Cent Eur J Public Health 1998, 6(2):148-151
Removal of volatile organic contaminants from soil and groundwater
- Berkeley Environmental Restoration Center, University of California, Berkeley, CA, USA
Reduction of health risks associated with the exposure to volatile toxic chemicals found in the soils and groundwater can be reduced by in situ cleanup of the compounds. In this paper, the removal of volatile and semi-volatile contaminants from the heterogeneous domain of the subsurface by in situ technologies is described. For soils contaminated by volatile liquids that are less dense than water, soil vapor extraction from the unsaturated zone above the watertable is recommended since vaporization processes are relatively effective. For dense; volatile non-aqueous phase liquids (DNAPLs) such as perchloroethene and trichloroethene, vaporization processes are inhibited by the fact that these compounds can migrate to locations below the water table. For such situations, groundwater pump-and-treat is recommended for containment. However, time-frames for remediation by that method is measured in terms of centuries. The subsequent losses of resources and uncertainties regarding long-term stewardship of pump-and-treat systems, present problems for the long-term acceptance of that technology. But thermal methods are now being recognized as applicable to the in situ removal of such compounds. Several mechanisms have been identified which account for the remarkable effectiveness of thermal methods to restore subsurface environments: vaporization of components with low boiling points, enhanced evaporation of semi-volatile components, physical displacement of low viscosity liquids, and removal of aqueous phase volatile contaminants by in situ steam generation. For sites of regions of sufficient permeability, steam injection and subsequent steam zone depressurization has been shown to be particularly effective in the removal of both the NAPL phase and aqueous phase contamination.
Zveřejněno: 1. červen 1998 Zobrazit citaci