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

-------
        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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 20.  Seaview Thermal Systems. Marketing Brochures,  circa
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Engineering Bulletin:  Thermal Desorption Treatment
                                                                .S. GOVERNMENT PRINTING OFFICE: 19*4 - 550-0*7/80195

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