Wastewater Treatment and Simultaneous Production of Biogas and Electricity through Algae-assisted Microbial Fuel Cell

Abstract

Water pollution and resource scarcity have become major issue due to rapid growth in population and industrialization. This has led to the exploration of energy efficient and resource recovery technology to treat and utilize wastewater. In recent past, energy generation with treatment of wastewater through microbial fuel cell (MFC) has gained considerable attention. With its potential to provide high level of wastewater treatment, MFC also offers additional advantage of reducing operational cost. In this study, a novel, double chamber, algae assisted MFC (AMFC) was developed to simultaneously generate electricity and biogas while treating sugar industry wastewater. Synthetic sugar industry wastewater was used as the substrate in the anode chamber, and synthetic domestic wastewater was used in cathode chamber as growth medium for Scenedesmus sp. The reactor was operated in semi-continuous mode at organic loading rates (OLRs) of 3.3, 5 and 10 g COD/L.d, which were applied to the anode compartment. For the second objective, effect of initial algae concentrations of 1, 3 and 5 g/l inoculated in cathode chamber was evaluated on the performance of AMFC at constant OLR of 3.3 g COD/L.d. Results demonstrated that the maximum biogas yield of 125.5 ml/COD/d and voltage of 250 mV were achieved at an OLR of 3.3 COD/L·d, with a COD removal efficiency of 83-92%. However, increasing the OLR to 5 and 10 g COD/L.d resulted in lower biogas yield and current production, indicating that excess OLR can restrain the system and cause failure. A higher initial algal concentration of 5 g/L yielded the maximum dissolved oxygen level of 8.8 mg/L, accompanied by significant voltage production of 293.911 mV. Moreover, this concentration also favored high removal efficiency of 36.66% for NH4-N and 39.11 % for PO4 3 -P. Thus, the current research shows that energy recovery from microbial fuel cell can be enhanced by optimizing the OLR according to reactor size, and algae concentration also play crucial role in performance of algae assisted MFC. Keywords: Microbial fuel cell, organic loading rate, anaerobic digestion, algae, nutrient removal