Novel Multi-anode/cathode Microbial Fuel Cells (MAC-MFCs) for Large Scale Bioelectricity Recovery in Wastewater Treatment

Date of Completion

January 2010

Keywords

Alternative Energy|Engineering, Environmental

Degree

Ph.D.

Abstract

Microbial Fuel Cell is a next-generation biofuel that could contribute to the energy sustainability. The objective of this study is to develop a multi-anode/cathode MFC to increase the power production and demonstrate the viability of MFCs in real-world applications. Lab-scale studies demonstrated that increasing the number of electrodes increased the power production and 4-anode/cathode MFCs produced higher power densities than 2-anode/cathode MFCs. Based on the success of lab-scale studies, pilot-scale 12-anode/cathode MFC systems were developed and operated treating wastewater in Johnstown Wastewater Treatment Plant. Multi-anode/cathode MFCs exhibited a good power production and COD removal on wastewater. The upflow and downflow modes were compared and no significant difference was found in terms of the power output and COD removal. Upflow mode was employed in later MFCs to prevent clogging of the reactor. The power density of multi-anode/cathode MFCs achieved 0.4 W/m 2 and the COD removal was 80% when operated on real wastewater. The power production of MFCs demonstrated an increase (0.3 to 0.4 W/m2 ) as the organic loading rate increased (0.19 to 0.66 kgCOD/m 3/d). In one MFC, 8 of the 12 anode/cathode pairs were disconnected and the 4-anode/cathode MFC was operated for four weeks to confirm the effect of increasing the number of electrodes. The 12-anode/cathode MFCs produced the equivalent power density per channel as the 4-anode-anode/cathode MFC, indicating that increasing the number of electrodes could effectively increase the total power production of MFCs. 30% TKN removal but minimal total phosphorus removal was achieved by multi-anode/cathode MFCs. High total solids removal was achieved due to the use of granular activated carbon bed. Cathode fouling was noticed as a problem that severely lowered the power output and increased the internal resistance of MFCs. Fouling deposits were analyzed and the results suggested that the interior cathode fouling was caused by CaCO3 and the exterior fouling was caused by diffusion of water through cathodes. Finally, an economic analysis revealed that the capital cost of MFCs needs to be reduced and the power harvested from MFCs needs to be increased to make MFCs an economic technology for wastewater treatment applications. ^

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