Lecture 24: Groundwater Remediation
Key Questions Understand the ideas behind the following technologies
1. Capping
2. Pump-and-treat
3. Air stripping tower
4. Activated carbon
5. Soil-vapor extraction and air sparging
6. Bioremediation
7. Excavation
8. Incineration
Organic Liquids are another common source of groundwater contamination
Fuel products - LNAPLSFuels
Solvents
LNAPL = Light Non-Aqueous Phase Liquid
LNAPLS are lighter than water so they float
LNAPL
water
Fuels are LNAPLs
LNAPL
• Gasoline• Kerosine• Fuel oil• Jet fuel• Diesel fuel
DNAPL = Dense Non-Aqueous Phase Liquid
DNAPLS are heavier than water so they sink
DNAPL
water
Solvents are DNAPLs• Trichloroethylene (TCE) or dry-cleaning fluid• Trichloroethane (TCA) e.g., parts cleaner, degreaser• Carbon tetrachloroide (CTET) is a reagent• Toluene – paint thinner• Turpentine – paint thinner
Groundwater Remediation
http://www.clu-in.org/remediation/
1. Capping
Caps are used to contain the waste and to eliminate rain infiltration
Area 6 Landfill
Whidbey Island Naval Air Station (NAS)
Landfill with fuel products and organic solvents
Area 6 Landfill
http://www.clu-in.org/remediation/
2. Pump-and-Treat
pumping wells
pipeline
treatment facility
Area 6 Landfill
http://www.clu-in.org/remediation/
3. Air Stripping Tower
pumping wells
pipeline
treatment facility
Stripping Tower, Area 6, Whidbey Island Naval Air Station (NAS)
http://www.clu-in.org/remediation/
Pump and treat is safe, but cleanup is a slow process. It will usually last at least five to ten years, but can last for decades.
At the Area 6, about 6.3 million gallons of groundwater are pumped and treated every month. Only 1.3 gallons of DNAPL is recovered.
One Olympic swimming pool is 650,000 gallons. Therefore, for every 10 pool-volumes treated, only 1.3 gallons on NAPL are recovered.
http://www.clu-in.org/remediation/
4. Activated Carbon
4. Activated Carbon
Hydrocarbons like to adhere “sorb” onto the surfaces of activated carbon.
And, activated carbon has a lot of surface area.
chemicals
Hanford Site
100 Area (Reactors)
Pump & Treat systems are used at the Hanford Site in Eastern, WA
Many LNAPLs and DNAPLs are Volatile Organic Carbons (VOCs)
i.e., they evaporate into the air vapors and are hazardous
http://www.clu-in.org/remediation/
Organic vapors are extracted (removed) from the ground by applying a vacuum to pull the vapors out of the unsaturated porous media.
5. Soil-Vapor Extraction (SVE)
http://www.clu-in.org/remediation/
Air Sparging
Air is pumped into the groundwater to volatize the organics out of the water which are then removed by SVE.
SVE
Air Sparging and Soil Vapor Extraction
Hanford Site
200 Areas
http://www.clu-in.org/remediation/
Microbes that live in soil and groundwater like to metabolize organics found in fuel and solvent.
When microbes completely digest these chemicals, they change them into water and harmless gases such as carbon dioxide.
6. Bioremediation
Bioremediation can be enhanced by keeping the microbes happy by
1. Pumping oxygen into the subsurface
2. Introducing nutrients like nitrogen, phosphorous, and potassium
3. Adding heat
6. Bioremediation
7. Excavation
http://www.clu-in.org/remediation/
8. IncinerationIncineration is the process of burning hazardous materials to destroy harmful chemicals and reduces the amount of material that must be disposed in a landfill.
