Research On The Efficiency Of Treating Municipal Tailwater By Electric Field Coupled Iron-carbon Biofilte

At present,denitrification biological filter is a hot research field in wastewater advanced treatment,which can effectively solve the problem of excessive total nitrogen（TN）in municipal tailwater caused by high nitrate（NO₃^--N）concentration.Most studies focused on the effect of carbon source type and adding ratio on nitrogen removal in biofilter,but ignored the value of refractory dissolved organic matter（R-DOM）in municipal tailwater.In view of the low C/N ratio of municipal wastewater and the difficulty of organic matter degradation,a new process of electric field coupled iron carbon biological filter（E-ICBF）was constructed,and compared with quartz sand biological filter（SBF）and iron carbon biological filter（ICBF）,the feasibility of reducing pollutants in municipal tailwater by E-ICBF was discussed.Different operating parameters were optimized,and the response of decontamination efficiency to the types of organic compounds in municipal tailwater was discussed.Finally,the microbial community characteristics and metabolic characteristics of the process’s decontamination function were analyzed using microbiological methods.The following conclusions are reached:（1）Study on start-up and operational efficiency of E-ICBF process.In order to verify the feasibility of removing TN from municipal tailwater using E-ICBF without additional carbon sources,the decontamination efficiency of E-ICBF,ICBF,and SBF was investigated.The results showed that the E-ICBF process can effectively treat the pollutants in the tailwater,and the effluent TN concentration was always below 4 mg/L.（2）Study on optimization of operation conditions of E-ICBF process.In order to further improve the decontamination efficiency of E-ICBF,HRT,electrode material,and voltage were optimized.When the HRT was 20 h,the electrode material was graphite felt and the voltage was 8 V,the TN removal rate was 80.24±3.29%,the NO₃^--N removal rate was94.78±3.36%,the TP removal rate was 82.83±3.62%,the NH₄⁺-N removal rate was55.95±5.06%,and the COD removal rate was 52.66±7.22%.（3）Response of E-ICBF process’s decontamination efficiency to the types of organic matter in municipal tail water.In order to investigate the response of the decontamination efficiency of the E-ICBF process to different organic matter types in municipal tailwater,humic acid,peptone and polyethylene glycol were selected as organic matter in municipal tailwater.E-ICBF operated under optimal conditions and was controlled by ICBF and SBF.Compare the decontamination efficiency of each filter,and the results showed that the E-ICBF process could effectively treat pollutants in municipal tailwater.（4）Study on decontamination mechanism of E-ICBF process.In order to analyze the contaminant removal mechanism,characterization methods and high-throughput sequencing technology were used to analyze the packing interface reaction,microbial community characteristics and metabolic pathway.The result showed that the main forms of Fe were FeO,Fe₂O₃,Fe₃O₄,FeOOH,Fe C.The dominant genus of Fe-C fillers and cathodes were Thauera,and the dominant bacteria of the anode were unclassified＿f＿Comamonadaceae;Hydrogenophaga、Methylophilus、Erysipelothrix、Thiobacillus、Nitrosomonas、Thauera、unclassified＿f＿Comamonadaceae had a good correlation with TN removal.Electroactive bacteria and iron circulation bacteria had good correlation with most bacterial species.The microbial functional pathways in the filter were mainly amino acid metabolism and carbohydrate metabolism,and their proportion gradually decreases from bottom to top.