JP7732273B2 - Water treatment system and method for sterilizing the water treatment system - Google Patents

Description

The present invention relates to a water treatment system and a method for sterilizing a water treatment system.

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

Generally, water is heated in a tank to produce hot water for sterilizing a water treatment system. However, to save energy used to produce hot water, a known technique involves circulating hot water between a heating device that heats water inline, 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 a heat exchanger and an inactivation device, a reverse osmosis membrane device, and an EDI device that are connected in series.

Patent No. 5459704

Activated carbon filtration devices have a large water retention capacity, and the responsiveness of the temperature change in the outflowing water to the temperature change in the supplied water is often poor. For this reason, with 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 the temperature increase in 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, around 2°C/min. To prevent the rate of change in 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.

For this reason, the present invention aims 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.

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 of 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 reflux line connecting the inactivated water line upstream of the inactivated water shut-off valve to a flow path upstream of the inactivation means to form a first circulation flow path including the inactivation means; a first temperature adjustment device disposed in the first circulation flow path for adjusting the water temperature; a second reflux line connecting the flow path downstream of the reverse osmosis membrane device to the inactivated water line downstream of the inactivated water shut-off valve to form a second circulation flow path including the reverse osmosis membrane device; and a second temperature adjustment device disposed in the second circulation flow path for adjusting the water temperature.

The above-mentioned water treatment system may further include an EDI device that uses electrical regeneration demineralization to obtain pure water by removing ions from the permeate and electroconcentrated water with an increased ion content, and the second reflux line may be connected to the flow path of the membrane-concentrated water flowing out of the reverse osmosis membrane device, the flow path of the pure water flowing out of the EDI device, and the flow path of the electroconcentrated water flowing out of the EDI device.

In the above-described water treatment system, the distance between the connection point of the first return line in the inactivated water line and the inactivated water shutoff valve, and the distance between the connection point of the second return line and the inactivated water shutoff valve may be no more than six times the inner diameter of the inactivated water line.

One aspect of the present invention provides 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 of the inactivation means to the reverse osmosis membrane device. The method comprises the steps of: connecting the inactivated water line to a flow path upstream of the inactivation means, forming a first circulation flow path for circulating water, which includes the inactivation means and a first temperature control device for adjusting the water temperature; 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, which includes the reverse osmosis membrane device and a second temperature control device for adjusting the water 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, forming a second circulation flow path for circulating water, 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.

The present invention provides 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.

1 is a schematic diagram showing the configuration of a water treatment system according to one embodiment of the present invention.

Embodiments of the present invention will now be described with reference to the drawings. Figure 1 is a schematic diagram showing the configuration of a water treatment system 100 according to one embodiment of the present invention.

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 also 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.

The raw water tank 1 stores raw water. For example, tap water or other purified water containing a disinfectant can be used as raw water.

Inactivation means 2 inactivates the disinfectant in the raw water to obtain inactivated water, and can be an inactivation device that performs inactivation unmanned, or chemical injection equipment that provides workers with access to the raw water for inactivation treatment. Examples of inactivation devices include activated carbon filtration devices and chemical injection systems equipped with chemical injection devices. Examples of chemical injection equipment include water tanks into which workers can inject chemicals.

The reverse osmosis membrane device 3 separates the inactivated water using a reverse osmosis membrane into permeate that has passed through the reverse osmosis membrane and membrane-concentrated water that has not passed through the reverse osmosis membrane.

The EDI device 4 uses electrical regeneration desalination to remove ions from the permeate, producing pure water, and electro-concentrated water, which has an increased ion content in the permeate.

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

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 with a heat source such as an electric heater or burner. The first temperature adjustment device 6 may only have the function of heating water, or it 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.

The second temperature control device 7, like the first temperature control device 6, adjusts the temperature of the water passing through or temporarily retained.

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.

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 with the first return line 70 and the connection point with the second return line.

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.

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.

The return section 41 is preferably arranged in a straight line. 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 the inner diameter of the return section 41, and more preferably no more than five times. 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.

The pure water line 50 guides the pure water flowing out of 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 outside the system.

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

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 the 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 to the raw water line 10, 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 out of the system.

By opening the first inlet shutoff valve 72 and the first outlet shutoff valve 73, the first reflux line 70, together with a portion of the raw water line 10 and a portion of the inactivated water line 20, forms a loop-shaped first circulation flow path L1 that includes the inactivation means 2 and the first temperature adjustment device 6.

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 shut-off valve 21 is preferably no more than six times the inner diameter of the first reflux line 70, and more preferably no more than five times. This allows the water circulating through the first circulation flow path L1 to reach the valve body of the inactivated water shut-off valve 21, so 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 shut-off valve 21 can be sterilized.

The second reflux line 80 connects the flow paths downstream of the reverse osmosis membrane device 3, specifically the membrane concentrated water line 40, pure water line 50, and electroconcentrated water line 60, to the inactivated water line 20 downstream of the inactivated water shut-off valve 21. The second reflux line 80 may be configured to include a second circulation pump 81 that creates 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 electroconcentrated water switching valve 84 that allows water to flow from the electroconcentrated water line 60 into the second reflux line 80, and a second outlet shut-off 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 upstream of the second outlet shutoff valve 85, which discharges water outside the system. Note that the pure water switching valve 83 and the electrically concentrated water switching valve 84 may each be configured with two shutoff valves.

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 from the membrane concentrated water line 40 into the second reflux line 80 without being discharged outside the system, the pure water switching valve 83 switches the flow path so that water is introduced from the pure water line 50 into the second reflux line 80 without being introduced into the pure water tank, and the electroconcentrated water switching valve 84 switches the flow path so that water is introduced from the electroconcentrated water line 60 into the second reflux line 80 without being discharged outside the system. Furthermore, by opening the second outlet shutoff valve 85, a loop-shaped second circulation flow path L2 is formed that includes the reverse osmosis membrane device 3, EDI device 4, and second temperature control device 7, along 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 electroconcentrated water line 60.

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 shut-off valve 21 is preferably no more than six times the inner diameter of the inactivated water line 20, and more preferably no more than five times. This allows the water circulating through the second circulation flow path L2 to reach the valve body of the inactivated water shut-off valve 21, so 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 shut-off valve 21 can be sterilized.

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 to produce pure water using the water treatment system 100, a sterilization operation to sterilize the water treatment system 100, and a regeneration operation to regenerate the EDI device 4. The sterilization operation is an operation that implements the sterilization method for a water treatment system according to the present invention.

The production operation may include an initial blowing process, a water flowing process, and a flushing process. In the initial blowing process, until the operating conditions stabilize and sufficiently clean pure water is obtained, water flowing out of the EDI device 4 into the pure water line 50 is discharged from the system through the pure water discharge valve 51 without being introduced into the pure water tank 5. The initial blowing process 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 out of the system through the second circulating water discharge valve 86. In the water flowing process, 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. During the flushing process, the opening of the membrane concentrate control valve 45 is increased to reduce the impurity concentration in the space on the membrane concentrate side inside the reverse osmosis membrane device 3 and in the water inside the membrane concentrate line 40, and the permeate is discharged outside the system through the permeate discharge valve 32.

The sterilization operation includes a preparatory process in which water remaining in the permeate line 30, membrane-concentrated water line 40, pure water line 50, and electroconcentrated water line 60 is discharged from the system to reduce the amount of impurities within the system; a first-stage sterilization process in which a first circulation flow path L1 is formed, including an inactivation means 2 and a first temperature control device 6, for circulating water, and the output of the first temperature control device 6 disposed in the first circulation flow path L1 is adjusted to bring the temperature of the inactivation means 2 closer to the target temperature; and a second-stage sterilization process in which a second circulation flow path L2 is formed, including a reverse osmosis membrane device 3, an EDI device 4, and a second temperature control device 7, for circulating water, and the output of the second temperature control device 7 disposed in the second circulation flow path L2 is adjusted to bring the temperatures of the reverse osmosis membrane device 3 and the EDI device 4 closer to the target temperatures. The first-stage sterilization process and the second-stage sterilization process can be performed independently or in parallel. Typically, the first-stage sterilization process and the second-stage sterilization process are initiated simultaneously and controlled independently.

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.

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 by detecting the temperature of the circulating water at the outlet of the inactivation means 2.

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

In the first temperature maintenance step, the first circulation pump 71 circulates water in the first circulation flow path L1, and the first temperature adjustment device 6 adjusts the amount of heat applied to the circulating water so that the temperature of the inactivation means 2 is maintained 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.

In the first temperature reduction 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 condition of the second circulation flow path L2, the inactivated water shutoff valve 21 may be opened to allow excess circulating water to flow downstream.

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.

In the second heating 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 control 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 heating step can be set to, for example, approximately 2°C/min to protect the reverse osmosis membrane.

In the second heating step, in order to ensure the flow rate of 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 concentrate control valve 45 may be adjusted to maintain the ratio of the flow rate of circulating water flowing out from the reverse osmosis membrane device 3 to the permeate line 30 (value detected by the permeate flow meter 31) to the flow rate of circulating water flowing out to the membrane concentrate line 40 (value detected by the membrane concentrate flow meter 44).

In the second temperature maintenance step, the second circulation pump 81 circulates water in the second circulation flow path L2, and the second temperature adjustment device 7 adjusts the amount of heat applied to the circulating water 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.

In the second temperature holding step, the aperture of the membrane concentrate regulating valve 45 may be adjusted as in the second heating step, or the aperture of the membrane concentrate regulating valve 45 may be maintained at the aperture at the end of the second heating step. In the second temperature holding step, the temperature of the reverse osmosis membrane device 3 is maintained constant, so the permeation resistance of the reverse osmosis membrane does not change. Therefore, if the aperture of the membrane concentrate regulating valve 45 is not changed, the flow rate of the circulating water flowing into the permeate line 30 will not change.

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 shut-off valve 21 and introducing circulating water in the first circulation flow path L1 or 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, approximately 2°C/min, similar to the second temperature-raising step, in order to protect the reverse osmosis membrane.

When the first and second sterilization stages are started simultaneously, as described above, the temperature gradient is limited during the second temperature-raising and second temperature-lowering stages, so the first temperature-lowering stage proceeds before the second temperature-lowering stage, allowing relatively low-temperature water to be introduced into the second circulation flow path L2 from upstream during the second temperature-lowering stage.

During regeneration operation, the EDI device 4 is energized, and water flowing out of 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.

The water treatment system 100 includes a first reflux line 70 that forms a first circulation flow path L1 for circulating water whose temperature is regulated by the first temperature regulator 6 through the inactivation means 2, and a second reflux line 80 that forms a second circulation flow path L2 for circulating water whose temperature is regulated by the second temperature regulator through the reverse osmosis membrane device 3 and the EDI device 4. Therefore, 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, can be performed independently. This allows a large amount of heat to be supplied to the inactivation means 2 without regard to the rate of temperature change, and allows the temperature change of the reverse osmosis membrane device 3 to be adjusted quickly and accurately, enabling hot water sterilization of the entire water treatment system 100 to be completed in a relatively short time.

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 of the present invention, the EDI device may be omitted, or another device may be installed in place of the EDI device, or 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 located anywhere within the first circulation flow path, and the second temperature control device may be located anywhere within the second circulation flow path. Furthermore, flow meters, control valves, etc. may be located in different positions as long as their functionality is not impaired.

REFERENCE SIGNS LIST 1 raw water tank 2 inactivation means 3 reverse osmosis membrane device 4 EDI device 5 pure water tank 6 first 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 flow meter 45 membrane concentrated water adjustment valve 50 pure water line 51 pure water discharge valve 60 electrolytic concentrated water line 70 first reflux line 71 first circulation pump 72 first inlet shutoff valve 73 first outlet shutoff valve 74 first circulation 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 system L1 First circulation flow path L2 Second circulation flow path

Claims (4)

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: 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. The water treatment system of 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 shutoff valve, and the distance between the connection point of the second return line and the inactivated water shutoff valve, are no more than six times the inner diameter of the inactivated water line. 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 .