.m.) was greater than with previous feeds. Fifty pounds of wet sludge was mixed with five pounds of straw. It was very difficult to secure a good moisture and not a sufficient amount was prepared to run a complete test. Air circulation was determined by reading an anemometer placed in eight positions in the exhaust opening at the top of the drier. The air discharge with opening twenty-five and a half inches wide and twelve to fifteen inches long was approximately 2700 cubic feet a minute. Summary. It was difficult to secure sufficiently high boiler pressures at all times. The sludge could not be fed in the sludge tank and be carried upward on the belt at a practicable rate. The best results were secured by mixing with a granular material which prevented pressing the sludge into the interstices of the belt and allowed it to fall off from the top belt. A considerable part of wet sludge applied to the top belt with a broom or trowel adhered to that belt during one or more complete revolutions. The maximum rate of feed obtained, excepting with the mixture of ashes, was fifty pounds of eighty per cent sludge in an hour. FILTER PRESS EXPERIMENTS. A Patterson filter press, Fig. 30, a heavy-duty press of the cir- cular leaf central feed type, with thirty-inch leaves, was used for a brief series of experiments, the results of which are given below. The irregular quality and quantity of sludge obtained from the acti- vated sludge tanks made further filter press experiments seem inadvisable. A series of ten tests of dewatering activated sludge with a filter press were made during the period from July 8 to 25, 1921. The first test was not recorded; the others have been recorded separately and are appended. It was found necessary after the first test to place all thirty (By A. A. Brensky and S. L. Neave.) 109 Fig. 30 plates in the press to safely operate. A steel plate, three-fourths of an inch thick, served as a blind to limit the number of plates used. The number used varied from two to six, depending upon the quan- tity of sludge prepared for pressing, or the possibility of increasing thickness of a cake by decreasing the number of plates. Preparation of Sludge for Press. About 900 to 925 gallons of sludge were drawn from tray No. 2 of the Dorr-Peck apparatus, and after settling in sludge tank No. 3 for from one to one and a half hours, the supernatant liquid was decanted. The settled sludge was used untreated in the first three tests and acidified in other tests. One hour after the sludge was acidified, most of it floated. This thick- ened sludge was run into a pressure tank, ready for pressing. In some experiments the sludge remained in the sludge tank over night, while in others it was used immediately. Conditions of Operation. The pressure was furnished by a duplex air compressor, three and a half bore by four inch stroke. Air was pumped to the steel pressure tank. The valve between the pressure tank and press was opened at the time of starting so that the pressure on the plates varied from zero to maximum. The press- ure was controlled by a waste air valve in the pressure tank. The rate of increase of the pressure on the plates varied from one-third of a pound to one and a fourth pounds per square inch per minute. Sometimes the pressure was allowed to remain on the plates after operation ceased, while at other times the pressure wras removed immediately and the press opened. In six of the tests leakage be- tween cloths at the periphery of adjacent plates limited the maximum 110 pressure. It required from three to four men to tighten the plates. The summary of the data collected at the press, and of the chemical results ,is given in Table XIX. TABLE XIX. FILTER PRESS EXPERIMENTS. July 8-25, 1921. No. of Test or Experiment. 2 3 4 5 6 7 8 9 10 Gallons sludge drawn from Tray 2 900 -925 gallons Settled sludge after iy2 hours 400 520 465 610 580 580 490 580 C.c. of H2SO4 per gal. sludge 1.5 1.5 1.9 2.0 1.7 0.6 0.7 Strength of acid.* Per cent 94 94 90 90 92 92 92 Hours of operation ll/2 2 1 5 2 2 2 2 2 Maximum rates of flow, 1 IV, 6 2.9 1.6 0.6 0.5 0.5 Minimum rates of flow, filtrate after iy2 hrs.. .75 0.7 0.5 0.7 0.6 0.3 0.3 0.3 0.3 No. of plates used 6 6 4 4 3 3 2 2 2 Maximum pressure at- tained, lbs. per sq. in. 85 80 65 110 75 55 50 50 65 Press feed—Moisture % 99.6 99.7 98.8 99.2 99.5 98.6 98.7 99.0 99.0 Press cake—Moisture % 91.2 92.3 90.1 92.5 89.9 87.6 89.5 92.6 90.0 Press filtrate—pH 6.4 6.4 4.8 4.4 5.0 5.8 5.2 Press filtrate — Turbid- ity (p.p.m.) 68 55 55 100 120 65 75 '110 90 Filter Cloth. No. 10 oz. duck filter cloths were used in all of the tests. Observation. 1. The rates of flow through the press were at a maximum when starting. (Generally when the pressure was below ten pounds.) After the first half hour of operation, the rate of flow7 rapidly approached the minimum rate as given in the tabulation. 2. The filtrate was clear until a pressure of about fifty pounds per square inch was reached, when the turbidity increased. 3. When opening press to examine the formation of cake, part of the contents was fluid enough to drop or splash out. 4. The thickest cake always formed in the last plate (farthest from inlet), while very little remained in the other plates. 5. The average thickness of the cake over the entire plates was from one-eighth to one-fourth of an inch; over one-half inch sludge cake was generally found at the periphery of all plates. The length of operation wms limited by the rapid decrease of filtration after the first one and a half hours. In some of the tests, the flow decreased to practically zero, even 'with continued increase of pressure. In test No. 5, after two hours, the rate of one-third of a gal]on per minute rapidly decreased to practically zero for the next three hours. Remarks. The slow rate of filtration was attributed to (a) the clogging of the pores of the filter cloth (b) the pressure on the cloths 111 forcing the cloth into the corrugations of the plate, thus preventing the filtrate from flowing down between the plate and cloth to the drip holes below. Two attempts were made to keep the cloth a little distance away from the corrugations by placing first, slats between the plate and cloth, and second, by a circular perforated disk of galvanized iron. (Refer to test No. 3.) In neither case was the effect of increasing the rate of filtration through the press, nor building up a better cake accomplished. OLIVER FILTER. Through the courtesy of the Oliver Filtration Company of New York, a laboratory type of continuous filter was at our disposal for a limited time, and some experiments on dehydration of activated Fig. 31 sludge were conducted early in January, 1921. The machine (Fig. 31) is described in their catalogs. “It consists of a drum or cylinder rotating on a horizontal axis with the lower portion submerged in a tank containing the material to be filtered. The surface of the drum is divided into compartments or sections, the dividing partitions being 112 parallel to the main shaft. These sections are covered with screen for supporting the filter medium which is held in place and protected from wear by a wire winding. Each of these sections of the drum is connected by means of pipes passing through a hollow trunnion to an automatic valve, which controls the application of the vacuum for forming and washing the cake and also for admission of air for dis- charging the cake. “A scraper is fitted across the face of the drum and rests against the wire winding in such a manner that the cake or residue is re- moved after being released by the air pressure. ’ ’ Other apparatus furnished by the Company were the vacuum pump, centrifugal pump, vacuum receiver and release valve, moisture trap and other small accessories. The experiments were confined to sludge previously prepared by secondary sedimentation. In some cases the sludge was acidified cold to a pH of 4.5 to 5.0, and in some cases ground rock phosphate was added. Sludge particles very quickly filled the pores and blinded the filter. Several screening mediums were tried but the same blind- ing resulted and in no case was a cake obtained. Part of the work was done with the co-operation of Mr. Tracy of the Oliver Company, who spent several days in our laboratory. CENTRIFUGE. In the latter part of December, 1920, a few experiments were made on reducing the water content of sludge as received from sec- ondary sedimentation with a centrifuge. The machinery used was a Tolhurst twelve-inch laboratory centrifuge, equipped with an imper- forated basket. The lip of this basket was one and a half inches deep. Vertical vanes attached to the periphery and extending almost to the edge of the lip prevented excessive slipping of the load with sudden change in speed. A speed of 1900 revolutions per minute was used. Sludge entered through a one-inch pipe, dropped to the bottom of the basket, and was thrown to the periphery by the centri- fugal force. This force caused the liquid sludge to stand in a vertical wall, the heavier sludge particles collecting on the outside of the wall and the clarified liquor or effluent on the inner side. After sludge had been added, sufficient to occupy all the space under the upper lip, any further addition caused clarified liquor to flow out over the top of the basket. It is apparent that this operation of the centrifuge is in the nature of a sedimentation process in which centrifugal force is sub- stituted for gravity. At the speed used, the centrifugal force was approximately 250 X gravity. The operation of the machine was 113 intermittent, the dewatered sludge being removed by hand. Running with a sufficiently low rate of feed to give a well clarified effluent did not produce a firm cake. By increasing the feed as suggested by Pro- fessor Bartow it was possible to obtain a cake of 85 per cent moisture, but the effluent contained a large amount of very light, fluffy sludge. At the high rate of feed the weight of cake appeared to be only 15 to 20 per cent of the solids in the sludge. BIBLIOGRAPHY. 1. Mohlman, F. W., and Bartow, E., The activated sludge method of se’wage treatment; Historical Review, Bull. 14, 77. 2. Dupre, A., and Dibdin, W. J., Report to Royal Commission on the Metropolitan sewage disposal; 2 (1SS4). 3. Clark, H. W., and Adams, G. O., Sewage treatment by aeration and contact in tanks containing layers of slate; Eng. Record, 69, 158 (1914). 4. Mason, W. P., and Hine, S. K., Note on the direct oxidation of organic matter in water, J. Ame’r. Chem. Soc., 14, 233-8 (1892). 5. Rafter, G. W., and Baker, M. N., Sewage disposal in the United States, 535, London (1894). 6. Fowler, G. J., Annual report of the Rivers Department of the Corporation of Manchester (1897). 7. Black, W. M., and Phelps, E. B., Report location of sewer outlets and dis- charge of sewage into New York Harbor, 64-78 (1911). 8. Clark, H. W., and Gage, S. DeM., The purification of sewage; Mass. State Board of Health, 45th Annual Report, 228-304 (1913). 9. Fowler, G. J., Annual report of the Rivers Department of the Corporation of Manchester (1897). 10. Ardern, E., and Lockett, W. T., Experiments on the oxidation of sewage with- out the aid of filters, J. Soc. Chem. Ind., 33, 523-39, 1122-4 (1914). 11. Bartow, E., and Mohlman, F. W., Purification of sewage by aeration in the presence of activated sludge, I and II; J. Ind. and Eng. Chem. 7, 318-23 (1915); 8, 15-16 (1916); Eng. News, 73, 647-8 (1915); 74, 1096-7 (1915); Eng. and Contracting, 43, 310 (1915); 44, 433-4 (1915); Eng. Record, 71, 421-2 (1915). 12. Bartow, E., Purification of sewage by aeration in the presence of activated sludge, III, J. Ind. and Eng. Chem., 9, 845-50. 13. Metcalf and Eddy, Sewerage and Sewage Disposal, Chap. XIV. 14. Coulter, W. S., Air diffusion in activated sludge, Eng. News-Record, 78, 255. 15. Brosius, A. M., Activated sludge novelties at Hermosa Beach, Cal., Eng. News-Record, 76, 890. 16. Orbison, R. V., Test of Trent activated sludge devices at Pasadena, Eng. Ndws-Record, 85, 1287. 17. Haworth, John, Report on sewage disposal at Sheffield, Eng. July, 1921. 18. “Simplex” sewage plants, The Surveyor, London, April ,21, 1922; Eng. and Contracting, 57, 527. 19. 'Hurd, C. H., Clarification and activation for Indianapolis se’wage, Eng. News- Record, 88, 484. 20. Ure, W. G., Large scale activated sludge plant at Woodstock, Ont., Can. Eng., 41, No. 5, 1, 7. 21. Burn, G. A. H., Intermittent aeration in activated sludge process, Can. Eng., 40, No. 24, 1. 22. Frank, L. C., Process of purifying sewage or other wastes, J. Soc. Che’m. Ind., 34, 680. 23. Martin, E. B., Method of and apparatus for the treatment and purification of sewage, J. Soc. Chem. Ind., 36, 160. 24. Hammond, G. T., The aeration and activation of sewage, Surveyor, 49, 255-7. 25. Moord, G., Sewage treatment, J. Soc. Chem. Ind., 37, 603 A. 114 26. Adams, S. H., Separation of sludge and scum from sewage and other liquids, J. Soc. Chem. Ind., 39, 581. 27. Pearse and Mohlman, Report to the Board of Trustees of the San. Dist. of Chicago, 1921, 39. 28. Me’tcalf and Eddy, Amer. Sewerage Practice, 3, 816. 29. Hatton, T. Chalkley, Activated sludge experiments at Milwaukee, Eng. News, 75, 306. 30. Revised report of committee on activated sludge proce'ss, Porter’s Bibliogra- phy, 1921, 5. 31. Herring, Rudolph, Fundamental principles of sewage purification on land, Eng. News, 61, No. 18, 493, 583, 605. 32. Dorr-Peck activated sludge proce'ss has been given up, Eng. News-Record, 83, 251. 33. Pearse, Langdon, Second report on industrial wastes from the stockyards and Packingtown in Chicago, 1921, 29. 34. Hatton, T. Chalkley, Conclusions on activated sludge process at Milwaukee, Eng. News-Re’cord, 79, No. 18, Nov. 1917, 840. 35. Russel, E. J., Soil conditions and plant growth, 4th ed., 1921. 36. Marshall, C. E., Microbiology, 3rd ed., 1921. 37. Robinson, R. H., and Tartar, H. V., The decomposition of protein substances through the action of bacteria, J. Biol. Chem., 30, 135. 38. Dakin, H. D., Oxidation and reduction in the animal body, J. Biol. Chem., 1908, 4, 63 (Longmans 1921). 39. Ehrlich, Paul, Zeitsch. Vere'in. Rubenzucker-Industrie, 1905, 539-567. 40. Marchal, Emile, Sur la production de 1’ ammoniaque dans le sol par les mi- crobes, Bull. Roy. Belgique, 1893, (3) XXV, 727-71. 41. Conn, H. J., Ammonification of manure in soils, N. Y. Tech. Bull., 67, 1919. 42. Waksman, S. A., Importance of mould action in the soil, Soil Sci., 1918, VI, 137-55 (Bibliography) Cultural studie’s of species of Actinomyces, Soil Sci., 1919, VIII, 71-207. 43 Waksman, S. A., and Curtis, R. E., Actinomyces in soil, Soil Sci., 1916, I, 99-134; 1918, VI, 309. 44. Doryland, C. J. T., The influence of energy material upon the relation of soil micro-organisms to soluble plant food, N. Dak. Agri. Expt. Sta. Bull., 1916, 116. 45. Chick, Harrietts, A study of the proce’ss of nitrification with reference to the purification of sewage, Proc. Roy. Soc., 1906, LXXVIII, 241-66. 46. Adney, W. E., App. VI to Fifth Report of Royal Commission on Sewage Dis- posal, 1908, 13-20. 47. Muntz, A., and Laine, E., Etudes sur les eaux d’ egout, Ann. Inst. Nat. Agronomique, 1907, VI, 15-143. 48. Scheringa, K., Relx of Cent. Lab. Publ. Health, Netherlands, 1920, U. S. P. H. Abstracts 22. 49. Koch, A., and Pettit, H., Uber den verschiedenen Verlauf der Denitrifikation im Boden und in Flussigkeiten, Centralbl. f. Bakteriol. Abt. II, 26, 335. 50. Doryland, C. J. T., Expt. Sta. Bull., 116, 1916. Voorhe’es and Lipman, New Jersey Agricultural Expt. Station, Bull. 221. 51. Fowler, C. J., The nitrogen in activated sludge, J. Indian Inst, of Sci., 3, 256-264. 52. Richards, E. H., and Sawyer, G. C., Further experiments with activated sludge, J. Soc. Chem. Ind., 41, 62T. 53. Buswell, A. M., Brehsky, A. A., and Neave, S. L., Chemical and biological reactions in the Dorr-Peck tank, Amer. Jour. Publ. Health, April, 1922. 54. Crawford, F. N., and Bartow, E., Composition of the effluent air from an activated sludge tank, J. Ind. and Eng. Chem., 8, No. 7, 646 (1916). 55. Richards, E. H., and Weeks, M. G., Straw filters for sewage' purification, J. Soc. Chem. Ind., 40, 252 R. 56. Hatton, T. Chalkley, and Copeland, W. R., Activated sludge defined, Eng. News, 75, 503. 57. Eddy, H. P., Lights and shadows of the activated sludge process for the’ treatment of sewage and industrial wastes, J. Western Soc. Eng., 26, 259. 115 58. Fowler, G. J., The activated sludge process: of seWage purification, J. Inst. San. Engrs., 20, 29-38. 59. Ardern, E., Second report on colloid chemistry, British Assoc, for Advance- ment of Sci., 88, 1918. 60. Clark, H. W., and Gage, S. DeM., 41th Annual Report State Board Health, Mass., 1912, 275. 61. Jone's, Jones and Atwood, British Patent No. 729. 62. Russell, R., and Bartow, E., Bacteriological study of sewage purification by aeration, 111. State Water Survey Bull., No. 13, 348. 63. Fowler, G. J., and Mumford, E. M., Conservation of nitrogen with special reference to activated sludge, J. Roy. San. Inst., 34, 467. 64. Purdy, W. C., Treatment of strawboard wastes, U. S. Pub. Health Service Bull., 97, 45. 65. Clark, H. W., 44th Annual Report of the State Board of Health, Mass., 1912, 292. 66. Bartow, E., Mohlman, F. W., and Smith, F., Purification of sewage by aera- tion in the presence of activated sludge, 111. State Water Sur. Bull., No. 13, 329. 67. Dienert, F., Activated sludge, Compte Rendu, 170, 762, 899; 173, 184. 68. CambitT, R., Purification of sewage with activated sludge, Compte Rendu, 170, 417, 681; 171, 57. 69. Courmont, Paul, The disappearance of pathogenic bacteria from sewage in the course of treatment. Compte Rendu, 170, 75, 976, 1134; 172, 1696. 70. Buswell, A. M. and Larson, C. C., Paper presented before Section C. of Amer. Assoc, for the Advancement of Sci., University of Chicago, Dec. 28, 1920. 71. Hatfield, W. D., The fertilizer value of activated sludge, 111. State Water Survey Bull., No. 16, 94. 72. Mohlman, F. W., The activated sludge method of sewage treatment, 111. State Water Survey Bull., No. 14, 75. 73. Clark, W. M. and Lubs, H. A., The colorimetric determination of hydrogen ion concentration and its application in bacteriology, J. of Bact., 1916, Pt. I, 1-35; Pt. II, 109-136; Pt. Ill, 191-236. 74. Loth, Jacques. The proteins and colloid chemistry, Science, Nov. 12, 1920. 75. Eng. and Contracting, 57, 35, No. 2 (1922). 116 APPENDIX. Sampling and Analytical Procedure. In general 250ec. samples of the unscreened sewage, screened sewage (tank influent), overflow from the first tank, effluent from the second tank (final effluent) and sludge as drawn were collected hourly by the attendant in charge of the plant. During the earlier part of the experiment samples of the sludge from the settling chamber were collected after drawing a tank of sludge. Other samples, as for example the contents of the aeration chamber and sludge in the peripheral down-cast wells were taken for special microscopic examination and tests on the volume of settleable solids, in accordance with the schedule posted from time to time. Changes in the method and manner of the collection of samples were given in the instruction sheets. The places at which the samples were taken are given in figure 8 and are also indicated on the detailed instructions for collection. The hourly samples were composited at the plant and preserved by the addition of from 5 to 10 cc. of chloroform. Eight of these hourly samples from a given place constituted a “shift composite” so named because they correspond to the three working shifts of the day which ran from 8:30 a. m. to 4:30 p. m.; from 4:30 p. m. to 12:30 a. m.; and from 12:30 a. m. to 8:30 a. m. During part of the experiment some of these samples were further composited in the laboratory before analysis. The procedure of analysis is given below and is also indicated in the tabulations. Samples of the effluent for methylene blue stability tests were taken at 8 :30 a. m., 4 :30 p. m. and 12 :00 a. m. and were transported to the laboratory for incubation. Settling tests to determine volume of sludge in the aeration chambers and in the peripheral downcast wells were taken from May 3 to December 30, 1921. Four daily samples were taken at 7 :00 a. m., 1 :00 p. m., 6 :00 p. m., and 12:00 a. m. in a liter cylinder and were by necessity settled out at the plant. The settleable solids were expressed as the per cent of the volume of sludge after settling for one hour. A number of tests on settling rates of sludges during the first hour were made from time to time. Schedule of Tests on Dorr-Peck Activated Sludge Process to De- termine (a) Nitrogen Balance or Fertilizer (b) Quality Effluent. December 18, 1920. 1. Sampling arrangements have been made to by-pass a small portion of effluent through the pump house. On the hour 250 cc. samples of effluent and screened sewage are to be added to the bottles designated for the effluent composite and influent composite. 117 Proceeding in this manner the composite sample of the influent and effluent is to be taken for each shift. A five-gallon sludge sample is to be taken from the sludge settling tank immediately after sludge is drawn, care being taken to see that it is thoroughly mixed. These samples will be trans- ported to the laboratory in the morning between nine and ten o’clock. A grab sample for methylene blue test is to be taken from the effluent from the second tank at 8.30 a. m. and 4:30 p. m. Methylene bine bottles are brought into the laboratory for incu- bation. Grab sample of overflow from tank No. 1 is to be taken between 11:00 and 12:00 o’clock and brought into the laboratory at noon. 2. ANALYSES. The two-day shift composites of effluent and influent respectively are to be composited in the laboratory. Samples actually analyzed will consist of: 1. Composite of influent for two day shifts. 2. Composite of influent for night shift. 3. Composite of effluent for two day shifts- 4. Composite of effluent for night shift. 5. Sludge sample. 6. 11:30 overflow sample from first tank. 7. Stability samples at 8 :30 a. m. and 4 :30 p. m. The determinations to be made are as follows: (a) First four samples determine free ammonia by distillation and organic nitro- gen by Kjeldahl process on residue from distillation; determine NO a -fNOi nitrogen by reduction method; determine turbidity, (b) Sample 5, sludge; determine solids settleable in one hour; de- termine free ammonia, organic nitrogen and nitrates-f-nitrites as outlined for samples one to four, on supernatant liquid; determine total organic nitrogen on the settled sludge; determine moisture in settled sludge. (c) On sample No. 6 the settleable solids are to be determined by Imhoff cone sedimentation and the turbidity is to be determinel on the supernatent liquid. (d) Stability of sample No. 7 is to be recorded according to Standard Methods. Schedule of Tests on Dorr-Peck Activated Sludge Process to Deter- mine Amount of Purification and Quality of Effluent with Varying Rates of Flow and Amount of Air. Beginning February 21st samples will be taken and analyzed as indicated below: Samples: A. Unscreened sewage: a composite to be taken for each shift. This composite is made up of 250 cc. hourly samples. B. Screened sewage: One composite for each shift, taken as above. 118 C. Effluent : composite for each shift taken as above. Stabil- ity samples at 8 :30 a. m., and 4:30 p. m. D. Overflow from tank No. 1 : liter sample to be taken at 12:00 p. m. E. Sludge: a composite sample of sludge to be taken at reg- ular intervals depending upon the rate of flow into the measuring tank. These samples will be transported to the laboratory between 8 and 9 o’clock in the morning. TESTS. Samples will be analyzed as follows: A. The settleable solids (cone) and turbidity on the super- natant liquid are to be determined on each of the shift composites on unscreened sewage. B. Screened sewage: Settleable solids and turbidity of the supernatant liquid are to be determined on each of the shift com- posites. After these tests are made the two day shift composites are to be composited and this composite sent through the “sanitary room.” The night shift composite is likewise to be sent through the “sanitary room.” C. Of the three effluent samples, the two day shifts com- posites are to be composited and sent through the “sanitary room.” The night shift composite is also to be sent through the “sanitary room.” The stability samples are to be transported to the labora- tory for incubation and observation. Samples of overflow from No. 1 are tested according to pre- vious directions. Schedule of Tests on Dorr-Peck Activated Sludge Process to Deter- mine Amount of Purification and Quality of Effluent with Varying Rates of Flow and Amount of Air. Beginning March 29 samples will be taken and analyzed as indicated below: A. Unscreened sewage: A composite will be taken for each shift. This composite is made np of 500 cc. hourly samples. B. Screened sewage: one composite for each shift, taken as above. C. Effluent: composite for each shift taken as above. Stabil- ity samples at 8 :30 a., m. and 4:30 p. m. These samples will be transported to the laboratory between 9:00 and 10:00 o’clock, and analyzed as follows: D. Overflow from tank No. 1 : sample to be collected at 5 :00 p. m. E. Sludge samples as before. TESTS: A. The settleable solids (cone) and turbidity on the super- Samples: 119 natant liquid are to be determined on each of the shift composites of unscreened sewage. B. Screened sewage: 100 cc. from each shift sample are to be taken to furnish a 300 cc. sample for T.O.N. Settleable solids and turbidity of the supernatant liquid are to be determined on each of the shift composites. After the operations are complete the two day shift composites are to be composited and this composite sent through the “sanitary room,” omitting residue and color. The night shift composite is likewise to be sent through the “sani- tary room.” Omit residue and color. C. 100 cc. from each shift sample are taken to furnish a 300 cc. sample for T.O.N. The two day shift composites are com- posited and sent through the sanitary room. The night shift com- posite is also sent through the “sanitary room.” The stability sam- ples are transported to the laboratory for incubation and obser- vation. D. Samples of overflow, 5:00 p. m. from No. 1 are tested according to previous directions. E. Sludge according to previous directions. Beginning with May 4, samples A, B, C, D, and E are to be collected and analyzed as given in the instruction sheet of March 29. A daily sample of the screenings from the Dorrco screen is to be collected and sent to the laboratory for moisture content de- termination. (This was only done from July 6 to August 18). Starting August 22, samples of the sludge in the aeration chamber and in peripheral wells of tank No. 2 are to be collected at 8 :30 a. m. and sent to the laboratory for total solids determina- tion. The overflow (sample D) collected at 8:00 p. m. is to be superceded by a twenty-four hour composite taken the same as samples A and B. All other samples were collected in accordance with previous instructions. Starting September 21 a twenty-four hour composite of the effluent and influent was to be made at the laboratory for analyses and raw sewage samples are to be discontinued. Determination of the total solids of the aeration chamber and tray sludge of both tanks are to be made on a daily composite collected at six-hour intervals. A 250 cc. sample of the aeration chamber content is to be collected at 8:00 a. m. and sent to the laboratory for micro- scopic examination. Another methylene blue sample is to be taken at 12 :00 a. m. Analytical Procedure. The determinations included settleable solids, (Imlioff cone), turbidity, oxygen consumed (KMn04), alka- linity, chlorides, total solids, free NI13, albuminoid N., total organic N, nitrites and nitrates. These determinations were made on all influent and effluent samples. Determinations for nitrogen and solids were made upon the sludge while those for settleable solids and turbidity were made on the unscreened sewage. The value of such tests as chlorides and alkalinity when ap- 120 plied to sewage analysis may be questioned. They were included principally to avoid changing the routine of our water analysis laboratory. Since The laboratory personnel was limited, since furthermore the experiment was concerned largely with determining two factors: first, the quality of the effluent of the Dorr-Peck tank, and second, the amount of nitrogen that could be recovered in solid form, it did not seem advisable to adopt as a routine the Gooch crucible deter- mination of filterable solids. We followed the analytical proced- ures given in the 1917 edition of Standard Methods of the American Public Health Association. 121 Influent Effluent ‘ Sludge g 0 p 2 O + *3 CD a> Z ►3 o O H3 o £ Tot. N Inf. N. g Q P 5! O + V H a> a> z HJ o O Tot. N. 0 55 Eff. N. Gallons Tot. Lb Date O 3 U2 o X w? 2 ■d 3 t"1 o' M Tot. O 3 w Z o X qq Z p.p.m r* o' M o g Lbs. g w r1 o' CO 'Z 12/18/20 . 57,480 33,360 64,440 33,360 . 68,780 34,480 . 66,800 .5 7 22 20 .2 5.2 27.2 25.9 .226 .215 12.96 7.16 56,586 33,360 .2 1 16.6 23.2 6 12.4 17.4 36.6 .1445 .308 8.16 10.15 900 1.699 12/19/20 ... .8 1 8 23.2 18 10 5.2 34.0 25.0 .282 .2037 18.21 6.96 63,540 33,360 .9 .1 18.4 45.6 6 5.2 25.3 31.8 .210 .264 13.34 8.80 900 i.734 12/20/20 ... 1.0 1 5 23.2 22 24 6 48.2 29.5 .400 .245 27.5 8.44 67,800 34.480 .75 .28 23 22 7.4 12 31.15 34.28 .258 .284 17.52 9.80 900 i.889 12/21/20 ... .5 33.6 10 12 46.1 18.0 .383 .1495 25.57 5.22 65,000 35,000 .22 23 17.2 8.4 6 31.62 23.7 .2625 .1965 16.15 6.88 i, 800 4.17 35,000 . 66,600 33 300 20.72 6.14 2,700 4.62 12/22/20 ... 2.0 3 3 24 16 42 16.0 .349 .1328 23.21 4.42 63,900 33,300 .5 20 12 18.6 10 39.1 22.2 .3245 .1842 10.35 6 84 2,700 3.819 12/23/20 . . . . 66^000 1.0 20 10 10 31.0 17.7 .257' .147 16.98 4.85 63,300 33,000 .3. J2 9.4 15.2 10 9.6 19.7 25.0 .1635 .207 33,000 . 66,600 33 000 10.81 6.18 4,500 9.19 12/24/20 ... 1.3 2.0 18 13.2 17.6 4.4 36.9 19.6 .306 .1626 20.4 5.37 62,100 33.000 .28 .2 13 16 7.69 6.4 20.97 22.6 .174 .1875 12/25/20 ... . 62^340 26 200 .8 1.8 22 17.2 14.8 5.6 37.6 24.6 .312 .204 19.45 5.34 57,840 26,200 .22 .4 15.6 18 9.2 6.4 25.0 24.8 .2075 .206 12.01 5.49 4,500 8.2ii 12/26/20 ... . 44,680 32 320 .7 1.8 23.2 13.6 14 4.8 37.9 20.2 .315 .1675 15.3 5.42 48.680 32.320 .24 .2 17 18 8 9.6 25.24 27.80 .2095 .2306 10.20 7.46 12/27/20 . .. . 48,000 .77 20 12 .5 21.27 16.16 .1765 .138 8.48 2.44 48.000 17.670 .26 .28 15.6 16 10.8 0 9 26.66 25.48 .221 .2115 10.62 3.74 17,670 .. 29,400 8.8 10 25.8 28.8 12/28/20 ... .68 21.2 11.2 33.08 .2557 29.400 12.4 21.50 . 1685 412 5.25 5 68 .26 13 800 12.4 17.2 30.2 .251 3.46 13,800 11.2 49.60 .330 .3599 12.22 7.22 12/29/20 .. . .. 37,000 20,180 50,150 .6 1 3 20.8 14 3.6 4.8 25.0 41.5 .2075 .345 7.68 6.96 37.000, 20.180 .54 .52 13.4 14 39.74 43.32 9 ’ 400 's’. ii5 12/30/20 .. . .36 21.2 13.6 .36 21.92 20.0 .182 .166 9.12 5.18 40,750 34,200 .28 .36 17 16 29 26.4 46.28 42.76 .384 .3555 15.65 12.15 34 200 12/31/20 ... . . 67,420 .4 19.6 20 40.0 .332 22.4 67,420 .3 18 10.2 28.50 28.60 .2368 .2375 15.96 7.99 33 640 1.6 9.2 5.6 16.4 .1363 4.58 33,640 .2 12.4 16 1/1/21 67,600 2.8 14.8 .8 18.40 .153 10.35 67,600 .91 9.4 9.6 19.91 .1651 11.17 5.88 33,400 7.7 8 - 2.0 17.7 .1470 4.91 33,400 3.6 9.6 8.0 21.20 .1760 NITROGEN BALANCE 12/18/20-2/18/21. APPENDIX I. 122 Influent Effluent Sludge S 2 o o o F o 3 g 2 O *1 n a> F o Tot H3 0 H P* Q £ Tot Date 0 £ o 3 00 + o a> 2 a o CK) 3 p p ■d 3 3 F cr N. Tot. Q p o 3 CO H” O z a o ■I g o V 2 F cr CO g o O 3 CO Lbs, SI \ § F 3 s F o' 2 • N) CO ; in fi7 710 2.0 4.8 18 11.2 7 2 27.20 19.60 .226 .163 15.31 67.710 3.5 13.2 5.2 21.90 .1820 12.3 32^090 3.6 5.22 32,090 .56 16.8 5.6 22.96 .1905 6.11 1/3/21 .. 59,300 3.5 13.2 5.2 21.90 .1820 10.80 57,670 2 18 2.4 20.60 .171 9.86 i, 630 i.7 34,700 4.4 10 4 18.40 .1529 5.30 34,700 .28 18 9.2 27.48 .228 7.91 1/4/21 65,850 8 24 12 36.80 .306 20.15 65.000 .4 20 2.6 23.0 .1910 12.44 850 32,400 3.6 12 6 21.60 .1795 5.81 32,400 .12 19.2 6 21.72 .1805 5.84 4.U7 1/5/21 66,000 6 23.2 1.2 30.4 .2525 16.65 63,240 .16 19 16 35.16 .292 18.47 2,760 33,000 2.8 12 6 20.8 .1725 5.70 33.000 .52 11.2 6 17.72 .1470 4.85 io! 6i 1/6/21 67,070 .52 12 16 28.52 .237 15.93 58.900 1.04 18.6 25 19.89 .1650 9.70 8, i.70 34,480 .52 11.2 6 17.72 .1472 5.38 34.480 .16 20.8 12 21.08 .175 6.03 "5! 8i7 1/7/21 66,020 .52 24 16 40.52 .3365 22.22 61.750 .16 18 11 29.16 .242 14.94 4,275 31,480 .88 16 .8 17.68 .1468 5.10 31.480 .4 18 1.2 19.6 .163 5.12 4,570 2! 63* 1/8/21 .. 57,880 .88 24 17.2 42.08 .349 20.20 53,310 .24 18.6 18.2 37.04 .3071 16.4 34.060 2.32 12 5.2 19.52 .1622 5.52 34,060 .36 20 8.8 29.16 .242 8.24 3,700 ’.’2535 1/9/21 66,700 .88 24 17.2 42.08 .349 23.3 63.000 .5 19 4.8 24.30 .202 12.72 1 /10/21 . . , . 33,300 2.4 18 5.2 25.6 .2125 7.04 33,300 .4 22 .4 26.4 .219 7.29 1/10/21 . . . . 67,700 .72 24 .2 24.92 .207 14.02 65.000 .18 21.2 21.8 43.18 .359 23.32 2.700 i. 702 36,000 2.4 14 22.0 .1825 6.58 36.000 .28 17.2 17.2 34.68 .2875 10.35 900 !56i 1/11/21 .... .. 61,800 .8 24 .4 25.2 .209 12.94 60,700 .48 13.6 14.2 27.98 .2321 14.1 1/12/21 34,000 . . 64,330 2.32 .28 14 24 .02 13.2 16.34 37.48 .1355 .311 4.61 20.0 34.000 64,330 .28 .24 19.2 19.4 5.2 5.14 24.68 24.78 .205 .2059 6.96 13.23 32,000 1. 18.8 .08 20.6 .171 5.47 32,000 .32 20 .20 20.60 .1713 5.48 1/13/21 . . 66,900 .32 20 13.2 33.52 .278 18.6 66.900 .38 28.8 18.6 47.78 .3135 20.95 34,000 1.6 17.2 6 24.80 .206 7.0 34,000 .12 18 22 40.12 .3335 11.4 22 8 19 2 42.50 .353 23.12 65,490 .28 20.4 6.8 27.48 .228 14.94 33,800 2 16 6 24. .1993 6.74 33,800 .48 22.8 .4 23.68 .196? 6.64 1/15/21 . . 71,400 .2 32 18 50.2 .417 29.8 71.400 .44 16 11.2 11.80 .098 6.99 34,800 60,000 1 16 28 8 25.0 .2078 7.22 34,800 .28 19.2 .4 19.88 .165 5.47 1/16/21 .52 18 46.52 .3865 23.2 60.000 .28 18 4 e). 22.48 .1866 11.2 31,000 2.2 18 4 24.20 .201 6.22 31,000 .28 22 18 40.28 .3304 10.36 NITROGEN BALANCE 12/18/20-2/18/21 APPENDIX I—Continued. 123 1/17/21 ... ... 52,000 .28 28 1 29.28 .243 12.65 52,000 .3 20 15 35.3 .293 15.25 24,000 1 16 2.8 19.80 .1644 3.95 24,000 .28 24 18 25.08 .208 4.99 1/18/21 ... ... 49,000 . .2 28 16 44.20 .367 18.0 49,000 .2 20 13 33.20 .276 13.51 25,800 1 18 6 25.0 .2075 5.36 25,800 .2 22 26 48.20 .400 10.32 1/19/21 ... .. 49,700 .52 28 18 46.52 .387 18.95 49,700 .24 19 15 34.24 .2422 12.05 21,600 1.8 16 8 25.80 .2142 4.63 21,600 .2 20 20 40.20 .3325 7.18 1/20/21 . .. ... 43,400 .52 24 4 28.52 .237 10.78 43,400 .26 19 17 36.26 .301 13.05 23,000 1.2 18 8 27.20 .226 5.2 23,000 .28 20 14 34.28 .2845 6.54 1/21/21 . .. . .. 48,200 .4 24 12 36.40 .304 14.56 48,200 .32 19 16 35.32 .2935 14.15 24,500 2.4 12 6 20.40 .1695 4.15 24,500 .2 18 4 22.20 .1845 4.52 1/22/21 ... ... 52,700 .52 22 18 40.52 .2365 17.75 52,700 .54 16 12 28.54 .237 12.50 29,000 2.4 16 2.8 21.20 .176 5.11 29,000 .28 18 16 34.28 .2843 8.25 1/23/21 ... .. . 57,700 1 24 12 37 .307 17.72 57.700 .36 18 9.4 27.76 .2307 13.30 29,000 4.8 16 5.2 26 .216 6.26 29,000 .52 20 10 30.52 .2535 7.21 1/24/21 ... ... 58,000 6 22 18 40.6 .337 19.55 58.000 .17 21 6.6 28.30 .235 13.64 28,000 3.6 12 6 21.6 .1795 5.02 28.000 .2 18 12 30.20 .2508 7.02 1/25/21 ... ... 58.600 .92 24 14 38.92 .323 18.95 58.600 3.4 17 17 37.40 .3102 18.20 29,000 2.4 16 5.2 23.60 .196 '5.69 29.000 .2 18 14 32.20 .2672 7.75 1/26/21 ... . .. 58,300 .92 24 14 38.92 .323 18.85 58.300 .2 17 11 28.20 .2341 13.65 29,000 3.6 14 6 23.60 .196 5.69 29.000 .32 18 16 34.32 .285 8.26 1/27/21 ... ... 56.300 .8 18 12 30.80 .2557 14.4 56.300 .4 16 19 35.40 .294 16.55 28,700 1.4 20 10 31.40 .261 7.48 28,700 .4 20 18 38.40 .319 9.15 1/28/21 ... ... 58,000 1.2 24 13.2 28.20 .234 13.57 58,000 .36 17.6 11.4 29.36 .244 14.14 28,400 2.32 14 14 30.32 .252 7.16 28.400 .4 20 16 36.40 .3041 8.58 1/29/21 ... . .. 52,000 .8 23.2 13.1 37.1 .308 16.01 52,000 .23 11 11 45.20 .3755 19.55 29,000 4.8 10 16 30.8 . 356 7.42 29,000 .32 16.8 14 31.12 .2582 7.49 1/30/21 ... ... 57,300 2.32 20 8 30.22 .252 14.45 57.300 .5 14.4 10 24.90 .207 11.85 27,000 6.4 9.2 3.6 19.20 .1595 4.31 27,000 ..52 14 15.5 30.02 .2497 6.74 1/31/21 ... . .. 58,400 1.2 20 14.8 36.0 .299 17.46 58.400 1.16 16.6 15 32.76 .2.72 15.89 28,800 6.4 12 5.2 23.60 .196 5.64 28.800 .2 12 12.8 25.0 .2077 5.98 2/1/21 . .. 56.700 1.4 22.8 10 34.20 .284 16.11 54,900 .24 13.4 15 28.64 .238 13.06 1,825 2.734 29.000 4.4 10 5.2 19.60 .1627 4.72 29,000 .28 14 18 32.28 .268 7.76 2/2/21 ... 58,000 1 23.2 20 44.20 .367 21.3 58.000 .2 14.6 18 32.80 .2726 15.91 29,000 2.4 16 9.2 27.60 .229 6.64 29.000 .2 15.2 14 29.40 .2441 7.08 2/3/21 .... . . . 58,000 1.4 20 14 35.40 .294 17.05 55,300 .24 14 12 26.24 .218 12.06 2,700 2.85 29,000 4 14 6 24. .1994 5.78 29,000 .2 14 14 28.20 .2341 6.79 2/4/21 . .. 54,800 1 20 10 31. .2573 14.11 50,300 .24 13 15 28.24 .2345 11.8 4,550 5.00 29,000 4 12 8 24. .1993 5.78 29,000 .2 14 14 28.20 .234 6.78 2/5/21 ... 56,000 .6 18 14 32.60 .2705 15.15 53.200 .34 12 10.6 22.94 .2421 12.94 2,800 1.53 28,000 2 12 7.2 21.20 .176 4.93 28,000 .2 14 10 24.20 .201 5.62 2/6/21 . . . 58,000 i 20 12 33 .274 15.9 57.100 .4 15 14.4 29.80 .2475 14.12 900 1.261 29,000 2.4 14 8 24.40 .203 5.88 29.000 .28 18 8 26.28 .2180 6.33 2/7/21 ... 57,000 1.2 16. 6 23.2 .1926 10.98 57,000 4.4 20 16.6 41.0 .3401 19.4 28,000 4.8 8 8.4 17.60 .1461 4.09 28,000 .2 18 8 26.20 .2175 6.45 2/8/21 .... .. 57,500 1 24 20 35 .291 16.72 55,650 3.4 16 13 32.4 .2691 15.00 1,850 7.22 28,500 3.2 14 6 23.20 .1926 5.49 28.500 .28 14 8 22.28 .185 5.27 124 Influent Effluent Sludge g 2 a ►3 b-1 g 3 a ►3 a G h3 G s» o 3 o a> o 0 o Q P o 0 o o a P o Date + 5! O a> 3 a o -! an? p p ts z a z o + 3 o a a O -S T5 a « a a a o 3 Ul o' M a 3 CQ a Ui Ul \ g F cr 3 g a qq a : • qq W 2/9/21 .. 56,650 1 24 16 41.0 .3405 19.32 53,000 .26 17 14 31.26 .2595 13.76 3,650 5.75 29,000 4 10 5.2 19.20 .1595 4.62 29,000 .04 16 8 24.04 . 2000 5.8 2/10/21 .. 58,600 1.2 22 14 37.20 .309 18.12 54,000 23». 4 16 14 53.40 .441 23.8 4,600 10.46 29,000 4 12 8 24.0 .1992 5.78 29,000 .12 14 10 24.12 .2005 5.81 2/11/21 .... . . 58,000 1 22 14 37.0 .3074 17.85 000 .44 16 16 32.44 .2695 15.63 29,000 4.8 16 6 26.80 .2225 6.45 29,000 .28 18 10 28.28 .235 6.8 2/12/21 .... .. 55,000 1 20 14 35.0 .2905 15.98 55,000 .4 17 17 34.40 .2856 15.71 28,000 2.4 16 6 24.4 .1995 5.08 28,000 .2 18 12 30.20 .2517 7.01 2/13/21 58,000 1 20 12 33 22.40 .2740 15.90 58,000 .4 17 14 31.40 .2508 15 11 29,000 2.4 14 6 .1860 5'. 40 29,000 .28 20 8 28.28 .235 6.81 2/14/21 .. 57,700 .6 20 12 32.60 .2708 15.62 57,500 .5 20 15 35.50 .295 16.97 29,000 2.4 10 5.2 17.60 .1461 4.24 29.000 .2 19.2 8 27.40 .2275 6.6 2/15/21 57,700 .4 22 14 36.40 .302 17.42 55,850 29.900 2.8 15 14 31.80 .264 14.76 1,850 .8685 29,900 2.2 12 5.2 19.40 .1611 4.82 .12 16 10 26.12 .217 6.49 2/16/21 .. 59,000 .6 24 16 30.60 .254 15.00 59,000 .16 18 12 30.16 .2505 14.76 29,000 4.8 14 5.2 24.0 .241 6.98 29,000 .28 16 10 26.28 .218 6.31 2/17/21 . 57,200 00 24 14 38.6 .323 18.46 55,400 .12 15 10 25.12 .2086 11.85 1.850 1.266 30,000 2.4 14 5.2 21.6 .1794 5.38 30,000 .28 18 8 26.28 .2181 6.54 2/18/21 ... . . . 58,000 .56 24 14 38.56 .3202 18.6 55.200 .24 15.6 8 23.84 .1971 10.89 2,775 1.56 29,200 3.2 12 5.2 20.4 .1694 4.95 29,200 .20 18 10 28.2 .234 6.84 Totals. . . .5,556,310 1,423.83 5.468,810 1. 417.81 87,205 85.66 NITROGEN BALANCE 12/18/20-2/18/21 APPENDIX I—Continued. Net Loss N2 = 0.43%. 125 Period 0 0 Turbidity t? H Oxygen Consumed S' H Alkalinity a H £ Residue 5* H $ Free NH3 s* a & Albumined NHa a h $ M 3 T. O. M M. p CD p to a c 3 as a ps at as at as a as a r* r8 a M» as a <5 < < Tank No. 2 Screened Sewage Per cent Settle- able Solids. OwSSmSSoSKE Infl. Turbidity SSSSSsSiaSsI Effl. cent Removal bboococobcHCocoaow SSsSSSSStSSS Infl. Oxygen Consumed sggggggsisss CO Efifi. ggsgsssssisfc Per cent Removal MOWCCOCHOCOOC5K Inti. Alkalinity mmmmm S3 Efifi. 1M M M M M !*■ Per cent Removal 948 957 1012 883 925 906 980 914 912 960 940 Infl. Residue on Evap. ISliSIsi; ii Efifi. C -1 OX o Per cent Removal Date. Fref Ammonia Ammon'a Albuminoid Total Organic Nitrogen Nitrates Nitrites Effluent Stability, Days Influent Chlorides P. P. M. May Inn. Effi. Per cent Removal Inn. E a Per cent Removal Infl. s a Per cent Removal Inti. Effi. a P % o u « • a> d Effi. Per cent Removal 3. .. 1 1 4 10.7 10.2 4.7 4 5 3. Si 15.6 11.2 7.2 .35.6 4.1 3.2 21.9 .59 2.0 68 7 4 29.5 4.4 2 8 30.3 10.0 6.0 40.0 3.7 2.8 24.3 .59 .60 74 0 15.1 71.0 2.3 2.5 1. 8.8 8.0 9.1 2.3 2.1 8.7 .53 .54 67 7 11.2 9.0 14.3 3.3 1 2i 63.5 10.0 6.0 40.0 2.3 1.8 21.7 .56 .40 28.5 67 8 10.0 11.1 3.2 1.2 | 62.5 8.0 2.8 4.3 1.5 65.0 .47 14.5 69 9 11.7 12.3 0.3 1 .2 1 81 .0 io.o 4.0 60.0 3.3 2.0 39.3 .52 .25 51.9 5 82 10 15.2 11.3 25.7| 3.9 1.21 69.2 11.2 2.8 75.0 1.9 1.0 47.3 .56 .26 53.4 7 101 11 14.1 13.4 5.01 2.4 1.8] 25.0 8.8 4.0 54.5 1 .8 1 .0 44.3 .28 .27 3.6 79 12 12.0 15.2 4.1 2.31 43.8 8.0 4.0 51.0 2.8 1.1 00.1 .28 .16 42.8 10 77 13 13.7 14.7 1 2 1.5!. 10.0 3.2 68.0 2.3 78.2 .28 .10 64.2 4 116 Ave 12.5 17.6 (—40.8)1 3.6 1 1 .91 1 47.3 9.6 4.8 50.0 2.9 1.6 44.8 ■ .47 .36 23.4 6.51 88 i TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—MAY 3-13—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—MAY 3-13. Remarks: May 3rd, plant started up 10 P. M. May 12tU to 13th, inclusive, air leak. No. 2 Tank. 127 May Date. ljlllllll Total Flow Gal. Champaign Sewage. 883S32S89&8 -i mVw© 8§8§§88§5 Test Plant Feed. nmnm Cu. Ft. Gal. h 882222Sgg Per cent to No. 1 Tank. Tank No. 1. Sfl 111 £88g2gB£B Tank No. 2. S28gS£gg3 Screened Sewage, Per cent. III Infl. Turbidity. s8?o8ioiii’8ii Effl. 8§gS3?i§^ »eiex9 May Date. -i o -I -i ~ c* oocomro^^ocM Infl. Free Ammonia. cjS^SSiSiSm^ -iWOQOtCDMOM Effl. •MM • • M -a • O M 00 • • CN oc © ■ to © © • • w Removal. Removal. MMMtOCOCiOlMW 45®WOl®©-JG0© Infl. Albuminoid Ammonia. ©®WO«tO£n-4WtO Effl. 66.6 72.8 70.1 75.0 60.2 40.0 48.8 50.0 63.6 Per cent Removal. ©OCCOOHO'/lO (io baoboiooob Infl. Total Organic Nitrogen. 45. 01 Cl IO to 0*-11 os Ot O' io 10 X CC O IO ® to Effl. SSfeggfcfcgg t0®000®4500© Per cent Removal. IOmmwMIOWMM mwmoojomm® Infl. Nitrates. 0®0©©®©0© io -i m w ro w io -i Infl. SSSSSSSS3 wuoooobowbcb Per cent Removal. tSSSSSSfegS Infl. Nitrites. 3S§^SSi?£i Effl. sissssggg ctfobwoxiooa) Per cent Removal. M . ’ W M M M |0 W bo- • Influent Stability, Days. 77 72 77 09 100 110 111 120 96 Influent Chlorides, P. P. M. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—MAY 14-21—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DI Tl ON S—M AY 14-21. 128 Date. Champaign Sewage. Air Used. Fer cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. May Total Flow Gal. Test Plant Feed. Cu. Ft. Gal. Per cent to No. 1 Tank. Tank No. 1. Tank No. 2. Screened Sewage, Infl. Effl. Per cent Removal. InB. Effl. Per cent Removal. Ina. Effl. Per cent Removal. InB. Effl. Per cent Removal. 22 1,043,000 87,830 .660 67 .31 229 133 41.9 57 40 29.8 440 466 1106 1036 6.3 . 23 1,104,000 57 37 61 .33 163 24 1,468,000 52 79 86 .32 182 25 2,150,000 89.000 .740 63 90 77 .41 337 75 . 77.6 55 31 25.4 296 399 1080 775 28.2 26 2,544,000 88,700 .745 60 70 72 .14 173 25 85.6 32 30 6.7 237 262 948 821 13.4 27 2,453,000 88,700 .740 60 73 82 .16 162 17 89.5 30 30 0.0 285 304 918 823 10.4 28 2,185,000 87,700 .740 65 63 62 .18 180 29 83.8 43 29 32.6 327 345 933 832 29 2,082,000 89,200 .725 65 59 33 .22 170 35 79 5 42 23 45 323 922 82.3 7 8 30 2,117,003 89,500 .735 64 33 .14 180 25 86.0 36 23 36.2 349 368 908 9.3 31 2,130,000 89,200 .735 65 70 32 .22 190 20 89.5 43 25 41.8 365 388 886 747 15.7 June 1. 2,131,000 87,100 .735 64 69 60 .23 220 19 91 .2 40 26 35.0 372 393 882 772 12.4 Ave... 1,951,000 88,500 .730 61.7 66.5 59.8 .24 199 42 78.9 42 28.6 31.9 333 365 T—9.8)| 962 1 856 11.1 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Influent Stability, Days. Influent Chlorides, P. P. M. May Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. d Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. 22 18.5 20.0 3.9 ! 2.4) 38.4 12.0 12.0 1 7 0.1 94.1 0.16 0.0 100.0 142 23 24 13.1 11.6 11.4 9 a 3 21 10 0 5 21 93.8 26 5.3 3.8 28.3 1.41 0.91 35.7 4.0 2.8 30.0 14.6 9.3 36.3 3 69 27 7.2 6.4 11.2 1 .7 1 .2 29.4 4.0 2.8 30.0 10.0 10.7 28 7.2 9.4 n.fti 05 | 44.3 5.6 4.0 28 6 7 3 29 7.6 9.6 1.9 0.7 1 63.1 0.0 2.8 53.3 8.0 4^7 41.3 1.80| 0.82 55.61 3 76 7.8 9.6 1.2| 0.41 66.8 6.0 2.8 53.3 4.3 1.6 62.8 1.171 0.93 25.0! 10 80 31 7.8 10.0 2 3| 1 2' 47 8 8 0 4 0 June 1 8.9 9.8 2.5I 0.9| 63.9 8.0 2.8 65.0 4.0 1.01 75.0 0.321 O’. 03 90.5 2 79 Ave 9.3 10.0 (—8.1) 2.0! 1.3! 1 1 36.8 7.1 4.4 38.3 6.4 3.9 38.8 0.82 0.76 7.3| 5.4 1 85 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—MAY 22-JUNE 1—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—MAY 22-JUNE 1. Remarks: May 22, trouble with blower; May 23 and 24, Tank No 2 Septic—aerated 24 hours without feed. 129 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. June Total Flow Gal. Test Plant Feed. Cn. Ft. Gal. Per cent to No. 1 Tank. Tank No. 1. Tank No. 2. Screened Sewage, Infl. i Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Removal. Per cent 2 2,056,000 93,800 .700 64 65 66 .22 163 9 94.4 49 24 51.0 381 386 990 772 22.1 3 1,900,000 96,000 .69 > 64 60 67 .19 183 12 93.3 51 28 45.2 387 391 860 857 0.4 4 1,778,000 94,600 .700 63 56 66 .21 180 13 92.8 48 29 39.6 386 397 978 826 15.5 5 1,630,000 94,410 .710 65 51 68 .18 170 2.3 86.2 57 29 49.2 380 395 964 792 17.8 6 1,660,000 96,300 . 680 63 49 57 .34 189 62 67.2 60 37 38.3 367 410 1013 1018 7 1,580,000 95,600 .670 62 41 59 .23 180 32 82.0 57 28 » 50.8 397 412 884 776 12.1 8 1,392,010 91,500 .690 62 37 54 .23 152 5.3 65.2 45 29 35.6 399 412 1036 805 22.3 9 1,370.000 96,400 .670 61 41 61 .27 9.99 23 89.6 49 29 40.7 391 406 929 773 16.8 10 1,290,000 94,200 .680 61 39 69 .23 173 39 77.5 55 31 43.7 411 415 1000 764 23.6 11 1,282,000 92,810 .700 61 41 67 .31 250 4.3 82.5 46 27 41 .3 398 .398 967 727 24.9 12 1,103,000 94,000 .690 62 34 59 .16 180 29 83.8 53 25 52.8 405 416 912 776 14.9 13 1,122,000 92,200 . 700 61 29 48 .26 939 53 77.9 55 33 40.0 431 449 1094 935 14.6 14 1,136,010 62,300 1.040 63 25 50 .19 26.3 77 70.6 67 .39 41.8 432 407 5.8 1019 973 4.5 1,145,000 86,000 .730 64 30 49 .26 267 73 72.8 67 3.3 50.7 44.3 449 1001 852 14 8 Ave... 1,460,000 93,600 .720 62.4 43 60 .23 201 38 80.5 54 30 44.5 401 410 (—2.4) 903 817 9.5 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. June Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. 2 7.6 9.6 0.7 53.2 10.0 2.8 72.0! 3.6 0.1 88.9 0.20 0.02 90.0 5 127 3 8.6 9.7 2.9 1.6 44.8 8.8 2.8 68.21 4.0 0.2 94.8 0.44 0.02 95.4 10 89 4 ii.i 10.7 3.6 2.3 1.6 30.4 7.2 2.8 61.1 2.1 0.2 90.3 0.39 0.13 66.7 10 82 5 11.8 10.2 13.6 3.7 1.3 64.8 10.0 5.2 48.0| 2.8 0.' 85.6 0.30 0.11 63.3 79 6 9 3 10 7 1.8 2.5 12.0 12.0 1.5 0.2 86.7 0.23 0.06 73. S 97 7 10.6 9.4 11.3 2.4 1.1 54.2 10.0 4.0| 60.0 2.5 0.1 95.8 0.23 0.02 91.2 4 81 8 12.1 8.6 28.8 4.3 1.5 64.9 10.0 5.2 48.01 2.2 0.1 95.4 0.23 0.00 100.0 6 135 9 11.3 9.8 13.2 5.3| 1.1 79.2 9.6 5.2| 45.8| 2.9 0.2 93.1 0.17 0.00 100.c 3 103 10 13.7 9.6 29.8 4.71 2.0 57.3 10.0 5.2| 48.01 1.6 o.: 81.2 0.17 0.00 100.0 4 160 11 15.6 8 71 44.2 5 2 1.7! 67.3 12.C 20.01. 1.3 0.4 69.2 0.1C 0.04 100. c 3 97 12 14 2 12 2 14 ll 3.91 1.21 69.1 14.0 18.0!. 1.9 0.1 94.8 0.13 0.00 100.0 98 13 14.2 11.3 20.4 4.4| 2.31 47.7 10.0 6.0! 40.0 1.3 0.2 84.6 0.11 0.00 100.0 3 185 14 15.6 7.8 50.0 5.3! 2.Ot 62.2 10. t 8.0| 20. o| 1.3 0.1 92.1 0.13 0.00 100.c 1 109 15 17.0 12.5 26.4 6.01 1.3 78.3 14.C 6.01 57.1 1.5 0.1 93.1 0.11 0.01 90.9 3 117 Ave 12.3 10.0 18.7 3.8! 1.61 59.0 1 1 11.1 6.8' ! 38.71 1 2.2 0.2 90.9 0.20 0.03 85.0 4.8 111 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—JUNE 2-15—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DI Tl ON S—J U N E 2-15. Remarks: June 3, 4, 5, 6 and 14, air leak, No. 2 Tank. 130 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. AlkaCnity. Residue on Evap. £ o d C4 o a mi d ■e .. r t—i 1 &H £ c tx 2/ P 0> > § t P > sg 0) a DC S o *3 5 £ £ s- d d “I a- 0/ d d Ss d d u d d 1% . *“3 f-fc. 6c c-fc H H XX cu H Cl, a M W 0-i CC £ H cl, si M W 16 1,219.00 > 96,700 .660 64 32 48 .24 237 67 71 .8 72 37 48.4 453 444 1.9 988 875 11.4 17 1,040,000 87,500 .720 68 30 51 .30 259 67 74.1 59 29 .50.8 435 443 998 860 13.8 18 U002.000 89,200 .71 l 66 22 39 .28 263 87 66.9 46 33 28.2 431 430 0.2 952 19 900,000 88,100 .730 64 23 29 .20 267 110 58.8 68 36 47.1 435 435 0.0 882 990 20 l,182,000i 87,200 .730 64 22 33 .39 297 133 55.2 66 47 28.8 441 450 978 940 3.9 21 1,057,000 85,500 . 750 66 23 36 .25 277 113 59.1 65 15.4 437 4.5 840 900 22 i;w4;ooo 87'000 .730 64 24 36 .29 303 153 49.4 81 54 33.4 461 462 1127 2075 23 1,045,000 84,700 .750 63 25 20 .47 223 103 53.7 62 40 35.5 444 460 978 900 8.0 24 994,000 88.700 .720 63 21 37 .23 230 140 39.2 55 39 29.1 467 463 0.9 968 964 0.4 25 945,000 85,900 .740 64 23 36 .45 253 126 50.1 69 43 37.7 431 456 105S 950 10.2 26 802,000 84,500 .750 63 25 36 28 257 107 58.2 68 45 33 8 440 451 976 960 1.6 27 959,000 87,000 .730 64 27 36 .31 287 123 56.9 71 40 43.7 453 453 0.0 1068 960 10.0 28 990,000 86,900 .730 64 32 38 .20 267 75 71.81 59 40 32.2 4.35 420 3.4 1068 788 28.0 29 925,000 88,200 .720 60 30 .35 .28 187 160 14.41 53 41 22.6 451 448 0.8 978 1050 30 850,000 87.40C .730 61 24 41 .24 129 147 S3 73 12.4 471 451 4.2 1052 999 K 0 Ave... 997,000 87,600 .726 64 25.6 36 .39 249 114 54.2 65 1 43.5 30.1 443 442 0.3 991.3 1011 (—1.9) TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—J U N E 16-30. 131 CO to tO tO tO tC tO tO tO tC tsC >-1 M *-* o . June • Date. CD GO 05 CD o CJi *1 05 C'» -I C'l C« 4- Ot Cl -l Illfl. Free Ammonia. 10.3 10.0 10.8 10.8 13.5 10.1 12.8 14.1 13.1 15.0 15.6 16.2 11.0 15.7 15.4 Vi. 9 Effl. tCWMWMWHHM tO CO M CO CO to CO CC tO Ot 4-* C5 tO 4- Ot CD 4- C5 4- tO 05 CO ro 05 to ch -i co cd to m cm m o:cd 05 Per cent Removal. 4- CO CO 4- CO 4- CO 4- 4- 05 10 CTt O'l tO C5 4- 05 CO 4- -1 X CO 4- 4*. Ol CD 00 0500 O CM Infl. Albuminoid Ammonia. CO CO 'C0C0C04^C04*.tO4^COtOtOtO 4- CM -1 tO 4- CD —i CO H-* CM CO C 4- +* IO Effl. 51.2 60.0 17.3 46.3 18.8 13.8 36.8 25.0 6.8 18.8 8.1 27.2 2.8 22.7 Per cent Removal. to 4* O -- -• t0> c; O OCC00 4- to M to to *jto6obbb©bcbooM(»o Infl. Total Organic Nitrogen. to tO H4M4H4H"1 W4*IOO005 05t0OXHt0OGCOG0 MOOOOOCOOOtOO.P coo Effl. i - CO'***- • 4-4 t—* to to CO • O • O • • • • O O • 4*- 05 X f—4 CO wO- X* • • • © © • CO •>$ 05 QO CO Per cent Removal. b^xcocjbojoci-^H^toototo Infl. Nitrites. OOOOOOOOOOOOOOOO tOCOtO-‘4-COCOMMCOi--tO^*r-itOtO Effl. oo^^ocoHccoco^xceoooxx © X CM 10 CO © © (X X tv CM r-4 <—1 X CO CO O^OtOWOOOOOOGCwOibtOtO Per cent Removal. ooooobcooooooobo 05 05 50 CM © 05 CD N-4 © *5 X X Effl. Nitrates. oooooocooooooooo oooboboooobbbboo Effl. 100 100 100 100 100 100 ioo 100 1(K) 100 100 100 100 100 100 100 Per cent Removal. Effluent Stability, Days. 1—i M M *—1IU“1 —4 ‘--i1 >—4 i—i t—iip-1 M M MtCHMMtC^lCtOtCtC^^^-^H oo^cocMOcDXco^r^cc^-^icMtotc Influent Chlorides, P. P. M. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—J U N E 16-30—Continued. Remarks: June 10 to July 10, inclusive—Sludge allowed to overflow with effluent 132 July Date. 886,000 956,00) 757,000 752,000 857,000 1,195,000 976,00) 1,046,000 867.000 755,000 904.700 • Total Flow Gal. Champaign Sewage. 1 84,000 85.700 86,200 88,600 66.700 85,100 87.700 88,900 86,400 88.700 84,800 Total Flow Feed, Gal. Cu. Ft. Gal. Air Used. .860 .840 .830 .810 .820 .870 .830 .830 850 .830 ,840 Per cent to No. 1 Tank. 19 25 25.5 22 22.5 21.5 17 20.5 26 19 21.8 Tank No. 1. Per cent Sludge by Vol. Cl Cl Cl Cl Cl Cl Tank No. 2. Screened Sewage, Per cent. Settle able Solids. “infills! Infl. Turbidity. Effl. ssfcgfessgs Per cent Removal. h-* to • co co a © © a Inti. Oxygen Consumed. Effl. Per cent Removal. M CO • HWOOW^ isiiii nm Infl. Alkalinity. iiiiiiiiiia Effl. O • • 00 • H* • to Per cent Removal. to- COO- • CO- M- 00 965 928 1099 985 1183 910 985 924 880 998 986 Infl. Residue on Evap. iiiiliiiii Effl. O - • to CO • tfk. • 00 to Per cent Removal. 0C • • CD 05 • CD • 7 8 9 10 Ave 1 2 3 4 5 6 July Date. MMMHH 05 CD 05 t0 4“ wowioo 18.0 15.1 16.9 19.4 17.0 Infl. Free Ammonia. H-4MH-IMMMI—‘MMMM Effl. 28.6 22.5 11.2 4.7 18.8 to to I-1 M 00 CO-100 00 to 05 CO CO Per cent Removal. 4»- CO tO CH -1 ?0 M 50 OX 05 4* 4* Infl. Albuminoid Ammonia. 4>*CJX-lC04».4^C04>-C0t0C0 CO-14^K*-14^GC~14>-:OtO Effl. 27.2 34.1 47.7 0.0 26.9 0.0 4.4 Per cent Removal. WOoE3a>004^^GC^C5 4* Infl. Total Organic Nitrogen. OQoMOCi^^HOCO Effl. T: : : to * • * • • o • to • o * o x GO • Per cent Removal Infl. Nitrates OOOPOMOOOOO 054*>co^-JO^i05aooxo5 OOqOOOOOOOO WM|0)-^tO^Mt5COM4^ Effl. Ol C3X CO • M © OX 05 tO O CO OOw 4f- O 35 tO O CO Per cent Removal. Infl. Nitrites. O O o o o ox co ro oo 05 boooo CO 05 Ox 05 05 OOOOOOOOOOO OOqOMOOOOOO Effl. i 83.3 1 100 I 100 I 100 I 98.2 100 100 100 100 100 Per cent Removal. Effluent Stability, Days. 1 115 1 121 1 128 1 128 1 101.3 1 1 M 1—1 r-* 4- CO 00 to IO 05' 00 -1 © Influent Chlorides, Influent TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—JULY 1 -10—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CO N DI Tl ONS—J U LY 1-10. Remarks: July 10—Rakes catching on tray—shut down for repairs. 133 July Date. 790,000 844,000 761,000 1,152,000 852,000 814,000 818,000 818,000 818,000 685,000 841,000 833,000 1,140,000 1,100,000 943,000 880,000 711,000 876,000 Total Flow Gal. • 5 P ■a 07,300 86,70 > 86,800 85.400 88,600 87,000 85.800 87.800 83,700 89.500 72.500 48.600 64.600 74.800 74.400 76,100 74,400 78.600 Test- Plant Feed, Gal. ?! iiiiiiiiiiieiiiiii Cu. Ft. Gal. Air Used. 8SSS2SS228gS Per cent to No. 1 Tank. at at at Tank No. 1. *P?? &8S&S3S83588SSSSS: at at at at at at at* Tank No. 2. lf| BSSSSSSSKSSSSSSSSP Screened Sewage, Per cent. Settle- able Solids. m&mwmsmmi Infl. sssslisifegsilssifel at Effl. | Per cent Removal. Infl. Effl. Oxygen Consumed. 31.0 44.3 20.4 29.8 23.7 26.3 14.0 18.8 44.1 23.2 45.2 48.1 36.8 5.9 41.0 51.5 35.6 33.4 Per cent Removal. aiiiisisiiiiniigi Infl. Effl. | 7.3 8.1 0.4 63.0 66.0 29.1 32.8 36.0 18.0 19.4 14.4 Per cent Removal. imrnmmmmm Infl. liSSllSilgilSSSSSi Effl. Residue on Evap. S5oooS£!cow-a!^fii-*o-5Soio!cn rooscsatat'^^at^bo^-bo^bo^^at^ Per cent Removal. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIO NS—J U LY 134 y July c & ? tsjtO^MH-tO^tOtOtO^tOtO^^tOMtO ©tooooo-ico©©totooo©©©4*-^aoto ©©©©CO©CO4‘-tO©l©©©00©©©© Infl. > B M B 2 § a j» OCrfkQ04*4^©©00 -!WMffiffl»OOWOOffiOM*10MO Effl. 18.8 9.4 35.0 20.0 12.6 29.1 3.2 15.6 13.6 16.7 1.9 26.7 4.1 13.3 12.9 21.3 16.5 Per cent Removal. Albuminoid Ammonia. Infl. ©©bbo©©COCO©MCO©COCOI-i4^4»-© *0)_»l--MtOCOMtOCOtOi-l!--‘COt0 4^+-tOCO OX © © -1 £51 CO CO © to -5 4*- © © CO M Effl. 10 © *•■ • I-* • _ IO t© ©~i©©©to©tototocoi-*- oo* © o< to ©CO©CO©©CHM©©«■— © CJ1 Per cent. Removal. MM MM M M (-* h— H* M M ©©©OOtOMM^tOtOOC©M©tO©tOOO bt©'©©©©©©ooo©©©©©oo© Infl. Total Organic Nitrogen. ©©00©0ofot0^©0°©t0t04^t000©t© © © © b © © b©bo©©©oo©Mo Effl. m to to co m ! • co • • • © to -i • •_ © © 0< CO 4* . © • CO • • • © © © © • S© © ©4* CO • ©• CO- • . -©©©00* Per cent Removal. ©©©©M©£>©©©©©©©M©©© bMMb©tocobob©oi©oo~itoMio4- Infl. Nitrates. ©©©©©©©©©©©©©©©©© MH^HMHH^ioloHOtO^HtOMW to Effl. -1 Q0©CJ|l©00Cn©0C©COQC©©jCjCJ OX © © © © © Ci © © © © 10 OX Hi © © © -i © © © © © © b © © © co ci © © © Per cent Removal. >JLtOMMQOCo3£COCOI0 4*4-<-iOCCOCOMCO Infl. z OOOSOoOOOOCOOOOO ©©©©bbbo©©©©©©©©©© to Effl. ©©©©©©©©©©©©©©©©©00 OX ©©©©©©©©©©©•©©©©© 00 ©b©©b©b©b©©©©-i©©©oo Per cent Removal. Effluent Stability, Days. 95 85 103 120 118 131 111 121 69 113 122 | 145 117 131 121 99 107 112 1 Influent Chlorides, P. f\ M. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DI Tl O NS—J U LY 15-31—Continued. Remarks: July 15 to 81, inclusive—Sludge very light and overflowed in spite of drawing 88,000 gallons during run. 135 < «*•!>. COMM Aug. Date. Total Flow Gal. Champaign Sewage. iiiiiiiliiiiilSi Test Plan{ Feed, Gal. llillllliiisl111 Cu. Ft. Gal. Air Used. £5S2£££8£j:S£££S§ Per cent to No. 1 Tank. Tank No. 1. -if S23g*3333g3£:]££3s-: Tank No. 2. It I BSSSSSSBESSSSSSEg Screened Sewage, Per cent. Settle- able Solids. Infl. §SS88ti8£3fcJ3888!2S8 Effl. I 3S8SS§gg;38$3£g£3 M0ww»l0000s«000»fle000ll»© Per cent Removal. §3£3328g£g£gSS2g Infl. 8S5§££Sfe58S!$S£3& Effl. § C |8 £$28g2S8SfeS28E82 Moosaa^ctoiDCOuecooGo Per cent Removal. isasiSiSsiiiSSSsS Infl. llllllllllllll Effl. > S? aoicit- i— w• • ■ *-• 5il- c$ W 4- Cl • CD CD • • • bl • cr. n: • O CD Per cent Removal. 9 SSIIIlllllillill Infl. iHiiiiii^iiin Effl. s« 11 W®CiCCCC<»IOCOH-COW«lb5CDC©CD Per cent Removal. •a * Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. Aug. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. 1 17.0 1S.0 7.2 a. a 54.1 18.0 10.0 44.5 0.8 0.1 87.5 .05 0.0 100.0 143 16.5 13.7 17.0 4.0 1.61 60.0 14.0 6.0 57.0 0.7 0.1 85.7 .14 0.0 100.0 2.0 89 3 20.0 16.5 17.5 4.0| 2.41 40.0 10.0 10.0 0.0 0.7 0.1 85.7 .06 0.0 100.0 2.0 107 4 20.0 16.5 17.5 7.31 1.61 78.0 14.0 6.0 57.0 0.8 0.1 87.5 .05 0.0 100.0 1.5 125 5 18.3 13.8 24.6 4.01 2.01 50.0 12.0 6.0 50.0 0.2 0.0 100.0 .0.3 0.0 100.0 1.0 106 <•> 10.5 15.2 22.1 4.11 2.1 48.7 12.01 6.0 50.0! 0.2 0.0 100.0 .04 0.0 ioo.o 1.0 107 7 24.6 18.6 24.4 4.71 2.5 46.8 16.0| 10.0 37.5 0.3 0.0 100.0 .03 0.0 100.0 1.0 123 8 19.31 17.6 8.8 5.91 4.01 32.2 14.01 12.0 14.3| 0.5 0.1 80.0 .03 0.0 100.0 1.0 142 0 19.5 16.0 18.0 4.71 3.5 25.5 10.0 10.0 0.0 0.4 0.0 100.0 .04 0.0 100.0 0.5 157 10 16.31 12.4 23.0 8.41 3.5 58.8 16.0 14.0 12.5 0.8 0.4 50.0 .09 0.0 100.0 1.5 85 11 14.71 7.7 47.7 3.5 1.71 51.5 10.01 5.2 48.01 2.1 0.1 95.2 .24 0.0 100.0 3.0 84 12 18.0 16.5 8.3 4.71 1.61 65.9 12.0| 4.0 66.61 0.8 0. ' 12.5 .03 0.1 66.7 8.0 113 13 18.3| 15.2 16.9 5.9| 1.7 71.2 16.0| 4.0! 75.0| 1.1 0. L 91.0 .04 0.0 100.c ! 3.0 95 14 20.41 15.0 26.5 6.01 1.91 68.3 16.0| 5.2 67.4| 1.3 0 2 84.5 .03 0.0 100.0 1.5 125 15 18.61 17.1 8.1 4.0| 2.01 50.0 10.01 5.2 48.01 1.0 0.3 70.0 .02 0.0 100.0 1.0 167 Ave 18.71 15.3 I 18.2 5.21 2.31 55.8 1 I 13.7! 1 7.6 44.5 0.8 0.2 75.0 .06 0.0 97.8 2.0 118 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—AUG. 1 -15—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—A UG. 1-15. 136 Date. Champaign Sewage. ' Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. fci p < Total Flow Gal. Test Plant Feed, Gal. Cu. Ft. Gal. Per cent to No. 1 Tank. Tank No. 1. Tank }»o. 2. Screened Sewage, Per cent. Infl. E a Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Remtyval. 16 i 790,000 55,000 1.10 63 86 71 .27 233 22 90.0 103 50 51.3 492 457 7.1 1158 808 25.1 17 825,000 67,000 .91 64 80 83 .26 290 29 89.8 79 40 49.3 478 475 0.7 1101 853 22.5 18 698.000 55,300 1.10 66 75 72 .46 339 45 86.0 94 43 54.2 455 365 19.8 1560 830 40.7 19 739,0001 58,300 1.05 04 82 65 .32 270 25 90 5 80 41 48.8 470 336 28.5 1028 782 23.9 20 728,000 66,000 .93 63 68 60 .32 200 43 78.5 68 27 60.5 439 352 19.8 1004 SOI 20.1 21 622,000 68,800 .92 64 83 61 .10 240 37 84.8 78 47 39.7 443 415 6.3 1120 950 15.2 Ave... 734,000 1 62,000 1.00 . 04 79 69 .29 262 33 87.4 84 41 51.2 463 400 13.6 1162 847 27.1 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. ti p < Infl. Effl. Per cent Removal. Infl. B Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. u O 16 24.0 17.8 25.8 5.7 2.0 64.8 40.0 4.0 90.0 0.7 0.1 85.7 .01 0.0 100.0 1.0 172 17 19.6 18.3 6.6 6.4 1.6 75.0 18.0 5.2 71.0 0.6 0.1 83.3 .03 0.0 100.0 1.0 125 18 20.3 18.3 10.4 8.5 2.0 76.5 22.C 6.0 72.S 0.9 0.1 86.7 .04 0.0 100.0 1.0 95 19 21.0 16.0 23.8 5.2 2.0 61.5 18. C 5.2 71.2 0.9 0.1 86.7 0.0 0.0 100.0 1.5 142 20 19.3 10.0 48.3 4.1 1.7 58.6 16.(1 4.2 73.6 0.7 0.1 85.7 .01 0.0 100.0 2.0 117 21 22.2 22.5 5.9 2.3 61.0 16.0 12.0 25.0 1 .1 0.1 90.9 .02 0.0 100.0 0.5 103 Ave 21.0 17.1 18.6 5.9 1.9 67.8 21.6 0, 71.8 0.8 0.1 87.5 .02 0.0 100.0 1.2 126 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—AUG. 16-21—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—AUG. 16-21. 137 ? f Aug. Date. |ip!!ii5i Total Flow Gal. 3 B » w 63,700 65.600 62.600 63.800 66.900 67.900 65,100 64,000 63,400 65.800 62,600 64,600 Test Plant Feed, Gal. 1.13 1.16 1.21 1.20 1.17 1.15 1.20 1.22 1.15 1.16 1.25 1.18 Cu. Ft. Gal. Air Used. Per cent to No. 1 Tank. gsgaiessBisgss Tank No. 1. -Il Tank No. 2. If| Screened Sewage, Per cent. Settle- able Solids. Infl. Effl. | !-‘GOOtOtOOOtOCOOCOOOCC Per cent Removal. Infl. Effl. II 3: 2 O • 00 Per cent Removal. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—AUG. 22-SEPT. 1—Continued. Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. < Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. 22 20.8 18.5 11.0 11.3 1 1.61 80.0 28.0 8.0 71.4 0.9 0.1 88.S .01 0.0 100.0 1.0 191 22 16.3 14.7 9.8 7.2 1.71 76.4 18.0 5.2 71.1 0.9 0.1 88.8 .00 0.0 100.0 1.5 101 24 17.6 17.2 2.3 4.0 1.71 57.5 12.0 6.0 50.0 2.6 0.1 96.1 .02 0.0 100.0 3.0 134 25 18.3 17.2 6.0 4.1 1.91 53.7 14.0 4.0 71.5 0.7 0.1 85.6 .04 0.0 100.0 3.0 117 26 18.7 18.0 3.8 4.1 2.31 43.8 14.0 6.0 57.2 0.2 0.2 O.C .05 0.01 80.0 2.0 140 27 22.0 20.4 7.2 3.3 2.01 39.4 14.0 5.2 67.0 0.3 0.1 66.6 .03 0.0 100.0 2.0 129 28 22.8 22.0 3.6 4.2 1.91 54.8 14.0 4.0 71.5 0.0 0.1 83.3 .04 0.0 100.0 2.0 111 29 16.7 18.7 4.4 2.0| 54.5 12.0 4.0 66.6 0.5 0.1 80.C .02 0.0 100.0 2.5 152 30 20.0 20.0 0.0 3.2 1.9| 40.6 14.0 4.0 71.5 0.6 0.1 83.0 .06 0.0 100.0 1.5 123 31 21.5 20.0 6.9 3.2 1,9| 40.6 10.0 14.0 0.4 0.0 100. c .05 o.o 100.0 3.0 195 18.1 21.6 3.2 1.9| 40.6 14.0 4.0 71.5 0.4 0.1 75.0 .02 0.0 100.0 1.0 130 Ave 19.3 18.9 2.1 4.7 1.91 59.6 ! 15.0 5.9 60.7 0.7 0.1 87.4 .04 0.0 100.0 2.0 138 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DI Tl ONS—AUG. 22-SEPT. 1. 138 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. Sept. Total Flow Gal. Test Plant Feed. Cu. Ft. Gal. Per cent No. 1 Tank. Tank No. 1. Tank No. 2 Screened Sewage, Per cent. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. 2 1,107,000 64,100 1.19 59 43.5 67 .27 347 22 93.8 38 60 425 483 1150 830 27.8 3 1,623,000 59,700 1.39 59 61.5 75 .20 363 17 95.6 37 53 343 420 995 700 29.7 4 1,203,000 65,200 1.45 60 52 55 .19 200 22 89.0 43 27 37.2 324 393 905 700 22.7 5 1,223,000 67,200 1.39 59 37 40 .19 198 22 89.0 49 32 34.8 404 406 950 772 18.8 6 1,083,000 68,600 1.40 59 44 32 .25 228 27 88.3 65 28 56.9 431 402 6.7 995 855 14.1 7 1,109,000 67,200 1.43 58 53 52 .22 207 18 91.6 53 30 43.5 434 445 1045 900 13.8 8 940,000 67,500 1.44 58 56 48 .16 222 IS 92.0 50 30 40 420 444 1008 15.2 9 923,000 64,450 1.47 58 45 62 .17 223 17 92.8 57 32 43.9 433 453 963 856 11.1 10 906,000 67,500 1.41 58 55 73 .25 252 22 91.6 53 30 43.5 455 451 0.9 882 750 11 787,000 67,200 1.45 59 59 74 .24 230 28 87.7 61 35 34.0 448 450 950 760 20.0 12 939,000 67,600 1.43 61 61 79 .18 259 10 96.2 53 30 50.8 455 473 1050 800 23.8 13 954,000 66,100 1.43 61 58 85 .22 240 13 94.4 62 31 41.6 445 476 990 795 19.7 14 929.000 67.700 1.41 60 41 85 .23 272 10 96.3 63 30 51.7 476 463 2.7 1022 790 22.7 15 892,000 68,100 1.41 64 36 83 .20 270 10 96.3 90 25 72.3 494 469 5.1 980 750 23.5 16 1,238,0001 63,000 1.50 61 41 SO .26 327 10 97.0 47 27 42 6 435 17 1,114,0001 66,400 1.42 61 33 72 .13 237 34 85.9 53 29 50.8 440 405 7.9 897 820 8.6 18 950,000 69,600 1.39 61 38.5 59 .20 263 90 65.9 59 37 30.2 476 429 9.9 1010 965 4.5 19 1,108,0001 66,700 1.44 62 40 70 .30 373 155 58.7 53 49 17.0 486 454 6.6 1020 980 3.9 20 1.227.000 68.900 1.39 61 40 66 .23 303 SO 73.7 53 28 47.2 397 457 Aye... 1,069,0001 66,500 1 1.41 60 47 66 .22 264 26 90.1 55 34 38.2 433 443 991 816 l'i'.i TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—SEPT. 2-20. 139 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. Sept. Infl. Effl. Per cent Removal. Infl. Effl. Per cent Removal. 9 9 24 0.4 98.4 0.8 5.8 .09 2.65 8 91 19 21.3 22.6 4.7 3 61 23 4 20 20 0.0 0.6 0.7 .03 1.04 1 108 20 , 21.4 13 S 39 n 4 7 9 31 si 9 10 4 0 60.0 0.9 1.4 .05 .82 10 103 Aye 19.6 18.41 6.1 1 3.5 1.7 51.4 13 4.3 65.6 1.14 1.6 .12 .76 6.2 105 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—SEPT. 2-20—Continued. 140 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. Sept. £ o fc Hi . O c3 HO 5 E +■> d CO O' > O G W £ o O E K d p i—i i o c e H d a £ o fp > O E H 21 22 23 24 25 26 27 28 Ave.. . Per cen 1,117,000 1,099,000 1,057,000 1,272,000 1,020,000 1,086,000 1,070,000 1,033,000 1,094,300 61,230 64,870 65,440 68,730 65,350 05,600 68,910 72,660 66,600 1.25 1.08 1.06 1.03 1.09 1.09 1.01 .98 1.07 60 65 63 65 64 64 66 65 04 45 38.5 45 48.5 49 44 44 41.5 44.4 65 59 76 86 59 71 63 62 68 4.6 5.0 6.1 7.3 11.5 11.0 8.7 11.0 8.2 280 250 300 360 260 280 240 2Xn 281 70 55 60 75 60 95 70 140 78 72.3 40 10 10 43 40 90 100 190 65 76.9 50 26 33 60 37 52 53 44 44 45 24 32 36 28 26 25 55 34 22.7 26 27 24 28 22 32 33 26 27 38.6 432 476 496 426 436 478 480 404 461 460 486 492 424 420 480 472 480 464 438 460 472 486 410 460 474 472 459 0.4 1030 910 930 1010 980 1020 950 1110 991 810 760 680 770 740 870 950 980 820 17.2 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Effluent Days. Influent Chlorides, P. P. M. Sept. o e K d q w £ © S3 © > O e a a M £ o c u 4> ► O e a d q i © u © > O e c M £ © © ► o B a 21 22 23 24 25 26 27 28 Ave Per cent remov’l 19 19.7 22 18 20 20 22 24 20.6 » 17.6 20 16.6 17.6 19 16.6 23 18.4 10.7 13.0 10.0 12.0 19.0 14.0 18.0 16.5 20.6 15.4 39 Jj 2.8 3.2 3.2 12.8 0.4 8.0 4.0 4.0 5.0 ! 5.2| 2.0 0.01 0.0 0.0| 0.0 0.01 0.0 0.01 0.0 o.ol 0.0 2.8| 2.0 6.81 5.6 1.81 1.2 67.81 78.6 1 10 12 16 18 10 12 20 16 14.3 24 10 18 10 18 18 24 14 17 * 8.0 2.8 8.0 5.2 4.0 10.0 16.0 24.0 9.8 31.5 2.0 0.1 0.3 0.7 1.0 0.7 0.7 0.3 0.7 0.3 0.1 0.1 0.1 0.3 0.3 0.1 0.7 0.3 52.1 2.0 1.0 0.7 0.1 0.3 0.3 0.1 0.7 0.7 0.0 .1 .0 .0 .1 .1 .0 .02 .0 .04 .00 .00 .00 .00 .00 .00 .00 .00 .00 100 1.00 .25 .28 .00 .15 .15 .00 .00 .23 1.0 1.5 4.0 3.5 4.5 1.5 1.5 4.0 3.0 154 96 100 104 118 108 106 162 119 ! TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—SEPT. 21-28—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DI Tl O N S—SEPT. 21-28. 141 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. Sept. Total Plow Gal. Test Plant Peed. Cu. Ft. Gal. Per cent to No. 1 Tank. Tank No. 1. Tank No. 2. Overflow. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. 29 1,319,000 60,250 1.15 65 51 68 15.0 300 60 160 45 32 30 440 426 470 960 860 30 1,238,000 64,260 1.10 65 51 69 13.0 280 75 10 32 35 15 452 440 432 910 700 Oct. 1 1,125,000 61,460 1.20 65 57 79 25.0 240 85 150 50 28 40 476 476 470 910 820 2 941,000 56,200 1.16 82 95 20.0 230 90 180 52 35 27 478 500 474 930 880 3 1,087,000 68,300 1.08 65 69 94 25.0 340 130 380 60 34 34 490 500 494 1080 950 4 1 059 000 67 800 1.09 65 54 52 10.0 290 110 300 60 66 34 486 500 496 1050 990 5 1,038,000 64,800 1.08 66 68 93 30.0 280 70 320 52 33 27 480 484 484 960 940 6 1,074 000 67,400 1 05 66 54 77 20.0 270 75 220 52 30 34 488 478 490 910 910 Ave.. 1,234,600 63,810 i.ii 65 61 78 19.8 279 87 215 50 37 30 474 457 476 963 881 68.8 22.9 25.9 39.9 4.8 8.5 1 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. Sept. d d * o S3 O 4 d £ O S3 P > O 4 d d i © S3 >* o 4 K d a £ O S3 O e K 29 30 Oct. 1 2 3 4 5 6 Ave Per cent remov’l 18.6 21.4 24.0 23.6 22.7 24.0 23.0 25.0 22.8 17.6 20.0 22.0 23.0 21.6 21.6 23.0 23.0 21.5 5.7 18.1 17.6 21.6 22.0 23.6 22.0 20.4 20.6 20.7 9.2 4.0 4.0 2.8 2.8 4.0 4.0 4.8 2.8 3.7 1.2 2.0 2.0 2.0 2.0 2.8 2.0 2.0 2.01 45.9 1 2.8 2.8 2.0 2.0 2.8 2.0 2.0 2.8 2.4 35.2 18 10 10 10 14 8 14 14 12.3 24 4 28 28 28 7 28 28 22 16 4 10 20 20 20 17 18 15.6 0.3 1.3 0.3 0.7 0.3 0.7 0.5 0.7 0.6 0.7 1.3 0.5 0.5 1.0 0.3 0.1 6.0 1.3 0.3 0.7 0.1 0.5 0.3 0.3 0.1 2.5 0.6 00 .15 .0 .0 0.5 .0 .10 .10 .0 .05 .0 .0 .0 .0 .0 .0 .0 .0 .0 100 .0 .15 .0 .0 .0 .0 .0 .0 .021 60.0 1 2.5 4.0 3.5 2.0 1.5 3.0 3.5 1.0 2.61 90 88 96 114 116 110 96 110 103 i TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—SEPT. 29-OGT. 6—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—SEPT. 29-OCT. 6. 142 Date. Champaign Sewage. • Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. Oct. Total Flow Gal. Test Plant Feed. Cn. Ft. Gal. Per cent to No. 1 Tank. Tank No. 1. Tank No. 2. Overflow. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. 7 1,484,000 ! 84,000 67 71 95 16.0 200 95 10 52 107 23 386 406 430 830 820 8 1,'323i 000 [102,'400 .64 67 50 95 10.2 240 60 10 38 32 12 450 448 438 940 680 9 1.036.00C 102.800 .62 66 40 96 5.0 240 65 10 45 38 17 464 454 458 980 710 10 1,137,000|117 100 65 67 40 93 5.0 290 90 10 63 33 21 482 498 47,8 730 11 1,132,000| 103,200 .03 66 42 92 3.0 280 105 10 65 38 31 484 476 476 950 790 12 1,080,000| 105 800 .64 66 44 93 3 o 330 125 10 56 40 30 488 492 482 970 755 13 1,093,0001104,400 .63 67 45 91 2.3 260 100 15 67 35 23 438 500 476 950 690 14 1,156,0001101,800 .64 66 42 94 2.5 280 120 15 55 32 25 476 486 480 1060 780 15 1,090,0001101,700 .65 66 42 94 3.0 270 100 25 52 29 470 474 480 920 860 16 938 0001100,300 .59 66 45 96 4 0 240 90 30 58 20 23 468 472 470 900 740 1 147 500 102 350 .63 66 46 94 5.4 263 95 15 55 40 23 461 471 467 961 63.9 ..94.3 27.2 58.2 21.4 1 1 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. * £ i 4-> P? & O C A a 33 03 03 03 * a Ji o Z > E d Z > E d Z > E d o> E d O) > E = E £ E i3 S' O a o o w £ o K £ o K) HH C K W m O 5 o ai 7 17.4 22.0 16.0 2.0 2.0 1.2 5.2 28 8.0 2.0 0.3 0.5 .30 .00 .10 3 78 8 21.0 18.0 16.0 4.0 1.6 1.2 14.0 16 5.0 0.3 0.1 0.7 .00 .00 .30 8 88 9 22.0 20.0 20.0 4.8 2.8 1.2 12.0 14 4.0 1.0 0.1 0.5 .00 .00 .18 7 104 10 32.0 19.0 22.0 5.2 4.0 1.6 12.0 14 14.0 1.0 0.5 0.7 .04 .00 .01 2 128 11 20.6 18.0 20.0 2.0 2.8 1.3 18.0 20 5.2 1 .3 0.3 0.7 .05 .00 .00 6 94 12 22.0 19.0 19.0 5.2 2.0 2.0 10.0 24 10.0 1 .0 0.3 0.1 .02 .00 .00 5 110 13 21.0 20.0 18.6 4.8 4.4 2.0 14.2 12 5.2 1.0 0.1 0.1 .12 .00 .oc 2 94 14 21.0 21 .0 19.0 4.0 2.4 2.0 10.0 12 4.0 1 .3 0.3 0.1 . 1(1 .00 ■ Of 2 94 15 24.0 23.0 22.0 8.0 2.0 2.0 14.0 18 6.0 0.3 0.1 0.1 .08 .00 .01 1 100 16 33.0 24.0 22.0 2.6 1.2 1.6 16.0 18 5.2 0.5 0.1 0.1 .15 .00 .01 1.5 118 Ave 23.4 20.4 19.5 4.3 2.5 1.6 12.5 17.6 6.7 1.0 0.2 0.4 .01 .00 .06 3.7 101 12.8 16.7 41.8 62.8 46.4 80.0 60. ( 100 .: r TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—OCT. 7-16—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—OCT. 7-16. Remarks: During run from Oct. 7 to 16, inclusive, an average of 45.5 per cent of the overflow was by passed. During run from Oct. 17 to 31, inclusive, an average of 44.9 per cent of the overflow was by passed. 143 Oct. S’ ? !|||j!|j||| Total Flow Gal. Champaign Sewage. Test Plant Feed. SSSSSSSSSlISSSlS ilisiiiliig'iiiii — Cu. Ft. Gal. b 8888888283228832 £ggggggg§22gg£gg Per cent to No. 1 Tank. &88&8g3S8888g&8S Tank No. 1. m 3888883328888SS8 Tank No. 2. S3 35 05,53 S3 35 S3 CO Overflow. M g-ar i -joco:i biciobiox* ocioo Illililllliiilli Infl. m Oxygen Turbidity. Consumed. gsliissiisillilll b Overflow. ® Effl. Infl. 2£888£323S3S3£88 £$£88888888888883 to Overflow. k) Effl. i siiiiiiiii^ini Infl. Alkalinity. siiliisfegiHilisi b Overflow. oS3iS§iSI!ilsi!IS Effl. 1040 ... 1050 . . . 880 ... 990 990 920 . . . 1100 ... 1060 .. . 1040 ... 1030 . . . 1110 . .. 1250 . . . 940 930 ... 1080 . . . 1027 . .. Infl. Residue on Evap. sslssiislSliiglli b Overflow. Effl. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—OCT. 17-31. 144 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, [p. P. M. Oct. e Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. 17 24.0 21.0 22.0 4.0 2.8 2.0 16 14 4.0 0.5 0.3 0.1 .12 .00 .00 1.5 100 is. : 26.0 23.0 21.0 5.2 1.2 1.2 18 18 4.0 0.5 0.5 0.3 .08 .00 .00 3 108 19 29.0 22.0 20.01 4.0 5.2 2.0 10 22 2.8 0.5 0.5 0.1 .00 .00 .00 1 96 20 25.0 21.41 19.61 4.0 4.6 2.0 12 26 2.8 1.3 0.5 0.1 .05 .00 .00 1.5 112 21 29.0 21.0 20.0| 4.01 1.6 2.0 14 12 4.0 0.3 0.1 0.1 .00 .00 .00 2.5 116 22 25. C 23.0 22.0| 4.0| 2.C 2.0 14 18 5.2 1.3 0.1 23 29.0 25.0 23.01 5.2j 2.0 2.0 4 4.5 1.5 0.7 0.3 0.1 .04 .00 .00 3 160 25 24.0 20.0 23.01 5.2| 2.1 1.2 12 16 2.8 1 .0 0.7 0.3 .03 .00 .00 3 100 24 1 25.6 23.4 22.0 4.0 j 3.6| 1.2 16 26 4.0 1.0 0.1 0.1 .05 .00 .00 3 110 26 28.C 21.0 22.0 4.8! 2.8| 0.8 16 18 5.2 1.5 0.3 0.3 .15 .(X) .02 2 112 27 23.0 21.0 20. t 5.21 2.8| 0.8 16 14 2.8 0.7 0.1 0.1 .15 .00 .00 3 138 28 29. C 20.0 19.01 4.0| 4. Oj 1.2 12 24 6.0 0.7 0.3 0.1 .00 .(X) .00 5 296 29 24.6 23.0 21.01 4.01 2.81 0.4 16 20 4.0 1.3 0.1 0.1 .00 .00 .00 3 96 30 29.6 24.0 24.0| 5.21 2.8! 2.4 16 24 (i.O 1.0 0.3 0.1 .18 .00 .00 6 94 31 27.€ 24.0 24.01 5.21 3.21 1.2 16 26 10.0 1.3 0.5 0.1 .031 .00 .00 2.5 118 Ave , 20.4 22.2 21.5 4.51 2.91 1.5 14.2 19.7 4.3 0.9 0.3 0.1 .06 .06 .001 3.1 124 Per cent remov’l 15.0 18. G | 35.5 1 66.6 69.a 66.6 88. S 100 100 l TABULATION OF CHEMICAL DATA AND DAILY OPERATNG CONDITONS—OCT. 17-31—Continued. 145 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. £ C i-i CJ E a CH 6 £ 6 fc £ O £ £ £ 0 £ 0 > * 0 . O »H a s 03 Oi ► i sa *-< > e S3 S3 E S3* S3 01 ► E S3 sa > E HO Eh£ Co C-55 H 0 O H ►5 0 H hh. 0 w *-« ■ 0 9 7S 67 .20 500 150 120 38 56 46 360 420 470 1160 950 17 43 700 2,46 57 .10 280 80 75 55 40 35 406 .398 424 1050 830 18 2,302’0O0 72/200 1.95 59 4 1 .08 270 55 50 35 25 28 270 288 366 1080 810 (i 1 .03 90 50 •33 . 40 17 20 252 254 238 1080 958 20 2,008’000 79,000 1.27 61 6 2 .03 75 45 30 26 25 27 302 292 260 1020 1010 21 1 24 62 7 2 .02 140 37 25 28 16 16 364 .340 332 1010 980 22 l| 932^000 90i 800 1.0s 61 9 3 .00 140 30 20 20 17 23 366 344 354 1010 950 23 1,929,000 94,100 1.04 62 10 3 .00 160 30 25 30 25 22 376 358 364 970 860 62 12 3 .00 130 85 60 33 23 20 .368 366 358 910 820 25 2,239,000 91,900 1.05 62 14 2 .00 190 60 45 33 21 20 386 374 380 840 800 62 16 2 .00 75 25 20 18 20 16 376 .3.36 370 S70 810 27 1 06 63 90 9 .00 105 65 37 25 24 30 372 372 362 830 770 28 2|194|000 92,900 1.03 63 26 ■ 2 .05 190 75 80 35 35 30 .390 386 390 890 830 9 170 75 30 * 23 18 .392 390 390 sio 2]350|000 91.700 1.04 63 55 i .00 150 55 55 26 23 . 20 394 .394 402 940 800 Ave... 2.122.000 80,530 1.33 62 18 2 .03 178 59 50 32 26 25 358 354 364 977 865 66.6 72.0! 18.7 21 .8 1.1 11.5 1 1 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CON DITIONS—NOV. 16-30. 146 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. Nov. © e « a w £ o c Ah > © e K w a w E? o a u > © e H M o « Ah > © E £3 o G W ff c > O E K 16 17 18 19 20 ?l 22 23 24 25 26 27 28 29 30 Ave Per cent remov’l 15.0 17.8 12.6 7.0 5.4 10.6 8.0 11.0 8.0 11.6 , 9.6 12.0 9.6 12.6 11.0 10.8 17.6 17.0 11.0 4.0 6.0 6.0 7.6 8.6 9.6 8.6 14.0 13.6 12.0 14.0 13.4 10.9 21.0 25.0 14.0 6.6 6.6 8.0 8.0 12.0 9.0 12.0 11.0 14.3 12.6 11.6 13.4 12.3 0.0 2.4 1.2 0.4 1.2 2.0 2.4 2.0 0.0 4.0 1.2 2.8 2.4 2.4 1.2 1.7 2.8 2.4 2.0 0.4 0.0 0.4 0.0 0.4 0.0 0.4 1.2 2.0 1.2 2.0 0.4 1.0 41 .2 2.8 2.8 1.6 1.2 0.4 1.2 0.0 0.4 0.0 1.2 0.4 1.2 1.2 0.4 1.2 1.0 41 .2 12 10 10 8 8 10 10 8 10 14 8 10 12 12 16 10.5 10.0 8.0 6.0 6.0 6.0 6.0 5.2 6.0 8.0 6.0 6.0 6.0 5.2 5.2 5.2 6.3 40.0 10.0 8.0 6.0 5.2 4.0 5.2 4.0 4.0 6.0 4.0 4.0 4.0 8.0 5.2 5.2 5.5 47.6 1.0 5.0 22.0 5.5 24.0 20.0 6.0 3.0 4.5 1.0 0.5 1.3 1.5 1.3 0.5 6.5 1.3 3.5 12.0 5.0 24.0 20.0 7.0 3.0 5.0 5.0 5.5 6.0 4.5 4.0 3.0 7.2 0.5 4.0 6.0 6.0 26.0 18.0 7.0 6.5 6.5 6.0 4.5 3.5 4.5 3.5 2.5 7.0 .50 .50 .70 1.20 1.60 3.00 2.20 .05 1.12 .00 .00 .15 .45 .45 .00 .79 .60 .60 .60 1.12 1.20 2.00 2.20 1.00 1.00 .50 1.25 1.00 .45 .45 .45 .96 . . . . .25 .50 .60 1.12 1.20 2.00 2.00 1.00 1.20 .65 .70 1.00 .45 .45 .45 .90 1 2 2 8 2 3 5 2 2 2 1.5 1 2 2 2.6 80 112 86 70 66 156 110 78 86 74 116 64 68 86 98 90 I . 1 i i TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—NOV. 16-30—Continued. 147 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able Solids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. Dec. * o . o 73 HO • a cd Q. 03 'S O' 03 H fa m 5*3 oo OM -m cd OiH fed a, St 6 fc M a cd H > c e d W £ o t O' > E H d HH £ o d c o E H d a Hi £ o 0> O E « 1 9 3 4 5 6 7 2,087,000 1,911,000 1,711,000 1,785,000 1,842,000 1,701,000 1,980,000 1,859,500 66,100 65.900 66.900 65,300 78,500 91,400 92,:500 75,200 .96 .95 .96 .98 .79 .72 .71 .87 63 05 64 64 65 64 66 64 65 75 80 84 83 75 73 76 0 0 0 0 1 17 47 9 0.0 0.0 0.5 0.5 2.0 4.5 280 170 150 140 200 210 40 35 15 20 190 250 50 35 20 15 27 25 48 20 32 31 32 54 20 13 18 16 14 23 21 20 15 21 14 12 370 366 374 400 404 368 386 384 398 406 360 378 386 398 398 940 910 840 820 900 1080 740 740 730 690 730 750 Ave.. Per eeri 1.2 190 92 51 6 29 | 36 S4 . SI . . . . . 17 52.9 17 52.0 383 388 384 915 730 20.2 1 1 1 1 Date. Free Ammonia. Albuminoid Ammonia. Total Organic Nitrogen. Nitrates. Nitrites. Effluent Stability, Days. Influent Chlorides, P. P. M. Dec. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. 1 16 0 IS 0 i 25 5 2 14.0 14.0 12.0 2.8 1.2 1.2 10.0| 5.2 4.0 1.0 1.3 1.0 .45 .00 .10 3 86 3 13.6 17.0 14.6 2.0 0.8 1.2 14.01 4.0 6.0 4.5 1.5 2.0 .56 .12 .18 5 70 4 17.0 17.0 16.0 2.8 1.2 0.8 14.0! 8.0 6.0 5.5 1.5 1.5 .60 .20 .25 10 70 5 14.6 17.0 18.0 4.0 4.0 1.2 18.0| 18.0, 6.0| 4.5 1.5 2.0 .40 .18 .20 10 82 6 17.0 14.0 17.4 4.0 2.0 1.6 18.0| 27.01 6.0| 4.0 2. Oi 1.5 .40 .15 .18 8 80 7 7 Ave 15.4 15.3 14.8 3.0 1.5 1.1 14.6| 11.3| 5.3| 3.5 1.9] 1.7 .53 .17 .191 7 77 Per cent remov’l 0.6 3.9 50.0 63.3 23.3, 63.8i 1 45.7 51.4 67.6 64 11 1 i TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITlONS—DEC. 1-7—Continued. TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—DEC. 1-7. 148 Date. Champaign Sewage. Air Used. Per cent Sludge by Vol. Settle- able lolids. Turbidity. Oxygen Consumed. Alkalinity. Residue on Evap. is r4 -M CS 6 6 £ £ £ £ u* z z O O O O O M ■E u u 00 w S 6 3 & d > E > e d > e d > d o 80 a,Z h Eh 0 M 0 H M 0 a £ 0 H £ O H 8 1,818 000 71 700 78 68 70 58 0.5 180 110 20 50 30 13 392 402 388 870 710 9 1,908,000 85! 800 .76 67 74 63 4.5 185 270 20 55 20 20 416 404 400 890 720 10 1 741 000 190 240 10 30 25 15 402 390 390 930 730 11 i;56s;ooo 83,400 .77 67 68 66 3.5 190 170 10 20 14 12 382 388 392 930 730 12 1,590 000 80 100 08 230 240 10 04 31 17 428 398 404 950 730 13.. . 220 270 28 20 412 402 402 900 730 14 M2o!ooo 190 280 10 50 33 13 414 398 398 7Sf0 670 15 320 10 23 20 410 402 400 900 700 16 1,384,000 80,100 .79 70 68 72 5.5 300 350 5 66 30 10 360 390 390 940 680 17 83 300 78 06 240 160 20 35 10 15 370 342 354 860 7d0 18 84 300 180 48 28 16 384 374. 380 920 650 19 83’400 77 07 06 2 5 210 260 10 23 12 10 420 398 392 920 730 20 72 900 88 08 57 3 7 200 190 10 35 15 10 410 398 374 920 800 21 65 200 97 67 200 350 85 68 17 14 420 406 392 1100 850 22 79] 500 .80 69 04 78 3.0 210 250 20 47 28 13 400 392 396 960 770 23 81,500 .78 70 71 72 1.8 290 230 28 31 20 10 304 340 346 910 750 24 80,000 .81 70 06 57 0 1 100 85 10 35 18 10 214 318 296 920 800 750 25 80 900 80 70 67 64 0 5 100 90 15 27 15 15 330 324 334 870 840 790 26 83*000 78 70 04 73 0 2 140 95 15 33 18 10 354 336 336 910 820 820 27 84! 200 77 70 09 75 0.7 200 115 20 23 13 14 360 350 352 880 830 790 28. Ave... 77'800 .79 69 67 68 2.6 204 215 17 40 21 14 379 378 376 913 822 740 21 .5 1 42.4 65.0 .... 0.3 0.8 18.9 1 1 1 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—DEC. 8-28. 149 Date. 1 Free Ammonia. | Albuminoid Ammonia. Total Organic Nitrogen. Nitrite*. Nitrates. Effluent Stability, Days. Influent Chlorides, P. P. M. Dee. Infl. Overflow. Effl. Infl. Overflow. Effl. Infl. Overflow. Effl. i £ o E O Effl. Infl. Overflow. Effl. 8 16.0 13.0 14.0 4.0 >.J 1.2 1 12.0 16.0 4.0 4.0 1.0 1.0 .50 .00 .00 8 04 9 19.0 18.0 17.01 4.0| 2.8 1.6 18.0 16.0 4.0 4.5 0.5 0.7 .40 .05 .05 8 74 10 18.61 15.01 17.51 4.01 3.21 0.4 12.0 14.0 4.(1 4.0 0.7 1.0 .40 .05 .05 10 112 U 17.0 16.0 15.0 2.8 2.41 1.2 12.0 12.0 4.C 4.0 1 .0 1.0 .45 .15 • 1C 10 60 12 20.0 14.0 17.0 4.8 4.01 1 .2 16.0 20.0 2.8 3.0 0.5 1.0 .45 .15 ,l£ 10 90 13 19.0 12.0 13.C 4.0 2.01 1.2 10.0 20.0 2.8 4.0 0.5 0.7 .40 .00 .00 10 74 14 17.0 14.0 13.1 4.0 3.2 1 4.0 10.0 20.0 4.0 2 5 0.3 0.5 .25 .00 ,0( 10 118 15 10.0 15.0 15.0 4.0 4.0| 2.0 12.0 18.0 12.C 2.5 0.3 0.5 .30 .05 .05 10 88 16 18.0 15.0 16.0 4.0 4.0| 1.2 12.0 18.0 4.0 2.5 0.3 0.3 .40 .08 .05 9 72 17 16.0 13.4 13.( 2.0 2.01 1.6 9.4 12.0 3.2 3.5 0.5 1.0 .75 .15 • 1C 9 72 IS 17.0 15.6 15. C 2.8 2.8 | 0.8 14.0| 15.6| 3.2 4.5 2.3 2.0 .40 .40 .20 10 66 19 17.0 13.0 '15.2 2.8 2.8| 2.0 9.6 16 0 3.2 2.1 1 .4 0.7 .90 .20 ,2C 10 92 20 16.4 12.2 13.2| 4.0 4.0| 2.0 16.0 2.8 3.7 0.5 0.8 .40 .15 .15 9 86 21 17.S 14.8 14.6 5.2 2.0| 1.6 14.0 22.0 8.4 2.5 0.3 0.4 .25 .00 .10 9 136 22 14.4 10.8 13.4| 4.0 2.8| 1.6 12.0 12.0 3.2 4.0 2.0 0.9 .30 .00 .18 10 101 23 10.6 10.0 10.0] 3.2 4.01 1 .2 12.0 12.0 3.6 4.0 1.4 2.5 .30 .20 .20 10 61 24 9.4 13.2 7.81 2.0| 1.2 1.2 9.4 5.0 2.8 8.(5 6.6 5.3 .30 .60 .30 10 72 25 18.6 9.4 9.4] 2.0 l.( 1.2 8.0 8.4 2.8 11.0 8.0 7.6 .30 .30 .30 10 58 2(5 17.0 10.6 19.6| 3.6 2.01 3.6 9.2 6.0 5.2 9.0 7.2 7.0 .56 .60 .28 10 61 27 12.8 8.8 10.6] 2.8 2.8 0.0 11.2 8.0 3.2 7.0 4.4 4.6 .60 .50 .28 10 76 28. .. 14.0 13.21 4 0 10 Ave 16.4 12.9 13.9] 3.5 2.8i 1.5 11.8 15.1 4.2 4.5 1.9 2.0 .43 .18 .13 9.7 82 Per cent remov’l 21.3 15.2 90 01 57.1 64.4 57.8 55.6 58.1 69.8 1 TABULATION OF CHEMICAL DATA AND DAILY OPERATING CONDITIONS—OEC. 8-28—Continued. 150 Date December 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 1.28 1 Iron P.P.M. of Fe Fe So« Overflow Added lbs 0.8 6.8 14.0 1.4 0.4 25.5 1.5 ‘6’. 6 32.2 1.4 ‘6.4 30.5 0.8 'o’. 4 38.0 0.8 ‘6’.4 30.7 0.8 0.8 37.0 1.2 'o!i 35.0 4.0 14.0 0.5 33.0 1.4 6.0 0.3 29.5 1.2 8.0 0.4 31.0 1.2 10.0 0.5 36.5 0.9 9.0 0.8 32.2 1.8 14.0 4.0 26.7 0.9 7.0 0.9 31.7 2.6 12.0 1.4 36.2 0.8 0.6 2.0] 5.0 0.8| 0.9 36.5133.0 1 0.5 5.0 2.4 33.0 o.si 6.0| 3.2]. ... 32.713.95 1 Total weight of Fe SO* added during run 6|^?ibSpp Iron content of Fe SO4 used. q i».s r.« 9 6 n d m. Total weight of Fe added during run 131 lbs> or p,p' DATA ON IRON DOSING.