Purpose
Section 121(b) of the Comprehensive Environmental Re-
sponse, Compensation, and Liability Act (CERCLA) mandates
the Environmental Protection Agency (EPA) to select remedies
that "utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maxi-
mum extent practicable" and to prefer remedial actions in
which treatment "permanently and significantly reduces the
volume, toxicity, or mobility of hazardous substances, pollut-
ants and contaminants as a principal element." The Engineer-
ing Bulletins are a series of documents that summarize the latest
information available on selected treatment and site remedia-
tion technologies and related issues. They provide summaries
of and references for the latest information to help remedial
project managers, on-scene coordinators, contractors, and
other site cleanup managers understand the type of data and
site characteristics needed to evaluate a technology for poten-
tial applicability to their Superfund or other hazardous waste
site. Those documents that describe individual treatment tech-
nologies focus on remedial investigation scoping needs. This
document is an update of the original bulletin published in May
1991 [1].*
Abstract
Thermal desorption is an ex situ means to physically
separate volatile and some semivolatile contaminants from soil,
sediments, sludges, and filter cakes by heating them at temper-
atures high enough to volatilize the organic contaminants. For
wastes containing up to 10 percent organics or less, thermal
desorption can be used in conjunction with offgas treatment
for site remediation. It also may find applications in conjunc-
tion with other technologies at a site.
Thermal desorption is applicable to organic wastes and
generally is not used for treating metals and other inorganics.
The technology thermally heats contaminated media, gener-
ally between 300 to 1,000°F, thus driving off the water, volatile
contaminants, and some semivolatile contaminants from the
contaminated solid stream and transferring them to a gas
stream. The organics in the contaminated gas stream are then
treated by being burned in an afterburner, condensed in a
single- or multi-stage condenser, or captured by carbon ad-
sorption beds.
The use of this well-established technology is a site-specific
determination. Thermal desorption technologies are the se-
lected remedies at 31 Superfund sites [2]. Geophysical investi-
gations and other engineering studies need to be performed to
identify the appropriate measure or combination of measures
to be implemented based on the site conditions and constitu-
ents of concern at the site. Site-specific treatability studies may
be necessary to establish the applicability and project the likely
performance of a thermal desorption system. The EPA contact
indicated at the end of this bulletin can assist in the identifica-
tion of other contacts and sources of information necessary for
such treatability studies.
This bulletin discusses various aspects of the thermal
desorption technology including applicability, limitations of its
use, residuals produced, performance data, site requirements,
status of the technology, and sources of further information.
Technology Applicability
Thermal desorption has been proven effective in treating
organic-contaminated soils, sediments, sludges, and various
filter cakes. Chemical contaminants for which bench-scale
through full-scale treatment data exist include primarily volatile
organic compounds (VOCs), semivolatile organic compounds
(SVOCs), polychlorinated biphenyls (PCBs), pentachloro-
phenols (PCPs), pesticides, and herbicides [1][3][4][5][6][7].
The technology is not effective in separating inorganics from
the contaminated medium.
Extremely volatile metals may be removed by higher
temperature thermal desorption systems. However, the tem-
perature of the medium produced by the process generally
does not oxidize the metals present in the contaminated
medium [8, p. 85]. The presence of chlorine in the waste can
affect the volatilization of some metals, such as lead. Generally,
as the chlorine content increases, so will the likelihood of metal
volatilization [9].
* [reference number, page number]
Printed on Recycled Paper
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The technology is also applicable for the separation
of organicsfrom refinery wastes, coal tar wastes, wood-treating
wastes, creosote-contaminated soils, hydrocarbon-
contaminated soils, mixed (radioactive and hazardous) wastes,
synthetic rubber processing wastes, and paint wastes [4][1 0,
Table 1
RCRA Codes for Wastes Treated
by Thermal Desorption
Performance data presented in this bulletin should not be
considered directly applicable to other Superfund sites. A
number of variables, such as concentration and distribution of
contaminants, soil particle size, and moisture content, can all
affect system performance. A thorough characterization of the
site and well-designed and conducted treatability studies of all
potential treatment technologies are highly recommended.
Table 1 lists the codes for the specific Resource Conserva-
tion and Recovery Act (RCRA) wastes that have been treated by
this technology [4][10, p.7][11]. The indicated codes were
derived from vendor data where the objective was to determine
thermal desorption effectiveness for these specific industrial
wastes.
The effectiveness of thermal desorption on general con-
taminant groups for various matrices is shown in Table 2.
Examples of constituents within contaminant groups are pro-
vided in 'Technology Screening Guide For Treatment of CERCLA
Soils and Sludges" [8, p. 1 0]. This table has been updated and
is based on the current available information or professional
judgment where no information was available. The proven
effectiveness of the technology for a particular site or waste
does not ensure that it will be effective at all sites or that the
treatment efficiencies achieved will be acceptable at other sites.
For the ratings used for this table, demonstrated effectiveness
means that, at some scale, treatability was tested to show the
technology was effective for that particular contaminant and
medium. The ratings of potential effectiveness or no expected
effectiveness are both based upon expert judgment. Where
potential effectiveness is indicated, the technology is believed
capable of successfully treating the contaminant group in a
particular medium. When the technology is not applicable or
will likely not work for a particular combination of contaminant
group and medium, a no expected effectiveness rating is given.
Another source of general observations and average re-
moval efficiencies for different treatability groups is contained
in the Superfund Land Disposal Restrictions (LDR) Guide #6A,
"Obtaining a Soil and Debris Treatability Variance for Remedial
Actions," (OSWER Directive 9347.3-06FS, September 1990)
[12] and Superfund LDR Guide #6B, "Obtaining a Soil and
Debris Treatability Variance for Removal Actions," (OSWER
Directive 9347.3-06BFS, September 1990) [13].
A further source of information is the U.S. EPA's Risk
Reduction Engineering Laboratory Treatability Database (ac-
cessible via ATTIC).
Technology Limitations
Inorganic constituents or metals that are not particularly
volatile will unlikely be effectively removed by thermal desorp-
tion. If there is a need to remove a portion of them, a vendor
Wood Treating Wastes K001
Dissolved Air Flotation K048
Stop Oil Emulsion Solids K049
Heat Exchanger Bundles Cleaning Sludge K050
American Petroleum Institute (API)
Separator Sludge K051
Tank Bottoms (leaded) K052
Table 2
Effectiveness of Thermal Desorption on General
Contaminant Groups for Soil, Sludge, Sediments,
and Filter Cakes
Contaminant Croups
o
cT
•tt
e
1*
5
„
jj
QC
Halogenated volatiles
Halogenated semivolatiles
Nonhalogenated volatiles
Nonhalogenated semivolatiles
PCBs
Pesticides
Dioxins/Furans
Organic cyanides
Organic corrosives
Volatile metals
Nonvolatile metals
Asbestos
Radioactive materials
Inorganic corrosives
Inorganic cyanides
Oxidizers
Reducers
Effectiveness
Sedl- Filter
Soil Sludge merits Cokes
T
G
•
G
G
G
G
G
G
G
T
•
T
T
T
T
V
T
G
V
G
G
G
G
G
G
G
T
V
V
T
•
T
V
T
G
T
G
Q
G
G
G
G
Q
•
•
•
•
T
T
T
T
G
T
G
G
G
G
G
G
Q
• Demonstrated E ffectiveness: Successful treatability test at some scale
completed
V Potential Effectiveness: Expert opinion that technology will work
Q No Expected Effectiveness; Expert opinion that technology will not
work
process with a very high bed temperature is recommended due
to the fact that a higher bed temperature will generally result
in a greater volatilization of contaminants. If chlorine or
another chlorinated compound is present, some volatilization
of inorganic constituents in the waste may also occur [14, p.8].
The contaminated medium must contain at least 20 per-
cent solids to facilitate placement of the waste material into the
desorption equipment [3, p. 9]. Some systems specify a
minimum of 30 percent solids [15, p. 6].
Engineering Bulletin: Thermal Desorption Treatment
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As the medium is heated and passes through the kiln or
desorber, energy is consumed in heating moisture contained in
the contaminated soil. A very high moisture content may result
in low contaminant volatilization, a need to recycle the soil
through the desorber, or a need to dewater the material prior
to treatment to reduce the energy required to volatilize the
water.
Material handling of soils that are tightly aggregated or
largely clay can result in poor processing performance due to
caking. Rock fragments or particles greater than 1 to 2 inches
may have to be prepared by being crushed, screened, or
shredded in order to meet the minimum treatment size.
However, one advantage to soil preparation is that the con-
taminated medium is mixed and exhibits a more uniform
moisture and BTU content.
If a high fraction of fine silt or clay exists in the matrix,
fugitive dusts will be generated [8, p. 83], and a greater dust
loading will be placed on the downstream air pollution control
equipment [15, p. 6].
The treated medium will typically contain less than 1
percent moisture. Dust can easily form in the transfer of the
treated medium from the desorption unit, but can be mitigated
by water sprays. Normally, clean water from air pollution
control devices can be used for this purpose. Some type of
enclosure may be required to control fugitive dust if water
sprays are not effective.
Although volatile and semivolatile organics are the primary
target of the thermal desorption technology, the total organic
loading is limited by some systems to 10 percent or less [16, p.
11-30]. As in most systems that use a reactor or other equipment
to process wastes, a medium exhibiting a very high pH (greater
than 11) or very low pH (less than 5) may corrode the system
components [8, p. 85].
There is evidence with some system configurations that
polymers may foul or plug heat transfer surfaces [3, p. 9].
Laboratory/field tests of thermal desorption systems have docu-
mented the deposition of insoluble brown tars (presumably
phenolic tars) on internal system components [16, p. 76].
Caution should be taken regarding the disposition of the
treated material, since treatment processes may alter the
physical properties of the material. For example, this material
could be susceptible to such destabilizing forces as liquefaction,
where pore pressures are able to weaken the material on sloped
areas or places where materials must support a load (i.e., roads
for vehicles, subsurfaces of structures, etc.). To achieve or
increase the required stability of the treated material, it may
have to be mixed with other stabilizing materials or compacted
in multiple lifts. A thorough geotechnical evaluation of the
treated product would first be required [14, p.8].
There is also a possibility, that during the cleanup process
at a particular site dioxins and furans may form and be released
from the exhaust stack into the environment. The possibility of
this occurring should be determined on a case-by-case basis.
Technology Description
Thermal desorption is a process that uses either indirect or
direct heat exchange to heat organic contaminants to a tem-
perature high enough to volatilize and separate them from a
contaminated solid medium. Air, combustion gas, or an inert
gas is used as the transfer medium for the vaporized compo-
nents. Thermal desorption systems are physical separation
processes that transfer contaminants from one phase to an-
other. They are not designed to provide high levels of organic
destruction, although the higher temperatures of some sys-
tems will result in localized oxidation or pyrolysis. Thermal
desorption is not incineration, since the destruction of organic
contaminants is not the desired result. The bed temperatures
achieved and residence times used by thermal desorption
systems will volatilize selected contaminants, but usually not
oxidize or destroy them. System performance is usually mea-
sured by the comparison of untreated solid contaminant levels
with those of the processed solids. The contaminated medium
is typically heated to 300 to 1,000°F, based on the thermal
desorption system selected.
Figure 1 is a general schematic of the thermal desorption
process.
Material handling (1) requires excavation of the contam-
inated solids or delivery of filter cake to the system. Typically,
large objects (greater than 2 inches in diameter) are screened,
crushed, or shredded and, if still too large, rejected. The
material to be treated is then delivered by gravity to the
desorber inlet or conveyed by augers to a feed hopper [6, p. 1 ].
Desorption (2) of contaminants can be effected by use of
a rotary dryer, thermal screw, vapor extractor (fluidized bed),
or distillation chamber [15].
As the waste is heated, the contaminants vaporize, and are
then transferred to the gas stream. An inert gas, such as
nitrogen, may be injected as a sweep stream to prevent
contaminant combustion and to aid in vaporizing and remov-
ing the contaminants [4][10, p. 1 ]. Other systems simply direct
the hot gas stream from the desorption unit [3, p. 5][5].
The actual bed temperature and residence time are pri-
mary factors affecting performance in the desorption stage.
These factors are controlled in the desorption unit by using a
series of increasing temperature zones [10, p. 1], multiple
passes of the medium through the desorber where the operat-
ing temperature is sequentially increased, separate compart-
ments where the heat transfer fluid temperature is higher, or
sequential processing into higher temperature zones [17][18].
Heat transfer fluids used include hot combustion gases, hot oil,
steam, and molten salts.
Offgas from desorption is typically processed (3) to re-
move particulates that were entrained into the gas stream
during the desorption step. Volatiles in the offgas may be
burned in an afterburner, collected on activated carbon, or
recovered in condensation equipment. The selection of the gas
treatment system will depend on the concentrations of the
Engineering Bulletin: Thermal Desorption Treatment
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Clean Offgas
1
Excavation
Material
Handling
(1)
Desorption
(2)
ized Rejects
Paniculate
Removal/Gas
Treatment System
(3)
Partic
It
ulates
I
Treated
Medium
-»*- S
— ^- c
c
l ~^
\
1
1
1
1
1
^---1
Spent Carbon
Concentrated
Contaminants
Water
Figure 1
Schematic Diagram of Thermal Desorption
contaminants, air emission standards, and the economics of
the offgas treatment system(s) employed. Some methods
commonly used to remove the particulates from the gas stream
are cyclones, wet scrubbers, and baghouses. In a cyclone,
particulates are removed by centrifugal force. In a wet scrub-
ber, the contaminated gas stream passes upward through
water sprays, causing the particulates to be washed out at the
bottom of the scrubber. In a baghouse, particulates are caught
by bags and discharged out of the system.
Process Residuals
Operation of thermal desorption systems may create up to
six process residual streams: treated medium; oversized me-
dium and debris rejects; condensed contaminants and water;
spent aqueous and vapor phase activated carbon; particulate
dust; and clean offgas. Treated medium, debris, and oversized
rejects may be suitable for return onsite.
The vaporized organic contaminants can be captured by
condensation or passing the offgas through a carbon adsorp-
tion bed or other treatment system. Organic compounds may
also be destroyed by using an offgas combustion chamber or
a catalytic oxidation unit [14, p.5].
When offgas is condensed, the resulting water stream may
contain significant contamination depending on the boiling
points and solubility of the contaminants and may require
further treatment (i.e., carbon adsorption). If the condensed
water is relatively clean, it may be used to suppress the dust
from the treated medium. If carbon adsorption is used to
remove contaminants from the offgas or condensed water,
spent carbon will be generated, and is either returned to the
supplier for reactivation/incineration or regenerated onsite [14,
p.5].
Offgas from a thermal desorption unit will contain partic-
ulates from the medium, vaporized organic contaminants, and
water vapor. Particulates are removed by conventional equip-
ment such as cyclones, wet scrubbers, and baghouses. Collect-
ed particulates may be recycled through the thermal desorp-
tion unit or blended with the treated medium, depending on
the concentration of organic contaminants present on the
particulates. Very small particles (<1 micron) can cause a visible
plume from the stack [14, p.5].
When offgas is destroyed by a combustion process, com-
pliance with incineration emission standards may be required.
Obtaining the necessary permits and demonstrating compli-
ance may be advantageous, however, since the incineration
process would not leave residuals requiring further treatment.
[14, p.5].
Site Requirements
Thermal desorption systems typically are transported on
specifically adapted flatbed semitrailers. Most systems consist
of three components (desorber, particulate control, and gas
treatment). Space requirements onsite are typically less than
150 feet by 150 feet, exclusive of materials handling and
decontamination areas.
Standard 440V, three-phase electrical service is needed.
Water must be available at the site. The quantity of water
needed is vendor- and site-specific.
Treatment of contaminated soils or other waste materials
require that a site safety plan be developed to provide for
personnel protection and special handling measures. Storage
should be provided to hold the process product streams until
they have been tested to determine their acceptability for
disposal or release. Depending upon the site, a method to store
waste that has been prepared for treatment may also be
necessary. Storage capacity will depend on waste volume.
Onsite analytical equipment capable of determining the re-
Engineering Bulletin: Thermal Desorption Treatment
-------
sidual concentration of organic compounds in process residuals
makes the operation more efficient and provides better informa-
tion for process control.
Performance Data
Performance data in this bulletin are included as a general
guideline to the performance of the thermal desorption technol-
ogy and may not always be directly transferable to other
Superfund sites. Thorough site characterization and treatability
studies are essential in determining the potential effectiveness of
the technology at a particular site. Most of the data on thermal
desorption come from studies conducted for EPA's Risk Reduc-
tion Engineering Laboratory under the Superfund Innovative
Technology Evaluation (SITE) Program.
Seaview Thermal Systems (formerly T.D.I. Services, Inc.)
conducted a pilot-scale test of their HT-5 thermal desorption
system at the U.S. DOE's Y-12 plant at Oak Ridge, Tennessee.
The test was run to evaluate the capability of the unit to remove
and recover mercury from a soil matrix. Initial mercury concen-
trations in the soil were 1,140 mg/kg. The mercury was
removed to concentrations of 0.19 mg/kg with a detection limit
of 0.03 mg/kg. A full-scale cleanup (80 tons per day) using the
HT-5 system, was conducted for Chevron U.S.A. at their El
Segundo Refinery, The primary contaminants and their initial
and final concentrations are indicated in Table 3 [20].
In September 1992, an EPA SITE demonstration was per-
formed at a confidential Arizona pesticide site using Canonic
Environmental's Low Temperature Thermal Aeration (LTTA®)
system. The unit had a 35-ton-per-hour capacity. Approximate-
ly 1,180 tons of pesticide-contaminated soil were treated during
the demonstration over three 10-hour replicate runs. The
primary pesticides were di(chlorophenyl) trichloroethane
(DDT), di(chlorophenyl)dichloroethene (DDE), di(chlorophenyl)
dichloroethane (ODD), and toxaphene. Concentrations of
pesticides in contaminated soils ranged from 7,080 |ig/kg to
1,540,000 ^ig/kg. The LTTA® system obtained pesticide re-
moval efficiencies ranging from 82.4 percent to greater than
99.9 percent. All pesticides, with the exception of DDE, were
removed to near or below method detection limits in the soil.
Table 4 presents a summary of four case studies involving full-
scale applications of the LTTA® process [21].
An EPA SITE demonstration was performed at the Anderson
Development Company (ADC) Superfund site in Adrian, Michi-
gan using Roy F. Weston's Low Temperature Thermal Treatment
(LT3®) system. The untt had a 2.1-ton-per-hour capacity.
Approximately 80 tons of contaminated sludge were treated
during the demonstration which consisted of six 6-hour repli-
cate tests. The lagoon sludge was primarily contaminated with
VOCsand SVOCs, including 4,4'-methylenebis(2-chloroaniline)
(MBOCA). Initial VOC concentrations ranged from 35 to
25,000 pg/kg. In the treated sludge, VOC concentrations were
below method detection limits (less than 30 ng/kg) for most
compounds. MBOCA concentrations in the untreated sludge
ranged from 43.6 to 960 ing/kg. The treated sludge ranged in
concentration from 3 to 9.6 mg/kg. The LT3® system also
decreased the concentration of all SVOCs present in the sludge,
with two exceptions: chrysene and phenol. The increase of
Table 3
Full-Scale Cleanup Results of the H-T-5 System [20]
Feed Soil
Concentration
Contaminant (mg/kg)
Toluene
Benzene
Ethylbenzene
Xylenes
Naphthalene
2-Methylnaphthalene
Acenaphthlene
Phenanthrene
Anthracene
Pyrene
Benzo(a)Anthracene
Chrysene
Styrene
30
38
93
290
550
1400
57
320
320
38
36
45
13
Treated Soil Removal
Contentration Efficiency
(W/kg) (%)
<620
<620
<620
<620
<620
<330
<330
<330
<330
<330
<330
<330
<620
<97.93
<98.36
<99.79
<99.78
<99.89
<99.98
<99.42
<99.90
<99.90
<99.13
<99.08
<99.27
<99.23
chrysene concentration was likely caused by a minor leak of heat
transfer fluid. Chemical transformations during heating likely
caused the phenol concentrations to increase. PCDDs and
PCDFs were formed in the system, but were removed from the
exhaust gas by the unit's vapor-phase carbon column with
removal efficiencies, varying with congener, from 20 to 100
percent. Particulate concentrations in the stack gas ranged from
less than 8.5 x 10"4 to 6.7 x 1O'3 grains per dry standard cubic
meter (gr/dscm) and particulate emissions ranged from less
than 1.2 x 10"4 to 9.2 x 10"4 pounds per hour. Table 5 presents
a summary of three case studies involving pilot- and full-scale
applications of the LT3® system [22].
In May 1991, an EPA SITE demonstration was performed at
the Wide Beach Development site in Brand, New York using Soil
Tech's Anaerobic Thermal Processor (ATP) system. Approxi-
mately 104 tons of contaminated soil were treated during three
replicate test runs. The soil and sediment at the site were
primarily contaminated with PCBs, along with VOCs and SVOCs.
The average total PCB concentration was reduced from 28.2
mg/kg in the contaminated soil and sediment to 0.043 mg/kg
in the treated soil (a 99.8 percent removal efficiency). The test
indicated that an average concentration of 23.1 ng/dscm of
PCBs was discharged from the unit's stack to the atmosphere.
The high PCB concentrations in the emissions may have been
caused by low removal efficiencies in the unit's vapor phase
carbon system, high particulate loadings (0.467 gr/dscm) in the
stack, or a combination of the two. Low levels of dioxins and
furans were present in the feed soil, but none were detected in
the treated soils, baghouse fines, or the cyclone's flue gas. The
2,3,7,8-TCDD toxicity equivalents (TEQ) of the stack gas ranged
from 0.0106 to 0.0953 ng/dscm [23].
In June 1991, an EPA SITE demonstration test was per-
formed at the Waukegan Harbor Superfund site in Waukegan
Harbor, IL. The site was primarily contaminated with PCBs,
along with VOCs, SVOCs, and metals. Approximately 253 tons
Engineering Bulletin: Thermal Desorption Treatment
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Table 4
Full-Scale Cleanup Results of the LIT A* System [21]
Site
South Kearney
McKin
Ottati and Goss
Cannon Bridgewater
Former Spencer
Kellogg Facility
Volume/Mass
Treated
16,000 tons
11,500 cubic yards
4,500 cubic yards
11, 300 tons
6,500 tons
Primary
Contaminant(s)
Total VOCs
SVOCs
VOCs
SVOCs
1, 1, 1 TCA
TCE
Tetrachloroethene
Toluene
Ethylbenzene
Total Xylenes
VOCs
Total VOCs
SVOCs
Feed Soil
Concentration
(mg/kg)
308.2
0.7- 15
2.7- 3,310
0.44 - 1.2
12-470
6.5 - 460
4.9-1200
>87 - 3,000
>50 - 440
>170->1100
5.30b
5.42
0.15-4.7
Treated Soil
Contentration
(mg/kg)
0.51
ND- 1.0
<0.05a
<0.33-0.51
<0.025
<0.025
<0.025
<0.025-0.11
<0.025
<0.025 -0.14
<0.025
0.45
0.042 - <0.39
Average concentration
Maximum concentration
Table 5
Full-Scale Cleanup Results of the LT3® System [22]
Volume/Mass
Site Treated
Confidential 1,000 cubic feet
Tinker AFB, OK 3,000 cubic yards
Letterkenny Army Depot 7.5 tons
Primary
Contaminant(s)
Benzene
Toluene
Xylene
Ethylbenzene
Napthalene
PAHs
Volatiles
Semivolatiles
Benzene
Trichloroethene
Tetrachloroethene
Xylene
Other VOCs
Feed Soil
Concentration
1 ppm
24 ppm
110 ppm
20 ppm
4.9 ppm
0.890 - <6ppm
18^/kg- 37,250 ^g/kg
90 ng/kg - 53,000 ng/kg
590 ppm
2,680 ppm
1,420 ppm
27,200 ppm
39 ppm
Treated Soil
Contentration
5.2 ppb
5.2 ppb
<1.0 ppb
4.8 ppb
<0.33 ppm
<330 - 590 ppb
0.1 ng/L-2.3ng/L
6 ng/L - <500 jig/L
0.73 ppm
1.8 ppm
1.4 ppm
0.55 ppm
BDL
BDL Below detection limits
Engineering Bulletin: Thermal Desorption Treatment
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of contaminated soil were treated during four runs using Soil
Tech's ATP thermal desorption system. The system used was a
combination thermal desorption and dechlorination process.
The average PCB concentration in the feed soil was 9,173 mg/
kg; the average final concentration was 2 mg/kg, which is a
99.98 percent removal efficiency. The concentration of PCBs
in the stack gas was 0.834 ^ig/dscm (a 99.999987 percent
removal efficiency). Tetrachlorinated dibenzofurans were the
only dioxins and furans detected in the stack gas at an average
concentration of 0.0787 ng/dscm. The total concentration of
SVOCs in the feed soil was 61.8 mg/kg. In the treated soils
SVOC concentrations totaled only 8.52 mg/kg; only two samples
were identified below the detection limit. In the contaminated
soil, VOC concentrations totaled 17 mg/kg; while in the treated
soil the total was only 0.03 mg/kg. Concentrations of metals
were approximately the same in both the contaminated and
treated soil. This was because the unit does not operate at
temperatures high enough to significantly remove metals. The
pH of the soil rose from 8.59 in the contaminated soil to 11.35
in the treated soil. This was likely due to the addition of sodium
bicarbonate used to reduce PCB emissions [23].
In May 1992, an EPA SITE demonstration was performed
at the Re-Solve Superfund site in North Dartmouth, Massachu-
setts using the Chemical Waste Management X*TRAX™ sys-
tem. The unit had a capacity of 4.9 tons per hour. Approxi-
mately 215 tons of contaminated soil were treated over a
period of three duplicate 6-hour tests. The soil is primarily
contaminated with PCBs, along with some oil and grease and
metals. Initial PCB concentrations ranged from 181 to 515 mg/
kg. The PCB concentration in the treated soil was less than 1.0
mg/kg with an average concentration of 0.25 mg/kg (a 99.9
percent removal efficiency). PCDDs and PCDFs were not
formed during the demonstration. Concentrations of oil and
grease, total recoverable petroleum hydrocarbons, and tetra-
chloroethane were reduced to below detectable levels. Metal
concentrations were not reduced during the test. This was
expected because the unit does not operate at temperatures
high enough to significantly remove metals [24].
RCRA LDRs that require treatment of wastes to best dem-
onstrated available technology (BOAT) levels prior to land
disposal may sometimes be determined to be applicable or
relevant and appropriate requirements for CERCLA response
actions. Thermal desorption often can produce a treated waste
that meets treatment levels set by BOAT but may not reach
these treatment levels in all cases. The ability to meet required
treatment levels is dependent upon the specific waste constit-
uents, the waste matrix, and the thermal desorption system
operating parameters. In cases where thermal desorption does
not meet these levels, it still may, in certain situations, be
selected for use at the site if a treatability variance establishing
alternative treatment levels is obtained. Treatability variances
are justified for handling complex soil and debris matrices. The
following guides describe when and how to seek a treatability
variance for soil and debris: Superfund LDR Guide #6A,
"Obtaining a Soil and Debris Treatability Variance for Remedial
Actions" (OSWER Directive 9347.3-06FS, September 1990)
[12], and Superfund LDR Guide #6B, "Obtaining a Soil and
Debris Treatability Variance for Removal Actions" (OSWER
Directive 9347.3-06BFS, September 1990) [13].
Technology Status
Several firms have experience in implementing this tech-
nology. Therefore, there should not be significant problems of
availability. The engineering and configuration of the systems
are similarly refined, so that once a system is designed full-scale,
little or no prototyping or redesign is generally required.
An EPA SITE demonstration took place at the end of 1993
at the Niagara Mohawk Power Corporation site in Utica, New
York. The facility is a former gas manufacturing plant. Approxi-
mately 800 tons of contaminated soils were treated during the
demonstration. The soil is primarily contaminated with
polyaromatic hydrocarbons (PAHs); benzene, toluene,
ethylbenzene, and xylenes (BTEXs); lead; arsenic; and cyanide.
An EPA Innovation Technology Evaluation Report will be de-
veloped to evaluate the performance of and the cost to
implement the system.
Thermal desorption technologies are the selected reme-
dies at 31 Superfund sites. Table 6 presents the status of
selected Superfund sites employing the thermal desorption
technology [2],
Several vendors have experience in the operation of this
technology and have documented processing costs per ton of
feed processed. The overall range varies from approximately
$100 to $400 (1993 dollars) per ton processed. Caution is
recommended in using costs out of context because the base
year of the estimates varies. Costs also are highly variable due
to the quantity of waste to be processed, terms of the remedia-
tion contract, moisture content, organic constituency of the
contaminated medium, and cleanup standards to be achieved.
Similarly, cost estimates should include such items as prepara-
tion of Work Plans, permitting, excavation, processing, QA/QC
verification of treatment performance, and reporting of data.
EPA Contacts
Technology-specific questions regarding thermal desorp-
tion may be directed to:
Paul dePercin
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
(513)569 7797
James Yezzi
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
Releases Control Branch
2890 Woodbridge Avenue
Building 10(MS-104)
Edison, Nj 08837
•7
Engineering Bulletin: Thermal Desorption Treatment
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Selected Superfund Sites Specifying ThermS Desorption as the Remediation Technology [2]
. —
VOCs (Benzene, TCE, Toluene,
McKin
il
Jfctati & Goss
ifj
'Wide Beach Development
f
^tetaltec/Aerosystems
rCaJdwell Trucking
McKin, ME (1)
New Hampshire (1)
Brandt, NY (2)
Franklin Borough, N) (2)
Fairfield, N] (2)
VOCs (TCE, BTX)
Site remediated 2/87
VOCs, (TCE, PCE, 1,2-DCE, Benzene) Site remediated 9/89
hQutboard Marlne/Waukegan Harbor Waukegan Harbor, IL (5)
PCBs
VOCs (TCE)
VOCs (TCE, PCE, TCA)
PCBs
Dover Township, NJ (2) VOCs (TCE, PCE, TCA), SVOCs
North Dartmouth, MA (1) PCBs
Site remediated 6/92
Design completed
Design completed
Site remediated 6/92
Pre-design
Pilot study completed 5/9
New Jersey (2)
Burton, SC (4)
Fulton, NJ (2)
Adrian, Ml (5)
VOCs (TCE, PCE), Metals (Cadimum, Design completed
Chromium)
VOCs, BTX
VOCs (Xylene, TCE, Benzene, DCE)
VOCs, SVOCs
In design
In design
Site remediated 12/92
Anderson Development Company
•••"••••••^
The two Stauffer Chemical sites in Table 10 of the original Engineering Bulletin are not included in this table because EPA's
Ine ^w •*au'T .. „__„ tu.»... ,i ^.orrrtinn u/iil no onocr be molemented
aunerCnemcal sites in laoie iuui uieuiiyn.a, u,-a».—-^ --..—.----
al Report indicates that thermal desorption will no longer be implemented
(908)321-6703
,f This updated bulletin was prepared for the U.S. Environ-
mental Protection Agency, Office of Research and Develop-
tnent (ORD), Risk Reduction Engineering Laboratory (RREL),
Cincinnati Ohio, by Science Applications International Corpo-
nfon (SAIQ under Contract No. 68-CO-0048. Mr. Eugene
Harris served as the EPA Technical Project Monitor. Mr. Jim
lUwe(SAIC) was the Work Assignment Manager. He and Mr.
%fc Saytor (SAIQ co-authored the revised bulletin. The authors
are especially grateful to Mr. Paul dePercin of EPA-RREL, who
loiltributed significantly by serving as a technical consultant
during the development of this document. The authors also
f|pwnt to acknowledge the contributions of those who partici-
pated in the development of and are listed in the original
bulletin.
The following other contractor personnel have contrib-
uted their time and comments by participating in the expert
review of the document:
Mr. William Troxler Focus Environmental, Inc.
Dr. Steve Lanier
Energy and Environmental
Research Corp.
Engineering Bulletin: Thermal Desorption Treatment
-------
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7.
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Engineering Bulletin: Thermal Desorption Treatment
.S. GOVERNMENT PRINTING OFFICE: 19*4 - 550-0*7/80195
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