Sulfidogenic fluidized-bed treatment of metal-containing wastewater at 8 and 65∘C temperatures is limited by acetate oxidation

Acetate utilization in sulfidogenic fluidized-bed reactors (FBRs) was investigated for the treatment of iron containing wastewater at low (8∘C) and high (65∘C) temperatures. The FBRs operated at low and high temperatures were inoculated with cultures of sulfate-reducing bacteria (SRB) originally enriched from arctic and hot mining environments, respectively. Acetate was not utilized as a carbon and electron source for SRB at 8∘C. With ethanol, hydrogen sulfide was produced from ethanol to acetate oxidation, which precipitated the iron. Then, several attempts were made to obtain acetate oxidation at 8∘C. Inoculation of two different low temperature enrichments and operating the FBR for a long period of time (321 days) did not result in enrichment of acetate oxidizing SRB. Due to the absence of acetate oxidation at 8∘C, external alkalinity addition was required to keep the pH neutral. At 65∘C, average acetate and sulfate removals were 52±12%52±12% and 24±8%24±8% at 670 mg/L d acetate and 1500 mg/L d sulfate loadings, respectively. The produced alkalinity from acetate oxidation increased the pH from 6.4 to around 7.5 and electron flow to sulfate reduction averaged 65%. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes showed quite stable SRB community at 8∘C, whereas, at 65∘C SRB community was dynamic. In the FBRs, Desulfomicrobium apsheronum and Desulfosporosinus   sp. at 8∘C and Desulfotomaculum   sp. at 65∘C were detected.