JP2023112836A - Pure water manufacturing equipment and method of operating pure water manufacturing equipment - Google Patents

Abstract

To provide a pure water manufacturing equipment and its operation method capable of producing pure water with stable water quality even if the treated water quality of the reverse osmosis membrane device fluctuates in a pure water manufacturing device that has a reverse osmosis membrane device and an electro-deionization device and supplies treated water at high pH to the reverse osmosis membrane device.SOLUTION: A primary pure water production system has a reverse osmosis membrane device, an ultraviolet oxidation device, an electro-deionization device 8, and a feed water pump that supplies feed water to the electro-deionization device 8. In this primary pure water manufacturing device, the treated water W4 treated by the ultraviolet oxidation device is passed through a demineralization chamber 25 of the electro-deionizer 8 to produce demineralized water W5. At this time, the demineralized water W5 is separated as the supply water (electrode water) for a concentration chamber 26 and electrode chambers (anode chamber 27 and cathode chamber 28) of the electrode deionizer 8, and supplied in the reverse direction of the water flow direction in the demineralization chamber 25. When the conductivity of the treated water in the reverse osmosis membrane device 5 becomes 0.3 mS/m or higher, the flow rate of the treated water W4 to the desalination chamber 25 is controlled to decrease to less than 50 to 100%.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a method of operating a pure water production apparatus, and more particularly to a pure water production apparatus constituting an ultrapure water production system for producing ultrapure water used in the electronics industry such as semiconductors and liquid crystals, and a method of operating the same.

Conventionally, the ultrapure water used in the electronic industry field such as semiconductors is an ultrapure It is produced by treating raw water in a water production system.

For example, as shown in FIG. 1, an ultrapure water production system 1 is composed of three stages of devices: a pretreatment device 2 , a primary pure water production device (pure water production device) 3 , and a subsystem 4 . In the pretreatment device 2 of such an ultrapure water production system 1, the raw water W is subjected to pretreatment such as filtration, coagulation sedimentation, and microfiltration membranes, mainly removing suspended solids.

The primary pure water production device 3 includes a reverse osmosis membrane device 5 for treating the pretreated water W1, an ultraviolet oxidation device 6, an electrodeionization device 8, and a water supply pump 7 for supplying water to the electrodeionization device 8. have The primary pure water production apparatus 3 removes most of the electrolytes, fine particles, viable bacteria, etc. from the pretreated water W1 and decomposes organic matter to obtain primary pure water (pure water) W2.

The sub-system 4 includes a sub-tank 10, a supply pump 11, an ultraviolet oxidation device 6, a non-regenerative mixed-bed ion exchange device 13, and an ultrafiltration membrane (UF membrane) 14. Membrane) 14 is configured to flow back to sub-tank 10 via use point 15 . This subsystem 4 oxidatively decomposes trace amounts of organic substances (TOC components) contained in the primary pure water W2 produced by the primary pure water producing apparatus 3 to produce carbonate ions, organic acids, anionic substances, and metal ions. and cationic substances are removed, and finally fine particles are removed by an ultrafiltration (UF) membrane 14 to obtain ultrapure water W3, which is supplied to a point of use 15, and unused ultrapure water W3 is sent to a subsystem Reflux to the previous stage of 4.

In the primary pure water production device 3 of the ultrapure water production system 1 as described above, for the purpose of improving the treatment performance of the reverse osmosis membrane device 5, alkali such as NaOH is injected into the water supply of the reverse osmosis membrane device to achieve a pH of 8.5. As described above, treatment is performed by promoting ionization of various components.

However, when alkali is injected into the water supply of the reverse osmosis membrane device 5, the water quality (electrical conductivity, etc.) of the water supply to the subsequent electrodeionization device 8 increases, and the load on the electrodeionization device 8 increases. There is a problem. In particular, when the quality of the treated water from the reverse osmosis membrane device 5 further deteriorates due to fluctuations in the quality of the raw water or a change in the recovery rate of the reverse osmosis membrane device 5, the water (demineralized water) treated by the electrodeionization device 8 There is a problem that the water quality is also lowered, and this may make it impossible to obtain the pure water W2 having the desired quality.

The present invention has been made in view of the above problems. It is an object of the present invention to provide a pure water production apparatus capable of producing pure water with stable water quality even when the quality of water treated by the apparatus fluctuates, and to provide a method of operating the same.

In view of the above object, the present invention firstly comprises a reverse osmosis membrane device and an electrodeionization device in this order, and supplies treated water from the reverse osmosis membrane device to the desalination chamber of the electrodeionization device. A water purifying apparatus in which part of the treated water that has passed through the deionization chambers is passed through a concentration chamber in a direction opposite to the deionization chambers, wherein the conductivity or specific resistance value of the treated water of the reverse osmosis membrane device and a control means for controlling the amount of water supplied to the deionization chamber of the electrodeionization apparatus based on the measurement value of the measurement means, wherein the control means measures the measurement value of the measurement means The conductivity of the treated water of the reverse osmosis membrane device is 0 when the flow rate to the deionization chamber is 100% when the conductivity of the treated water of the reverse osmosis device is less than 0.3 mS / m based on Provided is a pure water production apparatus which is controlled to reduce the flow rate of the demineralization chamber to less than 50 to less than 100% when it reaches 3 mS/m or more (Invention 1).

According to this invention (Invention 1), it is possible to suppress deterioration of the water quality of the treated water of the electrodeionization apparatus. It is considered that this is due to the following reasons. That is, when the water quality of the treated water of the reverse osmosis membrane device deteriorates, the electrodeionization device is overloaded, and the water quality of the treated water (demineralized water) of the electrodeionization device tends to deteriorate. When the conductivity of the treated water in the device reaches 0.3 mS/m or more, it is conceivable to control the deionization chamber flow rate to decrease in order to reduce the load on the electrodeionization device. The ions adsorbed on the ion-exchange resin move to the concentrating compartment, and the ion concentration in the concentrating compartment increases, which increases the back diffusion of ions from the concentrating compartment to the demineralization compartment, resulting in a decrease in the quality of the treated water. do. Therefore, by passing a portion of the treated water that has passed through the desalting chambers of the electrodeionization apparatus through the concentrating chambers in the opposite direction to the desalting chambers, the ion concentration in the lower portions of the concentrating chambers can be maintained low, thereby improving the electrodeionization. It is possible to suppress the deterioration of the water quality of the treated water of the ion device.

In the above invention (invention 1), it is preferable to have an ultraviolet oxidation device between the reverse osmosis membrane device and the electrodeionization device (invention 2).

According to this invention (invention 2), by decomposing the TOC remaining in the reverse osmosis membrane-treated water with the ultraviolet oxidation device, the quality of the pure water obtained can be further improved.

In the above inventions (Inventions 1 and 2), it is preferable that the electrodeionization apparatus causes part of the treated water in the deionization chamber to flow through the electrode chambers of the electrodeionization apparatus (Invention 3).

According to this invention (invention 3), when the treated water treated by the reverse osmosis membrane device or the ultraviolet oxidation device flows through the electrode chamber of the electrodeionization device, the electrode of the electrodeionization device and the ion exchanger in the electrode chamber deterioration and scale formation are accelerated. Therefore, by passing part of the treated water in the desalting chamber of the electrodeionization apparatus through the electrode chamber of the electrodeionization apparatus, the deterioration and scale formation of the electrodes and the ion exchanger in the electrode chamber of the electrodeionization apparatus can be prevented. can be suppressed, and the electrodeionization apparatus can be stably operated for a long period of time.

Secondly, according to the present invention, a reverse osmosis membrane device and an electrodeionization device are provided in this order, water having a pH of 8.5 or higher is supplied to the reverse osmosis membrane device, In the method for operating a water purifying apparatus in which the treated water of the reverse osmosis membrane device is passed and part of the treated water that has passed through the desalting chambers is passed through the concentrating chambers in a direction opposite to the desalting chambers, The conductivity of the treated water of the reverse osmosis membrane device is 0.3 mS when the flow rate to the desalination chamber is 100% when the conductivity of the treated water of the reverse osmosis device is less than 0.3 mS / m. /m or more, there is provided a method of operating a water purifying apparatus for controlling the desalting chamber flow rate to be reduced to less than 50 to less than 100% (Invention 4).

According to this invention (Invention 4), when the water quality of the treated water of the reverse osmosis membrane device deteriorates, the electrodeionization device is overloaded, and the water quality of the treated water of the electrodeionization device tends to deteriorate. , When the conductivity of the treated water of the reverse osmosis membrane device becomes 0.3 mS / m or more, the desalination chamber flow rate is controlled to decrease to less than 50 to 100%, and the water passes through the desalination chamber of the electrodeionization device. By passing part of the treated water through the concentrating chambers in the opposite direction to the deionization chambers, it is possible to suppress deterioration in water quality of the treated water of the electrodeionization apparatus.

In the above invention (invention 4), it is preferable that the water purification device has an ultraviolet oxidation device between the reverse osmosis membrane device and the electrodeionization device (invention 5).

According to this invention (invention 5), by decomposing the TOC remaining in the reverse osmosis membrane-treated water with the ultraviolet oxidation device, the quality of the pure water obtained can be further improved.

In the above inventions (Inventions 4 and 5), it is preferable that part of the treated water in the deionization chamber of the electrodeionization apparatus is passed through the electrode chambers of the electrodeionization apparatus (Invention 6).

According to this invention (invention 6), when the treated water treated by the reverse osmosis membrane device or the ultraviolet oxidation device is passed through the electrode chamber of the electrodeionization device, the electrode of the electrodeionization device and the ion exchanger in the electrode chamber deterioration and scale formation are accelerated. Therefore, by passing part of the treated water in the desalting chamber of the electrodeionization apparatus through the electrode chamber of the electrodeionization apparatus, the deterioration and scale formation of the electrodes and the ion exchanger in the electrode chamber of the electrodeionization apparatus can be prevented. can be suppressed, and the electrodeionization apparatus can be stably operated for a long period of time.

According to the pure water production apparatus of the present invention, part of the treated water that has passed through the deionization chambers of the electrodeionization device is passed through the concentration chambers in the opposite direction to the deionization chambers, and the water is treated by the reverse osmosis membrane device. When the electrical conductivity of water reaches 0.3 mS/m or more, the demineralization chamber flow rate can be controlled to be reduced to less than 50% to less than 100%. It becomes possible to manufacture stably.

1 is a flow chart showing an ultrapure water production system equipped with a primary pure water production device to which a pure water production device operating method according to an embodiment of the present invention can be applied; FIG. It is a schematic diagram showing an example of the structure of the electrodeionization apparatus in the operation method of the pure water production apparatus according to the embodiment. 1 is a schematic diagram showing the structure of an electrodeionization apparatus used in Example 1. FIG. 5 is a graph showing changes in resistivity of treated water of the electrodeionization apparatus in the operation method of the pure water production apparatus of Example 1. FIG. 1 is a schematic diagram showing the structure of an electrodeionization apparatus used in Comparative Example 1. FIG. 5 is a graph showing changes in resistivity of treated water of the electrodeionization apparatus in the operating method of the pure water production apparatus of Comparative Example 1. FIG. 2 is a schematic diagram showing a test apparatus using the electrodeionization apparatus of Example 2. FIG. 5 is a graph showing changes in resistivity of treated water of the electrodeionization apparatus in Example 2. FIG. 3 is a schematic diagram showing a test apparatus using the electrodeionization apparatus of Comparative Example 2. FIG. 7 is a graph showing changes in resistivity of treated water of an electrodeionization apparatus in Comparative Example 2. FIG.

A method of operating a pure water production apparatus according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[Pure water production equipment]
FIG. 1 is a flow diagram showing an ultrapure water production system to which the operation method of the pure water production apparatus of the present embodiment can be applied. ) and a control means (not shown) for controlling the amount of water supplied to the deionization chamber of the electrodeionization apparatus 8 based on the measured value of the measurement means, the apparatus is the same as the conventional example described above. , the detailed description thereof will be omitted. In the primary pure water production device 3 as the pure water production device of this ultrapure water production system 1 , the water treated by the ultraviolet oxidation device 6 is passed through the electrodeionization device 8 .

(Electrodeionization device)
In FIG. 2, the electrodeionization apparatus 8 alternately arranges a plurality of anion exchange membranes 23 and cation exchange membranes 24 between electrodes (anode 21 and cathode 22) to alternately demineralize compartments 25 and concentrate compartments 26. An anode chamber 27 and a cathode chamber 28 are formed on both sides, and an ion exchanger (anion exchanger and cation exchanger) made of ion exchange resin, ion exchange fiber, graft exchanger, or the like is contained in the desalting chamber 25. body) is mixed or filled in multiple layers. The concentrating compartment 26, the anode compartment 27 and the cathode compartment 28 are similarly filled with ion exchangers.

In the electrodeionization apparatus 8, water to be treated W4 treated by the ultraviolet oxidation apparatus 6 is passed through the demineralization chamber 25 to take out the demineralized water W5. desalted water W5 is introduced into the concentrating chamber 26 from the side near the outlet of the desalted water W5 of the desalting chamber 25, and desalting is performed. Demineralized water W5 is introduced into the concentrating chamber 26 from the side near the entrance of the raw water (to-be-treated water W4) of the chamber 25, that is, from the direction opposite to the direction of flow of the to-be-treated water W4 in the demineralizing chamber 25, to obtain concentrated water. It is configured to eject W6. On the other hand, the desalted water W5 is divided into the anode chamber 27 and the cathode chamber 28 and circulated as electrode water, and discharged as anode discharge water W7 and cathode discharge water W8, respectively.

[Method of operating pure water production device]
A method of operating the primary pure water production apparatus 3 having the above-described configuration will be described with reference to FIGS. 1 and 2. FIG. First, the raw water W is pretreated by the pretreatment device 2, and the pretreated water W1 is supplied to the primary pure water production device 3. Alkali is injected to make pH 8.5 or higher. A reverse osmosis membrane (RO) device 5 removes ionic and colloidal TOC in addition to salts and ionizes and removes carbon dioxide gas. Then, the remaining organic matter is decomposed in the ultraviolet oxidation device 6 . The water to be treated W4 treated by the ultraviolet oxidation device 6 is passed through an electrodeionization device 8 to remove ionic impurities caused by organic matter decomposed by UV oxidation to produce primary pure water W2.

Specifically, as shown in FIG. 2, the treated water from the ultraviolet oxidation device 6 is supplied to the demineralization chamber 25 of the electrodeionization device 8 as the water to be treated W4. Then, the desalted water W5 that has passed through the desalting chamber 25 is collected and supplied to the concentrating chamber 26 and the electrode chambers (anode chamber 27 and cathode chamber 28). When the treated water (water to be treated W4) of the ultraviolet oxidation device 6 flows through the concentrating chamber 26 and the electrode chambers (anode chamber 27 and cathode chamber 28) of the electrodeionization device 8 as in the conventional case, the water to be treated W4 is saturated. Since it also contains hydrogen oxide, the deterioration of the electrodes 21 and 22 of the electrodeionization apparatus 8, the ion exchangers in the concentration chamber 26, the anode chamber 27, or the cathode chamber 28 is accelerated. Therefore, by supplying demineralized water W5 to the concentration chamber 26, the anode chamber 27 and the cathode chamber 28, the electrodes 21 and 22 of the electrodeionization apparatus 8, the ion exchangers in the concentration chamber 26, the anode chamber 27 and the cathode chamber 28 can be suppressed, the operating voltage of the electrodeionization device 8 can be suppressed, and the service life can be lengthened.

In particular, in the electrodeionization apparatus 8, part of the desalted water W5 that has passed through the desalting chambers 25 is used as the water to be concentrated, and is passed through the concentrating chambers 26 in a direction opposite to the water flow direction of the desalting chambers 25. Since the water is passed through and the concentrated water W6 is discharged from the concentration chamber 26 to the outside of the system, the concentration of ions in the water to be concentrated in the concentration chamber 26 becomes lower toward the take-out side of the deionization chamber 25, and the deionization chamber is caused by concentration diffusion. Since the effect on 25 is reduced, the removal rate of weak ions such as boron is improved.

In this embodiment, in the process of producing the primary pure water W2 as described above, the conductivity of the treated water of the reverse osmosis membrane device 5 is measured by measuring means (not shown), and the conductivity of the treated water of the reverse osmosis membrane device 5 is is less than 0.3 mS/m as a normal state, and the amount of water supplied to the deionization chamber 25 of the electrodeionization apparatus 8 at that time is set as 100%. Then, when the conductivity of the treated water of the reverse osmosis membrane device 5 reaches 0.3 mS/m or more, the flow rate of the treated water W4 to the demineralization chamber 25 is controlled to be reduced to 50 to less than 100%. Even if the flow rate of the water W4 to be treated is set to 50% or less, the quality of the desalted water W5 cannot be stabilized further, and the production amount of the primary pure water W2 decreases. The control of the flow rate of the water W4 to be treated to the demineralization chamber 25 is generally performed by varying it continuously or stepwise according to the value of the conductivity of the water W4 to be treated in the reverse osmosis membrane device 5. However, it may be set as a fixed value. The supply amount of the water to be treated W4 to the desalting chamber 25 as described above can be determined, for example, by providing a branch pipe in the supply path of the water to be treated W4 to the desalting chamber 25 of the electrodeionization apparatus 8, The amount of water to be treated W4 supplied to the demineralization chamber 25 may be controlled by increasing or decreasing the flow rate of the water to be treated W4.

Such control is performed for the following reasons. That is, when the water quality of the treated water of the reverse osmosis membrane device 8 deteriorates, the electrodeionization device 8 that processes it is overloaded, and the treated water (demineralized water) in the desalination chamber 25 of the electrodeionization device 8 There is a possibility of causing deterioration of the water quality of W5. Therefore, when the conductivity of the treated water of the reverse osmosis membrane device becomes 0.3 mS/m or more, the flow rate of the deionization chamber 25 is controlled to decrease in order to reduce the load on the electrodeionization device 8 . In this case, when the water to be treated W4 supplied to the desalting chambers 25 and the concentrated water supplied to the concentrating chambers 26 are passed in the same direction, the ions adsorbed on the ion exchange resin in the desalting chambers 25 are removed from the concentrating chambers. 26, the concentration of ions in the concentration compartment 26 increases, the reverse diffusion of ions from the concentration compartment 26 to the demineralization compartment 25 increases, and the water quality of the treated water (demineralized water) W5 deteriorates. In contrast, in the present embodiment, part of the treated water (demineralized water) W5 that has passed through the demineralization chambers 25 of the electrodeionization apparatus 8 is passed through the concentrating chambers 26 in the opposite direction to the demineralization chambers 25. As a result, the ion concentration in the lower portion of the concentrating chamber 26 can be maintained low, so that deterioration of water quality of the treated water (demineralized water) W5 of the electrodeionization apparatus 8 can be suppressed.

After the primary pure water W2 is produced in this manner, it is stored in the sub-tank 10, and the primary pure water W2 is supplied by the supply pump 11 and processed. In the subsystem 4 , treatment is performed by an ultraviolet oxidation device 6 , a non-regenerative mixed-bed ion exchange device 13 and an ultrafiltration membrane 14 . In the ultraviolet oxidizer 6, the TOC is decomposed into organic acids and further down to the level of CO ₂ by ultraviolet rays with a wavelength of 185 nm emitted from a UV lamp. The decomposed organic acid and CO ₂ are removed in the non-regenerative mixed-bed ion exchange unit 13 in the latter stage. The ultrafiltration membrane 14 removes microparticles, and also removes particles flowing out of the non-regenerative mixed-bed ion exchange device 13, so that secondary pure water (ultrapure water) W3 can be produced. After the ultrapure water W3 is supplied to the point of use 15, the unused portion is returned to the sub-tank 10, whereby the ultrapure water production system 1 can be operated.

Although the present invention has been described above based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications can be made. For example, as the ultrapure water production system 1 applicable in the present invention, if the primary pure water production device 3 is configured to treat the treated water of the reverse osmosis membrane device 5 with the electrodeionization device 8, the ultraviolet oxidation device 6 , and can be applied to various other configurations. Also, the configuration of the subsystem 4 is not particularly limited, and various general-purpose configurations can be applied.

The present invention will be described in more detail based on the following specific examples.

[Example 1]
The test electrodeionization apparatus having the structure shown in FIG. Constant current operation was used. Then, NaOH was added to the water supply (water to be treated) to adjust the pH to 10.5, and then the resistivity of the treated water was measured. The results are shown in FIG. The initial conductivity of the feed water was 0.25 mS/m, and the conductivity of the feed water after adding NaOH was 6.8 mS/m.

[Comparative Example 1]
In the same manner as in Example 1, except that the test electrodeionization apparatus was configured such that the water to be treated W4 was supplied in parallel to the desalting chamber 25 and the concentrating chamber 26 as shown in FIG. was measured. The results are shown in FIG.

As is clear from FIGS. 4 and 6, in Example 1, the addition of NaOH hardly changed the resistivity of the treated water (demineralized water) of the electrodeionization apparatus. This is probably because the diffusion of ions from the concentration chamber 26 to the demineralization chamber 25 was prevented by passing the treated water (demineralized water) through the concentration chamber 26 . In contrast, in Comparative Example 1, addition of NaOH significantly lowered the resistivity of the treated water (demineralized water) of the electrodeionization apparatus. It is believed that this is because the concentration of Na in the concentrating compartments 26 increased, causing ions to diffuse from the concentrating compartments 26 to the desalting compartments.

[Example 2]
A test apparatus for controlling the electrodeionization apparatus shown in FIG. 7 was prepared. This test apparatus 51 includes an ultrapure water (UPW) channel 52, an electrodeionization device 53, a demineralized water channel 54, a concentrated water channel 55, and a branch pipe 56 of the ultrapure water (UPW) channel 52. A flow meter 58A and a resistivity meter 59 are connected to the desalted water flow path 54, respectively. A flow meter 58B and a conductivity meter 57A are connected to the concentrated water flow path 55, respectively. Furthermore, a flow meter 58C and a conductivity meter 57B are connected to the branch pipe 56, respectively. In the ultrapure water channel 52, a sodium silicate (Na ₂ SiO ₃ ) solution tank 61 as a silica (SiO ₂ ) source, a sodium carbonate (NaHCO ₃ ) solution tank 62, and a boron source of boron hydroxide (B( OH) ₃ ) and a solution tank 63 are connected via chemical pumps 61A, 62A and 63A, respectively. IP-LXMX4-4 (manufactured by Evoqua) was used as the electrodeionization device 53, and the treated water (demineralized water) from the demineralization chamber was passed through the concentrating chamber in the opposite direction.

In the test apparatus as described above, the electrodeionization device 53 is operated at a constant current under the water supply conditions shown in Table 4 and the water supply conditions shown in Table 5, and the deionization chamber flow rate is set to 100% ( 4.7 L/min) to 60% (2.4 L/min) and again to 100% (4.7 L/min), the resistivity of the treated water (demineralized water) was measured. The results are shown in FIG.

[Comparative Example 2]
A test apparatus for controlling the electrodeionization apparatus shown in FIG. 9 was prepared. This test apparatus 51A has basically the same configuration as the test apparatus of the second embodiment described above, except that it has a structure in which water is supplied in parallel to the desalting chamber and the concentration chamber of the electrodeionization device 53 .

In this test apparatus, the electrodeionization device 53 is operated at a constant current under the water supply conditions shown in Table 4 and the water supply conditions shown in Table 5, and the deionization chamber flow rate is set to 100% (4.7 L). /min) to 60% (2.4 L/min) and again to 100% (4.7 L/min), the resistivity of the treated water (demineralized water) was measured. The results are shown in FIG.

As is clear from FIGS. 8 and 10, according to Example 2, when the flow rate to the demineralization chamber was reduced to 60%, the resistivity of the treated water increased and the water quality improved. It can be seen that there is almost no deterioration in water quality. In contrast, in Comparative Example 2, the resistivity of the treated water did not increase by reducing the flow rate to the demineralization chamber, and the resistivity decreased temporarily immediately after the flow rate decreased. It can be seen that water quality deterioration occurs.

This is because, in Comparative Example 2, when the flow rate in the deionization chamber decreases, the adsorption band in the deionization chamber shortens. Then, the ions adsorbed on the ion exchange resin in the desalting compartment move to the concentrating compartment. Therefore, the concentration of ions in the concentrating compartment increases. This increases the back diffusion of ions from the concentrating compartments to the desalting compartments and reduces the resistivity of the treated water. On the other hand, in Example 2, since the treated water is counter-flowed, the ion concentration in the lower part of the concentration chamber is kept low by passing the treated water through the concentration chamber. It is thought that there was not.

1 Ultrapure water production system 2 Pretreatment device 3 Primary pure water production device (pure water production device)
4 Subsystem 5 Reverse osmosis membrane device 6 Ultraviolet oxidation device 7 Water supply pump 8 Electrodeionization device 10 Subtank 11 Supply pump 12 Ultraviolet oxidation device 13 Non-regenerative mixed-bed ion exchange device 14 Ultrafiltration membrane (UF membrane)
15 point of use 21 anode (electrode)
22 cathode (electrode)
23 Anion exchange membrane 24 Cation exchange membrane 25 Demineralization compartment 26 Concentration compartment 27 Anode compartment 28 Cathode compartment W Raw water W1 Pretreated water W2 Primary pure water (pure water)
W3 Ultrapure water W4 Water to be treated W5 Demineralized water W6 Concentrated water W7 Anode discharge water W8 Cathode discharge water

Claims (6)

A reverse osmosis membrane device and an electrodeionization device are provided in this order, and the treated water of the reverse osmosis membrane device is passed through the desalination chamber of the electrodeionization device and part of the treated water that has passed through the desalination chamber. is passed through the concentrating chamber in a direction opposite to the desalting chamber,
measuring means for measuring the conductivity or specific resistance value of the treated water of the reverse osmosis membrane device; and control means for controlling the amount of water supplied to the desalting chamber of the electrodeionization device based on the measured value of the measuring means. has
The control means controls the reverse A water purifying apparatus, wherein the demineralization chamber flow rate is controlled to be reduced to less than 50 to less than 100% when the conductivity of treated water in the osmosis membrane apparatus reaches 0.3 mS/m or more. 2. The pure water production system according to claim 1, further comprising an ultraviolet oxidation device between said reverse osmosis membrane device and said electrodeionization device. 3. The pure water production apparatus according to claim 1, wherein said electrodeionization device passes a part of the treated water in the deionization chamber to the electrode chamber of said electrodeionization device. A reverse osmosis membrane device and an electrodeionization device are provided in this order, water having a pH of 8.5 or higher is supplied to the reverse osmosis membrane device, and treated water from the reverse osmosis membrane device is supplied to a desalination chamber of the electrodeionization device. A method of operating a water purifying apparatus in which part of the treated water that has passed through the desalting chambers is passed through the concentrating chambers in a direction opposite to that of the desalting chambers, the method comprising:
Assuming that the flow rate to the desalting chamber is 100% when the conductivity of the treated water of the reverse osmosis membrane device is less than 0.3 mS/m, the conductivity of the treated water of the reverse osmosis membrane device is 0.3 mS/m. A method of operating a pure water production apparatus, wherein the demineralization chamber flow rate is controlled to be reduced to less than 50% to less than 100% when the flow rate is 3 mS/m or more. 5. The method of operating a water purifier according to claim 4, wherein said water purifier has an ultraviolet oxidation device between said reverse osmosis membrane device and said electrodeionization device. 6. The method of operating a pure water production apparatus according to claim 4, wherein a portion of the treated water in the desalting chamber of said electrodeionization device is passed through the electrode chamber of said electrodeionization device.

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