长江流域丘陵城镇初期雨水污染特征与截流调蓄研究

THE CHARACTERISTICS OF INITIAL RAINWATER POLLUTION AND INTERCEPTION AND STORAGE IN HILLY TOWNS IN THE YANGTZE RIVER BASIN

为探究长江流域丘陵城镇初期雨水污染特征及初雨调蓄池的截流效果,以重庆市永川区部分分流制汇水区为研究对象,对雨水排口污染物COD、SS、TN、TP、NH_(3)-N浓度进行了监测,分析了各污染物随降雨历时的变化、降雨特征对污染物浓度的影响,并通过无量纲累积曲线和b参数法判断降雨对该区域的初期冲刷效应,采用SWMM管网模型模拟了不同重现期下研究区域系统排口负荷及截流调蓄效果。结果表明:研究区域雨水排口各污染物在不同降雨情况下均存在初期冲刷效应;降雨过程中大部分污染物浓度在降雨过程中呈下降趋势,且在降雨后期波动较小;各降雨特征因子与雨水排口各污染物平均浓度存在相关性;对于初期雨水调蓄池,当截流比例<30%时,污染物削减率增长率较大,当截流比例>30%时,污染物削减率增长率减缓;当截流比例相同且重现期增大时,SS和COD削减率增幅较大,TN、TP和NH_(3)-N削减率增幅较小;模拟重现期为0.5年和1年2种条件下调蓄池截流调蓄控制,截流20%的雨水径流体积时,最高可控制54.71%的污染负荷。

In order to explore the characteristics of initial rainwater pollution in hilly towns in the Yangtze River Basin and the interception effect of initial rainwater storage tanks,this paper took a part of the diversion system catchment area in Yongchuan District,Chongqing City as the research object,and the concentrations of COD,SS,TN,TP and NH_(3)-N were monitored at the stormwater outfalls.The changes of each pollutant with the time of rainfall and the effect of rainfall characteristics were analyzed.Meanwhile,the first flush effect of rainfall on the catchment area was judged by using the dimensionless cumulative curves and the b-parameter method.The SWMM pipe network model was used to simulate the stormwater outfall loads and interception and storage effects in the catchment area under different recurrence periods.The results showed that each pollutant in the drainage area showed the initial flush effect under different rainfall conditions,and the intensity was weak in general.The concentrations of most pollutants showed an overall decreasing trend during the rainfall and fluctuated little in the late rainfall period.There was a certain correlation between each rainfall characteristic factor and the average concentration of each pollutant in the rainwater outfall.For the initial rainwater storage pond,when the interception ratio was less than 30%,the growth rate of the pollutant reduction rate was large,and when the interception ratio was greater than 30%,the growth rate of the pollutant reduction rate slowed down.When the recurrence period increased,the reduction rates of SS and COD increased more,while the reduction rates of TN,TP and NH_(3)-N increased less.Under the simulation of the recurrence period of 0.5 a and 1 a,when 20%of the rainwater runoff volume was intercepted the maximum pollution load could be controlled by 54.71%.