Enrichment of Dehalococcoides mccartyi spp. from a municipal activated sludge during AQDS-mediated bioelectrochemical dechlorination of 1,2-dichloroethane to ethene

• 1,2-DCA can be treated in potentiostatically controlled bioelectrochemical systems.
• AQDS drives stoichiometric dechlorination of 1,2-DCA to ethene.
• Dehalococcoides mccartyi enriched during the bioelectrochemical dechlorination.
• Results provide new insights into the biogeochemical fate of 1,2-DCA in humics-rich aquifers.

The application of bioelectrochemical systems (BES) for the treatment of chloroethanes has been so far limited, in spite of the high frequency that these contaminants are detected at contaminated sites. This work studied the biodegradation of 1,2-dichloroethane (1,2-DCA) in a lab-scale BES, inoculated with a municipal activated sludge and operated under a range of conditions, spanning from oxidative to reductive, both in the presence and in the absence of the humic acid analogue anthraquinone-2,6-disulfonate (AQDS) as a redox mediator. The results showed stable dechlorination of 1,2-DCA to ethene (up to 65 ± 5 μmol/L d), when the BES was operated at a set potential of −300 mV vs. SHE, in the presence of AQDS. Sustained filled-and-draw operation resulted in the enrichment of Dehalococcoides mccartyi. The results of this work provide new insights into the applicability of BES for groundwater remediation and the potential interaction between biogeochemistry and 1,2-DCA in humics-rich contaminated aquifers.