JPH09299947A - Reverse osmotic membrane spiral element and treating system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reverse osmotic membrane spiral element dispensing with pretreatment and capable of operating at a low operation pressure and a treating system using the same. SOLUTION: The reverse osmotic membrane spiral element 1 is constructed by overlapping a reverse osmotic membrane 2 on both surfaces of a permeated water spacer 3 composed of a synthetic resin net and bonding the 3 sides to form an envelope type membrane 4, attaching the opening part of the envelope type membrane 4 to a water collecting pipe 5 and winding spirally with a raw water spacer 6 composed of a synthetic resin net having >=2mm to <=5mm thickness around the outer circumferential surface of the water collecting pipe 5. The reverse osmotic membrane 2 has a performance of >=0.8m<3> /m<2> .day permeation flux and >=99% removing ratio at 25 deg.C at the time of using an aq. solution having 500ppm NaCl concentration as a feed solution and operating at 7.5kgf/ cm<2> operation pressure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a reverse osmosis membrane spiral element for separating components in raw water and a treatment system using the same.

[0002]

2. Description of the Related Art A reverse osmosis membrane spiral element for separating ionic components and low-molecular components in raw water is used for desalting treatment and various manufacturing processes. FIG. 3 is a partially cutaway perspective view of a conventional reverse osmosis membrane spiral element.

In the reverse osmosis membrane spiral element 1 shown in FIG. 3, the reverse osmosis membranes 2 are superposed on both surfaces of the permeated water spacer 3 and three sides are adhered to each other to form an envelope-shaped membrane (bag-shaped membrane) 4. It is configured by attaching the opening of the envelope-shaped membrane 4 to the water collecting pipe 5 and spirally winding it around the outer peripheral surface of the water collecting pipe 5 together with the net-shaped (net-shaped) raw water spacer 6.

As shown in FIG. 3, raw water 7 is supplied from one end face side of the reverse osmosis membrane spiral element 1. The raw water 7 flows along the raw water spacer 6 and is discharged as concentrated water 9 from the other end surface side of the reverse osmosis membrane spiral element 1. In this way, the raw water spacer 6 forms a raw water flow path. In the process in which the raw water 7 flows along the raw water spacer 6, the permeated water 8 that has permeated the reverse osmosis membrane 2 flows along the permeated water spacer 3 into the water collecting pipe 5, and is discharged from the end portion of the water collecting pipe 5.

Normally, the thickness of the raw water spacer 6 is 1 mm or less, and the clearance (gap) at the raw water inflow portion of the end surface of the reverse osmosis membrane spiral element 1 is 1 mm or less. Therefore, when the raw water is supplied to the reverse osmosis membrane spiral element 1, it is necessary to remove the suspended matter in the raw water in advance.

FIG. 4 is a diagram showing the configuration of a conventional processing system using the reverse osmosis membrane spiral element 1 of FIG. In FIG. 4, an oxidizer 12 represented by an aqueous solution of sodium hypochlorite is injected into the raw water 7 for sterilization of microorganisms in the raw water 7 and oxidation of organic substances. The raw water 7 into which the oxidant 12 has been injected is supplied to the pretreatment device 10 by the raw water supply device 14. The pretreatment device 10 performs pretreatment such as coagulation and precipitation treatment, filtration treatment, and membrane treatment on the raw water 7. To the raw water pretreated by the pretreatment device 10, a reducing agent 13 represented by an aqueous solution of sodium bisulfite is injected in order to prevent deterioration of the reverse osmosis membrane due to residual oxidant. The raw water into which the reducing agent 13 has been injected is introduced into the raw water high pressure supply device 15.

The raw water high-pressure supply device 15 supplies raw water to the reverse osmosis membrane spiral element 1 through the safety filter 11 at a predetermined operating pressure. The reverse osmosis membrane spiral element 1 separates the supplied raw water into permeated water 8 and concentrated water 9.

[0008]

As described above, when the conventional reverse osmosis membrane spiral element is used, as shown in FIG.
It is necessary to remove the suspended matter in the raw water in advance by the pretreatment device 10 shown in FIG. In addition, the reverse osmosis membrane is generally 10
Since a high operating pressure of kgf / cm ² or more is required,
When using the reverse osmosis membrane spiral element, the raw water high pressure supply device 15 shown in FIG. 4 is required. Since the pretreatment device 10 and the raw water high-pressure supply device 15 are required in this way, the treatment system has high initial cost and operating cost. Therefore, the conventional treatment system has been limited to applications in which high cost is allowed, such as an ultrapure water production system and an organic substance separation process.

On the other hand, in recent years, river water, which is the raw water for drinking water,
Lake water, groundwater, etc. are contaminated with domestic wastewater, industrial wastewater, etc.,
Providing safe drinking water has become an important consideration. Among these pollutants, it is indispensable to remove dissolved components that cannot be removed by the turbidity treatment, particularly organic chlorine compounds and pesticides that are harmful to the human body. In order to remove these harmful substances,
A reverse osmosis membrane having high separation performance is required. However, in the treatment system using the reverse osmosis membrane spiral element, as described above, the pretreatment device 10 and the raw water high pressure supply device 15 are required, and the cost becomes high.
It was difficult to apply to drinking water that requires low cost.

Therefore, there has been a strong demand for a reverse osmosis membrane spiral element which requires no pretreatment and can be operated at a low operating pressure, and a treatment system using the same. It is an object of the present invention to provide a reverse osmosis membrane spiral element that requires no pretreatment and can be operated at a low operating pressure, and a treatment system using the same.

[0011]

Means for Solving the Problems and Effects of the Invention A reverse osmosis membrane spiral element according to the present invention is a reverse osmosis membrane spiral element in which a bag-shaped reverse osmosis membrane is wound around a water collecting pipe together with a raw water spacer. , The thickness of the raw water flow path formed between the reverse osmosis membranes by the raw water spacer is 2m
m or more, the reverse osmosis membrane has a NaCl concentration of 500 ppm
The operating pressure is 7.5 kgf / cm ² with the aqueous solution of
When operated at 25 ° C, the permeation flux is 0.8 m ³ / m ² ·
It has the ability to achieve a daily and NaCl removal rate of 99% or more.

In the reverse osmosis membrane spiral element according to the present invention, since the thickness of the raw water flow channel is 2 mm or more, clogging of the raw water flow channel by turbidity is prevented. Further, when the reverse osmosis membrane was operated at an operating pressure of 7.5 kgf / cm ² with an aqueous solution having a NaCl concentration of 500 ppm as a supply liquid, the permeation flux at 25 ° C. was 0.8 m ³ / m ² · day or more, and NaCl removal was performed. Since it has a performance of 99% or more, it maintains 10kgf / cm while maintaining the conventional separation performance.
It can be operated at a low operating pressure of ² or less.

This allows pretreatment and reverse osmosis membrane treatment at low operating pressure to be carried out simultaneously with the reverse osmosis membrane spiral element. Therefore, a pretreatment device and a high-pressure raw water supply device are not required, and a treatment system with low initial cost and operating cost is provided.

In particular, the raw water spacer is a net-shaped spacer made of synthetic resin and preferably has a thickness of 2 mm or more. This reduces pressure loss and
Since it is possible to secure the raw water flow passage having a thickness of not less than mm, it is possible to reliably prevent the raw water flow passage from being clogged with suspended matter. Further, it is more preferable that the raw water spacer has a thickness of 2 mm or more and 5 mm or less. This allows
It is possible to prevent clogging of the raw water flow path due to suspended matter while ensuring a large membrane area.

A negatively charged crosslinked polyamide system in which the reverse osmosis membrane is composed of a compound having two or more reactive amino groups and a polyfunctional acid halogen compound having two or more reactive acid halide groups. A composite reverse osmosis membrane in which the skin layer is supported by a microporous support, and the surface of the polyamide-based skin layer is covered with a cross-linking layer of an organic polymer having a positively chargeable group. The surface area is preferably 3 or more. As a result, the NaCl concentration is 500 pp
operating pressure of 7.5 kgf / cm.
^When operated at ² , the permeation flux at 25 ℃ is 0.8m
^{The performance is 3} / m ² · day or more, and the NaCl removal rate is 99% or more.

The treatment system according to the present invention comprises an oxidant injection means for injecting an oxidant into raw water, a reducing agent injection means for injecting a reducing agent into the raw water into which the oxidant has been injected by the oxidant injection means, and a reducing agent. The reverse osmosis membrane spiral element is provided with the raw water into which the reducing agent has been injected by the injection means.

In this processing system, the reverse osmosis membrane spiral
Prevents blockage of raw water flow path due to turbidity
And 10kgf / while maintaining the conventional separation performance
cm ^TwoIt can be operated at the following low operating pressures. That
Pretreatment and reverse osmosis membrane treatment at low operating pressure reverse osmosis
Simultaneously performed with a membrane spiral element. But
This eliminates the need for pretreatment equipment and high-pressure raw water supply equipment.
This reduces initial costs and operating costs.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of a reverse osmosis membrane spiral element according to the present invention and a processing system using the same will be described. The entire structure of the reverse osmosis membrane spiral element of the present invention is similar to the structure of the conventional reverse osmosis membrane spiral element shown in FIG. 3, but the raw water spacer and the reverse osmosis membrane are different. First, an example of the reverse osmosis membrane spiral element according to the present invention will be described with reference to FIG.

Reverse osmosis membrane spiral element 1 of the present invention
The reverse osmosis membrane 2 is superposed on both surfaces of the permeation spacer 3 made of a synthetic resin net, and the three sides are adhered to form an envelope-shaped membrane (bag-shaped membrane) 4, and the opening of the envelope-shaped membrane 4 is formed. This part is attached to the water collecting pipe 5 and is spirally wound around the outer peripheral surface of the water collecting pipe 5 together with the raw water spacer 6 made of a synthetic resin net.

The raw water flow path is formed by the raw water spacer 6. Therefore, by increasing the thickness of the raw water spacer 6, it is possible to prevent the raw water flow passage from being blocked even when the suspended matter flows in. On the other hand, if the raw water spacer 6 is too thick, the amount of the reverse osmosis membrane 2 that can be wound in the same diameter is reduced, so that the membrane area is reduced. Therefore, the thickness of the raw water spacer 6 is preferably 2 mm or more and 5 mm or less.

The reverse osmosis membrane 2 constituting the envelope membrane 4 is composed of a compound having two or more reactive amino groups and a polyfunctional acid halogen compound having two or more reactive acid halide groups. An organic polymer having a negatively charged crosslinked polyamide-based skin layer and a microporous support supporting the same, the polyamide-based skin layer has a specific surface area of 3 or more, and the surface of the polyamide-based skin layer has a positively chargeable group. A composite reverse osmosis membrane coated with a combined crosslinked layer is used.

The specific surface area of the polyamide-based skin layer on the surface of the composite reverse osmosis membrane is defined by the following equation. Specific surface area of skin layer = (surface area of skin layer) / (surface area of microporous support) Here, the surface area of the skin layer is the surface opposite to the surface in contact with the microporous support, that is, It is the surface area of the surface that is in contact with the supply liquid. The surface area of the microporous support is the surface area of the surface in contact with the skin layer.

The surface area and the specific surface area can be generally determined by a method for determining the surface roughness, and examples thereof include a surface area measuring device, a specific surface area measuring device, a scanning electron microscope (SEM or FE-SEM), and a transmission electron microscope. It can be measured using a scanning electron microscope (TEM). The measuring methods of the surface area and the specific surface area are not limited to these.

Reverse osmosis membrane spiral element 1 of the present invention
Reverse osmosis membrane 2 used in
Operation pressure 7.5 kgf /
cm ^TwoThe permeation flux at 25 ° C. is 0.
8m^Three/ M^Two・ It is more than a day, and the NaCl removal rate is 99%.
It has the above basic performance. This enables the reverse of the present invention.
The osmosis membrane 2 has the same NaCl as that of the conventional reverse osmosis membrane.
The operating pressure is reduced to less than half while maintaining the removal rate. sand
That is, the reverse osmosis membrane 2 of the present invention is operated in the same manner as a conventional reverse osmosis membrane.
When operating at operating pressure, a permeation flux of more than twice can be obtained.
It is.

Further, the reverse osmosis membrane spiral element 1
The turbidity is separated from the membrane surface of the reverse osmosis membrane 2 by performing cross-flow filtration on the raw water 7 side, appropriately performing flushing washing or bubble flow washing, and performing permeated water reverse pressure washing on the permeated water 8 side. You can Thereby, stable pretreatment and reverse osmosis membrane treatment can be realized.

FIG. 1 is a diagram showing the construction of a processing system using a reverse osmosis membrane spiral element 1 according to the present invention. An oxidant 12 such as an aqueous solution of sodium hypochlorite is injected into the raw water 7 for sterilization of microorganisms in the raw water and oxidation of organic matter. Further, in order to prevent the deterioration of the reverse osmosis membrane 2 due to the residual oxidant, the reducing agent 13 such as an aqueous solution of sodium bisulfite is added to the raw water 7 into which the oxidant 12 is injected.
Is injected. The raw water 7 into which the reducing agent 13 has been injected is supplied to the raw water supply device 16. The raw water supply device 16 supplies the raw water 7 to the reverse osmosis membrane spiral element 1 of the present invention through the security filter 11. The reverse osmosis membrane spiral element 1 separates raw water 7 into permeated water 8 and concentrated water 9.

In the treatment system of FIG. 1, the reverse osmosis membrane spiral element 1 of the present invention simultaneously performs pretreatment and reverse osmosis membrane treatment at a low operating pressure. Therefore, in order to remove the turbidity in the raw water, a pretreatment device for performing a pretreatment such as a coagulation and precipitation treatment, a filtration treatment, and a membrane treatment and a high-pressure raw water supply device are unnecessary, and the initial cost and the operating cost are reduced. .

[0028]

EXAMPLE A reverse osmosis membrane spiral element 1 of the example having the above structure was produced and used in the treatment system shown in FIG.

In this embodiment, the reverse osmosis membrane 2 is prepared by the following method.
Was produced. In addition, a polysulfone ultrafiltration membrane was used as the microporous support. An aqueous solution containing 3.0 wt% m-phenylenediamine, 0.15 wt% sodium lauryl sulfate, 3.0 wt% triethylamine, 6.0 wt% camphorsulfonic acid and 5 wt% isopropyl alcohol. The porous polysulfone support membrane was brought into contact with the support membrane for several seconds to remove the excess solution to form a layer of the solution on the support membrane.

Then, an IP1016 (isoparaffin hydrocarbon oil manufactured by Idemitsu Chemical Co., Ltd.) solution containing 0.20% by weight of trimesic acid chloride and 0.05% by weight of isopropyl alcohol was brought into contact with the surface of the support membrane, Then, the mixture was kept in a hot air drier at 120 ° C. for 3 minutes to form a polymer thin film on the support membrane to obtain a composite reverse osmosis membrane.

In this embodiment, a synthetic resin net having a thickness of 2 mm was used as the raw water spacer 6.
As the operating conditions of the treatment system of FIG. 1, river water with a turbidity of 10 degrees or less is used as raw water, and the operating pressure is 5 kgf /
cm ² and the recovery rate was 80% by cross-flow filtration. Further, flushing cleaning was performed once per hour, and permeated water reverse pressure cleaning was performed.

FIG. 2 shows the operation result of the processing system using the reverse osmosis membrane spiral element 1 of this embodiment. FIG.
As shown in, the comparatively stable operation was possible without pretreatment for a long period of about 6 months. The water quality of the permeated water of the reverse osmosis membrane spiral element 1 is 46% of the tap water quality standard.
It was sufficiently compatible with the items, and the turbidity showed a removal rate of 100%, and the organic matter showed a removal rate of 99% or more. In addition, since it was possible to operate at a low operating pressure of 5 kgf / cm ² without pretreatment, maintenance costs and required power costs were low, and drinking water with safe water quality was obtained with a relatively simple treatment system. I found out that

As described above, since the pretreatment and the reverse osmosis membrane treatment at a low operating pressure can be simultaneously performed in the reverse osmosis membrane spiral element 1, a treatment system capable of performing the reverse osmosis membrane treatment at a low cost is provided. To be done.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a processing system using a reverse osmosis membrane spiral element according to the present invention.

FIG. 2 is a diagram showing a measurement result of a relationship between an operation period and a permeation flux in a treatment system using a reverse osmosis membrane spiral element according to the present invention.

FIG. 3 is a partially cutaway perspective view showing one example of the structure of the present invention and the conventional reverse osmosis membrane spiral element.

FIG. 4 is a diagram showing an example of a processing system using a conventional reverse osmosis membrane spiral element.

[Explanation of symbols]

 1 Reverse Osmosis Membrane Spiral Element 2 Reverse Osmosis Membrane 3 Permeate Spacer 4 Envelope Membrane 5 Water Collection Tube 6 Raw Water Spacer 7 Raw Water 8 Permeate 9 Concentrated Water 11 Security Filter 12 Oxidizing Agent 13 Reducing Agent 16 Raw Water Supply Device

Front page continuation (72) Inventor Masahiko Hirose 1-2-1, Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (4)

[Claims] 1. A reverse osmosis membrane spiral element in which a bag-shaped reverse osmosis membrane is wound around a water collecting pipe together with a raw water spacer in a reverse osmosis membrane spiral element, wherein a thickness of a raw water flow path formed between the reverse osmosis membranes by the raw water spacer. The reverse osmosis membrane has a permeation flux of 0.8 m ³ / m ² · day at 25 ° C. when operated at an operating pressure of 7.5 kgf / cm ² with an aqueous solution having a NaCl concentration of 500 ppm as a supply liquid. A reverse osmosis membrane spiral element characterized by having the above-mentioned properties and a NaCl removal rate of 99% or more. 2. The reverse osmosis membrane spiral element according to claim 1, wherein the raw water spacer is a net-shaped spacer made of a synthetic resin and has a thickness of 2 mm or more. 3. The negatively charged crosslinked polyamide comprising the compound having two or more reactive amino groups and a polyfunctional acid halogen compound having two or more reactive acid halide groups. A composite reverse osmosis membrane in which a system skin layer is supported by a microporous support, and the surface of the polyamide skin layer is covered with a cross-linking layer of an organic polymer having a positively chargeable group. The reverse osmosis membrane spiral element according to claim 1 or 2, wherein the specific surface area is 3 or more. 4. An oxidizing agent injecting means for injecting an oxidizing agent into raw water, a reducing agent injecting means for injecting a reducing agent into the raw water into which the oxidizing agent has been injected by the oxidizing agent injecting means, and a reducing agent for injecting the reducing agent. A treatment system comprising the reverse osmosis membrane spiral element according to any one of claims 1 to 3, to which raw water infused with the agent is supplied.