Two Decades of Application of Permeable Reactive Barriers to Groundwater Remediation - Permeable Reactive Barrier: Sustainable Groundwater Remediation - page 26

of research at many academic institutions; it has become a common-place
addition to feasibility studies and alternative analysis documents for reme-
diation projects. As a consequence, PRBs have been the specific focus of
technical short courses and conferences, spanning the 1995 special session
on PRBs at the American Chemical Society's annual meeting in California,
USA, to Internet-based short-courses sponsored by the U.S. Environmental
Protection Agency (USEPA), to international meetings in the United
Kingdom, Germany, and Italy, and to the September 2011 Clean-Up confer-
ence in Adelaide, Australia. Considering that the first full-scale commercial
PRB composed of zero-valent iron (ZVI) was installed in November 1994
(Yamane, 1995) and continues to function, is the proof that this remedial
approach is truly one of the more sustainable and resource conservative
treatment concepts for chemically affected groundwater.
Although exact wording has morphed over the past two decades, the gen-
erally accepted definition of a PRB, as modified from Interstate Technology
and Regulatory Council (ITRC, 2005) is

an engineered, continuous, in situ permeable treatment zone designed
to intercept and remediate a contaminant plume. (Figure 2.1)

Historically, the PRB has taken additional descriptive names including
“permeable treatment zone,” “applied reactive treatment zone,” “perme-
able reactive treatment zone,” and so on. From these names and definition,
it is clear that the treatment of contaminated groundwater occurs within
the PRB, or immediately adjacent to it (e.g., the evolution of hydrogen from
a ZVI-based PRB may enhance biodegradation processes a short distance
down gradient from the PRB). This recognition is important because the
PRB, by itself, would not completely remediate a contaminant plume until

Permeable
reactive
barrier

Source
zone

Water
table

Remediated
water

Plume

Groundwater
flow direction

Low permeability horizon

FIGURE 2.1
General concept of a PRB for treating a plume of contaminated groundwater.