Integrated Evaluation of Leaching Processes for ... · Integrated Evaluation of Leaching Processes...

Integrated Evaluation of Leaching Processes for Environmental Assessment

David S. Kosson, Ph.D.*, 1

Florence Sanchez, Ph.D.*Andrew Garrabrants, Ph.D.*Hans A. van der Sloot, Ph.D**

Department of Civil and Environmental Engineering


*Vanderbilt University, Nashville, TN**Energy Research Center of the Netherlands (ECN), Petten, NL

NIEHS Workshop on Arsenic Leaching From Drinking Water Treatment Residues

28 February 2005

1e-mail: [email protected]

Comparison of Different Leaching TestsContaminated Soil

Contaminated soil CSO2

0.01

0.1

1

10

100

1000

1 3 5 7 9 11

pH

Leac

hed

(mg/

kg)

Cr0.01

0.1

1

10

100

1 3 5 7 9 11 13

pHLe

ach

ed (

mg/

kg)

EDTAHacCaCl2NaNO3EN-12457-3SCEPrEN 14429SCEPrEN 14429Total AR Cd

pH dependence test as reference basis



NIEHS Workshop28 February 2005

AN

C [

mol

/kg]

pH pHLe

ach

ed [

mg/

kg]

Consistent Leaching Behavior

Most relevant pH range for cement-bound materials




A class of materials behaves consistently accordingto controlling chemistry




Solubility & Release from Untreated and Treated Hg-contaminated Soils

0.000010.0001

0.0010.01

0.11

10100

0 2 4 6 8 10 12 14pH

Hg

[mg/

L]

-- TCLP limit=0.2mg/L

pH 6.8

--- DL=0.05µg/L

Untreated Am soil

0.000010.0001

0.0010.01

0.11

10100

0 2 4 6 8 10 12 14pH

Hg

[mg/

L]

pH 10.2

--- DL=0.05µg/L--- UTS TCLP limit=0.025mg/L

Vendor 3 treated Am soil(S/S process)

TCLP

TCLP

Vendor 3 treatment resulted in a significant increase in Hg solubility for pH between 4 and 8




Conceptual Approach to Leaching Evaluation(Kosson, van der Sloot et al., 2002, Environ. Engr. Sci., 19, 159-203)

Measure intrinsic leaching characteristics of material

Evaluate release in the context of field scenarioExternal influencing factors such as carbonation, oxidationHydrologyMineralogical changes

Use geochemical speciation and mass transfer models to estimate release for alternative scenarios

Model complexity to match information needsMany scenarios can be evaluated from single data set

Do NOT mimic field scenarios with specific tests!Too many tests with limited data comparability!




Measuring Intrinsic Leaching Characteristics

Aqueous-solid partitioning as a function of pH and Liquid to Solid ratio

Batch extractionsConstituent fraction readily leachedControlling mechanism for release (mineral dissolution and solubility, solid phase adsorption, aqueous phase complexation)

Release kineticsPercolation (column tests)Diffusion (monolithic or compacted granular tank leaching tests)

Use results in conjunction with understanding of pore water chemistry to determine mass transfer rate constants (e.g., effective diffusivities)




Main Types of Leaching Tests

Equilibrium-based leaching testsCarried out on size reduced materialAim to measure contaminant release related to specific chemical conditions (pH, LS ratio)

Mass transfer-based leaching testsCarried out either on monolithic material or compacted granular materialAim to determine contaminant release rates by accounting for both chemical and physical properties of the material

Percolation (column) leaching testsMay be either equilibrium or mass transfer rate




Equilibrium CharacterizationSolubility and Release as a Function of pH (SR002.1)

11 parallel solubility extractionsDI with HNO3 or KOH additionSize reduced materialContact time based on sizeLS ratio: 10 mL/g dryEndpoint pH

Distributed 3≤pH≤12

Contact timeParticle size

< 0.3 mm

< 2 mm

< 5 mm

18 hr

48 hr

168 hr

Titration curve and constituent solubility or release curves




Equilibrium CharacterizationSolubility and Release as a Function of LS (SR003.1)

5 parallel extractionsDI waterSize reduced materialContact time based on particle sizeLS ratios

0.5, 1, 2, 5, and 10 mL/g dry

Contact timeParticle size

< 0.3 mm

< 2 mm

< 5 mm

18 hr

48 hr

168 hr

Estimate of constituent concentration in the pore water




Arsenic Leaching Behavior From Soils and Solidified Wastes

0.1

1

10

100

1000

10000

100000

0 2 4 6 8 10 12 14

Leac

hed

(mg/

kg) Contaminated soil

0.1

1

10

100

1000

10000

0 2 4 6 8 10 12 14

S/S treated soil

0.0010.010.1

110

1001000

10000

0 2 4 6 8 10 12 14

S/S MeO - non carbonated

0.0010.010.1

110

1001000

10000

0 2 4 6 8 10 12 14pH

S/S MeO - carbonated

Same soil untreated &treated

Same S/S treated metal Oxide matrix with & Without exposure to Carbon dioxide (carbonation)

Cd

0.0001

0.001

0.01

0.1

1

10

100

1000

2 4 6 8 10 12Leachate pH

Cad

miu

m [m

g/l]

C-14

1

10

100

1,000

10,000

100,000

2 4 6 8 10 12 14 Leachate pH

Cal

cium

[mg/

l]

A-

0.0001

0.001

0.01

0.1

1

10

100

2 4 6 8 10 12 14Leachate pH

Ars

enic

[mg/

l]

.

B-

Ca AsCarbonate

Withoutcarbonati

Pb

4 62 8 10 12 140.001

0.01

0.1

1

10

100

Lead

[mg/

l]

.

1000

Leachate pHD-

epartment of Civil and ironmental Engineeringepartment of Civil and ironmental Engineering

NIEHS Workshop 28 February 2005

d

on

DEnv

DEnv

Portland Cement MatrixCarbonation and Matrix Solubility

Arsenic Leaching Behavior From a Range of Construction Materials

0.001

0.01

0.1

1

3 5 7 9 11 13

0.001

0.01

0.1

1

3 5 7 9 11 13

0.001

0.01

0.1

1

3 5 7 9 11 13

Lea

ched

(m

g/k

g)

0.001

0.01

0.1

1

3 5 7 9 11 13

Demolition debris

Blast furnace slag cement mortar

Drinkwater pipe Asphalt

0.001

0.01

0.1

1

3 5 7 9 11 13

0.001

0.01

0.1

1

3 5 7 9 11 13

pH

Portland cement mortar

Sintered brick







Arsenic Leaching Behavior From Treated Wood and a Few Waste Types

0.001

0.01

0.1

1

10

100

1000

2 4 6 8 10 12

Lea

ched

(mg/

kg)

CCA impregnated wood

0.001

0.01

0.1

1

10

100

2 4 6 8 10 12

Cu salt impregnated wood

0.0001

0.001

0.01

0.1

1

10

100

3 5 7 9 11 13

Galvanic sludge

0

0

1

10

100

3 5 7 9 11 13

MSWI Fly ash

0.01

0.1

1

10

100

3 5 7 9 11 13

Incinerated sewage sludge ash

0.001

0.01

0.1

1

10

100

3 5 7 9 11 13pH

MSWI bottom ash




Use of Sodium Ascorbate as a Reducing Agent(Mining Waste)

0.001

0.01

0.1

1

10

100

1000

0 2 4 6 8 10 12 14

pH

Fe [m

g/L]

--- DL = 0.006 mg/L

6.6

0.04(1)

(2)(3)

0.1

1

10

100

1000

0 2 4 6 8 10 12 14pH

As

[mg/

L]

--- DL = 0.3 mg/L

6.6

(3)

(2)

(4)

(1)

(5)

(1) Baseline, ORP = 410mV vs. NHE(2) 0.0075 mol L-1, ORP = 340 vs. NHE(3) 0.01 mol L-1, ORP = 345mV vs. NHE(4) 0.025 mol L-1, ORP = 5mV vs. NHE(5) 0.046 mol L-1, ORP = -7mV vs. NHE

(4)(5)

Chatain and Sanchez, 2005

0.1

1

10

100

1000

0 2 4 6 8 10 12 14pH

As

[mg/

L]

--- DL = 0.3 mg/L

6.6(1)

(2)(3)

(4)(5)

(6)

0.001

0.01

0.1

1

10

100

1000

0 2 4 6 8 10 12 14pH

Fe [m

g/L]

--- DL = 0.006 mg/L

6.6

0.04(1)

(2)(3)

(4)(5) (6)




Use of Sodium Borohydride as a Reducing Agent(Mining Waste)

(1) Baseline, ORP = 410 mV vs. NHE(2) 0.0075 mol L-1, ORP = 140 mV vs. NHE(3) 0.01 mol L-1, ORP = 150 mV vs. NHE(4) 0.025 mol L-1, ORP = -440 mV vs. NHE(5) 0.046 mol L-1, ORP = -445 mV vs. NHE(6) 0.075 mol L-1, ORP = -500 mV vs. NHE Chatain and Sanchez, 2005




Release Modes

Percolation through granular materials

Granular or highly permeable materialLocal equilibrium controls releasePreferential flow may be important

Flow around low permeability (monolithic) materials

Coupled diffusion and pore-water chemistry controls releaseBoundary conditions are important

Infiltration

Groundwater

Run-Off

Roadbase

Seepage Basins

Infiltration

Field pH

Contaminated soil




Long-term Assessment Models

Simple release modelsPercolation/equilibrium modelDiffusion model

More sophisticated release models to account forChemistry between solid-liquid phases (empirical or geochemical speciation)Effect of intermittent wettingEffect of external stresses (e.g., carbonation)

Use of probabilistic approach to allow forConsideration of a range of management sites and conditionsConsideration of a range of expected climate conditions and waste characteristicsBounded levels of confidence and distribution frequencies for release estimates

00.10.20.30.40.50.60.70.80.9

1

0 0.5 1 1.5 2 2.5

LS ratio [L/kg year]

Pro

babi

lity

Field dataFitted distribution (Gamma, (1))Simulated (2)

(2) (1)

0

0.2

0.4

0.6

0.8

1

5 6 7 8 9 10 11 12 13 14

pH

Pro

babi

lity

Field dataFitted distribution (Logistic, (1))Simulated (2)

(2) (1)

pH Field data

Fitted distribution Simulated

pH min 5.40 4.74 4.92pH - 5% 5.80 6.00 5.97pH - 95% 12.09 11.62 10.63Mean pH 8.10 8.13 7.86pH max 12.80 +infinity 12.50

LS 1 year Field data

Fitted distribution Simulated

LS min 1.0E-05 3.3E-04 3.3E-04LS - 5% 5.5E-04 4.9E-04 4.4E-04LS - 50% 0.06 0.08 0.08LS - 95% 1.50 1.07 1LS max 2.50 +infinity 1.99




Probabilistic Assessment of Release for Land Disposal (based on USEPA database)

MDLML

12.2

6.67MCL

0.001

0.01

0.1

1

10

100

1000

10000

2 4 6 8 10 12 14

pH

As [µg

/L]

SR2-BPB-0001 - ASR2-BPB-0001 - BSR2-BPB-0001 - C

5% 95%

5%

95%

BaselineAs total content*: 80.5 ± 1.9 µg/g

MDLML

9.5

4.8

MCL

0.001

0.01

0.1

1

10

100

1000

10000

2 4 6 8 10 12 14

pH

As [µg

/L]

SR2-BPT-0001 - ASR2-BPT-0001 - BSR2-BPT-0001 - C

5% 95%

5%

95%

w/ activated carbon injectionAs total content*: 27.9 ± 2.1 µg/g




ExampleArsenic Leaching as a Function of pH

5% 95%0.1

1

10

100

1000

10000

0 20 40 60 80 100

Percentile

100-

year

Mt [µg

/kg]

BPB BPT

Arsenic

50%

µg/kg % µg/kg %Mt min 0.2 0.0003 0.1 0.0003Mt - 5% 0.9 0.0011 0.1 0.0005Mt - 50% 152 0.2 22 0.0772Mt - 95% 2095 2.6 338 1.2Mean Mt 468 0.6 90 0.3Mt max 4693 5.8 10157 36.4

BPB BPT




ExampleProbability Distribution of 100 yr Release

Estimates for Land Disposal

Hierarchy in Testing

In the context of detailed characterization of a material, use simplified testing for compliance and quality control purposes

Establish material performance criteria for specified applicationTest material to establish

Performance consistent with initial characterization (new material source or significant process change?)Performance consistent with management acceptance criteria

Limit testing to critical parametersEstablish material quality control monitoring program




Release with time

Own pHLS=10

Leachability controls

pH

pH

LS [L/kg]

LS [L/kg]

Leac

hed

at

LS 1

0[m

g/kg

]

Leac

hed

[m

g/kg

]

Leac

hed

at

LS 1

0[m

g/kg

]

Leac

hed

[m

g/kg

]

Characterization

Compliance




Hierarchy in TestingCharacterization and Compliance Tests

DIFFERENT IMPACT SCENARIOS…….. 16 Dec. 2003 DG

ENVDrinking water wellLandfill

Road base

Industrially contaminated soilPlant

Agriculture

Coastal protection

Contaminated soil Drinking water

pipes

Mining

ConstructionRoof runoff

sewer

Road base

SOURCE TERM

L/S

[con

c]

TRANSPORT

IMPACT

Point of compliance

………. SIMILAR PROBLEM

Different for each scenario, material, changes over time (carbonation, redox), etc.

Transport in unsaturated zone and saturated zone to point of compliance similar for each scenario

LeachXS1 as a Decision Support Tool to Manage and Interpret Test Data

1LeachXS is a software tool being jointly developed by The Netherlands Energy Research Foundation (ECN), Vanderbilt University (USA) and DHI Water and Environment (Denmark), including test methods selection, database, data presentation, evaluation, geochemical speciation modeling, and scenario assessment.




LeachXS Structure

Scenarios(e.g., fill

characteristics,geometry, infiltration,

hydrology)

Materials(Leaching data,

Composition, Physicalcharacteristics)

Regulatory(Regulatory

thresholds andcriteria from different

jurisdictions)

Thermo-dynamic

Databases

Reports(Figures, Tables,

Scenario and MaterialDescriptions)

ExcelSpreadsheets(Data, Figures)

Other Models(Source Term and

Parameters forFate, Transport,and Risk Models)

LeachXS(Materials and

ScenariosEvaluation)

Orchestra(GeochemicalSpeciation and

Reactive TransportSimulator)

ScenarioDatabase

MaterialsLeachingDatabase

RegulatoryDatabase

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0 2 4 6 8 10 12 14pH

[Al]

(mol

/l)

LYS-NAUBoehmiteGibbsite[C]LYS-NAU-ORGBoehmiteGibbsite[C]

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

0.00001 0.0001 0.001 0.01 0.1 1 10

L/S (l/kg)

[Al]

(mol

/l)

NAU-COL BoehmiteGibbsite[C] NAU-COL-ORGAlbite[low ] BoehmiteGibbsite[C] NAU-LYSBoehmite Gibbsite[C]NAU-LYS-ORG BoehmiteGibbsite[C]

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0.01 0.1 1 10

L/S (l/kg)

[Al]

(mol

/l)

FIELD-NAU LEACHATE

Al[OH]3[a]

BoehmiteGibbsite[C]

GEOCHEMICAL MODELING

pH stat testL/S = 10, t = 48 hr

Percolation test L/S=0.1-10

Field leachate

Geochemical modeling

ORCHESTRA with extended MINTEQ database + Nicca Donnan

LeachXS

Pb

1.0E-10

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0 2 4 6 8 10 12 14pH

con

cen

trat

ion

(mo

l/L)

Harbour sediment (Rhine)Predictive model

Solid phase Pb

0.0E+00

5.0E-05

1.0E-04

1.5E-04

2.0E-04

2.5E-04

1187631pH

mo

l/L s

orb

ed

ClayFe-(hydr)oxidesPOM

Water phase Pb

0.0E+00

2.0E-01

4.0E-01

6.0E-01

8.0E-01

1.0E+00

1187631

pH

Par

titio

nin

g

OtherFreeDOM

Water phase Pb

0.0E+002.0E-054.0E-056.0E-058.0E-051.0E-041.2E-041.4E-041.6E-041.8E-042.0E-04

1187631

pH

mo

l/L s

orb

ed

OtherFreeDOM

Modelled solid and liquid phase speciationof Pb in a contaminated river sediment

SEDNETWorkshopJune 10, 2004San Sebastian,Spain

LeachXS

USEPA Evaluation of Coal Combustion Residues from Facilities with Enhanced Mercury Control

Extensive QAQC program developmentMethods validation with mass balance on reference CCR

QAQC within leaching methods, chemical analysis, data evaluation

Leaching characterizationRelease as function of pH (SR002.1)Release as function of LS (SR003.1)Mass transfer release (when considered necessary)

Comparison with field dataLeachate concentrations reported in USEPA databaseField sampling from CCR management facilities

Release Scenario AssessmentLand disposalProbabilistic release estimates based on range of conditions (pH, LS) reported in USEPA database (improved estimates to be based on EPRI data)Release estimates for default scenarios at 3 pHs (acid, alkali, own)




Key Messages

Measure intrinsic leaching characteristics, use geochemical speciation and mass transfer models in conjunction with management scenarios to estimate constituent release.

Use results to assess impacts, develop acceptance criteria and monitoring strategies.

The tools exist and data are currently being obtained to achieveassessments for specific scenarios of residue disposal. Tailoring for specific uses is needed.

“Classes” of drinking water treatment residues likely can be identified. After initial characterization, simplified testing (i.e., an index test) can be used to confirm conformance with previously defined class.




Acknowledgements

USEPA Office of Solid WasteNational Risk Management Research Laboratory (RTP)Northeast Hazardous Research Center

Consortium for Risk Evaluation with Stakeholder Participation (CRESP) with support from DOE-EM

Recycled Materials Resource Center (UNH/FHWA)

EU Research ProgramNetwork Harmonization of Leaching and Extraction Tests

Netherlands Ministry of Housing, Spatial Planning and Environment (VROM)




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