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/A newsletter about soil, sediment, and ground-water characterization and remediation technologies
January 2007
Issue 28
Environmental contamination by persistent organic pollutants (POPs) poses significant chal-
lenges due to their chemical stability, tendency to bioaccumulate, and ability to easily disperse.
Of the 12 globally recognized POPs, nine are pesticides and the remaining three are industrial
chemicals (PCBs) or industrial byproducts (dioxin and furans). As highlighted in this issue of
Technology News and Trends, degradation or destruction of POPs often relies on ex-situ tech-
nologies combining thermal, physical, and/or chemical processes, but increasing numbers of
less costly bioremediation and thermal applications are successful in-situ.
Sequential Thermodesorption and Non-Combustion Decomposition
Technologies Destroy Dioxins and Pesticide Waste
An onsite ex-situ process combining indirect
thermal desorption (ITD) with Base-Catalyzed
Decomposition™ (BCD) is operating in semi-
process mode at the former Spolana chemical
manufacturing complex inNeratovice, Czech
Republic. Over the course of operation, the
ITD and BCD plant will treat POPs in 3 5,000
tons of soil and contaminated building rubble,
1,000 tons of contaminated concentrate
generated by first-stage thermal desorption,
and 200 tons of pesticide waste intermediate
compounds. Based on the results of pilot-
scale operations showing that the combined
treatment approach reduced contaminant
concentrations to below cleanup criteria, full-
scale operations began in January 2007.
Manufacturing at this site, located just north
of Prague along the Elbe River, dates back to
1939, but releases of POPs became
pronounced in the 1960s when production
focused on agricultural chemicals, PVC, and
components for Agent Orange. Site
characterization from 2001 through 2005
identified high levels of POPs in soil
surrounding two of the abandoned
manufacturing buildings, including
concentrations reaching approximately
1,300 mg/kg hexachlorobenzene, 45,000 ng/kg
dioxin toxic equivalency (TEQ), and 200 mg/kg
lindane. The Czech Environmental Inspection
established site-specific cleanup levels for
soil and solid waste at 1 ng/g for dioxin and
5 mg/kg for the sum of other chlorinated
pollutants such as hexachlorobenzene,
lindane, ODD, DDE, DDT, tetrachloro-
benzenes, and pentachlorophenol.
Pre-treatment work involved enclosing the two
condemned buildings and constructing a
6,000-m2 decontamination facility. In the first
stage of treatment, 30-kg batches of
contaminated soil and other media are
transferred to an ITD chamber (rotating kiln) to
remove organic contaminants. The desorption
chamber is electrically heated to approximately
600°C, and to over 700°C for some batches.
Continuous introduction of nitrogen to the
desorption chamber ensures exclusion of
oxygen, thereby preventing formation of
additional dioxins such as polychlorinated
dibenzo-/>-dioxins (PCDDs) and poly-
chlorinated dibenzofurans(PCDFs). Heated
nitrogen gas containing gaseous desorption
products is directed to a dust filter with ceramic
fiber elements and then to water-cooled
condensers, where gas temperatures decrease
to 20-25°C and most desorption products
condense. Trace amounts of contaminants
remaining in cooled air are trapped in a two-
stage activated carbon filter.
In the second treatment stage, collected or
condensed PCDDs, PCDFs, pesticides and
other POPs are fed into a BCD reactor for non-
combustion destruction. Chemical destruction
occurs in the presence of a reagent mixture of
sodium hydroxide, a hydrogen donor
[continued on page 2]
Contents
Sequential
Thermodesorption and
Non-Combustion
Decomposition
Technologies Destroy
Dioxins and Pesticide
Waste page 1
EPA Evaluates Cost and
Performance of Blood
Meal-Enhanced
Anaerobic
Bioremediation of
Toxaphene-
Contaminated Soil page 2
Combined Mechanical/
Chemical Process
Removes POPs from
Soil and Sediment page 3
In-Situ Thermal
Remediation Completed
on Wood-Treatment
Waste page 4
CLU-IN Resources
CLU-IN's "Contaminant Focus"
on POPs provides assorted
technical reports, background
information, and links concerning
remediation strategies. Users
may download documents such
as EPA's Reference Guide to
Non-Combustion Technologies
for Remediation of Persistent
Organic Pollutants in Stockpiles
and Soil, or the United Nations
Environment Programme's
Review of Emerging, Innovative
Technologies for the Destruction
and Decontamination of POPS
and the Identification of Promis-
ing Technologies for Use in
Developing Countries. Visit CLU-
IN at http://www.cluin.org/POPs.
Recycled/Recyclable
Printed with Soy/Canola Ink on paper that
contains at least 50% recycted fiber
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[continued from page 1]
(hydrocarbon), and a catalyst. Blending of
this mixture at 290-3 50°C within the reactor's
nitrogen-rich environment releases highly
reactive hydrogen capable of cleaving
chemical bonds in target compounds.
Depending on contaminant concentrations,
treatment duration ranges from several to 90
minutes. This process releases no
greenhouse gases and creates byproducts
containing non-toxic carbon residue and
anionic sodium salts that are disposed at
offsite land disposal facilities.
Reactor steam is transferred into a
condensation system consisting of two water-
cooled condensers and a supercooling
condenser further reducing temperatures to
8°C. The cooled gas is passed through a two-
stage activated carbon filter system prior to
atmospheric release. Inorganic salts and
carbon residue are separated from the
unreacted oil by gravity or centrifugation, and
the oil and catalyst may be recovered for reuse
in other treatment cycles. Excess salts and
base may be removed from carbon residue by
washing with water.
Destruction efficiencies observed in selected
samples after ITD treatment during the current
full-scale operation are similar to those derived
from pilot-scale testing in 2004 (Figure 1).
Treatment through sequential ITD and BCD
reduced target contaminants by 99% in system
Sample Type
Soil
Building exterior:
mixed soil, ash,
demolition waste
Building interior:
mixed demolition
waste
Dioxin Compounds
Pre-/Post-Treatment
(ng/g)
45/0.003
185/0.22
2,420 / 0.0063
Hexachlorobenzene
Pre-/Post-Treatment
(mg/kg)
2,640/1.0
8,200/1.0
49,000/1.0
Lindane
Pre-/Post-Treatment
(mg/kg)
1.7/1.0
28/1.0
11/1.0
ITD Maximum
Temperature
and Time
675°C
240 minutes
706°C
240 minutes
647°C
240 minutes
1 Figure 1. Following an average residence time of 3 hours in the pilot-scale •
Spolana ITD high-temperature reactor, most contaminants are removed from
soil and waste material.
outfeed. Destruction efficiencies slightly vary,
depending on waste form and contaminant
content. Cleanup closure is anticipated in late
2008, at which time the treatment facility will be
dismantled and transferred to another site for
use. Total project costs are estimated at $90
million
Each of the two 10-m3 BCD reactors employed
at Spolana is capable of treating 1,000 tons/yr of
high chlorine-content (50%) PCBs or pesticides,
2,000 tons/yr of contaminated filter dust, or up
to 7,000 tons/yr of oil with moderate to low PCB
content. Depending on treatment volume and
facility size, typical BCD equipment may cost
from $500,000 to $2,500,000; transportable
plants with 2.5-m3 reactors may be used for
smaller treatment volumes. Originally developed
by the U.S. EPA's Risk Reduction Laboratory,
this technology has undergone commercial
development involving refinement to the BCD
catalyst over the past 10 years.
Alternate pre-treatment such as crushing of
large soil particles or adjustment of pH or
moisture content may be required. Pilot- and
full-scale applications indicate that the
technology may be used to destroy
chlorinated or non-chlorinated organics in
soil, sediment, solids, liquids, or sludge.
Contributed by Richard Pribyl, Czech
Ministry of the Environment
(richard_pribyl(a)env. cz). Martin Kubal,
Institute of Chemical Technology in
Prague (martin.kubal&vscht.cz or +420 2
24355029), and Grahame Hamilton, BCD
CZ (grahame.hamilton(a)bcdcz.cz or
+420 2 22922612)
EPA Evaluates Cost and Performance of Blood Meal-Enhanced Anaerobic Bioremediation
of Toxaphene-Contaminated Soil
The U. S. EPAEnvironmental Response Team
Center (ERTC) initiated field-scale studies in
January 2001 on the use of anaerobic
bioremediation for treating toxaphene-
contaminated soil at the Gila River Indian
Community (GRIC) site in Chandler, AZ. In
early 2003, a similar remediation strategy was
formulated for the Gila River Boundary (GRB)
site near Laveen, AZ, and another toxaphene-
contaminated site of the GRIC Reservation.
Both applications used blood meal as a
nutrient to stimulate contaminant
degradation by indigenous anaerobic
microorganisms. Using a toxaphene cleanup
goal of 17ppm, ERTC and EPA Region 9
recently evaluated the performance and cost
of these large-scale anaerobic applications.
The GRIC site once served as an airstrip for
crop dusters that applied pesticides (primarily
toxaphene). Discarded pesticide residue and
runoff from equipment washing contaminated
extensive areas of soil that eventually was
excavated and transported to a designated
area on the reservation for treatment.
Approximately 3,500yd3 of the contaminated
soil were mixed and placed in four 178-by 43-
foot anaerobic cells sloping to 7 feet in depth.
Using a large-scale pugmill, blood meal and
sodium phosphate (as pH buffer) were
combined in a ratio of 5:1, with equal amounts
of dibasic and monobasic phosphate salts
added to protect pH from alkaline ammonia
produced by the blood meal. This
amendment then was mixed with the soil in
the treatment cells.
Pre-treatment soil samples were collected
from the cells prior to amendment.
Toxaphene concentrations ranging from 29
[continued on page 3]
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[continued from page 2]
to 34 mg/kg of soil before treatment
decreased to 4-5 mg/kg after six months of
treatment, resulting in an average removal
rate of 86-93% for all four cells.
Soil contamination at the GRB site resulted
from pesticide spills. In 2004, after treatment
at GRIC was underway, EPA began treating
approximately 8,000 yd3 of toxaphene-
contaminated soil in six 100- by 20-ft by
10-ft-deep field cells (Figure 2). Before
adding similarly amended contaminated
soil, each cell was lined with an oversized
plastic liner that was folded, glued together,
and buried on edges to create a cover after
cell loading. Prior to covering, the cells
were flooded to achieve a 6- to 12-inch
depth of free-standing water needed to
establish and maintain anaerobic
conditions for reductive dechlorination by
indigenous bacteria.
After six months of treatment, toxaphene
concentrations in soil decreased from
initial concentrations of 23-110 mg/kg to
5-20 mg/kg, below the action level in all six
treatment cells. The average removal rate
ranged from 66 to 82%. Approximately
6,100 m3 of contaminated soil were treated
over two years of cell operation, and
cleanup was completed in early 2006. At
that point, the liner was punctured and left
in place with the treated soil.
Bioremediation at both sites involved cell
liners, microbial-enhancing flooding, and
sampling/ventilation ports for monitoring the
treatment cells and maintaining the cover
through off-gas. Due to high rates of
evaporation and a deep water table,
construction of a water collection system was
not required. The same amendments were used
at both sites, with one exception: based on
preliminary results from the GRIC application,
EPA determined that approximately 50% less
blood meal was required for effective soil
treatment. At the GRB site, this fraction of blood
meal was substituted with less costly starch.
EPA believes that facultative anaerobes in the
contaminated soil use the starch rather than
the blood meal during their early growth
phase, when driving out remaining oxygen.
Other improvements were made to reduce
project costs at the GRB site. Use of larger
treatment cells accommodating the high soil
volume, nearly double the GRIC volume,
ventilation/sampling ports
achieved savings through economy of scale.
Streamlining of field activities by deploying
the same contractor team at both sites also
reduced costs. Overall, the shorter treatment
period needed to meet cleanup goals at the
GRB site saved significant costs related to
longer-term monitoring/sampling.
The total cost for soil cleanup at GRIC is
estimated at $725,000 or approximately
$271/m3, while cleanup at the GRB site is
estimated at $793,000 or approximately
$130/m3. These costs are competitive with
other cleanup methods such as onsite
incineration and soil washing, which may
range from $290-430/m3 and $135-290/m3,
respectively. ERTC anticipates future studies
to identify more cost-effective nutrient
recipes for promoting rapid degradation of
toxaphene. Additional sites are targeted for
evaluation of blood meal-based anaerobic
bioremediation of soil containing other
chlorinated pesticides such as DDT.
Contributed by Harry L. Allen, U.S.
EPA ERTC (allen.harry&epa.gov
or 732-321-6747) and Harry L.
Allen IV, U.S. EPA Region 9
(alien. harryl(q),epa.gov or
415-972-3063)
Figure 2. Each GRB treatment cell was
equipped with three ventilation/
sampling ports to permit sampling and
off-gassing without removal of the
Combined Mechanical/Chemical Process Removes POPs from Soil and Sediment
The New Zealand Ministry for the
Environment and Tasman District Council are
collaborating in cleanup and reuse planning
for the Fruitgrowers Chemical Company (FCC)
site, the country's most highly contaminated
area. An onsite demonstration was conducted
in 2004 to evaluate performance of an
innovative technology using mechanical
energy to promote reductive dehalogenation
of POPs in soil and sediment. Successful
demonstration results for Mechanochemical
Destruction™ (MCD) led to full-scale
application of the technology later that year
to treat surface and subsurface material
containing high concentrations of DDT, DDD,
DDE (collectively DDX), aldrin, dieldrin, and
lindane (collectively ADL). Over the course of
treatment, nearly 65,000 m3 of soil/sediment,
comprising 200 individual cells segregated into
600 0.5-m layers, will be excavated for ex-situ
remediation (Figure 3).
The 4.2-ha FCC site was used for pesticide
production from 1932 until 1988 when
operations ceased and the site was abandoned,
leaving large areas of contaminated soil and
sediment. The site borders a recreational
estuary, residential area, tourist attractions,
and restaurants in the coastal town of Mapua
at the top of the South Island. Site
characterization on a 15-m grid at a 2-m depth
confirmed hot spots exceeding 12,000 ppm
DDXand 400 ppm ADL, and ex-situ pilottests
showed concentrations reaching 2,600 ppm
and 100 ppm, respectively. This
characterization gave rise to an estimated 6,600
m3 of soil requiring MCD treatment.
Approximately 85% of the soil exceeding the
[continued on page 4]
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[continued from page 3]
soil acceptance criteria (SAC) has been
remediated to levels generally 50% below
the SAC.
Based on the site's anticipated use for
commercial and recreational purposes, the
SAC were set at 200 ppm DDX and 60 ppm
ADL at depths greater than 0.5 m, and at 5
ppm DDX and 3 ppm ADL at depths less
than 0.5m. Cleanup plans require the use of
uncontaminated onsite soil or imported soil
for the 0.5-meter top layer in the site's
anticipated commercial/recreational areas and
for the full depth of planned residential zones.
During the MCD preconditioning phase,
layers of the target soil are excavated and
sorted through a 3-part screen to obtain a
particle-size fraction below 20 mm. This
fraction is dried in a diesel-fired rotary drum
unit at temperatures not exceeding 120°C to
achieve moisture content below 2%, and
sorted again in an aggressive rotary screen
to obtain a particle fraction less than 10 mm
that is further separated into coarse or fine
streams. Analytical testing of the 10- to 20-
mm extracted fraction on a volumetric basis
consistently indicates contaminants are
successfully "knocked off during rotary
screening to achieve DDX and ADL
concentrations at or below the target level;
the fraction is stored in an onsite silo for later
placement across the site. Gaseous emissions
throughout this conditioning process are
treated through a conventional air emission
treatment system, and captured particulate
contaminants are added to infeed of the
system's mechanochemical reactor.
MCD treatment involves blending readily
available commercial reagents, collectively
less than 2% by dry weight, with
contaminated soil/sediment as it is transferred
from a separate storage silo to the
mechanochemical reactor. The reagent blend
contains a base metal (typically an alkali-earth
metal, such as iron) and a hydrogen donor. The
reactor employs conventional vibratory ball-
mill technology to rupture soil crystals and form
reactive free radicals on the ruptured soil
surfaces. Crystal rupturing is accompanied by
emissions of electrons and photons and
generation of electrostatic charges, a
combination known as "triboplasma." An
organic pollutant within the triboplasma zone
typically becomes excited and reacts with the
highly reactive free radicals, resulting in
formation of inorganic halides and graphite
carbon. Two horizontally mounted vibratory
tubes within the reactor drive these chemical
reactions.
Dried material of particle size less than 10 mm is
fed into the MCD reactor through separate
streams of fine and coarse fractions on a
continuous basis. After a residence time
averaging 15 minutes at a temperature of 70-
100°C, material is transferred out of the reactor,
stockpiled, and analytically sampled prior to
onsite placement. The MCD currently processes
an average of 100 m3 of material each week.
By early December 2006, a total soil/sediment
volume of 55,250 m3 (85% of the target volume),
was excavated, screened, relocated or treated
onsite. Of this volume approximately 5,500m3
have been treated by the MCD process to date.
Figure 3. The 65-meter2MCD
facility at Mapua encompasses
units for soil/sediment multi-level
screening, drying, and treatment
within a mechanochemical reactor,
alone with an air emission control
Pre- and post-treatment analyses of
total chlorine and carbon content show
that carbon and chlorine concentrations
are constant, indicating that a
mechanochemical reaction rather than a
volatilization process is occurring within the
MCD reactor. Treatment byproducts primarily
consist of non-hazardous organics and metal
salts. Application at Mapua as well as pilot
testing at other sites indicate that this
technology also treats mixed solid-liquid waste
effectively but may be limited in treating high-
moisture clay.
Contaminated soil and sediment from portions
of the site not targeted for MCD treatment
were excavated and relocated dependant on
the end use criteria. Cleanup completion is
scheduled for March 2007 at a total project
cost of approximately $8 million, including
construction and continuous operation of the
entire facility for 2.5 years. Upon cleanup
closure, the Tasman District Council
anticipates allocating 40% of the land for
public open space. Pending final results, the
Ministry for the Environment anticipates that
this project will serve as a prototype for
remediating other POP-contaminated sites in
New Zealand.
Contributed by Bryan Black,
Environmental Decontamination Ltd.
(bblack(a).edl.net.nz or +64 21 960069)
under permission of New Zealand
Ministry of the Environment
In-Situ Thermal Remediation Completed on Wood-Treatment Waste
After four years of operation, full-scale in-
situ thermal remediation of soil at Southern
California Edison's former wood treatment site
in Alhambra, CA, concluded last spring.
Subsurface soil containing PAHs, PCP, and
dioxins/furans was treated by in-situ thermal
desorption (ISTD), a technology employing
the simultaneous application of thermal
conduction heating and vacuum to treat soil
without excavation. Treatment achieved
cleanup goals for approximately 16,500 yd3 of
[continued on page 5]
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[continued from page 4]
predominantly silty soil to a depth of 105 ft,
and provided the opportunity for property
reuse without restrictions.
The treatment area included the locations of
four below-ground creosote "dip" tanks
formerly used to preserve utility poles, an
aboveground storage tank farm, a boiler house,
and decommissioned pipelines that
remained in place during ISTD treatment. The
mean (and maximum) concentrations of
contaminants targeted during soil treatment
were 2,306 (35,000) mg/kg total PAH,
0.018 (0.194) mg/kg dioxins/furans (TEQ),
and 2.94 (58) mg/kg PCP. Due to the large
treatment area and associated electrical
power constraints, remediation occurred in
two phases. Phase 1 operated from 2002
through early 2004 and was immediately
followed by phase 2 operations, which
continued until September 2005. Site-specific
risk assessment established cleanup goals for
contaminants of concern: 0.065 mg/kg PAHs
(based on benzo(a)pyrene equivalents
[B(a)P-E]), 1 |lg/kg dioxins/furans (based on
TCDD TEQ), and 2.5 mg/kg PCP.
ISTD employs a network of horizontal or
vertical heater-only and heater-vacuum wells
containing electrically powered heating
elements with maximum operating
temperatures of 600-800°C. Silicon-controlled
rectifiers are used to control output of the
heating elements. Through direct surface
contact and conductivity, heated wells raise
the temperatures of surrounding soil. As soil
is heated, organic contaminants are vaporized
and drawn toward the heater-vacuum wells.
The vapors pass through the superheated
zone surrounding the heater-vacuum wells,
where potentially 99% of contaminant
destruction occurs. Mechanisms responsible
for contaminant destruction and/or
vaporization include evaporation, steam
distillation, boiling, oxidation, andpyrolysis.
Remaining trace contaminants are removed
in an aboveground air quality control (AQC)
system.
Treatability tests were conducted to
determine optimal operating temperatures and
residence times. Testing confirmed that
successful treatment of high-boiling point
PAHs occurs at temperatures significantly
lower than their boiling points. Modeling
indicated that exposure of this site's PAH-
contaminated soil to temperatures of 335°C
over three days would reduce contaminant
mass more than 99.9%. Limitations of the AQC
system, however, prevented operation of all
ISTD heaters at the full design temperature in
areas of high contaminant mass. Based on
earlier laboratory evaluation of PAH oxidation
rates, it was determined that achieving a
slightly lower temperature for a longer
duration would achieve site-specific cleanup
goals. Atreatment paradigm was designed to
sustain a 300°C operating temperature for
thirty days. Overall treatment duration was
driven by the last location of the treatment
zone to achieve target temperature.
Field preparations began with installation of
654 heater-only and 131 heater-vacuum wells
in a triangular pattern to average depths of
20 ft across the 31,430-ft2treatment zone. A
light cement aggregate layer was constructed
over the surface to prevent subsurface heat
loss during phase 1. Based on phase 1 results,
polystyrene insulating board was added to
the phase 2 cover between a bottom layer of
light aggregate material and a top layer of
insulating cement. Two 2,500-kVA
transformers were installed to provide power
for the ISTD system, including the vacuum
blowers, AQC system, and well heaters.
The vacuum blower system included
magnehelic gauges for monitoring well-field
vacuum and ensuring that field boundaries
remained under negative pressure.
Thermocouples encased in steel pipe were
placed at 164 temperature-monitoring points;
some thermocouples were installed adjacent
to the heating elements, while others were
installed in cooler centroid locations in order
to track heat migration through the
subsurface. Air monitoring activities included
monthly compliance tests, continuous
tracking of AQC system emissions, and four
source-test events. The source tests involved
analysis of air samples at the AQC influent
and effluent as well as locations between the
thermal oxidizer and each granular activated
carbon (GAC) vessel. Well-field vacuum data
were collected at 18 monitoring points three
times daily, and vacuums were adjusted if
needed.
Post-treatment analysis of soil samples (60
for PAHs, 18 for dioxins/furans) taken from
shallow, mid-depth, and deep soil cores at 25
treatment-zone centroid locations showed
contaminant reductions exceeding 99%
(Figure 4). The average post-treatment
concentration for PCP was 1.25 mg/kg, and
sitewide means for dioxins/furans (TCDD
TEQ) and PAHs (B(a)P-E) were 0.11 |lg/kg
and 0.059 mg/kg, respectively, all below
remediation goals.
Daily measurements of carbon dioxide
concentrations in stack gas indicate that a
total hydrocarbon mass of 870,000 Ibs
(expressed as naphthalene) was removed from
soil during the entire project. Additional but
unmeasured contaminant mass likely was
destroyed as a result of in-situ pyrolysis and
oxidation. Pre- and post-treatment
measurements of soil hydraulic conductivity
and porosity indicated that ISTD did not
significantly impact soil properties.
[continued on page 6]
Contact Us
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View, download, subscribe,
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Technology News and Trends
welcomes readers' comments
and contributions. Address
correspondence to:
John Quander
Office of Superfund Remediation
and Technology Innovation
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U.S. Environmental Protection Agency
Ariel Rios Building
1200 Pennsylvania Ave, NW
Washington, DC 20460
Phone: 703-603-7198
Fax: 703-603-9135
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Solid Waste and
Emergency Response
(5203P)
EPA 542-N-06-007
January 2007
Issue No. 28
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
Presorted Standard
Postage and Fees Paid
EPA "
Permit No. G-35
Official Business
Penalty for Private Use $300
100,000.0
-s 10,000.0
n
^ 1,000.0
§
'% 100.0
10.0
1.0
0,1
0.0
30,600
B(a)P Equivalent
Dioxins (2,3,7,8-TCDD TEQ)
Cleanup
Goals
65 (ig/kg
B(a)P
Pre Treatment
N=47
Post Treatment
N=60
Figure 4. Mean
concentrations of post-
treatment soil samples
showed nearly complete
removal or destruction of
PAH concentrations
(based on B(a)P-E) and
dioxins (based on 2,3,7,8-
tetrachlorodibenzodioxin
equivalents).
[continued from page 5]
Factors to be considered in future ISTD
applications include: (1) Additional
characterization of a facility's former
infrastructure (obscuring high contaminant
mass) may lead to the use of a higher-
capacity vapor-treatment system over a
shorter treatment time. (2) Enhanced
surface covers are needed to maximize
vapor seal, minimize heat loss, and prevent
surface-water infiltration; rigid polystyrene
insulation is susceptible to degradation and
should be avoided. (3) Horizontal collectors
or shallower heater-vacuum well screens,
connected into a coarse-textured fill layer
above the treatment zone, would accelerate
removal of contaminated vapors and steam.
(4) ISTD efficiency at sites with non-aqueous
phase liquids or high contaminant mass may
be maximized through a phased approach
such as thermally enhanced free-product
recovery followed by high-temperature
treatment.
The total project cost was $13 million,
estimated to be 40% lower than soil
excavation. Costs for ISTD implementation
at sites with similar settings could potentially
be reduced 47% by applying lessons learned
during the Alhambra application.
Contributed by Tedd Yargeau, Cal EPA
Department of Toxic Substances
Control (tyargeau(q),dtsc.ca.gov or
818-551-2864) and John Bierschenk,
TerraTherm, Inc.
(jbierschenk(a)terratherm.com or
978-343-0300)
Errata
In the November 2006 article
"Emulsified-Oil Biobarrier Provides
Long-Term Treatment of Perchlorate/
VOC Plume," contaminants were
erroneously printed in unit measures
of "mg/L" rather than "u,Q/L" Readers
are requested to note the following
correction: Average concentrations of
target contaminants in the treatment
area were 9,000 u,g/L perchlorate,
11,000 u,g/L TCA, 50 u,g/L PCE, and
90 ug/TCE.
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative treatment techniques and
technologies. The Agency does not endorse specific technology vendors.
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