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Two Union Square - 601 Union Street, Suite 601Seattle, WA 98101-2341
(206) 292-2078www.floydsnider.com
Field testing and modeling of in situ groundwater arsenic remediation through iron sulfide precipitation
near Tacoma, WashingtonBrett Beaulieu and Samantha Ewing
Overview
Arsenic cleanup at B&L Woodwaste SitePilot injection, two application rates of EHC-MModeling pyrite precipitation and oxidative dissolution
2009 GSA Annual Meeting, Portland OR
B&L Woodwaste Site
CleanupGoals
Physically contain sourceTreat leading plume edge in situRemediate plume remainder
Study area
100 ft
Groundwater Flow direction
Wetlands
Landfill
2009 GSA Annual Meeting, Portland OR
Shallow Alluvial Sand Aquifer
Groundwater Flow direction Study area
WetlandsLandfill
Groundwater arsenic plume
2009 GSA Annual Meeting, Portland OR
Goals of current study
Add to limited reductive precipitation field dataArsenic remediation pilot:
Effectiveness and time requiredDosagePermeable reactive barrier (PRB)Pyrite as arsenic sink Pyrite stability, pH in oxic groundwater
2009 GSA Annual Meeting, Portland OR
Methods
Pilot injection of EHC-MCommercial product (Adventus)Slurry: carbon, zerovalent iron, sulfateGroundwater monitoring
Kinetic reaction path modeling (Geochemist’s Workbench)
pyrite precipitation oxidative dissolution
Methods: Pilot Study
2009 GSA Annual Meeting, Portland OR
Groundwater monitoring5 events/6 monthsTotal and dissolved As, Fe Sulfate/sulfideDissolved organic carbon (DOC)Redox-sensitive metalspH, ORP, DO, T
Treated depth:12 – 22 feet below ground
Two injection zones:0.6% soil weight0.2% soil weight
0.2% 0.6%
PD-105 PD-106
PD-122
2009 GSA Annual Meeting, Portland OR
Methods: Pilot Injection
Methods: Pilot Injection
2009 GSA Annual Meeting, Portland OR
Methods: Pilot Injection
2009 GSA Annual Meeting, Portland OR
Methods: Pilot Injection
2009 GSA Annual Meeting, Portland OR
2009 GSA Annual Meeting, Portland OR
Baseline : Total As, Feb.
As concentrations over time
2009 GSA Annual Meeting, Portland OR
Results: Total As, March
As concentrations over time
2009 GSA Annual Meeting, Portland OR
Results: Total As, April
As concentrations over time
2009 GSA Annual Meeting, Portland OR
Results: Total As, May
As concentrations over time
2009 GSA Annual Meeting, Portland OR
Results: Total As, August
As concentrations over time
2009 GSA Annual Meeting, Portland OR
Results: Arsenic removal
Arsenic removal plotInjection
PD-105 (0.2%)
PD-122 (between treatment zones)
PD-106 (0.6%)
Results: Dissolved Iron
2009 GSA Annual Meeting, Portland OR
PD-105 (0.2%)
PD-106 (0.6%)
Injection
Results: Sulfate
2009 GSA Annual Meeting, Portland OR
Injection
PD-105 (0.2%)
PD-106 (0.6%)
Results: Pyrite oxidative dissolution
2009 GSA Annual Meeting, Portland OR
Dissolution rates ~10-10 mol/sec 20% dissolved in 30-day experiment83% dissolved in 1-year experiment/100% in 5-year
Results: pH and pyrite dissolution
2009 GSA Annual Meeting, Portland OR
pH decreases to below 5 in 1-year, 5-year experiment
Conclusions
EHC-M treatment at 0.2% soil weight removed 67% As in 5-m pilot Treatment at 0.6% (10% pore space) may hinder flux and treatmentPyrite a realistic sink for injection PRB application of EHC-MPyrite and pH stable during short- to medium-term oxic events
2009 GSA Annual Meeting, Portland OR
Full-scale treatment: Dec 2009
2009 GSA Annual Meeting, Portland OR
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