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

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  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 (K ow ) determines the relationship between phases in the saturated zone  Majority of mass (normally >80%) is sorbed and phase-separated Total Mass Evaluation Nature of Contamination 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, to 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 Concrete Wall Creek AW-02 AW-03 AW-01 PZ-01 PZ-02

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