heterogeneous materials, in which an important fraction of pollutants are macroscopic nonexplosive solids (e.g., bullets in soils from shooting galleries, aggregation
of soil particles and tars) or soiled building materials.
The on-site management method uses mobile soil washing systems. It decreases
the cost and the contaminants dissemination risks associated with the transport
(estimated to 10 € ton
À1 each 100 km) of the polluted materials. It requires low
energy technologies easy to implement, providing an effective and reliable treatment. On the one hand, in washing systems of excavated materials, the thorough
contact with the washing fluid may cause important losses of active agents by
adsorption onto the polluted material. In addition, materials with high content in
organic carbon (larger than 10%) and high cation-exchange capacity may cause
problems. On the other hand, most of in situ treatments are unable to destructurate
ground which makes the contaminant recovery more difficult. Indeed, soil-flushing
(SF) treatment is much more challenging, mainly because strongly limited by the
accessibility to the polluted zones, then by the monitoring of its efficiency and finally
by the contaminant recovery. Nevertheless, they avoid the release of contaminants in
the atmosphere and thereby reduce potential contamination risks. Therefore, a
geologic and hydrogeologic study of the site, as well as a selection of technologies
and operating conditions through treatability studies performed at laboratory scale
are essential, but they delay the start of fieldworks. Besides cost and efficiency, the
choice for treatment technologies is based on the risks associated to their implementation (Onwubuya et al. 2009; Caliman et al. 2011). Physical treatments that contain
or transfer contaminant from a compartment to another are preferred, because of
their robustness and the absence of chemical additives being themselves dangerous
(e.g., potentially hazardous for handlers, secondary pollutions, uncontrolled mobilization of contaminants).
Soil leaching (SL) for pollutant recovery is implemented when physical technologies are not adapted, because of contaminants properties (Sect. 1.2.1) or planned
land use. A scheme for SF is shown in Fig. 1.2. Its feasibility is limited by the soil
matrix permeability, which should be higher than 10
À5 m s
À1 . Soil fracturation
(pneumatic or hydraulic) or jet slurring may be used to improve the flow control in
low permeability zones (Thiruvenkatachari et al. 2008). Its efficiency is limited by
permeability contrasts within the treated zone and thus it is necessary to ensure that
the most permeable and slightly contaminated zones are blocked, in order to
concentrate the action on the most contaminated ones (Hirasaki et al. 1997).
Hence, geological and hydrogeological site characterizations are required. Such
studies focus on water permeability, porosity, particle size distributions, heterogeneity, organic carbon content, and cation-exchange capacity. The extraction kinetics
of targeted pollutants plays a major role in SF (Sect. 1.2.2). Because water is often
inefficient to mobilize contaminants that are strongly bound to soil, specific additives
can be added to improve the treatment effectiveness (Sect. 1.3). However, the
dilution of contaminated leachates by groundwater (GW) is also a problem for
their treatments, because the latter are generally less efficient and cost-effective on
diluted pollutions and the large volumes to deal with. The treatment strategy consists
in reducing the mass of pollutant and starts with high productivity technologies (e.g.,
6
N. Fatin-Rouge
of soil particles and tars) or soiled building materials.
The on-site management method uses mobile soil washing systems. It decreases
the cost and the contaminants dissemination risks associated with the transport
(estimated to 10 € ton
À1 each 100 km) of the polluted materials. It requires low
energy technologies easy to implement, providing an effective and reliable treatment. On the one hand, in washing systems of excavated materials, the thorough
contact with the washing fluid may cause important losses of active agents by
adsorption onto the polluted material. In addition, materials with high content in
organic carbon (larger than 10%) and high cation-exchange capacity may cause
problems. On the other hand, most of in situ treatments are unable to destructurate
ground which makes the contaminant recovery more difficult. Indeed, soil-flushing
(SF) treatment is much more challenging, mainly because strongly limited by the
accessibility to the polluted zones, then by the monitoring of its efficiency and finally
by the contaminant recovery. Nevertheless, they avoid the release of contaminants in
the atmosphere and thereby reduce potential contamination risks. Therefore, a
geologic and hydrogeologic study of the site, as well as a selection of technologies
and operating conditions through treatability studies performed at laboratory scale
are essential, but they delay the start of fieldworks. Besides cost and efficiency, the
choice for treatment technologies is based on the risks associated to their implementation (Onwubuya et al. 2009; Caliman et al. 2011). Physical treatments that contain
or transfer contaminant from a compartment to another are preferred, because of
their robustness and the absence of chemical additives being themselves dangerous
(e.g., potentially hazardous for handlers, secondary pollutions, uncontrolled mobilization of contaminants).
Soil leaching (SL) for pollutant recovery is implemented when physical technologies are not adapted, because of contaminants properties (Sect. 1.2.1) or planned
land use. A scheme for SF is shown in Fig. 1.2. Its feasibility is limited by the soil
matrix permeability, which should be higher than 10
À5 m s
À1 . Soil fracturation
(pneumatic or hydraulic) or jet slurring may be used to improve the flow control in
low permeability zones (Thiruvenkatachari et al. 2008). Its efficiency is limited by
permeability contrasts within the treated zone and thus it is necessary to ensure that
the most permeable and slightly contaminated zones are blocked, in order to
concentrate the action on the most contaminated ones (Hirasaki et al. 1997).
Hence, geological and hydrogeological site characterizations are required. Such
studies focus on water permeability, porosity, particle size distributions, heterogeneity, organic carbon content, and cation-exchange capacity. The extraction kinetics
of targeted pollutants plays a major role in SF (Sect. 1.2.2). Because water is often
inefficient to mobilize contaminants that are strongly bound to soil, specific additives
can be added to improve the treatment effectiveness (Sect. 1.3). However, the
dilution of contaminated leachates by groundwater (GW) is also a problem for
their treatments, because the latter are generally less efficient and cost-effective on
diluted pollutions and the large volumes to deal with. The treatment strategy consists
in reducing the mass of pollutant and starts with high productivity technologies (e.g.,
6
N. Fatin-Rouge