A review on design, material selection, mechanism, and modelling of permeable reactive barrier for community-scale groundwater treatment

Over the last thirty years, several techniques of groundwater (GW) remediation based on the principles of physical (air sparging), biological (bioventing), and chemical (e.g., ion exchange) processes have proven to be effective; however, only a handful of them could successfully be implemented at a community or regional scale due to issues like longevity, a requirement of significant investment and operation cost, skilled labours, and others. Therefore, considering the scope of Permeable Reactive Barriers (PRBs) to be implemented on a regional scale and its capability to be a significant replacement for several existing GW treatment methods, this review was prepared with the following objectives: (i) to compare the PRB method with the conventional methods of groundwater treatment along with the possibility and problems associated with the PRB installation in pilot-scale; (ii) to enlist all the probable sets of adsorbents (reactive materials) that can be used for different types of organic and inorganic contaminants; (iii) to understand the key mechanisms of degradation/removal of contaminants involved in PRB design; and (iv) to put forward the future research perspectives of this domain. Review augments that PRBs certainly has a low maintenance cost and a longer life span of ̃30 years that requires very ordinary skills. PRBs promise to be effective in developing countries like India, Bangladesh, and Sri Lanka for the removal of geogenic contaminants like arsenic and fluoride given the appropriate aquifer depth and hydrogeological settings like hydraulic gradient and transmissivity. Furthermore, reactive fillers required in PRBs are readily available, have longer expected life, and operate with no surrounding disturbances. With the advent of several green nanomaterials based adsorbents, PRB's performance can achieve another height, but it needs the experiences from several pilot and larger scale projects. Indeed PRBs are the need of the hour, but a more programming-based investigation would be expected for its superior comprehension.