The Influence Of Electron Flow Distribution On The Denitrification Performance Of EAM-MFC Coupled System And Its Principle Analysis

Microbial fuel cell?MFC?is one of bioelectrochemical systems,which uses nitrate as an electron acceptor and successfully achieves denitrification.However,the reactor design was complex and its construction was not cost-effective.Membrane aerated biofilm reactor?MABR?has some outstanding advantages comparing with the above-mentioned systems for the control of dissolved oxygen and nitrogen removal.In this study,the coupled electroconductivity aerated membrane-microbial fuel cell?EAM-MFC?system was developed to enhance simultaneous nitrification and denitrification?SND?by employing electrons from the anode.Maximum removal rates were attained up to 0.16 kg N m-3 NCC d-1 and 0.128 kg TN m-3 d-1 at the external load of 5 ?.Compared with an open-circuit system,the EAM-MFC coupled system's removal rates of NH4+-N and TN were improved by 9.48%and 19.80%at the COD/N ratio of 2.89 g COD g^-1 NH4+-N,respectively.These results demonstrated that this system has high potential to reduce organic materials and improve nitrogen removal while recovering energy in the form of electricity and thus reducing the system's operational costs.EMABR enabled the proper environment for SND process which can supply two different types of electron acceptors,such as,oxygen and nitrate.Considering that the redox potential of O₂/H₂O?+ 0.82 V?was higher than NO3-/0.5 N₂?+ 0.74 V?redox potential,oxygen may compete with nitrate to acquire electrons.A complete removal of nitrate was obtained with nitrate as the only electron acceptors,while when adding both of oxygen and nitrate,only 39.88%of nitrate was removed.Under the open-circuit condition,the lowest removal rate of nitrate was obtained at only 13.65%.Additionally,the cathode?NO3-?chambers reached the maximum coulombic efficiencies?CEs?of 42.84± 1.14%which was 12.11%higher than the cathode chambers under the close-circuit condition with two different kinds of electron acceptors.These results suggested that the EAM-MFC coupled system could optimize the utilization and distribution of the electrons transferring from anode chamber.In summary,the EAM-MFC coupled system had the capacity for adjusting the electrons distribution for nitrogen removal in the cathode chamber and also the excellent removal rate of COD and nitrogen at the low COD/N ratio.