Characterization of membrane biofouling and its effect on the performance of microbial fuel cell

During long-term operation of microbial fuel cells (MFCs), biofouling will gradually form on membrane surfaces. Biofouling is one of the major obstacles to the efficiency and economic operation of MFCs. The present study investigated and characterized the formation of biofouling on membranes at three different time frames within six months of MFC operations and the effect of biofouling on the performance of MFCs. The membranes were characterized by analyzing changes in the surface morphology, membrane structure, proton conductivity and resistance. The biofouling layer on the membrane increased over time during the MFCs' operation from 14.7 ± 0.4 μm (at two months), 165.1 ± 22.4 μm (at four months) to 250.1 ± 10.7 μm (at six months). The morphology observed using scanning electron microscopy showed the enhancement of the growth and compactness of the bacteria formed on the membranes' surfaces. Organic and inorganic elements were identified as binding factors that could strengthen the biofouling layer. The increase in the thickness of the biofouling layer resulted in the reduction of the proton conductivity of the Nafion 117 membrane, which led to an increment in membrane resistance due to restrictions in proton transfer through the biofouling membrane. Based on the performance results, the power density of the MFC showed a 55% reduction from 1 W/m2 at two months of operation to 0.45 W/m2 at six months of operation. Therefore, the cumulative effect of biofouling on the membranes' surfaces during long-term operation obstructed the mobility of protons across the membrane, causing MFC performance to deteriorate.