CONTROL OF TOC, PERCHLORATE, AND PFAS THROUGH ADVANCED OXIDATION AND SELECTIVE ION EXCHANGE PROCESS

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to U.S. Provisional Patent Application Serial No 62/733,149 as filed on September 28, 2018 and titled“CONTROL OF TOC, PERCHLORATE, AND PFAS THROUGH VANOX AOP AND SELECTIVE ION

EXCHANGE PROCESS,” the entire disclosure of which is hereby incorporated herein by reference in its entirety for all purposes.

FIELD OF THE TECHNOLOGY

Aspects relate generally to water treatment and, more specifically, to controlling the level of one or more target constituents in water.

BACKGROUND

There is rising concern about the presence of various contaminants in municipal wastewater, surface water, drinking water, and groundwater. For example, perchlorate ions in water are of concern, as well as per- and polyfluorinated alkyl substances (PFASs) and PFAS precursors, along with a general concern with respect to total organic carbon (TOC).

PFASs are organic compounds consisting of fluorine, carbon and heteroatoms such as oxygen, nitrogen and sulfur. The hydrophobicity of fluorocarbons and extreme

electronegativity of fluorine give these and similar compounds unusual properties. Initially, many of these compounds were used as gases in the fabrication of integrated circuits. The ozone destroying properties of these molecules restricted their use and resulted in methods to prevent their release into the atmosphere. But other PFAS such as fluoro-surfactants have become increasingly popular. Although used in relatively small amounts, these compounds are readily released into the environment where their extreme hydrophobicity as well as negligible rates of natural decomposition results in environmental persistence and

bioaccumulation. It appears as if even low levels of bioaccumulation may lead to serious health consequences for contaminated animals such as human beings, the young being especially susceptible. The environmental effects of these compounds on plants and microbes are as yet largely unknown. Nevertheless, serious efforts to limit the environmental release of PFAS are now commencing. SUMMARY

In accordance with one or more aspects, a method of treating water including perchlorate and/or per- and polyfluoroalkyl substances (PFASs) is disclosed. The method may comprise providing feed water having an initial concentration of perchlorate or PFAS, dosing the feed water with an oxidizer, exposing the dosed water to ultraviolet (UV) light to produce a first treated solution, and directing the first treated solution to a selective ion exchange resin to produce product water.

In some aspects, the oxidizer may comprise a persulfate compound. The persulfate compound may comprise ammonium persulfate, sodium persulfate, and/or potassium persulfate. The selective ion exchange resin may comprise a perchlorate selective resin. The perchlorate selective resin may comprise a strong base anion resin. The perchlorate selective resin may comprise a tri-butyl amine resin.

In some aspects, the method may further comprise monitoring a pressure,

temperature, pH, concentration, flow rate, or total organic carbon (TOC) level in the feed water, first heated solution, and/or product water. A TOC level of the first treated solution may be less than about 0.5 ppb. A perchlorate concentration in the product water may be less than about 6 ppb. The perchlorate concentration in the product water may be less than about 1 Ppb-

In some aspects, the method may further comprise recirculating at least a portion of the first treated solution to the feed water. The method may further comprise delivering the product water to a potable point of use. The method may further comprise replacing the selective ion exchange resin upon detecting perchlorate breakthrough that exceeds a threshold value.

In accordance with one or more aspects, a water treatment system is disclosed. The system may comprise an advanced oxidation process reactor (AOPR) having an inlet and an outlet, and at least one perchlorate selective resin bed fluidly connected downstream of the AOPR outlet.

In some aspects, the system may further comprise a source of water containing perchlorate and/or PFAS fluidly connected to the AOPR inlet. The AOPR may comprise first and second subreactors arranged in parallel. The AOPR may be fluidly connected to a source of persulfate and may comprise a UV light source. The system may comprise two

perchlorate selective resin beds arranged in parallel. In some aspects, the perchlorate selective resin bed may comprise a strong base anion resin. The perchlorate selective resin bed may comprise a tri-butyl amine resin. The tri-butyl amine resin may comprise a quaternary amine functional group.

In some aspects, the system may further comprise at least one sensor configured to detect a pressure, temperature, pH, concentration, flow rate, or total organic carbon (TOC) level. The system may still further comprise a controller in communication with the at least one sensor and configured to control a rate at which persulfate is introduced to the AOPR and/or control a dose of irradiation associated with the AOPR.

In some aspects, the system may further comprise a posttreatment unit fluidly connected downstream of at least one of the AOPR and the persulfate selective resin bed.

The posttreatment unit may comprise an activated carbon unit. Likewise, the system may further comprise a pretreatment unit operation fluidly connected upstream of the AOPR.

In accordance with one or more aspects, a method of retrofitting a water treatment system is disclosed. The method may comprise providing a persulfate selective resin bed, and fluidly connecting the persulfate selective resin bed downstream of an AOPR.

In some aspects, the method may further comprise integrating an activated carbon unit operation between the AOPR and the persulfate selective resin bed.

The disclosure contemplates all combinations of any one or more of the foregoing aspects and/or embodiments, as well as combinations with any one or more of the

embodiments set forth in the detailed description and any examples.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain illustrative features and examples arc described below with reference to the accompanying figures in which:

FIG. 1 presents a schematic of an advanced oxidation process reactor (AOPR) in accordance with one or more embodiments;

FIGS. 2-3 present schematics of water treatment systems involving AOPR paired with ion exchange resin beds in accordance with one or more embodiments; and

FIG. 4 presents data discussed in an accompanying Example.

It will be recognized by the person of ordinary skill in the art, given the benefit of this disclosure, that the figures are purely for illustrative purposes. Other features may be present in the embodiments disclosed herein without departing from the scope of the description. DETAILED DESCRIPTION

In accordance with one or more embodiments, systems and methods relate to the treatment of water. The level of one or more target constituents may be strategically controlled. Various unit operations may be coupled together as part of an integrated system in order to provide a product water meeting preestablished requirements. Beneficially, synergies between unit operations may be leveraged to produce a desired product water.

In accordance with one or more embodiments, water to be treated may contain one or more target compounds. For example, process water may contain various organic

compounds, i.e. recalcitrant organic contaminants, for example, l,4-dioxane,

trichloroethylene (TCE), perchloroethylene (PCE), urea, isopropanol, chloroform, atrazine, tryptophan, and formic acid. Process water may also contain perchlorate and/or PFAS as described herein.

In accordance with one or more embodiments, PFASs, also referred to as

perfluorinated chemicals (PFCs), may be targeted. These man-made chemical compounds are very stable and resilient to breakdown in the environment. They may also be highly water soluble because they carry a negative charge when dissolved. They were developed and widely used as a repellant and protective coating. Though they have now largely been phased out, elevated levels are still widespread. For example, water contaminated with PFAS or PFC may be found in industrial communities where they were manufactured or used, as well as near airfields or military bases where firefighting drills were conducted. PFAS or PFC may also be found in remote locations via water or air migration. Many municipal water systems are undergoing aggressive testing and treatment. In some specific non-limiting embodiments, common PFCs such as perfluorooctanoic acid (PFOA) and/or perfluorooctane sulfonic acid (PFOS) may be removed from water. The U.S. Environmental Protection Agency (EPA) developed revised guidelines in May 2016 of a combined lifetime exposure of 70 parts per trillion (ppt) for PFOS and PFOA. Federal, state, and/or private bodies may also issue relevant regulations.

Likewise, various local, federal, and/or private agencies may establish discharge requirements pertaining to perchlorate levels. EPA Regulations 314, 331, and 332 relate to measuring perchlorate ions. The state of California has a discharge requirement of less than 6 parts per billion (ppb) perchlorate, while the state of Massachusetts has a discharge requirement of less than lppb perchlorate.

In accordance with one or more embodiments, product water as described herein may be potable. In at least some embodiments, treatment techniques as described herein may find utility in the municipal water treatment market and may be used to produce drinking water.

In other embodiments, product water may be used for irrigation. In still other embodiments, product water may be returned to surface water or groundwater.

In accordance with one or more embodiments, an advanced oxidation process (AOP) may be implemented to target total organic carbon (TOC) levels in process water.

AOP generally utilizes UV activation of an oxidizing salt for the destruction of various organic species. Any strong oxidant may be used. In some non-limiting

embodiments, a persulfate compound may be used. In at least some embodiments, ammonium persulfate, sodium persulfate, and /or potassium persulfate may be used. Other strong oxidants, e.g. ozone or hydrogen peroxide, may also be used. The process water may be dosed with the oxidant.

In accordance with one or more embodiments, process water dosed with an oxidant may be exposed to a source of ultraviolet (UV) light. For instance, the systems and methods disclosed herein may include the use of one or more UV lamps, each emitting light at a desired wavelength in the UV range of the electromagnetic spectrum. For instance, according to some embodiments, the UV lamp may have a wavelength ranging from about 180 to about 280 nm, and in some embodiments, may have a wavelength ranging from about 185 nm to about 254 nm. According to various aspects, the combination of persulfate with UV light is more effective than using either component on its own.

According to some embodiments, a source of persulfate may first be introduced to the contaminated groundwater, which may be followed by exposure of the contaminated groundwater to UV light. According to other embodiments, the persulfate addition and the UV exposure may occur at approximately the same time, i.e., simultaneously or nearly simultaneously. According to various aspects, the persulfate and the UV light function to oxidize organic contaminant into non-hazardous compounds, including carbon dioxide and water.

According to some embodiments, adjusting a dose of the ultraviolet light may comprise at least one of adjusting an intensity of the UV light and adjusting an exposure time of the UV light to the first treated aqueous solution. For instance, the first treated aqueous solution may be held or otherwise contained within a reactor or vessel and be exposed to UV light for a predetermined exposure time while the solution is housed within the reactor or vessel . According to some embodiments, baffles or other flow control devices positioned within the reactor or vessel may also contribute to containing the first treated aqueous solution for a predetermined exposure time. According to other embodiments, adjusting a dose of the ultraviolet light may comprise adjusting a flow rate of the first treated aqueous solution. For instance, the first treated aqueous solution may pass through a conduit that is configured to allow UV light to pass through to the conduit to irradiate the first treated aqueous solution. According to other embodiments, the dose of the UV light may be adjusted by adjusting a power setting of the UV light, or by adjusting the wavelength of the UV lamp.

According to at least one embodiment, a controller, as discussed further below, may be used to control the oxidant and/or UV dose for batch and flow-through processes, including the lamp power, the exposure time, and the flow rate. Process control may be based on input from one or more sensors monitoring various inlet and outlet concentrations, such as a TOC concentration associated with an AOP reactor. For example, a higher dose of oxidant and/or UV may be appropriate when the concentration of organics is high. Other parameters such as temperature, pressure, pH level, and flow rate, may also be controlling variables.

In some embodiments, AOP may reduce TOC levels to about 1 ppb or less. In at least some embodiments, AOP may reduce TOC levels to about 0.5 ppb or less.

In accordance with one or more embodiments, AOP may typically involve a persulfate feed system in front of UV lamps. AOP is commonly known, including Vanox ^® AOP system commercially available from Evoqua Water Technologies LLC (Pittsburgh,

PA), which may be implemented. Some related patents and patent application publications are hereby incorporated herein by reference in their entireties for all puiposes including: U.S. Patent No. 8,591,730; 8,652,336; 8,961,798; US201602077813; and US20180273412 all to Evoqua Water Technologies LLC.

FIG. 1 presents a schematic illustrating the Vanox ^® AOP system. Feed water is mixed with a persulfate ion and then exposed to UV light. Process control may be implemented with respect to various parameters such as but not limited to pressure, temperature, and recycle volume. Water exiting the AOP system may be further processed as described further herein.

In accordance with one or more embodiments, AOP may generally be effective at removing organic compounds and may be used to control TOC. AOP may have difficulty in removing certain compounds depending on process conditions. For example, AOP may have difficulty removing PFAS at a neutral pH level.

Notably, it has been recognized that undesirable oxidation byproducts may be generated via AOP. For example, perchlorate may be produced as an AOP byproduct.

Treatment of difficult to remove TOCs via AOP may be associated with even greater perchlorate generation. A large excess of persulfate may be required in response to a high TOC level and/or low UV transmittance of the water. Also, PFAS may be generated from PFAS precursors during oxidation. Beneficially, perchlorate and/or PFAS may be targeted for removal by one or more downstream processes in accordance with various embodiments.

In accordance with one or more embodiments, AOP product water may be further processed to remove target contaminants not removed by AOP. In some embodiments, AOP may be supplemented as part of a larger water treatment system in order to remove certain contaminants such as perchlorate and/or PFAS. In at least some embodiments, AOP may be combined with selective ion exchange resin as described further herein.

In accordance with one or more embodiments, AOP product water may be treated with an ion selective resin to remove one or more further target constituents. In some embodiments, ion selective resin may remove perchlorate and/or PFAS from water. FIG. 2 presents a schematic of a combination system comprising AOP coupled with a selective ion exchange process to remove perchlorate ions and/or PFAS. As illustrated, parallel resin columns may be implemented in order to ensure sufficient processing capability and continuity.

In accordance with one or more embodiments, an ion selective resin bed may be effective to bring perchlorate levels down to regulatory levels. For example, a concentration of perchlorate in treated effluent may be less than about 6 ppb, e.g. about 1 ppb or less.

In accordance with one or more embodiments, the ion selective resin may be an anion selective resin, i.e. a strong base anion resin. In some embodiments, the resin may be a perchlorate selective ion exchange resin. Perchlorate selective resins will generally also target PFAS. In at least some embodiments, the resin may be a tri-butyl amine resin. For example, the resin may be a Dowex® PSR-2 or ResinTech® SIR-l 10-HP tri-butyl amine resin. In some non-limiting embodiments, a tri-butyl amine resin may have a quaternary amine functional group. Table 1 provides specifications for one non-limiting example of a perchlorate selective resin effective for removal of both perchlorate ions and PFAS in accordance with various embodiments. Table 1 : Specifications of Sample Perchlorate Selective Resin

Matrix _ Styrene-divinylbenzene, gel

Type _ Strong base anion

Physical Form _ White to yellow spherical beads

Ionic Form as Shipped Cf Form

Total Exchange Capacity > 0.7 eq/L

Water Retention Capacity 25 - 35%

Particle Size

Particle Diameter ^b 700 ± 50 pm

Uniformity Coefficient < 1.1

< 300 pm _ 1 ¾ max _

Particle Density _ 1.07 g/tnl

Bulk Density, as Shipped ^c 690 g/L (43 ib/ft ³ )

In accordance with one or more embodiments, a sorption or filtration technology may also be implemented to remove excess oxidizer downstream of the AOP. In some embodiments, an activated carbon unit may process AOP product water in order to remove excess oxidizer. In at least some embodiments the activated carbon unit is directly downstream of the AOPR while in other embodiments the activated carbon unit may be integrated downstream of the ion exchange resin bed.

FIG. 3 presents a detailed schematic of a water treatment system in which an AOPR is coupled to an ion exchange resin bed. The system includes a granular activated carbon (GAC) bed downstream of the AOPR. The illustrated system also optionally includes an effluent break tank.

In accordance with one or more embodiments, one or more sensors may measure a PFAS level upstream and/or downstream of the ion exchange resin bed. A controller may receive input from the sensor(s) in order to monitor PFAS levels, intermittently or continuously. Monitoring may be in real-time or with lag, either onsite or remotely and either manually or automatically. In some embodiments, samples may be sent offsite for analysis. A detected PFAS level downstream of the ion exchange resin bed may be compared to a threshold level that may be considered unacceptable, such as may be dictated by a controlling regulatory body. The resin bed may be replaced in response to detecting an unacceptable breakthrough level. Parallel resin beds may facilitate continuous opertin during maintenance. Additional properties such as but not limited to pH, pressure, flow rate, temperature, perchlorate concentration, and TOC levels may be monitored by various interconnected or interrelational sensors throughout the system. The controller may be in communication with these various sensors. The controller may send one or more control signals to adjust various operational parameters. For example, in response to detected levels of organics, one or more properties of the AOPR may be adjusted. In some embodiments, oxidant dosage and/or applied UV levels may be adjusted in response to sensor input as described above.

In accordance with one or more embodiments, an existing water treatment system may be retrofitted. For example, an existing system involving an AOPR may be retrofitted to control perchlorate and/or PFAS levels. An ion exchange resin bed as described herein may be provided. The resin bed may be fluidly connected downstream of the AOPR. An activated carbon unit may also be installed as described herein to address excess oxidant.

The function and advantages of these and other embodiments will be more folly understood from the following examples. The examples are intended to be illustrative in nature and are not to be considered as limiting the scope of the materials, systems, and methods discussed herein.

EXAMPLE 1

Various categories of anion exchange resins were tested to determine their respective perchlorate breakthrough profiles. Associated data is presented in FIG. 4 and indicates that tributylamine resin, generally characterized as being perchlorate selective, provides superior performance. Over 1.2 million gallons of water per cubic foot of resin was processed prior to breakthrough. In comparison, trimethylalamine (type 1 resin) experienced perchlorate breakthrough prior to processing 200,000 gallons of water per cubic foot. Triethylamine, known as a nitrate selective resin, experienced perchlorate breakthrough after processing around 400,000 gallons per cubic foot.

EXAMPLE 2

A combined AOP and ion exchange resin water treatment system was operated. The process water flow rate to the system was 20 gpm and the water to be treated had a TOC level of 1.4 mg/1. In the AOPR, sodium persulfate was used as the oxidant at a dose of 81 mg/1. A perchlorate-selective (Dowex® PSR2 Plus) ion exchange resin was used downstream of the AOPR. Data pertaining to measured concentrations of 1 ,4-dioxane and perchlorate are presented in Table 2.

Table 2: i , 4-Dioxane and Perchlorate Data

The data illustrates that only trace amounts of 1 ,4-dioxane was present in the treated product effluent. The AOPR appeared to generate perchlorate but the ion exchange resin was consistently effective at bringing the perchlorate levels down to only trace amounts in the treated product effluent.

The phraseology and terminology used herein is for the puipose of description and should not be regarded as limiting. As used herein, the term“plurality” refers to two or more items or components. The ter “comprising,”“including,”“carrying,”“having,� �

“containing,” and“involving,” whether in the written description or the claims and the like, are open-ended terms, i.e., to mean“including but not limited to.” Thus, the use of such terms is meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items. Only the transitional phrases“consisting of’ and“consisting essentially of,” are closed or semi-closed transitional phrases, respectively, with respect to the claims. Use of ordinal terms such as“first,”“second,”“third,” and the like in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

Having thus described several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Any feature described in any embodiment may be included in or substituted for any feature of any other embodiment. Such alterations, modifications, and improvements are intended to be part of this disclosure and are intended to be within the scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.

Those skilled in the art should appreciate that the parameters and configurations described herein are exemplary and that actual parameters and/or configurations will depend on the specific application in which the disclosed methods and materials are used. Those skilled in the art should also recognize or be able to ascertain, using no more than routine experimentation, equivalents to the specific embodiments disclosed.