1 Section 5 Limitations 2 ISCO Limitations u

1 Section 5: Limitations

2 ISCO Limitations u u u Saturated Zone vs Unsaturated Zone Chemistry Co. Solvents Geology /Geochemistry/Hydrogeology NAPL

3 ISCO Saturated Zone vs Unsaturated u u u 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 Oxidant Peroxide/Fe Ozone Amenable contaminants of Reluctant Recalcitrant concern contaminants of concern TCA, PCE, TCE, DCE, VC, BTEX, DCA, CH 2 Cl 2, PAHs, CHCl 3, pesticides chlorobenzene, phenols, 1, 4 carbon tetrachloride, dioxane, MTBE, tert-butyl alcohol PCBs (TBA), high explosives PCE, TCE, DCE, VC, BTEX, DCA, CH 2 Cl 2, PAHs TCA, carbon chlorobenzene, phenols, MTBE, tetrachloride, CHCl 3, TBA, high explosives PCBs, pesticides TCA, PCE, TCE, DCE, VC, BTEX, DCA, CH 2 Cl 2, PAHs, CHCl 3, pesticides chlorobenzene, phenols, 1, 4 carbon tetrachloride, dioxane, MTBE, TBA, high PCBs explosives Benzene, TCA, carbon Permanganate PCE, TCE, DCE, VC, TEX, PAHs, Pesticides phenols, high explosives tetrachloride, CHCl 3, (K/Na) PCBs PCE, TCE, DCE, VC, BTEX, PAHs, explosives, None Activated chlorobenzene, phenols, 1, 4 pesticides Sodium dioxane, MTBE, TBA, PAHs, Persulfate PCBs Ozone/ Peroxide

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

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 -5 m 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 ISCO PAH DNAPL, TRENTO, IT Pilot Test Area Future Treatment Area

11 ISCO PAH DNAPL SITE, TRENTO, IT AW-03 Creek Concrete Wall AW-02 PZ-01 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 Ø Flow was 2 l/min and increased to 5 l/min after hydrogen Peroxide application through Concurrent Application in All AW’s Ø Temperatures were increased to 40 °C in all AW’s Ø All DNAPL was removed from AW wells and PZ 01 within 2 days Ø All hydrocarbon odor eliminated from all wells Ø Secondary indications of Sodium Persulfate Oxidation Activity for 6 weeks Ø Dissolved concentrations less than 100 ppb and no residual sheen or NAPL

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

16 Conclusions u u 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 nonrecoverable NAPL and prevents rebound