1152
IKDUSTRIAL AND ENGINEERING CHEMISTRY
LITERATURE CITED (1) Council on Dental Therapeutics, J . Ana. Dental Assoc., 17, 1943 (1930). (2) Ibid., 18, 548 (1931). (3) Ibid., 18, 1785 (1931). (4) Ibid., 18, 2009 (1931). (5) Ibid., 19, 328 (1932).
Vol. 24, No. 10
(6) Feirer and Leonard, Ibid., 14, 1049 (1927). (7) Ferguson, Sci. Progress,9,429 (1915); DuNoiiy. J . GPU.Physiol., 1, 521 (1919); Klopsteg, Science, 60, 319-20 (1924), and 63, 599-600 (1926). (8) Gies and Collahorators, J. Dental Research, 1, 507, 511 (1919). and 2, 299 (1920); J . Am. Med. dSSOC., 68, 1278 (1917). RECEIVED M a y 26, 1932.
Studies on Hydrogen Sulfide Formation in Sewage a
Ty
w. RUDOLFS* ~ N DW. H. BAUMGARTNER, Agricultural Experiment Station, y e w Brunswick, N. J .
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DORS are often a serious
Owing to the greater hardIncubation of domestic sewage under anaerobic problem in the vicinity ness of the water supplies, the conditions shows the presence of a very small proof sewage plants where sulfate c o n t e n t of s e w a g e in portion of combined sulfides as compared with growth of the community necesthe West and Middle West is volatile sulJide (hydrogen suljde) throughout the usually high compared to that sitates the construction of dwellcourse qf decomposition. T w o distinct peaks of ing adjacent to these plants. found in the e a s t e r n U n i t e d Complaints have also been heard S t a t e s . A n a l y s i s of the raw sulfide formation are characteristic of the decomfrom dwellers near sewer lines, sewage a t the Plainfield, N. J., position (slight changes in p H values). Exdisposal plant showed 70 p. p. m. catch-basins, pumping stations, perimental results point to the presence of interof sulfate. etc. (Figure 1). These odors mediate organic sulfur compounds as sources of There is a v a r i a t i o n in the are especially noticeable where hydrogen salJide. Additions of thiosulfate, sultype of sulfur compound preorganic sewage solids accumudominating in different domeslate and decompose under parfite, and sulfate showed that all forms were attial anaerobic conditions. tic wastes, w h e t h e r it be caltacked at about the same rate. Sodium, ammocium, magnesium, sodium, or S t u d i e s c o n d u c t e d in this nium, magnesium, calcium, and ferrous sulfates laboratory with a n u m b e r of ferrous s u l f a t e , etc. The inwere all potential sources of hydrogen sulfide. organic sulfur may be present odor-producing substances seem There was a distinct retardation in the decompoto some extent as thiosulfate, to indicate that hydrogen sulfide sulfite, etc. is the chief constituent of these sition of ferric sulfate. During the first day of The different salt,s apparently odors. The fact t h a t this incubation, the carious sulfates added (with the give rise to different quantities gas is carried by gentle winds exception of ferrous sulfate) produced hydrogen of hydrogen sulfide when suband air c u r r e n t s a n d can be sulfide at about the same rate as the control. jected to the same conditions. detected in extremely small diluRudolfs found a wide variations in the atmosphere often accounts for the nuisances created (Figure 2). Bach (2) tion in the amount of hydrogen sulfide formed from sulfates states that bad odors in sewage are due to sulfur compounds when they mere added to fresh sewage sludge and subseand not to nitrogenous compounds. Inorganic sulfur pre- quently incubated under anaerobic conditions. His results ponderates over organic sulfur to a great extent in raw sewage. showed sulfide formation to diminish in order of the folBuswell (3) found that raw sewage rarely contained over 1.0 lowing arrangement: Ammonium, magnesium, calcium, copp. p. m. of organic sulfur, whereas inorganic sulfur in some per, sulfate, sulfuric acid, sodium, aluminum, zinc, and ferrous cases was as high as 90 p. p. m. In one case organic sulfur was sulfate. An attempt has been made to study the availability of these registered as a trace and inorganic sulfur 92 8 p. p. m. It appeared, therefore, that the decomposition of sulfates should various sulfur compounds as potential sources of hydrogen be given the most important consideration in any study of the sulfide. Studies have been made on the effect of pH, temperature, seeding, strength of sewage, concentration of sulproduction of hydrogen sulfide from sewage. fates, certain pure compounds, and control substances as There are four sources of sulfiir in sewage-namely: chlorine, iron salts, etc., on the formation of hydrogen sulfide 1. Sulfur in inorganic combination as sulfates, thiosulfates, in sewage. The results of this work will be published later. etc., present in the water supply of the community. 2. Sulfur in inorganic combinations as sulfates, thiosulfates, METHODS etc., present in the ground or surface maters which find their way Sewage used in these experiments was taken from the inby infiltration into the sewer. 3. Sulfu: in inorganic combinations, proteins, etc., or as in- fluent channel of the Plainfield, N. J., senage disposal plant organic sulfates from human excreta. after it had passed through the Reinsch Wurl screen. It was 4. Sulfur in organic or inorganic combination present in intaken a t 11 A. 11. as representative of sewage of average daily dustrial wastes. composition. This sewage is domestic, averaging 220 p. p. m. Of these four sources, in general those from water supplies suspended solids. It is approximately six hours old when it and due to infiltration are probably the most important. In- reaches the plant. However, the sewer leading to the plant filtration water is often very high in sulfate content. Sulfur was designed to give a rapid flow with little collection of solids entering from human excreta is negligible in comparison with in it. All samples were incubated in 500-cc. stoppered the other sources, whereas sulfur in industrial waste is found bottles. Two methods were employed to determine hydrogen sulfide. in special cases.
~ r t i l i mI .
'rRICKLINo FILTERS, FREQUENTLY
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The oiie method, that of Almy ( I ) , modified by Ruswell (9) for sewage analysis, was used when the hydrogen sulfide content did not exceed one or two p. p. In. The other niethod employed was the one in vhi& bydrogen sulfide is allowed t.o react with standardized iodine solution. In both cases the hydrogen sulfide was driven out of the sewage by carbon dioxide to remove the interfering substances. This was accomplished by constructing an aerator frorn large-bore glitss tubing. An alundurn filter disk was fastened in the lower end of the tube. Carbon dioxide, led into the cylindrical chamber uiider this plate through a tuhe, diffused through the plate, giving an even flow of fine hubhles up through the whole of the liquid. A tube at the top of the agrator led the gases off to a ten-bulb absorption tube where hydrogen sulfide was absorbed in either zinc acetate solution or allowed to react with standard iodine solution, depending on the method used. In determining total sulfides, concentrated hydrochloric acid was added to the sample being aerated; this accelezated the removal of hydrogen sulfide from the liquid and also decomposed the combined sulfides. One-half hour to one-hour adration, depending on the amount of sulfide present, sufficed to drive out the sulfides from the sample. When hydrochloric acid was not added, as would be the case where only volatile sulfide or free hydrogen sulfide was determined, longer aeration periods were required. Even then it could riot be ascertained that all the hydrogen sulfide was renioved, although the amount remaining would be negligible. This would tend to make the determinations of combined sulfide slightly higher than they were act,uaUy.
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