Energy Production in Mediator-Less Microbial Fuel Cells with High Internal Resistance: The Effects of Nitrate and Sulfate

Microbial fuel cells (MFCs) simultaneously provide waste treatment while capturing energy in the form of electricity. These devices are being deployed in engineered and natural environments where nitrate or sulfate may inhibit power production, but 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, but this was not primarily due to the biochemical reduction of nitrate or sulfate, but probably because of the inhibition of exoelectrogens.