Liquid transport remediation

A continuous circulation of groundwater is generated in the area surrounding the remediation well, as aquifer waters replace the annulus water. The circulation thus delivers new contaminants to the stripping zone. Volatile contaminants dissolved in the groundwater are transferred from the liquid to the gas phase and are extracted from the groundwater surface via a double-cased screen. Soil air from the unsaturated zone is also extracted and transported to the off-gas treatment system. 

Waste management The proper collection, handling, treatment, transportation, and disposal of unusable liquids, solids, or gases. Proper waste management minimizes the negative impacts of wastes on the environment. While waste management seeks to prevent negative environmental impacts, the purpose of remediation is to restore sites that have already been contaminated into an environmental acceptable condition. 

Fountain, J.C. (1992) Field tests of surfactant flooding -mobility control of dense nonaqueous-phase liquids. In D.A. Sabatini and R.C. Knox (eds), Transport and Remediation of Subsurface Contaminants, ACS Symposium Series 491. American Chemical Society, Washington, DC, pp. 182-191. 

The most cost-effective solution to both problems would be the on-site destruction of any available liquid waste containing persistent residues such as PCBs, PCDD and PCDF. This option would eliminate the transportation cost as well as risk in addition to removing any future risk, liabilty and cost. Remedial measures must not simply divert residue movement from the water into the air, such as in landfill remediation where temporary storage lagoons for leachate can allow rapid volatilization of PCBs, PCDD and PCDF. 

Conversely, dissolved-phase heavy metals in pore fluid are easily removed by the transport mechanisms mentioned above electromigration and/or electroosmosis. Even though heavy metals in the liquid phase can easily move toward the electrode compartment, there is always the possibility that they will be readsorbed onto the solid particles. As shown by the double arrow in the above illustration, the reaction is reversible. For these reasons, the adsorption capacity (affinity), which is the physicochemical property of each heavy metal, has a high impact on the efficiency of electrokinetic remediation. 

This ability of surfactants to solubilize NAPL components and coalesce into thermodynamically stable microemulsions is of critical importance in their selection for use in NAPL remediation. This is because microemulsions are highly fluid and can easily flow through permeable media and transport contaminants with them under the very low hydraulic gradients typical of shallow, unconfined aquifers. By contrast, macroemulsions, which are physical mixtures or dispersions of one liquid phase interspersed in another liquid phase are unstable, often very viscous, and do not flow easily or in a way that is predictable or easy to control, and thus are highly undesirable. 

Electrokinetic remediation involves the installation of electrodes into multiple wells within a contaminated zone, followed by the application of a low electric potential. Ideally, the contaminants migrate toward the electrodes due to different transport mechanisms, and, upon reaching the wells, contaminant-laden liquids are extracted and treated. Although implementation is simple, the geochemical processes that occur within soils during electrokinetic remediation are complex and dependent on system variables such as soil type, pollutant type, treatment time, electrolyte solution, and applied voltage. 

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