JP2001162141A - Aerobic biological treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sufficiently dissolve the oxygen in air bubbles into liquid to be treated and to efficiently progress the biological treatment by activated sludge with an aerobic biological treating device including membrane elements 32. SOLUTION: A diffusion plate 34 which disperses the air bubbles diffused from an air diffusing means is disposed between the membrane elements 32 and the air diffusing means 34 of the aerobic biological treating device including a reaction chamber 30, the membrane elements 32 immersed into the reaction chamber 30 and the air diffusing means 34 arranged under the membrane elements 32, by which the contact efficiently between the air bubbles and the water to be treated is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aerobic biological treatment apparatus, and more particularly to an aerobic biological treatment apparatus having a membrane element immersed in a reaction tank.

[0002]

2. Description of the Related Art As an aerobic biological treatment apparatus of this type, there is known an apparatus in which a membrane element 12 is immersed in a reaction tank 10 and an aeration means 14 is arranged below the membrane element 12, as shown in FIG. Have been. The water to be treated flows into the reaction tank 10 through the pipe 16 and stays there for a predetermined time.
The activated sludge comes into contact with the sludge, and the organic components in the water to be treated are oxidatively decomposed and purified by the biological action of the activated sludge.

[0003] A suction pump 20 is connected to the membrane element 12 via a pipe 18, and water permeating the membrane element 12 is taken out of the apparatus as treated water by the suction force of the suction pump 18.

[0004] From the air diffuser 14 connected to the blower 22, fine air bubbles are diffused. Aeration has three purposes. The first is to maintain the water to be treated under aerobic conditions in order to supply oxygen necessary for the oxidative decomposition of organic components in the water to be treated. The second object is to form a circulating flow F in the reaction tank 12 by the lift action of the diffused bubbles, thereby increasing the contact efficiency between the water to be treated and the activated sludge. The third object is to constantly clean the membrane surface by colliding with and contacting the membrane surface of the membrane element 12 while the air bubbles rise between the membrane elements 12.

As described above, this type of aerobic biological treatment apparatus can use diffused air bubbles for a variety of purposes, and forcibly removes treated water by the membrane element 12 to increase the activated sludge in the reaction tank 10. There is an advantage that the concentration can be maintained and highly efficient aerobic biological treatment can be performed. For this reason, it is attracting attention as a biological treatment apparatus that can significantly reduce the required site area as compared with the activated sludge treatment method using a conventional sedimentation pond.

[0006]

However, as described above, as a result of maintaining the activated sludge in the reactor 10 at a high concentration, the mixture of the liquid to be treated and the activated sludge in the reactor 10 becomes muddy and viscous. High and low fluidity. For this reason, the fine bubbles diffused from the diffuser 14 are hardly diffused into the liquid, and the rising speed is also slow, so that they are likely to stay at the diffused position.
Therefore, the phenomenon of coalescence with the subsequent bubble that has been continuously diffused occurs continuously, and eventually a large bubble is formed. Once the bubbles become larger, the ascending speed increases, and the bubbles quickly pass through the space between the membrane elements and float on the water surface.

As a result, the efficiency of contact between the diffused bubbles and the liquid to be treated is reduced, and oxygen in the bubbles is not sufficiently dissolved in the liquid to be treated. As a result, there is a problem that the amount of dissolved oxygen required for biological treatment with activated sludge is insufficient, and the performance of biological treatment is reduced.

An object of the present invention is to solve the above-mentioned problems of the prior art, to sufficiently dissolve oxygen in bubbles in a liquid to be treated, and to provide an aerobic biological treatment apparatus excellent in biological treatment performance with activated sludge. To provide.

[0009]

SUMMARY OF THE INVENTION The present invention provides an aerobic biological treatment apparatus comprising a reaction tank, a membrane element immersed in the reaction tank, and a diffuser disposed below the membrane element. Wherein a dispersing means for dispersing air bubbles diffused from the diffusing means is disposed between the membrane element and the diffusing means.

Further, the present invention is characterized in that the dispersing means is a dispersing plate or a stirrer.

[0011]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention. A plurality of plate-like membrane elements 32 are immersed in the reaction tank 30 at predetermined intervals in the horizontal direction. A diffuser 34 is arranged below these membrane elements 32 at a predetermined distance. In a region 36 between the lower end of the membrane element 32 and the air diffusing means 34, a partition 38 surrounding the lower part of the membrane element 32 is provided, and a dispersion plate 40 is attached to the partition 38.

As shown in FIG. 2, the dispersing plate 40 is formed by vertically assembling a thin plate 42 in the X direction and a thin plate 44 in the Y direction at a narrow pitch. Has formed.

[0013] The water to be treated flows into the reaction tank 30 from the pipe 46, and contacts the activated sludge in the reaction tank 30 while staying there for a predetermined time. Organic components are oxidatively decomposed and purified. A suction pump 50 is connected to the membrane element 32 via a pipe 48, and the water permeated through the membrane element 32 is taken out of the apparatus as treated water by the suction force of the suction pump 50.

Fine air bubbles are diffused from the diffusing means 34 connected to the blower 52. As described above, when the activated sludge in the reaction tank 30 is maintained at a high concentration, the mixture of the liquid to be treated and the activated sludge becomes mud-like, and has high viscosity and low fluidity. For this reason, the fine bubbles diffused from the diffusing means 34 are difficult to diffuse into the liquid, and the rising speed is slow, so that they are likely to stagnate at the diffused position. Therefore, the phenomenon of continuous coalescence with the subsequent bubble that has been diffused occurs continuously, and eventually becomes a large bubble, and the upper membrane element 32
Trying to soar towards.

The dispersing plate 40 has a function of suppressing the rise of the unified and enlarged bubbles and dividing the bubbles. As shown in FIG. 3, when the bubble 54 rising with the circulation of the water to be treated hits the lower end of the thin plate 42 or 44 constituting the dispersion plate 40 as shown in FIG. After that, the buoyancy of the bubble 54 itself and the upward flow of the water to be treated cause the bubble 54 to become thinner 42 or 4 as shown in (b).
4 and finally, as shown in FIG.
A is divided into A and 54B, and starts rising again.

By suppressing the rise of the bubbles 54, the contact time between the water to be treated and the bubbles is increased. Further, the division of the bubbles 54 increases the surface area of the bubbles. Since these two actions are continuously performed at a plurality of locations on the entire surface of the dispersion plate 40, the chance of contact between the water to be treated and the bubbles increases, and the oxygen in the bubbles can be sufficiently dissolved in the water to be treated. . For this reason, the amount of dissolved oxygen required for the biological treatment by the activated sludge mixed with the water to be treated is satisfied, and the biological treatment proceeds efficiently.

The water to be treated and the bubbles passing through the dispersion plate 40 further rise and pass between the plurality of membrane elements 32.
In this process, membrane separation is performed by the membrane element 32,
The water that has passed through the membrane surface is taken out of the apparatus through the suction pump 50 as treated water. Further, the bubbles circulate the water to be treated in the direction of arrow A by the lift action based on the buoyancy. In addition, the air bubbles rise as the membrane element 12
Activated sludge and other solids adhering to the membrane surface due to collision and contact with the membrane surface are peeled off, and the membrane surface is constantly washed. Since activated sludge multiplies with the treatment, excess sludge is withdrawn from the conduit 56 to maintain the sludge concentration in the reaction tank 30 within a certain range.

FIG. 4 is a longitudinal sectional view showing a second embodiment of the present invention. In this embodiment, a stirrer 60 is provided in a region surrounded by a partition 62 between the membrane element 32 and the air diffuser 34. The air bubbles diffused from the air diffuser 34 tend to be united with each other and become larger as described above. However, the air bubbles are subdivided while being in intense contact with the water to be treated by the stirring energy of the stirrer 60. Therefore, the surface area of the bubbles increases, and the rising speed of the bubbles also decreases. Therefore, the chance of contact between the water to be treated and the bubbles increases, so that the oxygen in the bubbles can be sufficiently dissolved in the water to be treated, and thus the biological treatment can efficiently proceed.

In this embodiment, the partition 6
Numeral 2 guards the bubbles dispersed and fragmented by the stirrer 60 so as not to deviate from the region immediately below the membrane element 32, and guides all the bubbles to pass between the membrane elements 32. Partition 3 in the first embodiment
8 also has a similar guard action.

FIG. 5 shows a modification of the dispersion means according to the present invention. A plurality of dispersing devices 6 are provided above the air diffuser (not shown).
4 and 66 are arranged in two stages in the direction perpendicular to the paper surface. These dispersing devices 64 and 66 have a downwardly open cross section having a mountain shape, and a large number of small holes 68 and 7 are provided at the upper portion.
Has zero. Also, the lower dispersing tool 64 and the upper dispersing tool 6
6 is off-center.

In the above-described configuration, the large bubbles 72 that have risen together with the water to be treated from below are distributed to the lower stage
Alternatively, the air flows into the pocket of the dispersing tool from one of the lower release surfaces of the dispersing tool 66 in the upper stage, and forms an air reservoir 74. Many small bubbles 76 are generated from these air reservoirs 74 through the large number of small holes 68 and 70. Excess air exceeding the volume of the air reservoir 74 rises as small bubbles 78 from the lower end of the dispersing tool. As described above, by temporarily retaining large bubbles and dispersing them into small bubbles, the chance of contact between the water to be treated and the bubbles increases, and the oxygen in the bubbles can be sufficiently dissolved in the water to be treated. .

[0022]

As described above, in the aerobic biological treatment apparatus including the membrane element immersed in the reaction tank and the aeration means disposed below the membrane element, Between the means, dispersing means such as a dispersion plate or a stirrer for dispersing the bubbles diffused from the diffusing means, so that the oxygen in the bubbles sufficiently dissolved in the liquid to be treated, activated sludge Biological treatment can proceed efficiently.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is a partial perspective view of a dispersion plate according to the present invention.

FIG. 3 is an explanatory view showing a state of dividing air bubbles in a dispersion plate according to the present invention.

FIG. 4 is a longitudinal sectional view showing a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a modification of a dispersing unit according to the present invention.

FIG. 6 is a longitudinal sectional view illustrating an aerobic biological treatment device according to the related art.

[Explanation of symbols]

 30 reaction tank 32 membrane element 34 air diffuser 38 partition 40 dispersion plate 60 stirrer 62 partition 64 dispersion device

Continuing from the front page (72) Inventor Hiroyuki Ichikawa 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Inside Hitachi Plant Construction Co., Ltd. (72) Inventor Hiroki Ando 1-1-1 Uchikanda, Chiyoda-ku, Tokyo Sun 4D006 GA02 HA41 HA93 JA29A JA32A KA31 KA44 KB22 KE08P PA01 PB08 PC62 4D028 BC17 BC24 BC26 4D029 AA01 AB07 CC03 DD01

Claims (2)

[Claims] 1. An aerobic biological treatment apparatus comprising a reaction tank, a membrane element immersed in the reaction tank, and an aeration unit disposed below the membrane element. An aerobic biological treatment apparatus, wherein a dispersing means for dispersing bubbles diffused from the diffusing means is arranged between the means and the means. 2. The aerobic biological treatment apparatus according to claim 1, wherein said dispersing means is a dispersion plate or a stirrer.