Effect of increasing anode surface area on the performance of a single chamber microbial fuel cell

Abstract

The anode material and its configuration represent an important parameter in a microbial fuel cell (MFC), as it influences the development of the microbial community involved in the electrochemical bio-reactions. The aim of this work was to evaluate single chamber microbial fuel cells (SCMFCs) with high anode surface area, achieved by using packed beds of irregular graphite granules. The performance of the SCMFC with the packed bed anode configuration was studied using a mixed microorganism culture from real wastewaters in batch and continuous mode operation. The current output was found to increase with the increase in thickness of the anode bed and with the approximate anode area. The best performance was obtained with the 3 cm anode bed depth SCMFC. When the latter was operated in batch mode, Coulombic efficiencies varied from 30% to 74%, depending upon feed COD. In continuous mode operation, the COD removal was 89% and Coulombic efficiency 68% with a feed COD of 50 ppm, and at a flow rate of 0.0028 cm 3 min −1 . Power performance was also reasonable with a volumetric power density of 1.3 W m −3 , with respect to the net anodic volume (12.5 cm 3 ). Comparable performance was achieved with real wastewater. Over the duration of tests current output was stable. The investigation performed in this study represent a step forward for implementing real applications of MFC technology. A model of the current distribution in the packed bed electrode was applied, which correlates the effective utilization of the electrode to its specific area, solution conductivity and slope of the polarization curve. This model could function as a starting point in designing appropriate electrode geometries.