Contaminants migration control contamination remediation

In extreme situations, incompatibility between injection fluids and reservoir components can be so great that deep-well disposal will not be the most cost-effective approach to waste disposal. In other situations, such remedial measures as pretreatment or controlling fluid concentrations or temperatures can permit injection even when incompatibilities exist. In addition to operational problems, waste-reservoir incompatibility can cause wastes to migrate out of the injection zone (casing/confining-layer failure) and even cause surface-water contamination (well blowout). 

Extraction wells are usually necessary to maintain hydraulic control of the plume and to ensure that the plume does not migrate into clean areas or accelerate migration toward sensitive receptors. Placement of extraction wells is especially important with systems that use nutrient injection wells or infiltration galleries. These sources of fluids can alter natural groundwater flow patterns, which may cause contaminant migration in an unintended direction or rate. If the natural groundwater system has a sufficient concentration of electron acceptors and nutrients, to achieve remediation at an acceptable rate, it may not be necessary to add any additional materials. 

Local flora and fauna analysis to permit determination as to whether the contaminants have entered the food chain and to assess the tendency of various species to concentrate or eliminate individual contaminants. In some cases, it is necessary to supplement the field investigations with controlled bench- or pilot-scale studies. These studies may be performed to simulate a mobilization or dispersion mechanism, or the complex chemical interactions between the waste form, surrounding matrix, or soil pathways, and/or the effectiveness of certain technologies in preventing migration or providing the required level of isolation. These pilot studies are often defined as feedback and obtained from the assessment of remedial alternatives. 

The remediation of chromium-contaminated sites requires knowledge of the processes that control migration and transformation of chromium. Chromium(VI) can be reduced to chromium(III) in the presence of ferrous iron, reduced sulfur compounds, or organic matter in soil. However, chromiu-m(III) also can be oxidized by manganese dioxide, a common mineral found in many soils (Bartlett 1991 Palmer and Wittbrodt 1991 Pandey etal. 2003). Usually, Part of any chromium(VI) added to a soil or sediment will be reduced very rapidly, especially under acid conditions. On the other hand, excess chromium(VI) may persist for years in soils or lagoons without reduction (Bolan et al. 2003). The addition of organic amendments such as manure enhanced the rate of reduction of chromium(VI) to chromium(III) in soils low in organic matter (Bolan et al. 2003). 

The implications of these electrolysis reactions are enormous in that they impact transport, transformation, and degradation processes that control the contaminant migration, removal, and degradation during electrochemical treatment. The different transport, transfer, and transformation processes induced by the applied electric field and how these processes are impacted by the electrolysis reactions at the electrodes are fundamental to the understanding of the electrochemical remediation technologies and are briefly presented in this section. 

The migration of pore fluid, ions, charged particles, colloids, and bacteria can be utilized to remove contaminants from polluted soil and/or to inject enhancement agents, nutrients, and so on to facilitate various remediation processes. The geochemical processes can be used to provide the necessary environmental conditions to control the direction of electroosmotic flow and to solubilize contaminants in the soil, so as to enhance the efficiency of the electrochemical remediation processes. 

Advection and dispersion of contaminants can be modeled using analytical and numerical methods. Advancement of computer technology now permits the use of complex numerical computational methods on portable computers. Modeling is helpful in evaluating factors that control contaminant migration, assessing the extent of contamination, and evaluating the effectiveness of remedial measures. 

Containment and/or remediation of contaminated aquifers typically utilizes pump and treat technologies to control contaminant plume migration and ultimately restore the... 

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