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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
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
A class of materials behaves consistently accordingto controlling chemistry
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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!
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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)
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
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NIEHS Workshop28 February 2005
Department of Civil and Environmental Engineering
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NIEHS Workshop28 February 2005
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
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NIEHS Workshop28 February 2005
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)
Department of Civil and Environmental Engineering
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NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
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NIEHS Workshop28 February 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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
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NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
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NIEHS Workshop28 February 2005
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
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NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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.
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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)
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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.
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005
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)
Department of Civil and Environmental Engineering
Department of Civil and Environmental Engineering
NIEHS Workshop28 February 2005