JP5915643B2 - Biological treatment method and apparatus for organic wastewater - Google Patents

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 generally about 0.5 to 0.8 kg / m ³ / d, a large site area is required. Moreover, since 20 to 40% of the decomposed BOD is converted into bacterial cells, that is, sludge, a large amount of excess sludge is generated.

As a method for treating organic wastewater with a high load, a fluidized bed method in which a carrier is added is known. In this method, it is possible to operate with a BOD volume load of ³ kg / m ³ / d or more. However, in this method, the amount of generated sludge is about 30 to 50% of the decomposed BOD, which is larger 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 and 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.

  JP-A-2006-51414, JP-A-2006-51415, JP-A-2006-247494, JP-A-2008-36580, and JP-A-2009-202115 also describe a multi-stage activated sludge method utilizing the predatory action of micro-animals.

  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.

  As invention regarding the multistage process of a fluidized bed and an activated sludge process, there exists a thing as described in the 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 JP 2006-51414 A JP 2006-51415 A JP 2006-247494 A JP 2008-36580 A JP 2009-202115 A

  In biological treatment, the biological treatment tank can be downsized by increasing the tank load. However, in the multistage activated sludge method using the predatory action of micro-animals, when high load treatment is performed, the quality of the treated water deteriorates. That is, when the organic matter contained in the wastewater is converted into dispersed cells in the biological treatment tank in the previous stage, and the dispersed cells are preyed on by the minute animals in the biological treatment tank in the subsequent stage, the amount of minute animals is less than the amount of dispersed cells. In some cases, leftovers are generated, and the wastewater does not settle in the settling tank and flows into the treated water.

  There are two types of micro-animals that contribute to sludge reduction: the filtration predation type and the aggregate predation type. Among these, the aggregate predation type micro-animal can be preyed while gnawing the flocked sludge. Therefore, when the aggregate predation type micro-animal is prioritized, the quality of the treated water is deteriorated. Therefore, in order to improve the quality of treated water, it is effective to give priority to the filter predation type among micro-animals. However, conventionally, no method has been proposed for controlling the growth of filtration predation type micro-animals and the growth of aggregate predation type micro-animals, and sludge reduction using micro-animals is performed particularly in wastewater treatment at high loads. In some cases, depending on the operating conditions, an unexpected deterioration of the treated water occurs.

The present invention solves the above conventional problems, the multistage activated sludge method using predation action of micro animals, _{COD Cr} volumetric loading 1.0kg ^{/ m} 3 ^/ d or more, or BOD volume load 0.5 kg ^{/ m} 3 / In performing high load treatment such as d or more, the filter predation type micro-animal is positively prioritized, and the growth of the aggregate predation type micro-animal causing deterioration of the treated water is suppressed, thereby improving the treatment efficiency, sludge It is an object of the present invention to provide a biological treatment method and apparatus for organic wastewater that can reduce the volume and improve the quality of treated water.

  As a result of intensive studies to solve the above problems, the present inventors have provided a tank for treating organic matter in a transient manner in the biological treatment tank in the previous stage in the multistage activated sludge method utilizing the predatory action of micro-animals, In order to suppress the growth of aggregates (floc) predation type micro-animals that generate dispersed bacteria, actively prioritize necessary micro-animals in the latter-stage biological treatment tank, and cause deterioration of treated water quality, In the treatment tank, the sludge is extracted with a residence time that exceeds the growth rate of the aggregate-feeding type micro-animal, and the micro-animal holding carrier is provided in this biological treatment tank to efficiently feed the dispersal bacteria and separate the sludge into solid and liquid. It has been found that a stable high-load treatment can be achieved by holding a fixed filtration predation type micro-animal that contributes to improving the quality and quality of treated water.

  The present invention has been achieved based on such knowledge.

In the organic wastewater biological treatment method of the present invention, the load on the whole biological treatment tank is set to a CODCr volumetric load of 1.0 kg / m ³ / d or higher or a BOD volumetric load of 0.5 kg / m ³ / d or higher. A biological treatment method for organic wastewater that performs biological treatment below, wherein the aerobic biological treatment tank is provided in two or more stages, and the organic wastewater is introduced into the first biological treatment tank and biologically treated with bacteria. The first biological treatment water containing the dispersed bacteria from the first biological treatment tank is passed through the biological treatment tank after the second biological treatment tank for biological treatment, and the biological treatment after the second biological treatment tank In the biological treatment method for organic wastewater, in which the treated water in the tank is solid-liquid separated in a sedimentation tank and a part of the separated sludge is returned to the biological treatment tank after the second biological treatment tank. A biological treatment tank is provided with a carrier for holding micro-animals, and the second biological treatment tank or later The carrier provided in the biological treatment tank is made of a synthetic resin foam and has a side length of 100 to 400 cm, a side perpendicular to the length of 5 to 200 cm, and a thickness of 0.5 to 5 cm. a sheet-like, and at least a part of which is vertically fixed directly or through fasteners organism treatment tank carrier of the carrier.

In the organic wastewater biological treatment apparatus of the present invention, the load of the whole biological treatment tank is set to a CODCr volumetric load of 1.0 kg / m ³ / d or more or a BOD volumetric load of 0.5 kg / m ³ / d or more. It is a biological treatment device for organic wastewater that performs biological treatment below, provided with aerobic biological treatment tanks in multiple stages of two or more stages, introduced organic wastewater into the first biological treatment tank and biologically treated with bacteria, The first biological treatment water containing the dispersed bacteria from the first biological treatment tank is passed through the biological treatment tank after the second biological treatment tank for biological treatment, and the biological treatment tank after the second biological treatment tank In a biological treatment apparatus for organic wastewater that separates solid-liquid separation of treated water in a sedimentation tank and returns a part of the separated sludge to the biological treatment tank after the second biological treatment tank, biological treatment after the second biological treatment tank The tank is provided with a carrier for holding a micro animal, and the tank after the second biological treatment tank The carrier provided in the biological treatment tank is made of a synthetic resin foam and has a side length of 100 to 400 cm, a side perpendicular to the length of 5 to 200 cm, and a thickness of 0.5 to 5 cm. a sheet-like, at least a portion of said carrier is a carrier which is fixed in a vertical direction directly or via a fixture organism treatment tank.

  The soluble BOD sludge load on the sludge in the biological treatment tank after the second biological treatment tank is preferably 0.025 to 0.050 kg / kg-MLSS / d.

  A part of the organic waste water may be introduced into the biological treatment tanks after the second biological treatment tank without passing through the first biological treatment tank.

  The SRT (solid content residence time) of the biological treatment tanks after the second biological treatment tank is preferably 50 days or less, particularly preferably 10 to 50 days.

In the present invention, a multi-stage utilizing the predatory action of a micro animal even in a high load treatment such as a COD _Cr volumetric load of 1.0 kg / m ³ / d or higher or a BOD volumetric load of 0.5 kg / m ³ / d or higher. In the activated sludge method, an aggregate that deteriorates the quality of treated water by providing a micro-animal holding carrier in a biological treatment tank that holds micro-animals and withdrawing sludge with a residence time that exceeds the growth rate of aggregate-feeding micro-animals The growth of predatory type micro-animals is suppressed, and in this biological treatment tank, fixed filtration predatory type micro-animals that contribute to improving the quality of treated water by improving the quality of treated water by efficiently feeding on dispersal bacteria. It becomes possible to hold it stably.

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

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.

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

1 and 2 are system diagrams showing an embodiment of a biological treatment method and apparatus for organic wastewater according to the present invention.
1 and 2, 1 is a first biological treatment tank, 2 is a second biological treatment tank, 3 is a precipitation tank, 11 and 21 are aeration tubes, and 22 is a micro-animal holding carrier. The same reference numerals are given to members that perform the following.

  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% of the organic component (soluble BOD) is obtained by dispersible bacteria (non-aggregating bacteria). More preferably, 85% or more is oxidatively decomposed. The pH of the first biological treatment tank 1 is 6 or more, preferably 8 or less. However, the pH may be 8 or more when the raw water such as food manufacturing wastewater contains a lot of oil, or when the raw water such as semiconductor manufacturing wastewater or liquid crystal manufacturing wastewater contains a lot of organic solvent or cleaning agent.

The water flow to the first biological treatment tank 1 is preferably a transient type. The BOD volumetric load of the first biological treatment tank 1 is 1 kg / m ³ / d or more, for example 1 to 20 kg / m ³ / d, HRT (raw water residence time) is 24 h or less, preferably 8 h or less, for example 0.5 to 8 h As a result, treated water in which dispersible bacteria are dominant can be obtained, and waste water having a low BOD concentration can be treated with a high load by shortening the HRT.

By returning a part of the sludge from the subsequent biological treatment tank to the first biological treatment tank 1, making the first biological treatment tank 1 a multistage configuration of two or more tanks, or adding a carrier , High load processing with a BOD volumetric load of 5 kg / m ³ / d or more is also possible.

  When adding a support | carrier to the 1st biological treatment tank 1, the shape of a support | carrier is arbitrary, such as spherical shape, a pellet form, a hollow cylinder shape, a thread form, a plate shape, and a magnitude | size is arbitrary in the diameter of about 0.1-10 mm. is there. Further, the material of the carrier is any material such as a natural material, an inorganic material, and a polymer material, and a gel material may be used. Moreover, when the filling rate of the support | carrier added to the 1st biological treatment tank 1 is high, a dispersal microbe does not produce | generate but bacteria adheres to a support | carrier or a filamentous bacterium grows. Therefore, by setting the filling rate of the carrier added to the first biological treatment tank 1 to 10% or less, desirably 5% or less, it is possible to produce dispersed bacteria that are not affected by the concentration fluctuation and are easy to prey.

  The first biological treatment tank 1 may suppress the growth of filamentous bacteria by setting the dissolved oxygen (DO) concentration to 1 mg / L or less, preferably 0.5 mg / L or less.

  When the 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 there is not enough nutrients for the growth of micro-animals. It becomes a 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, desirably 85 to 90%.

  The treated water in the first biological treatment tank 1 (first biological treated water) is passed through the second biological treatment tank 2 in the subsequent stage, where the remaining organic components are oxidatively decomposed and the dispersible bacteria are self-degraded. And reduce excess sludge by 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 autolysis of the bacteria. . Therefore, it is desirable to use the activated sludge method for returning the sludge to the second biological treatment tank 2. Moreover, this 2nd biological treatment tank 2 is good also as a multistage structure of two or more tanks.

  In the present invention, the minute animal holding carrier 22 is provided in the second biological treatment tank 2. Furthermore, by setting the soluble BOD sludge load to the sludge in the tank to 0.025 to 0.050 kg / kg-MLSS / d, it is possible to efficiently prey on micro-animals, especially dispersal bacteria, and to separate the sludge into solid and liquid. Increases the amount of fixed filtration predatory micro-animals retained in the tank that contributes to improved treated water quality.

  That is, in the second biological treatment tank 2, not only the filtration and predation type micro animals that prey on the dispersed cells, but also the aggregate predation type micro animals that can prey on the floc sludge. Since the latter prey on flocs while swimming, if prioritized, sludge is eaten and becomes sludge in which fine floc pieces are scattered. This floc piece deteriorates the quality of treated water. Therefore, in the present invention, in the second biological treatment tank 2, the soluble BOD sludge load with respect to the sludge in the tank is set to 0.025 to 0.050 kg / kg-MLSS / d. In addition, in order to periodically replace the tank sludge, that is, to thin out minute animals and feces, the SRT (solid content retention time) of the second biological treatment tank 2 is desirably 50 days or less, particularly 45 days or less, particularly 40 days or less. Further, it is desirably controlled to be constant within a range of 10 days or more, particularly 20 days or more. Here, SRT = (floating sludge concentration in tank / aeration tank volume) / (drawing sludge concentration / drawing amount per day).

  In addition, a micro-animal holding carrier 22 is provided in the second biological treatment tank 2 in order to maintain the filtration predation type micro-animal that prey on the dispersed cells in the second biological treatment tank 2. That is, this kind of micro animal is fixed to the sludge floc and maintained in the system, but since the sludge is drawn out of the system with a certain residence time, it is necessary to provide a supply source in the system. At this time, if the carrier is a granular or square fluidized bed, the shearing force for fluidization cannot stably maintain a high concentration, so the carrier filling rate must be increased.

  Therefore, in the present invention, the carrier provided in the second biological treatment tank 2 is not a fluid carrier, but at least a part of the carrier is directly or fixed to any one of the bottom surface, the side surface, the upper part and the like of the second biological treatment tank 2. It is preferable to use a fixed carrier that is fixed via a gap. In this case, the shape of the carrier 22 is arbitrary such as a thread shape, a plate shape, or a strip shape. The material of the carrier 22 is arbitrary such as a natural material, an inorganic material, or a polymer material, and a gel material may be used. Desirably, it is a synthetic resin foam such as porous polyurethane foam. The carrier preferably has a plate shape or a strip shape having a side length of 100 to 400 cm, a side length orthogonal to the length of 5 to 200 cm, and a thickness of 0.5 to 5 cm. In the embodiment of FIG. 1, the left and right ends of the sheet-like fixing carrier are respectively fixed to two rod-shaped fixtures 23 that are fixed to the bottom surface of the second biological treatment tank 2 in a vertical direction.

  In the second biological treatment tank 2, a large amount of scaffolding for maintaining micro-animals is required. However, if the filling rate of the carrier is excessively high, mixing in the tank, sludge decay, etc. may occur. The filling rate is desirably about 0.1 to 20%.

  In the present invention, when a large amount of organic matter remains in the first biological treatment water charged into the second biological treatment tank 2, the oxidative decomposition is performed in the subsequent treatment tank. It is known that when oxidative degradation of organic matter by bacteria occurs in the second biological treatment tank 2 where a large amount of micro animals are present, as a countermeasure to escape from predation of micro animals, it grows in a form that is difficult to be predated. The bacterial group thus grown is not preyed on by the micro-animals, and their decomposition depends only on autolysis, and the effect of reducing the amount of sludge generated is reduced. Therefore, as described above, in the first biological treatment tank, it is necessary to decompose most of the organic matter, that is, 70% or more of the raw water BOD, desirably 80% or more, and convert it into cells. Therefore, it is preferable to operate at 0.025 to 0.050 kg / kg-MLSS / d in terms of the sludge load in the tank due to the soluble BOD in the subsequent biological treatment tank. If the soluble BOD sludge load on the sludge in the tank is larger than 0.050 kg / kg-MLSS / d, the sludge reduction effect is impaired, and if it falls below 0.025 kg / kg-MLSS / d, the sedimentation separation is performed in the settling tank. There are things that cannot be done. The tank sludge is the sum of floating sludge and carrier-attached sludge.

  In FIG. 1, the treated water from the second biological treatment tank 2 is fed to the precipitation tank 3 for solid-liquid separation, and the separated water is taken out as treated water, and a part of the separated sludge is removed from the second biological treatment tank 2. To the upstream (which may be the second biological treatment tank 2), and the remainder is discharged out of the system as surplus sludge.

  The aspect shown in FIG. 2 is that a part of raw water, for example, about 5 to 50%, particularly about 5 to 20%, is directly introduced into the second biological treatment tank 2 without passing through the first biological treatment tank 1. Unlike the embodiment shown in FIG. In this way, by introducing a part of the raw water directly into the second biological treatment tank 2, an effect of avoiding the load shortage of the second biological treatment tank when the raw water fluctuates (when the load is reduced) is achieved.

  1 and 2 show an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one. For example, the first biological treatment tank and the second biological treatment tank may have a multi-stage configuration of two or more stages as described above. Therefore, in the present invention, the biological treatment tank may be provided in three or more stages.

In any aspect, according to the present invention, the load on the whole biological treatment tank is a high load such as a COD _Cr volumetric load of 1.0 kg / m ³ / d or higher or a BOD volumetric load of 0.5 kg / m ³ / d or higher. In performing the treatment, a micro animal holding carrier is provided in the biological treatment tank after the second biological treatment tank, and the soluble BOD sludge load with respect to the sludge in the tank is set to 0.025 to 0.050 kg / kg-MLSS / d. Thus, by suppressing the priority of the aggregate predation type micro-animal, it is possible to achieve both the sludge reduction and the improvement of the quality of the treated water, and a stable high-load treatment becomes possible.

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

[Example 1]
As shown in FIG. 1, the present invention uses an experimental apparatus in which a first biological treatment tank 1 with a capacity of 36 L, a second biological treatment tank 2 with a capacity of 150 L, and a sedimentation tank 3 with a capacity of 50 L are connected. Treatment of organic wastewater by The raw water contains artificial substrate of COD _Cr : 2000 mg / L, BOD: 1280 mg / L.
The treatment conditions for each biological treatment tank were as follows.

<First biological treatment tank>
DO: 0.5 mg / L
BOD volumetric load: 7.7 kg-BOD / m ³ / d
HRT: 4h
pH: 7.0
<Second biological treatment tank>
DO: 4 mg / L
Carrier filling rate: 2%
HRT: 17h
SRT: 25 days pH: 7.0

In addition, plate-like polyurethane foam (100 cm × 30 cm × 1 cm / 1 sheet) is used as the carrier 12 of the second biological treatment tank 2, and it is in a position symmetrical to the air diffuser 21 with respect to the vertical plane at the center of the tank. The bottom and the left and right sides were fixed to the tank wall surface.
Moreover, the BOD volumetric load in the whole apparatus is 1.5 kg-BOD / m < ³ > / d, HRT in the whole apparatus is 21 h, and the soluble BOD sludge load with respect to the sludge in the tank of the 2nd biological treatment tank 2 is 0 0.046 kg / kg-MLSS / d.

As a result, the sludge flocs in the second biological treatment tank 2 and the filter-precipitating microanimals (Villus elegans, scallop) are prioritized on the carrier, and the sludge conversion rate is 0.10 kg-MLSS / kg-COD _Cr. It was.
The quality of the treated water (separated water in the precipitation tank 3) was always in good condition throughout the test period, with a soluble COD _Cr concentration of less than 50 mg / L and SS of less than 20 mg / L.

[Comparative Example 1]
The treatment was performed under the same conditions as in Example 1 except that no carrier was provided in the second biological treatment tank.
Raw water quality, treatment conditions of the first and second biological treatment tanks, overall BOD volumetric load and HRT are the same as in Example 1.
As a result, the sludge conversion rate was _{0.10kg-MLSS / kg-COD Cr} . However, the quality of treated water deteriorated due to the predominance of the number of aggregate predatory microanimals, and the solubility COD _Cr of treated water was 80 mg / L or more and treated water SS was 50 mg / L or more throughout the test period. .

[Example 2]
Using raw water containing an artificial substrate of COD _Cr : 670 mg / L, BOD: 430 mg / L, BOD volume load on the first biological treatment tank: 2.6 kg-BOD / m ³ / d, overall BOD volume ^{load: 0.5kg-BOD / m 3 /d(0.78kg-CODcr/m} 3 / d), HRT21h, soluble BOD sludge load on intracisternal sludge in the second biological treatment tank 0.025 kg / kg-MLSS The treatment was performed under the same conditions as in Example 1 except that the operation was performed under the conditions of / d.
As a result, the sludge floc and carrier of the second biological treatment tank were preferentially fixed filter-feeding microanimals (Vorticella, Hirugattamushi), and the sludge conversion rate was 0.08 kg-MLSS / kg-COD _Cr . The treated water quality was always in good condition throughout the test period, with the soluble COD _Cr concentration being less than 30 mg / L and the SS being less than 10 mg / L.

[Comparative Example 2]
The treatment was performed under the same conditions as in Example 2 except that the carrier was not provided in the second biological treatment tank.
Raw water quality, treatment conditions of the first and second biological treatment tanks, overall BOD volumetric load and HRT are the same as in Example 2.
As a result, the sludge conversion rate was _{0.08kg-MLSS / kg-COD Cr} . However, the quality of the treated water deteriorated because the number of aggregate predatory microanimals dominates regularly. For more than half of the test period, the treated water-soluble COD _Cr is 50 mg / L or more, and the treated water SS is 30 mg / L. More than L and worse than Example 2.

[Example 3]
Using raw water containing artificial substrates of COD _Cr : 6700 mg / L, BOD: 4350 mg / L, BOD volume load to the first biological treatment tank: 17.5 kg-BOD / m ³ / d, total BOD volume Load: 5 kg-BOD / m ³ / d, first biological treatment tank HRT6h, second biological treatment tank HRT15h, carrier filling rate of the second biological treatment tank 5%, SRT 50 days, against sludge in the tank of the second biological treatment tank The treatment was performed under the same conditions as in Example 1 except that it was operated under the condition of a soluble BOD sludge load of 0.05 kg / kg-MLSS / d.
As a result, the sludge floc of the second biological treatment tank and the fixed filter predation type micro-animals (Villus elegans, Hirata rotifer) were prioritized, and the sludge conversion rate was 0.09 kg-MLSS / kg-COD _Cr . The water quality of the treated water was always in good condition throughout the test period, with a soluble COD _Cr concentration of less than 60 mg / L and SS of less than 30 mg / L.

  From Example 3, it was recognized that wastewater could be treated as such even if the volume load was large.

[Comparative Example 3]
No carrier is provided in the second biological treatment tank, and raw water containing an artificial substrate of COD _Cr : 550 mg / L, BOD: 350 mg / L is used. BOD volumetric load on the first biological treatment tank: 2.1 kg-BOD / M ³ / d, overall BOD volumetric load: 0.4 kg-BOD / m ³ / d, soluble BOD sludge load with respect to sludge in the tank of the second biological treatment tank 0.025 kg / kg-MLSS / d The treatment was performed under the same conditions as in Example 1 except that the operation was performed at
As a result, the sludge floc and carrier of the second biological treatment tank were preferentially fixed filter-feeding microanimals (Vorticella, Hirugattamushi), and the sludge conversion rate was 0.08 kg-MLSS / kg-COD _Cr . The treated water quality was always in good condition throughout the test period, with the soluble COD _Cr concentration being less than 30 mg / L and the SS being less than 10 mg / L.

  From Comparative Example 3, it was confirmed that when the overall BOD volumetric load was small, the quality of the treated water was improved even without a carrier.

[Example 4]
The same raw water as in Example 1 is used as the raw water, the first biological treatment tank HRT is set to 5.7 h, the second biological treatment tank HRT is set to 17 h, and the BOD volume load on the first biological treatment tank is 5.4 kg-BOD. / M ³ / d, overall BOD volumetric load: 1.5 kg-BOD / m ³ / d, soluble BOD sludge load 0.06 kg against sludge in the tank of the second biological treatment tank by bypassing raw water by 30% The treatment was performed under the same conditions as in Example 1 except that the operation was performed under the conditions of / kg-MLSS / d.
As a result, the sludge floc of the second biological treatment tank and the fixed filter predation type micro-animals (Villus elegans, scallop) were prioritized and the sludge conversion rate was 0.11 kg-MLSS / kg-COD _Cr . The water quality of the treated water was always in good condition throughout the test period, with a soluble COD _Cr concentration of less than 60 mg / L and SS of less than 30 mg / L.

  From Example 4, it was recognized that the water quality of the treated water is reasonably good even if the sludge load is large.

[Example 5]
The carrier of the second biological treatment tank is a fluidized bed sponge carrier (carrier filling rate is 2%), and the soluble BOD sludge load with respect to the sludge in the second biological treatment tank SRT 30 days is 0.04 kg / The treatment was performed under the same conditions as in Example 1 except that the operation was performed under the conditions of kg-MLSS / d.
As a result, the sludge floc of the second biological treatment tank and the fixed filter predation type micro-animals (Villus elegans, scallop) were prioritized and the sludge conversion rate was 0.11 kg-MLSS / kg-COD _Cr . The water quality of the treated water was always in good condition throughout the test period with a soluble COD _Cr concentration of less than 50 mg / L and SS of less than 30 mg / L.

  Even in Example 5, the wastewater could be treated almost satisfactorily, but it was confirmed that the number of micro-animals fixed on the carrier was small.

[Example 6]
In Example 2, treatment was performed under the same conditions as in Example 2 except that 10% of the raw water was directly supplied to the second biological treatment tank and the SRT of the second biological treatment tank was 45 days. It was.
As a result, the sludge floc of the second biological treatment tank and the fixed filter predation type micro-animals (Villus elegans, Hirata rotifer) were prioritized, and the sludge conversion rate was 0.07 kg-MLSS / kg-COD _Cr . The treated water quality was always in good condition throughout the test period, with the soluble COD _Cr concentration being less than 30 mg / L and the SS being less than 10 mg / L.

  From Example 6, it was recognized that even if a portion of the raw water was bypassed, treated water having a water quality equivalent to or higher than that obtained when bypassing was not obtained.

[Example 7]
The same raw water as in Example 1 is used as the first biological treatment tank HRT4h, the second biological treatment tank HRT17h, the second biological treatment tank SRT is 60 days, the solubility BOD for the sludge in the tank of the second biological treatment tank The treatment was performed under the same conditions as in Example 1 except that the operation was performed under a sludge load of 0.03 kg / kg-MLSS / d.
As a result, the sludge floc and carrier of the second biological treatment tank were preferentially fixed filter-feeding microanimals (Vorticella, Hirugattamushi), and the sludge conversion rate was 0.08 kg-MLSS / kg-COD _Cr . The quality of the treated water was always in good condition at all times during the test period, with the soluble COD _Cr concentration being less than 70 mg / L and the SS being less than 50 mg / L. However, it was confirmed that the number of micro-animals fixed on the carrier was smaller than that in Example 1.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.
The present application is based on a Japanese patent application filed on March 16, 2011 (Japanese Patent Application No. 2011-058035) and a Japanese patent application filed on January 6, 2012 (Japanese Patent Application No. 2012-001290). Which is incorporated by reference in its entirety.

Claims (15)

Biological treatment of organic wastewater that performs biological treatment under aerobic conditions with the load of all biological treatment tanks set to CODCr volumetric load 1.0 kg / m ³ / d or more or BOD volumetric load 0.5 kg / m ³ / d or more The aerobic biological treatment tank is provided in multiple stages of two or more stages, organic wastewater is introduced into the first biological treatment tank and biologically treated with bacteria, and the aerobic biological treatment tank is in a dispersed state from the first biological treatment tank. The first biological treatment water containing bacteria is passed through the biological treatment tank after the second biological treatment tank for biological treatment, and the treated water in the biological treatment tank after the second biological treatment tank is solid-liquid separated in the sedimentation tank. In the biological treatment method for organic wastewater, a part of the separated sludge is returned to the biological treatment tank after the second biological treatment tank.
Providing a carrier for holding a micro animal in the biological treatment tank after the second biological treatment tank, and the carrier provided in the biological treatment tank after the second biological treatment tank is made of a synthetic resin foam. Is a sheet having a length of 100 to 400 cm, a side perpendicular to the length of 5 to 200 cm, and a thickness of 0.5 to 5 cm.
Biological treatment method of organic waste water, wherein at least a portion of said carrier is a carrier which is fixed in a vertical direction directly or via a fixture organism treatment tank.   The organic waste water according to claim 1, wherein a soluble BOD sludge load with respect to the sludge in the biological treatment tank after the second biological treatment tank is 0.025 to 0.050 kg / kg-MLSS / d. Biological treatment method.   The biological treatment of organic wastewater according to claim 1 or 2, wherein a part of the organic wastewater is introduced into a biological treatment tank after the second biological treatment tank without passing through the first biological treatment tank. Method.   The biological treatment method for organic wastewater according to any one of claims 1 to 3, wherein an SRT (solid content retention time) of the biological treatment tanks after the second biological treatment tank is 50 days or less.   5. The biological treatment method for organic waste water according to claim 4, wherein the SRT (solid content retention time) of the biological treatment tank after the second biological treatment tank is 10 to 50 days.   The biological treatment method for organic wastewater according to any one of claims 1 to 5, wherein the first biological treatment tank has an HRT of 0.5 to 8 hours. In any one of Claims 1 thru | or 6,
Filling the first biological treatment tank with a carrier;
The filling rate of the carrier in the first biological treatment tank is 10% or less, and the filling rate of the carrier in the biological treatment tank after the second biological treatment tank is 0.1 to 20%. Biological treatment method for organic wastewater. The biological treatment method for organic waste water according to any one of claims 1 to 7 , wherein the synthetic resin foam is polyurethane foam. Biological treatment of organic wastewater that performs biological treatment under aerobic conditions with the load of all biological treatment tanks set to CODCr volumetric load 1.0 kg / m ³ / d or more or BOD volumetric load 0.5 kg / m ³ / d or more An apparatus comprising a plurality of aerobic biological treatment tanks in two or more stages, introducing organic wastewater into the first biological treatment tank, biologically treating with bacteria, and dispersed bacteria from the first biological treatment tank The first biological treatment water containing water is passed through the biological treatment tank after the second biological treatment tank for biological treatment, and the treated water in the biological treatment tank after the second biological treatment tank is separated into solid and liquid in the precipitation tank and separated. In a biological treatment apparatus for organic wastewater that returns a part of sludge to a biological treatment tank after the second biological treatment tank,
A carrier for holding a micro animal is provided in the biological treatment tank after the second biological treatment tank;
And the support | carrier provided in the biological treatment tank after the said 2nd biological treatment tank is a synthetic resin foam, the length of one side is 100-400 cm, and the length of the side orthogonal to it is 5-200 cm, It is a sheet having a thickness of 0.5 to 5 cm,
At least a part of the biological treatment apparatus of an organic waste water, which is a carrier fixed to a vertical direction directly or via a fixture organism processing tank on the carrier. The organic waste water according to claim 9 , wherein a soluble BOD sludge load with respect to sludge in a biological treatment tank after the second biological treatment tank is 0.025 to 0.050 kg / kg-MLSS / d. Biological treatment equipment. According to claim 9 or 10, organic waste water, characterized in that it comprises means for introducing a portion of the organic wastewater to the biological treatment tank of the second biological treatment tank after without going through the first biological treatment tank Biological treatment equipment. The biological treatment apparatus for organic wastewater according to any one of claims 9 to 11 , wherein an SRT (solid content residence time) of the biological treatment tanks after the second biological treatment tank is 50 days or less. The biological treatment apparatus for organic wastewater according to any one of claims 9 to 12 , wherein the first biological treatment tank has an HRT of 0.5 to 8 hours. In any one of claims 9 to 13 ,
Filling the first biological treatment tank with a carrier;
The filling rate of the carrier in the first biological treatment tank is 10% or less, and the filling rate of the carrier in the biological treatment tank after the second biological treatment tank is 0.1 to 20%. Biological treatment equipment for organic wastewater. The biological treatment apparatus for organic wastewater according to any one of claims 9 to 14 , wherein the synthetic resin foam is polyurethane foam.

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