Metal-induced inhibition of anaerobic metabolism of volatile fatty acids and hydrogen

Toxicity of copper to acetoclastic and hydrogenotrophic activities of methanogens and sulfate reducers in anaerobic sludge

Heavy metals could potentially negatively impact microorganisms in anaerobic sulfate reducing bioreactors. The objective of this is study was to evaluate the inhibitory effect of copper to acetoclastic and hydrogenotrophic activities of methanogens and sulfate reducers in sludge obtained from a full-scale sulfate reducing bioreactor. The 50% inhibiting concentration (50%IC) of Cu(2+) to acetoclastic and hydrogenotrophic methanogens was 20.7 and 8.9 mg l(-1), respectively. The 50%IC of Cu(2+) to acetoclastic sulfate reduction was 32.3 mg l(-1). The hydrogenotrophic sulfate reducers were only inhibited by 27% at the highest concentration of Cu(2+) tested, 200 mg l(-1), indicating a high level of tolerance. The soluble Cu(2+) was observed to decrease rapidly in both the methanogenic and sulfate reducing assays. The highest level of decrease was observed in the hydrogenotrophic sulfate reducing assay which was over 99% in 5h. The results of this study indicate that sulfate reducing biotechnologies would be robust at relatively high inlet concentrations of Cu(2+).

Biological hydrogen production by enriched anaerobic cultures in the presence of copper and zinc

Batch experiments were carried out to examine the productions of hydrogen and volatile fatty acids from glucose by enriched anaerobic culture in the presence of Cu and Zn. Results showed the specific hydrogen production rate was enhanced by the dosage of Cu at 50-100 mg/dm3 or the dosage of Zn at 10-250 mg/dm3, but was inhibited by Cu over 200 mg/dm3 or Zn at 500 mg/dm3. The hydrogen production yield was enhanced by Cu of 5-400 mg/dm3 or Zn of 5-500 mg/dm3. Productions of acetate and propionate were inhibited by Cu of 5-400 mg/dm3 or Zn of 5-500 mg/dm3. On the other hand, production of butyrate was stimulated, whereas production of ethanol was not affected. In terms of the CI,50 values. Cu was more toxic than Zn. The modified Gompertz equation was able to properly describe the cumulative hydrogen production in the presence of Cu or Zn.