Study On The Evaluation Of Whole-process Remediation Of City's Black And Odorous River Based On The Improved Matterelement Extension Model

Under the background of rapid urbanization,a large number of sewage is discharged into the river,and the speed of infrastructure construction is far slower than the speed of the development of urbanization,which leads to serious pollution of urban rivers and black odor phenomenon.The black odor of urban river threatens the health of river ecosystem,endangers human health.After a series of national policies were issued,the upsurge of black and odorous river regulations and studies were raised nationwide.2020 is the year of examination of the realignment of urban black and odorous river.However,the research on the assessment of the realignment effect of urban black and odorous river has not formed a complete theoretical system,which leads to the problems that it is unable to accurately judge whether the regulation measures are effective,whether the regulation scheme is reasonable,resulting in the uncertainty of the realignment direction,and the realignment effect is difficult to maintain.The establishment of a scientific and effective assessment system helps to clarify the key to the regulation of black and odorous river.Therefore,it has become an urgent need to form an effective evaluation system and method when the examination of the realignment of urban black and odorous river comes.Based on the three theories of urban river ecosystem health,the impact of urbanization on river and Sponge City,this study constructs the evaluation index system of the whole process of urban black and odorous river realignment.Taking Minfeng River,the key black and odorous river which is ordered realignment in Wuxi,as the empirical object,it evaluates the whole process of Minfeng River realignment from both qualitative and quantitative perspectives.The main conclusions are as follows:(1)On the basis of a large number of theories,five aspects which include pollution control and interception,water quality control,water habitat restoration,coastal zone restoration and long-term mechanism are selected.Taking the pollution characteristics and realignment measures of Minfeng River into full consideration,18 indexes from both qualitative and quantitative perspectives are selected,so as to establish three-level index system of target level,criterion level and index level.The study uses expertencertain analytic hierarchy process to empower indexes.According to the definition and assignment of indexes,the evaluation grades of the whole process of urban black and odorous river realignment are divided into five grades including Level ?(very invalid),Level ?(invalid),Level ?(general),Level ?(effective)and Level ?(very effective).The improved matter-element extension method is used to construct the evaluation model.(2)The proportion of pollution control and interception is the largest,which indicates that at present,the thought of black and ordorous river realignment is gradually changing from the traditional end-of-pipe treatment to both symptoms and root causes.The proportion of water quality control and water habitat restoration is smaller than that of pollution control and interception and coastal zone restoration,which indicates that river pollution control should not only pay attention to the water body itself,but also trace the source and fundamentally solve the problem;The proportion of long-term mechanism is the smallest,reflecting the problems such as imperfect management organization plan,inadequate implementation of river chief system and incomplete monitoring.However,compared with the existing researches,the proportion has been increased by a small margin.It can be seen that in recent years,with the vigorous promotion of river chief system and information management,the awareness of long-term management is gradually improving.(3)The improved matter-element extension model is applied to the assessment of the whole process of Minfeng River realignment in Wuxi,and the assessment grade is Level II(effective),which basically reflects the status quo after realignment.The fuzzy probability assessment method is used to verify the assessment results to ensure the applicability and popularization of the assessment index system.According to the evaluation results,the paper analyzes the imperfections of the control measures,mainly including single non-point source control measures,small quantities of works,small scope of river revetment control,lack of detailed management organization plan,imperfect monitoring indicators,low public participation in the long-term management process,and puts forward the targeted measures,including increasing non-point source control measures,enriching the species of grass planting ditch plants,and expanding the scope of revetment,clearing the personnel and responsibilities of management and protection team,further refining the composition and responsibilities of the office of the river chief,implementing the assessment and accountability system,guaranting special fund support,increasing real-time monitoring indexes,strengthening publicity to realize the medium process of the public participating in river management with the information management platform of the river chief system,so as to provide basis for the further improvement and maintenance of the water quality of the river and to provide reference direction for other urban river management at the same time.