United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA 540/R-94/528a
January 1995
E PA SITE Technology Capsule
KAI Radio Frequency
Heating Technology
Introduction
In 1980 the U.S. Congress passed the Comprehensive
Environmental Response, Compensation, and Liability Act
(CERCLA), also known as Superfund, committed to protecting
human health and the environment from uncontrolled hazard-
ous waste sites. CERCLA was amended by the Superfund
Amendments and Reauthorization Act (SARA) in 1986. These
amendments emphasize the long-term effectiveness and per-
manence of remedies at Superfund sites. SARA mandates
implementing permanent solutions and using alternative treat-
ment technologies or resource recovery technologies, to the
maximum extent possible, to clean up hazardous waste sites.
State and Federal agencies, as well as private parties,
are now exploring a growing number of innovative technolo-
gies for treating hazardous wastes. The sites on the National
Priorities List total more than 1,200 and comprise a broad
spectrum of physical, chemical, and environmental conditions
requiring varying types of remediation. The U.S. Environmen-
tal Protection Agency (EPA) has focused on policy, technical,
and informational issues related to exploring and applying
new remediation technologies applicable to Superfund sites.
One such initiative is EPA's Superfund Innovative Technology
Evaluation (SITE) Program, which was established to acceler-
ate development, demonstration, and use of innovative tech-
nologies for site cleanups. EPA SITE Technology Capsules
summarize the latest information available on selected inno-
vative treatment and site remediation technologies and re-
lated issues. These capsules are designed to help EPA
remedial project managers, EPA on-scene coordinators, con-
tractors, and other site cleanup managers understand the
type of data and site characteristics needed to effectively
evaluate a technology's applicability for cleaning up Super-
fund sites. Additional details regarding technology demon-
strations are presented in the Innovative Technology Evaluation
Reports.
This capsule provides information on the in situ radio
frequency heating (RFH) technology developed by KAI Tech-
nologies, Inc. This technology was developed to remove
semivolatile organic compounds (SVOCs) and volatile organic
compounds (VOCs) from the soil without excavation. The KAI
RFH process was evaluated under the SITE Program from
January through July 1994 at Kelly Air Force Base (AFB) in
San Antonio, Texas. This demonstration was performed in
conjunction with a technology evaluation performed by the
U.S. Air Force (USAF). Information in this capsule empha-
sizes specific site characteristics and results of the SITE field
demonstration at Kelly AFB. This capsule presents the follow-
ing information:
Abstract
Technology description
Technology applicability
Technology limitations
Process residuals
Site requirements
Performance data
Technology status
Sources of further information
References
Abstract
RFH technologies use electromagnetic energy in the ra-
dio frequency (RF) band to heat soil in situ, thereby potentially
enhancing the performance of standard soil vapor extraction
(SVE) technologies. Contaminants are removed from in situ
soils and transferred to collection or treatment facilities. Con-
taminant removal during the demonstration was evaluated by
measuring contaminant concentrations in the soil before and
after treatment.
The KAI RFH process was evaluated under the SITE
Program at a site containing various organic contaminants in
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Printed on Recycled Paper
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a heterogeneous soil matrix. The original treatment zone was
10 feet wide, 15 feet long, and 20 feet deep. Because RF heat
was actually applied only to the upper half of the original
treatment zone, this upper region is being designated the
"revised treatment zone." A comparison of pre- and post-
treatment soil samples within these two zones yielded the
following results:
Within the original treatment zone, the mean removal for total
recoverable petroleum hydrocarbons (TRPH) was 30 percent, which
was statistically significant at the 80 percent confidence interval.
Concentrations in the pre-treatment samples varied from less than
169 to 105,000 parts per million (ppm); post-treatment samples
varied from less than 33 to 53,200 ppm.
Within the revised treatment zone, the mean removal for TRPH was
49 percent, which was statistically significant at the 95 percent
confidence interval. Concentrations in the pre-treatment samples
varied from less than 169 to 6,910 ppm; post-treatment concentra-
tions varied from less than 33 to 4,510 ppm.
Pre- and post-treatment concentrations of individual SVOCs were
also measured. Benzo(b)fluoranthene, benzo(a)pyrene, and bis(2-
ethylhexyl)phthalate exhibited statistically significant removals within
the original treatment zone. Benzo(b)fluoranthene, benzo(a}pyrene,
chrysene, pyrene, and fluoranthene exhibited statistically significant
removals within the revised treatment zone.
Pre- and post-treatment concentrations of individual VOCs were
also measured, but these data did not indicate any statistically
significant removals. This was partially a result of the low pretreat-
ment concentrations of many VOCs.
The migration of contaminants into and out the revised treatment
zone was also evaluated. Downward migration out of the revised
treatment zone may have occurred due to the design and operation
of the SVE system.
The cost to treat approximately 10,000 tons of contaminated soil
using a proposed full-scale in situ RFH system (including costs
associated with SVE) was estimated by scaling up costs for the
original treatment zone. Cleanup costs are estimated to be $315 per
ton if the system is utilized 90 percent of the time.
Contaminant removals were not as high as projected.
Because of timing and funding limitations placed on the project
by the USAF, only a portion of the revised treatment zone
reached the target temperature of 100 to 130°C. It appears
that the treatment zone did not achieve adequate temperature
to achieve the goal of 90 percent removal of TRPH, The
design and operation of the SVE system and problems with the
available electrical power may have also adversely affected
contaminant removals.
The KAI RFH technology was evaluated based on the nine
criteria used for decision making in the Superfund feasibility
study (FS) process. Results of the evaluation are summarized
in Table 1.
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 radiative 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.
Figure 1 is a schematic diagram of the KAI RFH system
used for the SITE Technology Demonstration at Kelly AFB.
The Quality Assurance Project Plan (QAPP) developed under
the SITE Program described KAI's original treatment zone,
which was 10 feet wide, 15 feet long, and 20 feet deep. To
adapt to budgetary and time constraints associated with the
USAF funding, KAI modified their system to treat the revised
treatment zone, which was 10 feet wide and 15 feet long but
only extended from 4 feet below ground surface (bgs) to 14
feet bgs.
A 25-kW, 27.12-MHz RF generator served as the energy
source for the system. Coaxial transmission lines supplied
energy alternately to two antennae installed near the center of
the revised treatment zone, progressively heating the soil in a
radial direction from each antenna. Water and contaminants
volatilized as the soil was heated.
RF energy was initially applied to antenna A2 for 28.9
days, was then applied to antenna A1 for 8.2 days, and back to
antenna A2 for 12.9 days. At any given time, the soil near the
antenna to which RF energy was being applied absorbed more
energy than the soil located further away from that antenna.
Extraction wells were installed prior to treatment. The
system used during the SITE Demonstration employed six
extraction wells on the edges of the revised treatment zone
and two extraction wells near the center of the revised treat-
ment zone. These extraction wells are shown and labelled in
Figure 1. Only two of the extraction wells (E2 and E7) had
screened intervals that approximately matched the depth of the
revised treatment zone. These two wells were screened from
0 to 10 feet bgs; the other six extraction wells were screened
from 10 to 20 feet bgs.
An SVE system provided a vacuum to one or more extrac-
tion wells. The vacuum level and the extraction wells to which
the vacuum was applied were varied periodically. Vacuum
was not applied to wells E6, E7, or E8 at any time, and they
were capped for most of the demonstration. The SVE system
initially operated at a suction pressure of 30 inches of water
column for 22 days. The vacuum was gradually reduced
throughout the rest of the demonstration to a low of 7 inches of
water column while heat was being applied. The flow rate
through the vapor treatment system was approximately 120
standard cubic feet per minute (scfm). The SVE system was
operated for 8 days before heating was initiated, throughout
the heating portion of the demonstration (50 days), and for 14
days as the soil cooled down after treatment.
The vapors collected during the demonstration were treated
using standard techniques. Condensate that formed in the
vapor collection and treatment systems was collected, and
then transferred to a Kelly AFB wastewater treatment facility.
Uncondensed vapors were burned in a propane flare. This
vapor treatment system was site- and contaminant-specific and
was not evaluated as part of the RFH system. Samples of the
vapors being extracted from the soil were, however, collected
and analyzed periodically to characterize the vapor stream.
At the end of the treatment period, the soil was allowed to
cool. Soil contamination was measured both before and after
treatment. Concentrations of TRPH and specific SVOCs and
VOCs were measured in matched pairs of pre- and post-
treatment soil samples. Within the original treatment zone, 40
matched pairs of soil samples were collected; 22 of these
matched pairs were within the revised treatment zone. Outside
the original treatment zone, 24 matched pairs of soil samples
were collected. As specified in the QAPP, all matched pairs of
samples were analyzed for TRPH, and half of the matched
pairs were analyzed for specific SVOCs and VOCs.
The implementation of the KAI RFH system varies de-
pending on site size and characteristics. Vapor collection or
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Table 1. Evaluation Criteria for the KAIRFH Technology
Evaluation Criteria
Performance
Overall Protection of Human
Health and the Environment
The contaminant removals achieved may not provide adequate protection.
Requires measures to protect workers during installation and treatment.
During Ihe limited time period of the SITE demonstration, soil samples exhibited
average TRPH removals of 30 percent in the original treatment zone and 49 percent in the revised treatment
zone.
Vapor collection and treatment are needed to ensure compliance with air quality standards.
Construction and operation of onsite vapor treatment unit may require compliance with location-specific
ARARs.
RF generator must be operated in accordance with Occupational Safety and Health Administration (OSHA) and
Federal Communication Commission (FCC) requirements.
The contaminant removals achieved during the limited demonstration period may not and Performance
adequately remove the contamination source.
Involves some residuals treatment (vapor stream).
Potentially reduces waste volume by volatilizing contaminants, which are then collected
(in a more concentrated form) by an SVE system.
Potentially reduces long-term contaminant mobility by volatilizing contaminants, which are then removed from
the soil and collected by an SVE system.
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 OSHA and FCC requirements.
Other pilot-scale tests have been completed; no full-scale applications to date.
$315 per ton.
No excavation is required, which should improve state acceptance.
No excavation is required, which should improve community acceptance.
May require some community education to assure residents that the operation of the RFH system is compliant
with OSHA safety requirements.
1 ARARs = Applicable or Relevant and Appropriate Requirements
2 Actual cost of a remediation technology is highly site-specific and dependent on the original target cleanup level, contaminant concentrations, soil
characteristics, and volume of soil. Cost data presented in this table are based on the treatment of approximately 10,000 tons of soil, and include
costs associated with SVE.
Compliance with Federal ARAR1
Long-term Effectiveness
Reduction of Toxicity, Mobility,
or Volume through Treatment
Short-term Effectiveness
Implementability
Cos?
State Acceptance
Community Acceptance
TD1 & TD2
3-Phase, 6OHz AC Power
TD3Q
E1
E2
E3
/\ = antenna
O= pressure transducer
£ = extraction well
| - infrared temperature and electric
field profiling wells
= thermowell
X = thermocouple string
?5ğkW?7 1?>MH7
Instrumentation & Controls
<
,
1
r W XTC1 *
R F2
1 VI
. | Switch | -.
A]T s-s-s-l1-
,...R ^ .." ,
pff..,_ ,. 9 - =^=1
TC2 - TC3
x--- Ox O
TD6 & TD3 TD5 & TD2
,
F
1
i
Vapor
Treatment System
O
TD4
E6
E7
E8
TD7 & TD8
Figure 1. Schematic diagram of KAI RFH system.
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treatment techniques, numbers and configurations of extraction
wells and antennae, and other design details are site-specific.
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 pos-
sible to remove SVOCs that would not normally be removed by
standard SVE technologies. RFH may also speed the recov-
ery of VOCs, which can be removed by standard SVE tech-
nologies. Contaminants that can potentially be removed using
RFH include a wide variety of organics such as halogenated
and nonhalogenated solvents and straight-chain and polycyclic
aromatic hydrocarbons found in gasoline, jet fuel, and diesel
fuel.
Technology Limitations
The KAI RFH technology cannot be used as a stand-alone
technology. Vaporized contaminants and steam must be col-
lected for reuse or treatment. In some cases, residual con-
taminants may remain in the soil after treatment.
This technology currently may be limited to unsaturated
soils. Groundwater pumping may be used to lower the water
table and increase the depth to which the soil can be treated.
Soils composed primarily of sand and other coarse materials
may be best suited to this technology. Nonvolatile organics,
metals, and inorganics will not normally be removed by RFH or
SVE technologies.
Process Residuals
The KAI RFH process generates one process waste stream
that contains vaporized contaminants and steam mixed with
extraction air. This waste stream can be treated by any of a
number of standard vapor treatment technologies including
vapor-phase carbon, condensation, or incineration. During the
demonstration, steam and some contaminants in the vapor
stream were condensed and collected. These condensed
residuals were handled along with other site wastes at Kelly
AFB. A propane flare was used to treat uncondensed contami-
nants in the vapor waste stream. When groundwater is pumped
to lower the water table, the groundwater must also be handled
as a liquid residual.
Some soil contaminants may remain after treatment. At a
given site, the removals achieved and site-specific cleanup
requirements will determine whether the soil will require addi-
tional treatment.
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. After treatment is completed, system demobilization
may take up to one week. Access roads are needed for
equipment transport. Approximately 4,600 square feet of flat
ground are needed to accommodate the trailer-mounted RF
transmitters, controllers, and other support equipment. A bermed
area is needed for decontamination of the drill rig. Areas are
also needed for storage of condensed vapors, if applicable,
and the selected vapor treatment system.
Remediation using the RF heating process will require that
certain utilities be available at the site. Water must be avail-
able for steam cleaning and other equipment and personnel
decontamination activities. Electrical power must also be avail-
able. If carbon adsorption is used to treat vapors, compressed
air may be required for system control, and steam or hot air will
be needed if the carbon is regenerated onsrte. Natural gas or
propane will be required if a flare is used to control vapors.
The operation of a RFH system is specifically addressed
by the FCC under regulations governing industrial, scientific,
and medical equipment. Health and safety issues are regu-
lated under OSHA. All requirements were reportedly met by
the developer during the SITE Demonstration. The system is
relatively quiet, and only during installation will dust and vapors
be a potential problem. Therefore, the RFH technology can be
applied near residential areas.
Performance Data
The demonstration system was designed to heat the soil
in the revised treatment zone to a temperature of 100 to 130°C.
Soil temperatures within and outside the revised treatment
zone were monitored at various depths throughout the demon-
stration using thermocouples, infrared temperature sensors and
fiber-optic temperature probes. All temperature measuring
devices were mounted in lined boreholes, which made direct
readings of the soil temperature impossible. The developer
claims that actual soil temperatures were higher than the mea-
surements indicate; however, this difference cannot be quanti-
fied. The maximum measured temperature on the perimeter of
the revised treatment zone was 61 °C. The maximum mea-
sured temperature near the center of the revised treatment
zone was 234°C, but this peak was not representative of the
majority of the temperature measurements at this location.
During most of the heating period, temperatures between 100
and 150°C were measured near the antenna to which energy
was being applied. Although not observed during the demon-
stration, the developer claims that temperatures will become
more uniform after all moisture is removed from around the
antennae.
Soil samples were collected before and after the soil was
treated using KAI's RFH technology. The soil samples were
collected as matched pairs; each post-treatment sample was
collected as near as possible to its corresponding pretreatment
sample. Only complete matched pairs were used in the evalu-
ation of the data. For each contaminant, the mean percent
removal was calculated, and a t-test was conducted to deter-
mine whether the mean removal was statistically significant at
the 80 percent confidence interval or higher.
EPA Method 418.1 [1] was used to determine TRPH
concentrations in the soil samples following extraction with
freon according to EPA Method 9071 [2]. TRPH data are listed
in Tables 2 and 3. For each complete matched pair of TRPH
data, sample location and depth (of the pretreatment sample),
pretreatment concentration, post-treatment concentration, and
percent removal are shown. The mean removals in the original
and revised treatment zones are 30 percent and 49 percent,
respectively. These removals were accepted at the 80 and 95
percent significance levels, respectively.
SVOCs and VOCs were designated as noncritical mea-
surements for this demonstration because samples collected
prior to the demonstration indicated that the soil at the site
generally contained low concentrations of SVOCs and VOCs.
Because SVOCs and VOCs were noncritical measurements,
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Table 2. TRPH Concentrations Within the Revised Treatment Zone'
Sample Pretreatment Post-treatment
Location and Depth Concentration (ppm) Concentration (ppm) Percent Removal2
E1, 10-1?
E6, 8-10'
F1, 4-6'
F1, 10-12'
E4, 7-9'
E4.9-11'
F4, 12-14'
E2, 10-12'
F3, 4-6'
F3, 10-12'
E7, 12-14'
E5, 4-6'
E5, 6-8'
E5, 10-12'
E5, 12-14'
F5, 12-14'
A2, 4-6'
A2, 10-12'
A2, 12-14'
E8, 6-8'
3,350
1,860
6,910
1,240
1,310
729
1,790
168.5 3
4,920
336
1,400
2,710
1,530
668
739
1,220
1,530
1,290
622
655
1,160
930
828
1,580
1,090
593
643
582
702
4,510
825
673
587
330
1,450
1,530
154
33.3s
106
861
65.4%
50.0%
88.0%
(27%)
16.8%
18.7%
64.1%
(>245%)
85.7%
(1,240%)
41.1%
75.2%
61.6%
50.6%
(96.2%)
(25.4%)
89.9%
>97.4%
83.0%
(31.5%)
1 These data were used to determine the mean percent removal of TRPH within the revised treatment zone. These data were also used, in
conjunction with the data presented in Table 3, to determine the mean percent removal of TRPH within the original treatment zone. The mean
percent removals were calculated using the geometric mean, since the data are log-normally distributed.
2 Parentheses around a value in this column indicate a percent increase, rather than a percent removal.
3 TRPH was not detected in this sample above the practical quantitation limit; therefore, the practical quantitation limit is provided.
Table 3. TRPH Concentrations Within the Original Treatment Zone But Outside the Revised Treatment Zone'
Sample Pretreatment Post-treatment
Location and Depth Concentration (ppm) Concentration (ppm) Percent Removal2
E1, 0-2'
E1, 16-18'
A1, 0-2'
A1, 16-18'
A1, 18-20'
E6, 16-18'
F1, 18-20'
F4, 0-2'
F4, 16-18'
E2, 0-2'
E7, 2-4'
F2, 14-16'
E5, 18-20'
F5, 16-18'
F5, 18-20'
E3, 14-16'
E3, 16-18'
A2, 0-2'
A2, 2-4'
A2, 16-18'
352
22,000
458
79,700
39,300
3,160
5,440
1,220
1,090
1,730
492
3,250
105,000
22,100
35,000
1,210
7,410
2,330
203
23,800
4,830
19,200
184
20,800
28,300
253
23,100
448
12,500
3,620
161
555
35,800
20,900
53,200
1,770
2,820
8,850
2,570
6,500
(1,270%)
12.7%
59.8%
73.9%
28.0%
92.0%
(325%)
63.3%
(1,050%)
(109%)
67.3%
82.9%
65.9%
5.43%
(52.0%)
(46.3%)
61.9%
(280%)
(1,170%)
72.7%
1 These data were used, in conjunction with the data presented in Table 2, to determine the mean percent removal of TRPH within the original
treatment zone. The mean percent removal was calculated using the geometric mean, since the data are log-normally distributed.
2 Parentheses around a value in this column indicate a percent increase, rather than a percent removal.
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their concentrations were measured in only half of the soil
samples. SVOC samples were extracted by EPA Method 3540
[2] prior to analysis by EPA Method 8270 [2]. VOC concentra-
tions were determined using EPA Method 8240 [2].
Concentrations of individual SVOCs and VOCs in the soil
samples were evaluated statistically using the same proce-
dures described above for TRPH. Concentrations of several
SVOCs exhibited statistically significant changes (at an 80
percent significance level) within the original and revised treat-
ment zones. Statistically significant changes in SVOC concen-
trations within the original and revised treatment zones are
presented in Table 4. None of the individual VOCs exhibited
statistically significant changes (at an 80 percent significance
level) within the original or revised treatment zone.
Several hypotheses may help explain the bw contaminant
removals measured during the demonstration. Because only a
portion of the revised treatment zone reached the target tem-
perature of 100 to 130°C, it seems most likely that the system
did not achieve an adequate temperature. The low tempera-
tures were at least partially due to problems with the electrical
power available at the site. The design and operation of the
SVE system, which is described in the Technology Description
portion of this capsule, may have caused the contaminants to
migrate downward out of the revised zone.
Technology Status
Information is currently available from two pilot-scale KAI
RFH demonstrations: the Kelly AFB SITE demonstration docu-
mented in this capsule, and a demonstration conducted at
Savannah River. KAI has conducted other tests for private
clients, but the results of these tests are not available to the
public. KAI has tentative plans for additional pilot-scale dem-
onstrations. KAI also has long-term plans for larger-scale
demonstrations investigating applicators that can travel the
length of a horizontal or vertical borehole.
The cost of full-scale RFH treatment using a 200-kW
generator is estimated to be $315 per ton for a site containing
approximately 10,000 tons of contaminated soil. This cost
estimate is based on a scale-up of the original treatment zone.
The estimate includes costs associated with SVE, since SVE is
an integral part of treatment using an RFH system. Major
components of the cost estimate are equipment costs; startup
and fixed costs; operating costs during treatment; supplies
costs; consumables costs; facility modification, repair, and re-
placement costs; and site demobilization costs. The estimate
does not include costs associated with analyses, site prepara-
tion, permitting, effluent treatment and disposal, or residuals
and waste shipping, which are considered site-specific costs
that will be assumed by the site owner or responsible party.
Table 4. Summary of SVOC Removals
Contaminant
Mean Percent Removal in
Original Treatment Zone
Mean Percent Removal in
Revised Treatment Zone
Benzo(b)fluoranthene
Benzo(a)pyrene
Bis(2-ethylhexyl)phthalate
Chrysene
Pyrene
Fluoranthene
441
443
55 4
*ğ*5
*Ğ*5
*ğ*5
402
432
***5
402
604
S32
1 Accepted at the 97.5 percent significance level.
2 Accepted at the 80 percent significance level.
3 Accepted at the 95 percent significance level.
4 Accepted at the 90 percent significance level.
6 No statistically significant change at the 80 percent significance level.
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Disclaimer
While the conclusions from this technology demonstration
may not change, these data have not been reviewed by EPA
Risk Reduction Engineering Quality Assurance personnel at
this time.
Sources of Further Information
EPA Project Manager:
Laurel Staley
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513)569-7348
Kelly AFB Project Engineer:
Victoria Wark
SA/ALC/EMRO
305 Tinker Drive, Suite 2, Building 305
Kelly AFB, TX 78241-5915
(210)925-1812
USAF Technical Program Manager,
Site Remediation Division:
Paul F. Carpenter
AL/EQW-OL
139 Barnes Drive, Suite 2
Tyndall AFB, FL 32403
(904)283-6187
USAF Contractor:
Clifton Blanchard
Brown & Root Environmental
800 Oak Ridge Turnpike, Suite A600
Oak Ridge, TN 37830
(615)483-9900
Process Vendor:
Raymond Kasevich
KAI Technologies, Inc.
170 West Road, Suite 7
Portsmouth, NH 03801
(603)431-2266
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
-------
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
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