United States
Environmental Protection
Agency
Office of
Research and Development
Cincinnati, OH 45268
EPA/540/R-00/502
September 2000
SITE Technology Capsule
NoVOCs™ Evaluation at
MAS North Island
Abstract
The MACTEC, Inc. (MACTEC), NoVOCs™ in-well volatile
organic compound (VOC) stripping process is an in situ
groundwater remediation technology designed for cleaning
up groundwater contaminated with VOCs. In this process,
air injected into a specially designed well simultaneously
lifts groundwater, strips VOCs from the groundwater, and
allows the groundwater to reinfiltrate into the aquifer.
The NoVOCs™ technology was evaluated under the
Superfund Innovative Technology Evaluation (SITE)
Program at Installation Restoration Site 9 of Naval Air
Station (NAS) North Island in San Diego, CAto assess the
technology's ability to treat groundwatercontaminated with
high levels of chlorinated and aromatic hydrocarbons. This
project was performed in conjunction with EPA's
Technology Innovation Office, Naval Facilities Engineering
Command Southwest Division (SWDIV), Navy Environ-
mental Leadership Program, and Clean Sites, Inc. This site
was particularly challenging because the groundwater
contained total dissolved solids (TDS) ranging from
18,000-41,000 milligrams per liter (mg/L), considerably
higher concentrations of TDS than typical drinking water
aquifers.
Operational difficulties associated with biofouling and
precipitation of iron and other compounds on the
NoVOCs™ well during the evaluation resulted in an
incomplete evaluation of the performance and cost
characteristics of the NoVOCs™ technology. The system
was limited to four main operating periods and operated
about 71% of the time, excluding system startup and
shakedown. During system operation, valuable information
was collected regarding (1) the operation and maintenance
of the NoVOCs™ technology, and (2) site-specific factors
that may influence the performance and cost of the system.
This information may be useful to decision-makers when
carrying out specific remedial actions using this technology
or conducting further performance evaluations of the
NoVOCs™ technology. Data from the SITE evaluation
may require extrapolation to estimate the operating ranges
in which the technology will perform satisfactorily. Since the
evaluation was stopped as a result of operational
difficulties, only limited conclusions can be drawn from the
field evaluation of the NoVOCs™ technology.
VOC results for groundwater samples collected from the
influent and effluent of the NoVOCs™ system indicated
that 1,1-dichloroethene (1,1-DCE), cis-1,2-dichloroethene
(cis-1,2-DCE), and trichloroethene (TCE) concentrations
were reduced by greater than 98, 95, and 93%,
respectively. The mean concentrations of 1,1-DCE, cis-
1,2,-DCE, and TCE in the untreated water were
approximately 3,530, 45,000, and 1,650 micrograms per
liter (ug/L), respectively, and the mean concentrations of
1,1-DCE, cis-1,2-DCE, and TCE in the treated water
discharged from the NoVOCs™ system were 27, 1,400,
and 32 ug/L, respectively. The average total VOC mass
removed by the NoVOCs™ system ranged from 0.01 to
0.14 pound per hour and averaged 0.10 pound per hour.
Accounting forthe intermittent operation of the NoVOCs™
system, the mass of total VOCs removed during the entire
operation period from 4/20-6/19/98 was estimated to be
approximately 92.5 pounds.
Because of the intermittent operation of the NoVOCs™
system, a direct evaluation of the radial extent of the
NoVOCs™ treatment cell was not conducted. However,
results from the dipole flow test show that measurable
pressure changes occur at crossgradient locations 30 feet
from the NoVOCs™ well and may be observed at farther
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
* * Printed on Recycled Paper
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distances. The resulting changes in pressure head provide
an indication of the potential for flow in the surrounding
aquifer and are used to provide an estimate of the radial
extent of influence created by the NoVOCs™ well.
However, the pressure head changes do not accurately
represent flow patterns orcontaminant transport, so nofirm
conclusions can be drawn about the radial extent of the
NoVOCs™ treatment cell.
The NoVOCs™ technology was evaluated based on the
nine criteria used for decision-making in the Superfund
feasibility study process. Results of the evaluation are
summarized in Table 1.
Introduction
The EPA SITE Program was established in 1986 to
accelerate the development, evaluation, and use of
innovative technologies that offer permanent cleanup
alternatives for hazardous waste sites. One component of
the SITE Program is the Demonstration Program, under
which engineering, performance, and cost data are
developed for innovative treatment technologies. Data
developed underthe SITE Demonstration Program enable
potential users to evaluate each technology's applicability
to specific waste sites. EPA SITE Technology Capsules
summarize the latest information available on selected
innovative treatment and site remediation technologies
and related issues.
This Technology Capsule summarizes the findings of an
evaluation of the MACTEC NoVOCs™ in-well VOC
stripping system and provides information regarding
lessons learned and recommendations for future
evaluations of the technology. The NoVOCs™ system was
evaluated under the EPA SITE Program at Installation
Restoration Site 9 at NAS North Island in San Diego, CA
over an 11-month period from 2/98-1/99. The NoVOCs™
system was designed to operate continuously; during the
evaluation, however, the system experienced significant
operational difficulties and was limited to four main
operating periods. The evaluation focused on the ability of
the NoVOCs™ system to treat groundwater contaminated
with VOCs, specifically, chlorinated and aromatic
hydrocarbons.
The evaluation was conducted in partnership with SWDIV,
the Navy Environmental Leadership Program, the EPA
Technology Innovation Office, and Clean Sites, Inc.
MACTEC designed and provided technical support during
installation and operation of the NoVOCs™ system, and
the system was operated and monitored by SWDIV's
support contractor, Bechtel National, Inc. (Bechtel).
This Technology Capsule presents the following informa-
tion about the NoVOCs™ technology and the SITE
Prog ram evaluation:
• Technology Description
• Technology Applicability
• Technology Limitations
• Process Residuals
• Site Requirements
• Performance Data
• Summary of Results
• Economic Analysis
• Lessons Learned and Recommendations For Future
Studies
• Technology Status
• SITE Program
• Sources of Additional Information
• References
Technology Description
MACTEC's NoVOCs™ system is a patented in-well
stripping process for in situ removal of VOCs from
groundwater. In this process, air injected into a specially
designed well simultaneously lifts groundwater, strips
VOCs from the groundwater, and allows the groundwater
to reinfiltrate into the aquifer.
A schematic of the NoVOCs™ treatment process is shown
in Figure 1. The NoVOCs™ well installed at NAS North
Island consisted of a well casing installed into the
contaminated saturated zone, with two screened intervals
below the water table, and an air injection line extending
into the groundwater within the well. Contaminated
groundwater enters the well through the lower screen and
is pumped upward within the well by pressurized air
supplied through the air injection line, creating an air-lift
pump effect. As the water is air-lifted within the well,
dissolved VOCs in the water volatilize into the airspace at
the air-water interface. The treated water rises to a
deflector plate and is forced out the upper screen to
recharge the aquifer. The stripped VOC vapors are
removed by a vacuum applied to the upper well casing. At
NAS North Island, the stripped vapors were treated by the
Thermatrix flameless oxidation process. Other offgas
treatment systems can be used with the NoVOCs™
technology, and the Thermatrix system is not an integral
part of the NoVOCs™ treatment system. The equipment
used to operate the NoVOCs™ system, including blowers,
a control panel, and air temperature, pressure, and flow
rate gauges, is housed in an on-site control trailer.
The NoVOCs™ well configuration installed at NAS North
Island incorporated recharge screens in the saturated
zone; the recharge screens of most NoVOCs™ wells is
located in the vadose zone. This modification is atypical
because of concerns that a hydraulic barrier was present
between the vadose zone and the intake screen, which
could adversely affect the formation of the circulation cell.
Technology Applicability
The NoVOCs™ technology is applicable for the treatment
of dissolved-phase VOCs in groundwater. In addition, the
chemical and physical dynamics established by the
recirculation of treated water make this technology suitable
for remediation of contaminant source areas.
The technology is primarily applicable to sandy aquifers
with moderate to high hydraulic conductivities and can
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Table 1. Evaluation Criteria for the NoVOCs™ Technology
Evaluation Criteria Performance
Overall Protection of Human Health
and the Environment
The technology eliminates contaminants in the groundwaterwith minimal
exposure to on-site workers and the community. Air emissions are
reduced by using an offgas treatment system.
Compliance with Federal ARARS
Requires compliance with RCRA hazardous waste treatment, storage,
and land disposal reguilations. Emission controls may be needed to
ensure compliance with air quality standards.
Long-term Effectiveness and
Permanence
Contaminants are permanently removed from the groundwater.
Treatment residuals require proper off-site treatment and disposal.
Reduction of Toxicity, Mobility, or
Volume through Treatment
Contaminant mobility is initially increased, which facilitates the long-term
remediation of the groundwater within the system's treatment cell. The
movement of contaminants toward the NoVOCs™ system prevents
further migration of those contaminants and ultimately reduces the
volume of contaminated media.
Short-term Effectiveness
During site preparation and installation of the treatment system, no
adverse impacts to the community, workers, or the environment are
anticipated. Short-term risks to workers, the community, and the
environment are presented by increased mobility of contaminants during
the initial start-up phase of the system and from the system's air stream.
Adverse impacts from the air stream are mitigated by passing the
emissions through an offgas treatment system before discharge to the
ambient air. The time for treatment using the NoVOCs™ system is
dependent on site conditions and may require several years.
Implementability
The site must be accessible to large trucks. The entire system requires
about 500 square feet of space. Services and supplies may include a
drill rig, carbon adsorption regeneration/disposal (or other off-gas
treatment system), laboratory analysis, and electrical utilities.
Cost
Capital costs for installation are estimated at $190,000 and operation
and maintenance costs for the first year are estimated to be $160,000
and $150,000 annually thereafter.
State Acceptance
State acceptance is anticipated because of the NoVOCs™ system uses
well-documented and widely-accepted processes for the removal of
VOCs from groundwater and for treatment of the process air emissions.
State regulatory agencies may require permits to operate the treatment
system, for air emissions, and to store contaminated soil cuttings and
purge water for greater than 90 days.
Community Acceptance
The small risks presented to the community along with the permanent
removal of the contaminants make public acceptance of the technology
likely.
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Figure 1. NoVOCs™ schematic.
readily be adapted to fit a variety of aquifergeometries. The
technology employs readily available equipment and
materials, and the material handling requirements and site
support requirements are minimal.
The vendor claims that the technology can also be used as
a groundwater interdiction system to prevent further
migration of a contaminant plume, and can clean up
aquifers contaminated with semivolatile organic com-
pounds (SVOC) that are amenable to aerobic biodegrada-
tion. According to the vendor, the NoVOCs™ technology is
also capable of simultaneous recovery of soil gas from the
vadose zone and treatment of contaminated groundwater
from the aquifer as a result of the in situ vacuum. For soil
gas recovery, the upperscreened portion of the NoVOCs™
well is completed within the vadose zone. The vendor
further claims that the circulation cell established by the
NoVOCs™ well can be used to distribute nutrients,
catalysts, surfactants, and other compounds to enhance in
situ remediation processes such as biodegradation.
At NAS North Island, one NoVOCs™ well was installed to
remediate VOCs in a portion of the aquifer downgradient
from a contaminant source area. The ability of the system
to act as an interdiction system or to remove contaminants
other than VOCs, in particular chlorinated and aromatic
hydrocarbons, was not assessed during this field
evaluation. Other vendor claims such as the ability of the
NoVOCs™ technology to reduce VOCs from soil gas in the
vadose zone and to act as a distribution system for other
compounds also were not evaluated.
The NoVOCs™ system can be designed to work in a
variety of hydrogeologic conditions. The recharge screen
can be placed within the saturated or vadose zone,
although placement of the recharge screen in the vadose
zone is typical. Recharge into the vadose zone can be
enhanced by using an infiltration gallery. The initial design
for the NoVOCs™ well at NAS North Island included the
extraction of groundwater from the lower portion of the
aquifer and injection of treated water into the vadose zone
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through an infiltration gallery. Because of concerns that a
hydraulic barrier may be present between the vadose
zone and the intake screen, however, the well was
redesigned to include the extraction of groundwaterfrom
the lower portion of the aquifer and injection of treated
groundwater in the saturated zone, just below the
hydraulic barrier.
The unique dual screen construction of a NoVOCs™ well
in conjunction with in situ air stripping facilitates the
stripping of VOCs and reinfiltration of the groundwater. As
a result, remediation of the aquifer occurs without
extracting groundwater, lowering the groundwater table,
or generating wastewater, all of which are typical of
traditional groundwater remediation systems. In addition,
the vendor claims that the continuous flushing of the
saturated zone with recirculated treated water and the
increased horizontal and vertical groundwater flow within
the saturated zone can facilitate the removal of adsorbed
and nonaqueous-phase contaminants.
Technology Limitations
The NoVOCs™ technology has limitations in areas with
very shallow groundwater (at or nearthe ground surface).
In such areas, it may be difficult to establish a stripping
zone long enough to remove contaminants from the
aqueous phase. The technology has further limitations in
thin aquifers; the saturated zone must be of sufficient
thickness to allow installation of the system. In addition,
the thickness of the saturated zone affects the size of the
treatment cell; the smaller the aquifer thickness, the
smaller the potential diameter of the treatment area.
Furthermore, the technology may have difficulty
performing at sites with low hydraulic conductivity or with
highly variable hydraulic conductivity between the upper
and lower screened intervals. Under variable hydraulic
conductivity conditions, balancing the flow rate with
optimum stripping conditions might prove difficult. This
diffculty may be overcome by using an infiltration galley to
increase the storage capacity and the infiltration area of
the recharge zone.
High concentrations of VOCs typically require more than
one pass through the system to achieve remediation
goals. The number of passes depends on the initial
contaminant concentration, amount of recirculation, and
the removal efficiency of the system. Moreover, if
recirculation is not well established, treated water
containing contaminant concentrations greater than the
remediation goal may be dispersed by the system and
migrate downgradient. The effectiveness ofthe NoVOCs™
system's ability to remove contaminants is directly related
to the volatility of the contaminants. Contaminants with
high volatility and low water solubility are easierto remove
than compounds with low volatility and high water
solubility.
Based on the results of the SITE evaluation of the
NoVOCs™ system at NAS North Island and other
recirculating well evaluations, well fouling is a recognized
problem that requires an appropriate design, as well as
operation and maintenance activities, for successful
management. Groundwater injection and extraction wells,
including in-well stripping systems and recirculating wells
such as the NoVOCs™ system, are subjectto fouling from
a variety of common causes. The three most common
causes of fouling in recirculating wells and groundwater
wells in general are (1) formation of chemical precipitates
and insoluble mineral species (chemical fouling), (2)
biofouling by colonizing microorganisms, and (3)
accumulation of silt in the well structure. These issues
may be controlled through groundwater pH control to
manage formation of chemical precipitates and insoluble
mineral species, injection of a suitable biocide, and
appropriate design and construction of filter pack and well
screens. However, any design that does not provide
geochemical controls based on site-specific hydrogeologic
and geochemical conditions is likely to experience
significant operation and maintenance problems due to
fouling.
Some ofthe geochemical effects may be easierto control
in a closed-loop design than in a comparable open-loop
design. In a closed-loop design, the stripping air is
captured and used in subsequent stripping cycles.
Carbon dioxide or an alternative type of gas such as
nitrogen can be added to the stripping air to decrease the
amount of carbon dioxide removed and the amount of
oxygen added to the treated water. By reducing carbon
dioxide removal from the groundwater, changes in pH in
the treated water can be minimized. Additionally, by
reducing the amount of oxygen added to the treated water,
anaerobic conditions can be maintained and biological
growth can be minimized. Geochemical and biological
fouling caused by changes in pH and increased biological
growth can also be managed by injecting acid and biocide
into the treated water. The use of acid or biocide in
recirculating wells may receive varying acceptance from
the regulatory community, depending on the site-specific
conditions and nearby water uses.
Process Residuals
The NoVOCs™ system generates a vapor offgas waste
stream that can be treated by several different standard
vapor treatment technologies applicable to VOCs,
including activated granular carbon. During the SITE
evaluation at NAS North Island, the Thermatrixflameless
oxidation system was used to treat contaminants in the
vapor waste stream. The Thermatrix system reduced
contaminant concentrations in the vaporwaste stream by
greater than 99.99%. Use of the Thermatrix system
resulted in the destruction of contaminants; therefore, no
process residuals were generated that required disposal.
Soil cuttings, purge water, and decontamination wastes
are generated during installation ofthe NoVOCs™ well
and monitoring wells, and during well development and
sampling activities. Disposal options for these wastes
depend on local requirements and on the concentrations
of contaminants.
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Site Requirements
Space to set up the offgas treatment system and electricity
are the only site support requirements for the NoVOCs™
system. The electrical power requirements for the
NoVOCs™ system depend on several parameters that
must be specified in the system design, including airflow
rate and the pressure at which the air is injected into the
aquifer. The space requirements for the aboveground
components of the NoVOCs™ well, including the control
trailer, aboveground piping, and offgas treatment system
are approximately 500 square feet. A security fence to
prevent unauthorized access to the NoVOCs™ well and
control trailer is also recommended. Other requirements
for installation and routine monitoring of the system include
temporary storage of drilling cuttings, purge water, and
decontamination wastes.
Performance Data
The NoVOCs™ technology was evaluated to determine its
ability to remove VOCs from groundwater. The critical
objectives of the evaluation were to (1) evaluate the
removal efficiency of the NoVOCs™ well system for VOCs
in groundwater, (2) determine the radial extent of the
NoVOCs™ treatment cell, and (3) quantify the average
monthly total VOC mass removed from groundwater.
Because of operational difficulties with the NoVOCs™
system during the evaluation, objectives 2 and 3 could not
be evaluated. In these cases, results and conclusions are
presented based on the limited data available.
For this evaluation, groundwater samples were collected
from the NoVOCs™ influent and effluent using two
piezometers installed adjacent to the NoVOCs™ well and
from 10 groundwater monitoring wells installed upgradient,
crossgradient, and downgradient from the NoVOCs™ well.
The groundwater monitoring wells were installed at
different depths and radii from the NoVOCs™ well to
evaluate changes in contaminant concentrations within the
aquifer associated with operation of the NoVOCs™
system. Air samples were collected from four sampling
locations to evaluate the concentration of contaminants in
the influent and effluent of both the NoVOCs™ and
Thermatrix systems. Groundwater and air samples were
collected weekly for the first month of operation and
monthly thereafter. However, only one monthly sampling
event was conducted because of operational problems
with the NoVOCs™ system. All samples were analyzed for
the targeted VOCs.
Operation and maintenance of the NoVOCs™ system was
conducted primarily by Bechtel with technical guidance
from MACTEC. The NoVOCs™ system was designed to
operate continuously, 24 hours per day, 7 days per week.
During the evaluation, however, the system experienced
significant operational difficulties and was limited to four
main operating periods: System Startup and Shakedown
(2/26-3/26/98), Early System Operation (4/20-6/19/98),
Reconfiguration Operation (9/24-10/30/98), and Final
Configuration Operation (12/4/98-1/4/99). Excluding sys-
tem startup and shakedown, the system operated about
71% of the time during the remaining three operational
periods.
Summary of Results
The site was particularly challenging because the
groundwater contained TDS at concentrations ranging
from 18,000 to 41,000 mg/L, which are considerably higher
than concentrations of TDS in typical drinking water
aquifers.
In early May 1998, the NoVOCs™ system began
experiencing operating problems associated with high
water levels in the NoVOCs™ well and low pumping rates.
Evaluation participants initially thought that the flow sensor
was not accurately measuring the pumping rate. As system
operation progressed, however, the continued low
pumping rate and increased frequency of high water levels
in the NoVOCs™ well suggested that a more significant
problem was occurring. By June 1998, the pumping rate
had been reduced from the design rate of 25 gallons per
minute (gpm) to approximately 5 gpm. Based on
discussions between the Navy and MACTEC, the system
was shut down on June 19,1998 to evaluate the cause of
the poor performance. Although iron fouling was confirmed
in May 1999, other suspected causes for the poor
performance included (1) biofouling orscaling of the screen
intervals and formation near the NoVOCs™ well, (2)
possible differences in hydraulic characteristics between
the upper and lower portions of the aquifer, and (3) design
problems with the NoVOCs™ well, in particular the length
of the recharge screen.
To evaluate the recharge capacity of the NoVOCs™
system and provide information regarding the hydraulic
characteristics of the aquifer in the vicinity of the
NoVOCs™ system, a down-well video survey and a series
of aquifer hydraulic tests were conducted. Based on the
aquifer testing, it was concluded that the length of the
screened intervals of the NoVOCs™ well should be able to
sustain the design pumping rate of 25 gpm. During the
video survey, fouling of the NoVOCs™ well screens by
microbiological growth and iron precipitation was
observed. This fouling appeared to have impaired the
performance of the NoVOCs™ system by obstructing the
well screen and filter pack. Microbiological testing of the
groundwater confirmed the presence of biofouling
organisms. Efforts to control fouling by addition of various
acids, dispersants, and biocides met with varying degrees
of success (only iron precipitation fouling was successfully
controlled). Citric acid was added to sequesterthe iron but
could have also increased biofouling. Failure to completely
control the biofouling of the recharge screen eventually
caused the termination of the evaluation in January 1999.
Because of operational difficulties with the NoVOCs™
system throughout the demonstration, only limited data
were collected to evaluate the technology. The conclusions
that may be drawn based on the limited data collected
during the SITE evaluation are presented below. A detailed
discussion of the evaluation results and conclusions is
provided in the NoVOCs™ Technology Evaluation Report
(Tetra Tech 2000).
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1. Comparison of VOC results for groundwater samples
taken adjacent to the influent and effluent of the
NoVOCs™ well indicated that 1,1-DCE, cis-1,2-DCE,
and TCE concentrations were reduced by greater than
98, 95, and 93%, respectively, in all the events except
the first Bechtel sampling event, which was conducted
during system shakedown activities. A summary of
contaminant removal is presented in Table 2.
Excluding the first sampling event, the mean
concentrations of 1,1-DCE, cis-1,2,-DCE, and TCE in
the untreated waterwere approximately 3,530, 45,000,
and 1,650 ug/L, respectively, and the mean concen-
trations of 1,1-DCE, cis-1,2-DCE, and TCE in the
treated water discharged from the NoVOCs™ system
were approximately 27, 1,400, and 32 ug/L, respec-
tively. The 95% upper confidence limits of the means for
1,1-DCE, cis-1,2-DCE, and TCE in the treated
groundwater were calculated to be approximately 36,
1,740, and 45 ug/L, respectively. The maximum
contaminant levels (MCL) for these compounds in
groundwater are 6 ug/L for 1,1-DCE, 6 ug/Lforcis-1,2-
DCE, and 5 ug/L for TCE. MACTEC claims that the
NoVOCs™ system can reduce effluent VOC concentra-
tions to below MCLs if the contaminant source has been
removed. Since dense nonaqueous-phase liquids may
be present in the aquifer at the site and may act as a
continuing source of groundwater contamination,
MACTEC did not make any claims for reduction of VOC
concentrations in groundwater at Site 9.
2. Because of the sporadic operation of the NoVOCs™
system, a direct evaluation of the radial extent of the
NoVOCs™ treatment cell was not conducted. In lieu of
a direct evaluation method, aquifer hydraulic tests were
conducted to assess the hydrogeologic characteristics
of the site and to indirectly evaluate the potential radial
extent of the NoVOCs™ treatment cell. Although the
aquifer pump tests cannot be directly applied to
evaluate the radial extent of the NoVOCs™ treatment
cell or even that groundwater recirculation was
established, the test data do provide information on the
radius of influence of the well under pumping (2-
dimensional) and dipole (3-dimensional) flow condi-
tions. The resulting changes in pressure head provide
an indication of the potential for flow in the surrounding
aquifer and are used to provide an estimate of the radial
extent of influence created by the NoVOCs™ well.
However, the pressure head changes do not accurately
represent flow patterns or contaminant transport.
Consequently, no firm conclusions can be drawn about
the radial extent of the NoVOCs™ treatment cell.
During the constant discharge rate (discharge = 20
gpm) pumping test, measurable drawdowns (+/- 0.01
feet) were observed at approximately 100 feet from the
NoVOCs™ well in all directions and at different depths.
This information indicates that the radius of resulting
from extraction at 20 gpm could be as large as 100 feet.
The dipole flow test data showed that measurable
pressure responses occured at crossgradient locations
30 feet from the NoVOCs™ well and may be observed
at greater distances. However, no drawdowns orwater
level rises could be positively measured in monitoring
wells beyond the 30-foot distance.
3. Because of operational problems with the NoVOCs™
system, the mass of VOCs removed by the NoVOCs™
system was evaluated during five sampling events
within a period of limited operation from April 28 to June
8,1998. During this period, the average total VOC mass
removed by the NoVOCs™ system ranged from 0.01 to
0.14 pound perhourand averaged 0.10 pound perhour.
Accounting forthe sporadic operation of the NoVOCs™
system, the mass of total VOCs removed during the
entire operation period from April 20 through June 19,
1998 was estimated to be approximately 92.5 pounds. A
summary of the total VOC mass removed is presented
in Table 3.
Economic Analysis
An economic analysis for the NoVOCs™ technology to
treat VOC-contaminated groundwater was conducted
based on the SITE evaluation and cost information
provided by the Navy and MACTEC. One-time capital
costs for a NoVOCs™ system were estimated to be
$190,000; annual operation and maintenance costs were
estimated to be $160,000 per year for the first year and
$150,000 per year thereafter. Since the time required to
remediate an aquifer is site-specific, costs have been
estimated for operation of a NoVOCs™ system over a
range of time for comparison purposes. Based on these
estimates and an annual inflation rate of 4%, the total cost
for operating a single NoVOCs™ system was calculated to
be $350,000 for 1 year; $670,000 for 3 years; $1,000,000
for 5 years; and $2,000,000 for 10 years. The cost of
treatment per unit volume of water was not calculated
because of the number of assumptions required to make
such a calculation. Additionally, costs per unit volume of
water were not calculated for this project because of the
site-specific nature of treatment costs.
Costs for implementing a NoVOCs™ system at another
site may vary substantially from this estimate forthe SITE
evaluation. A number of factors affect the cost of treatment
using the NoVOCs™ system, including soil type,
contaminant type and concentration, depth to groundwa-
ter, site geology and hydrogeology, groundwater
geochemistry, site size and accessibility, required support
facilities and available utilities, type of offgas treatment unit
used, and treatment goals. It is important to (1)
characterize the site thoroughly before implementing this
technology to ensure that treatment is focused on
contaminated areas, and (2) determine the redius of the
circulation cell forthe well and the resulting numberof wells
needed to remediate a particular site.
Lessons Learned and Recommendations for
Future Studies
The evaluation of innovativetechnologies, especially insitu
processes, poses significant technical difficulties even
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Table 3. Summary of Total VOC Mass Removed
Effluent Sampling
Event (Date
1st Weekly
(4/28/98)
2nd Weekly
(5/6/98)
3rd Weekly
(5/12/98)
4th Weekly
(5/21/98)
1st Monthly
(6/8/98)
Average
Total
Effluent Total VOC
Concentration per
Event (ppb v/v)
15,060
104,100
125,700
136,000
93,900
95,000
NC
Effluent Air Flow
Rate During Event
(scfm)
50*
68
69
63
61
64.2
NC
Effluent Total VOC
Mass Removed
Over 1-Hour
Sampling Event**
(Ibs/hr)
0.0145
0.1134
0.1391
0.1372
0.0914
0.0991
NC
System
Operation
(hr)
261.5
126.75
101.25
183.5
383
NC
1056
Total VOC Mass
Removed (Ibs)
3.8
14.4
14.1
25.2
35.0
NC
92.5
Notes:
Flow meter not installed at sampling time; measurement obtained from NoVOCs™ trailer.
Mass calculated using the Ideal Gas Law, assuming standard samle temperature (6°F) and pressure (1 atmosphere)
under ideal site conditions. Since these remediation
processes occur in the subsurface and cannot readily be
observed or easily measured, the evaluator must rely on a
limited number of discrete measurements to provide an
indication of changes in the subsurface caused by the
technology. This task is further complicated by the typical
lack of sufficient site characterization data to provide a
thorough and detailed understanding of the hydrogeology
and contaminant distribution at a site.
When applying an innovative /ns/fry technology such as the
NoVOCs™ system to a complex site such as MAS North
Island Site 9, a team of experts with applied experience in
recirculating well engineering, geology, hydrology, and
geochemistry should be used. The NoVOCs™ system did
not function without operational difficulties, partly because
this site's groundwater, which contained TDS concentra-
tions ranging from 18,000 to 41,000 mg/L, considerably
higher concentrations of TDS than typical drinking water
aquifers.
The NoVOCs™ system affects the groundwatergeochem-
istry and subsurface environmental conditions through the
removal of carbon dioxide from the groundwater, injection
of air, and movement of contaminants to the well. In
carbonate-rich groundwater, the removal of carbon dioxide
affects the buffering capacity of groundwater and may
result in increases in pH. These changes can affect
chemical equilibria in the subsurface and cause the
precipitation or dissolution of inorganic compounds. The
oxygenation of the groundwater during air stripping and
increased contaminant movement near the well may
provide an environment for enhanced microbiological
growth. The precipitation of inorganic compounds and
increased microbiological growth can adversely affect the
performance of the system by decreasing the ability of the
well screens, filter pack, and adjacent formation to transmit
water. Addressing the potential forthese fouling issues and
their proper management is critical during project planning
and design.
Contaminant transport associated with the NoVOCs™
system is also complicated by the 3-dimensional
groundwater flow induced within the aquifer surrounding
the well and the lack of detailed site characterization
information. When applying an induced flow to the
subsurface, migration is typically confined to preferential
pathways and is strongly controlled by the heterogeneity
and anisotropy of the aquifer. Modeling of the contaminant
transport during evaluation planning is recommended to
provide an understanding of groundwater flow and to
optimize placement of monitoring and measurement ports.
Even given a team of experienced professionals, problems
may arise. To help minimize these problems, a summary of
recommendations is provided to assist those involved in
future evaluation of the NoVOCs™ system and
groundwater circulation wells in general. Based on the
NoVOCs™ evaluation at NAS North Island, Site 9,
recommendations for (1) site specific characterization
activities; (2) assessment of fouling potential (chemical
precipitation, biological fouling, and siltation); and (3)
integration of system controls are provided below.
Site-specific Characterization
A thorough site characterization is required to design a
recirculating well system. Some of the characterization
requirements are common geological practices, others are
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more specific to the technology being deployed. The
recommended approaches are described below.
Geological Description
Discrete core samples (for example, samples collected
every 5 feet) should not be considered until a sufficient
number of continuous cores have been evaluated to
develop a confident conceptual model of the site
stratigraphy. At Site 9, the continuous coring performed
specifically for the NoVOCs™ evaluation resulted in not
only revision of the NoVOCs™ system conceptual design,
but revision of the entire stratigraphic conceptual model of
that portion of MAS North Island.
Aquifer Testing
A variety of aquifer testing approaches are applicable to
recirculating well system design. These approaches
include permeability testing of representative intact cores
from the stratigraphic column. Grain size analysis of
representative samples can provide some indication of
formation permeability, but cannot provide assessment of
the formation structure, which plays an important role in
water conductivity. Site evaluation should include two
aquifertests at a minimum; one extraction pumping test to
evaluate the productivity of the extraction zone and one
injection test to evaluate the capacity of the recharge zone.
A combined pumping and recharge test, known as a
modified "dipole" test, can provide additional information
regarding potential system performance. The dipole test
can also provide information on site-specific anisotropy.
Anisotropy is the ratio of the hydraulic conductivity in the
horizontal direction to that in the vertical direction and
strongly influences the extent of the groundwater
circulation cell and capture zone. During all aquifertests,
pressure head changes should be monitored and recorded
in all accessible monitoring locations.
Assessment of Fouling Potential
Site conditions should be evaluated for the three primary
sources of fouling discussed below, and the system should
be designed and operated to control the impacts of fouling.
Chemical Precipitation
Chemical precipitation may occur for both recirculating
wells and extraction wells, and requires planning and
careful implementation for successful control. During the
design phase, system planners should perform the
following tests:
• An aeration/titration test to identify the anticipated pH
change with aeration, evaluate the potential for calcite
precipitation, and estimate the water's demand for
acidification to prevent calcite formation.
• Determination of total and dissolved iron and
manganese concentrations in the water to assess the
potential for fouling through precipitation of ferric
hydroxide after aeration. Also evaluate the redox
potential of the aquifer. Grossly polluted and saline
aquifers may contain substantial reduced iron and
manganese species that may become more soluble as
the aquifer becomes more aerobic. The concentration
of dissolved iron in the water can also indicate the
potential for iron-related bacteria to develop in the
system.
• An iron precipitation test can provide an estimate of the
magnitude of iron precipitation that may occur in the
system. The test can be conducted by determining the
iron content of a water sample, then aerating the
sample, allowing the ferric hydroxide to precipitate,
and measuring the iron concentration in the remaining
water again.
• Monitor pH and iron status in the aquifer regularly
during system operation.
The results of the tests should be used to incorporate
precipitation control features into the system design. For
example, a closed-loop system might be chosen over an
open-loop system, a stripping gas other than air might be
selected, and injection of chemicals might be required. As
with the control of biological growth, provisions should be
made to inject chemicals to control precipitation into the
well inlet filter pack as well as into the treated water being
returned to the formation.
Biological Fouling
Biofouling is a demonstrated problem for recirculating and
extraction wells. A recommended approach to minimizing
biofouling problems is to evaluate the overall aquifer
microbial ecology to assess both the fouling potential and
potential control alternatives. A minimal evaluation of the
microbial ecology of a candidate site includes the
identification of the presence of natural and contaminant-
related substrates within the aquifer (as measured by
biological oxygen demand and chemical oxygen demand).
The evaluation also should determine oxidation-reduction
potential (aerobic versus anaerobic), temperature and
pressure, and the presence of indigenous organisms
(determined by culturing aquifer samples). System
designers and operators must remain aware of aquifer
ecology changes that may occur during system operation.
In the case of the NoVOCs™ technology, which vigorously
aerates the groundwater coincidental with removal of
dissolved VOCs, aerobic microbial communities can be
expected to develop in previously anaerobic locations.
Facultative anaerobes that were present as very minor
fractions of the overall microbial community may become
dominant. Specialized microbes, such as iron-related
bacteria may also become established in locations where a
constant supply of fresh substrate is available and physical
conditions favor colonization (for example, in the well
screens). If fouling microbes are present, provisions should
be made to inject biocides into the well inlet filter pack as
well as into the treated water being returned to the
formation.
10
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Siltation
Although siltation was not a problem at MAS North Island,
recirculating wells are subject to fouling due to
accumulation of aquifer solids, just as are any extraction or
recharge well. The grain size and structure of the strata in
which well screens will be placed must be thoroughly
evaluated to ensure that the appropriate combination of
screen and filter pack is designed for the well in each
screened interval. After well construction, the screened
intervals must be thoroughly and aggressively developed
to achieve very low levels of suspended solids (less than 5
nephelometric turbidity units suspended solids). If the
recirculating well uses an air lift action, like the NoVOCs™
technology, thorough development is essential. If not
properly developed, the air lift action will develop the inlet
screen and the resulting solids will be deposited in the
recharge zone, effectively plugging the well.
Integration of System Controls
System designers should maximize the use of available
electronic control technology. Recent development has
produced dramatic increases in the capability and reduced
associated costs for sophisticated supervisory, control,
and data acquisition systems. The mechanical system,
well, and offgas treatment system can be readily integrated
with sensors for key parameters, automatic control for off-
normal shutdowns, data recording, remote data acquisi-
tion, and remote control of the system. All aspects of the
recirculating well design should be assessed as a system
to identify critical control and monitoring functions, as well
as supplemental control functions that will increase system
efficiency and reduce downtime and on-site labor.
Technology Status
The concepts of the NoVOCs™ in-well VOC stripping
system were initially proposed by researchers at Stanford
University in the late 1980s (Gvirtzman and Gorelick 1992)
and were further developed undera collaboration between
Stanford University, EG&G Environmental, and the U.S.
Department of Energy (DOE). An initial patent for the
NoVOCs™ system (U.S. Patent No. 5,18,503) was
granted to Stanford University; EG&G subsequently
obtained an exclusive license to the technology.
In 1996, Stanford University and DOE carried out the first
full-scale evaluation of the technology at Edwards Air Force
Base, California. During this evaluation, TCE was removed
from groundwater. In December 1997, MACTEC acquired
the exclusive license to the NoVOCs™ system from
EG&G. At the time of MACTEC's acquisition of the
technology, there were more than 30 applications of the
NoVOCs™ system at both private and government sites.
According to the developer, the technology provides a
viable alternative to traditional groundwater remediation
systems, especially where pump-and-treat type systems
have failed or are not removing significant contaminant
mass. Like other groundwater remediation technologies,
the NoVOCs™ system requires proper geologic and
design considerations, and is not applicable to all types of
contaminants or geologic settings.
SITE Program
In 1980, the U.S. Congress passed the Comprehensive
Environmental Response, Compensation, and Liability Act
(CERCLA), also known as Superfund. CERCLA was
amended by the Superfund Amendments and Reauthori-
zation Act (SARA) in 1986. The SITE Program is a formal
program established in response to SARA. The primary
purpose of the SITE Program is to maximize the use of
alternative technologies in cleaning up hazardous waste
sites by encouraging the development and evaluation of
new, innovative treatment and monitoring technologies.
The NoVOCs™ technology was evaluated under the
Demonstration Program. Other documentation resulting
from this SITE evaluation include a Technology Evaluation
Report that expands on results and conclusions presented
in this Technology Capsule.
Sources of Additional Information
EPA Contact
Michelle Simon
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive
Cincinnati, Ohio 45268
Phone: 513-569-7469; FAX: 513-569-7676
E-mail: simon.michelle@epa.gov
Technology Developer Contact
Joe Aiken
MACTEC, Inc.
1819 Denver West Drive, Suite 400
Golden, Colorado 80401
Phone: 303-278-3100; FAX: 303-278-5000
E-mail: http://www.mactec.com/.
References
Gvirtzman, H. and S.M. Gorelick. 1992. The Concept of In-
situ Vapor Stripping for Removing VOCs from Groundwa-
ter, Transport in Porous Media, Vol. 8, No. 1, p. 71-92.
Tetra Tech EM Inc. (Tetra Tech). 2000. Technology
Evaluation Report for the NoVOCs™ Technology
Evaluation at NAS North Island. June.
11
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Environmental Protection Agency
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Research Laboratory, G-72
Cincinnati, OH 45268
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