JPH0884998A - Organic sewage treatment device - Google Patents

Abstract

PURPOSE: To secure the nitrification efficiency of a ammoniac nitrogen in an aerobic filter bet and to increase nitrogen removal efficiency by arranging a carrier layer for immobilization in the downside of an organic substance removal layer, immobilizing and retaining nitrifier in the carrier layer for immobilization. CONSTITUTION: An organic sewage treatment device is equipped with both a denitrification tank 3 in which an anaerobic filter bed 4 denitrifying nitrate nitrogen is arranged and a nitrification tank 6. In the nitrification tank 6, and aerator 18 is arranged under an aerobic filter bed 7 for BOD oxidation and nitrification of ammoniac nitrogen. The aerobic filter bed 7 is constituted of an organic substance removal layer 19 holding a filter medium consisting of a granular carrier and of a carrier layer 20 for immobilization which is arranged in the downside of the layer 19 and holds a carrier on which nitrifier immobilized for nitrifying ammoniac nitrogen in a perforated vessel consisting of mesh-like ball bodies 23. Therefore, the concentration of microorganisms is increased by the carrier having immobilized nitrifier. Nitrification efficiency of ammoniac nitrogen is increased in the carrier layer for immobilization. Nitrification velocity of ammoniac nitrogen is increased and thereby denitrification efficiency in the tank 3 is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic wastewater treatment system for removing BOD components and nitrogen in organic wastewater containing ammoniacal nitrogen.

[0002]

2. Description of the Related Art In recent years, removal of nutrient salts (nitrogen, phosphorus) has become important from the viewpoint of environmental conservation of water bodies, as seen in eutrophication of closed water bodies such as lakes.

Conventionally, as a biological method for removing BOD components and nitrogen from wastewater such as sewage, several modified methods based on the activated sludge method have been considered. At present, as a method mainly used for practical use, there is a nitrification solution circulation type modified activated sludge circulation method. This modified activated sludge circulation method oxidizes ammonia nitrogen (NH ₄ —N) to nitrate nitrogen (NO ₃ —N) (nitrification), and converts the generated nitrate nitrogen to nitrogen gas (N ₂ ). It is performed by a combination of denitrification. That is, (NH ₄ -N) → (NO ₃ -N) →
It causes a reaction of (N ₂ ).

This modified method of circulating the nitrification liquid activated sludge is
As shown in FIG. 9, the anaerobic tank 10 for denitrifying the front stage is used.
1. The latter stage is an aerobic tank 102 for BOD oxidation and nitrification of ammonia nitrogen, and the effluent from the aerobic tank 102,
That is, a part of the nitrification solution is circulated in the anaerobic tank 101 in the preceding stage by the nitrification solution circulation pump 103. In this modified activated sludge circulation method, as shown in FIG. 10, a reaction of (NO ₃ -N) → (N ₂ ) occurs in the anaerobic tank 101 in the front stage and (NH ₄ ) in the aerobic tank 102 in the rear stage. −
N) → (NO ₃ —N), and the removal reaction of BOD component and SS component occurs.

In the modified method of activated sludge circulation of the nitrifying solution circulation type, the time required for treating the organic wastewater is 1
2-16 hours are required. Because aerobic tank 10
The growth of nitrifying bacteria in 2 is slower than other microorganisms in the activated sludge, and especially at low water temperature in winter, the ratio of nitrifying bacteria in the activated sludge decreases, and the activity also decreases. This is because a long processing time is required to promote the nitrification reaction.

Therefore, in order to shorten the treatment time, as shown in Japanese Patent Application No. 4-16099, an organic sewage treatment apparatus using an anaerobic fluidized bed as an anaerobic tank has been filed (see FIG. 11). (Shown).

In the figure, this organic sewage treatment apparatus 20 is shown.
1 is an anaerobic fluidized bed 202 for denitrification, and an aerobic filter bed 203 for BOD oxidation and nitrification of ammoniacal nitrogen.
And the overflow liquid from the anaerobic fluidized bed 202 to the aerobic filter bed 20.
3, and a second pipe 205 for returning the nitrification liquid from the aerobic filter bed 203 to the anaerobic fluidized bed 202.
And a circulation pump 206 provided in the second pipe 205.

The nitrate nitrogen contained in the returned liquid from the aerobic filter bed 203 at the subsequent stage is denitrified in the anaerobic fluidized bed 202, and the overflow water from this anaerobic fluidized bed 202 is aerated. BOD contained in the overflow water
Components and SS components are removed and ammoniacal nitrogen is nitrified, a part of the nitrification liquid from the aerobic filter bed 203 is returned to the anaerobic fluidized bed 202, and the carrier in the anaerobic fluidized bed 202 is mixed with the raw water. The concentration of microorganisms adhering to the carrier while flowing is increased.

According to the organic sewage treatment apparatus 201, since the aerobic filter bed 203 having excellent nitrification performance and the anaerobic fluidized bed 202 having excellent denitrification performance are combined, the treatment time of organic sewage is shortened and high. Nitrogen removal performance is secured.

[0010]

According to the above-mentioned organic sewage treatment apparatus 201, the water quality analysis results shown in Table 1 below are obtained.

[0011]

[Table 1]

However, as shown in Table 1 above,
Organic sewage treatment device 2 that shortens the treatment time of organic sewage
In the case of 01, the nitrifying bacteria concentration is lowered, and therefore the reaction rate of ammoniacal nitrogen to nitrate nitrogen is slowed down, and the ammoniacal nitrogen oxidation (nitrification) efficiency in the aerobic filter 203 is reduced. This is the BOD in the aerobic filter bed 203.
Since the bacteria and nitrifying bacteria are mixed, it is said that the growth of nitrifying bacteria, which is a recessive bacterium, is insufficient, and that the slow-growing nitrifying bacteria flow out from the other end of the filter bed.

As a result of a decrease in the concentration of nitrifying bacteria in the aerobic filter bed 203, the nitrogen removal efficiency is lowered particularly when the inflowing organic wastewater quality is changed and the load becomes high, or in the low water temperature period of winter. It has been proved as a result of the proof test.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to secure the oxidation (nitrification) efficiency of ammonia nitrogen in an aerobic filter bed and to improve the nitrogen removal efficiency. It is to provide an organic sewage treatment device that can be used.

[0015]

The invention according to claim 1 is a denitrification tank comprising an anaerobic filter bed for denitrifying nitrate nitrogen, and aerobic for BOD oxidation and nitrification of ammonia nitrogen. In an organic sewage treatment apparatus having a nitrification tank in which an aeration device is arranged under a filter bed, the aerobic filter bed is
An organic matter removal layer containing a filter medium, and an immobilized carrier layer arranged below the organic matter removal layer and containing a carrier in which nitrifying bacteria nitrifying ammonia nitrogen are immobilized in a porous container. It is characterized by

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the depth dimension of the immobilized carrier layer is 2/3 or less of the depth dimension of the aerobic filter bed. Claim 3
According to the invention described in claim 1 or 2,
The porous container is characterized by being provided in a nitrification tank and held by a support member through which organic waste water can pass.

The invention as claimed in claim 4 is as follows.
In any one of the inventions, the porous container is a mesh ball body.

[0018]

According to the first aspect of the present invention, in the aerobic filter bed, BOD bacteria live in the organic matter removing layer, and nitrifying bacteria live in the immobilized carrier layer. That is, BOD bacteria and nitrifying bacteria inhabit in different areas.

Therefore, in the organic matter removal layer of the aerobic filter bed,
Organic substances (BOD component, SS component) and solids contained in the overflow water are removed by the BOD bacteria on the filter medium. Therefore, the organic sewage that has passed through the organic matter removal layer is purified to clean water containing ammoniacal nitrogen.

When the clean water containing ammoniacal nitrogen that has passed through the organic substance removal layer enters the immobilization carrier layer, it is nitrified by the nitrifying bacteria immobilized on the carrier of the porous container of the immobilization carrier layer, and the nitrification solution is formed. Occurs.

In the invention according to claim 2, since the depth dimension of the immobilization carrier layer is 2/3 or less of the depth dimension of the aerobic filter bed, removal of BOD components by BOD bacteria in the organic substance removal layer. Is sufficiently performed, and therefore, in the immobilization carrier layer,
The amount of BOD component in the clean water after passing is small and nitrifying bacteria can be sufficiently secured.

According to the invention of claim 3, claim 1
In the invention described, since the porous container is provided in the nitrification tank and is held by the support member through which the organic wastewater can pass, the carrier does not flow out even in the backwash by the aeration device, and the nitrifying bacteria are fixed. The carrier enhances the microbial concentration.

In the invention according to claim 4, since the porous container is a mesh-shaped ball, it can be easily arranged in the immobilized carrier layer.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. An embodiment of the organic sewage treatment apparatus of the invention according to claims 1 to 4 will be described with reference to FIGS. 1 to 8.
The organic wastewater to be purified in this example contains ammonia nitrogen having a content of 10 mg / l or more,
For example, it applies to urban sewage.

In FIG. 1, reference numeral 1 represents a first sedimentation tank, and the first sedimentation tank 1 communicates with a denitrification tank 3 via a raw water supply pipe 2. The denitrification tank 3 is provided with an anaerobic filter bed 4 composed of an anaerobic fluidized bed. A raw water supply pump 5 is provided in the raw water supply pipe 2.

The denitrification tank 3 has a first pipe 8 for introducing the overflow liquid into the aerobic filter bed 7 of the nitrification tank 6 and a second pipe 9 for returning the nitrification liquid from the aerobic filter bed 7 to the denitrification tank 3. It is installed.
A nitrification solution circulation pump 10 is provided in the second pipe 9.

The anaerobic filter bed 4 is filled with a granular material (sand, activated carbon, plastic filter material, etc.) as a carrier 11, and is made to flow by an upward flow. Carrier 11 in anaerobic filter bed 4
May be such that it flows according to the total flow rate of the nitrification liquid circulation amount from the aerobic filter bed 7 and the raw water supply amount, which will be described later. If it is light, the one having a large particle size is generally used.

The denitrification tank 3 has a supply part 12 for connecting the raw water supply pipe 2 to the second pipe 9, a dispersion nozzle 13 provided in the supply part 12, and a biofilm stripping device 14 provided on the upper part. .

The carrier 11 from which the biofilm has been separated by the biofilm separating device 14 settles on the upper part of the anaerobic filter bed 4, and the separated sludge is returned to the first settling tank 1 via a sludge discharge pipe (not shown). .

On the other hand, in the nitrification tank 6, the first pipe 8 is connected to the upper part and the nitrification liquid reservoir 15 is provided to the lower part. Further, inside the nitrification tank 6, an aeration device 18 that communicates with the blower 16 via a pipe 17 is arranged. Further, the nitrification liquid flows from the aerobic filter bed 7 into the nitrification liquid reservoir 15 at the lower part.

The aerobic filter bed 7 has an organic substance removal layer 1
9 and the immobilization carrier layer 20. The organic substance removal layer 19 contains a filter medium composed of a granular carrier 21 over a predetermined distance in the vertical direction from the upper surface. Granular carrier 21
Examples include anthracite and plastic filter media.

In FIGS. 1 to 4, the immobilization carrier layer 2
0 is arranged below the organic substance removing layer 19 and is constituted by accommodating a carrier 22 on which nitrifying bacteria that nitrify ammonia nitrogen are fixed in a porous container composed of mesh ball bodies 23. As a material of the mesh ball body 23, for example, S
US material or plastic material is used and its diameter is 5
0 mm to 150 mm, hole width is 1.5 mm to 2.0 mm
Has become. The apparent specific gravity of the mesh-shaped ball body 23 containing the carrier 22 is equal to that of the granular carrier 21.

The immobilization carrier layer 20 comprises a first layer 20A formed by holding mesh balls 23 arranged in a horizontal row on both upper and lower sides with nets 24A and 24B, and a mesh ball 23 arranged in a horizontal row. A second layer 20B having upper and lower sides supported by nets 25A and 25B, and a third layer 20C having upper and lower sides of the mesh-shaped ball bodies 23 arranged in one horizontal row supported by nets 26A and 26B. Has been done. Note that the first
Even if the mesh-shaped ball bodies 23 of the two or three layers 20A, 20B, and 20C are stacked, the carrier 22 is protected by the mesh-shaped ball bodies 23 and therefore does not collapse. In addition, the mesh ball body 23 has an inlet portion 2
3A is formed, the carrier 22 is inserted from the inlet 23A, and the inlet 23A is closed by the screw lid 23B.

The depth dimension of the immobilization carrier layer 20 is equal to or less than the depth dimension H of the aerobic filter bed 7 × 2/3. This is because when the depth dimension of the immobilization carrier layer 20> the depth dimension H of the aerobic filter bed H × 2/3, the depth dimension of the organic substance removal layer 19 is small, and therefore the organic substance removal layer 19 has a small depth dimension. BOD
The removal of the BOD component by the bacterium is not sufficient, and in the immobilized carrier layer 20, BOD is added to the clean water after passing through the organic matter removal layer 19.
This is because the components are contained, the amount of nitrifying bacteria cannot be sufficiently secured, and the nitrification efficiency is not secured, and the value of 2/3 or less is determined by an experiment. That is, the depth dimension of the immobilized carrier layer 20 = the depth dimension H of the aerobic filter bed H x 2/3
The ratio of the depth dimension of the immobilization carrier layer 20 to the depth dimension of the aerobic filter bed 7 is determined by the BOD component amount of organic wastewater / N (nitrogen amount) within the range. To be In the case of organic sewage having a BOD / N of about 4 (for example, in the case of municipal sewage), the depth dimension of the immobilization carrier layer 20 is equal to or less than the depth dimension H of the aerobic filter bed H × 1/2. ing. In the case of organic wastewater having a BOD / N of 4 or more (domestic wastewater (excluding human waste)), the depth dimension of the immobilization carrier layer 20 = the depth dimension H of the aerobic filter bed H x 1/2 It can be even smaller. For organic wastewater having a BOD / N of 4 or less, such as human waste or digestive desorption liquid of human urine, the depth dimension of the immobilization carrier layer 20 = the depth dimension H of the aerobic filter bed 1
The range is / 2 or more and 2/3 or less. By the way, the depth dimension from the upper surface 19A of the organic substance removing layer 19 of this embodiment is 1250 mm, and the immobilization carrier layer 20 is 500 mm from the lower face 19B of the organic substance removing layer 19. Therefore, the depth dimension of the immobilization carrier layer 20 / the depth dimension of the aerobic filter bed = 750 mm / 2000 mm = 0.375
Has become. Further, since the depth dimension of the immobilized carrier layer 20 is equal to or less than the depth dimension H of the aerobic filter bed 7 × 2/3, the power for backwashing can be saved.

Then, as shown in FIG.
A second pipe 9 and a treated water discharge pipe 27 are attached to the. A valve 28 is attached to the treated water discharge pipe 27. Further, the treated water discharge pipe 27 communicates with the treated water tank 29.

The treated water tank 29 communicates with the nitrification solution reservoir 15 via a backwash pipe 30. The backwash pipe 30 is provided with a backwash pump 31. A backwash blower pipe 32 is attached to the nitrification solution reservoir 25. The backwash blower pipe 32 is provided with a backwash blower 33.

The backwash water sent from the backwash pump 31 and the air sent from the backwash blower 33 are jetted to the immobilized carrier layer 20 through the nozzle 34. The backwash causes the mesh-shaped balls 23 to receive a force that flows upward,
Although some amount floats, the nets 24A, 24B, 25A,
Since it is regulated by a support member composed of 25B, 26A, and 26B, it is held by the immobilization carrier layer 20. Moreover, since the specific gravity of the mesh-shaped ball body 23 containing the carrier 22 is almost the same as that of the carrier 11, it is sunk and restored to the original state. That is, the mesh-shaped balls 23 are prevented from flowing out to the organic substance removal layer 19, and the immobilization carrier layer 20 is prevented.
Held in.

Next, the operation of this embodiment will be described. Organic wastewater (raw water) containing ammonia nitrogen, such as city sewage, is stored in the first sedimentation basin 1.

Raw water is supplied from the first settling tank 1 to the raw water supply pump 5
Is sent to the supply unit 12 of the denitrification tank 3 via the raw water supply pipe 2. At the same time, the nitrification solution from the nitrification tank 6 is sent by the nitrification solution circulation pump 10 to the confluence section 9A via the second pipe 9, and is sent to the supply section 12 in a state of being mixed with the raw water.

Then, it is introduced into the anaerobic filter bed 4 by the dispersion nozzle 13. Here, raw water and the subsequent nitrification tank 6
The carrier 11 is de-nitrogenated by the returned liquid from the carrier.

When the flow interface rises as the biofilm grows on the surface of the carrier 11, the biofilm peeling device 14 is operated to control the flow interface of the carrier 11 to maintain the flow interface at a constant height.・ Controlled.

Next, the overflow water from the anaerobic filter bed 4 is sent to the nitrification tank 6 through the first pipe 8, where the BOD and SS components contained in the overflow water are removed and ammonia nitrogen is removed. Nitrification is performed.

More specifically, in the aerobic filter bed 7, BOD bacteria live in the organic matter removing layer 19, and nitrifying bacteria live in the immobilization carrier layer 20. That is, BOD
Bacteria and nitrifying bacteria live in separate areas. Aerobic filter bed 7
In the organic substance removal layer 19, the organic substance (BOD component, SS component) and solid matter contained in the overflow water are removed by the granular carrier 21. Therefore, the organic wastewater that has passed through the organic substance removal layer 19 is purified to clean water containing ammoniacal nitrogen. As a result, the mesh-shaped balls 23 of the immobilized carrier layer 20 will not be clogged with the SS component. Since the carrier 22 in the mesh ball body 23 is constantly moving and floating by aeration, the carrier 22 itself does not block. In the unlikely event of mesh balls 2
Even when 3 is clogged by the carrier 22 itself, or when the SS component is clogged at the bottom of the mesh-shaped ball body 23 to cause clogging, the clogging is eliminated by backwashing once per day.

The clean water containing ammoniacal nitrogen after passing through the organic substance removing layer 19 passes through the immobilizing carrier layer 20. The clean water containing ammonia nitrogen is accelerated by the nitrifying bacteria immobilized on the carrier 22 of the mesh-shaped ball body 23 of the immobilization carrier layer 20 to promote the nitrification action of ammonia nitrogen, thereby producing a nitrification solution.

Then, the nitrifying liquid reservoir 15 of the aerobic filter bed 7
A part of the nitrification solution that has flowed into the tank is returned to the supply section 12 of the denitrification tank 3 by the nitrification solution circulation pump 10 via the second pipe 9, and the carrier 11 in the anaerobic filter bed 4 is made to flow with the raw water. The concentration of microorganisms attached to 11 is increased.

By this flow, the carrier 1 in the anaerobic filter bed 4
The total surface area of No. 1 is provided as a place for adhering microorganisms, the specific surface area of the carrier 11 is dramatically increased as compared with that before flowing (that is, in a fixed bed state), and a microbial film is formed on the surface of the carrier 11. Since the denitrifying bacteria accumulate in the form of formation, a high concentration (10,000 mg / l to 50,000 mg / l) is achieved. Therefore, denitrification is possible in 10 to 15 minutes.

Then, the following experiment has confirmed the concept of removing organic substances (BOD components, SS components) and solids in the organic substance removing layer 19 and nitrifying ammoniacal nitrogen in the immobilized carrier layer 20. . That is, by using the experimental apparatus shown in FIGS. 5 and 6, the concentrations of total BOD, dissolved BOD, ammoniacal nitrogen, and nitrate nitrogen in the depth direction of the aerobic filter bed 7 were analyzed. 7, the water quality results shown in FIG. 8 and Tables 2 and 3 are obtained.

First, the experimental apparatus for the nitrification capacity of the aerobic filter bed of this example and the conventional aerobic filter bed is shown in FIG.
As the target raw water, the sewage primary treated water discharged from the first sedimentation basin 1 is used. Water flow rate of aerobic filter bed (= supply to filter bed / filter bed cross section) is 25m / day, filter bed cross section is 0.2
m ² , the filter bed filling height is 2000 mm, and the water temperature is 13.9 ° C.

In the experiment using such an apparatus, the results of the concentrations of ammonia nitrogen and nitrate nitrogen shown in the following Table 2 and FIGS. 7 and 8 are shown.

[0050]

[Table 2]

From the above experimental results, the following can be found.
As shown in FIG. 8, total BOD (T-BOD), dissolved BO
Regarding D (S-BOD), about 80% of all BOD and dissolved BOD are removed in the depth region where the depth dimension from the upper surface of the aerobic filter bed is about 1200 mm in FIG.

Further, as shown in FIG. 7, regarding the depth region where the ammoniacal nitrogen is nitrified, the depth dimension from the upper surface of the aerobic filter bed is about 700 mm or less, and the ammonia caused by the action of nitrifying bacteria is ammonia. Nitrogen is nitrifying.

Therefore, BOD bacteria act strongly in the depth range from the upper surface of the aerobic filter bed up to about 1200 mm, and the depth dimension from the upper surface of the aerobic filter bed is about 700 mm.
It has been shown that nitrifying bacteria act strongly in the following areas.

Next, FIG. 6 shows a denitrification experimental apparatus using the aerobic filter bed of this embodiment and a conventional aerobic filter bed. The target raw water is the sewage primary treated water that has left the first sedimentation basin 1. The throughput is 4m ³ / day, the filtration bed water flow rate is 2
0m / day, filter bed cross-sectional area 0.2m ² , filter bed filling height 2
000 mm, liquid circulation ratio from aerobic filter bed to anaerobic filter bed (circulation amount to filter bed / raw water supply amount) = 2, water temperature 14.9 ° C.
Is set to Further, the aerobic filter bed shown in Fig. 5 is used as the aerobic filter bed, and the carrier of the aerobic filter bed has a diameter of 5 mm.
Used anthracite.

In the experiment using such an apparatus, the concentrations of ammoniacal nitrogen and nitrate nitrogen are shown in Table 3 below.

[0056]

[Table 3]

Table 3 above shows that the nitrogen removal rate in this example is higher than the conventional nitrogen removal rate. According to the above configuration, the immobilization carrier layer 20 disposed below the organic matter removal layer 19 even when the inflowing quality of the organic sewage fluctuates and the load becomes high, or even in the low water temperature period of winter. In the inside, by immobilizing nitrifying bacteria in the immobilizing carrier layer 20 and taking measures to prevent the nitrifying bacteria from flowing out even in backwashing by the aeration device 18, the carrier on which nitrifying bacteria are immobilized enhances the microbial concentration, and aerobic filtration is performed. The efficiency (oxidation (nitrification)) of ammonia nitrogen in the immobilized carrier layer 20 of the bed 7 is increased, and it is possible to prevent slow-growing nitrifying bacteria from flowing out by the other end to reduce the nitrifying bacteria concentration, thereby increasing the nitrification rate of ammonia nitrogen. It is possible to increase the reaction efficiency of ammonia nitrogen to nitrate nitrogen. Consequently, the nitrogen removal efficiency in the denitrification tank 3 can be improved.

Even if the immobilizing carrier layer 20 for nitrifying bacteria is arranged, BOD removal and S removal in the organic substance removing layer 19 on the upper side thereof are possible.
Since the filtration performance of S does not deteriorate, removal of BOD components and SS
Filtration of the components can have performance similar to aerobic filter beds of conventional organic wastewater treatment equipment.

Further, although the immobilization carrier layer 20 is arranged below the organic substance removing layer 19, the mesh-shaped ball body 2 is formed.
By storing the carrier 22 in 3, the carrier 22 is protected, and the stable purification performance can be secured without causing inversion or mixing with the granular carrier 21 of the upper organic substance removal layer 19.

In the present embodiment, the mesh ball 23 has a diameter of 50 mm to 150 mm and a hole width of 1.5 mm to 2.0 mm, but it is not limited to these values.

Further, in this embodiment, the mesh-shaped balls 23 are mentioned as the porous container, but the present invention is not limited to this, and for example, a porous trough can be used. In this case, for example, a SUS material or a plastic material is used as the material of the porous trough, and the diameter is 50 mm to 150 mm, the length is 1000 mm, the pore width is 1.5 mm to 2.0 mm, and the opening ratio is 30 to 40%. Has been done. Alternatively, a porous box-shaped body or a porous ellipsoid may be used as the porous container.

Further, in this embodiment, the nets 24A, 24B, 25A, 25B, 26A, and
26B is used, and the upper and lower sides of the mesh ball body are the net 2
By being held by 4A, 24B, 25A, 25B, 26A, 26B, it is arranged on the immobilization carrier layer 20, but as a support member, the nets 24A, 24B, 25A, 2
It is not limited to 5B, 26A and 26B. A rod bridging between the nitrification tanks 6 may be used as the support member. That is, the upper and lower sides of the mesh-shaped ball body can be restricted between the rods, and the mesh-shaped ball body can be held on the immobilization carrier layer 20.

In this embodiment, the porous container is provided in the nitrification tank and is held by the support member through which the organic waste water can pass. However, even if the support member is not provided, the porous container has a proper specific gravity. The porous container can be held by being immersed in the immobilization carrier layer by selecting a suitable container.

In this embodiment, the anaerobic filter bed is an anaerobic fluidized bed, but the anaerobic filter bed is not limited to this.

[0065]

As described above, according to the invention of claim 1, in the nitrification tank, the immobilization carrier layer is arranged below the organic matter removal layer, and the nitrifying bacteria are present in the immobilization carrier layer. Since it is immobilized and retained, it is possible to increase the concentration of microorganisms by a carrier on which nitrifying bacteria are immobilized, increase the oxidation (nitrification) efficiency of ammonia nitrogen in the immobilized carrier layer, and increase the nitrification rate of ammonia nitrogen. . As a result, the nitrogen removal efficiency in the denitrification tank can be increased.

Even if the immobilizing carrier layer for nitrifying bacteria is arranged, the BOD component can be removed or S in the organic substance removing layer on the upper side thereof.
Since the filtration performance of the S component does not deteriorate, the removal of the BOD component and the filtration of the SS component can have the same performance as the aerobic filter bed of the conventional organic wastewater treatment equipment.

According to the second aspect of the present invention, the depth dimension of the immobilization carrier layer is 2/3 or less of the depth dimension of the aerobic filter bed. The removal is sufficiently performed, and therefore, in the immobilized carrier layer, the amount of BOD component in the clean water after passing is small, and nitrifying bacteria can be sufficiently secured.

According to the invention described in claim 3, in the invention described in claim 1, since the porous container is provided in the nitrification tank and is held by the support member through which the organic waste water can pass, the aeration device. The carrier does not flow out even in backwashing with, and the microbial concentration can be increased by the carrier on which the nitrifying bacteria are fixed.

In the fourth aspect of the invention, since the porous container is a mesh-shaped ball body, it can be easily arranged in the immobilization carrier layer.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an organic sewage treatment apparatus according to the invention described in claims 1 to 4.

FIG. 2 is an enlarged cross-sectional view showing a nitrification tank of the organic wastewater treatment device in FIG.

FIG. 3 is an enlarged view showing an inlet portion of the carrier of the mesh ball body of FIG.

FIG. 4 is an enlarged view of the mesh ball body of FIG.

FIG. 5 is a comparison diagram of a nitrification capacity test device for an aerobic filter bed of the present example and a conventional aerobic filter bed.

FIG. 6 is an explanatory diagram of a denitrification experiment device using the aerobic filter bed of the present example and a conventional aerobic filter bed.

FIG. 7 is an explanatory diagram showing a comparison of the concentration of ammonia nitrogen and the nitrification capacity of the aerobic filter bed of the present example and the conventional aerobic filter bed.

FIG. 8: T-BOD component and S-BO in aerobic filter bed
It is explanatory drawing which shows the density | concentration of D component.

FIG. 9 is an explanatory view showing a conventional nitrification solution circulation type activated sludge circulation modification method.

FIG. 10 is an explanatory view showing a biological reaction in the modified nitrification solution circulation type activated sludge circulation method of FIG. 9.

FIG. 11 is an explanatory diagram showing a conventional organic sewage treatment apparatus.

[Explanation of symbols]

 3 Denitrification tank 4 Anaerobic filter bed 6 Nitrification tank 7 Aerobic filter bed 19 Organic matter removal layer 20 Immobilized carrier layer 21 Granular carrier (filter material) 22 Carrier 23 Mesh ball body (porous container) 24A mesh (support member) 24B Net (support member) 25A Net (support member) 25B Net (support member) 26A Net (support member) 26B Net (support member)

Claims (4)

[Claims] 1. A denitrification tank comprising an anaerobic filter bed for denitrifying nitrate nitrogen, and an aerator under the aerobic filter bed for BOD oxidation and nitrification of ammonia nitrogen. In an organic sewage treatment apparatus equipped with a nitrification tank, the aerobic filter bed is disposed below the organic matter removal layer containing the filter medium and below the organic matter removal layer to fix nitrifying bacteria that nitrify ammonia nitrogen. An organic sewage treatment apparatus, comprising: an immobilized carrier layer, which is obtained by accommodating the modified carrier in a porous container. 2. The depth dimension of the immobilized carrier layer is 2/3 or less of the depth dimension of the aerobic filter bed.
The organic sewage treatment apparatus described. 3. The organic sewage treatment apparatus according to claim 1 or 2, wherein the porous container is provided in a nitrification tank and is held by a support member through which organic sewage can pass. 4. The organic sewage treatment apparatus according to claim 1, wherein the porous container is a mesh ball body.