Current Operating Status And Diagnostic Evaluation Of Rural Domestic Sewage Treatment Facilities In Zhejiang Province

Treatment of domestic sewage is one of the important contents of Chinese Revitalizing Strategy for Rural Region.For that purpose,Zhejiang is pushing aggressively into constructing massive amounts of sewage treatment facilities in recent years and approaches relatively good social and economic benefit.However,restricted by technological and management factors,opearting performance for some facilities are not satisfied in the real cases,triggering province-wide reconstrction work and desire for the optimal management.Thus,in order to carry out the relevant work in a scientific and orderly manner,a targeted evaluation system is needed to diagnose the technical and management status of the facilities.It can not only make clear the key problems and the priority level of the facilities that need to be upgraded,but also guide local governments to make scientific decisions and carry them forward in an orderly manner.At present,there is no proper evaluation system to diagnose the technical and management problems of the facilities.Therefore,it is of great importance and urgency to construct an objective and practical diagnostic evaluation system for the technology and management of rural sewage treatment facilities.At the begining,the study has carried out thorough investigation on the operating performance of 300 facilities across 10 counties and districts.And then,according to the investigation results,the related indexes which can represent the technical and management status of the facilities are selected and constitute the index system.Comprehensive weight of corresponding index is derived by entropy weight integrated with coefficient of variation method.Further more,the study uses transformation function and expert meeting method to determine the method of index assignment,and divides the evaluation grade of the comprehensive index.Finally,it forms the diagnostic evaluation system for the technology and management of rural sewage treatment facilities.The constructed evaluation systems is applied to analysis cases in Changxing county and provide targeted advices for facilities'reconstrction work and optimal management.The main results of this study is as following:?1?Result of investigation show that applicability of rural domestic sewage treatment process is generally good.Existing problems mainly lie in the unsatisfied treatment performance,insufficient justification for the facilities design,improper constrction management and lacking of normative maintenance.The main performance are as follow:57%of the facilities'effluent quality does not meet the discharge standard,37%of the facilities'daily treatment capacity is insufficient and other technical problems,16%of the facilities'front-end pipe network construction quality is poor and other construction problems,as well as 16%of the facilities'pre-treatment unit maintenance is not timely and other operation and maintenance problems?2?The study has built the diagnostic evaluation system for the technology and management of rural sewage treatment facilities.Technical indexs and its corresponding weight are listed as following:Removal Efficiency of COD?0.061?,Removal Efficiency of NH3-N?0.128?,Removal Efficiency of TP?0.121?,Removal Efficiency of TN?0.170?,Compliance of Effluent?0.201?,Stability of Treatment Process?0.021?,Constructing Cost for the Treatment of per tons sewage?0.057?,Treatment Cost for per tons sewage?0.079?,Rationality of Terminal Site?0.043?and Rationality of Design Parameters?0.119?.Management indexs and its corresponding weight are listed as following:Quality of Structure?0.072?,Integrity of the Key Equipments and Assembly?0.098?,Quality of Constrution of Sewer Pipe Net?0.202?,Maintenance of Pretreatment Compartment?0.110?,Maintenance of Main Treatment Compartment?0.148?,Maintenance of Auxiliary Facilities?0.141?,Maintenance of Sanitation?0.172?.?3?Case study of Changxing county reveals that 63.3%facilities need enjoy the priority of reconstrction work,4.2%facilities need enjoy the priority of optimal management.The mian technical problems are insufficient removal of NH₃-N,TP,TN,low compliance percentages of effluent and unreasonable design parameters.And the main mangement problems are the maintenance of pretreatment compartment,equipments and sanitation not in a timely manner.The key points of regional renovation in Changxing County should include improving pollutant reduction efficiency,optimize design parameters,and improve operation and maintenance management.The evaluation system constructed in this study can realize the scientific diagnosis of technology and management problems in facilities,and make clear the reconstruction content of the facility site and the key points of the regional reconstruction,and identify the priority level of facilities'upgrading and optimization,so as to provide a strong guide for the local government to carry out related work.