JPH08267083A - Activated sludge treating device - Google Patents

Abstract

PURPOSE: To make it possible to induce water flow adequate for oxygen supply and washing of membrane surfaces even at a small amt. of air diffusion by specifying the capacity of an aeration tank and the size of immersion type membrane separators of a tank having the immersion type membrane separators arranged with air diffusers below membrane cartridges within the aeration tank. CONSTITUTION: An immersion type membrane separators 3 are formed by juxtaposing the inside of a casing with a membrane cartridges 4 and arranging the air diffuser below the membrane cartridges 4. The oxygen in the air dissolves in a liquid 2 mixed with activated sludge and the membrane surfaces of the membrane cartridges 4 are washed by the flow mixture composed of the air and the liquid, by which sepn. performance is maintained. At this time, the capacity of an aeration tank 1 and the size of the membrane separators 3 are so set that the area of the aeration tank 1 occupying the same horizontal section is >=3 times the sum of the areas of the respective membrane separators 3. The membrane separators 3 are arranged at prescribed intervals. As a result, the membrane surface washing of the membrane cartridges 4 and the oxygen supply to the liquid 2 mixed with the activated sludge are adequately executed. The efficient sepn. of the solid from the liquid and activated sludge treatment are thus executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an activated sludge treatment device equipped with an immersion type membrane separation device.

[0002]

2. Description of the Related Art Conventionally, as a method for solid-liquid separation of an activated sludge mixed solution which has been treated in an aeration tank, a part of the activated sludge mixed solution is introduced into a sedimentation tank to cause the activated sludge to settle by gravity, and the supernatant in the sedimentation tank Gravity sedimentation separation methods have been used in which the liquid is removed as treated water. However, with this separation method, when the concentration of activated sludge in the aeration tank is increased, solid-liquid separation in the sedimentation tank becomes insufficient, and activated sludge is mixed into the treated water, or activated sludge in the aeration tank There was a problem that the activated sludge could not be maintained at an appropriate concentration due to the outflow, resulting in insufficient treatment.

For this reason, a method for increasing the concentration of activated sludge in the aeration tank and efficiently treating the activated sludge by using a membrane separator has been developed and put into practical use. As such a membrane separation device, there is an immersion type membrane separation device 3 which is installed by immersing it in the activated sludge mixed liquid 2 in the aeration tank 1 as shown in FIGS. 2 and 3. In the device 3 (hereinafter referred to as a membrane separation device), flat plate-shaped membrane cartridges 5 vertically arranged inside a box-shaped casing 4 having upper and lower openings are juxtaposed at appropriate intervals, and are placed below the membrane cartridge 5 outside the tank. Air diffuser 7 connected to the air supply means such as the blower 6 of
Has been arranged.

In such a structure, the air bubbles 8 flowing out from the air diffuser 7 ascend in the activated sludge mixed liquid 2 and move from the lower part of the membrane cartridge 5 to the membrane cartridges 5, 5.
It flows into the gap between them, rises in the gap to the upper part of the membrane cartridge 5, and then exits above the water surface. As the bubbles 5 rise, an upward flow of the activated sludge mixed liquid 2 as shown by an arrow is generated inside the membrane separation device 3, and the upward flow is generated from the lower portion of the membrane cartridge 5 to the membrane cartridges 5, 5. After flowing into the gap between the membranes 5 and ascending to the upper portion of the membrane cartridge 5 in the gap, it turns around near the water surface and becomes a downward flow descending outside the membrane separation device 3. During this time, oxygen in the air is dissolved in the activated sludge mixed liquid 2, and the gas-liquid mixed flow cleans the membrane surface of the membrane cartridge 5 to maintain the separation performance. Therefore, the submerged membrane separation device 3 can be said to be a device having two major functions, an oxygen supply function and a solid-liquid separation function, which are indispensable for activated sludge treatment.

[0005]

The aeration tank capacity in the treatment of activated sludge is determined by the amount of inflowing raw water, the concentration of pollutants, and the concentration of activated sludge for treating pollutants. In the activated sludge treatment that uses MLSS, the concentration is approximately 5 times the concentration (MLSS15000 to 20000mg / ml) that can be solid-liquid separated by the conventional gravity sedimentation separation method (MLSS3000mg / l).
Since the activated sludge mixed solution of l) can be separated into solid and liquid, the capacity of the aeration tank can be reduced as much as the concentration of activated sludge can be increased. However, when reducing the capacity of the aeration tank, the area is often reduced together with the depth of the tank, so that the flow of the activated sludge mixed solution circulating in the tank may be deteriorated and the treatment may be adversely affected.

On the other hand, the size of the submerged membrane separation device installed in the aeration tank is determined based on the required number of membrane cartridges calculated from the throughput per membrane cartridge.

Therefore, when treating inflowing raw water such as human waste, which has a very high concentration of pollutants and a small amount of water, a large aeration tank capacity is required, but the immersion type membrane separation device can be small. As shown in FIG. 4, it is possible to have a relatively loose layout in which the submerged membrane separation device 3 is arranged inside the aeration tank 1 at intervals. Therefore, the water flow A formed by aeration smoothly flows, the oxygen absorption efficiency is increased, the clogging of the membrane due to the non-uniformity of the water flow is prevented, and the activated sludge treatment and the solid-liquid separation are favorably performed. .

On the other hand, when treating inflow raw water such as sewage, domestic wastewater, etc., which has a low concentration of pollutants and a large amount of water, the aeration tank capacity may be relatively small,
Since a large submerged membrane separation device in which a large number of membrane cartridges are arranged is required, a cramped layout in which the submerged membrane separation devices 3 are arranged inside the aeration tank 1 at intervals as shown in FIG. . Therefore, the water flow A formed by the aeration is obstructed by the wall surface of the aeration tank 1, the adjacent membrane separation device 3 or the water flow A formed by the aeration and becomes difficult to flow, and not only the oxygen absorption efficiency is not improved. The degree of contamination of the film surface due to the non-uniformity of the water flow increases, and the film is likely to be clogged. In order to avoid such a situation, the capacity of the aeration tank 1 is actually determined based on the installation area of the submerged membrane separation device 3.

In view of the above situation, the present inventors have
The present invention has been completed by conducting research to set the arrangement conditions of an aeration tank and a submerged membrane separation device that can generate a water flow suitable for supplying oxygen and cleaning the membrane surface even with a small amount of air diffusion.

[0010]

In order to achieve the above object, the present invention provides an activated sludge in which an immersion type membrane separation device having an air diffuser disposed below a membrane cartridge is installed inside an aeration tank. In the treatment apparatus, the capacity of the aeration tank and the size of the submerged membrane separation apparatus are set so that the area of the aeration tank occupying the same horizontal section is three times or more the area of the submerged membrane separation apparatus. The present invention provides an activated sludge treatment device in which a submerged membrane separation device is arranged at appropriate intervals around the periphery.

[0011]

According to the above construction, an appropriate space is provided between the aeration tank and the immersion type membrane separation device, and between the immersion type membrane separation devices when there are a plurality of immersion type membrane separation devices. , A circulating flow caused by air diffusion, that is, a circulating flow consisting of an upward flow rising inside the submerged membrane separator and a downward flow falling outside the submerged membrane separator is a wall surface of the aeration tank or Flows smoothly without being obstructed by the adjacent submerged membrane separation device or its downward flow. Oxygen supply and film surface cleaning are suitably performed by this circulating flow containing air.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Since the activated sludge treatment device of this embodiment has substantially the same configuration as the conventional one described with reference to FIGS. 2 and 3, a schematic plan view is shown in FIG. 1 and the same reference numerals as those in FIGS. Is attached and detailed description is omitted.

The feature of the activated sludge treatment device of this embodiment is that the capacity of the aeration tank 1 and the size of the immersion type membrane separation device 3 (hereinafter referred to as a membrane separation device) occupy the same horizontal section. 1 is set to be three times or more the sum of the areas of the membrane separation devices 3 (3.4 in the figure).
2 times) and each membrane separation device 3 is arranged at appropriate intervals around the periphery. Here, the area of the aeration tank 1 means the area surrounded by the inner peripheral surface 1a of the aeration tank 1, and the area of the membrane separation device 3 means the area surrounded by the casing.

According to the above-mentioned structure, since the proper intervals are provided between the inner peripheral surface 1a of the aeration tank 1 and the membrane separation device 3, and between the membrane separation devices 3 and 3, the respective membrane separation devices are provided. The downward flow A that descends outside of 3 smoothly flows without being obstructed by the inner peripheral surface 1a of the aeration tank 1, the adjacent membrane separation device 3 or the downward flow A thereof. Therefore, this downward flow A
And the upward flow rising in the membrane separation device 3 smoothly circulates. This circulation flow agitates the activated sludge mixed liquid 2 to supply oxygen and the membrane surface of the membrane cartridge. As a result of washing, the activated sludge treatment and solid-liquid separation are favorably performed.

If the ratio of the area of the aeration tank 1 to the sum of the areas of the membrane separation devices 3 is too large, the amount of air diffused by the air diffusion device of the membrane separation device 3 is sufficient to mix the activated sludge in the entire aeration tank 1. Since the liquid 2 cannot be agitated and the activated sludge process is hindered, it is necessary to determine the capacity of the aeration tank 1 and the size of the membrane separation device 3 in consideration of this point as well. The aeration tank 1 may have a tank shape in which the depth of the tank is reduced and the area thereof is increased.

In Table 1 below, the area ratio (ratio of the area of the aeration tank to the sum of the areas of the immersion type membrane separators on the same horizontal section) and the cleaning frequency (times / year) (1 as an index of the degree of membrane contamination)
The number of membrane cartridge cleanings per year) is shown.

[0017]

[Table 1]

In Table 1, when the area ratio is less than 3, the cleaning frequency is very high.
In the above case, it is apparent that the membrane cleaning is preferably performed by the water flow generated by the air diffusion.

[0019]

As described above, according to the present invention, the volume of the aeration tank and the size of the submerged membrane separation device are three times the area of the submerged membrane separation device occupying the same horizontal section. By setting as described above, an appropriate space is provided between the aeration tank and the immersion type membrane separation device and between the immersion type membrane separation devices. As a result, the water flow generated by the air diffuser can be smoothly circulated between the inside and outside of each submerged membrane separation device, and the membrane surface of the membrane cartridge is cleaned and oxygen is added to the activated sludge mixed liquid of the entire aeration tank. It is possible to favorably perform the supply and to improve the solid-liquid separation and the activated sludge treatment.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing the overall configuration of an activated sludge treatment device according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a conventional activated sludge treatment device.

FIG. 3 is a longitudinal sectional view showing the activated sludge treatment device from another direction.

FIG. 4 is a schematic plan view showing an embodiment of an arrangement of an aeration tank and a submerged membrane separation device in the activated sludge treatment device.

FIG. 5 is a schematic plan view showing another embodiment of the arrangement of an aeration tank and a submerged membrane separation device in the activated sludge treatment device.

[Explanation of symbols]

 1 Aeration tank 3 Immersion type membrane separation device 4 Membrane cartridge 7 Air diffuser

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masafumi KUTSUTA Co., Ltd. 2-47 Shikitsu Higashi, Naniwa-ku, Osaka-shi, Osaka (72) Inventor Yuji Soeda Toichi Shikazu, Naniwa-ku, Osaka-shi, Osaka 2-47, Kubota Co., Ltd. (72) Inventor, Masaharu Nuri, 2-47 Shikitsu East, Naniwa-ku, Osaka City, Osaka Prefecture Kubota Co., Ltd.

Claims (1)

[Claims] 1. An activated sludge treatment device in which an immersion type membrane separation device, in which an air diffuser is arranged below a membrane cartridge, is installed inside an aeration tank, the capacity of the aeration tank and the immersion type membrane. The size of the separation device was set so that the area of the aeration tank occupying the same horizontal cross section was three times or more the area of the immersion type membrane separation device, and the immersion type membrane separation device was arranged at appropriate intervals around it. An activated sludge treatment device characterized in that