Quantitative assessment of the impact factors upon remediation performance of the PRB technique in conjunction with pumping/recharge

Abstract

Installation of pumping/recharge wells adjacent to contaminant plume and permeable reactive barrier (PRB) can effectively improve PRB's performance by artificially altering groundwater flow field attracting more contaminants to pass through PRB within a shorten time. However, the impact factors affecting the performance of PRB in conjunction with pumping/recharge (abbreviated as PRB-PR technique) have not been quantitatively assessed. In this study, numerical approach was adopted and multiple scenarios were implemented based on the developed MODFLOW and MT3MDS models to quantitatively evaluate the influences of impact factors on PRB-PR's remediation performance over a hypothetical contaminated site. Simulation results indicated that: (1) PRB should be installed nearby the downstream boundary of contaminant plume; (2) PRB's contaminant removal efficiency (η), pumping/recharge rate (Q), and aquifer hydraulic conductivity (K) affect PRB-PR's performance significantly, and a linear relationship exists between contaminant removal rate (R) and the product of K and Q no matter η changes (a series of fitting equations representing the linear relationship between R and KQ under various η were yielded based on data fitting); and (3) PRB's hydraulic conductivity, pumping/recharge wells' locations, and pumping/recharge wells' quantity do not affect PRB-PR's performance seriously. The equations indicating PRB-PR's remediation performance and key impact factors can be utilized to calculate the minimum values of Q and η that can meet the requirements of remediation objectives of real contaminated sites, contributing to supervising the installation and operation of the PRB-PR technique accordingly.