Reverse osmosis membrane treatment system and reverse osmosis membrane treatment method

Abstract

To provide a reverse osmosis membrane treatment system capable of efficiently performing reverse osmosis membrane treatment.SOLUTION: In a reverse osmosis membrane treatment system of the present embodiment, a water-to-be-treated tank stores water to be treated in which silica is dissolved. A reverse osmosis membrane treatment unit performs reverse osmosis membrane treatment in which water to be treated is introduced from the water-to-be-treated tank into a concentrated water chamber, and water components of the water to be treated introduced into the concentrated water chamber are reverse-osmotically transferred from the concentrated water chamber through a reverse osmosis membrane into a permeate water chamber. A measurement unit measures at least a temperature and a silica concentration of the water to be treated stored in the water-to-be-treated tank. A control device controls an execution of the reverse osmosis membrane treatment in accordance with a measurement result obtained by the measurement unit. Here, the control device controls the execution of the reverse osmosis membrane treatment by adjusting the water to be treated so that the silica concentration dissolved in the water to be treated is equal to or lower than a solubility of silica at the temperature measured by the measurement unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reverse osmosis membrane treatment system and a reverse osmosis membrane treatment method. [Background technology]

[0002] 2. Description of the Related Art In various facilities such as power plants, water treatment systems are installed to purify water that has been used. Examples of the water treatment system include reverse osmosis membrane treatment systems.

[0003] In a reverse osmosis membrane treatment system, water to be treated (waste liquid) is introduced into a concentrated water chamber, and reverse osmosis membrane treatment is performed in which water components of the water to be treated introduced into the concentrated water chamber are reverse-osmotically transferred as permeated water to the permeated water chamber via a reverse osmosis membrane. Scale components such as silica (water-soluble silica) are dissolved in the water to be treated. For this reason, if reverse osmosis membrane treatment is performed for a long period of time in a reverse osmosis membrane treatment system, scale components such as silica contained in the water to be treated may precipitate as scale on the reverse osmosis membrane. As a result, in the reverse osmosis membrane, the permeation resistance when the water components permeate increases, and the water flow differential pressure when the water components permeate increases, which may reduce the operating rate of the reverse osmosis membrane treatment system.

[0004] Various techniques have been proposed to prevent a decrease in the operating rate of a reverse osmosis membrane treatment system due to the deposition of scale on the reverse osmosis membrane. For example, it has been proposed to perform chemical cleaning to remove scale from the reverse osmosis membrane. It has also been proposed to reduce the deposition of scale on the reverse osmosis membrane by adjusting the pH of the water to be treated. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-299454 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the above-mentioned related techniques, a large amount of chemicals are used for cleaning and pH adjustment, which may reduce the workability of the reverse osmosis membrane treatment and increase the cost required to carry out the reverse osmosis membrane treatment.

[0007] Due to these circumstances, it has not been easy to efficiently carry out reverse osmosis membrane treatment in the past.

[0008] Therefore, an object of the present invention is to provide a reverse osmosis membrane treatment system and a reverse osmosis membrane treatment method that are capable of efficiently performing reverse osmosis membrane treatment. [Means for solving the problem]

[0009] The reverse osmosis membrane treatment system of this embodiment includes a water tank and a reverse osmosis membrane treatment section. The water tank stores water to be treated in which silica is dissolved. The reverse osmosis membrane treatment section performs reverse osmosis membrane treatment in which the water to be treated is introduced from the water tank to a concentrated water chamber, and the water components of the water to be treated introduced into the concentrated water chamber are reverse-osmotically transferred from the concentrated water chamber to a permeate water chamber via a reverse osmosis membrane. The reverse osmosis membrane treatment system of this embodiment includes a measurement section and a control device. The measurement section measures at least the temperature and the silica concentration of the water to be treated stored in the water tank to be treated. The control device controls the execution of the reverse osmosis membrane treatment in accordance with the measurement results measured by the measurement section. Here, the control device controls the execution of the reverse osmosis membrane treatment by adjusting the water to be treated so that the concentration of silica dissolved in the water to be treated is equal to or lower than the solubility of silica at the temperature measured by the measurement section. Effect of the Invention

[0010] According to the present invention, it is possible to provide a reverse osmosis membrane treatment system and a reverse osmosis membrane treatment method capable of efficiently performing reverse osmosis membrane treatment. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating a reverse osmosis membrane treatment system according to the first embodiment. [Diagram 2] FIG. 2 is a flow diagram showing an overview of the reverse osmosis membrane treatment method according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing the relationship between the temperature T2 of the water to be treated F2 and the solubility S of silica in the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating a reverse osmosis membrane treatment system according to the second embodiment. [Diagram 5] FIG. 5 is a diagram illustrating a reverse osmosis membrane treatment system according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] First Embodiment [A] Reverse osmosis membrane treatment system FIG. 1 is a diagram illustrating a reverse osmosis membrane treatment system according to the first embodiment.

[0013] 1, the reverse osmosis membrane treatment system of this embodiment is a water treatment system that performs reverse osmosis membrane treatment and includes a tank 2 for water to be treated, a reverse osmosis membrane treatment section 4, a permeated water tank 6, and a control device 500. Each section of the reverse osmosis membrane treatment system of this embodiment will be described below in order.

[0014] [A-1] Treated water tank 2 The untreated water tank 2 is provided for storing the untreated water F2. The untreated water F2 contains dissolved silica as a scale component.

[0015] In this embodiment, feed water F1 having silica dissolved therein is supplied via a flow path FP1 to the treated water tank 2. A feed water pump P1 is installed in the flow path FP1, and the feed water F1 is supplied by the feed water pump P1.

[0016] In addition, concentrated water F51 is supplied to the treated water tank 2 from the reverse osmosis membrane treatment unit 4 via a flow path FP51. A concentrated water pump P51 and a back pressure valve V51 are installed in the flow path FP51 from the reverse osmosis membrane treatment unit 4 toward the treated water tank 2, and the concentrated water pump P51 supplies the concentrated water F51 via the back pressure valve V51.

[0017] Thus, in this embodiment, the water tank 2 is configured to store the feed water F1 and the concentrated water F51 as the water F2 to be treated. The silica concentration of the water F2 to be treated is the same as the silica concentration of the feed water F1 in the initial stage before reverse osmosis membrane treatment is performed. Then, the concentrated water F51 is mixed with the feed water F1 by performing reverse osmosis membrane treatment. As a result, the silica concentration in the water F2 to be treated increases, and the silica concentration becomes higher than that of the feed water F1. In other words, the silica concentration of the water F2 to be treated is equal to or higher than that of the feed water F1 and is lower than that of the concentrated water F51.

[0018] [A-1-1] Mixer 21 An agitator 21 is installed in the water to be treated tank 2. The agitator 21 agitates the water to be treated F2 stored in the water to be treated tank 2. This causes the components dissolved in the water to be treated F2 to be homogenized.

[0019] [A-1-2] Measurement section 23 Further, a measuring unit 23 is installed in the water to be treated tank 2. The measuring unit 23 includes a temperature detector and a concentration detector, and is configured to measure the temperature T2 and silica concentration C2 of the water to be treated F2 stored in the water to be treated tank 2. In addition, the measuring unit 23 is configured to include a water hardness detector, a pH detector, and an oxidation-reduction potential detector to measure the water hardness, pH, and oxidation-reduction potential of the water to be treated F2.

[0020] [A-2] Reverse osmosis membrane processing section 4 The reverse osmosis membrane processing unit 4 includes a concentrated water chamber 41 and a permeated water chamber 42, with a reverse osmosis membrane 400 interposed between the concentrated water chamber 41 and the permeated water chamber 42, and is configured to perform reverse osmosis membrane processing.

[0021] In this embodiment, in the reverse osmosis membrane treatment section 4, the water to be treated F2 is introduced from the water to be treated tank 2 through a flow path FP3 into the concentrated water chamber 41. A water to be treated pump P3 is installed in the flow path FP3, and the water to be treated F2 is supplied by the water to be treated pump P3.

[0022] In the reverse osmosis membrane treatment unit 4, the water components of the water to be treated F2 introduced into the concentrated water chamber 41 undergo reverse osmosis as permeate F52 from the concentrated water chamber 41 to the permeate chamber 42 via the reverse osmosis membrane 400. As a result, the water to be treated F2 is concentrated in the concentrated water chamber 41, and concentrated water F51 having a higher silica concentration than the water to be treated F2 is obtained.

[0023] [A-3] Permeate tank 6 The permeated water tank 6 is configured to store the permeated water F52 that has been subjected to reverse osmosis in the permeated water chamber 42 in the reverse osmosis membrane processing unit 4 as the stored permeated water F6. In this embodiment, the permeated water F52 is introduced from the permeated water chamber 42 via a flow path FP52 into the permeated water tank 6 and is stored therein.

[0024] The permeated water F6 stored in the permeated water tank 6 is discharged to the outside via a flow path FP6. A permeated water discharge pump P6 is installed in the flow path FP6, and the permeated water F6 is discharged by the permeated water discharge pump P6.

[0025] [A-4] Control device 500 The control device 500 is configured to control the operation of each part of the reverse osmosis membrane treatment system and execute reverse osmosis membrane treatment, for example, by a calculator performing arithmetic processing using a program stored in a memory device.

[0026] The control device 500 has a setting section 510, a confirmation section 520, and a control section 530, and controls the execution of the reverse osmosis membrane process according to the measurement results obtained by the measurement section .

[0027] In this embodiment, the control device 500 controls the execution of reverse osmosis membrane treatment by adjusting the water to be treated F2 so that the concentration C2 of silica dissolved in the water to be treated F2 is equal to or lower than the solubility of silica at the temperature T2 measured by the measurement unit 23.

[0028] [A-4-1] Setting section 510 In the control device 500, the setting unit 510 sets an upper limit value for the concentration rate at which the treated water F2 is concentrated to concentrated water F51 in the reverse osmosis membrane treatment unit 4 based on the temperature T2 and silica concentration C2 of the treated water F2 measured by the measurement unit 23.

[0029] [A-4-2] Verification Section 520 In the control device 500, the confirmation unit 520 confirms whether the concentration rate at which the water to be treated F2 is concentrated into the concentrated water F51 in the reverse osmosis membrane processing unit 4 is equal to or lower than the upper limit determined by the setting unit 510.

[0030] [A-4-3] Control unit 530 In the control device 500, the control unit 530 controls the operation of the supply water pump P1 based on the confirmation result in the confirmation unit 520. The specific control content will be described later.

[0031] [B] Reverse osmosis membrane treatment method A reverse osmosis membrane processing method for performing reverse osmosis membrane processing using the reverse osmosis membrane processing system of this embodiment will be described.

[0032] When performing reverse osmosis membrane treatment in the reverse osmosis membrane treatment system, first, the feed water F1 is supplied to the water tank 2 to be treated using the feed water pump P1. As a result, the feed water F1 is stored in the water tank 2 as the water to be treated F2. Then, the water to be treated F2 is introduced from the water tank 2 to the concentrated water chamber 41 of the reverse osmosis membrane treatment unit 4 using the water to be treated pump P3. In the reverse osmosis membrane treatment unit 4, the water components of the water to be treated F2 introduced into the concentrated water chamber 41 undergo reverse osmosis from the concentrated water chamber 41 to the permeated water chamber 42 via the reverse osmosis membrane 400. As a result, the concentrated water F51 concentrated in the concentrated water chamber 41 flows to the water tank 2 to be treated by the concentrated water pump P51 and is stored as the water to be treated F2. At the same time, the permeated water F52 reverse osmosised in the permeated water chamber 42 flows to the permeated water tank 6 and is stored as the permeated storage water F6. The permeated water F6 stored in the permeated water tank 6 is discharged from the permeated water tank 6 to the outside by using a permeated water discharge pump P6 (see FIG. 1).

[0033] In the reverse osmosis membrane treatment system, the reverse osmosis membrane treatment is performed for a predetermined time, and when the amount of the water to be treated F2 stored in the water to be treated tank 2 reaches a preset lower limit, the control device 500 instructs to stop the reverse osmosis membrane treatment. Then, the supply of the feed water F1 is performed, and after the amount of the water to be treated F2 stored in the water to be treated tank 2 reaches a preset value, the reverse osmosis membrane treatment is resumed. Although not shown, for example, the control device 500 stops and resumes the reverse osmosis membrane treatment based on the result of a sensor that detects the liquid level of the water to be treated F2 stored in the water to be treated tank 2. The reverse osmosis membrane treatment is resumed a predetermined number of times, and when the concentration of the water to be treated F2 exceeds a predetermined value, for example, the whole of the water to be treated F2 stored in the water to be treated tank 2 is replaced. Note that the reverse osmosis membrane treatment may be performed while the supply of the feed water F1 is continuously performed without being temporarily stopped (see FIG. 1).

[0034] In the reverse osmosis membrane treatment system of this embodiment, when performing the reverse osmosis membrane treatment as described above, the following steps are separately performed.

[0035] FIG. 2 is a flow diagram showing an overview of the reverse osmosis membrane treatment method according to the embodiment.

[0036] As shown in Fig. 2, in the reverse osmosis membrane treatment method of this embodiment, reverse osmosis membrane treatment is performed by sequentially executing a measurement step (ST10) and a reverse osmosis membrane treatment step (ST20). After the reverse osmosis membrane treatment cycle consisting of the measurement step (ST10) and the reverse osmosis membrane treatment step (ST20) is started in response to a start command, it is repeatedly executed at a predetermined time interval until it is stopped in response to a stop command. The specific contents of each step in the reverse osmosis membrane treatment method of this embodiment will be sequentially described.

[0037] [B-1] Measurement process (ST10) In the measurement step (ST10), the measurement unit 23 measures the temperature T2 and the silica concentration C2 of the water to be treated F2 stored in the water to be treated tank 2. In addition, in this embodiment, the water hardness, pH, and oxidation-reduction potential of the water to be treated F2 are measured by the measurement unit 23. The measurement data measured by the measurement unit 23 is output to the control device 500.

[0038] [B-2] Reverse osmosis membrane treatment process (ST20) In the reverse osmosis membrane treatment step (ST20), the control device 500 controls each unit in accordance with the measurement results obtained in the measurement step (ST10), thereby performing reverse osmosis membrane treatment. Here, the reverse osmosis membrane treatment is performed by adjusting the water to be treated F2 so that the concentration C2 of silica dissolved in the water to be treated F2 becomes equal to or lower than the solubility of silica at the temperature T2 measured in the measurement step (ST10).

[0039] In this embodiment, in the reverse osmosis membrane treatment step (ST20), as shown in FIG. 2, a setting step (ST210), a checking step (ST220), and a control step (ST230) are executed in this order.

[0040] [B-2-1] Setting process (ST210) In the setting process (ST210), the setting unit 510 sets an upper limit of the concentration rate at which the treated water F2 is concentrated to concentrated water F51 in the reverse osmosis membrane treatment unit 4 based on the temperature T2 and concentration C2 of the treated water F2 measured by the measurement unit 23.

[0041] Here, the upper limit of the concentration rate is set so that the silica concentration C2 of the treated water F2 measured by the measurement unit 23 is equal to or lower than the solubility S of silica at the temperature T2 of the treated water F2 measured by the measurement unit 23.

[0042] In this embodiment, the state in which silica, a scale component, is precipitated as scale is evaluated based on the thermodynamic equilibrium theory, and the solubility S of silica is calculated, thereby setting the upper limit of the concentration rate. The evaluation based on the thermodynamic equilibrium theory is performed taking into consideration the water hardness, pH, and oxidation-reduction potential in addition to the temperature T2 measured by the measurement unit 23. Specifically, the upper limit of the concentration rate is set to be higher as the measured temperature T2 becomes higher.

[0043] FIG. 3 is a diagram showing the relationship between the temperature T2 of the water to be treated F2 and the solubility S of silica in the first embodiment.

[0044] As shown in Fig. 3, when the temperature T2 of the water to be treated F2 is 18°C, the solubility S of silica in the water to be treated F2 is about 45 ppm. Therefore, when the temperature T2 of the water to be treated F2 is 18°C, the setting unit 510 sets the upper limit of the concentration rate so that the concentration C2 of the water to be treated F2 is equal to or less than the solubility S of silica, which is about 45 ppm. The setting unit 510 sets the upper limit of the concentration rate from the measurement results of the temperature T2, etc. of the water to be treated F2, for example, using a lookup table that associates the temperature T2, etc. of the water to be treated F2 with the upper limit of the concentration rate. The upper limit of the concentration rate is set to a larger value, for example, as the temperature T2 of the water to be treated F2 increases.

[0045] [B-2-2] Confirmation process (ST220) In the confirmation step (ST220), the confirmation unit 520 confirms whether the concentration rate at which the water to be treated F2 is concentrated into the concentrated water F51 in the reverse osmosis membrane treatment unit 4 is equal to or lower than the upper limit determined by the setting unit 510.

[0046] The concentration rate at which the water to be treated F2 is concentrated into the concentrated water F51 is determined using the measurement result of the silica concentration C2 of the water to be treated F2 measured by the measurement unit 23. For example, the concentration rate at which the water to be treated F2 is concentrated into the concentrated water F51 is determined from the ratio of the silica concentration C2 of the water to be treated F2 divided by the silica concentration of the feed water F1. Alternatively, the silica concentration of the concentrated water F51 may be measured separately using a concentration detector (not shown), and the concentration rate may be determined as the ratio of the measured silica concentration of the concentrated water F51 divided by the silica concentration C2 of the water to be treated F2.

[0047] Then, the confirmation unit 520 performs a process of comparing the concentration rate at which the water to be treated F2 is concentrated into the concentrated water F51 with the upper limit value of the concentration rate determined by the setting unit 510, thereby executing a confirmation step (ST220).

[0048] [B-2-3] Control process (ST230) In the control step (ST230), the control unit 530 controls the operation of the supply water pump P1 based on the confirmation result in the confirmation step (ST220).

[0049] [B-2-3-1] When the concentration rate is below the upper limit When it is confirmed in the confirmation step (ST220) that the concentration rate is equal to or lower than the upper limit, the operation of the supply water pump P1 is maintained in order to maintain the flow rate of the supply water F1 to the water tank 2. For example, when the supply of the supply water F1 to the water tank 2 is stopped, the control unit 530 maintains the stopped state of the supply water pump P1.

[0050] In this case, the silica concentration C2 of the water to be treated F2 stored in the water to be treated tank 2 is equal to or lower than the solubility of silica.

[0051] [B-2-3-2] When the concentration rate exceeds the upper limit On the other hand, when it is confirmed in the confirmation step (ST220) that the concentration rate exceeds the upper limit, the operation of the supply water pump P1 is controlled to increase the flow rate of the supply water F1 to the water tank 2. For example, when the supply of the supply water F1 to the water tank 2 is stopped, the control unit 530 releases the stopped state of the supply water pump P1 and drives the supply water pump P1.

[0052] The feed water F1 has a lower silica concentration than the water to be treated F2. The feed water F1 is supplied to the water to be treated tank 2, for example, in accordance with the result of the silica concentration C2 of the water to be treated F2 measured in the measurement step (ST10). Here, for example, the feed water F1 is supplied so that the silica concentration C2 of the water to be treated F2 is lower than the solubility of silica by a predetermined value. This makes it possible to make the concentration rate equal to or lower than the upper limit value. As a result, the water to be treated F2 maintains a state in which the silica concentration C2 is equal to or lower than the solubility of silica, so that it is possible to effectively prevent silica from precipitating as scale on the reverse osmosis membrane 400.

[0053] [C] Summary As described above, in the reverse osmosis membrane treatment system of this embodiment, the amount of concentrated water F51 mixed into the water to be treated F2 stored in the water to be treated tank 2 increases as a result of the reverse osmosis membrane treatment, and the silica concentration increases. Therefore, if the silica concentration in the water to be treated F2 exceeds the solubility, silica may precipitate as scale on the reverse osmosis membrane 400. However, in this embodiment, the reverse osmosis membrane treatment is performed in a state in which the concentration C2 of silica dissolved in the water to be treated F2 is maintained at or below the solubility of silica at the temperature T2 measured by the measurement unit 23.

[0054] Therefore, in this embodiment, as described above, it is possible to reduce the deposition of scale on the reverse osmosis membrane 400 without using chemicals or the like, and therefore the reverse osmosis membrane treatment can be carried out efficiently.

[0055] <Second embodiment> [A] Reverse osmosis membrane treatment system FIG. 4 is a diagram illustrating a reverse osmosis membrane treatment system according to the second embodiment.

[0056] As shown in Fig. 4, the reverse osmosis membrane treatment system of this embodiment is configured to supply permeated stored water F6 from the permeated water tank 6 to the treated water tank 2, unlike the first embodiment (see Fig. 1). Except for this point and related points, this embodiment is similar to the first embodiment. Therefore, explanations of overlapping points will be omitted as appropriate.

[0057] In this embodiment, as shown in Fig. 4, the permeated storage water F6 is introduced into the water to be treated tank 2 from the permeated water tank 6 via a flow path FP61 together with the concentrated water F51 and the feed water F1. A permeated storage water supply pump P61 is installed in the flow path FP61, and the permeated storage water F6 is supplied by the permeated storage water supply pump P61. That is, in this embodiment, the water to be treated tank 2 stores the concentrated water F51, the feed water F1, and the permeated storage water F6 as the water to be treated F2.

[0058] [B] Reverse osmosis membrane treatment method A reverse osmosis membrane processing method for performing reverse osmosis membrane processing using the reverse osmosis membrane processing system of this embodiment will be described.

[0059] In this embodiment, as in the first embodiment, reverse osmosis membrane processing is performed by sequentially executing a measurement step (ST10) and a reverse osmosis membrane processing step (ST20). In the reverse osmosis membrane processing step (ST20), a setting step (ST210), a confirmation step (ST220), and a control step (ST230) are sequentially performed (see FIG. 2).

[0060] However, in the control process (ST230) of this embodiment, unlike the first embodiment, the control unit 530 controls the operation of the permeate storage water supply pump P61 (see Figure 4) based on the confirmation results in the confirmation process (ST220) and the silica concentration C2 of the treated water F2 measured in the measurement process (ST10).

[0061] [B-1] When the concentration rate is below the upper limit In this embodiment, when it is confirmed in the confirmation step (ST220) that the concentration rate is equal to or lower than the upper limit, the operation of the permeated storage water supply pump P61 is maintained in order to maintain the flow rate of the permeated storage water F6 to the treated water tank 2. For example, when the supply of the permeated storage water F6 to the treated water tank 2 is stopped, the control unit 530 maintains the stopped state of the permeated storage water supply pump P61.

[0062] In this case, the silica concentration C2 of the water to be treated F2 stored in the water to be treated tank 2 is equal to or lower than the solubility of silica. Therefore, silica, which is a scale component, does not precipitate on the reverse osmosis membrane 400 as scale.

[0063] [B-2] When the concentration rate exceeds the upper limit On the other hand, in this embodiment, when it is confirmed in the confirmation step (ST220) that the concentration rate exceeds the upper limit, the operation of the permeated storage water supply pump P61 is controlled to increase the flow rate of the permeated storage water F6 to the treated water tank 2. For example, when the supply of the permeated storage water F6 to the treated water tank 2 is stopped, the control unit 530 releases the stopped state of the permeated storage water supply pump P61 and drives the permeated storage water supply pump P61.

[0064] The permeated storage water F6 is the permeated water F52 that has been subjected to reverse osmosis into the permeated water chamber 42, and has a lower silica concentration than the water to be treated F2. The supply of the permeated storage water F6 to the water to be treated tank 2 is performed according to the result of the concentration C2 of the water to be treated F2 measured in the measurement step (ST10). For example, the supply of the permeated storage water F6 is performed so that the silica concentration C2 of the water to be treated F2 is lower than the solubility of silica by a predetermined value. This makes it possible to make the concentration rate equal to or lower than the upper limit value. As a result, the water to be treated F2 maintains a state in which the silica concentration C2 is equal to or lower than the solubility of silica, making it possible to prevent silica, which is a scale component, from precipitating as scale on the reverse osmosis membrane 400.

[0065] [C] Summary As described above, in this embodiment, as in the first embodiment, reverse osmosis membrane treatment is performed in a state in which the concentration C2 of silica dissolved in the treated water F2 is maintained below the solubility of silica at the temperature T2 measured by the measurement unit 23.

[0066] Therefore, in this embodiment, as described above, it is possible to reduce the deposition of scale on the reverse osmosis membrane 400 without using chemicals or the like, and therefore it is possible to efficiently perform reverse osmosis membrane treatment.

[0067] [D] Variation In the above embodiment, the case where the operation of the permeate storage water supply pump P61 is controlled in the control step (ST230) has been described, but similarly to the first embodiment, the operation of the supply water pump P1 may also be controlled at the same time.

[0068] <Third embodiment> [A] Reverse osmosis membrane treatment system FIG. 5 is a diagram illustrating a reverse osmosis membrane treatment system according to the third embodiment.

[0069] As shown in Fig. 5, the reverse osmosis membrane treatment system of this embodiment includes a heater 25, unlike the first embodiment (see Fig. 1). Except for this point and related points, this embodiment is similar to the first embodiment. Therefore, descriptions of overlapping points will be omitted as appropriate.

[0070] In this embodiment, the heater 25 is installed, for example, at the bottom of the tank 2 for water to be treated. The heater 25 is provided to heat the water to be treated F2 stored in the tank 2 for water to be treated.

[0071] [B] Reverse osmosis membrane treatment method A reverse osmosis membrane processing method for performing reverse osmosis membrane processing using the reverse osmosis membrane processing system of this embodiment will be described.

[0072] In this embodiment, as in the first embodiment, reverse osmosis membrane processing is performed by sequentially executing a measurement step (ST10) and a reverse osmosis membrane processing step (ST20). In the reverse osmosis membrane processing step (ST20), a setting step (ST210), a confirmation step (ST220), and a control step (ST230) are sequentially performed (see FIG. 2).

[0073] [B-1] Setting process (ST210) However, in the setting step (ST210) of this embodiment, the setting unit 510 not only sets an upper limit value for the concentration rate as in the first embodiment, but also sets a lower limit value, unlike in the first embodiment, based on the temperature T2 of the water to be treated F2 measured by the measurement unit 23. Here, the lower limit value of the concentration rate is set, for example, by multiplying the upper limit value of the concentration rate by a predetermined ratio (e.g., 80%). That is, in this embodiment, a range of the concentration rate is set.

[0074] [B-2] Confirmation process (ST220) In the confirmation step (ST220) of this embodiment, the confirmation unit 520 not only confirms whether the concentration rate is equal to or lower than the upper limit value determined by the setting unit 510, as in the first embodiment, but also, unlike the first embodiment, confirms whether the concentration rate is equal to or higher than the lower limit value determined by the setting unit 510.

[0075] [B-3] Control process (ST230) Then, in the control process (ST230) of this embodiment, the control unit 530 controls the operation of the supply water pump P1, as in the first embodiment, based on the confirmation result in the confirmation unit 520 and the concentration C2 of the treated water F2 measured by the measurement unit 23, and also controls the operation of the heater 25, unlike the first embodiment.

[0076] [B-3-1] When the concentration rate is above the lower limit In this embodiment, when the confirmation process (ST220) confirms that the concentration rate is equal to or higher than the lower limit, the operation of the heater 25 is controlled so that the temperature of the water to be treated F2 stored in the water to be treated tank 2 is maintained.

[0077] [B-3-2] When the concentration rate is below the lower limit On the other hand, in this embodiment, when it is confirmed in the confirmation step (ST220) that the concentration rate is below the lower limit, the operation of the heater 25 is controlled so that the temperature of the water to be treated F2 stored in the water to be treated tank 2 rises to a predetermined temperature. This makes it possible to raise the concentration rate to or above the lower limit.

[0078] [C] Summary As described above, in this embodiment, the control unit 530 controls the operation of the heater 25, so that the reverse osmosis membrane process can be efficiently performed with a concentration rate within an appropriate range.

[0079] As shown in Fig. 3, the solubility S of silica increases as the temperature T2 of the water to be treated F2 increases. For example, when the temperature T2 of the water to be treated F2 is 18°C, the solubility S of silica in the water to be treated F2 is about 45 ppm, whereas when the temperature T2 of the water to be treated F2 is 50°C, the solubility S of silica in the water to be treated F2 is about 80 ppm. Therefore, by increasing the temperature T2 of the water to be treated F2, the deposition of scale on the reverse osmosis membrane 400 can be more effectively reduced.

[0080] [D] Variation In the above embodiment, the heater 25 is installed in the tank 2 for water to be treated in the first embodiment, but the present invention is not limited to this. In the second embodiment, the heater 25 may be installed in the tank 2 for water to be treated.

[0081] In the above embodiment, the operation of the heater 25 is controlled depending on whether the concentration rate is less than the lower limit value in the confirmation step (ST220), but this is not limited thereto. When it is confirmed in the confirmation step (ST220) that the concentration C2 of the water to be treated F2 measured by the measuring unit 23 is higher than a predetermined value, the heater 25 may be driven to increase the temperature T2 of the water to be treated F2. Even in this case, the solubility S of silica in the water to be treated F2 is increased by increasing the temperature T2 of the water to be treated F2, so that the deposition of scale on the reverse osmosis membrane 400 can be more effectively reduced.

[0082] <Fourth embodiment> [A] Reverse osmosis membrane treatment system The reverse osmosis membrane processing system of this embodiment has the same configuration as that of the first embodiment (see FIG. 1). In this embodiment, a part of the reverse osmosis membrane processing method for performing reverse osmosis membrane processing using the reverse osmosis membrane processing system is different from that of the first embodiment. Except for this point and related points, this embodiment is similar to the first embodiment. Therefore, explanations of overlapping points will be omitted as appropriate.

[0083] [B] Reverse osmosis membrane treatment method The reverse osmosis membrane treatment method of this embodiment will be described.

[0084] In this embodiment, as in the first embodiment, reverse osmosis membrane processing is performed by sequentially executing a measurement step (ST10) and a reverse osmosis membrane processing step (ST20). In the reverse osmosis membrane processing step (ST20), a setting step (ST210), a confirmation step (ST220), and a control step (ST230) are sequentially performed (see FIG. 2).

[0085] However, in the control process (ST230) of this embodiment, unlike the first embodiment, the control unit 530 controls the operation of the treated water pump P3 and the operation of the backpressure valve V51 based on the confirmation results in the confirmation process (ST220) (see Figure 1).

[0086] [B-1] When the concentration rate is below the upper limit If it is confirmed in the confirmation process (ST220) that the concentration rate is below the upper limit, the operation of the treated water pump P3 and the back pressure valve V51 are maintained in order to maintain the pressure of the treated water F2 in the concentrated water chamber 41.

[0087] In this case, the silica concentration C2 of the water to be treated F2 stored in the water to be treated tank 2 is equal to or lower than the solubility of silica. Therefore, silica, which is a scale component, does not precipitate on the reverse osmosis membrane 400 as scale.

[0088] [B-2] When the concentration rate exceeds the upper limit On the other hand, if it is confirmed in the confirmation process (ST220) that the concentration rate exceeds the upper limit, the operation of the treated water pump P3 and the back pressure valve V51 are controlled so that the pressure of the treated water F2 in the concentrated water chamber 41 is reduced.

[0089] Specifically, the operation of the water to be treated pump P3 is controlled so that the flow rate of the water to be treated F2 introduced from the water to be treated tank 2 into the concentrated water chamber 41 decreases, thereby reducing the pressure in the concentrated water chamber 41. At the same time, the flow rate of the concentrated water F51 discharged from the concentrated water chamber 41 increases, and the opening of the back pressure valve V51 is increased so that the pressure in the concentrated water chamber 41 decreases.

[0090] This allows the concentration rate to be reduced to or below the upper limit, and the silica concentration C2 in the water to be treated F2 can be maintained at or below the solubility of silica. As a result, it is possible to prevent silica, which is a scale component, from precipitating as scale on the reverse osmosis membrane 400.

[0091] [C] Summary As described above, in this embodiment, as in the first embodiment, reverse osmosis membrane treatment is performed by adjusting the water to be treated F2 so that the concentration C2 of silica dissolved in the water to be treated F2 is equal to or lower than the solubility of silica at temperature T2 measured by measurement unit 23.

[0092] Therefore, in this embodiment, as described above, it is possible to reduce the deposition of scale on the reverse osmosis membrane 400 without using chemicals or the like, and therefore it is possible to efficiently perform reverse osmosis membrane treatment.

[0093] [D] Variation In the above embodiment, in the first embodiment, the operation of the treated water pump P3 and the operation of the back pressure valve V51 are controlled in the control step (ST230) based on the confirmation result in the confirmation step (ST220), but this is not limited to the above. As in the first embodiment, the operation of the feed water pump P1 may also be controlled. Moreover, in the second and third embodiments, the above control may also be performed in the same manner.

[0094] In the above embodiment, the case where both the operation of the water pump P3 and the operation of the back pressure valve V51 are controlled has been described, but this is not limited thereto. It may be configured to control either the operation of the water pump P3 or the operation of the back pressure valve V51. In other words, at least one of the operation of the water pump P3 and the operation of the back pressure valve V51 may be controlled.

[0095] <Other> The present invention is not limited to the above-described embodiment, and can be implemented in various forms other than the above-described examples at the implementation stage. Various omissions, additions, substitutions, and modifications can be made to the present invention without departing from the spirit of the invention. These embodiments and modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0096] 2: tank for treated water, 4: reverse osmosis membrane processing section, 6: permeated water tank, 21: agitator, 23: measuring section, 25: heater, 41: concentrated water chamber, 42: permeated water chamber, 400: reverse osmosis membrane, 500: control device, 510: setting section, 520: confirmation section, 530: control section, F1: supply water, F2: water for treatment, F51: concentrated water, F52: permeated water, F6: permeated water storage, P1: supply water pump, P3: water for treatment pump, P51: concentrated water pump, P6: permeated water storage discharge pump, P61: permeated water storage supply pump, V51: back pressure valve

Claims

1. a treated water tank for storing the treated water having dissolved silica; A reverse osmosis membrane processing unit that performs reverse osmosis membrane processing in which the water to be treated is introduced from the water to be treated tank into a concentrated water chamber, and the water components of the water to be treated introduced into the concentrated water chamber are reverse-osmotically transferred from the concentrated water chamber to a permeate water chamber through a reverse osmosis membrane; A reverse osmosis membrane treatment system comprising: A measurement unit that measures at least a temperature and a silica concentration of the water to be treated stored in the water to be treated tank; a control device that controls the execution of the reverse osmosis membrane treatment in accordance with the measurement result measured by the measurement unit; and having The control device controls the execution of the reverse osmosis membrane treatment by adjusting the water to be treated so that the concentration of silica dissolved in the water to be treated is equal to or lower than the solubility of silica at the temperature measured by the measurement unit. Reverse osmosis treatment system.

2. The treated water tank is configured to receive concentrated water that has been concentrated so that the silica concentration in the concentrated water chamber is higher than that of the treated water, and to receive supply water in which silica is dissolved by a supply water pump, and to store the concentrated water and the supply water as the treated water, The control device includes: A setting unit that sets at least an upper limit value for a concentration rate at which the water to be treated is concentrated into the concentrated water in the reverse osmosis membrane processing unit based on the results of the temperature and the silica concentration measured by the measurement unit; A confirmation unit that confirms whether the concentration rate is equal to or lower than the upper limit value determined by the setting unit; a control unit that controls an operation of the supply water pump based on a confirmation result by the confirmation unit; Equipped with The setting unit sets the upper limit value so that the silica concentration measured by the measurement unit is equal to or lower than the solubility of silica at the temperature measured by the measurement unit, When the confirmation unit confirms that the concentration rate exceeds the upper limit value, the control unit drives the supply water pump to supply the supply water to the treated water tank. The reverse osmosis membrane treatment system according to claim 1 .

3. A permeate tank for storing the permeate that has been subjected to reverse osmosis in the permeate chamber as permeate storage water. Equipped with The treated water tank is configured to receive concentrated water that has been concentrated in the concentrated water chamber so that the silica concentration is higher than that of the treated water, and supply water in which silica is dissolved, and to receive the permeated storage water stored in the permeated water tank by a permeated storage water supply pump, and to store the concentrated water, the supply water, and the permeated storage water as the treated water, The control device includes: A setting unit that sets at least an upper limit value for a concentration rate at which the water to be treated is concentrated into the concentrated water in the reverse osmosis membrane processing unit based on the result of the temperature measured by the measurement unit; a confirmation unit that confirms whether the concentration rate when the reverse osmosis membrane processing is performed in the reverse osmosis membrane processing unit is equal to or lower than the upper limit value determined by the setting unit; A control unit that controls the operation of the permeate storage water supply pump based on the confirmation result by the confirmation unit; Equipped with The setting unit sets the upper limit of the silica concentration measured by the measurement unit to be equal to or lower than the solubility of silica at the temperature measured by the measurement unit, When the confirmation unit confirms that the concentration rate exceeds the upper limit value, the control unit drives the permeated water supply pump to supply the permeated water to the treated water tank. The reverse osmosis membrane treatment system according to claim 1 .

4. A heater for heating the water to be treated stored in the water to be treated tank. Equipped with The setting unit sets a lower limit value for the concentration rate based on the temperature measured by the measurement unit, When the confirmation unit confirms that the concentration rate is less than the lower limit value, the control unit drives the heater to increase the temperature of the water to be treated stored in the water to be treated tank. The reverse osmosis membrane treatment system according to claim 2 .

5. The treated water tank is configured so that the concentrated water is supplied through a back pressure valve, The reverse osmosis membrane treatment unit is configured such that the water to be treated is introduced from the water to be treated tank to the concentrated water chamber by a water to be treated pump, When the confirmation unit confirms that the concentration rate exceeds the upper limit value, the control unit controls the operation of at least one of the back pressure valve and the treated water pump so that the pressure of the treated water in the concentrated water chamber is reduced. The reverse osmosis membrane treatment system according to any one of claims 2 to 4.

6. A reverse osmosis membrane treatment method comprising: introducing water to be treated from a water tank storing the water to be treated in which silica is dissolved, into a concentrated water chamber; and performing reverse osmosis membrane treatment in which a water component of the water to be treated introduced into the concentrated water chamber is reverse osmotically transferred from the concentrated water chamber to a permeate water chamber through a reverse osmosis membrane, A measuring step of measuring at least a temperature and a silica concentration of the water to be treated stored in the water to be treated tank; a reverse osmosis membrane treatment step of performing the reverse osmosis membrane treatment in accordance with the measurement results obtained in the measurement step; Including, In the reverse osmosis membrane treatment step, the reverse osmosis membrane treatment is performed by adjusting the water to be treated so that the concentration of silica dissolved in the water to be treated is equal to or lower than the solubility of silica at the temperature measured in the measurement step. Reverse osmosis membrane treatment method.

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