A Study On Integrated Modeling Based Planning For Urban Water Pollution Control

With the rapid development of urbanization and global climate change,there are many cities in China facing the issue of urban water pollution and regional water problem.While point-source pollution is to some extent controlled successfully in these years,non-point source pollution is turning into a main or major part in urban water pollution.The occurrence of urban non-point source water pollution is highly associated with rainfall events and drainage system,showing the features of high dynamic and uncertainty.To deal with this situation,a method of urban water pollution control planning with integrated modeling of drainage system is established in this study.The northern drainage part of Kunming is selected for the case study to test the feasibility of this method.The framework of integrated-modeling-based planning for urban water pollution control is presented in the study.The method focuses on the control of urban non-point source pollution,as well as paying attention to point source control and other measures.In order to meet the need of urban water pollution control planning,the function of urban drainage modeling is enhanced in this study by the linking of sewer system,wastewater treatment plant?WWTP?and urban rivers,the preparation of distributed rainfall input,and the flexibility in water quality process routing.For rainfall input data,which is one of the key inputs in urban drainage modeling,an approach to preparing distributed rainfall input is presented.The results from the case study show that rainfall data generated from radar reflectivity is applicable for the decrease of rainfall uncertainty.A relative deviation of 30%⁴0%is reached with this approach,dropping from 50%⁸0%.For the water quality process in urban drainage modeling,an extended water quality routing module is developed basing on SWMM to meet the need of integrated drainage modeling.This module enables the routing of biochemistry and physical process?settling and wash-off,e.g.?in sewer and rivers.The drainage model of the study area is calibrated and validated via using field data of water quality.The relative deviations of average pollutant concentrations are below 15%,indicating that the model is suitable for further simulation.The water volumes and pollutant loads of point and non-point source water pollution are estimated for the study area.The results show that non-point pollution only takes up 11%of the total water volumes,but accounts for 40%,45%and 62%for COD,TP,and NH₃-N loads respectively?in 2014?.Selecting the average water quality in 2020of the effluent of Panlongjiang River as the control objective,the effect and cost of schemes with the measures of non-point source control,wetland construction and introduced water are estimated.To reach an average TN concentration of 4.0 mg/L for example,the lowest cost is estimated to be 5.0 billion yuan.To reach a COD concentration of 12 mg/L,the lowest cost is 3.1 billion yuan.Considering the control effect and cost,wetland construction,stormwater treatment and permeable pavement are measures recommended to be taken firstly,followed by green roofs measures,and stormwater tanks as the last to be recommended.Introduced water is only recommended for the control of TN concentration.