Application

Case Study Histories from the FRTR Cost and Performance Database
This is a selection of sites that used in situ anaerobic bioremediation to address chlorinated volatile and some metal contamination.

A Hydrogen Recirculation System for the Treatment of TCE-Impacted Groundwater
Aziz, C. E., S.K. Farhat, E.A. Higgins, C.J. Newell, and J. Hansen. Proceedings of the Seventh International In Situ and On-Site Bioremediation Symposium (Orlando, FL; June 2003), 6 pp, 2003

To speed the rate of reductive dechlorination of trichloroethylene (TCE)-impacted groundwater at the Old Jet Engine Test Site, Offutt AFB, Nebraska, an in situ pilot-scale dissolved hydrogen addition system was installed. The test area consisted of an injection well, a recovery well, and five monitoring wells within an 8.5 mx 4.3 m (28 ft x 14 ft) test plot. Groundwater was pumped from the recovery well at a flow rate of 1.5 L/min (0.4 gpm), amended with hydrogen at 20 mL/min, and injected into the injection well, thereby creating a recirculation system. The results of the first 6months of operation are presented in this paper. After 6 months of operation, the oxidation-reduction potential and dissolved oxygen of the groundwater decreased. Despite background sulfate levels of 280 mg/L, the mean TCE concentration declined 63% from 2.9 µmol/L to 1.07 µmol/L. Significant production of cis-1,2-dichloroethene (cDCE) was observed within the test area (i.e., 0.7to 3.0 µmol/L), indicating that the hydrogen was promoting reductive dechlorination. The cDCE:TCE ratio increased more than tenfold from 0.25 to 2.8, despite decreasing groundwater temperatures. In summary, the dissolved hydrogen recirculation system was effective in removing TCE from groundwater without significant vinyl chloride production.

Advances in Anaerobic Benzene Bioremediation: Microbes, Mechanisms, And Biotechnologies
Dworatzek, S., J. Webb, E. Edwards, N. Bawa, S. Guo C. Toth, K. Bradshaw R. Peters, et al.
REMTECH 2020: The Remediation Technologies Symposium, 14-15 October, Virtual Meeting, abstract, 2020

A field pilot test examining benzene biodegradation using DGG-B® bioaugmentation was conducted in November 2019 at a site in Saskatchewan contaminated with BTEX. The pilot test included three injection points, two of which received up to 10 L of the DGG-B culture. A third injection point received killed culture, which served as a control to rule out if dead cells or media components could promote benzene degradation. These first-to-field projects will establish clear guidelines and approaches for using bioaugmentation cultures, including a better understanding of dosing requirements, timeframes for obtaining results, and ranges of conditions over which the cultures are effective.

Applications of Anaerobic Petroleum Hydrocarbon Bioremediation
Roberts, J., S. Dworatzek, J. Webb, E. Edwards, N. Bawa, S. Guo C. Toth, K. Bradshaw, R. Peters, K. Stevenson, C. McGarvey, and A. Wang. | REMTECH 2021: The Remediation Technologies Symposium, Banff, AB, Canada, 13-15 October, 34 slides, 2021 [Abstract]

Recent advancements in molecular genomics led to the identification of microorganisms responsible for anaerobic benzene, toluene, and xylene (BTX) transformation and the commercialization of an anaerobic BTX culture DGG™ Plus for field application. The microbial composition of DGG Plus is relatively complex as the enrichments, a mixture of prokaryotic Bacteria and Archaea, originate from diverse natural microbial communities. Results from laboratory treatability studies demonstrated bioaugmentation promoted enhanced benzene biodegradation rates and provided information to aid in field pilot-test design. A pilot test performed at a site in Saskatchewan included three injection points, two of which received up to 10 L of the culture. A third injection point receives killed culture that serves as a control to rule out if dead cells, or media components, can promote benzene degradation. As observed in corresponding treatability studies, benzene degradation rates are anticipated to accelerate in situ through bioaugmentation. Two additional field applications with DGG-B™ and one field injection with DGG Plus are also being monitored. These first-to-field projects provide a better understanding of dosing requirements, timeframes for obtaining results, and ranges of conditions over which the cultures are effective. Additional information: Slides

Biodegradation of Dense Non-Aqueous Phase Liquids (DNAPLs) through Bioaugmentation of Source Areas - Dover National Test Site, Dover, Delaware: ESTCP Cost and Performance Report
Environmental Security Technology Certification Program (ESTCP), Project ER-0008, 59 pp, Aug 2008

This demonstration was conducted to determine if bioaugmentation can stimulate complete dechlorination of a DNAPL to nontoxic end products, as well as increase the mass flux from a source zone when biological dehalorespiration activity is enhanced through nutrient addition and/or bioaugmentation. The demonstration was able to prove that biological systems can be applied to promote enhanced dissolution of a PCE DNAPL source zone. Conservatively, the study appears to demonstrate an average increase in mass discharge ranging from 2.2 to 4.5 during the bioaugmentation phase relative to baseline (groundwater extraction only) conditions. If the increase in degradation rates is insufficient to enhance DNAPL removal significantly, rapid biodegradation of the high VOC concentrations typically encountered in DNAPL source zones will provide biological containment of the groundwater plume, thereby reducing cleanup times and/or reducing the O&M cost of conventional containment using pump and treat.

Bioremediation of Source Zone and Migrated Plumes
Blomgren , N., P.K. Juriasingani, and J.R. Woertz.
Third International Symposium on Bioremediation and Sustainable Remediation Technologies, 18-21 May 2015, Miami, Florida. Poster abstract, 2015

The former Unocal distribution facility in Wichita, Kansas, blended and packaged bulk chemicals for industrial customers. During historical operations, PCE was released to the site groundwater. Remedial technologies implemented at the site since 1989 to treat chlorinated VOCs in the groundwater include SVE, P&T, excavation, bioremediation, and phytoremediation. Despite these measures, contaminated groundwater has migrated a quarter mile from the primary source area to adjacent properties. During annual groundwater monitoring conducted in 2013, PCE and its daughter products were present at concentrations over 10,000 µg/L. A phased treatment approach is being implemented at the site. EHC® and EHC® Liquid were selected to stimulate both biodegradation and chemical reduction. Baseline monitoring was conducted in June 2014, and the first round of injections began in July 2014. A total of ~29,500 lb EHC (as 30% slurry) and 1,850 gal EHC Liquid (diluted to make a 5% solution) were injected among six barriers and one injection grid through 165 injection points over a one-month period. Performance monitoring results (Nov 2014 and Mar 2015) indicate the amendments are conditioning the aquifer to promote reductive dechlorination. Additional information: Interim Measure Injection Completion Report, Former Unocal Chemical Distribution Facility (2015) and Interim Measure Performance Monitoring Report, March 2015 Event

Case Study: In Situ Accelerated Anaerobic Bioremediation
Bloom, B. Lyon, and L. Stenberg.
E2S2 2010: Environment, Energy Security, and Sustainability Symposium and Exhibition, 14-17 June 2010, Denver, Colorado. National Defense Industrial Association (NDIA), Abstract 9778, 34 slides, 2010

Accelerated anaerobic bioremediation (AAB) was applied at Dover AFB to a large, multi-source plume of chlorinated ethenes and some ethanes. The Area 6 plume is ~1 mile in length and over 1,000 feet wide and originates from at least 5 separate source areas that commingle in the subsurface. Remediation involved targeted direct AAB injection of a substrate mixture of sodium lactate, EVO, and nutrients in source areas. After 3 years of treatment, plume-wide degradation is being observed. PCE and TCE concentrations within the AAB treatment areas have declined by over 80% in many wells, and the presence of ethene is increasing in areal extent over time. See longer abstract; More Information

Challenges in Planning for Groundwater Remedy Transition at a Complex Site
O'Steen, W.N. and R.O. Howard, Jr. U.S. EPA Region 4, 12 pp, 2014

Complex groundwater contamination sites require comprehensive, structured groundwater monitoring in planning for transition to a new groundwater remedy. This paper provides as an example the Medley Farm Superfund site, a former waste solvent dump located in South Carolina. PCE, TCE, and their degradation products in the groundwater were addressed with pump and treat from 1995 to 2004. Between October 2004 and April 2012, injection of a lactate solution to promote enhanced reductive dechlorination (ERD) was conducted on multiple occasions, with positive responses in hydrogeochemistry and groundwater quality. In 2012, EPA issued an amended ROD, changing the groundwater remedy to ERD. MNA was selected as a contingency remedy in anticipation that as cleanup progresses, ERD may transition to MNA. Restructuring the site's monitoring and data evaluation program will enable EPA to discern treatment effects more clearly and facilitate MNA evaluation.

Cleanup Chlorinated Ethene-Polluted Groundwater Using an Innovative Immobilized Clostridium Butyricum Column Scheme: A Pilot-Scale Study
Lo, K.-H., C.-W. Lu, C.-C. Chien, Y.-T. Sheu, W.-H. Lin, S.-C. Chen, and C.-M. Kao. Journal of Environmental Management 311:114836(2022) [Abstract]

An innovative immobilized Clostridium butyricum (ICB) (hydrogen-producing bacteria) column scheme was applied in a field test to clean up cis-DCE-contaminated groundwater in situ via anaerobic reductive dechlorinating processes. The study also characterized changes in microbial communities after ICB application. Three remediation wells and two monitor wells were installed within the cis-DCE plume. In one of the remediation wells, a 1.2-m PVC column was filled with ICB beads, and 20 L of a slow, polycolloid-releasing substrate (SPRS) was supplied for hydrogen production enhancement and primary carbon supply. Groundwater samples from remediation and monitor wells were analyzed periodically for cis-DCE and its degradation byproducts, microbial diversity, reductive dehalogenase, and geochemical indicators. Cis-DCE significantly decreased within the ICB and SPRS influence zone. Following ICB injection in a well, ~98.4% of cis-DCE removal was observed with ethene production after 56 days of system operation. Up to 0.72 mg/L of hydrogen was observed in remediation wells after 14 days of ICB and SPRS introduction, corresponding with the increased population of Dehalococcoides spp. Results of metagenomics analyses show that the SPRS and ICB introduction significantly impacted the bacterial communities, increasing Bacteroides, Citrobacter, and Desulfovibrio populations, which significantly contributed to the reductive dechlorination of cis-DCE. Applying ICB could effectively result in increased populations of Dhc and RDase genes, which corresponded with improved dechlorination of cis-DCE and vinyl chloride. The introduction of ICB and SPRS could be applied as a potential in situ remedial option to enhance the anaerobic dechlorination efficiencies of chlorinated ethenes.

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

Comparative Demonstration of Active and Semi-Passive In Situ Bioremediation Approaches for Perchlorate Impacted Groundwater: Active In Situ Bioremediation Demonstration (Aerojet Facility)
Cox, E. and T. Krug.
ESTCP Project ER-200219, 848 pp, 2012

During the demonstration of active enhanced in situ bioremediation at the inactive Rancho Cordova test site in California, groundwater containing perchlorate and TCE was extracted from the shallow aquifer, amended with ethanol, and recharged to the shallow aquifer. The active biobarrier provided treatment and containment of a 600-ft wide section of the plume in the shallow aquifer using two groundwater extraction wells and a single groundwater recharge well. Indigenous bacteria were able to biodegrade perchlorate concentrations as high as 4,300 µg/L to less than 4 µg/L within 50 ft of the recharge well. TCE dechlorination followed bioaugmentation of the shallow aquifer with KB-1 to introduce dehalorespiring bacteria.

Degradation of Carbon Tetrachloride in the Presence of Zero-Valent Iron
Alvarado, J.S., C. Rose, and L. LaFreniere. Journal of Environmental Monitoring, Vol. 12, No. 8, p. 1524-1530, 2010

Efforts to achieve the decomposition of carbon tetrachloride through anaerobic and aerobic bioremediation and chemical transformation have met with limited success because of the conditions required and the formation of hazardous intermediates. After using particles of zero-valent iron (ZVI) with limited success for in situ remediation of carbon tetrachloride, the authors investigated the application of a modified microparticulate product that combines controlled-release carbon with ZVI for stimulation of in situ chemical reduction of persistent organic compounds in groundwater. With this product, physical, chemical, and microbiological processes were combined to create very strongly reducing conditions that stimulate rapid, complete dechlorination of organic solvents. In principle, the organic component of ZVI microparticles is nutrient rich and hydrophilic and has high surface area capable of supporting the growth of bacteria in the groundwater environment. The investigators found that as the bacteria grew, oxygen was consumed, and the redox potential decreased to values reaching -600 mV. The small modified ZVI particles provide substantial reactive surface area that, in the conditions of the study, directly stimulates chemical dechlorination and cleanup of the contaminated area without accumulation of undesirable breakdown products. The objective of this work was to evaluate the effectiveness of ZVI microparticles in reducing carbon tetrachloride under laboratory and field conditions. Changes in concentrations and in chemical and physical parameters were monitored to determine the role of the organic products in the reductive dechlorination reaction. Results of laboratory and field studies are presented.

Designing, Assessing, and Demonstrating Sustainable Bioaugmentation for Treatment of DNAPL Sources in Fractured Bedrock: ESTCP Cost and Performance Report
ESTCP Project ER-201210, 100 pp, 2017

A small portion of a (presumably) much larger PCE source area was targeted at Edwards AFB, Calif., and the DNAPL mass and distribution were quantified in two separate depth intervals with discrete fractures. Geophysical testing showed that the well capacities within the source area were sufficient to distribute the amendments in conductive fractures and that there was hydraulic connectivity in both zones in the two wells used for the field test. During biological treatment (SDC-9 culture), enhanced dissolution of the DNAPL sources was observed in both the shallow and deep fractures intervals. In the shallow fracture zone, the measured DNAPL mass removal was ~100%, but only 45% over the same period in the deep zone. This difference in mass removal was attributed to the DNAPL architecture, as the flow field in the deep zone was more complex, and more DNAPL was present in mass transfer controlled zones. Rebound testing showed no increase in the sum of chlorinated ethenes and ethane in the shallow zone 10 months after active treatment, but concentrations did rebound significantly in the deep zone, likely owing to residual DNAPL mass.

Direct-Push Injection and Circulation Biobarrier to Remediate a TCE Groundwater Plume
Kovacich, M., D. Beck, and P. Rich (GeoTrans, Inc.); M. Zack and M. Cannert (Visteon Corporation). Proceedings of the 5th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California, May 2006, Battelle Press, Columbus, OH.

A study was conducted to determine if direct-push drilling methods combined with a ground-water circulation system could be used to establish a passive biobarrier in a very transmissive aquifer contaminated with trichloroethene (TCE) at a site located in central Indiana. The site has a plume consisting primarily of dissolved-phase TCE that is approximately 1,100 feet wide, 6,300 feet long, and up to 50 feet deep. The horizontal groundwater flow velocity is estimated to be 2.0 to 5.0 feet/day. Site geochemical and volatile organic compound (VOC) data showed no evidence of the natural attenuation of TCE. After a bench-scale test indicated that bioaugmentation could be applied successfully at the site, emulsified vegetable oil with 5% lactate was applied via direct-push injection at 14 drive points in the upgradient portion of a circulation cell. Positive results were evident within weeks, suggesting that the combination of direct injection and circulation accelerated the establishment of the biobarrier. Halorespiring bacteria have been quantified in the circulation area using real-time polymerase chain reaction techniques. Recent VOC, geochemical, and microbial data indicate that the biobarrier has persisted in the circulation zone more than six months after system shut-down. These results led the Indiana Department of Environmental Management to approve a work plan for full-scale implementation of biobarriers at the site.

Edible Oil Barriers for Treatment of Chlorinated Solvent Contaminated Groundwater
Lieberman, M.T. and R.C. Borden.
ESTCP Project ER-0221, 228 pp, 2009

A pilot test was conducted between 2003 and 2007 at Charleston Naval Weapons Station, SC, to evaluate the effectiveness of EOS®, a commercially available emulsified oil substrate, for enhancing the biodegradation of dissolved-phase chlorinated VOCs in groundwater and aquifer material in a treatment cell. The cell contained 4,000 cubic ft of contaminated aquifer material with up to 16,000 µg/kg TCE in soil and >20,000 µg/L TCE in groundwater. Phase I involved site characterization, baseline sampling, EOS injection, and monitoring for 28 months. Phase II involved a bench-scale treatability study, development and injection of a newly formulated pH-buffered substrate to overcome a pH problem, and an additional 11 months of monitoring to measure the effect of the second substrate. The buffered EOS raised the pH and alkalinity of the aquifer, which allowed the native dehalorespiring populations to re-initiate their metabolism of TCE and DCE and biodegrade TCE throughout the test cell. Over the entire 41-month monitoring period in Phases I and II, the total chlorinated VOC concentration decreased from 198 µM to 17 µM, a decline of 91%. See also the ESTCP Cost and Performance Report.

Electrokinetic-Enhanced (EK-Enhanced) Amendment Delivery for Remediation of Low Permeability and Heterogeneous Materials
Cox, E., J. Wang, D. Reynolds, D. Gent, M. Singletary, and A. Wilson.
ESTCP Project ER-201325, 204 pp, 2018

Electrokinetic (EK)-enhanced amendment delivery for in situ bioremediation (EK-BIO) via enhanced reductive dechlorination of a PCE source area in clay was conducted at Naval Air Station Jacksonville, Florida. The EK-enhanced amendment delivery technology entails the establishment of an electric field in the subsurface using a network of electrodes. The electrical current and voltage gradient established across a direct-current electric field provide the driving force to transport remediation amendments, including electron donors, chemical oxidants, and even bacteria, through the subsurface. The EK demonstration system consisted of 9 electrode wells and 8 supply wells located within a target treatment area measuring ~40 ft by 40 ft. The remediation amendments distributed by the EK system included electron donor (lactate provided as potassium lactate), pH control reagents (potassium carbonate), and a dechlorinating microbial consortium (KB-1®) containing Dehalococcoides. Project results showed that EK could achieve relatively uniform transport in low-permeability materials. Additional information: ESTCP Cost and Performance Report .

Electrokinetically-Delivered, Thermally-Activated Persulfate Oxidation (EK-TAP) for the Remediation of Chlorinated and Recalcitrant Compounds in Heterogeneous and Low Permeability Source Zones
Cox, E., M. Watling, D. Gent, M. Singletary, and A. Wilson., ESTCP Project ER-201626, 175 pp, 2021

This project demonstrated electrokinetic (EK)-enhanced amendment delivery for in-situ bioremediation (EK-BIO) via enhanced reductive dechlorination (ERD) of a tetrachloroethene source area in clay. The EK-enhanced amendment delivery technology established a direct-electric field in the subsurface using a network of electrodes. The electrical current and voltage gradient provided the driving force to transport remediation amendments, including electron donors, chemical oxidants, and bacteria, through the subsurface. This project showed that EK could achieve relatively uniform transport in low-permeability materials.

Enhanced Amendment Delivery to Low Permeability Zones for Chlorinated Solvent Source Area Bioremediation
Adamson, D., C. Newell, M. Truex, and L. Zhong.
ESTCP Project ER-200913, 202 pp, 2014

A demonstration of the use of shear-thinning fluid based technology to improve treatment within low-permeability (low-k) zones of heterogeneous subsurface environments was conducted in a test cell within the Area D TCE plume at Joint Base Lewis-McChord. Low-k zones, which can serve as a long-term secondary source of contamination when transport is diffusion-controlled, are difficult to target using standard injection-based treatment approaches. A shear-thinning fluid can be used to distribute a bioremediation amendment (e.g., lactate) around an injection well such that the solution achieves better penetration and delivers the amendments to zones of both high and low permeability. When injected at a relatively high velocity compared to natural groundwater flow velocities, the shear-thinning nature of the solution allows it to flow more readily, promoting cross-flow from high- to low-permeability zones. During the demonstration, the shear-thinning fluid improved amendment distribution by ~41% with enhanced persistence and treatment effectiveness within the lower-k zones of the heterogeneous aquifer. Permeability contrasts of 1-2 orders of magnitude may be amenable to this technology (e.g., improving distribution to silt layers within a sand matrix, but not clay layers). Field work began in August 2013, and performance monitoring events were completed in February and May 2014. Additional Information: ESTCP Cost and Performance Report

Enhanced Attenuation of Unsaturated Chlorinated Solvent Source Zones Using Direct Hydrogen Delivery
Newell, C.J., A. Seyedabbasi, D.T. Adamson, T.M. McGuire, B. Looney, P.J. Evans, J.B. Hughes, M.A. Simon, and C.G. Coyle.
ESTCP Project ER-201027, 532 pp, 2013

Over a 6-month test period, a total of 830,000 standard cubic feet of gas—10% hydrogen, 79% nitrogen, 10% propane, and 1% carbon dioxide—was injected into a fine-grained vadose zone at a former missile silo site in Nebraska . The hydrogen gas was designed to stimulate biodegradation of TCE and its breakdown products that persisted after three years of SVE. Although the system was successful at converting TCE, a "cis-DCE stall" condition occurred. ESTCP Cost & Performance Report

Enhancing Reductive Dechlorination with Nutrient Addition
Fowler, T. and K. Reinauer.
Remediation Journal 23(1):25-35(2013)

This paper presents three case studies where the addition of a balanced macro- and micro-nutrient source (e.g., BounTA^™) substantially accelerated the biodegradation of chlorinated ethenes (TCE, PCE), independent of the electron-donor substrate (i.e., sodium lactate, EHC^®, ethyl lactate) applied. [This paper is Open Access via the "Get PDF" link.]

Ethylene Dibromide In Situ Biodegradation Pilot Test Report Bulk Fuels Facility Solid Waste Management Units ST-106 and SS-111, Kirkland Air Force Base, New Mexico
U.S. Army Corps of Engineers Omaha District, 247 pp, 2019

A pilot test was conducted at Units ST-106 and SS-111 to investigate potential treatment amendments for anaerobic in situ bioremediation of ethylene dibromide (EDB) at the Bulk Fuels Facility on Kirtland AFB. Using one injection and groundwater circulating, two extraction, and six monitoring wells and the pilot test evaluated baseline conditions followed by biostimulation in the subsurface after distribution of treatment amendments in recirculated groundwater, bioaugmentation, and long-term monitoring. Baseline EDB concentrations ranged from 20.1-432 µg/L in shallow wells; virtually no EDB was detected in intermediate wells suggesting biologically active subsurface. At the pilot conclusion, EDB reductions were >97% in the shallow wells; four wells exhibited a two log reduction (>99%), and two of the wells exhibiting three-log reductions (>99.9%). EDB degradation was evident through comparison with benzene and toluene concentrations, and the production of EDB degradation products ethene, ethane, and bromide suggested that the degradation occurred by reductive debromination.

Expedited DNAPL Destruction via Biostimulation
Armstrong, K.C. ǀ RemTech Europe 2020: European Conference on Remediation Market and Technologies, 21-25 September, virtual, 15 minutes, 2020

Releases of TCE at a former electronics manufacturer impacted shallow overburden-bedrock groundwater with DNAPL. Baseline TCE in bedrock ranged from 55-550 mg/L, up to ≈30% of TCE's aqueous solubility limit; cis-1,2-DCE was ≤15 mg/L, and VC was not detected above method detection limits. A pump and treat system managed plume migration though a low-impact, low-cost and sustainable strategy was desired to achieve enhanced reductive dechlorination (ERD) to target DNAPL destruction. A 3-year proof-of-concept (POC) study evaluated ERDenhanced™, a biostimulant formulated with a proprietary blend of micronutrients to determine the additives' ability to enhance native microbial populations, stimulate enhanced reductive dechlorination, and optimize syntropic relationships between dechlorinators and fermenters. Following successful treatment in the POC, a 20-month pilot study (PS) was performed to determine the transferability of POC study data and collect pre-design data for full-scale remedy. Two bedrock injection wells and a performance network of 8 bedrock wells were utilized. Performance data collected from monitoring wells within amended zones at the POC and PS locations indicated biostimulation with ERDenhanced provided robust and complete dechloration of TCE DNAPL and cis-1,2-DCE by optimizing the syntropy between dechlorinators and fermenters. Data demonstrated biostimulation with ERDenhanced expedited dechlorination rates, extended effect-residence times (8+ years) resulted in three orders-of-magnitude reductions in cVOC contaminant mass.

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.

Final Report for the Enhanced Anaerobic Bioremediation Pilot Test, Bountiful/Woods Cross Superfund Site, Bountiful, Utah
Bureau of Reclamation, Denver, CO. 66 pp, 2006

This biostimulation/bioaugmentation pilot study to address TCE contamination involved a side-by-side comparison in 3 test cells of 3 different bioremediation substrates: sodium lactate, chitin, and emulsified soybean oil. Following the first round of substrate injection and sampling, all 3 test cells were inoculated with a commercially available dechlorinating culture containing Dehalococcoides ethenogenes. Based on the results of the pilot test, full-scale enhanced anaerobic bioremediation was selected for the site's 2006 Record of Decision. Emulsified oil is recommended as the electron donor.

Fracture-Emplacement and 3-D Mapping of a Microiron/Carbon Amendment in TCE-Impacted Sedimentary Bedrock (Abstract)
Bures, G., J.A Skog, D. Swift, J. Rothermel, R. Starr, and J. Moreno
Seventh International Conference on Remediation of Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2010)

An in situ pilot remediation project was carried out on behalf of the U.S. Army Corps of Engineers (Omaha District) at the F.E. Warren Air Force Base Former Atlas E Missile Site No. 12 in Colorado. Between 6,000 and 32,000 lbs of microiron/carbon amendment was emplaced at each borehole by mixing it as a biodegradable, linear protein gel slurry to carry the amendment in a uniform suspension. Hydraulic fracturing was conducted in 9 pre-drilled boreholes to deliver the amendment slurry at 5-ft increments between depths of 35 to 63 ft in bedrock. Hydraulic fracturing was successful in emplacing greater than 98% of the total design mass of 205,550 lb. of EHC-G™ zero valent micro-iron/carbon within TCE-impacted bedrock sediments across an area of approximately 64,000 ft2. The implications of this work are that massive quantities of micro-iron (or other) amendments can be cost-effectively emplaced in challenging geologic environments (e.g., deep bedrock) to treat large plume areas using few injection borings.

Geophysical Imaging for Investigating the Delivery and Distribution of Amendments in the Heterogeneous Subsurface of the F.E. Warren AFB
Kelley, B., S. Hubbard, J. Ajo-Franklin, J. Peterson, Y. Wu, E. Gasperikova, B. Butler-Veytia, V. Shannon, and R. Coringrato.
ESTCP Project ER-200834, 80 pp, 2012

In 2009, a remedial action involving hydraulic fracturing and in situ bioremediation was conducted at Spill Site 7, the location of a TCE plume at F.E. Warren AFB. The June 2010 field demonstration involved an evaluation of the progress of in situ bioremediation (HRC[r]) via hydraulic fracturing and the use of geophysical imaging (time-lapse electrical resistivity tomography and seismic datasets) to monitor fracture emplacement and amendment distribution at the site. Additional information: ESTCP Cost & Performance Report

Groundwater Remediation Startup Report, Site Monitoring & Performance Evaluation Report, Revision 1.0: Chemical Injections & Attenuation Monitoring, 2nd & Kirby Site, Hutchinson, Kansas
Kansas Department of Health & Environment (KDHE), Topeka. 235 pp, 2015

Dissolved-phase TCE and related contaminants have been found in the site groundwater at this truck transportation facility. The site contractor used direct-push injections to introduce emulsified vegetable oil (EVO) to provide the electron donor needed to produce the reducing and anaerobic conditions that stimulate contaminant biodegradation. A total of ~9,000 gal of EVO-water solution (900 gal EVO product, specifically SRS^®-FRL) was injected throughout the course of the project. The presence of cDCE as a degradation product of TCE indicates some degree of ongoing reductive dechlorination. This report details the specific measures applied to accelerate the chemical and biological degradation of TCE in the site groundwater.

How to Address Low Ph During In Situ Bioremediation
Elkins, B. | Global Enviro Summit 4-6 April, Charlotte, NC, abstract only, 2022

SERDP/ESTCP published a base-addition design tool to help practitioners develop a comprehensive pH management plan utilizing commonly used bases. A method was developed to alter the surface charge of Mg(OH)₂ to improve subsurface transport and injectability. Lab studies validated that a colloidal suspension of Mg(OH)₂ could be transported through sand-packed columns without significant permeability loss. The proprietary formula of colloidal Mg(OH)₂ was commercialized into the product CoBupH™. The base-addition design tool and lab titration data were used to successfully remediate a chlorinated-impacted site in NC. CoBupH and potassium bicarbonate were selected as the buffers, with EOS® Pro co-injected as the electron donor. The site had two distinct water-bearing zones; the shallower zone contained groundwater with an average pH of ~4 standard units due to an acid release from an off-site source. Post-injection monitoring since 2016 shows nearly complete conversion of chlorinated solvents to ethene while maintaining a neutral aquifer pH. Base addition design tool

Improving Effectiveness of Bioremediation at DNAPL Source Zone Sites by Applying Partitioning Electron Donors (PEDS)
Lebron, C.A ., D. Major, M. McMaster, and C. Repta.
ESTCP Project ER-200716, CR-NAVFAC-EXWC-EV-1402, 3,859 pp, 2014

Partitioning electron donors (PEDs) are water-soluble electron donors that partition directly into a target DNAPL to effect enhanced in situ bioremediation. A PED technology field demonstration was conducted at a TCE source zone at NASA Launch Complex 34 using n-butyl acetate (nBA), a colorless liquid that volatilizes to form dense vapors that have the potential to form an explosive mixture with air. Introduced to the source area using direct-push injection equipment, nBA was able to promote biodegradation and achieved sustained production of dechlorination products, even in the presence of co-contaminant 1,1,2-trichloro-1,2,2-trifluoroethane (CFC113). This project showed that nBA can (1) achieve high rates of biologically enhanced DNAPL dissolution; (2) be easily and effectively delivered; and (3) sustain donor supply at an effective concentration at the DNAPL:water interface to promote the growth and activity of the dechlorinating biomass. [Note: See the first 112 pages of the PDF file for the main report; the subsequent appendices contain lab forms, boring logs, and other field data.] Additional information: ESTCP Cost and Performance Report.

In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies
Interstate Technology & Regulatory Council (ITRC) Bioremediation of DNAPLs Team.
BioDNAPL-2, 173 pp, 2007

Contains the following case studies: (1) cleanup of a TCE residual source area and a dissolved-phase plume at the Test Area North site of Idaho National Engineering and Environmental Laboratory; (2) a pilot-scale demonstration to evaluate the effects of biological activity on enhancing dissolution of an emplaced PCE DNAPL source at Dover National Test Site; (3) a TCE cleanup field study at Cape Canaveral's Launch Complex 34, Kennedy Space Center; (4) a PCE demonstration project undertaken by ARCADIS at a private-sector U.S. site; (5) a cleanup of PCE groundwater impacts at an active dry cleaner located in a strip mall in Portland, OR; and (6) use of Emulsified Oil Substrate (EOS®) to remediate a TCE source area at the Tarheel Army Missile Plant, Burlington, NC.

In Situ Bioremediation of The Source Zone for Chlorinated Solvents in Groundwater – Successes And Challenges
LaPat-Polasko, L. and M. Hayes. | Environmental Professionals of Arizona 16th Annual Gatekeeper Regulatory Roundup, 4-5 March, Tempe, AZ, 37 slides, 2020

Two separate VOC plumes, one with low 1,4-dioxane and one with high 1,4-dioxane, are present at a former manufacturing company. Following decades of operation, a pump and treat system was found to have little impact on the source area and downgradient plumes, and current activities at the site require a remedial approach that does not disrupt operations. This presentation summarizes the site geology, groundwater data, soil microbial data, and in situ testing that led to the decision to test biostimulation followed by bioaugmentation in the source zone. Monitoring results as well as Bio-Trap and in situ microcosm studies suggest that bioaugmentation using Pseudonocardia dioxanivorans CB1190 may be appropriate for in situ biodegradation of dioxane at the site. Preparations are starting for field implementation. Additional information: More information on the 7th Avenue & Bethany Home site

In Situ Bioremediation of a Chlorinated Hydrocarbon Plume: A Superfund Site Field Pilot Test
Guerra, P., A. Bauer, R.A. Reiss, and J. McCord. ǀ Applied Sciences 11:10005(2021)

Pilot testing was conducted in the source zone and hotspot areas of groundwater plumes contaminated with TCE, DCE's isomers, and VC extending over three hydrostratigraphic units at the North Railroad Avenue Superfund Site to select an enhanced reductive dichlorination (ERD) treatment formulation (dose and dosing frequency). Pilot testing was used to refine the site’s hydrogeologic conceptual site model and design parameters. Four test cells containing well pairs of injection and downgradient extraction wells were used to test ethyl lactate, dairy whey, emulsified vegetable oil (EVO), and a combination of EVO and a hydrogen gas infusion as bio-amendment formulations. Bromide was added to the recirculation flow to record tracer breakthrough, peak, and dissipation at extraction wells. Results were used to reassess the hydraulic conductivity and hydrodynamic dispersity used in the remedial design. Groundwater samples were analyzed for biological analyses before, during, and after bioamendment addition. Analyses of phospholipid fatty acids and DNA extracts from fresh groundwater samples informed decisions on the capacity for complete ERD without DCE stalling and tracked the shifts in the bacterial and archaeal taxonomy and phylogeny stemming from bioamendment addition. EVO was the most suitable bioamendment based on support of the native microbial consortia for ERD, mechanics and hydraulics of the remediation system, and sustainability/retention of the substrate in the subsurface. Adding a nutrient broth derived from brewery waste accelerated and sustained the desired conditions, microbial diversity, and population levels. Results were also used to assess the utilization kinetics of the injected substrates based on total organic carbon (TOC) concentrations measured in the groundwater. A full-scale treatment dosing and dose frequency were designed around a TOC threshold of 300 mg/L, assuming the maximum substrate utilization would yield optimum ERD.

In Situ Bioremediation of the Source Zone for Chlorinated Solvents in Groundwater - Successes and Challenges
LaPat-Polasko, L. and M. Hayes. | 16th Annual Gatekeeper Regulatory Roundup 4-5 March, virtual, 37 slides, 2020

In situ bioremediation was conducted to remediate two plumes containing cVOCs and 1,4-dioxane in the groundwater at an aluminum pipe manufacturing company. A treatment zone was established using a temporary recirculation system upgradient of source area. Quick-release carbon substrate was injected to biostimulate microbes, followed by injection of a slow-release carbon substrate to support extended bioremediation of cVOCs.

In Situ Treatment of a Dilute Chlorinated Solvent Plume in an Acidic Aerobic Aquifer
Alexander, M. | Remediation 30(2): 25-35(2020)

In situ bioremediation was selected to remediate a 29‐acre dilute, acidic and aerobic, chlorinated solvent plume (mainly TCE and 1,1,-DCE) at the Monitor Devices Inc./Intercircuits Inc. Superfund site in New Jersey. Remediation began in late 2010 and continued over 9 years. The amendments injected included electron donor and bicarbonate buffer solution and, once anaerobic aquifer conditions became established, a bioaugmentation culture. Amendments were injected in multilevel injection wells (IWs), to maintain control over the vertical interval of amendment delivery. The areal coverage of the plume has been reduced by 59% based on the 10µg/L TCE isocontour and the contaminant mass has been reduced by 79%. Lessons learned from this project include the need for bioaugmentation in the acidic aquifer and an efficient and effective manner of well construction and amendment injection using multiscreen single casing IWs and packer systems. Also, there were differences in longevity of the electron donor amendment versus the bicarbonate neutralization additive, and varied amendment delivery techniques (IWs, direct injection, horizontal well installation) were needed in selected lower permeable zones to attain treatment.

In-Situ Substrate Addition to Create Reactive Zones for Treatment of Chlorinated Aliphatic Hydrocarbons: Hanscom Air Force Base
Lutes, C.C., V. D'Amato, A. Frizzell, M. Hansen, G. Gordon, P. Palmer, and S. Suthersan.
Environmental Security Technology Certification Program (ESTCP), 431 pp, 2003.

The general purpose of this demonstration project was to evaluate the efficacy of the In-Situ Reactive Zone/Enhanced Reductive Dechlorination (IRZ/ERD) technology to remove TCE from impacted groundwater in a range of geologic conditions and TCE concentrations. The active treatment phase of the demonstration took place from October 2000 to October 2002, during which time 47 injections conducted in a single injection well delivered 1,250 gallons of raw blackstrap molasses, 11,250 gallons of dilution water, 7,575 gallons of push water, and 4,732 grams of potassium bromide. During the two-year demonstration project, complete TCE removal was observed in a source area that had a long history of fairly stable TCE concentrations before treatment.

In-Situ Substrate Addition to Create Reactive Zones for Treatment of Chlorinated Aliphatic Hydrocarbons: Vandenberg Air Force Base
Lutes, C.C., A. Frizzell, B. Molnaa, and P. Palmer.
Environmental Security Technology Certification Program (ESTCP). 335 pp, 2004.

This report documents an evaluation of the efficacy of the In-Situ Reactive Zone/Enhanced Reductive Dechlorination (IRZ/ERD) technology in removing TCE from impacted ground water in a range of geologic conditions and TCE concentrations. The active treatment phase of the demonstration took place between February 2001 and April 2003. A total of 683 gallons of raw molasses, 6,830 gallons of dilution water, 1,500 gallons of push water, 7,718 grams of potassium bromide tracer and 669 pounds of NaHCO₃ buffer were injected into three injection wells. Thirty one injections were completed. During the active treatment period and up to 10 months after the last injection, the treatment system demonstrated slow but effective TCE removal via bioremediation. The dissolved phase plume showed very limited TCE degradation before treatment.

Investigative Area 6 (IA-6) IRM Progress Report Addendum: April/May & July 2019 Groundwater Sampling for the Former Hoffmann-La Roche Inc. Facility, Nutley, New Jersey
Hoffmann-La Roche Inc., 102 pp, 2020

This report presents 3- and 6-month post-injection results of enhanced in situ bioremediation (EISB) to remediate groundwater contaminated with PCE+ (PCE and its degradation products) at IA-6. ABC^® electron donor; TSI DC^® Dehalococcoides ethenogenes bioaugmentation culture; sodium ascorbate, sugar, and yeast to create anaerobic conditions; and pH buffer was injected into source area injection wells. Injection was combined with recirculation to facilitate the amendment transport and distribution within the treatment zone (taken from the April 2019 Interim Remedial Measure Progress Report). July 2019 sampling results indicated that concentrations of PCE and its degradation products were below the groundwater quality standards (GWQS) at eight of the 13 wells within the treatment zone. One or more of the target PCE+ constituent concentrations were above GWQS at the remaining five wells within the IRM treatment zone but were mostly only slightly above GWQS. The effectiveness of EISB for the remediation of PCE in groundwater throughout the targeted treatment area was demonstrated through multiple lines of evidence including biodegradation of PCE into daughter products to below GWQS, the presence of VC as the primary PCE degradation product, individual target constituent trends that showed evidence of biodegradation of PCE>daughter products>ethene and ethane, and the presence of anaerobic and reducing geochemical conditions necessary to support ongoing biodegradation. Additional information: April 2019 Interim Remedial Measure Progress Report

Limited-Access Bioremediation in a Factory Setting
Farnsworth, D.R., W.A. Murray, and D.L. Bronson.
Proceedings of the Annual International Conference on Soils, Sediments, Water and Energy, Vol 15 Article 2, 7 pp, 2010

At a factory in New Hampshire, TCE released through a storm-water outfall pipe contaminated the groundwater. Tight soils, shallow water table, access limitations, and a pending property sale complicated the cleanup. Due to the low permeability of the soil, effective introduction of the Hydrogen Release Compound (HRC) required many injection points and applications. After the start of HRC application, VOC levels at the outfall dropped to below the state regulatory standard. The treatment has not interfered with site activities or the sale of the property, and site closure is expected to be completed in a reasonable timeframe.

Long-Term Performance Assessment at a Highly Characterized and Instrumented DNAPL Source Area Following Bioaugmentation
Schaefer, C., G. Lavorgna, M. Annable, and A. Haluska.
ESTCP Project ER-201428, 167 pp, 2018

In a study of long-term behavior in a TCE DNAPL source area following in situ bioaugmentation in heterogeneous media, monitoring performed up to 3.7 years following active bioremediation showed that biogeochemical conditions remained favorable for reductive dechlorination of chlorinated ethenes despite the absence of lactate, lactate fermentation transformation products, or hydrogen. While ethene levels suggested relatively low dechlorination of the parent TCE and daughter products, CSIA showed the extent of complete dechlorination was much greater than indicated by ethene generation. Results of push-pull tracer testing confirmed that DNAPL remained in a portion of the source area, consistent with soil and groundwater data. Overall results suggest biological processes have the potential to persist to treat chlorinated ethenes for years after active bioremediation ends. Additional information: ESTCP Cost & Performance Report; Conceptual site model paper

Low Cost Bioremediation Using Dextrose and Recirculation to Treat PCE-Contaminated Groundwater at Drycleaners
Hanson, D. Oregon Department of Environmental Quality SCRD Fall Meeting, Austin, Texas, 2006

This presentation discusses enhanced anaerobic bioremediation using dextrose at two dry cleaning sites in Oregon. The NuWay II Cleaners pilot project involved delivery of dextrose into a recirculation system continuously (about 480 mg/L dextrose solution). Reductive dechlorination was observed. After five months, PCE and TCE concentrations declined from over 100 to less than 10 µg/L; DCE and VC concentrations increased from less than 10 to greater than 10 µg/L; and ethene/ethane concentrations increased from less than 1 µg/L to below10 µg/L. The pilot system has continued to treat chlorinated solvents 11 months after recirculation ceased. The Plaza Cleaners Removal full-scale project involved excavation of source soil to the water table. About 4,800 lbs of dextrose were injected into a groundwater recirculation system in weekly batches (with nutrients). After 58 days of treatment PCE concentrations fell from 2,700 ppb at baseline to 170 ppb, with no buildup of TCE. A rapid conversion to DCE was observed. At both sites, greater success was observed with recirculation (extraction, amendment, and then re-injection) over gravity feed/slug injections.

Methodology and Lessons Learned Conducting In-Situ Bioremediation Using an Emulsified Vegetable Oil
Rackow, J. and T. Titus | Environmental Professionals of Arizona 16th Annual Gatekeeper Regulatory Roundup, 4-5 March, Tempe, AZ, 32 slides, 2020

Presentation describes the design, implementation, and performance monitoring of in situ injections of emulsified vegetable oil, Dehalococcoides, and vitamin B12 at former dry cleaners to bioremediate groundwater impacted with PCE.

Natural Attenuation and Biostimulation for In Situ Treatment of 1,2-Dibromoethane (EDB)
Koster van Groos, P., P. Hatzinger, G. Lavorgna, P. Philip, and T. Kuder. ESTCP Project ER-201331, 782 pp, 2022

The goals of this project were to improve understanding of EDB attenuation, particularly novel compound-specific isotope analysis tools, and determine whether biostimulation or bioaugmentation could effectively enhance in situ treatment of EDB. Improved methods to measure carbon isotope composition with low EDB concentrations were developed and applied. Differences in the isotopic composition of EDB among field samples provided valuable insights into EDB degradation processes. A lactate-based anaerobic in situ bioremediation approach was also applied in an impacted source area for chlorinated VOCs. The ISB effort aimed to demonstrate that higher EDB concentration source areas can be treated when attenuation processes are insufficient to protect receptors.

Performance Assessment of Past Bioremediation Approaches for Chlorinated Solvent Source Zones
Hatzinger, P., M. Tucker, J. Myers, M. Annable, A. Haluska, and F. Loffleler. ESTCP Project ER-201427, 636 pp, 2020

Two approaches were used to evaluate the success or failure of different bioremediation applications and to evaluate factors that may have contributed to those outcomes. Fifteen sites with chlorinated ethenes as the primary contaminant were selected that were treated using common bioremediation techniques and had data that allowed statistical evaluation of remedial performance over time. Sites with extensive pre-and post-treatment data were prioritized, and overburden aquifers were selected over bedrock aquifers. Statistical analyses of the large database were performed to identify factors that may promote or prevent successful application of bioremediation strategies. Assessment tools were applied, and additional well sampling was conducted at 5 of the 15 sites to quantify contaminant mass flux, the presence of key dehalogenating organisms and genes, and determine whether biodegradation was still occurring. Pre-treatment data and post-treatment data were compared with information on site conditions and treatment methods. The data were used to draw conclusions about the long-term effectiveness of VOC bioremediation.

Post-Remediation Evaluation of EVO Treatment: How Can We Improve Performance?
Borden, R.C.
ESTCP Project ER-201581, 151 pp, 2017

Field, lab, and design evaluations of emulsified vegetable oil (EVO) use for enhanced reductive dechlorination (ERD) of TCE contamination at two sites at the former Naval Training Center Orlando are presented. Although the remediation systems at both sites initially achieved substantial reductions in TCE concentrations, concentrations of cDCE and VC increased in some wells due to TCE degradation and remain elevated. Results from the project evaluations were used to identify the reasons for the ERD systems' failure to meet cleanup goals and to develop new approaches and procedures to improve performance. Additional information: Excel Spreadsheet Design Tool

Promoting Reductive Dechlorination of Chlorinated Ethenes in Groundwater Via Biostimulation
LaPat-Polasko, L. | Global Enviro Summit, 1-3 September, virtual, abstract only, 2020

An in situ bioremediation (ISB) system was used to biostimulate reductive dechlorination of chlorinated ethenes in groundwater in combination with bioaugmentation in source areas. Two distinct plumes contain >10 mg/L of various chlorinated volatile organic compounds cVOCs; the western plume also contains elevated levels of 1,4-dioxane. A recirculation well was installed in each plume to promote biostimulation with an emulsified oil substrate and bioaugmentation with Dehalococcoides microbial consortium and Pseudonocardia dioxanivorans. Within two months after the injection, groundwater monitoring showed a significant decline in ORP levels to less than -150 millivolts, and the Dehalococcoides population and key enzymes significantly increased in downgradient wells. Groundwater geochemistry indicated that competing electron acceptors were reduced, and conditions were suitable for reductive dechlorination. Dioxane levels are being evaluated post the bioaugmentation event.

Remedial Action Completion Report (CDRL A001B) and Preliminary Closeout Report, Former Air Force Plant PJKS, Waterton Canyon, Colorado
Air Force Center for Engineering and the Environment, 44 pp, 2013

A pilot study conducted at PJKS in 2004-2005 to evaluate the effectiveness of in situ anaerobic reductive dechlorination (ARD) of TCE and NDMA in bedrock source areas showed a decline in TCE contamination, which in 2006 led to the expansion of an interim corrective measure to stimulate ARD in the D-1 area groundwater plume. Horizontal and vertical injection wells delivered sodium lactate, emulsified edible oil (EEO), nutrients, and Dehalococcoides (dhc) to the Fountain Formation aquifer. In 2008, two full-scale biobarriers were constructed via injection of EEO, sodium lactate, and dhc into direct-push boreholes to target the alluvial transition groundwater areas, provide a barrier to plume migration, and further deplete TCE contamination in the downgradient plume. A technical impracticability waiver is recorded in the ROD for NDMA in the crystalline bedrock due to geological and technological limitations, although the VOCs in the bedrock are expected to meet MCLs. Additional information: PJKS EE/CA (2005); Focused Feasibility Study (2010); Case Study Slides (2012)

Remedial Action Status Report: McNatt's Cleaners, 5297 Ehrlich Road, Tampa, Hillsborough County, Florida
Florida Department of Environmental Protection, 278 pp, 2018

The facility is an active drycleaner that currently uses petroleum-based drycleaning solvent. The remediation system is designed to recover PCE and daughter products identified in the vadose zone. Although multi-phase extraction was initially recommended as a remedial technology, a phased remedial approach was selected that began in 2004 with the design and implementation of a soil vapor extraction (SVE) system to remediate shallow soils and was followed in 2009 with injections of biostimulation materials (SRS®). Installation of an additional SVE well and completion of additional biostimulation and bioaugmentation injections took place in 2017. Contaminant mass removal through the most recent reporting period is estimated at ~444.9 lbs and appears to have leveled off. Additional information: McNatt Project Website

Solar-Powered Remediation and pH Control: ESTCP Cost and Performance Report
ESTCP Project ER-201033, 73 pp, 2017

The primary project goal was to demonstrate a solar-powered technology—Proton Reduction Technology (PRT)—to generate hydrogen in situ and reduce aquifer acidity to promote reductive dechlorination. During operation, PRT uses a low voltage potential applied across electrodes installed within an aquifer to impress a direct current in the subsurface. PRT was tested on a plume of dissolved-phase TCE and cis-DCE in a low-pH aquifer at Joint Base McGuire-Dix-Lakehurst, New Jersey. The demonstration used electrodes inserted into PVC wells within the contaminated low-pH aquifer for 507 days of operation coupled with aquifer bioaugmentation to ensure the presence of dechlorinating bacteria to support biodegradation. Solar panels and deep-cycle 12-volt batteries provided electricity to operate the system. PRT resulted in partial reductive dechlorination of CVOCs in the low-pH aquifer, but TCE dechlorination was incomplete under the demonstration conditions, which was attributed to the borderline pH and reducing conditions achieved.

Sulfidated Nano Zerovalent Iron (S-NZVI) for In Situ Treatment of Chlorinated Solvents: A Field Study (Abstract)
Garcia, A.N., H.K.Boparai, A.I.A. Chowdhury, C.V.de Boer, C.M.D. Kocur, E. Passeport, B.S. Lollar, L.M. Austrins, J. Herrera, and D.M. O’Carroll. Water Research 174:115594(2020)

S-nZVI stabilized with carboxymethyl cellulose (CMC) was synthesized and injected into the subsurface at a site contaminated with cVOCs. Downgradient and upgradient transport of CMC-S-nZVI resulted in a significant decrease in concentrations of aqueous-phase cVOCs. Compound specific isotope analysis, changes in concentrations of intermediates, and increase in ethene concentrations confirmed dechlorination of cVOCs. Dissolution from the DNAPL pool into the aqueous phase at the deepest levels (4.0-4.5 m bgs) was identifiable from the increased cVOCs concentrations during long-term monitoring. However, at the uppermost levels (~1.5 m above the source zone), a contrasting trend was observed, indicating successful dechlorination. No accumulation of lower chlorinated VOCs, particularly vinyl chloride, was observed during the CMC-S-nZVI field treatment. Post-treatment soil cores also revealed significant decreases in cVOC concentrations throughout the targeted treatment zones. Results suggest that sulfidation is a suitable amendment for developing more efficient nZVI-based in situ remediation technologies.

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