JP3729585B2 - Wastewater treatment facility - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wastewater treatment facility , and more particularly, to a wastewater treatment facility equipped with a fluidized bed wastewater treatment device that treats sewage with a fluidized bed using a biofilm-attached carrier.
[0002]
[Prior art]
Since the wastewater treatment method using a fluidized bed has a large amount of living organisms and a high agitation force, the treatment efficiency is good and sufficient wastewater treatment can be performed with a compact apparatus. For this reason, a lot of research has been done so far, but there are practical examples in a small-scale facility for industrial wastewater treatment, but there are few practical examples on a relatively large scale such as public sewage treatment.
[0003]
FIG. 5 shows a fluidized bed using a conventional biofilm-adhered carrier, and shows an example of a fluidized bed that performs an aerobic treatment. The fluidized bed 1 includes a raw water inflow portion 3 provided at the bottom of the treatment tank 2, a treated water outflow portion 4 provided at the top of the tank, a support layer 5 and an air diffuser 6 provided at the bottom of the tank, It is formed by the separation cylinder 7 for preventing carrier outflow provided in the large-diameter portion 2a at the top of the tank.
[0004]
In the conventional fluidized bed 1, silica sand, granular activated carbon, anthracite, etc. are used as the biofilm adhesion carrier 8, and the 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. When such a carrier is used, the fluidization rate of the fluidized bed is usually about 300 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. The efficiency decreases, and if it is too high, the carrier may flow out with the treated water. In general, a reduction in processing efficiency should be avoided as much as possible, so that the outflow of the carrier from the processing tank can be prevented even when the fluidization rate increases, that is, about 100% or more. In order to allow the fluidization rate, a sufficient margin is provided in the upper part of the tank.
[0005]
[Problems to be solved by the invention]
In the fluidized bed as described above, the fluidization speed is determined by the specific gravity and size of the carrier used. Therefore, in the conventional carrier, the fluidization speed is about 300 to 800 m / day, and the effective height of the fluidized bed is about 3 m. Then, the reaction time is about 2 to 5 minutes. This reaction time does not necessarily coincide with the biological purification time, and for that purpose, it is necessary to devise such as a circulation treatment or a multi-stage treatment.
[0006]
In addition, when using a carrier having a relatively large specific gravity, it is necessary to reduce the size in consideration of the fluidization speed. However, if a carrier having a small size is used, the separated biofilm or suspended components in the influent water and the carrier are used. It becomes difficult to separate them. Usually, as a means for preventing the carrier from flowing out from the treatment tank, a carrier separation device is provided at the upper part of the tank. However, in the case of an aerobic treatment tank, it is necessary to separate gas such as diffused air. For this reason, in general, the water area at the top of the tank is increased and a large separation device is provided. For this reason, there existed a problem which the installation area of a processing tank will become large.
[0007]
Further, since the separation of the carrier and the gas and the treated water uses gravity and is greatly affected by the flow rate fluctuation, a device for maintaining a constant flow rate, for example, a flow rate adjusting tank is provided upstream of the processing tank. There was a need. However, even if the flow rate is constant, the fluidization rate (expansion rate) of the carrier changes depending on the amount of the biofilm attached and the water temperature. Therefore, the carrier separation means and the carrier washing means that is the biofilm control means Unless there was, there was a considerable margin at the top of the treatment 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.
[0008]
Therefore, the present invention provides a wastewater treatment facility equipped with a fluidized bed wastewater treatment device that can perform efficient wastewater treatment by using a carrier that is easy to separate from treated water and has little loss due to wear. It is an object.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the wastewater treatment apparatus of the present invention uses a plastic bioadhesive carrier whose specific gravity can be arbitrarily adjusted as a carrier, and includes a washing means for washing the biofilm adhering to the carrier, A wastewater treatment facility that treats sewage by using a treatment tank having a wedge wire screen for separating a carrier at the top of the tank as an anaerobic fluidized bed and an aerobic fluidized bed. and the floatation separation device for processing the floatation separation, and the anaerobic fluidized bed to perform the floatation on the treated water in the separation device by anaerobic treatment denitrification, treated water of the anaerobic fluidized bed said aerobic fluidized bed to perform nitrification and aerobic processes, and a filtration tank for filtering process this aerobic fluidized bed of treated water disposed in this order, further, the aerobic fluidized bed of treated water Part of the nitrification solution E Bei circulation piping which circulates join the incoming water into the anaerobic fluidized bed extraction with, BOD, is characterized by performing the processing of SS and nitrogen.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic cross-sectional view showing an example of a wastewater treatment apparatus used in the wastewater treatment facility of the present invention. At the bottom of a treatment tank 11, raw water inflow portion 12 and biofilm adhesion carrier 13 similar to those described above are provided. A support layer 14 and an air diffuser 15 are provided, and a treated water outflow portion 17 having a wedge wire screen 16 for carrier separation is provided at the upper part of the tank.
[0011]
2 and 3 show an example of the wedge wire screen 16. The wedge wire screen 16 used in the present embodiment is formed in a drum shape by holding a large number of wedge-shaped wires 16a formed in a ring shape at a predetermined interval by a plurality of support rods 16b and closing both ends. The piping which forms the said treated water outflow part 17 is connected to the end. Such a wedge wire screen 16 can discharge the treated water and sludge efficiently while suppressing clogging by appropriately setting the interval between the wedge-shaped wires 16a, and can prevent the carrier 13 from flowing out.
[0012]
The carrier 13 is a plastic carrier obtained by adding an inorganic substance such as silica or calcium for adjusting the specific gravity or metal powder to plastic (for example, polypropylene (specific gravity about 0.9) or polyethylene (specific gravity about 0.92). The specific gravity can be arbitrarily adjusted by adjusting the addition amount of silica or the like. The shape of the carrier 13 is arbitrary as long as it can be molded, such as a spherical shape or a pipe shape. However, the surface of the carrier 13 is preferably a rough one having fine irregularities to which a biofilm is easily attached. Further, those having pores of about 50 to 300 μm suitable for microbial inhabiting are particularly preferable.
[0013]
The specific gravity and size of the carrier 13 are set in an optimum range according to the shape, configuration and treatment conditions of the fluidized bed. However, if the specific gravity is 1 or less, the carrier 13 floats on the treated water. On the other hand, if the specific gravity is 3 or more, the flow rate has to be increased to fluidize the carrier 13, so that it is difficult to take sufficient residence time in the fluidized bed. is there. That is, the residence time in the fluidized bed is set in consideration of the treatment time required for biological reaction, thereby obtaining the treatment speed (rising speed of the treated water), so that a sufficient fluid state can be obtained in this speed range. The specific gravity of the carrier 13 may be set. Moreover, since the size of the carrier can be arbitrarily selected according to the specific gravity, the surface area, etc., the size is set to about 2 to 20 mm, which is larger than the conventional size in consideration of separability from the treated water and cleanability. be able to. Further, such a plastic carrier also has an advantage that there is less loss due to wear compared to the aforementioned anthracite, granular activated carbon, and the like.
[0014]
Therefore, since it is possible to use the carrier 13 having a specific gravity and a size corresponding to the inflow raw water amount, it is possible to set the biological retention amount and stirring force to an optimum state, and to greatly improve the processing efficiency. Can do. Furthermore, by using a relatively large carrier 13 and providing a wedge wire screen 16 in the treated water outflow portion 17 to separate the carrier, the water area at the upper part of the tank is increased as in the conventional case, or due to aeration. There is no need to provide gas separation means, and the apparatus can be simplified and made compact. If the size of the carrier is less than 2 mm, the wedge wire screen 16 must be made finer, the manufacturing cost of the wedge wire screen itself increases, and the possibility of clogging increases. On the other hand, if the carrier has a size exceeding 20 mm, the specific surface area (effective area) of the carrier is reduced, which adversely affects the processing efficiency. In this way, by using the carrier 13 of an appropriate size and physically separating the carrier 13 using the wedge wire screen 16, the carrier 13 does not flow out due to flow rate fluctuations and the like, and stable processing is continued. can do.
[0015]
Furthermore, the amount of biofilm adhering to the carrier 13 can be controlled by washing the carrier 13. This cleaning of the carrier 13 can be performed by various methods, for example, by increasing the amount of air diffused from the air diffuser 15 more than usual and vigorously stirring the inside of the tank. At this time, the carrier 13 floats to the upper part of the wedge wire screen 16 with the expansion of the treated water, but is separated from the treated water (washed waste water) by the wedge wire screen 16, so There is no spillage. Moreover, the washing waste water that has flowed out to the treated water outflow portion 17 may be sent to the subsequent treatment facility as it is, or may be returned to the raw water side.
[0016]
In consideration of cleaning efficiency, after the treated water in the treatment tank 11 is appropriately drawn out using the raw water inflow portion 12 or through a separately provided drainage path, the air diffuser 15 or separately provided for air washing It is also possible to perform air washing by introducing air from the air introduction path, and then wash water by introducing washing water from the raw water inflow portion 12 or from a separately provided washing water introduction path. Furthermore, air washing and water washing may be used in combination.
[0017]
By cleaning the carrier 13 and controlling the amount of biofilm adhering to the carrier 13 as described above, the inside of the treatment tank 11 can be managed to the most effective fluidization rate (expansion rate).
[0018]
FIG. 4 shows an example of the waste water treatment facility of the present invention using the above waste water treatment apparatus, and the same treatment tank is used for the anaerobic fluidized bed 31 and the aerobic fluidized bed 32 to treat sewage. In addition to BOD and SS processing, nitrogen processing is also performed.
[0019]
The inflowing sewage (raw water) flows into the raw water tank 34 through the screen 33, and then is sent to the pressurized levitation separator 37 through the pipe 36 by the pump 35. The raw water sent to the pressurized flotation separation device 37 is mixed with the pressurized air dissolved water supplied from the pipe 38 at the inflow portion to the pressurized flotation separation device 37, and the suspended components in the raw water are dissolved in the pressurized air. The apparent specific gravity is reduced by adhering to fine bubbles generated from water, and separated as floating sludge (floss) at the upper part of the tank of the pressurized flotation separator 37. The levitation sludge is scraped by the scraper 39 and sent from the path 40 to the sludge storage tank 41, and the sludge that has settled at the bottom of the pressurized levitation separator 37 is sent from the path 42 to the sludge storage tank 41. The sludge density | concentration at this time is 3 to 5%, and is high concentration compared with the gravity concentration in the conventional sludge concentration tank.
[0020]
A part of the water treated by the pressurized levitation separator 37 is extracted into the pipe 43 on the outlet side, pressurized by the pump 44, mixed with the compressed air supplied from the compressor 45 in the mixing tank 46, and then added. The compressed air dissolved water is supplied and mixed from the pipe 38 to the raw water. The raw water that has been processed by the pressurized flotation separator 37 and flows into the anaerobic fluidized bed 31 from the pipe 47 is mixed with the nitrating liquid that circulates and flows in from the circulation pipe 48 and flows into the bottom of the anaerobic fluidized bed 31, Ascend in the tank at a rising speed. In this anaerobic fluidized bed 31, a denitrification reaction is mainly performed by anaerobic treatment. The treated water in the anaerobic fluidized bed 31 is withdrawn via the wedge wire screen 16 in the upper part of the tank and flows into the bottom of the aerobic fluidized bed 32 from the pipe 49. The water that has flowed into the aerobic fluidized bed 32 rises in the tank together with the air supplied from the air diffuser 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 an air diffuser, but an appropriate air diffuser can be provided for adjusting the amount of oxygen in the bed and for cleaning the carrier.
[0021]
The treated water in the aerobic fluidized bed 32 is sent from the pipe 51 to the filtration tank 52 and a part thereof (100 to 300% with respect to the amount of raw water) is extracted as the nitrification liquid into the circulation pipe 48 and anaerobic. Circulates and merges with the inflowing water to the fluid bed 31. The filtration tank 52 shown here is an upward flow type filtration device, and is mainly subjected to a finishing process by removing SS components, and the filtered water is discharged into a river or the like through the treated water tank 53. .
[0022]
The filtration tank 52 is provided with a drawing pipe 54, an air washing pipe 55, and a water washing pipe 56 at the lower part of the tank as washing means for washing the filter medium. 34 is returned. In this way, 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 and mixed with the raw water, and then subjected to the floatation separation treatment by the pressurized flotation separation device 37 again, thereby In a relatively small-scale sewage treatment facility where unification and high concentration can be achieved and the amount of sludge generated greatly affects the running cost, the running cost can be greatly reduced.
[0023]
Furthermore, since the water treated by the pressurized flotation separator 37 has a higher removal rate of suspended components than the normal precipitation treatment, the inflow load to the anaerobic fluidized bed 31 in the subsequent stage can be reduced. It is possible to reduce the capacity of the fluid bed 31. Further, in the floatation process, components that easily float, such as hair, oil, and scum, can be removed almost completely, so that the occurrence of blockage and scum in the anaerobic fluidized bed 31 is reduced. In addition, since stable and good treatment is possible in the anaerobic fluidized bed 31, the treatability in the aerobic fluidized bed 32 into which the water treated in the anaerobic fluidized bed 31 flows is also improved.
[0024]
Therefore, by combining the anaerobic fluidized bed 31 and the aerobic fluidized bed 32 and the pressurized flotation separation device 37 made of the fluidized bed using the plastic carrier described above, the treatment efficiency of the wastewater treatment facility is greatly improved. And the equipment can be downsized.
[0025]
【The invention's effect】
As described above, the wastewater treatment apparatus of the present invention can improve the treatment efficiency in a fluidized bed by using a plastic carrier whose specific gravity can be arbitrarily adjusted. In particular, by installing a wedge wire screen in the treated water outflow part, the carrier can be reliably separated, and the carrier can be easily washed.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a wastewater treatment apparatus used in a wastewater treatment facility of the present invention.
FIG. 2 is a cross-sectional front view of a wedge wire screen.
FIG. 3 is a cross-sectional side view of a wedge wire screen.
4 is a system diagram showing an example of the waste water treatment facility of the present invention using the waste water treatment apparatus of FIG . 1. FIG.
FIG. 5 is a schematic sectional view showing an example of a conventional fluidized bed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Treatment tank, 12 ... Raw water inflow part, 13 ... (Biofilm adhesion) support | carrier, 14 ... Support layer, 15 ... Air diffusion means, 16 ... Wedge wire screen, 17 ... Treatment 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 piping, 50 ... Aeration means, 52 ... Filtration tank, 53 ... Treatment Aquarium

Claims (1)

A treatment tank in which a plastic bioadhesive carrier whose specific gravity can be arbitrarily adjusted is used as a carrier, provided with washing means for washing the biofilm attached to the carrier, and a wedge wire screen for separating the carrier is installed in the upper part of the vessel Is used as an anaerobic fluidized bed and an aerobic fluidized bed to treat sewage wastewater, the wastewater treatment facility comprising a pressurized flotation separation device for subjecting raw water to pressurized flotation separation, said anaerobic fluidized bed to perform the treated water anaerobic treatment to denitrification on floatation separation device, the aerobic fluidized bed the anaerobic fluidized bed of treated water performing aerobic process to nitrification And a filtration tank for filtering the treated water of the aerobic fluidized bed in this order, and further, a part of the treated water of the aerobic fluidized bed is withdrawn as a nitrification liquid to the anaerobic fluidized bed. Circulating and merged with inflow water Bei give a circulation piping that, BOD, wastewater treatment facilities and performing processing of SS and nitrogen.

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