JPH10216787A - Waste water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an equipment compact by disposing an air diffusion means in the middle of the up and down direction of a treatment tank, forming a section above the air diffusion means into an aerobic fluidized bed and a section below the air diffusion means into an anaerobic fluidized bed and forming an inflow section for water to be treated on the lower section of the treatment tank and an outflow section for water to be treated on the upper section of the treatment tank. SOLUTION: A screen 11 for separating a carrier is disposed in the middle of a treatment tank 10, and the inside of the tank is divided into the upper and the lower, and an air diffusion means 12 is disposed on the lower section of the screen 11. A section above the screen 11 and the air diffusion means 12 is formed into an aerobic fluidized bed 13, while a section below them is formed into an anaerobic fluidized bed 14. An inflow section 15 for water to be treated is disposed on the bottom of the treatment tank 10, while an outflow section 17 for water to be treated is disposed on an uppermost section through the screen 11 for separating a carrier. Also for the purpose of carrying out the waste water treatment mainly for removing nitrogen, a circulating line 18 for circulating a part of treated water flowing out of the outflow section 17 into the lower section of the anaerobic fluidized bed 14 is formed. The nitrogen removal, the excessive carbon source removal and the like can be carried out with good efficiency by the arrangement to make an equipment compact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment apparatus, and more particularly, to a wastewater treatment apparatus for treating wastewater by a fluidized bed using a biofilm-adhered carrier.

[0002]

2. Description of the Related Art In a wastewater treatment method using a fluidized bed using a fluidized carrier, since a large amount of organisms are retained and a high agitation force can be obtained, sufficient wastewater treatment is performed with a good treatment efficiency and a compact apparatus. It is possible. For this reason, many studies have been made so far, but there are practical examples in small-scale facilities in industrial wastewater treatment, but few practical examples in relatively large-scale such as public sewage treatment.

FIG. 6 is a system diagram showing an example of a conventional wastewater treatment facility using a fluidized bed. The main purpose of this wastewater treatment equipment is to remove nitrogen. After the inflow sewage (raw water) is first sent from the raw water tank 1 to the sedimentation basin 2 and subjected to sedimentation treatment, the wastewater is treated in the first fluidized bed. It is sent to a certain anaerobic fluidized bed 3, where the denitrification treatment is performed by the anaerobic fluidized bed. The treated water of the anaerobic fluidized bed 3 subsequently flows into the aerobic fluidized bed 4 which is the second fluidized bed, and the nitrification treatment is performed by the fluidized bed which is in the aerobic state due to the aeration from the aeration device 5. Done. A part of the treated water of the aerobic fluidized bed 4 circulates and flows from the circulation path 6 into the inflow part of the anaerobic fluidized bed 3 as a nitrification liquid, and the remaining part is sent to the filtration tank 7 for finishing. Thereafter, the water is discharged to a river or the like via the treatment water tank 8.

[0004]

As described above, nitrogen removal requires anaerobic denitrification treatment and aerobic nitrification treatment. Therefore, conventional wastewater treatment equipment for nitrogen removal is required. In this method, the anaerobic fluidized bed 3 and the aerobic fluidized bed 4 are separately provided, and the nitrification liquid is treated by circulating the nitrified liquid from the aerobic fluidized bed 4 to the anaerobic fluidized bed 3. Therefore, it is necessary to install two fluidized beds in series, and there is a problem that the difference in water level becomes large because the total number of treatment tanks increases and the pressure loss is relatively large. In particular, in a small-scale facility, since each processing tank becomes very small, there has been a problem that it is difficult to construct a concrete structure. Furthermore, in the case of a processing tank of a type in which the water area at the top of the processing tank is increased to prevent the outflow of the fluid carrier, the installation space is further increased by increasing the total number of processing tanks.

[0005] Treated water (NO
_{When a} denitrification treatment is performed by adding a carbon source such as methanol to a nitrification solution containing an oxidized nitrogen such as _2- N or NO ₃ -N,
An anaerobic fluidized bed for denitrification treatment and a contact aeration tank for oxidizing excess carbon source are provided, and there is a problem in installation space and the like.

Accordingly, it is an object of the present invention to provide a wastewater treatment apparatus capable of performing an efficient nitrogen removal treatment with a single fluidized bed and reducing the size of the apparatus.

[0007]

In order to achieve the above object, a wastewater treatment apparatus according to the present invention is provided with a diffuser at an intermediate portion in a vertical direction of a treatment tank, and an aerobic fluidized bed is provided above the diffuser. The lower part is an anaerobic fluidized bed, the inflow part of the to-be-treated water is provided in the lower part of the treatment tank, and the outflow part of the treated water is provided in the upper part.

In this wastewater treatment apparatus, BOD, SS and denitrification are performed in an anaerobic fluidized bed at the lower part of the treatment tank, and nitrification is mainly performed in an aerobic fluidized bed at the upper part. Nitrogen removal can be performed by circulating the nitrification liquid treated in the bed through the circulation path to the lower part of the anaerobic fluidized bed. In the case where denitrification treatment is performed on the treated water (nitrified liquid) that has been previously nitrified in the previous stage, a carbon source such as methanol is added to the nitrified liquid (water to be treated), and the anaerobic flow at the bottom of the treatment tank is added. By performing the denitrification treatment on the bed and performing the oxygen treatment of the excess carbon source in the upper aerobic fluidized bed, the denitrification treatment and the removal of the excess carbon source can be performed.

[0009]

FIG. 1 is a sectional view showing an embodiment of a wastewater treatment apparatus according to the present invention. In this wastewater treatment apparatus, a screen 11 for separating carriers is provided in an intermediate portion of a treatment tank 10 to partition the inside of the tank into upper and lower parts, and a diffuser 12 is provided below the screen 11. An aerobic fluidized bed 13 above the means 12 and an anaerobic fluidized bed 14 below the means 12. At the bottom of the processing tank 10,
An inflow portion 15 of the water to be treated is provided, and an outflow portion 1 of the water to be treated is provided at the uppermost portion through a screen 16 for separating carriers.
7 are provided. Further, in order to perform wastewater treatment mainly for removing nitrogen, a circulation path 18 for circulating a part of the treated water flowing out of the outflow portion 17 to a lower portion of the anaerobic fluidized bed 15 is provided.

The screens 11 and 16 are provided with fluid carriers 14 a and 13 in the anaerobic fluidized bed 14 and the aerobic fluidized bed 13, respectively.
This is provided for separating a from the treated water, and wedge wire screens are used for the screens 11 and 16. 2 and 3 show an example of a cylindrical screen 16 provided in the outflow portion 17. This screen 16 (wedge wire screen) includes a plurality of ring-shaped multiple wedge-shaped wires 16a. The support rods 16b are held at predetermined intervals, and by appropriately setting the arrangement intervals of the wedge-shaped wires 16a, it is possible to efficiently discharge treated water and sludge while suppressing clogging of the screen 16, It has a function of reliably preventing the outflow of the fluid carrier 13a. In addition, the screen 11 which partitions the processing tank 10 up and down has the same structure and is formed in a plane.

The fluid carriers 13a and 14a used in the aerobic fluidized bed 13 and the anaerobic fluidized bed 14 include plastics such as polypropylene (specific gravity of about 0.9) and polyethylene (specific gravity of about 0.92). In addition, a plastic carrier to which an inorganic substance such as silica or calcium for adjusting the specific gravity or a metal powder is added is used. This plastic carrier is
The specific gravity can be arbitrarily adjusted by adjusting the amount of silica or the like to be added, and a fluid carrier having an appropriate specific gravity can be obtained. The shape of the plastic carrier is arbitrary as long as it can be molded, such as a sphere or a pipe.
The surface has fine irregularities to which the biofilm easily attaches,
A rough one is preferred. Further, those having pores of about 50 to 300 μm suitable for the inhabitation of microorganisms are particularly preferable.

The specific gravity and size when used as the fluidized carriers 13a and 14a are set in an optimum range according to the shape, configuration and processing conditions of the fluidized bed. It does not function as a carrier attached to a biofilm because it floats.On the other hand, if the specific gravity is 3 or more, the flow velocity must be increased in order to fluidize the carrier. There is a disadvantage that it becomes difficult. That is, the residence time in the fluidized bed is set in consideration of the treatment time required for the biological reaction, and thereby the treatment speed (the rising speed of the treated water) is determined, so that a sufficient fluidized state can be obtained in this speed range. The specific gravity of the carrier can be set. In addition, the size of the carrier can be arbitrarily selected according to the specific gravity, the surface area, and the like. be able to. Further, such a plastic carrier also has an advantage that loss due to abrasion is small as compared with the above-described anthracite, granular activated carbon, and the like.

[0013] Therefore, it is possible to use a carrier having a specific gravity and a size corresponding to the amount of the inflowing raw water, so that the amount of living organisms and the stirring power can be set to an optimum state, and the treatment efficiency is greatly improved. Can be done. Furthermore, by using a relatively large carrier and using a wedge wire screen for separation from the treated water, it is necessary to increase the water area at the top of the tank and to provide a means for separating gas due to aeration as in the past. Is eliminated, and the apparatus can be simplified and downsized. If the size of the carrier is less than 2 mm, the wedge wire screen has to be finer, which increases the production cost of the wedge wire screen itself and increases the possibility of clogging. Conversely, if the size of the support exceeds 20 mm, the specific surface area (effective area) of the support will decrease, which will adversely affect the processing efficiency. By using a carrier of an appropriate size in this way and physically separating the carrier using a wedge wire screen, the carrier does not flow out due to flow rate fluctuations and the like, and stable processing can be continued. .

Further, the amount of biofilm attached to the carrier can be controlled by washing the carrier. This carrier can be washed in various ways,
For example, in the aerobic fluidized bed 13, it can also be performed by increasing the amount of air diffused from the air diffuser 12 more than usual and stirring the tank vigorously. At this time, the fluid carrier 13a
Is floated above the screen 16 with the expansion of the treated water. However, by separating the treated water and the fluidized carrier 13a by the screen 16 made of a wedge wire screen, the fluidized carrier 13a is separated from the treated water ( Washing water)
From the processing tank 10 can be prevented. Further, also in the anaerobic fluidized bed 14, the fluid carrier 14a can be washed by providing a diffuser means and a washing water introducing means below. Further, after the treated water in the treatment tank 10 is appropriately extracted using the inflow portion 15 or through a separately provided drainage path,
Empty washing or water washing may be performed. By washing the carrier in this way and controlling the amount of biofilm adhering to the carrier, the inside of the treatment tank 10 can be controlled to the most effective fluidization rate (expansion rate).

In the wastewater treatment apparatus formed as described above, the water to be treated is mixed with a part of the treated water (nitrified liquid) circulated from the circulation path 18 and flows into the treatment tank 1 from the inflow section 15.
0, and flows upward through the anaerobic fluidized bed 14 and the aerobic fluidized bed 13 through the support layer 10a. The water to be treated is mainly denitrified when passing through the anaerobic fluidized bed 14 operated in an anaerobic state, and then passes through the screen 11 to ascend to the aerobic fluidized bed 13 and diffuse. Aerobic fluidized bed 1 operating in aerobic condition by aeration from means 12
When passing through No. 3, nitrification treatment is mainly performed. Outflow part 17
Of treated water that has flowed out to
About 00% is returned to the inflow portion 15 of the processing tank 10 by the circulation path 18 and circulated.

Therefore, by disposing the anaerobic fluidized bed 14 and the aerobic fluidized bed 13 in the treatment tank 10, an efficient nitrogen removal treatment utilizing the advantages of the fluidized bed system can be performed in a single treatment. Since the processing can be performed in the tank 10, the workability can be improved and the apparatus can be made compact by reducing the total number of processing tanks.

FIG. 4 is a sectional view showing another embodiment of the wastewater treatment apparatus of the present invention. This wastewater treatment device is a treatment tank 2
A support layer 22 for supporting the fluid carrier and an air diffuser 23 are provided at an intermediate portion of the support layer 1 and the support layer 22 and the air diffuser 23.
Above the aerobic fluidized bed 24, below the anaerobic fluidized bed 25
It is what it was. Further, at the bottom of the treatment tank 21, an inflow portion 26 of the water to be treated and a support layer 21a are provided, and at the top, an outflow portion 27 of the treatment water and a circulation path 2 for circulating the nitrification liquid.
8 are provided.

In this embodiment, as the fluid carrier used in the aerobic fluidized bed 24 and the anaerobic fluidized bed 25, conventionally used anthracite, silica sand, granular activated carbon and the like are used. In the upper part, a large-diameter portion 21b for increasing the water area to prevent the outflow of the fluid carrier is provided, and a tubular member 29 for degassing is also provided.

In the wastewater treatment apparatus having this structure, the anaerobic fluidized bed 25 at the lower part of the treatment tank is also provided in the same manner as the apparatus of the above embodiment.
, And the nitrification treatment can be performed in the aerobic fluidized bed 24 above the aeration means 23. Therefore, the nitrogen removal treatment can be performed in the single treatment tank 21.

The treatment tanks 10 and 21 described above are provided downstream of the nitrification-promoting aeration tank, and the treated water (NO ₂ -N,
When performing a denitrification treatment of a nitrification solution containing an oxidized nitrogen such as NO ₃ -N, etc., the treatment tank 1 is used as shown by a broken line in FIGS.
By providing a carbon source addition path 19 for adding a carbon source such as methanol to the inflow sections 15 and 26 of 0 and 21 and adding the carbon source to the inflow water, the anaerobic fluidized bed 14 and
The denitrification treatment is performed at 25, and the upper aerobic fluidized beds 13, 24
In this way, the carbon source added in excess can be oxidized and removed. At this time, the circulation paths 18 and 28 can be omitted or can be provided as they are.

FIG. 5 shows an example of a wastewater treatment facility using the wastewater treatment apparatus of the present invention. The treatment tank 10 having the structure shown in FIG. 1 is used for nitrogen removal, and is used for sewage treatment. , BOD, and SS, nitrogen processing is also performed.

After the inflow sewage (raw water) flows into the raw water tank 32 through the screen 31, the pump 33 and the path 34
To the pressure flotation device 35 The raw water sent to the pressurized flotation device 35 is mixed with the pressurized air-dissolved water supplied from the passage 36 at the inlet to the pressurized flotation device 35, and the suspended component in the raw water is dissolved in the pressurized air-dissolved water. It adheres to the microbubbles generated from water to reduce the apparent specific gravity, and is separated as floating sludge (floss) at the upper part of the tank of the pressure flotation / separation device 35. The floating sludge is scraped by the scraper 37 and sent to the sludge storage tank 39 from the path 38, and the sludge settled at the bottom of the pressurized flotation device 35 is sent to the sludge storage tank 39 from the path 40. The sludge concentration at this time is 3-5%
Which is higher in concentration than gravity concentration in a conventional sludge concentration tank.

A portion of the water treated by the pressurized flotation device 35 is withdrawn from the outlet 41 through a passage 41, pressurized by a pump 42, and mixed with compressed air supplied from a compressor 43 in a mixing tank 44. Thereafter, the mixture is supplied to the raw water from the passage 36 as pressurized air-dissolved water. Pressure flotation separator 35
The floating treatment water which flows into the processing tank 10 from the path 45 after being processed in the processing tank 10 flows into the bottom of the processing tank 10 in a state of being mixed with the nitrification liquid circulating from the circulation path 18 at the inflow portion 15 of the processing tank 10, It rises in the tank at a predetermined rising speed.

In the processing tank 10, as described above, the denitrification treatment is performed in the lower anaerobic fluidized bed 14, and the upper aerobic fluidized bed is moved from the diffuser 12 into which the air from the compressor 46 is introduced. At 13 a nitrification treatment is performed. Processing tank 10
Treated water flows out of the outlet 1 through the screen 16 at the top of the tank.
, And a part thereof is circulated by the pump 47 to the circulation path 1.
Circulating through 8 to the inlet 15. The remaining treated water is sent from the path 48 to the upward-flow-type filtration tank 49, where the finishing treatment is mainly performed by removing SS components, and is discharged to a river or the like via the treated water tank 50. Further, the washing wastewater from the filtration tank 49 and the like is returned to the raw water tank 32 through the path 51. As described above, the washing wastewater of the filtration tank 49 and the washing wastewater of the fluidized beds 13 and 14 are returned to the raw water tank 32, mixed with the raw water, and floated and separated again by the pressurized flotation device 35, whereby the sludge generation location is reduced. Unification and high concentration can be achieved, and the running cost can be significantly reduced in a relatively small-scale sewage treatment facility where the amount of generated sludge greatly affects the running cost.

Furthermore, since the water treated by the pressure flotation device 35 has a higher removal rate of suspended components than ordinary sedimentation treatment, the inflow load into the subsequent treatment tank 10 can be reduced. The capacity of the processing tank 10 can be reduced. In addition, in the surfacing process, components that easily float, such as hair, oil, and scum, can be almost completely removed.
The occurrence of clogging and scum in each of the fluidized beds 13 and 14 is reduced.

Therefore, by combining the processing tank 10 having an anaerobic and aerobic fluidized bed using the above-mentioned plastic carrier with the pressurized flotation separator 35, the processing efficiency of the wastewater treatment equipment can be greatly improved. The size of the equipment can be reduced. In addition, the above wastewater treatment facilities
The processing tank 21 having the structure shown in FIG. 4 can be used, and effects such as a reduction in the total number of processing tanks can be obtained.

[0027]

As described above, in the wastewater treatment apparatus of the present invention, the aerobic fluidized bed and the anaerobic fluidized bed are disposed in a single treatment tank, so that efficient nitrogen removal processing and deaeration can be achieved. Nitrogen treatment and surplus carbon source removal treatment can be performed, and the apparatus can be simplified and downsized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a wastewater treatment apparatus according to the present invention.

FIG. 2 is a sectional front view of a tubular wedge wire screen.

FIG. 3 is a sectional side view of the wedge wire screen.

FIG. 4 is a sectional view showing another embodiment of the wastewater treatment apparatus of the present invention.

FIG. 5 is a system diagram showing an example of a wastewater treatment facility using the wastewater treatment device of the present invention.

FIG. 6 is a system diagram showing an example of a conventional wastewater treatment facility using a fluidized bed.

[Explanation of symbols]

10 treatment tank, 11 screen, 12 diffuser, 1
3 ... aerobic fluidized bed, 13a ... fluidized carrier, 14 ... anaerobic fluidized bed, 14a ... fluidized carrier, 15 ... inflow, 16 ... screen, 16a ... wedge-shaped wire, 16b ... support rod, 17 ... outflow, 18 Circulation path, 19: carbon source addition path, 21: treatment tank, 22: support layer, 23: diffuser, 24: aerobic fluidized bed, 25: anaerobic fluidized bed, 26 ...
Inflow section, 27 outflow section, 28 circulation path, 32 raw water tank, 35 pressurized flotation separator, 39 sludge storage tank, 44
... mixing tank, 49 ... filtration tank, 50 ... treated water tank

Claims (3)

[Claims] 1. A diffuser is provided at an intermediate portion in the vertical direction of a treatment tank, an aerobic fluidized bed above the diffuser and an anaerobic fluidized bed below the diffuser, and water to be treated flows into a lower part of the treatment tank. A wastewater treatment apparatus, wherein a treated water outflow part is provided at an upper part. 2. An anaerobic fluidized bed at the bottom of the treatment tank
D, SS and denitrification treatments, and mainly nitrification treatment in the upper aerobic fluidized bed, and circulating the nitrified liquid treated in the aerobic fluidized bed below the anaerobic fluidized bed The wastewater treatment apparatus according to claim 1, further comprising: 3. A carbon source such as methanol is added to the water to be treated, a denitrification treatment is performed in an anaerobic fluidized bed at the lower part of the treatment tank, and an oxygen treatment of an excess carbon source is performed in an aerobic fluidized bed at the upper part. The wastewater treatment apparatus according to claim 1, wherein the wastewater treatment is performed.