WO2016028972A1

WO2016028972A1 - Water treatment system and method

Info

Publication number: WO2016028972A1
Application number: PCT/US2015/046033
Authority: WO
Inventors: Joseph GIFFORD; Tricia BUTLAND; Michael Shaw; Li-Shiang Liang; Xiangyi Qiao; YingHong LU; Nicholas Armstrong; Jacob Telepciak; Jonathan Wood
Original assignee: Evoqua Water Technologies Llc
Priority date: 2014-08-20
Filing date: 2015-08-20
Publication date: 2016-02-25

Abstract

Systems and methods for treating water having a high mineral content are provided. The systems and methods for treating water having a high mineral content include electrodialysis and electrodeionization. The systems and methods may remove silica and total dissolved solids from water, and may increase water recovery and reduce power consumption.

Description

WATER TREATMENT SYSTEM AND METHOD

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Serial No. 62/039,621 filed on August 20, 2014, titled "Treatment of Reverse Osmosis Reject with Electrodialysis Reversal and Electrodeionization to Increase water Recovery" the entire disclosure of which is hereby incorporated herein by reference in its entirety for all purposes. FIELD OF THE DISCLOSURE

Aspects relate generally to water treatment and, more particularly, to electrochemical systems and methods for treatment of high mineral content water.

SUMMARY

Aspects relate generally to high mineral content water treatment systems and energy.

According to some embodiments, a water treatment system is provided. The water treatment system comprises a reverse osmosis unit having a feedwater inlet, a filtrate water outlet, and a retentate water outlet, and an electrodialysis unit having a dilute compartment connected to the retentate water outlet, and having a first product water outlet, a concentrate compartment having a concentrate water outlet; and an electrodeionization unit having a depleting compartment connected to the first product water outlet and having a second product water outlet, and a concentrating compartment having a reject water outlet.

In some aspects, the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins. In some embodiments, the mixed bed comprises about 70% anion exchange resins and about 30% cation exchange resins. In some embodiments, the depleting compartment further comprises a layer of anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the depleting compartment comprises anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof. In some aspects, the system further comprises a second depleting compartment comprising an anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the concentrating compartment comprises a mixture of anion exchange resins and cation exchange resins.

In some aspects, the electrodialysis unit is capable of reversing polarity.

In some aspects, the first product water outlet is fluidly connected to the feedwater inlet.

In some aspects, the second product water outlet is fluidly connected to the feedwater inlet.

In some aspects, the system may further comprise a precipitator fluidly connected to at least one of the concentrate water outlet and the reject water outlet.

In some aspects, the system further comprises an ion exchange membrane positioned in the electrodialysis unit between the dilute compartment and the concentrate compartment, comprising a crosslinked ion transferring polymer comprising at least one functional monomer, at least one cross-linking monomer, and at least one quaternizing agent.

In some embodiments, the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole. In some embodiments, the at least one crosslinking monomer is selected from the group consisting of: divinylbenzene, ethylene glycol dimethacrylate, vinylbenzyl chloride, dichloroethane, propylene glycol dimethacrylate, isobutylene glycol dimethacrylate, Ci6H₂₄0i₂Si₈, C32H72O20S116, (CH₂CH)_n(Si0₁.5)_n wherein n= 8, 10, or 12, C₁₄I½0₁₂Si7, C₂₈H₆₆0₁₂Si₇, C₅6H₁₂₂0₁₂Si₇, C₁₆H560₂oSi₁₆, H₈0₁₂Si₈, (C₈Hi₃0)n(SiOi.5)n wherein n= 8, 10, 12, (C₆Hn0₂)_n(SiOi.₅)n wherein n= 8, 10, or 12, (C₇H_n0₂)n(SiOi.5)n wherein n= 8, 10, or 12, and (C₆H₉0₂)_n(SiOi.5)n wherein n= 8, 10, or 12. In some embodiments, the quaternizing agent is selected from the group consisting of benzyl chloride, benzyl bromide, vinyl benzyl chloride, dichloroethane, or methyl iodide.

In some aspects, the crosslinked ion transferring polymer further comprises a polymerization initiator. In some embodiments, the polymerization initiator is selected from the group consisting of organic peroxides, 2,2' azobis[2,[2-imdazolin-2-yl]- propane] dihydrochloride, α,α'-azoisobutyronitrile, 2,2'-azobis[2- methylpropioaminidinejdihydrochloride, 2,2' azobis[2,[2-imdazolin-2-yl]propane], or dimethyl2,2'azobis [2-methylpropionate] .

In some aspects, the system may further comprise a microporous membrane support having a porous first side, a porous second side, and a continuous porous structure extending from the first side to the second side. In some embodiments, the crosslinked ion transferring polymer fills the continuous porous structure. In some embodiments, the microporous support comprises polyprophylene, high molecular weight polyethylene, ultrahigh molecular weight polyethylene or polyvinylidene fluoride. In some embodiments, the thickness of the microporous support is greater than about 55 microns and less than about 155 microns. In some embodiments, the thickness of the microporous support is greater than about 20 microns and less than about 55 microns.

According to some embodiments, a method of facilitating treatment of high mineral content water is provided. The method comprises providing an electrodialysis unit having a dilute compartment having a first product water outlet, and a concentrate compartment comprising a concentrate water outlet, fluidly connecting a source of high mineral content water outlet to the dilute compartment, providing an electrodeionization unit comprising a depleting compartment having a second product water outlet and a concentrating

compartment having a reject water outlet; and fluidly connecting the first product water outlet to the depleting compartment

In some aspects, the electrodialysis unit comprises an ion exchange membrane positioned between the dilute compartment and the concentrate compartment, comprising a crosslinked ion transferring polymer comprising at least one functional monomer, at least one crosslinking monomer, and at least one quaternizing agent.

In some aspects, the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole. In some embodiments, the at least one crosslinking monomer is selected from the group consisting of divinylbenzene, ethylene glycol dimethacrylate, vinylbenzyl chloride, dichloroethane, propylene glycol dimethacrylate, isobutylene glycol dimethacrylate, Ci6H₂₄0i₂Si₈, C32H72O20S116, (CH₂CH)_n(Si0₁.5)_n wherein n= 8, 10, or 12, C₁₄I½0₁₂Si7, C₂₈H₆₆0₁₂Si₇, C₅6H₁₂₂0₁₂Si₇, C₁₆H560₂oSi₁₆, H₈0₁₂Si₈, (C₈Hi₃0)n(SiOi.5)n wherein n= 8, 10, 12, (C₆Hn0₂)_n(SiOi.₅)n wherein n= 8, 10, or 12, (C₇H_n0₂)n(SiOi.5)n wherein n= 8, 10, or 12, and (C₆H₉0₂)_n(SiOi.5)n wherein n= 8, 10, or 12. In some embodiments, the quaternizing agent is selected from the group consisting of benzyl chloride, benzyl bromide, vinyl benzyl chloride, dichloroethane, or methyl iodide.

In some aspects, the source of high mineral content water is a reverse osmosis unit retentate stream.

In some aspects, the method may further comprise periodically reversing a polarity of the electrodialysis unit.

In some aspects, the first product water has a silica concentration greater than 8 ppm. In some aspects, the first product water has a TDS concentration lower than about 2,000 ppm.

In some aspects, the method may further comprise fluidly connecting a first product water outlet to the source of high mineral content water.

35. In some aspects, the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins. In some embodiments, the mixed bed comprises about 70% anion exchange resin and about 30% cation exchange resin. In some embodiments, the depleting compartment further comprises a layer of anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof. In some embodiments, the depleting compartment comprises anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof. In some embodiments, the electrodeionization unit further comprises a second depleting compartment comprising anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the concentrating compartment comprises a mixture of anion exchange resins and cation exchange resins. In some embodiments, the concentrating compartment consists of anion exchange resin.

In some aspects, the method further comprises connecting a second product water outlet to the source of high mineral content water.

In some aspects, the method further comprises providing a precipitator. In some embodiments, the method further comprises fluidly connecting at least one of the concentrate water outlet and the reject water outlet to the precipitator.

In some embodiments, a system for treating high mineral content water is provided. The system comprises an electrodialysis unit comprising a dilute compartment having a first product water outlet, a concentrate compartment having a concentrate water outlet, and an ion exchange membrane positioned between the dilute compartment and the concentrate compartment, the ion exchange membrane comprising a crosslinked ion transferring polymer comprising at least one functional monomer, at least one cros slinking monomer, and an electrodeionization unit comprising a depleting compartment fluidly connected to the first product water outlet and having a second product water outlet and a concentrating compartment having a reject water outlet.

In some aspects, the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole. In some aspects, at least one of the concentrate water outlet and the reject water outlet is fluidly connected to a precipitator.

In some aspects, the electrodialysis unit is capable of reversing polarity.

In some aspects, the depleting compartment comprises a mixed bed of anion and cation exchange resin. In some embodiments, the mixed bed comprises about 70% anion exchange resin and about 30% cation exchange resin. In some embodiments, the depleting compartment further comprises a layer of anion exchange resin. In some embodiments, the anion exchange resin is selected form the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the depleting compartment comprises anion exchange resin. In some embodiments, the anion exchange resin is selected form the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the method further comprises a second depleting compartment comprising an anion exchange resin. In some embodiments, the anion exchange resin is selected form the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some embodiments, a method of treating high mineral content water is provided. The method comprises introducing a high mineral content water to a dilute compartment of an electrodialysis unit to produce a first product water, the electrodialysis unit further comprising a concentrate compartment having a concentrate water outlet, introducing the first product water to a depleting compartment of an electrodeionization unit to produce a second product water, introducing the first product water to a concentrating compartment of the electrodeionization unit to produce a reject water, and combining the reject water and the concentrate water to recycle to the concentrate compartment.

In some aspects, the electrodialysis unit further comprises an ion exchange membrane positioned between the dilute compartment and the concentrate compartment, and having a crosslinked ion transferring polymer comprising at least one functional monomer. In some aspects, the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole

In some aspects, the method further comprises introducing a first product water to a depleting compartment of an electrodeionization unit to produce a second product water. In some embodiments, the method further comprises introducing a first product water to a concentrating compartment of an electrodeionization unit to produce a reject water. In some aspects, the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins. In some embodiments, the mixed bed comprises about 70% anion exchange resin and about 30% cation exchange resin.

In some aspects, the depleting compartment further comprises a layer of anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the depleting compartment comprises anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the system further comprises a second depleting compartment comprising an anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the concentrating compartment comprises a mixture of anion exchange resin and cation exchange resin.

In some aspects, the second product water has a pH that is higher than the first product water pH. In some embodiments, the pH of the second product water is capable of ionizing silica. In some embodiments, the pH of the reject water is lower than the pH of the first product water.

In some embodiments, a system for treating high mineral content water is provided. The system comprises an electrodialysis unit comprising a dilute compartment having a first product water outlet and a concentrate compartment having a concentrate water outlet, and an electrodeionization unit comprising a depleting compartment fluidly connected to the first product water outlet and having a second product water outlet and a concentrating compartment fluidly connected to the concentrate compartment and having a reject water outlet, the reject water outlet fluidly connected to a reject water recycle inlet of the concentrate compartment.

In some aspects, the depleting compartment comprises a mixed bed comprising anion exchange resins and cation exchange resins. In some embodiments, the mixed bed comprises about 70% anion exchange resin and about 30% cation exchange resin.

In some aspects, the depleting compartment further comprises a layer of anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof. In some aspects, the depleting compartment comprises anion exchange resin. In some embodiments, the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

In some aspects, the concentrating compartment comprises a mixture of anion exchange resin and cation exchange resin. In some embodiments, the mixture comprises 70% anion exchange resin and about 30% cation exchange resin.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one embodiment are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the invention. Where technical features in the figures, detailed description or any claim are followed by references signs, the reference signs have been included for the sole purpose of increasing the intelligibility of the figures and description. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure. In the figures:

FIG. 1 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIG. 2 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIG. 3 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIG. 4 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIG. 5 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIGS. 6A and 6B present charts comparing the effects of pH on silica and TDS removal at different currents; FIGS. 7 A and 7B present charts comparing the effects of flowrate on silica and TDS removal at different currents;

FIG. 8 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIG. 9 presents a schematic of a process flow diagram in accordance with one or more embodiments;

FIG. 10 presents a schematic of a process flow diagram in accordance with one or more embodiments; and

FIG. 11 presents a graph showing the effect of overall recovery on module current efficiency.

DETAILED DESCRIPTION

High mineral content water is used and reused throughout the world due to a higher fresh water demand than supply. High mineral content water may have a high total dissolved solids (TDS) concentration. As such, there is a need to remove the TDS for use or storage. High mineral content water poses a challenge to traditional systems of water treatment.

Reverse osmosis (RO) is commonly used to demineralize or deionize water by pushing it under pressure through a semi-permeable RO membrane. The RO membrane allows the passage of water, but not the majority of contaminants, including dissolved salts, minerals, organic compounds, and bacteria. As is well understood, the contaminants are concentrated and discharged as a process water brine, for example, as a retentate stream. The retentate stream typically goes to drain as waste or may be further treated in an evaporation and crystallization process, or in a second RO unit. Because the retentate stream is more concentrated than the feedwater stream, a higher pressure must be applied to a second RO unit in order to force the retentate stream through the membrane. This leads to low recovery, a further retentate stream, high energy costs, and precipitated minerals, including silica.

Further, the particulates that remain in the second RO unit may clog the membranes and filters. To mitigate these effects, extensive pre-treatment and post- treatment may be required.

High mineral content water may have minerals that are difficult to remove. For example, silica may be difficult to remove from high mineral content water. Excess silica in water is undesirable for many membrane-related water treatment processes, due to the potential formation of silica scales on the membrane surface.

To address these issues, in some embodiments, the high mineral content water, for example, the retentate stream, may be fed to an electrochemical process unit. Devices for purifying fluids with electrical fields are commonly used to treat water and other liquids having a high mineral content. In some embodiments, additional system components that are capable of treating high concentrations of hardness, silica, and other sealants, may be included.

Two types of electrochemical devices that may be used to treat the high mineral content water are electrodialysis (ED) and electrodeionization (EDI) units. The ED unit may treat a high mineral content water stream of various flow rates. The ED unit may be an electrodialysis with polarity reversal (EDR) unit to prohibit scaling. Within these electrochemical devices are concentrating and diluting compartments separated by ion- selective membranes. An ED unit typically includes ion exchange membranes. Spaces between the membranes are configured to create liquid flow compartments with inlets and outlets. An applied electric field imposed via electrodes causes dissolved ions, attracted to their respective counter-electrodes, to migrate through the ion exchange membranes. This generally results in the liquid of the diluting compartment being depleted of ions, and the liquid in the concentrating compartment being enriched with the transferred ions. The polarity reversal of the EDR unit may prevent hardness and accumulation of scaling components in the EDR concentrate stream. The EDR unit may remove TDS from the RO reject prior to treatment by an EDI.

As used herein, "high mineral content water" refers to water having a TDS of greater than 500 ppm and having high percentages of commonly occurring earth minerals in various sources of water. For example, high mineral content water may have high percentages of chloride, sodium, magnesium, sulfur, calcium, potassium, bromine, or carbon. In some embodiments, high mineral content water may have a TDS of greater than 1,000 ppm. In some embodiments, high mineral content water may have a TDS of greater than 10,000 ppm. In some embodiments, high mineral content water may have a TDS of greater than 20,000 ppm. In some embodiments, high mineral content water may have a TDS of greater than 50,000 pp. In some embodiments, high mineral content water may have a TDS of greater than 100,000 ppm. For example, high mineral content water may have a TDS of about 200,000 ppm. High mineral content water may have a high silica concentration. For example, high mineral content water may have a silica concentration of at least about 5 ppm. In some embodiments, the high mineral content water may have a silica concentration greater than 5 ppm. For example, high mineral content water may have a silica concentration of about 8 ppm. In some embodiments, high mineral content water may have a silica concentration of greater than 20 ppm. In some embodiments, high mineral content water may have a silica concentration greater than 50 ppm. For example, high mineral content water may have a silica concentration of about 80 ppm.

In some embodiments, the high mineral content water may be pumped to treatment devices or may be readily available. As such, the high mineral content water may have varied pressure. For example, the high mineral content water may have a pressure of about 0 PSI. In some embodiments, the high mineral content water may have a pressure of greater than about 0 PSI. In some embodiments, the high mineral content water may have a pressure of about 20 PSI. In some embodiments, the high mineral content water may have a pressure of about 40 PSI. In some embodiments, the high mineral content water may have a pressure of up to about 80 PSI. The high mineral content water may have varied temperature. In some embodiments, the high mineral content water may have a temperature of about 5°C. In some embodiments, the high mineral content water may have a temperature of greater than about 5°C. In some embodiments, the high mineral content water may have a temperature of greater than about 20°C. In some embodiments, the high mineral content water may have a temperature of up to about 45°C. The high mineral content water may have varied conductivity. In some embodiments, the high mineral content water may have a conductivity of about 1,500 μ8 :ιη. In some embodiments, the high mineral content water may have a conductivity of greater than about 1,500 μ8/αη. In some embodiments, the high mineral content water may have a conductivity of greater than about 10,000 μ8/αη. In some embodiments, the high mineral content water may have a conductivity of greater than about 50,000 μδ/οιη. In some embodiments, the high mineral content water may have a conductivity of greater than about 100,000 μδ/cm. In some embodiments, the high mineral content water may have a conductivity of greater than about 250,000 μδ/οιη. In some embodiments, the high mineral content water may have a conductivity of greater than about 300,000 μδ/οιη. In some embodiments, the high mineral content water may have a conductivity of greater than about 400,000 μδ/cm. In some embodiments, the high mineral content water may have a conductivity of greater than about 500,000 μδ/οιη.

As used herein, "TDS" is the total amount of mobile charged ions, including minerals, salts, or metals dissolved in a given volume of water, expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm). TDS is directly related to the purity and quality of water and water purification systems and affects everything that consumes, lives in, or uses water, whether organic or inorganic. The term "dissolved solids" refers to any minerals, salts, metals, cations or anions dissolved in water, and includes anything present in water other than the pure water (H₂0) molecule and suspended solids. In general, the total dissolved solids concentration is the sum of the cations and anions in the water. Parts per million (ppm) is the weight- to -weight ratio of any ion to water. TDS is based on the electrical conductivity (EC) of water, with pure water having virtually no conductivity. The TDS of the source of water may be greater than about 750 ppm. For example, the TDS may be greater than about 1,000 ppm. In some embodiments, the TDS may be greater than about 1,500 ppm. In some embodiments, the TDS may be greater than about 2,000 ppm. In some embodiments, the TDS may be greater than about 2,500 ppm.

In some embodiments, a treated ED concentrate stream may be returned to an RO system. However, the ED unit does not remove all of the TDS from the high mineral content water. For example, the ED unit does not remove silica from the high mineral content water, and without further treatment, the silica may build up and lead to silica precipitation within the RO system. Accordingly, silica is a limiting factor for the RO system. In some embodiments, the blending of a high silica, low TDS EDR product with feed water upstream of the RO system may limit the RO concentrate to the saturation limit of silica. In some embodiments, an anti-scalant may be used in the RO system to prohibit sealant, such as silica, precipitation. Under these conditions, a further treatment for silica is needed. To address this, in some embodiments, an ED product water stream may be directed to an EDI unit for further treatment.

EDI is a process that removes, or at least reduces, one or more ionized or ionizable species from water using electrically active media and an electric potential to influence ion transport. EDI units have previously been used to remove only low levels of silica (i.e., 1-2 ppm) from water. The electrically active media typically serves to alternately collect and discharge ionic and/or ionizable species and, in some cases, to facilitate the transport of ions, which may be continuously, by ionic or electronic substitution mechanisms. EDI units can comprise electrochemically active media of permanent or temporary charge, and may be operated batch-wise, intermittently, continuously, and/or even in reversing polarity modes. EDI units may be operated to promote one or more electrochemical reactions specifically designed to achieve or enhance performance. Further, EDI units may comprise electrically active membranes, such as semi-permeable or selectively permeable ion exchange or bipolar membranes. Continuous electrodeionization (CEDI) units are EDI units known to those skilled in the art that operate in a manner in which water purification can proceed

continuously, while ion exchange material is continuously recharged. CEDI techniques can include processes such as continuous deionization, filled cell electrodialysis, or

electrodiaresis. Under controlled voltage and salinity conditions, in CEDI systems, water molecules can be split to generate hydrogen or hydronium ions or species and hydroxide or hydroxyl ions or species that can regenerate ion exchange media in the device and thus facilitate the release of the trapped species therefrom. In this manner, a water stream to be treated can be continuously purified without requiring chemical recharging of ion exchange resin.

In EDI and EDR units, a plurality of adjacent cells or compartments are typically separated by selectively permeable membranes that allow the passage of either positively or negatively charged species, but typically not both. Dilution or depletion compartments are typically interspaced with concentrating or concentration compartments. As water flows through the depletion compartments, ionic and other charged species are typically drawn into concentrating compartments under the influence of an electric field, such as a DC field. Positively charged species are drawn toward a cathode, typically located at one end of a stack of multiple depletion and concentration compartments, and negatively charged species are likewise drawn toward an anode of such devices, typically located at the opposite end of the stack of compartments. The electrodes are typically housed in electrolyte compartments that are usually partially isolated from fluid communication with the depletion and/or concentration compartments. Once in a concentration compartment, charged species are typically trapped by a barrier of selectively permeable membrane at least partially defining the concentration compartment. For example, anions are typically prevented from migrating further toward the cathode, out of the concentration compartment, by a cation selective membrane. Once captured in the concentrating compartment, trapped charged species can be removed in a concentrate stream.

The ion exchange membranes may be membranes described in U.S. Patent No.

8,969,424, issued on March 3, 2015, and assigned to Evoqua Water Technologies LLC, the contents of which are incorporated herein by reference. In some embodiments, ion exchange membranes comprising functional monomers having a tertiary amine group with a quaternizing chemical are included in the ED and EDI units. In some embodiments, the functional monomers include vinyl compounds having nitrogen containing rings. For example, the functional monomers may comprise vinylimidazole and/or vinylcarbazole. These membranes have low resistance, high permeability, and good chemical resistance. The quaternary ammonium functional groups are strongly basic and ionized to act over the pH range of 0 to 13, allowing for a broad operational range.

The tertiary amine containing monomer may be polymerized with at least one crosslinking monomer and at least one quaternizing agent and one or more polymerization initiators to form the ionogenic polymer in the pores of the porous substrate. In some embodiments, the tertiary amine containing monomer may be polymerized with at least one secondary functional monomer such as, but not limited to, vinylbenzyltrimethylammonium chloride, trimethylammonium ethylmethacrylic chloride,

metacrylamideopropyltrimethylammonium chloride, (3- acrylamideopropyl)trimethylammonium chloride, 2-vinylpyridine, and 4-vinylpyridine, at least one crosslinking monomer, at least one quaternizing agent, and one or more polymerization initiators. The cross-linked polymer is contained in the pores of a microporous membrane substrate. The porous membrane substrate may be less than about 155 microns thick. In some embodiments, the porous membrane substrate may be less than about 55 microns thick.

In some embodiments, the membranes may have a porosity of greater than about 45%. For example, the membranes may have a porosity of greater than about 60%. In some examples, the membranes may have a porosity of greater than about 70%. The membranes may have a rated pore size of from about approximately 0.05 microns to about approximately 10 microns, with a more preferred range of from about approximately 0.1 microns to about approximately 1.0 microns. In some embodiments, the membranes have a rated pore size of from about approximately 0.1 microns to about approximately 0.2 microns.

The microporous membrane supports may be manufactured from polyolefins, polyolefin blends, polyvinylidene fluoride, or other polymers.

The membranes may further comprise at least one added non- functional secondary monomer such as, but not limited to, styrene, vinyl toluene, 4-methylstyrene, t-butyl styrene, alpha-methylstryrene, methacrylic anhydride, methacrylic acid, n-vinyl-2-pyrolidone, vinyltrimethoxysilane, vinyltriethoxysilance, vinyl-tris-(2-methoxyethoxy)silane, vinylidene chloride, vinylidene fluoride, vinylmethyldimethoxysilane, 2, 2, 2, -trifluoroethyl methacrylate allyamine vinylpyridine, maleic anhydride, glycidyl methacrylate,

hydroxyethylmethacrylate, methylmethacrylate, or ethylmethacrylate.

In some embodiments, at least one crosslinker of the membrane may be

divinylbenzene or ethylene glycol dimethacrylate. In some embodiments, at least one crosslinker may be chosen from propylene glycol dimethacrylate, isobutylene glycol dimethacrylate, Octa- vinyl POSS® (Hybrid Plastics, OL1160) (Ci₆H₂₄0i₂Si₈),

Octavinyldimethylsilyi POSS® (Hybrid Plastics, OL1163) (C₃2H72O2₀S116), Vinyl POSS® Mixture (Hybrid Plastics, OL1170) ((CH₂CH)„(SiOi.₅)„, wherein n= 8, 10, or 12,

Trisilabolethyl POSS® (Hybrid Plastics, S01444) (Cw^O^Si_?), Trisilanolisobutyl POSS® (Hybrid Plastics, O1450) (C₂8H₆₆Oi2Si₇), Trisilanolisooctyl POSS® (Hybrid Plastics, S01455) (CseHmOizSiT), Octasilane POSS® (Hybrid Plastics, SH1310) (CieHseOzoSiie), Octahydro POSS® (Hybrid Plastic, SH1311) (H₈0i₂Si₈), epoxycyclohexyl-POSS® cage mixture (Hybrid Plastics, EP04080) ((C₈H₁₃0)„(SiOi.₅)„, wherein n=8, 10, or 12), glycidyl- POSS® cage mixture (Hybrid Plastics, EP0409) (C₆Hn0₂)„(SiOi.₅)„, wherein n= 8, 10, or 12, methacryl POSS® Cage Mixture (Hybrid Plastics, MA0735) ((C₇Hn0₂)n(SiOi.₅)„, wherein n=8, 10, or 12, or Acrylo POSS® Cage Mixture (Hybrid Plastics, MA0736)

((C₆H₉0₂)„(SiOi.5)„, wherein n= 8, 10, or 12.

The membranes may further comprise an initiator. The initiator may be a free radical initiator. In some embodiments, the initiators may include benzoyl peroxide (BPO), ammonium persulfate, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2- methylpropionamidine)dihydrochloride, 2,2'-Azobis[2-(2-imidazolin- 2yl)propane]dihydrochloride, 2-2'-Azobis[2-(2-imidazolin-2-yl)propane] and dimethyl 2,2'- azobis(2-methylpropionate).

As used herein, the term "permselectivity" refers to an ion exchange membrane's ability to be permeable to one chemical species but impermeable with respect to another chemical species. For example, in certain instances the ion exchange membrane may be permeable to counter-ions, but impermeable to co-ions. This means, for example, that when an electric current is applied to an electrochemical cell having both anion and cation exchange membranes, cations in solution will cross the cation membrane but anions will not cross. When, as in this example, anions are allowed to cross the cation membrane, the overall efficiency of the process is reduced. In certain instances it may be desirable to have membranes with a high permselectivity, where the membranes are highly permeable to counter-ions and highly impermeable to co-ions.

The ion exchange membrane may be constructed from a polymeric substrate that is covered by a polymeric layer. In various aspects, the polymeric layer may be cross-linked. In at least one embodiment, the cross-linked polymeric layer may react with the polymeric substrate to yield a hydrophobic surface.

The ion exchange membranes may comprise polymeric materials that facilitate the transport of either positive or negative ions across the membrane. Ion exchange membrane properties, including resistivity and permselectivity, may be controlled, in part, by the amount, type, and distribution of fixed ionic groups in the membrane. For example, strong base anion exchange membranes may generally comprise quaternary amines, and weak base anion exchange membranes may generally comprise tertiary amines. The amines may have fixed positive charges that allow anionic species to permeate across the membrane.

In various embodiments, the ion exchange membranes may be generally

heterogeneous membranes. The heterogeneous membranes may include a polymeric layer that is coated on top of a substrate and the polymeric layer may provide fixed charges on the outer surface of the membrane. In other embodiments, the ion exchange membranes may be generally homogeneous. Homogeneous membranes may be produced by the polymerization of monomers and may include a polymeric microporous substrate. Reactive monomers may be used to fill the pores of the substrate, yielding a membrane with a highly uniform microstructure. The reactive monomers may be selected to functionally remove specific ions. For example, the reactive monomer may be selected to remove bicarbonate.

In some embodiments, the components of the electrodialysis unit may comprise polyvinyl chloride, nylon/ ABS, polyphenylene oxide, polypropylene, silicon, ion-selective membranes, ion exchange resins, and thermoplastic elastomer. The components of the electrodialysis unit may further comprise fiberglass reinforced plastic (FRP).

In both ED and EDI devices, the DC field is typically applied to the cells from a source of voltage and electric current applied to the electrodes (anode or positive electrode, and cathode or negative electrode). The voltage and current source (collectively "power supply") can be itself powered by a variety of means such as an AC power source, or for example, a power source derived from solar, wind, or wave power. At the electrode/liquid interfaces, electrochemical half cell reactions occur that initiate and/or facilitate the transfer of ions through the membranes and compartments. The specific electrochemical reactions that occur at the electrode/interfaces can be controlled to some extent by the concentration of salts in the specialized compartments that house the electrode assemblies. For example, a feed to the anode electrolyte compartments that is high in sodium chloride will tend to generate chlorine gas and hydrogen ion, while such a feed to the cathode electrolyte compartment will tend to generate hydrogen gas and hydroxide ion.

Plate- and-frame and spiral wound designs have been used for various types of electrochemical deionization devices including but not limited to ED and EDI devices.

Commercially available ED devices are typically of plate-and-frame design, while EDI devices are available in both plate and frame and spiral configurations. Various embodiments are applicable to plate-and frame, spiral wound, and cross-flow designs.

In some embodiments, the systems and methods described herein are directed to water treatment or purification systems and methods of providing treated water in industrial, commercial, residential, household, and municipal settings. For example, one or more embodiments may be suitable for treating water supplied to a municipal water treatment facility. According to another example, one or more embodiments may be suitable for treating water supplied to an industrial process, such as a manufacturing or production facility. One or more embodiments will be described using water as the fluid but should not be limited as such. For example, where reference is made to treating water, it is believed that other fluids can be treated according to the systems and methods described herein. Moreover, the treatment systems and apparatuses described herein are believed to be applicable in instances where reference is made to a component of the system or to a method that adjusts, modifies, measures or operates on the water or a property of the water. The fluid to be treated may also be a fluid that is a mixture comprising water.

In at least one aspect, the systems and methods described herein provide purified or treated water from a variety of source types. Possible feedwater sources include brackish water, well water, surface water, municipal water, seawater, and rain water. The treated product may be for general use, industrial use, pharmaceutical use, or for human consumption or other domestic uses, for example, bathing, laundering, and dishwashing. As used herein, the term "treated" in reference to water or fluid, references water exhibiting properties that are suitable for one or more various applications, such as residential, commercial, industrial, municipal, and the like.

In accordance with one or more embodiments, the process stream may generally comprise a water stream deliverable to a RO device for treatment. In some embodiments, the process stream may generally comprise a mineral solution. A mineral solution may contain a single mineral species or a mixture of mineral species, for example, as may be present in seawater. In at least one embodiment, the process stream may comprise non-potable water. Potable water typically has a TDS content of less than about 1,500 ppm. In some

embodiments, potable water may have a TDS of less than about 1,000 ppm. In some cases, potable water may have a TDS content of less than about 500 ppm. In some non-limiting embodiments, potable water may have a TDS content of less than about 250 ppm. Examples of non-potable water may include seawater or salt water, brackish water, gray water, and some industrial water.

In some embodiments of the disclosure, a method of providing a source of potable water is provided. In certain embodiments, a method of facilitating the production of potable water from seawater is provided. In at least one embodiment, the systems and methods provide a dilution or product stream that is in compliance with water quality criteria established by the World Health Organization (WHO). For example, current WHO standards require drinking water to have a pH of between about 6.5 and about 8.5 and a TDS of no more than 500 ppm. The method may comprise providing an electrical purification apparatus comprising a cell stack. The method may further comprise fluidly connecting a RO retentate water stream to a dilute compartment of an ED unit. In some embodiments, the method may further comprise fluidly connecting a dilute compartment of an ED unit to a depleting compartment of an EDI unit. The method may further comprise fluidly connecting an ED product water stream to a feedwater stream of the RO device. The method may further comprise fluidly connecting an EDI product water stream to the feedwater stream of the RO unit.

In accordance with one or more embodiments an ED unit is provided. The ED unit may include at least one ion exchange membrane. The at least one ion exchange membrane may be an anion or a cation exchange membrane. In various aspects, ion exchange membranes may have low electrical resistance, high permselectivity, high chemical stability, and high mechanical strength. Ion exchange membranes that are suitable for use in the systems and methods disclosed herein are available from Evoqua Water Technologies LLC. The ED unit may include a series of alternating anion and cation exchange membranes. The ED unit may further comprise at least one compartment to house the ion exchange membrane(s). In certain embodiments, the ED unit may include a plurality of alternating depleting compartments and concentrating compartments positioned between a pair of electrodes. The alternating depleting compartments and concentrating compartments may be referred to as cell pairs. The number of cell pairs may vary. For example, the number of cell pairs may depend on the size of the unit, the quality of the water, or the desired treatment. In some non-limiting embodiments, there may be up to about 1,000 repeating cell pairs in a module. The pair of electrodes may be a cathode and an anode. The water treatment system may include a concentrate stream and a dilution stream. The concentrate stream and dilution stream may be in fluid communication with at least one ion exchange membrane.

As water is passed through the cell pairs, an electric field generated by a direct current (DC) power supply may be imposed perpendicular to the water flow. This may result in the migration of ions from the dilute compartment to the concentrate compartment through the ion exchange membranes. Cations will transfer through the cation membrane and anions will transfer through the anion membrane. Water from the cell pairs may be combined in manifolds within the ED unit. Two water streams may exit the ED unit, a first product stream and a concentrate stream. Unlike an ED unit, an EDI unit may use cation exchange and anion exchange membranes separated by a spacer with a void volume filled with an ion exchange material such as ion exchange beads, felts and the like. In some embodiments, an EDI unit may include an ion exchange screen. In accordance with one or more embodiments, an ion exchange screen may be a functionalized screen, such as a screen having cation and/or anion functionality. The use of ion exchange material in place of an inert screen may improve the ability of the EDI unit to remove ions from water when the water is dilute, for example, less than about 5000 mg/1 of ionic concentration. The ion exchange material can comprise either cation exchange or anion exchange material and combinations thereof.

The treatment system, in some embodiments of the systems and methods described herein, further comprises one or more sensors or monitoring devices configured to measure at least one property of the water or an operating condition of the treatment system. Non- limiting examples of sensors include composition analyzers, pH sensors, temperature sensors, conductivity sensors, pressure sensors, and flow sensors. In certain embodiments, the sensors provide real-time detection that reads, or otherwise senses, the properties or conditions of interest. A few non-limiting examples of sensors suitable for use in one or more

embodiments include optical sensors, magnetic sensors, radio frequency identification (RFID) sensors, Hall effect sensors, and any combination thereof.

In certain non- limiting embodiments of the systems and methods described herein, the treatment system further comprises a flowmeter for sensing the flow of fluid. A non-limiting example of a flowmeter suitable for certain aspects of the treatment system disclosed here includes a Hall effect flowmeter. Other non-limiting examples of flowmeters suitable for certain aspects of the treatment system include mechanical flowmeters, including a mechanical-drive Woltman-type turbine flowmeter.

According to one or more aspects, the systems and methods disclosed herein may include a control system disposed or configured to receive one or more signals from one or more sensors in the treatment system. The control system can be further configured to provide one or more output or control signals to one or more components of the treatment system. One or more control systems can be implemented using one or more computer systems. The computer system may be, for example, a general-purpose computer such as those based on readily available systems. In some embodiments, the control system can include one or more processors connected to one or more memory devices. Software, including readily available programming code that implements embodiments of the systems and methods disclosed herein, may be used by the control system. Components of a control system may be coupled by one or more interconnection mechanisms, which may include one or more busses, for example, between components that are integrated within a same device, and/or one or more networks, for example, between components that reside on separate discrete devices.

The control system can further include one or more input devices, for example, a keyboard, mouse, trackball, microphone, touch screen, and one or more output devices, for example, a printing device, display screen, or speaker. In addition, the control system may contain one or more interfaces that can connect to a communication network.

According to one or more embodiments, one or more input devices may include one or more sensors for measuring the one or more parameters of the fluids in the treatment system. For example, sensors may be configured as input devices that are directly connected to the control system. For purposes of this disclosure, the term "monitoring" may be defined to include, in a non-limiting manner, acts such as recording, observing, evaluating, identifying, etc.

In certain embodiments, the treatment system also includes a controller for adjusting, monitoring, or regulating at least one operating parameter and its components of the treatment system. In certain embodiments, the controller regulates the operating conditions of the treatment system in an open-loop or closed-loop control scheme. In yet another embodiment, the controller can further comprise a communication system, for example, a remote communication device, for transmitting or sending the measured operating condition or operating parameter to a remote station.

In accordance with one or more embodiments, an ED or EDI unit may be modular. Each modular unit may generally function as a sub-block of an overall ED system. A modular unit may include any desired number of cell pairs. In some embodiments, the number of cell pairs per modular unit may depend on the total number of cell pairs and passes in the separation device. It may also depend on the number of cell pairs that can be thermally bonded and potted in a frame with an acceptable failure rate when tested for cross-leaks and other performance criteria. The number can be based on statistical analysis of the manufacturing process and can be increased as process controls improve. In some non- limiting embodiments, a modular unit may include up to about 100 cell pairs. Modular units may be individually assembled and quality control tested, such as for leakage, separation performance and pressure drop prior to being incorporated into a larger system. In some embodiments, a cell stack may be mounted in a frame as a modular unit that can be tested independently. A plurality of modular units can then be assembled together to provide an overall intended number of cell pairs in an electrochemical separation device. In some embodiments, an assembly method may generally involve placing a first modular unit on a second modular unit, placing a third modular unit on the first and second modular units, and repeating to obtain a plurality of modular units of a desired number. In some embodiments, the assembly or individual modular units may be inserted into a pressure vessel for operation. Multi-pass flow configurations may be possible with the placement of blocking membranes and/or spacers between modular units or within modular units. A modular approach may improve manufacturability in terms of time and cost savings. Modularity may also facilitate system maintenance by allowing for the diagnosis, isolation, removal and replacement of individual modular units. Individual modular units may include manifolding and flow distribution systems to facilitate an electrochemical separation process. Individual modular units may be in fluid communication with one another, as well as with central manifolding and other systems associated with an overall electrodialysis process.

In some embodiments, the plurality of ion exchange membranes secured to one another may alternate between cation exchange membranes and anion exchange membranes to provide a series of ion diluting compartments and ion concentrating compartments.

The geometry of the membranes may be of any suitable geometry such that the membranes may be secured within a cell stack. In certain embodiments, a particular number of corners or vertices on the cell stack may be desired so as to suitably secure the cell stack within a housing. In certain embodiments, particular membranes may have different geometries than other membranes in the cell stack. The geometries of the membranes may be selected to assist in at least one of securing the membranes to one another, to secure spacers within the cell stack, to secure membranes within a modular unit, to secure membranes within a support structure, to secure a group of membranes such as a cell stack to a housing, and to secure a modular unit into a housing.

In some embodiments of the disclosure, an ED unit comprising a cell stack is provided. The ED unit may comprise a first compartment, such as a dilute compartment, comprising ion exchange membranes and may be constructed and arranged to provide a direct fluid flow in a first direction between the ion exchange membranes. The ED unit may also comprise a second compartment, such as a concentrate compartment, comprising ion exchange membranes and may be constructed and arranged to provide a direct fluid flow in a second direction. Each of the first compartment and the second compartment may be constructed and arranged to provide a predetermined percentage of surface area or membrane utilization for fluid contact. In accordance with one or more embodiments, water is purified under the presence of an electric field. Water in the dilute compartment becomes purer while the water in the adjacent concentrate compartment becomes enriched with ionic compounds. This may result in the electrical resistance of the module increasing since the dilute water is not very conductive. Furthermore, if the water in the dilute compartment becomes too pure, water will dissociate near the ion exchange membrane leading to a layer of very high electrical resistance water directly adjacent to the ion exchange membrane that increases the overall applied voltage. This inefficiency can limit the ED process to conditions where these phenomena will not occur. In order to minimize this effect also referred to as concentration polarization, various process modifications can be performed in accordance with one or more embodiments.

The EDI unit typically comprises at least one concentrating compartment and at least one depleting compartment, which constitute a cell pair, and disposed in ionic

communication with each other and, preferably, between and with an anode compartment and a cathode compartment. In an advantageous embodiment of the invention, the EDI unit can further comprise at least one barrier cell that can trap migrating species. For example, the EDI unit can have barrier or neutral cells and disposed adjacent anode compartment and cathode compartment. Barrier cells typically provide a buffer for an electrode compartment to separate or prevent species from forming localized scale. An EDI unit typically generates hydroxide ions which can raise the pH at localized regions, especially at the points or surfaces conducive to electrolytic reactions. Such localized regions, or even at the electrode compartments, typically have pH conditions much greater than the bulk of the liquid. The barrier cells can serve to isolate such high pH regions from scale-forming species transported from the one or more depleting compartments during treatment of the water, thereby inhibiting or at least reducing the potential for scale formation. An EDI unit can comprise a barrier cell that ionically isolates at least one precipitatable component from a component that contributes to scale formation. Typically, one or more barrier cells can be defined, at least partially, by an anion selective membrane that permits migration of anionic species while inhibiting the further migration of cationic species into an adjacent compartment. As illustrated, a barrier cell can be disposed adjacent concentrating compartment. One or more such barrier cells can also further be partially defined by a cation selective membrane.The components of the EDI unit may comprise polyvinyl chloride, nylon/ ABS, polyphenylene oxide, polypropylene, silicone, ion-selective membranes, ion exchange resins, and thermoplastic elastomer. The components of the EDI unit may comprise fiberglass reinforced plastic.

Other embodiments of the invention can involve barrier cells that separate neutral or weakly ionized, or at least ionizable, species, such as, but not limited to silica, Si0₂. Silica can precipitate from the bulk liquid if the concentration is high enough or where a pH change occurs, such as change from a high pH to a neutral pH. In an EDI unit, silica is typically removed while in its ionized state, at high pH. One or more barrier cells can be disposed to ionically isolate an anode compartment of the EDI unit, wherein hydrogen ions are generated and consequently can have low or neutral pH liquid flowing therein. After silica migrates from the depleting compartment into the concentrating compartment through anion selective membrane, it is trapped by barrier cell containing high pH liquid flowing therein and inhibited from further migration into the low or neutral pH compartment with neutral or near neutral pH, and thereby reduce the likelihood of polymerizing into silica scale. Further, one or more of the barrier cells can further comprise inert media or other filler material that can facilitate assembly of the EDI unit or provide a desirable characteristic such as resistance or flow distribution during, for example, operation of the apparatus. In some embodiments, at least one of the concentrating compartment and the depleting compartment comprise ion exchange resin. It may be preferable that the resins support transport of undesired particles. In some embodiments, it may be preferable that the ion exchange resins in the depleting compartment are comprised of a majority of anion exchange ions. In an embodiment, the depleting compartment consists entirely of anion exchange resins. Likewise, one or more of the concentrating compartments, the depleting compartments, and the electrode

compartments can contain, at least partially, a mixture of anion and cation exchange resins in various ratios, depending on desired performance, targeted species, and conditions and quality of the feedwater to the EDI unit. In some embodiments, the concentrating compartment comprises a mixture of about 50% anion exchange resins and about 50% cation exchange resins. In some embodiments, the concentrating compartment comprises a mixture of about 60% anion exchange resins and about 40% cation exchange resins. It has been found that 70% anion exchange resins and about 30% cation exchange resins is an optimal mixture in certain embodiments. In some embodiments, the concentrating compartment also comprises a mixture of anion exchange resins and cation exchange resins. In one embodiment, there are about 80% anion exchange resins and about 20% cation exchange resins. In some embodiments, the concentrating compartment comprises a mixture of about 40% anion exchange resins and about 60% cation exchange resins. In an example, the anion exchange resins comprise translucent beads in a styrene- DVB gel. The anion exchange resins may comprise a functional group, for example a quaternary amine. The anion exchange resins may have a moisture retention capacity. In some embodiments, the anion exchange resins may have a moisture retention capacity of about 50%. In some embodiments, the anion exchange resins may have a moisture retention capacity of greater than 50%. In some embodiments, the anion exchange resins may have a moisture retention capacity of up to about 72%. The anion exchange resins may have a maximum particle size uniformity. In some embodiments, the maximum particle size uniformity coefficient may be about 0.5. In some embodiments, the maximum particle size uniformity coefficient may be greater than about 0.5. In some embodiments, the maximum particle size uniformity coefficient may be about 0.7. In some embodiments, the maximum particle size uniformity coefficient may be about 0.9. In some embodiments, the maximum particle size uniformity coefficient may be about 1.1. In some embodiments, the anion exchange resin may have a harmonic mean diameter. In some embodiments, the anion exchange resin may have a harmonic mean diameter of about 575 μιη + 50 μιη. In other embodiments, the anion exchange resins may have a harmonic mean diameter of about 610 μιη + 50 μιη. The anion exchange resins may have a particle density. In some embodiments, the anion exchange resins may have a particle density of about 0.5 g/mL. In some embodiments, the anion exchange resins may have a particle density of greater than 0.5 g/mL. In some embodiments, the anion exchange resins may have a particle density of about 0.6 g/mL. In some embodiments, the anion exchange resins may have a particle density of about 0.7 g/mL. In some embodiments, the anion exchange resins may have a particle density of about 0.8 g/mL. In some embodiments, the anion exchange resins may have a particle density of about 0.9 g/mL. In some embodiments, the anion exchange resins may have a particle density of up to about 1.06 g/mL. In some embodiments, the anion exchange resins may have a particle density of up to about 1.08 g/mL. In some embodiments, the anion exchange resins may be Dowex™ Marathon™ A Resin (available from The Dow Chemical Company).

In some embodiments, the anion exchange resins may be a Type I resins. The Type I resin is a strong base anion resin. The Type I resins may comprise a quaternized amine functional group. The Type I resins may have a greater affinity for weak acids such as silicic acid and carbonic acid. In some embodiments, Type I resins may be regenerated at various temperatures. In an example, Type I resins may be regenerated up to about 50°C. In some embodiments, the anion exchange resin may be a Type II resin. The Type II resins may be obtained by the reaction of the styrene-DVB copolymer with

dimethylethanolamine. The quaternary amine of the Type II resins may have a lower basicity than that of the Type I resins, but are capable of removing weak acid anions.

In some embodiments, the anion exchange resins may lower the pH in the concentrating compartment. For example, the pH of the concentrating compartment may be lower than about 5. In some embodiments, the pH of the concentrating compartment may be lower than about 2. The reject water stream from the concentrating compartment may be recycled to the concentrate compartment and combined with the concentrate water stream to prohibit scaling in the concentrate compartment. In addition, the high pH of the second product water stream in the depleting compartment allows silica to ionize.

In some embodiments, the cation exchange resins comprise translucent spherical beads in a styrene-DVB gel. The cation exchange resins may comprise a functional group, for example a sulfonic acid. The cation exchange resins may have a moisture retention capacity. In some embodiments, the cation exchange resins may have a moisture retention capacity of about 50%. In some embodiments, the cation exchange resins may have a moisture retention capacity of less than 50%. In some embodiments, the cation exchange resins may have a moisture retention capacity of less than about 45%. For example, the cation exchange resins may have a moisture retention capacity of about 42%. In some embodiments, the cation exchange resins may have a moisture retention capacity of up to about 56%. The cation exchange resins may have a maximum particle size uniformity. In some embodiments, the cation exchange resins may have a maximum particle size uniformity coefficient of up to about 0.5. In some embodiments, the maximum particle size uniformity coefficient may be greater than about 0.5. In some embodiments, the maximum particle size uniformity coefficient may be about 0.7. In some embodiments, the maximum particle size uniformity coefficient may be about 0.9. In some embodiments, the maximum particle size uniformity coefficient may be about 1.1. In some embodiments, the cation exchange resins may have a harmonic mean diameter. In some embodiments, the cation exchange resins may have a harmonic mean diameter of about 585 μιη + 50 μιη. In other embodiments, the cation exchange resins may have a harmonic mean diameter of about 600 μιη + 50 μιη. The cation exchange resins may have a particle density. In some embodiments, the cation exchange resins may have a particle density of about 0.6 g/mL. In some embodiments, the cation exchange resins may have a particle density of greater than 0.6 g/mL. In some embodiments, the cation exchange resins may have a particle density of about 0.7 g/mL. In some embodiments, the cation exchange resins may have a particle density of about 0.8 g/mL. In some embodiments, the cation exchange resins may have a particle density of about 0.9 g/mL. In some embodiments, the cation exchange resins may have a particle density of about 1.0 g/mL. In some embodiments, the cation exchange resins may have a particle density of up to 1.20 g/mL. In some embodiments, the cation exchange resins may have a particle density of up to about 1.28 g/mL. In some embodiments, the anion exchange resins may be Dowex™ Marathon™ C Resin (available from The Dow Chemical Company).

In accordance with one or more embodiments, the depleting compartment of the EDI unit comprises a mixed bed of ion exchange resins. The mixed bed may comprise cation exchange resins and anion exchange resins. In some embodiments, the mixed bed may comprise strong acid cation exchange resins and strong base anion exchange resins. In some embodiments, the mixed bed may comprise between about 1% and about 99% anion exchange resins and about 99% to about 1% cation exchange resins. In some embodiments, the mixed bed may comprise about 50% anion exchange resins and 50% cation exchange resins. In some embodiments, the mixed bed may comprise about 60% anion exchange resins and about 40% cation exchange resins. In some embodiments, the mixed bed may comprise about 70% anion exchange resins and about 30% cation exchange resins. In some embodiments, the anion exchange resin comprises from about 0% to about 100% of Type I resins and about 0% to about 100% of Type II resin. For example, the anion exchange resin may comprise about 10% of Type I resin and about 90% of Type II resin. In some embodiments, the anion exchange resin may comprise about 20% of Type I resin and about 80% of Type II resin. In some embodiments, the anion exchange resin may comprise about 30% of Type I resin and about 70% of Type II resin. In some embodiments, the anion exchange resin may comprise about 40% of Type I resin and about 60% of Type II resin. In some embodiments, the anion exchange resin may comprise about 50% of Type I resin and about 50% of Type II resin. In some embodiments, the depleting compartment of the EDI unit further comprises at least one layer of anion exchange resin and at least one layer of mixed bed ion exchange resins. In some embodiments, the mixed bed of ion exchange resins may alternate with the anion exchange resin in consecutive depleting compartments. In some embodiments, consecutive depleting compartments are in the same EDI module. In some embodiments, consecutive depleting compartments are in consecutive EDI modules. In some embodiments, the anion exchange resin comprises from about 0% to about 100% of Type I resin and about 0% to about 100% of a Type II resin. For example, the anion exchange resin may comprise about 10% of a Type I resin and about 90% of a Type II resin. In some embodiments, the anion exchange resin may comprise about 20% of a Type I resin and about 80% of a Type II resin. In some embodiments, the anion exchange resin may comprise about 30% of a Type I resin and about 70% of a Type II resin. In some embodiments, the anion exchange resin may comprise about 40% of a Type I resin and about 60% of a Type II resin. In some embodiments, the anion exchange resin may comprise about 50% of a Type I and about 50% of a Type II resin.

In accordance with one or more embodiments of the ED or EDI units, many cell pairs are bounded by a set of electrodes including an anode and cathode. The cathode material may comprise 316L stainless steel, Hastelloy C, or other materials that are resistant to corrosion. The anode material can comprise a base metal such as titanium coated with a noble metal such as platinum or a rare earth oxide such as iridium or ruthenium oxide or combination thereof. A liquid may be used to flush the electrode compartments in order to remove gases and chemicals that are generated. In some embodiments, the liquid used in the electrode compartments to minimize the voltage drop may be modified to reduce the power consumption. One method of reducing the voltage drop in the electrode compartments is to use a liquid with a very high conductivity. Many concentrated salt solutions can be used such as sodium chloride or sodium sulfate. This liquid can comprise concentrated seawater for instance. In another embodiment, strong acids and bases may be used to flush the electrode compartments.

In accordance with one or more embodiments, a controller may be configured to reverse polarity of an electric current applied through the device. The controller may be in communication with one or more sensors configured to provide a measurement signal which is representative of a concentration of a target species in a stream associated with the device, for example, a product stream exiting a compartment of the device. In some embodiments, a conductivity level, pressure or concentration measurement may be detected by a sensor and communicated to the controller. The controller may be configured to generate a control signal in response a received measurement being above or exceeding a predetermined level. The control signal may reverse polarity of an electric current applied through the device so as to regenerate a membrane or media in a compartment therein. In some embodiments, the control signal may be sent to a power supply associated with the device based at least partially on the measurement signal.

In some embodiments, pretreatment of feedwater in the unit can be employed. For example, pretreatment techniques may be utilized on a feed water that may contain solids or other materials that may interfere with or reduce the efficiency of any stage or device, such as by scaling or fouling. An optional initial treatment may be provided to remove at least a portion of suspended solids, colloidal substances and/or solutes of elevated molecular weight. Pretreatment processes may be performed upstream of the EDI device and may include, for example, particulate filtration, sand filtration, carbon filtration, ultrafiltration, nanofiltration, microfiltration, such as cross-flow microfiltration, combinations thereof and other separation methods directed to the reduction of particulates. Adjustments to the pH and/or alkalinity of feed water may also be performed by, for example, the addition of an acid, base or buffer, or through aeration. Electrochemical separation may follow any pretreatment operation to provide water having a desired final purity.

The electrochemical units may be operated in any suitable fashion that achieves the desired product and/or effects the desired treatment. For example, the various embodiments can be operated continuously, or essentially continuously or continually, intermittently, periodically, or even upon demand. Multi-pass systems may also be employed wherein feed is typically passed through the device two or more times, or may be passed through an optional second device. An electrical separation device may be operatively associated with one or more other units, assemblies, and/or components. Ancillary components and/or subsystems may include pipes, pumps, tanks, sensors, control systems, as well as power supply and distribution subsystems that cooperatively allow operation of the system.

Purified water may be sent for use or storage as potable water. Potable water may be preserved or further disinfected, if desired, and may find use in various applications including agriculture and industry, such as for semiconductor fabrication. The concentrate stream of the EDI unit and/or the reject stream of the EDI unit may be collected and discharged to waste, recycled through the system, or fed to a downstream unit operation for further treatment. Product streams may be further processed prior to downstream use, upstream use, or disposal. For example, a pH level of a product acid or product base stream may be adjusted. In some embodiments, it may be desirable to mix, in part or in whole, one or more product streams. One or more additional unit operations may be fluidly connected downstream of the electrochemical unit. For example, one or more unit operations may be configured to receive and process a target product stream, such as before delivering it to a point of use. For example, the additional unit operation may be a polisher, such as an evaporation and crystallization unit. Further polishing units, such as those involving chemical or biological treatment, may also be present to treat a product or effluent stream of the device prior to use or discharge. It should be understood that the systems, techniques and methods may be used in connection with a wide variety of systems where the processing of one or more liquids may be desired. Thus, the electrical separation device may be modified by those of ordinary skill in the art as needed for a particular process, without departing from the scope of the invention.

FIG. 1 is a process flow diagram of a water treatment system 100 in accordance with one or more embodiments. A feedwater stream 105 may be fed to an RO unit 110. Feedwater stream 105 may be any source of high mineral content water. The high mineral content water may comprise a contaminant such as silica. For example, feedwater stream 105 may include brackish water, well water, surface water, municipal water, seawater, and rain water. RO unit 110 may use a source of pressure to push feedwater stream 105 through a semi -permeable reverse osmosis membrane. The reverse osmosis membrane allows the passage of water, but not the majority of contaminants, including dissolved salts, minerals, organic compounds, and bacteria. The treated water is discharged as a filtrate water stream 115 through a filtrate water outlet. The contaminants, including silica, are concentrated and discharged in a reject, or a retentate water 120 through a retentate water outlet.

Water treatment system 100 may further comprise a liquid circuit that allows fluid communication between one or more outlets of RO unit 110 and an ED unit 125. For example, a valve may be in fluid communication with at least one outlet of RO unit 110. The liquid circuit may include one or more pumps to aid in directing fluid throughout the treatment system 100, for example, for directing fluid into one or more inlets of ED unit 125. Retentate stream 120 may be fed to ED unit 125. In some embodiments, ED unit 125 is a reversible electrodialysis unit. ED unit 125 may comprise a dilute compartment 125a connected to the retentate water outlet and a concentrate compartment 125b separated from the dilute compartment 125a by an ion-selective membrane. ED unit 125 may include a series of alternating anion and cation exchange membranes. In some embodiments, the ED unit includes a plurality of alternating dilute compartments and concentrate compartments positioned between a pair of electrodes. These alternating compartments are referred to as cell pairs. In some embodiments, there may be between about 100 and about 1000 repeating cell pairs in the electrodialysis unit 125. An applied electric field imposed via electrodes causes dissolved ions, attracted to their respective counter-electrodes, to migrate through the ion exchange membranes. The liquid in the dilute compartment 125a is depleted of ions, and the liquid in the concentrate compartment is enriched with the transferred ions. The treated water from dilute compartment 125a may be discharged as a first product water stream 135 through a first product water outlet for recycle to reverse osmosis unit 110. The concentrate compartment 125b may produce a concentrate water stream 130 for discharge for use or storage.

In accordance with certain embodiments of the systems and methods described herein, treatment system 100 may also comprise one or more probes or sensors, for example, a water property sensor, capable of measuring at least one physical property in treatment system 100. For example, the sensor can be a device that measures water conductivity, pH, temperature, pressure, composition, and/or flow rates. The probe or sensor can be installed or positioned within treatment system 100 to measure a particularly preferred water property. For example, a probe or sensor can be a water conductivity sensor installed in or otherwise placed in fluid communication with feedwater stream 105 so that it measures the conductivity of the water. In another embodiment, the probe or sensor can comprise a series or a set of sensors in various configurations or arrangements in treatment system 100. The set of sensors can be constructed, arranged, and connected to a controller so that the controller can monitor, intermittently or continuously, the quality of water in, for example, filtrate water stream 115. This arrangement allows the performance of treatment system 100 to be further optimized.

In accordance with other embodiments of the systems and methods described herein, treatment system 100 may include a combination of sets of sensors in various locations in the liquid streams or other components throughout treatment system 100. For example, the probe or sensor can be a flow sensor measuring a flow rate from feedwater stream 105, and can further include any one or more of a pH meter, a nephelometer, a composition analyzer, a temperature sensor, and a pressure sensor monitoring the operating conditions of treatment system 100.

The systems and methods described herein further provide a treatment system where a controller may provide a signal that actuates a valve so that fluid flow is adjusted based on a variety of operating parameters. These parameters may include, but are not limited to, the properties of water from feedwater stream 105, the properties of water in filtrate stream 115, the properties of water in first product water stream 135, the properties of water in concentrate water stream 130, and any combination thereof. Specific measured parameters may include, but are not limited to, water conductivity, pH, turbidity, composition, temperature, pressure, flow rate, and any combination thereof.

In one or more embodiments, a controller may receive signals from one or more sensors so that the controller is capable of monitoring the operating parameters of treatment system 100. For example, a conductivity sensor may be positioned within storage system 140 so that the conductivity is monitored by the controller. In one or more embodiments, a controller may receive a signal from one or more sensors so that the controller is capable of monitoring the operating parameters of the first product water stream, such as conductivity. In operation, the controller may increase, decrease, or otherwise adjust the voltage, current, or both, supplied form a power source to one or more components of the treatment system. The controller may include algorithms that may modify an operating parameter of treatment system 100 based on one or more measured properties of the liquid flowing in the system. For example, in some embodiments, the controller may increase or decrease the flow rate of the first product water stream 135 and the concentrate water stream 130.

The controller may be configured, or configurable by programming, or may be self- adjusting such that it is capable of maximizing any of the service life, the efficiency, or reducing the operating cost of water treatment system 100. For example, the controller may include a microprocessor having user-selectable set points or self-adjusting set points that adjust the applied voltage, current, or both, to valves, the flow rate through concentrate stream 130, and the flow rate to first product water stream 135.

In accordance with another embodiment of the systems and methods described herein, the controller regulates the operation of the treatment system by incorporating adaptive or predictive algorithms, which are capable of monitoring demand and water quality and adjusting the operation of any one or more components of the treatment system 100.

In certain non- limiting embodiments, radio frequency identification (RFID) is utilized to provide real-time detection of certain properties or conditions in treatment system 100. In certain embodiments, a plurality of inline identifying tag readers or optical sensors are configured to track or sense certain properties or conditions of the liquid as it is transported through the treatment system. The RFID may be combined with one or more additional sensors, for example, a flowmeter.

Water treatment system 100 may further comprise storage system 140. Storage system 140 may store or accumulate water from filtrate stream 115. In certain non-limiting embodiments, the storage system comprises a tank that has a volume capacity in a range of from about 5 gallons to about 200 gallons. In certain non-limiting embodiments, storage system 140 may comprise several tanks or vessels, and each tank or vessel, in turn, may have several inlets and/or outlets positioned at various locations.

Storage system 140 may further comprise various components or elements that perform desirable functions or avoid undesirable consequences. For example, the tanks or vessels may have internal components, such as baffles, that are positioned to disrupt any internal flow currents or areas of stagnation. In some embodiments, storage system 140 further comprises a heat exchanger for heating or cooling the stored fluid. For example, storage system 140 may comprise a vessel constructed with a heating coil, which can have a heating fluid at an elevated temperature relative to the temperature of the fluid in the vessel. The heating fluid can be hot water in a closed-loop flow with a furnace or other heat- generating unit so that the heating fluid temperature is raised in the furnace. The heating fluid, in turn, raises the vessel fluid temperature by heat transfer. Other examples of auxiliary or additional components include, but are not limited to, pressure relief valves designed to relieve internal pressure in the storage system. In accordance with further embodiments, the treatment system can comprise at least two tanks or vessels or two zones in one or more tanks or vessels, each of which can be, at least partially, fluidly isolated from the other. For example, the treatment system can comprise two vessels fluidly connected to a feed stream and to one or more treatment devices. The two tanks or vessels can be fluidly isolated from each other by conduits and valves so that the first can be placed in service with one or more treatment devices while the second can be removed from service for, for example, maintenance or cleaning. In accordance with one or more embodiments of the systems and methods described herein, the tank or reservoir system is connected to, or in thermal communication with, a heat exchanger and, optionally, to a fluid treatment device. The fluid treatment device can be an electrochemical water treatment device, a reverse osmosis device, an ion-exchange resin bed, an electrodialysis device, a capacitive deionization device, or combinations thereof.

In order to remove silica from retentate stream 110, an EDI unit 240 may be used in water treatment system 200, as seen in FIG. 2. EDI unit 240 comprises at least one depleting compartment 240a and one concentrating compartment 240b. Depleting compartment 240a and concentrating compartment 240b constitute a cell pair. The compartments of the cell pair are disposed in ionic communication with each other and between and with an anode and a cathode. In some embodiments, EDI unit 240 further comprises at least one barrier cell that can trap migrating species, including silica. One or more of the concentrating compartments 240b, the depleting compartments 240a, and the electrode compartments can contain, at least partially, a mixture of anion and cation exchange resin. In some embodiments, the depleting compartment 240a comprises primarily anion exchange resin. In some embodiments, the depleting compartment 240a consists of only anion exchange resin. In some embodiments, the concentrating compartment 240b comprises a mixture of anion exchange resin and cation exchange resin. The treated water from depleting compartment 240a may be discharged as a second product water stream 250 through a second product water outlet for recycle to reverse osmosis unit 110. The concentrating compartment may produce a reject water stream 245 through a reject stream outlet for use or storage.

As shown in FIG. 3, polisher 360 may be used in water treatment system 300.

Concentrate water stream 130 and reject water stream 245 may be fed to polisher 360 for further treatment. Polisher 360 may be any process unit configured to receive and process a target product stream, such as before delivering it to a point of use. Polisher 360 may, for example, involve chemical or biological treatment. In some embodiments, polisher 360 may be an evaporation and crystallization unit. Polisher 360 may produce a third product water stream 370 and a waste stream 365. Waste stream 365 may be discharged to a point of use or storage. Third product water stream 370 may be discharged through a third product water outlet for recycle to reverse osmosis unit 110.

As shown in FIG. 4, water treatment system 400 comprises two ED units used in series to treat high mineral content water. Feedwater stream 420 may be discharged from high mineral content water source 410. Feedwater stream 420 may comprise silica. In some embodiments, feedwater stream 420 may comprise greater than 8 ppm silica. In some embodiments, feedwater stream 420 may comprise greater than 10 ppm silica. In some embodiments, feedwater stream 420 may comprise greater than 20 ppm silica.

In some embodiments, ED units 425, 440 are capable of reversing polarity. ED unit 425 may comprise a dilute compartment 425a connected to the feedwater stream 410 and a concentrate compartment 425b separated from the dilute compartment 425a by an ion- selective membrane. ED unit 425 may include a series of alternating anion and cation exchange membranes. In some embodiments, the ED unit includes a plurality of alternating dilute compartments and concentrate compartments positioned between a pair of electrodes. These alternating compartments are referred to as cell pairs. In some embodiments, there may be between about 100 and about 1,000 repeating cell pairs in the ED unit 425. An applied electric field imposed via electrodes causes dissolved ions, attracted to their respective counter-electrodes, to migrate through the ion exchange membranes. The liquid in the dilute compartment 425a is depleted of ions, and the liquid in the concentrate

compartment is enriched with the transferred ions. The concentrate compartment 425b may produce a concentrate water stream 435 for discharge for use or storage. The treated water from dilute compartment 125a may be discharged as a first product water stream 430.

First product water stream 430 may be discharged to ED unit 440. ED unit 440 may comprise a dilute compartment 440a connected to the first product water stream 430 and a concentrate compartment 440b separated from the dilute compartment 440a by an ion- selective membrane. ED unit 440 may include a series of alternating anion and cation exchange membranes. In some embodiments, the ED unit includes a plurality of alternating dilute compartments and concentrate compartments positioned between a pair of electrodes. These alternating compartments are referred to as cell pairs. In some embodiments, there may be between about 100 and about 1,000 repeating cell pairs in the ED unit 440. An applied electric field imposed via electrodes causes dissolved ions, attracted to their respective counter-electrodes, to migrate through the ion exchange membranes. The liquid in the dilute compartment 440a is depleted of ions, and the liquid in the concentrate

compartment is enriched with the transferred ions. The concentrate compartment 440b may produce a concentrate water stream 450 for discharge for use or storage. The treated water from the dilute compartment 440a may be discharged as a second product water stream 445.

As shown in FIG. 5, an electrodialysis unit and an electrodeionization unit may be used in series to treat high mineral content water. Feedwater stream 520 may be discharged from high mineral content water source 510. Feedwater stream 520 may comprise silica. In some embodiments, feedwater stream 520 may comprise greater than 8 ppm silica. In some embodiments, feedwater stream 520 may comprise greater than 10 ppm silica. In some embodiments, feedwater stream 520 may comprise greater than 20 ppm silica.

In some embodiments, ED units 525, 540 are capable of reversing polarity. ED unit 525 may comprise a dilute compartment 525a connected to the feedwater stream 510 and a concentrate compartment 525b separated from the dilute compartment 525a by an ion- selective membrane. ED unit 525 may include a series of alternating anion and cation exchange membranes. In some embodiments, the ED unit includes a plurality of alternating dilute compartments and concentrate compartments positioned between a pair of electrodes. These alternating compartments are referred to as cell pairs. In some embodiments, there may be between about 100 and about 1,000 repeating cell pairs in the electrodialysis unit 525. An applied electric field imposed via electrodes causes dissolved ions, attracted to their respective counter-electrodes, to migrate through the ion exchange membranes. The liquid in the dilute compartment 525a is depleted of ions, and the liquid in the concentrate

compartment is enriched with the transferred ions. The concentrate compartment 525b may produce a concentrate water stream 535 for discharge for use or storage. The treated water from dilute compartment 525a may be discharged as a first product water stream 530.

First product water stream 530 may be discharged to EDI unit 540. EDI unit 540 comprises at least one depleting compartment 540a and one concentrating compartment 540b. Depleting compartment 540a and concentrating compartment 540b constitute a cell pair. The compartments of the cell pair are disposed in ionic communication with each other and between and with an anode and a cathode. In some embodiments, EDI unit 540 further comprises at least one barrier cell that can trap migrating species, including silica. In some embodiments, the concentrating compartment 540b can contain, at least partially, a mixture of anion and cation exchange resin. In some embodiments, the depleting compartment 540a comprises primarily anion exchange resin. In some embodiments, the depleting compartment 540a consists only of anion exchange resin. The treated water from depleting compartment 540a may be discharged as a second product water stream 445. The concentrating compartment 540b may produce a reject water stream 550. Reject water stream 550 may be discharged for use or storage.

Those of ordinary skill should recognize that the treatment system can be adjustable to accommodate fluctuations in demand as well as variations in water quality requirements. For example, the systems and methods described herein may produce low Langelier

Saturation Index (LSI) water that is available to the treatment system as a whole, during extended idle periods. The low LSI water, in some embodiments, may be used to flush the wetted components of the treatment system, which may reduce the likelihood of scaling and increase the service life not only the individual components, but also the treatment system as a whole. In accordance with some embodiments, the systems and methods described herein provide for producing treated liquids, such as water, having a low conductivity. The treatment system may comprise a fluid circuit that provides treated or, in some cases, softened water or, in other cases, low conductivity water, and/or low LSI water, to one or more product streams and subsequently, one or more points of use.

In another embodiment of the systems and methods described herein, treatment system may comprise one or more flow regulators for regulating liquid flow. For example, a flow regulator may regulate the volume of fluid discharged from the system via a waste stream. According to another embodiment of the systems and methods described herein, the flow regulator may be a valve that may be intermittently opened and closed according to a predetermined schedule for a predetermined period of time to allow a predetermined volume of water to flow. The volume of flowing fluid may be adjusted by, for example, changing the frequency and/or duration that the flow regulator is opened and closed. In some

embodiments, the flow regulator may be controlled or regulated by a controller, through, for example, an actuation signal. The controller may provide an actuation signal, such as a radio, current or a pneumatic signal, to an actuator, with a motor or diaphragm that opens and closes the flow regulator. The fluid regulated by a valve or flow regulator may be any fluid located in the water treatment system. The function and advantages of these and other embodiments will be more fully understood from the following non-limiting example. The example is intended to be illustrative in nature and is not to be considered as limiting the scope of the embodiments discussed herein.

EXAMPLES

Example 1: RO Retentate with High TDS

In an experimental set-up shown in the schematic flow diagram of FIG. 2, an RO feed stream having a TDS of about 400 ppm was fed to a reverse osmosis unit. The resulting RO retentate stream having a nominal flow rate of 5 gpm and a TDS of about 1,500 ppm was fed to a reversible electrodialysis (EDR) unit having a nominal recovery rate of about 68% to about 80%. The EDR had a nominal TDS reduction of about 50% per module. The EDR produced a first product water stream having a nominal flow rate of 5 gpm, a TDS of less than about 750 ppm, a conductivity of less than about 1,500 μ8-αη, and a silica concentration of greater than about 30 ppm silica. The first product water stream was fed to an

electrodeionization unit to produce a second product water stream. The resulting second product water stream had a TDS of about 400 ppm, and a silica concentration of about 19 ppm. The overall recovery rate of the system was about 97%. The data show that the combination of reverse osmosis, electrodialysis, and electrodeionization reduces the TDS of the high mineral content water RO retentate stream to a level sufficient for blending with the RO feed stream, and reduces the silica concentration from the first product water. Example 2A: The Effect of Current on Silica and TDS Removal in a CEDI process

In the following examples, a synthetic solution representing first product water stream 135 of FIG. 2 was prepared by dosing concentrated NaCl and silica solution (sodium metasilicate) in RO permeate water. A feedwater having a dilute flowrate of 1.25 gpm and a concentrate flowrate of 0.25 gpm and 83.3% water recovery was fed to a CEDI unit, such as EDI unit 240 of FIG. 2. Anion exchange resins in a mixture of 90% Type I resin and 10% Type II resin were filled in the depleting compartment of the EDI.

Silica and TDS removal were shown to increase as current increased. In the current example, the feed pH was adjusted by 30% HC1 solution and 50% NaOH. Initially silica removal increased from 9.5% to 36.2% with increasing amperage from 4 A to 8 A. This may be due to the higher extent of resin/membrane regeneration. With further increasing current to 10 A, the silica removal decreased slightly because the limiting factor for silica removal is the residence time. TDS removal was stable and increased with increasing amperage. These data show that both silica and TDS removal increases with increasing current, until the limiting factor for silica removal is the residence time instead of current.

Table 1 The Silica and TDS removal for different current.

Silica removal TDS removal

Current Feed Silica Feed TDS

(A) Silica (ppm) removal conductivity^S/cm) removal

4 38.8 9.5% 784.2 53.4%

6 39.7 1 1.6% 997.1 54.2%

8 38.8 36.2% 861 .6 58.8%

10 41.3 32.0% 863.2 64.0% Example 2B: The Effect of pH on Silica and TDS Removal in a CEDI process

Using the set-up of Example 2A above, a high mineral content feedwater was fed to a CEDI unit. A higher pH was shown to correspond to a higher TDS and silica removal. As can be seen in FIGS. 6A and 6B, silica removal was enhanced from 4.48% to 36.2% when feed pH increased from 8.35 to 11.2 at 8 A. Silica removal was enhanced from 11.46% to 31.3% with pH increasing from 8.43 to 11.26 at 10 A. This may be because silica is easily ionized at higher pH. TDS removal was also high at a higher feed pH for both 8 and 10 A. The data indicate that a higher pH corresponds to both higher TDS and silica removal at 8 A and at 10 A. In addition, the data indicate that a high pH corresponds to both higher TDS and silica removal at 10 A than for the same conditions at 8 A.

Example 2C: The Effect of Flowrate on Silica and TDS Removal in CEDI process Using the set-up of Example 2A above, a high mineral content feedwater was fed to a CEDI unit. TDS removal was shown to increase with a decreasing flowrate. As can be seen in FIGS. 7A and 7B, silica removal was enhanced from 4.48% to 46.44% at 8 A and from 11.46% to 42.74 at 10 A when the dilute flowrate decreased from 1.25 gpm to 0.625 gpm with the same recovery. This may be because of an increased hydraulic retention time from a lower flowrate. TDS removal was slightly higher when dilute flowrate decreased from 1.25 gpm to 0.625 gpm with the same recovery. Example 3 : The Effect of pH on Scale Formation

In an system schematically shown in FIGS. 8 and 9, a downward shift in pH in the concentrating compartment of an ED unit was shown to inhibit the formation of scale. A first product water from an ED unit having a pH of 8.35 and a conductivity of 918.26μ8/αη was fed to a depleting compartment of an electrodeionization unit at an operating current of 8 A and an operating voltage of 34.82 V. The depleting compartments of the electrodeionization unit comprised 30 g per channel of anion resin only. The anion resin produces an increasing pH shift in the depleting compartment, and the silica ionizes. Specifically, the pH of the second product water from the depleting compartment increases from 8.35 to 11.27. The concentrating compartments of the electrodeionization unit comprised 30 g per channel of a mixture of 70% anion exchange resin and 30% cation exchange resin. The mixture produces a decreasing pH shift in the reject water of the concentrating compartment. The downward shift in the pH in the concentrating compartments inhibits the formation of scale.

Specifically, the pH of the depleting compartment decreases from 8.35 to 2.29.

In another experiment using the same design as above, combining an electrodialysis concentrate stream with an electrodeionization reject stream was shown to increase the hardness tolerance for both streams. A first product water from an electrodialysis unit having a pH of 8.43 and a conductivity of 843.57 μ8/αη was fed to a depleting compartment of an electrodeionization unit at an operating current of 10 A and an operating voltage of 47.37 V. The pH of the second product water from the depleting compartment increased from 8.43 to 11.17, and the pH of the reject water from the concentrating compartment decreased from 8.43 to 2.29.

The reject stream was then combined with a concentrate stream of an electrodialysis unit, as can be seen in FIG. 8. This allows the acid that is generated in the

electrodeionization unit to lower the pH of both streams and thus increases the hardness tolerance for both streams. As such, both stages may run at higher recovery rates. In another embodiment, as shown in FIG. 9, the reject bleed position may be moved to the front of the electrodeionization unit so that all of the acid produced in the CEDI stage is directed through the electrodialysis stage before reaching the bleed position. In another embodiment, as shown in FIG. 10, a reject stream may be combined with the concentrate stream and with a high mineral content water stream. The reject bleed is positioned at the front of the electrodeionization unit so that all of the acid produced in the CEDI stage is directed through the electrodialysis stage before reaching the bleed position. The combined reject and concentrate streams also allow each stage to run at a lower individual recovery to produce the same overall recovery. It has been shown that running electrodialysis at high recovery can exhibit high electrical resistance due to the Donnan voltage created by the concentration gradient that is formed. The increased electrical resistance not only increases the module voltage, but an increased current leakage takes place, thus lowering the current efficiency, as can be seen in FIG. 11, which shows data of the desalination process from about 1,000 ppm to about 400 ppm with varying recovery. By sharing the reject water streams of two or more stages, a high overall recovery is achievable even without running an individual stage efficiently. Having now described some illustrative embodiments of the invention, it should be apparent to those skilled in the art that the foregoing is merely illustrative and not limiting, having been presented by way of example only. Numerous modifications and other embodiments are within the scope of one of ordinary skill in the art and are contemplated as falling within the scope of the invention. In particular, although many of the examples presented herein involve specific combinations of method acts or system elements, it should be understood that those acts and those elements may be combined in other ways to accomplish the same objectives.

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 systems and techniques of the invention 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 of the invention. It is therefore to be understood that the embodiments described herein are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; the invention may be practiced otherwise than as specifically described.

Moreover, it should also be appreciated that the invention is directed to each feature, system, subsystem, or technique described herein and any combination of two or more features, systems, subsystems, or techniques described herein and any combination of two or more features, systems, subsystems, and/or methods, if such features, systems, subsystems, and techniques are not mutually inconsistent, is considered to be within the scope of the invention as embodied in the claims. Further, acts, elements, and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments. As used herein, the term "plurality" refers to two or more items or components. The terms "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.

Claims

1. A water treatment system, comprising:

a reverse osmosis unit having:

a feedwater inlet;

a filtrate water outlet; and

a retentate water outlet; and

an electrodialysis unit having:

a dilute compartment connected to the retentate water outlet, and having a first product water outlet;

a concentrate compartment having a concentrate water outlet; and an electrodeionization unit having:

a depleting compartment connected to the first product water outlet, and having a second product water outlet; and

a concentrating compartment having a reject water outlet.

2. The system of claim 1, wherein the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins.

3. The system of claim 2, wherein the mixed bed comprises about 70% anion exchange resins and about 30% cation exchange resins.

4. The system of claim 2, wherein the depleting compartment further comprises a layer of anion exchange resin.

5. The system of claim 4, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

6. The system of claim 1, wherein the depleting compartment comprises anion exchange resin.

7. The system of claim 6, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

8. The system of claim 2, further comprising a second depleting compartment comprising an anion exchange resin.

9. The system of claim 8, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

10. The system of claim 1, wherein the concentrating compartment comprises a mixture of anion exchange resins and cation exchange resins.

11. The system of claim 1, wherein the electrodialysis unit is capable of reversing polarity.

12. The system of claim 1, wherein the first product water outlet is fluidly connected to the feedwater inlet.

13. The system of claim 1, wherein the second product water outlet is fluidly connected to the feedwater inlet.

14. The system of claim 1, further comprising a precipitator fluidly connected to at least one of the concentrate water outlet and the reject water outlet.

15. The system of claim 1, further comprising an ion exchange membrane positioned in the electrodialysis unit between the dilute compartment and the concentrate compartment, comprising a crosslinked ion transferring polymer comprising at least one functional monomer, at least one crosslinking monomer, and at least one quaternizing agent.

16. The system of claim 15, wherein the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole.

17. The system of claim 15, wherein the at least one crosslinking monomer is selected from the group consisting of: divinylbenzene, ethylene glycol dimethacrylate, vinylbenzyl chloride, dichloroethane, propylene glycol dimethacrylate, isobutylene glycol dimethacrylate, Ci6H₂₄0₁₂Si₈, C₃₂H₇₂0₂oSi₁₆, (CH₂CH)_n(Si0_{1 5})n wherein n= 8, 10, or 12, C₁₄H₃₈0₁₂Si7, C₂₈H₆₆0₁₂Si₇, C₅₆H₁₂₂0₁₂Si₇, C₁₆H₅60₂oSi₁₆, H₈0₁₂Si₈, (C₈H₁₃0)_n(Si0_{1 5})_n wherein n= 8, 10, 12, (C₆Hn0₂)n(SiOi.5)n wherein n= 8, 10, or 12, (C₇Hn0₂)_n(SiOi.₅)n wherein n= 8, 10, or 12, and (C₆H₉0₂)_n(SiOi.5)n wherein n= 8, 10, or 12.

18. The system of claim 15, wherein the quaternizing agent is selected from the group consisting of benzyl chloride, benzyl bromide, vinyl benzyl chloride, dichloroethane, or methyl iodide.

19. The system of claim 15, wherein the crosslinked ion transferring polymer further comprises a polymerization initiator.

20. The system of claim 19, wherein the polymerization initiator is selected from the group consisting of organic peroxides, 2,2' azobis[2,[2-imdazolin-2-yl]- propane] dihydrochloride, α,α'-azoisobutyronitrile, 2,2'-azobis[2- methylpropioaminidinejdihydrochloride, 2,2' azobis[2,[2-imdazolin-2-yl]propane], or dimethyl2,2'azobis [2-methylpropionate] .

21. The system of claim 15, further comprising a microporous membrane support having a porous first side, a porous second side, and a continuous porous structure extending from the first side to the second side.

22. The system of claim 21, wherein the crosslinked ion transferring polymer fills the continuous porous structure.

23. The system of claim 21, wherein the microporous support comprises polypropylene, high molecular weight polyethylene, ultrahigh molecular weight polyethylene or polyvinylidene fluoride.

24. The system of claim 21, wherein a thickness of the microporous porous support is greater than about 55 microns and less than about 155 microns.

25. The system of claim 24, wherein a thickness of the microporous porous support is greater than about 20 microns and less than about 55 microns.

26. A method of facilitating treatment of high mineral content water, comprising: providing an electrodialysis unit having a dilute compartment having a first product water outlet and a concentrate compartment comprising a concentrate water outlet;

fluidly connecting a source of high mineral content water to the inlet of the dilute compartment;

providing an electrodeionization unit comprising a depleting compartment having a second product water outlet and a concentrating compartment having a reject water outlet; and

fluidly connecting the first product water outlet to the depleting compartment

27. The method of claim 26, wherein the electrodialysis unit comprises an ion exchange membrane positioned between the dilute compartment and the concentrate compartment, comprising a crosslinked ion transferring polymer comprising at least one functional monomer, at least one cros slinking monomer, and at least one quaternizing agent.

28. The method of claim 27, wherein the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole.

29. The method of claim 27, wherein the at least one crosslinking monomer is selected from the group consisting of: divinylbenzene, ethylene glycol dimethacrylate, vinylbenzyl chloride, dichloroethane, propylene glycol dimethacrylate, isobutylene glycol dimethacrylate, Ci6H₂₄0₁₂Si₈, C₃₂H₇₂0₂oSi₁₆, (CH₂CH)_n(Si0_{1 5})n wherein n= 8, 10, or 12, C₁₄H₃₈0₁₂Si7, C₂₈H₆₆0₁₂Si₇, C₅6H₁₂₂0₁₂Si₇, C₁₆H560₂oSi₁₆, H₈0₁₂Si₈, (C₈H₁₃0)_n(Si0_{1 5})n wherein n= 8, 10, 12, (C₆Hn0₂)_n(SiOi.₅)n wherein n= 8, 10, or 12, (C₇Hn0₂)_n(SiOi.₅)n wherein n= 8, 10, or 12, and (C₆H₉0₂)_n(SiOi.5)n wherein n= 8, 10, or 12.

30. The method of claim 27, wherein the quaternizing agent is selected from the group consisting of benzyl chloride, benzyl bromide, vinyl benzyl chloride, dichloroethane, or methyl iodide.

31. The method of claim 26, wherein the source of high mineral content water is a reverse osmosis unit retentate stream.

32. The method of claim 26, further comprising periodically reversing a polarity of the electrodialysis unit.

33. The method of claim 26, wherein the first product water has a silica concentration greater than 8 ppm.

34. The method of claim 26, wherein the first product water has a total dissolved solids concentration of lower than about 2,000 ppm.

35. The method of claim 26, further comprising fluidly connecting a first product water outlet to the source of high mineral content water.

36. The method of claim 26, wherein the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins.

37. The method of claim 36, wherein the mixed bed comprises about 70% anion exchange resin and about 30% cation exchange resin.

38. The method of claim 36, wherein the depleting compartment further comprises a layer of anion exchange resin.

39. The method of claim 38, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

40. The method of claim 26, wherein the depleting compartment comprises anion exchange resin.

41. The method of claim 40, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

42. The method of claim 36, further comprising a second depleting compartment comprising anion exchange resin.

43. The method of claim 42, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

44. The method of claim 26, wherein the concentrating compartment comprises a mixture of anion exchange resins and cation exchange resins.

45. The method of claim 26, further comprising connecting a second product water outlet to the source of high mineral content water.

46. The method of claim 26, further comprising providing a precipitator.

47. The method of claim 46, further comprising fluidly connecting at least one of the concentrate water outlet and the reject water outlet to the precipitator.

48. A system for treating high mineral content water, comprising:

an electrodialysis unit comprising a dilute compartment having a first product water outlet, a concentrate compartment having a concentrate water outlet, and an ion exchange membrane positioned between the dilute compartment and the concentrate compartment, the ion exchange membrane comprising a crosslinked ion transferring polymer comprising at least one functional monomer; and

an electrodeionization unit comprising a depleting compartment fluidly connected to the first product water outlet and having a second product water outlet and a concentrating compartment having a reject water outlet.

49. The system of claim 48, wherein the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole.

50. The system of claim 48, further comprising at least one of the concentrate water outlet and the reject water outlet fluidly connected to a precipitator.

51. The system of claim 48, wherein the electrodialysis unit is capable of reversing polarity.

52. The system of claim 48, wherein the depleting compartment comprises a mixed bed of anion and cation exchange resin.

53. The system of claim 52, wherein the mixed bed comprises about 70% anion exchange resins and about 30% cation exchange resins.

54. The system of claim 52, wherein the depleting compartment further comprises a layer of anion exchange resins.

55. The method of claim 54, wherein the anion exchange resin is selected from the group consisting of Type I resins, Type II resins, and mixtures thereof.

56. The method of claim 48, wherein the depleting compartment comprises anion exchange resins.

57. The method of claim 56, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

58. The method of claim 52, further comprising a second depleting compartment comprising an anion exchange resin.

59. The method of claim 58, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

60. A method of treating high mineral content water, comprising:

introducing a high mineral content water to a dilute compartment of an electrodialysis unit to produce a first product water, the electrodialysis unit further comprising a concentrate compartment having a concentrate water outlet;

introducing the first product water to a depleting compartment of an

electrodeionization unit to produce a second product water;

introducing the first product water to a concentrating compartment of the

electrodeionization unit to produce a reject water; and

combining the reject water and the concentrate water to recycle to the concentrate compartment.

61. The method of claim 60, further comprising an ion exchange membrane positioned between the dilute compartment and the concentrate compartment, and having a crosslinked ion transferring polymer comprising at least one functional monomer.

62. The method of claim 61, wherein the at least one functional monomer is selected from the group consisting of vinylimidazole and vinylcarbazole.

63. The method of claim 60, wherein the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins.

64. The method of claim 63, wherein the mixed bed comprises about 70% anion exchange resins and about 30% cation exchange resins.

65. The method of claim 63, wherein the depleting compartment further comprises a layer of anion exchange resin.

66. The method of claim 65, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

67. The method of claim 60, wherein the depleting compartment comprises anion exchange resin.

68. The method of claim 67, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

69. The method of claim 63, further comprising a second depleting compartment comprising an anion exchange resin.

70. The method of claim 69, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

71. The method of claim 60, wherein the concentrating compartment comprises a mixture of anion exchange resin and cation exchange resin.

72. The method of claim 60, wherein the second product water has a pH that is higher than the first product water pH.

73. The method of claim 72, wherein the pH of the second product water is capable of ionizing silica.

74. The method of claim 60, wherein the pH of the reject water is lower than the pH of the first product water.

75. A system for treating high mineral content water, comprising:

an electrodialysis unit comprising a dilute compartment having a first product water outlet and a concentrate compartment having a concentrate water outlet.

an electrodeionization unit comprising a depleting compartment fluidly connected to the first product water outlet and having a second product water outlet and a concentrating compartment fluidly connected to the concentrate compartment and having a reject water outlet, the reject water outlet fluidly connected to a reject water recycle inlet of the concentrate compartment.

76. The system of claim 75, wherein the depleting compartment comprises a mixed bed of anion exchange resins and cation exchange resins.

77. The system of claim 73, wherein the mixed bed comprises about 70% anion exchange resin and about 30% cation exchange resin.

78. The system of claim 76, wherein the depleting compartment further comprises a layer of anion exchange resins.

79. The system of claim 78, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

80. The system of claim 75, wherein the depleting compartment comprises anion exchange resin.

81. The system of claim 80, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

82. The system of claim 76, further comprising a second depleting compartment comprising an anion exchange resin.

83. The system of claim 82, wherein the anion exchange resin is selected from the group consisting of Type I resin, Type II resin, and mixtures thereof.

84. The system of claim 75, wherein the concentrating compartment comprises a mixture of anion exchange resins and cation exchange resins.

The system of claim 84, wherein the mixture comprises about 70% anion exchang and about 30% cation exchange resin.