RELATED APPLICATIONS

This application claims benefit of and priority to U.S. Patent Application Serial No. 17/666,870 filed February 8, 2022, under §§119, 120, 363, 365, and 37 C.F.R. §1.55 and §1.78, and that application and this application also claim benefit of and priority to U.S. Provisional Application Serial No. 63/147,924 filed February 10, 2021, under 35 U.S.C. §§119, 120, 363, 365, and 37 C.F.R. §1.55 and §1.78, which are incorporated herein by this reference.

FIELD OF THE INVENTION

This invention relates to a system and method for removing per- and polyfluorinated sulfonic acids (PFSAs) and per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins.

BACKGROUND OF THE INVENTION

PF AS are a class of man-made compounds that have been used to manufacture consumer products and industrial chemicals, including, inter alia, aqueous film forming foams (AFFFs). AFFFs have been the product of choice for firefighting at military and municipal fire training sites around the world. AFFFs have also been used extensively at oil and gas refineries for both fire training and firefighting exercises. AFFFs work by blanketing spilled oil/fuel, cooling the surface, and preventing re-ignition. PFAS in AFFFs have contaminated the groundwater at many of these sites and refineries, including more than 100 U.S. Air Force sites. PFAS may be used as surface treatment/coatings in consumer products such as carpets, upholstery, stain resistant apparel, cookware, paper, packaging, and the like, and may also be found in chemicals used for chemical plating, electrolytes, lubricants, and the like, which may eventually end up in the water supply.

PFAS are bio-accumulative in wildlife and humans because they typically remain in the body for extended periods of time. Laboratory PFAS exposure studies on animals have shown problems with growth and development, reproduction, and liver damage. In 2016, the U.S. Environmental Protection Agency (EPA) issued the following health advisory levels (HALs) for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA): 0.07 pg/L for both the individual constituents and the sum of PFOS and PFOA concentrations, respectively. Additionally, PFAS are highly water soluble in water, result in large, dilute plumes, and have a low volatility.

PFAS are very difficult to treat largely because they are extremely stable compounds which include carbon-fluorine bonds. Carbon-fluorine bonds are the strongest known bonds in nature and are highly resistant to breakdown.

The vast majority of available conventional water treatment systems and methods to remove PFAS from water have proven to be ineffective. See e.g., Rahman, et al., Behaviour and Fate of Perfluoroalkyl and Poly fluoroalky I Substances (PFASs) in Drinking Water Treatment, Water Research 50, pp. 318-340 (2014), incorporated by reference herein. Conventional activated carbon adsorption system and methods to remove PFAS from water have shown to be somewhat effective on the longer-chain PFAS, but have difficulty in removing branched and shorter chain compounds, see e.g., Dudley, Master’s Thesis: Removal of Perfluorinated Compounds by Powdered Activated Carbon, Superfine Powdered Activated Carbon, and Anion Exchange Resins, North Carolina State University (2012), incorporated by reference herein.

Appleman et al., Treatment of Poly- and Perfluor oalkly Substances in U.S. Full-Scale Treatment Systems, Water Research 51, pp. 246-255 (2014), incorporated by reference herein, reported that, similar to activated carbon, some conventional anion exchange resins may be more effective at treating longer chain PFAS than the shorter chain compounds. Other conventional anion exchange resins have shown some success in removing a broader range of PFAS, including the shorter-chain compounds, see e.g., Dudley, cited supra.

Conventional anion exchange treatment systems and methods typically utilize anion exchange resin where positively charged anion exchange resin beads are disposed in a lead vessel which receives a flow of water contaminated with anionic contaminants, such as PFAS. The negatively charged contaminants are trapped by the positively charged resin beads and clean water flows out of the lead anion exchange vessel into a lag vessel, also containing anion exchange resin beads. A sample tap is frequently used to determine when the majority of the anion exchange beads in the lead exchange vessel have become saturated with contaminants. When saturation of the resin anion exchange beads is approached, a level of contaminants will be detected in the effluent tap. When this happens, the lead vessel is taken off-line and the contaminated water continues flowing to the lag vessel which now becomes the lead vessel. The lead-lag vessel configuration ensures that a high level of treatment is maintained at all times.

As discussed above, some conventional anion exchange resins can also be used to remove PFAS from water. A number of known methods exist to regenerant the anion exchange beads in the anion exchange vessel. Some known methods rely on flushing the resin with a brine or caustic solution. Other known methods may include the addition of solvents, such as methanol or ethanol, to enhance the removal of the PFAS trapped on the anion exchange beads. Effective resin regeneration has been demonstrated by passing a solvent (e.g., methanol or ethanol), blended with a sodium chloride or sodium hydroxide solution, through the resin. See e.g., Deng et al., Removal of Perfluorooctane Sulfonate from Wastewater by Anion Exchange Resins: Effects of Resin Properties and Solution Chemistry, Water Research 44, pp. 5188-5195 (2010) and Chularueangaksorn et al., Regeneration and Reusability of Anion Exchange Resin Used in Perfluorooctane Sulfonate Removal by Batch Experiments, Journal of Applied Polymer Science, 10.1002, pp. 884-890 (2013), both incorporated by reference herein. However, such methods may generate a large amount of toxic regenerant solution which must be disposed of at significant expense.

Du et al., Adsorption Behavior and Mechanism of Perfluorinated Compounds on Various Adsorbents - A Review, J. Haz. Mat. 274, pp. 443-454 (2014), incorporated by reference herein, discloses a need to further treat the waste regenerant solution to concentrate the PFAS and reduce the volume of waste. This is a key step because resin regeneration produces a significant volume of toxic waste.

The known methods for removing PFAS from water discussed above typically do not optimize the anion exchange resin and may have limited capacity for removing PFAS mass. Such known methods may also incompletely regenerant the anion exchange resin by attempting to desorb the PFAS from the resin, such known methods may incompletely regenerant the anion exchange resin which may lead to a loss of capacity, otherwise known as active sites, during each successive loading and regeneration cycle. This cumulative buildup of PFAS on the ion exchange resin is often referenced to as a “heel,” and results in reduced treatment effectiveness as the heel builds up over time. Such known methods may also not reclaim and reuse the spent regenerant solution which may increase the amount spent regenerant solution with removed PF AS therein. This increases the amount of toxic spent regenerant solution with PFAS, which must be disposed of at significant expense.

Conventional systems and methods for attempting to remove PFAS from water also include biological treatment, air stripping, reverse osmosis, and advanced oxidation. All of these conventional techniques are ineffective and/or extremely expensive.

Some manufacturing facilities produce contaminated wastewater and/or contaminated cooling water containing long and short-chain PFAS compounds. Long-chain PFAS compounds typically are designated having six or more carbons for perfluoroalkyl sulfonic acids and having seven or more carbons for perfluoroalkyl carboxylic acids. Short-chain PFAS compounds typically have less than six carbons for perfluoroalkyl sulfonic acids and less than seven carbons for perfluoroalkyl carboxylic acids.

Removal of PFAS compounds from contaminated water may be accomplished using anion exchange resin and/or granular activated carbon (GAC) discussed above. One advantage of using anion exchange resins is the anion exchange resin can be regenerated on site, which may substantially reduce cost of operation.

In general, anion exchange resins have a higher affinity for long-chain PFAS compounds. Therefore, short-chain PFAS compounds tend to break through anion exchange resins faster than long-chain PFAS compounds. Significant measures may be employed to minimize the breakthrough of short-chain PFAS compounds. Premature breakthrough of short-chain PFAS compounds may result in more frequent regeneration of the anion exchange resins or costly replacement of the anion exchange resins. To date, there are no known systems or methods which can effectively and efficiently remove both short and long-chain PFAS compounds from contaminated water using regenerable resin. Long-chain PFAS compounds in contaminated waters are easier to remove from the water with an anion exchange resin than short-chain PFAS compounds because the long-chain PFAS compounds have a longer hydrophobic tail with more surface area to bind to the anion exchange resin.

For the same reason, long-chain PFAS compounds are harder to remove from anion exchange resin during regeneration than short-chain PFAS compounds.

PFAS compounds may include per- and polyfluorinated sulfonic acids (PFSAs) and per- and polyfluorinated carboxylic acids (PFCAs).

PFSAs, e.g., perfluorooctanesulfonic acid (PFOS) and similar PFSAs, are easier to remove from contaminated water with an anion exchange resin than PFCAs, e.g., perfluorooctanoic acid (PFOA) and similar type PFCAs, because the negative charge of the sulfonates on the PFSAs is more strongly attached to the positively charged sites (N ⁺ of amine group) on the anion exchange resin than the negative charge on the carboxylates of the PFCAs.

PFSAs are harder to remove from an anion exchange resin during regeneration than PFCAs because their strong negative charge has a higher affinity to the positively charged sites on the anion exchange resin. Long-chain PFSAs are the hardest to remove (desorb) during regeneration because of their strong positive charge and their increased hydrophobic surface area.

Short-chain PFCAs are the hardest to remove from contaminated water with an anion exchange resin because of their shorter hydrophobic tail with less surface area and their weaker negative charge.

For the same reason, short-Chain PFCAs are the easiest to remove from an anion exchange resin during regeneration. Additionally, a regeneration solution of an alcohol, salt, and water is typically used to regenerate the anion exchange resin. The alcohol desorbs the hydrophobic tails of the long and short-chain PFAS (PFSAs and PFCAs) and the salt displaces the hydrophilic heads.

Methanol, ethanol, and similar type solvents in the regenerant solution are effective at desorbing the hydrophobic tails of the PFAS (PFSAs and PFCAs) from an anion exchange resin. Methanol is more effective than ethanol for regenerating an anion exchange resin because it can contain a higher dissolved salt concentration, i.e., methanol has a higher salt solubility. The higher salt concentration facilitates more effective desorption of the anionic heads of the PFAS compounds from the positively charged sites on the anionic exchange resin during regeneration. This is especially important for PFSAs, given their higher affinity for the positively charged sites. However, methanol may be a hazardous air pollutant and may be subject to certain environmental regulations. Therefore, it is sometimes preferable to use ethanol in the regenerant solution.

When ethanol or similar type two- or three-carbon chain solvent is used as part of the regenerant solution, the lower salt concentration associated with ethanol reduces the effectiveness of the regenerant solution to desorb PFSAs (both short and long-chain) from certain types of regenerable anion exchange resins.

In general, anion exchange resins have a higher affinity for long-chain PFAS than shortchain PFAS. In addition, anion exchange resins have a higher affinity for PFSAs than PFCAs. Therefore, PFCAs, especially short-chain PFCAs, tend to break through anion exchange resins faster than PFSAs. Significant measures may be employed to minimize the breakthrough of PFCAs, especially short-chain PFCAs. Premature breakthrough of PFCAs may result in more frequent regeneration of the anion exchange resins or costly replacement of the anion exchange resins.

To date, there are no known systems or methods which can effectively and efficiently remove both short- and long-chain PFSAs and PFCAs from contaminated water using regenerable resin and which may use an ethanol, denatured ethanol, or similar type two- or three- carbon chain solvent based regenerant solution.

SUMMARY OF THE INVENTION

In one aspect, a system for removing long-chain and short-chain per- and polyfluoroalkyl substances (PFAS) from contaminated water using a regenerable anion exchange resin is featured. The system includes at least one first anion exchange resin vessel configured to receive a flow of water contaminated with long and short-chain PFAS compounds. The at least one first anion exchange resin vessel includes a first regenerable anion exchange resin therein having a high affinity for long-chain PFAS compounds configured such that a majority of the long-chain PFAS compounds sorb to the first regenerable anion exchange resin to remove a majority of the long-chain PFAS compounds from the contaminated water and produce a flow of water having a majority of the long-chain PFAS compounds removed. The system also includes at least one second anion exchange resin vessel configured to receive the flow of water having a majority of the long-chain PFAS compounds removed. The at least one second anion exchange resin vessel includes a second regenerable anion exchange resin therein having a high affinity for short-chain PFAS compounds and configured such that a majority of the short-chain PFAS compounds sorb to the second anion exchange resin to remove a majority of the short-chain PFAS compounds from the contaminated water and produce a treated flow of water having a majority of the long and short-chain PFAS compounds removed. In one embodiment, a resin regeneration subsystem may be configured to introduce a flow of a regenerant solution into the at least one second anion exchange resin vessel to regenerant the second regenerable anion exchange resin and produce a flow of a first spent regenerant solution. The resin regeneration subsystem may include introducing the flow of the first spent regenerant solution or another flow of regenerant solution into the at least one first regenerable anion exchange vessels to regenerate the first regenerable anion exchange resin and produce a flow of a second spent regenerant solution. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second anion exchange resin may include a macroporous resin including functional groups configured to increase the affinity of the short-chain PFAS compounds to the second anion exchange resin and increase the capacity of the second anion exchange resin to remove the short-chain PFAS compounds from the flow of water having a majority of the long- chain PFAS compounds already removed. The length and basicity of the functional groups may be selected to increase the affinity of the short-chain PFAS compounds to the second anion exchange resin. The at least one first anion exchange vessel may include at least one lead vessel and at least one lag vessel. The at least one second anion exchange vessel may include at least one lead vessel and at least one lag vessel.

In another aspect, a system for removing long-chain and short-chain per- and polyfluoroalkyl substances (PFAS) from contaminated water using a regenerable anion exchange resin is featured. The system includes at least one anion exchange resin vessel configured to receive a flow of water contaminated with long and short-chain PFAS compounds. The at least one anion exchange resin vessel includes a first regenerable anion exchange resin therein having a high affinity for long-chain PFAS compounds configured such that a majority of the long-chain PF AS compounds sorb to the first regenerable anion exchange resin to remove a majority of the long-chain PFAS compounds from the contaminated water and produce a flow of water having a majority of the long-chain PFAS compounds removed. The at least one anion exchange resin vessel further includes a second regenerable anion exchange resin therein configured to receive the flow of water having a majority of the long-chain PFAS compounds removed. The second regenerable anion exchange resin has a high affinity for short-chain PFAS compounds and is configured such that a majority of the short-chain PFAS compounds sorb to the second anion exchange resin to remove a majority of the short-chain PFAS compounds from the contaminated water and produce a treated flow of water having a majority of the long and short-chain PFAS compounds removed.

In one embodiment, the at least one first anion exchange vessel may include at least one lead vessel train and at least one lag vessel train. The system may include a resin regeneration subsystem configured to introduce a flow of a regenerant solution into the second regenerable anion exchange resin to regenerate the second regenerable anion exchange resin and produce a flow of a first spent regenerant solution. The resin regeneration subsystem may include introducing the flow of the first spent regenerant solution or another flow of regenerant solution into first regenerable anion exchange resin to regenerate the first regenerable anion exchange resin and produce a flow of a second spent regenerant solution. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second anion exchange resin may include a macroporous resin including functional groups configured to increase the affinity of the short-chain PFAS compounds to the second anion exchange resin and increase the capacity of the second anion exchange resin to remove the short-chain PFAS compounds from the flow of water having a majority of the long-chain PFAS compounds already removed. The length and basicity of the functional groups may be selected to increase the affinity of the short-chain PFAS compounds to the second anion exchange resin. The at least one lead vessel train may include one or more anion exchange vessels connected in series such that at least one anion exchange vessel may be configured to receive the flow of contaminated water and includes the first regenerable anion exchange resin therein to remove a majority of the long-chain PFAS compounds from the contaminated water and produce a flow of water having a majority of the long-chain PFAS compounds removed and at least one anion exchange vessel may be configured to receive the flow of water having a majority of the long-chain PFAS compounds removed and may include the second regenerable anion exchange resin therein to remove a majority of the short-chain PFAS compounds and produce a treated flow of water having a majority of the long and shortchain PFAS compounds removed. The at least one lag vessel train may include one or more anion exchange vessels connected in series configured to receive the treated flow of water which may have carryover short-chain PFAS compounds therein and output a treated flow of water having a majority of the long and short-chain PFAS compounds removed.

In another aspect, a method for removing long-chain and short-chain per- and polyfluoroalkyl substances (PFAS) from contaminated water using a regenerable anion exchange resin is featured, the method includes receiving a flow of water contaminated with long and short-chain PFAS compounds, sorbing a majority of the long-chain PFAS compounds to a first regenerable anion exchange resin having a high affinity for long-chain PFAS compounds to remove a majority of the long-chain PFAS compounds from the flow of contaminated water and produce a flow of water having a majority of the long-chain PFAS compounds removed, and receiving the flow of water having a majority of the long-chain PFAS compounds removed and sorbing a majority of the short-chain PFAS compounds to a second anion exchange resin having a high affinity for short-chain PFAS compound to remove a majority of the short-chain PFAS compounds from the contaminated water and produce a treated flow of water having a majority of the long and short-chain PFAS compounds removed.

In one embodiment, the method may include a resin regeneration process which may be configured to introduce a flow of a regenerant solution into the second regenerable anion exchange resin to regenerant the second regenerable anion exchange resin and produce a flow of a first spent regenerant solution. The method may include introducing the flow of the first spent regenerant solution or another flow of regenerant solution into the first regenerable anion exchange resin to regenerate the first regenerable anion exchange resin and produce a flow of a second spent regenerant solution. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second anion exchange resin may include a macroporous resin including functional groups configured to increase the affinity of the short-chain PFAS compounds to the second anion exchange resin and increase the capacity of the second anion exchange resin to remove the shortchain PFAS compounds from the flow of water having a majority of the long-chain PFAS compounds already removed. The length and basicity of the functional groups may be selected to increase the affinity of the short-chain PFAS compounds to the second anion exchange resin.

In another aspect, a system for removing per- and polyfluorinated sulfonic acids (PFSAs) and per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins is featured. The system includes at least one first anion exchange resin vessel configured to receive a flow of water contaminated with PFSAs and PFCAs. The at least one first anion exchange resin vessel includes a first regenerable anion exchange resin therein configured to remove a majority of the PFSAs from the flow of water contaminated PFSAs and PFCAs and produce a flow of water having a majority of the PFSAs removed. The system also includes at least one second anion exchange resin vessel which is configured to receive the flow of water having a majority of the PFSAs removed. The at least one second anion exchange resin vessel includes a second regenerable anion exchange resin therein configured to remove a majority of the PFCAs from the flow of water having a majority of PFSAs removed and produce a flow of treated water having a majority of the PFSAs and PFCAs removed.

In one embodiment, the system may include a resin regeneration subsystem which may be configured to introduce a flow of a regenerant solution into at least one of the first regenerable anion exchange vessel or the second anion exchange resin vessel to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin and produce a flow of a at least one spent regenerant solution. The regenerant solution may comprises a mixture of a salt, a solvent, and water. The solvent may include one or more of a two or three-carbon chain solvent. The solvent may include one or more of ethanol, denatured ethanol, isopropyl alcohol, ethane, ethene, propane, or propene. The solvent may include methanol. The mixture of the salt, the solvent and the water may include a predetermined amount of the salt by weight, at least one of a predetermined amount of the ethanol, the denatured ethanol, or the isopropyl alcohol by volume, and a predetermined amount of the water by volume which may be configured to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second regenerable anion exchange resin may include a macroporous resin including functional groups configured to increase the affinity of the PFCAs to the second regenerable anion exchange resin and increase the capacity of the second regenerable anion exchange resin to remove the PFCAs from the flow of water having a majority of the PFSAs removed. The length and basicity of the functional groups on the second regenerable anion exchange resin may be selected to increase the affinity of the PFCAs to the second regenerable anion exchange resin. The at least one first anion exchange vessel may include at least one lead vessel and at least one lag vessel. The at least one second anion exchange vessel may include at least one lead vessel and at least one lag vessel.

In another aspect, a system for removing per- and polyfluorinated sulfonic acids (PFSAs) and per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins is featured. The system includes at least one anion exchange resin vessel configured to receive a flow of water contaminated with PFSAs and PFCAs. The at least one first anion exchange resin vessel includes a first regenerable anion exchange resin therein configured to remove a majority of the PFSAs from the contaminated water and produce a flow of water having a majority of the PFSAs removed. The at least one anion exchange resin vessel also includes at least one second regenerable anion exchange resin therein configured to receive the flow of water having a majority of the PFSAs removed and is configured to remove a majority of the PFCAs from the flow of water having a majority of the PFSAs removed and produce a flow of treated water having a majority of the PFSAs and PFCAs removed.

In one embodiment, the system may include a resin regeneration subsystem which may be configured to introduce a flow of a regenerant solution into the at least one of the first regenerable anion exchange vessel or the second anion exchange resin vessel to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin and produce a flow of a at least one spent regenerant solution. The regenerant solution may comprises a mixture of a salt, a solvent, and water. The solvent may include one or more of a two or three-carbon chain solvent. The solvent may include one or more of ethanol, denatured ethanol, isopropyl alcohol, ethane, ethene, propane, or propene. The solvent may include methanol. The mixture of the salt, the solvent and the water may include a predetermined amount of the salt by weight, at least one of a predetermined amount of the ethanol, the denatured ethanol, or the isopropyl alcohol by volume, and a predetermined amount of the water by volume and may be configured to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second regenerable anion exchange resin may include a macroporous resin including functional groups which may be configured to increase the affinity of the PFCAs to the second regenerable anion exchange resin and increase the capacity of the second regenerable anion exchange resin to remove the PFCAs from the flow of water having a majority of the PFSAs removed. The length and basicity of the functional groups on the second regenerable anion exchange resin may be selected to increase the affinity of the PFCAs to the second regenerable anion exchange resin. The at least one first anion exchange vessel may include at least one lead vessel and at least one lag vessel. The at least one first anion exchange vessel may include at least one lead vessel train and at least one lag vessel train. The at least one lead vessel train may include at least one anion exchange vessel including the first regenerable anion exchange resin therein which may be connected in series with at least one anion exchange vessel including the second regenerable anion exchange resin. The at least one lag vessel train may include at least one anion exchange vessel including the first regenerable anion exchange resin therein which may be connected in series with at least one anion exchange vessel including the second regenerable anion exchange resin therein.

In another aspect, a method system for removing per- and polyfluorinated sulfonic acids (PFSAs) and per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins is featured. The method includes receiving a flow of water contaminated with PFSAs and PFCAs, removing a majority of the PFSAs from the contaminated water with a first anion exchange resin and producing a flow of water having a majority of the PFSAs removed, and receiving the flow of water having a majority of the PFSAs removed and removing a majority of the PFCAs with a second regenerable anion exchange resin and producing a flow of treated water having a majority of the PFSAs and PFCAs removed.

In one embodiment, the resin regeneration subprocess may be configured to introduce a flow of a regenerant solution into at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin and produce a flow of a at least one spent regenerant solution. The regenerant solution may comprise a mixture of a salt, a solvent, and water. The solvent may include one or more of a two or three-carbon chain solvent. The solvent may include one or more of ethanol, denatured ethanol, isopropyl alcohol, ethane, ethene, propane, or propene. The solvent may include methanol. The mixture of the salt, the solvent and the water may include a predetermined amount of the salt by weight, at least one of a predetermined amount of the ethanol, the denatured ethanol, or the isopropyl alcohol by volume, and a predetermined amount of the water by volume configured to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second regenerable anion exchange resin may include a macroporous resin including functional groups which may be configured to increase the affinity of the PFCAs to the second regenerable anion exchange resin and increase the capacity of the second regenerable anion exchange resin to remove the PFCAs from the flow of water having a majority of the PFSAs removed. The length and basicity of the functional groups on the second regenerable anion exchange resin may be selected to increase the affinity of the PFCAs to the second regenerable anion exchange resin.

In another aspect, a system for removing long and short-chain per- and polyfluorinated sulfonic acids (PFSAs) and long and short-chain per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins is featured. The system includes at least one first regenerable anion exchange resin vessel configured to receive a flow of water contaminated with long and short-chain PFSAs and long and short-chain PFCAs. The at least one first regenerable anion exchange resin vessel includes a first regenerable anion exchange resin therein configured to remove a majority of long-chain and short-chain PFSAs and long-chain PFCAs from the contaminated water and produce a flow of water having a majority of the long and short-chain PFSAs and long-chain PFCAs removed. The system also includes at least one second anion exchange resin vessel configured to receive the flow of water having a majority long and short-chain PFSAs and long-chain PFCAs removed. The at least one second anion exchange resin vessel includes a second regenerable anion exchange resin therein configured to remove a majority of the short-chain PFCAs from the flow of water having a majority of the long-chain and short-chain PFSAs and long-chain PFCAs removed and produce a treated flow of water having a majority of the long and short-chain PFCAs and the long and short-chain PFSAs removed. In one embodiment, the system may include a resin regeneration subsystem configured to introduce a flow of a regenerant solution into at least one of the first regenerable anion exchange vessel or the second anion exchange resin vessel to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin and produce a flow of a at least one spent regenerant solution. The regenerant solution may comprises a mixture of a salt, a solvent, and water. The solvent may include one or more of a two or three-carbon chain solvent. The solvent may include one or more of ethanol, denatured ethanol, isopropyl alcohol, ethane, ethene, propane, or propene. The solvent may include methanol. The the mixture of the salt, the solvent and the water includes a predetermined amount of the salt by weight, at least one of a predetermined amount of the ethanol, the denatured ethanol, or the isopropyl alcohol by volume, and a predetermined amount of the water by volume configured to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second regenerable anion exchange resin may includes a macroporous resin including functional groups configured to increase the affinity of the short-chain PFCAs to the second regenerable anion exchange resin and increase the capacity of the second regenerable anion exchange resin to remove short-chain PFCAs from the flow of water having a majority of the long and short-chain PFSAs and long-chain PFCAs removed. The length and basicity of the functional groups on the second regenerable anion exchange resin may be selected to increase the affinity of the shortchain PFCAs to the second regenerable anion exchange resin. The at least one first regenerable anion exchange vessel may include at least one lead vessel and at least one lag vessel. The at least one second anion exchange resin vessel may include at least one lead vessel and at least one lag vessel.

In another aspect, a method for removing long and short-chain per- and polyfluorinated sulfonic acids (PFSAs) and long and short-chain per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins is featured. The method includes receiving a flow of water contaminated with long and short-chain PFSAs and long and short-chain PFCAs, removing a majority of the long-chain and short-chain PFSAs and long-chain PFCAs from the flow of water contaminated with long and short-chain PFSAs and long and short-chain PFCAs with a first anion exchange resin and producing a flow of water having a majority of the long- and short-chain PFSAs and long-chain PFCAs removed, and receiving the flow of water having a majority of the long- and short-chain PFSAs and long-chain PFCAs removed and removing a majority of the short-chain PFCAs with a second regenerable anion exchange resin and producing a flow of treated water having a majority of the long and short-chain PFCAs and the long and short-chain PFSAs removed

In one embodiment, the resin regeneration subprocess may be configured to introduce a flow of a regenerant solution into at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin and produce a flow of a at least one spent regenerant solution. The regenerant solution may comprise a mixture of a salt, a solvent, and water. The solvent may include one or more of a two or three-carbon chain solvent. The solvent may include one or more of ethanol, denatured ethanol, isopropyl alcohol, ethane, ethene, propane, or propene. The solvent may include methanol. The mixture of the salt, the solvent and the water may include a predetermined amount of the salt by weight, at least one of a predetermined amount of the ethanol, the denatured ethanol, or the isopropyl alcohol by volume, and a predetermined amount of the water by volume configured to regenerate at least one of the first regenerable anion exchange resin or the second regenerable anion exchange resin. The first regenerable anion exchange resin and the second regenerable anion exchange resin may include a macroporous, strong base, anion exchange resin. The second regenerable anion exchange resin may include a macroporous resin including functional groups which may be configured to increase the affinity of the short-chain PFCAs to the second regenerable anion exchange resin and increase the capacity of the second regenerable anion exchange resin to remove the shortchain PFCAs from the flow of water having a majority of the long and short-chain PFSAs and long chain PFCAs removed. The length and basicity of the functional groups on the second regenerable anion exchange resin may be selected to increase the affinity of the short-chain PFCAs to the second regenerable anion exchange resin.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

Fig. 1 shows an example of a typical PFAS with a hydrophobic non-ionic tail and an anionic head;

Fig. 2 shows a three-dimensional view depicting the complex three-dimensional structure of a typical anion exchange resin bead showing examples of positively charged anion exchange sites on the resin bead binding to negatively charged hydrophilic heads of PFAS molecules and the hydrophobic carbon-fluorine tails of the PFAS sorbing to the hydrophobic backbone of the anion exchange resin bead;

Fig. 3 is a schematic block diagram showing the primary components of one example of system for removing long-chain and short-chain PFAS from contaminated water;

Fig. 4 is a schematic block diagram showing the primary components of another example of system for removing long-chain and short-chain PFAS from contaminated water;

Fig. 5 is a schematic block diagram showing one example of lead and lag vessels which may be utilized with the system shown in Figs. 3 and 4;

Fig. 6 is a schematic block diagram showing the primary components of another example of system for removing long-chain and short-chain PFAS from contaminated water;

Fig. 7 is a schematic block diagram showing one example of one or more lead and lag vessels which may be utilized with the system shown in Fig. 6;

Fig. 8 is a schematic block diagram showing one example of one or more anion exchange vessels configured in series to reduce the height of the anion exchange vessel shown in Fig. 6;

Fig. 9 is a schematic block diagram showing one example of the system shown in Fig 8 arranged in lead-lag vessel configuration;

Fig. 10 is a flow chart showing the primary steps of one example of method for removing long-chain and short-chain PFAS from contaminated water;

Fig. 11 is a schematic block diagram showing the primary components of one example of a system for removing PFSAs and PFCAs from contaminated water using regenerable anion exchange resins;

Fig. 12 is a schematic block diagram showing the primary components of another example of a system for removing PFSAs and PFCAs from contaminated water using regenerable anion exchange resins;

Fig. 13 is a schematic block diagram showing one example of lead and lag vessels which may be utilized with the system shown in Figs. 11 and 12; Fig. 14 is a schematic block diagram showing the primary components of another example of a system for removing PFSAs and PFCAs from contaminated water using regenerable anion exchange resins;

Fig. 15 is a schematic block diagram showing one example of one or more lead and lag vessels which may be utilized with the system shown in Fig. 14;

Fig. 16 is a schematic block diagram showing one example of one or more anion exchange vessels configured in series to reduce the height of the anion exchange vessel shown in Fig. 14;

Fig. 17 is a schematic block diagram showing one example of the system shown in Fig.

16 arranged in lead-lag vessel configuration;

Fig. 18 is a flow chart showing the primary steps of one example of method for removing PFSAs and PFCAs from contaminated water using regenerable anion exchange resins; and

Fig. 19 is a flow chart showing the primary steps of one example of method for removing long and short-chain PFSAs and long and short-chain PFCAs from contaminated water using regenerable anion exchange resins.

DETAILED DESCRIPTION OF THE INVENTION

Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer.

As discussed in the Background section, anion exchange resins are highly effective at removing PFAS from water because of the multiple removal methods involved. The molecular structure of most PFAS compounds can be broken into two functional units including the hydrophobic non-ionic “tail,” comprised of the fluorinated carbon chain and the hydrophilic anionic “head,” having a negative charge. Fig. 1 shows an example of a typical PFAS 10 with hydrophobic non-ionic tail 12 and hydrophilic anionic head 14, in this example, a sulfonate group, although anionic head 14 may be a carboxylate group or similar type group.

Anion exchange resins are essentially adsorbents with anion exchange functionality. The resin beads are typically composed of neutral copolymers (plastics) that have positively charged exchange sites. Fig. 2 shows an example of the complex three-dimensional structure of a typical anion exchange resin bead 16 with positively charged exchange sites exemplarily indicated at 18. Anion exchange resins tend to be effective at removing PFAS from water because they take advantage of the unique properties of both the anion exchange resin bead and the perfluorinated contaminants, or PFAS, using a dual mechanism of adsorption and anion exchange. For example, hydrophobic carbon-fluorine tail 12, Figs. 1 and 2 of PFAS 10, adsorbs to the hydrophobic backbone on anion exchange resin 16, Fig. 2, comprised of cross-linked polystyrene polymer chains, exemplarily indicated at 20 and divinylbenzene cross-links exemplarily indicated at 22. The negatively-charged hydrophilic heads 24 (sulfonate groups) or 26 (carboxylate groups) of PFAS 10 are attracted to positively-charged anion exchange sites 18 on anion exchange resin bead 16. The negatively charged heads 24, 26 of PFAS 10 displaces exchangeable inorganic counter ion 38, e.g., a chloride ion which is provided on anion exchange bead 18 when it is manufactured. The hydrophobic, uncharged carbon-fluorine tails 12 are adsorbed to the uncharged hydrophobic backbone comprised of polystyrene polymer chain 20 and divinylbenzene crosslink 22 via Van der Waals forces as shown.

Depending on the specific properties of both resin bead 16 and the PFAS 10, this dual mechanism of removal may be highly effective at removing PFAS from water and certain anion exchange resins have very high removal capacity for PFAS from water.

While the dual mechanism of PFAS removal discussed above may be highly effective at removing PFAS from water because the adsorption of the hydrophobic tails of the PFAS to the hydrophobic backbone of the anion resin exchange bead, it also makes resin regeneration and reuse more difficult. A high concentration of a brine or base solution, e.g., a solution of a salt, such as NaCl, and water, or a solution of a base, such as NaOH and water, may be used to effectively displace the anionic head of the PFAS from the anion exchange site of the anion exchange resin bead, but the hydrophobic carbon-fluorine tail tends to stay adsorbed to the resin backbone. Similarly, an organic solvent, e.g., methanol or ethanol, may be used to effectively desorb the hydrophobic tail from the backbone, but then the anionic head of the PFAS stays attached to the resin anion exchange site. Research to date has demonstrated that effective regeneration techniques must overcome both mechanisms of attraction. Solutions combining organic solvents and a salt or base, such as NaCl or NaOH, have shown the most successful results to date, e.g., as disclosed in Deng et al., 2010, and Chularueangaksom et al., 2013, discussed in the Background section. Other research has focused on using combinations of ammonium salts, including ammonium hydroxide and ammonium chloride, e.g., as disclosed by Conte et al., Poly fluorinated Organic Micropollutants Removal from Water by Ion Exchange and Adsorption, Chemical Engineering Transactions, Vol. 43 (2015), incorporated by reference herein.

There is shown in Fig. 3 one example of system 50 for removing long and short-chain PFAS from contaminated water using a regenerable anion exchange resin. System 50 includes at least one first anion exchange vessel, e.g., anion exchange vessel 52, which receives flow 54 of water contaminated with long and short-chain PFAS compounds. Anion exchange resin vessel 52 includes first regenerable anion exchange resin therein, exemplarily indicated at 56, having a high affinity for long-chain PFAS compounds. First regenerable anion exchange resin 56 is configured such that a majority of long-chain PFAS compounds in flow 54 sorb to regenerable anion exchange resin 56 to remove a majority of the long-chain PFAS compounds from flow 54 of contaminated water 54 to produce flow 58 having a majority of the long-chain PFAS compounds removed.

System 50 also includes at least one second anion exchange resin vessel, e.g., second anion exchange vessel 60 which receives flow 58 of water having a majority of long-chain PFAS removed. Second anion exchange resin vessel 60 includes second regenerable anion exchange resin therein, exemplarily indicated at 62, having a high affinity for short-chain PFAS compounds and is configured such that a majority of the short-chain PFAS compounds in flow 58 sorb to second anion exchange resin 62 to remove a majority of the short-chain PFAS compounds from flow 58 and produce treated flow 64 of water having a majority of long and short-chain PFAS compounds removed.

The result is both long and short-chain PFAS compounds are effectively and efficiently removed from flow 54 of water contaminated with long and short-chain PFAS compounds. As discussed below, first regenerable anion exchange resin 56 and second regenerable anion exchange resin 62 are highly regenerable which preferably reduces the frequency of regeneration of anion exchange resin and therefore reduces costs.

In one example, second regenerable anion exchange resin 62 preferably includes a macroporous resin including functional groups configured to increase the affinity of short-chain PF AS compounds to second anion exchange resin 62 and increase the capacity of second anion exchange resin 62 to remove short-chain PFAS compounds from flow 58 of water having the majority of the long-chain PFAS compounds already removed.

In one design, the length and basicity of the functional groups of second anion exchange resin 62 are preferably selected to increase the affinity of short-chain PFAS compounds to second anion exchange resin 62. As known by those skilled in the art, increasing the length of the functional group of an anion exchange resin provides more surface area for sorption of PFAS compounds (both long-chain and short-chain). Shorter chain PFAS compounds have less surface area than long-chain PFAS compound and are therefore more difficult to remove from contaminated water but are easier to remove from the resin during regeneration. When the length of the anion exchange resin functional groups is increased this renders the resin more effective at removing short-chain compounds. However, increasing the length of the functional group makes it more difficult to regenerate the resin.

Additionally, increasing the length of the functional group of an anion exchange resin causes the nitrogen (i.e., the amine group) on the functional group to have a stronger positive charge because it increases the basicity and thus increases its ability to attract short-chain PFAS molecules.

When the length of the anion exchange resin functional groups is decreased this renders the resin easier to regenerate. However, this decrease in the length of the resin's functional group also deceases its capacity to remove PFAS compounds. In summary, the longer the length functional group of the anion exchange resin the more effective the resin is at removing both long and short-chain PFAS. However, it is very difficult to remove long-chain PFAS from resins with increased length functional groups during regeneration. The shorter the length functional group of the anion exchange resin the easier it is to regenerate.

Thus, system 50 overcomes the problem discussed in the Background section and provides a solution for effectively and efficiently removing both short and long-chain PFAS compounds from contaminated water by utilizing first regenerable anion exchange resin 52 with a reduced length functional group to remove a majority of the long-chain PFAS compounds followed by second regenerable anion exchange resin 62 with an increased length functional group to remove a majority of the short-chain PFAS compounds.

Thus, to effectively remove both short and long-chain PFAS compounds from flow 54 of contaminated water, system 50 initially utilizes first regenerable anion exchange resin 56, Figs. 3 and 4, preferably having functional groups of reduced length which results in a high affinity for long-chain PFAS compounds and effectively and efficiently removes long-chain PFAS compounds from flow 54 of contaminated water. First regenerable anion exchange resin 56 is preferably highly regenerable for removing long-chain PFAS compounds sorbed to first regenerable anion exchange resin 56 using a regenerant solution, as discussed in detail below. The reduced length of the functional group of first regenerable anion exchange resin 56 may not effectively remove short-chain PFAS compounds.

Then, system 50 utilizes second regenerable anion exchange resin 62 having functional groups with increased length which results in an increased affinity of short-chain PFAS compounds to second regenerable anion exchange resin 62 to effectively and efficiently remove the short-chain PFAS compounds in flow 58. Second regenerable anion exchange resin 62 is preferably highly regenerable for removing short-chain PFAS compounds sorbed onto second regenerable anion exchange resin 62 using a regenerant solution as discussed below.

In one example, first regenerable anion exchange resin 56 and second regenerable anion exchange resin 56 each preferably includes a macroporous, strong base anion exchange resin. In one example, first regenerable anion exchange resin 56 may include SORB EX REPURE™ available from Montrose Environmental Group, Little Rock, AR 72118 or similar type regenerable anion exchange resins. In one example, second regenerable anion exchange resin 62 may include SIR-110-MP, available from ResinTech, Camden, NJ 08105.

The result is system 50 may utilize first regenerable anion exchange resin 56 in first anion exchange resin vessel 52 to remove a majority of the long-chain PFAS compounds and then use second regenerable anion exchange resin 62 that is specifically designed with functional groups that increase the affinity for short-chain PFAS compounds to effectively and efficiently remove the short-chain PFAS compounds. Both first regenerable anion exchange resin 56 and second regenerable anion exchange resin 62 are preferably highly regenerable, as discussed below. Such a design uses regenerable anion exchange resins to efficiently and cost effectively remove both short and long-chain PFAS compounds from contaminated water.

System 50, Fig. 3, preferably includes resin regeneration subsystem 70 configured to introduce flow 72 of a regenerant solution into at least one second anion exchange resin vessel 60 to regenerate second regenerable anion exchange resin 62 and produce flow 74 of first spent regenerant solution. Resin regenerant subsystem 70 may also include introducing flow 74 of first spent regenerant solution into at least one first regenerable anion exchange vessel 52 to regenerate first regenerable anion exchange resin 56 and produce flow 76 of second spent regenerant solution.

In one example, first spent regenerant solution 74 and/or second spent regenerant solution 76 preferably includes the solvent, water, and salt. In one example, the solvent may include an alcohol.

Resin regenerant subsystem 70 may also include separation and recovery subsystem 80 including at least one of an evaporation subsystem, a distillation subsystem and a membrane separation subsystem, e.g., as disclosed in U.S. Patent Nos. 10,287,185 and 11,174,175, owned by the assignee hereof, both incorporated by reference herein. Separation and recovery subsystem 80 preferably produces flow 82 of reclaim solvent. Resin regenerant subsystem 70 also preferably includes solvent purification subsystem 84 which receives flow 82 of reclaim solvent and preferably removes any carryover PFAS which may be present in flow 82 to provide flow 86 of purified reclaim solvent 86 for reuse. In one design, flow 86 may be input to flow 72 of regenerant solution as shown. In one example, solvent purification subsystem 84 may include additional anion exchange resin, exemplarily indicated at 88, e.g., SORBEX REPURE™, discussed supra, or similar type anion exchange resin, housed in vessel 90 as shown in caption 92.

In one design, separation and recovery subsystem 80 may also produce solution 98 comprising concentrated PFAS, salt and water. Separation and recovery subsystem 80 may include a super- loading recovery subsystem which receives solution 98 of concentrated PFAS, salt and water and separates and further concentrates the PFAS from the solution by sorbing the concentrated PFAS onto a sorbtive media to produce a concentrated PFAS waste product e.g., as disclosed in commonly owned U.S. Patent No. 10,287,185 and 11,174,175, cited supra. The super loading subsystem may also generate a solution comprised of concentrated salt and water. In another example, system 50', Fig. 4, preferably includes resin regenerant subsystem 70 which similarly introduces flow 72 of regenerant solution into at least one second anion exchange vessel 60 having second anion exchange resin 62 therein. However, in this example, system 50' preferably independently introduces flow 100 of regenerant solution into at least one first regenerable anion exchange resin vessel 52 to regenerate first regenerable anion exchange resin 56 and produce flow 102 of second spent regenerant solution which is preferably introduced to separation and recovery subsystem 80' which operates similar as discussed above with reference to Fig. 3. In this example, separation and recovery subsystem 80’ also receives flow 74 of first spent regenerant solution from second anion exchange vessel 60. Separation and recovery subsystem 80' preferably produces flow 82' of reclaimed solvent similar as discussed above and may include solvent purification subsystem 84' similar as discussed above which preferably provides flow 86' of purified reclaimed solvent which may be input to flow 72 of regenerant solution input to second anion exchange resin vessel 60 and preferably also the input to flow 100 of regenerant solution input into first anion exchange resin vessel 52 as shown.

In one design, system 50" Fig. 5 may include anion exchange vessel 52 with first regenerable anion exchange resin 56 therein configured as a lead vessel which receives flow 54 of water contaminated with short and long-chain PFAS compounds. Similar as discussed above, first regenerable anion exchange resin 56 removes a majority of long-chain PFAS compounds from flow 54. System 50" also preferably includes anion exchange vessel 120 with first regenerable anion exchange resin 56 therein configured as lag vessel 120 as shown. Lag vessel 120 with first regenerable anion exchange resin 56 preferably captures any long-chain PFAS compounds that may break through lead vessel 52 in flow 58. System 50" also preferably includes sample tap 122 which is used to detect a predetermined breakthrough concentration of long-chain PFAS compounds in flow 58. When this happens, lead vessel 52 is temporarily taken offline for regeneration of first regenerable anion exchange resin 56 and flow 54 of water contaminated with long-chain PFAS compounds and short-chain PFAS compounds is directed to lag vessel 120 as flow 54' as shown and lag vessel 120 becomes the new lead vessel and outputs flow 58 having a majority of the long-chain PFAS compounds removed. First regenerable anion exchange resin 56 is preferably regenerated using flow 100 of regenerant solution similar as discussed above. Spent regenerant solution 102 is preferably directed to separation and recovery as discussed above. Once first regenerable anion exchange resin 56 in anion exchange vessel 52 is successfully regenerated, anion exchange vessel 52 functions as the new lag vessel and receives flow 58' having a majority of long-chain PFAS compounds removed and captures any long-chain PFAS compounds that may breakthrough lead vessel 120. System 50" also preferably includes sample tap 124 which preferably detects a predetermined breakthrough concentration of long-chain PFAS compounds in flow 58', as discussed above. Additional details of switching between lead and lag vessels is also disclosed in commonly owned U.S. Patent No. 10,695,709, incorporated by reference herein.

Similarly, system 50" also preferably includes anion exchange vessel 60 with second regenerable anion exchange resin 62 therein configured as a lead vessel which receives flow 58 having a majority of the long-chain PFAS compounds removed and outputs flow 78 of treated water as discussed above. System 50" also preferably includes anion exchange vessel 130 with second regenerable anion exchange resin 62 therein configured as lag vessel 130 as shown. Lag vessel 130 with second regenerable anion exchange resin 62 therein preferably captures any short-chain PFAS compounds in flow 78 that may break though lead vessel 60. System 50" also preferably includes sample tap 132 which is preferably used to detect a predetermined breakthrough concentration of short-chain PFAS compounds in flow 78. When this happens, anion exchange vessel 60 is temporarily taken offline so that second regenerable resin 62 can be regenerated. Second regenerable anion exchange resin 62 is preferably regenerated using flow 72 of regenerant solution similar as discussed above. Flow 58 is directed to lag vessel 130 as flow 58' and lag vessel 130 now becomes the new lead vessel and outputs flow 64 of treated water.

Once second regenerable anion exchange resin 62 in lag vessel 60 is successfully regenerated, anion exchange vessel 60 preferably functions as the lag vessel and receives flow 76' having a majority of the short-chain PFAS compound removed. System 50" also preferably includes tap 134 which preferably detects any breakthrough of short-chain PFAS compounds in flow 78' output by lead vessel 130.

Although as discussed above with reference to one or more of Figs. 1-5, system 50, 50', 50" preferably includes first regenerable anion exchange resin 56 housed in one or more anion exchange vessels and second regenerable anion exchange resin 62 housed in one more separate anion exchange vessels, in another design, system 50'", Fig. 6, preferably includes first regenerable anion exchange resin 56 housed in anion exchange vessel 200 and second regenerable anion exchange resin 62 also housed in anion exchange vessel 200. In this design, anion exchange vessel 200 receives flow 54 of water contaminated with long and short-chain PFAS compounds. Similar as discussed above, first regenerable anion exchange resin 56 removes a majority of the long-chain PFAS compounds in flow 54 and outputs flow 58' having a majority of the long-chain PFAS compounds removed. Second regenerable anion exchange resin 62 receives flow 58' and removes a majority of the short-chain PFAS compounds and outputs flow 64 of treated water having a majority of the short and long-chain PFAS compounds removed. Preferably, the height, h-260, of first regenerable anion exchange resin 56 in anion exchange vessel 200 is of sufficient height to accommodate a sufficient amount of first regenerable anion exchange resin 56 to efficiently and effectively remove long-chain PFAS compounds in flow 54. Similar, height, h-262, of second regenerable anion exchange resin 62 in anion exchange vessel 200 is preferably of sufficient height to accommodate a sufficient amount of second regenerable anion exchange resin 62 remove short-chain PFAS compounds from flow 58'. In this example, height h-262 is typically greater than height h-260 because short-chain PFAS compounds are more difficult to remove from contaminated water than long-chain PFAS compounds because the short-chain PFAS compounds have less surface area for sorption to the anion exchange resin. In one example, h-260 is about 4 feet and h-262 is about 8 feet. In another example, h-260 is about 3 feet and h-262 is about 6 feet. H-260 and h-262 may be longer or shorter than as discussed above, as known by those skilled in the art.

System 50" also preferably outputs flow 74 of spent regenerant solution similar as discussed above which is preferably processed by separation and recovery as discussed above.

System 50 ^IV , Fig. 7, may include anion exchange vessel 200 having first regenerable anion exchange resin 56 and second regenerable anion exchange resin 62 therein configured as a lead vessel as shown. Similar as discussed above, anion exchange vessel 200 receives flow 54 of water contaminated with long-chain PFAS compounds and short-chain PFAS compounds. First regenerable anion exchange resin 56 removes a majority of the long-chain PFAS compounds in flow 54 and outputs flow 58' having a majority of the long-chain PFAS compounds removed. Second regenerable anion exchange resin 62 receives flow 58' and removes a majority of the short-chain PFAS compounds and produces flow 230 of treated water having a majority of long- chain PFAS compounds and short-chain PFAS compounds removed.

System 50 ^IV also preferably includes anion exchange vessel 250 having first regenerable anion exchange resin 56 and second regenerable anion exchange resin 62 therein configured as a lag vessel as shown. Anion exchange vessel 250 preferably captures any long-chain PFAS compounds and/or short-chain PFAS compounds in flow 230 that may break though lead vessel 200. System 50 ^IV also preferably includes sample tap 252 which is preferably used to detect a predetermined breakthrough concentration of short-chain PFAS compounds in flow 230. When this happens, anion exchange vessel 200 is temporarily taken offline so that first regenerable anion exchange resin 56 and second regenerable resin 62 in anion exchange vessel 200 can be regenerated, as discussed below. Flow 54 of contaminated water is directed to lag vessel 250 as flow 54' and lag vessel 250 now becomes the new lead vessel and outputs flow 64 of treated water. First regenerable anion exchange resin 56 and second regenerable anion exchange resin 62 in offline anion exchange vessel 200 is preferably regenerated using flow 254 of regenerant solution. Spent regenerant solution 256 is preferably directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-6. Additional details of switching between lead and lag vessels is also disclosed in commonly owned U.S. Patent No. 10,695,709, discussed supra.

As discussed above with reference to Fig. 6, the height, h-260, of first regenerable anion exchange resin 56 in anion exchange vessel 200 is preferably of sufficient height to provide a sufficient amount of first regenerable anion exchange resin 56 to efficiently and effectively remove long-chain PFAS compounds from flow 54. The height, h-262, of second regenerable anion exchange resin 62 in anion exchange vessel 200 is preferably of sufficient height to provide a sufficient amount of second regenerable anion exchange resin 62 to efficiently and effectively remove short-chain PFAS compounds from flow 58'. In this example, height h-262 is typically greater than height h-260 because short-chain PFAS compounds are more difficult to remove from contaminated water than long-chain PFAS compounds because the short-chain PFAS compounds have less surface area for sorption.

In another design, system 50 ^v , Fig 8, preferably includes anion exchange vessel 300 having first regenerable anion exchange resin 56 therein at a height, h-302, preferably of sufficient height to provide a sufficient amount of first regenerable anion exchange resin 56 to effectively and efficiently remove long-chain PFAS compounds from flow 54 of contaminated water and output flow 304 having a majority of the long-chain PFAS compounds removed. In order to reduce height h-262, Fig, 6 of anion exchange vessel 200 and/or anion exchange vessel 250, Fig. 7, system 50 ^v , Fig 8, preferably includes anion exchange vessel 306 having second regenerable anion exchange resin 62 therein connected in series to anion exchange vessel 300 to receive flow 304. The height, h-308, of second regenerable anion exchange resin 62 in anion exchange vessel 306 preferably provides a sufficient amount of second regenerable anion exchange resin 62 to remove a substantial portion of short-chain PFAS compounds in flow 304 and output flow 312 having a substantial portion of long-chain PFAS compounds removed.

System 50 ^v also preferably includes anion exchange vessel 310 having second regenerable anion exchange resin 62 therein coupled in series with anion exchange vessel 306 and receives flow 312 having the long-chain PFAS compounds removed and a substantial portion of the short-chain PFAS compounds removed. Anion exchange vessel 310 preferably has a height, h-328, which is of sufficient height to provide a sufficient amount of second regenerable anion exchange resin 62 to remove a majority of carryover short-chain PFAS compounds in flow 316 and produce flow 64 of treated water having a majority of long-chain PF AS compounds and short-chain PFAS compounds removed. In one example, h-302, h-308, and h-328 are each about 12 feet. H-302, h-308, and h-328 may be longer or shorter than as discussed above, as known by those skilled in the art.

Thus, system 50 ^v utilizes three anion exchange vessels in series as shown which each preferably have a have a height equal to the height of anion exchange vessel 200 shown in Fig. 6. This provides the ability to utilize more anion exchange resin within a given height constraint to substantially increase overall system capacity to remove a majority of long and short chain PFAS from contaminated water.

In one example, second regenerable anion exchange resin 62 in anion exchange vessel 310 may be regenerated by temporarily taking system 50 ^v offline and introducing flow 314 of regenerant solution into anion exchange vessel 310. Flow 316 of spent regenerant solution is preferably directed to anion exchange vessel 306 to regenerate second regenerable anion exchange resin 62 in anion exchange vessel 306. Flow 316 of spent regenerant solution is then preferably directed to anion exchange vessel 300 to regenerate first regenerable anion exchange resin 56. Flow 320 of spent regenerant solution may be directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-7.

In another example, flow 314 of regenerant solution may be separately introduced to anion exchange vessel 300, anion exchange vessel 306, and/or anion exchange vessel 310 as shown to regenerate first regenerable anion exchange resin 56 and second regenerable anion exchange resin 62. Flow 320' of spent regenerant solution may be directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-7.

System 50 ^VI , Fig. 9, may include anion exchange vessel 300 having first regenerable anion exchange resin 56 coupled in series with anion exchange vessel 306 having second regenerable anion exchange resin 62 therein coupled in series with anion exchange vessel 310 having second regenerable anion exchange resin 62 therein configured as lead vessel train 330 as shown. Similar as discussed above with reference to Fig. 8, anion exchange vessels 300, 306, and 310 remove a majority of the long-chain PFAS compounds and short-chain PFAS compounds from flow 54 of contaminated water and output flow 64 of treated water having a majority of the long-chain PFAS compounds and short-chain PFAS compounds removed.

System 50 ^VI , Fig. 9, also preferably includes lag vessel train 360 including anion exchange vessel 350 having first regenerable anion exchange resin 56 coupled in series with anion exchange vessel 352 having second regenerable anion exchange resin 62 therein coupled in series with anion exchange vessel 354 having second regenerable anion exchange resin 62 therein configured as lag vessel train 360 as shown.

Anion exchange vessel 350 preferably has a height, h-302, similar to anion exchange vessel 300, anion exchange vessel 352 preferably has a height, h-308, similar to anion exchange vessel 306, and anion exchange vessel 354 preferably has a height, h-328, similar to anion exchange vessel 310. Anion exchange vessels 350, 352, and 354 preferably operate similar to anion exchange vessel 300, 306, and 310, respectively, as discussed above.

Anion exchange vessel 350 of lag vessel train 360 preferably captures any long-chain PFAS compounds and/or short-chain PFAS compounds in flow 64 that may break though lead vessel train 330. System 50 ^IV also preferably includes sample tap 356 which is preferably used to detect a predetermined breakthrough concentration of long-chain and/or short-chain PFAS compounds in flow 64. When this happens, lead vessel train 330 is temporarily taken offline so that first regenerable anion exchange resin 56 in anion exchange vessel 300 and second regenerable resin 62 in anion exchange vessels 306 and 310 can be regenerated, as discussed below. Flow 54 of contaminated water is directed to anion exchange vessel 350 as flow 54' and lag vessel train 360 now becomes the new lead vessel train and outputs flow 64 of treated water.

In one example, second regenerable anion exchange resin 62 in offline anion exchange vessel 310 may be regenerated by introducing flow 314 of regenerant solution into anion exchange vessel 310. Flow 316 of spent regenerant solution is preferably directed to anion exchange vessel 306 to regenerate second regenerable anion exchange resin 62 in anion exchange vessel 306. Flow 318 of spent regenerant solution is then the preferably directed to anion exchange vessel 300 to regenerate first regenerable anion exchange resin 56. Flow 320 of spent regenerant solution may be directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-7.

In another example, flow 314 of regenerant solution may be separately introduced to anion exchange vessel 300, anion exchange vessel 306, and/or anion exchange vessel 310 as shown to regenerate first regenerable anion exchange resin 56 and second regenerable anion exchange resin 62. Flow 320' of spent regenerant solution may be directed to separation and recovery, as discussed above with reference to one or more of Figs. 2-8. Additional details of switching between lead and lag vessel is also disclosed in U.S. Patent No. 10,695,709, discussed supra.

System 50, Figs. 4-9, may include a sample tap as shown which may be used to detect a predetermined breakthrough concentration of long-chain PFAS compounds and/or short-chain PF AS compounds in flow 64.

One example of the method for removing long and short-chain PFAS compounds from contaminated resin may include receiving a flow of water contaminated with long and short- chain PFAS compounds, step 400, Fig. 10. The method also includes sorbing a majority of the long-chain PFAS compounds to a first regenerable anion exchange resin having a higher affinity for long-chain PFAS compounds to remove a majority of the long-chain PFAS compounds from the flow of contaminated water and produce a flow of water having a majority of the long-chain PFAS compounds removed, step 402. The method also includes receiving the flow of water having the majority of the PFAS compounds removed, step 404 and sorbing a majority of the short-chain PFAS compounds to a second regenerable anion exchange resin having a high affinity for short-chain PFAS to remove a majority of the short-chain PFAS compounds from the contaminated water and produce a treated flow of water having a majority of the long and shortchain PFAS compounds removed, step 406.

As discussed in the Background section above, there is a need for a system and method can effectively and efficiently remove both PFSAs and PFCAs from contaminated water using regenerable anion exchange resins and which may use an ethanol, denatured ethanol, or similar two- or three-carbon chain solvent to regenerate the anion exchange resins.

Fig. 11 shows one example of system 500 for removing PFSAs and PFCAs from contaminated water using one or more regenerable anion exchange resins. System 500 includes at least first one anion exchange vessel, e.g., anion exchange vessel 552, which receives flow 554 of water contaminated with PFSAs and PFCAs. Anion exchange resin vessel 552 includes first regenerable anion exchange resin therein, exemplarily indicated at 556, having a high affinity for PFSAs. First regenerable anion exchange resin 556 is configured such that a majority of PFSAs in flow 554 sorb to regenerable anion exchange resin 556 to remove a majority of the PFSAs from flow 554 to produce flow 558 having a majority of the PFSAs removed. As defined herein, a majority is greater than about 50%. System 500 also preferably includes at least one second anion exchange resin vessel, e.g., second anion exchange resin vessel 560 which receives flow 558 of water having a majority of PFSAs removed. Second anion exchange resin vessel 560 includes second regenerable anion exchange resin therein, exemplarily indicated at 562, having a high affinity for PFCAs and is configured such that a majority of the PFCAs in flow 558 sorb to second regenerable anion exchange resin 562 to remove a majority of the PFCAs from flow 558 and produce flow 564 of treated water having a majority of the PFSAs and PFCAs removed.

To effectively remove PFSAs and PFCAs from flow 554 of water contaminated with PFSAs and PFCAs, system 500 utilizes second regenerable anion exchange resin 562 which effectively and efficiently removes the PFCAs. However, if any PFSAs breakthrough anion exchange vessel 552 with first regenerable anion exchange resin 556, it would be very difficult to remove the PFSAs from second regenerable anion exchange resin 562 during regeneration using a regenerate solution comprising salt, water and ethanol, denatured ethanol or similar type two- or three-carbon chain solvent, e.g., isopropyl alcohol, ethane, ethene, propane, propene, and the like, because these solvents have lower salt solubility than methanol. Thus, system 500 utilizes anion exchange vessel 552 with first regenerable anion exchange resin 556 which removes a majority of the PFSAs and prevents a majority of the PFSAs from reaching second regenerable anion exchange resin 562. This allows system 500 to effectively and efficiently regenerate second regenerable anion exchange resin 562 using ethanol, denatured ethanol or similar type two- or three-carbon chain solvent based regenerant solution, as discussed in detail below. System 500 also preferably regenerates first regenerable anion exchange resin 556 using ethanol, denatured ethanol or similar type two- or three-carbon chain solvent based regenerant solution. Using ethanol, denatured ethanol or similar type two- or three-carbon chain solvent based regenerant solution discussed above preferably overcomes any problems associated with hazardous air pollutants, e.g., methanol, that may be subject to certain environmental regulations, as discussed in the Background section above.

The result is PFSAs and PFCAs are effectively and efficiently removed from flow 554 of water contaminated with PFSAs and PFCAs using regenerable anion exchange resins that can be efficiently regenerated.

As discussed below, first regenerable anion exchange resin 556 and second regenerable anion exchange resin 562 are highly regenerable which preferably reduces the frequency of regeneration of anion exchange resin and therefore reduces costs.

In one example, second regenerable anion exchange resin 562 preferably includes a macroporous resin including functional groups which preferably increase the affinity of PFCAs to second regenerable anion exchange resin 562 and increase the capacity of second regenerable anion exchange resin 562 to remove PFCAs compounds from flow 558 of water having the majority of the PFSAs already removed.

In one design, the length and basicity of the functional groups of second regenerable anion exchange resin 562 are preferably selected to increase the affinity of PFCAs to second regenerable anion exchange resin 562. As known by those skilled in the art, increasing the length of the functional group of an anion exchange resin provides more surface area for sorption of PFCAs. When the length of the anion exchange resin functional groups is increased this renders the resin more effective at removing PFCAs. However, increasing the length of the functional group makes it more difficult to regenerate the resin.

Additionally, increasing the length of the functional group of an anion exchange resin causes the nitrogen (i.e., the amine group) on the functional group to have a stronger positive charge because it increases the basicity and thus increases its ability to attract PFCAs.

When the length of the anion exchange resin functional groups is decreased this renders the resin easier to regenerate. However, this decrease in the length of the resin's functional group also deceases its capacity to remove PFSAs and PFCAs.

In summary, the longer the length functional group of the anion exchange resin, the more effective the resin is at removing PFSAs and PFCAs. However, it is difficult to remove PFSAs from resins with increased length functional groups during regeneration. The shorter the length functional group of the anion exchange resin, the easier it is to regenerate.

Thus, system 500 overcomes the problem discussed in the Background section and provides a solution for effectively and efficiently removing PFSAs and PFCAs from contaminated water by utilizing first regenerable anion exchange resin 552 with a reduced length functional group to remove a majority of the PFSAs followed by second regenerable regenerable anion exchange resin 562 with an increased length functional group to remove a majority of PFCAs.

Therefore, to effectively remove PFSAs and PFCAs from flow 554 of water contaminated with PFSAs and PFCAs, system 500 initially utilizes first regenerable anion exchange resin 556, preferably having functional groups of reduced length which results in a high affinity for PFSAs and effectively and efficiently removes PFSAs from flow 554 of water contaminated with PFSAs and PFCAs. First regenerable anion exchange resin 556 is preferably highly regenerable for desorbing PFSAs sorbed to first regenerable anion exchange resin 556 using a regenerant solution, as discussed above and in further detail below. The reduced length of the functional group of first regenerable anion exchange resin 556 may not effectively remove

PFCAs, especially short-chain PFCAs. Then, system 500 utilizes second regenerable anion exchange resin 562 having functional groups with increased length which results in an increased affinity of PFCAs to second regenerable anion exchange resin 562 to effectively and efficiently remove the PFCAs in flow 558. Second regenerable anion exchange resin 562 is preferably highly regenerable for desorbing PFCAs sorbed onto second regenerable anion exchange resin 662 using a regenerant solution as discussed below.

In one example, first regenerable anion exchange resin 556 and second regenerable anion exchange resin 562 each preferably include a macroporous, strong base anion exchange resin. In one example, first regenerable anion exchange resin 556 may include SORB EX REPURE™ available from Montrose Environmental Group, Little Rock, AR 72118 or similar type regenerable anion exchange resin.

The result is system 500 may utilize first regenerable anion exchange resin 556 in first anion exchange resin vessel 552 to remove a majority of the PFSAs and then use second regenerable anion exchange resin 562 that is designed with functional groups that increase the affinity for PFCAs to effectively and efficiently remove the PFCAs. Both first regenerable anion exchange resin 556 and second regenerable anion exchange resin 562 are preferably highly regenerable, as discussed below. Such a design uses multiple regenerable anion exchange resins in series to efficiently and cost effectively remove both PFSAs and PFCAs from contaminated water.

System 500 preferably includes resin regeneration subsystem 570 configured to introduce flow 572 of a regenerant solution into at least one second anion exchange resin vessel 560 to regenerate second regenerable anion exchange resin 562 and produce flow 574 of first spent regenerant solution. Flow 572 of regenerant solution is preferably comprised of salt, water and ethanol, denatured ethanol or similar type two- or three-carbon chain solvents, e.g., isopropyl alcohol, ethane, ethene, propane, propene, and the like when it is desirable for system 500 to not use methanol or similar type solvent that may produce a hazardous air pollutant and may be subject to certain environmental regulations. In one example, flow 572 of a regenerant solution example may comprise about 80% ethanol by volume, about 20% water by volume, and about 1% NaCl by weight. In another example, flow 572 of regenerant solution may comprise about 70% ethanol by volume, about 30% water by volume, and about 1.5% NaCl by weight. In yet another example, flow 572 of regenerant solution may comprise about 80% ethanol by volume, about 20% water by volume, and about 1.5% NaCl by weight. Other examples of flow 572 of regenerant solution will occur to those skilled in the art.

Resin regenerant subsystem 570 may also include introducing flow 574 of first spent regenerant solution into at least one first regenerable anion exchange vessel 552 to regenerate first regenerable anion exchange resin 556 and produce flow 576 of second spent regenerant solution.

In another example, flow 572 of regenerant solution may be comprised of salt, water, and methanol. As discussed above, methanol may be more effective than ethanol for regenerating second regenerable anion exchange resin 562 and/or first regenerable anion exchange resin 556 because it has a higher salt solubility and therefore can contain a higher dissolved salt concentration.

Similar as discussed above with reference to Fig. 3, resin regenerant subsystem 570, Fig. 11, may also include separation and recovery subsystem 580 including at least one of an evaporation subsystem, a distillation subsystem and/or a membrane separation subsystem, e.g., as disclosed in U.S. Patent Nos. 10,287,185 and 11,174,175, owned by the assignee hereof, both incorporated by reference herein. Separation and recovery subsystem 580 preferably produces flow 582 of reclaimed solvent. Resin regeneration subsystem 570 also preferably includes solvent purification subsystem 584 which receives flow 582 of reclaimed solvent and preferably removes any carryover PFSAs or PFCAs which may be present in flow 582 to provide flow 586 of purified reclaimed solvent 86 for reuse. In one design, flow 586 may be input to flow 572 of regenerant solution as shown. In one example, solvent purification subsystem 584 may include additional anion exchange resin, exemplarily indicated at 588, e.g., SORBEX REPURE™, discussed supra, or similar type anion exchange resin, housed in vessel 590 as shown in caption 592.

In one design, separation and recovery subsystem 580 may also produce solution 598 comprising concentrated PFSAs and/or PFCAs, salt and water. Separation and recovery subsystem 580 may include a super-loading recovery subsystem which receives solution 598 of concentrated PFSAs and/or PFCAs, salt and water and separates and further concentrates the PFSAs and/or PFCAs from the solution by sorbing the concentrated PFSAs and/or PFCAs onto a sorbtive media to produce a concentrated PFSAs and/or PFCAs waste product e.g., as disclosed in commonly owned U.S. Patent No. 10,287,185 and 11,174,175, cited supra. The super loading subsystem may also generate a solution comprised of concentrated salt and water.

In another example, system 500', Fig. 12, preferably includes resin regeneration subsystem 570 which similarly introduces flow 572 of regenerant solution into at least one second anion exchange resin vessel 560 having second regenerable anion exchange resin 562 therein. However, in this example, system 500' preferably independently introduces flow 600 of regenerant solution, having a similar composition as flow 572, into at least one first regenerable anion exchange resin vessel 552 to regenerate first regenerable anion exchange resin 556 and produce flow 602 of second spent regenerant solution which is preferably introduced to separation and recovery subsystem 580' which operates similar as discussed above with reference to Fig. 11. In this example, separation and recovery subsystem 580' also receives flow 574 of first spent regenerant solution from second anion exchange resin vessel 560. Separation and recovery subsystem 580' preferably produces flow 582' of reclaimed solvent similar as discussed above and may include solvent purification subsystem 584' similar as discussed above which preferably provides flow 586' of purified reclaimed solvent which may be input to flow 572 of regenerant solution input to second anion exchange resin vessel 560 and preferably also be input to flow 600 of regenerant solution into first anion exchange resin vessel 552 as shown.

In one design, system 500" Fig. 13 may include anion exchange vessel 552 with first regenerable anion exchange resin 556 therein configured as a lead vessel which receives flow 554 of water contaminated with PFSAs and PFCAs. Similar as discussed above, first regenerable anion exchange resin 556 removes a majority of PFSAs from flow 554. System 500" also preferably includes anion exchange vessel 520 with first regenerable anion exchange resin 556 therein configured as lag vessel 520 as shown. Lag vessel 520 with first regenerable anion exchange resin 556 preferably captures PFSAs that may break through lead vessel 552 in flow 558. System 500" also preferably includes sample tap 522 which is used to detect a predetermined breakthrough concentration of PFSAs in flow 558. When this happens, lead vessel 552 is temporarily taken offline for regeneration of first regenerable anion exchange resin 556 and flow 554 of water contaminated PFSAs and PFCAs is directed to lag vessel 520 as flow 554' as shown and lag vessel 520 becomes the new lead vessel and outputs flow 558 having a majority of the PFSAs removed. First regenerable anion exchange resin 556 is preferably regenerated using flow 600 of regenerant solution similar as discussed above. Spent regenerant solution 602 is preferably directed to separation and recovery as discussed above. Once first regenerable anion exchange resin 556 in anion exchange vessel 552 is successfully regenerated, anion exchange vessel 552 functions as the new lag vessel and receives flow 558' having a majority of PFSAs removed and captures any PFSAs that may breakthrough lead vessel 520. System 500" also preferably includes sample tap 524 which preferably detects a predetermined breakthrough concentration of PFSAs in flow 558', as discussed above. Additional details of switching between lead and lag vessels is also disclosed in commonly owned U.S. Patent No. 10,695,709, incorporated by reference herein.

Similarly, system 500" also preferably includes anion exchange vessel 560 with second regenerable anion exchange resin 562 therein configured as a lead vessel as shown which receives flow 558 having a majority of the PFSAs removed. Similar as discussed above, second regenerable anion exchange resin 562 removes a majority of the PFCAs and outputs flow 564 of treated water having a majority of the PFSAs and PFCAs removed. System 500" also preferably includes anion exchange vessel 530 with second regenerable anion exchange resin 562 therein configured as lag vessel 530 as shown. Lag vessel 530 with second regenerable anion exchange resin 562 therein preferably captures any PFCAs in flow 564 that may break though lead vessel 560. System 500" also preferably includes sample tap 532 which is preferably used to detect a predetermined breakthrough concentration of PFCAs in flow 564. When this happens, anion exchange vessel 560 is temporarily taken offline so that second regenerable resin 562 can be regenerated. Second regenerable anion exchange resin 562 is preferably regenerated using flow 572 of regenerant solution similar as discussed above. Flow 558 is preferably directed to lag vessel 530 as flow 558' and lag vessel 530 now becomes the new lead vessel and outputs flow

564 of treated water. Once second regenerable anion exchange resin 562 in former lead vessel 560 is successfully regenerated, anion exchange vessel 560 preferably functions as the new lag vessel and receives flow treated flow 564' having a majority of the PFSAs and PFCAs removed. System 500" also preferably includes tap 534 which preferably detects breakthrough of PFCAs in flow 564' output by lead vessel 530.

Although as discussed above with reference to one or more of Figs. 11-13. system 500, 500', 500", preferably includes first regenerable anion exchange resin 556 housed in one or more first anion exchange vessels and second regenerable anion exchange resin 562 housed in one more second anion exchange vessels. In another design, system 500'", Fig. 14, preferably includes first regenerable anion exchange resin 556 housed in at least one anion exchange vessel 700 and second regenerable anion exchange resin 562 also housed in at least one anion exchange vessel 700. In this design, anion exchange vessel 700 receives flow 554 of water contaminated with PFSAs and PFCAs. Similar as discussed above, first regenerable anion exchange resin 556 removes a majority of the PFSAs in flow 554 and outputs flow 558' having a majority of the PFSAs removed. Second regenerable anion exchange resin 562 receives flow 558' and removes a majority of the PFCAs and outputs flow 564 of treated water having a majority of the PFSAs and PFCAs removed.

Preferably, the height, h-702, of first regenerable anion exchange resin 556 in anion exchange vessel 700 is of sufficient height to accommodate a sufficient amount of first regenerable anion exchange resin 556 to efficiently and effectively remove PFSAs in flow 554. Similarly, height, h-704, of second regenerable anion exchange resin 562 in anion exchange vessel 700 is preferably of sufficient height to accommodate a sufficient amount of second regenerable anion exchange resin 562 remove PFCAs from flow 558'. As discussed above, PFSAs are easier to remove from a flow 554 of water contaminated with PFSAs and PFCAs with an anion exchange resin than PFCAs because the negative charge of the sulfonates on the PFSAs is more strongly attached to the positively charged sites (N ⁺ of amine group) on the anion exchange resin than the negative charge on the carboxylates of the PFCAs. Thus, to address this problem, in one example, height h-704 of second regenerable anion exchange resin 562 is typically greater than height h-702 first regenerable anion exchange resin 556 so that system 500"' can efficiently remove a majority of the PFCAs in flow 558' and produce treated flow 564 having a majority of the PFSAs and PFCAs removed. In one design, h- 702 may be about 4 feet and h-704 may be about 8 feet. In another example, h-702 may be about 3 feet and h-704 may be about 6 feet. H-702 and h-704 may be longer or shorter than as discussed above as needed to effectively remove a majority of the PFSAs and PFCAs from flow 554 of water contaminated with PFSAs and PFCAs, as known by those skilled in the art.

System 500'" also preferably outputs flow 574 of spent regenerant solution similar as discussed above which is preferably processed by separation and recovery as also discussed above.

System 500 ^IV , Fig. 15, may include anion exchange vessel 700 having first regenerable anion exchange resin 556 and second regenerable anion exchange resin 562 therein configured as lead vessel 712 as shown. Similar as discussed above, anion exchange vessel 700 receives flow 554 of water contaminated with PFSAs and PFCAs. First regenerable anion exchange resin 556 removes a majority of the PFSAs in flow 554 and outputs flow 558' having a majority of the PFSAs removed. Second regenerable anion exchange resin 562 receives flow 558' and removes a majority of the PFCAs from flow 558' and produces flow 564 of treated water having a majority of the PFSAs and PFCAs removed. System 500 ^IV also preferably includes anion exchange vessel 750 having first regenerable anion exchange resin 556 and second regenerable anion exchange resin 562 therein configured as a lag vessel as shown. Anion exchange vessel 750 preferably captures any PFSAs and/or PFCAS in flow 564 that may break though lead vessel 712. System 500 ^IV also preferably includes sample tap 552 which is preferably used to detect a predetermined breakthrough concentration of PFSAs and/or PFCAs in flow 564. When this happens, lead vessel 712 is temporarily taken offline so that first regenerable anion exchange resin 556 and second regenerable resin 562 therein can be regenerated, as discussed below. Flow 554 of water contaminated with PFSAs and PFCAs is then preferably directed to lag vessel 750 as flow 554' and lag vessel 750 now becomes the new lead vessel and outputs flow 564 of treated water. First regenerable anion exchange resin 556 and second regenerable anion exchange resin 562 in offline anion exchange vessel 712 is preferably regenerated using flow 572 of regenerant solution. Spent regenerant solution 574 is preferably directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-13. Additional details of switching between lead and lag vessels is also disclosed in commonly owned U.S. Patent No. 10,695,709, discussed supra.

Similar as discussed above with reference to Fig. 14, the height, h-702, Fig. 15, of first regenerable anion exchange resin 556 in anion exchange vessel 700 is preferably of sufficient height to provide a sufficient amount of first regenerable anion exchange resin 556 to efficiently and effectively remove PFSAs from flow 554. The height, h-704, of second regenerable anion exchange resin 562 in anion exchange vessel 712 is preferably of sufficient height to provide a sufficient amount of second regenerable anion exchange resin 562 to efficiently and effectively remove PFCAs from flow 558'. In this example, height h-704 is typically greater than height h- 702, similar as discussed above with reference to Fig 14.

In another design, system 500 ^v , Fig 16, preferably includes anion exchange vessel 800 having first regenerable anion exchange resin 556 therein at a height, h-802, preferably of sufficient height to provide a sufficient amount of first regenerable anion exchange resin 556 to effectively and efficiently remove PFSAs from flow 554 of water contaminated with PFSAs and PFCAs and output flow 558 having a majority of the PFSAs removed. In order to reduce the overall height of anion exchange resin vessel 700 in Fig. 14, system 500 ^v , Fig. 15, also preferably includes anion exchange vessel 806 at a height h-808 having second regenerable anion exchange resin 562 therein connected in series to anion exchange vessel 800 as shown. System 500 ^v also preferably includes anion exchange vessel 812 at a height h-814 having second regenerable anion exchange resin 562 therein connected in series to anion exchange vessel 806 as shown. The combined height, h-808, of second regenerable anion exchange resin 562 in anion exchange vessel 806 and h-814 of second regenerable anion exchange resin 562 in anion exchange vessel 812 preferably provides a sufficient amount of second regenerable anion exchange resin 562 to remove a majority of PFCAs in flow 558 and output flow 564 of treated water having a majority of the PFSAs and the PFCAs removed.

In one example, h-802, h-808, and h-814 are each about 12 feet. H-802, h-808, and h-814 may be longer or shorter than as discussed above as needed to effectively remove a majority of the PFSAs and PFCAs from flow 554 of water contaminated with PFSAs and PFCAs, as known by those skilled in the art.

Thus, system 500 ^v utilizes three anion exchange vessels in series as shown which each preferably have a have a height approximate equal to about the height of anion exchange vessel 700 shown in Fig. 14. This provides the ability to utilize more anion exchange resin within a given height constraint to substantially increase overall system capacity to remove a majority of PFSAs and PFCAs from flow 554 of water contaminated with PFSAs and PFCAs.

In one example, second regenerable anion exchange resin 562 in anion exchange vessel 812 may be regenerated by temporarily taking system 500 ^v offline and introducing flow 572 of regenerant solution, similar as discussed above with reference to one or more of Figs. 11 to 15, into anion exchange vessel 812. Flow 816 of spent regenerant solution is preferably directed to anion exchange vessel 806 to regenerate second regenerable anion exchange resin 562 in anion exchange vessel 806. Flow 818 of spent regenerant solution is then preferably directed to anion exchange vessel 800 to regenerate first regenerable anion exchange resin 556. Flow 820 of spent regenerant solution may be directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-15.

In another example, flow 572 of regenerant solution may be separately introduced to anion exchange vessel 800, anion exchange vessel 806, and/or anion exchange vessel 812 as shown to regenerate first regenerable anion exchange resin 556 and/or second regenerable anion exchange resin 562. Flow 820' of spent regenerant solution may be directed to separation and recovery, as discussed above with reference to one or more of Figs. 3-15.

System 50 ^VI , Fig. 17, may include anion exchange vessel 800 having first regenerable anion exchange resin 556 coupled in series with anion exchange vessel 806 having second regenerable anion exchange resin 562 therein coupled in series with anion exchange vessel 812 having second regenerable anion exchange resin 562 therein as discussed above configured as lead vessel train 830 as shown. Similar as discussed above with reference to Fig. 16, anion exchange vessels 800, 806 and 812 remove a majority of the PFSAs and PFCAs from flow 554 of water contaminated with PFSAs and PFCAs and output treated flow 564 of water having a majority of the PFSAs and PFCAs removed.

System 50 ^VI also preferably includes lag vessel train 860 including anion exchange vessel 862 having first regenerable anion exchange resin 556 therein coupled in series with anion exchange vessel 864 having second regenerable anion exchange resin 562 therein coupled in series with anion exchange vessel 868 having second regenerable anion exchange resin 562 therein, similar as discussed above.

In this example, anion exchange vessel 862 preferably has a height, h-802, similar to anion exchange vessel 800, anion exchange vessel 864 preferably has a height, h-806, similar to anion exchange vessel 806, and anion exchange vessel 868 preferably has a height, h-814, similar to anion exchange vessel 812. Anion exchange vessels 862, 864, and 868 preferably operate similar to anion exchange vessel 800, 806, and 812 respectively, as discussed below.

Anion exchange vessel 862 of lag vessel train 860 preferably captures PFSAs and/or PFCAs in flow 564 that may break though lead vessel train 830. System 500 ^IV also preferably includes sample tap 856 which is preferably used to detect a predetermined breakthrough concentration of PFSAs and/or PFCAs in flow 564. When this happens, lead vessel train 830 is temporarily taken offline and lag vessel train 860 becomes the new lead vessel train. Then first regenerable anion exchange resin 556 in anion exchange vessel 800 and second regenerable resin 562 in anion exchange vessels 806 and 812 can be regenerated, e.g., using flow 572 of regenerant solution and a similar technique as discussed above with reference to Fig. 9.

The regenerant solution used for 500, Figs. 11- 17, is preferably comprised of salt, water and ethanol, denatured ethanol or similar type two- or three-carbon chain solvents, e.g., isopropyl alcohol, ethane, ethene, propane, propene, and the like when it is desirable to not use methanol or similar type solvent that may produce a hazardous air pollutant and may be subject to certain environmental regulations, as discussed above. In other examples, the regenerant solution used for system 500, Figs. 11-17, may be comprised of salt, water and methanol.

System 500, Figs. 11-17, may include a sample tap as shown which may be used to detect a predetermined breakthrough concentration of PFSAs and PFCAs in flow 564 of treated water.

One example of the method for removing PFSAs and PFCAs from contaminated water using regenerable anion exchange resins includes receiving a flow of water contaminated with PFSAs and PFCAs, step 900, Fig 18. The method also includes sorbing a majority of the PFSAs to a first regenerable anion exchange resin to remove a majority of the PFSAs from the flow of water contaminated with PFSAs and PFCAs and producing a flow of water having a majority of the PFSAs removed, step 902. The method also includes receiving the flow of water having a majority of the PFSAs removed and sorbing a majority of the PFCAs to a second regenerable anion exchange resin to remove a majority of the PFCAs and produce a flow treated flow of water having a majority of the PFSAs and PFCAs removed, step 904.

As discussed in the Background section above, long-chain PFAS compounds in contaminated waters are easier to remove from the water with an anion exchange resin than short-chain PFAS compounds because the long-chain PFAS compounds have a longer hydrophobic tail with more surface area to bind to the anion exchange resin.

PFSAs are easier to remove from contaminated water with an anion exchange resin than PFCAs. Short-chain PFCAs are the hardest to remove from contaminated water with an anion exchange resin because of their shorter hydrophobic tail with less surface area and their weaker negative charge.

In some examples, second regenerable anion exchange resin 556 discussed above may have an affinity for long-chain PFCAs such that the ethanol based regenerant solution discussed above may not be able desorb some long-chain PFCAs, such as PFOA and similar type long- chain PFCAs. To overcome this problem, system 500, shown in one or more of Figs. 11-18, preferably utilizes first regenerable anion exchange resin 556 which receives flow 554 of water contaminated with long and short-chain PFSAs and long and short-chain PFCAs. In this example, first regenerable anion exchange resin 556 removes short- and long-chain PFSAs and long-chain PFCAs to produce flow 558 of water having a majority of the short- and long-chain PFSAs and long-chain PFCAs removed. In this example, system 500, shown in one or more of Figs. 11-18 also preferably includes second regenerable anion exchange resin 562 including functional groups where the length and basicity of the functional groups preferably increase the affinity of short-chain PFCAs to second regenerable anion exchange resin 556 to increase the capacity of the second regenerable anion exchange resin 556. In this example, second regenerable anion exchange resin 556 shown in one or more of Figs. 11-18 receives the flow of water having a majority long-chain and short-chain PFSAs and long-chain PFCAs removed and removes a majority of the short-chain PFCAs to produce flow 564 of treated flow of water having a majority of the long and short-chain PFCAs and the long and short-chain PFSAs removed.

One example of the method for removing long and short-chain per- and polyfluorinated sulfonic acids (PFSAs) and long and short-chain per- and polyfluorinated carboxylic acids (PFCAs) from contaminated water using regenerable anion exchange resins includes receiving a flow of water contaminated with long and short-chain PFSAs and long and short-chain PFCAs, step 920, Fig. 19. The method also includes removing a majority of the long-chain and shortchain PFSAs and long-chain PFCAs from the flow of water contaminated with long and short- chain PFSAs and long and short-chain PFCAs with a first anion exchange resin and producing a flow of water having a majority of the long- and short-chain PFSAs and long-chain PFCAs removed, step 922. The method further includes receiving the flow of water having a majority of the long- and short-chain PFSAs and long-chain PFCAs removed and removing a majority of the short-chain PFCAs with a second regenerable anion exchange resin and producing a flow of treated water having a majority of the long and short-chain PFCAs and the long and short-chain PFSAs removed, step 924.

Although specific features of the invention are shown in some drawings and not in others, this is for convenience only, as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. Other embodiments will occur to those skilled in the art and are within the following claims.

In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for any claim element amended.

What is claimed is: