The Study On The Construction Of Ecological Rainwater System In Lanzhou New Area The First Waste Water Treatment Factory

With the accelerating process of urbanization,the hardening of buildings and roads causes more surface runoff when raining,which can cause waterlogging in the city.On the other hand,urban surface pollutants,through the erosion of rainfall runoff,Into the natural water,easily lead to non-point source pollution.Ecological rainwater is a new type of rainwater system proposed in recent years.It refers to the process of infiltration,storage and regulation,so that the rainwater has a process of infiltration,stagnation,storage,net,use and row.Compared with the traditional pipe network system,the ecological rainwater system can reduce the total runoff and runoff peak in the process of rainfall,and also have good removal effect on runoff and rainwater pollutants,and can hold the groundwater.In this paper,combined with the actual situation of Lanzhou New Area,the first sewage treatment plant was selected as the research object,and the feasibility of applying the ecological rainwater system in Lanzhou New Area was analyzed..SWMM is a storm runoff management model that allows dynamic simulation of runoff and water quality for single rain or continuous rainfall.The rainfall data of Lanzhou New Area were collected and analyzed,and the rainfall law of the area was studied as the rainfall model of SWMM.The sewage pipe network system of a sewage plant will be simplified,and the plant area will be divided into different sub-catchment area according to the field runoff,which will be used as the convergence model of SWMM.The parameters such as soil permeability coefficient and other impervious surface depression are measured in accordance with the relevant literature,and SWMM is used to provide the surface underlay model of runoff process.At present,the rainwater drainage network system of the first sewage treatment plant in Lanzhou New District has been planned and simulated by SWMM software to simulate the runoff of traditional rainwater pipe network system.The natural rainwater and surface runoff water quality of the plant were measured in situ,and the concentration of rainwater pollutants in the area was analyzed and studied.In order to carry out the research on ecological rainwater system planning,a small experiment was carried out on the rainwater garden,planting grass ditch,concave green land and other ecological rainwater system,and the effect of rainwater water and water quality was studied.On this basis,the ecological rainwater system planning for the plant,runoff rain into the nearby concave green space,more than the depth of the depth of the rain overflow to the grass ditch,plant ing grass ditch will rain transferred to the rain garden,rain garden Super rain overflow to municipal pipe network.The SWMM model was used to simulate the rainwater runoff after the construction of the ecological rainwater system.The feasibility of the application of the ecological rainwater system in the first sewage treatment plant of Lanzhou New District was studied by comparing the water quality and water quality of the traditional rainwater pipe network system and the ecological rainwater system.We can get the following conclusions:(1)The rainfall data of Lanzhou New District show that the average annual precipitation of Lanzhou New District is 322.8mm,and the distribution of rainfall time is mainly from May to October,accounting for 89.53% of the annual rainfall and less rainfall in other months.(2)The simulation results of SWMM simulation show that there is a full flow condition in the pipeline in the case of a 2-hour rainfall.10 years to resume the beginning of the plant a number of rain wells overflow.The actual rainfall process simulation shows that the greater the rainfall intensity,the larger the runoff peak,the greater the runoff flow.The results show that the natural rainfall of the first sewage treatment plant in Lanzhou New District generally meets the standard of surface water Ⅴ,and the runoff rainwater quality is poor.(3)rain water garden small test results show that after the construction of rain garden,runoff rain water quality has been a marked increase in rainwater garden can resist the flood once a year.The results showed that the removal rate of turbidity,COD,ammonia nitrogen and total phosphorus was good,and the removal rate of pollutants was also increased with the increase of planting furrow length.Planting ditch can effectively reduce the total amount of runoff rainwater and have the effect of delaying the arrival time of runoff.The results show that the concave green space has a good removal effect on the runoff rainwater,and the removal rate of COD,ammonia nitrogen and total phosphorus is higher.1 year,2 years to reproduce the situation,the concave green space can control all the runoff rainwater,3 years to reproduce the situation,the concave green land in the rainwater runoff later there will be a small amount of rain overflow.And the effect of actual rainwater regulation and SWMM model is higher.(4)Simulation study of SWMM model shows that there is no surface runoff rainwater in the 1-year recurrence period,and there will be effluent runoff from the 3-year recurrence period.The ecological rainwater system has the effect of reducing the total amount of runoff rainwater,delaying the peak arrival time and reducing the peak flow rate of runoff.The actual rainfall process SWMM model simulation analysis shows that throughout the year 2016,the plant does not produce any surface runoff rainwater,rainwater all infiltration,conservation of groundwater.(5)Through the economic and technical analysis of different rainwater systems,it can be seen that the ecological rainwater system is superior to the traditional pipe network system in terms of water quality and water quality.The cost of the traditional pipe network system is about 1.153 million yuan,the cost of the ecological rainwater system is about 483,000 yuan,and the ecological rainwater system is superior to the traditional pipe network system in terms of construction cost.(6)The application of ecological rainwater technology to a sewage plant in Lanzhou New District not only can reduce floods,reduce the rainwater treatment load of sewage plant,make full use of rainwater resources,but also provide landscape effect and improve plant greening rate.The research of this subject will provide support for the construction of ecological rainwater system in a sewage plant in Lanzhou New Area,and provide assistance for the utilization of rainwater resources in Lanzhou New District,and even provide reference for the construction of ecological rainwater system in new towns in northwest China.