A study on the impact of electrode and membrane modification in stacked microbial fuel cells for wastewater treatment

Abstract

This study investigates the efficacy of treating wastewater using microbial fuel cell (MFC) technology to the safe limits for discharge in the environment. It has been demonstrated that MFC directly converts organic matter present in wastewater into energy. The present study uses a cell design based on simple plate geometry, carbon felt electrodes and Nafion117 as proton exchange membrane separating the anode and cathode chambers. The anode was then modified with heat and acid treatment and PEM was treated with PVDF to improve the performance of the cell. Synthetic dairy wastewater with initial COD of 2412 mg/l was used to test the operation of stack consisting of four cells which were hydraulically connected in series. The stack operated with continuous flow of wastewater. COD removal of the feed water was tested in successive cells to achieve the permissible limits for safe discharge of the effluent. COD decreased from 2412 mg/l to 126 mg/l after the fourth cell. For the power output each cell was treated individually. The power density of each cell was directly proportional to the COD of the influent. The power density of the first cell that has the highest COD was measured at 77.9 mW/m², which is two times that for the cell with unmodified anode and membrane. For the first cell COD removal was the highest at 57 % and 2.6 times more than the cell with the unmodified anode and membrane. These results suggest that targeted modifications to the anode and membrane can significantly boost the MFC performance both in terms of COD removal and corresponding power output. Secondly, up to 93.66 % COD removal may be achieved by four cells hydraulically connected in series. The paper offers some insights for stacking options for implementing at scale up of the MFC technology for wastewater treatment plants.