Continuous flow self-circulation aerobic granular sludge-membrane bioreactor constructed based on satiation-starvation alternating strategy and application of continuous flow self-circulation aerobic granular sludge-membrane bioreactor

Abstract

The invention relates to the technical field of water treatment, and discloses a continuous flow self-circulation aerobic granular sludge-membrane bioreactor constructed based on a satiation-starvation alternating strategy and application thereof, and the continuous flow self-circulation aerobic granular sludge-membrane bioreactor comprises an aerobic zone and an anaerobic zone which are arranged in series. The method is characterized in that in the anaerobic zone, raw sewage and aerobic granular sludge are in full contact and react through the shearing force of a stirring paddle and the separation effect of gravity selection pressure, and a satiation period is formed. And then, under the aeration action of the aerobic zone, the mud-water mixture further reacts to form a starvation period. The liquid level difference and the sludge density difference formed between the two areas provide self-driven backflow power for the system. According to the scheme, the reactor adopts three-low operation conditions (low aeration rate, low circulation rate and low stirring rate), rapid in-situ culture and high granulation rate of the aerobic granular sludge are realized in a continuous flow mode, the obtained granular sludge has the characteristics of large particle size, smooth surface, compact structure and the like, and the effluent quality reaches the surface water class III standard.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a saturation-starvation alternation strategy and its application. Background Technology

[0002] Amid global energy shortages, urban wastewater treatment facilities must balance achieving water quality standards with minimizing energy consumption, and may even transform into energy-producing facilities. Aerobic granular sludge (AGS) technology, based on microbial self-aggregation to form spherical aggregates with a particle size exceeding 200 μm, offers advantages over traditional activated sludge processes, including strong interspecies synergy, high biomass, superior settling, and strong shock resistance, thereby minimizing energy consumption, land occupation, and controlling excess sludge production. Its dissolved oxygen gradient stratification (aerobic-anoxic-anaerobic) enables simultaneous removal of organic matter and nutrients within a single reactor, but relies on the rapid formation and long-term stability of granular sludge. Sequencing batch reactors (SBRs) offer significant advantages in AGS cultivation due to their precise control over saturation-starvation cycles and hydraulic selective pressure, but their intermittent operation requires large-scale water storage facilities, limiting large-scale application. Continuous flow systems, due to their low construction costs and ease of operation and management, have become the mainstream process for large-scale wastewater treatment plants. Based on this, the industry is exploring continuous flow AGS technology and also attempting to couple it with membrane bioreactors to mitigate membrane fouling and reduce energy consumption and maintenance costs.

[0003] Currently, most mainstream continuous flow reactors are designed based on hydraulic shear force or sludge settling. In addition, there are patents (such as CN115974263A, which discloses an intermittent aeration continuous flow aerobic granular sludge reactor and its operation method) that promote AGS formation by creating a saturated-starved environment through intermittent aeration. However, the existing technology still has the following technical problems: (1) granular pyrolysis is prone to occur during long-term operation of continuous flow AGS. Existing enhancement methods (such as adding granular activated carbon and other carriers, metal ion supplementation, functional bacterial inoculation, and electric / magnetic field enhancement) are also difficult to apply industrially due to cost, safety, and environmental protection issues. (2) Existing continuous flow reactors have complex structures, low efficiency, and do not pay attention to the periodic saturated-starved strategy, which affects the granule formation efficiency. (3) The AGS obtained by the patent (such as CN 109912029 B, which discloses a self-flowing internal circulation aerobic granular sludge continuous flow reactor) is not formed by in-situ cultivation (the inoculated sludge is AGS matured by SBR cultivation), and after 60 days of operation, the effluent COD can only be lower than 15 mg / L and TN can only be lower than 6 mg / L. (4) The existing technology CN115974263A not only has many power-consuming components and high energy consumption, but also cannot adapt to the complex working conditions such as diurnal temperature difference, seasonal temperature change and influent water quality fluctuations that are common in actual municipal sewage treatment, which can easily lead to unstable system operation. At the same time, the effluent water quality after treatment can only meet the first-level standard stipulated in the "Discharge Standard of Pollutants for Urban Wastewater Treatment Plants" (GB18918-2002), which cannot meet the higher water quality discharge requirements, thus limiting its application in scenarios with higher requirements for effluent water quality.

[0004] Therefore, the development and application of a continuous flow self-circulating aerobic granular sludge-membrane bioreactor based on a saturation-starvation alternation strategy not only effectively compensates for the shortcomings of existing technologies, but also has great significance for improving wastewater treatment efficiency and in-situ granulation efficiency. Summary of the Invention

[0005] The present invention aims to provide a continuous flow self-circulating aerobic granular sludge-membrane bioreactor and its application based on a saturation-starvation alternation strategy, in order to solve the technical problem that existing continuous flow membrane bioreactors based on the saturation-starvation alternation strategy cannot form a stable AGS.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a saturation-starvation alternation strategy, comprising an aerobic zone and an anaerobic zone of sub-reactors arranged in series, with reactor supports below the aerobic and anaerobic zones, and a lower guide pipe and an upper guide pipe connecting the aerobic and anaerobic zones; an inlet is provided on the upper side wall of the anaerobic zone, and a stirring paddle is provided inside the anaerobic zone; a sludge discharge port is provided at the bottom of the aerobic zone, and an aeration device composed of an aeration pipe and an aeration disc is provided above the sludge discharge port, with an air inlet connected to the outside on the side of the aeration device; a membrane module support is provided on the upper part of the aerobic zone, and a membrane module is fixed on the membrane module support, with an outlet at the top of the membrane module.

[0007] Preferably, as an improvement, the effective volume ratio of the anaerobic zone to the aerobic zone is 1:4 to 1:1, as shown in the following formula: .

[0008] Preferably, as an improvement, both the lower guide pipe and the upper guide pipe are equipped with pipe diameter adjustment joints; both the lower guide pipe and the upper guide pipe are inclined, with the upper guide pipe having an inclination angle of 10~50° and the lower guide pipe having an inclination angle of 20~60°.

[0009] Preferably, as an improvement, the number of blades can be selected as 2 to 4, the tilt angle is 20 to 60°, and the rotation direction is consistent with the tilt angle direction of the blades.

[0010] Preferably, as an improvement, the aerobic zone and the anaerobic zone are provided with a number of sampling ports that communicate with the outside at equal intervals along the long axis of the sidewall.

[0011] Preferably, as an improvement, this solution also provides an application of a continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a saturation-starvation alternation strategy, in which the aerobic and anaerobic zones easily form independent saturation / starvation environments, including the following steps: Step S1: After the wastewater to be treated flows into the anaerobic zone through the peristaltic pump, it is fully mixed and reacted with the aerobic granular sludge under the shear force of the stirring paddle and gravity separation, and the zone forms a saturation period. Step S2: The mud-water mixture in the anaerobic zone enters the aerobic zone through the lower guide pipe, and obtains the dissolved oxygen required for microbial metabolism under the action of aeration, promoting further reaction, and the zone forms a starvation period; Step S3: Under aeration, a liquid level difference and a sludge density difference are formed between the aerobic zone and the anaerobic zone; driven by this, the sludge-water mixture located above the aerobic zone flows back to the anaerobic zone through the upper guide pipe. Step S4: Repeat steps S1-S2-S3 to form a satiety / hunger cycle.

[0012] Preferably, as an improvement, the circulation control of the mud-water mixture between the aerobic and anaerobic zones is achieved by adjusting the aeration rate of the aeration device and the speed of the stirring paddle. The aeration rate is adjusted in the range of 50~1000 L / h, the stirring paddle speed is adjusted in the range of 10~100 r / min, and the number of internal circulations is 30~300 times / day.

[0013] The principles and advantages of this scheme are: 1. This solution achieves periodic saturation-starvation operating conditions in space. Compared to systems based on time sequence (such as intermittent aeration and intermittent influent modes), it is more adaptable to the characteristics of municipal wastewater, such as seasonal and diurnal temperature variations and influent water quality fluctuations, providing an economically feasible solution to improve the treatment capacity of existing wastewater treatment plants. Furthermore, compared to existing continuous flow reactors, this invention employs a design that independently separates the aerobic and anaerobic zones, reducing mutual disturbance between the two zones and facilitating the formation of stable saturation-starvation alternation, gravity selective pressure, and hydraulic shear conditions.

[0014] 2. This solution features a simple structure, convenient operation, high equipment utilization, and a high degree of automation. In terms of design, while meeting the hydraulic shear force required for aerobic granulation, a lower height-to-diameter ratio is adopted, significantly reducing construction difficulty and investment costs in actual engineering projects, and facilitating its promotion and application in large-scale wastewater treatment plants.

[0015] 3. This solution, based on reactor development (requiring no recirculation equipment), combines "three-low" operating conditions (low aeration rate, low circulation rate, and low stirring rate) with the application of carbon source concentrations similar to municipal wastewater, achieving a shorter start-up time and stable operating performance. It effectively solves the bottleneck problems of existing continuous-flow aerobic granular sludge systems, such as long start-up cycles, poor long-term stability, and high energy consumption. Except for total nitrogen (TN), other effluent indicators (chemical oxygen demand and ammonia nitrogen) meet the Class III surface water standard, demonstrating good engineering feasibility and economic advantages. Attached Figure Description

[0016] Figure 1 This is a cross-sectional schematic diagram of the continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starvation alternation strategy in Embodiment 1 of the present invention.

[0017] Figure 2 This is a top view of the continuous flow bioreactor in Embodiment 1 of the present invention.

[0018] Figure 3 This is a partial enlarged view of the guide pipe equipped with a pipe diameter adjustment joint in Embodiment 1 of the present invention.

[0019] Figure 4 This is a simulated three-dimensional view of the continuous flow bioreactor in Embodiment 1 of the present invention.

[0020] Figure 5 This is an AGS optical microscope image taken during the system operation process in Embodiment 2 of the present invention.

[0021] Figure 6 This is a graph showing the trend of average particle size variation of sludge in the system in Embodiment 2 of the present invention.

[0022] Figure 7 This is an AGS digital camera image showing the system running for 61 days in Embodiment 2 of the present invention.

[0023] Figure 8 The material balance of COD in the system in Embodiment 2 of the present invention is obtained based on the results measured after 71 days of continuous operation of the reactor; all material flows are expressed using the daily average load rate.

[0024] Figure 9 This is a graph showing the trend of average particle size variation of sludge in the system of Comparative Example 1 of the present invention.

[0025] Figure 10 This is an AGS optical microscope image of the system in Comparative Example 1 of the present invention after running for 71 days.

[0026] The reference numerals in the accompanying drawings include: aerobic zone 1, anaerobic zone 2, inlet 3, outlet 4, air inlet 5, membrane module 6, membrane module support 7, sampling port 8, sludge discharge port 9, aeration pipe 10, aeration disc 11, lower guide pipe 12, reactor support 13, stirring paddle 14, upper guide pipe 15, and pipe diameter adjustment joint 16. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials and reagents used can all be obtained commercially.

[0028] Example 1 This embodiment provides a continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a saturation-starvation alternation strategy, such as... Figures 1-4As shown, the reactor includes an aerobic zone 1 and an anaerobic zone 2, with a reactor support 13 located below both zones. A lower guide pipe 12 and an upper guide pipe 15 connect the aerobic zone 1 and the anaerobic zone 2, forming a forward flow path and a return flow path respectively, thus creating independent saturated / starved environments. Both the lower guide pipe 12 and the upper guide pipe 15 are inclined, such that the liquid flow direction in the lower guide pipe 12 is from the anaerobic zone 2 to the aerobic zone 1, and the liquid flow direction in the upper guide pipe 15 is from the aerobic zone 1 to the anaerobic zone 2. For reference, the inclination angle of the upper guide pipe is 10~50°, and the inclination angle of the lower guide pipe is 20~60°. Both the lower guide pipe 12 and the upper guide pipe 15 are equipped with pipe diameter adjustment joints 16 of different inner diameters (e.g., ...). Figure 3 As shown in the figure, it is convenient to flexibly adjust the pipe diameter according to operating conditions such as aeration rate and biomass, so as to achieve ingenious and precise control of the system's self-circulation rate.

[0029] Specifically, the upper sidewall of anaerobic zone 2 is equipped with an inlet 3, which is connected to a peristaltic pump for introducing wastewater into the reactor. This design also includes other pre-installed valves on the same side as inlet 3, which can serve as backup inlets. An agitator 14 is installed inside anaerobic zone 2 to enhance the mixing effect of the sludge mixture within anaerobic zone 2 and to facilitate gravity-assisted propulsion of the liquid in anaerobic zone 2 into aerobic zone 1 via the lower guide pipe 12 for subsequent aerobic reactions. The number of blades can be selected as 2-4, with an inclination angle of 20-60°, ensuring that the rotation direction is consistent with the blade inclination angle to generate thrust matching the flow direction.

[0030] The bottom of the aerobic zone 1 is equipped with a sludge discharge port 9, and above the sludge discharge port is an aeration device consisting of an aeration pipe 10 and an aeration disc 11. The aeration pipe 10 can effectively prevent sludge accumulation in the dead corners of the reactor, and the aeration disc 11 is used to physically flush the membrane surface.

[0031] Both the aerobic zone 1 and the anaerobic zone 2 have several sampling ports 8 at equal intervals along the long axis of their sidewalls, communicating with the outside. A membrane module support 7 is installed within the aerobic zone 1, and a membrane module 6 is fixed to the support 7. The top of the membrane module 6 has an outlet 4 connecting the aerobic zone 1 to the outside. For reference, the membrane module support 7 is an H-shaped support. A fixing seat is provided on the inner wall of the aerobic zone corresponding to the membrane module support 7. Threaded holes are provided at the ends of the fixing seat and the membrane module support 7, and the membrane module support 7 is fixedly connected to the fixing seat using external bolts and nuts. The membrane module support 7 has a fixing hole through which the membrane module 6 passes. One end of the membrane module 6 passes through the fixing hole and is inserted below the liquid surface, while the upper part of the membrane module 6 protrudes above the liquid surface. The treated wastewater in the aerobic zone 1 is discharged through the outlet 4.

[0032] This scheme limits the effective volume ratio of anaerobic zone 2 to aerobic zone 1 to control the duration of each stage in the "feeding-starvation alternation strategy," thereby improving wastewater treatment efficiency and accelerating the formation of stable AGS. As an improvement, the effective volume ratio of anaerobic zone 2 to aerobic zone 1 is 1:4 to 1:1, and the relevant calculation formula is as follows: .

[0033] More preferably, the effective volume ratio of anaerobic zone 2 to aerobic zone 1 is 3:8 to 3:4.

[0034] For reference, in this embodiment, the effective working volume of the continuous flow reactor (including aerobic zone 1 and anaerobic zone 2) is 40 L, and the effective volume ratio is 1:2. The system uses membrane module 6 to produce constant flow water at a flow rate of 4 L / h, and forms the corresponding saturation-starvation phase time ratio through internal self-circulation of the mixed liquor.

[0035] In this embodiment, the aerobic zone 1 adopts a cylindrical structure (or cube) with a height-to-diameter ratio of 3.4 (optionally 1~8.0), and is internally equipped with a submerged microfiltration hollow fiber BOF050M003 membrane (0.5 m). 2 Surface area; modified PVDF material, 0.03 μm pore size), membrane flux maintained at 8 L / (m²). 2 •h). The aeration rate of the aeration device is adjustable from 100 to 200 L / h, which can meet the oxygen demand of microbial metabolism and nitrification processes, and also provide the shear force required for granulation, thereby improving the granulation effect without significantly increasing energy consumption. The membrane module 6 is made of materials including but not limited to hollow fiber membranes, ceramic membranes, or curtain membranes.

[0036] Anaerobic zone 2 adopts a combined structure of an upper cylinder and a lower cone (or a combination of a cube and a square pyramid). The inner diameter of anaerobic zone 2 is the same as that of aerobic zone 1. The stirring impeller is preferably operated at a speed of 30 r / min (10~100 r / min is optional) and a blade diameter of 10 cm to provide downward fluid thrust and thorough mixing of the mud-water mixture. Based on this, in this embodiment, the internal circulation frequency between aerobic zone 1 and anaerobic zone 2 is 80~250 times / day, and circulation control is achieved by combining and adjusting the aeration rate of the aeration device and the stirring impeller speed.

[0037] The specific implementation process is as follows: From a fluid dynamics perspective, the reactor in this design consists of two fully mixed sub-reactors connected in series. The anaerobic zone 2 has an inlet on one side, operating as a high-load reactor, while the aerobic zone 1 has an outlet above it, operating at a lower organic load. During operation, the rotation of the agitator 14 in the anaerobic zone 2 and the gravity-selective pressure separation of the sludge provide a suitable driving force for the sludge to flow towards the aerobic zone 1. Subsequently, under the influence of the liquid level difference and sludge density difference between the two zones generated by the aeration device, the sludge mixture can self-circulate back to the anaerobic zone, thus achieving a spatially based saturation-famine alternation condition in the continuous flow reactor.

[0038] During the saturation phase (i.e., when the wastewater is in anaerobic zone 2), the rapidly biodegradable external matrix is ​​transformed into an intracellular storage matrix, creating favorable conditions for microbial proliferation and the formation of AGS.

[0039] During the starvation phase (i.e., when the wastewater is in aerobic zone 1), due to the lack of organic matter and nutrients in the sludge entering the aerobic zone, the microorganisms inside the AGS mainly rely on the internal matrix for growth, which helps to regulate the adhesion behavior of the microorganisms. At the same time, under the action of hydraulic shear, the AGS constantly collide, aggregate and rub, which enhances the hydrophobicity of the cell surface by inducing the secretion of extracellular polymers, thereby improving the structural compactness and outline clarity of the AGS.

[0040] Example 2 This embodiment provides an application of a continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on the satiated-starved alternation strategy of Embodiment 1, including the following steps: Step S1: After the wastewater to be treated flows into the anaerobic zone via a peristaltic pump, it is fully mixed and reacted with aerobic granular sludge under the shear force and gravity separation of the stirring paddle (the stirring paddle speed can be adjusted from 10 to 100 r / min, and the stirring paddle speed is specifically 30 r / min in this embodiment). This zone forms a saturation period. Step S2: The mud-water mixture in the anaerobic zone enters the aerobic zone through the lower guide pipe, and obtains the dissolved oxygen required for microbial metabolism under aeration, promoting further reactions. This zone enters a starvation period. Step S3: Under aeration (the aeration rate is adjustable from 50 to 1000 L / h, specifically 100 to 200 L / h in this embodiment), a liquid level difference and a sludge density difference are formed between the aerobic zone and the anaerobic zone; driven by this, the sludge-water mixture located above the aerobic zone flows back to the anaerobic zone through the upper guide pipe. Step S4: Repeat steps S1-S2-S3 to form a satiety / hunger cycle (the number of internal cycles can be selected from 30 to 300 times / day), and in this embodiment, it is 80 to 250 times / day.

[0041] Specifically, activated sludge from the secondary sedimentation tank of a municipal wastewater treatment plant was used as the inoculum for this device. The initial mixed liquor suspended solids concentration was controlled at around 3000 mg / L, and the average particle size was 39.7 μm.

[0042] Artificially synthesized wastewater was used as the influent for sludge cultivation. Detailed formulation and concentrations are shown in Table 1. In Table 1, sodium acetate was used as the carbon source, (NH4)2SO4 as the nitrogen source, and KH2PO4 as the phosphorus source in the artificially synthesized wastewater. Micronutrients such as Mg, Mn, Ca, and Fe were also added to meet the microbial growth requirements. The influent chemical oxygen demand (COD) was 352 mg / L, and the ammonia nitrogen (NH4)2SO4 concentration was [not specified in the original text]. + The concentrations of total nitrogen (TN) and total phosphorus (TP) were 17.6 mg / L, and the COD:N:P ratio was 100:5:1 to ensure the supply of nutrients and energy required for microbial metabolism. NaHCO3 was used to regulate the pH of the system, maintaining it within the range of 7.0 to 8.5 to prevent the expansion of filamentous bacteria.

[0043] Table 1. Composition and Concentration of Artificially Synthetic Wastewater

[0044] Under the above operating conditions, the initial formation of AGS particles was observed after 4 days of reactor operation, indicating that the system had been successfully started. Figure 5 As shown, the particles at this stage are brownish-red, small in size, and irregular in shape. Subsequently, the SVI5 / SVI ratio of the sludge in the system... 30 The ratio dropped to around 1, and the average particle size steadily increased, reaching 168.2 μm on day 15. Figure 6 This indicates a significant improvement in sludge granulation. During this stage, the AGS profile becomes more regular, mostly ellipsoidal, with a small amount of flocculent material adhering to the surface, showing a trend of continuous particle size increase. When the system reaches day 32, sludge biomass steadily increases, while settling performance significantly improves, and SVI (Sludge Viscosity Index) increases. 30 The concentration dropped sharply to 139.7 mL / g. Simultaneously, the particle size and particle size increased continuously, resulting in AGS with a smooth surface and dense structure. These data indicate that the system has entered a more stable and efficient operating state. When the system reached day 61, the AGS exhibited larger particle size and clearer outlines. Figure 7 On day 71, the average particle size in the system rapidly increased to 308.2 μm, and the particle size distribution reached as high as 85.4%, verifying that the reactor design based on the saturation-starvation alternation strategy has extremely high feasibility and reliability, providing a key theoretical basis for the industrialization and promotion of the technology.

[0045] Furthermore, experiments on the "three low" operating conditions (low aeration volume, low circulation volume, and low stirring rate) of this scheme show that the process can achieve efficient granulation under low energy consumption conditions, which is conducive to its promotion and application in practical engineering and provides important technical support for the green transformation of my country's environmental protection industry.

[0046] Furthermore, during the granulation process, the dissolved oxygen in the aerobic zone of the reactor is maintained above 2 mg / L, while the dissolved oxygen in the anaerobic zone is controlled below 0.2 mg / L. The system temperature is maintained within the range of 15~25℃.

[0047] Under these conditions, the pollutant removal efficiency of the reactor steadily improved in the early stages of operation, but was significantly affected by system operating conditions. After 32 days of operation, COD and NH4... + The average removal rates of -N and TN significantly increased to 97.3%, 96.7%, and 91.6%, respectively, corresponding to effluent COD consistently below 25 mg / L and NH4+... + -N is below 1.2 mg / L and TN is below 3.8 mg / L, and the effluent quality fully meets the Class A standard of the "Discharge Standard of Pollutants for Urban Wastewater Treatment Plants".

[0048] When the particle size and particle size distribution in the system reach their maximum values, i.e., on day 61, COD and NH4... + The average removal rates of -N and TN continued to increase and stabilized at around 97.8%, 97.8%, and 94.7%, respectively, corresponding to effluent COD consistently below 13 mg / L and NH4+... + -N is below 1.0 mg / L and TN is below 1.7 mg / L. Except for TN, the effluent quality can consistently meet the Class III surface water standard. The results show that the device of this invention has a high-efficiency wastewater treatment capacity, can be used as a wastewater reuse technology, and has good prospects for engineering promotion.

[0049] Based on the average measured concentration of water quality, a material balance for COD in the two zones was established, such as... Figure 8As shown in the figure, during stable system operation, compared to the aerobic zone, the contribution of the anaerobic zone to COD removal significantly increased from 51.9% to 90.4%, and the daily average COD load rate of the system effluent also decreased from 3.7% to 1.3-2.7%. Therefore, material balance analysis confirms that the anaerobic and aerobic zones operate under saturated and starved conditions, respectively, generating a biological selective pressure conducive to sludge granulation. Specifically, under starved conditions, granular microorganisms grow on the internal matrix, reducing surface negative charge and accelerating microbial aggregation and adhesion under the synergistic effect of hydraulic shear force. Under saturated conditions, microorganisms grow on the external matrix, increasing the cell density of the outer layer of the granules, thereby enhancing the stability of the AGS. In addition, the periodic saturated-starved operating conditions affect the ecological niche of the microbial community within the AGS (mainly manifested in the selection and enrichment of bacteria with more hydrophobic surfaces and the inhibition of the growth and reproduction of filamentous microorganisms), thus affecting the granulation process and stability of the system, which is a key factor in controlling the initial co-aggregation between cells. It is evident that the above research results will provide a strong guarantee for the long-term stable operation of this process.

[0050] Comparative Example 1 Compared with Examples 1 and 2, the main difference of this comparative example is that under the high aeration rate (specifically 4000 L / h) operating condition, a large amount of sludge internal circulation is generated between the two areas, thereby destroying the system's ability to maintain the dissolved oxygen gradient difference and making it difficult to form a stable saturation-starvation alternation environment.

[0051] In this comparative example, the continuous-flow integrated aerobic granular sludge-membrane bioreactor (i.e., a continuous-flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a saturation-starvation alternation strategy) had a designed aeration rate of 4000 L / h, making the dissolved oxygen content in both regions of the system tend to be uniform (5.5~7.6 mg / L). Under these conditions, a small amount of initial AGS only began to appear in the reactor on the 10th day, indicating that the hydraulic shear force generated by the high aeration intensity was not the decisive factor for continuous-flow aerobic granulation. Subsequently, the particle size growth rate and granulation rate were significantly lower than in Example 2 (…). Figure 9 Furthermore, the cultured particles exhibited characteristics such as small particle size (the average particle size of the system was only 261.6 μm on day 71), loose structure, and irregular outline. Figure 10 Meanwhile, the system SVI 30 The concentration reached as high as 192.5 mL / g, and filamentous and non-filamentous bulking of the sludge occurred. In the later stages of system operation (days 60-71), the pollutant removal performance fluctuated: COD and NH4... + The average removal rates of -N and TN were 96.2%, 91.4%, and 58.1%, respectively, corresponding to effluent COD below 23.7 mg / L and NH4+ below 58.1%. +-N was below 4.7 mg / L and TN was below 16.64 mg / L, and the effluent quality only met the Class B standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants". Material balance analysis of COD in the two zones revealed that, compared with the aerobic zone, the anaerobic zone contributed only 77.0% to COD removal, and the daily average load rate of COD in the system effluent reached 5.6%.

[0052] In summary, the above results further confirm that by regulating the aeration rate to establish an effective saturated-starved alternating environment, in-situ rapid granulation of continuous flow systems can be achieved, thereby improving wastewater treatment performance.

[0053] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A continuous-flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy, characterized in that: The reactor comprises an aerobic zone and an anaerobic zone connected in series. Reactor supports are located below the aerobic and anaerobic zones, which are connected by a lower guide pipe and an upper guide pipe. An inlet is located on the upper side wall of the anaerobic zone, and a stirring paddle is located inside the anaerobic zone. A sludge discharge port is located at the bottom of the aerobic zone, and an aeration device consisting of aeration pipes and aeration discs is located above the sludge discharge port. An air inlet connecting to the outside is located on the side of the aeration device. A membrane module support is located above the aerobic zone, and membrane modules are fixed on the support. An outlet is located at the top of the membrane modules.

2. The continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy according to claim 1, characterized in that: The effective volume ratio of the anaerobic zone to the aerobic zone is 1:4 to 1:1, and the relevant formula is as follows: 。 3. The continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy according to claim 1, characterized in that: Both the lower and upper guide pipes are equipped with pipe diameter adjustment joints; both the lower and upper guide pipes are inclined, with the upper guide pipe having an inclination angle of 10~50° and the lower guide pipe having an inclination angle of 20~60°.

4. The continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy according to claim 1, characterized in that: The number of blades can be selected as 2 to 4, the tilt angle is 20 to 60°, and the rotation direction is ensured to be consistent with the tilt angle direction of the blades.

5. A continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy according to claim 1, characterized in that: The aerobic and anaerobic zones are provided with several sampling ports that are connected to the outside at equal intervals along the long axis of the sidewalls.

6. The application of the continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy according to claim 1, characterized in that: Aerobic and anaerobic zones can easily form independent satiated / starved environments, which involves the following steps: Step S1: After the wastewater to be treated flows into the anaerobic zone through the peristaltic pump, it is fully mixed and reacted with the aerobic granular sludge under the shear force of the stirring paddle and gravity separation, and the zone forms a saturation period. Step S2: The mud-water mixture in the anaerobic zone enters the aerobic zone through the lower guide pipe, and obtains the dissolved oxygen required for microbial metabolism under the action of aeration, promoting further reaction, and the zone forms a starvation period; Step S3: Under aeration, a liquid level difference and a sludge density difference are formed between the aerobic zone and the anaerobic zone; driven by this, the sludge-water mixture located above the aerobic zone flows back to the anaerobic zone through the upper guide pipe. Step S4: Repeat steps S1-S2-S3 to form a satiety / hunger cycle.

7. The application of the continuous flow self-circulating aerobic granular sludge-membrane bioreactor constructed based on a satiated-starved alternation strategy according to claim 1, characterized in that: The circulation control of the mud-water mixture between the aerobic and anaerobic zones is achieved by adjusting the aeration rate of the aeration device and the speed of the stirring paddle. The aeration rate is adjustable from 50 to 1000 L / h, and the stirring paddle speed is adjusted from 10 to 100 r / min, resulting in an internal circulation frequency of 30 to 300 times per day.

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