Environmental Engineering Reference
In-Depth Information
material to support vegetation and can affect its technical properties. The loss of
ground structure and its organic contents can also increase its leaching potential,
which poses a problem if there are still heavy metals in the treated product. An
additional treatment may thus be required before the material is acceptable for re-
use.
This process requires control of the gases produced. A rigorous inspecting device
is generally installed to avoid any atmospheric pollution.
15.5.4.
Excavation/put in discharge
This process indicates the removal of ground contaminated for treatment or
setting in discharge. In this case we either have an
in situ
environmental remediation
of the excavated grounds or transport of the ground to treatment plants. The options
depend on the contaminants as well as local conditions (presence of buildings, etc.).
This process with its broad spectrum makes it possible to treat all the pollutants,
since the method rests on ground displacement.
Excavated grounds present can contain pollutant concentrations exceeding an
acceptable threshold. In this case, they are sent for discharge processing in waste
disposal centers.
15.5.5.
Biological breakdown in situ
Biological breakdown
in situ
typically involves a combination of injecting wells
(or galleries) and one or more recovery wells, as shown in Figures 15.15a and b.
There are two scenarios:
- if the contamination is in the unsaturated zone, the solution that contains the
nutrients and oxygen is infiltrated from the surface (see Figure 5.15a) causing the
degradation and passage of pollution;
- if the contamination is in the saturated zone, an aqueous solution is injected
into the nappe in order to increase the natural activity of the micro-organisms and
thus increase biological degradation (aerobic and anaerobic) of the contaminants
(see Figure 5.15b). In this case the system can be passive (the solution is carried
downstream and crosses the contaminated zone, which it treats) or active (water can
be pumped and recycled/reinjected in the circuit). This process can be used in the
presence of biodegradable organic pollutants.
