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Transcript of 1 Section 5: Limitations. 2 ISCO Limitations Saturated Zone vs Unsaturated Zone Chemistry ...
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Section 5: Limitations
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ISCO Limitations
Saturated Zone vs Unsaturated Zone Chemistry CoSolvents Geology /Geochemistry/Hydrogeology NAPL
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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
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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, CH2Cl2, PAHs, carbon tetrachloride, PCBs
CHCl3, pesticides
Ozone PCE, TCE, DCE, VC, BTEX, chlorobenzene, phenols, MTBE, TBA, high explosives
DCA, CH2Cl2, PAHs TCA, carbon tetrachloride, CHCl3, PCBs, pesticides
Ozone/ Peroxide
TCA, PCE, TCE, DCE, VC, BTEX, chlorobenzene, phenols, 1,4-dioxane, MTBE, TBA, high explosives
DCA, CH2Cl2, PAHs, carbon tetrachloride, PCBs
CHCl3, pesticides
Permanganate (K/Na)
PCE, TCE, DCE, VC, TEX, PAHs, phenols, high explosives
Pesticides Benzene, TCA, carbon tetrachloride, CHCl3, PCBs
Activated Sodium Persulfate
PCE, TCE, DCE, VC, BTEX, chlorobenzene, phenols, 1,4-dioxane, MTBE, TBA, PAHs, PCBs
PAHs, explosives, pesticides
None
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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
6What 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
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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.
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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
Total Mass EvaluationNature of Contamination
Graphic source: Suthersan, 1996
9ISCO Pilot PAH DNAPL SITE, TRENTO, IT
Site information
Old Petroleum Tar Chemical Distillation Plant
Contamination from Closed Treatment Ponds
Geology0 –2 m bgs till, stone and heterogeneous soil with brick fragments2 -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.
HydrogeologyThe water table is –2.7 m bgs but locally confined
10ISCOPAH DNAPL, TRENTO, IT
Pilot Test Area Future Treatment Area
11ISCO PAH DNAPL SITE, TRENTO, IT
Concrete Wall
Creek
AW-02
AW-03
AW-01
PZ-01
PZ-02
12ISCO PAH DNAPL SITE, TRENTO, IT
DNAPL in AW’s prior to Treatment
13ISCO PAH DNAPL SITE, TRENTO, IT
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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
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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 NAPLPersistence 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.
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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