CN115010212A

CN115010212A - Water treatment method and water treatment device

Info

Publication number: CN115010212A
Application number: CN202210175986.0A
Authority: CN
Inventors: 高田明广; 中野彻; 若山圣
Original assignee: Organo Corp
Current assignee: Organo Corp
Priority date: 2021-03-05
Filing date: 2022-02-25
Publication date: 2022-09-06
Anticipated expiration: 2042-02-25
Also published as: TW202302472A; CN115010212B; JP2022135710A

Abstract

Even when the quality of the water to be treated fluctuates in the concentration treatment of water using the semipermeable membrane module, stable treatment can be performed. The water treatment method comprises the following steps: a pressurizing step for pressurizing the water to be treated containing the total dissolved solid content to 0.1MPa or more; a first reverse osmosis membrane treatment step of introducing the pressurized water to be treated into a first reverse osmosis membrane to obtain a first RO permeate and a first RO concentrate; a semipermeable membrane treatment step of introducing first RO concentrated water into the first space using a semipermeable membrane module having first and second spaces separated by a semipermeable membrane, pressurizing the first space to allow water contained in the first RO concentrated water to permeate the semipermeable membrane to obtain concentrated water, and introducing a part of the first RO concentrated water or at least a part of the concentrated water into the second space to obtain diluted water; and a flow rate adjustment step of measuring the flow rate of the concentrate and the flow rate of the diluent, and adjusting the flow rates so that the measured values of the flow rates of the concentrate and the diluent become preset target flow rate values.

Description

Water treatment method and water treatment device

Technical Field

The present invention relates to a water treatment method and a water treatment apparatus for performing concentration treatment of water containing Total Dissolved Solids (TDS) and the like.

Background

In recent years, a treatment for reducing the amount of discharged water discharged from a factory or the like as much as possible has been performed, and a method of reducing the volume of discharged water by concentrating the discharged water using a reverse osmosis membrane or the like and recovering the permeated water has been adopted. There is a tendency that the water recovery rate is improved as much as possible, and plants and the like are increased in which the water is recovered substantially in the entire amount by a method such as evaporation concentration, and the like, and the amount of ZLD (Zero Liquid Discharge) is discharged by solidifying the total dissolved solid content and the like.

A method of heating water such as evaporation concentration requires a large amount of energy and increases the cost, and therefore a method of concentrating drain water to a high concentration by a method of not heating as much as possible has been desired. The reverse osmosis membrane method consumes less energy than the evaporation concentration method, but concentration is insufficient due to the influence of osmotic pressure, and the volume may not be reduced to the target water amount.

Patent document 1 describes the following method: raw water or concentrated water thereof is passed through a first space and a second space separated by a semipermeable membrane of a multistage semipermeable membrane module, and the first space is pressurized to concentrate the water. The method of patent document 1 is a method of concentrating a semi-permeable membrane module to a high concentration with less pressurization power, that is, with less energy, as compared with a general concentration method using a reverse osmosis membrane, by reducing a concentration difference (osmotic pressure difference) between a first space and a second space.

The concentration method described in patent document 1 requires not only the first space of the semipermeable membrane module but also the control of the flow rate and concentration in the second space, and therefore, compared to the reverse osmosis membrane method, the water balance is likely to be impaired due to the fluctuation in the quality of raw water (water to be treated), and it is likely to be difficult to stably reduce the volume of discharged water. In addition, when such a method of concentrating water to a high concentration is used, the quality of the recovered water may deteriorate and become unsuitable for recovery.

Prior art documents

Patent literature

Patent document 1: japanese patent laid-open publication No. 2018-069198

Disclosure of Invention

(problems to be solved by the invention)

An object of the present invention is to provide a water treatment method and a water treatment apparatus which can perform stable treatment even when there is a fluctuation in the quality of water to be treated (raw water) in a concentration treatment of water using a semi-permeable membrane module.

(means for solving the problems)

The invention is a water treatment method, comprising: a pressurizing step of pressurizing the water to be treated containing the total dissolved solid content to 0.1MPa or more; a first reverse osmosis membrane treatment step of introducing the pressurized water to be treated to a first reverse osmosis membrane to obtain a first RO permeate and a first RO concentrate; a semipermeable membrane treatment step of introducing the first RO-concentrated water into a first space separated by a semipermeable membrane by using a semipermeable membrane module having the first space and a second space, pressurizing the first space by the pressurization in the pressurization step to allow water contained in the first RO-concentrated water to permeate the semipermeable membrane to obtain concentrated water, and introducing a part of the first RO-concentrated water or at least a part of the concentrated water into the second space to obtain diluted water; and a flow rate adjustment step of measuring the flow rate of the concentrate and the flow rate of the dilution water, and adjusting the flow rate of the concentrate and the flow rate of the dilution water so that the measured values become preset target flow rate values.

The invention relates to a water treatment method, which comprises the following steps: a pressurizing step of pressurizing the water to be treated containing the total dissolved solid content to 0.1MPa or more; a first reverse osmosis membrane treatment step of introducing the pressurized water to be treated to a first reverse osmosis membrane to obtain a first RO permeate and a first RO concentrate; a semipermeable membrane treatment step of introducing the first RO-concentrated water into a first space of a semipermeable membrane module of a first stage using a semipermeable membrane module having a plurality of stages connected to each other and including a first space and a second space separated by a semipermeable membrane, pressurizing the first space by the pressurization in the pressurization step to allow water contained in the first RO-concentrated water to permeate the semipermeable membrane to obtain concentrated water, further using a semipermeable membrane module of a subsequent stage to obtain concentrated water from the concentrated water, and introducing a part of the first RO-concentrated water, or at least a part of the diluted water obtained from another semipermeable membrane module to a second space of the semipermeable membrane module of each stage to obtain diluted water; and a flow rate adjustment step of measuring the flow rate of the concentrate and the flow rate of the dilution water, and adjusting the flow rate of the concentrate and the flow rate of the dilution water so that the measured values become preset target flow rate values.

In the water treatment method, it is preferable that the first reverse osmosis membrane has a membrane surface effective pressure of 1MPa and a membrane surface effective pressure of 0.2 to 0.7m at 25 ℃ ³ /m ² A pure water permeation flux in a range of one day and has a NaCl removal rate (under the condition that NaCl is 32,000 mg/L) of 99.5% or more at a standard operating pressure.

In the water treatment method, it is preferable that the permeate flux of the semipermeable membrane module in the semipermeable membrane treatment step is set to a range of 0.005m/d to 0.05m/d under a membrane surface effective pressure of 1MPa and at 25 ℃.

In the water treatment method, it is preferable that the pressure of the first RO-concentrated water immediately after the first reverse osmosis membrane step is 7MPa or more, and the method further includes a pressure reduction step of reducing the pressure of the first RO-concentrated water to less than 7MPa before the semipermeable membrane treatment step.

In the water treatment method, it is preferable that the method further comprises: and a second reverse osmosis membrane treatment step of introducing the dilution water to a second reverse osmosis membrane to obtain a second RO permeate and a second RO concentrate.

In the water treatment method, it is preferable that the method further comprises: and a third reverse osmosis membrane treatment step of passing at least one of the first RO permeate and the second RO permeate through a third reverse osmosis membrane to obtain a third RO permeate and a third RO concentrate.

In the water treatment method, it is preferable that the first RO concentrated water has a sulfate ion concentration of 20000mg/L or more and at least one of a sodium ion and an ammonium ion concentration of 10000mg/L or more.

The present invention is a water treatment apparatus, including: a pressurizing unit that pressurizes the water to be treated containing the total dissolved solid content to 0.1MPa or more; a first reverse osmosis membrane treatment unit configured to introduce the pressurized water to be treated into a first reverse osmosis membrane to obtain first RO permeate water and first RO concentrate water; a semipermeable membrane treatment unit that uses a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, introduces the first RO-concentrated water into the first space, pressurizes the first space by the pressurization unit, and allows water contained in the first RO-concentrated water to permeate the semipermeable membrane to obtain concentrated water, and introduces a part of the first RO-concentrated water or at least a part of the concentrated water into the second space to obtain diluted water; and a flow rate adjusting means for measuring the flow rate of the concentrate and the flow rate of the dilution water and adjusting the flow rate of the concentrate and the flow rate of the dilution water so that the measured values become preset target flow rate values.

The present invention is a water treatment apparatus, including: a pressurizing unit that pressurizes water to be treated containing a total dissolved solid content to 0.1MPa or more; a first reverse osmosis membrane treatment unit configured to introduce the pressurized water to be treated into a first reverse osmosis membrane to obtain first RO permeate water and first RO concentrate water; a semipermeable membrane treatment unit that uses semipermeable membrane modules having a first space and a second space separated by a semipermeable membrane and connected in multiple stages, introduces the first RO concentrate into the first space of the semipermeable membrane module of the first stage, pressurizes the first space based on the pressurization of the pressurizing unit to allow water contained in the first RO concentrate to permeate the semipermeable membrane to obtain concentrate, further uses the semipermeable membrane modules of the subsequent stages to obtain concentrate, and introduces a part of the first RO permeate or at least a part of the concentrate or at least a part of the dilution obtained from the other semipermeable membrane modules into the semipermeable second space of each stage to obtain dilution water; and a flow rate adjusting means for measuring the flow rate of the concentrate and the flow rate of the dilution water and adjusting the flow rate of the concentrate and the flow rate of the dilution water so that the measured values become preset target flow rate values.

In the water treatment apparatus, it is preferable that the first reverse osmosis membrane has a membrane surface effective pressure of 1MPa and a membrane surface effective pressure of 0.2 to 0.7m at 25 ℃ ³ /m ² A pure water permeation flux in a range of one day and has a NaCl removal rate (under the condition that NaCl is 32,000 mg/L) of 99.5% or more at a standard operating pressure.

In the water treatment apparatus, it is preferable that the water treatment apparatus further comprises a permeate flux adjusting means for adjusting the permeate flux of the semipermeable membrane module in the semipermeable membrane treatment means so that the permeate flux is in the range of 0.005m/d to 0.05m/d under a membrane surface effective pressure of 1MPa and at 25 ℃.

In the water treatment apparatus, it is preferable that the pressure of the first RO concentrated water immediately after the first reverse osmosis membrane unit is 7MPa or more, and a pressure reducing unit that reduces the pressure of the first RO concentrated water to less than 7MPa is further provided in a stage preceding the semipermeable membrane treatment unit.

Preferably, the water treatment apparatus further includes: and a second reverse osmosis membrane treatment unit which supplies the dilution water to a second reverse osmosis membrane to obtain second RO permeate water and second RO concentrate water.

Preferably, the water treatment apparatus further includes: and a third reverse osmosis membrane treatment unit configured to pass at least one of the first RO permeate and the second RO permeate through a third reverse osmosis membrane to obtain a third RO permeate and a third RO concentrate.

In the water treatment apparatus, it is preferable that the first RO concentrated water has a sulfate ion concentration of 20000mg/L or more and at least one of a sodium ion and an ammonium ion concentration of 10000mg/L or more.

(effect of the invention)

According to the present invention, it is possible to provide a water treatment method and a water treatment apparatus which can perform stable treatment even when there is a fluctuation in the quality of water to be treated (raw water) in the concentration treatment of water using a semi-permeable membrane module.

Drawings

Fig. 1 is a schematic configuration diagram showing an example of a water treatment apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 3 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 4 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 5 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 6 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 7 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 8 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 9 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Fig. 10 is a schematic configuration diagram showing another example of the water treatment apparatus according to the embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described below. The present embodiment is an example of carrying out the present invention, and the present invention is not limited to the present embodiment.

Fig. 1 schematically shows an example of a water treatment apparatus according to an embodiment of the present invention, and the configuration thereof will be described.

The water treatment apparatus 1 shown in fig. 1 includes a pressure pump 26 as a pressurizing means for pressurizing water to be treated containing total dissolved solid components to 0.1MPa or more, a first reverse osmosis membrane treatment apparatus 100 as a first reverse osmosis membrane treatment means for passing the pressurized water to be treated through a first reverse osmosis membrane to obtain first RO permeate and first RO concentrate, and includes, for example, a first-stage membrane module unit 12, a second-stage membrane module unit 14, a third-stage membrane module unit 16, a fourth-stage membrane module unit 18, and a fifth-stage membrane module unit 20 as semipermeable membrane treatment means for passing water contained in the first RO concentrate through a semipermeable membrane by using a single-stage or multistage semipermeable membrane module having a first space (concentration side) and a second space (permeation side) partitioned by the semipermeable membrane, introducing the first RO concentrate into the first space, pressurizing the first space by the pressure pump 26 to permeate the water contained in the first RO concentrate, and passing a portion of the first RO concentrate or at least a portion of the concentrate to the second space to obtain dilution water. The water treatment apparatus 1 is provided with a pressurizing pump as pressurizing means for pressurizing the water to be treated containing the total dissolved solid content to 0.1MPa or more only at the front stage of the first reverse osmosis membrane treatment apparatus 100.

The first-stage membrane module unit 12 includes, for example, 6 membrane modules connected in parallel, the second-stage membrane module unit 14 includes, for example, 5 membrane modules connected in parallel, the third-stage membrane module unit 16 includes, for example, 4 membrane modules connected in parallel, the fourth-stage membrane module unit 18 includes, for example, 3 membrane modules connected in parallel, and the fifth-stage membrane module unit 20 includes, for example, 3 membrane modules connected in parallel. Each membrane module has a first space 11 and a second space 13 separated by a semi-permeable membrane 15. The water treatment apparatus 1 may include: a water tank 10 for storing water to be treated; a concentrated water tank 22 that stores concentrated water from the membrane module unit of the final stage (in the example of fig. 1, concentrated water from the fifth-stage membrane module unit 20); and a first dilution water tank 24 that stores dilution water from the first-stage membrane module unit (in the example of fig. 1, dilution water from the first-stage membrane module unit 12).

In the water treatment apparatus 1 shown in fig. 1, a pipe 38 is connected to a treated water inlet of the treated water tank 10. The outlet of the treated water tank 10 and the inlet of the first reverse osmosis membrane treatment apparatus 100 are connected to each other by a pipe 40 via a pressure pump 26. The concentrated water outlet of the first reverse osmosis membrane treatment apparatus 100 and the first space inlet of each membrane module of the first-stage membrane module unit 12 are connected in parallel by a first RO concentrated water pipe 106. A first RO permeate pipe 108 is connected to the permeate outlet of the first reverse osmosis membrane treatment apparatus 100. The first space outlet of each membrane module of the first-stage membrane module unit 12 and the first space inlet of each membrane module of the second-stage membrane module unit 14 are connected in parallel by a pipe 42. The first space outlet of each membrane module of the second-stage membrane module unit 14 and the first space inlet of each membrane module of the third-stage membrane module unit 16 are connected in parallel by a pipe 44. The first space outlet of each membrane module of the third-stage membrane module unit 16 and the first space inlet of each membrane module of the fourth-stage membrane module unit 18 are connected in parallel by a pipe 46. The first space outlet of each membrane module of the fourth-stage membrane module unit 18 and the first space inlet and the second space inlet of each membrane module of the fifth-stage membrane module unit 20 are connected in parallel by a pipe 48. The first space outlet of each membrane module of the fifth-stage membrane module unit 20 and the inlet of the concentrated water tank 22 are connected by a pipe 50 via a valve 32. A pipe 52 is connected to the outlet of the concentrated water tank 22 via the pump 28. The second space outlet of each membrane module of the fifth-stage membrane module unit 20 and the second space inlet of each membrane module of the fourth-stage membrane module unit 18 are connected in parallel by a pipe 54. The second space outlet of each membrane module of the fourth-stage membrane module unit 18 and the second space inlet of each membrane module of the third-stage membrane module unit 16 are connected in parallel by a pipe 56. The second space outlet of each membrane module of the third-stage membrane module unit 16 and the second space inlet of each membrane module of the second-stage membrane module unit 14 are connected in parallel by a pipe 58. The second space outlet of each membrane module of the second-stage membrane module unit 14 and the second space inlet of each membrane module of the first-stage membrane module unit 12 are connected in parallel by a pipe 60. The second space outlet of each membrane module of the first-stage membrane module unit 12 and the inlet of the first dilution water tank 24 are connected by a pipe 62. A pipe 64 is connected to an outlet of the first dilution water tank 24. The water treatment apparatus 1 may or may not include the concentrated water tank 22, the pump 28, and the pipe 52. The water treatment apparatus 1 may or may not include the first dilution water tank 24 and the pipe 64.

The pressure pump 26 is provided in a preceding stage of the first reverse osmosis membrane treatment apparatus 100, and is driven at a rotational speed corresponding to an input driving frequency, for example, to suck water to be treated and discharge the water to the first reverse osmosis membrane treatment apparatus 100. The pressure pump 26 is provided with, for example, a first inverter 30 that outputs a drive frequency corresponding to an input command signal to the pressure pump 26. A first flow rate measuring device 34 is provided as a first flow rate measuring means for measuring the flow rate of the concentrate passing through the first space of the final-stage membrane module unit (in the example of fig. 1, the fifth-stage membrane module unit 20) between the valve 32 in the pipe 50 and the inlet of the concentrate tank 22. The pipe 62 is provided with a second flow rate measuring device 36 as a second flow rate measuring means for measuring the flow rate of the dilution water passing through the second space of the membrane module unit of the first stage (the membrane module unit 12 of the first stage in the example of fig. 1). The valve 32 is provided at a stage subsequent to the final-stage membrane module unit (in the example of fig. 1, the fifth-stage membrane module unit 20), and is, for example, a proportional control valve whose opening degree is adjusted based on the measurement values of the first flow rate measuring device 34 and the second flow rate measuring device 36. The water treatment apparatus 1 includes a control device 66, and the control device 66 is connected to the first inverter 30, the first flow rate measuring device 34, and the second flow rate measuring device 36 by wired or wireless electrical connections or the like. The control device 66 may be connected to the valve 32 by a wired or wireless electrical connection or the like.

The water treatment method and the operation of the water treatment apparatus 1 according to the present embodiment will be described.

The water treatment apparatus 1 is as follows: for example, a multistage membrane module having a first space 11 and a second space 13 partitioned by a semipermeable membrane 15 is used, and first RO concentrated water obtained by a first reverse osmosis membrane treatment apparatus 100 for subjecting water to be treated containing total dissolved solid components to reverse osmosis membrane treatment is introduced in series into the first space 11 of the multistage membrane module, concentrated water of a preceding membrane module (fourth membrane module 18 in the example of fig. 1) is distributed to the first space 11 and the second space 13 of a final membrane module (fifth membrane module 20 in the example of fig. 1), diluted water of the final membrane module is returned in series and introduced into the second space 13 of the preceding membrane module, and water contained in the first space 11 is allowed to permeate into the second space 13 by pressurizing the first space 11 to concentrate the water. That is, in the water treatment apparatus 1, the first RO concentrated water is concentrated using the semipermeable membrane 15, and the concentrated water is further concentrated using the semipermeable membrane 15 of the next stage. The first RO concentrate is supplied to the first space 11 of the first-stage membrane module unit (first-stage membrane module unit 12 in the example of fig. 1), and the concentrate of the preceding stage (fourth-stage membrane module unit 18 in the example of fig. 1) is supplied to both the first space 11 and the second space 13 of the final-stage membrane module. Then, the dilution water having passed through the second space 13 of the final stage membrane module is supplied to the second space 13 of the upstream membrane module, and the first space 11 of each stage membrane module is pressurized to allow the water contained in the first space 11 to permeate into the second space 13.

Specifically, in the water treatment apparatus 1, the water to be treated containing the total dissolved solid content is stored in the water tank 10 to be treated through the pipe 38 as needed, pressurized to 0.1MPa or more by the pressure pump 26 from the water tank 10 to be treated (pressurizing step), and sent to the first reverse osmosis membrane treatment apparatus 100 through the pipe 40. In the first reverse osmosis membrane treatment apparatus 100, the pressurized water to be treated is passed through the first reverse osmosis membrane to obtain a first RO permeate and a first RO concentrate (first reverse osmosis membrane treatment step). The first RO permeate is discharged through the first RO permeate pipe 108. As will be described later, at least a part of the first RO permeate may be further sent to the third reverse osmosis membrane treatment apparatus 104, and reverse osmosis membrane treatment may be performed in the third reverse osmosis membrane treatment apparatus 104 (third reverse osmosis membrane treatment step).

The first RO-concentrated water is sent to the first space 11 of each membrane module of the first-stage membrane module unit 12 through the first RO-concentrated water pipe 106. On the other hand, the dilution water returned from the fifth-stage membrane module unit 20 of the final stage to be described later via the second space 13 of the fourth-stage membrane module unit 18, the second space 13 of the third-stage membrane module unit 16, and the second space 13 of the second-stage membrane module unit 14 is sent to the second space 13 of each membrane module of the first-stage membrane module unit 12 through the pipe 60. In each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized by the pressurization of the pressurization pump 26, and water contained in the first space 11 is allowed to permeate into the second space 13 (concentration step (first stage)).

The concentrated water in the first-stage membrane module unit 12 is sent to the first space 11 of each membrane module in the second-stage membrane module unit 14 through the pipe 42. On the other hand, the dilution water returned from the fifth-stage membrane module unit 20 of the final stage, which will be described later, via the second space 13 of the fourth-stage membrane module unit 18 and the second space 13 of the third-stage membrane module unit 16 passes through the pipe 58 and is sent to the second space 13 of each membrane module of the second-stage membrane module unit 14. In each membrane module of the second-stage membrane module unit 14, the first space 11 is pressurized and water contained in the first space 11 is allowed to permeate into the second space 13 (concentration step (second stage)), as in the first stage.

The concentrated water in the second-stage membrane module unit 14 is sent to the first space 11 of each membrane module in the third-stage membrane module unit 16 through the pipe 44. On the other hand, the dilution water returned from the fifth-stage membrane module unit 20 of the final stage to be described later via the second space 13 of the fourth-stage membrane module unit 18 is sent to the second space 13 of each membrane module of the third-stage membrane module unit 16 through the pipe 56. In each membrane module of the third-stage membrane module unit 16, as in the first and second stages, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (concentration step (third stage)).

The concentrated water in the third-stage membrane module unit 16 is sent to the first space 11 of each membrane module in the fourth-stage membrane module unit 18 through a pipe 46. On the other hand, the dilution water returned from the fifth-stage membrane module unit 20 of the final stage described later is sent to the second space 13 of each membrane module of the fourth-stage membrane module unit 18 through the pipe 54. In each membrane module of the fourth-stage membrane module unit 18, as in the first, second, and third stages, the first space 11 is pressurized, and water contained in the first space 11 is allowed to pass through to the second space 13 (concentration step (fourth stage)).

The concentrated water in the fourth-stage membrane module unit 18 is distributed and sent to the first space 11 and the second space 13 of each membrane module in the fifth-stage membrane module unit 20 at the final stage through the pipe 48. In the fifth-stage membrane module unit 20, the first space 11 is pressurized and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fifth stage)) as in the first to fourth stages. Here, the pressure pump 26, the piping 48, and the like function as supply means for supplying the concentrate of the preceding stage to both the first space and the second space of the semi-permeable membrane module of the final stage.

The concentrated water in the fifth-stage membrane module unit 20 is sent to and stored in the concentrated water tank 22 as needed through the pipe 50 with the valve 32 opened. At least a part of the concentrated water is discharged from the concentrated water tank 22 as treated water to the outside of the system through the pipe 52 by the pump 28. At least a part of the concentrated water may be sent to the treated water tank 10 and mixed with the treated water in the treated water tank 10.

The dilution water in the fifth-stage membrane module unit 20 is sent to the second space 13 of each membrane module in the fourth-stage membrane module unit 18 through the pipe 54. As described above, in each membrane module of the fourth-stage membrane module unit 18, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fourth stage)).

The dilution water in the fourth-stage membrane module unit 18 is sent to the second space 13 of each membrane module in the third-stage membrane module unit 16 through the pipe 56. As described above, in each membrane module of the third-stage membrane module unit 16, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (third stage)).

The dilution water in the third-stage membrane module unit 16 is sent to the second space 13 of each membrane module in the second-stage membrane module unit 14 through a pipe 58. As described above, in each membrane module of the second-stage membrane module unit 14, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (concentration step (second stage)).

The dilution water in the second-stage membrane module unit 14 is sent to the second space 13 of each membrane module in the first-stage membrane module unit 12 through the pipe 60. As described above, in each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (concentration step (first stage)).

The dilution water in the first-stage membrane module unit 12 is sent to and stored in the first dilution water tank 24 through a pipe 62 as needed, and then discharged to the outside of the system through a pipe 64. At least a part of the dilution water may be sent to the water tank 10 to be treated, and mixed with the water to be treated in the water tank 10 to be treated. At least a part of the dilution water may be sent to the second reverse osmosis membrane treatment apparatus 102 as described later, and reverse osmosis membrane treatment may be performed in the second reverse osmosis membrane treatment apparatus 102 (second reverse osmosis membrane treatment step).

By performing the above-described treatment, treated water (final-stage concentrated water) and diluted water in which substances such as total dissolved solid components are concentrated are obtained from treated water containing total dissolved solid components and the like as a treatment target, and volume reduction of the treated water is performed.

In the water treatment method and the water treatment apparatus 1 according to the present embodiment, the flow rate of the concentrate that has passed through the first space of the semi-permeable membrane module of the final stage is measured (first flow rate measurement step), the flow rate of the diluent that has passed through the second space of the semi-permeable membrane module of the first stage is measured (second flow rate measurement step), and the flow rate of the first RO concentrate supplied to the first space of the semi-permeable membrane module of the first stage is adjusted so that the measured value of the flow rate of the concentrate of the final stage and the measured value of the flow rate of the diluent of the first stage become the preset target flow rate values (flow rate adjustment step).

For example, the control device 66 functions as a flow rate adjustment means for adjusting the flow rate of the first RO concentrate supplied to the first space of the semi-permeable membrane module of the first stage so that the measured value of the flow rate of the concentrate in the membrane module unit of the final stage (the membrane module unit 20 of the fifth stage in the example of fig. 1) measured by the first flow rate measurement device 34 and the measured value of the flow rate of the diluent in the membrane module unit of the first stage (the membrane module unit 12 of the first stage in the example of fig. 1) measured by the second flow rate measurement device 36 become predetermined target flow rate values. The controller 66 calculates the drive frequency using, for example, an arbitrary arithmetic expression, outputs a command signal corresponding to the calculated value to the first inverter 30 to control the pressurizing pump 26, and adjusts the flow rate of the first RO concentrate supplied to the first space 11 of the first-stage membrane module unit (in the example of fig. 1, the first-stage membrane module unit 12) so that the measurement values of the first flow rate measuring device 34 and the second flow rate measuring device 36 become the preset target flow rate values.

As a result, in the water concentration treatment using the semipermeable membrane module, even when the volume of the discharged water is reduced by the reverse osmosis membrane method and the water quality of the water to be treated (raw water) fluctuates, stable treatment can be performed.

Specifically, for example, the pressure pump 26 is started to fully open the valve 32 (opening degree 100%), for example, and the output value of the first inverter 30 attached to the pressure pump 26 is gradually increased. When the measured value of the first flow rate measuring device 34 reaches the target flow rate, the valve 32 is closed at, for example, a predetermined arbitrary ratio (for example, the opening degree is 10% with respect to the full opening). Since the measurement value of the first flow rate measuring device 34 decreases, the output of the first inverter 30 of the pressurizing pump 26 is increased until the measurement value of the first flow rate measuring device 34 reaches the target flow rate. When the valve 32 is closed, the measurement value of the second flow rate measuring device 36 increases. Thereafter, the measurement values of the first flow rate measuring device 34 and the second flow rate measuring device 36 may be adjusted to the target flow rates by repeating the operation of increasing the output of the first inverter 30 → increasing the measurement value of the first flow rate measuring device 34 → closing the valve 32 → decreasing the measurement value of the first flow rate measuring device 34 and increasing the measurement value of the second flow rate measuring device 36.

When the recovery rate of the water to be treated changes, for example, the output value of the first inverter 30 and the opening degree of the valve 32 are automatically controlled to change the flow rate of the first RO concentrated water so that the recovery rate of the water to be treated based on the measurement value of the first flow rate measuring device 34 and the measurement value of the second flow rate measuring device 36 (the recovery rate is equal to the second flow rate measurement value/(the first flow rate measurement value + the second flow rate measurement value) × 100) becomes as constant as possible. When the flow rate of the first space measured by the first flow rate measuring device 34 is smaller than the set flow rate, the output value of the first inverter 30 may be fixed and the opening degree of the valve 32 may be increased (that is, the valve is opened). The opening degree of the valve 32 may be adjusted by, for example, repeating the following steps: the flow rate of the first space measured by the first flow rate measuring device 34 is observed for a predetermined time (for example, 1 minute) by opening an arbitrary predetermined ratio (for example, the opening degree is set to 10% with respect to the full opening). Alternatively, the opening degree of the valve 32 may be fixed, and the output value of the first inverter 30 may be increased to increase the flow rate of the first space.

When the flow rate of the first space measured by the first flow rate measuring device 34 is larger than the set flow rate, the opening degree of the valve 32 may be fixed and the output of the first inverter 30 may be reduced. However, when the pressure pump 26 reaches the output lower limit value for the guarantee operation, the opening degree of the valve 32 is decreased (closed valve). The adjustment of the opening degree of the valve 32 may be performed by, for example, repeating the following steps: the flow rate of the first space measured by the first flow rate measuring device 34 is observed for a predetermined time (for example, 1 minute) with an arbitrary predetermined ratio being closed (for example, the opening degree is set to 10% with respect to the full opening). Alternatively, the flow rate of the first space may be reduced by reducing the opening degree of the valve 32 while fixing the output value of the first inverter 30.

When the flow rate of the second space measured by the second flow rate measuring device 36 is less than the set flow rate, the flow rate of the first space is increased, and therefore, the output value of the first inverter 30 may be fixed and the opening degree of the valve 32 may be decreased. Alternatively, the opening degree of the valve 32 may be fixed to increase the output value of the first inverter 30. When the flow rate of the second space measured by the second flow rate measuring device 36 is larger than the set flow rate, the output value of the first inverter 30 may be fixed and the opening degree of the valve 32 may be increased because the flow rate of the first space is decreased. Alternatively, the opening degree of the valve 32 may be fixed, and the output value of the first inverter 30 may be decreased.

The proportional control valve that adjusts the opening degree based on the measurement values of the first flow rate measuring device 34 and the second flow rate measuring device 36 may be provided with one or more than one valve 32 in the piping of the first space 11, for example, in the

piping

106, 42, 44, 46, and 48, may be manually adjusted in the opening degree, or may be automatically adjusted in the opening degree by the control device 66.

In addition to the first flow rate measuring device 34 that measures the flow rate of the concentrate passing through the first space of the membrane module unit of the final stage, one or more flow rate measuring devices that measure the flow rate of the first space 11 may be provided in the piping of the first space 11, for example, the piping 106, 42, 44, 46, and 48.

In addition to the second flow rate measuring device 36 that measures the flow rate of the dilution water passing through the second space of the membrane module unit of the first stage, one or more flow rate measuring devices that measure the flow rate of the second space 13 may be provided in the piping of the second space 13, for example, in the

piping

54, 56, 58, and 60.

In the water treatment apparatus 1, the flow rate of the dilution water passing through the second space of the final-stage membrane module unit may be measured, and the flow rate of the first RO concentrate supplied to the first space of the first-stage membrane module unit and the flow rate of the dilution water supplied to the second space of the preceding stage of the final stage may be adjusted so that the measured value of the flow rate of the final-stage concentrate, the measured value of the flow rate of the first-stage dilution water, and the measured value of the flow rate of the final-stage dilution water become predetermined target flow rate values. Fig. 2 shows a water treatment apparatus having such a structure.

The water treatment apparatus 2 shown in fig. 2 further includes a second dilution water tank 68 in which dilution water from the last-stage membrane module unit (in the example of fig. 2, dilution water from the fifth-stage membrane module unit 20) is stored. In the water treatment apparatus 2, the second space outlet of each membrane module of the fifth-stage membrane module unit 20 and the dilution water inlet of the second dilution water tank 68 are connected by a pipe 76. An outlet of the second dilution water tank 68 and a second space inlet of each membrane module of the fourth-stage membrane module unit 18 are connected in parallel via a second pressurizing pump 70 and a pipe 78. The water treatment apparatus 2 may or may not include the concentrated water tank 22, the pump 28, and the pipe 52. The water treatment apparatus 2 may or may not include the first dilution water tank 24 and the pipe 64.

The dilution water in the fifth-stage membrane module unit 20 is supplied to and stored in the second dilution water tank 68 through the pipe 76, and then supplied from the second dilution water tank 68 to the second space 13 of each membrane module in the fourth-stage membrane module unit 18 through the pipe 78 by the second pressure pump 70. As described above, in each membrane module of the fourth-stage membrane module unit 18, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fourth stage)).

The pipe 76 is provided with a third flow rate measuring device 74 as a third flow rate measuring means for measuring the flow rate of the dilution water passing through the second space of the final-stage membrane module unit (in the example of fig. 2, the fifth-stage membrane module unit 20). The second booster pump 70 is provided at a stage subsequent to the final-stage membrane module unit (in the example of fig. 2, the fifth-stage membrane module unit 20), and is driven at a rotational speed corresponding to an input driving frequency, for example, and is a second booster pump that sucks the dilution water of the final-stage membrane module unit (in the example of fig. 2, the dilution water of the fifth-stage membrane module unit 20) and discharges the dilution water to the previous-stage membrane module unit (in the example of fig. 2, the fourth-stage membrane module unit 18). The second pressure pump 70 is provided with, for example, a second inverter 72 that outputs a drive frequency corresponding to the input command signal to the second pressure pump 70. The locations where the second dilution water tank 68, the second pressurizing pump 70, and the flow rate measuring device 74 are installed are not limited to the positions shown in fig. 2, and may be installed in any of the pipes for dilution water in the middle, for example, any of the

pipes

56, 58, and 60. The water treatment apparatus 2 includes a control device 66, and the control device 66 is connected to the first inverter 30, the second inverter 72, the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 74 by wired or wireless electrical connection or the like. The control device 66 may also be connected to the valve 32 by a wired or wireless electrical connection or the like.

In the water treatment method and the water treatment apparatus 2 according to the present embodiment, the flow rate of the concentrate passing through the first space of the membrane module unit of the final stage is measured (first flow rate measurement step), the flow rate of the dilution water passing through the second space of the membrane module unit of the first stage is measured (second flow rate measurement step), and measuring the flow rate of the dilution water having passed through the second space of the final-stage membrane module unit (third flow rate measuring step), adjusting the flow rate of the first RO concentrated water supplied to the first space of the first-stage membrane module unit and the flow rate of the dilution water supplied to the second space of the preceding-stage membrane module unit, the measured value of the flow rate of the final stage concentrate, the measured value of the flow rate of the first stage dilution water, and the measured value of the flow rate of the final stage dilution water are set to predetermined target flow rate values (flow rate adjustment step).

For example, the control device 66 functions as a flow rate adjustment unit that adjusts the flow rate of the first RO concentrate supplied to the first space of the first-stage membrane module unit and the flow rate of the diluent supplied to the second space of the last-stage membrane module unit so that the measured value of the flow rate of the concentrate of the last-stage membrane module unit (the fifth-stage membrane module unit 20 in the example of fig. 2) measured by the first flow rate measurement device 34, the measured value of the flow rate of the diluent of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 2) measured by the second flow rate measurement device 36, and the measured value of the flow rate of the diluent of the last-stage membrane module unit measured by the third flow rate measurement device 74 become predetermined target flow rate values. The controller 66 calculates the drive frequency using, for example, an arbitrary arithmetic expression, outputs a command signal corresponding to the calculated value to the first inverter 30 to control the pressure pump 26, outputs the command signal to the second inverter 72 to control the second pressure pump 70, and adjusts the flow rates of the first RO concentrate supplied to the first space 11 of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 2) and the dilution water supplied to the second space 13 of the membrane module unit preceding the final stage (the fourth-stage membrane module unit 18 in the example of fig. 2) so that the measurement values of the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 74 become the preset target flow rate values.

As a result, in the water concentration treatment using the semipermeable membrane module, even when the volume of the discharged water is reduced by the reverse osmosis membrane method and the quality of the water to be treated (raw water) fluctuates, more stable treatment can be performed. By storing the dilution water having passed through the second space of the final stage in the second dilution water tank 68, the flow rate can be easily adjusted even when the water balance between the first space and the second space is disrupted due to the change in the quality of the water to be treated. Further, by using the second pressure pump 70 as the second pressure pump for sucking the dilution water of the last-stage membrane module unit and discharging the dilution water to the preceding-stage membrane module unit, even when the pressure required for water passage is insufficient due to an increase in the number of the membrane module units by only the pressure pump 26, the load on the pressure pump 26 can be reduced, and the pressure required for water passage can be suppressed from being insufficient.

Specifically, for example, the pressure pump 26 is started to fully open the valve 32 (opening degree 100%), for example, and the output value of the first inverter 30 attached to the pressure pump 26 is gradually increased. When the measured value of the first flow rate measuring device 34 reaches the target flow rate, the valve 32 is closed at a predetermined arbitrary ratio (for example, the opening degree is set to 10% with respect to the full opening). Since the measured value of the first flow rate measuring device 34 decreases, the output of the first inverter 30 of the pressure pump 26 is increased until the measured value of the first flow rate measuring device 34 reaches the target flow rate. When the valve 32 is closed, the value measured by the third flow rate measuring device 74 is increased. Thereafter, the measurement values of the first flow rate measuring device 34 and the third flow rate measuring device 74 may be adjusted to the target flow rates by repeating the operation of increasing the output of the first inverter 30 → increasing the measurement value of the first flow rate measuring device 34 → closing the valve 32 → decreasing the measurement value of the first flow rate measuring device 34 and increasing the measurement value of the third flow rate measuring device 74. Further, the output value may be set by the second inverter 72 attached to the second pressurizing pump 70, and the measurement value of the second flow rate measuring device 36 may be adjusted to the target flow rate.

When the recovery rate of the water to be treated changes, for example, the output value of the first inverter 30, the output value of the second inverter 72, and the opening degree of the valve 32 are automatically controlled to change the flow rate of the first RO concentrate and the flow rate of the dilution water so that the recovery rate of the water to be treated based on the measurement value of the first flow rate measuring device 34 and the measurement value of the second flow rate measuring device 36 becomes as constant as possible. When the flow rate of the first space measured by the first flow rate measuring device 34 is smaller than the set flow rate, the output value of the first inverter 30 may be fixed and the opening degree of the valve 32 may be increased (that is, the valve is opened). The opening degree of the valve 32 may be adjusted by, for example, repeating the following steps: the flow rate of the first space measured by the first flow rate measuring device 34 is observed for a predetermined time (for example, 1 minute) while closing a predetermined arbitrary ratio (for example, the opening degree is set to 10% with respect to the full opening). Alternatively, the opening degree of the valve 32 may be fixed, and the output value of the first inverter 30 may be increased to increase the flow rate of the first space.

When the flow rate of the first space measured by the first flow rate measuring device 34 is larger than the set flow rate, the opening degree of the valve 32 may be fixed and the output of the first inverter 30 may be reduced. However, when the pressure pump 26 reaches the output lower limit value for the guarantee operation, the opening degree of the valve 32 is decreased (closed valve). The adjustment of the opening degree of the valve 32 may be performed by, for example, repeating the following steps: the first flow rate measuring device 34 measures the flow rate of the first space in a predetermined time (for example, 1 minute) by closing the valve at a predetermined arbitrary ratio (for example, the opening degree is set to 10% with respect to the full opening). Alternatively, the flow rate of the first space may be reduced by reducing the opening degree of the valve 32 while fixing the output value of the first inverter 30.

When the flow rate of the second space measured by the second flow rate measuring device 36 is smaller than the set flow rate, the opening degree of the valve 32 may be fixed and the output value of the second inverter 720 may be increased. When the flow rate of the second space measured by the second flow rate measuring device 36 is larger than the set flow rate, the opening degree of the valve 32 may be fixed and the output value of the second inverter 72 may be decreased.

When the flow rate of the second space measured by the third flow rate measuring device 74 is smaller than the set flow rate, the output value of the first inverter 30 may be fixed and the opening degree of the valve 32 may be decreased because the flow rate of the first space is increased. Alternatively, the opening degree of the valve 32 may be fixed to increase the output value of the first inverter 30. When the flow rate of the second space measured by the third flow rate measuring device 74 is larger than the set flow rate, the flow rate of the first space is decreased, and therefore, the output value of the first inverter 30 may be fixed and the opening degree of the valve 32 may be increased. Alternatively, the opening degree of the valve 32 may be fixed, and the output value of the first inverter 30 may be decreased.

The proportional control valve that adjusts the opening degree based on the measurement values of the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 74 may be provided with one or more than one of the valves 32, for example, the

pipes

106, 42, 44, 46, and 48 in the first space 11, may be manually adjusted to adjust the opening degree, or may be automatically adjusted by the control device 66.

In addition to the first flow rate measuring device 34 that measures the flow rate of the concentrate water that has passed through the first space of the membrane module unit at the final stage and the third flow rate measuring device 74 that measures the flow rate of the dilution water that has passed through the second space of the membrane module unit at the final stage, one or more flow rate measuring devices that measure the flow rate of the first space 11 may be provided in the piping of the first space 11, for example, the piping 106, 42, 44, 46, and 48.

In addition to the second flow rate measuring device 36 that measures the flow rate of the dilution water that has passed through the second space of the membrane module unit of the first stage, one or more flow rate measuring devices that measure the flow rate of the second space 13 may be provided in the piping of the second space 13, for example, in the

piping

78, 56, 58, and 60.

One or more proportional control valves whose opening degrees are adjusted based on the measurement values of the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 74 may be provided in the pipes of the first space 11, for example, the

pipes

106, 42, 44, 46, and 48.

The water treatment apparatus 2 may not be provided with the second dilution water tank 68. Fig. 3 shows a water treatment apparatus having such a structure.

In the water treatment apparatus 3 shown in fig. 3, the pipe 54 is provided with a third flow rate measuring device 84 as third flow rate measuring means for measuring the flow rate of the dilution water passing through the second space of the final-stage membrane module unit (in the example of fig. 3, the fifth-stage membrane module unit 20). The second space outlet of each membrane module of the fifth-stage membrane module unit 20 and the second space inlet of each membrane module of the fourth-stage membrane module unit 18 are connected in parallel by a pipe 54 via a second pressurizing pump 80. The water treatment apparatus 3 may or may not include the concentrated water tank 22, the pump 28, and the pipe 52. The water treatment apparatus 3 may or may not include the first dilution water tank 24 and the pipe 64.

The second booster pump 80 is provided with, for example, a second inverter 82 that outputs a drive frequency corresponding to the input command signal to the second booster pump 80. The water treatment apparatus 3 includes a control device 66, and the control device 66 is connected to the first inverter 30, the second inverter 82, the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 84 by wired or wireless electrical connection or the like. The control device 66 may also be connected to the valve 32 by a wired or wireless electrical connection or the like.

In the water treatment method and the water treatment apparatus 3 according to the present embodiment, the flow rate of the concentrate passing through the first space of the membrane module unit of the final stage is measured (first flow rate measurement step), the flow rate of the dilution water passing through the second space of the membrane module unit of the first stage is measured (second flow rate measurement step), and measuring the flow rate of the dilution water having passed through the second space of the final-stage membrane module unit (third flow rate measuring step), adjusting the flow rate of the first RO concentrated water supplied to the first space of the first-stage membrane module unit and the flow rate of the dilution water supplied to the second space of the preceding-stage membrane module unit, the measured value of the flow rate of the final stage concentrate, the measured value of the flow rate of the first stage dilution water, and the measured value of the flow rate of the final stage dilution water are set to predetermined target flow rate values (flow rate adjustment step).

For example, the control device 66 functions as a flow rate adjustment unit that adjusts the flow rate of the first RO concentrate supplied to the first space of the first-stage membrane module unit and the flow rate of the diluent supplied to the second space of the last-stage membrane module unit so that the measured value of the flow rate of the concentrate of the last-stage membrane module unit (the fifth-stage membrane module unit 20 in the example of fig. 2) measured by the first flow rate measurement device 34, the measured value of the flow rate of the diluent of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 2) measured by the second flow rate measurement device 36, and the measured value of the flow rate of the diluent of the last-stage membrane module unit measured by the third flow rate measurement device 84 become preset target flow rate values. The controller 66 calculates the drive frequency using, for example, an arbitrary calculation formula, outputs a command signal corresponding to the calculated value to the first inverter 30 to control the booster pump 26, and outputs the command signal to the second inverter 82 to control the second booster pump 80, and adjusts the flow rates of the first RO concentrate supplied to the first space 11 of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 2) and the dilution water supplied to the second space 13 of the last-stage membrane module unit (the fourth-stage membrane module unit 18 in the example of fig. 2) such that the measurement values of the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 84 become predetermined target flow rate values.

As a result, in the water concentration treatment using the multistage semipermeable membrane module, even when the volume of the discharged water is reduced by the reverse osmosis membrane method and the quality of the water to be treated (raw water) fluctuates, more stable treatment can be performed. Further, by using the second pressure pump 80 as the second pressure pump for sucking the dilution water of the last-stage membrane module and discharging the dilution water to the preceding-stage membrane module, even if the pressure required for water passage is insufficient due to an increase in the number of the membrane modules by only the pressure pump 26, the load on the pressure pump 26 can be reduced, and the pressure required for water passage can be suppressed from being insufficient.

Fig. 4 schematically shows another example of a water treatment apparatus according to an embodiment of the present invention.

The water treatment apparatus 4 shown in fig. 4 is different from the water treatment apparatus 1 shown in fig. 1 in that: the first space outlet of each membrane module of the fourth-stage membrane module unit 18 and the first space inlet of each membrane module of the fifth-stage membrane module unit 20 are connected in parallel by a pipe 88, and the downstream side of the pump 28 in the pipe 52 and the second space inlet of each membrane module of the fifth-stage membrane module unit 20 are connected in parallel by a pipe 90 via a valve 86.

The water treatment apparatus 4 is as follows: using a multistage membrane module having a first space 11 and a second space 13 partitioned by a semipermeable membrane 15, the first RO concentrate is introduced into the first space 11 of the multistage membrane module in series, the concentrate of the final-stage membrane module is distributed to the second space 13 of the final-stage membrane module (in the example of fig. 4, the fifth-stage membrane module 20), the diluent of the final-stage membrane module is returned to the second space 13 of the preceding-stage membrane module in series, and the water contained in the first space 11 is permeated into the second space 13 by pressurizing the first space 11, thereby concentrating the water. That is, in the water treatment apparatus 4, the first RO concentrated water is concentrated using the semipermeable membrane 15, and the concentrated water is further concentrated using the semipermeable membrane 15 at the next stage. The first RO concentrate is supplied to the first space 11 of the membrane module unit of the first stage (the first-stage membrane module unit 12 in the example of fig. 4), and after the concentrate passes through the first space 11 of the membrane module unit of the final stage (the fifth-stage membrane module unit 20 in the example of fig. 1), at least a part of the concentrate of the final stage is supplied to the second space 13 of the membrane module of the final stage. Then, the dilution water having passed through the second space 13 of the last-stage membrane module is supplied to the second space 13 of the upstream membrane module, and the first space 11 of each-stage membrane module is pressurized to allow the water contained in the first space 11 to permeate into the second space 13.

Specifically, in the water treatment apparatus 4, the water to be treated containing the total dissolved solid content is stored in the water tank 10 to be treated through the pipe 38 as needed, pressurized to 0.1MPa or more by the pressure pump 26 from the water tank 10 to be treated (pressurizing step), and sent to the first reverse osmosis membrane treatment apparatus 100 through the pipe 40. In the first reverse osmosis membrane treatment apparatus 100, the pressurized water to be treated is passed through the first reverse osmosis membrane to obtain a first RO permeate and a first RO concentrate (first reverse osmosis membrane treatment step). The first RO permeate water is discharged through the first RO permeate water pipe 108. As will be described later, at least a part of the first RO permeate may be sent to the third reverse osmosis membrane treatment apparatus 104, and reverse osmosis membrane treatment may be performed in the third reverse osmosis membrane treatment apparatus 104 (third reverse osmosis membrane treatment step).

The first RO-concentrated water is sent to the first space 11 of each membrane module of the first-stage membrane module unit 12 through the first RO-concentrated water pipe 106. On the other hand, the dilution water returned from the fifth-stage membrane module unit 20 of the final stage, which will be described later, via the second space 13 of the fourth-stage membrane module unit 18, the second space 13 of the third-stage membrane module unit 16, and the second space 13 of the second-stage membrane module unit 14 passes through the pipe 60 and is sent to the second space 13 of each membrane module of the first-stage membrane module unit 12. In each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized, and water contained in the first space 11 is allowed to permeate into the second space 13 (concentration step (first stage)).

The concentrated water in the third-stage membrane module unit 16 is sent to the first space 11 of each membrane module in the fourth-stage membrane module unit 18 through a pipe 46. On the other hand, the dilution water returned from the fifth-stage membrane module unit 20 of the final stage described later is sent to the second space 13 of each membrane module of the fourth-stage membrane module unit 18 through the pipe 92. In each membrane module of the fourth-stage membrane module unit 18, as in the first, second, and third stages, the first space 11 is pressurized, and water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fourth stage)).

The concentrated water in the fourth-stage membrane module unit 18 is sent to the first space 11 of each membrane module in the fifth-stage membrane module unit 20 in the final stage through the pipe 88. On the other hand, the concentrated water returned from the fifth-stage membrane module unit 20 of the final stage described later is sent to the second space 13 of each membrane module of the fifth-stage membrane module unit 20 through the pipe 90. In the fifth-stage membrane module unit 20, the first space 11 is pressurized and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fifth stage)) as in the first to fourth stages.

The concentrated water in the fifth-stage membrane module unit 20 is sent to and stored in the concentrated water tank 22 as needed through the pipe 50 with the valve 32 opened. When the valve 86 is closed, at least a part of the concentrated water is discharged from the concentrated water tank 22 to the outside of the system as treated water by the pump 28 through the pipe 52. At least a part of the concentrated water may be sent to the treated water tank 10 and mixed with the treated water in the treated water tank 10.

At least a part of the concentrate of the fifth-stage membrane module unit 20 is sent from the concentrate tank 22 to the second space 13 of each membrane module of the fifth-stage membrane module unit 20 by the pump 28 through the pipe 52 and the pipe 90 with the valve 86 opened. As described above, in each membrane module of the fifth-stage membrane module unit 20, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fifth stage)). Here, the pump 28, the

pipes

52, 90, and the like function as supply means for supplying at least a part of the concentrate of the final stage to the second space of the semi-permeable membrane module of the final stage. As shown in the water treatment apparatus 17 of fig. 10, the concentrated water tank 22 and the pump 28 may be omitted, and the concentrated water in the fifth-stage membrane module unit 20 may be sent to the second space 13 of each membrane module in the fifth-stage membrane module unit 20 through the pipe 50 and the pipe 91 in the open state of the valve 87 by branching off from the pipe 50 at the upstream side of the valve 32 from the first space outlet of each membrane module in the fifth-stage membrane module unit 20 and connecting the pipe 91 to the second space inlet of each membrane module in the fifth-stage membrane module unit 20. The water treatment apparatus 4 may or may not include the first dilution water tank 24 and the pipe 64.

The dilution water in the fifth-stage membrane module unit 20 is sent to the second space 13 of each membrane module in the fourth-stage membrane module unit 18 through a pipe 92. As described above, in each membrane module of the fourth-stage membrane module unit 18, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fourth stage)).

The dilution water in the second-stage membrane module unit 14 is sent to the second space 13 of each membrane module in the first-stage membrane module unit 12 through a pipe 60. As described above, in each membrane module of the first-stage membrane module unit 12, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (first stage)).

In the above-described treatment, treated water (final-stage concentrated water) and dilution water in which substances such as total dissolved solids are concentrated are obtained from treated water containing total dissolved solids and the like to be treated, and the volume of the treated water is reduced.

For example, the control device 66 functions as a flow rate adjustment unit that adjusts the flow rate of the first RO concentrate supplied to the first space of the membrane module unit of the first stage so that the measured value of the flow rate of the concentrate of the membrane module unit of the final stage (the membrane module unit 20 of the fifth stage in the example of fig. 1) measured by the first flow rate measurement device 34 and the measured value of the flow rate of the diluent of the membrane module unit of the first stage (the membrane module unit 12 of the first stage in the example of fig. 1) measured by the second flow rate measurement device 36 become predetermined target flow rate values. The controller 66 calculates the drive frequency using, for example, an arbitrary calculation formula, outputs a command signal corresponding to the calculated value to the first inverter 30 to control the pressurizing pump 26, and adjusts the flow rate of the first RO concentrate supplied to the first space 11 of the first-stage membrane module unit (in the example of fig. 1, the first-stage membrane module unit 12) so that the measurement values of the first flow rate measuring device 34 and the second flow rate measuring device 36 become the preset target flow rate values.

In the water treatment apparatus 4, similarly to the water treatment apparatus 2 shown in fig. 2, the flow rate of the dilution water passing through the second space of the final-stage membrane module unit may be further measured, and the flow rate of the first RO concentrate supplied to the first space of the first-stage membrane module unit and the flow rate of the dilution water supplied to the second space of the preceding stage of the final stage may be adjusted so that the measured value of the flow rate of the final-stage concentrate, the measured value of the flow rate of the first-stage dilution water, and the measured value of the flow rate of the final-stage dilution water become predetermined target flow rate values. Fig. 5 shows a water treatment apparatus having such a structure.

The water treatment apparatus 5 shown in fig. 5 further includes a second dilution water tank 68 that stores dilution water from the final-stage membrane module unit (in the example of fig. 5, dilution water from the fifth-stage membrane module unit 20). In the water treatment apparatus 5, the second space outlet of each membrane module of the fifth-stage membrane module unit 20 and the dilution water inlet of the second dilution water tank 68 are connected by a pipe 94. An outlet of the second dilution water tank 68 and a second space inlet of each membrane module of the fourth-stage membrane module unit 18 are connected in parallel via a second pressurizing pump 70 and a pipe 78. Similarly to the water treatment apparatus 17 in fig. 10, the concentrated water tank 22 and the pump 28 may be omitted, and the concentrated water in the fifth-stage membrane module unit 20 may be sent to the second space 13 of each membrane module in the fifth-stage membrane module unit 20 through the pipe 50 and the pipe 91 in the open state of the valve 87 by branching off from the pipe 50 at the upstream side of the valve 32 from the first space outlet of each membrane module in the fifth-stage membrane module unit 20 and connecting the pipe 91 to the second space inlet of each membrane module in the fifth-stage membrane module unit 20 via the pipe 91 of the valve 87. The water treatment apparatus 5 may or may not include the first dilution water tank 24 and the pipe 64.

The dilution water in the fifth-stage membrane module unit 20 is supplied to and stored in the second dilution water tank 68 through the pipe 94, and then supplied from the second dilution water tank 68 to the second space 13 of each membrane module in the fourth-stage membrane module unit 18 through the pipe 78 by the second pressure pump 70. As described above, in each membrane module of the fourth-stage membrane module unit 18, the first space 11 is pressurized, and the water contained in the first space 11 is allowed to permeate into the second space 13 (the concentration step (fourth stage)).

The pipe 94 is provided with a third flow rate measuring device 74 as third flow rate measuring means for measuring the flow rate of the dilution water passing through the second space of the final-stage membrane module unit (in the example of fig. 5, the fifth-stage membrane module unit 20). The second booster pump 70 is provided at a stage subsequent to the final-stage membrane module unit (in the example of fig. 2, the fifth-stage membrane module unit 20), and is driven at a rotational speed corresponding to an input driving frequency, for example, and is a second booster pump that sucks the dilution water of the final-stage membrane module unit (in the example of fig. 2, the dilution water of the fifth-stage membrane module unit 20) and discharges the dilution water to the previous-stage membrane module unit (in the example of fig. 2, the fourth-stage membrane module unit 18). The second pressure pump 70 is provided with, for example, a second inverter 72 that outputs a drive frequency corresponding to the input command signal to the second pressure pump 70. The locations where the second dilution water tank 68, the second pressure pump 70, and the flow rate measuring device 74 are installed are not limited to the positions shown in fig. 5, and may be installed in any of the pipes for dilution water in the middle, for example, any of the

pipes

56, 58, and 60. The water treatment apparatus 5 includes a control device 66, and the control device 66 is connected to the first inverter 30, the second inverter 72, the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 74 by wired or wireless electrical connection or the like. The control device 66 may also be connected to the valve 32 by a wired or wireless electrical connection or the like.

In the water treatment method and the water treatment apparatus 5 according to the present embodiment, the flow rate of the concentrate passing through the first space of the membrane module unit of the final stage is measured (first flow rate measurement step), the flow rate of the dilution water passing through the second space of the membrane module unit of the first stage is measured (second flow rate measurement step), and measuring the flow rate of the dilution water that has passed through the second space of the final-stage membrane module unit (third flow rate measuring step), the flow rate of the first RO concentrate supplied to the first space of the membrane module unit at the first stage and the flow rate of the dilution water supplied to the second space of the membrane module unit at the preceding stage at the final stage are adjusted, the measured value of the flow rate of the final stage concentrate, the measured value of the flow rate of the first stage dilution water, and the measured value of the flow rate of the final stage dilution water are set to predetermined target flow rate values (flow rate adjustment step).

For example, the control device 66 functions as a flow rate adjustment means for adjusting the flow rate of the first RO concentrate supplied to the first space of the first-stage membrane module unit and the flow rate of the diluent supplied to the second space of the last-stage membrane module unit so that the measured value of the flow rate of the concentrate of the last-stage membrane module unit (the fifth-stage membrane module unit 20 in the example of fig. 5) measured by the first flow rate measurement device 34, the measured value of the flow rate of the diluent of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 5) measured by the second flow rate measurement device 36, and the measured value of the flow rate of the diluent of the last-stage membrane module unit measured by the third flow rate measurement device 74 become predetermined target flow rate values. The controller 66 calculates the drive frequency using, for example, an arbitrary arithmetic expression, outputs a command signal corresponding to the calculated value to the first inverter 30 to control the pressure pump 26, outputs the command signal to the second inverter 72 to control the second pressure pump 70, and adjusts the flow rates of the first RO concentrate supplied to the first space 11 of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 5) and the dilution water supplied to the second space 13 of the membrane module unit preceding the final stage (the fourth-stage membrane module unit 18 in the example of fig. 5) so that the measurement values of the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 74 become the preset target flow rate values.

As a result, in the water concentration treatment using the semipermeable membrane module, even when the volume of the discharged water is reduced by the reverse osmosis membrane method and the quality of the water to be treated (raw water) fluctuates, more stable treatment can be performed. By storing the dilution water having passed through the second space of the final stage in the second dilution water tank 68, the flow rate can be easily adjusted even when the water balance between the first space and the second space is disrupted due to the change in the quality of the water to be treated. Further, by using the second pressure pump 70 as the second pressure pump for sucking the dilution water of the last-stage membrane module and discharging the dilution water to the preceding-stage membrane module, even when the pressure required for water passage is insufficient due to an increase in the number of the membrane modules by only the pressure pump 26, the load on the pressure pump 26 can be reduced, and the pressure required for water passage can be suppressed from being insufficient.

In the water treatment apparatus 5, the second dilution water tank 68 may not be provided, as in the water treatment apparatus 3 shown in fig. 3. Fig. 6 shows a water treatment apparatus having such a structure.

In the water treatment apparatus 6 shown in fig. 6, the pipe 92 is provided with a third flow rate measuring device 84 as third flow rate measuring means for measuring the flow rate of the dilution water passing through the second space of the final-stage membrane module unit (in the example of fig. 6, the fifth-stage membrane module unit 20). The second space outlet of each membrane module of the fifth-stage membrane module unit 20 and the second space inlet of each membrane module of the fourth-stage membrane module unit 18 are connected in parallel by a pipe 92 via a second pressurizing pump 80. Similarly to the water treatment apparatus 17 in fig. 10, the concentrated water tank 22 and the pump 28 may be omitted, and the concentrated water in the fifth-stage membrane module unit 20 may be sent to the second space 13 of each membrane module in the fifth-stage membrane module unit 20 through the pipe 50 and the pipe 91 in the open state of the valve 32 by branching off from the pipe 50 at the upstream side of the valve 32 from the first space outlet of each membrane module in the fifth-stage membrane module unit 20 and connecting the pipe 91 to the second space inlet of each membrane module in the fifth-stage membrane module unit 20 via the valve 87. The water treatment apparatus 6 may or may not include the first dilution water tank 24 and the pipe 64.

The second booster pump 80 is provided with, for example, a second inverter 82 that outputs a drive frequency corresponding to the input command signal to the second booster pump 80. The water treatment device 6 includes a control device 66, and the control device 66 is connected to the first inverter 30, the second inverter 82, the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 84 by wired or wireless electrical connection or the like. The control device 66 may also be connected to the valve 32 by a wired or wireless electrical connection or the like.

In the water treatment method and the water treatment apparatus 6 according to the present embodiment, the flow rate of the concentrate passing through the first space of the membrane module unit of the final stage is measured (first flow rate measurement step), the flow rate of the dilution water passing through the second space of the membrane module unit of the first stage is measured (second flow rate measurement step), and measuring the flow rate of the dilution water that has passed through the second space of the final-stage membrane module unit (third flow rate measuring step), the flow rate of the first RO concentrated water to be supplied to the first space of the membrane module unit of the first stage and the flow rate of the dilution water to be supplied to the second space of the membrane module unit of the preceding stage of the final stage are adjusted, the measured value of the flow rate of the final stage concentrate, the measured value of the flow rate of the first stage dilution water, and the measured value of the flow rate of the final stage dilution water are set to predetermined target flow rate values (flow rate adjustment step).

For example, the control device 66 functions as a flow rate adjustment means for adjusting the flow rate of the first RO concentrate supplied to the first space of the first-stage membrane module unit and the flow rate of the diluent supplied to the second space of the last-stage membrane module unit so that the measured value of the flow rate of the concentrate of the last-stage membrane module unit (the fifth-stage membrane module unit 20 in the example of fig. 6) measured by the first flow rate measurement device 34, the measured value of the flow rate of the diluent of the first-stage membrane module unit (the first-stage membrane module unit 12 in the example of fig. 6) measured by the second flow rate measurement device 36, and the measured value of the flow rate of the diluent of the last-stage membrane module unit measured by the third flow rate measurement device 84 become preset target flow rate values. The controller 66 calculates the drive frequency using, for example, an arbitrary arithmetic expression, outputs a command signal corresponding to the calculated value to the first inverter 30 to control the pressurizing pump 26, outputs the command signal to the second inverter 82 to control the second pressurizing pump 80, and adjusts the flow rates of the first RO concentrate supplied to the first space 11 of the membrane module unit of the first stage (the first-stage membrane module unit 12 in the example of fig. 6) and the dilution water supplied to the second space 13 of the membrane module unit of the preceding stage (the fourth-stage membrane module unit 18 in the example of fig. 6) so that the measurement values of the first flow rate measuring device 34, the second flow rate measuring device 36, and the third flow rate measuring device 84 become the preset target flow rate values.

As a result, in the water concentration treatment using the semipermeable membrane module, even when the volume of the discharged water is reduced by the reverse osmosis membrane method and the water quality of the water to be treated (raw water) fluctuates, more stable treatment can be performed. Further, by using the second pressure pump 80 as the second pressure pump for sucking the dilution water of the last-stage membrane module unit and discharging the dilution water to the preceding-stage membrane module unit, even when the pressure required for water passage is insufficient due to an increase in the number of the membrane module units by only the pressure pump 26, the load on the pressure pump 26 can be reduced, and the pressure required for water passage can be suppressed from being insufficient.

In the water treatment method and the water treatment apparatus according to the present embodiment, the number of stages of the membrane module unit may be determined according to the concentration of target treated water or the like. For example, when it is desired to obtain more concentrated treated water from less concentrated treated water, the number of stages of membrane module units may be increased.

The number of membrane modules in each membrane module unit may be determined by the flow rate of the first RO permeate water, etc.

In the water treatment method and the water treatment apparatus according to the present embodiment, it is preferable that a pressure pump as a pressure means for pressurizing the water to be treated including the total dissolved solid content to 0.1MPa or more is provided only in the preceding stage of the first reverse osmosis membrane treatment apparatus 100. That is, it is preferable that a pressurizing unit (such as a pump) is not provided between the first reverse osmosis membrane treatment apparatus 100 and the first-stage membrane module unit 12, and the first RO concentrated water in the first reverse osmosis membrane treatment apparatus 100 is directly fed to the first-stage membrane module unit 12 by being pressurized by the pressurizing pump 26. By operating the reverse osmosis membrane device and the semipermeable membrane module by 1 pressure pump, the equipment cost, the power cost, the equipment space, and the like can be reduced.

The first reverse osmosis membrane used in the first reverse osmosis membrane treatment apparatus 100 preferably has a membrane surface effective pressure of 1MPa and a membrane surface effective pressure of 0.2 to 0.7m at 25 DEG C ³ /m ² A pure water permeation flux in a range of one day, and has a characteristic of a NaCl removal rate (under a condition that NaCl is 32,000 mg/L) of 99.5% or more at a standard operating pressure. More preferably, the first reverse osmosis membrane has a membrane surface effective pressure of 1MPa and a membrane surface effective pressure of 0.3-0.6 m at 25 DEG C ³ /m ² Pure water permeation flux in the range of/day, and has a characteristic of NaCl removal of 97% or more at standard operating pressure. Under the conditions of the effective pressure of the membrane surface of 1MPa and the temperature of 25 ℃, the permeation flux of pure water is less than 0.2m ³ /m ² Day time, a sufficient RO permeate amount, exceeding 0.7m, may not be obtained ³ /m ² In the case of one day, the RO permeate amount becomes excessive, and membrane clogging may occur.

The first reverse osmosis membrane treatment apparatus 100 may be a multistage reverse osmosis membrane treatment apparatus. In this case, the RO concentrated water of each stage may be passed to the next stage of the reverse osmosis membrane treatment apparatus to perform the reverse osmosis membrane treatment, and the RO concentrated water of the final stage may be sent to the first space 11 of each membrane module of the first-stage membrane module unit 12 as the first RO concentrated water. The RO permeate at each stage may be discharged, and at least a part of the RO permeate may be sent to the third reverse osmosis membrane treatment apparatus 104 as described later, and subjected to reverse osmosis membrane treatment in the third reverse osmosis membrane treatment apparatus 104 (third reverse osmosis membrane treatment step).

The permeate flux of the semipermeable membrane module in the semipermeable membrane treatment step is preferably in the range of 0.005m/d to 0.05m/d, more preferably in the range of 0.015m/d to 0.04m/d, under the conditions of an effective membrane surface pressure of 1MPa and 25 ℃. If the permeate flux of the semipermeable membrane module is less than 0.005m/d under the conditions of the effective membrane surface pressure of 1MPa and 25 ℃, the number of semipermeable membrane modules required may be increased, and if it exceeds 0.05m/d, membrane clogging may occur.

In the water treatment method and the water treatment apparatus according to the present embodiment, it is preferable that the pressure of the first RO-concentrated water immediately after the first reverse osmosis membrane step is 7MPa or more, and the method further includes a pressure reduction step of reducing the pressure of the first RO-concentrated water to less than 7MPa before the semipermeable membrane treatment step (first-stage membrane module unit 12). An example of such a structure is shown in fig. 7.

In the water treatment apparatus 7 of fig. 7, the concentrated water outlet of the first reverse osmosis membrane treatment apparatus 100 and the first space inlet of each membrane module of the first-stage membrane module unit 12 are connected in parallel via a first RO concentrated water pipe 106 via a pressure reducing valve 118 as a pressure reducing means. The other configuration is the same as that of the water treatment apparatus 1 of fig. 1. In the water treatment apparatuses 2 to 6, 17 of fig. 2 to 6, 10, a pressure reducing valve 118 may be provided in the first RO concentrate pipe 106. According to this configuration, the first RO concentrate can be depressurized to a pressure lower than the upper limit of the pressure resistance of the semipermeable membrane module, i.e., 7MPa, before the semipermeable membrane treatment step. In the water treatment apparatus 7, it is preferable that a pressurizing unit (pump or the like) is not provided between the first reverse osmosis membrane treatment apparatus 100 and the first-stage membrane module unit 12, and the first RO concentrated water in the first reverse osmosis membrane treatment apparatus 100 is depressurized by the pressure reducing valve 118 with the pressure pressurized by the pressurizing pump 26 and then is directly fed to the first-stage membrane module unit 12. The water treatment apparatus 7 may or may not include the concentrated water tank 22, the pump 28, and the pipe 52. The water treatment apparatus 7 may or may not include the first dilution water tank 24 and the pipe 64.

The pressure of the first RO concentrated water immediately after the first reverse osmosis membrane step is preferably 7MPa or more, more preferably in the range of 7MPa to 12MPa, and still more preferably in the range of 7MPa to 10 MPa. When the pressure of the first RO concentrated water immediately after the first reverse osmosis membrane step is 7MPa, the first RO concentrated water may not be efficiently concentrated to a high concentration, and the upper limit is preferably 12MPa from the viewpoint of pressure resistance of the reverse osmosis membrane.

From the viewpoint of the pressure resistance of the semipermeable membrane module, the first RO concentrate is preferably depressurized to less than 7MPa, more preferably to a pressure in the range of 3.0MPa to 6.9MPa, before the semipermeable membrane treatment step (first-stage membrane module unit 12).

The pressure reducing unit is not particularly limited as long as it can reduce the pressure of the first RO concentrate, and includes a pressure reducing valve, an orifice, and the like.

The water treatment method and the water treatment apparatus according to the present embodiment may further include a second reverse osmosis membrane treatment step of passing the dilution water through a second reverse osmosis membrane to obtain a second RO permeate and a second RO concentrate. An example of such a structure is shown in fig. 8.

In the water treatment apparatus 8 shown in fig. 8, the outlet of the first dilution water tank 24 and the inlet of the second reverse osmosis membrane treatment apparatus 102 are connected to each other by a pipe 64 via a pump 120. A second RO concentrate pipe 110 is connected to the concentrate outlet of the second reverse osmosis membrane treatment apparatus 102, and a second RO permeate pipe 112 is connected to the permeate outlet. The other configuration is the same as that of the water treatment apparatus 1 of fig. 1. The water treatment apparatuses 2 to 7 and 17 shown in fig. 2 to 7 and 10 may be provided with a second reverse osmosis membrane treatment apparatus 102. The water treatment apparatus 8 may or may not include the concentrated water tank 22, the pump 28, and the pipe 52. The water treatment apparatus 8 may or may not include the first dilution water tank 24. In this case, the pipe 62 may be connected to the pipe 64, and the pump 120 may be provided in the pipe 62 or the pipe 64, or may not be provided.

At least a part of the dilution water is sent to the second reverse osmosis membrane treatment apparatus 102 through the pipe 64 by the pump 120, and reverse osmosis membrane treatment is performed in the second reverse osmosis membrane treatment apparatus 102 to obtain second RO concentrate and second RO permeate (second reverse osmosis membrane treatment step). The second RO permeate obtained by the second reverse osmosis membrane treatment apparatus 102 is discharged to the outside of the system through the second RO permeate pipe 112. The third RO-concentrated water obtained by the reverse osmosis membrane treatment may be discharged to the outside of the system through the second RO-concentrated water pipe 110, or may be sent to the water tank 10 to be treated and mixed with the water to be treated in the water tank 10 to be treated. According to this configuration, the dilution water can be reused as the second RO permeate water.

The water treatment method and the water treatment apparatus according to the present embodiment may further include a third reverse osmosis membrane treatment step of passing at least one of the first RO permeate and the second RO permeate through a third reverse osmosis membrane to obtain a third RO permeate and a third RO concentrate. An example of such a structure is shown in fig. 9.

In the water treatment apparatus 9 of fig. 9, the permeate outlet of the first reverse osmosis membrane treatment apparatus 100 and the inlet of the third reverse osmosis membrane treatment apparatus 104 are connected by a first RO permeate pipe 108. A third RO concentrate pipe 114 is connected to the concentrate outlet of the third reverse osmosis membrane treatment apparatus 104, and a third RO permeate pipe 116 is connected to the permeate outlet. The other configuration is the same as that of the water treatment apparatus 1 of fig. 1. The water treatment apparatuses 2 to 8 and 17 shown in fig. 2 to 8 and 10 may be provided with a third reverse osmosis membrane treatment apparatus 104. The water treatment apparatus 9 may or may not include the concentrated water tank 22, the pump 28, and the pipe 52. The water treatment apparatus 9 may or may not include the first dilution water tank 24 and the pipe 64.

At least a part of the first RO permeate is sent to the third reverse osmosis membrane treatment apparatus 104 through the first RO permeate pipe 108, and reverse osmosis membrane treatment is performed in the third reverse osmosis membrane treatment apparatus 104 to obtain third RO concentrated water and third RO permeate (third reverse osmosis membrane treatment step). The third RO permeate obtained by the third reverse osmosis membrane treatment apparatus 104 is discharged to the outside of the system through a third RO permeate pipe 116. The third RO-concentrated water obtained by the reverse osmosis membrane treatment may be discharged to the outside of the system through the third RO-concentrated water pipe 114, or may be sent to the water tank 10 to be treated and mixed with the water to be treated in the water tank 10 to be treated. According to this configuration, the third RO permeate can be reused.

The water treatment apparatus 8 shown in fig. 8 may further include a reverse osmosis membrane treatment step of passing the second RO permeate through a reverse osmosis membrane to obtain RO permeate and RO concentrate.

Examples of the semipermeable membrane 15 included in the membrane module include semipermeable membranes such as a reverse osmosis membrane (RO membrane), a forward osmosis membrane (FO membrane), and a nanofiltration membrane (NF membrane). The semipermeable membrane is preferably a reverse osmosis membrane, a forward osmosis membrane or a nanofiltration membrane. When a reverse osmosis membrane, a forward osmosis membrane, or a nanofiltration membrane is used as the semipermeable membrane, the pressure of the target solution in the first space 11 is preferably 0.5 to 10.0 MPa.

The material constituting the semipermeable membrane 15 is not particularly limited, and examples thereof include cellulose resins such as cellulose acetate resins, polysulfone resins such as polyether sulfone resins, and polyamide resins. The material constituting the semipermeable membrane 15 is preferably cellulose acetate resin.

Examples of the shape of the semipermeable membrane 15 include a flat membrane, a hollow fiber membrane, and a spiral membrane.

The water to be treated is not particularly limited as long as it contains substances such as Total Dissolved Solids (TDS), and examples thereof include factory wastewater, brine, seawater, chemical waste liquid, and concentrated wastewater after reverse osmosis membrane treatment. The water treatment method and the water treatment apparatus according to the present embodiment can be suitably applied to a case where the TDS (total dissolved solid content) concentration of the water to be treated is, for example, 50000mg/L or more, preferably 60000mg/L or more, and more preferably 100000mg/L or more. The TDS (total dissolved solid content) contains, for example, chlorides such as sodium chloride, carbonates such as calcium carbonate and magnesium carbonate, sulfates such as calcium sulfate and magnesium sulfate, and the like as components.

The water treatment method and the water treatment apparatus according to the present embodiment can be suitably applied to the case where the first RO concentrated water has a sulfate ion concentration of 20000mg/L or more and at least one of a sodium ion and an ammonium ion concentration of 10000mg/L or more. The concentration of the sulfate ion in the first RO concentrated water is preferably 40000mg/L or more, and more preferably in the range of 40000 to 250000 mg/L. The concentration of at least one of sodium ions and ammonium ions in the first RO concentrated water is preferably 20000mg/L or more, and more preferably in the range of 20000 to 100000 mg/L.

(description of reference numerals)

1. 2, 3, 4, 5, 6, 7, 8, 9, 17 water treatment apparatus, 10 treated water tank, 11 first space, 12 first stage membrane module unit, 13 second space, 14 second stage membrane module unit, 15 semi-permeable membrane, 16 third stage membrane module unit, 18 fourth stage membrane module unit, 20 fifth stage membrane module unit, 22 concentrated water tank, 24 first dilution water tank, 26 pressurizing pump, 28, 120 pump, 30 first inverter, 32, 86, 87 valve, 34 first flow rate measuring device, 36 second flow rate measuring device, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 76, 78, 88, 90, 91, 92, 94 piping, 66 control device, 68 second dilution water tank, 70, 80 second pressurizing pump, 72, 82 second inverter, 74, 84 third flow rate measuring device, 100 first reverse osmosis membrane device, 102 second reverse osmosis membrane device, 104 a third reverse osmosis membrane device, 106 a first RO concentrated water pipe, 108 a first RO permeated water pipe, 110 a second RO concentrated water pipe, 112 a second RO permeated water pipe, 114 a third RO concentrated water pipe, 116 a third RO permeated water pipe, and 118 a pressure reducing valve.

Claims

1. A method of water treatment, comprising:

a pressurizing step of pressurizing the water to be treated containing the total dissolved solid content to 0.1MPa or more;

a first reverse osmosis membrane treatment step of introducing the pressurized water to be treated to a first reverse osmosis membrane to obtain a first RO permeate and a first RO concentrate;

a semipermeable membrane treatment step of introducing the first RO concentrate into a first space separated by a semipermeable membrane using a semipermeable membrane module having the first space and a second space, pressurizing the first space by the pressurization in the pressurization step to allow water contained in the first RO concentrate to permeate the semipermeable membrane to obtain concentrated water, and introducing a part of the first RO concentrate or at least a part of the concentrated water into the second space to obtain diluted water; and

and a flow rate adjustment step of measuring the flow rate of the concentrate and the flow rate of the dilution water, and adjusting the flow rate of the concentrate and the flow rate of the dilution water so that the measured values become preset target flow rate values.

2. A method of water treatment, comprising:

a first reverse osmosis membrane treatment step of introducing the pressurized water to be treated to a first reverse osmosis membrane to obtain first RO permeate water and first RO concentrate water;

a semipermeable membrane treatment step of introducing the first RO-concentrated water into a first space of a semipermeable membrane module of a first stage using a semipermeable membrane module having a plurality of stages connected to each other and including a first space and a second space separated by a semipermeable membrane, pressurizing the first space by the pressurization in the pressurization step to allow water contained in the first RO-concentrated water to permeate the semipermeable membrane to obtain concentrated water, further using a semipermeable membrane module of a subsequent stage to obtain concentrated water from the concentrated water, and introducing a part of the first RO-concentrated water, or at least a part of the diluted water obtained from another semipermeable membrane module to a second space of the semipermeable membrane module of each stage to obtain diluted water; and

3. The water treatment method according to claim 1 or 2,

the first reverse osmosis membrane has the effective pressure of 0.2-0.7 m under the conditions that the membrane surface is 1MPa and the temperature is 25 DEG C ³ /m ² A pure water permeation flux in a range of one day and has a characteristic that a NaCl removal rate under a standard operating pressure, which is a NaCl removal rate under a condition that NaCl is 32,000mg/L, is 99.5% or more.

4. The water treatment method according to any one of claims 1 to 3,

the pressure of the first RO-concentrated water immediately after the first reverse osmosis membrane step is 7MPa or more, and the water treatment method further comprises a pressure reduction step of reducing the pressure of the first RO-concentrated water to less than 7MPa before the semipermeable membrane treatment step.

5. The water treatment method according to any one of claims 1 to 4,

the water treatment method further comprises: and a second reverse osmosis membrane treatment step of introducing the dilution water to a second reverse osmosis membrane to obtain a second RO permeate and a second RO concentrate.

6. A water treatment device is characterized by comprising:

a pressurizing unit that pressurizes water to be treated containing a total dissolved solid content to 0.1MPa or more;

a first reverse osmosis membrane treatment unit configured to introduce the pressurized water to be treated into a first reverse osmosis membrane to obtain first RO permeate water and first RO concentrate water;

a semipermeable membrane treatment unit that uses a semipermeable membrane module having a first space and a second space separated by a semipermeable membrane, introduces the first RO-concentrated water into the first space, pressurizes the first space by the pressurization unit, and allows water contained in the first RO-concentrated water to permeate the semipermeable membrane to obtain concentrated water, and introduces a part of the first RO-concentrated water or at least a part of the concentrated water into the second space to obtain diluted water; and

and a flow rate adjusting means for measuring the flow rate of the concentrate and the flow rate of the dilution water and adjusting the flow rate of the concentrate and the flow rate of the dilution water so that the measured values become preset target flow rate values.

7. A water treatment device is characterized by comprising:

a pressurizing unit that pressurizes the water to be treated containing the total dissolved solid content to 0.1MPa or more;

a semipermeable membrane treatment unit that uses semipermeable membrane modules having a first space and a second space separated by a semipermeable membrane and connected in multiple stages, introduces the first RO-concentrated water into the first space of the semipermeable membrane module of the first stage, pressurizes the first space based on the pressurization of the pressurizing unit, and allows water contained in the first RO-concentrated water to permeate the semipermeable membrane to obtain concentrated water, and further uses the semipermeable membrane modules of the subsequent stages to obtain concentrated water, and introduces a part of the first RO-concentrated water, or at least a part of the concentrated water, or at least a part of dilution water obtained from other semipermeable membrane modules into the second space of the semipermeable membrane module of each stage to obtain dilution water; and

8. The water treatment apparatus according to claim 6 or 7,

the first reverse osmosis membrane has the membrane surface effective pressure of 1MPa and the membrane surface effective pressure of 0.2-0.7 m at the temperature of 25 DEG C ³ /m ² Pure water permeation flux in the range of/day, and has a characteristic of NaCl removal rate of 99.5% or more at a standard operating pressure, which is a NaCl removal rate under the condition of NaCl of 32,000 mg/L.

9. The water treatment apparatus according to any one of claims 6 to 8,

the pressure of the first RO concentrated water immediately after the first reverse osmosis membrane unit is 7MPa or more, and the water treatment apparatus further comprises a pressure reducing unit for reducing the pressure of the first RO concentrated water to less than 7MPa in a preceding stage of the semipermeable membrane treatment unit.

10. The water-treating device according to any one of claims 6 to 9,

the water treatment apparatus further includes a second reverse osmosis membrane treatment unit configured to introduce the dilution water to a second reverse osmosis membrane to obtain a second RO permeate and a second RO concentrate.