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O'Flaherty, V,Colohan, S,Mulkerrins, D,Colleran, E
1999
May
Bioresource Technology
Effect of sulphate addition on volatile fatty acid and ethanol degradation in an anaerobic hybrid reactor. II: Microbial interactions and toxic effects
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sulphate-reducing bacteria propionate acetate sulphide inhibition H2S anaerobic sulphate-adapted non-sulphate-adapted methanogenesis hybrid reactor SULFATE-REDUCING BACTERIA DESULFOBULBUS-PROPIONICUS METHANOGENIC GRANULES SULFIDE INOCULATION COMPETITION INHIBITION HYDROGEN SLUDGES ACETATE
68
109
120
The microbial interactions occurring in an anaerobic hybrid reactor which was seeded with non-sulphate-adapted sludge and subsequently exposed to sulphate over a prolonged period of 423 days were studied. The population changes upon inoculation of the reactor with sulphate-adapted sludge from a full-scale treatment plant were also analysed. Addition of sulphate (4000 mg/l) to the reactor influent resulted in a complete inhibition of syntrophic propionate degradation and severe inhibition of acetoclastic methanogenesis. No propionate or acetate-utilising sulphate-reducing bacteria (SRB) could be detected in the sulphate-fed reactor sludge. Toxicity tests carried out on sludge samples from a control reactor showed that acetoclastic methanogenesis was the most sensitive step in sulphide inhibition, with 50% inhibition observed at concentrations of 220-980 mg total sulphide/l (69-150 mg free H2S/l) over the pH range 6.5-8.0. The propionate-utilising syntrophs present in the sludge appeared to be irreversibly inhibited by sulphide and were also inhibited by acetate concentrations as low as 300 mg/l. The inoculation of fullscale sulphate-adapted sludge resulted in the establishment of propionate and hydrogen-utilising SRB in the biofilm section, but not in the granular sludge bed section, of the anaerobic hybrid reactor. (C) 1998 Elsevier Science Ltd. All rights reserved.
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