JP3478241B2 - Biological treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biological treatment apparatus for removing organic matter under aerobic conditions.

[0002]

2. Description of the Related Art The activated sludge method for biodegrading BOD components is a method in which a liquid to be treated is mixed with activated sludge and aerated to aerobically decompose the BOD components to obtain treated water by solid-liquid separation and sludge. Is a method of returning the product, which is simple and easy to operate, and is the most widely used processing method at present. However, there is a problem that it is difficult to perform a high load treatment in which the BOD volume load is 1.5 kg / m ³ / d or more, and a large installation space is required for a large reaction tank. Therefore, as a method of reducing the reaction tank of the activated sludge method, a method of connecting a plurality of reaction tanks in series, that is, a method generally called a two-stage activated sludge method has been proposed (for example, JP-A-55).
-28759).

FIG. 2 is a system diagram showing a treatment apparatus using a conventional two-stage activated sludge method. In FIG. 2, 41 is a first reaction tank, 42 is a second reaction tank, and 43 is a solid-liquid separation tank. First
And the second reaction tanks 41 and 42 are diffusers 44 and
45, which are connected to the air supply paths 46 and 47, respectively, and are configured to perform aerobic treatment.

In the treatment method using the above apparatus, first, the liquid to be treated and the sludge to be returned are introduced into the first reaction tank 41 from the liquid to be treated 51 and the sludge to be returned 52, respectively, and are mixed with the activated sludge in the tank to be sent. Air diffuser 44 by sending air from airway 46
Aeration is carried out from BOD to decompose BOD by aerobic biological reaction. The mixed liquid in the first reaction tank 41 is introduced from the line 53 into the second reaction tank 42 to be mixed with the activated sludge in the tank, and the air supply passage 47
Air is sent from the air diffuser 45 to aerate the air, and BOD is decomposed by an aerobic biological reaction, and activated sludge is flocculated. The mixed liquid in the second reaction tank 42 is introduced from the line 54 into the solid-liquid separation tank 43 for solid-liquid separation, the separated liquid is taken out as a treatment liquid from the treatment liquid passage 55, and sludge is treated as a sludge passage 56.
From the waste sludge path 52, and the remaining part is taken out from the waste sludge path 57 as excess sludge.

The above-mentioned two-stage activated sludge method is a method for maintaining a high BOD concentration in the first reaction tank 41 by setting a high load in the first reaction tank 41 in the first step, thereby obtaining a high decomposition rate. is there. At this time, in the first stage, a decomposition rate 10 times or more the design value of the standard activated sludge method can be obtained. Therefore, if only removal of soluble components is considered, the reaction tank volume can be significantly reduced. However, the microorganisms that grow in the high-load first reaction tank 41 are in a dispersed state, which makes solid-liquid separation difficult.

[0006] In order to produce flocs capable of solid-liquid separation, conditions under which various microorganisms such as protozoa having a relatively low growth rate can exist are required. Therefore, as the second and subsequent reaction tanks, the second reaction tank 42 must have a sufficient sludge retention time SRT even if the BOD load is small, and the tank capacity must be large. Therefore, the total reaction tank volume including the second and subsequent stages is usually only reduced by about 30% of the standard activated sludge method. Further, even when the average sludge retention time in the second reaction tank 42 is sufficiently secured, a part of the in-tank liquid flows out of the second reaction tank 42 earlier than the retention in the average reaction time of the second reaction tank 42, and a short-pass easily occurs. There is a point. When the short path occurs, the bacteria in a dispersed state flowing in from the first reaction tank will flow out before coming into contact with the sludge flocs in the second reaction tank and being taken in. Therefore, the sludge separability in the solid-liquid separation tank 43 May decrease.

On the other hand, as another treatment method for reducing the volume of the reaction tank, a method has been proposed in which a carrier that adheres and holds microorganisms is added to the high-load biological reaction tank and the low-load biological reaction tank (see, for example, Japanese Patent Application Laid-Open No. 2000-242242). 2000-42584). This method can form sludge flocs with good solid-liquid separation, but since the high-load biological reaction tank is filled with the carrier, the effective volume of the high-load biological reaction tank is consumed by the carrier and reduced. To do.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biological treatment apparatus capable of stably and efficiently removing organic substances under high load and forming sludge having good solid-liquid separation. Is to provide.

[0009]

The present invention is the following biological treatment device. (1) A high-load bioreaction tank that decomposes organic substances by performing aeration under a high BOD load, and a mixed solution in the high-load bioreaction tank that is placed downstream of this high-load bioreaction tank and performs aeration under a low BOD load In a biological treatment apparatus provided with a low-load biological reaction tank for decomposing organic matter and flocculating sludge, and a solid-liquid separation means for performing solid-liquid separation of a mixed liquid of the low-load biological reaction tank into treated water and sludge , The volume of the low-load bioreactor
The product is 3 to 100 times the volume of the high load reaction tank,
The low-load bioreactor is a biotreatment device composed of at least two flocculation tanks connected in series. (2) The biological treatment device according to (1), wherein at least one of the flocculation tanks is filled with a microbial carrier. (3) The high-load biological reaction tank has a circulation path for circulating the liquid in the tank, a mixing device for mixing the oxygen-containing gas with the circulating liquid, and the gas-liquid mixture mixed by this mixing device is jetted into the liquid in the tank. The biological treatment apparatus according to (1) or (2) above, which is provided with a nozzle to perform and a circulation pump. (4) One of the sludges separated by the solid-liquid separation means
Equipped with a return path for returning all or part of the amount to the high-load reactor
The biological treatment according to any one of (1) to (3) above
Processing equipment.

In the present specification, the term "low-load bioreaction tank" is used as a collective term for a plurality of flocculation tanks connected in series, which are provided in the subsequent stage of the high-load bioreaction tank. Further, the term “first flocculating tank” refers to the first flocculating tank provided immediately after the high-load biological reaction tank in a plurality of floc tanks connected in series, and hereinafter, in the direction of the solid-liquid separation means. Second floc tank, third floc tank. ． ． This is called the final floc tank.
When the low-load biological reaction tank is composed of two flocking tanks, the second flocking tank is the final flocking tank.

The liquid to be treated in the present invention is an effluent containing an organic substance which is treated by a usual aerobic biological treatment method, but contains a hardly biodegradable organic substance or an inorganic substance. In addition, ammonia nitrogen or organic nitrogen may be contained. Examples of such organic drainage liquid include sewage, human waste, food factory drainage, chemical plant drainage, and other industrial drainage. The nitrogen concentration (TN) of the organic waste liquid is 1/10 of the soluble BOD concentration.
Below, it is desirable that it is 1/20 or less. When the nitrogen concentration is 1/10 or less of the soluble BOD concentration,
Since the amount of nitrogen gas generated from the nitrification denitrification reaction by the microorganisms is reduced, the solid-liquid separation failure due to the sludge floating due to the nitrogen gas in the solid-liquid separation step is prevented.

In the present invention, the high-load and low-load biological reaction tanks, the aeration means and the solid-liquid separation means can have basically the same constitutions as the conventional ones. In the present invention, in such a conventional device, The high-load bioreaction tank is not filled with the microorganism holding carrier, and the low-load bioreaction tank is composed of a plurality of flocculation tanks of 2 or more, preferably 2 to 4. Flocking tank is a conventional low-load bioreaction tank (aeration tank)
Can be used, and one aeration tank can be divided into a plurality of flocking tanks by partitioning means such as a partition plate,
It is also possible to connect different aeration tanks in series to form a plurality of flocculation tanks. When partitioning one aeration tank, it is partitioned perpendicularly to the direction of the liquid to be treated from the inlet or the direction against the flow. At least one of the flocking tanks is preferably a flocking tank filled with a microorganism holding carrier.

In the high-load biological reaction tank, the liquid to be treated is introduced and aerated by aeration means to bring it into contact with microorganisms under aerobic conditions to decompose organic substances. Mainly soluble BO in high-load bioreactors
Decompose D at high BOD load. As the high-load bioreactor, air, oxygen, or oxygen-enriched air may be used, which may be equipped with a normal aeration means such as an air diffuser, but an aeration means capable of increasing the oxygen dissolution efficiency as much as possible. It is preferable to use those equipped with, for example, those that eject a gas-liquid mixture into a liquid in a tank to generate fine bubbles; those that mechanically shred and disperse the bubbles; those that dissolve under pressure. it can. Among these, it is preferable to eject the gas-liquid mixture into the liquid in the tank to generate fine bubbles. As such a high-load biological reaction tank, a circulation path for circulating the liquid in the tank, a mixing device for mixing an oxygen-containing gas with the circulating liquid in the circulation path, and a gas-liquid mixture mixed by this mixing device are used as a tank. One that includes a nozzle that ejects into the internal liquid and a circulation pump can be given. In such a high-load bioreactor,
The mixed liquid in the reaction tank is sucked by a circulation pump, an oxygen-containing gas is mixed in the sucked circulating liquid by a mixing device, and the obtained gas-liquid mixture is introduced into the tank liquid from a nozzle provided at the tip of the circulation path. It is possible to increase the efficiency of dissolving oxygen by generating fine bubbles by ejecting the fine bubbles.

The low-load bioreaction tank is placed after the above-mentioned high-load bioreaction tank, and the mixed solution of the high-load bioreaction tank is reduced to a low BO.
It is a flocculating tank that aerates with D load to decompose organic matter and flocs sludge, and is composed of at least two tanks connected in series. By providing a plurality of flocking tanks connected in series, the averaging of the residence time is promoted, and the short path hardly occurs. Therefore, the bacteria in a dispersed state flowing in from the high-load bioreaction tank come into sufficient contact with the sludge flocs in the low-load bioreaction tank to be taken up by the flocs, which causes sludge in the solid-liquid separation step in the subsequent stage. Separation is prevented from lowering, and flocs with excellent solid-liquid separation are obtained.

The high-load bioreaction tank has a high BOD load, and the low-load bioreaction tank has a low BOD load.
The load is based on the load of soluble BOD, and the load of the soluble BOD sludge is from 2 to 40 kg-BOD in the high-load biological reaction tank.
/ Kg-VSS / d, preferably 3 to 10 kg-BOD
/ Kg-VSS / d is desirable. By setting the above load, the predominance of filamentous bacteria can be prevented. Low load biological reaction tank is 0.01-0.5kg-BOD
/ Kg-VSS / d, preferably 0.05 to 0.3 kg
-BOD / kg-VSS / d is desirable. The load of the low-load biological reaction tank is the load for the entire flocculation tank.

In the low load biological reaction tank, the effluent of the high load biological reaction tank is introduced to carry out the low load reaction. Generally, the mixed liquid of the high-load biological reaction tank is directly introduced into the first floc tank, and then the second floc tank. ． ． The final flocculating tank is introduced in this order, and aeration is carried out under a low BOD load that causes the sludge load as described above as a whole to decompose organic substances. In this case, the volume of the low-load bioreaction tank (the entire flocculation tank) can be made larger than the volume of the high-load bioreaction tank, and the residence time can be lengthened. The volume ratio of the high-load biological reaction tank to the low-load biological reaction tank is 3 to 100 times, preferably 5 to 50 times, the volume of the low-load biological reaction tank to the high-load biological reaction tank. Biological reaction tank is 0.1 to 1200 hours, preferably 0.2 to 24 hours
r, the low load biological reaction tank can be 0.5 to 24000 hr, preferably 1 to 1200 hr.

At least one of the flocculation tanks is preferably filled with a microbial carrier (hereinafter sometimes simply referred to as a carrier). By filling the carrier, the tank volume can be made smaller. The material, structure, shape, size, etc. of this carrier are not limited as long as they can retain microorganisms on the surface and / or inside, but polymer resins, inorganic materials and the like can be used as the material. Moreover, it is preferable that the structure is porous, and the pore size is 0.5 to 20 m.
m, preferably 1 to 5 mm is suitable. The shape may be a shape that can be fixed in the reaction tank, but a granular shape that can flow is preferable. In this case, the shape of the particles is spherical,
It may be of any shape such as cubic or indeterminate, and the particle size may be in a flowable range, but is 3 to 30 mm, preferably 5 to 20 m.
m, a specific gravity of 0.5 to 3.0, preferably 0.8 to 1.2.

The packing rate of the carrier in the flocculation tank is 20.
It is desirable to be 90%, preferably 30-60%. The above-mentioned filling rate shows the ratio of the apparent volume of the carrier before the attachment of microorganisms to the volume of the low-load biological reaction tank. In a floc tank filled with a carrier, microorganisms can be attached to the carrier by aerating with aeration means. When the carrier is filled, it is preferable to provide a carrier separating means such as a screen so that the carrier can be separated and the mixed liquid can be taken out.

The above-mentioned high-load biological reaction tank carries out a high-load reaction step, and this step may be composed of one aeration tank or may be composed of a plurality of aeration tanks. The plurality of aeration tanks may be provided in parallel, or may be provided in series (stepwise).
By providing a plurality of aeration tanks as the high load biological reaction tank, it is possible to easily and stably perform the high load biological reaction even when the water quality of the liquid to be treated changes. Especially, when they are installed in series, the effect of preventing filamentous bacteria is great. Further, an intermediate step or another step may be interposed between the high load and low load reaction steps.

As the solid-liquid separation means in the solid-liquid separation step, known solid-liquid separation means such as a precipitation separation tank, a pressure flotation tank and a membrane separation device can be used. Alternatively, the whole amount is returned to the reaction tank. Usually, it is returned to the high-load bioreaction tank, but it may be returned to the low-load bioreaction tank or both. If the BOD concentration of the liquid to be treated is very high, the return may not be necessary in some cases.

In the treatment by the biological treatment apparatus of the present invention, the liquid to be treated is introduced into the high-load biological reaction tank as a high-load reaction step and aerated under a high BOD load to decompose organic substances. In the high-load biological reaction tank, the BO in the reaction tank is subject to high-load processing.
It is necessary to maintain a high D concentration,
It is preferable to set the load to 40 kg-BOD / kg-VSS / d, especially in the above range. Since the carrier is not added to the high-load bioreactor, the consumption of the effective volume by the carrier does not occur, and thus the treatment can be performed at a higher load.

In the low-load reaction step, the mixed solution of the high-load biological reaction tank is sequentially introduced from the first flocculating tank to the final flocculating tank to aerate at a low BOD load to remove BOD under aerobic conditions. Floc the sludge. Contrary to the high-load bioreactor, the low-load bioreactor can lower the BOD load to some extent to enable flocculation of microorganisms with a small reaction tank volume. When the carrier is filled, it is desirable to add 20 to 90%, preferably 30 to 60% of carrier. Many types of microorganisms are involved in the process of flocculation, and there are many unclear parts.However, it is necessary to maintain diverse species by mixing protozoa that prey on bacterial bodies and bacteria with a low growth rate. , The sludge retention time SRT required for that is 4
It is said that it takes about 10 days. By providing a plurality of flocculation tanks, it is possible to promote averaging of residence times and make it difficult for short paths to occur. Therefore, flocs having excellent solid-liquid separation properties can be formed. Further, when the carrier is filled, it becomes possible to maintain a sufficient amount of these microorganisms that require the above SRT in the system, and stable flocculation can be achieved with a smaller reaction tank volume.

The reason why the BOD load is set low is as follows.
This is because the protozoa prey on the bacteria in the dispersed state generated by the high-load treatment in the preceding stage, and promote the production of mucous substances for the flocculation of the bacteria. When the carrier is filled, oxygen can be supplied to the microorganisms inside the carrier when the BOD load is low, so that a large amount of microorganisms having a long required SRT can be retained in the reaction tank. Therefore, the tank volume can be further reduced. The sludge load suitable for keeping the oxygen supply inside the carrier suitable is within the above range, and in order to facilitate the oxygen supply to a large amount of the carrier, the carrier is preferably granular.

By performing aeration in this way, B
As the OD is removed, the dispersible sludge introduced from the high-load bioreactor becomes floc. Excessively attached sludge is peeled off to form floating flocs, which are sent to the solid-liquid separation step as a mixed liquid. Further, since the low-load bioreaction tank is always supplied with undissolved soluble BOD components in the high-load bioreaction tank, that is, the relatively difficult-to-decompose soluble BOD component, the carrier is relatively hard-to-degrade organic matter. It is also possible to prevent the increase of COD in the treated water by accumulating microorganisms that decompose the water.

In the solid-liquid separation step, the mixed liquid in the final flocculation tank is subjected to solid-liquid separation, the separated liquid is taken out as a treatment liquid, and if necessary, part or all of the separated sludge is returned to the high-load bioreaction tank to remove excess sludge. If it occurs, send it to the dehydration system.

[0026]

Industrial Applicability The biological treatment apparatus of the present invention comprises a high-load bioreaction tank for decomposing organic substances by aeration under a high BOD load,
And a low load bioreactor to floc the sludge with decomposing organic matter mixed solution by performing aeration with low BOD load of high load biological reactor, the volume of the low-load bioreactor is
3 to 100 times the volume of the high load reaction tank, and low
Since the loaded biological reaction tank is composed of at least two tanks connected in series, it is possible to stably and efficiently remove organic substances with a high load and to form sludge with good solid-liquid separation. You can

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of the treatment apparatus of the embodiment, and shows an example in which two flocking tanks are provided in series as low-load biological reaction tanks, and both flocking tanks are filled with a carrier.

In FIG. 1, a high-load biological reaction tank 1 is provided with a circulation path 2 for circulating the liquid in the tank, and a downward pipe 3 having both ends opened and vertically supported in the liquid in the tank. A circulation pump 4 and an air mixing device 5 are provided in the passage 2. A nozzle 6 is provided at the tip of the circulation path 2 while being accommodated in the upper end opening portion of the downward tube 3. An air supply path 7 is connected to the air mixing device 5, air and the circulating liquid are mixed by the air mixing device 5, and this gas-liquid mixture is jetted from the nozzle 6 into the liquid in the tank to perform aerobic treatment. Is configured. The high load biological reaction tank 1 is connected to a liquid passage 11 to be treated and a return sludge passage 12. The high load biological reaction tank 1 is not filled with a carrier.

First and second flocculating tanks 13, 14
Are provided in series by partitioning one aeration tank by a partition plate 15 in a direction perpendicular to the direction of the liquid to be treated from the inlet, and these constitute a low-load biological reaction tank. The partition plate 15 is provided so that the mixed liquid in the first floc tank 13 overflows the partition plate 15 and flows into the second floc tank 14. Although it is possible to form a circulation hole in the partition plate 15, a shape that does not cause back mixing is preferable. The first and second flocculating tanks 13 and 14 are the air diffuser 1 respectively.
9 and 20 are provided to communicate with the air supply passages 21 and 22, respectively,
It is configured to perform aerobic treatment.

The first and second flocculation tanks 13 and 14 are filled with granular carriers 23 and 24, respectively. Further, the first and second flocking tanks 13 and 14 are provided with carrier separating screens 25a and 25b, respectively.
The first and second flocking tanks 13 and 14 are installed in the latter stage of the high-load biological reaction tank 1, and the high-load biological reaction tank 1 and the first flocking tank 13 communicate with each other via a line 27, and B in the liquid to be treated is connected.
Most of the OD is decomposed in the high load biological reaction tank 1. As a result, the high load biological reaction tank 1 has a high BOD load, and the first and second floc tanks 13 and 14 have a low BOD load.

The second flocculation tank 14 and the solid-liquid separation tank 31 are connected by a line 28. To the solid-liquid separation tank 31, the treated water channel 32 communicates with the upper part, and the sludge channel 33 communicates with the lower part.
The sludge passage 33 branches into the return sludge passage 12 and the discharged sludge passage 34.

In the treatment method using the above apparatus, first, as a high-load reaction step, the high-load biological reaction tank 1 is provided with a liquid passage 11 to be treated.
Further, the liquid to be treated and the returned sludge are introduced from the returned sludge path 12 and mixed with the activated sludge in the tank, and the organic matter is decomposed by the aerobic biological reaction. In this case, circulation pump 4
The liquid in the tank is sucked by the circulating liquid and the air mixing device 5
In the air is mixed with the air supplied from the air supply path 7,
The obtained gas-liquid mixture is jetted downward from the nozzle 6 toward the liquid in the tank of the downward tube 3. By aeration in this way, fine bubbles are generated, and aerobic treatment can be performed in a state where the oxygen dissolution efficiency is maintained high.

In the high load biological reaction tank 1, the treatment is carried out with a high BOD load, and the soluble BOD is mainly decomposed. The BOD load of the high load biological reaction tank 1 is 2 to 40 as the sludge load.
kg-BOD / kg-VSS / d, preferably 3-10
It is desirable to set kg-BOD / kg-VSS / d.
Microorganisms grow due to high concentration BOD loading, and BO is efficiently
D is removed. The mixed liquid of the high load biological reaction tank 1 is sent from the line 27 to the first flocculating tank 13 to perform the low load reaction step.

In the low load reaction step, the mixed liquid in the high load biological reaction tank 1 is introduced from the line 27 into the first flocculating tank 13 to be mixed with the activated sludge in the tank, and air is sent from the air supply passage 21. Aeration is performed from the air diffuser 19 to attach the microorganisms to the carrier 23, decompose BOD by aerobic biological reaction, and flocculate the activated sludge. The mixed liquid in the first floc tank 13 overflows the partition plate 15 and flows into the second floc tank 14. The carrier 23 is separated by a screen 25a. The influent is mixed with the activated sludge in the second flocculation tank 14, and air is sent from the air supply passage 22 to diffuse the air.
Aeration is performed from 0 to attach microorganisms to the carrier 24, decompose BOD by aerobic biological reaction, and flocculate the activated sludge.

The BOD load in the first and second floc tanks 13 and 14 is 0.01 to 0.5 k as sludge load.
g-BOD / kg-VSS / d, preferably 0.05-
0.3 kg-BOD / kg-VSS / d is desirable. By performing aeration in the presence of the carriers 23 and 24 to which the microorganisms are attached, BOD is removed and the dispersible sludge introduced from the high load biological reaction tank 1 is flocculated. Excessively adhered sludge peels off and becomes sludge flocs. The carrier 24 is separated by the screen 25b
The mixed liquid in the flocculation tank 14 is sent to the solid-liquid separation tank 31 to perform the solid-liquid separation step.

In the solid-liquid separation step, the mixed liquid in the second flocculation tank 14 is introduced from the line 28 into the solid-liquid separation tank 31 to perform solid-liquid separation into treated water and sludge, and the separated liquid is treated as treated water. 32, the sludge is taken out of the sludge path 33,
A part is returned as return sludge from the return sludge passage 12, and the rest is taken out from the waste sludge passage 34 as excess sludge.

In the above treatment method, the high load biological reaction tank 1
Since no carrier is added to the carrier, the effective volume consumed by the carrier does not occur, and thus it is possible to process at a higher load. Further, since the circulation path 2 is provided and fine gas bubbles are generated by jetting the gas-liquid mixture for aerobic treatment, the oxygen dissolution efficiency can be increased and the treatment can be performed with a higher load. Further, since the first and second flocculation tanks 13 and 14 are provided for the low-load reaction process, the averaging of the residence time is promoted, and the short path hardly occurs. Bacteria in a dispersed state flowing in from the biological reaction tank 1 come into sufficient contact with the sludge flocs in the first and second flocculation tanks 13 and 14 to be taken up by the flocs, forming sludge having good solid-liquid separation properties. can do. Further, since the carriers 23 and 24 are filled, the tank volume can be further reduced.

[0038]

EXAMPLES The present invention will be described below with reference to test examples.

Test Example Using the apparatus of FIG. 1, BOD concentration of 3560 mg / L, SS
Wastewater of a chemical manufacturing plant having a concentration of 13.5 mg / L was treated. However, in the case of the comparative example, a partition plate was not provided to form one tank, and in the example, two partition plates were used to provide the first, second and third floc tanks. RUN1 to RU under different conditions
The N6 test was conducted. RUN1 to RUN4 are comparative examples, R
UN5 and 6 are examples. The test conditions are shown in Table 1. The MLSS of the reaction tank was set to about 5000 mg / L. The total capacity of the high-load bioreactor and the low-load bioreactor is the same for all RUNs, and the sludge load on the high-load bioreactor is adjusted by changing the volume ratio of the high-load bioreactor and the low-load bioreactor. did.

RUN1 to RUN3 were tested by changing the sludge load of the low load bioreactor. For RUN4, the carrier was added to the low load bioreactor. In RUN5, the first to third flocculating tanks were provided, but the carrier was not added to any tank. In RUN6, the carrier was added to all of the first to third flocculation tanks. The carrier is a cube with a side of 10 mm,
A polyurethane sponge having a pore size of 1.0 mm was used. The filling rate was 60% in all tanks. The results are shown in Tables 2 and 3.

[0041]

[Table 1] * 1: Unit is kg-BOD / kg-VSS / d

[0042]

[Table 2]

[0043]

[Table 3]

As a result of the test, RUN1 caused bulking by filamentous bacteria. RUN 2 and 3 did not cause bulking. As can be seen from the results in Table 3, when the low-load biological reaction tank is a plurality of tanks connected in series, it is effective in reducing the SS concentration of the treated water, and RUN6 <RUN5≈R.
UN4 <RUN3. It can also be seen that the addition of a carrier is effective.

[Brief description of drawings]

FIG. 1 is a system diagram of a high load biological treatment apparatus according to an embodiment.

FIG. 2 is a system diagram of a conventional high load biological treatment apparatus.

[Explanation of symbols]

1 High load biological reaction tank 2 circuit 3 Downward tube 4 circulation pumps 5 Air mixing device 6 nozzles 7 Air supply path 11,51 liquid path to be treated 12,52 Return sludge path 13 1st floc tank 14 Second floc tank 19, 20, 44, 45 Air diffuser 21, 22, 46, 47 Airway 23, 24 carrier 25a, 26b screen 27, 28, 53, 54 lines 31, 43 Solid-liquid separation tank 32 treated waterways 33,56 sludge path 34, 57 Waste sludge path 41 First Reaction Tank 42 Second reaction tank 55 Processing liquid path

Claims (4)

(57) [Claims] 1. A high-load bioreaction tank for decomposing organic matter by performing aeration under a high BOD load, and a mixed solution in the high-load bioreaction tank, which is arranged in a subsequent stage of the high-load bioreaction tank, is aerated under a low BOD load. Biological treatment with a low-load bioreaction tank for decomposing organic matter and flocculating sludge, and a solid-liquid separation means for performing solid-liquid separation of the mixed liquid of the low-load bioreaction tank into treated water and sludge. In the device, the volume of the low-load biological reaction tank is the volume of the high-load reaction tank.
3 to 100 times, and the low-load bioreaction tank is composed of at least two floc tanks connected in series. 2. The biological treatment apparatus according to claim 1, wherein at least one of the flocculation tanks is filled with a microorganism carrier. 3. A high-load biological reaction tank, a circulation path for circulating the liquid in the tank, a mixing device for mixing an oxygen-containing gas with the circulating liquid, and a gas-liquid mixture mixed by this mixing device in the liquid in the tank. 2. A nozzle for jetting to a nozzle and a circulation pump are provided.
Or the biological treatment apparatus according to 2. 4. The dirt separated by the solid-liquid separation means.
A return route for returning part or all of the mud to the high-load reactor
The biological treatment facility according to any one of claims 1 to 3, which comprises:
Processing equipment.