数值模拟减压集流式可渗透反应墙技术修复地下水

使用可渗透反应墙（PRB）技术修复受污染地下水，当地下水污染羽宽度和深度过大时，PRB的开挖、填料与安装成本较高.为打破PRB技术这一局限性，开发了减压集流式可渗透反应墙技术，通过集流井、输水管道和布水廊道的共同作用缩小污染羽范围并将受污染地下水输送至PRB，通过非完整井减压吸水方式捕获较深的受污染地下水.首先采用地下水井流公式计算减压集流井的关键初始参数，随后进行数值模拟优化参数并确定其它重要参数.在MODFLOW中通过改变减压集流井的井径、井数量、井间距及井与PRB的距离等参数，探究不同参数变化对减压集流效果的影响规律.模拟结果表明在合理的减压集流参数设置下，该设施可有效调控PRB上游的地下水流场，缩小污染羽的范围，在设定条件下受污染地下水断面减小了约50%.该技术显著降低了PRB的规模，拓宽了PRB的应用范围，使其可以处理污染羽范围较大、污染深度大的地下水.

Numerical simulation for remediation of polluted ground water by a novel convergent flow permeable reactive barrier

Conventional permeable reactive barrier (PRB) for ground water remediation might be inapplicable for a wide pollution plume because constructing a large PRB underground might be too expensive, as the costs of excavation, remediation material and installation increase greatly with the scale. This investigation proposed a novel approach of convergent flow permeable reactive barrier (CF-PRB). In CF-PRB, some decompression wells were installed at the upstream of PRB to converge the groundwater flow to wells. As a result, the plume was converged to a relatively small scale. Partially penetrating decompression wells installed could also extract the deeply-bearing polluted water, making the PRB available to remediate deeper pollution. The convergent polluted ground water was conveyed to the PRB through water pipelines and distributed at the buffer slot in front of the PRB. The slot was distributed evenly the polluted water along the PRB so that the water could flow through the PRB homogeneously. CF-PRB could make the PRB design be determined primarily by flow rate and average pollutant concentrations, independent to the plume scale. Analytical solutions of well flow were used to calibrate the initial parameters in CF-PRB, and then MODFLOW numerical simulation was adopted for optimization. In MODFLOW simulation, parameters such as well radius, number of wells, spacings between wells and the distances from wells to PRB were tested to analyze their impacts on CF-PRB. Results showed that CF-PRB approach could make the upstream groundwater flow convergently to the decompression wells, resulting in the reduction of reactive barrier length by 50%. CF-PRB approach can significantly reduce the PRB scales and can therefore be used to remediate the polluted groundwater with a large plume width and depth.