Polychlorofluoro- carboxylic acids (Cl-PFCAs) derived from the widely used polychlorotrifluoroethylene (PCTFE) and its oligomers may enter and influence the aquatic environment. Here, we report on significant anaerobic biodefluorination of Cl-PFCAs by an activated sludge community via novel defluorination pathways triggered by anaerobic microbial dechlorination. Microbial reductive, hydrolytic, and eliminative dechlorination first occurred, and it was the hydrolytic dechlorination that led to significant spontaneous defluorination. As the number of Cl-substitutions increased, simultaneous hydrolytic dechlorination at multiple Cl-substitutions was more likely to occur. It led to substantially higher defluorination and chainshortening diacid products of CTFE tetramer carboxylic acid than the tri- and dimer acids. The H-substituted products from reductive dechlorination were more recalcitrant to anaerobic biodefluorination. Isolates exhibiting defluorination activities of CTFE tetramer acid possess haloacid dehalogenase-like hydrolases but not reductive dehalogenases. It implies the critical role played by anaerobic non-respiratory hydrolytic dechlorination in the fate of chlorofluorochemicals in the hydrosphere.

Significant defluorination of polychlorofluoro-carboxylic acids triggered by anaerobic microbial hydrolytic dechlorination

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