表面活性剂增强修复地下水中PCE的砂箱实验及模拟

Experiment and numerical simulation of surfactant-enhanced aquifer remediation in PCE contaminated laboratory sandbox

在石英砂充填的二维砂箱中开展表面活性剂(Tween 80)冲洗四氯乙烯(PCE)的修复实验,基于图像分析技术监测不同污染源区结构条件下NAPL相的去除过程.由于实验条件限制,实验中缺乏溶解相浓度数据.为此进一步基于UTCHEM数值模拟方法来理解NAPL相和溶解态之间的质量传输过程,并探讨表面活性剂浓度、注入速率等因素对修复效率的影响.综合砂箱实验和数值模拟结果表明:介质均质和非均质条件下会形成不同类型DNAPL污染源区结构,表现为离散状PCE与池状PCE体积比(GTP)差异.由于离散状污染物与表面活性剂的接触面积更大,更易被优先去除;初始GTP值越高,污染物的修复速率和修复效率也越高.增大表面活性剂浓度或提高表面活性剂的注入速率,虽然能提高DNAPL的修复速率,但会明显降低表面活性剂的修复效率,实验过程中修复效率降幅可达93%.线性驱动溶解模型可以有效地模拟表面活性剂修复DNAPLs过程,基于数值模拟方法选择合适的表面活性剂配比可有效的节省实际污染场址修复经费和时间成本.

The experiment of remediating PCE with surfactant(Tween 80)was carried out in two-dimensional sandbox filled with quartz sand,and the removal processes of NAPL phase under different source zone architectures(SZA)were monitored via image analysis technology.Considering the lack of experimental data on dissolved phase NAPL concentration,numerical simulation using UTCHEM software was further performed to understand the mass transfer process between NAPL phase and aqueous phase,and the effects of surfactant concentration and injection rate on the DNAPL remediation efficiency were investigated.Results from Sandbox experiments and numerical simulations confirmed that:subsurface heterogeneity largely governs the DNAPL SZA,resulting discrepancies in ganglia-to-pool(GTP)ratio.Due to the larger contact area of discrete ganglia with surfactant,DNAPL ganglia is preferentially removed.The higher the initial GTP ratio,the higher the remediation rate and the remediate efficiency of DNAPL;Though the DNAPL remediation rate could be increased by increasing the surfactant concentration or the injection rate,the surfactant remediate efficiency was reduced significantly by 93%over the course of the test.The linear driving force dissolution model can effectively simulate the process of surfactant remediation for DNAPL.Numerical simulation is an important quantitative tool for the assessment of SEAR in the field DNAPL-contaminated sites.