污水管道沉积物分层冲刷的起动规律及其污染贡献特性

Starting law and pollution contribution characteristics of stratified sediment scouring in sewage pipes

为探明管道沉积物的断面污染物分布特征,揭示梯度冲刷强度下沉积物的分层冲刷起动规律及其污染贡献特性,通过建立一套污水管道沉积物冲刷模拟装置,基于管道沉积物分层分布理论,揭示了沉积物不同断面颗粒粒径以及碳、氮、磷等污染物的含量变化规律.此外,根据无黏性沉积物初始运动的临界剪应力公式进行计算,结果表明,随粒径的增大,不同分层颗粒下理论临界剪切应力从0.038N/m^(2)增加0.261N/m^(2);随设计水流剪切力从0.1N/m^(2)增加到0.3N/m^(2)时,沉积物对污水的TCOD贡献率从6.4%增加到46.3%,TN贡献率从25.3%增加到40.6%,而TP从42.9%降低到25.1%,且在各类污染物的附着含量对比下,随水流强度增大,冲刷起动的悬浮物为有机类污染物的占比最高.据此可知,粒径大小对污染物的污染负荷分布具有较大影响,且污染负荷分布对水流冲刷的溢流污染物浓度变化具有相关性.因此,明确管道沉积物分层冲刷水流强度及溢流污染物浓度变化有助于有效控制水体污染情况.

To explore the distribution characteristics of pollutants in the vertical section of sewer sediment,the mechanism of layered erosion initiation and pollution contribution characteristics of sediment under gradient erosion intensity were revealed.It could be an important foundation for scientific control of combined overflow pollutants(CSO).In this study,a pilot sewer system which could simulate the sediment erosion process was established.And based on the theory of layered distribution of sewer sediment,the characteristics of particle size,carbon and nitrogen pollutants were revealed.The results show that the theoretical critical shear stress under different layered particles increases from 0.038N/m^(2)to 0.261N/m^(2)with the increase of particle size.As the flow shear force increased from 0.1N/m^(2)to 0.3N/m^(2),the contribution rate of sediment of TCOD increased from 6.4%to 46.3%;the contribution rate of TN increased from 25.3%to 40.6%;and TP decreased from 42.9%to 25.1%.Moreover,in comparison with the attachment content of various pollutants,as the flow intensity increased,the proportion of suspended solids that start flushing was the highest among organic pollutants.It can be concluded that,the particle size has a significant impact on the distribution of pollution load of pollutants,and the distribution of pollution load has a correlation with the concentration changes of overflow pollutants caused by water flow erosion.Thus,clarifying the flow intensity and concentration changes of overflow pollutants caused by layered sediment erosion in pipelines can help effectively control water pollution.