Effects of flow rate and chemical oxygen demand removal characteristics on power generation performance of microbial fuel cells

Abstract

Two microbial fuel cells with different oxygen supplies in the cathodic chamber were constructed. Electrogenic capabilities of both cells were compared under the same operational conditions. Results showed that binary quadratic equations can express the relationships between chemical oxygen demand degradation rate and chemical oxygen demand loading and between chemical oxygen demand removal rate and chemical oxygen demand loading in both cells. Good linear relationships between power output (voltage or power density) and flow rate and between power output and chemical oxygen demand degradation rate were only found on the cell with mechanical aeration in the cathodic chamber, but not on the cell with algal photosynthesis in the cathodic chamber. The relationships between power output and chemical oxygen demand removal rate and between power output and effluent chemical oxygen demand concentration on both cells can be expressed as binary quadratic equations. The optimum flow rates to obtain higher power density and higher Coulombic efficiency in the cell with mechanical aeration in the cathodic chamber (=0.85 mW/m2 and 0.063%) and in the cell with algal photosynthesis in the cathodic chamber (=0.65 mW/m2 and 0.05%) are about 1000 and 1460 μL/min, respectively. The optimum chemical oxygen demand removal rates to obtain higher power density and higher Coulombic efficiency in the cell with mechanical aeration in the cathodic chamber (=1.2 mW/m2 and 0.064%) and in the cell with algal photosynthesis in the cathodic chamber (=0.81 mW/m2 and 0.051%) are about 40.5 and 36.5%, respectively.