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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,
| 24 October 2012 | © ARCADIS 2012Slide 4
• 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
| 24 October 2012 | © ARCADIS 2012Slide 5
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
| 24 October 2012 | © ARCADIS 2012Slide 9
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
| 6 December 2011 | © ARCADIS 2011Dia 10
• Soil vapor extraction• Air sparging• Bacterial biotreatment / MNA
Ineffective in-situtechnologies
• Bacterial biotreatment / MNA• Hydroxyl radical oxidation• In-situ reduction• Hydrolysis
| 24 October 2012 | © ARCADIS 2012Slide 11
Possibly effective
• In-Situ and Ex-Situ Immobilization• Six Phase Heating?• Ex-Situ Thermal Vacuum Treatment?
| 24 October 2012 | © ARCADIS 2012Slide 12
• 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
| 24 October 2012 | © ARCADIS 2012Slide 14
• 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
| 6 December 2011 | © ARCADIS 2011Dia 17
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
| 6 December 2011 | © ARCADIS 2011Dia 18
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
| 6 December 2011 | © ARCADIS 2011Dia 19
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