soil contamination and remediation remediation...
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Soil contamination and remediation
Remediation technologies
Immobilization techniques –S/S technologies –
vitrification - capping - cut off walls – in situ waste
containment
Solidification/Stabilization
S/S technologies uses additives or processes to chemically bind or encapsulate contaminant
Metals, radionuclides, nonvolatile organic compounds
Solidification/StabilizationSolidificationTreatment that encapsulate the waste in a monolithic solid of high
structural integrity• does not necessarily involve chemical interactions• may be due to mechanical binding of the waste in the monolith• usually involves the reduction or elimination of free liquids in
the waste• Decrease mobility by decreasing the surface area exposed to
leaching or isolating waste within a capsule• long term integrity
StabilizationTechniques to limit the hazard potential of contaminants by
converting them to their least soluble, toxic and mobile forms• may or may not change or improve the physical characteristics • leachability testing is typically performed to measure the
immobilization of contaminants.• also called fixation or chemical fixation
Solidification/Stabilization materials
Cement based S/S (portland cement, + fly ash, bentonite)
Suitable for metals, PCBs, oils, and other organic compound
Pozzolanic based S/S (fly ash, pumice lime kiln dusts, aluminosilicates) forms cementitioussubstances when combined with water
Applicable for metals and waste acids.
Solidification/Stabilization materials
Thermoplastic S/S (bitumen, polyethylen) microencapsulation process, chemically inert encapsulating material.
Applicable for metals, radionuclides and organics.
Organic polymerization S/S (urea-formaldehyd) fly ash, pumice lime kiln dusts
Applicable for metals and waste acids.
Solidification/Stabilization
Final decision about S/S material, is done on basis of an experiment.
Solidification/Stabilization technologies
http://www.new-technologies.org/ECT/Other/soilmixing.htmhttp://www.geocon.net/
Mixing in-situShallow mixing:Up to 12m depth,Mixing tool diameter up to 4msemi-volatile compunds -> off gas hoodCena 50 – 80 USD/m3
Solidification/Stabilization
http://www.new-technologies.org/ECT/Other/soilmixing.htm
Mixing in-situShallow mixing:
Solidification/Stabilization
http://www.geocon.net/
Mixing in-situShallow mixing:
Solidification/Stabilization
In situ technologyDeep soil mixingup to 40 m depth2-4 mixing toolsStabilizing reagents are fedinto augerincrease o soil volume ~15%price 190 – 300 USD/m3
http://www.new-technologies.org/ECT/Other/soilmixing.htm
In situ technologyDeep soil mixing
http://www.new-technologies.org/ECT/Other/soilmixing.htm
In Situ Vitrification (ISV)
http://www.bnl.gov/
Use of heat to melt and convert the contaminated soil into a stable glass or crystalline product
• Organic compounds are burnt or volatilized• Heat is produced by electric current between two – four
graphite electrodes ~2000°C.
http://www.frtr.gov/
In Situ Vitrification (ISV)
• Applicable to mixture of contaminants (mixture of radionuclides, metals and organics)
• Up to 1000 tons in one step
• Volume of soil reduces by 25-50%
• Cost ~280 – 600 USD/ton soil (depends on initial water content)
http://www.bnl.gov/
Surface caps or covers
or silt
Surface caps or covers Goals:• Prevent direct contact of human and animals
with contaminated material• Minimize infiltration• Eliminate contamination of surface water
which would otherwise contact contaminated material
• Prevent generation of contaminated dust or volatilization of contaminants
http://www.bnl.gov/
Surface caps - Configuration and materials
Source: Federal Remediation and Technologies Roundtable, February 12, 2003. 4.30 Landfill Cap
Surface caps - Configuration and materials
Source: Federal Remediation and Technologies Roundtable, February 12, 2003. 4.30 Landfill Cap
30 cm
30 cm
VEGETATION
Purpose:• Erosion control• Infiltration
reduction by• Evapotranspiration
Characteristics:• Shallow rooted
plants• Low nutrient needs• Drought and heat
resistant
Surface caps - Configuration and materials
http://www.bnl.gov/
30 cm
30 cm
TOPSOIL
Purpose:• Support vegetation• Protect underlying
layers
Characteristics:• Typically 60-cm
thick
Surface caps - Configuration and materials
http://www.bnl.gov/
PROTECTION LAYER
Purpose:• also called biotic
barrier”• 90-cm layer of cobbles
to stop burrowing animals and deep roots
Characteristics• Not always included
Surface caps - Configuration and materials
http://www.bnl.gov/
FILTER LAYER
Purpose:• Prevents clogging
of drainage layer by fines from soil layer
Characteristics:• May be
geosynthetic filterfabric or 30-cm sand
Surface caps - Configuration and materials
http://www.bnl.gov/
DRAINAGE LAYER
Purpose:• Prevents ponding of
water on geomembrane liner
• Drains by gravity to toe drains
Characteristics:• At least 30 cm of
sand with K = 10-2 cm/sec or equivalent geosynthetic
Surface caps - Configuration and materials
http://www.bnl.gov/
LOW K LAYER
Purpose:• Low K prevents
infiltration• of water into waste:
hydraulic barrier
Characteristics:• Geomembrane: at
least 0.5 mm thick• Compacted clay: at
least 60 cm withK<= 10-7 cm/s
Surface caps - Configuration and materials
http://www.bnl.gov/
GAS VENT LAYER
Purpose:• Needed if waste will
generate methane(explosive) or toxic gas
Characteristics:• Similar to drainage
layer: 30 cm of sand orequivalent geosynthetic
• Connected to horizontalventing pipes (minimalnumber to maintain capintegrity)
Liner installation
Vertical barriers
Also known as vertical cutoff barriers, vertical cutoffwalls, or barrier walls
Goals:• To contain contaminant• Redirect groundwater flow• To prevent contaminant spreading in the
aquiefer
Vertical barriers - Waste containment
Horizontální izolace
Těsnící zářez
Kontainant
Odčerpávání průsakové vody
Vertical barriers – Hanging barrier
„Zavěšená“ těsnící stěnaLNAPL
Nepropustné podloží (ve velké hloubce)
Containment vs. Downgradient cutoffwall
Containment Downgradient
Slurry wall encirclesand isolates waste
Slurry wall delayseventual migration
orOften combined with extraction wells
Slurry walls
Most common cut-off wall technologyMaterials:
bentonite + soil (SB)common hydraulic conductivityK = 10-7 – 5x10-9 m.s-1
cement + bentonite (CB)higher permeability, but also highercompactness
SB slurryMost common cut-off wall technology
Sharma and Reddy, 2004
Slurry wall construction• Trench excavation under slurry• Slurry overcome the active pressure of trench
walls• Backfill is placed continuously• Povrch je uzavřen betonovou hlavicí
HPV
Slurry wall construction
http://www.mp.usbr.gov/mpco/showcase/bradbury.html.
Issues in slurry walls constructions
Original direction of groundwater flow
Potentialsources ofof failure
• Improperly mixed backfill (CB, SB)
• Sloughing or spalling of soils into trench
• Inadequate bottom excavation for wall key
• Freeze – thawcycles
• Wet dry cycles
Alternative - sheet piles
Waterloo Barrier Inc. http://www.oceta.on.ca/
Jet Grouting
SKANSKA http://www.skanska.co.uk/skanska/templates/Page.asp?id=8581
Examples of containmenttechnologies used in CZ
SPOLANA A. S., NERATOVICESlurry walls containment (27 640m2), 110
mil CZKKEMAT s.r.o., Skalná u Chebu (funded
by FNM)double wall containment, inner wall done
using jet grouting (42 mil CZK)LETIŠTĚ PRAHA RUZYNĚ4 containments at four places 6 m3 each
standard grouting (0,5 mil CZK)
SOLETANCHE http://www.soletanche.cz/
ReferencesSharma, H.D., Reddy, K.R. Geoenvironmental engineering, Wiley, 2004Domenico, P.A. a Schwarz, F.A. Physical and Chemical Hydrogeology, 1990EMOMONITOR Chrudim, Využití biodegradačních metod při sanacích znečištění, 1997MIT Open courseware http://ocw.mit.edu/OcwWeb/Civil-and-Environmental-Engineering/1-
34Spring2004/LectureNotes/index.htm