Method of operating deionized water production system, and system of producing deionized water

Abstract

To provide a method of operating a deionized water production system and a deionized water production system, capable of reducing power consumption and the amount of effluent in an electric deionized water production device, while preventing the deterioration of the quality of treated water.SOLUTION: A method of desalinating seawater, provided with a water intake / regeneration mode of flowing water to be treated through a desalination chamber to obtain treated water and flowing water at least through either of a concentration chamber and an electrode chamber, while energizing the electric deionized water production device with a first electric current, and provided with a water intake mode of flowing water to be treated through the desalination chamber in an energized state energized by a second electric current smaller than the first electric current, or in an unenergized state, alternately operates at least two electric deionized water production devices among the plurality of electric deionized water production devices each comprising water channels connected in parallel or in series, in the water intake mode and the water intake / regeneration mode, and operates the plurality of electric deionized water production devices in the water intake / regeneration mode at least at two different starting and finishing timings.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for operating a deionized water production system including an electrodeionized water production apparatus, and to a deionized water production system. [Background technology]

[0002] There is known a deionized water production system in which water to be treated is passed through an ion exchanger such as an ion exchange resin to perform deionization through an ion exchange reaction. Such a system generally includes an apparatus having an ion exchanger, and produces deionized water (e.g., pure water) by utilizing the ion exchange reaction caused by the ion exchanger. However, in an apparatus including an ion exchanger, the ion exchange groups of the ion exchanger become saturated as the water to be treated is passed through, and the deionization performance decreases. Therefore, a process is required to restore the deionization performance of the ion exchanger (hereinafter referred to as "regenerating").

[0003] Known methods for regenerating ion exchangers include periodically replacing the ion exchanger with a new one, periodically regenerating the ion exchanger using a chemical such as an acid or alkali, and continuously regenerating the ion exchanger using an electrodeionization water production apparatus (also called an EDI (ElectroDeIonization) apparatus).

[0004] The method of periodically replacing the ion exchanger does not allow deionized water to be produced during the replacement work, and therefore has a problem in that deionized water cannot be produced continuously. Furthermore, when a large flow rate of water to be treated is passed through the ion exchanger to produce deionized water, the deionization performance deteriorates quickly, and the ion exchanger must be replaced relatively frequently. Therefore, the method is not suitable for producing deionized water from a large flow rate of water to be treated. Furthermore, the ion exchanger that was used is discarded after replacement, which increases waste.

[0005] The method of regenerating ion exchangers using chemicals requires the laborious procurement of chemicals such as acids and alkalis, and has the problem that deionized water cannot be produced continuously because deionized water cannot be produced while the ion exchangers are being regenerated.

[0006] In a method for periodically replacing an ion exchanger or a system for regenerating an ion exchanger using a chemical, a method for the system to continuously produce deionized water may be considered, for example, by preparing a current ion exchanger and a spare ion exchanger and alternately switching between them. However, such a method requires the preparation of equipment for filling the ion exchanger and equipment for injecting the chemicals required for regeneration.

[0007] The EDI device is configured such that an electrode chamber, a concentration chamber, and a deionization chamber are formed by arranging a plurality of anion exchange membranes and cation exchange membranes between electrodes (anodes and cathodes), and the deionization chambers are filled with ion exchangers (anion exchangers and cation exchangers). Water to be treated is supplied to the deionization chamber, and water (e.g., water to be treated, deionized water, etc.) is supplied to the electrode chamber and the concentration chamber. The EDI device applies a voltage between the electrodes to pass an electric current, causing a dissociation reaction of water, generating hydrogen ions (H + ) and hydroxide ion (OH - ) and exchanges them with the ions attached to the ion exchanger in the deionization chamber, thereby maintaining the deionization performance. Therefore, by using the EDI device, it is possible to continuously produce deionized water and regenerate the ion exchanger. The EDI device is described in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2018 / 117035 Summary of the Invention [Problem to be solved by the invention]

[0009] In order to prevent deterioration of the quality of deionized water (treated water) due to a decrease in the deionization performance of the ion exchanger, the EDI device is usually always powered on during operation. Therefore, a deionized water production system equipped with an EDI device has a problem of high power consumption. In addition, during operation, water to be treated is supplied to the deionization compartment, and water is also supplied to the concentration compartment and the electrode compartment, so that deionized water is produced in the deionization compartment, and concentrated water containing ions that have migrated from the deionization compartment is discharged from the concentration compartment, and electrode water is discharged from the electrode compartment. Therefore, another problem with the EDI device is that a large amount of wastewater is discharged.

[0010] The present invention has been made to solve the problems inherent in the background art as described above, and has an object to provide a method for operating a deionized water production system and a deionized water production system that can reduce the power consumption and wastewater volume of an electrodeionized water production apparatus while suppressing deterioration of the water quality of the treated water. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a method for operating a deionized water production system that produces deionized water from water to be treated using a plurality of electrodeionized water production devices having water flow paths connected in parallel or series, the method comprising the steps of: a water sampling and regeneration mode in which, while a first current is applied to the electrodeionization water production apparatus, the water to be treated is passed through the deionization chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; a water sampling mode in which the treated water is passed through a desalting chamber of the electrodeionization water production apparatus in an energized state in which a second current smaller than the first current is passed through the electrodeionization water production apparatus, or in an unenergized state in which no current is passed through the electrodeionization water production apparatus, to obtain treated water; Among the plurality of electrodeionized water production apparatuses, at least two of the electrodeionized water production apparatuses are alternately operated in the water collection mode and the water collection and regeneration mode, The method includes performing operation in the water sampling and regeneration mode in the plurality of electrical deionized water production apparatuses that alternately operate in the water sampling mode and the water sampling and regeneration mode at at least two different start and end timings.

[0012] Alternatively, the method for operating a deionized water production system of the present invention is a method for operating a deionized water production system that produces deionized water from water to be treated using a plurality of electrodeionized water production apparatuses having water flow paths connected in parallel or in series, comprising the steps of: a water sampling and regeneration mode in which, while a first current is applied to the electrodeionization water production apparatus, the water to be treated is passed through the deionization chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; a water sampling mode in which the treated water is passed through a desalting chamber of the electrodeionization water production apparatus in an energized state in which a second current smaller than the first current is passed through the electrodeionization water production apparatus, or in an unenergized state in which no current is passed through the electrodeionization water production apparatus, to obtain treated water; among the plurality of electrodeionized water production apparatuses, at least one first electrodeionized water production apparatus is alternately operated in the water collection mode and the water collection and regeneration mode; The method includes operating a second electrodeionization water production apparatus, which is different from the first electrodeionization water production apparatus, in the water collection and regeneration mode.

[0013] On the other hand, the deionized water production system of the present invention comprises: a plurality of electrodeionized water production devices, each having a water flow passage connected in series, for producing deionized water from water to be treated; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current smaller than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least two of the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; having The control device includes: In the plurality of electrical deionized water production apparatuses which alternately operate in the water sampling mode and the water sampling and regeneration mode, operation in the water sampling and regeneration mode is performed at least at two different start and end timings.

[0014] Alternatively, the deionized water production system of the present invention includes a plurality of electrodeionized water production devices, each of which produces deionized water from water to be treated, and each of which has a water flow passage connected in series; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current smaller than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least one first electrodeionization water production apparatus among the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; having The control device includes: A second electrodeionized water production apparatus different from the first electrodeionized water production apparatus is operated in the water sampling and regeneration mode.

[0015] Alternatively, the deionized water production system of the present invention includes a plurality of electrodeionized water production devices, each of which produces deionized water from water to be treated, and each of which has a water flow passage connected in parallel; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current smaller than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least two of the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; a confluence section for confluence the treated water from the plurality of electrodeionized water production apparatuses; having The control device includes: In the plurality of electrical deionized water production apparatuses which alternately operate in the water sampling mode and the water sampling and regeneration mode, operation in the water sampling and regeneration mode is performed at least at two different start and end timings.

[0016] Alternatively, the deionized water production system of the present invention includes a plurality of electrodeionized water production devices, each of which produces deionized water from water to be treated, and each of which has a water flow passage connected in parallel; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current smaller than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least one first electrodeionization water production apparatus among the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; a confluence section for confluence the treated water from the plurality of electrodeionized water production apparatuses; having The control device includes: A second electrodeionized water production apparatus different from the first electrodeionized water production apparatus is operated in the water sampling and regeneration mode. Effect of the Invention

[0017] According to the present invention, it is possible to reduce the power consumption and the amount of wastewater discharged from an electrodeionization water production apparatus while suppressing deterioration of the water quality of the treated water. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a configuration example of a deionized water producing system according to a first embodiment. [Diagram 2] 2 is a schematic diagram showing an example of a schematic configuration of the EDI device shown in FIG. 1. [Diagram 3] 2 is a schematic diagram showing another example of the schematic configuration of the EDI device shown in FIG. 1. [Figure 4] 2 is a schematic diagram showing another example of the schematic configuration of the EDI device shown in FIG. 1. [Diagram 5] 2 is a block diagram showing a configuration example of a junction section shown in FIG. 1. [Figure 6] FIG. 2 is a block diagram showing a modified example of the deionized water producing system according to the first embodiment. [Figure 7] FIG. 11 is a block diagram showing another modified example of the deionized water producing system according to the first embodiment. [Figure 8] FIG. 11 is a block diagram showing a configuration example of a deionized water producing system according to a second embodiment. [Figure 9] FIG. 11 is a block diagram showing a modified example of the deionized water production system according to the second embodiment. [Figure 10] 1 is a graph showing the change in current efficiency of an EDI device and the change in the conductivity of treated water versus the regeneration time of an ion exchanger. [Figure 11] 4 is a graph showing an example of transition of an operation mode of the EDI device of the first embodiment. [Figure 12] 4 is a graph showing an example of the transition of the electrical conductivity of the water to be treated and the electrical conductivity of the treated water in the first embodiment. [Figure 13] 4 is a graph showing an example of transition of the salt rejection rate of treated water and the power consumption of the EDI device in the first embodiment. [Figure 14] 11 is a graph showing an example of transition of an operation mode of an EDI device of a comparative example. [Figure 15] 1 is a graph showing an example of the change over time in the electrical conductivity of the untreated water and the electrical conductivity of the treated water in a comparative example. [Figure 16] 13 is a graph showing an example of time course of changes in the salt rejection rate of treated water and the power consumption of an EDI device in a comparative example. [Figure 17] 13 is a graph showing an example of the transition of the electrical conductivity of the water to be treated and the resistivity of the water treated by each EDI device in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, the present invention will be described with reference to the drawings. (First embodiment) Fig. 1 is a block diagram showing a configuration example of a deionized water production system according to a first embodiment. Fig. 2 is a schematic diagram showing a schematic configuration example of the EDI device shown in Fig. 1. Figs. 3 and 4 are schematic diagrams showing other schematic configuration examples of the EDI device shown in Fig. 1.

[0020] 1, the deionized water production system of the first embodiment comprises EDI devices 11 and 12 having water flow paths connected in parallel for producing deionized water from water to be treated, power supply devices 21 and 22 for applying a required DC voltage necessary to maintain the deionization performance to the EDI devices 11 and 12, a control device 3 for controlling the operation of the entire deionized water production system, and a junction section 4 for junctioning the treated waters from the EDI devices 11 and 12. The water to be treated is fed to the desalting compartments (D) of the EDI devices 11 and 12, respectively, using, for example, a pump not shown, and treated water (deionized water) is produced by the desalting compartments (D).

[0021] 1 shows an example of the configuration of a deionized water production system having two EDI devices 11 and 12 whose water flow paths are connected in parallel. The deionized water production system of the first embodiment may be configured to have three or more EDI devices 1 whose water flow paths are connected in parallel. In the following, a plurality of EDI devices will be collectively referred to as an EDI device 1, and a plurality of power supply devices will be collectively referred to as a power supply device 2.

[0022] The water quality of the water to be treated and the treated water is measured using well-known water quality measuring instruments 5 (51 and 52). It is not necessary to measure the water quality of the water to be treated. The water quality measuring instrument 5 may be, for example, a conductivity meter that measures the conductivity of the water to be treated and the treated water, a resistivity meter that measures the resistivity of the water to be treated and the treated water, or a concentration meter that measures the ion concentration in the water to be treated and the treated water. The deionized water production system may be equipped with a well-known flow meter (integrating flow meter) 6 that measures the discharge amount (production amount) of treated water from the desalting chambers (D) of the EDI devices 11 and 12.

[0023] The control device 3 is connected to the water quality measuring device 5 and the flow meter 6 via known communication means, and transmits measurement data on the quality of the water to be treated and the treated water, as well as data on the production amount of treated water. The control device 3 may receive output voltage (DC voltage) values ​​of the power supply devices 21 and 22 from the power supply devices 21 and 22, respectively. The control device 3 also controls starting and stopping the supply of the water to be treated to the concentration chambers (C) and electrode chambers (E) of the EDI devices 11 and 12 using a pump (not shown) and a valve 7. The concentrated water discharged from the concentration chamber (C) and the electrode water discharged from the electrode chamber (E) are each discharged into a drain tank 8.

[0024] FIG. 1 shows an example in which water to be treated is supplied to the concentration chamber (C) and the electrode chamber (E) of the EDI devices 11 and 12, respectively. Treated water may be supplied to the concentration chamber (C) and the electrode chamber (E), or water may be supplied from a system other than the deionized water production system shown in FIG. 1. The EDI device 1 may also be configured to share the electrode chamber (E) and the concentration chamber (C). In that case, the electrode chamber (E) and the concentration chamber (C) share the same flow path, and the operation method is to pass water through only one of them. In a configuration in which water is supplied to the concentration chamber (C) and the electrode chamber (E) from a system other than the deionized water production system shown in FIG. 1, the EDI device 1 can be operated without changing the flow rate of the water to be treated supplied to the desalting chamber (D).

[0025] The control device 3 is connected to the power supply device 2, the pump, and the valve 7 via known communication means, and can control the operation of the power supply device 2, the pump, and the valve 7. The control device 3 controls the on / off of the power supply device 2, and also controls the supply and stop of the water to be treated to the desalting chamber (D) of the EDI device 1, and the supply and stop of the water to be treated to the concentration chamber (C) and the electrode chamber (E) of the EDI device 1, using the pump and the valve 7. The control device 3 also operates the EDI device 1 in two operation modes (water sampling mode and water sampling and regeneration mode) described later. The communication means between the control device 3 and the power supply device 2, the pump, the valve 7, the water quality measuring device 5, and the flow meter 6 may be either known wired communication means or wireless communication means, and any known communication standard may be used.

[0026] The control device 3 can be realized by, for example, a well-known PLC (Programmable Logic Controller). The control device 3 may also be realized by a well-known information processing device (computer) equipped with a CPU (Central Processing Unit), a storage device, an I / O interface, a communication device, etc. The control device 3 realizes the operation method of the deionized water production system of the present invention by having a processor of the PLC or the information processing device execute processing according to a program stored in advance in the storage device.

[0027] Although not shown in FIG. 1, in order to obtain deionized water with a sufficiently reduced impurity concentration, the deionized water production system of the present invention may have a reverse osmosis membrane device equipped with a well-known reverse osmosis membrane (RO membrane) in the stage preceding the EDI device 1. The deionized water production system may have a configuration having multiple stages (for example, two stages) of reverse osmosis membrane devices with water flow passages connected in series. When a two-stage reverse osmosis membrane device is provided, raw water stored in a storage tank or the like is passed through the first-stage reverse osmosis membrane device, the permeated water is passed through the second-stage reverse osmosis membrane device, and the permeated water of the second-stage reverse osmosis membrane device is supplied to the desalting chamber of the EDI device 1 as the water to be treated. The reverse osmosis membrane device may have a configuration including a general reverse osmosis membrane used, for example, in producing pure water.

[0028] As shown in Fig. 2, the EDI device 1 has a configuration in which a plurality of pairs of cation exchange membranes and anion exchange membranes (two pairs in Fig. 2) are arranged between two electrodes (anode 31 and cathode 32) to form electrode chambers 41 and 45, concentration chambers 42 and 44, and deionization chamber 43. The electrode chamber (anode chamber) 41 is formed by the anode 31 and a cation exchange membrane 61, and the electrode chamber (cathode chamber) 45 is formed by the cathode 32 and an anion exchange membrane 64. The deionization chamber 43 is formed by an anion exchange membrane 62 and a cation exchange membrane 63, and two concentration chambers 42 and 44 are formed with the deionization chamber 43 sandwiched between them. The concentration chamber 42 on the anode 31 side is formed by the cation exchange membrane 61 and the anion exchange membrane 62, and the concentration chamber 44 on the cathode 32 side is formed by the cation exchange membrane 63 and the anion exchange membrane 64. An ion exchanger containing a mixture of a cation exchanger and an anion exchanger is filled in the deionization chamber 43. The electrode chambers 41 and 45 and the concentration chambers 42 and 44 may be filled with an ion exchanger as appropriate.

[0029] As shown in Fig. 3, the EDI device 1 may have a configuration in which a plurality of basic components (cell sets) consisting of the concentration compartment 42, deionization compartment 43, and concentration compartment 44 shown in Fig. 2 are arranged side by side between the anode 31 and the cathode 32. In this case, adjacent cell sets can share adjacent concentration compartments. Fig. 3 shows a configuration example in which N (N is an integer of 1 or more) cell sets are arranged between the anode 31 and the cathode 32. In the EDI device 1 shown in Fig. 3, the electrode compartment (anode compartment) 41 is filled with a cation exchanger (CER), the concentration compartments 42 and 44 and the electrode compartment (cathode compartment) 45 are filled with an anion exchanger (AER), and the deionization compartment 43 is filled with an ion exchanger (MB) which is a mixture of a cation exchanger and an anion exchanger. Moreover, the EDI device 1 shown in FIG. 3 is configured such that water is not supplied to the electrode chamber (anode chamber) 41 from the outside, but outlet water of the electrode chamber (cathode chamber) 45 is supplied to the electrode chamber (anode chamber) 41.

[0030] The EDI device 1 may have a configuration in which an intermediate ion exchange membrane 66 is disposed between two concentration compartments 42 and 44 to form two deionization compartments 46 and 47, as shown in FIG. 4. In the EDI device 1 shown in FIG. 4, the deionization compartment 46 is filled with an anion exchanger (AER), the deionization compartment 47 is filled with a cation exchanger (CER), and the water to be treated is passed through the deionization compartment 47 and then through the deionization compartment 46. The amounts of ion exchangers filled in the two deionization compartments 46 and 47 do not need to be the same. For example, one deionization compartment may be filled with a cation exchanger and an anion exchanger, and the other packed compartment may be filled with only a cation exchanger. Alternatively, one deionization compartment may be filled with a cation exchanger and an anion exchanger, and the other packed compartment may be filled with only an anion exchanger.

[0031] As described above, the EDI device 1 may be configured so that the ion exchanger (anion exchange membrane 64 or cation exchange membrane 61) that separates the electrode chamber from the concentration chamber is eliminated, and the electrode chamber and the concentration chamber are combined. In this case, the electrode chamber and the concentration chamber share the same flow path, so that the operation method is such that water passes through only one of them.

[0032] The junction 4 may be configured as shown in FIG. 5(a) to join the water flow paths of the treated water from the EDI devices 11 and 12, as shown in FIG. 5(b), to store the treated water from the EDI devices 11 and 12 in a common tank 9 and output it as treated water, or as shown in FIG. 5(c), to combine these. In order to prevent the drawings from becoming complicated, FIG. 5(a) to (c) omit the control device 3, the water quality measuring device 5, the flow meter 6, and the communication paths between the control device 3 and the power supply device 2, the valve 7, the water quality measuring device 5, and the flow meter 6. In FIG. 5(b) and (c), the drainage tank 8 is also omitted. FIG. 5(a) to (c) show a configuration example in which one power supply device 2 shown in FIG. 6 is shared by two EDI devices 11 and 12, which will be described later.

[0033] In such a configuration, the inventors have found that the efficiency of power utilization for regeneration is improved when the ion exchanger has a higher salt-form ratio during regeneration of the ion exchanger in the EDI device 1. The inventors have also found that by producing deionized water by passing the water to be treated only through the desalting compartments and not through the concentration compartments and electrode compartments of the EDI device 1 when no current is applied, it is possible to obtain deionized water of the same quality as when the EDI device 1 is operated continuously while being energized, and to reduce power consumption and wastewater volume.

[0034] In this embodiment, the EDI device 1 has two operating modes: a water collection mode in which treated water is passed through the desalting compartment (D) without applying electricity to the EDI device 1 to obtain treated water, and a water collection and regeneration mode in which treated water is passed through the desalting compartment (D) while applying electricity to the EDI device 1 to obtain treated water, and water is passed through at least one of the concentration compartment (C) and the electrode compartment (E) to regenerate the ion exchanger. In order to reduce the amount of wastewater discharged from the EDI device 1 while suppressing the power consumption of the EDI device 1, the EDI device 1 is operated alternately between the water collection mode and the water collection and regeneration mode. In the water collection mode, water is basically not passed through the concentration compartment (C) and the electrode chamber (E) (no water is passed through).

[0035] There is no reason why water should not be passed through the concentration chamber (C) and the electrode chamber (E) of the EDI device 1 when no current is applied, and it is also possible to pass water through the concentration chamber (C) and the electrode chamber (E) in the water collection mode. The amount of water passed through the concentration chamber (C) and the electrode chamber (E) in the water collection mode may be an amount that makes the amount of water discharged from the EDI device 1 in the water collection mode less than the amount of water discharged from the EDI device 1 in the water collection and regeneration mode. In order to achieve the object of the present invention of reducing the amount of water discharged from the EDI device 1, it is preferable that the amount of water passed through the concentration chamber (C) and the electrode chamber (E) in the water collection mode is 1 / 2 or less of the amount of water passed through in the water collection and regeneration mode. More preferably, the amount of water passed through the concentration chamber (C) and the electrode chamber (E) in the water collection mode is 1 / 5 or less of the amount of water passed through in the water collection and regeneration mode.

[0036] When water is passed through the concentration chamber (C) and the electrode chamber (E) in the water collection mode, water may be passed through at least one of the concentration chamber (C) and the electrode chamber (E). "No water passing", in which no water is passed through the concentration chamber (C) and the electrode chamber (E), is not limited to a state in which no water is supplied to the concentration chamber (C) and the electrode chamber (E), but also includes a state in which a small amount of water is supplied.

[0037] Additionally, the term "no current" used here refers to a state in which the water dissociation reaction does not proceed within the EDI device 1, and includes the application of a weak voltage between the electrodes for the purpose of preventing ion diffusion from the concentration compartment (C) to the deionization compartment (D). For example, since the theoretical voltage required for water dissociation is 0.83 V, this includes the application of a voltage of 0.83 V or less per deionization compartment (D).

[0038] It is also possible to energize the EDI device 1 in the water sampling mode. However, the current passed through the EDI device 1 in the water sampling mode is a current (second current) that is less than the current (first current) passed through the EDI device 1 during normal operation (water sampling and regeneration mode). When energizing the EDI device 1 in the water sampling mode, it is preferable that the second current be 1 / 2 or less of the first current, in order to achieve the object of the present invention of reducing the power consumption of the EDI device 1. More preferably, the second current is 1 / 5 or less of the first current.

[0039] The above-mentioned water sampling mode has the advantage that no or little water is discharged from the concentration chamber (C) and the electrode chamber (E) of the EDI device 1, but the deionization performance of the EDI device 1 decreases over time, so the quality of the treated water gradually deteriorates. On the other hand, the water sampling and regeneration mode has the advantage that the deionization performance of the EDI device 1 is regenerated over time, so the quality of the treated water gradually improves, but the amount of water discharged from the concentration chamber (C) and the electrode chamber (E) of the EDI device 1 is large. Therefore, when the EDI device 1 is operated alternately between the water sampling mode and the water sampling and regeneration mode, the quality of the treated water varies relatively greatly.

[0040] In a deionized water production system, for example, in order to produce deionized water by passing a large flow rate of water to be treated, a configuration is available which has multiple EDI devices 1 (two in FIG. 1) with water flow paths connected in parallel, as shown in FIG. 1.

[0041] Therefore, in the deionized water production system of the first embodiment, the two EDI devices 1 are alternately operated in the water sampling mode and the water sampling and regeneration mode, and while one EDI device 1 is operating in the water sampling mode, the other EDI device 1 is operating in the water sampling and regeneration mode. At this time, the deionized water production system may include a period in which multiple EDI devices 1 are operating simultaneously in the water sampling and regeneration mode.

[0042] In the case of a deionized water production system having three or more EDI devices 1, in the first embodiment, the operation of the EDI devices 1 in the water sampling and regeneration mode is set to different start and end timings. For example, it is possible to sequentially operate the EDI devices 1 in the water sampling and regeneration mode. Alternatively, in the first embodiment, the operation of the EDI devices 1 in the water sampling and regeneration mode is set to different start and end timings for each of the units divided into two or more groups. For example, in the case of a deionized water production system having four EDI devices 1 with water flow paths connected in parallel, it is possible to provide two units each consisting of two EDI devices 1, and while one unit is operating in the water sampling mode, the other unit is operating in the water sampling and regeneration mode.

[0043] Note that a deionized water production system having three or more EDI devices 1 may include an EDI device 1 that does not switch operation modes, for example, that always operates in the water sampling and regeneration mode. That is, in the first embodiment, among the multiple EDI devices 1, at least two EDI devices 1 are alternately operated in the water sampling mode and the water sampling and regeneration mode, and the operation in the water sampling and regeneration mode in the multiple EDI devices 1 that alternately operate in the water sampling mode and the water sampling and regeneration mode is performed at least two different start and end timings.

[0044] The operation modes of the multiple EDI devices 1 may be switched by the control device 3 using a timer, or may be switched based on the water quality of the treated water measured by the water quality measuring device 5. When switching the operation modes using a timer, the control device 3 may alternate between the water sampling / regeneration mode and the water sampling mode, for example, based on the preset operation times of the water sampling / regeneration mode and the water sampling mode. When switching the operation modes based on the water quality of the treated water measured by the water quality measuring device 5, the control device 3 may, for example, switch to the water sampling / regeneration mode when the water quality of the treated water deteriorates below a preset first threshold value during operation in the water sampling / regeneration mode, and switch to the water sampling mode when the water quality of the treated water exceeds a preset second threshold value during operation in the water sampling / regeneration mode (when the water quality becomes good).

[0045] By controlling the operation mode of each EDI device 1 in this manner using the control device 3, the treated water after merging includes treated water from the EDI device 1 operating in the water sampling and regeneration mode. Therefore, in the deionized water production system of the first embodiment, by having the merging section 4, the quality of the treated water from the multiple EDI devices 1 is averaged, thereby suppressing fluctuations in the quality of the treated water after merging. Furthermore, by including the water sampling mode in the operation modes of the EDI device 1, the amount of wastewater from the EDI device 1 can be reduced while reducing the power consumption of the entire deionized water production system.

[0046] 1 shows an example of a configuration having two power supply devices 21 and 22 corresponding to the two EDI devices 11 and 12. In such a configuration, for example, it is possible to operate one of the EDI devices 1 in a water sampling and regeneration mode at all times. Even in this case, by including a water sampling mode in the operation mode of the other EDI device 1, i.e., at least one of the EDI devices 1, it is possible to reduce the amount of wastewater from the EDI device 1 while reducing the power consumption of the entire deionized water production system.

[0047] Furthermore, in the deionized water production system of the first embodiment, when at least one EDI device 1 is operating in the water sampling and regeneration mode, if the other EDI devices 1 are operating in the water sampling mode, it is also possible for one power supply device 2 to be shared by multiple EDI devices 1. For example, Fig. 6 shows a configuration example in which one power supply device 2 is shared by two EDI devices 11 and 12. Fig. 7 shows a configuration example of a deionized water production system in which a power supply device 21 is shared by two EDI devices 11 and 12, and a power supply device 22 is shared by two EDI devices 13 and 14.

[0048] In a configuration in which one power supply device 2 is shared by multiple EDI devices 1, a period in which DC voltage is not supplied to all EDI devices 1, i.e., a period in which all EDI devices 1 are operated in the water sampling mode, may be included in order to ensure the time required for switching the connection between the power supply device 2 and the EDI devices 1. In this case, a switching valve for switching the water flow path for the water to be treated for the EDI devices 11 and 12 may be used for the valve 7. FIGS. 1, 5, and 6 each show an example of a configuration in which a switching valve is used for the valve 7. The connection of the power supply device 2 to the multiple EDI devices 1 may be switched using a well-known switch (not shown) that can communicate with the control device 3 and can be operated by the control device 3.

[0049] In order to prevent the drawing from becoming complicated, Fig. 6 omits the control device 3, the water quality measuring device 5, the flow meter 6, and the communication paths between the control device 3 and the power supply device 2, the valve (switching valve) 7, and the water quality measuring device 5 and the flow meter 6. In addition to the components omitted in Fig. 6, Fig. 7 further omits the water flow paths to the concentration chamber (C) and the electrode chamber (D) including the valve (switching valve) 7, and the water flow paths from the concentration chamber (C) and the electrode chamber (D) including the drainage tank 8.

[0050] In this way, if one power supply device 2 is shared by multiple EDI devices 1, the number of power supply devices 2 provided in the deionized water production system can be reduced, thereby reducing the installation space for the power supply devices 2. Furthermore, reducing the number of power supply devices 2 also reduces the cost of the deionized water production system equipped with multiple EDI devices 1. (Second embodiment) FIG. 8 is a block diagram showing an example of the configuration of a deionized water producing system according to the second embodiment.

[0051] As shown in FIG. 8, the deionized water production system of the second embodiment has a configuration including a plurality of EDI devices 1 with water flow paths connected in series. In such a configuration, for example, raw water stored in a storage tank or the like is passed through the deionization chamber (D), the concentration chamber (C) and the electrode chamber (E) of the first-stage EDI device 1, and the treated water is passed through the deionization chamber (D), the concentration chamber (C) and the electrode chamber (E) of the second-stage EDI device 1, and the treated water of the second-stage EDI device 1 is taken out as the treated water of the deionized water production system. In the deionized water production system of the second embodiment, since the water flow paths of the plurality of EDI devices 1 are connected in series, the junction 4 shown in the first embodiment is not necessary. In addition, an opening and closing valve may be used as the valve 7 for controlling the supply and stop of water to the concentration chamber (C) and the electrode chamber (E) of the EDI device 1. Valves 7 (on-off valves) may be provided, for example, for each water flow path to the concentration chambers (C) and electrode chambers (E) of the EDI devices 11 and 12. In the deionized water producing system of the first embodiment, when a period is included in which multiple EDI devices 1 are simultaneously operated in the water sampling and regeneration mode, on-off valves may be provided for each water flow path for the water to be treated to the concentration chambers (C) and electrode chambers (E) of the EDI devices 11 and 12. The other configurations and operating methods are similar to those of the first embodiment, and therefore description thereof will be omitted.

[0052] In the deionized water production system of the second embodiment, the water flow paths of the multiple EDI devices 1 are connected in series, so that treated water from the EDI device 1 at each stage is supplied to the desalting chamber (D) of the subsequent EDI device 1. This improves the deionization performance of the entire deionized water production system, and produces treated water of better quality than the deionized water production system of the first embodiment, which has multiple EDI devices 1 with water flow paths connected in parallel.

[0053] In the deionized water production system of the second embodiment, the two EDI devices 11 and 12 are alternately operated in the water sampling mode and the water sampling and regeneration mode, and when one EDI device 1 is operating in the water sampling mode, the other EDI device 1 is operated in the water sampling and regeneration mode. That is, among the multiple EDI devices 1, at least two EDI devices 1 are alternately operated in the water sampling mode and the water sampling and regeneration mode, and the operation in the water sampling and regeneration mode in the multiple EDI devices 1 that alternately operate in the water sampling mode and the water sampling and regeneration mode is performed at least two different start and end timings. By controlling the operation mode of each EDI device 1 using the control device 3 in this way, it is possible to suppress fluctuations in the water quality of the treated water of the EDI device 1 at the subsequent stage, as in the first embodiment. Furthermore, by including the water sampling mode in the operation mode of each EDI device 1, it is possible to reduce the amount of wastewater from the EDI device 1 while reducing the power consumption of the entire deionized water production system.

[0054] Also, in the deionized water production system of the second embodiment, if the system has a configuration having a plurality of power supply devices 2 corresponding to each EDI device 1, it is possible to operate one of the EDI devices 1 (for example, the second-stage EDI device 1) always in the water sampling and regeneration mode. Even in this case, by including the water sampling mode in the operation mode of the other EDI device 1, i.e., at least one EDI device 1, it is possible to reduce the amount of wastewater from the EDI device 1 while reducing the power consumption of the entire deionized water production system. In a configuration in which the latter-stage EDI device 1 is always operated in the water sampling and regeneration mode, treated water of better water quality can be obtained from the deionized water production system than in a configuration in which the former-stage EDI device 1 is always operated in the water sampling and regeneration mode.

[0055] Furthermore, in the deionized water production system of the second embodiment, when at least one EDI device 1 is operating in the water sampling and regeneration mode, if the other EDI devices 1 are operating in the water sampling mode, it is possible to share one power supply device 2 among multiple EDI devices 1. For example, Fig. 9 shows a configuration example in which one power supply device 2 is shared by two EDI devices 11 and 12. Note that in Fig. 9, in order to prevent the drawing from becoming too complicated, the control device 3, water quality measuring device 5, flow meter 6, and communication paths between the control device 3 and the power supply device 2, valve (on-off valve) 7, water quality measuring device 5, and flow meter 6 are omitted.

[0056] In a configuration in which one power supply device 2 is shared by multiple EDI devices 1, in order to switch the supply destination of DC voltage to the multiple EDI devices 1, a period may be included in which DC voltage is not supplied to all EDI devices 1, i.e., a period in which all EDI devices 1 are operated in water sampling mode.

[0057] In this way, if one power supply device 2 is shared by multiple EDI devices 1, the number of power supply devices 2 provided in the deionized water production system can be reduced, thereby reducing the installation space for the power supply devices 2. Furthermore, reducing the number of power supply devices 2 also reduces the cost of the deionized water production system equipped with multiple EDI devices 1. EXAMPLES

[0058] Next, an embodiment of the present invention will be described. (Basic principle) This basic principle shows that when the ion exchanger of the EDI device 1 is regenerated, the efficiency of using power for regeneration is improved when the salt-form ratio of the ion exchanger is high. Here, a salt-form (chloride ion-form) ion exchange resin is prepared as an anion exchanger, and is filled in the desalting compartment of the EDI device 1 together with a regenerated cation exchange resin. Then, when pure water is passed through each of the desalting compartment, the concentration compartment, and the electrode compartment to regenerate the ion exchanger, the ratio of the current used to discharge chloride ions (regenerating the ion exchange resin) from the concentration of chloride ions discharged as concentrated water relative to the amount of electricity passed through the EDI device 1, that is, the current efficiency, is calculated and graphed. The graph also shows the transition of the water quality of the treated water based on the measurement results of the electrical conductivity. Note that only one EDI device 1 is operated.

[0059] 10 is a graph showing the change in current efficiency and electrical conductivity of treated water versus regeneration time of the ion exchanger. The lower the electrical conductivity, the better the water quality, since the lower the electrical conductivity is.

[0060] As shown in Figure 10, the current efficiency can be operated at a high efficiency of 90% or more for about 2 hours after the start of energizing the EDI device 1, but after that, it gradually decreases and reaches 50% or less after 10 hours. It can also be confirmed that when energizing the EDI device 1 is started, treated water with a conductivity of 1 μS / cm (0.1 mS / m) or less, which indicates better water quality as specified by the Japanese Industrial Standard (JIS K 0557), can be achieved in about 1 hour after the start of energizing.

[0061] It is therefore clear that operation with a higher salt-form ratio in the ion exchanger results in higher current efficiency of the EDI device 1. For this reason, if operation in the water collection and regeneration mode in which current is passed through the EDI device 1 is started before the water quality falls below the value required for the deionized water production system, and if current is stopped and operation is resumed in the water collection mode when the water quality has recovered to a certain extent, the EDI device 1 can be operated at a constantly high current efficiency while suppressing deterioration of the treated water quality. (First embodiment) In the first example, similarly to the first embodiment, the deionized water production system has two EDI devices 11 and 12 whose water flow paths are connected in parallel, and one power supply device 2 shared by the two EDI devices 11 and 12. Also, as shown in Fig. 6, when one EDI device 1 is operating in the water sampling mode, the other EDI device 1 is operating in the water sampling and regeneration mode, so that one power supply device 2 is shared by the two EDI devices 11 and 12.

[0062] The EDI device 1 was an EDI device (EDI-HF2-0500 stack) manufactured by Organo Corporation, and the water to be treated was constantly passed through the desalting chamber (D) at 750 L / h throughout the water collection and regeneration mode and the water collection mode. In addition, during operation in the water collection and regeneration mode, the EDI device 1 was set to a constant current operation of a direct current of 2.5 A. The desalting chamber (D) of the EDI device 1 was supplied with 4±0.2 μS / cm permeate that had passed through two stages of reverse osmosis membrane devices connected in series. The concentration chamber of the EDI device 1 was passed through 50 L / h of water to be treated only in the water collection and regeneration mode, and the electrode chamber was passed through 20 L / h of water to be treated only in the water collection and regeneration mode. These conditions are the same as those of the comparative example described below.

[0063] The operation mode of each EDI device 1 was switched using a timer, and during the period when the first EDI device 11 was operating in the water sampling mode, the second EDI device 11 was operating in the water sampling and regeneration mode, and during the period when the second EDI device 12 was operating in the water sampling mode, the first EDI device 11 was operating in the water sampling and regeneration mode. The operation time of the water sampling mode was 5 hours, and the operation time of the water sampling and regeneration mode was 3 hours, and the water sampling mode and the water sampling and regeneration mode were alternately and repeatedly operated. In this case, before and after the period when either the first EDI device 11 or the second EDI device 12 was operating in the water sampling and regeneration mode, there was a period (=1 hour) when both the first EDI device 11 and the second EDI device 12 were operating in the water sampling mode. An example of the transition of the operation mode of the first EDI device 11 and the second EDI device 12 in 24 hours (=1 day) is shown in FIG. 11.

[0064] An example of the change over time in the electrical conductivity of the water to be treated and the electrical conductivity of the treated water is shown in Figure 12, and an example of the change over time in the salt rejection rate of the treated water and the power consumption of the first EDI device 11 and the second EDI device 12 is shown in Figure 13. The smaller the electrical conductivity value, the cleaner the water quality. The salt rejection rate was calculated using the following formula. Desalination rate [%] = {1-(treated water conductivity ÷ untreated water conductivity)} x 100 In addition, the power consumption [W] was calculated by multiplying the output current [A] of the power supply device 2 by the voltage [V] when the EDI device 1 was in power-on operation. (Comparative Example) The deionized water production system of the comparative example has two EDI devices 11 and 12 with water flow paths connected in parallel, and two power supply devices 21 and 22 corresponding to the two EDI devices 11 and 12, as shown in Fig. 1. In this comparative example, the operation modes of the first EDI device 11 and the second EDI device 12 are switched using a timer, and the first EDI device 11 and the second EDI device 12 are simultaneously operated in the water sampling mode for 5 hours and in the water sampling and regeneration mode for 3 hours, so that the water sampling mode and the water sampling and regeneration mode are alternately repeated. The transition of the operation modes of the first EDI device 11 and the second EDI device 12 over 24 hours (= 1 day) is as shown in Fig. 14.

[0065] An example of the change in the electrical conductivity of the water to be treated and the electrical conductivity of the treated water at this time is shown in Figure 15, and an example of the change in the salt rejection rate of the treated water and the power consumption of the first EDI device 11 and the second EDI device 12 is shown in Figure 16. The calculation formulas for the salt rejection rate and the power consumption [W] are the same as those in the first embodiment. (Second Example) The second example, like the second embodiment, is an example in which a deionized water production system has two EDI devices 1 with water flow paths connected in series and two power supply devices 2 corresponding to the two EDI devices 1, and the first (front stage) EDI device 11 is operated alternately between a water sampling mode and a water sampling and regeneration mode, while the second (back stage) EDI device 12 is constantly operated in the water sampling and regeneration mode.

[0066] For the first EDI device 11, an EDI-HF2-0500 stack manufactured by Organo Corporation was operated under the same conditions as in the first embodiment. When the water quality (resistivity) of the treated water fell below 3 MΩ·cm, the water sampling and regeneration mode was implemented, and when the water quality of the treated water exceeded 5 MΩ·cm, the process of switching to the water sampling mode was repeated.

[0067] The second EDI device 12 was an EDI-XP2-0500 stack manufactured by Organo Corporation, and 680 L / h of water to be treated was constantly passed through the desalting compartment, 50 L / h through the concentration compartment, and 20 L / h through the electrode compartment. The power supply device 22 was operated at a constant current of 2.5 A.

[0068] 17 shows an example of the transition of the water quality (electrical conductivity) of the water to be treated, and the water quality (resistivity) of the water treated by the first EDI device 11 in the front stage and the second EDI device 12 in the rear stage. Resistivity is the reciprocal of electrical conductivity, and a larger value indicates cleaner water quality. (Comparison results) As shown in the comparative example, when the first EDI device 11 and the second EDI device 12 are simultaneously operated in the water sampling mode and the water sampling and regeneration mode, respectively, the water quality of the treated water fluctuates relatively greatly, as shown in Fig. 15. In contrast, when one EDI device 1 is operated in the water sampling and regeneration mode while the other EDI device 1 is operated in the water sampling mode, as in the first embodiment, the fluctuation in the water quality of the treated water is suppressed, as shown in Fig. 12.

[0069] Similarly, when the first EDI device 11 and the second EDI device 12 are simultaneously operated in the water sampling mode and the water sampling and regeneration mode, respectively, as in the comparative example, the salt rejection rate also fluctuates relatively greatly, as shown in Fig. 16. On the other hand, when one EDI device 1 is operated in the water sampling and regeneration mode during the period when the other EDI device 1 is operated in the water sampling mode, as in the first embodiment, the fluctuation in the salt rejection rate is also suppressed, as shown in Fig. 13.

[0070] Therefore, according to the deionized water production system of the present invention, it is possible to operate a plurality of EDI devices 1 at a constantly high current efficiency while suppressing fluctuations in the quality of the treated water.

[0071] Furthermore, by including the above-mentioned water collection mode in the operation of the deionized water production system, it is possible to reduce the power consumption of the EDI device 1 and the amount of wastewater discharged from the EDI device 1 as compared to conventional deionized water production systems. Therefore, in the deionized water production system of this embodiment, it is possible to reduce the power consumption and amount of wastewater discharged from the deionized water production system while suppressing deterioration of the water quality of the treated water. [Explanation of symbols]

[0072] 1, 11, 12, 13, 14 EDI equipment 2, 21, 22 Power supply 3. Control device 4 Junction 5, 51, 52 Water quality meter 6 Flow meter 7 Valve 8 Drain tank 9. Tank 31 Anode 32 Cathode 41, 45 Electrode chamber 42, 44 Concentration chamber 43, 46, 47 Desalination room 61, 63 Cation exchange membrane 62, 64 Anion exchange membrane 66 Intermediate ion exchange membrane

Claims

1. A method for operating a deionized water production system for producing deionized water from water to be treated using a plurality of electrodeionized water production apparatuses each having a water flow passage connected in parallel or in series, comprising the steps of: a water sampling and regeneration mode in which, while a first current is applied to the electrodeionization water production apparatus, the water to be treated is passed through the deionization chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; a water sampling mode in which the treated water is passed through a desalting chamber of the electrodeionization water production apparatus in an energized state in which a second current smaller than the first current is passed through the electrodeionization water production apparatus or in a non-energized state in which no current is passed through the electrodeionization water production apparatus, among the plurality of electrodeionized water production apparatuses, at least two of the electrodeionized water production apparatuses are alternately operated in the water collection mode and the water collection and regeneration mode, A method for operating a deionized water production system, in which operation in the water collection and regeneration mode in the multiple electrical deionized water production devices that operate alternately in the water collection mode and the water collection and regeneration mode is performed at least two different start and end timings.

2. A method for operating a deionized water production system for producing deionized water from water to be treated using a plurality of electrodeionized water production apparatuses each having a water flow passage connected in parallel or in series, comprising the steps of: a water sampling and regeneration mode in which, while a first current is applied to the electrodeionization water production apparatus, the water to be treated is passed through the deionization chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; a water sampling mode in which the treated water is passed through a desalting chamber of the electrodeionization water production apparatus in an energized state in which a second current smaller than the first current is passed through the electrodeionization water production apparatus or in a non-energized state in which no current is passed through the electrodeionization water production apparatus, among the plurality of electrodeionized water production apparatuses, at least one first electrodeionized water production apparatus is alternately operated in the water collection mode and the water collection and regeneration mode; A method of operating a deionized water production system, comprising operating a second electrodeionized water production apparatus different from the first electrodeionized water production apparatus in the water collection and regeneration mode.

3. a plurality of electrodeionized water producing devices each having a water flow passage connected in series, each of which produces deionized water from water to be treated; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current smaller than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least two of the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; having The control device includes: A deionized water production system, in which operation in the water collection and regeneration mode in the plurality of electrical deionized water production devices that alternately operate in the water collection mode and the water collection and regeneration mode is performed at least at two different start and end timings.

4. a plurality of electrodeionized water producing devices each having a water flow passage connected in series, each of which produces deionized water from water to be treated; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current less than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least one first electrodeionization water production apparatus among the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; having The control device includes: A deionized water production system, comprising: a second electrodeionized water production apparatus different from the first electrodeionized water production apparatus, the second electrodeionized water production apparatus being operated in the water collection and regeneration mode.

5. a plurality of electrodeionized water producing devices each having a water flow passage connected in parallel, each of which produces deionized water from water to be treated; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current smaller than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least two of the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; a confluence section for confluence the treated water from the plurality of electrodeionized water production apparatuses; having The control device includes: A deionized water production system, in which operation in the water collection and regeneration mode in the plurality of electrical deionized water production devices that alternately operate in the water collection mode and the water collection and regeneration mode is performed at least at two different start and end timings.

6. a plurality of electrodeionized water producing devices each having a water flow passage connected in parallel, each of which produces deionized water from water to be treated; a power supply device that applies a required DC voltage to the electrodeionized water production apparatus; a water sampling / regeneration mode in which, while energizing the electrodeionization water production apparatus with a first current, the water to be treated is passed through the desalting chamber to obtain the treated water, and water is passed through at least one of the concentration chamber and the electrode chamber of the electrodeionization water production apparatus; and a water sampling mode in which, in an energized state in which the electrodeionization water production apparatus is energized with a second current less than the first current, or in an energized state in which no current is passed through the electrodeionization water production apparatus, the water to be treated is passed through the desalting chamber of the electrodeionization water production apparatus to obtain treated water, and a control device which alternately operates at least one first electrodeionization water production apparatus among the plurality of electrodeionization water production apparatuses between the water sampling mode and the water sampling / regeneration mode; a confluence section for confluence the treated water from the plurality of electrodeionized water production apparatuses; having The control device includes: A deionized water production system, comprising: a second electrodeionized water production apparatus different from the first electrodeionized water production apparatus, the second electrodeionized water production apparatus being operated in the water collection and regeneration mode.

7. 6. The deionized water producing system according to claim 3, wherein the power supply device is shared by a plurality of the electrodeionized water producing apparatuses.

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