Beyond Dig and Haul: A survey of Remedial Technologies

NYS Department of Environmental Conservation

Beyond Dig and Haul: A survey of Remedial

Technologies

NYS Department of Environmental Conservation

Agenda (20 Minutes)

• Excavations• Bioremediation• ISCO• SVE• Thermal treatment

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Remedy Selection• Do not select the remedy before you

investigate the site• First and foremost, the remedy must be

protective of people and the environment

• Second, you have to follow the rules (i.e. comply with the applicable standards, criteria and guidelines)

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DER-31 Green Remediation

• Consider all environmental effects of the cleanup– Minimize emissions (CO2, contaminants)– Use of resources (landfills, minerals,

energy)– Maintain or improve habitat

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Climate Change Resilience

• Sea level rise (Coastal areas, Hudson River Estuary)– Will your soil cover be under water and

wash away in 20 years? • Flood plains

– Increased frequency and intensity of storms.

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Hierarchy• Permanently destroy it• Permanently remove it• Permanently eliminate the risk• Prevent exposure

– Engineering controls– Institutional controls

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Excavations• There will always be a role for

excavation and off-site treatment and disposal.– It is permanent– Verification (you know what did and did not

get accomplished)– Target source areas. Most accessible. – Note on backfill (BUDs)

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Combining Technologies

• Many of the in-situ treatment technologies have limited effectiveness on source material

• Excavation is usually the right technology for the most accessible source material.

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Disposal vs treatment

• Disposal: Contaminated soil can be used as alternate daily cover, conserving mineral resources

• Treatment:– Thermal desorption– Chemical stabilization

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Chemical Stabilization

• Most commonly used on lead– Raise pH, react lead to create an insoluble

mineral– Eliminate the hazardous characteristic– Performing in-situ avoids some regulatory

issues (its not a hazardous waste until it is “generated”)

• Can work with other metals

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Things that make excavations less implementable

• Buildings and other obstructions• Odors and vapors (Sprung structures)• Infrastructure (roads and bridges)• Geotechnical (shoring)• Water

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In-Situ Chemical Oxidation

ISCO

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What Works• Set Clear Goals

– Probably not meeting GW standards– Often combine with bio or MNA

• Permanganate and persulfate are beginning to dominate the market

• Focusing mainly on CVOCs• Source areas (but not NAPL)• Below the water table (SVE above water)

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What Doesn’t Work

• Tight Soils – Matrix diffusion– Rebound

• Poor delineation• NAPL – some success, but I’m not sold

yet

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Enhanced Bioremediation

Reductive Dechlorination

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Chlorinated Solvents

•PCE, TCE, TCA

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When to use enhanced bio• Where it’s already working• Plume control• Anywhere you don’t want to use ISCO

– Tight soils– Poor access– Poor delineation– High ISCO demand

• Mention carbon injection

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Non-Chlorinated Organics

• Air injection (sparging).• Oxygen injection• Green options• ORC thrown into hole after excavation:

– No significant effect. Would generally not bother.

• Sulfate and nitrate amendments

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Note on MNA

• Monitored natural attenuation• Very specific definition• You need to set a goal and a deadline• Establish a fallback technology if you

don’t meet your goal by that time.

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Phytoremediation• Uptake of contaminants

– Accumulated in plants which then need to be disposed

– Expired into the air (essentially a dilution remedy, but mention photodegradation).

• Degrading chemicals– White rot fungus was oversold– Bacteria appear to be far more effective

than plants

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Soil Vapor Extraction (SVE)

• Vadose zone source (very high soil vapor)• Permeable soil remedy• Source areas• Hit it hard and get it done• Running the system for a long time is not

cost effective or sustainable

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NYS Department of Environmental Conservation

Combining Technologies

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In-Situ Thermal

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Where excavation and AS/SVE are not good fits,

in-situ thermal treatment has emerged as a legitimate

alternative.

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Think Thermal When

• Deep contamination• Excavation is impractical• Low permeability soils• You need complete cleanup fast• You know where your source is• Volatile organics

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Thermal Desorption

• Think of it as thermally enhanced AS/SVE– Expansion during phase change– Includes vapor extraction

• Advantages:– Short duration, final– Works in all materials, including bedrock and

clay

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Delivery of heat

• Electrical Resistive Heating (ERH)– Ideal for clay, heterogeneous soils– We have had good luck in sandy soils too– Be aware of stray current potential

• Thermal Conductive Heating– Works everywhere– The only choice if you need to get above

100ºC

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Ideal Cleaners – IRM construction

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Ideal Cleaners – ISTD operating

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Power Control Units and Cooling Towers

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Condensers, 40hp Blowers, PCUs

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Vapor Phase Carbon Vessels

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Vapor Phase Carbon Vessels

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Interior Bldg 57A

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Interior Bldg 57A – Quiz 2

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Sustainability

• Carbon footprint for electrically heating is comparable to digging and hauling it 65 miles– (source: TerraTherm)

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Limitations

• We have had the most success with VOCs– SVOCs need higher temps, dewatering

• High permeability = heating a lot of water

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Steam

• Has been used effectively (Visalia) • Adding a lot of water to the system• Seems more like thermally enhanced

pump and treat than Thermally enhanced SVE

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Brief mention of STAR

• Full-scale implementation underway at a coal tar site in Newark, New Jersey.

• deep sand unit located up to 35 feet below the water table

• destroying coal tar at a rate of approximately one ton per day.

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NYS Department of Environmental Conservation