soil contamination and remediation remediation...

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