Application And Evaluation Of UNITANK + High Efficiency Sedimentation + BAF In Upgrading Of Sewage Treatment Plant

At present,the state and local governments have continuously issued higher standards for pollutant discharge requirements of urban sewage treatment plants,local sewage treatment plants are also constantly upgrading and transforming,and various transformation processes are emerging one after another.Combined with the reality of a municipal sewage treatment plant and making full use of the existing process,this study puts forward the standard upgrading and transformation technology of the sewage treatment plant with"UNITANK+high efficiency sedimentation+BAF"process as the core,studies the transformation effect based on the process combination,and carries out the full life cycle environmental impact assessment of the sewage treatment plant.The main achievements are as follows:（1）Through comparative analysis,the upgrading process of sewage treatment plant is determined based on Unitank+high efficiency sedimentation tank+BAF（N+DN）+rotary filter tank.Three mechanical grilles（coarse grilles,medium grilles and fine grilles）and aerated sedimentation tank were used in the process pretreatment unit after modification.The secondary treatment is Unitank.Advanced treatment units are efficient flocculation sedimentation tank,denitrifying filter,fiber rotary filter and sodium hypochlorite disinfection;The odor gas produced by each process unit is controlled by the combined process of biological enhancement deodorization and biological drip filter tower deodorization.The sludge treatment unit extended the sludge concentration time to 16.8h/d,and the water content of the sludge decreased to less than 80%after dewatering.（2）According to the analysis of water quality in and out of the sewage treatment plant after upgrading the standard,the discharge standard of the sewage treatment plant before upgrading is Level 1 B,and the discharge standard of the sewage treatment plant after upgrading is Level 1 A.The average concentrations of CODcr,BOD₅,SS,NH₃-N,TN and TP in effluent after upgrading are 43.6mg/L,9.9mg/L,9.36mg/L,4.1mg/L,14.2mg/L and 0.45mg/L,respectively.The effluent quality index can reach the discharge standard of national standard grade A stably.After upgrading the sewage treatment plant,the environmental,economic and social benefits are remarkable.In terms of environment,the reduction of CODcr,BOD₅,SS,NH₃-N,TN,TP is large,and the environmental benefit is obvious.In terms of economy,the total investment cost of the sewage treatment plant renovation project of the project is 632.64 million yuan,the operating cost is 0.6634 yuan/ton,and the return of water is 3285million yuan/year,with significant economic benefits.In terms of social benefits,the overall improvement of local water quality and reduction of water pollution are conducive to beautification of the environment and human health,as well as the introduction of foreign investment and real estate appreciation to promote the economic development of the city.（3）Using simapro9.0,the environmental impact of the sewage treatment plant in the whole life cycle is comprehensively evaluated from the construction stage,operation stage and demolition stage,the environmentally sensitive processes in the system are found out and optimization suggestions are put forward.The results show that the operation stage has a great impact on the environment,and the carbon emissions account for 82.9%of the total emissions respectively.In the operation stage,there is little difference between the carbon emissions of PAC dosing and operation energy consumption,accounting for 28.6%and 27%of the operation stage respectively.It can be seen that PAC and operation energy consumption are the main sources of carbon emissions in the operation stage.Secondly,the carbon emission in the construction stage can not be ignored.The use of concrete is the main source of carbon emission in the construction stage,accounting for about 15.1%.Therefore,in practical engineering,we should improve the utilization efficiency of chemicals,control the stable and efficient operation of the system,and reduce energy consumption,so as to better improve the economic and environmental benefits.