A comprehensive review on permeable reactive barrier for the remediation of groundwater contamination.

Groundwater quality is deteriorating due to contamination from both natural and anthropogenic sources. Traditional "Pump and Treat" techniques of treating the groundwater suffer from the disadvantages of a small-scale and energy-intensive approach. Permeable reactive barriers (PRBs), owing to their passive operation, offer a more sustainable strategy for remediation. This promising technique focuses on eliminating heavy metal pollutants and hazardous aromatic compounds by physisorption, chemisorption, precipitation, denitrification, and/or biodegradation. Researchers have utilized ZVI, activated carbon, natural and manufactured zeolites, and other by-products as reactive media barriers. Environmental parameters, i.e., pH, initial pollutant concentration, organic substance, dissolved oxygen, and reactive media by-products, all influence a PRB's performance. Although their long-term impact and performance are uncertain, PRBs are still evolving as viable alternatives to pump-and-treat techniques. The use of PRBs to remove anionic contaminants (e.g., Fluoride, Nitrate, etc.) has received less attention since precipitates can clog the reactive barrier and hinder groundwater flow. In this paper, we present an insight into this approach and the tremendous implications for future scientific study that integrates this strategy using sustainability and explores the viability of PRBs for anionic pollutants.