U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Dense Nonaqueous Phase Liquids (DNAPLs)

Treatment Technologies


Halogenated Alkenes

Conventional S/S is not commonly the technology of choice for treating soils or sediments contaminated with high concentrations of organic material. In situ and ex situ S/S is more often applied to soils contaminated by heavy metals and other inorganic compounds; however, stabilization of soils that contain low levels of organic constituents is feasible, even for volatile organics (Druss 2003). Air collection and treatment devices may be needed to capture organic compounds that volatilize during the S/S process.

Although conventional S/S is not a presumptive remediation approach at sites affected primarily by chlorinated solvents, new technologies are being developed that combine oxidative or reductive treatment with immobilization, as sequential steps in some methodologies and simultaneously in others. Most of the literature on these new approaches concerns laboratory studies rather than remediation in the field; however, several field applications have been documented of a hybrid technology that combines aspects of S/S with in situ reduction by zero-valent iron (ZVI).

Druss, D.L. 2003. Guidelines for design and installation of soil-cement stabilization. Grouting and Ground Treatment. ASCE, Geotechnical Special Publication No 120, ISBN: 0-7844-0663-4, p 527-539.

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General Resources | Case Studies: Chlorinated Solvents | Case Studies: PCE

General Resources

Adobe PDF LogoLiterature Review of Stabilization/Solidification of Volatile Organic Compounds and the Implications for Hanford Grouts
R.D. Spence and S.C. Osborne.
ORNL/TM-11824, 55 pp, 1993

Briefly summarizes a survey of the S/S literature and concludes that limestone-containing grout will not permanently immobilize VOCs due to a lack of available additives that could guarantee permanent immobilization.

Adobe PDF LogoProposal of a Sequential Treatment Methodology for the Safe Reuse of Oil Sludge-Contaminated Soil
L. Mater, R.M. Sperb, L.A.S. Madureira, A.P. Rosin, A.X.R. Correa, and C.M. Radetski.
Journal of Hazardous Materials, Vol 136 No 3, p 967-971, 2006

Sequential steps used to treat and immobilize oil constituents of an oil sludge-contaminated soil sample involved initial oxidation treatment by a Fenton-type reaction for a period of 80 h, followed by S/S of the oxidized sample for 2 h with clay and lime, and then solidification of this mixture with sand and Portland cement. Leachability and solubility test results following the Fenton process showed that it was partially efficient in degrading the oil contaminants in the soil, with residual concentrations of PAH and BTEX compounds observed. Leachability tests following the S/S treatments showed that combining the oxidized sample with clay and lime followed by Portland cement efficiently immobilized the recalcitrant and hazardous constituents of the contaminated soil. The two-step S/S processes were designed to minimize leachability and render the final product economically profitable. The treated waste is safe enough to be used in environmental applications, like roadbeds blocks. This process is applicable to a wide variety of sites containing different classes of contaminants, such as PCBs, PAHs, organic pesticides and herbicides, halogenated and non-halogenated SVOCs, and metals.

Case Studies: Chlorinated Solvents

Adobe PDF LogoIn-Situ Remediation of Chlorinated Solvents using Zero Valent Iron and Clay Mixtures: A Case History
C. Shackelford, T. Sale, and M. Liberati.
Geo-Frontiers 2005, 24-26 January 2005, Austin, Texas. American Society of Civil Engineers (ASCE), Reston, VA. Geotechnical Special Publication 142, ISBN: 0-7844-0769-X, 2005

A field application of ZVI/clay to treat 8,000 cubic yards of soil contaminated by up to 30 mg/kg carbon tetrachloride was completed in Martinsville, VA, in 2002. Chloroform, dichloromethane, TCE, and PCE also were discovered at the site in lesser concentrations. To inject the ZVI/clay, granular iron was first placed in shallow pits and then a drill injected a clay/water grout to mix and distribute the iron to the plan depths via 76 columns using an 8-ft-diameter mixing tool. Subsequent sampling results indicated that 99% degradation of chlorinated compounds (including byproducts) was achieved. The bulk of degradation was completed within the first year.

Adobe PDF LogoResurgence of In Situ Soil Mixing for Treating NAPL Source Areas
T. Palaia.
2007 Air Force ESOH Training Symposium, 24 pp, 2007

A backhoe and specialty mixing augers can be used to move and mix soil in situ with a variety of treatment chemicals: chemical oxidants (permanganate and persulfate), chemical reductants (ZVI), enhanced bioremediation reagents, and stabilizing/solidifying agents (cement, bentonite). This technology is best suited for highly concentrated LNAPL or DNAPL source zones. In situ mixing and addition of clay and ZVI slurry occur concurrently. The ZVI treats chlorinated contaminants, and clay provides contaminant migration control and acts as a lubricant during mixing, thus creating a relatively impermeable zone of soil to reduce contaminant mass flux. DuPont developed the technology, patented it in 1998, and donated it to Colorado State University in 2003. Efficient field processes are still being developed for this relatively young technology. Case 1: After 17 days of active mixing to address 14 tons of PCE at Site 88, Camp Lejeune, in February 2005, this technique achieved > 90% PCE reduction by Feb 2006. The work involved delivery of 200 tons ZVI (2% by wt) and 100 tons of bentonite (1% by wt). GAC offgas control was necessary. Case 2: Another application took place at SWMU 16 in a former burn and leach area, Arnold AFB, TN, Dec 2005-Jan 2006. With dissolved TCE up to 27 mg/L, residual DNAPL was suspected. The vadose zone source was removed prior to treatment. Two years after emplacement of 36 tons of iron (1.5%) and 48 tons of bentonite (2%), ~70% reduction in groundwater concentrations was observed.

Case Studies: PCE

Adobe PDF LogoDNAPL 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.

Abstracts of Journal Articles

Action and Distribution of Organic Solvent Contaminations in Hydrating Cement: Time-Resolved Insights into Solidification of Organic Waste
N. Nestle, C. Zimmermann, M. Dakkouri, and R. Niessner.
Environmental Science & Technology, Vol 35 No 24, p 4953-4956, 2001

When dealing with materials contaminated with organic solvents, it is important to have an idea about the interaction between the solvents and the hydrating cement. In this study, all solvents were found to lead to some delay in the hydration kinetics. The delay was minor for nonpolar compounds and qualitatively led to the same hydrating kinetics as in an uncontaminated cement mixture, whereas polar solvents led to pronounced delays in the hydration kinetics.

Reactivity of Fe(II)/Cement Systems in Dechlorinating Chlorinated Ethylenes
I. Hwang, H.-J. Park, W.-H. Kang, and J.-Y. Park.
Journal of Hazardous Materials, Vol 118 Nos 1-3, p 103-111, 2005

Fe(II) combined with Portland cement can immobilize and reductively degrade chlorinated organics simultaneously. Reactivities of chlorinated ethenes (PCE, TCE, 1,1-DCE, VC) in Fe(II)/cement systems were characterized in batch slurry reactors, demonstrating the order of reactivity as TCE > 1,1-DCE > PCE > VC. Reduction of TCE and PCE mainly yielded acetylene, suggesting that the transformation of the two compounds occurred mainly via reductive beta-elimination pathways. 1,1-DCE and VC transformation gave rise primarily to ethylene, indicating that major degradation pathways likely were reductive alpha-elimination for the former and hydrogenolysis for the latter. Amendment of Fe(II)/cement systems with Fe(III) increased the reactivity, but the extent of the increase might be dependent on the source of the cement and/or the compounds tested.

Stabilization/Solidification of Wastes Containing Volatile Organic Compounds in Commercial Cementitious Waste Forms
R.D. Spence, T.M. Gilliam, I.L. Morgan, and S.C. Osborne.
Stabilization and Solidification of Hazardous, Radioactive, and Mixed Wastes, Volume 2.
ASTM, West Conshohocken, PA. STP1123-EB, 12 pp, 1992

S/S is one of the most widely used techniques for waste treatment, but application with VOCs is controversial due to the belief that the necessary mechanical mixing and exothermic cementitious reactions would vaporize the VOCs. This study examined whether S/S is a viable alternative for a sludge heavily contaminated (about 1%) with relatively immobile metals, but lightly contaminated (<0.04%) with VOCs (TCE, PCE, MEK, 1,2-DCE, chloroform, chlorobenzene). Mass balance indicated that > 50% of the VOCs were retained in cementitious samples cured for 28 days. Performance tests indicated the commercial products could attain leachability indices from 7 to > 9 for the eight VOCs studied; distribution coefficients of > 10 could be attained for all eight and > 100 for some compounds.