Water treatment system and method for operating same

Abstract

To perform hot water sterilization at a higher frequency in areas prone to bacterial growth.SOLUTION: A water treatment system 1 includes at least a tank 11 for storing water to be treated, water treatment means 12, 13 for treating the water to produce treated water, a pretreatment means having at least an activated carbon filter 17 and performing pretreatment on water to be treated supplied to the water treatment means, supply lines L1 and L4 leading to water treatment means 12, 13 via the tank 11 and the activated carbon filter 17, a reflux line L6 branching from supply lines L1 and L4 at downstream side of the tank 11 and the activated carbon filter 17 and returning to the upstream side of the tank 11 and the activated carbon filter 17, and heating means 16 provided between the branch point of the tank 11 and the reflux line L6 of the supply lines L1 and L4 and heating the water to be treated flowing through the supply lines L1 and L4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water treatment system and a method for operating the same. [Background technology]

[0002] Conventionally, known systems for producing pure water (such as purified water and water for injection) for use in pharmaceutical manufacturing and the like include a combination of a membrane separation device that separates raw water, such as industrial water, well water, or city water, into permeate and concentrated water, and an electrodeionization water production system that produces deionized water (pure water) by passing the permeate from the membrane separation device through an ion exchanger. Because such pure water production systems produce pure water for use in pharmaceutical manufacturing and the like, they periodically undergo a sterilization treatment to reduce the number of viable bacteria in the system by passing hot water at 60°C or higher through the system to ensure compliance with the requirements of the Japanese Pharmacopoeia.

[0003] One known method for sterilizing the above-mentioned pure water production system involves passing hot water through both the membrane separation system and the electrodeionized water production system at the same time (see, for example, Patent Document 1). In this method, hot water is sequentially supplied to the membrane separation system and the electrodeionized water production system, and then returned to the raw water tank, so that the entire system is sterilized simultaneously by the circulating hot water. This reduces the amount of water used and the number of steps, enabling more efficient sterilization treatment compared to sterilizing the membrane separation system and the electrodeionized water production system separately. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-107617 Summary of the Invention [Problem to be solved by the invention]

[0005] In many cases, pure water production systems are equipped with activated carbon filters to remove residual chlorine from raw water as a pretreatment means for pretreating the raw water supplied to the membrane separation device. However, because live bacteria are likely to grow in the activated carbon filters, more frequent sterilization is required. However, in the above-mentioned method of sterilizing the entire system at once, the timing of sterilization is generally determined based on the convenience of the membrane separation device and the electrodeionized water production device, which are easily damaged by heat and pressure. Therefore, the frequency of sterilization may not be sufficient for the activated carbon filter, which may result in the proliferation of live bacteria in the activated carbon filter. The same applies to the raw water tank where the raw water is stored.

[0006] Therefore, an object of the present invention is to provide a water treatment system and an operating method thereof that can more frequently perform sterilization treatment with hot water in places where live bacteria are likely to grow. [Means for solving the problem]

[0007] In order to achieve the above-mentioned objectives, the water treatment system of the present invention comprises a tank for storing water to be treated, a water treatment means for treating the water to be treated to produce treated water, a pretreatment means including at least an activated carbon filter for pretreatment of the water to be treated that is supplied to the water treatment means, a supply line that passes through the tank and the activated carbon filter to the water treatment means, a reflux line that branches off from the supply line downstream of the tank and downstream of the activated carbon filter and returns to the upstream side of the tank and upstream of the activated carbon filter, and a heating means that is provided in the supply line between the branch point with the tank and the reflux line and that heats the water to be treated flowing through the supply line. In one aspect, the water treatment system has a return line that returns treated water from the water treatment means to the tank, and a control means that controls the operation of the water treatment system, and the control means performs a first process of causing at least a portion of the hot water to flow into the reflux line when the heating means heats the water to be treated flowing through the supply line to generate hot water, and the activated carbon filter is provided on the supply line upstream of the tank, and in the first process, the control means causes a portion of the hot water to flow from the supply line through the water treatment means to the return line and causes the remainder to flow into the reflux line. In another aspect, the pretreatment means includes other pretreatment means other than the activated carbon filter, and the other pretreatment means is provided on the supply line downstream of a branch point with the reflux line, but not upstream of the branch point.

[0008] In addition, the operating method of the water treatment system of the present invention is a method for operating a water treatment system having a tank for storing water to be treated, a water treatment means for treating the water to be treated to produce treated water, a pretreatment means including at least an activated carbon filter for pretreatment of the water to be treated that is supplied to the water treatment means, and a supply line that passes through the tank and the activated carbon filter to the water treatment means, and includes the steps of circulating the water to be treated in the tank through the supply line and heating the circulating water to produce hot water, and returning at least a portion of the hot water to the tank and the activated carbon filter through a return line branching off from the supply line downstream of the tank and downstream of the activated carbon filter. In one aspect, the activated carbon filter is provided upstream of the tank in the supply line, and the step of returning at least a portion of the hot water includes returning all of the hot water to the tank and the activated carbon filter to sterilize the tank and the activated carbon filter, and returning a portion of the hot water from the activated carbon filter to the tank and supplying the remainder to the water treatment means and then returning it to the tank to sterilize the tank, the activated carbon filter, and the water treatment means. In another aspect, the step of returning at least a portion of the hot water includes not passing the hot water through any pretreatment means other than the activated carbon filter among the pretreatment means. [Effects of the Invention]

[0009] According to the present invention, hot water sterilization treatment can be carried out more frequently in places where live bacteria are likely to grow. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a water treatment system according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a schematic configuration diagram of a water treatment system according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The water treatment system of the present invention produces pure water, specifically purified water or water for injection, for use in pharmaceutical manufacturing and supplies it to a point-of-use facility. It is suitable for treating chlorine-containing city water (tap water) as the treated water. In this specification, "purified water" refers to tap water purified by ion exchange, reverse osmosis (RO), ultrafiltration (UF), or a combination thereof. "Water for injection" refers to purified water or water that has undergone appropriate pretreatment, which has been subjected to distillation or ultrafiltration (RO / UF) to pass pyrogen (endotoxin) tests and viable bacterial tests. Examples of such purified water and water for injection include those specified in the Japanese Pharmacopoeia. In this specification, "pure water used in pharmaceutical manufacturing" includes not only the purified water and water for injection described above, but also the wash water used to clean containers containing them or containers containing pharmaceuticals.

[0012] (First embodiment) 1 is a schematic diagram of a water treatment system according to a first 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.

[0013] The water treatment system 1 is composed of a pure water production device 10 that sequentially treats the water to be treated (raw water) to produce pure water, and a pure water supply device 20 that circulates and stores the pure water thus produced, and supplies a portion of it to a use point 2 as needed.

[0014] The pure water production system 10 has a raw water tank 11, a membrane separation device 12, and an electrodeionized water production system (hereinafter also referred to as an "EDI device") 13. As will be described in detail below, the pure water production system 10, which produces pure water used in pharmaceutical production, periodically performs a sterilization process using hot water to reduce the number of viable bacteria in the system between normal operations (pure water production). The pure water production system 10 also has a control unit (control means) 14 that executes such hot water sterilization process.

[0015] The membrane separation device 12 is a device that removes impurities from raw water to produce treated water. It 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 from which the impurities have been removed. The separation membrane of the membrane separation device 12 is not limited to an RO membrane as long as it is heat-resistant to the hot water used for heat sterilization, as described below. For example, a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), or a nanofiltration membrane (NF membrane) can be used. However, from the viewpoint of improving the quality of treated water, an NF membrane or an RO membrane is preferably used, and an RO membrane is more preferably used. Note that 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 water to be treated is sequentially treated by multiple RO membranes, and that the permeate separated by the upstream RO membrane between two adjacent RO membranes is supplied to the downstream RO membrane as the water to be treated. 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.

[0016] The membrane separation device 12 is connected to a water supply line L1 that supplies raw water to the membrane separation device 12, a permeate line L2 that distributes permeate from the membrane separation device 12, and an RO concentrate line L3 that distributes concentrated water (hereinafter also referred to as "RO concentrate") from the membrane separation device 12. The water supply line L1 is connected upstream to a raw water tank 11 via an on-off valve V1, and a raw water make-up line L4 is connected to the raw water tank 11 via an on-off valve V2, through which raw water is supplied as needed, as described below. Therefore, it can be said that the water supply line L1 and the raw water make-up line L4 function as supply lines that lead to the membrane separation device 12 via the raw water tank 11. The permeate line L2 is connected downstream to the EDI device 13, and the RO concentrate line L3 is connected downstream to the raw water tank 11. A bypass line L5 is provided between the water supply line L1 and the raw water supply line L4 to supply raw water from the raw water supply line L4 to the water supply line L1 without passing through the raw water tank 11. The bypass line L5 branches off from the raw water supply line L4 upstream of the on-off valve V2 and is connected to the water supply line L1 via an on-off valve V3 downstream of the on-off valve V1. The on-off valve V1 of the water supply line L1 is always open during normal operation of the pure water production system 10 and is opened and closed during the sterilization process described below. The on-off valve V3 of the bypass line L5 is always closed during normal operation of the pure water production system 10 and is opened and closed during the sterilization process described below.

[0017] The water supply line L1 is provided with a water pump 15, a heat exchanger 16, an activated carbon filter 17, a filter 18, and a pressure pump 19. The positions of the heat exchanger 16 and the activated carbon filter 17 may be reversed.

[0018] The water pump 15, together with the pressure pump 19, functions to supply raw water stored in the raw water tank 11 to the membrane separation device 12, and its rotation speed may be controlled by an inverter (not shown). The heat exchanger 16 is used to maintain a constant temperature (e.g., 25°C) for the raw water, which fluctuates due to various factors such as seasonal temperature fluctuations and heat generation from equipment. It also serves as a heating means for generating hot water for thermal sterilization during the sterilization process described below. The activated carbon filter 17, together with the filter 18, performs pretreatment of the raw water supplied to the membrane separation device 12 and has the function of removing residual chlorine from the raw water using activated carbon. The filter 18 has the function of capturing and removing pulverized coal generated by the activated carbon filter 17. The filter 18 is not particularly limited as long as it has the above function, and for example, an MF membrane or an UF membrane can be used. The pressure pump 19 may be equipped with an inverter (not shown) that controls its rotation speed, thereby adjusting the supply pressure of the raw water to the membrane separation device 12.

[0019] An on-off valve V4 is provided in the water supply line L1 between the activated carbon filter 17 and the filter 18, and a hot water reflux line L6 is connected to the upstream side of the on-off valve V4 via an on-off valve V5. The hot water reflux line L6 is connected downstream to the raw water supply line L4, specifically, connected downstream to the on-off valve V6 provided in the raw water supply line L4. Therefore, the hot water reflux line L6 can also be considered a line that branches off from the water supply line L1 downstream of the activated carbon filter 17 and returns to the upstream side of the raw water tank 11. During normal operation of the pure water manufacturing system 10, the on-off valve V4 of the water supply line L1 is always open, and the on-off valve V5 of the hot water reflux line L6 is always closed. On the other hand, during the sterilization process described below, the control unit 14 controls the opening and closing of the on-off valves V4 and V5 to adjust the flow rate (including zero) of hot water flowing from the water supply line L1 into the hot water reflux line L6. Instead of the on-off valves V4 and V5, a three-way valve may be provided at the branch point between the water supply line L1 and the hot water return line L6.

[0020] Although not shown, the permeate line L2 may be provided with a degassing device such as a membrane degassing device or a decarbonation tower. The degassing device has the function of removing oxygen and carbon dioxide dissolved in the permeate from the membrane separation device 12. In particular, by reducing the concentration of dissolved carbon dioxide in the water to be treated supplied to the EDI device 13, the load of the deionization (desalination) process, which will be described later, can be reduced. The location of the degassing device is not limited to the permeate line L2 downstream of the membrane separation device 12. It may also be located upstream of the membrane separation device 12 in order to reduce the dissolved oxygen concentration in the water to be treated, thereby suppressing microbial growth and thereby biofouling of the RO membrane. Furthermore, although not shown, the RO concentrate line L3 is connected to a drainage line for discharging the RO concentrate to the outside during normal operation of the pure water production system 10.

[0021] The EDI device 13 simultaneously deionizes (demines) the water to be treated using an ion exchanger and regenerates the ion exchanger. It produces deionized water (pure water) by treating the permeate water supplied from the membrane separation device 12 through the permeate line L2. The EDI device 13 is connected to a pure water line L7, which distributes pure water from the EDI device 13, and an EDI concentrated water line L8, which distributes concentrated water (hereinafter also referred to as "EDI concentrated water") from the EDI device 13. The pure water line L7 is connected downstream to a pure water tank 21 (described later) of the pure water supply device 20, and the EDI concentrated water line L8 is connected downstream to the raw water tank 11. Although not shown, the EDI concentrated water line L8 may be connected to a drainage line, for example, for discharging the EDI concentrated water to the outside during normal operation of the pure water production system 10. Furthermore, although not shown, an electrode water discharge line that discharges electrode water from the EDI device 13 to the outside may be connected to the EDI device 13, and an electrode water return line that returns the electrode water to the raw water tank 11 when power is not applied to the EDI device 13 may be connected to the electrode water discharge line.

[0022] As an example, the EDI device 13 has an anode and a cathode, a deionization compartment disposed 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 compartments disposed on either side of the deionization compartment via an ion exchange membrane. Permeated water from the membrane separation device 12 is supplied to the deionization compartment as water to be treated via the permeate line L2, and the concentration compartment is supplied with the permeated water from the membrane separation device 12 as concentrated water. The electrode compartments, which house the anode and cathode, are also supplied with the permeated water from the membrane separation device 12 as electrode water. When the permeated water is supplied from the membrane separation device 12 to the deionization compartment, the ionic components in the permeated water are removed by ion exchange in the ion exchangers in the deionization compartment. The permeated water from which the ionic components have been removed is discharged as deionized water (pure water) from the deionization compartment via the pure water line L7 and the EDI device 13. At this time, the ionic components removed in the deionization compartment are desorbed from the ion exchanger due to the potential difference generated by applying a DC voltage between the two electrodes and migrate to the concentrating compartment adjacent to the deionization compartment. The ionic components that have migrated to the concentrating compartment in this way are taken up by the concentrated water flowing through the concentrating compartment and discharged from the EDI device 13 via the EDI concentrated water line L8. Meanwhile, in the deionization compartment, a water dissociation reaction (a reaction in which water dissociates into hydrogen ions and hydroxide ions) is continuously occurring, and these hydrogen ions and hydroxide ions are exchanged for the ionic components held in the ion exchanger in the deionization compartment, regenerating the ion exchanger in the deionization compartment.

[0023] An on-off valve V7 is provided on the pure water line L7, and a pure water return line L9 is connected upstream of the line L7 via an on-off valve V8. The pure water return line L9 is connected downstream to the raw water tank 11. This allows for pure water circulation within the pure water production system 10, for example, when the system is started up or restarted, or when there is no demand for pure water at the point of use 2 and the water level in the pure water tank 21 (described later) of the pure water supply system 20 remains constant. That is, by closing the on-off valve V7 on the pure water line L7 and opening the on-off valve V8 on the pure water return line L9, pure water produced by the EDI device 13 can be returned to the raw water tank 11 via the pure water return line L9. This pure water circulation operation can suppress the growth of viable bacteria due to stagnation of pure water. Instead of the on-off valves V7 and V8, a three-way valve may be provided at the connection between the pure water line L7 and the pure water return line L9.

[0024] Although not shown, a filter and an ultraviolet sterilizer may be provided on the pure water line L7 upstream of the connection with the pure water return line L9. The filter has the function of capturing and removing crushed resin generated from the EDI device 13. Such a filter is not particularly limited as long as it has the above function, and for example, an MF membrane or an UF membrane can be used. The ultraviolet sterilizer is used to sterilize the pure water flowing through the pure water line L7 by irradiating it with ultraviolet light. Note that since pure water contains few impurities, the positions of the filter and the ultraviolet sterilizer may be reversed. Also, although not shown, a drainage line for discharging the pure water to the outside may be connected to the pure water return line L9 as needed.

[0025] During normal operation of the pure water production system 10, a water sampling process is carried out in which raw water stored in the raw water tank 11 is sequentially treated in the membrane separation device 12, the EDI device 13, etc., and the pure water thus obtained is supplied to the pure water supply system 20 via the pure water line L7. Specifically, the raw water stored in the raw water tank 11 is supplied to the heat exchanger 16 via the water supply line L1 by operation of the water pump 15. The raw water is adjusted to a constant temperature (e.g., 25°C) in the heat exchanger 16, where residual chlorine is removed in the activated carbon filter 17 and foreign matter is removed in the filter 18. The raw water thus pretreated is supplied to the membrane separation device 12 by operation of the pressure pump 19, where it is separated into permeate and RO concentrated water by membrane separation treatment. The permeate is supplied to the EDI device 13 through the permeate line L2, and the RO concentrate is returned to the raw water tank 11 through the RO concentrate line L3 or discharged from the RO concentrate line L3 to the outside through a drain line (not shown). The permeate supplied to the EDI device 13 has ionic components removed by desalination treatment, and is then sent as pure water to the pure water supply device 20 through the pure water line L7. At this time, at least a portion of the EDI concentrate is returned to the raw water tank 11 through the EDI concentrate line L8 or is discharged from the EDI concentrate line L8 to the outside through a drain line (not shown). In addition, all of the electrode water from the EDI device 13 is discharged to the outside through an electrode water discharge line (not shown).

[0026] A water level sensor (not shown) is provided in the raw water tank 11, and during the water sampling process described above, raw water is supplied through the raw water supply line L4 according to the water level detected by the water level sensor in the raw water tank 11. Specifically, when the water level in the raw water tank 11 falls below a predetermined lower limit, the on-off valves V2 and V6 of the raw water supply line L4 are opened to supply raw water, and when the water level in the raw water tank 11 reaches a predetermined upper limit, the on-off valve V2 or the on-off valve V6 of the raw water supply line L4 is closed to stop the supply of raw water.

[0027] The pure water supply device 20 includes a pure water tank 21 that stores pure water supplied from the pure water manufacturing device 10 via the pure water line L7, a circulation line L10 that circulates the pure water in the pure water tank 21, and a circulation pump 22 provided on the circulation line L10. A water supply line L11 is connected to the circulation line L10 via an on-off valve (not shown), and the water supply line L11 is connected downstream to the point of use 2. This allows the pure water supply device 20 to store and circulate pure water along the circulation line L10 and supply a portion of the pure water to the point of use 2 as needed. This pure water circulation operation is constantly performed regardless of whether there is a demand for pure water at the point of use 2, thereby preventing bacteria from adhering to the inside of the piping that constitutes the circulation line L10 and preventing biofilms from maturing. Note 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 20 may supply pure water to multiple points of use 2.

[0028] As described above, the pure water line L7 is connected to the pure water tank 21, and pure water is supplied from the pure water manufacturing apparatus 10 in accordance with the water level in the pure water tank 21 detected by, for example, a water level sensor (not shown). Specifically, when the water level in the pure water tank 21 falls below a predetermined lower limit, the on-off valve V7 of the pure water line L7 is opened (and the on-off valve V8 of the pure water return line L9 is closed), thereby supplying pure water to the pure water tank 21 through the pure water line L7. Then, when the water level in the pure water tank 21 reaches a predetermined upper limit, the on-off valve V7 of the pure water line L7 is closed (and the on-off valve V8 of the pure water return line L9 is opened), thereby stopping the supply of pure water to the pure water tank 21.

[0029] The circulation line L10 is provided with an ultraviolet sterilizer (not shown) and a heat exchanger 23. The ultraviolet sterilizer is used to sterilize the pure water flowing through the circulation line L10 by irradiating it with ultraviolet light. Like the heat exchanger 16 of the pure water production system 10, the heat exchanger 23 is used to generate hot water for heated sterilization when the pure water supply system 20 performs a sterilization process using hot water. The heat exchanger 23 also has a cooling function to suppress a rise in the temperature of the circulating pure water in case the temperature of the circulating pure water rises above the required temperature at the point of use 2 due to heat generated by the pure water pump 22 or the ultraviolet sterilizer. Although not shown, a drainage line (not shown) is connected to the circulation line L10 downstream of the heat exchanger 23 for discharging the circulating pure water to the outside. This allows the quality of the circulating pure water to be restored, for example, by discharging a portion of the circulating pure water to the outside and then replenishing it with new pure water from the pure water production system 10.

[0030] As described above, in the pure water production system 10 that produces pure water used in pharmaceutical production, a sterilization process using hot water to reduce the number of viable bacteria in the system is periodically performed by the control unit 14 during normal operation. Specifically, an activated carbon sterilization process, which sterilizes the activated carbon filter 17 alone, and a total sterilization process, which sterilizes not only the activated carbon filter 17 but also the membrane separation device 12 and the EDI device 13, are periodically and independently performed. These two sterilization processes are described below.

[0031] (Activated carbon sterilization process) The activated carbon sterilization step is a step of sterilizing a part of the system including the activated carbon filter 17 with hot water. Specifically, it is a step of circulating raw water stored in the raw water tank 11 through a predetermined path while heating it to 60°C or higher, preferably 80°C or higher, using the heat exchanger 16, maintaining the temperature for a certain period of time, and then cooling it until the temperature in the path becomes suitable for membrane separation treatment by the membrane separation device 12. Although not described in detail here, permeated water from the membrane separation device 12 or deionized water (pure water) from the EDI device 13 may be used instead of raw water as the hot water for thermal sterilization.

[0032] When the activated carbon sterilization process is started, the operation of the EDI device 13 (application of DC voltage) is preferably stopped, and after the permeate from the membrane separation device 12 has been passed through at least the electrode chambers in this state, the pressure pump 19 is stopped and the water supply to the EDI device 13 is stopped. This reduces the risk of oxidizing gases, such as hydrogen gas, chlorine gas, and oxygen gas, generated in the electrode chambers remaining in the EDI device 13 and deteriorating components such as the ion exchange membrane and ion exchange resin. There are no particular restrictions on the amount of water passed and the time for passing water, but from the perspective of the above-mentioned gas dischargeability, it is preferable to pass water at a rate similar to that during the water sampling process for about 30 seconds. Then, the on-off valve V4 of the water supply line L1 and the on-off valve V6 of the raw water supply line L4 are closed, and the on-off valve V5 of the hot water return line L6 and the on-off valve V2 of the raw water supply line L4 are opened (first process). As a result, all of the raw water flowing through the water supply line L1 flows into the hot water return line L6 and is returned to the raw water tank 11 via the raw water supply line L4. That is, the raw water in the raw water tank 11 is circulated through the water supply line L1, the hot water return line L6, and the raw water supply line L4. At the same time, a heat medium (e.g., steam) is supplied to the heat exchanger 16, and the circulating raw water is heated to and maintained at 60°C or higher, preferably 80°C or higher. In this way, the circulation of the raw water (hot water) maintained at a high temperature sterilizes a portion of the system, including the raw water tank 11 and the activated carbon filter 17.

[0033] After the hot water has been circulated for a certain period of time, the supply of the heat medium to the heat exchanger 16 is stopped, and instead, a refrigerant (e.g., cold water) is supplied to the heat exchanger 16, thereby starting to cool the hot water. Then, when the circulating hot water is cooled to a temperature suitable for membrane separation treatment by the membrane separation device 12 (e.g., below 45°C), normal operation of the pure water production system 10 is resumed. That is, the on-off valve V4 of the water supply line L1 is opened, the on-off valve V5 of the hot water reflux line L6 is closed, and at the same time, the pressure pump 19 is started, thereby resuming the supply of raw water from the raw water tank 11 to the membrane separation device 12. Then, the operation of the EDI device 13 is resumed, and normal operation of the pure water production system 10 is resumed. When normal operation is resumed, the on-off valve V7 of the pure water line L7 is opened, and the on-off valve V8 of the pure water return line L9 is closed, thereby supplying pure water produced in the pure water production system 10 to the pure water supply device 20 via the pure water line L7 as needed.

[0034] (Whole sterilization process) The total sterilization step is a step of sterilizing the entire system including the membrane separation device 12 and the EDI device 13 with hot water. Specifically, after raw water stored in the raw water tank 11 is replaced with pure water, the pure water is circulated throughout the system while being heated to 60°C or higher, preferably 80°C or higher, by the heat exchanger 16, and after maintaining this temperature for a certain period of time, is cooled until the temperature within the system becomes suitable for membrane separation treatment by the membrane separation device 3. As in the activated carbon sterilization step, raw water may be used as the hot water for thermal sterilization; however, it is preferable to use pure water in consideration of the ion load on the EDI device 13 during sterilization treatment.

[0035] In the total sterilization process, first, water is drained from the raw water tank 11 in two stages through a drain line (not shown). That is, when the total sterilization process is started, the operation of the water supply pump 15 and the pressure pump 19 continues until the water level in the raw water tank 11 falls below a predetermined lower limit, thereby discharging the raw water stored in the raw water tank 11 to the outside through a drain line connected to the RO concentrated water line L3. Then, when a water level sensor (not shown) confirms that the water level in the raw water tank 11 has fallen below the predetermined lower limit, the on-off valve V1 of the water supply line L1 is closed and the water supply pump 15 and the pressure pump 19 are stopped, thereby discharging the raw water through a drain line connected to the water supply line L1 upstream of the on-off valve V1. Note that the raw water is preferably discharged until the raw water tank 11 is as empty as possible, because pure water will be stored in the raw water tank 11 in the subsequent process.

[0036] After the raw water is discharged in this manner, the pure water production system 10 produces pure water in the same manner as during the water sampling process, and the resulting pure water is supplied to and stored in the raw water tank 11. Specifically, the on-off valve V6 of the raw water supply line L4 and the on-off valve V3 of the bypass line L5 are opened, and the on-off valve V2 of the raw water supply line L4 is closed, thereby supplying raw water from the raw water supply line L4 to the water supply line L1 through the bypass line L5 without passing through the raw water tank 11. The water supply pump 15 and the pressure pump 19 are then started, and the pure water production system 10 produces pure water in the same manner as during the water sampling process. At this time, the on-off valve V7 of the pure water line L7 is closed, and the on-off valve V8 of the pure water return line L9 is opened, thereby supplying deionized water (pure water) from the EDI device 13 from the pure water line L7 through the pure water return line L9 to the raw water tank 11 and storing it there. At least a portion of the RO concentrated water is discharged to the outside through a drain line (not shown) connected to the RO concentrated water line L3.

[0037] Thereafter, for example, when a water level sensor (not shown) confirms that the water level in the raw water tank 11 has reached a predetermined upper limit, operation of the EDI device 13 (application of DC voltage) is stopped. Then, the on-off valve V6 of the raw water supply line L4 and the on-off valve V3 of the bypass line L5 are closed, and the supply of raw water from the raw water supply line L4 to the water supply line L1 is also stopped. The on-off valve V1 of the water supply line L1 is opened, and the supply of pure water from the raw water tank 11 to the water supply line L1 is started. As a result, the pure water in the raw water tank 11 is sequentially supplied to the membrane separation device 12 and the EDI device 13 via the water supply line L1 and the permeated water line L2, and then returned to the raw water tank 11 via the pure water line L7 and the pure water return line L9. That is, the pure water in the raw water tank 11 is circulated through the water supply line L1, the permeated water line L2, the pure water line L7, and the pure water return line L9. At the same time, a heat medium (e.g., steam) is supplied to the heat exchanger 16, and the circulating pure water is heated and maintained at 60°C or higher, preferably 80°C or higher. In this way, the circulation of pure water (hot water) maintained at a high temperature sterilizes the entire system, including the raw water tank 11, the activated carbon filter 17, the membrane separation device 12, and the EDI device 13. At this time, hot water is also passed through the RO concentrated water line L3 and the EDI concentrated water line L8, and these are sterilized.

[0038] During the circulation of the hot water described above, the on-off valve V5 of the hot water reflux line L6 may be opened (and accordingly the on-off valve V2 of the raw water supply line L4 may also be opened), thereby allowing hot water to flow through the portion of the raw water supply line L4 downstream of the connection with the hot water reflux line L6 for sterilization. Alternatively, the on-off valve V5 of the hot water reflux line L6 may remain closed. In other words, as long as the on-off valve V1 of the water supply line L1 is open, the on-off valve V5 of the hot water reflux line L6 may be opened or closed as desired (second process).

[0039] After the hot water has been circulated for a certain period of time, the supply of the heat medium to the heat exchanger 16 is stopped, and instead, a refrigerant (e.g., cold water) is supplied to the heat exchanger 16, thereby starting to cool the hot water. When the circulating hot water is cooled to a temperature suitable for membrane separation treatment by the membrane separation device 12 (e.g., less than 45°C), the on-off valve V5 on the hot water reflux line L6 is closed (if it was open during the above-mentioned circulation of the hot water), and operation of the EDI device 13 is resumed, thereby resuming normal operation of the pure water production system 10. When normal operation is resumed, the on-off valve V7 on the pure water line L7 is opened, and the on-off valve V8 on the pure water return line L9 is closed, so that pure water produced in the pure water production system 1 is supplied to the pure water supply device 20 via the pure water line L7 as needed.

[0040] The temperature of the hot water in each of the above-described sterilization steps is adjusted, for example, by adjusting the amount of heat medium supplied to heat exchanger 16 based on the detection value of a temperature sensor (not shown) installed in the hot water circulation path. The location of the temperature sensor is not particularly limited, but is preferably as far away from heat exchanger 16 as possible in the hot water circulation direction, and more preferably between the pure water line L7 and the pure water return line L9 and near the inlet of heat exchanger 16. That is, at this location, the temperature of the hot water is lowest due to the influence of heat radiation. Therefore, by adjusting the temperature of the hot water at this location so that it does not fall below the desired sterilization temperature, a sufficient sterilization effect can be ensured. Meanwhile, a temperature sensor may also be installed near the outlet of heat exchanger 16 to monitor the temperature of the hot water generated by heat exchanger 16. In order to minimize damage to each device due to a sudden temperature change, the heating rate during the temperature rise process is preferably 15°C / min or less in the activated carbon sterilization step and 2°C / min or less in the total sterilization step. To reduce the effects of sudden temperature changes, the cooling rate during the temperature drop process is preferably 15°C / min or less in the activated carbon sterilization step and 2°C / min or less in the total sterilization step. The flow rate of hot water in each sterilization step is adjusted so that the time required for the hot water flow range to be heated to the desired sterilization temperature is, for example, about 10 to 30 minutes in the activated carbon sterilization step and about 30 to 60 minutes in the total sterilization step.

[0041] In addition, the pure water supply apparatus 20 also periodically performs a hot water sterilization treatment, either simultaneously with or separately from the sterilization process of the pure water manufacturing apparatus 10 described above. Specifically, the pure water circulating along the circulation line L10 is heated by the heat exchanger 23 to, for example, 60°C or higher, preferably 80°C or higher, thereby sterilizing the inside of the pure water supply apparatus 20 system, including the pure water tank 21 and the circulation line L10. After such hot water circulation has been performed for a certain period of time, the circulating hot water is cooled by the heat exchanger 23 or by repeatedly discharging the circulating hot water and replenishing it from the pure water manufacturing apparatus 10; specifically, until it reaches or falls below the appropriate temperature for use at the point of use 2. In the hot water sterilization treatment in the pure water supply apparatus 20, there are no particular limitations on the rate at which the pure water is heated or cooled.

[0042] On the other hand, in the pure water supply device 20, if hot water sterilization treatment is not performed during each sterilization step of the pure water production device 10, the supply of pure water from the pure water production device 10 is stopped, but the pure water circulation operation continues and the supply of pure water to the point of use 2 also continues. However, when the water level in the pure water tank 21 reaches a predetermined lower limit, the supply of pure water to the point of use 2 is stopped and only the pure water circulation operation continues from the viewpoint of suppressing the growth of live bacteria due to stagnation of pure water. When the sterilization step of the pure water production device 10 is completed, the supply of pure water begins, and when the water level in the pure water tank 21 reaches or exceeds the predetermined water level, the supply of pure water to the point of use 2 begins again.

[0043] As described above, according to this embodiment, it is possible to individually sterilize only the raw water tank 11 and the activated carbon filter 17, in addition to sterilizing the entire system including the membrane separation device 12 and the EDI device 13. This makes it possible to more frequently sterilize with hot water the locations in the pure water production system 10 where live bacteria are likely to grow, i.e., the raw water tank 11 where raw water accumulates and the activated carbon filter 17 that removes residual chlorine from the raw water.

[0044] During the water sampling process of the pure water production system 10, the on-off valve V5 of the hot water reflux line L6 is constantly closed, which means that raw water and pure water circulated during each sterilization process tend to stagnate in the hot water reflux line L6. Therefore, to minimize such stagnation, it is preferable to make the length of the hot water reflux line L6 as short as possible. That is, it is preferable to make the lengths of the portions on the primary side and secondary side of the on-off valve V5 as short as possible. Furthermore, during the activated carbon sterilization process, the on-off valve V4 of the water supply line L1 is closed and the on-off valve V5 of the hot water reflux line L6 is open. This means that raw water tends to stagnate in the portion of the water supply line L1 from its branch with the hot water reflux line L6 to the on-off valve V4. This may result in insufficient hot water reaching the stagnation portion, resulting in insufficient sterilization. From this perspective, it is preferable to position the on-off valve V4 as close as possible to the branch in the water supply line L1. For the same reason, it is preferable that the opening / closing valve V6 of the raw water supply line L4 be located as close as possible to the connection point with the hot water reflux line L6.

[0045] As mentioned at the beginning, the illustrated configuration of the water treatment system 1 is merely an example, and the configuration of the pure water production apparatus 10 is not limited to the illustrated configuration, as long as it can produce pure water that meets predetermined water quality standards (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). For example, in addition to the membrane separation apparatus 12, a non-regenerative or regenerative mixed-bed ion exchange apparatus may be provided instead of the EDI apparatus 13 as water treatment means for treating raw water to produce pure water (treated water). Meanwhile, the water supply line L1 may be provided with a water softener that removes hardness components (such as calcium and magnesium) from the raw water in addition to the activated carbon filter 17 and filter 18 as pretreatment means for pretreatment of the raw water supplied to the membrane separation apparatus 12. The water softener may be located, for example, upstream of the activated carbon filter 17, but because the ion exchange resin (cation exchange resin) filling the water softener is more susceptible to thermal degradation than activated carbon, it is preferably located in a position where hot water does not flow during the activated carbon sterilization process, which is performed more frequently, that is, downstream of the on-off valve V4. The location of the filter 18 is not particularly limited, but for the same reason, it is preferably located downstream of the on-off valve V4 shown in the figure.

[0046] The hot water reflux line L6 may be connected directly to the raw water tank 11, rather than to the raw water supply line L4. Even in this case, the raw water tank 11 and the activated carbon filter 17 can be sterilized separately by opening the on-off valve V5 of the hot water reflux line L6 and refluxing hot water from the water supply line L1 to the raw water tank 11 during the activated carbon sterilization process. In this case, the on-off valve V5 of the hot water reflux line L6 does not need to be opened during the total sterilization process. The on-off valve V4 of the water supply line L1 may be a control valve that can be adjusted to any opening degree. For example, the opening degree during the total sterilization process may not be fully open but may be a predetermined intermediate opening degree. The on-off valve V5 of the hot water reflux line L6 may also be a control valve that can be adjusted to any opening degree. For example, the opening degree during the activated carbon sterilization process may not be fully open but may be a predetermined intermediate opening degree, and the opening degree during the total sterilization process may not be fully closed but may be a predetermined intermediate opening degree.

[0047] (Second embodiment) FIG. 2 is a schematic configuration diagram of a water treatment system according to a second embodiment of the present invention.

[0048] This embodiment differs from the first embodiment in that the activated carbon filter 17 is provided not in the feedwater line L1 but in the raw water supply line L4, specifically, downstream of the connection with the hot water reflux line L6. Accordingly, the opening and closing operation of the on-off valve V5 of the hot water reflux line L6 during the total sterilization step also differs from that of the first embodiment. That is, in the first embodiment, the on-off valve V4 of the feedwater line L1 is opened during the total sterilization step, while the on-off valve V5 of the hot water reflux line L6 does not necessarily need to be opened in some cases (although it is preferable that it be opened in the configuration shown in FIG. 1 ). However, in this embodiment, it must be opened (first process). This is because, if the on-off valve V5 of the hot water reflux line L6 is not opened during the total sterilization step, the hot water flowing through the feedwater line L1 will not pass through the hot water reflux line L6 to the raw water supply line L4, and therefore the activated carbon filter 17 will not be sterilized. The other configurations of this embodiment are the same as those of the first embodiment, and the effects obtained thereby are also the same as those of the first embodiment, except that the activated carbon filter 17 can be made smaller because the amount of water flowing through the raw water supply line L4 is smaller than that through the water supply line L1. [Explanation of symbols]

[0049] 1. Water treatment system 2 Use Points 10 Pure water production equipment 11 Raw water tank 12 Membrane separation equipment 13 EDI equipment 14 Control Unit 15 Water pump 16 Heat exchanger 17 Activated carbon filter 18 Filters 19 Pressure pump 20 Pure water supply equipment 21 Pure water tank 22 Pure water pump 23 Heat exchanger L1 water supply line L2 permeate line L3 RO concentrated water line L4 raw water supply line L5 bypass line L6 Hot water reflux line L7 Pure water line L8 EDI concentrate line L9 Pure water return line L10 Circulation Line L11 Water supply line V1~V8 on-off valves

Claims

1. A water treatment system, a tank for storing the water to be treated; a water treatment means for treating the water to be treated to produce treated water; a pretreatment means including at least an activated carbon filter for pretreating the water to be treated that is to be supplied to the water treatment means; a supply line passing through the tank and the activated carbon filter to the water treatment means; a return line branching from the supply line downstream of the tank and downstream of the activated carbon filter and returning to the upstream of the tank and upstream of the activated carbon filter; a return line for returning treated water from the water treatment means to the tank; a heating means provided in the supply line between the tank and the branching portion of the return line, for heating the water to be treated flowing through the supply line; a control means for controlling the operation of the water treatment system; The control means executes a first process of causing at least a portion of the hot water to flow into the reflux line when the heating means heats the water to be treated flowing through the supply line to generate hot water, the activated carbon filter is provided in the supply line upstream of the tank; In the first treatment, the control means causes a portion of the hot water to flow from the supply line through the water treatment means to the return line, and causes the remainder to flow into the reflux line.

2. A tank for storing water to be treated; a water treatment means for treating the water to be treated to produce treated water; a pretreatment means including at least an activated carbon filter for pretreating the water to be treated that is to be supplied to the water treatment means; a supply line passing through the tank and the activated carbon filter to the water treatment means; a return line branching from the supply line downstream of the tank and downstream of the activated carbon filter and returning to the upstream of the tank and upstream of the activated carbon filter; a heating means provided in the supply line between the tank and the branching portion of the return line, for heating the water to be treated flowing through the supply line; the pretreatment means includes a pretreatment means other than the activated carbon filter, A water treatment system, wherein the other pretreatment means is provided downstream of a branch point of the supply line with the return line, and is not provided upstream of the branch point.

3. a control means for controlling the operation of the water treatment system; The water treatment system described in claim 2, wherein the control means performs a first process in which, when the heating means heats the treated water flowing through the supply line to produce hot water, at least a portion of the hot water is flowed into the return line.

4. The water treatment system according to claim 3 , wherein the control means causes all of the hot water to flow into the reflux line in the first treatment.

5. a return line for returning treated water from the water treatment means to the tank; the activated carbon filter is provided in the supply line upstream of the tank; The water treatment system according to claim 3 , wherein the control means, in the first treatment, causes a portion of the hot water to flow from the supply line through the water treatment means to the return line, and causes the remainder to flow into the reflux line.

6. a return line for returning treated water from the water treatment means to the tank; the activated carbon filter is provided in the supply line downstream of the tank; The water treatment system according to claim 3 or 4, wherein the control means executes a second treatment in which at least a portion of the hot water is circulated from the supply line through the water treatment means to the return line.

7. the pretreatment means includes a pretreatment means other than the activated carbon filter, The water treatment system according to claim 1 , wherein the other pretreatment means is provided downstream of a branch point of the supply line with the return line, but not upstream of the branch point.

8. The water treatment system according to claim 1 , which is used to produce pure water for use in pharmaceutical manufacturing.

9. A method for operating a water treatment system comprising: a tank for storing water to be treated; water treatment means for treating the water to be treated to produce treated water; pretreatment means including at least an activated carbon filter for pretreatment of the water to be treated that is supplied to the water treatment means; and a supply line that passes through the tank and the activated carbon filter and leads to the water treatment means, the activated carbon filter being provided on the supply line upstream of the tank, the method comprising: a step of circulating the water to be treated in the tank through the supply line and heating the circulating water to be treated to generate hot water; and returning at least a portion of the hot water to the tank and the activated carbon filter through a return line branching from the supply line downstream of the tank and downstream of the activated carbon filter, A method for operating a water treatment system, wherein the step of returning at least a portion of the hot water includes: returning all of the hot water to the tank and the activated carbon filter, thereby sterilizing the tank and the activated carbon filter; and returning a portion of the hot water from the activated carbon filter to the tank, supplying the remainder to the water treatment means, and then returning it to the tank, thereby sterilizing the tank, the activated carbon filter, and the water treatment means.

10. A method for operating a water treatment system having a tank for storing water to be treated, water treatment means for treating the water to be treated to produce treated water, pretreatment means including at least an activated carbon filter for pretreatment of the water to be treated that is supplied to the water treatment means, and a supply line that passes through the tank and the activated carbon filter to the water treatment means, a step of circulating the water to be treated in the tank through the supply line and heating the circulating water to be treated to generate hot water; and returning at least a portion of the hot water to the tank and the activated carbon filter through a return line branching from the supply line downstream of the tank and downstream of the activated carbon filter, A method for operating a water treatment system, wherein the step of refluxing at least a portion of the hot water includes not passing the hot water through any pretreatment means other than the activated carbon filter among the pretreatment means.

11. 11. The method of operating a water treatment system according to claim 10, wherein the step of returning at least a portion of the hot water includes returning all of the hot water to the tank and the activated carbon filter to sterilize the tank and the activated carbon filter.

12. the activated carbon filter is provided in the supply line upstream of the tank; 12. The method for operating a water treatment system according to claim 11, wherein the step of returning at least a portion of the hot water further comprises returning a portion of the hot water from the activated carbon filter to the tank and supplying the remainder to the water treatment means and then returning it to the tank, thereby sterilizing the tank, the activated carbon filter, and the water treatment means.

13. the activated carbon filter is provided in the supply line downstream of the tank; 11. The method of operating a water treatment system according to claim 10, further comprising the step of supplying at least a portion of the hot water to the water treatment means through the supply line and then returning it to the tank, thereby sterilizing the tank, the activated carbon filter and the water treatment means.

14. 10. The method for operating a water treatment system according to claim 9, wherein the step of refluxing at least a portion of the hot water includes not passing the hot water through any pretreatment means other than the activated carbon filter among the pretreatment means.

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