Permeable Reactive Barriers as an In Situ Groundwater Remediation Technique for Open Solid Waste Dumpsites: a Review and Prospect

Waste generation is increasing rapidly worldwide; compared to 2018, there will be a 19% upsurge in developed countries and a 40% increase in developing countries by 2050. Currently, 33% of municipal solid waste (MSW) generated globally is dumped on open sites; in contrast, nearly all the waste generated in developing countries is openly dumped, where no pollution prevention mechanisms are available. The leachate may contain various unspecified contaminants, including pharmaceuticals, heavy metals, volatile organic compounds, xenobiotic organic compounds, and other organic and inorganic compounds; thus, the pH and ionic strength of leachate may vary spatially and temporally. According to the literature, the review has identified the natural attenuation of heavy metals such as Fe2+, Cu2+, and Cr3+ and inorganic ions (NO3−, Cl−) in and around dumpsites were significant and discussed the consequences caused by pH and ionic concentration changes of leachate on contaminant transport processes. However, several cases noted groundwater pollution at open dumpsites due to the deep percolation of leachate. Thus, the significance of having an effective, perceptible groundwater remediation treatment method and the limitations of currently available leachate treatment technologies were discussed. This review highlights the permeable reactive barriers (PRB) as a promising technology in the remediation of already contaminated groundwater at open dumpsites and various possible PRB materials for leachate treatment that can withstand a wide range of pH and ionic strength. The significant attributes of continuous monitoring of PRB at open dumpsites were recognized while discussing the impact of damage caused by the leachate. Novel technologies and limitations in PRB applications have been highlighted, suggesting adaptability to different environmental conditions. The review provides up-to-date information on groundwater remediation at open dumpsites using PRBs. A shortfall of data on lab, pilot scale experiments, and field monitoring data on PRB studies was noticed during this review study, recommending fulfilling these research gaps.