A single-chamber microbial fuel cell without an air cathode.

Microbial fuel cells (MFCs) represent a novel technology for wastewater treatment with electricity production. Electricity generation with simultaneous nitrate reduction in a single-chamber MFC without air cathode was studied, using glucose (1 mM) as the carbon source and nitrate (1 mM) as the final electron acceptor employed by Bacillus subtilis under anaerobic conditions. Increasing current as a function of decreased nitrate concentration and an increase in biomass were observed with a maximum current of 0.4 mA obtained at an external resistance (R(ext)) of 1 KΩ without a platinum catalyst of air cathode. A decreased current with complete nitrate reduction, with further recovery of the current immediately after nitrate addition, indicated the dependence of B. subtilis on nitrate as an electron acceptor to efficiently produce electricity. A power density of 0.0019 mW/cm(2) was achieved at an R(ext) of 220 Ω. Cyclic voltammograms (CV) showed direct electron transfer with the involvement of mediators in the MFC. The low coulombic efficiency (CE) of 11% was mainly attributed to glucose fermentation. These results demonstrated that electricity generation is possible from wastewater containing nitrate, and this represents an alternative technology for the cost-effective and environmentally benign treatment of wastewater.

Comparative bioelectricity production from various wastewaters in microbial fuel cells using mixed cultures and a pure strain of Shewanella oneidensis.

Current and power density from four wastewaters, agriculture (AWW), domestic (DWW), paper (PWW), and food/dairy (FDWW), were comparatively evaluated in combination with three inocula: wastewater endogenous microbes (MFC1), Shewanella oneidensis MR-1 (MFC2), and wastewater endogenous microbes with MR-1 (MFC3) in single chamber microbial fuel cells (MFC). Using AWW (0.011 mA/cm(2); 0.0013 mW/cm(2)) and DWW (0.017 mA/cm(2); 0.0036 mW/cm(2)), MFC2 was the best candidate providing the maximum current, whereas AWW-MFC1 and DWW-MFC1 were unable to construct a well-established MFC. FDWW produced a maximum current from MFC3 (0.037 mA/cm(2); 0.015 mW/cm(2)), and confirmed the unsuitability of MFC2 at an alkaline pH. FDWW-MFC3 also performed best with the highest substrate degradation and coulombic efficiency. Mixed culture in MFC3 resulted in higher current generation under the influence of MR-1 (except in PWW), indicating the endogenous microbes were not solely responsible for the current but the outperformance was significantly attributed to the association of MR-1.