Water treatment system and method for operating same

Abstract

A water treatment system 1 comprises: a tank 11 for storing pure water; a pump 12 for sending out pure water in the tank 11; a supply line L11 connecting the tank 11 and the suction side of the pump 12; a discharge line L12 connecting the discharge side of the pump 12 and the tank 11; an air vent line L13 connecting the discharge line L12 and an air vent port 12a provided to a casing upper part of the pump 12; and a first valve AV1 provided to the discharge line L12 at a portion upstream of a portion connected to the air vent line L13. The first valve AV1 is closed when, after the tank 11 storing the pure water becomes empty, supply of pure water to the tank 11 is to be started in a state where the pump 12 is stopped, and is opened before the pump 12 is started.

Description

Water treatment system and method for operating same

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

[0002] Known devices for supplying pure water (such as purified water or water for injection) used in pharmaceutical manufacturing to points of use include those that constantly circulate pure water from a pure water tank along a circulation line, regardless of whether there is demand for it at the point of use, in order to prevent the growth of live bacteria due to stagnation (see, for example, Patent Documents 1 and 2). Because these pure water supply devices handle pure water used in pharmaceutical manufacturing, they periodically perform a sterilization process using high-temperature steam (e.g., 121°C or higher) to sterilize the system between normal operations (pure water circulation operations) in order to prevent the growth of bacteria and microorganisms.

[0003] When a pure water supply system undergoes steam sterilization and resumes normal operation, it is necessary to vent the air that has filled the system (air venting). In particular, sufficient air venting from the circulation pump is necessary to prevent damage due to cavitation and performance degradation due to air entrapment. One possible method for this is to introduce pure water into the system, return the remaining air in the circulation pump along with the pure water to the pure water tank, and then discharge it to the outside through a vent filter. Specifically, for example, it is possible to directly connect the air vent port of the circulation pump to the pure water tank with an air vent line. However, this would require a long, sanitary air vent line, resulting in high construction costs. Therefore, a common method is to connect an air vent line to the discharge side (discharge line) of the circulation line and return the remaining air in the circulation pump to the pure water tank through the discharge line.

[0004] JP 2006-095479 A JP 2017-196587 A

[0005] However, in the method of connecting the air vent line to the discharge line, if the discharge line is filled with pure water before the air vent line when pure water is introduced into the system, the air vent line may become water-sealed, and the remaining air in the circulation pump may not be sufficiently discharged.

[0006] Therefore, an object of the present invention is to provide a water treatment system and an operating method thereof that suppress the occurrence of poor air removal due to water sealing.

[0007] In order to achieve the above-mentioned object, the water treatment system of the present invention comprises a tank for storing pure water, a pump for discharging the pure water in the tank, a supply line connecting the tank to the suction side of the pump, a discharge line connecting the discharge side of the pump to the tank, an air vent line connecting an air vent port provided at the top of the pump casing to the discharge line, and a first valve provided on the discharge line upstream of the connection point with the air vent line, wherein the first valve is closed when the supply of pure water to the tank begins after the tank storing pure water has been emptied and the pump is stopped, and is opened before the pump is started.

[0008] In addition, the method of operating a water treatment system of the present invention is a method of operating a water treatment system having a tank for storing pure water, a pump for discharging the pure water in the tank, a supply line connecting the tank to the suction side of the pump, a discharge line connecting the discharge side of the pump to the tank, and an air vent line connecting an air vent port provided on the top of the pump casing to the discharge line, and includes the steps of: emptying the tank in which the pure water was stored, and then, with the pump stopped, closing a first valve provided on the discharge line upstream of the connection with the air vent line to supply pure water to the tank; and, after starting the supply of pure water to the tank, opening the first valve and starting the pump at a predetermined timing.

[0009] As described above, according to the present invention, it is possible to suppress the occurrence of poor air removal due to water sealing.

[0010] 1 is a schematic configuration diagram of a pure water supply device according to an embodiment of the present invention.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification, a pure water supply device that supplies pure water used in pharmaceutical manufacturing, specifically purified water or water for injection, to a point of use is exemplified as the water treatment system of the present invention, but the present invention is not limited thereto. In this specification, purified water refers to tap water purified by distillation, ion exchange, reverse osmosis, ultrafiltration, or a combination thereof, and water for injection refers to purified water that has been sterilized and conforms to pyrogen (endotoxin) testing and sterility testing. Examples of such purified water and water for injection include those specified in the Japanese Pharmacopoeia.

[0012] 1 is a schematic diagram of a pure water supply system according to one embodiment of the present invention. Note that the configuration of the pure water supply 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 pure water supply apparatus 1 includes a pure water tank 11 for storing pure water, a circulation line L1 for circulating the pure water in the pure water tank 11, and a circulation pump 12 provided on the circulation line L1 and for discharging the pure water from the pure water tank 11 through the circulation line L1. The circulation line L1 includes a supply line L11 connecting the pure water tank 11 to the suction side of the circulation pump 12 and a discharge line L12 connecting the discharge side of the circulation pump 12 to the pure water tank 11. A water supply line L2 is connected to the discharge line L12 via an on-off valve V1, and the water supply line L2 is connected downstream to a use point 2. This allows for a circulation operation in which the pure water in the pure water tank 11 is circulated along the circulation line L1, while a portion of the pure water can be supplied to the use point 2 as needed. The number of water supply lines L2 is not limited to one and may be multiple. In other words, the pure water supply apparatus 1 may be configured to supply pure water to multiple use points 2.

[0014] A pure water supply line L3 is connected to the pure water tank 11, and pure water is supplied from a pure water production device (not shown) in accordance with the water level in the pure water tank 11 detected by, for example, a water level sensor (not shown). Specifically, when the water level in the pure water tank 11 falls below a predetermined lower limit, an open / close valve (not shown) of the pure water supply line L3 is opened, thereby supplying pure water to the pure water tank 11. When the water level in the pure water tank 11 reaches a predetermined upper limit, the open / close valve (not shown) of the pure water supply line L3 is closed, thereby stopping the supply of pure water to the pure water tank 11.

[0015] An air vent port 12a is provided at the top of the casing of the circulation pump 12 for discharging air from the circulation pump 12 to the outside. An air vent line L13 is connected to the air vent port 12a, and the air vent line L13 is connected downstream to the discharge line L12. An automatic on-off valve (first valve) AV1 is provided upstream of the connection point of the discharge line L12 with the air vent line L13, and an automatic on-off valve (second valve) AV2 is also provided on the air vent line L13. The automatic on-off valve AV1 of the discharge line L12 is always open during normal operation (pure water circulation operation) of the pure water supply system 1, and is opened and closed when a steam sterilization process (described later) is performed. Furthermore, the automatic on-off valve AV2 of the air vent line L13 is preferably always open during normal operation of the pure water supply system 1 to prevent the growth of viable bacteria due to stagnation of pure water, and is opened and closed when a steam sterilization process (described later) is performed. As will be described in detail later, the air vent line L13 may be provided with a capacitance sensor 13 that detects whether the inside of the air vent line L13 is filled with pure water.

[0016] A first drain line L14 is connected to the discharge line L12 upstream of the automatic on-off valve AV1 via an on-off valve V11. An on-off valve V12 is provided downstream of the connection of the discharge line L12 with the water supply line L2, and a second drain line L15 is connected upstream of the on-off valve V12 via an on-off valve V13. An on-off valve V14 is provided in the discharge line L12 near the pure water tank 11, and a third drain line L16 is connected upstream of the on-off valve V14 via an on-off valve V15. The drain lines L14-L16 are used not only to discharge pure water from within the system to the outside, but also to discharge steam introduced into the system during the steam sterilization process described below and condensed water generated during the process to the outside. Instead of the on-off valves V12 and V13, a three-way valve may be provided at the connection between the discharge line L12 and the second drain line L15, and instead of the on-off valves V14 and V15, a three-way valve may be provided at the connection between the discharge line L12 and the third drain line L16. Furthermore, on the secondary side of the on-off valves V11, V13, and V15 of each of the drain lines L14 to L16, an on-off valve with a micro-hole may be provided. The on-off valve with a micro-hole is an on-off valve that is closed as necessary during the steam sterilization process described below and has a micro-hole formed therein that allows only condensed water to pass through. Examples of such on-off valves include a grooved diaphragm valve and a perforated ball valve.

[0017] Although not shown, an ultraviolet sterilizer and a heat exchanger are provided in the discharge line L12, for example, downstream of the on-off valve V12. The ultraviolet sterilizer is used to sterilize the pure water flowing through the circulation line L1 by ultraviolet irradiation. The heat exchanger is used to generate hot water by heating the pure water circulating along the circulation line L1 to, for example, 60°C or higher, preferably 80°C or higher, during a hot water sterilization process that is periodically performed between normal operations. The hot water is then used to sterilize the pure water tank 11 and the circulation line L1. The pure water circulation operation is also performed during periods when there is no demand for pure water at the point of use 2, such as at night or on holidays. However, if this operation continues for a long period of time, the temperature of the pure water may rise due to heat generated by the circulation pump 12 or the ultraviolet sterilizer, and may exceed the required temperature at the point of use 2. Therefore, the heat exchanger may be equipped with a cooling function to suppress such temperature rise.

[0018] During normal operation of the pure water supply apparatus 1, as described above, a circulation operation is constantly performed in which the pure water in the pure water tank 11 is circulated along the circulation line L1. Specifically, the automatic on-off valves AV1 and AV2 in the discharge line L12 and the air vent line L13 and the on-off valves V12 and V14 in the discharge line L12 are opened, the on-off valves V11, V13, and V15 in each of the drainage lines L14 to L16 are closed, and the circulation pump 12 is operated, thereby circulating the pure water stored in the pure water tank 11 through the circulation line L1. Then, in response to a water sampling request from the point of use 2, the on-off valve V1 in the water supply line L2 is opened, and a portion of the pure water circulating through the circulation line L1 is supplied to the point of use 2 through the water supply line L2.

[0019] In the pure water supply system 1 that handles the pure water used in pharmaceutical manufacturing, a sterilization process is periodically performed (e.g., once a week to once a year) between normal operations to prevent the growth of bacteria and microorganisms. The system, including the pure water tank 11 and circulation line L1, is sterilized with steam. To achieve this, the pure water supply system 1 includes a steam inlet line L4 equipped with an on-off valve V2, a clean air inlet line L5 equipped with an on-off valve V3, and a control unit 14 that executes the steam sterilization process. The series of steps in this steam sterilization process will be described in detail below.

[0020] (Sterilization Preparation Step) The sterilization preparation step is a step of discharging the pure water in the system of the pure water supply apparatus 1 to the outside in preparation for sterilizing the inside of the system of the pure water supply apparatus 1 with steam.

[0021] In the sterilization preparation process, first, the pure water tank 11 is drained. Specifically, the on-off valve (not shown) of the pure water supply line L3 is closed to stop the supply of pure water to the pure water tank 11. Furthermore, if pure water was previously used at the point of use 2, the on-off valve V1 of the water supply line L2 is closed. Then, while the circulation pump 12 continues to operate, the on-off valve V14 of the discharge line L12 is closed and the on-off valve V15 of the third drain line L16 is opened. In this way, the operation of the pure water supply device 1 (circulation of pure water) is stopped, and the pure water stored in the pure water tank 11 is discharged from the circulation line L1 through the third drain line L16 to the outside by the operation of the circulation pump 12. Thereafter, the circulation pump 12 is stopped, and the discharge of pure water from the pure water tank 11 is stopped. Note that the discharge of pure water from the pure water tank 11 may be continued until the pure water tank 11 is completely empty; however, in this case, there is a risk of damage to the circulation pump 12 due to dry operation. Therefore, it is preferable to stop the operation of the circulation pump 12 before the pure water tank 11 becomes completely empty, that is, when the water level in the pure water tank 11 has dropped to a certain level (for example, when it has reached the top end of the bottom end plate of the pure water tank 11).

[0022] When the draining of the pure water tank 11 is completed, the on-off valve V3 of the clean air introduction line L5 is opened to introduce clean air into the pure water tank 11, and the pressure of the air is used to drain the water from the circulation line L1.

[0023] Draining of the circulation line L1 is performed in three stages. Specifically, first, the automatic on-off valves AV1 and AV2 of the discharge line L12 and the air vent line L13 are closed, and the on-off valve V11 of the first drain line L14 is opened. As a result, in the first stage, the pure water in the supply line L11, the circulation pump 12, and the portion of the discharge line L12 from its most upstream portion to its connection with the first drain line L14 (hereinafter also referred to as the "upstream portion") is drained to the outside.

[0024] In this case, to prevent water from puddling in the supply line L11, it is preferable that the supply line L11 be connected to the lowest part of the pure water tank 11 and be arranged so as to have a downward slope toward the downstream side. The magnitude of the downward slope is not particularly limited, but is preferably 1 / 100 or greater. The downward slope of the supply line L11 is also advantageous in that it prevents air from entering the circulation pump 12 from the pure water tank 11 during normal operation of the pure water supply apparatus 1. Furthermore, to ensure that water is drained from the circulation pump 12, it is preferable that the discharge port of the circulation pump 12 be opened horizontally at the bottom of the casing. Additionally, the upstream portion of the discharge line L12 and the portion of the first drain line L14 from the most upstream portion to the on-off valve V11 are preferably arranged so as to have a downward slope toward the downstream side, to prevent water from puddling in these portions. The magnitude of the downward slope is not particularly limited, but is preferably 1 / 100 or greater. From the viewpoint of drainage of the circulation pump 12, the discharge port of the circulation pump 12 may open vertically downward at the bottom of the casing, and accordingly, the discharge line L12 may be drawn downward from the circulation pump 12. However, if the discharge line L12 is drawn downward, the legs of the pure water tank 11 must be made higher than necessary, which results in the overall height of the apparatus being higher than necessary. Therefore, as described above, it is preferable that the discharge port of the circulation pump 12 open horizontally at the bottom of the casing.

[0025] When the first stage of drainage is complete, the on-off valve V11 of the first drainage line L14 is closed, and the automatic on-off valves AV1 and AV2 of the discharge line L12 and the air vent line L13 are opened. Then, the on-off valve V12 of the discharge line L12 is closed, and the on-off valve V13 of the second drainage line L15 is opened. As a result, in the second stage, the pure water in the air vent line L13 and the portion of the discharge line L12 from its connection with the first drainage line L14 to its connection with the second drainage line L15 (hereinafter also referred to as the "midstream portion") is discharged to the outside. When the second stage of drainage is complete, the on-off valve V13 of the second drainage line L15 is closed, and the on-off valve V12 of the discharge line L12 is opened. Then, the on-off valve V14 of the discharge line L12 is closed, and the on-off valve V15 of the third drainage line L16 is opened. As a result, in the final stage, the pure water in the portion of the discharge line L12 from its connection with the second drain line L15 to its connection with the third drain line L16 (hereinafter also referred to as the "downstream portion") is discharged to the outside. When the draining in the final stage is completed, the on-off valve V15 of the third drain line L16 is closed. Note that draining in each stage is continued until it is confirmed that pure water is no longer being discharged from each of the drain lines L14 to L16.

[0026] (Steam sterilization process) The steam sterilization process is a process of sterilizing the inside of the system of the pure water supply apparatus 1 with steam. Specifically, the process is a process of sterilizing the inside of the system of the pure water supply apparatus 1 by introducing steam into the circulation line L1 through the pure water tank 11 and holding it for a certain period of time.

[0027] The steam sterilization process begins when the on-off valve V3 of the clean air inlet line L5 is closed, stopping the introduction of clean air and completing the draining of the circulation line L1. In the steam sterilization process, steam is first introduced into the circulation line L1 in three stages, similar to the draining of the circulation line L1 described above. Specifically, the on-off valve V2 of the steam inlet line L4 is opened, and simultaneously the automatic on-off valves AV1 and AV2 of the discharge line L12 and the air vent line L13 are closed, and the on-off valve V11 of the first drain line L14 is opened. This allows steam to be introduced into the pure water tank 11, the supply line L11, the circulation pump 12, and the upstream portions of the discharge line L12. Thereafter, the micro-hole on-off valve (not shown) of the first drain line L14 is closed as necessary, and the automatic on-off valves AV1 and AV2 of the discharge line L12 and the air vent line L13 are opened. Then, the on-off valve V12 of the discharge line L12 is closed and the on-off valve V13 of the second drainage line L15 is opened, thereby introducing steam into the air vent line L13 and the midstream portion of the discharge line L12. Furthermore, the on-off valve with micro-holes (not shown) of the second drainage line L15 is closed as necessary, and the on-off valve V12 of the discharge line L12 is opened. Then, the on-off valve V14 of the discharge line L12 is closed and the on-off valve V15 of the third drainage line L16 is opened, thereby introducing steam into the downstream portion of the discharge line L12.

[0028] Finally, the micro-hole on-off valve (not shown) of the third drain line L16 is closed as necessary, and the on-off valve V14 of the discharge line L12 is opened. In this manner, steam is introduced into the circulation line L1 through the pure water tank 11 and maintained for a certain period of time, thereby sterilizing the system of the pure water supply apparatus 1. The pressure of the introduced steam is not particularly limited as long as it can maintain a temperature that properly sterilizes the system. For example, to introduce steam at 121°C or higher, a gauge pressure of approximately 0.11 MPa (absolute pressure of 0.21 MPa) is required. Furthermore, when the length of piping to be sterilized by steam sterilization is long, when the pure water tank 11 to be sterilized is large, when there are many devices to be sterilized, when there are many piping branches from the circulation line L1, or when steam needs to be reliably supplied to locations far from the steam supply source, steam at 121°C or higher can be introduced by adjusting the gauge pressure to approximately 0.15 to 0.19 MPa. In addition, the introduction of steam into the circulation line L1 can be carried out in three stages as described above, or it can be carried out in one stage by simultaneously opening the on-off valves V11, V13, and V15 of each drainage line L14 to L16.

[0029] (Water Supply Preparation Step) The water supply preparation step is a step of removing air from the circulation line L1 and filling the inside with pure water before the normal operation of the pure water supply apparatus 1 is resumed.

[0030] After the steam introduction has been performed for a certain period of time, the on-off valve V2 of the steam introduction line L4 is closed, and the introduction of steam is stopped. When the steam sterilization process is thus completed, the water supply preparation process is initiated. In the water supply preparation process, the on-off valve V3 of the clean air introduction line L5 is first opened, and clean air is introduced into the circulation line L1 through the pure water tank 11, thereby cooling the system of the pure water supply apparatus 1. The method of introducing clean air into the circulation line L1 is not particularly limited. For example, it may be performed in three stages, as with the introduction of steam during the steam sterilization process, or in one stage. That is, clean air may be introduced into the upstream, midstream, and downstream portions of the discharge line L12 in three stages by sequentially opening the on-off valves V11, V13, and V15 of each drainage line L14 to L16. Alternatively, the on-off valves V11 and V13 of the first and second drainage lines L14 and L15 may not be opened, and the on-off valve V15 of the third drainage line L16 may be opened, thereby introducing clean air in one stage to the downstream portion of the discharge line L12.

[0031] Thereafter, for example, when the temperature in the pure water tank 11 drops below 90°C, the on-off valve V3 in the clean air inlet line L5 is closed, stopping the introduction of clean air into the circulation line L1 through the pure water tank 11. Then, the on-off valve (not shown) in the pure water supply line L3 is opened, starting the supply of pure water to the pure water tank 11. At this time, the on-off valve V11 in the first drain line L14 is closed, and the automatic on-off valves AV1 and AV2 in the discharge line L12 and the air vent line L13 are also closed. This prevents pure water from flowing from the pure water tank 11 into the supply line L11, and ultimately into the discharge line L12 and the air vent line L13, while supplying pure water to the pure water tank 11. When a water level sensor (not shown) installed in the pure water tank 11 confirms that the water level in the pure water tank 11 has reached a set water level, the automatic on-off valve AV2 in the air vent line L13 is opened. As a result, the pure water stored in the pure water tank 11 flows from the supply line L11 through the circulation pump 12 to the air vent line L13, pushing any remaining air in the circulation pump 12 into the air vent line L13 and discharging it into the discharge line L12.

[0032] Thereafter, when the air vent line L13 is filled with pure water, the automatic on-off valve AV1 of the discharge line L12 is opened, and the pure water stored in the pure water tank 11 flows into the discharge line L12, starting the circulation pump 12. At this time, the on-off valves V12 and V14 of the discharge line L12 are opened, and the on-off valves V13 and V15 of the second and third drainage lines L16 are closed, causing the air that filled the discharge line L12 to return to the pure water tank 11 together with the pure water delivered by the circulation pump 12. The air is then discharged to the outside through a vent filter (not shown) provided in the pure water tank 11. In this way, the circulation line L1 is filled with pure water, and the circulation of pure water along the circulation line L1 is resumed.

[0033] To summarize the above, in the water supply preparation step, the automatic on-off valve AV1 of the discharge line L12 is closed when the supply of pure water to the pure water tank 11 begins, and is opened before the circulation pump 12 is started, specifically, after the automatic on-off valve AV2 of the air vent line L13 is opened to vent air from the circulation pump 12. This reduces the possibility of air venting failure due to water sealing in the air vent line L13. That is, if the automatic on-off valve AV1 of the discharge line L12 remains open since the steam sterilization step, the head pressure of the pure water stored in the pure water tank 11 causes pure water to flow into the discharge line L12 until its level reaches the same level as the water level in the pure water tank 11. Then, when this water reaches the connection with the air vent line L13, the air vent line L13 is sealed with water, which could prevent the remaining air from being discharged from the circulation pump 12, resulting in air venting failure. Therefore, by opening and closing the automatic on-off valve AV1 of the discharge line L12 at the timing described above, the discharge line L12 will not be filled with pure water before the air vent line L13, thereby reducing the possibility of air venting failure.

[0034] Note that the inflow of pure water into the discharge line L12 can be suppressed regardless of the opening and closing operation of the automatic on-off valve AV2 of the air purge line L13, as long as the automatic on-off valve AV1 of the discharge line L12 is closed. Not only from this perspective, but also from the perspective of shortening the time until normal operation of the pure water supply apparatus 1 resumes, the automatic on-off valve AV2 of the air purge line L13 does not need to be closed when the supply of pure water to the pure water tank 11 begins. That is, it may remain open from the steam sterilization step onward. Furthermore, the automatic on-off valve AV2 of the air purge line L13 does not necessarily need to be provided. Even in this case, as pure water is supplied to the pure water tank 11, pure water flows from the supply line L11 through the circulation pump 12 into the air purge line L13, thereby pushing out and discharging any remaining air in the circulation pump 12.

[0035] However, in order to effectively bleed air from the circulation pump 12, it is preferable to increase the flow rate of the pure water flowing from the pure water tank 11 into the supply line L11. To achieve this, it is preferable to utilize the head pressure of the pure water stored in the pure water tank 11. From this perspective, as described above, it is preferable that the automatic on-off valve AV2 of the air bleed line L13 be closed when the supply of pure water to the pure water tank 11 begins and be opened when the water level in the pure water tank 11 reaches a set water level. This allows the automatic on-off valve AV2 of the air bleed line L13 to be opened with the head pressure of the pure water in the pure water tank 11 increased, thereby further increasing the flow rate of the pure water flowing into the supply line L11. Note that the set water level at this time is not particularly limited, but is preferably the highest water level that can be stored in the pure water tank 11 (a predetermined upper water level) in order to maximize the use of the head pressure of the pure water in the pure water tank 11.

[0036] On the other hand, even if the head pressure of the pure water stored in the pure water tank 11 is utilized, the remaining air in the circulation pump 12 may not be completely discharged, and may not be fully discharged. Therefore, in order to discharge the remaining air, it is preferable to repeatedly open and close the automatic on-off valve AV1 in the discharge line L12 after the automatic on-off valve AV2 in the air vent line L13 is opened and before the circulation pump 12 is started. That is, it is preferable that the automatic on-off valve AV1 in the discharge line L12 is opened, closed, and then opened again. As a result, each time the automatic on-off valve AV1 in the discharge line L12 is opened, the pure water stored in the pure water tank 11 flows through the circulation pump 12 and into the discharge line L12, imparting movement to the fluid in the circulation pump 12 and imparting movement to the air latent therein. As a result, the air that was not completely discharged by simply opening the automatic on-off valve AV2 in the air vent line L13 is pushed out of the circulation pump 12 and discharged. Thereafter, when the circulation pump 12 is started, the circulation operation of the pure water along the circulation line L1 is resumed according to the procedure described above. At this time, the automatic on-off valve AV2 of the air vent line L13 does not have to remain open. For example, it may be closed before the automatic on-off valve AV1 of the discharge line L12 is first opened, and then opened after the automatic on-off valve AV1 of the discharge line L12 is closed.

[0037] In the example described above, the automatic on-off valve AV1 of the discharge line L12 is opened twice (specifically, opened, closed, and then opened again). However, to more reliably discharge remaining air from the circulation pump 12, it may be opened three or more times. Furthermore, after the automatic on-off valve AV2 of the air purge line L13 is first opened, the subsequent opening and closing of the automatic on-off valves AV1 and AV2 and the subsequent activation of the circulation pump 12 may be controlled by a timer. That is, they may be performed at predetermined timings. Alternatively, the respective timings may be determined based on the detection results of the capacitance sensor 13 provided in the air purge line L13. In particular, the timing at which the automatic on-off valve AV1 of the discharge line L12 is finally opened and the subsequent activation of the circulation pump 12 may be determined based on the determination result of the control unit (determination means) 14 based on the change in capacitance in the air purge line L13 as to whether the air purge line L13 is filled with pure water. However, in consideration of cost and ease of control, it is preferable that each timing be set in advance, and therefore it is preferable that the opening and closing of the automatic on-off valves AV1 and AV2 and the start of the circulation pump 12 be controlled by a timer.

[0038] The automatic on-off valves AV1 and AV2 may be control valves that can be adjusted to any opening degree, but from the viewpoint of cost, simple on-off valves are preferable. Also, manual on-off valves may be used instead of the automatic on-off valves AV1 and AV2, but it is preferable to use automatic on-off valves because they can automatically resume the circulation operation of pure water after the steam sterilization process is completed, which contributes to labor saving and reduction of human error.

[0039] Furthermore, the water detection sensor for detecting the presence or absence of pure water in the air vent line L13 is not limited to the capacitance sensor 13, and other types of sensors may be used. Examples of such sensors include a pressure sensor that detects pressure changes due to the generation of head pressure when the line is filled with pure water, a temperature sensor that detects temperature changes when residual heat (e.g., 90°C) after the introduction of clean air is cooled by the inflow of pure water, and a water level sensor that detects the water level in a pot connected to the air vent line L13.

[0040] In the above-described embodiment, an example was given of a case where water was drained from the system for steam sterilization treatment, but the present invention is not limited to this and can also be applied to cases where water is drained from the system for other reasons, such as during maintenance or part replacement.

[0041] 1 Pure water supply device 2 Use point 11 Pure water tank 12 Circulation pump 13 Capacitance sensor 14 Control unit L1 Circulation line L11 Supply line L12 Discharge line L13 Air vent line L14 to L16 Drainage lines L2 Water supply line L3 Pure water supply line L4 Steam introduction line L5 Clean air introduction line AV1, AV2 Automatic on-off valves V1 to V3, V11 to V15 On-off valves

Claims

1. A water treatment system comprising: a tank for storing pure water; a pump for discharging the pure water in the tank; a supply line connecting the tank to the suction side of the pump; a discharge line connecting the discharge side of the pump to the tank; an air vent line connecting an air vent provided in the upper part of the casing of the pump to the discharge line; and a first valve provided on the discharge line upstream of the connection point with the air vent line, wherein the first valve is closed when the supply of pure water to the tank begins after the tank that stored the pure water has been emptied and the pump is stopped, and is opened before the pump is started.

2. The water treatment system of claim 1, further comprising a second valve provided in the air vent line, the second valve being closed when the supply of pure water to the tank begins after the tank storing pure water has been emptied with the pump stopped, and being opened before the first valve is opened.

3. The water treatment system according to claim 2, further comprising a water level sensor that detects the water level in the tank, and wherein the second valve is opened when the water level detected by the water level sensor reaches a set water level.

4. The water treatment system of claim 2 or 3, wherein the first valve is opened at least twice after the second valve is opened.

5. A water treatment system as described in claim 2 or 3, comprising: a water detection sensor that detects the presence or absence of pure water in the air vent line; and a judgment means that determines whether or not to start the pump based on the detection result of the water detection sensor after the second valve is opened.

6. A method for operating a water treatment system having a tank for storing pure water, a pump for discharging the pure water in the tank, a supply line connecting the tank to the suction side of the pump, a discharge line connecting the discharge side of the pump to the tank, and an air vent line connecting an air vent port provided on the top of the pump casing to the discharge line, comprising the steps of: after emptying the tank in which pure water has been stored, and with the pump stopped, closing a first valve provided on the discharge line upstream of the connection with the air vent line to supply pure water to the tank; and after starting the supply of pure water to the tank, opening the first valve and starting the pump at a predetermined timing.

7. The method for operating a water treatment system according to claim 6, wherein the step of supplying pure water includes closing a second valve provided in the air vent line to supply pure water to the tank, and further includes the step of opening the second valve before opening the first valve.

8. The method of operating a water treatment system according to claim 7, wherein the step of opening the second valve includes opening the second valve when the water level in the tank reaches a set water level.

9. The method for operating a water treatment system according to claim 7 or 8, wherein the first valve is opened at least twice after the second valve is opened.

10. A method for operating a water treatment system as described in claim 7 or 8, comprising the steps of: detecting whether the inside of the air vent line is filled with pure water after opening the second valve; and determining whether to start the pump based on the result of the detection.

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