The effects of heavy metals on anaerobic biotransformation reactions

The reductive dechlorination of various chlorophenols (CPs) was examined in anoxic freshwater sediment slurries in the presence and absence of various metals. The preference for dechlorination of CPs in freshwater sediments was in the order ;The effects of metals on the reductive dechlorination of CPs in CP-adapted sediments were also investigated. The differences in the order of metal inhibition for each adapted sediment were examined. In the case of ortho- and meta-CP adapted sediments, the dechlorination activities were more susceptible to Cd. In case of para-CP adapted sediments, Cd was less inhibitory than Cu and less inhibitory than Cr for 3,4-DCP adapted sediments. Chemical fractionation of experimental sediment slurries (plus metals) revealed that Cd was the most bioavailable of the metals tested.;The potential for cross-acclimation of CP-adapted sediments was also investigated. At least two distinct activities in the cross-acclimation studies were demonstrated.;A hybrid anaerobic bioreactor, containing a ceramic matrix for biofilm development over a granular sludge bed, was found to be an effective system for the treatment of alcohol distillery feedstock. The biotransformation kinetic constants for VFA transformation and the effects of metals on VFA transformation were investigated using biomass collected from the hybrid bioreactor. Propionate transformation was likely the rate-limiting reaction in the overall biotransformation process. Lead was found to be the least inhibitory of the metals tested for inhibition of organic acid transformation, while Cu and Cr were the most inhibitory of the metals tested.