JP7599536B2 - Biological treatment device and biological treatment method - Google Patents

Description

The present invention relates to a biological treatment device and a biological treatment method.

Water treatment systems are known that perform biological treatment using microorganisms such as anaerobic and aerobic bacteria held on gel-like or fibrous carriers. Organic matter contained in the water to be treated that is supplied to a biological reactor is decomposed by the microorganisms. The carriers that hold the microorganisms flow inside the biological reactor. A screen is installed at the outlet of the biological reactor to prevent the carriers from flowing out. Patent No. 3668358 discloses a biological reactor in which an outlet is formed that extends from the main body of the biological reactor toward the outlet side and a screen is installed at the outlet.

In the biological reactor disclosed in Patent No. 3668358, the liquid-contacting portion of the screen is substantially opposite the main body, and the liquid in the main body and the carriers contained therein flow into the outlet in a substantially horizontal direction. Almost all of the carriers that flow into the outlet reach the screen and are captured by the screen. As a result, a large amount of carriers adhere to the screen, making it necessary to clean the screen periodically.

The present invention aims to provide a biological treatment device that can suppress adhesion of carriers to a screen.

The biological treatment apparatus of the present invention comprises a first biological treatment tank in which carriers having microorganisms fixed thereto for biologically treating water to be treated flow, a partition wall provided in the first biological treatment tank and separating the first biological treatment tank into a first region including a supply section for water to be treated and a second region communicating with the first region at the bottom of the first biological treatment tank and having an outflow section for treated water treated in the first biological treatment tank at its upper part, and a carrier capture device provided with a screen at the outflow section, the screen preventing the carriers from outflowing from the first biological treatment tank. The carriers are filled in the first region, the first biological treatment tank has a first side wall facing the partition wall, the second region is formed between the partition wall and the first side wall, the treated water flows out of the first biological treatment tank beyond the first side wall, and the carrier capture device is provided at the top of the first side wall. When the separation distance between the partition wall and the bottom of the first biological treatment tank is D and the vertical distance between the top of the first side wall and the bottom of the first biological treatment tank is H, D is less than 1/2 of H.

According to the present invention, the biological reactor is separated into a first region and a second region by a partition wall. The second region is connected to the first region at the bottom of the biological reactor, and the outlet of the treated water is formed at the top of the second region. The second region extends vertically. The carriers that flow into the second region settle due to gravity, so the amount of carriers that reach the screen is reduced. Therefore, according to the present invention, adhesion of the carriers to the screen can be reduced.

The above and other objects, features, and advantages of the present application will become apparent from the following detailed description taken in conjunction with the accompanying drawings illustrating the present application.

Hereinafter, an embodiment of the biological treatment device of the present invention will be described with reference to the drawings. The biological treatment device is used as a part of a water treatment system. First, an example of the configuration of a water treatment system including a biological treatment device 2 will be described. FIG. 1 shows a schematic configuration of a water treatment system 1. The water treatment system 1 has a biological treatment device 2 and a settling tank 3. The biological treatment device 2 is composed of a denitrification treatment tank 2A (first biological treatment tank) and an aerobic treatment tank 2B (second biological treatment tank). A supply line L1 for the water to be treated and a recirculation line L2 equipped with a recirculation pump 5 are connected to the denitrification treatment tank 2A. The water to be treated is supplied to the denitrification treatment tank 2A through the supply line L1. In the denitrification treatment tank 2A, denitrification treatment or anaerobic treatment is performed. In the denitrification treatment, in an environment where oxygen is not present in the water, nitric acid in the water to be treated is used for respiration to consume organic matter of microorganisms, and the organic matter is decomposed into nitrogen, carbon dioxide, and water. In anaerobic treatment, organic matter is decomposed into methane gas, carbon dioxide gas, and water by microorganisms in an environment where dissolved oxygen and oxygen from nitrite (NO ^2- ) and nitrate (NO ^3- ) are not present in the water. The water (treated water) treated in the denitrification treatment tank 2A is sent to the aerobic treatment tank 2B. Aerobic treatment is carried out in the aerobic treatment tank 2B. The aerobic treatment tank 2B is equipped with an aeration device 55. Air is sent to the aerobic treatment tank 2B by the aeration device 55, and residual organic matter is decomposed into carbon dioxide gas and water by microorganisms. The water treated in the aerobic treatment tank 2B is sent to the settling tank 3, and microbial sludge is separated from the treated water. A part or the whole amount of the microbial sludge is returned to the denitrification treatment tank 2A through the recirculation line L2 by the recirculation pump 5. Hereinafter, the water containing the microbial sludge returned to the denitrification treatment tank 2A through the recirculation line L2 will be referred to as "treated water" together with the water to be treated supplied from the supply line L1.

Next, the configuration of the biological treatment device 2 will be described with reference to Figures 2 to 6. Figure 2 is a partial perspective view of the biological treatment device 2 in the water treatment system 1 shown in Figure 1, with the third side wall 15 omitted. Figure 3 is a cross-sectional view showing the denitrification treatment tank 2A of the biological treatment device 2 shown in Figure 2. Figure 4 is a plan view showing the denitrification treatment tank 2A of the biological treatment device 2 taken along line A-A in Figure 3. Figure 5 is an enlarged view of part B in Figure 3. Figure 6 is a partial perspective view of the screen 27. In the following description, the width direction W refers to the direction parallel to the first and second side walls 13, 14 of the denitrification treatment tank 2A.

The denitrification tank 2A contains the water to be treated and carriers on which microorganisms (anaerobic bacteria) are fixed. The biological treatment device 2 is a reinforced concrete structure, and has a bottom plate 12 that constitutes the bottom 12A of the denitrification tank 2A and the aerobic treatment tank 2B, four side surfaces 13-16 connected to the bottom plate 12, and a top plate 17. The side wall on the outlet side of the denitrification tank 2A is called the first side wall 13, the side wall on the inlet side of the denitrification tank 2A located opposite the first side wall 13 is called the second side wall 14, and the side walls of the denitrification tank 2A and the aerobic treatment tank 2B that are perpendicular to the first and second side walls 13, 14 are called the third and fourth side walls 15, 16.

The denitrification tank 2A is provided with a partition wall 18. The denitrification tank 2A is separated into a first region 19 and a second region 20 by the partition wall 18. The first region 19 is a region for mainly denitrifying the water to be treated. The first region 19 has a supply section 22 for the water to be treated and an agitator 23. The supply section 22 for the water to be treated consists of a supply line L1 and a recirculation line L2. The position, number and specifications of the agitator 23 are determined by general selection criteria so that the carrier in the denitrification tank 2A can be sufficiently agitated. Since the denitrification tank 2A performs anoxic or anaerobic treatment, an aeration device for supplying air is not provided. In order to prevent the intrusion of oxygen as much as possible, the first region 19 is covered with a top plate 17. The top plate 17 is provided with an opening 17A through which the supply line L1 and the recirculation line L2 pass. The partition wall 18 extends downward from the top plate 17, and its lower end is separated from the bottom 12A of the denitrification tank 2A. Therefore, the first area 19 and the second area 20 communicate with each other through a communication part 21 at the bottom of the denitrification tank 2A. The partition wall 18 is made of reinforced concrete, but may also be made of metal plates. Metal plates include, for example, stainless steel plates and stainless steel-lined steel plates.

The supply line L1 and the recirculation line L2 are provided on the inlet side of the denitrification treatment tank 2A, i.e., near the second side wall 14. The supply line L1 and the recirculation line L2 are provided on both sides of the center line in the width direction W of the second side wall 14, at positions approximately symmetrical with respect to the center line. Therefore, the water to be treated supplied from the supply line L1 and the recirculation line L2 flows toward the second region 20 in a direction approximately perpendicular to the second side wall 14. The side surfaces of the supply line L1 and the recirculation line L2 are formed with a plurality of supply ports 24 that open into the denitrification treatment tank 2A and supply the water to be treated to the denitrification treatment tank 2A. The plurality of supply ports 24 face the second side wall 14 and release the water to be treated toward the second side wall 14. The water to be treated collides with the second side wall 14, then changes direction in the opposite direction and flows toward the second region 20. Therefore, the water to be treated is less likely to drift significantly within the first region 19, and the flow rate of the water to be treated and the agitator 23 allow the carrier to flow efficiently within the first region 19.

Furthermore, by providing the first baffle plate 51, it is possible to make it more difficult for drift to occur in the first region 19. There are no limitations on the shape or arrangement of the first baffle plate 51, as long as it can suppress drift in the first region 19. In this embodiment, as shown in Figures 3 and 4, the first baffle plate 51 is a wall similar to the partition wall 18 provided downstream of the supply line L1 and the recirculation line L2. If the first baffle plate 51 is not provided, the flow of the treated water supplied from the upper part of the supply line L1 or the recirculation line L2 toward the communication part 21 with the second region 20 will not be uniform in the first region 19, and drift will occur in the water near the upper part of the partition wall 18 of the first region 19, and the drift may cause the carrier to reach the screen. By providing the first baffle plate 51, the treated water supplied to the first region 19 becomes uniform across the first baffle plate 51, preventing the occurrence of drift in the water near the top of the partition wall 18.

The second region 20 includes the outflow portion 25 of the water (treated water) treated in the denitrification treatment tank 2A, and its volume is smaller than that of the first region 19. The second region 20 is defined by the first side wall 13, the third side wall 15, the fourth side wall 16, and the partition wall 18. The top plate 17 is not provided in the second region 20. The outflow portion 25 of the treated water is formed only in the upper part of the second region 20, more precisely, in the top portion 13A of the first side wall 13. The top portion 13A of the first side wall 13 is a horizontal plane lower than the tops of the third side wall 15, the fourth side wall 16, and the partition wall 18, and the treated water that flows into the second region 20 flows out over the top portion 13A of the first side wall 13 into the aerobic treatment tank 2B.

A carrier capture device 26 is provided at the outflow section 25, more precisely at the top 13A of the first side wall 13, to prevent the carrier from flowing out of the denitrification treatment tank 2A. The carrier capture device 26 has a screen 27 and a support portion 28, and the support portion 28 is fixed to the top 13A of the first side wall 13. The screen 27 is a wedge wire screen. As shown in Figures 5 and 6, the screen 27 is composed of a plurality of wire rods 29 and a plurality of support rods 30. The wire rods 29 are arranged parallel to each other and spaced apart from each other. The support rods 30 extend in a direction perpendicular to the wire rods 29, and are arranged parallel to each other and spaced apart from each other. The spacing between the support rods 30 is greater than the spacing between the wire rods 29. Each wire rod 29 has an inverted triangular cross-sectional shape having a wide surface 29A and a narrow surface 29B, and the narrow surface 29B is fixed to the support rod 30. The gap between the adjacent wide faces 29A is a dimension that allows the flow of the treated water and is sufficiently smaller than the average diameter of the carrier. The support rod 30 is fixed to the support portion 28. The support portion 28 is made of a metal plate and is fixed to the top portion 13A of the first side wall 13 by a bolt (not shown). The screen 27 is arranged so that the wide face 29A is on the upstream side in the flow direction of the treated water (indicated by an arrow in FIG. 6) and the narrow face 29B is on the downstream side in the flow direction of the treated water. The treated water passes between the wide faces 29A of the wire rod 29, and the carrier contained in the treated water is captured by the wide face 29A or in the gap between the wide faces 29A. The configuration of the screen 27 is not limited to a wedge wire screen, and any screen can be used as long as it can pass the treated water and capture the carrier. For example, a punched metal with many small holes formed therein can be used as the screen 27.

As shown in FIG. 5, it is preferable that the screen 27 is inclined with respect to the vertical direction V. That is, the screen 27 and the support portion 28 intersect at an angle other than 90 degrees. By inclining the screen 27, the liquid contact area of the screen 27 can be increased. The screen 27 may be inclined toward the second region 20, or may be inclined toward the opposite side of the second region 20 (the aerobic treatment tank 2B side). The former configuration is more preferable because the carriers attached to the screen 27 fall into the second region 20.

The carrier capture device 26 can be equipped with a cleaning device 31 on the opposite side of the screen 27 to the second region 20 (the aerobic treatment tank 2B side). The cleaning device 31 sprays a cleaning fluid onto the screen 27. The cleaning device 31 has a pipe 32 for supplying the cleaning fluid. The pipe 32 extends in the width direction W of the screen 27, facing almost the entire width of the screen 27. A number of nozzles 33 for spraying the cleaning fluid are formed on the surface of the pipe 32 facing the screen 27. As will be described later, the amount of carriers that adhere to the screen 27 is limited, but it is difficult to completely prevent the carriers from adhering to the screen 27. For this reason, it is desirable to periodically remove the carriers that have adhered to the screen 27. The cleaning fluid is preferably water or air. The cleaning device 31 may be provided on the second region 20 side, or may be provided on both the second region 20 side and the opposite side of the second region 20.

Next, referring to FIG. 3, the procedure of the water treatment method using the biological treatment device 2, and the operation of the biological treatment device 2, particularly the denitrification treatment tank 2A, will be described. As described above, the water to be treated supplied to the first region 19 of the denitrification treatment tank 2A is subjected to anoxic or anaerobic treatment by the microorganisms fixed to the carriers C while flowing through the first region 19 toward the second region 20. The treated water flows into the second region 20 through the communication part 21 between the first region 19 and the second region 20. The treated water rises in the second region 20, and the carriers C also rise in the second region 20 accompanying the upward flow of the treated water. However, since the specific gravity of the carriers C is greater than that of the treated water, most of the carriers C do not reach the outflow part 25 and descend or settle due to gravity. In the region from the communication part 21 to the lower part of the second region 20, the flow of treated water and carriers C toward the outlet 25 due to the flow generated by the treated water flowing into the second region 20 and the flow generated by the agitator 23, and the flow of carriers C descending the second region 20 and returning to the first region 19 are thought to coexist. It is thought that most of the carriers C that enter the second region 20 rise in the second region 20, then descend and return to the first region 19. The flow of treated water returning from the communication part 21 to the first region 19 prevents carriers C from accumulating in the bottom 12A of the second region 20 or the communication part 21.

The treated water reaches the outflow section 25 of the second region 20 and exceeds the top 13A of the first side wall 13. The treated water passes through the screen 27 and flows out from the denitrification treatment tank 2A to the aerobic treatment tank 2B. Most of the carriers C in the first region 19 remain in the first region 19 due to the flow generated by the agitator 23. Some of the carriers C flow out to the second region 20 due to the flow from the side wall 14 to the side wall 13, but because the specific gravity of the carriers C is greater than the specific gravity of the liquid, they settle in the second region 20. However, some of the carriers C that flow out to the second region 20 may reach the outflow section 25 of the second region 20 without settling. The carriers C that reach the outflow section 25 of the second region 20 are captured by the screen 27 provided at the top 13A of the first side wall 13 and are prevented from flowing out of the denitrification treatment tank 2A.

It is desirable to set the separation distance D between the partition wall 18 and the bottom 12A of the denitrification treatment tank 2A within a predetermined range. If the separation distance D is too small, the pressure loss in the communication part 21 increases, and a sufficient amount of water cannot be supplied to the second region 20. For example, the predetermined range is desirably set so that the area calculated by multiplying the separation distance D by the dimension in the width direction W of the denitrification treatment tank 2A is equal to or greater than the flow path cross-sectional area of the second region 20. In addition, since there is no liquid flow when the biological treatment device 2 is stopped, the carrier C with a large specific gravity descends and accumulates on the bottom surface of the first region 19. If the separation distance D is small, the carrier C accumulated on the bottom 12A may block the communication part 21. If the biological treatment device 2 is restarted in this state, the carrier blocking the communication part 21 is pushed out to the second region 20. As a result, a large amount of carriers may reach the screen 27, causing the screen 27 to become blocked. Therefore, it is preferable that the separation distance D is greater than the thickness of the carrier layer deposited on the bottom surface when the biological treatment device 2 is stopped. This ensures that a flow path is established above the carrier deposited on the bottom surface in the communication section 21, and the liquid in the first region 19 flows above the carrier into the second region 20.

The thickness of the carrier layer deposited on the bottom 12A of the denitrification tank 2A depends on the carrier packing rate. The packing rate means the volume ratio of the carrier to the volume of the liquid held in the denitrification tank 2A. Since the denitrification tank 2A is almost a rectangular parallelepiped, the packing rate roughly corresponds to the ratio of the separation distance D between the partition wall 18 and the bottom 12A of the denitrification tank 2A to the vertical distance H between the top 13A of the first side wall 13 and the bottom 12A of the denitrification tank 2A. From the above, it is desirable that the separation distance D between the partition wall 18 and the bottom 12A of the denitrification tank 2A is greater than the vertical distance H between the top 13A of the first side wall 13 and the bottom 12A of the denitrification tank 2A multiplied by the carrier packing rate. The packing rate varies depending on the water quality of the water to be treated. However, the packing rate rarely exceeds 40%, and almost never exceeds 50%. Therefore, in reality, there is no need to ensure that the separation distance D is at least 1/2 of the vertical distance H between the top 13A of the first side wall 13 and the bottom 12A of the denitrification treatment tank 2A. In other words, the separation distance D may be less than 1/2 of the vertical distance H between the top 13A of the first side wall 13 and the bottom 12A of the denitrification treatment tank 2A.

As described above, in the second region 20, the carriers settle against the upward flow of the treated water, so that the flow velocity V of the treated water in the second region 20 is desirably at least smaller than the settling velocity of the carriers. The settling velocity can be determined in advance based on the properties of the treated water and the type of carrier. The flow velocity V of the treated water in the second region 20 is determined by the flow rate of the water to be treated supplied to the denitrification treatment tank 2A (i.e., the flow rate of the treated water supplied to the second region 20) and the cross section of the flow path of the second region 20. In order to ensure that the carriers settle, it is desirably to determine the flow velocity V of the treated water in the second region 20 taking into account the safety factor. It is desirably to determine the safety factor from a range of about 1.2 to 2.0. In other words, it is desirably to set the flow velocity V of the treated water in the second region 20 to 0.5 to 0.8 times the settling velocity of the carriers. When the treatment volume per unit time of the biological treatment device 2 is fixed, it is desirable to determine the flow path cross section of the second region 20 so that the flow velocity V of the treated water in the second region 20 is a predetermined value.

The flow of water overflowing from the second region 20 to the first side wall 13 depends on the flow rate determined by the supply line L1 and the circulation line L2, but as described above, the drift caused by the agitator 23 may reach the top of the second region 20 together with the carriers, causing the carriers to adhere to the screen. By providing the second baffle plate 52, the flow caused by the agitator 23 can be suppressed and the amount of carriers C reaching the carrier capture device 26 can be suppressed. There are no limitations on the shape, arrangement, etc. of the second baffle plate 52 as long as it can suppress the amount of carriers C reaching the carrier capture device 26. In this embodiment, as shown in Figures 3 and 4, the second baffle plate 52 is a baffle plate that protrudes laterally from the first side wall 13. The second baffle plate 52 suppresses the upward flow of the treated water in the second region 20. As shown in Figure 3, the second baffle plate 52 is inclined downward. This prevents carriers from accumulating on the upper surface of the second baffle plate 52, and carriers that have risen can descend or settle along the upper surface of the second baffle plate 52. By providing the second baffle plate 52, the amount of carriers C that reach the carrier capture device 26 can be reduced, allowing the screen 27 of the carrier capture device 26 to be made smaller.

This embodiment has the following advantages. As described above, the inlet (communication part 21) of the second region 20 is located at the bottom of the denitrification treatment tank 2A, and the outlet of the second region 20 is only at the top of the second region 20. In other words, the outflow part 25 or the screen 27 is located above the communication part 21 and in a position that cannot be directly seen horizontally from the first region 19. With this configuration, the treated water always flows as an upward flow just before it flows out of the denitrification treatment tank 2A, and the carriers are separated from the treated water. Since the number of carriers that reach the screen 27 is significantly reduced compared to the number of carriers that pass through the communication part 21, the liquid contact area of the screen 27 can be small. In other words, since most of the carriers are separated from the treated water by the vertical flow path configuration of the second region 20, the screen 27 mainly functions as a backup. For this reason, it is possible to reduce the size and cost of the screen 27. The frequency and/or cleaning time of the screen 27 can also be reduced.

In the conventional screen, many parts were submerged in the denitrification treatment tank 2A, so the method of cleaning the screen was limited. Although cleaning can be easily performed by draining the denitrification treatment tank 2A, this method requires the biological treatment device 2 to be stopped. Special equipment is required to clean the submerged parts during operation, which increases cleaning costs. In contrast, in this embodiment, the screen 27 is provided at a location where the treated water overflows, so cleaning can be easily performed during operation and cleaning costs can be reduced. In addition, the screen 27 can be efficiently cleaned because almost the entire area is exposed simply by stopping the supply of the water to be treated without draining the water in the tank. This advantage is particularly noticeable in anoxic or anaerobic treatment. As mentioned above, an aeration device is generally provided in aerobic treatment, and the screen 27 is constantly cleaned by air sprayed from the aeration device. However, since it is desirable to avoid air flowing into the denitrification treatment tank 2A in anoxic or anaerobic treatment, cleaning using an aeration device reduces the treatment efficiency. In addition, since the efficiency of dissolving air during aeration increases with the depth of the water, it is disadvantageous if the screen 27 has a submerged portion. For this reason, aeration conditions must be relaxed in anaerobic treatment compared to aerobic treatment, and carriers are more likely to adhere to the screen 27. In this embodiment, the screen 27 is easy to clean, so this problem in anaerobic treatment is easily solved. In addition, in this embodiment, the first area 19 is separated from the second area 20 by the partition wall 18, so air is less likely to flow into the first area 19. For this reason, air can be used as a cleaning fluid when cleaning the screen 27 with the cleaning device 31.

Although the present invention has been described above by way of one embodiment, the present invention is not limited to this embodiment and can be modified in various ways depending on the type and concentration of the substance to be removed. For example, the water discharged from the denitrification treatment tank 2A can be supplied to the settling tank 3 without providing the aerobic treatment tank 2B. A similar carrier capture device 26 can also be provided in the aerobic treatment tank 2B. The carriers that fix the aerobic bacteria are formed from a lightweight material such as a sponge, and therefore are less likely to settle due to gravity than carriers for anaerobic microorganisms. However, the specific gravity of the carrier containing water may be greater than that of the water to be treated, and the effect of the present invention may be obtained. In addition, generally, a sufficient effect of separating the carrier from the liquid can be obtained by providing only one partition wall 18 as in this embodiment, but if, for example, the specific gravity of the carrier is close to that of the treated water and the effect of separating the carrier due to gravity is small, another partition wall rising from the bottom plate 12 can be provided upstream of the partition wall 18.

The present invention can be applied to a method for modifying a biological treatment device. For example, a biological treatment device in which a large screen is attached to one side of a biological reaction tank can be modified into a biological treatment device having a similar configuration to this embodiment. The modification work can be performed in the following procedure. First, the large screen is removed and a first side wall 13 is provided. A partition wall 18 is provided inside the biological reaction tank, and a carrier capture device 26 including a small screen 27 of this embodiment is provided on the top 13A of the first side wall 13. From the viewpoint of workability, it is preferable to make the partition wall 18 from a metal plate.

Although certain preferred embodiments of the present invention have been shown and described in detail, it will be understood that various changes and modifications can be made therein without departing from the spirit or scope of the appended claims.

1 is a cross-sectional view of a water treatment system according to one embodiment of the present invention. FIG. 2 is a partial perspective view of a biological treatment device in the water treatment system shown in FIG. 1 . FIG. 3 is a partial cross-sectional view of the biological treatment device shown in FIG. 2 . FIG. 4 is a partial plan view of the biological treatment device taken along line AA in FIG. 3. FIG. 4 is an enlarged view of part B in FIG. 3 . FIG.

2 Biological treatment device 2A Denitrification treatment tank (first biological treatment tank)
2B Aerobic treatment tank (second biological treatment tank)
12 Bottom plate 13 to 16 First to fourth side walls 17 Top plate 18 Partition wall 19 First region 20 Second region 21 Communication section 22 Supply section 25 Outlet section 26 Carrier capture device 27 Screen 31 Cleaning device C Carrier

Claims (10)

a first biological treatment tank in which carriers having microorganisms fixed thereon for biologically treating the water to be treated flow;
A partition wall is provided in the first biological treatment tank and separates the first biological treatment tank into a first region including a supply portion of the water to be treated and a second region that communicates with the first region at a lower portion of the first biological treatment tank and has an outflow portion for the treated water treated in the first biological treatment tank at an upper portion thereof;
A screen is provided in the outflow section, and the screen has a carrier capture device that prevents the carrier from outflowing from the first biological treatment tank,
The carrier is filled in the first region,
The first biological treatment tank has a first side wall facing the partition wall, the second region is formed between the partition wall and the first side wall, the treated water flows out of the first biological treatment tank beyond the first side wall, and the carrier capture device is provided on the top of the first side wall ,
A biological treatment apparatus, wherein when the separation distance between the partition wall and the bottom of the first biological treatment tank is D and the vertical distance between the top of the first side wall and the bottom of the first biological treatment tank is H, D is less than 1/2 of H. The biological treatment device according to claim 1, wherein the second region is configured to allow the carriers flowing from the first region to settle through a portion communicating with the first region. The biological treatment device according to claim 1 or 2, wherein the flow rate of the treated water in the second region is smaller than the settling rate of the carrier. The biological treatment device according to any one of claims 1 to 3, wherein the specific gravity of the carrier is greater than the specific gravity of the treated water. The biological treatment device according to any one of claims 1 to 4, wherein the volume of the second region is smaller than the volume of the first region. The biological treatment device according to any one of claims 1 to 5, wherein the first region is covered with a top plate, and the top plate is provided with an opening for the supply section. The biological treatment device according to any one of claims 1 to 6, which has a second biological treatment tank that biologically treats the treated water that has flowed out of the first biological treatment tank beyond the first side wall, and an aeration device is provided in the second biological treatment tank. The biological treatment device according to claim 7, wherein denitrification is performed in the first biological treatment tank and aerobic treatment is performed in the second biological treatment tank. a first biological treatment tank in which carriers having microorganisms fixed thereon for biologically treating the water to be treated flow;
A partition wall is provided in the first biological treatment tank and separates the first biological treatment tank into a first region including a supply portion of the water to be treated and a second region that communicates with the first region at a lower portion of the first biological treatment tank and has an outflow portion for the treated water treated in the first biological treatment tank at an upper portion thereof;
A screen is provided in the outflow section, and the screen has a carrier capture device that prevents the carrier from outflowing from the first biological treatment tank,
The carrier is filled in the first region,
The first biological treatment tank has a first side wall facing the partition wall, the second region is formed between the partition wall and the first side wall, and the carrier capture device is provided on the top of the first side wall ,
A biological treatment method using a biological treatment device, in which D is a separation distance between the partition wall and the bottom of the first biological treatment tank, and H is a vertical distance between the top of the first side wall and the bottom of the first biological treatment tank, and D is less than 1/2 of H,
Biologically treating the water to be treated in the first biological treatment tank;
Allowing treated water in the first biological treatment tank to flow out of the first biological treatment tank beyond the first side wall;
allowing the carriers that have flowed from the first region into the second region through a portion communicating with the first region to settle in the second region;
The biological treatment method according to claim 1, The biological treatment method according to claim 9, further comprising spraying a cleaning fluid from the opposite side of the second region of the screen.

Images