United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA 540/R-94/529a
June 1995
SITE Technology Capsule
Subsurface Volatilization and
Ventilation System (SVVS)®
Abstract
The Subsurface Volatilization and Ventilation System®
is an integrated technology used for attacking all phases of
volatile organic compound (VOC) contamination in soil and
groundwater. The SVVS® technology promotes insitu
remediation of soil and groundwater contaminated with or-
ganic compounds through the injection of air into the satu-
rated and unsaturated zones, and extraction of vapors from
the vadose zone. Through this process, volatile and semivolatile
organic compounds are stripped from the soil and groundwa-
ter. The subsurface circulation of air also increases dissolved
oxygen concentrations in the saturated zone, capillary fringe,
and vadose zone, thereby promoting aerobic microbiological
processes. The contaminated air extracted from the wells can
be treated at the surface before being discharged to the
environment.
The SVVS® process was evaluated under the SITE
program at the EV facility in Buchanan, Ml. The soils were
contaminated with aromatic hydrocarbons, and halogenated
and non-halogenated volatile and semivolatile organic com-
pounds (SVOCs) through discharge into a dry well. Baseline
data indicated that approximately 1,000 kg of VOC and SVOC
contamination was present in the dry well area soils, princi-
pally in a subsurface sludge layer. The developer claimed that
their technology would reduce the sum of seven target VOCs
by 30% over a 1 -yr period.
The results from the demonstration indicate the SVVS®
technology greatly exceeded their claims by providing a site
average 80.6% reduction of volatile organics in the vadose
zone. Furthermore, aerial and vertical reductions across the
site did not indicate the presence of any zones that were not
treated by the system. The SVVS® process proved to be
reliable and required minimal operator oversight. The technol-
ogy did not experience significant operational difficulties dur-
ing the evaluation period.
The SVVS® remediation technology was evaluated
based on seven criteria used for decision making in the
Superfund feasibility study (FS) process. Results of the evalu-
ation are summarized in Table 1.
Introduction
In 1980, the U.S. Congress passed the Comprehen-
sive Environmental Response, Compensation, and Liability
Act (CERCLA), also known as Superfund, committed to pro-
tecting human health and the environment from uncontrolled
hazardous waste sites. CERCLA was amended by the Super-
fund Amendments and Reauthorization Act (SARA) in 1986.
These amendments emphasize the achievement of long-term
effectiveness and permanence of remedies at Superfund sites.
SARA mandates implementing permanent solutions and us-
ing alternative treatment 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 over 1,700 and represent a broad spec-
trum of physical, chemical, and environmental conditions re-
quiring various types of remediation. The U.S. Environmental
Protection Agency (EPA) has focused on policy, technical,
and informational issues related to exploring and applying
new remediation technologies to Superfund sites. One such
initiative is EPA's Superfund Innovative Technology Evalua-
tion (SITE) program, which was established to accelerate
development, demonstration, and use of innovative technolo-
gies for site cleanups. EPA SITE Technology Capsules sum-
marize the latest information available on selected innovative
treatment and site remediation technologies and related is-
sues. These Capsules are designed to help EPA remedial
project managers, EPA on-scene coordinators, contractors,
and other site cleanup managers understand the types of
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Printed on Recycled Paper
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&EPA
United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA 540/R-94/529a
June 1995
SITE Technology Capsule
Subsurface Volatilization and
Ventilation System (SVVS)®
Abstract
The Subsurface Volatilization and Ventilation System®
is an integrated technology used for attacking all phases of
volatile organic compound (VOC) contamination in soil and
groundwater. The SVVS® technology promotes insitu
remediation of soil and groundwater contaminated with or-
ganic compounds through the injection of air into the satu-
rated and unsaturated zones, and extraction of vapors from
the vadose zone. Through this process, volatile and semivolatile
organic compounds are stripped from the soil and groundwa-
ter. The subsurface circulation of air also increases dissolved
oxygen concentrations in the saturated zone, capillary fringe,
and vadose zone, thereby promoting aerobic microbiological
processes. The contaminated air extracted from the wells can
be treated at the surface before being discharged to the
environment.
The SVVS® process was evaluated under the SITE
program at the EV facility in Buchanan, Ml. The soils were
contaminated with aromatic hydrocarbons, and halogenated
and non-halogenated volatile and semivolatile organic com-
pounds (SVOCs) through discharge into a dry well. Baseline
data indicated that approximately 1,000 kg of VOC and SVOC
contamination was present in the dry well area soils, princi-
pally in a subsurface sludge layer. The developer claimed that
their technology would reduce the sum of seven target VOCs
by 30% over a 1 -yr period.
The results from the demonstration indicate the SVVS®
technology greatly exceeded their claims by providing a site
average 80.6% reduction of volatile organics in the vadose
zone. Furthermore, aerial and vertical reductions across the
site did not indicate the presence of any zones that were not
treated by the system. The SVVS® process proved to be
reliable and required minimal operator oversight. The technol-
ogy did not experience significant operational difficulties dur-
ing the evaluation period.
The SVVS® remediation technology was evaluated
based on seven criteria used for decision making in the
Superfund feasibility study (FS) process. Results of the evalu-
ation are summarized in Table 1.
Introduction
In 1980, the U.S. Congress passed the Comprehen-
sive Environmental Response, Compensation, and Liability
Act (CERCLA), also known as Superfund, committed to pro-
tecting human health and the environment from uncontrolled
hazardous waste sites. CERCLA was amended by the Super-
fund Amendments and Reauthorization Act (SARA) in 1986.
These amendments emphasize the achievement of long-term
effectiveness and permanence of remedies at Superfund sites.
SARA mandates implementing permanent solutions and us-
ing alternative treatment 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 over 1,700 and represent a broad spec-
trum of physical, chemical, and environmental conditions re-
quiring various types of remediation. The U.S. Environmental
Protection Agency (EPA) has focused on policy, technical,
and informational issues related to exploring and applying
new remediation technologies to Superfund sites. One such
initiative is EPA's Superfund Innovative Technology Evalua-
tion (SITE) program, which was established to accelerate
development, demonstration, and use of innovative technolo-
gies for site cleanups. EPA SITE Technology Capsules sum-
marize the latest information available on selected innovative
treatment and site remediation technologies and related is-
sues. These Capsules are designed to help EPA remedial
project managers, EPA on-scene coordinators, contractors,
and other site cleanup managers understand the types of
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Printed on Recycled Paper
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Table 1. FS Criteria Evaluation For The SVVS® Technology
FS Criteria
Overall Protection
of Human Health
and the Environ-
ment
Provides both short-
and long-term pro-
tection by eliminating
organic contami-
nants in soil.
Compliance with
Federal ARARs
Requires compli-
ance with RCRA
treatment, storage,
and land disposal
regulations (of a
hazardous waste).
Long-Term
Effectiveness
and Permanence
Effectively removes
contamination
source.
Reduction of
Toxicity, Mobility,
or Volume Through
Treatment
Significantly reduces
toxicity, mobility, and
volume of soil contam-
inants through
treatment.
Short-Term
Effectiveness
Presents potential
short-term risks to
workers and com-
munity from vola-
tiles released
during system
installation.
Implementability
Involves few
administrative
difficulties.
Cost
$192,237 to clean
2 1,300 yd3 ($9/
yd3) over 3 yr
excluding effluent
treatment &
disposal
Prevents further
groundwater con-
tamination and
off-site migration.
Requires mea-
sures to protect
workers and com-
munity during
excavation, hand-
ling, and treatment.
Excavation, con-
struction and
operation of on-site
treatment unit may
require compliance
with location specific
ARARs.
Emission controls
may be needed to
ensure compliance
with air quality stand-
ards if VOCs are
present.
Involves well dem-
onstrated technique
for removal of con-
taminants.
Involves some
residuals treat-
ment, i.e.
extracted air
and minor soil
from installation.
System is easy to
install and operate.
$356,737 ($16.75/
yd3) including
vapor phase GAC
for effluent treat-
ment & disposal
data and site characteristics needed to effectively evaluate a
technology's suitability for cleaning up Superfund sites.
This Capsule provides information on the Subsurface
Volatilization and Ventilation System (SVVS)® process, an insitu
technology developed to increase oxygen flow to subsurface
materials, to facilitate microbial decomposition of organics while
volatilizing and removing volatile organic contaminants. The
SVVS® process was evaluated under EPA's SITE program
during a 12-month period from April 1993 to April 1994 at the
Electro-Voice, Incorporated (EV) facility in Buchanan, Ml. The
evaluation focused primarily on assessing the effectiveness of
the SVVS® process for remediating the "dry well" area soils
contaminated with aromatic hydrocarbons, and halogenated
and non-halogenated volatile, and semivolatile organic com-
pounds. Information in this capsule emphasizes specific site
characteristics and results of the SITE field demonstration at
the EV facility. This capsule presents the following information:
• Abstract
• Technology description
• Technology applicability
• Technology limitations
• Process residuals
• Site requirements
• Performance data
• Technology status
• Source of further information
Technology Description
The SVVS® process utilizes soil vapor extraction in con-
junction with insitu bioremediation to clean soil, sludge, and
groundwater. A typical SVVS® installation comprises a series of
air injection and vacuum/extraction wells designed to circulate
air below ground to 1) increase the flow of oxygen in the soil to
enhance the rate of organics destruction by indigenous soil
microbes and 2) volatilize and remove volatile organic contami-
nants from the soil. The configuration of the SVVS® is pre-
sented in Figure 1. A schematic cross-section of the system is
presented in Figure 2. This system consisted of three individu-
ally plumbed rows of alternating vacuum extraction and air
injection wells referred to as reactor lines. Each reactor line is
plumbed to a single central vapor control unit (VCU) used to
house air injection and vacuum pumps and gauging, as well as
emissions control equipment.
The injection wells are installed below the groundwater
table and are used to inject air into the groundwater. The
developer claims that the air strips volatile contaminants from
the soil and water as it percolates through this saturated zone.
Extraction wells installed in the vadose zone pull the perco-
lated air through the soil under vacuum, further stripping con-
taminants. In addition, the increase in air circulation in the soil,
specifically oxygen, increases the rate of biodegradation by soil
microbes, according to the developer, and transforms contami-
nants into harmless end products such as carbon dioxide and
water. To aid in the circulation process, sand chimneys can be
installed. These are sand-packed borings which provide pas-
sive airflow between the subsurface layers, increasing both the
soil vapor extraction and the biodegradation rates.
If required by permits, off-gas extracted from the vacuum
extraction wells can be routed through a configuration of Bio-
logical Emissions Control™ (BEC™) units (a patent pending
system which, according to the developer, through biodegrada-
tion, achieves up to 80% reductions in concentrations of VOCs
in stack emissions at approximately 20% of traditional emission
control costs). The off-gas is then expelled to the atmosphere
through a vent pipe affixed to the extraction pump. Vacuum
extraction emissions may also be favorably controlled within
regulatory limits by adjusting the air injection and vacuum
extraction rates. However, if the levels of VOCs in the off-gas
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Figure 2. Cross-sectional schematic of the Sl/VS®.
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are in excess of acceptable levels, the off-gas exiting the
BEC™ units can be routed through an activated carbon ad-
sorption unit as a final polishing step prior to discharge.
Technology applicability
The SWS® process is applicable to sites contaminated
with gasoline, diesel fuels, and other hydrocarbons, including
halogenated compounds. The system is very effective on ben-
zene, toluene, ethylbenzene, and xylene (BTEX) contamina-
tion. The process can also be used to contain contaminant
plumes through its unique vacuum and air injection techniques.
The technology should be effective in treating soils contami-
nated with virtually any material that has some volatility or
biodegradability. The technology can be applied to contami-
nated soil, sludge, free-phase hydrocarbon product, and ground-
water. By changing the injected gases, anaerobic conditions
can be developed, and a microbial population can be used to
remove nitrate from groundwater. The aerobic SVVS® can also
be used to treat heavy metals in groundwater by raising the
redox potential of the groundwater and precipitating the heavy
metals.
Over the past five years, SVVS® has been employed at
over 130 sites where petroleum hydrocarbons have been re-
leased. The soil and groundwater at several of these sites
have been cleaned to applicable regulatory standards within
and before the predicted remedial time frame. SVVS® has also
been implemented to remediate halogenated aliphatic com-
pounds in the subsurface.
Technology Limitations
In the application of any insitu air sparging technology,
the potential exists for migration of contaminant vapors off site.
It is imperative that the overall site remediation plan include a
properly engineered soil vapor extraction (SVE) system to
capture the contaminated vapors emanating from the saturated
zone. Therefore, the application of this technology is generally
limited to sites where SVE is feasible. One possible exception
to this is a site that relies on a remediation system that
maximizes the insitu biodegradation component of the technol-
ogy to destroy less volatile contaminants in the saturated zone
and vadose zone.
The effectiveness of SVVS® is sensitive to the lithology
and stratigraphy of the saturated and unsaturated zones. In
highly stratified soils, air may travel far from the well along
coarser strata before reaching the vadose zone, potentially
bypassing the target contaminant areas. The lateral migration
of the air within the saturated zone will generally be accompa-
nied by a lateral spread in the dissolved contaminant plume.
The overall remediation system design should incorporate mea-
sures to control the potential contaminant plume spread.
In situations in which dense non-aqueous phase liquids
(DNAPLs) are present, it is possible to spread the immiscible
phase and increase the size and concentrations of the VOC
plume. This may actually be used as an advantage in a site
remediation through the mobilization of the residuals and, in
conjunction with groundwater control, the realization of a more
efficient mass removal process.
SVVS® may not be economically beneficial for
remediation of materials of a very low permeability, such as
stiff clay. Additionally, potential inorganic geochemical changes
incurred through the application of the technology may cause
clogging of the aquifer. The potential for fouling may be evalu-
ated using available geochemical models, and avoided by
using a more appropriate gaseous medium.
Process Residuals
The SVVS® process generates one major wastestream-
vapors from the vacuum extraction wells. Depending upon
regulatory requirements, the extracted air may be treated above
ground or released directly to the atmosphere. In the early
stages of SVVS® implementation, the overall rate of mass
transfer of contamination to the vapor phase may exceed
biodegradation rates. It is during this period, which lasts any-
where from two weeks to a few months, that extracted vapors
may need to be treated above ground before release to the
atmosphere. However, the magnitude of treatment will de-
crease steadily over this period until biodegradation rates sur-
pass the net rate of transfer of contaminant mass into the
circulating air. When this point is reached, the vapor extraction
off-gas will consist predominantly of carbon dioxide, which is
the major gaseous by-product resulting from the biodegrada-
tion process. Consequently, the extent of exsitu treatment is
reduced significantly over that required by conventional SVE
systems, resulting in decreased capital and operations costs to
the implementer. To reduce these costs further and promote
additional VOC destruction, the SVVS® design employs the use
of proprietary biofilters for treatment of the extracted vapors.
A minor process residual from the implementation of a
SVVS® system is soil generated during system-well installation
drilling activities. This soil can be containerized and disposed
in accordance with the appropriate regulatory criteria.
Site Requirements
The SVVS® soil remediation system consists of several
major mechanical components and requires the installation of
injection/extraction wells, and, possibly, sand chimneys. The
system includes a positive displacement blower or air com-
pressor, vacuum pump(s), emissions control equipment, and
various monitoring equipment.
The remediation area must be accessible to drill rigs
and other heavy equipment such as front-end loaders, back
hoes, and/or trenching equipment. The site must also accom-
modate the VCU used to house the SVVS® pumps and associ-
ated equipment. System installation time depends upon the
size of the plot and the depth to groundwater.
Performance Data
The SVVS® process was evaluated for its ability to
reduce volatile organic contaminants in the vadose zone soil of
the "dry well" area at the Electro-Voice, Inc. site in Buchanan,
Ml. The primary objective of the demonstration was to evaluate
the developer's claim of a 30% reduction in the sum of seven
specific volatile organic compounds (i.e., benzene, toluene,
ethylbenzene, xylene, tetrachloroethene, trichloroethene, and
1,1-dichloroethene) in vadose zone soils of the treatment plot
over a 12-mo period of operation. A 1-yr time frame was
chosen for testing purposes only, and the reduction claim does
not reflect the limits of the technology. Under an actual reme-
dial clean-up, the system may require a longer time than was
possible during the present study.
Reductions in the volatile organics were proposed to
occur through the combined effects of insitu biodegradation
and soil vapor extraction. These reductions were evaluated by
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comparing the sum of the concentrations of the select volatile
organic contaminants in the matrix prior to system startup and
after 12 mo of system operation. Secondary objectives were
established to determine the relative contributions of insitu
biodegradation and vapor extraction to the removal and degra-
dation of volatile organics from the subsurface.
Soil samples were collected from borings within the
physical boundaries of the SVVS® system and sampled in a
manner such that the entire vertical section of the vadose zone
was represented. Five distinct subsurface zones were identi-
fied based on lithology and contaminant occurrence. These
included the upper horizon (above the contaminant source),
sludge layer (predominant source of contamination), and lower
horizons A1, A2, and B (below the contaminant source).
Since the developer's claims were to reduce seven
volatile organic contaminants by 30%, benzene, toluene,
ethylbenzene, and xylenes (BTEX), tetrachloroethene (PCE)i
trichloroethene (TCE), and 1,1-dichloroethene (1,1-DCE) were
considered the critical analytes for this demonstration. Analy-
ses were also performed on select samples for the following
non-critical parameters: total carbon (TC), total inorganic car-
bon (TIC), nutrients (nitrate, phosphate), total metals plus mer-
cury, cyanide, pH, and particle size distribution (PSD). An
additional objective of this demonstration was to develop data
on operating costs for the SVVS ® technology.
The extracted vapor streams were analyzed by continu-
ous emission monitoring (CEM) for O2, CO2, and total hydro-
carbons (THC). Grab samples of the extracted vapor stream
were collected for determining the concentration and distribu-
tion of individual volatile organic compounds.
Shut-down tests were periodically performed to assess
the presence and magnitude of biological processes in the
destruction of organic constituents in the subsurface. During a
shut-down test, the injected air stream is temporarily turned off
resulting in the cessation of oxygen delivery to the subsurface.
If there is a robust aerobic microbial population in the subsur-
face, the available oxygen will be quickly depleted. The shut-
down test tracks the magnitude and rate of oxygen drop-off
over a 24-hr period.
At the Electro-Voice site, the SVVS® process achieved
an overall 80.6% reduction of the sum of the seven critical
VOCs over a 1-yr period from vadose zone soils. This level of
reduction greatly exceeded the developer's claim of a 30%
reduction over a 1-yr time frame. The average concentration of
the sum of the seven analytes from the hot zone in the study
area, prior to installation of the SVVS®, was 341.5 mg/kg. The
average concentration of the sum of the seven analytes after
one year of operation was 66.20 mg/kg.
Reductions for each subsurface horizon are presented
in Table 2 and graphically depicted in Figure 3. The data reveal
that the most contaminated zone is the sludge layer, with an
average reduction of 81.5%. The other less contaminated hori-
zons exhibited reductions ranging from 97.8% to 99.8%.
The reductions over the areal extent of the site, as
determined from the individual boreholes, ranged from 71% to
over 99%. This indicates the system operated relatively uni-
formly over the entire vadose zone of the treatment plot, and
no significant untreated areas were encountered, regardless of
VOC concentration or lithology.
The shut-down testing indicates that microbiological ac-
tivity was stimulated at the site. Due to the inherently high
organic content of the soil, it was not clear how much of this
stimulation was due to contamination. The microbiological ac-
tivity, as determined from the first shut-down test, was great-
est in portions of the site where the VOCs were greatest, and
least active in areas of the site where the contamination was
small or absent. Seasonal variations as evidenced in the back-
ground wells, where presumably no contamination existed,
introduced uncertainty in data interpretation. A comparison of
three shut-down tests indicates that biological activity was
greatest during the beginning of remediation and progressively
decreased throughout the remainder of the demonstration, but
at a rate that was less than the VOC mass removal rates
attributed to vapor extraction alone. This would indicate that
biological processes play an increasingly important, but not a
dominant, role relative to vapor extraction as the remediation
proceeds.
An analysis of the volatiles from the vapor extraction
outlet is presented in Figure 4. The graph reveals that the
highest mass of volatiles was removed during the early phase
of the project. Furthermore, the mass of volatiles in the off-gas
stream gradually decreases to a low and constant level after
approximately 230 days of operation.
The SVVS® experienced no major operational problems
over the 12-mo study period. Once implemented, the system
was easy to monitor and required minimal maintenance and/or
operator attention.
The Biological Emissions Control™ (BEC™) unit, in-
stalled to biologically degrade VOCs from the off-gas stream,
was removed from the system after a few months of operation
and was not evaluated. Dispersive air modelling results showed
Table 2. S VVS® Performance Summary Zone 1 ("Hot Zone")
Treatment Plot Horizons
Upper Horizon
Sludge Layer
Lower Horizon A1
Lower Horizon A2
.Lower Horizon B
Before
321.77
1661.03
96.42
37.68
13.57
Critical VOCs*
Concentration (mg/kg)
After
0.74
307.69
0.98
0.42
0.30
% Reduction
99.77%
81.48%
98.99%
98.88%
97.79%
*Sum of Benzene, Toluene, Ethylbenzene, Xylene, 1,1-Dichloroethene, Trichloroethene, and Tetrachloroethene
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Non-Sludge Layers
Sludge Layers
o 1000
o
o
o
Lower Horizon A1 Lower Horizon B
Upper Horizon Lower Horizon A2
Sludge Layers
Figures. Sl/l/S®performance.
03
140
120
100
80
60
40
20
0
0
50
100
150 200 250
Elapsed Time (days)
Figure 4. Total Mass Flow Rate of Critical VOCs Versus Time.
300
350
400
that contaminant concentrations were below established air
quality standards and discharge criteria for the site were met
without any additional treatment.
The SVVS® was installed at the site based on contami-
nant distribution information derived from remedial investigation
data. During the baseline sampling event under the SITE Dem-
onstration, it became evident that a portion of the system was
installed within a clean area of the site. Operation of the system
was easily adjusted while maintaining the existing hardware to
concentrate remedial action in more contaminated areas. How-
ever, installation of the system in the non-contaminated area
impacted costs since materials and labor were expended. The
excess installation did not in any way impact the performance
of the system. This situation stresses the importance of accu-
rately defining the extent and magnitude of contamination prior
to the implementation of insitu technologies. Insitu technolo-
gies may require site characterization in greater detail than is
commonly available from remedial investigations.
The cost to remediate 21,300 yd3 of vadose zone soils
during a full-scale cleanup over a 3-yr period at the Electro-
Voice Superfund site in Buchanan, Ml was estimated to be
$192,237 or $9/yd3, not including effluent treatment and dis-
posal. The majority of this was incurred in the first year,
primarily due to well drilling and associated site preparation. If
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