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Contaminated Land

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Title: 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

4
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

5
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

6
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

7
Soil washing
8
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)

9
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

10
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

11
SVE
12
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

13
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)

14
(No Transcript)
15
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)

16
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

17
electrokinetics
18
Chemical Remediation Technologies
  • Overview and Principles
  • Chemical Technologies
  • Examples
  • Ex Situ
  • Soil Washing (with chemicals)
  • Chemical Reactors
  • In Situ
  • Soil Flushing
  • Funnel and Gate

19
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

20
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
21
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

22
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

23
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)

24
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

25
Soil flushing
26
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

27
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)

28
Thermal Remediation Technologies
  • Overview and Principles
  • Thermal Technologies
  • Examples
  • Ex Situ
  • Thermal Desorption
  • Incineration
  • (Vitrification)

29
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

30
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)

31
Thermal desorption
32
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)

33
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
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