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AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg.

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Presentation on theme: "AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg."— Presentation transcript:

1 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg An Introduction To Permeable Reactive Barriers (PRB) Volker Birke Ernst Karl Roehl University of Applied Sciences Fachhochschule Nordostniedersachsen University of Karlsruhe Applied Geosciences Karlsruhe

2 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg EPA (1999), Remedial Technology Fact Sheet, 542-R Definition: Permeable Reactive Barriers are "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."

3 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Source:

4 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg GW DNAPL plume Aquitard contamination source heavy metals Aquifer LNAPL reactive barrier clean groundwater LNAPL = light non-aqueous phase liquids DNAPL = dense non-aqueous phase liquids

5 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg "Emission oriented remediation approach"  Decontamination of the plume (vs. removal of the contaminant source) Passive system  No active pumping of groundwater  Low maintenance following installation PRB Concept:

6 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Basic Concept: "Emission oriented remediation approach"  Clean-up of the plume, not the source Passive system:  No pumping required Application:  Unclear location of source(s)  Slow contaminant release from source  Low solubility of contaminants  Large volumes of contaminated soil  Built-up areas

7 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Treatability Study:  Choice of attenuation mechanism and reactive material  Column tests  Determination of required residence time  Calculation of barrier thickness Site Characteristics:  Flow field (hydraulics)  Contaminant concentrations  Total contaminant mass expected  Groundwater characteristics

8 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Degradation: Chemical and/or biological reac- tions converting the contaminants to harmless by-products. Sorption: Contaminant removal from ground- water through adsorption or complexation. Precipitation: Fixation of contaminants in insoluble compounds and minerals. Types of reactive walls:

9 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Types of reactive walls: a) Continuous Barrier (CRB)b) Funnel-and-gate (F&G) system

10 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Source: Gavaskar et al. 1998

11 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg  High contaminant attenuation  Good selectivity for target contaminants  Fast reaction rates  High hydraulic permeability  Long-term stability  Environmental compatibility  Sufficient availability in homogenous quality  Cost-effectiveness Reactive Material Requirements

12 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Main source: Dahmke et al. (1996) + own additions Reactive Materials targeting Organic Contaminants

13 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Main source: Dahmke et al. (1996) + own additions Reactive Materials targeting Inorganic Contaminants

14 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Hydraulic conductivity: A minimum permeability must be guaranteed during barrier operation to avoid that contaminated groundwater by-passes the system. Homogeneity: In areas of favoured flow-paths there is the danger of a fast consumption of the reactive material's contaminant attenuation capability. PRB Operating Requirements

15 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Period during which the reactive material keeps its ability to remove the target contaminants from the groundwater. Barrier life-time: Period during which the PRB keeps its hydraulic performance. PRB Operating Requirements

16 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg  Type and concentration of contaminants  Type and kinetics of sorption and/or degradation processes.  Type and mass of reactive material  Hydraulic characteristics of the site (flow velocity)  Geochemical characteristics of the ground- water (Eh, pH, composition) Long-term Performance Aspects The barrier life-time is governed by:

17 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Considerations on mass flux Hydraulic model of the former gas works site in Portadown, Northern Ireland. Source: Kalin, R., presentation at PRB-net Workshop, April 2001, Belfast, Northern Ireland Long-term Performance Aspects

18 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg  Coatings on the particle surface of the reactive material by  precipitation of secondary minerals  corrosion ("rust") Processes that might impair the long-term performance of PRBs:  Clogging of the pore space between the particles by  precipitation of secondary minerals  gas formation (H 2 )  Biomass production  Consumption of the reactivity by  arriving at the material's sorption capacity  dissolution of the reactive material Long-term Performance Aspects

19 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg granular Fe 0 foamed Fe 0 aggregates Organic contaminants: abiotic reductive degradation of chlorinated hydrocarbons (e.g., PCE, TCE, VC) Inorganic contaminants: abiotic reductive immobilisation of heavy metals and others (e.g., Cr, U, Mo, Tc, As, NO 3 ). Costs: €/t Zero-valent Iron (Fe 0 ) Walls

20 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg 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 (Fe 0 ) Walls

21 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Degradation of chlorinated hydrocarbons Electron transfer from Fe 0 surface (oxidation) to the chlorinated hydrocarbon (reduction, dehalogenation): 2Fe 0  2Fe e - 3H 2 O  3H + + 3OH - 2H + + 2e -  H 2 X-Cl + H + + 2e -  X-H + Cl - 2Fe 0 + 3H 2 O + X-Cl  2Fe OH - + H 2 + X-H + Cl - Zero-valent Iron (Fe 0 ) Walls

22 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Source: Removal of uranium and molybdenum from contaminated groundwater in porous Fe 0 aggregates of a PRB system (Durango uranium mill tailings, Colorado, USA). Uranium Molybdenum Zero-valent Iron (Fe 0 ) Walls

23 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Reductive immobilisation of heavy metals Reduction of mobile and oxidised metal compounds followed by mineral precipitation Chromium:Fe 0  Fe e - 2H 2 O  2H + + 2OH - 2H + + 2e -  H 2 Fe 0  Fe e - Cr (VI) O H 2 O + 3e -  Cr (III) (OH) 3 + 5OH - Fe 0 + Cr (VI) O H 2 O  Fe (III) Cr (III) (OH) 6 + 2OH - Zero-valent Iron (Fe 0 ) Walls

24 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Source: Powell & Associates Science Services 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 (Fe 0 ) Walls

25 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Iron corrosion Anoxic:Fe 0  Fe e - 2H 2 O  2H + + 2OH - 2H + + 2e -  H 2 Fe 0 + 2H 2 O  Fe 2+ + H 2 + 2OH - Oxic:Fe 0  Fe e - H 2 O  H + + OH - ½O 2 + 2e -  O 2- Fe 0 + H 2 O + ½O 2  Fe OH - Zero-valent Iron (Fe 0 ) Walls

26 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Precipitation of secondary minerals Carbonates HCO OH -  CO H 2 O Fe 2+ + CO 3 2-  FeCO 3 (s) Ca 2+ + CO 3 2-  CaCO 3 (s) Iron minerals Fe OH -  Fe(OH) 2 (s) 3Fe(OH) 2 (s)  Fe 3 O 4 (s) + 2H 2 O + H 2 Magnetite Calcite Siderite Zero-valent Iron (Fe 0 ) Walls

27 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Stability fields for the system Fe-CO 2 -H 2 O with the following solid phases: Am. iron hydroxide Fe(OH) 3 Siderite FeCO 3 Iron hydroxide Fe(OH) 2 Zero-valent iron Fe (25°C, Fe total = M, C total = M, from: Stumm & Morgan 1996). Iron geochemistry Zero-valent Iron (Fe 0 ) Walls

28 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Source: McMahon, P.B., Dennehy, K.F. & Sandstrom, M.W. (1999), Ground Water, 37, Carbonate, Ca and Fe concentration in ground- water passing through a Fe 0 wall. Obvious precipitation of calcite and siderite, especially in the upstream pea gravel (Denver Federal Center, Denver, USA). Clogging Zero-valent Iron (Fe 0 ) Walls

29 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Carbonate precipitation Source: Vogan, J.L. et al. (2000), J. Haz. Mat., 68, Carbonate concentrations in the zero-valent iron filling of a Fe 0 wall (industrial site contaminated by chlorinated hydrocarbons, New York, USA). Zero-valent Iron (Fe 0 ) Walls

30 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Silicon dioxide Distribution of dissolved silicon dioxide in a Fe 0 wall (Moffett Naval Station, Mountain View, CA). Source: Gavaskar et al. (2000) Zero-valent Iron (Fe 0 ) Walls

31 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Dissolved iron with pH in Fe 0 column experiments (ZVI): Clear dissolution of iron, but only relevant at pH values < 7. Source: U.S. Department of Energy Grand Junction Office (GJO) Consumption Zero-valent Iron (Fe 0 ) Walls

32 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg  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 (Fe 0 ) Walls

33 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Mass balancing Precipitation in a Fe 0 wall, Copenhagen, Denmark (Kiilerich et al., 2000): 13,3 kg iron hydroxides, 2,7 kg CaCO 3, 2,7 kg FeCO 3 and 0,8 kg FeS per 1000 kg iron filling per year Loss of porosity in a Fe 0 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 (Fe 0 ) Walls

34 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Activated carbon: Adsorption of organic contaminants Specific surface: approx m 2 /g Granular Reaction kinetics: Diffusion controlled  Critical parameter: contact time! Activated Carbon

35 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Retardation factor: f(c) = adsorption isotherm (linear, Freundlich, Langmuir) v a = groundwater flow velocity v S = contaminant transport velocity Retardation: PAH:R > 3000(Schad & Grathwohl, 1998) Trichloroethene:R  Chlorobenzene:R  (Köber et al., 2001) Activated Carbon

36 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg d = reactive wall thickness v a = 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 Activated Carbon

37 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg 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

38 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg PRB Construction

39 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Karlsruhe, Germany

40 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Monitoring Targets: Validation of Performance Longevity

41 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg  Checking of hydraulics  Checking groundwater chemistry Hydrochemical parameters: pH, electr. conductivity cations: Ca 2+, Mg 2+, Fe t, anions: HCO 3 -, SO 4 2-, Cl -, PO 4 2-, NO 3 -  Investigation of the reactive material Coring: carbonate, XRD, REM Longevity: Monitoring

42 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg 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.

43 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg Current Research: Tri-Agency-Initiative Tri-Agency Initiative, USA:

44 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg 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.

45 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg 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.

46 AGK Applied Geosciences University of Karlsruhe Karlsruhe University of Applied Sciences Fachhochschule Nordostniedersachsen Lüneburg Buxtehude Suderburg 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.


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