Water treatment system and method for sterilizing the water treatment system

Abstract

To provide a water treatment system capable of completing hot water sterilization in a short time by supplying a sufficient amount of hot water to a secondary processor via a reverse osmosis membrane device.SOLUTION: A water treatment system relating to one embodiment of the present invention comprises: a reverse osmosis membrane device for membrane-separating target water to permeated water and membrane concentrated water; a supply line for supplying the target water to the reverse osmosis membrane device; a permeated water line having a permeated water flow meter which leads the permeated water from the reverse osmosis membrane device and detects a flow rate of the permeated water; a membrane concentrated water line having a membrane concentrated water flow meter which leads the membrane concentrated water from the reverse osmosis membrane device and detects a flow rate of the membrane concentrated water and a flow rate regulating valve which regulates the flow rate of the membrane concentrated water; a temperature regulator for regulating a temperature of germicidal treatment water; and a controller for controlling an output of the temperature regulator so that the temperature of the germicidal treatment water shows a predetermined change when the germicidal treatment water is supplied to the supply line as well as controlling an opening of the flow rate regulating valve so as to maintain a ratio of a detection value of the permeated water flow meter and a detection value of the membrane concentrated water flow meter at a set value.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 a reverse osmosis membrane device that separates target water into permeate and concentrate using a reverse osmosis membrane, and a secondary treatment device such as an EDI device that further treats the permeate flowing out of the reverse osmosis membrane device. When using such a water treatment system to produce water for manufacturing pharmaceuticals, foods, 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 proliferation of microorganisms in the water treatment system. For example, Patent Document 1 discloses 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, an EDI device, and a heat exchanger, all of which are connected in series. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5459704 Summary of the Invention [Problem to be solved by the invention]

[0004] Many water treatment systems equipped with reverse osmosis membrane devices are configured to return the concentrated water flowing out of the reverse osmosis membrane device to the upstream side of the reverse osmosis membrane device, thereby increasing the amount of water supplied to the reverse osmosis membrane, preventing clogging of the membrane surface due to fluid shear force and preventing scale formation due to high concentration caused by membrane surface concentration polarization. In hot water sterilization in water treatment systems with such a configuration, only the hot water flowing into the permeate flow path is supplied to the secondary treatment device, but because the flow rate of the permeate fluctuates with temperature changes, it takes time to heat the entire system.

[0005] 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 by supplying a sufficient amount of hot water to a secondary treatment device through a reverse osmosis membrane device. [Means for solving the problem]

[0006] a temperature regulator that regulates the temperature of sterilized water supplied to the supply line to sterilize the reverse osmosis membrane device; and a control device that controls the output of the temperature regulator so that the temperature of the sterilized water changes as specified when the sterilized water is supplied to the supply line, and that controls the aperture of the flow rate regulator valve so that the ratio between the detected value of the permeate flow rate meter and the detected value of the membrane concentrate flow rate meter is maintained at a set value.

[0007] In the above-described water treatment system, the control device may control the output of the temperature adjustment device so as to raise the temperature of the sterilization treatment water to a predetermined sterilization temperature, then maintain the temperature of the sterilization treatment water at the sterilization temperature for a predetermined holding time, and then lower the temperature of the sterilization treatment water, and may control the aperture of the flow rate adjustment valve so as to maintain the ratio of the detection value of the permeate flow meter to the detection value of the membrane concentrated water flow meter at a set value at least while the temperature of the sterilization treatment water is being raised and while the temperature of the sterilization treatment water is being lowered.

[0008] The above-described water treatment system may further include a secondary treatment device that treats the permeate discharged from the permeate line.

[0009] In the above-described water treatment system, the secondary treatment device may be an EDI device that obtains purified water by removing ions from the permeate water through regenerative desalination and electrically concentrated water with an increased content of the ions.

[0010] The water treatment system described above may further include a thermal sterilization line that supplies the sterilized water to the supply line and returns the sterilized water from the reverse osmosis membrane device onward to the temperature adjustment device.

[0011] In the above-described water treatment system, the thermal sterilization line may have a sterilization pump that circulates the sterilized water, and the control device may supply the sterilized water to the supply line while stopping the pump that supplies the target water to the reverse osmosis membrane device.

[0012] A sterilization method for a water treatment system according to one aspect of the present invention is a sterilization method for sterilizing a water treatment system comprising: a reverse osmosis membrane device that membrane-separates target water into permeate and membrane concentrate using a reverse osmosis membrane; a supply line that supplies the target water to the reverse osmosis membrane device; a permeate line that draws the permeate from the reverse osmosis membrane device and has a permeate flow meter that detects the flow rate of the permeate; and a membrane concentrate line that draws the membrane concentrate from the reverse osmosis membrane device and has a membrane concentrate flow meter that detects the flow rate of the membrane concentrate and a flow control valve that adjusts the flow rate of the membrane concentrate, by supplying temperature-adjusted sterilization water to the supply line, the method comprising the steps of: raising the temperature of the sterilization water to a predetermined sterilization temperature; maintaining the temperature of the sterilization water at the sterilization temperature for a predetermined retention time; and lowering the temperature of the sterilization water, and controlling the aperture of the flow control valve so as to maintain the ratio of the detection value of the permeate flow meter to the detection value of the membrane concentrate flow meter at a set value at least during the heating step and the temperature lowering step. [Effects of the Invention]

[0013] 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 by supplying a sufficient amount of hot water to a secondary treatment device through a reverse osmosis membrane device. [Brief explanation of the drawings]

[0014] [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

[0015] 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.

[0016] The water treatment system 100 includes a target water tank 1, a reverse osmosis membrane device 2, an EDI device 3, a purified water tank 4, and a temperature control device 5. The water treatment system 100 further includes a supply line 10, a permeate line 20, a membrane concentrated water line 30, a reflux line 40, a purified water line 50, an electrically concentrated water line 60, a thermal sterilization line 70, and a control device 80.

[0017] As will be described in detail later, the water treatment system 100 repeatedly performs a production operation in which target water is treated using a reverse osmosis membrane device 2 and an EDI device 3 to produce purified water, a sterilization operation in which each component is sterilized with hot water using sterilized water whose temperature is controlled by a temperature control device 5, and a regeneration operation in which the EDI device 3 is regenerated.

[0018] The target water tank 1 stores target water (raw water). The target water is assumed to be relatively clean water, and for example, water that has been purified in advance, such as tap water, can be used.

[0019] The reverse osmosis membrane device 2 separates the target water by membrane separation using a reverse osmosis membrane, that is, separates the target water into permeate that has permeated the reverse osmosis membrane and membrane-concentrated water that has not permeated the reverse osmosis membrane.

[0020] The EDI device 3 removes ions from the permeate by electrical demineralization to produce purified water (pure water), and electro-concentrated water, which has an increased ion content in the permeate. The EDI device 3 is an example of a secondary treatment device that further treats the permeate discharged from the reverse osmosis membrane device 2.

[0021] The purified water tank 4 stores the purified water produced by the EDI device 3.

[0022] The temperature adjustment device 5 adjusts the temperature of the water passing through or temporarily retained. As a specific example, the temperature adjustment device 5 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 temperature adjustment device 5 may have only the function of heating water, or it may also have the function of cooling water. For example, the temperature adjustment device 5 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.

[0023] The supply line 10 supplies target water from the target water tank 1 to the reverse osmosis membrane device 2. The supply line 10 may be configured to include, in this order, a target water shutoff valve 11 that shuts off the target water and a supply pump 12 that pressurizes the target water. A thermal sterilization line 70 and a reflux line 40 are connected to the supply line 10, in this order, between the target water shutoff valve 11 and the supply pump 12.

[0024] The permeate line 20 leads the permeate from the reverse osmosis membrane device 2 and guides the permeate to the EDI device 3. The permeate line 20 may be configured to include, in this order: a permeate flow meter 21 that detects the flow rate of the permeate, a permeate discharge valve 22 that discharges the permeate outside the system, and a permeate pump 23 that pressurizes the permeate.

[0025] The membrane concentrated water line 30 leads the membrane concentrated water from the reverse osmosis membrane device 2 and discharges it outside the system. The membrane concentrated water line 30 may be configured to include, in this order: a membrane concentrated water flow meter 31 that detects the flow rate of the membrane concentrated water being discharged outside the system; a membrane concentrated water flow rate control valve 32 that adjusts the flow rate of the membrane concentrated water being discharged outside the system; and a membrane concentrated water switching valve 33 that switches the flow path during sterilization operation so that the sterilized water flowing into the membrane concentrated water line 30 is returned to the thermal sterilization line 70. The membrane concentrated water line 30 extends from the reverse osmosis membrane device 2 and is piped so as to wrap around near the permeate pump 23. This makes it possible to pipe the return line 40 linearly and shorten its length.

[0026] The reflux line 40 connects the upstream side of the membrane concentrated water flow meter 31 of the membrane concentrated water line 30 to the upstream side of the supply pump 12 of the supply line 10. The reflux line 40 has a check valve 41 that prevents flow from the supply line 10 side to the membrane concentrated water line 30 side. The reflux line 40 is arranged in a straight line. Furthermore, the reflux line 40 is preferably composed of a pipe with a constant diameter that matches the nominal diameter of the check valve 41. Furthermore, the check valve 41 is preferably arranged in the center of the reflux line 40.

[0027] The upper limit of the distance from the valve body of the check valve 41 to each end of the reflux line 40 is preferably six times, and more preferably three times, the inner diameter of the reflux line 40. By setting the distance from the valve body of the check valve 41 to the end of the reflux line 40 at or below the above upper limit, when the reverse osmosis membrane device 2 is sterilized with hot water, the hot water passing through the supply line 10 and the membrane-concentrated water line 30 can enter the inside of the reflux line 40 without flowing hot water through the reflux line 40, thereby enabling sufficient heat sterilization of the entire reflux line 40, including the check valve 41. The end of the reflux line 40 is defined as the intersection of the center line of the reflux line 40 and the center line of the supply line 10 or the membrane-concentrated water line 30.

[0028] The purified water line 50 leads purified water from the EDI device 3 and guides the purified water to the purified water tank 4. The purified water line 50 may be configured to include, in this order, a purified water discharge valve 51 that discharges purified water to the outside of the system, and a purified water switching valve 52 that switches the flow path so that sterilized water flowing into the purified water line 50 during sterilization operation is returned to the thermal sterilization line 70.

[0029] The electrolytically concentrated water line 60 leads out the electrolytically concentrated water from the EDI device 3 and discharges the electrolytically concentrated water to the outside of the system. The electrolytically concentrated water line 60 may be configured to have an electrolytically concentrated water switching valve 61 that switches the flow path so that the sterilized water flowing into the electrolytically concentrated water line 60 is returned to the thermal sterilization line 70 during sterilization operation.

[0030] The thermal sterilization line 70 supplies sterilized water used to sterilize the reverse osmosis membrane device, i.e., water whose temperature is adjusted by the temperature adjustment device 5 and which can become hot water during sterilization, to the supply line 10, and recovers sterilized water from the reverse osmosis membrane device 2 and beyond, i.e., the membrane concentrated water line 30, the purified water line 50, and the electroconcentrated water line 60. In other words, the thermal sterilization line 70 circulates sterilized water through the supply line 10, the reverse osmosis membrane device 2 and the EDI device 3, the permeate line 20 and the membrane concentrated water line 30, the EDI device 3, the purified water line 50, and the electroconcentrated water line 60. For this reason, the thermal sterilization line 70 is provided with the temperature adjustment device 5 and a sterilization pump 71 that delivers sterilized water through the temperature adjustment device 5. The thermal sterilization line 70 may also be configured to include a sterilized water shutoff valve 72 that cuts off connection with the supply line 10, and a sterilized water discharge valve 73 that discharges the sterilized water to the outside of the system.

[0031] The control device 80 controls the operation of the water treatment system 100 by controlling the operation of the other components of the water treatment system 100. In other words, the control device 80 controls the other components to repeatedly perform a production operation in which purified water is produced by the water treatment system 100 and a sterilization operation in which the water treatment system 100 is sterilized. Furthermore, the control device 80 may control the other components to perform a regeneration operation in which the EDI device 3 is regenerated, in addition to the production operation and the sterilization operation. The sterilization operation is an operation for carrying out one embodiment of the sterilization method according to the present invention.

[0032] 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 pure purified water is obtained, water flowing out of the purified water line 50 from the EDI device 3 is discharged to the outside of the system through the purified water discharge valve 51 without being introduced into the purified water tank 4. The initial blowing step may be performed by omitting the purified water discharge valve 51 and instead using the purified water switching valve 52 to flow water from the purified water line 50 into the heat sterilization line 70, and then discharging the water that has flowed into the heat sterilization line 70 to the outside of the system through the sterilized water discharge valve 73. In the water passing step, purified water that flows out of the purified water line 50 through the reverse osmosis membrane device 2 and the EDI device 3 is introduced into the purified water tank 4. In the flushing step, the aperture of the membrane concentrate flow control valve 32 is increased to reduce the impurity concentration in the space on the membrane concentrate side inside the reverse osmosis membrane device 2 and in the membrane concentrate line 30, and the permeate is discharged to the outside of the system through the permeate discharge valve 22.

[0033] The sterilization operation includes a preparation process in which water remaining in the permeate line 20, membrane concentrated water line 30, purified water line 50, and electrically concentrated water line 60 is discharged from the system to reduce the amount of impurities in the system, and a sterilization process in which sterilized water is circulated between the reverse osmosis membrane device 2, the EDI device 3, and the temperature control device 5, and the output of the temperature control device 5 is adjusted so that the temperatures of the reverse osmosis membrane device 2 and the EDI device 3 approach the target temperature.

[0034] In the sterilization process, the sterilization pump 71 circulates the sterilized water while the supply pump 12 and the permeate pump 23 are stopped, and the temperature regulator 5 is controlled so that the temperature of the sterilized water changes to a predetermined value. By circulating the sterilized water in this manner, hot water sterilization can be performed using a relatively small amount of sterilized water, thereby reducing the consumption of water and energy for sterilization. Furthermore, by stopping the supply pump 12, the sterilized water that flows out of the reverse osmosis membrane device 2 into the membrane concentrate line 30 is not resupplied to the reverse osmosis membrane device 2 through the reflux line 40. This allows the temperature of the reverse osmosis membrane device 2 to be accurately controlled, enabling rapid and appropriate hot water sterilization. Furthermore, by not using the supply pump 12 and the permeate pump 23 in the sterilization process, the specifications of the supply pump 12 and the permeate pump 23 can be optimized for production operation.

[0035] The sterilization process may include a temperature-raising process in which the temperatures of the reverse osmosis membrane device 2 and the EDI device 3 are raised to a predetermined sterilization temperature; a temperature-holding process in which the temperatures of the reverse osmosis membrane device 2 and the EDI device 3 are maintained at a predetermined sterilization temperature for a predetermined holding time; and a temperature-lowering process in which the temperatures of the reverse osmosis membrane device 2 and the EDI device 3 are lowered. That is, when sterilized water is supplied to the supply line 10, the control device 80 controls the output of the temperature adjustment device 5 so that the temperature of the sterilized water undergoes a predetermined change: it is raised to a predetermined temperature, maintained at the sterilization temperature for a holding time, and then lowered. The sterilization temperature may be, for example, 80°C or higher and 85°C or lower. The holding time may be, for example, 30 minutes to 1 hour, depending on the sterilization temperature. The temperature gradient of the reverse osmosis membrane device 2 and the EDI device 3 during the temperature-raising process and the temperature-lowering process may be set to, for example, about 2°C / min to protect the reverse osmosis membrane.

[0036] The control device 80 controls the aperture of the membrane concentrate flow rate control valve 32 so as to maintain the ratio of the detection value of the permeate flow rate meter 21 to the detection value of the membrane concentrate flow rate meter 31 at a set value at least during the temperature increase and decrease steps, and preferably throughout the entire sterilization step. This allows sufficient sterilized water to be supplied downstream of the reverse osmosis membrane device 2, and allows downstream components such as the EDI device 3 to change temperature with little delay compared to the reverse osmosis membrane device 2, so that the entire system can be sterilized with hot water in a relatively short time.

[0037] In the regeneration operation, power is applied to the EDI device 3, and water flowing out from the EDI device 3 into the purified water line 50 is discharged to the outside of the system from the sterilized water discharge valve 73 via the purified water discharge valve 51 or the thermal sterilization line 70. This allows the EDI device 3 to be regenerated to a state where it can remove impurity ions from the permeate water.

[0038] As is clear from the above explanation, one embodiment of the sterilization method of the present invention performed by the control device 80 is a sterilization method for sterilizing the water treatment system 100 by supplying temperature-adjusted sterilization water to the supply line 10, and includes a step of raising the temperature of the sterilization water to a predetermined sterilization temperature, a step of maintaining the temperature of the sterilization water at the sterilization temperature for a predetermined retention time, and a step of lowering the temperature of the sterilization water, and controls the opening of the membrane concentrated water flow rate control valve 32 so as to maintain the ratio of the detection value of the permeate flow meter 21 to the detection value of the membrane concentrated water flow meter 31 at a set value at least during the temperature raising step and the temperature lowering step.

[0039] As described above, in the water treatment system 100, the control device 80 maintains the ratio of the flow rate of sterilized water flowing out into the permeate line 20 and the flow rate of sterilized water flowing out into the membrane concentrate line 30 at a set value during hot water sterilization, so that sufficient sterilized water can be supplied downstream of the reverse osmosis membrane device 2. This allows other components downstream of the reverse osmosis membrane device 2, such as the EDI device 3, to have an appropriate thermal history, so that the entire system can be appropriately sterilized with hot water in a relatively short time.

[0040] 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, the temperature control devices, pumps, flow meters, control valves, and the like in the above-described embodiments may be arranged in different positions as long as their functionality is not impaired. Furthermore, the configuration for switching the flow path may use a single three-way valve or two shut-off valves. Furthermore, in the water treatment system of the present invention, the EDI device may be omitted, or other secondary treatment devices, such as a UF membrane filtration device or an ion exchange device, may be provided instead of or in addition to the EDI device. Furthermore, in the water treatment system of the present invention, the reflux line may be omitted. Furthermore, the water treatment system of the present invention may be configured to discharge sterilized water outside the system without circulating it. [Explanation of symbols]

[0041] 1. Target water tank 2 Reverse osmosis membrane device 3 EDI equipment 4 Purified water tank 5 Temperature control device 10 Supply Line 11 Target water shutoff valve 12 Supply pump 20 Permeate line 21 Permeate flow meter 22 Permeate discharge valve 23 Permeate pump 30 Membrane concentrated water line 31 Membrane concentrated water flow meter 32 Membrane concentrated water flow control valve 33 Membrane concentrated water switching valve 40 Reflux line 41 Check valve 50 Purified water line 51 Purified water discharge valve 52 Purified water switching valve 60 Electric concentrated water line 61 Electric concentrated water switching valve 70 Heat sterilization line 71 Sterilization Pump 72 Disinfected water shutoff valve 73 Disinfected water discharge valve 80 Control device 100 Water Treatment Systems

Claims

1. a reverse osmosis membrane device that separates target water into permeate and membrane-concentrated water using a reverse osmosis membrane; a supply line for supplying the target water to the reverse osmosis membrane device; a permeate line that leads the permeate from the reverse osmosis membrane device and has a permeate flow meter that detects the flow rate of the permeate; a membrane concentrated water line that discharges the membrane concentrated water from the reverse osmosis membrane device and has a membrane concentrated water flow meter that detects the flow rate of the membrane concentrated water and a flow rate control valve that adjusts the flow rate of the membrane concentrated water; a secondary treatment device for treating the permeated water discharged from the permeated water line; A heat sterilization line that supplies sterilized water to the supply line to sterilize the reverse osmosis membrane device and the secondary treatment device, and has a sterilization pump through which the sterilized water is returned from the reverse osmosis membrane device and onward and circulates the sterilized water; A temperature control device provided in the heat sterilization line and controlling the temperature of the sterilization treatment water; a control device that supplies the sterilized water, the temperature of which has been adjusted by the temperature adjustment device, to the supply line while a pump that supplies the target water to the reverse osmosis membrane device is stopped, and controls the output of the temperature adjustment device so that the temperature of the sterilized water changes in a predetermined manner when the sterilized water is supplied to the supply line, and controls the aperture of the flow rate adjustment valve so that the ratio of the detection value of the permeate flow meter and the detection value of the membrane concentrated water flow meter is maintained at a set value; A water treatment system comprising:

2. The control device controlling the output of the temperature adjustment device so that the temperature of the sterilizing water is raised to a predetermined sterilizing temperature, the temperature of the sterilizing water is maintained at the sterilizing temperature for a predetermined holding time, and then the temperature of the sterilizing water is lowered; 2. The water treatment system according to claim 1, wherein the opening degree of the flow rate control valve is controlled so as to maintain the ratio of the detection value of the permeate flow meter to the detection value of the membrane concentrated water flow meter at a set value at least while the temperature of the sterilization treatment water is being increased and while the temperature of the sterilization treatment water is being decreased.

3. 3. The water treatment system according to claim 1, wherein the secondary treatment device is an EDI device that obtains purified water by removing ions from the permeate water through regenerative desalination and electrically concentrated water in which the content of the ions is increased.

4. a reverse osmosis membrane device that separates target water into permeate and membrane-concentrated water using a reverse osmosis membrane; a supply line for supplying the target water to the reverse osmosis membrane device; a permeate line that leads the permeate from the reverse osmosis membrane device and has a permeate flow meter that detects the flow rate of the permeate; a membrane concentrated water line that discharges the membrane concentrated water from the reverse osmosis membrane device and has a membrane concentrated water flow meter that detects the flow rate of the membrane concentrated water and a flow rate control valve that adjusts the flow rate of the membrane concentrated water; a secondary treatment device for treating the permeated water discharged from the permeated water line; A sterilization method for sterilizing a water treatment system comprising: supplying temperature-controlled sterilized water to the supply line; raising the temperature of the sterilized water to a predetermined sterilization temperature; maintaining the temperature of the sterilized water at the sterilization temperature for a predetermined period of time; A step of lowering the temperature of the sterilized water; Equipped with In the temperature increasing step, the maintaining step, and the temperature decreasing step, the sterilized water whose temperature has been adjusted by a temperature adjustment device is supplied to the supply line while a pump that supplies the target water to the reverse osmosis membrane device is stopped, and the sterilized water is circulated by a sterilization pump so that the temperature of the sterilized water discharged from the reverse osmosis membrane device and thereafter is adjusted by a temperature adjustment device and then returned to the supply line; A sterilization method for a water treatment system, wherein the opening degree of the flow control valve is controlled so as to maintain the ratio of the detection value of the permeate flow meter to the detection value of the membrane concentrated water flow meter at a set value at least during the temperature increasing step and the temperature decreasing step.

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