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Section 6- ISCO DESIGN

Section 6- ISCO DESIGN. Initial Site Evaluation ISCO Compatibility ISCO Modeling and Dosage Considerations Bench Testing Pilot Testing/Delivery System Evaluation Full Scale Combination Technologies. ISCO Design Process. Initial Technology Screening Modeling

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Section 6- ISCO DESIGN

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  1. Section 6- ISCO DESIGN • Initial Site Evaluation • ISCO Compatibility • ISCO Modeling and Dosage Considerations • Bench Testing • Pilot Testing/Delivery System Evaluation • Full Scale • Combination Technologies

  2. ISCO Design Process • Initial Technology Screening • Modeling • Design Parameter Evaluation and Bench Testing • Field Pilot/Initial Application • Full Scale Application

  3. Example Laboratory Test • Oxidation Estimating Tool (OET) is predictive • empirical model to estimate overall oxidant demand (OD) • Stochiometry is only a small fraction of the actual oxidant • required for ISCO • Treatability test is run on several formulations to develop • an efficiency curve and confirm OD • The primary purposes of the OET are: • 1. To determine the reactivity of the site media • 2. To select the optimum reagent formulation • 3. To observe adverse reactions, if any

  4. OET Model Site Geochemistry/Geology Well Contaminants-Total Mass Treatment Volume Estimate •

  5. Site Geochemistry/Geology •

  6. Site Geochemistry/Geology •

  7. Contaminant Mass PSH, Sorbed, Dissolved •

  8. Treatment Volume Estimate •

  9. Design of Delivery Systems • Sufficient number of wells to provide adequate overlap of “effective zones” • Can use trenches • Usually multiple application events • Oxidant transport can be reaction limited • Effective radius of treatment will be substantially smaller than hydraulic/pneumatic radius of influence • Higher oxidation reaction rates lead to smaller treatment radii • Caution should be used when designing injection / monitoring wells • Stainless steel injection points may be needed

  10. Pilot Test Design • Bench test predicts best oxidant and combination of reagents only • Pilot Calibrates Bench Prediction • Identifies application parameters for full site design • Develops optimal delivery process

  11. Conditions that Require Special Delivery Consideration • Low permeable soils • Deep aquifers • LNAPL/DNAPL • Confined formations • Swamps or high organic soils • Old landfills and dumps • River embankments • Under buildings

  12. Important Delivery System Considerations • Only treat sites that have been properly characterized • Treat from the perimeter of the target zone • Never treat within or down-gradient of contamination • Perform treatment to address all phases of Contaminant • If rebound occurs, realized that it is an indication of contamination not be contacted (within, above, next to, or below) not that ISCO does not work.

  13. Total Mass EvaluationNature of Contamination • Contamination mass exists in four phases in the contaminated zone • Soil gas • Sorbed • Dissolved • Non-aqueous phase liquid (NAPL) or phase-separated • Geochemistry, partitioning coefficient (Kow) determines the relationship between phases in the saturated zone • Majority of mass (normally >80%) is sorbed and phase-separated Graphic source: Suthersan, 1996

  14. Delivery SystemsBatch vs. Recirculation Oxidant Recirculation Batch Oxidant Injection Contaminant Injection wells Extraction wells Injection location Contaminant Radius of treatment

  15. Delivery Systems Application Conventional delivery configurations • Direct injection • Horizontal injection • Pulsing • Soil mixing • Density-driven flow • Lance permeation Treated soil columns Water table Auger Soil Bedrock

  16. Delivery Systems Enhancement Innovations to increase effectiveness • Recirculation • Pneumatic fracturing • Hydraulic fracturing • Ozone sparging • Unsaturated zone delivery

  17. Design Conclusions • Always perform limited Bench Evaluation • Pilot is needed to optimize delivery of Reagents • Mass transfer technologies limited in their effectiveness because they must rely on the natural slow and inefficient desorption of the contaminants of concern from the soil • ISCO enhances mass transfer from soil to groundwater by breaking down natural organic matter (NOM) (and sorption sites) and increasing temperature (peroxide co-addition) • Biological System rebounds effectively after ISCO

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