Aquifer Restoration: Which Method?

Ground-water contamination is an increasing problem, especially in large urban areas. Toxics that seep into water supplies threaten the health of the community and it's difficult to control the sources of contaminants but there are various remediation options including cotainment and physical, chemical and biological treatment. Containment techniques include various types of impermeable and hydraulic barriers, and surface water and leachate controls. Impermeable barriers that contain, capture or redirect ground-water flow may be slurry walls, grout curtains or sheet pilings. Surface water and leachate control systems manage surface water flows at waste disposal sites. System types include dikes, berms, terraces and benches to prevent or intercept run-on/runoff; channels, waterways, chutes and downpipes to collect and transfer water; seepage basins and ditches to store and discharge it; and sedimentation basins and ponds. Physical treatment depends on the volatile, adsorptive and/or insoluble properties of the contaminant. Types include phase-separated hydrocarbon recovery, air stripping, activated carbon adsorption and filtration. Other physical treatment types include dewatering residuals, hyperfiltration or reverse osmosis, and resin adsorption/ion exchange. Chemical treatment of ground water includes coagulation-precipitation, redox reactions and neutralization. Field performance of ground-water treatment technologies has generally been less than satisfactory. Although pump-and-treat strategies can effectively remove contaminants from ground water pumped to the surface, removal of the subsurface source of contaminants is more difficult.