JP7776256B2 - Water treatment method and water treatment device - Google Patents

Description

The present invention relates to a water treatment method and water treatment device for concentrating water containing dissolved solids (TDS) and other substances.

In recent years, methods for reducing the volume of wastewater from factories and other facilities 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.

In addition, as disclosed in Patent Document 1, a method is known in which the water to be treated or its concentrate is passed through a first space and a second space separated by a semipermeable membrane in a semipermeable membrane module, and the first space is pressurized to concentrate the water. Compared to conventional reverse osmosis methods, this type of concentration method using a semipermeable membrane reduces the osmotic pressure difference between the first and second spaces, thereby enabling wastewater to be highly concentrated and reduced in volume with less energy consumption.

The concentration method described in Patent Document 1 requires control of the flow rates in the first and second spaces of the membrane to ensure stable volume reduction of the 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.

However, because the first spatial line of the semipermeable membrane is pressurized and at high pressure, the flow measuring equipment used must be highly pressure-resistant or special ultrasonic type, which increases initial costs. Furthermore, in the case of equipment using multiple semipermeable membrane modules, if a flow measuring device is installed at each stage, the number of flow measuring devices increases with each stage, further increasing initial costs.

Japanese Patent Application Laid-Open No. 2018-069198

The object of the present invention is to provide a water treatment method and water treatment device that can perform stable water concentration treatment at low cost using a semipermeable membrane module.

The present invention provides a semipermeable membrane treatment process using a semipermeable membrane module 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, the first space is pressurized to cause the water contained in the water to permeate through the semipermeable membrane, thereby obtaining 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 process measuring the flow rate of the concentrated water at the outlet of the first space of the semipermeable membrane module; This water treatment method includes a second space inlet flow rate measuring step of measuring the flow rate of concentrated water, and 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, wherein the pressure of the water to be treated in the first space is greater than 1.0 MPa and not more than 10.0 MPa, and the flow rate of the water to be treated at the first space inlet of the semipermeable membrane module is not measured, but the flow rate of the water to be treated at the first space inlet 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.

The present invention relates to 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 the concentrated water is further obtained using semipermeable membrane modules of subsequent stages and thereafter, and dilution water is obtained by 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; a final stage first space outlet flow rate measuring process; and 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; This water treatment method includes 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 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, wherein the pressure of the water to be treated in the first space is greater than 1.0 MPa and not more than 10.0 MPa, and the flow rate of the water to be treated at the first space inlet of the semipermeable membrane module is not measured, but the flow rate of the water to be treated or the concentrated water at the first space inlet 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.

In the water treatment method, it is preferable to control the flow rate of the concentrated water or 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 water to be treated.

In the water treatment method, it is preferable that the pressure at the flow rate measurement points in the first space outlet flow rate measuring step or 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 is 1 MPa or less.

The present invention provides a semipermeable membrane treatment means for obtaining dilution water by passing water to be treated containing dissolved solid components through the first space, pressurizing the first space to cause the water contained in the water to permeate through the semipermeable membrane, and passing a portion of the water to be treated or at least a portion of the concentrated water through the second space, using a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane; a first space outlet flow rate measuring means for measuring the flow rate of the concentrated water at the outlet of the first space of the semipermeable membrane module; and a second space measuring the flow rate of the water to be treated or the concentrated water at the inlet of the second space 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 , wherein the pressure of the water to be treated in the first space is greater 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, but the water treatment device is provided with a calculation means for calculating the flow rate of the water to be treated at the first space inlet 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.

The present invention uses semipermeable membrane modules connected in multiple stages, each having a first space and a second space separated by a semipermeable membrane, and includes a semipermeable membrane treatment means for passing water to be treated that contains 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 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 the concentrated water at the outlet of the first space of the semipermeable membrane module of the final stage; and a flow rate measuring means for measuring the flow rate of the concentrated water at the outlet of the first space of the semipermeable membrane module of the most upstream stage on the second space side or the second space of the semipermeable membrane module of each stage. 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 inlet; and 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, wherein the pressure of the water to be treated in the first space is greater 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, and the water treatment device is equipped with a calculation means for calculating the flow rate of the water to be treated or the concentrated water at the first space inlet 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.

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

In the water treatment device, it is preferable 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.

The present invention provides a water treatment method and water treatment device that can perform stable water concentration treatment at low cost using a semipermeable membrane module.

1 is a schematic diagram illustrating an example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention. FIG. 10 is a schematic configuration diagram illustrating another example of a water treatment device according to an embodiment of the present invention.

An embodiment of the present invention will be described below. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

An example of a water treatment device according to an embodiment of the present invention is outlined in Figure 1, and its configuration will be described below.

The water treatment device 1 shown in FIG. 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 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 membrane module 10, for example, serves 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 treated water tank for storing the water to be treated.

In the water treatment device 1 shown 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.

A first space outlet flow rate measuring device 18 is installed in pipe 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 membrane module 10. A second space inlet flow rate measuring device 20 is installed in pipe 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 membrane module 10. A second space outlet flow rate measuring device 22 is installed in pipe 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 membrane module 10.

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. Water to be treated is passed through the first space 14 from the first space inlet of the membrane module 10 and through the second space inlet to the second space 16. By pressurizing the first space 14, 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, concentrating the water. In other words, 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 performs a concentration treatment by supplying water to both the first space 14 and the second space 16 of the membrane module 10.

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 process) and dilution water in the second space 16 (dilution process). A portion of the concentrated water obtained in the first space 14 is discharged outside the system through piping 28.

Here, the pipes 24, 26, etc. function as a 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.

The diluted water obtained in the second space 16 may be discharged outside the system through piping 30, or, if necessary, may be sent to a dilution water tank and stored there, and then discharged outside the system. At least a portion of the diluted water may be sent to a tank for treated water 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 undergoes reverse osmosis membrane treatment (reverse osmosis membrane treatment process). 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 sent to a tank for treated water and mixed with the water to be treated there.

In this way, treated water (concentrated water) containing concentrated dissolved solids and other substances is obtained from the treated water, which contains dissolved solids and other substances, and dilution water, thereby reducing the volume of the treated water.

As described above, the piping 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 piping 24 must be highly pressure-resistant or special ultrasonic type, 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, and 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.

The flow rate of the water to be treated at the primary inlet can be calculated from the values of the flow rate measuring devices at the primary outlet, secondary inlet, and secondary outlet. This can be done manually or automatically. When calculating automatically, the water treatment device 1 may be equipped with a calculation device as a calculation means for calculating the flow rate of the water to be treated 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 each of the first space outlet flow rate measuring device 18, second space inlet flow rate measuring device 20, and second space outlet flow rate measuring device 22. The calculation device is composed of a microcomputer and electronic circuits, including, 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. The calculation device has the function of calculating the flow rate of the water to be treated 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.

An outline of another example of a water treatment device according to an embodiment of the present invention is shown in Figure 2, and its configuration will be described below.

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. Water to be treated, including 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. At least a portion of the concentrated water is passed through the second space to obtain dilution water. The membrane module 10, for example, serves 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 treated water tank for storing the water to be treated.

In the water treatment device 2 shown 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 off 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.

A first space outlet flow rate measuring device 18 is installed downstream of the branch point to pipe 32 on pipe 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 membrane module 10. A second space inlet flow rate measuring device 20 is installed on 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 membrane module 10. A second space outlet flow rate measuring device 22 is installed on 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 membrane module 10.

The water treatment device 2 in Figure 2 uses a membrane module 10 having a first space 14 and a second space 16 separated by a semipermeable membrane 12. Water to be treated is passed through the first space inlet of the membrane module 10 and into the first space 14. At the same time, at least a portion of the concentrated water discharged from the first space outlet of the first space 14 of the membrane module 10 is passed through the second space inlet of the membrane module 10 and into the second space 16. By pressurizing the first space 14, 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, concentrating the water. In other words, in the water treatment device 1, the water to be treated is concentrated using the semipermeable membrane 12. The water treatment device 1 supplies the 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.

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

In the water treatment device 2, water to be treated containing dissolved solids (TDS) is pressurized and pumped through pipe 24 from the first space inlet of the membrane module 10 to the first space 14. A portion of the water contained in the pressurized water permeates from the first space 14 to the second space 16 via the semipermeable membrane 12. Because 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 concentrated water pumped through pipe 32 merges with the permeate water with a low TDS concentration that permeated the semipermeable membrane 12, creating a dilution effect. The concentrated water obtained in the first space 14 is discharged through pipe 28 from the first space outlet, and at least a portion of the concentrated water is pumped through pipe 32, branching off from pipe 28, to the second space inlet of the membrane module 10 and passed through pipe 34. The diluted water obtained in the second space 16 is discharged through pipe 34 from the second space outlet. 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 process) and dilution water in the second space 16 (dilution process). A portion of the concentrated water obtained in the first space 14 may be discharged outside the system through piping 28. At least a portion of the concentrated water is pumped and passed through piping 28 and 32 to the second space 16 of the membrane module 10 as described above.

Here, pipes 24, 28, 32, etc. function as a supply means that supplies the 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.

The diluted water obtained in the second space 16 may be discharged outside the system through piping 34, or, if necessary, may be sent to a dilution water tank and stored there, 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 process). 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 sent to a water tank to be treated and mixed with the water to be treated there.

In this way, treated water (concentrated water) containing concentrated dissolved solids and other substances is obtained from the treated water, which contains dissolved solids and other substances, and dilution water, thereby reducing the volume of the treated water.

In the water treatment method and water treatment device 2 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, and 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. In other words, in the water treatment device 2, flow rate measuring 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 rate measuring devices used, enabling stable treatment at low cost.

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 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 water to be treated at the inlet of the first space. An example of a water treatment device configured in this way is shown in Figures 3 and 4.

The water treatment device 3 shown in Figure 3 has the same configuration as the water treatment device 1 shown in Figure 1, but also includes a pump 36 upstream of the branch 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.

The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to the input drive frequency, sucking in the water to be treated and discharging it to the membrane module 10. The pump 36 is equipped with, for example, an inverter 38 that outputs to the pump 36 a drive frequency corresponding to the input command signal. 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.

The water treatment device 3 may be equipped with 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 are composed of, for example, a calculation means such as a CPU that calculates a program, and storage means such as 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 and closing degree of the valve 40, etc. Note that the control device 42 may be the same device as the calculation device described above, or may be a separate device.

In water treatment device 3, similar to water treatment device 1, treated water containing dissolved solid components and the like is treated to obtain treated water (concentrated water) in which the dissolved solid components and other substances have been concentrated, and dilution water, thereby reducing the volume of the treated water.

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 process), 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 process), 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 process). Then, for example, the flow rate of water to be treated at the first space inlet is controlled to a predetermined value 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 process, second space inlet flow rate measuring process, and second space outlet flow rate measuring process (control process).

For example, the control device 42 calculates the drive frequency using an arbitrary formula based on the flow rate of the water to be treated at the inlet of the first space = FI1 + (FI3 - FI2), which is calculated from the 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, thereby controlling 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.

In the water treatment method and water treatment device 3 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. 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. The flow rate of the water to be treated at the primary side inlet is then adjusted from the calculated flow rate of the water to be treated at the primary side inlet. This reduces the number of flow measuring devices used, enabling stable treatment at low cost. Furthermore, by controlling the flow rate of the water to be treated at the primary side inlet, even more stable treatment can be achieved.

The water treatment device 4 shown in FIG. 4 has the same configuration as the water treatment device 2 shown in FIG. 2, but also includes a pump 36 in the piping 24 and a valve 40 upstream of the installation point of the second space inlet flow rate measuring device 20 in the piping 32. The water treatment device 4 may also 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 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 via electrical connections, etc.

In water treatment device 4, similar to water treatment device 2, treated water containing dissolved solids and other substances is treated to obtain treated water (concentrated water) in which the dissolved solids and other substances have been concentrated, and dilution water, thereby reducing the volume of the treated water.

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 process), 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 process), 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 process). Then, for example, the flow rate of treated water at the first space inlet is controlled to a predetermined value based on the flow rate of treated water 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 process, second space inlet flow rate measuring process, and second space outlet flow rate measuring process (control process).

For example, the control device 42 calculates the drive frequency using an arbitrary formula based on the flow rate of the water to be treated at the inlet of the first space = FI1 + (FI3 - FI2), which is calculated from the 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, thereby controlling 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.

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, and 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 from 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, by controlling the flow rate of the water to be treated at the primary side inlet, even more stable treatment can be achieved.

In 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 can be increased, for example, 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 can be gradually closed to adjust the flow rate of the water to be treated at the primary inlet to the predetermined value.

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

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

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

The water treatment method and water treatment device according to this embodiment may use a multi-stage semipermeable membrane module. An example of a water treatment device with such a configuration is shown in Figures 5, 6, 7, and 8.

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 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, yielding concentrated water. This concentrated water is then further purified using subsequent semipermeable membrane modules. Furthermore, 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. Semipermeable membrane treatment means include, 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 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 supplies the water to be treated to the first and second spaces of the first-stage membrane module, and sequentially supplies the concentrated water to the first and second spaces of the next-stage membrane module to perform a concentration treatment.

In the water treatment device 5 of Figure 5, a pipe 46 is connected to the first space inlet of the first-stage membrane module 10a via a pump 36. A pipe 54 branching off from the pipe 46 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 a pipe 56. 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 58 branching off from the pipe 48 is connected to the second space inlet of the second-stage 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 60. 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. Pipe 62 branching from pipe 50 is connected to the second space inlet of the third-stage membrane module 10c via 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 pipe 64. Pipe 52 is connected to the first space outlet of the third-stage membrane module 10c.

Pipe 52 is equipped with a first space outlet flow measuring device 18 as a final-stage first space outlet flow measuring means for measuring the flow rate (FI1) of concentrated water at the first space outlet of the final-stage membrane module 10c. Pipes 54, 58, and 62 are equipped with second space inlet flow measuring devices 20a, 20b, and 20c as second space inlet flow measuring means for measuring the flow rate (FI2, FI4, and FI6) of the water to be treated or concentrated water at the second space inlet of each stage of membrane module 10a, 10b, and 10c. Pipes 56, 60, and 64 are equipped with second space outlet flow measuring devices 22a, 22b, and 22c as second space outlet flow measuring means for measuring the flow rate (FI3, FI5, and FI7) of dilution water at the second space outlet of each stage of membrane module 10a, 10b, and 10c.

The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to the input drive frequency, sucking in the water to be treated and discharging 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 the input command signal to the pump 36. The valves 40a, 40b, and 40c are, for example, proportional control valves that adjust their opening 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.

The water treatment device 5 may be equipped with a control device 42 as a control means for controlling the flow rate of the water to be treated or 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, 20c, the second space outlet flow rate measuring devices 22a, 22b, 22c, the inverter 38, and the valves 40a, 40b, 40c. The control device 42 is composed of a microcomputer and electronic circuits, including, 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, 40c.

The water treatment device 5 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water to be treated is supplied to the first space and the second space of the first-stage membrane module, and the resulting concentrated water is sequentially supplied to the first space and the second space of the next-stage membrane module. The first space 14 of each stage is pressurized, causing the water contained in the first space 14 to permeate through the semipermeable membrane 12 into the second space 16, thereby concentrating the water. In other words, 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.

Specifically, in the water treatment device 5, the water to be treated, which contains 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. 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 process (first stage)). Dilution water is obtained in the second space 16a of the first-stage membrane module 10a through the pipe 56, where it is stored in the dilution water tank 44a as needed, and then discharged outside the system.

The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is sent via piping 48 to the first space 14b of the second-stage membrane module 10b, and the concentrated water branched off from piping 48 is sent via 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 process (second stage)), and dilution water is obtained in the second space 16b (dilution process (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 via piping 60 and then discharged outside the system.

The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent via piping 50 to the first space 14c of the third-stage membrane module 10c, and the concentrated water branched off from piping 50 is sent via 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 process (third stage)), and dilution water is obtained in the second space 16c (dilution process (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 via piping 64 and then discharged outside the system.

Here, the pump 36, pipes 46, 48, 50, 54, 58, 62, 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.

The dilution water obtained in the second spaces 16a, 16b, and 16c of the membrane modules 10a, 10b, and 10c of each stage may be discharged outside the system, or, if necessary, may be sent to and stored in the dilution water tanks 44a, 44b, and 44c, 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 process). 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.

In this way, treated water containing dissolved solids and other substances is obtained from the treated water (final stage concentrated water) and diluted water (diluted water from each stage), thereby reducing the volume of the treated water.

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, 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 based on the flow rate of the water to be treated or the concentrated water at the first space inlet of each stage, which is calculated from the flow rates (FI1, FI2, FI3, FI4, FI5, FI6, FI7) measured in the final-stage first space outlet flow rate measuring process, the second space inlet flow rate measuring process, and the second space outlet flow rate measuring process (control process). 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).

For example, the control device 42 calculates the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a = FI1 + (FI7 - FI6) + (FI5 - FI4) + (FI3 - FI2), and the flow rate of the concentrated water at the first space inlet 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 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. A command signal corresponding to this calculated value is output to the inverter 38 to control the pump 36, which in turn controls 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.

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 rate of the water to be treated or concentrated water at the primary side inlet of each stage is 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 outlet of each stage. In other words, 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 concentrated 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 concentrated water at the primary inlet of each stage. This allows for a significant reduction in the number of flow rate measuring devices used, enabling stable treatment at low cost. Furthermore, by controlling the flow rate of the water to be treated or the concentrated water at the primary inlet of each stage, even more stable treatment can be achieved.

The water treatment device 6 shown in Figure 6 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 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, yielding concentrated water. This concentrated water is then further purified 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. Semipermeable membrane treatment means include, 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 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 supplies the water to be treated to the first space of the first-stage membrane module, and then sequentially supplies the concentrated water to the first space of the next-stage membrane module and its own second space to perform a concentration treatment.

In the water treatment device 6 shown in 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 a 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. Pipe 74, branching off from pipe 52, is connected to the inlet of the second space of membrane module 10c via valve 40c. The outlet of the second space of the third-stage membrane module 10c is connected to the inlet of the dilution water tank 44c by pipe 76.

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

The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to the input drive frequency, sucking in the water to be treated and discharging 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 the input command signal to the pump 36. The valves 40a, 40b, and 40c are, for example, proportional control valves that adjust their opening 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.

The water treatment device 6 may be equipped with a control device 42 as a control means for controlling the flow rate of the concentrated water at the first space inlet 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 first space inlet 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, 20c, the second space outlet flow rate measuring devices 22a, 22b, 22c, the inverter 38, and the valves 40a, 40b, 40c. The control device 42 is composed of a microcomputer and electronic circuits, including, 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, 40c.

The water treatment device 6 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water to be treated is supplied to the first space of the first-stage membrane module, and the resulting concentrated water is sequentially supplied to the first space of the next-stage membrane module and its own second space. The first space 14 of each stage is pressurized, causing the water contained in the first space 14 to permeate through the semipermeable membrane 12 into the second space 16, thereby concentrating the water. In other words, in the water treatment device 6, the water to be treated is concentrated using the semipermeable membrane 12, and the concentrated water is then further concentrated using the semipermeable membrane 12 of the next stage.

Specifically, in the water treatment device 6, the water to be treated, containing dissolved solids (TDS), is pumped by the pump 36 through the pipe 46 into 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 process (first stage)). Dilution water is obtained in the second space 16a (dilution process (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is pumped through the pipe 48 to the first space 14b of the second-stage membrane module 10b. The concentrated water branched off from the pipe 48 is pumped through the 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 the dilution water tank 44a as needed via piping 68, and then discharged outside the system.

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 process (second stage)), and dilution water is obtained in the second space 16b (dilution process (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is sent via piping 50 to the first space 14c of the third-stage membrane module 10c, and the concentrated water branched off from piping 50 is sent via piping 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 the dilution water tank 44b as needed via piping 72 and then discharged outside the system.

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 process (third stage)), and dilution water is obtained in the second space 16c (dilution process (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.

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.

The dilution water obtained in the second spaces 16a, 16b, and 16c of the membrane modules 10a, 10b, and 10c of each stage may be discharged outside the system, or, if necessary, may be sent to and stored in the dilution water tanks 44a, 44b, and 44c, 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 process). 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.

In this way, treated water containing dissolved solids and other substances is obtained from the treated water (final stage concentrated water) and diluted water (diluted water from each stage), thereby reducing the volume of the treated water.

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 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, the flow rate of the concentrated water at the first space inlet of each stage is controlled to a predetermined value based on the flow rate of the concentrated water at the first space inlet of each stage, which is calculated from the flow rates (FI1, FI2, FI3, FI4, FI5, FI6, FI7) measured in the final-stage first space outlet flow rate measuring process, second space inlet flow rate measuring process, and second space outlet flow rate measuring process (control process). 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).

For example, the control device 42 calculates the flow rate of the water to be treated at the first space inlet of the first-stage membrane module 10a = FI1 + (FI7 - FI6) + (FI5 - FI4) + (FI3 - FI2), and the flow rate of the concentrated water at the first space inlet 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 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. A command signal corresponding to this calculated value is output to the inverter 38 to control the pump 36, which in turn controls 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.

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 rate of the water to be treated or concentrated water at the primary side inlet of each stage is 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 outlet of each stage. In other words, 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 concentrated 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 concentrated water at the primary inlet of each stage. This allows for a significant reduction in the number of flow rate measuring devices used, enabling stable treatment at low cost. Furthermore, by controlling the flow rate of the water to be treated or the concentrated water at the primary inlet of each stage, even more stable treatment can be achieved.

When using multi-stage membrane modules, water may be passed through the second space in series. An example of such a water treatment device is shown in Figure 7. The water treatment device 7 shown in Figure 7 uses multiple connected semipermeable membrane modules having a first space (concentration side) and a second space (permeation side) separated by a semipermeable membrane. Water to be treated, including dissolved solids (TDS), is passed through the first space of the first-stage semipermeable membrane module, and the first space is pressurized to permeate the water contained in the water through the semipermeable membrane to obtain concentrated water. This concentrated water is then further obtained using subsequent semipermeable membrane modules. At least a portion of the concentrated water is passed through the second space of each semipermeable membrane module to obtain dilution water. Semipermeable membrane treatment means include, 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 that stores dilution water from the first-stage membrane module 10a. The water treatment device 7 supplies the water to be treated to the first space of the 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.

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. 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. 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 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. The second space outlet of the third-stage membrane module 10c and the second space inlet of the second-stage membrane module 10b are connected by a pipe 78. The second space outlet of the second-stage membrane module 10b and the second space inlet of the first-stage membrane module 10a are connected by a pipe 80. The second space outlet of the first-stage membrane module 10a and the inlet of the dilution water tank 44 are connected by a pipe 68.

A first space outlet flow rate measuring device 18 is installed downstream of the branch point to pipe 74 on pipe 52 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, the final stage. A second space inlet flow rate measuring device 20 is installed on pipe 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 on pipe 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.

The pump 36 is, for example, a pressure pump that is driven at a rotational speed corresponding to the input drive frequency, sucking in the water to be treated and discharging 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 the 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.

The water treatment device 7 may be equipped with a control device 42 as a control means for controlling the flow rate of the water to be treated at the first space inlet 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 first space inlet 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 a microcomputer and electronic circuits, for example, 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, and has the function of controlling the flow rate of the pump 36, the opening and closing degree of the valve 40, etc.

The water treatment device 7 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water to be treated is supplied to the first space of the first membrane module, and the resulting concentrated water is passed serially through the first space of the succeeding membrane module. At least a portion of the concentrated water from the final membrane module is supplied to its own second space, and the resulting diluted water is passed serially through the second space 16 of the preceding membrane module. The first space 14 of each stage is pressurized, causing the water contained in the first space 14 to permeate through the semipermeable membrane 12 into the second space 16, thereby concentrating the water. 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.

Specifically, in the water treatment device 7, the water to be treated, containing 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. Meanwhile, dilution water, which has been pumped via the second space 16c of the third-stage membrane module 10c (described below) and the second space 16b of the second-stage membrane module 10b, is pumped through the 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 through the semipermeable membrane 12a into the second space 16a (concentration process (first stage)). Dilution water is then obtained in the second space 16a (dilution process (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is pumped through the 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 stored in the dilution water tank 44 as needed via piping 68, and then discharged outside the system.

In the second-stage membrane module 10b, dilution water is delivered via the second space 16c of the third-stage membrane module 10c (described below) to the second space 16b of the second-stage membrane module 10b through piping 78. 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 process (second stage)), and dilution water is obtained in the second space 16b (dilution process (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is delivered via piping 50 to the first space 14c of the third-stage membrane module 10c. The dilution water obtained in the second space 16b of the second-stage membrane module 10b is delivered via piping 80 to the second space 16a of the first-stage membrane module 10a.

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 pipes 52 and 74 as described below. 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 process (third stage)), and dilution water is obtained in the second space 16c (dilution process (third stage)). The concentrated water obtained in the first space 14c of the third-stage membrane module 10c is discharged through pipe 52, and the concentrated water branched off from pipe 52 is sent to the second space 16c of the third-stage membrane module 10c through 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 pipe 78.

Here, the pump 36, piping 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.

The diluted water obtained in the second space 16a of the membrane module 10a may be discharged outside the system, or, if necessary, may be sent to the dilution water tank 44, stored therein, and then discharged outside the system. At least a portion of the diluted water may be mixed with the water to be treated in the first-stage membrane module 10a. 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 process). 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.

In this way, treated water containing dissolved solids and other substances is converted into treated water (final stage concentrated water) with concentrated dissolved solids and other substances, and dilution water (dilution water from each stage), thereby reducing the volume of the treated water.

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 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 process), 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 process). 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 process, the second space inlet flow rate measuring process, and the second space outlet flow rate measuring process (control process).

For example, the control device 42 calculates the drive frequency using an arbitrary 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 calculated from the 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, which in turn controls the opening and closing degree of the valve 40, thereby controlling the flow rate of the water to be treated at the first space inlet.

In the water treatment method and water treatment device 7 of 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 of the final stage membrane module 10c, the secondary side inlet of membrane module 10c, which is the most upstream stage on the second space 16 side, and the secondary side outlet of membrane module 10a, which is the most downstream stage on the second space 16 side, respectively. No flow measuring devices are installed at the primary side inlets of membrane modules 10a, 10b, and 10c of each stage, or the secondary side inlets of first-stage membrane module 10a and second-stage membrane module 10b, and the flow rate of the treated water at the primary side inlet of the first stage is calculated from the values of the flow 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 final-stage membrane module 10, the secondary side inlet of the membrane module 10 in the most upstream stage on the second space 16 side, and the secondary side outlet of the membrane module 10 in the most downstream stage on the second space 16 side. The flow rate of the water to be treated at the primary side inlet of the first stage is then adjusted from the calculated flow rate of the water to be treated at the primary side inlet of the first stage. This allows for a significant reduction in the number of flow rate measuring devices used, enabling stable treatment at low cost.

In the water treatment device 7 of Figure 7, if a water supply pressure of, for example, 1 MPa or more is required on the second space side, or if a relay tank for concentrated water is required, a pump may be used to supply water to the second space side. An example of a water treatment device with such a configuration is shown in Figure 8. The water treatment device 8 shown in Figure 8 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 dissolved solids (TDS) and other substances, 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 obtained using subsequent semipermeable membrane modules. At least a portion of the concentrated water is passed through the second space of each semipermeable membrane module to obtain dilution water. Semipermeable membrane treatment means include, 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 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 supplies the water to be treated to the first space of the 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.

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. 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. 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 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 and the second space inlet of the membrane module 10c are connected by a pipe 90 via a pump 84. The second space outlet of the third-stage membrane module 10c and the second space inlet of the second-stage membrane module 10b are connected by a pipe 78. The second space outlet of the second-stage membrane module 10b and the second space inlet of the first-stage membrane module 10a are connected by a pipe 80. The second space outlet of the first-stage membrane module 10a and the inlet of the dilution water tank 44 are connected by piping 68.

A first space outlet flow rate measuring device 18 is installed downstream of the branch point to pipe 88 on pipe 52 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, the final stage. A second space inlet flow rate measuring device 20 is installed upstream of pump 84 on pipe 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, the most upstream stage on the second space 16 side. A second space outlet flow rate measuring device 22 is installed on pipe 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, the most downstream stage on the second space 16 side.

The pump 36 is a pressure pump that is driven, for example, at a rotational speed corresponding to the 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 to the pump 36 a drive frequency that corresponds to the 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.

The water treatment device 8 may be equipped with a control device 42 as a control means for controlling the flow rate of the water to be treated at the first space inlet 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 first space inlet 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 a microcomputer and electronic circuits, for example, including a calculation means such as a CPU that calculates a program, and storage means such as ROM and RAM that store the program and calculation results, and has the function of controlling the flow rate of the pump 36, the flow rate of the pump 84, etc.

The water treatment device 8 uses a multi-stage membrane module having a first space 14 and a second space 16 separated by a semipermeable membrane 12. The water to be treated is supplied to the first space of the first membrane module, the resulting concentrated water is passed serially through the first space of the succeeding membrane module, at least a portion of the concentrated water of the final membrane module is supplied to its own second space, and the resulting diluted water is passed serially through the second space 16 of the preceding membrane module. The first space 14 of each stage is pressurized, causing the water contained in the first space 14 to permeate through the semipermeable membrane 12 into the second space 16, thereby concentrating the water. That is, in the water treatment device 8, 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.

Specifically, in the water treatment device 8, the water to be treated, containing 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. Meanwhile, dilution water, which has been pumped via the second space 16c of the third-stage membrane module 10c and the second space 16b of the second-stage membrane module 10b (described below), is pumped through the 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 through the semipermeable membrane 12a into the second space 16a (concentration process (first stage)). Dilution water is then obtained in the second space 16a (dilution process (first stage)). The concentrated water obtained in the first space 14a of the first-stage membrane module 10a is pumped through the 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 stored in the dilution water tank 44 as needed via piping 68, and then discharged outside the system.

In the second-stage membrane module 10b, dilution water is delivered via the second space 16c of the third-stage membrane module 10c (described below) to the second space 16b of the second-stage membrane module 10b through piping 78. 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 process (second stage)), and dilution water is obtained in the second space 16b (dilution process (second stage)). The concentrated water obtained in the first space 14b of the second-stage membrane module 10b is delivered via piping 50 to the first space 14c of the third-stage membrane module 10c. The dilution water obtained in the second space 16b of the second-stage membrane module 10b is delivered via piping 80 to the second space 16a of the first-stage membrane module 10a.

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, the concentrated water tank 82, and pipe 90, as described below. 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 process (third stage)), and dilution water is obtained in the second space 16c (dilution process (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 off from pipe 52 is stored in the concentrated water tank 82 via 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 to the second space 16b of the second-stage membrane module 10b through piping 78.

Here, pumps 36, 84, pipes 46, 48, 50, 52, 88, 90, 78, 80, etc. function as supply means for supplying treated water 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.

The diluted water obtained in the second space 16a of the membrane module 10a may be discharged outside the system, or, if necessary, may be sent to the dilution water tank 44, stored therein, and then discharged outside the system. At least a portion of the diluted water may be mixed with the water to be treated in the first-stage membrane module 10a. 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 process). 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.

In this way, treated water containing dissolved solids and other substances is converted into treated water (final stage concentrated water) with concentrated dissolved solids and other substances, and dilution water (dilution water from each stage), thereby reducing the volume of the treated water.

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 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 process), 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 process). 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 process, the second space inlet flow rate measuring process, and the second space outlet flow rate measuring process (control process).

For example, the control device 42 calculates the drive frequency using an arbitrary 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 calculated from the 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 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.

In the water treatment method and water treatment device 8 of 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 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 measuring devices are installed at the primary side inlets of the membrane modules 10a, 10b, and 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 treated water at the primary side inlet of the first stage is calculated from the values of the flow 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 final-stage membrane module 10, the secondary side inlet of the membrane module 10 in the most upstream stage on the second space 16 side, and the secondary side outlet of the membrane module 10 in the most downstream stage on the second space 16 side. The flow rate of the water to be treated at the primary side inlet of the first stage is then adjusted from the calculated flow rate of the water to be treated at the primary side inlet of the first stage. This allows for a significant reduction in the number of flow rate measuring devices used, enabling stable treatment at low cost.

When using multi-stage membrane modules like those used in water treatment devices 5, 6, 7, and 8, the number of membrane module stages can be determined based on factors such as the concentration of the target treated water. 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.

A membrane module unit comprising multiple membrane modules connected in parallel may be used as each stage of membrane module. The number of membrane modules in each membrane module unit can be determined based on factors such as the flow rate of the water to be treated.

A pipe may be provided to send the dilution water from the second space 16 of each membrane module to the second space 16 of the membrane module of the next stage.

One or more stages of membrane modules may be provided with a concentrated water tank or a dilution water tank, or each stage of membrane module may be provided with a concentrated water tank or a dilution water tank.

Examples of the semipermeable membrane 12 provided in the membrane module include reverse osmosis membranes (RO membranes), forward osmosis membranes (FO membranes), and nanofiltration membranes (NF membranes). Reverse osmosis membranes, forward osmosis membranes, and nanofiltration membranes are preferred semipermeable membranes. When a reverse osmosis membrane, forward osmosis membrane, or 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.

The material constituting the semipermeable membrane 12 is not particularly limited, but examples include cellulose-based resins such as cellulose acetate-based resins, polysulfone-based resins such as polyethersulfone-based resins, and polyamide-based resins. It is preferable that the material constituting the semipermeable membrane 12 be cellulose acetate-based resin.

Examples of the shape of the semipermeable membrane 12 include a flat membrane, a hollow fiber membrane, a spiral membrane, etc.

The pressure at the flow measurement points by the first space outlet flow measurement device 18, the second space inlet flow measurement devices 20, 20a, 20b, 20c, and the second space outlet flow measurement devices 22, 22a, 22b, 22c in the 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 preferably 1 MPa or less. There are no particular restrictions on the flow measurement devices used as long as they are capable of measuring flow rates. However, if the pressure at the flow measurement points is 1 MPa or less, a general-purpose flow meter can be used as the flow measurement device; it is not necessary to use a special device with high pressure resistance or an ultrasonic type.

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

TDS (dissolved solids) include, for example, chlorides such as sodium chloride, carbonates such as calcium carbonate and magnesium carbonate, and sulfates such as calcium sulfate and magnesium sulfate.

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 Pump, 38, 86 Inverter, 40, 40a, 40b, 40c Valve, 42 Control device, 44, 44a, 44b, 44c Dilution tank, 82 Concentration tank.

Claims (8)

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. 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. 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. 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. 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: 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: 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. 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.