Design And Research On The Expansion Project Of Sewage Treatment Plant In A County

With the development of economy and the improvement of people's living standards,more and more attention has been paid to the prevention and control of water environment pollution.Especially in recent years,with the continuous promotion of urbanization construction,some urban sewage plants need to further improve their production capacity to meet the development needs in order to adapt to the new development requirements.This paper analyzes the main problems existing in the operation of a high ammonia nitrogen sewage treatment plant after upgrading the standard,and discusses the specific design content and scheme of the expansion project,respectively from the project background and necessity analysis,highlighting the problems to be solved,the research and demonstration of the design scheme,the specific design content,the analysis of the treatment effect before and after the expansion,the problem suggestions,etc This paper discusses in detail,especially for the design comparison and selection of the expansion content and process scheme of the high ammonia nitrogen sewage treatment plant in the county,so as to achieve the goal of the stable effluent quality of the sewage treatment plant in the county reaching the discharge standard,and finally achieve the long-term planning goal of the sewage treatment plant in the county to effectively solve the main problems existing in the plant at present.According to the new requirements of relevant national infrastructure construction and economic development,combined with the specific contents of the short-term and longterm planning in the county's urban master plan,combined with the current situation of the county's population and industrial enterprise drainage,through analysis and prediction,the design scale of the sewage treatment plant of the project is finally determined:28000 m³/d in the short term?2020?and 48000 m³/d in the long term?2030?,including the treatment capacity of the existing sewage treatment plant is 8000 m³/d,the newly increased treatment capacity in the near future?2020?is 20000m³/d,and the newly increased treatment capacity in the long term?2030?is20000 m³/d.after treatment,the tail water meets the class I B standard in the discharge standard of pollutants for urban sewage treatment plant?GB18918-2002?,and then it will be discharged.According to the long-term investigation of the treatment results of the original sewage treatment plant,the influent water quality of the original sewage treatment plant before the expansion was COD_cr?550mg/L,BOD5?250mg/L,SS?250mg/L,NH₃-N?85mg/L,TN?100mg/L.Compared with the influent water quality of the general domestic sewage,it can be seen that the content of CODCr,NH3-N,TN in the sewage from the municipal sewage collection outlet of the county is significantly higher than that of the general domestic sewage,which belongs to the typical high concentration sewage Degree ammonia nitrogen sewage.According to the specific planning contents and requirements of the sewage treatment plant in the county,the main tail water quality indexes after expansion are COD_cr?60mg/L,BOD5?20mg/L,SS?20mg/L,NH3-N?8mg/L,TN?20mg/L,which meet the discharge standards of the first class B of the national urban sewage treatment.In view of the high concentration of ammonia nitrogen,total nitrogen and total phosphorus in the water quality of the county,the reasons for the formation of the water quality characteristics and the related treatment processes are analyzed.The specific characteristics of the bottom aeration oxidation ditch,A/A/O process,SBR process and Carrousel oxidation ditch process are emphatically compared.Combined with the requirements of tail water discharge,the bottom aeration oxidation ditch is finally determined based on the construction of the original sewage plant material treatment process,in which sludge treatment is mechanical concentration+plate and frame pressure filtration process as the main process to expand the sewage treatment plant.In addition,on the basis of the specific process,the paper directly uses the design parameters of the existing sewage treatment plant buildings and other monomers,such as the treatment unit coarse grid,sewage lifting pump house,water distribution well,oxidation ditch,final sedimentation tank,contact tank,chlorination,dosing room,sludge pump house,sludge storage tank,sludge dewatering machine room,sodium acetate dosing workshop,power transformation and distribution room,blower room and auxiliary buildings.According to the characteristics of high ammonia nitrogen and total nitrogen in the sewage of the county,combined with the previous measures to improve such sewage treatment,the basic parameters of oxidation ditch process design are as follows:design flow 20000m³/D,sludge age 25.4?d,BOD sludge load0.048 kg BOD5/kg MLSS?d,TN sludge load 0.017 kg TN/kg MLSS?d,mixed reflux ratio 400%.Compared with the effect of the previous treatment process,the final effluent quality design and scheme demonstration results show that the actual values of COD_cr and TP deviate greatly from the design values.Except for TP,they can basically meet the class a standard of discharge standard of pollutants for urban sewage treatment plant?GB18918-2002?.After the expansion,the process and treatment capacity have good effect and promotion,which can achieve the treatment goal after the expansion.At the end of the paper,through the analysis of the problems existing in the actual operation process,and put forward relevant suggestions.According to the characteristics of the sewage quality of the county and the existing problems after the upgrading,the effluent quality of the expansion project basically reaches the stable discharge standard after the actual operation,and the overall operation effect is good,meeting the future development needs and long-term planning objectives of the county.