&EPA
Untied states
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA/540/R-94/527a
March 1995
SITE Technology Capsule
IITRI Radio Frequency
Heating Technology
Abstract
Radio frequency heating (RFH) technologies use electro-
magnetic energy in the radio frequency (RF) band to heat soil
insitu, thereby potentially enhancing the performance Of Stan-
dard soil vapor extraction(SVE) technologies. Contaminants
are remove d from in situ soils and transferred to collection or
treatment facilities.
The Illinois Institute of Technology Research Institute
(IITRI) RFH process was evaluated under the U. S. Environ-
mental Protection Agency (EPA) Superfund InnovatlveTech-
nology Evaluation (SITE) Program at a site containing various
organic contaminants in a heterogeneous soil matrix. Due to
changes in the original design and operational problems ex-
perienced during the demonstration, the treatment area was
evaluated as two separate zones: the "revised' design treat-
ment zone and the "heated' zone. The revised design treat-
ment zone reflects both changes made to the design of the
RFH system and operational problems associatsd with shal-
low groundwater at the test site. The heated zone consists of
the area that achieved the target temperature of 150°C.
Concentration changes were calculated from paired pre-
and post-demonstration soil samples; these concentration
changes were evaluated for statistical significance. Conclu-
sions have been drawn based only on data thai were statisti-
cally significant at greater than or equal to the 90 percent
confidence level.
Within the revised design treatment zonethe estimated
mean concentration decrease for Total Recoverable Petro-
leum Hydrocarbons (TRPH) was 60 percent. Estimated mean
concentration decreases for twosemivolatile organic com-
pounds (SVOCs), pyrene and bis(2-ethylhexyl)phthalate were
87 and 48 percent respectively. There were statistically sig-
nifiiant increases in the concentrations of four volatile organic
compounds (VOCs); the estimated mean concentration in-
creases were 457 percent for 2-hexanone; 263 percent for 4-
methyl-2-pentanone; 1,073 percent for acetone; and 683
percent for methyl ethyl ketone.
Outside of the revised design treatment zone, only TRPH
showed a statistically significant change with an estimated 88
percent increase in the mean concentration.
Within the heated zone the estimated mean concentra-
tion decrease was 95 percent for TRPH.
Outside the heated zone, the estimated mean concentra-
tion decrease was 37 percent for bls(2-ethylhexyl)
phthalate; estimated mean concentration increases were 423
percent for 2-hexanone: 249 percent for 4-methyl - 2-pentanone;
1,347 percen t for acetone: and 1,049 percent for methyl ethyl
ketone.
Several possible reasons exist for changes In concentra-
tion observed. They include inward contaminant migration,
low extraction rates, widely varying soil temperatures, low
pretreatment contaminant concentrations in the soil, and the
potential degradation of TRPH and SVOCs.
The estimated cost to treat 10,152 tons of contaminated
soil based on a scaleup of the revised design treatment zone
is $619 per ton; the estimated cost to treat 8,640 tons of
contaminated soil based on IITRI's theoretical system design
is $340 per ton.
The IITRI RFH technology was evaluated based on the
nine criteria used for decision making in the Superfund feasi-
bility study (FS) process. Results of the evaluation ars sum-
marized in Table 1. This evaluation was based on information
from the SITE demonstration conducted at Kelly Air Force
Base (AFB).
Introduction
In 1980, the U.S. Congress passed the Comprehensive
Environmental Response, Compensation, and Liability Act
(CERCLA), also known as Superfund, committed to protect-
ing human health and the environment from uncontrolled
hazardous waste sites. CERCLA was amended by the Super-
fund Amendment and Reauthorization Act (SARA) in 1986.
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Printed on Recycled Paper
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Table 1. Evaluation Criteria for the IITRI RFH Technology1
Evaluation Criteria
Performance
Overall Protection of Human Health and the
Environment
Compliance with Federal ARARs1
Long-form Effectiveness and Performance
Reduction of Toxicity, Mobility, or Volume
through Treatment
Short-term Effectiveness
Implementability
Cost3
State Acceptance
Community acceptance
Site-specific treatability studies will be needed to verify #10 levels of
contaminant removal achievable
Requires measures to protect workers during installation and treatment
Additional contaminants may form at high temperatures if not properly
designed or operated
Vapor collection and treatment are needed to ensure compliance with air
quality standards
Construction and operation of an onsite vapor treatment unit may require
compliance witfi location-specific ARARs
RF generator must be operated in accordance with National Institute of
Occupational Safety and Health (NIOSH) and Federal Communication
Commission (FCC) requirements
As with all SVE-based systems, the contamination source may not be
adequately removed
Involves some residuals treatment (vapor stream)
Potentially concentrates contaminants, reducing waste volume
Potentially reduces contaminant mobility, although downward mobility of
contaminants during treatment has not been quantified
May form new contaminants, thereby potentially reducing or increasing
toxicity, if not properly designed or operated
Presents minimal short-term risks to workers and community from air
release during treatment
No excavation is required, although drilling will disturb the soil to some
extent
RF generator must be operated in accordance with NIOSH and FCC
requirements
Pilot-scale tests have been completed at two other sites to evaluate the
technology; no full-scale applications to date
Because of operational problems experienced during the SITE
demonstration, consistent soil heating was not observed
Cost evaluation based on revised design treatment zone is $619 per ton;
cost evaluation based on IfTRI's theoretical system design is $340 per ton
No excavation is required, which should improve state acceptance
No excavation Is required, which should improve community acceptance
Potential health effects of RF fields may be an issue
Based on the results of the SITE demonstration at Kelly AFB
ARARs = Applicable or Relevant and Appropriate Requirements
Actual cost of a remediation technology is site-specific and dependent on the target cleanup level, contaminant concentrations,
soil characteristics, and volume of soil. Cost data presented in this table are based on the treatment of 10,152 tons of soil
(scale-up based on the revised design treatment zone) and 8,640 tons of soil (based on IITRI's theoretical system design).
These amendments emphasize the achievement of long-term
effectiveness and permanence of remedies at Superfund sites.
SARA mandates implementing permanent solutions and using
alternative treatment technologies or resource recovery tech-
nologies, to the maximum extent possible, to clean up hazard-
ous waste sites.
State and federal agencies, as well as private parties, are
now exploring a growing number of innovative technologies for
treating hazardous wastes. The sites on the National Priorities
List total more than 1,200 and comprise a broad spectrum of
physical, chemical, andenvironmental conditions requiring vary-
ing types of remediation. The EPA has focused on policy,
technical, and informational issues related to exploring and
applying new remediation technolo gy applicable to Super-
fund sites. One such initiative is EPA's SITE Program, which
was established to accelerate development, demonstration,
and use of innovative technologies for site cleanups. EPA SITE
Technology Capsules summarize the latest information avail-
able on selected innovative treatment and site remediation
technologies and related issues. These capsules are designed
to help EPA remedial project managers, EPA on-scene coordi-
nators, contractors, and other site cleanup managers under-
stand the type of data and site characteristics needed to
effectively evaluate a technology's applicability for cleaning up
Superfund sites. Additional details regarding technology dem-
onstrations are presented in the Innovative Technology Evalu-
ation Reports.
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This capsule provides information on thellTRI in situ RFH
technology. This technology was developed to improve the
removal ofVOCs and SVOCs from the soil using standard
SVE technologies. The IITRI RFH process was evaluated un-
der the SITE Program from January through August 1993 at
Kelly AFB in San Antonio, Texas. This demonstration was
performed In conjunction with a technology evaluation per-
formed by the U.S. Air Force (USAF). Information in this cap-
sule emphasizes specific site characteristics and results of the
SITE field demonstration at Kelty AFB. The capsule presents
the following information:
Technology Description
• Technology Applicability
• Technology Limitations
• Process Residuals
Site Requirements
• Performance Data
• Technology Status
• Sources of Further Information
References
Technology Description
RFH technologies use RF energy to heat soil in situ,
thereby potentially enhancing the performance of standard
SVE technologies. The RF energy causes dielectric heating of
the soil, which is a faster and more efficient mechanism for
heating solids than is convective heating. Some conductive
heating also occurs in the soil.
In IITRI's proprietary system, an RF generator supplies
energy to exciter electrodes, which are copper pipes installed
in vertical boreholes. Copper balls welded onto the ends of the
exciter pipes help distribute the energy, which tends to concen-
trate at these points. As the soil is heated due to the dissipa-
tion of the RF energy, contaminants and moisture in the soil
are vaporized and pulled toward ground electrodes, which also
serve es vapor extraction wells. The vaporized water may act
as a steam sweep to further enhance the removal of organic
contaminants. A standard SVE system provides a vacuum to
the ground electrodes and transfers the vapors to collection or
treatment facilities. Contaminants are treated using standard
vapor treatment techniques. After soil treatment is complete,
the soil is allowed to cool. The SVE system may be operated
during part or all of this cooling period. The exact numbers of
exciter and ground electrodes, electrode configurations, vapor
collection or treatment techniques, and other design details are
site-specific.
Figure 1 is a schematic diagram of the IITRI RFH system
used for the SITE technology demonstration at Kelly AFB;
Figure 2 is a cross-section of IITRI's RFH system. A 40-kW RF
generator served as the energy source for the system. Energy
was supplied to the exciter electrodes for approximately 9
weeks via coaxial cables. Reflected energy was measured,
and the electrical characteristics of the transmitted RF energy
were adjusted as necessary. Exciter electrodes were con-
structed of 2.5 and 4-inch (nominal diameter) copper pipe and
were installed in 10-inch boreholes to a depth of 19.5 feet
below the surface. The boreholes were backfilled around the
electrodes using a material similar to the surrounding soil. Four
exciter electrodes spaced 2.5 feet apart were installed in a row.
Two rows of eight ground electrodes each were installed
parallel to and on either side of the exciter electrode row. The
ground electrodes were fabricated from 2-inch-diameter alumi-
num pipes. The electrode configuration was designed to direct
the flow of RF energy through the soil and contain the energy
within the treatment zone. With the exception of the four corner
electrodes that were not perforated, the ground electrodes
were perforated on the side facing the treatment zone to permit
the collection of vapors from the soil. They were perforated in 8
uniform pattern over the full length of the electrodes. Each
perforated ground electrode was connected to a manifold,
which led to the vapor treatment system. Two additional perfo-
rated vapor extraction pipes were installed parallel to the ground
surface to prevent buildup of vapors below the vapor barrier.
As shown in Figure 1, the insulated vapor barrier extended
several feet over the surface of the ground end exciter elec-
trodes to prevent heat loss, contaminant emission, and air
infiltration. A sheet of expanded aluminum covered the same
area as the vapor barrier and was designed to contain RF
energy. An arched aluminum shield that covered only the
electrodes in the treatment zone was also designed to ocntain
RF energy. To complete the RF ocntainment system, the
arched RF shield was electrically connected to the ground
electrodes by aluminum wire mesh.
The system was designed to heat the soil evenly to a
temperature of approximately 150°C. The soil heating began at
the top of the treatment zone near the exciter electrodes, and
the heated zone expanded outward and downward over time.
The original area to be treated measured 10 feet wide by 17.5
feet long by 29 feet deep. Due to shallow groundwater and
operational problems encountered during the demonstration,
the treatment zone was revised to 10 feet wide by 14.1 feet
long by 23.3 feet deep. The RFH syaem was evaluated using
this '"revised" design treatment zone. The RFH system was
also evaluated using the "heated" zone, which is the area that
achieved the target temperature of 150°C. This zone measures
5.7 feet wide by 10.3 feet long by 20.0 feet deep. Tempera-
tures wtihin and outside both treatment zones were monitored
at various depths throughout treatment. Contaminant removals
inside and outside each of these zones were evaluated sepa-
rately; results of these evaluations are presented in the Perfor-
mance Data Section.
The vapor extraction system was operated throughout the
9-week heating period and for approximately 2 months during
the cooldown period. The vapor extraction system was oper-
ated at a suction pressure of at least 7 inches of water column
while heat was being applied to the soil. Vapors were extracted
from the soil at a rate of approximately 120 standard cubic feet
per minute (scfm). Condensate that formed in the system was
collected; uncondensed vapors were burned in a propane flare.
Technology Applicability
The heat provided by the RFH process increases the
vapor pressure of contaminants In the soil, thereby potentially
improving the effectiveness of SVE. RFH may make it possible
to remove SVOCs that would not normally be removed by
standard SVE technologies. RFH may also speed the removal
of VOCs, which can be removed by standard SVE technolo-
gies. Contaminants that can potentially be removed using RFH
include a wide variety of organics such as halogenated and
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60 Hz
AC Power
Distribution!
Vapor Barrier Perimeter
Gratmd ElectrodBS
A1 A2
A3
A5 A6 A7
1&5
Exciter Electrodes
'1 TW2 31 82
XXX
TW3 TW4 TW6
Ground Eec-trodes
C1 C2 C3
C4
TW7
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Vapor
Collection
Manifold
Stage 1
Matching
Network
Teirperature
Measurement
Probe Lines
Figure 1. Schematic diagram otltTRt's RFH system.
nonhalogenated solvents and straight-chain and polycyclic aro-
matic hydrocarbons found in gasoline, jet fuel, and diesel fuel.
Inorganics, metals, and other nonvolatile contaminants will not
normally be treated by SVE or RFH technologies.
A previous study (not sponsored by the SITE program)
conducted at Volk AFB indicated that IITRI's RFH system
effectively removed VOCs and SVOCs from a small treatment
zone containing homogenous, sandy soils. The soil in the Kelly
AFB treatment zone was a heterogeneous mixture of sand,
clay, and gravel. Due to the operational problems encountered
during the Kelly AFB study, it cannot be determined how the
heterogeneous soil matrix affected RFH system effectiveness.
However, soils containing large amounts of silt, clay, and
humic substances tend to adsorb organic contaminants more
tightly. Soils containing a large fraction of clay may also have
insufficient air permeability for adequate contaminant removal
by SVE or RFH technologies. Site-specific, in situ treatability
studies will need to be conducted to confirm the applicability of
this technology.
Technology Limitations
IITRI claims its technobgy is not ready for commercializa-
tion. Considerable development and optimization of the pro-
cess would be required before a full-scale system would be
ready for field use. For example, IITRI must demonstrate the
system's ability to treat an entire site and to use an RF
generator that can supply more than 40 kW of RF energy. The
IITRI RFH technology cannot be used as a stand-alone tech-
nology. Vaporized contaminants and steam must be collected
for reuse or treatment. In some cases, residual contaminants
may remain in the soil after treatment
This technology currently appears to be limited to unsatur-
ated soils, although groundwater pumping may be used to
lower the water table and extend the treatment zones. RFH is
further limited to soils contaminated wirh VOCs and SVOCs.
Nonvolatile organics, metals, and inorganics will not normally
be removed by RFH or SVE technologies.
Process Residuals
The IITRI RFH process generates one process waste
stream that contains vaporized oontaminants and steam di-
luted in extraction air. This waste stream can be treated by any
of a number of standard vapor treatment technologies includ-
ing vapor-phase carbon, condensation, or incineration. During
the SITE demonstration at Kelly AFB, a propane flare was
used to treat uncondensed contaminants in the vapor waste
stream.
Steam and contaminants in the vapor stream that con-
densed in the vapor collection system were collected prior to
the flare. These condensed residuals were handled along with
other site wastes at Kelly AFB. When groundwater is pumped
to lower the water table, the groundwater must also be handled
as a liquid residual.
Soms soil contaminants may remain after treatment. Sig
nificant quantities of several organics remained In the soil after
treatment was completed at Kelly AFB, although remediation of
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{corrugated
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Protective teflon tubing
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measurements)
Coaxial cable (supplies
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Figure 2. Cross-section of IITRI's RFH system.
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the site was not an objective of the demonstration. Further
treatment will be required to fully remediate these soils.
Site Requirements
Onsite assembly of the full-scale system will take several
weeks, including drilling time. It is expected that medium to
large sites will be divided into several sections that will be
treated consecutively. The soil must be allowed to cool before
final soil samples can be collected to confirm cleanup of each
section. Soil cooldown will take up to several months if portions
of the soil reach 1,000°C, as they did during the SITE demon-
stration. However, with proper disign and operation, soil heat-
ing may be more uniform, resulting in lower soil temperatures
and faster cooldown. After treatment is completed, system
demobilization may take up to a week. Access roads are
needed for equipment transport. Approximately 4,600 ft2 of
level ground are needed to accommodate the trailer-mounted
RF generators, controllers, and other support equipment. A
bermed area IS needed for decontamination of the drill rig.
Area is also needed for storage of condensed vapors, if appli-
cable, and the selected vapor treatment system.
Remediation using the RFH process will require that cer-
tain utilities be available at the site. Water must be available for
steam-cleaning and other equipment and personnel decon-
tamination acivities. Electrical power must also be available.
The RF generator requires 480-volt, 3-phase power, and most
of the minor system components require 240-volt, single-phase
power. If carbon adsorption is used to treat vapors, com-
pressed air may be required for system control, and steam or
hot air will be needed if the carbon is regenerated onsite.
Natural gas or propane will be required if a flare is used to
control vapors.
The ground electrodes, expanded aluminum sheet, arched
aluminum shield, and aluminum wire mesh minimize RF en-
ergy emissions. Monitoring should be conducted to ensure that
the RF field outside of the treatment zone does not exceed
NIOSH or FCC requirements. These regulations were report-
edly met during the SITE demonstration and other previous
field studies. The system is relatively quiet, and only during
installation will dust and vapors be a potential problem. There-
fore, the RFH technology can be applied near residential ar-
eas.
Performance Data
The system was designed to heat the soil evenly to a
temperature of approximately 150°C. Soil temperatures were
monitored by the vendor throughout the 61 day treatment pe-
riod during which RF energy was applied to the soil. Before
treatment began, the soil temperature throughout the area was
approximately 20°C. During the SITE demonstration, the RF
energy applied to the exciter electrodes progressed gradually
from the surface to the deepest point of each exciter electrode.
The soil temperature near the ground electrodes increased
gradually as RF energy flowed from the exciter electrodes to
the ground electrodes. Near the end of the demonstration all
exciter electrode temperatures varied widely; maximum tem-
peratures near the exciter electrodes exceeded 1,3000°C. Tem-
peratures near the ground electrodes did not exceed 112°C
near the surface, and did not exceed 52°C below 24 feet.
Based on temperature measurements, it appears that a system
malfunction could have resulted in incomplete heating of the
revised design treatment zone. IITRI believes this malfunction
was a result of electrical problems due to shallow groundwater.
Groundwater levels may have been higher than originally
expected by the vendor. Due to the presence of shallow ground-
water, IITRI shortened the exciter electrodes to avoid potential
system operational problems. Groundwater levels were moni-
tored infrequently, so insufficient data are available to deter-
mine exact water levels during the demonstration. However,
exciter electrodes removed after the demonstration had melted.
Since copper melts at approximately 1,100°C, these electrodes
provide evidence of a system malfunction that prevented full
utilization of RF power for soil heating. Based on IITRI's soil
temperature logs, it appears that the system malfunction oc-
curred during the last weeks of the heating period.
Contaminant removal during the demonstration was evalu-
ated by measuring contaminant concentrations in the soil be-
fore and after treatment. Soil samples were collected using
split spoons with stainless steel sleeves before and after the
soil was treated. The samples were collected as matched
pairs; each post-treatment sample was collected as near as
possible to its corresponding pretreatment sample. Within the
revised design treatment zone, 26 matched pairs of soil samples
were collected; 9 matched pairs of soil samples were collected
outside this zone. Within the heated zone, 6 matched pairs of
soil samples were collected; 31 matched pairs of soil samples
were collected outside this zone. Only complete matched pairs
were used in the evaluation of the data. A complete matched
pair was defined as a matched pair in which both pre- and
post-treatment samples were collected and analyzed, and in
which the compound being evaluated was measured at a
concentration greater than the detection limit in at least one of
the two samples. The number of complete matched pairs was
limited by the low pretreatment concentrations of many con-
taminants in the soil. This made t difficult to determine any
change after treatment because pretreatment concentrations
were often below analytical quantitation limits.
For each contaminant, the population distribution of the
concentration data was evaluated. Most contaminants were
log-normally distributed, and as a result, concentration data
were log transformed. The ratio of post-treatment concentra-
tion to pretreatment concentration was calculated for each
complete matched pair. The resulting set of ratios for each
contaminant of interest was evaluated using a t-test to deter-
mine whether the contaminant concentration exhibited a statis-
tically significant change between the pre- and post-treatment
sampling events. The mean ratio of post-treatment concentra-
tion to pretreatment concentration was also calculated for each
contaminant. The mean ratio was then converted to either the
mean percent decrease or the mean percent increase, as
appropriate. Conclusions have been drawn based only on
changes that were statistically significant at the 90 percent
confidence level or greater.
Because of the high concentrations of TRPH expected at
the site, TRPH was designated as an indicator (i.e., critical)
contaminant. Method 418.1 [I] was used to determine TRPH
concentrations in the soil samples following extraction with
Freon according to Method 9071 [2].
Soil samples were extracted by Method 3540 [2] and
analyzed for SVOCs using Method 8270 [2]. Five SVOCs were
designated as indicator (i.e., critical) compounds because their
concentrations were expected to be significant. These included
2-methylnaphthalene; naphthalene; 1,2-dichlorobenzene; 1,3-
dichlorobenzene; and 1,4-dichlorobenzene. Because a prelimi-
nary statistical evaluation did not indicate any significant changes
in the concentrations of these compounds, none of them were
included in the final statistical evaluation and no conclusions
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can be drawn. Two other (i.e., non-critical) SVOCs were statis-
tically evaluated because they exhibited concentration de-
cre ases.
Method 824 0 [2] was used to determine VOC concentra-
tions in the soil samples. Benzene, toluene, ethylbenzene, total
xylene. and chlorobenzene were designa d as indicator (i.e.,
critical )VOCs because of their expected high concentrations.
A preliminary statistical evaluation conducted for these five
compounds indicated that only chlorobenzene exhibited a
change in concentration, and was, therefore, the only indicator
VOC included in the final evaluation. However in the final
statistical evaluation, chlorobenzene did not exhibit a statisti-
cally significant change at the 90 percent confidence level.
Four othe rVOCs were statistically evaluated because they
exhibite d concentration increases.
Revised Design Treatment Zone Results
The following results were observed within the revised
design treatment zone:
* There was a statistically significant decrease in TRPH con-
centration at the 95 percent confidence level: the estimated
decrease in the mean concentration was 60 percent.
• No conclusions can be drawn regarding the five indicator
SVOCs.
There were statiscally significant decreases in the concen-
trations of two other SVOCs, pyrene and bis(2-.
ethylhexyl)phthalate, at the 97.5 percent confidence level;
estimated decreases in the mean concentrations were 87
and 48 percent .respectively.
The decreases in TRPH and SVOCs are likely due to the
performance of the RFH system, which may have resulted in
the volatilization of contaminants, allowing them to be collected
by the SVE system. These decreases may also have been
caused by the degradation of these compounds from the el-
evated temperatures of the RFH system. Decreases from out-
ward migration are unlikely, since the configuration of the SVE
system would limit this type of migration.
For th eVOCs within the revised design treatment zone,
the following results were observed:
* There wss no statistically significant change in the concen-
tration o fchlorobenzene at the 90 percent confidence level.
No conclusions can be drawn regarding the other four
indicator VOCs.
- There were statistically significant increases in the concen-
trations of four other VOCs (all ketones) at the 99 percent
confidence level; estimated increases in the mean concen-
trationswere 457 percent for 2-hexanone, 263 percent for
methyl-2.pentanone, 1,073 percent for acetone, and 683
percent for methyl ethyl ketone.
The ketones may have been formed by the degradation of
TRPH and SVOCs near the exciter electrodes,, where soil
temperatures were highest. A possible degradation pathway
may be the pyrolytic conversion of TRPH to unsaturated hydro-
carbons. In the presence of sufficient oxygen and a catalyst
(e.g., silica in the soil), the RF energy may convert these
hydrocarbons into ketones. The increase in ketones may also
have been caused by inward migration. Possible sources of
ketones are the groundwater, which was not sampled, and the
soil beyond the sampled area, although these sourc es cannot
be verified. However, there are insufficient data to confirm or
disprove either of these hypotheses. Statistically significant
changes in TRPH, SVOC, and VOC concentrations in the
revised design treatment zone are listed in Table 2.
Outside of the revised design treatment zone, only TRPH
showed a statistically significant change at the 95 percent
confidence level, with an estimated 88 percent mean concen-
tration increas e. Based on the configuration of the SVE sys-
tem, this increase may have been due to inward migration;
however, it is not likely this increase was due to outward
migration from the revised design treatment zone.
Heated Zone Results
The following results were observed within the heated
zone:
• There was a statistically significant decrease in TRPH con-
centration at the 97.5 percent confidence level the estimated
decrease in the mean concentration was 95 percent.
• No conclusions can be drawn regarding the five indicator
SVOCs.
• No conclusions can be drawn regarding the five indicator
VOCS.
The TRPH decrease may be the result of the SVE system
pulling the contaminants out of the heated zone into the vacuum
wells. As in the revised design treatment zone, this decrease
may also have been the result of the degradation of these
compounds caused by the elevated temperatures of the RFH
system.
There was also a statistically significant decrease in the
concentration of bis(2-ethylhexyl)phthalate at the 90 percent
confidence level outside the heated zone; the estimated de-
crease in the mean concentration was 37 percent. As inside
the two zones, this decrease may be caused by the SVE
system pulling the contaminant into the vacuum wells or by
degradation due to the elevated temperatures of the RFH
system.
There were statistically significant increases at the 99
percent confidence level in the concentrations of four other
VOCs (all ketones) outside the heated zone. The estimated
mean increases for these four ketones were 423 percent for 2-
hexanone, 249 percent for 4-methyl-2-pentanone, 1,347 per-
cent for acetone, and 1,049 percent for methyl ethyl ketone. As
previously explained, these ketones may have been formed by
the degradation of TRPH and SVOCs or inward migration.
Several possible reasons exist for changes in concentra-
tion observed. They include inward contaminant migration, low
extraction rates, low soil temperatures achieved in some areas,
and low pretreatment contaminant concentrations in the soil.
Two-dimensional modeling of gas flow rates was used to
qualitatively evaluate inward migration and treatment zone ex-
traction rates. The results of this modeling indicate inward gas
flows. Due to inefficiencies in the design of the SVE system,
gas flows between the outer edge of the impermeable cap and
the extraction wells are five times greater than those between
the two rows of extraction wells. As a result, contaminant
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migration into the treatment zone is possible, especially near
the outer edges, and contaminant removal from the treatment
zone may have been relatively slow as compared to inward
contaminant migration.
Concentrations of TRPH and specificVOCs and SVOCs In
the gas stream were monitored by a USAF subcontractor and
were not part of the SITE demonstration. However, the appro-
priateness of the methods used and the quality of the data are
unknown. The results appear to qualitatively indicate removals
of TRPH and certain VOCs and SVOCs. Because of limitations
of the sampling and analytical methods, the quantity of con-
taminants removed cannot be estimated .
Technology Status
Information Is currently available from IITRI on two field
studies (not sponsored by the SITE program) conducted at
VolkAFB and Rocky Mpuntain Arsenal [3][4]. IITRI is perform-
ing a larger test at Sandi a National Laboratory. Results of the
Kelly AFB demonstration are documented in this capsule.
IITRI claims itstechnology is not ready for commercializa-
tion. Considerable development and optimization of the pro-
cess would be required before a 1
ready for field use.
ll-scale system would be
A 300-kW full-scale syste m has been proposed. The cost
of a full-seal etreatment system , based on the result s obtained
from the revised deslg n treatment zone, is estimated to be
$619 per ton for a site containing 10,192 tons of contaminated
soil. The cost of a full-scale system treatment system, based
on IITRI's theoretical system design, Is $340 per ton for a site
containing 9,640 tons of contaminated soil. Costs associated
with analyses, site preparation, permitting, effluent treatment
and disposal, and residuals and waste shipping are considered
site-specific coststhat will be assumed by the site owner or
responsible party. As a result, these costs are not included in
the per ton cost estimates.
Disclaimer
Although the technology conclusions presented in this
report may not change, the data have not been reviewed by
EPA Risk Reductio n Engineering Laboratory Quality Assur-
ance personnel at this time.
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Sources of Further Information
EPA Contact:
Laurel Staley
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati. OH 45268
Telephone No.: 513-569-7863
Fax No.: 513-569-7620
Technology Developer:
Harsh Dev
NT Research Institute
10 West 35th Street
Chicago, IL 60616-3799
Telephone No.: 312-567-4257
Kelly AFB Project Engineer for Site S-1 RFH
Field Demonstration:
Victoria Wark
SA-ALC/EMRO
305 Tinker Drive, Suite 2, Building 305
Kelly AFB, TX 78241-5915
Telephone No.: 210-925-1812
Brown and Root Environmental Project
Manager:
Clifton Blanchard
Brown and Root Environmental
800 Oak Ridge Turnpike, Suite A600
Oak Ridge, TN 37830
Telephone No.: 615-483-9900
References
1. U.S. Environmental Protection Agency, EPA Methods for
Chemical Analysis of Water and Wastes. 1983.
2. U.S. Environmental Protection Agency, Test Methods for
Evaluating Solid Waste (SW-846): Third Edition, Novem-
ber, 1986, and Final Update I, September, 1990.
3. Program Manager for Rocky Mountain Arsenal, Final
Rocky Mountain Arsenal Task 012 In Situ Radio Fre-
quency/Vapor Extraction Pilot Test Plan. Document Con-
trol Number 53300-01-12-AACB.
4. Illinois Institute of Technology, In Situ Soil Decontamina-
tion by Radio-Frequency Heating Field Test, September
1989.
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