Anaerobic biotransformation of trichlorofluoroethene in groundwater microcosms

The biological reduction of trichlorofluoroethene (TCFE) was investigated i n anaerobic groundwater microcosms. TCFE was reductively dehalogenated by m icroorganisms to produce three dichlorofluoroethene isomers, with cis-1,2-d ichlorofluoroethene (c-DCFE) being the main isomer formed. Further sequenti al biological transformation of these compounds to mono-chlorofluoroethene isomers was incomplete and occurred at much slower rates. The rates of TCFE reduction were compared to the rates of reduction of two common chlorinate d solvents, perchloroethene (PCE) and trichloroethene (TCE), when present a t similar concentrations. Aqueous concentrations ranged from 7.0 to 14.0 mg /L for TCFE and from 7.5 to 15.0 mg/L for PCE and TCE. Similar rates of PCE and TCE transformation relative to TCFE were observed in single-compound t ests (PCE, TCE, and TCFE in separate microcosms) and when the contaminants were present together as mixtures in the microcosms. The close similarities between the time course and kinetics of TCFE degradation and the degradati on of both PCE and TCE, when present at comparable initial concentrations, suggest that TCFE could potentially be used as a benign reactive tracer to measure in-situ rates of PCE and TCE transformation in contaminated environ ments.