Study On Class V Discharge Treatment Technology Of Township Sewage Treatment Plant

With the implementation of the action plan for the prevention and control of water pollution,the comprehensive elimination of inferior class V water has become a key target for the treatment of water pollution.As an important part of China's urban system,the status of wastewater treatment in the township will have a great impact on the environmental conditions and sustainable economic development.In this study,the water quality and discharge characteristics of sewage in typical township were determined through investigation.Combined with the characteristics of denitrification deep bed filter,the treatment process with A²O and denitrification deep bed filter was proposed.In addition,the engineering practice exploration was carried out on the treatment of sewage in the township with the example of Xiali county.The characteristics of wastewater quality and discharge in the township were determined through investigation.The results showed that sewage from small towns mainly comes from domestic sewage,industrial wastewater and agricultural wastewater.Sewage water quality was affected by industrial structure,regional characteristics,seasonal and other factors.The concentration of main pollutants in water was SS:90³00 mg/L,BOD₅:70²00 mg/L,COD_cr:120³00 mg/L,TN:20⁵0 mg/L,NH₃-N:20⁴0 mg/L,TP:6¹0 mg/L.The BOD₅/COD_Cr ratio of sewage in small towns was mainly distributed between0.4 and 0.6,which demonstrated that sewage biodegradability is good.However,the nitrogen and phosphorus removal capacity of conventional secondary biological treatment process was limited,and the effluent could not reach the water quality requirement stably.In view of the above problems,this study combined with the characteristics of township sewage water quality,determined the deep sewage treatment process with denitrification deep bed filter as the core.The reaction system was constructed to explore the optimal operating conditions and treatment characteristics of the denitrification deep bed filter.The results showed that the treatment effect of the denitrification deep bed filter was the best when sodium acetate was used as the external carbon source,the influent C/N was 5,and the hydraulic retention time was 30 min.Under the optimal conditions,the COD of the system effluent was stable below 20 mg/L,and the average concentration of NO₃^--N in the effluent was 1.97 mg/L.On this basis,combined with chemical dephosphorization and other processes,the depth treatment of secondary effluent can be achieved.Based on the characteristics of the sewage of township and denitrifying process characteristics of deep bed filter,a sewage treatment process with"swirling sedimentation tank+A²/O+denitrification deep bed filter"as the main body was proposed.Taking xiali township,a typical small town in northwest China,as an example,the engineering practice of sewage treatment plants in small towns was carried out,and the design of sewage treatment structures and the selection of main processing equipment were completed,which provided important basis for technical and economic analysis and preliminary design of sewage treatment projects in small towns in China.The treatment of sewage in small towns will greatly reduce the adverse impact of urban sewage on local ecological environment,thus greatly improving the quality of local ecological environment and improving the living conditions of residents,which is of great significance for promoting the coordinated and sustainable development of the region.