Water treatment method and water treatment device

Abstract

To provide a water treatment method and water treatment equipment which can perform stable treatment at low cost in water concentration treatment using a semipermeable module.SOLUTION: A water treatment method is provided, including: a semipermeable treatment step of passing treatment-object water including a dissolution solid component through a first space 14 using a semipermeable module, pressurizing the first space 14 and causing water included in the treatment object water to penetrate through a semipermeable film 12, thereby obtaining concentrated water, passing a part of the treatment object water or at least a part of the concentrated water through a second space 16, thereby obtaining diluted water; a first space outlet flow volume measurement step of measuring a flow volume of the concentrated water in a first space outlet; a second space inlet flow volume measurement step of measuring a flow volume of the treatment object water or the concentrated water in a second space inlet; and a second space outlet flow volume measurement step of measuring a flow volume of the diluted water in a second space outlet. In the water treatment method, the flow volume of the treatment object water in the first space inlet of the semipermeable module is calculated using each of the measured flow volumes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a water treatment method and a water treatment device for concentrating water containing total dissolved solids (TDS) and the like. [Background technology]

[0002] BACKGROUND ART In recent years, methods for reducing the volume of wastewater from factories and the like have become known, including evaporation using an evaporator and reverse osmosis, which uses a reverse osmosis membrane to recover permeate and reduce the volume of wastewater.

[0003] Also known is a method of concentrating water by passing water to be treated or a concentrated water thereof through a first space and a second space separated by a semipermeable membrane in a semipermeable membrane module and pressurizing the first space, as described in Patent Document 1. This type of concentration method using a semipermeable membrane reduces the osmotic pressure difference between the first space and the second space, making it possible to highly concentrate wastewater and reduce its volume with less energy consumption than common reverse osmosis methods.

[0004] The concentration method described in Patent Document 1 requires control of the flow rates in the first and second spaces of the membrane in order to stably reduce the volume of wastewater, and therefore requires the installation of flow rate measuring devices at the inlet and outlet of the first space and the inlet and outlet of the second space.

[0005] However, since the first space line of the semipermeable membrane is pressurized and at high pressure, the flow rate measuring device used must be highly pressure-resistant or a special ultrasonic type, which leads to an increase in initial costs. Also, in the case of a device using multiple semipermeable membrane modules, if a flow rate measuring device is installed in each stage, the number of flow rate measuring devices increases as the number of stages increases, further increasing the initial costs. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-069198 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a water treatment method and a water treatment device that can perform stable treatment at low cost in a water concentration treatment using a semipermeable membrane module. [Means for solving the problem]

[0008] The present invention includes a semipermeable membrane treatment step of using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, passing water to be treated that contains dissolved solid components through the first space, pressurizing the first space to cause the water contained in the water to permeate the semipermeable membrane, thereby obtaining concentrated water, and passing a portion of the water to be treated or at least a portion of the concentrated water through the second space, thereby obtaining dilution water; a first space outlet flow rate measuring step of measuring the flow rate of the concentrated water at the first space outlet of the semipermeable membrane module; a second space inlet flow rate measuring step of measuring the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module; and a second space outlet flow rate measuring step of measuring the flow rate of the dilution water at the second space outlet of the semipermeable membrane module, The pressure of the water to be treated in the first space is more than 1.0 MPa and not more than 10.0 MPa, and the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module is not measured, This is a water treatment method, in which the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module is calculated from the flow rates measured in the first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step.

[0009] The present invention includes a semipermeable membrane treatment process using semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, in which water to be treated containing dissolved solid components is passed through the first space of the semipermeable membrane module of a first stage, the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water, and this concentrated water is further used to obtain concentrated water using semipermeable membrane modules of subsequent stages and at least a part of the water to be treated or the concentrated water is passed through the second space of the semipermeable membrane module of each stage to obtain dilution water; a final stage first space outlet flow rate measuring process for measuring the flow rate of the concentrated water at the first space outlet of the semipermeable membrane module of the final stage; a second space inlet flow rate measuring process for measuring the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module of the most upstream stage on the second space side or of each stage; and a second space outlet flow rate measuring process for measuring the flow rate of the dilution water at the second space outlet of the semipermeable membrane module of the most downstream stage on the second space side or of each stage, The pressure of the water to be treated in the first space is more than 1.0 MPa and not more than 10.0 MPa, and the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module is not measured, This is a water treatment method in which the flow rate of the water to be treated or the concentrated water at the inlet of the first space of the semipermeable membrane module of the first stage or each stage is calculated from the flow rates measured in the final stage first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step.

[0010] In the water treatment method, it is preferable to control the flow rate of the concentrated water or the water to be treated at the inlet of the first space to a predetermined value based on the calculated flow rate of the concentrated water or the water to be treated.

[0011] In the water treatment method, the first space outlet flow rate measuring step or the final stage first space outlet flow rate measuring step It is preferable that the pressure at the flow rate measurement point in the second space inlet flow rate measurement step and the second space outlet flow rate measurement step is 1 MPa or less.

[0012] The present invention provides a semipermeable membrane treatment means that uses a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, passes water to be treated that contains dissolved solid components through the first space, pressurizes the first space to cause the water contained in the water to permeate through the semipermeable membrane, thereby obtaining concentrated water, and passes a portion of the water to be treated or at least a portion of the concentrated water through the second space, thereby obtaining dilution water; a first space outlet flow rate measuring means that measures the flow rate of the concentrated water at the first space outlet of the semipermeable membrane module; a second space inlet flow rate measuring means that measures the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module; and a second space outlet flow rate measuring means that measures the flow rate of the dilution water at the second space outlet of the semipermeable membrane module. The pressure of the water to be treated in the first space is more than 1.0 MPa and not more than 10.0 MPa, and a first space inlet flow rate measuring means for measuring the flow rate of the water to be treated at the first space inlet of the semipermeable membrane module is not installed, The water treatment device is provided with: a first space outlet flow rate measuring means; a second space inlet flow rate measuring means; and a calculation means for calculating the flow rate of water to be treated at the inlet of the first space of the semipermeable membrane module from the flow rates measured by the first space outlet flow rate measuring means, the second space inlet flow rate measuring means, and the second space outlet flow rate measuring means.

[0013] The present invention provides a semipermeable membrane treatment means that uses semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, and that passes water to be treated that contains dissolved solid components through the first space of the semipermeable membrane module of a first stage, pressurizes the first space, and causes the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water, and that further uses the concentrated water to obtain concentrated water using semipermeable membrane modules of subsequent stages and passes a portion of the water to be treated or at least a portion of the concentrated water through the second space of the semipermeable membrane module of each stage to obtain dilution water; a final stage first space outlet flow rate measuring means that measures the flow rate of the concentrated water at the first space outlet of the semipermeable membrane module of the final stage; a second space inlet flow rate measuring means that measures the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module of the most upstream stage on the second space side or of each stage; and a second space outlet flow rate measuring means that measures the flow rate of the dilution water at the second space outlet of the semipermeable membrane module of the most downstream stage on the second space side or of each stage. The pressure of the water to be treated in the first space is more than 1.0 MPa and not more than 10.0 MPa, and a first space inlet flow rate measuring means for measuring the flow rate of the water to be treated at the first space inlet of the semipermeable membrane module is not installed,The water treatment device comprises a calculation means for calculating the flow rate of the water to be treated or the concentrated water at the inlet of the first space of the semipermeable membrane module of the first stage or each stage from the flow rates measured by the final stage first space outlet flow rate measuring means, the second space inlet flow rate measuring means, and the second space outlet flow rate measuring means.

[0014] It is preferable that the water treatment device further comprises a control means for controlling the flow rate of the concentrated water or the water to be treated at the inlet of the first space to a predetermined value based on the calculated flow rate of the concentrated water or the water to be treated.

[0015] In the water treatment device, the first space outlet flow rate measuring means or the final stage first space outlet flow rate measuring means It is preferable that the pressure at the flow rate measurement points by the second space inlet flow rate measurement means and the second space outlet flow rate measurement means is 1 MPa or less. [Effects of the Invention]

[0016] According to the present invention, a water treatment method and a water treatment apparatus can be provided that can perform stable treatment at low cost in a water concentration treatment using a semipermeable membrane module. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram illustrating an example of a water treatment device according to an embodiment of the present invention. [Figure 2] FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. [Figure 3] FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. [Figure 4] FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. [Figure 5] FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. [Figure 6] FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. [Figure 7]FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. [Figure 8] FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0019] An example of a water treatment apparatus according to an embodiment of the present invention is outlined in FIG. 1, and its configuration will be described.

[0020] The water treatment device 1 shown in Figure 1 uses a semipermeable membrane module having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane. Water to be treated, including total dissolved solids (TDS) and the like, is passed through the first space, and the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane, thereby obtaining concentrated water. Also, a portion of the water to be treated is passed through the second space to obtain dilution water. The water treatment device 1 includes, for example, a membrane module 10 as semipermeable membrane treatment means. The membrane module 10 has a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water treatment device 1 may also include a water tank for storing the water to be treated.

[0021] In the water treatment device 1 in Figure 1, a pipe 24 is connected to the inlet of the first space of the membrane module 10, and a pipe 26 branching from the pipe 24 is connected to the inlet of the second space of the membrane module 10. A pipe 28 is connected to the outlet of the first space of the membrane module 10, and a pipe 30 is connected to the outlet of the second space of the membrane module 10.

[0022] A first space outlet flow rate measuring device 18 is installed in the piping 28 as a first space outlet flow rate measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10. A second space inlet flow rate measuring device 20 is installed in the piping 26 as a second space inlet flow rate measuring means for measuring the flow rate (FI2) of water to be treated at the second space inlet of the membrane module 10. A second space outlet flow rate measuring device 22 is installed in the piping 30 as a second space outlet flow rate measuring means for measuring the flow rate (FI3) of dilution water at the second space outlet of the membrane module 10.

[0023] The water treatment device 1 in Figure 1 uses a membrane module 10 having a first space 14 and a second space 16 separated by a semipermeable membrane 12, and is an apparatus in which water to be treated is passed from the first space inlet of the membrane module 10 to the first space 14 and from the second space inlet to the second space 16, and the first space 14 is pressurized, causing the water contained in the water to be treated in the first space 14 to permeate into the second space 16 via the semipermeable membrane 12, thereby concentrating the water. That is, in the water treatment device 1, the water to be treated is concentrated using the semipermeable membrane 12. The water treatment device 1 is an apparatus in which the water to be treated is supplied to both the first space 14 and the second space 16 of the membrane module 10 and subjected to a concentration treatment.

[0024] In the water treatment device 1, water to be treated containing dissolved solids (TDS) is pressurized and pumped from the first space inlet of the membrane module 10 to the first space 14 through pipe 24. The water to be treated is also pumped from the second space inlet of the membrane module 10 to the second space 16 through pipe 26, which branches off from pipe 24. A portion of the water contained in the pressurized water to be treated permeates from the first space 14 to the second space 16 through the semipermeable membrane 12. Since most of the dissolved solids cannot permeate the semipermeable membrane 12, the water in the first space 14 that did not permeate the semipermeable membrane 12 is concentrated. Meanwhile, in the second space 16, a portion of the water to be treated pumped through pipe 26 and the permeate with a low TDS concentration that permeated the semipermeable membrane 12 merge, resulting in a dilution effect. The concentrated water obtained in the first space 14 is discharged from the first space outlet through pipe 28, and the diluted water obtained in the second space 16 is discharged from the second space outlet through pipe 30. Here, in the membrane module 10, the first space 14 is pressurized, and the water contained in the water to be treated in the first space 14 permeates through the semipermeable membrane 12 into the second space 16, producing concentrated water in the first space 14 (concentration step), and dilution water in the second space 16 (dilution step). A portion of the concentrated water produced in the first space 14 is discharged to the outside of the system through the pipe 28.

[0025] Here, the pipes 24 , 26 and the like function as supply means for supplying the water to be treated to both the first space 14 and the second space 16 of the membrane module 10 .

[0026] The diluted water obtained in the second space 16 may be discharged outside the system through the pipe 30, or may be sent to a dilution water tank and stored there as necessary, and then discharged outside the system. At least a portion of the diluted water may be sent to a water tank to be treated and mixed with the water to be treated there. At least a portion of the diluted water may be further sent to a reverse osmosis membrane treatment device, where it may undergo reverse osmosis membrane treatment (reverse osmosis membrane treatment step). The RO permeate obtained by the reverse osmosis membrane treatment is discharged outside the system. The RO concentrated water obtained by the reverse osmosis membrane treatment may be sent to a water tank to be treated and mixed with the water to be treated there.

[0027] In this manner, treated water (concentrated water) containing concentrated substances such as dissolved solid components and diluted water are obtained from the treated water, which is the target of treatment and contains dissolved solid components, and the volume of the treated water is reduced.

[0028] As described above, the pipe 24 at the first space inlet of the membrane module 10 is pressurized and at high pressure. Therefore, the flow measurement device used for the pipe 24 must be highly pressure-resistant or specially designed for ultrasonic use, which increases initial costs. In the water treatment method and water treatment device 1 according to this embodiment, a first space outlet flow measurement device 18, a second space inlet flow measurement device 20, and a second space outlet flow measurement device 22 are installed at the primary side outlet, secondary side inlet, and secondary side outlet of the membrane module 10, respectively. No flow measurement device is installed at the primary side inlet. The flow rate of the water to be treated at the primary side inlet is calculated from the values ​​of the flow measurement devices at the primary side outlet, secondary side inlet, and secondary side outlet. In other words, in the water treatment device 1, flow measurement devices are installed only at the primary side outlet, secondary side inlet, and secondary side outlet of the membrane module 10. This reduces the number of flow measurement devices used, enabling stable treatment at low cost.

[0029] The flow rate of the untreated water at the primary inlet can be calculated from the values ​​measured by the flow rate measuring devices at the primary outlet, secondary inlet, and secondary outlet. This calculation can be performed manually or automatically. When calculating automatically, the water treatment device 1 may include a calculation device as a calculation means for calculating the flow rate of the untreated water at the first space inlet from the flow rates measured by the flow rate measuring devices at the primary outlet, secondary inlet, and secondary outlet. The calculation device may be electrically connected to the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22. The calculation device may be configured, for example, by a microcomputer and electronic circuits, including a calculation means such as a CPU that executes programs and storage means such as ROM and RAM that store programs and calculation results. The calculation device has the function of calculating the flow rate of the untreated water at the first space inlet from the flow rates measured by the flow rate measuring devices at the primary outlet, secondary inlet, and secondary outlet.

[0030] Another example of a water treatment device according to an embodiment of the present invention is outlined in FIG. 2, and its configuration will be described.

[0031] The water treatment device 2 shown in Figure 2 uses a semipermeable membrane module having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane, and includes, for example, a membrane module 10 as semipermeable membrane treatment means for passing water to be treated, which contains total dissolved solids (TDS) and the like, through the first space, pressurizing the first space to cause the water contained in the water to permeate through the semipermeable membrane, thereby obtaining concentrated water, and passing at least a portion of the concentrated water through the second space to obtain dilution water. The membrane module 10 has a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water treatment device 1 may also include a water tank to store the water to be treated.

[0032] In the water treatment device 2 in Figure 2, a pipe 24 is connected to the inlet of the first space of the membrane module 10. A pipe 28 is connected to the outlet of the first space of the membrane module 10. A pipe 32 branching from the pipe 28 is connected to the inlet of the second space of the membrane module 10. A pipe 34 is connected to the outlet of the second space of the membrane module 10.

[0033] A first space outlet flow rate measuring device 18 is installed downstream of the branch point of the pipe 28 to the pipe 32 as a first space outlet flow rate measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10. A second space inlet flow rate measuring device 20 is installed in the pipe 32 as a second space inlet flow rate measuring means for measuring the flow rate (FI2) of water to be treated at the second space inlet of the membrane module 10. A second space outlet flow rate measuring device 22 is installed in the pipe 34 as a second space outlet flow rate measuring means for measuring the flow rate (FI3) of dilution water at the second space outlet of the membrane module 10.

[0034] The water treatment device 2 of Figure 2 uses a membrane module 10 having a first space 14 and a second space 16 separated by a semipermeable membrane 12, and passes water to be treated through the first space 14 from the inlet of the first space of the membrane module 10, and passes at least a portion of the concentrated water discharged from the first space outlet of the first space 14 of the membrane module 10 through the inlet of the second space of the membrane module 10, and by pressurizing the first space 14, the water contained in the water to be treated in the first space 14 is permeated into the second space 16 through the semipermeable membrane 12, thereby concentrating the water. That is, in the water treatment device 1, the water to be treated is concentrated using the semipermeable membrane 12. The water treatment device 1 is a device that supplies water to be treated to the first space 14 of the membrane module 10 and supplies at least a portion of the concentrated water obtained from the outlet of the first space 14 to the second space 16 of the membrane module 10 to perform a concentration treatment.

[0035] The water treatment method and the operation of the water treatment device 2 according to this embodiment will be described.

[0036] In the water treatment device 2, water to be treated containing dissolved solids (TDS) is pressurized and pumped from the first space inlet of the membrane module 10 to the first space 14 through the pipe 24. A portion of the water contained in the pressurized water to be treated permeates from the first space 14 to the second space 16 through the semipermeable membrane 12. At this time, most of the dissolved solids cannot permeate the semipermeable membrane 12, so the water in the first space 14 that did not permeate the semipermeable membrane 12 is concentrated. Meanwhile, in the second space 16, a portion of the concentrated water pumped through the pipe 32 and the permeated water with a low TDS concentration that permeated the semipermeable membrane 12 merge, resulting in a dilution effect. The concentrated water obtained in the first space 14 is discharged from the first space outlet through the pipe 28, and at least a portion of the concentrated water is pumped from the second space inlet of the membrane module 10 through the pipe 32 branching off from the pipe 28 to the second space 16. The diluted water obtained in the second space 16 is discharged from the second space outlet through the pipe 34. Here, in the membrane module 10, the first space 14 is pressurized, and the water contained in the water to be treated in the first space 14 is permeated through the semipermeable membrane 12 into the second space 16, thereby obtaining concentrated water in the first space 14 (concentration step) and dilution water in the second space 16 (dilution step). A portion of the concentrated water obtained in the first space 14 may be discharged to the outside of the system through the pipe 28. At least a portion of the concentrated water is sent and passed through the pipes 28 and 32 to the second space 16 of the membrane module 10 as described above.

[0037] Here, the pipes 24, 28, 32, etc. function as a supply means for supplying the water to be treated to the first space 14 of the membrane module 10 and supplying at least a portion of the concentrated water obtained from the outlet of the first space 14 to the second space 16 of the membrane module 10.

[0038] The diluted water obtained in the second space 16 may be discharged outside the system through the pipe 34, or may be sent to a dilution water tank and stored therein as necessary, and then discharged outside the system. At least a portion of the diluted water may be sent to a water tank to be treated and mixed with the water to be treated therein. At least a portion of the diluted water may be further sent to a reverse osmosis membrane treatment device, where it may undergo reverse osmosis membrane treatment (reverse osmosis membrane treatment step). The RO permeate obtained by the reverse osmosis membrane treatment is discharged outside the system. The RO concentrated water obtained by the reverse osmosis membrane treatment may be sent to a water tank to be treated and mixed with the water to be treated therein.

[0039] In this manner, treated water (concentrated water) containing concentrated substances such as dissolved solid components and diluted water are obtained from the treated water, which is the target of treatment and contains dissolved solid components, and the volume of the treated water is reduced.

[0040] In the water treatment method and water treatment device 2 according to this embodiment, a first space outlet flow measuring device 18, a second space inlet flow measuring device 20, and a second space outlet flow measuring device 22 are installed at the primary side outlet, secondary side inlet, and secondary side outlet of the membrane module 10, respectively, and no flow measuring device is installed at the primary side inlet, and the flow rate of the water to be treated at the primary side inlet is calculated from the values ​​of the flow measuring devices at the primary side outlet, secondary side inlet, and secondary side outlet. That is, in the water treatment device 2, flow measuring devices are installed only at the primary side outlet, secondary side inlet, and secondary side outlet of the membrane module 10. This allows the number of flow measuring devices to be reduced, enabling stable treatment at low cost.

[0041] In the water treatment method and water treatment device according to this embodiment, it is preferable to control the flow rate of the concentrated water or the water to be treated at the inlet of the first space so that it becomes a predetermined value based on the calculated flow rate of the concentrated water or the water to be treated at the inlet of the first space. An example of a water treatment device having such a configuration is shown in Figures 3 and 4.

[0042] The water treatment device 3 shown in Figure 3 has the same configuration as the water treatment device 1 shown in Figure 1, and in addition, it is equipped with a pump 36 upstream of the branching point of the pipe 24 to the pipe 26, and a valve 40 upstream of the installation point of the second space inlet flow measuring device 20 on the pipe 26.

[0043] The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to an input drive frequency, and sucks in the water to be treated and discharges it to the membrane module 10. The pump 36 is equipped with, for example, an inverter 38 that outputs a drive frequency corresponding to an input command signal to the pump 36. The valve 40 is, for example, a proportional control valve that adjusts its opening based on the measured values ​​of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22.

[0044] The water treatment device 3 may include a control device 42 as a control means for controlling the flow rate of the water to be treated at the inlet of the first space to a predetermined value based on the calculated flow rate of the water to be treated at the inlet of the first space. The control device 42 may be electrically connected to each of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, the second space outlet flow rate measuring device 22, the inverter 38, and the valve 40. The control device 42 is composed of a microcomputer and electronic circuits, which include, for example, a calculation means such as a CPU that executes programs and storage means such as ROM and RAM that store programs and calculation results, and has the function of controlling the flow rate of the pump 36, the opening / closing degree of the valve 40, etc. The control device 42 may be the same device as the calculation device or a different device.

[0045] In the water treatment device 3, similarly to the water treatment device 1, treated water containing dissolved solid components, etc., which is the target of treatment, is converted into treated water (concentrated water) in which substances such as dissolved solid components have been concentrated, and diluted water, thereby reducing the volume of the treated water.

[0046] Here, for example, the first space outlet flow rate measuring device 18 measures the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10 (first space outlet flow rate measuring step), the second space inlet flow rate measuring device 20 measures the flow rate (FI2) of water to be treated at the second space inlet of the membrane module 10 (second space inlet flow rate measuring step), and the second space outlet flow rate measuring device 22 measures the flow rate (FI3) of dilution water at the second space outlet of the membrane module 10 (second space outlet flow rate measuring step). Then, for example, based on the flow rate of water to be treated at the first space inlet = FI1 + (FI3 - FI2), which is calculated from the flow rates (FI1, FI2, FI3) measured in the first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step, the flow rate of water to be treated at the first space inlet is controlled to a predetermined value (control step).

[0047] For example, the control device 42 calculates the drive frequency using an arbitrary arithmetic formula based on the flow rate of the water to be treated at the inlet of the first space = FI1 + (FI3 - FI2), which is obtained from the respective flow rates (FI1, FI2, FI3) measured by the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22, so that the flow rate of the water to be treated at the inlet of the first space becomes a predetermined value, and outputs a command signal corresponding to this calculated value to the inverter 38 to control the pump 36, and controls the opening and closing degree of the valve 40, thereby controlling the flow rate of the water to be treated at the inlet of the first space.

[0048] In the water treatment method and water treatment device 3 according to this embodiment, a first space outlet flow rate measuring device 18, a second space inlet flow rate measuring device 20, and a second space outlet flow rate measuring device 22 are installed at the primary side outlet, secondary side inlet, and secondary side outlet of the membrane module 10, respectively. No flow rate measuring device is installed at the primary side inlet. The flow rate of the water to be treated at the primary side inlet is calculated from the values ​​of the flow rate measuring devices at the primary side outlet, secondary side inlet, and secondary side outlet. The flow rate of the water to be treated at the primary side inlet is then adjusted based on the calculated flow rate of the water to be treated at the primary side inlet. This reduces the number of flow rate measuring devices used, enabling stable treatment at low cost. Furthermore, controlling the flow rate of the water to be treated at the primary side inlet enables even more stable treatment.

[0049] 4 has the same configuration as the water treatment device 2 shown in FIG. 2, but also includes a pump 36 in the pipe 24 and a valve 40 on the pipe 32 upstream of the installation point of the second space inlet flow rate measuring device 20. The water treatment device 4 may also include a control device 42 as control means for controlling the flow rate of the water to be treated at the inlet of the first space to a predetermined value based on the calculated flow rate of the water to be treated at the inlet of the first space. The control device 42 may be connected to each of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, the second space outlet flow rate measuring device 22, the inverter 38, and the valve 40 by electrical connection or the like.

[0050] In the water treatment device 4, similarly to the water treatment device 2, treated water containing dissolved solid components, etc., which is the target of treatment, is converted into treated water (concentrated water) in which substances such as dissolved solid components have been concentrated, and diluted water, thereby reducing the volume of the treated water.

[0051] Here, for example, the first space outlet flow rate measuring device 18 measures the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10 (first space outlet flow rate measuring step), the second space inlet flow rate measuring device 20 measures the flow rate (FI2) of concentrated water at the second space inlet of the membrane module 10 (second space inlet flow rate measuring step), and the second space outlet flow rate measuring device 22 measures the flow rate (FI3) of dilution water at the second space outlet of the membrane module 10 (second space outlet flow rate measuring step). Then, for example, based on the flow rate of water to be treated at the first space inlet = FI1 + (FI3 - FI2), which is calculated from the respective flow rates (FI1, FI2, FI3) measured in the first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step, the flow rate of water to be treated at the first space inlet is controlled to a predetermined value (control step).

[0052] For example, the control device 42 calculates the drive frequency using an arbitrary arithmetic formula based on the flow rate of the water to be treated at the inlet of the first space = FI1 + (FI3 - FI2), which is obtained from the respective flow rates (FI1, FI2, FI3) measured by the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22, so that the flow rate of the water to be treated at the inlet of the first space becomes a predetermined value, and outputs a command signal corresponding to this calculated value to the inverter 38 to control the pump 36, and controls the opening and closing degree of the valve 40, thereby controlling the flow rate of the water to be treated at the inlet of the first space.

[0053] In the water treatment method and water treatment device 4 according to this embodiment, a first space outlet flow rate measuring device 18, a second space inlet flow rate measuring device 20, and a second space outlet flow rate measuring device 22 are installed at the primary side outlet, secondary side inlet, and secondary side outlet of the membrane module 10, respectively. No flow rate measuring device is installed at the primary side inlet. The flow rate of the water to be treated at the primary side inlet is calculated from the values ​​of the flow rate measuring devices at the primary side outlet, secondary side inlet, and secondary side outlet. The flow rate of the water to be treated at the primary side inlet is then adjusted based on the calculated flow rate of the water to be treated at the primary side inlet. This reduces the number of flow rate measuring devices used, enabling stable treatment at low cost. Furthermore, controlling the flow rate of the water to be treated at the primary side inlet enables even more stable treatment.

[0054] In the water treatment devices 3 and 4, if the flow rate of the water to be treated at the primary inlet is lower than a predetermined value, the output value of the inverter 38 of the pump 36 may be increased to adjust the flow rate of the water to be treated at the primary inlet to the predetermined value, or the valve 40 at the secondary inlet may be gradually closed to adjust the flow rate of the water to be treated at the primary inlet to the predetermined value.

[0055] If the flow rate of the water to be treated at the primary inlet is higher than a predetermined value, the output value of the inverter 38 of the pump 36 may be lowered to adjust the flow rate of the water to be treated at the primary inlet to the predetermined value. Alternatively, the valve 40 at the secondary inlet may be gradually opened to adjust the flow rate of the water to be treated at the primary inlet to the predetermined value.

[0056] In the water treatment devices 3 and 4, the inverter 38 and the valve 40 may be adjusted automatically or manually.

[0057] The predetermined value of the flow rate of the water to be treated at the primary inlet may be determined based on, for example, the flow rate range, recovery rate, amount of water to be treated, salt concentration of the water to be treated, etc., determined by the membrane manufacturer, etc. The recovery rate (%) can be calculated, for example, as [(FI3-FI2) / (FI1+FI3-FI2)]×100.

[0058] In the water treatment method and water treatment device according to this embodiment, a multi-stage semipermeable membrane module may be used. An example of a water treatment device with such a configuration is shown in Figures 5, 6, 7 and 8.

[0059] The water treatment device 5 shown in Figure 5 uses multiple stages of semipermeable membrane modules connected together, each having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane. Water to be treated, including total dissolved solids (TDS), is passed through the first space of the first-stage semipermeable membrane module, and the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water. This concentrated water is then further purified using subsequent semipermeable membrane modules to obtain concentrated water. At the same time, a portion of the water to be treated or at least a portion of the concentrated water is passed through the second space of each semipermeable membrane module to obtain dilution water. The system includes, for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c as semipermeable membrane treatment means. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water treatment device 5 may include a dilution water tank 44a that stores dilution water from the first-stage membrane module 10a, a dilution water tank 44b that stores dilution water from the second-stage membrane module 10b, and a dilution water tank 44c that stores dilution water from the third-stage membrane module 10c. The water treatment device 5 is an apparatus that supplies the water to be treated to the first space and the second space of the first-stage membrane module, and sequentially supplies the concentrated water thereof to the first space and the second space of the membrane module of the next stage to perform a concentration treatment.

[0060] In the water treatment device 5 of Figure 5, a pipe 46 is connected to the inlet of the first space of the first-stage membrane module 10a via a pump 36. A pipe 54 branching from the pipe 46 is connected to the inlet of the second space of the membrane module 10a via a valve 40a. The outlet of the second space of the first-stage membrane module 10a is connected to the inlet of the dilution water tank 44a via a pipe 56. The outlet of the first space of the first-stage membrane module 10a is connected to the inlet of the first space of the second-stage membrane module 10b via a pipe 48. A pipe 58 branching from the pipe 48 is connected to the inlet of the second space of the second-stage membrane module 10b via a valve 40b. The outlet of the second space of the second-stage membrane module 10b is connected to the inlet of the dilution water tank 44b via a pipe 60. The outlet of the first space of the second-stage membrane module 10b is connected to the inlet of the first space of the third-stage membrane module 10c via a pipe 50. A pipe 62 branching from the pipe 50 is connected to the inlet of the second space of the third-stage membrane module 10c via a valve 40c. The second space outlet of the third-stage membrane module 10c and the inlet of the dilution water tank 44c are connected by a pipe 64. A pipe 52 is connected to the first space outlet of the third-stage membrane module 10c.

[0061] A first space outlet flow rate measuring device 18 is installed in the pipe 52 as a final-stage first space outlet flow rate measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the final-stage membrane module 10c. Second space inlet flow rate measuring devices 20a, 20b, and 20c are installed in the pipes 54, 58, and 62, respectively, as second space inlet flow rate measuring means for measuring the flow rate (FI2, FI4, FI6) of the water to be treated or concentrated water at the second space inlet of the membrane modules 10a, 10b, and 10c of each stage. Second space outlet flow rate measuring devices 22a, 22b, and 22c are installed in the pipes 56, 60, and 64, respectively, as second space outlet flow rate measuring means for measuring the flow rate (FI3, FI5, FI7) of dilution water at the second space outlet of the membrane modules 10a, 10b, and 10c of each stage.

[0062] The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to an input drive frequency, and sucks in the water to be treated and discharges it to the first-stage membrane module 10a. The pump 36 is equipped with, for example, an inverter 38 that outputs a drive frequency corresponding to an input command signal to the pump 36. The valves 40a, 40b, and 40c are, for example, proportional control valves that adjust their openings based on the measured values ​​of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring devices 20a, 20b, and 20c, and the second space outlet flow rate measuring devices 22a, 22b, and 22c.

[0063] The water treatment device 5 may include a control device 42 as control means for controlling the flow rate of the water to be treated or the concentrate at the inlet of the first space of each stage to a predetermined value based on the calculated flow rate of the water to be treated or the concentrate at the inlet of the first space of each stage. The control device 42 may be electrically connected to each of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring devices 20a, 20b, and 20c, the second space outlet flow rate measuring devices 22a, 22b, and 22c, the inverter 38, and the valves 40a, 40b, and 40c. The control device 42 is composed of a microcomputer and electronic circuits, which include, for example, a computing means such as a CPU that executes programs and storage means such as ROM and RAM that store programs and calculation results, and has the function of controlling the flow rate of the pump 36 and the opening and closing degrees of the valves 40a, 40b, and 40c.

[0064] The water treatment device 5 uses a multistage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, supplies water to be treated to the first space and the second space of a first-stage membrane module, sequentially supplies the resulting concentrated water to the first space and the second space of the membrane module of the next stage, and concentrates the water by pressurizing the first space 14 of each stage, causing the water contained in the first space 14 to permeate through the semipermeable membrane 12 into the second space 16. That is, in the water treatment device 5, the water to be treated is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 of the next stage.

[0065] Specifically, in the water treatment device 5, the water to be treated, which contains total dissolved solids (TDS), is pumped by the pump 36 through the pipe 46 to the first space 14a of the first-stage membrane module 10a, and the water to be treated branched from the pipe 46 is pumped through the pipe 54 to the second space 16a of the first-stage membrane module 10a. In the first-stage membrane module 10a, the first space 14a is pressurized, causing the water contained in the first space 14a to permeate through the semipermeable membrane 12a into the second space 16a (concentration step (first stage)), and dilution water is obtained in the second space 16a (dilution step (first stage)). The dilution water obtained in the second space 16a of the first-stage membrane module 10a is stored in the dilution water tank 44a as needed through the pipe 56 and then discharged outside the system.

[0066] The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is sent through piping 48 to the first space 14b of the second-stage membrane module 10b, and the concentrated water branched from piping 48 is sent through piping 58 to the second space 16b of the second-stage membrane module 10b. In the second-stage membrane module 10b, the first space 14b is pressurized, causing the water contained in the first space 14b to permeate through the semipermeable membrane 12b into the second space 16b (concentration step (second stage)), and dilution water is obtained in the second space 16b (dilution step (second stage)). The dilution water obtained in the second space 16b of the second-stage membrane module 10b is stored in the dilution water tank 44b as needed through piping 60 and then discharged outside the system.

[0067] The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent through piping 50 to the first space 14c of the third-stage membrane module 10c, and the concentrated water branched from piping 50 is sent through piping 62 to the second space 16c of the third-stage membrane module 10c. In the third-stage membrane module 10c, the first space 14c is pressurized, causing the water contained in the first space 14c to permeate through the semipermeable membrane 12c into the second space 16c (concentration step (third stage)), and dilution water is obtained in the second space 16c (dilution step (third stage)). The dilution water obtained in the second space 16c of the third-stage membrane module 10c is stored in the dilution water tank 44c as needed through piping 64 and then discharged outside the system.

[0068] Here, the pump 36, pipes 46, 48, 50, 54, 58, 62, etc. function as supply means for supplying the water to be treated or concentrated water to the first spaces 14a, 14b, 14c and second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage.

[0069] The dilution water obtained in the second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage may be discharged outside the system, or may be sent to and stored in dilution water tanks 44a, 44b, 44c as needed, and then discharged outside the system. At least a portion of the dilution water may be mixed with the water to be treated in the first-stage membrane module 10a. At least a portion of the dilution water may be further sent to a reverse osmosis membrane treatment device, where it may undergo reverse osmosis membrane treatment (reverse osmosis membrane treatment step). The RO permeate obtained by the reverse osmosis membrane treatment is discharged outside the system. The RO concentrate obtained by the reverse osmosis membrane treatment may be mixed with the water to be treated in the first-stage membrane module 10a.

[0070] In this way, treated water containing dissolved solid components, etc., which is the target of treatment, is converted into treated water (final stage concentrated water) in which substances such as dissolved solid components are concentrated, and diluted water (diluted water of each stage), thereby reducing the volume of the treated water.

[0071] Here, for example, the first space outlet flow rate measuring device 18 measures the flow rate (FI1) of concentrated water at the first space outlet of the final stage membrane module 10c (final stage first space outlet flow rate measuring process), the second space inlet flow rate measuring devices 20a, 20b, 20c measure the flow rates (FI2, FI4, FI6) of the treated water or concentrated water at the second space inlet of the membrane modules 10a, 10b, 10c of each stage (second space inlet flow rate measuring process), and the second space outlet flow rate measuring devices 22a, 22b, 22c measure the flow rates (FI3, FI5, FI7) of dilution water at the second space outlet of the membrane modules 10a, 10b, 10c of each stage (second space outlet flow rate measuring process). Then, for example, based on the flow rate of the water to be treated or the concentrated water at the first space inlet of each stage calculated from the flow rates (FI1, FI2, FI3, FI4, FI5, FI6, FI7) measured in the final-stage first space outlet flow rate measuring step, second space inlet flow rate measuring step, and second space outlet flow rate measuring step, the flow rate of the water to be treated or the concentrated water at the first space inlet of each stage is controlled to a predetermined value (control step). For example, the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a is calculated as FI1 + (FI7 - FI6) + (FI5 - FI4) + (FI3 - FI2), the flow rate of the concentrated water at the first space inlet of the second-stage membrane module 10b is calculated as FI1 + (FI7 - FI6) + (FI5 - FI4), and the flow rate of the concentrated water at the first space inlet of the third-stage membrane module 10c is calculated as FI1 + (FI7 - FI6).

[0072] For example, the control device 42 calculates the flow rate of the water to be treated at the inlet of the first space of the first-stage membrane module 10a = FI1 + (FI7 - FI6) + (FI5 - FI4) + (FI3 - FI2), and the flow rate of the concentrated water at the inlet of the first space of the second-stage membrane module 10b = FI1 + (FI5 - FI6) + (FI5 - FI4) + (FI3 - FI2), which are calculated from the flow rates (FI1, FI2, FI3, FI4, FI5, FI6, FI7) measured by the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring devices 20a, 20b, 20c, and the second space outlet flow rate measuring devices 22a, 22b, 22c. Based on the flow rate of the concentrated water at the inlet of the first space of the third-stage membrane module 10c = FI1 + (FI7 - FI6), an arbitrary calculation formula can be used to calculate the drive frequency so that the flow rate of the water to be treated or the concentrated water at the inlet of the first space of each stage becomes a predetermined value, and a command signal corresponding to this calculation value can be output to the inverter 38 to control the pump 36, thereby controlling the opening and closing of the valves 40a, 40b, and 40c, thereby controlling the flow rate of the water to be treated or the concentrated water at the inlet of the first space of each stage.

[0073] In the water treatment method and water treatment device 5 according to this embodiment, a first space outlet flow measuring device 18, second space inlet flow measuring devices 20a, 20b, 20c, and second space outlet flow measuring devices 22a, 22b, 22c are installed at the primary side outlet of the final-stage membrane module 10c and the secondary side inlets and secondary side outlets of the membrane modules 10a, 10b, 10c of each stage, respectively. No flow measuring devices are installed at the primary side inlets of the membrane modules 10a, 10b, 10c of each stage, and the flow rates of the water to be treated or concentrated water at the primary side inlets of each stage are calculated from the values ​​of the flow measuring devices at the primary side outlet of the final stage, the secondary side inlets of each stage, and the secondary side outlets of each stage. That is, in the water treatment device 5, flow measuring devices are installed only at the primary side outlet of the final-stage membrane module 10 and the secondary side inlets and secondary side outlets of the membrane modules 10 of each stage. The flow rate of the water to be treated or the concentrate water at the primary inlet of each stage is then adjusted based on the calculated flow rate of the water to be treated or the concentrate water at the primary inlet of each stage. This allows the number of flow rate measuring devices to be significantly reduced, enabling stable treatment at low cost. Furthermore, by controlling the flow rate of the water to be treated or the concentrate water at the primary inlet of each stage, even more stable treatment can be achieved.

[0074] The water treatment device 6 shown in Figure 6 uses semipermeable membrane modules connected in multiple stages, each having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane. Water to be treated, including total dissolved solids (TDS), is passed through the first space of the first-stage semipermeable membrane module, and the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water. This concentrated water is then further purified using subsequent semipermeable membrane modules to obtain concentrated water. At least a portion of the concentrated water is passed through the second space of each semipermeable membrane module to obtain dilution water. The system includes, for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c as semipermeable membrane treatment means. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water treatment device 6 may include a dilution water tank 44a that stores dilution water from the first-stage membrane module 10a, a dilution water tank 44b that stores dilution water from the second-stage membrane module 10b, and a dilution water tank 44c that stores dilution water from the third-stage membrane module 10c. The water treatment device 6 is an apparatus that supplies the water to be treated to the first space of the first-stage membrane module, and sequentially supplies the concentrated water thereof to the first space of the next-stage membrane module and its own second space to perform a concentration treatment.

[0075] In the water treatment device 6 of Figure 6, a pipe 46 is connected to the first space inlet of the first-stage membrane module 10a via a pump 36. The first space outlet of the first-stage membrane module 10a and the first space inlet of the second-stage membrane module 10b are connected by a pipe 48. A pipe 66 branching from the pipe 48 is connected to the second space inlet of the membrane module 10a via a valve 40a. The second space outlet of the first-stage membrane module 10a and the inlet of the dilution water tank 44a are connected by the pipe 68. The first space outlet of the second-stage membrane module 10b and the first space inlet of the third-stage membrane module 10c are connected by a pipe 50. A pipe 70 branching from the pipe 50 is connected to the second space inlet of the membrane module 10b via a valve 40b. The second space outlet of the second-stage membrane module 10b and the inlet of the dilution water tank 44b are connected by a pipe 72. A pipe 52 is connected to the first space outlet of the third-stage membrane module 10c. A pipe 74 branching from the pipe 52 is connected to the inlet of the second space of the membrane module 10c via a valve 40c. The outlet of the second space of the third-stage membrane module 10c and the inlet of the dilution water tank 44c are connected by a pipe 76.

[0076] A first space outlet flow rate measuring device 18 is installed downstream of the branch point of the pipe 52 to the pipe 74 as a final-stage first space outlet flow rate measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the final-stage membrane module 10c. Second space inlet flow rate measuring devices 20a, 20b, and 20c are installed in the pipes 66, 70, and 74, respectively, as second space inlet flow rate measuring means for measuring the flow rate (FI2, FI4, FI6) of concentrated water at the second space inlet of the membrane modules 10a, 10b, and 10c of each stage. Second space outlet flow rate measuring devices 22a, 22b, and 22c are installed in the pipes 68, 72, and 76, respectively, as second space outlet flow rate measuring means for measuring the flow rate (FI3, FI5, FI7) of dilution water at the second space outlet of the membrane modules 10a, 10b, and 10c of each stage.

[0077] The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to an input drive frequency, and sucks in the water to be treated and discharges it to the first-stage membrane module 10a. The pump 36 is equipped with, for example, an inverter 38 that outputs a drive frequency corresponding to an input command signal to the pump 36. The valves 40a, 40b, and 40c are, for example, proportional control valves that adjust their openings based on the measured values ​​of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring devices 20a, 20b, and 20c, and the second space outlet flow rate measuring devices 22a, 22b, and 22c.

[0078] The water treatment device 6 may include a control device 42 as control means for controlling the flow rate of the concentrated water at the inlet of the first space of each stage to a predetermined value based on the calculated flow rate of the water to be treated or the concentrated water at the inlet of the first space of each stage. The control device 42 may be electrically connected to each of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring devices 20a, 20b, and 20c, the second space outlet flow rate measuring devices 22a, 22b, and 22c, the inverter 38, and the valves 40a, 40b, and 40c. The control device 42 is composed of a microcomputer and electronic circuits, which include, for example, a computing means such as a CPU that executes programs and storage means such as ROM and RAM that store programs and calculation results, and has the function of controlling the flow rate of the pump 36 and the opening and closing degrees of the valves 40a, 40b, and 40c.

[0079] The water treatment device 6 uses a multistage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, supplies water to be treated to the first space of a first-stage membrane module, and sequentially supplies the resulting concentrated water to the first space of the membrane module of the next stage and its own second space, and by pressurizing the first space 14 of each stage, the water contained in the first space 14 is permeated through the semipermeable membrane 12 into the second space 16, thereby concentrating the water. That is, in the water treatment device 6, the water to be treated is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 of the next stage.

[0080] Specifically, in the water treatment device 6, water to be treated containing total dissolved solids (TDS) is pumped by a pump 36 through a pipe 46 to the first space 14a of the first-stage membrane module 10a. In the first-stage membrane module 10a, the first space 14a is pressurized, causing the water contained in the first space 14a to permeate through the semipermeable membrane 12a into the second space 16a (concentration step (first stage)), and dilution water is obtained in the second space 16a (dilution step (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is pumped through a pipe 48 to the first space 14b of the second-stage membrane module 10b, and the concentrated water branched from the pipe 48 is pumped through a pipe 66 to the second space 16a of the first-stage membrane module 10a. The dilution water obtained in the second space 16a of the first-stage membrane module 10a is stored in a dilution water tank 44a as needed through the pipe 68 and then discharged to the outside of the system.

[0081] In the second-stage membrane module 10b, the first space 14b is pressurized, causing the water contained in the first space 14b to permeate through the semipermeable membrane 12b into the second space 16b (concentration step (second stage)), and dilution water is obtained in the second space 16b (dilution step (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent through a pipe 50 to the first space 14c of the third-stage membrane module 10c, and the concentrated water branched off from the pipe 50 is sent through a pipe 70 to the second space 16b of the second-stage membrane module 10b. The dilution water obtained in the second space 16b of the second-stage membrane module 10b is stored in a dilution water tank 44b as needed through a pipe 72 and then discharged outside the system.

[0082] In the third-stage membrane module 10c, the first space 14c is pressurized, causing the water contained in the first space 14c to permeate through the semipermeable membrane 12c into the second space 16c (concentration step (third stage)), and dilution water is obtained in the second space 16c (dilution step (third stage)). The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through piping 52, and the concentrated water branched off from piping 52 is sent to the second space 16c of the third-stage membrane module 10c through piping 74. The dilution water obtained in the second space 16c of the third-stage membrane module 10c is stored in the dilution water tank 44c as needed through piping 76 and then discharged outside the system.

[0083] Here, the pump 36, pipes 46, 48, 50, 66, 70, 74, etc. function as supply means for supplying the water to be treated or the concentrated water to the first spaces 14a, 14b, 14c and second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage.

[0084] The dilution water obtained in the second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage may be discharged outside the system, or may be sent to and stored in dilution water tanks 44a, 44b, 44c as needed, and then discharged outside the system. At least a portion of the dilution water may be mixed with the water to be treated in the first-stage membrane module 10a. At least a portion of the dilution water may be further sent to a reverse osmosis membrane treatment device, where it may undergo reverse osmosis membrane treatment (reverse osmosis membrane treatment step). The RO permeate obtained by the reverse osmosis membrane treatment is discharged outside the system. The RO concentrate obtained by the reverse osmosis membrane treatment may be mixed with the water to be treated in the first-stage membrane module 10a.

[0085] In this way, treated water containing dissolved solid components, etc., which is the target of treatment, is converted into treated water (final stage concentrated water) in which substances such as dissolved solid components are concentrated, and diluted water (diluted water of each stage), thereby reducing the volume of the treated water.

[0086] Here, for example, the first space outlet flow rate measuring device 18 measures the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10c in the final stage (final stage first space outlet flow rate measuring process), the second space inlet flow rate measuring devices 20a, 20b, 20c measure the flow rates (FI2, FI4, FI6) of concentrated water at the second space inlet of the membrane modules 10a, 10b, 10c in each stage (second space inlet flow rate measuring process), and the second space outlet flow rate measuring devices 22a, 22b, 22c measure the flow rates (FI3, FI5, FI7) of dilution water at the second space outlet of the membrane modules 10a, 10b, 10c in each stage (second space outlet flow rate measuring process). Then, for example, based on the flow rate of the concentrated water at the first space inlet of each stage calculated from the flow rates (FI1, FI2, FI3, FI4, FI5, FI6, FI7) measured in the final-stage first space outlet flow rate measuring step, second space inlet flow rate measuring step, and second space outlet flow rate measuring step, the flow rate of the concentrated water at the first space inlet of each stage is controlled to a predetermined value (control step). For example, the flow rate of the concentrated water at the first space inlet of the first-stage membrane module 10a is calculated as FI1 + (FI7 - FI6) + (FI5 - FI4) + (FI3 - FI2), the flow rate of the concentrated water at the first space inlet of the second-stage membrane module 10b is calculated as FI1 + (FI7 - FI6) + (FI5 - FI4), and the flow rate of the concentrated water at the first space inlet of the third-stage membrane module 10c is calculated as FI1 + (FI7 - FI6).

[0087] For example, the control device 42 calculates the flow rate of the water to be treated at the inlet of the first space of the first-stage membrane module 10a = FI1 + (FI7 - FI6) + (FI5 - FI4) + (FI3 - FI2), and the flow rate of the concentrated water at the inlet of the first space of the second-stage membrane module 10b = FI1 + (FI5 - FI6) + (FI5 - FI4) + (FI3 - FI2), which are calculated from the flow rates (FI1, FI2, FI3, FI4, FI5, FI6, FI7) measured by the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring devices 20a, 20b, 20c, and the second space outlet flow rate measuring devices 22a, 22b, 22c. Based on the flow rate of the concentrated water at the inlet of the first space of the third-stage membrane module 10c = FI1 + (FI7 - FI6), an arbitrary calculation formula can be used to calculate the drive frequency so that the flow rate of the water to be treated or the concentrated water at the inlet of the first space of each stage becomes a predetermined value, and a command signal corresponding to this calculation value can be output to the inverter 38 to control the pump 36, thereby controlling the opening and closing of the valves 40a, 40b, and 40c, thereby controlling the flow rate of the water to be treated or the concentrated water at the inlet of the first space of each stage.

[0088] In the water treatment method and water treatment device 6 according to this embodiment, a first space outlet flow measuring device 18, second space inlet flow measuring devices 20a, 20b, 20c, and second space outlet flow measuring devices 22a, 22b, 22c are installed at the primary side outlet of the final-stage membrane module 10c and the secondary side inlets and secondary side outlets of the membrane modules 10a, 10b, 10c of each stage, respectively. No flow measuring devices are installed at the primary side inlets of the membrane modules 10a, 10b, 10c of each stage, and the flow rates of the water to be treated or concentrated water at the primary side inlets of each stage are calculated from the values ​​of the flow measuring devices at the primary side outlet of the final stage, the secondary side inlets of each stage, and the secondary side outlets of each stage. That is, in the water treatment device 6, flow measuring devices are installed only at the primary side outlet of the final-stage membrane module 10 and the secondary side inlets and secondary side outlets of the membrane modules 10 of each stage. The flow rate of the water to be treated or the concentrate water at the primary inlet of each stage is then adjusted based on the calculated flow rate of the water to be treated or the concentrate water at the primary inlet of each stage. This allows the number of flow rate measuring devices to be significantly reduced, enabling stable treatment at low cost. Furthermore, by controlling the flow rate of the water to be treated or the concentrate water at the primary inlet of each stage, even more stable treatment can be achieved.

[0089] When using multistage membrane modules, water may be passed through the second spaces in series. An example of a water treatment device with such a configuration is shown in FIG. 7. The water treatment device 7 shown in FIG. 7 uses multistage semipermeable membrane modules connected in multiple stages, each having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane. Water to be treated, including total dissolved solids (TDS), is passed through the first space of the first-stage semipermeable membrane module, and the first space is pressurized to allow the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water. This concentrated water is then further obtained using subsequent semipermeable membrane modules to obtain concentrated water. At least a portion of the concentrated water is passed through the second space of each semipermeable membrane module to obtain dilution water. The semipermeable membrane treatment means includes, for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water treatment device 7 may also include a dilution water tank 44 for storing dilution water from the first-stage membrane module 10a. The water treatment device 7 is a device that supplies water to be treated to the first space of a first-stage membrane module, and then sequentially supplies the concentrated water to the first space of the next-stage membrane module to perform concentration treatment.

[0090] In the water treatment device 7 of Figure 7, a pipe 46 is connected to the first space inlet of the first-stage membrane module 10a via a pump 36. A pipe 48 connects the first space outlet of the first-stage membrane module 10a to the first space inlet of the second-stage membrane module 10b. A pipe 50 connects the first space outlet of the second-stage membrane module 10b to the first space inlet of the third-stage membrane module 10c. A pipe 52 is connected to the first space outlet of the third-stage membrane module 10c. A pipe 74 branching from the pipe 52 is connected to the second space inlet of the membrane module 10c via a valve 40. A pipe 78 connects the second space outlet of the third-stage membrane module 10c to the second space inlet of the second-stage membrane module 10b. A pipe 80 connects the second space outlet of the second-stage membrane module 10b to the second space inlet of the first-stage membrane module 10a. A pipe 68 connects the second space outlet of the first-stage membrane module 10a to the inlet of the dilution water tank 44.

[0091] A first space outlet flow rate measuring device 18 is installed downstream of the branch point of the piping 52 to the piping 74 as a first space outlet flow rate measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the third-stage membrane module 10c, which is the final stage. A second space inlet flow rate measuring device 20 is installed in the piping 74 as a second space inlet flow rate measuring means for measuring the flow rate (FI2) of concentrated water at the second space inlet of the third-stage membrane module 10c, which is the most upstream stage on the second space 16 side. A second space outlet flow rate measuring device 22 is installed in the piping 68 as a second space outlet flow rate measuring means for measuring the flow rate (FI3) of dilution water at the second space outlet of the first-stage membrane module 10a, which is the most downstream stage on the second space 16 side.

[0092] The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to an input drive frequency, and sucks in the water to be treated and discharges it to the first-stage membrane module 10a. The pump 36 is equipped with, for example, an inverter 38 that outputs a drive frequency corresponding to an input command signal to the pump 36. The valve 40 is, for example, a proportional control valve that adjusts its opening based on the measured values ​​of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22.

[0093] The water treatment device 7 may include a control device 42 as control means for controlling the flow rate of the water to be treated at the inlet of the first space of the first-stage membrane module 10a to a predetermined value based on the calculated flow rate of the water to be treated at the inlet of the first space of the first-stage membrane module 10a. The control device 42 may be electrically connected to each of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, the second space outlet flow rate measuring device 22, the inverter 38, and the valve 40. The control device 42 is composed of, for example, a microcomputer and electronic circuits, which are composed of a calculation means such as a CPU that calculates a program and storage means such as a ROM and RAM that store the program and calculation results, and has the function of controlling the flow rate of the pump 36, the opening / closing degree of the valve 40, etc.

[0094] The water treatment device 7 uses a multistage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, supplies water to be treated to the first space of the first-stage membrane module, passes the resulting concentrated water in series to the first spaces of the membrane modules of the succeeding stages, supplies at least a portion of the concentrated water of the final-stage membrane module to its own second space, passes the resulting diluted water in series to the second spaces 16 of the membrane module of the preceding stage, and concentrates the water by pressurizing the first spaces 14 of each stage, causing the water contained in the first spaces 14 to permeate into the second space 16 through the semipermeable membrane 12. That is, in the water treatment device 7, the water to be treated is concentrated using the semipermeable membrane 12, and the concentrated water is further concentrated using the semipermeable membrane 12 of the next stage.

[0095] Specifically, in the water treatment device 7, water to be treated containing total dissolved solids (TDS) is pumped by a pump 36 through a pipe 46 to the first space 14a of the first-stage membrane module 10a. Meanwhile, dilution water, which has been pumped via the second space 16c of the third-stage membrane module 10c (described later) and the second space 16b of the second-stage membrane module 10b, is pumped through a pipe 80 to the second space 16a of the first-stage membrane module 10a. In the first-stage membrane module 10a, the first space 14a is pressurized, causing the water contained in the first space 14a to permeate into the second space 16a through the semipermeable membrane 12a (concentration step (first stage)), and dilution water is obtained in the second space 16a (dilution step (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is pumped through a pipe 48 to the first space 14b of the second-stage membrane module 10b. The dilution water obtained in the second space 16a of the first-stage membrane module 10a is passed through a pipe 68 and stored in the dilution water tank 44 as needed, and then discharged outside the system.

[0096] In the second-stage membrane module 10b, dilution water sent via the second space 16c of the third-stage membrane module 10c (described later) is sent to the second space 16b of the second-stage membrane module 10b through the piping 78. The first space 14b is pressurized, and the water contained in the first space 14b permeates into the second space 16b through the semipermeable membrane 12b (concentration step (second stage)), and dilution water is obtained in the second space 16b (dilution step (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent to the first space 14c of the third-stage membrane module 10c through the piping 50. The dilution water obtained in the second space 16b of the second-stage membrane module 10b is sent to the second space 16a of the first-stage membrane module 10a through the piping 80.

[0097] In the third-stage membrane module 10c, the concentrated water obtained in the first space 14c of the third-stage membrane module 10c is sent to the second space 16c through the pipes 52 and 74 as described below. The first space 14c is pressurized, and the water contained in the first space 14c is permeated through the semipermeable membrane 12c into the second space 16c (concentration step (third stage)), and dilution water is obtained in the second space 16c (dilution step (third stage)). The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through the pipe 52, and the concentrated water branched off from the pipe 52 is sent to the second space 16c of the third-stage membrane module 10c through the pipe 74. The dilution water obtained in the second space 16c of the third-stage membrane module 10c is sent to the second space 16b of the second-stage membrane module 10b through the pipe 78.

[0098] Here, the pump 36, pipes 46, 48, 50, 52, 74, 78, 80, etc. function as supply means for supplying the water to be treated or the concentrated water to the first spaces 14a, 14b, 14c and second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage.

[0099] The dilution water obtained in the second space 16a of the membrane module 10a may be discharged outside the system, or may be sent to the dilution water tank 44, stored therein, and then discharged outside the system, as necessary. At least a portion of the dilution water may be mixed with the water to be treated in the first-stage membrane module 10a. At least a portion of the dilution water may be further sent to a reverse osmosis membrane treatment device, where it may undergo reverse osmosis membrane treatment (reverse osmosis membrane treatment step). The RO permeate obtained by the reverse osmosis membrane treatment is discharged outside the system. The RO concentrate obtained by the reverse osmosis membrane treatment may be mixed with the water to be treated in the first-stage membrane module 10a.

[0100] In this way, treated water containing dissolved solid components, etc., which is the target of treatment, is converted into treated water (final stage concentrated water) in which substances such as dissolved solid components are concentrated, and diluted water (diluted water of each stage), thereby reducing the volume of the treated water.

[0101] Here, for example, the first space outlet flow rate measuring device 18 measures the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10c in the final stage (final stage first space outlet flow rate measuring step), the second space inlet flow rate measuring device 20 measures the flow rate (FI2) of concentrated water at the second space inlet of the membrane module 10c, which is the most upstream stage on the second space 16 side (second space inlet flow rate measuring step), and the second space outlet flow rate measuring device 22 measures the flow rate (FI3) of dilution water at the second space outlet of the membrane module 10a, which is the most downstream stage on the second space 16 side (second space outlet flow rate measuring step). Then, for example, the flow rate of treated water at the first space inlet of the first stage is controlled to a predetermined value based on the flow rate of treated water at the first space inlet of the first stage = FI1 + (FI3 - FI2), which is calculated from the flow rates (FI1, FI2, FI3) measured in the final stage first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step (control step).

[0102] For example, the control device 42 calculates the drive frequency using an arbitrary arithmetic formula based on the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a = FI1 + (FI3 - FI2), which is obtained from the respective flow rates (FI1, FI2, FI3) measured by the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22, so that the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a becomes a predetermined value, outputs a command signal corresponding to this calculated value to the inverter 38 to control the pump 36, and controls the opening / closing degree of the valve 40, thereby controlling the flow rate of the water to be treated at the first space inlet.

[0103] In the water treatment method and water treatment device 7 according to this embodiment, a first space outlet flow rate measuring device 18, a second space inlet flow rate measuring device 20, and a second space outlet flow rate measuring device 22 are installed at the primary side outlet of the final stage membrane module 10c, the secondary side inlet of the membrane module 10c which is the most upstream stage on the second space 16 side, and the secondary side outlet of the membrane module 10a which is the most downstream stage on the second space 16 side, respectively. No flow rate measuring devices are installed at the primary side inlets of the membrane modules 10a, 10b, 10c of each stage, or the secondary side inlets of the first-stage membrane module 10a and the second-stage membrane module 10b, and the flow rate of the water to be treated at the primary side inlet of the first stage is calculated from the values ​​of the flow rate measuring devices at the primary side outlet of the final stage, the secondary side inlet of the most upstream stage on the second space 16 side, and the secondary side outlet of the most downstream stage on the second space 16 side. That is, in the water treatment device 7, flow rate measuring devices are installed only at the primary-side outlet of the membrane module 10 in the final stage, the secondary-side inlet of the membrane module 10 in the most upstream stage on the side of the second space 16, and the secondary-side outlet of the membrane module 10 in the most downstream stage on the side of the second space 16. Then, the flow rate of the water to be treated at the primary-side inlet of the first stage is adjusted from the calculated flow rate of the water to be treated at the primary-side inlet of the first stage. This allows the number of flow rate measuring devices to be used to be significantly reduced, enabling stable treatment at low cost.

[0104] In the water treatment device 7 of FIG. 7, if a water supply pressure of, for example, 1 MPa or more is required in the second space, or if a relay tank for concentrated water is required, a pump may be used to supply water to the second space. An example of a water treatment device with such a configuration is shown in FIG. 8. The water treatment device 8 shown in FIG. 8 uses multiple-stage semipermeable membrane modules connected together, each having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane. Water to be treated, including total dissolved solids (TDS) and other substances, is passed through the first space of the first-stage semipermeable membrane module, pressurizing the first space to permeate the water contained in the water through the semipermeable membrane, thereby obtaining concentrated water. This concentrated water is then further obtained using subsequent semipermeable membrane modules, and at least a portion of the concentrated water is passed through the second space of each semipermeable membrane module to obtain dilution water. The device includes, for example, a first-stage membrane module 10a, a second-stage membrane module 10b, and a third-stage membrane module 10c as semipermeable membrane treatment means. Each membrane module has a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water treatment device 8 may include a concentrated water tank 82 that stores concentrated water from the third-stage membrane module 10c, and a dilution water tank 44 that stores diluted water from the first-stage membrane module 10a. The water treatment device 8 is a device that supplies the water to be treated to the first space of the first-stage membrane module, and sequentially supplies the concentrated water to the first space of the next-stage membrane module to perform concentration treatment.

[0105] In the water treatment device 8 of Figure 8, a pipe 46 is connected to the first space inlet of the first-stage membrane module 10a via a pump 36. A pipe 48 connects the first space outlet of the first-stage membrane module 10a to the first space inlet of the second-stage membrane module 10b. A pipe 50 connects the first space outlet of the second-stage membrane module 10b to the first space inlet of the third-stage membrane module 10c. A pipe 52 is connected to the first space outlet of the third-stage membrane module 10c. A pipe 88 branching from the pipe 52 is connected to the inlet of the concentrated water tank 82. The outlet of the concentrated water tank 82 is connected to the second space inlet of the membrane module 10c via a pipe 90 via a pump 84. A pipe 78 connects the second space outlet of the second-stage membrane module 10b to the second space inlet of the first-stage membrane module 10a. A pipe 80 connects the second space outlet of the second-stage membrane module 10b to the second space inlet of the first-stage membrane module 10a. The outlet of the second space of the first-stage membrane module 10 a is connected to the inlet of the dilution water tank 44 by a pipe 68 .

[0106] A first space outlet flow rate measuring device 18 is installed downstream of the branch point of the piping 52 to the piping 88 as a first space outlet flow rate measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the third-stage membrane module 10c, which is the final stage. A second space inlet flow rate measuring device 20 is installed upstream of the pump 84 in the piping 90 as a second space inlet flow rate measuring means for measuring the flow rate (FI2) of concentrated water at the second space inlet of the third-stage membrane module 10c, which is the most upstream stage on the second space 16 side. A second space outlet flow rate measuring device 22 is installed in the piping 68 as a second space outlet flow rate measuring means for measuring the flow rate (FI3) of dilution water at the second space outlet of the first-stage membrane module 10a, which is the most downstream stage on the second space 16 side.

[0107] The pump 36 is a pressure pump that is driven, for example, at a rotational speed corresponding to an input drive frequency, and sucks in water to be treated and discharges it to the first-stage membrane module 10a. The pump 36 is equipped with, for example, an inverter 38 that outputs to the pump 36 a drive frequency that corresponds to an input command signal. The pump 84 is a pressure pump that is driven, for example, at a rotational speed corresponding to the input drive frequency, and sucks in concentrated water and discharges it to the third-stage membrane module 10c. The pump 84 is equipped with, for example, an inverter 86 that outputs to the pump 84 a drive frequency that corresponds to the input command signal.

[0108] The water treatment device 8 may include a control device 42 as control means for controlling the flow rate of the water to be treated at the inlet of the first space of the first-stage membrane module 10a to a predetermined value based on the calculated flow rate of the water to be treated at the inlet of the first space of the first-stage membrane module 10a. The control device 42 may be electrically connected to each of the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, the second space outlet flow rate measuring device 22, the inverter 38, and the inverter 86. The control device 42 is composed of, for example, a microcomputer and electronic circuits, which are composed of a calculation means, such as a CPU, that executes programs, and storage means, such as a ROM and RAM, that store programs and calculation results, and has the function of controlling the flow rate of the pump 36, the flow rate of the pump 84, etc.

[0109] The water treatment device 8 uses a multistage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12, supplies water to be treated to the first space of a first-stage membrane module, passes the resulting concentrated water in series to the first spaces of the membrane modules of the succeeding stages, supplies at least a portion of the concentrated water of the final-stage membrane module to its own second space, passes the resulting diluted water in series to the second spaces 16 of the membrane modules of the preceding stages, and concentrates the water by pressurizing the first spaces 14 of each stage, causing the water contained in the first spaces 14 to permeate through the semipermeable membranes 12 into the second spaces 16. That is, in the water treatment device 8, the water to be treated is concentrated using the semipermeable membranes 12, and the concentrated water is further concentrated using the semipermeable membranes 12 of the next stage.

[0110] Specifically, in the water treatment device 8, the water to be treated, which contains total dissolved solids (TDS), is pumped by a pump 36 through a pipe 46 to the first space 14a of the first-stage membrane module 10a. Meanwhile, dilution water, which has been pumped via the second space 16c of the third-stage membrane module 10c (described later) and the second space 16b of the second-stage membrane module 10b, is pumped through a pipe 80 to the second space 16a of the first-stage membrane module 10a. In the first-stage membrane module 10a, the first space 14a is pressurized, and the water contained in the first space 14a is permeated into the second space 16a through the semipermeable membrane 12a (concentration step (first stage)). Dilution water is obtained in the second space 16a (dilution step (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is pumped through a pipe 48 to the first space 14b of the second-stage membrane module 10b. The dilution water obtained in the second space 16a of the first-stage membrane module 10a is passed through a pipe 68 and stored in the dilution water tank 44 as needed, and then discharged outside the system.

[0111] In the second-stage membrane module 10b, dilution water sent via the second space 16c of the third-stage membrane module 10c (described later) is sent to the second space 16b of the second-stage membrane module 10b through the piping 78. The first space 14b is pressurized, and the water contained in the first space 14b permeates into the second space 16b through the semipermeable membrane 12b (concentration step (second stage)), and dilution water is obtained in the second space 16b (dilution step (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent to the first space 14c of the third-stage membrane module 10c through the piping 50. The dilution water obtained in the second space 16b of the second-stage membrane module 10b is sent to the second space 16a of the first-stage membrane module 10a through the piping 80.

[0112] In the third-stage membrane module 10c, concentrated water obtained in the first space 14c of the third-stage membrane module 10c is sent to the second space 16c through pipes 52, 88, a concentrated water tank 82, and pipe 90, as described below. The first space 14c is pressurized, and the water contained in the first space 14c is permeated into the second space 16c through the semipermeable membrane 12c (concentration step (third stage)), and dilution water is obtained in the second space 16c (dilution step (third stage)). The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through pipe 52, and concentrated water branched from pipe 52 is stored in the concentrated water tank 82 through pipe 88 as needed. The concentrated water stored in the concentrated water tank 82 is sent by pump 84 through pipe 90 to the second space 16c of the third-stage membrane module 10c. The dilution water obtained in the second space 16c of the third-stage membrane module 10c is sent through the pipe 78 to the second space 16b of the second-stage membrane module 10b.

[0113] Here, the pumps 36, 84, pipes 46, 48, 50, 52, 88, 90, 78, 80, etc. function as supply means for supplying the water to be treated or concentrated water to the first spaces 14a, 14b, 14c and second spaces 16a, 16b, 16c of the membrane modules 10a, 10b, 10c of each stage.

[0114] The dilution water obtained in the second space 16a of the membrane module 10a may be discharged outside the system, or may be sent to the dilution water tank 44, stored therein, and then discharged outside the system, as necessary. At least a portion of the dilution water may be mixed with the water to be treated in the first-stage membrane module 10a. At least a portion of the dilution water may be further sent to a reverse osmosis membrane treatment device, where it may undergo reverse osmosis membrane treatment (reverse osmosis membrane treatment step). The RO permeate obtained by the reverse osmosis membrane treatment is discharged outside the system. The RO concentrate obtained by the reverse osmosis membrane treatment may be mixed with the water to be treated in the first-stage membrane module 10a.

[0115] In this way, treated water containing dissolved solid components, etc., which is the target of treatment, is converted into treated water (final stage concentrated water) in which substances such as dissolved solid components are concentrated, and diluted water (diluted water of each stage), thereby reducing the volume of the treated water.

[0116] Here, for example, the first space outlet flow rate measuring device 18 measures the flow rate (FI1) of concentrated water at the first space outlet of the membrane module 10c in the final stage (final stage first space outlet flow rate measuring step), the second space inlet flow rate measuring device 20 measures the flow rate (FI2) of concentrated water at the second space inlet of the membrane module 10c, which is the most upstream stage on the second space 16 side (second space inlet flow rate measuring step), and the second space outlet flow rate measuring device 22 measures the flow rate (FI3) of dilution water at the second space outlet of the membrane module 10a, which is the most downstream stage on the second space 16 side (second space outlet flow rate measuring step). Then, for example, the flow rate of treated water at the first space inlet of the first stage is controlled to a predetermined value based on the flow rate of treated water at the first space inlet of the first stage = FI1 + (FI3 - FI2), which is calculated from the flow rates (FI1, FI2, FI3) measured in the final stage first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step (control step).

[0117] For example, the control device 42 calculates a drive frequency using an arbitrary arithmetic formula based on the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a = FI1 + (FI3 - FI2), which is obtained from the respective flow rates (FI1, FI2, FI3) measured by the first space outlet flow rate measuring device 18, the second space inlet flow rate measuring device 20, and the second space outlet flow rate measuring device 22, so that the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a becomes a predetermined value, and outputs a command signal corresponding to this calculated value to the inverter 38 to control the pump 36, and outputs it to the inverter 86 to control the pump 84, thereby controlling the flow rate of the water to be treated at the first space inlet.

[0118] In the water treatment method and water treatment device 8 according to this embodiment, a first space outlet flow rate measuring device 18, a second space inlet flow rate measuring device 20, and a second space outlet flow rate measuring device 22 are installed at the primary side outlet of the final stage membrane module 10c, the secondary side inlet of the membrane module 10c in the most upstream stage on the second space 16 side, and the secondary side outlet of the membrane module 10a in the most downstream stage on the second space 16 side, respectively. No flow rate measuring devices are installed at the primary side inlets of the membrane modules 10a, 10b, 10c in each stage, or the secondary side inlets of the first-stage membrane module 10a and the second-stage membrane module 10b, and the flow rate of the water to be treated at the primary side inlet of the first stage is calculated from the values ​​of the flow rate measuring devices at the primary side outlet of the final stage, the secondary side inlet of the most upstream stage on the second space 16 side, and the secondary side outlet of the most downstream stage on the second space 16 side. That is, in the water treatment device 8, flow rate measuring devices are installed only at the primary-side outlet of the membrane module 10 in the final stage, the secondary-side inlet of the membrane module 10 in the most upstream stage on the side of the second space 16, and the secondary-side outlet of the membrane module 10 in the most downstream stage on the side of the second space 16. Then, the flow rate of the water to be treated at the primary-side inlet of the first stage is adjusted from the calculated flow rate of the water to be treated at the primary-side inlet of the first stage. This allows the number of flow rate measuring devices to be used to be significantly reduced, enabling stable treatment at low cost.

[0119] When using multi-stage membrane modules as in water treatment devices 5, 6, 7, and 8, the number of membrane module stages can be determined based on the target concentration of treated water, etc. For example, if it is desired to obtain treated water with a higher concentration from water to be treated with a lower concentration, the number of membrane module stages can be increased. The water treatment method and water treatment device according to this embodiment can be suitably applied when using multi-stage membrane modules.

[0120] Each stage of the membrane module may be a membrane module unit having a plurality of membrane modules connected in parallel. The number of membrane modules in each membrane module unit may be determined depending on the flow rate of the water to be treated, etc.

[0121] A pipe may be provided for sending the dilution water from the second space 16 of the membrane module of each stage to the second space 16 of the membrane module of the next stage.

[0122] A concentrated water tank and a dilution water tank may be provided in one or more stages of membrane modules, or a concentrated water tank and a dilution water tank may be provided in each stage of membrane module.

[0123] Examples of the semipermeable membrane 12 included in the membrane module include a reverse osmosis membrane (RO membrane), a forward osmosis membrane (FO membrane), and a nanofiltration membrane (NF membrane). The semipermeable membrane is preferably a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane. When a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane is used as the semipermeable membrane, the pressure of the water to be treated in the first space 14 is preferably 0.5 to 10.0 MPa.

[0124] The material constituting the semipermeable membrane 12 is not particularly limited, but examples thereof include cellulose-based resins such as cellulose acetate-based resins, polysulfone-based resins such as polyethersulfone-based resins, polyamide-based resins, etc. The material constituting the semipermeable membrane 12 is preferably a cellulose acetate-based resin.

[0125] The shape of the semipermeable membrane 12 may be a flat membrane, a hollow fiber membrane, a spiral membrane, or the like.

[0126] The pressure at the flow rate measurement points by the first space outlet flow rate measurement device 18, the second space inlet flow rate measurement devices 20, 20a, 20b, 20c, and the second space outlet flow rate measurement devices 22, 22a, 22b, 22c in the first space outlet flow rate measurement step, the second space inlet flow rate measurement step, and the second space outlet flow rate measurement step is preferably 1 MPa or less. The flow rate measurement devices used are not particularly limited as long as they can measure flow rates, but as long as the pressure at the flow rate measurement points is 1 MPa or less, a general-purpose flow meter can be used as the flow rate measurement device, and it is not necessary to use a special device with high pressure resistance or an ultrasonic type.

[0127] The water to be treated is not particularly limited as long as it contains substances such as total dissolved solids (TDS), but examples include industrial wastewater, salt water, seawater, chemical wastewater, and concentrated wastewater after reverse osmosis membrane treatment.

[0128] TDS (dissolved solids) includes, for example, chlorides such as sodium chloride, carbonates such as calcium carbonate and magnesium carbonate, and sulfates such as calcium sulfate and magnesium sulfate. [Explanation of symbols]

[0129] 1,2,3,4,5,6,7,8 Water treatment device, 10 Membrane module, 10a First stage membrane module, 10b Second stage membrane module, 10c Third stage membrane module, 12,12a,12b,12c Semipermeable membrane, 14,14a,14b,14c First space, 16,16a,16b,16c Second space, 18 First space outlet flow rate measuring device, 20,20a,20b,20c Second space inlet flow rate measuring device, 22,22a,22b,22c Second space outlet flow rate measuring device, 24,26,28,30,32,34,46,48,50,52,54,56,58,60,62,64,66,68,70,72,74,76,78,80,88,90 Piping, 36, 84 Pumps, 38, 86 Inverters, 40, 40a, 40b, 40c Valves, 42 Control devices, 44, 44a, 44b, 44c Dilution tank, 82 Concentration tank.

Claims

1. a semipermeable membrane treatment step in which a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane is used, and water to be treated containing dissolved solid components is passed through the first space, and the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water, and a part of the water to be treated or at least a part of the concentrated water is passed through the second space to obtain dilution water; a first space outlet flow rate measuring step of measuring the flow rate of concentrated water at the first space outlet of the semipermeable membrane module; a second space inlet flow rate measuring step of measuring the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module; a second space outlet flow rate measuring step of measuring the flow rate of dilution water at the second space outlet of the semipermeable membrane module; Including, The pressure of the water to be treated in the first space is greater than 1.0 MPa and less than 10.0 MPa, A water treatment method characterized in that the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module is not measured, and the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module is calculated from the flow rates measured in the first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step.

2. a semipermeable membrane treatment step in which semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, are used to pass water to be treated that contains dissolved solid components through the first space of a first-stage semipermeable membrane module, and the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water, which is then further passed through a subsequent stage semipermeable membrane module to obtain concentrated water, and at least a portion of the water to be treated or the concentrated water is passed through the second space of the semipermeable membrane module of each stage to obtain dilution water; a final stage first space outlet flow rate measuring step of measuring the flow rate of concentrated water at the first space outlet of the final stage semipermeable membrane module; a second space inlet flow rate measuring step of measuring the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module of the most upstream stage or each stage on the second space side; a second space outlet flow rate measuring step of measuring the flow rate of dilution water at the second space outlet of the semipermeable membrane module of the most downstream stage or each stage on the second space side; Including, The pressure of the water to be treated in the first space is greater than 1.0 MPa and less than 10.0 MPa, A water treatment method characterized in that the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module is not measured, and the flow rate of the water to be treated or the concentrated water at the inlet of the first space of the semipermeable membrane module of the first stage or each stage is calculated from the flow rates measured in the final stage first space outlet flow rate measuring step, the second space inlet flow rate measuring step, and the second space outlet flow rate measuring step.

3. The water treatment method according to claim 1 or 2, A water treatment method comprising controlling the flow rate of the concentrated water or the water to be treated at the inlet of the first space to a predetermined value based on the calculated flow rate of the concentrated water or the water to be treated.

4. The water treatment method according to any one of claims 1 to 3, A water treatment method characterized in that the pressure at the flow rate measurement points in the first space outlet flow rate measurement process or the final stage first space outlet flow rate measurement process, the second space inlet flow rate measurement process, and the second space outlet flow rate measurement process is 1 MPa or less.

5. a semipermeable membrane treatment means for passing water to be treated containing dissolved solid components through the first space using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, pressurizing the first space to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water, and passing a portion of the water to be treated or at least a portion of the concentrated water through the second space to obtain dilution water; a first space outlet flow rate measuring means for measuring the flow rate of concentrated water at the first space outlet of the semipermeable membrane module; a second space inlet flow rate measuring means for measuring the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module; a second space outlet flow rate measuring means for measuring the flow rate of dilution water at the second space outlet of the semipermeable membrane module; Equipped with The pressure of the water to be treated in the first space is greater than 1.0 MPa and less than 10.0 MPa, a calculation means for calculating the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module from the flow rates measured by the first space outlet flow rate measuring means, the second space inlet flow rate measuring means, and the second space outlet flow rate measuring means, without installing a first space inlet flow rate measuring means for measuring the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module; A water treatment device comprising:

6. a semipermeable membrane treatment means using semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, for passing water to be treated containing dissolved solid components through the first space of the semipermeable membrane module of a first stage, pressurizing the first space to cause the water contained in the water to permeate through the semipermeable membrane to obtain concentrated water, and further using the concentrated water to obtain concentrated water using semipermeable membrane modules of subsequent stages, and for passing a portion of the water to be treated or at least a portion of the concentrated water through the second space of the semipermeable membrane module of each stage to obtain dilution water; a final stage first space outlet flow rate measuring means for measuring the flow rate of concentrated water at the first space outlet of the final stage semipermeable membrane module; a second space inlet flow rate measuring means for measuring the flow rate of the water to be treated or the concentrated water at the second space inlet of the semipermeable membrane module of the most upstream stage or each stage on the second space side; a second space outlet flow rate measuring means for measuring the flow rate of dilution water at the second space outlet of the semipermeable membrane module of the most downstream stage or each stage on the second space side; Equipped with The pressure of the water to be treated in the first space is greater than 1.0 MPa and less than 10.0 MPa, a calculation means for calculating the flow rate of the water to be treated or the concentrated water at the inlet of the first space of the semipermeable membrane module of the first stage or each stage from the flow rates measured by the final stage first space outlet flow rate measuring means, the second space inlet flow rate measuring means, and the second space outlet flow rate measuring means, without installing a first space inlet flow rate measuring means for measuring the flow rate of the water to be treated at the inlet of the first space of the semipermeable membrane module; A water treatment device comprising:

7. The water treatment device according to claim 5 or 6, A water treatment device further comprising a control means for controlling the flow rate of the concentrated water or the water to be treated at the inlet of the first space to a predetermined value based on the calculated flow rate of the concentrated water or the water to be treated.

8. The water treatment device according to any one of claims 5 to 7, A water treatment device characterized in that the pressure at the flow rate measurement points by the first space outlet flow rate measuring means or the final stage first space outlet flow rate measuring means, the second space inlet flow rate measuring means, and the second space outlet flow rate measuring means is 1 MPa or less.

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