Continuous bioelectricity production and sustainable wastewater treatment in a microbial fuel cell constructed with non-catalyzed granular graphite electrodes and permeable membrane.

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/m(3) net anodic compartment (NAC) was obtained at a current density of 11+/-0.5 A/m(3) 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/m(3) 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.

Nitrifying biocathode enables effective electricity generation and sustainable wastewater treatment with microbial fuel cell.

Simultaneous organics removal and nitrification using a novel nitrifying biocathode microbial fuel cell (MFC) reactor were investigated in this study. Remarkably, the introduction of nitrifying biomass into the cathode chamber caused higher voltage outputs than that of MFC operated with the abiotic cathode. Results showed the maximum power density increased 18% when cathode was run under the biotic condition and fed by nitrifying medium with alkalinity/NH4+-N ratio of 8 (26 against 22 mW/m2). The voltage output was not differentiated when NH4+-N concentration was increased from 50 to 100 mg/L under such alkalinity/NH4+-N ratio. However, interestingly, the cell voltage rose significantly when the alkalinity/NH4+-N ratio was decreased to 6. Consequently, the maximum power density increased 68% in compared with the abiotic cathode MFC (37 against 22 mW/m2). Polarization curves demonstrated that both activation and concentration losses were lowered during the period of nitrifying biocathode operation. Ammonium was totally nitrified and mostly converted to nitrate in all cases of the biotic cathode conditions. High COD removal efficiency (98%) was achieved. In light of the results presented here, the application of nitrifying biocathode is not only able to integrate the nitrogen and carbon removal but also to enhance the power generation in MFC system. Our system can be suggested to open up a new feasible way for upgrading and retrofitting the existing wastewater treatment plant by the use of MFC-based technologies.

Simultaneous organics removal and bio-electrochemical denitrification in microbial fuel cells.

Simultaneous organics removal and bio-electrochemical denitrification using a microbial fuel cell (MFC) reactor were investigated in this study. The electrons produced as a result of the microbial oxidation of glucose in the anodic chamber were transferred to the anode, which then flowed to the cathode in the cathodic chamber through a wire, where microorganisms used the transferred electrons to reduce the nitrate. The highest power output obtained on the MFCs was 1.7 mW/m(2) at a current density of 15 mA/m(2). The maximum volumetric nitrate removal rate was 0.084 mg NO(3)(-)-N cm(-2) (electrode surface area) day(-1). The coulombic efficiency was about 7%, which demonstrated that a substantial fraction of substrate was lost without current generation.