JP2024131100A - Water treatment system and method for operating same - Google Patents

Abstract

To maintain good water quality of circulating pure water while suppressing wasteful consumption of water. [Solution] The water treatment system 1 includes treatment means 13, 14, a water supply line L2 that supplies water to be treated to the treatment means 13, 14, a pure water line L5 that circulates the pure water from the treatment means 13, 14, a pure water tank 21 that stores the pure water from the pure water line L5, a circulation line L10 that circulates the pure water in the pure water tank 21, a return line L13 that branches off from the circulation line L10 and is connected to the water supply line L2, a pure water quality detection means 24 provided in the circulation line L10, and a control means 25 that executes a water quality restoration process in which, when it is determined based on the detection result of the water quality detection means 24 that the quality of the pure water circulating through the circulation line L10 does not meet a predetermined water quality, at least a portion of the circulating pure water is returned from the return line L13 to the water supply line L2, treated by the treatment means 13, 14, and then stored in the pure water tank 21 through the pure water line L5. [Selected Figure] Figure 1

Description

The present invention relates to a water treatment system and an operating method thereof.

A pure water supplying device is known as a device for supplying pure water (such as purified water or water for injection) used in pharmaceutical manufacturing to a point of use, in which the pure water in a pure water tank is circulated along a circulation line and a portion of the water is supplied to the point of use as needed (see, for example, Patent Documents 1 and 2). In such a pure water supplying device, the pure water is constantly circulated to prevent the growth of live bacteria due to stagnation, regardless of the presence or absence of demand at the point of use.

JP 2006-095479 A JP 2017-196587 A

The pure water that circulates through the circulation line and is returned to the pure water tank is usually sprayed into the pure water tank using a shower ball. During this process, the pure water comes into contact with air that flows into the pure water tank through the vent filter, and carbon dioxide in the air can dissolve in the pure water. This can increase the conductivity of the pure water, which may result in the water not meeting the water quality standards required at the point of use. In order to restore water quality that has deteriorated in this way, a method is often used in which a portion of the circulating pure water is discharged to the outside and new pure water is replenished from the pure water production device accordingly. However, this method of restoring water quality leads to wasteful consumption of water and is undesirable from the perspective of water conservation.

The object of the present invention is to provide a water treatment system and an operating method thereof that maintains good water quality of the circulating pure water while suppressing wasteful water consumption.

In order to achieve the above-mentioned object, the water treatment system of the present invention has a treatment means including at least one of a degassing device and an ion removal device, a water supply line that supplies the water to be treated to the treatment means, a pure water line that circulates the pure water obtained by the treatment means, a pure water tank that stores the pure water that has circulated through the pure water line, a circulation line that circulates the pure water in the pure water tank, a return line that branches off from the circulation line and is connected to the water supply line, a water quality detection means that is provided in the circulation line and detects the water quality of the pure water circulating through the circulation line, and a control means that, when it is determined based on the detection result of the water quality detection means that the water quality of the pure water circulating through the circulation line does not satisfy a predetermined water quality, executes a water quality restoration process in which at least a portion of the pure water circulating through the circulation line is returned from the return line to the water supply line, treated by the treatment means, and then stored in the pure water tank through the pure water line.

The method of operating the water treatment system of the present invention is a method of operating a water treatment system having a treatment means including at least one of a degassing device and an ion removal device, a water supply line that supplies the water to be treated to the treatment means, a pure water line that circulates the pure water obtained by the treatment means, and a pure water tank that stores the pure water that has circulated through the pure water line, and includes the steps of circulating the pure water stored in the pure water tank along the circulation line, detecting the water quality of the pure water circulating through the circulation line and determining whether the detected water quality meets a predetermined water quality, and, if the detected water quality does not meet the predetermined water quality, supplying at least a portion of the pure water circulating through the circulation line to the treatment means through a reflux line branched from the circulation line and connected to the water supply line, for treatment, and then storing the pure water in the pure water tank through the pure water line.

The present invention makes it possible to maintain good water quality of the circulating pure water while suppressing wasteful consumption of water.

1 is a schematic configuration diagram of a water treatment system according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. In this specification, purified water means ordinary water that has been purified by distillation, ion exchange, reverse osmosis, ultrafiltration, or a combination of these, and water for injection means purified water that has been sterilized and conforms to pyrogen (endotoxin) tests and sterility tests. Examples of such purified water and water for injection include those specified in the Japanese Pharmacopoeia.

Figure 1 is a schematic diagram of a water treatment system according to one embodiment of the present invention. Note that the configuration of the water treatment system shown in the figure is merely an example and does not limit the present invention, and it goes without saying that it can be modified as appropriate depending on the purpose, application, and required performance of the system.

The water treatment system 1 is composed of a pure water production apparatus 2 and a pure water supply apparatus 3. The pure water production apparatus 2 produces pure water by sequentially treating the water to be treated (raw water), and the pure water supply apparatus 3 circulates and holds the pure water produced by the pure water production apparatus 2, and supplies a portion of it to a point of use 4 as needed.

The pure water production system 2 has a raw water tank 11, a membrane separation device 12, a deaeration device 13, and an electrically deionized water production system (hereinafter also referred to as an "EDI device") 14.

The membrane separation device 12 is a device that removes impurities contained in raw water such as city water to generate treated water, and has a reverse osmosis membrane (RO membrane) that separates the raw water supplied from the raw water tank 11 into concentrated water containing impurities and permeate water (treated water) from which the impurities have been removed. The separation membrane of the membrane separation device 12 is not limited to an RO membrane, and for example, a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), a nanofiltration membrane (NF membrane), etc. can be used. However, from the viewpoint of improving the quality of the treated water, it is preferable to use an NF membrane or an RO membrane, and it is more preferable to use an RO membrane. The membrane separation device 12 may have multiple RO membranes, which may be connected in series, in parallel, or in a combination of series and parallel. Here, "connected in series" means that the treated water is treated sequentially by multiple RO membranes, and in two adjacent RO membranes, the permeate separated by the upstream RO membrane is supplied to the downstream RO membrane as the treated water. In this case, the permeate separated by the upstream RO membrane is further treated by the downstream RO membrane, resulting in treated water of better quality.

The membrane separation device 12 is connected to a raw water line L1 that supplies raw water to the membrane separation device 12, a permeate line L2 that circulates the permeate from the membrane separation device 12, and an RO concentrated water line L3 that circulates concentrated water (hereinafter also referred to as "RO concentrated water") from the membrane separation device 12. The raw water line L1 is connected to a raw water tank 11 on its upstream side. The permeate line L2 is connected to an EDI device 14 on its downstream side. In addition, a degassing device 13 is provided in the permeate line L2. Therefore, the permeate line L2 also functions as a water supply line that supplies permeate as the water to be treated to the degassing device 13 and the EDI device 14. In addition, the RO concentrated water line L3 is connected to the raw water tank 11 on its downstream side. A raw water supply line L4 is connected to the raw water tank 11, and raw water is supplied as needed.

The raw water line L1 is provided with a pressure pump 15. The pressure pump 15 has the function of supplying the raw water stored in the raw water tank 11 to the membrane separation device 12, and the rotation speed of the pressure pump 15 is controlled by an inverter (not shown), so that the pressure pump 15 also has the function of adjusting the supply pressure of the raw water to the membrane separation device 12.

Although not shown, a water supply pump, a heat exchanger, a water softener, an activated carbon filter, and a filter may be provided upstream of the booster pump 15 in the raw water line L1, preferably in this order from the upstream side. The water supply pump, together with the booster pump 15, has the function of supplying raw water stored in the raw water tank to the membrane separation device 12. The heat exchanger is used to control the temperature of the raw water, which varies with the seasons, to a constant temperature (e.g., 25°C). In this embodiment, when the pure water produced is used for pharmaceutical production, a hot water sterilization process is periodically performed between normal operations (pure water production) of the pure water production device 2 to reduce the number of live bacteria in the system using hot water of, for example, 60°C or higher, and the heat exchanger is also used to generate the hot water at that time. The water softener is filled with ion exchange resin (cation exchange resin) and has the function of removing hardness components such as calcium and magnesium from the raw water supplied to the membrane separation device 12. The activated carbon filter has a function of removing residual chlorine from the raw water supplied to the membrane separation device 12, and the filter has a function of capturing and removing pulverized coal generated by the activated carbon filter. The location of the water softener is not particularly limited, but if an activated carbon filter is provided, it is preferable that it is located upstream of the activated carbon filter, as described above. This allows the raw water to pass through the water softener before the residual chlorine contained in the raw water is removed by the activated carbon filter, thereby suppressing the proliferation of live bacteria in the water softener.

The permeate line L2 is provided with a flow control valve CV1 and a flow sensor 16. The flow control valve CV1 functions as a flow control means for adjusting the flow rate of the permeate flowing through the permeate line L2, and the flow sensor 16 functions as a flow detection means for detecting the flow rate of the permeate flowing through the permeate line L2. These are used to adjust the flow rate of the permeate supplied from the membrane separation device 12 to the degassing device 13 and the EDI device 14 to a set flow rate during normal operation of the pure water production system 2, and may also be used in the water quality recovery process described later in detail. In addition, the permeate line L2 is provided with an on-off valve V1 used in the water quality recovery process. The RO concentrated water line L3 is connected to a drain line (not shown) for discharging the RO concentrated water to the outside during normal operation of the pure water production system 2, or discharging hot water to the outside during the above-mentioned hot water sterilization process.

The degassing device 13 is provided in the permeate line L2 and has the function of removing gases such as oxygen and carbon dioxide dissolved in the permeate from the membrane separation device 12. The configuration of the degassing device 13 is not particularly limited, and an appropriate known degassing device can be used depending on the type of gas to be removed. Examples of such degassing devices include a membrane degassing device, a decarbonation tower, a vacuum degassing tower, and a catalytic deoxidation tower. The position of the degassing device 13 is not limited to the downstream side of the membrane separation device 12 shown in the figure, and may be upstream of the membrane separation device 12 in order to reduce the dissolved oxygen concentration in the treated water to suppress the growth of microorganisms, thereby suppressing biofouling of the RO membrane.

The EDI device 14 is a device that simultaneously performs deionization (desalting) of the water to be treated using an ion exchanger and regeneration of the ion exchanger, and produces deionized water (pure water) by treating the permeate water supplied from the membrane separation device 12 through the permeate water line L2. The EDI device 14 is connected to a pure water line L5 that distributes the pure water from the EDI device 14 and an EDI concentrated water line L6 that distributes concentrated water (hereinafter also referred to as "EDI concentrated water") from the EDI device 14. The pure water line L5 is connected downstream to a pure water tank 21 (described later) of the pure water supply device 3, and the EDI concentrated water line L6 is connected downstream to the raw water tank 11. In addition, although not shown, the EDI device 14 is connected to an electrode water discharge line that discharges the electrode water from the EDI device 14 to the outside.

As an example, the EDI device 14 has an anode and a cathode, a deionization chamber arranged between the anode and the cathode and filled with at least one of a cation exchanger and an anion exchanger, and a pair of concentration chambers arranged on both sides of the deionization chamber via an ion exchange membrane. Permeated water from the membrane separation device 12 is supplied to the deionization chamber as the water to be treated through the permeated water line L2, and permeated water from the membrane separation device 12 is supplied to the concentration chamber as concentrated water. In addition, permeated water from the membrane separation device 12 is also supplied to the electrode chambers that respectively house the anode and the cathode as electrode water. When permeated water is supplied from the membrane separation device 12 to the deionization chamber, the ion components in the permeated water are ion-exchanged by the ion exchanger in the deionization chamber and removed. The permeated water from which the ion components have been removed is discharged from the deionization chamber as deionized water (pure water) through the pure water line L5 from the EDI device 14. At this time, the ionic components removed in the desalting compartment are desorbed from the ion exchanger and move to the concentrating compartment adjacent to the desalting compartment due to the potential difference generated by applying a DC voltage between the two electrodes. The ionic components that have moved to the concentrating compartment in this way are taken up by the concentrated water flowing through the concentrating compartment and are discharged from the EDI device 14 through the EDI concentrated water line L6. Meanwhile, in the desalting compartment, a water dissociation reaction (a reaction in which water dissociates into hydrogen ions and hydroxide ions) is continuously progressing, and these hydrogen ions and hydroxide ions are exchanged for the ionic components held in the ion exchanger in the desalting compartment, regenerating the ion exchanger in the desalting compartment.

The pure water line L5 is provided with an on-off valve V2, and the pure water return line L7 is connected to the upstream side thereof via an on-off valve V3. This allows the pure water to be circulated in the pure water production apparatus 2, for example, when the apparatus is started up or restarted, or when there is no demand for pure water at the use point 4 and the water level in the pure water tank 21 of the pure water supply apparatus 3 does not change. That is, the on-off valve V2 of the pure water line L5 is closed and the on-off valve V3 of the pure water return line L7 is opened, so that the pure water produced by the EDI device 14 can be returned to the raw water tank 11 through the pure water return line L7. Note that instead of the on-off valves V2 and V3, a three-way valve may be provided at the connection between the pure water line L5 and the pure water return line L7.

Although not shown, a filter and an ultraviolet sterilizer may be provided upstream of the connection between the pure water line L5 and the pure water return line L7. The filter has the function of capturing and removing the crushed resin generated from the EDI device 14, and the ultraviolet sterilizer is used to sterilize the pure water flowing through the pure water line L5 by ultraviolet irradiation. In addition, it is preferable to provide an ultraviolet sterilizer when the pure water produced is used as purified water for pharmaceutical production, or when the viable cell count of the pure water needs to be controlled. In addition, a drainage line may be connected to the EDI concentrated water line L6, for example, for discharging the EDI concentrated water to the outside during normal operation of the pure water production device 2, or for discharging the hot water to the outside during the above-mentioned hot water sterilization process, and a similar drainage line may be connected to the pure water return line L7.

In the illustrated example, the degassing device 13 is disposed upstream and the EDI device 14 is disposed downstream, but the reverse may be true, i.e., the EDI device 14 may be disposed upstream and the degassing device 13 may be disposed downstream. In other words, the permeate line L2 may be connected to the degassing device 13 downstream, and the EDI device 14 may be provided on the permeate line L2. Note that, as a treatment means for treating the permeate from the membrane separation device 12, it is not necessary to provide both the degassing device 13 and the EDI device 14, i.e., only one of them may be provided. Alternatively, instead of the EDI device 14, a non-regenerative or regenerative mixed bed ion exchange device may be provided as an ion removal device for removing ion components in the permeate from the membrane separation device 12.

The pure water supplying device 3 includes a pure water tank 21 for storing pure water supplied from the pure water manufacturing device 2 through the pure water line L5, a circulation line L10 for circulating the pure water in the pure water tank 21, and a circulation pump 22 provided on the circulation line L10 for circulating the pure water in the pure water tank 21 through the circulation line L10. A water supplying line L11 is connected to the circulation line L10 via an on-off valve (not shown), and the water supplying line L11 is connected to the use point 4 downstream of the line L10. This allows the pure water supplying device 3 to hold the pure water while circulating it along the circulation line L10, and to supply a part of it to the use point 4 as needed. The circulation operation of the pure water is always performed regardless of the presence or absence of demand at the use point, so that it is possible to suppress the adhesion of bacteria to the inside of the piping constituting the circulation line L10 and the maturation of a biofilm. From the viewpoint of suppressing such bacterial contamination, it is preferable that the circulation of the pure water at this time is performed at a flow rate with a Reynolds number of 4000 or more, or a flow rate of 1 m/sec or more, so that the flow inside the piping becomes turbulent. The Reynolds number Re is expressed by the following formula, where the inner diameter of the pipe is d (m), the flow velocity in the pipe is u (m/sec), the density of the fluid is ρ (kg/m ³ ), and the viscosity of the fluid is μ (Pa·s):
Re = d u ρ/μ
The flow inside the piping is in a transition region between laminar flow and turbulent flow when the Reynolds number Re is 2000 to 3000, and generally becomes turbulent when the number is greater than that. The number of water supply lines L11 is not limited to one, and may be multiple. In other words, the pure water supply device 3 may be configured to supply pure water to multiple use points 4.

As described above, the pure water line L5 is connected to the pure water tank 21, and pure water is supplied from the pure water production device 2 according to the water level in the pure water tank 21 detected by a water level sensor (not shown), for example. Specifically, when the water level in the pure water tank 21 falls below a predetermined lower limit, the on-off valve V2 of the pure water line L5 is opened (and the on-off valve V3 of the pure water return line L7 is closed), and pure water is supplied to the pure water tank 21 through the pure water line L5. Then, when the water level in the pure water tank 21 reaches a predetermined upper limit, the on-off valve V2 of the pure water line L5 is closed (and the on-off valve V3 of the pure water return line L7 is opened), and the supply of pure water to the pure water tank 21 is stopped.

Downstream of the connection of the circulation line L10 with the water supply line L11, there are provided an ultraviolet sterilizer (not shown), a heat exchanger (not shown), a pressure sensor 23, and a conductivity sensor 24.

The ultraviolet sterilizer is used to sterilize the pure water flowing through the circulation line L10 by ultraviolet irradiation, but it does not necessarily have to be provided when there is no need to manage the viable bacteria count of the pure water supplied to the point of use 4. The heat exchanger is used in the hot water sterilization process that is periodically performed between normal operations (pure water circulation operations) of the pure water supply device 3, and is used to heat the pure water circulating along the circulation line L10 to, for example, 60°C or higher, preferably 80°C or higher to generate hot water, and to sterilize the pure water tank 21 and the circulation line L10 with the hot water. In addition, as described above, it is preferable that the ultraviolet sterilizer and the heat exchanger are provided downstream of the connection part with the water supply line L11 of the circulation line L10, in order to reduce the processing volume of each. However, the positions of the ultraviolet sterilizer and the heat exchanger are not limited to this, and may be upstream of the connection part, and it is preferable that they are upstream, especially when it is required to supply the hot water to the point of use 4 without circulating it (so-called one-pass). The pressure sensor 23 is used to grasp the usage status of the pure water at the point of use 4, and may also be used to adjust the water supply pressure of the pure water to the point of use 4. That is, the rotation speed of the circulation pump 22 may be controlled by an inverter (not shown) based on the detection value of the pressure sensor 23, and the water supply pressure of the pure water to the point of use 4 may be adjusted. The conductivity sensor 24 functions as a water quality detection means for detecting the water quality (conductivity) of the pure water circulating through the circulation line L10, and is used in the water quality restoration process described below.

In addition, an on-off valve V4 is provided downstream of the conductivity sensor 24 in the circulation line L10, and the pure water discharge line L12 is connected to the upstream side thereof via an on-off valve V5. Furthermore, an on-off valve V6 is provided downstream of the on-off valve V4, and the pure water return line L13 is connected to the upstream side thereof via an on-off valve V7. The pure water return line L13 branches off from the circulation line L10 and is connected to the permeate line L2 (specifically, between the on-off valve V1 and the flow rate control valve CV1). Note that instead of the on-off valves V4 and V5, a three-way valve may be provided at the connection between the circulation line L10 and the pure water discharge line L12, and instead of the on-off valves V6 and V7, a three-way valve may be provided at the connection between the circulation line L10 and the pure water return line L13. Also, the on-off valve V4 does not necessarily have to be provided, and its function may be substituted by the on-off valves V6 and V7.

By the way, it is preferable that the circulation line L10 is connected to the pure water tank 21 via a water spraying means such as a shower ball on the downstream side, so that hot water can also be sprayed on the inner wall surface of the pure water tank 21 during the hot water sterilization process. However, in such a configuration, during normal operation of the pure water supply device 3, the pure water sprayed into the pure water tank 21 comes into contact with the air flowing into the pure water tank 21 through a vent filter (not shown), and carbon dioxide in the air may dissolve in the pure water. As a result, the conductivity of the pure water increases, and there is a risk that the water quality standard required at the point of use 4 (for example, according to the United States Pharmacopeia, the allowable conductivity at 25°C for purified water for pharmaceutical production is 1.3 μS/cm) may not be met. In response to this, it is possible to discharge a part of the pure water circulating along the circulation line L10 to the outside through the pure water discharge line L12 and replenish new pure water from the pure water production device 2 accordingly, but such a method leads to wasteful consumption of water and is not preferable from the viewpoint of water saving.

Therefore, the pure water supply device 3 of this embodiment is provided with a control unit (control means) 25 that executes operation control to restore the water quality (conductivity) of the pure water when it deteriorates as described above. In the operation control by this control unit 25, first, based on the detection result of the conductivity sensor 24, it is determined whether the water quality of the pure water circulating through the circulation line L10 satisfies a predetermined water quality (for example, whether the detection value of the conductivity sensor 24 is equal to or lower than the allowable conductivity). Then, if it is determined that the predetermined water quality is not satisfied, the following water quality restoration process (water quality restoration treatment) is performed until the water quality of the pure water circulating through the circulation line L10 is restored.

When the water quality recovery process is started, the pressure pump 15 is stopped, and at the same time, the on-off valve V2 of the pure water line L5 and the on-off valve V7 of the pure water return line L13 are opened, and the on-off valve V1 of the permeate line L2 and the on-off valve V3 of the pure water return line L7 are closed. At this time, the on-off valve V6 of the circulation line L10 may be left open as in the normal operation of the pure water supply device 3 from the viewpoint of suppressing the generation of live bacteria due to the stagnation of pure water, or may be closed to prevent the return of pure water that does not meet the specified water quality to the pure water tank 21. The on-off valve V6 of the circulation line L10 may be a control valve that can be adjusted to an arbitrary opening degree, so that pure water can be reliably flowed from the circulation line L10 to the pure water return line L13 by adjusting the opening degree even when the on-off valve V6 is opened. Also, a check valve may be provided instead of or in addition to the on-off valve V1 of the permeate line L2.

As a result, at least a portion of the pure water circulating through the circulation line L10 is returned to the permeate line L2 through the pure water return line L13, and after being treated in the degassing device 13 and the EDI device 14, it is returned to the pure water tank 21 through the pure water line L5. That is, the pure water returned to the permeate line L2 is returned to the pure water tank 21 after the carbon dioxide gas is mainly removed by the degassing device 13 and the carbonate ions are mainly removed by the EDI device 14, and the water quality is restored by removing dissolved carbon dioxide. In this way, even if the water quality (conductivity) of the pure water circulating through the circulation line L10 deteriorates, the consumption of pure water to restore it can be suppressed, and as a result, the quality of the pure water in the pure water supply device 3 can be maintained at a good level while suppressing wasteful consumption of water. At this time, EDI concentrated water and electrode water are discharged from the EDI device 14, but to increase the water-saving effect, the EDI concentrated water may be returned to the raw water tank 11 through the EDI concentrated water line L6.

During the water quality recovery process, the supply of pure water to the point of use 4 may be stopped, or the criterion for whether or not to perform the water quality recovery process may be set to a lower level (for example, 70% of the above-mentioned allowable conductivity according to the United States Pharmacopoeia), and the water quality recovery process may be performed while continuing to supply pure water to the point of use 4. However, if the water quality recovery process is not completed in time and the water quality standard required at the point of use 4 is not met, it is preferable to stop the supply of pure water to the point of use 4 midway and perform only the water quality recovery process. Note that, since the water quality recovery process involves drainage from the EDI device 14 as described above, the water level in the pure water tank 21 may reach a predetermined lower limit regardless of whether or not pure water is supplied to the point of use 4. In that case, the water quality recovery process may be interrupted, and the pure water supply device 4 may switch to a circulation operation in which pure water is circulated along the circulation line L10 as in normal operation, while the pure water production device 2 may switch to normal operation (pure water production) and new pure water may be replenished to the pure water tank 21 through the pure water line L5.

For example, from the viewpoint of suppressing the deterioration of the quality of the pure water described above, it is possible to provide a treatment means such as a degassing device or EDI device in the circulation line L10 and perform decarbonation (removal of carbon dioxide) of the pure water in the pure water supply device 3. However, adding new equipment to the pure water supply device 3 may lead to the risk of live bacteria proliferation, which may ultimately lead to bacterial contamination of the pure water supplied to the use point 4. Therefore, as in this embodiment, it is preferable to return at least a portion of the pure water in the pure water supply device 3 to the permeate line L2 depending on the deterioration of the water quality, and perform decarbonation in the degassing device 13 and EDI device 14 in the pure water production device 2. This makes it possible to restore the quality of the deteriorated pure water without increasing the risk of live bacteria generation in the pure water supply device 3.

In the water quality recovery process, it is preferable to perform flow control for the pure water supplied to the degassing device 13 and the EDI device 14 in the same manner as during normal operation of the pure water production system 2. That is, it is preferable to adjust the opening of the flow control valve CV1 based on the detection result of the flow sensor 16 to adjust the flow rate of the pure water supplied to the degassing device 13 and the EDI device 14 to a set flow rate. Instead of or in addition to this, the rotation speed of the circulation pump 22 may be adjusted by an inverter (not shown) based on the detection result of the flow sensor 16 to adjust the flow rate of the pure water supplied to the degassing device 13 and the EDI device 14 to a set flow rate. That is, the circulation pump 22 can also function as a flow rate adjustment means for adjusting the flow rate of the pure water (water to be treated) supplied to the degassing device 13 and the EDI device 14. Note that the set flow rate at this time is preferably a value smaller than the set flow rate of the permeated water supplied during normal operation of the pure water production system 2, which improves the processing capacity of the degassing device 13 and the EDI device 14 and efficiently restores the water quality.

In the illustrated example, the flow rate sensor 16 is provided upstream of the degassing device 13, but the location is not particularly limited as long as the flow rate of the pure water to the degassing device 13 and the EDI device 14 can be appropriately controlled, and may be, for example, downstream of the EDI device 14. The location of the flow rate control valve CV1 is also not limited to the location shown in the figure, as long as it is downstream of the connection of the permeate line L2 with the pure water return line L13, and may be, for example, on the pure water line L5 downstream of the EDI device 14. Alternatively, the flow rate control valve CV1 may be provided in the pure water return line L13 instead of the on-off valve V7, and may be omitted when the above-mentioned flow rate control is performed by the circulation pump 22.

The means for detecting the quality of the pure water in the pure water supply device 3 is not limited to the conductivity sensor 24, and may be, for example, a resistivity meter or a total dissolved solids (TDS) meter, as long as it can detect an increase in conductivity due to the dissolution of carbon dioxide. Alternatively, instead of conductivity, the quality of the pure water may be detected by measuring the inorganic carbon (IC) concentration, and for this purpose, an IC meter or a total organic carbon (TOC) meter may be used.

In addition, the quality of the pure water may not be restored even after a certain period of time has elapsed since the above-mentioned water quality restoration process was performed, for example, because the surrounding air contains components (e.g., organic solvents) that cannot be removed by the degassing device 13 or the EDI device 14. If this is detected, for example, by a conductivity sensor (not shown) installed at the outlet of the degassing device 13 or the EDI device 14, the water quality restoration process may be stopped by closing the on-off valve V7 of the pure water reflux line L13 and stopping the reflux of pure water from the pure water reflux line L13 to the permeate water line L2. Then, the on-off valve V4 of the circulation line L10 is closed and the on-off valve V5 of the pure water discharge line L12 is opened to discharge a portion of the circulating pure water to the outside, and the pure water production device 2 is operated normally accordingly, and new pure water is replenished to the pure water tank 21 through the pure water line L5, thereby restoring the quality of the pure water in the pure water supply device 3. The location of the pure water discharge line L12 is not particularly limited, but it is preferable that it be located downstream of the conductivity sensor 24 as shown in the figure in order to monitor the quality of the discharged pure water while discharging a portion of the circulating pure water from the pure water discharge line L12.

As described above, only one of the degassing device 13 and the EDI device 14 may be provided as a means for treating the permeate from the membrane separation device 12, and therefore, in the water quality recovery process, the pure water returned to the permeate line L2 may be treated (decarbonated) by only one of them. Also, even when both the degassing device 13 and the EDI device 14 are provided as in this embodiment, the decarbonation of the pure water may not necessarily be performed by both of them in the water quality recovery process, and only one of them may be used. As an example, the EDI device 14 may be provided upstream of the degassing device 13 as described above, but in this case, the position of the EDI device 14 may be further upstream of the connection part of the permeate line L2 with the pure water return line L13. In other words, in the water quality recovery process, the pure water returned to the permeate line L2 may be treated by only the degassing device 13. Furthermore, this configuration is advantageous in terms of achieving further water saving effects, since it is possible to stop the operation of the EDI device 14 during the water quality restoration process, and it is possible to eliminate the discharge of EDI concentrated water and electrode water from the EDI device 14.

REFERENCE SIGNS LIST 1 Water treatment system 2 Pure water production device 3 Pure water supply device 4 Point of use 11 Raw water tank 12 Membrane separation device 13 Deaerator (treatment means)
14 EDI device (processing means)
15 Pressure pump 16 Flow rate sensor (flow rate detection means)
21 Pure water tank 22 Circulation pump (flow rate adjustment means)
23 Pressure sensor 24 Conductivity sensor (water quality detection means)
25 Control unit (control means)
L1 Raw water line L2 Permeate water line (supply line)
L3 RO concentrated water line L4 Raw water supply line L5 Pure water line L6 EDI concentrated water line L7 Pure water return line L10 Circulation line L11 Water supply line L12 Pure water discharge line L13 Pure water return line CV1 Flow rate control valve (flow rate control means)
V1 to V7 Opening and closing valves

Claims (10)

a processing means including at least one of a degasser and an ion remover;
a water supply line for supplying the water to be treated to the treatment means;
a pure water line for circulating the pure water obtained by the treatment means;
a pure water tank for storing the pure water circulated through the pure water line;
a circulation line for circulating the pure water in the pure water tank;
a return line branched from the circulation line and connected to the water supply line;
a water quality detection means provided in the circulation line for detecting the quality of the pure water circulating through the circulation line;
a control means for executing a water quality restoration process in which, when it is determined based on the detection result of the water quality detection means that the water quality of the pure water circulating through the circulation line does not meet a predetermined water quality, at least a portion of the circulating pure water is returned from the return line to the water supply line, treated by the treatment means, and then stored in the pure water tank via the pure water line. A flow rate detection means for detecting a flow rate of the water to be treated supplied to the treatment means;
A flow rate adjusting means for adjusting the flow rate of the water to be treated supplied to the treatment means,
2. The water treatment system according to claim 1, wherein the control means controls the flow rate adjustment means based on a detection result of the flow rate detection means in the water quality restoration process, thereby adjusting a flow rate of the pure water supplied to the treatment means. the flow rate adjusting means is a flow rate adjusting valve provided downstream of a connection between the water supply line and the return line of the pure water line or in the return line,
The water treatment system according to claim 2 , wherein the control means adjusts an opening degree of the flow rate regulating valve based on a detection result of the flow rate detection means in the water quality restoration process. the flow rate adjusting means is a circulation pump provided in the circulation line to circulate the pure water in the pure water tank through the circulation line;
The water treatment system according to claim 2 , wherein the control means adjusts a rotation speed of the circulation pump based on a detection result of the flow rate detection means during the water quality restoration operation. The water treatment system according to any one of claims 2 to 4, wherein the control means controls the flow rate adjustment means so that the flow rate of the pure water supplied to the treatment means during the water quality restoration process is smaller than the flow rate of the water to be treated during normal operation of the water treatment system. The water treatment system according to any one of claims 1 to 4, which is used to produce pure water for use in pharmaceutical manufacturing. A method for operating a water treatment system having a treatment means including at least one of a degassing device and an ion removal device, a water supply line for supplying water to be treated to the treatment means, a pure water line for circulating the pure water obtained by the treatment means, and a pure water tank for storing the pure water circulated through the pure water line, comprising:
circulating the pure water in the pure water tank along a circulation line;
detecting the quality of the pure water circulating through the circulation line and determining whether the detected water quality satisfies a predetermined water quality;
and if the detected water quality does not satisfy the specified water quality, supplying at least a portion of the pure water circulating through the circulation line to the treatment means via a return line branching off from the circulation line and connected to the water supply line, for treatment, and then storing the pure water in the pure water tank via the pure water line. The step of supplying at least a portion of the pure water to the processing means comprises:
detecting a flow rate of the pure water supplied to the processing means;
The method for operating a water treatment system according to claim 7 , further comprising the step of: adjusting a flow rate of the pure water supplied to the treatment means based on the detected flow rate. The method for operating a water treatment system according to claim 8, wherein the step of adjusting the flow rate of the pure water includes adjusting the opening of a flow rate adjustment valve provided on the downstream side of the connection between the supply water line and the return line of the pure water line, or on the return line. The method for operating a water treatment system according to claim 8, wherein the step of adjusting the flow rate of the pure water includes adjusting the rotation speed of a circulation pump provided in the circulation line and circulating the pure water in the pure water tank through the circulation line.

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