Acclimation of anaerobic systems to biodegrade tetrachloroethene in the presence of carbon tetrachloride and chloroform

Two concerns in remediating tetrachloroethene (PCE)-contaminated sites are the stimulation of PCE degradation and the effect of other contaminants on PCE degradation. In ethanol-fed microcosms receiving 8.3 mu M PCE, increasi ng the yeast extract concentration from 2 to 100 mg L-1 decreased the time required to produce cis-1,2-dichloroethene (DCE) from 36 to 9 days. The add ition of 19 mu M carbon tetrachloride to microcosms completely inhibited PC E degradation, as did 4 mu M chloroform although 0.7 mu M chloroform was no t inhibitory. PCE-degrading capability had not developed in a column receiv ing carbon tetrachloride after 161 days although carbon tetrachloride was t ransformed to chloroform and dichloromethane. Once carbon tetrachloride was removed and the yeast extract concentration increased, PCE degradation to cis-1,2-DCE was observed within 45 days, although measurable degradation of cis-1,2-DCE to vinyl chloride and ethene required another 130 days. These results suggest that multiple-zone remediation strategies may be required f or sites contaminated with mixtures of PCE, carbon tetrachloride and/or chl oroform. (C) 1999 Elsevier Science Ltd. All rights reserved.