Development of microbial fuel cells (MFCs) using efficient acclimation and various substrates

Microbial fuel cells (MFCs) are an emerging technology which converts organic matter to electricity using a biofilm on the electrode as the biocatalyst. It has recently been shown that a wastewater treatment method based on microbial fuel cells (MFCs) can be used to treat domestic or industrial organic wastewater and simultaneously produce electricity. Various techniques to enrich electrochemically active bacteria on an electrode using anaerobic sludge as an inoculum were studied using a two-chambered microbial fuel cell. Use of a ferric oxide coated electrode increased power density and coulombic efficiency (CE) to 30 mW/m 2 and 80%, as compared with carbon electrode (8 mW/m2 and 40%). The methanogen inhibitor 2-bromoethanesulfonate (BES) also increased the CE to 70%. A paste of bacteria from an electrode already producing electricity to a new electrode increased the power density to 40 mW/m2. These results indicate that sewage sludge can be used as an inoculum with the proper acclimation techniques to increase the effectiveness of electricity generation using domestic or industrial wastewater.;The physical properties (oxygen and acetate diffusion coefficients) of several different membranes, including NafionRTM 117, CMI-7000, AMI-7001, CM2 and three UF membranes (molecular cut-off, 0.5K, 1K and 3K), were investigated. Internal resistances of the membranes were monitored with impedence analysis using a potentiostat. The coulombic loss by diffusion through the membrane and biomass production in MFC was estimated using measured diffusivities of oxygen and acetate. The maximum power density and coulombic efficiency of the AMI-7001 anion exchange membrane were significantly higher (610 mW/m 2 and 72%, respectively) than values obtained for cation exchange membranes due to ability of the phosphate buffer to prevent pH changes in the anode chamber and transport of the phosphate ions through the membrane.;Swine wastewater treatment was investigated in two different types of MFCs producing electricity. A two-chambered MFC with an aqueous cathode and more extensive single-chamber MFC with air cathode produced a maximum power density of 45 mW/m2 and 261 mW/m2 (200 O resistor). Ammonium was removed from anode by electricity generation and charge disproportion from redox reactions in the MFC. It was found that the removal of odorous chemicals in swine wastewater was enhanced by electricity production compared to an open circuit control. Long chain fatty acid biodegradation was accelerated when bacteria could transfer electrons, thereby decreasing acetate accumulation.;Alcohols are expected to be transient liquid fuels for hydrogen fuel cells due to easy storage and transportation. MFCs using alcohol as a substrate for electricity generation have not been previously reported. The maximum power density and CE using ethanol in a 2-chamber MFC system were found here to be 40 mW/m2 at 0.3 mA and 42% to 61%, respectively. Methanol was also examined as a possible substrate, but it did not result in appreciable electricity generation. The analysis of byproducts indicated that ethanol was oxidized to CO2 via acetate as an intermediate. Single chamber MFCs with air cathodes using ethanol produced a maximum power density of 488 +/- 12 mW/m2 and approximately CE of ∼10%. A community analysis using 16S rDNA-based techniques indicated Proteobacterium Core-1 (33.3% of clone library sequences), Azoarcus sp. (17.4%), and Desulfuromonas sp. M76 (15.9%) were significant members of the anode chamber community.