reached. The management methods cover ex situ, on site, or in situ remediation
activities, whereas the strategies on risks elimination in relation to source zones are
the contaminant recovery, the immobilization, and the degradation in innocuous
metabolites (US Department of Energy 1999).
The ex situ management method is traditionally used because it considerably
reduces the uncertainties for reaching the remediation objectives. It consists in
excavating the polluted zone before transporting it into a secured landfill site or a
processing plant. Limitations for storage in landfill are, on the one hand, the
regulatory requirements regarding the type of materials, the contaminant concentrations, and their leaching potential and, on the other hand, the Nimby factor. The
processing units implement thermal treatments (i.e., vitrification, incineration,
desorption) or immobilization (stabilization and solidification) or degradation
(biopiles) or washing, which depend on characteristics of the material (e.g., nature,
moisture content and type and concentration of contaminants, Khan et al. 2004).
Washing units are similar to those used for mining of ores and water is primarily
used to mobilize the targeted compounds from fines (lower than 63 μm), since the
majority of pollutants are immobilized by adsorption or capillarity (US EPA 2002).
They implement crushing (optional), sorting (lower than 100 mm and magnetic
sorting for the removal of macroscopic metallic pollutants), water-enhanced soil
disintegration, screening between 1 and 100 mm, sieving between 0.04 and 1 mm
and cycloning of the polluted sludge, coagulation and flotation to remove dissolved
and colloidal fractions of pollutants (Zhang et al. 2001; Dermont et al. 2008). All
these steps allow reducing the amount of leached soil and facilitate the accessibility
to pollutants and their recovery from soil particles. Chemicals are added to improve
the physical processes, especially surfactants. Figure 1.1 shows a scheme about this
approach. This treatment method is preferentially suitable for unsaturated
Air
Coagulant
/ Polymer
Reused Water
Sludges
Sludges
Active Agents
Polluted
Soil
Coarse
Fraction
Reused Water
Fig. 1.1 Pictorial working principle of soil-washing (SW) processes
1 Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching. . .
5
activities, whereas the strategies on risks elimination in relation to source zones are
the contaminant recovery, the immobilization, and the degradation in innocuous
metabolites (US Department of Energy 1999).
The ex situ management method is traditionally used because it considerably
reduces the uncertainties for reaching the remediation objectives. It consists in
excavating the polluted zone before transporting it into a secured landfill site or a
processing plant. Limitations for storage in landfill are, on the one hand, the
regulatory requirements regarding the type of materials, the contaminant concentrations, and their leaching potential and, on the other hand, the Nimby factor. The
processing units implement thermal treatments (i.e., vitrification, incineration,
desorption) or immobilization (stabilization and solidification) or degradation
(biopiles) or washing, which depend on characteristics of the material (e.g., nature,
moisture content and type and concentration of contaminants, Khan et al. 2004).
Washing units are similar to those used for mining of ores and water is primarily
used to mobilize the targeted compounds from fines (lower than 63 μm), since the
majority of pollutants are immobilized by adsorption or capillarity (US EPA 2002).
They implement crushing (optional), sorting (lower than 100 mm and magnetic
sorting for the removal of macroscopic metallic pollutants), water-enhanced soil
disintegration, screening between 1 and 100 mm, sieving between 0.04 and 1 mm
and cycloning of the polluted sludge, coagulation and flotation to remove dissolved
and colloidal fractions of pollutants (Zhang et al. 2001; Dermont et al. 2008). All
these steps allow reducing the amount of leached soil and facilitate the accessibility
to pollutants and their recovery from soil particles. Chemicals are added to improve
the physical processes, especially surfactants. Figure 1.1 shows a scheme about this
approach. This treatment method is preferentially suitable for unsaturated
Air
Coagulant
/ Polymer
Reused Water
Sludges
Sludges
Active Agents
Polluted
Soil
Coarse
Fraction
Reused Water
Fig. 1.1 Pictorial working principle of soil-washing (SW) processes
1 Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching. . .
5