Enhanced simultaneous removal of nitrate and perchlorate from groundwater by bioelectrochemical systems (BESs) with cathodic potential regulation

Abstract Nitrate and perchlorate widely exist in groundwater and can be reduced by autotrophic bacteria on a biocathode without any external organic input. However, the low ionic strength of groundwater increases the overpotential and hinders the electron transport of bioelectrochemical systems (BESs). Thus, in this study, the cathodic potential was regulated (172 to −800 mV vs SHE) to simultaneously remove nitrate and perchlorate from groundwater. Results showed that, with the biocathode potential controlled at -200 mV vs SHE, the reduction rates of nitrate and perchlorate were 16.05 ± 1.06 mg-N L-1 d-1 and 9.87 ± 0.54 mg L-1 d-1, respectively, which were 53.74% and 38.04% higher than those of an MFC without potential control. Moreover, the energy consumption was the second lowest (-200 mV vs SHE); hence, it is the optimal cathode potential in the synchronous treatment of pollutants by BESs. The presence of nitrate inhibited the reduction of perchlorate. However, applying a negative potential shortened the suppression period. Finally, the mechanism of pollutant removal (that the cathode worked as the main electron donor for the autotrophic bacteria) was clarified, and the functional populations on the cathode were analyzed to be of the class Betaproteobacteria.