JPH0810589A - Method for cleaning membrane module - Google Patents

Abstract

PURPOSE:To easily release a cake layer in a short time and to apply this method to any kind of membrane module by moving a gas-liq. interface in a treating tank over the whole region between the upper and lower ends of the membrane face of a membrane module and generating bubbles in the treating tank. CONSTITUTION:A membrane module 15 dipped in the water W to be treated in a treating tank 11 to filter the water W to obtain the treated water is cleaned as follows. Namely, a gas-liq. interface in the treating tank 11 is moved over the whole region between the upper and lower ends of the membrane face of the module 15, and bubbles are generated in the tank 11. In this case, the air injected into the tank forms bubbles to produce a diffused-air current, and the membrane face of the module is vibrated with the current to release a cake layer. Since the bubbles burst at the gas-liq. interface, the make-up water at a high flow velocity is irregularly moved vertically, and the membrane face is strongly rubbed by the make-up water. Accordingly, the cake layer is more effectively released, and the cake layer is easily released.

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 a membrane module.

[0002]

2. Description of the Related Art Conventionally, clear water (hereinafter referred to as “treated water”) is obtained by filtering raw water (hereinafter referred to as “treated water”) containing contaminants, sludge and the like (hereinafter referred to as “impurities”). A membrane module such as a microfiltration membrane or an ultrafiltration membrane is used to obtain the water.) In this case, the treated water is supplied to the treatment tank so that the membrane module is immersed in the treated water. Has become. Then, the treated water side of the membrane of the membrane module is pressurized or the treated water side is depressurized so that only the treated water in the treated water can permeate the membrane.

On the other hand, impurities in the water to be treated remain in a concentrated state on the water side of the membrane to be treated. Therefore, the impurities are discharged from the processing tank. However, when the water to be treated is repeatedly treated, impurities are gradually attached to the surface of the membrane of the membrane module (hereinafter referred to as “membrane surface”) to form a cake layer, which lowers the permeability of the membrane. . Therefore, the membrane module is cleaned by various methods to remove impurities from the membrane surface.

That is, a method of blowing air bubbles to the membrane module (air bubbling) while the membrane module is immersed in the water to be treated, a method of taking the membrane module out of the treatment tank and rubbing the membrane surface with a brush, A method of supplying high-pressure water or air from the treated water side of the membrane to the treated water side and applying a back pressure to the membrane, a method of mechanically vibrating the membrane module, and a method of supplying a cleaning chemical to the treatment tank are is there.

[0005]

However, in the above-mentioned conventional method for cleaning a membrane module, in the method of blowing bubbles to the membrane module while the membrane module is immersed in the water to be treated, vibration due to the bubbles is caused by the water to be treated. Will decay. As a result, the vibration applied to the film is reduced, and the effect of peeling (peeling) the cake layer is reduced.

Further, in the case of the method of taking out the membrane module from the treatment tank and rubbing the membrane surface with a brush, not only the work for taking out the membrane module from the treatment tank and incorporating it into the treatment tank is troublesome but also the work The processing time of the water to be treated is shortened by the amount of time. Then, in the case of a method of supplying high-pressure water or air from the treated water side of the membrane of the membrane module to the treated water side and applying a reverse pressure to the membrane, the applicable membrane module is limited, and the flat membrane type Can not be applied to the membrane module of.

Further, in the case of the method of mechanically vibrating the membrane module, not only is it necessary to dispose a special vibration generator, but also the peeling effect of the cake layer becomes small. Then, in the case of the method of supplying the cleaning chemical to the processing tank, the waste water contains the chemical. INDUSTRIAL APPLICABILITY The present invention solves the above-mentioned problems of the conventional membrane module cleaning method, can easily and easily peel off the cake layer in a short time, and can be applied to any type of membrane module. It is an object of the present invention to provide a method for cleaning a membrane module that can be used.

[0008]

Therefore, in the method for cleaning a membrane module of the present invention, the membrane module is immersed in the water to be treated in the treatment tank, and the treated water is filtered to obtain treated water. The gas-liquid interface in the processing tank is moved over the entire area between the upper end and the lower end of the membrane surface of the membrane module.

Then, bubbles are generated in the processing tank. In another membrane module cleaning method of the present invention,
The membrane module is immersed in the water to be treated in the treatment tank, and the water to be treated is filtered to obtain treated water. The entire area between the upper and lower ends of the membrane surface of the membrane module is treated in the treatment tank. The membrane module is moved up and down so as to pass through the gas-liquid interface inside.

Then, bubbles are generated in the processing tank.

[0011]

According to the present invention, as described above, in the method for cleaning a membrane module, the membrane module is immersed in the water to be treated in the treatment tank, and the water to be treated is filtered to obtain the treated water. In addition, the gas-liquid interface due to makeup water or the like in the treatment tank is moved over the entire area between the upper end and the lower end of the membrane surface of the membrane module.

Then, bubbles are generated in the processing tank. In this case, the air jetted into the treatment tank becomes bubbles to form a diffused airflow, which vibrates the membrane surface of the membrane module to separate the cake layer. At the gas-liquid interface, the bubbles burst, so that the vertical movement of the makeup water having a high flow rate occurs irregularly, and the makeup water strongly rubs the membrane surface. During this time, the gas-liquid interface of the makeup water in the processing tank moves over the entire area between the upper end and the lower end of the membrane surface of the membrane module.

In another method for cleaning a membrane module of the present invention, the membrane module is immersed in the water to be treated in the treatment tank, and the treated water is filtered to obtain treated water. The membrane module is moved up and down so that the entire area between the upper and lower ends of the membrane surface of the module passes through the gas-liquid interface due to makeup water in the treatment tank. Then, bubbles are generated in the processing tank.

In this case, the air jetted into the processing tank becomes air bubbles to form a diffused air flow, which vibrates the membrane surface of the membrane module to separate the cake layer. At the gas-liquid interface, the bubbles burst, so that the vertical movement of the makeup water having a high flow rate occurs irregularly, and the makeup water strongly rubs the membrane surface. During this time, the membrane module is moved up and down, and the entire region between the upper end and the lower end of the membrane surface of the membrane module passes through the gas-liquid interface in the processing tank.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a sectional view of a processing tank according to an embodiment of the present invention. In the figure, 11 is a submerged membrane module biological treatment tank as a treatment tank, and the treated water W
Is supplied to the submerged membrane module biological treatment tank 11 through a line 12. An on-off valve 13 is arranged in the line 12, and the water W to be treated is supplied to the submerged membrane module biological treatment tank 11 by opening and closing the on-off valve 13 or to the submerged membrane module biological treatment tank 11. Treated water W
Can be stopped. The line 12
Is opened in the submerged membrane module biological treatment tank 11 above the frame 14, and the water W to be treated is supplied from above the submerged membrane module biological treatment tank 11.

In the submerged membrane module biological treatment tank 11, for example, treatment is carried out by a short cycle batch activated sludge method. By the treatment by the short cycle batch type activated sludge method, BOD components, COD components and the like in the treated water W are removed and the treated water W is denitrified and nitrified to form a mixed liquid of biologically treated water and biological sludge. become. Therefore,
Immersion Type Membrane Module The immersion type membrane module 15 as a membrane module is immersed in the water W to be treated in the biological treatment tank 11, and the mixed solution is filtered by the immersion type membrane module 15 to obtain biological treatment water and biological sludge. To be separated. Then, the biologically treated water is sucked by the biologically treated water pump P1 and supplied to the coagulation tank (not shown) via the line 18, and the biological sludge is sucked as excess sludge by the pump P2 and supplied to the sludge storage tank (not shown) via the line 19. To be done.
The line 19 is opened near the bottom of the submerged membrane module biological treatment tank 11, and an opening / closing valve 21 is arranged upstream of the pump P2.

Below the submerged membrane module 15 in the submerged membrane module biological treatment tank 11, an aeration and bubbling device 25 is arranged.
Bubbling device 25 is connected to blower 28 via line 26. Therefore, the blower 28 is operated to convey the compressed air through the line 26, and the compressed air is jetted into the submerged membrane module biological treatment tank 11 from the air diffuser 29 formed at the tip of the line 26. In addition, the line 26
An on-off valve 31 is provided in the submerged membrane module biological treatment tank 1 for opening compressed air by opening and closing the on-off valve 31.
1, or the supply of compressed air to the submerged membrane module biological treatment tank 11 can be stopped.

Then, the compressed air jetted into the submerged membrane module biological treatment tank 11 becomes bubbles to form a diffused air (gas-liquid mixed liquid), and the mixed liquid is agitated by the scattered air. While circulating, an aerobic atmosphere is formed in the submerged membrane module biological treatment tank 11. In addition,
Oxygen-containing gas may be used instead of compressed air.

The immersion type membrane module 15 comprises a plurality of flat membranes 33 arranged in parallel in the vertical direction.
The interval between them is set to 50 to 100 mm, and each flat membrane 3
A vertical passage for passing the diffused air is formed between the three. In the submerged membrane module biological treatment tank 11 having the above-described configuration, the treatment water introduction step, the denitrification step by anaerobic stirring, and the nitrification step by aeration stirring are cyclically repeated, while the submerged membrane module 15 allows the biological treated water to be treated. And biological sludge are separated.

Therefore, first, in the treated water introduction step, the treated water W is supplied to the submerged membrane module biological treatment tank 11 through the line 12, and the stirring pump (not shown) is operated. Then, oxygen dissolved in the water W to be treated is quickly consumed, and an anaerobic atmosphere is formed in the submerged membrane module biological treatment tank 11. Therefore,
In the denitrification process, the denitrification group oxidizes the organic matter in the water to be treated W in an anaerobic atmosphere (nitric acid respiration) by utilizing the nitrate ions, nitrite ions, etc. which were generated in the previous cycle and remained in the mixed solution. Work). At this time, most of nitrate ions, nitrite ions, etc. are reduced to nitrogen gas, and the treated water W
Removed from With this denitrification reaction, the amount of alkali increases quantitatively, and the alkali consumed by the nitrification reaction is stored in the next nitrification process.

[0021] In the nitrification step, the organic substances remaining unused due to the denitrification reaction in the denitrification step are oxidized in the aerobic atmosphere, and the reduced nitrogen compound (mainly the organic nitrogen compound) produced in the denitrification step. And ammonia) are oxidized to nitrite ion, nitrate ion and the like by nitrifying bacteria such as nitrite and nitrifying bacteria. By the way, when the water W to be treated is repeatedly treated, impurities are gradually attached to the membrane surface of the immersion membrane module 15 to form a cake layer, and the permeability of the flat membrane 33 is reduced. Therefore,
The immersion type membrane module 15 is cleaned to remove impurities from the film surface.

For that purpose, the makeup water H is supplied to the submerged membrane module biological treatment tank 11 through the line 36. An on-off valve 37 is arranged in the line 36, and by supplying the replenishing water H to the submerged membrane module biological treatment tank 11 by opening or closing the on-off valve 37, or replenishing the submerged membrane module biological treatment tank 11. The supply of water H can be stopped. The line 36 opens into the submerged membrane module biological treatment tank 11 above the frame 14, and make-up water H is supplied from above the submerged membrane module biological treatment tank 11.

A line 39 is arranged below the frame 14, and the waste water generated when the submerged membrane module 15 is washed can be discharged through the line 39. An on-off valve 40 is provided in the line 39, and by opening and closing the on-off valve 40, waste water can be discharged or discharge of waste water can be stopped. The line 39
Is opened in the submerged membrane module biological treatment tank 11 below the frame 14, and the wastewater is discharged from below the submerged membrane module biological treatment tank 11.

Next, a method of cleaning the immersion type membrane module 15 will be described. FIG. 2 is a diagram showing a cleaning process of the immersion type membrane module according to the embodiment of the present invention. In the figure, (a) shows a normal treatment process, (b) shows a water removal process, and (c) and (d).
Indicates a bubbling process. In the figure, 11 is a submerged membrane module biological treatment tank, 15 is a submerged membrane module, 2
5 is an aeration / bubbling device, 26, 36, 39 are lines, 28 is a blower, 29 is an air diffuser, 31, 37, 40 are open / close valves, W is treated water, and H is makeup water.

While the treatment is carried out in the submerged membrane module biological treatment tank 11, the on-off valves 37 and 40 are closed as shown in FIG. Further, the opening / closing valve 31 is closed in the denitrification step to form an anaerobic atmosphere in the submerged membrane module biological treatment tank 11, and the opening / closing valve 31 is opened in the nitrification step to allow the submerged membrane module biological treatment to be performed from the air diffuser 29. By injecting compressed air into the tank 11,
An aerobic atmosphere is formed in the submerged membrane module biological treatment tank 11. Then, the water to be treated W is filled in the submerged membrane module biological treatment tank 11 and treated to be a mixed liquid.

When the immersion type membrane module 15 is to be washed, first, as shown in FIG.
7 is closed and the on-off valve 40 is opened. Therefore, the wastewater generated during the cleaning of the submerged membrane module 15 will be discharged from the line 3
It is discharged from the submerged membrane module biological treatment tank 11 via 9. Then, as shown in FIG.
Is closed and the on-off valves 31 and 37 are opened. Then, makeup water H is gradually supplied to the submerged membrane module biological treatment tank 11, and compressed air is jetted from the air diffuser 29 into the submerged membrane module biological treatment tank 11 while raising the gas-liquid interface. The compressed air injected into the submerged membrane module biological treatment tank 11 becomes bubbles to form a diffused air, and the supplementary water H is agitated and circulated by the diffused air, and the membrane surface of the submerged membrane module 15 is agitated. Vibrate to peel off the cake layer. At the gas-liquid interface, the bubbles burst, so that the vertical movement of the makeup water H having a high flow velocity occurs irregularly, and the makeup water H strongly rubs the membrane surface. As a result, the peeling effect of the cake layer becomes extremely large, and the cake layer can be peeled effectively.

Particularly, in the immersion type membrane module 15 using the flat membrane type membrane module, a large amount of air bubbles enter the narrow vertical passages between the flat membranes 33, so that the cake layer peeling effect is further enhanced. be able to. Moreover, the makeup water H is gradually supplied so that the gas-liquid interface in the submerged membrane module biological treatment tank 11 is moved over the entire area between the upper end and the lower end of the membrane surface of the submerged membrane module 15. Therefore, the entire cake layer on the film surface can be peeled off.

In this case, the bubbling strength of bubbles is
Immersion type membrane module 5 to 100 per floor area in which the immersion type membrane module 15 in the biological treatment tank 11 is disposed
[M ³ / m ² / hr], but can be changed according to the strength of the film. The amount of the makeup water H is set so that the submerged membrane module biological treatment tank 11 reaches a specified water level in a bubbling time of about 20 to 60 minutes.

Then, as shown in (d) of the figure, when the makeup water H is supplied to the specified water level, the on-off valves 31, 37 are closed. In this way, the supply of makeup water H to the submerged membrane module biological treatment tank 11 and the injection of compressed air into the submerged membrane module biological treatment tank 11 are stopped. Further, if necessary, by repeating the water removal step of (b) of the figure and the bubbling step of (c) and (d) of the figure, the peeling effect of the cake layer on the film surface can be further enhanced.

In the water removal step of FIG. 3B, the opening / closing valve 31 is opened while the mixed liquid is gradually discharged from the submerged membrane module biological treatment tank 11 to lower the gas-liquid interface. From the air diffuser 29 to the immersion membrane module biological treatment tank 1
It is also possible to inject compressed air into 1. In this case, the discharge amount of the mixed liquid is set so that the submerged membrane module biological treatment tank 11 can be drained in a bubbling time of about 20 to 60 minutes.

Further, in the water draining process when the bubbling process of (c) and (d) of FIG.
It is also possible to inject compressed air into the submerged membrane module biological treatment tank 11. In addition, in this embodiment, while the mixed liquid is gradually discharged from the submerged membrane module biological treatment tank 11 to lower the gas-liquid interface, or the make-up water H is gradually added to the submerged membrane module biological treatment tank 11. Immersion type membrane module biological treatment tank 1 while supplying and raising the gas-liquid interface
Although the compressed air is injected into the inside of the No. 1, the air-liquid interface is maintained at a fixed position and the immersion type membrane module 15 is gradually raised or the immersion type membrane module 15 is gradually lowered. Compressed air may be injected into the mold membrane module biological treatment tank 11. In this case, the submerged membrane module 15 is moved up and down so that the entire area between the upper end and the lower end of the submerged membrane module 15 passes through the gas-liquid interface in the submerged membrane module biological treatment tank 11.

For that purpose, the immersion type membrane module 15
Is connected to a suspension device (not shown), and the immersion type membrane module 15 can be moved up and down by operating the suspension device by a drive source (not shown). In this case, the submerged membrane module 15 is lifted and lowered during the bubbling time of about 20 to 60 minutes. The test results of the cleaning method for the immersion type membrane module 15 as described above are as follows.

In this case, river water was supplied to the submerged membrane module biological treatment tank 11 as water W to be treated under the following conditions to purify the water. Water quality of river water Turbidity 10 to 30 [mg / l] Temperature 17 to 20 [° C] Addition rate of coagulant 1 [mg / l] Filtration rate 0.6 [m ³ / m ² / day] The coagulant As the material, polyaluminum chloride was used.

When river water is purified under the above conditions,
Table 1 shows the results of cleaning the immersion membrane module 15.

[0035]

[Table 1]

The bubbling strength is 40 [m ³ / m ²
/ Hr], the bubbling time was 30 minutes, and the suction pressure was converted into the suction pressure of the water W to be treated at 20 [° C.]. In this case, since the submerged membrane module biological treatment tank 11 performs constant pressure suction for depressurizing the treated water side of the membrane,
The smaller the suction pressure, the higher the permeability of the membrane.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0038]

As described in detail above, according to the present invention, in the method for cleaning a membrane module, the membrane module is immersed in the water to be treated in the treatment tank, and the treated water is filtered to obtain the treated water. The gas-liquid interface due to makeup water or the like in the treatment tank is moved over the entire area between the upper end and the lower end of the membrane surface of the membrane module.

Then, bubbles are generated in the processing tank. In this case, the air jetted into the treatment tank becomes bubbles to form a diffused airflow, which vibrates the membrane surface of the membrane module to separate the cake layer. At the gas-liquid interface, the bubbles burst, so that the vertical movement of the makeup water having a high flow rate occurs irregularly, and the makeup water strongly rubs the membrane surface.

Therefore, the peeling effect of the cake layer becomes extremely large, and the cake layer can be peeled easily and in a short time. Moreover, it can be applied to any type of membrane module. In another method for cleaning a membrane module of the present invention, the membrane module is immersed in the water to be treated in a treatment tank, and the treated water is filtered to obtain treated water. The membrane module is moved up and down so that the entire area between the upper and lower ends of the surface passes through the gas-liquid interface due to makeup water in the treatment tank.

Then, bubbles are generated in the processing tank. In this case, the air jetted into the treatment tank becomes bubbles to form a diffused airflow, which vibrates the membrane surface of the membrane module to separate the cake layer. At the gas-liquid interface, the bubbles burst, so that the vertical movement of the makeup water having a high flow rate occurs irregularly, and the makeup water strongly rubs the membrane surface.

Therefore, the peeling effect of the cake layer becomes extremely large, and the cake layer can be peeled easily and in a short time. Moreover, it can be applied to any type of membrane module.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a processing tank according to an embodiment of the present invention.

FIG. 2 is a process drawing of the immersion type membrane module according to the embodiment of the present invention.

[Explanation of symbols]

 11 Immersion Type Membrane Module Biological Treatment Tank 15 Immersion Type Membrane Module 33 Flat Membrane W Treated Water H Makeup Water

Claims (2)

[Claims] 1. A method of cleaning a membrane module for immersing in treated water in a treatment tank to obtain treated water by filtering the treated water, comprising: (a) a gas-liquid interface in the treatment tank; A method for cleaning a membrane module, wherein the membrane module is moved over the entire area between the upper end and the lower end of the membrane surface and (b) bubbles are generated in the treatment tank. 2. A method for cleaning a membrane module, wherein the membrane module is immersed in treated water in a treatment tank, and the treated water is filtered to obtain treated water, wherein (a) the upper and lower ends of the membrane surface of the membrane module. The method for cleaning a membrane module is characterized in that the membrane module is moved up and down so as to pass through the gas-liquid interface in the treatment tank, and (b) bubbles are generated in the treatment tank.