Anaerobic treatment of groundwater co-contaminated by toluene and copper in a single chamber bioelectrochemical system

Addressing the simultaneous removal of multiple coexisting groundwater contaminants poses a significant challenge, primarily because of their different physicochemical properties. Indeed, different chemical compounds may necessitate establishing distinct, and sometimes conflicting, (bio) degradation and/or removal pathways. In this work, we investigated for the first time the concomitant anaerobic treatment of toluene (5 mg/L) and copper (10 mg/L) in a single-chamber bioelectrochemical cell. The system was equipped with two graphite rods, one serving as anode and the other as cathode, and a potential difference of 1 V was applied between them. As a result, the electric current generated by the bioelectrocatalytic oxidation of toluene at the anode caused the abiotic reduction and precipitation of copper at the cathode, until the complete removal of both contaminants was achieved. OCP experiments confirmed that the removal of copper and toluene was primarily associated with polarization. Both electrodes were characterized by a comprehensive suite of chemical and microbiological analyses, evidencing a highly selected microbial community competent in the biodegradation of toluene in the anodic biofilm, and a uniform electrodeposition of spherical Cu2O nanoparticles over the cathode surface.