Micro-porous aerator and water treatment aeration system

Abstract

The application discloses a microporous aerator and a water treatment aeration system. The aeration system comprises an interface pipe (3) connected with a gas supply pipeline, a support body (1) in an ellipsoidal structure and having a long axis and a short axis, the long axis of the support body (1) being connected with the interface pipe (3) at one end, and the support body (1) being uniformly provided with first holes; and a microporous membrane (2) in a thin film piece with elasticity, the microporous membrane (2) being integrally coated on the outer surface of the support body (1) and uniformly provided with second holes; wherein the diameter of the first holes is larger than that of the second holes, and airflow enters the ellipsoidal inner cavity of the support body (1) from the interface pipe (3), passes through the first holes and the second holes and is discharged. The ellipsoidal design of the support body can obtain the beneficial effects of full liquid phase uniform aeration, no blind area at the bottom of the pool, long service life and stable operation.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a microporous aerator and a water treatment aeration system. Background Technology

[0002] In the field of water treatment, aerators are often used as terminal air diffusion devices in water treatment aeration systems. They are generally installed underwater and serve to oxygenate, distribute air, and agitate the water tank. Many existing aeration devices exist, such as aeration pipes, aeration discs, and diffuser aerators, but they all suffer from low oxygen utilization and are prone to breakage. Furthermore, aerators used in aerobic treatment tanks typically aerate upwards, resulting in aeration blind spots and sludge accumulation between the aerator's location and the tank bottom. Summary of the Invention

[0003] The purpose of this invention is to provide a microporous aerator and a water treatment aeration system. Through the design of the ellipsoidal support, the air pressure is evenly distributed, which extends the service life of the aerator. In addition, the ellipsoidal support allows the openings of the microporous rubber membrane to be arranged in all directions along the ellipsoid, increasing the number of openings and the air passage. At the same time, the openings facing the bottom of the pool can prevent the accumulation of sludge at the bottom of the pool during operation.

[0004] This invention provides a microporous aerator, comprising: An interface pipe, which is connected to the gas supply line; The support body is an ellipsoidal structure with a major axis and a minor axis. One end of the major axis of the support body is connected to the interface pipe. The support body has first holes evenly distributed on it. A microporous membrane, wherein the microporous membrane is an elastic thin film, the microporous membrane is entirely covered on the outer surface of the support, and the microporous membrane has second pores evenly distributed on it; The diameter of the first hole is larger than that of the second hole. The airflow enters the ellipsoidal cavity of the support body from the interface pipe and then exits through the first and second holes.

[0005] Optionally, a fixing clip is also included, which is disposed at the connection between the interface tube and the support body, and the edge of the microporous membrane is locked to the outer periphery of the interface tube by the fixing clip.

[0006] Optionally, it also includes a band that surrounds and binds the microporous membrane on the outer peripheral wall corresponding to the long axis of the support, in order to limit the radial expansion of the microporous membrane in the inflated state and prevent the membrane material from being overstretched and ruptured.

[0007] Optionally, the strap is a non-metallic flexible strap, which, after being tightened, leaves a gap between itself and the microporous membrane to allow the membrane material to expand slightly under rated air pressure. The strap is arranged around the outer peripheral wall of the middle part of the long axis of the support, and has a width of 5-20 mm; and / or, The interface tube is located at one end of the long axis, with its axis collinear with the long axis. The microporous membrane continuously transitions and wraps around the interface tube from the remaining surface of the ellipsoid. The fixing clip is a hose clamp or a spring clip locking device; and / or... A sealing ring is also provided between the outer peripheral wall of the interface tube and the fixing clip. The sealing ring is a corrosion-resistant rubber ring, which is used to prevent gas from leaking out from the connection between the interface tube and the microporous membrane.

[0008] Optionally, the ratio of the major axis to the minor axis of the support is 2.5:1 to 3.5:1.

[0009] Optionally, the support body is made of UPVC material; and / or, The support body and the interface tube are integrally formed; and / or, The interface pipe is an externally threaded pipe with an inner diameter of 20~30mm; and / or, The microporous membrane is made of rubber.

[0010] Optionally, the pore diameter of the first pore on the support body is in the range of 2~4mm; the pore diameter of the second pore of the microporous membrane is in the range of 50~100μm.

[0011] Optionally, the microporous membrane is a single-layer structure, and its wall thickness remains consistent from the interface tube end towards the ellipsoidal equator or gradually changes by a ratio not greater than 1.5:1.

[0012] Another aspect of the present invention provides a wastewater treatment aeration system, comprising: An aeration tank, an air supply pipeline laid at the bottom of the aeration tank, and multiple microporous aerators as described in the preceding item; The air supply pipeline includes a main aeration pipe and multiple aeration pipes connected to it. Each aeration pipe is arranged in parallel within the aeration tank, and each aeration pipe is equipped with multiple microporous aerators.

[0013] Optionally, two pairs of microporous aerators are symmetrically connected to both sides of the aeration pipe, and the major axis of the microporous aerators extends radially along the aeration pipe in the horizontal plane; or, The microporous aerators on two adjacent parallel aeration pipes are arranged in an alternating pattern on the bottom surface of the aeration tank to eliminate the aeration blind zone at the bottom of the tank. The ellipsoidal bottom of the paired microporous aerators faces the bottom of the tank, and the air outlet direction of the micropores is diagonally downward or laterally diffused.

[0014] The microporous aerator and wastewater treatment aeration system provided by this invention offer the following significant advantages compared to existing technologies: 1. The membrane material is subjected to uniform stress, resulting in a significantly extended service life. The ellipsoidal shell is a typical high-pressure-bearing structure with continuously varying curvature. Under operating air pressure, the ellipsoidal support can uniformly transfer internal air pressure to the microporous membrane, avoiding the stress concentration at the edges of disc aerators or the uneven axial linear stress in tubular aerators. Combined with the restraining effect of the straps on the mid-axis of the microporous membrane and the reserved micro-expansion gaps, it limits excessive expansion of the membrane material in non-operating states while ensuring normal expansion under rated air pressure. This greatly reduces local tensile fatigue, significantly extends the service life of the membrane material, and lowers the replacement frequency.

[0015] 2. Excellent ability to prevent mud accumulation, resulting in a high degree of cleanliness at the bottom of the pool. The ellipsoidal structure has excellent streamlined characteristics, and its surface is less prone to forming stagnant water dead zones. Especially in the installation mode with the long axis vertical or inclined downward, the lower half (bottom) of the ellipsoid can generate a "broom"-like hydraulic sweeping effect, using the upward force of the bubble plume to drive the bottom sludge to move, fundamentally solving the problem of sludge accumulation and the formation of dead sludge layers at the bottom of traditional disc aerators, and maintaining a high degree of cleanliness at the bottom of the pool.

[0016] 3. Uniform bubble distribution significantly enhances oxygen transfer efficiency. With an optimal ratio of 2.5:1 to 3.5:1 between the major and minor axes, a pressure gradient naturally forms as the gas flows within the cavity, encouraging more gas to flow towards the more curved end region and avoiding uneven gas output caused by the "end effect" in tubular aerators. Uniform microbubbles (50~100μm) significantly increase the gas-liquid contact area, contributing to improved oxygen transfer efficiency.

[0017] 4. Small and uniform bubble diameter, resulting in low energy consumption. The first pore (2-4 mm) on the support initially disperses the airflow, which is then further cut through the second pore (50-100 μm) on the microporous membrane, generating tiny and uniform bubbles. Furthermore, the UPVC support is lightweight and high-strength, and the integrated interface pipe reduces installation difficulty and pipeline load, achieving efficient aeration with low energy consumption.

[0018] 5. Compact structure, high rigidity, and good resistance to deformation. Compared to solid spheres or large-volume spherical structures, the ellipsoidal support significantly reduces the underwater windward area while maintaining the internal air chamber volume. Combined with the lightweight and high-strength properties of UPVC material and the restraint along the long axis, the entire aerator remains stable under water flow impact and high-frequency vibration, preventing displacement, overturning, or excessive deformation, thus ensuring operational reliability.

[0019] 6. The system is flexible in layout and provides aeration without dead zones. Based on the axisymmetric characteristics of the ellipsoidal structure, the system supports multiple modes, including horizontal radial extension and staggered arrangement. In the staggered arrangement, the bubble curtains generated by adjacent aerators overlap, and the streamlined surface of the ellipsoid guides the water flow to form an orderly large-scale circulation, completely eliminating dead corners at the bottom of the tank. This makes it particularly suitable for the aeration requirements of high-concentration activated sludge processes and deep-water tanks.

[0020] 7. High structural integration, stable and reliable operation. The microporous membrane features a single-layer structure with a gradually varying wall thickness, optimizing its elastic response speed and making its opening and closing more sensitive. The combination of non-metallic flexible straps and hose clamp-type fixing clips not only provides corrosion resistance but also adapts to the complex acid and alkaline environments of wastewater treatment sites, ensuring long-term stable operation of the equipment and reducing maintenance costs throughout its entire lifecycle.

[0021] 8. The equipment has a simple structure and is suitable for widespread application. With fewer overall components and an externally threaded interface pipe, coupled with a sealing ring, this device ensures excellent airtightness and facilitates easy disassembly and maintenance. Compared to traditional aeration equipment, this device simplifies the structure and reduces manufacturing costs while maintaining high performance, making it suitable for widespread application in various municipal and industrial wastewater treatment projects. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a plan view of a microporous aerator according to the present invention; Figure 2 This is a cross-sectional view of a microporous aerator according to the present invention, showing the ellipsoidal support, interface pipe and internal flow channel structure; Figure 3 This is a diagram showing the micropore arrangement of the microporous rubber membrane in this invention, illustrating the distribution of the second pores on the membrane surface; Figure 4 This is a top view of the connection arrangement of a microporous aerator according to the present invention, showing the installation position relationship of multiple aerators on the aeration pipe.

[0024] Explanation of reference numerals in the attached figures: 1-Support body; 2-Microporous membrane; 3-Interface tube; 4-Fixing clip; 5-Sealing ring; 6-Strap; 7-Aeration pipe. Detailed Implementation

[0025] Numerous specific details are set forth in the following description to provide a full understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] It should be understood that the terminology used in this invention is for describing specific embodiments only and is not intended to limit the invention. Regarding numerical ranges in this invention, intermediate values ​​between the upper and lower limits of the range are also specifically disclosed, as well as smaller ranges defined by any two of the stated values; unless the context clearly indicates otherwise, the upper and lower limits of the smaller ranges may be independently included within the scope of this invention.

[0027] Unless otherwise stated, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described in this invention, any methods and materials similar to or equivalent to those described herein may be used in the practice or testing of this invention.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0029] Combination Figures 1 to 4 As shown, a novel microporous aerator and wastewater treatment system according to an embodiment of the present invention includes a support body 1, a microporous membrane 2, an interface pipe 3, a fixing clip 4, a sealing ring 5, and a strap 6.

[0030] Example 1: Single-unit structure of microporous aerator like Figure 1 (Plan view of microporous aerator) and Figure 2 (Cross-sectional view of the microporous aerator) As shown in this embodiment, a novel microporous aerator is provided.

[0031] 1. Support structure The support body 1 is ellipsoidal, with a preferred ratio of 3:1 between its major and minor axes. This ratio has been optimized for hydrodynamics, ensuring sufficient internal air space while maintaining a streamlined underwater profile, which helps reduce water flow resistance and enhances the sweeping effect on the pool bottom. The support body 1 is made of UPVC (rigid polyvinyl chloride), a material with excellent corrosion resistance, high mechanical strength, and moderate density, making it suitable for long-term immersion in wastewater environments.

[0032] Except for the area where the interface pipe 3 is located, the rest of the support body 1 is a UPVC board with uniformly perforated holes. Specifically, the hole diameter is set to 3mm, and the total number of holes is 70. This uniform and dense perforation design can quickly and evenly distribute the airflow from the interface pipe 3 to the entire ellipsoidal cavity, thereby ensuring that the microporous membrane 2 covering the outer surface of the support body 1 is subjected to uniform stress and avoiding damage to the membrane material caused by excessive local air pressure.

[0033] 2. Microporous aeration components The microporous membrane 2 is an elastic thin film component, preferably made of ethylene propylene diene monomer (EPDM) rubber, which possesses excellent resistance to aging, ozone, and acids and alkalis. The microporous membrane 2 has a large number of micropores distributed on it, with the pore size strictly controlled within the range of 50~100μm. This small pore size ensures that the produced bubbles are small and uniform in diameter, thereby significantly improving the gas-liquid contact area and oxygen transfer efficiency. The microporous membrane 2 is tightly adhered to the outer surface of the support 1, and undergoes elastic deformation with changes in internal gas pressure, thus opening and closing the micropores.

[0034] 3. Connection and sealing structure The interface pipe 3 is located at one end of the long axis of the support body 1, with its axis collinear with the long axis. The interface pipe 3 and the support body 1 can be detachably connected or integrally injection molded, preferably as a plastic part. The interface pipe 3 has an external thread interface, which can be directly threaded to the aeration pipe, making installation and disassembly extremely convenient. The inner diameter of the interface pipe 3 is set to 25mm, a size that can match the diameter of conventional air supply branch pipes, ensuring smooth air intake. At the innermost part of the interface pipe 3 (i.e., the root where it connects to the support body 1), a sealing ring 5 is provided, preferably made of rubber. This sealing ring 5 undergoes elastic deformation after the interface pipe 3 is tightened, filling the connection gap and playing a crucial sealing role in preventing gas leakage.

[0035] 4. Membrane material fixing and protection device The fixing clip 4 is located at the interface tube 3, specifically on the outer peripheral wall of the interface tube 3. Its function is to firmly lock the edge of the microporous membrane 2 (i.e., the open end of the membrane) to the support body 1, preventing the membrane material from shifting or falling off during operation. The fixing clip 4 is preferably a hose clamp type structure, which has strong fastening force and is corrosion resistant.

[0036] To prevent excessive expansion or even rupture of the microporous membrane 2 under high ventilation rates or pressure fluctuations, a brace 6 is provided along the long axis of the support 1. Figure 2 As shown, the reinforcing band 6 is arranged around the major axis (i.e., the maximum circumference) of the ellipsoid of the support 1. The reinforcing band 6 is usually made of a non-metallic material (such as reinforced nylon or polyester fiber) with certain rigidity and toughness. Its function is to physically restrain the microporous membrane 2, limiting its radial expansion range under inflated conditions. When the internal air pressure is too high, the reinforcing band 6 will resist the expansion force of the membrane material, thereby effectively preventing excessive expansion and cracking of the microporous membrane 2 caused by excessive air velocity or abnormal pressure, and significantly extending the service life of the membrane material.

[0037] The technical effect mechanism of this embodiment: The ellipsoidal support 1 design allows for more even air pressure distribution, extending the lifespan of the frame. Furthermore, the ellipsoidal support increases the coverage area of ​​the microporous membrane 2, and the 70 through-holes increase the number of ventilation holes, thereby increasing the airflow of a single aerator. Compared to traditional disc or tubular aerators, the ellipsoidal structure in this embodiment effectively reduces the aeration blind zone at the bottom of the pool, minimizing sludge accumulation.

[0038] Example 2: Micropore distribution characteristics of microporous membranes like Figure 3 As shown in the diagram of microporous rubber membrane micropore arrangement, the micropores on the microporous membrane 2 are not randomly distributed, but are arranged in a uniform array or a non-uniformly dense arrangement.

[0039] In the preferred embodiment, the micropore density of the microporous membrane 2 is slightly higher on the side facing the bottom of the tank (i.e., the lower half of the ellipsoid) than on the upper half. This design is based on hydrodynamic considerations: when the aerator is working, the bubbles move upward due to buoyancy. Appropriately increasing the air output of the lower half can more effectively agitate the sludge deposited at the bottom of the tank, preventing sludge compaction. Simultaneously, the pore size range of 50~100μm ensures that the bubbles can form a good micron-sized bubble cluster when leaving the membrane surface, improving oxygen utilization. The microporous membrane 2 adopts a single-layer structure, with the wall thickness remaining consistent from the interface pipe 3 end towards the equator of the ellipsoid, ensuring consistent elastic response throughout the membrane material.

[0040] Example 3: Wastewater Treatment Aeration System and Application Case like Figure 4 (As shown in the connection arrangement diagram of the application example of the novel microporous aerator), the present invention also provides a sewage treatment aeration system, which includes an aeration tank, an aeration main pipe laid at the bottom of the tank, multiple aeration pipes 7 connected thereto, and multiple microporous aerators as described in Example 1.

[0041] Installation and Connection: Each aeration pipe 7 is arranged in parallel at the bottom of the aeration tank. Multiple novel microporous aerators are connected to each aeration pipe 7 via an interface pipe 3 (using its 25mm inner diameter threaded structure). A sealing ring 5 at the base of the interface pipe 3 ensures a tight seal, preventing air leakage or wastewater seepage into the pipe.

[0042] Deployment mode: To maximize aeration and eliminate dead zones, the microporous aerators on adjacent parallel aeration pipes 7 are arranged in a staggered or symmetrical pattern on the bottom of the aeration tank. Combined with... Figure 4 Two microporous aerators are arranged in pairs and connected symmetrically on both sides of the aeration pipe, and the long axis of the microporous aerators extends radially along the aeration pipe in the horizontal plane.

[0043] In another embodiment, the microporous aerators on two adjacent parallel aeration pipes are staggered on the bottom surface of the aeration tank to eliminate aeration blind zones at the bottom. The ellipsoidal bottoms of the paired microporous aerators face the bottom of the tank, and the air outlet direction is obliquely downward or laterally diffused. In this mode, the ellipsoidal bottoms of the paired microporous aerators face the bottom of the tank, and the air outlet direction is obliquely downward or laterally diffused. Due to the ellipsoidal structure of the support 1, it has excellent streamlined characteristics underwater, and the bubble plume generated during aeration can continuously sweep across the bottom of the tank, preventing sludge deposition.

[0044] Working principle: After the blower is started, compressed air enters the ellipsoidal cavity of the support body 1 through the aeration pipe 7 and the interface pipe 3. The airflow is initially dispersed through 70 3mm through holes (the first hole), and then compresses the microporous membrane 2. Under the rated air pressure, the microporous membrane 2 slightly bulges over the restraint of the strap 6, the micropores open, and the airflow passes through the micropores to form tiny bubbles that enter the water. Due to the continuous change in curvature of the ellipsoidal support body 1, the internal air pressure can be evenly transmitted to all parts of the microporous membrane 2, making the air output more uniform across the entire membrane surface. When the air supply stops, the microporous membrane 2 automatically adheres to the support body 1 under its own elastic restoring force and water pressure, the micropores close, and the mixed liquid is prevented from flowing back into the support body.

[0045] Experimental results show that the microporous aerator with the aforementioned ellipsoidal structure provides approximately 20% more service area than a disc aerator of the same size. Due to the sweeping effect of the ellipsoidal base on the tank bottom, the sludge thickness at the bottom is reduced by more than 80%. Furthermore, thanks to the graded flow channels (a combination of through-holes and micropores) and uniform membrane stress, the aerator exhibits excellent oxygen transfer efficiency (OTE) in clear water tests, and the microporous membrane showed no signs of rupture or tearing after continuous operation, resulting in a significantly extended service life.

[0046] In summary, the novel microporous aerator and system provided by this invention has the advantages of simple structure, convenient installation, large air volume, long service life and significant anti-sludge effect, and is suitable for promotion and application in various sewage treatment projects.

[0047] It should be noted that although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims of the present invention.

Claims

1. A microporous aerator, characterized in that, include: Interface pipe (3), which is connected to the gas supply pipeline; Support body (1), the support body (1) is an ellipsoidal structure with a major axis and a minor axis, one end of the major axis of the support body (1) is connected to the interface pipe (3), and the support body (1) has first holes evenly distributed on it; Microporous membrane (2), the microporous membrane (2) is an elastic thin film, the microporous membrane (2) is entirely covered on the outer surface of the support (1), and the microporous membrane (2) has second pores evenly distributed on it; The diameter of the first hole is larger than that of the second hole. After the airflow enters the ellipsoidal cavity of the support (1) through the interface pipe (3), it is discharged through the first hole and the second hole.

2. The microporous aerator according to claim 1, characterized in that, It also includes a fixing clip (4), which is set at the connection between the interface tube (3) and the support (1) to lock the edge of the microporous membrane (2) to the outer periphery of the interface tube (3).

3. The microporous aerator according to claim 2, characterized in that, It also includes a band (6), which surrounds and binds the microporous membrane (2) on the outer peripheral wall corresponding to the long axis of the support (1) to limit the radial expansion of the microporous membrane (2) in the inflated state and prevent the membrane material from being overstretched and ruptured.

4. The microporous aerator according to claim 3, characterized in that, The strap (6) is a non-metallic flexible strap. After being tightened, it leaves a gap between itself and the microporous membrane (2) to allow the membrane material to expand slightly under rated air pressure. The strap (6) is arranged around the outer peripheral wall of the middle part of the long axis of the support (1), and its width is 5-20 mm; and / or, The interface tube (3) is located at one end of the long axis, and the axis of the interface tube (3) is collinear with the long axis. The microporous membrane (2) continuously transitions and wraps around the interface tube (3) to the rest of the ellipsoidal surface. The fixing clip (4) is a hose clamp or snap ring locking device; and / or, A sealing ring (5) is also provided between the outer peripheral wall of the interface tube (3) and the fixing clip (4). The sealing ring (5) is a corrosion-resistant rubber ring used to prevent gas from leaking out from the connection between the interface tube (3) and the microporous membrane (2).

5. The microporous aerator according to claim 1, characterized in that, The ratio of the major axis to the minor axis of the support (1) is 2.5:1 to 3.5:

1.

6. The microporous aerator according to claim 1, characterized in that, The support (1) is made of UPVC material; and / or, The support (1) and the interface tube (3) are integrally formed; and / or, The interface pipe (3) is an externally threaded pipe with an inner diameter of 20~30mm; and / or, The microporous membrane (2) is made of rubber.

7. The microporous aerator according to claim 1, characterized in that, The diameter of the first hole on the support (1) is in the range of 2~4mm; the diameter of the second hole on the microporous membrane (2) is in the range of 50~100μm.

8. The microporous aerator according to claim 1, characterized in that, The microporous membrane (2) is a single-layer structure, and its wall thickness remains consistent from the end of the interface tube (3) toward the ellipsoidal equator or gradually changes by a ratio of no more than 1.5:

1.

9. A wastewater treatment aeration system, characterized in that, It includes an aeration tank, an air supply pipeline laid at the bottom of the aeration tank, and a plurality of microporous aerators as described in any one of claims 1 to 8; The air supply pipeline includes an aeration main pipe and multiple aeration pipes (7) connected to it. Each aeration pipe (7) is arranged in parallel in the aeration tank, and each aeration pipe (7) is equipped with multiple microporous aerators.

10. The wastewater treatment aeration system according to claim 9, characterized in that, Two microporous aerators are arranged in pairs and connected to both sides of the aeration pipe (7) in a symmetrical structure, and the long axis of the microporous aerators extends radially along the aeration pipe (7) in the horizontal plane. or, The microporous aerators on two adjacent parallel aeration pipes (7) are arranged in an alternating pattern on the bottom surface of the aeration tank to eliminate the aeration blind zone at the bottom of the tank. The bottom of the ellipsoid of the microporous aerators in pairs faces the bottom of the tank, and the air outlet direction of the micropores is diagonally downward or laterally diffused.

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