Water treatment method and water treatment system

Abstract

To provide a water treatment method for producing demineralized treated water by removing silica and boron components from water to be treated while preventing deterioration of the electric type deionized water production apparatus (EDI apparatus) due to Joule heat and the like.SOLUTION: An EDI apparatus 10 with an anode chamber 21 equipped with an anode 11 and a cathode chamber 23 equipped with a cathode 12, and a desalination chamber 22 filled with ion exchangers, divided by an anion exchange membrane 31 disposed on the side facing the anode 11 and a cation exchange membrane 32 disposed on the side facing the cathode 12. When applying a DC current between the anode 11 and the cathode 12 and supplying water to be treated to the desalination chamber 22, the current value of the DC current per unit flow rate with respect to the total amount of treated water supplied to the desalination chamber 22 is greater than 0.4×10-3 A-min / mL and less than or equal to 16.0×10-3 A-min / mL.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a water treatment method and a water treatment system for removing silica components and boron components from water to be treated, and more particularly to a water treatment method and a water treatment system using an electrodeionization water producing apparatus (EDI (Electrodeionization) apparatus). [Background technology]

[0002] In order to remove ionic components from the water to be treated and produce pure water or deionized water, the water is subjected to an ion exchange treatment. Among the ionic components, weak acid components such as boron and silica components are difficult to remove by a general ion exchange treatment in which the water to be treated is simply passed through a layer of an ion exchange resin, which is at least one of an anion exchange resin and a cation exchange resin. In view of this, attempts have been made to use an electrodeionized water production apparatus (EDI apparatus). The EDI apparatus is an apparatus that produces deionized water from the water to be treated by combining electrophoresis and electrodialysis, and is provided with a desalting chamber filled with an ion exchanger, partitioned between an anode and a cathode by a pair of ion exchange membranes, the pair being made up of a first ion exchange membrane arranged on the side facing the anode and a second ion exchange membrane arranged on the side facing the cathode. In the EDI apparatus, deionized water is obtained from the desalting chamber by supplying the water to be treated to the desalting chamber while applying a direct current between the anode and the cathode. The EDI apparatus has the advantage of eliminating the need for a treatment to regenerate the ion exchange resin with a chemical. However, even in the case of an EDI device, simply filling the desalting compartment with a normal ion exchange resin as an ion exchanger may not provide sufficient removal performance for boron components, silica components, and the like.

[0003] Patent Document 1 discloses a method for reducing the silica concentration in water to be treated to 5 ppb or less using a reverse osmosis (RO) membrane device or the like, and then introducing the water to be treated into an EDI device, where the current density is preferably 600 mA / dm 2 More than 1000mA / dm 2The following describes the removal of boron from water to be treated: Patent Document 2 discloses the removal of boron and silica components from water to be treated by using an EDI device in which the thickness of the desalting compartment, the operating voltage (or operating current), or the space velocity of water passing through the desalting compartment is set so that raw water with a pH of 8.5 or less is treated without adding an alkaline agent to obtain a pH that is 1.0 or more higher than the raw water.

[0004] Patent Document 3, which is a technology related to EDI devices in general, discloses that in an EDI device, in order to suppress the generation of scale in the cathode chamber where the cathode is provided, electrode water discharged from the anode chamber where the anode is provided is supplied to the cathode chamber. When the anode chamber in the EDI device is filled entirely with a cation exchanger, hydrogen ions (H + ) and hydroxide ion (OH - ) occurs, and the heat of neutralization at that time can deteriorate the anion exchange membrane (causing so-called membrane burning). In order to prevent such deterioration of the anion exchange membrane, Patent Document 4 discloses that a cation exchanger is arranged in the anode chamber so that the cation exchanger and the anion exchanger are in contact with each other, that is, the cation exchanger is arranged so that it is not in contact with the anion exchange membrane but is in contact with the anode, and the anion exchanger is arranged so that it is not in contact with the anode but is in contact with the anion exchange membrane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-140548 A [Patent Document 2] JP 2001-113281 A [Patent Document 3] JP 2001-58186 A [Patent Document 4] JP 2011-189315 A Summary of the Invention [Problem to be solved by the invention]

[0006] The method described in Patent Document 1 aims to increase the current density in the EDI device to improve the efficiency of removing boron components and the like, but if the current density is increased, heat generated throughout the EDI device due to Joule heat and the like, in addition to heat generated by the neutralization reaction between hydrogen ions and hydroxide ions, increases, and there is a greater risk of the ion exchangers and ion exchange membranes that make up the EDI device being deteriorated by the heat. The method described in Patent Document 2 also requires an increase in current density, which may lead to problems associated with heat generation. Furthermore, the method described in Patent Document 2 utilizes the difference in mobility between hydrogen ions and hydroxide ions in water to create an environment in the desalting chamber where there are many hydroxide ions, i.e., an alkaline atmosphere, and therefore the sodium ions (Na + ) and potassium ions (K + ) cannot be removed.

[0007] An object of the present invention is to provide a water treatment method and a water treatment device that can remove silica components and boron components from the water to be treated using an EDI device while suppressing deterioration of the EDI device due to Joule heat, etc., to obtain desalted treated water. [Means for solving the problem]

[0008] A water treatment method according to one embodiment of the present invention uses an electrodeionization water production apparatus (EDI apparatus) having a desalting compartment filled with an ion exchanger, partitioned between an anode chamber equipped with an anode and a cathode chamber equipped with a cathode by a pair of ion exchange membranes, the pair being made up of a first ion exchange membrane arranged on the side facing the anode and a second ion exchange membrane arranged on the side facing the cathode, and the desalting compartment is partitioned between the anode and the cathode and filled with an ion exchanger. The method applies a direct current between the anode and the cathode while supplying water to be treated to the desalting compartment to obtain treated water, and the current value of the direct current per unit flow rate for the total amount of water to be treated supplied to the desalting compartment in the EDI apparatus is 0.4×10 -3 A min / mL and 16.0×10 -3 A·min / mL or less.

[0009] A water treatment device according to one embodiment of the present invention is a water treatment device that removes silica components and boron components from water to be treated, and is equipped with an EDI device having an anode chamber equipped with an anode, a cathode chamber equipped with a cathode, and a desalting compartment filled with an ion exchanger, the desalting compartment being partitioned by a pair of ion exchange membranes arranged between the anode chamber and the cathode chamber, the pair being made up of a first ion exchange membrane arranged on the side facing the anode and a second ion exchange membrane arranged on the side facing the cathode, and the current value of a direct current applied between the anode and the cathode is 0.4×10 per unit flow rate related to the total amount of water to be treated supplied to the desalting compartment in the EDI device. -3 A min / mL and 16.0×10 -3 A·min / mL or less. Effect of the Invention

[0010] According to the present invention, it is possible to obtain desalted treated water by removing silica components and boron components from water to be treated using an EDI device while suppressing deterioration of the EDI device. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a water treatment device according to a first embodiment. [Diagram 2] FIG. 4 is a diagram illustrating another example of the water treatment device according to the first embodiment. [Diagram 3] FIG. 4 is a diagram showing yet another example of the water treatment device according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing a water treatment device according to a second embodiment. [Diagram 5] FIG. 11 is a diagram illustrating another example of the water treatment device according to the second embodiment. [Figure 6] FIG. 11 is a diagram illustrating still another example of the water treatment device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, an embodiment of the present invention will be described with reference to the drawings.

[0013] [First embodiment] FIG. 1 shows the configuration of a water treatment device according to the first embodiment. The water treatment device shown in the figure performs a desalination process on water to be treated to obtain deionized water as treated water, and is composed of an electrodeionized water production device (EDI device) 10. In particular, this water treatment device is configured to remove weak acid components such as silica components and boron components, which are difficult to remove by normal ion exchange processes, from the water to be treated, and the operating conditions are set. The EDI device 10 has at least one desalination chamber 22 between an anode chamber 21 equipped with an anode 11 and a cathode chamber 23 equipped with a cathode 12, and the desalination chamber 22 is partitioned by a first ion exchange membrane located on the side facing the anode 11 and a second ion exchange membrane located on the side facing the cathode 12. The anode chamber 21 and the cathode chamber 23 are collectively called electrode chambers. In the example shown here, the first ion exchange membrane is a cation exchange membrane (CEM) 31, and the anode chamber 21 and the deionization chamber 22 are adjacent to each other with the cation exchange membrane 31 sandwiched therebetween, and the second ion exchange membrane is an anion exchange membrane (AEM) 32, and the deionization chamber 22 and the cathode chamber 23 are adjacent to each other with the anion exchange membrane 32 sandwiched therebetween. That is, one deionization chamber 22 is provided between the anode chamber 21 and the cathode chamber 23 with the cation exchange membrane 31 and the anion exchange membrane 32 interposed therebetween. In general EDI devices, a concentration chamber is often interposed between the electrode chamber and the deionization chamber, but in the EDI device 10 of this embodiment, as in the EDI device disclosed in Patent Document 4, the anode chamber 21 itself has a function as a concentration chamber, and the cathode chamber 23 also has a function as a concentration chamber, and therefore no concentration chamber is provided adjacent to the electrode chamber.

[0014] The deionization chamber 22 is filled with an ion exchanger, which is at least one of an anion exchanger and a cation exchanger. In the example shown here, the deionization chamber 22 is filled with, for example, a mixed bed of an anion exchange resin (AER) which is an anion exchanger and a cation exchange resin (CER) which is a cation exchanger. The cathode chamber 23 is filled with an anion exchange resin. The anode chamber 21 is filled with a layer of anion exchange resin and a layer of cation exchange resin so as to be in contact with each other. In the anode chamber 21, the layer of anion exchange resin is arranged so as to be in contact with the anion exchange membrane 31 but not with the anode 11, and the layer of cation exchange resin is arranged so as to be in contact with the anode 11 but not with the anion exchange membrane 31. If the anode chamber 21 were filled with only cation exchange resin, hydrogen ions (H + ) and hydroxide ion (OH - ) a neutralization reaction occurs.

[0015] H + + OH - = H2O + 56.5kJ / mol

[0016] The neutralization heat of this neutralization reaction is large, and the anion exchange membrane 31 may deteriorate due to this neutralization heat, causing holes in the anion exchange membrane 31 or increasing the operating voltage of the EDI device 10. Therefore, in this embodiment, a layer of anion exchange resin and a layer of cation exchange resin are filled in the anode chamber 21 so that the cation exchange resin does not come into contact with the anion exchange membrane 31. As a result, the above-mentioned hydration reaction occurs at a position in the anode chamber 21 where the layer of anion exchange resin and the layer of cation exchange resin come into contact with each other, thereby preventing the anion exchange membrane 31 from being deteriorated due to the neutralization heat. In the anode chamber 21, oxidizing substances with high 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 arranged in the anode chamber 21, so a layer of cation exchange resin is provided in the anode chamber 21 so as to be in contact with the anode 11.

[0017] In the water treatment device shown in FIG. 1, water to be treated is supplied to the deionization chamber 22 of the EDI device 10, and feed water is supplied to the anode chamber 21, and the feed water that has passed through the anode chamber 21 is then supplied to the cathode chamber 23. A part of the water to be treated may be diverted and supplied to the anode chamber 21 as feed water, or water from a supply source independent of the water to be treated may be supplied to the anode chamber 21 as feed water. In the anode chamber 21, hydrogen ions generated by an electrode reaction are released into the water at the position where the cation exchange resin contacts the anion exchange resin, so that water containing hydrogen ions is supplied to the cathode chamber 23. As a result, the atmosphere inside the cathode chamber 23 becomes acidic, and it is possible to prevent the generation of scale in the cathode chamber 23. Electrode water is discharged from the cathode chamber 23. The flow directions in the deionization chamber 22 and the electrode chambers on both sides thereof (the anode chamber 21 and the cathode chamber 23) are countercurrent in the illustrated example, but they do not necessarily have to be countercurrent.

[0018] Next, the operation of the water treatment device shown in Fig. 1 will be described. While applying a direct current between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21, and water to be treated is supplied to the desalting chamber 22. As a result, desalting is performed in the EDI device 10, and deionized water flows out from the desalting chamber 22 as treated water. At this time, in order to remove weak acid components such as silica and boron components from the water to be treated, the direct current applied between the anode 11 and the cathode 12 is set to a current value of 0.4 x 10 per unit flow rate of the water to be treated supplied to the EDI device 10, i.e., the water to be treated supplied to the desalting chamber 22. -3 A min / mL > 16.0 × 10 -3A·min / mL or less. The flow rate of the water to be treated here refers to the total flow rate of the water to be treated supplied to the desalting compartments 22 of the EDI device 10 when the EDI device 10 is equipped with a plurality of desalting compartments 22 as described later. In this embodiment, by setting the current value per flow rate of the water to be treated in this manner, weak acid components such as silica and boron can be removed at a high removal rate, as will be apparent from the examples described later. The flow rate of the water to be treated in the desalting compartments 22 is preferably less than 920 mL / min, and more preferably 25 mL / min to 100 mL / min. The flow rate in each of the electrode chambers (anode chamber 21 and cathode chamber 23) is preferably 150 mL / min or more. In addition, the current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0019] In the water treatment device shown in FIG. 1, strong alkaline components such as sodium ions and potassium ions are also removed, but since the operating conditions are adjusted to match the removal of weak acid components, there is a risk that strong alkaline components may not be removed efficiently. The water treatment device shown in FIG. 2 is a water treatment device in which a non-regenerative ion exchange device (also called a cartridge polisher (CP)) 42 is added to the water treatment device shown in FIG. 1 in order to efficiently remove strong alkaline components as well. The outlet water from the desalting chamber 22 of the EDI device 10 is supplied to the non-regenerative ion exchange device 42. The outlet water of the non-regenerative ion exchange device 42 is treated water (deionized water) from this water treatment device. The non-regenerative ion exchange device 42 is filled with anion exchange resin and cation exchange resin, for example, in a mixed bed form. The space velocity SV of the water passing through the non-regenerative ion exchange device 42 is, for example, 5 h -1 More than 50 hours -1 It is preferable to set the space velocity SV of the water passage to about 1000 mm / s. The space velocity SV of the water passage indicates how many times the apparent volume of the ion exchange resin the amount of water passes through the ion exchange resin per unit time.

[0020] Furthermore, in the water treatment device shown in FIG. 2, a portion of the water to be treated that should be supplied to the deionization compartment 22 is branched off to be used as feed water to be supplied to the anode compartment 21. For this purpose, a pipe 17 is provided that branches off from the pipe 16 that supplies the water to be treated to the deionization compartment 22 and connects to the anode chamber 21. A constant pressure valve 41 is provided on the pipe 17. By providing the constant pressure valve 41, the flow rate of the water to be treated that is supplied to the anode chamber 21 can be made constant without manual adjustment. In a typical EDI device, when a portion of the water to be treated that is supplied to the deionization compartment is branched off to be supplied to the electrode chamber or the concentration compartment as feed water, a manual adjustment valve and a flow meter are provided on the pipes that connect to the electrode chamber or the concentration compartment, and the flow rate is adjusted by manually operating the adjustment valve while monitoring the measured value on the flow meter.

[0021] In the EDI device 10 constituting the water treatment device of this embodiment, a plurality of deionization compartments 22 can be arranged between the anode 11 and the cathode 12. The plurality of deionization compartments 22 are electrically arranged in series with each other between the anode 11 and the cathode 12, and the water to be treated is distributed and supplied to the plurality of deionization compartments 22. The outlet water from the plurality of deionization compartments 22 is joined to become the treated water from the EDI device 10. In this case, a concentration compartment 24 is interposed between adjacent deionization compartments 22. The concentration compartment 24 is filled with, for example, a cation exchange resin, and is supplied with the same supply water as the supply water supplied to the anode compartment 21. Concentrated water is discharged from the concentration compartment 24, and this concentrated water is joined with the outlet water from the anode compartment 21 and supplied to the cathode compartment 23. The number of deionization compartments 22 provided between the anode 11 and the cathode 12 is called the number of cells. By increasing the number of cells and decreasing the flow rate of the water to be treated distributed to each deionization chamber 22, the current value per flow rate can be increased in each deionization chamber 22, which is effective in removing weak acid components. However, if the flow rate of the water to be treated to the entire deionization chamber 22 is made too small, it becomes difficult to distribute the water to be treated evenly to the multiple deionization chambers 22, and the deionization efficiency of the EDI device 10 decreases, and in particular the performance of removing weak acid components such as silica components and boron components decreases. Furthermore, deterioration of the ion exchanger including the ion exchange membrane occurs, such as membrane burning. In order to suppress such a decrease in deionization efficiency and to suppress deterioration of the ion exchanger including the ion exchange membrane, it is preferable that the flow rate of the water to be treated for each deionization chamber 22 is 25 mL / min or more, and further, the number of cells, i.e., the number of deionization chambers 22, is 1 to 4.

[0022] 3 shows a water treatment device of the first embodiment in which the number of cells is 2. In this water treatment device, the anode chamber 21 and the first deionization chamber 22 are adjacent to each other via the anion exchange membrane 31, the first deionization chamber 22 and the concentrating chamber 24 are adjacent to each other via the cation exchange membrane 32, the concentrating chamber 24 and the second deionization chamber 22 are adjacent to each other via the anion exchange membrane 31, and the second deionization chamber 22 and the cathode chamber 23 are adjacent to each other via the cation exchange membrane 32.

[0023] 3, 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 water to be treated is supplied to each deionization chamber 22. As a result, desalination is performed in the EDI device 10, and deionized water flows out from the deionization chamber 22 as treated water. At this time, in order to remove weak acid components such as silica components and boron components from the water to be treated, the direct current applied between the anode 11 and the cathode 12 has a current value of 0.4×10 per unit of water to be treated supplied to the EDI device 10, as in the case of the water treatment device shown in FIG. -3 A min / mL > 16.0 × 10 -3 Furthermore, in the water treatment device shown in FIG. 3, the current value per flow rate of the water to be treated per one desalting compartment 22, i.e., per one cell, is 1.7×10 -3 A cell min / mL. This current value is 4.0 × 10 -3 A·cell·min / mL or more 16.0×10 -3 A·cell·min / mL or less is more preferable. The flow rate of the water to be treated in each deionization compartment 22 is preferably less than 920 mL / min, and more preferably 25 mL / min or more and 100 mL / min or less. The current value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0024] [Second embodiment] A water treatment device of the second embodiment will be described. In general, in an EDI device, the desalting compartment itself is divided into two small desalting compartments by an ion exchange membrane, and each small desalting compartment is filled with an ion exchange resin, and water to be treated passes through one small desalting compartment, and water flowing out from the one small desalting compartment is supplied to the other small desalting compartment. The water treatment device of the second embodiment is similar to the water treatment device of the first embodiment, but differs from the water treatment device of the first embodiment in that the desalting compartment 22 is divided into two small desalting compartments 26, 27 by an intervening ion exchange membrane in the EDI device 10 constituting the water treatment device.

[0025] FIG. 4 shows an example of the configuration of the water treatment device of the second embodiment. The water treatment device of the second embodiment shown in FIG. 4 is also configured with an EDI device 10 similar to that used in the water treatment device shown in FIG. 1. However, the EDI device 10 shown in FIG. 4 is obtained by dividing the desalting compartment 22 into a first small desalting compartment 26 located closer to the anode 11 and a second small desalting compartment 27 located closer to the cathode 12 through an anion exchange membrane 33, which is an intermediate ion exchange membrane, in the EDI device 10 shown in FIG. 1. The first small desalting compartment 26 is filled with an anion exchange resin, and the second small desalting compartment 27 is filled with a cation exchange resin. The water to be treated is first supplied to the second small desalting compartment 27, and the outlet water of the second small desalting compartment 27 is supplied to the first small desalting compartment 26. The outlet water from the first small desalting compartment 26 is deionized water, which is treated water from this water treatment device. The flow direction of the water to be treated in the first small deionization chamber 26 and the second small deionization chamber 27 is parallel to each other, but this is not necessarily required.

[0026] Next, the operation of the water treatment device shown in Fig. 4 will be described. While applying a direct current between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21, and water to be treated is supplied to the second small desalting chamber 27. The water to be treated flows through the second small desalting chamber 27 and then the first small desalting chamber 26, during which it is subjected to a desalting process. As a result, deionized water flows out from the first small desalting chamber 26 as treated water. At this time, in order to remove weak acid components such as silica components and boron components from the water to be treated, the current value per total amount of water to be treated supplied to the desalting chamber 22 of the EDI device 10, i.e., the total flow rate of water to be treated supplied to the second small desalting chamber 27 provided in the EDI device 10, is 0.4 x 10 -3 A min / mL > 16.0 × 10 -3 A·min / mL or less. The flow rate of the water to be treated in the deionization chamber 22 consisting of the first small deionization chamber 26 and the second small deionization chamber 27 combined is preferably less than 920 mL / min, and more preferably 25 mL / min or more and 100 mL / min or less. The current value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0027] In the water treatment device shown in Fig. 4, the first small desalting chamber 26 closer to the anode 11 is filled with anion exchange resin, the second small desalting chamber 27 closer to the cathode 12 is filled with cation exchange resin, and the water to be treated flows from the second small desalting chamber 27 to the first small desalting chamber 26 in that order, thereby preventing the generation of scale when the water to be treated contains a large amount of impurities, and removing silica components, boron components, etc. at a high removal rate. Note that the first small desalting chamber 26 can be filled with anion exchange resin, and the second small desalting chamber 27 can be filled with anion exchange resin and cation exchange resin, and the water to be treated can be passed through the first small desalting chamber 26 and then the second small desalting chamber 27, which can further increase the removal rate of silica components, boron components, etc.

[0028] In the water treatment device of the second embodiment, similarly to the case shown in FIG. 3, a plurality of deionization compartments 22 can be arranged between the anode 11 and the cathode 12 with the concentration compartment 24 interposed therebetween. FIG. 5 shows the water treatment device of the second embodiment in which the number of cells is two. In the water treatment device shown in FIG. 5, while applying a direct current between the anode 11 and the cathode 12, feed water is supplied to the anode chamber 21 and the concentration compartment 24, and water to be treated is also supplied to each of the second small deionization compartments 27. As a result, deionization is performed in the EDI device 10, and deionized water flows out from each of the first small deionization compartments 26 as treated water. At this time, in order to remove weak acid components such as silica components and boron components from the water to be treated, similarly to the case of the water treatment device shown in FIG. 4, the current value per total flow rate of the water to be treated supplied to the second small deionization compartment 27 in the EDI device 10 is 0.4×10 -3 A min / mL > 16.0 × 10 -3 5, the current value per flow rate of the water to be treated per one deionization compartment 22 (i.e., the first small deionization compartment 26 and the second small deionization compartment 27), i.e., per cell, is 1.7×10 -3 A cell min / mL. This current value is 4.0 × 10 -3 A·cell·min / mL or more 16.0×10 -3A·cell·min / mL or less is more preferable. The flow rate of the water to be treated in each deionization compartment 22 is preferably less than 920 mL / min, and more preferably 25 mL / min or more and 100 mL / min or less. The current value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more.

[0029] In the water treatment device of the second embodiment as well, a non-regenerative ion exchange device can be arranged downstream of the EDI device 10 in order to increase the efficiency of removing strong alkaline components. FIG. 6 shows the water treatment device shown in FIG. 5 in which the outlet water from the first small desalting compartment 26 is supplied to a non-regenerative ion exchange device 42. The outlet water from the non-regenerative ion exchange device 42 is treated water (deionized water) from this water treatment device. The non-regenerative ion exchange device 42 is filled with anion exchange resin and cation exchange resin, for example, in a mixed bed form. The space velocity SV of water passing through the non-regenerative ion exchange device 42 is, for example, 5h -1 More than 50 hours -1 It is preferable to set the flow rate at about 100%. Here, for the purpose of managing the treated water, a flow meter 43 and a water quality meter 44 are provided in the pipe through which the outlet water from the first small deionization chamber 26 is supplied to the non-regenerative ion exchange device 42, but the flow meter 43 and the water quality meter 44 are not necessary. Furthermore, in the water treatment device shown in FIG. 6, a part of the water to be treated that should be supplied to the deionization chamber 22 is branched off to be used as the supply water to be supplied to the anode chamber 21 and the concentration chamber 24. For this purpose, a pipe 17 is provided which branches off from the pipe 16 that supplies the water to be treated to the deionization chamber 22 and connects to the anode chamber 21, and this pipe is further branched off and connected to the concentration chamber 24. A constant pressure valve 41 is provided in the pipe 17. By providing the constant pressure valve 41, the flow rate of the water to be treated that is supplied to the anode chamber 21 can be kept constant without manual adjustment. EXAMPLES

[0030] Next, the present invention will be described in more detail with reference to examples and comparative examples.

[0031] [Example 1] The water treatment device shown in FIG. 4 was assembled with the number of cells in the desalting chamber 22 set to 1. The anode chamber 21, the cathode chamber 23, the first small desalting chamber 26, and the second small desalting chamber 27 were each provided with a frame-shaped frame with an opening shaped like a square of 10 cm×10 cm and a thickness of 1 cm. The frame of each chamber was filled with ion exchange resin, and these frames were stacked in the thickness direction with an ion exchange membrane sandwiched between them to form the EDI device 10. Electrode plates (anode 11 and cathode 12) were disposed on both ends of the stacked frames. Ultrapure water to which silica, boron, and sodium were added was prepared as test water. The silica concentration in the test water was 1.2 mg / L, the boron concentration was 49 μg / L, and the sodium concentration was 2.1 mg / L. This test water was supplied to the second small desalting chamber 27 as the water to be treated, and was also supplied to the anode chamber 21 as the feed water. The flow rate of the water to be treated in the deionization chamber 22 consisting of the first small deionization chamber 26 and the second small deionization 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. The space velocity of the water passing through the deionization chamber 22 was 29 h -1 The current value per unit flow rate of the water to be treated in the desalting chamber 22 was 4.0×10 -3 A direct current of 0.4 A was applied between the anode 11 and the cathode 12 so that the solubility in the treated water was 0.2 A·min / mL. Then, 1000 hours after the start of operation, the silica concentration, boron concentration, and sodium concentration in the treated water discharged from the first small deionization chamber 26 were measured. The results are shown in Table 1.

[0032] [Example 2] The water treatment device shown in FIG. 5 was assembled with the number of cells in the deionization chamber 22 set to 2. As in Example 1, a frame having a square shape with an opening of 10 cm x 10 cm and a thickness of 1 cm was used for each of the anode chamber 21, the cathode chamber 23, the concentration chamber 24, the first small deionization chamber 26, and the second small deionization chamber 27. An ion exchange resin was filled in the frame of each chamber, and these frames were stacked in the thickness direction with an ion exchange membrane sandwiched between them to form the EDI device 10. The same test water as that used in Example 1 was prepared, and this test water was supplied to the second small deionization chamber 27 as the water to be treated, and was also supplied to the anode chamber 21 and the concentration chamber 24 as the feed water. The flow rate in the deionization chamber 22 consisting of the first small deionization chamber 26 and the second small deionization chamber 27 was 100 mL / min, and the combined flow rate of the anode chamber 21 and the concentration chamber 24 was 150 mL / min. Therefore, the flow rate in the cathode chamber 23 was also 150 mL / min. The space velocity of the water passing through the desalting chamber 22 is 14h -1 The current value per unit flow rate of the water to be treated in the entire desalting chamber 22 was 4.0×10 -3 A·min / mL, that is, the current value per unit flow rate of the water to be treated in one cell of the desalting chamber 22 is 8.0×10 -3 A direct current of 0.4 A was applied between the anode 11 and the cathode 12 so that the flow rate was A·cell·min / mL, and the silica concentration, boron concentration, and sodium concentration in the treated water discharged from the first small deionization chamber 26 were measured 1000 hours after the start of operation. The results are shown in Table 1.

[0033] [Comparative Example 1] A water treatment device was assembled in the same manner as in Example 2, except that the number of cells in the deionization chamber 22 was four. Ultrapure water to which silica and sodium were added was prepared as test water. The silica concentration in the test water was 1.9 mg / L, and the sodium concentration was 2.0 mg / L. This test water was supplied to each chamber. The flow rate in the deionization chamber 22 consisting of the first small deionization chamber 26 and the second small deionization chamber 27 was 920 mL / min, and the flow rate in the concentration chamber 24 was 100 mL / min. The spatial velocity of the water passing through the deionization chamber 22 was 60 h -1 The current value per unit flow rate of the water to be treated in the entire desalting chamber 22 was 0.4×10 -3A·min / mL, that is, the current value per unit flow rate of the water to be treated in one cell in the desalting chamber 22 is 1.7×10 -3 A direct current was applied between the anode 11 and the cathode 12 so that the flow rate was A·cell·min / mL, and the silica concentration and sodium concentration in the treated water discharged from the first small deionization chamber 26 were measured 1000 hours after the start of operation. The results are shown in Table 1.

[0034] [Table 1]

[0035] In Comparative Example 1, the test water did not contain boron, but boron, like silica, is an anion component that is difficult to remove with a general EDI device. The large amount of silica leaking from the treated water can be assumed to mean that a large amount of boron components is also leaking. In contrast, the results of Examples 1 and 2 show that the water treatment method and device according to the present invention can effectively remove silica components and boron components from the treated water in addition to sodium from the treated water. The results of Example 1 and Comparative Example 1 also show that increasing the current value per flow rate of the treated water in the EDI device 10 or decreasing the flow rate in the desalting chamber 22 from, for example, 920 mL / min to 100 mL / min is very effective in removing silica components and boron components. Sodium was not affected by the current value per flow rate of the treated water. If the flow rate of the water to be treated in the deionization chamber 22 is too small, the water to be treated will not be distributed evenly within the deionization chamber 22 or between multiple deionization chambers 22, which may result in a deterioration in the quality of the treated water and accelerate the deterioration of the ion exchange resin and ion exchange membrane. For this reason, the flow rate of the water to be treated per cell in the deionization chamber 22 is preferably 25 mL / min or more. Similarly, the flow rate of the electrode chambers and the concentration chamber 24 is preferably 25 mL / min or more. If the current value is too low, the ability to remove weak acid components decreases, so the current value of the direct current applied between the anode 11 and the cathode 12 is preferably 0.4 A or more. For the same reason, the current value per amount of water to be treated for the entire deionization chamber 22 in the EDI device 10 is preferably 0.4×10-3 A min / mL and 16.0×10 -3 It is preferable that the concentration is A·min / mL or less.

[0036] [Example 3] A water treatment device shown in FIG. 6 was assembled with the number of cells in the desalting chamber 22 set to 2, and a test was carried out in the same manner as in Example 2. This water treatment device is equipped with a flowmeter 43, a water quality meter 44, and a non-regenerative ion exchange device 42 in this order downstream of the EDI device 10. Ultrapure water to which silica, boron, and sodium were added was prepared as test water. The silica concentration in the test water was 1.0 mg / L, the boron concentration was 40 μg / L, and the sodium concentration was 1.3 mg / L. This test water was supplied to the second small desalting chamber 27 as the water to be treated, and was also supplied to the anode chamber 21 and the concentration chamber 24 via the constant pressure valve 41. The space velocity of the water passing through the EDI device 10 was set to the same as in Example 2, and the water treatment device was operated, and the silica concentration, boron concentration, and sodium concentration were measured in the outlet water from the EDI device 10 (measurement point A) and the outlet water from the non-regenerative ion exchange device 42 (measurement point B) after 2400 hours. The results are shown in Table 2. In addition, the space velocity SV of the water passing through the non-regenerative ion exchange device 42 is 6 h -1 The non-regenerative ion exchange device 42 was managed based on the water flow time, and the non-regenerative ion exchange device 42 was replaced every time the set time was reached.

[0037] [Table 2]

[0038] From the results shown in Table 2, it was confirmed that by providing the non-regenerative ion exchange device 42 downstream of the EDI device 10, the sodium removal rate was improved, the amount of residual sodium could be significantly reduced, and the resistivity approached the theoretical value for pure water. On the other hand, the presence of the non-regenerative ion exchange device 42 had almost no effect on the removal rates of silica and boron components. Therefore, it was found that highly pure water can be efficiently obtained by removing silica and boron components with the EDI device 10 provided in the upstream side of the water treatment device and removing strong alkaline components such as sodium components with the non-regenerative ion exchange device 42 provided in the downstream side. [Explanation of symbols]

[0039] 10. Electrodeionized water production equipment (EDI equipment) 11 Anode 12 Cathode 21 Anode chamber 22 Desalination room 23 Cathode Chamber 24 Concentration chamber 26,27 Small desalination room 31 Anion exchange membrane 32,33 Cation exchange membrane 41 Constant pressure valve 42 Non-regenerative ion exchanger (CP) 43 Flow meter 44 Water quality meter

Claims

1. A water treatment method using an electrodeionization water production apparatus having a desalting compartment partitioned by a pair of ion exchange membranes, the pair being made up of a first ion exchange membrane arranged on the side facing the anode and a second ion exchange membrane arranged on the side facing the cathode, between an anode chamber equipped with an anode and a cathode chamber equipped with a cathode, and filled with an ion exchanger, wherein a direct current is applied between the anode and the cathode while water to be treated is supplied to the desalting compartment to obtain treated water, The current value of the DC current per unit flow rate with respect to the total amount of the water to be treated supplied to the deionization compartment in the electrodeionization water production apparatus is 0.4×10 －３ A min / mL and 16.0 x 10 －３ A water treatment method, wherein the concentration of chlorine in the water is less than or equal to A min / mL.

2. 2. The water treatment method according to claim 1, wherein the direct current applied between the anode and the cathode of the electrodeionization water production apparatus has a current value of 0.4 A or more as a whole.

3. 3. The water treatment method according to claim 1, wherein a flow rate of the water to be treated in the desalting compartment is less than 920 mL / min.

4. 3. The water treatment method according to claim 1, wherein outlet water from the desalting compartment is passed through a non-regenerative ion exchange device, and outlet water from the non-regenerative ion exchange device is used as the treated water.

5. 3. The water treatment method according to claim 1, wherein a portion of the water to be treated that is to be supplied to the deionization compartment is branched off and supplied to the anode compartment while controlling the flow rate through a constant pressure valve.

6. the electrodeionization water production apparatus has four or less of the deionization compartments arranged electrically in series with each other between the anode and the cathode, 3. The water treatment method according to claim 1, wherein the water to be treated is distributed and supplied to the four or less deionization compartments.

7. Among the deionization compartments provided in the electrodeionization manufacturing apparatus, the deionization compartment closest to the anode is adjacent to the anode chamber via the first ion exchange membrane, which is an anion exchange membrane; The anode chamber is filled with an anion exchanger and a cation exchanger, 3. The water treatment method according to claim 1, wherein in the anode chamber, the anion exchanger is disposed on the side of the anion exchange membrane so as not to come into contact with the anode, and the cation exchanger is disposed on the side of the anode so as not to come into contact with the anion exchange membrane and is in contact with the anion exchanger.

8. 3. The water treatment method according to claim 1, wherein, among the deionization compartments provided in the electrodeionization manufacturing apparatus, the deionization compartment closest to the anode is adjacent to the anode chamber via the first ion exchange membrane, and the deionization compartment closest to the cathode is adjacent to the cathode chamber via the second ion exchange membrane.

9. 3. The water treatment method of claim 1, wherein the desalting compartment comprises an intermediate ion exchange membrane located between the pair of ion exchange membranes, and the intermediate ion exchange membrane divides the desalting compartment into a first small desalting compartment located closer to the anode and a second small desalting compartment located closer to the cathode, and the first small desalting compartment and the second small desalting compartment are connected so that the water to be treated is supplied to one of the first and second small desalting compartments and water flowing out from the one small desalting compartment flows into the other small desalting compartment.

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

11. A water treatment device for removing silica components and boron components from water to be treated, comprising: an electrodeionization water production apparatus including an anode chamber having an anode, a cathode chamber having a cathode, and a deionization chamber filled with an ion exchanger, the deionization chamber being partitioned by a pair of ion exchange membranes arranged between the anode chamber and the cathode chamber, the pair being made up of a first ion exchange membrane arranged on the side facing the anode and a second ion exchange membrane arranged on the side facing the cathode; The current value of the direct current applied between the anode and the cathode is 0.4×10 per unit flow rate related to the total amount of the water to be treated supplied to the deionization compartment in the electrodeionization water production apparatus. －３ A min / mL and 16.0 x 10 －３ A water treatment device having a water permeability of 0.1 to 100% by mass spectrometry.

12. The water treatment device of claim 11 , further comprising a non-regenerative ion exchange device supplied with outlet water from the desalting compartment of the electrodeionization water production device.

13. 13. The water treatment device according to claim 11 or 12, wherein the desalting compartment comprises an intermediate ion exchange membrane located between the pair of ion exchange membranes, and is divided by the intermediate ion exchange membrane into a first small desalting compartment located closer to the anode and a second small desalting compartment located closer to the cathode, and the first small desalting compartment and the second small desalting compartment are connected so that the water to be treated is supplied to one of the first and second small desalting compartments and water flowing out from the one small desalting compartment flows into the other small desalting compartment.

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