Study On Key Problems In Design Of Non-point Source Pollution Interception Control Scheme For Pingshan River Main Stream

With the significant improvement of the point source pollution control effect,non-point source pollution has gradually become the main source of pollution load of the Pingshan River.Therefore,to deepen the water quality of the main stream of Pingshan River,non-point source pollution control is the key.To this end,Pingshan has built a interception system for the combination of intercepting and regulating tanks to intercept the non-point source pollution load,installing SS online monitoring equipment at the rainwater discharge port,controlling the rainwater intercepting well gate according to the SS monitoring data,and adjusting to enter the storage tank.The water quantity and water quality are based on the principle of cut-off and lightness,and achieve accurate and efficient interception of non-point source pollution load.The determination of SS threshold is a key problem in the design of non-point source pollution interception control scheme for Pingshan River mainstream,and it is also an urgent need for the operation and management of Pingshan River non-point source pollution interception control project.Based on SWMM,the non-point source pollution model of the Pingshan River is established.The non-point source pollution load in the study area is analyzed by model simulation.Based on this,the typical hydrological and meteorological conditions are selected to explore various SS threshold determination methods in the study area.The study can provide technical support for the formulation of the control scheme of non-point source pollution interception in Pingshan River mainstream,and also provide reference for similar research ideas and methods.The main contents and achievements of this paper include:(1)Analyze the influence of several major factors causing non-point source pollution on the non-point source pollution load in the study area.Simulate the total pollution of total non-point source pollution,the average concentration of rainfall runoff and the process of pollution generation in the study area under different wet weather days,different rainfall intensity and different rain patterns.The simulation results show that the influence of different meteorological conditions on the non-point source pollution load from high to low is the rainfall intensity,the number of dry days before the rain,and the rain type.The large and strong rainfall runoff water quality is better than the small and weak rainfall runoff water quality,and the pollutant concentration is stable and the stable concentration is small.Therefore,the non-point source pollution caused by small and weak rainfall is the focus of non-point source pollution interception.(2)Study on SS threshold determination method of non-point source pollution interception control scheme in study area.The preferred simulation analysis determines the correlation between SS and other water quality indicators;secondly,calculates the interception effect corresponding to the SS threshold and threshold corresponding to the concentration and total control schemes of different water quality indicators,and evaluates the control scheme from the aspects of interception effect and operability;The method for determining the SS threshold when the water quality of the cross-section is met is proposed.The results show that when the same water quality target is used,the average emission concentration of the concentration control scheme is the smallest,but the intercepted water volume is large.With the change of the non-point source pollution load,the SS has more control values and the rate determination process is complicated;the total control scheme guarantees the average emission concentration.At the same time,the amount of intercepted water is the least,the SS control value is small,the modification rate is simple,and the operability is strong.The total control scheme for determining the SS threshold with total phosphorus is the most conservative and enforceable interception control scheme in the study area;the total control scheme for determining the SS threshold with ammonia nitrogen can ensure the average emission concentration of COD and ammonia nitrogen meets the standard,and can take into account the average phosphorus average.The emission concentration is 0.33-0.34 mg/L,and the intercepted water volume is 30% lower than the most conservative scheme.