Effect of gradual transition of substrate on performance of flat-panel air-cathode microbial fuel cells to treat domestic wastewater

•FA-MFCs were operated by substrate transition from acetate to domestic wastewater.•Coulombic efficiency in acetate was similar to that in domestic wastewater.•Maximum power density had higher correlation with acetate than with COD.•FA-MFCs could maintain low internal resistance and overcome decreasing conductivity.

In order to confirm the effects of the low conductivity and biodegradability of wastewater, flat-panel air-cathode microbial fuel cells (FA-MFCs) were operated by supplying substrates with different volume ratios of domestic wastewater mixed with an artificial medium: the artificial medium only, 25% wastewater, 50% wastewater, 75% wastewater, 100% of wastewater with 500 mg-COD/L by adding acetate, and raw domestic wastewater (230 mg-COD/L). With the increase of wastewater ratio, the maximum power density and organic removal efficiency decreased from 187 to 60 W/m3 and 51.5 to 37.4%, respectively, but the Coulombic efficiency was maintained in the range of 18.0-18.9%. The FA-MFCs could maintain their low internal resistances and overcome the decreasing conductivity. The acetate concentration was more important than the total organics for power production. This study suggests that the FA-MFC configuration has great applicability for practical applications when supplied by domestic wastewater with low conductivity and biodegradability.