JP2001087763A - Immersion type membrane separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an immersion type membrane separation device capable of surely producing a uniform flow with a relatively simple structure, and preventing clogging of a membrane due to sticking of sludge. SOLUTION: This immersion type membrane separation device produces treated water by filtration through the membrane constituting a flat membrane module installed in a sewage treating device, and is provided with the plural flat membrane modules arranged in a casing mutually in parallel, and an aeration pipe arranged at the lower part of these flat membrane modules, and the aeration pipe is constituted of two pipes having plural aeration ports, which are mutually in parallel, and these two pipes are fixed so as to be horizontal and parallel to membrane surfaces of the flat membrane modules, and air is fed from both sides of these two pipes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion type membrane separation apparatus for obtaining treated water by solid-liquid separation of sludge with a microfiltration membrane constituting a flat membrane module, which is immersed in a wastewater treatment tank.

[0002]

2. Description of the Related Art Conventionally, as a wastewater treatment method for domestic wastewater and industrial wastewater, there is known an immersion type membrane separation activated sludge method in which activated sludge and treated water are separated by a membrane separation device installed in a treatment tank. . Such a membrane separation device includes a plurality of flat membrane modules arranged at regular intervals that are deployed in a vertical plane, a casing holding the flat membrane modules, and an air diffuser provided below the flat membrane modules. Comprising
Activated sludge is solid-liquid separated by reducing the pressure inside the flat membrane module to obtain treated water.

In the immersion type membrane separation activated sludge method, during the solid-liquid separation of activated sludge, when solids adhere to the membrane surface, and particularly when there is a dead zone, the shear force that separates the solids in the dead zone. Does not work, there is a problem that a high concentration of sludge is deposited and clogging of the membrane occurs, thereby reducing the effective membrane area and decreasing the membrane permeation flow rate. There is also a problem that the maintenance frequency increases due to a decrease in the permeation flow rate.

[0004] In order to prevent such a problem, for example, in Japanese Patent Application Laid-Open No. 10-33955, a membrane filtration unit including a plurality of flat membrane modules is disposed in a casing.
A membrane separation device having an air diffusion tube below the membrane filtration unit, wherein a plurality of lateral air diffusion holes are formed at both sides of a tube wall of the air diffusion tube at intervals in a length direction. An apparatus is disclosed.

In this membrane separation device, bubbles are evenly diffused from a diffuser pipe into a casing, and the membrane surface is cleaned by a shearing effect of a water flow generated by the diffusion of the bubbles and an air scrubbing effect.

However, in such an immersion type membrane separation device, a large amount of air bubbles are ejected from the air diffuser at a position closer to the blower, and a skewed flow is formed, so that a dead flow region is generated. Sludge will adhere in the dead watershed.

[0007] Further, when manufacturing a membrane separation apparatus or installing the membrane separation apparatus in a treatment tank, the membrane separation apparatus itself often tilts. In this case, there is a problem that the air diffuser is also inclined, the amount of air bubbles from the air diffuser port located closer to the water surface is increased, and a biased flow is formed, resulting in a dead flow area.

Further, the velocity of the water flow due to the bubbles from the air diffuser port decreases as the distance from the central axis of the air diffuser port increases, and the flow velocity in the central portion of the casing increases due to the effect of the swirling flow flowing from the lower side of the casing. Therefore, there is also a problem that the flow is concentrated at the center and the sludge easily adheres to both ends of the membrane.
However, unnecessarily increasing the number of air diffusers for even diffusion of air bubbles causes an increase in the capacity of the blower.

[0009]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide an immersion type in which a relatively simple structure can reliably produce an even flow and prevent clogging of a membrane due to sludge adhesion. It is an object to provide a membrane separation device.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a submerged membrane separation apparatus which is installed in a sewage treatment apparatus and obtains treated water by filtration through a membrane constituting a flat membrane module. The flat membrane module includes a plurality of flat membrane modules arranged in parallel, and an air diffuser arranged below the flat membrane modules. The air diffuser includes two parallel pipes having a plurality of air diffusers. The two pipes are fixed so as to be horizontal and parallel to the membrane surface of the flat membrane module, and air is supplied from both sides of the two pipes. It is a membrane separation device. Hereinafter, the present invention will be described in detail.

[0011]

FIG. 1 is a perspective view schematically showing an immersion type membrane separation apparatus of the present invention, and FIG. 2 is a schematic view showing the above immersion type membrane separation apparatus installed in a sewage treatment tank. FIG.

As shown in FIG. 1, the immersion type membrane separation device of the present invention comprises a plurality of flat plate-like membrane modules 2 arranged in a casing 3 in parallel with each other. And a diffuser tube 4 disposed therein.

The flat membrane module 2 has a structure in which two microfiltration membranes are bonded via a spacer.
The upper end is provided with a water collecting port 8 for sucking the treated water. As the microfiltration membrane, those usually used for such wastewater treatment can be used,
The material is not particularly limited.

The air diffuser 4 comprises two parallel pipes 4a and 4b having a plurality of air diffusers 9.
These two pipes 4a, 4b are connected to each other at both ends by a pipe to which the vertical pipe 10 is connected. The vertical pipe 10 is connected to a blower (not shown),
Therefore, through the vertical pipe 10, these two pipes 4a,
Air is supplied from both sides of 4b.

The two pipes 4a and 4b are
The vertical tubes 10 support and fix the air bubbles in a direction that is horizontal and parallel to the membrane surface of the flat membrane module 2 so that the air bubbles diffuse over the entire surface of the flat membrane module 2.

The distance c between the central axes of the two pipes 4 a and 4 b of the air diffuser 4 is determined by the size of the casing 3. The ratio between the width b of the casing in the direction perpendicular to the membrane surface of the flat membrane module 2 and the distance c between the central axes of the two pipes 4a and 4b is in the range of 5: 3 to 5: 4. It is preferred that

The ratio of the width b of the casing to the distance c between the center axes of the two pipes, that is, (the width b of the casing b /
If the value of the distance c) between the center axes of the pipes is larger than 5/4, the jetted bubbles are difficult to reach the peripheral portion of the casing, and a dead flow area is easily generated. On the other hand, the value is 5/3. If it is smaller than this, the jetted bubbles flow too much around the casing, and a dead flow region is likely to be generated at the center.

It is preferable that the diffuser port 9 of the diffuser tube 4 is opened vertically downward so that air bubbles can be easily diffused.
The ratio between the distance d between the air diffusers 9 and the horizontal width a of the flat membrane module 2 is preferably in the range of 1: 3 to 1: 5.

If the value of (distance d between the air diffusers / width a in the horizontal direction of the flat membrane module) is larger than 1/5, that is, if the distance between the air diffusers becomes longer, the density of the bubbles will decrease. Since the size is small, there is a possibility that a dead area is generated. On the other hand, if the above value is smaller than 1/3, it is necessary to provide a large number of air diffusers, and the amount of air bubbles increases, which is not economical.

Although the number of air diffusers 9 is five in FIG. 2, it is not limited to this number. Also,
The diameter of the air diffuser is also preferably 5 mm, but is not limited to this.

The distance e (see FIG. 2) between the air diffuser 4 and the lower end of the flat membrane module 2 is preferably at least の of the horizontal width a of the flat membrane module 2.

Distance e between diffuser tube and lower end of flat membrane module
However, if the horizontal width a of the flat membrane module is less than ２, the distance between the air diffuser and the lower end of the flat membrane module is too short, so that it is difficult for air bubbles to diffuse throughout the flat membrane module.

As shown in FIG. 2, the immersion type membrane separation apparatus having such a configuration is installed inside the processing tank 1 and
When the sewage flows into the inside, air is supplied to the air diffuser 4 and bubbles are generated, the sewage and the activated sludge 6 are mixed, and oxygen in the supplied air causes the aerobic microorganisms in the activated sludge 6 to become organic. Decomposes toxic substances.

Then, the water collecting port 8 of the flat membrane module 2 constituting the immersion type membrane separation apparatus is connected to the suction pump 11 and the pressure is reduced, whereby the activated sludge 6 is solid-liquid separated and the treated water 5 is efficiently obtained. be able to.

[0025]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

The submerged membrane separator according to Embodiment example, the same structure as the submerged membrane separator shown in FIG. 1, is installed in the sewage treatment apparatus shown in FIG. Hereinafter, a more specific configuration of the immersion type membrane separation device will be described.

The flat membrane module 2 has a horizontal width a50.
It is a flat plate having a thickness of 0 mm, a vertical length of 1000 mm, and a thickness of 7 mm. Two microfiltration membranes are attached to each other via a spacer. Of water collecting port 8 is provided.

The casing 3 has a width b (hereinafter, referred to as vertical) 175 mm, a width of 600 mm, a height of 1300 mm, and a width b (hereinafter referred to as vertical) of the casing 3 in a direction perpendicular to the membrane surface of the flat membrane module 2.
It is a rectangular cylinder having a thickness of 10 mm, and a plurality of slits for inserting and holding the flat membrane module 2 are provided inside the rectangular cylindrical body. Are inserted and held in parallel at regular intervals.

On the other hand, the air diffuser 4 is provided below the flat membrane module 2 and is composed of two parallel pipes each having a plurality of air diffusers and having an inner diameter of 13 mm. , 4b are two vertical tubes 10
Are fixed so as to be horizontal and parallel to the membrane surface of the flat membrane module 2, respectively.

That is, the two pipes 4a and 4b are connected on both sides by joints, and the joint is further connected and fixed to two vertical pipes 10 fixed to the casing 3. The two vertical pipes 10 are connected to a blower 7 having an air flow rate of 90 liters / min. By operating the blower 7, air is sufficiently supplied from both sides of these two pipes 4a and 4b to diffuse air. Air bubbles are ejected from the mouth 9.

The two pipes 4a and 4b are located at a position 300 mm below the flat membrane module 2, and the center distance c is maintained at 140 mm. Therefore, the distance e300 mm between the air diffuser 4 and the lower end of the flat membrane module is equal to or more than の of the horizontal width a500 mm of the flat membrane module, and the casing 3 in the direction perpendicular to the membrane surface of the flat membrane module 2. Width of b175mm and 2 forming the diffuser tube
The ratio of the pipe to the center axis distance c140 mm is 5:
4.

The diffuser pipe 4 is provided with a total of 10 circular diffuser ports 9 having a diameter of 5 mm, five for each pipe. Further, the air diffuser 9 is opened vertically downward at intervals of 125 mm in the longitudinal direction of the two pipes 4a and 4b,
The ratio between the distance d125 mm between the air diffusers and the horizontal width a500 mm of the flat membrane module is 1: 4.

[0033]

According to the immersion type membrane separation device of the present invention, the rising air bubbles and flows which are likely to be concentrated at the center in the casing are generally removed by the air diffusion in the two parallel diffuser tubes. It can be evenly diffused in space. In addition, by supplying air from both sides of the air diffuser, air bubbles of uniform size can be ejected from all air diffusers, and it is hard to be affected by slight inclination of the air diffuser. And a uniform flow can be produced, and clogging due to the adhesion of sludge to the membrane surface constituting the flat membrane module can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an immersion type membrane separation device of the present invention.

FIG. 2 is a longitudinal sectional view schematically showing the immersion type membrane separation device of FIG. 1 installed in a sewage treatment tank.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 treatment tank 2 flat membrane module 3 casing 4, 4 a, 4 b diffuser pipe 5 treated water 6 activated sludge 7 blower 8 water collecting port 9 diffuser port 10 vertical pipe 11 suction pump

Claims (4)

[Claims] 1. A immersion type membrane separation device installed in a sewage treatment device and obtaining treated water by filtration through a membrane constituting a flat membrane module, wherein the plurality of immersion type membrane separation devices are arranged in parallel in a casing. A flat membrane module, and an air diffuser arranged below the flat membrane module, wherein the air diffuser is constituted by two parallel pipes having a plurality of air diffusers, and the two pipes are An immersion type membrane separation device, wherein each of the two pipes is fixed so as to be horizontal and in a direction parallel to the membrane surface of the flat membrane module, and air is supplied from both sides of the two pipes. 2. The ratio of the width of the casing in the direction perpendicular to the membrane surface of the flat membrane module to the distance between the central axes of two pipes constituting the diffuser is 5: 3 to 5: 4. The immersion type membrane separation device according to claim 1. 3. The air diffuser according to claim 1, wherein the air outlet of the air diffuser is opened vertically downward, and a ratio of a distance between the air diffusers to a horizontal width of the flat membrane module is 1: 3 to 1: 5. Item 3. An immersion type membrane separation device according to item 1 or 2. 4. The immersion type membrane separation according to claim 1, wherein a distance between the air diffuser and a lower end of the flat membrane module is at least の of a horizontal width of the flat membrane module. apparatus.