Water treatment methods and water treatment devices

Abstract

This invention relates to a water treatment method and a water treatment apparatus. The water treatment apparatus for removing silica and boron from treated water includes an electro-deionized water production device (EDI device) (10). The EDI device (10) has a desalination chamber (22) between an anode chamber (21) containing an anode (11) and a cathode chamber (23) containing a cathode (12). The desalination chamber (22) is defined by a first ion exchange membrane (31) disposed on the side facing the anode (11) and a second cation exchange membrane (32) disposed on the side facing the cathode (12), and is filled with ion exchangers. The current value applied between the anode (11) and cathode (12) per unit flow rate, relative to the total amount of treated water supplied to the desalination chamber (22) within the EDI device (10), is greater than 0.4 × 10⁻⁶. ‑3 A·min / mL and 16.0×10 ‑3 A·min / mL or less.

Description

Technical Field

[0001] This invention relates to a water treatment method and apparatus for removing silica and boron components from water to be treated, and particularly to a water treatment method and apparatus using an electro-deionization (EDI) water production device. Background Technology

[0002] To remove ionic components from treated water and generate pure or deionized water, the treated water undergoes ion exchange treatment. Among the ionic components, weak acidic components such as boron and silica are difficult to remove through conventional ion exchange treatments, such as simply passing the treated water through a layer of ion exchange resin, which is at least one of anion exchange resin and a cation exchange resin. Therefore, an electro-deionized water production device (EDI device) is attempted. An EDI device generates deionized water from treated water by combining electrophoresis and electrodialysis. It has a desalination chamber between the anode and cathode, defined by a pair of ion exchange membranes consisting of a first ion exchange membrane disposed on the anode side and a second ion exchange membrane disposed on the cathode side, and filled with ion exchangers. In the EDI device, deionized water is obtained from the desalination chamber by simultaneously supplying treated water to the desalination chamber while applying a direct current between the anode and cathode. The EDI device has the advantage of not requiring the regeneration of the ion exchange resin using chemicals. However, even with EDI devices, when only ordinary ion exchange resins are filled in the desalination chamber as ion exchangers, sufficient removal performance is sometimes not achieved for components such as boron and silica.

[0003] Patent Document 1 discloses a method for reducing the silica concentration in water to below 5 ppb using a reverse osmosis (RO) membrane device or the like, and then introducing the treated water into an EDI device, wherein the current density in the EDI device is preferably 600 mA / dm² or more and 1000 mA / dm² or less, thereby removing boron from the treated water. Patent Document 2 discloses a method for removing boron and silica from water using an EDI device, wherein the desalination chamber thickness, operating voltage (or operating current), or water flow velocity in the desalination chamber of the EDI device is set such that, when treating raw water with a pH below 8.5 without adding an alkali, a pH 1.0 or higher than the original water can be obtained.

[0004] Although it is a technology common to EDI devices, Patent Document 3 discloses that in an EDI device, in order to suppress the generation of scale in the cathode chamber provided with a cathode, electrode water discharged from the anode chamber provided with an anode is supplied to the cathode chamber. In an EDI device, when a cation exchanger is filled in the entire anode chamber, at the position where the anion exchange membrane in contact with the anode chamber contacts the cation exchanger, hydrogen ions (H + ), and hydroxide ions (OH - ) undergo a neutralization reaction, and sometimes the anion exchange membrane deteriorates due to the heat of neutralization at this time. This deterioration phenomenon is sometimes also referred to as "membrane burn (Japanese original text: "膜焼け"). In order to prevent the deterioration of such an anion exchange membrane, Patent Document 4 discloses that in the anode chamber, the cation exchanger is arranged in such a manner that the cation exchanger and the anion exchanger are in contact with each other, in a manner that does not contact the anion exchange membrane but contacts the anode, and the anion exchanger is arranged in a manner that does not contact the anode but contacts the anion exchange membrane.

[0005] Prior Art Documents Patent Documents Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017 - 140548 Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001 - 113281 Patent Document 3: Japanese Unexamined Patent Application Publication No. 2001 - 58186 Patent Document 4: Japanese Unexamined Patent Application Publication No. 2011 - 189315 Summary of the Invention Technical Problem to be Solved by the Invention The method described in Patent Document 1 aims to improve the removal efficiency of boron components and the like by increasing the current density in the EDI device. However, if the current density is increased, in addition to the heat caused by the neutralization reaction between hydrogen ions and hydroxide ions, the overall heat generation of the EDI device caused by Joule heat and the like also increases, and the ion exchangers and ion exchange membranes constituting the EDI device may deteriorate due to heat. The method described in Patent Document 2 also has to increase the current density, and there may be problems accompanied by heat generation. Moreover, the method described in Patent Document 2 is a method of creating an alkaline atmosphere where a large amount of hydroxide ions exist in the desalination chamber by utilizing the difference in the migration rates of hydrogen ions and hydroxide ions in water, so it is impossible to remove sodium ions (Na + ), potassium ions (K + ) contained in the water to be treated.

[0006] An object of the present invention is to provide a water treatment method and a water treatment device that can suppress the deterioration of an EDI device caused by Joule heat and the like, and at the same time can remove silica components and boron components in the water to be treated by using the EDI device, thereby obtaining treated water after desalination.

[0007] Technical solutions for solving technical problems One aspect of the present invention is a water treatment method using an electro-deionization (EDI) water production apparatus. This method involves supplying treated water to a desalination chamber while applying a direct current between the anode and cathode to the water to be treated. The EDI apparatus has a desalination chamber between an anode chamber containing an anode and a cathode chamber containing a cathode. This desalination chamber is defined by a pair of ion exchange membranes, consisting of a first ion exchange membrane disposed on the anode side and a second ion exchange membrane disposed on the cathode side, and is filled with ion exchangers. The direct current value per unit flow rate, relative to the total amount of treated water supplied to the desalination chamber within the EDI apparatus, is greater than 0.4 × 10⁻⁶. - ³A·min / mL and 16.0×10 - Below 3A·min / mL.

[0008] One aspect of the present invention is a water treatment apparatus for removing silica and boron components from treated water. This apparatus includes an EDI (Electronic Dioxide) device comprising: an anode chamber having an anode; a cathode chamber having a cathode; and a desalination chamber disposed between the anode and cathode chambers, demarcated by a pair of ion exchange membranes consisting of a first ion exchange membrane disposed facing the anode and a second ion exchange membrane disposed facing the cathode, and filled with ion exchangers. The direct current applied between the anode and cathode has a flow rate greater than 0.4 × 10⁻⁶ units relative to the total amount of treated water supplied to the desalination chamber within the EDI device. -3 A·min / mL and 16.0×10 -3 A·min / mL or less.

[0009] According to the above method, while suppressing the deterioration of the EDI device, the silica and boron components in the treated water can be removed by using the EDI device, thereby obtaining desalinated treated water. Attached Figure Description

[0010] Figure 1 This is a diagram showing the water treatment apparatus according to the first embodiment.

[0011] Figure 2 This is a diagram showing another example of the water treatment apparatus according to the first embodiment.

[0012] Figure 3 This is a diagram showing another example of the water treatment apparatus according to the first embodiment.

[0013] Figure 4 This is a diagram showing the water treatment apparatus according to the second embodiment.

[0014] Figure 5 This is a diagram showing another example of the water treatment apparatus according to the second embodiment.

[0015] Figure 6 This is a diagram showing another example of a water treatment apparatus according to the second embodiment. Detailed Implementation

[0016] Next, the method for carrying out the present invention will be described with reference to the accompanying drawings.

[0017] [First Implementation Method] Figure 1 The diagram illustrates the structure of a water treatment apparatus according to the first embodiment. The illustrated water treatment apparatus desalinates the water to be treated to obtain deionized water, and is comprised of an electro-deionization (EDI) apparatus 10. Specifically, this water treatment apparatus is configured to remove weak acid components such as silica and boron, which are difficult to remove from the water in conventional ion exchange processes, and operating conditions are set accordingly. The EDI apparatus 10 has at least one desalination chamber 22 between an anode chamber 21 with an anode 11 and a cathode chamber 23 with a cathode 12. The desalination chamber 22 is defined by a first ion exchange membrane located towards the anode 11 and a second ion exchange membrane located towards the cathode 12. The anode chamber 21 and cathode chamber 23 are collectively referred to as electrode chambers. In the example shown, the first ion exchange membrane is an anion exchange membrane (AEM) 31, which is adjacent to the anode chamber 21 and the desalination chamber 22, sandwiching the anion exchange membrane 31. The second ion exchange membrane is a cation exchange membrane (CEM) 32, which is adjacent to the desalination chamber 22 and the cathode chamber 23, sandwiching the cation exchange membrane 32. That is, a desalination chamber 22 is provided between the anode chamber 21 and the cathode chamber 23, with anion exchange membrane 31 and cation exchange membrane 32 sandwiched between them. In general EDI devices, the concentration chamber is usually sandwiched between the electrode chamber and the desalination chamber. However, in the EDI device 10 of this embodiment, similar to the EDI device disclosed in Patent Document 4, the anode chamber 21 itself has the function of serving as a concentration chamber, and the cathode chamber 23 also has the function of serving as a concentration chamber. Therefore, there is no concentration chamber adjacent to the electrode chamber.

[0018] The desalination chamber 22 is filled with an ion exchanger, which is at least one of anion exchanger and cation exchanger. In the example shown here, the desalination chamber 22 is filled in, for example, a mixed bed configuration with anion exchange resin (AER) as anion exchanger and cation exchange resin (CER) as cation exchanger. The cathode chamber 23 is filled with anion exchange resin. In the anode chamber 21, the layers of anion exchange resin and cation exchange resin are filled in contact with each other. In the anode chamber 21, the layers of anion exchange resin are arranged in a manner that do not contact the anode 11 but contact the anion exchange membrane 31, and the layers of cation exchange resin are arranged in a manner that do not contact the anion exchange membrane 31 but contact the anode 11. Assuming that only cation exchange resin is filled in the anode chamber 21, hydrogen ions (H+) are generated at the interface between the cation exchange resin and the anion exchange membrane 31 as shown in the following formula. + ) and hydroxide ions (OH) - The neutralization reaction of ).

[0019] H + +OH - =H₂O + 56.5 kJ / mol The neutralization reaction generates a large heat of neutralization, which may cause the anion exchange membrane 31 to deteriorate, develop pores, or increase the operating voltage of the EDI device 10. Therefore, in this embodiment, the anion exchange resin layer and the cation exchange resin layer are filled in the anode chamber 21 in a manner where the cation exchange resin does not contact the anion exchange membrane 31. As a result, the aforementioned hydration reaction occurs at the location in the anode chamber 21 where the anion exchange resin layer and the cation exchange resin layer are in contact, thereby preventing the anion exchange membrane 31 from deteriorating due to the heat of neutralization. In addition, in the anode chamber 21, oxidizing substances with strong oxidizing power, such as oxygen, ozone, hydrogen peroxide, and chlorine, are generated near the anode 11. These oxidizing substances may oxidize and deteriorate the anion exchange resin disposed in the anode chamber 21; therefore, a cation exchange resin layer is provided in the anode chamber 21 in a manner that contacts the anode 11.

[0020] exist Figure 1In the water treatment apparatus shown, while the treated water is supplied to the desalination chamber 22 of the EDI unit 10, feed water is supplied to the anode chamber 21. The feed water entering the anode chamber 21 is then supplied to the cathode chamber 23. A portion of the treated water can be diverted and supplied to the anode chamber 21 as feed water, or water from a separate supply source can be supplied to the anode chamber 21 as feed water. In the anode chamber 21, hydrogen ions generated by the electrode reaction are released into the water at the contact point between the cation exchange resin and the anion exchange resin, thus supplying water containing hydrogen ions to the cathode chamber 23. As a result, an acidic atmosphere is created inside the cathode chamber 23, preventing scale formation. It should be noted that the electrode water is discharged from the cathode chamber 23. The flow direction in the desalination chamber 22 and the electrode chambers on either side of it (i.e., the anode chamber 21 and the cathode chamber 23) is convection in the illustrated example, but it does not necessarily have to be convection.

[0021] Next, the explanation Figure 1 The operation of the water treatment apparatus is shown. While a direct current is applied between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21, and treated water is supplied to the desalination chamber 22. As a result, desalination treatment is performed in the EDI apparatus 10, and deionized water flows out from the desalination chamber 22 as treated water. At this time, in order to remove weak acid components such as silica and boron from the treated water, the current applied between the anode 11 and the cathode 12 is such that the current value per unit flow rate of the treated water supplied to the EDI apparatus 10, i.e., the treated water supplied to the desalination chamber 22, is greater than 0.4 × 10⁻⁶. -3 A·min / mL and 16.0×10 -3 A·min / mL or less. The flow rate of the treated water referred to here means the total flow rate of the treated water supplied to the desalination chambers 22 of the EDI device 10 when the EDI device 10 is equipped with the plurality of desalination chambers 22 described later. In this embodiment, by setting the current value per unit flow rate of the treated water in this way, as can be seen from the embodiments described later, weak acid components such as silica and boron can be removed with a high removal rate. The flow rate of the treated water in the desalination chamber 22 is preferably less than 920 mL / min, more preferably 25 mL / min or more and 100 mL / min or less. The flow rate of each electrode chamber (anode chamber 21 and cathode chamber 23) is preferably 150 mL / min or more. Furthermore, the current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0022] exist Figure 1 In the water treatment device shown, strong alkaline components such as sodium ions and potassium ions are also removed. However, because the operating conditions are adjusted in conjunction with the removal of weak acid components, it may not be able to remove strong alkaline components efficiently. Figure 2 The water treatment device shown is designed to efficiently remove strong alkaline components. Figure 1The water treatment apparatus shown is further supplemented with a non-regenerative ion exchange unit (also known as a cylindrical polisher (CP)) 42. Figure 2 In the water treatment apparatus shown, the effluent from the desalination chamber 22 of the EDI unit 10 is supplied to a non-regenerative ion exchange unit 42. The effluent from the non-regenerative ion exchange unit 42 is treated water (deionized water) from the water treatment apparatus. The non-regenerative ion exchange unit 42 is filled with anion exchange resin and cation exchange resin in, for example, a mixed bed configuration. The space velocity SV of the water flow in the non-regenerative ion exchange unit 42 is preferably set, for example, to 5 h. -1 Above and 50 hours -1 Below the left and right. It should be noted that the spatial velocity SV of water flow indicates whether a quantity of water, several times the apparent volume of the ion exchange resin, is passed through the ion exchange resin per unit time.

[0023] Moreover, in Figure 2 In the water treatment apparatus shown, a portion of the treated water intended for the desalination chamber 22 is supplied as feed water to the anode chamber 21. Therefore, a pipe 17 is provided, branching off from the pipe 16 supplying the treated water to the desalination chamber 22 and connecting to the anode chamber 21. A pressure regulating valve 41 is installed on the pipe 17. By installing the pressure regulating valve 41, the flow rate of the treated water supplied to the anode chamber 21 can be kept constant without manual adjustment. It should be noted that in typical EDI apparatuses, when a portion of the treated water supplied to the desalination chamber is supplied as feed water to the electrode chamber and concentration chamber, a manual regulating valve and a flow meter are installed on the pipes connecting to the electrode chamber and concentration chamber. The flow rate is adjusted by manually operating the regulating valve while monitoring the measured value in the flow meter.

[0024] In the EDI device 10 constituting the water treatment apparatus of this embodiment, a plurality of desalination chambers 22 can be arranged between the anode 11 and the cathode 12. The plurality of desalination chambers 22 are arranged in series between the anode 11 and the cathode 12, and the water to be treated is distributed and supplied to the plurality of desalination chambers 22. The outlet water from the plurality of desalination chambers 22 is combined to become the treated water from the EDI device 10. In this case, a concentration chamber 24 is sandwiched between adjacent desalination chambers 22. The concentration chamber 24 is filled with, for example, cation exchange resin, and is supplied with the same supply water as that supplied to the anode chamber 21. The concentrated water is discharged from the concentration chamber 24, but this concentrated water is combined with the outlet water of the anode chamber 21 and supplied to the cathode chamber 23. The number of desalination chambers 22 provided between the anode 11 and the cathode 12 is called the number of units. By increasing the number of units, the flow rate of the water to be treated allocated to each desalination chamber 22 is reduced, and the current value per unit flow rate in each desalination chamber 22 can be increased, which is effective for the removal of weak acid components. However, when the flow rate of the treated water relative to the total flow rate of the desalination chambers 22 is too low, it becomes difficult to distribute and circulate the treated water equally among the multiple desalination chambers 22, resulting in a decrease in the desalination efficiency of the EDI device 10, particularly in its ability to remove weak acid components such as silica and boron. Furthermore, deterioration of the ion exchangers, including the ion exchange membrane, occurs, such as membrane burn. To suppress this decrease in desalination efficiency and the deterioration of the ion exchangers, it is preferable to set the flow rate of the treated water in each desalination chamber 22 to 25 mL / min or more, and further, to set the number of units, i.e., the number of desalination chambers 22, to 1 or more and 4 or less.

[0025] Figure 3 This describes a water treatment apparatus according to a first embodiment with two units. In the water treatment apparatus, the anode chamber 21 and the first desalination chamber 22 are adjacent to each other across anion exchange membrane 31, the first desalination chamber 22 and the concentration chamber 24 are adjacent to each other across a cation exchange membrane 32, the concentration chamber 24 and the second desalination chamber 22 are adjacent to each other across anion exchange membrane 31, and the second desalination chamber 22 and the cathode chamber 23 are adjacent to each other across a cation exchange membrane 32.

[0026] exist Figure 3 In the water treatment apparatus shown, while a direct current is applied between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21 and the concentration chamber 24, and treated water is supplied to each desalination chamber 22. As a result, desalination treatment is performed in the EDI device 10, and deionized water flows out from the desalination chamber 22 as treated water. At this time, in order to remove weak acid components such as silica and boron from the treated water, [further action is taken]. Figure 1 Similarly, in the water treatment apparatus shown, the direct current applied between the anode 11 and the cathode 12 is such that the current value supplied to the EDI device 10 per unit of treated water is greater than 0.4 × 10⁻⁶. -3A·min / mL and 16.0×10 -3 Below A·min / mL. Moreover, in Figure 3 In the water treatment apparatus shown, the current value of the water being treated per unit flow rate in each desalination chamber 22, i.e., each unit, is greater than 1.7 × 10⁻⁶. -3 A·unit min / mL. This current value is more preferably 4.0 × 10⁻⁶ min / mL. -3 A·unit·min / mL or higher and 16.0×10 -3 A·unit·min / mL or less. The flow rate of the water to be treated in each desalination chamber 22 is preferably less than 920 mL / min, more preferably 25 mL / min or more and 100 mL / min or less. The value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0027] [Second Implementation] The water treatment apparatus of the second embodiment will be described. Typically, in an EDI apparatus, the desalination chamber itself is divided into two smaller desalination chambers by an ion exchange membrane. Ion exchange resin fills each smaller desalination chamber, while the water to be treated passes through one smaller desalination chamber, and the water flowing out of this smaller desalination chamber can be supplied to the other smaller desalination chamber. The water treatment apparatus of the second embodiment is the same as that of the water treatment apparatus of the first embodiment, but differs in that, in the EDI apparatus 10 constituting the water treatment apparatus, the desalination chamber 22 is divided into two smaller desalination chambers 26 and 27 by an interposed ion exchange membrane.

[0028] Figure 4 This illustrates an example of the structure of the water treatment apparatus according to the second embodiment. Figure 4 The water treatment apparatus of the second embodiment shown also consists of... Figure 1 The EDI device used in the water treatment apparatus shown is the same as EDI device 10. However, Figure 4 The EDI device 10 shown is in Figure 1 Based on the EDI device 10 shown, the desalination chamber 22 is divided into a first small desalination chamber 26 near the anode 11 and a second small desalination chamber 27 near the cathode 12, separated by an anion exchange membrane 33 serving as an intermediate ion exchange membrane. The first small desalination chamber 26 is filled with anion exchange resin, and the second small desalination chamber 27 is filled with cation exchange resin. The water to be treated is first supplied to the second small desalination chamber 27, and the outlet water of the second small desalination chamber 27 is supplied to the first small desalination chamber 26. The outlet water from the first small desalination chamber 26 is deionized water, and is treated water from the aforementioned water treatment device. Although the flow direction of the water to be treated is parallel to that of the first small desalination chamber 26 and the second small desalination chamber 27, parallel flow is not necessary.

[0029] Next, the explanation Figure 4 The operation of the water treatment apparatus is shown. While applying a direct current between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21, and treated water is supplied to the second small desalination chamber 27. The treated water first flows into the second small desalination chamber 27, then flows through the first small desalination chamber 26, undergoing desalination treatment during this process. As a result, deionized water flows out from the first small desalination chamber 26 as treated water. At this time, in order to remove weak acid components such as silica and boron from the treated water, the current applied between the anode 11 and the cathode 12 is such that the current value per unit of total flow rate of the treated water supplied to the desalination chamber 22 of the EDI device 10, i.e., the treated water supplied to the second small desalination chamber 27 in the EDI device 10, is greater than 0.4 × 10⁻⁶. -3 A·min / mL or higher and 16.0×10 -3 The flow rate of the water to be treated in the desalination chamber 22, which is formed by merging the first small desalination chamber 26 and the second small desalination chamber 27, is preferably less than 920 mL / min, more preferably 25 mL / min or more and 100 mL / min or less. The value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0030] exist Figure 4 In the water treatment apparatus shown, the first small desalination chamber 26 near the anode 11 is filled with anion exchange resin, and the second small desalination chamber 27 near the cathode 12 is filled with cation exchange resin. The water to be treated flows sequentially from the second small desalination chamber 27 to the first small desalination chamber 26, thereby preventing scale formation when the water contains a large amount of impurities, and removing silica, boron, etc., with a high removal rate. It should be noted that the structure can also be configured such that the first small desalination chamber 26 is filled with anion exchange resin, and the second small desalination chamber 27 is filled with both anion exchange resin and cation exchange resin. The water to be treated first enters the first small desalination chamber 26 and then the second small desalination chamber 27. With this structure, the removal rate of silica, boron, etc., can be further improved.

[0031] and Figure 3 Similarly, in the water treatment apparatus of the second embodiment, multiple desalination chambers 22 can be configured by sandwiching a concentration chamber 24 between the anode 11 and the cathode 12. Figure 5 This refers to the water treatment apparatus of the second embodiment when the number of units is set to 2. Figure 5In the water treatment apparatus shown, while applying direct current between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21 and the concentration chamber 24, and treated water is also supplied to each of the second small desalination chambers 27. As a result, desalination treatment is performed in the EDI device 10, and deionized water flows out as treated water from each of the first small desalination chambers 26. At this time, in order to remove weak acid components such as silica and boron from the treated water, and with Figure 4 Similarly, in the water treatment apparatus shown, the current applied between the anode 11 and the cathode 12 is such that the current value per unit of total flow rate of the treated water supplied to the second small desalination chamber 27 within the EDI device 10 is greater than 0.4 × 10⁻⁶. -3 A·min / mL and 16.0×10 -3 Below A·min / mL. Moreover, in Figure 5 In the water treatment apparatus shown, the current value of the treated water per unit flow rate in each desalination chamber 22 (i.e., the first small desalination chamber 26 and the second small desalination chamber 27), i.e., each unit, is greater than 1.7 × 10⁻⁶. -3 A·unit·min / mL. This current value is more preferably 4.0 × 10⁻⁶. -3 A·unit·min / mL or higher and 16.0×10 -3 A·unit·min / mL or less. The flow rate of the water to be treated in each desalination chamber 22 is preferably less than 920 mL / min, more preferably 25 mL / min or more and 100 mL / min or less. The value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0032] In the water treatment apparatus of the second embodiment, in order to improve the removal efficiency of strong alkaline components, a non-regenerative ion exchange device may be configured after the EDI device 10. Figure 6 Is Figure 5 Based on the water treatment apparatus shown, the effluent from the first small desalination chamber 26 is supplied to a non-regenerative ion exchange unit 42. The effluent from the non-regenerative ion exchange unit 42 is treated water (deionized water) from the water treatment apparatus. The non-regenerative ion exchange unit 42 is filled with anion exchange resin and cation exchange resin in, for example, a mixed bed configuration. The space velocity SV of the water flow in the non-regenerative ion exchange unit 42 is preferably set, for example, to 5 h. -1 Above and 50 hours -1 Below left and right. Here, for water management purposes, a flow meter 43 and a water quality meter 44 are installed on the piping supplying the outlet water from the first small desalination chamber 26 to the non-regenerative ion exchange unit 42; alternatively, the flow meter 43 and water quality meter 44 may not be installed. Furthermore, in Figure 6In the water treatment apparatus shown, a portion of the treated water intended for supply to the desalination chamber 22 is branched off as supply water to the anode chamber 21 and the concentration chamber 24. Therefore, a pipe 17 is provided, branching from the pipe 16 supplying the treated water to the desalination chamber 22 and connecting to the anode chamber 21, and further branching to the concentration chamber 24. A pressure regulating valve 41 is provided on the pipe 17. By providing the pressure regulating valve 41, the flow rate of the treated water supplied to the anode chamber 21 can be kept constant without manual adjustment.

[0033] Example Next, the present invention will be further described in detail through examples and comparative examples.

[0034] [Example 1] The assembly sets the number of units in desalination chamber 22 to 1. Figure 4 The water treatment apparatus shown is as follows. In the anode chamber 21, cathode chamber 23, first small desalination chamber 26, and second small desalination chamber 27, square frames with openings of 10cm x 10cm and a thickness of 1cm are used. Ion exchange resin is filled into each frame, and these frames are stacked in the thickness direction, sandwiching ion exchange membranes, to form the EDI device 10. Electrode plates (anode 11 and cathode 12) are respectively arranged at both ends of the stacked frames. Water containing added silica, boron, and sodium is prepared as test water. The silica concentration in the test water is 1.2 mg / L, and the boron concentration is 49 mg / L. μ The sodium concentration was 2.1 mg / L. This test water was supplied as the treated water to the second small desalination chamber 27 and as feed water to the anode chamber 21. The flow rate of the treated water in the desalination chamber 22, which includes the first small desalination chamber 26 and the second small desalination chamber 27, was 100 mL / min, and the flow rate of the feed water in the anode chamber 21 and the cathode chamber 23 was 150 mL / min. It should be noted that the spatial velocity of the water in the desalination chamber 22 was 29 h⁻¹. -1 Furthermore, a direct current of 0.4 A is applied between the anode 11 and the cathode 12, such that the current value per unit flow rate of water treated in the desalination chamber 22 is 4.0 × 10⁻⁶. -3 A·min / mL. Then, at 1000 hours after the start of operation, the concentrations of silica, boron, and sodium in the treated water discharged from the first small desalination chamber 26 were measured. The results are shown in Table 1.

[0035] [Example 2] The number of units in the desalination chamber 22 is set to 2. Figure 5The water treatment apparatus shown is similar to that in Example 1. In the anode chamber 21, cathode chamber 23, concentration chamber 24, first small desalination chamber 26, and second small desalination chamber 27, a frame-shaped frame with an opening of 10cm × 10cm and a thickness of 1cm is used. Ion exchange resin is filled into the frame of each chamber, and these frames are stacked in the thickness direction with the ion exchange membrane sandwiched between them to form the EDI device 10. Test water identical to that used in Example 1 is prepared and supplied as the water to be treated to the second small desalination chamber 27, and as supply water to the anode chamber 21 and concentration chamber 24. The flow rate in the desalination chamber 22, which includes the first small desalination chamber 26 and the second small desalination chamber 27, is 100 mL / min, and the flow rate of the combined anode chamber 21 and concentration chamber 24 is 150 mL / min. Therefore, the flow rate in the cathode chamber 23 is also 150 mL / min. It should be noted that the spatial velocity of water flowing through the desalination chamber 22 is 14 h. -1 A direct current of 0.4 A is applied between the anode 11 and the cathode 12, such that the current per unit flow rate of the treated water in the desalination chamber 22 is 4.0 × 10⁻⁶. -3 A·min / mL, that is, the current value per unit flow rate of the treated water in one unit of the desalination chamber 22 is 8.0 × 10⁻⁶. -3 A·unit·min / mL, after 1000 hours from the start of operation, the concentrations of silica, boron, and sodium in the treated water discharged from the first small desalination chamber 26 were measured. The results are shown in Table 1.

[0036] [Comparative Example 1] Except that the number of units in desalination chamber 22 is set to 4, the water treatment apparatus is assembled in the same manner as in Example 2. Water containing added silica and sodium is prepared as test water. The silica concentration in the test water is 1.9 mg / L, and the sodium concentration is 2.0 mg / L. This test water is supplied to each chamber. The flow rate in desalination chamber 22, which includes the first small desalination chamber 26 and the second small desalination chamber 27, is 920 mL / min, and the flow rate in concentration chamber 24 is 100 mL / min. It should be noted that the spatial velocity of water flowing through desalination chamber 22 is 60 h⁻¹. -1 A direct current is applied between the anode 11 and the cathode 12, such that the current value per unit flow rate of the treated water in the entire desalination chamber 22 is 0.4 × 10⁻⁶. -3 A·min / mL, that is, the current value per unit flow rate of the treated water in one unit of the desalination chamber 22 is 1.7 × 10⁻⁶. -3 A·unit·min / mL, measuring the silica and sodium concentrations in the treated water discharged from the first small desalination chamber 26 after 1000 hours from the start of operation. The results are shown in Table 1.

[0037] [Table 1] In Comparative Example 1, the test water did not contain boron, but boron, like silica, is an anionic component that is difficult to remove in conventional EDI devices. Since the amount of silica leakage in the treated water was significant, it can be inferred that a large amount of boron also leaked in Comparative Example 1. In contrast, the results of Examples 1 and 2 show that, according to the water treatment method and apparatus based on the present invention, silica and boron components, in addition to sodium, can be effectively removed from the treated water. Furthermore, the results of Examples 1 and Comparative Example 1 show that increasing the current value per unit flow rate of the treated water in the EDI device 10, or reducing the flow rate in the desalination chamber 22 from, for example, 920 mL / min to 100 mL / min, is very effective for the removal of silica and boron components. Regarding sodium, it is not affected by the current value per unit flow rate of the treated water. It should be noted that if the flow rate of the treated water in the desalination chamber 22 is too low, the distribution of the treated water within the desalination chamber 22 or among multiple desalination chambers 22 will not be uniform, leading to deterioration of the treated water quality or accelerated degradation of the ion exchange resin and ion exchange membrane. Therefore, the flow rate of the treated water in each unit of the desalination chamber 22 is preferably 25 mL / min or higher. Similarly, the flow rate in the electrode chamber and concentration chamber 24 is also preferably 25 mL / min or higher. If the current value is also too low, the removal capacity for weak acid components will decrease; therefore, the DC current applied between the anode 11 and the cathode 12 is preferably 0.4 A or higher. For the same reason, the current value per unit volume of treated water relative to the overall volume of the desalination chambers 22 in the EDI device 10 is greater than 0.4 × 10⁻⁶. -3 A·min / mL and 16.0×10 -3 A·min / mL or less.

[0038] [Example 3] The number of units in the desalination chamber 22 is set to 2. Figure 6The water treatment apparatus shown was tested in the same manner as in Example 2. This water treatment apparatus includes a flow meter 43, a water quality meter 44, and a non-regenerative ion exchange unit 42 sequentially downstream of the EDI unit 10. Water containing added silica, boron, and sodium was prepared as test water. The concentrations of silica, boron, and sodium in the test water were 1.0 mg / L, 40 μg / L, and 1.3 mg / L. This test water was supplied as the water to be treated to the second small desalination chamber 27 and then to the anode chamber 21 and concentration chamber 24 via a pressure regulating valve 41. The water treatment apparatus was operated with the same flow velocity in the EDI unit 10 as in Example 2, and the silica, boron, and sodium concentrations were measured in the outlet water (measurement point A) from the EDI unit 10 and the outlet water (measurement point B) from the non-regenerative ion exchange unit 42 after 2400 hours. The results are shown in Table 2. It should be noted that the flow velocity SV in the non-regenerative ion exchange unit 42 was 6 h⁻¹. -1 The non-regenerative ion exchange device 42 is managed based on the water flow time, and is replaced whenever the set time is reached.

[0039] [Table 2] Based on the results shown in Table 2, it was confirmed that by installing a non-regenerative ion exchange unit 42 after the EDI unit 10, the sodium removal rate was increased, resulting in a significant reduction in residual sodium, and the resistivity was also close to the theoretical value under pure water conditions. On the other hand, the presence of the non-regenerative ion exchange unit 42 had almost no effect on the removal rates of silica and boron. Therefore, it can be concluded that in a water treatment device, by using the EDI unit 10 installed at the upstream stage to remove silica and boron, and by using the non-regenerative ion exchange unit 42 installed at the downstream stage to remove strong alkaline components such as sodium, high-purity water can be obtained efficiently.

[0040] Explanation of reference numerals in the attached figures 10. Electro-deionized water production unit (EDI unit) 11 Anode 12 Cathode 21 Anode Chamber 22 Desalination Chamber 23 Cathode Chamber 24 Concentration Chamber Small desalination chambers 26 and 27 31 Anion exchange membrane 32, 33 Cation exchange membranes 41 Pressure regulating valve 42 Non-regenerative ion exchanger (CP) 43 Flowmeter 44. Water quality meter.

Claims

1. A water treatment method, characterized in that, An electro-deionized water manufacturing apparatus is used, wherein the apparatus has a desalination chamber between an anode chamber having an anode and a cathode chamber having a cathode. The desalination chamber is defined by a pair of ion exchange membranes and filled with ion exchangers. The pair of ion exchange membranes consists of a first ion exchange membrane disposed on the side facing the anode and a second ion exchange membrane disposed on the side facing the cathode. In the water treatment method described above, treated water is obtained by using the electro-deionized water production apparatus, where a direct current is applied between the anode and the cathode while water to be treated is supplied to the desalination chamber. The value of the direct current, relative to the total amount of water being treated supplied to the desalination chamber within the electro-deionized water production apparatus, is greater than 0.4 × 10⁻⁶. -3 A·min / mL and 16.0×10 -3 A·min / mL or less.

2. The water treatment method according to claim 1, wherein, For the electro-deionized water manufacturing apparatus as a whole, the current value of the direct current applied between the anode and the cathode is set to 0.4A or more.

3. The water treatment method according to claim 1 or 2, wherein, The flow rate of the water to be treated in the desalination chamber is less than 920 mL / min.

4. The water treatment method according to claim 1 or 2, wherein, The effluent from the desalination chamber is fed into a non-regenerative ion exchange device, and the effluent from the non-regenerative ion exchange device is used as the treated water.

5. The water treatment method according to claim 1 or 2, wherein, A portion of the treated water that should be supplied to the desalination chamber is supplied to the anode chamber by means of a pressure regulating valve.

6. The water treatment method according to claim 1 or 2, wherein, The electro-deionized water manufacturing apparatus has four or fewer desalination chambers arranged in series with each other between the anode and the cathode. The desalination chambers, numbering four or fewer, are allocated and supplied with the water to be treated.

7. The water treatment method according to claim 1 or 2, wherein, In the desalination chamber of the electro-deionized water manufacturing apparatus, the desalination chamber closest to the anode is adjacent to the anode chamber via the first ion exchange membrane, which serves as an anion exchange membrane. The anode chamber is filled with anion exchangers and cation exchangers. In the anode chamber, the anion exchanger is disposed on one side of the anion exchange membrane in a manner that does not contact the anode, and the cation exchanger is disposed on one side of the anode in a manner that does not contact the anion exchange membrane but is in contact with the anion exchanger.

8. The water treatment method according to claim 1 or 2, wherein, In the desalination chambers of the electro-deionized water manufacturing apparatus, the desalination chamber closest to the anode is adjacent to the anode chamber through the first ion exchange membrane, and the desalination chamber closest to the cathode is adjacent to the cathode chamber through the second ion exchange membrane.

9. The water treatment method according to claim 1 or 2, wherein, The desalination chamber includes an ion exchange membrane located between the pair of ion exchange membranes, and the intermediate ion exchange membrane divides a first small desalination chamber located near the anode and a second small desalination chamber located near the cathode. The first small desalination chamber and the second small desalination chamber are connected so that water to be treated is supplied to one of the first small desalination chambers and water flowing out of the first small desalination chamber can flow into the other small desalination chamber.

10. The water treatment method according to claim 9, wherein, The first small desalination chamber is filled with anion exchange resin, and the second small desalination chamber is filled with cation exchange resin.

11. A water treatment device, characterized in that, It is a water treatment device that removes silica and boron from the water being treated. The water treatment device includes an electro-deionized water production unit. The electro-deionized water manufacturing apparatus has the following features: Anode chamber, which contains an anode; Cathode chamber, which includes a cathode; and A desalination chamber, disposed between the anode chamber and the cathode chamber, is defined by a pair of ion exchange membranes and filled with ion exchangers. The pair of ion exchange membranes consists of a first ion exchange membrane disposed on the side facing the anode and a second ion exchange membrane disposed on the side facing the cathode. The direct current applied between the anode and the cathode has a value greater than 0.4 × 10⁻⁶ per unit flow rate relative to the total amount of water being treated supplied to the desalination chamber within the electro-deionized water production apparatus. -3 A·min / mL and 16.0×10 -3 A·min / mL or less.

12. The water treatment apparatus according to claim 11, wherein, The water treatment apparatus includes a non-regenerative ion exchange device, and the outlet water of the desalination chamber of the electro-deionized water production apparatus is supplied to the non-regenerative ion exchange device.

13. The water treatment apparatus according to claim 11 or 12, wherein, The desalination chamber includes an ion exchange membrane located between the pair of ion exchange membranes, and the intermediate ion exchange membrane divides a first small desalination chamber located near the anode and a second small desalination chamber located near the cathode. The first small desalination chamber and the second small desalination chamber are connected so that water to be treated is supplied to one of the first small desalination chambers and water flowing out of the first small desalination chamber can flow into the other small desalination chamber.

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