长江流域平原河网地区合流制排水系统溢流污染特征研究

Study on overflow pollution characteristics of combined drainage system in plain river network area of Yangtze River basin

在平原河网地区丹金溧漕河金坛段选取3个典型合流制溢流排口及管道检查井进行溢流污染监测,分析溢流水质水量变化。以合流制管道沉积物为试验材料进行冲刷模拟试验,探究沉积物冲刷规律。结果表明,累积降雨量≥2 mm就会产生溢流现象;溢流水量变化主要受降雨等级、降雨强度及居民用水量影响,且溢流量峰值较降雨强度峰值滞后;溢流污染物浓度与前期干旱天数、排口性质、降雨等级和降雨强度有直接联系,其变化基本均呈先上升后下降趋势,且无论哪种降雨等级溢流口在产生径流后约20~30 min后污染物浓度会较高。沉积物对溢流污染贡献占比较大,管道冲刷过程中沉积颗粒物呈阶段交替式运动,各污染指标在降雨形成径流一段时间后出现峰值。

In the plain area of the Danjinlicao River Jintan sections were selected to monitor the overflow pollution at three typical combined flow overflow outlets and the pipeline inspection wells.The characteristics of water quality and water quantity changes in the network overflow of the Danjinlicao River Jintan section were analyzed.Simulate flushing tests using sediment in a converging pipe as the experimental material to explore the sediment erosion rule.The results showed that the overflow occurred when the accumulated rainfall exceeded 2 mm;The variation in overflow water volume was mainly influenced by rainfall level,rainfall intensity and residential water consumption,and the peak overflow volume lagged behind the peak rainfall intensity.The concentration of overflow pollution was directly related to the number of preceding dry days,the nature of the outlets,rainfall level and rainfall intensity.Overall,the concentration exhibited an initial increase followed by a decrease trend,and regardless of the type of rainfall,the overflow outlets would experience higher levels of pollution approximately 20-30 minutes after the runoff began.Sediments contribute significantly to overflow pollution.During the flushing process,sediment particles exhibit alternating stages of motion.The peak value of each pollution index appeared after a period of time when the rainfall formed runoff.