A cooperative microbial fuel cell system for waste treatment and energy recovery

A cooperative microbial fuel cell (MFC) system was developed and investigated for its performance in waste treatment and bioenergy production. The system consisted of a conventional MFC and a dual-cathode MFC that was specially designed for nitrogen removal. Three feeding solutions, including a synthetic solution (acetate as an organic source), digested sludge and landfill leachate, were used as substrates. The MFC system removed more than 99% of chemical oxygen demand (COD) from the synthetic solution, and the organic removal mainly occurred in the anodes of the MFCs. Nitrogen, on the other hand, was removed in the cathodes of the MFC system, which achieved more than 98% removal of ammonium and 96% removal of total nitrogen. The MFC system also effectively treated the actual wastes and removed more than 85% of the total COD and 50-70% of the total nitrogen from the digested sludge and landfill leachate. The organic removal rates with the actual wastes were significantly higher than in other MFC systems. In general, the MFC system consumed less than 0.06 kWh/m3 or 0.1 kWh/kg COD, demonstrating that low energy consumption is a major advantage of MFC technology. The MFC system produced 0.1023 kWh/kg COD from the synthetic solution, much higher than the 0.0097 kWh/kg COD and 0.0019 kWh/kg COD from the actual wastes, resulting in a theoretically positive energy balance with the synthetic solution; however, the net energy with the actual wastes was negative.