Water treatment device and method for operating same

Abstract

This water treatment device 1 includes: an ultrafiltration membrane device 10 having at least one ultrafiltration membrane module 11-14, at least one ultrafiltration membrane module 11-14 having a first permeated water outlet provided close to a concentrated water outlet on one end side and a second permeated water outlet provided close to a treated water inlet on the other end side; a first line L2 connected to the first permeated water outlet; a second line L4 connected to the second permeated water outlet; an opening / closing valve V2 provided in the second line L4; and a third line L7 branched from the second line L4 on the upstream side of the opening / closing valve V2 and joined to the first line L2.

Description

Water treatment device and method for operating same

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

[0002] In recent years, from the viewpoints of energy efficiency and economy, ultrafiltration (UF) membrane devices have been used instead of distillers as devices for producing pure water (purified water, water for injection, etc.) for use in pharmaceutical manufacturing, etc. In such pure water production devices, a sterilization treatment is periodically performed using high-temperature (e.g., 121°C or higher) steam to sterilize the system, as in the past, in order to prevent the growth of bacteria and microorganisms (see, for example, Patent Document 1).

[0003] In a UF membrane device in which steam sterilization is performed, a permeate line is usually connected only to the upper permeate outlet of the two permeate outlets provided at the top and bottom of the UF membrane module, and a discharge line is connected to the lower permeate outlet for discharging condensed water generated during the sterilization process to the outside (see, for example, Patent Document 2).

[0004] Patent No. 7365479 International Publication No. 2013 / 137027

[0005] However, since the above-mentioned discharge line provided in the UF membrane module is not used during normal operation (pure water production), water may remain inside the discharge line, which may cause contamination by bacteria and the like.

[0006] Therefore, an object of the present invention is to prevent water from accumulating in a water treatment device that performs steam sterilization treatment.

[0007] In order to achieve the above-mentioned object, the water treatment device of the present invention comprises an ultrafiltration membrane device having at least one ultrafiltration membrane module, the at least one ultrafiltration membrane module having a first permeate outlet provided at one end side adjacent to a concentrate outlet and a second permeate outlet provided at the other end side adjacent to an inlet for water to be treated, a first line connected to the first permeate outlet, a second line connected to the second permeate outlet, an on-off valve provided on the second line, and a third line branching off from the second line upstream of the on-off valve and joining the first line.

[0008] Furthermore, the method for operating a water treatment device of the present invention is a method for operating a water treatment device having an ultrafiltration membrane device, the at least one ultrafiltration membrane module having a first permeate outlet provided at one end adjacent to a concentrated water outlet and a second permeate outlet provided at the other end adjacent to an inlet for water to be treated, a first line connected to the first permeate outlet, and a second line connected to the second permeate outlet, and includes the steps of: circulating the permeate from the ultrafiltration membrane device through the first line and the second line; and merging the permeate flowing through the second line with the permeate flowing through the first line via a third line branching off from the second line upstream of an on-off valve provided on the second line.

[0009] According to the present invention, it is possible to prevent water from accumulating in a water treatment device in which steam sterilization treatment is performed.

[0010] 1 is a schematic diagram illustrating the configuration of an apparatus for preparing water for injection according to one embodiment.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this specification, the water treatment device of the present invention will be exemplified as an apparatus for producing pure water used in pharmaceutical production, specifically, an apparatus for producing water for injection by treating purified water, but the present invention is not limited thereto. Furthermore, in this specification, an ultrafiltration (UF) membrane device constituting the apparatus for producing water for injection is exemplified as having four UF membrane modules, but the present invention is not limited thereto. The number of UF membrane modules constituting the UF membrane device may be three or less or five or more. In this specification, purified water refers to water obtained by purifying ordinary water by ion exchange, reverse osmosis (RO), ultrafiltration (UF), or a combination thereof. Water for injection refers to purified water or water that has been appropriately pretreated and is treated by distillation or ultrafiltration (RO / UF) to be suitable for pyrogen (endotoxin) testing and viable bacteria testing. Examples of such purified water and water for injection include those specified in the Japanese Pharmacopoeia.

[0012] 1 is a schematic diagram of an apparatus for preparing water for injection according to one embodiment of the present invention. Note that the configuration of the apparatus for preparing water for injection 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 apparatus.

[0013] The water for injection production apparatus 1 is an apparatus that produces water for injection by sterilizing purified water, which is water to be treated, by ultrafiltration, and includes a purified water tank 2 and a UF membrane device 10.

[0014] The UF membrane device 10 treats purified water stored in a purified water tank 2 to produce permeate (water for injection). It has multiple (four in the illustrated example) UF membrane modules 11-14 connected in parallel. Each UF membrane module 11-14 is a hollow fiber membrane module in which numerous hollow fiber UF membranes (hereinafter also referred to as "hollow fiber membranes") are bundled and packed into a cylindrical housing. Its filtration method is an internal pressure crossflow system in which water to be treated is supplied from the inside of the hollow fiber membrane parallel to the membrane surface, permeate is extracted from the outside, and the water that does not permeate the membrane is discharged as concentrate. Each UF membrane module 11-14 has a water to be treated inlet and a concentrate outlet at both ends in the longitudinal direction. The UF membrane modules 11-14 are vertically arranged with the water to be treated inlet facing downward and the concentrate outlet facing upward. Each UF membrane module 11-14 also has two permeate outlets on its side, one above the other and one near the concentrate outlet and the other near the water to be treated inlet. Each of the UF membrane modules 11 to 14 is not limited to an internal pressure type hollow fiber membrane module, but may be an external pressure type in which water to be treated is supplied from the outside of the hollow fiber membrane and permeated water is taken out from the inside.

[0015] The water for injection manufacturing apparatus 1 also has a water supply line L1 that supplies purified water from the purified water tank 2 to the UF membrane device 10, a water delivery line L2 that circulates permeate water from the UF membrane device 10 and supplies it to a water for injection tank (not shown) as water for injection, a concentrated water line L3 that circulates concentrated water from the UF membrane device 10 and returns it to the purified water tank 2, and a first discharge line L4 that discharges hot water, steam, and condensed water introduced into the UF membrane device 10 during steam sterilization treatment, which will be described later, to the outside.

[0016] The water supply line L1 is connected to the treated water inlets of the UF membrane modules 11-14 via a header section 15 consisting of four branch lines. The water supply line (first line) L2 is connected to the permeate outlets (first permeate outlets adjacent to the concentrated water outlets) at the upper side of the UF membrane modules 11-14 via a header section 16 consisting of four branch lines. The concentrated water line L3 is connected to the concentrated water outlets of the UF membrane modules 11-14 via a header section 17 consisting of four branch lines. The first discharge line (second line) L4 is connected to the permeate outlets (second permeate outlets adjacent to the treated water inlets) at the lower side of the UF membrane modules 11-14 via a header section 18 consisting of four branch lines. A purified water supply line L5 is connected to the purified water tank 2, and purified water is supplied from a purified water production device (not shown) as needed.

[0017] A pressure pump 3 is provided in the water supply line L1, and a heat exchanger 4 is provided in the concentrated water line L3. The pressure pump 3 functions to pressurize the purified water in the purified water tank 2 and supply it to the UF membrane device 10. The heat exchanger 4 is used to generate hot water for heat sterilization during hot water sterilization, which is performed periodically between normal operations to reduce the number of viable bacteria in the system, and also to generate hot water for preheating during steam sterilization, which will be described later. Furthermore, the heat exchanger 4 may be used to heat the purified water or water for injection in the system so that the water is drawn into the water for injection tank at a high temperature (e.g., 80°C or higher). Although not shown, temperature sensors are provided near the inlet and outlet of the heat exchanger 4, respectively, to confirm that the temperature in the system has risen to a predetermined temperature in the above-mentioned cases. Furthermore, the water supply line L2 may be provided with water quality detection means, such as a conductivity meter, a total organic carbon (TOC) meter, a particle meter, a microorganism measuring device, or an endotoxin measuring device, to check the water quality of the permeate from the UF membrane device 10.

[0018] A bypass line L6 is connected to the water supply line L1, branching off from the water supply line L1 downstream of the pressure pump 3 and merging with the concentrated water line L3 upstream of the heat exchanger 4. The bypass line L6 is provided with an on-off valve V1 that is closed during normal operation (production of water for injection) of the water for injection producing apparatus 1 and is opened, for example, when hot water is produced by the heat exchanger 4. The first discharge line L4 is provided with an on-off valve V2, and a confluence line (third line) L7 that branches off from the first discharge line L4 and merges with the water supply line L2 is connected upstream of the on-off valve V2. This allows permeated water from the UF membrane device 10 to also flow through the first discharge line L4 during normal operation. The confluence line L7 is provided with a flow control valve FV1 as a flow rate control means for regulating the flow rate of permeated water flowing from the first discharge line L4 through the confluence line L7 to the water supply line L2. Although not shown, the concentrated water line L3 is connected to a drain line for discharging a portion of the concentrated water to the outside during normal operation (production of water for injection) of the water for injection producing apparatus 1. Similarly, although not shown, the water supply line L2 (specifically, downstream of the junction with the junction line L7) is connected to a return line for returning and circulating the permeated water from the UF membrane device 10 to the purified water tank 2 when there is no request to collect water from the water for injection tank.

[0019] Furthermore, the water supply line L1 and the concentrated water line L3 are connected to a plurality of discharge lines L8-L10 for discharging hot water, steam, and condensed water introduced into the system during steam sterilization, which will be described later. Specifically, an on-off valve V3 is provided downstream of the connection of the water supply line L1 with the bypass line L6, and a second discharge line L8 is connected downstream of the connection via an on-off valve V4. A third discharge line L9 is connected to the downstream end of the water supply line L1 via an on-off valve V5. An on-off valve V6 is provided upstream of the connection of the concentrated water line L3 with the bypass line L6, and a fourth discharge line L10 is connected upstream of the connection via an on-off valve V7.

[0020] The first to fourth discharge lines L4, L8 to L10 are each provided with temperature sensors 5 to 8 and micro-hole on-off valves CV1 to CV4. The micro-hole on-off valves CV1 to CV4 are preferably on-off valves equipped with a condensed water discharge mechanism that allows only condensed water to pass through even when fully closed, specifically, on-off valves with micro-holes. Examples of such on-off valves include grooved diaphragm valves and perforated ball valves. By providing these micro-hole on-off valves CV1 to CV4, it is possible to discharge only the condensed water from the steam to the outside while maintaining the pressure in the space into which steam is introduced during the steam sterilization process described below at or above the saturated vapor pressure of water.

[0021] During normal operation of the water for injection manufacturing apparatus 1, a water sampling process is performed in which purified water stored in the purified water tank 2 is treated by the UF membrane device 10, and the resulting water for injection is supplied to a water for injection tank (not shown) through a water supply line L2. Specifically, permeated water from the upper permeated water outlet of each UF membrane module 11 to 14 flows through the water supply line L2, and permeated water from the lower permeated water outlet flows from the first discharge line L4 through the confluence line L7 and merges with the water supply line L2 when the on-off valve V2 of the first discharge line L4 is closed. In this manner, the permeated water (water for injection) obtained by the UF membrane device 10 is supplied to the water for injection tank through the water supply line L2. At this time, a portion of the concentrated water from the UF membrane device 10 is discharged to the outside through a drain line (not shown) to suppress the progression of concentration of impurities within the system, and the remainder is returned to the purified water tank 2 through a concentrated water line L3. However, when there is no request to collect water from the injection water tank and circulation operation is performed in which all of the permeated water from the UF membrane device 10 is returned to the purified water tank 2, there is no risk of the above-mentioned concentration progressing, so all of the concentrated water may be returned to the purified water tank 2.

[0022] In the water for injection manufacturing apparatus 1 that produces water for injection used in the manufacture of pharmaceuticals and the like, a sterilization process is periodically performed between the above-mentioned normal operations to sterilize the system, including the UF membrane device 10, with steam at 121°C or higher to prevent the growth of bacteria and microorganisms. To this end, the water for injection manufacturing apparatus 1 has a steam introduction line L11 that is connected to the concentrated water line L3 via an on-off valve V8 as steam introduction means for introducing steam into the system. The series of steps in this steam sterilization process will be described in detail below.

[0023] (Preheating Step) The preheating step is a step of raising the temperature in the system to a predetermined temperature, for example, 80 to 90°C, in preparation for sterilizing the inside of the system of the water for injection manufacturing apparatus 1 with steam, in order to prevent a sudden rise in temperature due to the introduction of high-temperature steam. However, if high-temperature water that is higher than room temperature (for example, 25°C) is circulated in the system during normal operation, the preheating step can be omitted.

[0024] During the preliminary heating step, water is not drawn into the water for injection tank, and accordingly, concentrated water is not discharged from the UF membrane device 10 to the outside. The apparatus for producing water for injection 1 produces water for injection in the same manner as during normal operation, except that. At the same time, a heat medium (e.g., steam) is supplied to the heat exchanger 4, thereby heating the concentrated water returned to the purified water tank 2, and the water circulating within the system of the apparatus for producing water for injection 1 is also heated and maintained at, for example, 80 to 90°C. By circulating hot water within the system in this manner, the temperature of the entire system is raised to approximately the same temperature. At this time, the on-off valve V1 of the bypass line L6 is opened, and a portion of the hot water flowing through the water supply line L1 is returned to the purified water tank 2. This allows the water in the purified water tank 2 to be efficiently heated, even when the capacity of the purified water tank 2 is relatively large. In addition, when steam is used as the heat medium for the heat exchanger 4, the steam inlet line L11 may be branched and connected to the heat exchanger 4, thereby supplying steam to the heat exchanger 4 from the steam inlet line L11.

[0025] Thereafter, the on-off valve V3 of the water supply line L1 and the on-off valve V6 of the concentrated water line L3 are closed, so that hot water is continuously circulated only between the purified water tank 2 and the bypass line L6, and the circulation of hot water elsewhere is stopped. The on-off valves V2, V4, V5, and V7 of each discharge line L4, L8-L10 and the micro-hole on-off valves CV1-CV4 are then opened, and clean air is introduced, for example, through a clean air inlet line (not shown), pushing out the hot water in the system except for the circulation path and discharging it to the outside through each discharge line L4, L8-L10. Note that a discharge line similar to the second discharge line L8 is also connected to the return line (not shown) connected to the water supply line L2, and the hot water in the return line is also discharged to the outside through that discharge line.

[0026] (Steam Sterilization Step) The steam sterilization step is a step of sterilizing the inside of the system of the apparatus for producing water for injection 1 with steam, specifically a step of introducing steam into the system through the concentrated water line L3 and maintaining it for a certain period of time.

[0027] When it is confirmed that hot water has ceased to be discharged from each of the discharge lines L4, L8 to L10, and the introduction of clean air through the clean air inlet lines is stopped, the steam sterilization process is initiated. In the steam sterilization process, first, the on-off valve V8 of the steam inlet line L11 is opened, and accordingly, the on-off valve V4 of the second discharge line L8, the on-off valve V7 of the fourth discharge line L10, and the on-off valve (not shown) of the water supply line L2 are closed, thereby introducing steam into the UF membrane device 10 through the concentrated water line L3. The introduced steam flows through the primary sides of each of the UF membrane modules 11 to 14, and is then discharged to the outside from the water supply line L1 through the third discharge line L9. It also passes through the secondary sides of each of the UF membrane modules 11 to 14 and is discharged to the outside through the first discharge line L4.

[0028] As a method for introducing steam into the UF membrane device 10, for example, steam can be introduced vertically upward from the treated water inlets of each UF membrane module 11-14 through the water supply line L1. However, residual water is likely to remain near the treated water inlets, and it is difficult to push such residual water out using steam from below. As a result, repeated collisions between the residual water and the steam occur, which may cause a water hammer and damage the UF membranes. Therefore, it is preferable to introduce steam into the UF membrane device 10 vertically downward from the concentrated water outlets of each UF membrane module 11-14 through the concentrated water line L3, as in this embodiment.

[0029] Thereafter, when the UF membrane device 10 is heated to a predetermined temperature (e.g., 98°C or higher), the micro-hole valves CV1 and CV3 in the first and third discharge lines L4 and L9 are closed. This stops the discharge of steam from the first and third discharge lines L4 and L9, and only condensed water is discharged. At this time, the first discharge line L4 is preferably arranged so as to have a downward slope toward the downstream side so as to prevent water accumulation in the first discharge line L4. The magnitude of the downward slope is not particularly limited, but is preferably 1 / 100 or greater. Whether the UF membrane device 10 has been heated to the predetermined temperature can be confirmed by determining whether the detected values ​​of the temperature sensors 5 and 7 are equal to or greater than a predetermined value.

[0030] Once steam is introduced into the UF membrane device 10, the introduction of steam into the remaining system begins, gradually expanding the range of steam introduction. Specifically, first, the on-off valve V4 of the second discharge line L8 is opened, and the steam introduced into the UF membrane device 10 is discharged from the water supply line L1 to the outside through the second discharge line L8. This allows steam to be introduced into the portion of the water supply line L1 up to its connection with the second discharge line L8. When the temperature of this portion is confirmed to have risen to a predetermined temperature by the detection value of the temperature sensor 6 exceeding a predetermined value, the micro-hole on-off valve CV2 of the second discharge line L8 is closed so that only condensed water is discharged from the second discharge line L8. At the same time, the on-off valve V7 of the fourth discharge line L10 is opened, and the steam introduced from the steam introduction line L11 is discharged from the concentrated water line L3 to the outside through the fourth discharge line L10. This allows steam to be introduced into the portion of the concentrated water line L3 up to its connection with the fourth discharge line L10. When it is confirmed that the temperature of that portion has risen to a predetermined temperature by the temperature sensor 8 reaching a predetermined value or higher, the micro-hole on-off valve CV4 in the fourth discharge line L10 is closed so that only condensed water is discharged from the line L10. Although not described in detail, steam is also introduced into a return line (not shown) connected to the water supply line L2 in the same manner as described above.

[0031] In this way, when the microporous on-off valves CV1 to CV4 of the discharge lines L4, L8 to L10 are closed, the pressure in the system including the UF membrane device 10 increases, and the temperature in the system is further raised to the desired sterilization temperature (for example, 121°C or higher). This state is then maintained for a certain period of time, thereby carrying out the sterilization treatment of the water for injection manufacturing apparatus 1.

[0032] (Temperature-reducing step) The temperature-reducing step is a step of lowering the temperature in the system to a temperature at which water can be collected into the water for injection tank when normal operation of the water for injection manufacturing apparatus 1 is resumed after the steam sterilization step is completed.

[0033] After the steam introduction has been performed for a certain period of time, the on-off valve V8 of the steam introduction line L11 is closed, and the introduction of steam is stopped. Thus, the steam sterilization process is completed. For example, when the temperature in the system drops to 105°C or below, the temperature-reducing process is initiated. In the temperature-reducing process, first, the on-off valves V2, V4, V5, and V7 of the discharge lines L4, L8-L10 are closed, and the on-off valve V3 of the water supply line L1 and the on-off valve V6 of the concentrated water line L3 are opened. As a result, the hot water circulating between the purified water tank 2 and the bypass line L6 during the steam sterilization process flows through the water supply line L1 into the system, resulting in the same circulation of hot water as during the preliminary heating process. Subsequently, the amount of heat medium supplied to the heat exchanger 4 is gradually reduced, or a portion of the circulating hot water is discharged to the outside. Accordingly, room-temperature purified water is gradually supplied to the purified water tank 2 through the purified water supply line L5, thereby starting the cooling of the hot water. When the circulating hot water is cooled to about room temperature, normal operation of the water for injection manufacturing apparatus 1 is resumed, and in response to a request to collect water from the water for injection tank, water for injection manufactured by the water for injection manufacturing apparatus 1 is supplied to the water for injection tank through the water supply line L2. Note that when high-temperature water is circulated within the system during normal operation, cooling of the hot water can be omitted.

[0034] As described above, according to this embodiment, the first discharge line L4 connected to the lower permeate outlet of each UF membrane module 11-14 is connected to the water supply line L2 connected to the upper permeate outlet via the confluence line L7. This allows the permeate obtained in each UF membrane module 11-14 to be extracted from the first discharge line L4 during the water sampling process. That is, since the permeate flows through the first discharge line L4 even during the water sampling process, condensed water generated during the steam sterilization process can be prevented from accumulating in the first discharge line L4. Additionally, the confluence line L7 is provided with a flow control valve FV1 for adjusting the flow rate balance of the permeate flowing through two flow paths, namely, the flow path upstream of the confluence with the confluence line L7 in the water supply line L2 and the flow path from the first discharge line L4 to the confluence line L7. This allows the permeate to flow evenly through the two flow paths, even if the pressure loss from the water inlet to the upper permeate outlet in each UF membrane module 11-14 exceeds the pressure loss from the water inlet to the lower permeate outlet. The flow control valve FV1 is not particularly limited as long as it can adjust the flow rate of the permeate flowing through the merging line L7, and may be, for example, an automatic valve or a manual valve. If the flow control valve FV1 is an automatic valve, a flow sensor may be provided in at least one of the two flow paths, and the opening of the flow control valve FV1 may be automatically adjusted based on the detection result. Alternatively, a flow control mechanism such as an orifice may be used instead of the flow control valve FV1.

[0035] Furthermore, it is preferable that water be passed as evenly as possible not only within each UF membrane module 11-14 but also among the multiple UF membrane modules 11-14. To this end, as shown in the figure, the multiple UF membrane modules 11-14 are preferably connected to the water supply line L2 and the first discharge line L4 so that the UF membrane module located upstream of the water supply line L1 (closer to the pressure pump 3) is located upstream of the water supply line L2 (farther from the junction with the junction line L7) and upstream of the first discharge line L4 (farther from the branch point with the junction line L7). That is, it is preferable that the first UF membrane module 11 located most upstream with respect to the water supply line L1 is also located most upstream with respect to the water supply line L2 and the first discharge line L4. It is also preferable that the fourth UF membrane module 14 located most downstream with respect to the water supply line L1 is also located most downstream with respect to the water supply line L2 and the first discharge line L4. This makes it possible to make the pressure loss from the water supply line L1 to the water transmission line L2 as uniform as possible among the multiple UF membrane modules 11 to 14. For the same reason, the multiple UF membrane modules 11 to 14 are preferably connected to the concentrated water line (fourth line) L3 such that the UF membrane modules located more upstream of the water supply line L1 are located more upstream of the concentrated water line L3 (farther from the heat exchanger 4), as shown in the figure.

[0036] During the water sampling process, the on-off valve V2 of the first discharge line L4 is closed, which tends to cause permeate to stagnate in the portion of the first discharge line L4 from its connection with the confluence line L7 to the on-off valve V2. To minimize the effects of such dead legs, for example, it is preferable that the distance from the center of the main pipe to the closing mechanism at the end of the branch pipe be within six times the inner diameter of the branch pipe. That is, the distance from the center of the confluence line L7 at its connection with the first discharge line L4 to the closed position of the on-off valve V2 is preferably within six times the inner diameter of the first discharge line L4, and more preferably within three times. Alternatively, instead of the on-off valve V2, a sanitary T-branch valve that achieves zero dead legs may be provided at the connection between the first discharge line L4 and the confluence line L7.

[0037] In the above-described embodiment, an example has been described in which only one UF membrane device 10 is provided, but a plurality of UF membrane devices may be provided. In this case, the plurality of UF membrane devices may be connected in series, in parallel, or in a combination of series and parallel.

[0038] 1 Water for injection production apparatus (water treatment apparatus) 2 Purified water tank 3 Pressure pump 4 Heat exchanger 5 to 8 Temperature sensor 10 UF membrane device 11 to 14 UF membrane module 15 to 18 Header section L1 Water supply line L2 Water supply line (first line) L3 Concentrated water line (fourth line) L4 First discharge line (second line) L5 ​​Purified water supply line L6 Bypass line L7 Merging line (third line) L8 to L10 Second to fourth discharge lines L11 Steam introduction line (steam introduction means) V1 to V8 On-off valves CV1 to CV4 On-off valves with micro holes FV1 Flow rate adjustment valve (flow rate adjustment means)

Claims

1. A water treatment device comprising: an ultrafiltration membrane device having at least one ultrafiltration membrane module, the at least one ultrafiltration membrane module having a first permeate outlet provided at one end adjacent to a concentrate outlet and a second permeate outlet provided at the other end adjacent to an inlet for water to be treated; a first line connected to the first permeate outlet; a second line connected to the second permeate outlet; an on-off valve provided on the second line; and a third line branching off from the second line upstream of the on-off valve and joining the first line.

2. A water treatment device as described in claim 1, further comprising a steam introduction means for introducing steam into the ultrafiltration membrane device to sterilize the ultrafiltration membrane device, wherein the on-off valve is opened when the steam introduced by the steam introduction means flows through the second line and is closed when the permeated water from the ultrafiltration membrane device flows through the second line.

3. The water treatment device according to claim 2, further comprising a condensed water discharge mechanism provided in the second line downstream of the on-off valve.

4. A water treatment device as described in any one of claims 1 to 3, wherein the distance from the center of the third line at the connection point with the second line to the closed position of the on-off valve is within six times the inner diameter of the second line.

5. A water treatment device as described in any one of claims 1 to 3, having a flow rate adjusting means provided in the third line for adjusting the flow rate of permeate water flowing from the second line through the third line to the first line.

6. A water treatment device as described in any one of claims 1 to 3, wherein the at least one ultrafiltration membrane module includes a plurality of ultrafiltration membrane modules connected in parallel, and the plurality of ultrafiltration membrane modules are connected to the first line and the second line so that the more upstream the ultrafiltration membrane module is located on the water supply line that supplies the water to be treated to the plurality of ultrafiltration membrane modules, the more upstream the ultrafiltration membrane module is located on the first line and upstream of the second line.

7. A water treatment device as described in claim 6, further comprising a fourth line connected to the concentrated water outlets of the plurality of ultrafiltration membrane modules, and the plurality of ultrafiltration membrane modules are connected to the fourth line so that the more upstream the ultrafiltration membrane module is located on the upstream side of the water supply line, the more upstream of the fourth line it is located.

8. A method for operating a water treatment device having an ultrafiltration membrane device with at least one ultrafiltration membrane module, the at least one ultrafiltration membrane module having a first permeate outlet provided at one end adjacent to a concentrate outlet and a second permeate outlet provided at the other end adjacent to an inlet for water to be treated, a first line connected to the first permeate outlet, and a second line connected to the second permeate outlet, the method comprising the steps of: circulating permeate from the ultrafiltration membrane device through the first line and the second line; and merging the permeate flowing through the second line with the permeate flowing through the first line via a third line branching off from the second line upstream of an on-off valve provided on the second line.

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