JP2005324132A - Method and apparatus for treating waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating waste water capable of specifically realizing a method and an apparatus for filtering out a nitrogen content in the waste water by denitrification using an anaerobic ammonia oxidizing bacteria since start-up of a treatment tank in waste water treatment using the anaerobic ammonia oxidizing bacteria having an extremely low proliferation rate can be made high-speed and also a denitrification reaction in normal operation of the treatment tank after start-up can be made high-speed, and its apparatus. <P>SOLUTION: In the waste water treatment method for filtering out a nitrogen component in the waste water by denitrification with suspended microbe flocks in the treatment tank 16, the concentration of bacteria of the suspended microbe flocks is so adjusted that the total number of bacteria ranges 10<SP>7</SP>bacteria/mL or more as the concentration in the treatment tank 16 and also the anaerobic ammonia oxidizing bacteria ranges from 1/10 to 1/1,000 to the total number of bacteria by introducing the suspended microbe flocks into the treatment tank 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment method and apparatus for removing nitrogen components in wastewater, and more particularly to a technique for speeding up denitrification treatment using anaerobic ammonia oxidizing bacteria.

  Nitrogen components contained in sewage and industrial wastewater need to be removed for reasons such as causing eutrophication of lakes and marshes and reducing dissolved oxygen in rivers. Nitrogen components contained in sewage and industrial wastewater are mainly nitrogen components such as ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and organic nitrogen.

  Conventionally, this type of wastewater, if the nitrogen concentration is low, is also removed by ion exchange method and oxidation by chlorine, ozone, but in the case of medium to high concentration, biological treatment is adopted, Generally, it is operated under the following conditions.

  Biological treatment involves aerobic nitrification and anaerobic denitrification, and in aerobic nitrification, ammonia oxidizing bacteria (Nitrosomonas, Nitrosococcus, Nitrosospira, Nitrosolobus, etc.) and nitrite oxidizing bacteria (Nitrobactor, Nitrospina, Nitrococcus, Nitrospira, etc.) oxidize ammonia nitrogen and nitrite nitrogen, while anaerobic denitrification involves denitrification by heterotrophic bacteria (Pseudomonas denitrificans, etc.).

A nitrification tank for performing aerobic nitrification is operated within a load range of 0.2 to 0.3 kg-N / m ³ / day, and an anaerobic denitrification denitrification tank is loaded with a load of 0.2 to 0.4 kg-N / m. It is operated in the range of ³ / day. In order to treat the total nitrogen concentration of sewage of 30 to 40 mg / L, a residence time of 6 to 8 hours was required in the nitrification tank and 5 to 8 hours were required in the denitrification tank, and a large-scale treatment tank was required. In industrial wastewater containing only inorganic substances, nitrification tanks and denitrification tanks are designed with the same load as before, but organic substances are required for denitrification, and methanol with a concentration of 3 to 4 times the nitrogen concentration was added. . For this reason, there is a problem that not only the initial cost but also a great running cost is required.

  In contrast, recently, a wastewater treatment method using anaerobic ammonia-oxidizing bacteria has attracted attention (for example, Patent Document 1). This anaerobic ammonia oxidation is a method in which ammonia and nitrous acid are simultaneously denitrified by anaerobic ammonia oxidizing bacteria using ammonia as a hydrogen donor and nitrous acid as a hydrogen acceptor.

According to this method, since ammonia is used as a hydrogen donor, there are merits such as greatly reducing the amount of methanol used for denitrification and reducing the amount of sludge generated. It is considered to be an effective method.
JP 2001-37467 A

By the way, anaerobic ammonia oxidizing bacteria that undergo anaerobic ammonia oxidation reaction are typically Planctomycete, and it is thought that there are many other species and genera, but the growth rate is extremely slow at 0.001 h ^-1. (Strous, M. et al .: Nature, 400, 446 (1999). Therefore, in order to construct an actual wastewater treatment method and apparatus using anaerobic ammonia oxidizing bacteria, this growth rate is extremely slow. It is necessary to start up a treatment tank in wastewater treatment using anaerobic ammonia-oxidizing bacteria at a high speed and to perform a denitrification reaction of the treatment tank after the start-up at a high speed.

  However, this method has the drawback that the reaction characteristics have not been sufficiently elucidated, and it is difficult to increase the startup speed and denitrification rate.

  The present invention has been made in view of such circumstances, and can speed up the start-up of a treatment tank in wastewater treatment using anaerobic ammonia-oxidizing bacteria with a very slow growth rate. Since the denitrification reaction in the steady operation of the treatment tank can be accelerated, a method and apparatus for removing nitrogen components in wastewater by denitrification using anaerobic ammonia-oxidizing bacteria will be specifically realized. It is an object of the present invention to provide a wastewater treatment method and an apparatus for the same.

  The present inventor believes that anaerobic ammonia-oxidizing bacteria have specific characteristics in symbiotic relationships with other bacteria, and that anaerobic ammonia oxidation utilizing these characteristics can be performed in wastewater treatment using anaerobic ammonia-oxidizing bacteria. We obtained the knowledge that it is extremely important for the high-speed denitrification reaction in the high-speed start-up of the treatment tank and the steady operation of the treatment tank after the start-up. In other words, if the anaerobic ammonia-oxidizing bacteria in the floating microorganism group or the immobilized microorganism group to be put into the treatment tank for wastewater treatment is simply high, the start-up and the denitrification reaction during steady operation cannot be accelerated. The symbiotic balance, which is the ratio of anaerobic ammonia-oxidizing bacteria to the total number of bacteria in the group, was found to be important. Here, the floating microorganism group is, for example, sludge floating in a treatment tank, and the immobilized microorganism group is, for example, sludge adhered and fixed to a flowable carrier or entrapped or fixed to a fixed bed. Sludge. The present invention has been made based on such findings.

In order to achieve the above object, claim 1 of the present invention is a wastewater treatment method in which nitrogen components in wastewater are denitrified and removed by a floating microorganism group in a treatment tank. The floating microorganism group is charged into the treatment tank, the total bacterial count is 10 ⁷ / mL or more as the concentration in the treatment tank, and the anaerobic ammonia oxidizing bacteria is 1/10 to 1/1000 of the total bacterial count. It adjusts so that it may become a range, It is characterized by the above-mentioned.

Claim 1 is the case where the anaerobic ammonia oxidizing bacteria are present as part of the microorganisms in the floating microorganism group floating in the treatment tank. In this case, the bacteria of the floating microorganism group at the time when the microorganism is introduced into the treatment tank The body concentration is adjusted to 10 ⁷ cells / mL or more and the anaerobic ammonia-oxidizing bacteria are adjusted to a range of 1/10 to 1/1000 of the total cell count, so that the treatment tank can be started up at high speed. In addition, a stable denitrification reaction can be performed at a high speed even in a steady operation of the treatment tank after the start-up. In addition, in other words, the time when it is put into the treatment tank corresponds to the start of the start-up of the treatment tank.

According to a second aspect of the present invention, in order to achieve the above object, in the wastewater treatment method for removing nitrogen components in wastewater by denitrification with an immobilized microorganism group in a treatment tank, the immobilized microorganism group is treated with the treatment. The cell concentration of the immobilized microorganism group when put into the tank is such that the total number of bacteria is 10 ⁶ cells / mL or more and the anaerobic ammonia-oxidizing bacteria are in the range of 1/10 to 1/1000 of the total number of bacteria. It is characterized by being.

Claim 2 is the case where the anaerobic ammonia oxidizing bacteria are present as part of the microorganisms in the immobilized microorganism group charged into the treatment tank. In this case, the immobilized microorganism at the time when it is charged into the treatment tank By adjusting the bacterial cell concentration of the group to a total bacterial count of 10 ⁶ cells / mL or more and anaerobic ammonia oxidizing bacteria in the range of 1/10 to 1/1000 of the total bacterial count, In addition, it is possible to perform a stable denitrification reaction at a high speed even in a steady operation of the treatment tank after the startup. In addition, when the microbial group is a floating microbial group and when the microbial group is an immobilized microbial group, the immobilized microbial group can be started up even if the total number of bacteria is smaller.

  A third aspect of the present invention is an apparatus for carrying out the wastewater treatment method according to the first or second aspect of the invention in order to achieve the object.

  Claim 3 is configured as an apparatus for carrying out the wastewater treatment method of claim 1 or claim 2.

  According to a fourth aspect of the present invention, in order to achieve the above object, a treatment tank for performing an anaerobic ammonia oxidation reaction for carrying out the wastewater treatment method of the first or second aspect, and nitrogen denitrified in the treatment tank And a decompression device for pulling out the product under reduced pressure.

Since the pressure in the treatment tank for performing the anaerobic ammonia oxidation reaction for carrying out the wastewater treatment method of claim 1 or claim 2 is reduced as in claim 4, the nitrogen gas generated in the treatment tank ( N ₂ gas) bubbles are removed, the contact between the substrate and the floating microorganism group, or the substrate and the immobilized microorganism group is improved, and the nitrogen removal performance is improved.

  As described above, according to the wastewater treatment method and apparatus of the present invention, it is possible to speed up the start-up of a treatment tank in wastewater treatment using anaerobic ammonia oxidizing bacteria having a very slow growth rate. The denitrification reaction in the steady operation of the subsequent treatment tank can be speeded up.

  Therefore, the method and apparatus for removing the nitrogen component in wastewater by denitrification using anaerobic ammonia oxidizing bacteria can be specifically realized.

  Hereinafter, preferred embodiments of a wastewater treatment method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  In the present invention, the most important point is that the specific characteristics in the symbiotic relationship between the anaerobic ammonia oxidizing bacteria and other bacteria can be clarified, and the characteristics will be described below.

  A major factor that has not been able to elucidate the cell concentration of the anaerobic ammonia-oxidizing bacteria themselves and the symbiotic balance with other bacteria is that there is no measurement method for anaerobic ammonia-oxidizing bacteria and the number of bacteria cannot be determined. Therefore, in the present invention, the following method for measuring anaerobic ammonia-oxidizing bacteria has been newly developed to enable measurement of the number of anaerobic ammonia-oxidizing bacteria. And it is possible to perform a high-speed denitrification reaction in the steady operation of the treatment tank after the start-up and the treatment tank using the anaerobic ammonia-oxidizing bacteria by performing the processing taking advantage of the characteristics. did.

(Anaerobic ammonia-oxidizing bacteria count method)
Table 1 shows the media developed for the measurement of anaerobic ammonia oxidizing bacteria.

(Note) This medium is used with a few drops of 10% bromothymol blue solution.

  The inorganic medium shown in Table 1 was dispensed in 50 mL test tubes, placed in a Durham tube, and sterilized at 121 ° C. by an autoclave. This medium was diluted and inoculated with a sample for measuring the number of bacteria according to the most probable method (Tatsuhiko Suzuki, “Soil Microbial Experiment Method”, Yokendo, P21-41 (1978)). In this culture, inoculation was performed in an anaerobic glow box, and cultured at 37 ° C for 3 months under anaerobic conditions. After the culture, anaerobic ammonia-oxidizing bacteria were judged to be positive in the test tube in which gas was accumulated in the Durham tube and the medium color changed from green to blue. This color change means that nitrogen gas was generated and changed to alkaline. After positive / negative determination, the number of anaerobic ammonia-oxidizing bacteria was converted according to the most probable value method. In addition, the number of bacteria in the inclusion carrier in which the anaerobic ammonia-oxidizing bacteria are entrapped and immobilized is obtained by homogenizing the inclusion carrier and using the same medium as in the previous suspension to determine the number of anaerobic ammonia-oxidizing bacteria using the most probable method. Converted.

As an example, the following formula shows how to convert the number of anaerobic ammonia-oxidizing bacteria in the entrapping carrier.
(Expression 1) Xp = Xo × (Vp + Vw) / Vp
Where Xp: number of anaerobic ammonia oxidizing bacteria inside the carrier (units / mL)
Xo: Anaerobic ammonia-oxidizing bacteria count in stock solution inoculated to medium (cells / mL)
Vp: Amount of carrier used for preparation of stock solution (mL)
Vw: The amount (mL) of sterilized water added to the preparation of the stock solution.

  FIG. 1 is an investigation of specific characteristics in the symbiotic balance between anaerobic ammonia-oxidizing bacteria and other bacteria using the method for measuring anaerobic ammonia-oxidizing bacteria. .

  That is, when the total number of floating microorganisms at the time of charging into the treatment tank for removing nitrogen components in waste water and the ratio (E) of anaerobic ammonia oxidizing bacteria to the total number of bacteria are changed, We investigated how the number of days until anaerobic ammonia oxidation rises. The ratio (E) of anaerobic ammonia-oxidizing bacteria on the horizontal axis in FIG. 1 is defined by the following equation. The total number of bacteria was measured with a bioprolar.

E = X / Xa
Here, X: the number of anaerobic ammonia oxidizing bacteria (units / mL)
Xa: Total number of bacteria (cells / mL)
The wastewater used for the test was an inorganic synthetic wastewater containing an inorganic nitrogen and an ammoniacal nitrogen concentration of 300 mg / L and a nitrite nitrogen concentration of 280 mg / L. In addition, as anaerobic ammonia oxidizing bacteria seed sludge, anaerobic ammonia oxidizing bacteria accumulated sludge acclimatized from activated sludge in sewage treatment plants (loading inorganic wastewater containing ammonia and nitrous acid at 3 kg-N / m ³ / day) Acclimatized sludge) was used. And it was operated at a load of 1 kg-N / m ³ / day while diluting the nitrite concentration in the treatment tank to be 60 mg / L or less, and when the TN (total nitrogen) removal rate obtained 70%. It was judged that he stood up.

As is clear from FIG. 1, the total number of floating microorganisms is 10 ⁷ / mL or more and the range of anaerobic ammonia oxidizing bacteria is 1/10 to 1/1000 of the total number of bacteria (the number of anaerobic ammonia oxidizing bacteria It can be seen that the rise is very fast under the symbiotic balance condition satisfying 10 ⁴ to 10 ⁶ / mL in terms of conversion. That is, the seed sludge of the anaerobic ammonia-oxidizing bacteria at the start of start-up satisfies the above symbiotic balance condition, so that the start-up of the treatment tank can be speeded up and the treatment tank after the start-up In operation, the above-mentioned symbiotic balance condition is satisfied, so that the denitrification reaction can be accelerated.

  As an example of the immobilized microorganism group, FIG. 2 shows a symbiotic balance between anaerobic ammonia-oxidizing bacteria and other bacteria, as in the case of the suspended microorganism group described above. It investigated about a specific characteristic. The waste water used for the test is the same as that of the floating microorganism group in FIG.

The entrapping immobilization carrier used for the test was prepared as follows. That is, the anaerobic ammonia-oxidizing bacteria-containing sludge (sludge acclimatized with a load of 3 kg-N / m ³ / day of inorganic wastewater containing ammonia and nitrous acid) was mixed with the activated sludge of the sewage treatment plant, and anaerobic The seed sludge for entrapping and fixing the number of ammonia oxidizing bacteria and total number of bacteria was obtained. This seed sludge was suspended in polyethylene glycol diacrylate having a molecular weight of 4000 and polymerized by adding potassium persulfate, whereby the seed sludge was entrapped and immobilized in the gel. Table 2 shows the composition ratios of the components used for comprehensive fixation.

  The entrapping immobilization support was molded into a 3 mm square, and a start-up test of the treatment tank was performed.

As is clear from FIG. 2, the total number of bacteria in the microbial group inside the entrapping immobilization carrier is 10
Symbiotic balance condition that satisfies ⁶ or more / mL and anaerobic ammonia oxidizing bacteria within the range of 1/10 to 1/1000 of the total number of bacteria (10 ³ to 10 ⁵ / mL in terms of anaerobic ammonia oxidizing bacteria number) It can be seen that the rise is fast. That is, in the case of a entrapping immobilization support, the seed sludge of anaerobic ammonia oxidizing bacteria inside the entrapping immobilization support can satisfy the above symbiotic balance condition, thereby speeding up the start-up of the treatment tank. At the same time, the denitrification reaction can be speeded up by satisfying the above symbiotic balance condition in the steady operation of the treatment tank after startup. In addition, in the case of the entrapping immobilization carrier, it can be seen that the activity of anaerobic ammonia oxidation rises when the total number of bacteria is 10 ⁶ / mL, which is one order of magnitude less than in the case of the previous floating microorganism group. It is thought that the stability of the bacteria was increased by the entrapping immobilization, and the same tendency was obtained with adhesion immobilization and granules other than the entrapping immobilization.

  From the results of FIG. 1 and FIG. 2, there is a symbiotic linkage relationship between the total number of bacteria and the number of anaerobic ammonia-oxidizing bacteria, and when the ratio (E) of anaerobic ammonia-oxidizing bacteria to the total number of bacteria is low, the number of bacteria does not rise. Even if it passes, it turns out that the rise is bad. This is because when the ratio (E) is low, it is easily assumed that the anaerobic ammonia-oxidizing bacteria are reduced by predation of the microorganisms, but when the ratio is too high, the rise period is increased by the anaerobic ammonia-oxidizing bacteria. It is presumed that the activity promoting factor supplied from these bacteria decreases.

  FIG. 3 is an example of a wastewater treatment apparatus suitable for carrying out the wastewater treatment method of the present invention, and shows a case where an anaerobic ammonia oxidation reaction is carried out in a floating microorganism group. In addition, the processing tank described below is a tank in which anaerobic ammonia oxidizing bacteria acts, and is a tank which performs denitrification. In this treatment tank, the reaction proceeds even if it is not completely anaerobic, and it may be a tank under anaerobic conditions or microaerobic conditions in a steady state.

As shown in FIG. 3, in the wastewater treatment apparatus 10, wastewater containing ammonia and nitrous acid flows into the treatment tank 16 by the raw water pump 14 through the raw water pipe 12. In the treatment tank 16, ammonia and nitrous acid are simultaneously denitrified by the anaerobic ammonia oxidizing bacteria in the floating microorganism group, and the treated water is discharged via the treated water pipe 18. The cell concentration of the floating microorganism group that is put into the treatment tank 16 and started up is such that the total number of bacteria is 10 ⁷ / mL or more and the anaerobic ammonia oxidizing bacteria is 1/10 to 1/1000 of the total number of bacteria. The range is adjusted. In this way, by adjusting the total number of bacteria and the number of anaerobic ammonia-oxidizing bacteria relative to the total number of bacteria, the symbiotic balance between the anaerobic ammonia-oxidizing bacteria present in the floating microorganism group and other bacteria can be adjusted to an appropriate balance. Since it can be set, the treatment tank 16 can be started up at a high speed, and a stable denitrification reaction can be carried out at a high speed even during steady operation.

Further, it is preferable that a nitrogen gas diffusing pipe 20 is provided at the bottom in the processing tank 16, and nitrogen gas is diffused into the processing tank 16 at the start of the start-up of the processing tank 16 to degas oxygen in the water to be treated. . This is because oxygen inhibits the activity of anaerobic ammonia-oxidizing bacteria, and the startup speed can be further increased by removing oxygen from the wastewater during startup. In addition, the amount of waste water flowing from the raw water pipe 12 and the installation position of the treated water pipe 18 are adjusted so that the head space part 22 is formed at the upper end in the treatment tank 16, and the head space part 22 and the vacuum It is preferable to connect the pump 24 via a decompression pipe 26 and decompress the inside of the processing tank 16. This is because the nitrogen removal activity of the anaerobic ammonia oxidizing bacteria increases when the inside of the treatment tank 16 is depressurized. The reason why the nitrogen removing activity is increased is presumed that the molecular nitrogen on the surface of the anaerobic ammonia oxidizing bacteria is removed by reducing the pressure and the diffusion of the substrate is improved. In the case of the anaerobic ammonia oxidation reaction by the floating microorganism group, it is preferable to provide a reverse bowl-shaped bowl 28 in the upper part of the treatment tank 16 and provide a suction port for the treated water pipe 18 in the upper part of the bowl 28. Thereby, it can suppress that the floating microorganism group which floats in the processing tank 16 entrains with a treated water, and flows out from the treated water piping 18. FIG. Further, it is preferable that the bottom and top of the treatment tank 16 are communicated with each other by a circulation pipe 30 and the water to be treated is circulated by a circulation pump 32 provided in the circulation pipe 30. Thereby, the floating microorganism group floats evenly in the entire treatment tank 16 and efficiently contacts the wastewater, so that the startup speed can be increased. A ventilation line speed of 1 to 5 cm / sec is effective.

  FIG. 4 shows another example of a wastewater treatment apparatus suitable for carrying out the wastewater treatment method of the present invention, in which an anaerobic ammonia oxidation reaction is carried out with a entrapping immobilization support. In addition, the same member and apparatus as FIG. 3 attaches | subjects a same sign, and demonstrates. Further, in the case of the anaerobic ammonia oxidation reaction by the entrapping immobilization carrier, complete mixing may be sufficient.

As shown in FIG. 4, the wastewater treatment apparatus 10 is configured such that wastewater containing ammonia and nitrous acid flows into the treatment tank 16 through the raw water pipe 12 and is supplied into the treatment tank 16. Ammonia and nitrous acid are simultaneously denitrified by the anaerobic ammonia oxidizing bacteria immobilized on the chemical carriers 34, 34... And the treated water is discharged via the treated water pipe 18. Further, a screen 36 is provided in the vicinity of the suction port of the treated water pipe 18, thereby preventing the entrapping immobilization carrier 34 from flowing out along with the treated water. The microbial cell concentration of the entrapping immobilization carrier 34 that is put into the treatment tank 16 and started up is such that the total cell count is 10 ⁶ cells / mL or more and the anaerobic ammonia-oxidizing bacteria are 1/10 to 10% of the total cell count. The range is adjusted to 1/1000. Thus, by adjusting the total number of bacteria and the number of anaerobic ammonia-oxidizing bacteria with respect to the total number of bacteria, an appropriate symbiotic balance between the anaerobic ammonia-oxidizing bacteria present in the entrapping immobilization carrier 34 and other fungi is adequate. Since the balance can be set, the treatment tank 16 can be started up at a high speed, and a stable denitrification reaction can be carried out at a high speed even during the steady operation of the treatment tank 16.

  Also in the case of the anaerobic ammonia oxidation reaction by the entrapping immobilization support 34, as in the case of the floating microorganism group, nitrogen gas is diffused into the treatment tank 16 from the diffuser tube 20 at the start of the start-up of the treatment tank 16, It is preferable to deaerate oxygen in the water to be treated. Moreover, it is preferable to depressurize the inside of the processing tank 16. Furthermore, it is preferable to provide a stirrer 38 for stirring the inside of the treatment tank 16. As a result, the entrapping immobilization carrier 34 flows evenly throughout the processing tank 16 and efficiently contacts the waste water, so that the start-up of the processing tank 16 can be accelerated.

  In FIG. 4, the entrapping immobilization carrier 34 has been described as an example of the immobilized microorganism group. However, adhesion fixation or granule can be used.

  In adhesion fixation, immobilization materials having many irregularities such as spherical or cylindrical carrier materials, string-like materials, gel-like carriers, and nonwoven fabric materials are likely to adhere, and the removal rate is improved. In the above-described entrapping immobilization, a mixed solution in which anaerobic ammonia oxidizing bacteria and an immobilizing material (monomer, prepolymer) are mixed is polymerized to immobilize the anaerobic ammonia oxidizing bacteria in the gel. As the monomer material, acrylamide, methylenebisacrylamide, triacryl formal and the like are preferable. The prepolymer material is preferably polyethylene glycol diacrylate or polyethylene glycol methacrylate, and derivatives thereof can be used. The entrapping immobilization carrier 34 has a spherical or cylindrical inclusion carrier, a string-like inclusion carrier, or a non-woven fabric inclusion carrier with many irregularities, which has good contact efficiency and an improved denitrification rate.

In order to investigate the denitrification rate of a carrier on which anaerobic ammonia-oxidizing bacteria were immobilized by adhesion immobilization or entrapping immobilization, a test was conducted with the apparatus configuration of FIG. That is, various types of carriers shown in FIG. 4 were filled in a treatment tank so that the carrier filling rate was 25%, and ammonia wastewater was treated. The seed sludge used for immobilization is a sludge with a denitrification rate of 1.2 kg-N / m ³ / day, obtained by accumulating and culturing with ammonia and nitrous acid, and has anaerobic ammonia-oxidizing bacteria concentration. It was 8 × 10 ⁶ cells / mL, and the total number of bacteria was 8 × 10 ⁸ cells / mL.

As a result, as shown in Table 3, after 4 weeks, it was possible to obtain a high denitrification rate of 200 (mg-N / L-carrier / h) or more in any case of any attached carrier or inclusion carrier. . In this experiment, wastewater having 500 mg / L of TN (total nitrogen) having an ammonia nitrogen concentration and a nitrite nitrogen concentration of 5: 4 was used. The column at the end of Table 3 shows the denitrification rate when the pressure is reduced. When the pressure was reduced, N ₂ bubbles were removed, the contact between the substrate and the carrier was good, and the denitrification rate was improved.

    * ... 260mmHg vacuum culture treatment

(First embodiment)
Examples of the present invention will be described below, but the present invention is not limited to these examples.

  1st Example is a case where the waste-water-treatment method of this invention is performed by the floating microorganism group.

An accumulation culture sludge having a denitrification rate of 1.2 kg-N / m ³ / day obtained by accumulation culture with ammonia and nitrous acid was used for the test. The concentration of the anaerobic ammonia-oxidizing bacteria in this integrated culture sludge was 8 × 10 ⁸ cells / mL. And this accumulation culture sludge and activated sludge are mixed, 4000 mg / L as sludge density | concentration (MLSS) is thrown into the processing tank 16 in the wastewater treatment apparatus 10 of FIG. The operation was started at x10 ⁸ cells / mL and anaerobic ammonia oxidizing bacteria 8 × 10 ⁵ cells / mL.

Wastewater starts operation at a load of 1 kg-N / m ³ / day using 1000 mg / L of wastewater TN (total nitrogen) at a ratio of ammonia nitrogen concentration and nitrite nitrogen concentration of 5: 4. While monitoring the ammonia nitrogen concentration and the nitrite nitrogen concentration, it was diluted with tap water so that the ammonia nitrogen concentration was 50 to 100 mg / L and the nitrite nitrogen concentration was 30 to 80 mg / L. . The first 10 days required a 4-fold dilution, but then gradually decreased the dilution rate, and after 4 weeks of operation, the TN (total nitrogen) removal rate was 80 at a load of 1 kg-N / m ³ / day. % And then rises up and then stabilizes at 80-90%.

For comparison, the cell concentration of the floating microorganism group is 8 × 10 ⁵ cells / mL and the anaerobic ammonia oxidizing bacteria are 8 × 10 ⁵ cells / mL, that is, all the bacteria are anaerobic ammonia oxidizing bacteria. Some sludge was adjusted, and this sludge was thrown into the treatment tank 16 to start operation, but even after 100 days from the start of operation, the TN (total nitrogen) removal rate could not be raised to 40% or less, After that, it changed between 30-60%.

(Second embodiment)
In the second embodiment, the wastewater treatment method of the present invention is carried out with a entrapping immobilization support prepared as follows.

The seed sludge for entrapping and fixing is sludge with a capacity of 1.2 kg-N / m ³ / day, which is obtained by accumulating and culturing with ammonia and nitrous acid, with an initial concentration of 3 × 10 ⁸ pieces / mL. It was used as an inoculum for immobilization. The inoculum is collected by centrifugation, and the combined fungus in which activated sludge is mixed with this fungus is suspended in polyethylene glycol diacrylate (an immobilizing material) having a molecular weight of 4000, and polymerized by adding potassium persulfate. A entrapping immobilization carrier having the composition shown below was prepared.
Anaerobic ammonia oxidizing bacteria: 4 × 10 ⁵ / mL
・ Total number of bacteria: 3 × 10 ⁸ cells / mL
-Polyethylene glycol diacrylate: 10%
-Potassium persulfate: 0.25%
This gel was formed into a 3 mm square and filled in the treatment tank 16 of the wastewater treatment apparatus 10 shown in FIG.

Wastewater starts operation at a load of 0.5 kg-N / m ³ / day using 600 mg / L of wastewater TN (total nitrogen) with a ratio of ammonia nitrogen and nitrite nitrogen of 5: 4. did. Gradually increase the load, 4 weeks after the start of operation, the TN (total nitrogen) removal rate rises to 80% or more at a load of 1.5 kg-N / m ³ / day, and then rises to 80-90%. It was stable.

For comparison, the total number of bacteria in the microbial group was 3 × 10 ⁸ cells / mL, anaerobic ammonia-oxidizing bacteria 4 × 10 ³ cells / mL, and the anaerobic ammonia-oxidizing bacteria were 1/100000 with respect to the total number of bacteria. A entrapping immobilization support in the case of falling below the lower limit of the symbiotic balance condition (1/10 to 1/1000) was prepared, and this entrapping immobilization support was put into the treatment tank 16, and the operation was started. It did not stand up and remained unstable between 20 and 40%.

  As can be seen from the first embodiment and the second embodiment, if the suspended microorganisms in the treatment tank 16 or the anaerobic ammonia-oxidizing bacteria in the entrapping immobilization carrier is simply high, the denitrification reaction during startup or steady operation can be accelerated. The symbiotic balance, which is the ratio of anaerobic ammonia-oxidizing bacteria to the total number of floating microorganisms or entrapping immobilization carriers, is important.

Explanatory drawing explaining the symbiotic balance of anaerobic ammonia-oxidizing bacteria and other fungi with floating microorganisms Explanatory drawing explaining the symbiotic balance of anaerobic ammonia-oxidizing bacteria and other fungi as an example of an immobilized microorganism group using a entrapped immobilization carrier Configuration diagram of an apparatus suitable for a floating microorganism group in a wastewater treatment apparatus for implementing the wastewater treatment method of the present invention Configuration diagram of an apparatus suitable for a entrapping immobilization carrier in a wastewater treatment apparatus for carrying out the wastewater treatment method of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Waste water treatment apparatus, 12 ... Raw water piping, 14 ... Raw water pump, 16 ... Treatment tank, 18 ... Treatment water piping, 20 ... Nitrogen gas diffusion pipe, 22 ... Head space part, 24 ... Vacuum pump, 26 ... Decompression piping , 28 ... 庇, 30 ... circulation piping, 32 ... circulation pump, 34 ... entrapping immobilization carrier, 36 ... screen, 38 ... stirrer

Claims (4)

In a wastewater treatment method for denitrifying and removing nitrogen components in wastewater with floating microorganisms in the treatment tank,
The cell concentration of the floating microorganism group is such that the floating microorganism group is charged into the treatment tank, the total number of bacteria is 10 ⁷ / mL or more as the concentration in the treatment tank, and the anaerobic ammonia oxidizing bacteria is the total number of bacteria. The wastewater treatment method is characterized in that it is adjusted to be in the range of 1/10 to 1/1000 of the above. In a wastewater treatment method for denitrifying and removing nitrogen components in wastewater with immobilized microorganisms in the treatment tank,
The cell concentration of the immobilized microorganism group when the immobilized microorganism group is introduced into the treatment tank is such that the total number of bacteria is 10 ⁶ cells / mL or more and anaerobic ammonia-oxidizing bacteria are 1 / of the total number of bacteria. A wastewater treatment method characterized by being in the range of 10 to 1/1000.   A wastewater treatment apparatus, which is an apparatus for carrying out the wastewater treatment method according to claim 1 or 2. A treatment tank for performing an anaerobic ammonia oxidation reaction for carrying out the wastewater treatment method according to claim 1 or 2;
A wastewater treatment apparatus comprising: a decompression device for extracting nitrogen denitrified in the treatment tank under reduced pressure.

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