| The northern rivers bear the functions of flood control,drainage,and pollution in the basin.The destruction of the water environment has seriously affected the production and life of the people in the basin.At present,most of the engineering schemes are used to river pollution,and the theory of river management is still insufficient.Through the investigation of the current situation of Yanhe River in Yan'an City,the paper analyzes the status of river pollution by using three water quality assessment methods,and uses MIKE software to simulate river water quality and determine the amount of pollutant reduction.Finally,combined with the status quo of pollution and the amount of reduction,a water quality improvement plan is proposed for the northern water-deficient rivers with Yanhe as an example.The conclusions of the study are as follows:(1)Based on the Yanhe water quality monitoring section,this paper divides Yan'an Yanhe River into three units,named separately Wangyao Reservoir Control Unit,Zhujiagou Control Unit and Yanjiatan Control Unit.Due to the siltation of the river's loess,the river contains a lot of sediment;The Yanhe River has small runoff;the water quality of some sections is seriously exceeding the Class III water quality standard;the main stream pollution mainly comes from domestic sewage,industrial wastewater and agricultural non-point sources.(2)The comprehensive evaluation of the water quality of Yanhe River was carried out by single factor index evaluation method,comprehensive index evaluation method and over-standard multiple evaluation method.The water quality of the monitoring section of Wangyao Reservoir reached the standard,but the remaining monitoring sections had different degrees of pollution.Among them,the pollution between the monitoring section of Zhujiagou and the monitoring section of Ganguyi is the most serious.River pollution indicators include chemical oxygen demand,ammonia nitrogen and total phosphorus,and biochemical oxygen demand.(3)The MIKE software is used to establish the water quality model of the Yan'an Hydro-logical Station to the Ganguyi Hydro-logical Station.The water quality changes are simulated by changing the river pollutants into the river,and the reduction of pollutants is determined.When the emission of ammonia nitrogen,total phosphorus and chemical oxygen demand is reduced by 26.909t/a,3.285t/a,and 303.627 t/a,the water quality of each monitoring section in the river section can be guaranteed to reach the standard water quality;When the pollutants in the section are intercepted and discharged to the sewage treatment plant,the water quality of the river is obviously improved.Therefore,the treatment policy for improving the water discharge standard and the pollution control source of the sewage treatment plant is determined.(4)Taking the amount of reduction as the theoretical guidance,combined with the current situation of water pollution in different control units of Yanhe,the corresponding treatment plan is proposed.As soon as possible,the water quality of the sewage plant will be implemented to meet the requirements of Class IV of the surface level.The government upgraded the level of ecological environment restoration in the control unit of Wangyao Reservoir,reconstructed the drainage network system in the control unit of Zhujiagou,and unifiedly managed the standardized production of rural agriculture in the control unit of Yanjiatan,etc.According to the type of project,there are seven categories including urban pipe network construction,water environment improvement and other projects.From the management's point of view: it is necessary to refine the river long system responsibility and river water quality management system,strengthen the public's awareness of environmental protection,and prevent the smuggling of emissions and excessive discharge.Only by improving the water quality of polluted rivers from the source,and comprehensively improving the water environment quality of the water-deficient river basins in the north. |
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