DOE
United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA/540/R-97/509a
December 1998
S/TE Technology Capsule
In Situ Electrokinetic
Extraction System
Abstract
AspartoftheSuperfund Innovative Technology Evaluation
(SITE) program, the U.S. Environmental Protection
Agency (EPA) demonstrated the In Situ Electrokinetic
Extraction(ISEE) system at the U.S. Department of Energy
(DOE) Sandia National Laboratories (SNL) Chemical
Waste Landfill site in Albuquerque, New Mexico. This
demonstration was funded by DOE's Office of Science and
Technology through the Subsurface Contamination Focus
Area. The ISEE system treated chromate-contaminated
soil at the Unlined Chromic Acid Pit (UCAP) of the SNL
Chemical Waste Landfill site.
The SITE demonstration results show that the ISEE
system removed hexavalent chromium in the form of
chromate from soil under unsaturated conditions. At SNL's
preferred operating conditions, (1) approximately 200
grams (g) of hexavalent chromium were removed during
about 700 hours of system operation, (2) the overall
removal efficiency for the system was approximately
0.14 g of hexavalent chromium per kilowatt hour (kWh),
and (3) the average removal rate for the entire system was
approximately 0.29 g/ hour.
Potential sites for appropriate application of this technology
include Superfund and other hazardous waste sites where
soils are contaminated with hexavalent chromium under
unsaturated conditions. Economic data indicate that soil
remediation costs are very high, perhaps because the
system demonstrated at UCAP requires significant
improvements.
Introduction
The SITE program was established in 1986 to accelerate
the development, demonstration, and use of innovative
new technologies that offer permanent cleanup alterna-
tives for hazardous wastes. One component of the SITE
program is the demonstration program, under which
engineering, performance, and costdata are developed for
innovative treatment technologies. Data developed under
the SITE demonstration program enables potential users to
evaluate each technology's applicability to specific waste
sites.
The SITE demonstration of the SNL ISEE system was
conducted at the UCAP within the Chemical Waste Landfill
site at Technical Area III. The system was evaluated from
May 15 to November 24, 1996, to determine its
effectiveness for treating unsaturated soil contaminated
with hexavalent chromium.
This technology capsule was developed by EPA's Office of
Research and Development in Cincinnati, Ohio, to
announce key findings of the ISEE SITE demonstration,
which is fully documented in two separate reports: the
innovative technology evaluation report (ITER) and the
technology evaluation report. These reports can be
obtained by contacting Mr. Randy Parker (see "Source of
Further Information" below).
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Printed on Recycled Paper
-------
This capsule summarizes the following information:
Technology description
Technology applicability
Technology limitations
SITE demonstration overview
Treatment residual
Site preparation requirements
Demonstration results
Operating problems
Comparison to Superfund feasibility evaluation criteria
Estimated treatment costs
Technology status
Source of further information
Technology Description
The ISEE system was developed by SNL to remove
hexavalent chromium from unsaturated soil. The ISEE
system used for the demonstration was housed in two
buildings: a control trailer and a temporary structure. The
control trailer contained the control panels, the power
supply, and the data logging system. The temporary
structure protected the electrokinetic technology equip-
ment and personnel and maintained the operational
exclusion zone required during ISEE system operation.
The technology involves the in situ application of direct
current to soil, which results in dissolved chromate ions
migrating through water in soil pores to the anode, a
phenomenon known as electromigration. In addition to
electromigration cathode, a bulk flow of pore water occurs
toward the cathode, a phenomenon known as electroos-
mosis. Chromate ions are extracted in the anode effluent.
The SNL ISEE system consists of the following: an
electrode system, a vacuum control system, a water
control system, a power supply, a monitoring system, and
ancillary equipment. Figure 1 shows the ISEE system's
main components. Figure 2 shows the electrode layout of
the ISEE system used during the SITE demonstration. The
system consisted of an anode row oriented east to west
and four rows of cathodes parallel to the anode row, two
rows north and two rows south of the anode row. Two types
of cathodes were used during the SITE demonstration:
cathodes similar to the anodes, which will be referred to as
"cathodes," and simple design cathodes, which will be
referred to as "cold finger cathodes" (identified as "CF" if
they are standalone or "CFG" if they are adjacent to
cathode casings). The treatment zone was determined by
the active portion of these electrodes and extended from 8
to 14 feet bgs.
The innovative feature of the ISEE system is that lysimeter
technology is used in the construction of the anodes and
cathodes to hydraulically and electrically create a
continuum between the electrolyte and the pore water. The
electrode fluid is held inside the electrode by an applied
vacuum, keeping the fluid from saturating soil. This feature
allowed the removal of chromate from unsaturated soil
Power Supply System
Compressed Air
Vacuum Control System
Ground Surface
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r
0.75-inch-Diameter
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Cathode
- 3 feet -
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PVC Casing
3.5-inch-Diameter
Ceramic Casing
I rid i urn-Coated
Titanium Pipe -
(Anode)
Anode Casing —
Bladder Pump -
Electrode System
Figure 1. ISEE system schematic diagram.
-------
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LEGEND
C6 - Cathode 6
Al - Anode 1
CF1 - Cold finger cathode 1
CFC1 - Cold finger at cathode 1
Tl - Temperature probe 1
NT1 - Neutron hydroprobe access station I
| / | - Test 13 zone of influence
NOTE
The area displayed measures 12 by 12 feel.
Each square measures 3 by 3 feet.
Figure 2. Test area electrode layout.
during the demonstration without significantly altering the
soil moisture content. The vacuum control system
maintains the vacuum in the anode electrode, which
creates the pressure gradient between the anode's porous
ceramic casing and the surrounding soil necessary to
hydraulically control water movement between the anode
casing and the soil. Hydrogen gas, which is produced by
electrolysis reactions resulting from direct current
application, was purged from the cathode casing to
eliminate the danger of explosion.
The water control system consists of water circulation and
pH control systems. The anode water circulation system
mixes the anolyte in the electrode, removes and samples
anolyte, monitors the chemical condition of the anolyte, and
maintains the anolyte temperature at about 12 °C.
Circulation is maintained in a recycle flow loop by a bladder
pump. Because the bladder pump is contained in the
electrode casing, under subatmospheric conditions, an
additional vacuum source is necessary for its operation.
The cold finger cathode water control system consists of a
chillerthat cools water pumped to the cathodes and has no
recirculation system. The pH control system maintains the
pH of the anolyte at about 9 using a 10 percent sodium
hydroxide solution.
The power supply energizes the electrodes. The
demonstration system consisted of four 10-kilowatt (kW)
powersupply units. Each unit was ope rated independently
under constant voltage conditions. The current applied to
each electrode was monitored and limited to 15 amperes
(A).
The monitoring system records water control system
information such as anode casing water level, recycle flow
rate, influent and effluent rates, recycle flow temperature,
conductivity, and pH. The monitoring system also records
air purge rates, the vacuum in the anodes, and ancillary
equipment information such as soil temperature and
voltage profiles of subsurface soil. The monitoring system
can shut down the entire ISEE system if operational
parameters are not within established ranges.
Technology Applicability
The ISEE technology developed by SNL is applicable for
treating unsaturated soil contaminated with hexavalent
chromium. According to SNL, this technology can be
modified to treat saturated contaminated soil and to
remove contaminants dissolved in the pore water besides
chromate. Because other anions will compete with the
-------
targeted contaminant ions to be removed, it is necessary to
determine the electrical conductivity of the soil pore water
and the target ion concentration to determine the
applicability of the technology.
Technology Limitations
Prior to implementing electrokinetic remediation at a
specific site, field and laboratory screening tests should be
conducted to determine if the site is amenable to this
technology.
Field conductivity surveys are necessary to determine the
soil's electrical conductivity. Also, buried metallic objects
and utility lines could short-circuit the current path, thereby
influencing the voltage gradient and affecting the
contaminant extraction rate. Electromagnetic surveys
should be conducted to determine the presence of buried
metallic objects.
In addition, if volatile organic compounds (VOC) are
present in soil at the site undergoing electrokinetic
treatment, the VOCs will likely be stripped from the soil to
significantly increase the soil vapor VOC concentrations
that could result in significant VOC migration from the
treatment area, if soil temperature exceeds 50°C. Special
measures therefore need to be taken to contain and control
VOC emissions.
SITE Demonstration Overview
The ISEE technology SITE demonstration was initiated on
May 15,1996, and was terminated on November24,1996.
During this period, the system operated for a total of about
2,800 hours. The test areas ranged from 36 to 72 square
feet, and contaminated soil at 8 to 14 feet bgs was treated.
Predemonstration soil samples collected within the test
areas contained hexavalent chromium at concentrations
ranging from below the detection limit of 0.4 milligram per
kilogram (mg/kg) to 6,890 mg/kg and total chromium at
concentrations ranging from 7.7 to 26,800 mg/kg.
Evaluation of hexavalent chromium removal from soil by
the ISEE system was the primary project objective
because the ISEE system is primarily designed to remove
hexavalent chromium. To accomplish this objective, SNL
collected and analyzed anolyte samples for hexavalent
chromium at the field laboratory throughout the
demonstration period. An independent check of field
analytical data was provided by EPA through split sample
analysis at an off-site laboratory. Field analytical data were
therefore deemed adequate to estimate the amount of
hexavalent chromium removed from soil by the ISEE
system.
Predemonstration and postdemonstration soil samples
collected by EPA were analyzed for hexavalent chromium
to verify the hexavalent chromium removal estimate based
on anolyte sample analysis.
The secondary objectives of the technology demonstration
were to determine whether treated soil meets the toxicity
characteristic leaching procedure (TCLP) regulatory
criterion for chromium and to evaluate the ISEE system's
ability to remove trivalent chromium from site soil.
To conduct the demonstration, SNL was required to meet
the conditions of the New Mexico Environmental
Department's Resource Conservation and Recovery Act
(RCRA) Research, Development, and Demonstration
permit for the ISEE system. Predemonstration testing
results indicated that some of the soil in the demonstration
area is hazardous (EPA waste code D007) because
chromium concentrations exceeded the TCLP criterion for
chromium. Therefore, the permit required that SNL
perform postdemonstration TCLP testing to determine the
impact of the ISEE system on soil known to be
contaminated. SNL therefore collected a large number of
treated soil samples for total chromium analysis after
extraction using TCLP.
Because incidental removal of trivalent chromium will likely
be accomplished by the ISEE system, evaluation of
trivalent chromium removal was a secondary project
objective of this project. To accomplish this objective, the
Predemonstration and postdemonstration soil samples
collected for hexavalent chromium analysis were also
analyzed for total chromium so that the trivalent chromium
concentrations could be calculated as the difference
between the total and hexavalent chromium concentra-
tions.
During the SITE demonstration, 13 tests were performed
during six phases. The test areas ranged from 36 to 72
square feet, and contaminated soil from 8 to 14 feet bgs
was treated. The first 12 tests were conducted so that SNL
could determine the preferred operating conditions fortest
13 and to facilitate the migration of hexavalent chromium
toward the central portion of the test area. Test 13
consisted of system performance testing under SNL's
preferred operating conditions forthe SITE demonstration.
Table 1 summarizes key conditions of the 13 tests.
Treatment
The ISEE system treatment residual consists of anolyte.
This effluent contains hexavalent chromium extracted from
the soil in the form of chromate solution. The ISEE system
does not have the capability to treat this waste stream;
therefore, this treatment residual should be characterized
and disposed of as hazardous waste.
-------
Table 1. Test Conditions for SNL ISEE System SITE Demonstration
Test Area
1 South Side
(A1-A5toC6-
C10)
2 North Side
(A1-A5toCFC1-
CFC5)
3 Southern Half
of North Side
(A1-A5toCF1-
CF5)
4 South Side
(A1-A5toCFC6-
CFC10)
5 Northern Half of
South Side
(A1-A5toCF6-
CF10)
6 Central Portion
(CF1-CF5to
CF6-CF10)
Test
No. Phase
1 A1.A2, A3,
A4, and A5
2 A1.A3, A4,
and A5
3 A1.A3, A4,
and A5
4 A1.A3, A4,
and A5
5 A1.A3, A4,
and A5
6 A1.A3, A4,
and A5
7 A1.A3, A4,
and A5
8 A1,A3, A4,
and A5
9 A1 , A3, A4,
and A5
10 A1,A3, A4,
and A5
11 A1 , A3, A4,
and A5
12 A1.A3, A4,
and A5
13 A1.A3, A4,
and A5
Cathodes Used
C6, C7, C8, C9, anddO
C6, C7, C8, C9, andCIO
C6, C8, C9, andCIO
C6, C8, C9, andCIO
C6,C8,C9, andCIO
C6,C8,C9, andCIO
CFC1.CFC3, CFC4, and
CFC5
CFC1, CFC3, CFC4, and
CFC5
CFC1, CFC3, CFC4. and
CFC5
CF1.CF3, CF4, andCFS
CFC6, C8, CFC9, and
CFC10
CF6, CF8, CF9, and CF10
CF1, CF3 through CF6, and
CF8 through CF10
Average Average
Current Power
(A) (kW)
19.45 1.3
21.09 1.68
20.08 1.77
34.25 4.65
42.15 5.76
41.07 4.56
29.27 4.14
20.94 1.9
20.79 1.87
30.31 2.7
33.49 2.38
39.31 2.86
35.92 2.1
Analyte
Extraction
Rate
(L/hour)
0.44
0.87
0.879
2.026
3.54
3.957
3.404 "
0.376
0.723
0.51
0.5
0.848
0.662
Test
Duration
(hour)
106
368
283
244
34
181
75
89
333
176
20
111
707
Site Preparation Requirements
This section describes site preparation requirements for
the ISEE technology. Some of these requirements may
apply to situations in which the ISEE system is used to
remediate contaminated soil. During the demonstration, in
addition to the test area, an additional 8,800 square feet
were necessary to accommodate the control trailer, water
tanks, and supply storage. Based on the design of the
ISEE system, which can transmit system information off
site, no personnel are required to be present on site for
system operation. The system is equipped with a CR7
data-logger that monitors system parameters and can shut
down the system (such as by cutting off power to the
electrodes and terminating the water supply). The data-
logger consequently sends a signal to the system operator
identifying the problem. Technical service personnel
should be available on an as-need basis to remediate any
problems. According to the developer, maintenance and
routine sampling and analysis requirements for a full-scale
system should require the on-site presence of a technician
for 8 hours a week.
The ISEE system demonstrated at UCAP was powered by
four 10-kW power supply units. The units were capable of
operating independently or in parallel. When connected in
parallel, the maximum output was 64 A at 600 volts of direct
current. According to the developer, a three-phase, 230-
volt, 150-kW power supply is necessary to operate a full-
scale system.
-------
Potable and decontamination water are also necessary to
operate the system. The monitoring system requires
connection to a telephone line or cellular telephone to
download data to an off-site computer and to transmit a
signal indicating that the system has shut down to
maintenance personnel.
A temporary structure may be required to protect the ISEE
system and personnel from the weather and also to provide
an exclusion zone during system operation. The data-
logger, control panels, and other analytical equipment can
be housed in a trailer. If the ISEE system is used outdoors
in a cold climate, provisions should be made for insulating
the exposed portions of the water control system to prevent
freezing.
Demonstration Results
The following sections summarize results of the ISEE
system SITE demonstration according to the primary and
two secondary project objectives.
Removal ofHexavalent Chromium
The primary objective of the ISEE system demonstration
was to estimate the amount of hexavalent chromium
removed from soil by the ISEE system. The mass of
hexavalent chromium removed was to be determined from
the amount of hexavalent chromium extracted in the
anolyte during the demonstration.
As mentioned before, 13 tests were performed in six
phases during the demonstration. The first 12 tests,
performed between May 15 and October 18, 1996, were
used by SNL to determine preferred operating conditions of
the system. Test 13 was performed between October 21
and November 24, 1996, to determine system perfor-
mance and the operating costs. Test 13 was conducted in
the central portion of the demonstration area, which
measured 12 by 6 feet. The system was operated for 707
hours in this configuration. Table 2 summarizes ISEE
system performance results during the 13 tests performed.
The total mass of hexavalent chromium extracted by the
ISEE system should have been verified by calculating the
difference between hexavalent chromium mass in treated
soil before and after the demonstration. However, soil
results for hexavalent chromium exhibited a high spatial
variability resulting from (1) the nonhomogeneous distribu-
tion of chromate concentrations in soil before the
demonstration and (2) the fact that the demonstration was
terminated before chromate removal was completed. In
addition, limited data appearto indicate that contaminants
had likely migrated from areas outside of and near the
treatment area. Thus, a determination of the mass of
hexavalent chromium removed based on soil sampling
results was not possible.
Hexavalent chromium soil sampling results are as follows:
(1)51 predemonstration soil samples contained hexavalent
chromium-concentrations from below the detection limit of
Table 2. ISEE System Hexavalent Chromium Removal Results
Test
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
Test Duration
(hour)
106
368
283
244
34
181
75
89
333
176
20
111
707
Hexavalent Chromium
Mass Removed (g)
7.84
35.7
22.5
56.0
11.5
38.2
11.1
9.01
59.0
36.0
4.71
25.4
204
Hexavalent Chromium
Removal Rate (g/hour)
0.074
0.097
0.079
0.230
0.338
0.211
0.149
0.101
0.176
0.204
0.236
0.229
0.288
Hexavalent Chromium
Removal Efficiency (g/kWh)
0.057
0.058
0.046
0.049
0.058
0.047
0.036
0.053
0.094
0.075
0.094
0.081
0.136
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0.4 mg/kg to 6,890 mg/kg; and (2) 84 postdemonstration
soil samples contained hexavalent chromium concentra-
tions from below the detection limit of 0.4 mg/kg to 4,730
mg/kg. Of the 48 locations sampled both before and after
the demonstration, 21 locations contained
postdemonstration hexavalent chromium in concentra-
tions that exceeded predemonstration concentrations. As
stated earlier, soil analytical results could not be used to
verify the estimated mass of hexavalent chromium
removed based on anolyte results.
Compliance with TCLP Regulatory Criterion for
Chromium
Table 3 presents TCLP results for chromium for soil
samples collected before and afterthe demonstration from
the treatment zone from approximately 8 to 14 feet bgs. Of
the 43 predemonstration soil samples analyzed by TCLP,
18 exceeded the TCLP limit of 5 milligrams per liter (mg/L)
of total chromium at concentrations ranging from 5.6 to 103
mg/L, with a median concentration of 15.4 mg/L.
Table 3. ISEE System TCLP Chromium Results
Sampling
Location
No.
A1
A2
A3
A5
C1a
C2a
C3a
C4a
C5a
C6
C7
C8
C9
C10
CF1
CF4
CF5
CF6
CF7a
CF9
CF10
NTS
NT7
NTS
8 to 10
Predemonstration
(mg/L)
0.64
<0.5
<3.3
2.5
<1
< 1
< 1
-
<0.5
0.37
—
0.49
—
3.1
—
13
—
—
—
—
—
9.2
19.7
5
feet bas
Postdemonstration
(mg/L)
-
-
--
-
-
--
-
0.078
~
-
1
-
0.24
~
0.92
1.1
21
0.99
0.072
3.8
29.9
--
-
--
Sampling Depth
10 to 12 feet bas
Predemonstration
(mg/L)
20.8
3
17.8
103
<0.5
-
<0.5
-
<0.5
0.007
-
5.6
27.4
-
-
49.3
-
-
-
-
-
5.6
35.5
1.7
Postdemonstration
(mg/L)
19.7
--
9.4
-
-
-
-
0.017
--
-
0.6
-
0.35
--
6
12
4.9
15.2
6.6
57.2
62.4
-
40.6
1.2
12 to 14
Predemonstration
(mg/L)
0.52
1.8
20.8
19.5
<0.5
—
<0.5
-
<0.5
<0.5
~
6.1
1
-
-
8.6
—
-
-
-
--
7.1
7.9
6
feet bas
Postdemonstration
(mg/L)
-
14
..
„
-
—
—
8.9
—
-
3.6
--
0.011
-
32.8
1.9
0.052
13.8
43.9
67
22.2
-
—
-
Notes:
Numbers presented in bold font exceed the TCLP limit of 5 mg/L.
a These locations are not shown in Figure 2 because electrodes at these locations were not used during the
demonstration.
- No sample analyzed from this depth.
-------
Postdemonstration results indicate that 18 out of 35 soil
samples exceeded the TCLP regulatory criterion for
chromium at concentrations ranging from 6 to 67 mg/L, with
a median concentration of 20.4 mg/L.
Removal of Trivalent Chromium
Trivalent chromium concentrations were to be determined
by calculating the difference between total and hexavalent
chromium concentrations. In general, the ratio of trivalent
chromium to total chromium ranged from 7.6 to
94.9 percent in the predemonstration samples and from
27.6 to 99.6 percent in the postdemonstration samples.
This large variability precluded the calculation of trivalent
chromium concentrations as originally intended because it
would have further increased the data variability.
Total chromium concentrations in the 51 predemonstration
samples analyzed ranged from 7.7 to 26,800 mg/kg; and
total chromium concentrations in the 84 postdemonstration
samples ranged from 8.2 to 16,200 mg/kg. Of the 48
locations sampled both before and afterthe demonstration,
31 locations contained postdemonstration trivalent
chromium concentrations that exceeded predemonstration
concentrations.
This increase may be the result of chromium migration in
the treatment area in addition to inherent variability at the
test areas. Therefore, no conclusion was drawn regarding
the ISEE system's ability to remove trivalent chromium.
Operating Problems
The ISEE system's operation was observed during the
demonstration, and the problems and their resolutions
were recorded by SNL personnel. The demonstration
lasted over approximately 4,230 hours. The system was
not operable for 36 percent of the time. Table 4 presents
the reasons for the shut downs and the percentages of
shutdown times relative to the entire duration of the
demonstration. In addition, the system was not energized
for 3 percent of the time (approximately 140 hours) to
perform anolyte sampling and soil moisture measurements
using the neutron probe.
Comparison to Superfund Feasibility Evalua-
tion Criteria
Table 5 summarizes the ISEE system's performance
compared to the Superfund feasibility evaluation criteria.
This table is provided to assist Superfund decision-makers
in considering the ISEE system for remediation of
contaminated soil at hazardous waste sites.
Estimated Treatment Costs
Based on information provided by SNL and the results and
experiences gained from the SITE demonstration, an
economic analysis was performed to examine 12 separate
cost categories for using the ISEE technology to remediate
hexavalent chromium-contaminated, unsaturated soils.
According to SNL, a full-scale commercial system design
would significantly differ from the system operated during
the demonstration. In addition, the developer has not
completed a full-scale design of a commercial ISEE
system. Therefore, it is not possible to prepare a cost
estimate fora full-scale ISEE system. Because SNL states
that the full-scale treatment system design will be
significantly modified based on the performance of the
system used during the demonstration, the treatment cost
of a full-scale system will also differ from the treatment cost
of the system operated during the demonstration. When
the technology is ready for commercialization, further
economic analysis should be performed.
This cost estimate is based on the system's performance at
SNL's preferred operating conditions during test 13 of the
SITE demonstration and the following parameters:
(1) configuration of four anodes and eight cold finger
cathodes, (2) a treatment area of 16 cubic yards, (3) a
Table 4. System Shutdown Information
Reason for System Shutdown
Shut Down Time
(percent)
Intentional shutdown to perform maintenance and modifications to
the system
Problems related to electrode water (such as bladder pumps, float
switches, and chiller leakage)
Power supply failures and problems
pH control system problems
Data-logger problems
Total
21
4
2
2
36
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Table 5. Superfund Feasibility Evaluation Criteria for the ISEE Technology
Criterion
Discussion
Overall Protection of Human
Health and the Environment
The ISEE technology is expected to protect human health by lowering the concentration of
hexavalent chromium in soil under unsaturated conditions. According to the developer, the
technology can also treat soil contaminated with other heavy metals under both saturated and
unsaturated conditions, but this capability was not evaluated during the SITE demonstration.
Overall reduction of human health risk should be evaluated on a site-specific basis because
VOCs could be stripped from soil during treatment and released to ambient air. Also, the system
effluent (anolyte) contains hexavalent chromium and therefore needs to be characterized and
handled and disposed of as hazardous waste.
The technology protects the environment by curtailing migration of hexavalent chromium in soil.
Protection of the environment at and beyond the point of anolyte extraction depends on how the
anolyte is handled and disposed of. Protection of the environment also depends on the extent of
VOC emissions.
Compliance with Applicable
or Relevant and Appropriate
Requirements (ARAR)
According to the developer, the technology has the potential to comply with existing federal,
state, and local ARARs (for example, TCLP limits) for several inorganic contaminants (for
example, chromium). However, about 51 percent of the postdemonstration samples did not meet
the chromium TCLP limit of 5 mg/L.
Long-Term
Effectiveness and
Permanence
Human health risk can be reduced to acceptable levels by treating soil to a 1 x 10~6 excess
lifetime cancer risk level. The time needed to achieve cleanup goals depends primarily on
contaminated soil characteristics.
The treatment achieved is permanent because contaminants are contained in the anolyte, which
is extracted from the soil for disposal.
Periodic review of treatment system performance is needed because application of the
technology to contaminated soil at hazardous waste sites is new.
Reduction of Toxicity,
Mobility, or Volume Through
Treatment
The technology reduces the volume and mobility of contaminants in soil because contaminants
are contained in the anolyte, which is extracted from the soil for disposal.
The technology can effectively control soil contaminant migration because contaminants are
contained in the anolyte, which is extracted from the soil for disposal.
Short-Term Effectiveness
About 51 percent of postdemonstration samples did not meet the chromium TCLP limit of 5 mg/L.
This failure may be because the developer did not have the state permit required to carry out the
demonstration for a longer period of time.
Implementability
The technology is still in the development stage. No commercial system is currently available
from SNL.
State and local permits must be obtained to operate the ISEE system.
Cost
Treatment costs vary significantly depending on the size of the treatment system used,
contaminant characteristics and concentrations, cleanup goals, the volume of contaminated soil
to be treated, and the length of treatment. Economic data indicate that soil remediation costs are
very high, perhaps because the system demonstrated at UCAP was not of commercial scale and
requires significant improvements.
State Acceptance
This criterion is generally addressed in the record of decision. State acceptance of the
technology will likely depend on (1) expected residual contaminant in soil, (2) how the anolyte is
handled and disposed of, and (3) the steps taken to reduce the potential for VOC emissions.
Community Acceptance
This criterion is generally addressed in the record of decision after community responses have
been received during the public comment period. Because communities are not expected to be
exposed to harmful levels of fugitive emissions, the level of community acceptance of the
technology is expected to be moderate.
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hexavalent chromium removal rate of 0.29 g/hour, (4) a
hexavalent chromium removal efficiency of 0.14 g/kWh,
and (5) an on-line time of 85 percent. The total treatment
costs for the ISEE system to treat 16 cubic yards of soil are
estimated to be $1,400 per cubic yard for removing 200 g of
hexavalent chromium. The estimate will vary depending on
cleanup goals, soil type, treatment volume, and system
design changes. The estimate is order-of-magnitude
estimate, as defined by the American Association of Cost
Engineers, with an expected accuracy of+50 percentto -30
percent. A detailed explanation of these costs, including
the 12 cost categories examined, is presented in the ITER.
Technology
The SNL ISEE system is not commercially available for
treatment of contaminated soils. The system evaluated
during the SITE demonstration is a prototype and not the
system that will be used foractual remediation. To conduct
actual soil remediation, SNL's research team plans to
design and build a system that is low-maintenance and that
can be operated unsupervised for a long time. SNL states
that the cost of remediation will be significantly reduced as
a result of these improvements.
of Further Information
EPA Project Manager:
Mr. Randy Parker
U.S. Environmental Protection Agency
National Risk Management Research Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
Telephone No.: 513-569-7271
Fax No.: 513-569-7571
e-Mail Address: Parker.Randy@epamail.epa.gov
10
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