Groundwater and soil contamination

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. 

The Arctic Foundations, Inc. (AFl), frozen soil barrier technology is constructed by artificially freezing the soil pore water. As the pore water freezes, the soil permeability decreases, thereby forming an impermeable barrier that surrounds and contains the contaminants. When properly installed, the frozen soil barrier prevents the migration of contaminants within groundwater and soil. Contaminants are contained in situ, with the frozen native soils serving as the containment medium. The contaminants are isolated by the wall until appropriate remediation techniques can be applied. 

Although DUS is extremely effective in the absence of liquids (i.e., in soils above the water table), it usually is not cost-effective compared to alternative technologies in these instances. The DUS technology is labor-intensive, requiring significant held expertise to implement. It is best applied to sites with contaminants above and below the water table (i.e., groundwater and soil contamination) and complex sites that are very difficult to clean up. 

Perc spills have led to groundwater and soil contamination. Of 1190 National Priorities List sites in the United States, nearly two-thirds (771) have perchloroethylene contamination (ATSDR, 1995). Even filters and lint from perc machines must be disposed of as hazardous waste. In addition, ever-increasing taxes and regulations on the use of perchlor-othethylene reflect the growing public concern over continued use of this solvent. 

Underground Storage Tanks 40 CFR 280 Protection against groundwater and soil contamination ... 

In situ groundwater treatment is an alternative to the conventional pump-and-treat methods. In situ treatment uses biological or chemical agents or physical manipulations that degrade, remove, or immobilize contaminants. In situ treatment technologies can usually treat both contaminated groundwater and soil. In many instances a combination of in situ and aboveground treatment will achieve the most cost-effective treatment at an uncontrolled waste site. 

Hot water injection via injection wells heats the soil and groundwater and enhances contaminant release. Hot water injection also displaces fluids (including LNAPL and DNAPL free product) and decreases contaminant viscosity in the subsurface to accelerate remediation through enhanced recovery. 

Exposure Levels in Environmental Media. There is limited information available on the levels of fuel oils found in soil or water where fuel oils are used or stored. Most monitoring studies have been conducted in the aquatic environment following an accidental spill (EPA 1981 Teal et al. 1978). More data on levels of fuel oils or their components in the air, water, and soil around facilities where fuel oils are produced, stored, and used would be useful. Data on levels in contaminated surface water, groundwater, and soil are needed to assess the potential risk from these likely sources of exposure. 

According to the vendor, the following factors can have a significant impact on the cost of remediation. The most important factors are the depth of the groundwater and the contaminant concentration. In addition, soil characteristics, site preparation, and labor rates are important (D10033K, p. 36). 

Bioslurping is a commercially available, in situ technology that combines vacuum-enhanced free-product recovery with bioventing of subsurface soils to simultaneously remediate petroleum-hydrocarbon-contaminated groundwater and soils. Vacuum-enhanced recovery utilizes negative pressure to create a partial vacuum that extracts free product and water from the subsurface. Bioventing is forced aeration to accelerate in situ bioremediation of hydrocarbons and non-aqueous-phase liquids (NAPLs). 

Dowex Optipore is a polymeric adsorbent used to treat chlorinated volatile organic compound (CVOC) contaminated off-gas streams from remediation processes such as air stripping of groundwater and soil vapor extraction. According to the vendor Dowex Optipore adsorbent has the following advantages over activated carbon ... 

TCE-degrading bacteria is a patented technology for the treatment of soil, groundwater and wastewater contaminated with trichloroethylene (TCE). The particular strain of bacteria used in this technology does not require the addition of a toxic co-substrate to activate the bacterial destruction of TCE. The technology can be used to remediate virtually any media type contaminated with one or more volatile organic compounds (VOCs), including TCE, and can be used for in situ or ex situ bioremediation. 

At a former manufactured gas plant in Long Beach, California, IT Corporation ozonation and in situ air sparging were combined to treat contaminants such as benzene, naphthalene, and benzo(a)pyrene in groundwater and soil. Construction and operation costs from 1998 to 2000 were estimated to be 1,000,000 (D19400N, p. 6). 

The technology has been applied primarily at sites contaminated with petroleum hydrocarbons. The Vacu-Polnt technology can remove hydrocarbons and chlorinated solvents from contaminated groundwater and soil. The developer asserts that the technology can treat VOCs, and all phases of non-aqueous-phase liquids (NAPLS) and dense non-aqueous-phase liquids (DNAPLS). 

Two-phase extraction uses a vacuum source to remove contaminated groundwater and soil vapor from the subsurface. The vacuum is applied to an extraction tube within a water well to increase groundwater removal rates and to volatilize and extract VOCs. According to the vendor, vacuum lift of water is not a limiting factor in the application of the technology. Since a mixed vapor/liquid column is extracted from the weU, the two-phase extraction technology allows a single piece of equipment (a vacuum source) to remove contaminants in both the liquid and vapor phases. 

Groundwater and Soil. Pumping out the liquid phase is an obvious first step if die contaminant is likely to be mobile, but in situ bioremediation is a promising option. Thus, the U.S. Department of Energy is investigating the use of anaerobic in situ degradation of carbon tetrachloride with nitrate as electron acceptor, and acetate as electron donor. 

Ray, A.K. (1999). Chemistry of arsenic and arsenic minerals relevant to contamination of groundwater and soil from subterranean source. Everyman s Science, 35(1). 

Chemical residues and waste generated in the manufacturing of methamphetamine pose a serious danger to the environment. This waste is often poured down the drain, into storm sewers, or into crudely dug pits in the ground. These chemicals can leach into the soil and groundwater and cause contamination for many years. 

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