The influence of psychrophilic and mesophilic start-up temperature on microbial fuel cell system performance

The successful scale-up of microbial fuel cells (MFC) for wastewater treatment in temperate regions requires the development of reactor systems that are robust to seasonal fluctuations and are energy efficient. Therefore, as part of this study, a MFC was acclimated for operation over a 8-35 degrees C temperature range. Employing single chamber air cathode MFCs, system performance was initially examined at three different operating temperatures (10 degrees C, 20 degrees C and 35 degrees C). At each temperature a maximum steady-state voltage of 0.49 +/- 0.02 V was achieved after an operational period of 47 weeks, with the time to reach steady-state voltage being dependent on acclimation temperature. The highest COD removal rates of 2.98 g COD L-1 d(-1) were produced in the 35 degrees C reactor but coulombic efficiencies (CEs) were found to be significantly higher at psychrophilic temperatures. Acclimation at different temperatures was found to a have a significant effect on the dynamic selection of psychrophilic, psychrotolerant and mesophilic anode respiring bacteria (ARB). This was demonstrated by subsequent static temperature studies which showed that only the 20 degrees C acclimated reactor was capable of optimal operation over a 10-35 degrees C temperature range and this was facilitated by the activity of psychrotolerant microorganisms. These results show that MFC systems may be successfully adapted for use in temperate climates to provide a stable method of bioenergy recovery and organic contaminant removal as part of wastewater treatment processes.