remedial methods and strategies for perflourinated...
TRANSCRIPT
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Remedial methods and strategies
for perflourinated compounds
Niklas Törneman, Sweco
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The project on remedial methods is part of the overall Environmental project which is
initiated, entirely financed and also led by Avinor.
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Background
Avinor, the Norwegian aviation authority in 2011 instigated investigations of its airports as part
of their efforts to map the environmental status at their facilities.
Aqueous Film Forming Foam has been used to suppress fires at fire fighting training sites at
airports (as well as industries etc.) potentially resulting in contamination of soil and
groundwater by perflourinated compounds (PFCs).
Several PFCs have properties that hinders the usage of commonly used remedial methods
Avinor has initiated the present project to determine possible remedial methods and strategies
for PFCs
Scientific literature review. Technical reports. Contact with consultants, scientists etc.
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The most important solution has already been implemented!
AVINOR will have replaced PFC containing AFFF with PFC free Moussol at all
airports during 2012
PFC usage/emission of > 3 tonnes yearly have been completely stopped
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Why a talk on remediation of perflourinated compounds (PFCs)?
1. Unfavorable properties, i.e. no biodegradation, low volatility – many
classic in situ techniques unsuitable
2. Highly variable properties – difficult to address all substances?
3. Environmental fate not well known and highly variable – modeling and
prediction complicated or (at present) not possible
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PFCs of interest (at fire fighting training sites)
Soil Groundwater Biota
(earthworm)
Sediment Surface
water
6:2 FTS X X X X X
PFOSA X X X
N-Me-FOSA X
N-et-FOSA X X
PFBS X X X X X
PFHxS X X X X X
PFOS X X X X X
PFDcS X X X
PFHxA X X X X X
PFHpA X X X X
PFOA X X X X
PFNA X X X X X
PFDcA X X X X
PFUnA X X X X
PFDoA X X X X
PFTriA x X X
PFTeA x X
Four fire fighting training sites at airports in Norway
Aquatic biota at background localities and
close to airports/fire fighting training sites
in Norway
PFC Number of detects Average concentration
in all biota (ug/kg)
Riskprioritering
PFBA 0
PFPeA 0
PFHxA 0
PFHpA 0
PFOA 8 0.32 5
PFNA 20 1.71 4
PFDA 24 0.87 4
PFBS 0
PFHxS 18 6.10 2
PFOS 105 87.44 1
FTS-6:2 5 2.52 3
FTS-8:2 10 3.09 3
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Most important – persistence and volatility
PFOA and PFOS are highly persistent. Not biodegradable and has a very long hydrolysis and
photolysis half life
Some PFCs are biodegradable with possibly harmless end-products
Some PFCs biodegrade with PFOS and/or PFOA partly as end-products. 8:2 FTS is one example1
1 starting with hydrolysis of the ester linkage with PFOA as one utlimate degradation product
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> Many PFCs highly water soluble
> Koc Covers the whole range of other substances
> Koc Highly variable for individual substances due to both interaction with organic
carbon and interaction with charged surfaces / ionic interaction
Partitioning (Koc)
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Fate
Many PFCs including PFOS and PFOA occur mostly in ionized forms complicated
fate/transport/leaching behavior
PFCs occur through the whole unsaturated soil profile with different PFC compositions at different
depths. Has been found at high conc. at 10 – 20 m depth.
Depth of highest PFC concentration variable
Major transport pathway is groundwater for most PFCs related to AFFF
Total site loss through groundwater transport is highly variable and site specific. 0.05% - 10% per
year
Free phase behavior not reported. Assumed non important at present.
No models developed that predict fate (of ionized organic chemicals/PFCs) at the site scale.
Fugacity models developed but of less use for modeling/predicting site remediation
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Contaminated matrix
LNAPL/DNAPL
Pore gas
Soil
Groundwater
()
PFCs
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Excavation
Pump and treat
Pore gas extraction/air injection
In situ soil flushing
Thermal treatment
Biological in situ treatment
In Situ oxidation
In Situ reduction
Phytoremediation
MNA
Yes/(No)
Yes/(No)
No not volatile
Yes/No
Yes/No
No not biodegradable
Yes/No?
?
?
No persistent
Applicability of remedial technologies based on fate and
physicochemical properties
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Description
Physical removal and off site transport followed by i.e. landfill disposal or treatment
Established technique for many contaminants
Mostly unsaturated source zone, but also saturated
Well known, experienced contractors, fast and thorough mass reduction
Applicability for PFCs (at fire fighting training sites)
Limited vertical reach – PFC may occur at very large depths
Negative impact on day to day operations (i.e. at airports)
Risk of mobilization during excavation
Not fully appropriate for landfill disposal:
• Many PFCs highly water soluble and persistent low retention in landfills and high concentrations In landfill leachate
• PFOS and PFOA may be produced in landfill due to biodegradation of precursor PFCs
Thermal treatment and/or soil flushing may be more appropriate
Very costly
Excavation and off site treatment
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Description
Contaminated groundwater is removed and treated on-site
Established technique for many contaminants
Only saturated zone. Both source zone and plume.
Well known, experienced contractors
Requires very good knowledge of geohydrology
Applicability for PFCs (at fire fighting training sites)
Removal of PFCs from extracted groundwater
• Bioreactors and air stripping can not be used
• Traditional sorbents such (G)AC has variable success due to high water solubility and low partitioning of many PFCs,
especially short chain carboxylates. (G)AC may require frequent sorbent replacement. Better sorbent (ion exchange
resin, zeolites etc.) are being developed and put into use.
• Advanced and/or destructive techniques (i.e. ozonation, reverse osmosis etc. ) has been tested for drinking
water/water works and waste water. Most suited for fixed installations.
Long treatment time: 10 – 500 years. Depends on loss through groundwater transport. Possibly non-
linear.
Low on-site disturbance
Cost dependent on treatment time
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Pump and treat / hydraulic containment
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Description
Addition of a (very) strong oxidizer causes oxidation of the contaminants to harmless end-
products
Injection/addition of oxidizer directly into the contaminated matrix
Mostly Source zone treatment
Established methods, experienced contractors available
Applicability for PFCs (at fire fighting training sites)
Has been tested at laboratory scale:
Permanganate +(++)
Fenton's reagents +(++)
Activated Persulfate ++(++)
Mostly used for saturated zone treatment, but PFCs occur also in
unsaturated zone
• Only few projects with injection into the saturated zone
• Soil blending down to several m depth
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Chemical In Situ Oxidation
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Methodology Availability of experienced contractors non PFCs
Status / maturity of technology – non PFCs
Scale at which it has been tested for PFCs
Effectiveness for PFCs based on fate
Effectiveness for PFCs based on physico-chemical properties
Time for remediation
Disturbance ongoing operations
Cost Efficiency
Excavation and ex situ treatment
5 5 Full scale 2-5 2-4 4-5 1-3 1-3
Pump and treat 4-5 4-5 Full scale 4-5 3-4 1-2 4-5 1-5
In Situ Chemical Oxidation
3-4 3-5 Lab scale - soil 3-5 2-5 3-5 4-5 2
In Situ Electro-Chemical Oxidation
? 2-5 Lab scale and pilot field study (?)
2-5 3-5 3-5 4-5 ?
In situ soil flushing
? 2-4 Lab scale 3-4 2-4 1-5 3-5 2-5
Thermal in situ methods (ISTD)
3 3-5 ?
3-5 2-5 4-5 4-5 2-5
Stabilization / solidification
3-5 4-5 Bench scale - soil
2-4 2-5 2-5 1-3 Unknown
Barrier technologies
2-3 3-5 Unknown – DOD / SERDP project
3-5 2-4 1-5 2-4 Unknown
Applicability of remedial technologies for PFCs at Avinors sites - technology evaluation
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Project review
32 projects worldwide has been reviewed
Airports, Landfills, PFC production sites, municipal fire fighting training sites, soil
dumping sites etc..
Excavation at 8 sites
Pump and treat 17 sites – Mostly GAC although some are changing sorbent type
Several sites are implementing intermittent strategies until better solutions are
available
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Strategies
Generic decision methods were developed to support the choice of long and short term remediation
strategies for PFCs at Avinors fire fighting training sites. Take into account:
Which PFCs that are present and their physicochemical properties
Geohydrological conditions
The off-site and on-site risks at present and in the future
Acceptable time frames for remediation
Costs for remediation
Acceptable disturbance on day to day operations
The choice of strategy is a process between Avinor and the Norwegian Climate and Pollution Agency,
KLIF):
The decision models can support Avinor and KLIF in this work
This process is important since KLIF or the County Governor has to approve the strategies/solutions for
each individual site
Remediation technologies for PFCs are under development:
the strategies may involve short term solutions (e.g. pump and treat or administrative measures) until
appropriate methodologies for site remediation has been developed.
Is there a high risk with PFCs Yes
Urgent technical and administrative protective measures
No
Is there an ongoing off site transport of PFCs ?
Yes
No remedial measures. Monitoring program
developed in cooperation with authroities
No Is it off site transport expected in the long term
Yes
No
Is it (risk) acceptable?
Yes
No
Risk assessment
Is these also a (different)
long term risk Both short and
long term strategies
No
Does PFCs in the unsaturated zone pose an on-site risk?
Is monitoring necessary?
No further activities
No
Yes No
Yes
Evaluate remedial measures in soil
(scheme 1) and groundwater
(scheme 2) based on risk reduction
and costs
Yes
Är grävsanering möjligt utan att störa verksamheten?
Ja / delvis
Är kostnader för grävsanering acceptabla ?
Detta kan exempelvis gälla om:
• föroreningar i ytjord finns på en sådan plats att exempelvis hangarer, uppställningsplatser eller start- och landningsbanor måste rivas/förflyttas.
• Det förekommer ledningar (el , tele, vatten etc.) i saneringsområdet som inte får störas
Detta kan då innebära ett så allvarligt ingrepp i verksamheten att en grävsanering inte är möjligt ur ett kostnads-nytto perspektiv. Detta bör motiveras väl i åtföljande rapport.
Ja / delvis
För att kunna beräkna kostnad bör följande kunna bedömas grovt:
1) Vertikal och horisontell utbredning av förorening i ytjord
2) Nyckeltal för utgrävning, deponering etc.
3) Metod för omhändertagande (deponering eller förbränning är aktuella för PFCs)
OBS! viktigt att samma nyckeltal används för flygplatser med liknande förhållanden t.ex. avstånd till deponi etc. Om kostnader är acceptabel kan beskrivas med en kostnads-nytto analys, men bör i vilket fall motiveras väl i rapport.
Utvärdera t.ex. nedanstående metoder. Om det finns stora osäkerheter i deras funktion fundera på tillfälliga åtgärder eller om åtgärder kan vänta tills bättre metoder finns tillgängliga
1. Inneslutning
2. Stabilisering/solidifiering
3. Kemisk oxidation
4. Termiska metoder
Grävsanering av ytjord utvärderas.
2. Åtgärder i jord och/eller kombinerade metoder för både jord och grundvatten Flygplats: XXXXXXX
Brandövningsplats: XXXX
Är alternativa metoder möjliga för åtgärder i jord/grundvatten ?
Nej/ tveksamt
Börja med båda
Alternativa åtgärder för jord/grundvatten utvärderas
Är alternativa åtgärder färdigutvecklade
Ja
Ja
Nej
Är det möjlig att vänta med åtgärder
Utvärderas ej vidare
Nej
Eventuellt tillfälliga åtgärder (administrativa, inneslutning etc.) tills
metoder är färdig för åtminstone pilotförsök
Nej/ tveksamt
Utvärderas ej vidare
Nej/ tveksamt
Utvärderas ej vidare
Möjliggör geologi/hydrologi uppsamling av grundvatten
Information som kan behövas är exempelvis:
• Vertikal och horisontell spridning av PFCs i grundvatten
• Årlig mäng grundvatten som behöver samlas upp
• Bedömd influensradie om grundvattenextraktion sker med brunnar
• grad av kontakt mellan ytlig och djupare akvifär
3. Åtgärder endast i grundvatten Flygplats: XXXXXXX
Brandövningsplats: XXXX
Rapport: XXXXXXXXX
Möjliggör geologi/hydrologi barriärlösning och eller inneslutning
Ja Ja
Behandling av PFCs i uppsamlat grundvatten Kostnader och teknisk genomförbarhet jämförs för möjliga metoder. Den mest fördelaktiga metoden väljs: - Kolfilter - Andra filtermaterial - Destruktiva metoder (ultraljud, oxidation termiska
etc.)
Är behandlingstid och eller behandlingseffektivitet acceptabel?
Kan kräva behandlingsförsök. Viktigt att långsiktig effektivitet och kostnad bedöms.
Barriärmetoder eller inneslutning är en möjlig åtgärd för att förhindra transport av PFCs i
grundvatten
Är återinfiltration en möjlig metod tills det finns bättre metoder för behandling av PFCs i uppsamlat grundvatten
?
Kan i vissa fall endast bedömas efter lab- eller fullskaletest
Uppsamling och behandling av grundvatten är en möjlig åtgärd för att förhindra transport av PFCs i grundvatten
Erfarenhetsmässigt är det känt att behandling av grundvatten måste hålla på under mycket lång tid, 100 tals år. Kan ses som en tillfällig metod.
Ja
Återinfiltration är en möjlig metod
Ja
Kostnader och riskreduktion jämförs. Utvärderas eventuellt mot lösningar i jord
och jord/grundvatten
Utvärderas ej vidare
Nej Nej
Utvärderas ej vidare
Nej
Utvärderas ej vidare
Nej
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Take home message
Identify critical PFCs
Excavation is not always fully appropriate
Pump and treat: 1) GAC alternatives 2) evaluate time frame
Some promising methods for in situ remediation are being developed –
have patience
The correct strategies will be site specific
.