JP6149489B2 - Operation method of reverse osmosis membrane device - Google Patents

Description

The present invention relates to a reverse osmosis membrane device for treating water containing a macromolecular organic substance that adsorbs to a membrane and causes membrane contamination, such as MBR-treated water, and an operation method thereof.
The present invention also relates to a method for treating biologically treated water using the reverse osmosis membrane device.

  A reverse osmosis membrane is conventionally used for removing ions, organic substances, and the like in raw water in seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, and the like (for example, Non-Patent Document 1). . Reverse osmosis membranes may have reduced permeation flux due to the growth of microorganisms on the membrane surface or adsorption of organic matter, or module differential pressure may increase due to blockage by turbidity. It is necessary to recover the differential pressure between the raw water side and concentrated water side of the element (hereinafter referred to as element differential pressure).

  As a reverse osmosis membrane structure, it is generally known to use an element having a membrane structure called a spiral structure. As an example of a conventional spiral membrane element, a bag-like membrane is formed by superimposing a reverse osmosis membrane on both sides of a permeate spacer and adhering three sides, and the opening of the bag-like membrane is used as a permeate water collecting pipe. Attached to the outer peripheral surface of the permeate water collecting pipe together with the net-like raw water spacer is one that is formed by spirally winding. In such a spiral membrane element, raw water is supplied from one end face side of the element, flows along the raw water spacer, and is discharged as concentrated water from the other end face side. In the process of flowing along the raw water spacer, the raw water permeates through the reverse osmosis membrane to become permeated water. This permeated water flows along the permeated water spacer into the permeated water collecting pipe and is discharged from the end of the permeated water collecting pipe. Is done.

Thus, in the spiral membrane element, the raw water path is formed by the raw water spacers disposed between the bag-like membranes wound around the permeate water collecting pipe.
Therefore, by increasing the thickness of the raw water spacer of the spiral membrane element, it is difficult for turbidity to block the raw water flow path, and it is possible to avoid an increase in element differential pressure due to accumulation of turbidity and a decrease in the amount of permeate and permeate. In recent years, spiral-type reverse osmosis membrane elements in which the thickness of the raw water spacer is increased have been put on the market in order to improve occlusion due to turbidity.

However, when the raw water spacer is thickened, the membrane area per element is reduced, and the amount of permeated water per element is reduced. The membrane area of the commercially available spiral reverse osmosis membrane element is 42 m ² (440 ft ² ) or less.

  On the other hand, even if the thickness of the raw water spacer is increased, an improvement effect on the decrease in permeation flux due to adsorption of membrane contaminants cannot be expected. Further, when the thickness of the raw water spacer is reduced in order to increase the membrane area per element, blockage of the flow path due to turbidity becomes a problem.

  By the way, activated sludge treatment of organic sewage such as sewage in a biological treatment tank, and a membrane separation activated sludge method (MBR: membrane) in which the activated sludge mixed liquid is separated into solid and liquid using an immersion type membrane separation apparatus immersed in the biological treatment tank. Bioreactors) are becoming widespread because they can obtain treated water with stable water quality and can perform high-load treatment by increasing the activated sludge concentration. In addition, a method for treating organic wastewater in which MBR-treated water (membrane filtered water of a submerged membrane separation device) is directly supplied to a reverse osmosis membrane device to perform reverse osmosis membrane separation treatment has also been proposed (for example, non-patent literature). 2).

  However, MBR-treated water contains a large amount of high-molecular organic matter having a molecular weight of 10,000 or more, which becomes a membrane pollutant. In a reverse osmosis membrane device for treating MBR-treated water, the permeation flux decreases with time or the transmembrane pressure difference decreases. There is a problem that the increase is large.

"Practical Membrane Separation Technology for Users" (April 30, 1996, first edition, 1st edition, published by Nikkan Kogyo Shimbun), page 6. "Water Treatment Membrane Technology and Material Evaluation" (January 30, 2012, 1st edition, 1st edition, Science & Technology Co., Ltd.), page 11

  The present invention uses a reverse osmosis membrane device capable of stably treating raw water containing a large amount of membrane contaminants such as MBR treated water while preventing a reduction in the amount of permeated water, an operating method thereof, and this reverse osmosis membrane device. It is an object of the present invention to provide a method for treating biologically treated water.

The reverse osmosis membrane is known to cause a phenomenon called concentration polarization on the membrane surface due to water flow, and when the concentration polarization increases, the solute concentration on the membrane surface increases. As a result of analyzing the flow conditions of the spiral type reverse osmosis membrane element, the following knowledge was obtained.
1) When the permeation flux of the membrane is reduced, the concentration polarization is reduced.
2) Concentration polarization decreases when the water passage speed on the membrane surface is increased.
3) The concentration polarization increases as the molecular weight of the solute increases.
The present inventors also confirmed that the causative substance causing fouling due to membrane contamination is a high molecular weight organic substance having a molecular weight of 10,000 or more, particularly a biological metabolite such as a polysaccharide or a protein, and the high molecular weight organic substance has a concentration. It was found that when the membrane surface concentration was increased by polarization, the permeation flux and the permeated water amount decreased significantly.

Therefore, as a result of further studies to solve the above problems, the membrane area per element can be increased by reducing the film thickness of the reverse osmosis membrane. The permeation flux can be made smaller than that of the membrane element, and further, the concentration polarization can be reduced by operating with a permeation flux of a certain value or less, and the decrease in the permeation flux and the permeated water amount can be suppressed. I found.
As described above, if the thickness of the raw water spacer is reduced in order to increase the membrane area, in the case of raw water with a large amount of turbidity, there is a greater concern about blockage of the flow path, but the raw water spacer is reduced by reducing the thickness of the membrane substrate. The film area per element can be increased without reducing the thickness.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] In a method for operating a reverse osmosis membrane device in which water containing a polymer organic material is treated as raw water, the raw water contains a polymer organic material having a molecular weight of 10,000 or more at a concentration of 0.01 ppm or more, and the reverse osmosis The membrane device has a reverse osmosis membrane element comprising a membrane unit in which a raw water spacer is provided on one surface of a reverse osmosis membrane having a thickness of 0.1 mm or less and a permeable water spacer is provided on the other surface. A method for operating a reverse osmosis membrane device, wherein the device is operated at a permeation flux of 0.6 m / d or less.

[2] The operation method of the reverse osmosis membrane device according to [1], wherein the permeation flux is 0.45 m / d or less.

[3] The method of operating a reverse osmosis membrane device according to [1] or [2], wherein the reverse osmosis membrane element is a spiral type reverse osmosis membrane element.

[4] The method for operating a reverse osmosis membrane device according to any one of [1] to [3], wherein the raw water is treated water by membrane separation activated sludge method.

According to the present invention, raw water containing a large amount of membrane contaminants such as MBR treated water can be stably subjected to reverse osmosis membrane separation treatment while preventing a decrease in the amount of permeated water.
That is, according to the present invention, the membrane area per element can be increased by reducing the film thickness of the reverse osmosis membrane, and the permeation flux is higher than that of the conventional spiral type reverse osmosis membrane element even at the same amount of permeate. Furthermore, by operating with a permeation flux below a certain value, the concentration polarization on the membrane surface can be reduced and the decrease in the amount of permeated water can be suppressed. Can continue.

It is a systematic diagram which shows embodiment of the processing method of the biologically treated water of this invention. It is a graph which shows the relationship between the permeation | transmission flux and the concentration rate in the reverse osmosis membrane separation process which uses the water containing NaCl aqueous solution or the water containing the high molecular organic substance of average molecular weight 10,000 as raw water. It is typical sectional drawing which shows the structure of the flat film cell used in the Example.

  Hereinafter, embodiments of the present invention will be described in detail.

<Raw water>
In the present invention, the raw water subjected to the reverse osmosis membrane separation treatment by the reverse osmosis membrane device is water containing a high molecular weight organic substance having a molecular weight of 10,000 or more at a concentration of 0.01 ppm or more. High-molecular organic substances having a molecular weight of 10,000 or more, particularly biological metabolites such as polysaccharides and proteins, easily contaminate the membrane and easily cause a decrease in permeation flux. In the present invention, water containing 0.01 ppm or more, for example, 0.05 to 0.5 ppm of such a high molecular organic substance and greatly reducing the permeation flux of the reverse osmosis membrane by passing water is used as raw water.

  As such high molecular organic substance-containing water, recovered water from various wastewaters or biologically treated water, particularly MBR treated water is preferably used.

  In addition, there is no restriction | limiting in particular in the measuring method of the water concentration of the high molecular weight organic substance more than 10,000, Molecular weight fractionation by chromatography, such as LC-OCD (liquid chromatography-organic carbon measurement) and HPLC (high performance liquid chromatography). Using a device that measures TOC, etc., or separating a substance with a molecular weight of 10,000 or more and a substance with a molecular weight of less than 10,000 using a UF membrane with a molecular weight cut off of 10,000 in advance, and performing a TOC analysis. It can be measured by using a technique.

<Reverse osmosis membrane>
The reverse osmosis membrane used in the present invention has a thickness of 0.1 mm or less. Since the thickness of an existing reverse osmosis membrane is usually about 0.13 mm, a thinner reverse osmosis membrane is used in the present invention. When the thickness of the reverse osmosis membrane exceeds 0.1 mm, there is not much difference from the existing reverse osmosis membrane, and the effect of increasing the membrane area per element and the effect of improving the permeated water amount by using a thin reverse osmosis membrane are sufficiently obtained. I can't.
However, if the reverse osmosis membrane is too thin, the membrane strength may be insufficient. Therefore, the reverse osmosis membrane used in the present invention has a thickness of 0.01 to 0.1 mm, particularly 0.03 to 0.07 mm. It is preferable that it is a grade.

  Although there is no restriction | limiting in particular as a material of a reverse osmosis membrane, Since a membrane with a high removal rate is preferable, the aromatic polyamide membrane synthesize | combined on the base material using phenylenediamine and an acid chloride is preferable. Such an aromatic polyamide film is synthesized, for example, by the method described in JP-A-8-224452, JP-A-9-253455, JP-A-10-174852, JP-A-2006-95476, and the like. be able to.

  The substrate of the reverse osmosis membrane is not particularly limited and can be suitably used as long as it is in the form of a sheet. However, the strength of the thin film is maintained, and a polymer layer such as a polysulfone layer to be coated is used. The nonwoven fabric which consists of a long fiber is used suitably from the point which can make thin. As such a base material, for example, a long fiber nonwoven fabric described in JP 2009-57654 A, International Publication WO 2010/126109, International Publication WO 2010/126113, or the like can be used.

  In order to obtain a reverse osmosis membrane having a suitable thickness as described above, the reverse osmosis membrane used in the present invention is formed by forming an aromatic polyamide dense layer on a long fiber nonwoven fabric through a polymer layer such as a polysulfone layer. In the case of the permeable membrane, it is preferable that the long fiber nonwoven fabric has a thickness of 10 to 100 μm, the polymer layer has a thickness of 1 to 40 μm, and the aromatic polyamide dense layer has a thickness of 0.01 to 1 μm.

<Reverse osmosis membrane element>
As a reverse osmosis membrane element to be loaded in the reverse osmosis membrane device in the present invention, a raw water spacer for passing raw water is arranged on the primary side (one surface) of the flat membrane of the reverse osmosis membrane, and the secondary side (the other side) A membrane unit having a permeated water spacer for passing permeated water on the surface thereof, or a laminate of a plurality of membrane units, or a spiral shape formed by winding this membrane unit, that is, a spiral type A reverse osmosis membrane element can be used. In consideration of space utilization efficiency, a spiral type reverse osmosis membrane element can be suitably used.
There is no restriction | limiting in particular as a diameter of a spiral type reverse osmosis membrane element, What was called 4 inches, 8 inches, and 16 inches is usually used. The length of the element is usually about 1 m.

  The shape of the raw water spacer and the permeated water spacer is not particularly limited, but a plurality of wires having the same or different diameters made of resin such as polyethylene or polypropylene are arranged at equal intervals, and an angle of 45 to 90 degrees. In general, mesh spacers stacked so as to cross each other are generally used.

If the thickness of the raw water spacer is too thin, it is likely to cause a problem of blockage due to turbidity, and if it is too thick, the membrane area per element becomes small and the permeation flux decreases, so the range of 0.6 to 0.9 mm. It is preferable that Currently, raw water spacers that are generally employed include 0.69 mm (26 mil), 0.71 mm (28 mil), and 0.86 mm (34 mil) thicknesses.
Although there is no restriction | limiting in particular as thickness of a permeated water spacer, 0.1-0.25 mm is used suitably. If the thickness of the permeated water spacer is too thick, the membrane area per element becomes small as in the case of the raw water spacer, and if it is too thin, the differential pressure increases and the amount of permeated water decreases.

<Permeation flux>
In the present invention, a reverse osmosis membrane device using a reverse osmosis membrane having a thickness of 0.1 mm or less as described above is operated at a permeation flux of 0.6 m / d or less.

In general, the pure water permeation flux at the standard operating pressure of the reverse osmosis membrane device is 0.7 to 0.85 m / d, and when raw water containing inorganic salts and organic substances is passed, 0.5 to 0. Usually, it is set to about 7 m / d.
The inventors of the present invention indicate that a polymer organic substance having a molecular weight of 10,000 or more is a substance that contaminates a reverse osmosis membrane, and that the permeation flux decreases significantly when the membrane surface concentration of the polymer organic substance concentration exceeds 1 ppm. Experimentally confirmed that, in raw water containing 0.01 ppm or more of a high molecular weight organic material having a molecular weight of 10,000 or more, the permeation flux decreases significantly when the concentration ratio of the membrane surface concentration exceeds 100 times. It was. In order to prevent the concentration rate from exceeding 100 times, the permeation flux needs to be 0.6 m / d or less. Therefore, in the present invention, the reverse osmosis membrane device is operated at a permeation flux of 0.6 m / d or less, preferably 0.45 m / d or less. However, if the permeation flux is too low, the required number of membranes increases, which is not economical. Therefore, the permeation flux is preferably 0.2 m / d or more.
In addition, about the amount of concentrated water, 2.0-8.0 m < ³ > / h is suitable in the case of an 8-inch spiral type reverse osmosis membrane element, for example. The linear velocity at this time is 0.05 to 0.15 m / s.

<Treatment of biologically treated water>
Especially the reverse osmosis membrane apparatus of this invention is used suitably for the reverse osmosis membrane part process of biologically treated water.

FIG. 1 is a system diagram showing an embodiment of the biological treatment water treatment method of the present invention using the reverse osmosis membrane device of the present invention.
As a treatment procedure of the treatment method of the biologically treated water of the present invention, for example, as shown in FIG. 1 (a), aerobic and / or anaerobic biological treatment means 1, agglomeration treatment means 2, and solidification such as pressure levitation A method of introducing the biologically treated water treated by the liquid separating means 3 and the filtering means 4 into the reverse osmosis membrane device 6 through the safety filter 5 and performing the reverse osmosis membrane separation treatment, as shown in FIG. A method in which water obtained by solid-liquid separation of the treated water directly by filtration means 4 such as a membrane filtration device is introduced into a reverse osmosis membrane device 6 and subjected to a reverse osmosis membrane separation treatment, or as shown in FIG. (Immersion type membrane separation apparatus) The method of introducing the treated water of 7 directly into the reverse osmosis membrane apparatus 6 and the like can be mentioned, but it is not limited to these methods.

  Hereinafter, the present invention will be described more specifically with reference to verification examples, examples, and comparative examples.

[Verification Example 1]
In an 8-inch spiral reverse osmosis membrane element with a raw water spacer thickness of 0.71 mm and a permeate spacer thickness of 0.23 mm, the membrane area per element when the thickness of the reverse osmosis membrane is changed, and the permeation The results obtained by calculating the permeation flux when the amount of water is 1.1 m ³ / h are shown in Table 1 below.

  From Table 1, it can be seen that by reducing the thickness of the reverse osmosis membrane, the membrane area per element can be increased, and the permeation flux can be lowered while maintaining the same amount of permeate.

[Verification Example 2]
Results of analyzing the relationship between the permeation flux and the concentration ratio (membrane surface concentration / average bulk concentration) in the case of reverse osmosis membrane separation treatment using NaCl aqueous solution or water containing a high molecular weight organic material with an average molecular weight of 10,000 as raw water The relationship shown in FIG. 2 was obtained.
As shown in FIG. 2, although there are some differences depending on the type of polymer, the membrane surface concentration of the polymer organic material is generally increased by increasing the permeation flux and decreasing the average linear velocity as compared with substances having a low molecular weight such as NaCl. It can be seen that it increases significantly.

[Example 1]
<Manufacture of non-woven fabric>
According to the method described in JP2009-57654A, a long fiber nonwoven fabric was produced as follows.
Polyethylene terephthalate containing titanium oxide and copolymerized polyester containing titanium oxide having an isophthalic acid copolymerization ratio of 10 mol% were melted at 295 ° C. and 280 ° C., respectively, and polyethylene terephthalate was used as the core component and the copolymer polyester was used as the sheath component. After spinning from the pores at a base temperature of 300 ° C. and a weight ratio of core: sheath = 80: 20, it was spun by an ejector to obtain a core-sheath filament, which was collected as a fiber web on a moving net conveyor. The collected fiber web was thermocompression bonded with a pair of upper and lower flat rolls to obtain a spunbond long fiber nonwoven fabric having a thickness of 70 μm.

<Formation of polymer layer>
After heating and dissolving 18 parts by weight of polysulfone in 82 parts by weight of dimethylformamide at 80 ° C., filtration and defoaming were performed to obtain a polysulfone solution for forming a polymer layer. After applying this polysulfone solution to one side of the above-mentioned long-fiber non-woven fabric, it is phase-separated in coagulated water at 35 ° C., and then washed with water to remove the solvent remaining in the membrane, thereby removing the thickness of 30 μm. A polysulfone layer was formed.

<Formation of an aromatic polyamide dense layer>
Next, a polyamide-based dense layer was formed on the polysulfone layer by the following procedure.
An aqueous solution containing 3.0% by weight of m-phenylenediamine and 0.15% by weight of sodium lauryl sulfate was applied to the polysulfone layer on the long-fiber nonwoven fabric obtained above to a thickness of 5 mm. It was removed with a rubber blade wiper. Next, it was brought into contact with a solution of paraffinic hydrocarbon oil containing 0.15% by weight of trimesic acid chloride for 5 seconds, and then transported to a drying furnace at 125 ° C., dried and cured for about 2 minutes, thereby having a thickness of 0.2 μm. An aromatic polyamide dense layer was formed.

  The film thickness (total thickness) of the reverse osmosis membrane obtained by forming the polymer layer and the aromatic polyamide dense layer on the long fiber nonwoven fabric in this way was 0.10 mm, and was removed at an evaluation pressure of 0.75 MPa. The rate was 99.3% and the permeation flux was 1.2 m / d.

<Water flow test>
Assuming an 8-inch spiral reverse osmosis membrane element with a membrane area of 44.0 m ² , the above reverse osmosis membrane is cut into a width of 50 mm × length of 800 mm, a polypropylene raw water spacer with a thickness of 0.71 mm and a ceramic with a thickness of 3 mm (porous A sintered ceramic material) and a permeated water spacer were attached to the test flat membrane cell shown in FIG.
In the flat membrane cell shown in FIG. 3, the raw water spacer 11 and the permeated water spacer 12 are reversed in a space formed by combining the flow path forming members 21, 22, 23 made of acrylic and the pressure-resistant reinforcing members 24, 25 made of SUS. The laminated membrane unit is held via the osmotic membrane 10.
The raw water flows into the primary side of the reverse osmosis membrane 10 from the raw water inlet 13 and flows along the raw water spacer 11, and the permeated water that has permeated the reverse osmosis membrane 10 in the meantime passes through the permeated water spacer 12 and passes through the permeated water outlet 15. Taken from. The concentrated water is taken out from the concentrated water outlet 14.

Water that was obtained by coagulating and filtering biologically treated water as raw water was passed through at a permeation flux of 0.6 m / d and a flow rate of concentrated water at a linear velocity of 0.11 m / s, and the permeated water amount after 500 hours was examined.
The initial permeated water amount in terms of an 8-inch element was 1.04 m ³ / h.
Moreover, the density | concentration of the high molecular organic substance of molecular weight 10,000 or more in raw | natural water was 0.05 ppm.

[Example 2]
According to the method described in WO2010 / 126113, a long fiber nonwoven fabric was produced as follows.
As a first surface layer, polyethylene terephthalate was extruded by a spunbond method at a spinning temperature of 300 ° C. toward the moving net surface, and a long fiber web was produced on the collection net. Next, polyethylene terephthalate was used as an intermediate layer, and spinning was performed at a spinning temperature of 300 ° C. by a melt blown method, and the meltblown long fiber layer was sprayed onto the long fiber web by the above spunbond method. Furthermore, after laminating the long fiber web layer as the second surface layer in the same manner as the long fiber web of the first surface layer directly on the laminated web obtained above, thermocompression bonding with a heated flat calender roll, A laminated web comprising a spunbond long fiber layer / meltblown long fiber layer / spunbond long fiber layer was obtained. Subsequently, the obtained laminated web is thermocompression bonded to the second surface layer side with a calender roll, and immediately after that, quenched with a water-cooled roll, and then the first surface layer side is thermocompression bonded with a calender roll under the same conditions. Thus, thermocompression bonding was performed from the front and back sides to obtain a long fiber nonwoven fabric.

The obtained long fiber nonwoven fabric is composed of long fibers having a fiber diameter of 9 μm and 10 μm as the first surface layer and the second surface layer, respectively, on both surfaces of the intermediate layer composed of a long fiber nonwoven fabric layer having a fiber diameter of 1.7 μm. It was a long fiber nonwoven fabric with a thickness of 50 μm.
A reverse osmosis membrane was obtained by forming a polymer layer having a thickness of 10 μm and an aromatic polyamide dense layer having a thickness of 0.2 μm on the obtained long fiber nonwoven fabric in the same manner as in Example 1.
This reverse osmosis membrane had a film thickness (total thickness) of 0.06 mm, an evaluation rate of 0.75 MPa, a removal rate of 99.3%, and a permeation flux of 1.2 m / d.

Assuming an 8-inch spiral reverse osmosis membrane element with a membrane area of 47.3 m ² , the above reverse osmosis membrane is cut into a width of 50 mm and a length of 800 mm, and the test flat is used together with the raw water spacer and the permeated water spacer in the same manner as in Example 1. The membrane cell was filled, and a water passage test similar to that in Example 1 was performed to examine the amount of permeated water after 500 hours. The initial permeated water amount in terms of 8 inch elements was 1.18 m ³ / h.

[Example 3]
According to the method described in WO2010 / 126109, a long fiber nonwoven fabric was produced as follows.
As the first surface layer, polyethylene terephthalate is used and extruded by a spunbond method toward the collection net surface where the filament group is moved at a spinning temperature of 310 ° C., and is sufficiently opened by corona charging to form a long fiber web. Prepared on a collection net. Next, as an intermediate layer, polyethylene terephthalate was spun by a melt blown method at a spinning temperature of 300 ° C. and sprayed on the long fiber web. Further, a long fiber web is laminated on the laminated web obtained as described above in the same manner as the long fiber web of the first surface layer, and a length consisting of a spunbond long fiber layer / meltblown long fiber layer / spunbond long fiber layer is formed. A fiber nonwoven fabric was obtained. Subsequently, thermocompression bonding was performed in the same manner as in Example 2.

The obtained long fiber nonwoven fabric is composed of long fibers having a fiber diameter of 9 μm and 10 μm as the first surface layer and the second surface layer, respectively, on both surfaces of the intermediate layer composed of a long fiber nonwoven fabric layer having a fiber diameter of 1.7 μm. It was a long fiber nonwoven fabric with a thickness of 20 μm.
A reverse osmosis membrane was obtained by forming a polymer layer having a thickness of 10 μm and an aromatic polyamide dense layer having a thickness of 0.2 μm on the obtained long fiber nonwoven fabric in the same manner as in Example 1.
This reverse osmosis membrane had a film thickness (total thickness) of 0.03 mm, a removal rate of 99.3%, and a permeation flux of 1.2 m / d at an evaluation pressure of 0.75 MPa.

Assuming an 8-inch spiral reverse osmosis membrane element having a membrane area of 50.2 m ² , the above reverse osmosis membrane is cut into a width of 50 mm and a length of 800 mm, and the test flat is used together with the raw water spacer and the permeated water spacer in the same manner as in Example 1. The membrane cell was filled, and a water passage test similar to that in Example 1 was performed to examine the amount of permeated water after 500 hours. In addition, the initial permeate flow rate in terms of 8 inch elements was 1.26 m ³ / h.

[Example 4]
Except that the permeation flux was 0.5 m / d, the same test as in Example 3 was performed, and the permeated water amount after 500 hours was examined. The initial permeated water amount in terms of an 8-inch element was 1.05 m ³ / h.

[Example 5]
Except that the permeation flux was 0.45 m / d, the same test as in Example 3 was performed, and the permeated water amount after 500 hours was examined. The initial permeated water amount in terms of an 8-inch element was 0.94 m ³ / h.

[Example 6]
Except that the permeation flux was 0.4 m / d, the same test as in Example 3 was performed, and the amount of permeated water after 500 hours was examined. In addition, the initial permeated water amount in terms of 8 inch elements was 0.84 m ³ / h.

[Comparative Example 1]
A flat membrane was cut out from Toray RO element “SUL-G20” into a width of 50 mm and a length of 800 mm, and filled into a test flat membrane cell together with a raw water spacer (thickness: 0.71 mm) and a permeated water spacer in the same manner as in Example 1. SUL-G20 had a removal rate of 99.7, a permeation flux of 0.85 m / d, and a film thickness of 0.13 mm at an evaluation pressure of 0.75 MPa. The permeation amount after 500 hours was examined by conducting the same water flow test as in Example 1 with a permeation flux of 0.7 m / d. The initial permeate flow rate in terms of 8 inch elements was 1.22 m ³ / h.

[Comparative Example 2]
Except for using a polypropylene raw water spacer having a thickness of 0.86 mm, a water flow test was performed in the same manner as in Comparative Example 1, and the amount of permeated water after 500 hours was examined. The initial permeated water amount in terms of 8-inch element was 1.08 m ³ / h.

[Comparative Example 3]
A test similar to Comparative Example 1 was performed except that raw water having a molecular weight of 10,000 or more of high molecular organic material of 0.005 ppm was used, and the amount of permeated water after 500 hours was examined. The initial permeated water amount in terms of an 8-inch element is 1.22 m ³ / h as in Comparative Example 1.

  The water flow test results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 2 below.

As is clear from Table 2, in Examples 1 to 6, a high permeated water amount could be stably obtained even after 500 hours had passed. In particular, in Examples 5 and 6, the permeated water amount did not decrease even after 500 hours.
On the other hand, in Comparative Examples 1 and 2, the initial amount of permeated water was high, but the amount of permeated water decreased significantly after 500 hours. As in Comparative Example 3, when the organic polymer having a molecular weight of 10,000 or more in the raw water was low, the permeation flux decreased slowly.

  The present invention can be applied to various reverse osmosis membrane devices used for seawater desalination, ultrapure water production, industrial water treatment, wastewater recovery treatment, etc., and in particular, treats biologically treated water, especially MBR treated water. It is suitably applied to a reverse osmosis membrane device.

DESCRIPTION OF SYMBOLS 1 Biological treatment means 2 Aggregation treatment means 3 Solid-liquid separation means 4 Filtration means 5 Security filter 6 Reverse osmosis membrane apparatus 7 MBR (immersion type membrane separation apparatus)
10 Reverse osmosis membrane 11 Raw water spacer 12 Permeated water spacer

Claims (4)

  In a method for operating a reverse osmosis membrane device in which water containing a polymer organic material is treated as raw water, the raw water contains a polymer organic material having a molecular weight of 10,000 or more at a concentration of 0.01 ppm or more, and the reverse osmosis membrane device comprises: A reverse osmosis membrane element comprising a membrane unit in which a raw water spacer is provided on one surface of a reverse osmosis membrane having a thickness of 0.1 mm or less and a permeable water spacer is provided on the other surface, and passes through the reverse osmosis membrane device. A method for operating a reverse osmosis membrane device, wherein the operation is performed at a flux of 0.6 m / d or less.   The method of operating a reverse osmosis membrane device according to claim 1, wherein the permeation flux is 0.45 m / d or less.   The method of operating a reverse osmosis membrane device according to claim 1, wherein the reverse osmosis membrane element is a spiral type reverse osmosis membrane element. The method of operating a reverse osmosis membrane device according to any one of claims 1 to 3, wherein the raw water is membrane-separated activated sludge process water.

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