esm223_09__Lecture_Notes

esm223_09__Lecture_Notes - ESM223, Winter 2008, Norm Brown...

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Lecture 9 – Containment and Cleanup (II) Above-Ground Treatment (I) ESM223, Winter 2008, Norm Brown Containment and Cleanup Technologies Cleanup Technologies ± Containment ± Hydraulic (pump-and-treat) ± Physical (e.g., membrane, slurry wall, steel wall. ..) ± SVE ± Bioventing ± in situ Bioremediaton ± Air Sparging ± in situ Air Stripping Cleanup Technologies ± NAPL/Product Recovery ± Skimmers, slurpers, vacuum and liquid pumps ± Thermal ± Steam (why not air?) ± Electrical Resistivity ± Fracturing – Pneumatic, Hyrdraulic ± Electrokinetic
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Cleanup Technologies ± Abiotic Oxidation ± Reductive Dechlorination ± Abiotic Metal Reduction ± Monitored Natural Attenuation ± Other … Cleanup Technologies ± in situ Treatment Zones (PRBs) ± Biological ± Air Stripping ± Adsorption ± Chem Ox (abiotic) ± O/H RC ± KMnO4 ± Reductive dechlorination ± Metals precipitation/mineralization (abiotic) ± Phytoremediation ± Degradation, Volatilization, Sequestration ± Vitrification / Stabilization Phytoremediation In-situ Vitrification ± Apply electric heating to soils to achieve very high temperatures ± Temperatures achieved can be 1300-1600 o C (2,400-2,900 o F ) ± Melt sand particles (forming glass) ± Organics present are oxidized via pyrolysis ± As glass cools, it immobilizes contaminants ± heavy metals and radionuclides ± 4 electrodes are placed around “melt zone”
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In-situ Vitrification ± The “technique” can be applied adjacent to a previous melt to form contiguous monolith ± Requires 0.7 to 1.1 kWh/kg of soil In-situ Vitrification ± Vitrification can also be used for soils with ± high PCB concentrations ± “legacy” pesticides (DDT and other OCs) ± Off-gases have to be collected, cooled and treated (GAC) in these cases ± Current treatment cost estimates for nonradioactive sites are in the range of $350- 450/ton Steam Injection ± Steam is best way to deliver a large amount of heat into subsurface ± as steam condenses it releases lots of heat ± Useful for semi-volatile organic liquids (e.g. heavier fraction of diesel fuels, fuel oil, DNAPLs) ± cannot be removed via traditional SVE ± Higher T ± Volatilizes heavier compounds ± Lowers the viscosity of pollutants ± May increase solubility and decrease sorption, and promote HPO Steam Injection ± Inject high-quality (i.e. high temperature, “superheated”) steam through injection well(s) at or below contamination ± Additional wells operated under vacuum (SVE) ± create a pressure gradient in soil to draw liquids (water and NAPL) and vapors through soil ± Above ground treatment of both vapor and water streams is needed
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Steam Injection ± Steam injection is most applicable to contaminants with a boiling point below ~250 o C ± Heavier contaminants may be mobilized (pushed along) by the NAPL front that is formed ± Can achieve some in situ destruction through hydrous pyrolysis/oxidation Steam Injection Case Study Underground imaging & data provided by ERT & thermocouples.
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esm223_09__Lecture_Notes - ESM223, Winter 2008, Norm Brown...

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