Electricity generation from swine wastewater using microbial fuel cell

Abstract

Electricity generation from swine wastewater using microbial fuel cell (MFC) was investigated. Swine wastewater was collected into a dual-chambered (aerobic and anaerobic) fuel cell. The maximum power output using copper and carbon electrodes were 250.54 and 52.33 μW, respectively, while 10.0 and 5.0 cm salt bridge length between the cathode and anode gave maximum power outputs of 279.50 and 355.26 μW, respectively. Cathodic potassium permanganate and distilled water gave maximum power outputs of 1287.8 and 139.18 μW, respectively. MFCs utilized microbial communities to degrade organic materials found within wastewater and converted stored chemical energy to electrical energy in a single step. The initial bacterial and fungal counts were 7.4×106 and 1.1×103 CFU ml-1. Bacterial counts steadily increased with time to 1.40×107 CFU ml-1 while fungal count declined to 4.4×106 CFU ml-1 after day 60. The decline in microbial counts may be attributed to the time necessary for acclimatization of microbes to the anode. The genera identified were Bacillus, Citrobacter, Pseudomonas, Lactobacillus, Escherichia coli, Aspergillus and Rhizopus. These microbes acted as primary and secondary utilizers, utilizing carbon and other organics of the wastewater. Chemical parameters indicated that the biochemical oxygen demand decreased from 91.4-23.2 mg/L, giving 75% while the chemical oxygen demand ranged from 243.1-235.2 mg/L, representing 3.3% reduction. Although, the metabolic activities of microbes were responsible for the observed degradation, leading to electricity, the overall power output depended on the distance between the anode and cathode ompartments, types of electrode materials and mediators and oxygen reaction at the cathode.