JP7741220B2 - Water treatment system and method for operating same - Google Patents

Description

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

One type of equipment that supplies pure water (such as purified water or water for injection) used in pharmaceutical manufacturing to points of use is known, which constantly circulates pure water from a pure water tank along a circulation line regardless of whether there is demand 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 such pure water supply systems handle pure water used in pharmaceutical manufacturing, they periodically perform a sterilization process between normal operations (pure water circulation operations) to sterilize the system with high-temperature steam (for example, 121°C or higher) in order to prevent the growth of bacteria and microorganisms.

When resuming normal operation of a pure water supply system after steam sterilization, it is necessary to vent the air that has filled the system (air venting). In particular, it is necessary to thoroughly vent the air from the circulation pump to prevent damage due to cavitation and performance degradation due to air entrapment. One method for doing this is to introduce pure water into the system and return the remaining air in the circulation pump along with the pure water to the pure water tank, where it is then discharged to the outside through a vent filter. Specifically, for example, an air vent line could be directly connected between the circulation pump's air vent and the pure water tank. However, this would require a sanitary air vent line that is long and increases construction costs. Therefore, a common method is to connect an air vent line to the discharge side of the circulation pump (discharge line) and return the remaining air in the circulation pump to the pure water tank via the discharge line.

Japanese Patent Application Laid-Open No. 2006-095479 Japanese Patent Application Laid-Open No. 2017-196587

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

The object of the present invention is to provide a water treatment system and an operating method thereof that suppresses the occurrence of poor air removal due to water sealing.

To achieve the above-mentioned objectives, the water treatment system of the present invention comprises a tank for storing pure water, a pump for discharging the pure water from 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; the first valve is 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 is opened before the pump is started.

The method for operating a water treatment system of the present invention includes a tank for storing pure water, a pump for discharging the pure water from 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 at the top of the pump casing to the discharge line. The method 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 in 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.

As described above, the present invention can prevent poor air venting caused by water sealing.

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

Embodiments of the present invention will be described below with reference to the drawings. In this specification, a pure water supply device that supplies pure water used in pharmaceutical manufacturing, etc., 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 to this. In this specification, purified water refers to tap water that has been 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.

Figure 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 is merely an example and does not limit the present invention. It goes without saying that it can be modified as appropriate depending on the purpose, application, and required performance of the system.

The pure water supply system 1 includes a pure water tank 11 that stores pure water, a circulation line L1 that circulates the pure water in the pure water tank 11, and a circulation pump 12 that is attached to the circulation line L1 and pumps the pure water from the pure water tank 11 through the circulation line L1. The circulation line L1 consists of a supply line L11 that connects the pure water tank 11 to the suction side of the circulation pump 12, and a discharge line L12 that connects 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 circulation of the pure water in the pure water tank 11 along the circulation line L1, while also allowing a portion of the water to be sent 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 system 1 may supply pure water to multiple use points 2.

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) depending on the water level in the pure water tank 11 detected by a water level sensor (not shown), for example. Specifically, when the water level in the pure water tank 11 falls below a predetermined lower limit, an on-off valve (not shown) on the pure water supply line L3 opens, and pure water is supplied to the pure water tank 11. Then, when the water level in the pure water tank 11 reaches a predetermined upper limit, the on-off valve (not shown) on the pure water supply line L3 closes, and the supply of pure water to the pure water tank 11 stops.

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 this 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 on the discharge line L12 upstream of its connection 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 on the discharge line L12 is always open during normal operation (pure water circulation operation) of the pure water supply system 1 and opens and closes when the steam sterilization process described below is performed. Furthermore, the automatic on-off valve AV2 on 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 opens and closes when the steam sterilization process described below is performed. As will be described in more detail below, the air vent line L13 may be provided with a capacitance sensor 13 that detects whether its interior is filled with pure water.

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 point 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 on the discharge line L12 adjacent to 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 the 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-off valves with micro-holes may be provided on the secondary side of the on-off valves V11, V13, and V15 of each drain line L14-L16. The on-off valves with micro-holes are on-off valves with micro-holes that are closed as necessary during the steam sterilization process described below and allow only condensed water to pass through. Examples of such on-off valves include grooved diaphragm valves and perforated ball valves.

Although not shown, an ultraviolet sterilizer and a heat exchanger are provided on 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 irradiating it with ultraviolet light. The heat exchanger is used in a hot water sterilization process, which is performed periodically during normal operation. It heats the pure water circulating along the circulation line L1 to, for example, 60°C or higher, preferably 80°C or higher, to produce hot water, which 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 continues for a long period of time, the temperature of the pure water may rise due to heat generated by the circulation pump 12 and 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 increases.

During normal operation of the pure water supply system 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 on the discharge line L12 and the air vent line L13 and the on-off valves V12 and V14 on the discharge line L12 are opened, while the on-off valves V11, V13, and V15 on each of the drainage lines L14 to L16 are closed. The circulation pump 12 is operated, and the pure water stored in the pure water tank 11 is circulated through the circulation line L1. Then, when a water sampling request is made from the point of use 2, the on-off valve V1 on the water supply line L1 is opened, and a portion of the pure water circulating through the circulation line L1 is supplied to the point of use 2 via the water supply line L1.

In the pure water supply system 1 that handles the pure water used in pharmaceutical manufacturing, a sterilization process is performed periodically (e.g., once a week to once a year) between normal operations to prevent the growth of bacteria and microorganisms. The system uses steam to sterilize the inside of the system, including the pure water tank 11 and circulation line L1. 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 a similar on-off valve V3, and a control unit 14 that executes the steam sterilization process. The series of steps in this steam sterilization process are described in detail below.

(Sterilization preparation process)
The sterilization preparation step is a step of discharging the pure water in the system of the pure water production system 1 to the outside in preparation for sterilizing the inside of the system of the pure water supply system 1 with steam.

The sterilization preparation process begins with draining the pure water tank 11. Specifically, the on-off valve (not shown) on the pure water supply line L3 is closed, stopping the supply of pure water to the pure water tank 11. If pure water was previously used at the point of use 2, the on-off valve V1 on the water supply line L1 is closed. Then, while the circulation pump 12 continues to operate, the on-off valve V14 on the discharge line L12 is closed and the on-off valve V15 on the third drain line L16 is opened. In this way, operation of the pure water supply device 1 (pure water circulation) 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. The circulation pump 12 is then stopped, stopping the discharge of pure water from the pure water tank 11. Note that the pure water may be discharged from the pure water tank 11 until the pure water tank 11 is completely empty, but in that case, there is a concern that the circulation pump 12 may be damaged due to dry operation. Therefore, it is preferable to stop the operation of the circulation pump 12 before the pure water tank 11 is 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 of the bottom end plate of the pure water tank 11).

Once the draining of the pure water tank 11 is complete, the on-off valve V3 on the clean air inlet line L5 is opened, allowing clean air to be introduced into the pure water tank 11, and the resulting pressure is used to drain the water from the circulation line L1.

Draining of the circulation line L1 is carried out in three stages. Specifically, first, the automatic on-off valves AV1 and AV2 on the discharge line L12 and air vent line L13 are closed, and the on-off valve V11 on 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 up to its connection with the first drain line L14 (hereinafter also referred to as the "upstream portion") is discharged to the outside.

In this case, to prevent water from pooling 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 that it slopes downward toward the downstream side. The magnitude of the downward slope is not particularly limited, but is preferably 1/100 or greater. Having the supply line L11 slope downward 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 system 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 opens horizontally at the bottom of the casing. Additionally, it is preferable that the upstream portion of the discharge line L12 and the portion of the first drain line L14 up to the on-off valve V11 be arranged so that they slope downward toward the downstream side, to prevent water from pooling in those portions. The magnitude of the downward slope is not particularly limited, but is preferably 1/100 or greater. From the perspective 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. For this reason, it is preferable that the discharge port of the circulation pump 12 open horizontally at the bottom of the casing, as described above.

When the first stage of drainage is complete, the on-off valve V11 of the first drain line L14 is closed, and the automatic on-off valves AV1 and AV2 of the discharge line L12 and 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 drain 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 drain line L14 to its connection with the second drain line L15 (hereinafter 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 drain 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 drain line L16 is opened. As a result, in the final stage, the pure water in the section 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 section") is discharged to the outside. When the final stage of drainage is complete, the on-off valve V15 of the third drain line L16 is closed. Note that drainage at each stage continues until it is confirmed that pure water is no longer being discharged from each of the drain lines L14 to L16.

(Steam sterilization process)
The steam sterilization process is a process of sterilizing the inside of the system of the pure water supply apparatus 1 using steam. Specifically, it 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 2 and holding it for a certain period of time.

The steam sterilization process begins when the on-off valve V3 on the clean air inlet line L5 is closed, stopping the introduction of clean air and completing the draining of the circulation line L1. During 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 on the steam inlet line L4 is opened, and the automatic on-off valves AV1 and AV2 on the discharge line L12 and the air vent line L13 are closed, and the on-off valve V11 on the first drain line L14 is opened. This allows steam to be introduced into the pure water tank 11, supply line L11, circulation pump 12, and the upstream portions of the discharge line L12. The micro-hole on-off valve (not shown) on the first drain line L14 is then closed as necessary, and the automatic on-off valves AV1 and AV2 on 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, allowing steam to be introduced 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, allowing steam to be introduced into the downstream portion of the discharge line L12.

Finally, the micro-hole valve (not shown) on the third drain line L16 is closed as necessary, and the valve V14 on the discharge line L12 is opened. In this way, steam is introduced into the circulation line L1 via the pure water tank 11 and maintained for a certain period of time, sterilizing the system of the pure water supply system 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, the pure water tank 11 to be sterilized is large, there are many instruments to be sterilized, there are many piping branches from the circulation line L1, or steam needs to be reliably supplied to locations far from the steam source, adjusting the gauge pressure to approximately 0.15-0.19 MPa enables the introduction of steam at 121°C or higher. In addition to being introduced into the circulation line L1 in three stages as described above, it may also be introduced in one stage by simultaneously opening the on-off valves V11, V13, and V15 on each of the drainage lines L14 to L16.

(Water supply preparation process)
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.

After steam has been introduced for a certain period of time, the on-off valve V2 on the steam inlet line L4 is closed, stopping the introduction of steam. When the steam sterilization process is thus completed, the water supply preparation process begins. In the water supply preparation process, the on-off valve V3 on the clean air inlet line L5 is first opened, and clean air is introduced into the circulation line L1 via the pure water tank 11, thereby cooling the system within the pure water supply device 1. There are no particular limitations on the method for introducing clean air into the circulation line L1; for example, it may be done in three stages, similar to the introduction of steam during the steam sterilization process, or in one stage. In other words, the on-off valves V11, V13, and V15 of each drainage line L14 to L16 can be opened sequentially in three stages, in the upstream, midstream, and downstream portions of the discharge line L12, or the on-off valves V11 and V13 of the first and second drainage lines L14 and L15 can be left open, and the on-off valve V15 of the third drainage line L16 can be opened, in one stage up to the downstream portion of the discharge line L12.

Then, for example, when the temperature inside the pure water tank 11 drops below 90°C, the on-off valve V3 on the clean air inlet line L5 closes, halting the introduction of clean air into the circulation line L1 through the pure water tank 11. The on-off valve (not shown) on the pure water supply line L3 opens, starting the supply of pure water to the pure water tank 11. At this time, the on-off valve V11 on the first drain line L14 closes, and the automatic on-off valves AV1 and AV2 on the discharge line L12 and air vent line L13 also close. 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 air vent line L13, while still 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 the set water level, the automatic on-off valve AV2 on the air vent line L13 opens. 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 out into the discharge line L12.

Once the air vent line L11 is filled with pure water, the automatic on-off valve AV1 on 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 on the discharge line L12 are opened, and the on-off valves V13 and V15 on the second and third drainage lines L16 are closed. The air that filled the discharge line L12 is returned to the pure water tank 11 along with the pure water delivered by the circulation pump 12, and is then discharged to the outside through a vent filter (not shown) installed 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.

In summary, during the water supply preparation process, 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. In other words, if the automatic on-off valve AV1 of the discharge line L12 remains open since the steam sterilization process, the head pressure of the pure water stored in the pure water tank 11 will cause pure water to flow into the discharge line L12 until its level reaches the same as the water level in the pure water tank 11. When this water reaches the connection with the air vent line L13, the air vent line L13 will be sealed with water, preventing the remaining air from being discharged from the circulation pump 11, potentially 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.

In addition, 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. From this perspective, as well as from the perspective of shortening the time until normal operation of the pure water supply system 1 resumes, the automatic on-off valve AV2 of the air purge line L13 does not have 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 process. Furthermore, the automatic on-off valve AV2 of the air purge line L13 does not necessarily have 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.

However, 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 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 a higher head pressure of the pure water in the pure water tank 11, thereby further increasing the flow rate of the pure water flowing into the supply line L11. The set water level at this time is not particularly limited, but is preferably set to the highest water level (predetermined upper water level) that can be stored in the pure water tank 11 in order to maximize the use of the head pressure of the pure water in the pure water tank 11.

However, 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 expelled. Therefore, to expel this 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 any air that may be present therein. As a result, any air that was not completely expelled by simply opening the automatic on-off valve AV2 in the air vent line L13 is forced out of the circulation pump 12 and expelled. After that, when the circulation pump 12 is started, the circulation of 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.

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, it may be opened three or more times to more reliably discharge any remaining air from the circulation pump 12. Furthermore, after the automatic on-off valve AV2 of the air vent 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, i.e., may be performed at a predetermined timing. Alternatively, the respective timings may be determined based on the detection results of the capacitance sensor 13 provided in the air vent 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 result of a determination by the control unit (determination means) 14 as to whether the air vent line L13 is filled with pure water based on a change in capacitance in the air vent line L13. However, considering 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.

The automatic on-off valves AV1 and AV2 may be control valves that can be adjusted to any opening degree, but from a cost perspective, simple on-off valves are preferable. Manual on-off valves may also 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 of pure water after steam sterilization has been completed, thereby contributing to labor savings and a reduction in human error.

Furthermore, the water detection sensor that detects the presence or absence of pure water in the air vent line 13 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 13.

In the above-described embodiment, an example was given in which water was drained from the system for steam sterilization, but the present invention is not limited to this and can also be applied when water is drained from the system for other reasons, such as during maintenance or part replacement.

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 (10)

a tank for storing pure water;
a pump for discharging the pure water in the tank;
a supply line connecting the tank and the suction side of the pump;
a discharge line connecting the discharge side of the pump and the tank;
an air vent line connecting an air vent port provided in an upper part of a casing of the pump and the discharge line;
a first valve provided in the discharge line upstream of a connection portion with the air vent line,
A water treatment system, 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 with the pump stopped, and is opened before the pump is started. Further, a second valve is provided in the air vent line,
2. The water treatment system of claim 1, wherein the second valve is 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 is opened before the first valve is opened. a water level sensor for detecting the water level in the tank;
The water treatment system according to claim 2 , wherein the second valve is opened when the water level detected by the water level sensor reaches a set water level. The water treatment system of claim 2 or 3, wherein the first valve is opened at least twice after the second valve is opened. a water detection sensor that detects the presence or absence of pure water in the air vent line;
4. The water treatment system according to claim 2, further comprising: a determination means for determining whether to start the pump based on a detection result of the water detection sensor after the second valve is opened. 1. 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 an intake 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 provided in an upper part of a casing of the pump to the discharge line, comprising:
a step of emptying the tank in which the pure water has been stored, and then supplying the pure water to the tank by closing a first valve provided in the discharge line upstream of a connection portion with the air vent line while stopping the pump;
and after starting the supply of pure water to the tank, opening the first valve and starting the pump at a predetermined timing. the step of supplying the pure water includes closing a second valve provided in the air vent line and supplying the pure water to the tank;
7. The method of operating a water treatment system of claim 6, further comprising the step of opening the second valve before opening the first valve. The method for 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. The method for operating a water treatment system described in claim 7 or 8, wherein the first valve is opened at least twice after the second valve is opened. detecting whether the inside of the air vent line is filled with pure water after opening the second valve;
The method for operating a water treatment system according to claim 7 or 8, further comprising: determining whether or not to start the pump based on the detected result.