Performance of Microbial Fuel Cells Integrated with a Photo-Bioreactor: Effects of Light Regimes and Microalgae (Chlorella vs. Scenedesmus)

Abstract

Microbial fuel cells (MFCs) represent a promising technology for wastewater treatment and energy recovery, because of their ability to simultaneously convert organic matter into electricity via electroactive bacteria in anode chambers. This technology can significantly decrease the high energy costs typically associated with conventional wastewater treatment. The incorporation of green microalgae to self-supply oxygen may further enhance the environmental sustainability of the MFC system. This study evaluates the feasibility of integrating a double-chamber MFC with a photo-bioreactor (PBR) using specific microalgae under different light conditions. The experimental results indicated that chemical oxygen demand (COD) removal efficiencies using Chlorella vulgaris and Scenedesmus protuberans were 76.28% and 86.71%, respectively. A notable variation in cell voltage was observed when shifting from continuous illumination to a 12-hour light/12-hour dark (12/12) cycle. Under the 12/12 light/dark regime, Chlorella and Scenedesmus produced voltages of 350 mV and 340 mV, respectively, while continuous light resulted in higher voltages of 390 mV and 400 mV. Power densities achieved under continuous and 12/12 lighting were 1,140 mW/m3 and 975 mW/m3 for Chlorella, and 1,350 mW/m3 and 1160 mW/m3 for Scenedesmus, respectively. Overall, the system’s performance could be substantially improved by stabilizing influent concentration and flow rate. The integration of PBR into MFCs proved effective for simultaneous wastewater treatment and bioenergy recovery, with Scenedesmus and continuous illumination yielding superior performance.