JP2020138114A - Liquid treatment device and liquid treatment method - Google Patents

Abstract

To provide a liquid treatment device and a liquid treatment method using a positive permeable membrane, which can suppress solute from inversely leaking from a draw solution side toward liquid to be treated (a feed solution) side.SOLUTION: A liquid treatment device 1 comprises: a treatment part 4 having a first chamber 1 and a second chamber 2 partitioned by a positive permeable membrane 3; a first flow path L1 through which liquid to be treated is supplied to the first chamber 1; a second flow path L2 through which a draw solution higher in osmotic pressure than the liquid to be treated is supplied to the second chamber 2; a third flow path L3 through which the concentrated liquid to be treated in the first chamber 1 is discharged after some moisture of the liquid to be treated are transmitted from the first chamber 1 to the second chamber 2 through the positive permeable membrane 3; and a fourth flow path L4 through which diluted draw solution in the second chamber 2 is discharged after some moisture of the liquid to be treated is transmitted from the first chamber 1 to the second chamber 2 through the positive permeable membrane 3, where intermembrane pressure difference between the first chamber 1 and the second chamber 2 is larger than 0 MPa and is equal to 0.06 MPa or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a liquid processing apparatus and a processing method using a forward osmosis membrane.

The membrane separation method has been conventionally used as a technique for separating and recovering fresh water from seawater or concentrating a liquid containing water. As the membrane separation method, a FO method using a forward osmosis Membrane (FO membrane) and an RO method using a reverse osmosis Membrane (RO membrane) are known.

By separating the solution with low osmotic pressure and the solution with high osmotic pressure by a semipermeable membrane, water permeates from the solution side with low osmotic pressure to the solution side with high osmotic pressure due to the difference in osmotic pressure between the two solutions. The FO method utilizes the phenomenon that water permeates due to this osmotic pressure difference.

On the other hand, in the RO method, a solution with low osmotic pressure and a solution with high osmotic pressure are separated by a semi-permeable film, and a high pressure exceeding the osmotic pressure difference between the two solutions is applied to the solution side with high osmotic pressure to increase the osmotic pressure. This is a technique for allowing water to permeate backward from the high solution side to the low osmotic solution side. Since the RO method applies a high pressure exceeding the osmotic pressure difference to cause reverse osmosis, a very high energy is required. Therefore, attention has been paid to the FO method in which the osmotic pressure difference is used as the driving force without applying pressure for the permeation of water.

However, in the FO method, a reverse leakage phenomenon occurs in which a solute contained in a solution having a high osmotic pressure (draw solution) leaks to a solution having a low osmotic pressure (feed solution) via a semipermeable membrane. This reverse leakage phenomenon is caused by the formulas (3) and (4) described in P47 of Non-Patent Document 1, the formulas (2) and (3) described in P96 of Non-Patent Document 2, and further to the left of P116 of Non-Patent Document 3. Based on the description in column 5-7, if the amount of permeated water that permeates the forward osmosis membrane or the permeated flux of water is increased by applying a pressure higher than that of the draw solution to the feed solution, the amount of back leakage of the solute also increases. It is generally recognized by those skilled in the art that the increase will occur. When the back leakage phenomenon occurs, the solute contained in the draw solution is mixed in the feed solution. Therefore, when the FO method is used for concentrating, for example, beverages, liquid foods, liquid cosmetics, etc., there is a problem that the quality of the feed solution as the raw material solution is deteriorated. Further, since the solute flows out on the draw solution side, a loss of the solute is caused, and the draw solution needs to be replenished by the amount of the loss, which causes a problem that the cost increases.

As described in paragraph 0020 of Patent Document 1, the above-mentioned back leakage phenomenon can be made less likely to occur by making the solute of the draw solution having a high molecular weight. However, when the molecular weight of the solute becomes large, the viscosity of the draw solution becomes high, so that a high pressure is required to feed the draw solution, and there is a problem that the load of the liquid feed pump increases.

JP-A-2018-158300

Shingo Terashima, 5 others, "Penetration characteristics of freshwater flow in hollow fiber type forward osmosis membrane module", Nagasaki University Graduate School of Engineering Research Report Vol. 45, No. 84, January 2015, P44-50 Masahiro Yasukawa, 2 others, "Development of water permeability analysis method for hollow fiber membrane type forward osmosis membrane", Bulletin of the Society of Sea Water Science, Japan, 68, 94-101 (2014) Tomoki Takahashi, 2 others, "Concentration characteristics of latex particles using forward osmosis method", Bulletin of the Society of Sea Water Science, Japan, 69, 111-117 (2015)

The present invention has been made to solve the above problems, and is a liquid treatment apparatus and a liquid treatment method using a forward osmosis membrane, in which the solute is reversed from the draw solution side to the liquid to be treated (feed solution) side. It is an object of the present invention to provide a liquid treatment apparatus and a liquid treatment method capable of suppressing leakage.

As a result of diligent studies to solve the above problems, the present inventor applies a pressure higher than that of the draw solution to the solution to be treated (feed solution), and the solute contained in the draw solution is covered through the forward osmosis membrane. Although it was generally recognized by those skilled in the art that a reverse leakage phenomenon that leaked to the treatment solution side occurred, the solution to be treated was continuously applied at a slightly higher pressure within a range in which the amount of permeated water did not change significantly compared to the draw solution. It has been found that the amount of back leakage of the solute leaking from the draw solution side to the object to be treated side can be suppressed by applying pressure. The present invention has been completed as a result of further research based on such findings.

That is, in the present invention, the processing unit having the first chamber and the second chamber separated by the forward osmosis membrane, the first flow path for supplying the solution to be treated to the first chamber, and the subject to the second chamber. After the second flow path for supplying a draw solution having a higher osmotic pressure than the treatment liquid and a part of the water content of the liquid to be treated have permeated from the first chamber to the second chamber via the forward osmosis membrane. After the third flow path for discharging the concentrated solution to be treated in the first chamber and a part of the water content of the solution to be treated have permeated from the first chamber to the second chamber via the forward osmosis membrane. It is provided with a fourth flow path for discharging the diluted draw solution in the second chamber, and a pressure higher than that of the draw solution passing through the second chamber is applied to the liquid to be treated passing through the first chamber. Provided is a liquid processing apparatus in which the pressure difference between the membranes between the first chamber and the second chamber is set to 0.06 MPa or less, which is larger than 0 MPa so as to be continuously applied.

In the liquid processing apparatus of the present invention, the pressure difference between the membranes between the first chamber and the second chamber is preferably 0.01 MPa or more and 0.03 MPa or less.

In the liquid processing apparatus of the present invention, a measuring means for measuring the intermembrane pressure difference, a setting means for setting the intermembrane pressure difference, the measuring means, and a control means connected to the setting means. It is preferable that the control means adjusts the pressure difference between the membranes by receiving a signal from the measuring means and controlling the operation of the setting means.

Further, in the present invention, the liquid to be treated is supplied to the first chamber of the treatment unit having the first chamber and the second chamber partitioned by the forward osmosis membrane, while the second chamber is more permeated than the liquid to be treated. In a liquid treatment method in which a part of the water content of the liquid to be treated is permeated from the first chamber to the second chamber via the forward osmosis membrane by supplying a draw solution having a high pressure, the solution passes through the first chamber. The pressure difference between the membranes between the first chamber and the second chamber is larger than 0 MPa so that a pressure higher than that of the draw solution passing through the second chamber is continuously applied to the liquid to be treated. A liquid treatment method set to .06 MPa or less is provided.

In the liquid treatment method of the present invention, the pressure difference between the membranes between the first chamber and the second chamber is preferably 0.01 MPa or more and 0.03 MPa or less.

According to the present invention, it is possible to suppress the amount of back leakage of the solute that leaks from the draw solution side through the forward osmosis membrane to the liquid to be treated (feed solution) side.

It is a schematic diagram which shows the schematic structure of the liquid processing apparatus of one Embodiment of this invention. It is a schematic diagram which shows the schematic structure of the liquid processing apparatus of another embodiment of this invention. It is a graph which shows the relationship between the pressure difference between membranes and the amount of back leakage and the amount of permeated water. It is a graph which shows the relationship between the pressure difference between membranes and the amount of back leakage and the amount of permeated water.

Hereinafter, the actual form of the present invention will be described with reference to the accompanying drawings. The liquid treatment apparatus and liquid treatment method of the present invention are used, for example, when separating and recovering fresh water from seawater, or separating water from a liquid containing water and concentrating the liquid. The present invention relates to a liquid treatment apparatus and a liquid treatment method using membrane separation using a forward osmosis membrane.

Examples of the liquid containing water include an oral liquid and an external liquid. Oral liquid means something that humans or animals eat, such as beverages such as concentrated juices and soft drinks, liquid foods such as noodle soup, various soup stocks, seasonings, soups, and liquid health supplements. Examples include foods and oral medicines. In addition, external liquids are a general term for liquids that are applied to the body of humans or animals, such as lotions and lotions, liquid cosmetics such as liquid hand creams, and liquid medicines that are applied or sprayed on the skin or mouth. Can be mentioned. In addition, the liquid means that it contains water and has fluidity, and also includes gel-like and sherbet-like ones. Furthermore, whether it is an oral liquid or an external liquid, it is not limited to the final use by consumers or patients, but also includes raw materials.

FIG. 1 is a schematic view showing a schematic configuration of the liquid processing apparatus 10 of the present embodiment. The liquid treatment apparatus 10 treats the treatment unit 4 having the first chamber 1 and the second chamber 2 separated by the forward osmosis membrane (FO membrane) 3 and the above-mentioned liquid to be treated (feed solution). The first flow path L1 for supplying to the first chamber 1 of 4 and the second flow path L2 for discharging the concentrated liquid to be treated from the first chamber 1 of the treatment unit 4, and the draw solution are processed in the processing unit. At least a third flow path L3 for supplying to the second chamber 2 of 4 and a fourth flow path L4 for discharging the diluted draw solution from the second chamber 2 of the processing unit 4 are provided.

The processing unit 4 has a closed tank (or housing, casing, etc.) structure and is made of metal or synthetic resin. The inside of the processing unit 4 is divided into a first chamber 1 and a second chamber 2 by a forward osmosis membrane 3.

As the forward osmosis membrane 3, a conventionally known material such as cellulose acetate, polyamide, polysulfone, or aquaporin (protein) can be used. Further, as the forward osmosis membrane 3, a conventionally known structure such as a flat membrane or a hollow fiber membrane can be used. When the forward osmosis membrane 3 is a flat membrane, the forward osmosis membrane 3 can be held in a posture by a support such as a wire mesh. When the forward osmosis membrane 3 is a hollow fiber membrane, it is preferable that the first chamber 1 is on the active layer side of the hollow fiber membrane and the second chamber 2 is on the support layer side of the hollow fiber membrane.

The liquid to be treated is introduced into the first chamber 1, and a draw solution having a higher osmotic pressure than the liquid to be treated is introduced into the second chamber 2. As the draw solution, a conventionally known solution can be used. For example, in addition to a solution containing sodium chloride as a solute (saline solution), a mixture of potassium nitrate, calcium chloride, sodium hydrogen carbonate and ammonium hydroxide is used as the solute. A solution, a solution containing a temperature-sensitive substance as a solute, or a solution having the same components as the solution to be treated and having a higher concentration than the solution to be treated can be used.

In the treatment unit 4, part of the water in the liquid to be treated is removed from the first chamber 1 due to the difference in osmotic pressure between the liquid to be treated supplied to the first chamber 1 and the draw solution supplied to the second chamber 2. It penetrates through the forward osmosis membrane 3 and moves to the second chamber 2. As a result, the solution to be treated in the first chamber 1 is concentrated, and the draw solution in the second chamber 2 is diluted. In the figure, the processing unit 4 is placed horizontally, and the first room 1 is on the top and the second room 2 is on the bottom, but the first room 1 is on the bottom and the second room 2 is on the top. It may be. Further, the processing unit 4 may be arranged in a vertically oriented posture.

The first flow path L1 is connected to one end of the first chamber 1 (the left end in the figure), and the second flow path L2 is connected to the other end of the first chamber 1 (the right end in the figure). .. A pump P1 is provided in the first flow path L1, and by driving the pump P1, the liquid to be treated is supplied from the storage tank 5 of the liquid to be treated into the first chamber 1 through the first flow path L1 and is concentrated. The treatment liquid is discharged to the outside of the first chamber 1 through the second flow path L2.

The third flow path L3 is connected to one end of the second chamber 2 (the right end in the figure), and the fourth flow path L4 is connected to the other end of the second chamber 2 (the left end in the figure). .. A pump P2 is provided in the third flow path L3 and / or the fourth flow path L4, and the draw solution is supplied into the second chamber 2 through the third flow path L3 by driving the pump P2, and the diluted draw solution is supplied. Is discharged to the outside of the second chamber 2 through the fourth flow path L4.

In the present embodiment, a draw solution regeneration unit 6 is provided between the third flow path L3 and the fourth flow path L4. The regenerating unit 6 concentrates the diluted draw solution discharged from the second chamber 2 of the processing unit 4, increases the concentration of the draw solution, and supplies it to the second chamber 2 again. In the figure, the regenerating unit 6 is composed of a reverse osmosis membrane device having a reverse osmosis membrane (RO membrane). The diluted draw solution is introduced into the reverse osmosis membrane device, which is the regeneration unit 6, in a state of being pressurized by the pump P2 provided in the fourth flow path L4, and the water content in the diluted draw solution is pressurized by pressure. It is concentrated by being separated through the RO membrane, and a high-concentration draw solution is produced. Then, a high-concentration draw solution is supplied into the second chamber 2 of the processing unit 4 through the third flow path L3.

For example, an evaporation device can be used for the reproduction unit 6. When the regeneration unit 6 is composed of an evaporator, although not shown, a pump P2 is provided in the third flow path L3, and the draw solution is driven by the pump P2 to pass through the third flow path L3 to the processing unit 4. The diluted draw solution supplied into the second chamber 2 is discharged to the outside of the second chamber 2 through the fourth flow path L4 and introduced into the evaporator which is the regeneration unit 6. By evaporating and concentrating the diluted draw solution in the evaporator, a high-concentration draw solution is generated, and the high-concentration draw solution is supplied again into the second chamber 2 of the processing unit 4 through the third flow path L3. To.

The regenerating unit 6 is not limited to a reverse osmosis membrane device or an evaporation device as long as it can separate the water content in the diluted draw solution and concentrate the draw solution, and other devices may be used. You can also.

The regeneration unit 6 does not necessarily have to be provided between the third flow path L3 and the fourth flow path L4, and is driven by the pump P2 provided in the third flow path L3 to store the draw solution (shown in the figure). The draw solution is supplied into the second chamber 2 through the third flow path L3, and the diluted draw solution is discharged to the outside of the second chamber 2 through the fourth flow path L4 in a recovery tank (not shown). You may collect it.

In the liquid treatment apparatus 1 having the above-described configuration, in the treatment unit 4, the amount of permeated water does not change significantly with respect to the liquid to be treated passing through the first chamber 1 as compared with the draw solution passing through the second chamber 2. By continuously applying a slightly higher pressure, the pressure difference between the membranes between the first chamber 1 and the second chamber 2 (the physical pressure difference between the liquid to be treated and the draw solution in the forward osmosis membrane 3). ) Is caused.

As a method of creating an intermembrane pressure difference between the first chamber 1 and the second chamber 2 of the processing unit 4, for example, (1) the pressure of sending the liquid to be processed into the first chamber 1 by the pump P1 is used. The pressure is set higher than the pressure at which the draw solution is sent into the second chamber 2 by the pump P2 (the pressure is higher than the pump P2), and (2) the pump P1 and the first chamber 1 of the processing unit 4 are connected. A pressurizing means such as a booster pump for pressurizing the liquid to be treated is provided between them. (3) A step-down means such as an automatic adjustment valve for reducing the pressure of the draw solution between the pump P2 and the second chamber 2 of the processing unit 4. (4) By making the inside of the first chamber 1 under a higher pressure than the inside of the second chamber 2 or the inside of the second chamber 2 under a lower pressure than the inside of the first chamber 1, through the forward osmosis membrane 3. It can be mentioned that the first chamber 1 side is always pressurized more than the second chamber 2 side.

The pressure difference between the films of the first chamber 1 and the second chamber 2 of the processing unit 4 is larger than 0 MPa and 0.06 MPa or less. In the membrane separation method (FO method) using the forward osmosis membrane 3, water permeates the forward osmosis membrane 3 from the side of the first chamber 1 having a low osmotic pressure due to the difference in osmotic pressure and moves to the side of the second chamber 2 having a high osmotic pressure. However, at the same time, a reverse leakage phenomenon occurs in which the solute contained in the draw solution of the second chamber 2 leaks to the first chamber 1 side where the liquid to be treated is located through the forward osmosis membrane 3. However, in the liquid treatment apparatus 1 of the present embodiment, a slightly higher pressure is applied to the liquid to be treated passing through the first chamber 1 than in the draw solution passing through the second chamber 2 in a range in which the amount of permeated water does not change significantly. Therefore, this reverse leakage phenomenon can be suppressed.

As a result, it is possible to prevent the solute contained in the draw solution from being mixed into the liquid to be treated. Therefore, when the liquid to be treated is a beverage, liquid food, liquid cosmetics, or the like, it is possible to prevent deterioration of the quality of the liquid to be treated as a raw material solution. Further, since the outflow of the solute can be suppressed on the draw solution side as well, the amount of replenishment of the draw solution due to the loss of the solute can be reduced, and the cost can be reduced.

The pressure difference between the films of the first chamber 1 and the second chamber 2 of the processing unit 4 is not particularly limited, but is preferably 0.01 MPa or more and 0.06 MPa or less, and 0. It is more preferably 01 MPa or more and 0.03 MPa or less, or 0.03 MPa or more and 0.06 MPa or less.

Although the details will be described later, by setting the pressure difference between the membranes to 0.01 MPa or more, the amount of back leakage of the above-mentioned solute can be effectively reduced. Further, as will be described in detail later, when the solute in the draw solution has a low molecular weight such as an inorganic salt, the amount of back leakage of the above-mentioned solute does not change significantly when the pressure difference between the membranes is 0.03 MPa or more. On the other hand, if the pressure difference between the membranes is increased and a high pressure is applied to the forward osmosis membrane 3, the forward osmosis membrane 3 may be damaged. Therefore, the pressure difference between the membranes is 0.06 MPa or less. It is preferably 0.03 MPa or less, and more preferably 0.03 MPa or less. On the other hand, when the solute in the draw solution has a high molecular weight such as a temperature-sensitive substance, the pressure difference between the films is preferably 0.03 MPa or more and 0.06 MPa or less.

For the above-mentioned pressure difference between membranes, for example, pressure gauges 7A and 7B are provided in the first flow path L1 and the third flow path L3 on the liquid inlet side with respect to the first chamber 1 and the second chamber 2 of the processing unit 4, respectively. It can be measured by installing it and using the measured values of the pressure gauges 7A and 7B. The measuring means for measuring the pressure difference between the membranes described above is not limited to the pressure gauges 7A and 7B, and various other devices can be used.

As described above, according to the liquid treatment apparatus 10 and the liquid treatment method of the present embodiment, when a pressure higher than that of the draw solution is applied to the liquid to be treated (feed solution), the solute contained in the draw solution passes through the forward osmosis membrane. Contrary to the general recognition in the art that a reverse leakage phenomenon occurs that leaks to the liquid to be treated, the liquid to be treated is 0.06 MPa or less, which is within the range where the amount of permeated water does not change significantly compared to the draw solution. By continuously pressurizing with a slightly higher pressure, it became possible to suppress the amount of back leakage of the solute leaking from the draw solution side through the forward osmosis membrane to the liquid to be treated side.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the liquid processing apparatus 10 of the above embodiment, as shown in FIG. 2, the control means 8 constantly monitors the pressure difference between the membranes between the first chamber 1 and the second chamber 2 of the processing unit 4, and the membrane is concerned. The pumps P1 and P2, the pressurizing means, the step-down means, and the like may be controlled so that the pressure difference between them is within a predetermined range.

The control means 8 may be composed of a computer including a microcomputer, a memory, an HDD, or the like, or may be composed of an electronic circuit. Measuring means for measuring the above-mentioned intermembrane pressure difference, for example, pressure gauges 7A and 7B are connected to the control means 8, and the control means 8 receives a signal from the measuring means, so that the control means 8 describes the above. The pressure difference between the membranes is monitored. Further, the control means 8 is connected to the setting means for setting the above-mentioned intermembrane pressure difference such as the pumps P1 and P2, the pressurizing means, and the step-down means, and the setting means is set based on the signal received from the measuring means by the control means 8. By controlling the operation of, the control means 8 adjusts the pressure difference between the films described above to be within a predetermined range.

Examples of the present invention will be shown below, and the present invention will be described in more detail, but the present invention is not limited to the following examples.

As Examples 1 and 2, a liquid treatment apparatus 1 having the same configuration as that in FIG. 1 was used to treat a liquid to be treated made of pure water. Two types of draw solutions were used: 1 mol / L saline solution (Example 1) and a 40% aqueous solution of polypropylene glycol having an average molecular weight of 400 (Example 2). For the forward osmosis membrane 3 of the treatment unit 4, a flat membrane made of polyamide (FO membrane manufactured by Aquaporin, model number FO08 / 02B2) was used.

For each of Examples 1 and 2, the treatment was performed for 1.5 hours with the intermembrane pressure difference between the first chamber 1 and the second chamber 2 of the processing unit 4 being 0.01 MPa, 0.03 MPa, and 0.06 MPa. In this case, the amount of reverse leakage of the solute leaking from the second chamber 2 side through the forward osmosis membrane 3 to the first chamber 1 side, and the amount of solute permeating through the forward osmosis membrane 3 from the first chamber 1 side to the second chamber 2 The amount of permeated water moving to the side was measured. Further, as a comparative example, the amount of reverse leakage of the solute and the amount of permeated water were measured when the pressure difference between the membranes between the first chamber 1 and the second chamber 2 of the treatment unit 4 was 0 MPa. The intermembrane pressure difference was measured with a pressure gauge, and the amount of back leakage was measured with a conductivity meter (manufactured by Shimadzu Corporation) in Example 1 while it was measured with an all-organic carbon meter (manufactured by Shimadzu Corporation) in Example 2. , The amount of permeated water was measured by a balance. The measurement results are shown in FIGS. 3 and 4.

According to FIGS. 3 and 4, it was confirmed that the back leakage of the solute can be suppressed by applying a slightly higher pressure of 0.06 MPa or less than the draw solution to the liquid to be treated. It was also confirmed that the amount of back leakage of the solute can be effectively reduced by setting the pressure difference between the membranes to 0.01 MPa or more. Further, when the solute in the draw solution has a high molecular weight such as a temperature-sensitive substance (Example 2), the amount of back leakage of the solute can be more effectively reduced by setting the pressure difference between the membranes to 0.03 MPa or more. On the other hand, when the solute in the draw solution has a low molecular weight such as an inorganic salt (Example 1), it was confirmed that the amount of back leakage of the solute does not change significantly even if the pressure difference between the membranes is 0.03 MPa or more. Therefore, when the solute in the draw solution has a low molecular weight such as an inorganic salt (Example 1), the pressure difference between the membranes is preferably 0.01 MPa or more and 0.03 MPa or less, and the solute in the draw solution is felt. In the case of a high molecular weight such as a warm substance (Example 2), it was confirmed that the pressure difference between the films is preferably 0.03 MPa or more and 0.06 MPa or less. On the other hand, in both Example 1 and Example 2, it was confirmed that the amount of permeated water did not change significantly as compared with the case where no pressure was applied (0 MPa). Therefore, it is possible to suppress the back leakage of the solute by applying a slight pressure within the range in which the amount of permeated water does not change significantly compared to the case where no pressure is applied to the solution to be treated (0 MPa). I understand.

1 Room 1 2 Room 2 3 Forward osmosis membrane 4 Processing unit 7A, 7B Pressure gauge (measuring means)
8 Control means P1, P2 pump (setting means)
L1 1st flow path L2 2nd flow path L3 3rd flow path L4 4th flow path

Claims (5)

A processing unit having a first chamber and a second chamber separated by a forward osmosis membrane,
A first flow path for supplying the liquid to be treated to the first chamber,
A second flow path for supplying a draw solution having a higher osmotic pressure than the liquid to be treated to the second chamber,
A third flow path for discharging the concentrated liquid to be treated in the first chamber after a part of the water content of the liquid to be treated has permeated from the first chamber to the second chamber via the forward osmosis membrane. ,
A fourth flow path for discharging the diluted draw solution of the second chamber after a part of the water content of the liquid to be treated has permeated from the first chamber to the second chamber through the forward osmosis membrane. With
Intermembrane pressure difference between the first chamber and the second chamber so that a pressure higher than that of the draw solution passing through the second chamber is continuously applied to the liquid to be treated passing through the first chamber. Is set to 0.06 MPa or less, which is larger than 0 MPa, and is a liquid processing apparatus. The liquid processing apparatus according to claim 1, wherein the pressure difference between the membranes between the first chamber and the second chamber is 0.01 MPa or more and 0.03 MPa or less. A measuring means for measuring the intermembrane pressure difference, a setting means for setting the intermembrane pressure difference, and a measuring means and a control means connected to the setting means are further provided.
The liquid processing apparatus according to claim 1 or 2, wherein the control means adjusts the pressure difference between the membranes by receiving a signal from the measuring means and controlling the operation of the setting means. The liquid to be treated is supplied to the first chamber of the treatment unit having the first chamber and the second chamber partitioned by the forward osmosis membrane, while the draw solution having a higher osmotic pressure than the liquid to be treated is supplied to the second chamber. In a liquid treatment method in which a part of the water content of the liquid to be treated is permeated from the first chamber to the second chamber via the forward osmosis membrane by supplying the liquid.
Intermembrane pressure difference between the first chamber and the second chamber so that a pressure higher than that of the draw solution passing through the second chamber is continuously applied to the liquid to be treated passing through the first chamber. Is a liquid treatment method in which is set to 0.06 MPa or less, which is larger than 0 MPa. The liquid treatment method according to claim 4, wherein the pressure difference between the membranes between the first chamber and the second chamber is 0.01 MPa or more and 0.03 MPa or less.