The effect of nitrate and sulfate on mediator-less microbial fuel cells with high internal resistance

Microbial fuel cells (MFCs) simultaneously provide waste treatment while capturing energy in the form of electricity. Although these devices are being used in engineered and natural environments where nitrate or sulfate may inhibit power production, the effects of these electron acceptors have not been fully explored. This research investigated the effect of nitrate and sulfate on MFC power production when these chemicals are present at the anode. Nitrate decreased the maximum current and power density by 15 and 17%, respectively, when present at 20 mg/L, and sulfate caused the maximum current and power density to decrease by 4 and 7%, respectively (also at 20 mg/L). Stronger inhibition was observed at higher nitrate and sulfate concentrations, but power production persisted. Coulombic efficiency decreased as nitrate and sulfate levels increased, although this was not primarily due to the biochemical reduction of nitrate or sulfate; rather, it was probably because of the inhibition of exoelectrogens.