JP3142238B2 - Purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for purifying sewage containing organic matter by using microorganisms.

[0002]

2. Description of the Related Art Restaurants, hotels, factories, public facilities,
The sewage discharged from livestock facilities and the like is generally provided with an adjustment tank for receiving the discharged raw water, an agglutination reaction tank for receiving the sewage discharged from the adjustment tank and aggregating fine solids with a coagulant, Purification apparatus including: a separation tank that receives wastewater discharged from a tank to separate solids (granules) and a liquid; and a storage tank that receives and stores solids (granules) separated by the separation tank. Processing.

[0003] The flocculation reaction tank is for flocculating small particles in wastewater into large particles by a flocculant, and therefore a large amount of flocculant is added to the wastewater in the reaction tank. The separation tank separates and removes agglomerated particulates or solids from the liquid. The solid separated in the separation tank is supplied to a storage tank together with a small amount of sewage. The solid matter in the storage tank is a high concentration of sludge, which is removed at a predetermined time and discarded.

However, in the conventional purification apparatus, a large amount of sludge is generated because the solid matter separated in the separation tank is merely stored in the storage tank. Further, since a large amount of coagulant is added to the wastewater, the amount of sludge generated further increases. Furthermore, since the solid matter in the storage tank is simply disposed of as excess sludge, the cost required for disposal of the excess sludge is enormous.

[0005]

An object of the present invention is to reduce the amount of sludge to be disposed of.

[0006]

A purifying apparatus according to the present invention comprises a first treatment tank into which sewage to be treated flows, and a first treatment tank for supplying oxygen to the sewage in the first treatment tank. A first air diffuser disposed at the bottom of the first processing tank, a first discharger for discharging sewage in the first treatment tank, and a sewage discharged by the discharger for separating solid matter from the sewage. Separating means, a second processing tank for receiving the solid matter separated by the separating means, and a second processing tank arranged at the bottom of the second processing tank to supply oxygen to the sludge in the second processing tank. It includes a second air diffuser and a second discharger for returning sludge in the second processing tank to the first processing tank.

[0007] The sewage to be treated generally contains organic matter. Such sewage is stirred by receiving oxygen from the first air diffuser in the first treatment tank, whereby the microorganisms are activated, and activated sludge containing the activated microorganisms is generated in the first treatment tank. . For this reason, the organic matter in the first treatment tank is subjected to the adsorption action and the oxidation action by the activated sludge.

In the second treatment tank, microorganisms are supplied together with or as a part of the solid matter from the separation means.
The contents in the second processing tank are sludge having fluidity and contain high-concentration solids. Such sludge is agitated by receiving oxygen from the second air diffuser, whereby the microorganisms are activated again in the second treatment tank. The microorganisms activated in the second treatment tank are returned to the first treatment tank as activated sludge, and again contribute to organic substance adsorption and oxidation in the first treatment tank.

Since the energy of the microorganisms in the second treatment tank is low, the microorganisms in the second treatment tank are starved by the activation of the second diffuser for a predetermined period.
For this reason, many microorganisms auto-oxidize in the second processing tank, and the solids in the second processing tank decrease. In addition, the starved microorganisms are returned to the first treatment tank,
In the first treatment tank, it greatly contributes to adsorption and oxidation of a large amount of organic substances.

According to the present invention, the microorganisms are activated in the first treatment tank for receiving the sewage to be treated, thereby contributing to the adsorption of organic substances, and the second treatment for receiving the solid matter separated in the separation tank.
The microorganisms are reactivated and starved in the first treatment tank to contribute to the reduction of sludge in the second treatment tank, and the starved microorganisms are returned to the first treatment tank and returned to the first treatment tank.
In the second treatment tank, the adsorption of the organic matter is again performed, so that the adsorption of the organic matter by the microorganisms and the reduction of the sludge in the second treatment tank are effectively performed. Therefore, the amount of the sludge to be discarded is reduced. Significantly reduced compared to conventional purifiers.

Since activated sludge generally has an action of adsorbing pollutants in sewage, activated sludge (particles) in sewage supplied to the separation means can be applied to the separation means without adding a flocculant. By adsorbing each other or other particulates until they reach them, they grow into solids of some size. Therefore, a flocculant may or may not be added to the sewage supplied to the separation means. When a coagulant is added, the amount may be significantly smaller than that of a conventional purification device.

For the solid-liquid separation in the separation means, an appropriate means such as spontaneous sedimentation separation of solid matter and natural or forced levitation separation of solid matter can be used. However, it is preferable that the separation unit is a unit that separates the solid by floating the solid by attaching air bubbles to the solid with pressurized water. Thereby, since the concentration of the separated solid is higher than the case where the solid is separated by natural settling and natural levitation,
Sludge reduction and microbial activation in the second treatment tank are more effectively performed.

[0013] The purifying apparatus further includes a circulating means for returning a part of the sewage discharged by the first discharge means to the first treatment tank, and the first treatment tank is adapted to cause the sewage to be treated to flow down sequentially. A plurality of processing chambers sequentially communicated with each other at the bottom are provided, the first discharging means discharges sewage in the lowermost processing chamber of the first processing tank, and the circulating means discharges sewage discharged by the first discharging means. It is preferable that a part is returned to the uppermost stream processing chamber of the first processing tank, and the first air diffusing means includes an air diffusing pipe arranged at the bottom of each processing chamber of the second processing tank. Thereby, the concentration of the sewage in the first treatment tank is made uniform, and therefore, the circulation of the sewage in the first treatment tank is combined with the arrangement of the diffuser pipe in each treatment chamber. First
The purifying action in the processing tank is enhanced.

[0014] In the purification apparatus of the present invention, the second processing tank includes a plurality of processing chambers through which solids from the separation means flow sequentially, and the second discharging means includes a plurality of processing chambers. The sludge in the downstream processing chamber is discharged, and the reflux means returns a part of the sludge discharged by the second discharging means to the uppermost processing chamber of the second processing tank, and the second air diffuser The means includes an air diffuser disposed in each processing chamber of the second processing tank. Therefore, according to the present invention, furthermore, the circulation of the sludge in the second processing tank and the arrangement of the diffuser tube in each processing chamber combine to allow the microorganisms to pass through the second processing tank. In the second embodiment, the sludge is more effectively reduced in the second treatment tank.

[0015] Each of the first and second discharging means includes:
A pump for discharging sewage and a sensor for detecting the level of sewage in the corresponding treatment tank, and an output signal of the sensor for maintaining the level of sewage in the corresponding treatment tank within a predetermined range. It is preferable to drive the pump based on the following. This stabilizes the processing capacity in the first and second processing tanks.

Further, the apparatus may include bypass means for supplying a part of the sewage discharged by the first discharge means to the second treatment tank.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG.
Is a first treatment tank 12 into which sewage to be treated flows, a plurality of first air diffusers 14 for supplying oxygen to sewage in the first treatment tank, and a sewage liquid in the first treatment tank 12. The first to discharge
Discharge means 16, separation means 18 for receiving the sewage discharged by the discharge means and separating solids from the sewage, and a second treatment tank 2 for receiving the solids separated by the separation means
0, a plurality of second air diffusers 22 for supplying oxygen to the sludge in the second processing tank, and the first sludge in the second processing tank 20.
A second discharging means 24 for returning to the uppermost stream portion of the processing tank 14,
Part of the wastewater discharged by the first discharging means 16
A circulation pipe 26 for returning to the uppermost stream of the processing tank 14, a recirculation pipe 28 for returning part of the sewage discharged by the second discharging means 24 to the uppermost stream of the second processing tank 20, 1
And a bypass pipe 30 for supplying a part of the sewage discharged by the discharging means 16 to the uppermost stream portion of the second treatment tank 14.

As shown in FIGS. 1, 2 and 3, the first
Of the processing tanks 12a, 12b, 12 in the example shown in FIG.
c. Adjacent processing chambers are defined by partition walls 32. Each partition has at the bottom a communication hole 34 that allows sewage to be treated to flow from the upstream processing chamber to the downstream processing chamber.

The sewage to be treated is a raw water introduction pipe 36
Is supplied to the most upstream processing chamber 12a. Sewage returned by circulation means or circulation pipe 26 and second
The sludge supplied by the discharging means 24 is also supplied to the uppermost processing chamber 12a. The sewage in the uppermost processing chamber 12a sequentially flows down from the uppermost processing chamber 12a to the lowermost processing chamber 12c through one or more intermediate processing chambers 12b.

A plurality of (two in the illustrated example) first air diffusers 14 are arranged at the bottom of each processing chamber of the first processing tank 12. Each first air diffuser 14 has a number of air blowing devices (not shown), and the air supply pipe 3
8 are connected to a common air supply pump 40. For this reason, the sewage in the first processing tank 12 is agitated and blown out by the air jetted from each diffuser 14 to the bottom of the processing chamber.

The first discharge means 16 is provided in the first processing tank 12.
A sewage discharge pump 42 for discharging sewage therein, and a level sensor 44 for detecting the level of sewage in a corresponding treatment tank are provided. The pump 42 is driven based on the output signal of the sensor 44 to maintain the level of wastewater in the corresponding treatment tank within a predetermined range. The pump 42 discharges sewage at the bottom of the most downstream treatment room 12c. The sewage discharged by the pump 42 is supplied to the separation unit 18 via a sewage discharge pipe 46, a screen unit 48, a flow control valve 50, and a sewage supply pipe 52.

The screen unit 48 includes the flow control valve 5
It has a function of adjusting the amount of sewage supplied to zero, a function of removing residue from sewage, and a function of spilling sewage supplied from the pump 42 to the circulation pipe 26. The residue in the sewage is received by a bucket arranged in the screen unit 48 and taken out from the screen unit 48 together with the bucket. The flow control valve 50 has a function of diverting a part of the sewage supplied from the screen unit 48 to the bypass means, that is, the bypass pipe 30.

The separation means 18 includes a separation tank 56 for separating solids in the sewage supplied from the sewage supply pipe 52, and a pressurizing means for pressurizing the sewage in the separation tank and forming pressurized water in which air is dissolved. The pump includes a pump 58 and a pressurized water tank 60 for storing pressurized water formed by the pressurized pump 58.

The separation tank 56 releases the pressurized water supplied from the pressurized water tank 60 to normal pressure in the separation tank 56 to cause the bubbles in the pressurized water to adhere to the particles in the sewage in the separation tank 56, that is, solids. The floating solid is separated by a suitable removing means such as a scraper or a skimmer blade.

The pressurizing pump 58 sucks the sewage in the separation tank 56 and the air through the valve 62, pressurizes the both to create pressurized water, and pressurizes the created pressurized water into the pressurized water tank 6
Supply 0. The suction part of the sewage and the supply part of the pressurized water in the separation tank 56 are separated from each other. Pressurized water tank 60
Temporarily stores the pressurized water supplied from the pressurizing pump 58 and supplies the stored pressurized water to the separation tank 56.

The solid separated in the separation tank 56 is
The sludge is discharged to the uppermost stream portion of the second treatment tank 20 by the sludge discharge pipe 64. The solids which have naturally settled at the bottom of the separation tank 56 are passed through the second processing tank 20 from the bottom of the separation tank 56 via a pipe 66 for discharging sludge, a valve 68 and a pipe 64.
Is supplied to the uppermost stream. A part of the sewage in the separation tank 56 is supplied to the upstream part of the second treatment tank 20 together with the separated solid matter and the solid matter that has settled naturally. Separation tank 56
The clear water inside flows out through the treated water outflow pipe 70.

As shown in FIGS. 1, 4 and 5, the second
Is provided with a plurality of (three in the illustrated example) processing chambers 20a, 20b, and 20c for sequentially flowing down sludge. Adjacent processing chambers are defined by partition walls 72. The most upstream processing chamber 20a and the processing chamber 12 following the processing chamber
b, the sludge and the sewage are disposed in the treatment chamber 20a.
An overflow hole 74 is provided at the upper part of the overflow hole 74, which allows the overflow to the processing chamber 20b. On the other hand, each partition separating adjacent processing chambers 20b and 20c other than the processing chamber 20a has a communication hole 76 that allows sludge and wastewater to flow from the upstream processing chamber to the downstream processing chamber. Have at the bottom.

The solid matter is supplied to the uppermost processing chamber 20a by a sludge discharge pipe 64. The sludge supplied by the reflux means, that is, the sludge supplied by the reflux pipe 28, and the sewage supplied by the bypass pipe 30 are also disposed in the most upstream treatment chamber 20a.
Supplied to The contents in the second processing tank 20 are sludge having fluidity and contain high-concentration solids. The sludge in the uppermost processing chamber 20a is discharged from the uppermost processing chamber 20a by 1
Through the above intermediate processing chamber 20b, the lowermost processing chamber 20
c.

A plurality of (two in the illustrated example) second diffuser tubes 22 are arranged at the bottom of each processing chamber of the second processing tank 20. Each second air diffuser 22 has a number of air blowing devices (not shown), and the air supply pipe 7
8 are connected to a common air supply pump 80. For this reason, the sewage in the second processing tank 20 is agitated and blown out by the air jetted from each diffuser pipe 22 to the bottom of the processing chamber.

The second discharging means 20 includes a second processing tank 20.
A wastewater discharge pump 82 for discharging wastewater in the tank; and a level sensor 84 for detecting the level of wastewater in the corresponding treatment tank. The pump 82 is based on the output signal of the sensor 84,
The liquid is driven to maintain the liquid level in the corresponding processing tank within a predetermined range. The pump 82 is connected to the most downstream processing chamber 2.
Discharge the sludge at the bottom of 0c. The sludge discharged by the pump 82 is passed through a sludge discharge pipe 86 and a diversion unit 88 to form a sludge return pipe 90 and a return pipe 2.
And 8.

The reflux unit 88 has a function of adjusting the amount of sludge returned to the first treatment tank 12 via the pipe 90 and a function of dividing the sludge supplied from the pump 82 to the reflux pipe 28. The pipe 90 returns the sludge to the uppermost processing chamber 12 a of the first processing tank 12.

In the illustrated example, the diffuser tubes 14 and 22 each extend in the width direction of the corresponding processing tank. However, if the arrangement is suitable for the air supply function and the stirring function in the processing tank,
It can be arranged in an appropriate state such as a state in which the processing tank extends in the longitudinal direction. The flow control valve 50 is connected to the level sensor 8 so that the liquid level in the second processing tank 20 becomes a predetermined value.
4 by the control of the sensing signal, the flow control valve 5
The amount of sewage supplied to the second treatment tank 20 may be adjusted from 0.

Although not shown, the second processing tank 2
0 is provided with a means for discharging excess sludge from the second processing tank 20 when the amount of sludge in the second processing tank 20 becomes too large.

In the purification device 10, the sewage supplied to the first treatment tank 12 by the pipe 36 is supplied to the first treatment tank 1.
In 2, the air is agitated by the air spouted from each first air diffuser 14 and receives oxygen. Thereby, the first
Microorganisms in the processing tank 12 are activated, and activated sludge containing the activated microscopic substances is generated in the first processing tank 12. Thereby, the organic matter in the first treatment tank 12 is subjected to the adsorption action and the oxidation action by the activated sludge.

The sewage in the first treatment tank 12 is supplied to a pump 42
Is discharged to the separation tank 56 via the pipe 46, the screen unit 48, the flow control valve 50, and the pipe 52. However, since a part of the sewage discharged by the pump 42 is returned to the processing chamber 12 a by the circulation pipe 26, even if the sewage is not supplied from the pipe 36, the sewage in the first processing tank 12 is removed from the processing chamber 12. 12a, 12b and 12c are forcibly circulated and purified.

The activated sludge (particles) in the sewage supplied to the separation means 18 absorbs each other or other particulate matter in the first treatment tank 12 and during the supply to the separation tank 56. Grow into solids of some size.

The sewage containing such activated sludge receives pressurized water from a pressurized water tank 60 in a separation tank 56. Thereby, many solids in the sewage in the separation tank 56 are floated and separated by the bubbles attached by the pressurized water. In addition, a part of the solids settles naturally in the separation tank 56.

The solids separated in the separation tank 56 and the solids settled in the separation tank 56 are connected to pipes 64 and 66.
Is supplied to the processing chamber 20 a of the second processing tank 20.
Further, a part of the sewage discharged by the pump 42 is also supplied to the processing chamber 20a by the bypass pipe 30.

The contents of the second processing tank 20 are sludge having fluidity and contain high-concentration solids. Such sludge is agitated by air jetted from the second air diffuser 22 and replenished with oxygen. Thereby, microorganisms supplied from the separation tank 56 together with or as a part of the solid matter are activated again in the second treatment tank 20, and activated sludge is generated in the second treatment tank 20.

However, since the energy of the microorganisms in the second processing tank 20 is small, the microorganisms in the second processing tank 20 are starved by the long-term activation by the second air diffuser 24. Therefore, many microorganisms are auto-oxidized in the second processing tank 20, and solid matter, that is, sludge in the second processing tank 20 is significantly reduced.

The sewage in the second treatment tank 20 is fed by a sludge discharge pump 82 to a sludge discharge pipe 86 and a reflux unit 8.
8 and the first treatment tank 1 via the sludge return pipe 90.
Returned to 2. However, since a part of the sludge discharged by the pump 82 is returned to the processing chamber 20a by the reflux pipe 28, the sewage in the second processing tank 20 is discharged to the processing chamber 20a.
a, 20b, and 20c are forcibly circulated, and the activated sludge is
Be more activated and starved. For this reason,
More microorganisms are auto-oxidized in the second treatment tank 20, and the sludge in the second treatment tank 20 is further reduced.

The microorganisms that have survived despite being starved in the second treatment tank 20, that is, activated sludge, have been returned to the first treatment tank 12 by the return pipe 90, so that the first treatment is performed. In the tank 12, a large amount of organic matter is adsorbed and oxidized.

The sewage that has been purified by the purification device 10 is supplied to the first treatment tank 12 through the pipe 36 as new sewage, and the liquid level of the entire device rises.
It flows out from the pipe 70 of the separation tank 56 as clarified water. The clarified water flowing out of the pipe 70 is discharged to the sewer as it is or supplied to the secondary treatment facility. Inorganic substances in the sewage to be treated are removed by the screen unit 48. The inorganic substance may be removed from the second storage tank 20 by an appropriate means.

In the purification device 10, the amount of sludge in the second treatment tank 20 gradually increases. However, when the operation of the purification device 10 is continued, the increase in the amount of sludge in the second treatment tank 20 is gradually reduced without performing the sludge disposal treatment, and the continuous operation period becomes 2 hours.
When the time reaches about 0 to 60 days, the amount of sludge in the second treatment tank 20 is stabilized at a substantially constant value. Therefore, the amount of sludge to be disposed of as excess sludge is significantly smaller than that of a conventional purification device.

In the purifying apparatus 10, sludge is effectively reduced without adding a chemical. However, a bioactivator of bacilli or a sludge activator such as phosphorus, nitrogen, silica or magnesium may be added to the sewage. These chemicals can be added, for example, to the uppermost processing chamber 12a of the first processing tank 12.

Experimental example

The purifier 10 and the conventional purifier described in the section of the prior art were operated for 30 days. For raw water, wastewater from a food factory was divided into two parts, a purification device 10 and a conventional purification device, to give a treatment amount of 120 cubic meters per day.

In a conventional purifying apparatus, PAC is set to 2100 kg / month and NaOH is set to 100
0 kg / month and PAA were added at a rate of 21 kg / month. On the other hand, in the purification device, the bio-biochemical was 4.0 k
g / month and sludge activator were added at a rate of 75 kg / month.

As a result of the experiment, the amount of sludge generated per day after the lapse of 30 days was 1.6 cubic meters in the conventional purifier.
However, it was only 0.06 cubic meters in the purification device 10. Therefore, according to the purification device 10, the amount of sludge to be disposed of is significantly reduced as compared with the conventional case.

The reason why the amount of sludge to be discarded is reduced by the purification device 10 is that microorganisms (organic sludge) are activated in the first treatment tank 12 to contribute to the decomposition of organic substances,
In the second treatment tank 20 receiving the separated solid matter (sludge), the microorganisms are activated again to be starved, and the starved microorganisms (activated sludge) are returned to the first treatment tank 12 for the first treatment. Activated sludge has a function of adsorbing pollutants in sewage water, and the activated sludge (particles) supplied to the separation tank 56 contains a flocculant. Even if it is not added, by adsorbing each other or other particulate matter until it reaches the separation tank 56, it grows into a solid matter having a certain size.

As a result of the above, according to the purifying apparatus 10, solid substances, particularly organic substances, are effectively decomposed by microorganisms, so that the amount of sludge to be disposed of is significantly reduced as compared with the conventional purifying apparatus. There is no need to add a flocculant to the sewage supplied to the separation tank 56, and the amount of sludge to be disposed of is further reduced. However, a coagulant may be added to the sewage supplied to the separation tank 56 to increase the solid-liquid separation efficiency in the separation tank 56. Further, according to the purification device 10, since the activated sludge circulates through the purification device 10, the odor is effectively absorbed by the activated sludge, and the generated odor is significantly reduced.

Like the purifier 10, the first and second processing tanks 12 and 20 are divided into a plurality of processing chambers, and sewage and sludge are circulated in the first and second processing tanks 12 and 20. If it is, the microorganisms can be effectively activated, and the decomposition of organic substances can be effectively enhanced. However, the first and second processing tanks 12 and 20 do not need to be divided into a plurality of processing chambers, and the first and second processing tanks 12 and 20 do not need to be partitioned.
It is not necessary to circulate sewage and sludge in the treatment tanks 12 and 20 of the above.

In the purifier 10, the first discharging means 16
Uses a common pump 42 for supplying sewage to the separation tank 56, refluxing the sewage to the first treatment tank 12, and bypassing the sewage to the second treatment tank 20. A pump may be used. Similarly, the second discharging means 2
4 is a return pump for returning sludge to the first treatment tank;
A recirculation pump for recirculating the sludge to the second treatment tank 20 may be provided.

In the purification device 10, the activated sludge in the second treatment tank is directly returned to the first treatment tank, but the activated sludge in the second treatment tank is temporarily returned to another tank. The sludge in the second treatment tank may be indirectly returned to the first treatment tank, such as returning the activated sludge returned to the tank to the first treatment tank together with the wastewater in the tank. For example, in the case of a purification device having a raw water receiving tank that receives raw water for pumping up, the sludge in the second treatment tank is returned to the raw water receiving tank, and the activated sludge returned to the raw water receiving tank is returned to the raw water receiving tank. You may make it pump up with sewage and supply it to a 1st processing tank. Thereby, the odor generated in the raw water receiving tank is significantly reduced by the activated sludge.

The present invention is preferably applied to a purification system for raw water discharged from restaurants, hotels, factories, public facilities, livestock facilities, etc., but it is necessary to reprocess treated water discharged from raw water treatment facilities. The present invention may be applied to other purification devices such as a purification device for the next treatment and a public sewer purification treatment device.

The present invention is not limited to the above embodiment. For example, instead of using a pressurized flotation separation device as the separation means 18, another separation device such as a natural sedimentation type separation device may be used.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a purification device according to the present invention.

FIG. 2 is a cross-sectional view of a first processing tank used in the purification device of FIG.

FIG. 3 is a longitudinal sectional view of a first processing tank of FIG. 2;

FIG. 4 is a cross-sectional view of a second processing tank used in the purification device of FIG.

FIG. 5 is a longitudinal sectional view of a second processing tank in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Purification apparatus 12 1st processing tank 14 1st air diffuser 16 16 1st exhaust means 20 2nd processing tank 22 2nd air diffuser 24 2nd exhaust means 26 Circulation pipe 28 Reflux pipe 30 Bypass Pipe 36 Raw water introduction pipe 40, 80 Air supply pump 42, 82 Discharge pump 44, 84 Level sensor 56 Separation tank 12a, 12b, 12c Processing chamber 20a, 20b, 20c of first processing tank Second processing Processing chamber of tank

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Claims (6)

(57) [Claims] 1. A first treatment tank into which sewage to be treated flows, and a first dispersion tank disposed at the bottom of the first treatment tank to supply oxygen to sewage in the first treatment tank. Gas means, first discharge means for discharging sewage in the first treatment tank, separation means for receiving sewage discharged by the discharge means and separating solids from sewage, separation by the separation means A second processing tank for receiving the solid matter, a second air diffuser disposed at the bottom of the second processing tank for supplying oxygen to the sludge in the second processing tank, A second discharge means for returning the sludge in the processing tank to the first processing tank, and a reflux means for returning a part of the sludge discharged by the second discharging means to the second processing tank, The second processing tank includes a plurality of processing chambers for sequentially flowing solids from the separation unit, and the second discharge unit includes the processing chamber. Discharging the sludge in the lowermost processing chamber of the second processing tank, the reflux means returns a part of the sludge discharged by the second discharging means to the uppermost processing chamber of the second processing tank, The purifying apparatus, wherein the second air diffuser includes an air diffuser disposed in each processing chamber of the second processing tank. 2. The purifying apparatus according to claim 1, wherein the separation unit is a unit that separates the solid by floating the solid by attaching air bubbles to the solid with pressurized water. 3. A circulating means for returning a part of the sewage discharged by the first discharge means to the first treatment tank, wherein the first treatment tank causes the sewage to be treated to flow down sequentially. A plurality of processing chambers that are sequentially communicated at the bottom thereof, wherein the first discharging means discharges sewage in a processing chamber located at the most downstream of the first processing tank, and the circulating means is provided by the first discharging means. A part of the discharged sewage is returned to the uppermost processing chamber of the first processing tank, and the first air diffuser is provided with an air diffuser disposed at the bottom of each processing chamber of the first processing tank. The purification device according to claim 1, wherein the purification device is provided. 4. A processing chamber on the upstream side of the second processing tank and a next processing chamber are communicated with each other at an upper portion so that sewage in the processing chamber on the upstream side of the second processing tank overflows. The purification device according to claim 1, 2 or 3. 5. Each of the first and second discharging means includes a pump for discharging sewage and a sensor for detecting a level of sewage in a corresponding treatment tank, wherein the pump is provided with a sensor for detecting the level of the sewage. The purification device according to any one of claims 1 to 4, wherein the purification device is driven based on the output signal so as to maintain the level of the wastewater in the corresponding treatment tank within a predetermined range. 6. The purification system according to claim 1, further comprising a bypass unit for supplying a part of the sewage discharged by the first discharge unit to the second treatment tank. apparatus.