United States
Environmental Protection
Agency
Solid Waste and
Emergency Response
(5102G)
EPA 542-F-96-004
April 1996
vvEPA
A Citizen's Guide to
Chemical Dehalogenation
Technology Innovation Office
Technology Fact Sheet
What is chemical dehalogenation?
Chemical dehalogenation is a chemical process to re-
move halogens (usually chlorine) from a chemical con-
taminant, rendering it less hazardous. Halogens are a
class of chemical elements that include chlorine, bro-
mine, iodine, and fluorine. Polychlorinated biphenyls
are halogenated compounds that once were used in high
voltage electrical transformers because they conducted
heat well while being fire resistant and good electrical
insulators. In addition, halogenated compounds are
used to produce pesticides because their addition
causes the toxicity needed to control pests. Haloge-
nated compounds also are commonly used in water
treatment, swimming pool chemicals, and plastic piping
and textile production. The chemical dehalogenation
process can be used on common halogenated contami-
nants such as PCBs and dioxins which are usually
found in soil and oils.
How does it work?
There are two common versions of the chemical
dehalogenation process in use: glycolate dehalogen-
ation and the base-catalyzed decomposition process.
Glycolate Dehalogenation
Glycolate dehalogenation makes use of a chemical re-
agent called APEG. APEG consists of two parts: an
alkali metal hydroxide (the "A" in APEG) and
polyethylene glycol (PEG), a substance similar to anti-
freeze. Sodium hydroxide and potassium hydroxide are
two common alkali metal hydroxides. Potassium poly-
ethylene glycolate is the most common APEG reagent.
The process consists of mixing and heating the con-
taminated soils with the APEG reagent. During heat-
ing, the alkali metal hydroxide reacts with the halogen
from the contaminant to form a non-toxic salt; and the
PEG takes the location in the PCB molecule formerly
occupied by the halogen making it less hazardous.
The glycolate dehalogenation process consists of five
steps: preparation, reaction, separation, washing, and
dewatering (Figure 1). During the preparation step, the
contaminated waste (soil, for example) is excavated
and sifted to remove debris and large objects such as
boulders and logs. Next, in the reaction step, the con-
taminated soils and the APEG reagent are blended in a
large container called a reactor, mixed, and heated for
four hours.
Vapors resulting from the heating process are col-
lected. The vapor is separated into water and the gas-
eous contaminants by means of a condenser. The
water can be used during a later step in the process and
the gaseous contaminants are passed through activated
carbon filters to capture the contaminant.
A Quick Look at Chemical Dehalogenation
Used to treat halogenated aromatic organic contaminants, particularly PCBs and dioxins.
Chemically converts toxic materials to less toxic or non-toxic materials.
Involves heating and physically mixing contaminated soils with chemical reagents.
Is a transportable technology that can be brought to the site.
^Printed on Recycled Paper
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The soil-APEG mixture, after treatment in the reactor,
goes to the separator, where the APEG reagent is sepa-
rated from the soil and recycled for future use in the
system. The treated soil contains products of the treat-
ment which are less toxic chemicals resulting from the
dehalogenation reaction. These new chemical products
are a non-toxic salt and a less toxic, partially
dehalogenated organic compound.
The soil passes from the separation step to a washer,
where the water collected in the earlier reaction step is
added. The last traces of residual APEG reagent are
extracted from the soil and recycled. The soil proceeds
to a dewatering phase where the water and soil are
separated. The water is treated to remove contami-
nants before discharge to a municipal water treatment
system, a receiving stream, or other appropriate dis-
charge areas. The soil is retested for contaminant con-
centrations. If it still contains contaminants above
targeted treatment concentrations, it is recycled
through the process or put into an environmentally safe
landfill; if the soil is clean, it can be returned to its
original location on the site.
Base-Catalyzed Decomposition
A second type of chemical dehalogenation, the base-
catalyzed decomposition (BCD) process, was devel-
oped by the U.S. Environmental Protection Agency as
a clean, inexpensive way to remediate liquids, sludge,
soil, and sediment contaminated with chlorinated
organic compounds, especially PCBs, pesticides, some
herbicides and dioxins.
In the BCD process (Figure 2 on page 3), contaminated
soil is excavated and screened to remove debris and
large particles, then crushed and mixed with sodium bi-
carbonate at roughly one part sodium bicarbonate to
ten parts soil. This mixture is heated in a reactor. The
heat separates the halogenated compounds from the
soil by evaporation. The soil left behind is removed
from the reactor and can be returned to the site. The
contaminated gases, condensed into a liquid form, pass
into a liquid-phase reactor. The dehalogenation reac-
tion occurs when several chemicals including sodium
hydroxide (a base) are mixed with the condensed con-
taminants and heated in the reactor. The resulting liq-
uid mixture can be incinerated or treated by other
technologies and recycled. The BCD process elimi-
nates the need to remove the reactants from the treated
soil as in the glycolate dehalogenation process.
The BCD process components are easily transported
and safely operated. The process employs off-the-shelf
equipment and requires less time and space to mobi-
lize, set up, and take down than an incinerator—which
is a common alternative treatment for PCB-contami-
nated wastes.
Figure 1
The Glycolate Dehalogenation Process
Emissions
Emissions Control
(Activated Carbon)
Treated
Emissions
77V
Vapors
Water
Separator
Washer
Dewatering
System
Debris
Mix with
APEG
reagent
Recycled
Reagent
^H
Water
to Publicly
Owned
Treatment
Works
Collect Decontaminated
Soils
I
Further
Testing and
Treatment if
Necessary
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What Is An Innovative Treatment Technology?
Treatment technologies are processes applied to hazardous waste or contaminated materials to permanently alter their
condition through chemical, biological, or physical means. Treatment technologies are able to alter, by destroying or
changing, contaminated materials so that they are less hazardous or are no longer hazardous. This may be done by
reducing the amount of contaminated material, by recovering or removing a component that gives the material its
hazardous properties or by immobilizing the waste. Innovative treatment technologies are those that have been tested,
selected, or used for treatment of hazardous waste or contaminated materials but still lack well-documented cost and
performance data under a variety of operating conditions.
Why consider chemical dehalogenation?
Dehalogenation can be an effective process for remov-
ing halogens from hazardous organic compounds, such
as dioxins, furans, PCBs, and certain chlorinated pesti-
cides. The treatment time is short, energy require-
ments are moderate, and operation and maintenance
costs are relatively low. The technology can be
brought to the site, so hazardous wastes do not have to
be transported.
Will dehalogenation work at every site?
Characteristics of the contaminated material that inter-
fere with the effectiveness of chemical dehalogenation
are high clay or water content, acidity, or high natural
organic content of the soil. Glycolate dehalogenation is
not designed for large waste volumes or wastes with
concentrations of chlorinated contaminants above 5%.
Since contaminated soil must be excavated and
screened before treatment, there must be sufficient
space at the site to conduct this pretreatment process.
Where is dehalogenation being used?
Some Superfund sites where chemical dehalogenation
has been selected as a treatment method are listed in
Table 1 on page 4. The BCD process also has been
used by the Navy at a Public Works Center in Guam to
treat PCB-contaminated soil. The BCD process was
successful at meeting EPA's cleanup goals for the soil.
Figure 2
The Base-Catalyzed Decomposition Process
Contaminated
Soil
Mix with
dehalogenation
chemicals
Condense
contaminated
vapors
t
Collect
contaminated
vapors
t
Solids
Reactor
Heat mixture
at 600-800°F
Mix with sodium
bicarbonate
Debris
Liquid
Reactor
Heat mixture at
650°F.
Contaminants
dehalogenated.
Mixture
disposed of or
recycled off-site
Collect
decontaminated
soil
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Table 1
Examples of Superfund Sites Using Chemical Dehalogenation*
Name of Site
Wide Beach Development, NY
Myers Property, NJ
Saunders Supply Co., VA
Status*
Process
Completed Glycolate dehalogenation
In design BCD
In design To be determined
Contaminants
Polychlorinated biphenyls (PCBs)
Semi-volatile organic compounds
(SVOCs), pesticides
SVOCs, dioxins
For a listing of Superfund sites at which innovative treatment technologies have been used or selected for use,
contact NCEPI at the address in the box below for a copy of the document entitled Innovative Treatment
Technologies: Annual Status Report (7th Ed.), EPA 542-R-95-008. Additional information about the sites listed
in the Annual Status Report is available in database format. The database can be downloaded free of charge from
EPA's Cleanup Information bulletin board (CLU-IN). Call CLU-IN at 301-589-8366 (modem). CLU-IN's help line is
301-589-8368. The database also is available for purchase on diskettes. Contact NCEPI for details.
Not all waste types and site conditions are comparable. Each site must be individually investigated and tested.
Engineering and scientific judgment must be used to determine if a technology is appropriate for a site.
' As of August 1995
For More Information
The publications listed below can be ordered free of charge by calling NCEPI at 513-489-8190 or faxing your request
to 513-489-8695. If NCEPI is out of stock of a document, you may be directed to other sources. Write to NCEPI at:
National Center for Environmental Publications and Information (NCEPI)
P.O. Box42419
Cincinnati, OH 45242
• Selected Alternative and Innovative Treatment Technologies for Corrective Action and Site Remediation: A
Bibliography of EPA Information Sources, January 1995, EPA 542-B-95-001. A bibliography of EPA
publications about innovative treatment technologies.
Physical/Chemical Treatment Technology Resource Guide, September 1994, EPA 542-B-94-008. A bibliography
of publications about chemical dehalogenation and other innovative treatment technologies.
• Engineering Bulletin: Chemical Dehalogenation Treatment: APEG Treatment, September 1990, EPA 540-2-90-015.
• SITE Program Technology Profiles (7th Ed.), November 1994, EPA 540-R-94-526.
NOTICE: This fact sheet is intended solely as general guidance and information. It is not intended, nor can it be relied upon, to create any rights enforceable by any
party in litigation with the United States. The Agency also reserves the right to change this guidance at any time without public notice.
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