Optimal temperature for microbes in an acetate fed microbial electrolysis cell (MEC)

•Optimum temperature for COD reduction in MEC batch reactor was 31 °C.•Biomass concentration decreased in MECs but rate of reduction was less at 30 and 31 °C.•Biomass concentration and temperature significantly affected the reactor performance.

Temperature is one of the important parameters which can significantly effect on the activity/selection of microorganism and subsequently on the reactor's performance. Two microbial electrolysis cells (MECs) were operated at different temperature settings with acetate as a carbon source. On average, COD removal rates of 16.8, 24.7, 34.0, 36.2 and 18.1 mg/l/h were recorded at 25, 29, 30, 31 and 35 °C, respectively. The results of volatile suspended solids analysis indicated that biomass concentration continued to drop at all temperatures, but the drop was the lowest at 30 °C. Consideration of biomass drop and specific COD removal rate showed 31 °C as the optimum temperature. These significant results imply that effect of temperature and change in biomass concentration should be considered in future experiments when expressing the removal rates.