Study On Electric Production Denitrification And Characteristics Of Production Of N₂O And NO In Double-chamber Microbial Fuel Cell

Microbial fuel cell（MFC）is a new water treatment technology that can both generate electricity and treat sewage.In this study,a double-chamber MFC was used to explore the effect of dissolved oxygen（DO）on the denitrification and electricity generation of double-inlet MFC and single-inlet circulating MFC,and to study different operating conditions（NH₄⁺-N concentration,aeration mode,anode COD concentration and switching circuit）affect the denitrification and electricity generation of the system,explore the characteristics of MFC cathode nitric oxide（NO）and nitrous oxide（N₂O）produce,identify the anode and cathode microbial communities of MFC,and discuss the mechanism of MFC action to obtain the following research results:（1）Study the effect of DO on double-inlet MFC and single-inlet circulating MFC denitrification and electricity generation.（1）double-inlet MFC and single-inlet circulating MFC both increase the ammonia nitrogen（NH₄⁺-N）removal efficiency as DO increases,double-inlet MFC total nitrogen（TN）removal efficiency decreases,TN removal efficiency of single-inlet circulating MFC increases first and then decreases and reaches the maximum when DO=2mg/L.Under the same DO conditions,the residual COD in the single-inlet circulating MFC cathode consumes part of the DO and synchronous nitrification heterotrophic denitrification occurs,making the removal efficiency of NH₄⁺-N lower than double-inlet MFC,but the removal efficiency of TN is higher than double-inlet MFC.（2）With the increase of DO,the power generation performance of double-inlet MFC and single-inlet circulating MFC continues to increase,but the power generation performance of single-inlet circulating MFC is less than double-inlet MFC under different DO conditions.This is because the COD in the cathode of single-inlet circulating MFC will compete with the cathode electrode for DO and nitrate（NO₃^--N）,the electrode electron acceptor is reduced compared with double-inlet MFC,so that its power generation performance is lower than double-inlet MFC.（2）Explore the changing characteristics of MFC in each operation mode（NH₄⁺-N concentration,aeration mode,anode COD concentration and switching circuit）.（1）Increasing the concentration of NH₄⁺-N in the water inlet can accumulate more NO₂^--N and inhibit the reduction of N₂O,thereby increasing the production of N₂O.When the concentration of NH₄⁺-N in the influent was 500 mg/L,the amount of N₂O produced was the largest with a value of1.271 mg/L.In the three cases of this experiment,there was no production and accumulation of NO.（2）As the concentration of the anode substrate decreases,the voltage shows a downward-stable trend,the cathode DO has been rising,and the amount of TN removal has decreased.（3）Open circuit is conducive to the removal of NH₄⁺-N,but not conducive to the denitrification process.In the open circuit operation mode,the cathode generates a large amount of N₂O and a small amount of NO.After the circuit is turned on,the dissolved N₂O rapidly drops at the initial stage and increases the voltage by about 20 m V.Compared with nitrite,NO and N₂O are easier to accept electrons on the electrode to complete electrode denitrification.（3）（1）The dominant bacteria in the anode chamber based on the level of the phylum are mainly Firmicutes,Proteobacteria,Chloroflexi and Bacteroidetes.Firmicutes account for a maximum of 33.2%.The genus of Desulfovibrio,Clostridium,Geobacter and Enterobacter are all electrogenus and the sum of the proportions is 8.6%.（2）The dominant bacteria in the cathode chamber based on the level of the phylum are mainly Proteobacteria,Bacteroidetes,and Chloroflexi.The proportion of Proteobacteria is up to 35.9%.Nitrosomonas bacteria include Nitrosomonas,and denitrifying bacteria genus include Pseudomona,Paracoccu,Arenimona,Truepera,Ignavibacterium,Planctomycetes and Comamonas.