城市雨水地下回灌过程中悬浮物表面堵塞规律

雨洪资源地下回灌是缓解城市供水压力、解决地下水过量开采引起环境负效应的有效途径之一,但堵塞问题却是制约回灌技术推广的关键问题。基于前人理论,研究了入渗介质与悬浮物粒径中值之比(D50/d50)对堵塞层空间分布的影响。以建立表面堵塞预测模型为目的,利用城市雨水回灌细粒石英砂介质开展室内实验,观测雨水回灌的表面堵塞过程并获取渗透性变化的观测数据。根据物理、化学与生物堵塞的产生条件及堵塞特点,判断雨水回灌产生的堵塞性质为物理堵塞。引入过滤模型描述堵塞的发展过程,确定了模型用于模拟细砂表面堵塞的参数值:孔隙堵塞系数(α)为0.15m2/kg,阻力增长系数(f′R′)为20 000m/kg。在不改变以上2个参数值的条件下,用该模型模拟不同悬浮物粒径悬浊水回灌细粒石英砂的堵塞过程,取得了较好的拟合效果。此过滤模型可以用于模拟入渗介质与悬浮物粒径D50/d50值小于5的表面堵塞的发展过程,可定量预测堵塞对回灌速率的影响。

Suspended Solid Surface Clogging During Urban Stormwater Groundwater Recharge

Stormwater resources for groundwater recharge is one of the effective techniques to deduce and control negative environmental effects of groundwater over-exploitation,but clogging problem of infiltration system is always the key restrict factor to broaden its practices.Based on the previous studies,the influence of D50/d50 ratio which indicated infiltration media size and suspended solid size on clogging layer distribution has been analyzed in the paper.As the aim to set up a predictive model to describe the surface clogging process,the urban stormwater had been adopted to recharge into fine quartz sand under a laboratory scale,and the observation data of hydraulic conductivity obtained by monitoring surface clogging process.According to the clogging generation conditions of the physical,chemical and biological,and the characteristics,it drew a conclusion that clogging property of this experiment belonged to physical clogging.Due to the clogging mechanism is as well as a membrane filtration,so cake filtration model was introduced to represent clogging development during the artificial recharge.The overall results manifested calculated data had a reasonably agreement with the observed outflow rate,and parameters α and f′R′ were determined as 0.15 m2/kg and 20 000 m/kg respectively.In order to verify the application of the model,different suspended solid sizes were simulated with model under the condition of parametersαand f′R′ kept constant,and the fitness were good.Hence,it is proved that the model could depict the real condition of surface clogging development when the ratio of infiltration media size to suspended solid size(D50/d50) less than 5,and it can be used to quantificational predict the clogging effect of recharge rate.