JP5433633B2 - Seawater desalination system using forward osmosis membrane - Google Patents

Seawater desalination system using forward osmosis membrane Download PDF

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JP5433633B2
JP5433633B2 JP2011125932A JP2011125932A JP5433633B2 JP 5433633 B2 JP5433633 B2 JP 5433633B2 JP 2011125932 A JP2011125932 A JP 2011125932A JP 2011125932 A JP2011125932 A JP 2011125932A JP 5433633 B2 JP5433633 B2 JP 5433633B2
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osmosis membrane
seawater
chamber
osmotic pressure
solution
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JP2012250200A (en
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浩人 横井
晃治 陰山
豊 三宮
秀之 田所
隆広 舘
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株式会社日立製作所
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Description

  The present invention relates to a seawater desalination system using a forward osmosis membrane for obtaining fresh water from seawater using a forward osmosis membrane.

  In recent years, the application of seawater desalination technology using membranes has increased. In the reverse osmosis membrane method, a pressure more than twice the osmotic pressure of seawater (about 2.5 MPa) is applied to a reverse osmosis membrane made of materials such as cellulose and polyamide, so that water does not permeate the membrane without allowing salt to permeate the membrane. Is a method of obtaining fresh water by permeating water.

  On the other hand, in the forward osmosis membrane method, water in seawater is once recovered into a high-concentration (high osmotic pressure) solution through an osmotic membrane made of a material such as cellulose, and then salt is added from the high osmotic pressure solution. It is a method of removing. By selecting the salt to be added to the hyperosmotic solution, the driving force in the positive direction, that is, not only recovering the water in the seawater into a high-concentration solution but also easily separating it from the solution, There is a possibility that the energy for manufacturing can be reduced as compared with the reverse osmosis membrane method.

  Semipermeable membranes used for reverse osmosis membranes and forward osmosis membranes are membranes that remove ions in raw water. During operation, so-called fouling is likely to occur, in which the pores of the membrane are clogged by inorganic and organic components in raw water and additive chemicals, and organic components derived from living organisms. In the plant of the reverse osmosis membrane method that has already been put into practical use, in order to reduce the equipment cost for seawater desalination, injection of a scale inhibitor and periodic cleaning and replacement of the membrane are performed.

  [Patent Document 1] discloses a seawater desalination method using a reverse osmosis membrane connected in series in two stages. Boron, one of the components in seawater, has a relatively low rejection rate by reverse osmosis membranes, and it is difficult to satisfy water quality standards. In [Patent Document 1], in order to efficiently remove boron, a cleaning solution (organic acid or a component obtained by adding ammonia to an organic acid) is periodically supplied to the surface of the second-stage reverse osmosis membrane to deteriorate the membrane. It is set as the structure which prevents in advance. However, in recent years, fouling generated in the first-stage reverse osmosis membrane has become a problem from the viewpoint of further extending the life of the apparatus, and the configuration of [Patent Document 1] cannot satisfy this problem. .

  [Patent Document 2] discloses a seawater desalination method using reverse osmosis membranes connected in series in order to improve the removal performance of boron, as in [Patent Document 1]. It is set as the structure provided with the backwashing means which distribute | circulates the concentrated seawater obtained by the reverse osmosis membrane process in the direction opposite to the raw | natural water distribution direction of each reverse osmosis membrane element. Thereby, it is supposed that a reverse osmosis membrane module can be used over a long period of time.

  However, since concentrated water is used as a cleaning solution for backwashing, pressurization by a high-pressure pump is required to allow water to permeate the reverse osmosis membrane and flow out to the seawater raw water side. The salt concentration of the concentrated water depends on the fresh water recovery rate in the reverse osmosis treatment, but generally has a problem that the energy of back washing is large because it is twice or more that of seawater.

  Moreover, regarding the system for forward osmosis membrane treatment, there is no literature describing backwashing for the purpose of long-term use of the membrane.

JP 2006-122787 A JP 2003-117552 A

  An object of the present invention is to provide a seawater desalination system using a forward osmosis membrane having a backwashing function for extending the life of the membrane with a small amount of energy consumption.

  In order to achieve the above object, the seawater desalination system using the forward osmosis membrane of the present invention is a first room in which seawater that is raw water in contact with the forward osmosis membrane is supplied during seawater desalination treatment, A forward osmosis membrane treatment means comprising a second chamber supplied with a high osmotic pressure solution for permeating the membrane from seawater and collecting water; a purification means for removing solutes or particles in the high osmotic pressure solution; A pipe for supplying the second chamber with a solution having an osmotic pressure lower than seawater obtained by the purification means, and using the osmotic pressure difference between the first chamber and the second chamber as a driving force, the second chamber The structure was such that water contained in the room was permeated through the forward osmosis membrane to remove substances adhering to the forward osmosis membrane in contact with the first chamber.

  Further, when a solution having an osmotic pressure lower than that of seawater is supplied to the second chamber, a solution having a higher osmotic pressure than seawater recovered by the purification means is supplied to the first chamber, and the forward osmosis membrane It was set as the structure which removes the substance adhering to.

  In addition, it is configured to have means for adding cleaning chemicals to the liquid supplied to the first chamber.

  Further, any one of a surfactant, an inorganic acid, an organic acid, and an alkali agent is used as a cleaning chemical.

  It also has means for measuring the flow rate of water supplied to the first room and the second room, measures each flow rate during seawater desalination treatment, and based on the measurement results, the osmotic pressure is Control means for supplying a lower solution to the second chamber.

  It also has means for measuring the conductivity of water supplied to and discharged from the second room, and measures each conductivity during seawater desalination treatment, and the osmotic pressure is determined based on the measurement results. It was set as the structure which has a control means which supplies the solution lower than seawater to said 2nd chamber.

  According to the present invention, since the backwashing of the forward osmosis membrane can be carried out using the difference in the concentration of water supplied to both sides of the membrane as a driving force, the pump power for backwashing can be reduced. Moreover, it is possible to extend the life of the film by performing backwashing.

1 is a block diagram of a seawater desalination system according to a first embodiment of the present invention. It is explanatory drawing of the water treatment in 1st Embodiment of this invention. It is a block diagram of the seawater desalination system which concerns on 2nd Embodiment of this invention. It is a block diagram of the seawater desalination system which concerns on 3rd Embodiment of this invention. It is a flowchart which judges implementation of backwashing based on a measurement result.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram of a seawater desalination system according to a first embodiment of the present invention.

  The present system takes in seawater 1 and performs pretreatment on pretreatment means 2, connected to the pretreatment means 2, pretreatment drainage tank 8 to which sludge discharged from the pretreatment means 2 is sent, and pumps to the pretreatment means 2 Forward osmosis membrane treatment means 3 connected to P1 and supplied with pretreated seawater, concentrated seawater tank 9 connected to forward osmosis membrane treatment means 3 and recovering seawater containing fouling substances, forward osmosis membrane treatment means 3 is connected to the primary purification treatment means 4 and the primary purification treatment means 4 connected to the high osmotic pressure solution via the valve V1 and connected to the forward osmosis membrane treatment means 3 via the valve V2. The adjustment tank 5 is composed of a primary purified water storage tank 6 connected to the primary purification processing means 4 and fed with a liquid whose osmotic pressure is lowered. The adjustment tank 5 is forward osmosis membrane processed via a pump P2 and a valve V3. Mean 3 Purified water storage tank 6 is connected through a pump P3 and valve V4 to the forward osmosis membrane treatment unit 3.

  The pretreatment means 2 performs MF membrane filtration treatment of seawater 1 taken by a pump (not shown), thereby removing turbidity and obtaining seawater with water quality suitable for the forward osmosis membrane treatment means 3. The pretreatment means 2 measures the differential pressure of the MF membrane (Microfiltlation, microfiltration membrane) and the filtration duration, and the measured values of the differential pressure and the filtration duration are either the preset filtration duration or the differential pressure value. When this is exceeded, backwashing of the MF membrane is performed for a set time. The sludge discharged by backwashing is sent to the pretreatment drainage tank 8. These are discarded after concentration and dehydration processes.

  The forward osmosis membrane treatment means 3 includes rooms on both sides of the forward osmosis membrane, supplies the seawater obtained by the pretreatment means 2 to one room (first room), and the other room (second Supply hyperosmotic solution to room). At this time, the osmotic pressure of each liquid can be calculated from Equation 1.

[Equation 1]
Π = iRTC (1)
Here, Π is the osmotic pressure, R is the gas constant, T is the absolute temperature, C is the molar concentration of the solution, and i is the Fant-Hoff coefficient.

  The Phanto-Hoff coefficient i is a coefficient representing the effect of ionization when the solute is an electrolyte. Between the forward osmosis membranes, a difference in osmotic pressure between the two solutions and a driving force according to the membrane pressure are generated. The osmotic pressure of the high osmotic pressure solution is made larger than the osmotic pressure of seawater, and water is recovered from the seawater into the high osmotic pressure solution. At this time, some of the ions in the seawater are not removed and leak to the highly osmotic solution side.

  FIG. 2 shows an explanatory diagram of the relationship between the type of liquid and the osmotic pressure.

  In FIG. 2, (1) high osmotic pressure solution (forward osmosis membrane treatment inlet) indicates the osmotic pressure of the high osmotic pressure solution supplied from the adjustment tank 5 to the forward osmosis membrane treatment means 3. The osmotic pressure solution (forward osmosis membrane treatment outlet) indicates the osmotic pressure of the high osmotic pressure solution fed from the forward osmosis membrane treatment means 3 to the primary purification treatment means 4, and (3) seawater (forward osmosis membrane treatment) (Inlet) indicates the osmotic pressure of seawater sent from the pretreatment means 2 to the forward osmosis membrane treatment means 3, and (4) the high osmotic pressure solution (primary purification treatment outlet) is the primary purified water storage tank 6 The osmotic pressure is shown.

  Then, the forward osmosis membrane treatment is performed using the difference between the osmotic pressure of the high osmotic pressure solution (forward osmosis membrane treatment inlet) and the osmotic pressure between seawater (forward osmosis membrane treatment inlet) and seawater (forward osmosis membrane treatment). It shows that the backwash process is performed using the difference in the osmotic pressure between the osmotic pressure at the inlet) and the high osmotic pressure solution (primary purification treatment outlet).

The solute or particles of the high osmotic pressure solution may be any substance that can make the osmotic pressure higher than seawater. For example, inorganic salts (such as AlK (SO 4 ) 2 , Na 2 HPO 4 , KCl, CaCl 2 ), sugar Solutions (glucose, fructose, etc.), gases with high solubility in water (NH 3 , CO 2 , SO 2, etc.), organic substances (alcohol, imidazole derivatives), low melting point substances (ethylene carbonate, etc.), magnetic fine particles (2-Pyrol) -MNP, TREG-MNP, etc.) are applicable.

  A material such as cellulose acetate or polyamide can be applied to the forward osmosis membrane. Further, the liquid temperature inside the forward osmosis membrane treatment means 3 is kept in the range of 20 to 50 ° C. in order to reduce the permeation resistance of the membrane. The concentrated seawater discharged from the forward osmosis membrane treatment means 3 is sent to the concentrated seawater tank 9 and discharged to the ocean after the wastewater treatment operation.

  The process at the time of fresh water manufacture in this seawater desalination system is demonstrated below.

  The high osmotic pressure solution obtained by the forward osmosis membrane treatment means 3 is sent to the primary purification treatment means 4 via the valve V1. Here, the substance added to increase the osmotic pressure is separated from the high osmotic pressure solution. As the unit treatment method of the primary purification treatment means 4, a suitable one is selected according to the type of substance added. For example, inorganic salts and low-melting-point substances include crystallization treatment, gas diffusion in the case of a gas with high solubility in water, magnetic separation in the case of magnetic fine particles, and ion exchange in the case of a sugar solution. Common separation methods include distillation and reverse osmosis membrane treatment.

  The liquid containing the separated substance at a high concentration is sent to the adjustment tank 5. The osmotic pressure of the liquid sent to the adjustment tank 5 differs depending on the specifications of the primary purification processing means 4, but becomes at least higher than the osmotic pressure at the inlet of the primary purification processing means 4.

  On the other hand, the liquid whose osmotic pressure has been lowered (liquid that has been primarily purified as fresh water) is sent to the primary purified water storage tank 6. The osmotic pressure of the liquid sent to the primary purified water storage tank 6 varies depending on the specifications of the primary purification processing means 4, but is at least lower than seawater. The obtained primary purified water 7 is sent to the next step.

  The high osmotic pressure solution whose concentration and temperature are adjusted in the adjustment tank 5 is returned to the high osmotic pressure solution side of the forward osmosis membrane treatment means 3 through the valve V3 by the pump P2. In these operations, the valves V2 and V4 are closed and the pump P3 is stopped.

  By the above treatment, forward osmosis membrane treatment and primary purification treatment are performed, and primary purified water can be continuously produced.

  Next, the process at the time of forward osmosis membrane backwashing in the seawater desalination system will be described.

  The back washing operation is performed by periodically operating the pump and the valve by a control means (not shown). The operating time interval depends on the quality of the raw water supplied to the forward osmosis membrane treatment means 3, but is set between one day and two months, and the backwash time is preferably 5 to 15 minutes.

  At the time of backwashing, first, the valve V3 is closed, the pump P2 is stopped, the pump P3 is started, and the valve V4 is controlled to be opened. By this operation, the low osmotic pressure water stored in the primary purified water storage tank 6 becomes backwash water on the high osmotic pressure solution side of the forward osmosis membrane treatment means 3 (a room different from the room where seawater is supplied). Supplied.

  In the initial stage of backwashing, since the concentration of the high osmotic pressure solution discharged from the forward osmosis membrane treatment means 3 is high, this liquid is sent to the primary purification treatment means 4 through the valve V1. Thereafter, when backwash water corresponding to the capacity of the forward osmosis membrane treatment means 3 is supplied, the valve V2 is opened, the valve V1 is closed, and the backwash water is sent to the adjustment tank 5. This is to avoid performance deterioration of the purification process, that is, influence on the quality of the product (fresh water) due to a large change in the concentration of the high osmotic pressure solution supplied to the primary purification treatment means 4.

  The forward osmosis membrane treatment means 3 is supplied with seawater on one side and primary purified water on the other side across the forward osmosis membrane. At this time, since the osmotic pressure is higher on the seawater side, water molecules on the primary purified water side pass through the forward osmosis membrane and flow to the seawater side. By this flow, the fouling substance adhering to the surface or inside of the forward osmosis membrane can be physically peeled and washed. Seawater containing fouling substances is collected in the concentrated seawater tank 9 and discharged into the ocean after wastewater treatment.

  After the backwash process for the set time is completed, a control means (not shown) controls the valve V4 to be closed, the pump P3 to be stopped, the pump P2 to be activated, and the valve V3 to be opened. Then, after supplying a high osmotic pressure solution corresponding to the volume on the high osmotic pressure solution side of the forward osmosis membrane treatment means 3, the valve V1 is opened, the valve V2 is closed, and a seawater desalination treatment state is set.

  With such a configuration, the membrane can be washed by a water flow with the osmotic pressure difference of the solution sandwiching the forward osmosis membrane as a driving force, and fouling can be suppressed, so that the life of the membrane can be extended. For backwashing, it is usually necessary to pass water through a forward osmosis membrane having a large pressure loss. However, since this configuration does not require a high-pressure pump, there is an effect that the energy consumed for backwashing can be reduced.

  Thus, according to this embodiment, since the backwashing of the forward osmosis membrane can be carried out using the difference in the concentration of water supplied to both sides of the membrane as a driving force, the pump power for backwashing is reduced. be able to. Moreover, it is possible to extend the life of the film by performing backwashing.

[Second Embodiment]
FIG. 3 is a block diagram of a seawater desalination system according to the second embodiment of the present invention. This system is configured in the same manner as in the first embodiment. In this embodiment, a valve V21 is provided on the downstream side of the pump P1, and the cleaning chemical is supplied from the cleaning chemical supply means 21 on the downstream side of the valve V21. And a three-way valve 22 is provided between the pump P2 and the forward osmosis membrane treatment means 3, and one of the three-way valves is connected to the high osmotic pressure solution side of the forward osmosis membrane treatment means 3.

  In the process for producing fresh water in this embodiment, the valve V21 is opened and the cleaning chemical supply means 21 is stopped. The three-way valve V22 is switched so as to supply the high osmotic pressure solution supplied from the pump P2 to the high osmotic pressure solution side of the forward osmosis membrane treatment means 3.

  At the time of backwashing, first, the valve V21 is closed, the pump P1 is stopped, the pump P3 is activated, and the valve V4 is opened. Thereafter, the three-way valve V22 is switched to the raw water (seawater) side of the forward osmosis membrane treatment means 3, and the cleaning chemical is supplied from the cleaning chemical supply means 21. Thereby, the low osmotic pressure water stored in the primary purified water storage tank 6 is supplied as backwash water to the high osmotic pressure solution side of the forward osmosis membrane treatment means 3 (a room different from the room where the seawater was supplied). The high osmotic pressure solution is supplied to the raw water side. In the initial stage of backwashing, since the concentration of the high osmotic pressure solution discharged from the forward osmosis membrane treatment means 3 is high, this liquid is sent to the primary purification treatment means 4 through the valve V1. Thereafter, when backwash water corresponding to the capacity of the forward osmosis membrane treatment means 3 is supplied, the valve V2 is opened, the valve V1 is closed, and the backwash water is sent to the adjustment tank 5.

  The forward osmosis membrane treatment means 3 is supplied with a high osmotic pressure solution on one side and primary purified water on the other side with the forward osmosis membrane interposed therebetween. At this time, the osmotic pressure is higher on the high osmotic pressure solution side, and the membrane can be backwashed by this effect. In addition, chemical fouling substances are also dissolved by the cleaning agent, and deposits that are difficult to remove by physical cleaning alone can be removed.

  The high osmotic pressure solution containing the fouling substance and the cleaning agent is collected in the concentrated seawater tank 9 and disposed of after the waste water treatment.

  As a cleaning chemical, a chemical capable of removing calcium sulfate, magnesium sulfate, calcium carbonate, and silicate adhering to the scale, or an organic substance generated by a living organism and causing biofouling is used. For example, a surfactant, an acid agent (an inorganic acid such as hydrochloric acid, an organic acid such as a carboxylic acid), or an alkali agent (such as caustic soda) can be used.

  After the backwash process for the set time is completed, the control means (not shown) first stops the cleaning chemical supply means 21, opens the valve V1, stops the pumps P2 and P3, closes the valve V4, and closes the three-way valve V22. Is switched to the high osmotic pressure solution supply side. When the seawater flow into the room on the raw water side of the forward osmosis membrane treatment means 3 is performed for a set time, the control means opens the valve V1, closes the valve V2, activates the pump P2, and desalinates the seawater. State.

  With such a configuration, the difference in osmotic pressure on both sides of the forward osmosis membrane is larger than that in the first embodiment, so the flux of water that permeates the membrane increases and the physical backwash effect is increased. In addition, since the fouling substance is removed by cleaning chemicals, the life of the film can be extended.

  Here, when it is not necessary to remove the fouling substance by the cleaning chemical, the cleaning chemical supply means 21 can be omitted.

  Moreover, in the forward osmosis membrane treatment of seawater desalination treatment, some of the ions in the raw water (seawater) pass through the membrane and move to the high osmotic pressure solution side and accumulate. In order to ensure the necessary fresh water quality, it is necessary to periodically update the hyperosmotic solution. In the configuration of this embodiment, partial renewal of the highly osmotic solution and membrane cleaning can be performed simultaneously. Therefore, compared with the case where these are implemented separately, the burden concerning a waste water treatment system can be reduced.

  Thus, according to this embodiment, since the backwashing of the forward osmosis membrane can be carried out using the difference in the concentration of water supplied to both sides of the membrane as a driving force, the pump power for backwashing is reduced. be able to. Moreover, it is possible to extend the life of the film by performing backwashing.

  Further, the combined use of physical and chemical cleaning has the effect of improving the cleaning effect and further extending the life of the film.

[Third Embodiment]
FIG. 4 is a block diagram of a seawater desalination system according to a third embodiment of the present invention. This system is configured in the same manner as in the first embodiment, but in this embodiment, measuring instruments S1 to S4 are added to the configuration of Example 1, and a backwash operation is executed based on these measurement results. is there.

  A case where, for example, conductivity and flow rate are used as measurement items will be described. The conductivity is an index having a correlation with the concentration of the solute in the high osmotic pressure solution. Therefore, it can be an index for judging a change in water flux in the forward osmosis membrane treatment. Measuring instrument S1 and measuring instrument S2 are conductivity meters, measuring instrument S1 is installed between valve V3 and forward osmosis membrane processing means 3, and measuring instrument S2 is installed between valve V1 and primary purification processing means 4. The measuring instruments S3 and S4 are flow meters, and each measure the amount of inflow into the forward osmosis membrane processing means 3.

FIG. 5 shows the operation control flow of the backwash process using the conductivity.
In S501, the elapsed time from the previous backwashing is compared with the set value. If the elapsed time exceeds the set value, backwashing is executed in S507.

  If not exceeded, the degree of fouling is determined in S502 to S506. In S502, the conductivity before and after the forward osmosis membrane processing means 3 is acquired from the measuring instruments S1 and S2. In S503, the respective inflow rates on the raw water side and the high osmotic pressure solution side of the forward osmosis membrane treatment means 3 are acquired. In step S504, the number of used modules operating in the system is acquired. Using these as inputs, in S505, the conductivity (σ1 ′) is calculated as a criterion for performing backwashing. The obtained σ1 ′ is compared with the measured conductivity value (σ1). If σ1> σ1 ′, that is, if the inflow of water from the seawater to the hyperosmotic pressure solution is less than the standard, backwashing is performed in S507. Run.

  As a method of calculating σ1 ′ in S505, there is a method of investigating the relationship between conductivity and flow rate in advance using a forward osmosis membrane module applied in a seawater desalination system. For example, a table or an empirical formula showing the relationship is created and used in S505. The larger the flow rate, the smaller the amount of membrane permeate water per unit flow rate, so the change in conductivity (σ0−σ1) becomes smaller.

  In the above control method, the conductivity of the high osmotic pressure solution obtained at the outlet of the forward osmosis membrane treatment means is calculated from the conductivity, flow rate, and the number of modules of the inflowing high osmosis solution, and the result is compared with the actual measurement value. Judgment was made on washing. As a simpler method, it is also possible to set a conductivity value (a constant value) when backwashing is performed, and to perform backwashing processing when an actual measurement value exceeds this value.

  Moreover, although conductivity was mentioned and demonstrated as an example of a measurement item, it will not be restrict | limited especially if it has a correlation with the solute of a high osmotic pressure solution, and the density | concentration of particle | grains. For example, pH (in the case of acid / alkali), total organic carbon (in the case of organic matter), and the number of particles (in the case of particles) can be applied.

  In addition to monitoring the concentration of the solute, it is also possible to apply a flow meter to the measuring instruments S1 and S2 as a means for evaluating the flux in the forward osmosis membrane treatment. In this case, the measuring instruments S3 and S4 are not necessary. If the flow rate at the outlet is reduced with respect to the flow rate of the high osmotic pressure solution into the forward osmosis membrane treatment means, the flux is reduced with respect to the driving force due to the concentration difference. It can be determined that the pressure loss is increasing (fouling is in progress).

  In general water purification membrane treatment, fouling is judged based on the differential pressure between membranes, but in forward osmosis membrane treatment, the differential pressure is determined by the osmotic pressure difference of the solution, so the fouling status of the membrane is determined by the differential pressure. It will be difficult to judge.

  With the configuration shown in the present embodiment, in addition to the effects described in the first embodiment, it is possible to perform backwashing according to the state of fouling. Compared to the case, it is possible to improve the yield of fresh water and reduce energy.

  Thus, according to this embodiment, since the backwashing of the forward osmosis membrane can be carried out using the difference in the concentration of water supplied to both sides of the membrane as a driving force, the pump power for backwashing is reduced. be able to. Moreover, it is possible to extend the life of the film by performing backwashing.

  In addition, it is possible to implement backwashing according to fouling conditions using flow rate and water quality as an indicator. Therefore, compared with the case where backwashing is carried out at regular intervals for preventive maintenance, the yield of fresh water is improved and energy is reduced. Is possible.

2 Pretreatment means 3 Forward osmosis membrane treatment means 4 Primary purification treatment means 5 Adjustment tank 6 Primary purified water storage tank 8 Pretreatment drainage tank 9 Concentrated seawater tank 21 Cleaning chemical supply means

Claims (6)

  1. A first chamber that is partitioned by a forward osmosis membrane and supplied with seawater;
    Forward osmosis membrane treatment means comprising a second chamber to which a high osmotic pressure solution for allowing the permeation of the forward osmosis membrane from the seawater and recovering water is supplied;
    A primary purification treatment means connected to the second chamber to remove solutes or particles in the hyperosmotic pressure solution;
    A primary purified water storage means for storing a solution having an osmotic pressure obtained by the primary purification treatment means lower than that of the seawater;
    At the time of backwashing the forward osmosis membrane, a pipe for supplying the solution stored in the primary purified water storage means to the second chamber, a pump , and
    A seawater desalination system using a forward osmosis membrane, comprising a pipe and a pump for supplying a liquid containing a high concentration of the solute or particles separated by the primary purification means to the first chamber .
  2. A first room in contact with the forward osmosis membrane and supplied with seawater as raw water,
    A forward osmosis membrane treatment means comprising a second chamber supplied with a high osmotic pressure solution for permeating the membrane from seawater and collecting water;
    Purification means for removing solutes or particles in the hypertonic solution;
    A pipe for supplying the second chamber with a solution having a lower osmotic pressure than seawater obtained by the purification means,
    At the time of backwashing, water contained in the second chamber is permeated through the forward osmosis membrane using the osmotic pressure difference between the first chamber and the second chamber as a driving force, and the positive pressure is in contact with the first chamber. Removing substances adhering to the osmotic membrane ,
    When supplying a solution having a lower osmotic pressure than seawater to the second chamber, a solution having a higher osmotic pressure than seawater recovered by the purification means is supplied to the first chamber and adheres to the forward osmosis membrane. A seawater desalination system using a forward osmosis membrane characterized in that the removed material is removed .
  3. In the seawater desalination system using the forward osmosis membrane according to claim 1 or 2,
    A seawater desalination system using a forward osmosis membrane, comprising means for adding a cleaning chemical to the liquid supplied to the first chamber.
  4. In the seawater desalination system using the forward osmosis membrane according to claim 3,
    The seawater desalination system , wherein the cleaning chemical is one of a surfactant, an inorganic acid, an organic acid, and an alkali agent.
  5. In the seawater desalination system using the forward osmosis membrane according to any one of claims 1 to 4,
    A plurality of flow rate measuring means for measuring the flow rate of water supplied to the first room and the second room, each flow rate being measured by the plurality of flow rate measuring means; A seawater desalination system using a forward osmosis membrane, characterized in that a solution having a lower osmotic pressure than seawater is supplied to the second chamber based on the results.
  6. In the seawater desalination system using the forward osmosis membrane according to any one of claims 1 to 5,
    It has means for measuring the conductivity of water supplied to and discharged from the second room, measures each conductivity during seawater desalination treatment, and the control means is based on this measurement result. A seawater desalination system using a forward osmosis membrane, wherein a solution having an osmotic pressure lower than seawater is supplied to the second chamber.
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