雨水花园对屋面雨水的滞蓄与净化效果

2017年对西咸新区某小区内设置有淹没区并添加给水厂污泥(WTR)的新建雨水花园进行连续监测,结果显示,雨水花园有很好的径流量滞留能力,对中小雨(日降雨量<25 mm)的径流量削减率基本可达到60%以上;填料淋洗对径流污染物去除效果有不同程度的影响,其中总氮和硝态氮去除率所受影响最大。8月20日以后雨水花园运行基本趋于稳定,径流污染物去除率均有一定上升,SS、COD、总氮、氨氮、硝态氮和总磷的去除率分别为23%~40%、14.69%~80%、20%~45%、15%~55%、-10%~45%、20%~55%。从径流污染物负荷削减率来看,雨水花园对COD、氨氮、SS和总磷负荷均有良好的削减效果,基本可达到68%以上,受填料淋洗影响,雨水花园对总氮和硝态氮负荷的削减率为负值。

A STUDY OF DRAG COEFFICIENT RELATED WITH VEGETATION BASED ON THE FLUME EXPERIMENT

This study is focused on the effects of ecological factors （diameter and flexibility） and vegetation community composition on the drag coefficient related with vegetation. The single leafy shrub and three mixed communities （including shrub-grass, shrub-reed and reed-grass community） were studied. The flow velocity and water level were measured and used to calculate the drag coefficient based on the Bernoulli＇s equation, Darcy drag formula and the expression for the drag coefficient related with Darcy drag factor. The trend of the drag coefficient in the vertical direction was analyzed against flow depth, diameter, diameter P（eynolds number, flow depth Reynolds number and relative roughness height in different discharges. The results show that beside the dense leafy shrubs community, the vertical trend of the drag coefficient among other cases against flow depth, diameter, diameter Reynolds number, flow depth Reynolds number and relative roughness height can be approximately expressed by power law functions under different flow discharges. Moreover, in a mixed community with two plants with distinctly different ecological factors, the one with the most distinct variations of ecological factors determines the vertical trend of the drag coefficient; the other one only affects the magnitude of the drag coefficient. Furthermore, if the ecological factors of the vegetation in the vertical direction are kept almost not changed, the drag coefficient can be approximately regarded as a constant.