A parallel dual biochemical sewage treatment process and sewage treatment system

Abstract

The present invention proposes a parallel dual biochemical sewage treatment process. According to the fluctuation of the incoming water volume, the sludge amount in the biochemical section is adjusted to ensure that the sludge load rate is in a relatively stable range, thereby achieving a stable sewage treatment effect. According to the process, the present invention also proposes a parallel dual biochemical sewage treatment system, which is particularly suitable for the construction of small rural sewage treatment stations.

Description

Technical Field

[0001] The invention relates to sewage treatment technology, in particular to a parallel dual biochemical sewage treatment process and a sewage treatment system. Background Art

[0002] In the activated sludge method of sewage treatment, activated sludge plays a decisive role. Its principle is to use the characteristics of microorganisms to achieve the purpose of nitrogen and phosphorus removal. To achieve the ideal treatment effect, the sludge load rate (i.e. the ratio of organic matter to microorganisms) needs to be in a more reasonable interval. The lower the sludge load rate, the easier the process is to run, the more stable the treatment efficiency is, and the amount of residual sludge is less, but the capital construction and operation costs are generally higher. A reasonable sludge load rate can make the sewage treatment process have good sludge settling performance at a stable metabolic depth, and achieve better sewage treatment effects under smaller capital construction conditions.

[0003] At present, activated sludge process is widely used in rural sewage treatment plants. In these areas, there are few industrial enterprises, and the infrastructure scale of sewage treatment plants is mainly small-scale. The source of sewage is mainly daily water. The amount of daily water is small, but it has a fluctuation cycle of 1-5 hours. The water quality and quantity change greatly within a fluctuation cycle. In this case, for small sewage treatment plants with poor infrastructure conditions, it is difficult for the equipment to maintain the basic environment for the survival of microorganisms in the biochemical stage. Even during individual fluctuation peaks, the original biochemical system is instantly destroyed, and the sludge load rate rises sharply, which greatly damages the sewage treatment effect. Summary of the invention

[0004] In view of the problems raised in the background technology, the purpose of the present invention is to provide a parallel dual biochemical sewage treatment process, which can ensure that the sludge load rate is in a relatively stable range by adjusting the sludge amount in the biochemical section according to the fluctuation of the incoming water volume, thereby achieving a stable sewage treatment effect. According to the process, the present invention also proposes a parallel dual biochemical sewage treatment system, which is particularly suitable for the construction of small rural sewage treatment stations.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A parallel dual biochemical sewage treatment process comprises the following steps:

[0007] Step S1, the sewage inflow is a normal water volume Z, the sewage enters the first AAO biochemical section from the regulating tank through the first pipeline, and at the same time, the sewage also enters the second AAO biochemical section from the regulating tank through the second pipeline, and the water inflow of the second AAO biochemical section remains constant, only maintaining the basic activity of the activated sludge; the sewage treated by the first AAO biochemical section and the second AAO biochemical section are discharged to the secondary sedimentation tank;

[0008] Step S2, the sewage inflow increases, and the water inflow of the second AAO biochemical section remains unchanged. Assuming that the water volume in the first pipeline increases to T, the increment is △T, and the activated sludge corresponding to the second AAO biochemical section and the first AAO biochemical section is transferred to the first AAO biochemical section in a timely manner, so that the ratio H of the sludge volume M transferred from the second AAO biochemical section to △T remains constant, and the internal reflow ratio r1 and the external reflow ratio R1 of the first AAO biochemical section remain constant, and at the same time, the external reflow ratio R2 of the second AAO biochemical section is increased, so that the amount of activated sludge in the second AAO biochemical section is compensated, and the compensation amount m is less than M;

[0009] Step S3, the sewage water volume decreases from T, so that the water volume of the second AAO biochemical section remains unchanged, and the activated sludge of the second AAO biochemical section is stopped from transferring to the first AAO biochemical section, and the internal reflow ratio r1 and the external reflow ratio R1 of the first AAO biochemical section are still kept constant, and at the same time, the compensation amount m of the activated sludge volume of the second AAO biochemical section is reduced;

[0010] Step S4: When the sewage inflow volume is restored from T to Z, the amount of activated sludge in the second AAO biochemical stage is restored to the initial value, and the operation returns to step S1.

[0011] In the step S1, the external reflux ratio R1 of the first AAO biochemical section and the external reflux ratio R2 of the second AAO biochemical section remain unchanged, and the value ranges thereof are both 50%-100%.

[0012] In step S2, the ratio of H to the sludge load rate of the first AAO biochemical stage is a constant value.

[0013] The present invention also proposes a sewage treatment system that runs the parallel dual biochemical sewage treatment process as described above, comprising a regulating tank, a first AAO biochemical section, a second AAO biochemical section and a secondary sedimentation tank, wherein the regulating tank is connected to an external sewage source via a sixth pipeline, and a flow sensor is provided on the sixth pipeline for detecting the sewage flow rate of the sixth pipeline; a first gas stripping device and a second gas stripping device are provided in the regulating tank; the first AAO biochemical section and the second AAO biochemical section are connected in parallel between the regulating tank and the secondary sedimentation tank, the first AAO biochemical section is composed of a first anaerobic tank, a first anoxic tank and a first aerobic tank connected in series in sequence, and the first anaerobic tank is connected to the regulating tank via a first pipeline The first gas stripping device in the first aerobic tank is connected to the first anoxic tank through a first pipeline, the first anoxic tank is connected to the first aerobic tank through a second pipeline, the first aerobic tank is provided with a fourth gas stripping device, and the fourth gas stripping device is connected to the second sedimentation tank through a third pipeline; the second AAO biochemical section is composed of a second anaerobic tank, a second anoxic tank and a second aerobic tank connected in series in sequence, the second anaerobic tank is connected to the second gas stripping device through a second pipeline, the second anaerobic tank is connected to the second anoxic tank through a third pipeline, the second anoxic tank is connected to the second aerobic tank through a fourth pipeline, the second aerobic tank is provided with a sixth gas stripping device, and the sixth gas stripping device is connected to the second sedimentation tank through a fourth pipeline;

[0014] The first anaerobic tank is connected to the second anaerobic tank through a first mud-water mixture gas stripping device, the first anoxic tank is connected to the second anoxic tank through a second mud-water mixture gas stripping device, and the first aerobic tank is connected to the second aerobic tank through a third mud-water mixture gas stripping device;

[0015] The first gas lift device, the second gas lift device, the fourth gas lift device, the sixth gas lift device, the first mud-water mixture gas lift device, the second mud-water mixture gas lift device, and the third mud-water mixture gas lift device are all supplied with air by an external Roots blower, and the air inlet pipelines of the first gas lift device, the fourth gas lift device, the first mud-water mixture gas lift device, the second mud-water mixture gas lift device, and the third mud-water mixture gas lift device are all provided with pressure reducing solenoid valves with controllable opening, and the pressure reducing solenoid valves are all connected to an external control system, and the flow sensor on the sixth pipeline is also connected to the external control system.

[0016] The second sedimentation tank is provided with a fourth mud-water mixture gas stripping device and a fifth mud-water mixture gas stripping device. The fourth mud-water mixture gas stripping device is connected to the first anaerobic tank through a first external return pipeline, and is used for sludge return of the first AAO biochemical section; the fifth mud-water mixture gas stripping device is connected to the second anaerobic tank through a second external return pipeline, and is used for sludge return of the second AAO biochemical section; the fourth mud-water mixture gas stripping device and the fifth mud-water mixture gas stripping device are both provided with a pressure reducing solenoid valve with controllable opening, and the pressure reducing solenoid valve is connected to an external control system.

[0017] A first internal reflux pipeline is provided between the first anoxic tank and the third pipeline for reflux of the mud-water mixture of the first AAO biochemical section; a second internal reflux pipeline is provided between the second anoxic tank and the fourth pipeline for reflux of the mud-water mixture of the second AAO biochemical section.

[0018] The first anaerobic tank is provided with a first pneumatic flow-pushing device for driving the sewage in the first anaerobic tank to flow and push the sewage from the first anaerobic tank to the first anoxic tank; the first anoxic tank is provided with a second pneumatic flow-pushing device for driving the sewage in the first anoxic tank to flow and push the sewage from the first anoxic tank to the first aerobic tank.

[0019] A third pneumatic flow-pushing device is provided in the second anaerobic tank, which is used to drive the sewage in the second anaerobic tank to flow and push the sewage from the second anaerobic tank to the second anoxic tank; a fourth pneumatic flow-pushing device is provided in the second anoxic tank, which is used to drive the sewage in the second anoxic tank to flow and push the sewage from the second anoxic tank to the second aerobic tank.

[0020] Beneficial effects of the invention: The parallel dual biochemical sewage treatment process and sewage treatment system proposed in the invention realize stable control of the sludge load rate of small sewage treatment stations in rural areas by controlling the ratio of water intake to the amount of transferred sludge. The sewage treatment effect is stable, and the construction cost and operation cost are low. It is suitable for sewage treatment projects in rural areas and scenic spots. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a flow chart of the parallel dual biochemical sewage treatment process proposed by the present invention;

[0022] Figure 2 This is a top plan view of the parallel dual biochemical sewage treatment system proposed by the present invention.

[0023] Figure 3 This is the operating principle diagram of the first AAO biochemical section.

[0024] Figure 4 The schematic diagram of the control system in one embodiment of the present invention is shown in FIG.

[0025] Figure 5 It is a schematic structural diagram of the first gas stripping device.

[0026] In the figure, 1, a first gas stripping device, 2, a second gas stripping device, 4, a fourth gas stripping device, 6, a sixth gas stripping device, 7, a first gas stripping device for a mud-water mixture, 8, a second gas stripping device for a mud-water mixture, 9, a third gas stripping device for a mud-water mixture, 10, a fourth gas stripping device for a mud-water mixture, 11, a fifth gas stripping device for a mud-water mixture;

[0027] Regulating tank, 21, first pipeline, 22, second pipeline, 23, third pipeline, 24, fourth pipeline, 26, sixth pipeline, 27, flow sensor;

[0028] The first anaerobic tank, 32, the first anoxic tank, 33, the first aerobic tank;

[0029] Second sedimentation tank, 41, second anaerobic tank, 42, second anoxic tank, 43, second aerobic tank;

[0030] a first external return line, 52, a second external return line;

[0031] a first internal return line, 62, a second internal return line;

[0032] The first pneumatic flow-pushing device is 72, the second pneumatic flow-pushing device is 73, the third pneumatic flow-pushing device is 74, and the fourth pneumatic flow-pushing device is 74.

[0033] Figure 3 In the figure, the dotted line represents the sludge pipeline, and the thick solid line represents the sewage pipeline. Implementation

[0034] The technical solution of the present invention will be described clearly and completely below in conjunction with the drawings of the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] like Figure 1-Figure 4 As shown, the present invention first proposes a parallel dual biochemical sewage treatment process, comprising the following steps:

[0036] Step S1, the sewage inflow is a normal water volume Z, the sewage enters the first AAO biochemical section from the regulating tank through the first pipeline, and at the same time, the sewage also enters the second AAO biochemical section from the regulating tank through the second pipeline, and the water inflow of the second AAO biochemical section remains constant, only maintaining the basic activity of the activated sludge; the sewage treated by the first AAO biochemical section and the second AAO biochemical section are discharged to the secondary sedimentation tank;

[0037] Step S2, the sewage inflow increases, and the water inflow of the second AAO biochemical section remains unchanged. Assuming that the water volume in the first pipeline increases to T, the increment is △T, and the activated sludge corresponding to the second AAO biochemical section and the first AAO biochemical section is transferred to the first AAO biochemical section in a timely manner, so that the ratio H of the sludge volume M transferred from the second AAO biochemical section to △T remains constant, and the internal reflow ratio r1 and the external reflow ratio R1 of the first AAO biochemical section remain constant, and at the same time, the external reflow ratio R2 of the second AAO biochemical section is increased, so that the amount of activated sludge in the second AAO biochemical section is compensated, and the compensation amount m is less than M;

[0038] Step S3, the sewage water volume decreases from T, so that the water volume of the second AAO biochemical section remains unchanged, and the activated sludge of the second AAO biochemical section is stopped from transferring to the first AAO biochemical section, and the internal reflow ratio r1 and the external reflow ratio R1 of the first AAO biochemical section are still kept constant, and at the same time, the compensation amount m of the activated sludge volume of the second AAO biochemical section is reduced;

[0039] Step S4: When the sewage inflow volume is restored from T to Z, the amount of activated sludge in the second AAO biochemical stage is restored to the initial value, and the operation returns to step S1.

[0040] In the step S1, the external reflux ratio R1 of the first AAO biochemical section and the external reflux ratio R2 of the second AAO biochemical section remain unchanged, and the value ranges thereof are both 50%-100%.

[0041] In step S2, the ratio of H to the sludge load rate of the first AAO biochemical stage is a constant value.

[0042] The present invention also proposes a sewage treatment system that runs the above-mentioned parallel dual biochemical sewage treatment process, including a regulating tank 20, a first AAO biochemical section, a second AAO biochemical section and a secondary sedimentation tank 40, wherein the regulating tank 20 is connected to an external sewage source through a sixth pipeline 26, and a flow sensor 27 is provided on the sixth pipeline 26 for detecting the sewage flow of the sixth pipeline 26; a first gas stripping device 1 and a second gas stripping device 2 are provided in the regulating tank 20; the first AAO biochemical section and the second AAO biochemical section are connected in parallel between the regulating tank 20 and the secondary sedimentation tank 40, and the first AAO biochemical section is composed of a first anaerobic tank 31, a first anoxic tank 32 and a first aerobic tank 33 connected in series in sequence, and the first anaerobic tank 31 is connected to the regulating tank 20 through the first pipeline 21. The first stripping device 1, the first anaerobic tank 31 is connected to the first anoxic tank 32, the first anoxic tank 32 is connected to the first aerobic tank 33 through the third stripping device 3, the first aerobic tank 33 is provided with a fourth stripping device 4, and the fourth stripping device 4 is connected to the second sedimentation tank 40 through the third pipeline 23; the second AAO biochemical section is composed of a second anaerobic tank 41, a second anoxic tank 42 and a second aerobic tank 43 connected in series, the second anaerobic tank 41 is connected to the second stripping device 2 through the second pipeline 22, the second anaerobic tank 41 is connected to the second anoxic tank 42, the second anoxic tank 42 and the second aerobic tank 43 are connected through the fifth stripping device 5, the second aerobic tank 43 is provided with a sixth stripping device 6, and the sixth stripping device 6 is connected to the second sedimentation tank 40 through the fourth pipeline 24;

[0043] The first anaerobic tank 31 is connected to the second anaerobic tank 41 through a first mud-water mixture gas stripping device 7, the first anoxic tank 32 is connected to the second anoxic tank 42 through a second mud-water mixture gas stripping device 8, and the first aerobic tank 33 is connected to the second aerobic tank 43 through a third mud-water mixture gas stripping device 9; specifically, the feed port of the first mud-water mixture gas stripping device 7 is placed in the second anaerobic tank 41, and the discharge port is placed in the first anaerobic tank.

[0044] The first gas lift device 1, the second gas lift device 2, the fourth gas lift device 4, the sixth gas lift device 6, the first mud-water mixture gas lift device 7, the second mud-water mixture gas lift device 8, and the third mud-water mixture gas lift device 9 are all supplied with air by an external Roots blower, and the air inlet pipelines of the first gas lift device 1, the fourth gas lift device 4, the first mud-water mixture gas lift device 7, the second mud-water mixture gas lift device 8, and the third mud-water mixture gas lift device 9 are all provided with pressure reducing solenoid valves with controllable opening, and the pressure reducing solenoid valves are all connected to an external control system, and the flow sensor 27 on the sixth pipeline 26 is also connected to the external control system.

[0045] The second sedimentation tank 40 is provided with a fourth mud-water mixture gas stripping device 10 and a fifth mud-water mixture gas stripping device 11. The fourth mud-water mixture gas stripping device 10 is connected to the first anaerobic tank 31 through a first external return line 51, and is used for sludge return of the first AAO biochemical section; the fifth mud-water mixture gas stripping device 11 is connected to the second anaerobic tank 41 through a second external return line 52, and is used for sludge return of the second AAO biochemical section; the fourth mud-water mixture gas stripping device 10 and the fifth mud-water mixture gas stripping device 11 are both provided with a pressure reducing solenoid valve with controllable opening, and the pressure reducing solenoid valve is connected to an external control system.

[0046] A first internal return pipeline 61 is provided between the first anoxic tank 32 and the third pipeline 23 for the return of the mud-water mixture of the first AAO biochemical section; a second internal return pipeline 62 is provided between the second anoxic tank 42 and the fourth pipeline 24 for the return of the mud-water mixture of the second AAO biochemical section.

[0047] The first anaerobic tank 31 is provided with a first pneumatic flow-pushing device 71 for driving the sewage in the first anaerobic tank 31 to flow and push the sewage from the first anaerobic tank 31 to the first anoxic tank 32; the first anoxic tank 32 is provided with a second pneumatic flow-pushing device 72 for driving the sewage in the first anoxic tank 32 to flow and push the sewage from the first anoxic tank 32 to the first aerobic tank 33.

[0048] The second anaerobic tank 41 is provided with a third pneumatic flow-pushing device 73 for driving the sewage in the second anaerobic tank 41 to flow and push the sewage from the second anaerobic tank 41 to the second anoxic tank 42; the second anoxic tank 42 is provided with a fourth pneumatic flow-pushing device 74 for driving the sewage in the second anoxic tank 42 to flow and push the sewage from the second anoxic tank 42 to the second aerobic tank 43.

[0049] As is known, both the first AAO biochemical section and the second AAO biochemical section are provided with an aeration device.

[0050] The first gas stripping device 1, the second gas stripping device 2, the fourth gas stripping device 4 and the sixth gas stripping device 6 are all prior art, and their structures are as follows: Figure 5 As shown, its operating mechanism is as follows: when air is taken in and water is discharged, the solenoid valve A509 is opened, the solenoid valve B510 is closed, and the pressurized air enters the submersible tube 503 from the air intake pipe 501. Under the action of air pressure, the one-way valve A507 is closed, the one-way valve B508 is opened, and the air pressure discharges the water in the submersible tube 503 from the drain pipe 506; when air is released and water is allowed in, the solenoid valve A509 is closed, the solenoid valve B510 is opened, and the pressurized air in the submersible tube 503 is discharged from the exhaust pipe 502. Affected by the water pressure, the one-way valve A507 is opened, water enters the submersible tube 503, and the one-way valve B508 is closed.

[0051] The structures of the first mud-water mixture gas stripping device 7, the second mud-water mixture gas stripping device 8, the third mud-water mixture gas stripping device 9, the fourth mud-water mixture gas stripping device 10 and the fifth mud-water mixture gas stripping device 11 are as shown in the company's authorized patent (CN202220798179), which can lift mud-water mixtures and also lift sludge with higher concentrations.

[0052] The structure of the pneumatic flow-pushing device 9 is the pneumatic flow-pushing device described in Patent 203346102U, or other airflow-driven flow-pushing stirring equipment with similar functions.

[0053] Specifically, in the technical solution of the present application, the internal reflow ratio refers to the ratio of the flow rate of the mud-water mixture returned from the outlet pipe of the aerobic tank to the anaerobic tank to the inlet flow rate of the AAO biochemical section, and its main function is repeated denitrification and phosphorus removal; the external reflow ratio refers to the ratio of the sludge flow rate returned from the secondary sedimentation tank to the anoxic tank to the inlet flow rate of the AAO biochemical section. The external reflow ratio is determined based on the sludge concentration to be maintained in the AAO biochemical section and the sludge concentration at the bottom of the secondary sedimentation tank. In the prior art, its main function is to maintain the sludge concentration of the AAO biochemical section. For those skilled in the art, the definitions of the internal reflow ratio and the external reflow ratio belong to well-known techniques.

[0054] The control principle of the sewage treatment system proposed by the present invention is as follows: Figure 4As shown, the external control system receives the signal of the flow sensor 27. If the flow rate changes, it first controls the pressure reducing solenoid valve of the first gas stripping device 1 to increase the air intake pressure of the first gas stripping device 1 and increase its drainage flow rate. At the same time, it controls the first mud-water mixture gas stripping device 7, the second mud-water mixture gas stripping device 8, and the third mud-water mixture gas stripping device 9 to open, and transports the sludge in the second AAO biochemical section to the first AAO biochemical section at an appropriate flow rate to increase the sludge amount in the first AAO biochemical section. At this time, due to the mud-water mixture flow rate of the first AAO biochemical section Increased, therefore, it is necessary to control the flow rate of the fourth gas lift device 4 to increase so as to increase the flow rate of the first internal return pipeline 61, and control the flow rate of the fourth mud-water mixture gas lift device 10 to increase so as to increase the flow rate of the first external return pipeline 51; and the sludge in the second AAO section decreases, therefore, it is necessary to control the flow rate of the fifth mud-water mixture gas lift device 11 to increase so as to compensate for the sludge in the second AAO section. Since the operation of the second AAO section only maintains the basic activity of the activated sludge, its inlet flow rate remains unchanged, and only the external return ratio is changed, the effect on the sludge activity therein is very small and can be ignored.

[0055] The parts not described in detail in this invention are prior art.

Claims

1. A parallel dual biochemical sewage treatment process, characterized by: The following steps are involved: Step S1, the sewage inflow is a normal water volume Z, the sewage enters the first AAO biochemical section from the regulating tank through the first pipeline, and at the same time, the sewage also enters the second AAO biochemical section from the regulating tank through the second pipeline, and the water inflow of the second AAO biochemical section remains constant, only maintaining the basic activity of the activated sludge; the sewage treated by the first AAO biochemical section and the second AAO biochemical section are discharged to the secondary sedimentation tank; Step S2, the sewage water volume increases to T, and the water inflow of the second AAO biochemical section remains unchanged, then the water volume in the first pipeline increases to T, and the increment is △T, and the activated sludge corresponding to the second AAO biochemical section and the first AAO biochemical section is transferred to the first AAO biochemical section in a timely manner, so that the ratio H of the sludge volume M transferred from the second AAO biochemical section to △T remains constant, and the internal reflow ratio r1 and the external reflow ratio R1 of the first AAO biochemical section remain constant, and at the same time, the external reflow ratio R2 of the second AAO biochemical section is increased, so that the activated sludge volume of the second AAO biochemical section is compensated by the external reflow, and the external reflow compensation amount m is less than M; Step S3, the sewage water volume decreases from T, so that the water volume of the second AAO biochemical section remains unchanged, and the activated sludge of the second AAO biochemical section is stopped from transferring to the first AAO biochemical section, and the internal reflow ratio r1 and the external reflow ratio R1 of the first AAO biochemical section are still kept constant, and at the same time, the external reflow compensation amount m of the activated sludge volume of the second AAO biochemical section is reduced; Step S4: When the sewage inflow volume is restored from T to Z, the amount of activated sludge in the second AAO biochemical stage is restored to the initial value, and the operation returns to step S1.

2. The parallel dual biochemical sewage treatment process according to claim 1 is characterized by: In the step S1, the external reflux ratio R1 of the first AAO biochemical section and the external reflux ratio R2 of the second AAO biochemical section remain unchanged, and the value ranges thereof are both 50%-100%.

3. The parallel dual biochemical sewage treatment process according to claim 1 is characterized by: In step S2, the ratio of H to the sludge load rate of the first AAO biochemical stage is a constant value.

4. A sewage treatment system operating the process according to any one of claims 1 to 3, characterized in that: The invention comprises a regulating tank (20), a first AAO biochemical section, a second AAO biochemical section and a secondary sedimentation tank (40); the regulating tank (20) is connected to an external sewage source via a sixth pipeline (26); a flow sensor (27) is provided on the sixth pipeline (26) for detecting the sewage flow rate of the sixth pipeline (26); a first gas stripping device (1) and a second gas stripping device (2) are provided in the regulating tank (20); the first AAO biochemical section and the second AAO biochemical section are connected in parallel between the regulating tank (20) and the secondary sedimentation tank (40); the first AAO biochemical section is composed of a first anaerobic tank (31), a first anoxic tank (32) and a first aerobic tank (33) which are connected in series in sequence; the first anaerobic tank (31) is connected to the first gas stripping device (1) in the regulating tank (20) via a first pipeline (21); the first anaerobic tank (31) and the first anoxic tank (32) are connected to the first aerobic tank (33); (32) are connected via a first pipeline, the first anoxic tank (32) and the first aerobic tank (33) are connected via a second pipeline, a fourth gas stripping device (4) is provided in the first aerobic tank (33), and the fourth gas stripping device (4) is connected to the second sedimentation tank (40) via a third pipeline (23); the second AAO biochemical section is composed of a second anaerobic tank (41), a second anoxic tank (42) and a second aerobic tank (43) connected in series in sequence, the second anaerobic tank (41) is connected to the second gas stripping device (2) via a second pipeline (22), the second anaerobic tank (41) and the second anoxic tank (42) are connected via a third pipeline, the second anoxic tank (42) and the second aerobic tank (43) are connected via a fourth pipeline, a sixth gas stripping device (6) is provided in the second aerobic tank (43), and the sixth gas stripping device (6) is connected to the second sedimentation tank (40) via a fourth pipeline (24); The first anaerobic tank (31) and the second anaerobic tank (41) are connected via a first mud-water mixture gas stripping device (7), the first anoxic tank (32) and the second anoxic tank (42) are connected via a second mud-water mixture gas stripping device (8), and the first aerobic tank (33) and the second aerobic tank (43) are connected via a third mud-water mixture gas stripping device (9); The first gas lift device (1), the second gas lift device (2), the fourth gas lift device (4), the sixth gas lift device (6), the first mud-water mixture gas lift device (7), the second mud-water mixture gas lift device (8), and the third mud-water mixture gas lift device (9) are all supplied with gas by an external Roots blower. The air inlet pipelines of the first gas lift device (1), the fourth gas lift device (4), the first mud-water mixture gas lift device (7), the second mud-water mixture gas lift device (8), and the third mud-water mixture gas lift device (9) are all provided with pressure reducing solenoid valves with controllable openings. The pressure reducing solenoid valves are all connected to an external control system. The flow sensor (27) on the sixth pipeline (26) is also connected to the external control system.

5. The sewage treatment system according to claim 4, characterized in that: A fourth mud-water mixture gas stripping device (10) and a fifth mud-water mixture gas stripping device (11) are provided in the secondary sedimentation tank (40); the fourth mud-water mixture gas stripping device (10) is connected to the first anaerobic tank (31) via a first external return line (51) for sludge return from the first AAO biochemical section; the fifth mud-water mixture gas stripping device (11) is connected to the second anaerobic tank (41) via a second external return line (52) for sludge return from the second AAO biochemical section; the fourth mud-water mixture gas stripping device (10) and the fifth mud-water mixture gas stripping device (11) are both provided with pressure reducing solenoid valves with controllable openings, and the pressure reducing solenoid valves are both connected to an external control system.

6. The sewage treatment system according to claim 4, characterized in that: A first internal return pipeline (61) is provided between the first anoxic tank (32) and the third pipeline (23) for returning the mud-water mixture of the first AAO biochemical section; and a second internal return pipeline (62) is provided between the second anoxic tank (42) and the fourth pipeline (24) for returning the mud-water mixture of the second AAO biochemical section.

7. The sewage treatment system according to claim 4, characterized in that: The first anaerobic tank (31) is provided with a first pneumatic flow-pushing device (71) for driving the sewage in the first anaerobic tank (31) to flow and push the sewage from the first anaerobic tank (31) to the first anoxic tank (32); the first anoxic tank (32) is provided with a second pneumatic flow-pushing device (72) for driving the sewage in the first anoxic tank (32) to flow and push the sewage from the first anoxic tank (32) to the first aerobic tank (33).

8. The sewage treatment system according to claim 4, characterized in that: The second anaerobic tank (41) is provided with a third pneumatic flow-pushing device (73) for driving the sewage in the second anaerobic tank (41) to flow and pushing the sewage from the second anaerobic tank (41) to the second anoxic tank (42); the second anoxic tank (42) is provided with a fourth pneumatic flow-pushing device (74) for driving the sewage in the second anoxic tank (42) to flow and pushing the sewage from the second anoxic tank (42) to the second aerobic tank (43).

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