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Application and Discussion of Ion Exchange Resin and PFAS Removal
Thomas Baker, PMPSales & Applications Specialist
Presentation outline
• Intro to ECT
• Construction of target synthetic medias, properties, and how they function
• Mechanisms of ion exchange resin to remove PFAS
• Water chemistry background and implications on process efficacy and application success
• Design Options and Requirements
• Comparing resin vs. GAC: Bench to pilot studies
• Full scale applications
• Other technologies & applications
Introduction to ECT
• Treatment technology solutions provider focused on emerging contaminants
• Initial focus was on 1,4-dioxane: partnership with Dow Chemical
• Interest by DOD to find alternate solution for PFAS
• “Synthetic Media” – Synthetic adsorbents and Ion Exchange resins
• Regenerable, sustainable, cost-effective technologies
What are the emerging contaminants?
• Primary focus today. . .
• PFAS (formerly PFCs) – Per- and Polyfluoroalkyl Substances (PFOA, PFOS, GenX)
• 1,4-Dioxane
• . . .but there are others
• 1,2,3-Trichloropropane (TCP)
• N-Nitrosodimethylamine – suspected human carcinogen (NDMA or DMN)
• Pharmaceuticals and personal care products
• Tungsten - Linked with leukemia
• Tributyltin - wood preservative, biocide in certain paints
• Ethylene dibromide - pesticide, fumigant
• Hex chrome – carcinogen, taking another look and dropping levels
Focus on the top two
PFAS (PFOA is pictured) 1,4-dioxaneBy Manuel Almagro Rivas - Own work using: Avogadro, Discovery Studio, GIMP, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=47567609
Leader in testing and applying IX resins for emerging contaminants
Standardized design components
SORBIX VESSEL SKID
PUMP SKIDFOR REGEN SYSTEM
PFAS: The emerging contaminant in the headlines
Synthetic Medias: Types, Construction, and Functionality
• Structure
• Co-polymer matrix of DVB and styrene typically
• Functional groups are added to the chemical makeup to interact with ions of interest based on electrochemical charge
• Cationic – removes positively charged ions
• Anionic – removes negatively charged ions
• Functional groups also determine strength of attraction and bond
• Spherically shaped “bead”
• Crosslinking chemistry is added to matrix to impart porosity
Synthetic Medias: Types, Construction, and Functionality
• Typical resin is therefore a complex 3 dimensional structure, consisting of the
• Polystyrene chains crosslinked together to form a backbone or bead structure,
• Attached functional groups fixed to the polymer chains that determine the type of ion it can hold and exchange,
• Pores located in the structure that are determined by the level of crosslinking used in the manufacture
• Exchangable counterions attached to the functional groups
Porosity in synthetic medias
• Porosity essentially determines the size of a molecule or ion that can enter the resin bead structure, and its rate of diffusion.
• This is very similar to LGAC medias, which are graded on performance by the porosity and their ability to uptake (adsorb) organics from aqueous mediums.
• Porosity also determines a resins resistance to chemical attack, osmotic shock, and expansion/contraction if regenerated.
• This is an important aspect in the use of resin for PFAS, as we will see.
Resin Capacity
• Expressed as
• Total Capacity
• Operating Capacity
• Total capacity is basically the equivalent value of the total number of fixed sites assumed on the unit of resin that can functionally exchange ions.
• Operating capacity is the measure of useful performance of resin unit under loading conditions. These are influenced by (not a complete list)
Flow Temperature Vessel design Bed depth
Feed concentration Background water matrix Selectivity or competition Foulants
Common Technology Parameters of Consideration
Terminology that is important to understand
• Bed Volume (BV) – the amount volume of a vessel has that is usable and typically filled with media. Generally expressed as cubic feet
BEDBED DEPTH
CROSS SECTION
Common Technology Parameters of Consideration
• Empty Bed Contact Time (EBCT) – the amount of time, expressed in minutes, that a volume of water is in contact with the media bed.
BEDTime
Final contact
Initial contact
PFOS & PFOA
PFOS – Sulfonated end, C8 (8 carbons)Highly ionized
PFOA – Acid end, C8 (8 carbons)Highly ionized
Common Features Important for Treatment
• PFOA & PFOS most common form• Very stable compound, carbon fluorine bond is strongest in
nature, and considered inert • Exhibits strong negative charge• C-F “Tail” is hydrophobic (non-water soluble) and
oleophobic (non-fat soluble)• Each molecule has a functional group “Head” that is
hydrophilic – extremely soluble in water.• Compounds that have >6 carbons (as shown) are considered
to be Long Chain, and are known to be more stable and more difficult to breakdown
• Compounds that have <6 carbon atoms are considered “short chained compounds”, and can be either degraded long chain materials, or individual compounds themselves.
How does IEX resin remove PFAS?
PFOS Molecule
Simplified Resin Bead
Dual mechanism of removal: IEX and adsorption
Feed Water Quality & Resin
Design needs to take into consideration the selectivity that’s exhibited by ion exchange resin, and in some cases, that competition for exchange sites
• Normally, resin has an excellent capacity for PFAS removal in “normal waters”, however the following ions can cause some complications for applications:
• Sulfate
• Chloride
• Excessive alkalinity
• Iron
• pH
• Iron in reduced form should pass through resin, however can oxidize, fouling the bed
• Any sediment or TSS needs to be removed before water is introduced into the bed, or it could cause plugging or channeling of the flow, thus reducing bed throughput.
Operating Capacity Impacts from Competition and Fouling
Types of Applications for PFAS Removal
• Outside of water quality, primary determining factor is feed concentrations of the specific PFAs compounds, relative to their ability to be adsorbed or exchanged in the resin.
• By order of magnitude, a balance is incorporated into a design relative to feed concentration, expected operating capacity of the resin based on all factors, and the calculated replacement interval and cost of the resin.
• A determination is made to either use:
• Single Use resin – 1 time and disposed of, typically where low foulant, low feed concentrations are present, with longer term bed volumes processed to breakthrough. Generally DWS applications and barrier wells
• Regenerable resin – typically fed with higher feed concentrations where replacement would be cost or OPEX prohibitive, such as extraction/recovery wells
SORBIX™ PURE Single Use Process Flow
SORBIX PURE IEX Resin
INFLUENT WATER
SORBIX PURELEAD
SORBIX PURELAG
TREATED WATER
Bag Filter10 micron
Resin Resin
EBCT: 2.5 – 5 min per vessel36” min bed depth
Space Velocity: 6-12 gpm/ft2
Backwash at startup onlyClassify the bed
SORBIX™ A3F Regenerable Process Flow
Regenerable IEX ResinSORBIX A3F
NH Installation
Applications – Pilot through Full Scale
Evaluating Real World Applications against GAC
Case study: What happened at New England Air Base?
• Community of roughly 21,000
• PFOA and PFOS detected in public drinking water supply
• PFAS tied to health impacts; citizens become concerned
• Contamination originated from firefighting foam use at the AFB
© Amec Foster Wheeler 2016.24
Pilot test Process Flow Diagram
Proof of Performance Testing – IEX vs LGAC
PFOA breakthrough at 5-min EBCT
GAC
Resin
PFOS breakthrough at 5-min EBCT
GAC
Resin
© Amec Foster Wheeler 2016.28
Pilot test: IEX resin vs. GAC
Processpumps
Cartridge filters for solids removal
GAC (front) and resin (rear)
vessels
0.00
0.50
1.00
1.50
2.00
2.50
Conc
entr
atio
n (p
pb)
Date
GAC - PFOS + PFOA
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
First sample at 574 gals Treated
2860 BVs
HAL – 70 ppt PFOS+PFOA 0
0.5
1
1.5
2
2.5
Conc
entr
atio
n (p
pb)
Date
IX - PFOS + PFOA
70 ppt
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Breaks 50ppt at 13,000 BV’s or 10,400 gals Treated (10 min EBCT)
IX Resin is ND after 171,000 BV’s or 34,300 gals Treated (2.5 min EBCT)
Removal Comparison – PFOA + PFOS
0.0
1.0
2.0
3.0
4.0
5.0
Conc
entr
atio
n (p
pb)
Date
GAC - TOTAL PFAS
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
First sample at 574 gals Treated
2860 BVs
0.0
1.0
2.0
3.0
4.0
5.0
Conc
entr
atio
n (p
pb)
Date
IX - TOTAL PFAS
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Treated 10,400 Gals or 13,000 BVs through 10 min EBCT IX Resin Treated 34,400 Gals or 171,000 BVs through 2.5 min EBCT
All PFBA48,000 BVs
Removal Comparison – PFAS
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Conc
entr
atio
n (p
pb)
Date
GAC - PFBA
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
First sample at 574 gals Treated
2860 BVs
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Conc
entr
atio
n (p
pb)
Date
IX - PFBA
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Treated 10,400 Gals or 13,000 BVs through 10 min EBCT IX Resin Treated 34,400 Gals or 171,000 BVs through 2.5 min EBCT
10 min EBCT18,950 gals23,600 BVs
10 min EBCT3,800 gals4,740 BVs
Removal Comparison – PFBA
0
0.005
0.01
0.015
0.02
0.025
0.03
Conc
entr
atio
n (p
pb)
Date
GAC - PFNA
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
0
0.005
0.01
0.015
0.02
0.025
0.03
Conc
entr
atio
n (p
pb)
Date
IX - PFNA
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Treated 10,400 Gals or 13,000 BVs through 10 min EBCT IX Resin Treated 34,400 Gals or 171,000 BVs through 2.5 min EBCT
First sample at 574 gals Treated
2860 BVs
Removal Comparison – PFNA
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Conc
entr
atio
n (p
pb)
Date
GAC - PFBS
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
First sample at 574 gals Treated
2860 BVs
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Conc
entr
atio
n (p
pb)
Date
IX - PFBS
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Treated 10,400 Gals or 13,000 BVs through 10 min EBCT IX Resin Treated 34,400 Gals or 171,000 BVs through 2.5 min EBCT
Removal Comparison – PFBS
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Conc
entr
atio
n (p
pb)
Date
GAC - PFHxA
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Conc
entr
atio
n (p
pb)
Date
IX - PFHxA
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Treated 10,400 Gals or 13,000 BVs through 10 min EBCT IX Resin Treated 34,400 Gals or 171,000 BVs through 2.5 min EBCT
First sample at 574 gals Treated
2860 BVs
Removal Comparison – PFHxA
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Conc
entr
atio
n (p
pb)
Date
GAC - PFHxS
GAC 10.0 min
GAC 5.0 min
GAC 2.5 min
INFLUENT
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Conc
entr
atio
n (p
pb)
Date
IX - PFHxS
IX 10.0 min
IX 5.0 min
IX 2.5 min
INFLUENT
GAC Treated 10,400 Gals or 13,000 BVs through 10 min EBCT IX Resin Treated 34,400 Gals or 171,000 BVs through 2.5 min EBCT
First sample at 574 gals Treated
2860 BVs
Removal Comparison – PFHxS
Full Scale Process
Life Cycle Cost and Design
Activated Carbon and Resin Piloting – Haven Well
0
10
20
30
40
50
60
70
- 5,000 10,000 15,000 20,000 25,000 30,000PF
OS+
PFO
A (p
pt)
Gallons Treated (Pilot Scale)
Haven Well PFOS+PFOA Results
GAC - 10 Min EBCT
Resin - 5 Min EBCT
HA Limit – 70 ppt
½ HA Limit – 35 ppt
Trigger for GAC Change out
(3) Lead/Lag IX Resin Trains In Parallel
(3) GAC Vessels In Parallel
LGAC VesselsResin Vessels
Influent Well Manifold
Full Scale Rendering DWS
Summary and Lessons Learned – Single Use
Compared IX Resin vs GAC on a gallons treated basis. • GAC: 50 ppt PFOS+PFOA break through in 10 min EBCT effluent after 13,000 BVs or 10,400 gallons treated
• IX resin: Non-Detect PFOS+PFOA in 2.5 min EBCT effluent after 171,000 BVs or 34,300 gallons treated
IX Resin provides dual mechanism for PFAS removal: Adsorption & Ion Exchange• Higher Capacity and Faster Kinetics
Full Scale Life Cycle Cost Comparison revealed IX Resin Hybrid System provided:• 1/2 Capital cost
• 1/3 O&M Media cost
• 1/2 Total Present Worth Cost
Regenerable System Development – Pease Site 8
Goals for Regenerable System Development
• Address remediation of localized area around firefighting zone (Site 8) to extract water, treat, and return water to aquifer free of PFAS.
• Because of high concentrations in remediation wells vs DWS wells, treatment needed to be designed to be regenerable, and not single use, which would be cost prohibitive to operate.
• Water quality should not be altered on returned water to aquifer such that it could cause prevention of use for public water supply. No adverse characteristics.
Influent Data
PFAS Compound Average Influent Concentration (µg/L)
PFOA 11.5
PFOS 27.4
Other PFAS 55.6
Total PFAS 94.5
Successful Regeneration
0.0
1.0
2.0
3.0
4.0
5.0
6.0
- 2,000 4,000 6,000 8,000
Tota
l PFA
S Co
ncen
trat
ion
(ppb
)
Volume Treated (Bed Volumes)
Total PFAS Concentration from Lead IX Media Bed
Virgin Media
Post Regen
Full-scale Site 8 resin system
In-vessel resin regeneration system
Distillation for recovery of regen solution
Influent / Effluent from Full Scale System
Regeneration process and applications
• The regeneration process results in a smaller volume of waste, currently processed through super loaders (GAC with very low flow) that requires disposal or further treatment. Not determined to be hazardous at this point, but landfilling is not considered an option, incineration is preferred method.
• Regenerable systems are not, at this time, acceptable to be used in the US for drinking water applications, due to the use of the regenerant chemistry. While these resins do carry NSF certification, this is a long term driver to get the process certified for drinking water.
• Two promising technologies are on the forefront for regenerant destruction
• Plasma destruction
• Electrochemical treatment.
• Both are bench scale development stage, and scale up and cost design analysis needs to be completed
Current Status of Site 8
• System has processed more than 10 million gallons of water as of mid-November, 2018
• System has undergone 5 regeneration sequences since commissioning with less than 2% difference in throughput volumes until breakthrough.
• System has consistently returned ND PFAS water back to aquifer for re-injection.
