JPH10211499A - Apparatus for treating wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform solid-liquid separation securely and efficiently and make compact an entire installation by a method wherein an anaerobic tank and an aerobic tank are formed by a fluidized bed respectively and a pressure flotation apparatus for performing solid-liquid separation is provided between the anaerobic tank and the aerobic tank. SOLUTION: Treated water treated with an anaerobic fluidized bed 11 is separated by a wedged screen 18 from biomembrane-sticking carrier 17 and sent to a pressure flotation apparatus 13 from piping 19. The pressure flotation apparatus 13 mixes treated water fed from the piping 19 with pressurized air- dissolving water fed from piping 20 to stick suspended component on micro bubbles generated and float them. Floating sludge and sedimentary sludge are fed to a sludge storaging tank 23. The water treated by solid-liquid separation- with the pressure flotation apparatus 13 is fed to the bottom part of an aerobic fluidized bed 12 from piping 29 and rises together with air fed from a compressor 30 within the aerobic fluidized bed 12, and aerobic clarification treatment, mainly nitrification reaction, is conducted by microorganisms sticking to biomembrane-sticking carriers 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wastewater treatment apparatus, and more particularly, to a wastewater treatment apparatus for removing nitrogen by an anaerobic aerobic circulation method in addition to removing BOD and SS.

[0002]

2. Description of the Related Art A wastewater treatment method using a fluidized bed has a high treatment efficiency because a large amount of organisms are retained and a high stirring force can be obtained, and it is possible to perform sufficient wastewater treatment with a compact apparatus. . 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.

[0003] In recent years, studies have been conducted on a nitrogen removal system using a fluidized bed because a fluidized bed has high nitrification and denitrification capabilities. However, since the solid-liquid separation is not performed in principle in the fluidized bed itself, it is necessary to combine another solid-liquid separation device. Since the filter and the filtration device were used as they were, the performance of the fluidized bed could not be sufficiently exhibited.

FIG. 2 shows an example of a conventional wastewater treatment facility for removing nitrogen while removing BOD and SS using a fluidized bed. This wastewater treatment equipment first performs solid-liquid separation of inflow sewage (raw water) flowing into a raw water tank 1 in a sedimentation tank 2, and then uses an anaerobic fluidized bed 3 and an aerobic fluidized bed 4 by an anaerobic aerobic circulation method. It is formed so that nitrogen is removed, and finally filtration is performed in the filtration tank 5 and then discharged through the treated water tank 6. Further, the sediment in the first sedimentation basin 2 is extracted and treated in the sludge storage tank 7.

[0005]

As described above, conventionally, even when a fluidized bed is used, a general gravity-type sedimentation basin is used as a solid-liquid separation device. An area was required, and the entire equipment could not be sufficiently compact. That is, the fluidized bed can increase the flow rate to 600 to 800 m / day, but the flow rate of the gravity type sedimentation basin is generally 20 to 10 m.
It was 0 m / day, and a sedimentation basin having a large area for the throughput of the fluidized bed had to be installed.

In addition, since the suspended components from the anaerobic fluidized bed 3 flow into the aerobic fluidized bed 4 as they are, the BOD and SS loads of the aerobic fluidized bed 4 increase, and the processing efficiency, particularly,
The nitrification reaction efficiency sometimes decreased.

Further, in the filtration tank 5, since the BOD and SS loads in the aerobic fluidized bed 4 are high, the amount of suspended components flowing out from the aerobic fluidized bed 4 is increased, and the filtration is performed stably for a long time. It was difficult to continue driving.

Accordingly, the present invention provides a wastewater treatment apparatus capable of reliably and efficiently performing a solid-liquid separation treatment, fully utilizing the advantages of a fluidized bed, and reducing the size of the entire facility. It is an object.

[0009]

In order to achieve the above object, a wastewater treatment apparatus according to the present invention uses a anaerobic aerobic circulation method using an anaerobic tank and an aerobic tank to remove BOD and SS and remove nitrogen. Wherein the anaerobic tank and the aerobic tank are each formed of a fluidized bed, and a pressurized flotation apparatus for performing a solid-liquid separation process is provided between the anaerobic tank and the aerobic tank. It is characterized by. In the present invention,
It is characterized in that the pressure flotation device is a chemical-free pressure flotation device or a coagulation pressure flotation device for adding a flocculant for removing phosphorus.

[0010]

FIG. 1 shows an example of a wastewater treatment facility using a wastewater treatment apparatus according to the present invention. It has a facility configuration provided with a pressure flotation separator 13.

After the inflow sewage (raw water) flows into the raw water tank 15 through the screen 14, it is sent to the bottom of the anaerobic fluidized bed 11 by the pump 16 and adheres to the biofilm while rising inside the anaerobic fluidized bed 11. An anaerobic purification treatment, mainly a denitrification reaction, is performed by microorganisms attached to the carrier 17.

As the biofilm-adhering carrier 17, a conventionally used carrier such as anthracite or granular activated carbon can be used. However, inorganic materials such as silica and calcium for adjusting specific gravity, and polypropylene and polyethylene can be used.
It is preferable to use a plastic carrier to which metal powder is added. The specific gravity of such a plastic carrier can be arbitrarily adjusted by adjusting the amount of the silica or the like added thereto, and the specific gravity and size of the biofilm-adhered carrier 17 are adjusted according to the shape of the anaerobic fluidized bed 11. , The optimum range can be set according to the configuration and processing conditions.

Further, the size of the biofilm-adhering carrier 17 is relatively large depending on the specific gravity and the surface area, for example, 2 to 20 m.
By setting it to about m, the separation property from the treated water and the cleaning property can be improved. Therefore, anaerobic fluidized bed 1
Since it is possible to use the biofilm-adhering carrier 17 having a specific gravity and a size corresponding to the amount of the inflowing raw water 1, it is possible to set the holding amount of the living organisms and the stirring power in an optimum state, thereby greatly increasing the treatment efficiency. Can be improved. The shape of the biofilm-adhering carrier 17 is not limited as long as it can be molded, such as a sphere or a pipe. However, it is preferable that the surface thereof has fine irregularities to which the biofilm can easily adhere. Further, those having pores of about 50 to 300 μm suitable for the inhabitation of microorganisms are particularly preferable.

The treated water (fluidized bed treated water) treated in the anaerobic fluidized bed 11 is separated from the biofilm-adhered carrier 17 by a wedge wire screen 18 provided on the upper part of the bed and floats under pressure from a pipe 19. It is sent to the separation device 13. The wedge wire screen 18, for example, holds a large number of wedge-shaped wires formed in a ring shape at predetermined intervals by a plurality of support rods, closes both ends to form a drum shape, and treats one end with treated water. The pipe 19 for the outflow is connected, and by appropriately setting the interval between the wedge-shaped wires, it is possible to efficiently discharge the treated water and sludge while suppressing clogging, Outflow can be reliably prevented. Therefore, by using the wedge wire screen 18 for separation of the biofilm-adhered carrier 17, it is not necessary to increase the water area on the upper part or to provide a gas separating means accompanying aeration as in a conventional fluidized bed. The anaerobic fluidized bed 11 can be simplified and made compact.

The pressurized flotation device 13 mixes the fluidized bed treated water supplied from the pipe 19 with the pressurized air dissolved water supplied from the pipe 20, and converts the fine bubbles generated from the pressurized air dissolved water into fine bubbles. The floating sludge (floss) which floats by adhering the suspended components in the fluidized-bed treated water to reduce the apparent specific gravity is lifted. The sludge sent to the bottom 23 and settled at the bottom is sent from the passage 24 to the sludge storage tank 23. The sludge concentration at this time is 3 to 5%, which is higher than gravity concentration in a conventional sludge concentration tank.

A part of the water treated by the pressure flotation device 13 is withdrawn from a pipe 25 at an outlet side, pressurized by a pump 26, and mixed with compressed air supplied from a compressor 27 in a mixing tank 28. After that, it is supplied to the fluidized-bed treated water from the pipe 20 and mixed as pressurized air-dissolved water.

The treated water subjected to the solid-liquid separation treatment in the pressurized flotation apparatus 13 (pressurized flotation treated water) is sent from a pipe 29 to the bottom of the aerobic fluidized bed 12 and supplied from a compressor 30. The ascending air rises in the aerobic fluidized bed 12 together with the air, and the microorganisms adhering to the biofilm-adhering carrier 31 perform an aerobic purification treatment, mainly a nitrification reaction. This aerobic fluidized bed 1
In 2 also, by using the same plastic carrier as the biofilm-adhering carrier 17 of the anaerobic fluidized bed 11 as the biofilm-adhering carrier 31, the processing efficiency and the like can be improved.

The treated water treated in the aerobic fluidized bed 12 is separated from the biofilm-adhered carrier 31 by the same wedge wire screen 32 provided at the upper part of the bed, and the piping 33
It is extracted to. A part of the treated water drawn out to the pipe 33, about 100 to 300% of the inflowing raw water, is supplied by the nitrification liquid circulation pipe 34 and the pump 35 to the anaerobic fluidized bed 11.
Circulates as a nitrifying solution.

The remaining portion of the treated water corresponding to the amount of the inflowing raw water flows into the bottom of the filtration tank 37 from the pipe 36 and is mainly
Finishing treatment is performed by removing components, and the filtered water is discharged to a river or the like via a treated water tank 38. This filter tank 37 has a cleaning means for cleaning the filter medium.
In the lower part of the tank, a pull-out pipe 39, an empty washing pipe 40, and a flush pipe 4
The washing drainage is returned to the raw water tank 15 by a pipe 42. As described above, the washing wastewater from the filtration tank 37 is returned to the raw water tank 15, mixed with the raw water, and treated again, so that not only the sludge generation site can be unified into the pressure flotation device 13, but also, Since the concentration of the generated sludge can be increased, the running cost of a relatively small-scale sewage treatment facility in which the amount of generated sludge greatly affects the running cost can be significantly reduced.

As described above, by providing the non-chemical injection pressurized flotation device 13 between the anaerobic fluidized bed 11 and the aerobic fluidized bed 12, the suspension in the fluidized-bed treated water flowing out of the anaerobic fluidized bed 11 is provided. Since most of the turbid components can be separated and removed, the BOD and SS loads on the aerobic fluidized bed 12 can be reduced, and the nitrification reaction efficiency can be improved.
Further, also in the filtration tank 37, the BOD and SS loads in the aerobic fluidized bed 12 are reduced, and the amount of suspended components flowing out from the aerobic fluidized bed 12 is reduced, so that a stable filtration operation is continued for a long time. be able to.

Further, since the pressure flotation apparatus 13 can perform high-speed processing, the installation area of the apparatus can be reduced as compared with the ordinary gravity sedimentation processing, and the equipment can be downsized. In addition, the pressure flotation device 13 is
Since the removal rate of suspended components is higher than that of the ordinary gravity sedimentation treatment, the filtration tank 37 may not be installed depending on the required quality of treated water, and a sufficient solid-liquid separation treatment can be performed only by the pressure flotation device 13. It is possible to do. In addition, in the floating separation processing, components that easily float, such as hair, oil, and scum, can be almost completely removed, so that clogging in the filtration tank 37 and generation of scum are reduced.

Therefore, by combining the fluidized beds 11, 12 and the pressure flotation device 13, the treatment efficiency of the wastewater treatment equipment can be greatly improved, and the equipment can be downsized. Further, by adding the filtration tank 37, the quality of treated water can be greatly improved.
In addition, although illustration is omitted, the washing | cleaning equipment of a support | carrier is provided in both the fluidized beds 11 and 12, and it can also control an organism attachment amount.
In addition, the filter tank 37 may be set to a downward flow instead of an upward flow, and the filter medium configuration of the filter tank 37 may be a multilayer type, and the type of the filter medium may be anthracite, silica sand, or other plastics. A filter material or the like can be used, and is not particularly limited.

Further, in the same configuration, the pressure flotation device 13 may be a coagulation pressure flotation device provided with a path for adding a coagulant for removing phosphorus. As the coagulant to be added, a coagulant which reacts with phosphate ions in water to form a poorly water-soluble phosphate is used. For example, aluminum sulfate, polyaluminum chloride, ferric chloride, ferrous sulfate and the like are used. Can be used.
Phosphates and the like generated by the addition of this flocculant are
Like the S component, it can be floated and separated by the pressure flotation device 13 and can be discharged as floss by the scraper 21. As described above, by using the coagulation pressure flotation apparatus, it is possible to remove nitrogen and phosphorus in addition to removing BOD and SS.

[0024]

As described above, the wastewater treatment apparatus of the present invention combines a fluidized bed with excellent treatment efficiency and a pressurized flotation apparatus with a high removal rate of suspended components, thereby increasing the treatment capacity. The size of the equipment can be reduced without any loss.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an example of a wastewater treatment facility using a wastewater treatment device of the present invention.

FIG. 2 is a system diagram showing an example of a conventional wastewater treatment facility.

[Explanation of symbols]

11: Anaerobic fluidized bed, 12: Aerobic fluidized bed, 13: Pressurized flotation separator, 15: Raw water tank, 17: Biofilm-adhered carrier,
18 ... wedge wire screen, 21 ... scraper, 2
3: Sludge storage tank, 28: Mixing tank, 31: Biofilm attached carrier, 32: Wedge wire screen, 37: Filtration tank, 38: Treated water tank

Claims (3)

[Claims] 1. A wastewater treatment apparatus for removing BOD and SS and removing nitrogen by an anaerobic aerobic circulation method using an anaerobic tank and an aerobic tank, wherein the anaerobic tank and the aerobic tank are each formed of a fluidized bed. A wastewater treatment apparatus comprising a pressurized flotation device for performing solid-liquid separation between the anaerobic tank and the aerobic tank. 2. The wastewater treatment apparatus according to claim 1, wherein the pressure flotation device is a non-chemical injection pressure flotation device. 3. The wastewater treatment apparatus according to claim 1, wherein the pressure flotation device is a coagulation pressure flotation device for adding a coagulant for removing phosphorus.