Gravity-driven backflow sewage treatment device and working method thereof

Abstract

The present application relates to the technical field of domestic sewage treatment, and particularly relates to a gravity-driven backflow sewage treatment device and a working method thereof. The sewage treatment device comprises an anoxic tank, an aerobic tank, a sedimentation tank and a backflow assembly. The anoxic tank, the aerobic tank and the sedimentation tank are arranged in parallel in sequence. The upper side of the anoxic tank is provided with a water inlet pipe. The lower side of the aerobic tank is communicated with the lower side of the anoxic tank. The upper side of the sedimentation tank is communicated with the upper side of the aerobic tank. The upper side of the sedimentation tank is provided with a drainage weir. The backflow assembly comprises a clean water tank and a backflow pipe. The clean water tank is vertically slidably arranged in the anoxic tank. The clean water tank is provided with a water outlet pipe at the bottom. The backflow pipe is communicated with the drainage weir and the lower side of the clean water tank. The present application solves the problems of high energy consumption and high dissolved oxygen caused by the backflow of nitrification liquid in the commonly used sewage treatment process.

Description

Technical Field

[0001] This invention relates to the field of domestic sewage treatment technology, and in particular to a gravity-driven recirculation sewage treatment device and its working method. Background Technology

[0002] Domestic sewage is wastewater discharged from residents' daily lives, mainly originating from residential and public buildings. The pollutants contained in domestic sewage are primarily organic matter. Organic matter in domestic sewage is extremely unstable and easily decomposes, producing foul odors. Bacteria and pathogens use the organic matter in domestic sewage as nutrients to multiply rapidly, leading to the spread of infectious diseases. Therefore, domestic sewage must be purified through sewage treatment equipment before being discharged.

[0003] Currently, the most commonly used nitrogen removal process in wastewater treatment is the "nitrification-denitrification" process. Nitrifying bacteria and other microorganisms oxidize ammonia nitrogen into nitrate, while denitrifying bacteria reduce nitrate back to nitrogen gas, thus achieving the removal of total nitrogen (TN) nutrients. The "nitrification-denitrification" process generally uses lift pumps or airlift recirculation. Pump recirculation significantly increases equipment investment costs and operating energy consumption, and also leads to a higher overall equipment failure rate. Airlift recirculation, which uses aeration to drive the return water, reduces equipment investment costs to some extent, but the air volume required for nitrification liquor recirculation also necessitates a larger blower size, increasing equipment operating costs. Simultaneously, the recirculation of the mixed liquor from the aerobic tank to the anoxic tank via airlift increases the dissolved oxygen content in the anoxic tank, inhibiting denitrification and reducing TN treatment efficiency. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a gravity-driven recirculation wastewater treatment device to solve the problems of energy consumption and excessive dissolved oxygen caused by the recirculation of nitrification liquid in commonly used wastewater treatment processes.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] A gravity-driven recirculation wastewater treatment device includes an anoxic tank, an aerobic tank, a sedimentation tank, and a recirculation assembly. The anoxic tank, aerobic tank, and sedimentation tank are arranged in parallel. An inlet pipe is provided on the upper side of the anoxic tank, the lower side of the aerobic tank is connected to the lower side of the anoxic tank, and the upper side of the sedimentation tank is connected to the upper side of the aerobic tank. A drainage weir is provided on the upper side of the sedimentation tank. The recirculation assembly includes a clear water tank and a recirculation pipe. The clear water tank is slidably installed vertically inside the anoxic tank, and an outlet pipe is provided at the bottom of the clear water tank. The recirculation pipe connects the drainage weir and the lower side of the clear water tank.

[0007] Optionally, the reflux assembly further includes a guide rail bracket, which is fixedly installed inside the anoxic pool, and the clear water pool is slidably installed inside the guide rail bracket and can move up and down along the guide rail bracket.

[0008] Optionally, the return pipe includes a connected return rigid pipe and a return flexible pipe. The inlet of the return rigid pipe is connected to the drainage weir, and the return rigid pipe is arranged at an angle. The end connected to the drainage weir is higher than the end connected to the return flexible pipe. The outlet of the return flexible pipe is connected to the lower side of the clear water tank, and an outlet flexible pipe is connected between the outlet pipe and the clear water tank.

[0009] Optionally, a first electric valve for controlling the opening and closing is provided on the return pipe, and a second electric valve for controlling the opening and closing is provided on the outlet pipe.

[0010] Optionally, a first grid plate is provided at the connection between the aerobic tank and the anoxic tank, and a second grid plate is provided at the connection between the sedimentation tank and the aerobic tank.

[0011] Optionally, the anoxic pool is provided with a packing support, which is a cubic structure, and rope-shaped packing is installed on the packing support.

[0012] Optionally, the bottom of the aerobic tank is equipped with an aeration system, and the aerobic tank is equipped with aerobic biological carrier packing material.

[0013] Optionally, an inclined plate is provided on the upper side of the sedimentation tank, a sludge hopper is provided on the lower side of the sedimentation tank, and a sludge discharge pipe is provided on the lower side of the sludge hopper.

[0014] Optionally, a guide plate is provided on the side of the sedimentation tank, the upper side of the guide plate is connected to the aerobic tank, and the lower opening of the guide plate is located between the inclined plate of the sedimentation tank and the sludge hopper.

[0015] This invention also provides a method for operating the gravity-driven recirculation wastewater treatment device as described above, comprising:

[0016] At the beginning of an influent cycle, the clear water tank is full and completely submerged in the anoxic tank. At this time, the liquid level in the anoxic tank is higher than that in the aerobic tank. The equipment carries out biological reaction according to the "anoxic-aerobic" process, and the sewage flows from the anoxic tank into the aerobic tank by gravity.

[0017] At the start of the denitrification cycle, the clear water in the clear water tank is drained. At this time, the anoxic tank floats out of the clear water tank, and the liquid level in the anoxic tank begins to fall below the liquid level in the aerobic tank. The nitrified liquid begins to flow back, and the flow ends when the liquid levels in the two tanks are the same.

[0018] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0019] This equipment utilizes a floating clear water tank within the anoxic tank to achieve reflux from the aerobic to the anoxic zone via level difference and gravity. This significantly reduces operating energy consumption and solves the problem of excessive dissolved oxygen in the refluxed nitrification liquid. Compared to pump-based reflux, the equipment controls the water levels in the anoxic and aerobic tanks by the floating clear water tank, using the level difference to achieve reflux of the nitrification liquid, greatly reducing the power consumption required for reflux. Compared to air-lift reflux, the refluxed nitrification liquid contains less dissolved oxygen, making dissolved oxygen in the anoxic zone easier to control and ensuring the smooth progress of the denitrification reaction. Simultaneously, the selected blower is relatively smaller, significantly reducing overall operating costs.

[0020] Advantages of additional aspects of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application 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 recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the wastewater treatment equipment provided in an embodiment of the present invention;

[0023] Figure 2 This is a top view of the wastewater treatment equipment provided in an embodiment of the present invention;

[0024] Figure 3 This is a schematic diagram showing the positional relationship between the clear water pool and the anoxic pool provided in an embodiment of the present invention.

[0025] Figure 4 This is a schematic diagram showing the positional relationship of the clear water tank completely floating in the anoxic tank according to an embodiment of the present invention;

[0026] In the diagram: 1. Inlet pipe; 2. Anoxic tank; 3. Aerobic tank; 4. Sedimentation tank; 5. Clear water tank; 6. Outlet pipe; 7. First grating plate; 8. Second grating plate; 9. Guide plate; 2.1. Packing support; 2.2. Rope packing; 3.1. Aeration system; 3.2. Aerobic biological carrier packing; 4.1. Inclined plate; 4.2. Sludge hopper; 4.3. Sludge discharge pipe; 4.4. Drainage weir; 4.5. First electric valve; 4.6. Return rigid pipe; 5.1. Guide rail support; 5.2. Return hose; 5.3. Outlet hose; 5.4. Second electric valve;

[0027] The distances or dimensions between parts have been exaggerated to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0028] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] Example 1

[0030] like Figure 1 , Figure 2 As shown in the figure, this embodiment proposes a gravity-driven recirculation wastewater treatment device, including an anoxic tank 2, an aerobic tank 3, a sedimentation tank 4, and a recirculation assembly. The anoxic tank 2, aerobic tank 3, and sedimentation tank 4 are arranged in parallel. An inlet pipe 1 is provided on the upper side of the anoxic tank 2. The lower side of the aerobic tank 3 is connected to the lower side of the anoxic tank 2. The upper side of the sedimentation tank 4 is connected to the upper side of the aerobic tank 3. A drainage weir 4.4 is provided on the upper side of the sedimentation tank 4. The recirculation assembly includes a clear water tank 5 and a recirculation pipe. The clear water tank 5 is slidably installed vertically in the anoxic tank 2. An outlet pipe 6 is provided at the bottom of the clear water tank 5. The recirculation pipe connects the drainage weir 4.4 and the lower side of the clear water tank 5.

[0031] The tank is divided into an anoxic tank 2, an aerobic tank 3, and a sedimentation tank 4 by partitions. This tank is taller than conventional above-ground container-type tanks, increasing the effective water depth and improving the oxygen transfer efficiency of the aerators. This allows for the selection of smaller blowers, saving on equipment operating costs. An inlet pipe 1 is installed on the outside of the tank to introduce the wastewater to be treated. Inlet pipe 1 is installed in the upper middle part of the anoxic tank 2, and a 90° elbow is installed inside the tank to prevent water flow from scouring the clear water tank 5. The installation height of inlet pipe 1 is 10-20 cm higher than the maximum liquid level of the anoxic tank 2. The lower side of the aerobic tank 3 is connected to the lower side of the anoxic tank 2, allowing the wastewater treated in anoxic conditions to flow smoothly into the aerobic tank 3 and achieve backflow. The upper side of the sedimentation tank 4 is connected to the upper side of the aerobic tank 3, allowing the wastewater after aerobic treatment to enter the sedimentation tank 4 for solid-liquid separation. The clear water tank 5 is vertically slidably installed inside the anoxic tank 2. Its bottom is equipped with an outlet pipe 6 to control the water level in the clear water tank 5, enabling the return flow of nitrified liquid between the aerobic tank 3 and the anoxic tank 2. The return pipe connects the drainage weir 4.4 to the lower side of the clear water tank 5, utilizing the water level difference and gravity to achieve the return flow.

[0032] This equipment utilizes a floating clear water tank 5 within the anoxic tank 2 to achieve reflux from the aerobic zone to the anoxic zone via liquid level difference and gravity. This significantly reduces operating energy consumption and solves the problem of excessive dissolved oxygen in the refluxed nitrification liquid. Compared to pump reflux, the equipment controls the water levels in the anoxic tank 2 and aerobic tank 3 by the floating clear water tank 5, using the liquid level difference to achieve reflux of the nitrification liquid, greatly reducing the power consumption required for reflux. Compared to airlift reflux, the refluxed nitrification liquid contains less dissolved oxygen, making the dissolved oxygen in the anoxic zone easier to control and ensuring the smooth progress of the denitrification reaction. At the same time, the selected blower is relatively smaller, greatly reducing the overall operating cost.

[0033] The reflux assembly also includes a guide rail bracket 5.1, which is fixedly installed inside the anoxic tank 2. The clear water tank 5 is slidably installed inside the guide rail bracket 5.1 and can move up and down along the guide rail bracket 5.1. The clear water tank 5 is cylindrical and is installed via the guide rail bracket 5.1, which is connected to the tank body, ensuring that the clear water tank 5 can only move longitudinally along the guide rail bracket 5.1.

[0034] The return pipe includes a connected rigid return pipe 4.6 and a flexible return pipe 5.2. The inlet of the rigid return pipe 4.6 is connected to the drainage weir 4.4, and the rigid return pipe 4.6 is arranged at an angle, with the end connected to the drainage weir 4.4 (right end) higher than the end connected to the flexible return pipe 5.2 (left end). The return is achieved by utilizing the gravity difference, ensuring smooth water flow. The outlet of the flexible return pipe 5.2 is connected to the lower side of the clear water tank 5. A flexible outlet pipe 5.3 is connected between the outlet pipe 6 and the clear water tank 5, and the flexible outlet pipe passes outward from the bottom of the anoxic tank 2.

[0035] The return pipe 4.6 is equipped with a first electric valve 4.5 for controlling its opening and closing, and the outlet pipe 6 is equipped with a second electric valve 5.4 for controlling its opening and closing. These two electric valves, in conjunction with the inlet booster pump, allow the operator to precisely control the start and end of the return process according to the needs of the treatment process. This better maintains the stability of the inlet and outlet water flow, improves the stability of equipment operation, and enhances the system's automation level and ease of operation.

[0036] A first grid plate 7 is installed at the connection point between the aerobic tank 3 and the anoxic tank 2, and a second grid plate 8 is installed at the connection point between the sedimentation tank 4 and the aerobic tank 3. The pore size of the grid plate is smaller than the size of the carrier in the aerobic tank 3, preventing large particles of solid matter from entering the next treatment unit and ensuring the smoothness and efficiency of the treatment process.

[0037] Anoxic tank 2 is equipped with packing support 2.1, which consists of several independent cubic structures. The packing support 2.1 is arranged in a U-shape within the anoxic tank 2, with space reserved in the middle for installing a floating clear water tank 5. Rope-shaped anoxic biological carrier packing is installed on the packing support 2.1. This design provides a larger attachment area for microorganisms, promotes the reaction, and improves wastewater treatment efficiency.

[0038] The aerobic tank 3 has a Y-shaped support at its bottom, and the microporous aerator assembly is installed on the Y-shaped support and fixed with pipe clamps. Aerobic biological carrier packing 3.2 (suspended carrier) is installed inside the aerobic tank 3. The aeration system 3.1 provides oxygen to the aerobic microorganisms, promoting the degradation of organic matter and the nitrification of ammonia nitrogen. The aerobic biological carrier packing 3.2 increases the attachment area for microorganisms, improving the aerobic treatment efficiency.

[0039] An inclined plate 4.1 is installed on the upper side of the sedimentation tank 4, and a sludge hopper 4.2 is installed on the lower side of the sedimentation tank 4.2. A sludge discharge pipe 4.3 is installed below the sludge hopper 4.2, and a manual ball valve is installed on the sludge discharge pipe 4.3. The design of the inclined plate 4.1 helps to improve the sedimentation efficiency, and the sludge hopper 4.2 and the sludge discharge pipe 4.3 are used to collect and remove the settled sludge, keeping the sedimentation tank 4 clean.

[0040] A guide plate 9 is provided on the side of the sedimentation tank 4. The upper side of the guide plate 9 is connected to the aerobic tank 3, and the lower opening of the guide plate 9 is located between the inclined plate 4.1 and the sludge hopper 4.2 of the sedimentation tank 4. The combination of the guide plate 9 and the inclined plate 4.1 optimizes the water flow path, improves sedimentation efficiency, and reduces sludge resuspension.

[0041] The working principle of this wastewater treatment equipment is as follows: At the beginning of an influent cycle, the clear water tank 5 is full, the first electric valve 4.5 is closed, and the clear water tank 5 is completely submerged in the anoxic tank 2 (e.g., Figure 3 As shown in the diagram, at this time, the liquid level in the anoxic tank 2 is higher than that in the aerobic tank 3. The equipment proceeds with the biological reaction according to the "anoxic-aerobic" cycle, and the wastewater flows by gravity from the anoxic tank 2 into the aerobic tank 3. After the influent cycle ends, the next denitrification reaction cycle begins. At the start of the denitrification reaction cycle, the second electric valve 5.4 of the drain pipe of the clear water tank 5 is opened to drain the clear water in the clear water tank 5. At this time, the clear water tank 5 gradually floats out of the anoxic tank 2 along the guide rail (as shown in the diagram). Figure 4As shown, the liquid level in the anoxic tank 2 initially falls below that in the aerobic tank 3. The nitrified liquid begins to flow back into the anoxic tank 2 through the bottom of the aerobic tank 3. The backflow ends when the liquid levels in the anoxic tank 2 and aerobic tank 3 are equal. The backflow rate is 3-4 times Q (the volume of the clear water tank 5). After the denitrification cycle ends, the next influent cycle begins. The first electric valve 4.5 opens, and the settled wastewater flows into the clear water tank 5 by gravity. The clear water tank 5 gradually sinks until it is completely submerged in the anoxic tank 2. The influent cycle and the denitrification reaction cycle alternate sequentially to achieve the nitrified liquid backflow process.

[0042] Example 2

[0043] This embodiment provides the working method of the sewage treatment equipment in Embodiment 1:

[0044] Wastewater first enters the anoxic tank 2 through inlet pipe 1, where it comes into full contact with the rope-shaped packing material 2.2. The rope-shaped packing material 2.2 is fixed at both ends to packing support 2.1, which is then arranged sequentially around the anoxic tank. The denitrifying microorganisms and other bacterial communities growing on the rope-shaped packing material 2.2 convert nitrate nitrogen in the wastewater into nitrogen gas, reducing total nitrogen and other pollutants, thus purifying the water.

[0045] After treatment in the anoxic tank 2, the wastewater flows through the first bottom grid plate 7 to the aerobic tank 3. An aeration system 3.1 is installed at the bottom of the aerobic tank 3. The aeration system 3.1 is rationally arranged at the bottom of the aerobic tank 3 according to the equipment's processing capacity and the blower's air volume, employing microporous or perforated aeration methods. Hydrophilic polyurethane sponge aerobic biological carrier packing material 3.2 is added to the aerobic tank 3. The microbial community growing on it can degrade COD in the wastewater and convert organic nitrogen, ammonia nitrogen, etc., into nitrate nitrogen.

[0046] After treatment in the aerobic tank 3, wastewater flows into the guide plate 9 through the top second grid plate 8. The lower opening of the guide plate 9 is located between the inclined plate of the sedimentation tank and the sludge hopper. Its purpose is to optimize the flow pattern, allowing wastewater to pass through the inclined plate from low to high as it enters the sedimentation tank, achieving rapid sludge sedimentation and reducing SS ("Suspended Solids"). As the wastewater flows upward, it passes through the inclined plate 4.1 to further enhance sedimentation efficiency. The sediment falls into the sludge hopper 4.2 and is periodically discharged through the sludge discharge pipe 4.3.

[0047] After sedimentation, the wastewater flows through the sedimentation tank drainage weir 4.4, and then by gravity into the bottom of the clear water tank 5 via the return rigid pipe 4.6 and return flexible hose 5.2. The transition between the return rigid pipe 4.6 and the return flexible hose 5.2 is located at the partition between the anoxic tank 2 and the aerobic tank 3. A first electric valve 4.5 is installed on the sedimentation tank return rigid pipe 4.6. The sedimentation tank return rigid pipe 4.6 slopes downwards from its inlet to its outlet at a gradient of 0.02.

[0048] After the clear water tank 5 is filled with water, the first electric valve 4.5 closes, and the clear water tank 5 completely sinks into the anoxic tank 2. At this time, the liquid level in the anoxic tank 2 is higher than that in the aerobic tank 3, and the wastewater flows into the aerobic tank by gravity through the liquid level difference, realizing the "anoxic-aerobic" treatment process. The second electric valve 5.4 is opened to discharge the clear water in the clear water tank 5, and the clear water gradually floats to the surface. At this time, the liquid level in the anoxic tank gradually decreases until it is lower than that in the aerobic tank. The nitrified liquid in the aerobic tank flows back into the anoxic tank 2 through the first grid plate 7 at the bottom, realizing the nitrification liquid return.

[0049] This method utilizes wastewater introduced through the inlet pipe and gravity-driven recirculation, eliminating the need for additional power and reducing energy consumption. At the same time, by precisely controlling the water level in the clear water tank, it achieves efficient nitrification liquid recirculation, thereby improving wastewater treatment efficiency.

[0050] To make the technical solution provided in this embodiment clearer, an example is used to illustrate the method:

[0051] Assuming the water inflow rate of the equipment in one water inflow cycle is Q, the volume of the designed clear water tank 5 should be greater than 4Q, and the size of the clear water tank 5 should be determined according to the specific tank size.

[0052] At the beginning of an influent cycle, the clear water tank 5 is full, the first electric valve 4.5 is closed, and the clear water tank 5 is completely submerged in the anoxic tank 2. At this time, the liquid level in the anoxic tank 2 is higher than the liquid level in the aerobic tank 3. The equipment carries out biological reaction according to the "anoxic-aerobic" cycle, and the sewage flows from the anoxic tank 2 into the aerobic tank 3 by gravity.

[0053] After the water intake cycle ends, the next denitrification reaction cycle begins. At the start of the denitrification reaction cycle, the second electric valve 5.4 of the clear water tank drain pipe is opened to drain the clear water in the clear water tank 5. At this time, the clear water tank 5 gradually floats out of the anoxic tank 2 along the guide rail 5.1. The liquid level in the anoxic tank 2 begins to be lower than the liquid level in the aerobic tank 3. The nitrified liquid begins to flow back into the anoxic tank through the bottom of the aerobic tank. When the liquid levels in the anoxic tank and the aerobic tank are the same, the backflow ends. The backflow rate is 3 to 4 times Q (the volume of the clear water tank).

[0054] After the denitrification cycle ends, the next influent cycle begins. The first electric valve 4.5 opens, and the settled wastewater flows into the clear water tank 5 by gravity. The clear water tank 5 gradually sinks until it is completely submerged in the anoxic tank 2. The influent cycle and the denitrification reaction cycle alternate sequentially to achieve the nitrification liquid recirculation process.

[0055] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A gravity-driven recirculation wastewater treatment device, characterized in that, Includes anoxic tank, aerobic tank, sedimentation tank, and reflux assembly; The anoxic tank, aerobic tank, and sedimentation tank are arranged in parallel. An inlet pipe is provided on the upper side of the anoxic tank, the lower side of the aerobic tank is connected to the lower side of the anoxic tank, the upper side of the sedimentation tank is connected to the upper side of the aerobic tank, and a drainage weir is provided on the upper side of the sedimentation tank. The reflux assembly includes a clear water tank and a reflux pipe. The clear water tank is slidably installed vertically inside the anoxic tank. An outlet pipe is provided at the bottom of the clear water tank. The reflux pipe connects the drainage weir and the lower side of the clear water tank. The return pipe includes a connected return rigid pipe and a return flexible pipe. The inlet of the return rigid pipe is connected to the drainage weir, and the return rigid pipe is arranged at an angle. The end connected to the drainage weir is higher than the end connected to the return flexible pipe. The outlet of the return flexible pipe is connected to the lower side of the clear water tank. An outlet flexible pipe is connected between the outlet pipe and the clear water tank. The return pipe is equipped with a first electric valve for controlling its opening and closing, and the outlet pipe is equipped with a second electric valve for controlling its opening and closing.

2. The gravity-driven recirculation wastewater treatment equipment as described in claim 1, characterized in that, The reflux assembly also includes a guide rail bracket, which is fixedly installed inside the anoxic pool, and the clear water pool is slidably installed inside the guide rail bracket and can move up and down along the guide rail bracket.

3. The gravity-driven recirculation wastewater treatment equipment as described in claim 1, characterized in that, A first grid plate is installed at the connection point between the aerobic tank and the anoxic tank, and a second grid plate is installed at the connection point between the sedimentation tank and the aerobic tank.

4. The gravity-driven recirculation wastewater treatment equipment as described in claim 1, characterized in that, The anoxic pool is equipped with a packing support, which is a cubic structure, and rope-shaped packing is installed on the packing support.

5. The gravity-driven recirculation wastewater treatment equipment as described in claim 1, characterized in that, An aeration system is installed at the bottom of the aerobic tank, and aerobic biological carrier packing material is installed inside the aerobic tank.

6. The gravity-driven recirculation wastewater treatment equipment as described in claim 1, characterized in that, An inclined plate is provided on the upper side of the sedimentation tank, a sludge hopper is provided on the lower side of the sedimentation tank, and a sludge discharge pipe is provided on the lower side of the sludge hopper.

7. The gravity-driven recirculation wastewater treatment equipment as described in claim 6, characterized in that, A guide plate is provided on the side of the sedimentation tank. The upper side of the guide plate is connected to the aerobic tank, and the lower opening of the guide plate is located between the inclined plate of the sedimentation tank and the sludge hopper.

8. A method of operating a gravity-driven recirculation wastewater treatment device as described in any one of claims 1-7, characterized in that, include: At the beginning of an influent cycle, the clear water tank is full and completely submerged in the anoxic tank. At this time, the liquid level in the anoxic tank is higher than that in the aerobic tank. The equipment carries out biological reaction according to the "anoxic-aerobic" process, and the sewage flows from the anoxic tank into the aerobic tank by gravity. At the start of the denitrification cycle, the clear water in the clear water tank is drained. At this time, the anoxic tank floats out of the clear water tank, and the liquid level in the anoxic tank begins to fall below the liquid level in the aerobic tank. The nitrified liquid begins to flow back, and the flow ends when the liquid levels in the two tanks are the same.

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