pure phase recovery or excavation) before the treatment of the residual fraction. It is
on this level that SF occurs. However, it can be used to enhance pure nonaqueous
phase liquid (NAPL) recovery during the last stage of this preliminary treatment.
Leaching solutions are injected upstream or within the polluted zone. The injection
system involves vertical or horizontal wells, trenches or water-spray equipment.
Polluted leachates are recovered using underground drainage systems before being
pumped up to the surface level for treatment. Treated wastewater may be discharged
in sewer or into the polluted zone. At the end of the treatment, the remaining
contaminant in soil and in the treated wastewater should be at the mg kg
À1 level
or less. It is considered that washing may reduce pollutant concentrations up to two
orders of magnitude, depending on the selected treatment strategy; for soil-washing
(SW) removal yield can reach value higher than 95% and for SF removal yield
ranges between 0 and 95% (Atteia et al. 2013). For in situ treatments, the assessment
of the pollutant mass still present as residual and its delineation are essential.
Sampling strategies that allow for qualitative and quantitative analyses within
statistic frameworks are required (Zhang 2007). When the contaminants are hydrocarbons, the partitioning interwell tracer test (PITT) may be advantageously used for
that purpose (Burt and Christians 2001; Park et al. 2009). The monitoring of
pollutant concentrations in soil leachates and their volumes allows to assess the
remaining amount of pollutant on the basis of mass balances analyses. Pollutant
concentrations and their leaching potential are both considered since the risks are
related to the mobile fraction (ter Laak et al. 2007). SL is attractive, because it
enables a treatment of soils displaying pollutant concentrations as high as tens of
Fig. 1.2 Schematic illustration of soil flushing
1 Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching. . .
7
on this level that SF occurs. However, it can be used to enhance pure nonaqueous
phase liquid (NAPL) recovery during the last stage of this preliminary treatment.
Leaching solutions are injected upstream or within the polluted zone. The injection
system involves vertical or horizontal wells, trenches or water-spray equipment.
Polluted leachates are recovered using underground drainage systems before being
pumped up to the surface level for treatment. Treated wastewater may be discharged
in sewer or into the polluted zone. At the end of the treatment, the remaining
contaminant in soil and in the treated wastewater should be at the mg kg
À1 level
or less. It is considered that washing may reduce pollutant concentrations up to two
orders of magnitude, depending on the selected treatment strategy; for soil-washing
(SW) removal yield can reach value higher than 95% and for SF removal yield
ranges between 0 and 95% (Atteia et al. 2013). For in situ treatments, the assessment
of the pollutant mass still present as residual and its delineation are essential.
Sampling strategies that allow for qualitative and quantitative analyses within
statistic frameworks are required (Zhang 2007). When the contaminants are hydrocarbons, the partitioning interwell tracer test (PITT) may be advantageously used for
that purpose (Burt and Christians 2001; Park et al. 2009). The monitoring of
pollutant concentrations in soil leachates and their volumes allows to assess the
remaining amount of pollutant on the basis of mass balances analyses. Pollutant
concentrations and their leaching potential are both considered since the risks are
related to the mobile fraction (ter Laak et al. 2007). SL is attractive, because it
enables a treatment of soils displaying pollutant concentrations as high as tens of
Fig. 1.2 Schematic illustration of soil flushing
1 Contaminant Mobilization from Polluted Soils: Behavior and Reuse of Leaching. . .
7