Remedial methods and strategies for perflourinated compounds. Niklas Törneman, Sweco

Transkript

1 Remedial methods and strategies for perflourinated compounds Niklas Törneman, Sweco 1

2 The project on remedial methods is part of the overall Environmental project which is initiated, entirely financed and also led by Avinor.

3 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. 3

4 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 4

5 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 5

6 PFCs of interest (at fire fighting training sites) Four fire fighting training sites at airports in Norway Soil Groundwater Biota (earthworm) Sediment 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 Surface water 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) PFBA 0 PFPeA 0 PFHxA 0 PFHpA 0 PFOA PFNA PFDA PFBS 0 PFHxS PFOS FTS-6: FTS-8: Risk 6

7 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 example 1 1 starting with hydrolysis of the ester linkage with PFOA as one utlimate degradation product 7

8 Partitioning (Koc) > 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 8

9 . 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 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 9

10 Contaminated matrix PFCs LNAPL/DNAPL Pore gas Soil () Groundwater

11 Applicability of remedial technologies based on fate and physicochemical properties Excavation Yes/(No) Pump and treat Yes/(No) Pore gas extraction/air injection No not volatile In situ soil flushing Yes/No Thermal treatment Yes/No Biological in situ treatment No not biodegradable In Situ oxidation Yes/No? In Situ reduction? Phytoremediation? MNA No persistent 11

12 Excavation and off site treatment 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 12

13 Pump and treat / hydraulic containment 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: years. Depends on loss through groundwater transport. Possibly nonlinear. Low on-site disturbance Cost dependent on treatment time 13

14 Chemical In Situ Oxidation Description Addition of a (very) strong oxidizer causes oxidation of the contaminants to harmless endproducts 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 14

15 Applicability of remedial technologies for PFCs at Avinors sites - technology evaluation Methodology Excavation and ex situ treatment 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 physicochemical properties Time for remediation Disturbance ongoing operations 5 5 Full scale Pump and treat Full scale Cost Efficiency In Situ Chemical Oxidation In Situ Electro- Chemical Oxidation In situ soil flushing Lab scale - soil ? 2-5 Lab scale and pilot field? study (?)? 2-4 Lab scale Thermal in situ methods (ISTD) 3 3-5? Stabilization / solidification Barrier technologies Bench scale - soil Unknown DOD / SERDP project Unknown Unknown

16 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 16

17 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. 17

18 Risk assessment Is there a high risk with PFCs Yes No Is it off site transport expected in the long term Yes No No Is there an ongoing off site transport of PFCs? Yes Both short and long term strategies Yes Is these also a (different) long term risk Yes Is it (risk) acceptable? No No Does PFCs in the unsaturated zone pose an on-site risk? Yes No No Is monitoring necessary? Yes Evaluate remedial measures in soil (scheme 1) and groundwater (scheme 2) based on risk reduction and costs Urgent technical and administrative protective measures No further activities No remedial measures. Monitoring program developed in cooperation with authroities

19 2. Åtgärder i jord och/eller kombinerade metoder för både jord och grundvatten Flygplats: XXXXXXX Brandövningsplats: XXXX 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. 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 Börja med båda Nej Nej/ tveksamt Är alternativa metoder möjliga för åtgärder i jord/grundvatten? Utvärdera s ej vidare Ja Är alternativa åtgärder färdigutvecklade 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 Nej 1. Inneslutning 2. Stabilisering/solidifiering 3. Kemisk oxidation 4. Termiska metoder Nej/ tveksamt Utvärdera s ej vidare Är det möjlig att vänta med åtgärder Ja Utvärdera s ej vidare Eventuellt tillfälliga åtgärder (administrativa, inneslutning etc.) tills metoder är färdig för åtminstone pilotförsök Nej/ tveksamt Grävsanering av ytjord utvärderas. Alternativa åtgärder för jord/grundvatten utvärderas

20 3. Åtgärder endast i grundvatten Flygplats: XXXXXXX Brandövningsplats: XXXX Rapport: XXXXXXXXX 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 Är återinfiltration en möjlig metod tills det finns bättre metoder för behandling av PFCs i uppsamlat grundvatten? Nej Ja Möjliggör geologi/hydrologi uppsamling av grundvatten Ja Nej Utvärdera s ej vidare Nej Möjliggör geologi/hydrologi barriärlösning och eller inneslutning Ja Utvärdera s ej vidare Kan kräva behandlingsförsök. Viktigt att långsiktig effektivitet och kostnad bedöms. Erfarenhetsmässigt är det känt att behandling av grundvatten måste hålla på under mycket lång tid, 100 tals år. Kan ses som en tillfällig metod. 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? Nej Kan i vissa fall endast bedömas efter lab- eller fullskaletest Utvärdera s ej vidare Ja Återinfiltration är en möjlig metod Uppsamling och behandling av grundvatten är en möjlig åtgärd för att förhindra transport av PFCs i grundvatten Barriärmetoder eller inneslutning är en möjlig åtgärd för att förhindra transport av PFCs i grundvatten Kostnader och riskreduktion jämförs. Utvärderas eventuellt mot lösningar i jord och jord/grundvatten

21 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. 21