In situ chemical reduction
Application
This section contains information on sites where in situ reduction has been used for remediation. It is divided into sites with inorganic contamination (principally chromium VI) and organic contamination (principally chlorinated solvents).
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Inorganic Contamination |
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Combined Organics-Inorganics
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Inorganic Contamination
Coast Wood Preserving, Ukiah, California Superfund Site
EPA Region 9
Since 1999, this Superfund site has used injection of calcium polysulfide solution to convert chromium VI to a trivalent chromium hydroxide. Eight separate direct push injection events using calcium polysulfide reductant have been completed at the site with the result being the concentrations of Cr+6 have fallen to below MCLs in many areas.
Frontier Hard Chrome Vancouver, Washington Superfund Site
Source Area Treatment
Areas were pre-excavated to a depth of approximately 20 feet to remove buried debris prior to treatment. Soil treatment on large scale began in June 2003. Treatment of hexavalent chromium in the source area soil and groundwater was completed by using insitu soil mixing equipment to mix a proprietary reducing agent (ECOBOND®) into the subsurface soils and groundwater. Treatment depths varied from 20 to 33 feet below ground surface. The concentrations of the soil samples were below the site cleanup standard of 19 mg/kg for hexavalent chromium.
Groundwater
One of the main components of the remedy was the installation of the In situ Redox Manipulation Treatment Wall, which occurred in the spring and summer of 2003. Eight pairs of injection wells were installed during ISRM Wall Installation. Each pair of wells included a deep well (screened from 28 to 33 feet below ground surface) and a shallow well (screened from. 23 to 28 feet below ground surface). Each well pair was injected with 5,000 gallons of sodium dithionite reagent. The reagent was mixed with water prior to injection such that a total of approximately 40,000 gallons were injected into each well pair. The treatment wall is approximately 240 feet long and greater than 33 feet deep. The ground water quality concentrations in all 33 monitoring wells for total chromium concentrations as of August 2007 were below the site standard of 50 µg/l.
- The 2008 Five Year Review provides a brief description of the system
- General site information
- Cost and Performance Report
- 2018 Close-Out Report
Hard Chrome Plating, Los Angeles, Calinfornia (PPT)
Yargeau, Tedd
California Environmental Protection Agency, DTSC, 27 pp, 2008
Initial concentrations of hexavalent chromium at the site were 9,800 mg/kg in soil and 1,700 mg/L in groundwater. Calcium polysufide was injected into the vadose zone and groundwater to reduce hexavalent chromium to chromium hydroxide precipitate. The response action achieved substantial reductions in hexavalent chromium in the source areas.
In Situ 'Deliverability' Trials Using Calcium Polysulphide to Treat Chromium Contamination at Shawfield, Glasgow
Bewley, R. and G. Sojka.
CL:AIRE (Contaminated Land: Applications in Real Environments), Technology Demonstration Project Bulletin TDP30, 8 pp, 2013
Following earlier field trials that indicated the effectiveness of calcium polysulfide (CaSx) application in reducing Cr(VI) associated with chromite ore processing residue, another field trial was conducted in 2009 to identify the most effective CaSx delivery mechanism into the subsurface. The methods investigated for CaSx delivery were (1) a groundwater recirculation system (which also achieved situ flushing of contaminated soil); (2) direct-push injection using close grid spacing; and (3) soil mixing. All three trials provided evidence of total Cr mobilization as a combination of chemical-physical action. [NOTE: The bulletin is available without charge on the CL:AIRE website to registered users (also free) at http://www.claire.co.uk/.]
In Situ Chemical Reduction at the Morses Pond Culvert, Wellesley, Massachusetts (Chromium)
The Morses Pond Culvert Site is located in Wellesley, Massachusetts. The southern portion of the site includes an earthen railroad embankment, divided by a culvert into eastern and western portions. It is suspected that chromium-laden pigment from a former paint factory was used as fill material for improving the embankment and was the source of chromium contamination at the site. Due to slope stability and structural concerns with the steep embankment area, in situ chemical reduction using calcium polysulfide was selected as the remedy for treating chromium-contaminated soil at the site.
The injection system consisted of a total of 40 well points installed to depths ranging from 5 to 25 ft bgs. A total of 56,800 gallons of calcium polysulfide reagent was injected, treating 1,025 cubic yards of soil. The non-binding goals of treatment for hexavalent chromium were 200 mg/kg and 1 mg/kg using the TCLP. Post-treatment hexavalent chromium concentrations ranged from zero to 5,600 mg/kg in the western embankment, and from zero to 5,000 mg/kg in the eastern embankment. Total chromium concentrations after treatment ranged from 140 to 67,000 mg/kg in the western embankment, and from 92 to 35,000 mg/kg in the eastern embankment. The total cost for the treatment was approximately $119,719, including $69,296 for the calcium polysulfide, $13,900 in labor costs, and $36,523 for installing the injection wells and collecting pre- and post-treatment soil borings.
In Situ Groundwater Remediation of Heavy Metals at an Active Manufacturing Facility
McCall, Patti J., Lesa A. Bagby, and Jason E. Blocker
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010)
The contaminants of concern at this site are hexavalent chromium, nickel, and lead in groundwater. The selected remedy was chemical fixation using EHC-M™. To date, 71,000 pounds of EHC-M™ slurry have been injected at 166 locations. Hexavalent chromium concentrations as high as 24,400 (µg/L) are below laboratory reporting levels and have remained reduced for more than one year.
In Situ Redox Manipulation at U.S. DOE Hanford Site, 100-H and 100-D Areas (Chromium demonstration)
A demonstration of in situ redox manipulation (ISRM) was conducted in the 100-H and 100-D areas at the Hanford Superfund site that consisted of field-scale demonstrations. ISRM is a passive barrier technique that uses injection of buffered sodium dithionite solution (Na2S2O4) to react with natural iron in the subsurface and form reduced iron (Fe2+); the reduced iron reacts with chromate to form insoluble chromium oxides. Results from the field demonstration test showed that initial chromate concentrations of 60 µg/L in the 100-H area and 910 µg/L in the 100-D area were reduced to less than 8 µg/L in a one month period. In addition, 87-90% of the dithionite solution was recovered during the withdrawal phase, along with most of the mobilized metals (Fe, Mn, Zn). [Note a full scale treatment zone was constructed between 1999 and 2003 to a length of 680 meters (2,231 feet)].
In Situ Source Treatment of Cr(VI) Using a Fe(II)-Based Reductant Blend: Long-Term Monitoring and Evaluation (Abstract)
Ludwig, R.D., C. Su, T.R. Lee, R.T. Wilkin, and B.M. Sass
J. Environ. Eng., 134, 8: 651–658, 2008
A high pH chromite ore processing solid waste fill material was investigated. Two pilot injection studies using ferrous sulfate and sodium dithionite showed sustained treatment of Cr(VI) over evaluation periods of more than 1,000 days. Analysis of post treatment core samples suggested >85% treatment effectiveness of solid phase Cr(VI).
Macalloy Corporation Charleston, Charleston County, South Carolina Superfund Site
One of the remedies selected for this site was injection of a buffered sodium dithionite solution with a ferrous sulfate solution into the subsurface. The injection technique was not particularly successful and a barrier wall technique with in situ mixing was adopted. Vadose zone soil was treated with calcium polysulfide to reduce leaching of hexavalent chromium. As of 2010, the groundwater remedy had reduced hexavalent chromium to below cleanup goals in 19 of 23 monitoring wells with concentrations falling in the remaining 4.
Precision National Plating Services, Inc.: Response Action Plan
U.S. EPA Region 3, 101 pp, July 2012
Precision National Plating Services, Inc. operated a chrome plating facility from 1958 to 1999 in Clarks Summit, PA. This response action plan gives the site background and describes the strategy for continued in situ chemical reduction (ISCR) of Cr(VI) in the site's overburden and bedrock. Following previous successful ISCR activities completed from 2008 through 2011, the proposed supplemental bedrock injections of calcium polysulfide (CaSx) are designed to treat the remaining Cr(VI) in the overburden and shallow bedrock beneath the former building slab and downgradient areas of the site. The final cleanup is expected to take several years. Additional information: Precision National Plating website
Treatability Test Report for Calcium Polysulfide in the 100-K Area
Department of Energy, DOE/RL-2006-17, 138 pp, 2006
This report presents the results of a treatability test performed in the 100-K Area during the summer of 2005. The test used calcium polysulfide to remediate hexavalent chromium that was present in the groundwater. The treatment also chemically reduced a portion of the aquifer materials to form a permeable reactive barrier that will continue to treat hexavalent chromium in the groundwater.
Valley Wood Preserving, Inc, Turlock, California Superfund Site
EPA Region 9
To address a Chromium VI groundwater plume, a recirculation well system was employed to distribute calcium polysulfide. After 33 months of operation the recirculation well system had eliminated the chromium plume. The site also had an arsenic groundwater plume. The additional in-situ treatment of arsenic involved the injection of ViroBind™ F Blend reagent slurry (a product produced from clay with high iron content) into gridded injection points. The objective was to hydrofracture the subsurface, allowing for the creation of a series of sub-horizontal fractures that would allow the reagent to migrate laterally away from injection points. Sulfate, iron and manganese concentrations increased significantly after the injections. Arsenic concentrations in the vicinity of the injection area dropped by as much as two orders of magnitude following the in-situ treatment.
Voluntary Cleanup Report: Cross Manufacturing, Inc., Lewis, Kansas
Kansas Dept. of Health and Environment, Bureau of Environmental Remediation, 215 pp, 2015
Past operations at the Cross plant included chrome plating. A voluntary cleanup in situ Cr reduction and fixation remedy was completed at the site between 2012 and 2015 to reduce the toxic, soluble, and mobile Cr(VI) species to the much less toxic and mobile Cr(III) species. The remedy was completed by delivering the reducing agent calcium polysulfide (CPS) by direct injection and through amendment infiltration galleries, with treatments performed in October 2014 and May 2015. This report describes the completed in situ Cr reduction and fixation remedy, performance monitoring, and site restoration activities.
Organic Contamination
Active Manufacturing Site Northern Area, New Jersey
Injection of ZVI and emulsified oil.
The initial approach was to use molasses to biostimulate the dechlorination of PCE. The injection of molasses was carried out in both the source and plume areas. While source area molasses injections continued, use of nanoscale zero valent iron was initiated as a more aggressive approach for source area remediation. A pilot test of nanoscale ZVI was conducted in 2003, and (with the approval of the regulatory agency) full scale activities were performed in late 2005. Injection of approximately 800 lb of nanoscale ZVI was performed in 4 injection wells in the shallow source area in Nov-Dec 05. Fracturing was performed prior to ZVI injection in order to improve hydraulic communication and the ability to distribute ZVI throughout the source area. Performance monitoring of the ZVI injection indicated significant impacts on source area geochemistry, including increased pH levels (~9) and low ORP values (-500 mV). Currently molasses injections are conducted on a bimonthly frequency focusing on the source area and areas of contaminant flux.
Biogeochemically Enhanced Reductive Dechlorination of Chlorinated Organics (Abstract)
Leigh, D. | AEHS Foundation 30th Annual International Conference on Soil, Water, Energy, and Air, 22-25 March, Virtual, abstract only, 2021
Laboratory and field studies were conducted to evaluate the effectiveness of Geoform&trade Extended Release and Geoform™ Soluble for biogeochemical reduction (BGCR) of CVOCs at two sites. The two sites had similar hydrogeologic and geochemical conditions, but soil and groundwater at Site 1 had high concentrations of chlorinated ethenes (Ces), while Site 2 had high concentrations of Ces, chloroethanes (Cas), and chloromethanes (CMs). Bench tests demonstrated that BGCR enhancement significantly increased the reactivity of the ISCR reagent, while field tests demonstrated that the biological establishment of highly reducing conditions reduced the supplied sulfate to sulfide. The sulfide combined with the supplied ferrous iron causing rapid generation of reactive iron sulfide minerals and sulfidation of ZVI. BGCR enhancement increased the PRB downgradient reactive zone at Site 1. The combination of ERD and ISCR with BGCR at Site 2 resulted in rapid treatment of mixed CVOCs to the remedial goals. Site 2 received a no further action determination after 15 months of monitoring.
Combining Low-Energy Electrical Resistance Heating With Biotic and Abiotic Reactions for Treatment of Chlorinated Solvent DNAPL Source Areas
Macbeth, T., M.J. Truex, T. Powell, and M. Michalsen.
ESTCP Project ER-200719, 383 pp, 2012
Low-temperature subsurface heating was combined with either ZVI or in situ bioremediation to enhance DNAPL remediation performance through both increased degradation reaction rates and contaminant dissolution. Moderate heating and minor operational costs enhanced efficiency and effectiveness of in situ treatment of TCE. Capture and treatment of contaminated vapor—a major cost element of standard thermal treatment—was not needed as the heating infrastructure was limited to subsurface electrodes and a power control unit. See also the 2015 ESTCP Cost & Performance Report
DNAPL Remediation at Camp Lejeune Using ZVI-Clay Soil Mixing
C. Bozzini, T. Simpkin, T. Sale, D. Hood, and B. Lowder.
The Fifth International Conference Remediation of Chlorinated and Recalcitrant Compounds, 22-25 May 2006, Monterey, California.
Soil mixing with ZVI/clay addition was implemented at the site in a 17-day period in February 2005. The ZVI treated the chlorinated solvents (primarily PCE), while the clay created a low permeability zone that limited flow of groundwater into and out of the treated area. A crane was used to turn a 10-ft auger while injecting the ZVI/clay slurry. A total of 200 tons of ZVI and 100 tons of bentonite was mixed to create 146 overlapping columns. Off-gas was treated with activated carbon. After allowing six weeks for settlement, 196 tons of cement were added to the top 5 feet of soil over the treatment area to stabilize the site for a parking lot. One year after treatment, PCE soil concentrations had decreased significantly, with concentrations over the entire treatment area averaging an 82% decrease and a median concentration reduction of 99%. Reductions were lower (61%) in about one-fifth of the area where mobile DNAPL had been present prior to treatment but 99% in the remaining treated area. ZVI was still present in the treatment area, so continued treatment should occur. Groundwater concentrations of PCE were reduced by > 96% in the treatment area, but DCE concentrations did increase significantly in one groundwater well. Downgradient water quality improved after treatment, with PCE reduction of 67 and 90%. Hydraulic conductivity within the treatment area decreased 50 to 400 times (one to two orders of magnitude) with a post-treatment hydraulic conductivity of 0.013 ft/day, so there should be a significant reduction in mass flux from the treated area. Additional information: Olson et al., Chlorinated Solvent Source-Zone Remediation via ZVI-Clay Soil Mixing: 1-Year Results (Abstract). Ground Water Monitoring & Remediation 32(3):63-74(2012); Technology summary
Field Application of a Reagent for In Situ Chemical Reduction and Enhanced Reductive Dichlorination Treatment of an Aquifer Contaminated with Tetrachloroethylene (PCE), Trichloroethylene, 1,1-Dichloroethylene, Dichloropropane and 1,1,2,2-Tetrachloroethane (R-130)
Leombruni, A., M. Mueller, A. Seech, and D. Leigh.
Environmental Engineering and Management Journal 19(10):1791-1796(2020)
Groundwater at an abandoned industrial area near Bergamo, Italy, was contaminated by PCE (>100 µg/L) and, to a lesser extent, TCE, DP, and 1,1,2,2-tetrachloroethane (R-130). EHC® Liquid was selected to remediate the groundwater. The reagent was provided as EHC® Liquid Mix (a soluble organo-iron salt) and ELS® Microemulsion (a lecithin-based carbon substrate), designed to promote both in situ chemical reduction and enhanced reductive dechlorination. The two components were mixed with water and injected into the subsurface. Once in groundwater, EHC Liquid rapidly generated highly reduced conditions, favoring both biotic and abiotic dechlorination reactions. Less than 6 months after the injection of EHC Liquid in the main source area, concentrations of the target contaminants reached the site-specific remediation target values) in the main monitoring piezometers, demonstrating the effective establishment of enhanced biotic and abiotic reducing conditions and degradation of the target compounds.
Fracture-Emplacement and 3-D Mapping of a Microiron/Carbon Amendment in TCE-Impacted Sedimentary Bedrock
Bures, Gordon, et al.
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010)
This paper describes a pilot test to evaluate the performance of fracture-emplacement and amendment mapping technologies prior to developing the proposed remedy. The pilot work involved the emplacement of over 100 tons of a zero valent microiron/complex carbon treatment amendment ("EHC-G™") into deep bedrock sediments to attain optimal distribution throughout the contaminant plume. The EHC-G microiron/carbon amendment was distributed into bedrock sediments across an area of approximately 64,000 ft2. Initial groundwater quality results show significant decrease of 50% to 90% TCE within first 90 days.
Helena Chemical Company Tampa Florida Superfund Site
A pilot study at this NPL site is being conducted (2010-2011) in the sulfur area to determine whether buffering pH and introducing zero-valent iron will allow degradation of benzene hexachloride (BHC) and sulfates in the source area through biological or physical mechanisms.
Hunters Point Naval Shipyard, San Francisco, California Superfund Site
EPA Region 9
In 2009 the Navy finished a treatability study utilizing zero valent iron for remediating chlorinated solvents in groundwater in Parcel G. The study was successful, and the final remedial goals were obtained during the course of the study. Monitoring continues to verify the long-term effectiveness.
In Situ Biogeochemical Treatment Demonstration: Lessons Learned from ESTCP Project ER-201124
Stroo, H.F., J.T. Wilson, P.J. Evans, C.A. Lebron, B.M. Henry, D.E. Latta, R.S. Ghosh, and A. Leeson.
ESTCP Project ER-201124, 80 pp, 2015
Although the demonstration was not successful, this report explains the reasons for the disappointing results, summarizes the findings, and captures lessons learned from this effort to demonstrate biogeochemical transformation of TCE and daughter products at field scale.
Innovative Injection Technique to Treat DNAPL in Granular and Fine Grained Matrices
Noland, S., R. Boyle, and T.A. Harp.
The Eighth International Conference for Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, May 21-24, 2012. Battelle Press, Columbus, OH. 8 pp, 2012
High-energy, low-volume pulses of a water-based suspension of BOS 100®, a granular activated carbon impregnated with metallic iron, were employed to remediate DNAPL at a large urban industrial facility, with injections facilitated using conventional hydraulic fracturing. Although large portions of the dissolved-phase plume responded to this technique, some areas were resistant, suggesting input from unknown sources. High-resolution sampling indicated the presence of localized thin seams of DNAPL-impacted soils at several locations in the vicinity of the former TCE underground storage tank. A modified "jetting" approach was developed that allowed extremely accurate placement and injectant/soil mixing over a relatively thick zone.
Marine Corps Logistics Base Albany Georgia Superfund Site
EPA Region 4
After failure of a biostimulation program, the ROD was changed to use sodium permanganate injection to address TCE contamination and zero valent iron injection to address carbon tetrachloride contamination in groundwater. Based on monitoring results, in situ groundwater treatment of injecting permanganate and ZVI in the plume areas was effective in achieving its objective. Contaminant mass and contaminant concentrations were reduced in source areas, and this treatment stimulated contaminant reductions in the resultant plumes. COC concentrations in the vast majority of wells have stabilized at levels less than MCLs during the past 3 years (2011 Five Year Review).
NRC Corp. Millsboro, Deleware Superfund Site
EPA Region 3
Between November 2005 and October 2008, lactate, vegetable oil and/or zero valent iron was injected into the subsurface to treat chlorinated solvents in groundwater at this NPL site. The injections resulted in a reduction of contaminant concentrations.
Naval Surface Warfare Center, Silver Spring, Maryland
EPA Region 3 (RCRA site)
From January 10, through February 3, 2005 pneumatic fracturing and zero valent iron (ZVI) injection were conducted at the Site 5/13. After removing the temporary casing, the saprolitic bedrock was pneumatically fractured in 3.5 foot intervals by applying high pressure nitrogen gas for about 10 seconds. The range of influence was monitored via pressure gauges installed on nearby monitoring wells and injection boreholes. A total of 77,150 pounds of ZVI mixed with 23,506 gallons of water were injected into the subsurface. Based on the elevated pressure readings in the monitoring wells, pneumatic fracturing and ZVI were successful. Monitoring data indicate that the ZVI injection has significantly reduced the contaminant concentrations with 4 of the 6 COCs, having met the PRGs.
Orchard Supply Company Facility Groundwater Remediation, 1731 17th Street, Sacramento, Sacramento County
Central Valley Regional Water Quality Control Board, GeoTracker website, 2017
This in situ groundwater remediation project consisted of injecting a slurry solution of EHC into the source area shallow and deep groundwater to treat concentrations of 1,2-DCA, 1,2-DCP, and carbon tetrachloride. EHC is a mixture of controlled-release carbon, zero-valent iron, and nutrients for stimulating in situ chemical reduction of otherwise persistent chemicals in groundwater. A total volume of 24,525 gal of injection substrate containing 68,000 lb of EHC (30% EHC solids mixed with water) was injected using direct push tooling in the source area groundwater. The injections were completed between July 2015 and September 2015. No further injections are planned for the site. Additional groundwater monitoring is being conducted under a separate agreement. Additional information: Site Documents
Patrick Air Force Base Brevard County, Florida
EPA REGION 4 (RCRA)
Groundwater concentrations of TCE indicated the presence of DNAPL. Much of the contamination was limited to the saturated sandy calcareous clay of the Caloosahatchee Marl, which also can have discontinuous layers of silt and sand. A large diameter (8-10 feet) two bladed auger was chosen to deliver steam, hot air, and ZVI to the subsurface. The auger loosens the soil and mixes the steam and hot air with the soil to provide even heating and vaporization of contaminants. A hood at the surface applies a vacuum to the auger hole and captures the vaporized contaminants for surface treatment. Mixing the ZVI into the soil column provides a long term treatment source. Approximately 13,272 lbs, 389 lbs, and 11,439 lbs of total VOCs were recovered from SLC-15, SPCC, and Facility 1381 respectively. The cleanup cost averaged $190/yd3. A remedial efficiency of greater than 99.8% was found for both soil and groundwater. Post treatment sampling one year after remediation showed no rebound or back diffusion. Monitoring wells at Facility 1381 that showed values of up to 800 mg/L of TCE in 2006 before the remedial action had been reduced to 3 µg/L by 2008
- Emulsified Zero-Valent Iron (EZVI) Treatment of Chlorinated Solvents
- Draft Environmental Assessment and Finding of No Significant Impact For The Beddown And Flight Operations Of Unmanned Aircraft Systems at Cape Canaveral Air Force Station, Florida
- In Situ Soil Mixing and Injection Using Large Diameter Auger
Permeable Reactive Barrier Downgradient of the Southern Source Area, Former Tecumseh Products Company Site, Tecumseh, Michigan: Construction Documentation Report
U.S. EPA Region 5, 148 pp, 2012
The PRB was installed in May 2011. Site COCs include chlorinated VOCs (mainly TCE, TCA, and daughter products), SVOCs, 1,4-dioxane, metals, cyanide, and PCBs. Where the target treatment zone is relatively shallow, the design called for in situ soil blending to deliver DARAMEND(r) (a pelletized form of controlled-release carbon and ZVI) to the subsurface. The design included the use of injections to deliver ABC(r)+ (a patented mixture of ethyl lactate and glycerin, plus ZVI) to portions of the PRB farther beneath ground surface. ABC(r)+ also was used for shallow injections around an existing sewer pipe. Additional resources: Tecumseh website .
Remediation of a Former Dry Cleaner Using Nanoscale Zero Valent Iron
Jordan, M., N. Shetty, M.J. Zenker, and C. Brownfield.
Remediation Journal 24(1):31-48(2013)
Beneath a former dry cleaner located in Chapel Hill , NC , PCE was observed in site soil at concentrations up to 2,700 mg/kg and in shallow groundwater at concentrations up to 41 mg/L. NZVI was injected as an interim measure to treat the PCE source area. To achieve a design loading rate of 0.001 kg of iron per kg of aquifer material, ~725 kg of NanoFe(tm) was injected over a 2-week period into a saprolite and partially weathered rock aquifer. The injections resulted in near elimination of PCE within one month, while cis-1,2-DCE accumulated at high concentrations (>65 mg/L) for 12 months. Mass reduction of PCE and total ethenes was estimated at 96% and 58%, respectively, compared to baseline conditions. Detections of ethene confirmed complete dechlorination of PCE. Based on hydrogen gas generation, NZVI reactivity lasted 15 months. This paper is Open Access at the Remediation Journal website.
State Coalition for Remediation of Drycleaners
These sites are drycleaners with PCE contamination that utilized zero valent iron in their cleanup.
T.H. Agriculture & Nutrition Co. Montgomery, Alabama Superfund Site
EPA Region 4
Following several years of operating a pump and treat system, the site began a four-week series of HRC™ (time release lactic acid) injections in February 2002 to treat pesticides, PCE and TCE. The injections were followed by a period of groundwater monitoring events. The analytical results of the monitoring resulted in the site initiating a three-week series of EHC™ injections (carbon source plus ZVI) in 2005. The injection of HRC™ and EHC™ were accomplished using standard drilling direct-push (Geoprobe™) methods. Both additives were injected in the upper sand aquifer of the saturated zone (15-35 ft below ground surface. HRC™ was injected using the bottom-up direct-push approach, while EHC™ injection was conducted using the top-bottom direct-push method. Analytical data have shown evidence of VOC and pesticides reduction in groundwater following those injections in the groundwater monitoring events. Most COCs are nearing or below MCLs.
The Biogeochemical Reductive Dehalogenation Groundwater Treatment Process: Commercialization Status at Bench, Pilot and Full Scale
Studer, J.E.
Abstracts of the 21 st Annual Florida Remediation Conference, Orlando, October 8-9, 2015
A novel in situ remediation technology that combines biological and abiotic processes has been commercialized as the BiRD biogeochemical reductive dehalogenation treatment process. The technology generates amorphous and crystalline forms of iron sulfide (referred to as FexSy) in situ, which can dehalogenate compounds such as PCE, TCE, and other chlorinated aliphatics at significant rates. The FexSy reactive zone is created rapidly and can treat passing groundwater over a relatively long period of time. The process can be applied via direct injection or trenching techniques using inexpensive nontoxic reactants that are readily available in either liquid or solid form. The technology is compatible with enhanced bioremediation and zero-valent iron treatments. Additional information: Presentations to the California State Water Resources Control Board .
Updated ISCR Pilot Test Results, Indiana Machine Works, 135 East Harrison Street, Mooresville, Indiana
Indiana Department of Environmental Management, 101 pp, 2014
A successful ISCR pilot test was conducted at Indiana Voluntary Remediation Program Site 6051201 in 2013 to address groundwater affected by PCE, TCE, cis-1,2-DCE, VC, 1,1,1-TCA, and 1,1-DCA. After ISCR pilot treatment, monitoring results within the MW-14 test area showed concentrations of PCE and TCE below detection limits (<0.005 µg/L). Concentrations of daughter breakdown products cis-1,2-DCE and VC initially increased as the parent compounds declined, but within 6 months, all COC concentrations were below detection limits. At MW-30 (~30 ft downgradient of the ISCR test area), PCE and TCE respectively fell 96% and 58% to 0.022 µg/L and 0.016 µg/L. Full-scale enhanced reductive dechlorination via ISCR is proposed in a Work Plan to treat the site's two groundwater plumes.
Combined Organics-Inorganics
Remediation of Contaminated Soil And Groundwater Using Chemical Reduction and Solidification/Stabilization Method: A Case Study (Abstract)
Lu, S.-F., Y.-L. Wu, Z. Chen, T. Li, C. Shen, L.-K. Xuan, and L. Xu.
Environmental Science and Pollution Research [Published online 22 October 2020 prior to print]
A past industrial site in Shanghai, China, was treated for both heavy metals and organic contamination in soil and groundwater. Both laboratory and field tests were conducted to determine the optimum parameters for contaminant removal and found that the remediation goal of hexavalent chromium in soil could be achieved with the mass content of added sodium hydrosulfite and ferrous sulfate reaching 3% + 6%. Total chromium in the groundwater was effectively removed when the mass ratio of sodium metabisulfite was not less than 3 g/L, and the added quick lime raised the pH to >e;9. The concentrations of arsenic and 1,2-dichloropropane in decreased after extraction and mixing of groundwater. Following onsite remediation, the removal efficiency of the contaminants demonstrated that it was feasible to use chemical reduction and solidification/stabilization methods for the onsite, ex situ remediation of this site.
Third Five-Year Review Report for Boomsnub/Airco Superfund Site, Hazel Dell, Washington
U.S. EPA Region 10, 141 pp, 2013
Cr(VI) and TCE were released to soil and groundwater at this Superfund site during historical commercial chrome plating (Boomsnub) and compressed gas production (Airco). In September 2006, a toe-of-plume pilot study was initiated for in situ reduction of residual contamination in an area believed to be located in the low-permeability silt layer at a depth of ~80-90 ft bgs. EHC-M™, a combination of controlled-release carbon and ZVI particles, was injected into the alluvial aquifer to stimulate reductive dechlorination of TCE and chemical reduction-precipitation of chromium. Post-remediation monitoring indicates EHC-M was effective at reducing TCE and chromium concentrations below cleanup levels. Additional information: Work plan for in situ treatment of areas of residual contamination
