Research On Scale Design Method Of Combined Sewer Overflow Pollution Control Facility

With the acceptance of the pilot projects of various sponge cities in China,the Ministry of Housing and Urban-Rural Construction issued and approved the <Evaluation Standard for Sponge City Construction>(No.GB/T51345-2018)on December 26,2018 as the national standard,which will be implemented on August 1,2019.Among them,the control standard of combined sewer overflow is put forward.The CSO control standard is proposed in this paper.At the same time,according to the <Action Plan for Water pollution Prevention and Control>,issued by the State Council,by the end of 2020,the black and smelly water bodies in the built-up areas above the prefecture level will be controlled to less than 10%.Among them,how to reduce the cost and reduce the treatment capacity of CSO,how to effectively control CSO in existing wastwater treatment plants,and how to deal with peak flow are the practical problems that need to be faced urgently in our country at present.Based on the research results of long-term control of CSO in developed countries,combined with the above research background,this paper adopts literature reading,data comparative analysis,SWMM simulation and other research methods.Taking the United States as the starting point,the whole cycle of CSO pollution control from scheme formulation to actual construction monitoring is studied,and the control experience of CSO in developed countries is summarized.This paper focuses on the formulation of control standards in the states of the United States,and grasps the control concept of developed countries as a whole.Summarizes and combs the American CSO control standard and its origin that mainly includes annual overflow frequency,annual overflow volume control rate and total pollutant control.The determination of the control standard is guided by the water quality of the receiving water body and based on the data.Furthermore,three methods of dividing CSO events are put forward:MIET empirical assignment method;Determining CSO events with MIET of Independent rainfall events;Determining CSO event MIET by overflow characteristics.The statistical calculation results of CSO events based on overflow characteristics are more scientific and accurate.It is deduced that MIETx is the best MIET for Nx=N under different MIET.In this paper,the model continuous simulation of 30 years rainfall data of eight typical cities in China under the condition of the same confluence system is studied,and the overflow data are statistically calculated.Finally,on the basis of control standard and event division,the scale and size of control facilities are determined,which provides the design basis for CSO pollution control in China.Three methods of sizing are introduced:Simulation method based on SWMM Model;Design rainstorm method;Empirical formula method.This paper makes a comparative analysis of the typical urban data brought into the typical urban data by different scale design methods.It is found that the model continuous simulation method has certain advantages under the realistic condition that the planning and design of CSO pollution control project starts late and the monitoring data is seriously insufficient.Through the research and summary of this paper,it provides an important reference for the planning,design and management of cso control based on cso frequency control in our country,and perfects the design method of cso control facility scale in our country at the same time.