V. Uberoi et Sk. Bhattacharya, INTERACTIONS AMONG SULFATE REDUCERS, ACETOGENS, AND METHANOGENS IN ANAEROBIC PROPIONATE SYSTEMS, Water environment research, 67(3), 1995, pp. 330-339
The complex process of propionate oxidation in anaerobic systems in th
e presence of excess sulfate is based on combinations of six biologica
l reactions. Laboratory batch and continuous experiments were conducte
d to study which of these reactions were predominant in propionate oxi
dation by sulfate-reducing bacteria in the presence of acetogens and m
ethanogens. The engineering significance of the feed propionate to sul
fate ratio was studied. In batch serum bottle experiments, sulfide was
more toxic to sulfate-reducing bacteria (SRB) than to acetogens and m
ethanogens. Acetate was the least favored substrate for sulfate reduct
ion. Two mechanisms appear possible under sulfate-limited conditions:
(1) propionate use by both SRB and non-SRB acetogens and acetate and h
ydrogen use by methanogens and (2) propionate use by non-SRB acetogens
followed by acetate use by methanogens and hydrogen use by both SRB a
nd methanogens. In the chemostats, at a feed propionate:sulfate ratio
of 2.2 (sulfate-limited condition), the acetate formed was primarily u
sed by methanogens. With a gradual decrease in feed propionate:sulfate
ratio from 2.2 to 0.44 (sulfate-rich condition), SRB outcompeted meth
anogens for acetate. In the chemostat study un-ionized HIS concentrati
ons of up to 178 mg S/L (total sulfide 464 mg S/L) did not inhibit sul
fate reduction.