浅基质层干植草沟运行效果的现场实验

为避免设施出水下渗污染地下水并防止市政管道雨污倒灌进入设施,于上海市区高架路下方建造一座排水管上弯的不透型浅层干植草沟.根据2019年汛期内进、出水量及水质的长期监测,对设施水文及水质控制效果进行评价.结果表明监测期内设施径流总量控制率为39.4%,对初始雨强小于8.0 mm·h~(-1)的降雨具有明显峰值削减效果;设施能有效去除道路径流中总悬浮固体(TSS)、化学需氧量(COD)、总磷(TP)和总氮(TN),污染物负荷去除率分别为95.4%、 83.1%、 90.0%和57.7%;设施基质层添加的发酵木屑和排水管上弯的构造可在进水期实现反硝化并在前期无雨期(ADP)维持一定反硝化效果,设施水力负荷(HLR)的增大及无雨期的延长分别影响进水期与无雨期硝酸盐氮(NO~-_3-N)的去除.在基质层饱和渗透速率较高、厚度较浅条件下,设施有效改善了道路径流水质.不透型干植草沟可与市区河道的调蓄容积结合,共同承担起高地下水位地区实现年径流总量与污染负荷控制率的任务.

Performance Assessment of Field-scale Dry Grass Swale with Shallow Substrate Layer

A field-scale dry grass swale with impermeable bottom and shallow substrate layer was built in Shanghai, where the groundwater table is very high, to avoid groundwater pollution caused by runoff infiltration. The underdrain pipe of the facility was up bended to avoid outside water flowing backward because local ground elevation is very low. Performance of the facility under the actual precipitation conditions was evaluated in the rainy season of 2019. The average runoff volume reduction is 39.4%, and the peak flow is reduced effectively when rain intensity is lower than 8.0 mm ·h^-1. Influent mass load reduction of TSS, COD, TP, and TN are 95.4%, 83.1%, 90.0%, and 57.7%, respectively. Wood chips in the substrate layer and the saturated zone are effective for denitrification during the wet and dry periods, respectively. Hydraulic loading rate and antecedent drying period are the main factors affecting denitrification. Improved influent quality combined with the storage volume supplied by the local urban river network could meet the goal of annual runoff volume reduction and annual pollution load removal in districts with high groundwater levels.