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I" ;'~ ’1 ‘9 ‘ film ‘1 V ”Cr . h- 3:? .' j; ‘l .‘ (fl$.»52 r‘ 'Q’u"_ 'r 6‘1 ‘Vufi‘ 'o ‘— 43 . r'" '0 (. - ‘ ‘ 1' ("m AI" in J A Study of Total Solids as a Measure of Sewage Plant Efficiency A Thesis Submitted to The Faculty of- MICHIGAN STATE COLLEGE of AGRICULTURE AND APPLIED SCIENCE BY NiA. Rosenberg Candidate for the Degree of Bachelor of Science June 1934 .-.. . TH ESI‘S 94762 Acknowledgement The writer wishes to express his sincere appreciation to Mr. E.F. Eldridge and Professor F.E. Theroux for their guidance and helpful suggestions which made possible the completion of this work. T A B L E O F C O N T E N T 8 STATEMENT OF THE PROBLEM INTRODUCTION DISCUSSION OF~THE FUNCTION OF TREATMENT PLANT UNITS Primary Settling Activated Sludge Chemical Treatment Filtration DATA FROM VARIOUS TREATXENT PLANTS Primary Settling Grand Rapids, Michigan Flint, Michigan Pontiac, Michigan Jackson Prison, Michigan Traverse City, Michigan Dearborn, Michigan Muskegon Heights, Michigan Aurora, Illinois Geneva, Illinois Worcester, Massachusetts Activated Sludge Muskegon Heights, Michigan Geneva, Illinois Sanitary District of Indiana Chemical Treatment Dearborn, Michigan Filtration Flint, Michigan Pontiac, Michigan Aurora, Illinois Worcester, Massachusetts RESULTS OF LABORATORY STUDY GENERAL CONCLUSION STATEMENT OF THE PROBLEM To determine the advisability of substituting the total solids determinations for the suspended solids as a measure of sewage plant efficiencies. INTRODUCTION The efficiency of a sewage treatment plant is usually measured by the biochemical oxygen demand, settleable solids, and suspended solids determinat« ions. In various reports from sewage plants, where both the suspended and total solids determinations .are made, ther is sometimes a varying difference in the removal of solids as shown by these two determinations. This difference may be due to a removal of solids other than suspended, that is, colloidal and perhaps dissolved. If this is true the treatment processes which effect a removal of colloidal material by coagulation should show a greater total solids removal than is possible by the removal of all of the suspended solids. Also, this difference should not show in thos units used for primary settling only because they do not effect the colloidal matter. For these reasons if the total solids could be substituted for the suspended solids determination a more accurate means of measuring the efficiency of plant removal might be obtained. The problem then has been to determine if this substitution would be advisable. While much study and experimental work has been completed on the removal of suspended solids and total solids no reports or papers could be found re- ferring to the direct comparison of the types as a measure of plant efficiency. For the purpose of studying the substitution, data of actual results of a number of sewage plants for the past few years has been collected and tabul- ated. The data was collected from all types of sew- age treatment plants and the units were considered separately. The problem was continued into the lab- oratory where a further study of chemical treatment was made by treating sewage with ferric chloride. DISCUSSION OF THE PROBLEM OF TREATMENT PLANT UNITS Primary Settling The most generally used type of unit is one used for primary settling purposes only. This in- cludes the separate settling tanks, both horizontal and vertical flow types Imhoff tanks, and septic tanks. These units serve as preliminary clarification preced- ing oxidation and disinfection processes, or preced— ing disposal without further treatment. The only effect of these tanks on solids removal is the removal of settleable solids. Activated Sludge The activated sludge units are used after the sewage has passed through grit chambers and a primary settling tank or through a fine screen. The air which is allpied to the sewage either by being blown in through diffusion plates or by water absorption from mechanical action, offers a suitable amount of dissolved oxygen. In this treatment it is necessary for the sludge to become "activated" with great numbers of aerobic and facultative anaerobic bact- eria.i These bacteria cause the floculaticn and decomposition of organic matter and the conversion of the nitrogen into nitriteand nitrates. The activated sludge is added to the sewage in proport- ion to about one to five. Sufficient air is added to provide enough dissolved oxygen to maintain aero— bic conditions, and the mixture is agitated until practically all of the suspended and colloidal matter has been floculated or absorbed by the floc introduced into the sewage. The mixture is then conducted into tanks where the floc is removed by sedimentation and the clear supernatant water passes away as effluent. Chemical Treatment Chemical precipitation tanks are much the same as plain sedimentation tanks, the only difference being that a chemical is added which in one way or another forms a floc in the liquid. This floc draws to itself the substances that are to be removed, thereby presenting a method of increasing the sediment— ation of suspended matter and inducing that of the colloidal matter. The coagulation is allowed to act thoroughly through the sewage then the floc is allowed to settle and carries the suspended matter with it. Many different substances have been used as precipitants. The most common ones are calcium or lime, ferric chloride, alum, and ferrous sulphate. In most cases further treatment is advisable such as, addition of chloride, use of rapid sand filters, or passage of the clanfied effluent through a bed of zeolite. A more complete degree of treatment is possible by using one of the aboved named methods. Although chemical precipitation was one of the first processes used in sewage treatment it has not been used to a great extent in past years. The reasons for this are the high costs of chemicals and the treatment of the large amount of bulky sludge obtained. The present trend is toward a renewal of interest in the use of chemicals in sewage treatment. New processes have been investigated experminentally and seem to be producing very successful results. The Laughlin process, which uses lime and ground paper pulp, followed by ferric chloride, is one of a few processes installed on a large scale. This plant is giving satisfactory results at Dearborn, Michigan. It has been found that a profitable reduction can be made in some of the processes and also that a spent coagulant can be regenerated. For these and other reasons chemical-treatment will undoubtedly be of importance in the next few years. Filtration Filtration of sewage is one of the processes which is termed oxidation or biological methods of treatment., Much the same action is involved as in the Activated Sludge process, only the manner in which suspended solids and colloidal and dissolved materials are removed is very complex. In the three common types of units, intermittent sand filters, contact beds, and trickling filters, the mechanical straining-out of the larger suspended solids is a simple matter. The removal of colloidal and dissolv- ed matter is caused by a coagulation and a develop- ment upon the filtering medium of a slimy, gelatinous growth of bacteria and other organisms such as fungi, protozoa, and certain higher forms of life. It is further associated with the contact between the sew- age and the film. The filters must be permitted to rest between doses, in order that the biological jelly may dissolve or absorb a sufficient amount of oxygen from the air to maintain oxidation reactions. , The products of decomposition of organic matter are chiefly carbon dioxide, nitrates, and a humus-like substance. The carbon dioxide escapes into the atmos- phere and the nitrates go into the effluent. The humus- like substance must either be mechanically removed, as in the intermittent sand filters and contact beds, or will leugh off from time to time as in trickling filters. The sloughing off of solids must be consid- ered when making a suspended solids or total solids determination. DATA FROM VARIOUS TREATMENT PLANTS Data from sewage treatment plants mostly in the Mid-West was collected and a comparison of the remov- al of suspended solids and total solids was made in each case. Most of the results were taken from annual reports and some are of daily determinations. Each unit at every plant was considered as acting separately when the data allowed such a separation. Because of the lack of total solids determination being made at a number of plants the reports were limited especially in the case of Activated Sludge units. Only one report on Chemical treatment was obtained, that being of the Laughlin process at Dearborn, Michigan. All negative signs in the total difference column show that a greater removal of suspended solids was obtained than that of total solids. Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Primary Settling Grand Rapids Sewage Treatment Plant The primary units consist of four 80 ft. diameter settling tanks. About twenty million gallons of sew— age are treated per day. The sludge is removed cont~ inuously. The samples from which the results were obtained were taken from twenty-four hour composites collected each day and the daily results were made into monthly averages. Monthly Averages for Year 1933. Total Solids Suspended Solids Total pcpomo pop-mo popomo Raw Primary REw Primary Diff- Sewage Effluent Removal Sewage Effluent Removal erence 933 867 66 148 73 75 - 9 1098 958 140 213 87 126 14 1095 984“ 111 187 84 103 8 1049 944 105 184 83 101 4 1105 1008 97 168 78 90 7 1366 1251 115 206 84 122 - 7 1418 1295 123 199 77 122 l 1371 1255 116 189 78 111 5 1324 1251 73 164 71 93 -20 1318 1234 84 175 80 95 —11 1066 1000 66 172 87 85 ~19 997 929 68 171 95 76 — 8 Average - 3 Jan Feb Mar Apr May June Julty Aug Sept Oct Nov Dec The primary units at Flint, Michigan consist of Flint Sewage Treatment Plant four Imhoff tanks each of which has a capacity of four MOGOD. discussion of the efficiency of the tanks. consist of eighteen hexagonal cells with the outside A unique design of the tanks has caused much Each tank ring of cells, twelve in number, acting as the struct~ Ural frame. practise when each tank handles four N.G.D. A detention period of four hours is in yonthly Averages for Year 1932. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary Raw Primary Diff: Sewage Effluent Removal Sewage Effluent Removal erence 884 733 151 186 52 134 17 948 772 186 230 65 165 21 970 827 143 241 84 157 ~14 891 750 141 221 79 142 ~ 1 936 795 141 265 119 146 ~ 5 938 773 175 240 61 179 ~ 4 883 682 201 224 41 183 18 908 713 195 225 34 191 4 900 714 186 216 33 183 3 903 733 170 220 45 175 - 5 883 731 152 187 45 142 10 890 737 153 206 53 153 0 Average 4 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec 1928 1929 1930 1931 Flint Sewage Treatment Plant Continued Monthly averages for Year 1933. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. WI imary Wmary EFF: Sewage Effluent Removal Sewage Effluent Removal erengg 842 708 134 189 57 132 2 875 746 129 198 58 138 ~ 9 857 710 147 193 52 141 8 767 654 113 153 35 118 ~ 5 908 747 181 221 52 169 ~ 8 981 797 184 268 75 191 ~ 7 944 744 200 259 54 204 ~ 4 949 740 209 290 47 243 ~34 976 734 242 290 42 848 ~ 8 930 729 201 238 45 193 8 948 785 183 233 48 187 ~ 4 880 738 142 182 47 135 7 Average ~ 5 Yearly Averages 928 750 178 255 85 170 8 895 718 177 256 79 177 0 880 709 151 225 75 150 1 947 751 198 271 77 194 2 Pontiac Sewage Treatment Plant Pontiac has four small Imhoff tanks in which the seW~ age is treated after going through a Dorrco Far screen. The sludge is removed at intervals to two large sludge digestion tanks. The effluent from the Imhoff tanks flows by gravity to the trickling filters. Monthly Averages for Year 1932. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary ::Raw Primary Diff- Sewage Effluent Removal Sewage Effluent Removal erence, Jan 784 845 139 209 73 138 3 Feb 808 658 150 208 73 '133 17 Mar 785 847 138 208 83 125 13 Apr 848 683 183 208 83 125 38 May 830 688 142 216 . 77 139 3 June 798 880 118 200 78 124 ~ 6 July 792 880 132 200 74 126 8 Aug 885 697 - 188 253 75 178 ~10 Sept 850 892 158 241 70 171 ~13 Oct 826 655 171 249 80 169 2 Nov 920 785 155 231 73 158 ~ 3 Dec 1020 888 154 222 81 141 13 Average 5 n v Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec 1932 1931 Pontiac Sewage Treatment Plant Continued Monthly Averages for Year 1933. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary Raw Primary —Diff~ Sewage Effluent Removal Sewage Effluent Removal erence 1078 948 130 218 81 137 ~ 7 1040 898 144 208 84 122 22 1018 920 98 190 87 103 — 7 1010 938 74 149 77 72 2 835 749 88 147 79 88 18 1000 840 180 207 80 127 33 1025 835 190 218 75 141 49 986 822 144 243 78 187 ~23 1008 845 163 253 83 170 — 7 1150 927 223 259 78 183 40 1105 935 170 250 79 171 ~ 1 1122 931 191 242 84 158 33 Average 11 Ye arly Averages 845 895 150 220 75 145 5 851 871 180 265 85 180 O Jan Feb mar Apr May June July Aug Sept Oct Nov Dec Jackson Prison Sewage Treatment Plant At Jackson Prison they have two small Imhoff tanks for the primary units. The average flow is about one M.G.D. The sewage is rather weak which is characteristic of institutional sewage. Monthly Averages for Year 1933. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary Raw Primary 33' SewagefiEffluent Removal Sewage Effluent Removal Difference 1156 1075 81 127 74 53 28 1167 1181 8 102 59 43 ~37 1221 1195 28 113 65 48 ~12 1218 1188 48 118 61 57 ~ 9 1179 1126 53 111 55 56 ~ 3 1245 1207 38 135 59 78 ~38 1275 1187 88 128 59 89 19 1387 1223 184 139 71 88 98 1285 1128 139 133 58 75 64 1305 1223 82 133 70 63 70 1328 1251 75 157 79 78 79 1343 1270 73 180 81 79 81 Average 28 Traverse City Sewage Treatment Plant After passing through a grit chamber and a Dorrco bar screen the sewage at Traverse City, Michigan passes into four settling tanks. A detention peroid of three hours is obtained with a two N.G.D. flow. Approximately ninety six per cent of the settleable solids are re- moved. Chlorine is applied to the sewage with a fifteen minute contact period. The sewage is then conveyed to the river. Monthly Averages for Year 1933. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Piimary Raw —Primary Diff- Sewgge Effluent Removal Sewage Effluent Removal erengg= Jan 583 451 132 227 98 129 3 Feb 524 409 115 187 79 109 8 Mar 480 377 103 155 71 94 9 Apr 476 401 75 173 71 102 ~27 May 480 383 97 151 63 88 9 June 499 413 88 181 73 108 ~22 July 809 485 124 175 70 105 19 Aug 53? 410 127 177 70 107 20 Sept 537 .405 132 181 71 110 22 Oct 537 408 131 169 84 105 28 Nov 506 384 122 150 53 97 25 Dec 571 402 189 185 69 118 53 Average 12 Dearborn Sewage Treatment Plant East Side Plant Four Imhoff tanks have been converted and are now used as plain settling tanks. Each tank has three flowing~through channels which are partitioned to pro- vide controlled flow in each tank. An average sewage flow of sixteen million gallons a day is handled. The average removal of suspended solids is sixty- seven per cent and that of total solids is forty-nine per cent. Monthly Averages for Years 1932-33. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary D_Raw Primary Diff- Sewage Effluent Removal Sewage Effluent Removal erence May 942 788 ' 178 274 105 189 7 June 737 701 38 146 65 81 ~45 July 821 552 69 144 74 70 ~ 1 Aug 827 585 42 118 87 - 51 ~ 9 Sept 797 820 177 223 73 150 27 Oct 725 600 125 178 59 117 8 Nov 785 835 150 183 33 150 0 Dec 735 827 108 150 38 112 ~ 4 1933 Jan 710 549 161 152 32 120 41 Feb 624 583 61 108 47 81 0 Mar 798 551 245 286 47 239 6 Apr 884 815 89 111 42 89 0 Average 3 lst 2nd 3rd 4th 5th 8th 7th 8th Muskegon Heights Sewage Treatment Plant The sewage at Nuskegon Heights, through a bar primary settling tanks. screen, Michigan passes grit chamber and then into two The sludge is removed to drya ing.beds. The effluent.from the tanks flows directly into the activated sludge basins. Daily Determinations for April 1934. Total Solids Suspended Solids Total p.p.m. pop-mo p.p.m- Raw Primary Raw Primary Diffi- APril Sewgge Effluent Removal Sewage Effluent Removal erence 1018 732 286 492 204 288 - 2 808 636 172 268 124 144 28 758 566 192 280 138 142 50 868 628 240 288 134 154 86 774 584 190 300 142 158 32 846 632 214 380 132 248 ~ 34 774 512 262 448 112 336 - 74 1298 758 540 612 214 398 142 Average 28 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Aurora Sewage Treatment Plant Four clarifiers fifty feet square and ten feet deep are the primary units at Aurora, Illinois. They have a detention period of two hours. The solids are gathered towards the center and "thickened" by slow moving "bridges". Monthly Averages for Year 1931. Total Solids Suspended Solids Total p'p’m‘ . p.p.m. p.p.m. Raw Primary Raw Primary Diff— __§ewage Effluent Removal Sewage Effluent Removal erence 1082 1082 ~20 186 121 85 85 1117 1049 88 186 122 84 4 969 913 58 181 102 79 ~23 928 874 54 148 92 58 ~ 2 989 923 48 193 131 80 ~14 947 881 88 '171 118 55 11 887 820 47 160 108 54 7 847 785 82 167 95 72 ~10 789 744 45 189 111 55 ~10 851 831 20 173 130 43 ~23 882 798 88 153 95 58 8 804 749 55 119 72 47 8 Average ~11 Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec Jan Feb Mar Apr Nay June July Aug Sept Oct Nov Dec Aurora Sewage Treatment Plant Continued Monthly Averages for Year 1932. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary Raw Primary Diff- Sewage Effluent Removal Sewage Effluent Removal erence 720 876 44 94 51 43 l 791 756 35 126 71 55 ~20 738 897 41 107 83 44 ~ 3 866 819 47 113 55 58 ~11 914 828 86 182 53 129 ~41 889 774 95 182 51 111 ~18 895 772 123 178 65 113 10 890 803 87 140 83 77 10 814 780 54 135 51 84 ~30 883 786 77 142 64 78 - l 1212 901 111 162 77 82 29 908 818 88 143 62 81 7 Average ~ 5 Monthly Average for Year 1933. 878 843 35 111 83 48 ~13 955 876 79 128 88 58 ~21 922 805 117 113 69 44 73 932 888 64 98 58 40 14 890 872 18 88 49 39 ~21 912 845 87 134 88 86 1 935 850 85 137 82 55 30 880 815 65 123 89 54 11 899 863 38 127 82 45 ~ 9 902 829 73 148 88 80 ~ 7 1010 905 105 185 69 118 ~11 917 814 103 171 82 109 ~ 8 Average 4 lst 2nd 3rd 5th 8th 7th 8th 9th 10th 12th 13th 14th 15th 18th 17th 19th 20th let 22nd 23rd 24th 28th 27th 28th Geneva, Illinois Sewage Treatment Plant A primary tank with a plain hopper bottom is the only primary unit at Geneva. The suspended solids values run exceptionally high for a city of this size. The effluent flows directly into the aeration units. Daily Determinations for February 1934. Total Solids Suspended Solids Total popomo p.p.m. p.p.m. Raw Primary ‘““"“aaw 'Primary Diffi— Sewage Effluent Removal Sewage Effluent Removal erencg_ 970 800 170 150 74 78 94 ' 760 840 ~ 80 188 108 80 ~180 820 808 12 192 198 ~ 6 18 1032 780 272 680 270 410 ~138 1028 804 224 176 54 122 102 .818 812 4 142 52 90 ~ 86 898 660 239 154 78 78 181 804 888 116 144 94 . 50 86 864 844 220 232 80 152 88 1116 884 232 358 138 222 10 1156 816 340 282 104 178 182 808 836 172 210 78 132 40 912 778 138 198 110 88 48 1228 872 358 ‘150 84 88 270 932 856 276 170 80 110 166 1264 1108 156 350 - 118 232 ~ 76 1012 820 192 224 90 134 5 938 804 332 322 . 88 234 98 864 840 224 328 90 236 ~ 12 900 712 188 220 80 140 48 948 716 232 272 . 52 .220 12 1436 958 480 358 182 194 286 1388 1004 384 428 , 150 278 108 '948 928 20 21 86 130 ~110 Average 51 Dec Jan Feb Mar Apr Mav June July Aug Sept Oct Nov Worcester, Massachusetts Sewage Treatment Plant Treatment consists of Imhoff tanks which handle twenty million gallons per day with an average detention ‘period of three hours. Composite samples were taken and the removal of suspended solids was fifty-seven per cent. Considerable industrial waste liquors are contained in the regular sewage. Nonthly Average for Year 1932. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Raw Primary #:Raw Primary Diff— Sewage Effluent Removal Sewage Effluent Removal erence 885 565' 120_ 227 92 '135 ~ 15 810 510 100 183 95 98 2 800 510 90 162 90 72 18 531 480 51 142 95 47 4 500 450 50 117 86 31 19 881 542 139 218 91 117 22 724 582 162 242 79 ‘163 ~ 1 820 490 130 195 80 115 15 830 500 130 205 75 130 0 608 538 70 188 97 91 ~ 21 507 442 85 150 104 48 19 475 411 84 135 93 42 22 Average 7 12th 13th 14th 15th 16th 17th 18th The activated sludge unit at spiral paddles. ACTIVATED SLUDGE UNITS Muskegon Heights Sewage Treatment Plant Muskegon Heights, Xichigan is equipped with filter diffusion plates and Activated sludge is added to the sew~ age in a one to five proportion. The effluent after leaving the activated sludge tanks flows into two secondary settling tanks and this effluent is directed either onto contact filter beds or directly into the river, the choice depending upon the quality of the effluent. Daily determinations of April 1933. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. seedy? Secdy. Secdy y. Se cdy Diff- Influent Settled. Removal Influent Settled Removal erence 872 425 247 180 54 108 141 721 440 281 148 38 108 173 833 432 201 184 28 158. 43 812 432. 180 100 28 74 108 813 455 158 160 30 110 48 577 428 149 104 50 54 95 .746 703 43 192 328 ~l34 17? Average 112 Muskegon Heights Sewage Treatment Plant Continued Daily Determinations for February 1934. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Secdy. Secdy. Secdy. Secdy. Diff- ‘lgfluent Settled Removal Influent Settled Removal erence let 884 428 458 400 35 385 93 2nd 888 408 482 480 28 352 130 3rd 1388 410 958 818 31 585 373 4th 1142 442 700 318 28 288 28 5th 890 584 308 392 30 382 30 8th' 770 474 298 232 35 197 35 7th 914 428 488 388 34 334 34 8th 994 410 ' 584 404 33 371 33 9th 940 402 538 378 30 348 30 10th 1080 358 722 388 23 345 23 11th 788 412 374 278 25 251 25 12th 892 384 528 348 32 318 32 13th 788 402 384 304 31 273 31 14th 884 480 344 378 33 343 33 Average 88 Daily Determinations for March 1934. lat 728 432 294 228 27 201 93 2nd 842 454 188 338 38 300 -112 3rd 802 418 388 288 24 244 142 5th 940 400 540 400 32 388 172 8th 850 392 258 . 240 28 214 44 7th 812 388 424 380 30 350 74 8th 954 484 490 28 22 238 252 9th 858 302 354 332 20 312 42 10th 1132 444 888 740 27 713 — 25 11th 1132 408 728 592 19 573 153 12th 858 458 ' 388 308 19 298 ‘100 13th 724 434 290 258 . 16 240 50 Muskegon Heights Sewage Treatment Plant Continued Daily Determinations for March 1934 - continued- Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. -_*Secdy. Secdy. Secdy. SeEdy. DIET— Influent Settled Removal Influent Settled Removal erence 14th 840 424 418 292 29 283 153 15th 952 822 330 280 14 288 84 18th 798 388 432 378 35 341 91 Average 86 Daily Determinations for April 1934. let 732 ' 424 308 204 31 173 135 2nd 636 416 220 124 13 111 109 3rd 566 428 138 138 26 112 126 4th 628 450 178 134 23 111 167 5th 584 510 74 142 26 116 - 42 6th 632 440 192 132 25 107 85 7th 512 396 116 112 20 92 24 8th 758 400 358 214 18 196 162 Average 94 Geneva Illinois Sewage Treatment Plant The secondary treatment_consists of nine aeration tanks, of which five were in use at this time, and a secondary settling tank. The aeration tanks have a detention period of eight hours and the secondary tank has two hours detention. The aerators, made by the Simplex Ejector & Aerator Corporation, have a revolv— ing cone which is fitted with vanes to throw the liquid over the tank surface. A rotor pumps the liquid up the tube from the bottom of the tank. Daily Determinations for February 1934. Total Solids ' Suspended Solids Total p.p.m. p.p.m. p.p.m. Secdy. Secdy. Secdy. Secdy. Diff- Influent Settled Removal Influent Settled Removal erence lst 800 800 0 74 5 89 - 89 2nd 840 780 80 108 28 82 - 22 3rd 808 792 18 198 17 181 -185 5th 780 848 -88 270 18 152 -240 8th 804 472 332 54 2 52 280 7th 812 740 72 52 4 48 24 8th 880 538 122 78 10 88 58 9th 888 820 88 94 19 75 - 7 10th 644 558 88 80 2.4 78 10 12th 884 704 180 138 4.4 132 48 13th 818 892 124 104 8.8 97 27 14th 838 588 48 78 3 75 ~27 l5th 778 828 148 110 4 108 42 18th 872 848 ~ 224 84 5.8 58 188 17th 858 584 92 80 2 58 34 19th 1108 808 300 118 12.4 108 194 20th 820 780 80 90 5.8 - 84 - 24 21st 804 580 44 88 4.5 83 - 43 22nd 23rd 24th 28th 27th 28th Geneva, Illinois Sewage Treatment Plant Continued Daily Determinations for February 1934 - Continued Total Solids. Suspended Solids Total p.p.m. p.p.m. p.p.m. Secdy. Secdy. Secdy. Secdy. Diff- lnfluent Settled Removal Influent Settled Removal erence 840_ 488 172 90 ll 79 93 712 828 84 80 8.5 73 11 718 820 98 52 1 51 45 958 738 220 182 9 153 87 1004 838 188 150 18 134 34 928 928 O 88 10.5 78 ~78 Average 19 1930 1931 Sanitary District of Indianapolis, Indiana The activated sludge plant at Indianapolis consists of seven units, five full size and two are of half size. Filtro plates are used in the tanks and are so placed at the sides to cause a spiral flow. The plates cover 7.5 per cent of the total tank area. The tanks are 238 ft. long, 15 ft. deep and 20 ft. wide. About one cubic foot of air per gallon is applied to the sewage. The sewage in revolving about the tank travels about six miles through the tanks during its spiral flow. Yearly Averages for Years 1930 and 1931 Total Solids Suspended Solids Total P-p-m. p.p.m. P-P-m- Secdy. Secdy. Secdy. Secdy. :Diff- Influent Effluent Removal Influent Effluent Removal erence 1040 797 243 198 39 157 88 1037 779 258 200 32 188 90 Average 88 Oct. 30th 3lst Nov. lst 2nd 3rd 4th 5th Dearborn Sewage Treatment Plant West Side Unit The units at Dearborn consist of two Dorr Traction type clarifiers. They are sixty feet in diameter and equipped with Laughlin magnitite filters. Each has a volume of 200,000 gallons and a capacity of four K.C.D. The plant ordinarily handles sewage from the West Side and all of the sludge from the East Side plant. The report included here was made with just the sewage from the West Side. Lime, Pulp Paper and ferric chloride are used in the treatment process. Daily Determinations of Experimental Run, October and November 1933. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. '_—aa"w'_0—'Tiari ied him 01 afihed Diff- Sewage Effluent Removal Sewage Effluent Removal erence 838 514 324 400 18 382 ~ 58 838 533 305 378 23 353 - 48 l028 588 482 512 22 490 - 28 894 591 103 142 17 125 - 22 849 55" 93 91 22' 89 24 583 343 220 213 15 148 22 588 554 34 130 24 106 _ 72 Dearborn Sewage Treatment Plant West Side Unit - Continued Daily_Determinations of Experimental Run, October and November 1933. - Continued Total Solids Suspended Solids Total p.p.m. p.p.m. pop-mo Raw Clarifiéa """"“fi§i ciarifiea 018?: Nov. _Sewagp Effluent Removal Sewage Effluent Removal erenog 8th 732 578 154 128 20 108 148 7th 752 440 312 398 8 392 ~~80 8th 897 570 127 173 20 153 - 28 9th 528 508 20 88 10 88 - 48 10th 895 283 432 159 5 154 278 11th 813 558 55 131 18 113 - 58 12th 735 832 102 189 22 187 - 85 13th 879 508 173 211 18 193 - 20 14th 587 480 87 137 10 127 - 40 15th 575 528 49 103 10 93 — 24 18th 820 838 -18 72 12 80 — 78 17th 550 547 3 74 ll 83 - 80 18th 423 441 ~18 187 25 142 -180 19th 489 529 —80 213 21 192 ~252 20th 848 598 50 188 22 148 ' - 08 let 887 527 180 233 35 19 - 38 22nd 848 803 245 388 19 389 ~124 23rd 1190 588 804 947 14 943 «339 24th 740 82: 115 144 7 139 - 24 25th 724 490 234 312' 34 278 - 44 28th 749 840 109 185 18 187 - 58 27th 840 488 154 174 8 188 - 12 28th 487 587 ~100 187 24 143 — 43 utes at a sixteen M.C.D. Flint has two ten foot deep filters with a net effective area of three and a half acres. in the filters varies from 1.5 to 2.5 inches upon screening. 1,088 type "D" circular spray nozzles are FILTRATION UNITS Flint Sewage Treatment Plant in use on the beds. The filter is followed by four final settling The stone tanks which have a detention period of forty-four min~ rate of flow. Monthly Averages for Year 1932. Jan Feb Mar April May June July Aug Sept Oct Nov Dec 'Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. "filter fiant filter Plant . Diff~ Influent Effluent Removal Influent Effluent Removal erence 733 718 15 52 25 27 ~ 12 772 721 1 85 41 24 ~ 23 827 741 88 84 71 13 73 750 710 40 79 99 ~20 80 795 770 25 119 217 ~98 123 773 791 —18 81 70 ~ 9 ~ 9 882 751 ~89 41 57 ~18 ~ 53 713 743 ~30 34 39 ~ 5 ~ 25 714 740 ~28 33 31 2 ~ 28 733 754 ~21 45 38 7 ~ 28 731 723 8 45 25 20 ~ 12 737 720 17 53 23 2O - 3 5 Average Flint Sewage Treatment Plant ' - Continued I Monthly Averages for Year 1933. Total Solids Suspended Solids Total p.p.m. ’ p.p.m. p.p.m. Filter Plant Filter Plant Diff- lnjluent Effluent Removal Influent effluent Removal erence Jan 708 838 72 57 23 34 38 Feb 748 885 81 58 23 35 28 Mar 710 858 52 52 20 32 20 April 854 834 21 35 15 20 1 May 747 707 40 52 48 4 38 June 797 828 ~31 75 141 ~88 35 July 744 737 7 54 48 8 1 Aug 740 740 0 47 39 8 ~ 8 Sept 734 732 2 42 37 5 ~ 3 Oct 729 780 ~31 45 35 10 — 41 Nov 785 780 5 48 28 20 ~ 15 Dec 738 718 22 47 22 25 ~ 3. Average 7 Jan Feb Mar April May June July Aug Sept Oct Nov Dec Pontiac Sewage Treatment Plant Pontiac has seven 100 ft. diameter trickling filters. They are all of the revolving.arm type and an rulby grav~ ity. The filter effluent passes through a secondary settling tank, which is too small to provide a satisfactory detention period. through this tank into the river. The filter effluent passes directly Monthly Averages for Year 1932. Total Solids Suspended Solids Total p.pm. p.p.m. p.p.m. 'Fllter Plant :Filter Plant Eiff- __1nf1uent Effluent Removal Influent Efflgggt Removal erence 845 800 45 73 24 49 ~ 4 858 804 52 73 27 48 8 847 594 53 83 31 52 l 883 815 88 83 42 41 27 888 880 8 77 88 11 ~ 3 880 738 ~58 78 134 ~58 — 2 .880 887 ~ 7 74 81 13 ~20 897 879 20 75 41 34 ~14 892 870 22 70 4O 30 ~ 8 855 848 7 80 43 37 ~30 785 733 32 73 38 37 ~ 5 888 838 30 81 42 39 ~ 9 Average ~ 5 Pontiac Sewage Treatment Plant - Continued Konthly Averages for Year 1933. Total Solids Suspended Solids Total p’p'm° p.p.m. p.p.m. Filter Plant Filter Plant Diff- Influent Effluent Removal Influent Effluent Removal erence Jan 948 932 18 81 58 25 ~ 9 Feb 898 835 81 84 31 53 12 Mar . 920 - 888 52 87 38 51 1 April 938 883 53 77 32 45 8 May 749 824 ~75 79 104 ~‘25 ~50 June 840 942 ~102 80 147 ~ 87 ~35 July 835 875 ~40 75 72 3 ~43 Aug 822 820 2 78 87 9 ~ 7 Sept 845 833 12 83 82 21 ~ 9 Oct 927 942 ~15 78 59 17 ~32 Nov 935 895 40 79 82 17 23 Dec 931 870 81 84 82 22 39 Average ~ 8 Yearly Averages 1933 881 876 5 80 66 14 e 9 1932 695 672 23 75 49 26 - 3 1931 671 635 36 85 45 4O - 5 Aurora, Illinois Sewage Treatment Plant The filters are beds of crushed stone six feet deep and cover four acres in area. They are equipped with a spray system and have a tile under drainage. About eight million gallons are handled per day. After leaving the filters the effluent is released directly into the Fox river. Nonthly Averages for Years 1931,32,33. Total Solids Suspended Solids Total p.p.m. pop-mo . p.p.m. 1q31 Filter Plant ‘ 1__ ' Filter Plant Diff— ” Influent Effluent Removal Influent Effluent Removal erence April 874 712 182 92 ll , 81 81 May 923 811 112 131 40 91 21 June 881 809 72 115 ~48 70 2 July 820 756 74 106 47 59 5 Aug 783 737 48 95 51 44 4 Sept 744 680 64 111 41 7O - 6 Oct 831 766 65 130 41 89 ~24 Nov 796 ' 733 63 95 46 49 14 Average 8 1932 May 828 815 13 5 21 32 ~19 June 774 708 6 51 19 32 34 July 772 717 55 85 32 33 22 Aug 803 778 27 8 28 25 2 Sept 78 737 23 51 23 28 ~ 5 Oct 786 733 53 64 32 32 21 Nov 901 930 ~29 77 33 44 ~72 Average — 1 1933 June July Aug Sept Oct Nov Aurora, Illinois Sewage Treatment Plant - COT] tinued Monthly Averages for Years l931,32,33. - COD tinued Total Solids Suspended Solids Total p'p'm" p.p.m. p.p.m. Filter Plant Filter Plant DiffG Influent Effluent Removal Inflggnt_Effluent Removal erence 845 787 78 88 30 38 40 850 797 53 82 41 41 12 815 771 44 89 33 38 12 883 888 17 80 49 31 ~14 829 809 20 88 28 42 ~20 905 889 18 89 28 41 ~25 Average 5 Dec Jan Feb Mar April May June July Aug Sept Oct Nov Worcester Massachusetts Sewage Treatment Plant Dosing tanks and spray nozzle filters are used at Worcester. The filters run at a rate of 1.4 M.G.D. The filter effluent flows out of tile drains, into two secondary tanks which have a satisfactory detention period. Monthly Averages for Year 1932. Total Solids Suspended Solids Total p.p.m. p.p.m. p.p.m. Filter Plantw Filter Plant 91?}. __1nf1uent Effluent Removal Influent Effluent Removal erence 585 450 115 92 31 81 54 510 415 95 95 33 82 33 510 423 87 90 18 74 13 480 420 80 95 4O 55 5 450 427 23 88 52 34 ~11 542 543 ~ 1 91 81 30 ~31 582 597 ~30 79 72 7 ~37 490 480 10 80 2O 80 ~50 500 425 75 75 25 50 ' 25 538 435 103 97 23 . '74 29 442 382 80 104 49 55 5 411 380 51 93 51 42 9 Average 4 LABORATORY SET-UP APPARATUS. Motor Three pulleys Three- 3 liter jars Three brakes Three brackets RESULTS OF LABORATORY STUDIES Because of the lack of data on Chemical Treatment of sewage, it was decided to set up a small unit in the laboratory and treat sewage with ferric chloride. The equipment consisted of three 3 liter battery jars each having a two bladed pr0pellor type floculator. A sheet metal brake was used in the jar to prevent-the liquid from rotating. A small motor was attached to the pr0p~ ellors which were regulated to turn at a rate of thirty R.P.E. Because of the high water in the Red Cedar River in the Spring of the year the sewage treatment plant was shut down, thereby, making it necessary to collect the sewage from man—holes on the sewage line. The first quantity of sewage was taken from a man— hole on the intereepter. After taking the sewage into the laboratory it was decided this sewage was too weak to make a favorable test. Evidently seepage from the river had caused dilution of the sewage. Sewage was taken then from the main sewer line through a man-hole at East Grand River and Charles Street. This sewage proved to be satisfactory but because of the inconvenience of taking it out of this man-hole, the remaining amount of the sewage tested was taken from the same main at a man-hole located southeast of the college gymnasium. The sewage in all of the samples collected was muc weaker than usually obtained at the treatment plant, It was, however, typical domestic sewage without industrial wastes. I In the laboratory the sewage was placed in the three 3 liter jars and one grain per gallon of ferric chloride was added. This amount was chosen because of the results of various experiments with ferric chloride at Palo Atlo and elsewhere which showed that one grain per gallon gives a very satisfactory floc. The sewage in the jar was floc- ulated at 30 R.P.M. for twenty minutes and then allowed to settle for one hour. The raw sewage was tested for total solids and suspended solids. After the treated sewage had settled the supernatant liquid was also tested for total solids and suspended solids. To prevent error as much as possible, all porcelain dishes and gooch~crucibles were used. It would have been better to use platimum dishes but it was impossible to obtain enough of them to make the test at the time desired. The dishes were all comparatively new, thereby eliminating some of the error which might have been introduced had a mixture of old and new been used. The dishes and crucibles were heated in the oven over night before weighing and also were left over night in the oven for drying of the solids. Methods for the proceedurazwhich were followed in making the total solids and suspended solids determinations 3’38 given below: Total Solids Ignite cool, and weigh a clean dish. ’1 Thoroughly mix the sample and measure out 1C0 C.u. into a 103 C.C. graduate. (Care must be taken to keep the solids in suspension while measuring.) Pour the 100 C.C. sample into the dish and then sev— D eral rinsings of the raduat, using -sall portions of (D r water. Evaporate to dryness over the water bath. Dry in the oven at 103 degrees C. for about one hour. Cool the dish in the desiccator and weigh. Calculations - Weight of solids x 10,000 = F.P.M. total solids. (I) uspended Solids Prepare a dilute ehulsion of asbestos fiber and pour through a gooch crucible in a suction flask until a mat of about 8 m.m. thick is obtained. Pass istilled water through the crucible until no asbestos fibers are carried through. Dry in the oven and ignite in the furnace or over a burner. Cool in a desiccator and weigh. 5. 6. 7. 8. 9. Measure 100 0.0. of the well mixed sewage into a graduate. Place the crucible in the suction flask and pour the measured sewage over the filter. Rinse the graduate several times with small amounts of water and pour rinsings over the filter. Dry the crucible for one hour at 103 degrees 0. Cool in a desiccator and weigh. Calculations - Weight of solids x 10,000 = P.P.M. suspended solids. Laboratory Results. The table shown below shows the results obtained from treating sewage with one grain per gallon of ferric chloride Total Solids Suspended Solids Total % Remv.of p.p.m. p.p.m. p,p.m. Solids ‘__ Based on Raw Raw Diff; Sus. Soli: Sewage Effluent Removal Sewage Effluent Removal_erence Removal A—l 688 614 74 100 45 55 19 135 2 688 612 76 100 51 49 27 155 3 688 603 85 100 33 67 18 127 B-l 694 616 78 95 3O 65 13 120 2 694 608 86 95 35 60 26 143 3 694 639 55 95 22. ' 73 —22 76 0-1 807 669 138 141 23 118 20 117 2 807 658 149 141 20 121 28 123 0—1 727 583 144 201 46 155 —ll 93 2 727 563 164 201 43 158 6 104 Average 12.4 119 GENERAL COECLUSION The table shown below gives the average differences between total and suspended solids removed by the various units in the plants studied and also in the laboratory. Plain Activated Settling Sludge Chemical Filters Grand Rapids - 3.0 _ Flint 1.9 6.0 Pontiac 7.0 -6.0 Traverse City 12.0 Dearborn 3.0 ~49.0 Jackson Prison 26.0 Muskgeon Heights 28.0 89.0 Aurora, Illinois - 4.0 v.0 Geneva, Illinois 51.0 19.0 Worcester, Mass. 7 4.0 Sanitary Dist. Ind. 88.0 Laboratory Results 12.4 Primary Settling Plain settling which involves only settling solids should not show a difference between the total and sus— pended solids removed. In all of the plants studied except Jackson Prison, Muskegon Heights and Geneva the difference of removal is so slight that they can be considered as being equal. I The plants at Muskegon Heights and Geneva are both activated sludge plants and the reason for such a high difference may be the addition of the excess activated sludge to the primary tanks. This sludge may floculate a portion of the colloidal and fine suspended matter. There is no apparent reason or explanation of the high difference obtained at Jackson Prison. It can be concluded from this data that in the primary settling units the total solids and suspended solids determinations show the same amount of removal. The substitution of the total solids for the suspended solids determination would not be an advantage except where the laboratory equipment would be better suited for this determination. Activated Sludge Of the three plants studied, Muskegon Heights and the Sanitary District of Indiana both show about the same difference between the total and suspended solids removed. The two plants both have diffused air aerat- ors and their removals check fairly close. Because of the decided increase in removal shown in the activated sludge units it would be advisable to substitute the total solids for the suspended solids determinations. The suspended solid test does not show the full amount of removal and the substitution would show better plant efficiency. Chemical Treatment The large amount of total solids in the effluent at Dearborn may be caused from the soluble inorganic material added along with the large quantities of lime, paper pulp, and ferric chloride. In most chemical processes it has been found that too large a quantity of chemicals are being used to give a maximum efficiency of removal, therefore, if the quantity of chemicals were reduced it might result in a different removal of total solids. The results obtained in the laboratory show con~ clusively that the total solids determination shows a greater amount of removal than the suspended solids when sewage is treated with small amounts of ferric chloride. Therefore, plants treating sewage with ferric chloride or a similar chemical, in small quantities mould show a greater removal if the total solids deter- mination replaced the suspended solids determination. Filtration The table shows conclusively that there is very little, if any difference, in the removal shown by the two deterinations in the case Of the trickling filters. No substitution would be advisable unless other factors warranted such a change. In conclusion the total solids determination would better show the efficiency in solids removal in the case of activated sludge and chemical treatment units than does the suspended solids. This is not the case with primary and filter units. 711.1351» s... a p“ to o. ‘. Q. J M U bTATE L r‘ x 2, ‘fl’\)"\ A." wii ma~..b..-L - . . . . . . . _ . . . , . V . . .. . . . . . , .. . . . . . v . J . n n c . c . .. — . p, . o q . . s . . . . . . r .. . . U .v I l u y . I gr0~.0.. .. . , . i . . . r . . . , ., o. r ' . . . o t I I A . . l . '