Identifying optimized conditions for concurrent electricity production and phosphorus recovery in a mediator-less dual chamber microbial fuel cell

Abstract

Understanding the impact of key operational variables on concurrent electricity production and phosphorus recovery in a microbial fuel cell is required to improve the process and to reduce the operational costs. In this study, a novel mathematical modelling approach, including full factorial design and central composite designs, was employed in a dual-chamber microbial fuel cell to: (i) identify the effect of influent chemical oxygen demand concentration and cathode aeration flow rate on electricity production and phosphorus recovery and (ii) optimise microbial fuel cell power density and phosphorus recovery. Phosphorus was precipitated at the cathode chamber, and the precipitated crystals were verified as struvite using X-ray diffraction and scanning electron microscopy analysis. Response surface methodology showed that influent chemical oxygen demand concentration and cathode aeration flow rate had a joint significant effect on power density, coulombic efficiency, phosphorus precipitation efficiency and phosphorus precipitation rate at the cathode. The effect of varying cathode aeration flow rates on power density and phosphorus recovery was dependent on chemical oxygen demand concentration. Phosphorus precipitation on the cathode electrode was negatively affected by the generated current during batch duration. The response surface mathematical model showed that concurrent high electricity production and high phosphorus recovery cannot be achieved under the same operating conditions; however, operating the microbial fuel cell at high chemical oxygen demand and high cathode aeration flow rate enhanced electricity production and phosphorus recovery. This was confirmed by the experimental results. These findings highlight the importance of operational conditions, such as influent chemical oxygen demand concentration and cathode aeration flow rate, on electricity production and phosphorus recovery.