Evaluation And Analysis Of Water Environment And Its Treatment Of Some River Courses In Kunshan City

Since modern times,with the rapid development of urban economy,people have ignored the protection of water resources,and the pollution of river water environment has gradually become one of the difficult problems faced by urban development.The polluted river can not only meet people’s basic drinking and irrigation needs,but also further restrict the development of urban economy and society.With the development of economy and society,Kunshan city also has serious river water pollution problem.In this study,a total of 13 river channels in Kunshan city were selected,including Jingwangbang River,Zhujing Central River,Yanjiajiao River,Xupu River,Jiangpu River,Fotang River,Shao Village Central River,Guangpu River,Greenland Landscape River,Zhangming River,Laolunipu River,Changjing River and Central Park River.In order to improve river water quality,the 13 river channels selected by this study were treated,including sewage interception,sediment dredging,ecological restoration,etc.On the selected river water quality monitoring,the period of one year using a variety of types of evaluation method for the analysis and evaluation,(1)the single factor analysis and evaluation of water quality,for each of the p H value of the river water quality,transparency,dissolved oxygen,potassium permanganate index and 5th biochemical oxygen demand,ammonia nitrogen,nitrate nitrogen,total nitrogen,dissolved phosphorus,total phosphorus and chlorophyll a and so on carries on the analysis and evaluation;(2)Comprehensive index analysis and evaluation of water quality,using comprehensive pollution index method,comprehensive water quality identification index method,organic pollution comprehensive index method,comprehensive nutritional status index method to analyze and evaluate the water quality of the thirteen river channels.(1)Evaluation results of comprehensive water pollution index for 13 river courses: Zhujing Central River,Jiangpu River,Fotang River belong to the mild to moderate pollution range.Jingwangbang River,Yanjiajiao River,Xupu River,Guangpu River,Shao Village Central River,Greenland Landscape River,Zhangming River,Laolunipu River,Changjing River and Central Park River belong to the mild to heavy pollution range.(2)Evaluation results of comprehensive water quality identification index for each river channel: Zhujing Central River belong to class ⅱ ～ ⅳ,Fotang River and Guangpu River belong to class ⅱ ～ ⅴ,Jiangpu River belongs to class ⅲ ～ ⅳ,Yanjiajiao River,Changjing River belong to class ⅲ ～ⅴ,Greenland Landscape River,Xupu River,Shao Village Central River and Central Park River belong to class ⅲ ～ inferior ⅴ,Jingwangbang River,Zhangming River and Laolunipu River belong to class ⅳ ～ inferior ⅴ.(3)Evaluation results of organic pollution comprehensive index for each river channel: Zhujing Central River,Yanjiajiao River,Fotang River and Guangpu River belong to the good to basically qualified range.Jiangpu River,Zhangming River,Laolunipu River,Changjing River and Central Park River belong to the range of good to mild pollution,Jingwangbang River,Xupu River and Shao Village Central River belong to the range of good to moderate pollution,Greenland Landscape River belongs to the range of good to heavy pollution.(4)Evaluation results of comprehensive nutrient state index for each river channel: Zhujing Central River,Guangpu River belong to the nutrition to moderate eutrophication interval,Yanjiajiao River,Xupu River,Jiangpu River and Changjing River belong to the mild rich nutrition to moderate eutrophication interval,Fotang River,Shao Village Central River,Zhangming River,Laolunipu River and Central Park River belong to the mild rich nutrition to severe eutrophication interval,Jingwangbang River and Greenland Landscape River belong to the moderate eutrophication to severe eutrophication interval.The results were obtained from the comprehensive index analysis of water quality in thirteen river channels,the water quality of Guangpu River and Zhujing Central River is good,but the water quality of Jingwangbang River,Yanjiajiao River,Xupu River,Jiangpu River,Fotang River,Shao Village Central River,Green Landscape River,Zhangming River,Laolunipu River,Changjing River and Central Park River is poor.Guangpu River and Zhujing Central River are independent water bodies with less passenger water exchange and less pollutants from the outer river.There are ecological floating islands in Hanoi,and the purification effect of aquatic plants is obvious.Guangpu River is equipped with aerator,which can accelerate the decomposition of pollutants in water by microorganisms.Zhujing Central River is connected with wetlands,and exogenous pollutants can be intercepted through wetlands.Jingwangbang River,Yanjiajiao River,Xupu River,Shao Village Central River,Greenland Landscape River,Changjing River and Central Park River are adjacent to residential areas.Domestic sewage contains a large amount of nitrogen and phosphorus pollutants,leading to poor water quality.There are aerators in Jingwangbang River,Yanjiajiao River and Xupu River,which can accelerate the decomposition of pollutants in water by microorganisms.Yanjiajiao River,Shao Village Central River,Green Landscape River and Jiangpu River are equipped with ecological floating beds,which can effectively absorb and transform pollutants in water.In the residential areas near Jiangpu River and Fotang River,the untreated domestic sewage directly discharged into the river contains a large number of nitrogen and phosphorus pollutants.There are vegetable fields or farmland around the river,and the surface runoff brings in fertilizers and other pollutants,but no aerator is installed.Zhangming River and Laolunipu River are adjacent to the factory,and there are a lot of pollutants in the tail water from the factory,without relevant treatment measures,making the water quality worse.In this paper,other evaluation methods of water quality at home and abroad are integrated for comparative analysis,such as fuzzy comprehensive evaluation method,gray correlation evaluation method,etc.Through comparative analysis,it is found that the water quality grade of comprehensive water quality identification index method is the highest,followed by comprehensive pollution index method,grey correlation evaluation method,and fuzzy comprehensive evaluation method is the lowest.In this study,sediment samples from 13 river channels in Kunshan city were collected and analyzed in October 2020 and July 2021.The organic pollution index of sediment in October 2020 ranged from 6.65 to 9.13,indicating heavy pollution.In October 2020,the comprehensive pollution index of the sediments ranged from 5.27 to 9.13,indicating heavy pollution.In July 2021,the organic pollution index of sediment ranged from 0.18 to 7.32,and the proportion of mild pollution was 7.69%,which was the Central Park River.Moderate pollution accounted for 30.77%,which were Zhujing Central River,Guangpu River,Greenland Landscape River and Zhangming River.The proportion of heavy pollution was 61.54% in Jingwangbang River,Yanjiajiao River,Xupu River,Jiangpu River,Fotang River,Shao Village Central River,Laolunipu River and Changjing River.In July 2021,the comprehensive pollution index of sediment ranged from 1.35 to 6.20,and the evaluation result was good.The light pollution accounted for 30.77%,which were Guangpu River,Greenland Landscape River,Zhangming River and Central Park River.Moderate pollution accounted for 15.38%,respectively,Zhujing Central River and Shao Village Central River;Severe pollution accounted for 53.85% of the total,including Jingwangbang River,Yanjiajiao River,Xupu River,Jiangpu River,Fotang River,Laolunipu River and Changjing River..Based on the sediment analysis of 13 river channels in Kunshan city in October 2020 and July 2021,it is concluded that the sediment of Guangpu River,Greenland Landscape River,Zhangming River and Central Park River were good.The sediment of Jingwangbang River,Zhujing Central River,Yanjiajiao River,Xupu River,Jiangpu River,Fotang River,Shao Village Central River,Laolunipu River and Changjing River were poor.The independent water body of Guangpu River is equipped with aerator and artificial leaf salvage.The vegetation filter belt on the river bank can effectively intercept the pollutants in the surface runoff,reduce the input of exogenous pollutants and make the bottom quality better.Green Landscape River is close to residential areas,equipped with aerators,ecological floating beds,and artificial fishing dead leaves,reducing the input of exogenous pollutants,and accelerate the decomposition of pollutants,making the bottom quality better;Zhangming River is an independent water body with less pollutant input from the outer river and better substrate quality.In the connected water body of the Central Park River,the pollutants can be transferred and diluted,the pollutant concentration decreases,and the substrate becomes better.Jingwangbang River,Zhujing Central River,Yanjiajiao River,Xupu River,Jiangpu River and Shao Village Central River are adjacent to residential areas,contain a large amount of pollutants from sewage,water pollutants concentration increases,enrichment in the sediment,make qualitative difference.Fotang River is close to residential areas,farmland and factories.Fertilizer,domestic sewage containing nitrogen and phosphorus and industrial wastewater with incomplete treatment brought by surface runoff increase the concentration of pollutants in the water,and finally concentrate in the bottom mud,making the water quality worse.Laolunipu River and Changjing River are adjacent to the industrial zone,and there are a lot of pollutants in the industrial tail water,which increase the concentration of pollutants in the water without relevant treatment measures,and finally enrich in the bottom mud,making the bottom quality worse.In order to improve the water environment of the river,this study puts forward suggestions from four aspects: water habitat,coastal habitat,coastal land use and water environment management quality improvement strategy.