Sewage treatment equipment capable of driving backflow by gravity and working method of sewage treatment equipment

Abstract

The invention relates to the technical field of domestic sewage treatment, in particular to sewage treatment equipment for gravity-driven backflow and a working method thereof. The sewage treatment equipment 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 sequentially arranged in parallel, a water inlet pipe is arranged on the upper side of the anoxic tank, 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, and a drainage weir opening is formed in the upper side of the sedimentation tank; the backflow assembly comprises a clean water tank and a backflow pipe, the clean water tank is slidably mounted in the anoxic tank in the vertical direction, a water outlet pipe is arranged at the bottom of the clean water tank, and the backflow pipe is communicated with the drainage weir opening and the lower side of the clean water tank. The problems of energy consumption and over-high dissolved oxygen caused by nitrification liquid backflow in the current common sewage treatment process are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of domestic sewage treatment, and in particular to a gravity-driven reflux sewage treatment device and a working method thereof. Background Art

[0002] Domestic sewage is wastewater discharged from residents' daily lives. It mainly comes from residential buildings and public buildings. The pollutants contained in domestic sewage are mainly organic matter. The organic matter in domestic sewage is extremely unstable and easily decomposes to produce odor. Bacteria and pathogens multiply in large numbers using organic matter in domestic sewage as nutrition, leading to the spread of infectious diseases. Therefore, domestic sewage must be purified by sewage treatment equipment before being discharged.

[0003] At present, the denitrification process commonly used in sewage treatment is mainly the "nitrification-denitrification" process. Nitrifying bacteria and other microorganisms oxidize ammonia nitrogen into nitrates, and denitrifying bacteria reduce nitrates to nitrogen gas, thereby achieving the purpose of removing total nitrogen nutrients. The "nitrification-denitrification" process generally uses a lift pump or air lift reflux. The pump reflux greatly increases the investment cost and operating energy consumption of the equipment, and also leads to an increase in the overall failure rate of the equipment. The air lift reflux uses aeration to drive the return water, which reduces the equipment investment cost to a certain extent, but the amount of gas required for the nitrification liquid reflux will also lead to an increase in the fan model, which increases the equipment operation cost. At the same time, the mixed liquid returns from the aerobic tank to the anoxic tank through air lift, which will also increase the dissolved oxygen content in the anoxic tank, inhibit denitrification, and reduce the TN treatment efficiency. Summary of the invention

[0004] In view of the deficiencies in the prior art, an embodiment of the present invention aims to provide a gravity-driven reflux sewage treatment device to solve the problems of energy consumption and excessive dissolved oxygen caused by reflux of nitrification liquid in the currently commonly used sewage treatment process.

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

[0006] A sewage treatment device with gravity-driven backflow 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, an inlet pipe is arranged 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 arranged on the upper side of the sedimentation tank; the backflow assembly comprises a clear water tank and a backflow pipe, the clear water tank is vertically slidably installed in the anoxic tank, an outlet pipe is arranged at the bottom of the clear water tank, and the backflow pipe connects the drainage weir and the lower side of the clear water tank.

[0007] Optionally, the reflux assembly further comprises a guide rail bracket, wherein the guide rail bracket is fixedly installed in the anoxic tank, and the clean water tank is slidably installed in the guide rail bracket and can be lifted and lowered along the guide rail bracket.

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

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

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

[0011] Optionally, a filler bracket is provided in the anoxic pool, and the filler bracket is a cubic structure, and a rope-shaped filler is installed on the filler bracket.

[0012] Optionally, an aeration system is provided at the bottom of the aerobic pool, and aerobic biological carrier fillers are provided in the aerobic pool.

[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] The embodiment of the present invention further provides a working method of the gravity-driven reflux sewage treatment equipment as described above, comprising:

[0016] At the beginning of a water inflow cycle, the clean water tank is full of water 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 performs biological reactions according to the "anoxic-aerobic" principle, and the sewage flows from the anoxic tank into the aerobic tank by gravity.

[0017] At the beginning of the denitrification reaction cycle, the clean water in the clean water tank is drained. At this time, the clean water tank floats out of the anoxic tank, the liquid level in the anoxic tank begins to be lower than the liquid level in the aerobic tank, and the nitrification liquid begins to flow back. When the liquid levels in the two tanks are the same, the reflux ends.

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

[0019] The equipment uses a clear water tank that can float up and down inside the anoxic tank, and uses the liquid level difference and liquid gravity reflux to achieve reflux from the aerobic zone to the anoxic zone, which can greatly reduce operating energy consumption and solve the problem of too high dissolved oxygen in the refluxed nitrification liquid. Compared with pump reflux, the equipment controls the water level of the anoxic tank and the aerobic tank by floating up and down the clear water tank, and uses the liquid level difference to achieve reflux of the nitrification liquid, greatly reducing the power energy consumption required for reflux. Compared with air lift reflux, the refluxed nitrification liquid of this equipment 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 fan selection is relatively smaller, which greatly reduces the overall operating cost.

[0020] Advantages of additional aspects of the present invention will be given in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 1 is a schematic diagram of a sewage treatment device provided by an embodiment of the present invention;

[0023] Figure 2 is a top view of a sewage treatment device provided by an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the positional relationship of a clean water tank completely immersed in an anoxic tank provided by an embodiment of the present invention.

[0025] Figure 4 Schematic diagram of the positional relationship of the clean water tank completely floating out of the anoxic tank provided by an embodiment of the present invention;

[0026] In the figure: 1, water inlet pipe; 2, anoxic tank; 3, aerobic tank; 4, sedimentation tank; 5, clean water tank; 6, water outlet pipe; 7, first grid plate; 8, second grid plate; 9, guide plate; 2.1, filler bracket; 2.2, rope filler; 3.1, aeration system; 3.2, aerobic biological carrier filler; 4.1, inclined plate; 4.2, sludge bucket; 4.3, sludge pipe; 4.4, drainage weir; 4.5, first electric valve; 4.6, reflux hard pipe; 5.1, guide rail bracket; 5.2, reflux hose; 5.3, water outlet hose; 5.4, second electric valve;

[0027] In order to show the positions of various parts, the distances or sizes between them are exaggerated and the schematic diagram is for reference only. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, it should also be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0029] Example 1

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

[0031] The tank body is divided into an anoxic tank 2, an aerobic tank 3, and a sedimentation tank 4 by a partition. The tank body is higher than the conventional ground container tank body, which increases the effective water depth in the tank, makes the oxygen transfer efficiency of the aerator higher, and can select a fan with smaller power, saving equipment operation costs. An inlet pipe 1 is provided on the outside of the tank body for introducing sewage to be treated. The inlet pipe 1 is installed in the middle part of the upper part of the anoxic tank 2, and a 90° elbow is installed inside the tank body to prevent the water flow from scouring the clear water tank 5. The installation height of the inlet pipe 1 is 10 to 20 cm greater than the maximum liquid level height of the anoxic tank 2. The lower side of the aerobic tank 3 is connected to the lower side of the anoxic tank 2, so that the sewage treated with anoxic treatment can flow smoothly into the aerobic tank 3 and realize backflow. The upper side of the sedimentation tank 4 is connected to the upper side of the aerobic tank 3, and the sewage after aerobic treatment enters the sedimentation tank 4 for solid-liquid separation. The clean water tank 5 is vertically slidably installed in the anoxic tank 2, and a water outlet pipe 6 is provided at the bottom thereof for controlling the water level in the clean water tank 5 to realize the reflux of the nitrified liquid between the aerobic tank 3 and the anoxic tank 2. The reflux pipe connects the drainage weir 4.4 and the lower side of the clean water tank 5, and realizes the reflux by using the water level difference and gravity.

[0032] The device uses a clear water tank 5 that can float up and down inside the anoxic tank 2, and uses the liquid level difference and liquid gravity reflux to achieve reflux from the aerobic zone to the anoxic zone, which can greatly reduce operating energy consumption and solve the problem of too high dissolved oxygen in the refluxed nitrification liquid. Compared with pump reflux, the equipment controls the water levels of the anoxic tank 2 and the aerobic tank 3 by floating the clear water tank 5 up and down, and uses the liquid level difference to achieve the reflux of the nitrification liquid, which greatly reduces the power energy consumption required for reflux. Compared with air lift reflux, the nitrification liquid refluxed by this equipment 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 selection of the fan is relatively smaller, which greatly reduces the overall operating cost.

[0033] The reflux assembly further comprises a guide rail bracket 5.1, which is fixedly mounted in the anoxic pool 2, and the clean water pool 5 is slidably mounted in the guide rail bracket 5.1 and can be raised and lowered along the guide rail bracket 5.1. The clean water pool 5 is cylindrical, and the clean water pool 5 is mounted through the guide rail bracket 5.1, and the guide rail bracket 5.1 is connected to the pool body to ensure that the clean water pool 5 can only move longitudinally along the guide rail bracket 5.1.

[0034] The reflux pipe includes a connected reflux hard pipe 4.6 and a reflux hose 5.2. The inlet of the reflux hard pipe 4.6 is connected to the drainage weir 4.4, and the reflux hard pipe 4.6 is arranged obliquely, and the end (right end) connected to the drainage weir 4.4 is higher than the end (left end) connected to the reflux hose 5.2, and the gravity difference is used to achieve reflux to ensure smooth water flow. The outlet of the reflux hose 5.2 is connected to the lower side of the clean water tank 5, and an outlet hose 5.3 is connected between the outlet pipe 6 and the clean water tank 5, and the outlet hose passes through the tank body at the bottom of the anoxic tank 2.

[0035] The reflux hard pipe 4.6 is provided with a first electric valve 4.5 for controlling opening and closing, and the outlet pipe 6 is provided with a second electric valve 5.4 for controlling opening and closing. The arrangement of these two electric valves in conjunction with the water inlet lift pump allows the operator to accurately control the start and end of the reflux process according to the needs of the treatment process, which can better maintain the stability of the water inlet and outlet of the equipment, improve the stability of the equipment operation, and improve the automation level of the system and the convenience of operation.

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

[0037] A filler support 2.1 is installed inside the anoxic pool 2. The filler support 2.1 is a plurality of cubic structures that are independent of each other. The filler support 2.1 is evenly distributed in the anoxic pool 2 in a "mouth" shape when placed, and a space required for installing a floating clean water pool 5 is reserved in the middle of the support. Rope-shaped anoxic biological carrier fillers are installed on the filler support 2.1. This design provides a larger attachment area for microorganisms, promotes the reaction, and improves the sewage treatment efficiency.

[0038] A "Y"-shaped support is provided at the bottom of the aerobic pool 3, and the microporous aerator assembly is installed on the "Y"-shaped support and fixed by a pipe clamp. An aerobic biological carrier filler 3.2 (suspended carrier) is provided in the aerobic pool 3. The aeration system 3.1 provides oxygen for aerobic microorganisms, promotes the degradation of organic matter and the nitrification of ammonia nitrogen. The aerobic biological carrier filler 3.2 increases the attachment area of ​​microorganisms and improves the aerobic treatment efficiency.

[0039] The upper side of the sedimentation tank 4 is provided with an inclined plate 4.1, the lower side of the sedimentation tank 4 is provided with a sludge bucket 4.2, the lower side of the sludge bucket 4.2 is provided with a sludge discharge pipe 4.3, 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 bucket 4.2 and the sludge discharge pipe 4.3 are used to collect and discharge the settled sludge to keep 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 cooperation between the guide plate 9 and the inclined plate 4.1 optimizes the water flow path, improves the sedimentation efficiency, and reduces the resuspension of the sludge.

[0041] The working principle of the sewage treatment equipment is as follows: at the beginning of a water inlet cycle, the clean water tank 5 is full of water, the first electric valve 4.5 is closed, and the clean water tank 5 is completely immersed in the anoxic tank 2 (such as Figure 3 As shown), at this time, the liquid level of anoxic tank 2 is higher than that of aerobic tank 3, and the equipment performs biological reaction according to "anoxic-aerobic", and sewage flows from anoxic tank 2 into aerobic tank 3 by gravity. After the water inlet cycle is over, the next denitrification reaction cycle begins. At the beginning of the denitrification reaction cycle, open the second electric valve 5.4 of the drainage pipe of the clear water tank 5 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 FIG. Figure 4As shown in the figure, the liquid level of anoxic tank 2 begins to be lower than that of aerobic tank 3, and the nitrified liquid begins to flow back to anoxic tank 2 through the bottom of aerobic tank 3. When the liquid levels of anoxic tank 2 and aerobic tank 3 are consistent, the reflux ends, and the reflux volume is 3 to 4 times Q (volume of clean water tank 5). After the denitrification cycle is over, the next water inlet cycle begins. The first electric valve 4.5 is opened, and the sewage after sedimentation flows into the clean water tank 5 by gravity. The clean water tank 5 gradually sinks until it is completely submerged in the anoxic tank 2. The water inlet cycle and the denitrification reaction cycle are alternated in sequence to realize the nitrified liquid reflux process.

[0042] Example 2

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

[0044] Sewage first enters the anoxic tank 2 through the water inlet pipe 1 and fully contacts the rope-shaped filler 2.2. The upper and lower ends of the rope-shaped filler 2.2 are respectively fixed on the filler bracket 2.1, and the filler bracket 2.1 is placed around the anoxic tank in sequence. The denitrifying microorganisms and other bacterial flora growing on the rope-shaped filler 2.2 can convert nitrate nitrogen in the sewage into nitrogen gas, reduce pollutants such as total nitrogen, and purify the water body.

[0045] After being treated in the anoxic tank 2, the sewage flows to the aerobic tank 3 through the first grid plate 7 at the bottom. An aeration system 3.1 is installed at the bottom of the aerobic tank 3. The aeration system 3.1 is reasonably arranged at the bottom of the aerobic tank 3 according to the equipment processing capacity, fan air volume, etc., and adopts a microporous or perforated aeration type. Hydrophilic polyurethane sponge aerobic biological carrier filler 3.2 is added to the aerobic tank 3, and the biological flora grown on it can degrade COD in the sewage and convert organic nitrogen, ammonia nitrogen, etc. into nitrate nitrogen.

[0046] After being treated in the aerobic tank 3, the sewage flows into the guide plate 9 through the second grid plate 8 at the top. The lower opening of the guide plate 9 is located between the inclined plate and the sludge hopper of the sedimentation tank. The purpose is to optimize the water flow method so that the sewage can pass through the inclined plate from low to high when entering the sedimentation tank, so as to achieve the purpose of rapid sedimentation of sludge and reduce SS ("Suspended Solids"). The sedimentation efficiency is improved through the inclined plate 4.1 during the upward flow of sewage. The sediment falls into the sludge hopper 4.2 and is discharged regularly through the sludge discharge pipe 4.3.

[0047] The precipitated sewage flows into the bottom of the clean water tank 5 through the drainage weir 4.4 of the sedimentation tank, the return pipe 4.6 and the return hose 5.2 by gravity. The transition between the return pipe 4.6 and the return hose 5.2 is located at the partition between the anoxic tank 2 and the aerobic tank 3. The first electric valve 4.5 is installed on the sedimentation tank return pipe 4.6. The sedimentation tank return pipe 4.6 is inclined downward from its inlet to its outlet, and the slope is 0.02.

[0048] After the clear water tank 5 is filled with water, the first electric valve 4.5 is closed, and the clear water tank 5 will completely sink into the anoxic tank 2. At this time, the liquid level of the anoxic tank 2 is higher than the liquid level of the aerobic tank 3, and the sewage 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 clean water in the clear water tank 5, and the clear water tank gradually floats up. At this time, the liquid level of the anoxic tank gradually decreases until it is lower than the liquid level of the aerobic tank. The nitrification 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 reflux.

[0049] This method utilizes sewage introduced by the water inlet pipe and cooperates with gravity to drive the backflow, without the need for additional power, thus reducing energy consumption. At the same time, by precisely controlling the water level in the clear water tank, efficient nitrification liquid backflow is achieved, thereby improving sewage treatment efficiency.

[0050] In order to make the technical solution provided by this embodiment clearer, the method is described with an example:

[0051] Assuming that the water intake of the equipment in one water intake cycle is Q, the designed volume of the clean water tank 5 should be greater than 4Q, and the size of the clean water tank 5 should be determined according to the size of the tank body.

[0052] At the beginning of a water inlet cycle, the clean water tank 5 is full of water, the first electric valve 4.5 is in a closed state, and the clean water tank 5 is completely immersed in the anoxic tank 2. At this time, the liquid level of the anoxic tank 2 is higher than the liquid level of the aerobic tank 3. The equipment performs a biological reaction according to the "anoxic-aerobic" method, and the sewage flows from the anoxic tank 2 into the aerobic tank 3.

[0053] After the water inlet cycle is over, the next denitrification cycle begins. At the beginning of the denitrification 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, and the liquid level of the anoxic tank 2 begins to be lower than the liquid level of the aerobic tank 3. The nitrified liquid begins to flow back to the anoxic tank through the bottom of the aerobic tank. When the liquid levels of the anoxic tank and the aerobic tank are consistent, the reflux ends, and the reflux amount is 3 to 4 times Q (the volume of the clear water tank).

[0054] After the denitrification cycle is over, the next water inlet cycle begins. The first electric valve 4.5 is opened, and the sewage after sedimentation flows into the clear water tank 5 by gravity, and the clear water tank 5 gradually sinks until it is completely submerged in the anoxic tank 2. The water inlet cycle and the denitrification reaction cycle are carried out alternately to realize the nitrification liquid reflux process.

[0055] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it 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 on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A gravity-driven reflux sewage treatment equipment, characterized in that: Includes anoxic tanks, aerobic tanks, sedimentation tanks and return flow components; The anoxic tank, the aerobic tank and the sedimentation tank are arranged in parallel in sequence, a water inlet pipe is arranged 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 arranged on the upper side of the sedimentation tank; The reflux assembly comprises a clear water tank and a reflux pipe. The clear water tank is vertically slidably installed in the anoxic tank. An outlet pipe is arranged at the bottom of the clear water tank. The reflux pipe communicates with the drainage weir and the lower side of the clear water tank.

2. The gravity-driven reflux sewage treatment equipment according to claim 1, characterized in that: The reflux component also includes a guide rail bracket, which is fixedly installed in the anoxic tank. The clean water tank is slidably installed in the guide rail bracket and can be lifted and lowered along the guide rail bracket.

3. The gravity-driven reflux sewage treatment equipment according to claim 1, characterized in that: The reflux pipe includes a connected reflux rigid pipe and a reflux hose, the inlet of the reflux rigid pipe is connected to the drainage weir, and the reflux rigid pipe is arranged obliquely, the end connected to the drainage weir is higher than the end connected to the reflux hose, the outlet of the reflux hose is connected to the lower side of the clean water tank, and an outlet hose is connected between the outlet pipe and the clean water tank.

4. The gravity-driven reflux sewage treatment equipment according to claim 3, characterized in that: The reflux rigid pipe is provided with a first electric valve for controlling opening and closing, and the outlet pipe is provided with a second electric valve for controlling opening and closing.

5. The gravity-driven reflux sewage treatment equipment according to claim 1, characterized in that: A first grid plate is provided at a communication position between the aerobic tank and the anoxic tank, and a second grid plate is provided at a communication position between the sedimentation tank and the aerobic tank.

6. The gravity-driven reflux sewage treatment equipment according to claim 1, characterized in that: A filler support is arranged in the anoxic pool. The filler support is a cubic structure, and a rope-shaped filler is installed on the filler support.

7. The gravity-driven reflux sewage treatment equipment according to claim 1, characterized in that: An aeration system is arranged at the bottom of the aerobic pool, and aerobic biological carrier fillers are arranged in the aerobic pool.

8. The gravity-driven reflux sewage treatment equipment according to claim 1, characterized in that: An inclined plate is arranged on the upper side of the sedimentation tank, a sludge bucket is arranged on the lower side of the sedimentation tank, and a sludge discharge pipe is arranged on the lower side of the sludge bucket.

9. The gravity-driven reflux sewage treatment equipment according to claim 8, characterized in that: A guide plate is arranged on the side of the sedimentation tank, the upper side of the guide plate is communicated with 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.

10. A method for operating a gravity-driven reflux sewage treatment device as claimed in any one of claims 1 to 9, characterized in that: include: At the beginning of a water inlet cycle, the clean water tank is full of water 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 performs biological reactions according to the "anoxic-aerobic" principle, and the sewage flows from the anoxic tank into the aerobic tank by gravity. At the beginning of the denitrification reaction cycle, the clean water in the clean water tank is drained. At this time, the clean water tank floats out of the anoxic tank, the liquid level in the anoxic tank begins to be lower than the liquid level in the aerobic tank, and the nitrification liquid begins to flow back. When the liquid levels in the two tanks are the same, the reflux ends.

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