beyond dig and haul: a survey of remedial technologies

NYS Department of Environmental Conservation

Beyond Dig and Haul: A survey of Remedial

Technologies


Agenda (20 Minutes)

• Excavations• Bioremediation• ISCO• SVE• Thermal treatment


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)


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


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.


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

– Engineering controls– Institutional controls


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)


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.


Disposal vs treatment

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

• Treatment:– Thermal desorption– Chemical stabilization


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


Things that make excavations less implementable

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


In-Situ Chemical Oxidation

ISCO


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)


What Doesn’t Work

• Tight Soils – Matrix diffusion– Rebound

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

yet


Enhanced Bioremediation

Reductive Dechlorination


Chlorinated Solvents

•PCE, TCE, TCA


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


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


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.


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


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


Combining Technologies


In-Situ Thermal


Where excavation and AS/SVE are not good fits,

in-situ thermal treatment has emerged as a legitimate

alternative.


Think Thermal When

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


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


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


Ideal Cleaners – IRM construction


Ideal Cleaners – ISTD operating


Power Control Units and Cooling Towers


Condensers, 40hp Blowers, PCUs


Vapor Phase Carbon Vessels


Interior Bldg 57A


Interior Bldg 57A – Quiz 2


Sustainability

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


Limitations

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

• High permeability = heating a lot of water


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


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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