Operating method of reverse osmosis membrane apparatus and reverse osmosis membrane system

Abstract

This invention provides a reverse osmosis membrane system and an operating method for a reverse osmosis membrane apparatus that can appropriately control the amount of permeate produced and maintain good permeate quality, such as when replacing an existing high-removal-efficiency reverse osmosis membrane with a high-permeability reverse osmosis membrane. [Solution] A reverse osmosis membrane apparatus equipped with a high-removal-rate reverse osmosis membrane has a permeation flux of 2.0 m per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)) 3 / (m 2 A method for operating a reverse osmosis membrane apparatus, wherein the reverse osmosis membrane has been replaced with a highly permeable reverse osmosis membrane that has a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, wherein the method involves alternating between periods of operation and periods of shutdown of the water supply pump to the reverse osmosis membrane apparatus.

Description

[Technical Field]

[0001] The present invention relates to a method for operating a reverse osmosis (RO) membrane apparatus and a reverse osmosis membrane system, and more particularly to a method for operating a reverse osmosis membrane apparatus and a reverse osmosis membrane system that controls the amount of permeate produced by starting and stopping a pump. [Background technology]

[0002] Reverse osmosis membrane systems are used for treating wastewater discharged from various manufacturing processes, such as in the electronics industry, as well as river water. Because reverse osmosis membrane systems use high-pressure pumps to pressurize and supply the water to be treated, they consume a significant amount of power.

[0003] In particular, conventionally widely used reverse osmosis membranes have a permeation flux of 0.8 m³ per 1 MPa effective membrane pressure (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 • This reverse osmosis membrane has a high removal efficiency of 98% or more NaCl removal rate at a membrane surface effective pressure of 1 MPa, water temperature of 25°C, and pH 7.0, and the reverse osmosis membrane device consumes a lot of power.

[0004] Therefore, in recent years, the permeation flux of 2.0 m³ per 1 MPa effective membrane pressure (water temperature 25°C, pure water (RO permeate)) has been 3 / (m 2 Highly permeable reverse osmosis membranes that achieve a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, water temperature of 25°C, and pH 7.0 are increasingly being used. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-70396 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In general, as shown in FIG. 8, when the feed water pressure to the reverse osmosis membrane device is increased, the permeate water flow rate increases, and when the feed water pressure is decreased, the permeate water flow rate decreases.

[0007] In the case of a high rejection rate reverse osmosis membrane, even if the feed water pressure is increased, the desalination rate hardly changes as shown in FIG. 9. Therefore, when the feed water pressure to the reverse osmosis membrane device is increased, the permeate water flow rate increases, the salt concentration of the permeate water decreases, and the water quality improves (for example, the electrical conductivity decreases). Conversely, when the feed water pressure is decreased, the permeate water flow rate decreases, but the desalination rate hardly changes, so the water quality of the permeate water deteriorates (for example, the electrical conductivity increases).

[0008] In an existing reverse osmosis membrane apparatus equipped with a high rejection rate reverse osmosis membrane, when the reverse osmosis membrane is replaced with a high water permeability reverse osmosis membrane in order to reduce power consumption, if the apparatus is operated at the same feed water pressure as before, the permeate water flow rate will be considerably larger than the previous amount (FIG. 8), resulting in production of an excessive amount of permeate water.

[0009] In a reverse osmosis membrane apparatus equipped with a high rejection rate reverse osmosis membrane, it is conceivable to control the pump by an inverter to reduce the feed water pressure and the feed water flow rate in order to reduce the permeate water flow rate, but this will degrade the water quality of the permeate water.

[0010] One aspect of the present invention is to provide an operation method of a reverse osmosis membrane apparatus and a reverse osmosis membrane system that can make the production amount of permeate water appropriate and maintain good water quality of the permeate water, for example, when an existing high rejection rate reverse osmosis membrane is replaced with a high water permeability reverse osmosis membrane. [Means for Solving the Problems]

[0011] In the operation method of a reverse osmosis membrane apparatus according to one aspect of the present invention, the permeate flux per 1 MPa of effective membrane surface pressure (water temperature 25°C, pure water (RO permeate water)) is 2.0 m 3 / (m 2·day) or more, and a high-permeability reverse osmosis membrane having a NaCl rejection rate of 95% or more at an effective membrane surface pressure of 1 MPa, a water temperature of 25°C and pH 7.0, wherein an operation period for operating a water supply pump to the reverse osmosis membrane device and a stop period for stopping the water supply pump are alternately performed.

[0012] In one aspect of the present invention, a method for operating a reverse osmosis membrane device comprises replacing a high-rejection reverse osmosis membrane of a reverse osmosis membrane device equipped with the high-rejection reverse osmosis membrane with a high-permeability reverse osmosis membrane having a permeate flux of 2.0 m per 1 MPa of effective membrane surface pressure (water temperature 25°C, pure water (RO permeate)) 3 / (m 2 ·day) or more, and a NaCl rejection rate of 95% or more at an effective membrane surface pressure of 1 MPa, a water temperature of 25°C and pH 7.0, wherein the operation period for operating the water supply pump to the reverse osmosis membrane device and the stop period for stopping the pump are alternately performed.

[0013] In one aspect of the present invention, the high-rejection reverse osmosis membrane has a permeate flux of 0.8 m per 1 MPa of effective membrane surface pressure (water temperature 25°C, pure water (RO permeate)) 3 / (m 2 ·day) or more, and a NaCl rejection rate of 98% or more at an effective membrane surface pressure of 1 MPa, a water temperature of 25°C and pH 7.0.

[0014] In one aspect of the present invention, the permeate flux of the reverse osmosis membrane device during the operation period is set to 0.5 m 3 / (m 2 ·day).

[0015] In one aspect of the present invention, the length of one operation period and the length of one stop period are set in advance.

[0016] In one aspect of the present invention, the length of one operation period is defined as the time required to produce a preset target permeate water production amount during one pump operation period.

[0017] In one aspect of the present invention, the operating time and stopping time of the water supply pump to the reverse osmosis membrane apparatus are determined based on a predetermined length of a reference period, a target production permeate volume for the reference period, and a predetermined number of pump stopping periods within the reference period.

[0018] In one aspect of the present invention, the reference period is a period selected from between 1 and 168 hours.

[0019] In one aspect of the present invention, the water supply pump operating rate, which is the ratio of the length of the operating period to the sum of the length of one operating period and the length of one shutdown period, is 30 to 90%.

[0020] In one aspect of the present invention, the length of a single stop period is 10 minutes or more.

[0021] In one aspect of the present invention, multiple units, each consisting of a reverse osmosis membrane device and a water supply pump to the reverse osmosis membrane device, are installed in parallel, and the start and stop timings of each unit are staggered.

[0022] A reverse osmosis membrane system according to one aspect of the present invention has a permeation flux of 2.0 m³ per membrane surface effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 The reverse osmosis membrane apparatus comprises a reverse osmosis membrane with a high water permeability, which has a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, and a NaCl removal rate of 95% or more; a water supply pump for the reverse osmosis membrane apparatus; and a control means that alternates between an operating period in which the water supply pump is operated and a stopping period in which the water supply pump is stopped.

[0023] A reverse osmosis membrane system according to one aspect of the present invention is a reverse osmosis membrane apparatus equipped with a high-removal-efficiency reverse osmosis membrane, wherein the high-removal-efficiency reverse osmosis membrane has a permeation flux of 2.0 m³ per membrane surface effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)) 3 / (m 2The reverse osmosis membrane apparatus comprises a reverse osmosis membrane that has been replaced with a highly permeable reverse osmosis membrane with a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, and which has a NaCl removal rate of 95% or more; a water supply pump for the reverse osmosis membrane apparatus; and a control means that alternates between an operating period in which the water supply pump is operated and a stopping period in which the water supply pump is stopped.

[0024] In a reverse osmosis membrane system according to one aspect of the present invention, the permeate flux of the reverse osmosis membrane device during the operating period is 0.5 m 3 / (m 2 • (Days) or more [Effects of the Invention]

[0025] In this invention, by switching the operation and stopping of the water supply pump and adjusting the water supply pressure during operation to an appropriate pressure for the highly permeable reverse osmosis membrane, permeate with good water quality can be obtained. Furthermore, by operating the water supply pump intermittently, the amount of permeate produced can be adjusted to an appropriate level. In this invention, since the reverse osmosis membrane of the reverse osmosis membrane apparatus is a highly permeable reverse osmosis membrane, power consumption is low. [Brief explanation of the drawing]

[0026] [Figure 1] This is a diagram illustrating an example of the reverse osmosis membrane system of the present invention. [Figure 2] This flowchart shows an example of how to operate the reverse osmosis membrane apparatus of the present invention. [Figure 3] This is a diagram illustrating an example of the reverse osmosis membrane system of the present invention. [Figure 4] This flowchart shows an example of how to operate the reverse osmosis membrane apparatus of the present invention. [Figure 5] This flowchart shows an example of an operating method for the reverse osmosis membrane apparatus of the present invention. [Figure 6] This is a diagram illustrating an example of the reverse osmosis membrane system of the present invention. [Figure 7] This flowchart shows an example of how to operate the reverse osmosis membrane apparatus of the present invention. [Figure 8] This is a diagram illustrating the operating characteristics of a reverse osmosis membrane system. [Figure 9] This is a diagram illustrating the operating characteristics of a reverse osmosis membrane system. [Figure 10] This is a diagram illustrating the operating characteristics of a reverse osmosis membrane system. [Modes for carrying out the invention]

[0027] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below.

[0028] Figure 1 is a diagram showing an example of the reverse osmosis membrane system of the present invention. Raw water (water to be treated) from raw water piping 1 is pressurized by a water supply pump (high-pressure pump) 2 and supplied to the reverse osmosis membrane device 3. The permeate from the reverse osmosis membrane 3a of the reverse osmosis membrane device 3 is taken out via piping 4, and the concentrated water is taken out via piping 5. The pumps are controlled by a controller 7. A back pressure valve 6 is provided in piping 5.

[0029] The reverse osmosis membrane system of this embodiment replaces the high-removal-rate reverse osmosis membrane previously installed in the reverse osmosis membrane device 3 with a high-permeability reverse osmosis membrane, but is not limited to this. The present invention can also be applied to reverse osmosis membrane systems configured for high-permeability permeable membranes.

[0030] As mentioned above, a high-efficiency reverse osmosis membrane has a permeation flux of 0.8 m³ per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 • (Days) or more, for example, 0.8~1.9m 3 / (m 2 It is a reverse osmosis membrane that achieves a NaCl removal rate of 98% or more at an effective membrane pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0.

[0031] As mentioned above, a highly permeable reverse osmosis membrane has a permeation flux of 2.0 m³ per 1 MPa of effective membrane pressure (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 • (Days) or more, for example, 2.0~4.0m 3 / (m 2The reverse osmosis membrane is capable of removing 95% or more (e.g., 95-99%) of NaCl at an effective membrane pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0.

[0032] In this embodiment, pump 2 is an existing pump for a high-efficiency reverse osmosis membrane, and therefore its capacity is excessive for the high-permeability reverse osmosis membrane device 3. If the rotation speed of pump 2 is reduced to decrease the amount of permeate, the quality of the permeate deteriorates due to the aforementioned trade-off relationship. Therefore, in this embodiment, the pump is operated intermittently to reduce the amount of permeate produced. However, the discharge pressure of the pump is set to an appropriate pressure for the high-permeability reverse osmosis membrane to ensure good quality of the permeate.

[0033] Furthermore, the relationship between the permeate flux and the desalination rate of a highly permeable reverse osmosis membrane is shown in Figure 10. Therefore, in order to maintain the desalination rate, the flux should be 0.5 m 3 / (m 2 • (Days) or more, especially 0.6m 3 / (m 2 It is preferable to have a minimum of 2 days.

[0034] Furthermore, based on the desalination rate-effective pressure relationship shown in Figure 9, it is preferable to apply an effective pressure of 0.25 MPa or higher to the reverse osmosis membrane, particularly 0.25 to 0.75 MPa.

[0035] Figure 2 shows an example of a control method for pump 2. This control method involves repeatedly alternating between an operating period in which pump 2 is operated for a specified time T0 and a stopping period in which it is stopped for a specified time S0.

[0036] When the controller 7 receives an ON command signal for the reverse osmosis membrane device, the pump 2 starts and the timer T on the controller 7 begins (steps 11-12). As a result, the water supplied from the pump 2 is processed by the reverse osmosis membrane device 3, producing permeate and concentrated water.

[0037] In the flowchart of Figure 2, pump 2 is operated at a predetermined effective pressure within the preferred range described above for a predetermined time T0, and then stopped for a predetermined time S0. When the timer T reaches T0, pump 2 is stopped, timer T is reset, and the pump pause timer S is started (steps 13-14).

[0038] When the timer S reaches the preset time S0, the timer S is reset, and the process returns to step 12 (steps 15-17).

[0039] If a signal to stop the reverse osmosis membrane device is given during this time, the process returns to step 11.

[0040] In this way, by repeatedly operating pump 2 at a predetermined effective pressure for a predetermined time T0 and stopping it for a predetermined time S0, an appropriate amount of permeate with good water quality can be produced.

[0041] Furthermore, the operating rate R of pump 2, i.e., T0 / (T0+S0)×100%, is preferably 30-90%. Also, the length of a single stop period S0 is preferably 10 minutes or more, particularly 10-4000 minutes, and especially 10-1000 minutes. The same applies to other embodiments described later.

[0042] [Figures 3 and 4: Reverse Osmosis Membrane System and Flowchart] In Figure 2, the operating time T0 and rest time S0 of pump 2 are predetermined, but in the embodiments shown in Figures 3 and 4, the operating time T0 of pump 2 is determined based on the detection that a target amount of permeate has been produced.

[0043] In the reverse osmosis membrane system shown in Figure 3, a flow meter 8 is installed in the piping 4, and the detection signal from the flow meter 8 is input to the controller 7. The other configurations are the same as in Figure 1, and the same reference numerals indicate the same parts. The controller 7 has software installed to integrate the flow rate detected by the flow meter 8.

[0044] Figure 4 shows an example of the control of the reverse osmosis membrane apparatus shown in Figure 3.

[0045] Similar to Figure 2, when the controller 7 is given an ON command signal for the reverse osmosis membrane device, the pump 2 starts at a predetermined effective pressure and the timer T of the controller 7 starts. In this embodiment, at the same time, the calculation of the cumulative water volume of the flow rate FI detected by the flow meter 8, i.e., the production water volume Q, is started (steps 21-22). Then, the pump 2 is operated until the production water volume Q reaches a predetermined specified water volume Q0 (step 23). When the production water volume Q reaches Q0, the pump 2 is stopped, the memory of the production water volume Q is reset, and the pump pause timer S is started (step 24).

[0046] When the timer S reaches a predetermined time S0, the timer S is reset and the process returns to step 22 (steps 25-27). If a signal to stop the reverse osmosis membrane device is given during this time, the process returns to step 21. Note that S0 is set so that the production volume Q0 during the total time of one pump operation period and one pump shutdown period becomes the target volume.

[0047] In this way, by repeating the cycle of operating pump 2 until the amount of produced water reaches the specified amount Q0, and stopping it for a predetermined time S0, it is possible to produce an appropriate amount of permeate with good water quality.

[0048] As mentioned above, in this embodiment as well, the operating rate R of pump 2 is preferably 30 to 90%.

[0049] [Another flowchart for the reverse osmosis membrane system in Figure 3 (Figure 5)] In Figure 4, the target water production volume Q0 for one pump operation period is predetermined. However, in the flowchart of Figure 5, the target water production volume W0 for a reference period L (for example, 1 day or 1 week, or 10 hours or 100 hours, preferably selected from 1 hour to 30 days, particularly 1 to 168 hours) is set, and the number of times n the pump 2 is stopped during this reference period L is also set. Then, the target water production volume W0 / (n+1) for one pump operation period is calculated according to this specified number n.

[0050] Furthermore, the length of one pump downtime (t·[(100-R) / R], described later, is calculated from the length (hours) of one pump downtime and the number of pump downtimes n within the aforementioned reference period L. Pump 2 is controlled based on these W0 / (n+1) and t·[(100-R) / R].

[0051] Specifically, as in Figure 4, when the controller 7 is given an ON command signal for the reverse osmosis membrane device, the pump 2 starts up at a predetermined effective pressure. In Figure 5, at the same time, the integration of the detected flow rate FI of the flow meter 8 begins. In addition, a timer T is started to measure the elapsed time since the pump 2 started operating (steps 21-22').

[0052] Next, proceed to step 23', where the current production volume Q is compared with the target production volume W0 / (n+1) for one pump operation period.

[0053] In step 23', pump 2 is kept running until the production water volume Q reaches the target production water volume W0 / (n+1). Once the production water volume Q reaches the target production water volume W0 / (n+1), the process proceeds to step 24', where pump 2 is stopped, the operating time of pump 2 (i.e., the time from the start to the stop of pump 2) is stored in memory t, and then timer T is reset. Furthermore, the production water volume Q is reset, and the pump pause timer S is started.

[0054] Next, proceed to step 25', where the timing of the pump pause timer S is compared with the specified pause time t·[(100-R) / R].

[0055] In this formula t·[(100-R) / R], R is the operating rate of pump 2, and is the ratio (%) of the pump operating time to the sum of the length of the pump operating period (operating time) and the length of the pump stopping period (downtime).

[0056] The sum of the pump operating time and the pump downtime is the time obtained by dividing the reference period L by (n+1), where L is a preset time. t is the pump operating time for one cycle and is the measured value stored in memory t in step 24'. Since L and n are both set values ​​and t is a measured value, the operating rate R is a uniquely calculated value.

[0057] The operating rate R is the average value of the instantaneous permeate flow rate F(m³) of the permeate flow meter 8. 3 The recommended value may be calculated from ( / h) and W0 using the following formula.

[0058] R(%) = W0 / F × 100 / 24

[0059] In step 25', when the timer S reaches the aforementioned time t·[(100-R) / R], the timer S is reset, and the process returns to step 22' (steps 25' to 27).

[0060] If a signal to stop the reverse osmosis membrane device is given during this time, the process returns to step 21.

[0061] In this way, by repeating the cycle of operating pump 2 until the target production volume W0 / (n+1) of permeate is produced in one pump operating period, and stopping the pump for a predetermined time t·[(100-R) / R], it is possible to produce an appropriate amount of permeate with good water quality.

[0062] As mentioned above, the operating rate of pump 2 is preferably 30-90%. When the reference period L is 24 hours, n is preferably 1-10. Also, since a single pump stop period of 10 minutes or more is preferable, n should be set with this in mind.

[0063] [Figures 6 and 7: Reverse osmosis membrane system and flowchart] Figure 6 is a diagram illustrating the configuration of a reverse osmosis membrane system in a different configuration.

[0064] In the reverse osmosis membrane system shown in Figure 6, permeate from the piping 4 is introduced into a permeate tank 9, where it is temporarily stored, and then supplied to the customer. A water level sensor 10 is installed in the permeate tank 9, and its detection signal is input to a controller 7, which controls the pump 2.

[0065] The other components of Figure 6 are the same as those in Figure 1, and the same reference numerals indicate the same parts.

[0066] In the reverse osmosis membrane system shown in Figure 6, as shown in Figure 7, the pump 2 is controlled so that the water level detected by the water level sensor 10 is between the lower limit water level La and the upper limit water level Lb. That is, when the water level drops to La, the pump 2 starts operating, and when the water level rises to the upper limit water level Lb, the pump 2 stops.

[0067] This reverse osmosis membrane system also makes it possible to produce an appropriate amount of permeate with good water quality.

[0068] As described above, in one aspect of the present invention, the permeation flux is 2.0 m per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 In a method for operating a water treatment device equipped with a highly permeable reverse osmosis membrane that has a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, the flux is set to 0.5 m / day or more, and the start and stop operations include a stop period of 10% or more.

[0069] In one aspect of the present invention, in this reverse osmosis membrane apparatus, the pump is started and stopped if the pump's capacity (minimum discharge rate, head) is higher than the required water volume and / or required operating pressure.

[0070] In one aspect of the present invention, the reverse osmosis membrane apparatus may be equipped with a device for recording the cumulative flow rate of treated water and / or the operating status of the apparatus.

[0071] Since the quality of the permeate water in a reverse osmosis membrane system is poor for several minutes at startup, in one aspect of the present invention, when operating a reverse osmosis membrane system having multiple units (combinations of reverse osmosis membrane systems and water supply pumps) installed in parallel, the start and stop timings of the pumps are staggered so that the treated water volume and treated water quality are leveled out.

[0072] One aspect of the present invention is an apparatus comprising a plurality of reverse osmosis membranes, 1. Having multiple vessels arranged in parallel, or 2. Having multiple bank configurations or multiple stage configurations of multiple vessels arranged in series, or 3. In any case of multiple mixtures within the vessel, or when using them in combination, One or more reverse osmosis membranes have a permeation flux of 2.0 m³ per membrane surface effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)). 3 / (m 2 The device is equipped with a highly permeable reverse osmosis membrane that has a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, and is used to start and stop the device.

[0073] In the present invention, there are no particular restrictions on the raw water used for RO membrane treatment, but examples include wastewater discharged from the electronics industry, the steel manufacturing industry, petrochemical complexes, etc. [Examples]

[0074] The present invention will be described in more detail below with reference to examples.

[0075] [Comparative Example 1] High-efficiency reverse osmosis membrane (permeation flux of 1.2 m³ per membrane at an effective pressure of 1 MPa (water temperature 25°C, pure water (RO permeate)) 3 / (m 2(In Japan, and with an effective membrane pressure of 1 MPa, water temperature of 25°C, and pH 7.0, the NaCl removal rate was 98% or higher), and three membrane elements were directly connected within a single vessel (membrane area of ​​41 m² per element). 2 ) For a reverse osmosis membrane apparatus, raw water with a NaCl concentration of 0.05% is incubated at 25°C for 7 m³ 3 When water was passed through at an effective pressure of 0.5 MPa at 0 / h, the NaCl rejection rate was 99% and the permeate volume was 3 m³. 3 The result was / h. The target was a NaCl rejection rate of 96% or more, and a total permeate of 72 m³ per day. 3 It met the requirements.

[0076] [Comparative Example 2] Highly permeable reverse osmosis membrane (permeation flux of 2.0 m³ per 1 MPa effective pressure (water temperature 25°C, pure water (RO permeate)) 3 / (m 2 A membrane system was constructed using a membrane with a surface pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, achieving a NaCl removal rate of 95% or more. Three membrane elements were directly connected within a single vessel (membrane area of ​​41 m² per element). 2 ) The above raw water is heated to 25°C for 10 m³ of reverse osmosis membrane equipment. 3 When water was passed through at an effective pressure of 0.5 MPa at 0 / h, the NaCl rejection rate was 97% and the permeate volume was 6 m³. 3 The per-hour rate was obtained using three elements. The NaCl rejection rate was over 96%, but the total permeate per day was 144 m³. 3 This amount was twice that of Comparative Example 1, resulting in an excess.

[0077] [Comparative Example 3] Compared to a reverse osmosis membrane apparatus using the same high-permeability reverse osmosis membrane as in Comparative Example 2, the above raw water was subjected to 7 m³ of water at 25°C. 3 When water was passed through at an effective pressure of 0.25 MPa at 0 / h, the NaCl rejection rate was 95% and the permeate volume was 3 m³. 3 The value was / h. The total permeate per day was 72m³. 3 The target value was achieved, but the NaCl inhibition rate was lower than 96%.

[0078] [Example 1] Compared to a reverse osmosis membrane apparatus using the same high-permeability reverse osmosis membrane as in Comparative Example 2, the above raw water was subjected to 10 m³ of 25°C. 3 When water was passed through at an effective pressure of 0.5 MPa per hour with a pump operating rate of 50%, the NaCl rejection rate was 97%, and the permeate volume during pump operation was 6 m³. 3 The result was / h. This Example 1 achieved a target NaCl rejection rate of 96% or more and a total permeate of 72 m³ per day. 3 It met the requirements. [Explanation of symbols]

[0079] 1. Raw water piping 3 Reverse osmosis membrane device 6. Back pressure valve 7. Controller 9. Permeate water tank 10 Water level sensor

Claims

1. Permeation flux of 2.0 m per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)) ３ / (m ２ A method for operating a reverse osmosis membrane apparatus equipped with a highly permeable reverse osmosis membrane that has a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, A method for operating a reverse osmosis membrane system, which involves alternating between periods of operation and periods of shutdown of the water supply pump to the reverse osmosis membrane system.

2. A reverse osmosis membrane apparatus equipped with a high-removal-efficiency reverse osmosis membrane has a permeation flux of 2.0 m per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)). ３ / (m ２ A method for operating a reverse osmosis membrane apparatus, wherein the membrane is replaced with a highly permeable reverse osmosis membrane that has a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, A method for operating a reverse osmosis membrane system, which involves alternating between periods of operation and periods of shutdown of the water supply pump to the reverse osmosis membrane system.

3. The aforementioned high-efficiency reverse osmosis membrane has a permeation flux of 0.8 m per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)). ３ / (m ２ A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the reverse osmosis membrane is a high-removal-efficiency reverse osmosis membrane with a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, and has a NaCl removal rate of 98% or more.

4. The permeation flux of the reverse osmosis membrane apparatus during the aforementioned operating period was 0.5 m ３ / (m ２ A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the apparatus is configured to operate in a specific location.

5. A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the length of one operating period and the length of one shutdown period are set in advance.

6. A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the length of one operating period is the time until a predetermined target amount of permeate is produced during one pump operating period.

7. A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the operating time and stopping time of the water supply pump to the reverse osmosis membrane apparatus are determined based on the length of a predetermined reference period and the target production permeate volume for the reference period, and the number of pump stopping periods within the reference period, which are predetermined.

8. The method for operating a reverse osmosis membrane apparatus according to claim 7, wherein the aforementioned reference period is a period selected from between 1 and 168 hours.

9. A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the water supply pump operating rate is 30 to 90%, which is the ratio of the length of the operating period to the sum of the length of one operating period and the length of one shutdown period.

10. The method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the length of one stop period is 10 minutes or more.

11. Multiple units, each consisting of a reverse osmosis membrane device and a water supply pump for the reverse osmosis membrane device, are installed in parallel. A method for operating a reverse osmosis membrane apparatus according to claim 1 or 2, wherein the start and stop timings of each unit are staggered.

12. A permeate flux of 2.0 m per 1 MPa of effective membrane surface pressure (water temperature 25°C, pure water (RO permeate)) ３ / (m ２ ·day) or more, and a reverse osmosis membrane device equipped with a high water permeability reverse osmosis membrane having a NaCl removal rate of 95% or more at an effective membrane surface pressure of 1 MPa, a water temperature of 25°C and a pH of 7.0, A water supply pump for the reverse osmosis membrane apparatus, The operating period for running the water supply pump, A control means that alternates between stopping the water supply pump and stopping the pump. A reverse osmosis membrane system equipped with this feature.

13. A reverse osmosis membrane apparatus equipped with a high-removal-efficiency reverse osmosis membrane has a permeation flux of 2.0 m per 1 MPa effective pressure on the membrane surface (water temperature 25°C, pure water (RO permeate)). ３ / (m ２ A reverse osmosis apparatus that replaces the membrane with a highly permeable reverse osmosis membrane that has a NaCl removal rate of 95% or more at a membrane surface effective pressure of 1 MPa, a water temperature of 25°C, and a pH of 7.0, A water supply pump for the reverse osmosis membrane apparatus, The operating period for running the water supply pump, A control means that alternates between stopping the water supply pump and stopping the pump. A reverse osmosis membrane system equipped with this feature.

14. The permeation flux of the reverse osmosis membrane apparatus during the aforementioned operating period was 0.5 m ３ / (m ２ The reverse osmosis membrane system according to claim 12 or 13, wherein the system is 7 days or longer.

15. The system includes a permeate tank for receiving the permeate from the reverse osmosis membrane apparatus, and a water level sensor for detecting the water level in the permeate tank. The reverse osmosis membrane system according to claim 12 or 13, wherein the control means controls the water supply pump so that the water level in the permeate tank is within a predetermined range.

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