| At the present stage,the application of model software to simulate runoff pollution has become an important means to grasp the laws of pollutant transport in rainwater runoff.SWMM as a commonly used model software,one of the key elements of modeling and simulating surface runoff pollution is to determine the applicable water quality model and parameters,including pollutant accumulation and scour models and corresponding parameters.However,the water quality model parameters have strong regional characteristics,and the parameter values of different areas are quite different,so it is necessary to determine them before modeling.Taking different types of roads on campus(residential branch roads,residential main roads,square trails)as the research objects.Firstly,measure the change of street dust quality in different dry weather days,the content of various pollutants(SS,COD,TP,TN)in street dust(mg/g),and the change of pollutant concentration with runoff process,then determine the suitable model and parameters of pollutant accumulation and scour.Secondly,based on pollutant accumulation and scour model parameters,simulate long-term rainfall runoff pollution through SWMM.On the one hand,the rainfall is classified according to the degree of rainfall runoff pollution,and the rainfall with large runoff pollution(important rainfall)was found;On the other hand,the initial rainfall is classified according to the efficiency of pollutant interception,and the suggested value of initial rainfall interception is given.The main results of the thesis include the following aspects:(1)Applicable water quality model and parameter determinationThe research proposes methods to determine the applicable models and parameters of pollutant accumulation and scour,and apply them to different types of roads on campus.The results show that the accumulation and scour models of different types of road pollutants conform to the index accumulation model function,index scour model function;the determined index accumulation and index scour model parameters of various pollutants have good applicability after testing.(2)The content of various pollutants in street dust and collection methodsThe content of COD and TN in street dust in different types of roads are in the order of square trails> residential main roads > residential branches roads,while the content of SS and TP in street dust in different types of roads are relatively close.The mass proportion of COD and SS collected by the "dry method" varies within a small range(50%～60%).Street dust can be collected by the "dry method",and the COD and SS content in the street dust can be estimated according to the proportion;while the mass proportion of TP and TN collected by "dry method" was not fixed.When measuring the content of TP and TN in street dust,it is still necessary to collect street dust by combining "dry method" and "wet method".(3)Classification of rainfall importance and initial rainfall interceptionA rainfall importance classification method was proposed and applied to different types of roads on campus.According to the rainfall characteristic parameters(drought time and rainfall),the fuzzy C-means clustering method was used to divide rainfall into three categories: important rainfall,general rainfall and unimportant rainfall.The results show that:by drawing rainfall distribution maps with different importance,various rainfall distribution areas were relatively divided and a classification standard was established.However,rainfalls in fuzzy areas needed to be distinguished by combining other factors.Propose the classification method of initial rainfall,fuzzy clustering is used to divide the initial rainfall into three categories: high efficiency,medium efficiency,and low efficiency.Its distribution range is 1mm～2.5mm(high efficiency),2.5mm～5mm(medium efficiency),5mm～10mm(low efficiency)in different types of roads.According to the pollutant interception target and interception efficiency,the initial rainfall interception recommended value is given. |
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