JPH11156388A - Wastewater treatment tank containing organic solids - Google Patents

Abstract

(57) [Problem] To provide an organic solid-containing wastewater treatment tank capable of effectively reducing suspended solids in organic solid-containing wastewater. SOLUTION: A multi-stage aeration tank 50 in which at least two aeration tanks 5 are connected in series is provided, and organic solid matter-containing wastewater is sequentially transferred from the first aeration tank 5 to the subsequent aeration tank 5. The structure is such that suspended solids in the wastewater are reduced step by step, and the multi-stage aeration tank 50 is used to concentrate the organic solid matter-containing wastewater that may flow in large amounts to a higher concentration. Degrading by adding the amount (5% of the capacity of the multi-stage aeration tank, more preferably about 2% or less) not only reduces the BOD of the wastewater containing organic solids and prevents the bulking of the treated water, but also the organic solids Effectively reduce suspended solids in wastewater containing waste.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wastewater containing organic solids having a function of reducing suspended solids (SS) and biochemical oxygen demand (BOD) of organic solids such as kitchen solids. More specifically, the treatment tank includes at least two aeration tanks (multi-stage aeration tanks) connected in series,
The present invention relates to an organic solid matter-containing wastewater treatment tank capable of effectively decomposing organic solid matter-containing wastewater by microorganisms that grow under aerobic conditions.

[0002]

2. Description of the Related Art Conventional multi-stage aeration tanks are mainly used to reduce the BOD of wastewater containing relatively low concentration of organic solids and to prevent bulking in a sedimentation tank into which water (treated water) after decomposition treatment flows. And

[0003] In such a multi-stage aeration tank, the BOD of the organic solid-containing wastewater is reduced by introducing a relatively low concentration of the organic solid-containing wastewater into at least two aeration tanks connected in series. A biological treatment tank for organic solid matter-containing wastewater, characterized in that the wastewater is treated so as to be reduced step by step.

[0004] For example, Japanese Patent Application Laid-Open No. 9-70596 discloses a biological treatment method for organic wastewater having a multistage aeration tank.

In this method, a large amount of organic wastewater is directly charged into a multistage aeration tank, so that the time (residence time) that can be spent for the decomposition treatment of the wastewater in each tank of the multistage aeration tank cannot be shortened. Although not obtained, it has sufficient performance to achieve the objectives of reducing the BOD of organic wastewater and preventing the bulking of treated water in the sedimentation tank provided after the aeration tank.

[0006]

By the way, in general, BO
Since D reduction progresses more easily than suspended matter reduction,
According to the method described in the above-mentioned publication, B
Although the OD can be reduced, there is a problem that sufficient performance cannot be obtained with respect to the decomposition treatment of some suspended substances contained in the organic wastewater because the residence time is short in this method.

The present invention has been made in view of such circumstances, and has as its object to provide an organic solid-containing wastewater treatment tank capable of effectively reducing suspended solids in organic solid-containing wastewater. And

[0008]

In order to achieve the above-mentioned object, an organic solid-containing wastewater treatment tank according to the present invention is provided with an aeration for decomposing wastewater containing organic solids under aerobic conditions. A wastewater treatment tank provided with a multi-stage aeration tank in which at least two tanks are connected in series, wherein as the organic solid matter-containing wastewater sequentially shifts from the first aeration tank to the subsequent aeration tank, the Are characterized in that the suspended solids are configured to be reduced step by step.

In the organic solid matter containing wastewater treatment tank of the present invention, when there is a possibility that a large amount of the organic solid matter containing wastewater flows into the aeration tank, the organic solid matter containing wastewater is directly charged into a multi-stage aeration tank. Instead, the wastewater containing organic solids, which is more concentrated than the wastewater containing organic solids that has flowed in, is introduced into the first aeration tank using a device having a precipitation separation function.

Further, in order to make the organic solid matter-containing wastewater treatment tank of the present invention to function effectively, the organic solid matter-containing wastewater which may flow in a large amount is concentrated to a higher concentration. (5% of the capacity of the multi-stage aeration tank, more preferably about 2% or less) and decomposition treatment by the multi-stage aeration tank not only reduces the BOD of the organic solid matter-containing wastewater but also prevents the bulking of the treated water, Even the suspended solids in the organic solid matter-containing wastewater can be effectively reduced.

In the organic solid matter-containing wastewater treatment tank of the present invention, the shape of each tank of the aeration tank is not particularly limited. For example, the side wall is a cylindrical body having an appropriate shape such as a cylindrical shape or a square shape. The lower structure may have a flat bottom surface, or may be a structure provided with a transfer unit and a collecting unit, which will be described later.

Further, as a material constituting each aeration tank,
Although not particularly limited, for example, FRP and FR
Examples thereof include a synthetic resin such as TP, a metal such as an iron plate or a stainless steel plate having a rust-proof coating on the surface, or concrete subjected to a water leakage prevention treatment.

In the organic solid matter-containing wastewater treatment tank of the present invention, as each aeration tank, as shown in FIG. 1, the organic solid matter in the tank is inclined downward from the tank side wall. A transfer section 5a to be sent to the lower part, a collecting section 5b of the organic solid formed near the end of the transfer section 5a, and an air diffuser (aeration pipe 6) are provided near the deepest portion of the collecting section 5b. The air diffusion unit 5c is separated from the transfer unit 5a, the collection unit 5b, and the air diffusion unit 5c, and the openings 7b and 7 are formed at the deepest position of the collection unit 5b and near the upper water surface of the transfer unit 5a.
It is preferable to use a tank provided with a rectifying partition 7 having a.

When each of the aeration tanks is structured as described above, the wastewater containing the organic solids is continuously and continuously scattered by bubbles ejected from the air diffuser provided near the deepest part of the collecting part 5b. Since the water is wound up and a rising water flow is formed along the rectifying partition wall 7, the organic solid matter is sucked by the rising water flow, quickly collected in the collecting part 5 b, decomposed by the aerobic microorganisms, and untreated. Is circulated to the transfer section 5a.

In the aeration tank 5 shown in FIG. 1, the inclination of the transfer section 5a may be linearly inclined, or may be inclined with a curved surface such as a parabola. . Further, the inclination may be one step, or may be a multi-step inclined surface having a different inclination within the inclined surface.

The inclination angle of the transfer section 5a is not particularly limited, but is preferably at most 60 ° with respect to a vertical plane or a vertical line above the air diffusion section 5c. The angle of inclination of the transfer unit 5a is 60 degrees with respect to the vertical plane or vertical line
When the temperature exceeds 0 ° C., the organic solid matter easily stays in the transfer section 5a, and it is difficult to keep the entire inside of the tank in a stirring state, so that rapid processing cannot be performed. In addition, the biodegradation environment of the organic solid in the stagnant portion is deteriorated, which may cause odor.

In the aeration tank 5 shown in FIG.
Is provided with an air diffuser at the deepest position or above the deepest position of the collecting portion 5b. The air diffuser is not particularly limited, and supplies air (oxygen) at a required pressure. A blower (usually provided outside the tank), a nozzle for dispersing the air in the form of fine bubbles in kitchen wastewater, and a ventilator for drainage treatment that connects both of them may be used.

As the nozzle, for example, a synthetic resin pipe such as a polyethylene pipe, a polypropylene pipe, a vinyl chloride resin pipe or the like in which a plurality of small holes are formed (aeration tube), and a plurality of small holes are respectively provided. Examples thereof include those in which a dispersion nozzle is attached to make air more easily dispersed, and sintered bodies having a porous structure made of synthetic resin, ceramics, metal, or the like.

Rectifying partition 7 used in aeration tank 5 shown in FIG.
Are the transfer section 5a and the collecting section 5b, and the diffusing section 5c
And has openings 7b and 7a near the deepest position of the collecting part 5b and near the upper water surface of the transfer part 5a, and the material and shape of the rectifying partition wall 7 are between the side walls of the aeration tank 5. In addition, any material can be used as long as the solid waste can be continuously wound up by the rising water flow by the air diffuser and kept constantly in a stirring state. Specifically, a plate made of a wooden plate, a metal plate, a synthetic resin plate, or the like can be given. Further, such a rectifying partition 7 is provided with each aeration tank 5.
May be arranged so as to be parallel to the side wall of the tank, or may be arranged such that the width of the water channel becomes narrower toward the upper part of the tank.

In the aeration tank 5 shown in FIG.
The gap between the air diffusion unit 5c and the tank side wall is not particularly limited, but may be set to be equal to or slightly larger than the width (thickness) of the air diffusion device (the air diffusion tube 6). preferable.

The lower edge of the rectifying partition 7 and the collecting portion 5b
7b formed between the deepest aeration tank bottom wall and
The clearance is not particularly limited, but it is preferable to make the clearance as small as possible, as long as the point that the organic solid passes without clogging can be satisfied. <Action> According to the organic solid matter-containing wastewater treatment tank of the present invention according to claims 1 to 3, organic solid matter such as kitchen solid matter contained in wastewater flowing down from kitchens, restaurants, food factories and the like. The substance is quickly concentrated by some method, and the organic solid matter-containing wastewater containing the organic solid matter at a higher concentration is transferred to an appropriate amount in a multi-stage aeration tank, and then is sequentially decomposed in a multi-stage aeration tank. Is what is done.

The wastewater containing organic solids which may be generated in a large amount in this way is not directly introduced into the multi-stage aeration tank, but is discharged from the wastewater containing organic solids which has flowed in by a device having a sedimentation separation function. Also, an appropriate amount of concentrated organic solids-containing wastewater (5% of the capacity of the multi-stage aeration tank, more preferably about 2% or less) is charged and the organic solids-containing wastewater is decomposed by the multistage aeration tank. Not only the BOD can be reduced and the bulking of the treated water can be prevented, but also the suspended solids in the wastewater containing organic solids can be effectively reduced.

According to the organic solid matter-containing wastewater treatment tank of the present invention, the separated wastewater obtained by separating the sludge in the treatment liquid in the former settling tank flows into the latter aeration tank. With such a configuration, by allowing the separated wastewater to flow into the subsequent aeration tank, a decrease in pH in the subsequent aeration tank can be suppressed, and a decrease in the decomposition rate of the organic solid can be suppressed.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing an example of the wastewater treatment tank containing organic solid matter according to the present invention. The wastewater treatment tank containing organic solids shown in FIG. 1 mainly includes a sedimentation separation tank 2 and a multistage aeration tank 50 in which three aeration tanks 5 are connected in series.

The sedimentation / separation tank 2 is a tank for separating the wastewater A containing organic solids supplied through the inflow pipe 1 into solid wastewater and concentrated wastewater. The part 3) is a multi-stage aeration tank 50 through the transfer pipe 4.
Is transferred to

Each of the aeration tanks 5 constituting the multi-stage aeration tank 50
Is a tank that decomposes wastewater containing organic solids under aerobic conditions, is processed into a shape that is inclined downward from the tank side wall, and transports organic solids to the lower part of the tank. It has an organic solid collecting part 5b formed near the end of the transfer part 5a, and an air diffusing part 5c provided with an air diffusing tube 6 near the deepest part of the collecting part 5b.

In each aeration tank 5, a transfer section 5a and a collecting section 5b, and a diffuser section 5c are defined, and at the deepest position of the collecting section 5b and near the upper surface of the transfer section 5a. A rectifying partition 7 having openings 7b and 7a is provided.

Of these aeration tanks 5, the first aeration tank 5 and the second aeration tank 5 are respectively connected to the subsequent aeration tank 5 through the advancing port 5d, and the last aeration tank 5 5
Is connected to an outflow pipe 8.

In the present embodiment, a large amount of the wastewater A containing organic solids is not directly charged into the multi-stage aeration tank 50, and the wastewater B containing a higher concentration of organic solids concentrated in the sedimentation separation tank 2 is discharged. An appropriate amount (5% of the capacity of the multi-stage aeration tank 50, more preferably about 2% or less) is put into the multi-stage aeration tank 50, and the multi-stage aeration tank 50 decomposes the BOD of the organic solid-containing wastewater. It is characterized by not only realizing reduction and preventing bulking of treated water, but also effectively reducing suspended solids in wastewater containing organic solids.

In the present embodiment, each aeration tank 5
As described above, the transfer unit 5a, the collecting unit 5b, and the air diffusing unit 5
c and the rectifying bulkhead 7, so that organic solids in the wastewater containing organic solids to be treated for wastewater (such as kitchen solids)
Are temporarily gathered in the gathering part 5b promptly along the transfer part 5a. Then, in the air diffuser 5c, an upward water flow is formed by the air diffused from the air diffuser 6, and the organic solids temporarily collected in the gathering portion 5b are continuously put on the upward water flow. While being wound up all the time, while constantly maintaining the stirring state, it flows again into the aeration tank 5 through the opening 7a at the upper part of the rectifying partition wall 7, thereby forming a circulating flow toward the transfer section 5a.

In this way, the organic solid matter-containing waste water in the aeration unit 5c is uniformly distributed throughout the aeration tank 5, and as a result, a favorable environment for aerobic microbial decomposition is formed.

[0033]

Next, examples of the present invention will be described together with comparative examples. [Example 1] The concentration of suspended solids (SS), which is one of the indices for knowing the concentration of solid matter contained in a solution, was 820 mg.
/ L of organic waste containing garbage waste A is put into the sedimentation separation tank 2 having a capacity of 200 L as shown in FIG. 1 every day, and after 30 minutes or more, 10 L of the concentrated sediment portion 3 is taken every day. Each was transferred to a multi-stage aeration tank 50 having a capacity of 1000 L, and a separation process was performed in the multi-stage aeration tank 50.

The aeration device used a synthetic resin sintered body as an aeration nozzle, and aerated each aeration tank 5 at an aeration rate of 12 L / min to treat organic solid-containing kitchen wastewater. [Comparative Example 1] As shown in FIG. 2, an organic solid-containing wastewater treatment tank consisting of only one aeration tank 105 having the same capacity as the multi-stage aeration tank of FIG.
g / L of organic solid-containing wastewater A was directly charged 140 L each day to treat organic solid-containing kitchen wastewater. Comparative Example 2 As shown in FIG. 3, a single aeration tank 105 and a sedimentation separation tank 102 having the same capacity as the multistage aeration tank of FIG.
The organic solid-containing kitchen wastewater A was treated in the same manner as in the example, without changing the conditions, except that the number of aeration tanks was changed using an organic solid-containing wastewater treatment tank consisting of .

Then, the above Example 1 and Comparative Examples 1 and 2
To evaluate the performance of wastewater treatment tanks containing organic solids,
One month, two months, and three months after the start of use, the concentration of suspended solids flowing out of the final aeration tank of the organic solid matter-containing wastewater treatment tank was measured.

Table 1 shows the results.

[0037]

[Table 1]

As is clear from the above measurement results, the kitchen wastewater decomposed by the organic solid matter-containing wastewater treatment tank of Example 1 of the present invention has a suspended substance concentration at any of the measurement points, which is the same as that of the comparative example. 200 mg / for 1 and 2
L or more.

This indicates that the decomposition treatment of kitchen solid waste containing organic solids by microorganisms is effectively progressed by dividing the aeration tank into multiple stages, and the suspended matter in the final water quality is effectively reduced. Is shown.

Further, since the concentration of suspended solids in Comparative Example 2 was lower than that in Comparative Example 1 by 100 mg / L or more,
It is shown that, in a device having a sedimentation separation function installed in front of an aeration tank, it is possible to more effectively reduce suspended solids by introducing concentrated and higher-concentration organic solid-containing kitchen wastewater.

FIG. 4 is a diagram schematically showing another example of the wastewater treatment tank containing organic solid matter of the present invention. The organic solid-containing wastewater treatment tank shown in FIG. 4 can be used for treating organic solid-containing wastewater generated from houses and the like in a sewerage development area, and a sedimentation tank 12 communicating with the bottom of the tank is provided. It is mainly constituted by a rear aeration tank 13 and a contact aeration tank 15 in which a pre-stage aeration tank 11 and a sedimentation tank 14 communicating with the bottom of the tank are provided. Numerals 110 and 130 denote boundary walls for separating the aeration tanks 11 and 13 and the sedimentation tanks 12 and 14.
The upper ends of 10, 130 project upward from the water surface.

The aeration tank 11 in the first stage is for maintaining the inside of the tank in an aerobic atmosphere by air blown out from a diffuser 121 provided at the bottom of the tank. An inflow pipe 1 is connected to collectively flow the wastewater from the disposer and the wastewater from the kitchen by pulverizing the garbage produced by the disposer.

In the aeration tank 11, the solids contained in the organic solid matter-containing wastewater are mainly decomposed by the action of the aerobic microorganisms, and the treated water is subjected to the subsequent aeration by the air lift pump 131 and the transfer pipe 112. It is to be transferred to the tank 13.

The latter aeration tank 13 has the same structure as the former aeration tank 11. In the aeration tank 13, the treated water is transferred to the contact aeration tank 15 by the air lift pump 141 and the transfer pipe 114.

The sedimentation tank 12 communicating with the aeration tank 11 at the former stage is for sedimenting the sludge in the aeration tank 11, and the bottom of the tank is communicated with the inside of the aeration tank 11 through a communication port 12A. The separated wastewater containing the soluble organic matter treated in the sedimentation tank 12 flows into the subsequent aeration tank 13 via the transfer pipe 111 and the pipe 20.

On the other hand, the sludge separated in the sedimentation tank 12 flows into the aeration tank 11 through the communication port 12A at the bottom of the tank, and is stirred by the air diffuser 121 at the bottom of the aeration tank 11 while being stirred. The transfer pipe 112 transfers the gas to the aeration tank 13 at the subsequent stage.

The sedimentation tank 14 communicating with the bottom of the aeration tank 13 in the latter stage is also the sedimentation tank 1 communicating with the bottom of the aeration tank 11 in the former stage.
2 has the same structure. The separated wastewater containing the soluble organic matter treated in the sedimentation tank 14 flows into the contact aeration tank 15 via the transfer pipe 113 and the pipe 30.

The contact aeration tank 15 also performs aerobic biological treatment. The inside of the tank is maintained in an aerobic atmosphere by air jetted from a diffuser 161 at the bottom of the tank, and the wastewater is separated by aerobic microorganisms. Decomposes the soluble organic matter.

The separated drainage from the aeration tank 13 via the pipe 30 and the inflow of the treated water via the transfer pipe 114 allow the treated water from the contact aeration tank 15 to be discharged from the tank by overflow via the transfer pipe 115. It has become.

In the wastewater treatment tank containing organic solid matter of the present invention shown in FIG. 4, the separated wastewater from the sedimentation tank 12 communicating with the aeration tank 11 in the former stage is transferred to the transfer pipe 111 and the pipe 2.
By flowing into the subsequent aeration tank 13 via 0, a decrease in the pH of the aeration tank 13 can be suppressed, and a decrease in the decomposition rate of the organic solid can be suppressed.

Example 2 Using the wastewater treatment tank containing organic solid matter of the present invention shown in FIG. 4, wastewater mixed with kitchen wastewater and garbage wastewater crushed by a disposer (BOD:
(850 mg / L, suspended substance: 720 mg / L). Comparative Example 3 The same wastewater as in Example 2 was treated using the wastewater treatment tank containing organic solids shown in FIG. In the organic solid matter-containing wastewater treatment tank shown in FIG.
23, a sedimentation tank 22, and a contact aeration tank 24. The aeration tank 21 is a diffuser 22 provided at the bottom of the tank.
The inflow pipe 1 is connected to the aeration tank 21 for maintaining the inside of the tank in an aerobic atmosphere by air ejected from the tank 1. In the aeration tank 21, the solids contained in the organic solid matter-containing wastewater are mainly decomposed by the action of the aerobic microorganisms, and the treated water is transferred to the subsequent aeration tank 23 by the air lift pump 231 and the transfer pipe 212. It has become. In the aeration tank 23, the treated water overflows when flowing into the treatment water via the transfer pipe 212 from the preceding aeration tank 21 and is transferred to the contact aeration tank 24. The sedimentation tank 22 precipitates sludge in the aeration tank 21, and the bottom of the tank communicates with the inside of the aeration tank 21. The separated wastewater containing the soluble organic matter treated in the sedimentation tank 22 is transferred to the contact aeration tank 24 via the transfer pipe 211 and the pipe 20. On the other hand, the sludge separated in the sedimentation tank 22 flows into the aeration tank 21 through the communication port 22A at the bottom of the tank, and the diffusion device 2 at the bottom of the aeration tank 21.
21 and the air lift pump 231
The transfer pipe 212 transfers the gas to the aeration tank 23 at the subsequent stage.

The contact aeration tank 24 also performs aerobic biological treatment. The inside of the tank is maintained in an aerobic atmosphere by air jetted from a diffuser 251 at the bottom of the tank, and the separated aeration water is discharged by aerobic microorganisms. Decomposes the soluble organic matter.

The effluent overflowing from the settling tank 22 flows into the contact aeration tank 24 via the transfer pipe 211, and the treated water flows from the aeration tank 23 into the contact aeration tank 24 via the transfer pipe 213 and the pipe 30. Aeration tank 2
From 4, the treated water is discharged to the outside of the tank by overflow via the transfer pipe 214.

[Evaluation] The quality and pH of the effluent discharged from the wastewater treatment tank containing organic solids of Example 2 and Comparative Example 3 were measured. The results shown in Tables 2 and 3 were obtained.

[0055]

[Table 2]

As shown in Table 2, the water discharged from the wastewater treatment tank containing organic solids of Example 2 was low in both BOD (biochemical oxygen demand) and suspended solids (SS). The wastewater treatment tank containing substances is excellent.

[0057]

[Table 3]

As shown in Table 3, the pH of the water discharged from the wastewater treatment tank containing an organic solid in Example 2 was suppressed from decreasing.

[0059]

According to the organic solid matter containing wastewater treatment tank of the present invention, there is provided a multistage aeration tank in which at least two aeration tanks are connected in series, and the organic solid matter containing wastewater is the first aeration tank. The structure is such that the suspended solids in the wastewater gradually decrease gradually as the water gradually shifts to the subsequent aeration tank, and the organic solid matter-containing wastewater that may flow in large quantities into the multistage aeration tank is increased. An appropriate amount (5% or less, more preferably about 2% or less of the capacity of the multi-stage aeration tank) is added to the concentrated solution to decompose the organic solids. Not only the BOD can be reduced and the bulking of the treated water can be prevented, but also the suspended solids in the wastewater containing organic solids can be effectively reduced.

In particular, according to the organic solid matter-containing wastewater treatment tank of the present invention, it is possible to suppress a decrease in pH in the latter aeration tank by allowing the separated wastewater to flow into the latter aeration tank. As a result, the organic solid can be decomposed in a relatively short time because a decrease in the decomposition rate of the organic solid can be suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of an organic solid matter-containing wastewater treatment tank of the present invention.

FIG. 2 is a view schematically showing a configuration of an organic solid matter-containing wastewater treatment tank used in Comparative Example 1 of the present invention.

FIG. 3 is a diagram schematically showing a configuration of an organic solid matter-containing wastewater treatment tank used in Comparative Example 2 of the present invention.

FIG. 4 is a diagram schematically showing another example of the organic solid matter-containing wastewater treatment tank of the present invention.

FIG. 5 is a diagram schematically showing a configuration of an organic solid matter-containing wastewater treatment tank used in Comparative Example 3 of the present invention.

[Description of Signs] A Organic solid matter-containing wastewater B Concentrated organic solid matter-containing wastewater 1 Inflow pipe 11, 13 Aeration tank 110 Boundary wall 12, 14 Precipitation tank 130 Boundary wall 15 Contact aeration tank 2 Precipitation separation tank 3 Sedimentation part 4 Transfer pipe 5 · 5 Aeration tank 5a Transfer part 5b Assembly part 5c Aeration part 50 Multi-stage aeration tank 6 Aeration pipe 7 Rectifying bulkhead 8 Outflow pipe

Claims (4)

[Claims] 1. A wastewater treatment tank comprising a multistage aeration tank in which at least two aeration tanks for decomposing wastewater containing organic solids under aerobic conditions are connected in series, Organic solid matter characterized in that, as the organic solid matter-containing wastewater sequentially shifts from the first aeration tank to the subsequent aeration tank, suspended solids in the wastewater are gradually reduced in a stepwise manner. Contained wastewater treatment tank. 2. The wastewater treatment tank according to claim 1,
An organic solids-containing wastewater treatment tank, wherein a device for concentrating organic solids-containing wastewater to be charged into the multistage aeration tank is provided in a stage preceding the multistage aeration tank. 3. The wastewater treatment tank according to claim 1, wherein each of the aeration tanks constituting the multi-stage aeration tank has a shape in which the organic solid matter in the tank is inclined downward from the side wall of the tank. A transfer unit for sending to the lower part, a collection part of the organic solid formed near the end of the transfer part, an air diffusion unit provided with an air diffusion device near the deepest part of the collection part; An organic solid matter-containing wastewater treatment tank, comprising a rectifying partition having an opening at the deepest position of the collecting part and near the upper water surface of the transfer part, while partitioning the part and the collecting part from the air diffusing part. . 4. A wastewater treatment tank comprising a multistage aeration tank in which at least two aeration tanks for decomposing wastewater containing organic solids under aerobic conditions are connected in series, Each aeration tank is provided with a settling tank communicating with the bottom of the tank,
An organic solid matter-containing wastewater treatment tank, characterized in that separated wastewater obtained by separating sludge in a treatment liquid in a precipitating sedimentation tank is caused to flow into a subsequent aeration tank.