As compared with anaerobic toxicity assays (ATA) for industrial toxica
nts focused only on the acetoclastic methanogens, two phase-separated
ATAs for sulfate and sulfide have been conducted by means of acidogeni
c and methanogenic cultures. Seed sludge was obtained from a two-phase
upflow anaerobic sludge blanket (UASB) reactor which operated on gluc
ose as a substrate. The obtained results were compared with those of m
ixed culture. In the acidogenic ATA, the glucose utilization rate coul
d be expressed in a first-order reaction kinetic. Gas production and s
ubstrate utilization were affected slightly when sulfate concentration
was up to 6000 mg SO4-S/1. However, the substrate conversion to aceta
te was retarded by sulfate addition. When sulfide over 800 mgS/1 was a
dded in test bottles, glucose utilization rate was retarded and the fi
rst-order kinetic constant decreased. From the results of the methanog
enic ATA, it was found that methanogens were more sensitive than acido
gens as the sulfate and sulfide concentrations increased. Although met
hane production was slightly retarded by added sulfate, methane was pr
oduced up to 60% of the control when the sulfate was 6000 mg SO4-S/1.
Methane production was not inhibited up to 200 mgS/1; however, it was
severely retarded at 400 mg S/1. The methane production was completely
inhibited in excess of 800 mg S/1. In mixed culture, the inhibiting e
ffects of sulfate and sulfide on mixed culture differed from those of
phase-separated anaerobes. Methane production was only slightly inhibi
ted when sulfate and sulfide concentrations reached up to 4000 mg SO4-
S/1 and 1200 mg S/1, respectively.