Engineering Technical Support Center (ETSC)
- Biological Technologies
- Physical/Chemical Technologies
Physical/chemical treatments typically make use of known chemical properties or reactions coupled with material transformation of the hazardous substance. Almost all physical or chemical treatments are considered active treatment systems.
- Thermal Technologies
Table of Contents
- Soil Vapor Extraction (SVE)
- Slurry WallSolidification/Stabilization
- Soil Flushing
- Chemical Oxidation
- Electrokinetic Separation
Soil vapor extraction uses a vacuum to bring a controlled flow of contaminated air above the water table where engineers employ other methods to treat volatile organic compounds (VOCs) and some semivolatile organic compounds (SVOCs). Ideal conditions for SVE treatment are well-drained, highly permeable soils (e.g. sand and gravel) with a low organic carbon content. Soils with mixed contaminants are not normally treated by soil vapor extraction; SVE is commonly utilized to treat organic contaminants.
A slurry is a watery mixture of insoluble material (like mud). A slurry wall is a trench filled with a non-permeable or low-permeability material (i.e. bentonite) that obstructs or filters groundwater. For instance, a lime-slurry mixture can neutralize acidic pH levels.
Solidification and stabilization are similar techniques for treating radioactive, organic and mixed wastes by combining physical and chemical processes.
Solidification encapsulates and immobilizes hazardous wastes, decreasing toxicity, mobility, and exposure to humans and the environment.
Stabilization reduces pollution risk by converting compounds into less mobile forms. Lime may be used to stabilize mine-related wastes by converting lead into less toxic forms (precipitation).
Soil flushing uses a prepared solution to bring a controlled flow of contaminated fluid to the surface where engineers treat or properly dispose of the waste. To remove metals, acidic solutions may be injected into the soil. Firms in the energy sector regularly use flushing for enhanced petroleum recovery from underground deposits.
Chemical oxidation converts hazardous contaminants into less harmful varieties like a chemical Robin Hood. The reaction steals electrons from one reactant (oxidation) and gives them to another (reduction), thus making the bad guys less toxic or mobile, more stable or even inert. The reduction and oxidation process is known as a redox reaction.
Common chemical oxidants include permanganate, Fenton's catalyzed hydrogen peroxide, sodium persulfate and ozone. In situ chemical oxidation is frequently investigated before using it to decontaminate groundwater. More about chemical oxidation.
Electrokinetic separation of radionuclides, heavy metals, and organic contaminants from unsaturated areas stimulates electrotransport by sending a low-density, direct current across electric conductors inserted in the soil, sludge, or sediment. Although the results from electrokinetic separation have been mixed, the Lasagna™ technology appeared effective on soils in Paducah, KY EPA/505/F-99/004.
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