JP2015058407A - Draw solution, water treatment apparatus and water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a draw solution used for a forward osmosis method capable of recovering a water component at a low cost and quickly.SOLUTION: A draw solution 211 is used for water treatment using a forward osmosis method, dissolves water-soluble gas 212 into water at such a concentration as to exhibit an osmotic pressure larger than an osmotic pressure of liquid 221 to be treated and recovers a water component by release to atmosphere after completion of forward osmosis operation. The draw solution is preferably prepared such that an osmotic pressure after 1 hr elapse since the release to atmosphere is 0 to 10% of the osmotic pressure upon the starting of the release to atmosphere. A water treatment apparatus 100 provided with a treatment tank 200 which brings the draw solution into contact with liquid to be treated via a forward osmosis membrane 230, and a water treatment method which includes a forward osmosis operation process of bringing the liquid to be treated into contact with the draw solution prepared by dissolving water-soluble gas with the concentration via the forward osmosis membrane and moving the water component in the liquid to be treated to the draw solution; and a water component recovery process of releasing the draw solution after the forward osmosis operation process to the atmosphere, separating the water-soluble gas from the draw solution and recovering the water component contained in the draw solution are provided.

Description

  The present invention relates to an induction solution used for water treatment by a forward osmosis method. The present invention also relates to a water treatment apparatus and a water treatment method using the induction solution.

  Conventionally, the reverse osmosis method is known as an effective method in the field of water treatment. However, the forward osmosis method (FO method) attracts attention as a water treatment method that replaces the reverse osmosis method. In the water treatment method using the FO method, the liquid to be treated and the induction solution are brought into contact with each other through the FO method semipermeable membrane, and the water in the liquid to be treated is absorbed by the induction solution. Subsequently, high-purity water can be obtained by separating and collecting the water from the induction solution that has absorbed the water of the liquid to be treated.

  In the FO method, moisture is transferred from the liquid to be treated to the induction solution using an osmotic pressure difference between the liquid to be treated and the induction solution. Therefore, the FO method can reduce the energy cost for the desalination of seawater and brine and the treatment of wastewater as compared with the RO method. Patent Documents 1 and 2 disclose water treatment by the FO method.

  Patent Document 1 discloses a method for separating the solute of the induction solution and the generated solvent from the induction solution using a plurality of distillation columns. In the separation method, a solution in which ammonia and carbon dioxide are dissolved in water is used as the induction solution. When separating and recovering moisture transferred from the liquid to be treated from such an induction solution, the induction solution must be heated under reduced pressure. Therefore, the above method requires heat energy.

  Patent Document 2 discloses a wastewater treatment method and the like for obtaining treated water having low organic matter concentration and low dissolved ion concentration by using FO method and RO method for wastewater after anaerobic treatment. In the forward osmosis separation step of the wastewater treatment method, a solution in which an electrolyte or an organic substance is dissolved in water is used as the induction solution. In the above method, after the FO method step, an RO membrane or a nanofilter is used for water recovery from the induction solution. In the membrane separation method using such a membrane, a filtration operation is performed at a high pressure, and thus electric energy for managing the pump is required.

  As described above, in the water treatment method using the conventional FO method, an energy cost is required in the water recovery process from the induction solution. Therefore, it is desired to develop a water treatment method that can recover water at a lower cost.

JP 2009-539584 A JP 2011-173040 A

  The subject of this invention is providing the induction | guidance | derivation solution which can collect | recover water | moisture contents quickly at low cost in the water treatment method by FO method.

The present invention is used for water treatment by the forward osmosis method, wherein a water-soluble gas is dissolved in water at a concentration that expresses an osmotic pressure P _d1 greater than the osmotic pressure P _{f of the} liquid to be treated, and the forward osmosis operation ends. It is an induction solution that recovers moisture by the atmospheric release performed later. In the above-described induction solution, the osmotic pressure P _d3 after 1 hour from the start of the atmospheric release is 0% or more and 10% or less of the osmotic pressure P _d2 at the start of the atmospheric release. The water-soluble gas is preferably dimethyl ether.

This invention includes a water treatment apparatus provided with the processing tank which makes a to-be-processed liquid and said induction | guidance | derivation solution contact through a forward osmosis membrane. In addition, the present invention provides a contact between a liquid to be treated and an induction solution obtained by dissolving a water-soluble gas in water at a concentration that expresses an osmotic pressure P _d1 greater than the osmotic pressure P _{f of the} liquid to be treated through a forward osmosis membrane. The normal osmosis operation step in which the moisture of the liquid to be treated is transferred to the induction solution, and the induction solution after the completion of the normal osmosis operation step is released to the atmosphere to separate the water-soluble gas from the induction solution, and the moisture contained in the induction solution A water recovery method including a water recovery step of recovering water. In the above water recovery step, the induction solution after the end of the normal osmosis operation is released to the atmosphere, and the osmotic pressure P _d3 when 1 hour has elapsed from the start of the release to the osmotic pressure P _d2 of the induction solution at the start of the release of the atmosphere. It is preferable to reduce it to 0% or more and 10% or less.

  The induction solution used in the forward osmosis method of the present invention can quickly separate moisture at a low cost. Thereby, in the water treatment method by the forward osmosis method using the above-described induction solution, the energy cost can be suppressed and water can be recovered quickly.

It is the schematic which shows the example of the water treatment apparatus of this invention.

The induction solution used for water treatment by the forward osmosis method of the present invention is obtained by dissolving a water-soluble gas in water. The dissolved amount of the water-soluble gas is adjusted so that the osmotic pressure P _d1 of the induction solution is larger than the osmotic pressure P _{f of the} liquid to be treated. The induction solution having such osmotic pressure absorbs moisture of the liquid to be treated by forward osmosis operation. The water-soluble gas dissolved in the induction solution of the present invention is highly volatile. Therefore, when the induction solution is released to the atmosphere after the forward osmosis operation is completed, the water-soluble gas is volatilized from the induction solution. As a result, the present invention can easily recover moisture from the induction solution.

  In the present invention, after the forward osmosis operation is completed, the moisture can be recovered simply by releasing to the atmosphere. That is, according to the present invention, it is not necessary to adjust the pressure or temperature of the induction solution for water recovery. Therefore, the energy cost and management cost of moisture recovery can be suppressed. Hereinafter, the present invention will be described with reference to FIG.

  FIG. 1 is a schematic view showing an example of the water treatment apparatus of the present invention. In FIG. 1, 100 is a water treatment apparatus, 200 is a treatment tank, 210 is an induction solution chamber, 220 is a liquid chamber to be treated, and 230 is a forward osmosis membrane. Reference numeral 211 denotes an induction solution tank, 212 denotes a water-soluble gas tank, 213 denotes an induction solution liquid feed pump, 221 denotes a liquid tank to be processed, and 222 denotes a liquid supply pump to be processed. The induction solution tank 211 and the induction solution chamber 210 of the treatment tank 200 are connected so that the induction solution can be circulated. Further, the liquid to be processed is connected to the liquid tank to be processed 221 and the liquid chamber 220 to be processed so that the liquid to be processed can circulate.

  The water-soluble gas supplied from the water-soluble gas tank 212 to the induction solution tank 211 is dissolved in water in the induction solution tank 211 and stored in the induction solution tank 211 as an induction solution having a predetermined osmotic pressure. The induction solution in the induction solution tank 211 is sent to the induction solution chamber 210 of the processing tank 200 using the induction solution liquid feed pump 213. On the other hand, the liquid to be processed stored in the liquid tank 221 to be processed is sent to the liquid chamber 220 of the processing tank 200 using the liquid feed pump 222.

The induction solution and the liquid to be processed, which are sent to the induction solution chamber 210 and the liquid chamber 220 to be processed, respectively, of the processing tank 200 are in contact with each other through the forward osmosis membrane 230. The concentration of the water-soluble gas is adjusted so that the osmotic pressure P _{d1 of the} induction solution fed to the induction solution chamber 210 is larger than the osmotic pressure P _{f of the} liquid to be treated. For this reason, when the liquid to be treated and the induction solution come into contact with each other, the water in the liquid to be treated passes through the forward osmosis membrane 230 and moves from the liquid chamber 220 to be treated to the induction solution chamber 210.

The greater the osmotic pressure difference between the osmotic pressure of the liquid to be treated and the osmotic pressure of the induction solution, the greater the amount of moisture transferred from the liquid to be processed to the induction solution. From the viewpoint of increasing the amount of moisture transfer, the osmotic pressure of the present invention is higher than the osmotic pressure of the liquid to be treated, and the osmotic pressure difference is preferably as large as possible. When the osmotic pressure difference from the osmotic pressure P _{f of the} liquid to be treated at the start of the forward osmosis operation is 0 MPa or more and less than 0.3 MPa, no water movement from the liquid to be treated to the induction solution occurs or the amount of water movement is small. Efficient water treatment cannot be performed. The osmotic pressure of the induction solution or the liquid to be treated can be measured by a conventionally known method such as a freezing point depression method.

  Examples of the liquid to be treated to be brought into contact with the induction solution of the present invention include industrial wastewater, domestic wastewater, brine, and seawater containing organic compounds, inorganic compounds, inorganic ions, organic ions, and fine particles. The osmotic pressure of industrial wastewater and household wastewater can be exemplified as a range of about 0.1 to 3 MPa. The osmotic pressure of brackish water is approximately 0.5 to 2.5 MPa, and the osmotic pressure of seawater is 2.3 to 2.7 MPa.

Therefore, the osmotic pressure P _d1 at the start of the forward osmosis operation using the induction solution of the present invention is preferably 0.4 to 10 MPa, more preferably 1 to 10 MPa, and more preferably 2 to 10 MPa when treating industrial water or domestic wastewater. Is particularly preferred. The osmotic pressure P _d1 at the start of the forward osmosis operation of the induction solution is larger than the osmotic pressure P _{f of the} solution to be treated within the above preferable range, and the osmotic pressure difference between the non-treatment solution and the induction solution is 0.3 MPa or more. Adjusted to. If osmotic pressure P _d1 is less than 0.3 MPa, osmotic pressure difference is impossible to easily efficient water treatment reduced the osmotic pressure of the liquid to be treated. It is substantially difficult to osmotic pressure P _d1 is adjusted using the methods disclosed in the present invention the draw solution in excess of 10 MPa.

  The induction solution of the present invention uses water as a solvent and water-soluble gas as a solute. Moreover, a small amount of additives can be included as long as the effects of the present invention are not impaired. Examples of the additive include carbon dioxide, methyl fluoride, chlorine dioxide, organic electrolyte, inorganic electrolyte, organic substance, and inorganic substance. These additives can be removed using means such as air release or membrane filtration.

The osmotic pressure P _d1 at the start of the forward osmosis operation of the induction solution is adjusted by the concentration of the water-soluble gas, the temperature of the induction solution, the molecular weight, and the like. Moreover, when using the pressurization apparatus demonstrated later, it adjusts also in consideration of the pressure concerning induction solution by a pressurization apparatus. Under the condition of 25 ° C., the induction solution of the present invention having an osmotic pressure P _d1 within the above preferred range preferably has a water-soluble gas concentration of 1 to 20% by mass, more preferably 3 to 15% by mass, More preferably, it can be obtained by dissolving a water-soluble gas so as to be 5.0 to 10% by mass. When the concentration of the water-soluble gas is less than 1% by mass, the osmotic pressure _Pd1 of the induction solution becomes low, and the amount of moisture transferred from the liquid to be treated is suppressed. It is substantially difficult to prepare a derivative solution having a water-soluble gas concentration exceeding 20% by mass using the method disclosed in the present invention.

  The amount of water-soluble gas dissolved in the induction solution is determined by measuring the supply amount of the water-soluble gas in the induction solution and in the water recovery process described later, the induction solution at the start of air release, and when 1 hour has elapsed from the start of air release. It can measure based on the mass change with the induction solution.

  The water-soluble gas used in the present invention is preferable as its solubility increases. Here, the solubility is defined by the mass (in g) of a water-soluble gas dissolved in 100 g of water. Specifically, it is preferably 1 to 25, more preferably 3 to 15 under conditions of 1 atm and 20 ° C. When a water-soluble gas having a solubility of less than 1 is used, the water-soluble gas is difficult to dissolve in water, and the osmotic pressure of the induction solution is unlikely to become a value within the above preferred range. However, even in such a case, dissolution of the water-soluble gas can be promoted by stirring, pressurizing, and the osmotic pressure of the induction solution can be adjusted to a desired value. When the solubility exceeds 25, it takes time to volatilize the water-soluble gas. For this reason, it becomes difficult to easily and quickly recover the water by releasing the atmosphere after the forward osmosis operation.

In the present invention, a highly volatile water-soluble gas is preferably used from the viewpoint of simply and quickly collecting water by releasing into the atmosphere. Examples of the volatility index include osmotic pressure lowering ability after the induction solution is released to the atmosphere. That is, in the atmospheric release of the induction solution after the end of the normal osmosis operation, when the osmotic pressure of the induction solution at the start of the atmospheric release is P _d2 , the osmotic pressure P _d3 of the induction solution after 1 hour from the start of the atmospheric release is The osmotic pressure P _d2 is preferably 0 to 10%, more preferably 0 to 5%.

  As the water-soluble gas used in the present invention, a water-soluble gas having the above-described solubility and volatility is preferably used. Specific examples include dimethyl ether, carbon dioxide, methyl fluoride, chlorine dioxide and the like. The induction solution of the present invention containing such a water-soluble gas in the concentration described above can move a large amount of water from the liquid to be treated by forward osmosis operation, and after the forward osmosis operation is finished, By releasing, water with good purity can be recovered simply and quickly at low cost. The water obtained by the forward osmosis operation using the induction solution of the present invention has its solute concentration suppressed to 5 to 10,000 ppm as the sum of the mixed solute from the liquid to be treated and the remaining water-soluble gas. Depending on its purity, it can be used for drinking water, industrial water and the like.

[Water treatment equipment]
The water treatment apparatus of the present invention induces moisture of the liquid to be treated by bringing the predetermined induction solution and the liquid to be treated into contact with each other through the forward osmosis membrane, and the difference in osmotic pressure between the induction solution and the liquid to be treated. Can be moved to solution. A specific example of the apparatus configuration of the present invention is the water treatment apparatus shown in FIG.

  That is, the present invention includes a processing tank including an induction solution chamber and a liquid chamber to be processed that are partitioned by a forward osmosis membrane. A liquid tank to be processed for supplying the liquid to be processed is connected to the liquid chamber to be processed. An induction solution tank for supplying an induction solution is connected to the induction solution chamber. A water-soluble gas tank that supplies a predetermined water-soluble gas is connected to the induction solution tank. By adjusting the amount of water-soluble gas supplied from the water-soluble gas tank to the induction solution tank, the concentration of the water-soluble gas in the induction solution can be adjusted to a concentration at which the osmotic pressure of the induction solution is greater than the osmotic pressure of the liquid to be treated. . In order to improve the solubility of the water-soluble gas, a pressure device or a stirring device may be provided in the induction solution tank.

  When a pressure device is provided in the induction solution tank, the pressure applied to the induction solution by the pressure device is made smaller than the osmotic pressure difference between the osmotic pressure of the induction solution and the osmotic pressure of the liquid to be treated. Specifically, the difference between the osmotic pressure of the induction solution in which the water-soluble gas is dissolved by applying pressure and the liquid to be treated is 0.3 to 10 MPa. For pressurization of the induction solution, the internal pressure of a water-soluble gas tank that stores the water-soluble gas supplied to the induction solution may be used. The pressure applied to the induction solution by the above-described pressurization device is considered when adjusting the osmotic pressure of the induction solution. That is, the osmotic pressure difference between the sum of the pressure related to the induction solution and the osmotic pressure of the induction solution and the osmotic pressure of the liquid to be treated is adjusted so as to be within the preferable range.

  0-50 degreeC is preferable and, as for the temperature conditions in a processing tank, 10-30 degreeC is more preferable. The induction solution is supplied from the induction solution tank to the induction solution chamber of the treatment tank, and the treatment liquid is supplied from the treatment liquid tank to the treatment liquid chamber of the treatment tank. When the liquid to be treated comes into contact with the forward osmosis membrane, the moisture of the liquid to be treated is absorbed by the induction solution. If the temperature in the treatment tank is lower than 0 ° C, there is a risk of freezing. When it is higher than 50 ° C., the water-soluble gas is hardly dissolved in the induction solution. In the present invention, a forward osmosis membrane having semi-permeability can be used without limitation. Specifically, a composite film made mainly of cellulose, cellulose acetate, crosslinked polyamide or the like is used.

[Water treatment method]
The water treatment method of the present invention includes a predetermined forward osmosis operation step and a water recovery step. When applying the present invention to desalination of a liquid to be treated having an osmotic pressure of P _f under a temperature condition of 25 ° C., first, the osmotic pressure P _d1 of the induction solution is set to be larger than the osmotic pressure P _{f of the} liquid to be treated. Adjust. The osmotic pressure difference d between the osmotic pressure P _d1 of the induction solution and the osmotic pressure P _{f of the} liquid to be treated at the start of the forward osmosis operation is preferably 0.3 to 8 MPa, more preferably 0.5 to 8 MPa, and further preferably 1 to 8 MPa. . Based on the osmotic pressure P _{f of the} liquid to be treated, the concentration of the water-soluble gas in the induction solution is adjusted so as to achieve the above osmotic pressure difference, so that an appropriate osmotic pressure P _d1 is obtained. As the osmotic pressure difference d is greater than or equal to 0.3 MPa, the moisture transfer amount can be increased. However, the concentration of the water-soluble gas in the induction solution needs to be a concentration at which the water-soluble gas can be quickly separated from the induction solution in the moisture recovery process. Osmotic pressure _{P d1} of therefore draw solution is preferably adjusted to 0.3 to 10 MPa. As a result, the osmotic pressure difference d is preferably in the above range.

  When the induction solution and the liquid to be treated are brought into contact with each other through the forward osmosis membrane and the forward osmosis operation is started, only moisture of the liquid to be treated passes through the forward osmosis membrane and moves to the induction solution. As a result, the osmotic pressure of the induction solution decreases and the osmotic pressure of the liquid to be processed increases. Therefore, the osmotic pressure difference between the induction solution and the liquid to be treated gradually decreases until the osmotic pressure difference d at the start of the forward osmosis operation is maximized until the forward osmosis operation ends. Theoretically, it is possible to transfer moisture from the liquid to be treated to the induction solution until the osmotic pressure difference disappears, and the normal osmosis operation can be continued.

  The induction solution after completion of the forward osmosis operation is collected for performing a moisture collecting step. The water recovery in the present invention is only required to release the induction solution to the atmosphere. The temperature condition of the induction solution during the air release is preferably 0 to 50 ° C, more preferably 15 to 35 ° C. Since the induction solution used in the present invention uses a predetermined water-soluble gas having high volatility as a solute, the water-soluble gas can be volatilized naturally by being released to the atmosphere without performing a pressure operation or the like. Therefore, the induction solution can be easily desalted.

In the present invention, the induction solution can be quickly desalinated by the above-described release into the atmosphere. In the water recovery step of the present invention, the osmotic pressure P _d3 of the induction solution after 1 hour has elapsed from the start of the atmospheric release is reduced to 0 to 10% of the osmotic pressure P _d2 of the induction solution at the start of the atmospheric release. Preferably it falls to 0-5%. That is, according to the present invention, the volatilization rate of the water-soluble gas in the induction solution after being released into the atmosphere is high, and the desalination treatment can be performed quickly. When the decrease rate of the osmotic pressure is out of the above range, means such as stirring the induction solution, a degassing membrane, or a vacuum degassing tower may be used. Thereby, the decreasing rate of the osmotic pressure of the induction solution can be within a preferable range.

  It is also preferable to introduce the water-soluble gas separated from the induction solution into an induction solution tank that stores the induction solution and reuse it in order to supply the treatment tank. Thereby, the water treatment method of this invention can implement | achieve further cost reduction.

  Since the present invention can quickly separate water-soluble gas from the induction solution, water having a solute concentration of 5 to 10000 ppm can be obtained by releasing to the atmosphere for 3 to 24 hours. Furthermore, water with higher purity can be obtained by extending the air release time. The water treatment method of the present invention is suitable for purification of industrial wastewater and domestic wastewater, and can also be applied to brine or seawater desalination. The obtained treated water can be used for drinking water, industrial water and the like.

The present invention will be further described with reference to examples. However, the present invention is not limited to the following examples.
[Example]
Water treatment using the present invention was performed using a water treatment apparatus having the apparatus configuration shown in FIG. In this example, the osmotic pressure of the induction solution and the liquid to be treated was measured by the freezing point depression method.

  A 0.5% by mass sodium chloride aqueous solution was used as the liquid to be treated. The osmotic pressure of the liquid to be treated was 0.42 MPa. The liquid to be processed was stored in a liquid tank to be processed and was sent to the liquid chamber of the processing tank using a liquid feed pump. Gaseous dimethyl ether (DME) was stored in the water-soluble gas tank. The above DME was supplied from the water-soluble gas tank to the induction solution tank and dissolved in the induction solution using water as a solvent to prepare an induction solution having a DME concentration of 7% by mass.

Osmotic pressure _{P d1} of the draw solution was 2.07 MPa. Moreover, the pressure concerning an induction | guidance | derivation solution at the time of DME supply was 0.12 MPa. Therefore, the difference between the osmotic pressure of the induction solution and the pressure applied to the induction solution at the start of the forward osmosis operation in this example was 1.95 MPa, and the difference between the osmotic pressure of the liquid to be treated and 0.42 MPa was 1.53 MPa. The above induction solution was fed to the induction solution chamber of the treatment tank.

The induction solution 0.5L sent to the treatment tank and the treatment solution 0.5L are brought into contact with each other through a cross-linked polyamide semipermeable membrane (SW30, Dow Chemical Co., Ltd.) having an area of 60 cm ² at a temperature condition of 25 ° C. for 60 minutes. After the moisture of the liquid to be treated was moved to the induction solution, the forward osmosis operation was terminated. The permeation rate of the moved water was 2.9 L per hour in terms of the forward osmosis membrane area of 1 m ² . When the osmotic pressure of the induction solution at the end of the forward osmosis operation was measured, it was 2.01 MPa. Further, the rejection rate of sodium chloride contained in the liquid to be treated was 91.8%.

After completion of the forward osmosis operation, 50 cc of the induction solution that absorbed the moisture of the liquid to be treated was collected in a 100 cc beaker. The recovered induction solution was opened to the atmosphere at 25 ° C. Osmolality _{P d2} draw solution at atmospheric release initiation was 2.01MPa. The osmotic pressure P _d3 of the induction solution after 1 hour from the start of the atmospheric release was 0.16 MPa, 8% of the osmotic pressure P _d2 at the start of the atmospheric release. That is, the rate of decrease in osmotic pressure from the start of air release was 92%.

  Furthermore, air release was continued, and osmotic pressure of the induction solution was measured again 24 hours after the start of air release. The osmotic pressure of the induction solution after 24 hours from the start of the atmospheric release was 0.03 MPa. The induction solution was mixed with 410 ppm of sodium chloride mixed in the induction solution from the liquid to be treated in the forward osmosis operation step. The osmotic pressure due to the sodium chloride is estimated to be 0.035 MPa. That is, in the present invention, it is possible to quickly and easily separate the water-soluble gas in the induction solution simply by releasing it to the atmosphere, and to obtain highly pure water. Furthermore, the purity of the water obtained can further be improved by removing said sodium chloride using a reverse osmosis membrane or a nano filter.

[Comparative example]
The forward osmosis operation step and the water recovery step were performed in the same manner as in Example except that the induction solution was a magnesium chloride aqueous solution of 3.5% by mass and osmotic pressure 2.56 MPa, and no pressure was applied to the induction solution. . The permeation rate of the moisture transferred from the liquid to be treated to the induction solution by the forward osmosis operation was 3.2 L per hour in terms of the forward osmosis membrane area of 1 m ² .

  The osmotic pressure of the induction solution was measured at the start of forward osmosis operation, at the start of atmospheric release, at 60 minutes after the start of atmospheric release, and at 24 hours after the start of atmospheric release. Each measurement result shows that the osmotic pressure at the start of forward osmosis operation is 2.56 MPa, the osmotic pressure at the start of atmospheric release is 2.36 MPa, and the osmotic pressure after 60 minutes and 24 hours have elapsed from the start of atmospheric release. There was no change from the beginning, and it was 2.36 MPa. In the above induction solution, magnesium chloride could not be separated only by opening to the atmosphere, and pure water could not be obtained.

DESCRIPTION OF SYMBOLS 100 Water treatment apparatus 200 Treatment tank 210 Induction solution chamber 211 Induction solution tank 212 Water-soluble gas tank 213 Induction solution liquid feed pump 220 To-be-treated liquid chamber 221 To-be-treated liquid tank 222 To-be-treated liquid feed pump 230 Forward osmosis membrane

Claims (6)

Atmosphere used for water treatment by the forward osmosis method, wherein a water-soluble gas is dissolved in water at a concentration that causes an osmotic pressure P _d1 greater than the osmotic pressure P _{f of the} liquid to be treated, and is performed after completion of the forward osmosis operation. An induction solution that collects moisture upon release. 2. The induction solution according to claim 1, wherein an osmotic pressure P _d3 at the time when 1 hour has elapsed from the start of the atmospheric release is 0% or more and 10% or less of the osmotic pressure P _d2 at the start of the atmospheric release.   The induction solution according to claim 1 or 2, wherein the water-soluble gas is dimethyl ether.   A water treatment apparatus provided with the processing tank which makes a to-be-processed liquid and the induction | guidance | derivation solution of any one of Claims 1 thru | or 3 contact through a forward osmosis membrane. The liquid to be treated is brought into contact with the inducing solution formed by dissolving a water-soluble gas in water at a concentration that expresses an osmotic pressure P _d1 greater than the osmotic pressure P _{f of the} liquid to be treated through the forward osmosis membrane. Moisture recovery for recovering the water contained in the induction solution by separating the water-soluble gas from the induction solution by releasing the induction solution to the atmosphere after the forward osmosis operation step is completed. A water treatment method including a process. After the forward osmosis operation is completed, the induction solution is released to the atmosphere, and the osmotic pressure P _d3 after 1 hour from the start of the release to 0% or more and 10% or less of the osmotic pressure P _d2 of the induction solution at the start of the release to the atmosphere The water treatment method of Claim 5 including the water | moisture-content recovery process to reduce.