Steel structure sewage treatment primary AO biochemical tank

Abstract

The utility model relates to the technical field of sewage treatment, and mainly discloses a steel structure sewage treatment primary AO biochemical tank body, which comprises an annular cylindrical zone O and a circular cylindrical zone A which are arranged at an interval, the zone O is communicated with the zone A, a water inlet pipe and a sludge inlet pipe are laid at the top of the zone A, an aerator is arranged in the zone O and is communicated with an aeration main pipe, and the aeration main pipe is communicated with the aeration main pipe. A water collecting tank is arranged above the area O, the water collecting tank is communicated with an internal reflux pump pit and an outlet water collecting pit, the internal reflux pump pit is communicated with the area A through an internal reflux pump and a pipeline, and the outlet water collecting pit is communicated with a water outlet pipe; and an area A punching net is arranged in the area A, and an area O punching net is arranged in the area O. The problem that in a traditional AO process, the area A and the area O are arranged side by side front and back, and the field area utilization efficiency is low under the condition of a circular steel structure tank is solved, the MBBR transformation function is reserved, and capacity expansion can be rapidly and conveniently achieved under the condition that water is not cut off.

Description

Technical Field

[0001] The utility model relates to the technical field of sewage treatment, in particular to a steel structure sewage treatment first-level AO biochemical tank. Background Art

[0002] The AO process is the mainstream process for biological denitrification of wastewater. It uses the aeration environment of the O zone to convert ammonia nitrogen into nitric nitrogen, and uses an internal reflux pump to send the mixed liquid containing nitric nitrogen at the end of the O zone back to the A zone. The non-aeration environment of the A zone is used to convert nitric nitrogen into nitrogen gas, thereby achieving denitrification. 3 Sewage treatment projects with a capacity of more than 1000 m / d generally use rectangular steel-concrete tanks with Zones A and O arranged side by side. A utility model patent (authorization announcement number CN 209957590U) discloses a composite ecological village sewage AO treatment device, which adopts a rectangular structure with Zones A and O arranged side by side. 3 / d) can be quickly fabricated with steel structures in rural sewage treatment scenarios, but cannot be applied to large-scale (>5000 m 3 / d) sewage treatment projects. This is because, while steel tank structures offer the advantage of rapid construction, rectangular steel tank structures are prone to cracking at corner welds, while circular steel tank structures have low site utilization efficiency when arranged side by side.

[0003] The biological fluidized bed process (MBBR) in wastewater treatment utilizes biofilms attached to suspended media to purify wastewater. Its biomass is two to three times greater than that of conventional activated sludge processes, and its efficiency in removing organic matter and total nitrogen is far superior. The MBBR process can significantly reduce the footprint and operating costs of municipal wastewater treatment plants, and is gaining increasing attention and application. However, in practical applications, it is primarily used for expansion and renovation where site space is limited. This renovation process requires the tank to be shut down and emptied, significantly inconvenient for production operations. Utility Model Content

[0004] The purpose of this utility model is to solve the technical problems existing in the prior art and provide a steel structure sewage treatment first-level AO biochemical tank, specifically a circular steel structure sewage treatment AO biochemical tank with reserved MBBR transformation function, which not only maximizes the site utilization efficiency, but also can achieve rapid expansion without water outage, and the single pool treatment scale reaches 30,000 m 3 / d.

[0005] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a steel structure sewage treatment first-level AO biochemical tank, including a tank body, the tank body including a cylinder wall and a cylinder bottom, the cylinder wall and the cylinder bottom forming a cylindrical tank body with an upper opening, the tank body including an annular cylindrical O zone and a circular cylindrical A zone arranged at intervals, the O zone and the A zone being connected, the cylinder wall of the tank body including, from the outside to the inside, a two-layer structure of an outer cylinder wall of the O zone and an outer cylinder wall of the A zone, an annular cylindrical O zone is formed between the outer cylinder wall of the O zone and the outer cylinder wall of the A zone and the cylinder bottom of the tank body, a circular cylindrical A zone is formed inside the outer cylinder wall of the A zone and the cylinder bottom, the O zone and the A zone are connected, a water inlet pipe and a mud inlet pipe are laid on the top of the A zone, an aerator is provided in the O zone, the aerator is connected to the aeration main pipe, a water collecting trough is provided above the O zone for collecting the sewage purified in the O zone, the water collecting trough is connected to the inner The reflux pump pit and the outlet collection pit are both connected, and the water in the sump enters the internal reflux pump pit first. The bottom of the internal reflux pump pit can be flush with the bottom of the outlet collection pit or the bottom of the internal reflux pump pit is lower than the bottom of the outlet collection pit, so that the water in the sump enters the internal reflux pump pit first. The internal reflux pump pit is connected to area A through an internal reflux pump and a pipeline to provide the internal reflux required by the AO process. The outlet collection pit is connected to the outlet pipe. Through the above-mentioned layout of area O and area A, the problem of low site area utilization efficiency in the traditional AO process of arranging areas A and O side by side in a circular steel structure tank body is solved. In order to realize the reserved transformation function of the MBBR process of the AO biochemical tank body, further, the area A is provided with an area A perforated mesh for preventing the MBBR filler in area A from entering the area O, and the area O is provided with an area O perforated mesh for preventing the MBBR filler in area O from entering the sump.

[0006] During initial operation according to a conventional activated sludge process, return sludge flows through a sludge inlet pipe and water flows through a water inlet pipe, both overhead and directly into Zone A. When capacity expansion is needed, the AO biochemical tank provided by this utility model can be increased by gradually adding MBBR filler, eliminating the need for water shut-off or retrofitting. Later, when operating according to the MBBR process, sludge return is unnecessary; only the water inlet pipe, overhead and directly into Zone A, flows through the entire AO biochemical tank.

[0007] A further solution of the present invention is that the water collecting trough is annular, and is welded by an annular plate with an L-shaped cross-section. The annular plate is made of stainless steel, and the bottom outer wall of the annular plate is welded to the upper end of the outer cylinder wall of the O zone, and a water collecting trough is formed between the vertical side wall of the annular plate and the outer cylinder wall of the O zone.

[0008] A further solution of the present invention is that a portion of the water collection tank in the circumferential direction is partially expanded to form an internal reflux pump pit, which is used to install an internal reflux pump to provide the internal reflux required by the AO process; a portion of the water collection tank symmetrical to the internal reflux pump pit in the circumferential direction is partially sunken to form a water outlet collection pit, through which the purified sewage in the O zone enters the outlet pipe of the entire AO biochemical tank body.

[0009] A further solution of the present invention is that the bottom of the internal return pump pit is 3-5 cm lower than the bottom of the outlet collection pit. Furthermore, the outlet collection pit is equipped with water retaining plates in the sump on both sides of the water inlet direction. Water flows over the retaining plates before entering the outlet collection pit. This also ensures that the purified sewage in Zone O enters the internal return pump pit first, preventing the internal return pump pit from being drained.

[0010] A further solution of the present invention is that the O zone and the A zone are connected through a circular water hole arranged at the bottom of the outer cylinder wall of the A zone, allowing sewage and sludge to enter the O zone through this. The circular water holes are evenly distributed along the circumference of the outer cylinder wall of the A zone.

[0011] A further solution of the present invention is that the number of the circular water holes is 4 to 12, and the diameter of the circular water holes is 200 to 600 mm. Preferably, the number of the circular water holes is 8, and the diameter of the circular water holes is 400 mm.

[0012] A further solution of the present invention is that the aerator comprises several sets of sector-shaped perforated tube aerators, which are arranged on the bottom of the cylinder at the bottom of zone O. Preferably, there are eight sets of sector-shaped perforated tube aerators. The diameter of the aeration holes in the aerators is 4-6 mm, which produces relatively large bubbles. This strongly stirs and mixes the MBBR packing as it rises from the bottom of the water. Ordinary tubular or disc-type microporous aerators cannot achieve this effect.

[0013] A further solution of the present invention is that an A-zone flow pusher is provided inside the A-zone, and an O-zone flow pusher is provided inside the O-zone.

[0014] A further solution of the present invention is that the flow generator in zone A is arranged at a radius of 1 / 2 to 2 / 3 of the center point along the diameter of the bottom of zone A. There are 1 to 2 flow generators in zone A. The two flow generators can be arranged side by side or rotationally symmetrically along the diameter of zone A. The flow generator in zone A is used to maintain the MBBR filler in a suspended state to prevent it from settling or floating. It can also cause the filler to rotate along the perforated mesh wall, which has a friction and cleaning effect on the perforated mesh, preventing the filler from accumulating near the perforated mesh due to the thrust of the water flow, thereby obstructing normal water flow.

[0015] A further solution of the present invention is that the O-zone flowmaker is arranged at the bottom of the O-zone at a distance of 1 / 2 to 2 / 3 of the ring width from the outer cylinder wall of the A-zone along its diameter direction. There are 1 to 2 O-zone flowmakers, and the two O-zone flowmakers can be arranged side by side or rotationally symmetrically along the diameter of the O-zone. The O-zone flowmaker is used to maintain the MBBR filler in a suspended state to prevent it from settling or floating. It can also cause the filler to roll up and down and suspend while rotating along the perforated mesh wall, which has a frictional cleaning effect on the perforated mesh, preventing the filler from accumulating near the perforated mesh due to the thrust of the water flow, thereby obstructing normal water flow.

[0016] A further solution of the present invention is that the power of the flow generator in zone A and zone O is 3-7W / m 3 According to relevant specifications, the power required for stirring in ordinary activated sludge systems is about 3-8W / m 3 In practical applications, 10W / m 3 In the MBBR system, the specific gravity of the filler is about 0.95, and it tends to float spontaneously. Related research shows that under normal circumstances, the power required to maintain the filler suspension is 30W / m 3 In this scheme, due to the use of a circular cylinder, the hydraulic conditions are good and the stirring power is greatly reduced to only 3~7W / m 3 .

[0017] A further solution of the present invention is that the height of the perforated mesh in zone A is 50% to 100% of the height of the outer cylinder wall of zone A; the height of the perforated mesh in zone O is 50% to 100% of the height of the outer cylinder wall of zone O; preferably, the perforated mesh in zone A and zone O are made of stainless steel, and the mesh diameters of the perforated mesh in zone A and zone O do not exceed 0.6 times the diameter of the MBBR filler.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. The utility model provides an AO biochemical tank body with a circular steel structure. By arranging an annular cylindrical O zone and a circular cylindrical A zone, the problem of low site area utilization efficiency in the traditional AO process in which the A zone and the O zone are arranged side by side in a circular steel structure tank body is solved. By providing an internal return pump pit and a water collection pit connected to the sump, it is ensured that the purified sewage in the O zone enters the internal return pump pit first, avoiding the internal return pump pit from being drained out.

[0020] 2. The utility model provides an AO biochemical tank body. By arranging a perforated mesh in zone A between zone A and zone O, and a perforated mesh in zone O between zone O and the sump, the MBBR transformation function is reserved. The treatment scale can be increased by gradually adding MBBR fillers, and the capacity can be expanded quickly and conveniently without stopping the water supply. Furthermore, by arranging flow pushers in zone O and zone A, the fillers can be caused to roll up and down while rotating along the perforated mesh wall, which has a friction and cleaning effect on the perforated mesh, and prevents the fillers from accumulating near the perforated mesh due to the thrust of the water flow, thereby obstructing the normal water flow. The bubbles generated by the fan-shaped perforated tube aerator have a larger diameter, and have a strong stirring and mixing effect on the MBBR fillers during the process of rising from the bottom of the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a schematic diagram of the overall structure of the biochemical tank of the present utility model;

[0023] Figure 2 This is a schematic diagram of the upper structure of the biochemical tank of the present utility model;

[0024] Figure 3 This is a schematic diagram of the lower structure of the biochemical tank body of the present utility model.

[0025] In the figure: 1. Outer cylinder wall of area A, 2. Perforated mesh of area A, 3. Outer cylinder wall of area O, 4. Perforated mesh of area O, 5. Aerator, 6. Flow pusher of area A, 7. Flow pusher of area O, 8. Internal reflux pump, 9. Collection tank, 10. Internal reflux pump pit, 11. Outlet collection pit, 12. Circular water hole, 13. Aeration main pipe, 14. Water inlet pipe, 15. Mud inlet pipe, 16. Outlet pipe, 17. Water baffle. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] Example 1

[0028] like Figure 1-3 As shown, Figure 1 The upper, lower, left and right directions are the relative upper, lower, left and right directions of the biochemical tank. Figure 2-3 The upper, lower, left and right directions are the relative front, rear, left and right directions of the biochemical tank.

[0029] A steel structure sewage treatment first-level AO biochemical tank comprises a steel structure tank body, wherein the tank body comprises a cylinder wall and a cylinder bottom, and the cylinder wall and the cylinder bottom form a cylindrical tank body with an upper opening.

[0030] The tank body includes an annular cylindrical O zone and a circular cylindrical A zone, which are spaced apart. The O zone and the A zone are connected. The tank body wall includes a two-layer structure, from the outside to the inside, namely the O zone outer cylinder wall 3 and the A zone outer cylinder wall 1. The O zone outer cylinder wall 3 and the A zone outer cylinder wall 1 form an annular cylindrical O zone with the bottom of the tank body. The A zone outer cylinder wall 1 and the inside of the cylinder bottom form the circular cylindrical A zone. The O zone and the A zone are connected. Specifically, the O zone and the A zone are connected through a circular water hole 12 provided at the bottom of the A zone outer cylinder wall 1, allowing sewage and sludge to enter the O zone. The circular water holes 12 are evenly distributed along the circumference of the A zone outer cylinder wall 1. Furthermore, the number of the circular water holes 12 is 4 to 12, and the diameter of the circular water holes 12 is 200 to 600 mm. Preferably, the number of the circular water holes 12 is 8, and the diameter of the circular water holes 12 is 400 mm.

[0031] The top of the A zone is provided with a water inlet pipe 14 and a mud inlet pipe 15. The O zone is provided with an aerator 5, which is connected to the aeration main pipe. Figure 1 As shown, a water collection trough 9 is provided above the O zone for collecting the purified sewage in the O zone. The water collection trough 9 is connected to the internal reflux pump pit 10 and the outlet collection pit 11. Specifically, the water collection trough 9 is annular and is welded by an annular plate with an L-shaped cross-section. The annular plate is made of stainless steel, and the bottom outer wall of the annular plate is welded to the upper end of the outer cylinder wall 3 of the O zone. The water collection trough 9 is formed between the vertical outer wall of the annular plate and the inner side of the outer cylinder wall 3 of the O zone.

[0032] A circumferential portion of the sump 9 is partially enlarged to form an internal reflux pump pit 10, which is used to house the internal reflux pump 8 and provide the internal reflux required for the AO process. A circumferential portion of the sump 9, symmetrical to the internal reflux pump pit 10, is partially sunken to form an outlet collection pit 11, through which the purified wastewater from Zone O enters the outlet pipe of the entire AO biochemical tank. The bottom of the internal reflux pump pit 10 is lower than the bottom of the outlet collection pit 11. Specifically, the bottom of the internal reflux pump pit 10 is 3-5 cm lower than the bottom of the outlet collection pit 11. This also ensures that the purified wastewater from Zone O enters the internal reflux pump pit 10 first, preventing it from being drained. As an alternative, when the bottom of the internal reflux pump pit 10 is flush with the bottom of the effluent collection pit 11, the effluent collection pit 11 is equipped with water retaining plates 17 within the sump 9 on both sides of the water inlet direction. Water flows over the retaining plates 17 before entering the effluent collection pit 11. The internal reflux pump pit 10 is connected to Area A via the internal reflux pump 8 and pipelines, providing the internal reflux required for the AO process. The effluent collection pit 11 is connected to the effluent pipe 16.

[0033] The above-described layout of Zones O and A solves the problem of low site utilization efficiency in the traditional AO process, where Zones A and O are arranged side by side in a circular steel tank structure. Initially, during conventional activated sludge operation, return sludge flows through the sludge inlet pipe 15 and water flows through the water inlet pipe 14, overhead, directly into Zone A.

[0034] Example 2

[0035] This embodiment is based on Example 1. In order to realize the reserved modification function of the MBBR process of the AO biochemical tank, a further solution is that the A zone is provided with an A zone perforated mesh 2 for preventing the MBBR filler in the A zone from entering the O zone, and the O zone is provided with an O zone perforated mesh 4 for preventing the MBBR filler in the O zone from entering the sump.

[0036] A further solution of the present invention is that an A-zone flow promoter 6 is provided inside the A-zone, and an O-zone flow promoter 7 is provided inside the O-zone.

[0037] Specifically, the flow generator 6 in zone A is arranged at a radius of 1 / 2 to 2 / 3 from the center point along the diameter direction of the bottom of zone A. One or two flow generators 6 in zone A are provided. One flow generator 6 in zone A can be arranged on one side along the diameter direction of zone A. Two flow generators 6 in zone A are arranged rotationally symmetrically along the diameter of zone A. The flow generator 6 in zone A is used to maintain the MBBR filler in a suspended state so as not to settle or float. It can also cause the filler to rotate and flow along the perforated mesh wall, which has a friction and cleaning effect on the perforated mesh, thereby preventing the filler from accumulating near the perforated mesh due to the thrust of the water flow, thereby obstructing the normal water flow.

[0038] The O zone flow generator 7 is set at the bottom of the O zone at a distance of 1 / 2 to 2 / 3 of the ring width from the outer cylinder wall 1 of the A zone along its diameter direction. There are 1 or 2 O zone flow generators 7. When there is 1 O zone flow generator 7, it can be set on one side along the diameter direction of the O zone. The 2 O zone flow generators 7 are arranged rotationally symmetrically along the diameter of the O zone. The O zone flow generator 7 is used to maintain the MBBR filler in a suspended state to prevent it from settling or floating. It can also make the filler roll up and down and suspend while rotating along the perforated mesh wall, which has a friction and cleaning effect on the perforated mesh, and prevents the filler from accumulating near the perforated mesh due to the thrust of the water flow, thereby obstructing the normal water flow.

[0039] The power of flow generator 6 in zone A and flow generator 7 in zone O is 3~7W / m 3 According to relevant specifications, the power required for stirring in ordinary activated sludge systems is about 3-8W / m3, and 10W / m3 is often used in practical applications. 3 In the MBBR system, the specific gravity of the filler is about 0.95, and it tends to float spontaneously. Related research shows that under normal circumstances, the power required to maintain the filler suspension is 30W / m 3 In this scheme, due to the use of a circular cylinder, the hydraulic conditions are good and the stirring power is greatly reduced to only 3~7W / m 3 .

[0040] The height of the perforated mesh 2 in zone A is 50% to 100% of the height of the outer cylinder wall 1 in zone A; the height of the perforated mesh 4 in zone O is 50% to 100% of the height of the outer cylinder wall 3 in zone O; preferably, the perforated mesh 2 in zone A and the perforated mesh 4 in zone O are made of stainless steel, and the mesh diameters of the perforated mesh 2 in zone A and the perforated mesh 4 in zone O do not exceed 0.6 times the diameter of the MBBR filler.

[0041] The aerator 5 includes several sets of fan-shaped perforated tube aerators, which are arranged on the bottom of the cylinder at the bottom of zone O. Preferably, there are eight sets of fan-shaped perforated tube aerators. The aeration holes of the aerator 5 have a diameter of 4-6 mm, which produces large bubbles. As they rise from the bottom of the water, they can strongly stir and mix the MBBR filler. Ordinary tubular or disc-type microporous aerators cannot achieve this effect.

[0042] When capacity expansion is needed, the AO biochemical tank provided by this invention can be increased by gradually adding MBBR filler, without the need for water shut-down or modification. Later, when operating according to the MBBR process, sludge return is not required, and only the water inlet pipe 14 is overhead, directly entering Zone A.

[0043] Specific example

[0044] According to the above technical solution, this specific example has a daily processing capacity of 30,000 m 3 / d reserved MBBR transformation function circular steel structure sewage treatment AO biochemical tank, the design scale of this embodiment is 30,000 m 3 / d, the designed water depth is 7.5m, and the designed volumes of Zone A and Zone O are 1580m 3 and 7370m 3 Therefore, the diameter of the outer cylinder wall 1 of zone A is 16.4m, and the diameter of the outer cylinder wall 3 of zone O is 39m. Eight circular water holes 12 with a diameter of 400mm are evenly distributed along the circumference at the bottom of the outer cylinder wall 1 of zone A. A water collection trough 9 with a depth of 500mm and a width of 500mm is set on the inner side of the outer cylinder wall 3 of zone O to collect the purified sewage in zone O. The water collection trough 9 on the left side of the outer cylinder wall 3 of zone O is partially expanded to form an internal reflux pump pit 10, and the water collection trough 9 on the right side of the cylinder wall of zone O is partially sunken to form a water collection pit 11. 5cm high water retaining plates 17 are set on the front and back sides of the bottom of the water collection trough 9 near the water collection pit 11.

[0045] A stainless steel perforated mesh 2 is installed inside the outer cylinder wall 1 of Zone A, with a mesh height of 4.0m. A perforated mesh 4 is installed inside the outer cylinder wall 3 of Zone O, intercepting the MBBR filler and preventing it from entering the sump 9 and causing blockage in the pipeline. The MBBR filler used in the design has a diameter of 25mm, a mesh size of 12mm, and a mesh height of 4.0m.

[0046] One A-zone flowmaker 6 is set at 5.0m from the center point in the diameter direction of zone A, with a single power of 5.5kw. Two O-zone flowmakers 7 are set at both sides of the bottom of zone O, with a single power of 5.5kw. The average power is 3.48W / m 3 .

[0047] At the bottom of zone O, 8 sets of fan-shaped perforated tube aerators are set up, with aeration holes of 4 mm in diameter. Each set is provided with 2 flange interfaces connected to the aeration main pipe 13.

[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the present invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed within the present invention. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A steel structure sewage treatment first-level AO biochemical tank, characterized by: The invention comprises a tank body, wherein the tank body comprises an annular cylindrical O zone and a circular cylindrical A zone arranged at intervals, wherein the O zone and the A zone are connected, a water inlet pipe (14) and a mud inlet pipe (15) are laid on the top of the A zone, an aerator (5) is provided in the O zone, and the aerator (5) is connected to the aeration main pipe, a water collecting trough (9) is provided above the O zone, the water collecting trough (9) is connected to both the internal reflux pump pit (10) and the outlet water collecting pit (11), water in the water collecting trough (9) preferentially enters the internal reflux pump pit (10), the internal reflux pump pit (10) is connected to the A zone through the internal reflux pump (8) and the pipeline, and the outlet water collecting pit (11) is connected to the outlet water pipe (16); the A zone is provided with an A zone perforated net (2) for preventing the MBBR filler in the A zone from entering the O zone, and the O zone is provided with an O zone perforated net (4) for preventing the MBBR filler in the O zone from entering the water collecting trough.

2. A steel structure sewage treatment first-level AO biochemical tank according to claim 1, characterized in that: The water collecting trough (9) is annular, and a portion of the water collecting trough (9) in the circumferential direction thereof is partially enlarged to form an inner reflux pump pit (10), and a portion of the water collecting trough (9) in the circumferential direction thereof that is symmetrical to the inner reflux pump pit (10) is partially sunken to form an outlet water collecting pit (11), and the outlet water collecting pit (11) is provided with water retaining plates (17) in the water collecting trough (9) on both sides of the water inlet direction thereof.

3. A steel structure sewage treatment first-level AO biochemical tank according to claim 2, characterized in that: The tank body comprises a cylinder wall and a cylinder bottom, and the cylinder wall and the cylinder bottom form a cylindrical tank body with an upper opening. The cylinder wall of the tank body comprises two layers of structures, namely, an outer cylinder wall (3) of the O zone and an outer cylinder wall of the A zone, from the outside to the inside. The outer cylinder wall (3) of the O zone and the outer cylinder wall of the A zone form the O zone with the cylinder bottom of the tank body, and the outer cylinder wall of the A zone and the inside of the cylinder bottom form the A zone. The O zone and the A zone are connected through a circular water hole (12) provided at the bottom of the outer cylinder wall of the A zone, and the circular water hole (12) is evenly distributed along the circumference of the outer cylinder wall of the A zone.

4. A steel structure sewage treatment first-level AO biochemical tank according to claim 3, characterized in that: The number of the circular water holes (12) is 4 to 12, and the diameter of the circular water holes (12) is 200 to 600 mm.

5. A steel structure sewage treatment first-stage AO biochemical tank according to any one of claims 1 to 4, characterized in that: The aerator (5) comprises a plurality of groups of fan-shaped perforated tube aerators, and the plurality of groups of fan-shaped perforated tube aerators are arranged on the bottom of the cylinder at the bottom of the O zone.

6. A steel structure sewage treatment first-level AO biochemical tank according to claim 5, characterized in that: An A-zone flow pusher (6) is provided inside the A-zone, and an O-zone flow pusher (7) is provided inside the O-zone.

7. A steel structure sewage treatment first-level AO biochemical tank according to claim 6, characterized in that: The A zone flow pusher (6) is arranged at the bottom of the A zone at a radius of 1 / 2 to 2 / 3 from the center point along the diameter direction thereof, and 1 to 2 A zone flow pushers (6) are provided.

8. The steel structure sewage treatment first-level AO biochemical tank according to claim 6, characterized in that: The O zone flow promoter (7) is arranged at the bottom of the O zone at a distance of 1 / 2 to 2 / 3 of the ring width from the outer cylinder wall (1) of the A zone along the diameter direction thereof, and 1 to 2 O zone flow promoters (7) are provided.

9. The steel structure sewage treatment first-stage AO biochemical tank according to claim 5, characterized in that: The fan-shaped perforated tube aerators are provided in 8 groups, and the diameter of the aeration holes is 4-6 mm.

10. A steel structure sewage treatment first-stage AO biochemical tank according to any one of claims 6-8, characterized in that: The height of the perforated mesh (2) in zone A is 50% to 100% of the height of the outer cylinder wall (1) in zone A; the height of the perforated mesh (4) in zone O is 50% to 100% of the height of the outer cylinder wall (3) in zone O; and the mesh diameters of the perforated mesh (2) in zone A and the perforated mesh (4) in zone O do not exceed 0.6 times the diameter of the MBBR filler.

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