In Situ Remediation Basics
Transcript of In Situ Remediation Basics
In-Situ Remediation ApplicationsIn-Situ Remediation Applications1
Key Factors for Success The Right Chemistry
fundamental understanding of geochemistry and microbiology to pick right chemistry
Good Delivery contact with the contamination intensity of the delivery and distribution
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Understand the Site Hydrogeology Geochemistry Contaminants Microbial populations
A good understanding of contaminant source, contaminant migration, means a better design for remediation plan
Metals Objective: change the valence state to bind metals and
restrict migration VOCs:
Petroleum: can use biodegradation, either aerobic (oxygen) or anaerobic (sulfate); oxidation; inject heat to volatilize and enhance extraction
Chlorinated: anaerobic bio; oxidation; chemicalreduction
SVOCs: oxidation PCBs: oxidation
Concentrations Define source area Delineate dissolved plume
Transformations Degradation products of solvents indicate the
types of bacteria present, can they be utilized or need to be augmentedWill there be complete degradation to
ethene/ethane, a stall at cis-DCE, or a vinyl chloride build-up
Chemical Oxidation Chemical Reduction
(zero valent iron) Aerobic Bioremediation Anaerobic Bioremediation Thermal (steam) injection Metals Stabilization
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Chemical Oxidation Direct chemical destruction of volatile organics,
petroleum and chlorinated hydrocarbons Typical oxidants:
Potassium and sodium permanganate Sodium persulfate Hydrogen peroxide, Fenton’s chemistry Ozone
Typical response time: immediate to 4 months
Chemical Reduction Direct destruction of volatile organics through
abiotic reduction Zero valent iron (ZVI)
Typically injected, placed as a reactive wall or barrier
Commonly used for chlorinated hydrocarbons
Typical response time: immediate to years
Aerobic Bioremediation Addition of oxygen source to feed bacteria
that consume petroleum hydrocarbonsAir spargingOxygen release productsOxygenated water injection
Typical effective treatment: 1 to 6 months, or the length of sparging period
Anaerobic Bioremediation Sulfate reduction of petroleum
Magnesium sulfate (Epsom salt, EAS®), gypsum Chlorinated hydrocarbon enhanced reductive
dechlorination (ERD)Adding hydrogen source to feed bacteria
Fatty acids Edible oil Sodium/ethyl lactate esters Molasses and sugars
Typical effective treatment: 6 to 24 months
Why enhanced? Aquifers are sometimes limited by carbon (or
food) source for bacteria In some instances, the proper bacteria (e.g.
dehalogenators) are not present Can bioaugment with Dehalococcoides ethenogenes
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Lactates, fatty acids , edible oils ferment anaerobically:
Hydrogen is produced plus a new shortened fatty acid (lactic, linoleic, palmitic, propionitic acids); the shortened fatty acid is then cleaved, forming more hydrogen and acetic acid. The acetic acid breaks down to methane and carbon dioxide
Breakdown product acids degrade under lower hydrogen partial pressures, serve as a hydrogen storage, provide a longer hydrogen source
Does not overstimulate (typical problem when using sugars): Sugar overstimulates methanogens; much slower breakdown,
incomplete degradation, excess methane gas produced (health hazard)
Anaerobic microorganisms that degrade chlorinated organics (halorespirers) use the hydrogen as an electron donor and the chlorinated organics as electron acceptors
First notice a decline in parent material (PCE, TCE, TCA) with a corresponding increase in cis-DCE; then vinyl chloride. Then degradation products are degraded, resulting in ethenes/ethanes.
Can use a mixture of hydrogen source plus ZVI Combines anaerobic bioremediation and
chemical reduction (from ZVI) Less likely to form vinyl chloride Adventus holds patent to add ZVI to
carbon amendment
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Volume, rates of injection are monitored for each well for the duration of the injection
Direct Push (Geoprobe) Injection