Groundwater Circulation Enhanced Electrobioremediation of 1,2-Dichloroethane in a Simulated Heterogeneous Aquifer

This study demonstrates a groundwater circulation enhanced electrobioremediation process for 1,2-dichloroethane (1,2-DCA) degradation in a simulated heterogeneous aquifer, in which a pair of electrodes were separately implanted between an injection well and an abstraction well and groundwater circulation carries anodic O2 and cathodic H2 sequentially into the aquifer forming oxidation and reduction regions. A two-dimensional tank was filled with interbedded sandy-clayed sediments to simulate the field aquifer conditions. It is expected that the interbedded clayed sediments could supply bacteria for biological degradation and also supply Fe(II) for chemical oxidation in the presence of O2 due to hydroxyl radical (•OH) production. At a constant circulation flow rate of ∼3.5 PVs/day, 1,2-DCA at an initial concentration of ∼8.07 mg/L was degraded to ∼0.65 mg/L (91.9% removal) after 33-day treatment, in which 80–100 mA current was applied to the electrodes after the initial stage of 8-day circulation. Batch experiments proved that 1,2-DCA degradation was mainly attributed to aerobic biological oxidation, with likely contribution of anaerobic reductive dechlorination in certain areas. Chemical 1,2-DCA oxidation was negligible. This study suggests that coupling groundwater circulation and separated electrolysis is effective for stimulating biological 1,2-DCA degradation in heterogeneous aquifers.