JP6562592B2 - Aerobic / anaerobic combined reaction tank and operation method thereof - Google Patents

Description

  The present invention relates to an aerobic / anaerobic combined reaction tank and a method for operating the same, and relates to a technique used in a water treatment facility such as a sewage treatment plant.

  Conventionally, as this kind of aerobic / anaerobic combined reaction tank, for example, there is the one shown in FIG. In this, a plurality of air diffusers 82 to 84 are installed at the bottom of the tank 81, and a stirring device 85 is provided at the top of the tank 81. The stirring device 85 has a stirring blade 86 and a driving device 87 that rotates the stirring blade 86.

The central air diffuser 82 is located directly below the stirring blade 86, and the remaining air diffusers 83 and 84 are located on both sides of the central air diffuser 82.
For example, in the winter season, the aerobic / anaerobic reaction tank performs an aerobic operation in which the agitating device 85 is stopped and the aeration devices 82 to 84 are operated as shown in FIG. As a result, a large number of bubbles are discharged from the air diffusers 82 to 84 into the treated water 88 and rise, and the upward flow 90 and the upward flow 90 are reversed in the vicinity of the water surface to the treated water 88 in the tank 81. Thus, a descending flow 91 descending is formed.

  Further, in the summer, as shown in FIG. 12, the stirring device 85 is operated and the air diffusers 82 to 84 are stopped, so that the downward flow 91 is generated directly below the stirring blade 86 by the rotation of the stirring blade 86. To do.

  For example, Patent Document 1 is a prior art document of such aerobic / anaerobic combined reaction tank.

JP 2013-27810 A

  However, in the above-described conventional configuration, the downward flow 91 hits the air diffuser 82 positioned directly below the stirring blade 86, so that the bottom of the tank 81 (the portion between the bottom surface of the tank 81 and the air diffusers 83 and 84). ) Of the flow 92 (hereinafter referred to as the bottom flow velocity) decreases, the sludge in the tank 81 separates from the flow and settles to the bottom, and the sludge cannot be maintained in the state where it is diffused in the tank 81. There is a problem that the efficiency of processing is reduced.

  An object of the present invention is to provide an aerobic / anaerobic combined reaction tank capable of spreading a swirling flow over the entire region in the tank and preventing sludge from partially sedimenting in the tank, and an operating method thereof. And

In order to solve the above problems, the operation method of the aerobic / anaerobic combined reaction tank of the present invention alternately repeats an aerobic operation and an anaerobic operation, and in the aerobic operation, the aeration apparatus located at the bottom of the tank diffuses. In the anaerobic operation, an upward flow generator located in the center of the tank body in the width direction is used in an anaerobic operation to mix the liquid in the tank. pushes up the processing liquid to generate upward flow at the position of the upward flow generating device causes a swirling flow of the liquid to be treated in the tank due to the upward flow, the swirling flow, and the upflow the upward flow is reversed in the liquid level vessel, followed by the diffusion flow extending flow to ambient bath wall along the intracisternal liquid surface, it flows along the Sokabenai side, an air diffuser and Sokabenai Formed between the diffuser parts of the diffuser by flowing down between the side and the flow path between the diffuser and the tank bottom Has passed through the liquid passing part made from the component stream of the tank bottom stream to converge to the upward stream flows upwardly, bath undercurrent, in the horizontal plane occupied by the liquid passing part in the region immediately below the upward flow generating device It flows out upward through each liquid passing portion whose area occupancy is set larger than that of other regions outside the region immediately below.

  In the above configuration, the flow of the liquid to be treated is the upward flow created by the upward flow generator, and this upward flow is reversed on the liquid level in the tank, and then along the liquid level in the tank to the surrounding tank wall A diffusion flow that spreads, a flow that flows along the inner surface of the tank wall, a downward flow that flows into the flow path from between the diffuser and the inner surface of the tank wall, and a flow path between the diffuser and the tank bottom, It consists of each component flow of the tank bottom flow that passes through the liquid passage portion formed between the plurality of air diffusion portions of the air diffuser and flows upward and converges to the upward flow.

  The upward flow pushes up the sludge in the tank to the liquid level in the tank, and the liquid to be treated including the sludge that floats on the liquid level in the tank spreads to the tank wall as a diffusion flow. Spreading is promoted. The tank bottom flow that flows through the flow path between the air diffuser and the tank bottom flows up through the liquid passing part formed between the air diffusers of the air diffuser over the sludge at the tank bottom. Therefore, it is possible to prevent the sludge from partially sedimenting in the tank.

  In the anaerobic and anaerobic combined reaction tank operation method of the present invention, in the anaerobic operation, an upward flow generating device composed of a mechanical stirrer generates an upward flow of the liquid to be treated, and the upward flow causes the liquid to enter the tank. The inside of the tank is agitated and mixed by the generated swirling flow.

In the above configuration, since the mechanical stirrer can generate an upward flow at an arbitrary flow rate, it is possible to achieve a tank bottom flow in which sludge does not settle by adjusting the bottom flow rate.
In the operation method of the aerobic / anaerobic combined reaction tank of the present invention, the amount of dissolved oxygen in the liquid to be treated in the tank is measured, and when the measured value of the amount of dissolved oxygen falls below the lower limit set value, the upward flow is generated. The device is stopped and the aeration device is operated to perform the aerobic operation.When the measured value of the dissolved oxygen amount exceeds the upper limit set value, the aeration device is stopped and the upward flow generator is An anaerobic operation is performed by operating.

According to the above configuration, excessive aeration is suppressed, and bulking due to excessive aeration can be prevented.
Aerobic anaerobic combined reactor of the present invention is located in the central portion in the width direction of the tank body a vessel top, running when anaerobic operation, to generate an upward flow pushes up the liquid to be treated in the vessel, the An upward flow generator that generates a swirling flow of the liquid to be treated in the tank due to the upward flow, and an air diffuser that is located at the bottom of the tank and operates during aerobic operation and diffuses into the liquid to be treated And a flow passage formed between the air diffuser and the tank bottom surface, and between the air diffuser and the tank wall inner surface, the air diffuser has a plurality of air diffusers, and between the air diffusers. The liquid to be treated can pass upward, and the area occupancy in the horizontal plane occupied by the liquid passing part in the area directly below the upward flow generator is larger than that in other areas outside the area directly below. is set, swirl flow, wherein the upward flow, the upward flow is reversed in the liquid level vessel, diffusive flow spreading flow to ambient of the vessel wall subsequently along the intracisternal liquid surface A plurality of air diffusers in the air diffuser, flowing along the inner surface of the tank wall, flowing down between the air diffuser and the inner surface of the tank wall, and flowing in the flow path between the air diffuser and the tank bottom surface. It consists of each component flow of the tank bottom flow which passes through the liquid flow part formed between the parts, flows out upwards, and converges on the said upward flow.

  The aerobic / anaerobic combined reaction tank having the above-mentioned structure diffuses air from an air diffuser located at the bottom of the tank during aerobic operation, and causes an upward flow of the liquid to be treated by an air lift to mix the inside of the tank. Is possible. Further, during anaerobic operation, an upward flow generating device located in the upper part of the tank generates an upward flow of the liquid to be treated, and the inside of the tank is stirred and mixed by a swirl flow generated in the tank due to the upward flow. It is possible.

In the aerobic / anaerobic combined reaction tank of the present invention, each aeration unit is made of a membrane type aeration device, and the upward flow generation device is made of a mechanical stirrer.
In the aerobic / anaerobic combined reaction tank of the present invention, the vertical distance from the tank bottom to the diffuser is set to 200 mm or more in the flow path, and the horizontal distance from the tank wall inner surface to the diffuser is 200 mm. It is characterized by being set above.

  According to the above configuration, the downward flow can smoothly flow into the flow path without being obstructed by the diffuser when passing between the inner surface of the tank wall and the diffuser. In addition, the tank bottom flow flowing along the tank bottom surface can flow while maintaining the bottom flow velocity that entrains the sludge at the tank bottom without being disturbed by the diffuser.

  In the aerobic / anaerobic combined reaction tank of the present invention, the area occupancy in the horizontal plane occupied by the liquid passing portion in the region directly below the upward flow generator is set to be larger than those in other regions outside the region directly below. It is characterized by.

  According to the said structure, it becomes easy to converge a tank bottom flow to the area | region directly under an upward flow generator, a swirl flow is formed smoothly, and stirring efficiency improves.

  As described above, according to the present invention, since the tank bottom flow flows while maintaining the bottom flow velocity entraining the sludge at the bottom of the tank, the sludge can be prevented from sinking to the bottom of the tank. Processing efficiency is improved.

It is a figure of the biological treatment tank provided with the aerobic anaerobic combined reaction tank in the 1st Embodiment of this invention. It is a horizontal sectional view of an aerobic anaerobic combined reaction tank. It is a partially cutaway perspective view of the aerobic / anaerobic combined reaction tank. FIG. 3 is an XX arrow view in FIG. 2 and shows an aerobic operation. It is sectional drawing at the time of the anaerobic driving | running of the aerobic anaerobic combined reaction tank. It is a perspective view of the diffuser of the aerobic anaerobic combined reaction tank. It is a partial expanded sectional view of the diffuser of an aerobic and anaerobic combined reaction tank, (a) shows an aeration stop state, (b) shows an aeration state. It is a block diagram of a control system of the aerobic anaerobic combined reaction tank. It is a time chart explaining the operating method of the aerobic anaerobic combined reaction tank in the 2nd Embodiment of this invention. It is a time chart explaining the operating method of the aerobic anaerobic combined reaction tank in the 3rd Embodiment of this invention. It is sectional drawing of the conventional aerobic anaerobic combined reaction tank, and shows the time of an aerobic driving | operation. It is sectional drawing of an aerobic anaerobic combined reaction tank, and shows the time of anaerobic operation.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
In the first embodiment, as shown in FIG. 1, reference numeral 1 denotes a biological reaction tank for biologically treating organic raw water 2 (an example of a liquid to be treated) in a sewage treatment facility. The biological treatment tank 1 has an anaerobic tank 5, an aerobic anaerobic combined reaction tank 6, and first and second aerobic tanks 7 and 8 from the upstream side toward the downstream side.

The anaerobic tank 5 has a stirring device 11 for stirring the raw water 2 in the tank. Moreover, the 1st and 2nd aerobic tank 7 and 8 has the aeration apparatus 12 and 13 in each tank inner bottom part.
As shown in FIGS. 2 to 5, the aerobic / anaerobic combined reaction tank 6 is an upward flow generating device for generating an upward flow 15 by pushing up the rectangular tank body 20 and the raw water 2 in the tank in plan view. And an aeration device 22 that is installed at the bottom of the tank and diffuses the raw water 2. Assuming that the long side direction of the tank body 20 is the length direction L and the short side direction is the width direction W, the tank body 20 has a pair of tank walls 23 facing in the length direction L and a pair facing in the width direction W. The tank wall 24, the bottom wall 25, and the ceiling wall 26 are provided.

The stirrer 21 has a stirrer blade 30 suspended from the ceiling wall 26 via a rotating shaft 29, and a drive unit 31 that rotates the stirrer blade 30. Here, the stirrer 21 is a low-power machine. It is an energy-saving type consisting of a mechanical stirrer and 3 W / m ³ or less. As shown in FIG. 4, the stirring blade 30 is arranged at the center in the width direction W in the tank body 20.

  The air diffuser 22 has a plurality of air diffusers 22a, and has a liquid passage 22b through which the liquid to be processed can pass upward between the air diffusers 22a. In the present embodiment, three (a plurality of) diffusers 22a are arranged in the width direction W, and two (a plurality) are arranged in the length direction L, and a plurality of diffusers 22a are arranged in the diffuser 22a. A membrane diffuser is provided. The area occupancy in the horizontal plane occupied by the liquid passing portion 22b in the region directly below the stirring device 21 is set to be larger than those in other regions outside the region directly below.

  As shown in FIG. 6, each air diffuser 22 is provided with a diffuser film 35 on the upper surface of a base plate 34 and provided with an air supply port 36 at a predetermined position. It communicates with the air membrane 35. The diffuser film 35 is formed by providing a large number of openable and closable small diffuser holes 37 on an elastic film that can be expanded and contracted, such as a synthetic resin film or a synthetic rubber film. The structure is fixed to

  An air supply pipe (not shown) for supplying air to each air diffuser 22 is connected to the air supply port 36, and an air supply valve 39 (see FIG. 8) that can be opened and closed is provided on the air supply pipe. . The air supply valve 39 is an automatic valve or a control valve. When the air supply valve 39 is opened, the air diffuser 22 is activated, and when the air supply valve 39 is closed, the air diffuser 22 is stopped.

  When the air diffuser 22 is stopped, as shown in FIG. 7A, the air diffuser film 35 receives water pressure and comes into contact with the upper surface of the base plate 34. At this time, the air diffuser hole 37 is closed. Become. When the air diffuser 22 is in operation, compressed air is supplied from the air supply port 36 between the base plate 34 and the air diffuser film 35 and receives the pressure of the compressed air as shown in FIG. As a result, the diffuser film 35 swells away from the upper surface of the base plate 34 and the diffuser holes 37 are opened, and bubbles are released into the raw water 2 through the diffuser holes 37.

As shown in FIGS. 2 to 4, these air diffusers 22 are provided on the bottom of the tank body 20 with both ends supported by a support frame 40 installed on the bottom wall 25 of the tank body 20. Yes.
As shown in FIG. 4, a flow passage 41 is formed between the air diffuser 22 and the bottom surface of the tank body 20, and a flow passage 42 is formed between the air diffuser 22 and the inner surface of the tank wall 24. Is formed. The vertical distance D from the bottom surface in the tank body 20 to the air diffuser 22 is set to 200 mm or more. Further, the horizontal distance E from the inner surface of the tank wall 24 to the air diffuser 22 is set to 200 mm or more.

  Further, as shown in FIG. 8, in the aerobic / anaerobic combined reaction tank 6, the drive device 31 is controlled to control the operation and stop of the stirring device 21, and the air supply valve 39 is controlled to control the air diffuser 22. A control device 44 is provided for controlling the operation and stop of the motor.

Hereinafter, the operation of the above configuration will be described.
As shown in FIG. 1, the raw water 2 is first supplied to the anaerobic tank 5, and sequentially from the upstream anaerobic tank 5, the downstream aerobic / anaerobic combined reaction tank 6, the first aerobic tank 7, and the second aerobic tank. While flowing into the tank 8, the biological treatment is performed in each of the tanks 5 to 8, and then discharged from the second aerobic tank 8 on the most downstream side as treated water 46. At this time, the raw water 2 in the anaerobic tank 5 is stirred by the stirring device 11, and the raw water 2 in the first and second aerobic tanks 7 and 8 is diffused by the air diffusers 12 and 13, respectively.

The aerobic / anaerobic combined reaction tank 6 performs the following aerobic operation in winter and performs the following anaerobic operation in summer.
At the time of aerobic operation, as shown in FIG. 4, the stirring device 21 is stopped and each air diffuser 22 is operated. Thereby, compressed air is supplied between the base plate 34 and the diffuser film 35 from the air supply port 36, and the diffuser film 35 receives the pressure of the compressed air as shown in FIG. The air diffuser 37 expands away from the upper surface, and a large number of air bubbles 37 are released from the air diffuser 37 into the raw water 2 and rise.

As a result, as shown in FIG. 4, an upward flow 16 is generated in the tank, the upward flow 16 is reversed near the water surface to become a downward flow 15, and the raw water 2 is circulated in the tank and stirred.
Moreover, at the time of anaerobic operation, as shown in FIG. 5, while stirring apparatus 21 is operated, each aeration apparatus 22 is stopped. As a result, the stirring blade 30 of the stirring device 21 rotates to generate the upward flow 15, and the inside of the tank is stirred and mixed by the swirling flow generated in the tank due to the upward flow 15.

  The swirling flow includes an upward flow 15 created by the stirring device 21, a diffusion flow 17 that reverses the upward flow 15 at the liquid level in the tank, and then flows to the surrounding tank wall along the liquid level in the tank. , Flowing along the inner surface of the tank wall, flowing down between the diffuser 22 and the inner surface of the tank wall into the flow passage 42, and flowing through the flow path 41 between the diffuser 22 and the tank bottom surface, It consists of each component flow of the tank bottom flow F that flows upward through the liquid passing portion 22b formed between the plurality of air diffusion portions 22a of the air diffusion device 22 and converges to the upward flow 15.

  In this anaerobic operation, the upward flow 15 pushes up the sludge in the tank to the liquid level in the tank, and the liquid to be treated including the sludge floating on the liquid level in the tank becomes a diffusion flow 17 and spreads to the tank wall. Thus, the diffusion of sludge in the tank is promoted. The tank bottom flow F flowing through the flow passage 41 between the air diffuser 22 and the tank bottom surface covers the sludge at the tank bottom, and the liquid passing part 22b formed between the air diffusers 22a of the air diffuser 22 is formed. Since it passes through and flows upward and converges to the upward flow, it is possible to prevent the sludge from partially sedimenting in the tank. Since the area occupancy in the horizontal plane occupied by the liquid passing portion 22b in the region immediately below the stirring device 21 is set to be larger than those in other regions outside the region immediately below, the tank bottom flow F converges to the region directly below the stirring device 21. The swirling flow is smoothly formed and the stirring efficiency is improved.

  As described above, in the summer when the reaction rate is high, the aerobic / anaerobic combined reaction tank 6 is anaerobically operated so that nitrification is performed in the first and second aerobic tanks 7 and 8, thereby Denitrification can be performed in the anaerobic combined reaction tank 6. Further, in the winter when the reaction rate is slow, the aerobic / anaerobic combined reaction tank 6 is aerobically operated to perform nitrification in the aerobic / anaerobic combined reaction tank 6 and the first and second aerobic tanks 7 and 8. Denitrification can be performed in the tank 5.

  As shown in FIG. 5, when each air diffuser 22 is stopped during anaerobic operation, the air diffuser film 35 contracts due to water pressure and contacts the upper surface of the base plate 34 as shown in FIG. 7A. Because the air diffuser 37 is closed, even if a foreign object falls on the air diffuser 22, it does not enter the air diffuser 37. Also, when each air diffuser 22 is operated by switching to aerobic operation, the air diffuser 22 is not diffused. The air film 35 swells to remove foreign substances, and the air holes 37 can be prevented from being clogged.

  Moreover, as shown in FIG. 4, since the distance D is set to 200 mm or more and the distance E is set to 200 mm or more, when the downward flow 16 passes between the tank wall inner surface and the air diffuser 22, The tank bottom flow F that flows along the tank bottom surface is not obstructed by the air diffuser 22, and the tank bottom flow F that flows along the tank bottom surface traps sludge at the tank bottom without being obstructed by the air diffuser 22. It keeps flowing at the bottom flow velocity.

(Second Embodiment)
In the first embodiment, the aerobic operation and the anaerobic operation of the aerobic / anaerobic combined reaction tank 6 are switched between winter and summer, but in the second embodiment, as shown in FIG. A timer 50 may be provided in the control device 44, and aerobic operation and anaerobic operation may be alternately repeated in a predetermined time zone.

For example, as shown in FIG. 9, even if the aerobic driving is performed during the time period from 7:00 am to 3:00 am the next day and the anaerobic driving is performed during the time period from 3:00 am to 7:00 am Good.
Each time described in the second embodiment is an example, and is not limited to these times.

(Third embodiment)
In the third embodiment, as shown in FIG. 10, aerobic driving is performed during the daytime from 7 am to 7 pm (19:00), and from 7 pm to 7 am on the following day. Alternating aerobic and anaerobic during night time. In the aerobic / anaerobic alternating operation, for example, after an anaerobic operation is performed for 10 minutes, an aerobic operation is alternately performed for 5 minutes.

  Thereby, in the night time zone when the inflow of the raw water 2 flowing into the aerobic / anaerobic combined reaction tank 6 is reduced, excessive aeration is suppressed by alternately repeating the aerobic operation and the anaerobic operation, Bulking due to over-aeration can be prevented.

Each time and time described in the third embodiment is an example, and is not limited to these times and times.
(Fourth embodiment)
In the fourth embodiment, as shown in FIGS. 1 and 8, a DO meter 53 is provided in the second aerobic tank 8 at the end of the biological treatment tank 1 on the downstream side of the aerobic / anaerobic combined reaction tank 6. The DO meter 53 measures the DO (dissolved oxygen) of the raw water 2 in the second aerobic tank 8, and performs the aerobic operation and the anaerobic operation in the aerobic / anaerobic combined reaction tank 6 based on the measured DO value. Switch.

  Specifically, if the DO value measured by the DO meter 53 falls below, for example, 0.5 mg / L (an example of a lower limit setting value), the aerobic / anaerobic combined reaction tank 6 is switched from anaerobic operation to aerobic operation. . As a result, the stirring device 21 of the aerobic / anaerobic combined reaction tank 6 is stopped and the diffuser 22 is activated to perform the aeration, so the DO of the raw water 2 in the aerobic / anaerobic combined reaction tank 6 increases, Along with this, the DO value measured by the DO meter 53 increases.

  When the DO value measured by the DO meter 53 rises to, for example, 2 mg / L (an example of the upper limit set value) or more, the aerobic / anaerobic combined reaction tank 6 is switched from an aerobic operation to an anaerobic operation. As a result, the stirring device 21 of the aerobic / anaerobic combined reaction tank 6 is activated and the aeration from the diffuser 22 is stopped, and the DO of the raw water 2 in the aerobic / anaerobic combined reaction tank 6 is reduced. As a result, the DO value measured by the DO meter 53 decreases.

  Then, when the DO value measured by the DO meter 53 decreases to, for example, 0.5 mg / L or less, the aerobic / anaerobic combined reaction tank 6 is repeatedly switched from anaerobic operation to aerobic operation. Thereby, excessive aeration is suppressed and the bulking by overaeration can be prevented.

In addition, the numerical value of each DO described in the said 4th Embodiment is an example, Comprising: It is not limited to these numerical values.
In each said embodiment, as shown in FIG. 2, although the tank main body 20 of the aerobic anaerobic combined reaction tank 6 is made into the rectangular shape in planar view, it is not limited to a rectangular shape, For example, square shape It may be.

2 Raw water (liquid to be treated)
6 Aerobic / anaerobic combined reaction tank 15 Upstream flow 16 Downflow flow 17 Diffusion flow 21 Stirring device 22 Air diffusion device 24 Tank wall 35 Air diffusion film 37 Air diffusion holes 41 and 42 Flow paths D and E Distance

Claims (6)

Repeat aerobic driving and anaerobic driving alternately,
In the aerobic operation, the inside of the tank is agitated and mixed by the upward flow of the liquid to be treated generated by the air lift by aeration from the air diffuser located at the bottom of the tank,
Under anaerobic operation, to generate upward flow at the position of the upward flow generating device pushes up the liquid to be treated in the tank by the upward flow generating device positioned at the center in the width direction of the tank body a vessel upper part, the A swirling flow of the liquid to be treated is generated in the tank due to the upward flow,
Swirling flow, and the upper counter-current, the upward flow is reversed in the liquid level vessel, and then along the intracisternal liquid surface extends flows to the periphery of the bath wall diffusive flow, along Sokabenai side Flow, downward flow flowing between the air diffuser and the inner surface of the tank wall, and flow through the flow path between the air diffuser and the tank bottom surface, and the liquid flow formed between the plurality of air diffusers of the air diffuser made from each component stream of the tank bottom stream to converge to the upward stream flowing upward through the parts, bath undercurrent, the area occupancy rate of the horizontal plane occupied by the liquid passing part in the region immediately below the upward flow generating device Flows out upward through each liquid passing portion set larger than those in other regions outside the region directly below, and the method for operating an aerobic / anaerobic combined reaction tank.   In anaerobic operation, the upward flow generating device composed of a mechanical stirrer generates an upward flow of the liquid to be treated, and the inside of the tank is stirred and mixed by a swirling flow generated in the tank due to the upward flow. The operation method of the aerobic / anaerobic combined reaction tank according to claim 1.   When the amount of dissolved oxygen in the liquid to be treated in the tank is measured and the measured value of the dissolved oxygen amount falls below the lower limit set value, the upward flow generator is stopped and the diffuser is activated. A gas operation is performed, and when the measured value of the dissolved oxygen amount exceeds the upper limit set value, the air diffuser is stopped, and the upward flow generator is operated to perform the anaerobic operation. The operation method of the aerobic anaerobic combined reaction tank of 1 or 2. Centrally to the width direction of the tank body a vessel top, running when anaerobic operation, to generate an upward flow pushes up the liquid to be treated in the vessel, the in the tank due to the upflow An upward flow generating device that generates a swirling flow of the processing liquid, an air diffusion device that is located at the bottom of the tank, operates during aerobic operation, and diffuses into the liquid to be processed, and between the air diffusion apparatus and the tank bottom And a flow passage formed between the air diffuser and the inner surface of the tank wall, the air diffuser has a plurality of air diffusers, and the liquid to be treated can pass upward between the air diffusers. Part
The area occupancy rate in the horizontal plane occupied by the liquid passing part in the area directly below the upward flow generator is set larger than that in other areas outside the area directly below,
Swirling flow, said a upflow, and the upward flow is reversed in the liquid level vessel, then along the intracisternal liquid surface extends flows to the periphery of the bath wall diffusive flow, along Sokabenai side Flow, downward flow flowing between the air diffuser and the inner surface of the tank wall, and flow through the flow path between the air diffuser and the tank bottom surface, and the liquid flow formed between the plurality of air diffusers of the air diffuser aerobic anaerobic combined reaction tank, characterized in that it consists each component stream of the tank bottom stream to converge to the upward stream flowing upward through the part.   Each aeration part consists of a membrane-type aeration apparatus, and an upward flow generation apparatus consists of a mechanical stirrer, The aerobic anaerobic combined reaction tank of Claim 4 characterized by the above-mentioned. In the flow path, the vertical distance from the tank bottom to the air diffuser is set to 200 mm or more,
6. The aerobic / anaerobic combined reaction tank according to claim 4, wherein a horizontal distance from the inner surface of the tank wall to the air diffuser is set to 200 mm or more.

Images