JP2015128747A - Water treatment apparatus and water treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment apparatus and a water treatment method capable of performing more stable water treatment by suppressing exfoliation of microbe from a carrier inputted into a reaction tank.SOLUTION: A water treatment apparatus includes: a treatment tank (denitrification tank 5) for storing a microbe catalyst 10 formed by immobilizing self-granulation type anaerobic microbe on the outer surface of a carrier, and liquid to be treated, and treating the liquid to be treated under an anaerobic condition; and gas agitation means 51 for agitating the liquid to be treated and the microbe catalyst 10 by supplying inert gas into the treatment tank.

Description

  The present invention relates to a water treatment apparatus and a water treatment method, and more particularly to a water treatment apparatus and a water treatment method using an anaerobic microorganism having a characteristic of self-granulating.

  An anaerobic ammonia oxidation technique is a technique that has attracted attention in recent years. For example, in JP 2011-251255 A (Patent Document 1), a waste liquid ER containing nitrite nitrogen and ammonia nitrogen and anamox granule AG are accommodated in a treatment tank, and a rotary stirring member is used. A waste liquid treatment method and apparatus for removing a nitrogen component in a waste liquid as nitrogen gas by generating a liquid flow in the treatment tank are described.

  In International Publication No. 2010/074008 (Patent Document 2), as shown in FIG. 3, a nitrite type nitrifying bacterium is arranged outside, and an anaerobic ammonia oxidizing bacterium is arranged inside the nitrite type nitrifying bacterium. A carrier carrying a layered microbial membrane is put into a reaction vessel equipped with an impeller and a draft tube as shown in FIG. 2, and denitrification of the water to be treated is performed while the carrier is flowed by stirring in the reaction vessel. A biological nitrogen removal method and apparatus are described.

  In Japanese Patent No. 5150993 (Patent Document 3), an autotrophic denitrifying microorganism is allowed to enter and adhere to the inside of a granular carrier, and the treated sludge supported three-dimensionally is held in a denitrification tank and floated. A denitrification method and apparatus capable of performing a denitrification process by contacting the liquid in an anaerobic state are described.

JP 2011-251255 A International Publication No. 2010/074008 Japanese Patent No. 5150993

  In order to perform anaerobic ammonia oxidation efficiently, it is necessary to efficiently bring the substrate and the microorganism into contact with each other, and for this purpose, appropriate stirring is required. The method generally used at present is mechanical stirring using a stirrer as described in Patent Documents 1 to 3.

  However, it is known that microorganisms such as anaerobic ammonia oxidizing bacteria used for an anaerobic ammonia oxidation treatment method have a characteristic of forming a self-granulated mass. When mechanical agitation as described in Patent Documents 1 to 3 is performed on a binding-immobilized carrier in which such self-granulating microorganisms are immobilized on the surface, the microorganisms are peeled off from the carrier and removed from the reaction vessel. It was found that a phenomenon that flows into As a result, it is difficult to always keep a certain amount or more of microorganisms in the reaction tank, and it may be difficult to perform stable water treatment.

  In view of the above problems, the present invention provides a water treatment apparatus and a water treatment method capable of suppressing detachment of microorganisms from a carrier charged into a reaction tank and performing more stable water treatment.

  The present inventors diligently investigated the relationship between the characteristics of a microbial catalyst in which microorganisms are immobilized on a carrier and agitation, and found that the self-granulating anaerobic microorganisms were immobilized on the outer surface of the carrier. It has been found that the use of a specific stirring means can suppress detachment of microorganisms from the carrier. As a result, it has been found that a water treatment apparatus and a water treatment method capable of significantly suppressing the outflow of microorganisms detached from the carrier to the outside of the reaction tank and capable of performing a more stable denitrification treatment than in the past can be obtained. It was.

  The present invention completed on the basis of the above knowledge, in one aspect, contains a microbial catalyst in which self-granulating anaerobic microorganisms are immobilized on the outer surface of a carrier and a liquid to be treated, and is subjected to an anaerobic condition. There is provided a water treatment apparatus comprising a treatment tank for treating a treatment liquid, and a gas stirring means for stirring the liquid to be treated and the microbial catalyst by supplying an inert gas into the treatment tank.

  In one embodiment, the water treatment apparatus according to the present invention has irregular irregularities on the outermost surface of the microbial catalyst.

  In one embodiment of the water treatment apparatus according to the present invention, the microbial catalyst comprises a microbial membrane containing anaerobic microorganisms having a maximum thickness of 100 μm or more on the outer surface of the carrier.

  In another embodiment of the water treatment apparatus according to the present invention, the microbial catalyst includes that at least one recess having a depth from the outermost surface of 50 μm or more is formed.

  In still another embodiment of the water treatment apparatus according to the present invention, the anaerobic microorganism is an anaerobic ammonia oxidizing bacterium.

In still another embodiment of the water treatment apparatus according to the present invention, the gas stirring means includes supplying an inert gas into the treatment tank at 10 to 450 L / (m ² · min).

  In still another embodiment, the water treatment apparatus according to the present invention further includes gas circulation means for circulating the inert gas supplied into the treatment tank into the treatment tank.

  In another aspect, the present invention provides a nitrification tank for obtaining a nitritation treatment liquid by partially oxidizing a part of ammonia nitrogen contained in a liquid to be treated into nitrite nitrogen by the action of nitrite bacteria. And a denitrification tank that anaerobically oxidizes nitrogen in the nitritation solution using a microbial catalyst in which self-granulating anaerobic microorganisms are immobilized on the outer surface of the carrier, and a denitrification tank. There is provided a water treatment apparatus comprising a gas stirring means for stirring a nitritation treatment liquid and a microbial catalyst by supplying an inert gas.

  In yet another aspect of the present invention, a first denitrification liquid is obtained by anaerobically denitrifying a liquid to be treated containing nitrogen and organic matter by a denitrification reaction using heterotrophic bacteria. A denitrification tank, a nitrification tank for oxidizing a part of ammonia nitrogen contained in the first denitrification treatment liquid into nitrite nitrogen by the action of nitrite bacteria to obtain a nitritation treatment liquid, and nitrous acid Nitrifying solution circulating means for circulating a part of the nitrifying solution to the first denitrification tank, ammonia nitrogen in the nitrating solution, and self-granulating anaerobic microorganisms on the outer surface of the carrier A second denitrification tank that performs anaerobic oxidation treatment using a fixed microbial catalyst, and a gas stirring means that stirs the nitritation solution and the microbial catalyst by supplying an inert gas into the second denitrification tank. A water treatment device is provided.

  In another aspect of the present invention, a microbial catalyst in which self-granulating anaerobic microorganisms are immobilized on the outer surface of a carrier and a liquid to be treated are accommodated in a treatment tank, and the inert gas is contained in the treatment tank. A water treatment method including treating the liquid to be treated by stirring the microbial catalyst and the liquid to be treated under anaerobic conditions is provided.

  In one embodiment of the water treatment method according to the present invention, the anaerobic microorganism is an anaerobic ammonia oxidizing bacterium.

  ADVANTAGE OF THE INVENTION According to this invention, the water treatment apparatus and water treatment method which can suppress peeling of the microorganisms from the support | carrier thrown into the reaction tank and can perform more stable water treatment can be provided.

It is the schematic showing an example of the water treatment apparatus which concerns on embodiment of this invention. It is explanatory drawing showing the example of the stirring means employable for the denitrification tank of FIG. It is explanatory drawing showing the example of another stirring means employable for the denitrification tank of FIG. FIG. 4A is a cross-sectional view showing an example of the microbial catalyst according to the embodiment of the present invention, and FIG. 4B is a diagram in which a part of the microbial film of the microbial catalyst in FIG. FIG. 4C is a cross-sectional view showing a state, FIG. 4C is a cross-sectional view of a conventional entrapping immobilization support, and FIG. 4D is a cross-sectional view showing another example of a microbial catalyst according to an embodiment of the present invention. It is. It is a photograph which shows an example of the cross section of the microbial catalyst which concerns on embodiment of this invention. It is a photograph showing the depth of the unevenness | corrugation of the outermost surface of the microbial catalyst which concerns on embodiment of this invention. It is the schematic showing an example of the water treatment apparatus which concerns on the modification of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention specifies the structure, arrangement, etc. of components as follows. Not what you want.

  In the following description, an apparatus and a method related to an anaerobic ammonia oxidation treatment will be exemplified as the water treatment apparatus and the water treatment method according to the present invention. However, it goes without saying that the present invention can also be applied to other apparatuses and methods that use a microbial catalyst in which an anaerobic microorganism having a self-granulating property is immobilized on the surface of a carrier.

  As shown in FIG. 1, a water treatment apparatus according to an embodiment of the present invention includes a nitritation tank 3, a sedimentation tank 4 connected to the nitritation tank 3, and nitritation via the sedimentation tank 4. And a denitrification tank 5 (anaerobic ammonia oxidation tank) connected to the tank 3.

In the nitritation tank 3, a part of ammonia nitrogen (NH ₄ -N) contained in the liquid to be treated (raw water) is converted into nitrite nitrogen (NO ₂ -N) by the action of nitrite bacteria. Partial nitritation treatment is performed. In the partial nitritation treatment, it is desirable to stably maintain ammonia oxidizing bacteria as nitrite bacteria in the nitritation tank 3. Examples of a method for stably maintaining the ammonia-oxidizing bacteria include adding a fluid carrier capable of adhering and fixing the ammonia-oxidizing bacteria in the nitritation tank 3.

  Gels using synthetic polymers such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyacrylamide, and photocurable resin, and polymers such as carrageenan and sodium alginate as a fluid carrier filled in the nitritation tank 3 Examples thereof include a carrier, a carrier made of polyethylene, polyurethane, polypropylene, or a carrier made of activated carbon.

  As the shape of the carrier, any of a spherical shape, a square shape, and a cylindrical shape can be used, and the effective diameter thereof is 2 to 20 mm that can be stably separated from the screen provided at the outlet of the nitritation tank 3, and more preferably It is preferably 3 to 15 mm, more preferably 3 to 10 mm. The specific gravity of the carrier is preferably 1.01 to 1.15, more preferably 1.01 to 1.10, and still more preferably 1.01 to 1.05, which enables uniform flow in the aerated state. The carrier filling amount is preferably 5 to 30 V%, and more preferably 10 to 20 V%, which enables uniform flow of mixing.

  In the nitritation tank 3, it is desirable that the carrier is added and the suspended activated sludge coexists. Even if the quality of the raw water flowing into the nitritation tank 3 fluctuates due to the coexistence of the floating activated sludge, it can be averaged by the activated sludge treatment. Therefore, there is almost no influence on the microorganism carrier due to the adhesion of ammonia oxidizing bacteria, and a stable nitritation treatment can be obtained.

  In the settling tank 4, the suspended activated sludge contained in the nitritation solution is settled and separated. The supernatant liquid obtained by sedimentation separation is sent to the denitrification tank 5. A part of the sludge settled and separated in the settling tank 4 can be supplied to the nitritation tank 3 as return sludge. Part of the excess sludge generated in the settling tank 4 is sent to the sludge treatment facility.

  The denitrification tank 5 is a treatment tank that anaerobically oxidizes ammoniacal nitrogen in the nitritation solution after separation of suspended activated sludge using a microbial catalyst. In the denitrification tank 5, as a stirring means for stirring the nitritation treatment liquid and the microbial catalyst in the tank, the nitritation treatment liquid and the microbial catalyst 10 are supplied by supplying an inert gas to the denitrification tank 5. A gas stirring means 51 for stirring is arranged.

  The details of the gas agitating means 51 are not particularly limited, but can be constituted by, for example, a blower that supplies gas to the liquid, a compressor, and a diffuser (a diffuser, a diffuser, a sparger, a diffuser plate, a membrane) or the like. For example, as shown in FIG. 2, a gas supply port 51A is provided at the bottom of the denitrification tank 5, an inert gas is supplied upward from the gas supply port 51A to the denitrification tank 5, An apparatus for generating a liquid flow (rotating flow) in the mixed liquid can also be suitably employed.

  Alternatively, as shown in FIG. 3, a draft tube 52B is disposed above the gas supply port 51B provided at the bottom of the denitrification tank 5, and a liquid flow is generated in the liquid mixture of the nitritation solution and the microbial catalyst. The apparatus for this can also be used suitably as the gas stirring means 51.

  As shown in FIG. 1, a gas circulation means 53 that circulates the inert gas supplied into the denitrification tank 5 again into the denitrification tank 5 may be further provided. By disposing the gas circulation means 53, the gas used for stirring can be used effectively, so the amount of inert gas used can be reduced and more efficient processing can be performed. In the case of anaerobic ammonia oxidation, since the nitrogen gas generated in the process itself is an inert gas, a more efficient process can be performed by circulating and using the nitrogen gas generated in the process.

The gas stirring means 51 preferably supplies a compressed gas made of an inert gas such as nitrogen gas into the denitrification tank 5. Supply of compressed gas, for example 10~450L / m ² · min, more preferably 30~300L / m ² · min, more preferably be fed to the denitrification tank 5 at 50~150L / m ² · min desirable.

  A schematic diagram of the microbial catalyst 10 used in the present embodiment is shown in FIG. The denitrification tank 5 is supplied with a microbial catalyst 10 in which an anaerobic microorganism having a characteristic of self-granulation (hereinafter referred to as “self-granulation type”) is fixed on the outer surface S1 of the carrier 10A. In the case of anaerobic ammonia oxidation treatment, an anaerobic ammonia oxidizing bacterium is preferably used as the self-granulating anaerobic microorganism.

  As shown in FIG. 4A, the microbial catalyst 10 includes a carrier 10A and a microbial membrane 10B disposed on the outer surface S1 of the carrier 10A. Examples of the material of the carrier 10A include polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyacrylamide, a synthetic polymer such as a photocurable resin, a gel carrier using a polymer such as carrageenan and sodium alginate, polyethylene, polyurethane, Examples thereof include a carrier made of polypropylene or the like, or granular activated carbon.

  As the shape of the carrier 10A, any of a spherical shape, a square shape, and a cylindrical shape can be used, and the effective diameter is preferably 1 to 20 mm that can be stably separated from the screen at the outlet of the denitrification tank. A carrier having a large number of fine pores on the surface and an infinite number of irregularities on the surface can quickly attach and fix the anaerobic ammonia-oxidizing bacteria, and high denitrification performance can be obtained in a short time. Furthermore, since the anaerobic ammonia oxidizing bacteria in the denitrification tank can be maintained at a high concentration for a long period of time, stable denitrification performance can be obtained.

The specific surface area of the carrier 10A is preferably 200 to 10000 m ² / m ³ , more preferably 200 to 20000 m ² / m ³ , still more preferably 200 to 30000 m ² / m ³ . The carrier specific gravity is preferably 1.01 to 1.15, more preferably 1.01 to 1.10, and still more preferably 1.01 to 1.05, which can flow uniformly by stirring in an anaerobic state. The carrier filling amount is preferably 5 to 30 V% which enables uniform mixing and flow, more preferably 10 to 30 V%, still more preferably 10 to 20 V%.

  Nitrogen is generated in the denitrification tank 5 by the action of the anaerobic ammonia oxidizing bacteria. When the nitrogen produced by the reaction does not leave from the anaerobic ammonia oxidizing bacteria, the anaerobic ammonia oxidizing bacteria can easily float and flow out of the denitrification tank 5. In the present embodiment, the phenomenon that the anaerobic microorganisms flow out of the denitrification tank 5 can be suppressed by immobilizing the anaerobic microorganisms on the carrier 10A having a specific gravity higher than that of water. Microorganisms can be stably retained.

  The carrier 10A used in this embodiment is preferably a bound and immobilized carrier. The “bound immobilization carrier” means a carrier on which microorganisms are immobilized mainly by a binding immobilization method in which microorganisms adhere or grow on the outer surface of the carrier 10A. By using the bound and immobilized carrier in the anaerobic ammonia oxidation treatment, the transport efficiency of the substrate to the microorganism is increased, and the reaction rate is improved. Moreover, the effect which becomes easy to discharge | release the nitrogen gas generated by reaction into a liquid is also acquired. In the case of the entrapping immobilization carrier that is the other immobilization method, if too much microorganisms are retained, the carrier may collapse from the inside with nitrogen gas generated from the microorganisms retained inside the carrier, In this respect, the bound and immobilized carrier is more effective for microorganisms that generate gas in the reaction.

  However, it is known that self-granulating anaerobic microorganisms such as anaerobic ammonia-oxidizing bacteria are microorganisms that self-granulate in an indefinite form. When the catalyst 10 is produced, irregular irregularities including large and small irregularities are formed on the outermost surface S2 of the microorganism membrane 10B.

  In conventional stirring by mechanical stirring, the microbial catalyst 10 collides with the stirring blade. As shown in FIG. 4 (a), irregular irregularities are formed on the outermost surface S2 of the microbial membrane 10B. When the stirring blades are caught in the irregularities, the microorganisms as shown in FIG. 4 (b). A part of the film 10B is peeled off. Further, not only direct contact with the stirring blade but also strong turbulence generated in the vicinity of the stirring blade may cause a part of the microbial membrane 10B to peel off from the unevenness of the outermost surface S2 of the microbial membrane 10B. In the present invention, partial peeling of the microbial membrane 10B of the microbial catalyst 10 can be effectively suppressed by performing stirring by the gas stirring means 51 instead of mechanical stirring.

  On the other hand, regarding the use of self-granulating anaerobic microorganisms commonly used in the present anaerobic ammonia oxidation technology, as shown in FIG. A method using the carrier 11 immobilized by the “entrapping immobilization method” that takes in and immobilizes inside (the dot portion inside the carrier 11 in FIG. 4C indicates a microorganism immobilized inside the resin) is used. However, in the method of flowing the carrier fixed by the entrapping immobilization method, since the microorganisms are entrapped by the resin, there is no opportunity for the resin to directly collide with the stirring blade, and the problem of microbial membrane peeling by mechanical stirring is It does not occur very much. Another method of using a self-granulated microorganism agglomerate itself as a microbial catalyst (granule method) does not cause microorganisms to adhere to the carrier, so it is called detachment of the microbial film. The problem itself does not exist.

  In the embodiment of the present invention, the effect of suppressing separation of the microbial membrane 10B that is particularly effective for the microbial catalyst 10 having the following surface properties can be obtained.

  As shown in FIG. 4A, when the thickness of the portion of the microbial catalyst 10 where the microbial membrane 10B is formed to be the thickest is defined as “the maximum thickness (Tmax) of the microbial membrane 10B”, gas stirring is performed. Agitation by the means 51 provides a microbial membrane 10B peeling suppression effect that is particularly effective for the microbial catalyst 10 having a maximum thickness (Tmax) of the microbial membrane 10B of 100 μm or more, more preferably 150 μm or more, and even 200 μm or more. The upper limit of the maximum thickness Tmax of the microbial membrane 10B is generally about 10 mm when the carrier 10A having an effective diameter of 1 to 20 mm is used.

  The minimum thickness (Tmin) of the microbial membrane 10B of such a biocatalyst 10 is at least 10 μm. Note that the maximum thickness and the minimum thickness (Tmax, Tmin) of the microbial membrane 10B are evaluated by, for example, taking a photograph of the microbial catalyst 10 and evaluating its thickness, or observing a cross-sectional state by cutting the microbial catalyst 10 ( (See FIG. 5).

As shown in FIG. 6, the microbial catalyst 10 suitable for the present invention has irregular irregularities on the outermost surface S2. For example, as seen in the region R, the granularity formed with one or more, more specifically 1 to 10 ⁶ , and more preferably about 10 to 10 ⁴ recesses having a depth from the outermost surface of 50 μm or more. It is a body (one section of FIG. 6 represents 1 mm). Here, the “depth from the outermost surface” is defined as the size when the height difference between the bottom of the dent and the surrounding high portion is measured. There are one or more, more specifically 5 to 10,000, such recesses in the surface area of 50 mm ^{2 of the} carrier 10A.

  According to the water treatment apparatus according to the embodiment of the present invention, the microbial membrane 10B is detached from the microbial catalyst 10 introduced into the denitrification tank 5 by arranging the gas stirring means 51 instead of mechanical stirring. Can be suppressed. Thereby, constant microorganisms always exist in the denitrification tank 5, thereby providing a water treatment apparatus and a water treatment method capable of performing more stable water treatment than in the prior art.

(Modification)
A water treatment apparatus according to a modification of the present invention is shown in FIG. The water treatment apparatus is a concentration / dehydration apparatus 1 that removes suspended solids (SS) components in the raw water by concentrating and dehydrating raw water (liquid to be treated) containing nitrogen and organic matter, and a concentration / dehydration apparatus. A first denitrification tank 2 which obtains a first denitrification treatment liquid by anaerobically denitrifying the treatment liquid obtained from 1 by a denitrification reaction using heterotrophic bacteria; and in the first denitrification treatment liquid A part of the ammonia nitrogen contained in the nitrite is oxidized to nitrite nitrogen by the action of nitrite bacteria to obtain a nitrite treatment solution, and a part of the nitrite treatment solution is first removed. Using the nitrite treatment liquid circulating means 7 circulating to the nitriding tank 2, and the microbial catalyst 10 in which ammonia nitrogen in the nitrite treatment liquid is fixed on the outer surface of the carrier with a self-granulating anaerobic microorganism. A second denitrification tank 5 that performs anaerobic oxidation treatment, and the second denitrification tank 5 is in the second denitrification tank 5. And a gas stirring means 51 for stirring the liquid to be treated and the microbial catalyst 10 by supplying an inert gas.

  That is, the water treatment apparatus shown in FIG. 7 is further provided with a concentration / dehydration apparatus 1 and a first denitrification tank 2 upstream of the nitritation tank 3 of FIG. 1 is different from the water treatment apparatus shown in FIG. 1 in that a circulation means 7 for circulating the treatment liquid to the first denitrification tank 2 is provided, and the sedimentation tank 6 is disposed on the outlet side of the denitrification tank 5.

  As the concentrating / dehydrating apparatus 1, various apparatuses can be used. For example, when a human waste and a septic tank sludge mixed solution are used as raw water, it is generally preferable to separately perform concentration and dehydration treatment on the human waste and the septic tank sludge mixed solution. If the sludge is concentrated in advance and the dehydrated sludge is dehydrated, dehydrated sludge having a low water content can be obtained.

  As the concentration method, both gravity concentration and mechanical concentration are effective concentration methods. When the concentration treatment with the addition of the polymer flocculant is performed, the concentrated sludge concentration can be increased to about 10% at the maximum. If this concentrated sludge is dehydrated, a dehydrated sludge having a moisture content of 70% or less is obtained, and a remarkable sludge volume reduction effect is obtained. This low moisture content dehydrated sludge has a high calorie, and self-combustion without auxiliary fuel is possible in incineration, resulting in energy saving and low cost.

  Since the liquid to be processed that has been concentrated / dehydrated by the concentration / dehydration apparatus 1 has a greatly reduced concentration of organic substances such as BOD and SS, the volume of each treatment tank in the subsequent stage can be made compact. In particular, when the BOD / TN ratio of the liquid to be treated is lower than 3, the application merit of the anaerobic ammonia oxidation method by the water treatment apparatus of FIG.

In the 1st denitrification tank 2, the heterotrophic denitrification reaction which generate | occur | produces nitrogen gas is advanced using the denitrifying bacteria which are heterotrophic bacteria, using the organic substance in a to-be-processed liquid as an electron donor. The amount of NO _x -N that can be denitrified by the heterotrophic denitrification reaction depends on the amount of BOD that flows into the first denitrification tank 2. Normally, about 3 g of BOD is required for 1 g of NO _x -N. The BOD flowing into the first denitrification tank 2 can be measured in advance by measuring the BOD of the liquid to be treated. Therefore, the liquid to be treated NO _x -N amount contained nitrite treatment liquid circulating nitrite of tank 3 to be described later to the first denitrification tank 2, which is processed by the denitrification process in the first denitrification tank 2 so that theoretically required amount (e.g., about 1/3) with respect to BOD content in, by adjusting the amount of circulating nitrite treatment liquid, the NO _x -N reliably in the first denitrification tank 2 In addition to being able to be removed, the BOD in the liquid to be treated can be consumed at the same time, and the BOD in the liquid to be treated can be reduced.

As a result, the first denitrification treatment liquid obtained from the first denitrification tank 2 has little BOD residue, and mainly contains ammoniacal nitrogen (NH ₄ -N) as a nitrogen component. Moreover, since the total nitrogen concentration (TN) of the 1st denitrification process liquid processed by the 1st denitrification tank 2 is reduced compared with the case where a nitritation process liquid is not circulated, it mentions later. The TN load of 2 denitrification tank 5 (anaerobic ammonia oxidation tank) can also be reduced, and the 2nd denitrification tank 5 becomes compact.

  The second denitrification treatment liquid obtained in the second denitrification tank 5 may be circulated to the first denitrification tank 2 via the second denitrification treatment liquid circulation means 8. Thereby, compared with the case where only the circulation means 7 is provided, treated water that can achieve a higher nitrogen removal rate is obtained.

  The activated sludge concentrated and settled in the settling tank 6 may be returned to the first denitrification tank 2 as the return sludge 9. The return flow rate of the return sludge 9 is generally set to 0.25 to 1.0 times as a ratio to the inflow rate of the liquid to be treated into the first denitrification tank 2 according to the sludge settling property and the required sludge concentration. Can do.

  According to the modification of the water treatment apparatus according to the embodiment of the present invention, the nitrogen concentration in the finally obtained treated water can be further reduced, and the treatment in each reaction tank can be stably advanced. .

(Other variations)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention.

  For example, in the above embodiment, an example in which an anaerobic ammonia oxidizing bacterium is used as the self-granulating anaerobic microorganism has been described. However, as the self-granulating anaerobic microorganism, for example, other bacteria such as a group of methane fermentation bacteria used for methane fermentation can be used.

  In addition, the microbial catalyst 10 shown in FIG. 4 (a) shows a cross-sectional view of a state in which a plurality of microbial conglomerates are reassembled on the surface of the carrier. However, as shown in FIG. It is needless to say that this embodiment can also include a form in which the mass grows integrally.

  Moreover, it is not necessary that all the microbial catalysts filled in the reaction tank satisfy the shape defined in the above embodiment. In some cases, if there is a microbial catalyst satisfying the shape, when the mechanical stirring is performed, the microbial catalyst is peeled off, resulting in a decrease in processing performance. The present invention can also be applied when the shape defined in the above embodiment is satisfied.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

(Example)
In the anaerobic ammonia oxidation apparatus shown in FIG. 1, water treatment was performed using the sewage digested sludge dehydrated filtrate generated when the sludge after digesting the sewage sludge in the digestion tank was dehydrated with a dehydrator or the like as the liquid to be treated. In the nitritation tank, an average particle size of 4.2 mm, a specific gravity of 1.02, and a polymer gel carrier (PEG carrier) mainly composed of polyethylene glycol (20 V%) were added. In the denitrification tank, the nitritation treatment solution obtained in the nitritation tank is put, and in that, the average particle diameter of 4.0 mm, the specific gravity of 1.02, and the polyvinyl alcohol-based bond-immobilized support (PVA support). 20V% was added. The water temperature in each reactor was approximately 25-30 ° C.

A compressed gas composed of nitrogen gas is supplied from the bottom of the denitrification tank at 100 L / (m ² · min) to stir the nitritation solution and the microbial catalyst, and anaerobic ammonia-oxidizing bacteria on the outer surface of the PVA carrier When a maximum thickness of 2,000 μm was deposited, a steady state was reached, and the microbial catalyst was removed and its surface properties were observed. As a result, the number of microbial catalysts in which the microbial membrane peeled was 10% or less of the total.

(Comparative example)
On the other hand, as the stirring means, except that the nitrite treatment liquid and the microbial catalyst were stirred by mechanical stirring having a stirring blade, the conditions were the same as in the example. It was about 20 to 30% of the whole.

1 ... Concentration / dehydration device 2 ... Denitrification tank (first denitrification tank)
3 ... nitritation tank 4 ... settling tank 5 ... denitrification tank (second denitrification tank)
6 ... Settling tank 7 ... Nitrite treatment liquid circulation means 8 ... Denitrification treatment liquid circulation means 9 ... Return sludge 10 ... Microbial catalyst 10A ... Carrier 10B ... Microbial membrane 51 ... Gas stirring means 51A ... Gas supply port (gas stirring means) )
51B ... Gas supply port (gas stirring means)
52B ... Draft tube 53 ... Gas circulation means

Claims (11)

Containing a microbial catalyst in which self-granulating anaerobic microorganisms are immobilized on the outer surface of the carrier and a liquid to be treated, and a treatment tank for treating the liquid to be treated under anaerobic conditions;
A water treatment apparatus comprising: a gas stirring means for stirring the liquid to be treated and the microbial catalyst by supplying an inert gas into the treatment tank.   The water treatment apparatus according to claim 1, wherein irregular irregularities are formed on the outermost surface of the microbial catalyst.   The water treatment apparatus according to claim 1 or 2, wherein the microbial catalyst includes a microbial film containing the anaerobic microorganisms having a maximum thickness of 100 µm or more on an outer surface of the carrier.   The water treatment apparatus according to claim 1, wherein the microbial catalyst includes at least one recess having a depth of 50 μm or more from the outermost surface.   The water treatment apparatus according to any one of claims 1 to 4, wherein the anaerobic microorganism is an anaerobic ammonia oxidizing bacterium. The water treatment device according to any one of claims 1 to 5, wherein the gas stirring means includes supplying the inert gas into the treatment tank at 10 to 450 L / (m ² · min).   The water treatment apparatus according to any one of claims 1 to 6, further comprising a gas circulation means for circulating the inert gas supplied into the treatment tank into the treatment tank. A nitritation tank that partially oxidizes a part of ammonia nitrogen contained in the liquid to be treated into nitrite nitrogen by the action of nitrite bacteria to obtain a nitritation treatment liquid;
A denitrification tank that anaerobically oxidizes the nitrogen in the nitrite treatment solution using a microbial catalyst in which a self-granulating anaerobic microorganism is fixed on the outer surface of the carrier;
A water treatment apparatus comprising: a gas stirring means for stirring the nitritation treatment liquid and the microbial catalyst by supplying an inert gas into the denitrification tank. A first denitrification tank that obtains a first denitrification treatment liquid by anaerobically denitrifying the treatment liquid containing nitrogen and organic matter by a denitrification reaction using heterotrophic bacteria;
A nitritation tank that oxidizes a part of ammonia nitrogen contained in the first denitrification treatment liquid to nitrite nitrogen by the action of nitrite bacteria to obtain a nitritation treatment liquid;
A nitrite treatment liquid circulating means for circulating a part of the nitrite treatment liquid to the first denitrification tank;
A second denitrification tank for anaerobically oxidizing ammonia nitrogen in the nitritation solution using a microbial catalyst in which a self-granulating anaerobic microorganism is fixed on the outer surface of the carrier;
A water treatment apparatus comprising: a gas stirring unit that stirs the nitritation solution and the microbial catalyst by supplying an inert gas into the second denitrification tank.   A microorganism catalyst in which self-granulating anaerobic microorganisms are immobilized on the outer surface of the carrier and a liquid to be treated are accommodated in a treatment tank, and an inert gas is supplied into the treatment tank to perform anaerobic conditions. And treating the liquid to be treated by stirring the microbial catalyst and the liquid to be treated.   The water treatment method according to claim 10, wherein the anaerobic microorganism is an anaerobic ammonia oxidizing bacterium.