Solidification/Stabilization Remediation TechnologySolidification/Stabilization Remediation Technology

Presentation to CEAA Joint Review Panel for the Sydney Tar Ponds and Coke Ovens Sites Remediation Project

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Questions answered by this presentation

• What is Solidification/Stabilization?

• How is S/S designed and implemented?

• When and where has S/S been employed?

• Why is S/S a viable solution for STP?

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Definition: Solidification/Stabilization

• STABILIZATION• Reduces hazard potential of the hazardous

waste by converting contaminants into their least soluble forms.

• SOLIDIFICATION• Converts liquids, sludges and other

physically non-stable hazardous wastes into stable solids.

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What is Solidification/Stabilization?

• Involves mixing portland cement into contaminated media such as soil, sediment, sludge or industrial waste.

• S/S treatment protects human health and the environment by immobilizing hazardous constituents within treated material. ● Established treatment technology.

● Selected by USEPA for 24% of Source Control Remedies in the Superfund Program.

● Proven technology that treats a wide variety of hazardous constituents.

● Remediation of Brownfield Sites enabling them to be redeveloped.

● Cost effective – treated material can often be used at the site.

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Utilization of S/S

USEPA Superfund Projects, 1982-2002

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Solidification/Stabilization – S/S

• Concrete vs. Cement

• Concrete vs. S/S

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Concrete vs. Cement

Fine Aggregate

Coarse AggregateWater

Cement

Concrete Components• Cement

• Water

• Fine Aggregate

• Coarse Aggregate

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Concrete vs. Solidification/Stabilization

ContaminatedSediment

Water

Cement

• Mix the waste with reagents (binders) that convert the target constituents into relatively immobile species

• Encapsulate the low mobility species in a matrix that reduces access by potential leachates and provides the necessary physical properties for handling and disposal

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Basics of S/S Technology

Cement

Kiln Dust

Fly Ash

Clay

GGBFS - Slag

Soluble Silicate

• Ties up water

• Supplies alkali for pH control

• Forms low-solubility metal species

• Matrix is durable and proven

• Ready available

• Stable competitive product

Why cement binder is most often used?

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Solidification/Stabilization of Constituents

• InorganicHazardous constituents are made less soluble or less toxic.

Hazardous constituents are encapsulated in cement matrix.

Hydraulic conductivity and surface area are reduced

• OrganicContaminants are physically bound in the cement matrix

Hydraulic conductivity is reduced

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Immobilization/Containment Mechanisms - Metals

• Reducing solubility in a water environment• Control of pH to minimize solubility zone• Reaction to a less soluble form

• Controlling Oxidation/Reduction Potential• Adsorption of contaminants on binder surface• Coating of the waste particle surface• Reducing access of water to contaminants• Encapsulating in a low permeability matrix

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Immobilization/Contamination Mechanism - Organics

• Reactions which destroy or alter organic compounds• Fixation on an insoluble substrate - chemisorption

• Chemical Reactions (contaminant specific):• Hydrolysis

• Oxidation

• Reduction

• Compound Formation

• Physical processes such as encapsulation

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Effectiveness and use of S/STable I. Effectiveness of S/S on General Contaminant Groups for Soil and Sludges.[4]

Contaminant Groups EffectivenessOrganic Halogenated volatiles Non-halogenated volatiles Halogenated semivolatiles Non-halogenated semivolatiles and non-volatiles PCBs Pesticides Dioxin/Furans Organic cyanides Organic corrosives Inorganic Volatile metals Non-volatile metals Asbestos Radioactive materials Inorganic corrosives Inorganic cyanides Reactive Oxidizers Reducers

Key: Demonstrated Effectiveness: Successful treatability test at some scale complete. Potential Effectiveness: Expert opinion that technology will work. No Expected Effectiveness: Expert opinion that technology will/does not work.

• United States Environmental Protection Agency (1993)

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Properties of Cement-based S/S Systems- SUMMARY

• Relatively low cost• Good long-term

stability• Documented use

over time• Wide-spread

acceptance• Non-toxicity of

ingredients• Treat hazardous

waste (bottom ash)

• Wide range of volume increase factors

• Inert to radiation• Resistant to

biodegradation• Low water solubility• Relatively low water

permeability• Good physical

characteristics

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S/S Process Implementation

• Treatability Studies• Laboratory Formulation• Testing of Solidified Product

• Engineering Design• Contractor Implementation

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Laboratory Formulation

Solidified samples in test cups Large scale laboratory mixing in drum

Mixer with sample cups

Solidified samples prepared for strength and permeability testing

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Testing of Solidified Product

• Chemical - Leachability• Physical

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Terminology: Leaching is …

• Leaching is the removal of soluble constituents from a waste by contact with a liquid, especially rain-, surface-, or ground-water.

• This process is called leaching, the water is the leachant, and the contaminated water that has been in contact with the waste is the leachate. The capacity of the waste to leach is called the leachability.

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Leachability is measured by …

• Exposing the waste to a leachant that simulates the environment in which it is to be disposed of.

• The test is run under controlled conditions designed to accelerate the natural leaching process, thus predicting long-term leachability or a worst-case situation.

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Feasibility and Mix Design TestsChemical (Leaching)

Specification (Extraction) Tests – QA/QC

• Synthetic Precipitation Leaching Procedure (SPLP)

• Toxicity Characteristic Leaching Procedure (TCLP)

• Multiple Extraction Procedure

Leaching Tests – Support modeling

• Equilibrium Leach

• ANS/ANSI 16.1

• Dynamic Leach

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Leach Test Schematics

Ref.114

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Leachability Testing

Column Leaching Test Setup

Analytical InstrumentsTCLP Extraction Tumbler

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Testing of Solidified Product

• Chemical - Leachability

• Physical

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Feasibility and Mix Design TestsPhysical

• Hydraulic Conductivity/ Permeability

• Unconfined Compressive Strength –measure of free liquids & durability

• Freeze-Thaw & Wet-Dry Durability

• Paint Filter Test (PFT) – free liquids

• Moisture Content

• Density

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Physical Testing

Permeability testing apparatus

Liquid Extractor Tester

Solidified samples prepared for strength and permeability testing

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Long Term Durability

Long Term Durability Determination• Experience from Actual Projects

• Physical Testing

• Mathematical Modeling from Leachability Testing

• Structural Determination

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Long Term Durability

Experience From Actual Projects – U.S.

• 35+ Years of Industrial Experience

• 50+ Years of Nuclear Experience

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Long Term Durability

Physical Testing• Unconfined Compressive Strength –

measure of free liquids & durability

• Hydraulic Conductivity/Permeability

• Freeze-Thaw & Wet-Dry Durability

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Long Term Durability

Mathematical Modeling• Uses information from leachability tests

• ANS/ANSI 16.1 (U.S. Nuclear Regulations)

• Modified MCC-1 (U.S. Nuclear Regulations

• Dynamic Leach Test (Environment Canada)

• Models – Based on worst-case hydrology for a monolithic landfill immersed in moving groundwater• Source Term Model (STM)

• Remedial Options Assessment Modeling (ROAM)

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Long Term Durability

Structural Determination• Based on known scientific information on

longevity of cement-based materials as related to microstructure

• Investigation of solid phase geochemistry of S/S products – Light Microscopy, SEM, ERXRA, XRD, TG, DTG, DSC, FTIR, etc.

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Engineering Design

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Field Implementation

• Facility

• Mechanical Approaches – many configurations• Ex-Situ

• Waste and chemical feeders

• Conveyors

• Mixers

• Discharge and measurement

• In-Situ• Chemical feeders

• In-situ Mixers

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In-situ Solidification/Stabilization

• No excavation or replacement steps required

• Originally used for liquids in pits and lagoons, where accurate reagent feed and mixing not critical

• Techniques and equipment have evolved to provide good mixing and feed control

• Auger/mixing systems can be used for depths up to 25 meters

• Control of fugitive emissions

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In-situ S/S Process Equipment

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Labour Involvement

• Engineering• Environmental Engineers - testing• Materials Engineers – mix design, testing• Civil Engineers• Geotechnical Engineers• Other Specialist Scientists

• Contractors• Heavy Civil• Equipment Operators• Laboratory Personnel• QC/QA Field Technicians/Chemists

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Remediation Project Example

• PROJECT AND LOCATION: Pepper’s Steel and Alloy Co., Medley, Florida

• TIME: 1988

• REASON FOR TREATMENT: The contaminated soil depth extends into the Biscayne Aquifer, which is the primary drinking water source for a large area of southeastern Florida.

• CONTAMINANT LEVELS:• PCBs (Arochlor 1260) 42 to 116 ppm

• Lead 836 to 16980 ppm

• Arsenic 0 to 76 ppm

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Pepper’s Steel and Alloy Co., Medley, FL

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S/S Remediation Technology Selected

• PROJECT PLAN: Excavate the contaminated soil, treat it and return it to the excavated area as structural fill.

• CONTRACTOR: Qualtech Inc., a Florida Power and Light Company

• WASTE TREATED: Soil contaminated with heavy metals (lead and arsenic) and PCBs

• QUANTITY OF WASTE TREATED: 85,000 yd3 at depth of 2 to 8 feet below ground level.

• TECHNOLOGY EMPLOYED: Cement-based solidification/solidification

• TREATMENT RATE: 400 to 800 tons/hour/unit.

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Pepper’s Steel and Alloy Co., Medley, FL

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Test Results – Chemical/Physical

• LEACHING TESTS AND RESULTS:• USEPA EPTox: Metals and PCBs met (former) EPTox

standards, with PCB results below detection limits

• ANS 16.1: PCB Leachability Index: >14 (i.e. non- detectable)

• PHYSICAL TESTS AND RESULTS:• Compressive strength: > 50 psi (specification level was

20.9 psi) to 700 psi @ 500 days

• Darcy Permeability: < 10-8 cm/s (specification level was <10-6 cm/s)

RESULT: Cement-based S/S treatment technology was successfully employed to remediate contaminants.

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Pepper’s Steel and Alloy Co., Medley, FL

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References – Submitted into Record

• (100) Solidification of Petroleum-Based Tar Material with Cap Closure

• (101) "Georgia Power Company, MGP Site - Coumbus, GA (1-page summary)“; Williams Environmental Services, Inc

• (102) "Fixation/Solidification of Hazardous Waste At Chemical Waste Management's Vickery, Ohio Facility“; Michael F.R. Curry

• (103) “Remediation of Oil Refinery Sludge Basin”; Wayne Adaska, Wayne Ten, Steven Day

• (104) “Stabilization and Solidification of Contaminated Soils and Sludges Using Cementitious Systems: Selected Case History”; Michael MacKay and John Emery

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References

• (105) “Material Handling Equipment for the Preparation of Wastes for Stabilization Treatment”; Paul Lear, Daniel Schitz and Roger Brickner"

• (106) “RCRA Closure of Refinery Sludge Basin Using In-Situ Solidification and Containment”; Daniel Bodineand Fernando Trevino

• (107) “Recent Findings on Immobilization of Organics as Measured by Total Constituent Analysis”; Jesse R. Conner

• (108) “Immobilization of Volatile Organic Compounds in Commercial Cement-Based Waste Forms”; Oak Ridge National Laboratory

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References

• (110) “Physical and Chemical Behavior of Stabilized Sewage Sludge locks in Seawater”; Chih-Chin Shiehand Frank J. Roethel

• (111) “Mobility of Dioxins and Furans Associated with Stabilized Incineration Residues in the Marine Environment“; Frank J. Roethel, Vincent T. Breslin and Kenneth Alous"

• (112) “Long-Term Processes in a Stabilized Coal-Waste Block Exposed to Seawater”; Daryl E. Hockley and Hans A. van der Sloot

• (113) Figure 1. “Predicted Cumulative Fractions Leached in ANS. 16.1”

• (114) “Long-Term Stability of Solidified Wastes in the Proposed OWMC Landfill”; Environment Canada

• (115) “Comparison of U.S. and Foreign Test Protocols on Stabilized Hazardous Wastes”; Jesse R. Conner and James M. Huffman

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References

• (116) “Stabilization of Hazardous Waste Landfill Leachate Treatment Residue” Jesse R. Conner, Alan Li and Sherwood Cotton

• (117) “Stabilization of Mixed-Code Hazardous Waste Incinerator Residues Under the RCRA Landbans”; Jesse R. Conner, Sherwood Cotton and Paul Lear

• (118) “Comments on Long-Term Durability”; Jesse R. Conner

• (119) “In-Situ Stabilization of Mixed Waste Contaminated Soil”; Robert Liegrist, Steven R. Cline, T. Michael Gilliam and Jesse R. Conner"

• (120) “In Situ Immobilization of PCB's at the Pepper's Steel and Alloy Site A Success Story”; Dr. Les Dole