JP4821809B2 - Microbial carrier manufacturing method and biological denitrification apparatus - Google Patents

Description

The present invention relates to a method for producing a microorganism carrier and a denitrification apparatus that reduce ammonia nitrogen and nitrite nitrogen to nitrogen gas by autotrophic denitrifying bacteria (Anamox bacteria).

  In recent years, in the field of wastewater treatment, ammonia nitrogen and nitrite nitrogen have been reduced to nitrogen gas by anammox bacteria, which are autotrophic denitrifying bacteria. This nitrogen removal reaction using bacteria is called an anammox reaction, and it is known that nitrogen removal can be performed more efficiently than conventional nitrification and denitrification methods.

  FIG. 5 is a flow of a conventional nitrogen removal system using anammox bacteria. Raw water containing ammonia nitrogen is introduced into the partial nitritation tank. Ammonia nitrogen in raw water is partially oxidized to nitrite nitrogen by aerobic nitrification reaction by ammonia oxidizing bacteria in the partial nitrification tank. Next, after removing impurities and the like in the precipitation tank, it is introduced into a biological denitrification tank and reduced to nitrogen gas by an anammox reaction under anaerobic conditions.

Since anammox bacteria are autotrophic, they have the economic advantage of not requiring the supply of organic matter, the bacteria conversion rate is small, and the generation of excess sludge can be kept to a minimum. There are environmental advantages such as no generation of N ₂ O.

  However, anammox bacteria are susceptible to inhibition by oxygen and residual organic matter, and the growth rate is low, so it takes a long time to increase the concentration in the tank, and it was difficult to maintain the high concentration. .

  Patent Document 1 discloses a method in which an elongated carrier in which anammox bacteria are supported on a net or nonwoven fabric is suspended in a reaction tank, and ammonia in wastewater is reduced to nitrogen gas and removed by an anammox reaction. Has been.

Patent Document 2 discloses a biofilm dual structure in which an anammoxic entrapping fixed gel or self-granulated product or a carrier carrying anammoxic bacteria on its surface is held in a nitrification tank, and the outer periphery is covered with ammonia oxidizing bacteria. And a method of reducing ammonia nitrogen to nitrogen gas by this biofilm double structure is disclosed.
International Publication Number WO2005 / 095289 JP 2002-346593 A

  In the method using the long carrier carrying the anammox bacteria, the degree of freedom of the nonwoven fabric shape is low, and therefore, the size and shape of the reaction tank are limited, and uniform installation is difficult. Also, when a long carrier with anammox bacteria attached to the tank is put in, the nonwoven fabric holds a large amount of moisture, so it takes a lot of labor at the time of loading, and peeling of the anammox bacteria carried is also carried out. appear. Furthermore, it is difficult to set various conditions at the time of start-up because the amount of anammox bacteria attached is difficult to grasp and the amount of cells in the loaded carrier is small. There is a problem that anammox bacteria separated from a carrier such as a nonwoven fabric float and flow out due to nitrogen gas generated during the anammox reaction.

  Incorporating and fixing anammox bacteria on a polymer gel solves the problem that anammox bacteria are detached from the carrier, but only anammox bacteria near the gel surface effectively act as denitrification treatment, so the processing efficiency is low There's a problem. In addition, those using anammox self-granulated materials can maintain a high concentration in the tank, but the nitrogen gas generated during the anammox reaction contains the self-granulated materials and floats, so the processing efficiency And a device for preventing the self-granulated product from flowing out is required. Furthermore, it is difficult to grasp the amount of anammox bacteria attached on the surface of the carrier carrying anammox bacteria, and the anammox bacteria separated from the carrier by the nitrogen gas produced during the anammox reaction Since there is a problem, there is a problem that the microbial concentration management in the tank is complicated.

  Generally, in order to prevent anammox bacteria from flowing out of the tank, there is a case where a screen or the like is installed near the outlet, but it takes time for maintenance such as clogging elimination and countermeasures. In addition, as a countermeasure against SS in the inflowing water, which is an inhibitory factor for the anammox reaction, a sedimentation tank and pretreatment tank are installed, and SS is removed by sedimentation and removal or filtration with a filter medium. There is a problem that it is vulnerable to fluctuations in water load.

  The present invention is intended to solve the problems associated with the prior art as described above, and by using a microbial carrier having a high working efficiency, it is possible to suppress the separation of anammox bacteria from the carrier and to easily manage the concentration in the reaction vessel. It is to provide a wastewater treatment apparatus.

The gist of the present invention is to cultivate a microorganism carrier of a denitrification apparatus in which an autotrophic denitrification bacterium is filled inside a denitrification tank and ammonia nitrogen in raw water supplied to the denitrification tank is continuously removed as nitrogen gas. After filtering the anammox bacteria with a support sheet, it is rolled into a cylindrical shape with the filtration surface inside, and cut into a predetermined width to form a roll-shaped support. Therefore, it is possible to use a carrier having a high degree of freedom, and it is easy to install in a tank and work efficiency is good. Moreover, since the carrier is wound in a roll shape, the peeling of the anammox bacteria from the carrier is extremely small.

  In a biological denitrification device that fills the inside of the denitrification tank with autotrophic denitrification bacteria and continuously removes ammonia nitrogen in the raw water supplied to the denitrification tank as nitrogen gas, anammox bacteria adheres to one side and forms a cylinder A roll-shaped carrier having a predetermined width wound around is disposed in a denitrification tank, and the outer peripheral surface of the roll-shaped carrier is inscribed in the denitrification tank, and there is extremely little peeling from the carrier of anammox bacteria, It can be immobilized at a high concentration inside the carrier. Moreover, installation in the tank is easy and work efficiency is good.

  Since the roll-shaped carrier is sandwiched between press plates having through holes in the upper and lower sides and installed in the denitrification tank, it is possible to prevent displacement of the installation place and inclination of the roll-shaped carrier, as well as rewinding and water flow. Prevents shape collapse.

  If the roll-shaped carrier sandwiched between the presser plates is arranged in multiple stages in the denitrification tank with a predetermined interval, the raw water that has not been sufficiently denitrified will come into contact with anammox bacteria on the subsequent roll-shaped carrier. Then, a denitrification process is performed. Further, even if the anammox bacteria are separated from the roll-shaped carrier by the water flow, they can be captured by the next-stage roll-shaped carrier, and the microorganism concentration in the tank is not lowered.

  The present invention is configured as described above, and does not use a carrier during culturing of anammox bacteria, and since the cultured cells can be easily supported on the carrier, a carrier having a high degree of freedom is used. It is easy to install in the tank and the work efficiency is good. Further, since the carrier is wound in a roll shape, the anammox bacteria are hardly peeled off from the carrier, and can be immobilized at a high concentration inside the carrier. Furthermore, since the carrier is installed in multiple stages in the tank, it is possible to reduce the size of the reaction tank, the substrate can be uniformly contacted with anammox bacteria, and the high concentration in the tank can be easily maintained. It is easy to set conditions at startup.

  FIG. 1 is a longitudinal sectional view of a biological denitrification apparatus, and a stock solution is supplied from a stock solution supply pipe 3 connected to the bottom of a sealed denitrification tank 2. The stock solution that has flowed into the denitrification tank 2 rises in an upward flow and reaches the lower presser plate 5 that sandwiches the roll-shaped carrier 4. The raw water that has entered through the through holes 5a of the presser plate 5 comes into contact with the anammox bacteria 6 supported between the fibers while passing between the fibers of the roll-shaped carrier 4, and a denitrification process called an anammox reaction is performed. . Ammonia nitrogen and nitrite nitrogen in the stock solution are reduced to nitrogen gas by the anammox bacteria 6 and discharged from the exhaust pipe 8 above the denitrification tank 2. The denitrified treatment liquid flows out from the through hole 5a of the upper presser plate 5 sandwiching the roll-shaped carrier 4, and flows out from the treated water pipe 7 communicating above the denitrification tank 2.

  The roll-shaped carrier 4 provided in the denitrification tank 2 may be installed in multiple stages at predetermined intervals in the height direction. The number of installation stages is appropriately selected depending on the height / diameter ratio of the denitrification tank, the processing amount, the set concentration, and the like. The roll-shaped carrier 4 is sandwiched at the top and bottom by a pressing plate 5 having a large number of through-holes 5a to prevent the shape from being deformed by rewinding or water flow. The presser plate 5 is fixed to the inner wall of the denitrification tank 2 to prevent the displacement of the installation place and the inclination of the roll-shaped carrier 4.

  FIG. 2 is a perspective view in which anammox bacteria are supported on a support sheet, and the support sheet 9 is made of a nonwoven fabric, a woven fabric or a net-like material composed of fibers or filaments. It is preferable to use a nonwoven fabric that is excellent in moldability and strength, has good adhesion to microorganisms, and can ensure an appropriate porosity.

  When the cultured anammox bacteria 6 is filtered over the entire surface of one side of the carrier sheet 9, the anammox bacteria 6 adheres to the fibers of the carrier sheet 9. The carrier sheet 9 is wound into a columnar shape with the filtration surface set to the inner peripheral side. The carrier sheet 9 wound to a diameter corresponding to the inner diameter of the denitrification tank 2 is cut at an appropriate thickness to form a roll-shaped carrier 4 as shown in FIG. The anammox bacteria 6 can be fixed at a high density in the roll-shaped carrier 4 and the filtration surface is on the inner peripheral side, so that the anammox bacteria 6 is hardly peeled off. Since there is an appropriate thickness in the height direction, the anammox bacteria 6 in the roll-shaped carrier 4 and the raw water can sufficiently come into contact with each other. Moreover, since it is wound closely, the anammox bacteria 6 is retained in the roll-shaped carrier 4 even if it is granulated and granulated. Nitrogen gas generated during the anammox reaction passes between the fibers and rises above the denitrification tank 2.

  Since the outer peripheral surface of the roll-shaped carrier 4 is inscribed in the denitrification tank 2 and the cut surface is perpendicular to the water flow direction, the raw water that rises in the denitrification tank 2 from the center portion wound in a roll shape to the outer peripheral portion. Make even contact with the upward flow. Further, since there is a width in the height direction, when the raw water passes, the contact time with the anammox bacteria 6 becomes long, and an efficient denitrification treatment can be performed.

  FIG. 4 is a perspective view of the presser plate, in which the roll-shaped carrier 4 is sandwiched up and down and fixed at a predetermined position of the denitrification tank 2. A large number of through holes 5a are provided in the thin disk, so that the raw water can flow evenly over the entire surface of the roll-shaped carrier 4, and the pressure loss does not increase by preventing the raw water from flowing. The number and shape of the through holes 5a are not particularly limited as long as they do not hinder biological treatment, and may be configured in a lattice shape.

  When the roll-shaped carrier 4 is installed in multiple stages with gaps at regular intervals in the height direction, the raw water that has not been sufficiently denitrified by the upstream-side roll-shaped carrier 4 is converted into the subsequent roll-shaped carrier. 4 is contacted with anammox bacteria 6 and denitrification treatment is performed. Further, even if the anammox bacteria 6 is separated from the roll-shaped carrier 4 by the water flow, it can be captured by the subsequent roll-shaped carrier 4 and the microbial concentration in the tank is not lowered.

  Fine SS and impurities contained in the raw water supplied to the denitrification tank 2 and surplus sludge generated by the anammox reaction accumulate at the bottom of the denitrification tank 2 by its own weight. The bottom of the denitrification tank 2 is preferably conical so that impurities and excess sludge are easily deposited, and a discharge pipe 10 for discharging the tank to the outside of the tank is connected. When the roll-shaped carriers 4 are installed in multiple stages, discharge pipes 10a, 10b,... Are connected below the gaps between the roll-shaped carriers 4.

  A circulating pipe 11 for returning a part of the treated water to the denitrification tank 2 as circulating water is connected to the treated water pipe. In this embodiment, the other end of the circulation pipe 11 is connected to the raw water supply pipe 3, but it may be directly connected to the denitrification tank 2, and the treated water is circulated using a circulation pump 12. Also good.

  The biological denitrification apparatus according to the present invention can easily maintain and increase the concentration in the tank by the roll-shaped carrier to which anammox bacteria adhere. Since the outflow of anammox bacteria to the outside of the tank is extremely small, it is not necessary to provide a screen or the like near the outlet in order to prevent the outflow, and maintenance is easy. The carrier can be easily taken out, replenished, and re-introduced at the initial stage and at the start-up after the operation is stopped, and no culture period in the tank is required. Further, by installing the carrier in multiple stages in the tank, it is strong against load fluctuations, and the apparatus can be miniaturized, and a large installation area is not required. Since it is easy to handle bacteria and has good work efficiency, it can be easily installed in wastewater treatment facilities that require denitrification.

It is a longitudinal cross-sectional view of the biological denitrification apparatus which concerns on this invention. Similarly, it is a perspective view of a carrying sheet. Similarly, it is a perspective view of a roll-shaped carrier. Similarly, it is a perspective view of a holding plate. It is a flowchart of the nitrogen removal system using the conventional anammox bacteria.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Biological denitrification apparatus 2 Denitrification tank 4 Roll-shaped carrier 5 Holding plate 5a Through-hole 6 Anammox bacteria 9 Carrier sheet

Claims (4)

The anammox cultivated in the microorganism carrier of the denitrification apparatus that fills the inside of the denitrification tank with autotrophic denitrifying bacteria and continuously removes ammonia nitrogen in the raw water supplied to the denitrifying tank (2) as nitrogen gas (6) is filtered through the support sheet (9), wound in a cylindrical shape with the filtration surface inside, and cut into a predetermined width to form a roll-shaped support (4). Body manufacturing method . In the denitrification tank (1), which is filled with autotrophic denitrification bacteria inside the denitrification tank and continuously removes ammonia nitrogen in the raw water supplied to the denitrification tank (2) as nitrogen gas, anammox bacteria on one side A roll-shaped carrier (4) having a predetermined width wound with a column (6) is disposed in the denitrification tank (2), and the outer peripheral surface of the roll-shaped carrier (4) is disposed on the denitrification tank (2). A biological denitrification apparatus characterized by being inscribed in The roll-shaped carrier (4) is sandwiched between press plates (5, 5) having through-holes (5a ...) in the vertical direction, and is installed in the denitrification tank (2). The biological denitrification apparatus described in 1. The biological denitrification according to claim 3, characterized in that the roll-shaped carrier (4) sandwiched between the press plates (5, 5) is arranged in multiple stages in the denitrification tank (2) at a predetermined interval. apparatus.