Sewage enhanced treatment device with biological carrier

Abstract

The utility model discloses an enhanced sewage treatment device with a biological carrier, which comprises a tank body for accommodating the biological carrier, an adjusting component, a water outlet pipe arranged on the tank body, and a first screen drum and a second screen drum which are arranged in the tank body, and the second screen drum is communicated with the water outlet pipe through a first telescopic pipe; the first screen drum is fixed in the pool body through an adjusting assembly, the arrangement position of the first screen drum can be adjusted through the adjusting assembly, and the second screen drum is fixedly connected with the first screen drum; a water pumping device is arranged in the first screen drum, and a water outlet pipe of the water pumping device extends out of the first screen drum; the bottom of the first screen drum and the bottom of the second screen drum are closed, a plurality of first screen holes are formed in the side wall of the first screen drum, a plurality of second screen holes are formed in the side wall of the second screen drum, and the size of the first screen holes and the size of the second screen holes are equal and smaller than the size of the biological carrier. The sewage treatment device disclosed by the utility model solves the technical problem that a biological carrier is easy to block an intercepting net in the prior art.

Description

Technical Field

[0001] This utility model belongs to the field of wastewater treatment technology, specifically relating to a wastewater enhanced treatment device with a biological carrier. Background Technology

[0002] Wastewater biological carrier enhancement is an artificial enhancement technology that improves the efficiency of wastewater treatment systems by introducing specific biological carrier materials and combining them with highly efficient microbial communities. Its core lies in utilizing the carrier to create a stable microbial attachment environment, promoting the efficient degradation of pollutants. Currently, the use of biological carriers in wastewater treatment ponds presents five main challenges: 1. Biological carriers easily clog interceptor screens. To prevent clogging, large-area interceptor screens are typically used, but these screens are prone to breakage during operation, leading to carrier loss; 2. Biological carriers tend to accumulate at the end of the pond, resulting in low biofilm renewal efficiency and wastewater treatment efficiency; 3. Uneven aeration, especially excessive aeration below the interceptor screens, leading to localized dissolved oxygen deficiency; 4. The density of existing biological carriers is mismatched with the hydraulic conditions of the pond, resulting in uneven carrier distribution across the cross-section; 5. After the pond is emptied, the biological carriers fall evenly onto the aeration discs, making disc maintenance difficult.

[0003] Chinese Utility Model Patent Publication No. CN214734787U discloses an aerated biological fluidized bed, including a bed body with an inlet and an outlet. A water distribution wall is located at the inlet, with multiple circular holes communicating with the interior of the bed body. Several baffles are vertically and evenly distributed between the inlet and outlet. The lower ends of the odd-numbered baffles arranged from the inlet to the outlet have through holes, while the height of the even-numbered baffles is lower than that of the odd-numbered baffles. The biological carrier is confined to the middle of the bed body by upper and lower intercepting nets. A guide tube is located at the bottom of the bed body, consisting of several guide plates arranged symmetrically. A sludge discharge pipe is located at the concave bottom of the guide tube, and an aeration pipe is located at the convex top. This fluidized bed has a simple structure, large biomass, and high mass transfer efficiency, greatly improving the utilization of the biological carrier and significantly increasing water treatment efficiency. However, biological carriers still easily clog the upper and lower interception nets of this utility model, affecting the efficiency of sewage treatment. Utility Model Content

[0004] In view of the existing technical problems, this utility model aims to provide a wastewater enhanced treatment device with a biological carrier, which can solve the technical problem that the biological carrier is prone to clogging the interception net in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0006] A wastewater enhancement treatment device with a biological carrier includes a tank containing the biological carrier and an outlet pipe installed on the tank. Its structural features include: an adjustment component and a first and second screen cylinder installed within the tank; the second screen cylinder is connected to the outlet pipe via a first telescopic pipe; the first screen cylinder is fixed within the tank by the adjustment component, and its position can be adjusted by the adjustment component; the second screen cylinder is fixedly connected to the first screen cylinder; a pumping device is installed inside the first screen cylinder, and the outlet pipe of the pumping device extends outward from the first screen cylinder; the bottoms of the first and second screen cylinders are closed; the sidewall of the first screen cylinder has multiple first screen holes, and the sidewall of the second screen cylinder has multiple second screen holes; the sizes of the first and second screen holes are equal and both smaller than the size of the biological carrier.

[0007] In use, the wastewater enhanced treatment device of this application allows wastewater treated by biological carriers in the tank to enter the first screen cylinder only through the first screen aperture and the second screen cylinder only through the second screen aperture. Wastewater in the first screen cylinder is pumped back into the tank by a pumping device, while wastewater in the second screen cylinder is discharged through an outlet pipe. The outlet flow rate of the second screen cylinder can be simulated by adjusting the flow rate of the pumping device. When biological carriers accumulate near the first and second screen cylinders, they prevent wastewater from entering, causing the liquid level in the first screen cylinder to drop. By adjusting the position of the first screen cylinder, when it moves to a position with low biological carrier density, wastewater can smoothly enter the first screen cylinder, causing the liquid level to rise. At this time, the second screen cylinder moves with the first screen cylinder to a position with low biological carrier density, allowing wastewater in the tank to smoothly exit through the second screen cylinder. Furthermore, since the apertures of both the first and second screen apertures are smaller than the size of the biological carriers, the biological carriers will not clog the first and second screen cylinders. The flow rate of the pumping device can be calculated based on the flow rate of sewage in the tank, the area of ​​the second screen hole on the second screen cylinder, and the area of ​​the first screen hole on the first screen cylinder. In actual application, the flow rate of the pumping device can be slightly larger than the calculated flow rate, allowing for early warning. When the tank needs to be emptied, water can be pumped from the outlet to prevent the biological carrier from being pumped out along with it. In addition, by adjusting the position of the first screen cylinder, the deposition position of the biological carrier can be adjusted, preventing the biological carrier from settling near damaged aeration devices and facilitating maintenance. Currently, the commonly used shape of biological carrier is sphere or cylinder, and the first and second screen holes can be circular holes with a diameter 5-10 mm smaller than the diameter of the biological carrier. This utility model of a sewage enhanced treatment device with biological carriers discharges sewage by setting a second screen cylinder, and the placement of the second screen cylinder can be adjusted according to the density of biological carriers in the area. This prevents the second screen cylinder from being located at the biological carrier accumulation point and effectively prevents biological carrier blockage, thus allowing sewage in the tank to be discharged normally and effectively improving sewage treatment efficiency. This wastewater enhancement treatment device with biological carriers can guide the biological carriers to different locations during venting by controlling the positions of the first and second screen cylinders, making it convenient to maintain the aeration device.

[0008] Preferably, the adjustment assembly includes at least two motors and support ropes disposed on the output ends of the motors, the outer ends of which are all connected to the first screen cylinder; the first screen cylinder is fixed in the pool body by the support ropes, and the motors are driven to adjust the tension length of each support rope, thereby adjusting the setting position of the first screen cylinder.

[0009] Preferably, a level gauge is provided on or inside the first screen cylinder, and both the level gauge and the motor are electrically connected to the control system. The operation of the motor is controlled by the feedback of the liquid level in the first screen cylinder through the level gauge, thereby allowing the setting position of the first screen cylinder to be adjusted in real time.

[0010] Preferably, the bottom of the tank is provided with multiple sets of aeration components along its length, and each set of aeration components contains multiple aeration heads; the multiple aeration heads are spaced apart along the length of the tank, with the vertical height of the multiple aeration heads gradually increasing from the inlet pipe to the outlet pipe. The higher the vertical height of the aeration head, the greater the air output, which correspondingly drives the water to flow upward at a faster speed, thereby enabling the biological carrier to circulate internally and reducing the accumulation of biological carrier as it flows to the end of the sewage flow.

[0011] Preferably, the height difference between two adjacent aeration heads in each aeration assembly is 0.1 to 0.3 m, and the distance between two adjacent aeration assemblies is 2 to 4 m.

[0012] Preferably, each aeration assembly has at least one vertical guide plate above it. The guide plate is located downstream of the aeration head with the highest vertical height in the aeration assembly, and is inclined towards the aeration head. By setting the guide plate, the flow direction of the sewage is further guided, allowing the sewage to undergo multi-stage internal circulation at the guide plate.

[0013] Preferably, the distance h between the top of the guide plate and the liquid surface of the pool is 0.5 to 1 m, the length L of the guide plate is 0.5 to 1.5 m, and the angle between the bottom of the guide plate and the horizontal plane is 15 to 60°.

[0014] Specifically, the first screen cylinder is vertically arranged, and the top of the second screen cylinder is fixedly connected to the bottom wall of the first screen cylinder; the first telescopic tube is arranged at the bottom of the second screen cylinder and is connected to the second screen cylinder.

[0015] Preferably, a rinsing device is provided below the second screen cylinder, and the rinsing device is connected to the second screen cylinder via a support frame; the air outlet pipe of the blower device located outside the tank extends into the tank, and the air inlet of the rinsing device is connected to the air outlet pipe of the blower device via a second telescopic pipe. The rinsing device is provided with multiple air outlets. By setting up the rinsing device to locally rinse the area near the first and second screen cylinders, the aeration gas can be distributed to other areas of the tank, solving the problem of insufficient dissolved oxygen in some areas.

[0016] Preferably, the biological carrier includes a first type of biological carrier and a second type of biological carrier. The density of the first type of biological carrier is greater than the density of the wastewater being treated in the tank, and the density of the second type of biological carrier is less than the density of the wastewater being treated in the tank. The density of the biological carrier can be adjusted by loading carbon black on its surface and calcium or barium salts internally. By setting biological carriers of different densities, the biological carriers are more evenly distributed across the cross-section of the tank, thereby improving wastewater treatment efficiency.

[0017] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0018] 1. The wastewater enhanced treatment device with biological carrier of this utility model discharges wastewater by setting a second screen cylinder. The setting position of the second screen cylinder can be adjusted according to the density of biological carriers in the area, avoiding the second screen cylinder being located at the accumulation point of biological carriers, effectively preventing the biological carriers from clogging, thereby allowing the wastewater in the tank to be discharged normally and effectively improving the wastewater treatment efficiency.

[0019] 2. The wastewater enhanced treatment device with biological carrier of this utility model can guide the biological carrier to different positions when venting by adjusting the positions of the first screen cylinder and the second screen cylinder, which facilitates the maintenance of the aeration device.

[0020] 3. The wastewater enhanced treatment device with biological carrier of this utility model guides the flow of wastewater by setting aeration components and guide plates, so that the wastewater undergoes multi-stage internal circulation at the guide plates, which alleviates the accumulation of biological carrier as it flows to the end of the wastewater.

[0021] 4. The wastewater enhanced treatment device with biological carrier of this utility model solves the problem of insufficient local dissolved oxygen by setting up a flushing device to locally flush the area near the first screen cylinder and the second screen cylinder.

[0022] 5. The wastewater enhanced treatment device with biological carriers of this utility model improves wastewater treatment efficiency by setting biological carriers of different densities, making the biological carriers more evenly distributed on the cross-section of the pool. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the wastewater enhanced treatment device with biological carrier in this utility model.

[0024] Figure 2 yes Figure 1 A schematic diagram of the first sieve cylinder structure.

[0025] In the figure

[0026] 1—Pool body; 2—Inlet pipe; 3—Guide plate; 4—Biological carrier; 401—Class I biological carrier; 402—Class II biological carrier; 5—Adjustment component; 501—Motor; 502—Support rope; 6—First telescopic pipe; 7—Control system; 8—First screen cylinder; 9—Second screen cylinder; 10—Outlet pipe; 11—Second telescopic pipe; 12—Support frame; 13—Flushing device; 1301—Air outlet; 14—Blower; 15—Aeration component; 1501—Aeration head; 16—First screen hole; 17—Second screen hole; 18—Pumping device; 19—Level gauge. Detailed Implementation

[0027] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other. For ease of description, the terms "upper," "lower," "left," and "right" appearing below only indicate that they correspond to the upper, lower, left, and right directions in the accompanying drawings and do not limit the structure.

[0028] like Figure 1 As shown, the wastewater enhanced treatment device with biological carrier in this embodiment includes a tank 1, which is long and narrow. An inlet pipe 2 and an outlet pipe 10 are respectively provided at both ends along the length of the tank 1. A biological carrier 4 is placed inside the tank 1. The biological carrier 4 is a cylindrical or spherical structure made of PE or PP material. An aeration device 14 is provided outside the tank 1. This aeration device 14 is a blower, and the blower's outlet pipe extends into the tank 1 and connects to four sets of aeration components 15. The four sets of aeration components 15 are spaced apart along the length of the tank 1, with a spacing of 2-4 meters between adjacent sets. Oxygen is supplied to the tank 1 through the blower and the aeration components 15 to maintain the oxygen requirements of the microorganisms on the biological carrier 4 within the tank 1. Each aeration assembly 15 contains three aeration heads 1501, spaced apart along the length of the tank body 1, extending from the inlet pipe 2 to the outlet pipe 10. The vertical height of the aeration heads 1501 gradually increases, with a height difference of 0.1–0.3 m between adjacent aeration heads 1501. Each aeration assembly 15 has a vertical guide plate 3 at its top. This guide plate 3 can be made of concrete, steel, or polymer materials and possesses certain wear-resistant properties. The guide plate 3 is positioned downstream of the tallest aeration head 1501 in the aeration assembly 15, and is inclined towards that aeration head 1501. The distance h between the top of the guide plate 3 and the liquid surface of the tank body 1 is 0.5–1 m, the length L of the guide plate 3 is 0.5–1.5 m, and the angle between the bottom of the guide plate 3 and the horizontal plane is 15–60°. Inside the pool body 1, near the outlet pipe 10, are vertically arranged a first screen cylinder 8 and a second screen cylinder 9. Both the first screen cylinder 8 and the second screen cylinder 9 are cylindrical structures made of stainless steel or polymer materials. The top of the second screen cylinder 9 is fixedly connected to the bottom of the first screen cylinder 8, and the bottom of the second screen cylinder 9 is connected to the outlet pipe 10 through a first telescopic pipe 6. Figure 1 and Figure 2As shown, the bottom of the first screen cylinder 8 is closed. A pumping device 18 and a level gauge 19 are installed inside the first screen cylinder 8. The pumping device 18 is a water pump, and the outlet pipe of the water pump extends outward from the first screen cylinder 8. The flow rate of the water pump is calculated based on the flow rate of the sewage in the tank 1, the area of ​​the second screen holes 17 on the second screen cylinder 9, and the area of ​​the first screen holes 16 on the first screen cylinder 8. In actual application, the flow rate of the water pump can be slightly larger than the calculated flow rate to provide early warning. The flow velocity of the sewage in the tank 1 is obtained by dividing the flow rate of the sewage in the tank 1 by the total area of ​​the second screen holes 17 on the second screen cylinder 9. This flow velocity is multiplied by the area of ​​the first screen holes 16 on the first screen cylinder 8 to obtain the calculated flow rate of the water pump. The operating flow rate of the water pump can be designed with a certain margin based on the calculated flow rate. Multiple first screen holes 16 are provided on the side wall of the first screen cylinder 8, and multiple second screen holes 17 are provided on the side wall of the second screen cylinder 9. The first screen hole 16 and the second screen hole 17 are both round holes of equal size, with a diameter of 15-20 mm. The first screen cylinder 8 is fixed inside the tank body 1 by an adjusting assembly 5, and the position of the first screen cylinder 8 can be adjusted by the adjusting assembly 5. The adjusting assembly 5 includes two motors 501 and support ropes 502 set on the output end of the motors 501. The outer ends of the support ropes 502 are all connected to the top of the first screen cylinder 8. The level gauge 19 and the two motors 501 are all electrically connected to the control system 7. The first screen cylinder 8 is fixed inside the tank body 1 by the support ropes 502. The drive motors 501 adjust the tension length of each support rope 502, thereby adjusting the position of the first screen cylinder 8. A rinsing device 13 is provided below the second screen cylinder 9. The rinsing device 13 is connected to the second screen cylinder 9 by a support frame 12. The air inlet of the rinsing device 13 is connected to the air outlet of the blower 14 through a second telescopic pipe 11. The rinsing device 13 is provided with multiple air outlets 1301. The blower 14 can deliver air to the rinsing device 13 through the second telescopic pipe 11, and output it through the air outlet 1301 to rinse the area around the first screen cylinder 8 and the second screen cylinder 9.

[0029] like Figure 1 As shown, the biological carrier 4 includes a first type of biological carrier 401 and a second type of biological carrier 402. The density of the first type of biological carrier 401 is greater than the density of the wastewater being treated in the tank 1, and the density of the second type of biological carrier 402 is less than the density of the wastewater being treated in the tank 1. The density of the first type of biological carrier 401 is 1.02 g / cm³. 3 It has a diameter of Φ25mm and is surface-loaded with carbon black. The second type of biological carrier 402 includes two biological carriers, one of which has a density of 0.98 g / cm³. 3 One type of biological carrier has a diameter of Φ20mm and is internally loaded with calcium or barium salts to adjust its density; another type of biological carrier has a density of 0.95g / cm³. 3The biological carrier 4, with a diameter of Φ25mm, is made of pure HDPE or modified materials. During operation, only slight aeration is needed to achieve uniform stratification of the biological carrier 4 on the cross-section of the tank 1. The conventional air-to-water ratio during aeration in the tank 1 is generally set to 4:1. The second type of biological carrier 402, which is lighter than water, is mainly distributed in the upper and middle layers, while the first type of biological carrier 401, which is heavier than water, is mainly distributed in the lower and middle layers. This ensures uniform mixing of the biological carrier 4 with the water and improves the treatment effect.

[0030] In this embodiment, the wastewater enhancement treatment device with biological carrier is used to aerate the tank 1 via a blower and aeration heads 1501. Since the aeration heads 1501 at higher elevations produce more air, the water flows upwards at a faster speed. Figure 1 As indicated by the arrows, the biological carrier 4 within the tank 1 undergoes multi-stage internal circulation along the guide plate 3, thereby slowing down the accumulation of the biological carrier 4 as it flows with the sewage towards the end of the tank 1. The second screen hole 17 on the second screen cylinder 9 can effectively intercept the biological carrier 4 and allow sewage to flow into the second screen cylinder 9 and out through the outlet pipe 10. The water pump inside the first screen cylinder 8 can pump the sewage in the first screen cylinder 8 to the outside of the first screen cylinder 8 to lower the liquid level inside the first screen cylinder 8. By setting the first screen cylinder 8 and the water pump to detect and provide feedback on the density of the biological carrier 4 around the first screen cylinder 8, when there is an accumulation of biological carrier 4 around the first screen cylinder 8, the biological carrier 4 will prevent water from flowing into the first screen cylinder 8, causing the liquid level inside the first screen cylinder 8 to drop. The level gauge 19 transmits the signal to the intelligent control system 7. The intelligent control system 7 controls the motor 501 to work according to the signal strength. The motor 501 controls the extension length of the support rope 502, thereby moving the first screen cylinder 8 left and right. The first screen cylinder 8 drives the second screen cylinder 9 to move. When the first screen cylinder 8 moves to a position where the density of the biological carrier 4 is low, water can smoothly enter the first screen cylinder 8. The liquid level rise signal of the first screen cylinder 8 is sent to the intelligent control system 7, and the motor 501 stops working. The positions of the first screen cylinder 8 and the second screen cylinder 9 can be adjusted according to the density of the biological carrier in the area to avoid the second screen cylinder 9 being in the area where the biological carrier 4 accumulates, and to effectively prevent the biological carrier 4 from clogging, so that the sewage in the tank 1 can be discharged normally, which can effectively improve the sewage treatment efficiency. During maintenance, the extension length of the support rope 502 is controlled by the two motors 501, so that the first screen cylinder 8 and the second screen cylinder 9 sink to the area where the aeration is not damaged, and then water is pumped out from the outlet pipe 10 to empty the tank. Pumping water from the outlet pipe 10 can avoid the biological carrier 4 being pulled out together, thus avoiding damage to the empty water pump and loss of the biological carrier 4. In addition, as the water is pumped out, the biological carrier 4 will gradually settle near the first screen cylinder 8 and the second screen cylinder 9, and the damaged aeration head 1501 will leak out from the accumulated biological carrier 4, which facilitates maintenance.

[0031] The above embodiments should be understood as being used only to illustrate the utility model more clearly, and not to limit the scope of the utility model. After reading this utility model, any modifications of the embodiments by those skilled in the art in various equivalent forms fall within the scope defined by the appended claims.

Claims

1. A sewage enhanced treatment device with biological carrier, comprising a pool body (1) containing biological carrier (4) and a water outlet pipe (10) arranged on the pool body (1), characterized in that: It also includes an adjustment component (5) and a first screen cylinder (8) and a second screen cylinder (9) disposed in the pool body (1), the second screen cylinder (9) being connected to the outlet pipe (10) through a first telescopic pipe (6); The first screen cylinder (8) is fixed inside the pool body (1) by the adjustment component (5), and the setting position of the first screen cylinder (8) can be adjusted by the adjustment component (5). The second screen cylinder (9) is fixedly connected to the first screen cylinder (8). The first screen cylinder (8) is equipped with a water pumping device (18), and the water outlet pipe of the water pumping device (18) extends outward from the first screen cylinder (8); The bottoms of the first sieve cylinder (8) and the second sieve cylinder (9) are closed. The side wall of the first sieve cylinder (8) is provided with a plurality of first sieve holes (16), and the side wall of the second sieve cylinder (9) is provided with a plurality of second sieve holes (17). The size of the first sieve holes (16) and the second sieve holes (17) are equal and both smaller than the size of the biological carrier (4).

2. The device for enhanced treatment of sewage with biological carriers according to claim 1, characterized in that: The adjustment component (5) includes at least two motors (501) and support ropes (502) set on the output end of the motors (501). The outer ends of the support ropes (502) are all connected to the first screen cylinder (8). The first screen cylinder (8) is fixed in the pool body (1) by the support ropes (502). The drive motors (501) adjust the stretching length of each support rope (502) to adjust the setting position of the first screen cylinder (8).

3. The wastewater enhanced treatment device with a biological carrier according to claim 2, characterized in that: A level gauge (19) is provided on or inside the first screen cylinder (8), and the level gauge (19) and the motor (501) are electrically connected to the control system (7).

4. The wastewater enhanced treatment device with a biological carrier according to claim 1, characterized in that: The bottom of the pool (1) is provided with multiple sets of aeration components (15) along the length direction, and each set of aeration components (15) is provided with multiple aeration heads (1501); the multiple aeration heads (1501) are spaced apart along the length direction of the pool (1), and the vertical height of the multiple aeration heads (1501) gradually increases from the water inlet pipe (2) of the pool (1) to the water outlet pipe (10).

5. The wastewater enhanced treatment device with a biological carrier according to claim 4, characterized in that: The height difference between two adjacent aeration heads (1501) in each aeration component (15) is 0.1 to 0.3 m, and the distance between two adjacent aeration components (15) is 2 to 4 m.

6. The wastewater enhanced treatment device with a biological carrier according to claim 4, characterized in that: Each aeration assembly (15) is provided with at least one guide plate (3) above it. The guide plate (3) is located downstream of the aeration head (1501) with the highest vertical height in the aeration assembly (15), and the guide plate (3) is inclined toward the aeration head (1501).

7. The wastewater enhanced treatment device with a biological carrier according to claim 6, characterized in that: The distance h between the top of the guide plate (3) and the liquid surface of the pool body (1) is 0.5 to 1 m, the length L of the guide plate (3) is 0.5 to 1.5 m, and the angle between the bottom of the guide plate (3) and the horizontal plane is 15 to 60°.

8. The wastewater enhanced treatment device with a biological carrier according to any one of claims 1 to 7, characterized in that: The first screen cylinder (8) is vertically arranged, and the top of the second screen cylinder (9) is fixedly connected to the bottom wall of the first screen cylinder (8); the first telescopic tube (6) is arranged at the bottom of the second screen cylinder (9) and is connected to the second screen cylinder (9).

9. The wastewater enhanced treatment device with a biological carrier according to any one of claims 1 to 7, characterized in that: A rinsing device (13) is provided below the second screen cylinder (9). The rinsing device (13) is connected to the second screen cylinder (9) through a support frame (12). The air outlet pipe of the blower (14) provided outside the pool body (1) extends into the pool body (1). The air inlet of the rinsing device (13) is connected to the air outlet pipe of the blower (14) through a second telescopic pipe (11). The rinsing device (13) is provided with multiple air outlet holes (1301).

10. The wastewater enhanced treatment device with a biological carrier according to any one of claims 1 to 7, characterized in that: The biological carrier (4) includes a first type of biological carrier (401) and a second type of biological carrier (402). The density of the first type of biological carrier (401) is greater than the density of the sewage treated in the pool (1), and the density of the second type of biological carrier (402) is less than the density of the sewage treated in the pool (1).

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