Water treatment method, water treatment device, slime inhibitor, and cleaning method

Abstract

This water treatment device is provided with: an electrodeionized water production device (EDI device) (10) in which at least a portion of an ion exchanger filled in a desalination chamber (23) is an anion exchanger; and an addition means for adding an iodine-containing oxidizing agent as a slime inhibitor to the water to be treated supplied to the EDI device (10). The iodine-containing oxidizing agent is, for example, a solution in which iodine and iodide are dissolved in water.

Description

Technical Field

[0001] The present invention relates to a water treatment method using an electrodeionized water manufacturing device, a water treatment device, a slime inhibitor used for the electrodeionized water manufacturing device, and a cleaning method for the electrodeionized water manufacturing device. Background Art

[0002] As one of the devices for generating deionized water from treated water, there is an electro-deionized water manufacturing device (also called EDI (Electro De Ionization) device). The EDI device is a device that combines electrophoresis and electrodialysis, and has a structure in which a desalination chamber divided by a pair of ion exchange membranes is arranged between the anode and the cathode. In the EDI device, at least an ion exchanger such as an ion exchange resin is filled in its desalination chamber, a DC voltage is applied between the anode and the cathode, and the treated water is passed through the desalination chamber, so that the treated water with the ion components removed flows out of the desalination chamber, and the ion exchanger in the desalination chamber is regenerated. The EDI device has the advantage of not requiring the use of a reagent to regenerate the ion exchanger. In the EDI device, the concentration chamber is adjacent to the desalination chamber across the ion exchange membrane that divides the desalination chamber. In the concentration chamber, due to the ion components moved from the desalination chamber, the ion concentration is likely to become high, and slime derived from live bacteria is likely to be generated. For example, as described in Patent Document 1, when slime is generated, the flow of water is hindered, so the water pressure difference is likely to rise.

[0003] Generally, in a water treatment device, in order to suppress the generation of slime, there is a method of adding a slime inhibitor, also known as a slime control agent, to the water supplied to the device. The slime inhibitor is composed of, for example, hypochlorous acid, hydrogen peroxide, ozone, etc., which have a bactericidal effect. However, hypochlorous acid, hydrogen peroxide, ozone, etc. are oxidants. If these oxidants flow into the EDI device, as described in Patent Documents 1 and 2, the ion exchange resin and ion exchange membrane constituting the EDI device deteriorate, and sometimes the water quality of the treated water drops sharply, and the water pressure difference in the concentration chamber and the desalination chamber increases. Patent Document 1 discloses that when a direct current is applied between the anode and cathode of the EDI device, the deterioration of the EDI device caused by the oxidant proceeds faster, so when water containing an oxidizing bactericide is passed through the EDI device in order to remove the slime, the voltage application between the anode and the cathode is stopped or weakened. Patent Document 3 discloses that when the water pressure difference increases due to the generation of slime in the EDI device, a cleaning treatment is performed using a reagent containing hydrazine monohydrate and an alkali to remove the slime.

[0004] Similar to the EDI device, sludge may also be generated in a reverse osmosis membrane device having a reverse osmosis membrane, and the membrane such as the reverse osmosis membrane may also deteriorate due to contact with an oxidant. As a sludge inhibitor capable of inhibiting the degradation of the reverse osmosis membrane, Patent Document 4 discloses the use of a stabilized hypobromous acid composition, and Patent Document 5 discloses the use of an iodine-containing oxidant containing water, iodine, and an iodide.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-51453

[0008] Patent Document 2: Japanese Patent Application Publication No. 2000-279967

[0009] Patent Document 3: Japanese Patent Application Publication No. 2004-113973

[0010] Patent Document 4: Japanese Patent Application Publication No. 2015-62889

[0011] Patent Document 5: International Publication No. 2021 / 192582 Summary of the invention

[0012] Technical problem to be solved by the invention

[0013] When the sludge generated in the concentration chamber of the EDI device is removed by cleaning with chemicals as described in Patent Document 3, the cleaning process itself requires a long time, for example, several days, and there is a technical problem that the EDI device cannot be used during this period. In addition, it is difficult for the chemical solution to flow in the space blocked by the sludge, and as a result, it is difficult to completely remove the sludge in the space. When water containing a sludge inhibitor as an oxidant is passed through the EDI device, although clogging due to sludge can be prevented, as described in Patent Document 1, when the sludge inhibitor is supplied to the EDI device, the voltage application in the EDI device has to be stopped or reduced, and during this period, the water to be treated cannot be desalinated in the EDI device.

[0014] The object of the present invention is to provide a water treatment method and device, which is a water treatment method and device using an EDI device, which can make the EDI device work without causing a decrease in the quality of treated water in the EDI device and an increase in the water pressure difference.

[0015] Another object of the present invention is to provide a slime inhibitor and an EDI device cleaning method that can be used in a working EDI device without causing a decrease in the treated water quality in the EDI device and an increase in the water pressure difference.

[0016] Technical solutions for solving technical problems

[0017] The water treatment method of one embodiment of the present invention comprises: an adding step, in which a chemical is added to the treated water to obtain the treated water containing iodine and having an oxidizing ability; and a treating step, in which the treated water after the adding step is supplied to an EDI device (electrodeionized water manufacturing device) and treated in the EDI device, and at least a part of the ion exchanger filled in the desalination chamber of the EDI device is an anion exchanger. The chemical added in the adding step is, for example, an iodine-containing oxidant. When the treated water already contains an oxidant, the chemical may be an iodide. When the treated water already contains an iodide, the chemical may be an oxidant.

[0018] A water treatment device in one embodiment of the present invention comprises: an adding unit, which adds a chemical to the treated water to make it iodine-containing and oxidizing water; and an EDI device, at least a part of the ion exchanger filled in the desalination chamber of the EDI device is an anion exchanger, and the treated water to which the chemical is added by the adding unit is supplied to the EDI device. The chemical added by the adding unit is, for example, an iodine-containing oxidant, and when the treated water already contains an oxidant, the chemical may be an iodide, and when the treated water already contains an iodide, the chemical may be an oxidant.

[0019] A slime inhibitor according to one embodiment of the present invention includes an iodine-containing oxidant and is used in an EDI device.

[0020] In a cleaning method according to one embodiment of the present invention, a cleaning liquid containing the slime inhibitor of the present invention is passed through an EDI device to clean the EDI device.

[0021] Effects of the Invention

[0022] According to the present invention, the EDI device can be operated without causing a decrease in the quality of treated water and an increase in the water flow pressure difference in the EDI device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a figure which shows the water treatment apparatus which concerns on one Embodiment of this invention.

[0024] Figure 2 This is a diagram showing an example of the configuration of an EDI device.

[0025] Figure 3 It is a diagram showing another structural example of the water treatment device.

[0026] Figure 4 This is a diagram showing still another configuration example of the water treatment device.

[0027] Figure 5 This is a diagram showing another example of the structure of the EDI device.

[0028] Figure 6 This is a graph showing changes in the resistivity of the treated water in Example 1.

[0029] Figure 7 This is a graph showing changes in the water flow pressure difference of the desalination chamber in Example 1.

[0030] Figure 8 This is a graph showing changes in the water flow pressure difference of the concentration chamber in Example 1.

[0031] Fig. 9 This is a graph showing changes in the available iodine concentration in concentrated water in Example 3. DETAILED DESCRIPTION

[0032] Next, preferred embodiments of the present invention will be described with reference to the drawings. Figure 1 It is a diagram showing the structure of a water treatment device according to one embodiment of the present invention. Figure 1 The water treatment device shown is equipped with an electrodeionized water manufacturing device (EDI device) 10, and treated water is passed into the EDI device 10. The EDI device 10 performs, for example, desalination treatment on the treated water supplied, and discharges the treated water. Further, the water treatment device is equipped with a mechanism that adds an iodine-containing oxidant as a slime inhibitor to the treated water supplied to the EDI device 10. The details of the iodine-containing oxidant used as a slime inhibitor will be described later.

[0033] Figure 2 An example of the structure of the EDI device 10 is shown. The EDI device 10 includes a desalting chamber 23 between an anode chamber 21 and a cathode chamber 25, wherein the anode chamber 21 includes an anode 11, and the cathode chamber 25 includes a cathode 12, and a concentrating chamber 22 is arranged on the side of the desalting chamber 23 facing the anode chamber 21, and a concentrating chamber 24 is arranged on the side of the desalting chamber 23 facing the cathode chamber 25. The anode chamber 21 and the concentrating chamber 22 are separated by a cation exchange membrane 31, and the concentrating chamber 22 and the desalting chamber 23 are separated by an anion exchange membrane 32. The desalting chamber 23 and the concentrating chamber 24 are separated by a cation exchange membrane 33, and the concentrating chamber 24 and the cathode chamber 25 are separated by an anion exchange membrane 34. As a result, the desalting chamber 23 is divided by the anion exchange membrane 32 located on the side of the anode 11 and the cation exchange membrane 33 located on the side of the cathode 12. The desalting chamber 23 is filled with an ion exchange resin. In the example shown in the figure, the anion exchange resin (AER) and the cation exchange resin (CER) are filled in a mixed bed form (MB). In addition, the anode chamber 21 is filled with a cation exchange resin, and the concentrating chamber 22, the concentrating chamber 24 and the cathode chamber 25 are filled with an anion exchange resin. The concentrating chamber 22 and the concentrating chamber 24 may also be filled with an anion exchange resin (AER) and a cation exchange resin (CER) in a mixed bed form.

[0034] Next, Figure 1 The operation of the water treatment device shown in the figure is explained. When the supply water is passed through the anode chamber 21, the concentration chamber 22, the concentration chamber 24 and the cathode chamber 25 of the EDI device 10 respectively and a direct current is applied between the anode 11 and the cathode 12, the treated water to which the iodine-containing oxidant is added is passed through the desalination chamber 23. If the treated water is passed through the desalination chamber 23, the ion components (i.e., anions and cations) in the treated water are adsorbed on the ion exchange resin in the desalination chamber 23. At this time, in the desalination chamber 23, due to the potential difference generated at the interface of different types of ion exchange materials by the applied current, the water dissociation reaction shown in formula (1) occurs, and hydrogen ions (H + ) and hydroxide ions (OH - ).

[0035] H2O→H + +OH - (1)

[0036] Through the hydrogen ions and hydroxide ions generated in this way, the ion components previously adsorbed on the ion exchange resin in the desalination chamber 23 are ion exchanged and detached from the ion exchange resin. The anions in the detached ion components move to the concentration chamber 22 close to the anode 11 via the anion exchange membrane 32, and are discharged from the concentration chamber 22 as concentrated water. Similarly, the cations move to the concentration chamber 24 close to the cathode 12 via the cation exchange membrane 33, and are discharged from the concentration chamber 24 as concentrated water. As a result, the ion components in the treated water supplied to the desalination chamber 23 move to the concentration chamber 22 and the concentration chamber 24 and are discharged, and the ion exchange resin in the desalination chamber 23 is also regenerated. The treated water, i.e., deionized water, from which the ion components have been removed is discharged from the desalination chamber 23. Electrode water is discharged from the anode chamber 21 and the cathode chamber 25, respectively. The application of direct current can be performed continuously or intermittently when the treated water is passed through the water. It should be noted that in order to prevent the iodine component derived from the iodine-containing oxidant added to the treated water from leaking into the treated water, at least a portion of the ion exchanger filled in the desalination chamber 23 needs to be an anion exchanger, and preferably at least a portion of the ion exchanger filled in the concentration chamber 24 is an anion exchanger.

[0037] exist Figure 2 In the EDI device 10 shown, a basic structure consisting of [concentrating chamber (C) 22 | anion exchange membrane (AEM) 32 | desalting chamber (D) 23 | cation exchange membrane (CEM) 33 | concentrating chamber (C) 24] is arranged between the anode 11 and the cathode 12. This basic structure is called a unit group. In practice, a plurality of such unit groups are arranged in parallel between the electrodes, and the plurality of unit groups are electrically connected in series, and the anode 11 is arranged at one end of the series connection and the cathode 12 is arranged at the other end, so that the processing capacity can be increased. Figure 2In the figure, the case where a plurality of unit groups are arranged in parallel is marked as "×N groups". In this case, since adjacent unit groups can share adjacent concentration chambers, as the structure of the EDI device 10, if the repeating unit composed of [AEM|D|CEM|C] is represented by X, it can be set to a structure of [anode chamber|CEM|C|X|X|···|X|AEM|cathode chamber]. In this series structure, with respect to the desalination chamber 23 closest to the anode chamber 21, the anode chamber 21 itself can function as the concentration chamber 22, without providing an independent concentration chamber 22 between the desalination chamber 23 and the anode chamber 21. Similarly, with respect to the desalination chamber 23 closest to the cathode chamber 25, the cathode chamber 25 itself can function as the concentration chamber 24, without providing an independent concentration chamber 24 between the desalination chamber 23 and the cathode chamber 25.

[0038] Next, the iodine-containing oxidant added to the treated water is described. Although the EDI device 10 generally has a structure that allows the treated water to flow through the space of the ion exchange body filled with granular ion exchange resins and the like at a large flow rate, sludge derived from live bacteria may also be generated in such an EDI device. In the EDI device, blockage is likely to occur when sludge is generated, and the resulting increase in the water flow pressure difference and the performance degradation caused by the uneven flow of water tend to develop easily. Generally, in order to suppress the generation of sludge, as a sludge inhibitor (i.e., sludge control agent), a bactericide with oxidizing properties that flows through the water is effective. However, a bactericide with oxidizing properties must be an oxidant, and generally, the oxidant deteriorates the ion exchange resins and ion exchange membranes that constitute the EDI device. Therefore, in the past, it was necessary to avoid supplying water containing oxidants to the EDI device, especially to the EDI device in operation with direct current applied.

[0039] The inventors of the present invention have studied a method for suppressing the generation of slime in an EDI device and suppressing the degradation of ion exchange resins and ion exchange membranes in the EDI device, and found that the degradation of performance in the EDI device can be suppressed by using an iodine-containing oxidant as a slime inhibitor. It can be seen from the embodiments described below that when hypochlorous acid or hypochlorite, which is generally used as a slime inhibitor, is added to the treated water and the EDI device is operated, the water quality of the treated water discharged from the EDI device deteriorates at an early stage. It is believed that the deterioration of the water quality is caused by the degradation of the ion exchange membrane and the ion exchange resin, and when the iodine-containing oxidant is used, the water quality of the treated water from the EDI device is well maintained for a long time.

[0040] In the present invention, iodine-containing oxidant refers to an oxidant containing iodine as an element, which can be an iodine compound that functions as an oxidant itself, or a reactant of an iodine compound and an oxidant. The simple substance of iodine (i.e., I2) also has oxidizing power, so a solution containing simple substance of iodine is also included in the scope of iodine-containing oxidant. The iodine contained as an element in the iodine-containing oxide can be in any form, for example, any one of molecular iodine, iodide, polyiodide, iodic acid, hypoiodous acid, hydrogen iodide, and iodine coordinated with organic solvents such as polyvinyl pyrrolidone and cyclodextrin, in addition, these forms can also be combined. As a method for obtaining iodine in these arbitrary forms, the following methods can be used, etc.: a method for dissolving simple substance of iodine in non-polar solvents such as benzene, carbon tetrachloride, and alcohols, a method for dissolving simple substance of iodine using an alkali agent and water, or a method for dissolving simple substance of iodine using iodide and water. Total iodine can also be obtained by adding an acid or an oxidant to a solution containing at least one of iodide and iodide ions. Alternatively, iodine coordinated to polyvinyl pyrrolidone, cyclodextrin or the like may be obtained by using povidone iodine, which is iodine coordinated to polyvinyl pyrrolidone; iodine-cyclodextrin inclusion complex, which is iodine enclosed in cyclodextrin; iodine iodine supported on an organic polymer or surfactant; or the like.

[0041] As an iodine-containing oxidant, from the viewpoints of ease of operation, small influence on the water quality of the treated water and the treated water, it is preferred to use a solution formed by dissolving iodine elemental substance using iodide and water without using organic matter, i.e. a solution containing water, iodine and iodide. The solubility of iodine elemental substance in water is low alone, but it becomes dissolved in water by the coexistence of iodide or iodide ions. Moreover, in the solution formed by dissolving iodine elemental substance using iodide and water, an oxidant having a relatively high concentration and a stable one-liquid type is obtained, which is easy to operate. It should be noted that iodide refers to an iodine compound having an oxidation number of -1. As iodide, for example, potassium iodide, sodium iodide, lithium iodide, hydrogen iodide, silver iodide, copper iodide, zinc iodide, etc. are cited. These iodides are dissolved in water and dissociated, thereby providing iodide ions.

[0042] In the case of obtaining an iodine-containing oxidant as a reactant of an iodine compound and an oxidant, as an iodine compound, for example, potassium iodide, sodium iodide, lithium iodide, hydrogen iodide, silver iodide, copper iodide, zinc iodide, etc. can be used, and two or more of them can also be used simultaneously. As the iodine compound at this time, from the viewpoints of cost, etc., sodium iodide or potassium iodide is preferably used. As an oxidant reacting with an iodine compound, an oxidant having a redox potential (ORP) higher than that of iodine is preferably used. As examples of oxidants that can be used, combined chlorine, stabilized hypobromous acid compositions, etc. are also cited, and from the viewpoints of the speed of the reaction, it is preferred that an oxidant that is detected as a free chlorine form is detected. As an oxidant that is detected as a free chlorine form, hypochlorous acid, hypobromous acid or their salts, etc. are representatively cited. It should be noted that the stabilized hypobromous acid composition refers to the reaction product of a bromine-based oxidant and an aminosulfonic acid compound, or a product obtained by further reacting an aminosulfonic acid compound in a reactant of a bromine compound and a chlorine-based oxidant. Examples of the bromine-based oxidizing agent mentioned here include simple bromine, bromine chloride, bromic acid, and bromates.

[0043] In the case where the iodine-containing oxidant is a solution comprising water, iodine and iodide, from the viewpoint of the solubility of iodine relative to water, the molar ratio of iodide relative to iodine is preferably more than 1, and from the viewpoint of stability, the pH of the solution is preferably more than 3 and less than 9, more preferably more than 3 and less than 7, and further preferably more than 4 and less than 6.5. If the pH is less than 3, there is the possibility of crystallization of iodine, and if it exceeds 9, there is the possibility of significant reduction of the active ingredient. Considering the transportation cost of the slime inhibitor, etc., it is preferred that the active ingredient is high concentration and stable, so the total iodine concentration in the iodine-containing oxidant is preferably more than 3% by mass, more preferably more than 3% by mass and less than 40% by mass, and more preferably more than 10% by mass and less than 25% by mass. The total iodine concentration mentioned here refers to the concentration calculated based on the total chlorine concentration, whether it is iodide or iodine element, etc.

[0044] The iodine-containing oxidant is used as a slime inhibitor for the EDI device 10, but can also be used to clean each chamber (anode chamber 21, concentration chamber 22, concentration chamber 24, desalination chamber 23 and cathode chamber 25) of the EDI device 10. When cleaning the EDI device 10, the iodine-containing oxidant is dissolved in pure water to form a cleaning solution while the operation of the EDI device 10 is stopped, and the cleaning solution is passed into each chamber of the EDI device 10.

[0045] In the case of managing the concentration of the iodine-containing oxidant in the treated water, various quantitative methods related to iodine can be used. In particular, when the iodine-containing oxidant is a solution containing water, iodine and iodide, the iodine that is not iodide is an effective iodine as an oxidant, and the effective iodine shows the same color reaction as the residual chlorine when the total chlorine (or total residual chlorine) in the water is measured by the DPD method, that is, the colorimetric method using DPD (N, N-diethyl-p-phenylenediamine). Therefore, based on the premise that there is no residual chlorine, the total chlorine concentration meter based on the DPD method is used for measurement, and the concentration of iodine that is effective as an oxidant can be managed with the measured value. By using a residual chlorine quantitative method or a total chlorine quantitative method other than the DPD method, the effective iodine concentration can also be managed. For example, as a quantitative method for residual chlorine, a method is known to quantify the iodine freed by oxidation of potassium iodide by redox titration based on sodium thiosulfate. If the method is applied to the treated water for redox titration based on sodium thiosulfate, the effective iodine concentration in the treated water can be obtained as a value converted to the total chlorine concentration. In the following description, when the effective iodine concentration is referred to instead of the total iodine concentration, it may be expressed as a total chlorine concentration conversion value. The total chlorine concentration conversion value refers to the value obtained as the total chlorine concentration when the effective iodine concentration is measured using the method for measuring the total chlorine concentration. It is a value obtained by converting the effective iodine concentration into the total chlorine concentration. When the effective iodine concentration is expressed as a total chlorine concentration conversion value, "(in terms of Cl2)" is added to make this clear.

[0046] The concentration of the iodine-containing oxidant when added to the treated water needs to have sufficient bactericidal ability. If from such a viewpoint, when the iodine-containing oxidant is added to the treated water, the effective iodine concentration of the oxidant in the treated water supplied to the EDI device 10 is preferably 0.05 mg / L (in terms of Cl2) or more. Even if the effect of the iodine-containing oxidant on the EDI device is slight compared to hypochlorous acid, etc., there is a possibility of causing the EDI device to deteriorate when the concentration of the iodine-containing oxidant is too high. Therefore, the effective iodine concentration in the treated water supplied to the EDI device 10 is preferably less than 10.0 mg / L (in terms of Cl2).

[0047] The addition of the iodine-containing oxidant to the treated water can be carried out continuously or intermittently. In order to suppress the generation of slime, it is preferred that the amount of iodine-containing oxidant added is large, but it is not necessary to continuously add the iodine-containing oxidant to the treated water, and the iodine-containing oxidant can be added to the treated water intermittently. By adding the iodine-containing oxidant intermittently, the degradation of the EDI device 10 can be further suppressed. The desalination treatment of the treated water is continuously carried out, and the period during which the iodine-containing oxide is added to the treated water is set as the addition period, and the period during which the iodine-containing oxide is not added to the treated water is set as the no-addition period. For example, the addition period can be set to the range of 10 seconds to 12 hours, and the no-addition period can be set to the range of 5 seconds to 320 hours. The iodine-containing oxidant is added to the treated water so that the addition period within any 24 hours is within 12 hours. When the iodine-containing oxidant is intermittently added to the treated water, it is inappropriate to evaluate the impact of the iodine-containing oxidant on the EDI device 10 only by the oxidant concentration in the treated water when the iodine-containing oxidant is added. Therefore, it is preferred to set the value of iodine concentration in the treated water that is effective as an oxidant when adding iodine-containing oxidant to the treated water converted to total chlorine concentration as C, calculate the cumulative amount of concentration C during the period T of adding iodine-containing oxidant to the treated water, that is, the CT value, and use the CT value as a management indicator.

[0048] In the above description, the treated water added with the iodine-containing oxidant is passed through the desalination chamber 23 of the EDI device 10, but the treated water added with the iodine-containing oxidant can also be further supplied to the concentration chamber 22, the concentration chamber 24 and the electrode chamber. The anode chamber 21 and the cathode chamber 25 are collectively referred to as the electrode chamber. Although there is no special restriction on the supply water for the concentration chamber 22, the concentration chamber 24 and the electrode chamber, the ion concentration of the concentration chamber 22 and the concentration chamber 24 is easy to become high, so the live bacteria are easy to reproduce, and it becomes an environment that is easy to produce mud. There is the following possibility: in the electrode chamber, depending on the type of supply water, the live bacteria also reproduce and produce mud. Therefore, by continuously or intermittently using water added with the iodine-containing oxidant as the supply water for the concentration chamber 22, the concentration chamber 24 and the electrode chamber, it is possible to suppress the generation of mud in the concentration chamber 22, the concentration chamber 24 and the electrode chamber.

[0049] In this embodiment, by using an iodine-containing oxidant as an oxidant used as a sludge inhibitor in the EDI device instead of a chlorine-based oxidant such as hypochlorous acid or hypochlorite, it is possible to prevent the deterioration of the EDI device and obtain a sufficient sterilization effect while continuously operating the EDI device without providing an oxidant removal unit at the front stage of the EDI device or performing stop control of the EDI device, and it is possible to inhibit the generation of sludge.

[0050] In water treatment apparatuses equipped with an EDI device, there are few examples in which the EDI device is used alone. In many cases, a membrane device having a separation membrane is provided in the upstream stage of the EDI device, and water to be treated that has passed through the separation membrane is supplied to the EDI device. Figure 3 Shown in Figure 1 In the water treatment device shown in the figure, a reverse osmosis membrane device 40 including a reverse osmosis membrane 41 as a separation membrane is provided as a water treatment device in the upstream stage of the EDI device 10. Figure 3 In the water treatment device shown, the water to be treated is first supplied to the reverse osmosis membrane device 40. The permeated water that has passed through the reverse osmosis membrane 41 of the reverse osmosis membrane device 40 is supplied to the desalination chamber 23 of the EDI device 10 as the water to be treated in the EDI device 10. The permeated water from the reverse osmosis membrane device 40 can also be supplied to the concentration chamber 22, the concentration chamber 24 and the electrode chamber of the EDI device 10. The water to be treated that has not passed through the reverse osmosis membrane 41 is discharged from the reverse osmosis membrane device 40 as concentrated water. Figure 3 In the water treatment device shown in the figure, a mechanism for adding an iodine-containing oxidant as a slime inhibitor to the water to be treated is provided in the front stage of the reverse osmosis membrane device 40. Figure 3 In the water treatment apparatus shown, since an iodine-containing oxidant is added to the water to be treated in the upstream stage of the reverse osmosis membrane device 40 , adhesion of sludge to the reverse osmosis membrane 41 can also be suppressed.

[0051] In the reverse osmosis membrane device 40, various organic substances and the like are removed, so the impurity concentration in the treated water that passes through the reverse osmosis membrane device 40 and is supplied to the EDI device 10 is lower than that in the reverse osmosis membrane device 40. Figure 1 The impurity concentration in the treated water supplied to the EDI device 10 in the water treatment device shown in FIG. Figure 3 In the water treatment device shown, Figure 1 Compared with the water treatment device shown in FIG. 1 , it is less likely to generate sludge in the EDI device 10. Therefore, when the reverse osmosis membrane device 40 is arranged in the front stage of the EDI device 10, the effective iodine concentration of the treated water at the inlet of the EDI device 10 as an oxidant can be lower than Figure 1 Available iodine concentration in the water treatment unit shown.

[0052] As a separation membrane provided in the front stage of the EDI device 10, in addition to Figure 3 In addition to the reverse osmosis membrane 41 in the example shown, for example, a nanofiltration membrane (NF membrane), an ultrafiltration membrane (UF membrane), a microfiltration membrane (MF membrane), a forward osmosis membrane (FO membrane), etc. can also be used, and these membranes can also be combined. The treated water that has passed through the separation membrane is supplied to the EDI device 10. In order to suppress the generation of sludge in these separation membranes, it is preferred to add an iodine-containing oxidant to the treated water in the front stage of the separation membrane.

[0053] Figure 4The structure of another water treatment device according to the present invention is shown. Figure 4 The water treatment device shown is Figure 3 In the water treatment device shown, a total chlorine concentration meter 50 based on the DPD method connected to the permeate outlet of the reverse osmosis membrane device 40 and a pipe for returning the permeate water of the reverse osmosis membrane device 40 to the previous stage of the reverse osmosis membrane device 40 are provided. The total chlorine concentration meter 50 is provided to obtain the concentration of the iodine-containing oxidant in the permeate water of the reverse osmosis membrane device 40, specifically, to obtain the effective iodine concentration. In this water treatment device, in order to reduce the effective iodine concentration as an oxidant in the treated water supplied to the subsequent EDI device 10, control is performed so that the effective iodine concentration as the residual chlorine concentration measured by the total chlorine concentration meter 50 is less than a given value. In order to reduce the effective iodine concentration in the permeate water, for example, the amount of iodine-containing oxidant added can be controlled based on the measurement value of the total chlorine concentration meter 50, the amount of permeate water discharged from the reverse osmosis membrane device 40 returned to the front side of the reverse osmosis membrane device 40 can be increased or decreased, or an activated carbon device can be set at the permeate water outlet of the reverse osmosis membrane device 40 to adjust the oxidant concentration in the treated water supplied to the EDI device 10.

[0054] exist Figure 3 and Figure 4 In the water treatment device shown, a reverse osmosis membrane device 40 is configured in the front stage of the EDI device 10, and an iodine-containing oxidant is added to the treated water supplied to the reverse osmosis membrane device 40. In these water treatment devices, the addition of the iodine-containing oxidant to the treated water can be carried out continuously or intermittently. In order to suppress the deterioration of the reverse osmosis membrane 41 and the EDI device 10 while suppressing the generation of slime, and to suppress the decline of the water quality in the treated water, even when the iodine-containing oxidant is added to the treated water in the front stage of the reverse osmosis membrane device 40, it is preferred to add the iodine-containing oxidant intermittently. As a method for continuously supplying treated water to the water treatment device, for example, the addition period can be set to a range of 10 seconds to 12 hours, and the non-addition period can be set to a range of 5 seconds to 320 hours, and the iodine-containing oxidant is added to the treated water supplied to the reverse osmosis membrane device 40, so that the addition period is within 12 hours within any 24 hours.

[0055] Figure 5 Shows that it is possible to Figure 1 , Figure 3 as well as Figure 4 Another example of an EDI device used in a water treatment plant is shown. Figure 5 The EDI device shown is the following EDI device: Figure 2The desalination chamber 23 of the EDI device 10 shown is divided by an intermediate ion exchange membrane, and the side closer to the anode 11 than the intermediate ion exchange membrane is set as the first small desalination chamber 27, and the side closer to the cathode 12 than the intermediate ion exchange membrane is set as the second small desalination chamber 28. As the intermediate ion exchange membrane, an anion exchange membrane 37 is used. Therefore, the first small desalination chamber 27 is divided by the anion exchange membrane 32 and the anion exchange membrane 37, and the second small desalination chamber 28 is divided by the anion exchange membrane 37 and the cation exchange membrane 33. In this EDI device, the treated water is first supplied to the first small desalination chamber 27, the outlet water of the first small desalination chamber 27 is supplied to the second small desalination chamber 28 as it is, and the treated water of the EDI device is discharged from the second small desalination chamber 28. In the example shown here, the first small desalination chamber 27 is filled with an anion exchange resin. The second small desalination chamber 28 has a multi-bed structure, and is filled with cation exchange resin on the upstream side and anion exchange resin on the downstream side along the flow direction of the treated water. Figure 5 In the EDI device shown, multiple groups of repeating units X can also be arranged in series between the concentration chamber 22 adjacent to the anode chamber 21 and the anion exchange membrane 34 in contact with the cathode chamber 25, wherein the repeating unit X is an arrangement consisting of the anion exchange membrane 32, the first small desalination chamber 27, the anion exchange membrane 37, the second small desalination chamber 28, the cation exchange membrane 33 and the concentration chamber 24.

[0056] As mentioned above, the iodine-containing oxidant used in the present embodiment refers to an oxidant containing iodine as an element, and by adding the iodine-containing oxidant, the treated water becomes oxidizing power. Therefore, in the case where the treated water itself already contains an oxidant and has oxidizing power, only by adding iodide in the treated water, the treated water becomes the same state as when the iodine-containing oxidant was added. Similarly, in the case where the treated water itself already contains iodide, only by adding an oxidant in the treated water, the treated water becomes the same state as when the iodine-containing oxidant was added. Therefore, as adding medicine to the treated water, the present invention not only includes the situation that the medicine is an iodine-containing oxidant, but also includes the following situation: the medicine added to the treated water when the treated water already contains an oxidant is iodide and the medicine added to the treated water when the treated water already contains an iodide is an oxidant. In addition, in order to generate the iodine-containing oxidant by mixing or reacting in the treated water, the situation that the medicine and the oxidant containing iodine are added to the treated water respectively is also included in the scope of the present invention.

[0057] Example

[0058] Next, the present invention will be described in further detail by way of examples and comparative examples. Hereinafter, the effective iodine concentration is a value obtained by measuring the total chlorine concentration based on the DPD method. Moreover, as described above, the CT value is a value obtained as a cumulative amount, which is a cumulative amount of the effective iodine concentration C in the treated water during the period T in which the iodine-containing oxidant is added.

[0059] [Example 1]

[0060] Assembly Figure 5 The EDI device 10 shown was operated by supplying treated water to which an iodine-containing oxidant was added as a slime inhibitor, and the resistivity of the treated water discharged from the second small desalination chamber 28, the change in the overall water pressure difference between the first small desalination chamber 27 and the second small desalination chamber 28, and the change in the water pressure difference in the concentration chamber 22 and the concentration chamber 24 were investigated. The overall water pressure difference between the first small desalination chamber 27 and the second small desalination chamber 28 was set as the water pressure difference of the desalination chamber. As the treated water, treated water obtained by treating well water from Sagamihara City, Japan through a reverse osmosis membrane device was used, and the effective iodine concentration in the treated water when the iodine-containing oxidant was added was set to 0.75 mg / L (in terms of Cl2). As the iodine-containing oxide, a solution containing water, iodine and iodide was used. In Figure 6 The results on the resistivity of the treated water are shown in Figure 7 The results of the water pressure difference in the desalination chamber are shown. Figure 8 The results of the water pressure difference in the concentrating compartment are shown. The horizontal axis in these figures represents the CT value.

[0061] [Comparative Example 1, Comparative Example 2]

[0062] Assembly Figure 5 The EDI device 10 shown was operated in the same manner as in Example 1, and the change in resistivity of the treated water was investigated. However, as the slime inhibitor added to the treated water, sodium hypochlorite was used in Comparative Example 1, and a stabilized hypobromous acid composition was used in Comparative Example 2. Table 1 shows the resistivity of the treated water before the start of the operation and the resistivity of the treated water obtained when the CT value became 100 mg·h / L (in terms of Cl2) after the start of the operation, together with the results of the above-mentioned Example 1.

[0063] [Table 1]

[0064]

[0065] As shown in Example 1, when an iodine-containing oxidant is used as a sludge inhibitor, the resistivity of the treated water of the EDI device is maintained high for a long time, and the water pressure difference of the desalination chamber and the concentration chamber is almost unchanged. In contrast, in Comparative Example 1 using sodium hypochlorite as a sludge inhibitor and Comparative Example 2 using a stabilized hypobromous acid composition as a sludge inhibitor, if the operation time of the EDI device becomes longer, the resistivity decreases and the water quality of the treated water deteriorates. As a trend of the change in resistivity, in Comparative Example 1 using sodium hypochlorite, the resistivity of the treated water drops sharply in the early stage from the start of the operation of the EDI device, and then the resistivity does not change much. In contrast, in Comparative Example 2 using a stabilized hypobromous acid composition, the resistivity gradually decreases. From these results, it can be seen that by using an iodine-containing oxidant as a sludge inhibitor, the decline in the quality of the treated water and the increase in the water pressure difference in the EDI device can be suppressed.

[0066] [Example 2, Comparative Example 3, Comparative Example 4]

[0067] The slime inhibitor was brought into contact with water containing live bacteria, and the number of live bacteria before the slime inhibitor was brought into contact and the number of live bacteria after the slime inhibitor was brought into contact for 1 hour were investigated. As the slime inhibitor, the same iodine-containing oxidant as used in Example 1 was used in Example 2, sodium hypochlorite was used in Comparative Example 3, and a stabilized hypobromous acid composition was used in Comparative Example 4. The concentration of the slime inhibitor was 0.1 mg / L (in terms of Cl2) in either case. The results are shown in Table 2.

[0068] [Table 2]

[0069]

[0070] From the above results, it can be seen that the iodine-containing oxidant has a stronger bactericidal power as a slime inhibitor than sodium hypochlorite and stabilized hypobromous acid composition. As mentioned above, since the use of the iodine-containing oxidant as a slime inhibitor can suppress the decline in the treated water quality and the increase in the water pressure difference in the EDI device, it can be seen that the iodine-containing oxidant is an excellent slime inhibitor that can also be used in the working EDI device.

[0071] [Example 3]

[0072] Assembly Figure 5The EDI device 10 shown in the figure was operated by supplying the treated water to which the iodine-containing oxidant was added as a slime inhibitor to the first small desalting chamber 27, the concentrating chamber 22, the concentrating chamber 24, and the electrode chamber of the EDI device 10. Then, the relationship between the ratio of the cumulative amount of available iodine that continuously flows into the EDI device 10 to the total volume of the anion exchange resin (AER) filled in the concentrating chamber 22 and the concentrating chamber 24 of the EDI device 10 and the available iodine concentration in the concentrated water discharged from the EDI device 10 was investigated. The results are shown in Fig. 9 Before the cumulative amount of effective iodine continuously flowing into the EDI device 10 reaches a certain value, no iodine component leaks into the concentrated water flowing out of the concentration chambers 22 and 24, indicating that iodine is captured by the anion exchange resin in the EDI device 10. The iodine component mentioned here also includes iodide ions and the like.

[0073] DESCRIPTION OF SYMBOLS 10 Electrodeionized water production device (EDI device) 40 Reverse osmosis membrane device

[0074] 41Reverse Osmosis Membrane

[0075] 50 Total chlorine concentration meter

[0076] 11 Anode

[0077] 12 cathode

[0078] 21 Anode chamber

[0079] 22, 24 Concentration Room

[0080] 23 Desalination Chamber

[0081] 25 cathode chamber

[0082] 27, 28 small desalination chamber

[0083] 31, 33 cation exchange membrane 32, 34, 37 anion exchange membrane.

Claims

1. A water treatment method comprising: an adding step of adding chemicals to the treated water to obtain treated water containing iodine and having oxidizing ability; and a treatment step of supplying the treated water after the adding step to an electrodeionized water production device and treating the water in the electrodeionized water production device, At least a part of the ion exchangers filled in the desalination chamber of the electrodeionized water production device is an anion exchanger.

2. The water treatment method according to claim 1, wherein: In the treatment step, the water to be treated after the adding step is treated by a separation membrane before being supplied to the electrodeionized water production device.

3. The water treatment method according to claim 1 or 2, wherein: The drug is a solution containing water, iodine and iodide.

4. A water treatment device comprising: an adding unit for adding chemicals to the treated water to obtain the treated water containing iodine and having oxidizing ability; and An electrodeionized water production device, wherein at least a portion of the ion exchangers filled in the desalination chamber of the electrodeionized water production device are anion exchangers, The water to be treated to which the chemical is added by the adding unit is supplied to the electrodeionized water production device.

5. The water treatment device according to claim 4, wherein: A separation membrane is provided at a position after the addition unit and before the electrodeionized water production device. The water to be treated to which the chemical is added is supplied to the electrodeionized water production device after being treated by the separation membrane.

6. The water treatment device according to claim 4 or 5, wherein: The drug is a solution containing water, iodine and iodide.

7. The water treatment device according to claim 4 or 5, wherein: At least a portion of the ion exchangers filled in the concentrating chamber of the electrodeionized water producing device is an anion exchanger.

8. A slime inhibitor comprising an iodine-containing oxidant and used in an electrodeionized water production device.

9. The slime inhibitor according to claim 8, wherein: The slime inhibitor is a solution comprising water, iodine and iodide.

10. A cleaning method, comprising passing a cleaning solution comprising the slime inhibitor according to claim 8 or 9 into an electrodeionized water production device to clean the electrodeionized water production device.

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