Treatment Technologies

1. 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) Treatment Technologies

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 • 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 • 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. Oxidant Comparison

25. Oxidant Comparison

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)