Water treatment system and method for sterilizing the water treatment system

Abstract

To provide a water treatment system capable of finishing hot water sterilization in a short time.SOLUTION: The water treatment system according to an embodiment of the present invention comprises: deactivation means that deactivates a bactericidal agent in raw water to obtain deactivated water; a reverse osmosis membrane device that separates the deactivated water into permeated water and membrane concentrated water by a reverse osmosis membrane; a deactivated water line that guides deactivated water flowing out of the deactivation means to the reverse osmosis membrane device and has a deactivated water shut-off valve shutting off the deactivated water; a first reflux line that connects an upstream side rather than the deactivated water shut-off valve of the deactivated water line and a channel on an upstream side of the deactivation means so as to form a first circulation channel including the deactivation means; a first temperature controller that is disposed in the first circulation channel to control a temperature of water; a second reflux line that connects a channel on a downstream side of the reverse osmosis membrane device and a downstream side rather than the deactivated water shut-off valve of the deactivated water line so as to form a second circulation channel including the reverse osmosis membrane device; and a second temperature controller that is disposed in the second circulation channel to control a temperature of water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Water treatment systems are currently in use that include an inactivation device, such as an activated carbon filtration device, that inactivates disinfectants in raw water, and a reverse osmosis membrane device that separates water using a reverse osmosis membrane.When using such a water treatment system to produce water for manufacturing pharmaceuticals, food, etc., it is known that hot water is passed through the water treatment system to sterilize the inside of the system in order to prevent the growth of microorganisms in the water treatment system.

[0003] Generally, hot water for sterilizing a water treatment system is produced by heating water in a tank, but in order to save energy required for producing hot water, a technique is also known in which hot water is circulated between a heating device that heats water inline to produce hot water, such as a heat exchanger, and the water treatment system. For example, Patent Document 1 describes an apparatus that can perform hot water sterilization without using a tank, by forming a circulation system that circulates hot water between an inactivation device, a reverse osmosis membrane device, and an EDI device connected in series, and a heat exchanger. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5459704 Summary of the Invention [Problem to be solved by the invention]

[0005] Activated carbon filtration devices have a large water retention capacity, and in many cases, the responsiveness of the temperature change of the outflowing water to the temperature change of the supplied water is poor. For this reason, in the configuration of Patent Document 1, there is a delay between raising the temperature of the water supplied to the activated carbon filtration device and raising the temperatures of the reverse osmosis membrane device and the EDI device. Furthermore, because reverse osmosis membranes are generally vulnerable to sudden temperature changes, the temperature change rate must be limited to, for example, about 2°C / min. To prevent the rate of change of the water temperature in the reverse osmosis membrane device from becoming too large, it is necessary to sufficiently reduce the temperature change rate of the water supplied to the activated carbon filtration device, taking into account the poor thermal responsiveness of the activated carbon filtration device. As a result, the configuration of Patent Document 1 requires a long time for hot water sterilization.

[0006] Therefore, an object of the present invention is to provide a water treatment system and a sterilization method for a water treatment system that can complete hot water sterilization in a short period of time. [Means for solving the problem]

[0007] A water treatment system according to one embodiment of the present invention comprises an inactivation means for obtaining inactivated water by inactivating a disinfectant in raw water; a reverse osmosis membrane device for separating the inactivated water into permeate and membrane-concentrated water using a reverse osmosis membrane; an inactivated water line for guiding the inactivated water flowing out from the inactivation means to the reverse osmosis membrane device and having an inactivated water shut-off valve for shutting off the inactivated water; a first return line connecting the upstream side of the inactivated water shut-off valve of the inactivated water line to a flow path upstream of the inactivation means to form a first circulation flow path including the inactivation means; a first temperature control device disposed in the first circulation flow path for adjusting the water temperature; a second return line connecting the downstream flow path of the reverse osmosis membrane device to a downstream side of the inactivated water line of the inactivated water shut-off valve to form a second circulation flow path including the reverse osmosis membrane device; and a second temperature control device disposed in the second circulation flow path for adjusting the water temperature.

[0008] The above-mentioned water treatment system may further include an EDI device that obtains pure water by removing ions from the permeate water through electrical regeneration desalination and electrically concentrated water with an increased content of the ions, and the second return line may be connected to a flow path of the membrane concentrated water flowing out from the reverse osmosis membrane device, a flow path of the pure water flowing out from the EDI device, and a flow path of the electrically concentrated water flowing out from the EDI device.

[0009] In the above-mentioned water treatment system, the distance between the connection point of the first return line in the inactivated water line and the inactivated water shut-off valve and the distance between the connection point of the second return line and the inactivated water shut-off valve may be less than six times the inner diameter of the inactivated water line.

[0010] A sterilization method for a water treatment system according to one embodiment of the present invention is a sterilization method for a water treatment system comprising: an inactivation means for obtaining inactivated water by inactivating a disinfectant in raw water; a reverse osmosis membrane device for separating the inactivated water into permeate and membrane-concentrated water using a reverse osmosis membrane; and an inactivated water line for guiding the inactivated water flowing out from the inactivation means to the reverse osmosis membrane device, the sterilization method comprising the steps of: forming a first circulation flow path for circulating water through the inactivation means and a first temperature control device for adjusting the water temperature by connecting the inactivated water line to a flow path upstream of the inactivation means; and adjusting the output of the first temperature control device to bring the temperature of the inactivation means closer to a target temperature by connecting a flow path downstream of the reverse osmosis membrane device to a portion of the inactivated water line downstream of the first circulation flow path, the second circulation flow path for circulating water through the reverse osmosis membrane device and a second temperature control device for adjusting the water temperature by connecting the flow path downstream of the reverse osmosis membrane device to a portion of the inactivated water line downstream of the first circulation flow path; forming a second circulation flow path for circulating water through the reverse osmosis membrane device; and adjusting the output of the second temperature control device to bring the temperature of the reverse osmosis membrane device closer to the target temperature. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a water treatment system and a sterilization method for a water treatment system that can complete hot water sterilization in a short time. [Brief explanation of the drawings]

[0012] [Figure 1]1 is a schematic diagram showing the configuration of a water treatment system according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a schematic diagram showing the configuration of a water treatment system 100 according to one embodiment of the present invention.

[0014] The water treatment system 100 includes a raw water tank 1, an inactivation means 2, a reverse osmosis membrane device 3, an EDI device 4, a pure water tank 5, a first temperature control device 6, and a second temperature control device 7. The water treatment system 100 further includes a raw water line 10, an inactivated water line 20, a permeate line 30, a membrane-concentrated water line 40, a pure water line 50, an electro-concentrated water line 60, a first reflux line 70, a second reflux line 80, and a control device 90.

[0015] The raw water tank 1 stores raw water. As the raw water, for example, purified water such as tap water and water containing a disinfectant can be used.

[0016] The inactivation means 2 inactivates the disinfectant in the raw water to obtain inactivated water, and may be an inactivation device that performs inactivation unmanned, or chemical injection equipment that provides an operator with access to the raw water for inactivation treatment. Examples of the inactivation device include an activated carbon filtration device and a chemical injection system equipped with a chemical injection device. Examples of the chemical injection equipment include a water tank into which an operator can inject chemicals.

[0017] The reverse osmosis membrane device 3 separates the inactivated water using a reverse osmosis membrane into permeate that has permeated the reverse osmosis membrane and membrane-concentrated water that has not permeated the reverse osmosis membrane.

[0018] The EDI device 4 obtains pure water by removing ions from the permeate water through electrical regeneration demineralization, and electro-concentrated water by increasing the ion content of the permeate water.

[0019] The pure water tank 5 stores the pure water produced by the EDI device 4.

[0020] The first temperature adjustment device 6 adjusts the temperature of the water passing through or temporarily retained. As a specific example, the first temperature adjustment device 6 can be a heat exchanger that adjusts the temperature of the water in the system by exchanging heat with a hot heat source fluid such as steam supplied from the outside, such as a boiler having a heat source such as an electric heater or a burner. The first temperature adjustment device 6 may have only the function of heating water, or may also have the function of cooling water. For example, the first temperature adjustment device 6 can be a heat exchanger that can exchange heat between the water in the system and a cold heat source fluid such as cooling water.

[0021] Similar to the first temperature adjustment device 6, the second temperature adjustment device 7 adjusts the temperature of the water that passes through or is temporarily stored.

[0022] The raw water line 10 supplies raw water from the raw water tank 1 to the inactivation means 2. The raw water line 10 may be configured to include, in this order, a raw water pump 11 that pressurizes the raw water and a raw water shutoff valve 12 that shuts off the raw water.

[0023] The inactivated water line 20 guides the inactivated water flowing out from the inactivation means 2 to the reverse osmosis membrane device 3. The inactivated water line 20 may be configured to include, in this order, an inactivated water shutoff valve 21 that shuts off the inactivated water, and an inactivated water pump 22 that pressurizes the inactivated water. It is preferable that the inactivated water line 20 be linear at least between the connection point of the first return line 70 and the connection point of the second return line.

[0024] The permeate line 30 guides the permeate flowing out from the reverse osmosis membrane device 3 to the EDI device 4. The permeate line 30 may be configured to include, in this order: a permeate flow meter 31 that detects the flow rate of the permeate, a permeate discharge valve 32 that discharges the permeate outside the system, and a permeate pump 33 that pressurizes the permeate.

[0025] The membrane concentrated water line 40 may be configured to include a return section 41 that returns a portion of the membrane concentrated water flowing out from the reverse osmosis membrane device 3 to the upstream side of the inactivated water pump 22 in the inactivated water line 20, and a membrane concentrated water discharge section 42 that discharges a portion of the membrane concentrated water flowing out from the reverse osmosis membrane device 3 to the outside of the system. The return section 41 may be provided with a check valve 43 that prevents water from flowing from the inactivated water line 20 into the membrane concentrated water line 40. The membrane concentrated water discharge section 42 may be provided with a membrane concentrated water flow meter 44 that detects the flow rate of the membrane concentrated water flowing into the membrane concentrated water discharge section 42, and a membrane concentrated water adjustment valve 45 that adjusts the flow rate of the membrane concentrated water discharged to the outside of the system.

[0026] The return section 41 is preferably arranged linearly. Furthermore, the distance from the valve body of the check valve 43 to each end of the return section 41 is preferably no more than six times, and more preferably no more than five times, the inner diameter of the return section 41. This allows the water circulating through the second circulation flow path L2 to reach the valve body of the check valve 43, so that the return section 41 can also be sterilized by circulating hot water through the second circulation flow path L2.

[0027] The pure water line 50 guides the pure water flowing out from the EDI device 4 to the pure water tank 5. The pure water line 50 may be configured to include a pure water discharge valve 51 that discharges the pure water to the outside of the system.

[0028] The electroconcentrated water line 60 discharges the electroconcentrated water flowing out of the EDI device 4 to the outside of the system.

[0029] The first return line 70 connects the upstream side of the inactivated water shutoff valve 21 of the inactivated water line 20 to the flow path upstream of the inactivation means 2, specifically, the downstream side of the raw water shutoff valve 12 of the raw water line 10, via a first temperature control device 6. The first return line 70 may be configured to include a first circulation pump 71 that creates a water flow from the inactivated water line 20 side to the raw water line 10 side, a first inlet shutoff valve 72 that prevents the inflow of inactivated water from the inactivated water line 20, and a first outlet shutoff valve 73 that prevents the inflow of raw water from the raw water line 10. The first return line 70 may also include a first circulating water discharge valve 74 upstream of the first outlet shutoff valve 73 that discharges water to the outside of the system.

[0030] By opening the first inlet shut-off valve 72 and the first outlet shut-off valve 73, the first reflux line 70 is combined with a portion of the raw water line 10 and a portion of the inactivated water line 20 to form a loop-shaped first circulation flow path L1 that includes the inactivation means 2 and the first temperature control device 6.

[0031] The distance between the connection point of the first reflux line 70 with the inactivated water line 20 and the valve body of the inactivated water shutoff valve 21 is preferably no more than six times, and more preferably no more than five times, the inner diameter of the first reflux line 70. This allows the water circulating through the first circulation flow path L1 to reach the valve body of the inactivated water shutoff valve 21, so that by circulating hot water through the first circulation flow path L1, the portion of the inactivated water line 20 between the first circulation flow path L1 and the inactivated water shutoff valve 21 can be sterilized.

[0032] The second reflux line 80 connects the flow paths downstream of the reverse osmosis membrane device 3, specifically the membrane concentrated water line 40, the pure water line 50, and the electrolytically concentrated water line 60, to the inactivated water line 20 downstream of the inactivated water shutoff valve 21. The second reflux line 80 may include a second circulation pump 81 that forms a water flow from the downstream side of the reverse osmosis membrane device 3 to the inactivated water line 20, a membrane concentrated water switching valve 82 that allows water to flow from the membrane concentrated water line 40 into the second reflux line 80, a pure water switching valve 83 that allows water to flow from the pure water line 50 into the second reflux line 80, an electrolytically concentrated water switching valve 84 that allows water to flow from the electrolytically concentrated water line 60 into the second reflux line 80, and a second outlet shutoff valve 85 that prevents inactivated water from flowing from the inactivated water line 20. The second reflux line 80 may have a second circulating water discharge valve 86 that discharges water to the outside of the system upstream of the second outlet shutoff valve 85. Note that the pure water switching valve 83 and the electrically concentrated water switching valve 84 may each be configured with two shutoff valves.

[0033] The second reflux line 80 is configured such that the membrane concentrated water switching valve 82 switches the flow path so that water is introduced into the second reflux line 80 without being discharged from the membrane concentrated water line 40 outside the system, the pure water switching valve 83 switches the flow path so that water is introduced into the second reflux line 80 from the pure water line 50 without being introduced into the pure water tank, and the electrically concentrated water switching valve 84 switches the flow path so that water is introduced into the second reflux line 80 from the electrically concentrated water line 60 without being discharged outside the system, and by opening the second outlet shut-off valve 85, a loop-shaped second circulation flow path L2 is formed which includes the reverse osmosis membrane device 3, the EDI device 4 and the second temperature control device 7, together with part of the inactivated water line 20, the entire permeate line 30, part of the membrane concentrated water line 40, part of the pure water line 50, and part of the electrically concentrated water line 60.

[0034] The distance between the connection point of the second reflux line 80 with the inactivated water line 20 and the valve body of the inactivated water shutoff valve 21 is preferably no more than six times, and more preferably no more than five times, the inner diameter of the inactivated water line 20. This allows the water circulating through the second circulation flow path L2 to reach the valve body of the inactivated water shutoff valve 21, so that by circulating hot water through the second circulation flow path L2, the portion of the inactivated water line 20 between the second circulation flow path L2 and the inactivated water shutoff valve 21 can be sterilized.

[0035] The control device 90 controls the operation of the water treatment system 100 by controlling the operation of the other components of the water treatment system 100. The control device 90 repeatedly performs a production operation for producing pure water using the water treatment system 100, a sterilization operation for sterilizing the water treatment system 100, and a regeneration operation for regenerating the EDI device 4. The sterilization operation is an operation for implementing the sterilization method for a water treatment system according to the present invention.

[0036] The production operation may include an initial blowing step, a water passing step, and a flushing step. In the initial blowing step, until the operating conditions stabilize and sufficiently clean pure water is obtained, water flowing out of the pure water line 50 from the EDI device 4 is discharged to the outside of the system through the pure water discharge valve 51 without being introduced into the pure water tank 5. The initial blowing step may be performed by omitting the pure water discharge valve 51 and instead using the pure water switching valve 83 to allow water to flow from the pure water line 50 into the second reflux line 80, and then discharging the water that has flowed into the second reflux line 80 to the outside of the system through the second circulating water discharge valve 86. In the water passing step, pure water that flows out of the pure water line 50 through the inactivation means 2, the reverse osmosis membrane device 3, and the EDI device 4 is introduced into the pure water tank 5. In the flushing process, the opening of the membrane concentrated water control valve 45 is increased to reduce the impurity concentration in the space on the membrane concentrated water side inside the reverse osmosis membrane device 3 and in the water inside the membrane concentrated water line 40, and the permeate is discharged outside the system through the permeate discharge valve 32.

[0037] The sterilization operation includes a preparatory step of discharging water remaining in the permeate line 30, membrane-concentrated water line 40, pure water line 50, and electroconcentrated water line 60 to reduce the amount of impurities in the system; a first-stage sterilization step of forming a first circulation flow path L1 for circulating water, including an inactivation means 2 and a first temperature controller 6, and adjusting the output of the first temperature controller 6 disposed in the first circulation flow path L1 to bring the temperature of the inactivation means 2 closer to a target temperature; and a second-stage sterilization step of forming a second circulation flow path L2 for circulating water, including a reverse osmosis membrane device 3, an EDI device 4, and a second temperature controller 7, and adjusting the output of the second temperature controller 7 disposed in the second circulation flow path L2 to bring the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 closer to the target temperatures. The first and second stages of sterilization can be performed independently or in parallel. Typically, the first and second stages of sterilization are started simultaneously and controlled independently.

[0038] The first-stage sterilization process may include a first temperature-raising process in which the temperature of the inactivation means 2 is raised to a predetermined first sterilization temperature, a first temperature-maintaining process in which the temperature of the inactivation means 2 is maintained at the first sterilization temperature for a predetermined first sterilization time, and a first temperature-lowering process in which the temperature of the inactivation means 2 is lowered.

[0039] In the first temperature raising step, the raw water shutoff valve 12 and the inactivated water shutoff valve 21 are closed, the first circulation pump 71 circulates water in the first circulation flow path L1, and the first temperature regulator 6 heats the circulating water, thereby raising the temperature of the inactivation means 2 to the first sterilization temperature. The temperature of the inactivation means 2 may be detected by detecting the temperature of the housing of the inactivation means 2, or the temperature of the circulating water at the outlet of the inactivation means 2.

[0040] The temperature gradient (rate of temperature rise) of inactivation means 2 in the first temperature rise step is not particularly limited, but is preferably set to a controllable value so as not to excessively overshoot the first sterilization temperature, taking into consideration factors such as the capacity of first temperature regulator 6, and it is more preferable to raise the temperature of inactivation means 2 to the first sterilization temperature at a predetermined constant temperature gradient. In other words, in the first temperature rise step, the amount of heat of first temperature regulator 6 may be adjusted throughout, with the first sterilization temperature being the target temperature of inactivation means 2, or the amount of heat of first temperature regulator 6 may be adjusted so that the temperature of inactivation means 2 approaches the target temperature that rises to the first sterilization temperature according to a predetermined profile.

[0041] In the first temperature maintenance step, the first circulation pump 71 circulates water in the first circulation flow path L1, and the amount of heat applied to the circulating water by the first temperature adjustment device 6 is adjusted so as to maintain the temperature of the inactivation means 2 at the first sterilization temperature. The first sterilization temperature may be, for example, 80°C or higher and 85°C or lower. The first sterilization time may be, for example, 30 minutes to 1 hour, depending on the first sterilization temperature.

[0042] In the first temperature-lowering step, the circulating water may be cooled by the first temperature control device 6, or the temperature of the circulating water may be lowered by opening the raw water shutoff valve 12 and introducing raw water into the first circulation flow path L1. When raw water is introduced, excess circulating water may be discharged from the first circulating water discharge valve 74, or depending on the state of the second circulation flow path L2, the inactivated water shutoff valve 21 may be opened to allow excess circulating water to flow downstream.

[0043] The second-stage sterilization process may include a second temperature-raising process in which the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 are raised to a predetermined second sterilization temperature, a second temperature-maintaining process in which the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 are maintained at the second sterilization temperature for a predetermined second sterilization time, and a second temperature-lowering process in which the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 are lowered.

[0044] In the second temperature-raising step, the inactivated water shutoff valve 21 is closed, the pure water switching valve 83 is switched to the second reflux line 80 side, the second circulation pump 81 circulates water in the second circulation flow path L2, and the second temperature adjustment device 7 heats the circulating water, thereby raising the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 to the second sterilization temperature. The temperatures of the reverse osmosis membrane device 3 and the EDI device 4 may be detected as the housing temperatures of the reverse osmosis membrane device 3 and the EDI device 4, the outlet temperature of the circulating water, etc. The temperature gradient of the reverse osmosis membrane device 3 and the EDI device 4 in the second temperature-raising step can be set to, for example, about 2°C / min to protect the reverse osmosis membrane.

[0045] In the second heating step, in order to ensure the flow rate of the circulating water supplied to the EDI device 4 and simultaneously heat the reverse osmosis membrane device 3 and the EDI device 4, the opening of the membrane concentrated water control valve 45 may be adjusted to maintain the ratio of the flow rate of the circulating water flowing out from the reverse osmosis membrane device 3 to the permeate line 30 (detection value of the permeate flow meter 31) to the flow rate of the circulating water flowing out to the membrane concentrated water line 40 (detection value of the membrane concentrated water flow meter 44).

[0046] In the second temperature maintenance step, the second circulation pump 81 circulates the water in the second circulation flow path L2, and the amount of heat applied to the circulating water by the second temperature adjustment device 7 is adjusted so that the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 are maintained at the second sterilization temperature. The second sterilization temperature may be, for example, 80°C or higher and 85°C or lower. The second sterilization time may be, for example, 30 minutes to 1 hour, depending on the second sterilization temperature.

[0047] In the second temperature holding step, the aperture of the membrane concentrate regulating valve 45 may be adjusted as in the second temperature raising step, or the aperture of the membrane concentrate regulating valve 45 may be maintained at the aperture at the end of the second temperature raising step. In the second temperature holding step, the temperature of the reverse osmosis membrane device 3 is kept constant, so the permeation resistance of the reverse osmosis membrane does not change, and therefore the flow rate of the circulating water flowing out to the permeate line 30 does not change unless the aperture of the membrane concentrate regulating valve 45 is changed.

[0048] In the second temperature-lowering step, the circulating water may be cooled by the second temperature control device 7. If the temperature of the inactivation means 2 is low, the temperature of the circulating water in the second circulation flow path L2 may be lowered by opening the inactivated water shutoff valve 21 and introducing the circulating water in the first circulation flow path L1 or the inactivated water supplied from the raw water line 10 and inactivated by the inactivation means. Excess circulating water can be discharged from the second circulating water discharge valve 86. The temperature gradient (temperature-lowering rate) of the reverse osmosis membrane device 3 and the EDI device 4 in the second temperature-lowering step may be set to, for example, about 2°C / min, as in the second temperature-raising step, in order to protect the reverse osmosis membrane.

[0049] When the first and second sterilization steps are started simultaneously, as described above, the temperature gradient is limited in the second temperature-raising step and the second temperature-lowering step, so the first temperature-lowering step proceeds before the second temperature-lowering step, and therefore, relatively low-temperature water can be introduced into the second circulation flow path L2 from the upstream side in the second temperature-lowering step.

[0050] In the regeneration operation, the EDI device 4 is energized, and the water flowing out from the EDI device 4 into the pure water line 50 is discharged from the system via the pure water discharge valve 51 or the second reflux line 80 and the second circulating water discharge valve 86. This allows the EDI device 4 to be regenerated to a state where it can remove impurity ions from the permeate water.

[0051] The water treatment system 100 includes a first reflux line 70 forming a first circulation flow path L1 for circulating water whose temperature is adjusted by the first temperature adjustment device 6 through the inactivation means 2, and a second reflux line 80 forming a second circulation flow path L2 for circulating water whose temperature is adjusted by the second temperature adjustment device through the reverse osmosis membrane device 3 and the EDI device 4. This allows for independent hot water sterilization of the inactivation means 2, which generally has a large water retention capacity, and hot water sterilization of the reverse osmosis membrane device 3, which is susceptible to sudden temperature changes. This allows for a large amount of heat to be supplied to the inactivation means 2 without regard to the rate of temperature change, and allows for rapid and accurate adjustment of the temperature change of the reverse osmosis membrane device 3, so that the hot water sterilization of the entire water treatment system 100 can be completed in a relatively short time.

[0052] Although the above describes various embodiments of the present invention, the present invention is not limited to the above-described embodiments and various modifications and variations are possible. For example, in the water treatment system according to the present invention, the EDI device may be omitted, or other devices may be provided in place of the EDI device. Other devices may be added before or after the EDI device (for example, a decarbonation device before the EDI and a UF membrane filtration device after the EDI). As another example, the first temperature control device may be disposed at any position within the first circulation flow path, and the second temperature control device may be disposed at any position within the second circulation flow path. Furthermore, flow meters, control valves, and the like may be disposed in different positions as long as their functions are not impaired. [Explanation of symbols]

[0053] 1 raw water tank 2 Inactivation means 3 Reverse osmosis membrane device 4 EDI equipment 5 Pure water tank 6 1st temperature control device 7 Second temperature control device 10 Raw Water Line 11 Raw water pump 12 Raw water shutoff valve 20 Inactivated water line 21 Inactivated water shutoff valve 22 Inactivated water pump 30 Permeate line 31 Permeate flow meter 32 Permeate discharge valve 33 Permeate pump 40 Membrane concentrated water line 41 Return section 42 Membrane concentrated water discharge section 43 Check valve 44 Membrane Concentrated Water Flowmeter 45 Membrane concentrated water control valve 50 Pure water line 51 Pure water discharge valve 60 Electric concentrated water line 70 First Reflux Line 71 First circulation pump 72 First inlet shutoff valve 73 First outlet shutoff valve 74 First circulating water discharge valve 80 Second reflux line 81 Second circulation pump 82 Membrane concentrated water switching valve 83 Pure water switching valve 84 Electric concentrated water switching valve 85 Second outlet shutoff valve 86 Second circulating water discharge valve 90 Control device 100 Water Treatment Systems L1 First circulation channel L2 Second circulation channel

Claims

1. an inactivation means for obtaining inactivated water by inactivating the disinfectant in the raw water; a reverse osmosis membrane device that separates the inactivated water into permeate and membrane-concentrated water using a reverse osmosis membrane; an inactivated water line that guides the inactivated water flowing out from the inactivation means to the reverse osmosis membrane device, the inactivated water line having an inactivated water shutoff valve that shuts off the inactivated water; a first reflux line connecting the upstream side of the inactivated water shutoff valve of the inactivated water line to a flow path upstream of the inactivation means so as to form a first circulation flow path including the inactivation means; a first temperature control device disposed in the first circulation flow path and configured to control a water temperature; a second return line connecting a flow path downstream of the reverse osmosis membrane device and a downstream side of the inactivated water shutoff valve of the inactivated water line so as to form a second circulation flow path including the reverse osmosis membrane device; a second temperature control device disposed in the second circulation flow path and configured to control the water temperature; a control device that simultaneously starts and independently controls a first-stage sterilization process in which water is circulated through the first circulation flow path and the output of the first temperature adjustment device is adjusted so that the temperature of the inactivation means approaches a target temperature, and a second-stage sterilization process in which water is circulated through the second circulation flow path and the output of the second temperature adjustment device is adjusted so that the temperature of the reverse osmosis membrane device approaches a target temperature; A water treatment system comprising:

2. The apparatus further includes an EDI device for obtaining pure water by removing ions from the permeated water through electrical regeneration demineralization and electrically concentrated water in which the content of the ions is increased, 2. The water treatment system of claim 1, wherein the second return line is connected to a flow path of the membrane concentrated water flowing out from the reverse osmosis membrane device, a flow path of the pure water flowing out from the EDI device, and a flow path of the electroconcentrated water flowing out from the EDI device.

3. A water treatment system as described in claim 1 or 2, wherein the distance between the connection point of the first return line in the inactivated water line and the inactivated water shut-off valve and the distance between the connection point of the second return line and the inactivated water shut-off valve are less than six times the inner diameter of the inactivated water line.

4. A sterilization method for a water treatment system comprising: an inactivation means for obtaining inactivated water by inactivating a disinfectant in raw water; a reverse osmosis membrane device for separating the inactivated water into permeate water and membrane-concentrated water using a reverse osmosis membrane; and an inactivated water line for guiding the inactivated water flowing out of the inactivation means to the reverse osmosis membrane device, a first-stage sterilization step in which a first circulation flow path is formed by connecting a midpoint of the inactivated water line to a flow path upstream of the inactivation means, the first circulation flow path including the inactivation means and a first temperature adjusting device that adjusts the water temperature, and the output of the first temperature adjusting device is adjusted so that the temperature of the inactivation means approaches a target temperature; a second-stage sterilization process in which a second circulation flow path is formed by connecting a flow path downstream of the reverse osmosis membrane device to a portion of the inactivated water line downstream of the first circulation flow path, the second circulation flow path including the reverse osmosis membrane device and a second temperature adjustment device that adjusts the water temperature, and the output of the second temperature adjustment device is adjusted so that the temperature of the reverse osmosis membrane device approaches a target temperature; Equipped with The method for sterilizing a water treatment system, wherein the first stage sterilization process and the second stage sterilization process are initiated simultaneously and controlled independently.

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