Achieving high energy harvest from a siphon boosted microbial fuel cell-constructed wetland system

Microbial fuel cell-constructed wetland (MFC-CW) coupling system is a kind of bio-electrochemical intensified CW system which upgrades CW into multi-functional wastewater treatment technology. Achieving robust electrical energy output is one of the critical challenges in MFC-CW. However, some critical factors limited power output of MFC-CW in terms of reactions on electrode. These inhibited cathodic reactions were mainly due to insufficient oxygen supporting and great overpotential of anode because of the excessive oxygen diffusion. This study reports a novel siphon containing MFC-CW and its operational strategy (namely a full siphon recirculation (FSR) mode), to boost power output of the MFC-CW. Consecutive tidal flow (TF) cycles were established by FSR in cathode chamber which contributed to the better performances of both the cathode and the anode. Results show that the highest power density, coulombic efficiency (CE) and normalized energy recovery (NER) in FSR mode were 1.15 mW/L, 19.28 %, 128.15 Wh/kg COD, respectively. Power output of MFC-CW with FSR mode were remarkable high and sustainable compared with other MFC-CW studies with normalized assessment criteria. FSR mode simultaneously shows advantages over the high cathode potential and low anode potential. This novel structure and the operation strategy can be regarded as a smart choice to level up power output of MFC-CW system.