EVALUATION OF A MODEL FOR THE EFFECTS OF SUBSTRATE INTERACTIONS ON THE KINETICS OF REDUCTIVE DEHALOGENATION

The effects of primary electron-donor and electron-acceptor substrates on the kinetics of TCA biodegradation in sulfate-reducing and methano genic biofilm reactors are presented. Of the common anaerobic electron -donor substrates that were tested, only formate stimulated the TCA bi odegradation rate in both reactors. In the sulfate-reducing reactor, g lucose also stimulated the reaction rate. The effects of formate and s ulfate on TCA biodegradation kinetics were analyzed using a model for primary substrate effects on reductive dehalogenation. Although some d ifferences between the model and the data are evident, the observed re sponses of the TCA degradation rate to formate and sulfate were consis tent with the model. Formate stimulated the TCA degradation rate in bo th reactors over the entire range of TCA concentrations that were stud ied (from 50 mu g TCA/L to 100 mg TCA/L). The largest effects occurred at high TCA concentrations, where the dehalogenation kinetics were ze ro order. Sulfate inhibited the first-order TCA degradation rate in th e sulfate-reducing reactor, but not in the methanogenic reactor. Molyb date, which is a selective inhibitor of sulfate reduction, stimulated the TCA removal rate in the sulfate-reducing reactor, but had no effec t in the methanogenic reactor.