Contaminated Land

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Contaminated Land Remediation Reclamation Techni
ques
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• 1GS312 CONTAMINATED LAND
• 1GS418 FUNDEMENTALS OF CONTAMINATED LAND

SCHOOL OF EARTH ENVIRONMENTAL
SCIENCES Contaminated Land Remediation
Reclamation Techniques
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Waste Remediation

• Contaminated Land Remediation Reclamation
  Techniques
• Aims
• Treatments Methods
• Innovative Technologies
• Data information sources

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Aims

• To return land to beneficial use
• To prevent contaminants on land from causing
  damage
• Principal determinants for choice of reclamation
  method
• Cost
• Regulatory Framework

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Treatment Of Contaminated Land

• Reduce the amount of toxic materials being dealt
  with by confinement in landfill
• Increase the separation of contaminants from the
  matrix which they are polluting
• Thus
• Reducing volumes of waste generated
• Conserving soil water

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Reclamation Methods

• Traditional methods
• Isolation
• Covering
• Removal
• Decontamination techniques

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Isolation Removal

• Isolation
• Capping
• Covering
• Vertical Barriers
• Diversion Trenches
• Break Layers
• Horizontal Barriers
• Removal
• Excavation
• Total Containment

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Decontamination Techniques

• Separation, Destruction, Stabilisation
• Vapour Extraction
• In-Situ Ex-Situ Bioremediation
• Soil Washing
• Containment
• Stabilisation / Solidification
• Vitrification
• Solvent Extraction
• Pump Treat
• Leaching

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Capping Covering

• Isolation of contaminants from potential targets
• Prevention of exposure to transport media
• Control of gas, leachate capillary water
• Ground improvement for construction
• Providing a substrate for vegetation
• Conflict between different aims may be difficult
  to overcome
• May lack permanency susceptible to damage
• Requires specialist input in design
  construction to ensure meets performance
  standards
• Ineffective against lateral groundwater movements

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Cover Systems

• Cover system for contaminated land incorporating
  a clay cap break layer

Geomembrane
Clay Cap
Break Layer
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Cover Systems

• Cover systems used in metalliferous mine
  reclamation schemes

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Diversion Trenches

• Cut-off drainage around contaminated areas
• Temporary measure during excavation
• Facilitates the removal of contaminants during
  pump treat operations
• To lower groundwater table to facilitate other
  measures
• Limited applicability to impermeable soils
• Need for specialist input
• Requires long-term monitoring maintenance

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In-ground Barriers

• Minimise lateral vertical movement of
  contaminants, gases water
• Vertical Barriers
• Displacement Barriers
• Excavated Barriers
• Injection Systems
• Horizontal barriers used where a contaminant
  source is underlain by permeable materials
• Usually installed using injection / grouting
  methods

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In-ground Barriers

• Specialist input needed
• Difficult to install in heterogeneous ground
  conditions
• Requires long-term maintenance monitoring
• Vertical membrane installation can be difficult
• If not properly installed can lead to costly
  remediation measures
• Sheet piles are costly to install are not
  impermeable

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Vertical Barrier

• Vertical barrier cut-off drainage in use with
  a simple capping system

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Excavation

• Used to remove materials from site for final
  disposal or treatment
• Disposal may be on or off - site, with or without
  treatment
• Both contamination poor ground conditions are
  remediated at the same time
• Complete removal of contaminants may not be
  achieved
• Does not destroy contaminants
• Long-term maintenance monitoring of disposal
  areasrequired

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Decontamination Techniques

• Thermal
• Separation
• Solidification / Stabilisation
• Chemical Methods
• Biological Methods
• In-Situ
• Ex-Situ

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Thermal Treatment

• Incineration
• Destructive
• Off-Site
• Waste Emissions / Ash
• Thermal Desorption
• Removes Volatiles Semi-Volatiles
• Vitrification
• Intense heat required
• Mixes silica other vitrification materials
• Drives off Volatiles

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Thermal Treatment

• Incineration Methods
• Rotary Kiln
• Infrared
• Fluidized Bed
• Desorption Methods
• Ex-Situ Thermal Desorption
• In-Situ Stripping

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Separation Techniques

• Vacuum Extraction
• Soil Washing
• Solvent Extraction
• Electrokinetics
• Leach, Pump Treat

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Vacuum Extraction

• Schematic vacuum extraction system

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Groundwater Treatment

• Dual pumping system for groundwater treatment

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Innovative Treatment Technologies

• Innovative Treatment Technologies
• Soil Vapour Extraction
• Bioremediation, Natural Attenuation
• Soil Washing, In-Situ Soil Flushing
• Chemical Dehalogenation
• Thermal Desorption
• Solvent Extraction
• Air Sparging
• Phytoremediation
• Treatment Walls
• Electrokinetics
• Fracturing

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Bioremediation

• Uses naturally occurring micro-organisms
• Breaks down hazardous substances into less toxic
  or non-toxic materials
• Cost-effective, natural process
• Applicable to many common organic wastes
• Techniques can be conducted on-site
• Indigenous or Exogenous Micro-organisms
• Aerobic or Anaerobic conditions
• In-Situ or Ex-Situ

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In-situ Bioremediation

• Permeable soils
• Bioventing
• Injection of Hydrogen Peroxide
• Groundwater

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Bioventing
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In-situ Chemical Oxidation
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Ex-situ Bioremediation

• Slurry-Phase Bioremediation
• Bioreactor
• Solid-Phase Bioremediation
• Landfarming
• Soil Biopiles
• Composting

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In-situ Biological Treatment
Idealised recirculating in-situ biological
treatmentprogramme
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Soil Washing

• Separates silt clay from sand gravel
• Significantly reduces the volume of contaminated
  soil
• Relatively low-cost alternative for separating
  waste minimising volume for subsequent
  treatment
• Transportable technology that can be brought to
  site
• Used to treat a wide range of contaminants
• Provides a closed system, unaffected by external
  conditions
• Allows hazardous wastesto be excavated
  treatedon-site
• Has the potential to remove a wide variety of
  chemical contaminants from the soil is cost
  effective

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Soil Washing Process
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In-situ Soil Flushing

• Injects a washing solution into unexcavated soils
• Flushes out the contaminants
• Most effective in soils with low silt or clay
  contents
• Requires the drilling of injection extraction
  wells on-site

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In-situ Soil Flushing

• Requires greater understanding of the sites
  geology than some other technologies
• Subsurface geological profile critical
• Extensive field investigations may be necessary
  to define the groundwater flow
• Groundwater flow must be understood
• Tailored to treat specific contaminants
• Not highly effective with cocktails

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In-situ Soil Flushing Process
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In-situ Soil Flushing
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Soil Flushing

• In-situ solvent flushing

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Phytoremediation

• Aesthetically-pleasing, passive, solar energy(!)
  driven clean-up technique
• Most useful at sites with shallow, low levels of
  contamination
• Useful for treating a wide variety of
  environmental contaminants
• Plants break down organic pollutants or
  stabilise metal contaminants
• Act as filters or traps

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Phytoremediation

• Metals Remediation
• Phytoextraction
• Rhizofiltration
• Treating Organic Contaminants
• Phytodegradation
• Enhanced Rhizosphere Biodegradation
• Phytovolitilization

Photograph of Hybrid Poplar Field
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Phytoremediation

• Rhizofiltration
• The absorption, concentration, precipitation of
  heavy metals by plant roots
• Phytoextraction
• The extraction accumulation of contaminants in
  harvestable plant tissues including roots
  surfaceshoots
• Phytotransformation
• The degradation of complex organic molecules to
  simple molecules the incorporation of these
  molecules intoplant tissues

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Phytoremediation

• Phytostimulation or plant-assisted bioremediation
• The stimulation of microbial fungal degradation
  by release of exudates/enzymes into the root zone
  (rhizosphere)
• Phytostabilization
• Involving absorption precipitation of
  contaminants, principally metals, by plants,
  reducing their mobility preventing their
  migration to groundwater (leaching) or air
  (wind transport), or entry into the food chain

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UPTAKE OF METALS

• Uptake of Nickel by Phytoextraction

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Destruction of Organics

• Destruction of organic contaminants by
  phytodegradation

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Chemical Dehalogenation

• Used to treat halogenated aromatic organic
  contaminants
• e.g. PCB's Dioxins
• Chemically converts toxic materials to less toxic
  or non-toxic substances
• Involves heating physically mixing
  contaminated soils with chemical reagents
• Transportable technology
• Glycolate Dehalogenation
• Base-Catalysed Decomposition Process

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Glycolate Dehalogenation
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Base-catalysed Decomposition
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Natural Attenuation

• Uses naturally occurring environmental process to
  clean-up site
• Non-invasive
• Allows site to be put to productive use while
  being cleaned-up
• Requires careful study of site conditions
  monitoring of contaminant levels
• Biodegradation
• Dilution Dispersion
• Adsorption

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Aerobic Biodegradation
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Solvent Extraction

• Separates contaminants so that they may be
  treated individually
• Solvent separates or removes hazardous organic
  contaminants
• Does not destroy contaminant but concentrates
  them
• Can then be easily recycled or destroyed by
  another technology
• Transportable technology
• Reduces volumes of contaminated materials
• Process up to 125 tonnes of waste per day
• Designed to operate without air emissions

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Solvent Extraction Process
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Soil Vapour Extraction

• Pulls contaminants from soil in vapour form
• Provides an oxygen source which may stimulate
  bioremediation of some contaminants
• Very commonly used technique
• Removes VOC's SVOC's from the unsaturated zone
• SVE with Thermal Enhancement
• Dual Phase Extraction

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Air Sparging

• Extends the effectiveness of soil vapour
  extraction to include contaminants that exist in
  groundwater
• Can accelerate clean-up at pump treat sites
• Provides an oxygen source which may stimulate
  bioremediation of some contaminants

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Air Sparging

• Involves the injection of air or another gas,
  under pressure, into the saturated zone
• Creates subsurface bubbles or air pathways
  horizontally and vertically from the injection
  point
• Causes contacting and mixing between the injected
  gas the subsurface soil and groundwater that
  partitions contaminants into the vapour phase

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Combined SVE Air Sparging
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Vacuum Extraction
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Thermal Desorption

• Heats soil at relatively low temperatures to
  vaporise contaminants remove them
• Most effective at treating VOC's, SVOC's other
  organic contaminants
• Such as PCB's, PAH's pesticides
• Useful for separating organic contaminants from
  refining wastes, coal tar wastes, wood treatment
  wastes paint wastes

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Thermal Desorption

• Thermal Desorption System
• Pre-treatment Material Handling System
• Desorption Unit (Rotary, Direct-fired,
  Indirect-fired)
• Post Treatment System

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Thermal Enhancements

• Soil heating effective in expelling organics
• RF heating
• Electrical resistance heating

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Thermal Desorption Process
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Treatment Walls

• Passive system that requires no mechanical
  equipment or energy source
• Allows the site to be put to productive use while
  they are being cleaned up
• Can be modified to treat different types of
  contaminants
• Completely breaks down some organic contaminants
• Sorption Barriers
• Precipitation Barriers
• Degradation Barriers

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Treatment Walls
Ground Surface
Treatment Wall
Contaminated Groundwater
Clean Groundwater
Direction of Groundwater Flow
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Treatment Walls

• Sorption

Zeolites or Active Carbon
Contaminants are pulled, unchanged, from
groundwater are held by wall surface
Treatment Wall
Clean Groundwater
Direction of Groundwater Flow
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Treatment Walls

• Precipitation

Limestone
Contaminants are changed into solid forms that
remain in the wall
Treatment Wall
Clean Groundwater
Direction of Groundwater Flow
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Treatment Walls

• Degradation

Iron Granules or Nutrients / Oxygen for
Biodegradation
Contaminants are broken down into harmless
products that flow through the wall
Treatment Wall
Clean Groundwater
Direction of Groundwater Flow
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Fracturing

• Pneumatic Fracturing
• Injection of highly pressurized air into
  consolidated sediments
• Extends existing fractures
• Creates a secondary network of fissures
  channels
• Enhances fracture network
• Accelerates removal of contaminants
• Vapour extraction
• Biodegradation
• Thermal treatment

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Pneumatic Fracturing

• Involves the injection of air or another gas
  under pressure, into unsaturated zone, creating
  micro-fractures for the advective transport of
  contaminants
• Increases the number of subsurface pathways for
  advective flow
• Results in increased contaminant mass removal
  accelerated remediation

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Fracturing

• Hydrofracturing
• Creates distinct sand filled fractures in low
  permeability over-consolidated clays or
  sediments
• Fractures serve as avenues for bioremediation,
  steam or hot air injection

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Electrokinetics

• Process that separates extracts heavy metals,
  radionuclides organic contaminants from
  saturated soils, sludges sediments
• Electro-osmosis

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Geochemical Fixation

• Geochemically fixes inorganic contaminants
  in-place
• Introduces chemical reagents
• Capable of altering pH or redox conditions to
  render the inorganic insoluble
• Geochemically react with metal or metal complex
  with natural soil or sediment material
• Cleaning up, or "fixing," the inorganic
  contaminant in-place

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Selected References

• Harris J., Birch P. Palmer J. (1996) Land
  Restoration Reclamation - Principles
  Practice, Longman
• Cairney T. (1987) Reclaiming Contaminated Land.
  Blackie.
• Smith M.A. (1985) Contaminated Land Reclamation
  Treatment. Plenum.
• Welsh Development Agency (1993) The WDA Manual on
  the remediation of Contaminated Land. WDA.
• Richards I.G. et al (1993) The Reclamation of
  Former Coal Mines Steelworks. Elsevier.

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Web Resources

• Hazardous Waste Clean-up Information
• http//www.clu-in.com
• Citizen's Guides to Understanding Innovative
  Treatment Technologies
• http//www.clu-in.com/citguide.htm
• Remediation Technologies Screening Matrix
  Reference Guide
• http//www.clu-in.com/remed1.htm
• Internet On-line Resources
• http//www.clu-in.com/resourc1.htm

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Web Resources

• US EPA Technology Innovation Office
• http//www.clu-in.org/

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Web Resources

• Tool Kit of Information Resources for Brownfields
  Investigation and Cleanup
• http//www.clu-in.org/products/toolkit99/start.htm

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Web Resources

• Terra Vac
• http//www.terravac.com/
• Ground-water Remediation Technologies Analysis
  Centre
• www.gwrtac.org