JPH08323349A - Washing method of immersing type membrane cartridge in tank - Google Patents

Abstract

PURPOSE: To provide a washing method of an immersing type membrane cartridge in tank capable of distributing a liq. agent to whole surfaces of the membrane cartridge. CONSTITUTION: A washing liq. agent having larger specific density than a membrane permeated liq. is injected to a permeated liq. passage of the immersing type membrane cartridge 17 immersed in a treating tank, and after injection of the washing liq. agent, aeration is executed from a bottom part of the treating tank 11, and an upward stream generated by the aeration is allowed to flow along the membrane surface of the immersing type membrane cartridge 17, and a filter membrane is washed by moving the washing liq. agent to an upper part side of the immersing type membrane cartridge 17 by an energization force of an upstream flow received via the filter membrane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning the inside of a tank of an immersion type membrane cartridge used for solid-liquid separation in a human waste treatment facility or the like.

[0002]

2. Description of the Related Art Conventionally, in a human waste treatment facility or the like, an immersion type membrane separator is provided in a treatment tank for separating activated sludge and coagulated sludge in a liquid to be treated. 2 to 4
As shown in FIG. 1, the submerged membrane separation device 1 is provided with a plurality of flat submerged membrane cartridges 3 in a box-shaped casing 2 having upper and lower openings in parallel in the vertical direction. An air diffuser 6 for supplying aeration air 5 to the liquid to be treated 4 in the tank is provided below the. As shown in FIGS. 3 to 4, the submerged membrane cartridge 3 has a filtration membrane 8 such as an ultrafiltration membrane that covers the surface of a membrane support plate 7, and the membrane support is provided on the back side of the filtration membrane 8. The plate 7 has a permeated liquid channel 9 on the surface or inside thereof.

Then, the natural water head in the tank acts as a driving pressure on the membrane surface of the filtration membrane of each submerged membrane cartridge 3, or a suction means (not shown) is provided in the permeated liquid passage 9 of the submerged membrane cartridge 3. By subjecting the liquid to be treated 4 to solid-liquid separation by applying a suction negative pressure by means of), the solid content such as activated sludge in the liquid to be treated 4 is captured by the filtration membrane of the submerged membrane cartridge 3 and permeated through the filtration membrane. The membrane permeated liquid that has flowed into the permeated liquid channel is taken out as the treatment liquid 10.

At this time, the bubbles of the aerated air supplied through the air diffuser 6 and the upward flow of the liquid to be treated 4 caused by the air lift action of the bubbles act on the membrane surface of the filtration membrane, and the upward flow is swept. By flowing on the membrane surface as a stream, the membrane surface of the immersion type membrane cartridge 3 is washed.

[0005]

As described above, since the immersion type membrane separation device has a self-cleaning function with aerated air, it has been unnecessary to wash it, but various cleaning methods are required due to a sudden change in concentration. For this reason, the cake layer attached to the film surface becomes thick and cleaning is required.

The cleaning method proposed in the prior art is as follows:
There is a problem that maintenance efficiency is extremely poor in terms of maintenance because it is necessary to take out the entire immersion type membrane separation device or individual immersion type membrane cartridges from the treatment tank and then immerse the immersion type membrane cartridge in the chemical cleaning tank. It was Also,
As another cleaning method, there is an in-tank chemical liquid cleaning method in which the film is cleaned while the immersion type membrane cartridge is immersed in the tank. In this in-tank chemical liquid cleaning method, the chemical liquid was injected into the permeate flow path of the immersion membrane cartridge in a state where suction was stopped, the chemical liquid was injected and left for several hours, and then the operation was restarted. If aeration is performed during this period, the chemical liquid in the submerged membrane cartridge is urged by the upward flow through the filtration membrane and does not fall, and there is a problem that the chemical liquid does not fully reach the lower side of the submerged membrane cartridge. . Further, even when the aeration is stopped, when the concentration of the liquid medicine is high, the specific gravity becomes large, and as shown in FIG. 3, the liquid medicine spreads only to the lower side of the immersion type membrane cartridge and the concentration of the liquid medicine is low. Had a problem that the specific gravity became small, and as shown in FIG. 4, the chemical solution spreads only to the upper side of the immersion type membrane cartridge.

The present invention solves the above-mentioned problems.
It is an object of the present invention to provide a bath cleaning method for an immersion type membrane cartridge, which is capable of spreading a chemical solution over the entire surface of the immersion type membrane cartridge.

[0008]

In order to solve the above-mentioned problems, a method for cleaning a submerged membrane cartridge in a tank according to the present invention comprises a permeated liquid in a permeated liquid channel of the submerged membrane cartridge immersed in a treatment tank. A cleaning liquid with a higher specific gravity is injected, and after the cleaning liquid is injected, aeration is performed from the bottom of the treatment tank, and the upward flow generated by the aeration is caused to flow along the membrane surface of the submerged membrane cartridge and is received through the filtration membrane. The cleaning chemical is moved to the upper side of the submerged membrane cartridge by the urging force of the countercurrent to clean the filtration membrane.

Further, after the cleaning chemical solution is moved to the upper side of the immersion type membrane cartridge, the aeration is stopped and it is left for several hours.

[0010]

With the above-described structure, the cleaning chemical liquid to be injected into the submerged membrane cartridge first settles downward due to the difference in specific gravity from the membrane permeated liquid, then spreads horizontally in the lower side of the submerged membrane cartridge, and The filtration membrane is infiltrated to the lower side and the filtration membrane is washed with a chemical solution. Since the upward flow generated by aeration after the injection work urges the cleaning chemicals upward through the filtration membrane, the cleaning chemicals infiltrate the upper part of the filtration membrane while moving to the upper side of the immersion type membrane cartridge. Then, the filtration membrane is chemically washed.

Therefore, the cleaning solution moves, spreads and spreads while moving over the entire area of the submerged membrane cartridge due to gravity settling due to the difference in specific gravity and upward urging force due to aeration, and permeates outside the filtration membrane to permeate the membrane. Be sure to wash the cake layer on the surface over the entire surface of the filtration membrane.

Further, by moving the cleaning chemical solution to the upper side of the submerged membrane cartridge and then leaving the aeration stopped, the cleaning chemical solution permeating to the outside of the filtration membrane and the cake layer on the membrane surface are sufficiently removed. In addition, the cleaning chemical liquid that has moved to the upper side of the submerged membrane cartridge infiltrates and overlaps the filtration membrane while settling and moving downward again, and a sufficient amount of the cleaning chemical liquid permeates the outside of the filtration membrane. As a result, the filtration membrane can be washed more reliably.

[0013]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a treatment tank 11 is an activated sludge treatment tank which stores therein a mixed liquid of raw water such as urine and activated sludge as a treated liquid 12, and an upper portion of the tank is for supplying the treated liquid 12 to the treated sludge. The supply system 13 is in communication with, and a discharge system 14 for discharging excess sludge is in communication with the lower part of the tank.

An immersion type membrane separator 1 is provided inside the processing tank 11.
5 is immersed. In the submerged membrane separation device 15, a casing 16 has a box shape and is open at the top and bottom, and a plurality of flat plate-shaped submerged membrane cartridges 17 are arranged inside the casing 16 in parallel in the vertical direction. There is. Each submerged membrane cartridge 17 has an organic filtration membrane such as an ultrafiltration membrane disposed so as to cover the surface of the membrane support plate, and a permeate flow channel is formed on the surface or inside of the membrane support plate on the back side of the filtration membrane. Have The header tube 18 communicates with the permeate flow path of each submerged membrane cartridge 17 via a tube 19,
A discharge pipe 20 for discharging the membrane-permeated liquid is connected to one side of the header pipe 18, and the opening of the discharge pipe 20 and the processing tank 1 are connected.
There is an appropriate distance h between the water surface and the water surface. Discharge pipe 20
A chemical solution injection pipe 22 arranged vertically above the on-off valve 21 communicates with the. Immersion type membrane cartridge 1
An air diffuser 23 is arranged below the array group 7 and a blower 25 communicates with the air diffuser 23 via an air supply pipe 24.

The operation of the above structure will be described below. In a normal operating state, the aerated air 26 supplied by the blower 25 through the air supply pipe 24 is aerated from the air diffuser 23 to the liquid to be treated 12 in the treatment tank 11, and oxygen is dissolved in the liquid to be treated 12 by the aeration. Together with aerated air 2
The liquid to be treated 12 in the tank is circulated by the upward flow generated by the air-lifting action of the bubbles of 6, thereby biologically decomposing the organic matter in the liquid to be treated 12.

On the other hand, the natural head h is caused to act on the filtration membrane of the submerged membrane cartridge 17 as a driving pressure, and the liquid to be treated 1
2 is solid-liquid separated. In each submerged membrane cartridge 17, the solid content is captured by the filtration membrane, and the permeated liquid that permeates the filtration membrane of the submerged membrane cartridge 17 and flows into the permeate flow path passes through the tube 19 to the header tube 18. It is guided and taken out of the system through the discharge pipe 20.

At this time, the bubbles of the aerated air 26 and the upward flow of the liquid to be treated 12 act on the membrane surface of the filtration membrane of each submerged membrane cartridge 17, and the bubbles cause the cake layer on the membrane surface due to the discontinuity. While exhibiting a piercing force for scooping, the upflow flows as a scavenging flow over the membrane surface, and the membrane surface of the immersion type membrane cartridge 17 is washed.

By the way, a treatment tank 11 for treating activated sludge.
The main component of the cake layer adhering to the membrane surface of the filtration membrane of the submerged membrane cartridge is organic matter. For this reason,
When cleaning the submerged membrane cartridge 17 for maintenance or the like, chemical cleaning is required.

When the submerged membrane cartridge 17 is washed in the tank, the liquid level in the tank and the liquid level in the header tube 19 are set to the same level to eliminate the natural head h, and the submerged membrane separation apparatus 1
The filtration operation of No. 5 is stopped and the on-off valve 21 is closed.

Next, with the immersion type membrane cartridge 17 immersed in the tank, the header tube 1 is passed through the chemical solution injection tube 22.
Inject cleaning chemicals into 8. This cleaning chemical has a higher specific gravity than the membrane permeate, or a chemical having a low specific gravity added with a chemical such as sodium chloride for adjusting the specific gravity to increase the specific gravity. The specific gravity of the cleaning chemical solution is preferably in the range of 1.001 to 1.200 times the specific gravity of the membrane permeate. In this example, a 1.5% oxalic acid solution was used as the chemical solution, and the specific gravity was adjusted to be 1.008 times that of the membrane permeate. The cleaning chemical solution is injected in an amount of 1 liter per one sheet of the immersion type membrane cartridge 17. This cleaning chemical solution is injected for about 3 minutes.

At this injection time, the cleaning chemical liquid injected into the immersion type membrane cartridge 17 first settles downward due to the difference in specific gravity from the membrane permeation liquid, and the immersion type membrane cartridge 17
Spreads horizontally in the lower side of the membrane and infiltrates the lower side of the filtration membrane to clean the filtration membrane with a chemical solution.

Immediately after the injection of the chemical liquid is finished, the drive of the blower 25 is restarted and the aerated air 2 supplied through the air supply pipe 24 is supplied.
6 is aerated from the air diffuser 23, and the aeration causes an upward flow along the membrane surface of the submerged membrane cartridge 17. This aeration is performed for 1 minute.

The upward urging force acts on the cleaning chemical in the submerged membrane cartridge 17 through the filtration membrane to move the cleaning chemical to the upper side of the submerged membrane cartridge 17. While the cleaning chemical moves to the upper side of the submerged membrane cartridge, it infiltrates the upper part of the filtration membrane to clean the filtration membrane with the chemical.

Therefore, the cleaning chemical solution spreads and spreads while moving across the entire area of the submerged membrane cartridge 17 by the gravity settling due to the difference in specific gravity and the upward flow biasing force due to aeration, and permeates to the outside of the filtration membrane. Be sure to wash the cake layer on the membrane surface over the entire surface of the filtration membrane.

After aeration is performed for 1 minute to move the cleaning chemical solution to the upper side of the immersion type membrane cartridge 17, the aeration is stopped and left for several hours in order to enhance the cleaning effect of the chemicals. By this standing, the cleaning chemical liquid that has permeated to the outside of the filtration membrane sufficiently reacts with the cake layer on the membrane surface, and the cleaning chemical liquid that has moved to the upper side of the immersion type membrane cartridge again settles downward and moves to the filtration membrane. A sufficient amount of the cleaning chemical liquid is infiltrated by permeating the filter membrane and permeating to the outside of the filtration membrane. As a result, the filtration membrane can be washed more reliably.
If the washing result is shown by the membrane permeation flux, 0.2% before washing.
^{m 3 / (m 2 · d} ) those which was a was restored to ^{1.0m 3 / (m 2 · d} ) after washing.

Example 2. In addition to oxalic acid, it is also possible to use sodium hypochlorite as the above-mentioned cleaning chemical liquid.
In this case, cleaning is performed by the following procedure. 1. The operation of the immersion type membrane cartridge with the membrane surface blocked is stopped. 2. Aeration is also stopped. 3. Inject the cleaning chemicals shown in the table below for about 3 minutes. 4. Immediately after injection, perform aeration for the aeration time shown in the table below. 5. Stop aeration and leave it for about 1 hour. 6. Repeat 4 to 5 as needed. 7. Restart the operation.

[0027]

[Table 1]

By the way, in the configuration of the above-mentioned embodiment, when the specific gravity of the cleaning chemical liquid is equal to that of the membrane permeation liquid,
The cleaning chemical solution spread only to the upper part of the immersion type membrane cartridge 17, and only about 30% of the membrane area could be washed. When the specific gravity of the cleaning chemical is 1.2 times or more that of the membrane-permeated liquid, the cleaning chemical does not sufficiently reach the upper part of the submerged membrane cartridge 17 only by the urging force of aeration.
Only about 75% of the membrane area could be washed. further,
If aeration is performed 10 minutes after injecting the cleaning solution,
During this period, the cleaning chemical liquid settled in the lower part of the submerged membrane cartridge 17 permeated through the filtration membrane and flowed out to reduce the amount of the cleaning chemical liquid, so that only about 90% of the membrane area could be cleaned.

[0029]

As described above, according to the present invention, the cleaning chemical liquid spreads and spreads while moving over the entire area of the submerged membrane cartridge by the gravity settling due to the difference in specific gravity and the upward flow biasing force due to aeration. Since it infiltrates, the cake layer on the membrane surface can be reliably washed over the entire surface of the filtration membrane.

Further, by moving the cleaning chemical solution to the upper side of the immersion type membrane cartridge and then stopping the aeration, the cleaning chemical solution permeating to the outside of the filtration membrane and the cake layer on the membrane surface are sufficiently removed. In addition, the cleaning chemical liquid that has moved to the upper side of the submerged type membrane cartridge infiltrates on the filtration membrane while settling and moving downward again, so that the cleaning chemical liquid that permeates the outside of the filtration membrane is sufficiently secured and filtered. The membrane can be washed more reliably.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an overall configuration of an immersion type membrane separation device showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an overall configuration of a conventional immersion type membrane separation device.

FIG. 3 is an explanatory diagram showing how a cleaning chemical solution spreads in a conventional cleaning method.

FIG. 4 is an explanatory diagram showing how a cleaning chemical solution spreads in a conventional cleaning method.

[Explanation of symbols]

 11 Treatment Tank 12 Liquid to be Treated 15 Immersion Type Membrane Separation Device 17 Immersion Type Membrane Cartridge 18 Header Pipe 20 Discharge Pipe 22 Chemical Liquid Injection Pipe 23 Air Diffuser

Front Page Continuation (72) Inventor Masafumi KUBOTA Co., Ltd. 2-47 Shikitsuhigashi, Naniwa-ku, Osaka City, Osaka Prefecture

Claims (2)

[Claims] 1. A cleaning chemical having a larger specific gravity than a membrane permeate is injected into a permeate flow path of an immersion type membrane cartridge immersed in a treatment tank, and after the cleaning chemical is injected, aeration is carried out from the bottom of the treatment tank, which is caused by aeration. Upflow is caused to flow along the membrane surface of the submerged membrane cartridge, and the cleaning liquid is moved to the upper side of the submerged membrane cartridge by the upward flow biasing force received through the filtration membrane to clean the filtration membrane. A method for cleaning a submerged membrane cartridge in a tank. 2. The method for cleaning the inside of a submerged membrane cartridge according to claim 1, wherein after the cleaning chemical is moved to the upper side of the submerged membrane cartridge, the aeration is stopped and the standing is continued for several hours.