WO2020022219A1 - Forward osmosis treatment method and forward osmosis treatment device - Google Patents

Abstract

A forward osmosis treatment method which includes a forward osmosis step for moving water contained in the feed solution to the draw solution, by causing a feed solution and a draw solution, which has a higher osmotic pressure than does the feed solution, to contact one another through a semipermeable membrane, wherein: a multi-stage forward osmosis treatment device equipped with a first module group containing one or more forward osmosis modules and a second module group containing one or more forward osmosis modules is used; each of the forward osmosis modules has a semipermeable membrane, a first chamber to which the feed solution is supplied, and a second chamber to which the draw solution is supplied; the first and second chambers are separated by the semipermeable membrane; the first chambers of the one or more forward osmosis modules included in the second module group are connected in series on the downstream side of the first chambers of the one or more forward osmosis modules included in the first module group; and the water recovery rate in the second module group is lower than the water recovery rate in the first module group during the forward osmosis step.

Description

Forward osmosis treatment method and forward osmosis treatment device

The present invention relates to a forward osmosis treatment method and a forward osmosis treatment apparatus.

(4) A forward osmosis treatment method for recovering fresh water from a liquid to be treated (feed solution) such as seawater, river water or wastewater using a forward osmosis phenomenon is known. The phenomenon of forward osmosis (hereinafter sometimes abbreviated as "FO") refers to the phenomenon that water in a low-concentration solution moves through a semipermeable membrane toward a higher-concentration (high osmotic pressure) solution. It is a phenomenon that does.

In the forward osmosis treatment, a draw solution (Draw Solution: sometimes abbreviated as “DS”) having a higher osmotic pressure than a feed solution (hereinafter sometimes abbreviated as “FS”) is used. In a forward osmosis (FO) module, when DS and FS are brought into contact via a semipermeable membrane, water moves from FS having low osmotic pressure to DS having high osmotic pressure. Then, fresh water can be recovered from the DS after passing through the FO module (that is, the DS from which water is recovered from the FS) using various methods.

Here, in order to recover water from FS such as wastewater, the cost is required for pre-treatment of FS and the like, and the processing cost of FS concentrated by FO is required, so that the amount of FS used is small. It is desirable. Therefore, it is desired to increase the recovery rate of water from FS.

However, when water is recovered from the FS (FS is concentrated), if the water recovery rate (or the FS concentration rate) from the FS exceeds a predetermined maximum recovery rate (or the maximum concentration rate), the semi-permeability is increased. Problems such as formation of scale on the film occur. The maximum recovery rate is determined by the water quality of the FS. For this reason, it is necessary to set the water recovery rate from the FS to a predetermined maximum recovery rate or less according to the water quality of the FS so as not to generate scale or the like. Thus, there is a limit to the amount of water that can be recovered from FS by one FO module.

Therefore, in order to increase the water recovery rate from the FS, a multistage forward osmosis treatment apparatus in which a plurality of FO modules are connected in series is being studied.

Patent Document 1 (Japanese Patent Application Laid-Open No. 2014-100224) discloses a conventional forward osmosis treatment apparatus in which FS-side flow paths and DS-side flow paths of a plurality of FO modules are connected in series. In order to solve the problem that the osmotic pressure difference in the module decreases and the water recovery rate decreases, by supplying the same concentration of DS to the FO module at the subsequent stage (instead of the DS after use from the previous stage) independently, In the following FO module, the osmotic pressure difference can be maintained at a high value to improve the water recovery rate.

JP 2014-100624 A

However, in Patent Literature 1, for example, in order to reduce the number of stages in order to reduce the size of the apparatus, the first stage FO module is implemented at a maximum recovery rate at which no scale is generated (water in the first stage FO module is not used). When recovering water from the FS concentrated in the first-stage FO module to the second-stage FO module (using the same concentration of DS as in the first-stage), the scale is increased. Is likely to be generated.

As described above, in the multistage forward osmosis treatment device described in Patent Document 1, when the water recovery rate in the first-stage FO module is increased, there is a problem that scale is generated in the subsequent FO module.

Therefore, the present invention provides a multistage forward osmosis treatment apparatus, which can suppress scale deposition in a subsequent forward osmosis module even when the water recovery rate in the first forward osmosis module is increased. An object of the present invention is to provide a permeation treatment method and a forward permeation treatment device.

[1] Forward osmosis in which water contained in the feed solution is moved into the draw solution by contacting the feed solution with a draw solution having a higher osmotic pressure than the feed solution via a semipermeable membrane. A forward osmosis treatment method including a step,
A multi-stage forward osmosis processing apparatus including a first module group including at least one forward osmosis module and a second module group including at least one forward osmosis module,
Each of the forward osmosis modules has the semipermeable membrane, and a first chamber to which the feed solution is supplied, and a second chamber to which the draw solution is supplied, and the first chamber and the second chamber. The chamber is partitioned by the semi-permeable membrane,
Downstream of a first chamber of at least one forward osmosis module included in the first module group, a first chamber of at least one forward osmosis module included in the second module group is connected in series,
In the forward osmosis step, the forward osmosis treatment method, wherein a water recovery rate in the second module group is lower than a water recovery rate in the first module group.

[2] In the forward osmosis step, the flow rate of the feed solution supplied to at least one forward osmosis module included in the second module group is supplied to at least one forward osmosis module included in the first module group. The forward osmosis treatment method according to [1], wherein the flow rate is larger than the flow rate of the feed solution to be performed.

[3] The first module group includes a plurality of forward osmosis modules,
The first chambers of the plurality of forward osmosis modules included in the first module group are connected in parallel,
The forward osmosis process according to [1] or [2], wherein the number of the plurality of forward osmosis modules included in the first module group is larger than the number of at least one forward osmosis module included in the second module group. Method.

[4] The water recovery rate in the first module group is lower than the water recovery rate at which scale deposition starts to occur at the site where scale deposition is most likely to occur in each of the forward osmosis modules constituting the first module group,
The water recovery rate in the second module group is lower than the water recovery rate at which scale deposition starts to occur at the site where scale deposition is most likely to occur in each of the forward osmosis modules constituting the second module group, [1] to [1]. 3] The forward osmosis treatment method according to any one of the above.

{[5]} The forward osmosis treatment method according to any one of [1] to [4], wherein the feed solution is wastewater.

{[6]} The forward osmosis treatment method according to any one of [1] to [5], wherein the draw solution is seawater.

{[7]} The forward osmosis treatment method according to any one of [1] to [6], wherein the semipermeable membrane is a hollow fiber membrane.

{[8]} The forward osmosis treatment method according to [7], wherein the draw solution is supplied inside the hollow fiber membrane, and the feed solution is supplied outside the hollow fiber membrane.

[9] A multi-stage forward osmosis treatment apparatus including a first module group including a plurality of forward osmosis modules and a second module group including at least one forward osmosis module,
Each of the forward osmosis modules has a semipermeable membrane, and a first chamber to which a feed solution is supplied, and a second chamber to which a draw solution is supplied, wherein the first chamber and the second chamber are Partitioned by the semipermeable membrane,
A first chamber of at least one forward osmosis module included in the second module group is connected in series downstream of a first chamber of each of the plurality of forward osmosis modules included in the first module group. ,
The plurality of first chambers of the plurality of forward osmosis modules included in the first module group are connected in parallel,
The forward osmosis treatment device, wherein the number of the plurality of forward osmosis modules included in the first module group is larger than the number of at least one forward osmosis module included in the second module group.

According to the present invention, in the multistage forward osmosis treatment apparatus, the water recovery rate in the second module group in the subsequent stage is lower than the water recovery rate in the first module group. Even when the water recovery rate is increased, scale precipitation in the forward osmosis module at the subsequent stage can be suppressed.

It is a mimetic diagram for explaining a forward osmosis processing method and a forward osmosis processing device of an embodiment. It is a mimetic diagram showing an example of a forward osmosis treatment method and a forward osmosis treatment device of an embodiment. FIG. 3 is a schematic diagram for explaining the effects of the forward osmosis treatment method and forward osmosis treatment device shown in FIG. 2. 3 is a schematic graph for explaining the effects of the forward osmosis treatment method and forward osmosis treatment device shown in FIG. 2. It is a cross section showing an example of a forward osmosis module (hollow fiber membrane module) used for a forward osmosis processing method and a forward osmosis processing device of an embodiment. FIG. 6 is a schematic graph showing the concentration distribution of FS in the forward osmosis module (hollow fiber membrane module) shown in FIG. 5.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<Forward osmosis treatment device>
First, an example of a forward osmosis treatment apparatus that can be suitably used in the forward osmosis treatment method of the present embodiment will be described.

Referring to FIG. 1, the forward osmosis treatment device of the present embodiment includes a first module group 1 including at least one forward osmosis module 11 and a second module group 2 including at least one forward osmosis module 21. It is a multi-stage forward osmosis treatment device provided.

Each of the forward osmosis modules 11 and 21 includes semipermeable membranes 110 and 210 and first chambers 111 and 211 to which a feed solution (FS) is supplied, and a second chamber 112 to which a draw solution (DS) is supplied. , 212, and the first chambers 111, 211 and the second chambers 112, 212 are separated by semipermeable membranes 110, 210.

Downstream of the first chamber 111 of at least one forward osmosis module 11 included in the first module group 1, the first chamber 211 of at least one forward osmosis module 21 included in the second module group 2 is connected in series. It is connected.

In FIG. 1, FS supplied from the tank 90 passes through the first chamber 111 of the FO module 11, is stored in the tank 91, and is supplied to the first chamber 211 of the FO module 21. Although it is depicted as being stored in the tank 92, this is for visualizing a state in which the amount of FS is decreasing due to water recovery, and the first FO module 11 of the FO module 11 is not provided without the tank 91 or the like. The chamber 111 and the first chamber 211 of the FO module 21 may be directly connected (the same applies to FIG. 2). As described above, the first chamber 111 and the first chamber 211 may be connected indirectly (via the tank 91) as shown in FIG. 2 or may be directly connected.

The second chamber 112 of at least one FO module 11 included in the first module group 1 and the second chamber 212 of at least one FO module 21 included in the second module group 2 are not connected. DS such as seawater is independently supplied to each of the second chamber 112 of the FO module 11 and the second chamber 212 of the FO module 21, and is discharged independently from each of them.

[Forward osmosis module]
The semipermeable membranes 110 and 210 used in the forward osmosis (FO) modules 11 and 21 are not particularly limited, and various known semipermeable membranes that can be used for forward osmosis can be used.

材料 A material constituting the semipermeable membrane is not particularly limited, and examples thereof include a cellulose resin, a polysulfone resin, and a polyamide resin. The semipermeable membrane is preferably made of a material containing at least one of a cellulose resin and a polysulfone resin.

The cellulose resin is preferably a cellulose acetate resin. Cellulose acetate resins have resistance to chlorine, which is a germicide, and can suppress the growth of microorganisms. The cellulose acetate-based resin is preferably cellulose acetate, and more preferably cellulose triacetate from the viewpoint of durability.

The polysulfone resin is preferably a polyethersulfone resin. The polyethersulfone-based resin is preferably a sulfonated polyethersulfone.

形状 The shape of the semipermeable membrane is not particularly limited, but examples include a flat membrane, a spiral membrane, and a hollow fiber membrane. Although FIG. 1 illustrates simplified flat films as the semi-permeable films 110 and 210, the invention is not limited to this. The hollow fiber membrane (hollow fiber type semipermeable membrane) is advantageous in that the membrane area per module can be increased and the efficiency of forward osmosis can be increased as compared with a flat membrane, a spiral membrane, or the like. is there.

The form of the FO modules 11 and 12 is not particularly limited, but when a hollow fiber membrane is used, a module in which a plurality of hollow fiber membranes are arranged in a straight line, or a cross-section in which a plurality of hollow fiber membranes are wound around a core tube. Wind-type modules and the like can be mentioned. When a flat membrane is used, a laminated module in which a plurality of flat membranes are stacked, a spiral module in which a plurality of flat membranes are enveloped and wound around a core tube, and the like are used.

(Hollow fiber membrane module)
Hereinafter, an example of an FO module (hollow fiber membrane module) using a hollow fiber membrane will be described with reference to FIG. The hollow fiber membrane module is a single element type hollow fiber membrane module in which one pressure vessel 7 is loaded with one hollow fiber membrane element. The feed solution (FS) flows outside the hollow fiber membrane 41 and the draw solution (DS) flows inside the hollow fiber membrane 41 (hollow portion). Thus, by taking out the fresh water in the FS to the DS, the DS can be diluted or the FS can be concentrated.

The hollow fiber membrane element includes a porous distribution pipe 5 having a plurality of holes 5a disposed at the center, a plurality of hollow fiber membranes 41 disposed therearound, a porous distribution pipe 5 and a plurality of hollow fiber membranes 41. And resin walls 61 fixed at both ends. Each of the plurality of hollow fiber membranes 41 has openings at both ends.

The hollow fiber membrane element has a DS supply port 71a and a discharge port 71b communicating with the inside of the plurality of hollow fiber membranes 41 and the outside of the hollow fiber membrane module, and the inflow side opening 41a of the hollow fiber membrane 41 has a DS supply port. The outlet 41b is connected to the DS outlet 71b.

The porous distribution pipe 5 is not particularly limited as long as it is a tubular body having a plurality of holes. By the porous distribution pipe 5, for example, FS supplied from the FS supply port 70a into the hollow fiber membrane module can be distributed to the outside 42 of the hollow fiber membrane. The holes are preferably provided radially in each direction. Further, it is preferable that the porous distribution pipe is located at a substantially central portion of the hollow fiber membrane element.

ΔDS flows into the hollow fiber membrane 41 from the inflow side opening 41a through the DS supply port 71a, flows out from the outflow side opening 41b, and flows out through the DS discharge port 71b.

FS flows into the inside of the porous distribution pipe 5 through the FS supply port 70a, flows out of the hole 5a, and is supplied to the outside 42 of the hollow fiber membrane 41. The FS that has passed through the outer side 42 of the hollow fiber membrane 41 flows out through the FS outlet 70b.

Here, the description has been given of the form in which FS is supplied outside the hollow fiber membrane and DS is supplied inside the hollow fiber membrane, but the present invention is not limited to this. That is, DS may be supplied outside the hollow fiber membrane, and FS may be supplied inside the hollow fiber membrane.

<Method of forward osmosis treatment>
The forward osmosis treatment method of the present embodiment is a method of separating and collecting water from a feed solution (FS: liquid to be treated) by forward osmosis using a semipermeable membrane.

In the present embodiment, the feed solution is not particularly limited as long as it is a solution containing water, and examples thereof include seawater, river water, brackish water, and drainage. Examples of the wastewater include industrial wastewater, domestic wastewater, oilfield or gasfield wastewater, and the like. The feed solution is preferably a solution whose use amount is small or whose volume is desired to be reduced for reasons such as the necessity of pretreatment costs and disposal costs. The feed solution is preferably wastewater, more preferably industrial wastewater. The feed solution may contain undissolved components.

The draw solution is not particularly limited as long as it is a liquid having a higher osmotic pressure than the feed solution. Examples of the draw solution include an inorganic salt solution, a sugar solution, and a gas having high solubility in water (such as ammonia and carbon dioxide). , An organic substance, a liquid containing magnetic fine particles or an organic polymer. The draw solution may contain undissolved components.

The forward osmosis treatment method of the present embodiment includes at least the following forward osmosis step.
(Forward osmosis process)
In this step, FS is caused to flow into the first chambers 111 and 211 of the FO modules 11 and 21 so that the FS is brought into contact with the surfaces of the semi-permeable membranes 110 and 210 on the first chamber 111 and 211 sides. , 21 are made to flow into the second chambers 112, 212, and the DS is brought into contact with the surfaces of the semipermeable membranes 110, 210 on the second chamber 112, 212 side. In this state, the water contained in the FS passes through the semi-permeable membranes 110 and 210 from the first chambers 111 and 211 to the second chambers 112 and 212 due to the forward osmosis phenomenon, and moves into the DS.

に お い て In this step, the water recovery rate in the second module group 2 is lower than the water recovery rate in the first module group 1. The “water recovery rate in the first module group” refers to the amount of water recovered in the DS from FS with respect to the amount of FS supplied to the first chamber 111 in the FO module 11 included in the first module group 1. It is a ratio. Similarly, the “water recovery rate in the second module group” refers to the water recovered in the DS from the FS with respect to the amount of FS supplied to the first chamber 211 in the FO module 21 included in the second module group 2. Is the ratio of the quantities.

こ と Thus, by making the water recovery rate in the second module group in the latter stage lower than the water recovery rate in the first module group, scale precipitation in the FO module in the latter stage is less likely to occur. Therefore, in a multistage forward osmosis treatment apparatus, even when the water recovery rate in the first-stage FO module is increased, it is possible to suppress scale deposition in the subsequent FO module.

Further, in this step, when a membrane module having the same performance and shape is used for the forward osmosis module constituting the first module group 1 and the forward osmosis module constituting the second module group 2, it is included in the second module group 2. It is preferable that the flow rate of the feed solution supplied to at least one forward osmosis module 21 is higher than the flow rate of the feed solution supplied to at least one forward osmosis module 11 included in the first module group 1. Thereby, the water recovery rate in the second module group 2 can be made sufficiently lower than the water recovery rate in the first module group 1. In a multistage forward osmosis treatment apparatus, even when the water recovery rate in the first-stage FO module is increased, it is possible to more reliably suppress scale deposition in the subsequent FO module.

水 It is preferable that the water recovery rate in the first module group 1 is lower than the water recovery rate at which scale deposition starts to occur at the site where scale deposition is most likely to occur in each of the forward osmosis modules 11 constituting the first module group 1. Similarly, the water recovery rate in the second module group is lower than the water recovery rate at which scale deposition starts to occur at the site where scale deposition is most likely to occur in each of the forward osmosis modules 21 constituting the second module group. preferable.

For example, referring to FIG. 6, when the FO module is a hollow fiber membrane module as shown in FIG. 5, the concentration distribution of FS in the hollow fiber membrane module is three-dimensional as shown in FIG. Distribution. That is, the concentration of FS is higher toward the outside in the radial direction of the hollow fiber membrane module. This is because the FS discharged from the porous distribution pipe 5 is gradually concentrated by water recovery by DS in the hollow fiber membrane 41 in the process of moving outward in the radial direction. Further, the concentration of FS is higher toward the inlet side in the axial direction of the hollow fiber membrane module. This is because the concentration of DS in the hollow fiber membrane 41 is higher toward the inlet side in the axial direction of the hollow fiber membrane module, and the amount of water recovered from the FS is larger. Therefore, the “portion where scale precipitation is most likely to occur in each of the forward osmosis modules” that constitutes the first module group or the second module group is a portion on the inlet side in the axial direction of the hollow fiber membrane module and on the outside in the radial direction. . If the water recovery rate is set such that scale deposition does not occur in such a portion, scale deposition can be easily prevented in the entire FO module.

FIG. 2 is a schematic diagram showing an example of the forward osmosis treatment method and the forward osmosis treatment device of the embodiment. In the forward osmosis treatment device shown in FIG. 2, the first module group 1 includes a plurality of forward osmosis modules 11, 12, and 13, and the first module group 1 includes a plurality of forward osmosis modules 11, 12, and 13 included in the first module group 1. One room 111, 121, 131 is connected in parallel. Then, the number of the plurality of forward osmosis modules included in the first module group is larger than the number of at least one forward osmosis module included in the second module group.

In FIG. 2, the second module group 2 includes one FO module 21, but is not limited thereto. The second module group 2 also includes a plurality of first chambers connected in parallel. An FO module may be included.

Since the number of FO modules of the first module group is greater than the number of FO modules of the second module group, the number of FO modules of the second module group is downstream of the first chamber of the FO modules of the first module group 1. If one chamber is connected in series, it is not necessary to particularly control the flow rate using a pump or the like, and the flow rate of FS supplied per FO module is higher than that of the first module group 1 in the second module group. 2 and more. Thereby, the water recovery rate in the second module group 2 can be made sufficiently lower than the water recovery rate in the first module group 1. In a multistage forward osmosis treatment apparatus, even when the water recovery rate in the first-stage FO module is increased, it is possible to more reliably suppress scale deposition in the subsequent FO module.

However, the forward osmosis processing apparatus of the present embodiment has the same performance and shape as the forward osmosis module constituting the first module group 1 and the forward osmosis module constituting the second module group 2 as shown in FIG. The size of the FO module 11 and the FO module 21 (diameter and the like), the type of the semipermeable membrane, and the like are different from each other in the embodiment shown in FIG. The water recovery rate in the second module group 1 may be lower than the water recovery rate in the first module group 1. For example, when the diameter of the FO module 11 is larger than that of the FO module 21, the maximum concentration of the feed solution is determined by the size of the diameter. Water can be further recovered by the FO module 21, and the water recovery rate in the second module group 2 can be lower than the water recovery rate in the first module group 1.

FIG. 3 is a schematic diagram for explaining the effects of the forward osmosis treatment method and the forward osmosis treatment device shown in FIG. FIG. 3 is a diagram in which the DS (seawater) flow path is omitted from FIG. 2 and various FS parameters are entered.

As shown in FIG. 3, after the first module group 1 performs water recovery by forward osmosis at the maximum recovery rate (48% by mass) at which no scale is deposited, the water is discharged from the three FO modules 11, 12, and 13. When the FSs collected are collected, the FO module 21 of the second module group 2 can increase the FS flow rate more than the first module group 1. As a result, the recovery rate of the second module group 2 in the FO module 21 is 28% by mass, and the maximum concentration of FS in the FO module is about the same as that of the first module group 1. Therefore, without depositing scale, Water can be recovered from FS (effluent) with high efficiency.

FIG. 4 is a schematic graph for explaining the effect of the forward osmosis treatment method and the forward osmosis treatment device shown in FIG. In FIG. 4, “dilution DS flow rate” means the flow rate of DS (seawater) at the outlet of the FO module per FO module. “FS flow rate” means the flow rate of FS (drainage) at the entrance of the FO module per FO module.

As shown in FIG. 4, according to the forward osmosis treatment method of the embodiment shown in FIG. 2 (graph of “Embodiment [dual (3: 1)]” in FIG. 4), the equivalent production amount (dilution DS) The amount of FS required to obtain the flow rate (FS flow rate) is smaller than the conventional forward osmosis treatment method using only a single FO module (the graph of “conventional [single]] in FIG. 4). I'm done. Therefore, the water recovery rate from FS can be improved.

(Treatment after forward osmosis treatment)
By passing through the second chamber 112, (122, 132,) 212 of the FO module 11, (12, 13,) 21, the water in the DS is recovered from the water in the FS by the forward osmosis phenomenon. Examples of the method for separation and recovery include reverse osmosis treatment and distillation.

In the reverse osmosis (RO) process, the diluted DS discharged from the FO module 1 is boosted to a pressure higher than the osmotic pressure of the diluted DS by the booster pump and supplied to the RO module. The diluted DS supplied to the RO module can pass through the RO membrane to obtain fresh water from the diluted DS. The remaining diluted DS that has not passed through the RO membrane is concentrated, and the concentrated diluted DS can be reused as DS.

In addition, when the draw substance contained in the DS is an inorganic salt, a low-melting substance, or the like, water in the DS may be separated and recovered by crystallization. When the draw material is a gas having high solubility in water, the water in the DS may be separated and recovered by gas release. When the draw substance is magnetic fine particles, water in the DS may be separated and recovered by magnetic separation. When the draw substance is a sugar solution, water in the DS may be separated and recovered by an RO membrane or an NF membrane.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 {first module group, 11, 12, 13} forward osmosis (FO) module, 110, 120, 130} semi-permeable membrane, 111, 121, 131 {first chamber, 112, 122, 132} second chamber, 2} second module group , 21 forward osmosis (FO) module, 210 semi-permeable membrane, 211 first chamber, 212 second chamber, 41 hollow fiber membrane, 41a inlet side opening, 41b outlet side opening, 42 outside of hollow fiber membrane, 5 perforated Distribution pipe, 5a hole, 6 resin wall, 7 vessel, 70a FS supply port, 70b FS discharge port, 71a DS supply port, 71b DS discharge port, 90, 91, 92 tank.

Claims (9)

A forward osmosis step of moving water contained in the feed solution into the draw solution by contacting the feed solution with a draw solution having a higher osmotic pressure than the feed solution through a semipermeable membrane. , A forward osmosis treatment method,
A multi-stage forward osmosis processing apparatus including a first module group including at least one forward osmosis module and a second module group including at least one forward osmosis module,
Each of the forward osmosis modules has the semipermeable membrane, and a first chamber to which the feed solution is supplied, and a second chamber to which the draw solution is supplied, and the first chamber and the second chamber. The chamber is partitioned by the semi-permeable membrane,
Downstream of a first chamber of at least one forward osmosis module included in the first module group, a first chamber of at least one forward osmosis module included in the second module group is connected in series,
In the forward osmosis step, the forward osmosis treatment method, wherein a water recovery rate in the second module group is lower than a water recovery rate in the first module group. In the forward osmosis step, the flow rate of the feed solution supplied to at least one forward osmosis module included in the second module group is supplied to at least one forward osmosis module included in the first module group. The forward osmosis treatment method according to claim 1, wherein the flow rate is larger than the flow rate of the feed solution. The first module group includes a plurality of forward osmosis modules,
The first chambers of the plurality of forward osmosis modules included in the first module group are connected in parallel,
The forward osmosis treatment method according to claim 2, wherein the number of the plurality of forward osmosis modules included in the first module group is larger than the number of at least one forward osmosis module included in the second module group. The water recovery rate in the first module group is lower than the water recovery rate at which scale precipitation starts to occur at a site where scale precipitation most easily occurs in each of the forward osmosis modules constituting the first module group,
4. The water recovery rate in the second module group is lower than the water recovery rate at which scale precipitation starts to occur at a site where scale deposition is most likely to occur in each of the forward osmosis modules constituting the second module group. The forward osmosis treatment method according to any one of the above. 正 The forward osmosis treatment method according to any one of claims 1 to 4, wherein the feed solution is wastewater. The forward osmosis treatment method according to any one of claims 1 to 5, wherein the draw solution is seawater. 正 The forward osmosis treatment method according to any one of claims 1 to 6, wherein the semipermeable membrane is a hollow fiber membrane. The forward osmosis treatment method according to claim 7, wherein the draw solution is supplied inside the hollow fiber membrane, and the feed solution is supplied outside the hollow fiber membrane. A multi-stage forward osmosis treatment device including a first module group including a plurality of forward osmosis modules and a second module group including at least one forward osmosis module,
Each of the forward osmosis modules has a semipermeable membrane, and a first chamber to which a feed solution is supplied, and a second chamber to which a draw solution is supplied, wherein the first chamber and the second chamber are Partitioned by the semipermeable membrane,
A first chamber of at least one forward osmosis module included in the second module group is connected in series downstream of a first chamber of each of the plurality of forward osmosis modules included in the first module group. ,
The plurality of first chambers of the plurality of forward osmosis modules included in the first module group are connected in parallel,
The forward osmosis treatment device, wherein the number of the plurality of forward osmosis modules included in the first module group is larger than the number of at least one forward osmosis module included in the second module group.

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