Long-term performance, configuration, and field challenges of permeable reactive barriers: Potential use in fluoride...

This review evaluates the long-term performance, configuration, and field challenges of permeable reactive barriers (PRBs) with a focus on their potential use in groundwater systems affected by fluoride and nutrients. Different PRB configurations, including continuous, funnel-and-gate (FG), sequential, and electrokinetic-assisted systems, are compared based on their treatment performance and field applicability. The reviewed studies show that PRB performance depends on groundwater flow conditions, aquifer characteristics, reactive media properties, and geochemical processes. FG systems provide better hydraulic control in heterogeneous aquifers, while sequential PRBs can treat multiple contaminants and their daughter products. Electrokinetic-assisted PRBs improve contaminant transport in low-permeability soils. Field applications report successful removal of heavy metals, chlorinated solvents, petroleum hydrocarbons, and various groundwater contaminants. However, long-term performance is often affected by mineral precipitation, biofouling, permeability reduction, preferential flow paths, and loss of reactive media activity. The review also highlights the role of hydrogeological, geochemical, and microbial processes in controlling contaminant removal and barrier longevity. Recent advances in reactive materials and bio-assisted systems improve treatment efficiency and operational stability. The findings suggest that PRBs provide a practical and sustainable option for groundwater remediation and have strong potential for decentralized treatment in fluoride- and nutrient-affected regions.