Numerical modelling and performance evaluation of multi-permeable reactive barrier system for aquifer remediation susceptible to chloride contamination

Abstract

Many in-situ groundwater remediation technologies have been developed, among which the permeable reactive barrier (PRB) technology has emerged as an efficient, cost-effective and sustainable remediation technique for the variety of contaminants. In this paper, a numerical model is developed, using Visual MODFLOW, to evaluate the performance of a multi-PRB system over the temporal and spatial groundwater quality variations. Model is simulated for a single contaminant, i.e., Chloride (Cl−), released from multiple point sources, over a hypothetical study area for a period of five years (1800 days). Initially, the model is simulated without any remediation barrier and later multiple barriers, using Activated wood charcoal (AWC) as a common reactive material, are introduced consecutively to contain the plume to a desirable limit. Various parameters, such as the dimensions of the barriers and continuous pumping, are taken into consideration for the performance evaluation of the multi-PRB system. The results indicate that the performance of the multi-PRB system is more efficient compared to the single PRB and natural attenuation system as the concentration in all the wells could be seen drastically declined with the installation of PRBs. Thicker PRB could produce better chloride removal rate due to the increase in residence time for the adsorption of chloride over the reactive media. Further, the continuous pumping would also increase the rate of remediation for the observation wells in its vicinity, however, up to a certain limit. Furthermore, the maximum efficiency of the multi-PRB system can be achieved at a lower depth compare to full study depth. Moreover, the PRBs adjacent to the contaminant source treat the contaminants in the plume capture zone with high efficiency than the far away PRBs. Finally, the numerical model shows that the contaminant plume, containing chloride, is efficiently captured by the multi-PRB system in the proximity of the point sources.