Simultaneous domestic wastewater treatment and renewable energy production using microbial fuel cells (MFCs)

Microbial fuel cells (MFCs) can be used in wastewater treatment and to simultaneously produce electricity (renewable energy). MFC technology has already been applied successfully in lab-scale studies to treat domestic wastewater, focussing on organic matter removal and energy production. However, domestic wastewater also contains nitrogen that needs to be treated before being discharged. The goal of this paper is to assess simultaneous domestic wastewater treatment and energy production using an air-cathode MFC, paying special attention to nitrogen compound transformations. An air-cathode MFC was designed and run treating 1.39 L d⁻¹ of wastewater with an organic load rate of 7.2 kg COD m⁻³ d⁻¹ (80% removal efficiency) and producing 1.42 W m⁻³. In terms of nitrogen transformations, the study demonstrates that two different processes took place in the MFC: physical–chemical and biological. Nitrogen loss was observed increasing in line with the power produced. A low level of oxygen was present in the anodic compartment, and ammonium was oxidised to nitrite and nitrate.