Post on 03-Feb-2022
transcript
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
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
http://www.clu-in.org/remediation/
1. Capping
Caps are used to contain the waste and to eliminate rain infiltration
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.
4. Activated Carbon
Hydrocarbons like to adhere “sorb” onto the surfaces of activated carbon.
And, activated carbon has a lot of surface area.
chemicals
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
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