Environmental Engineering Reference
In-Depth Information
are used. This technique can be employed for the treatment of volatile and semi-
volatile organic pollutants (HAP, phenols, creosote) and metals (zinc, lead, etc.).
Treated water (can be reused in the rinsing solution)
Concentrated residual
materials
Rinsing solution
Treatment
of pollutants
Rinsing
solution
Separater
Contamination
Treatment or
landfill
Mixing of rinsing solution
and contaminants
Injection shaft
Extraction shaft
Figure 15.14
.
Diagram of the in situ rinsing process using vertical shafts [USE 96]
Let us note that this process does not solely rely on the solubility of the
contaminants; it also depends on the Henry's law. In the case of the non-soluble
products, the application of this method to polluted sites is based on the principle of
a reduction of Henry's constant by the introduction of large quantities of flushing
water.
The success of this process of environmental remediation depends appreciably
on the geological conditions (type of ground, etc.) and on the surface-active agents
added to the water. Indeed, rinsing with water is more effective in homogenous and
permeable grounds, such as silty sands and sands with a high permeability. This is
not the case in argillaceous fine-grained soils, where environmental remediation is
slow and expensive. The extremely small ground pores limit the flow in which the
rinsing agents can be injected or extracted. However, vertical prefabricated drains
can be used to cleanse the site in the same way as vacuum extraction. In this case,
the polluted liquids are pumped towards the surface via extraction drains and the
