JPH10192878A - Wastewater treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate separation of a carrier from treated water, suppress wear loss, and efficiently carry out wastewater treatment by using a carrier made of a plastic whose specific gravity is optionally adjustable as the carrier in wastewater treatment carried out by a fluidized bed employing biological film-bearing carrier. SOLUTION: This wastewater treatment apparatus comprises a raw water flowing inlet part 12 in the bottom part of a treatment tank 11, a supporting layer 14 of a biological film-bearing carrier 13, and an aeration means 15 and on the other hand, a treated water flowing outlet part 17 equipped with a wedge wire screen 16 for carrier separation is installed in the upper part of the tank. In this case, a carrier made of a plastic such as polypropylene (specific gravity about 0.9) mixed with silica is used as the carrier 13 and the specific gravity is controlled to be 1-3 by adjusting the addition amount of silica. The carrier 13 preferably has fine unevenness on the surface to make the biological film easy to adhere to and a carrier 13 having voids with about 50-300μm size suitable for microbe to inhabit and a size within 2-20mm range is employed.

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 fluidized bed wastewater treatment apparatus for treating wastewater by a fluidized bed using a biofilm-adhered carrier.

[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.

FIG. 5 shows a fluidized bed using a conventional biofilm-adhered carrier, and shows an example of a fluidized bed for performing aerobic treatment. The fluidized bed 1 has a raw water inflow section 3 provided at the bottom of the treatment tank 2 and a treated water outflow section 4 provided at the top of the tank.
And a support layer 5 and a diffuser 6 provided at the lower part of the tank, and a separation tube 7 for preventing carrier outflow provided in the large-diameter portion 2a at the upper part of the tank.

In the above-mentioned conventional fluidized bed 1, silica sand, granular activated carbon, anthracite, etc. are used as the biofilm-adhering carrier 8, and its specific gravity is about 1.4 to 2.7. The size (size) of the carrier 8 is generally about 0.4 to 1 mm in diameter. The fluidization rate of a fluidized bed using such a carrier is usually 30
It is about 0 to 800 m / day. However, even when the same carrier is used and the flow rate is constant, the fluidization rate (expansion rate)
Is greatly affected by the water temperature and the amount of organisms attached to the carrier. If the fluidization rate is too low, the treatment efficiency is reduced. If the fluidization ratio is too high, the carrier may flow out with the treated water. Generally, a reduction in processing efficiency should be avoided as much as possible, so that the carrier can be prevented from flowing out of the processing tank even when the fluidization rate increases, that is, about 100% or more. A sufficient margin is provided above the tank so that the fluidization rate can be tolerated.

[0005]

In the fluidized bed as described above, the fluidization speed is determined by the specific gravity and size of the carrier used.
0-800m / day, effective bed height 3m
The reaction time is about 2 to 5 minutes. This reaction time does not always coincide with the biological purification time, and therefore, it is necessary to devise such means as performing a circulating treatment or performing a multi-stage treatment.

When a carrier having a relatively large specific gravity is used, it is necessary to reduce the size in consideration of the fluidization speed. However, when a carrier having a small size is used, a separated biofilm or suspension in inflow water is required. Separation of the components from the carrier becomes difficult. Usually, as means for preventing the carrier from flowing out of the treatment tank, a carrier separation device is provided at the top of the tank, but in the case of an aerobic treatment tank, it is necessary to also separate gas such as diffused air. Therefore, in general, the water area at the top of the tank is increased, and a large-scale separation device is provided. For this reason, there was a problem that the installation area of the processing tank became large.

Further, the separation between the carrier and the gas or treated water utilizes gravity and is greatly affected by fluctuations in the flow rate. Therefore, a device for keeping the flow rate constant, for example, a flow control tank is used for the treatment tank. It had to be provided upstream. However, even when the flow rate is constant, the fluidization rate (expansion rate) of the carrier changes depending on the amount of the attached biofilm and the water temperature, so that the carrier is effectively separated and the carrier is a means for controlling the biofilm. As long as there was no, a considerable margin had to be provided at the top of the processing tank. On the other hand, a carrier having a relatively small specific gravity, such as anthracite or granular activated carbon, has a problem that it is easily worn.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fluidized-bed wastewater treatment apparatus capable of performing efficient wastewater treatment by using a carrier which can be easily separated from treated water and has little loss due to abrasion. I have.

[0009]

In order to achieve the above object, a wastewater treatment apparatus of the present invention is a wastewater treatment apparatus for treating wastewater by a fluidized bed using a biofilm-adhered carrier. Characterized by using a plastic carrier that can be arbitrarily adjusted, in particular, the specific gravity of the carrier is more than 1 and less than 3,
The size of the carrier is 2 to 20 mm. Further, the present invention, in the treated water outflow portion of the fluidized bed using the carrier, that a wedge wire screen is installed to prevent the carrier outflow, the fluidized bed,
It is characterized in that it comprises a washing means for washing the biofilm adhered to the carrier by pulling out treated water in the fluidized bed, washing with water, washing with water, using a combination of washing with water and washing with water.

[0010]

FIG. 1 is a schematic sectional view showing an example of a wastewater treatment apparatus according to the present invention. In the bottom of a treatment tank 11, a raw water inflow section 12 and a biofilm-adhering carrier 13 similar to the above are provided.
And a diffuser 15 are provided, and a treated water outlet 17 provided with a wedge wire screen 16 for carrier separation is provided above the tank.

FIG. 2 and FIG. 3 show an example of the wedge wire screen 16. The wedge wire screen 16 used in the present embodiment is formed by holding a large number of ring-shaped wedge-shaped wires 16a at predetermined intervals by a plurality of support rods 16b and closing both ends to form a drum. One end thereof is connected to a pipe forming the treated water outflow portion 17. By appropriately setting the interval between the wedge-shaped wires 16a, the wedge wire screen 16 can efficiently discharge treated water and sludge while suppressing clogging, and can prevent the carrier 13 from flowing out.

The carrier 13 is made of plastic, for example,
A plastic carrier made of polypropylene (specific gravity of about 0.9) or polyethylene (specific gravity of about 0.92) to which inorganic substances such as silica and calcium for adjusting the specific gravity and metal powder are added. The amount of silica and the like is adjusted. The specific gravity can be arbitrarily adjusted thereby. The shape of the carrier 13 is arbitrary as long as it can be formed, such as a sphere or a pipe. However, the surface thereof is preferably rough and has fine irregularities to which a biofilm can easily adhere. Further, those having pores of about 50 to 300 μm suitable for the inhabitation of microorganisms are particularly preferable.

The specific gravity and size of the carrier 13 are set in optimal ranges according to the shape, configuration and processing conditions of the fluidized bed. However, if the specific gravity is 1 or less, the carrier 13 floats on the treated water. Does not function as a biofilm-attached carrier, whereas if the specific gravity is 3 or more, the flow rate must be increased in order to fluidize the carrier 13, and it is difficult to take a sufficient residence time in the fluidized bed. There is an inconvenience. That is,
The residence time in the fluidized bed is set in consideration of the treatment time required for the biological reaction, and the treatment speed (treatment water rising speed)
And the specific gravity of the carrier 13 may be set so that a sufficient fluidized state can be obtained in this speed range. 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.

Therefore, it is possible to use the carrier 13 having a specific gravity and a size corresponding to the amount of the inflowing raw water, so that the holding amount of the organism and the stirring power can be set to an optimum state, and the treatment efficiency can be greatly improved. Can be improved. Furthermore, by using a relatively large carrier 13 and providing a wedge wire screen 16 at the treated water outflow portion 17 to separate the carrier, the water area at the top of the tank can be increased as in the related art, There is no need to provide a gas separating means, and the apparatus can be simplified and downsized. If the size of the carrier is less than 2 mm, the wedge wire screen 16 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. As described above, by using the carrier 13 having an appropriate size and physically separating the carrier 13 using the wedge wire screen 16, the carrier 13 is prevented from flowing out due to a flow rate fluctuation or the like, and a stable process is continued. can do.

Further, the amount of biofilm adhering to the carrier 13 can be controlled by washing the carrier 13. The carrier 13 can be washed by various methods, for example, by increasing the amount of air diffused from the air diffuser 15 more than usual and stirring the inside of the tank vigorously. At this time, the carrier 13 floats above the wedge wire screen 16 due to the expansion of the treatment water.
Therefore, the wastewater is separated from the treated water (washing wastewater), and does not flow out of the treatment tank 11. In addition, the treated water outflow section 17
The washing wastewater that has flowed out of the system may be sent to a subsequent treatment facility as it is, or may be returned to the raw water side.

In consideration of the washing efficiency, the treated water in the treatment tank 11 is appropriately drawn out using the raw water inflow section 12 or through a separately provided drainage path.
Alternatively, air may be introduced by introducing air from a separately provided cleaning air introduction path, and then washing may be performed by introducing washing water from the raw water inflow section 12 or from a separately provided washing water introduction path. . Further, the empty washing and the water washing may be used in combination.

By cleaning the carrier 13 and controlling the amount of biofilm attached to the carrier 13 as described above, the inside of the treatment tank 11 is controlled to the most effective fluidization rate (expansion rate). Can be.

FIG. 4 shows an example of a wastewater treatment facility using the wastewater treatment apparatus of the present invention. The same treatment tank as described above is used for an anaerobic fluidized bed 31 and an aerobic fluidized bed 32.
As sewage treatment, nitrogen treatment is also performed in addition to BOD and SS treatment.

The inflow sewage (raw water) flows into a raw water tank 34 through a screen 33, and then is pumped by a pump 35 into a pipe 3.
6 to the pressure flotation device 37. Raw water sent to the pressure flotation device 37 is
Is mixed with the pressurized air-dissolved water supplied from the pipe 38 at the inflow portion of the raw water, and the suspended component in the raw water adheres to microbubbles generated from the pressurized air-dissolved water to reduce the apparent specific gravity,
Separated as floating sludge (floss) at the upper part of the tank of the pressure flotation / separation device 37. The floating sludge is scraped by the scraper 39 and sent to the sludge storage tank 41 from the path 40. The sludge settled at the bottom of the pressurized flotation device 37 is sent to the sludge storage tank 41 from the path 42. The sludge concentration at this time is 3 to 5
%, Which is higher than that of gravity concentration in a conventional sludge concentration tank.

A portion of the water treated by the pressurized flotation device 37 is withdrawn at the outlet side through a pipe 43, pressurized by a pump 44, and mixed with compressed air supplied from a compressor 45 in a mixing tank 46. Thereafter, the mixture is supplied to the raw water from the pipe 38 as pressurized air dissolved water. Pressure flotation separator 37
The raw water that has been treated in the above step and flows into the anaerobic fluidized bed 31 from the pipe 47 is mixed with the nitrifying liquid circulated from the circulation pipe 48, flows into the bottom of the anaerobic fluidized bed 31, and flows through the tank at a predetermined rising speed. To rise. In the anaerobic fluidized bed 31, a denitrification reaction is mainly performed by anaerobic treatment. The treated water of the anaerobic fluidized bed 31 is withdrawn through the wedge wire screen 16 at the top of the tank, and flows from the pipe 49 into the bottom of the aerobic fluidized bed 32. The water flowing into the aerobic fluidized bed 32 rises in the tank together with the air supplied from the aeration means 50, and the nitrification reaction is mainly performed by the aerobic treatment. Normally, the anaerobic fluidized bed 31 does not need to be provided with a diffuser, but an appropriate diffuser can be provided for adjusting the amount of oxygen in the bed and for washing the carrier.

The treated water of the aerobic fluidized bed 32 is sent from a pipe 51 to a filtration tank 52, and a part (100 to 300% of the raw water amount) is withdrawn to the circulation pipe 48 as the nitrification liquid. Then, it circulates and joins the inflow water into the anaerobic fluidized bed 31. The filtration tank 52 shown here is an upward-flow type filtration device, in which finishing treatment is mainly performed by removing SS components, and the filtered water is discharged to a river or the like via a treatment water tank 53. .

The filtration tank 52 is provided with a drawing pipe 54, an empty washing pipe 55, and a washing pipe 56 at the lower part of the tank as washing means for washing the filter medium. It is returned to the raw water tank. As described above, the washing wastewater from the filtration tank 52 and the washing wastewater from the fluidized beds 31 and 32 are returned to the raw water tank 34, mixed with the raw water, and floated and separated by the pressurized flotation device 37 again. The 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 37 has a higher removal rate of suspended components than the ordinary sedimentation treatment, the inflow load into the anaerobic fluidized bed 31 at the subsequent stage can be reduced. Accordingly, the capacity of the anaerobic fluidized bed 31 can be reduced. In the floating treatment, components that easily float, such as hair, oil, and scum, can be almost completely removed, so that the occurrence of blockage and scum in the anaerobic fluidized bed 31 is reduced. In addition, since the anaerobic fluidized bed 31 enables stable and good treatment, the anaerobic fluidized bed 31
The processability in the aerobic fluidized bed 32 into which the water treated in Step 1 flows is also improved.

Therefore, by combining the anaerobic fluidized bed 31 and the aerobic fluidized bed 32 composed of a fluidized bed using the above-mentioned plastic carrier with the pressurized flotation device 37, the treatment efficiency of the wastewater treatment equipment is greatly increased. And the size of the equipment can be reduced.

[0025]

As described above, in the wastewater treatment apparatus of the present invention, the treatment efficiency in the fluidized bed can be improved by using a plastic carrier whose specific gravity can be arbitrarily adjusted. In particular, by installing a wedge wire screen at the treated water outlet, the carrier can be reliably separated, and the carrier can be easily washed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a wastewater treatment device of the present invention.

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

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

FIG. 4 is a system diagram showing an example of a wastewater treatment facility using the wastewater treatment device of the present invention.

FIG. 5 is a schematic sectional view showing an example of a conventional fluidized bed.

[Explanation of symbols]

11 ... treatment tank, 12 ... raw water inflow part, 13 ... (biofilm attached) carrier, 14 ... support layer, 15 ... diffuser means, 16 ... wedge wire screen, 17 ... treated water outflow part, 31 ...
Anaerobic fluidized bed, 32 ... Aerobic fluidized bed, 33 ... Screen, 34 ... Raw water tank, 37 ... Pressurized flotation separator, 41 ... Sludge storage tank, 48 ... Circulation pipe, 50 ... Aeration means, 52 ... Filtration tank , 53… Treatment tank

Claims (5)

[Claims] 1. A wastewater treatment apparatus for treating wastewater by a fluidized bed using a biofilm-adhered carrier, wherein a plastic carrier whose specific gravity can be arbitrarily adjusted is used as the carrier. apparatus. 2. The wastewater treatment apparatus according to claim 1, wherein the specific gravity of the carrier is more than 1 and less than 3. 3. The wastewater treatment apparatus according to claim 1, wherein the size of the carrier is 2 to 20 mm. 4. The wastewater treatment apparatus according to claim 1, wherein a wedge wire screen for preventing the carrier from flowing out is provided at a treated water outlet of the fluidized bed using the carrier. 5. The wastewater treatment apparatus according to claim 1, wherein the fluidized bed using the carrier is provided with a washing means for washing a biofilm adhered to the carrier.