Upflow anaerobic filters fed acetate and propionate, and completely mi
xed, suspended growth reactors fed acetate, propionate, lactate, and g
lucose were used to investigate the effect of electron donor and react
or type on the interaction between sulfate-reducing bacteria (SRB) and
methanogens. Organic loading rates of 0.25-0.50 g chemical oxygen dem
and (COD)/L.d were used in suspended growth systems and 1.0-5.0 g COD/
L.d in filters. COD/sulfur ratios ranged from 20/1 to 2/1 for complete
ly mixed reactors, and 20/1 to 8/1 for anaerobic filters. Results indi
cated that organisms involved in the conversion of lactate and glucose
into simpler products were not affected by sulfide toxicity. Levels o
f 60-75 mg sulfur/L of hydrogen sulfide and 150-200 mg/L of dissolved
sulfide (DS) caused stress in all suspended growth reactors; 100-150 m
g sulfur/L of hydrogen sulfide and 200-400 mg DS/L could be tolerated
in lactate and glucose systems, although with diminished COD and sulfa
te removal. For similar loading conditions, lactate and glucose system
s had higher DS levels than acetate and propionate systems. A cyclic p
attern of variation of DS and hydrogen sulfide with volatile-acids COD
(VACOD) was observed in long-term experiments with suspended growth r
eactors. Anaerobic filters were able to tolerate higher DS and hydroge
n sulfide levels than suspended growth reactors. A propionate-fed filt
er could withstand more than 150 mg hydrogen sulfide/L of hydrogen sul
fide and 1000 mg DS/L, and an acetate-fed filter could tolerate more t
han 125 mg sulfur/L of hydrogen sulfide and 400 mg DS/L.