JP2022016896A - Water treatment method and water treatment device - Google Patents

Abstract

To provide a water treatment method and a water treatment device which can reduce an influence of concentration polarization in concentration treatment of water using a semipermeable membrane module.SOLUTION: A water treatment method comprises: a semipermeable membrane treatment step of using a semipermeable membrane module 12 having a first space 16 and a second space 18 divided by a semipermeable membrane 14 to pass water to be treated including a dissolved solid component through the first space 16 and pressurize the first space 16 to cause the water included in the water to be treated to penetrate the semipermeable membrane 14 to thereby obtain concentrated water while passing a part of the concentrated water through the second space 18, obtaining diluted water; and a circulation step of returning an additional part of the concentrated water to the side of the water to be treated of the semipermeable membrane module 12.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water treatment method and a water treatment apparatus for concentrating water containing a dissolved solid component (TDS) and the like.

In recent years, as a method for reducing the volume of wastewater from factories and the like, an evaporation method using an evaporator and a reverse osmosis method for recovering permeated water using a reverse osmosis membrane to reduce the volume of wastewater are known.

Further, as in Patent Document 1, water is discharged by flowing water to be treated or concentrated water thereof through the first space and the second space partitioned by the semipermeable membrane of the semipermeable membrane module and pressurizing the first space. A method of concentrating is known. Compared with the general reverse osmosis method, such a concentration method using a semipermeable membrane reduces the osmotic pressure difference between the first space and the second space, thereby highly concentrating wastewater with less energy consumption. The volume can be reduced.

However, in such a concentration method using a semipermeable membrane, a phenomenon in which the liquid is concentrated on the membrane surface of the semipermeable membrane and a larger osmotic pressure is applied (that is, when concentrating high-concentration water to be treated). The amount of water that permeates from the first space to the second space of the membrane may decrease due to the influence of concentration polarization). Further, when a multi-stage semipermeable membrane module is used as in Patent Document 1, the concentration of water passing through the first space of the membrane becomes higher toward the latter stage of the membrane unit, and the influence of concentration polarization is large. Therefore, the amount of water permeating from the first space to the second space of the membrane is reduced. As a result, high pressure is required to obtain concentrated water, and the number of membrane units required for concentration increases, leading to an increase in initial cost and running cost.

Japanese Unexamined Patent Publication No. 2018-069198

An object of the present invention is to provide a water treatment method and a water treatment apparatus capable of reducing the influence of concentration polarization in a water concentration treatment using a semipermeable membrane module.

In the present invention, the water to be treated containing a dissolved solid component is passed through the first space by using a semi-transparent module having a first space and a second space partitioned by a semi-permeable film, and the first space is described. Concentrated water is obtained by pressurizing the space and allowing the water contained in the water to be treated to permeate through the semi-permeable film, and a part of the concentrated water is passed through the second space to obtain diluted water. It is a water treatment method including a water-permeable treatment step and a circulation step of returning a part of the concentrated water to the water to be treated side of the semi-transparent module and circulating the water.

In the present invention, the water to be treated containing a dissolved solid component is passed through the first space by using a semi-transparent module having a first space and a second space partitioned by a semi-transparent film, and the first space is described. Concentrated water is obtained by pressurizing the space and allowing the water contained in the water to be treated to permeate through the semi-permeable film, and a part of the water to be treated is passed through the second space to obtain diluted water. It is a water treatment method including a semi-transparent film treatment step and a circulation step of returning at least a part of the concentrated water to the water to be treated side of the semi-transparent film module and circulating the semi-transparent film treatment step.

In the water treatment method, when the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value, the circulating concentration is provided so that the amount of permeated water permeating the semipermeable membrane is within a predetermined range. It is preferable to control the flow rate of water.

In the water treatment method, when the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value, the concentrated water that circulates with respect to the flow rate of the water to be treated supplied to the first space. It is preferable to control the flow rate of the circulating concentrated water so that the flow rate of the water is 200% or more.

In the water treatment method, the predetermined concentration value is preferably a concentration value at which the osmotic pressure of the water to be treated is 5 MPa or more.

In the present invention, the water to be treated containing a dissolved solid component is passed through the first space by using a semi-transparent module having a first space and a second space partitioned by a semi-permeable film, and the first space is described. Concentrated water is obtained by pressurizing the space and allowing the water contained in the water to be treated to permeate through the semi-permeable film, and a part of the concentrated water is passed through the second space to obtain diluted water. It is a water treatment apparatus including a water-permeable treatment means and a circulation means for returning a part of the concentrated water to the water to be treated side of the semi-transparent module and circulating the water.

In the present invention, the water to be treated containing a dissolved solid component is passed through the first space by using a semi-transparent module having a first space and a second space partitioned by a semi-transparent film, and the first space is described. Concentrated water is obtained by pressurizing the space and allowing the water contained in the water to be treated to permeate through the semi-permeable film, and a part of the water to be treated is passed through the second space to obtain diluted water. It is a water treatment apparatus including a semi-transparent film treatment means and a circulation means for returning at least a part of the concentrated water to the water to be treated side of the semi-transparent film module and circulating the semi-transparent film treatment means.

In the water treatment apparatus, when the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value, the circulating concentration is provided so that the amount of permeated water permeating the semipermeable membrane is within a predetermined range. It is preferable to further provide a control means for controlling the flow rate of water.

In the water treatment apparatus, the control means refers to the flow rate of the water to be treated supplied to the first space when the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value. It is preferable to control the flow rate of the circulating concentrated water so that the flow rate of the circulating concentrated water is 200% or more.

In the water treatment apparatus, the predetermined concentration value is preferably a concentration value at which the osmotic pressure of the water to be treated is 5 MPa or more.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a water treatment method and a water treatment apparatus capable of reducing the influence of concentration polarization in a water concentration treatment using a semipermeable membrane module.

It is a schematic block diagram which shows an example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the other example of the water treatment apparatus which concerns on embodiment of this invention. It is a schematic block diagram which shows the water treatment apparatus used in the comparative example 1. FIG. It is a graph which shows the 1st space side (primary side) flow rate (L / min) and the increase rate (%) of the permeation water amount in Examples 2-5.

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.

An outline of an example of the water treatment apparatus according to the embodiment of the present invention is shown in FIG. 1, and the configuration thereof will be described.

The water treatment apparatus 1 shown in FIG. 1 uses a semipermeable membrane module having a first space (concentration side) and a second space (permeation side) partitioned by a semipermeable membrane to prepare a dissolved solid component (TDS) and the like. As a semipermeable membrane treatment means for concentrating the contained water to be treated, for example, a membrane module 12 is provided. The membrane module 12 has a first space 16 and a second space 18 partitioned by a semipermeable membrane 14. The water treatment device 1 may include a water treatment tank 10 for storing water to be treated.

In the water treatment apparatus 1 of FIG. 1, a pipe 22 is connected to the water inlet of the water tank 10 to be treated. The outlet of the water tank 10 to be treated and the first space inlet of the membrane module 12 are connected by a pipe 24 via a pump 20. A pipe 26 is connected to the first space outlet of the membrane module 12. The pipe 28 branched from the pipe 26 is connected to the second space entrance of the membrane module 12. A pipe 30 is connected to the second space outlet of the membrane module 12. The pipe 32 branched from the pipe 26 is connected to the circulating water inlet of the water tank 10 to be treated.

The water treatment device 1 of FIG. 1 uses a film module 12 having a first space 16 and a second space 18 partitioned by a semi-permeable film 14, and allows water to be treated to be transferred from the first space inlet of the film module 12 to the first space. Along with passing water through 16, a part of the concentrated water discharged from the first space outlet of the first space 16 of the membrane module 12 is passed through the second space inlet of the membrane module 12 to the second space 18, and the first is By pressurizing the space 16, the water contained in the water to be treated in the first space 16 is permeated into the second space 18 through the semi-permeable film 14 to concentrate the water. That is, in the water treatment apparatus 1, the water to be treated is concentrated using the semipermeable membrane 14. The water treatment device 1 supplies water to be treated to the first space 16 of the membrane module 12, and supplies a part of the concentrated water obtained from the outlet of the first space 16 to the second space 18 of the membrane module 12. It is a device that performs concentration processing.

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

In the water treatment apparatus 1, the water to be treated containing dissolved solids (TDS) is stored in the water tank 10 to be treated as needed through the pipe 22, and then the film is passed from the water tank 10 to be treated through the pipe 24 by the pump 20. Pressurized liquid is sent from the entrance of the first space of the module 12 to the first space 16 and water is passed therethrough. A part of the water contained in the pressurized water to be treated permeates from the first space 16 to the second space 18 through the semipermeable membrane 14. At this time, since most of the dissolved solid components cannot pass through the semipermeable membrane 14, the water in the first space 16 that did not pass through the semipermeable membrane 14 is concentrated. On the other hand, in the second space 18, a part of the concentrated water passed through the pipe 28 and the permeated water having a low TDS concentration permeated through the semipermeable membrane 14 merge, so that the diluting effect works. The concentrated water obtained in the first space 16 is discharged from the first space outlet through the pipe 26, and a part of the concentrated water is passed through the pipe 28 branched from the pipe 26 and is second from the second space inlet of the membrane module 12. The liquid is sent to the space 18 and water is passed through it. The diluted water obtained in the second space 18 is discharged from the second space outlet through the pipe 30. Here, in the membrane module 12, the first space 16 is pressurized, and the water contained in the water to be treated in the first space 16 is permeated into the second space 18 via the semipermeable membrane 14, and the first space 16 is used. Concentrated water is obtained in (concentration step), and diluted water is obtained in the second space 18 (diluting step). A part of the concentrated water obtained in the first space 16 may be discharged to the outside of the system through the pipe 26. As described above, a part of the concentrated water is sent to and passed through the pipes 26 and 28 to the second space 18 of the membrane module 12, and a further part of the concentrated water is covered with the membrane module 12 through the pipe 32 as circulating water. It is returned to the treated water side, for example, the water tank 10 to be treated and circulated (circulation step). The circulating water may be returned to the pipe 24.

Here, the pump 20, pipes 24, 26, 28, etc. supply the water to be treated to the first space 16 of the semipermeable membrane module 12, and at least a part of the concentrated water obtained from the outlet of the first space 16 is used. It functions as a supply means for supplying the second space 18 of the semipermeable membrane module 12.

The diluted water obtained in the second space 18 may be discharged to the outside of the system through the pipe 30, or may be discharged to the diluted water tank as necessary, stored, and then discharged to the outside of the system. At least a part of the diluted 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 diluted water may be further sent to the reverse osmosis membrane treatment apparatus, and the reverse osmosis membrane treatment may be performed in the reverse osmosis membrane treatment apparatus (reverse osmosis membrane treatment step). The RO permeated water obtained by the reverse osmosis membrane treatment is discharged to the outside of the system. The RO concentrated water obtained by the reverse osmosis membrane treatment 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.

As described above, the treated water (concentrated water) in which the substance such as the dissolved solid component is concentrated and the diluted water are obtained from the treated water containing the dissolved solid component and the like, which is the treatment target, and the treated water is obtained. Volume is reduced.

In the water treatment method and the water treatment apparatus 1 according to the present embodiment, a pipe 32 is provided as a circulation means for returning a part of the concentrated water to the water to be treated side of the membrane module 12 and circulating it. By returning a part of the concentrated water to the water to be treated side of the membrane module 12 and circulating it to increase the amount of water supplied to the first space 16 of the semipermeable membrane module 12, it is possible to reduce the influence of concentration polarization. .. As a result, it is possible to reduce the operating power that gives pressure to obtain concentrated water, which leads to a reduction in initial cost and running cost, and it is possible to provide a low-cost water treatment method and water treatment apparatus.

An outline of another example of the water treatment apparatus according to the embodiment of the present invention is shown in FIG. 2, and the configuration thereof will be described.

The water treatment apparatus 2 shown in FIG. 2 uses a semipermeable membrane module having a first space (concentration side) and a second space (permeation side) partitioned by a semipermeable membrane to control dissolved solid components (TDS) and the like. As a semipermeable membrane treatment means for concentrating the contained water to be treated, for example, a membrane module 12 is provided. The membrane module 12 has a first space 16 and a second space 18 partitioned by a semipermeable membrane 14. The water treatment device 2 may include a water treatment tank 10 for storing water to be treated.

In the water treatment apparatus 2 of FIG. 2, a pipe 22 is connected to the water inlet of the water tank 10 to be treated. The outlet of the water tank 10 to be treated and the first space inlet of the membrane module 12 are connected by a pipe 24 via a pump 20, and the pipe 34 branched from the pipe 24 on the downstream side of the pump 20 in the pipe 24 is the membrane module 12. It is connected to the entrance of the second space. A pipe 26 is connected to the first space outlet of the membrane module 12, and a pipe 36 is connected to the second space outlet of the membrane module 12. The pipe 32 branched from the pipe 26 is connected to the circulating water inlet of the water tank 10 to be treated.

The water treatment device 2 of FIG. 2 uses a membrane module 12 having a first space 16 and a second space 18 partitioned by a semi-permeable membrane 14, and the water to be treated is transferred from the first space inlet of the membrane module 12 to the first space. By passing water from the 16 and the entrance of the second space to the second space 18 and pressurizing the first space 16, the water contained in the water to be treated in the first space 16 is seconded through the semitransparent membrane 14. It is a device that permeates the space 18 to concentrate water. That is, in the water treatment device 2, the water to be treated is concentrated using the semipermeable membrane 14. The water treatment device 2 is a device that supplies water to be treated to both the first space 16 and the second space 18 of the membrane module 12 to perform concentration treatment.

In the water treatment apparatus 2, the water to be treated containing dissolved solids (TDS) is stored in the water tank 10 to be treated as needed through the pipe 22, and then the film is passed from the water tank 10 to be treated through the pipe 24 by the pump 20. Pressurized liquid is sent from the entrance of the first space of the module 12 to the first space 16 and water is passed therethrough. Further, the water to be treated is sent from the second space inlet of the membrane module 12 to the second space 18 through the pipe 34 branched from the pipe 24, and is passed through the water. The concentrated water obtained in the first space 16 is discharged from the first space outlet through the pipe 26, and the diluted water obtained in the second space 18 is discharged from the second space outlet through the pipe 36. Here, in the membrane module 12, the first space 16 is pressurized, and the water contained in the water to be treated in the first space 16 is permeated into the second space 18 via the semipermeable membrane 14, and the first space 16 is used. Concentrated water is obtained in (concentration step), and diluted water is obtained in the second space 18 (diluting step). A part of the concentrated water obtained in the first space 16 may be discharged to the outside of the system through the pipe 26. At least a part of the concentrated water is returned as circulating water through the pipe 32 to the water to be treated side of the membrane module 12, for example, the water tank 10 to be treated (circulation step). The circulating water may be returned on the upstream side of the branch point of the pipe 24 with the pipe 34.

Here, the pump 20, the pipes 24, 34, etc. function as supply means for supplying the water to be treated to both the first space 16 and the second space 18 of the semipermeable membrane module 12.

The diluted water obtained in the second space 18 may be discharged to the outside of the system through the pipe 36, or may be discharged to the diluted water tank as necessary, stored, and then discharged to the outside of the system. At least a part of the diluted 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 diluted water may be further sent to the reverse osmosis membrane treatment apparatus, and the reverse osmosis membrane treatment may be performed in the reverse osmosis membrane treatment apparatus (reverse osmosis membrane treatment step). The RO permeated water obtained by the reverse osmosis membrane treatment is discharged to the outside of the system. The RO concentrated water obtained by the reverse osmosis membrane treatment 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.

As described above, the treated water (concentrated water) in which the substance such as the dissolved solid component is concentrated and the diluted water are obtained from the treated water containing the dissolved solid component and the like, which is the treatment target, and the treated water is obtained. Volume is reduced.

In the water treatment method and the water treatment apparatus 2 according to the present embodiment, at least a part of the concentrated water is returned to the water to be treated side of the membrane module 12, and a pipe 32 is provided as a circulation means for circulation. By returning at least a part of the concentrated water to the water to be treated side of the membrane module 12 and circulating it to increase the amount of water supplied to the first space 16 of the semipermeable membrane module 12, it is possible to reduce the influence of concentration polarization. do. As a result, it is possible to reduce the operating power that gives pressure to obtain concentrated water, which leads to a reduction in initial cost and running cost, and it is possible to provide a low-cost water treatment method and water treatment apparatus.

In the water treatment method and the water treatment apparatus according to the present embodiment, the TDS concentration of the water to be treated at the inlet of the first space 16 of the membrane module 12 is measured, and when the measured TDS concentration exceeds a predetermined concentration value, It is preferable to control the flow rate of the concentrated water (circulating water) that circulates so that the amount of permeated water that permeates the semipermeable membrane 14 from the first space 16 to the second space 18 is within a predetermined range. FIG. 3 shows an example of a water treatment device having such a configuration.

In addition to the same configuration as the water treatment device 2 shown in FIG. 2, the water treatment device 3 shown in FIG. 3 has the water to be treated at the inlet of the first space 16 of the membrane module 12 on the upstream side of the pump 20 in the pipe 24. As a concentration measuring means for measuring the concentration of the dissolved solid component, the concentration measuring device 44 and the first space treated water flow rate measurement for measuring the flow rate (FI1) of the treated water at the inlet of the first space 16 of the membrane module 12. As a means, a water flow rate measuring device 46 to be treated is provided. The pipe 32 is provided with a circulation flow rate measuring device 56 as a circulation flow rate measuring means for measuring the flow rate (FI2) of the circulating concentrated water (circulating water). A blow flow rate measuring device 54 is provided on the downstream side of the branch point of the pipe 26 with the pipe 32 as a blow flow rate measuring means for measuring the flow rate (FI3) of the concentrated water to be blown at the outlet of the first space 16 of the film module 12. .. An additional configuration similar to that of the water treatment device 3 may be added to the water treatment device 1 shown in FIG.

The pump 20 is, for example, a pressurizing pump that is driven at a rotation speed corresponding to an input drive frequency, sucks water to be treated, and discharges it to the membrane module 12. The pump 20 is equipped with, for example, an inverter 42 that outputs a drive frequency corresponding to the input command signal to the pump 20. The valve 60 is provided on the downstream side of the branch point of the pipe 26 with the pipe 32 and on the upstream side of the blow flow rate measuring device 54. The valve 60 is, for example, a proportional control valve that adjusts the opening degree based on the measured values of the water flow rate measuring device 46 to be treated and the blow flow rate measuring device 54. An inlet pressure measuring device 48 is installed on the downstream side of the pump 20 in the pipe 24 as an inlet pressure measuring means for measuring the pressure at the inlet of the first space 16, and is located upstream of the branch point with the pipe 32 in the pipe 26. May be equipped with an outlet pressure measuring device 58 as an outlet pressure measuring means for measuring the pressure at the outlet of the first space 16. The pipe 34 branched from the pipe 24 is connected to the inlet of the second space 18 of the membrane module 12 via the pump 52, and the water to be treated at the inlet of the second space 18 of the membrane module 12 is on the upstream side of the pump 52. As a second space treated water flow rate measuring means for measuring the flow rate (FI4), the treated water flow rate measuring device 50 may be installed.

The water treatment device 3 includes a control device 40 as a control means for controlling the flow rate of concentrated water that circulates so that the amount of permeated water falls within a predetermined range when the concentration of the dissolved solid component exceeds a predetermined concentration value. The control device 40 may be connected to the inverter 42, the concentration measuring device 44, the water flow rate measuring device 46 to be treated, the blow flow rate measuring device 54, the circulating flow rate measuring device 56, the valve 62, or the like by electrical connection or the like. May be. The control device 40 may be connected to the valve 60 by an electrical connection or the like. The control device 40 is composed of, for example, a microcomputer and an electronic circuit composed of a calculation means such as a CPU for calculating a program, a storage means such as a ROM and a RAM for storing the program and the calculation result, and the flow rate of the pump 20. It has a function of controlling the degree of opening / closing of the valve 62.

In the water treatment device 3, in the same manner as in the water treatment device 2, the treated water containing the dissolved solid component and the like to be treated is diluted with the treated water (concentrated water) in which the substance such as the dissolved solid component is concentrated. Water is obtained, and the volume of water to be treated is reduced.

Here, for example, the concentration of the dissolved solid component of the water to be treated at the inlet of the first space 16 of the membrane module 12 is measured by the concentration measuring device 44 (concentration measuring step), and the film is measured by the water flow measuring device 46 to be treated. The flow rate (FI1) of the water to be treated at the inlet of the first space 16 of the module 12 is measured (the flow rate measurement step of the water to be treated in the first space), and the flow rate of concentrated water (FI2) circulated by the circulation flow rate measuring device 56 is measured. It is measured (circulation flow rate measuring step), and the flow rate (FI3) of the concentrated water to be blown at the outlet of the first space 16 of the film module 12 is measured by the blow flow rate measuring device 54 (blow flow rate measuring step). Then, when the concentration of the dissolved solid component measured in the concentration measuring step exceeds a predetermined concentration value, for example, it is measured in the first space processed water flow rate measuring step, the circulating flow rate measuring step, and the blow flow rate measuring step. The flow rate of concentrated water circulating is controlled so that the amount of permeated water permeating from the first space 16 to the second space 18 = FI1- (FI2 + FI3), which is obtained from each flow rate (FI1, FI2, FI3), is within a predetermined range. (Control process).

For example, the control device 40 includes a water flow rate measuring device 46, a circulating flow rate measuring device 56, and a blow flow rate measuring device 54 when the concentration of the dissolved solid component measured by the concentration measuring device 44 exceeds a predetermined concentration value. The drive frequency is calculated using an arbitrary calculation formula so that the permeated water amount = FI1- (FI2 + FI3) obtained from each flow rate (FI1, FI2, FI3) measured by The corresponding command signal may be output to the inverter 42 to control the pump 20, control the open / close degree of the valve 62, and control the flow rate of the circulating concentrated water. The method of obtaining the permeated water amount is not limited to "the method of obtaining the permeated water amount from FI1, FI2, FI3 as FI1- (FI2 + FI3)". For example, a permeated water flow rate measuring device 51 is installed in the pipe 36 which is the outlet of the second space 18 as a permeated water flow rate measuring means, and the flow rate (FI4) of the water to be treated at the inlet of the second space 18 is measured (No. 1). (Two-space treated water flow rate measurement step), the flow rate of permeated water (FI5) at the outlet of the second space 18 is measured (permeated water flow rate measurement step), and the permeated water amount obtained from each flow rate (FI4, FI5) = FI5- The flow rate of the circulating concentrated water may be controlled so that the FI4 is within a predetermined range.

In the water treatment method and the water treatment apparatus 3 according to the present embodiment, the TDS concentration of the water to be treated at the inlet of the first space 16 of the membrane module 12 is measured, and when the predetermined concentration value is exceeded, the valve 62 is opened. The degree is adjusted, and at least a part of the concentrated water is returned to the water to be treated side of the membrane module 12 whose TDS concentration exceeds a predetermined concentration value, circulated, and supplied to the first space 16 of the semipermeable membrane module 12. Increase the amount of water to be treated. As a result, in the water concentration treatment using the semipermeable membrane module, the influence of concentration polarization can be reduced even when the concentration of the dissolved solid component of the water to be treated exceeds a predetermined concentration value.

For example, when the TDS concentration of the water to be treated exceeds a predetermined concentration value, the flow rate of the circulating concentrated water is 200% or more with respect to the flow rate of the water to be treated supplied to the first space 16 of the membrane module 12. It is preferable to control the flow rate of the concentrated water circulated so as to be, and it is more preferable to control the flow rate of the concentrated water circulated so that the flow rate of the circulated concentrated water is 250% or more. If the flow rate of the circulating concentrated water is less than 200%, the influence of concentration polarization may not be mitigated.

For example, the pump 20 is started, and the water to be treated is passed from the water tank 10 to be treated to the first space 16 of the membrane module 12. At this time, the device is operated with the valve 62 fully closed and the valve 60 open. When the TDS concentration of the water to be treated exceeds a predetermined concentration value (for example, 6%), the output value of the inverter 42 is increased by a predetermined ratio (for example, 10%). Since the value (FI3) measured by the blow flow rate measuring device 54 and the permeated water amount (FI1- (FI2 + FI3)) increase, the valve 60 is opened and the valve 62 is opened so that the permeated water amount is within a predetermined range. The opening degrees of the valve 60 and the valve 62 are adjusted. The operation may be repeated until the measured value (FI2) by the circulation flow rate measuring device 56 becomes a predetermined value (for example, 200% or more) with respect to the supply flow rate of the first space 16. When the TDS concentration of the water to be treated is equal to or less than the predetermined concentration value, the valve 62 may be closed and the flow rate of the circulating concentrated water may be adjusted to gradually reduce the concentration, or the valve 62 may be fully closed. , It is not necessary to circulate the concentrated water.

The "predetermined concentration value" of the TDS concentration of the water to be treated is preferably, for example, a concentration value at which the osmotic pressure of the water to be treated is 5 MPa or more, and a concentration value at which the osmotic pressure of the water to be treated is 8 MPa or more. It is more preferable to have. When the osmotic pressure of the water to be treated is a concentration value of less than 5 MPa, the influence of concentration polarization is small and the decrease in the amount of permeated water is slight. For example, when the dissolved solid component is sodium chloride (NaCl), the "predetermined concentration value" of the TDS concentration of the water to be treated is "6% by mass". The osmotic pressure is calculated by the following formula.
Osmotic pressure (MPa) = molar concentration (mol / L) x gas constant (Pa · L / (mol · K)) x absolute temperature (K) x ^10-6

In the water treatment method and the water treatment apparatus according to the present embodiment, a multi-stage semipermeable membrane module may be used. FIG. 4 shows an example of a water treatment device having such a configuration.

The water treatment apparatus 4 shown in FIG. 4 uses a semipermeable membrane module having a first space (concentration side) and a second space (permeation side) partitioned by a semipermeable membrane to control dissolved solid components (TDS) and the like. As a semipermeable membrane treatment means for concentrating the contained water to be treated and further concentrating the concentrated water using a semipermeable membrane module, for example, the first-stage membrane module 12a, the second-stage membrane module 12b, and the third-stage membrane module. 12c is provided. Each membrane module has a first space 16 and a second space 18 partitioned by a semipermeable membrane 14. The water treatment device 4 may include a water tank 10 to be treated for storing concentrated water from the second-stage membrane module 12b, that is, water to be treated of the third-stage membrane module 12c. The water treatment device 4 supplies water to be treated to the first space of the first stage membrane module, and after the concentrated water passes through the first space of the final stage semipermeable membrane module, one of the final stage concentrated water. This is a device that supplies the part to the second space of the semipermeable membrane module in the final stage to perform concentration processing.

In the water treatment apparatus 4 of FIG. 4, a pipe 68 is connected to the first space inlet of the first stage membrane module 12a via a pump 66. The first space outlet of the first-stage membrane module 12a and the first space inlet of the second-stage membrane module 12b are connected by a pipe 70. The first space outlet of the second stage membrane module 12b and the concentrated water inlet of the water tank 10 to be treated are connected by a pipe 72. The outlet of the water tank 10 to be treated and the first space inlet of the third stage membrane module 12c are connected by a pipe 24 via a pump 20. A pipe 26 is connected to the first space outlet of the third stage membrane module 12c via a valve 60. The pipe 28 branched from the upstream side of the valve 60 in the pipe 26 is connected to the second space inlet of the third stage membrane module 12c via the valve 64. The pipe 32, which is the upstream side of the valve 60 in the pipe 26 and is branched from the downstream side of the branch point of the pipe 28, is connected to the circulating water inlet of the water tank 10 to be treated via the valve 62. The second space outlet of the third stage membrane module 12c and the second space inlet of the second stage membrane module 12b are connected by a pipe 74. The second space outlet of the second stage membrane module 12b and the second space inlet of the first stage membrane module 12a are connected by a pipe 76. A pipe 78 is connected to the outlet of the first-stage membrane module 12a.

The water treatment device 4 shown in FIG. 4 is used as a concentration measuring means for measuring the concentration of the dissolved solid component of the water to be treated at the inlet of the first space 16 of the third stage membrane module 12c on the downstream side of the pump 20 in the pipe 24. As a first space treated water flow rate measuring means for measuring the flow rate (FI1) of the treated water at the inlet of the first space 16 of the concentration measuring device 44 and the third stage film module 12c, the treated water flow rate measuring device 46. And prepare. The pipe 32 is provided with a circulation flow rate measuring device 56 as a circulation flow rate measuring means for measuring the flow rate (FI2) of the circulating concentrated water (circulating water). A blow flow rate measuring device 54 is provided on the downstream side of the valve 60 in the pipe 26 as a blow flow rate measuring means for measuring the flow rate (FI3) of the concentrated water to be blown at the outlet of the first space 16 of the third stage film module 12c. A branched concentrated water flow rate measuring device 53 is provided on the downstream side of the valve 64 in the pipe 28 as a branched concentrated water flow rate measuring means for measuring the flow rate of the branched concentrated water. With these configurations, a device that supplies water to be treated to both the first space and the second space of the first-stage semipermeable membrane module, and both the first space and the second space of the final-stage semipermeable membrane module. It may be applied to a device for supplying concentrated water in the previous stage.

The pump 20 is driven, for example, at a rotation speed according to the input drive frequency, and sucks the concentrated water from the second-stage membrane module 12b, that is, the water to be treated of the third-stage membrane module 12c, to suck the third-stage membrane. It is a pressurizing pump that discharges to the module 12c. The pump 20 is equipped with, for example, an inverter 42 that outputs a drive frequency corresponding to the input command signal to the pump 20. The valve 60 is, for example, a proportional control valve that adjusts the opening degree based on the measured values of the water flow rate measuring device 46 to be treated and the blow flow rate measuring device 54.

The water treatment device 4 includes a control device 40 as a control means for controlling the flow rate of concentrated water that circulates so that the amount of permeated water falls within a predetermined range when the concentration of the dissolved solid component exceeds a predetermined concentration value. The control device 40 may include an inverter 42, a concentration measuring device 44, a water flow rate measuring device 46 to be treated, a branched concentrated water flow rate measuring device 53, a blow flow rate measuring device 54, a circulating flow rate measuring device 56, a valve 62, and the like. It may be connected by an electrical connection or the like. The control device 40 may be connected to the valve 60 by an electrical connection or the like. The control device 40 is composed of, for example, a microcomputer and an electronic circuit composed of a calculation means such as a CPU for calculating a program, a storage means such as a ROM and a RAM for storing the program and the calculation result, and the flow rate of the pump 20. It has a function of controlling the degree of opening / closing of the valve 62.

The water treatment device 4 uses a multi-stage membrane module having a first space 16 and a second space 18 partitioned by a semi-permeable film 14, and water to be treated is serialized in the first space 16 of the multi-stage membrane module. , The concentrated water of the final stage membrane module unit is sent to the second space 18 of the final stage membrane module unit (in the example of FIG. 4, the third stage membrane module 12c), and the final stage membrane. The diluted water of the module is passed in series to the second space 18 of the membrane module in the previous stage, and by pressurizing the first space 16, the water contained in the first space 16 is passed through the semi-permeable film 14. It is a device that concentrates water by allowing it to permeate through the two spaces 18. That is, in the water treatment apparatus 4, the water to be treated is concentrated using the semipermeable membrane 14, and the concentrated water is further concentrated using the semipermeable membrane 14 of the next stage. Water to be treated is supplied to the first space 16 of the first-stage membrane module unit (in the example of FIG. 4, the first-stage membrane module 12a), and the first stage (FIG. 4) thereof is supplied to the first space 16 of the final-stage membrane module. In the example of, the concentrated water of the second stage membrane module 12b) is supplied. Then, the diluted water that has passed through the second space 18 of the membrane module in the final stage is supplied to the second space 18 of the membrane module in each stage, and the first space 16 of the membrane module in each stage is pressurized. The water contained in the first space 16 is allowed to permeate through the second space 18.

Specifically, in the water treatment apparatus 4, the water to be treated containing the dissolved solid component (TDS) is sent to the first space 16 of the first stage membrane module 12a through the pipe 68 by the pump 66. On the other hand, the diluted water sent through the second space 18 of the third-stage membrane module 12c and the second space 18 of the second-stage membrane module 12b, which will be described later, passes through the pipe 76 and is the first of the first-stage membrane module 12a. The liquid is sent to the two spaces 18. In the first-stage membrane module 12a, the first space 16 is pressurized and the water contained in the first space 16 is permeated into the second space 18 (concentration step (first stage)).

The concentrated water obtained in the first space 16 of the first-stage membrane module 12a is sent to the first space 16 of the second-stage membrane module 12b through the pipe 70. On the other hand, the diluted water sent through the second space 18 of the third-stage membrane module 12c, which will be described later, is sent to the second space 18 of the second-stage membrane module 12b through the pipe 74. In the same manner as in the first stage, in the second stage membrane module 12b, the first space 16 is pressurized and the water contained in the first space 16 is permeated into the second space 18 (concentration step (second stage). )).

The concentrated water obtained in the first space 16 of the second stage membrane module 12b is stored in the water tank 10 to be treated as needed through the pipe 72, and then from the water tank 10 to be treated through the pipe 24 by the pump 20. Liquid is sent from the entrance of the first space of the step membrane module 12c to the first space 16 and water is passed therethrough. The concentrated water obtained in the first space 16 is discharged from the first space outlet through the pipe 26, and a part of the concentrated water is passed through the pipe 28 branched from the pipe 26 to the second space inlet of the third stage membrane module 12c. Liquid is sent from to the second space 18 and water is passed through. The diluted water obtained in the second space 18 is sent from the outlet of the second space to the second space 18 of the second stage membrane module 12b through the pipe 74. Here, in the third stage membrane module 12c, the first space 16 is pressurized and the water contained in the first space 16 is permeated into the second space 18, and concentrated water is obtained in the first space 16 (concentration). Along with the step (third step)), diluted water is obtained in the second space 18 (dilution step (third step)). With the valves 60 and 64 open and the valve 62 fully closed, a part of the concentrated water obtained in the first space 16 is discharged to the outside of the system through the pipe 26, and a part of the concentrated water is as described above. Liquid is sent and water is passed through the pipes 26 and 28 to the second space 18 of the third stage membrane module 12c. With the valves 60 and 64 open and the valves 62 open, a part of the concentrated water is returned as circulating water to the treated water side of the membrane module 12, for example, the treated water tank 10 and circulated (circulation). Process). The circulating water may be returned to the pipe 24.

Here, the pump 20, pipes 24, 26, 28, etc. supply the water to be treated to the first space 16 of the third stage membrane module 12c, and at least a part of the concentrated water obtained from the outlet of the first space 16. Functions as a supply means for supplying the second space 18 of the third stage membrane module 12c.

The diluted water obtained in the second space 18 of the third-stage membrane module 12c is sent to the second space 18 of the second-stage membrane module 12b through the pipe 74. As described above, in the second stage membrane module 12b, the first space 16 is pressurized and the water contained in the first space 16 is permeated into the second space 18 (concentration step (second stage)).

The diluted water obtained in the second space 18 of the second stage membrane module 12b is sent to the second space 18 of the first stage membrane module 12a through the pipe 76. As described above, in the first-stage membrane module 12a, the first space 16 is pressurized and the water contained in the first space 16 is permeated into the second space 18 (concentration step (first stage)).

The diluted water obtained in the second space 18 of the first-stage membrane module 12a may be discharged to the outside of the system through the pipe 78, or may be sent to the diluted water tank as necessary and stored, and then outside the system. It may be discharged to. At least a part of the diluted water may be mixed with the water to be treated of the first stage membrane module 12a. At least a part of the diluted water may be further sent to the reverse osmosis membrane treatment apparatus, and the reverse osmosis membrane treatment may be performed in the reverse osmosis membrane treatment apparatus (reverse osmosis membrane treatment step). The RO permeated water obtained by the reverse osmosis membrane treatment is discharged to the outside of the system. The RO concentrated water obtained by the reverse osmosis membrane treatment may be mixed with the water to be treated of the first stage membrane module 12a.

As described above, the treated water (concentrated water in the final stage) in which substances such as dissolved solid components are concentrated from the water to be treated containing the dissolved solid components, etc., and the diluted water (first stage), which are the objects to be treated, are used. Diluted water) is obtained, and the volume of the water to be treated is reduced.

Here, for example, the concentration measuring device 44 measures the concentration of the dissolved solid component of the water to be treated at the inlet of the first space 16 of the third stage membrane module 12c (concentration measuring step), and the water flow rate measuring device 46 to be treated. The flow rate (FI1) of the water to be treated at the inlet of the first space 16 of the third stage membrane module 12c is measured (measurement process of the flow rate of the water to be treated), and the flow rate of the concentrated water circulated by the circulation flow rate measuring device 56 ( FI2) is measured (circulation flow rate measuring step), and the flow rate (FI3) of the concentrated water to be blown at the outlet of the first space 16 of the third stage film module 12c is measured by the blow flow rate measuring device 54 (blow flow rate measuring step). ), The branch concentrated water flow rate measuring device 53 measures the flow rate (FI6) of the branched concentrated water at the inlet of the second space 18 of the third stage membrane module 12c (branched concentrated water flow rate measuring step). Then, for example, when the concentration of the dissolved solid component measured in the concentration measuring step exceeds a predetermined concentration value, the treated water flow rate measuring step, the circulating flow rate measuring step, the blow flow rate measuring step, and the branched concentrated water flow rate measuring step. The amount of permeated water permeating from the first space 16 to the second space 18 = FI1- (FI2 + FI3 + FI6) obtained from each flow rate (FI1, FI2, FI3, FI6) measured in the above is circulated so as to be within a predetermined range. Control the flow rate of concentrated water (control process).

For example, the control device 40 includes a water flow rate measuring device 46, a circulating flow rate measuring device 56, and a blow flow rate measuring device 54 when the concentration of the dissolved solid component measured by the concentration measuring device 44 exceeds a predetermined concentration value. , Permeated water amount obtained from each flow rate (FI1, FI2, FI3, FI6) measured by the branched concentrated water flow rate measuring device 53 = FI1- (FI2 + FI3 + FI6) using an arbitrary calculation formula so as to be within a predetermined range. The drive frequency may be calculated, a command signal corresponding to the calculated value may be output to the inverter 42 to control the pump 20, the open / close degree of the valve 62 may be controlled, and the flow rate of the circulating concentrated water may be controlled.

In the water treatment method and the water treatment apparatus 4 according to the present embodiment, the TDS concentration of the water to be treated at the inlet of the first space 16 of the third stage membrane module 12c is measured, and when the predetermined concentration value is exceeded, the valve is used. By adjusting the opening degree of 62, at least a part of the concentrated water is returned to the water to be treated side of the third stage membrane module 12c whose TDS concentration exceeds a predetermined concentration value and circulated to the third stage membrane module 12c. Increase the amount of water supplied to the first space 16. As a result, in the water concentration treatment using the multi-stage semipermeable membrane module, the water passing through the first space of the membrane becomes high concentration, and the final stage membrane module, which tends to be greatly affected by the concentration polarization, is treated. Even when the concentration of the dissolved solid component of water exceeds a predetermined concentration value, the influence of concentration polarization can be reduced.

When a multi-stage membrane module is used, the number of stages of the membrane module may be determined by the concentration of the target treated water or the like. For example, when it is desired to obtain a treatment water having a higher concentration from a water to be treated having a lower concentration, the number of stages of the membrane module unit may be increased. The water treatment method and the water treatment apparatus according to the present embodiment can be suitably applied when a multi-stage membrane module is used.

As the membrane module of each stage, a membrane module unit including a plurality of membrane modules connected in parallel may be used. The number of membrane modules in each membrane module unit may be determined by the flow rate of the water to be treated or the like.

The membrane module of each stage may be provided with a pipe for sending concentrated water from the first space 16 to the second space 18.

A treatment water tank or a dilution water tank may be provided in the membrane module of each stage.

Examples of the semi-permeable membrane 14 included in the membrane module include a semi-permeable membrane 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 water to be treated in the first space 16 is preferably 0.5 to 10.0 MPa.

The material constituting the semipermeable membrane 14 is not particularly limited, and examples thereof include a cellulosic resin such as a cellulose acetate resin, a polysulfone resin such as a polyethersulfone resin, and a polyamide resin. The material constituting the semipermeable membrane 14 is preferably a cellulose acetate-based resin.

Examples of the shape of the semipermeable membrane 14 include a flat membrane, a hollow fiber membrane, and a spiral membrane.

As the concentration measuring means, for example, a conductivity meter, a density meter, an ion densitometer, or the like can be used.

The water to be treated may be water containing a substance such as a dissolved solid component (TDS), and is not particularly limited. For example, factory wastewater, salt water, seawater, chemical waste liquid, concentrated waste water after reverse osmosis membrane treatment, etc. Can be mentioned.

The TDS (dissolved solid component) contains, for example, chlorides such as sodium chloride, carbonates such as calcium carbonate and magnesium carbonate, and sulfates such as calcium sulfate and magnesium sulfate.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

<Example 1>
The treatment was carried out using the water treatment apparatus 3 shown in FIG. As the membrane module, one 5-inch membrane (HP5255SI) manufactured by Toyobo Co., Ltd. was used. Sodium chloride (NaCl) was used as the TDS component. Sodium chloride was added to pure water to prepare test water having a TDS concentration of 6% by mass. The pumps 20 and 52 were started, and the operation was started so that the flow rate (FI1) at the inlet of the membrane module 12 was 5 L / min and the flow rate (FI4) at the inlet of the second space was 1 L / min. Adjust the value of the inverter 42 of the pump 20 and the opening degree of the valve 62 so that the measured values of the pressure (PI1) at the inlet of the first space and the pressure (PI2) at the outlet of the first space are as constant as possible (of the inverter 42). Since the pressure rises when the value is raised, the opening degree of the valve 62 is increased to lower the pressure), and the concentrated water is circulated until the flow rate (FI1) at the inlet of the first space reaches 10 L / min. From the values of the flow rate (FI1), the flow rate of circulating water (FI2), and the flow rate of concentrated water to be blown (FI3) at the inlet of the first space at this time, the concentration ratio (FI1 / FI3) and the permeated water amount (FI1- (FI2 + FI3)). ) Was calculated. The results are shown in Table 1.

<Comparative Example 1>
The treatment was carried out using the water treatment apparatus 5 shown in FIG. The water treatment device 5 is different from the water treatment device 3 in that it does not have a pipe 32 which is a circulation means, a circulation flow rate measuring device 56, and a valve 62. Sodium chloride (NaCl) was used as the TDS component. Sodium chloride was added to pure water to prepare test water having a TDS concentration of 6% by mass. The pumps 20 and 52 were started and operated so that the flow rate (FI1) at the inlet of the membrane module 12 was 10 L / min and the flow rate (FI4) at the inlet of the second space was 1 L / min. The concentration ratio (FI1 / FI3) and the permeated water amount (FI1-FI3) were calculated from the values of the flow rate (FI1) at the inlet of the first space and the flow rate (FI3) of the concentrated water to be blown at this time. The results are shown in Table 1.

In this way, by circulating the concentrated water to increase the flow rate on the first space side as in Example 1, the effect of concentration polarization is affected as compared with the case where the concentrated water is not circulated as in Comparative Example 1. It was possible to reduce the concentration, and it was possible to operate while maintaining a high concentration ratio.

<Example 2>
The treatment was carried out using the water treatment apparatus 3 shown in FIG. Sodium chloride (NaCl) was used as the TDS component. Pure water and sodium chloride were added to the water tank 10 to be treated, and the test water was sequentially prepared so that the NaCl concentration measured and converted by the conductivity meter was 6% by mass. The pumps 20 and 52 were started, and the operation was started so that the flow rate (FI1) at the inlet of the membrane module 12 was 5 L / min and the flow rate (FI4) at the inlet of the second space was 1 L / min. The value of the inverter 42 of the pump 20 and the opening degree of the valve 62 are adjusted so that the measured values of the pressure (PI1) at the inlet of the first space and the pressure (PI2) at the outlet of the first space are as constant as possible, and the first space is adjusted. Concentrated water was circulated until the flow rate (FI1) at the inlet reached 10 L / min. The permeated water amount (FI1- (FI2 + FI3)) was calculated from the values of the flow rate (FI1), the flow rate of circulating water (FI2), and the flow rate of concentrated water to be blown (FI3) at the inlet of the first space at this time. Further, the same operation is performed until the flow rate (FI1) at the first space inlet becomes 20 L / min, and at this time, the flow rate at the first space inlet (FI1), the flow rate of circulating water (FI2), and the flow rate of the concentrated water to be blown. The amount of permeated water was calculated from the value of (FI3). The results are shown in FIG.

<Example 3>
The operation was carried out in the same manner as in Example 2 except that the NaCl concentration was 3% by mass. The results are shown in FIG.

<Example 4>
The operation was carried out in the same manner as in Example 2 except that the NaCl concentration was 10% by mass. The results are shown in FIG.

<Example 5>
The operation was carried out in the same manner as in Example 2 except that the NaCl concentration was 15% by mass. The results are shown in FIG.

FIG. 6 shows the rate of increase in the amount of permeated water with respect to the amount of permeated water (100%) when the flow rate (FI1) at the inlet of the first space is 5 L / min. In particular, when the TDS concentration of the water to be treated was 6% by mass or more, the influence of concentration polarization was reduced by circulating the concentrated water, and a larger amount of permeated water could be obtained. When the NaCl concentration was 3% by mass, the effect of reducing the influence of the concentration polarization by circulating the concentrated water was obtained, but it was slight.

As described above, the water treatment apparatus and the water treatment method of the examples could reduce the influence of concentration polarization in the water concentration treatment using the semipermeable membrane module.

1,2,3,4,5 Water treatment equipment, 10 Water tank to be treated, 12 film module, 12a 1st stage film module, 12b 2nd stage film module, 12c 3rd stage film module, 14 semi-permeable film, 16th 1 space, 18 2nd space, 20, 52, 66 pump, 22, 24, 26, 28, 30, 32, 34, 36, 68, 70, 72, 74, 76, 78 piping, 40 control device, 42 inverter , 44 Concentration measuring device, 46, 50 Processed water flow measuring device, 48 Inlet pressure measuring device, 51 Permeated water flow measuring device, 53 Branch concentrated water flow measuring device, 54 Blow flow measuring device, 56 Circulating flow measuring device, 58 Outlet pressure measuring device, 60, 62, 64 valves.

Claims (10)

Using a semi-transparent module having a first space and a second space partitioned by a semi-transparent film, water to be treated containing a dissolved solid component is passed through the first space, and the first space is pressurized. A semi-transmissive treatment step of obtaining concentrated water by permeating the water contained in the water to be treated through the semi-transparent film and passing a part of the concentrated water through the second space to obtain diluted water. When,
A circulation step in which a part of the concentrated water is returned to the water to be treated side of the semipermeable membrane module and circulated.
A water treatment method comprising. Using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, water to be treated containing a dissolved solid component is passed through the first space, and the first space is pressurized. The semipermeable membrane treatment obtains concentrated water by allowing the water contained in the water to be treated to permeate through the semipermeable membrane, and also passes a part of the water to be treated through the second space to obtain diluted water. Process and
A circulation step in which at least a part of the concentrated water is returned to the water to be treated side of the semipermeable membrane module and circulated.
A water treatment method comprising. The water treatment method according to claim 1 or 2.
When the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value, the flow rate of the circulating concentrated water is controlled so that the amount of permeated water permeating through the semipermeable membrane falls within a predetermined range. A water treatment method characterized by that. The water treatment method according to claim 3.
When the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value, the flow rate of the circulating concentrated water is 200% or more with respect to the flow rate of the water to be treated supplied to the first space. A water treatment method comprising controlling the flow rate of the circulating concentrated water so as to be. The water treatment method according to claim 4.
A water treatment method, wherein the predetermined concentration value is a concentration value at which the osmotic pressure of the water to be treated is 5 MPa or more. Using a semi-transparent module having a first space and a second space partitioned by a semi-transparent film, water to be treated containing a dissolved solid component is passed through the first space, and the first space is pressurized. The semitransparent film treatment means for obtaining concentrated water by allowing the water contained in the water to be treated to permeate the semitransparent film and passing a part of the concentrated water through the second space to obtain diluted water. When,
A circulation means for returning and circulating a part of the concentrated water to the water to be treated side of the semipermeable membrane module.
A water treatment device characterized by being provided with. Using a semipermeable membrane module having a first space and a second space partitioned by a semipermeable membrane, water to be treated containing a dissolved solid component is passed through the first space, and the first space is pressurized. The semipermeable membrane treatment obtains concentrated water by allowing the water contained in the water to be treated to permeate through the semipermeable membrane, and also passes a part of the water to be treated through the second space to obtain diluted water. Means and
A circulation means for returning and circulating at least a part of the concentrated water to the water to be treated side of the semipermeable membrane module.
A water treatment device characterized by being provided with. The water treatment apparatus according to claim 6 or 7.
When the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value, the flow rate of the circulating concentrated water is controlled so that the amount of permeated water permeating through the semipermeable membrane falls within a predetermined range. A water treatment apparatus characterized by further comprising a control means. The water treatment apparatus according to claim 8.
The control means is the concentrated water that circulates with respect to the flow rate of the water to be treated supplied to the first space when the concentration of the dissolved solid component in the water to be treated exceeds a predetermined concentration value. A water treatment apparatus characterized in that the flow rate of the circulating concentrated water is controlled so that the flow rate is 200% or more. The water treatment apparatus according to claim 9.
A water treatment apparatus characterized in that the predetermined concentration value is a concentration value at which the osmotic pressure of the water to be treated is 5 MPa or more.

Images