Oxygen has been so far addressed as the most preferable terminal electron acceptor in the cathodes of microbial fuel cells (MFCs). However, to reduce the oxygen reduction overpotential at the cathode surface, eco-unfriendly and costly catalysts have been commonly employed. Here, we pursued the possibility of using a high surface area electrode to reduce the cathodic reaction overpotential rather than the utilization of catalyzed materials. A dual chambered MFC reactor was designed with the use of graphite-granule electrodes and a permeable membrane. The performance of the reactor in terms of electricity generation and organic removal rate was examined under a continuous-feed manner. Results showed that the maximum volumetric power of 4.4±0.2 W/m3 net anodic compartment (NAC) was obtained at a current density of 11±0.5 A/m3 NAC. The power output was improved by increasing the electrolyte ionic strength. An acceptable effluent quality was attained when the organic loading rate (OLR) of 2 kgCOD/m3 NAC d was applied. The organic removal rate seemed to be less affected by shock loading. Our system can be suggested as a promising approach to make MFC-based technology economically viable for wastewater treatment applications. This study shows that current generation can be remarkably improved in comparison with several other studies using a low-surface-area plain graphite electrode.
Keywords: granular graphite, microbial fuel cell, non-catalyzed electrodes, organic removal, permeable membrane