Multi-section self-circulation combined tower for treating different water qualities and wastewater treatment method

Abstract

The multi-section type self-circulation combined tower for treating different water qualities comprises an aeration column, an aerobic column, an anoxic column and an anaerobic column which are vertically arranged, and all main bodies are communicated through connecting columns or backflow columns; the low-concentration organic nitrogen-containing wastewater is treated by circulating flow of wastewater among the aeration column, the aerobic column and the anoxic column, and the high-concentration organic nitrogen-containing wastewater is treated by circulating flow of wastewater among the anaerobic column, the aeration column, the aerobic column and the anoxic column. And the removal of ammonia nitrogen and the consumption removal of organic matters are realized by utilizing the nitrification and denitrification effects of microorganisms. The wastewater treatment method disclosed by the invention can be used for effectively treating high-concentration and low-concentration organic nitrogen-containing wastewater, can be highly compatible with the flow layout and the operation mode of an existing sewage treatment plant, has the advantages of simplicity in engineering transformation, wide application range, convenience in operation and management and the like, and has good technical suitability and actual popularization value.

Description

Technical Field

[0001] This invention relates to a self-circulating combined tower and a wastewater treatment method, and more specifically, to a multi-stage self-circulating combined tower for treating different water qualities and a wastewater treatment method. Background Technology

[0002] With rapid industrialization and urbanization, the discharge of organic nitrogen-containing wastewater has become a significant challenge to aquatic environments. This type of wastewater mainly originates from industries such as chemicals, pesticides, pharmaceuticals, and dyeing. It is characterized by its complex composition, high toxicity, and difficulty in biodegradation, posing a serious threat to ecosystems and human health. Pollutants in organic nitrogen-containing wastewater can be converted into inorganic ammonia nitrogen in water bodies through ammonification, further exacerbating eutrophication and triggering environmental problems such as algal blooms and red tides. Therefore, developing efficient, economical, and sustainable technologies for treating organic nitrogen-containing wastewater has become a research hotspot in the field of environmental engineering.

[0003] Traditional organic nitrogen-containing wastewater treatment typically employs a combination of physicochemical and biological methods. The physicochemical treatment stage often serves as a pretreatment or advanced treatment unit, with specific methods including adsorption (using porous materials such as activated carbon and zeolite), flocculation and sedimentation (through the addition of coagulants and flocculants), ion exchange, and membrane separation technologies (such as reverse osmosis, nanofiltration, and ultrafiltration). While these methods can effectively remove some organic nitrogen, they generally face problems such as high operating costs, difficulties in regenerating adsorbents or membrane materials, and the potential for secondary pollution. Biological treatment technology, on the other hand, centers on the nitrification-denitrification process. Its principle is to utilize the metabolic activities of microorganisms to achieve nitrogen conversion: first, under aerobic conditions, nitrifying bacteria sequentially oxidize ammonia nitrogen (NH4⁺-N) to nitrite nitrogen (NO2⁻-N) and nitrate nitrogen (NO3⁻-N); then, under anoxic conditions, denitrifying bacteria use organic matter as a carbon source to reduce nitrate nitrogen back to nitrogen gas (N2), which is then discharged from the system.

[0004] Traditional aerobic biological treatment technologies face challenges in degrading organic nitrogen-containing wastewater, including high energy consumption, large sludge production, low efficiency under low-temperature conditions, and strong dependence on carbon sources. Meanwhile, single-anaerobic technologies, when treating high-concentration organic wastewater, often require months or even longer start-up times due to the slow proliferation rate and long generation cycle of anaerobic microorganisms. Therefore, in engineering practice, combined anaerobic and aerobic processes are frequently adopted to achieve simultaneous and efficient removal of carbon and nitrogen pollutants through synergistic effects. The core technology in this approach primarily utilizes aerobic granular sludge. However, as an emerging technology, the engineering application of aerobic granular sludge technology is still limited by bottlenecks such as long cultivation cycles, easy disintegration of the granular structure during long-term operation, and unclear strategies for controlling key process parameters. Early continuous flow reactors for cultivating aerobic granular sludge often had complex structures, high operating costs, and were prone to sludge loss or particle disintegration, making them difficult to scale up and apply in practice. While sequencing batch reactors and their variants were effective in cultivating aerobic granular sludge, they had limited water treatment capacity, low equipment utilization, high automation requirements, and were not easy to integrate with the continuous flow processes of existing wastewater treatment plants. Furthermore, their construction and automation systems were costly.

[0005] To address the aforementioned issues, this study aims to develop a novel and highly efficient biological treatment system. By optimizing the reactor structure and operating strategy, it achieves rapid acclimatization and stable maintenance of granular sludge. The system employs a modular design to allow for independent configuration of aeration units, flexibly adapting to the treatment needs of wastewater containing organic nitrogen at varying concentrations. Secondly, it utilizes oxygen concentration gradients and substrate distribution characteristics to construct a multi-stage reaction environment, enhancing pollutant degradation efficiency. Finally, through optimization of the hydraulic circulation structure, it achieves dozens of internal wastewater cycles without external power, ensuring thorough pollutant degradation and significantly reducing operating energy consumption. The ultimate goal of this system is to achieve stable effluent quality that meets discharge standards and to provide technical support for the low-energy treatment of high-concentration organic nitrogen wastewater. Summary of the Invention

[0006] In order to overcome the shortcomings of the above-mentioned technical problems, the present invention provides a multi-stage self-circulating combined tower for treating different water qualities and a wastewater treatment method.

[0007] The present invention relates to a multi-stage self-circulating combined tower for treating different water qualities, comprising vertically arranged aeration columns, aerobic columns, anoxic columns, and anaerobic columns. The upper part of the aeration column is connected to the bottom of the aerobic column via a first connecting column; the upper part of the aerobic column is connected to the lower part of the anoxic column via a second connecting column; the upper part of the anoxic column is connected to the lower part of the anaerobic column via a third connecting column; the upper parts of the anoxic column and the upper parts of the anaerobic column are respectively connected to the lower part of the aeration column via a first reflux column and a second reflux column; a pipe flow is provided on the second connecting column. The metering system includes a first circulation control valve and a second circulation control valve on the first reflux column and the third connecting column, respectively; a first inlet pipe and a second inlet pipe are connected to the tops of the second and third connecting columns, respectively; a first outlet pipe and a second outlet pipe are connected to the tops of the aerobic and anoxic columns, respectively; granular sludge is cultivated in the aerobic, anoxic, and anaerobic columns; an aeration disc connected to an aeration device is installed at the bottom of the aeration column; and a three-phase separator is installed at the top of the anaerobic column. Its features are: When treating low-concentration organic nitrogen-containing wastewater: the first inlet pipe, the first circulation control valve, and the first outlet pipe are all open, while the second inlet pipe, the second circulation control valve, and the second outlet pipe are all closed. Under the aeration action of the aeration discs, the wastewater to be treated and the granular sludge circulate in the anoxic column, the aeration column, and the aerobic column. The removal of ammonia nitrogen and the consumption and removal of organic matter are achieved by utilizing the nitrification and denitrification of microorganisms. When treating high-concentration organic nitrogen-containing wastewater: the second inlet pipe, the second circulation control valve, and the second outlet pipe are all open, while the first inlet pipe, the first circulation control valve, and the first outlet pipe are all closed. Under the aeration of the aeration discs, the wastewater to be treated circulates within the anaerobic, anoxic, aeration, and aerobic columns. The wastewater flowing through the anaerobic column undergoes an anaerobic reaction under the action of anaerobic microorganisms, causing the organic matter to degrade and produce biogas. The biogas is separated by a three-phase separator and collected by a biogas collection device. During the flow of the wastewater through the aerobic and anoxic columns, the nitrification and denitrification of microorganisms further remove ammonia nitrogen.

[0008] The present invention relates to a multi-stage self-circulating combined tower for treating different water qualities, comprising an inlet regulating tank, a variable frequency inlet pump, and a variable frequency blower. The variable frequency inlet pump transports the wastewater to be treated in the inlet regulating tank to a first inlet pipe or a second inlet pipe via a main inlet pipe. The main inlet pipe is equipped with an inlet control valve and an inlet flow meter. The first inlet pipe and the second inlet pipe are respectively equipped with a first inlet control valve and a second inlet control valve. The variable frequency blower supplies air to the aeration discs via an air supply pipeline, which is equipped with an air volume control valve and a gas flow meter.

[0009] The present invention relates to a multi-stage self-circulating combined tower for treating different water qualities, comprising a PLC controller and a host PC connected thereto, a DO meter, a nitrate nitrogen meter, a sludge concentration MLSS meter, a COD meter, and an ammonia nitrogen meter. The upper parts of the aeration column, aerobic column, and anoxic column 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 column and anoxic column are respectively equipped with a first nitrate nitrogen sensor and a second nitrate nitrogen sensor connected to the nitrate nitrogen meter. The upper parts of the aerobic column and anoxic column are respectively equipped with a first MLSS sensor and a second MLSS sensor connected to the sludge concentration MLSS meter. The influent equalization tank, aerobic column, and anoxic column are respectively equipped with a first COD sensor, a second COD sensor, and a third COD sensor connected to the COD meter. The influent equalization tank, aerobic column, and anoxic column are respectively equipped with a first ammonia nitrogen sensor, a second ammonia nitrogen sensor, and a third ammonia nitrogen sensor connected to the ammonia nitrogen meter. The first and second water outlet pipes are respectively equipped with a first water outlet control valve and a second water outlet control valve to control their on / off states; different input terminals of the PLC controller are respectively connected to the inlet flow meter, the pipeline flow meter and the gas flow meter, and different output terminals of the PLC controller are respectively connected to the variable frequency water inlet pump, the main inlet control valve, the first inlet control valve, the second inlet control valve, the first circulation control valve, the second circulation control valve, the first water outlet control valve, the second water outlet control valve, the variable frequency fan and the air volume control valve.

[0010] The present invention relates to a multi-stage self-circulating combined tower for treating different water qualities. The bottom of the aerobic column is provided with a water distribution pipe that is connected to the first connecting column, and the water distribution pipe is provided with downward-facing water distribution holes evenly distributed on it.

[0011] The present invention relates to a multi-stage self-circulating combined tower for treating different water qualities, wherein the height-to-diameter ratio of the aeration column, aerobic column, anoxic column and anaerobic column are all between 3 and 8.

[0012] The wastewater treatment method of the multi-stage self-circulating combined tower for treating different water qualities of the present invention is characterized by the following steps: Step 1: First, the concentrations of organic matter and ammonia nitrogen in the wastewater to be treated in the influent equalization tank are detected by the first COD sensor and the first ammonia nitrogen sensor to determine whether the wastewater to be treated is low-concentration or high-concentration organic nitrogen wastewater; if it is low-concentration organic nitrogen wastewater, proceed to step 2; if it is high-concentration organic nitrogen wastewater, proceed to step 3. Step Two: Three-column operation; The PLC controller controls the opening of the first circulation control valve, the first outlet control valve, the first inlet control valve, the main inlet control valve, and the air volume control valve, and controls the closing of the second circulation control valve, the second outlet control valve, and the second inlet control valve. The variable frequency inlet water pump and the variable frequency fan are turned on to allow water to enter through the first inlet pipe and exit through the first outlet pipe. The anoxic column is connected to the aeration column, while the anoxic column is not connected to the anaerobic column, so that the low-concentration organic nitrogen-containing wastewater to be treated circulates and is treated between the anoxic column, the aeration column, and the aerobic column. Step 3: Four-column operation; The PLC controller controls the opening and closing of the second circulation control valve, the second outlet control valve, the second inlet control valve, the main inlet control valve, and the air volume control valve, and controls the closing of the first circulation control valve, the first outlet control valve, and the first inlet control valve. The variable frequency inlet water pump and the variable frequency fan are turned on to allow water to enter through the second inlet pipe and exit through the second outlet pipe. The anoxic column is connected to the anaerobic column, while the anoxic column is not connected to the aeration column, so as to realize the circulation and treatment of the low-concentration organic nitrogen wastewater to be treated among the anaerobic column, the aeration column, the aerobic column, and the anoxic column.

[0013] The wastewater treatment method of the multi-stage self-circulating combined tower for treating different water qualities of the present invention is achieved through the following steps in the three-column operation: a) Circulation drive; Under the aeration action of the aeration disc, the wastewater entering the aeration column is oxygenated. After oxygenation, the density of the wastewater at the bottom of the aeration column decreases. Under the action of density difference, the wastewater in the upper part of the anoxic column flows into the bottom of the aeration column through the first return column, creating a liquid level difference between the anoxic column and the aerobic column. Under the action of liquid level difference, the wastewater in the aerobic column enters the anoxic column, and the wastewater in the aeration column enters the aerobic column. Finally, the wastewater circulates between the aeration column, aerobic column and anoxic column without the need for external power. b) Determining the sludge layer height; The concentration of granular sludge in the aerobic and anoxic columns is detected by the first and second MLSS sensors respectively to determine whether the sludge layer height has reached the height that allows the granular sludge to circulate throughout the aerobic, anoxic, and aeration columns. If it has not reached the height, it indicates that the flow rate is insufficient, and step c) is executed; if it has reached the height, step d) is executed. c) Increase flow rate; First, obtain and record the circulation flow rate and pipeline flow rate through the pipeline flow meter and gas flow meter. Then, increase the air supply of the variable frequency fan and simultaneously increase the opening of the first circulation control valve to increase the circulation flow rate. Execute step d). d) Nitrification reaction; As the wastewater flows through the aeration column and aerobic column, in an aerobic environment, nitrifying bacteria in the granular sludge oxidize the ammonia nitrogen in the wastewater into nitrite and nitrate in sequence. e) Denitrification reaction; During the process of the wastewater flowing through the anoxic column, under anoxic or low-oxygen conditions, the denitrifying bacteria in the granular sludge use organic matter as a carbon source to reduce nitrates to nitrogen gas and discharge it. f). Dissolved oxygen detection; the dissolved oxygen value (DO) of the aerobic column was detected by the second DO sensor (23) and the third DO sensor respectively. 23 And the dissolved oxygen (DO) value in the anoxic column 24 If DO 23 <0.5mg / L and DO 23 If the DO concentration is <0.2 mg / L, it indicates that the current aeration and oxygenation are appropriate and no adjustment is needed; if .... 23 <0.5 mg / L and DO 23 If either <0.2mg / L is not met, it indicates that the oxygen supply is too high, and the oxygen supply should be reduced. Proceed to step g). g) Reduce oxygen supply regulation; reduce the operating frequency of the variable frequency fan, and at the same time reduce the opening of the air volume control valve and the first circulation control valve to reduce oxygenation by reducing the aeration volume; h) Detection of ammonia nitrogen, COD, and nitrate nitrogen; The concentration of organic matter in the aerobic and anoxic columns is detected by the second and third COD sensors, respectively. If the concentration of organic matter is not lower than the set value, it indicates that it does not meet the standard, and step c) is executed to increase the circulation rate; The concentration of ammonia nitrogen in the aerobic and anoxic columns is detected by the second and third ammonia nitrogen sensors, respectively. If the concentration of ammonia nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step i) is executed to increase the oxygen supply; The concentration of nitrate nitrogen in the aerobic and anoxic columns is detected by the first and second nitrate nitrogen sensors, respectively. If the concentration of nitrate nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step g) is executed to decrease the oxygen supply; If the detected COD, ammonia nitrogen, and nitrate nitrogen concentrations all meet the standards, step j) is executed. i) Increase oxygen supply regulation; increase the operating frequency of the variable frequency fan, and at the same time increase the opening of the air volume control valve and the first circulation control valve to increase oxygenation by increasing the aeration volume; j) Increase water supply; increase water intake by increasing the operating frequency of the variable frequency water pump.

[0014] The wastewater treatment method of the multi-stage self-circulating combined tower for treating different water qualities of the present invention is achieved through the following steps in four-column operation: 1) Circulation Drive: Under the aeration action of the aeration disc, the wastewater entering the aeration column is oxygenated. After oxygenation, the density of the wastewater at the bottom of the aeration column decreases. Under the action of density difference, the wastewater in the upper part of the anaerobic column flows into the bottom of the aeration column through the second return column, creating a liquid level difference between the anaerobic and aerobic columns. Under the action of liquid level difference, the wastewater in the anoxic column enters the anaerobic column, the wastewater in the aerobic column enters the anoxic column, and the wastewater in the aeration column enters the aerobic column. Finally, the wastewater circulates between the aeration column, aerobic column, anoxic column, and anoxic column without the need for external power. 2) Determining the sludge layer height: The concentration of granular sludge in the aerobic and anoxic columns is detected by the first and second MLSS sensors, respectively, to determine whether the sludge layer height has reached the height required to retain granular sludge in the aerobic and anoxic columns. If it has not reached the height required, it indicates that the flow rate is insufficient, and step 3) is executed. If it has reached the height required, step 4) is executed. 3) Increase flow rate; First, obtain and record the circulation flow rate and pipeline flow rate through the pipeline flow meter and gas flow meter. Then, increase the air supply of the variable frequency fan and increase the opening of the second circulation control valve to increase the circulation flow rate. Execute step 4). 4) Anaerobic reaction; the wastewater entering the anaerobic column undergoes an anaerobic reaction under the action of anaerobic bacteria in the granular sludge, and the organic matter is degraded to produce a large amount of biogas. Some of the biogas is collected and recovered by the biogas collection device above. 5) Nitrification reaction; As the wastewater flows through the aeration column and aerobic column, in an aerobic environment, nitrifying bacteria in the granular sludge oxidize the ammonia nitrogen in the wastewater into nitrite and nitrate in sequence. 6) Denitrification reaction; During the process of the wastewater flowing through the anoxic column, under anoxic or low-oxygen conditions, the denitrifying bacteria in the granular sludge use organic matter as a carbon source to reduce nitrates to nitrogen gas and discharge it. 7) Dissolved oxygen detection; the dissolved oxygen (DO) value of the aerobic column is detected by the second and third DO sensors respectively. 23 And the dissolved oxygen (DO) value in the anoxic column 24 If DO 23 <0.5mg / L and DO 23 If the DO concentration is <0.2 mg / L, it indicates that the current aeration and oxygenation are appropriate and no adjustment is needed; if .... 23 <0.5 mg / L and DO 23 If either <0.2mg / L is not met, it indicates that the oxygen supply is too high and the oxygen supply should be reduced. Proceed to step 8). 8) Reduce oxygen supply regulation; reduce the operating frequency of the variable frequency fan, and at the same time reduce the opening of the air volume control valve and the second circulation control valve to reduce oxygenation by reducing the aeration rate; 9) Detection of ammonia nitrogen, COD, and nitrate nitrogen; The organic matter concentration in the aerobic and anoxic columns is detected by the second and third COD sensors, respectively. If the organic matter concentration is not lower than the set value, it indicates that it does not meet the standard, so step 3) is executed to increase the circulation rate; The ammonia nitrogen concentration in the aerobic and anoxic columns is detected by the second and third ammonia nitrogen sensors, respectively. If the ammonia nitrogen concentration is not lower than the set value, it indicates that it does not meet the standard, so step 10) is executed to increase the oxygen supply; The nitrate nitrogen concentration in the aerobic and anoxic columns is detected by the first and second nitrate nitrogen sensors, respectively. If the nitrate nitrogen concentration is not lower than the set value, it indicates that it does not meet the standard, so step 8) is executed to reduce the oxygen supply; If the detected COD, ammonia nitrogen, and nitrate nitrogen concentrations all meet the standards, step 11) is executed. 10) Increase oxygen supply regulation; increase the operating frequency of the variable frequency fan, and at the same time increase the opening of the air volume control valve and the first circulation control valve to increase oxygenation by increasing the aeration volume; 11) Increase water supply; increase water intake by increasing the operating frequency of the variable frequency water pump.

[0015] The beneficial effects of this invention are as follows: The multi-stage self-circulating combined tower and wastewater treatment method for treating different water qualities of this invention are equipped with aeration columns, aerobic columns, anoxic columns, anaerobic columns, and connecting columns and reflux columns connecting each column. When treating low-concentration organic nitrogen-containing wastewater, the aeration effect of the aeration discs allows the wastewater and granular sludge to circulate simultaneously in the "aeration column-aerobic column-anoxic column" cycle, utilizing nitrification and denitrification reactions to remove ammonia nitrogen while simultaneously consuming organic matter. When treating high-concentration organic nitrogen-containing wastewater, the aeration and oxygenation of the aeration discs, along with the circulation drive, allows the wastewater to circulate in the "anaerobic column-aerobic column" cycle. The system circulates between "column-aeration column-aerobic column-anoxic column," converting high-concentration organic matter into biogas and high-concentration ammonia nitrogen into nitrogen gas through anaerobic, nitrification, and denitrification reactions, thereby further consuming the organic matter. Therefore, this invention's multi-stage self-circulating combined tower and wastewater treatment method for treating different water qualities can effectively treat high- and low-concentration organic nitrogen-containing wastewater by selectively operating four or three columns. It is highly compatible with the process layout and operation mode of existing wastewater treatment plants, offering advantages such as simple engineering modification, wide applicability, and convenient operation and management, demonstrating good technical adaptability and practical promotion value.

[0016] Furthermore, the multi-stage self-circulating combined tower and wastewater treatment method of the present invention uses aeration as the sole power source, and can achieve autonomous circulation of liquid flow within the reaction system without the need for an external circulating water pump. This significantly reduces operating energy consumption and avoids physical damage to the particle structure caused by the shearing action of mechanical pumps.

[0017] Furthermore, the combined tower and wastewater treatment method of the present invention can form a stable upward flow velocity during operation. While realizing wastewater circulation, it can generate suitable hydraulic shear conditions, effectively promoting the formation and compaction of aerobic granular sludge, thereby strengthening the granulation process and realizing the rapid acclimatization and long-term stable maintenance of sludge.

[0018] Furthermore, the multi-stage self-circulating combined tower and wastewater treatment method of the present invention are equipped with a PLC controller and various instruments and sensors. It can not only control the on / off of the inlet water, inlet air and reflux columns, and measure and adjust the inlet water flow rate, circulation flow rate and inlet air volume, but also detect the DO, nitrate nitrogen, sludge concentration, COD and ammonia nitrogen concentration in the wastewater. Based on the detected data, the aeration rate, upward flow velocity and reflux ratio can be controlled. An automated intelligent control system can be built to achieve precise control of process operation and significantly reduce labor costs and operation and maintenance management difficulty. Attached Figure Description

[0019] Figure 1 This is a front view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention. Figure 2 This is a rear view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention. Figure 3 This is a top view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention. Figure 4 This is a left view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention. Figure 5 This is a right view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention. Figure 6 , Figure 7 The images are a rendered top view and a rendered three-dimensional view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention. Figure 8 This is a schematic diagram of the multi-stage self-circulating combined tower of the present invention equipped with water quality detection sensors and an automated control system; Figure 9 This is a control flow chart of the wastewater treatment method of the present invention; Figure 10 This is a flowchart of the detection and control of DO in the wastewater treatment method of the present invention; Figure 11 Flowchart for the detection and control of COD, ammonia nitrogen, and nitrate nitrogen; Figure 12 This is a schematic diagram of the morphology of granular sludge cultivated after long-term operation of the multi-stage self-circulating combined tower of the present invention. Figure 13 The diagram shows the control conditions and water quality changes of the multi-stage self-circulating combined tower for treating low-concentration organic nitrogen-containing wastewater according to the present invention. Figure 14 The diagram shows the control conditions and water quality changes of the multi-stage self-circulating combined tower for treating high-concentration organic nitrogen-containing wastewater according to the present invention.

[0020] In the diagram: 1 First inlet pipe, 2 Second inlet pipe, 3 Aeration column, 4 Aeration disc, 5 First connecting column, 6 Distribution pipe, 7 Aerobic column, 8 Second connecting column, 9 Pipeline flow meter, 10 Anoxic column, 11 Third connecting column, 12 Second circulation control valve, 13 Anaerobic column, 14 Second return column, 15 First return column, 16 First circulation control valve, 17 First effluent control valve, 18 First effluent pipe, 19 Second effluent control valve, 20 Second effluent pipe; 21 DO meter, 22 First DO sensor, 23 Second DO sensor, 24 Third DO sensor, 25 Nitrogen / Nitrogen meter, 26 First Nitrogen / Nitrogen sensor, 27 Second Nitrogen / Nitrogen sensor, 28 Sludge concentration MLSS meter, 29 First MLSS sensor, 30 Second MLSS sensor, 31 COD meter, 32 First COD sensor, 33 Second COD sensor, 34 Third COD sensor, 35 Ammonia nitrogen meter, 36 First ammonia nitrogen sensor, 37 Second ammonia nitrogen sensor, 38 Third ammonia nitrogen sensor, 39 Inlet water regulating tank, 40 Variable frequency inlet water pump, 41 Main inlet water control valve, 42 Inlet water flow meter, 43 Variable frequency fan, 44 Air volume control valve, 45 Gas flow meter, 46 First inlet water control valve, 47 Second inlet water control valve, 48 PLC controller, 49 Host PC. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] like Figures 1 to 5 As shown, the front view, rear view, top view, left view, and right view of the multi-stage self-circulating combined tower for treating different water qualities according to the present invention are given respectively. Figure 6 and Figure 7 The renderings show a top-down view and a 3D view of the multi-segment self-circulating combined tower, which consists of an aeration column 3, an aerobic column 7, an anoxic column 10, an anaerobic column 13, a first connecting column 5, a second connecting column 8, a third connecting column 11, a first reflux column 15, and a second reflux column 14. An aeration disc 4 is installed at the bottom of the aeration column 3, and a water distribution pipe 6 is installed at the bottom of the aerobic column 7. The first connecting column 5 connects the upper part of the aeration column 3 to the lower part of the aerobic column 7, i.e., it connects to the water distribution pipe 6 at the bottom of the aerobic column 7. The second connecting column 8 connects the upper part of the aerobic column 7 to the lower part of the anoxic column 10. The third connecting column 11 connects the upper part of the anoxic column 10 to the lower part of the anaerobic column 13. The upper part of the anoxic column 10 is connected to the bottom of the aeration column 3 via the first reflux column 15, and the upper part of the anaerobic column 13 is connected to the lower part of the aeration column 3 via the second reflux column 14.

[0023] Pipeline flow meters 9, first circulation control valves 16 and 12 are respectively installed on the second connecting column 8, the first reflux column 15, and the second reflux column 14. A first inlet pipe 1 and a second inlet pipe 2 are respectively installed at the upper ends of the second connecting column 8 and the third connecting column 11 to allow the wastewater to be treated to flow through. A first outlet pipe 18 is installed at the upper end of the aerobic column 7, and a second outlet pipe 20 is installed at the upper end of the anoxic column 10. A first outlet control valve 17 and a second outlet control valve 19 are respectively installed on the first outlet pipe 18 and the second outlet pipe 20 to control their on / off states.

[0024] When treating low-concentration organic nitrogen-containing wastewater, the wastewater enters from the first inlet pipe 1 and exits from the first outlet pipe 18. The second circulation control valve 12 is closed and the first circulation control valve 16 is opened. Under the aeration action of the aeration disc 4 at the bottom of the aeration column 3, oxygenation is achieved. At the same time, the wastewater circulates between the "aeration column-aerobic column-anoxic column" by relying on the density difference and liquid level difference generated by aeration. The wastewater is treated through nitrification and denitrification reactions.

[0025] When treating high-concentration organic nitrogen-containing wastewater, the wastewater enters through the second inlet pipe 2 and exits through the second outlet pipe 10. The first circulation control valve 16 is closed and the second circulation control valve 12 is opened. Under the aeration action of the aeration disc 4 at the bottom of the aeration column 3, not only is oxygenation achieved, but also the density difference and liquid level difference generated by aeration cause the wastewater to circulate between the "aeration column-aerobic column-anoxic column-anaerobic column". Through anaerobic reaction and nitrification and denitrification reactions, the organic matter and ammonia nitrogen in the wastewater are removed.

[0026] like Figure 8 The diagram shows a multi-stage self-circulating combined tower equipped with water quality detection sensors and an automated control system according to the present invention. It includes an inlet regulating tank 39, a variable frequency inlet pump 40, a variable frequency fan 43, a PLC controller 48, and a host PC 49. Connected to the PLC controller 38 are DO meter 21, nitrate nitrogen meter 25, sludge concentration MLSS meter 28, COD meter 31, and ammonia nitrogen meter 35. The variable frequency inlet pump 40 pumps wastewater from the inlet regulating tank 39 to the first inlet pipe 1 and the second inlet pipe 2. The outlet pipe of the variable frequency inlet pump 40 is equipped with an inlet main control valve 41 and an inlet flow meter 42. The first inlet pipe 1 and the second inlet pipe 2 are respectively equipped with a first inlet control valve 46 and a second inlet control valve 47. Thus, by selectively opening or closing the first and second inlet control valves (46, 47), water can be selected to enter through the first inlet pipe 1 or the second inlet pipe 2, and the flow rate can be detected and controlled.

[0027] A variable frequency blower 43 is connected to an aeration disc 4 via an air supply pipeline. An air volume control valve 44 and a gas flow meter 45 are installed on the air supply pipeline of the variable frequency blower 43 to detect and control the aeration flow rate. The upper parts of the aeration column 3, aerobic column 7, and anoxic column 10 are respectively equipped with a first DO sensor 22, a second DO sensor 23, and a third DO sensor 24 connected to a DO meter. The upper parts of aerobic column 7 and anoxic column 10 are respectively equipped with a first nitrate nitrogen sensor 26 and a second nitrate nitrogen sensor 27 connected to a nitrate nitrogen meter 25. The upper parts of aerobic column 7 and anoxic column 10 are respectively equipped with a first MLSS sensor 29 and a second MLSS sensor 30 connected to a sludge concentration MLSS meter 28. The influent equalization tank 39, the aerobic column 7 and the anoxic column 10 are respectively equipped with a first COD sensor 32, a second COD sensor 33 and a third COD sensor 34 connected to the COD meter 31. The influent equalization tank 39, the aerobic column 7 and the anoxic column 10 are respectively equipped with a first ammonia nitrogen sensor 36, a second ammonia nitrogen sensor 37 and a third ammonia nitrogen sensor 38 connected to the ammonia nitrogen meter 25.

[0028] This invention relates to a multi-stage self-circulating combined tower for treating different water qualities. Using aeration from aeration column 3 as the sole power source, it successfully drives wastewater through dozens of cycles between aeration column 3, aerobic column 7, anoxic column 10, and anaerobic column 13. This not only achieves thorough degradation of pollutants but also yields significant energy savings. Each column is equipped with various water quality sensors and corresponding online instruments, enabling real-time local monitoring of the treatment process. This data provides the PLC control system with essential operating parameters for determining equipment performance.

[0029] Under normal operating conditions, to ensure sufficient contact between sludge and water, the height of the sludge layer inside each main column should be within a certain range. If it is too low, it indicates that an effective suspended sludge layer has not been formed, resulting in poor sludge-water contact and unsatisfactory circulation treatment. Therefore, by adding MLSS sensors at specific heights to detect changes in sludge concentration at that height, the suspension state of the sludge within the column can be indicated. When the MLSS sensor reading at that height is lower than the normal value, it indicates that the sludge content at that height is low, and the sludge layer has not reached the required height. The automated control system then outputs corresponding commands to increase the upward flow velocity to raise the sludge layer height. The sludge layer height can be quickly adjusted by directly increasing the air volume of the blower to increase the upward flow velocity within the system. The installation height of the MLSS sensors depends on the actual situation and is generally lower than the upper connection height between the main columns.

[0030] Under the three-column operation control strategy, this process can effectively increase the overall upward flow velocity within the system by coordinating the aeration intensity of the aeration disc 4 and the opening of the circulation control valve 16. This velocity change will disrupt the force balance of the original sludge layers in the aerobic column 7 and the anoxic column 10, causing the sludge to rise faster than it settles, thus gradually increasing the height of the sludge layer. When the sludge layer reaches the height of the connection between the connecting column 8 and the return column (15), the sludge will circulate throughout the aerobic, anoxic, and aeration columns with the circulating water. In this state, the aeration column 3 is filled with sludge, and its function changes from simple oxygenation to a coordinated "oxygenation-oxygen consumption" process, which can further optimize the overall oxygen transfer and utilization efficiency of the system and enhance the nitrogen conversion effect. To detect the change in the height of the sludge layer and determine the flow state of the sludge inside each column, multiple MLSS sensors can be added at different heights in the aerobic column 7. The change in the height of the sludge layer inside the column can be determined by analyzing the changes in the values ​​of the MLSS sensors.

[0031] The system features an automated control system at the inlet end, enabling automatic detection and analysis of the influent water quality. COD sensor 32 and ammonia nitrogen sensor 36 in the influent regulating tank input influent water quality data to the PLC controller via their respective instruments. For low-concentration organic nitrogen-containing wastewater, the system opens circulation control valve 16, effluent control valve 17, and influent control valve 46, while simultaneously closing circulation control valve 12, effluent control valve 19, and influent control valve 47. For high-concentration organic nitrogen-containing wastewater, the system executes the opposite command. Through the coordinated action of the front-end water quality detection and automated control system, the system can intelligently switch the influent path. After opening the main influent control valve and the airflow control valve, the variable frequency influent pumps 40 and 43 are started. At this time, the influent flows through influent pipes 1 and 2, delivering wastewater to the designated column according to the opening and closing status of the front-end valves. With the opening of the valves and the start of the fans, the combined tower begins circulation.

[0032] Although the composition of pollutants fluctuates under different water quality conditions, the fluid dynamics within each core reaction column exhibit common characteristics: wastewater flows through the column in an upflow pattern, creating essentially consistent hydraulic conditions. Both the anoxic column 10 and the anaerobic column 13 possess high hydraulic load-bearing capacity, enabling the formation and maintenance of a stable granular sludge bed within the reactor. After aeration circulation is initiated, by precisely controlling the dynamic balance between the wastewater's upflow velocity and the sludge's settling properties, a highly controllable sludge layer can be formed within both columns, ensuring sufficient contact and reaction between the wastewater and the biological granular sludge.

[0033] The stability of the sludge layer height is mainly influenced by the synergistic effect of two key parameters: the settling performance of the sludge itself and the upward flow velocity of the wastewater within the system. As the granular sludge acclimation process progresses, its settling performance gradually improves. Simultaneously, the upward flow velocity can be flexibly controlled by precisely adjusting the aeration intensity and circulation valve opening through an automated control system. Under these optimized control conditions, the system can efficiently degrade most organic matter and nitrogenous pollutants, with the anaerobic column 13 showing particularly significant efficiency in removing organic matter.

[0034] This invention, under different operating strategies, can utilize the pressure difference formed within the column to automatically return wastewater from the upper parts of the anoxic column 10 and anaerobic column 13 to the aeration column 3 via connecting columns 15 and 14, respectively, for efficient oxygenation. The core control parameter of the oxygenation process is the dissolved oxygen (DO) concentration, which is precisely controlled through an integrated closed-loop control system. This system mainly consists of a variable frequency blower 43 connected to the aeration disc 4, an air volume control valve 44, and a gas flow meter 45. In actual operation, the variable frequency blower 43 acts as the main regulating unit, dynamically adjusting its speed based on real-time indicators such as the DO concentration from each column and the system gas flow rate to change the total oxygen supply; the air volume control valve 44 can further regulate the aeration volume based on the blower frequency; and the gas flow meter 45 is responsible for continuously monitoring the actual aeration volume, providing key feedback data to the control system. The above components work together to form an efficient "monitoring-feedback-regulation" closed-loop control structure, thereby ensuring that the DO concentration inside each column is stably maintained within the optimal range, creating a stable and efficient reaction environment for microbial metabolic pollutants.

[0035] The dissolved oxygen supply efficiency within the system is closely related to the fluid circulation intensity. The circulation flow rate is controlled by adjusting the opening of the circulation valve: under the same aeration conditions, increasing the circulation flow rate can improve the mass transfer efficiency of oxygen in the water and the overall supply. This mechanism, in conjunction with the aeration system, further optimizes the oxygen balance and control efficiency of the entire system.

[0036] Aeration column 3 employs a microporous aeration method, with an external variable frequency blower 43 supplying air to aeration disc 4. This causes air to form tiny bubbles and diffuse evenly, significantly increasing the gas-liquid contact area, improving oxygen transfer efficiency, and ensuring an effective increase in dissolved oxygen content in the wastewater within the column. The oxygenated wastewater undergoes a certain degree of expansion (approximately 20%–50%) due to bubble entrainment, resulting in a lower density of the mixed liquid at the bottom of the aeration column compared to the circulating wastewater in the adjacent return columns 14 and 15. This creates a stable density difference. This density difference, coupled with the liquid level gradient maintained by both influent and return flow within the system, constitutes the core driving force propelling wastewater circulation within the system.

[0037] The oxygenation efficiency of the aeration column directly determines the overall pollutant removal efficiency of the system. Efficient oxygen transfer provides the necessary conditions for the aerobic degradation of organic matter and the nitrification of ammonia nitrogen. Sufficient dissolved oxygen supply promotes the conversion of more ammonia nitrogen into nitrate nitrogen, thus providing ample substrate for the subsequent denitrification process under anoxic conditions and indirectly enhancing total nitrogen removal. Therefore, changes in oxygen supply conditions directly affect the concentrations of ammonia nitrogen and nitrate nitrogen in the effluent. To ensure stable effluent compliance, the automated system uses the detected water quality indicators as a basis and adjusts the oxygen supply balance to achieve optimal effluent quality.

[0038] As the sole source of dissolved oxygen in the system, the oxygen-enriched wastewater from the outlet of aeration column 3 enters the bottom of aerobic column 7, creating a suitable environment for aerobic microorganisms to degrade organic matter and carry out nitrification. As the wastewater rises along aerobic column 7, dissolved oxygen is gradually consumed by the microorganisms, and is essentially depleted before entering anoxic column 10, ensuring the low-oxygen or anoxic environment required by anoxic column 10 and anaerobic column 13. The automated control system calculates the oxygen supply and consumption relationship during operation by combining the DO values ​​measured by the first, second, and third DO sensors (22, 23, 24) with the system's circulation volume. When the values ​​of the first and second DO sensors (23, 24) are higher than the set values, it indicates that the current oxygen supply is too high, which will be detrimental to the system's denitrification performance. The automated control system will then output control commands to reduce the system's oxygen supply level by decreasing the blower air volume and circulation volume.

[0039] The entire system utilizes a dynamic cycle of dissolved oxygen—aeration and oxygenation—aerobic consumption—anoxic / anaerobic denitrification and carbon removal to stably provide the necessary oxygen environment for different functional units, achieving a gradient distribution and efficient utilization of dissolved oxygen in time and space. During system operation, the generation of microbubbles due to aeration and oxygenation within aeration column 3 leads to a decrease in the density of the mixed liquor, resulting in a significant density difference with adjacent columns. This density difference, coupled with the liquid level difference maintained by both influent and return flow, constitutes the core driving force for the circulation of wastewater within the system. Under this dual effect, the system can achieve efficient self-circulation without relying on an external circulating water pump, with a circulation flow rate reaching up to hundreds of times the influent flow rate.

[0040] The first, second, and third connecting columns (5, 8, 11) and the first and second return columns (14, 15) constitute the key channels for air-water-sludge transport between the main columns. The water distribution system at the lower end of the aerobic column 7 consists of the connecting column 5 and the water distribution pipe 6 connected to it. This water distribution pipe has a series of uniformly oriented downward water distribution holes, whose main function is to evenly distribute the circulating water from the aeration column 3 across the entire cross-section of the aerobic column 7. This design helps to form a uniform and stable upward flow within the aerobic column, thereby promoting a stable suspended state of the sludge bed and effectively preventing short-circuiting. A stable sludge bed is a prerequisite for ensuring sufficient contact between wastewater and microorganisms. The more stable the bed, the higher the mass transfer efficiency, which significantly improves the system's ability to degrade organic matter and the nitrification effect. Inside the aerobic column 7, wastewater flows upward through the column, making full contact with the aerobic granular sludge and flocculent sludge layer cultivated within the column. During this process, the remaining organic matter in the wastewater is further degraded by aerobic microorganisms; at the same time, nitrogen is also transformed through microbial action.

[0041] The physical essence of forming a stable sludge layer within each column lies in a dynamic balance between the settling velocity of sludge particles under gravity and the upward flow velocity of wastewater. As the sludge granulation and acclimation process progresses, the sludge becomes more compact and dense, significantly increasing its settling velocity. To maintain the preset sludge bed height, the upward flow velocity can be dynamically adjusted using the internal logic control program of the automated control system to adapt to changes in sludge settling performance. This automated system, integrating real-time detection of key parameters (such as gas flow rate and circulation flow rate) with precise feedback control from actuators, constitutes the core technology ensuring the long-term stable and efficient operation of this combined tower process.

[0042] The automated control system uses water quality sensors (COD, ammonia nitrogen, and nitrate nitrogen sensors) to monitor the water quality at the effluent in real time. Based on this, it determines the degree of wastewater treatment and effluent limiting factors, comprehensively analyzes the water quality situation, and finally outputs control commands. Through control steps such as adjusting the size of the first and second circulation control valves (16, 12) and the frequency of the variable frequency fan 43, the effluent water quality is adjusted. When the effluent water quality consistently meets the standards, the influent flow rate can be increased by adjusting the frequency of the variable frequency influent pump 40 to explore the treatment load of this combined tower process.

[0043] like Figure 9 The diagram shows the control flow chart of the wastewater treatment method of the present invention. The wastewater treatment method of the present invention, using a multi-stage self-circulating combined tower for treating different water qualities, is characterized by the following steps: Step 1: First, the concentrations of organic matter and ammonia nitrogen in the wastewater to be treated in the influent equalization tank (39) are detected by the first COD sensor (32) and the first ammonia nitrogen sensor (36) to determine whether the wastewater to be treated is low-concentration or high-concentration organic nitrogen wastewater; if it is low-concentration organic nitrogen wastewater, proceed to step 2; if it is high-concentration organic nitrogen wastewater, proceed to step 3. Step 2: Three-column operation; The PLC controller controls the opening of the first circulation control valve (16), the first outlet control valve (17), the first inlet control valve (46), the main inlet control valve (41), and the air volume control valve (44), and controls the closing of the second circulation control valve (12), the second outlet control valve (19), and the second inlet control valve (47). The variable frequency water pump and variable frequency fan are turned on to allow water to enter through the first inlet pipe and exit through the first outlet pipe. The anoxic column (10) is connected to the aeration column (3), and the anoxic column is not connected to the anaerobic column, so that the low-concentration organic nitrogen wastewater to be treated can circulate and be treated between the anoxic column, the aeration column, and the aerobic column. Step 3: Four-column operation; The PLC controller controls the opening and closing of the second circulation control valve, the second outlet control valve, the second inlet control valve, the main inlet control valve, and the air volume control valve, and controls the closing of the first circulation control valve, the first outlet control valve, and the first inlet control valve. The variable frequency inlet water pump and the variable frequency fan are turned on to allow water to enter through the second inlet pipe and exit through the second outlet pipe. The anoxic column is connected to the anaerobic column, while the anoxic column is not connected to the aeration column, so as to realize the circulation and treatment of the low-concentration organic nitrogen wastewater to be treated among the anaerobic column, the aeration column, the aerobic column, and the anoxic column.

[0044] Figure 10 A flowchart of the detection and control of DO in the wastewater treatment method of the present invention is provided. Figure 11 The detection and control flowcharts for COD, ammonia nitrogen, and nitrate nitrogen are provided. The three-column operation is achieved through the following steps: a). Circulation drive; Under the aeration action of the aeration disc (4), the wastewater entering the aeration column (3) is oxygenated. After the wastewater at the bottom of the aeration column is oxygenated, the density decreases. Under the action of density difference, the wastewater in the upper part of the anoxic column flows into the bottom of the aeration column through the first return column (15), so that there is a liquid level difference between the anoxic column and the aerobic column. Under the action of liquid level difference, the wastewater in the aerobic column enters the anoxic column and the wastewater in the aeration column enters the aerobic column. Finally, the wastewater circulates between the aeration column, the aerobic column and the anoxic column without the action of external power. b). Determination of sludge layer height: The concentration of granular sludge in the aerobic column (7) and the anoxic column (10) is detected by the first and second MLSS sensors (29, 30) respectively, to determine whether the sludge layer height has reached the height that allows the granular sludge to circulate throughout the aerobic column, the anoxic column and the aeration column. If it has not reached the height, it indicates that the flow rate is insufficient, and step c) is executed. If it has reached the height, step d) is executed. c). Increase flow rate; First, obtain and record the circulation flow rate and pipeline flow rate through the pipeline flow meter (9) and gas flow meter (45), then increase the air supply of the variable frequency fan (43) and increase the opening of the first circulation control valve (16) to increase the circulation flow rate, and execute step d). d) Nitrification reaction; As the wastewater flows through the aeration column and aerobic column, in an aerobic environment, nitrifying bacteria in the granular sludge oxidize the ammonia nitrogen in the wastewater into nitrite and nitrate in sequence. e) Denitrification reaction; During the process of the wastewater flowing through the anoxic column, under anoxic or low-oxygen conditions, the denitrifying bacteria in the granular sludge use organic matter as a carbon source to reduce nitrates to nitrogen gas and discharge it. f). Dissolved oxygen detection; the dissolved oxygen value (DO) of the aerobic column was detected by the second DO sensor (23) and the third DO sensor (24). 23 And the dissolved oxygen (DO) value in the anoxic column 24 If DO 23 <0.5mg / L and DO 23 If the DO concentration is <0.2 mg / L, it indicates that the current aeration and oxygenation are appropriate and no adjustment is needed; if .... 23 <0.5 mg / L and DO 23 If either <0.2mg / L is not met, it indicates that the oxygen supply is too high, and the oxygen supply should be reduced. Proceed to step g). g). Reduce oxygen supply regulation; reduce the operating frequency of the variable frequency fan (43), and at the same time reduce the opening of the air volume control valve (44) and the first circulation control valve (16) to reduce oxygenation by reducing the aeration volume; h). Detection of ammonia nitrogen, COD and nitrate nitrogen; The concentration of organic matter in the aerobic column and the anoxic column is detected by the second COD sensor (33) and the third COD sensor (34) respectively. If the concentration of organic matter is not lower than the set value, it indicates that it does not meet the standard, and step c) is executed to increase the circulation rate; The concentration of ammonia nitrogen in the aerobic column and the anoxic column is detected by the second ammonia nitrogen sensor (37) and the third ammonia nitrogen sensor (38) respectively. If the concentration of ammonia nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step i) is executed to increase the oxygen supply; The concentration of nitrate nitrogen in the aerobic column and the anoxic column is detected by the first nitrate nitrogen sensor (26) and the second nitrate nitrogen sensor (27) respectively. If the concentration of nitrate nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step g) is executed to reduce the oxygen supply; If the detected COD concentration, ammonia nitrogen concentration and nitrate nitrogen concentration all meet the standard, step j) is executed. i). Increase oxygen supply regulation; increase the operating frequency of the variable frequency fan (43), and at the same time increase the opening of the air volume control valve (44) and the first circulation control valve (16) to increase oxygenation by increasing the aeration volume; j) Increase water supply; increase water intake by increasing the operating frequency of the variable frequency water pump.

[0045] The operation of the Four Pillars of Destiny is achieved through the following steps: 1) Circulation drive; Under the aeration action of the aeration disc (4), the wastewater entering the aeration column (3) is oxygenated. After the wastewater at the bottom of the aeration column is oxygenated, the density decreases. Under the action of density difference, the wastewater at the top of the anaerobic column flows into the bottom of the aeration column through the second return column (14), so that there is a liquid level difference between the anaerobic column and the aerobic column. Under the action of liquid level difference, the wastewater in the anoxic column enters the anaerobic column, the wastewater in the aerobic column enters the anoxic column, and the wastewater in the aeration column enters the aerobic column. Finally, the wastewater circulates between the aeration column, aerobic column, anoxic column and anoxic column without the action of external power. 2). Judgment of sludge layer height: The concentration of granular sludge in the aerobic column (7) and the anoxic column (10) is detected by the first and second MLSS sensors (29, 30) respectively, to determine whether the sludge layer height has reached the height that allows the granular sludge to remain in the aerobic column and the anoxic column. If it has not reached the height, it indicates that the flow rate is insufficient, and step 3) is executed. If it has reached the height, step 4) is executed. 3). Increase flow rate; First, obtain and record the circulation flow rate and pipeline flow rate through the pipeline flow meter (9) and gas flow meter (45), then increase the air supply of the variable frequency fan (43) and increase the opening of the second circulation control valve (12) to increase the circulation flow rate, and execute step 4). 4) Anaerobic reaction; the wastewater entering the anaerobic column undergoes an anaerobic reaction under the action of anaerobic bacteria in the granular sludge, and the organic matter is degraded to produce a large amount of biogas. Some of the biogas is collected and recovered by the biogas collection device above. 5) Nitrification reaction; As the wastewater flows through the aeration column and aerobic column, in an aerobic environment, nitrifying bacteria in the granular sludge oxidize the ammonia nitrogen in the wastewater into nitrite and nitrate in sequence. 6) Denitrification reaction; During the process of the wastewater flowing through the anoxic column, under anoxic or low-oxygen conditions, the denitrifying bacteria in the granular sludge use organic matter as a carbon source to reduce nitrates to nitrogen gas and discharge it. 7) Dissolved oxygen detection; the dissolved oxygen (DO) values ​​of the aerobic column are detected by the second DO sensor (23) and the third DO sensor (24). 23 And the dissolved oxygen (DO) value in the anoxic column 24 If DO 23 <0.5mg / L and DO 23 If the DO concentration is <0.2 mg / L, it indicates that the current aeration and oxygenation are appropriate and no adjustment is needed; if .... 23 <0.5 mg / L and DO 23 If either <0.2mg / L is not met, it indicates that the oxygen supply is too high and the oxygen supply should be reduced. Proceed to step 8). 8). Reduce oxygen supply regulation; reduce the operating frequency of the variable frequency fan (43), and at the same time reduce the opening of the air volume control valve (44) and the second circulation control valve (12) to reduce oxygenation by reducing the aeration volume; 9) Detection of ammonia nitrogen, COD and nitrate nitrogen; The concentration of organic matter in the aerobic column and the anoxic column is detected by the second COD sensor (33) and the third COD sensor (34) respectively. If the concentration of organic matter is not lower than the set value, it indicates that it does not meet the standard, and step 3) is executed to increase the circulation rate; The concentration of ammonia nitrogen in the aerobic column and the anoxic column is detected by the second ammonia nitrogen sensor (37) and the third ammonia nitrogen sensor (38) respectively. If the concentration of ammonia nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step 10) is executed to increase the oxygen supply; The concentration of nitrate nitrogen in the aerobic column and the anoxic column is detected by the first nitrate nitrogen sensor (26) and the second nitrate nitrogen sensor (27) respectively. If the concentration of nitrate nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step 8) is executed to reduce the oxygen supply; If the detected COD concentration, ammonia nitrogen concentration and nitrate nitrogen concentration all meet the standard, step 11) is executed. 10). Increase oxygen supply regulation; increase the operating frequency of the variable frequency fan (43), and at the same time increase the opening of the air volume control valve (44) and the first circulation control valve (16) to increase oxygenation by increasing the aeration volume; 11) Increase water supply; increase water intake by increasing the operating frequency of the variable frequency water pump.

[0046] It should be noted that if the reduction of oxygen supply in step g) and the increase of oxygen supply in step i) affect the increase of flow rate in step c) on the adjustment of sludge layer height, and the reduction of oxygen supply in step 8) and the increase of oxygen supply in step 10) affect the increase of flow rate in step 3) on the adjustment of sludge layer height, the adjustment can be made by mixing nitrogen or oxygen into the air inlet of the variable frequency fan 43 to meet the requirements of sludge layer height adjustment.

[0047] like Figure 12 The diagram shows the morphology of granular sludge cultivated after long-term operation of the multi-stage self-circulating combined tower of the present invention. It can be seen that after a relatively long period of acclimatization, uniformly distributed and densely packed granular sludge can be cultivated. Figure 13 and Figure 14 As shown, the control conditions and water quality changes of the multi-stage self-circulating combined tower for treating low- and high-concentration organic nitrogen-containing wastewater according to the present invention are presented respectively. It can be seen that treating high-concentration organic nitrogen-containing wastewater requires higher aeration rates, increased upward flow rates, and higher circulation ratios compared to treating low-concentration wastewater. After treatment by the multi-stage self-circulating combined tower of the present invention, the COD and ammonia nitrogen removal rates of both high- and low-concentration organic nitrogen-containing wastewater can reach over 90%, demonstrating excellent treatment effects for both types of wastewater.

Claims

1. A multi-stage self-circulating combined tower for treating different water qualities, comprising an aeration column (3), an aerobic column (7), an anoxic column (10), and an anaerobic column (13), all vertically arranged. The upper part of the aeration column is connected to the bottom of the aerobic column via a first connecting column (5), the upper part of the aerobic column is connected to the lower part of the anoxic column via a second connecting column (8), and the upper part of the anoxic column is connected to the lower part of the anaerobic column via a third connecting column (11). The upper parts of the anoxic column and the upper parts of the anaerobic column are respectively connected to the lower part of the aeration column via a first reflux column (15) and a second reflux column (14). A pipe is provided on the second connecting column. The first and third connecting columns are respectively equipped with a first circulation control valve (16) and a second circulation control valve (12); the tops of the second and third connecting columns are respectively connected to a first inlet pipe (1) and a second inlet pipe (2); the tops of the aerobic and anoxic columns are respectively connected to a first outlet pipe (18) and a second outlet pipe (20); granular sludge is cultivated in the aerobic, anoxic, and anaerobic columns; an aeration disc (4) connected to the aeration device is provided at the bottom of the aeration column; and a three-phase separator is provided at the top of the anaerobic column; the feature is that: When treating low-concentration organic nitrogen-containing wastewater: the first inlet pipe, the first circulation control valve, and the first outlet pipe are all open, while the second inlet pipe, the second circulation control valve, and the second outlet pipe are all closed. Under the aeration action of the aeration discs, the wastewater to be treated and the granular sludge circulate in the anoxic column, the aeration column, and the aerobic column. The removal of ammonia nitrogen and the consumption and removal of organic matter are achieved by utilizing the nitrification and denitrification of microorganisms. When treating high-concentration organic nitrogen-containing wastewater: the second inlet pipe, the second circulation control valve, and the second outlet pipe are all open, while the first inlet pipe, the first circulation control valve, and the first outlet pipe are all closed. Under the aeration action of the aeration discs, the wastewater to be treated circulates in the anaerobic column, the anoxic column, the aeration column, and the aerobic column. The wastewater flowing through the anaerobic column undergoes an anaerobic reaction under the action of anaerobic microorganisms, causing the organic matter to degrade and produce biogas. The biogas is separated by a three-phase separator and collected by a biogas collection device. As wastewater flows through the aerobic and anoxic columns, ammonia nitrogen is further removed through nitrification and denitrification by microorganisms.

2. The multi-stage self-circulating combined tower for treating different water qualities according to claim 1, characterized in that: It includes an inlet regulating tank (39), a variable frequency inlet pump (40) and a variable frequency blower (43). The variable frequency inlet pump transports the wastewater to be treated in the inlet regulating tank to the first inlet pipe (1) or the second inlet pipe (2) through the inlet main pipe. The inlet main pipe is equipped with an inlet main control valve (41) and an inlet flow meter (42). The first inlet pipe and the second inlet pipe are respectively equipped with a first inlet control valve (46) and a second inlet control valve (47). The variable frequency blower supplies air to the aeration disc (4) through the air supply pipeline. The air supply pipeline is equipped with an air volume control valve (44) and a gas flow meter (45).

3. The multi-stage self-circulating combined tower for treating different water qualities according to claim 2, characterized in that: The system includes a PLC controller (48) and a host PC (49) connected to it, a DO meter (21), a nitrate nitrogen meter (25), a sludge concentration MLSS meter (28), a COD meter (31), and an ammonia nitrogen meter (35). The upper parts of the aeration column (3), the aerobic column (7), and the anoxic column (10) are respectively equipped with a first DO sensor (22), a second DO sensor (23), and a third DO sensor (24) connected to the DO meter. The upper parts of the aerobic column and the anoxic column are respectively equipped with a first nitrate nitrogen sensor (26) and a second nitrate nitrogen sensor connected to the nitrate nitrogen meter. (27) The upper part of the aerobic column and the anoxic column are respectively equipped with a first MLSS sensor (29) and a second MLSS sensor (30) connected to the sludge concentration MLSS meter. The influent equalization tank (39), the aerobic column and the anoxic column are respectively equipped with a first COD sensor (32), a second COD sensor (33) and a third COD sensor (34) connected to the COD meter. The influent equalization tank, the aerobic column and the anoxic column are respectively equipped with a first ammonia nitrogen sensor (36), a second ammonia nitrogen sensor (37) and a third ammonia nitrogen sensor (38) connected to the ammonia nitrogen meter. The first outlet pipe (18) and the second outlet pipe (20) are respectively equipped with a first outlet control valve (17) and a second outlet control valve (19) to control their on / off states; different input terminals of the PLC controller are respectively connected to the inlet flow meter (42), the pipeline flow meter (9) and the gas flow meter (45); different output terminals of the PLC controller are respectively connected to the variable frequency inlet water pump (40), the main inlet control valve (41), the first inlet control valve (46), the second inlet control valve (47), the first circulation control valve (16), the second circulation control valve (12), the first outlet control valve (17), the second outlet control valve (19), the variable frequency fan (43) and the air volume control valve (44).

4. The multi-stage self-circulating combined tower for treating different water qualities according to claim 1 or 2, characterized in that: The bottom of the aerobic column (7) is provided with a water distribution pipe (6) that is connected to the first connecting column (5), and the water distribution pipe is provided with downward-facing water distribution holes evenly distributed on it.

5. The multi-stage self-circulating combined tower for treating different water qualities according to claim 1 or 2, characterized in that: The height-to-diameter ratio of the aeration column (3), aerobic column (7), anoxic column (10) and anaerobic column (13) is between 3 and 8.

6. A wastewater treatment method based on the multi-stage self-circulating combined tower for treating different water qualities as described in claim 3, characterized in that, This can be achieved through the following steps: Step 1: First, the concentrations of organic matter and ammonia nitrogen in the wastewater to be treated in the influent equalization tank (39) are detected by the first COD sensor (32) and the first ammonia nitrogen sensor (36) to determine whether the wastewater to be treated is low-concentration or high-concentration organic nitrogen wastewater; if it is low-concentration organic nitrogen wastewater, proceed to step 2; if it is high-concentration organic nitrogen wastewater, proceed to step 3. Step 2: Three-column operation; The PLC controller controls the opening of the first circulation control valve (16), the first outlet control valve (17), the first inlet control valve (46), the main inlet control valve (41), and the air volume control valve (44), and controls the closing of the second circulation control valve (12), the second outlet control valve (19), and the second inlet control valve (47). The variable frequency water pump and variable frequency fan are turned on to allow water to enter through the first inlet pipe and exit through the first outlet pipe. The anoxic column (10) is connected to the aeration column (3), and the anoxic column is not connected to the anaerobic column, so that the low-concentration organic nitrogen wastewater to be treated can circulate and be treated between the anoxic column, the aeration column, and the aerobic column. Step 3: Four-column operation; The PLC controller controls the opening and closing of the second circulation control valve, the second outlet control valve, the second inlet control valve, the main inlet control valve, and the air volume control valve, and controls the closing of the first circulation control valve, the first outlet control valve, and the first inlet control valve. The variable frequency inlet water pump and the variable frequency fan are turned on to allow water to enter through the second inlet pipe and exit through the second outlet pipe. The anoxic column is connected to the anaerobic column, while the anoxic column is not connected to the aeration column, so as to realize the circulation and treatment of the low-concentration organic nitrogen wastewater to be treated among the anaerobic column, the aeration column, the aerobic column, and the anoxic column.

7. A wastewater treatment method based on the multi-stage self-circulating combined tower for treating different water qualities as described in claim 6, characterized in that, The three-column operation is achieved through the following steps: a). Circulation drive; Under the aeration action of the aeration disc (4), the wastewater entering the aeration column (3) is oxygenated. After the wastewater at the bottom of the aeration column is oxygenated, the density decreases. Under the action of density difference, the wastewater in the upper part of the anoxic column flows into the bottom of the aeration column through the first return column (15), so that there is a liquid level difference between the anoxic column and the aerobic column. Under the action of liquid level difference, the wastewater in the aerobic column enters the anoxic column and the wastewater in the aeration column enters the aerobic column. Finally, the wastewater circulates between the aeration column, the aerobic column and the anoxic column without the action of external power. b). Determination of sludge layer height: The concentration of granular sludge in the aerobic column (7) and the anoxic column (10) is detected by the first and second MLSS sensors (29, 30) respectively, to determine whether the sludge layer height has reached the height that allows the granular sludge to circulate throughout the aerobic column, the anoxic column and the aeration column. If it has not reached the height, it indicates that the flow rate is insufficient, and step c) is executed. If it has reached the height, step d) is executed. c). Increase flow rate; First, obtain and record the circulation flow rate and pipeline flow rate through the pipeline flow meter (9) and gas flow meter (45), then increase the air supply of the variable frequency fan (43) and increase the opening of the first circulation control valve (16) to increase the circulation flow rate, and execute step d). d) Nitrification reaction; As the wastewater flows through the aeration column and aerobic column, in an aerobic environment, nitrifying bacteria in the granular sludge oxidize the ammonia nitrogen in the wastewater into nitrite and nitrate in sequence. e) Denitrification reaction; During the process of the wastewater flowing through the anoxic column, under anoxic or low-oxygen conditions, the denitrifying bacteria in the granular sludge use organic matter as a carbon source to reduce nitrates to nitrogen gas and discharge it. f). Dissolved oxygen detection; the dissolved oxygen value (DO) of the aerobic column was detected by the second DO sensor (23) and the third DO sensor (24). 23 And the dissolved oxygen (DO) value in the anoxic column 24 If DO 23 <0.5mg / L and DO 23 If the DO concentration is <0.2 mg / L, it indicates that the current aeration and oxygenation are appropriate and no adjustment is needed; if .... 23 <0.5 mg / L and DO 23 If either <0.2mg / L is not met, it indicates that the oxygen supply is too high, and the oxygen supply should be reduced. Proceed to step g). g). Reduce oxygen supply regulation; reduce the operating frequency of the variable frequency fan (43), and at the same time reduce the opening of the air volume control valve (44) and the first circulation control valve (16) to reduce oxygenation by reducing the aeration volume; h). Detection of ammonia nitrogen, COD and nitrate nitrogen; The concentration of organic matter in the aerobic column and the anoxic column is detected by the second COD sensor (33) and the third COD sensor (34) respectively. If the concentration of organic matter is not lower than the set value, it indicates that it does not meet the standard, and step c) is executed to increase the circulation rate; The concentration of ammonia nitrogen in the aerobic column and the anoxic column is detected by the second ammonia nitrogen sensor (37) and the third ammonia nitrogen sensor (38) respectively. If the concentration of ammonia nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step i) is executed to increase the oxygen supply; The concentration of nitrate nitrogen in the aerobic column and the anoxic column is detected by the first nitrate nitrogen sensor (26) and the second nitrate nitrogen sensor (27) respectively. If the concentration of nitrate nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step g) is executed to reduce the oxygen supply; If the detected COD concentration, ammonia nitrogen concentration and nitrate nitrogen concentration all meet the standard, step j) is executed. i). Increase oxygen supply regulation; increase the operating frequency of the variable frequency fan (43), and at the same time increase the opening of the air volume control valve (44) and the first circulation control valve (16) to increase oxygenation by increasing the aeration volume; j) Increase water supply; increase water intake by increasing the operating frequency of the variable frequency water pump.

8. A wastewater treatment method based on the multi-stage self-circulating combined tower for treating different water qualities as described in claim 6, characterized in that, The operation of the Four Pillars of Destiny is achieved through the following steps: 1) Circulation drive; Under the aeration action of the aeration disc (4), the wastewater entering the aeration column (3) is oxygenated. After the wastewater at the bottom of the aeration column is oxygenated, the density decreases. Under the action of density difference, the wastewater at the top of the anaerobic column flows into the bottom of the aeration column through the second return column (14), so that there is a liquid level difference between the anaerobic column and the aerobic column. Under the action of liquid level difference, the wastewater in the anoxic column enters the anaerobic column, the wastewater in the aerobic column enters the anoxic column, and the wastewater in the aeration column enters the aerobic column. Finally, the wastewater circulates between the aeration column, aerobic column, anoxic column and anoxic column without the action of external power. 2). Judgment of sludge layer height: The concentration of granular sludge in the aerobic column (7) and the anoxic column (10) is detected by the first and second MLSS sensors (29, 30) respectively, to determine whether the sludge layer height has reached the height that allows the granular sludge to remain in the aerobic column and the anoxic column. If it has not reached the height, it indicates that the flow rate is insufficient, and step 3) is executed. If it has reached the height, step 4) is executed. 3). Increase flow rate; First, obtain and record the circulation flow rate and pipeline flow rate through the pipeline flow meter (9) and gas flow meter (45), then increase the air supply of the variable frequency fan (43) and increase the opening of the second circulation control valve (12) to increase the circulation flow rate, and execute step 4). 4) Anaerobic reaction; the wastewater entering the anaerobic column undergoes an anaerobic reaction under the action of anaerobic bacteria in the granular sludge, and the organic matter is degraded to produce a large amount of biogas. Some of the biogas is collected and recovered by the biogas collection device above. 5) Nitrification reaction; As the wastewater flows through the aeration column and aerobic column, in an aerobic environment, nitrifying bacteria in the granular sludge oxidize the ammonia nitrogen in the wastewater into nitrite and nitrate in sequence. 6) Denitrification reaction; During the process of the wastewater flowing through the anoxic column, under anoxic or low-oxygen conditions, the denitrifying bacteria in the granular sludge use organic matter as a carbon source to reduce nitrates to nitrogen gas and discharge it. 7) Dissolved oxygen detection; the dissolved oxygen (DO) values ​​of the aerobic column are detected by the second DO sensor (23) and the third DO sensor (24). 23 And the dissolved oxygen (DO) value in the anoxic column 24 If DO 23 <0.5mg / L and DO 23 If the DO concentration is <0.2 mg / L, it indicates that the current aeration and oxygenation are appropriate and no adjustment is needed; if .... 23 <0.5 mg / L and DO 23 If either <0.2mg / L is not met, it indicates that the oxygen supply is too high and the oxygen supply should be reduced. Proceed to step 8). 8). Reduce oxygen supply regulation; reduce the operating frequency of the variable frequency fan (43), and at the same time reduce the opening of the air volume control valve (44) and the second circulation control valve (12) to reduce oxygenation by reducing the aeration volume; 9) Detection of ammonia nitrogen, COD and nitrate nitrogen; The concentration of organic matter in the aerobic column and the anoxic column is detected by the second COD sensor (33) and the third COD sensor (34) respectively. If the concentration of organic matter is not lower than the set value, it indicates that it does not meet the standard, and step 3) is executed to increase the circulation rate; The concentration of ammonia nitrogen in the aerobic column and the anoxic column is detected by the second ammonia nitrogen sensor (37) and the third ammonia nitrogen sensor (38) respectively. If the concentration of ammonia nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step 10) is executed to increase the oxygen supply; The concentration of nitrate nitrogen in the aerobic column and the anoxic column is detected by the first nitrate nitrogen sensor (26) and the second nitrate nitrogen sensor (27) respectively. If the concentration of nitrate nitrogen is not lower than the set value, it indicates that it does not meet the standard, and step 8) is executed to reduce the oxygen supply; If the detected COD concentration, ammonia nitrogen concentration and nitrate nitrogen concentration all meet the standard, step 11) is executed. 10). Increase oxygen supply regulation; increase the operating frequency of the variable frequency fan (43), and at the same time increase the opening of the air volume control valve (44) and the first circulation control valve (16) to increase oxygenation by increasing the aeration volume; 11) Increase water supply; increase water intake by increasing the operating frequency of the variable frequency water pump.

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