JP2012192396A - Method and apparatus for biologically treating organic wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To substantially reduce the amount of generated sludge, to reduce the frequency of cleaning a membrane by preventing the membrane from clogging, to improve the treating efficiency in a high load operation, and to obtain stable treated-water quality, in the biological treatment of the organic wastewater employing a membrane-type activated sludge process.SOLUTION: The organic wastewater is introduced into a first biological treating tank 1 to be biologically treated with bacteria, a first biologically treated water containing the dispersed bacteria from the first biological treating tank 1 is fed to a second biological treating tank 2 for obtaining a second biologically treated water and the second biologically treated water is separated into solid and liquid. A microorganism-holding carrier 22 is installed in the second biological treating tank 2 and the treated water in the second biological treating tank 2 is separated into solid and liquid by a membrane separator 3. The microorganism-holding carrier 22 is disposed in the second biological treating tank 2 and thus the dispersed bacteria are efficiently preyed and filtration predatory microorganisms with sticking tendency which contribute to a solid-liquid separability of sludge and to improvement of treated-water quality are held, thereby facilitating a stable high-load treatment by preventing the membrane in the membrane separator 3 from blocking.

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 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 microbial cells, that is, sludge, a large amount of excess sludge treatment is also 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 to 50% of the decomposed BOD and is higher than that of the normal activated sludge method.

  In Patent Document 1, organic wastewater is first treated with bacteria in a first treatment tank, and organic matter contained in the wastewater is oxidatively decomposed and converted into non-aggregating bacterial cells, and then in a second treatment tank. It is described that excess sludge can be reduced by predatory removal of the sticking protozoa. Further, this method enables high-load operation and improves the processing efficiency of the activated sludge method.

Such activated sludge methods include a membrane activated sludge method that uses a membrane separator for solid-liquid separation of sludge and treated water, and a sedimentation basin type activated sludge method that uses a sedimentation basin.
The membrane activated sludge process maintains a higher sludge concentration than the sedimentation basin type activated sludge process and can be operated with a high volumetric load. There is an advantage that treated water of quality can be obtained.

  However, in the membrane activated sludge method, depending on the properties of the sludge in the activated sludge tank, the membrane is likely to be clogged, and the frequency of membrane cleaning is high.

  Patent Document 2 proposes a method of reducing sludge adhesion to the membrane and preventing the membrane from being blocked by adding a carrier to the aeration tank.

  In addition, there exists a thing of patent document 3 as invention regarding the multistage process of a fluidized bed and an activated sludge process. 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 Japanese Patent Laid-Open No. 9-294996 Japanese Patent No. 3410699

However, even when the carrier is added to the aeration tank, the membrane may not be sufficiently blocked.
Further, even when the activated sludge treatment is operated at a low load, fine SS is generated by sludge dismantling and the membrane is blocked. In addition, if the number of micro-animals that prey on flocs in activated sludge increases rapidly due to water temperature, load, and SRT (solid content retention time), refinement of sludge is promoted, leading to deterioration of treated water, and solid-liquid separation. There is also a problem that the operation management of the membrane separator becomes difficult.

  The present invention solves the above-mentioned conventional problems, and in the biological treatment of organic wastewater to which the membrane activated sludge method is applied, the generated sludge amount is greatly reduced and the membrane is prevented from being clogged to prevent the membrane from being washed. It is an object of the present invention to provide a biological treatment method and apparatus for organic wastewater that improves processing efficiency by high-load operation and achieves stable treated water quality.

  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, Inhibiting the growth of aggregate (floc) predatory micro-animals that cause membrane occlusion by generating dispersal bacteria and actively prioritizing the necessary micro-animals in subsequent biological treatment tanks; A micro-animal holding carrier is provided in the biological treatment tank in the latter stage, and the fixed predation type micro-animal that contributes to the solid-liquid separation property of sludge and the quality of the treated water is improved by efficiently precipitating the dispersal bacteria; Thus, it has been found that the membrane activated sludge method can prevent the membrane from being blocked and can perform stable high-load treatment.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

  The biological wastewater treatment method of the present invention (Claim 1) is a method of biologically treating bacteria by introducing organic wastewater into a first biological treatment tank of aerobic biological treatment tanks provided in two or more stages. 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 the organic wastewater biological treatment method for solid-liquid separation of the treated water, a biological treatment tank after the second biological treatment tank is provided with a carrier for holding a micro animal, and the biological treatment tank after the second biological treatment tank The solid-liquid separation of the treated water is performed by membrane separation treatment.

  The biological treatment method for organic waste water according to claim 2 is characterized in that, in claim 1, the membrane separation treatment is performed by an outside-type membrane separation apparatus.

  The biological treatment method for organic wastewater according to claim 3 is the carrier according to claim 1 or 2, wherein the carrier provided in the biological treatment tank after the second biological treatment tank is a carrier fixed to the biological treatment tank. It is characterized by.

  A biological treatment method for organic wastewater according to claim 4 is the method according to any one of claims 1 to 3, wherein a part of the organic wastewater is passed through the second biological treatment tank without passing through the first biological treatment tank. It is characterized by being introduced into a biological treatment tank.

  The biological treatment method for organic wastewater according to claim 5 is the biological treatment method according to any one of claims 1 to 4, wherein the SRT (solid content residence time) of the biological treatment tank after the second biological treatment tank is 60 days or less. It is characterized by drawing out sludge.

  The biological treatment method for organic wastewater according to claim 6 is the organic wastewater treatment method according to any one of claims 1 to 5, wherein a part of sludge in the biological treatment tank after the second biological treatment tank is extracted and treated in an oxygen-free tank. After that, it is returned to the biological treatment tank after the second biological treatment tank.

  The biological treatment apparatus for organic wastewater of the present invention (Claim 7) includes an aerobic biological treatment tank provided in two or more stages, and the organic wastewater is introduced into the first biological treatment tank so as to 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 organic wastewater biological treatment apparatus characterized by solid-liquid separation of the treated water in the tank, a carrier for holding micro animals is provided in the biological treatment tank after the second biological treatment tank. A membrane separation treatment apparatus is provided as a solid-liquid separation means for treated water in biological treatment tanks after the biological treatment tank.

  An organic wastewater biological treatment apparatus according to an eighth aspect of the present invention is characterized in that, in the seventh aspect, the membrane separation device is an outside-type membrane separation device.

  The biological wastewater treatment apparatus according to claim 9 is the organic wastewater treatment apparatus according to claim 7 or 8, wherein the carrier provided in the biological treatment tank after the second biological treatment tank is a carrier fixed to the biological treatment tank. It is characterized by.

  A biological treatment apparatus for organic wastewater according to claim 10 is the biological treatment apparatus according to any one of claims 7 to 9, wherein a part of the organic wastewater is passed through the second biological treatment tank without passing through the first biological treatment tank. It has the means to introduce | transduce into the biological treatment tank of this.

  The biological treatment apparatus for organic wastewater according to claim 11 is the biological treatment apparatus according to any one of claims 7 to 10, wherein the SRT (solid content residence time) of the biological treatment tank after the second biological treatment tank is 60 days or less. The sludge is drawn out as described above.

  The biological treatment apparatus for organic wastewater according to claim 12 is the organic wastewater treatment apparatus according to any one of claims 7 to 11, wherein a part of sludge in the biological treatment tank after the second biological treatment tank is extracted and treated. An oxygen-free tank that is returned to the biological treatment tank after the second biological treatment tank is provided.

  In the present invention, in the multi-stage activated sludge method utilizing the predatory action of micro animals, by providing a micro animal holding carrier in the bio treatment tank holding the micro animals, the dispersal bacteria are efficiently eaten in the bio treatment tank. It retains the fixed filtration and predation type micro-animals that contribute to the improvement of the sludge solid-liquid separation and the quality of the treated water, thereby blocking the membrane of the membrane separation device for membrane separation treatment of the biologically treated water in this biological treatment tank Therefore, it is possible to reduce the frequency of chemical cleaning of the membrane.

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. 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.

1-3 is a systematic diagram showing an embodiment of a biological treatment method and apparatus for organic wastewater of the present invention.
1-3, 1 is a 1st biological treatment tank, 2 is a 2nd biological treatment tank, 3 is a membrane separator, 4 is an anoxic tank, 11 and 21 are aeration pipes, 22 is a micro animal holding carrier, 41 is The members that are stirring means and have the same function in FIGS.

  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, when the raw water contains a large amount of oil, the pH may be 8 or more.

Moreover, the water flow to the 1st biological treatment tank 1 is normally made into a transient type, and the BOD volumetric load of the 1st biological treatment tank 1 is 1 kg / m < ³ > / d or more, for example, 1-20 kg / m < ³ > / d, By setting the HRT (raw water retention time) to 24 h or less, preferably 8 h or less, for example 0.5 to 8 h, it is possible to obtain treated water predominated by dispersible bacteria, and by shortening the HRT. Wastewater with a low BOD concentration can be treated with a high load.

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 20% or less, desirably 10% or less, it is possible to generate disperse bacteria that are easy to prey without being affected by concentration fluctuations.

Further, 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.
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, 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 or the membrane 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 case of the membrane activated sludge method, the membrane separation device may be either a tank internal type or a tank external type, but by using the tank external type, clogging of the membrane by dispersal bacteria whose predation was delayed at high loads is prevented. be able to.

  In the present invention, by providing the micro-animal holding carrier 22 in the second biological treatment tank 2, the micro-animals, particularly the dispersal bacteria, are efficiently eaten and contribute to improving the solid-liquid separation property of sludge and the quality of treated water. Increases the amount of filterable predatory microanimals that can be retained in the tank.

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. The floc pieces cause membrane clogging in the membrane activated sludge method. Therefore, in the present invention, in this second biological treatment tank 2, the tank sludge is periodically replaced, that is, in order to thin out minute animals and feces, the SRT (solid content retention time) is desirably 60 days or less, more desirably. It is controlled to be constant within a range of 45 days or less, more desirably 10 days or more and 45 days or less. However, when the sludge concentration (MLSS) in the second biological treatment tank 2 is 2000 mg / L or less, SRT> 60 days may be set. Here, SRT = (sludge concentration in tank × aeration tank volume) ÷ (drawn sludge concentration × amount drawn per day), and sludge concentration in tank (MLSS) indicates the concentration of floating sludge, exclude.
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 not only prevents stable retention at high concentrations, but also organic substances are completely processed in the fluidized bed, and sludge flocs are refined. This leads to membrane occlusion.

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 fixed to any one of the bottom surface, the side surface, the upper part and the like of the second biological treatment tank 2. A carrier is preferred. 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 porous polyurethane foam. For example, the second biological treatment tank 2 has a plate-like or strip-like shape having a length of 100 to 400 cm, a width of 5 to 200 cm, and a thickness of 0.5 to 5 cm. It is desirable to install it in a place where it does not hit.
The carrier is preferably such that the plate-like or strip-like longitudinal direction is in the depth direction of the second biological treatment tank 2, and the plate-like or strip-like carrier is in the vertical direction. The plate surface of the plate-shaped or strip-shaped carrier intersects the flow of water flowing into the second biological treatment tank 2 and flowing out of the second biological treatment tank 2 (preferably orthogonal) Installed in the second biological treatment tank 2 so as to be in the direction.
When the capacity of the second biological treatment tank is larger than the size of the carrier, a plurality of pieces with fasteners attached to the upper and lower surfaces of the carrier are prepared. Alternatively, a predetermined number of sheets are juxtaposed in the width direction, and a fastener attached to a carrier is fixed to a frame material made of a material such as SUS to form a unit, and the carrier unit is further installed in the second biological treatment tank as necessary. Provide multiple stages in the direction of water flow.

A porous sponge carrier such as a thin plate-like or strip-like polyurethane foam having such dimensions has sufficient elasticity and bends in the flow of water in the tank (the shape is not maintained). Therefore, even if it is thin, it has sufficient mechanical strength and does not break. Moreover, by bending, it mixes uniformly, without inhibiting the water flow in a tank, and a sludge containing liquid comes to flow uniformly also into the porous structure of a support | carrier. That is, as a material having elasticity and strength that does not impede water flow and is not easily damaged, in the present invention, the carrier is preferably a plate or strip having a specific size as described above. The polyurethane foam is used.
If the carrier shape with a small surface area is selected with an emphasis on water permeability, the water permeability is improved, but the number of micro-animals held on the carrier is limited, and biological treatment (decomposition of organic matter) in the second biological treatment tank is limited. , Sludge volume reduction).

  Conventionally, there are various types of porous carriers such as honeycombs, hollows, and meshes. However, if the thickness of the carrier is too large, the water permeability inside the carrier is lowered, so that the cells decay inside. The problem is likely to occur. For this reason, the thickness of the carrier is preferably reduced, and in the present invention, it is a plate or strip, preferably 0.5 to 5 cm. Such a plate-like or strip-like porous carrier can be produced, for example, by slicing a rectangular parallelepiped polyurethane foam into a plate-like or strip-like shape.

  Further, as the conditions for the foamed cells of the porous carrier, those having a uniform distribution of the foamed cells are preferable. Moreover, since the mechanical strength of a porous support | carrier will become small when there are too many foam cells or a cell diameter is too large, it is an upper limit as cell number / 25mm (cell number which exists in the range of 25 mm length). Is preferably about 125 pieces / 25 mm. Conversely, if the number of foamed cells is too small or the cell diameter is too small, the function as a porous carrier cannot be obtained sufficiently. The lower limit of / 25 mm is preferably about 5/25 mm. For the number of cells / 25 mm, a photo of the porous carrier taken with a scanning electron microscope was used to measure the number of foamed cells intersecting the straight line 25 mm in the length direction at a plurality of locations. The average value of the results can be calculated and obtained.

  In addition, as the surface area of the porous carrier is larger, it is preferable because the number of growing micro-animals is larger, but the length in the depth direction of the second biological treatment tank 2 is upstream and downstream due to aeration. Although it is not particularly limited because it does not affect the fluidity of water, the length in the short direction of the second biological treatment tank 2 (the width of the carrier) affects the fluidity of water. The width is preferably 5 to 200 cm, particularly 5 to 100 cm as described above. In addition, when the width | variety of the 2nd biological treatment tank 2 is wide, it is preferable to increase the number of support | carriers and to prevent a short circuit flow.

  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 desirable to operate at 0.025 to 0.05 kg-BOD / kg-MLSS / d in terms of sludge load due to the soluble BOD in the latter biological treatment tank. Again, MLSS refers to the concentration of suspended sludge and does not include sludge for carrier adhesion.

  In FIG. 1, the treated water from the second biological treatment tank 2 is supplied to the outside membrane separation apparatus 3, and the permeated water of the membrane separation apparatus 3 is taken out as treated water, and the concentrated water is treated as the second biological treatment. It returns to the upstream of the tank 2, and the excess sludge is extracted directly from the second biological treatment tank 2. Thus, when the membrane separation device 5 is used as the solid-liquid separation means, according to the present invention, since the growth of the aggregate predation type micro-animal is suppressed, the membrane as in the conventional membrane separation treatment of activated sludge The problem of clogging can be reduced, the membrane flux can be stabilized, the frequency of chemical cleaning can be reduced, and sudden sludge dispersal can be prevented, facilitating the operation management of the membrane separator. Can do.

  There is no restriction | limiting in particular as the membrane separation apparatus 3 outside a tank, An ultrafiltration (UF) membrane separation apparatus, a microfiltration (MF) membrane separation apparatus, etc. can be used.

  The embodiment shown in FIG. 2 is different from the embodiment shown in FIG. 1 in that a part of raw water, for example, about 5 to 50% is introduced directly into the second biological treatment tank 2 without going through the first biological treatment tank 1. The other configurations are the same. 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.

  In the embodiment shown in FIG. 3, by removing a part of the sludge in the second biological treatment tank 2 holding the minute animals, treating it in the anoxic tank 4, and returning it, the minute animal holding biological treatment tank 2 The growth of the aggregate predation type micro-animal is further suppressed to preferentially proliferate the filtration predation type micro-animal, and the other configuration is the same as that of the embodiment of FIG.

  That is, by providing the oxygen-free tank 4 and retaining the sludge extracted from the second biological treatment tank 2 in the oxygen-free tank 4 for a predetermined time, the growth of the swimming micro-animals is inhibited. Stabilize biota. In this case, the second biological treatment tank 2 is provided with a micro-animal holding carrier 22, and since a certain amount of the filter predation type micro animal is held on the carrier 22 side, the growth of the filter predation type micro animal is inhibited. Never happen. The sludge extracted from the second biological treatment tank 2 and treated in the anoxic tank 4 is returned to the second biological treatment tank 2.

  The amount of sludge withdrawn from the second biological treatment tank 2 to the oxygen-free tank 4 and the sludge residence time in the oxygen-free tank 4 are appropriately determined according to the treatment status. It is preferable that the sludge residence time in the anaerobic tank 4 is 0.5 hour or more.

  In the present invention, in the anaerobic tank 4, the ORP needs to be 0 mV or less in order to inhibit the growth of minute animals. Therefore, it is desirable not to perform aeration in the oxygen-free tank 4 but only to mechanical stirring. Moreover, in order to accelerate | stimulate the fall of ORP, a part of 1st biological treatment water and raw | natural water may be passed, and you may make it lower ORP by an acid production | generation reaction or a denitrification reaction.

Further, a carrier may be added to the oxygen-free tank 4 in order to stably advance the ORP reduction (denitrification reaction, acid generation reaction) in the oxygen-free tank 4. If the ORP in the anaerobic tank 4 is low, the decrease in the activity of the swimming micro-animal is promoted, so the residence time of the second biological treatment tank sludge in the anoxic tank 4 can be shortened, and the anaerobic tank 4 can be downsized. can do. In the case of a fluidized bed, the shape of the carrier to be added is arbitrary such as a spherical shape, a pellet shape, a hollow cylindrical shape, and a thread shape. A fixed bed may be used, and the shape of the carrier 22 in that case is arbitrary, such as a thread shape or a plate shape. Further, the material may be a natural material, an inorganic material, a polymer material or the like, and a gel material may be used.
When adding a support | carrier to the anoxic tank 4, the filling rate changes with the difference in the format and material of a fluid bed and a fixed bed, but it is desirable to set it as 0.5 to 40%.

  1-3 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, by providing a micro animal holding carrier in the biological treatment tanks subsequent to the second biological treatment tank, it is possible to reduce sludge reduction by suppressing the priority of aggregate predation type micro animals. And the quality of the treated water can be made compatible, and the biological treated water after this second biological treatment tank is solid-liquid separated by the membrane separator to prevent the membrane of the membrane separator from being blocked and stable. High load processing is possible.

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

[Example 1]
As shown in FIG. 1, using an experimental apparatus in which a first biological treatment tank 1 having a capacity of 36 L, a second biological treatment tank 2 having a capacity of 150 L, and a UF membrane separation device 3 are connected, Treatment of sexual wastewater was performed. The raw water contains artificial substrates of COD _Cr : 1000 mg / L, BOD: 640 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: 3.85 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: 30 days pH: 7.0

In addition, as the carrier 12 of the second biological treatment tank 2, one plate-like polyurethane foam (length 100 cm × width 30 cm × thickness 1 cm / 1 sheet; number of cells 50/25 mm) is used, and is arranged vertically in the tank. (The length direction of the carrier is defined as the depth direction of the tank). The upper and lower ends of the carrier 12 are fixed to a frame, and the frame is fixed to the wall surface of the tank. In addition, the carrier 12 is disposed so as to be isolated from the upper position of the air diffuser 21 so that the aerated air from the air diffuser 21 does not hit the carrier 12.
Moreover, the BOD volume load in the whole apparatus was 0.75 kg-BOD / m < ³ > / d, and HRT in the whole apparatus was 21 h.

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 0.1 kg-MLSS / kg-COD _Cr. It was.
The quality of the treated water (permeated water of the membrane separation device 3) was always in a good state during the test period, with a soluble COD _Cr concentration of less than 20 mg / L.
Further, there was almost no increase in the transmembrane pressure difference of the membrane separation apparatus 3, and a stable flux could be maintained without chemical cleaning for one month or longer.

[Comparative Example 1]
The treatment was performed under the same conditions as in Example 1 except that the first biological treatment tank was omitted, the capacity of the second biological treatment tank was 186 L, and no carrier was provided in the second biological treatment tank.
Raw water quality, DO and pH of the second biological treatment tank, overall BOD volumetric load and HRT are the same as in Example 1.
As a result, the sludge conversion rate was _{0.20kg-MLSS / kg-COD Cr} . However, every other month, the aggregate predatory microanimals (Holeoptera) prevailed, and during that time, the transmembrane pressure difference increased, requiring chemical cleaning of the membrane once every two weeks. In addition, the process water is also worse, soluble _{COD Cr} concentration was increased to more than 70 mg / L.

[Comparative Example 2]
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 _{0.12kg-MLSS / kg-COD Cr} . However, the number of filtered predatory micro-animals is not stable, and despite the use of a membrane separator, dispersal bacteria that escaped predation clog the membrane, resulting in frequent increases in transmembrane pressure. Chemical cleaning was required once every two weeks.

[Example 2]
As shown in FIG. 3, an oxygen-free tank 4 having a capacity of 5 L is provided, and after sludge in the second biological treatment tank 2 is extracted and treated in the oxygen-free tank 4, it is returned to the second biological treatment tank 2. Except for this, the treatment was performed under the same conditions as in Example 1. The quality of raw water, the treatment conditions of the first and second biological treatment tanks, and the overall BOD volumetric load and HRT are the same as in Example 1.
The processing conditions of the anoxic tank 4 were as follows.
<Anoxic tank>
ORP: -100 mV
HRT (= SRT): 12h

As a result, the sludge floc in the second biological treatment tank and the fixed filter predation type micro-animals (Villus elegans, Hirata rotifer) were prioritized on the carrier, and the sludge conversion rate was 0.075 kg-MLSS / kg-COD _Cr . .
The quality of the treated water was always in good condition during the test period with a soluble COD _Cr concentration of less than 20 mg / L. Moreover, there was almost no increase in transmembrane pressure, and a stable flux could be maintained without chemical cleaning for one month or longer.

  The biological treatment method and apparatus 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.

DESCRIPTION OF SYMBOLS 1 1st biological treatment tank 2 2nd biological treatment tank 3 Membrane separation apparatus 4 Anoxic tank

Claims (12)

The first organism containing the dispersed bacteria from the first biological treatment tank by introducing organic wastewater into the first biological treatment tank of the aerobic biological treatment tank provided in two or more stages and biologically treating with bacteria In the biological treatment method of organic waste water, the treated water is passed through a biological treatment tank after the second biological treatment tank to be biologically treated, and the treated water in the biological treatment tank after the second biological treatment tank is solid-liquid separated.
A biological treatment tank after the second biological treatment tank is provided with a carrier for holding a micro animal,
A biological treatment method for organic wastewater, wherein solid-liquid separation of treated water in biological treatment tanks after the second biological treatment tank is performed by membrane separation treatment.   The biological treatment method for organic wastewater according to claim 1, wherein the membrane separation treatment is performed by an outside-membrane type membrane separation device.   The biological treatment method for organic wastewater according to claim 1 or 2, wherein the carrier provided in the biological treatment tank after the second biological treatment tank is a carrier fixed to the biological treatment tank.   The organic material according to any one of claims 1 to 3, wherein a part of the organic waste water is introduced into a biological treatment tank after the second biological treatment tank without passing through the first biological treatment tank. Biological treatment method for effluent.   5. The organic waste water according to claim 1, wherein the sludge is extracted so that the SRT (solid content retention time) of the biological treatment tanks after the second biological treatment tank is 60 days or less. Biological treatment method.   6. The biological treatment tank according to any one of claims 1 to 5, wherein a part of the sludge in the biological treatment tank after the second biological treatment tank is extracted and treated in an oxygen-free tank, and thereafter the biological treatment tank after the second biological treatment tank. A method for biological treatment of organic wastewater, which is returned to the factory. The aerobic biological treatment tank is provided in two or more stages, the organic wastewater is introduced into the first biological treatment tank and biologically treated with bacteria, and the dispersed bacteria from the first biological treatment tank are contained. Organic wastewater characterized in that one biologically treated water is passed through a 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 biological treatment equipment of
A carrier for holding micro animals is provided in the biological treatment tank after the second biological treatment tank,
An organic wastewater biological treatment apparatus comprising a membrane separation treatment device as a solid-liquid separation means for treated water in biological treatment tanks after the second biological treatment tank.   8. A biological treatment apparatus for organic wastewater according to claim 7, wherein the membrane separation apparatus is an outside tank type membrane separation apparatus.   The biological treatment apparatus for organic wastewater according to claim 7 or 8, wherein the carrier provided in the biological treatment tank after the second biological treatment tank is a carrier fixed to the biological treatment tank.   In any 1 item | term of the Claims 7 thru | or 9, It has a means to introduce | transduce a part of said organic waste water into the biological treatment tank after the said 2nd biological treatment tank, without passing through the said 1st biological treatment tank. Biological treatment equipment for organic wastewater.   The organic material according to any one of claims 7 to 10, wherein the sludge is drawn so that the SRT (solid content retention time) of the biological treatment tank after the second biological treatment tank is 60 days or less. Wastewater biological treatment equipment.   In any one of Claims 7 thru | or 11, after a part of sludge in the biological treatment tank after the said 2nd biological treatment tank is extracted and processed, it does not return to the biological treatment tank after this 2nd biological treatment tank. An organic wastewater biological treatment apparatus characterized by providing an oxygen tank.

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