JP2984579B2 - Biological reaction tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to sewage,
In connection with the improvement of biological reaction tanks that purify wastewater such as wastewater,
In particular, the present invention relates to a biological reaction tank capable of stably purifying sewage for a long period of time and reducing initial costs and maintenance costs.

[0002]

BACKGROUND OF THE INVENTION The anaerobic-aerobic activated sludge method used for removing phosphorus in sewage such as sewage and wastewater is a variation of the standard activated sludge method, which is a method of BOD (biochemical oxygen demand) and phosphorus. It is a process that is effective for simultaneous removal and prevention of bulking (a phenomenon in which activated sludge expands due to the growth of filamentous bacteria and hardly sediments). Hereinafter, a description will be given with reference to FIGS. 8A and 8B of a schematic configuration explanatory view of a biological reaction tank for performing sewage treatment by the anaerobic-aerobic activated sludge method. The sewage 9 flowing out first flows into the anaerobic tank 2 of the biological reaction tank 1 including the anaerobic tank 2 as the first tank and the aerobic tank 4 as the second tank. In the anaerobic tank 2, the dissolution of oxygen into the sewage in the tank is suppressed as much as possible, and phosphorus is released from the activated sludge in the sewage while maintaining the sewage in an anaerobic state where oxygen is hardly dissolved. The treated water containing the activated sludge treated in the anaerobic tank 2 flows into the aerobic tank 4. Here, the dissolution of oxygen into the treated water is promoted, and while maintaining the aerobic state, the activated sludge absorbs more phosphorus than the amount released in the anaerobic tank 2 and flows into the final sedimentation basin 8. In the final sedimentation basin 8, water and phosphorus-containing activated sludge are separated and discharged as treated water 10, and a part of the activated sludge is sent to the anaerobic tank 2, while the remaining activated sludge is converted into excess sludge. It is sent to the process and processed.

In order to effectively remove phosphorus, it is important to maintain the anaerobic tank 2 in an anaerobic state and to sufficiently release phosphorus from the activated sludge. It is effective to stir. To stir the sewage while maintaining the anaerobic state, the sewage is stirred by a mechanical stirrer 5, or bubbles are released from the fine bubble diffusing device 6 into the sewage to stir. In this case, in order to suppress the dissolution of oxygen into the sewage, the amount of air supplied is reduced to a minimum amount at which activated sludge does not settle.

[0004] The recirculation-type nitrification and denitrification method used for removing nitrogen from wastewater is a modification of the standard activated sludge method and is a process that is effective for simultaneous removal of BOD and nitrogen, as described above. Hereinafter, a description will be given with reference to FIGS. 9 (a) and 9 (b) of a schematic configuration diagram of a biological reaction tank for performing sewage treatment by this circulation type nitrification and denitrification method. The sewage 9 such as sewage and drainage flows into the anoxic tank 3 of the biological reaction tank 1 including the anoxic tank 3 as the first tank and the aerobic tank 4 as the second tank. The nitrogen content, which is the ammonia nitrogen in the sewage, is promoted to dissolve in oxygen, and is nitrified by oxidation in the aerobic tank 4 in which the aerobic state is maintained, that is, converted into nitrate nitrogen. 60 of effluent from aerobic tank 4
８０80% is returned to the anoxic tank 3. In the oxygen-free tank 3, the dissolution of oxygen in the treated water is suppressed as much as possible, and the nitrate nitrogen is dissolved while the nitrate nitrogen is dissolved but the molecular oxygen is hardly dissolved. It is reduced and denitrified, that is, converted into nitrogen gas and released into the atmosphere.

In order to effectively remove nitrogen, an oxygen-free tank 3
It is important to maintain the oxygen free state and to sufficiently release the nitrate nitrogen, and it is effective to stir the wastewater in the anoxic tank 3 for this purpose. Therefore, similarly to the case of the sewage treatment by the anaerobic-aerobic activated sludge method, the sewage is stirred by the mechanical stirrer 5 or the fine bubble diffuser 6 while maintaining the oxygen-free state, and the sewage is discharged into the sewage. In order to suppress the dissolution of oxygen, the amount of air supplied is reduced to the minimum amount at which activated sludge does not settle.

[0006] In addition to the above, there is a sewage treatment disclosed in, for example, JP-A-5-317880. In this sewage treatment, the biological reaction tank is only an aerobic tank, and oxygen is supplied from an air diffuser so that the dissolved oxygen concentration in the sewage in the aerobic tank is maintained at an aerobic state of 0.5 mg / liter or less. Then, sewage is purified by simultaneously performing nitrification and denitrification.

[0007]

The mechanical stirrer and fine bubble diffuser used in the anaerobic tank and the oxygen-free tank of the biological reaction tank used for the anaerobic-aerobic activated sludge method and the circulating nitrification and denitrification method. Each has problems to be solved as described below. That is, in the former mechanical stirrer, the initial cost is high, the maintenance is difficult, and the overhaul frequency is high, so that the running cost increases. Further, in the latter fine bubble diffusing device, the solubility of oxygen in sewage becomes good, and it becomes difficult to stably maintain an anaerobic state or an anoxic state. Of course, an intermittent aeration method may be adopted in order to suppress the amount of dissolved oxygen by the fine bubble diffusing device.

[0008] The pores of the fine bubble diffuser may be clogged, and maintenance is difficult. If a mechanical stirrer is used for the anoxic tank, even if the carrier in which the microorganisms are immobilized can be put in the aerobic tank, the carrier (which is destroyed by the stirring blade) cannot be put in the anoxic tank, Improvement of sewage treatment efficiency cannot be expected in spite of running cost and difficulty of handling. On the other hand, if a fine bubble diffuser is used in the oxygen-free tank,
Carriers can be put into anaerobic tanks, anoxic tanks and aerobic tanks, but it is difficult to maintain stable anaerobic or anaerobic conditions in the anoxic tanks, making it difficult to continue stable sewage treatment. . That is, it is preferable that the anaerobic state or the anaerobic state of the anoxic tank can be easily maintained stably, and it is inexpensive and easy to handle.

Further, in the biological reaction tank disclosed in Japanese Patent Application Laid-Open No. 5-317880, an organic acid fermentation tank must be provided, and the concentration of dissolved oxygen at the end of the biological reaction tank suitable for nitrification is high. According to the facility design manual (draft) [Japan Sewage Works Association], it is about 1.5 mg / liter, and if the dissolved oxygen concentration is 0.5 mg / liter or less, the nitrification efficiency may decrease.

[0010] Accordingly, the present invention has been made in view of the above-mentioned circumstances, and provides an inexpensive and easy-to-handle biological reaction tank which enables stable operation to be continued.

[0011]

Means for Solving the Problems In order to solve the above problems, the main means employed in the biological reaction tank according to the first aspect of the present invention is that sewage such as sewage and drainage is treated in an anaerobic or anoxic state. A first tank for treating while stirring, and a second tank for treating treated water flowing from the first tank in a state where a predetermined amount of oxygen is dissolved while stirring by discharging fine bubbles from a fine bubble diffuser. And a stirrer for stirring sewage in the first tank is provided at the bottom of the first tank and has a plurality of pores having a diameter of 2 to 8 mm at a pitch of 100 to 1000 mm. It is a pneumatic device.

The main means employed by the biological reaction tank according to the second aspect of the present invention is a first tank for treating sewage such as sewage and drainage while stirring in an anaerobic state, and a processing while stirring in an oxygen-free state. Biological reaction comprising a second tank and a third tank for treating the treated water flowing from the second tank in a state in which a predetermined amount of oxygen remains while stirring by the release of fine bubbles from the fine bubble diffuser. In the tank, the first tank and the second tank
A stirrer for stirring sewage in the tank is provided at the bottom of at least one of the first and second tanks,
It is a coarse bubble diffuser having a plurality of pores having a diameter of 2 to 8 mm at a pitch of 000 mm.

The main means employed by the biological reaction tank according to claim 3 of the present invention is the biological reaction tank according to claim 1, wherein the microorganism is attached to a fixed carrier or a polymer substance to which microorganisms are adhered and immobilized. Wherein the incorporation-type carrier that has been immobilized by enclosing is introduced into at least one of the first tank and the second tank.

The main means adopted by the biological reaction tank according to claim 4 of the present invention is the biological reaction tank according to claim 2, wherein the microorganism is attached to the immobilized carrier or polymer substance to which the microorganism is adhered and immobilized. Wherein the entrapment-type carrier entrapping and immobilizing is loaded into at least one of the second tank and the third tank.

[0015]

According to the biological reactor according to claim 1 of the present invention,
The sewage in the first tank is agitated by the rise of coarse bubbles released from a plurality of pores having a diameter of 2 to 8 mm of the coarse bubble diffuser, but since the bubbles are coarse bubbles, oxygen in the bubbles dissolves in the sewage. It is difficult to reduce the amount of dissolved oxygen in the sewage. And since it is not necessary to use an intermittent aeration method as in the conventional fine bubble diffusing device, the pores of the coarse bubble diffusing device do not become clogged, and unlike the conventional mechanical stirring device. Since there are no moving parts, there is no need to frequently perform maintenance.

According to the biological reaction tank according to the second aspect of the present invention, the large bubbles released from the plurality of pores having a diameter of 2 to 8 mm of the large bubble diffuser increase the size of the first and second tanks. Each of the wastewater is agitated, but since the bubbles are coarse bubbles, oxygen in the bubbles is hardly dissolved in the wastewater, so that the amount of dissolved oxygen in the wastewater can be reduced. And since there is no need to use an intermittent aeration method as in the conventional fine bubble diffusing device, the pores of the coarse bubble diffusing device do not become clogged, and they can move like a conventional mechanical stirring device. There is no need for frequent maintenance because there are no departments.

According to the biological reaction tank of the third aspect of the present invention, microorganisms are adhered and fixed to at least one of the first tank and the second tank provided with the coarse bubble diffuser. Even if the incorporation of the incorporation-type carrier in which the microorganisms are includ- ed and immobilized in the combined-type carrier or the polymerized substance, the sewage is agitated by the rise of coarse bubbles released from the plurality of pores having a diameter of 2 to 8 mm. Because the carrier is not damaged, by the action of microorganisms that are immobilized by being attached to and immobilized on these binding-type carriers,
Wastewater in the tank can be purified with high efficiency.

According to the biological reaction tank according to the fourth aspect of the present invention, at least one of the second tank and the third tank provided with the coarse bubble diffuser is provided with the coarse bubble diffuser. 2
Since the agitation of sewage is caused by the rise of coarse bubbles released from a plurality of pores having a diameter of 〜8 mm, a combined type in which microorganisms are adhered and fixed to at least one of the second and third tanks. Even if the incorporation type carrier in which microorganisms are encapsulated and immobilized on the carrier or the high-molecular substance is thrown in, the wastewater is agitated by the rise of coarse bubbles released from a plurality of pores having a diameter of 2 to 8 mm,
Since these carriers are not damaged, the microorganisms attached to and immobilized on these bonded carriers or the microorganisms entrapped and immobilized in the inclusive carrier can efficiently remove wastewater in the tank. Purification can be performed.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described.
FIG. 1 is a schematic structural explanatory view of a biological reaction tank according to
(A), FIG. 1 (b) in the view of arrow A in FIG. 1 (a), and DO concentration (dissolved oxygen concentration) and ORP value (oxidation-reduction potential) when sewage in an anaerobic tank is stirred with coarse bubbles. FIG. 2 (a) of the distribution explanatory diagram, and FIG. 2 (b) of the DO concentration distribution and the ORP value distribution explanatory diagram when the sewage in the anaerobic tank is agitated by fine bubbles.
The relationship between the diameter of pores (pitch: 400 mm) that emits coarse bubbles and the ORP value with respect to the diameter of the pores will be described with reference to FIG.

In this embodiment, as can be clearly understood from FIG. 1A, sewage is purified by an anaerobic-aerobic activated sludge method. That is, the biological reaction tank 1 is an anaerobic tank 2 which is a first tank into which sewage 9 primarily treated from a first settling tank (not shown) flows, and an aerobic tank which is a second tank into which treated water flows from the anaerobic tank 2. And a tank 4. Anaerobic tank 2
As shown in FIG. 1 (b), a large bubble diffusing device 5 is provided at one corner of the bottom portion of the bottom plate, in which two perforated pipes having a plurality of pores 5a provided in a vinyl chloride pipe are arranged in parallel. ing. The diameter of the pores 5a of the coarse bubble diffuser 5 is 2 to 8 mm, and has a constant pitch of 100 to 1000 mm. Then, by feeding air from the air supply pipe 7 to the coarse bubble diffusing device 5, coarse bubbles are released into the wastewater from the plurality of pores 5a, and the wastewater is stirred by convection due to the rise of the coarse bubbles,
It is configured to suppress the dissolution of oxygen in sewage. The coarse bubble diffusing device 5 may be disposed at the center of the bottom of the anaerobic tank 2.

On the other hand, in the aerobic tank 4, the dissolution of oxygen into the treated water flowing from the anaerobic tank 2 is promoted. In this case, the dissolved oxygen per liter of water needs to be 1.5 mg or more.
A plurality of plate-shaped fine bubble diffusers 6 having a large number of fine pores of 00 μm are spread, air is supplied from an air supply pipe 7, and fine bubbles are discharged from the fine pores into the treatment water. It is configured to agitate the treated water.

The mode of operation of the biological reaction tank 1 having the above configuration will be described below. Phosphorus in sewage is removed by the same operation as the anaerobic-aerobic activated sludge method according to the conventional example. In the sewage purification process by removing phosphorus in the tank 1, the amount of air per tank supplied to the coarse bubble diffuser 5 is set to the minimum amount in which the sludge in the sewage does not settle, and the sewage is aerated and stirred. The amount of air supplied to the coarse bubble diffuser 5 naturally depends on the depth and size of the anaerobic tank 2, but is, for example, 7.
In the case of the anaerobic tank 2 having a length of 5 m, a length of 11 m, and a depth of 4.5 m, the flow rate is about 0.7 m ³ / min.

As described above, when the sewage is stirred by releasing coarse bubbles while suppressing the dissolution of oxygen in the sewage,
The O concentration distribution and the ORP value distribution are as shown in FIG. In this case, the diameter of the pore 5a of the coarse bubble diffuser 5 is 8
mm, and the pitch of the pores 5a is 400 mm. According to FIG. 2 (a), the DO concentration is about 0 mg / liter below the detection limit of the DO concentration meter at each measurement point, and the ORP value is the appropriate OR of the anaerobic tank 2.
It is maintained in the range of -300 to -200 mV, which is the P value range.

In order to verify the superiority of the coarse bubble diffusing device 5 according to this embodiment, a diameter of 26 mm is provided on the bottom half surface of the anaerobic tank 2.
A diffuser having a plurality of pores of 0 μm is spread, and aeration and agitation of sewage are performed by fine bubbles to obtain a DO concentration distribution and an ORP.
By examining the value distribution, it was confirmed that this example was extremely excellent. The result is as shown in FIG. That is, according to FIG. 2B, the DO concentration cannot be maintained at 0 mg / liter, and the ORP value is out of the preferable ORP value region for the anaerobic tank 2. The amount of air sent to the diffuser plate is smaller than that in the above embodiment, and is about 0.4 m ³ / m
in.

Next, a preferred diameter of the pores 5a (pitch: 400 mm) of the coarse bubble diffuser 5 will be described with reference to FIG. FIG. 3 is intended to find out a preferable range of the diameter of the pore 5a by examining how the ORP value of the sewage in the anaerobic tank 2 changes due to the difference in the diameter of the pore 5a. is there. That is, according to this figure, the suitable ORP value region of the anaerobic tank 2 is −200.
In order to secure mV or less, it is preferable to be 2 mm or more. On the other hand, even if the diameter of the pores 5a is considerably large,
Although the result that 300 mV or more can be secured is shown, if the diameter of the pores 5a is too large, the amount of consumed air becomes too large, so that 8 mm or less is practically preferable. Also,
Although the pitch of the pores 5a is not shown, if the pitch is too small, it becomes difficult to maintain the anaerobic state of the sewage in the anaerobic tank 2, and if the pitch is too large, the stirring ability is reduced and the sewage is reduced. Since the processing capacity decreases, practically 10
A preferable result is obtained when the thickness is in the range of 0 to 1000 mm.

A water quality survey was conducted to verify the effectiveness of the biological reaction tank according to the present embodiment for sewage treatment. The results are as shown in Table 1. In addition, the measurement of the water quality is based on the effluent from the first settling pond (not shown), the effluent from the anaerobic tank 2,
This is the effluent from the final sedimentation basin 8, and Table 1 also shows water quality data when the sewage in the anaerobic tank 2 is agitated by the release of fine bubbles from the fine bubble diffuser.
In Table 1, SS indicates suspended substances, S-BOD indicates soluble BOD, and STP indicates soluble total phosphorus.

[0027]

[Table 1]

According to Table 1, the SS concentration, the BOD concentration, and the STP concentration were better removed by stirring with coarse bubbles than by stirring with fine bubbles. Based on the P concentration, it is determined that the activated sludge discharges more phosphorus in the anaerobic tank 2 and ingests more phosphorus in the aerobic tank 4.

As described above, according to the biological reaction tank 1 according to the present embodiment for purifying sewage by the anaerobic-aerobic activated sludge method, the coarse bubble diffuser 5 has a diameter of 2 to 8 in a vinyl chloride pipe.
mm, so that the initial cost is lower than that of a conventional mechanical stirrer, and the running cost is lower because there is no need for overhaul. It is not necessary to use an intermittent aeration method unlike the conventional fine bubble diffusing device, and the pores 5 of the coarse bubble diffusing device 5 are not required.
Since a does not cause clogging, stable sewage treatment can be continued.

Further, in the aerobic tank 4, since the sewage is stirred by discharging the fine bubbles from the fine bubble diffuser, the sewage can have a dissolved oxygen concentration of 1.5 mg / liter or more. There is no need to provide an organic acid fermentation tank as in the biological reaction tank disclosed in Japanese Unexamined Patent Publication No. Hei 5-317880.

Next, a biological reaction tank according to a second embodiment of the present invention will be described with reference to FIG.
(A), FIG. 4 (b) in the view of arrow B in FIG. 4 (a), and DO concentration and O when sewage in the anoxic tank was stirred with coarse bubbles.
FIG. 5 (a) of the RP value distribution diagram, FIG. 5 (b) of the ORP value distribution diagram when the sewage in the anoxic tank is agitated with fine bubbles, and pores releasing coarse bubbles. The relationship between the ORP value and the diameter of (pitch 400 mm) will be described with reference to FIG.

This embodiment is an example of a biological reaction tank for performing a circulating nitrification denitrification method. As can be clearly understood from FIGS. 4 (a) and 4 (b), the main structure is as described above. The anaerobic tank 2 in Example 1 is replaced with an oxygen-free tank 3 as a first tank. The difference from Example 1 is that nitrification liquid is circulated from the aerobic tank 4 to the oxygen-free tank 3. This is a configuration in which a road is simply added.

Therefore, as in the prior art, the ammonia nitrogen in the sewage 9 flowing into the anoxic tank 3 from the first settling basin (not shown) is promoted by promoting the oxygen dissolution in the aerobic tank 4.
The ammoniacal nitrogen is oxidized to nitrate nitrogen while maintaining the aerobic state. And 60 of the effluent from the aerobic tank 4
~ 80% is returned to the anaerobic tank 3 where the oxygen dissolution in the sewage is minimized and the nitric nitrogen is dissolved but the molecular oxygen is hardly dissolved Denitrification is performed by maintaining the state and reducing nitrate nitrogen to nitrogen gas and releasing it into the atmosphere.

In such wastewater treatment by denitrification,
In the anoxic tank 3, the sewage is stirred by the bubbles released from the pores 5 a of the coarse bubble diffuser 5, while the treated water in the aerobic tank 4 flowing from the anoxic tank 3 has a large number of 260 μm in diameter. Stirring is performed by the fine bubbles released from the fine pore diffuser 6 having the fine pores, and the residual oxygen amount of the treated water in the aerobic tank 4 is kept at 1.5 mg / liter or more. Incidentally, the amount of air insufflated in the s husband coarse bubble diffuser 5 from the air supply pipes 7 and microporous diffuser 6 per tank respectively 0.7m ³ /min,0.4m ³ / min.

The DO concentration when agitating the sewage while suppressing the dissolution of oxygen in the sewage in the anoxic tank 3 with coarse bubbles,
The ORP value distribution is as shown in FIG. According to this figure, the DO concentration at each measurement point is about 0 mg / liter below the detection limit of the DO concentration meter.
The P value is an appropriate ORP value region of the anoxic tank 3-
It is maintained in the range of 300 to -200 mV.

Then, in order to verify the superiority of the coarse bubble diffuser 5 according to the present embodiment, a diffuser plate having a diameter of 260 μm is spread on the bottom of the oxygen-free tank 3 and aeration and stirring are performed by discharging fine bubbles. , DO concentration distribution and ORP value distribution were examined, and it was confirmed that this example was extremely excellent. That is, the results are as shown in FIG. 5 (b), and the DO concentration was 0 mg.
/ Liter cannot be maintained, and the ORP value is out of the preferable ORP value range for the anaerobic tank 2.
The preferred diameter of the pores 5a of the coarse bubble diffuser 5 is 2 to 8 mm as shown in FIG. 6 and the pitch is 100 to 1000 mm, as in the first embodiment. Thereby, -3
An appropriate ORP value range of 00 to -200 mV can be maintained.

Next, a water quality survey was conducted to verify the effectiveness of the wastewater treatment of this embodiment. The results are as shown in Table 2. The measurements are the effluent from the first sedimentation basin (not shown) and the effluent from the last sedimentation basin. Water quality data when stirring by release is also shown.

[0038]

[Table 2]

According to Table 2, the SS concentration, the BOD concentration, and the STN (soluble total nitrogen) concentration are better when stirring with coarse bubbles than when stirring with fine bubbles. Based on the -TN concentration, it is determined that more nitrogen has been removed. The coarse bubble diffusing device 5 provided in the oxygen-free tank 3 of the biological reaction tank 1 used for the circulating nitrification denitrification method has the same configuration as the coarse bubble diffusing device 5 in the first embodiment. Has exactly the same effect.

A biological reaction tank according to a third embodiment of the present invention will be described below with reference to FIG. That is, this biological reaction tank 1 purifies sewage by simultaneously removing phosphorus and nitrogen by a combination of an anaerobic-aerobic activated sludge method and a circulating nitrification denitrification method (anaerobic-anoxic-aerobic). Law). More specifically, the biological reaction tank 1 is an anaerobic tank 2 which is a first tank into which sewage water which has been subjected to primary treatment flows from a first settling basin (not shown), and a second tank into which treated water flows from the anaerobic tank 2. Anoxic tank 3,
An aerobic tank 4 as a third tank into which treated water flows from the anoxic tank 3. A nitrification liquid circulation path communicates from the aerobic tank 4 to the oxygen-free tank 3, and a sludge return path for returning a part of the sludge from the final sedimentation tank 8 to the anaerobic tank 2.

At one corner of the bottom of the anaerobic tank 2 and the anaerobic tank 3, although not shown, as in the case of the anaerobic tank and the anaerobic tank in the first and second embodiments, chloride Coarse-bubble diffusers 5 and 5 are provided in which two perforated pipes each having a plurality of pores are provided in a vinyl pipe. The pore diameter is 2
８8 mm and a constant pitch of 100 to 1000 mm. Then, by sending air from the air supply pipe 7 to the coarse bubble diffusing device 5, air bubbles are released into the sewage from the plurality of pores, and the sewage is stirred by convection due to the rise of the air bubbles.
It is configured to suppress the dissolution of oxygen in sewage.

Anaerobic tank 2 of biological reaction tank 1 according to this embodiment
The coarse bubble diffusing device 5 provided at the bottom of the and the oxygen-free tank 3 is the coarse bubble diffusing device 5 in the first and second embodiments.
This embodiment has the same configuration as that of the first and second embodiments.

A bioreactor according to Embodiment 4 corresponding to claim 3 of the present invention will be described. This embodiment is different from the bioreactor 1 described in Embodiment 1 or 2 based on FIG. 1 or FIG. Into the anaerobic tank 2 and the anoxic tank 3, a bonded type carrier in which specific microorganisms are adhered and immobilized on a porous substance or an inclusive type carrier in which specific microorganisms are encapsulated and immobilized on a polymer substance are charged. It is.

Conventionally, the combined carrier or the inclusive carrier could be introduced only into the aerobic tank 4 having the fine bubble diffusing device. However, since the stirring was performed by the mechanical stirring device, the oxygen-free tank was used. 3 could not be put into the wastewater.
However, according to this embodiment, even when the combined carrier or the inclusive carrier is charged, the sewage in the oxygen-free tank 3 is agitated by the bubbles released from the plurality of pores of 2 to 8 mm of the coarse bubble diffuser. Since the bonded carrier or the inclusive carrier is not destroyed, the efficiency of BOD and nitrogen removal is improved by the action of microorganisms immobilized on the bound or inclusive carrier, and the wastewater treatment capacity is improved. And the improvement of the sewage treatment capacity can reduce the size of the biological reaction tank for the same sewage treatment capacity, thereby contributing to a reduction in the cost of the biological reaction tank.

Next, a biological reaction tank according to a fifth embodiment of the present invention will be described with reference to FIG.
In the biological reaction tank 1 and the anaerobic tank 2 of the biological reaction tank 1 described in Example 3 based on the above, a specific microorganism is attached to a porous substance and immobilized by attaching a specific microorganism to the porous substance. The incorporation of the incorporation-type carrier in which the microorganisms are encapsulated and immobilized.

Therefore, even if the bound carrier or the inclusive carrier is introduced, the carrier is not destroyed, and the microorganisms immobilized on the bound carrier or the inclusive carrier act in the same manner as in Example 4 above. In addition, the efficiency of removing BOD and nitrogen is improved, which can contribute to the improvement of sewage treatment capacity, and the improvement of sewage treatment capacity can reduce the size of the biological reaction tank for the same sewage treatment capacity. This can contribute to cost reduction of the biological reaction tank.

[0047]

As described in detail above, claim 1 of the present invention
According to the biological reactor according to any one of (1) to (4), the coarse bubble diffuser 5
Has a configuration in which only a pore having a diameter of 2 to 8 mm is provided at a pitch of 100 to 1000 mm in the cylindrical member, so that the initial cost is lower than that of a conventional mechanical stirrer, and there is no movable part. Since there is no need to overhaul, running costs are also reduced. Also, unlike the conventional fine bubble diffuser, there is no need to use an intermittent aeration system, and the pores of the large bubble diffuser do not become clogged, so that stable sewage treatment can be continued. And can greatly contribute to the improvement of the economic efficiency and reliability of the biological reaction tank. Furthermore, according to the biological reaction tank according to claim 3 or 4 of the present invention, the first tank or the first and second tanks that conventionally treat sewage in an oxygen-free state may be destroyed. Since the bound carrier or the inclusive carrier which could not be introduced can be introduced, a great effect that the sewage treatment capacity is further improved by the action of the microorganisms fixed to the bound carrier or the inclusive carrier is obtained. is there.

[Brief description of the drawings]

FIG. 1 (a) is a schematic configuration explanatory view of a biological reaction tank according to Embodiment 1 of the present invention, and FIG. 1 (b) is FIG. 1 (a).
FIG.

FIG. 2A is an explanatory diagram of a DO concentration and an ORP value distribution when sewage in an anaerobic tank is stirred by coarse bubbles.
(B) shows the D when the wastewater in the anaerobic tank was stirred with fine bubbles.
It is an O density distribution and an ORP value distribution explanatory view.

Fig. 3 Pores releasing coarse bubbles (pitch: 400 mm)
FIG. 6 is an explanatory diagram showing a relationship between an ORP value and a diameter of a circle.

FIG. 4 (a) is a schematic structural explanatory view of a biological reaction tank according to Example 2 of the present invention, and FIG. 4 (b) is FIG. 4 (a).
FIG.

FIG. 5 (a) is an explanatory view of a DO concentration and an ORP value distribution when sewage in an anoxic tank is agitated by coarse bubbles, and FIG. FIG. 4 is an explanatory diagram of a DO concentration distribution and an ORP value distribution when agitating is performed.

FIG. 6 shows pores that emit coarse bubbles (pitch: 400 mm)
FIG. 6 is an explanatory diagram showing a relationship between an ORP value and a diameter of a circle.

FIG. 7 is a schematic structural explanatory view of a biological reaction tank according to Example 3 of the present invention.

FIGS. 8 (a) and 8 (b) are schematic illustrations of a biological reaction tank for performing sewage treatment by an anaerobic-aerobic activated sludge method according to a conventional example.

FIGS. 9 (a) and 9 (b) are schematic illustrations of a biological reactor for performing sewage treatment by a circulating nitrification denitrification method according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Biological reaction tank 2 ... Anaerobic tank 3 ... Anoxic tank 4 ... Aerobic tank 5 ... Large bubble diffuser 6 ... Fine bubble diffuser 7 ... Air supply pipe 8 ... Final sedimentation basin

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-328688 (JP, A) JP-A-8-1970088 (JP, A) JP-A-61-222595 (JP, A) JP-A-5-222 277486 (JP, A) JP-A-7-124582 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C02F 3/28-3/34

Claims (4)

(57) [Claims] 1. A first tank for treating sewage such as sewage and drainage while stirring it in an anaerobic state or an oxygen-free state, and treating the treated water flowing from the first tank with fine bubbles from a fine bubble diffuser. In a biological reaction tank comprising a second tank for treating in a state in which a predetermined amount of oxygen is dissolved while stirring by release, a stirrer for stirring sewage in the first tank is provided at the bottom of the first tank. , 2-8mm at 100-1000mm pitch
A biological reaction tank, which is a coarse bubble diffuser having a plurality of pores having different diameters. 2. A first tank for treating sewage such as sewage and drainage while being stirred in an anaerobic state, a second tank for treating while stirring in an oxygen-free state, and finely treating water flowing from the second tank. In a biological reaction tank consisting of a third tank for treating with a predetermined amount of oxygen remaining while stirring by the release of fine bubbles from the bubble diffuser, the wastewater in the first tank and the second tank is stirred. A stirring device is provided at the bottom of at least one of the first tank and the second tank;
A biological reaction tank, which is a coarse bubble diffuser having a plurality of pores having a diameter of 2 to 8 mm at a pitch of 0 mm. 3. A combined carrier in which microorganisms are adhered and immobilized, or an inclusive carrier in which microorganisms are encapsulated and immobilized in a polymer substance are charged into at least one of the first and second vessels. The biological reaction tank according to claim 1, wherein 4. A combined carrier to which microorganisms are adhered and immobilized or an inclusive carrier in which microorganisms are entrapped and immobilized in a polymer substance are charged into at least one of the second and third vessels. The biological reaction tank according to claim 2, wherein the reaction is performed.