Study On Environmental Characteristics And Water Purification Technology Of Drawdown Area In River Flow Into Reservoir

As an important source of concentrated water supply,the safety of reservoir water quality is very important to human production and life.The drawdown area of river flow to Reservoir is an important part of the reservoir,the ecological environment,connected with the drawdown area and the reservoir of information exchange,is the last barrier of pollutants into the reservoir,if not to control and protect,most of the pollutants will be untreated with surface runoff directly into the reservoir,impacted the health of water quality,posed a threat to water quality.In this paper,the environmental characteristics of the drawdown area of reservoir and the main existing ecological and environmental problems are analyzed.In view of its environmental problems,the water quality management needs are analyzed and the water purification technology scheme is proposed.Taking the drawdown area of Jiantang River as a typical research object,the regional characteristics and pollution status were analyzed,and the water purification technology was applied to the drawdown area of Jiantang River,and the safety and effectiveness of the purification project was analyzed.The main research results are as follows:(1)Analysis of environmental characteristics of the drawdown area of inflow to reservoir.The drawdown area of inflow to reservoir has the basic characteristics of openness,dynamic balance and transition,and is a dynamic and buffering system.There are many ecological and environmental problems,such as serious soil erosion,large amount of water pollution sources and decrease of biodiversity.According to the on-the-spot investigation of the drawdown area of Jiantang River.There are problems such as concentrated flow overflow in the sinking area of the Jiantang River,serious erosion in the main channel,sparse vegetation growth,and poor water vapor conditions.The pollution in the reservoir mainly comes from domestic pollution,hot spring wastewater pollution,Agricultural non-point source pollution and livestock and poultry farming pollution,of which livestock and poultry farming emissions accounted for the largest proportion,total pollutant emissions:TN is about 28.34 t/a,TP is about 9.3 t/a,COD is about 119.2 t/a.Water quality monitoring results show that water quality of the drawdown area of Jiantang River is poorer,TN and TP is higher than the standard inferior class?.(2)Research on water purification technology of the drawdown area of inflow to reservoir.Combined with the main ecological and environmental problems existing in the drawdown area of inflow to reservoir,the water quality control requirements for restricting riverbed erosion at the storage site,reducing interception and storage of pollutants,curbing illegal land reclamation in the drawdown area and improving the ecological conditions of the drawdown area are proposed.Four technical schemes for water quality control in the drawdown area are put forward.Through comparative analysis,it is considered that the multi-level ecological submerged dam technical scheme is more suitable for the treatment needs of the drawdown area.The treatment plan was applied to the drawdown area of the Jiantang River,and a five-level ecological submerged dam was set up.After the completion of the submerged dam project,a surface wetland of 150,000 m~2 could be formed,and the hydraulic retention time reached 5.6days.(3)This paper analyzes the safety and effectiveness of the multi-level ecological submerged dam technical scheme in the drawdown area of Jiantang River.The flood peak flow and flood process line of different frequency floods of Jiantang River were calculated by hydrological analysis.The flood process of Jiantang River had the characteristics of large main peak flow and steep rise and fall.MIKE 21 hydrodynamic model was established to simulate the water level and flow velocity before and after the construction of the submerged dam.The analysis results shows that:the construction of the submerged dam project resulted in the change of water flow pattern,and the water level in front of the dam was obviously high,which expanded the influence range of water flow and made the water flow diffuse to the surrounding beach.Before and after the project,the overall flow pattern of the water flow is similar,which is relatively smooth.The flow velocity of the main channel is relatively large,the beach flow velocity is relatively small,and the flow velocity of the main channel is relatively weak after the construction of the dam.Through the establishment of the first-order dynamic model,the average removal rate of TN,TP and COD in wetlands formed after the construction of submerged dam was 63.33%,68.75%and 63.22%.