Effect of temperature on the performance of microbial fuel cells

Abstract

Single and double chamber microbial fuel cells (MFCs) were tested in batch mode at different temperatures ranging from 4 to 35 °C; results were analysed in terms of efficiency in soluble organic matter removal and capability of energy generation. Brewery wastewater diluted in domestic wastewater (initial soluble chemical oxygen demand of 1200 and 492 mg L −1 of volatile suspended solids) was the source of carbon and inoculum for the experiments. Control reactors (sealed container with support for biofilm formation) as well as baseline reactors (sealed container with no support) were run in parallel to the MFCs at each temperature to assess the differences between water treatment including electrochemical processes and conventional anaerobic digestion (in the presence of a biofilm, or by planktonic cells). MFCs showed improvements regarding rate and extent of COD removal in comparison to control and baseline reactors at low temperatures (4, 8 and 15 °C), whilst differences became negligible at higher temperatures (20, 25, 30 and 35 °C). Temperature was a crucial factor in the yield of MFCs both, for COD removal and electricity production, with results that ranged from 58% final COD removal and maximum power of 15.1 mW m −3 reactor (8.1 mW m −2 cathode) during polarization at 4 °C, to 94% final COD removal and maximum power of 174.0 mW m −3 reactor (92.8 mW m −2 cathode) at 35 °C for single chamber MFCs with carbon cloth-based cathodes. Bioelectrochemical processes in these MFCs were found to have a temperature coefficient, Q10 of 1.6. A membrane-based cathode configuration was tested and gave promising results at 4 °C, where a maximum power output of 294.6 mW m −3 reactor (98.1 mW m −2 cathode) was obtained during polarization and a maximum Coulombic efficiency ( Y Q) of 25% was achieved. This exceeded the performance at 35 °C with cloth-based cathodes (174.0 mW m −3; Y Q 1.76%).