Study On The Efficiency Of Pyrite-based Biofilter-microbial Fuel Cell (BF-MFC) In Treating Rural Sewag

Recently,biofilter-microbial fuel cell（BF-MFC）due to the low construction and operation cost has been suitable for further used in rural areas limited by capital and technical requirements.However,the relevant achievements were only studied in the view of meeting level B discharge standards.In addition,fewer reports were on achieving level A and community microbial characteristics.Therefore,in this study,a pilot-scale BF-MFC was constructed and discussed the different removal performances in different influent characteristics.Meanwhile,different operation parameters were optimized and pyrite-filled BF-MFC systems were constructed to discuss the possibilities of enhancing nitrogen and phosphorus removal performance.Finally,microbiology was used to reveal the characteristics of functional microbial concerning pollutant-removing and electricity generation.The main conclusions were as followed:（1）The operation characteristics of BF-MFC were surveyed by single-factor test after the start-up of BF-MFC and then surveyed the pollutant-removing and electricity generation performance.The results showed that the effluent chemical oxygen demand（COD）and total nitrogen（TN）concentrations of BF-MFC met the discharge standard of level A while ammonia nitrogen（NH₄⁺-N）and total phosphorus（TP）do not meet in the 200 mg/L organic loads.（2）To solve the higher effluent concentration of NH₄⁺-N and TP,the parameters,such as the hydraulic retention time（HRT）,the number of anodes and pyrite filter material ratio,were optimized.The result showed that the optimal parameters were as follows:HRT,number of anodes,pyrite position were 20 h,singer anode and middle filter,respectively.Under these conditions,the removal rates of COD,NH₄⁺-N,TN and TP by BF-MFC system were80.13%±4.30%,53.31%±4.65%,87.99%±3.15%and 88.50%±1.31%,respectively.And the effluent water quality indexes met the level A discharged standard.The corresponding highest power density,internal resistance and coulomb efficiency were 6.44 m W/m²,155Ω,and 0.04%,respectively.（3）For revealing the mechanism of pyrite-filled BF-MFC in pollutant-removing and electricity generation,the characterization methods and high-throughput sequencing techniques were used to analyze the chemical composition,microbial community characteristics and metabolic pathways on the surface of filler and electrode.The chemical mechanism of pyrite showed that Fe（PO₃）₃and Fe OOH appeared in pyrite filler in late operation.The abundance and metabolic function of microbial communities on the filler and electrode surface were different due to the anode ratio and location of pyrite.Pyrite can promote the proportion of Geobacte and Geothrix on NH₄⁺-N removal on the filler surface.It can also promote the abundance of Geobacter,Geothrix,Hydrogenophaga and Dechloromonas related to electricity generation on the electrode surface.Meanwhile,microbial response results showed that the surface of pyrite-filled BF-MFC filler was dominated by amino acid metabolism and carbohydrate metabolism,and the energy metabolism on the electrode surface was the most dominant in the pyrite position of anode layer.