First study to explore the feasibility of simultaneously applying microbial fuel cell and microbial electrolysis cell in constructed wetland

Abstract

The microbial fuel cell-constructed wetland coupling system (MFC-CW) has been developed and regarded as a promising technology for wastewater treatment. However, its potential has been underestimated and there is still space for further expanding its scope to maximize its capacity for both power generation and wastewater treatment. In this study, we explored a number of novel MFC-CW coupled with a microbial electrolysis cell (MEC) systems (MFC-MEC-CW, referred as MFEC-CW) with various interconnected electrodes to effectively enhance the exogenous electric field (EEF) and consequently improve the wastewater treatment efficiency and power generation. The shared-anode MFEC-CW system exhibited best overall performance among other systems, particularly compared to traditional CW, MFC-CW, and MEC-CW systems, achieving a maximum power output of 63.9 μW, a maximum voltage output of 363 mV, an average net power generation of 36.75 μW, and NH₄⁺-N removal of 90.26 %. These findings confirm that the novel MFEC-CW system can enhance both wastewater treatment and net power generation. Furthermore, it reduced the energy consumption of conventional MEC-CW systems while boosting power generation. This study demonstrates that MFEC-CW exhibits significant promise as an innovative and effective technology to reflect the advancement of bio-electrochemical-based wetland systems (BES-CWs).Abbreviations: BES, Bioelectrochemical effects; BES-CW, Bioelectrochemical effects and CW coupling system; CE, Coulombic efficiency; COD, Chemical oxygen demand; CWs, Constructed wetlands; EEF, Exogenous electric field; EET, Extracellular electron transfer; E-HSCWs, Electrolysis-assisted horizontal subsurface-flow constructed wetlands; EPS, Extracellular polymeric substances; Fe₃O₄, Ferric oxide; MEC, Microbial electrolysis cell; MFC, Microbial fuel cell; MFEC-CWs, MFC-MEC-CW system; N, Nitrogen; N₂, Nitrogen; N₂O, Nitrous oxide; NER, Net energy recovery; NH₄⁺-N, Ammonium nitrogen; NO₂^—N, Nitrite nitrogen; NO₃^—N, Nitrate nitrogen; OPR_Ca/An, MFC average overpotential ratio of Cathode / Anode; OPR_Ca/An, Overpotential ratio of cathode and anode; ORP, Oxidation reduction potential; P, Phosphorus; PEM, Proton exchange membrane; P_in, Power input; P_net, Net power generation; PO₄^3-, Phosphate; P_out, Power output; SS, Stainless steel; SSM, Stainless steel mesh; TN, Total nitrogen.