Abstract United States Environmental Protection

Environmental ProtectionAgencyOffice of

Research and DevelopmentCincinnati, OH 45268

EPA/540/R-00/502September 2000

SITE Technology CapsuleNoVOCsTM Evaluation atNAS North IslandAbstract

The MACTEC, Inc. (MACTEC), NoVOCs™ in-well volatileorganic compound (VOC) stripping process is an in situgroundwater remediation technology designed for cleaningup groundwater contaminated with VOCs. In this process,air injected into a specially designed well simultaneouslylifts groundwater, strips VOCs from the groundwater, andallows the groundwater to reinfiltrate into the aquifer.The NoVOCs™ technology was evaluated under theSuperfund Innovative Technology Evaluation (SITE)Program at Installation Restoration Site 9 of Naval AirStation (NAS) North Island in San Diego, CA to assess thetechnology’s ability to treat groundwater contaminated withhigh levels of chlorinated and aromatic hydrocarbons. Thisproject was performed in conjunction with EPA’sTechnology Innovation Office, Naval Facilities EngineeringCommand Southwest Division (SWDIV), Navy Environ-mental Leadership Program , and Clean Sites, Inc. This sitewas particularly challenging because the groundwatercontained total dissolved solids (TDS) ranging from18,000-41,000 milligrams per liter (mg/L), considerablyhigher concentrations of TDS than typical drinking wateraquifers.

Operational difficulties associated with biofouling andprecipitation of iron and other compounds on theNoVOCs™ well during the evaluation resulted in anincomplete evaluation of the performance and costcharacteristics of the NoVOCs™ technology. The systemwas limited to four main operating periods and operatedabout 71% of the time, excluding system startup andshakedown. During system operation, valuable informationwas collected regarding (1) the operation and maintenanceof 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 whencarrying out specific remedial actions using this technologyor conducting further performance evaluations of theNoVOCs™ technology. Data from the SITE evaluationmay require extrapolation to estimate the operating rangesin which the technology will perform satisfactorily. Since theevaluation was stopped as a result of operationaldifficulties, only limited conclusions can be drawn from thefield evaluation of the NoVOCs™ technology.

VOC results for groundwater samples collected from theinfluent and effluent of the NoVOCs™ system indicatedthat 1,1-dichloroethene (1,1-DCE), cis-1,2-dichloroethene(cis-1,2-DCE), and trichloroethene (TCE) concentrationswere 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 wereapproximately 3,530, 45,000, and 1,650 micrograms perliter (µg/L), respectively, and the mean concentrations of1,1-DCE, cis-1,2-DCE, and TCE in the treated waterdischarged from the NoVOCs™ system were 27, 1,400,and 32 µg/L, respectively. The average total VOC massremoved by the NoVOCs™ system ranged from 0.01 to0.14 pound per hour and averaged 0.10 pound per hour.Accounting for the intermittent operation of the NoVOCs™system, the mass of total VOCs removed during the entireoperation period from 4/20-6/19/98 was estimated to beapproximately 92.5 pounds.

Because of the intermittent operation of the NoVOCs™system, a direct evaluation of the radial extent of theNoVOCs™ treatment cell was not conducted. However,results from the dipole flow test show that measurablepressure changes occur at crossgradient locations 30 feetfrom the NoVOCs™ well and may be observed at farther

Printed on Recycled Paperdistances. The resulting changes in pressure head providean indication of the potential for flow in the surroundingaquifer and are used to provide an estimate of the radialextent of influence created by the NoVOCs™ well.However, the pressure head changes do not accuratelyrepresent flow patterns or contaminant transport, so no firmconclusions can be drawn about the radial extent of theNoVOCs™ treatment cell.

The NoVOCs™ technology was evaluated based on thenine criteria used for decision-making in the Superfundfeasibility study process. Results of the evaluation aresummarized in Table 1.

•••••••••Site RequirementsPerformance DataSummary of ResultsEconomic Analysis

Lessons Learned and Recommendations For FutureStudies

Technology StatusSITE Program

Sources of Additional InformationReferences

Technology Description

MACTEC’s NoVOCs™ system is a patented in-wellstripping process for in situ removal of VOCs fromgroundwater. In this process, air injected into a speciallydesigned well simultaneously lifts groundwater, stripsVOCs from the groundwater, and allows the groundwaterto reinfiltrate into the aquifer.

A schematic of the NoVOCs™ treatment process is shownin Figure 1. The NoVOCs™ well installed at NAS NorthIsland consisted of a well casing installed into thecontaminated saturated zone, with two screened intervalsbelow the water table, and an air injection line extendinginto the groundwater within the well. Contaminatedgroundwater enters the well through the lower screen andis pumped upward within the well by pressurized airsupplied through the air injection line, creating an air-liftpump effect. As the water is air-lifted within the well,dissolved VOCs in the water volatilize into the air space atthe air-water interface. The treated water rises to adeflector plate and is forced out the upper screen torecharge the aquifer. The stripped VOC vapors areremoved by a vacuum applied to the upper well casing. AtNAS North Island, the stripped vapors were treated by theThermatrix flameless oxidation process. Other offgastreatment systems can be used with the NoVOCs™technology, and the Thermatrix system is not an integralpart of the NoVOCs™ treatment system. The equipmentused to operate the NoVOCs™ system, including blowers,a control panel, and air temperature, pressure, and flowrate gauges, is housed in an on-site control trailer.The NoVOCs™ well configuration installed at NAS NorthIsland incorporated recharge screens in the saturatedzone; the recharge screens of most NoVOCs™ wells islocated in the vadose zone. This modification is atypicalbecause of concerns that a hydraulic barrier was presentbetween the vadose zone and the intake screen, whichcould adversely affect the formation of the circulation cell.

Introduction

The EPA SITE Program was established in 1986 toaccelerate the development, evaluation, and use ofinnovative technologies that offer permanent cleanupalternatives for hazardous waste sites. One component ofthe SITE Program is the Demonstration Program, underwhich engineering, performance, and cost data aredeveloped for innovative treatment technologies. Datadeveloped under the SITE Demonstration Program enablepotential users to evaluate each technology’s applicabilityto specific waste sites. EPA SITE Technology Capsulessummarize the latest information available on selectedinnovative treatment and site remediation technologiesand related issues.

This Technology Capsule summarizes the findings of anevaluation of the MACTEC NoVOCs™ in-well VOCstripping system and provides information regardinglessons learned and recommendations for futureevaluations of the technology. The NoVOCs™ system wasevaluated under the EPA SITE Program at InstallationRestoration Site 9 at NAS North Island in San Diego, CAover an 11-month period from 2/98-1/99. The NoVOCs™system was designed to operate continuously; during theevaluation, however, the system experienced significantoperational difficulties and was limited to four mainoperating periods. The evaluation focused on the ability ofthe NoVOCs™ system to treat groundwater contaminatedwith VOCs, specifically, chlorinated and aromatichydrocarbons.

The evaluation was conducted in partnership with SWDIV,the Navy Environmental Leadership Program, the EPATechnology Innovation Office, and Clean Sites, Inc.MACTEC designed and provided technical support duringinstallation and operation of the NoVOCs™ system, andthe system was operated and monitored by SWDIV’ssupport contractor, Bechtel National, Inc. (Bechtel).This Technology Capsule presents the following informa-tion about the NoVOCs™ technology and the SITEProgram evaluation:••••

Technology DescriptionTechnology ApplicabilityTechnology LimitationsProcess Residuals

Technology Applicability

The NoVOCs™ technology is applicable for the treatmentof dissolved-phase VOCs in groundwater. In addition, thechemical and physical dynamics established by therecirculation of treated water make this technology suitablefor remediation of contaminant source areas.

The technology is primarily applicable to sandy aquiferswith moderate to high hydraulic conductivities and can

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Table1.EvaluationCriteriafortheNoVOCs™TechnologyEvaluationCriteriaOverallProtectionofHumanHealthandtheEnvironmentPerformanceThetechnologyeliminatescontaminantsinthegroundwaterwithminimalexposuretoon-siteworkersandthecommunity.Airemissionsarereducedbyusinganoffgastreatmentsystem.RequirescompliancewithRCRAhazardouswastetreatment,storage,andlanddisposalreguilations.Emissioncontrolsmaybeneededtoensurecompliancewithairqualitystandards.Contaminantsarepermanentlyremovedfromthegroundwater.Treatmentresidualsrequireproperoff-sitetreatmentanddisposal.Contaminantmobilityisinitiallyincreased,whichfacilitatesthelong-termremediationofthegroundwaterwithinthesystem'streatmentcell.ThemovementofcontaminantstowardtheNoVOCs™systempreventsfurthermigrationofthosecontaminantsandultimatelyreducesthevolumeofcontaminatedmedia.CompliancewithFederalARARSLong-termEffectivenessandPermanenceReductionofToxicity,Mobility,orVolumethroughTreatmentShort-termEffectivenessDuringsitepreparationandinstallationofthetreatmentsystem,noadverseimpactstothecommunity,workers,ortheenvironmentareanticipated.Short-termriskstoworkers,thecommunity,andtheenvironmentarepresentedbyincreasedmobilityofcontaminantsduringtheinitialstart-upphaseofthesystemandfromthesystem'sairstream.Adverseimpactsfromtheairstreamaremitigatedbypassingtheemissionsthroughanoffgastreatmentsystembeforedischargetotheambientair.ThetimefortreatmentusingtheNoVOCs™systemisdependentonsiteconditionsandmayrequireseveralyears.Thesitemustbeaccessibletolargetrucks.Theentiresystemrequiresabout500squarefeetofspace.Servicesandsuppliesmayincludeadrillrig,carbonadsorptionregeneration/disposal(orotheroff-gastreatmentsystem),laboratoryanalysis,andelectricalutilities.Capitalcostsforinstallationareestimatedat$190,000andoperationandmaintenancecostsforthefirstyearareestimatedtobe$160,000and$150,000annuallythereafter.StateacceptanceisanticipatedbecauseoftheNoVOCs™systemuseswell-documentedandwidely-acceptedprocessesfortheremovalofVOCsfromgroundwaterandfortreatmentoftheprocessairemissions.Stateregulatoryagenciesmayrequirepermitstooperatethetreatmentsystem,forairemissions,andtostorecontaminatedsoilcuttingsandpurgewaterforgreaterthan90days.Thesmallriskspresentedtothecommunityalongwiththepermanentremovalofthecontaminantsmakepublicacceptanceofthetechnologylikely.ImplementabilityCostStateAcceptanceCommunityAcceptance3

Figure 1. NoVOCs™ schematic.

readily be adapted to fit a variety of aquifer geometries. Thetechnology employs readily available equipment andmaterials, and the material handling requirements and sitesupport requirements are minimal.

The vendor claims that the technology can also be used asa groundwater interdiction system to prevent furthermigration of a contaminant plume, and can clean upaquifers contaminated with semivolatile organic com-pounds (SVOC) that are amenable to aerobic biodegrada-tion. According to the vendor, the NoVOCs™ technology isalso capable of simultaneous recovery of soil gas from thevadose zone and treatment of contaminated groundwaterfrom the aquifer as a result of the in situ vacuum. For soilgas recovery, the upper screened portion of the NoVOCs™well is completed within the vadose zone. The vendorfurther claims that the circulation cell established by theNoVOCs™ well can be used to distribute nutrients,catalysts, surfactants, and other compounds to enhance insitu remediation processes such as biodegradation.

At NAS North Island, one NoVOCs™ well was installed toremediate VOCs in a portion of the aquifer downgradientfrom a contaminant source area. The ability of the systemto act as an interdiction system or to remove contaminantsother than VOCs, in particular chlorinated and aromatichydrocarbons, was not assessed during this fieldevaluation. Other vendor claims such as the ability of theNoVOCs™ technology to reduce VOCs from soil gas in thevadose zone and to act as a distribution system for othercompounds also were not evaluated.

The NoVOCs™ system can be designed to work in avariety of hydrogeologic conditions. The recharge screencan be placed within the saturated or vadose zone,although placement of the recharge screen in the vadosezone is typical. Recharge into the vadose zone can beenhanced by using an infiltration gallery. The initial designfor the NoVOCs™ well at NAS North Island included theextraction of groundwater from the lower portion of theaquifer and injection of treated water into the vadose zone

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through an infiltration gallery. Because of concerns that ahydraulic barrier may be present between the vadosezone and the intake screen, however, the well wasredesigned to include the extraction of groundwater fromthe lower portion of the aquifer and injection of treatedgroundwater in the saturated zone, just below thehydraulic barrier.

The unique dual screen construction of a NoVOCs™ wellin conjunction with in situ air stripping facilitates thestripping of VOCs and reinfiltration of the groundwater. Asa result, remediation of the aquifer occurs withoutextracting groundwater, lowering the groundwater table,or generating wastewater, all of which are typical oftraditional groundwater remediation systems. In addition,the vendor claims that the continuous flushing of thesaturated zone with recirculated treated water and theincreased horizontal and vertical groundwater flow withinthe saturated zone can facilitate the removal of adsorbedand nonaqueous-phase contaminants.Technology Limitations

The NoVOCs™ technology has limitations in areas withvery shallow groundwater (at or near the ground surface).In such areas, it may be difficult to establish a strippingzone long enough to remove contaminants from theaqueous phase. The technology has further limitations inthin aquifers; the saturated zone must be of sufficientthickness to allow installation of the system. In addition,the thickness of the saturated zone affects the size of thetreatment cell; the smaller the aquifer thickness, thesmaller the potential diameter of the treatment area.Furthermore, the technology may have difficultyperforming at sites with low hydraulic conductivity or withhighly variable hydraulic conductivity between the upperand lower screened intervals. Under variable hydraulicconductivity conditions, balancing the flow rate withoptimum stripping conditions might prove difficult. Thisdiffculty may be overcome by using an infiltration galley toincrease the storage capacity and the infiltration area ofthe recharge zone.

High concentrations of VOCs typically require more thanone pass through the system to achieve remediationgoals. The number of passes depends on the initialcontaminant concentration, amount of recirculation, andthe removal efficiency of the system. Moreover, ifrecirculation is not well established, treated watercontaining contaminant concentrations greater than theremediation goal may be dispersed by the system andmigrate downgradient. The effectiveness of the NoVOCs™system’s ability to remove contaminants is directly relatedto the volatility of the contaminants. Contaminants withhigh volatility and low water solubility are easier to removethan compounds with low volatility and high watersolubility.

Based on the results of the SITE evaluation of theNoVOCs™ system at NAS North Island and otherrecirculating well evaluations, well fouling is a recognized

problem that requires an appropriate design, as well asoperation and maintenance activities, for successfulmanagement. Groundwater injection and extraction wells,including in-well stripping systems and recirculating wellssuch as the NoVOCs™ system, are subject to fouling froma variety of common causes. The three most commoncauses of fouling in recirculating wells and groundwaterwells in general are (1) formation of chemical precipitatesand insoluble mineral species (chemical fouling), (2)biofouling by colonizing microorganisms, and (3)accumulation of silt in the well structure. These issuesmay be controlled through groundwater pH control tomanage formation of chemical precipitates and insolublemineral species, injection of a suitable biocide, andappropriate design and construction of filter pack and wellscreens. However, any design that does not providegeochemical controls based on site-specific hydrogeologicand geochemical conditions is likely to experiencesignificant operation and maintenance problems due tofouling.

Some of the geochemical effects may be easier to controlin a closed-loop design than in a comparable open-loopdesign. In a closed-loop design, the stripping air iscaptured and used in subsequent stripping cycles.Carbon dioxide or an alternative type of gas such asnitrogen can be added to the stripping air to decrease theamount of carbon dioxide removed and the amount ofoxygen added to the treated water. By reducing carbondioxide removal from the groundwater, changes in pH inthe treated water can be minimized. Additionally, byreducing the amount of oxygen added to the treated water,anaerobic conditions can be maintained and biologicalgrowth can be minimized. Geochemical and biologicalfouling caused by changes in pH and increased biologicalgrowth can also be managed by injecting acid and biocideinto the treated water. The use of acid or biocide inrecirculating wells may receive varying acceptance fromthe regulatory community, depending on the site-specificconditions and nearby water uses.

Process Residuals

The NoVOCs™ system generates a vapor offgas wastestream that can be treated by several different standardvapor treatment technologies applicable to VOCs,including activated granular carbon. During the SITEevaluation at NAS North Island, the Thermatrix flamelessoxidation system was used to treat contaminants in thevapor waste stream. The Thermatrix system reducedcontaminant concentrations in the vapor waste stream bygreater than 99.99%. Use of the Thermatrix systemresulted in the destruction of contaminants; therefore, noprocess residuals were generated that required disposal.Soil cuttings, purge water, and decontamination wastesare generated during installation of the NoVOCs™ welland monitoring wells, and during well development andsampling activities. Disposal options for these wastesdepend on local requirements and on the concentrationsof contaminants.

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Site Requirements

Space to set up the offgas treatment system and electricityare the only site support requirements for the NoVOCs™system. The electrical power requirements for theNoVOCs™ system depend on several parameters thatmust be specified in the system design, including air flowrate and the pressure at which the air is injected into theaquifer. The space requirements for the abovegroundcomponents of the NoVOCs™ well, including the controltrailer, aboveground piping, and offgas treatment systemare approximately 500 square feet. A security fence toprevent unauthorized access to the NoVOCs™ well andcontrol trailer is also recommended. Other requirementsfor installation and routine monitoring of the system includetemporary storage of drilling cuttings, purge water, anddecontamination wastes.

71% of the time during the remaining three operationalperiods.

Summary of Results

The site was particularly challenging because thegroundwater contained TDS at concentrations rangingfrom 18,000 to 41,000 mg/L, which are considerably higherthan concentrations of TDS in typical drinking wateraquifers.

In early May 1998, the NoVOCs™ system beganexperiencing operating problems associated with highwater levels in the NoVOCs™ well and low pumping rates.Evaluation participants initially thought that the flow sensorwas not accurately measuring the pumping rate. As systemoperation progressed, however, the continued lowpumping rate and increased frequency of high water levelsin the NoVOCs™ well suggested that a more significantproblem was occurring. By June 1998, the pumping ratehad been reduced from the design rate of 25 gallons perminute (gpm) to approximately 5 gpm. Based ondiscussions between the Navy and MACTEC, the systemwas shut down on June 19, 1998 to evaluate the cause ofthe poor performance. Although iron fouling was confirmedin May 1999, other suspected causes for the poorperformance included (1) biofouling or scaling of the screenintervals and formation near the NoVOCs™ well, (2)possible differences in hydraulic characteristics betweenthe upper and lower portions of the aquifer, and (3) designproblems with the NoVOCs™ well, in particular the lengthof the recharge screen.

To evaluate the recharge capacity of the NoVOCs™system and provide information regarding the hydrauliccharacteristics of the aquifer in the vicinity of theNoVOCs™ system, a down-well video survey and a seriesof aquifer hydraulic tests were conducted. Based on theaquifer testing, it was concluded that the length of thescreened intervals of the NoVOCs™ well should be able tosustain the design pumping rate of 25 gpm. During thevideo survey, fouling of the NoVOCs™ well screens bymicrobiological growth and iron precipitation wasobserved. This fouling appeared to have impaired theperformance of the NoVOCs™ system by obstructing thewell screen and filter pack. Microbiological testing of thegroundwater confirmed the presence of biofoulingorganisms. Efforts to control fouling by addition of variousacids, dispersants, and biocides met with varying degreesof success (only iron precipitation fouling was successfullycontrolled). Citric acid was added to sequester the iron butcould have also increased biofouling. Failure to completelycontrol the biofouling of the recharge screen eventuallycaused the termination of the evaluation in January 1999.Because of operational difficulties with the NoVOCs™system throughout the demonstration, only limited datawere collected to evaluate the technology. The conclusionsthat may be drawn based on the limited data collectedduring the SITE evaluation are presented below. A detaileddiscussion of the evaluation results and conclusions isprovided in the NoVOCs™ Technology Evaluation Report(Tetra Tech 2000).

Performance Data

The NoVOCs™ technology was evaluated to determine itsability to remove VOCs from groundwater. The criticalobjectives of the evaluation were to (1) evaluate theremoval efficiency of the NoVOCs™ well system for VOCsin groundwater, (2) determine the radial extent of theNoVOCs™ treatment cell, and (3) quantify the averagemonthly total VOC mass removed from groundwater.Because of operational difficulties with the NoVOCs™system during the evaluation, objectives 2 and 3 could notbe evaluated. In these cases, results and conclusions arepresented based on the limited data available.

For this evaluation, groundwater samples were collectedfrom the NoVOCs™ influent and effluent using twopiezometers installed adjacent to the NoVOCs™ well andfrom 10 groundwater monitoring wells installed upgradient,crossgradient, and downgradient from the NoVOCs™ well.The groundwater monitoring wells were installed atdifferent depths and radii from the NoVOCs™ well toevaluate changes in contaminant concentrations within theaquifer associated with operation of the NoVOCs™system. Air samples were collected from four samplinglocations to evaluate the concentration of contaminants inthe influent and effluent of both the NoVOCs™ andThermatrix systems. Groundwater and air samples werecollected weekly for the first month of operation andmonthly thereafter. However, only one monthly samplingevent was conducted because of operational problemswith the NoVOCs™ system. All samples were analyzed forthe targeted VOCs.

Operation and maintenance of the NoVOCs™ system wasconducted primarily by Bechtel with technical guidancefrom MACTEC. The NoVOCs™ system was designed tooperate continuously, 24 hours per day, 7 days per week.During the evaluation, however, the system experiencedsignificant operational difficulties and was limited to fourmain 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 FinalConfiguration Operation (12/4/98-1/4/99). Excluding sys-tem startup and shakedown, the system operated about

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1. Comparison of VOC results for groundwater samplestaken adjacent to the influent and effluent of theNoVOCs™ well indicated that 1,1-DCE, cis-1,2-DCE,and TCE concentrations were reduced by greater than98, 95, and 93%, respectively, in all the events exceptthe first Bechtel sampling event, which was conductedduring system shakedown activities. A summary ofcontaminant removal is presented in Table 2.Excluding the first sampling event, the meanconcentrations of 1,1-DCE, cis-1,2,-DCE, and TCE inthe untreated water were approximately 3,530, 45,000,and 1,650 µg/L, respectively, and the mean concen-trations of 1,1-DCE, cis-1,2-DCE, and TCE in thetreated water discharged from the NoVOCs™ systemwere approximately 27, 1,400, and 32 µg/L, respec-tively. The 95% upper confidence limits of the means for1,1-DCE, cis-1,2-DCE, and TCE in the treatedgroundwater were calculated to be approximately 36,1,740, and 45 µg/L, respectively. The maximumcontaminant levels (MCL) for these compounds ingroundwater are 6 µg/L for 1,1-DCE, 6 µg/L for cis-1,2-DCE, and 5 µg/L for TCE. MACTEC claims that theNoVOCs™ system can reduce effluent VOC concentra-tions to below MCLs if the contaminant source has beenremoved. Since dense nonaqueous-phase liquids maybe present in the aquifer at the site and may act as acontinuing source of groundwater contamination,MACTEC did not make any claims for reduction of VOCconcentrations in groundwater at Site 9.

2. Because of the sporadic operation of the NoVOCs™system, a direct evaluation of the radial extent of theNoVOCs™ treatment cell was not conducted. In lieu ofa direct evaluation method, aquifer hydraulic tests wereconducted to assess the hydrogeologic characteristicsof the site and to indirectly evaluate the potential radialextent of the NoVOCs™ treatment cell. Although theaquifer pump tests cannot be directly applied toevaluate the radial extent of the NoVOCs™ treatmentcell or even that groundwater recirculation wasestablished, the test data do provide information on theradius of influence of the well under pumping (2-dimensional) and dipole (3-dimensional) flow condi-tions. The resulting changes in pressure head providean indication of the potential for flow in the surroundingaquifer and are used to provide an estimate of the radialextent of influence created by the NoVOCs™ well.However, the pressure head changes do not accuratelyrepresent flow patterns or contaminant transport.Consequently, no firm conclusions can be drawn aboutthe radial extent of the NoVOCs™ treatment cell.During the constant discharge rate (discharge = 20gpm) pumping test, measurable drawdowns (+/- 0.01feet) were observed at approximately 100 feet from theNoVOCs™ well in all directions and at different depths.This information indicates that the radius of resultingfrom extraction at 20 gpm could be as large as 100 feet.The dipole flow test data showed that measurablepressure responses occured at crossgradient locations30 feet from the NoVOCs™ well and may be observed

at greater distances. However, no drawdowns or waterlevel rises could be positively measured in monitoringwells 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 eventswithin a period of limited operation from April 28 to June8, 1998. During this period, the average total VOC massremoved by the NoVOCs™ system ranged from 0.01 to0.14 pound per hour and averaged 0.10 pound per hour.Accounting for the sporadic operation of the NoVOCs™system, the mass of total VOCs removed during theentire operation period from April 20 through June 19,1998 was estimated to be approximately 92.5 pounds. Asummary of the total VOC mass removed is presentedin Table 3.

Economic Analysis

An economic analysis for the NoVOCs™ technology totreat VOC-contaminated groundwater was conductedbased on the SITE evaluation and cost informationprovided by the Navy and MACTEC. One-time capitalcosts for a NoVOCs™ system were estimated to be$190,000; annual operation and maintenance costs wereestimated to be $160,000 per year for the first year and$150,000 per year thereafter. Since the time required toremediate an aquifer is site-specific, costs have beenestimated for operation of a NoVOCs™ system over arange of time for comparison purposes. Based on theseestimates and an annual inflation rate of 4%, the total costfor operating a single NoVOCs™ system was calculated tobe $350,000 for 1 year; $670,000 for 3 years; $1,000,000for 5 years; and $2,000,000 for 10 years. The cost oftreatment per unit volume of water was not calculatedbecause of the number of assumptions required to makesuch a calculation. Additionally, costs per unit volume ofwater were not calculated for this project because of thesite-specific nature of treatment costs.

Costs for implementing a NoVOCs™ system at anothersite may vary substantially from this estimate for the SITEevaluation. A number of factors affect the cost of treatmentusing the NoVOCs™ system, including soil type,contaminant type and concentration, depth to groundwa-ter, site geology and hydrogeology, groundwatergeochemistry, site size and accessibility, required supportfacilities and available utilities, type of offgas treatment unitused, and treatment goals. It is important to (1)characterize the site thoroughly before implementing thistechnology to ensure that treatment is focused oncontaminated areas, and (2) determine the redius of thecirculation cell for the well and the resulting number of wellsneeded to remediate a particular site.

Lessons Learned and Recommendations forFuture Studies

The evaluation of innovative technologies, especially in situprocesses, poses significant technical difficulties even

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0964C4N04517,59100789,1910023.9,992CNANAN00079,292)L/gu( ene0h0t969e,29o1rolhciTrD 0058629,1060375900355,691DD 00699771meemgekerttasatshySnycISeR)1(noti21nt00ec--cuZZrdePPPeR.10-ZP ta noitartnec.tnnoecv ee hgt n=i l)p2-mw(aCs dynlka ee2.wn0- ZhoittPru tuliaod f ngyoi.ndrttiasrar.udttednnnt ee-t2occv 0enes’t-Zso acgn nei P elddthpuna t mtSasi=a 1s)sd1 e0y-tllw-a(hiZnCgatia - P eeomnr lelwoa hat rfnw i ma d s;ed0ogrnt0fi cn1aseu tulxa lo op]dd)c1 egn m-itnoow(incCsmr / uees]) tre2-ideefw(iedwtt al nD lase- uved)1cri-llp rw(aetmecnfC iai[l[n sa aec ru= eeqnt mneayoi dwrtcifocitdtennaurduoemocobRh tr i%GarL%A59:seto)))N*D123(((Table 3. Summary of Total VOC Mass Removed

Effluent Total VOCMass RemovedOver 1-HourSampling Event**

(lbs/hr)

0.01450.11340.13910.13720.0914

Effluent SamplingEvent (Date1st Weekly(4/28/98)2nd Weekly(5/6/98)3rd Weekly(5/12/98)4th Weekly(5/21/98)1st Monthly(6/8/98)

Effluent Total VOCConcentration perEvent (ppb v/v)

15,060104,100125,700136,00093,900

Effluent Air FlowRate During Event

(scfm)

50*68696361

SystemOperation(hr)261.5126.75101.25183.5383

Total VOC MassRemoved (lbs)

3.814.414.125.235.0

Average95,00064.20.0991NCNCTotalNCNCNC105692.5Notes:*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 remediationprocesses occur in the subsurface and cannot readily beobserved or easily measured, the evaluator must rely on alimited number of discrete measurements to provide anindication of changes in the subsurface caused by thetechnology. This task is further complicated by the typicallack of sufficient site characterization data to provide athorough and detailed understanding of the hydrogeologyand contaminant distribution at a site.

When applying an innovative in situ technology such as theNoVOCs™ system to a complex site such as NAS NorthIsland Site 9, a team of experts with applied experience inrecirculating well engineering, geology, hydrology, andgeochemistry should be used. The NoVOCs™ system didnot function without operational difficulties, partly becausethis site’s groundwater, which contained TDS concentra-tions ranging from 18,000 to 41,000 mg/L, considerablyhigher concentrations of TDS than typical drinking wateraquifers.

The NoVOCs™ system affects the groundwater geochem-istry and subsurface environmental conditions through theremoval of carbon dioxide from the groundwater, injectionof air, and movement of contaminants to the well. Incarbonate-rich groundwater, the removal of carbon dioxideaffects the buffering capacity of groundwater and mayresult in increases in pH. These changes can affectchemical equilibria in the subsurface and cause theprecipitation or dissolution of inorganic compounds. Theoxygenation of the groundwater during air stripping andincreased contaminant movement near the well mayprovide an environment for enhanced microbiologicalgrowth. The precipitation of inorganic compounds and

increased microbiological growth can adversely affect theperformance of the system by decreasing the ability of thewell screens, filter pack, and adjacent formation to transmitwater. Addressing the potential for these fouling issues andtheir proper management is critical during project planningand design.

Contaminant transport associated with the NoVOCs™system is also complicated by the 3-dimensionalgroundwater flow induced within the aquifer surroundingthe well and the lack of detailed site characterizationinformation. When applying an induced flow to thesubsurface, migration is typically confined to preferentialpathways and is strongly controlled by the heterogeneityand anisotropy of the aquifer. Modeling of the contaminanttransport during evaluation planning is recommended toprovide an understanding of groundwater flow and tooptimize placement of monitoring and measurement ports.Even given a team of experienced professionals, problemsmay arise. To help minimize these problems, a summary ofrecommendations is provided to assist those involved infuture evaluation of the NoVOCs™ system andgroundwater circulation wells in general. Based on theNoVOCs™ evaluation at NAS North Island, Site 9,recommendations for (1) site specific characterizationactivities; (2) assessment of fouling potential (chemicalprecipitation, biological fouling, and siltation); and (3)integration of system controls are provided below.

Site-specific CharacterizationA thorough site characterization is required to design arecirculating well system. Some of the characterizationrequirements are common geological practices, others are

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more specific to the technology being deployed. Therecommended approaches are described below.Geological Description

Discrete core samples (for example, samples collectedevery 5 feet) should not be considered until a sufficientnumber of continuous cores have been evaluated todevelop a confident conceptual model of the sitestratigraphy. At Site 9, the continuous coring performedspecifically for the NoVOCs™ evaluation resulted in notonly revision of the NoVOCs™ system conceptual design,but revision of the entire stratigraphic conceptual model ofthat portion of NAS North Island.Aquifer Testing

A variety of aquifer testing approaches are applicable torecirculating well system design. These approachesinclude permeability testing of representative intact coresfrom the stratigraphic column. Grain size analysis ofrepresentative samples can provide some indication offormation permeability, but cannot provide assessment ofthe formation structure, which plays an important role inwater conductivity. Site evaluation should include twoaquifer tests at a minimum; one extraction pumping test toevaluate the productivity of the extraction zone and oneinjection test to evaluate the capacity of the recharge zone.A combined pumping and recharge test, known as amodified “dipole” test, can provide additional informationregarding potential system performance. The dipole testcan also provide information on site-specific anisotropy.Anisotropy is the ratio of the hydraulic conductivity in thehorizontal direction to that in the vertical direction andstrongly influences the extent of the groundwatercirculation cell and capture zone. During all aquifer tests,pressure head changes should be monitored and recordedin all accessible monitoring locations.

potential of the aquifer. Grossly polluted and salineaquifers may contain substantial reduced iron andmanganese species that may become more soluble asthe aquifer becomes more aerobic. The concentrationof dissolved iron in the water can also indicate thepotential for iron-related bacteria to develop in thesystem.

•An iron precipitation test can provide an estimate of themagnitude of iron precipitation that may occur in thesystem. The test can be conducted by determining theiron content of a water sample, then aerating thesample, allowing the ferric hydroxide to precipitate,and measuring the iron concentration in the remainingwater again.

•Monitor pH and iron status in the aquifer regularlyduring system operation.

The results of the tests should be used to incorporateprecipitation control features into the system design. Forexample, a closed-loop system might be chosen over anopen-loop system, a stripping gas other than air might beselected, and injection of chemicals might be required. Aswith the control of biological growth, provisions should bemade to inject chemicals to control precipitation into thewell inlet filter pack as well as into the treated water beingreturned to the formation.Biological Fouling

Biofouling is a demonstrated problem for recirculating andextraction wells. A recommended approach to minimizingbiofouling problems is to evaluate the overall aquifermicrobial ecology to assess both the fouling potential andpotential control alternatives. A minimal evaluation of themicrobial ecology of a candidate site includes theidentification of the presence of natural and contaminant-related substrates within the aquifer (as measured bybiological oxygen demand and chemical oxygen demand).The evaluation also should determine oxidation-reductionpotential (aerobic versus anaerobic), temperature andpressure, and the presence of indigenous organisms(determined by culturing aquifer samples). Systemdesigners and operators must remain aware of aquiferecology changes that may occur during system operation.In the case of the NoVOCs™ technology, which vigorouslyaerates the groundwater coincidental with removal ofdissolved VOCs, aerobic microbial communities can beexpected to develop in previously anaerobic locations.Facultative anaerobes that were present as very minorfractions of the overall microbial community may becomedominant. Specialized microbes, such as iron-relatedbacteria may also become established in locations where aconstant supply of fresh substrate is available and physicalconditions favor colonization (for example, in the wellscreens). If fouling microbes are present, provisions shouldbe made to inject biocides into the well inlet filter pack aswell as into the treated water being returned to theformation.

Assessment of Fouling PotentialSite conditions should be evaluated for the three primarysources of fouling discussed below, and the system shouldbe designed and operated to control the impacts of fouling.Chemical Precipitation

Chemical precipitation may occur for both recirculatingwells and extraction wells, and requires planning andcareful implementation for successful control. During thedesign phase, system planners should perform thefollowing tests:

•An aeration/titration test to identify the anticipated pHchange with aeration, evaluate the potential for calciteprecipitation, and estimate the water’s demand foracidification to prevent calcite formation.

•Determination of total and dissolved iron andmanganese concentrations in the water to assess thepotential for fouling through precipitation of ferrichydroxide after aeration. Also evaluate the redox

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Siltation

Although siltation was not a problem at NAS North Island,recirculating wells are subject to fouling due toaccumulation of aquifer solids, just as are any extraction orrecharge well. The grain size and structure of the strata inwhich well screens will be placed must be thoroughlyevaluated to ensure that the appropriate combination ofscreen and filter pack is designed for the well in eachscreened interval. After well construction, the screenedintervals must be thoroughly and aggressively developedto achieve very low levels of suspended solids (less than 5nephelometric turbidity units suspended solids). If therecirculating well uses an air lift action, like the NoVOCs™technology, thorough development is essential. If notproperly developed, the air lift action will develop the inletscreen and the resulting solids will be deposited in therecharge zone, effectively plugging the well.

viable alternative to traditional groundwater remediationsystems, especially where pump-and-treat type systemshave failed or are not removing significant contaminantmass. Like other groundwater remediation technologies,the NoVOCs™ system requires proper geologic anddesign considerations, and is not applicable to all types ofcontaminants or geologic settings.

SITE Program

In 1980, the U.S. Congress passed the ComprehensiveEnvironmental Response, Compensation, and Liability Act(CERCLA), also known as Superfund. CERCLA wasamended by the Superfund Amendments and Reauthori-zation Act (SARA) in 1986. The SITE Program is a formalprogram established in response to SARA. The primarypurpose of the SITE Program is to maximize the use ofalternative technologies in cleaning up hazardous wastesites by encouraging the development and evaluation ofnew, innovative treatment and monitoring technologies.The NoVOCs™ technology was evaluated under theDemonstration Program. Other documentation resultingfrom this SITE evaluation include a Technology EvaluationReport that expands on results and conclusions presentedin this Technology Capsule.

Integration of System ControlsSystem designers should maximize the use of availableelectronic control technology. Recent development hasproduced dramatic increases in the capability and reducedassociated costs for sophisticated supervisory, control,and data acquisition systems. The mechanical system,well, and offgas treatment system can be readily integratedwith 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 therecirculating well design should be assessed as a systemto identify critical control and monitoring functions, as wellas supplemental control functions that will increase systemefficiency and reduce downtime and on-site labor.

Sources of Additional InformationEPA Contact

Michelle Simon

U.S. Environmental Protection Agency26 W. Martin Luther King DriveCincinnati, Ohio 45268

Phone: 513-569-7469; FAX: 513-569-7676E-mail: simon.michelle@epa.govTechnology Developer Contact

Joe Aiken

MACTEC, Inc.

1819 Denver West Drive, Suite 400Golden, Colorado 80401

Phone: 303-278-3100; FAX: 303-278-5000E-mail: http://www.mactec.com/.Technology Status

The concepts of the NoVOCs™ in-well VOC strippingsystem were initially proposed by researchers at StanfordUniversity in the late 1980s (Gvirtzman and Gorelick 1992)and were further developed under a collaboration betweenStanford University, EG&G Environmental, and the U.S.Department of Energy (DOE). An initial patent for theNoVOCs™ system (U.S. Patent No. 5,18,503) wasgranted to Stanford University; EG&G subsequentlyobtained an exclusive license to the technology.

In 1996, Stanford University and DOE carried out the firstfull-scale evaluation of the technology at Edwards Air ForceBase, California. During this evaluation, TCE was removedfrom groundwater. In December 1997, MACTEC acquiredthe exclusive license to the NoVOCs™ system fromEG&G. At the time of MACTEC’s acquisition of thetechnology, there were more than 30 applications of theNoVOCs™ system at both private and government sites.According to the developer, the technology provides a

References

Gvirtzman, H. and S.M. Gorelick. 1992. The Concept of In-situ Vapor Stripping for Removing VOCsfrom Groundwa-ter, Transport in Porous Media, Vol. 8, No. 1, p. 71-92.Tetra Tech EM Inc. (Tetra Tech). 2000. TechnologyEvaluation Report for the NoVOCs™ TechnologyEvaluation at NAS North Island. June.

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