JPH08266875A - Method for washing inside of immersion type membrane cartridge in vessel - Google Patents

Abstract

PURPOSE: To make it possible to wash immersion type membrane cartridges and to facilitate the maintenance thereof without taking these cartridges out of a treating vessel by first injecting an oxidizing agent for decomposing org. matter into the insides of the membrane cartridges, then injecting an acid for dissolving inorg. matter therein at the time of washing the cartridges. CONSTITUTION: The respective immersion type membrane cartridges 17 in an immersion type membrane separator 15 in the treating vessel 11 are subjected to capturing of solid contents by filter membranes and the permeated liquid is introduced through tubes 18 to a liquid collecting section 19a of a header pipe 19, from which the liquid is taken outside of the system through a suction pipe 20. A first washing medicinal liquid 26 which is the oxidizing agent for decomposing the org. matter is injected into the header pipe 19 at the time of washing such cartridges 17 in the vessel. The first washing medicinal liquid 26 is held for the suitable time in the state that liquid permeates the filter membranes with microflow fluxes, by which the org. matter in cake layers is decomposed. The second washing medicinal liquid 27 which is the acid to decompose the inorg. matter is injected like in the first washing into the header pipe after discharge of the first washing medicinal liquid 26, by which the inorg. matter in the cake layers is dissolved.

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. As shown in FIG. 4, the submerged membrane separation apparatus 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 with each other 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 cartridge 3. The submerged membrane cartridge 3 has a filtration membrane such as an ultrafiltration membrane disposed so as to cover the surface of the membrane support plate, and has a permeate channel on the surface or inside of the membrane support plate on the back side of the filtration membrane. ing.

Then, suction negative pressure is applied to the permeate flow path of each submerged membrane cartridge 3 by a suction means (not shown), or the membrane surface of the filtration membrane of the submerged membrane cartridge 3 is filled with natural water in the tank. By acting as a driving pressure, 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 the permeated liquid that has permeated the filtration membrane and flowed into the permeated liquid channel. Is taken out as the processing liquid 7.

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-lifting action of the bubbles act on the membrane surface of the filtration membrane, and the bubbles become intermittent. The membrane surface of the submerged membrane cartridge 3 is cleaned by exerting a piercing force for scooping the cake layer and flowing the upward flow as a sweep stream over the membrane surface.

[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

The present invention solves the above-mentioned problems.
It is an object of the present invention to facilitate maintenance and extend the life of the immersion type membrane cartridge by cleaning the immersion type membrane cartridge in the processing tank without removing it from the processing tank.

[0008]

In order to solve the above-mentioned problems, the method for cleaning the inside of a submerged membrane cartridge according to the present invention is a method in which the submerged membrane cartridge is first immersed in an activated sludge treatment tank. An oxidant for decomposing organic substances is injected as the first cleaning chemical into the submerged membrane cartridge through the permeate flow path, and the first cleaning chemical causes the filtration membrane of the immersion membrane cartridge to pass from the permeate side to the treated liquid side. To the inside of the submerged membrane cartridge by injecting an acid that dissolves an inorganic substance as the second cleaning chemical solution after the first cleaning chemical solution has been discharged, and then the second cleaning chemical solution is immersed. The filtration membrane of the mold membrane cartridge is configured to be held for a proper period of time in a state where the filtration membrane permeates from the permeated liquid side to the treated liquid side with a minute flux.

In the method for cleaning the submerged membrane cartridge in the tank according to the present invention, the first cleaning chemical liquid is first introduced into the submerged membrane cartridge through the permeate flow path while the submerged membrane cartridge is immersed in the coagulation tank. As the first cleaning chemical solution, an acid that dissolves an inorganic substance is injected, and the first cleaning chemical solution is held for a suitable time in a state where the first cleaning chemical solution permeates the filtration membrane of the immersion type membrane cartridge from the permeate side to the treated liquid side with a minute flux, After discharging, an oxidizer for decomposing organic substances is injected as a second cleaning chemical into the submerged membrane cartridge, and the second cleaning chemical finely moves the filtration membrane of the submerged membrane cartridge from the permeate side to the treated liquid side. The configuration is such that it is maintained for a suitable period of time while being permeated by a flux.

[0010]

With the above structure, when the submerged membrane cartridge is used for solid-liquid separation in the activated sludge treatment tank, the cake layer adhered to the membrane surface of the filtration membrane of the submerged membrane cartridge is composed mainly of organic matter. Become. Therefore, the first
Decomposes organic substances in the cake layer with an oxidant that forms a cleaning chemical,
By decomposing a small amount of inorganic substances remaining on the membrane surface of the filtration membrane even after the decomposition of organic matters with the acid forming the second cleaning chemical solution, the cake layer adhered to the membrane surface is effective without removing the immersion type membrane cartridge from the tank. Of the submerged membrane cartridge can be easily cleaned, maintenance is facilitated, and the life of the immersion type membrane cartridge is extended.

When the submerged membrane cartridge is used for solid-liquid separation in the coagulation tank, the cake layer attached to the membrane surface of the filtration membrane of the submerged membrane cartridge has an inorganic substance as its main component. Therefore, first, the inorganic substance in the cake layer is dissolved with the acid forming the first cleaning chemical liquid, and a small amount of the organic substance remaining on the membrane surface of the filtration membrane after the inorganic substance is dissolved is decomposed by the oxidizing agent forming the second cleaning chemical liquid. As a result, the cake layer adhering to the membrane surface can be effectively washed without taking the immersion membrane cartridge out of the tank, which facilitates maintenance and extends the life of the immersion membrane cartridge.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. Example 1. 1 and 2, 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 the treated liquid 1 is provided on the upper part of the tank.
A supply system 13 for supplying 2 is connected, and a discharge system 14 for discharging excess sludge is connected to the lower part of the tank.

An immersion type membrane separation apparatus 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 a filtration membrane such as an ultrafiltration membrane disposed so as to cover the surface of the membrane support plate, and has a permeate channel on the surface or inside of the membrane support plate on the back side of the filtration membrane. are doing. Tube 1 for each immersion type membrane cartridge 17
In the header pipe 19 communicating with each other through 8, the liquid collecting portion 19a extending in the lateral direction and the liquid level adjusting portion 19b extending in the vertical direction are bent in an L shape, and one side opening of the liquid level adjusting portion 19b is formed. It is open to an appropriate height above the surface of the water. A suction pump 21 communicates with the liquid collecting portion 19a of the header tube 19 via a suction tube 20 that is raised to a predetermined height. An air diffuser 22 is arranged below the array of submerged membrane cartridges 17, and a blower 24 communicates with the air diffuser 22 via an air supply pipe 23.

The operation of the above structure will be described below. In a normal operating state, the aerated air 25 supplied from the blower 24 through the air supply pipe 23 is aerated from the air diffuser 22 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 5, so that the organic matter in the liquid to be treated 12 is biologically decomposed. On the other hand, the suction level performed by the suction pump 21 via the suction pipe 20 maintains the liquid level in the header pipe 19 at a position lower than the liquid level in the treatment tank 11, and the natural head h ₁ due to the difference between the two liquid levels. Is applied to the filtration membrane of the immersion type membrane cartridge 17 as a driving pressure to separate the liquid to be treated 12 into solid and liquid. In each submerged membrane cartridge 17, the solid content is captured by the filtration membrane, and the permeate that permeates the filtration membrane of the submerged membrane cartridge 17 and flows into the permeate flow path passes through the tube 18 and collects in the header tube 19. It is guided to the liquid portion 19a and taken out of the system through the suction pipe 20.

At this time, the bubbles of the aeration air 25 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 to be intermittent. 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 cleaning the submerged membrane cartridge 17 in the tank, the suction pump 21 is stopped and the liquid level in the tank and the liquid level in the liquid level adjusting section 19b of the header pipe 19 are made the same. When the level is reached, the natural head h ₁ is eliminated and the filtration operation of the submerged membrane separation device 15 is stopped.

Next, as shown in FIG. 2, with the submerged membrane cartridge 17 immersed in the tank, the first cleaning chemical solution 26 is injected into the header tube 19, and the header tube 19 is charged from the liquid level in the tank. The liquid level of the first cleaning chemical liquid 26 in the liquid level adjusting section 19b is set to a high level, and the first cleaning chemical liquid 26 is injected into the submerged membrane cartridge 17 by the natural head h ₂ due to the liquid level difference. The first cleaning chemical liquid 26 is an oxidizing agent for decomposing organic substances, and is sodium hypochlorite (concentration effective chlorine: 0.5 to 1%) in this embodiment, but other oxidizing agents are also possible. The first cleaning chemical liquid 26 was applied to the filtration membrane of the immersion type membrane cartridge 17 from the permeated liquid side to the treated liquid side at 0.70 m ³
Hold for 1-2 hours in a state of permeation with a small flux of / (m ² d),
Organic substances in the cake layer are decomposed with the sodium hypochlorite of the first cleaning chemical liquid 26.

After that, in order to avoid mixing of the cleaning chemicals,
The suction pump 21 is driven to cause the natural head to act like during filtration, and the first cleaning chemical liquid 26 remaining in the submerged membrane cartridge 17 is discharged. After discharging the first cleaning chemical liquid 26, the second cleaning chemical liquid 27 is subjected to the same procedure as in the case of the first cleaning chemical liquid 26 in order to remove a trace amount of inorganic substances remaining on the membrane surface of the filtration membrane even after the decomposition of the organic matter. By pouring into the inside of the immersion type membrane cartridge. The second cleaning liquid 27 is an acid that dissolves an inorganic substance, and in the present embodiment, oxalic acid (concentration:
5,000-10,000 mg / L) but other acids are possible. Second
The cleaning chemical solution 27 is kept for 30 minutes to 1 hour in a state in which the filtration membrane of the submerged membrane cartridge 17 permeates from the permeate side to the liquid side to be treated with a minute flux of 0.40 m ³ / (m ² d), and 2 cleaning chemicals 2
Dissolve the minerals in the cake layer with oxalic acid of 7.

As described above, first, the organic substances in the cake layer are decomposed with the sodium hypochlorite of the first cleaning chemical liquid 26, and the trace amount of the inorganic substances remaining on the membrane surface of the filtration membrane after the decomposition of the organic substances is secondarily removed.
By dissolving the cleaning liquid chemical 27 with oxalic acid, the cake layer adhering to the film surface can be effectively washed without taking out the immersion type membrane cartridge 17 from the tank, and the maintenance is facilitated and the immersion type membrane is facilitated. Cartridge 17
Can prolong life. Embodiment 2. FIG. In the same configuration as in Example 1, the processing tank 11
When forming a coagulation tank in a waste water treatment facility or the like, the main component of the cake layer attached to the membrane surface of the filtration membrane of the submerged membrane cartridge 17 is an inorganic substance.

Therefore, when the immersion type membrane cartridge 17 is cleaned with a chemical solution, an acid such as oxalic acid (concentration 5000 to 10000 mg / L) is used as the first cleaning chemical solution 0.65 m ³ / (m ² d).
Of the state passed through the column at small flux hold 30 minutes to 1 hour, sodium hypochlorite as the second wash liquor 27 (concentration effective chlorine 0.5 to 1%) 0.50 m an oxidizing agent such as ³ / The state of passing a liquid with a minute flux of (m ² d) is maintained for 1 to 2 hours.

In this case, first, the inorganic substances in the cake layer are dissolved with oxalic acid forming the first cleaning chemical liquid 26, and a trace amount of organic substances remaining on the membrane surface of the filtration membrane after the inorganic substances are dissolved is removed by the second cleaning chemical liquid. By decomposing it with sodium hypochlorite forming No. 27, the cake layer adhering to the membrane surface can be effectively washed without removing the submerged membrane cartridge 17 from the tank, which facilitates maintenance and dips The life of the mold film cartridge 17 can be extended. Example 3. Although FIG. 3 shows an apparatus configuration in another embodiment of the present invention, members having the same functions as those in the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 3, a suction pump 21 is connected to the header pipe 31 via a suction pipe 20, and a chemical liquid supply pipe 33 is connected to the top of the suction pipe 20 raised to a predetermined height via a valve 32. It is in communication.

In this structure, with the valve 32 closed, a suction negative pressure is applied to the inside of the submerged membrane cartridge 17 by the suction pump 21, and the liquid 12 to be treated is filtered by this suction negative pressure. For cleaning the immersion type membrane cartridge 17 with the chemical liquid, the valve 32 is opened to inject the first cleaning chemical liquid 26 and the second cleaning chemical liquid 27, and the chemical liquid is supplied by the natural head h ₃ between the liquid level in the tank. It is injected into the immersion type membrane cartridge 17. Other functions and effects are similar to those of the first and second embodiments.

[0025]

As described above, according to the present invention, in the activated sludge treatment tank, first, the organic matter in the cake layer is decomposed by the oxidizing agent forming the first cleaning chemical liquid, and after the organic matter is decomposed By decomposing a trace amount of inorganic substances remaining on the film surface with the acid forming the second cleaning chemical, in the coagulation tank, first the first
An inorganic substance in the cake layer is dissolved with an acid forming a cleaning chemical liquid, and a small amount of an organic substance remaining on the membrane surface of the filtration membrane even after the inorganic substance is dissolved is decomposed by an oxidizing agent forming a second cleaning chemical liquid, whereby an immersion type membrane cartridge The cake layer adhering to the membrane surface can be effectively washed without removing the cake from the tank, which facilitates maintenance and extends the life of the immersion type membrane cartridge.

[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 schematic view showing a cleaning action in the immersion type membrane separation apparatus of the same embodiment.

FIG. 3 is a schematic view showing an overall configuration of an immersion type membrane separation device showing another embodiment of the present invention.

FIG. 4 is a perspective view showing an overall configuration of a conventional immersion type membrane separation device.

[Explanation of symbols]

 11 Treatment Tank 12 Liquid to be Treated 15 Immersion Type Membrane Separation Device 17 Immersion Type Membrane Cartridge 19 Header Tube 20 Suction Tube 21 Suction Pump 22 Air Diffuser 26 First Cleaning Chemical Solution 27 Second Cleaning Chemical Solution

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoji Izumi 1-247 Shikitsu Higashi, Naniwa-ku, Osaka City, Osaka Prefecture Kubota Corporation

Claims (2)

[Claims] 1. An oxidizer for decomposing an organic substance as a first cleaning chemical liquid is first injected into the inside of the submerged membrane cartridge through the permeate flow path while the submerged membrane cartridge is immersed in the activated sludge treatment tank. Then, the first cleaning chemical solution is held for a suitable time in a state of permeating the filtration membrane of the immersion type membrane cartridge from the permeate side to the liquid side to be treated with a minute flux, and after the first cleaning chemical solution is discharged, the immersion type membrane cartridge An acid that dissolves an inorganic substance is injected as the second cleaning chemical solution, and the second cleaning chemical solution is maintained for a suitable time in a state in which the second cleaning chemical solution permeates the filtration membrane of the immersion type membrane cartridge from the permeate side to the treated liquid side with a minute flux. A method for cleaning a submerged membrane cartridge in a tank, comprising: 2. An immersion type membrane cartridge is immersed in an aggregating tank, and an acid that dissolves an inorganic substance is injected as a first cleaning chemical solution into the immersion type membrane cartridge through a permeate flow path first. The cleaning chemical solution is held for a suitable time in a state of permeating the filtration membrane of the immersion type membrane cartridge from the permeate side to the liquid side to be treated with a small flux, and after the first cleaning chemical solution is discharged, inside the immersion type membrane cartridge, (2) Injecting an oxidizing agent that decomposes organic substances as a cleaning chemical liquid, and maintaining the second cleaning chemical liquid for a suitable time in a state in which it permeates the filtration membrane of the submerged membrane cartridge from the permeate side to the treated liquid side with a minute flux. A method for cleaning a submerged membrane cartridge in a tank, which is characterized by: