Hydrogen peroxide in bioelectrochemical systems negatively affects microbial current generation

Hydrogen peroxide produced in the cathode of a bioelectrochemical system (BES) enables on-site disinfection of water using electrons derived from the wastewater organics at the microbial anode. While a proof of concept has been established, the long-term performance and putative impact of H2O2 on the anodic microbial community have not been studied extensively. Here, the performance of three BESs was monitored for a 28-day operation period with different concentrations of H2O2 (1 g L-1 and 5 g L-1) flowing in a compartment separated from the anolyte by a cation exchange membrane, which allowed H2O2 diffusion. The reactors exposed to 1 g L-1 H2O2 did not show any significant (p > 0.05) deterioration in catalytic activity during the studied period. Contrastingly, a notable drop in current production was observed in the reactors that were challenged with 5 g L-1 H2O2 in the adjacent chamber. There were no significant differences in the beta diversity of the anodic microbial community from the BESs exposed to H2O2 when compared with the control reactor (0 g L-1 H2O2). Even so, a relative decrease in putative electroactive microorganisms was observed in the reactors exposed to 5 g L-1 H2O2. A stainless-steel anodic current collector was corroded when the BESs were under open circuit and in the presence of H2O2, illustrating the risk of this oxidant during downtimes. These results indicate that whereas BESs are promising in this context, their stability can be compromised at higher peroxide concentrations, thereby limiting the attainable product in routine applications