JPH0515894A - Deep aeration tank - Google Patents

Abstract

PURPOSE:To offer a deep aeration tank having a simple structure regardless of its great height, capable of uniformly supplying air to the whole region in the tank and excellent in efficiency in supplying oxygen to sewage. CONSTITUTION:This deep aeration tank consists of an outer cylinder 1 and an inner cylinder 2 concentrically erected on the bottom 1a of the outer cylinder 1 and having an inlet opening 2a at its upper part. The opening 2a of the inner cylinder 2 is positioned below the outflow part of the outlet of the outer cylinder 2. The fluid in the inner cylinder 1 is sucked by a lower circulator 10 from the bottom or its vicinity and mixed with a large amt. of air, and the mixture is injected between the outer cylinder 1 and the inner cylinder 2. The fluid in the tank is sucked by an upper circulator 20 from the upper part of the outer cylinder 1 and mixed with a large amt. of air, and the mixture is injected between the outer cylinder 1 and inner cylinder 2 at the intermediate height.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aeration tank for purifying sewage with aerobic bacteria to improve the treatment efficiency of a vertically long cylindrical outer shape.

[0002]

2. Description of the Related Art As an aeration tank for biologically purifying sewage with aerobic bacteria, an aeration tank having a vertically long cylindrical shape has hitherto been disclosed in Japanese Utility Model Laid-Open No. Sho 58-100097 and Japanese Patent Laid-Open No. Sho 63-63. It is proposed in Japanese Patent No. 175692.

The vertically long cylindrical aeration tank has the advantage that the installation area required to secure a constant volume is small, and since the water pressure is high at the bottom of the tank, the solubility of oxygen is large and aerobic bacteria are absent. It has the advantage of improved activity.

By the way, the treatment capacity of the aeration tank increases as the time during which sewage and aerobic bacteria are in contact with each other in the presence of sufficient oxygen increases. In view of this, in the above-mentioned conventional example, a spiral partition wall is formed to extend the flow paths of the sewage and the air, and the contact time between the two is lengthened to improve the treatment efficiency.

[0005]

In the prior art described above, the spiral partition wall is formed in the aeration tank to extend the flow paths of sewage and air, so that air is stored on the lower surface of the spiral partition wall. However, there is a problem that the amount of oxygen supplied to the wastewater is reduced. The accumulated air has a specific surface area that decreases as the volume of the collected air increases, thereby deteriorating the efficiency of oxygen supply to wastewater. As a result, the amount of aeration required to obtain the required processing capacity increases, which causes various problems such as an increase in the size of equipment and an increase in operating costs. Moreover, this problem becomes more remarkable in a so-called deep aeration tank having a height dimension of 7 m or more.

[0006]

The present invention is a deep aeration tank designed to solve the above-mentioned drawbacks. The feature is a vertically elongated aeration tank equipped with a waste water supply part and a treated water outflow part, which sucks the fluid in the aeration tank and ejects it to the lower part in the aeration tank. And a higher-level circulation device for sucking the fluid in the aeration tank and ejecting the fluid into the aeration tank above the ejection part of the lower-level circulation device. The circulation device and the lower circulation device are composed of a pipe, a pump, and an ejector mechanism that mixes air into the fluid on the discharge side of the pump. The jetting direction of each of the upper circulation device and the lower circulation device swirls the fluid in the tank. That is, it is set so that it can flow.

[0007] A more preferable aspect of the present invention is that the aeration tank is composed of an outer cylinder provided with a waste water supply part and a treated water outflow part, and an inner cylinder concentrically arranged with the outer cylinder and having an inflow opening in the upper part. A lower part for sucking the fluid in the inner cylinder and ejecting the fluid into the space between the outer cylinder and the inner cylinder. A circulation device is provided, and an upper circulation device for sucking the fluid in the aeration tank and ejecting the fluid between the outer cylinder and the inner cylinder above the ejection portion of the lower circulation device is provided. That is, the jetting directions of the upper circulation device and the lower circulation device are set so that the fluid can swirl between the outer cylinder and the inner cylinder.

Further, when the height dimension of the aeration tank is large, in addition to the upper circulation device and the lower circulation device, fluid is introduced into the tank at an intermediate position between the ejection parts of the upper circulation device and the lower circulation device. It suffices to provide a medium-level circulating device for ejecting.

Incidentally, the number of the intermediate circulation devices can be appropriately increased according to the height dimension of the aeration tank.

[0010]

In the deep aeration tank according to the present invention, the sewage in the aeration tank is sucked by the upper and lower circulation devices, and then the
By ejecting sewage in a direction in which it can swirl in the tank, a flow force is given to the sewage in the tank to cause swirling flow. The swirling flow gradually propagates upward from the lower part of the aeration tank.

By the way, when the height of the aeration tank is large, if the circulation device is installed only in the lower part, the flow force applied to the sewage is attenuated on the way to reach the uppermost part, and the entire inside of the tank is attenuated. It is difficult to swirl the sewage at a speed higher than the required speed. It is generally said that sludge will settle if the flow velocity is less than 20 cm / sec. Therefore, in the present invention, an upper circulation device is provided above the lower circulation device installed in the lower part of the aeration tank, and this upper circulation device gives a new flow force to the wastewater at the intermediate height position of the aeration tank. Since this is done, it is possible to reliably generate a swirling flow having a flow velocity higher than the required velocity throughout the tank.

The height of the aeration tank is extremely large,
If the upper circulation device and the lower circulation device alone cannot provide a sufficient flow velocity to the sewage, by providing one or more intermediate circulation devices at the intermediate position between the two, swirling flow with a flow velocity higher than the required velocity can be achieved. It can be reliably generated.

Each of the upper circulation device, the lower circulation device, and the middle circulation device provided as necessary has an ejector mechanism for mixing air into the waste water on the discharge side of the pump. Is a state that contains a large amount of air in the form of foam. The foamy air ejected together with the sewage from each circulation device gradually moves upward following the swirling flow generated as described above, but without stopping. Therefore, the contact time between air and waste water is very long. In addition, the jet part of the lower circulation device is located at the bottom of the aeration tank with high water pressure. Therefore, since the bubble diameter of the jetted air is extremely small, the contact rate with the dirty water is large. Therefore, the oxygen in the supplied air can be efficiently dissolved in the waste water, and the aeration amount can be minimized.

Furthermore, since the ejected bubbles swirl and spread from the bottom to the top of the aeration tank, the dissolved oxygen is uniformly distributed in the tank, and there is no possibility of causing an oxygen deficiency region.

In a preferred embodiment of the present invention, when the aeration tank has a double structure consisting of an outer cylinder and an inner cylinder and a lower circulation device is used to suck the dirty water in the inner cylinder, the outer cylinder is used. Swirling flow of wastewater between the inner cylinder and
A downward flow occurs due to the suction of dirty water in the inner cylinder. The swirling flow and the downward flow are clearly separated by the inner cylinder so that they do not interfere with each other, so that the swirling flow over the entire area of the tank is generated more efficiently, and as a result, the bubble distribution is more uniform. become.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings showing the embodiments. FIG. 1 shows a deep aeration tank P according to the present invention.
An example is shown. The aeration tank P includes an outer cylinder 1 and an inner cylinder 2 which are concentrically arranged. A treated water outflow portion 3 is provided on the upper part of the outer cylinder 1, and a sludge supply pipe 5 and a sludge return pipe 6 for returning a part of the activated sludge that has flowed out together with the treated water are provided on the upper part of the inner cylinder 2. It is equipped. A diversion weir 4 is provided above the inner surface of the outer cylinder 1, and the treated water that has passed over the upper end of the diversion weir 4 is caused to flow out from the outflow portion 3 to the outside. Further, the sewage and the returned sludge are directly supplied into the inner cylinder 2 by facilitating the contact with the sewage activated sludge and promoting the initial adsorption by which the microorganisms in the activated sludge take in the substrate in the sewage. This is to improve the biological reaction.

The outer dimensions of the outer cylinder 1 are appropriately set according to the amount of sewage treated. On the other hand, if the diameter of the inner cylinder 2 is too large, not only does the treated area of the wastewater shrink, but it also acts as a resistance to the swirling flow of the wastewater, so it is 1/4 or less of the diameter of the outer cylinder 1, preferably 1 Set it to / 5 or less. However, if the diameter of the inner cylinder 2 is made smaller than necessary, the flow resistance in the cylinder is increased and the bridge of activated sludge is easily generated. Therefore, it is desirable that the inner cylinder 2 has a diameter of at least 300 mm or more.

The inner cylinder 2 is erected from the bottom portion 1a of the aeration tank P, and the inflow opening 2a at the upper portion thereof is located below the outflow portion 3 of the outer cylinder 1. That is, it is sufficient that the inflow opening 2a of the inner cylinder 2 is set to be lower than the stored water level of the dirty water, and the distance from the water surface is not particularly limited. Further, the height of the inner cylinder 2 is preferably 1 m or more in order to prevent sewage ejected from the bottom of the aeration tank P from flowing into the inner cylinder 2 in a short circuit without being aerated. .

A suction part 10a at one end is provided near the bottom 1a of the tank.
Is connected to the inner cylinder 2, and a lower circulation device 10 for sucking the dirty water in the inner cylinder 2 and ejecting the dirty water from an ejecting portion 10b arranged between the outer cylinder 1 and the inner cylinder 2 is provided. In addition, above the lower circulation device 10, a suction unit 20a arranged above the tank is provided.
Sewage is sucked from the sewage, and the sewage is sucked from the lower circulation device 10
An upper circulation device 20 for ejecting from the ejection portion 20b between the outer cylinder 1 and the inner cylinder 2 is provided above b. Each of these circulation devices 10 and 20 includes pipes 12 and 22, and pumps 11 and 2 provided in the middle of the pipes 12 and 22.
1 and a ventilation pipe 1 provided on the discharge side of each pump 11, 21.
5 and an ejector mechanism 13 for mixing the air taken in through 5 into the sewage.

The ejector mechanism 13 is the same as the Japanese Patent Application No. 2-159464 (1994, 6), which was filed by the present applicant.
The application is based on the ejector mechanism disclosed in U.S.A. 18th) and has an internal structure and functions as shown in FIG. That is, the pipe 12 (2 on the discharge side of the pump 11
The inside of the casing 13a connected to 2) is formed with a contracted flow portion 14 whose pipe diameter decreases toward the outflow side, and the casing 13a has a ventilation pipe 15 communicating with the outside air.
Also, a sub-inflow pipe 16 is provided which communicates with the aeration tank P and directly introduces the waste water into the casing 13a. Pipe 12 (2
The sewage fed from 2) is accelerated in the contracting section 14 to generate a negative pressure around the sewage, and the negative pressure is used to suck the outside air from the ventilation pipe 15 to collect the sewage. At the same time, the waste water in the tank is directly introduced into the casing 13a through the auxiliary inflow pipe 16. With this, the sewage is
It is jetted into the aeration tank P in a state of being vigorously stirred and atomized in the casing 13a. As a result, a very large intake air amount and oxygen dissolution amount can be obtained.

In this embodiment, as shown in FIGS.
The jetting directions of the jetting portions 10b and 20b of the lower circulation device 10 and the upper circulation device 20 are both substantially horizontal so that the flow effect of the sewage is large, and the jetting portion 10 is the same.
It was set to be substantially perpendicular to the radius r of the outer cylinder passing through b and 20b. As shown in FIG. 4, the suction part 20a of the upper circulation device 20 is provided such that the suction direction of the dirty water is in a position symmetrical with the spouting direction of the spouting part 20b in plan view and the central axis of the outer cylinder. Was made available for swirling flow of wastewater. However, these settings are not limited, and as long as the sewage can be swirled and flown, the jetting direction may be tilted vertically with respect to the horizontal, or may be tilted inward and outward with respect to the radius r. It doesn't matter. further,
It is generally considered that the ejection portions 10b and 20b are arranged closer to the outer cylinder 1 from the viewpoint of flow efficiency, but it does not prevent appropriate changes depending on the implementation situation.
In the present embodiment, the ejection part 10b of the lower circulation device 10 is provided near the bottom part 1a, but it may be installed slightly apart from the bottom part 1a depending on the implementation conditions.

When sewage is stored in the deep aeration tank P according to the present invention having the above-mentioned structure and each circulation device 10, 20 is started, the sewage in the inner cylinder 2 is pumped by the pump 11 by the lower circulation device 10. After being sucked, it is almost horizontal at a position closer to the outer cylinder 1 than the middle between the outer cylinder 1 and the inner cylinder 2 and the ejection portion 1
It is jetted almost perpendicular to the radius r of the outer cylinder passing through 0b.
Further, the sewage in the upper part of the tank P sucked from the suction part 20a by the upper circulation device 20 is jetted substantially horizontally at a position closer to the outer cylinder 1 than the middle between the outer cylinder 1 and the inner cylinder 2 at the intermediate height position. It is jetted almost perpendicular to the radius r of the outer cylinder passing through the portion 20b. At the same time, a downward flow of sewage occurs in the inner cylinder 2. Therefore, since the circulation of the sewage is started and the fluid force is imparted to the sewage at the tank bottom portion and the intermediate height position, even if the height of the aeration tank P is large, the required speed is not less than the required speed over the entire tank. The swirling flow of is surely generated.

The ejector mechanism 13 is attached to the discharged sewage.
A large amount of air is mixed in as a foam. The ejected bubbles follow the swirling flow of the sewage and spread throughout the tank, supplying oxygen efficiently to the sewage. Therefore, the activity of aerobic bacteria is high in any region between the outer cylinder 1 and the inner cylinder 2. Moreover, the spouted sewage rises while swirling, so it takes a long time to reach the uppermost portion, and the contact time between the sewage and aerobic bacteria is sufficiently secured. Therefore, the purification process of the dirty water is surely performed.

Table 1 shown below shows the results of a test demonstrating the effect of the aeration tank P according to the present invention. In this test, as shown in FIG. 5, the shape of the aeration tank P and the stored water level are constant, and two circulation devices 10 and 20 are provided [upper and lower] (the present invention: see FIG. (A)) and 2 The vertical distribution of the flow velocity is measured for each swirling flow in the case where only one circulation device 30 provided with a pump having a double capacity is provided in the lower order [Comparative example: see FIG. (B)]. . The flow velocity was measured near the inner peripheral surface of the outer cylinder 1. The test conditions are
Each is as follows.・ Outer cylinder diameter (D) …… 2.3m ・ Inner cylinder diameter (d) …… 0.3m ・ Inner cylinder height (h)… 8.5m ・ Reserved water level (H)… 9.0m ・ Pump output… …… Invention: 0.75 kW × 2 units Comparative example: 1.5 kW × 1 unit ・ Intake air amount ……… Invention: 80 liters / min (per pump) Comparative example: 160 liters / min ・ Higher level Suction part height position of circulation device ... 8m Ejection part height position ... 5m-Suction part height position of lower circulation device ... 0m (inner cylinder bottom) Spouting part height position ... 0.5m

[0025]

[Table 1]

As can be seen from Table 1, in the aeration tank according to the present invention, a flow velocity higher than the required velocity was obtained in any height region, whereas in the comparative example, the flow velocity was close to the jet portion. High, but decays rapidly as you go up. For this reason, it is much higher than expected to use two pumps with half the capacity for the lower circulation device 10 and the position circulation device 20, respectively, than to use one large pump. It can be seen that the swirling flow can be generated by.

By the way, in the above-mentioned embodiment, the circulation device should be installed at two places, the upper and lower positions. However, when the height of the aeration tank is extremely large, one or a plurality of medium circulation devices are installed. Will be needed.

Therefore, in order to estimate the interval at which the intermediate circulation device needs to be installed, the output of 0.75 kW provided for the above test
The swivel ability of the pump was measured. That is, in the same aeration tank (outer cylinder diameter 2.3 m, inner cylinder diameter 0.3 m) as described above, only the lower circulation device equipped with a pump with an output of 0.75 kW was used, and the water level when changing to the stored water level Each flow velocity is measured. The measurement was performed on the inner peripheral surface of the outer cylinder.
The results are shown in Table 2.

[0029]

[Table 2]

It can be seen from Table 2 that the circulation device equipped with the above-mentioned pump can maintain the flow velocity on the water surface above the required value when the water level is up to 5 m. Therefore, when a 0.75 kW pump is used, it can be said that it is desirable to provide the medium circulation device when the distance between the lower ejection part 10b and the upper ejection part 20b exceeds 5 m. By doing so, even if the height dimension of the aeration tank is extremely large, it is possible to reliably maintain the swirl flow state in which the entire area of the tank is equal to or higher than the required flow velocity.

The above is an embodiment in which the aeration tank has a double structure of an outer cylinder and an inner cylinder, but a structure in which the inner cylinder is omitted is also possible. This is shown in FIG. In this case, it is desirable that the ejection parts 10b and 20b of the lower circulation device 10 and the upper circulation device 20 are arranged near the peripheral wall of the aeration tank Q main body. After storing sewage in the aeration tank Q, the lower circulation device 10
By operating the upper circulation device 20 and the upper circulation device 20, an overall swirling flow of wastewater is generated, and at the same time, the jet parts 10b, 2
It is the same as the above that the bubbles ejected from 0b follow this swirling flow and spread all over the tank.

In addition, the embodiment of the present invention is not limited to the above, and various applications are possible. This will be described with reference to the drawings. Although the application example is illustrated only when the inner cylinder 2 is provided, the aeration tank Q in which the inner cylinder is omitted is shown.
The same application is possible for. Moreover, FIGS.
In FIG. 2, only the shape of the tank is shown, and in FIGS. 13 to 16, only the shape of the tank and the ejection portion of the circulation device are shown, and the other portions are not shown.

FIG. 7 shows the suction part 1 at the bottom of the inner cylinder 2 of the aeration tank P and the upper, middle, and lower parts of the peripheral wall of the outer cylinder 1.
0a, 20a, 30a, 40a are provided, and jet parts 20b, 30b, 10b are similarly provided at the upper, middle, and lower positions, respectively, and each suction part and each jet part are provided as a single large pump 1.
1 shows an example in which connection piping is connected to 1. Thus, when a large number of circulation devices are installed, not only can each be made independent, but one pump can be shared, as shown in FIG.

Next, regarding the shape of the tank, in order to promote the generation of swirling flow, as shown in FIG. 8, a bottom portion 1a and a peripheral wall 1b are provided.
It is conceivable that an inclined surface 31 is provided at a portion where is intersected with or that the entire bottom portion 1a is formed into a curved surface 32 as shown in FIG. Further, the entire shape of the tank P may be elliptical as shown in FIG. 10, egg-shaped as shown in FIG. 11, or gourd-shaped as shown in FIG.

The spout 10b (2) of the circulation device 10 (20)
0b) is arranged on the peripheral wall 1 of the tank P as shown in FIG.
The opening provided in b may be used as the ejection portion 10b (20b). Further, as shown in FIG. 14, the ejection portion 10b (20b)
A guide plate 40 may be provided on an extension line of the jetting direction to guide the swirling flow. Furthermore, the spout 10b
(20b) does not have to be a single unit. For example, as shown in FIG. 15, two ejection parts 10b (20b) are arranged symmetrically with respect to the central axis, or as shown in FIG. 16, they are arranged in parallel. You may. These examples are effective when the diameter of the tank P is large.

On the other hand, although not shown in the drawing, the suction section 20a (30a) of the upper or middle circulation device is shown.
May be connected to the inner cylinder 2 to suck the dirty water in the inner cylinder 2 even at the intermediate height position.

Regarding the inner cylinder 2, this is the bottom portion 1a of the tank P.
In addition to standing up from the bottom, as shown in FIG. 17, a structure in which the inner cylinder 2 is arranged above the tank bottom 1a by an appropriate supporting means 50 may be employed. By separating the lower end of the inner cylinder 2 from the tank bottom 1a, there is no possibility that sludge flowing into the inner cylinder 2 will form a bridge.

When the intermediate circulation device is provided, the number of installations and the installation interval are appropriately set according to the stored water level, pump output and the like. In other words, whether to reduce the output of each pump to increase the number of circulation devices installed, or conversely to increase the installation interval of circulation devices using a pump with a relatively large output depends on the construction environment and processing conditions. Just select it.

As the ejector mechanism 13 of the circulating device, the ejector mechanism 13 having the auxiliary inflow pipe 16 is adopted in the above-mentioned embodiment, but the auxiliary inflow pipe 16 is not essential and can be omitted.

When a plurality of circulation devices are installed, it is possible to use only the pump having no ejector mechanism as the upper circulation device for which the retention time of bubbles is short.

Further, when the pump, ejector mechanism, etc. of the circulation device are provided outside the aeration tank, the maintenance and inspection work is easy, but the arrangement of these inside the aeration tank is not hindered. Regarding the diameter and height of the outer and inner cylinders,
The optimum one is selected according to the mode of implementation.

[0042]

The deep aeration tank according to the present invention exhibits the effects listed below. The sewage ejected in the tank gradually rises while swirling and flowing, so that it takes a long time to reach the top. Therefore, the sewage is not short-circuited and discharged, and the biological treatment by the aerobic bacteria takes a long time, so that the purifying action is ensured. The foamy air supplied in the lower part of the tank rises following the swirling flow of sewage, so it stays in the tank for a long time and is in contact with sewage. At this time, the bubble diameter becomes very small, so that the specific surface area per unit volume becomes large. As a result, the efficiency of supplying oxygen to the wastewater becomes extremely high, so that the activity of aerobic bacteria is activated and the purification treatment capacity is improved. The upper circulation device, the lower circulation device, and the middle circulation device provided as necessary reliably generate swirling flow of the sewage over the entire area of the tank, and do not form a stagnant portion. And
The bubbles supplied rise along with the swirling flow from the lower part of the aeration tank to the uppermost part while swirling. Therefore, air bubbles can be spread all over the tank, and there is no risk of creating an oxygen-deficient region. Even if the height dimension of the aeration tank is extremely large, the effects (1) to (3) can be obtained by providing the intermediate circulation devices at appropriate intervals. That is, according to the present invention, it is possible to obtain an aeration tank having a very large height dimension and an excellent purification treatment capacity, so that it is possible to save the installation area.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing an example of a deep layer aeration tank according to the present invention.

FIG. 2 is a vertical cross-sectional view showing an ejector mechanism used in the present invention.

FIG. 3 is a plan view showing an example of a lower circulation device according to the present invention.

FIG. 4 is a plan view showing an example of a higher-level circulation device according to the present invention.

FIG. 5 schematically shows a deep aeration tank used in a test for investigating the effect of the present invention, in which (a) is a longitudinal section of the present invention and (b) is a comparative example. It is a figure.

FIG. 6 is a partially cutaway perspective view showing another embodiment of the deep aeration tank according to the present invention.

FIG. 7 is a vertical cross-sectional view showing another embodiment of the circulation device for the deep aeration tank according to the present invention.

FIG. 8 is a longitudinal sectional view of an essential part showing an embodiment of another aspect of the present invention.

FIG. 9 is a longitudinal sectional view of an essential part showing another embodiment of the present invention.

FIG. 10 is a vertical cross-sectional view of the entire aeration tank showing an embodiment of another aspect of the present invention.

FIG. 11 is a vertical cross-sectional view of the entire aeration tank showing another embodiment of the present invention.

FIG. 12 is a vertical cross-sectional view of the entire aeration tank showing another embodiment of the present invention.

FIG. 13 is a plan sectional view showing an embodiment of another aspect relating to the ejection portion of the circulation device used in the present invention.

FIG. 14 is a cross-sectional plan view showing another embodiment of the circulation device used in the present invention.

FIG. 15 is a plan sectional view showing an embodiment of another aspect relating to the ejection portion of the circulation device used in the present invention.

FIG. 16 is a plan cross-sectional view showing an embodiment of another aspect relating to the ejection portion of the circulation device used in the present invention.

FIG. 17 is a vertical cross-sectional view showing another embodiment of the deep aeration tank according to the present invention.

[Explanation of symbols]

P, Q ... Deep aeration tank 1 ... Outer cylinder (or tank body) 1a ...
Outer cylinder bottom 2 ... Inner cylinder 2a ... Inflow opening 3 ... Outflow section 5
… Sewage supply amount 6… Sludge return pipe 10… Lower-level circulation device
10a ... Suction part 10b ... Spout part 11 ... Pump 12
... Piping 13 ... Ejector mechanism 14 ... Constriction part 15
... Vent pipe 16 ... Sub-inflow pipe 20 ... Lower circulation device 20
a ... Suction part 20b ... Spouting part 21 ... Pump 22 ... Piping r ... Radius of outer cylinder

Claims (6)

[Claims] 1. A vertically elongated cylindrical aeration tank having a sewage supply part and a treated water outflow part for sucking fluid in the aeration tank and ejecting the fluid to the lower part in the aeration tank. A lower circulation device is provided, and a higher circulation device for sucking the fluid in the aeration tank and ejecting the fluid into the aeration tank above the ejection part of the lower circulation device is provided. The lower circulation device is composed of a pipe, a pump, and an ejector mechanism that mixes air into the fluid on the discharge side of the pump. The jetting direction of each of the upper circulation device and the lower circulation device causes the fluid to swirl in the tank. A deep aeration tank characterized by being set in the direction of obtaining. 2. A vertically elongated cylindrical aeration tank having a waste water supply part and a treated water outflow part for sucking fluid in the aeration tank and ejecting the fluid to the lower part in the aeration tank. A lower circulation device, an upper circulation device for sucking the fluid in the aeration tank and ejecting the fluid into the aeration tank above the ejection part of the lower circulation device, and sucking the fluid in the aeration tank. And a middle-level circulation device for ejecting this into the aeration tank at an intermediate position between the ejection parts of the upper circulation device and the lower circulation device, and the upper circulation device, the middle circulation device and the lower circulation device are , A pipe, a pump, and an ejector mechanism for mixing air into the fluid on the discharge side of the pump. The jetting direction of each of the upper circulation device, the middle circulation device, and the lower circulation device causes the fluid to swirl in the tank. To get Deep aeration tank, characterized in that it is a constant. 3. The deep aeration tank according to claim 2, wherein a plurality of the intermediate circulation devices are provided. 4. A vertically long aeration tank comprising an outer cylinder having a sewage water supply part and a treated water outflow part, and an inner cylinder concentrically arranged with the outer cylinder and having an inflow opening in the upper part thereof. The inflow opening of the inner cylinder is located below the outflow portion of the outer cylinder, and a lower circulation device for sucking the fluid in the inner cylinder and ejecting the fluid between the outer cylinder and the inner cylinder is provided. In addition, an upper circulation device is provided for sucking the fluid in the aeration tank and ejecting the fluid between the outer cylinder and the inner cylinder above the ejection portion of the lower circulation device, and the upper circulation device is provided. The device and the lower circulation device are composed of a pipe, a pump, and an ejector mechanism that mixes air into the fluid on the discharge side of the pump. The jetting direction of each of the upper circulation device and the lower circulation device causes the fluid to flow inside the outer cylinder. Set in a direction that allows swirling flow with the cylinder. Deep aeration tank, characterized in that it is. 5. A vertically long aeration tank comprising an outer cylinder having a sewage supply part and a treated water outflow part, and an inner cylinder arranged concentrically with the outer cylinder and having an inflow opening in the upper part thereof. The inflow opening of the inner cylinder is located below the outflow portion of the outer cylinder, and a lower circulation device for sucking the fluid in the inner cylinder and ejecting the fluid between the outer cylinder and the inner cylinder, An upper circulation device for sucking the fluid in the aeration tank and ejecting the fluid between the outer cylinder and the inner cylinder above the ejection portion of the lower circulation device, and sucking the fluid in the aeration tank. Then, a middle-level circulation device for ejecting this between the outer cylinder and the inner cylinder at an intermediate position between the ejection parts of the upper circulation device and the lower circulation device is provided. Circulators and subordinate circulation devices allow air to flow through the piping, pump, and discharge side of this pump. The upper circulation device, the middle circulation device, and the lower circulation device are formed of ejector mechanisms to be mixed in, and the ejection directions of the upper circulation device, the middle circulation device, and the lower circulation device are set so as to allow the fluid to swirl between the outer cylinder and the inner cylinder. Deep aeration tank characterized by that. 6. The deep aeration tank according to claim 5, wherein a plurality of the intermediate circulation devices are provided.