Remediation in situ

Iben lET et al. (1996) Thermal blanket for in-situ remediation of surficial contamination a pilot test. Environ Sci Technol 30 3144-3154. 

J. J. Kilbane, II, P. Chowdiah, K. J. Kayser, B. Misra, K. A. Jackowski, V. J. Srivastava, G. N. Sethu, A. D. Nikolov, and D. T. Wasan. In-situ remediation of contaminated soils using foams as carriers for chemicals, nutrients, and other amendments. In Proceedings Volume. 9th Inst Gas Technol Gas, Oil, Environ Biotechnol Int S)mip (Colorado Springs, CO, 12/9-12/11), 1996. 

Another important factor is the food/nutrient ratio. Many of the necessary nutrients may already be present in the aquifer, such as K, Mg, Ca, S, Na, Mn, Fe, and trace elements however, N and P may be deficient and need to be added. The optimum ratio of BOD N P is 100 5 1. It is not a good practice to inject a large quantity of nutrients in the aquifer at one go. They should be fed at the required usage rate throughout the cleanup process. Both the organic contaminants and the nutrients should be completely exhausted by the end of the in situ remediation of an aquifer. 

Integrated vapor extraction and steam vacuum stripping can simultaneously treat groundwater and soil contaminated with VOCs. The system developed by AWD Technologies consists of two basic processes a vacuum stripping tower that uses low-pressure steam to treat contaminated ground-water and a soil gas vapor extraction/reinjection process to treat contaminated soil. The two processes form a closed-loop system that provides simultaneous in situ remediation of contaminated groundwater and soil with no air emission. 

This section focuses on engineered in situ remediation technologies that use microorganisms to biodegrade pollutant chemicals. In situ bioremediation technologies are configured to either directly... 

U.S. EPA, Field Applications of In Situ Remediation Technologies Permeable Reactive Barriers, Office of Solid Waste and Emergency Response, United States Environmental Protection Agency, Washington, DC, January 2002. 

Mench M.J., Didier V.L., Loftier M., Gomez A., Masson P. A mimicked in-situ remediation study of metal-contaminated soils with emphasis on cadmium and lead. J Environ Qual 1994 23 58-63. 

Fustos, V. and Lieberman, P, 1996, Integrated In-Situ Remediation Environmental Protection, January, pp. 44-49. 

Cleanup strategies for hydrocarbon-affected soil will most likely be the last issue to be mandated from a regulatory perspective and certainly the most difficult technically to address. This difficulty reflects the large, deep-seated volumes of residual hydrocarbon present, and the current lack of efficient, cost-effective methodologies for in situ remediation of residual hydrocarbons in low-permeability, fine-grained soils. 

Keywords Military sites, explosives, TNT, in situ remediation, water treatment, eonstrueted wetlands... 

The contamination of groundwater by leakage of hydrocarbons or other pollutants from underground storage tanks, distribution systems and various industrial operations is a major environmental problem. Conventional treatment techniques suffer from serious shortcomings which limit their applicability and efficiency. These include high cost and maintenance requirements, the need to transfer the contamination from one medium to another, and the extended duration of the operation, since decades may be necessary to prevent continued growth of contaminant plumes (Yerushalmi et al., 1999). An alternative to these treatments lies in in situ remediation. 

Kun Z, Hui C, Guanghe L, et al. 1998. In situ remediation of petroleum compounds in groundwater aquifer with chlorine dioxide. Water Res 32(5) 1471-1480. 

The ARS Technologies, Inc., Ferox process is an in situ remediation technology for the treatment of chlorinated hydrocarbons, leachable heavy metals, and other contaminants. The process involves the subsurface injection and dispersion of reactive zero-valence iron powder into the saturated or unsaturated zones of a contaminated area. ARS Technologies claims that Ferox is applicable for treating the following chemicals trichloroethene (TCE), 1,1,1-trichloroethane (TCA), carbon tetrachloride, 1,1,2,2-tetrachloroethane, lindane, aromatic azo compounds, 1,2,3-trichloropropane, tetrachloroethene (PCE), nitro aromatic compounds, 1,2-dichloroethene (DCE), vinyl chloride, 4-chlorophenol, hexachloroethane, tribromomethane, ethylene dibromide (EDB), polychlorinated biphenyls (PCBs), Freon-113, unexploded ordinances (UXO), and soluble metals (copper, nickel, lead, cadmium, arsenic, and chromium). 

Because biosurfactants are natural, biodegradable products, they are an attractive alternative to synthetic surfactants, particularly for in situ remediation. Biosurfactants are also potentially useful agents for oil spill remediation, where they can be used to disperse pollutants that remain in the water or have washed up on land. 

Carus Chemical Company offers CAIROX potassium permanganate for the in situ remediation of volatile organic compounds (VOCs) in groundwater and soil. The method of oxidant delivery during treatment is tailored to site conditions. For unsaturated, low-permeability soils, CAIROX is introduced using deep soil mixing. In areas where the site has high permeability or the treatment media is saturated with water, well injection or recirculation can be used. 

The two-phase vacuum extraction (TPVE) technology allows for the in situ remediation of soils and groundwater contaminated with volatile organic compounds (VOCs). Two-phase vacuum extraction is similar to conventional vapor extraction in the equipment required, with the exception that it is designed to actively remove contaminated groundwater from the extraction well along with the vapor-phase contamination. 

The Ecolotree buffer uses phytoremediation, or plant processes, for environmental remediation purposes. Ecolotree buffers can be used to reduce the migration of subsurface water and surface runoff, while also acting as an in situ remediation technique for both organic and heavy-metal contaminants, including benzene, toluene, ethylbenzene, and xylene (BTEX) chlorinated solvents ammunition wastes and excess nutrients in soil or water. The technology is commercially available and has been used at landfill and waste treatment sites. 

Allows for in situ remediation in areas where it was previously considered ineffective (can be used under structures, in aquifers, and on bodies of water). 

The process of anaerobic biotransformation with steam injection is a technology for the in situ remediation of soils and groundwater contaminated with dense non-aqueous-phase liquids (DNAPLs). Using this approach for remediation, steam is injected into the soil to volatilize and remove DNAPLs, with the simultaneous introduction of nutrients. The resulting subsurface conditions are suitable for biotransformation of the dissolved phase, into compounds that are more easily removed by vapor and groundwater extraction. 

Approximately 6000 yd of soil at a service station in southeastern Maine were contaminated with kerosene and BTEX. According to the vendor, the cost of the full-scale, in situ remediation was approximately 40.00/yd (D10281Y, p. 13-16). 

Makes in situ remediation possible at sites where excavation was previously the only option. 

Reductive biotransformation of a contaminant can occur when the contaminant serves as the terminal electron acceptor. Many contaminants that are recalcitrant to bio-oxidation will undergo reductive biotransformations. These biotransformations can lead to detoxification, mineralization, or changes in the mobility of the targeted contaminant. Hexavalent chromium and tetra-chloroethene (PCE) have been investigated as candidates for reductive biotransformation. This technology may be most applicable for in situ remediation for the following scenarios PCE contamination, low-yield aquifers, areas contaminated by both alkylbenzenes and chlorinated ethenes, and deep aquifer contamination. 

Acoustically enhanced remediation (AER) is an in situ remediation technology that uses acoustic excitation fields (AEFs) to enhance rates of fluid and contaminant extraction from a wide variety of soil types. Bench-scale proof-of-concept tests have been completed and were followed by larger scale laboratory experiments. According to the vendor, a field-scale proof-of-principle step has been planned. The vendor indicates that this technology is currently commercially available however, it is uncertain whether these field-scale tests have occurred. 

PIRAMID Consortium (2003) Engineering Guidelines for the Passive Remediation of Acidic and/ or Metalliferous Mine Drainage and Similar Wastewaters. European Commission 5th Framework RTD Project no. EVK1-CT-1999-000021 Passive in-situ remediation of acidic mine/indus-trial drainage (PIRAMID). (Freely downloadable from www.piramid.org). University of Newcastle Upon Tyne, Newcastle Upon Tyne, UK, 164 pp. 

Starr, R. C. Cherry, J. A. 1994. In situ remediation of contaminated groundwater the funnel-and-gate system. Ground Water, 32, 465-476. 

Younger, P. L. 2003. Passive in situ remediation of acidic mine waste leachates progress and prospects. In Moore, H. M., Fox, H. R. Elliott, S. (eds) Land Reclamation - Extending the Boundaries. Balkema, Lisse (NL), 253-264. 

Mechanisms of attenuation of metal availability in in situ remediation treatments. Environmental Science Technology, 36, 2991-2996. 

Ho, S. V., Sheridan, P. W., Athmer, C. J., Brodsky, P. H., Heitkamp, M. A., and Brackin, J. M., Integrated In Situ Remediation Technology - The Lasagna Process, paper presented at the American Chemical Society meeting, Atlanta, GA, September 1993 (Paper 279, Session 43). 

Although the above studies conducted with packed columns are important from a fundamental standpoint as they relate to the mechanisms of cell sorption to solid surfaces, in situ remediation of contaminants in subsoils requires microbial transport in well-structured soils. The presence of soil macropores that facilitate preferential water flow is well appreciated (Thomas Phillips, 1979). Sorption phenomena are less important when bacterial transport occurs through structured soils in which cells pass unimpeded through relatively large conduits (Smith et al., 1985). 

One of the major focuses of the in situ use of surfactants is to accelerate the removal or degradation of free-phase products (DNAPL or oil globules) as variations of technologies used in the oil industry for enhanced tertiary oil recovery as described by Hill et al. (1973)- Such in situ remediation efforts often fail, however, primarily because of differences in the goals and expectations of the applications. For example, the enhanced oil recovery industry is often satisfied with > 30% enhanced removal whereas the remediation industry often strives for >99% removal in order to meet remedial guidelines. Unfortunately, removal of about 50% of the free product (i.e., DNAPL) at a PAH-contaminated site appears to represent the full extent of practical field expectations. 

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