An induced granulation type oxidation ditch reactor for continuous flow aerobic granular sludge cultivation and a method of using the same

Abstract

An induced granulation type oxidation ditch reactor for continuous flow aerobic granular sludge cultivation and a use method thereof, comprising a reaction cavity, which is divided into an aerobic zone and an anoxic zone by a flow baffle, a support is connected to the top of the aerobic zone, a selector is arranged above the support, the selector is communicated to the bottom of the aerobic zone through a selector effluent pipe, a sewage inlet pipe is communicated to the bottom of the side wall of one end of the selector, a multi-tank sedimentation tank is arranged at one side in the anoxic zone, the multi-tank sedimentation tank is communicated to the selector through a gas stripping pipe, a sedimentation tank inlet is arranged at one end of the multi-tank sedimentation tank, and a reactor effluent pipe is arranged at the other end; the selector, the multi-tank sedimentation tank and the gas stripping system are integrated, the sludge with different particle sizes or settling properties is screened through the multi-tank sedimentation tank, the sludge-water mixture is directionally backflowed to different positions in the selector through the gas stripping mode, the sludge with small particle size or poor settling performance is mixed with high-substrate sewage, the satiation stage is strengthened, and the large-particle-size sludge is backflowed to the low-substrate zone, so that the granulation is promoted and the system is stably operated.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation and its usage method. Background Technology

[0002] Activated sludge technology is one of the most widely used wastewater treatment technologies, with a history of nearly a century. Early activated sludge processes primarily relied on suspended activated sludge systems with flocculent sludge, and most wastewater treatment plants still primarily use flocculent suspended sludge systems. However, with rapid urbanization and increasingly stringent wastewater discharge standards, existing wastewater treatment facilities are facing mounting pressure and struggling to meet current nitrogen and phosphorus removal requirements. Therefore, there is an urgent need to upgrade wastewater treatment plants to improve treatment efficiency and meet higher discharge standards.

[0003] As a novel biological wastewater treatment technology, aerobic granular sludge (AGS) technology is an ideal choice for upgrading and retrofitting wastewater treatment plants due to its advantages such as high efficiency in removing organic matter and nutrients, high reactor volumetric loading, small footprint, excellent sludge settling performance, and strong resistance to shock loads.

[0004] However, the long-term application of AGS technology has primarily relied on Sequencing Batch Reactors (SBRs) for sludge cultivation and research. While SBRs can effectively cultivate aerobic granular sludge, their operation and management are complex, and they are suitable only for wastewater treatment plants with smaller flow rates. With the expansion of wastewater treatment facilities and the increase in treatment capacity, many wastewater treatment plants currently employ large-scale continuous flow systems. In this context, promoting sludge granulation through in-situ modification, rather than converting to an SBR system, offers greater economic benefits and practical application value. Therefore, research on AGS technology based on continuous flow reactors (CFRs) is particularly important and of practical significance.

[0005] Chinese invention patent application CN202410498211.6 discloses a method for treating wastewater and promoting sludge granulation using a combined granulation fluidized bed-bioreactor process. This method involves pretreatment at the front end, using reagents and seed crystals to screen the raw water, thereby providing a suitable environment for granular sludge growth in the bioreactor. Furthermore, the fluidized bed can enrich and recover insoluble substances that are difficult to treat biologically at the front end, further optimizing the wastewater treatment process. However, although this technology can enhance the cultivation effect of granular sludge, in large-scale wastewater treatment plants, the chemical dosing and front-end treatment processes are relatively complex, increasing operating and maintenance costs. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention aims to provide an induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation and its usage method. This reactor is an integrated reactor, incorporating a selector, a multi-tank sedimentation tank, and an air-lift pipe within the reaction chamber. The multi-tank sedimentation tank separates sludge with different settling properties or particle sizes, and the air-lift pipe returns the sludge-water mixture to different positions within the selector. This allows for the screening and differentiated return of activated sludge based on particle size or settling properties. Small-diameter sludge or sludge with poor settling properties is saturated in a high-substrate concentration zone, while large-diameter sludge or sludge with good settling properties is saturated in a low-substrate zone, thereby inducing accelerated sludge granulation. It has advantages such as compact structure, high granulation efficiency, strong operational stability, and savings in investment and land area.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] An induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation includes a reaction chamber 1, which is divided into an aerobic zone 15 and an anoxic zone 16 by a baffle plate 2. Several horizontally placed supports 14 are connected to the top of the aerobic zone 15, and selectors 3 are arranged above the supports 14. The selectors 3 are connected to the bottom of the aerobic zone 15 through selector outlet pipes 7. The bottom of one side wall of the selector 3 is connected to the sewage inlet pipe 5. A multi-tank sedimentation tank 4 is arranged on one side inside the anoxic zone 16. The multi-tank sedimentation tank 4 is connected to the selector 3 through an air lift pipe 10. A sedimentation tank inlet 9 is provided above one side wall of the multi-tank sedimentation tank 4, and a reactor outlet pipe 13 is provided above the other side wall of the multi-tank sedimentation tank 4.

[0009] Multiple evenly arranged triangular baffles 6 are provided between the inner walls of the selector 3. The top of one side wall of the selector 3 is connected to the inlet end of the selector outlet pipe 7. The selector outlet 8 of the selector outlet pipe 7 is connected to the bottom of the aerobic zone 15.

[0010] The multi-tank sedimentation tank 4 has multiple sedimentation tanks 12 at its bottom. Each sedimentation tank 12 is equipped with an air lift pipe 10 above it. The air lift pipes 10 are fixed to the inner wall of the multi-tank sedimentation tank 4. The bottom end of the air lift pipe 10 is connected to the top end of the gas injection pipe 11. The bottom end of the gas injection pipe 11 is connected to the bottom of the sedimentation tank 12. The top end of the air lift pipe 10 is bent and connected to the top of the selector 3. Each sedimentation tank 12 is equipped with a bottom inclined pipe 17 corresponding to the air lift pipe 10. The bottom inclined pipe 17 is connected to the anoxic zone 16.

[0011] The selector 3 is set to a rectangle.

[0012] Selector 3 is a plug flow reactor.

[0013] The present invention also provides a method for using an induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation, comprising the following steps:

[0014] Step 1: The wastewater to be treated enters the selector 3 through the bottom wastewater inlet pipe 5 and flows through the triangular baffle 6. At the same time, a part of the mud-water mixture in the sedimentation tank 12 flows back to the selector 3 through the air lift pipe 10, mixes with the wastewater to be treated, and then flows into the bottom of the aerobic zone 15 through the selector outlet pipe 7.

[0015] Step 2: Under the thrust of the water flow, the mud-water mixture in reaction chamber 1 undergoes biochemical reactions in the aerobic zone 15 and the anoxic zone 16. Then, it enters the multi-tank sedimentation tank 4 through the sedimentation tank inlet 9 to screen sludge with different particle sizes or settling properties. Due to the thrust of the water flow and gravity, the sludge settles into the sedimentation tank 12 and undergoes solid-liquid separation. Part of the mud-water mixture flows into the bottom of the anoxic zone 16 through the bottom inclined pipe 17 of the sedimentation tank 12, while the other part of the mud-water mixture flows back to the selector 3 through the air lift pipe 10. After mud-water separation is achieved through the multi-tank sedimentation tank 4, the treated wastewater is discharged from reaction chamber 1 through the reactor outlet pipe 13.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. Screening of sludge with different particle sizes or settling properties. This invention utilizes a multi-tank sedimentation tank 4. When the sludge-water mixture flows into the multi-tank sedimentation tank 4, a sorting and clarification process occurs under gravity. The sludge that settles to the sedimentation tank 12 on the inlet side of the multi-tank sedimentation tank 4 has a larger particle size or better settling properties, while the sludge that settles to the sedimentation tank 12 near the outlet usually has a smaller particle size or poorer settling properties. The multi-tank sedimentation tank 4 effectively achieves screening of sludge particle size or settling properties.

[0018] 2. Targeted cultivation of sludge with different particle sizes or settling properties. As mentioned in point one regarding beneficial effects, the sludge characteristics in different sedimentation tanks 12 are different. An airlift pipe 10 is designed above each sedimentation tank 12. After the sludge is airlifted back to the selector 3, it is mixed with wastewater in the selector 3. Since the selector 3 is a plug flow reactor, the substrate and microbial concentrations vary with space, resulting in different wastewater substrate concentrations at different locations. Therefore, when the sludge from different sedimentation tanks 12 is airlifted back, it is mixed with wastewater of different substrate concentrations. The sludge in the sedimentation tanks 12 near the outlet is usually smaller in particle size or has poorer settling properties. When this part of the sludge is returned to the selector 3, there is no other sludge reacting with the wastewater at the front end, so the wastewater substrate concentration it comes into contact with is the highest. Under anoxic conditions, this enhances the saturation stage of the microorganisms, promoting the granulation of small sludge. Similarly, the settling tank 12 near the inlet of the multi-tank settling tank 4 typically recycles larger-diameter sludge or sludge with better settling performance. After this sludge is recycled, it is close to the outlet of the selector 3, and the COD concentration in the substrate is low, resulting in a short sludge retention time and a smaller starvation stage. Therefore, smaller-diameter sludge or sludge with poorer settling performance can come into contact with more substrate, while larger-diameter sludge or sludge with better settling performance can come into contact with less substrate. This allows for the targeted cultivation of sludge with different characteristics, optimizes the particle size distribution in the reactor, enhances system stability, and promotes sludge granulation.

[0019] 3. In addition to the characteristics of general oxidation ditches, this invention also has the following advantages: Sludge sedimentation is achieved through the integration of a multi-tank sedimentation tank 4. The process flow is short, with fewer structures and equipment, eliminating the need for primary sedimentation tanks, equalization tanks, and separate secondary sedimentation tanks. The solid-liquid separation effect is superior to traditional secondary sedimentation tanks, which is beneficial for stable operation of the system within a wider flow or concentration range. The sludge-water mixture in the multi-tank sedimentation tank 4 is recirculated through an integrated air-lift pipe 10, eliminating the need for a separate recirculation pump station and avoiding the construction requirements of sludge pumping stations and supporting pipe networks. This significantly saves investment costs and land area, improving engineering adaptability and economic efficiency.

[0020] 4. The present invention uses a multi-tank sedimentation tank 4 to screen sludge of different particle sizes or settling properties, and uses an air lift pipe 10 to return sludge of different characteristics to the selector 3, thereby directionally enhancing the saturation stage of different sludge, promoting sludge granulation, and maintaining system stability.

[0021] In summary, this invention integrates a selector 3, a multi-tank sedimentation tank 4, and an air-lift pipe 10 into the reaction chamber 1, constructing a sorting and directional reflux mechanism based on differences in sludge particle size or settling performance. This enables small-diameter sludge or sludge with poor settling performance to undergo an enhanced saturation stage in the high substrate concentration zone, while large-diameter sludge or sludge with good settling performance undergoes saturation in the low substrate zone, thereby inducing accelerated sludge granulation. It has the advantages of a simple process flow, high granulation efficiency, strong operational stability, and reduced investment and land use, making it suitable for the efficient cultivation and engineering application of aerobic granular sludge under continuous flow conditions. Attached Figure Description

[0022] Figure 1 This is a front view of the overall structure of the present invention.

[0023] Figure 2 This is a top view of the overall structure of the present invention.

[0024] Figure 3 This is a three-dimensional view of the overall structure of the present invention.

[0025] Figure 4 This is a diagram illustrating the pollutant removal capacity according to an embodiment of the present invention; wherein, Figure 4 (a) is ammonia nitrogen (NH4) + -N) Remove capability map Figure 4 (b) is nitrite nitrogen (NO2) - -N) Remove capability map, Figure 4 (c) is nitrate nitrogen (NO3) - -N) Remove capability map Figure 4 (d) is a diagram of COD removal capacity.

[0026] Figure 5 This refers to the particle size distribution in an embodiment of the present invention.

[0027] Figure 6 This is a particle size distribution diagram of each sedimentation tank in an embodiment of the present invention.

[0028] The components are as follows: 1. Reaction chamber; 2. Baffle plate; 3. Selector; 4. Multi-tank sedimentation tank; 5. Inlet pipe; 6. Triangular baffle; 7. Selector outlet pipe; 8. Selector outlet; 9. Sedimentation tank inlet; 10. Air lift pipe; 11. Gas injection pipe; 12. Sedimentation tank; 13. Reactor outlet pipe; 14. Support; 15. Aerobic zone; 16. Anoxic zone; 17. Bottom inclined pipe. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention.

[0030] It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0031] In the description of this application, it should be understood that the terms "above", "left", "right", "bottom", "top", "inside", etc., which indicate orientation or positional relationship based on the orientation or positional relationship shown in the drawings, are only for the convenience of describing the present invention and simplifying the description, and are not intended to imply that the device or element referred to must have a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0032] Furthermore, the terms “first”, “second”, etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0033] In this invention, the size and structure of the selector are not fixed. The core purpose of the selector used in this invention is to ensure that sludge returned from different sedimentation tanks can come into contact with substrates of different concentrations in the selector. Those skilled in the art can modify the size and structure of the selector according to specific circumstances. The selector size and structure given in this application are only for the purpose of facilitating and simplifying the description of this invention, and therefore should not be construed as limiting the invention.

[0034] In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. The number of sedimentation tanks 12 in the multi-tank sedimentation tank 4 is not fixed at 5, but is only 5 in the embodiments described in this application.

[0035] In this application, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0036] This invention proposes an induced granulation oxidation ditch reactor and its usage method for continuous flow aerobic granular sludge cultivation. A multi-tank sedimentation tank is integrated into the reaction chamber 1, and sludge is returned to the selector 3 via an airlift pipe 10. The sludge is screened through the multi-tank sedimentation tank 4. After airlift return, sludge of different particle sizes or settling properties comes into contact with substrates of different concentrations, enhancing the saturation stage of the sludge and achieving targeted sludge cultivation.

[0037] like Figure 1 , Figure 2As shown, an induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation includes a reaction chamber 1, which is divided into an aerobic zone 15 and an anoxic zone 16 by a baffle plate 2. Several horizontally placed supports 14 are connected to the top of the aerobic zone 15, and selectors 3 are arranged above the supports 14. The selectors 3 are connected to the bottom of the aerobic zone 15 through selector outlet pipes 7. The bottom of one side wall of the selector 3 is connected to the sewage inlet pipe 5. A multi-tank sedimentation tank 4 is arranged on one side inside the anoxic zone 16. The multi-tank sedimentation tank 4 is connected to the selector 3 through an air lift pipe 10. A sedimentation tank inlet 9 is provided above one side wall of the multi-tank sedimentation tank 4, and a reactor outlet pipe 13 is provided above the other side wall of the multi-tank sedimentation tank 4.

[0038] like Figure 3 As shown, multiple evenly arranged triangular baffles 6 are provided between the inner walls of the selector 3. The top of one side wall of the selector 3 is connected to the inlet end of the selector outlet pipe 7. The selector outlet 8 of the selector outlet pipe 7 is connected to the bottom of the aerobic zone 15.

[0039] The triangular baffle 6 is used to enhance the hydraulic shear force inside the selector 3, increase the mixing reaction time of activated sludge and wastewater to be treated, strengthen the saturation stage, and promote the granulation of activated sludge.

[0040] The multi-tank sedimentation tank 4 has multiple sedimentation tanks 12 at its bottom. Each sedimentation tank 12 is equipped with an air lift pipe 10 above it. The air lift pipes 10 are fixed to the inner wall of the multi-tank sedimentation tank 4. The bottom end of the air lift pipe 10 is connected to the top end of the gas injection pipe 11. The bottom end of the gas injection pipe 11 is connected to the bottom of the sedimentation tank 12. The top end of the air lift pipe 10 is bent and connected to the top of the selector 3. Each sedimentation tank 12 is equipped with a bottom inclined pipe 17 corresponding to the air lift pipe 10. The bottom inclined pipe 17 is connected to the anoxic zone 16.

[0041] The selector 3 is set to a rectangle.

[0042] Selector 3 is a plug flow reactor.

[0043] The number of sedimentation tanks 12, air lift pipes 10 and bottom inclined pipes 17 in the multi-tank sedimentation tank 4 can be the same. The specific number is not fixed and can be set according to the specific situation.

[0044] The internal structure of selector 3 is not subject to fixed requirements and can be modified according to specific circumstances.

[0045] Furthermore, the multi-tank sedimentation tank 4 of the present invention can be modified as a prefabricated device, which has a simple process and a short construction period. By adding it, the sewage treatment plant can be upgraded.

[0046] The present invention also provides a method for using an induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation, comprising the following steps:

[0047] Step 1: The wastewater to be treated enters the selector 3 through the bottom wastewater inlet pipe 5 and flows through the triangular baffle 6. At the same time, a part of the mud-water mixture in the sedimentation tank 12 flows back to the selector 3 through the air lift pipe 10, mixes with the wastewater to be treated, and then flows into the bottom of the aerobic zone 15 through the selector outlet pipe 7.

[0048] Step 2: Under the thrust of the water flow, the mud-water mixture in reaction chamber 1 undergoes biochemical reactions in the aerobic zone 15 and the anoxic zone 16. Then, it enters the multi-tank sedimentation tank 4 through the sedimentation tank inlet 9 to screen sludge with different particle sizes or settling properties. Due to the thrust of the water flow and gravity, the sludge settles into the sedimentation tank 12 and undergoes solid-liquid separation. Part of the mud-water mixture flows into the bottom of the anoxic zone 16 through the bottom inclined pipe 17 of the sedimentation tank 12, while the other part of the mud-water mixture flows back to the selector 3 through the air lift pipe 10. After mud-water separation is achieved through the multi-tank sedimentation tank 4, the treated wastewater is discharged from reaction chamber 1 through the reactor outlet pipe 13.

[0049] Example

[0050] In this embodiment, the multi-tank sedimentation tank is equipped with 5 sedimentation tanks.

[0051] The reactor operating parameters are as follows:

[0052] Table 1 Oxidation Ditch System and its Operating Conditions

[0053]

[0054]

[0055] During reactor operation, the gas flow rate of each of the five gas stripping units was controlled at 1 ± 0.2 L / min. After 46 days of operation, the water quality was as follows: Figure 4 As shown. In this embodiment, ammonia nitrogen (NH4) + The removal of ammonia nitrogen (N-N) and chemical oxygen demand (COD) remained stable. The effluent concentration of ammonia nitrogen remained at a low level throughout the experiment, reaching 0.25 mg / L on day 3, demonstrating extremely high removal efficiency. With prolonged operation, the ammonia nitrogen removal rate remained above 95%, and by day 46, the effluent concentration had decreased to 0.02 mg / L, achieving near-complete removal. Figure 4 As shown in (a). This demonstrates that the system of the present invention can stably and efficiently remove ammonia nitrogen, meeting the requirements of wastewater treatment. Regarding COD removal, as... Figure 4As shown in (b), the influent COD concentration was maintained between 370-403 mg / L. After treatment, the effluent COD concentration was below 50 mg / L, with a maximum removal rate of 89.85%. On some days, especially day 35, the COD removal rate fluctuated, dropping to 57.16%, but overall, the COD removal effect remained stable and efficient, fully meeting the wastewater treatment requirements. Meanwhile, nitrite nitrogen (NO2) was also removed. - -N) and nitrate nitrogen (NO3) - The removal of nitrite nitrogen (N-N) was complex. The effluent nitrite nitrogen concentration reached 1.6 mg / L and 1.8 mg / L on days 23 and 35, respectively, indicating fluctuations in nitrite nitrogen removal during the treatment process. Figure 4 As shown in (c), the effluent has a high nitrate nitrogen concentration, such as... Figure 4 As shown in (d), the highest concentration was 6.31 mg / L (day 46). In summary, the system in this embodiment exhibits excellent stability and efficiency in the removal of ammonia nitrogen and COD. However, there are some fluctuations in the removal of nitrite nitrogen and nitrate nitrogen, which may be related to factors such as the biological reaction conditions within the reactor and changes in wastewater quality. Overall, the reactor of this invention can effectively handle the removal of multiple pollutants, meeting the needs of daily wastewater treatment.

[0056] like Figure 5As shown, the sludge particle size distribution reflects the changes in sludge morphology and structure within the reactor. It can be observed that the average particle size of the inoculated sludge was 46.91 μm, with the majority concentrated in the 10-50 μm range. Sludge larger than 100 μm accounted for a relatively low proportion, only 6.02%, indicating that the inoculated sludge particles were quite small and mostly within the smaller size range. As operation progressed, the particle size gradually increased. On day 4, the average particle size increased to 57.29 μm. While the proportion of sludge in the 10-50 μm range remained relatively large, the proportion of sludge larger than 100 μm increased to 10.68%, indicating that the granulation process had begun. By day 12, the average particle size further increased to 65.44 μm, and the proportion of sludge larger than 100 μm further increased to 15.62%, showing that the granulation effect was gradually becoming apparent. By day 39 of system operation, the average particle size reached 85.22 μm, with sludge larger than 100 μm accounting for 21.65%, indicating a significant increase in the proportion of large particles. On day 42, although the average particle size decreased slightly to 78.82 μm, the proportion of sludge larger than 100 μm remained at 20.81%. On days 43 and 46, the average particle size reached 94.55 μm and 92.55 μm, respectively, with sludge larger than 100 μm accounting for 23.06% and 22.45%, respectively, showing that the granulation process was further enhanced in the later stages, with a significant increase in the proportion of large-diameter particles. Overall, with the increase in reactor operating time, the average particle size of the sludge gradually increased, and the proportion of sludge larger than 100 μm significantly increased, reflecting the stable cultivation process of granulated sludge within the system. Finally, on day 46, the proportion of particles larger than 100 μm was 22.45%, indicating that the reactor of this invention successfully cultivated granular sludge.

[0057] At the same time, such as Figure 6The figure shows the particle size distribution at different locations inside the reactor on day 40. Sludge sampling locations 1-5 are designated as follows: location 1 is near the inlet of the multi-tank sedimentation tank, and location 5 is near the outlet. In sedimentation tank 1, the average sludge particle size is 89.98 μm, and particles larger than 100 μm account for 21.45%, indicating a larger particle size and higher degree of granulation at this location. The average particle size of the sludge in sedimentation tanks 2 and 3 further increases, reaching 86.23 μm and 90.76 μm respectively, with sludge larger than 100 μm accounting for 21.12% and 22.32% respectively, indicating stable sludge granulation at these locations. In contrast, the average particle size of the sludge in sedimentation tank 4 is 81.11 μm, with sludge larger than 100 μm accounting for 19.72%, showing a slight decrease in particle size, but the granulation level remains high. While the average particle size of the sludge in sedimentation tank 5 was 67.75 μm, and 42.12% of the sludge was smaller than 50 μm, 14.69% was larger than 100 μm, indicating a certain degree of granulation. Compared to the sludge in the sedimentation tank, the sludge particle size in the selector and aerobic zone showed significant differences. The average particle size in the selector was 72.83 μm, with 16.87% of the sludge larger than 100 μm, indicating a lower degree of granulation at this location. In contrast, the average particle size in the aerobic zone was 86.55 μm, with 21.12% of the sludge larger than 100 μm, showing a higher granulation effect and indicating that the granulation level in the aerobic zone was more stable and mature than in other locations. In summary, the sludge particle size distribution varied significantly across different locations within the reactor, with the aerobic zone exhibiting the highest degree of granulation, while the selector and other sedimentation tanks showed lower granulation levels, reflecting differences in the granulation process and stability of the sludge at different locations.

[0058] Based on the above experimental data, the multi-tank sedimentation tank 4 can be used to screen sludge by particle size or settling performance. This allows for enhanced feeding of different sludge types through air stripping and reflux, improving system stability and accelerating sludge granulation.

[0059] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. By screening the sludge in a multi-tank sedimentation tank and recirculating it to different locations in the influent, the saturation stage is enhanced, accelerating sludge granulation. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention.

Claims

1. An induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation, characterized in that, The reaction chamber (1) is divided into an aerobic zone (15) and an anoxic zone (16) by a baffle plate (2). Several horizontal supports (14) are connected to the top of the aerobic zone (15). A selector (3) is set above the support (14). The selector (3) is connected to the bottom of the aerobic zone (15) through the selector outlet pipe (7). The bottom of one side wall of the selector (3) is connected to the sewage inlet pipe (5). A multi-tank sedimentation tank (4) is set on one side inside the anoxic zone (16). The multi-tank sedimentation tank (4) is connected to the selector (3) through the air lift pipe (10). A sedimentation tank inlet (9) is set above one side wall of the multi-tank sedimentation tank (4). A reactor outlet pipe (13) is set above the other side wall of the multi-tank sedimentation tank (4). Multiple evenly arranged triangular baffles (6) are provided between the inner walls of the selector (3). The top of one side wall of the selector (3) is connected to the inlet end of the selector outlet pipe (7). The selector outlet (8) of the selector outlet pipe (7) is connected to the bottom of the aerobic zone (15). The bottom of the multi-sink sedimentation tank (4) is provided with multiple sedimentation tanks (12), and each sedimentation tank (12) is provided with an air lift pipe (10) above it. The air lift pipe (10) is fixed on the inner wall of the multi-sink sedimentation tank (4). The bottom end of the air lift pipe (10) is connected to the top end of the gas injection pipe (11). The bottom end of the gas injection pipe (11) is connected to the bottom of the sedimentation tank (12). The top end of the air lift pipe (10) is bent and connected to the top of the selector (3). Each sedimentation tank (12) is provided with a bottom inclined pipe (17) corresponding to the air lift pipe (10) below it. The bottom inclined pipe (17) is connected to the anoxic zone (16). The selector (3) is a plug flow reactor; When the sludge in different sedimentation tanks (12) is air-lifted back, it is mixed with wastewater of different substrate concentrations. The sludge in the sedimentation tank (12) near the outlet is usually smaller in particle size or has poor settling performance. When this part of the sludge is returned to the selector (3), there is no other sludge reacting with the wastewater at the front end. Therefore, the wastewater substrate concentration is the highest. Under hypoxic conditions, the saturation stage of microorganisms is enhanced, promoting the granulation of small sludge. Similarly, the sedimentation tank (12) near the inlet side of the multi-tank sedimentation tank (4) usually returns sludge with larger particle size or better settling performance. After this part of the sludge is returned, it is close to the outlet of the selector (3), and the COD concentration in the substrate is low. The sludge residence time is short and the starvation stage is small. Based on this, it is possible to achieve that sludge with small particle size or poor settling performance comes into contact with more substrate, while sludge with large particle size or better settling performance comes into contact with less substrate. This enables the directional cultivation of sludge with different characteristics and optimizes the particle size distribution in the reactor.

2. The induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation according to claim 1, characterized in that, The selector (3) is set to a rectangle.

3. A method of using the induced granulation oxidation ditch reactor for continuous flow aerobic granular sludge cultivation as described in claim 1 or 2, characterized in that, Includes the following steps: Step 1: The wastewater to be treated enters the selector (3) through the bottom wastewater inlet pipe (5) and flows through the triangular baffle (6). At the same time, a part of the mud-water mixture in the sedimentation tank (12) flows back to the selector (3) through the air lift pipe (10) and mixes with the wastewater to be treated. Then it flows into the bottom of the aerobic zone (15) through the selector outlet pipe (7). Step 2: The mud-water mixture in the reaction chamber (1) undergoes biochemical reaction in the aerobic zone (15) and the anoxic zone (16) under the action of water flow thrust. Then, it enters the multi-tank sedimentation tank (4) through the sedimentation tank inlet (9) to screen sludge with different particle sizes or settling properties. Due to the action of water flow thrust and gravity, the sludge settles into the sedimentation tank (12) and undergoes solid-liquid separation in the sedimentation tank (12). A portion of the mud-water mixture flows into the bottom of the anoxic zone (16) through the bottom inclined pipe (17) of the sedimentation tank (12), while the other portion of the mud-water mixture flows back to the selector (3) through the air lift pipe (10). After mud-water separation is achieved through the multi-tank sedimentation tank (4), the treated wastewater is discharged from the reaction chamber (1) through the reactor outlet pipe (13).

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