Degradation of trichloroethene in water by electron supplementation

Trichloroethene (TCE) is a common and recalcitrant contaminant in groundwater. Microbially catalyzed reductive dechlorination is a dominant pathway for TCE degradation, in which substrates and electron donors are essential. In this study, extraneous electron supplementation was attempted to enhance reductive dechlorination of TCE and its derivatives. Reactors were established with groundwater containing TCE, and a 6-V battery was used to supply an average current of 29 μA of dc power to feed electrons to the microcosms. We measured 80–90% depletion of TCE within 70 d in reactors (both sterile and non-sterile) containing 300–400 μg TCE/l and from 97 to 98% depletion in microcosms containing 10 mg TCE/l. No intermediate products such as dichloroethylene or vinyl chloride were detected during this study. Results demonstrate that electron-supplemented degradation of TCE appears to be an abiotic process that is unassociated with microbial populations or indigenous redox conditions. No apparent accumulation of TCE daughter products were observed and overall efficiency of this electroremediation process was calculated to be 6.9 g TCE degraded/kW h. This efficiency would make electron supplementation an attractive alternative to the substrate-amended biological reductive dechlorination of TCE.