Part 21

Dry sludge can be used for fertilizer or for filling low lands or it can be incinerated. Its fertilizing value is disputed except when produced by the activated sludge method. The filling in method is economical. Authorities advise the consideration of incineration by cities which burn their garbage.

Dr. Imhoff’s recommendations are the use of sludge for agricultural purposes and for filling in low land. “In both cases,” he says, “the sludge must first be dried and this is best effected upon a drying bed after the sludge has been decomposed in an inoffensive, odorless manner, in a separate tank through which sewage does not flow.”

Many unsuccessful efforts have been made to extract the valuable ingredients from sewage, but to date the experience has been that they have been more costly to recover than they are worth. Dr. McLean Wilson, Sanitary Inspector of the West Riding of Yorkshire Rivers Board, believes that the valuable ingredients of sewage will ultimately be recovered and used since many capable experimenters are at work on the problem. H. W. Clark, Chemist of the Massachusetts State Board of Health, is of the opinion that sludge has some value and that “it seems inevitable that as the processes of drying, pressing and fat separation are improved and as nitrogen advances in price sewage sludge will become of greater agricultural value than at present.” Experiments have been made at the Philadelphia Sewage Testing Station by burning dry sludge and wet sludge mixed with fine coal. The results were unsuccessful. Experiments have also been made at the Cleveland station where it was found that the sewage sludge contained about one-half as much nitrogen and one-third as much phosphates as does the garbage tankage.

Management and Supervision

No matter how well a sewage disposal plant is designed or constructed it will not do its work in a satisfactory manner and produce desired results unless it is efficiently managed. Every plant should be in charge of a man who has knowledge of sewage disposal principles, is thoroughly familiar with his plant and who can act intelligently in an emergency. The New Jersey State Sewerage Commission in one of its reports notes the tendency of local authorities to permit the deterioration of disposal plants usually through inattention. “It cannot be too strongly urged on those charged with these, as of other public works, that a competent man in charge is a primary necessity and that the plant should be kept continuously in the highest state of efficiency.” The same condition is complained of by the California State Board of Health and other state organizations. In one of its bulletins the California State Board says that “some of the plants are operating very indifferently well and some very badly. The general situation shows plainly the need of expert advice to municipalities with respect to general methods and necessary efficiencies from some central authority.”

D. C. Faber, Industrial Engineer of the Iowa State College, goes so far as to claim that practically all nuisances in connection with plants can be traced directly to failure to give them attention. He says that even where plants have been found too small increased care in many cases could be made to offset lack of capacity.

In several states, such as New York, Pennsylvania, New Jersey, Kansas, Ohio and Massachusetts, the State Boards of Health have supervision over the designing of new plants and the operation of those established. The good results obtained as a result of this supervision are evidence that similar powers should be granted to all state boards of health.

With a plant designed to meet local conditions, properly constructed and efficiently managed, a city should have no difficulty in disposing of its sewage economically, in a sanitary manner and without creating a nuisance.

Table II (a)

SEWAGE DISPOSAL IN AMERICAN CITIES

─────────────┬─────────────────────────────────────────────────────── Name of City │ GENERAL DATA ├──────────┬────────────────┬─────────────┬───────────── │Population│ General │ Annual Cost │ Gallons │ │ Description │ of │ Treated │ │ Plant │Operation[29]│ Annually │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ─────────────┼──────────┼────────────────┼─────────────┼───────────── Albany, N. Y.│ 110,000│Coarse screens, │ │ │ │ Imhoff tanks │ │ │ │ and pumping │ │ │ │ station. │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ Atlanta, Ga. │ 200,000│Coarse screens, │ $1.93 per│ │ │ grit chambers,│ [M.G.]X.│ │ │ Imhoff tanks, │ │ │ │ sprinkling │ │ │ │ filters. │ │ Akron, Ohio │ 150,000│Screens, grit │ │ │ │ chambers, │ │ │ │ Imhoff tanks, │ │ │ │ sludge beds, │ │ │ │ sprinkling │ │ │ │ filters. │ │ Alliance, │ 22,000│Cameron tanks. │ 2,200 per│ Ohio │ │ Contact and │ [M.G.]│ │ │ intermittent │ │ │ │ sand filters. │ │ │ │ Imhoff tanks │ │ │ │ and slag │ │ │ │ contact beds │ │ │ │ now under │ │ │ │ construction. │ │ Auburn, N. Y.│ 37,000│Two plants. Grit│ 8,500│ │ │ chambers, │ │ │ │ settling │ │ │ │ tanks, dosing │ │ │ │ tanks, contact│ │ │ │ beds. │ │ Brockton, │ 63,000│Revolving │ 12,000│ 768,000,000 Mass. │ │ screens, sand │ │ │ │ beds and │ │ │ │ sprinkling │ │ │ │ filters. │ │ Bloomington, │ 12,000│Septic tank, │ │ 275,000,000 Ill. │ │ center │ │ │ │ settling │ │ │ │ basin, 3 │ │ │ │ contact beds │ │ │ │ arranged │ │ │ │ around center │ │ │ │ basin, nozzle │ │ │ │ spray upon │ │ │ │ filter beds │ │ │ │ surrounding │ │ │ │ contact beds. │ │ Bristol, │ 15,000│Sand filter │ 5,000│ Conn. │ │ beds. │ │ Columbus, │ 220,000│Grit chamber, │ │5,163,000,000 Ohio. │ │ screens, │ │ │ │ pumps, Imhoff │ │ │ │ tanks, │ │ │ │ sprinkling │ │ │ │ filters, final│ │ │ │ settling │ │ │ │ basins. │ │ │ │ │ │ Canton, Ohio.│ 70,000│Imhoff tanks, │ 20,000│ 700,000,000 │ │ contact beds, │ │ │ │ crushed slag │ │ │ │ and gravel │ │ │ │ filter with │ │ │ │ automatic │ │ │ │ syphon, sludge│ │ │ │ drying beds, │ │ │ │ sand and pea │ │ │ │ gravel │ │ │ │ filling. Half │ │ │ │ of bed covered│ │ │ │ with │ │ │ │ greenhouse │ │ │ │ construction. │ │ │ │ Final effluent│ │ │ │ into creek. │ │ Danbury, │ 23,000│Irrigation and │ 7,500│ Conn. │ │ filtration. │ │ │ │ │ │ Dallas, Texas│ 120,000│Screens, grit │ │ │ │ chambers, │ │ │ │ Imhoff tanks │ │ │ │ and sludge │ │ │ │ beds. │ │ Fond du Lac, │ 20,000│Sewage collected│ 3,200│ Wis. │ │ in receiving │ │ │ │ well and │ │ │ │ pumped into │ │ │ │ Imhoff tanks. │ │ │ │ │ │ Fresno, Cal. │ 40,000│Partial │ 1,000│1,825,000,000 │ │ purification │ │ │ │ by settling │ │ │ │ and septic │ │ │ │ process, and │ │ │ │ disposal of │ │ │ │ effluent by │ │ │ │ irrigation of │ │ │ │ alfalfa. │ │ Gloversville,│ 21,000│Primary and │ 22,000│1,022,000,000 N. Y. │ │ secondary │ │ │ │ settling │ │ │ │ tanks, screen │ │ │ │ chambers and │ │ │ │ dosing tanks, │ │ │ │ sprinkling │ │ │ │ filters, │ │ │ │ sludge drying │ │ │ │ beds and sand │ │ │ │ filters. │ │ Houston, │ 140,000│Activated sludge│ 9.25 per│6,570,000,000 Texas │ │ method, │ [M.G.]│ │ │ reinforced │ │ │ │ concrete │ │ │ │ aeration │ │ │ │ tanks, [M.G.] │ │ │ │ settling tanks│ │ │ │ and re- │ │ │ │ aeration │ │ │ │ tanks. │ │ │ │ Continuous │ │ │ │ flow, power │ │ │ │ houses and │ │ │ │ blowers. │ │ Independence,│ 12,000│Cameron tanks │ │ Kas. │ │ and filter │ │ │ │ beds. │ │ Lackawanna, │ 17,500│788,400,000 │ │ N.Y. │ │ 95%. │ │ Milwaukee, │ 450,000│Trial plant │ │ Wis. │ │ operated since│ │ │ │ 1916. Now │ │ │ │ designing │ │ │ │ activated │ │ │ │ sludge plant │ │ │ │ to treat all │ │ │ │ sewage. │ │ Mt. Vernon, │ 38,000│Settling tanks, │ 17,675│ 750,000,000 N.Y. │ │ single story │ │ │ │ septic type, │ │ │ │ constructed in│ │ │ │ five units. │ │ │ │ Sprinkling │ │ │ │ overhead │ │ │ │ Phelps nozzle,│ │ │ │ dosing tanks │ │ │ │ with automatic│ │ │ │ syphon. │ │ New Britain, │ 55,000│Sand filtration.│ 12,000│ Conn. │ │ │ │ Oswego, N.Y. │ 24,000│ │ │ Pasadena, │ 42,000│Imhoff and │ │ 730,000,000 Cal. │ │ septic tanks, │ │ │ │ sludge bed and│ │ │ │ sewage farm. │ │ Providence, │ 249,616│Settling tanks; │ 54,954│9,078,620,000 R. I. │ │ disinfection. │ │ Philadelphia,│ 1,800,000│Pennypack Creek │ │ 450,000,000 Pa. │ │ sewage treated│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ Reading, Pa. │ 110,000│ │ 21,500│2,000,000,000 │ │ │ │ │ │ │ │ │ │ │ │ Rochester, N.│ 248,465│Detritus tanks, │ │ Y. │ │ fine screens │ │ │ │ Imhoff tanks. │ │ │ │ Plan made for │ │ │ │ effluent to │ │ │ │ run power │ │ │ │ plant. Sludge │ │ │ │ drying beds. │ │ Schenectady, │ 87,000│Imhoff tanks and│ 23,000│ N.Y. │ │ sprinkling │ │ │ │ filters. │ │ │ │ │ │ │ │ │ │ Sumter, S. C.│ 12,000│Sewage only │ 8,000│ │ │ partly │ │ │ │ treated. A │ │ │ │ settling │ │ │ │ chamber only. │ │ │ │ No filtering │ │ │ │ bed. │ │ Tallahassee, │ 6,000│Single contact │ 2,500│ Fla. │ │ system, 3 │ │ │ │ beds, coke and│ │ │ │ sand, │ │ │ │ filtration │ │ │ │ with automatic│ │ │ │ apparatus. │ │ Woonsocket, │ 43,000│Screening basin │ │ R. I. │ │ and filters. │ │ │ │ │ │ │ │ │ │ │ │ │ │ Worcester, │ 170,000│Chemical │ 60,000│6,094,000,000 Mass. │ │ precipitation,│ exclusive of│ │ │ sand filters. │ depreciation│ │ │ │and interest.│ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ │ ─────────────┴──────────┴────────────────┴─────────────┴─────────────