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EPA 540/R-98/501
Metal-Enhanced Dechlorination of Volatile Organic
Compounds Using an In-Situ Reactive Iron Wall
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Metal-Enhanced Dechlorination of Volatile Organic
Compounds Using an In-Situ Reactive Iron Wall (5.5M)
ABSTRACT
Metal-Enhanced Dechlorination of Volatile Organic
Compounds Using an In-Situ Reactive Iron Wall
Innovative Technology Evaluation Report
EPA 540/R-98/501
September 1998
Abstract EnviroMetal Technologies, Inc. (ETI), of Guelph, Ontario, Canada has
commercialized a metal-enhanced dechlorination technology that the University
of Waterloo, Canada developed to treat aqueous media contaminated with chlorinated
voatile organic compounds (VOCs). The technology employs an electrochemical
process that involves the oxidation of a reactive granular iron medium to induce
reductive dechlorination of chlorinated VOCs.
The Superfund Innovative Technology Evaluation (SITE) Program evaluated
an in-situ application of the technology during a 6-month demonstration
at a confidential site in central New York in 1995. For the demonstration
of the in-situ system, the technology was constructed as a subsurface,
reactive iron wall that fully penetrated a shallow sand and gravel
aquifer. The top of the wall was above the highest average seasonal
groundwater level, about 3 feet below grade, and was covered with a
layer of native topsoil. The wall extended downward from the top of
the saturated zone and was situated on top of an underlying, confining
clay layer. The reactive iron wall, referred to as the "gate," was
oriented perpendicular to the groundwater flow direction and was flanked
by impermeable sheet piling wings which also fully penetrated the
aquifer. The sheet piling formed a "funnel," creating a hydraulic
barrier that diverted groundwater flow from a 24-foot-wide upgradient
area through the gate, and prevented untreated groundwater from flowing
around the gate and mixing with treated groundwater on the downgradient
side.
During the demonstration, SITE Program personnel collected independent
data to evaluate the technology's performance with respect to primary
and secondary objectives. Groundwater samples were collected at locations
on the upgradient (influent) and downgradient (effluent) sides of the
iron, and also from locations within the iron. The groundwater samples
were analyzed for VOCs to evaluate the technology's ability to reduce
chlorinated VOC concentrations to applicable regulatory levels. The
efficiency with which the system removed certain chlorinated VOCs was
evaluated. Other data were collected to provide information about the
dechlorination process, as well as costs and operating and maintenance
requirements for the system.
The results of the sample analyses indicated that the technology
significantly reduced the concentrations of chlorinated VOCs in
groundwater passing through the gate. These chlorinated VOCs included
trichloroethene (TCE), cis-1,Zdichloroethene (cDCE), and vinyl chloride
(VC). All average critical parameter effluent concentrations, and 86 out
of 90 individual critical parameter measurements, achieved the applicable
U.S. Environmental Protection Agency (EPA) maximum contaminant levels or
New York State Department of Environmental Conservation target standards.
Removal efficiencies for TCE, cDCE, and VC were consistently greater than
90 percent. The results indicated no decrease in removal efficiency or
other significant changes in system performance over the 6-month
demonstration period.
EPA SITE Program personnel prepared this Innovative Technology Evaluation
Report (ITER) to present the results of the SITE Program demonstration.
The ITER evaluates the ability of the in-situ application of the metal-
enhanced dechlorination technology to treat chlorinated VOCs in
contaminated groundwater based on the demonstration results. Specifically,
this report discusses performance and economic data collected by SITE
Program personnel, and also presents case studies and additional
information about the technology provided by ETI.
Back to SITE Home Page
Posted April 2, 1999
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