Single-tower type multi-stage self-circulation sewage treatment device with built-in partitions and method

Abstract

The single-tower multi-stage self-circulation sewage treatment device with the built-in partitions comprises a tower body, a water inlet pipe, a water outlet pipe and a cross-shaped partition plate, the tower body is divided into an aeration area, an aerobic area, an anoxic area and an anaerobic area by the cross-shaped partition plate, and an aeration disc is arranged at the bottom of the aeration area; the aerobic zone, the anoxic zone, the anaerobic zone and the aeration zone are communicated through the first circulating column, the second circulating column, the third circulating column and the fourth circulating column, and granular sludge is inoculated in the aerobic zone, the anoxic zone and the anaerobic zone. The sewage treatment method comprises the following steps: a) self-circulation; b) carrying out denitrification reaction; c) aeration reaction; d) carrying out aerobic reaction; and e) carrying out anoxic reaction. According to the single-tower type multi-stage self-circulation sewage treatment device with the built-in partitions and the method, the whole device adopts a single-tower body, so that the space utilization rate is high, the arrangement is convenient, and an external power source is not needed; and a corresponding control strategy is adopted, so that the removal effect of ammonia nitrogen and organic matters in the sewage is ensured.

Description

Technical Field

[0001] This invention relates to a wastewater treatment apparatus and method, and more specifically, to a single-tower multi-stage self-circulating wastewater treatment apparatus and method with built-in partitions. Background Technology

[0002] Nitrogenous organic wastewater is widely generated in chemical, pharmaceutical, fine chemical, food processing, aquaculture, and urban sewage industries. It contains large amounts of organic pollutants and nitrogen compounds, characterized by high pollution load, complex composition, and significant treatment challenges. Direct discharge without effective treatment will cause serious harm to the ecological environment and human health. On the one hand, the degradation of organic matter in the wastewater consumes large amounts of dissolved oxygen in the water, and the high oxygen requirements for ammonia nitrification can easily lead to hypoxia or even anaerobic conditions, damaging aquatic ecosystems and inducing eutrophication and algal blooms. On the other hand, ammonia nitrogen, nitrite, and nitrate, once they enter drinking water sources, may endanger human health and affect drinking water safety. Furthermore, nitrogen pollutants have strong mobility and may cause long-term pollution of groundwater and soil. With increasingly stringent environmental regulations on ammonia nitrogen and total nitrogen emission limits, nitrogenous organic wastewater has become one of the most pressing problems to be solved in the field of water pollution control. Therefore, developing efficient, economical, and sustainable organic nitrogenous wastewater treatment technologies has become a research hotspot in the field of environmental engineering.

[0003] Traditional wastewater treatment technologies, especially the activated sludge process, face significant challenges in treating nitrogen-containing organic wastewater, such as sludge bulking, low treatment efficiency, and operational instability. Aerobic granular sludge, as a novel wastewater treatment technology, has gained widespread attention and application in the water treatment field in recent years due to its high settling properties, strong resistance to shock loads, and high treatment efficiency. Domestic and international scholars have conducted systematic research on the cultivation methods, formation mechanisms, granulation influencing factors, and engineering applications of aerobic granular sludge. However, existing research largely focuses on aerobic granular sludge in sequencing batch reactors (SBRs). Although these reactors can partially simulate actual wastewater treatment conditions, their intermittent flow operation mode still differs significantly from actual continuous flow systems. In the wastewater treatment field, continuous flow operation is highly valued due to its close resemblance to practical applications. Compared to intermittent flow systems, continuous flow reactors provide a more stable hydraulic environment, facilitating the integration of automated control modules, thereby improving treatment efficiency and reducing operation and maintenance costs. However, the stable cultivation and long-term maintenance of aerobic granular sludge in continuous flow systems still faces technical bottlenecks.

[0004] Therefore, the future research direction and breakthrough point for continuous flow aerobic granular sludge lies in deeply exploring the granulation mechanism in continuous flow, clarifying the roles of hydraulic shear force, selective pressure, and microbial community, developing novel continuous flow reactors, and enhancing granulation effect and operational stability by optimizing reactor structure and operation strategies. The aerated self-circulating reactor relies on independent aeration from aeration columns to create a pressure difference driving circulation. Through optimization of the hydraulic circulation structure, it achieves dozens of internal circulations of wastewater without external power, obtaining a high upward flow velocity to ensure sufficient pollutant degradation and the formation of aerobic granular sludge, significantly reducing operating energy consumption. By varying the oxygen concentration gradient, a multi-stage reaction environment is constructed, enhancing pollutant degradation efficiency. Its operating conditions are relatively strict, requiring the maintenance of a stable upward flow velocity to ensure shear force and prevent granular sludge disintegration. Because factors such as aeration and return valve opening can easily cause fluctuations in sludge bed height and operating status, traditional manual adjustment suffers from problems such as over-adjustment or directional deviation. Therefore, automated control technology is introduced into this device, combining online monitoring, logic control, and electric regulating equipment to achieve intelligent real-time regulation of the reactor. This not only improves operational stability and reduces reliance on manual labor and accident risks, but also compensates for the shortcomings of manual operation by continuously correcting and optimizing the regulation accuracy. Therefore, this paper proposes a single-tower multi-stage self-circulating wastewater treatment device and method with built-in partitioning. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned technical problems, the present invention provides a single-tower multi-stage self-circulating sewage treatment device and method with built-in partitions.

[0006] The present invention relates to a single-tower multi-stage self-circulating wastewater treatment device with built-in partitions, comprising a tower body, an inlet pipe, an outlet pipe, and a cross-shaped partition. The cross-shaped partition is located in the tower body and sequentially divides the internal cavity of the tower body into an aeration zone, an aerobic zone, an anoxic zone, and an anaerobic zone. The inlet pipe communicates with the upper part of the anoxic zone, and the outlet pipe communicates with the upper part of the aerobic zone. An aeration disc is provided at the bottom of the aeration zone. The device is characterized in that: a first circulation column is provided in the aerobic zone to connect the upper part of the aeration zone with the lower part of the aerobic zone; and a second circulation column is provided in the anoxic zone to connect the upper part of the aerobic zone with the lower part of the anoxic zone. The anaerobic zone is equipped with a third circulation column to connect the upper part of the anoxic zone and the lower part of the anaerobic zone. The aeration zone is equipped with a fourth circulation column to connect the upper part of the anaerobic zone and the lower part of the aeration zone. The lower ends of the first, second, third and fourth circulation columns are respectively connected to aerobic water distribution pipes, anoxic water distribution pipes, anaerobic water distribution pipes and aeration water distribution pipes placed at the bottom of the aerobic zone, anoxic zone, anaerobic zone and aeration zone. The second circulation column and the third circulation column are respectively equipped with liquid flow meters and reflux control valves. The aerobic zone, anoxic zone and anaerobic zone are all inoculated with granular sludge for wastewater treatment.

[0007] The single-tower multi-stage self-circulating sewage treatment device with built-in partitions of the present invention has downward-facing water distribution holes evenly opened on the aerobic water distribution pipe, the anoxic water distribution pipe, the anaerobic water distribution pipe and the aeration water distribution pipe.

[0008] The single-tower multi-stage self-circulating sewage treatment device with built-in partitions of the present invention includes a variable frequency blower. The air outlet of the variable frequency blower is connected to the aeration disc via an aeration pipeline. An air volume control valve and a gas flow meter are installed on the aeration pipeline between the variable frequency blower and the aeration disc.

[0009] The single-tower multi-stage self-circulating sewage treatment device with built-in partitions of the present invention includes a host PC, a PLC controller, and DO, nitrate nitrogen, COD, ammonia nitrogen and sludge concentration MLSS meters connected to the PLC controller. The PLC controller is connected to the host PC and the variable frequency fan (38). The upper parts of the aeration zone, aerobic zone and anoxic zone are respectively equipped with a first DO sensor, a second DO sensor and a third DO sensor connected to the DO meter. The upper parts of the aerobic zone, anoxic zone and anaerobic zone are respectively equipped with a first nitrate nitrogen sensor, a second nitrate nitrogen sensor and a third nitrate nitrogen sensor connected to the nitrate nitrogen meter. The upper parts of the aerobic zone, anoxic zone and anaerobic zone are respectively equipped with a first COD sensor, a second COD sensor and a third COD sensor connected to the COD meter. The upper parts of the aerobic, anoxic, and anaerobic zones are respectively equipped with a first ammonia nitrogen sensor, a second ammonia nitrogen sensor, and a third ammonia nitrogen sensor, all connected to an ammonia nitrogen meter. The upper parts of the aerobic, anoxic, and anaerobic zones are respectively equipped with a first MLSS sensor, a second MLSS sensor, and a third MLSS sensor, all connected to a sludge concentration MLSS meter. The upper part of the aerobic column is equipped with a pH sensor connected to the input terminal of a PLC controller. The liquid flow meter and the gas flow meter are both connected to the input terminal of the PLC controller. The output terminal of the PLC controller is connected to the control terminal of the reflux control valve and the air volume control valve.

[0010] The wastewater treatment method of the single-tower multi-stage self-circulating wastewater treatment device with built-in partitioning of the present invention is characterized by being implemented through the following steps: a) Self-circulation; Under the control of the PLC controller, the variable frequency blower aerates and oxygenates the bottom of the aeration zone through the aeration disc. The aeration significantly reduces the density of the mixed liquor at the bottom of the aeration zone, making the density of the mixed liquor at the bottom of the aeration zone less than the liquid density at the top of the anaerobic zone. At the same time, the liquid level at the top of the aeration zone is higher than the liquid level at the top of the aerobic zone. Under the action of density difference and liquid level difference, the sewage circulates back and forth between the aeration zone, aerobic zone, anoxic zone and anaerobic zone, without the need for a circulation drive device. b) Denitrification reaction: The wastewater to be treated enters the upper part of the anoxic zone through the inlet pipe, mixes with the return liquid from the anoxic zone, and then enters the anaerobic zone through the third circulation column; In the anaerobic zone, the wastewater entering through the inlet pipe comes into contact with and mixes with the nitrate-rich mixed liquid from the anoxic zone. Under the action of denitrifying bacteria in the granular sludge, the organic carbon source in the inlet water is used as an electron donor to carry out the denitrification reaction to reduce nitrate nitrogen to nitrogen gas, thus completing efficient nitrogen removal; c). Aeration reaction: The liquid at the top of the anaerobic zone enters the bottom of the aeration zone through the fourth circulation column. Under the aeration action of the aeration disc, it is oxygenated and rises. During this process, heterotrophic bacteria degrade the remaining organic matter in the mixed liquid, and autotrophic nitrifying bacteria oxidize ammonia nitrogen into nitrate nitrogen. d) Aerobic reaction; The mixture of high dissolved oxygen and nitrate nitrogen in the upper part of the aeration zone enters the aerobic zone through the first circulation column. As the mixture rises in the aerobic zone, it further degrades organic matter and completes nitrification. Part of the supernatant in the upper part of the aerobic zone is discharged through the effluent pipe, and the remaining supernatant is returned to the anoxic zone through the second circulation column. e) Anoxic reaction: In the anoxic zone, the nitrate nitrogen is initially denitrified using the carbon source of the raw water or endogenous metabolism, and then enters the anaerobic zone through the third circulation column to enter the next cycle.

[0011] The wastewater treatment method of the single-tower multi-stage self-circulating wastewater treatment device with built-in partitioning of the present invention has the following control strategy: 1) Judgment and treatment of sludge loss in aerobic zone; When the PLC controller detects through the first MLSS sensor that the sludge concentration in the upper part of the aerobic zone exceeds 2000mg / L and lasts for 10 minutes, it is determined that the sludge bed in the aerobic zone is too high and there is a risk of loss. The PLC controller then controls the return control valve to reduce the opening to reduce the upward flow rate and make the sludge in the aerobic zone fall back. 2) Dissolved oxygen gradient optimization: When the PLC controller detects that the total nitrogen concentration of the wastewater in the upper part of the aerobic zone exceeds 15 mg / L through the first nitrate nitrogen sensor and the first ammonia nitrogen sensor, it indicates that the total nitrogen value is too high. At the same time, the dissolved oxygen content of the water in the upper part of the aerobic zone is detected in real time by the second DO sensor to be >0.5 mg / L, while the parameters of other sensors remain within the normal range. It is then determined that the oxygen supply of the aeration disc is too high. By reducing the frequency of the variable frequency blower and the opening of the return control valve, the aeration volume and circulation flow are reduced to ensure the denitrification efficiency of the anoxic and anaerobic zones. 3) Judgment and treatment of excessive sludge deposition in anoxic and anaerobic zones: When the PLC controller detects that the sludge concentration in the upper part of the anoxic or anaerobic zone is below 1000 mg / L and the total nitrogen concentration in the upper part of the aerobic zone exceeds 15 mg / L, and other sensor parameters are normal, it is determined that excessive sludge deposition has occurred in the anoxic or anaerobic zone. At this time, through the negative feedback adjustment mechanism, the aeration rate and the opening of the return control valve are increased, the pressure difference and upward flow velocity between the columns are increased, and the sludge bed is re-expanded and raised to the target height to ensure sufficient contact between sludge and water. 4) COD and ammonia nitrogen judgment and treatment in the aerobic zone; when the PLC controller detects that the COD or ammonia nitrogen in the upper part of the aerobic zone exceeds the standard through the first COD sensor and the first ammonia nitrogen sensor, and the parameters of the other sensors are within the normal range, it is judged that the oxygen supply is insufficient. The frequency of the variable frequency fan and the opening of the reflux control valve are increased simultaneously to increase the aeration volume and reflux ratio to improve the COD or ammonia nitrogen removal rate. If COD or ammonia nitrogen levels in the upper aerobic zone exceed the standard, and the sludge concentration in the upper aerobic zone is detected to be below 1000 mg / L and dissolved oxygen is above 0.5 mg / L by the first MLSS sensor and the second DO sensor, it indicates that excessive sludge deposition has occurred in the aerobic zone, which has hindered the biochemical reaction process and caused a sharp drop in dissolved oxygen consumption. At this time, the aeration rate and the opening of the return control valve are increased through the negative feedback adjustment mechanism, and the pressure difference and upward flow velocity between the circulation columns are increased to re-expand the sludge bed to the target height, ensuring full contact between sludge and water. 5) Judgment and treatment of sludge accumulation in the anaerobic zone; When the sludge concentration in the upper part of the anaerobic zone detected by the PLC controller via the third MLSS sensor is more than 1000 mg / L higher than the sludge concentration in the upper part of the aerobic zone detected by the first MLSS sensor and remains higher for a period of time, and the parameters of the other sensors remain within the normal range, it is determined that sludge has accumulated in the anaerobic zone; at this time, the PLC controller triggers the "forced backflow" mode, synchronously increasing the frequency of the variable frequency fan and the opening of the backflow control valve to generate strong hydraulic flushing, "pulling" the sludge accumulated in the anaerobic zone back to the aeration zone, so as to redistribute the sludge of the entire wastewater treatment device.

[0012] The beneficial effects of this invention are as follows: The single-tower multi-stage self-circulating sewage treatment device and method with built-in partitions of this invention consists of an aeration zone, an aerobic zone, an anoxic zone, an anaerobic zone, an inlet pipe, an outlet pipe, and first, second, third, and fourth circulation columns. A cross-shaped baffle installed in the tower body divides the internal cavity of the tower body into four functional zones. The first, second, third, and fourth circulation columns connect the upper and lower parts of the aeration zone, aerobic zone, anoxic zone, and anaerobic zone. The sewage to be treated enters the anoxic zone through the inlet pipe. In the anaerobic zone, the wastewater to be treated and the circulating liquid circulate sequentially between the anaerobic zone, aeration zone, aerobic zone, and anoxic zone. Through denitrification, nitrification, and aerobic reactions, ammonia nitrogen and organic matter in the water are removed. The treated supernatant flows out through the effluent pipe at the top of the aerobic zone, ultimately achieving the treatment of organic nitrogen-containing wastewater. Since the entire device adopts a single tower body, the space utilization rate is high and the layout is convenient. It is only necessary to connect the effluent and influent pipes of the wastewater to be treated area to achieve effective treatment of continuous flow of wastewater for denitrification and removal of organic matter.

[0013] Furthermore, under the aeration effect of the aeration discs at the bottom of the aeration zone, the density of the mixed liquor at the bottom of the aeration zone is less than the density of the liquid at the top of the anaerobic zone, and the liquid level at the top of the aeration zone is higher than that at the top of the aerobic zone. Under the action of density difference and liquid level difference, the mixed liquor can circulate between the aeration zone, aerobic zone, anoxic zone and anaerobic zone without the need for an external power source. This not only reduces energy consumption in the sewage treatment process, but also avoids damage to granular sludge when using a circulating pump.

[0014] Furthermore, to ensure the removal effect of ammonia nitrogen and organic matter in wastewater, a PLC controller and sensors for DO, nitrate nitrogen, COD, ammonia nitrogen, and sludge concentration are installed. The wastewater treatment method of this invention adopts the following control strategies: (1) When the sludge concentration in the aerobic zone is detected to be too high (e.g., exceeding 2000 mg / L), it indicates that there is a risk of sludge loss in the aerobic zone. Therefore, the opening of the return control valve is reduced to allow the sludge in the aerobic zone to fall back. (2) When the total nitrogen concentration in the aerobic zone is detected to be too high (e.g., exceeding 15 mg / L), and the dissolved oxygen concentration in the aerobic zone is also too high (e.g., >0.5 mg / L), it indicates that the oxygen supply is too high, inhibiting the denitrification reaction. Therefore, the aeration volume and circulation flow rate are reduced. (3) When the total nitrogen concentration in the aerobic zone is too high, and the sludge concentration in the anoxic and anaerobic zones is too low (e.g., below 1000 mg / L), If excessive sludge deposition occurs in the anoxic and anaerobic zones, a control strategy of increasing aeration volume and reflux control valve opening is adopted to raise the sludge layer to the target height; (4) If COD or ammonia nitrogen in the aerobic zone is detected to be above the standard while other parameters are normal, it indicates insufficient oxygen supply. A strategy of increasing aeration volume and reflux ratio is adopted to improve COD or ammonia nitrogen removal rate; If COD or ammonia nitrogen in the aerobic zone is above the standard and the sludge concentration in the aerobic zone is low and dissolved oxygen is too high, it indicates excessive sludge deposition in the aerobic zone. A control strategy of increasing aeration volume and reflux control valve opening is adopted; (5) If the sludge concentration in the upper part of the anaerobic zone is detected to be higher than the sludge concentration in the upper part of the aerobic zone by a certain threshold (e.g., more than 1000 mg / L), it indicates that sludge has accumulated in the anaerobic zone. A "forced reflux" mode is adopted to "pull" the sludge accumulated in the anaerobic zone back to the aeration zone for redistribution. As can be seen, the wastewater treatment method of the present invention determines the unfavorable conditions for wastewater treatment in the entire treatment device based on the detected sludge concentration, dissolved oxygen content, ammonia nitrogen concentration, nitrate nitrogen concentration and COD concentration in the corresponding area, and adopts corresponding control strategies to ensure the removal effect of ammonia nitrogen and organic matter in wastewater. Attached Figure Description

[0015] Figure 1 This is a front view of the single-tower multi-stage self-circulating wastewater treatment device with built-in partitions according to the present invention. Figure 2 This is a rear view of the single-tower multi-stage self-circulating wastewater treatment device with built-in partitions according to the present invention. Figure 3 This is a top view of the single-tower multi-stage self-circulating sewage treatment device with built-in partitions according to the present invention. Figure 4 , Figure 5 The images are a top view and a perspective view rendered respectively of the single-tower multi-stage self-circulating sewage treatment device with built-in partitions of the present invention. Figure 6This is a schematic diagram of the wastewater treatment device of the present invention equipped with a water quality detection sensor and an automated control system; Figure 7 This is a flowchart illustrating the control strategy of the wastewater treatment method of the wastewater treatment device of the present invention. Figure 8 This is a graph showing the long-term operation control parameter changes of the wastewater treatment device of the present invention; Figure 9 This is a diagram showing the removal of chemical oxygen demand (COD) by the wastewater treatment device of the present invention; Figure 10 This is a diagram showing the total nitrogen (TN) removal of the wastewater treatment device of the present invention; Figure 11 This is a diagram showing the ammonia nitrogen removal and changes in nitrite and nitrate levels in the wastewater treatment device of the present invention; Figure 12 This is a diagram showing the morphology of granular sludge cultivated during long-term operation of the wastewater treatment device of the present invention.

[0016] In the diagram: 1. Inlet pipe; 2. Aeration zone; 3. Aeration distribution pipe; 4. Aeration disc; 5. First circulation column; 6. Aerobic distribution pipe; 7. Aerobic zone; 8. Liquid flow meter; 9. Second circulation column; 10. Anoxic distribution pipe; 11. Anoxic zone; 12. Return control valve; 13. Third circulation column; 14. Anaerobic distribution pipe; 15. Anaerobic zone; 16. Fourth circulation column; 17. Outlet pipe; 18. DO meter; 19. First DO sensor; 20. Second DO sensor; 21. Third DO sensor; 22. Nitrogen / Nitrogen meter; 23. First Nitrogen / Nitrogen sensor; 24. Second Nitrogen / Nitrogen sensor; 25. Third Nitrogen / Nitrogen sensor; 26. COD meter, 27 First COD sensor, 28 Second COD sensor, 29 Third COD sensor, 30 Ammonia nitrogen meter, 31 First ammonia nitrogen sensor, 32 Second ammonia nitrogen sensor, 33 Third ammonia nitrogen sensor, 34 Sludge concentration MLSS meter, 35 First MLSS sensor, 36 Second MLSS sensor, 37 Third MLSS sensor, 38 Variable frequency fan, 39 Air volume control valve, 40 Gas flow meter, 41 pH sensor, 42 PLC controller, 43 Host PC, 44 Tower body, 45 Cross-shaped baffle. Detailed Implementation

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] like Figure 1 , Figure 2 and Figure 3 As shown, the front view, rear view, and top view of the single-tower multi-stage self-circulating sewage treatment device with built-in partitions of the present invention are given respectively. Figure 4 and Figure 5The renderings show a top view and a perspective view of the wastewater treatment device, which consists of a tower body 44, a cross-shaped baffle 45, an inlet pipe 1, an outlet pipe 17, a first circulation column 5, a second circulation column 9, a third circulation column 13, a fourth circulation column 16, and an aeration disc 4. The tower body 44 is cylindrical, and the cross-shaped baffle 45 is installed inside the tower body 44, dividing the internal cavity of the tower body 44 into an aeration zone 2, an aerobic zone 7, an anoxic zone 11, and an anaerobic zone 15. The aeration disc 4 is located at the bottom of the aeration zone 2 and is used to aerate the mixed liquor entering the bottom of the aeration zone 2. The inlet pipe 1 is connected to the upper part of the anoxic zone 11 and is used to introduce the wastewater to be treated into the upper part of the anoxic zone 11; the outlet pipe 17 is connected to the upper part of the aerobic zone 7, and the supernatant after wastewater treatment flows out through the outlet pipe 17.

[0019] The first circulation column 5, the second circulation column 9, the third circulation column 13, and the fourth circulation column 16 are respectively installed in the aerobic zone 7, the anoxic zone 11, the anaerobic zone 15, and the aeration zone 2. The first circulation column 5 connects the upper part of the aeration zone 2 with the lower part of the aerobic zone 7; the second circulation column 9 connects the upper part of the aerobic zone 7 with the lower part of the anoxic zone 11; the third circulation column 13 connects the upper part of the anoxic zone 11 with the lower part of the anaerobic zone 15; and the fourth circulation column 16 connects the upper part of the anaerobic zone 15 with the lower part of the aeration zone 2. In this way, the four circulation columns connect the aeration zone 2, the aerobic zone 7, the anoxic zone 11, and the anaerobic zone 15. A liquid flow meter 8 is installed on the second circulation column 9 to measure the circulation flow rate; a reflux control valve 12 is installed on the third circulation column 13, and the circulation flow rate can be adjusted by controlling the opening of the reflux control valve 12.

[0020] The bottoms of the first circulation column 5, the second circulation column 9, the third circulation column 13, and the fourth circulation column 16 are respectively connected to an aerobic water distribution pipe 6, an anoxic water distribution pipe 10, an anaerobic water distribution pipe 14, and an aeration water distribution pipe 3. Each water distribution pipe has several evenly distributed downward-facing water distribution holes on its surface. The downward-facing water distribution holes ensure the uniform distribution of circulating water on the cross-section of each functional zone, which helps to form a stable sludge bed in each functional zone, enhances the contact mixing effect between sludge and sewage, and thus ensures the overall treatment efficiency.

[0021] When the aeration discs 4 in aeration zone 2 are running, the generated bubbles cause the water in aeration zone 2 to form a gas-liquid mixture, thereby significantly reducing the average density of the mixed fluid in this area. At the same liquid level, the fluid pressure in aeration zone 2 is lower than the fluid pressure in anaerobic zone 15. This pressure difference forms a pressure gradient between the zones. Under the action of this pressure gradient, the fluid in anaerobic zone 15 is forced into the bottom of aeration zone 2, which has a lower density, through the fourth circulation column 16. At the same time, the gas-liquid mixing causes the liquid level in aeration zone 2 to rise relatively, forming a decreasing liquid potential energy difference between the functional zones from aeration zone 2 to aerobic zone 7, anoxic zone 11, and anaerobic zone 15. Driven by this liquid potential energy difference, the wastewater flows sequentially through aerobic zone 7, anoxic zone 11, and anaerobic zone 15, and finally returns to aeration zone 2, thereby achieving automatic closed-loop circulation of liquid in the four functional zones without the need for an external circulation pump. It is evident that the wastewater treatment device of the present invention utilizes the airlift principle to achieve self-circulation without an external water pump, which not only reduces energy consumption in the wastewater treatment process, but also avoids the damage to granular sludge caused by the blades when using a circulating pump.

[0022] like Figure 6 The diagram shows a wastewater treatment device of the present invention equipped with a water quality detection sensor and an automated control system. The water quality detection sensor and automated control system includes a variable frequency fan 38, a PLC controller 42, a host PC 43, and DO meter 18, nitrate nitrogen meter 22, COD meter 26, ammonia nitrogen meter 30, and sludge concentration MLSS meter 34 connected to the PLC controller 42. The PLC controller 42 is communicatively connected to the host PC 43. The outlet of the variable frequency fan 38 is connected to the aeration disc 4 via an aeration pipe. An air volume control valve 39 and a gas flow meter 40 are installed on the aeration pipe between the variable frequency fan 38 and the aeration disc 4.

[0023] The upper portions of aeration zone 2, aerobic zone 7, and anoxic zone 11 are respectively equipped with a first DO sensor 19, a second DO sensor 20, and a third DO sensor 21, all connected to DO meter 18, to measure dissolved oxygen. The upper portions of aerobic zone 7, anoxic zone 11, and anaerobic zone 15 are respectively equipped with a first nitrate nitrogen sensor 23, a second nitrate nitrogen sensor 24, and a third nitrate nitrogen sensor 25, all connected to nitrate nitrogen meter 22, to measure nitrate nitrogen content. The upper portions of aerobic zone 7, anoxic zone 11, and anaerobic zone 15 are respectively equipped with a first COD sensor 27, a second COD sensor 28, and a third COD sensor 29, all connected to COD meter 26, to measure chemical oxygen demand.

[0024] The upper parts of aerobic zone 7, anoxic zone 11, and anaerobic zone 15 are respectively equipped with a first ammonia nitrogen sensor 31, a second ammonia nitrogen sensor 32, and a third ammonia nitrogen sensor 33, all connected to the ammonia nitrogen meter 30, to measure ammonia nitrogen. The upper parts of aerobic zone 7, anoxic zone 11, and anaerobic zone 15 are respectively equipped with a first MLSS sensor 35, a second MLSS sensor 36, and a third MLSS sensor 37, all connected to the sludge concentration MLSS meter 34, to measure sludge concentration. The upper part of aerobic zone 7 is equipped with a pH sensor 41 connected to the input terminal of PLC controller 42. Liquid flow meter 8 and gas flow meter 40 are both connected to the input terminals of PLC controller 42. The output terminal of PLC controller 42 is connected to the control terminals of reflux control valve 12 and airflow control valve 39.

[0025] A significant dissolved oxygen gradient is created within the device through aeration in aeration zone 2: aeration zone 2 serves as the sole power source and oxygenation zone of the system, maintaining the highest dissolved oxygen concentration; the circulating fluid carries dissolved oxygen into aerobic zone 7, where dissolved oxygen is largely consumed by organic matter degradation and nitrification; as the fluid enters anoxic zone 11 and anaerobic zone 15, the environment gradually transforms into anoxic and anaerobic states, thereby utilizing the influent carbon source and endogenous metabolic dominant bacteria for efficient denitrification.

[0026] Within each functional zone, wastewater flows upwards, allowing for deep contact between the fluid and the suspended sludge layer. By coordinating the aeration rate and the return flow control valve 12, the upward flow velocity of the liquid within the system is controlled between 10 m / h and 40 m / h, and the ratio of return flow to influent flow is maintained between 20 and 50. This high-velocity, high-return-ratio operating mode creates a high-shear hydraulic environment in each reaction zone. Under the continuous shearing action of the upward flow, the suspended sludge undergoes granular aggregation, gradually evolving into dense granular sludge with excellent settling properties, thereby significantly improving the system's volumetric loading and shock resistance.

[0027] During the initial startup and sludge acclimatization phases, the low-density flocculent sludge accumulated in the upper part of the aerobic zone 7 is mostly carried by the fluid through the second circulation column 9 into the circulation system. Through repeated circulation and shearing, it is induced to transform into granular sludge, with a small portion of the flocculent sludge being washed out of the system through the effluent pipe 17. As operation stabilizes, the sludge composition within the system gradually becomes dominated by granular sludge. To adapt to the fluctuations in bed height caused by changes in sludge morphology, this invention uses an online detection and feedback system to dynamically adjust the upward flow velocity of wastewater, ensuring a continuously stable sludge bed structure.

[0028] The wastewater to be treated first enters the upper part of the anoxic zone 11, mixes with the return liquid, and then enters the anaerobic zone 15 through the third circulation column 13. Here, it comes into contact with the nitrate-rich mixed liquid from the anoxic zone 11 and mixes with the organic carbon source in the influent as an electron donor to carry out a denitrification reaction, reducing nitrate nitrogen to nitrogen gas, thus completing the pre-denitrification. The denitrified mixed liquid is then airlifted back to the aeration zone 2 through the fourth circulation column 16. After aeration, heterotrophic bacteria degrade the remaining organic matter, and autotrophic nitrifying bacteria oxidize ammonia nitrogen to nitrate nitrogen. Subsequently, the circulating water rich in dissolved oxygen and nitrate nitrogen enters the aerobic zone 7 to continue deep organic matter degradation and ammonia nitrogen oxidation. The oxidized nitrified liquid enters the anoxic zone 11, where endogenous metabolism or the remaining carbon source is used to further reduce nitrate nitrogen. The treated fluid is then recirculated into the anaerobic zone 15, thus forming a closed-loop synchronous denitrification and carbon removal process.

[0029] To achieve long-term stable operation and unattended management of the device, this invention is equipped with an intelligent automated control system based on a PLC controller 42. This system collects multi-dimensional operating parameters in real time, including pH value, dissolved oxygen (DO), top sludge concentration (SS), chemical oxygen demand (COD), ammonia nitrogen concentration, and circulation flow rate. The system employs a closed-loop feedback control mechanism, calculating spatial gradients and time derivatives based on multi-sensor data and inputting the calculation results into a preset decision logic module. The controller automatically and precisely adjusts the actuators (especially the aeration intensity and the opening of the return control valve 12) according to the priority of the calculation results, thereby ensuring that the flow pattern, dissolved oxygen environment, and sludge distribution within the reactor are always maintained within the optimal predetermined range.

[0030] The wastewater treatment method of the single-tower multi-stage self-circulating wastewater treatment device with built-in partitions of the present invention is achieved through the following steps: a) Self-circulation; Under the control of PLC controller 42, variable frequency blower 38 aerates and oxygenates the bottom of aeration zone 2 through aeration disc 4. Aeration significantly reduces the density of the mixed liquor at the bottom of the aeration zone, making the density of the mixed liquor at the bottom of the aeration zone less than the liquid density at the top of the anaerobic zone. At the same time, the liquid level at the top of the aeration zone is higher than the liquid level at the top of the aerobic zone. Under the action of density difference and liquid level difference, the sewage circulates back and forth between "aeration zone-aerobic zone-anoxic zone-anaerobic zone", without the need for a circulation drive device. b) Denitrification reaction; the wastewater to be treated enters the upper part of the anoxic zone 11 through the inlet pipe 1, mixes with the return liquid from the anoxic zone 11, and then enters the anaerobic zone 15 through the third circulation column 13; in the anaerobic zone, the wastewater entering through the inlet pipe comes into contact with and mixes with the nitrate-rich mixed liquid from the anoxic zone. Under the action of denitrifying bacteria in the granular sludge, the organic carbon source in the inlet water is used as an electron donor to carry out the denitrification reaction to reduce nitrate nitrogen to nitrogen gas, thus completing efficient nitrogen removal; c). Aeration reaction; The liquid at the top of the anaerobic zone 15 enters the bottom of the aeration zone 2 through the fourth circulation column 16. Under the aeration action of the aeration disc, it is oxygenated and rises. During this process, heterotrophic bacteria degrade the remaining organic matter in the mixed liquid, and autotrophic nitrifying bacteria oxidize ammonia nitrogen into nitrate nitrogen. d) Aerobic reaction; The mixture of high dissolved oxygen and nitrate nitrogen in the upper part of the aeration zone 2 enters the aerobic zone 7 through the first circulation column 5. During the process of rising in the aerobic zone, the mixture further degrades organic matter and completes nitrification; Part of the supernatant in the upper part of the aerobic zone is discharged through the outlet pipe 17, and the remaining supernatant is returned to the anoxic zone through the second circulation column 9. e). Anoxic reaction: In the anoxic zone 11, the nitrate nitrogen is initially denitrified using the carbon source of the raw water or endogenous metabolism, and then enters the anaerobic zone 15 through the third circulation column 13 to enter the next cycle.

[0031] like Figure 7 As shown, a flowchart illustrating the control strategy of the wastewater treatment method of the wastewater treatment device of the present invention is presented, and the control strategy is as follows: 1) Judgment and treatment of sludge loss in aerobic zone; When the PLC controller 42 detects through the first MLSS sensor 35 that the sludge concentration in the upper part of aerobic zone 7 exceeds 2000mg / L and lasts for 10 minutes, it is determined that the sludge bed in aerobic zone is too high and there is a risk of loss. The PLC controller then controls the return control valve 12 to reduce the opening to reduce the upward flow rate and make the sludge in aerobic zone 7 fall back. 2) Dissolved oxygen gradient optimization: When the PLC controller 42 detects that the total nitrogen concentration of the wastewater in the upper part of the aerobic zone 7 exceeds 15 mg / L through the first nitrate nitrogen sensor 23 and the first ammonia nitrogen sensor, it indicates that the total nitrogen value is too high. At the same time, the dissolved oxygen content of the water in the upper part of the aerobic zone 7 is detected in real time by the second DO sensor 20 to be >0.5 mg / L, while the parameters of other sensors remain within the normal range, it is determined that the oxygen supply of the aeration disc is too high. The aeration volume and circulation flow are reduced by decreasing the frequency of the variable frequency blower 38 and the opening of the return control valve 12 to ensure the denitrification efficiency of the anoxic zone 11 and the anaerobic zone 15. 3) Judgment and treatment of excessive sludge deposition in anoxic and anaerobic zones; When the PLC controller 42 detects that the sludge concentration in the upper part of the anoxic zone 11 or anaerobic zone 15 is less than 1000 mg / L, and the total nitrogen concentration of the wastewater in the upper part of the aerobic zone 7 exceeds 15 mg / L, and the other sensor parameters are normal, it is determined that excessive sludge deposition has occurred in the anoxic zone 11 or anaerobic zone 15. At this time, through the negative feedback adjustment mechanism, the aeration rate and the opening of the return control valve are increased, the pressure difference and the upward flow velocity between the columns are increased, and the sludge bed is re-expanded and raised to the target height to ensure sufficient contact between sludge and water. 4) COD and ammonia nitrogen judgment and treatment in the aerobic zone; when the PLC controller 42 detects that the COD or ammonia nitrogen in the upper part of the aerobic zone 7 exceeds the standard through the first COD sensor 27 and the first ammonia nitrogen sensor 31, and the parameters of the other sensors are within the normal range, it is judged that the oxygen supply is insufficient, and the frequency of the variable frequency fan 38 and the opening of the reflux control valve 12 are increased simultaneously to increase the aeration volume and reflux ratio to improve the COD or ammonia nitrogen removal rate; If COD or ammonia nitrogen levels in the upper part of aerobic zone 7 exceed the standard, and the sludge concentration in the upper part of aerobic zone 7 is detected to be below 1000 mg / L and dissolved oxygen is >0.5 mg / L by the first MLSS sensor 35 and the second DO sensor 20, it indicates that excessive sludge deposition has occurred in aerobic zone 7, which has hindered the biochemical reaction process and caused a sharp drop in dissolved oxygen consumption. At this time, through the negative feedback regulation mechanism, the aeration rate and the opening of the return control valve are increased, the pressure difference and upward flow velocity between the circulation columns are increased, and the sludge bed is re-expanded and raised to the target height to ensure sufficient contact between sludge and water. 5) Judgment and treatment of sludge accumulation in the anaerobic zone; when the sludge concentration in the upper part of the anaerobic zone 15 detected by the third MLSS sensor 37 of the PLC controller 42 is more than 1000 mg / L higher than the sludge concentration in the upper part of the aerobic zone detected by the first MLSS sensor 35 for a period of time, and the parameters of the other sensors remain within the normal range, it is determined that sludge has accumulated in the anaerobic zone 15; at this time, the PLC controller 42 triggers the "forced backflow" mode, and simultaneously increases the frequency of the variable frequency fan 38 and the opening of the backflow control valve 12 to generate strong hydraulic flushing, "pulling" the sludge accumulated in the anaerobic zone 15 back to the aeration zone 2, so as to redistribute the sludge of the entire sewage treatment device.

[0032] like Figure 12 As shown, a morphological diagram of granular sludge cultivated during long-term operation of the wastewater treatment device of the present invention is presented. Figure 12 Figure (a) in the figure shows the actual state. Figure 12 Figure (b) shows an image of granular sludge under a microscope. It can be seen that under continuous flow shearing, the system successfully cultivated aerobic granular sludge with a dense structure and clear edges, and its settling velocity reached 10-40 m / h, which is much higher than that of ordinary flocculent sludge.

[0033] like Figure 8 As shown, a graph illustrating the long-term operation control parameters of the wastewater treatment device of the present invention is presented. It can be seen that when the circulation volume / influent volume changes, the upward flow velocity and aeration volume also change accordingly. By automatically adjusting the aeration volume and return ratio, the sludge concentration and dissolved oxygen environment of each functional zone are maintained within the set range, and no sludge loss or system collapse occurs. Figure 9A diagram showing the chemical oxygen demand (COD) removal of the wastewater treatment device of the present invention is provided. Despite fluctuations in influent COD, the effluent COD remains consistently at a low level, with a removal rate exceeding 90%, demonstrating excellent resistance to shock loads. Figure 10 shows a diagram showing the total nitrogen (TN) removal of the wastewater treatment device of the present invention. Through multi-stage alternating aerobic / anoxic environments, the system achieves efficient simultaneous nitrification and denitrification, ensuring stable effluent TN compliance. Figure 11 The diagrams showing the ammonia nitrogen removal and nitrite and nitrate changes of the wastewater treatment device of the present invention are provided, indicating that ammonia nitrogen is fully oxidized in the aeration and aerobic zones, while the generated nitrate nitrogen is effectively reduced in the anoxic and anaerobic zones, proving the effectiveness of the closed-loop denitrification pathway.

[0034] In summary, the single-tower multi-stage self-circulating sewage treatment device and method with built-in partitions of the present invention, through its unique single-tower partition structure and air-lift self-circulation, combined with an intelligent control method based on multi-dimensional parameter sensing, achieves efficient and low-energy sewage treatment and stable operation of granular sludge without the need for external water pumps.

Claims

1. A single-tower multi-stage self-circulating sewage treatment device with built-in partitions, comprising a tower body (44), an inlet pipe (1), an outlet pipe (17), and a cross-shaped baffle (45), wherein the cross-shaped baffle is located in the tower body and sequentially divides the internal cavity of the tower body into an aeration zone (2), an aerobic zone (7), an anoxic zone (11), and an anaerobic zone (15), wherein the inlet pipe is connected to the upper part of the anoxic zone, the outlet pipe is connected to the upper part of the aerobic zone, and an aeration disc (4) is provided at the bottom of the aeration zone; characterized in that: The aerobic zone is equipped with a first circulation column (5) for connecting the upper part of the aeration zone and the lower part of the aerobic zone. The anoxic zone is equipped with a second circulation column (9) for connecting the upper part of the aerobic zone and the lower part of the anoxic zone. The anaerobic zone is equipped with a third circulation column (13) for connecting the upper part of the anoxic zone and the lower part of the anaerobic zone. The aeration zone is equipped with a fourth circulation column (16) for connecting the upper part of the anaerobic zone and the lower part of the aeration zone. The lower ends of the first, second, third and fourth circulation columns are respectively connected to aerobic water distribution pipes (6), anoxic water distribution pipes (10), anaerobic water distribution pipes (14) and aeration water distribution pipes (3) placed at the bottom of the aerobic zone, anoxic zone, anaerobic zone and aeration zone, respectively. The second circulation column and the third circulation column are respectively equipped with liquid flow meters (8) and reflux control valves (12). The aerobic zone, anoxic zone and anaerobic zone are all inoculated with granular sludge for sewage treatment.

2. The single-tower multi-stage self-circulating sewage treatment device with built-in partitions according to claim 1, characterized in that: The aerobic water distribution pipe (6), the anoxic water distribution pipe (10), the anaerobic water distribution pipe (14), and the aeration water distribution pipe (3) are all uniformly provided with downward-facing water distribution holes.

3. The single-tower multi-stage self-circulating sewage treatment device with built-in partitions according to claim 1 or 2, characterized in that: It includes a variable frequency fan (38), the air outlet of the variable frequency fan is connected to the aeration disc (4) via an aeration pipe, and an air volume control valve (39) and a gas flow meter (40) are installed on the aeration pipe between the variable frequency fan and the aeration disc.

4. The single-tower multi-stage self-circulating sewage treatment device with built-in partitions according to claim 3, characterized in that: The system includes a host PC (43), a PLC controller (42), and DO meters (18), nitrate nitrogen meters (22), COD meters (26), ammonia nitrogen meters (30), and sludge concentration MLSS meters (34) connected to the PLC controller. The PLC controller is connected to both the host PC and the variable frequency fan (38). The upper parts of the aeration zone (2), aerobic zone (7), and anoxic zone (11) are respectively equipped with a first DO sensor (19), a second DO sensor (20), and a third DO sensor (21) connected to the DO meters. The upper parts of the aerobic zone, anoxic zone, and anaerobic zone are respectively equipped with a first nitrate nitrogen sensor (23), a second nitrate nitrogen sensor (24), and a third nitrate nitrogen sensor (25) connected to the nitrate nitrogen meter (22). The upper parts of the aerobic zone, anoxic zone, and anaerobic zone are respectively equipped with a first COD sensor (27), a second COD sensor (28), and a third COD sensor (29) connected to the COD meters. The upper parts of the aerobic zone, anoxic zone and anaerobic zone are respectively equipped with a first ammonia nitrogen sensor (31), a second ammonia nitrogen sensor (32) and a third ammonia nitrogen sensor (33) connected to the ammonia nitrogen meter (30). The upper parts of the aerobic zone, anoxic zone and anaerobic zone are respectively equipped with a first MLSS sensor (35), a second MLSS sensor (36) and a third MLSS sensor (37) connected to the sludge concentration MLSS meter (34). The upper part of the aerobic column is equipped with a pH sensor (41) connected to the input terminal of the PLC controller. The liquid flow meter (8) and the gas flow meter (40) are both connected to the input terminal of the PLC controller. The output terminal of the PLC controller is connected to the control terminal of the reflux control valve (12) and the air volume control valve (39).

5. A wastewater treatment method based on the single-tower multi-stage self-circulating wastewater treatment device with built-in partitions as described in claim 4, characterized in that, This can be achieved through the following steps: a) Self-circulation; Under the control of the PLC controller (42), the variable frequency blower (38) aerates and oxygenates the bottom of the aeration zone (2) through the aeration disc (4). The aeration significantly reduces the density of the mixed liquid at the bottom of the aeration zone, making the density of the mixed liquid at the bottom of the aeration zone less than the density of the liquid at the top of the anaerobic zone. At the same time, the liquid level at the top of the aeration zone is higher than the liquid level at the top of the aerobic zone. Under the action of density difference and liquid level difference, the sewage circulates back and forth in the "aeration zone-aerobic zone-anoxic zone-anaerobic zone", without the need for a circulation drive device. b). Denitrification reaction; the wastewater to be treated enters the upper part of the anoxic zone (11) through the inlet pipe (1) and mixes with the return liquid from the anoxic zone (11), and then enters the anaerobic zone (15) through the third circulation column (13); in the anaerobic zone, the wastewater entering through the inlet pipe comes into contact with the nitrate-rich mixed liquid from the anoxic zone and mixes with the denitrifying bacteria in the granular sludge under the action of the organic carbon source in the inlet water as an electron donor to carry out the denitrification reaction to reduce nitrate nitrogen to nitrogen gas, thus completing the efficient denitrification; c). Aeration reaction; The liquid at the top of the anaerobic zone (15) enters the bottom of the aeration zone (2) through the fourth circulation column (16). Under the aeration action of the aeration disc, oxygen is supplied and the liquid rises. During this process, heterotrophic bacteria degrade the remaining organic matter in the mixed liquid, and autotrophic nitrifying bacteria oxidize ammonia nitrogen into nitrate nitrogen. d). Aerobic reaction; The mixture of high dissolved oxygen and nitrate nitrogen in the upper part of the aeration zone (2) enters the aerobic zone (7) through the first circulation column (5). During the process of rising in the aerobic zone, the mixture further degrades organic matter and completes nitrification; Part of the supernatant in the upper part of the aerobic zone is discharged through the outlet pipe (17), and the remaining supernatant is returned to the anoxic zone through the second circulation column (9); e). Anoxic reaction: In the anoxic zone (11), the nitrate nitrogen is initially denitrified by using the carbon source of the raw water or endogenous metabolism, and then enters the anaerobic zone (15) through the third circulation column (13) to enter the next cycle.

6. The wastewater treatment method of the single-tower multi-stage self-circulating wastewater treatment device with built-in partitions according to claim 5, characterized in that, It has the following control strategies: 1). Judgment and treatment of sludge loss in aerobic zone; When the PLC controller (42) detects through the first MLSS sensor (35) that the sludge concentration in the upper part of the aerobic zone (7) exceeds 2000 mg / L and lasts for 10 minutes, it is determined that the sludge bed in the aerobic zone is too high and there is a risk of loss. The PLC controller then controls the return control valve (12) to reduce the opening to reduce the upward flow rate and make the sludge in the aerobic zone (7) fall back. 2). Dissolved oxygen gradient optimization: When the PLC controller (42) detects that the total nitrogen concentration of the wastewater above the aerobic zone (7) exceeds 15 mg / L through the first nitrate nitrogen sensor (23) and the first ammonia nitrogen sensor, it indicates that the total nitrogen value is too large. At the same time, the dissolved oxygen content of the water above the aerobic zone (7) is detected in real time by the second DO sensor (20) to be >0.5 mg / L, while the parameters of the other sensors remain within the normal range, it is determined that the oxygen supply of the aeration disc is too large. By reducing the frequency of the variable frequency blower (38) and the opening of the return control valve (12), the aeration volume and circulation flow are reduced to ensure the denitrification efficiency of the anoxic zone (11) and the anaerobic zone (15). 3). Judgment and treatment of excessive sludge deposition in anoxic and anaerobic zones; The PLC controller (42) detects that the sludge concentration in the upper part of the anoxic zone (11) or anaerobic zone (15) is less than 1000 mg / L through the second MLSS sensor (36) and the third MLSS sensor (37), and at the same time detects that the total nitrogen concentration of the sewage in the upper part of the aerobic zone (7) exceeds 15 mg / L, and the other sensor parameters are normal, then it is determined that the sludge in the anoxic zone (11) or anaerobic zone (15) has excessive deposition. At this time, through the negative feedback adjustment mechanism, the aeration volume and the opening of the return control valve are increased, the pressure difference and the upward flow velocity between the columns are increased, and the sludge bed is re-expanded and raised to the target height to ensure that the sludge and water are fully contacted. 4). COD and ammonia nitrogen judgment and treatment in the aerobic zone; when the PLC controller (42) detects that the COD or ammonia nitrogen in the upper part of the aerobic zone (7) exceeds the standard through the first COD sensor (27) and the first ammonia nitrogen sensor (31), and the parameters of the other sensors are within the normal range, it is judged that the oxygen supply is insufficient, and the frequency of the variable frequency fan (38) and the opening of the reflux control valve (12) are increased simultaneously to increase the aeration volume and reflux ratio to improve the COD or ammonia nitrogen removal rate; When COD or ammonia nitrogen exceeds the standard in the upper part of the aerobic zone (7), and the sludge concentration in the upper part of the aerobic zone (7) is less than 1000 mg / L and dissolved oxygen is >0.5 mg / L when the first MLSS sensor (35) and the second DO sensor (20) detect that the sludge concentration in the upper part of the aerobic zone (7) is less than 1000 mg / L and dissolved oxygen is >0.5 mg / L, it indicates that the sludge in the aerobic zone (7) has been excessively deposited, which leads to the obstruction of the biochemical reaction process and the sharp decrease in dissolved oxygen consumption. At this time, the aeration rate and the opening of the return control valve are increased through the negative feedback adjustment mechanism, the pressure difference and the upward flow velocity between the circulation columns are increased, and the sludge bed is re-expanded and raised to the target height to ensure that the sludge and water are fully contacted. 5) Assessment and treatment of sludge accumulation in the anaerobic zone; When the sludge concentration detected by the PLC controller (42) via the third MLSS sensor (37) in the upper part of the anaerobic zone (15) is more than 1000 mg / L higher than the sludge concentration detected by the first MLSS sensor (35) in the upper part of the aerobic zone for a period of time, and the parameters of the other sensors remain within the normal range, it is determined that the sludge has accumulated in the anaerobic zone (15). At this time, the PLC controller (42) triggers the "forced backflow" mode, and simultaneously increases the frequency of the variable frequency fan (38) and the opening of the backflow control valve (12) to generate a strong hydraulic flush, which "pulls" the sludge accumulated in the anaerobic zone (15) back to the aeration zone (2) so as to redistribute the sludge of the entire sewage treatment device.

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