基于数值模拟和响应面法的PRB设计影响研究

影响PRB设计的因素很多,利用COMSOL Multiphysics软件建立地下水连续PRB的流体流动和溶质运移的数值模型,采用响应面方法研究了PRB与含水层渗透系数的比log K、PRB的位置D及PRB的墙体厚度W对水力停留时间和捕获区域宽度的影响。多元回归分析得到水力停留时间的二次方程模型,方差分析结果显示PK的增加而变小,超过某一值时,并不变化。污染源与PRB距离越近,所需捕获区域宽度越小,墙体的厚度越大;距离越远,所需捕获区域宽度越大,污染范围越广,不利于污染物的治理与控制。设计PRB应用时,需平衡各因素之间的关系,兼顾效率与效益,同时注意安全因子的量化。

Effects of PRB design based on numerical simulation and response surface methodology

A numerical model, which had a continuous PRB containing the fluid flow and solute transport, was built using COMSOL Multiphysics, considering many factors. The effects of the variables, including the ratio of hydraulic conductivity about PRB and aquifer (log K), and the location (D) and the barrier thickness (W) of the PRB, on the hydraulic-residence time and the capture-zone width were studied using the response-surface methodology. The quadratic equation model was obtained from a multivariate regression analysis. ANOVA suggested that the selected model was appropriate with a high-fitting degree and significant difference (P<0.0001). The results showed that the barrier thickness was the most important factor. To some extent, the capture width decreased with increasing log K, while it remained unchanged beyond a definite value. A shorter distance of PRB and pollutant sources, shorter capture-zone width, and more thickness were gained. The farthest distance and greatest width were needed so that the pollution region would expand, which went against pollutant management and control. We had to balance the relations among the factors, considering both efficiency and benefit, to quantize the safety factor when designing and applying the PRB technology