JP2009202115A - Method and apparatus for biologically treating organic wastewater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To first maintain a stable treated water quality in a multistage activated sludge method using the predatory action of animalcules by improving a solid-liquid separation performance in a high-load operation and reducing the amount of a support charged into a fluid bed in a tank holding the animalcules and to further enhancing the treatment efficiency and to reduce a generated amount of surplus activated sludge. <P>SOLUTION: Organic wastewater is introduced into a first biological treatment tank 1 for a biological treatment with bacteria to obtain first biologically treated water, which is allowed one time to flow with the contained dispersed bacteria from the first biological treatment tank 1 into a fluid bed type second biological treatment tank 2 to obtain second biologically treated water, which is sent to a floating type third biological treatment tank 3 to obtain third biologically treated water, which undergoes a solid-liquid separation process in a settling tank 5 to separate into sludge and treated water. A part of the separated sludge is drawn out of the system as surplus sludge, a part of which is returned to the third biological treatment tank 3 as returned sludge. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biological treatment method and apparatus for organic wastewater that can be used for treatment of organic wastewater in a wide concentration range including domestic wastewater, sewage, food factories and pulp factories. The present invention relates to a biological treatment method and apparatus for organic wastewater that can improve the treatment efficiency and reduce the amount of excess sludge generation without deteriorating water quality.

The activated sludge method used when biologically treating organic wastewater is widely used for sewage treatment, industrial wastewater treatment, and the like because of its advantages such as good treated water quality and easy maintenance. However, since the BOD volumetric load in the activated sludge method is about 0.5 to 0.8 kg / m ³ / d, a large site area is required. Moreover, since 20% of the decomposed BOD is converted into microbial cells, that is, sludge, a large amount of excess sludge treatment also becomes a problem.

For high load treatment of organic waste water, a fluidized bed method with a carrier added is known. When this method is used, it is possible to operate with a BOD volume load of ³ kg / m ³ / d or more. However, this method has a disadvantage that the amount of generated sludge is about 30% of the decomposed BOD, which is higher than the normal activated sludge method.

  In Japanese Patent Laid-Open No. 55-20649, organic wastewater is first treated with bacteria in a first treatment tank, and the organic matter contained in the wastewater is oxidatively decomposed and converted into non-aggregating bacterial cells. It is described that excess sludge can be reduced by precipitating and removing the sticking protozoa in the second treatment tank. Further, this method enables high-load operation and improves the processing efficiency of the activated sludge method.

  In this way, many wastewater treatment methods using predation of protozoa and metazoans located at higher levels of bacteria have been proposed.

  For example, Japanese Patent Laid-Open No. 2000-210692 proposes a countermeasure against deterioration in processing performance due to fluctuations in the quality of raw water, which is a problem in the processing method of Japanese Patent Laid-Open No. 55-20649. As specific methods, “adjust BOD fluctuation of treated water to within 50% from median average concentration”, “measure water quality in first treatment tank and first treated water over time”, Methods such as “add seed sludge or microbial preparation to the first treatment tank when the quality of the first treated water deteriorates” have been proposed.

  In Japanese Examined Patent Publication No. 60-23832, bacteria, yeasts, actinomycetes, algae, molds, wastewater treatment primary sludge and surplus sludge are precipitated by protozoa and metazoans by ultrasonic treatment or mechanical stirring. Have proposed a method for making these foods smaller in size than the animal's mouth.

Moreover, as invention regarding the multistage process of a fluidized bed and an activated sludge method, there exists a thing as described in patent 3410699 gazette. In this method, the latter activated sludge method is operated at a low load of BOD sludge load 0.1 kg-BOD / kg-MLSS / d, so that the sludge can be self-oxidized and the amount of sludge extraction can be greatly reduced.
Japanese Patent Laid-Open No. 55-20649 JP 2000-210692 A Japanese Patent Publication No. 60-23832 Japanese Patent No. 3410699

The multistage activated sludge method using the predatory action of such minute animals is actually used for organic wastewater treatment. Depending on the target wastewater, the treatment efficiency is improved and the amount of generated sludge is reduced by about 50%. Is possible.
However, with this method,
(1) When the load is high, the concentration of sludge in the tank holding the micro-animal becomes high, making it difficult to separate solid and liquid.
(2) If the tank for holding micro-animals is a fluidized bed, the amount of carrier filling will increase and the construction cost will increase.
There was a problem.

  Therefore, the present invention is a multistage activated sludge method that uses the predatory action of micro-animals to improve the solid-liquid separation in high-load operation and to reduce the amount of fluid bed carrier in the tank holding micro-animals. It is an object of the present invention to provide a biological treatment method and apparatus for organic wastewater that aims to further improve the treatment efficiency and reduce the amount of excess sludge generation while maintaining stable treated water quality.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor made a part of the tank preferential to the fixed filter-feeding microanimal that prey on the dispersal bacteria as a fluidized bed, and dispersed in this fluidized bed. The present inventors have found that the above-mentioned problems can be solved by collecting fungi and further reducing sludge in a floating micro animal tank.

  The present invention has been achieved based on such knowledge, and the gist thereof is as follows.

[1] Organic wastewater is introduced into the first biological treatment tank of the biological treatment tank provided in three or more stages and biologically treated with bacteria, and the first containing the dispersed bacteria from the first biological treatment tank A biological treatment method for organic wastewater, wherein biological treatment water is sequentially passed through a second biological treatment tank and a third biological treatment tank for biological treatment, wherein the second biological treatment tank is a fluidized bed biological treatment tank, The third biological treatment tank is a floating biological treatment tank, and the first biological treatment water is passed through the second biological treatment tank in a transient manner to obtain second biological treatment water. The third biological treatment water obtained by passing the water through the third biological treatment tank is solid-liquid separated into sludge and treated water, a part of the separated sludge is drawn out as extra sludge, and at least the remaining part of the separated sludge A method for biological treatment of organic wastewater, wherein a part of the wastewater is returned to the third biological treatment tank as return sludge.

[2] In [1], the first biological treatment tank is a fluidized bed biological treatment tank having a carrier filling rate of 10% or less, and the second biological treatment tank is a fluidized bed biological treatment tank having a carrier filling rate of 10% or more. A biological treatment method for organic wastewater, characterized by being a tank.

[3] The biological treatment method for organic wastewater according to [1] or [2], wherein the dissolved oxygen concentration in the first biological treatment tank is controlled to 0.5 mg / L or less.

[4] The biological treatment method for organic wastewater according to any one of [1] to [3], wherein at least a part of the separated sludge is biologically treated in a fourth biological treatment tank to reduce the amount.

[5] The biological treatment method for organic waste water according to any one of [1] to [4], wherein the pH in at least one of the second and subsequent biological treatment tanks is 7 or less.

[6] The biological treatment method for organic wastewater according to any one of [1] to [5], wherein a nutrient is added to at least one of the second and subsequent biological treatment tanks.

[7] The biological wastewater treatment method according to any one of [1] to [6], wherein a part of the organic wastewater is directly introduced into the third biological treatment tank.

[8] In the organic wastewater biological treatment apparatus including biological treatment tanks provided in three or more stages, the first biological treatment tank is a tank for biologically treating organic wastewater with bacteria, and the second biological treatment The tank is a fluidized bed biological treatment tank in which the first biological treatment water containing the dispersed bacteria from the first biological treatment tank is passed in a transient manner, and the third biological treatment tank is the second biological treatment tank. Solid-liquid separation means for separating the third biological treatment water from the third biological treatment tank into sludge and treated water, which is a floating biological treatment tank into which the second biological treatment water from the tank is introduced, and separation An organic wastewater organism comprising: means for extracting a part of sludge out of the system as surplus sludge; and means for returning at least a part of the remaining sludge as return sludge to the third biological treatment tank. Processing equipment.

[9] In [8], the first biological treatment tank is a fluidized bed biological treatment tank having a carrier filling rate of 10% or less, and the second biological treatment tank is a fluidized bed biological treatment tank having a carrier filling rate of 10% or more. A biological treatment apparatus for organic wastewater characterized by being a tank.

[10] The biological treatment apparatus for organic wastewater according to [8] or [9], wherein the first biological treatment tank is controlled to a dissolved oxygen concentration of 0.5 mg / L or less.

[11] The biological treatment apparatus for organic wastewater according to any one of [8] to [10], further comprising a fourth biological treatment tank for biologically treating the separated sludge to reduce the amount.

[12] The biological treatment apparatus for organic wastewater according to any one of [8] to [11], wherein the pH in at least one of the second and subsequent biological treatment tanks is 7 or less. .

[13] The biological treatment apparatus for organic wastewater according to any one of [8] to [12], wherein a nutrient is added to at least one of the second and subsequent biological treatment tanks.

[14] The biological treatment apparatus for organic wastewater according to any one of [8] to [13], comprising means for directly introducing a part of the organic wastewater into the third biological treatment tank.

  In the present invention, in the multistage activated sludge method utilizing the predatory action of micro animals, the biological treatment tank holding the micro animals is divided into a fluidized bed type second biological treatment tank to which a carrier is added and a floating type third biological treatment process. The carrier as a whole is divided into tanks, precipitating most of the dispersal bacteria from the first biological treatment tank in the preceding fluidized bed biological treatment tank, and further removing the remainder in the subsequent floating biological treatment tank. It is possible to effectively reduce sludge while suppressing the filling amount (claims 1 and 8).

For this reason, according to this invention, the efficient biological treatment of organic waste_water | drain becomes possible, and the following effects are show | played.
1) Significant reduction of sludge generated during wastewater treatment 2) Improvement of treatment efficiency by high load operation 3) Maintenance of stable treated water quality

  In the present invention, in the first biological treatment tank, since it is necessary to decompose most of the organic matter and stably convert it into microbial cells, it is desirable that the first biological treatment tank be a fluidized bed type. When the filling rate of the carrier added to the first biological treatment tank is high, no dispersal bacteria are produced, and the bacteria adhere to the carrier or the filamentous bacteria grow. It is desirable that the filling rate be 10% or less because it is possible to generate disperse bacteria that are easy to prey without being affected by fluctuations in the quality of raw water. On the other hand, in the second biological treatment tank, since a large amount of scaffolding is required to maintain the micro-animal, the filling rate of the added carrier is desirably 10% or more (claims 2 and 9).

  Moreover, it is preferable to control the dissolved oxygen concentration of the 1st biological treatment tank to 0.5 mg / L or less in order to prevail the dispersal bacteria which are easy to prey in the 2nd biological treatment tank (Claims 3 and 10).

  Further, the separated sludge separated into solid and liquid may be further biologically treated in the fourth biological treatment tank to reduce the amount (claims 4 and 11).

  In addition, the second to fourth biological treatment tanks are preferably set to pH 7 or less in order to promote predation by micro animals (claims 5 and 12).

  Moreover, a nutrient may be added to the 2nd-4th biological treatment tank, and stabilization of a micro animal maintenance may be aimed at (Claims 6 and 13).

  Moreover, in order to ensure an appropriate organic load in the subsequent biological treatment tank, a part of the organic waste water that is the raw water may be directly introduced into the third biological treatment tank (Claims 7 and 14). .

  Embodiments of a biological treatment method and apparatus for organic wastewater according to the present invention will be described below in detail with reference to the drawings.

1-4 is a systematic diagram showing an embodiment of a biological treatment method and apparatus for organic wastewater of the present invention.
1-4, 1 is a 1st biological treatment tank, 2 is a 2nd biological treatment tank, 3 is a 3rd biological treatment tank, 4 is a 4th biological treatment tank, 5 is a sedimentation tank, and has the same function Are denoted by the same reference numerals.

In the embodiment of FIG. 1, raw water (organic wastewater) is introduced into the first biological treatment tank 1, and 70% or more, desirably 80% or more, more desirably 90% of the organic component (soluble BOD) by dispersible bacteria. % Or more is oxidatively decomposed. The pH of the first biological treatment tank 1 is 6 or more, preferably 8 or less. However, when the raw water contains a large amount of oil, the pH may be 8 or more.
Further, BOD volume load to the first biological treatment tank 1 is 1kg ^{/ m} 3 ^/ d or more, for example ^{1~20kg / m 3 / d, HRT} ( raw water retention time) is 24h or less, for example, 0.5~24h Therefore, it is possible to obtain treated water predominated by dispersible bacteria, and it is preferable because waste water having a low BOD concentration can be treated with a high load by shortening the HRT.

  Further, the dissolved oxygen concentration in the first biological treatment tank 1 is preferably controlled to 0.5 mg / L or less, particularly 0.1 mg / L or less, particularly 0.05 mg / L or less, whereby about 1 to 5 μm. The size of the dispersal bacteria becomes dominant, and these are rapidly preyed in the second biological treatment tank 2.

  In this first biological treatment tank, a part of the sludge from the subsequent biological treatment tank may be returned, or the first biological treatment tank may have a multistage configuration of two or more tanks.

  In addition, if HRT of the 1st biological treatment tank 1 becomes long compared with an optimal value, it will lead to the predominance of a filamentous bacteria and formation of a floc, and the bacteria which are hard to prey on in the 2nd biological treatment tank 2 of the latter stage will produce | generate. End up. Therefore, it is necessary to control the HRT of the first biological treatment tank 1 to be constant. Since this optimum HRT varies depending on the quality of raw water, it is necessary to obtain an HRT capable of removing 70 to 90% of organic components from a desktop test or the like. As a method of maintaining the HRT at the optimum value, when the raw water amount is reduced, a part of the treated water is returned, the amount of water flowing into the first biological treatment tank 1 is made constant, and the HRT of the first biological treatment tank 1 is stabilized. And a method of changing the water level of the first biological treatment tank 1 in accordance with the fluctuation of the amount of raw water. It is desirable that the width for stabilizing the HRT of the first biological treatment tank 1 be within the range of 0.75 to 1.5 times the optimum HRT obtained by the desktop test.

  In addition, when dissolved organic matter is completely decomposed in the first biological treatment tank 1, flocs are not formed in the second biological treatment tank 2, and nutrients for microanimal growth are insufficient, and sludge with low compactness is used. Only becomes the dominant biological treatment tank. Therefore, it is preferable that the decomposition rate of the organic component in the first biological treatment tank 1 is not 100% but 95% or less.

  The treated water in the first biological treatment tank 1 (first biological treated water) is sequentially passed through the second biological treatment tank 2 and the third biological treatment tank 3 in the subsequent stage, where the remaining organic components Reduce excess sludge by oxidative degradation, self-degradation of dispersible bacteria, and predation of micro-animals.

In the second biological treatment tank 2, it is necessary to use an operation condition and a treatment apparatus that allow the microanimal and the bacteria to remain in the system in order to use the action of the microanimal having a slower growth rate than the bacteria and the self-degradation of the bacteria. . Therefore, in the present invention, the second biological treatment tank 2 increases the retained amount of the micro animal in the tank by forming a fluidized bed in which the carrier 2A is added in the aeration tank. The shape of the carrier 2A added to the second biological treatment tank 2 is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape, and the size may be about 0.1 to 10 mm. The material of the carrier 2A is arbitrary such as a natural material, an inorganic material, or a polymer material, and a gel material may be used.
In the second biological treatment tank 2, since a large amount of scaffolding for maintaining the micro-animal is required, the filling rate of the carrier to be added is 10% or more, desirably 20% or more, for example, 20 to 40%. Is desirable.

  The first biological treatment water is passed through the second biological treatment tank 2 in a transient manner, and the treated water (second biological treatment water) in the second biological treatment tank 2 is then passed to the third biological treatment tank 3. The amount of sludge is further reduced by decomposing organic substances, dispersal bacteria, and solids derived from raw water introduced and not completely decomposed in the second biological treatment tank 2.

  The treated water from the third biological treatment tank 3 (third biological treated water) is then solid-liquid separated into sludge and treated water in the sedimentation tank 5, and a part of the separated sludge is returned as return sludge. That is, since the third biological treatment tank 3 is a floating type to which no carrier is added, the minute animals use sludge floc as a living place. Therefore, it is necessary to provide the sedimentation tank 5 and return the sludge to ensure a sludge residence time of 5 days or more and 30 days or less in the third biological treatment tank 3.

In the present invention, when a large amount of organic matter remains in the first biological treatment water introduced into the second biological treatment tank 2, the oxidative decomposition is performed in the second biological treatment tank 2. However, when oxidative degradation of organic matter by bacteria occurs in the second biological treatment tank 2 in which a large amount of micro animals are present, it is known that the bacteria grow in a form that is difficult to be predated as a countermeasure to escape from predation of the micro animals. Thus, the bacteria that have grown in this way are not preyed on by the micro-animals, and their decomposition depends only on autolysis, which reduces the effect of reducing the amount of sludge generated.
Therefore, as described above, in the first biological treatment tank 1, most of the organic components in the raw water, that is, 70% or more, preferably 80% or more, more preferably 90% or more of the raw water BOD, is decomposed into cells. It is necessary to convert stably. Therefore, as shown in FIG. 2, the first biological treatment tank 1 is desirably a fluidized bed type filled with a carrier 1A. However, when the filling rate of the carrier added to the first biological treatment tank 1 is high, dispersal bacteria are not generated, and the bacteria adhere to the carrier or the filamentous bacteria grow, so add to the first biological treatment tank 2 The carrier filling rate is 20% or less, desirably 10% or less, for example, 3 to 10%. This makes it possible to produce dispersed bacteria that are not affected by concentration fluctuations and are easy to eat.

  In addition, there is no restriction | limiting in particular as the support | carrier 1A with which this 1st biological treatment tank 1 is filled, The thing similar to the support | carrier 2A with which the above-mentioned 2nd biological treatment tank 2 is filled can be used.

  The embodiment shown in FIG. 2 differs from the embodiment shown in FIG. 1 in that the first biological treatment tank 1 is filled with the carrier 1A, and the other configurations are the same as those shown in FIG.

  In the present invention, as shown in FIG. 3, a fourth biological treatment tank 4 for further biologically treating the sludge separated into solid and liquid in the sedimentation tank 5 to reduce the volume may be provided to promote sludge reduction. In the embodiment of FIG. 4, after a part of the separated sludge is introduced into the fourth biological treatment tank 4 and treated, it is discharged out of the system as surplus sludge, and the remainder is returned to the third biological treatment tank 3 as return sludge. The

  The aspect shown in FIG. 3 is different from the aspect shown in FIG. 1 in that a fourth biological treatment tank 4 for biologically treating surplus sludge is provided, and other configurations are the same as those shown in FIG.

  In addition, as described above, in the first biological treatment tank 1, most of the organic components in the raw water, that is, 70% or more, preferably 80% or more, more preferably 90% or more of the raw water BOD, is decomposed into cells. However, since an appropriate organic load is also required in the subsequent biological treatment tank, a part of the raw water is bypassed directly to the third biological treatment tank 3 as shown in FIG. It is desirable to operate so that the sludge load due to the soluble BOD in the third biological treatment tank 3 is 0.025 kg-BOD / kg-MLSS / d or more.

  The embodiment shown in FIG. 4 is different from the embodiment shown in FIG. 1 in that a pipe for directly introducing a part of raw water into the third biological treatment tank 3 is provided, and other configurations are the same as those shown in FIG.

  In the present invention, in order to promote predation by a micro animal, any of the second to fourth biological treatment tanks 2 to 4, particularly the second biological treatment tank 2 has a pH of 7 or less, for example, pH 5.5 to 5.5. It is preferable that the condition is 6.5.

In addition, even if the operating conditions are set to be suitable for the growth of micro-animals, the micro-animals will not proliferate and the sludge reduction effect will not improve unless the raw water contains essential ingredients for the micro-animal growth. . Therefore, a nutrient is added to the second to fourth biological treatment tanks 2 to 4, particularly the second biological treatment tank 2 to stably maintain the micro-animals, thereby stabilizing the sludge reduction effect. May be. Moreover, you may accelerate | stimulate the weight loss effect by adding a nutrient to the 3rd biological treatment tank 3. FIG. In this case, nutrients include phospholipids, free fatty acids, lysophospholipids, sterols and lecithins containing these, liquid sugar, rice bran, beer pomace, vegetable oil pomace, soybean extract, sugar beet koji, Nutrients effective in promoting the growth of metazoans such as shellfish powder, eggshell, vegetable extract, fish meat extract, various amino acids and various vitamins can be used. These may be used alone or in combination of two or more.
When these nutrients are added, the addition amount is preferably about 0.5 to 10% of the amount of organic matter in the raw water.

  1 to 4 show an example of an embodiment of the present invention, and the present invention is not limited to the illustrated method unless it exceeds the gist.

  For example, as the solid-liquid separation means of the third biological treatment water, a membrane separation device, a floating separation tank, or the like may be used in addition to the precipitation tank. Moreover, you may perform a membrane separation type aerobic process by making a 3rd biological treatment tank into a membrane immersion type biological treatment tank which serves as a biological treatment tank and a solid-liquid separation means.

Further, instead of providing the fourth biological treatment tank 4 as shown in FIG. 3, the separated sludge is treated with any one of anaerobic treatment, physical treatment, chemical treatment, or a combination thereof, and the micro animal is killed. You may make it return to any one or more of the 1st biological treatment tank 1, the 2nd biological treatment tank 2, and the 3rd biological treatment tank 3.
Further, in the embodiment of FIG. 3, a means for solid-liquid separation of the treated water of the fourth biological treatment tank 4 is further provided, and an aerobic treatment method for returning sludge is performed, or a carrier is added to the fourth biological treatment tank 4 By using the fluidized bed type or membrane separation type aerobic treatment method, the sludge residence time in the fourth biological treatment tank 4 may be lengthened.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
As shown in FIG. 2, the first biological treatment tank (with no sludge return) 1 with a capacity of 2.5L, the second biological treatment tank (with no sludge return) 2 with a capacity of 2.5L, and a capacity of 4.2L. The organic wastewater (BOD 800 mg / L) according to the present invention was treated using an experimental apparatus in which a third biological treatment tank (with sludge return) 3 and a sedimentation tank 5 having a capacity of 4 L were connected.
The treatment conditions for each biological treatment tank were as follows.

<First biological treatment tank>
DO: 0.01 mg / L
Carrier filling rate: 5%
BOD volumetric load: 5.5 kg-BOD / m ³ / d
HRT: 3.5h
pH: 7
<Second biological treatment tank>
DO: 2-3 mg / L
Carrier filling rate: 40%
HRT: 2h
pH: 6.5
<Third biological treatment tank>
DO: 2-3 mg / L
HRT: 7.3h
pH: 7
Sludge residence time: 25d

As the carriers 1A and 2B of the first biological treatment tank 1 and the second biological treatment tank 2, sponge carriers were used.
Moreover, the BOD volumetric load in the whole apparatus was 1.5 kg-BOD / m < ³ > / d, and HRT in the whole apparatus was 12.8 h.
As a result, the sludge conversion rate was 0.25 kg-MLSS / kg-BOD, and the treated water BOD was below the detection limit.

Comparative Example 1
As shown in FIG. 5, a 2.5L first biological treatment tank (without sludge return) 1; a 6.7L second biological treatment tank (without sludge return) 2; and a 4L capacity sedimentation tank. 5 was used to treat organic waste water (BOD 800 mg / L).
The treatment conditions for each biological treatment tank were as follows.

<First biological treatment tank>
DO: 0.01 mg / L
Carrier filling rate: 5%
BOD volumetric load: 5.5 kg-BOD / m ³ / d
HRT: 3.5h
pH: 7
<Second biological treatment tank>
DO: 2-3 mg / L
HRT: 9.3h
pH: 7

A sponge carrier was used as the carrier 1A of the first biological treatment tank 1.
Moreover, the BOD volumetric load in the whole apparatus was 1.5 kg-BOD / m < ³ > / d, and HRT in the whole apparatus was 12.8 h.
As a result, the sludge conversion rate varied from 0.25 to 0.4 kg-MLSS / kg-BOD, and the amount of sludge generated was not stable. Further, the treated water BOD also fluctuated, and the treated water quality deteriorated during the period when the sludge generation amount decreased.

  The biological treatment method for organic wastewater of the present invention can be used for treatment of organic wastewater in a wide concentration range including domestic wastewater, sewage, food factories and pulp factories.

It is a systematic diagram which shows embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a systematic diagram which shows other embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a systematic diagram which shows other embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a systematic diagram which shows other embodiment of the biological treatment method and apparatus of the organic waste water of this invention. It is a systematic diagram showing the biological treatment apparatus used in Comparative Example 1.

Explanation of symbols

1 First biological treatment tank 2 Second biological treatment tank 3 Third biological treatment tank 4 Fourth biological treatment tank 5 Precipitation tank

Claims (14)

The first biological treatment water containing the dispersed bacteria from the first biological treatment tank by introducing organic wastewater into the first biological treatment tank of the biological treatment tank provided in three or more stages and biologically treating with bacteria A biological treatment method for organic wastewater, wherein the biological treatment is performed by sequentially passing water through a second biological treatment tank and a third biological treatment tank,
The second biological treatment tank is a fluidized bed biological treatment tank, the third biological treatment tank is a floating biological treatment tank,
The first biological treated water is passed through the second biological treatment tank in a transient manner to obtain a second biological treated water,
The third biological treatment water obtained by passing the second biological treatment water through the third biological treatment tank is solid-liquid separated into sludge and treated water, and a part of the separated sludge is drawn out as extra sludge. A biological treatment method for organic wastewater, wherein at least a part of the remaining portion of the separated sludge is returned to the third biological treatment tank as return sludge.   2. The first biological treatment tank according to claim 1, wherein the first biological treatment tank is a fluidized bed biological treatment tank with a carrier filling rate of 10% or less, and the second biological treatment tank is a fluidized bed biological treatment tank with a carrier filling rate of 10% or more. A method for biological treatment of organic wastewater.   The biological treatment method for organic wastewater according to claim 1 or 2, wherein the dissolved oxygen concentration in the first biological treatment tank is controlled to 0.5 mg / L or less.   The biological treatment method for organic wastewater according to any one of claims 1 to 3, wherein at least a part of the separated sludge is biologically treated in a fourth biological treatment tank to reduce the amount.   The biological treatment method for organic wastewater according to any one of claims 1 to 4, wherein the pH in at least one of the second and subsequent biological treatment tanks is 7 or less.   6. The organic wastewater biological treatment method according to any one of claims 1 to 5, wherein a nutrient is added to at least one of the second and subsequent biological treatment tanks.   The biological treatment method for organic wastewater according to any one of claims 1 to 6, wherein a part of the organic wastewater is directly introduced into the third biological treatment tank. In biological wastewater biological treatment equipment equipped with biological treatment tanks installed in multiple stages of three or more stages,
The first biological treatment tank is a tank that biologically treats organic wastewater with bacteria.
The second biological treatment tank is a fluidized bed biological treatment tank through which the first biological treatment water containing the dispersed bacteria from the first biological treatment tank is passed in a transient manner,
The third biological treatment tank is a floating biological treatment tank into which the second biological treatment water from the second biological treatment tank is introduced,
Solid-liquid separation means for solid-liquid separation of the third biological treatment water from the third biological treatment tank into sludge and treated water, means for drawing a part of the separated sludge out of the system as excess sludge, and the remainder of the separated sludge A biological treatment apparatus for organic wastewater, comprising: means for returning at least a part as return sludge to the third biological treatment tank.   9. The first biological treatment tank according to claim 8, wherein the first biological treatment tank is a fluidized bed biological treatment tank with a carrier filling rate of 10% or less, and the second biological treatment tank is a fluidized bed biological treatment tank with a carrier filling rate of 10% or more. A biological treatment apparatus for organic wastewater.   10. The organic wastewater biological treatment apparatus according to claim 8, wherein the first biological treatment tank is controlled to have a dissolved oxygen concentration of 0.5 mg / L or less.   The biological treatment apparatus for organic wastewater according to any one of claims 8 to 10, further comprising a fourth biological treatment tank for biologically treating the separated sludge to reduce the amount.   The biological treatment apparatus for organic wastewater according to any one of claims 8 to 11, wherein the internal pH of at least one of the second and subsequent biological treatment tanks is 7 or less.   The biological treatment apparatus for organic wastewater according to any one of claims 8 to 12, wherein a nutrient is added to at least one of the second and subsequent biological treatment tanks.   The biological treatment apparatus for organic wastewater according to any one of claims 8 to 13, further comprising means for directly introducing a part of the organic wastewater into the third biological treatment tank.

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