JP5019276B2 - Seawater desalination apparatus and seawater desalination method - Google Patents

Description

  The present invention relates to a separation membrane for seawater desalination pretreatment, a seawater desalination pretreatment device, a seawater desalination device, and a seawater desalination method capable of effectively removing seawater turbidity.

  One method of desalinating seawater is to desalinate and obtain fresh water by applying pressure to seawater and passing it through a reverse osmosis membrane (RO membrane, Reverse Osmosis Membrane). This reverse osmosis membrane is a semipermeable membrane having ultrafine pores with a diameter of about 0.1 to 0.5 nm, and has the property of selectively allowing only water molecules to permeate and not permeating impurities such as salts. .

  However, the seawater that is raw water often contains turbidity composed of coarse particles. Therefore, in order to prevent the contamination of the reverse osmosis membrane due to the turbidity, a pretreatment for removing the turbidity from the raw water is generally performed before the treatment with the reverse osmosis membrane.

  As an example of this pretreatment, sand filtration, filtration with a membrane having pores larger than those of a reverse osmosis membrane, for example, microfiltration (MF), ultrafiltration (UF), and combinations thereof are performed. (Non-Patent Document 1).

  Microfiltration refers to a method of removing turbidity by passing raw water through a microfiltration membrane (MF membrane) having a pore diameter of about 100 to 1000 nm, and ultrafiltration is an ultrafiltration having a pore diameter of about 1 to 100 nm. A method of removing turbidity by passing raw water through a filtration membrane (UF membrane).

Fukuoka District Waterworks Company “Mechanism of Desalination”, [online], [Search June 7, 2010], Internet <URL: http: // www. f-suiki. or. jp / seawater / facility / mechanism. php>

  However, in seawater, about 1 to several ppm of an adhesive substance called TEP (transparent epoxide polymer particles) secreted by plankton and microorganisms to the outside of cells exists. TEP is mainly composed of saccharides, and is a jelly-like particle having a particle size of about 1 to 200 μm that takes in water to the polymer cross-linked body and expands to a volume of 100 times. It was found that when filtered through a membrane, this TEP adheres to the membrane surface and spreads, causing fouling (clogging) of the MF membrane or UF membrane. And as fouling increases, the flux (unit area, amount of filtration per unit time) rapidly decreases.

  For this reason, the present inventors are considering removing TEP in advance using a filtration membrane (LF membrane) having an average pore diameter of 1 μm or more prior to filtration with an MF membrane or UF membrane. Even in this LF membrane, the decrease in the flux due to the occurrence of the fouling may be caused at an early stage, which is not sufficient.

  That is, in the conventional pretreatment, there is a negative correlation between the TEP removal rate and the flux, and when the removal rate is increased, fouling occurs in a shorter time, and the flow rate Incurs a rapid drop in bundles. For this reason, increasing the pressure according to the decrease in the flux keeps the flux constant and constantly supplies the raw water from which the TEP has been removed to the RO membrane.

  However, if the pressure rises, the membrane needs to be cleaned with chemicals and the like, increasing the cost. If the membrane is clogged, the membrane will not be recovered even after cleaning, and the membrane needs to be replaced, resulting in an increase in maintenance cost. In addition, when the flux is reduced, a large membrane area is required and the equipment cost is increased. And in order to raise a pressure, a more powerful pump is needed and an extra installation cost generate | occur | produces. Further, there is a limit to increasing the pressure from the viewpoint of the pressure resistance of the film.

  Accordingly, the present invention is a seawater that can supply a sufficient amount of raw water to the RO membrane constantly without increasing the pressure while maintaining a high flux while removing TEP at a high removal rate. It is an object to provide a separation membrane for desalination pretreatment, a seawater desalination pretreatment device, and a seawater desalination method.

  In the conventional pretreatment separation membrane, a porous body having communication holes is used to capture TEP having a large diameter due to the diameter of the pores. In consideration of the fact that a ring is generated and the flux is lowered, various experiments and examinations were conducted in search of a membrane material capable of reliably capturing TEP.

  As a result, it was found that polytetrafluoroethylene (PTFE) is suitable as this membrane material. That is, PTFE is a porous body having large pores formed by resin lumps distributed in an island shape and a fibril structure in which fine fibers are intertwined between the resin lumps. While a bundle can be secured, TEP can be captured by complicated fine fibers even when the hole diameter is larger than the diameter of TEP.

  Next, the present inventors used the standard flux A shown below as an index related to securing the flux, and the saccharide removal rate B shown below as an index related to the TEP removal rate, Evaluation was based on specific figures.

  The standard flux A is filtered at a constant flux, and P2 ≦ 1.5 × between the initial 30-minute average transmembrane pressure P1 and the 120-minute average transmembrane pressure P2 after 30 minutes. The highest flux value that can satisfy P1.

The saccharide removal rate B is used as an index related to the TEP removal rate because TEP is a jelly-like particle containing saccharide as a main component, and is obtained by the following equation.
Sugar removal rate B = (1-saccharide amount in filtered water / saccharide amount in raw water)

  In the calculation of the saccharide removal rate B, the amount of saccharide is obtained by quantitatively analyzing the amount of saccharide for each organic substance in water and totalizing them. However, since the number of organic substances in water is enormous, the present inventors measure organic substances in water as the total amount (carbon amount) of organic carbon as a method for measuring organic substances in water more easily. The focus was on TOC (Total Organic Carbon).

Then, using a TOC meter, TOC and DOC (Dissolved Organic Carbon) are measured for raw water and filtered water, and POC (Particulate Organic Carbon: granular organic carbon) is used as the difference between the two. It was found that the granular carbon removal rate C obtained by the following formula based on each obtained POC was useful as an index related to the TEP removal rate in place of the saccharide removal rate B.
Granular carbon removal rate C = (1−POC in filtered water / POC in raw water)

  As a result of conducting various studies for each of the above-mentioned indicators, the standard flux A is 2 m / d or more, and the saccharide removal rate B or the granular carbon removal rate C is 0.3 or more, preferably 0.5. It has been found that by using the above film material, TEP can be removed at a high removal rate while ensuring a sufficient flux.

Incidentally, m / d indicates a unit membrane area (1 m ²⁾ 1 day per filtration flow rate (day) ^{(m 3).}

  As a result of evaluating the PTFE based on each of the above indices, the standard flux A was about 1.5 m / d for the conventional membrane material, whereas it was 2 m / d or more for PTFE. In particular, it was confirmed that PTFE was excellent. Further, the saccharide removal rate B and the granular carbon removal rate C also show a removal rate of 0.4 or more, which was not obtained with the conventional membrane material in the case of PTFE. It was confirmed that it was clearly superior.

  Thus, by using a membrane material having a standard flux A of 2 m / d or more and a saccharide removal rate B or a granular carbon removal rate C of 0.3 or more, preferably 0.5 or more, a sufficient flow rate is obtained. TEP can be removed at a high removal rate while securing a bundle.

  The above evaluation results are not limited to the PTFE membrane material, and it is considered that the same evaluation results can be obtained if the porous body has large pores and fibril structures.

  Furthermore, when the value obtained by multiplying the above-mentioned standard flux A and the saccharide removal rate B or the granular carbon removal rate C is used as an index, when this value is 2 or more, the effect becomes synergistic and extremely excellent. It was found that pretreatment can be performed. PTFE also satisfies this value. The value is more preferably 5 or more, and even more preferably 10 or more.

The inventions according to claims 1 to 5 are based on these findings. That is, the invention described in claim 1
A separation membrane for seawater desalination pretreatment used for pretreatment of seawater desalination using a reverse osmosis membrane,
Filtration is performed at a constant flux, and P2 ≦ 1.5 × P1 is satisfied between the initial 30-minute average transmembrane pressure P1 and the 120-minute average transmembrane pressure P2 after the lapse of 120 minutes. The standard flux A, defined as the highest possible flux, is greater than or equal to 2 m / d,
The separation membrane for seawater desalination pretreatment is characterized in that the saccharide removal rate B represented by the following formula is 0.3 or more.
Sugar removal rate B = (1-saccharide amount in filtered water / saccharide amount in raw water)

And the invention of Claim 2 is
2. The separation membrane for seawater desalination pretreatment according to claim 1, wherein the saccharide removal rate B is 0.5 or more.

The invention according to claim 3
A separation membrane for seawater desalination pretreatment used for pretreatment of seawater desalination using a reverse osmosis membrane,
Filtration is performed at a constant flux, and P2 ≦ 1.5 × P1 is satisfied between the initial 30-minute average transmembrane pressure P1 and the 120-minute average transmembrane pressure P2 after the lapse of 120 minutes. The standard flux A, defined as the highest possible flux, is greater than or equal to 2 m / d,
A granular carbon removal rate C represented by the following formula is a separation membrane for seawater desalination pretreatment characterized by being 0.3 or more.
Granular carbon removal rate C = (1−POC in filtered water / POC in raw water)
However, POC: Suspended organic carbon content (difference between total organic carbon content and dissolved organic carbon content)

And the invention of Claim 4 is
4. The separation membrane for seawater desalination pretreatment according to claim 3, wherein the granular carbon removal rate C is 0.5 or more.

The invention according to claim 5
The seawater desalination pretreatment separation membrane according to any one of claims 1 to 4, wherein the seawater desalination pretreatment separation membrane is made of polytetrafluoroethylene.

Next, the invention according to claim 6 is:
The seawater desalination pretreatment separation membrane according to any one of claims 1 to 5, wherein a pore size of the seawater desalination pretreatment separation membrane is 1 µm or more.

  In the present invention, it is preferable to use an LF membrane having a pore diameter of 1 μm or more. Here, the pore diameter of the membrane is expressed as an average pore diameter. The average pore diameter means a pore diameter determined by a bubble point method (air flow method).

Specifically, the pore diameter is determined by using IPA bubble point value (pressure) measured in accordance with ASTM F316 using isopropyl alcohol as P (Pa), liquid surface tension (dynes / cm) as γ, and B as a capillary constant. Means a diameter d (μm) represented by the following formula. The same applies to the average pore diameters of MF membranes, UF membranes, and the like.
d = 4Bγ / P

  Since the LF membrane has an average pore diameter of 1 μm or more, the flow rate (flux) per unit membrane area can be increased, and from the reverse, a desired throughput can be obtained with smaller equipment. The smaller the average pore diameter of the LF membrane, the smaller particles can be removed, and the removal rate of organic particles such as turbidity and TEP in the pretreatment is improved. On the other hand, the smaller the average pore size of the LF membrane, the smaller the flow rate (flux) per unit membrane area. Accordingly, an optimum pore size is selected in consideration of a desired removal rate of organic particles such as turbidity and TEP and a flow rate (flux) per unit membrane area.

The invention described in claim 7
The seawater desalination pretreatment separation membrane according to any one of claims 1 to 6, wherein the seawater desalination pretreatment separation membrane is not hydrophilized.

  When the membrane is a polymer membrane made of a hydrophobic material such as a PTFE membrane (hydrophobic polymer membrane), in general, in order to improve the affinity with the liquid to be treated, for example, the PTFE membrane is made of vinyl. Hydrophilization is performed by a method of surface cross-linking with a hydrophilizing compound such as alcohol.

  However, when used as a pretreatment separation membrane, the inventors of the present application have not been subjected to a hydrophilization process for cross-linking and immobilizing a hydrophilic material on the membrane surface. It has been found that the granular carbon removal rate can be secured.

  Unlike such processing, the hydrophilization treatment is a method in which the membrane and hydrophilic alcohol are brought into contact before the liquid to be treated is permeated and the surface of the membrane (including the inside of the pores) is covered with hydrophilic alcohol. It is preferable to use it. Examples of the hydrophilic alcohol include ethanol and propanol, and isopropanol is particularly preferably used.

The invention according to claim 8 provides:
A seawater desalination pretreatment apparatus, wherein the separation membrane for seawater desalination pretreatment according to any one of claims 1 to 7 is used as a filtration membrane.

  Since a separation membrane for seawater desalination pretreatment that can sufficiently remove organic matter and sufficiently suppress the decrease in flux is used, a sufficient amount of organic matter removed in the seawater desalination device The raw water can be sent stably.

The invention according to claim 9 is:
A pretreatment means using a microfiltration membrane or an ultrafiltration membrane is provided after the pretreatment means using the separation membrane for seawater desalination pretreatment according to any one of claims 1 to 7. The seawater desalination pretreatment device according to claim 8, wherein:

  Excellent filtration characteristics that can further remove fine turbidity other than organic matter removed by the separation membrane for seawater desalination pretreatment by further arranging a microfiltration membrane or ultrafiltration membrane with a smaller pore size The seawater desalination pretreatment apparatus can be provided.

The invention according to claim 10 is:
The seawater desalination pretreatment device according to claim 8 or 9,
A seawater desalination apparatus having a desalination apparatus using a reverse osmosis membrane.

  By using a seawater desalination pretreatment device with excellent filtration characteristics, it is possible to supply raw water from which organic substances have been sufficiently removed, so a desalination treatment device using a reverse osmosis membrane for a long time, Even when the desalting treatment is performed, it is possible to provide a seawater desalination apparatus in which occurrence of fouling in the RO membrane is suppressed.

The invention according to claim 11
Raw water filtered using the seawater desalination pretreatment device according to claim 8 or 9,
It is a seawater desalination method characterized by performing desalination using a reverse osmosis membrane method.

  Since the desalting process is performed on the raw water from which the organic substances have been sufficiently removed, the occurrence of fouling in the RO membrane is suppressed even when the desalting process is performed for a long time.

  According to the present invention, while removing TEP at a high removal rate, a sufficient amount of raw water can be constantly supplied to the RO membrane without increasing the pressure while maintaining a high flux.

It is a figure explaining the separation membrane of this Embodiment, (a) is the schematic diagram which looked at the separation membrane planarly, (b) supplements the jelly-like target object M by the structure of a knot part and a fine fiber. It is a schematic diagram which shows a mode. It is a block diagram which shows the structure of the seawater desalination apparatus provided with the pre-processing apparatus using the separation membrane of this invention.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

1. Separation membrane First, the separation membrane for seawater desalination pretreatment according to the present embodiment will be described. FIG. 1 is a diagram illustrating a separation membrane according to this embodiment. FIG. 1A is a schematic view of the separation membrane as viewed in plan.

  The separation membrane according to the present embodiment is a porous membrane made of PTFE, and, as shown in FIG. 1 (a), a large number of nodules 1 and a thickness of 1 μm or less connecting the nodules 1 to each other. It is composed of fine fibers (fibrils) 3, and a large number of pores 2 are formed between the knot portions 1.

  FIG. 1B is a schematic diagram showing a state where the jelly-like object M is supplemented by the structure of the knot portion 1 and the fine fiber 3. Since the fine fibers 3 are present in a state of being irregularly arranged in the plane direction and the thickness direction, even if the pore diameter of the pores 2 is large, the jelly is mainly composed of saccharides throughout the thickness direction of the membrane. Of carbon can be reliably captured. By removing the jelly-like carbon, the total carbon (TOC) in the raw water is reduced, and in particular, the granular carbon (POC) is reduced. Thereby, for example, saccharides can be filtered at a high removal rate while maintaining a high flux as compared with a conventional separation membrane of 5 m / d and about 1.5 m / d.

2. Measurement of the flux The flux is filtered at a constant flux, and P2 ≦ 1.30 between the initial 30-minute average transmembrane pressure P1 and the 120-minute average transmembrane pressure P2. The maximum value of the flux that can satisfy 5 × P1 is obtained and set as the standard flux A.

3. Next, a method for measuring the removal rate will be described. The removal rate is generally evaluated by the saccharide removal rate, but it can also be evaluated by the granular carbon removal rate instead of the saccharide removal rate from the viewpoint of simplicity of measurement.

(1) Sugar removal rate Sugar removal rate is
Saccharide removal rate = 1-expressed by the amount of saccharide in filtered water / the amount of saccharide in raw water, and the amount of saccharide in filtered water and the amount of saccharide in raw water are measured by sugar analysis.

  Specifically, various sugars in water are quantitatively analyzed using a sugar analyzer, for example, a sugar analyzer ICS-3000 manufactured by Nippon Dionex Co., Ltd. equipped with an electrochemical detector, and the total is expressed in ppm.

(2) Granular carbon removal rate The granular carbon removal rate is
Granular carbon removal rate = 1-POC in filtered water / POC in raw water
The POC in filtered water and raw water is calculated by the following procedure.

A. The TOC of the sample (raw water and filtered water) is measured with a TOC meter.
B. The sample is filtered through a filter having a pore size of 0.1 μm (this removes 100% of POC, leaving only DOC in the filtered water).
C. DOC contained in filtered water is measured with a TOC meter.
D. From measured TOC and DOC
POC = TOC-DOC
To calculate POC.

  In the above, TOC indicates the total amount of carbon in the organic compound present in the raw water (total organic carbon), and DOC indicates the amount of carbon in the organic compound present in the filtered water (dissolved organic carbon, Dissolved). Organic Carbon), and POC indicates removed granular carbon (Particulate Organic Carbon).

  The TOC is measured by a combustion oxidation non-dispersion infrared absorption method. Specifically, an organic substance is combusted with high-purity air or oxygen at a high temperature using a platinum catalyst. The carbon dioxide concentration generated by combustion is measured with a gas analyzer, and the TOC is measured. As the TOC meter, for example, TOC-Vc series manufactured by Shimadzu Corporation is used.

4). Next, the seawater desalination apparatus will be described. The seawater desalination apparatus shown in FIG. 2 includes a pretreatment apparatus 11 and a desalination apparatus 10 for desalinating pretreated seawater. The arrows in the figure represent the flow of water to be treated, and a pump is disposed in the previous stage of the pretreatment device 11.

(1) Pretreatment device The pretreatment device 11 includes the separation membrane having the above-described configuration. A single-stage filtration using only the above-described separation membrane may be used, and the first pretreatment apparatus including the separation membrane having the above-described configuration and ultrafiltration using a UF membrane or microfiltration using an MF membrane are performed. The pretreatment device may be configured as two-stage filtration with the second pretreatment device. Even if one-stage filtration is effective in removing saccharides sufficiently, it is effective in that the membrane area of the entire pretreatment device can be reduced. However, by using two-stage filtration, filtration including other objects to be removed is also possible. Can be improved.

(2) Desalination apparatus The desalination apparatus 10 includes a reverse osmosis membrane having a pore diameter of about 1 to 2 nm. In the desalination apparatus 10, the reverse osmosis membrane may be a spiral type or a tubular type, or may be a hollow fiber membrane, but in order to process a large amount of seawater. It is necessary to have a structure of

  The seawater desalination apparatus configured as described above first pretreats seawater by passing it through the separation membrane described above with the pretreatment apparatus 11, and filters and removes organic turbidity and inorganic solids in the seawater. To do. Next, the seawater from which organic turbidity and inorganic solids have been removed by the pretreatment device 11 is passed through the desalting device 10 to be desalted to obtain fresh water.

  When the ability of the pretreatment device 11 or the desalinating device 10 is reduced due to long-term operation, the ability can be backwashed to restore the ability and used repeatedly for seawater desalination.

  The pretreatment device 11 for seawater desalination using the separation membrane of the present invention filters and removes organic turbidity and inorganic solids in seawater by passing through the separation membrane described above. For this reason, clogging in the desalting apparatus can be effectively prevented, the desalting apparatus can be downsized, and the desalting cost can be reduced.

  Hereinafter, a pretreatment apparatus using a separation membrane of the present invention will be described based on examples.

Example 1
In this embodiment, the separation membrane is evaluated using the granular carbon removal rate.

1. Filtration Seawater was used as raw water for filtration using a hydrophilic TT pretreatment apparatus equipped with the separation membrane of the present invention. Here, the hydrophilic TT method is a treatment method using a membrane having a fibril structure used in the present invention. A membrane obtained by crosslinking and fixing a hydrophilic polymer on the surface (LF made by PTFE) Membrane) is called “hydrophilic TT membrane”, and TT is named after the acronym of TEP Trap. The “hydrophobic TT method” to be described later refers to a method in the case of using a hydrophobic film that is not subjected to a hydrophilic treatment (the hydrophilic treatment with alcohol is performed first).

(1) Hollow fiber module A hollow fiber membrane module provided with a PTFE hollow fiber membrane having a fibril structure (PORFLON (registered trademark) type: TBW-2311-200) was used. The details of this hollow fiber membrane module are as follows.

Standard flux: 10 m / d
Hollow fiber membrane: 360 pieces
Effective length 1000mm
Hollow fiber outer diameter 2.3mm
Hollow fiber inner diameter 1.1mm
Hollow fiber film thickness 600μm
Pore size 2.0μm (average particle rejection 90% or more)
70% porosity
Here, porosity = 100 × {1− (hollow fiber resin volume cc) / hollow fiber bulk volume cc)}
Hollow fiber resin volume = hollow fiber weight g / PTFE density
Hollow fiber bulk volume = hollow fiber cross-sectional area cm ³ × length cm

(2) Filtration conditions Pressure: Filtration was performed under a pressure of 50 kPa.

2. Measurement of flux and removal rate (1) Measurement method a. Measurement of flux The flux was measured by the amount of filtered water accumulated in the graduated cylinder at a fixed time.

B. Measurement of granular carbon removal rate The granular carbon removal rate was measured using a combustion catalyst oxidation type TOC meter (total organic carbon meter), manufactured by Shimadzu Corporation, type TOC-Vc. For reference, silica, aluminum, and iron were also analyzed.

(2) Measurement results a. Flux The flux was 10 m / d.

B. The removal rate measurement results are shown in Table 1.

  From Table 1, it was found that POC was removed from 0.23 ppm to 0 ppm, that is, removed with a granular carbon removal rate of 1.0. It was confirmed that silica, aluminum, and iron were also removed.

  From the above, it can be seen that when the separation membrane for seawater desalination pretreatment of the present invention is used, the flux can be increased and the removal rate can be increased.

(Example 2)
In this example, the separation membrane is evaluated using the saccharide removal rate.
1. Filtration Using seawater along the coast of Shizuoka City, Shizuoka Prefecture as raw water, filtration was performed using a hydrophilic TT method and a hydrophobic TT method pretreatment apparatus equipped with the separation membrane of the present invention. For comparison, filtration was performed using a 2 μm mesh wire mesh. Example 1 is the same as Example 1 except for the following measurements.

2. Measurement (1) Measurement of saccharide removal rate The removal rate of TOC, galactose, and glucose was measured by sugar analysis. Specifically, the analysis was performed according to the following procedure.

a. Preparation of sample A sample of 980 mL (milliliter) was freeze-dried in several batches, washed with water to make exactly 100 mL.

b. Hydrolysis The prepared sample (1 mL) and 4 mol / L trifluoroacetic acid (1 mL) were mixed, and after sealed under reduced pressure, heated at 100 ° C. for 3 hours for hydrolysis.
After allowing to cool to room temperature, the solvent was distilled off with a centrifugal evaporator, and 1 mL of water was accurately added and irradiated with ultrasonic waves.
This solution was placed in a filter unit (0.45 μm) containing an ion exchange resin, and centrifuged (10000 rpm) for 1 minute to obtain a sample solution.

c. Standard solution preparation Water was added to 10 mg each of arabinose, glucose, galactose, fructose, mannose, and rhamnose to make exactly 50 mL. 5 mL of this solution was accurately taken, and water was added to make exactly 50 mL to obtain a standard solution. The standard solution was accurately diluted with water to prepare standard solution 1 (about 0.2 μg / mL each), standard solution 2 (about 1 μg / mL each), and standard solution 3 (about 5 μg / mL each).

d. Measurement conditions Sugar analyzer: ICS-3000 manufactured by Nippon Dionex
Detector: Electrochemical detector Column: CarboPacPA10 (4 mm ID x 250 mm)
Column temperature: constant temperature around 25 ° C. Mobile phase A: 10 mmol / L sodium hydroxide solution Mobile phase B: 200 mmol / L sodium hydroxide solution Gradient conditions are shown in Table 2.

(2) Removal rate measurement results Table 3 shows the results.

From Table 3, the saccharide removal rate is calculated as follows, and it can be seen that galactose and glucose are well removed compared to the wire mesh.
Sugar removal rate B = (1-amount of sugar in filtered water / amount of sugar in raw water)
Sugars in seawater: 0.021 + 0.031 = 0.052ppm
In hydrophilic TT filtrate: 0.012 + 0.022 = 0.034 ppm
In hydrophobic TT filtrate: 0.006 + 0.012 = 0.018 ppm
Therefore,
Sugar removal rate B of hydrophilic TT B = (1-0.034 / 0.052) = 0.34
Sugar removal rate B of hydrophobic TT B = (1−0.018 / 0.052) = 0.65

  Thus, according to the present invention, organic turbidity can be removed with high efficiency, clogging of the desalting apparatus can be prevented for a long time, and cost can be reduced. It can also be seen that the hydrophobic TT method is more effective than the hydrophilic TT method.

  Although the present invention has been described based on the embodiment, the present invention is not limited to the above embodiment. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Knot part 2 Pore 3 Fine fiber 10 Desalination apparatus 11 Pretreatment apparatus

Claims (7)

A seawater desalination apparatus comprising a seawater desalination pretreatment apparatus in which a separation membrane for seawater desalination pretreatment is used as a filtration membrane, and a desalination apparatus using a reverse osmosis membrane, wherein the seawater desalination apparatus The separation membrane for treatment is made of polytetrafluoroethylene that has been hydrophilized or not hydrophilized, and the average of the initial 30 minutes when filtering seawater to be desalinated at a constant flux Standard flux defined as the maximum value of flux that can satisfy P2 ≦ 1.5 × P1 between the transmembrane pressure P1 and the average transmembrane pressure P2 for 30 minutes after 120 minutes. A is 2 m / d or more, and when the desalinated seawater is filtered, the saccharide removal rate B shown by the following formula is 0.3 or more: apparatus.
Sugar removal rate B = (1-saccharide amount in filtered water / saccharide amount in raw water)) The saccharide removal rate B is Ri der 0.5 or more, the seawater desalination pretreatment separation membrane of claim 1, wherein the polytetrafluoroethylene der Rukoto which is not processed hydrophilic Seawater desalination equipment. A seawater desalination apparatus comprising a seawater desalination pretreatment apparatus in which a separation membrane for seawater desalination pretreatment is used as a filtration membrane, and a desalination apparatus using a reverse osmosis membrane, wherein the seawater desalination apparatus The separation membrane for treatment is made of polytetrafluoroethylene that has been hydrophilized or not hydrophilized, and the average of the initial 30 minutes when filtering seawater to be desalinated at a constant flux Standard flux defined as the maximum value of flux that can satisfy P2 ≦ 1.5 × P1 between the transmembrane pressure P1 and the average transmembrane pressure P2 for 30 minutes after 120 minutes. A is 2 m / d or more, and when the seawater to be desalinated is filtered, the granular carbon removal rate C shown by the following formula is 0.3 or more. Device.
Granular carbon removal rate C = (1−POC in filtered water / POC in raw water)
However, POC: Suspended organic carbon content (difference between total organic carbon content and dissolved organic carbon content)   The seawater desalination apparatus according to claim 3, wherein the granular carbon removal rate C is 0.5 or more.   The seawater desalination apparatus according to claim 1, wherein the separation membrane for seawater desalination pretreatment is not hydrophilized.   The seawater desalination apparatus according to any one of claims 1 to 5, wherein a pore size of the separation membrane for seawater desalination pretreatment is 1 µm or more.   The seawater desalination apparatus according to any one of claims 1 to 6, wherein the raw water filtered using the seawater desalination pretreatment apparatus is desalted using a reverse osmosis membrane method. A seawater desalination method characterized by that.

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