Influence of Very High Flow Rates on Performance of Biofilter-Microbial Fuel Cells

Abstract

Scaling-up microbial fuel cells for continuous-flow wastewater treatment is the conventional challenge for numbers of researchers. Here in this study, we constructed large volume biofilter-microbial fuel cells (BMFCs) by applying graphite electrodes to the low-cost biofilters. Very high flow rates of 625-2,667 mL/hr (15-35 L/day) were applied to the BMFCs to explore their influence on wastewater treatment and electricity generation. An effect of hydraulic retention time (HRT) was expunged from the experiment by using various chamber volumes under the same HRT of 5 hrs. The result revealed that 32-73 % of COD removal, 5-14% of TN removal, 13-18% of TP removal, and 16.2-53 mW/m2 of power output could be achieved by the BMFCs. Higher flow rates led to higher pollutant removal rates and higher power densities under the linear regression equations with determination coefficients (R2) of 0.81-0.99. As the power density was the linear function of the pollutant removal rates (R2 = 0.93-0.97), the increasing shear rate which accorded with the increasing flow rate was considered as the key factor to enrich biomass and provoke electrogenic activity in an anode chamber. Therefore, the highest pollutant removal rates and highest power density were observed at the highest flow rate.