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)

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

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

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

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?)

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

Phytoremediation

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

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

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

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

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

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

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

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+

Permanganate Application

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”

Fenton’s Reagent Application

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

Persulfate Application

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

Ozone Application

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

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

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 $1.60 - $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)

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

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)