PRB Strategies and Performance Monitoring for Remediation of Inorganic Contaminants

NRMRL

NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
GROUND WATER AND ECOSYSTEMS RESTORATION RESEARCH

PRB Strategies and Performance Monitoring for Remediation
of Inorganic Contaminants

Background

A permeable reactive barrier (PRB) is a zone of granular
reactive material that extends below the water table to
intercept the flow of contaminated ground water. As organic
or inorganic contaminants pass through a PRB, they are
ideally reduced to non-hazardous compounds or immobilized
to less soluble or less toxic forms. Research is focused on
assessing the geochemical, hydrogeological, and
microbiological factors that govern the performance and
functioning of PRBs. Understanding these factors is necessary
in order to predict the longevity of PRB systems, conduct
economic analyses, and to optimize the implementation of
this ground water cleanup technology for a wide variety of
hazardous compounds.

Objectives

As of 2002, the oldest zero-valent iron PRB systems were about 10 years old. In order to reach the best possible
technology-selection decisions and to optimize PRB design parameters for ground water cleanup at contaminated sites,
information is needed to identify the site-specific factors that govern continued PRB performance. Two PRB systems
installed in 1996 (one at the U.S. Coast Guard Support Center, Elizabeth City, North Carolina; the other at the Denver
Federal Center, Lakewood, Colorado) have been extensively monitored to track and evaluate system behavior through
time.

Approach

This project includes both field and laboratory research
components. Detailed performance monitoring data on full-scale
PRBs installed to treat contaminated ground water have been
collected at two different sites. The PRBs investigated in this
project are among the oldest full-scale systems available for
study and provide an opportunity to analyze the performance of
systems with more than 5 years of field history. In addition, the
PRBs examined here have contrasting design and
hydrogeochemical characteristics that are useful for gaining
insight about the factors that govern PRB longevity and long-
term performance.

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treated

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Geochemical studies include conventional low-flow ground water sampling and analysis, and solid-phase characterization
investigations. Laboratory batch and column tests using reactive media are conducted to determine the effectiveness of
reactive materials, such as zero-valent iron to treat a variety of hazardous substances. Contaminant-removal mechanisms
will be identified in careful water chemistry, geochemical modeling, and solid-phase characterization studies.

Accomplishments

Wilkin, R.T. and M.S. McNeil. (2003). Laboratory Evaluation of Zero-Valent Iron to Treat Water Impacted by Acid Mine
Drainage. Chemosphere, 53, 7: 715-725.

Wilkin, R.T., R.W. Puis, and G.W. Sewell. (2003). Long-Term Performance of Permeable Reactive Barriers Using Zero-
Valent Iron: Geochemical and Microbiological Effects. Ground Water, 41: 493-503.

Paul, C., M. McNeil, F. Beck, P. Clark, R. Wilkin, and R. Puis, R. Capstone Report on the Application. Monitoring, and
Performance of Permeable Reactive Barriers for Ground Water Remediation: Volume 2. Long-Term Monitoring of PRBs:
Soil and Ground Water Sampling (PDF) (145 pp, 5.07 MB) (EPA/600/R-03/045b) August 2003 - Abstract

Wilkin, R.T. and Puis, R.W. Capstone Report on the Application. Monitoring, and Performance of Permeable Reactive
Barriers for Ground Water Remediation: Volume 1. Performance Evaluations at Two Sites (PDF) (156 pp, 23.6 MB)
(EPA/600/R-03/045a) August 2003 - Abstract

Furukawa, Y., J. Kim, J. Watkins, and R. Wilkin. (2002). "Formation of Ferrihydrite and Associated Corrosion Products
in Permeable Reactive Barriers of Zero-Valent Iron." Environmental Science and Technology, 36: 5469-5475.

Wilkin, R.T., Su, C., Ford, R.G., and Paul, C.J. (2005). Chromium removal processes during groundwater remediation by
a zerovalent iron permeable reactive barrier. Environmental Science and Technology, v. 39, p. 4599-4605.

Wilkin, R.T., Acree, S.D., Beak, D.G., Ross, R.R., Lee, T.R., and Paul, C.J. (2008). Field application of a permeable
reactive barrier for treatment of arsenic in ground water, EPA Report, EPA/600/R-08/093, 88 pp.

He, Y., Wilson, J.T., and Wilkin, R.T. (2008). Transformation of reactive iron minerals ina permeable reactive barrier
(biowall) used to treat TCE in groundwater. Environmental Science and Technology, v. 42, p. 6690-6696.

Lee, T. R. and Wilkin, R. T. (2010). Iron hydroxy carbonate formation in zerovalent ironpermeable reactive barriers:
Characterization and evaluation of phase stability. Journal of Contaminant Hydrology, in press.

Investigators

Robert Puis
Richard Wilkin

U.S. EPA Ground Water and Ecosystem Restoration Division Ada, Oklahoma 74820 580-436-8874
Collaborators

Federal Tri-Agency Research Initiative (Department of Defense, Department of Energy)

Naval Research Laboratory

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