7
Permeable Reactive Barriers
1.3 Groundwater Remediation
Whilst soil remediation itself is recognized as a significant challenge
(Naidu, 2013), the presence of contaminants in groundwater together with
the dynamic nature of subsurface environment makes groundwater remediation among the most challenging and expensive environmental problems, and often the primary factor limiting closure of contaminated sites.
Many reports suggest that despite years of operation focusing on remediation, it has proven difficult and costly to meet applicable cleanup standards
(Scherer et al., 2000). The most common technology used for the remediation of groundwater has been ex situ pump and treat systems (Rao et al.,
1996). While such systems have been found to be suitable for certain sitespecific scenarios, limitations of this technology have also been recognized.
One such limitation being the cost associated with the technology and the
long-term nature of remediation that also makes it an energy-intensive
technology.
Although a variety of remediation technologies are available for the remediation of contaminated groundwater (Table 1.2), no single technology has
been found to be appropriate for all contaminant types and the variety of sitespecific conditions that exist at different contaminated sites. In an excellent
review, Khan et al. (2004) conclude that site conditions, contaminant types,
contaminant source, source control measures, and the potential impact of
the possible remedial measures determine the choice of a remediation strategy and technology employed. Often more than one remediation technology
is needed to effectively address most contaminated site problems. Multiple
technologies applied concurrently or sequentially are referred to as “treatment trains,” and are often formed to address an overall site remediation
strategy. It is recognized that no single specific remediation technology may
be considered as a solution for all contaminated site problems (FRTR, 2007b;
Khan et al., 2004). Remediation technology implemented at most contaminated sites is not a stand-alone, or one-size-fits-all remedy, but is generally
part of a “treatment train.” Hence, tailored approaches and remediation
techniques are needed on a site-by-site basis.
Over the last couple of decades, depending on the nature of contaminants,
many different technologies have been tested for groundwater remediation.
The list of remediation technologies and their applications has grown, driven
by improved technical knowledge, innovative ideas, technical and economic
resources, and more complex site issues (Hyman and Dupont, 2001; Leeson
et al., 2013; Naidu, 2013). The past 20 years of research have focused heavily
on the development of in situ treatment technologies. Among recent technologies, groundwater circulation wells and PRBs are increasingly being
used in the United States and Europe (USEPA, 1999a,b). The process of
groundwater circulation continuously removes volatile organic compounds
Permeable Reactive Barriers
1.3 Groundwater Remediation
Whilst soil remediation itself is recognized as a significant challenge
(Naidu, 2013), the presence of contaminants in groundwater together with
the dynamic nature of subsurface environment makes groundwater remediation among the most challenging and expensive environmental problems, and often the primary factor limiting closure of contaminated sites.
Many reports suggest that despite years of operation focusing on remediation, it has proven difficult and costly to meet applicable cleanup standards
(Scherer et al., 2000). The most common technology used for the remediation of groundwater has been ex situ pump and treat systems (Rao et al.,
1996). While such systems have been found to be suitable for certain sitespecific scenarios, limitations of this technology have also been recognized.
One such limitation being the cost associated with the technology and the
long-term nature of remediation that also makes it an energy-intensive
technology.
Although a variety of remediation technologies are available for the remediation of contaminated groundwater (Table 1.2), no single technology has
been found to be appropriate for all contaminant types and the variety of sitespecific conditions that exist at different contaminated sites. In an excellent
review, Khan et al. (2004) conclude that site conditions, contaminant types,
contaminant source, source control measures, and the potential impact of
the possible remedial measures determine the choice of a remediation strategy and technology employed. Often more than one remediation technology
is needed to effectively address most contaminated site problems. Multiple
technologies applied concurrently or sequentially are referred to as “treatment trains,” and are often formed to address an overall site remediation
strategy. It is recognized that no single specific remediation technology may
be considered as a solution for all contaminated site problems (FRTR, 2007b;
Khan et al., 2004). Remediation technology implemented at most contaminated sites is not a stand-alone, or one-size-fits-all remedy, but is generally
part of a “treatment train.” Hence, tailored approaches and remediation
techniques are needed on a site-by-site basis.
Over the last couple of decades, depending on the nature of contaminants,
many different technologies have been tested for groundwater remediation.
The list of remediation technologies and their applications has grown, driven
by improved technical knowledge, innovative ideas, technical and economic
resources, and more complex site issues (Hyman and Dupont, 2001; Leeson
et al., 2013; Naidu, 2013). The past 20 years of research have focused heavily
on the development of in situ treatment technologies. Among recent technologies, groundwater circulation wells and PRBs are increasingly being
used in the United States and Europe (USEPA, 1999a,b). The process of
groundwater circulation continuously removes volatile organic compounds