Study On Denitrification Of Microbial Fuel Cells With Membrane Aerated Biofilm Reactor As Cathode

Membrane aerated biofilm reactor (MABR) is a new process to remove nitrogen with the characteristics of simultaneous nitrification and denitrification (SND), and microbial fuel cell (MFC) can obtain clean electricity while treating wastewater. In order to improve the denitrification process efficiency, this study combined the MABR and MFC, which the MABR was a cathode of MFC. The anode degraded the organic of wastewater to generate electricity, and the electrons were transferred through an external circuit from anode to the cathode. Based on the MABR-MFC integrated system, the nitrogen and carbon removal efficiencies and electric performance were investigated. To achieve good performance, the effects of nitrogen load, COD/NH3-N and resistance on cathode chamber performance was analyzed to make sure the optimal operation parameters. Besides, the influence of electrons transferred from anode on cathode chamber performance was studied for closed circuit and open circuit.In this study, start-up of MABR-MFC took 30 d. After MABR-MFC came into stability, the voltage output of 0.58±0.01 V, internal resistance of 1100±50Ω, maximum power density of 0.0018 W/m2 and coulomb efficiency of 3.64% were obtained in the 30th day of stable operation. The cathode chamber achieved COD removal of 90.6%, NH3-N of 80.8%, as well as TN of 55.1%. MABR-MFC integrated system had the advantages of effluent quality and good electricity production performance.After start-up of MABR-MFC integrated system, the microbial populations of the biofilm of anode and cathode were rich. The microbial communities of inoculated sludge and biofilm of anode and cathode were detected by high-throughput sequencing technology for 30 bacteria populations, including Chorobi and Chloroflexi of autotrophic bacterias and Proteobacteria, Nitrospirae and Planctomycetes related to nitrogen removal. Compared with theinoculated sludge, the number, diversity and abundance of microorganisms were improved, so the more microbial populations of MABR-MFC integrated system, the stronger capacity to maintain the stability of system.The optimal operation parameters of MABR-MFC integrated systemwere that nitrogen load of influent was 0.16 g/(L-d), COD/NH3-N of influent was 3:1 and external resistance was 1000Ω, which achieved good effluent quality and electricity production performance with highest COD removal of 95.2%, NH3-N of 94.8%, TN of 83.4% and the maximumoutput voltageof 0.71 V, power density of 0.055 W/m2 and coulombic efficiency of 4.24%, respectively.The effluent quality of cathode chamber was investigated for closed circuit and closed circuit, which showed that heterotrophic bacteria and denitrifying bacteria had activity in both situations. However, the TN removal efficiency of cathode chamber under closed circuit condition was better than that of open circuit condition, because the electronstransferred from anode to cathode promoted denitrification process with more electronsparticipated NO3- reduction reaction, so that the denitrification rate was improved in a certain degree.