Environmental Engineering Reference
In-Depth Information
Advantages
Disadvantages
Established technology
Can require a sophisticated and expensive
vapor treatment
Minimal disruption of treatment site
Sensitive to permeability and stratification
Optimal conditions giving reasonable
treatment durations
Reduction in efficiency when there is a
reduction in the concentration of
contaminants; overall efficiency greater
than 90% difficult
Flexible on-site and off-site applications
Preliminary studies generally required
(experimental pilot)
Limited to the unsaturated zone; sites with
a saturated zone require other
environmental remediation methods
Table 15.7
.
Characteristics of the vacuum extraction system
15.5.2.1.1. Vacuum extraction using vertical prefabricated drains
The use of this technique can become less effective or ineffective in fine-grained
soils. A possible solution to this problem is to incorporate vertical prefabricated
drains in vacuum extraction. This solution has several advantages, including
shortening the channels of air circulation and accelerating the extraction time of the
contaminant. Indeed, the installation of drains with narrow spacings decreases the
need for air to pass through the ground. At the same time is increases the probability
of intercepting and contaminant vapors. The many points of passage or extraction
provided by the drains provides more options to better order of the mode of flow
(see Figure 15.9). Preliminary studies led by Monash University and Missouri-
Columbia University show promising results in this context [COL 00, COL 01].
(a) (b)
Figure 15.9.
(a) Aspiration and aeration drains; (b) direction of vapor flow
