JP2001219039A - Cleaning method of membrane module - Google Patents

Abstract

(57) [Problem] To provide a method for cleaning a membrane module capable of sufficiently removing metal hydroxides and organic substances from a membrane module obtained by membrane-separating coagulated water. SOLUTION: In a method for cleaning a membrane module for subjecting water to be treated to coagulation treatment and membrane filtration, a first step of acid cleaning,
A method for cleaning a membrane module, comprising a second step of performing alkali cleaning and a third step of performing acid cleaning. First
The acid may be replaced with a new one during the process. After the third step, alkali cleaning and acid cleaning may be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for cleaning a membrane module used in a membrane separation device such as a microfiltration device, an ultrafiltration device, a reverse osmosis membrane separation device, and more particularly to a method for cleaning a spiral type membrane module. It relates to a suitable cleaning method.

[0002]

2. Description of the Related Art Japanese Patent Publication No.
Japanese Patent No. 4728 discloses that after washing a membrane module with a citric acid aqueous solution, washing with an effective chlorine-containing alkaline aqueous solution,
Thereafter, a method of washing with water is described.

Further, Japanese Patent Application Laid-Open No. Hei 8-243361 discloses a method of washing a membrane module with an acid such as hydrochloric acid or sulfuric acid, and then washing the membrane module with an alkali such as sodium hydroxide.

When raw water to be subjected to membrane separation treatment is coagulation treatment water using an inorganic coagulation treatment agent, the raw water contains hydroxides such as ferric hydroxide and aluminum hydroxide. Although the material tends to cause clogging, this hydroxide can be dissolved and removed by acid washing.

[0005] Further, by subsequent alkali washing, it is possible to dissolve and remove film deposits such as humic acid and fulvic acid derived from raw water and various organic colloids.

[0006]

In the process of dissolving and removing hydroxides with an acid, if the washing time of the acid is excessively long, the dissolved iron ions and aluminum ions penetrate deep into the film, and these ions become During the alkaline cleaning in the process, it becomes hydroxide and precipitates and adheres to the deep part of the film, and cannot be easily removed.

The present invention solves the above problems and provides a method of cleaning a membrane module that can sufficiently remove metal hydroxides and organic deposits when cleaning a membrane module using coagulated water as raw water. The purpose is to do.

[0008]

A method for cleaning a membrane module according to the present invention is a method for cleaning a membrane module in which water to be treated is subjected to coagulation treatment and membrane filtration. And a third step of performing acid cleaning.

In this method of cleaning a membrane module, acid cleaning is performed a plurality of times, so that it is not necessary to lengthen one acid cleaning time excessively, and metal ions can penetrate deep into the membrane. Is prevented. Of course, since the acid cleaning is performed a plurality of times, the attached metal hydroxide is sufficiently removed.

In addition, since alkali cleaning is also performed, organic components are sufficiently removed.

In the present invention, the acid solution is preferably replaced with a new one during the first acid washing step. This allows the dissolved metal ions to diffuse into the new acid solution, preventing the penetration of the metal ions into the membrane.

In the present invention, after the third step, a fourth step consisting of alkali cleaning and acid cleaning may be performed.

The acid may be an inorganic acid such as hydrochloric acid or sulfuric acid, or citric acid. As the alkali, sodium hydroxide, sodium hypochlorite and the like can be used.

In the present invention, the membrane module to be cleaned is obtained by subjecting coagulated water to membrane separation. Examples of the coagulant include ferric chloride, polyaluminum chloride, and a sulfuric acid band.

In the present invention, the membrane module is a spiral type membrane module in which a permeated water flow path material is disposed inside a bag-shaped membrane and a raw water flow path material is disposed between the bag-shaped membranes. The membrane is substantially rectangular with first, second, third and fourth sides, the first, second and third sides are sealed, and the fourth side is partially Is an open portion, and the remaining portion is a closed portion. A first side perpendicular to the fourth side is applied to a shaft to wind a bag-like membrane to form a roll, and the fourth side is Facing the rear end face of the wound body, facing the second side facing the fourth side to the front end face of the wound body, the raw water flow path between the bag-shaped membranes is The third side portion is entirely sealed, and the fourth side portion is a closed portion where the portion overlapping with the open portion of the bag-like film is a closed portion, and the fourth side portion is closed. Overlap Where is preferably spiral wound membrane module that is the open portion.

In such a spiral type membrane module, raw water flows into the raw water flow path from the front end face of the wound body. The raw water flows through the raw water flow path in a direction substantially parallel to the axis of the wound body, and then flows out as concentrated water from the raw water flow path opening at the rear end face of the wound body.

The water that has passed through the bag-like membrane flows in the bag-like membrane in a direction substantially parallel to the axis of the wound body, and flows out from the bag-shaped membrane opening at the rear end face of the wound body.

As described above, since the permeated water flows in the bag-shaped membrane in a direction parallel to the axis of the wound body, the water collecting pipe used in the conventional spiral type membrane module becomes unnecessary. Then, there is no flow resistance when flowing into the water collecting pipe from inside the bag-shaped membrane, and the flow resistance of permeated water is reduced.

In addition, since the water collecting pipe is eliminated, the length of the bag-shaped membrane in the winding direction can be increased by that much.
The membrane area can be expanded. And even if the length of the bag-shaped membrane in the winding direction is increased, the flow resistance of permeated water does not increase,
The amount of permeated water can be increased.

In the method for cleaning a membrane module of the present invention, it is preferable to use the following cleaning apparatus. That is, a vessel for accommodating the membrane module, first and second tanks for accommodating the cleaning liquid for the membrane module, and the first and second tanks.
A pressurized gas supply device for supplying a pressurized gas into the tank and allowing the liquid to flow out of the tank, further supplying a pressurized gas into the first tank, and discharging the liquid in the first tank. Supplying the inside of the vessel to wash the membrane module, selecting a first flow path for causing the washing waste liquid to flow into the second tank from the inside of the vessel, and supplying a pressurized gas into the second tank; Second
Channel switching that supplies the liquid in the tank to the vessel to clean the membrane module, and switches between the second flow path selection in which the cleaning waste liquid flows from the vessel into the first tank. It is a cleaning device provided with means.

In such a membrane module cleaning apparatus, the liquid in the first tank is supplied to the vessel to clean the membrane module, and the cleaning waste liquid is stored in the second tank.
Thereafter, the liquid in the second tank is supplied to the vessel to wash the membrane module.

As described above, according to the cleaning apparatus, since the cleaning liquid is used repeatedly, the amount of the cleaning liquid can be reduced.

In the cleaning method using the cleaning device,
The flow path switching means is configured to supply the pressurized gas into the tank for a predetermined time even after all the liquid in the first or second tank is sent out to the vessel, and to send the pressurized gas into the vessel. By doing so, the membrane module in the vessel can be cleaned not only with the liquid but also with the gas-liquid multiphase flow and the gas.

[0024]

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

FIG. 6 is a system diagram of a cleaning apparatus suitable for use in the method for cleaning a membrane module according to the embodiment. The cleaning device for the membrane module includes a vessel 64 for storing the membrane module 66, a first tank 60 and a second tank 62 for storing the cleaning liquid for the membrane module 66, and pressurized air to the tanks 60 and 62. Supply compressor 68
It is mainly composed of The first tank 6
An alkaline solution is stored in 0 and an acid solution is stored in the second tank 62.

The compressor 68 is connected to the upper portions of the tanks 60 and 62 by pipes 70 and 72 having valves 74 and 76, and the lower portions of the tanks 60 and 62 are connected to valves 84 and 8 respectively.
6 are connected to the lower part of the vessel 64 by pipes 80 and 82 each having 6. The upper part of the vessel 64 has valves 94 and 96
Are connected to the upper portions of the tanks 60 and 62 by pipes 90 and 92 having the same. Above the tanks 60 and 62, pipings 100 and 10 for venting air having valves 104 and 106 are provided.
2 are connected.

The membrane module 66 is a spiral-type membrane module, and is formed by winding a bag-like separation membrane into a cylindrical shape as shown in FIGS. In this membrane module 66, raw water flows into the raw water flow path between the bag-shaped separation membranes from the upper end face in the figure, and concentrated water flows out from the inner peripheral side (inside the socket 25) of the lower end face in the figure. Then, the permeated water flows out of the socket 25.

In the state of FIG. 6, the second tank 62
The cleaning liquid (acid solution) is supplied into the vessel 64 to clean the membrane module 66, and the cleaning waste liquid is supplied to the first tank 60.
Has been introduced to.

That is, the valves 76, 86, 94 and 104 are opened,
The valves 74, 84, 96 and 106 are closed and the compressor 6
8, the pressurized air is supplied to the second tank 6
2, and the cleaning liquid level is pressurized with air. As a result, the cleaning liquid in the second tank 62 is
Is supplied to the raw water flow path of the membrane module 66 from the inside of the socket 25, flows upward through the raw water flow path, flows out from the upper end surface of the membrane module 66, and flows through the pipe 90 to the first tank. It flows into 60.

When this cleaning is continued, the second tank 62
Is emptied, air is supplied into the vessel 64, and the membrane module 66 is washed by the gas-liquid multi-phase flow, and thereafter,
All the liquid flows out of the membrane module 66 by being pushed by the air. Preferably, air is supplied for a predetermined time thereafter.

Further, it is preferable to provide a pressurized air supply means 110 on the permeated water flow path side of the membrane module 66 and perform a gas cleaning step of the permeated water flow path after the gas cleaning of the raw water flow path.

Thereafter, the opening and closing of each valve is reversed so that the cleaning liquid (alkaline solution) in the first tank 60 is introduced into the lower part of the vessel 64, and the membrane module 6
6 is washed and flows into the second tank 62.

That is, the valves 76, 86, 94 and 104 are closed,
The valves 74, 84, 96 and 106 are opened and the compressor 6
8, the pressurized air is supplied to the first tank 6
The cleaning liquid level is supplied to the upper part of the nozzle and the air is pressurized with air. As a result, the cleaning liquid in the first tank 60 is
Is supplied to the raw water flow path of the membrane module 66 from the inside of the socket 25, flows upward through the raw water flow path, flows out from the upper end surface of the membrane module 66, and flows through the pipe 90 to the second tank. 62.

When this cleaning is continued, the first tank 60
Is emptied, air is supplied into the vessel 64, and the membrane module 66 is washed by the gas-liquid multi-phase flow, and thereafter,
All the liquid flows out of the membrane module 66 by being pushed by the air. Preferably, air is supplied for a predetermined time thereafter.

As in the case described above, it is preferable to perform a gas cleaning step for the permeated water flow path after the gas cleaning of the raw water flow path.

After the alkali cleaning, the flow channel is selected again as shown in FIG. 6, and the membrane module 66 is cleaned with an acid.

If necessary, the membrane module 66 is sufficiently cleaned by further performing alkali cleaning and acid cleaning.

According to the membrane module cleaning apparatus, as described above, the cleaning liquid flows between the tanks 60 and 62 and is used repeatedly, so that the amount of the cleaning liquid can be reduced. (It is sufficient that the amount of the cleaning liquid is substantially the same as the volume of the vessel 64.) Further, the flow direction of the liquid between the tanks 60 and 62 only needs to reverse the opening and closing of the valve, which is extremely simple. Further, the membrane module 66 can be sufficiently cleaned by liquid cleaning, gas-liquid mixed-phase flow cleaning, and air cleaning.

In the description of FIG. 6, acid cleaning and alkali cleaning are performed alternately. However, as shown in FIGS. 5 (2) and (3), after acid cleaning, acid cleaning is performed once or a plurality of times. You may make it wash with an alkali and then wash with an acid. When the acid cleaning is performed a plurality of times continuously, the acid solution may be replaced with a new one during the process.

FIG. 5 illustrates a specific switching pattern between acid and alkali. Of FIG. 5, those of (2) and (3) are particularly preferable. Note that “acid” in the square frame in FIG. 5 means “acid cleaning”, and “alkali” means “alkali cleaning”. Further, "acid exchange" indicates that the acid solution is exchanged for a new one.

In the present invention, during the washing step using an acid or an alkali, washing is temporarily interrupted, city water or the like is passed through, the amount of permeated water and the transmembrane pressure difference are measured, and the degree of recovery of the membrane performance is checked. It is also possible to know whether or not the cleaning liquid (acid or alkali solution) needs to be replaced and the replacement time.

In the present invention, in the embodiment of FIG. 6, the cleaning liquid is circulated through the raw water flow path of the membrane module 66. However, the cleaning liquid may be supplied to the permeation flow path and the cleaning waste liquid may flow out of the raw water flow path. .

Although air is used as the gas in the above embodiment, various gases such as nitrogen and argon can be used.

Next, the spiral type membrane module 66
A preferred embodiment will be described with reference to FIGS.

FIG. 1A is a perspective view of one bag-like membrane used in the spiral membrane module and a shaft around which the bag-like membrane is wound. FIGS. 1B and 1C are cross-sectional views taken along lines BB and CC of FIG. 1A, respectively. FIG. 2 is a sectional view showing a method of winding a bag-like membrane around a shaft, FIG. 3 is a perspective view showing an engagement relationship between a wound body and a socket, and FIG. 4 is a side view of a spiral membrane module.

The bag-like membrane 1 used in this embodiment
0 is a square or rectangular shape, and the first side 1
1, second side 12, third side 13, and fourth side 1
Four. This bag-shaped membrane 10 is formed by folding one long separation membrane film into two at the second side portion 12 and separating the separation membrane films folded at the first side portion 11 and the third side portion 13 from each other. The fourth side portion 14 is formed in a bag shape with an open portion without being bonded by an adhesive or the like.

From the middle of the fourth side portion 14 to the third side portion 13, the separation membrane films of the bag-like membrane 10 are not adhered to each other, forming an open portion 30 for permeated water outflow.
Also, from the middle of the fourth side portion 14, the first side portion 11
In, the separation membrane films of the bag-like membrane 10 are adhered to each other to form a closed portion 31 that prevents outflow of permeated water.

A channel material (for example, a mesh spacer or the like) 15 is inserted and arranged in the bag-like membrane 10. In addition, the bag-shaped film 10 is not limited to a single long film folded in two at the second side 12,
The two separation membrane films are overlapped, and the first side portion 11,
The second side part 12, the third side part 13, and a part of the fourth side part 14 may be bonded.

On one surface of the bag-like film 10, an adhesive 1
6 is adhered and adhesives 17 and 18 are adhered to the other surface, and the bag-like film 10 is wound around the shaft 20. The adhesive 16 is applied along the first side 16, and the adhesive 17 is applied along the third side 13. The adhesive 18 is applied along the opening 30 for outflow of permeated water from the intermediate portion in the longitudinal direction of the fourth side portion 14 to the third side portion 13.

By winding a plurality of bag-like films 10 around the shaft 20, the overlapping bag-like films 10 are joined to each other at the adhesives 16, 17 and 18 in a water-tight manner. Thus, a raw water flow path through which raw water (and concentrated water) flows is formed between the bag-shaped membranes 10. Adhesive 18
As a result, the open portion for the outflow of raw water (concentrated water) is formed on the inner peripheral side on the rear end face of the wound body, and the closed portion for preventing the outflow of raw water is formed on the outer peripheral side.

The fin 19 extends from the boundary between the open portion 30 for permeated water outflow and the closed portion 31 for permeated water outflow prevention in the fourth side portion 14 toward the rear of the wound body. ing. The fins 19 are made of, for example, a synthetic resin film or sheet, and are preferably bonded to the bag-like film 10 by adhesion or the like.

By winding the bag-like film 10 around the shaft 20 via the mesh spacer 29 as shown in FIG. 2, a wound body 24 is formed as shown in FIG. The fin 19 extends from the rear end face of the wound body 24. The fins 1 are located at the same location on the fourth side 14 of each bag-like membrane 10.
By providing the fins 9, the fins 19 are located on the same radial position from the axis of the winding body 24, and the fins 19 form a ring-shaped protrusion by overlapping the fins 19. The rear end of the cylindrical socket 25 is inserted into the ring-shaped protrusion, and the socket 25 and the fin 19 are joined with an adhesive or the like. The socket 25 is connected to the fin 1
9 may be externally fitted. Alternatively, a cutting groove may be formed on the rear end face of the wound body 24 along the fins 19 with a lathe, and the end of the socket 25 may be embedded in the groove.

By joining the socket 25 and the fin 19 in this manner, a permeated water outflow area on the outer peripheral side of the rear end face of the wound body 24 and a concentrated water outflow area on the inner peripheral side of the socket 25 are defined. .

When the bag-like film 10 is wound around the shaft 20, a mesh spacer 29 is interposed between the bag-like films 10 as shown in FIG. The raw water flow path is formed by interposing these mesh spacers 29.

As shown in FIG. 4, a top ring 26 and an end ring 27 are provided on the leading edge and the trailing edge of the wound body 24, respectively.
Is formed by a synthetic resin mold or the like, and the top ring 26 is formed.
A brine seal 28 is provided around the outer periphery of.

In the spiral membrane module configured as described above, as shown in FIG. 4, raw water flows into the raw water flow path between the bag-like membranes 10 from the front end face of the wound body 24. This raw water flows through the raw water flow path in a direction substantially parallel to the axis of the wound body 24, and is taken out from the end face inside the socket 25 at the rear end of the wound body 24. Then, while the raw water flows through the raw water flow path, the water permeates into the bag-like membrane 10, and the permeated water flows out from the outer peripheral side of the socket 25 on the rear end surface of the wound body 24.

In this spiral membrane module, the permeated water flows in the bag-like membrane 10 in a direction parallel to the axis of the wound body 24 and is taken out from the rear end face. The used collecting pipe is unnecessary. For this reason, the flow resistance when flowing from the bag-like membrane into the water collecting pipe is eliminated, and the permeated water flow resistance is significantly reduced.

It should be noted that the water collecting pipe is omitted, and the length of the bag-like membrane 10 in the winding direction can be increased accordingly.
It is possible to increase the film area. Even if the length of the bag-like membrane in the winding direction is increased, the permeated water flow resistance does not increase,
The amount of permeated water can be increased.

In this membrane module, the outlet portion of the raw water flow path is provided only inside the socket 25, and the outlet (the most downstream portion) of the raw water flow path is narrowed.
The flow rate of the raw water (concentrated water) becomes sufficiently large also on the downstream side of the raw water flow path, and it is possible to prevent the adhesion of dirt in the downstream area of the raw water flow path. The area inside and outside the socket 25 (the length of the adhesive 18 in the side portion 14 direction) is preferably determined according to the water recovery rate of the spiral membrane module.

In this membrane module, the socket 25 is connected to the winding body 24 using the fins 19, and the connection strength between the socket 25 and the winding body 24 is high. Then, the inflow side of the raw water and the outflow side of the concentrated water are partitioned in a watertight manner by the socket 25.

In the membrane module shown in FIGS. 1 to 4, the permeated water outflow portion is arranged on the outer peripheral side of the socket 25 and the concentrated water outflow portion is arranged inside the socket 25. Socket 2 inside
5 may be configured to be a concentrated water outflow portion.

[0062]

As described above, according to the method for cleaning a membrane module of the present invention, metal hydroxides and organic substances can be sufficiently removed from a membrane module obtained by membrane-separating coagulated water.

[Brief description of the drawings]

FIG. 1A is a perspective view of a bag-like membrane of a membrane module suitable for cleaning by the apparatus of the present invention, and FIG.
A cross-sectional view taken along the line BB of the drawing, FIG.
It is sectional drawing which follows the C line.

FIG. 2 is a cross-sectional view showing a method of winding the bag-like film of FIG.

FIG. 3 is a perspective view showing an engagement relationship between a wound body and a socket in FIG. 1;

FIG. 4 is a side view of the spiral membrane module according to FIG. 1;

FIG. 5 is a process chart showing an example of the method of the present invention.

FIG. 6 is a system diagram of a membrane module cleaning apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 10 bag-like membrane 11 first side 12 second side 13 third side 14 fourth side 15 flow path material 16, 17, 18 adhesive 19 fin 20 shaft 24 wound body 25 socket 29 Mesh spacer 30 Open part for permeated water outflow 31 Closed part for permeated water outflow prevention 60 First tank 62 Second tank 64 Vessel 66 Membrane module 68 Compressor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masaki Misaki 3-7-4 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term (reference) in Kurita Kogyo Co., Ltd. 4D006 GA03 GA06 GA07 HA62 JA55A KA02 KB13 KC02 KC14 KC16 KD12 KD11 KD12 KD15 KD17 KD24

Claims (5)

[Claims] 1. A method for cleaning a membrane module for subjecting water to be treated to coagulation treatment and membrane filtration, comprising: a first step of acid cleaning, a second step of alkali cleaning, and a third step of acid cleaning. Characteristic method for cleaning membrane modules. 2. The method for cleaning a membrane module according to claim 1, wherein the acid solution is replaced during the first step and the film is washed again with a new acid solution. 3. The method for cleaning a membrane module according to claim 1, further comprising a fourth step of performing alkali cleaning and acid cleaning after the third step. 4. The cleaning device according to claim 1, wherein the cleaning device includes a vessel for accommodating the membrane module, a first tank and a second tank for accommodating a cleaning liquid for the membrane module.
A pressurized gas supply device for supplying a pressurized gas into the first and second tanks and causing a liquid to flow out of the tanks, further comprising: supplying a pressurized gas into the first tank; Supplying the liquid in the tank into the vessel to clean the membrane module, selecting a first flow path for allowing the cleaning waste liquid to flow from the vessel into the second tank; The pressurized gas is supplied, the liquid in the second tank is supplied into the vessel, the membrane module is washed, and the second flow path selecting the washing waste liquid from the vessel into the first tank. A cleaning method for a membrane module, wherein the above-described cleaning is performed using a membrane module cleaning device provided with a flow path switching unit capable of switching between the above-described steps. 5. The membrane module according to claim 1, wherein in the membrane module, a permeated water flow path material is disposed inside the bag-shaped membrane, and a raw water flow path material is disposed between the bag-shaped membranes. Wherein the bag-shaped membrane is a substantially rectangular shape having first, second, third and fourth sides, and wherein the first, second and third sides are provided. Is sealed,
A part of the fourth side is an open part and the remaining part is a closed part, and a first side perpendicular to the fourth side is applied to a shaft to wind a bag-like membrane. A body having a fourth side facing the rear end face of the wound body, a second side facing the fourth side facing the front end face of the wound body, In the raw water flow path between the membranes, the entire third side portion is sealed, and in the fourth side portion, a portion overlapping with the open portion of the bag-shaped membrane is a closed portion, A method of cleaning a membrane module, wherein the membrane module is a spiral-type membrane module in which a portion overlapping with a closed portion of the bag-shaped membrane is an open portion.