The Effects of
Sulfides  on Anaerobic Treatment
ALONZO W. LAWRENCE, Research Assistant
PERRY L. McCARTY, Associate Professor of Sanitary Engineering
Department of Civil Engineering
Stanford University
Stanford,   California
FERNAND, J. A. GUERIN, Assistant Engineer
Lalonde, Valois, Lamarre, Valois and Associates
Consulting Engineers
Montreal, Quebec
Anaerobic waste is a biological process. As such it depends for successful
operation on the maintenance of a proper environment for the organisms involved.
By delineating this proper environment, a more complete understanding of the
process will be attained. This will lead to an increase in the operational control
and predictability of anaerobic treatment. Temperature, pH, nutrient requirements, and materials producing toxic effects are among the important environmental parameters. Special attention must be focused on the problem of toxicity-
causing substances if anaerobic treatment, long a mainstay of municipal sewage
treatment, is to be successfully extended to the treatment of complex industrial
wastes. Many of these wastes are certain to contain a greater variety and higher
concentration of inorganic salts than would be expected m municipal wastes. Recent studies (1,2) have reported the effects of several cations on the methane
fermentation. Sulfide is an anion which occurs in many wastes, or can be produced by biological action on the wastes, and it may be a limiting factor in the
anaerobic neatment of many industrial wastes. The effects of high sulfide concentrations on anaerobic treatment are not well understood, and were explored in
this investigation.
PREVIOUS STUDIES
Reports on the role of sulfides in anaerobic treatment have appeared in the
literature at various times. Rudolfs and Zeller (3) reported the effects of several
sulfate salts on the digestion of seeded, fresh solids. Sulfate reduction to sulfide
was indicated. A decrease in gas production and volatile matter reduction occurred, the extent varying from salt to salt. In general, gas production was retarded more severely than volatile matter reduction.
In connection with the treatment of white water wastes, Rudolfs and Amberg
(4,5) investigated the effects of soluble sulfides on the digestion of both seeded
white water and sewage sludge. In the case of sewage sludge, the addition of
200 mg/1 of sulfides decreased gas production by 70 per cent, and volatile matter
reduction by 50 per cent. From a slug feed study of acetate fermentation, it was
concluded that methane fermentation was a linear function of soluble sulfide concentration, and that no methane was formed with sulfide additions above 165
mg/1 as sulfur. However, additions up to 300 mg/1 of soluble sulfides were felt to
have little effect on the production of volatile acids. These investigators studied
several methods for controlling the soluble sulfide concentration in laboratory digesters receiving white water concentrate.   It was concluded that stripping of the
- 343 -