Wascon Session 1 Ecn Vanderbilt

7/29/2019 Wascon Session 1 Ecn Vanderbilt

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An Overview of Leaching Assessment forWaste Disposal and Materials Use

Session 1

Assessment Framework and LeachingFundamentals

David S. Kosson, Ph.D.Florence Sanchez, Ph.D.

Department of Civil and

Environmental Engineering



Hans A. van der Sloot, Ph.D.Hans Meeussen, Ph.D.

WASCON 2003


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Current Application of Leaching Tests

Waste classificationHazardous

versusNon hazardous

Treatment process

effectivenessBest Demonstrated AvailableTechnology (BDAT)

Determination of EquivalentTreatment (DET)

Waste management optionsAlternative disposal andutilization scenarios

Site assessment andremediation endpoints

Contaminated soilsBrownfields sites

Source term evaluations

Release fluxRisk assessment

DOE performanceassessments


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Primary Raw

Materials

Alternative rawmaterials

Stage 1Raw material

supplies

Stage 2:Manufacture ofconstruction

materials and elements

Recycling ofconstructiondebris

Stage 4:Service Life

Stage 3:Construction

ProcessStage 5:

Demolition

Release into theenvironment

Energy

Dust, noise

emissions

Energy

End of Life

Environmental

impact (dusting)

CHARACTERIZATION AND COMPLIANCE

LEACHING TESTS IN DIFFERENT STAGES OF

THE BUILDING CYCLE

Supply ofinformation ontechnical andenvironmental

quality

Characterisation ofmonolith leachingbehaviour

Monolithcompliance

leaching test

Characterisationof granularleaching

Granular

compliance test


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Questions To Be Answered

Which management options are acceptable?e.g., treatment processes, residual contamination levels, reuse or

disposal options

Which wastes are suitable for disposal in a specific

disposal facility?

Is this secondary material acceptable for use incommerce?

e.g., as construction material, life cycle assessment

Different questions need to be answered for

different perspectives and roles in management !






Description Of The Scenario Relevant ForThe Specified Question

ENV 12920ROADBASE APPLICATION

INFILTRATION

GROUNDWATER

RUN-OFF

Material supply and processing

Geotechnical specifications of the application and materials used

Hydrology of the application






Leaching Assessment Approaches

Design laboratory tests to mimic key aspects of fieldscenarios

Requires unique test for each scenario

Uncertain comparability between scenarios

Extrapolation (scale-up, extended time frames) is uncertain

Carry out small-scale field assessmentsVery specific to specific waste and scenario

Good for validation, but expensive and require long testing times

Design laboratory tests to measure fundamental,intrinsic leaching characteristics and use masstransfer models to extend results to release estimatesfor specific scenarios

Requires knowledge of controlling factors and use of appropriate modelsMost versatile approach and allows comparability amongst materials andscenarios






Objectives of a Framework

for Evaluation of Contaminant ReleaseProvide conservative but realistic estimates

Broad range of waste types, constituents of concern, environmentalconditions and management options

Utilize testing strategies that can be carried out usingstandard laboratory practices in reasonable time frames

Provide for release estimates that consider site-specificconditions

Facilitate better waste management decisions, while

reducing overall management costs and improvingenvironmental protection

Provide tiered approach to balance information needs withevaluation costs






Recommended Approach to LeachingEvaluation

Define potential releasescenarios and leachingparameters needed

Test waste or materialto determine leachingparameters

Evaluate acceptance basedon projected impact

default criteria site-specific impact estimate comparability with prior

analogous experience

Calculate release based onmanagement scenario(s)and field conditions

default scenarios site-specific conditions compare with prior

knowledge (i.e., database)Select test methods to

measure neededleaching parameters






A Tiered Approach to Regulatory Use

MATERIAL

WASTE, SOIL OR PRODUCT

MANAGEMENT SCENARIO

y Specific disposal or

utilization scenario

y Default cases

SCREENING

TIER 1 Tier 1

TIER 2

TIER 3

MASS

TRANSFER RATE

Compliance

Tier 3A

LEVEL A LEVEL B LEVEL C

EQUILIBRIUM

Compliance

Tier 2A

EQUILIBRIUM

Characterization

Tier 2B

MASS

TRANSFER RATE

Characterization

Tier 3B

EQUILIBRIUM

Quality Control

(Material specific)

Tier 2C

MASS

TRANSFER RATE

Quality Control

(Material specific)

Tier 3C

Random compliance testing

Default ScenarioSpecific or

Default Scenario

User determines extent of testing needed based on waste quantity,potential management options, and prior knowledge


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Hierarchical Approach

Conservative Estimates (over-estimation of release) withless data

Total > Potential > Equilibrium Mass Transfer limited

Characterization TestingDetailed baseline evaluation of leaching behaviour for a class of materials

Compliance TestingIs the material tested the same as previously characterized class ofmaterials?

Prior characterization data available from similar material

Small quantity of material to be managed with limited options

Quality Control TestingIs the material changing significantly over time or from batch to batch?

Prior characterization data available, history with compliance testing

For management of large quantities of material with on-going production


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Release ScenariosGeneral Approach

Acceptable

Impact?

Treatment

Option

Mgmt

Scenario

Fundamental leachingproperties

Equilibrium data

Site information*

Assessment model


Availability data, Equilibrium

data, Mass Transfer data

Site information*

Assessment model

Material

Yes

Release Estimate

ExitYesNo

Flow-aroundPercolation

* Site-specific information orDefault scenarios

Acceptable

Impact?

Treatment

Option

Mgmt

Scenario


Equilibrium data

Site information*

Assessment model




Site information*

Assessment model

Material

Yes

Release Estimate

ExitYesNo


Acceptable

Impact?

Treatment

Option

Mgmt

Scenario


Equilibrium data

Site information*

Assessment model




Site information*

Assessment model

MaterialMaterial

Yes

Release Estimate

ExitYesNo


* Site-specific information orDefault scenarios


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Characterization of Material PropertiesConcept Leaching vs. Total Composition

Cumulat

iverelease[mg/kg]

LS [L/kg]

TIME [year]


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Intrinsic Material Leaching Characteristics

Aqueous-solid equilibrium as a function of pHSolubility

AdsorptionRelease

Potential

Acid/base neutralization capacity

Aqueous-solid equilibrium as a function of LSPore-water composition

Ionic-strength effects

Species wash-out or depletion

Mass transfer ratesRelease mechanism (diffusion, surface dissolution, coupleddissolution-diffusion, multiple processes)

Release rate (when not equilibrium controlled)


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Material Physical Characteristics

Needed for detailed evaluation

Moisture content

Physical form (granular, monolithic)

Porosity

Permeability

Density


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Main Types of Leaching Tests

Equilibrium-based leaching testsCarried out on size reduced material

Aims to measure contaminant release relatedto specific chemical conditions

pH

Liquid-to-solid ratio

Mass transfer-based leaching testsCarried out either on monolithic materialor compacted granular material

Aims to determine contaminant release rates

by accounting for both chemical andphysical properties of the material


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Relationships in Equilibrium Test Results

Si

1

10

100

1000

10000

3 5 7 9 11 13pH

Rel

ease(mg/kg)

LS =10

LS =5

LS =2

C l

100

1000

10000

3 5 7 9 11 13

pH

Release

(mg/kg)

LS =10

LS =5

LS =2

Si

0.1

1

10

100

1000

3 5 7 9 11 13pH

Co

nc.(mg/l)

LS =10

LS =5

LS =2

C l

100

1000

10000

3 5 7 9 11 13

pH

Conc.(mg/l)

LS =10

LS =5

LS =2


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Comparison of Different Leaching TestsContaminated Soil

pH dependence test as basis of reference

Contaminated

soil CSO2

0.01

0.1

1

10

100

1000

1 3 5 7 9 11

pH

Leached(mg/kg)

Cr

0.01

0.1

1

10

100

1 3 5 7 9 11 13

pH

Leached(mg/

kg)

EDTAHac

CaCl2NaNO3EN-12457-3

SCEPrEN 14429SCE

PrEN 14429Total AR Cd


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Consistent Leaching Behavior

Chemical speciation important for recycling, reuse andend-of-life judgment (carbonation)

ANC[mol/kg]

pH pH

Leached[mg/

kg]

Most relevantpH range forcement-bound

materials

ECRICEM


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Consistent Leaching BehaviorCompliance and Characterization (MSWI Bottom Ash)

Leached

[mg/kg]

Leached

[mg/kg]

Leached[mg/

kg]-Cumulative

Leached[mg

/kg]-Cumulative

pH LS [L/kg]

pH LS [L/kg]

Cu - Washout ofsoluble species

CEN TC 292Validation study

EN 12457 1 - 4Sb - Solubilitycontrol release


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Liquid-to-Solid Ratio Effects

0.1

1

10

100

1000

10000

0.1 1 10

L/S (l/kg)

Cumulativerelease

(

mg/kg)

Cl

S

Zn

Release processesderived from percolation

test

Cl - wash-out

SO4 - solubility

Zn - changes in pH


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Liquid-to-Solid Ratio EffectsBatch LS Testing - Cement-based Material

12.7

12.9

13.1

13.3

13.5

0 2 4 6 8 10

LS Ratio [mL/g]

pH

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10

LS Ratio [mL/g dry]

Na[mg/L]

0

200

400

600

800

1000

0 2 4 6 8 10

LS Ratio [mL/g]

Ca[mg/L]

0.0

0.1

0.2

0.3

0.4

0 2 4 6 8 10

LS Ratio [mL/g]

As[mg/L]


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Comparison of Laboratory and FieldResults

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

100

3 5 7 9 11 13pH

[Ni](mg/kg)

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

100

0.0001 0.001 0.01 0.1 1 10 100

L/S (l/kg)

C

um.release,

[Ni](m

g/kg)

Lab

Lysimeter

Field

Consistent behaviour in different scales of testing


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Leaching Behavior of ConstructionMaterials - Concrete

Aluminum release from cement in concrete drinking waterpipes

Leached[mg/kg]

pH

Leached[mg/m2]

Time [days]


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Aging Effects on Leaching

Chemical factorsCarbonation reaction of alkaline material with atmospheric CO2 toform carbonates, resulting in (i) shift in pH to between 7-9, (ii) re-speciation, (iii) change in adsorptive surfacesAcidification reaction with mineral or organic acids to reducenatural pH of the material

Oxidation or reduction may cause (i) valence state changes (e.g.,

Cr6+ to Cr3+), (ii) re-speciation (e.g., sulfide precipitation), (iii)change in adsorptive surfaces (e.g., Fe3+ to Fe2+)

Reduction in ionic strength or key species (e.g., Ba) by washout

Physical factors

Formation of surface layers (may cause sealing effects)Formation of cracks, increasing surface area

Heterogeneity results from aging (e.g., surface layers,internal gradients, near field external gradients)


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Carbonation and Matrix SolubilityPortland Cement Matrix

pH

Arsenic[mg/L]

As

Calcium

[mg/L]

pHCa

pH

Lead

[mg/L]

PbpH

Cad

mium

[mg/L]

Cd


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Lead Release

Cumulative release Flux

Cu

mulativePbrelease

[g

/m2]

Cumulative leaching time [days]

Pbflux[g

/m2s]

Total time [days]


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Arsenic Release

Cumulative release Flux

Cu

mulativeAsrelease

[g

/m2]

Cumulative leaching time [days]

Asflux[g

/m2s]

Total time [days]


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Effects of Dissolved Organic Carbon (DOC)

Influence ofDOC fromcompost added

in differentmixing ratioson Cu

mobilization inMSWI bottomash heated at500 C to

remove allresidual carbon0.01

0.1

1

10

100

1000

3 5 7 9 11 13

pH

Leachedmg/kg

BA100% BA99% BA97%

BA90% BA70% Compost

Cu

DOC

mobilization

Binding to

particulate

organic matter


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Effects of Reducing Conditions

-200 -100 0 100 200 300 400 500 600

EH

0.001

0.01

0.1

1

5

Leached(mg

/l)

Ba

Ba leaching from steel slag as a function of Eh


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Comparison With Regulations

Compliance of Portland cement concrete during recyclingor end-of-life conditions with the building material

decree (BMD)

Lea

ched[mg/kg]

pH pH

Lea

ched[mg/kg]

RELEVANT pHDOMAIN FORCONCRETE

Hi h i T ti


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Hierarchy in TestingCharacterization and Compliance Tests

Releasewith time

Own pHLS=10

Leachabilitycontrols

pH

pH

LS [L/kg]

LS [L/kg]

LeachedatLS10

[m

g/kg]

Leached[mg/kg]

Leache

datLS10

[m

g/kg]

Leache

d[mg/kg]

Characterization

Compliance


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Summary

Measurement of intrinsic leaching parameters allowsflexibility in assessment and comparison of materials and

scenarios.Equilibrium release as a function of pH, LS and masstransfer rate measurement provide important information.

Hierarchal approach allows flexibility in amount of testingneeded and effectively uses prior knowledge.

Life cycle analysis, including consideration of aging

effects, needed when uncontrolled use is considered.

Wascon Session 1 Ecn Vanderbilt

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