Environmental Engineering Reference
In-Depth Information
and Gillham, 1996; Roberts et al., 1996; McMahon et al., 1999; Vogan et al.,
1999; Schlicker et al., 2000), petroleum hydrocarbons (Guerin et al., 2002) and
heavy metals (Powell et al., 1995; Gu et al., 1998; Shokes and Möller, 1999). A
schematic diagram demonstrating the PRB technology is shown in Figure
4.1. The most important components of the design and implementation of the
PRB are a detailed understanding of the subsurface hydrogeology, the kinet-
ics of the reactive material chosen for the barrier, and the long-term monitor-
ing plan. The kinetics of the different reactive materials is well understood
and documented. While a number of different reactive materials have been
used, most of the PRBs installed worldwide utilize zerovalant iron (ZVI) as
the reactive material (Rabideau et al., 2005). An overview of hydrogeological
modeling for PRBs is given in Gupta and Fox (1999). The most challenging
component of PRB design and implementation is the site hydraulics, and sev-
eral case studies of PRBs demonstrate this aspect of the technology.
Building a reliable simulation model for the implementation of any reme-
diation technology requires reliable data from which a conceptual site model
(CSM) is developed that represents the subsurface hydrogeology of the site.
Adequacy of the design in this context often conflicts with the cost involved
in the characterization process. There are often various conflicting objectives
in the decision-making process and this requires a robust and optimal strat-
egy to minimize uncertainties involved with the system and maintain the
accuracy of the data.
Subsurface hydrogeology modeling is implemented at various stages of the
PRB technology. The general principles of PRB design and implementation
have been discussed in detail by Gavaskar et al. (1998). The two basic designs
of PRBs most widely applied are the funnel-and-gate and continuous-trench
barriers (McMohan et al., 1999). Further information on these is provided
Treated
groundwater
Permeable
treatment wall
VOC-bearing
groundwater
Source
area
FIGURE 4.1
A schematic diagram demonstrating the PRB technology. (With Permission from
Environmental Technologies Inc. (ETI). 2005. http://www.eti.ca/, accessed March 28, 2005, ETI,
Waterloo, Ontario, Canada.)
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