Anaerobic Microbial Dechlorination of 6:2 Chlorinated Polyfluorooctane Ether Sulfonate and the Underlying Mechanisms.

ABSTRACT

The microbial transformation potential of 62 chlorinated polyfluorooctane ether sulfonate (62 Cl-PFESA) was explored in anaerobic microbial systems. Microbial communities from anaerobic wastewater sludge, an anaerobic digester, and anaerobic dechlorinating cultures enriched from aquifer materials reductively dechlorinated 62 Cl-PFESA to 62 hydrogen-substituted polyfluorooctane ether sulfonate (62 H-PFESA), which was identified as the sole metabolite by non-target analysis. Rapid and complete reductive dechlorination of 62 Cl-PFESA was achieved by the anaerobic dechlorinating cultures. The microbial community of the anaerobic dechlorinating cultures was impacted by 62 Cl-PFESA exposure. Organohalide-respiring bacteria originally present in the anaerobic dechlorinating cultures, including Geobacter, Dehalobacter, and Dehalococcoides, decreased in relative abundance over time. As the relative abundance of organohalide-respiring bacteria decreased, the rates of 62 Cl-PFESA dechlorination decreased, suggesting that the most likely mechanism for reductive dechlorination of 62 Cl-PFESA was co-metabolism rather than organohalide respiration. Reductive defluorination of 62 Cl-PFESA was not observed. Furthermore, 62 H-PFESA exhibited 5.5 times lower sorption affinity to the suspended biosolids than 62 Cl-PFESA, with the prospect of increased mobility in the environment. These results show the susceptibility of 62 Cl-PFESA to microbially mediated reductive dechlorination and the likely persistence of the product, 62 H-PFESA, in anaerobic environments.