29
Two Decades of Application of PRBs to Groundwater Remediation
contaminants treated ranging from chlorinated hydrocarbons, to dissolved
reducible metals, to radioactive constituents such as strontium-90. Research
continues in various institutions to develop a better technical understanding
of many of the specific treatment mechanisms to not only develop treatments
for more chemical types, but also to better understand longevity of a given
treatment type so that appropriate contingencies can be invoked before PRB
performance is reduced beyond the objectives of a project.
Two principal design components of the PRB include: the treatment
matrix and the hydraulic control system. The treatment matrix may be
composed of any one, or more, of a variety of materials shown to have the
capability of directly destroying, enhancing natural treatment processes,
or immobilizing target chemicals (see Table 2.1). The hydraulic system is
TABLE 2.1
Example Reactive Treatment Materials for Use in PRBs
Constituents of Concern
Granular
Iron Metal
Biological
(C, H, O)
Phosphatic
(Apatite)
Zeolite
(Ion-Exchange)
Organophilic
Clay
Chlorinated aliphatic compounds (e.g., TCE)
X
X

Chlorinated methanes

Polycyclic aromatic hydrocarbons (PAHs)

Chlorinated pesticides
X

Chlorofluorohydrocarbons
X

Nitrobenzene
X

Benzene, toluene, ethylbenzene, and xylenes (BTEX)
X

Energetics
X
X

Perchlorate
X
X
X

Cationic metals (e.g., Cu, Ni, Zn)
X
X
X

Arsenic
X
X

Chromium(VI)
X
X

Uranium
X
X
X

Strontium-90
X
X

Selenium
X
X

Nitrate
X

Ammonium
X
X

Sulfate
X

Methyl tertiary butyl ether (MTBE)
X

X
Source: International Technology Regulatory Council (ITRC). 2011. Permeable Reactive Barrier:
Technology Update. Prepared by the Interstate Technology Regulatory Council Permeable
Reactive Barriers Team, Washington, DC, http://www.itrcweb.org (accessed 2011).
Note: Biological PRB includes the following enhancements: C (carbon), H (hydrogen), and O
(oxygen).