Contaminated Land

1
Contaminated Land

• Full-Scale Remediation Technologies
• Physical
• Chemical
• Thermal

2
Physical Remediation Technologies

• Overview and Principles
• Physical Technologies
• Ex Situ
• Soil Washing
• In Situ
• Soil Vapour Extraction
• Electro-Remediation
• Examples

3
Physical Remediation TechnologiesOverview and
Principles

• Soil Washing (Bergmann, Lurgi, BioTrol)
• intensive, water-based removal of non- and
  semi-volatile contaminants from soil
• washed fractions replaced
• contaminated fractions to disposal or further
  treatment
• Soil Vapour Extraction (SVE) or Venting
• extensive, vacuum extraction of vapour phase from
  between soil particles advection for sorbed
  organics
• extracted vapours further treated
• Electrokinetic Remediation (Geokinetics BV)
• electrical current (DC) transports charged
  (ionic) contaminants towards electrodes
• contaminants accumulate at electrode

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Physical Remediation TechnologiesEx Situ Soil
Washing

• Pretreatment
• screening, crushing
• Washing and Rinsing
• Slurrying, attrition scrubbing, ultrasonic
  treatment
• reduced to individual particle size
• Particle Sizing and Classification
  (Fractionation)
• sedimentation, hydrocyclones, sieving and
  screening
• (cf.sand and gravel operations)
• flotation
• flocculants, dewatering
• Clean Coarse Fractions
• Contaminated Fines - clays, humics
• Wastewater Treatment
• wash water recycle
• Process works better with coarser soils
• Soil structure impaired

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Physical Remediation TechnologiesEx Situ Soil
Washing

• Time
• Intensive process (days - weeks)
• Costs
• 20 - 160 per m3
• silt and clay content significant determinant
• (economic upper limit of 30 - 40)
• Resources
• plant and power
• Application Range
• most volatile and non-volatile organics
• inorganics, heavy metals
• Not Asbestos

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Example Ex Situ Soil Washing

• Site
• Canal Sediment, Birmingham
• Contamination
• Zinc, copper, nickel, chromium
• mineral oils
• Remediation Method
• soil washing
• landfill of contaminated fines
• Performance
• 90 contaminants concentrated into reduced
  volume
• (30 of original sediment)
• Time
• months due to low capacity of system (10m3 /day)
• Cost
• 30 per m3 including disposal off-site

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Soil washing
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Physical Remediation TechnologiesIn Situ Soil
Vapour Extraction

• Established Process (Terra Vac )
• also known as Soil Venting
• Extraction Wells
• slotted PVC pipe, grouted upper section
• depth 1.5m to 90m (Vadose only)
• numbers depend on soil permeability
• placement critical - short circuiting
• Soil surface preparation - compaction, membranes
• Infiltration Wells
• optional
• passive or forced flow
• Induced air flow aids bioremediation
• Groundwater Abstraction
• depression of groundwater table (greater
  exposure)

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Physical Remediation TechnologiesIn Situ Soil
Vapour Extraction

• Critical Factors
• Boiling point / vapour pressure
• volatility VOC only (KH gt 10-2 atm.l/mole )
• Subsurface temperature
• soil permeability
• soil organic matter content
• System Monitoring
• vapour concentration (pulsed extraction)
• mass balance
• Oxygen and Carbon dioxide (biodegradation)
• Treatment of Extracted Vapours
• to atmosphere
• Combustion engine
• thermal oxidation
• GAC adsorption

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Physical Remediation TechnologiesIn Situ Soil
Vapour Extraction

• Supplementary Methods
• Thermally Enhanced SVE (Steam Stripping)
• extends application to less volatile SVOCs
• Steam or hot air injected
• Air Sparging
• Air bubbled through contaminated groundwater
• strips VOC from water
• Directional Drilling
• contaminated zone geometry
• specific positioning of well around
• existing structures and obstructions
• Pneumatic or Hydraulic Fracturing
• new channels created

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SVE
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Physical Remediation TechnologiesIn Situ Soil
Vapour Extraction

• Time
• extensive (1 - 2 years)
• Costs
• 5 - 40 per m3
• 15 70 per m3 (with thermal enhancement)
• Resources
• Power
• Emission control equipment
• Application Range
• VOC (some SVOC)
• only certain soil types

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In Situ Soil Vapour Extraction Example

• Site
• Service Station
• Contamination
• 5000 litres fuel beneath road and forecourt
• max depth 3m
• Remediation Method
• Soil Vapour Extraction (Venting), then
  bioventing
• extraction at 25 - 60 m3/h
• Performance
• TPH from 10,000 mg/kg to 260 mg/kg
• half removal by biodegradation (bioventing)
• Time
• 2 years
• Cost
• estimated 60 per m3 (includes the bioventing
  time)

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Physical Remediation TechnologiesIn Situ
Electrokinetic Remediation

• New Full-Scale Process
• Patent licence Geokinetics International Inc.
• Electrodes
• spacing 1 - 2m
• graphite with membrane sheath
• electrolyte recirculation and regeneration
• Principle
• electrokinetic and electro-osmotic movement
• Electrode design (recirculated electrolye)
• Anions move to anode (ve electrode)
• Cations, metals move to Cathode
• Electrolysis of water produces H at anode
• Acid front sweeps through soil, extracts metals
• extensive process (in situ)
• intensive (ex situ)

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Physical Remediation TechnologiesIn Situ
Electrokinetic Remediation

• Power Requirement
• Low voltage DC 20 - 40 V/m
• current at a few Amps/m2
• 500 kWh/m3 at 1.5m electrode spacing
• Applicability
• Performs well in fine grained, saturated,
  low-permeability soils ( e.g. clays)
• vertical and horizontal process
• metal removal
• enhanced degradation of organics (Lasagne
  process)
• Considerations
• buried metal objects, power cables
• soil CEC and alkalinity
• safety - hydrogen and chlorine gas generation
• Soil Condition
• structure and fertility retained

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electrokinetics
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Chemical Remediation Technologies

• Overview and Principles
• Chemical Technologies
• Examples
• Ex Situ
• Soil Washing (with chemicals)
• Chemical Reactors
• In Situ
• Soil Flushing
• Funnel and Gate

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Chemical Remediation TechnologiesOverview and
Principles

• Extractive
• dissolve contaminant into extractant phase
• does not destroy contaminants
• Extractants require regeneration
• residual extractant left in soil
• Destructive
• most contaminants are unsuitable (unreactive)
• reactivity of soil interferes
• reagents may be environmentally unacceptable
• Detrimental to Soil Structure and Fertility
• Application
• few operational commercial processes in use
• numerous novel pilot demonstrations

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Chemical Remediation TechnologiesEx Situ Soil
Washing

• A Development of the Physical Soil Washing
  process
• acids
• Alkalis
• chelating agents (EDTA)
• surfactants
• Benefits
• All solid fractions treated
• contaminant moved into wash-waters
• water treatment possible
• Drawbacks
• soil structure
• residual extractant in soil

extractant class
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Chemical Remediation TechnologiesEx Situ
Chemical Reactors

• Ex Situ Solvent Extraction
• batch or continuous , single stage or
  counter-current reactors
• extraction into liquid solvent -
  water/triethylamine
• SCF super-critical fluid extractants - CO2 ,
  propane
• vegetable oil regeneration of extractant
• Drawbacks
• residual solvent contamination
• Soil structure
• Applications
• PCBs
• Viscous, non-VOC
• Metals

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Chemical Remediation TechnologiesEx Situ
Chemical Reactors

• Chemical Dehalogenation (Destructive)
• Soil Pretreated
• Soil Mixed with reagents
• APEG, alkaline polyethylene glycol, (KPEG)
• Heated
• 100 -180 C for 1 - 5 hours
• chlorine removed, glycol ether derivative is
  formed
• Neutralization
• Time
• intensive but limited plant capacity - (months
  per site)
• Application
• chlorinated contaminants, PCB, solvents, Dioxins
• Cost
• High 300 - 500 per m3

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Chemical Remediation TechnologiesEx Situ
Chemical Reactors

• Other Potential Destructive Methods
• Oxidation
• O3, H2O2 and Ferrous ion, ClO2, Wet Air Oxidation
• for PAH, TCE, PCP, phenols , Cyanide
• Hydrolysis
• reaction with water, better at high pH
• enzymes
• for Cyanide, organophosphorus pesticides,
• Reduction
• Sodium borohydride for many organics
• Iron (zero valent) powder for halogenated
  organics
• Polymerization
• pre-polymer contaminants (styrene, vinyl
  chloride)

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Chemical Remediation TechnologiesIn Situ Soil
Flushing

• In Situ version of Soil Washing
• no physical mixing
• Infiltration and recycle of extractant
• shallow soil (galleries, collection channels)
• deep soil (extraction well, Pump and Treat)
• Mild Extractants
• dilute acids, alkalis
• chelating agents
• surfactants
• External Treatment
• adsorption, flocculation, biological degradation
• Soil Neutralization
• must attenuate residual reagents

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Soil flushing
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Chemical Remediation TechnologiesExample Soil
Flushing

• Site
• Photographic Paper Factory, Holland
• Contamination
• 30,000 m3 soil with Cadmium (20 mg/kg)
• Complex site, buried structures (tanks)
• Remediation Method
• In Situ Soil Flushing (0.001M HCl)
• Ion exchange
• Performance
• Cd reduced to lt 1 mg/kg
• Time
• 1 year
• Cost
• experience limited, this case 90 per m3

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Chemical Remediation TechnologiesFunnel and
Gate(Permeable Reacive Barrier, PRB )

• Barriers (Funnel)
• divert groundwater flow
• focus contaminants
• Reactive Cell (Gate)
• Chemical dehalogenation (zero valent Iron
  filings)
• Oxidation
• chemical (oxygen precipitation of metal oxides)
• biological (bacterial oxidation of BTEX)
• Other types of reactive cell
• Adsorption (activated carbon)
• Biofilter media (biodegradation)

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Thermal Remediation Technologies

• Overview and Principles
• Thermal Technologies
• Examples
• Ex Situ
• Thermal Desorption
• Incineration
• (Vitrification)

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Thermal Remediation TechnologiesOverview and
Principles

• Ex-situ Method
• Fixed Centralized Plant or On-site Plant
• Standard Industrial Thermal Processors
• cement kiln, asphalt dryer
• Soil Destroyed
• inert ash
• Thermal Desorption
• organic contaminant moved from solid-phase to
  gas-phase
• relatively low temperatures 400 - 600 C
• Incineration
• organic contaminant degraded (oxidised or
  Pyrolysed)
• very high temperatures 800 - 1200 C
• Vitrification
• extremely high temperatures 1200 - 1600 C

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Thermal Remediation TechnologiesThermal
Desorption

• Treatment Train Process
• soil pretreatment
• desorption with Gas Emission Control
• cooling
• Kiln
• rotary, conveyor, screw
• direct or indirect heating
• Energy required 2500MJ per tonne (400 C, 20
  moisture)
• 300m3 gas per tonne
• Gas Treatment
• Thermal oxidation
• Cooling
• Scrubbers (acids)
• carbon adsorption
• Cost
• scale dependent 50 - 300 per m3
• water content (75 of costs for wet soil gt 20
  moisture)

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Thermal desorption
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Thermal Remediation TechnologiesIncineration

• Treatment train process but the main destruction
  occurs in the kiln
• Kiln
• Direct Fired Rotary Kiln
• Fluidised Bed
• infra-red incinerator
• Flue Gas
• PIC (products of incomplete combustion)
• dust
• water
• acid
• metals
• Costs
• Off-site plant 200 - 1000 per m3 (petroleum
  contaminant)
• 1000 - 5000 per m3 (for PCB contaminants)

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Thermal Remediation TechnologiesExample
Incineration

• Site
• Oil Refinery, USA
• Contamination
• 7,000 tonnes sediment
• PCB at 5 mg/kg
• Remediation Method
• Incineration
• Performance
• PCB lt 0.9 mg/kg
• Time
• 2 months
• Cost
• 500 per m3