AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersach sen Lüneburg Buxtehud e Suderbur An Introduction To Permeable Reactive Barriers (PRB) Volker Birke Ernst Karl Roehl University of Applied Sciences Fachhochschule Nordostniedersachs en University of Karlsruhe Applied Geosciences Karlsruhe
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AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg.
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AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
An Introduction ToPermeable Reactive Barriers (PRB)
Volker Birke Ernst Karl Roehl
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
University of Karlsruhe Applied GeosciencesKarlsruhe
AGK Applied Geosciences University of KarlsruheKarlsruhe
"passive in situ treatment zones of reactive material that degrades or immobilizes contaminants as ground water flows through it. PRBs are installed as permanent, semi-permanent, or replaceable units across the flow path of a contaminant plume. Natural gradients transport cont-aminants through strategically placed treatment media. The media degrade, sorb, precipitate, or remove chlo-rinated solvents, metals, radionuclides, and other pollutants."
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Source: http://www.eti.ca/eti.html
AGK Applied Geosciences University of KarlsruheKarlsruhe
Inorganic contaminants: abiotic reductive immobilisation of heavy metals and others (e.g., Cr, U, Mo, Tc, As, NO3).
Costs: 200 - 400 €/t
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Source: Gillham & O'Hannesin, 1994
Results of column tests conducted using commercial iron and groundwater from a contaminant plume at an industrial site. PCE dechlorination, formation of cDCE, and subsequent cDCE degradation.
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Degradation of chlorinated hydrocarbons
Electron transfer from Fe0 surface (oxidation) to the chlorinated hydrocarbon (reduction, dehalogenation):
2Fe0 2Fe2+ + 4e-
3H2O 3H+ + 3OH-
2H+ + 2e- H2
X-Cl + H+ + 2e- X-H + Cl-
2Fe0 + 3H2O + X-Cl 2Fe2+ + 3OH- + H2 + X-H + Cl-
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Removal of uranium and molybdenum from contaminated groundwater in porous Fe0 aggregates of a PRB system (Durango uranium mill tailings, Colorado, USA).
Uranium Molybdenum
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Reductive immobilisation of heavy metals
Reduction of mobile and oxidised metal compounds followed by mineral precipitation
Coatings might block access to the reactive surfaces. Further precipitation blocks the pore spaces between some iron particles increa-sing flow velocity and decrea-sing the residence time.
Coatings
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Iron corrosion
Anoxic: Fe0 Fe2+ + 2e-
2H2O 2H+ + 2OH-
2H+ + 2e- H2
Fe0 + 2H2O Fe2+ + H2 + 2OH-
Oxic: Fe0 Fe2+ + 2e-
H2O H+ + OH-
½O2 + 2e- O2-
Fe0 + H2O + ½O2 Fe2+ + 2OH-
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Precipitation of secondary minerals
Carbonates
HCO3- + OH- CO3
2- + H2O
Fe2+ + CO32- FeCO3 (s)
Ca2+ + CO32- CaCO3 (s)
Iron minerals
Fe2+ + 2OH- Fe(OH)2 (s)
3Fe(OH)2 (s) Fe3O4 (s) + 2H2O + H2
Magnetite
Calcite
Siderite
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Stability fields for the system Fe-CO2-H2O with the following solid phases:
• Am. iron hydroxide Fe(OH)3
• Siderite FeCO3
• Iron hydroxide Fe(OH)2
• Zero-valent iron Fe(25°C, Fetotal = 10-5 M, Ctotal = 10-3 M, from: Stumm & Morgan 1996).
Iron geochemistry
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Carbonate, Ca and Fe concentration in ground-water passing through a Fe0 wall.Obvious precipitation of calcite and siderite, especially in the upstream pea gravel (Denver Federal Center, Denver, USA).
Clogging
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Carbonate precipitation
Source: Vogan, J.L. et al. (2000), J. Haz. Mat., 68, 97-108.
Carbonate concentrations in the zero-valent iron filling of a Fe0 wall (industrial site contaminated by chlorinated hydrocarbons, New York, USA).
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Silicon dioxide
Distribution of dissolved silicon dioxide in a Fe0 wall (Moffett Naval Station, Mountain View, CA).
Source: Gavaskar et al. (2000)
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Dissolved iron with pH in Fe0 column experiments (ZVI): Clear dissolution of iron, but only relevant at pH values < 7.
Source: U.S. Department of Energy Grand Junction Office (GJO)http://www.doegjpo.com/perm-barr/
Consumption
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Decrease of concentration in the wall:Ca, Mg, Si, bicarbonate, sulphate, H+
Showing some influence on the reaction kinetics (corrosion, dehalogenation):Bicarbonate, sulphate, nitrate, phosphate, chloride, dissolved oxygen
Groundwater constituents
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Mass balancing
Precipitation in a Fe0 wall, Copenhagen, Denmark (Kiilerich et al., 2000):
13,3 kg iron hydroxides, 2,7 kg CaCO3, 2,7 kg FeCO3 and 0,8 kg FeS per 1000 kg iron filling per year
Loss of porosity in a Fe0 wall, Denver Federal Center, Denver, USA (McMahon et al., 1999):
0,35 % of total porosity per year (calculated only for the assumed precipitation of calcite and siderite)
Zero-valent Iron (Fe0) Walls
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Activated carbon:
• Adsorption of organic contaminants
• Specific surface: approx. 1000 m2/g
• Granular
Reaction kinetics: Diffusion controlled
Critical parameter: contact time!
Activated Carbon
AGK Applied Geosciences University of KarlsruheKarlsruhe
Chlorobenzene: R 10000 - 20000(Köber et al., 2001)
Activated Carbon
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
d = reactive wall thickness
va = groundwater flow velocity
R = retardation factor
Maximum barrier life-time estimation:
Horizontal flow through an activated carbon reactor of 1,8 m diameter with a flow velocity of 0,5 m/d and a retardation factor of R = 3000: maximum life-time = 30 years
Rvd
ta
S
Activated Carbon
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Groundwater composition
Competition effects: Natural groundwater constituents and contaminants compete for the adsorption sites
Precipitation of secondary minerals: Coatings block the access to the particle surfaces and alter the reaction kinetics
Formation of biomass
Negative effect: clogging of the free pore space
Positive effect: biological degradation of sorbed contaminants possible
Factors influencing barrier life-time:
Activated Carbon
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
PRB Construction
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Karlsruhe, Germany
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Monitoring
Targets:
Validation of Performance
Longevity
AGK Applied Geosciences University of KarlsruheKarlsruhe
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Focus of current R&D:
Selection of appropriate materials and processes for selective and efficient removal of groundwater pollutants.
Current Research
Evaluation of longevity and long-term performance; development of models.
Upscaling – applicability and transfer of lab-scale results into the field
Hydraulics of PRBs.
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Current Research: Tri-Agency-Initiative
Tri-Agency Initiative, USA:
US EPA US DOE US DoD
USCG Base,Elizabeth City, NC
Y-12 Plant, OakRidge, TN
Dover AFB, Dover,DE
Denver Fed.Center, Denver, CO
Kansas City Plant,Kansas City, MO
Lowery AFB,Denver, CO
SomersworthLandfill,Somersworth, NH
DOE Uranium Mill,Monticello, UT
Moffett NavalStation, MountainView, CA
Alameda NavalSta., Alameda, CA
Watervliet Arsenal,Watervliet, NY
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Current R&D
„Reaktionswände und -barrieren im Netz-werkverbund“ („RUBIN“), BMBF, Germany
PRB projects co-operating in a network (RUBIN) Launched May 2000, 3 years Financial means: ca. 4 Mill. Euro. Coordination: University of Applied Sciences (Prof. H.
Burmeier, Dr. V. Birke, Dipl.-Ing. D. Rosenau) 11 projects 8 projects dealing with design, erection and operation
of pilot- or full-scale PRBs in Germany and/or important general preparatory R&D work
3 projects addressing general issues and missions.
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Conclusions
PRB long-term behaviour is a function of the deployed reactive material.
PRB longevity is influenced by the pollutants to be treated and the groundwater ingredients, i.e., groundwater chemistry.
The main groundwater components reveal a specific, important influence predominantly due to their higher concentrations compared to the pollutant´s concentrations.
Surface reactions at the reactive material cause significant changes in geochemical conditions (pH, Eh) regarding pore space that is passed by groundwater and therefore hydrochemical changes in the composition of the groundwater.
AGK Applied Geosciences University of KarlsruheKarlsruhe
Universityof Applied Sciences
FachhochschuleNordostniedersachsen
LüneburgBuxtehudeSuderburg
Conclusions
Mineral formation (coatings), alteration of surfaces, gas evolution and biomass can influence reactivity and permeability of a PRB.
Alteration of surfaces and mineral formation can be mostly observed directly upgradient of a PRB.
However, only pertaining to a few cases, detrimental effects regarding efficiency of the PRB have been observed so far.
Geochemical processes are predominantly well-known and well understood. However, quantitative approaches for long-term behaviour/performance are still lacking. Current R&D projects address these issues.