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Perfluoroalkyl Substances (PFAS): The Treatment Toolbox
Eva Steinle-Darling, PhD, PE
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Overview
Physical & Chemical Properties
Treatment Approaches:1. What doesn’t work
2. What we know works
3. Potential future solutions
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Unique Chemical Properties Drive Uses
Properties: Desirable Less Desirable
Extreme chemical inertness Fire Fighting Difficult to destroy
Hydrophobic andLipophobic
Repels stains & prevents wrinkles
Accumulates in protein tissues &blood(not sequestered in fat)
Surface active Good Coating Material
Difficult to measure /sample accurately
PFOA PFOS
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PFAS Treatment: What doesn’t work
Edited from Figure 1. in Appleman et al, 2014. Water Research, 51, 246-255.
Limited/no removal
Formation!
Limits of Detection
UV/AOP
Cl2 / ClO2
O3APT
DAF
MF/UF
Frac
tion
Rem
oved
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Reverse Osmosis is Excellent for PFOS Removal
99% rejection and better
Edited from Figure 3a. in Tang et al, 2006. Environ. Sci. Technol., 40(23), 7343-7349.
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Nanofiltration (NF) removes most PFAS well
PFOSPFOA
Edited from Figure 1. in Steinle-Darling et al, 2008. Environmental Science and Technology, 42(14) 5292-5297.
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GAC is more effective for longer-chained PFASB e d Vo l u m e s ( x 1 0 , 0 0 0 )
C/
Co
0 1 2 3 4 5 6 7
1.5
1.0
0.5
0.0
10/2
6/06
4/26
/07
10/2
6/07
4/26
/08
Modified from Figure 2. in Appleman et al, 2014. Water Research, 51, 246-255.
Case Study“Utility 20” uses GAC
specificallyfor PFASremoval
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Anion exchange can also be effective
Figure 4.26 from Dudley et al, 2015, Water Research Foundation Web Report #4344.
CCR
ORW
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Summary of PFOS and PFOA Removal Across Various Full-Scale Treatment Processes
Figure 1. in Appleman et al, 2014. Water Research, 51, 246-255.
Frac
tion
Rem
oved
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Process Selection Depends on Treatment Goals
Process Effective for…? Capital Cost
Operation & Maintanance
CostResidual?
GAC Long-chainedPFAS Lower Low-Med
Spent carbon / regeneration
($)
AIX Dependson resin Lower Low-Med
Spent resin / regeneration
($)
NF / RO All (RO)Most (NF) High Med-High
Liquidconcentrate
($$$)
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BUT: All existing options have a fundamental flaw:
Sequestration not Destruction of PFAS
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One of Several Potential Future Solutions: Defluoridation using Persulfate AOP
HT/K2S2O8
UV/K2S2O8
Edited from Figure 1. in Yang et al, 2013. PLoS One, 8(10): e74877. doi:10.1371/journal.pone.0074877.
