Abstract: Permeable reactive barriers are an emerging alternative to traditional pump and treat systems for groundwater remediation. This technique has progressed rapidly over the past decade from laboratory bench-scale studies to full-scale implementation. Laboratory studies indicate the potential for treatment of a large number of inorganic contaminants, including As, Cd, Cr, Cu, Hg, Fe, Mn, Mo, Ni, Pb, Se, Tc, U, V, NO3, PO4 and SO4. Small-scale field studies have demonstrated treatment of Cd, Cr, Cu, Fe, Ni, Pb, NO3, PO4 and SO4. Permeable reactive barriers composed of zero-valent iron have been used in full-scale installations for the treatment of Cr, U, and Tc. Solid-phase organic carbon in the form of municipal compost has been used to remove dissolved constituents associated with acid-mine drainage, including SO4, Fe, Ni, Co and Zn. Dissolved nutrients, including NO3 and PO4, have been removed from domestic septic-system effluent and agricultural drainage.

Abstract: Parts of Britain have large accumulations of metalliferous tailings derived from mining in the lath, 19th and 20th centuries. These tailings were never subject to land reclamation schemes at the time of mining and are situated very close to water courses. They cause considerable environmental damage in terms of contamination of soils, dust blow and pollution of water courses and groundwater. In some parts of the country mine drainage is a major part of river pollution. In recent years, particularly in Wales, efforts have been made to “clean up” these sites. This has involved using techniques to isolate and contain the spoil, diversion of water courses, and the installation of water treatment facilities and drainage and the establishment of a vegetation cover. Research is also being initiated to investigate ways of decontaminating these metalliferous spoils as an alternative to using covering systems to reclaim them.