1. Treatment Technologies
In-Situ
Soil Vapor Extraction (s)
Solidification/Stabilization (s)
Soil Flushing (s)
Electrokinetic Separation (s)
Bioventing (s)
Enhanced Bioremediation (s,gw)
Phytoremediation (s,gw)
Chemical Oxidation (s,gw)
Thermal Treatment (s, gw)
Monitored Natural Attenuation (s,gw)
Air Sparging (gw)
Bioslurping (s,gw)
Dual Phase Extraction (s,gw)
In-Well Air Stripping (gw)
Passive/Reactive Treatment Walls (gw)
Ex-Situ
Biopiles (s)
Landfarming (s)
Slurry Phase Biological Treatment (s)
Chemical Extraction (s)
Soil Washing (s)
Solidification/Stabilization (s)
Incineration (s)
Thermal Desorption (s)
Excavation, Retrieval, and Off-Site (s)
Chemical Reduction/Oxidation (s,gw)
Bioreactors (gw)
Constructed Wetlands (gw)
Adsorption/Absorption (gw)
Advanced Oxidation Processes (gw)
Air Stripping (gw)
Granulated Activated Carbon (GAC) (gw)

2. Groundwater Remediation Approaches
1990s Technologies:
Air Sparging/Soil Vapor Extraction
Two-Phase Extraction (Bioslurping)
Permeable Reactive Barrier
HRC-ORC (Enhanced Bioremediation)
“New Millenium” Methods:
Air/Ozone Sparging
In-well Air Stripping
Phytoremediation
In situ Thermal Treatment
Chemical Oxidation

3. Air Sparging / Ozone Injection
Air sparging = air blown into groundwater

4. Air Sparging / Ozone Injection
Advantages:
Active, in-situ treatment of groundwater CVOCs
Off-the-shelf system for pilot studies
No ex-situ groundwater treatment or discharge
Limitations:
Short-circuiting to surface or adjacent wells
Variable conductivity can impact effectiveness
Requires electrical power
Can have high O&M/equip replacement costs

5. In-well Air Stripping Also “GW circulation wells” (GCW)
Dual casing and screen allow air to be blown in and stripped water to be recirculated
Stripped VOCs captured by vacuum extraction system
VOCs in air need treatment (GAC?)

6. In-well Air Stripping Advantages: Captures most VOC vapors
Radius of influence 3-5 times > sparge wells
Works in deep aquifers
Limitations:
Recovered vapors may need treatment Works only for VOCs and a few SVOCs Clayey horizons will limit recirculation
Susceptible to iron bacteria and scaling

7. Phytoremediation

8. Phytoremediation Applicability:
Will not work below root zone (trees <20 ft)
Advantages:
Works for most metals, VOCs, and SVOCs
Can control erosion and gw flow
Good for chemicals in shallow perched aquifers
Limitations:
Slow when new compared to active methods
Plants die in toxic groundwater

9. In Situ Thermal Treatment
Thermally enhanced SVE technology using hot-air/steam or electrical resistance (SPEH)/ electromagnetic/ radio frequency heating (RFH)
Stripped SVOCs and VOCs captured by SVE

10. In Situ Thermal Treatment
Advantages:
Can enhance poor soil conditions
Works in high moisture/poor soil conditions
Can treat SVOCs, VOCs, fuels, pesticides
Limitations:
Recovered vapors need treatment
Can be self-limiting (soil too dry)
High O&M costs

11. In-Situ Chemical Oxidation (ISCO)
Strong oxidizers can degrade chlorine bond
Strong oxidizers used for TCE: KMnO4, H2O2, ozone, Fenton’s reagent
Chem-ox potentially applicable to TCE at many sites with shallow groundwater
KMnO4 pilot test for TCE
in groundwater at Warren AFB

12. Contaminants Treated by ISCO
BTEX
MTBE
TPH
1,1,1-TCA
DCA
PCE
TCE
DCE
vinyl chloride
1,4-dioxane
PAHs
carbon tetrachloride
chlorinated benzenes
phenols
munitions (RDX, TNT, MHX)
PCBs

13. In-Situ Chemical Oxidation
Advantages:
Faster removal time than HRC/ORC
MCLs reached in days, not years
Expensive equipment not needed to inject
No O&M cost after last injection
Limitations:
Very high CVOC concentrations may not degrade
Multiple treatments if high Fe, CO3 and SO4
Chemicals more expensive than air or ozone

14. Five Major Oxidants Permanganate (KMnO4 or NaMnO4) Peroxide (H2O2)
Persulfate (S2O82-)
Ozone (O3)
Percarbonate (CO32-)

15. Permanganate Chemistry
Electron transfer reaction
PCE Oxidation
4KMnO4 + 3C2Cl4 + 4H2O 
6CO2 + 4MnO2(s) + 4K+ + 12Cl- + 8H+
TCE Oxidation
2KMnO4 + C2HCl3  2CO2 + 2MnO2(s) + 3Cl- + H+ + 2K+

16. Permanganate Application

17. Peroxide H2O2 + Fe2+  “Fenton’s Reagent”
Hydrogen peroxide alone is an oxidant
unable to degrade most contaminants before decomposition
2H2O2(aq)  2H2O + O2(g)
kinetically slow
Addition of ferrous iron dramatically increases oxidative strength
H2O2 + Fe2+  “Fenton’s Reagent”

18. Fenton’s Reagent Application

19. Persulfate Chemistry Direct oxidation through electron transfer:
3NaS2O8 + C2HCl3 + 4H2O 
2CO2 + 9H+ + 3Cl- + 3Na+ + 6SO42-
Sulfate free radical reactions
Chain-initiating
Chain-propagating
Chain-terminating

20. Persulfate Application

21. Ozone Chemistry Two types of reactions Indirect oxidation is faster
direct oxidation by O3
indirect oxidation, OH radical
Indirect oxidation is faster
Radical reactions
Chain-initiating
Chain-propagating
Chain-terminating

22. Ozone Application

23. Percarbonate Proprietary product, RegenOxTM
Similar to Fenton’s Reagent, though
Less exothermic
Longer lasting
No gas production

24. Permanganate (potassium)
Oxidant Comparison
Permanganate (potassium)
Fenton’s Reagent
Persulfate
Ozone
Strength
1.7 volts
2.8 and 1.8 volts
2.5 and 2.0 volts
2.8 and 2.1 volts
Contaminants Treated
Short list – ethenes, munitions; no TCA, BTEX?
Long list – BTEX, MTBE, ethenes, TCA and 1,4-dioxane
Moderate list – BTEX, ethenes, TCA and 1,4-dioxane; limited data
Moderate list – BTEX, MTBE, ethenes; no TCA or 1,4-dioxane unless H2O2 combo
SOD Reactivity
high
low
Handling Issues
-chemical
dust
- chemical
- explosion
- pressure
Ease of Injection
Easy - one solution, no off-gas
Difficult – 2 solutions, off-gas
Moderate – 2 solutions, no off-gas
Moderate – sparge system, no liquids

25. Permanganate (potassium)
Oxidant Comparison
Permanganate (potassium)
Fenton’s Reagent
Persulfate
Ozone
Persistence
Long (direct)
Short (OH radical)
Short (SO4 radical)
Residuals
MnO2 solid
oxygen
Sulfate
Sulfuric acid
Oxidant Cost
$ $2.00/lb
$0.59/lb (traditional)
$4.00/lb (modified-chelate)
$1.08/lb (alone)
$1.26/lb (iron chelate)
System costs: $2K to $26K/lb ozone
Predictability
Difficult
Regulatory Acceptance
Yes (UIC waiver)

26. Delivery Methods Direct push drilling and injection Well injection
Gravity fee or pressure inject
Continuous drip injection
Hydraulic fracturing with solid emplacement

27. Important Considerations
Choose oxidant based on site-specific conditions
Thoroughly characterize site geology
Thoroughly characterize contaminant distribution
Pay close attention to delivery method used (and the potential for good distribution)