Groundwater for Sustainable Development 10 (2020) 100317 Available online 9 December 2019 2352-801X/© 2019 Elsevier B.V. All rights reserved. Research paper Numerical modelling and performance evaluation of multi-permeable reactive barrier system for aquifer remediation susceptible to chloride contamination Rahul Singh a, b, * , Sumedha Chakma a , Volker Birke b a Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, India b Department of Mechanical Engineering / Process Engineering and Environmental Engineering, Hochschule Wismar, Wismar, Germany A R T I C L E INFO Keywords: Groundwater remediation Multi-permeable reactive barrier Visual MODFLOW Activated wood charcoal Continuous pumping ABSTRACT Many in-situ groundwater remediation technologies have been developed, among which the permeable reactive barrier (PRB) technology has emerged as an effcient, 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 fve 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 effcient 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 effciency 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 effciency than the far away PRBs. Finally, the numerical model shows that the contaminant plume, containing chloride, is effciently captured by the multi-PRB system in the proximity of the point sources. 1. Introduction Recent years have witnessed an increasing concern over the deteri- oration of groundwater quality due to various geogenic and anthropo- genic sources like agricultural runoff, industrial exertions, activated mine drainage, domestic and municipal solid wastes, etc. (Chakraborti et al., 2010; Schipper et al., 2010; Wiafe et al., 2013; Rodak et al., 2014). These sources have caused the emergence of numerous toxic and fatal contaminants in the groundwater like the chlorinated compounds, hy- drocarbons, heavy metals, etc., which have gathered worldwide atten- tion (Thiruvenkatachari et al., 2008; Obiri-Nyarko et al., 2014). More than 400,000 sites in the USA have been severely contaminated with toxic metals such as chlorinated compounds and radioactive materials. Similarly, over Europe and Australia, there are well-documented cases of groundwater pollution due to nitrates, hydrocarbons, chlorinated compounds, sulfates, phosphates, etc. (National Research Council NRC, 1994; Thiruvenkatachari et al., 2008; Chakraborti et al., 2010). The increasing concentration of groundwater contamination has not only led it unft for drinking but also caused an adverse effect on humans, ani- mals, and the environment (Thiruvenkatachari et al., 2008; Suhag, 2016). These severe incidents of groundwater contamination create demand for the development of an effcient groundwater remediation technique to eliminate the higher risk to health and the environment (Suhag, 2016). Many conventional groundwater remediation techniques have been developed, over the past few decades, among which the pump and treat * Corresponding author. Research Associate, Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, India. E-mail addresses: Rahul.Singh@civil.iitd.ac.in (R. Singh), chakma@civil.iitd.ac.in (S. Chakma), volker.birke@hs-wismar.de (V. Birke). Contents lists available at ScienceDirect Groundwater for Sustainable Development journal homepage: http://www.elsevier.com/locate/gsd https://doi.org/10.1016/j.gsd.2019.100317 Received 1 March 2019; Received in revised form 18 October 2019; Accepted 6 December 2019