United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA540/R-94/521a
February 1995
E PA SITE Technology Capsule
Terra-Kleen Solvent
Extraction Technology
Introduction
In 1980, the U.S. Congress passed the Comprehensive Envi-
ronmental Response, Compensation, and Liability Act
(CERCLA), also known as Superfund, which is committed to
protecting 'human health and the environment from uncon-
trolled hazardous waste sites. CERCLA was amended by the
Superfund Amendments and Reauthorization Act (SARA) in
1986 SARA mandates implementing permanent solutions
and using alternative treatment technologies or resource re-
covery technologies, to the maximum extent possible, to
clean up hazardous waste sites.
State and federal agencies and private organizations are now
exploring a growing number of innovative technologies for
treating hazardous wastes. The more than 1,200 sites on the
National Priorities List involve a broad spectrum of physical,
chemical, and environmental conditions requiring diverse re-
medial approaches
The U.S. Environmental Protection Agency (EPA) has fo-
cused on policy, technical, and informational issues related to
exploring and applying new technologies to Superfund site
remediation. One EPA initiative to accelerate the develop-
ment, demonstration, and use of innovative technologies for
site remediation is the Superfund Innovative Technology Evalu-
ation (SITE) Program.
EPA SITE Technology Capsules summarize the latest infor-
mation available on selected innovative treatment and site
remediation technologies. The Capsules assist EPA remedial
project managers, EPA on-scene coordinators, contractors,
and other remedial managers in the evaluation of site-specific
chemical and physical characteristics to determine a
technology's applicability for site remediation.
This Capsule provides information on the Terra-Kleen solvent
extraction technology, developed by Terra-Kleen Response
Group Inc. (Terra-Kleen). Terra-Kleen claims that the tech-
nology is designed to remove organic compounds from soil,
sludges, and sediments. In October 1993, the Terra-Kleen
technology was evaluated by EPA's SITE Program during a
treatability study on soils from three different sites; the tech-
nology was also evaluated in June 1994 during pilot-scale
demonstration tests on soils from Naval Air Station North
Island (NASNI). All soils treated were contaminated with poly-
chlorinated biphenyls (PCB) in the commercial formulation of
Aroclor 1260. Information in this Capsule presents specific
soil and contaminant characteristics and results of the
treatability study and the pilot-scale demonstration. Additional
information on the implementation of a full-scale Terra-Kleen
system to remediate soils contaminated with dichloro-
diphenyldichloroethene (DDE), dichlorodiphenyltri-chloroethane
(DDT) and dichlorodiphenyldichloroethane (ODD) at Naval
Communication Station (NCS), Stockton, CA, is provided in
the Technology Status section.
This Capsule presents the following technology information:
Abstract
Technology Description
Technology Applicability
Technology Limitations
Process Residuals
Site Requirements
Performance Data
Technology Status
Source of Further Information
Abstract
Remediation of PCBs in soils has been difficult to implement
on a full-scale, cost-effective basis. The Terra-Kleen solvent
extraction system has overcome many of the soil handling,
contaminant removal, and regulatory restrictions that have
made it difficult to implement a cost-effective PCB soil treat-
ment system.
The Terra-Kleen system is a batch process that operates at
ambient temperatures and removes organic contaminants from
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Printed on Recycled Paper
-------
soils using proprietary solvents. After soils are washed with
solvent, contaminated solvent passes through a recovery unit,
where contaminants are separated from the solvent and con-
centrated, reducing the contaminant volume for disposal. The
reclaimed solvent is then reused in the process.
Terra-Kleen demonstrated the technology during a treatability
study in October 1993 and a pilot-scale demonstration in June
1994. The demonstrations were conducted by the EPA SITE
Program with the assistance of PRO Environmental Manage-
ment, Inc. (PRC).
In October 1993, the SITE Program obtained 1-ton batches of
soil from each of 3 PCB-contaminated sites and shipped the
soil to Terra-Kleen's testing facility in Okmulgee, OK. Soils
were obtained from Sites 4 and 6 at NASNI near San Diego,
California, and from a third site in Anchorage, Alaska. Analyses
of all demonstration soils revealed that Aroclor 1260 was the
only PCB mixture present.
Successful removal of PCBs during the treatability study led to
a pilot-scale demonstration at NASNI in June 1994. The Naval
Environmental Leadership Program (NELP) contracted Terra-
Kleen to treat 5 tons of soil from Site 4 at NASNI. An agree-
ment between the SITE Program and NELP was also
established to help implement the pilot-scale demonstration.
The primary objective of both the treatability study and pilot-
scale demonstration was to determine the Terra-Kleen
technology's effectiveness at removing PCBs from soil. The
target treatment level for system evaluation was the Toxic
Substance Control Act's (TSCA) incineration equivalency per-
formance guidance level of 2 milligrams per kilogram (mg/kg)
of PCBs in soil.
PCB removal from soils and solvent was documented using
on-site and off-site analytical tests. During the treatability
study, soil was analyzed on site for PCBs using enzyme immu-
noassay (EIA) test kits, and during the pilot-scale demonstra-
tion using an on-site gas chromatograph (GC) with an electron
capture detector. These analytical procedures permitted rapid
(1-hr) evaluation of system performance during treatment. Spirt
samples of untreated soil, treated soil, and regenerated solvent
were sent to an off-site laboratory to confirm the system's
performance.
PCB concentrations in untreated soils for both demonstrations
ranged from 17 to 640 mg/kg. The removal efficiency for both
tests ranged from 95% to 99%. Treated soil concentrations for
the NASNI Site 4 demonstration were consistently below 2 mg/
kg. Only off-site laboratory data were reported, as these were
subjected to the more stringent quality control review specified
in the project quality assurance project plan.
The Terra-Kleen solvent extraction technology was evaluated
based on the nine criteria used for decision making in the
Superfund feasibility study process. Resutts of the evaluation
are summarized in Table 1.
Under current TSCA regulations, only incinerators and Re-
source Conservation Recovery Act (RCRA) subtitle C-certified
landfills have been permitted to dispose of PCB-contaminated
soils. The SITE demonstration successfully demonstrated the
Terra-Kleen system's ability to reduce the PCB concentration
in soils to less than 2 mg/kg in accordance with EPA TSCA
guidelines. The EPA Office of Pollution Prevention and Toxics
(administrative authority for TSCA) is reviewing Terra-Kleen's
permit application to treat PCB-contaminated soils. TSCA per-
mit approval will enable Terra-Kleen to operate at RCRA,
CERCLA, and private sites to remediate PCB-contaminated
soils and provide owners of sites with an alternative to conven-
tional disposal options.
Development of the Terra-Kleen system has continued into full-
scale remedial operations. A full-scale system began operating
in July 1994 on DDT-contaminated soils at NCS-Stockton.
Information on full-scale operations and the evaluation of dem-
onstration results will be published in the Innovative Technol-
ogy Evaluation Report (ITER), which will be available from
EPA.
Technology Description
The Terra-Kleen solvent extraction technology is a batch pro-
cess system that uses proprietary solvents to separate organic
contaminants from soils. The system also concentrates the
contaminants, reducing the volume of hazardous wastes for
final disposal.
Figure 1 presents a schematic diagram of the Terra-Kleen
system that was used in the SITE pilot-scale demonstration.
The system consisted of five extraction tanks (tanks A through
E), a sedimentation tank, a microfiltration unit, a solvent purifi-
cation station, a clean solvent storage tank, and a vacuum
extraction system. Because solvents are flammable, pneumatic
and spark-proof pumping systems transport the solvent and
vapor through the system to maintain an intrinsically safe
environment.
The Terra-Kleen treatment technology does not require soil
screening equipment to remove oversized materials before
treatment, although it may be advantageous to remove large
rocks, debris, or objects too large for safe handling during
loading and unloading of the treatment tanks. Oversized mate-
rials may be treated separately.
Multiple large extraction tanks (each with a 16- to 17-yd3
capacity) are used to treat larger volumes of contaminated
soils. The full-scale system in operation at NCS-Stockton con-
sists of 19 roll-off units simultaneously treating about 250 tons
of soil in a batch operation.
The system is transportable and can be configured to treat
both small or large quantities of soil. Many of the system
components are available from local vendors throughout the
U.S., easing the logistics for mobilization in most locations.
Solvent Extraction
Treatment begins after the excavated soil is loaded into the
extraction tanks. Clean solvent from the solvent storage tank is
pumped into the extraction tanks. Soil and solvent are held in
the extraction tank, allowing organic contaminants to solubilize
in the solvent, separating them from the soil. The retention time
in the extraction tanks is based on site soil characteristics and
the results of treatability tests.
The contaminant-laden solvent is then transferred from the
extraction tanks to the sedimentation tank. Suspended solids
-------
Table 1. Evaluation Criteria for the Terra-Kleen Solvent Extraction Technology
Criteria
o
stemPertormanca Evalua
V?
Not
Overall Protection
of Human Health
andtheEnvironmen
Provides both
short- and long-
term protection
by eSminating
exposure to
contaminants in
soil.
Sotvents must
be removed
from soils
prior to replace-
ment on site.
Worker protect-
ion required
when handling
contaminated
laboratory or
site wastes
and contam-
inant concen-
95;
Compliance
with Federal
! ARARS3
Terra-Kleen
system complies
with TSCA
incineration
equivalency guide-
lines for PCB
reduction.
Emission controls
must be In place
to comply with
volatile organic
emission restrict-
ions of the dean
Air Act. Regional
restrictions
will vary.
Requires com-
pliance with
RCRA treatment,
storage, and land
disposal regulat-
ions.
Long-Term
Effectiveness and
Performance
The only waste
product is a
contaminant
concentrate, which
is either recycled,
landfilled, or
incinerated, de-
pending on site-
specific
contaminants.
Effectively re-
moves contaminat-,
ion eliminating
any long term
contaminant
effects.
Solvent residuals
readily btodegrade.
Reduction of
Toxidty. Mobility, or
Contaminant Volume
Through Treatment
Toxidty and
mobility are
reduced with
removal of the
soil contaminants.
Volume reductions
depend on the con-
centration of con-
taminants in the
soils to be treated.
Lower levels of con-
tamir&ion in un-
treated soils should
yield a higher ratio
of contaminant
waste volume
reduction.
Short-Term
Effectiveness
Contaminants
are removed
immediately upon
completion of
treatment, which
ranges from 6
hours to several
days, depending
upon the number
of wash cycles
required.
Implementabirity
Commonly avail-
able system
components
enable the
Terra-Kleen
system to be
implemented at
nearly any location.
System can be
assembled In 3
days and removed
in 1 day for small-
scale systems.
Minimal site prep-
aration is required.
Total operating
time can be ex-
tensive if numer-
ous wash cycles
are required.
The system has
been demon-
strated only on
soils containing
fa«o thon 1GQ&
I9SS ulOif ID/o
clays.
Cost ^ Community
Acceptance
$165 to Absence of
$600 per ton combustion
of soil. stacks and use
of some solvents
that are approved
as food additives
by the FDA has
positive comm-
unity appeal.
However,
solvents are
flammable.
Minimal short-
term risks pre-
sented to the
community and
absence of long-
term risks have
favorable impact.
State Acceptance
California
Environmental
Protection
Agency Depart-
ment of Toxic
Substance
Control
approved im-
plementation
of the pilot
projects.
State and local
permits must be
obtained to
comply with air
emission restrict-
ions and to store
soils and solvents
for greater than 90
days if extended
operations are
planned.
a ARARS - Applicable or relevant and appropriate requirements
" Artnal rwsf af rams
diation is soecific to indivk
1ual sites. Reported cost t
jer ton is a range based or
j treatment of 1 ,000
yd3 of soil.
One yd3ofNASNI soil "1.5 tons.
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SOLVENT
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..PUMP'S3
SOLVENT
EXTRACTION
TANKS
Figure 1. The Terra-Kleen solvent extraction technology as demonstrated.
that settle or coagulate in the sedimentation tank are removed
and tested for contaminant content. When the solids are con-
firmed clean, they are added to the treated soil.
Solvent washes continue until a site-specific soil cleanup level
is attained. On-site GC and EIA equipment is used to monitor
organic concentration levels during treatment. Wash solvent
and treated soil are analyzed to measure the progress of
contaminant removal. Final treatment levels are confirmed by
off-site GC analysis.
Residual Solvent Removal
Following the solvent washes, any residual solvent in the soil is
removed using vacuum extraction and biological treatment.
Vacuum extraction removes most residual solvent by drawing
a vacuum on the extraction tank using a centrifugal blower.
During the demonstration solvent vapor and air were drawn out
of the tanks through a condenser and liquid filter, and vented to
the atmosphere. Full-scale operations recirculate treated air
back to the extraction tanks.
Following vapor extraction, an active biological culture and
nutrient media are introduced to the treated soil to biodegrade
residual solvent. After biological treatment, treated soils are
replaced on site.
Solvent Regeneration
The solvent regeneration process begins by pumping contami-
nant-laden solvent from the sedimentation tank through the
microfiltration unit and the proprietary solvent purification sta-
tion. The microfiltration unit removes fines remaining in the
solvent. The solvent purification station separates organic con-
taminants from the solvent and concentrates them, reducing
the volume of hazardous waste for off-site disposal.
Regenerated solvent is then pumped into the clean solvent
storage tank for use in subsequent wash cycles. During the
demonstration and treatability studies, solvent exiting the sol-
vent purification station was sampled to confirm that PCBs
were removed.
The Terra-Kleen system concentrates soil contaminants using
the solvent purification process. Concentrated contaminants
are removed for disposal. The chemical contaminants con-
tained in the concentrate determine the acceptable disposal
method.
Technology Applicability
The Terra-Kleen solvent extraction technology is a waste mini-
mization process designed to remove the following organic
contaminants from soils: PCBs, petroleum hydrocarbons, chlo-
rinated hydrocarbons, polynuclear aromatic hydrocarbons (PAH),
polychlorinated dibenzo-p-dioxins (PCDD), and polychlorinated
dibenzofurans (PCDF). The technology's capacity for removing
other organic contaminants, such as pesticides, has been suc-
cessfully implemented at full-scale capacity as part of the
remediation activities at NCS-Stockton.
The entire treatment system is transportable and can be con-
figured to treat a few cubic yards of soil as well as much larger
volumes generated at remedial sites. Pilot systems have been
-------
tested with 1-ton and 5-ton treatment volume capacities. A
250-ton system configuration is currently in operation.
Treatabil'rty tests are typically conducted before field implemen-
tation to ensure the system's capability to achieve the desired
remedial goals. Site-specific cleanup levels and contaminant
concentrations are the primary determinants for the number of
wash cycles and cycling time required to clean a particular soil
type. In general, as site-specific soil contaminant concentra-
tions increase, and remediation target concentrations become
more restrictive, more wash cycles and longer washing times
are required to reduce contamination. Treatability tests have
shown a wide range of washing cycles required to reduce soil
concentrations to target levels, depending on the specific soil
contaminants and resident soil types.
Treatability results from the NCS-Stockton site have shown
that the Terra-Kleen system can reduce pesticides in soil from
450 to 0.192 mg/kg after only 3 wash cycles. However, 57
wash cycles were required to lower PCB concentrations in the
Alaska soil from 300 to 6.0 mg/kg (see Table 2). The difference
in the number of wash cycles required to complete contami-
nant removal in these two cases is influenced by soil particle
size, moisture content, organic content, contaminant concen-
trations, contaminant mixtures, and contaminant identity.
Optimal soil conditions for treatment include soil containing
less than 15% clay and less than 20% moisture. Higher clay
concentrations require additional wash cycles and physical
handling to reduce clay aggregate size. Higher moisture con-
tent requires soil drying and solvent distillation to reduce water
accumulation in the solvent.
Technology Limitations
Contaminated soils with greater than 15% clays or fines are
difficult to treat because contaminants are strongly sorbed to
the soil particles. The soil particles also tend to form tight
aggregates, which are difficult to break up and prevent efficient
penetration of the solvent to transport contaminants out of the
soil. Additional soil handling steps may be required to treat
soils with a high clay content.
Soils containing more than 20% moisture must be dried prior to
treatment. Excess water dilutes the solvent, reducing contami-
nant solubilization and transport efficiency. Water buildup in
the stock solvent requires the addition of a distillation step to
maintain solvent integrity. If volatile soil contaminants are
present, soil must be dried in the closed extraction vessel.
Soils are typically placed in the extraction tanks by heavy
equipment. The potential for fugitive particulate and volatile
emissions must be considered during excavation and soil han-
dling activities.
The system did not remove metals. Inorganic analyses and
leachate tests conducted on treated soils during the treatability
study showed no change in inorganic or metal-leaching char-
acteristics after soil treatment.
The system is currently designed to operate at ambient out-
door temperatures above freezing. Cold temperatures reduce
I
TankE
Untreated soil
Treated soil
Figure 2. Aroclor 1260 concentrations in untreated and treated soils.
-------
solvent mobility. While current modifications to the full-scale
system incorporate a closed-loop heated vapor extraction sys-
tem, the extraction tanks themselves are not jacketed, and
operation in extreme cold weather can impede extraction effi-
ciency. In cold climates, a heated enclosure may be necessary
to implement all-weather operations.
Process Residuals
The Terra-Kleen solvent extraction technology maximizes its
waste reduction potential by (1) recycling the extraction solvent
as part of routine system operations, (2) maintaining a closed-
loop process to reduce volatile emissions, and (3) isolating its
waste streams to a proprietary contaminant-laden concentrate.
Five tons of soils were treated during the pilot-scale demon-
stration, generating three 55-gal drums of concentrate. The
contaminant concentration process had not reached its capac-
ity as evidenced by the absence of PCBs in the regenerated
solvents. Further evaluations will be performed to project the
system's theoretical volume reduction capacity. The results of
these evaluations will be presented in a Terra-Kleen Innovative
Technology Evaluation Report (ITER).
Of the 1100 gal of stock solvent used for the SITE demonstra-
tion, about 930 gal were drummed at the conclusion of the
demonstration. The majority of unrecovered solvent remained
as residuals in soil and in the bottoms of the extraction tanks
and pipelines. Under normal system operations, these final
residuals would also be removed and recovered. Terra-Kleen
reports that under normal operating conditions, the treatment
process consumes about 7 gal of solvent per ton of soil. Terra-
Kleen is researching vendors who will accept the purified
solvent for sale in secondary markets, enabling nearly com-
plete reuse.
Treated soils can be replaced on site once solvent residuals
have been reduced. The biological half-life of the solvent is 3
days. However, the solvent extraction process will remove
natural organic and some inorganic biological nutrients such as
nitrates and phosphates. Therefore, a nutrient supplement con-
taining natural organic and inorganic nutrients may be required
to continue residual solvent degradation after the soil is re-
placed on site.
During the pilot-scale operations, air emissions, consisting pri-
marily of solvent vapors, were released when sampling and
biological treatment activities required removal of the extraction
vessel's lids. Full-scale system configuration incorporates a
completely enclosed design that enables treatment without
exposing the soil to the open air. In addition, an internal
combustion engine fueled by solvent vapors can be used
during all vapor extraction operations to treat vapor emissions
prior to recycling them back to the extraction tanks.
Site Requirements
Site requirements for the Terra-Kleen system range from 300
ft2 for small-scale, single extraction vessel configurations for
treatability studies to 4,000 ft2 for larger operations, such as
those implemented at NCS-Stockton.
Fluid pumping systems are pneumatically driven by a 5-hp
compressor. Vapor extraction pumps are electric, 3-phase,
220-volt systems that operate continuously during vapor ex-
traction activities.
Sufficient water supplies are also required to mix the biological
slurries for final solvent consumption. The 1-ton vessels at
NASNI required about 20 gal per vessel. Future changes in
biological degradation procedures may increase water con-
sumption.
Performance Data
The primary objective of both the treatability study and pilot-
scale demonstration was to determine the Terra-Kleen
technology's effectiveness in removing PCBs from soil. The
TSCA incineration equivalency performance guidance level of
2 mg/kg of PCBs was used as a target treatment level for
system evaluation.
To provide additional information on the technology's capabili-
ties, samples were also collected and analyzed for volatile
organic compounds (VOC), semivolatile organic compounds
(SVOC), PCDDs, and PCDFs. However, PCDD and PCDF
concentrations in untreated soils were at or near their detection
limits (0.6 ng/g). Detection limits in treated soils for VOCs
Table 2. Analytical Results for the Terra-Kleen Treatability Study
NASNI Site 4
NASNI Site 6
Alaska Site
PCBs in Excavated Soil (mg/'kg)
PCBs in Untreated Soil (mg/kg) »
PCBs in Treated Soil (mg/kg) "
Percent Removal
Percent Clays and Fines Less Than .075mm
in Untreated Soil
Percent Moisture in Untreated Soil
Percent Total Volatile Solids in Untreated Soil
Number of Wash Cycles
Not reported a
17
0.78
95
3.51
0.4
0.16
12
260
28
1.4
95
792
1.3
0.34
24
300
640
6
99
14 4fi
15
0 65
57
Notes:
a Laboratory quality control values were outside acceptable range.
b PCB as Aroclor 1260 in mg/kg reported as dry weight
-------
(maximum 0.339 mg/kg) and SVOCs (maximum 0.675 mg/kg)
were greater than the concentration of these compounds in
untreated soil. Consequently, this data was inadequate for
evaluating system performance on these contaminants.
Treatabllity Study
The treatability study was conducted at the Terra-Kleen facility
in Okmulgee, OK, in October, 1993. The system used in the
study was a small pilot-scale system comprosed of a single 1-
ton extraction tank. Site soils were treated one batch at a time,
with washes running 3 to 11 days depending on contaminant
concentrations. Table 2 presents the results of the treatability
stu Jy.
Soils used for these treatability tests were excavated from the
areas at each site with the highest reported PCB concentra-
tions. Composite samples were then taken from each pile of
excavated soil before shipment to Okmulgee, OK.
Excavated soil was placed in drums for shipment, transported
by overland carrier, and delivered to the Okmulgee location.
Drummed soils were then hoisted over the extraction tank and
dumped. Soils were composited, sampled, and analyzed in
accordance with EPA guidance for sampling PCB spill sites to
document the effects of soil transport on the distribution of
PCBs in soil.
During soil treatment, EIA tests were ust*J ~< site to monitor
PCB concentrations in soil and solvent. Split samples of treated
soil and solvent were analyzed by art off-site laboratory for
reporting final data.
Treatability Study Results
PCB removal was effectively demonstrated in all treatability
study tests; for all three sites, contaminants were concentrated
by the solvent purification process. Regenerated solvent did
not contain PCBs above the detection limit (33.6 u,g/kg), en-
abling it to be used in subsequent wash cycles.
A large difference in PCB concentrations was documented
between excavated soil samples and untreated soil samples.
The discrepancy in PCB concentrations in untreated and exca-
vated soil was attributed to variable PCB distribution in the
soils and mixing with surrounding soils that contain lower or
higher PCB concentrations. Percent removal of PCBs was
calculated using the untreated soil samples because these
samples were considered more homogenous and representa-
tive of treated soils than the excavated soil.
The required treatment time increases with contaminant con-
centration, as shown by the number of wash cycles for the
three soils. The Alaskan soil contained a greater percentage of
soil fines and clay than the NASNI soils. Total volatile solids
analysis of untreated soils and visual observations also indi-
cated a higher percentage of natural organic material. These
factors may have contributed to the need for additional wash
cycles. Terra-Kleen's experience with these soil conditions
confirms that these soils' physical parameters affect the num-
ber of wash cycles needed to complete contaminant removal.
The Alaskan soil also required air drying to reduce soil mois-
ture prior to treatment. This additional step prevented excess
moisture from accumulating in the solvent during soil treatment
and solvent purification.
Pilot-Scale Demonstration
The pilot-scale demonstration took place at NASNI from May 2
to June 16, 1994. NASNI is located at the northern end of the
peninsula that forms the San Diego Bay. NASNI was officially
commissioned in 1917 as a support facility to provide services
and material for aviation activities and naval operations. Large
quantities of hazardous waste were generated and disposed of
at NASNI after the United States entered World War II.
As part of NELP, NASNI contracted Terra-Kleen to treat about
5 tons of PCB-contaminated soil. The demonstration was con-
ducted at Site 4, which is one of 12 areas identified for further
investigation under NASNI's Installation Restoration Program.
Site 4 consists of a 3-acre, unpaved, former salvage yard,
located next to a golf course. The site was used to store
miscellaneous materials, including electrical transformers con-
taining PCBs. Soils at Site 4 are contaminated with heavy
metals, VOCs, SVOCs, PCBs (Aroclor 1260), dioxins, and
furans.
Soils from a small area of Site 4 containing high concentrations
of PCBs were excavated and homogenized for use in the
demonstration. The soils were homogenized before being loaded
into the five extraction tanks, so that the PCB distribution would
be similar in each tank.
Pilot-Scale Demonstration Results
Terra-Kleen conducted 11 wash cycles in 7 days. Solvent
washing was discontinued when PCB concentrations in the five
extractions tanks were reported at 0.52 to 0.69 mg/kg by on-
srte GC. Vacuum extraction and biological treatment of the
soils continued for two additional weeks. Table 3 presents
preliminary results for treated soils.
Results of off-site laboratory analyses showed that the treated
soils contained about 5% moisture caused by incomplete drain-
ing of the treated soils after biological treatment. The moisture
consisted of both water and residual solvent. The demonstra-
tion time limits prevented completion of the solvent removal
process. Therefore, the presence of residual moisture in the
treated soils is not necessarily representative of system perfor-
mance.
Analytical results from the on-site laboratory indicated that
solvent concentration in soils after biological treatment ranged
from 5,144 mg/kg to 18,321 mg/kg. Results of stratified samples
collected at the top and bottom of tank A confirmed the pres-
ence of residual solvent in the bottom of the tank.
The off-site laboratory separated the residual solvent and wa-
ter from the treated soil to determine if both matrices contained
PCBs and to determine how the residual moisture affected
PCB concentrations in treated soils. These additional analyses
indicated that the residual moisture contained PCBs that con-
tributed to the treated soil concentrations reported in Table 3.
Table 4 presents data for treated soils without the moisture
component.
Repeat analyses confirmed these findings. The ITER will in-
clude recommendations that ensure accurate monitoring of
technology performance; the ITER will also address how final
contaminant concentrations are reported when residual solvent
and moisture are present in treated soils.
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Table 3. Results for the Pilot-Scale Terra-Kleen System
PCB Concentrations as Aroclor 1260 in mg/kg (wet weight)
Untreated
Treated Soil
Percent Removal
Tank A
129
1.70
98.7
TankB
139
1.54
98.9
TankC
133
1.69
98.7
TankD
146
1.77
98.8
TankE
168
1.85
98.9
Table 4. PCB Concentrations in Treated Soils Without Moisture
PCB Concentrations as Aroclor 1260 in mg/kg (wet weight)
Tank A
TankB
TankC
TankD
TankE
Treated Soil
Without Moisture
Percent Removal
Without Moisture
1.18
99.0
1.43
98.9
1.25
99.0
1.36
99.0
1.78
98.9
.c
2.00
1.90
1.80
1.70
1.60
1.50
1.40
1.30
1.20
1.10
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
Tank A
TankB
Treated soil
TankC
Legend
TankD
TankE
Treated soil without moisture
Figure 3. Aroclor 1260 concentration in treated soil and treated soil without moisture.
Table 5. Pesticide Removal for the Full-Scale Terra-Kleen System
Average Pesticide Concentrations in mg/kg
ODD
DDE
DDT
Untreated Soil
Treated Soil
Percent Removal
12.2
0.024
98.0
1.5
0.009
99.4
80.5
0.093
98.8
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Changes in PCB concentrations from solvent extraction and
laboratory soil washing are graphically illustrated in Figures 2
and 3. These illustrations show the system's consistent effec-
tiveness at treating the soils in all five tanks. Figure 3 shows
the effect of residual solvent on treated soil concentrations.
Successful completion of the pilot-scale study enabled Terra-
Kleen to implement a full-scale system to remediate a pesti-
cide-contaminated site at NCS-Stockton. The analytical results
of samples collected from the first 20-yd3 container of soil are
shown in Table 5. The pesticides were removed in three wash
cycles.
Technology Status
Completion of the pilot-scale demonstration at NASNI has
encouraged the U.S. Navy to select Terra-Kleen to implement
full-scale remediation at three PCB-contaminated NASNI sites,
totalling about 5,000 yd3 of soil. Remediation is scheduled to
begin in 1995. NCS-Stockton selected Terra-Kleen to imple-
ment full-scale treatment of 500 tons of pesticide-contaminated
soil. Upon successful completion of the first phase of work,
several thousand tons of material will be treated. Terra-Kleen
plans to expand the holding capacity of the NCS-Stockton
treatment system from 250 to 500 tons, based on successful
start-up operations. Terra-Kleen has also implemented im-
proved emission control methods to contain fugitive solvent
emissions.
Source of Further Information
EPA Project Manager:
Mark Meckes
U.S. EPA Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, Ohio 45268
(513) 569-7348 FAX: (513) 569-7676
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United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
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