Method for treating municipal domestic sewage by micro-nano bubble reinforced aerobic granular sludge

Abstract

This invention provides a method for treating municipal wastewater using micro-nano bubble-enhanced aerobic granular sludge. The method involves inoculating aerobic granular sludge capable of simultaneously accumulating nitrite and removing pollutants into a sequencing batch reactor (SBR); introducing municipal wastewater and aerating it with micro-nano bubbles, operating the reactor in an anaerobic / aerobic / anoxic mode; maintaining the dissolved oxygen concentration at 2-3 mg / L through micro-nano bubble aeration to achieve self-accumulation and stable operation of anaerobic ammonia-oxidizing bacteria within the aerobic granular sludge. This method utilizes the high oxygen mass transfer efficiency and long residence time of micro-nano bubbles to enhance the pollutant transformation process in the system and ensures a suitable anaerobic microenvironment for anaerobic ammonia-oxidizing bacteria within the aerobic granular sludge. Under municipal wastewater treatment conditions, the average concentrations of COD and ammonia nitrogen in the effluent are as low as 34.65 mg / L and 1.92 mg / L, respectively, with a total nitrogen removal rate of 82.53%.

Description

Technical Field

[0001] This invention relates to a method for treating domestic sewage, and more particularly to a method for treating urban domestic sewage using micro-nano bubble-enhanced aerobic granular sludge. Background Technology

[0002] Currently, biological treatment is the main technology for wastewater treatment. However, the biological nitrogen removal processes used in existing wastewater treatment plants are mainly based on activated sludge processes, which are difficult to further improve in terms of nitrogen removal efficiency. Furthermore, these processes suffer from high energy consumption, high chemical consumption, and greenhouse gas emissions (CO2, CH4, and N2O), making it difficult to meet current requirements for high-efficiency, low-energy, and low-emission nitrogen removal. Therefore, developing a process that can reduce pollution and carbon emissions, achieve synergistic efficiency improvements, and is suitable for urban domestic wastewater treatment is particularly crucial.

[0003] Anaerobic ammonia oxidation (AAO) technology, with its advantages of high nitrogen removal efficiency, no need for external carbon sources and aeration, low greenhouse gas emissions, and low sludge production, has become a research hotspot for green and low-carbon wastewater treatment processes and is considered a promising engineering technology for improving wastewater nitrogen removal efficiency. However, in practical applications, AAO still faces challenges such as long strain acclimation periods, difficulties in large-scale enrichment, and the production of key substrates (such as NO2). - Limited by factors such as insufficient N-type nitrogen (N) supply, and the presence of organic matter in domestic sewage inhibiting anaerobic ammonia-oxidizing bacteria, aerobic granular sludge is severely restricted in its engineering application. Aerobic granular sludge is defined as a granular microbial aggregate formed by bacterial growth and spontaneous flocculation. Its unique granular structure endows aerobic granular sludge with several advantages. However, aerobic granular sludge has high requirements for operating conditions; for example, organic load and dissolved oxygen concentration, hydraulic shear force, and fluctuations in influent water quality all significantly affect particle formation and stability. In actual domestic sewage treatment, due to large fluctuations in influent water quality and generally low organic matter concentrations, it is often difficult to maintain a stable granular structure, easily leading to granular loosening or even disintegration.

[0004] In recent years, micro- and nano-bubble aeration has attracted much attention due to its small bubble diameter (no more than 100 μm), high oxygen transfer efficiency, and strong slow-release properties. Compared with conventional aeration, micro- and nano-bubble aeration can significantly modify the composition and metabolic functions of microbial communities in biological treatment systems, particularly improving cellular respiration, ammonia oxidation, and nitrification. However, current research on micro- and nano-bubble aeration mainly focuses on organic matter removal in drinking water or activated sludge processes in wastewater treatment. Its mechanism of action in aerobic granular sludge systems remains unclear, especially under low-load domestic wastewater conditions. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for treating urban domestic sewage by enhancing aerobic granular sludge with micro-nano bubbles, thereby achieving the self-enrichment of anaerobic ammonia-oxidizing bacteria inside the aerobic granular sludge and synergistically improving the treatment performance of urban domestic sewage.

[0006] Technical solution: The method for treating urban domestic sewage using micro-nano bubble-enhanced aerobic granular sludge according to the present invention includes the following steps:

[0007] Inoculate aerobic granular sludge into a sequencing batch reactor to simultaneously accumulate nitrite and remove pollutants.

[0008] Urban domestic sewage is introduced and micro-nano bubble aeration is carried out. The sequencing batch reactor is operated in an anaerobic / aerobic / anoxic mode.

[0009] The micro-nano bubble aeration controls the dissolved oxygen concentration at 2-3 mg / L to achieve self-enrichment and stable operation of anaerobic ammonia-oxidizing bacteria in aerobic granular sludge.

[0010] Among them, an air compressor is used to aerate micro-nano bubbles, generating micro-nano bubbles with a particle size range of 100-300 nm.

[0011] The anaerobic time is 170-190 min, the aerobic time is 200-220 min, the anoxic time is 300-320 min, and the total hydraulic retention time is 11.5-12 hours.

[0012] This invention employs an anaerobic / aerobic / anoxic operating mode, with the anaerobic duration preferably being 180 min (including influent time), the aerobic duration preferably being 210 min, and the anoxic duration preferably being 300 min. During the anaerobic phase, the rapid adsorption and intracellular storage and transformation of organic matter are enhanced, providing a stable intracellular carbon source for subsequent reactions. The aerobic phase utilizes micro / nanobubbles for aeration. The small bubble size, large specific surface area, and long residence time of these bubbles improve the system's oxygen utilization efficiency, enabling further removal of organic matter and partial nitrification of ammonia nitrogen. The dissolved oxygen concentration is controlled at 2-3 mg / L, maintaining necessary nitrification capacity while providing an appropriate amount of NH4 for subsequent reaction stages. + -N and NO2 - -N; The anoxic phase promotes the synergistic process of endogenous short-cut denitrification and anaerobic ammonia oxidation by extending the reaction time, achieving efficient coupled nitrogen removal. At the same time, by controlling the total duration of the anaerobic and anoxic phases within a single cycle to a reasonable duration, preferably about 8 hours, a low dissolved oxygen environment conducive to the growth of anaerobic ammonia oxidizing bacteria is constructed, thereby achieving their directional enrichment and stable maintenance within the granular sludge.

[0013] This invention utilizes the layered structure of aerobic granular sludge to create a dissolved oxygen gradient from the outside to the inside of the granules, constructing a stable anoxic / anaerobic microenvironment. Simultaneously, by controlling the dissolved oxygen concentration in the aerobic phase at a low level (2-3 mg / L) and providing a longer anaerobic and anoxic reaction time, a suitable growth niche is provided for anaerobic ammonia-oxidizing bacteria, avoiding the inhibition of their activity by high dissolved oxygen levels and promoting their self-accumulation.

[0014] The inoculation concentration of the aerobic granular sludge is 4000-4500 mg / L.

[0015] The establishment and operation process of the aerobic granular sludge that can simultaneously accumulate nitrite and remove pollutants is as follows: the aerobic granular sludge and activated sludge to be inoculated are washed and placed in an SBR for cultivation, with an initial MLSS of 3800-4000 mg / L; simulated urban domestic sewage is introduced into the SBR for aerobic granular sludge cultivation and acclimatization.

[0016] The simulated urban domestic sewage sources were sodium acetate, NH4Cl, and KH2PO4, respectively; the influent COD concentration was 340-350 mg / L, ammonia nitrogen concentration was 65-75 mg / L, and phosphorus concentration was 4-5 mg / L; the operation mode was anaerobic / aerobic / anoxic, with a single cycle of 5.5-6.5 h; the anaerobic duration was 70-90 min, the aerobic duration was 110-130 min, and the anoxic duration was 150-170 min; the acclimatization period was 120 days or more.

[0017] Among them, ceramic membrane aeration discs are used for micro-nano bubble aeration.

[0018] The ceramic membrane aeration disc is fixed to the bottom side of the sequencing batch reactor, with an effective working area of ​​100 mm × 90 mm. The pore size of the ceramic membrane is 50-120 nm, and the average pore size is preferably 100 nm.

[0019] When the organic matter in the simulated urban domestic sewage includes soluble starch and sodium acetate, the ratio of COD equivalents is 3:1-5:1, preferably 4:1, and the COD concentration of the influent is 250-350 mg / L.

[0020] When the nitrogen in the simulated urban domestic sewage is in the form of ammonia nitrogen, the influent concentration is 50-70 mg / L;

[0021] When the phosphorus element in the simulated urban domestic sewage is in the form of phosphate, the influent concentration does not exceed 3 mg / L;

[0022] When simulating other components of urban domestic sewage, the following are preferred: MgSO4·7H2O 18-22 mg / L, CaCl2 18-22 mg / L, FeSO4·7H2O 3-7 mg / L; preferably: MgSO4·7H2O 20 mg / L, CaCl2 20 mg / L, FeSO4·7H2O 5 mg / L; trace element stock solution can be added or tap water can be used to prepare the solution to provide trace elements.

[0023] The pH value of the simulated urban domestic sewage is 7.5-8.5.

[0024] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0025] (1) This invention improves oxygen mass transfer efficiency and optimizes dissolved oxygen distribution by introducing a micro-nano bubble aeration mode, thereby enhancing the pollutant conversion process in the system and forming a stable dissolved oxygen gradient inside the aerobic granular sludge. This provides a suitable microenvironment for the growth of anaerobic ammonia oxidizing bacteria, thus promoting the self-enrichment of anaerobic ammonia oxidizing bacteria inside the granular sludge. The typical anaerobic ammonia oxidizing bacterium Candidatus Brocadia achieved significant enrichment in the system, with its relative abundance increasing to 4.944%.

[0026] (2) Compared with existing technologies that rely on high dissolved oxygen and high aeration intensity to maintain granulation and treatment effect, this invention maintains good nitrification performance of the system by controlling dissolved oxygen at a low level (2-3 mg / L), ensuring that the anaerobic ammonia-oxidizing bacteria are created inside the granules, and by enhancing the oxygen mass transfer process. This achieves the synergistic effect of multifunctional microorganisms under low dissolved oxygen conditions. Under the condition of treating urban domestic sewage, the average concentrations of COD and ammonia nitrogen in the effluent of the system are as low as 34.65 mg / L and 1.92 mg / L, respectively, and the total nitrogen removal rate reaches 82.53%.

[0027] (3) The present invention uses aerobic granular sludge with the ability to simultaneously accumulate nitrite and remove pollutants. This sludge can not only provide suitable substrates for anaerobic ammonia oxidizing bacteria, but also form a multi-layered microenvironment inside the granules, which is suitable for the growth of anaerobic ammonia oxidizing bacteria, thereby realizing the synergistic process of nitrification, denitrification and anaerobic ammonia oxidation, thereby improving the overall denitrification efficiency of the system.

[0028] (4) The process of this invention is simple to operate, requires no additional chemical reagents and is environmentally friendly. The denitrification performance of the system can be improved simply by adjusting the aeration method. It has the advantages of easy operation, stable operation and great potential for engineering application.

[0029] (5) This invention is applicable to the green and low-carbon treatment of urban domestic sewage. It has stable performance, safe operation, and mild conditions, providing a new strategy for synergistic effect of pollution reduction and carbon reduction. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the system structure used in the method of the present invention;

[0031] Figure 2 The graph shows the change of dissolved oxygen concentration in water over time during conventional aeration and micro / nano bubble aeration.

[0032] Figure 3 The fitting graphs of the oxygen mass transfer equations are shown for conventional aeration and micro / nano bubble aeration.

[0033] Figure 4 The graphs show the specific aerobic rate (SOUR) of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) at sludge concentrations of 3800, 4200 and 4500 mg / L, and the denitrification activity of denitrifying bacteria.

[0034] Figure 5 The diagram shows the activity of adenosine triphosphate (ATP) and electron transport system (ETSA) in microorganisms during conventional aeration and micro / nano bubble aeration.

[0035] Figure 6 The graph shows the changes in COD influent concentration, effluent concentration, and removal rate over 190 days of operation of the method of this invention.

[0036] Figure 7 The graph shows the changes in ammonia nitrogen influent concentration, effluent concentration, and removal rate over 190 days of operation of the method of the present invention.

[0037] Figure 8 The graph shows the changes in nitrite nitrogen concentration and nitrate nitrogen concentration in the effluent over 190 days of operation of the method of the present invention.

[0038] Figure 9 The graph shows the changes in total nitrogen influent concentration, effluent concentration, and removal rate over 190 days of operation of the method of the present invention.

[0039] Figure 10 This is a graph showing the changes in the relative abundance of anaerobic ammonia-oxidizing bacteria on days 1, 95, and 190 of the operation of the method of the present invention. Detailed Implementation

[0040] The present invention will now be described in further detail.

[0041] A method for treating urban domestic sewage using micro / nano bubble-enhanced aerobic granular sludge includes the following steps:

[0042] (1) Set up a sequencing batch reactor with an effective volume of 8 L, inoculate it with freeze-thawed aerobic granular sludge with the ability to simultaneously accumulate nitrite and remove pollutants, freeze it at -20℃ for more than 60 days, and the initial concentration of aerobic granular sludge is 4200 mg / L.

[0043] In this embodiment, the aerobic granular sludge capable of simultaneously accumulating nitrite and removing pollutants, as reported in the published literature DOI: 10.1016 / j.jclepro.2026.147612 (A novel mainstream application of aerobic granular sludge for nitrite supply to Anammox: insights from granule size and microbial stratification, ZongshuoHan, etc. Journal of Cleaner Production), is established and operated as follows:

[0044] One SBR reactor was set up, using frozen AGS (10% by mass) and activated sludge (90% by mass) as inoculum. Before the experiment, the sludge to be inoculated was washed three times with deionized water to remove residual matrix and soluble impurities. After washing, the sludge to be inoculated was placed in the SBR for cultivation, with an initial MLSS of approximately 4000 mg / L.

[0045] Artificial influent was used to simulate urban domestic sewage quality for the cultivation and acclimatization of aerobic granular sludge. The carbon, nitrogen, and phosphorus sources in the simulated influent were sodium acetate, NH4Cl, and KH2PO4, respectively. The influent COD concentration was 350 mg / L, ammonia nitrogen concentration was 70 mg / L, and phosphorus concentration was 5 mg / L. The system operated in an anaerobic / aerobic / anoxic mode, with a single cycle of 6 hours. The anaerobic period was 80 minutes, the aerobic period was 120 minutes, and the anoxic period was 160 minutes. The acclimatization period was approximately 120 days.

[0046] like Figure 1As shown, the system used in the method for treating urban domestic sewage according to the present invention includes a sewage inlet tank 1, a sequencing batch reactor 5, and a sewage outlet tank 6 connected in sequence; a peristaltic pump 2 is installed on the pipeline between the outlet of the sewage inlet tank 1 and the inlet of the sequencing batch reactor 5; a ceramic membrane module 3-2 is installed on the bottom side of the sequencing batch reactor 5, with an effective working area of ​​100 mm × 90 mm and an average pore size of 100 nm; an air compressor 3 is connected to the ceramic membrane module 3-2 through a pipeline, on which a flow meter 3-1 is installed, and the air compressor 3 is equipped with a pressure divider valve; the air compressor provides the working pressure, and the pressure divider valve regulates the working pressure, with an average working pressure of 0.04~0.06 MPa, an aeration flow rate of approximately 5-7 L / h, which can generate micro-nano bubbles with a particle size range of 100-300 nm, and the dissolved oxygen concentration is controlled at 2-3. mg / L; The sequencing batch reactor 5 is equipped with a stirring device 4, and the sequencing batch reactor 5 is equipped with an outlet 5-1. The pipeline between the outlet 5-1 and the wastewater outlet tank 6 is equipped with a valve; The upper part of the side wall of the sequencing batch reactor 5 is equipped with a sampling port 1 5-2, the lower part is equipped with a sampling port 2 5-3, and the bottom of the sequencing batch reactor 5 is equipped with a sludge discharge port 5-4. Valves are provided at the sampling port 1 5-2, the sampling port 2 5-3 and the sludge discharge port 5-4.

[0047] (2) The operating mode of the sequencing batch reactor 5 is anaerobic / aerobic / anoxic, with a hydraulic retention time of 11 h, of which the anaerobic time is 180 min, including the influent time; the aerobic time is 210 min; the anoxic time is 300 min, including the sedimentation and effluent time; the effluent ratio is 80%, and a mechanical stirrer is used for stirring at a speed of 150 rpm. The dissolved oxygen concentration in the aerobic stage is reduced from 4~5 mg / L to 2~3 mg / L.

[0048] (3) The sequencing batch reactor 5 operated for a total of 190 days. From day 1 to 95, it used fine sand aeration discs for aeration, i.e., conventional aeration, with an effective working area of ​​φ=8 cm and an average pore size of 100 μm. From day 1 to 39, the dissolved oxygen concentration was 4~5 mg / L, and from day 40 to 95, the dissolved oxygen concentration was 2~3 mg / L. From day 96 to 190, it used ceramic membrane aeration discs for aeration, i.e., micro-nano bubble aeration, with an effective working area of ​​100 mm × 90 mm, an average pore size of 100 nm, a working pressure of about 0.04 MPa, and an air flow rate of about 6 L / h.

[0049] (4) The initial influent components are: soluble starch (COD) 240 mg / L, sodium acetate (COD) 60 mg / L, ammonia nitrogen 60 mg / L, phosphorus 3 mg / L, MgSO4·7H2O 20 mg / L, CaCl2 20 mg / L, and tap water is used to provide trace elements.

[0050] Implementation results:

[0051] (1) such as Figure 2 and Figure 3 As shown, after 100 minutes of conventional aeration, the dissolved oxygen concentration in the water reached 7.06 mg / L, while micro / nano bubble aeration achieved a dissolved oxygen concentration of 7.81 mg / L within 60 minutes. The standard oxygen total mass transfer coefficient K for conventional aeration is... Las It is 0.0194 min. -1 K under micro-nano bubble aeration Las It is 0.0491 min. -1 This indicates that micro- and nano-bubbles have better mass transfer efficiency.

[0052] (2) such as Figure 4 As shown, when the sludge concentrations were 3800, 4200, and 4500 mg / L, the SOUR of AOB was 62.78, 61.58, and 50.25 mgO2 / gSS·h, respectively, and the SOUR of NOB was 18.25, 19.34, and 16.39 mgO2 / gSS·h, respectively, with denitrification activities of 1.23, 1.29, and 1.25 mgN / gSS·h, respectively. Based on a comprehensive analysis of the effects of nitrification and denitrification, 4200 mg / L was selected as the inoculum sludge concentration.

[0053] (3) such as Figure 5 As shown, compared with conventional aeration, the microbial ATP content and ETSA activity increased by 42.85% and 49.87% respectively under micro-nano bubble aeration conditions, and the microbial energy metabolism and electron transfer were enhanced.

[0054] (4) Figure 6-9 During the experiment, the aeration mode was used from day 1 to day 39, with a dissolved oxygen concentration of 4 to 5 mg / L; the aeration mode was used from day 40 to day 95, with a dissolved oxygen concentration of 2 to 3 mg / L; and the aeration mode was used from day 96 to day 190, with a dissolved oxygen concentration of 2 to 3 mg / L.

[0055] like Figure 6As shown, under the conventional aeration mode with a dissolved oxygen concentration of 4–5 mg / L (days 1–39), the average COD concentration of the effluent from the aerobic granular sludge system was 37.25 mg / L; under the conventional aeration mode with a dissolved oxygen concentration of 2–3 mg / L (days 40–95), the average COD concentration of the effluent from the aerobic granular sludge system was 42.69 mg / L; while keeping the above operating parameters unchanged, after introducing a micro / nano bubble aeration mode in the third operating stage (days 96–190), the average COD concentration of the system effluent further decreased to 34.65 mg / L. The introduction of micro / nano bubble aeration helps to enhance the breakdown and degradation of large organic molecules, assisting microorganisms in enhancing COD removal.

[0056] (5) such as Figure 7 , 8 As shown in Figure 9, under the conventional aeration mode with a dissolved oxygen concentration of 4–5 mg / L (days 1–39), the average ammonia nitrogen concentration in the effluent was 1.51 mg / L, and the average total nitrogen removal rate was 69.32%. Under the conventional aeration mode with a dissolved oxygen concentration of 2–3 mg / L (days 40–95), the average ammonia nitrogen concentration in the effluent was 4.21 mg / L, and the average total nitrogen removal rate was 77.95%. In the third operating stage (days 56–152) with the introduction of micro-nano bubble aeration mode, the denitrification performance of the system further improved. The average ammonia nitrogen concentration in the effluent decreased to 1.92 mg / L, the nitrite nitrogen concentration in the effluent was below the detection limit, the average nitrate nitrogen concentration in the effluent was 8.63 mg / L, and the average total nitrogen removal rate of the system increased to 82.53%. This indicates that micro-nano bubble aeration improves nitrogen conversion efficiency and enhances denitrification capacity.

[0057] (6) Figure 10 Day 95 was the conventional aeration mode, and day 190 was the micro-nano bubble aeration mode. For example... Figure 10 As shown, in the initial stage of system inoculation, i.e., day 1, the relative abundances of two typical anaerobic ammonia oxidizing bacteria, namely Candidatus Brocadia and Candidatus Kuenenia, were only 0.050% and 0.022%, respectively. At the end of the first operating phase, i.e., day 95, their relative abundances increased to 0.546% and 0.412%, respectively. At the end of the operating phase after the introduction of the micro-nano bubble aeration mode, i.e., day 190, Candidatus Brocadia achieved high enrichment, with its relative abundance increasing to 4.944%, while the relative abundance of Candidatus Kuenenia remained at 0.162%. This indicates that with the assistance of micro-nano aeration, anaerobic ammonia oxidizing bacteria self-accumulate within the system, and the anaerobic ammonia oxidation pathway gradually plays a role in the aerobic granular sludge system, improving the overall performance of the system.

Claims

1. A method for treating urban domestic sewage using micro / nano bubble-enhanced aerobic granular sludge, characterized in that, Includes the following steps: Inoculate aerobic granular sludge into a sequencing batch reactor to simultaneously accumulate nitrite and remove pollutants. Urban domestic sewage is introduced and micro-nano bubble aeration is carried out. The sequencing batch reactor is operated in an anaerobic / aerobic / anoxic mode. The micro-nano bubble aeration controls the dissolved oxygen concentration at 2-3 mg / L to achieve self-enrichment and stable operation of anaerobic ammonia-oxidizing bacteria in aerobic granular sludge.

2. The method for treating urban domestic sewage using micro-nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, Micro-nanobubbles with a particle size range of 100-300 nm are generated by using an air compressor for micro-nanobubble aeration.

3. The method for treating urban domestic sewage using micro-nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, The anaerobic time is 170-190 min, the aerobic time is 200-220 min, the anoxic time is 300-320 min, and the total hydraulic retention time is 11.5-12 hours.

4. The method for treating urban domestic sewage with micro-nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, The inoculation concentration of the aerobic granular sludge is 4000-4500 mg / L.

5. The method for treating urban domestic sewage with micro-nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, The establishment and operation process of the aerobic granular sludge that can simultaneously accumulate nitrite and remove pollutants is as follows: After washing the aerobic granular sludge and activated sludge to be inoculated, they are placed in an SBR for cultivation, with an initial MLSS of 3800-4000 mg / L; simulated urban domestic sewage is introduced into the SBR for aerobic granular sludge cultivation and acclimatization. The simulated urban domestic sewage sources were sodium acetate, NH4Cl, and KH2PO4, respectively. The influent COD concentration was 340-350 mg / L, ammonia nitrogen concentration was 65-75 mg / L, and phosphorus concentration was 4-5 mg / L. The operation mode was anaerobic / aerobic / anoxic, with a single cycle of 5.5-6.5 h. The anaerobic duration was 70-90 min, the aerobic duration was 110-130 min, and the anoxic duration was 150-170 min. The acclimatization period was 120 days or more.

6. The method for treating urban domestic sewage using micro / nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, Ceramic membrane aeration discs are used for micro-nano bubble aeration.

7. The method for treating urban domestic sewage with micro-nano bubble-enhanced aerobic granular sludge according to claim 6, characterized in that, The ceramic membrane aeration disc is fixed to the bottom side of the sequencing batch reactor, and the pore size of the ceramic membrane is 50-120 nm.

8. The method for treating urban domestic sewage with micro-nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, When the organic matter in the simulated urban domestic sewage includes soluble starch and sodium acetate, the COD equivalent ratio is 3:1-5:1, and the COD concentration in the influent is 250-350 mg / L. When the nitrogen in the simulated urban domestic sewage is in the form of ammonia nitrogen, the influent concentration is 50-70 mg / L; When the phosphorus element in the simulated urban domestic sewage is in the form of phosphate, the influent concentration does not exceed 3 mg / L; When the other components of the simulated urban domestic sewage are: MgSO4·7H2O 18-22 mg / L, CaCl2 18-22 mg / L, FeSO4·7H2O 3-7 mg / L, trace element stock solution can be added or tap water can be used to prepare trace elements.

9. The method for treating urban domestic sewage with micro-nano bubble-enhanced aerobic granular sludge according to claim 1, characterized in that, The pH value of the simulated urban domestic sewage is 7.5-8.5.

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