JPS649074B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wastewater treatment device, and more particularly to a device for biologically removing nitrogen components from wastewater.

[Conventional technology]

Conventional equipment of this kind consists of a denitrification tank, a nitrification tank, and a sedimentation tank, and by circulating sludge containing aerobic nitrifying bacteria and anaerobic denitrifying bacteria in a suspended state through each tank, nitrogen components in wastewater are removed. It was intended to remove.

Therefore, first, there was a drawback in terms of nitrogen removal efficiency, in that the nitrifying bacteria floating in the denitrification tank and the denitrifying bacteria floating in the nitrification tank were not effectively used for nitrogen removal.

Second, during the severe cold season, the activity of the nitrifying bacteria and denitrifying bacteria decreases, and their growth rate is also low, making it difficult to maintain an appropriate concentration of bacteria, making it impossible to achieve the intended purpose of nitrogen removal. The drawback was that it disappeared.

Thirdly, there was a problem in that the amount of surplus sludge that is separated in the settling tank is relatively large, and that processing and disposal thereof is expensive.

Thirdly, even though the treated water, which is the supernatant water of the settling tank, meets the discharge standards, it still has a high salt and solids concentration, making it difficult to reuse.

[Problem that the invention seeks to solve]

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
It is an object of the present invention to provide a wastewater treatment device that has good nitrogen removal efficiency, generates little surplus sludge, and can obtain clear treated water.

[Means for solving problems]

The present invention is based on the fact that immobilized microorganisms, which are immobilized in a polymeric carrier, are efficient in treating wastewater and generate less surplus sludge, and that a membrane module is used as a means to obtain clear treated water. The above objective has been achieved by focusing on the suitability of these technologies and applying these technologies to wastewater nitrogen removal technology.

That is, the present invention provides an anaerobic tank containing immobilized denitrifying bacteria, which is the denitrifying bacteria that is comprehensively immobilized on a polymer carrier, and an aerobic tank that contains the immobilized nitrifying bacteria, which is the nitrifying bacteria that is comprehensively immobilized on the polymer carrier. Equipped with In the anaerobic tank, wastewater to be treated is introduced in an upward flow and brought into contact with the immobilized denitrifying bacteria under anaerobic conditions. In the nitrification tank, the wastewater that has passed through the anaerobic tank is brought into contact with the immobilized nitrifying bacteria under aerobic conditions in a downward flow. A membrane module is arranged at the bottom of this aerobic tank, and an aeration means is provided below the membrane module. It also includes means for drawing out wastewater from the bottom of the aerobic tank, returning a portion of it to the anaerobic tank, and separating the remainder into solid and liquid.

[Effect]

Since denitrifying bacteria and nitrifying bacteria can be individually maintained at high concentrations in the anaerobic tank and the aerobic tank, nitrogen can be removed efficiently. The amount of surplus sludge generated is also small. The oxygen-containing gas aerated from the aeration means maintains the aerobic tank under aerobic conditions and is also used to clean the membrane surface of the membrane module.

〔Example〕

An embodiment of the present invention will be described based on FIG.

The anaerobic tank 10 is provided with perforated plates 12 and 14 on the upper and lower sides, and immobilized denitrifying bacteria 16 are accommodated between the perforated plates 12 and 14. Similarly, immobilized nitrifying bacteria 26 are accommodated in the aerobic tank 20 between perforated plates 22 and 24. A membrane module 28 is installed at the bottom of the aerobic tank 20.
is arranged, and an aeration means 30 is provided below the membrane module 28. The wastewater to be treated is introduced into the anaerobic tank 10 from the pipe 32 in an upward flow. A portion of the waste water drawn from the bottom of the aerobic tank 20 is also introduced in an upward flow into the anaerobic tank 10 through a pipe line 36 by the pump 34. As these wastewaters rise in the anaerobic tank 10, they come into contact with the immobilized denitrifying bacteria 16, and the nitrate nitrogen in the wastewater is decomposed into nitrogen gas by the action of the denitrifying bacteria. The generated nitrogen gas is transferred to anaerobic tank 1.
0 is dissipated into the atmosphere from the top open end. Anaerobic tank 1
The wastewater that has reached the upper part of the tank overflows and is introduced into the aerobic tank 20, and descends inside the aerobic tank 20. Aerobic tank 20
In this case, sufficient aerobic conditions are maintained by aeration with oxygen-containing gas such as air from the aeration means 30. As the wastewater flows downward, it comes into contact with the immobilized nitrifying bacteria 26, and ammonia nitrogen in the waste water is converted to nitrate nitrogen by the action of the nitrifying bacteria. Nitrate nitrogen is transferred to the anaerobic tank 10 by the wastewater circulation system from the aerobic tank 20 to the anaerobic tank 10.
decomposed into nitrogen gas. Therefore, the concentrations of ammonia nitrogen and nitrate nitrogen in the wastewater that has passed through the zone of immobilized nitrifying bacteria 26 in the aerobic tank 20 are extremely low. Membrane module 2 in aerobic tank 10
A portion of the wastewater that has reached zone 8 passes through this membrane module 28 and is discharged from the pipe 38. The driving force for liquid permeation in the membrane module is obtained by the water head difference in the aerobic tank 10. The permeate from membrane module 28 is clear and easy to reuse.

Since the aeration means 30 is provided below the membrane module 28, the aerated oxygen-containing gas agitates the wastewater near the membrane module 28, preventing concentration polarization on the membrane surface and cleaning the membrane surface. It also serves to maintain the zone of immobilized nitrifying bacteria 26 in aerobic conditions. A part of the wastewater extracted from the bottom of the aerobic tank 20 is returned to the anaerobic tank 10 through the pipe 36, and the rest is introduced into the settling tank 44 through the pipe 42 by the pump 40, where it is separated into solid and liquid. The precipitate is mainly surplus sludge inevitably generated by the series of treatments described above, and is discharged from the system through the pipe 46. Since the amount of surplus sludge generated is a fraction of that in the case of the floating sludge method according to the prior art, the cost required for the processing components can be reduced. The supernatant water in the settling tank 44 is discharged out of the system through a pipe 48.

That is, in the device of this embodiment, the pipe line 32
Raw wastewater flowing into the pipe undergoes a series of treatments, resulting in membrane-permeated water to pipe 38, supernatant water to pipe 48, and pipe 4.
The surplus sludge will be separated into 6 parts and discharged. The supernatant water from the conduit 48 may be returned to the anaerobic tank 10 or the aerobic tank 20, and all the treated water that is finally drained from the apparatus may be the membrane permeated water from the conduit 38.

The immobilized denitrifying bacteria and immobilized nitrifying bacteria can be produced, for example, by a method similar to the method described in JP-A-59-127693, in which activated sludge is immobilized inside a polymer carrier. Further, as the membrane module, a hollow fiber membrane, a rotating disk membrane, or the like is used.

In the above embodiment, as shown in FIG.
0, the sedimentation tank 44 shown in FIG. 1 may be omitted. In this example, excess sludge is discharged from the bottom of the settling section 50 via the pipe 52. Further, an extraction pipe 5 is provided below the aeration means 30.
4, and the waste water drawn out from this extraction pipe 54 is introduced into the anaerobic tank 10 from the pipe line 36 by the pump 34 in the same manner as shown in FIG.

In the embodiments described above, the effects of making the wastewater introduced into the anaerobic tank 10 flow upward and the wastewater introduced into the aerobic tank 20 flowing downward mainly reside in the following two points.

First of all, immobilized denitrifying bacteria and immobilized nitrifying bacteria are
Denitrifying bacteria or nitrifying bacteria are immobilized in a polymeric carrier, and a polymeric carrier having a specific gravity slightly higher than that of water, such as polyacrylamide, is preferably used. Therefore, these immobilized denitrifying bacteria and immobilized nitrifying bacteria have a considerable sedimentation property in wastewater. Since wastewater is introduced into the anaerobic tank 10 in an upward flow, the immobilized denitrifying bacteria that have sedimentation properties are fluidized by this upward flow, and the wastewater and the immobilized denitrifying bacteria come into contact efficiently. On the other hand, in the aerobic tank 20, bubbles aerated from the aeration means 30 disposed below the tank collide with the downwardly flowing wastewater, partially or entirely agitating the wastewater. Furthermore, the rising air bubbles fluidize the immobilized nitrifying bacteria that tend to settle, so that as a result, the oxygen-containing gas, the immobilized nitrifying bacteria, and the gas-solid-liquid wastewater come into contact with each other efficiently.

Second, the operating power of the device can be saved. That is, the anaerobic tank 10 does not require any special power to fluidize the immobilized denitrifying bacteria. Furthermore, since the immobilized denitrifying bacteria is fluidized by upward flow, the water flow resistance in the tank is small. The same can be said for the aerobic tank 20. Furthermore, when the liquid levels in the anaerobic tank and the aerobic tank are almost the same, the wastewater overflowing from the anaerobic tank can be directly introduced into the aerobic tank, thereby saving power for pumping the wastewater.

FIGS. 3 and 4 show other embodiments of the present invention.

In this embodiment, as shown in FIG. 4, an anaerobic tank 62 is arranged in the center of a common tank 60 having a rectangular cross section, and a plurality of aerobic tanks 64 are arranged in the peripheral part separated by a partition wall 66. An overflow weir 68 to the aerobic tank 64 is provided above the anaerobic tank 62 . Further, a sealing lid 70 is provided to cover the space above the anaerobic tank 62, and this sealing lid 70 is connected to the gas storage tank 72 by a pipe 72.
is connected to. A gas discharge pipe 76 and a gas circulation pipe 78 are connected to the gas storage tank 74.
A compressor 80 is provided in the conduit 78. conduit 78
The other end is connected to a gas lift pipe 82 provided in the center of the anaerobic tank 62. Middle part 84 of anaerobic tank 62
is a fluidization zone for immobilized denitrifying bacteria, and the middle portion 86 of the aerobic tank 64 is a fluidization zone for immobilized nitrifying bacteria. A rotating flat membrane type membrane module 88 is provided below the intermediate portion 86 of the aerobic tank 64, and an aeration means 90 is provided further below.

The wastewater to be treated is introduced from the pipe line 92 into a liquid reservoir section 94 at the bottom of the anaerobic tank, and from this liquid reservoir section 94 flows into the anaerobic tank 62 via a communication pipe 96. The inflowing wastewater passes through the intermediate section 84 in which the immobilized denitrifying bacteria flows as an upward flow, and undergoes denitrification treatment during this period. The nitrogen gas generated by this process is removed by the sealing lid 70.
As a result, it stays in the space above the anaerobic tank 62 and functions to maintain the anaerobic tank 62 under anaerobic conditions. Further, this nitrogen gas passes through the gas storage tank 74 from the pipe line 72, is pressurized by the compressor 80, and is circulated from the pipe line 78 to the gas lift pipe 82. In this gas lift pipe 82, due to the lifting action of the nitrogen gas blown into it, the waste water in the anaerobic tank 62 is drawn in from the lower end opening of the gas lift pipe 82 and discharged to the upper end opening. Therefore, the wastewater in the anaerobic tank is agitated by the action of the gas lift pipe 82 while forming an upward flow as a whole. For this reason,
Improved contact between wastewater and immobilized denitrifying bacteria,
Denitrification treatment progresses efficiently.

The wastewater that has reached the upper part of the anaerobic tank 62 overflows from the overflow weir 68 into the aerobic tank 64, forming a downward flow and undergoes nitrification treatment in the intermediate section 86, which is the zone of immobilized nitrifying bacteria. After this, some of the waste water is permeated through the membrane module 88 and discharged as clear water through the conduit 98. As shown in Japanese Patent Application No. 60-118483, a rotating flat membrane type membrane module is one in which a large number of disc-shaped membranes are attached to a rotating shaft at predetermined intervals and rotated around the shaft, and the permeated water is Collect in the hollow part of the rotating shaft. This membrane module has a disc-shaped membrane that constantly rotates, so there is little concentration polarization on the membrane surface.
It also suppresses the adhesion of sludge, etc. to the membrane surface. Therefore, it is a particularly suitable membrane module for carrying out the present invention. The effects of the oxygen-containing gas aerated from the aeration means 90 are as described above.

The wastewater that has reached the bottom of the aerobic tank 64 is drawn out from the pipe 100, and a portion is drawn out from the pipe 102 to the pump 10.
4 and then returned to the anaerobic tank 62 for circulation. The remainder passes through a pipe 106 to a pump 108 and is separated into solid and liquid in a settling tank (not shown).

In this embodiment, among the four aerobic tanks 64, 64, 64, 64 shown in FIG. It is convenient to leave it open for maintenance purposes.

As described above, according to this embodiment, since the anaerobic tank and the aerobic tank are compactly housed in one common tank, there is an advantage that the required installation area of the device is small. In addition, the nitrogen gas generated in the denitrification tank is used as a sealing gas to maintain anaerobic conditions.
It is also circulated in the anaerobic tank and reused to improve the contact efficiency between the wastewater and the immobilized denitrifying bacteria, which has the advantage of improving the efficiency of anaerobic treatment.

〔Effect of the invention〕

According to the present invention, since denitrifying bacteria and nitrifying bacteria can be maintained at high concentrations in the anaerobic tank and the aerobic tank, respectively, nitrogen components in wastewater can be efficiently removed. Since immobilized denitrifying bacteria and immobilized nitrifying bacteria are used, the amount of surplus sludge generated is small. The oxygen-containing gas aerated from the aeration means is used to prevent concentration polarization in the membrane module and to clean the membrane surface, and is then used to maintain the aerobic tank under aerobic conditions. That is, two different effects can be achieved by the aeration means. Since wastewater flows upward in an anaerobic tank and flows downward in an aerobic tank, immobilized denitrifying bacteria and immobilized nitrifying bacteria can be maintained in a fluid state. Therefore, sufficient contact between the wastewater and these immobilized microorganisms is achieved, and less power is required for water passage.

[Brief explanation of drawings]

Fig. 1 is an apparatus system diagram showing an embodiment of the present invention, Fig. 2 is an apparatus system diagram showing another embodiment of the aerobic tank according to the invention, and Fig. 3 is an apparatus system diagram showing another embodiment of the invention. The system diagram, FIG. 4 is a sectional view taken along the - arrow in FIG. 3. 10... Anaerobic tank, 16... Immobilized denitrifying bacteria, 20
... Aerobic tank, 26 ... Immobilized nitrifying bacteria, 28 ... Membrane module, 30 ... Aeration means, 44 ... Sedimentation tank.

Claims (1)

[Scope of Claims] 1. An anaerobic tank in which immobilized denitrifying bacteria, in which denitrifying bacteria are encircled and immobilized in a polymer carrier, is accommodated, and wastewater introduced in an upward flow is brought into contact with the immobilized denitrifying bacteria under anaerobic conditions. and an aerobic method in which immobilized nitrifying bacteria, in which nitrifying bacteria are encircled and immobilized in a polymer carrier, are housed inside, and the wastewater that has passed through the anaerobic tank is brought into contact with the immobilized nitrifying bacteria under aerobic conditions under aerobic conditions. a membrane module disposed at the bottom of the aerobic tank; an aeration means for aerating oxygen-containing gas from below the membrane module; and a part of the wastewater drawn from the bottom of the aerobic tank to the anaerobic tank. What is claimed is: 1. A wastewater treatment device characterized by comprising means for returning solid water to solid-liquid water and separating the remainder from solid-liquid. 2. The anaerobic tank and aerobic tank are installed next to each other in the same tank with a partition wall in between, so that wastewater that has passed through the anaerobic tank overflows from the top of the anaerobic tank and flows into the top of the aerobic tank. A wastewater treatment device according to claim 1, characterized in that: 3. The wastewater treatment apparatus according to claim 1 or 2, wherein the anaerobic tank is provided with means for circulating generated nitrogen gas to a lower part of the tank.