Per- and Perfluoroalkyl Substances (PFAS) in Water: An ...sfwater.org/cfapps/wholesale/uploadedFiles/2018...• Per and Polyfluoroalkyl substances (PFAS) are a class of man-made chemicals.
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EPA Provisional Health Advisory, 2009Short-term adverse health effectsPFOS: 200 ppt, PFOA: 400 ppt
EPA Health Advisory, 2016Long-term adverse health effectsPFOS: 70 ppt, PFOA: 70 ppt, PFOS + PFOA: 70 ppt
“EPA's health advisories are non-enforceable and non-regulatory and provide technical information to states agencies and other public health officials on health effects, analytical methodologies, and treatment technologies associated with drinking water contamination.”
Adsorption – GAC and AIX• GAC/AIX: Breakthrough correlates with chain length.1,2,3,4,7
• GAC/AIX: Faster breakthrough for PFCAs than for PFSAs of equal carbon chain length (PFOA faster than PFOS). 1,2,3,4
• GAC/AIX: Organic matter has a negative impact upon adsorption. 1,4
• GAC/AIX: Desorption of short-chain PFCAs during co-removal (C ≤ 6 PFCA). 2,3,4
• GAC: higher surface area and larger micropores are more effective.1,5
• GAC: Dual-contactor design, careful monitoring, frequent carbon changes have proven effective at removing PFOA/PFOS.2,6
1-Appleman, et al. 2013. Journal of Hazardous Materials, 260:740–746. 2-Appleman, et al. 2014. Water Research, 51:246–255.3-Inyang and Dickenson. 2017. Chemosphere, 184:168–175.4-McCleaf et al. 2017. Water Research, 120:77-87.
5-Merino et al. 2016. Environmental Engineering Science, 33:615-649.6-Bartell, et al. 2010. Environmental Health Perspectives, 118:222–228.7-Zaggia, et al. 2016. Water Research, 91:137–146.
Adsorption – AIX• Polystyrene strong base > polyacrylic
strong base > weak base resins.3
• Sorption correlates with increasing hydrophobicity of the resin.4
• pHpzc>pH (aqueous), but pH<10 5
• Conventional regeneration techniques are not sufficient. 1,2
1-Deng, et al. 2010. Water Research, 44:5188–5195. 2-Carter, et al. 2010. Separation Science and Technology, 45:762–767.3-Dudley, et al. 2015. Removal of Perfluoroalkyl Substances by PAC Adsorption and Anion Exchange, WRF #4344.4-Zaggia, et al. 2016. Water Research, 91:137–146.5-Gao, et al. 2017. Journal of Hazardous Materials, 323:550–557
• AIX produces a concentrated waste stream that contains high levels of PFAS that could be difficult to treat and dispose of.
1-Inyang and Dickenson. 2017. Chemosphere, 184:168–175 2-Wang et al. 2016. Environmental Pollution, 216:884-892.3-Yan, et al. 2014. Journal of Chemical & Engineering Data, 59:508–515.4-Wang, et al. 2014. Separation and Purification Technology, 138:7–12.5-Li, et al. 2011. Environmental Science and Technology, 45:8498.6-Yu, et al. 2008. Water Research, 42:3089.7-Lin, et al. 2015. Environmental Science and Technology, 49:10562.8-Horst et al. 2018. Groundwater Monitoring & Remediation, 38:13.
Membrane Filtration• Microfiltration and ultrafiltration provide poor removal1
• Reverse osmosis (RO) and nanofiltration (NF) provide good removal1,2,3,4,5,6,7
• RO is the most expensive to implement and operate.• RO and NF produces a concentrated waste stream that
contains high levels of PFAS that could be difficult to treat and dispose of.
1-Appleman, et al. 2013. Journal of Hazardous Materials, 260:740–746. 2-Appleman, et al. 2014. Water Research, 51:246–255.3-Tang, et al. 2006. Environmental Science & Technology, 40:7343–7349.4-Steinle-Darling, et al. 2008. Environmental Science & Technology, 42:5292–5297.5-Soriano, et al. 2017. Water Research, 112:147–156.6-Boiteux, et al. 2017. Science of the Total Environment, 583:393–400.7-Thompson, et al. 2011. Chemosphere, 82:9–17.
Chemical Oxidation• PFOA and PFOS are resistant to oxidation by ozonation and
advanced oxidation processes, such as peroxone, Fenton’s reagent, ferrate, and UV/hydrogen peroxide.1,2,3
• However, other advanced oxidation technologies have proven effective: photochemical, photocatalytic, direct photolysis, persulfate, and catalyzed H2O2 propagation.2,3,5,6
• Nonselective radicals: ●OH, O2●-, SO4
●-, CO3●-.
• In general more effective towards PFOA than PFOS and longer-chain PFAA.
1-Appleman, et al. 2014. Water Research, 51:246–255.2-Hori, et al. 2004. Environmental Science & Technology, 38:6118–6124.3-Moriwaki, et al. 2005. Environmental Science & Technology, 39:3388–3392.4-Pisarenko, et al. 2015. Environmental Science: Water Research & Technology, 1:668–678.5-Park, et al. 2016. Chemosphere, 145:376:383.6-Merino, et al. 2016. Environmental Engineering Science, 33:615–649.
Thermal/Nonthermal Destruction• Thermal-chemical reactions, incineration, sonochemistry, sub- or supercritical, microwave-
hydrothermal, E-Beam irradiation, electrochemical, and plasma electric discharge.1,2,3,4,5,6,7,8
• Thermal destruction (e.g., sonolysis) involves breaking C-C and C-F with high temperature.
• Non-thermal destruction (e.g., electrochemical, plasma) leverages both advanced oxidation and reduction processes.
• Limitations: production of toxic byproducts (for nonthermal), greenhouse gasses, and can be relatively more expensive than commercially available AOPs and sorption processes.
• Thermal destruction relies less on oxidizing and reducing radicals, thus toxic byproducts are less of an issue with these processes.
• Relevancy towards smaller volume concentrated waste streams, where reactions times can be manipulated to control energy requirements.1-Stratton, et al. 2017. Environmental Science & Technology, 51:1643–1648.2-Merino, et al. 2016. Environmental Engineering Science, 33:615–649.3-Schaefer, et al. 2015. Journal of Hazardous Materials, 295:170–175.4-Soriano, et al. 2017. Water Research, 112:147–156.5-Horst et al. 2018. Groundwater Monitoring & Remediation, 38:13.6-Urtiaga et al. 2015. Chemosphere, 129-20-26.7-Schaefer, et al. 2017. Chemical Engineering Journal, 3175:424-432.8-Vecitis, et al. 2009. Frontiers of Environmental Science & Engineering in China, 3:129-151.
• Title - Evaluation and Life Cycle Comparison of Ex-Situ Treatment Technologies for Poly- and Perfluoroalkyl Substances (PFASs) in Groundwater
• Lead Organization: The Water Research Foundation (PI: Kenan Ozekin)
• Research Team: Colorado School of Mines (Chris Bellona, Chris Higgins), North Carolina State University (Detlef Knappe), University of Colorado – Boulder (Sherri Cook), CDM Smith (Charles Schaefer)
• PFAS are extremely persistent and bioaccumulative• There are no Federal Regulations – only Health Advisories • Ineffective water treatment techniques: