Forms of Sulfur in Sewage Sludge

Most studies concerning the composition of sewage sludge have placed emphasis on total elemental analysis, including sulfur. This study was conducted to determine the forms of S and their relationships to other components in sludge. Analyses of the forms and amounts of S in sewage sludge produced by 11 Indiana cities showed that total S concentrations ranged from 0.7 to 2.1% and that from 1 to 27% of the total sludge S was inorganic S extractable with 0.1 M LiCl. Expressed as a percentage of total S, the sludge samples contained from < 1 to 35% sulfide S, from 18 to 53% inorganic nonsulfate S, from 18 to 56% carbon‐bonded S, from 0 to 35% ester sulfate S and inorganic sulfate S, and from 0 to 42% unidentified organic S. Analyses of seven sludge samples obtained over a 2‐year period from the same treatment plant indicated that the forms of S in sludge vary with time. No consistent relationships were found between the amounts of organic C, N, S, and P in sludges. Statistical analyses of the sludge components indicated that Pb and Zn were significantly correlated with sulfide S and that Cd was significantly correlated with organic S, ester sulfate S, and with 0.1 M LiCL extractable S. No significant relationships were found for other metals and the various S fractions.