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Section 5: Limitations

Section 5: Limitations

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Section 5: Limitations

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  1. Section 5: Limitations

  2. ISCO Limitations • Saturated Zone vs Unsaturated Zone • Chemistry • CoSolvents • Geology /Geochemistry/Hydrogeology • NAPL

  3. ISCO Saturated Zone vs Unsaturated • All ISCO are Aqueous Phase Technologies • Ozone is also an Unsaturated Zone Technology • In order for treatment to occur, both the contaminant and the oxidant must be in solution together. • Permanganate, solid peroxides, activated sodium persulfate can be used to treat the unsaturated zone if zone or soils are hydrated during treatment. • Percent saturated is dependent on the contaminant and the soil type

  4. What about Chemistry

  5. What About CoSolvents • All organic Mass is addressed by ISCO • Chlorinated Solvents dissolved into oils generally behave as the oil. ( sink or float) • Cosolvent must be oxidized to reduce target analytes • BETX is only a 20% portion of fuel contamination so remaining solvent must be oxidized

  6. What About Geology, Geochemistry, and Hydrogeology • If you can’t contact the contaminant with ISCO you can not treat it. • Tight Clays require special treatment • Heterogeneity requires special consideration for well locations and screen intervals. • High Flow Aquifers need to use recirculation to maintain contact • Carbonate formations can be treated but need to be tested for best ISCO approach

  7. What about NAPL • Very rarely does NAPL exist as free floating product • If NAPL can be recovered effectively, it should be • NAPL occupies the pore spaces of soil and exists in the colloidal spaces in the soil • Effective short-term ISCO treatment requires dissolution of the sorbed and NAPL phase in the colloidal spaces with heat- Only peroxide provides that heat in ISCO Treatments • NAPL has been and can be effectively and safely treated with ISCO using controlled temperatures at low pressures • NAPL must be treated with Submerged application of chemicals below NAPL Zone.

  8. 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

  9. ISCO Pilot PAH DNAPL SITE, TRENTO, IT Site information Old Petroleum Tar Chemical Distillation Plant Contamination from Closed Treatment Ponds Geology 0 –2 m bgs till, stone and heterogeneous soil with brick fragments 2 -5m silty/sandy soil black color and heavy hydrocarbon and naphthalene smell, 5 to –14.3 m sandy, 13.30 to 16.30 colour black w/ hydrocarbon smell. Flowing DNAPL tars are present in the last 10 cm. Hydrogeology The water table is –2.7 m bgs but locally confined

  10. ISCOPAH DNAPL, TRENTO, IT Pilot Test Area Future Treatment Area

  11. ISCO PAH DNAPL SITE, TRENTO, IT AW-03 Creek Concrete Wall PZ-01 AW-02 PZ-02 AW-01

  12. ISCO PAH DNAPL SITE, TRENTO, IT DNAPL in AW’s prior to Treatment

  13. ISCO PAH DNAPL SITE, TRENTO, IT

  14. DNAPL Reduction PAH DNAPL SITE, TRENTO, IT • Observations • Flow was 2 l/min and increased to 5 l/min after hydrogen Peroxide application through Concurrent Application in All AW’s • Temperatures were increased to 40 °C in all AW’s • All DNAPL was removed from AW wells and PZ 01 within 2 days • All hydrocarbon odor eliminated from all wells • Secondary indications of Sodium Persulfate Oxidation Activity for 6 weeks • Dissolved concentrations less than 100 ppb and no residual sheen or NAPL

  15. DNAPL Reduction PAH DNAPL SITE, TRENTO, IT • Observations • Controlled Applications of Hydrogen Peroxide can effectively dissolve large amounts of NAPL and Dissolved Mass by agitation and addition of heat at low pressure • Controlled application at low pressure controls migration of NAPL • Persistence of Activated Sodium Persulfate consumes dissolved organics for over six weeks eliminating repartitioning and rebound potential. • Augmentation of additional sodium Persulfate after initial application can be performed before repartitioning of dissolved mass.

  16. Conclusions • ISCO and the contaminant must be in an Aqueous solution for successful Treatment • ISCO can treat all organics • ISCO is not selective, it treats all organics including non-target Cosolvents and Natural Occurring Organics • ISCO can safely and effectively treat non-recoverable NAPL and prevents rebound