Selection and Implementation of Ex-Situ Chemical Oxidation for Treatment of TCE-contaminated Soil
Janis K. Tsang, USEPA Region I, Boston, MA

Ex-Situ Wellhead Treatment for 1,4-Dioxane Using Fenton’s Reagent
Jackson Kiker, ECC, Marlborough, MA
James Connolly, US Army Natick Soldier Systems Center, Natick, MA
Willard Murray, ECC, Marlborough, MA
Stuart Pearson, MACTEC, Portland, ME
Stanley Reed, MACTEC, Portland, ME
Robert Tess, ECC, Marlborough, MA  

Design and Evaluation of an In Situ Chemical Oxidation (ISCO) Pilot Test at the Massachusetts Military Reservation (MMR)
Mary O’Reilly, CH2M HILL, Otis ANG Base, MA
Patricia de Groot, CH2M HILL, Palm Beach, FL
Rose Forbes, Air Force Center for Engineering and the Environment, Otis ANG Base, MA
John Glass, CH2M HIILL, Chantilly VA
Tom Simpkin, CH2M HILL, Englewood, CO  

Use of Near Field-Scale Groundwater to Soil Ratios to Improve Natural Oxidant Demand Bench Testing
Matthew Burns, WSP Environment & Energy, Boxborough, MA
James E. Studer, ChemRem International LLC, Albuquerque, NM
Michael D. Lee, Ph.D., Terra Systems, Inc., Wilmington, DE

An Evaluation of Residual Effects Following Alkaline Activated Persulfate Treatment
Scott C. Crawford, XDD, LLC, Stratham, NH
Brant A. Smith, XDD, LLC, Stratham, NH
Karen O’Shaughnessy, XDD, LLC, Stratham, NH
Nathan W. Hagelin, Mactec Engineering and Consulting, Inc., Portland, ME
Richard J. Jacobson,  Mactec Engineering and Consulting, Inc., Portland, ME 

Prevalence and Persistence of Hexavalent Chromium During In-Situ Chemical Oxidation (ISCO) of Trichloroethylene with Permanganate
Antony D. G. Jones, ENVIRON, Irvine, CA
Carol L. Serlin, ENVIRON, Irvine, CA
Mauricio H. Escobar, ENVIRON, Los Angeles, CA
Devon Rowe, ENVIRON, Irvine, CA

Selection and Implementation of Ex-Situ Chemical Oxidation for Treatment of TCE-contaminated Soil

Janis K. Tsang, P.E., USEPA, Region I, One Congress Street, Suite 1100, Boston, MA 02114, USA, Tel: 617-918-1231, Fax: 617-918-0231, Email: tsang.janis@epa.gov

At the request of the Connecticut Department of Environmental Protection, EPA conducted a site investigation on a 5-acre property located in a residential area in Harwinton, Litchfield County, Connecticut. The investigation revealed concentrations of chlorinated volatile organic compounds (primarily trichloroethylene, TCE), ranging from 0.6 to 6,300 ppb in soil, and from non-detect to 3,150 ppb in groundwater.  A source area of approximately 2,000 cubic yards of TCE-contaminated soil located from 0-20 feet below ground surface (bgs) was a result of multiple improper disposals of chlorinated solvents during metal stamping and tooling operations by the former owner of the property.  Depth to groundwater ranges from 6 to 15 feet bgs. The groundwater classification for the area is GAA, which means that the groundwater is within the influence of private and potential water supply wells and is considered suitable for drinking without treatment.  The Site was deemed a Removal Action under the EPA Superfund Program.  From August 2007 to October 2007, EPA conducted a removal options assessment.  EPA determined that ex-situ chemical oxidation using sodium permanganate was the best option for treating contaminated soils from both saturated and unsaturated zones at the source area and that a conventional water treatment system could be used to treat groundwater removed during the excavation activities.  In September 2007, EPA mobilized to this Superfund site to conduct a time-critical removal action.  In September 2008, EPA completed the ex-situ treatment based on post-treatment soil sample results which indicated that the concentration of TCE had been reduced to below the treatment goal of 0.02 ppm, and below the Connecticut Pollutant Mobility Criteria (CTPMC) for GAA areas (0.1 ppm).  The treated soil was used as backfill.  EPA’s technology assessment analysis for selecting ex-situ chemical oxidation treatment, the implementation method, problems encountered, and the post-treatment sampling results will be discussed.

Ex-Situ Wellhead Treatment for 1,4-Dioxane Using Fenton’s Reagent

Jackson Kiker, ECC, 33 Boston Post Road West, Suite 340, Marlborough, MA 01752, USA, Tel: 508-229-2270, Fax: 508-229-7737, Email: jkiker@ecc.net
James Connolly, US Army Natick Soldier Systems Center ATTN: AMSSCB-OES(N), Kansas Street, Natick, MA 01760, USA, Tel: 508-233-5550, Email: James.B.Connolly@us.army.mil
Willard Murray, ECC, 33 Boston Post Road West, Suite 340, Marlborough, MA 01752, USA, Tel: 508-229-2270, Fax: 508-229-7737, Email: wmurray@ecc.net
Stuart Pearson, MACTEC, 511 Congress Street, Portland, ME 04112, USA, Tel: 207-775-5401, Fax: 207-775-4762, Email: scpearson@mactec.com
Stanley Reed, MACTEC, 511 Congress Street, Portland, ME 04112, USA, Tel: 207-775-5401, Fax: 207-775-4762, Email: swreed@mactec.com
Robert Tess, ECC, 33 Boston Post Road West, Suite 340, Marlborough, MA 01752, USA, Tel: 508-229-2270, Fax: 508-229-7737, Email: rtess@ecc.net

At the U.S. Army Natick Soldier System Center (NSSC) in Natick, Massachusetts, groundwater is being pumped and treated to provide containment of an historical trichloroethene (TCE) plume.  Upon discovering 1,4-dioxane (an emerging contaminant not previously monitored) at one of the monitoring wells above the Massachusetts Department of Environmental Protection drinking water goal of 3 µg/L, the existing on-site groundwater treatment system required augmentation to continue maintaining plume containment and meeting allowable discharge limits.  Existing treatment consists of air-stripping and granular activated carbon, which both have a low efficiency for treating 1,4-dioxane.  The concentration of 1,4-dioxane in the TCE plume requiring treatment is  less than 100 micrograms per liter (µg/L) and approximately 10 to 20 µg/L in the 4 to 6 gallon per minute (gpm) combined discharge stream from three new extraction wells.  Because 1,4-dioxane was only identified in a isolated portion of the TCE plume and not in the 75 to 90 gpm flow to the existing treatment system from this TCE plume and others, a goal was to provide in-situ or wellhead treatment for the 1,4-dioxane and not to treat the 75 to 90 gpm flow. 

An engineering study was conducted to evaluate 1,4-dioxane and TCE treatment options, with key considerations being that 1,4-dioxane was detected at a low concentration, the extracted water was  high in TSS and iron oxides, flow-rates needed for containment were small (< 6 gpm), 1,4-dioxane was highly localized, and the size of the physical plant had to be small.  Viable options that were considered included the following Advanced Oxidation Processes (AOPs):  Fenton's Reagent, hydrogen peroxide with ultraviolet (UV) light, hydrogen peroxide with ozone, and catalyzed persulfate. 

Based on the engineering study, ex-situ application of Fenton’s Reagent was selected as a practical cost-effective solution.  Bench-scale jar testing demonstrated that naturally occurring iron found in the water was sufficient to provide the metal catalyst needed for the Fenton’s reaction, and that stoichiometrically over-dosing hydrogen peroxide would decrease treatment residence-time necessary for achieving remediation goals and compensate for hydrogen peroxide dissipating side-competition reactions. 

Reagent dosing rates from the bench-scale tests were used in the design and construction of a small wellhead treatment unit utilizing Fenton’s Reagent.  Design of the treatment unit included optimizing the flow-through tank residence time for contact with the dosed Fenton’s Reagent.  The wellhead treatment unit is housed in a small storage shed. Treatment system components are off-the-shelf tanks and dosing units. The first six months of operation show that influent 1,4-Dioxane and CVOCs are removed by the wellhead unit down to non-detectable levels.

Design and Evaluation of an In Situ Chemical Oxidation (ISCO) Pilot Test at the Massachusetts Military Reservation (MMR) 

Mary O’Reilly, CH2M HILL, 318 East Inner Road, Otis, ANG Base, MA 02542, USA, Tel: 508-968-4670 x5629, Email: moreilly@ch2m.com
Patricia de Groot, CH2M HILL, 3001 PGA Blvd., Suite 300, Palm Beach, FL 33410, USA, Tel: 508-308-1453, Email: pdegroot@ch2m.com
Rose Forbes, Air Force Center for Engineering and the Environment, 322 East Inner Road, Otis ANG Base, MA 02542, USA, Tel: 508-968-4670 x5613, Email: rose.forbes@brooks.af.mil
John Glass, CH2M HIILL, 15010 Conference Center Drive, Suite 200, Chantilly VA 20151, USA, Tel: 703-376-5120, Email: jglass@ch2m.com
Tom Simpkin, CH2M HILL, 9191 South Jamaica Street, Englewood, CO 80112-5946, USA, Tel: 720-286-5394, Email: tsimpkin@ch2m.com 

An ISCO pilot test using sodium permanganate is being conducted at MMR to assess the potential of ISCO technology to reduce overall cleanup time and operational costs of groundwater remediation efforts being conducted at the site.  The pilot test area is located within a large trichloroethene (TCE) plume (approximately 3.5 miles long and 1 mile wide) that has been under active remediation by pump-and-treat technology since 1999.  The pilot test location was selected because of elevated TCE concentrations in this portion of the plume.  Contaminant transport modeling results suggest that this area may drive overall cleanup timeframes.

Due to the thickness of the plume (up to 140 feet) and varying hydrogeologic conditions at the site, three vertically-spaced injection well screens at one well cluster were utilized to allow for vertical distribution of the oxidant.  Direct push technology was employed to install the small-diameter injection wells to depths of up to 200 feet below ground surface.  A closely-spaced monitoring network included wells located upgradient, crossgradient, and downgradient of the injection cluster.  The monitoring network and sampling program were designed to obtain the information necessary to assess migration and persistence of the oxidant and to evaluate the impacts of oxidant injection on the general geochemistry of the aquifer.

Permanganate detections covered an area that was approximately 40 feet wide, 140 feet long, and 50 feet thick.  Permanganate still persists one year after the injection, primarily in the finer grained sediments near the bottom of the injection zone.  Differences in hydraulic conductivity with depth at the site caused a shearing effect in the trajectory of the permanganate as it migrated downgradient.  Analytical results and a calibrated groundwater flow and transport model are being used to predict the costs and potential benefits of ISCO on a larger scale in this portion of the plume. 

Use of Near Field-Scale Groundwater to Soil Ratios To Improve Natural Oxidant Demand Bench Testing

Matthew Burns, WSP Environment & Energy, 1740 Massachusetts Avenue, Boxborough, MA  01719.  Tel: 978-635-9600, Fax: 978-264-0537, Email: matt.burns@wspgroup.com
James E. Studer, ChemRem International LLC, 8100 M-4 Wyoming Blvd. NE #410, Albuquerque, New Mexico 87113-1923. Tel: 877-243-6736, Email: jstuder@ChemRem.com
Michael D. Lee, Ph.D., Terra Systems, Inc., 1035 Philadelphia Pike, Suite E Wilmington DE  19809. Tel: 302-798-9553, Fax: 302-798-9554, Email: mlee@terrasystems.net

Successful implementation of in-situ chemical oxidation (ISCO) requires application of sufficient oxidant to satisfy the demand exerted by target compounds and non-target materials naturally present in soil.  Because the Natural Oxidant Demand (NOD) is often greater than the demand exerted by target compounds, oxidant dosing is commonly expressed as a mass ratio of oxidant to the soil (solid) present within a treatment volume.  The lack of a sound theoretical foundation for predicting oxidant interaction across the range of natural settings and engineered circumstances forces the remediation professional to rely heavily on empirical means (i.e., personal experience and bench testing protocols) to identify full-scale oxidant requirements and to refine project cost estimates.

Bench-scale testing often yields NOD data that are in excess of the oxidant to soil mass ratios than those typically used for full-scale ISCO applications at sites with similar soil types. This overestimation of NOD in bench tests can lead to prematurely removing ISCO as a potentially applicable technology due to perceived high chemical oxidant costs. 

Aside from mixing, heterogeneity, and other issues that can not be controlled at the bench, a potential contributor to the scaling error between bench and field applications is the use of water in excess of field-scale groundwater to soil ratios to accommodate analytical testing at the bench.  By increasing the water to soil ratio in a dosing scheme tied to soil mass, the bench and field aqueous oxidant concentration are quite different.  Bench tests were completed on soils from several sites using near field-scale groundwater to soil ratios to assess activated persulfate NOD trend variation with increased initial aqueous oxidant concentrations.  Data from these studies show that NOD increases linearly as a function of the initial aqueous oxidant concentration. These data show that adjusting aqueous oxidant concentrations to accommodate use of water in excess of field-scale water to soil ratios can affect NOD results.  The increase of NOD with initial aqueous oxidant concentration is expected as demand exertion kinetics vary as an inverse function of time and oxidant concentration (Chick-Watson behavior).  With the time of the bench test held constant, the NOD predictably increases with increased aqueous oxidant concentration.

Limiting excess water during NOD testing decreases scaling variability and may provide a platform to better assess target compound oxidant treatment efficiency, metals mobilization, and the effect of sequential oxidant applications. 

An Evaluation of Residual Effects Following Alkaline Activated Persulfate Treatment

Scott C. Crawford, XDD, LLC, 22 Marin Way, Unit 3, Stratham, NH 03885, USA, Tel: 603-778-1100, Fax: 603-778-2121, Email: crawford@xdd-llc.com
Brant A. Smith, P.E., Ph.D. XDD, LLC, 22 Marin Way, Unit 3, Stratham, NH 03885, USA, Tel: 603-778-1100, Fax: 603-778-2121, Email: smith@xdd-llc.com
Karen O’Shaughnessy, XDD, LLC, 22 Marin Way, Unit 3, Stratham, NH 03885, USA, Tel: 603-778-1100, Fax: 603-778-2121, Email: oshaughnessy@xdd-llc.com
Nathan W. Hagelin, Mactec Engineering and Consulting, Inc., 511 Congress Street, Box 7050 Portland, ME 04112, USA Tel: 207-828-3508, Fax: 207-772-4762 , Email: nwhagelin@mactec.com
Richard J. Jacobson,  Mactec Engineering and Consulting, Inc., 511 Congress Street, Box 7050 Portland, ME 04112, USA Tel: 207-775-5401, Fax: 207-772-4762 , Email: rdjacobson@mactec.com

When considering In-Situ Chemical Oxidation (ISCO) treatment, potential side-effects of emplacing a large quantity of chemical reagents within the aquifer is an important factor.  Residual side-effects can include pH impacts, metals mobilization, and accumulation of various breakdown products.  These are normal side-effects of treatment, but it is prudent to consider whether these effects will attenuate, or if they will migrate beyond the treated area.  An examination of the long-term residual effects was performed following a full-scale alkaline activate persulfate (AAP) treatment.

AAP was selected to treat 1,1,1-trichloroethane (TCA), tetrachloroethene (PCE), and 1,4-dioxane contamination.  AAP technology involves adjustment of the aquifer pH to alkaline conditions (typically greater than pH 10.5).  Reaction of the oxidant (FMC Klozur^TM sodium persulfate) at high pH conditions promotes formation of aggressive oxidant radical species (including the sulfate radical SO₄^-●).  Approximately 15,400 kilograms (Kg) of sodium hydroxide was required to adjust pH.  A total of 31,100 Kg of FMC Klozur^TM was injected at field concentrations of 100 to 200 g/L. 

The remedial goal of 1 mg/L for each of the target compounds was achieved.  At over one year since treatment, there has been no significant rebound.  The residual effects of treatment, including elevated pH (pH > 11), increased metals concentrations (e.g., arsenic up to 15,000 g/L), and elevated sulfate concentrations (up to 3,200 mg/L), have remained persistent within the immediate target area.  Groundwater plume velocity calculations suggest that if the residual effects were migrating beyond the treated area, these effects should have been observed in downgradient wells.  Attenuation mechanisms (i.e., neutralization of pH via soil buffering capacity, re-precipitation of dissolved metals based on Eh-pH characteristics, and dilution mechanisms) have controlled migration of the residual effects.  General geochemical principles can be used to anticipate if a proposed ISCO treatment might adversely impact a sensitive aquifer. 

Prevalence and Persistence of Hexavalent Chromium During In-Situ Chemical Oxidation (ISCO) of Trichloroethylene with Permanganate

Antony D. G. Jones, ENVIRON International Corporation (ENVIRON), 18100 Von Karman, Suite 600, Irvine, CA 92612, USA, Tel: 949-798-3615, Fax: 949-261-6202, Email: ajones@environcorp.com
Carol L. Serlin, ENVIRON, 2010 Main Street Suite 900, Irvine, CA 92782, USA, Tel: 949-798-3615, Fax: 949-261-6202, Email: cserlin@environcorp.com
Mauricio H. Escobar, ENVIRON, 707 Wilshire Boulevard, Suite 4950, Los Angeles, CA 90017, USA, Tel: 213-943-6337, Email: mescobar@environcorp.com
Devon Rowe, ENVIRON, 18100 Von Karman Avenue, Ste. 600, Irvine, CA 92612  Tel: 949-261-5151 Fax: 949-261-6202 Email: drowe@environcorp.com

Historical use of chlorinated solvents, including trichloroethylene (TCE) at an industrial facility in Southern California has resulted in impacts to soil and groundwater.  A pilot study of ISCO using permanganate was tested for a site-wide remedial option.  Groundwater monitoring indicated the presence of hexavalent chromium [Cr(VI)] after injection.  The potential sources of Cr(VI), assessed by a bench-scale assessment (BSA) and chromium stable isotope analysis, are presented, and the long-term management of Cr(VI) after ISCO are discussed.

The BSA assessed three potential sources of Cr(VI); chromium as an impurity in the permanganate; oxidation of naturally-occurring chromium in soil; and oxidation of chromium in stainless steel well screens.  Chromium is present as an impurity in permanganate; in our assessment, analytical methods were developed to avoid matrix interference problems.  Cr(VI) was observed at 6,680 micrograms per liter (µg/l) in a 40% sodium permanganate solution.  The contribution of soil to Cr(VI) concentrations was quantified by mixing site soil with a range of permanganate concentrations.  Cr(VI) concentrations of up to 153.3 µg/l were observed.  The third source, stainless steel well screen, was assessed in a similar manner to the site soil.  Cr(VI) concentrations of up to 13,500 µg/l were present in the well screen reaction mixture.  Based on the BSA, all three sources produced or contained Cr(VI); the likely contribution of each source to a Cr(VI) plume will depend on site conditions.

Long-term management of Cr(VI) is ongoing.  Attenuation of Cr(VI) was assessed in the BSA, two soils were used in the test, and in the soil that best approximated site conditions, up to 82% attenuation of Cr(VI) was observed after 22 days.  Attenuation of Cr(VI) is also being assessed with chromium stable isotope analysis.  The analysis is ongoing and results will be presented as part of a management plan for Cr(VI) generated during ISCO.  

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