JP2004322084A - Biological filtration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biological filtration system having excellent stability in flow orientation in a contact filtration chamber, avoiding wear of a contact filter and exfoliation of a biological membrane, and further capable of continuously and stably performing from an anaerobic microbial treatment to an aerobic microbial treatment. <P>SOLUTION: This filtration system is vertically separated into the upper contact filtration chamber and a lower aeration chamber with a permeable partition. The contact filtration chamber is equipped with a discharge port for water to be treated, and the aeration chamber is equipped with a water pouring port for pouring circulation water treated for generating rotational flow in the horizontal direction and a dissolved oxygen supply means. Under the aeration chamber, an anaerobic filter bed chamber is provided. A permeable partition separates the aeration chamber from the anaerobic filter bed chamber. The anaerobic filter bed chamber is equipped with a water pouring port for pouring raw water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a biological treatment device for various kinds of wastewater or sewage.

There is a biological filtration method as a method of treating sewage wastewater with microorganisms.
In this method, a contact filter medium that supports microorganisms is installed in a biological filtration tank, and when treated water passes through the gap between carriers, biodegradation of organic matter is performed by microorganisms attached to the carrier, and the microorganisms are further suspended in treated water. This is a method of capturing solids that are present.
This method is known as a method having a high solids removal capability and capable of performing a high degree of treatment as compared with a conventional method for removing solids by a sedimentation tank.

The above methods are roughly classified into three types of processing methods.
First, the microbial carrier to be filled is settled in the biological filtration tank using a sedimentable carrier whose specific gravity is larger than the specific gravity of water, such as porous ceramics, and air is blown from below the carrier-filled part. This is a method in which treated water is passed while diffusing, organic substances are decomposed by microorganisms attached to the surface of the carrier, and solids are physically captured.
The second method uses a fiber contact agent as a microorganism carrier, fixes a plurality of the fiber carriers in a biological filtration tank, and passes the treated water while diffusing air from below the carrier fixing part. In this method, organic substances are decomposed by microorganisms attached to the floating fiber carrier.
The third method is to fill the biological filtration tank with a floating carrier whose specific gravity is relatively close to the specific gravity of water, such as a synthetic resin foam, and to diffuse air from below, thereby removing the granular carrier. This is a method in which organic substances are decomposed by microorganisms attached to the surface of a carrier while floating or flowing.

  When a floating fiber carrier or a floating carrier is used, the ability to capture solids suspended in the treated water is small, and microorganisms attached to the carrier surface are separated by friction between carriers and water flow, and the floating solids are removed. In order to deal with such a problem, Japanese Patent Application Laid-Open No. Hei 5-309382 discloses that a biological filtration tank is divided into two parts, and a carrier is fluidized to remove organic matter. A method is described in which a part mainly intended for decomposition is separated from a part for capturing a solid by stopping a carrier, and Japanese Patent Application Laid-Open No. 2002-361275 discloses a method for separating floating solids in treated water from microorganisms. After decomposing in a treatment tank that stores the water, a method of decomposing by passing through a water-permeable filter medium is described, but the generation of a large amount of excess sludge is inevitable, and the time and effort of sludge treatment are reduced. Expense The burden has become a problem.

  In addition, the use of carbon fiber as the fiber carrier has the characteristic that sludge activity is maintained for a long time, so that excess sludge is less generated, sticking sludge is less likely to occur, and the SS trapping efficiency is increased (Suguro Otani, U.S. Patent Application Publication No. US 2003/0128399 A1 discloses a wastewater treatment apparatus using a contact material made of carbon fiber using TANSO 2000 [No. 194] PP.276 to 287). In the air diffuser, the energy consumption is large but the ability to supply dissolved oxygen to the contact filter medium is small, and the water flow is biased in the contact filtration chamber, and the carbon fibers are cut and worn due to the shear force caused by the fluctuation of the water flow. In addition, there is a problem that separation of the biofilm is apt to occur, and excess sludge accumulates in the apparatus.

  In addition, a method for efficiently supplying dissolved oxygen to treated water using a microbubble generator is disclosed in Japanese Patent No. 2646442, Japanese Patent Application Laid-Open No. 5-64795, Japanese Patent Application Laid-Open No. 7-265057, and Japanese Patent Application Laid-Open No. 2000-2000. No. 618002, JP-A-2000-4747, JP-A-2001-58142, and JP-A-2002-370095 are systems in which aeration and agitation are performed using a discharge jet at the time of producing fine bubbles, It is difficult to stabilize the flow direction of the contact filtration chamber even if it is used as it is in a biological filtration tank as it is, and because it has an adsorption and coagulation effect as a characteristic of fine bubbles, it can be suspended in excess sludge or treated water. There is a problem in that the solid matter that is present is adsorbed and floated and is positively discharged from the contact filtration chamber.

Also, a combination of anaerobic microorganism treatment and aerobic microorganism treatment is being studied with the aim of reducing excess sludge. For example, Japanese Patent Application Laid-Open No. 2003-136087 discloses an example in which an aerobic portion is formed at an upper portion and an anaerobic portion is formed at a lower portion for the purpose of decomposing components harmful to aerobic microorganisms and reducing aeration energy. .
However, since the treated water is circulated up and down between the aerobic part and the anaerobic part, it is not suitable for continuously treating relatively low-concentration wastewater having a BOD of 1,000 mg / L or less, for example.

JP-A-5-309382 JP-A-2002-361275 JP-A-11-99399 Japanese Patent No. 2646442 JP-A-5-64795 JP-A-7-265057 JP 2000-618002 A JP-A-2000-4747 JP 2001-58142 A JP 2002-370095 A JP 2003-136087 A

  The present invention has excellent flow direction stability in a contact filtration chamber, prevents wear of a contact filter medium and detachment of a biofilm, and furthermore, a biological substance that can be continuously and stably treated from an anaerobic microorganism treatment to an aerobic microorganism treatment. It is intended to provide a filtration device.

  The technical gist of the biological filtration device according to the present invention is that an upper contact filtration chamber and a lower aeration chamber are vertically separated by a partition having permeability, and the contact filtration chamber is provided with an outlet for treated water. The room is provided with a water inlet for injecting raw water or treated circulating water so as to generate a horizontal swirling flow, and a dissolved oxygen supply means.

Here, the contact filtration chamber refers to a chamber in which a contact filter medium having microorganisms adhered to a carrier is disposed, and the aeration chamber refers to a chamber to which dissolved oxygen is added.
Providing a water injection port for injecting raw water or processing circulating water so that a horizontal swirling flow occurs in the aeration chamber means, for example, that a discharge port for processing circulating water is provided obliquely on the inner wall of the aeration chamber and water is injected. The purpose is to generate a substantially horizontal swirling flow in the water flow.
Therefore, the way of providing the water inlet differs depending on the shape of the aeration chamber. If it is a cylindrical shape, it may be discharged in the tangential direction as it is, and if it is a square shape, it is effective to attach an arc-shaped water flow plate.
In the present invention, by injecting raw water or treated circulating water into the aeration chamber, when a horizontal swirling flow occurs, the pressure at the center of the swirling flow becomes lower than the surroundings, and gentle vertical convection occurs. I do.
At that time, the upper contact filtration chamber and the lower aeration chamber were separated vertically by a partition having permeability, so that the partition suppressed the movement of treated water between the aeration chamber and the contact filtration chamber, and the contact filtration chamber Smooth the horizontal swirling flow of the water to make it a stable water flow, and by gentle convection in the vertical direction, the water is supplied from the lower aeration chamber to the upper contact filtration chamber, and the treated water is discharged from the discharge port. become.
Here, as for the water injected into the aeration chamber, raw waste water is supplied together with the circulating treated water. Not only a method of directly connecting the raw water by connecting a water injection pipe or the like to the aeration chamber, but also a method of supplying water to the contact filtration chamber. It is also possible to use a method in which raw water is supplied from above and indirectly injected into the aeration chamber by downward convection generated in the center.

In the present invention, the dissolved oxygen supply means refers to a means capable of supplying dissolved oxygen to treated water, and has an object of supplying sufficient oxygen to aerobic microorganisms disposed in a contact filtration chamber.
Therefore, it is not necessary to agitate the treated water, and a fine bubble generator is preferable because of its high oxygen dissolving efficiency.
Further, the contact filter medium (microorganism carrier) provided in the contact filtration chamber is not particularly limited. However, in the present invention, since the water flow in the contact filtration chamber is gentle, a horizontal swirling flow and a vertical convection, the It may be a filament or a stranded fiber string, and these fibers may be carbon fibers.

  The second technical gist is that the upper contact filtration chamber and the lower aeration chamber are vertically separated by a permeable partition wall, the contact filtration chamber is provided with an outlet for treated water, and the aeration chamber has a horizontal direction. A water inlet for injecting the treatment circulating water so as to generate a swirling flow, and a dissolved oxygen supply means, further provided with an anaerobic filter bed chamber below the aeration chamber, and provided between the aeration chamber and the anaerobic filter bed chamber. It is characterized in that it is separated by a partition having permeability and has an inlet for injecting raw water into the anaerobic filter bed chamber.

Here, the anaerobic filter bed chamber refers to a chamber in which a carrier to which anaerobic microorganisms are attached is arranged.
When raw water is injected into the anaerobic filter bed chamber, a horizontal swirling flow is generated in the aeration chamber located above the anaerobic filter bed chamber, so that the raw water is drawn in so as to pass through the gap between the microorganism carriers.
Hydrogen sulfide is generated when the organic matter is decomposed in the anaerobic part (anaerobic microorganism), but hydrogen sulfide gas is not generated from the apparatus because it is oxidized in the upper aerobic part and returns to sulfuric acid. .
Dissolved oxygen is added to the treated water drawn into the aeration chamber, and biological filtration is performed between the aeration chamber and the contact filtration chamber by the above-described horizontal swirling flow and gentle vertical convection.

In the biological filtration device of the present invention, the contact filtration speed is stabilized by gently swirling and convection in the flow of the contact filtration chamber, and the use of a fine bubble generating device enables efficient supply of high-concentration dissolved oxygen. The ability to capture solids floating in the treated water is high, there is no excess sludge flowing out due to flocculation and floating, preventing separation of biological filtration membranes and cutting of fiber filaments as contact filter media. The accumulation of excess sludge can be prevented.
In addition, when carbon fiber filaments are used as the contact filter media, the affinity for microorganisms is high and sludge adheres firmly, and the sludge separation is extremely small.
More specifically, the contact filter medium installed in the contact filtration chamber is formed by circulating the treated water in the aeration chamber by the circulating water flow and simultaneously controlling the amount of water passing between the contact filtration chamber and the aeration chamber by a permeable partition wall. Slowly stabilizes the swirling flow rate in contact with the water, stabilizes the biofilm, and prevents the wear of the fiber filaments. The treatment water containing dissolved oxygen in the aeration chamber is gently supplied to the contact filtration chamber by generating convection in the vertical direction, and excess sludge is collected at the bottom center by the swirling flow in the aeration chamber. The suction and pulverization in the microbubble generator and then the contact filtration treatment can reduce the accumulation of excess sludge.

In the present invention, in particular, an anaerobic filter bed chamber is further provided below the aeration chamber, the aeration chamber and the anaerobic filter bed chamber are separated by a partition having permeability, and raw water is injected into the anaerobic filter bed chamber. In the anaerobic filter bed, the organic components in the wastewater are anaerobically reduced and decomposed by anaerobic microorganisms such as sulfate-reducing bacteria, and then dissolved oxygen is added in the aeration chamber, and aerobic in the contact filtration chamber. Microbial oxidative degradation and solids supplementation are performed.
In addition, surplus sludge settling from the upper contact filtration chamber and the aeration chamber also has a function of decomposing in the lower anaerobic filter bed chamber.
In the present invention, the biological filtration device is separated into an upper contact filtration chamber and a lower aeration chamber by a partition having permeability, and the anaerobic filter bed chamber is further permeable under the aeration chamber. The aeration chamber has a simple structure with a water inlet for injecting raw water or treated circulating water so as to generate a horizontal swirling flow, and a dissolved oxygen supply means. It has high robustness, can gradually shift wastewater from anaerobic treatment to aerobic treatment, and can complete the reduction and oxidation cycle of sulfur as a series of flows.

FIG. 1 shows an example of the biological filtration device according to the present invention in which anaerobic treatment and aerobic treatment are integrally formed.
The main body of the apparatus forms a storage section of the processing water by the bottom plate 1 and the side wall 2 of the processing tank.
A contact filtration chamber 5 is formed in the upper part, and a contact filter medium (microorganism carrier) 7a is arranged.
An aeration chamber 6 is formed in the lower part of the contact filtration chamber, and the contact filtration chamber 5 and the aeration chamber 6 are separated by a partition 4a having a transmission hole 41a.
The arrangement and size of the permeation holes 41a are determined in consideration of the horizontal swirling flow of the contact filtration chamber and the supply amount of the treated water from the aeration chamber to the contact filtration chamber.
In the lower part of the aeration chamber 6, an anaerobic filter bed chamber 18 is formed and a microorganism carrier 7b is arranged. The anaerobic filter bed chamber 18 and the aeration chamber 6 are separated by a partition 4b having a permeation hole 41b.
Further, the water injection pipe 3 is connected to the vicinity of the bottom of the anaerobic filter bed room, and the drainage / sewage raw water 16 is injected. It is separated by a partition 4c.
The transmission hole 41c formed in the partition wall 4c is determined so that the drainage uniformly flows to the upper part.
The treated water is sucked by the circulating pump 10 from the water inlet 9 of the water intake pipe 12 and injected into the aeration chamber 6 from the discharge nozzle 15 to generate a horizontal swirling flow.
A microbubble generator 11 is connected in the middle of the circulation pipe to add dissolved oxygen efficiently.
FIG. 2 schematically shows the principle that treated water is taken into the aeration chamber 6 from the anaerobic filter bed chamber 18.
Since a swirling flow is generated in the aeration chamber on the upper side of the partition wall 4b, the upper part of the permeation hole 41b has a negative pressure from the anaerobic filter bed side, and is taken into the aeration chamber side.
In this case, as shown in FIG. 2, it is effective to form a raised portion 42b for accelerating the flow of the swirling flow near the transmission hole.
In order to slowly take in the anaerobic filter bed chamber into the aeration chamber, it is preferable to form a gap to some extent between the partition wall 4b and the microorganism carrier 7b.
The structures of the aeration chamber and the contact filtration chamber will be described later.

Next, an example of a structure in which a horizontal swirling flow and a vertical convection flow are generated will be described based on an embodiment of the biological filtration apparatus according to the present invention in a case where there is no anaerobic filter bed chamber below the aeration chamber.
3 is a schematic sectional view, FIG. 4 is a horizontal sectional view of the aeration chamber (Sec. AA), FIG. 5 is a horizontal sectional view of the contact filtration chamber (Sec. BB), and FIG. It is an image sectional view showing the treatment water flow direction inside the tank.
FIG. 7 is a cross-sectional view of the biological filtration device when raw water is supplied from the upper center of the contact filtration tank.

The biological filtration tank bottom plate 1 and the biological filtration tank side wall 2 constitute a cylindrical biological filtration tank.
The shape of the biological filtration tank may be a rectangular cube, but a cylindrical shape is desirable in order to smoothly flow a horizontal swirling flow.
The biological filtration tank is divided into an upper contact filtration chamber 5 and a lower aeration chamber 6 by a permeable partition wall 4a, and the partition wall 4a suppresses the movement of treated water in the vertical direction.
Further, the water injection pipe 3 for charging the raw water 16 has the same height as the partition wall 2, and the raw water 16 is poured into the aeration chamber 6.

The raw water 16 is agitated and mixed with the treated water by the swirling flow in the aeration chamber 6, is sucked from the water suction port 9 provided at the center of the bottom plate 1, passes through the water intake pipe 12, and is connected to the connection pipe by the flow force of the circulation pump 10. After being sent from 13 to the microbubble generator 11 and sufficiently supplied with dissolved oxygen, it is returned to the aeration chamber 6 from the discharge nozzle 15 via the water supply pipe 14, and becomes a swirling flow while aerating the treated water again. Stir and mix.
Then, the separated biofilm and excess sludge deposited in the aeration chamber by this swirling flow are drawn to the center of the bottom plate 1 and sent from the water inlet 9 to the circulation pump 10 and the fine bubble generator 11, and the inside of the circulation pump Is crushed by swirling jets and cavitation in the process of generating fine bubbles.
Note that a gas-liquid mixing pump is used for the fine airflow generator 11, but Japanese Patent No. 2646442 and JP-A-2002-370095 have a structure in which the fine bubble generator 11 and the circulation pump 10 are integrated, Japanese Patent Application Laid-Open No. 2001-58142 describes a microbubble generator using the discharge nozzle 15, and it is also possible to use an integrated type of these without using the circulation pump 10 and the microbubble generator 11 separately. It is possible.

The treated water in the aeration chamber 6 is swirled and aerated while circulating as described above, but partly permeates through the permeable partition wall 4a due to the centrifugal force due to the swirling flow and the rising force of the fine airflow, and the contact filtration chamber. 5 and is biologically filtered by the contact filter 7a by a slow horizontal swirling flow and a vertical convection.
Part of the treated water reaching the water surface at the upper edge of the contact filtration chamber due to the upward flow due to the convection in the contact filtration chamber 5 overflows the overflow weir 2 ′ whose upper part of the side wall 2 has been cut down at the discharge groove 8 and is discharged. The water falls into the groove 8 and is discharged from the discharge port 8 ′ to be discharged water 17. Most of the treated water is biologically filtered in the contact filter medium 7 a while turning horizontally, and gradually reaches the center of the contact filtration chamber. It is drawn and circulates through the contact filtration chamber on the downward convection, and a part of the water passes through the partition wall 4a and returns to the aeration chamber again.
In addition, by forming a water passage without arranging the contact filtration material 7a at the center of the contact filtration chamber, the downward water flow can be made smooth and the convection of the entire biological filtration tank can be promoted.

  Further, as shown in FIG. 7, raw water is introduced from the vicinity of the upper center of the contact filtration chamber without providing the water injection pipe 3, and the water suction port 9 is provided slightly away from the upper surface of the bottom plate 1, thereby providing biological filtration. It is also possible to simplify the structure of the device.

Next, an example of the results of a wastewater treatment experiment based on the continuous anaerobic / aerobic treatment biological filtration device shown in FIG. 1 will be described.
The wastewater used for the experiment was wastewater from a dyeing factory, and had a BOD of 200 to 300 mg / L.
COD: 300 to 400 mg / L, SS: 20 to 30 mg / L.
FIG. 8 shows a change in water temperature.
In this graph, the aerobic chamber indicates a contact filtration chamber, and the anaerobic chamber means an anaerobic filter bed chamber.
In addition, in this experiment, it compared with the activated sludge treatment tank in this dyeing factory.
Raw water had a relatively high water temperature due to drainage from the dyeing factory, and the activated sludge method was aerated by a pump, so the water temperature was high even in winter.
On the other hand, in the experimental plant, the temperature was reduced to 20 ° C. or less in winter due to the small size and the low energy generated by the circulation pump and the fine bubble generator.
Nevertheless, as shown in FIG. 9, a change in the removal rate of SS and a change in the removal rate of TOC (total organic carbon) in FIG.
Since the dyeing wastewater has a large variation in wastewater composition and a large amount of hardly decomposable substances because the dyeing process is a batch process, the TOC removal rate of 65 to 80% was secured by the activated sludge method. This is an excellent value as compared with the case where the TOC removal rate is 50 to 80% at a relatively high water temperature of 30 to 40 ° C.
Further, when the sludge generation rate is investigated, it is 1% or less per removed TOC, and considering that the value of the activated sludge method is 20 to 30%, this is a wastewater treatment method that generates very little sludge.
The SS removal effect was also superior to the activated sludge method as shown in FIG.
Due to this high SS removal effect, decolorization after wastewater treatment was also superior to the activated sludge method.
FIG. 11 shows the results of the investigation of changes in the sulfate concentration in the experimental apparatus.
It was confirmed that sulfate reduction occurred in the anaerobic chamber and oxidation occurred in the aerobic chamber.

1 shows a structural example of a biological filtration device (anaerobic / aerobic treatment) according to the present invention. FIG. 3 is an explanatory view of a mechanism for leaking treated water by a swirling flow. The structural example of a contact filtration room and an aeration room is shown. 1 shows a cross section (A-A line) of an aeration chamber. The cross section (BB line) of a contact filtration chamber is shown. The schematic diagram of a water flow is shown. Another example of the method for charging raw water will be described. 3 shows a change in water temperature in the experimental apparatus. The results of the SS removal rate change investigation are shown. The results of the TOC removal rate change investigation are shown. The results of the sulfate concentration change investigation are shown.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Bottom board of biological filtration tank 2 Side wall of biological filtration tank 3 Water injection pipes 4a, 4b, 4c Partition walls 41a, 41b, 41c Permeation hole of partition 5 Contact filtration room 6 Aeration room 7a Contact filtration material (microorganism carrier)
7b Microbial carrier in anaerobic chamber 8 Discharge groove 9 Water intake port 10 Circulation pump 11 Microbubble generator 12 Intake pipe 13 Connection pipe 14 Water supply pipe 15 Discharge nozzle 16 Raw water (drainage, sewage)
17 Discharged water 18 Anaerobic filter bed room (anaerobic room)

Claims (2)

  The upper contact filtration chamber and the lower aeration chamber are separated vertically by a permeable partition, and the contact filtration chamber is provided with an outlet for treated water. Alternatively, a biological filtration device comprising a water injection port for injecting treatment circulating water and a dissolved oxygen supply means.   An anaerobic filter bed chamber is further provided below the aeration chamber, the aeration chamber and the anaerobic filter bed chamber are separated by a partition having permeability, and an inlet for injecting raw water into the anaerobic filter chamber is provided. The biological filtration device according to claim 1, wherein

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