Organic contaminated soils, treatment using

While electrokinetic treatment of soils looks promising, most of the work performed was bench-scale, under carefully controlled laboratory conditions. For electrokinetic remediation to be a viable alternative for in-situ cleanup of waste sites, a number of factors will have to be investigated. All of the work to date has dealt with uniformly contaminated soil samples. Studies performed on partially saturated soils will yield different results. Further studies on the removal of mixed metal contaminated soils, using different soil types, are needed. The presence of organic compounds in the soil will also influence successful treatment of real contaminated soils. The use of reagents which could increase desorption and/or solubilization (without further contaminating the soil matrix) may also be areas of future investigation. Finally, field tests need to be performed to substantiate studies accomplished on the bench scale. 

Other configurations of treatment processes using thermal desorption as the primary separation technique can be applied to organically contaminated soils. Alternative physical/chemical processes can be used to treat the desorber off-gas and the contaminants. To achieve complete contaminant destruction, the off-gas can be treated by using conventional fume incineration or other thermal treatment technology. The choice of the type of desorber and off-gas treatment system depends on the concentration and properties of the chemical contaminants, soil characteristics, quantity of contaminated material, site characteristics, availability of off-site disposal, and regulatory and related requirements. 

Biological treatment processes can be used to treat organic contaminants in liquid, slurry, and soil matrices. However, it should be remembered that moisture is an essential need of the biomass both for... 

Equations 14.24 to 14.27 can be applied to most sites where soil cleanup regulations are known for metals or organic contaminants. Two examples follow, one for TCE treatment by phytotransformation and another for lead removal by phytoextraction, which demonstrate the use of the design equations. 

Complex mixtures of contaminants in the soil, such as a mixture of metals, nonvolatile organics, semivolatile organics, and so on, make it difficult to formulate a single suitable washing fluid that will remove all the different types of contaminants from the soil. Sequential washing steps, using different additives, may be needed. In fact, each type of contaminated soil requires a special treatment procedure, which is determined through laboratory or pre-industrial tests, so that system modifications and optimum operative conditions are specified. 

Thermal conduction (also referred to as electrical conductive heating or in situ thermal desorption) supplies heat to the soil through steel wells or with a blanket that covers the ground surface. As the polluted area is heated, the contaminants are destroyed or evaporated. Steel wells are used when the polluted soil is deep. The blanket is used where the polluted soil is shallow. Typically, a carrier gas or vacuum system transports the volatilized water and organics to a treatment system. 

Solvent extraction uses an organic solvent to extract toxic substances from contaminated liquid or solid.67 Examples can be found in the section dealing with the treatment of contaminated soil. 

Landtreat is a silicate-based inorganic polymer catalyst used for the ex situ treatment of contaminated soils. The vendor claims that it acts as a catalyst to degrade halogenated compounds and organic compounds containing nitrogen and sulfur. 

Laboratory studies indicate that aquathermolysis can be used to aid in the remediation of waste oils, chromium (Cr VI) and volatile organic compounds (VOCs) in contaminated soils and aquifers. Aquathermolysis is particularly useful in lowering the viscosity of oil and increasing its mobility to facilitate further treatment. Potential applications range from treating household and industrial refuse to destruction of chemical warfare agents. 

Electrokinetic treatment can be used to remediate soils, sludges, and sediments contaminated with heavy metals and organic hydrocarbons. Electrokinetic treatment works well on clay-type soils with low hydraulic permeability, which are difficult to treat using other in sitn technologies. Electrokinetic permeabilities for aqueous systems in clays have been demonstrated to be up to 1000 times greater than normal hydraulic permeabilities, and some heavy metals have exhibited removal efficiencies of up to 100%. 

Electrokinetics has been used to mobilize metals and dissolved contaminants to in situ treatment or recovery zones. Electrokinetic transport uses these mechanisms to move bacteria through the subsurface to the contaminated media. The technology can be used to treat organic contaminants that adsorb to aquifer soils including halogenated hydrocarbons and non-aqueous-phase liquids (NAPLs). 

Reclaim is a passive, in situ technology that uses a hydrophobic porous polymer to attract, adsorb, and concentrate petroleum hydrocarbons and volatile organic compounds (VOCs) from soils and/or groundwater. Reclaim is considered a passive treatment technology because it requires no mechanical equipment remediation consists of placing polymer-filled canisters in recovery wells and allowing the containers to attract and adsorb organic contaminants. Reclaim canisters are then recycled and contaminants recovered for analysis and/or disposal. This polymer extracts contaminants whether they are in liquid phase, vapor phase or dissolved phase in water. 

Klohn-Crippen Consultants, Ltd., has developed the ex situ ChemTech soil treatment process for the removal of heavy metals and organic contaminants from contaminated soil and sediment. The ChemTech process uses two mechanisms to remove contaminants physical scouring of the soil particle surface and chemical leaching of the contaminants from the soil particles. Processing takes place using a three-phase fluidized bed. The technology has been evaluated in pilot-scale... 

During the B.E.S.T. process, oUy sludges, soils, and sediments are separated into three phases. These phases include a water phase that can be treated by conventional treatment and discharged a dry, treated solid phase that can be used as backfill on site and an oil phase containing the organic contaminants. The oil phase constitutes a small volume (relative to the initial volume of contaminated material) that can be destroyed or recycled. 

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