Study on Generation of Bioelectricity Using Potassium Ferricyanide Electron Acceptor in Microbial Fuel Cell

Abstract

The capability of simultaneously generating bioelectricity and treating piggery wastewater using microbial fuel cell (MFC) with indigenous exoelectrogens was demonstrated. Three units of H – type MFCs were constructed using 0.1M potassium ferricynide (K3[Fe(CN)6]) as catholyte and carbon – carbon (CC), carbon – copper (CCu) and copper – copper (CuCu) electrodes of surface area 0.0071m2 each. The BOD and COD of the test piggery wastewater were 420mg/L and 1057mg/L respectively. While coulombic efficiency (CE) of the MFCs after 25 days were 76%, 72% and 5.10%, COD removal were 83%, 48% and 49% for CC, CCu and CuCu respectively. Highest voltage recorded were 752.4mV, 1027mV and 625.2mV across CC, CCu and CuCu respectively. Generation of voltage proportionally decreased with decreasing external resistors. Power density which increased with decreasing external resistance across each MFC until 200Ω beyond which decrease became evident, peaked at 60.94mW/m2 (92.6mA/m2), 39.94mW/m2 (75.0mA/m2) and 14.21mW/m2 (44.70mA/m2) across Rext = 1000Ω for CC, CCu and CuCu respectively. This depicts that carbon used as both cathode and anode produced more bioelectricity than other combinations. Bacteria isolated from the surface of anodes include, Lactobacillus spp., Corynebacterium spp., Streptococcus spp., Proteus mirabilis, Enterobacter spp., Escherichia coli, Pseudomonas spp., Bacillus spp., Aeromonas spp., Micrococus luteus, Corynebacterium spp. and Salmonella spp. Plasmid profile of the bacteria isolates in the original wastewater sample revealed that Lactobacillus spp., Proteus mirabilis, Escherichia coli, Pseudomonas spp., Bacillus spp., and Aeromonas spp had plasmids. These findings show that with better designs and optimization, the performance of the MFCs can be enhanced.