Experimental Study On Enhanced Purification Of Micro-Polluted River Water By Electrode-Biological Contact Oxidation

In this thesis,taking the micro-polluted river water of Fuyang River as the research object,an electrode biological contact oxidation system coupled with electrode biofilm and biological contact oxidation was constructed,and the ability of electrode enhanced biological contact oxidation system to remove target pollutants from micro-polluted river water was investigated.the effects of current density,arrangement of single and double cathode electrodes,carbon source,hydraulic retention time and packing ratio on electrode biological contact oxidation coupling system were analyzed.The optimal operating conditions of the system are determined.Through the analysis of microbial community structure and Fourier transform infrared spectroscopy of anode sediment,the mechanism of enhanced nitrogen and phosphorus removal by electrode biological contact oxidation coupling system was revealed.The main conclusions are as follows:The coupling system of electrode biofilm and biological contact oxidation was constructed by using single and double cathodes,and the removal ability of target pollutants from micro-polluted river water in flat season,flood season and low water season was investigated.The results showed that the removal rates of COD,TP and TN were higher than those of traditional biological contact oxidation system,and the electrode biological contact oxidation system with single cathode was better than that of double cathode system.The removal ability of target pollutants in micro-polluted river water is the best during the flood season,and the removal rates of COD,TP and TN reach87.46%,92.29%and 33.43%respectively,which are 5.15%,45.47%and 9.92%higher than those of biological contact oxidation.The main reason is that the water quality in the start-up period is in the flat water season,and the concentration of pollutants is higher than that in the flood season,so when the working conditions are changed,the microbial activity is higher.The extracellular polymer（EPS）and soluble microbial products（SMP）in the electrode biological contact oxidation system were more than those in the biological contact oxidation system during the three water quality periods,and the electrode enhanced the microbial activity.Through three-dimensional fluorescence spectrum analysis,the main components of EPS and SMP in the electrode biological contact oxidation system are tryptophan-like proteins.By changing the operating conditions of single cathode electrode biological contact oxidation coupling system,such as carbon source,current density,hydraulic retention time and packing filling ratio,the experimental results show that the operating effect of the system is the best when the carbon source is sodium acetate,and the optimal operating conditions are as follows:current density 0.09m A/cm2,hydraulic retention time（HRT）24 hours and packing filling ratio 40%.The removal rates of COD,NH₄⁺-N,TN and TP reached 86.55%,83.10%,56.46%and 97.53%,respectively.Except for TN,the effluent quality of COD,NH₄⁺-N and TP all meet the Class IV water quality standard of Surface Water Environmental quality Standard（GB3838-2002）.High-throughput sequencing technique was used to analyze the biofilm community structure of cathode packing module under biological contact oxidation start-up（GW）,single cathode biological contact oxidation start-up（ZYT）and optimal operating conditions（ZY）.The results showed that the electrode enhancement increased the microbial diversity of biological contact oxidation.Among the three samples,Proteobacteria,Bacteroidota and Acidobacteria were the dominant bacteria,and the abundance of denitrifying bacteria under the best working conditions of the single cathode biological contact oxidation system increased by 15.4%compared with the start-up of the biological contact oxidation system,which improved the nitrogen removal performance of the system.Due to the increase of the relative abundance of heterotrophic bacteria such as heterotrophic denitrifying bacteria under the optimum working conditions,the removal rate of COD in the electrode biological contact oxidation system increased.Fourier transform infrared spectrum analysis of the sediment near the anode shows that the main reason for the significant improvement of TP removal rate is the chemical reaction between iron anodic ionized iron ion and phosphorus in water,the formation of FeHPO₄and precipitation with PO₄^3-,and the combination of biological phosphorus removal and physicochemical phosphorus removal.