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I,YDCSTRIAL A S D Eal'GISEERISG CHEMISTRY
Vol. 21, KO. 6
Changes of Sulfur Comr>oundsduring Sewage Treatment',' A. L. Elder with A. M. Buswell STAT^ WATER SURVEYDIVISIOK,URBANA,ILL
Human excreta account for but a small percentage TABILIZATIOK of oris the case in raw sewage or of the sulfur found in sewage. Reduction of the sulfur ganic matter, by which effluents from units of treatcontent of sewage during sewage purification is small. is meant converting it ment processes, the method Absence of obnoxious odors during treatment of by either oxidation or reducof Bach4was used. For total sewage in nidus tanks was noted. tion into a form such that it sulfur in sewage sludge the Anaerobic sludge digestion produces disagreeable will not take u p d i s s o l v e d m e t h o d of Schreiberj w a s odors unless the pH of the digesting sludge is kept oxygen,. is normally a very used. above 7.0. The reduction of sulfates in raw sewage c o m p l i c a t e d process. The Hydrogen sulfide was deteris very rapid at 37" C., fairly rapid at 22" C., and slow at stabilization of sulfur commined by the colorimetric pounds, particularly in sew10" c. method described by Almy.6 The biochemical oxygen demand of several sulfur age, has not been studied in The method depends upon the detail. From the standpoint compounds has been determined. formation of methylene blue Methods for determining various forms of sulfur of odor control, stabilization by adding solutions of phave been adapted for use in sewage investigations. of sulfur compounds is paramino dimethylaniline hydroticularly important. An odor chloride and ferric chloride to nuisance ~$11 bring a complaint to a sewage-plant operator hydrogen sulfide solutions. The reagents used are: standard very quickly. The failure t o study the fate of sulfur com- hydrogen sulfide solution for preparing standards; 0.04 gram pounds in the degradation of organic matter is probably due p-aminodimethylaniline hydrochloride per 100 cc. I: 1 hydroto the extreme difficulties in making the analytical deter- chloric acid; 0.02 Jf ferric chloride; 0.6 p$r cent zinc acetate. Standards were prepared in 50-cc. Nessler tubes by adding 5 minations. The large number of sulfur compounds which might be CC. of p-aminodimethylaniline hydrochloride and 1 cc. of found in any waste, either domestic or industrial, may be ferric chloride to 44 cc. of distilled water containing a known divided into three groups: (1) those normally present in the quantity of hydrogen sulfide per 50-cc. tube. The standards dilution water, (2) those arising from industrial wastes, and ranged from 0.001 to 0.050 mg. of hydrogen sulfide per 50-cc. (3) those originating from human excreta. Sulfate and tube. To 1-liter samples which were used for determining hydrohydrogen sulfide sulfur may be present in dilution water. Ferrous sulfate, sulfuric acid, free sulfur, sulfocyanates, and gen sulfide in sewage, 50 cc. of concentrated hydrochloric acid organic sulfur compounds from certain dye industries are the were added and the flask containing the sample was aspirated most important sulfur compounds polluting streams. The with carbon dioxide for 30 minutes. The hydrogen sulfide greater part of the sulfur eliminated from the body is in the mas collected in 0.6 per cent zinc acetate and determined by oxidized form. Cammidge3 gives as average figures for the adding the reagents in proportions as given for preparing quantity of sulfur excreted per capita per day expressed as standards. For quick approximate estimation of hydrogen SOo: in the urine 1.8-2.8, feces 0.06-0.17, perspiration 0.005, sulfide, 10 cc. of sewage may be treated directly with 5 drops average 3.0 grams. Assuming that the excreta from each of p-aminodiniethylaniline hydrochloride and 1 drop of ferric individual is diluted with 100 gallons of water, the sulfur chloride solutions. A little experience will enable one to estimate the amount of hydrogen sulfide from the depth of addition amounts t o only 3 t o 4 p. p. m. in the sewage. color produced. Further work is being done on the developMethods for Determining Sulfur Compounds in ment of this test for field use. Organic Matter Such a small quantity of elementary sulfur is present in sewage that it is exceedingly difficult to determine it accuIt has been shown that sulfur in sewage may exist in various forms, the quantity of which is usually very small. Of all the rately. Extraction of the sulfur with carbon disulfide and sulfur compounds present in sewage, determinations have oxidation of the sulfur in the extracted material have been used. The presence of elementary sulfur in laboratory experiments thus far been made for inorganic, ethereal, organic, elemenwith sewage and sludge under complete anaerobic conditions tary, cystine, and cysteine sulfur, and hydrogen sulfide. For has not been detected. The procedure used for determining the determination of inorganic and ethereal sulfur the procystine and cysteine was the iodate method of Okuda7 as cedures given in standard texts of physiological chemistry modified by Mr. Neave of this laboratory. (A titration temwere used. The precipitates of barium sulfate obtained by these procedures were ignited and weighed. The figures perature of 20-25" C. was maintained to give a more rapid titration, and a starch-iodide end point used, not only t o inreported for inorganic sulfur represent both inorganic and crease the sensitivity of the determination, but also t o adapt ethereal sulfur. The quantity of ethereal sulfur was always it for use in colored or turbid culture media and sewages.) quite low and the significance of the figures obtained from its The following are the average results obtained for cysteine: determination does not appear t o warrant considering it raw sewage = 0, in nidus tank effluent = trace, in liquor from separately. If the quant,ity of organic sulfur was small, as digesting sludge -- 0-2 p. p. m. The cystine content of raw 1 Presented before the Division of Water, Sewage, and Sanitation Chemsewage and nidus tank effluents varied from 0 to 2 p. p. m., istry a t t h e 76th Meeting of the American Chemical Society, Swampscott, and liquor from digesting sludge varied from 2.1 t o 4.0 p. p. m. Mass., September 10 t o 14, 1928. 4 Bach, Gesundh. Ing , 46, 370 (1923). 2 Abstract of thesis submitted b y A. L. Elder in partial fulfilment of
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the requirements for t h e degree of doctor of philosophy in chemistry in t h e Graduate School of the University of Illinois. 3 Cammidge, "Feces of Children and Adults," p. 22 (1914).
Schreiber, U. S. Dept. Agr , Bur. Chem., Circ. 66 (1910). 6Almy, J . A m . Chem. Soc., 47, 1381 (1925). Okuda, C. A , , 21, 3212 (1927).
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INDCATRIAL 9.VD ENGISEERISG CHEMISTRY
June, 1929
Sulfur Removed during Sewage Treatment
The quantity of sulfur removed during sewage purification is so small that i t is necessary to collect composite samples over long periods in order that sampling error niay be minimized. From the data in Table I it appears that human excreta account for but a small percentage of the sulfur found in sewage. The Champaign-Urbana water supply contains only about 0.4 p. p. m. of sulfur, while the sulfur content of the sewage is about 40 p. p. m. This sewage contains practically no industrial wastes, so the increase in sulfur other than that accounted for by human excreta must come largely from other wastes and infiltration water which carries as much as 150 p. p. m. of sulfur. Determinations have been made of the quantity of sulfur removed during the purification of sewage. (Table I) From these data it appears that very little sulfur is removed duringsewage purification proce s s e s . ( T h e determinations made on activated-sludge plant samples w e r e c o l l e c t e d a t Decatur, Ill. Industrial wastes account for t h e h i g h s u l f u r content .)
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