Challenges of PFOS remediation

Tessa Pancras, Wim Plaisier, Arjan Barbier

(ARCADIS NL)

Joris Ondreka (ARCADIS DE)

Jeff Burdick, Elisabeth Hawley (ARCADIS US)

Imagine the result

AquaConsoil, 16-19 April 2013, Barcelona, ES

Outline presentation• Perfluorinated compounds

• Properties

| 24 October 2012 | © ARCADIS 2012Slide 2

• Remediation options

• Developments

Perfluorinatedcompounds• Chain: Hydrocarbon chain, in which all

hydrogen atoms are replaced by fluor atoms• Varied substance group

• Chain length• Branched and unbranched (straight)

| 24 October 2012 | © ARCADIS 2012Slide 3

• Branched and unbranched (straight) chains

• Partly fluorinated chains �Polyfluorinated surfactants

• Type of polar group, e.g. alcohol, betaine, carboxylate, alkyl sulphonate

• Representatives • Perfluorooctanoic acid (PFOA)• Perfluorooctane sulfonate (PFOS)

Production and usage• Manufactured since 1940s• Used in aqueous film-forming

foams (AFFF), fire suppression systems, hangars, fire trucks

• Other fluorosurfactant uses (chrome plating,

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• Other fluorosurfactant uses (chrome plating, stain repellants, photolithographic chemicals)

• Fluoropolymer coatings and products that resist heat, oil, stains, and grease (Scotchgard, Gore-Tex, Teflon, food packaging, fabrics, carpet)

Found everywhere• PFC do not occur naturally

• Global distribution of PFC• Atmosphere: Volatile PFC such as

fluorotelomer alcohols• Aquatic systems: Salts of the

perfluorinated carbonic and

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perfluorinated carbonic and alkylsulphonic acids such as PFOA and PFOS

• Persistence: The fluorinated chains of the PFC have long-term stability in the environment

• Biomagnification: PFOS is known to accumulate in the food chain

Environmentalbehaviour• PFCs are retarded to a comparatively low

extent by groundwater transport which, in combination with their persistence, can result in the formation of long plumes

• Retardation factors at f = 0.001:• Retardation factors at fOC = 0.001:• PFBS 1.0 (no retardation)• PFHxS 1.2• PFOA 1.6• PFOS 2.5

TPH

PAH

BTEX

Plumelenght of contaminants

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Plume length [m]

Average

MTBE

CHC

PFC

Parameter PFOS (Giesy, 2010; OECD, 2002) PFOA (EFSA, 2008)

CAS number 1763-23-1 335-67-1

Chemical formula C7H15COOH

Molar weight 538,23 g/mol 414,07 g/mol

Boiling point n.a. 189-192 °C

Solubility 680 mg/l (pure water)

370 mg/l (fresh water)

12.4 mg/l (sea water)

3400 - 9500 mg/l

Log Kow (octanol/water partitioning

coefficient)

-1.08 Not determined

Relevant properties of PFOS and PFOA

Solubility is high

Ionic changes in saltwater

affect solubility

PFOA is much more

soluble than PFOS

Very high boiling point

Henry’s law constant

very low

Henry’s law constant 3.05 x 10-9 atm. m3/mol (pure water)

4.7 x 10-9 atm. m3/mol (fresh water)

1.4 x 10-7 atm. m3/mol (sea water)

Not determined

Vapor pressure 3.31 x 10-4 Pa 4,2 Pa

Density 0.6 kg/l (potassium salt)

1.1 kg/l (ammonium salt)

1.8 kg/l

pKa -2.6 2-3

Vapor pressure is very low

pKa very low, in

groundwater PFOS PFOA

present in ionic form

Furthermore

• PFOS and PFOA are not biodegradable bybacteria

• Very persistent• Very long hydrolysis half-life• Very long hydrolysis half-life• Very long photolysis half-life• Retardation factor is relatively low

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Current technologies:

• Dig and dump• Not a sustainable solution• Landfill leachate needs treatment for PFC’s

• Incineration• Incineration• High temperature (1100 °C)

• Pump and treat• Activated carbon• Less effective for PFOA and smaller PFCs• Loading rate starts at 0.0012%• Regeneration at 800 °C

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• Soil vapor extraction• Air sparging• Bacterial biotreatment / MNA

Ineffective in-situtechnologies

• Bacterial biotreatment / MNA• Hydroxyl radical oxidation• In-situ reduction• Hydrolysis

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Possibly effective

• In-Situ and Ex-Situ Immobilization• Six Phase Heating?• Ex-Situ Thermal Vacuum Treatment?

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• Ex-Situ Thermal Vacuum Treatment?• In-Situ Water Flushing?• Use of fungi?

Developments

Slide 13

Chemical degradation

• Regular hydroxyl radical oxidation systems(Fenton, Ozone, Perozone) do not work or are very ineffective

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• ARCADIS/Imperial College London performed tests in 2008 (Kingshott) to improve degradation rates

• ARCADIS developed the SCISOR technology in 2011

Kingshott, 2008

• Different combinations of chemicals weretested in the laboratory

• Treatment of very high concentrations of PFOS (73-570 mg/l)PFOS (73-570 mg/l)

• PFOS degradation: 90 to 99,8%• Fluoride recovery max 28%

• Remarks:• Extreme concentrations of oxidants• Non-economical, unpractical and unsafe

for fieldscale application

| 6 December 2011 | © ARCADIS 2011Dia 15

Summary of ARCADIS labtests 2011

30000

40000

50000

60000

70000

80000

PFOS

(ng/l)

PFOA

(ng/l)

Dia 16

0

10000

20000

30000

On

be

ha

nd

eld

1-1

1-2

1-3

1-4

1-5

2-1

2-2

2-3

2-4

3-1

4-1

4-2

5-1

5-2

SCISORKINGSHOTTRegular oxidationuntreated

Results SCISOR in groundwater

• PFOS degradation 98.8 to 99.8% (<100 ng/l)

• PFOA degradation 91.8 to 99.5% (<100 ng/l)• PFOA degradation 91.8 to 99.5% (<100 ng/l)

• Additional tests in mix of soil andgroundwater

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25000

30000

35000H4PFOS

C7A

C7S

C8A

C4S

Results supernatant

H4PFOS

C7AC7S

C8AC4S

C5AC4A

C6AC6SC8S

0

5000

10000

15000

20000

Blanco SC2-1 SC2-2 SC2-3 SC2-4

C4S

C5A

C4A

C6A

C6S

C8S

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Results

• Reduction of contamination• Reduction PFOS 95% in water• Reduction PFOA 80% in water• Reduction PFOA 80% in water• 60% reduction in soil after one contact

phase• Reduction for all detected PFCs

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Innovative application:Advanced soil-washing

Slide 20

Cooperation ARCADIS-DV&VDW (DEC – DEME dredging)

Advanched soil washing

Sieve Clean debris

Original soil

> 2 mm

Sieve< 63 µm

Waste

Contaminated

water

SCISOR

technology

Water

< 2 mm

Sieve< 63 µm

Waste

0.063 - 2 mm

Upstream

separation ,

desorption (soil

washing +)

Clean sandSand 0.063 – 2 mm

Organic fraction

0.063 – 2 mmWaste

Polymer

Flocculation

water

Waste

Soil washing vsadvanced soil washing

Sample Status Concentration

(µg/kg)

Percentage

reduction (%)

Sample Status Concentration

(µg/kg)

Percentage

reduction (%)

| 24 October 2012 | © ARCADIS 2012Slide 22

(µg/kg) reduction (%)

Sample 1 Before treatment 5570

Sample 1 Regular soil

washing

18.5 99.7

Sample 1 Advanced soil

washing

(soil washing+)

3.7 99.9

(µg/kg) reduction (%)

Sample 1 Before treatment 5,570

Sample 1 Regular soil

washing

18.5 99.7

Conclusions

• PFCs are difficult compounds to remediate• Remediation is expensive• Alternatives are being developed• Alternatives are being developed• Next phase: pilot test

| 24 October 2012 | © ARCADIS 2012Slide 23

Imagine the result

Tessa Pancras

Apeldoorn, the Netherlands

+31 6 11032744

tessa.pancras@arcadis.nl