Integrated device for low-concentration domestic sewage and rapid cultivation method and application of aerobic granular sludge

Abstract

This invention discloses an integrated device and a method for rapid cultivation of aerobic granular sludge suitable for low-concentration domestic sewage, along with its application. The device comprises a batch reactor body integrating the following functional units: a full-area water distribution unit, including a main inlet pipe and distributed water distribution components; one end of the main inlet pipe is connected to the sewage source, and the other end extends to the bottom of the reactor cavity; the distributed water distribution components are connected to the main inlet pipe and equipped with multiple water distribution holes; a dual-zone aeration unit, including an air pump, a bottom aeration unit with a wide range of adjustable air volume, and a middle aeration unit with precise air volume control; a flow field optimization unit, located at the upper part of the reactor cavity and connected to the main inlet pipe; and a timing control unit, electrically connected to the full-area water distribution unit and the dual-zone aeration unit. The advantages of this invention are: by creating sedimentation selective pressure through dual-zone aeration to achieve sludge stratification, enhanced denitrification of heavy granular sludge, and removal of excess phosphorus from light flocculent sludge, it also has the advantages of shortening the cultivation cycle of aerobic granular sludge and highly efficient denitrification and phosphorus removal.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to an integrated device suitable for low-concentration domestic wastewater and a method and application for rapid cultivation of aerobic granular sludge. Background Technology

[0002] With the acceleration of urbanization and increasingly stringent environmental standards, the efficient and low-cost treatment of urban wastewater has become an urgent environmental problem. Firstly, due to the small population size and low water consumption in small and medium-sized towns, wastewater collection systems are generally small-scale, resulting in high unit construction and operation and maintenance costs for wastewater treatment projects. Secondly, influenced by differences in industrial structure and rainy season runoff, urban wastewater exhibits a "low concentration" characteristic, with chemical oxygen demand (COD) and biochemical oxygen demand (BOD) concentrations often far below traditional design standards. Severe carbon source insufficiency leads to competition between denitrifying bacteria and polyphosphate-accumulating bacteria for carbon, restricting biological activity and nitrogen and phosphorus removal efficiency, making it difficult for effluent to consistently meet standards.

[0003] Aerobic granular sludge technology represents a breakthrough in solving wastewater treatment challenges in small and medium-sized towns. Aerobic granular sludge exhibits excellent settling performance; this dense, compact microbial aggregate can simultaneously degrade organic matter, remove nitrogen and phosphorus, and simplify secondary sedimentation systems, thereby significantly reducing land area and economic costs. However, traditional aerobic granular sludge cultivation cycles are lengthy, lasting from weeks to months, and it is sensitive to water quality fluctuations. Especially when treating low-concentration domestic wastewater, the lack of sufficient extracellular polymers causes the granular structure to easily disintegrate or expand, severely hindering its large-scale application.

[0004] Currently, sequencing batch reactors (SBRs) are commonly used as stable culture carriers for aerobic granular sludge in laboratory research and engineering demonstrations. Their periodic hydraulic shear forces and selective pressures theoretically favor granulation. However, existing SBRs have significant limitations in water distribution and aeration methods: traditional water distribution devices struggle to achieve uniform distribution at low concentrations, easily creating dead zones; conventional single-aeration systems have low oxygen transfer efficiency and uneven shear force distribution, making it difficult to achieve rapid formation of dense granules. This lack of functional coordination not only prolongs the culture period but also leads to a decrease in treatment efficiency.

[0005] Therefore, optimizing the fluid dynamics environment, efficiently integrating water distribution and aeration functions, creating hydraulic conditions conducive to rapid granulation, and producing aerobic granular sludge has become the key to promoting the engineering application of this technology. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an integrated device and a method and application for rapid cultivation of aerobic granular sludge suitable for low-concentration domestic sewage, in order to solve the problem that existing reactors are difficult to stably form dense granules.

[0007] To achieve the above and other related objectives, the present invention provides an integrated device suitable for treating low-concentration domestic sewage, comprising a sequencing batch reactor body and integrating the following functional units:

[0008] The whole-area water distribution unit includes a main inlet pipe and distributed water distribution components set at the bottom of the main inlet pipe. One end of the main inlet pipe is connected to the sewage source, and the other end extends to the bottom of the reactor cavity of the main batch reactor body, for conveying low-concentration domestic sewage into the reactor cavity of the main batch reactor body. Each of the distributed water distribution components is connected to the main inlet pipe and is equipped with multiple water distribution holes for realizing the whole-area sewage distribution and mud-water mixing in the reactor cavity.

[0009] The dual-zone aeration unit includes an air pump, a bottom aeration unit, and a middle aeration unit. Both the bottom aeration unit and the middle aeration unit are connected to the air pump. The bottom aeration unit is located at the bottom of the main inlet pipe and is used to adjust the aeration rate over a wide range. The middle aeration unit is located in the middle of the main inlet pipe and is used to precisely control the aeration rate.

[0010] A flow field optimization unit, located at the upper part of the reactor cavity and fixedly connected to the main inlet pipe, is used to regulate the water flow pattern within the reactor cavity to enhance the sludge granulation process; and

[0011] The timing control unit is electrically connected to the whole-area water distribution unit and the dual-zone aeration unit. It is used to control the start-up and shutdown and operating parameters of each unit according to the preset sequential batch operation cycle, so as to realize the rapid cultivation of sludge particles under low-concentration domestic sewage conditions.

[0012] As a preferred embodiment of this application, the bottom aeration unit and the middle aeration unit are isomorphic derivative components, each including multiple coaxial and coplanar aeration rings, with several aeration components arranged circumferentially on the aeration rings, and the bottom aeration unit having more aeration rings than the middle aeration unit. The purpose of bottom aeration is twofold: First, by regulating the dissolved oxygen environment at the bottom, combined with the carbon source advantage of the bottom influent, it promotes the secretion of more extracellular polymeric substances (EPS) by heavy granular sludge, accelerating particle size growth. Simultaneously, it creates a suitable microenvironment for denitrifying bacteria, enhancing nitrogen removal efficiency. Second, the hydraulic disturbance created by moderate aeration ensures uniform mixing of the sludge and water at the bottom while preventing the heavy particles from being dispersed, stabilizing the selective pressure of "heavy particles remaining at the bottom," thus providing a basis for sludge stratification and targeted cultivation. Meanwhile, the aeration structure in the middle layer drives excessive phosphorus uptake by light sludge. The functions of middle-layer aeration are: 1. To provide sufficient dissolved oxygen to meet the metabolic needs of polyphosphate-accumulating bacteria for aerobic phosphorus uptake, prompting excessive phosphorus uptake by light granular and flocculent sludge distributed in this area. 2. To regulate sludge stratification and discharge: The hydraulic shear force generated by aeration maintains the light sludge in a suspended state in the upper and middle parts, facilitating the subsequent discharge of phosphorus-rich sludge through sludge removal operations, thus enhancing the system's phosphorus removal effect. III. Optimize the flow field and granulation process: The middle layer aeration and the bottom layer aeration form a gradient dissolved oxygen environment, which, together with the flow field optimization unit, regulates the flow pattern, avoids excessive sludge mixing, accelerates the directional differentiation and maturation of aerobic granular sludge, and shortens the cultivation cycle.

[0013] As a preferred embodiment of this application, the dual-zone aeration unit further includes a control valve, which is disposed on the pipeline between the bottom aeration unit and the middle aeration unit and the air pump, and is connected to the timing control unit for controlling the aeration volume of the bottom aeration unit and the middle aeration unit.

[0014] As a preferred embodiment of this application, the middle aeration unit has two aeration rings, and the bottom aeration unit has three aeration rings.

[0015] As a preferred embodiment of this application, the outer diameter of the outermost aeration ring of the middle aeration unit is smaller than the outer diameter of the outermost aeration ring of the bottom aeration unit. That is, the outer diameter of the outermost aeration ring of the middle aeration structure is smaller than the outer diameter of the outermost aeration ring of the bottom aeration structure.

[0016] As a preferred embodiment of this application, the ratio of the outer diameter of the outermost aeration ring of the middle aeration unit to the outermost aeration ring of the bottom aeration unit is 0.7-0.8:1.

[0017] As a preferred embodiment of this application, the ratio of the outer diameter of the outermost aeration ring of the bottom aeration unit to the inner diameter of the main body of the batch reactor is 0.85-0.9:1.

[0018] As a preferred embodiment of this application, the distributed water distribution assembly includes multiple water distribution branch pipes arranged radially, each water distribution branch pipe being coplanar and having its inner end connected to the main water inlet pipe, and each water distribution branch pipe having multiple water distribution holes spaced apart.

[0019] As a preferred embodiment of this application, the global water distribution unit further includes a water pump and an inlet ball valve configured on the main inlet pipe, wherein the inlet ball valve and the water pump are electrically connected to the timing control unit.

[0020] Preferably, the water distribution holes are located on the pipe wall facing the bottom of the main body of the batch reactor, forming an angle of 30-60° with the central axis of the water distribution branch pipe. These holes are used for water distribution and to utilize water flow to impact sludge deposition and promote granulation. More preferably, the angle is 45° to ensure that heavy sludge at the bottom can be flushed up.

[0021] As a preferred embodiment of this application, the distributed water distribution component has a cross-shaped structure, consisting of four orthogonally distributed water distribution branch pipes of equal length; the central axes of each water distribution branch pipe converge at the same position on the axis of the main water inlet pipe, and are connected to the main water inlet pipe through connectors to form a water distribution network.

[0022] As a preferred embodiment of this application, the flow field optimization unit is located in the upper part of the reactor cavity and sleeved outside the main inlet pipe. It includes a water passage section and a flow hood connected to the lower end of the water passage section. A water passage channel is formed between the water passage section and the main inlet pipe. The flow hood is a frustoconical structure that is narrow at the top and wide at the bottom. Its sidewall is a concave streamlined curved surface, which is used to guide the water flow to form a swirling flow in a preset direction and then discharge it from the water passage channel above. This enhances the collision and aggregation of sludge particles while avoiding particle breakage caused by local water flow turbulence.

[0023] As a preferred embodiment of this application, the water passage and the fairing are connected by an integral molding method and are both made of acrylic material.

[0024] As a preferred embodiment of this application, the bottom end of the shroud is located at 1 / 3 of the reactor, the ratio of its upper end diameter to the reactor's inner diameter is 0.15-0.2, the lower end diameter is consistent with the outer diameter of the outermost aeration ring of the central aeration structure, the total height is 1 / 6 of the reactor's height, and the cone inclination angle is 60°.

[0025] As a preferred embodiment of this application, the main body of the sequencing batch reactor is a cylindrical sequencing batch reactor with a height-to-diameter ratio of 0.25-0.3:1 and an effective volume ratio of 0.75-0.85:1.

[0026] As a preferred embodiment of this application, the ratio of the outer diameter of the main inlet pipe to the inner diameter of the reactor body is 0.2-0.25:1.

[0027] As a preferred embodiment of this application, the ratio of the diameter of the water distribution hole to the inner diameter of the water distribution branch pipe is 0.1-0.15:1.

[0028] As a preferred embodiment of this application, the sequential batch operation cycle is a staged process including effluent, influent, settling, aeration and settling, and the cultivation of sludge particles in a low-concentration domestic sewage environment is achieved by switching the timing of each stage.

[0029] As a preferred embodiment of this application, the timing control unit includes a controller and a timing switch connected to the controller, used to control the start-up and shutdown of each unit and the operating parameters according to a preset sequential batch operation cycle, so as to achieve rapid cultivation of sludge particles under low-concentration domestic sewage conditions.

[0030] As a preferred embodiment of this application, the timing control unit further includes a dissolved oxygen meter, which can monitor the dissolved oxygen concentration inside the reactor cavity in real time, providing accurate data support for the dynamic adjustment of the aeration strategy.

[0031] This invention also provides a method for rapidly forming aerobic granular sludge from low-concentration wastewater, comprising the following steps:

[0032] Step 1, Parameter Presetting: Based on the water quality characteristics of low-concentration domestic sewage and the sludge granulation target, set the sequential batch operation cycle and supporting strategies of the device, clarify the total number of operation cycles, the time allocation of each stage of effluent-influent-sedimentation-aeration-sedimentation, and the aeration timing and aeration volume of each aeration structure in the dual-zone aeration unit.

[0033] Step 2, Inoculation and Initial Water Distribution: Inoculate sludge and inject low-concentration domestic sewage into the reactor cavity at a uniform rate to the preset liquid level through the whole-area water distribution unit to complete the construction of the sludge-water mixing system;

[0034] Step 3, Periodic Operation and Cultivation: Start the timing control unit and automatically switch between different operating stages according to the preset periodic strategy: In the effluent stage, discharge the liquid treated in the previous cycle; in the influent stage, inject an equal volume of low-concentration domestic sewage simultaneously; in the settling stage, use gravity to promote the settling and stratification of sludge particles; in the aeration stage, construct a dissolved oxygen environment and matching hydraulic shear force through the aeration structure. Each stage is repeated until the aerobic granular sludge reaches the target requirements.

[0035] As a preferred embodiment of this application, the time ratio of the effluent stage, effluent stage, settling stage, aeration stage, and settling stage in each cycle is 2:9:6:18:1.

[0036] As a preferred embodiment of this application, the sequential batch operation cycle is one cycle per day or every two days in which both the middle and bottom aeration are fully activated, and in other cycles only the middle aeration is activated.

[0037] The present invention also provides an integrated device for rapid prototyping of aerobic granular sludge suitable for low-concentration domestic sewage, and the application of the cultivation method of aerobic granular sludge in the production of aerobic granular sludge or sewage treatment.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. This invention can be directly installed as a whole in a sequencing batch reactor, combining water distribution and aeration. It is simple to operate and can realize full-time automatic circulation of bottom water inlet and alternating aeration of the middle and bottom layers. Bottom layer aeration, combined with bottom water inlet, creates a suitable microenvironment for the retained heavy granular sludge, promoting the secretion of EPS, increasing particle size and enhancing denitrification. Middle layer aeration provides sufficient dissolved oxygen for the light sludge in the middle and upper layers, driving it to absorb excessive phosphorus. At the same time, the hydraulic shear force maintains the sludge stratification state, facilitating the discharge of phosphorus-rich sludge. Ultimately, it synergistically achieves rapid cultivation of aerobic granular sludge and efficient denitrification and phosphorus removal from wastewater, thereby achieving a long-lasting and stable optimization effect.

[0040] 2. This invention can rapidly improve the settling performance of activated sludge after incorporation, and through long-term continuous cultivation and screening, it can form aerobic granular sludge in a sequencing batch reactor and increase the particle size of the formed aerobic granular sludge.

[0041] 3. This invention can save the floor space of water distribution and aeration equipment, reduce the time of full aeration, reduce the cultivation time of aerobic granular sludge, and reduce operating costs. At the same time, it can improve the denitrification and phosphorus removal effect of the process. It is a high-efficiency, energy-saving, pollution-reducing and carbon-reducing sewage treatment facility. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the integrated device for rapid prototyping of aerobic granular sludge according to an embodiment of the present invention.

[0043] Figure 2 This is the SVI change curve of aerobic granular sludge one month after using the device.

[0044] Figure 3 This is the particle size change curve of aerobic granular sludge one month after using the device (b).

[0045] Figure 4 These are microscopic images of the inoculated sludge, where a is the inoculated sludge and b is the aerobic granular sludge one month after using the device.

[0046] In the diagram, 1-reactor body; 2-full-area water distribution unit; 21-main inlet pipe; 22-distributed water distribution assembly; 221-water distribution branch pipe; 222-water distribution hole; 223-connector; 3-dual-zone aeration unit; 31-bottom aeration unit; 32-middle aeration unit; 311-aeration ring; 4-flow field optimization unit; 41-water passage section; 42-rectifier hood. Detailed Implementation

[0047] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0048] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0049] Furthermore, it should be understood that the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, does not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated. It should also be understood that the combined connection relationship between one or more devices / apparatus mentioned in this invention does not preclude the existence of other devices / apparatus before or after the combined devices / apparatus, or the insertion of other devices / apparatus between these explicitly mentioned devices / apparatus, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or limiting the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0050] like Figure 1 As shown, the present invention provides an integrated device suitable for low-concentration domestic sewage, including a reactor body 1 with a reactor cavity, and also integrating the following functional units:

[0051] The full-area water distribution unit 2 includes a main inlet pipe 21 and a distributed water distribution assembly 22 disposed at the bottom of the main inlet pipe 21. One end of the main inlet pipe 21 is connected to a sewage source, and the other end extends to the bottom of the reactor cavity, for conveying low-concentration domestic sewage into the reactor cavity of the reactor body 1. Each of the distributed water distribution assemblies 22 is connected to the main inlet pipe 21 and is equipped with multiple water distribution holes 222, for realizing full-area sewage distribution and mud-water mixing in the reactor cavity.

[0052] The dual-zone aeration unit 3 includes an air pump, a bottom aeration unit 31, and a middle aeration unit 32. Both the bottom aeration unit 31 and the middle aeration unit 32 are connected to the air pump. The bottom aeration unit 31 is located at the bottom of the main inlet pipe 21 and is used to adjust the aeration rate over a wide range. The middle aeration unit 32 is located in the middle of the main inlet pipe 21 and is used to precisely control the aeration rate.

[0053] Flow field optimization unit 4, located in the upper part of the reactor cavity and fixedly connected to the main inlet pipe 21, is used to regulate the water flow pattern within the reactor cavity to enhance the sludge granulation process; and

[0054] The timing control unit is electrically connected to the whole-area water distribution unit 2 and the dual-zone aeration unit 3. It is used to control the start-up and shutdown and operating parameters of each unit according to the preset sequential batch operation cycle, so as to realize the rapid and directional cultivation of sludge particles under low-concentration domestic sewage conditions.

[0055] like Figure 1 As shown, the distributed water distribution assembly 22 includes multiple water distribution branch pipes 221 arranged radially. Each water distribution branch pipe 221 is coplanar and its inner end is connected to the main water inlet pipe 21. Each water distribution branch pipe 221 is provided with multiple water distribution holes 222 at intervals.

[0056] like Figure 1 As shown, the distributed water distribution component 22 has a cross-shaped structure, consisting of four orthogonally distributed water distribution branch pipes 221 of equal length; the central axes of each water distribution branch pipe converge at the same position on the axis of the main water inlet pipe, and are connected to the main water inlet pipe through connectors 223 to form a water distribution network.

[0057] like Figure 1 As shown, the water distribution hole 222 is disposed on the pipe wall facing the bottom of the reactor, with an angle of 30-60° to the central axis of the water distribution branch pipe 221, for distributing water and using water flow to impact sludge deposition and promote granulation. More preferably, the angle is 45° to ensure that heavy sludge at the bottom can be flushed up.

[0058] like Figure 1 As shown, the bottom aeration unit 31 and the middle aeration unit 32 are isomorphic derivative components, each including multiple coaxial and coplanar aeration rings 311. Each aeration ring 311 has several aeration components arranged circumferentially, and the bottom aeration unit has more aeration rings than the middle aeration unit. Figure 1 As shown, the middle aeration unit has two aeration rings, and the bottom aeration unit has three aeration rings. The plane of each aeration ring is perpendicular to the main inlet pipe.

[0059] In some embodiments of this application, the outer diameter of the middle aeration unit is smaller than the outer diameter of the bottom aeration unit; that is, the outer diameter of the outermost aeration ring of the middle aeration unit is smaller than the outer diameter of the outermost aeration ring of the bottom aeration unit.

[0060] In some embodiments of this application, the ratio of the outer diameter of the outermost aeration ring of the middle aeration unit to the outer diameter of the outermost aeration ring of the bottom aeration unit is 0.7-0.8:1.

[0061] In some embodiments of this application, the ratio of the outer diameter of the outermost aeration ring of the bottom aeration unit to the inner diameter of the reactor is 0.85-0.9:1.

[0062] like Figure 1 As shown, the flow field optimization unit 4 is located in the upper part of the reactor cavity and is sleeved outside the main water inlet pipe 21. It includes a water passage part 41 and a flow hood 42 connected to the lower end of the water passage part 41. A water passage channel is formed between the water passage part 41 and the main water inlet pipe 21. The flow hood 42 is a frustoconical structure that is narrow at the top and wide at the bottom. Its side wall is a concave streamlined curved surface, which is used to guide the water flow to form a vortex along a preset direction and then discharge it from the water passage above. This enhances the collision and aggregation of sludge particles while avoiding particle breakage caused by local water flow turbulence.

[0063] In some embodiments of this application, the water passage and the fairing are connected by an integral molding method and are both made of acrylic material.

[0064] like Figure 1 As shown, the sequential batch operation cycle is a staged process that includes effluent, influent, settling, aeration and settling. By switching the time sequence of each stage, sludge particles can be cultivated in a low-concentration domestic sewage environment.

[0065] In some embodiments of this application, the bottom end of the shroud is located at 1 / 3 of the reactor, the ratio of its upper end diameter to the reactor's inner diameter is 0.15-0.2, the lower end diameter is consistent with the outer diameter of the outermost aeration ring of the central aeration structure, the total height is 1 / 6 of the reactor's height, and the cone inclination angle is 60°.

[0066] In some embodiments of this application, the reactor is a cylindrical sequencing batch reactor with a height-to-diameter ratio of 0.25-0.3:1 and an effective volume ratio of 0.75-0.85:1.

[0067] In some embodiments of this application, the ratio of the outer diameter of the main inlet pipe to the inner diameter of the reactor body is 0.2-0.25:1.

[0068] In some embodiments of this application, the ratio of the diameter of the water distribution hole to the inner diameter of the water distribution branch pipe is 0.1-0.15:1.

[0069] In some embodiments of this application, the timing control unit includes a controller and a timing switch connected to the controller, used to control the start-up and shutdown of each unit and the operating parameters according to a preset sequential batch operation cycle, so as to achieve rapid cultivation of sludge particles under low-concentration domestic sewage conditions.

[0070] In some embodiments of this application, the timing control unit further includes a dissolved oxygen meter, which can monitor the dissolved oxygen concentration inside the reactor cavity in real time, providing accurate data support for the dynamic adjustment of the aeration strategy.

[0071] This invention provides a method for cultivating aerobic granular sludge based on the aforementioned integrated device for rapid prototyping of aerobic granular sludge suitable for low-concentration domestic sewage, comprising:

[0072] Step 1, Parameter Presetting: Based on the water quality characteristics of low-concentration domestic sewage and the sludge granulation target, set the sequential batch operation cycle and supporting strategies of the device, clarify the total number of operation cycles, the time allocation of each stage of effluent-influent-sedimentation-aeration-sedimentation, and the aeration timing and aeration volume of the bottom aeration unit 31 and the middle aeration unit 32 in the dual-zone aeration unit 3.

[0073] Step 2, Inoculation and Initial Water Distribution: Inoculate sludge and add it into the reactor cavity at a ratio of 30%-50% of the effective reactor volume. Then, inject low-concentration domestic sewage into the reactor cavity at a uniform speed through the whole-area water distribution unit 2 to the preset liquid level to complete the construction of the sludge-water mixing system.

[0074] Step 3, Periodic Operation and Cultivation: Start the timing control unit 5 and automatically switch between different operating stages according to the preset periodic strategy: In the effluent stage, discharge the liquid treated in the previous cycle; in the influent stage, inject an equal volume of low-concentration domestic sewage simultaneously; in the settling stage, use gravity to promote the settling and stratification of sludge particles; in the aeration stage, construct a dissolved oxygen environment and matching hydraulic shear force through the dual-zone aeration unit 3. Each stage is repeated until the aerobic granular sludge reaches the target requirements.

[0075] In some embodiments of this application, the duration ratio of the effluent stage, effluent stage, settling stage, aeration stage, and settling stage in each cycle is 2:9:6:18:1.

[0076] In some embodiments of this application, the sequential batch operation cycle is one cycle per day or every two days in which the middle aeration unit and the bottom aeration unit are fully open, and in other cycles only the middle aeration unit is open.

[0077] The present invention also provides an application of the integrated device for treating low-concentration domestic sewage or the cultivation method of the aerobic granular sludge in the production of aerobic granular sludge.

[0078] The present invention also provides the application of the integrated device for treating low-concentration domestic sewage or the aerobic granular sludge cultivated by the aerobic granular sludge cultivation method in the treatment of low-concentration domestic sewage.

[0079] The verification was conducted using actual domestic sewage from the fine screen stage at a wastewater treatment plant in Yuhang District, Hangzhou City. Influent water quality: COD, NH4. + The concentrations of -N, TN, and TP were 222.8±31.8 mg / L, 49.7±2.3 mg / L, 51.6±2.0 mg / L, and 4.8±0.5 mg / L, respectively. The inoculated sludge was taken from the aerobic ditch of the second phase of the wastewater treatment plant.

[0080] Specifically, the integrated device has a total volume of 188 L, an effective volume of 150 L, an inner diameter of 40 cm, a height of 150 cm, and an exchange ratio of 40%. The reactor receives water first through the main inlet pipe from the center, then disperses the water through a distributed water distribution assembly at the bottom. The bottom aeration unit consists of three coaxial and coplanar aeration rings, with the outermost stainless steel aeration ring having an outer diameter of 35 cm. The middle aeration unit consists of two coaxial and coplanar aeration rings, with the outermost stainless steel aeration ring having an outer diameter of 25 cm. Both aeration structures are fixed to the main inlet pipe at a spacing of 25 cm, and an air pump controlled by an external time-controlled switch is activated according to the specified procedure. The upper shroud is installed 75 cm above the middle aeration disc. It has an upper diameter of 6 cm, a lower diameter of 24 cm, a total height of 25 cm, and a cone inclination angle of 60°. The upper section has three built-in acrylic vertical bars, which are connected to the main water inlet pipe through the grooves on the vertical bars.

[0081] The treatment process is carried out in four cycles per day, each cycle lasting six hours. The process for each cycle is as follows: 20 minutes of effluent discharge, 90 minutes of effluent inflow, 60 minutes of settling, 180 minutes of aeration, 10 minutes of settling, and then the next cycle of effluent discharge begins. The aeration strategy is as follows: only in the second cycle of each day, the middle and bottom aeration are fully activated, with aeration rates of 6 L / min and 8 L / min respectively; in the other three cycles, only the middle aeration is activated, with an aeration rate of 8 L / min.

[0082] The average particle size (D50) of the inoculated activated sludge was 115.3 μm, and the average particle size (D95) was 252.8 μm. After double aeration treatment and 30 days of cultivation in a sequencing batch reactor, the average particle size (D50) of the activated sludge increased to 141.7 μm, and the average particle size (D95) increased to 323.6 μm. Figure 2 ). Analyzing from the perspective of SVI ( Figure 3Alternating dual aeration is a rapid and significant method for improving the settling performance of activated sludge. After 15 days of using the dual aeration structure, the SVI in the upper and lower zones decreased from 99.8 mL / g to 82.5 mL / g and 67.3 mL / g, respectively, and further decreased to 51.8 mL / g and 47.3 mL / g by day 30. The extracellular polymeric substance (ePC) content increased from 72.46 mg / g VSS at the inoculation stage to 154.46 mg / g VSS, and the PN / PS ratio increased from 5.1 at inoculation to 6.5. Figure 4 In cases a and b, the activated sludge clearly aggregated to form aerobic granular sludge, demonstrating the effectiveness of the device structure and its ability to promote extracellular polymer secretion and activated sludge granulation.

[0083] The dual-zone aeration unit provides stable and efficient control over the effluent water quality, specifically in terms of NH4. + The average removal efficiency of -N was 90.9%, and NH4 was... + The average effluent concentration of nitrogen (N) was 4.67 mg / L. The average removal efficiency of total nitrogen (TN) was 55.9%, and the average effluent concentration of TN was 28.71 mg / L. The average removal efficiency of total phosphorus (TP) was 51.51%, and the average effluent concentration of TP was 2.47 mg / L. No external carbon source or phosphorus removal agent was added during the experiment.

[0084] This structure and method utilizes the characteristics of heavy particles, light particles, and light flocculent sludge to give different zones of the reactor specialized functions. Selective pressure is created through sedimentation, causing heavier particles to aggregate and remain at the bottom of the reactor. Under bottom-feed conditions, these particles preferentially acquire carbon sources and secrete more EPS (extracellular polymeric substances), increasing the particle size of the heavy particles and enhancing denitrification. Meanwhile, the lighter particles and flocculents are distributed in the middle aeration discs and above, absorbing excess phosphorus during aeration. Their discharge enhances phosphorus removal, thereby shortening the aerobic granular sludge cultivation cycle, achieving efficient simultaneous nitrogen and phosphorus removal, saving reactor space, and reducing energy consumption.

[0085] This invention discloses an integrated device suitable for treating low-concentration domestic sewage, mainly composed of a central inlet pipe, upper and lower double-layer aeration units, and a flow field optimization unit. Through the synergistic effect of bottom directional water distribution, alternating aeration in the middle and bottom, and upper rectification, the fluid distribution within the reactor is optimized, shear force is enhanced, and selective pressure is established to solve the technical problems of long AGS formation cycle, small particle size, and low efficiency in treating low-concentration urban sewage in existing technologies. By coupling water distribution, aeration, and zoned screening mechanisms, the enrichment of heavy particles and the secretion of extracellular polymers are promoted. Experimental results show that this device can significantly improve sludge settling performance and achieve highly efficient nitrogen and phosphorus removal without the addition of external carbon sources and phosphorus removal agents, offering significant advantages such as shortening the AGS cultivation cycle, saving space, and reducing energy consumption.

[0086] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications listed herein, as well as variations in the methods and compositions of the invention, will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. An integrated device suitable for treating low-concentration domestic sewage, comprising a sequencing batch reactor body (1), characterized in that, It also integrates the following functional units: The whole-area water distribution unit (2) includes a main water inlet pipe (21) and a distributed water distribution component (22) set at the bottom of the main water inlet pipe (21). One end of the main water inlet pipe (21) is connected to the sewage source, and the other end extends to the bottom of the reactor cavity of the sequence batch reactor body (1) for conveying low-concentration sewage to the reactor cavity of the sequence batch reactor body (1). The distributed water distribution component (22) is connected to the main water inlet pipe (21) and is equipped with multiple water distribution holes (222) for realizing the whole-area sewage distribution and mud-water mixing in the reactor cavity. The dual-zone aeration unit (3) includes an air pump, a bottom aeration unit, and a middle aeration unit. The bottom aeration unit and the middle aeration unit are both connected to the air pump. The bottom aeration unit is located at the bottom of the main inlet pipe (21) and is used to adjust the aeration volume over a wide range. The middle aeration unit is located in the middle of the main inlet pipe (21) and is used to precisely control the aeration volume. The flow field optimization unit (4) is set at the upper part of the reactor cavity and fixedly connected to the main water inlet pipe (21) to regulate the water flow pattern in the reactor cavity to enhance the sludge granulation process. as well as The timing control unit is electrically connected to the whole-area water distribution unit (2) and the dual-zone aeration unit (3) to control the start-up and shutdown and operating parameters of each unit according to the preset sequential batch operation cycle, so as to realize the rapid cultivation of sludge particles under low-concentration sewage conditions.

2. The integrated device for treating low-concentration domestic sewage according to claim 1, characterized in that, The bottom aeration unit and the middle aeration unit are isomorphic derivative components, each including multiple coaxial and coplanar aeration rings (311). The aeration rings (311) are arranged with several aeration components along the circumference, and the number of aeration rings (311) in the bottom aeration unit is greater than the number of aeration rings (311) in the middle aeration unit.

3. The integrated device for treating low-concentration domestic sewage according to claim 2, characterized in that, The middle aeration unit has 2 aeration rings, and the bottom aeration unit has 3 aeration rings. The outer diameter of the outermost aeration ring in the middle aeration unit is smaller than that in the bottom aeration unit.

4. The integrated device for treating low-concentration domestic sewage according to claim 1, characterized in that, The distributed water distribution assembly (22) includes multiple water distribution branch pipes (221) arranged radially. Each water distribution branch pipe (221) is coplanar and its inner end is connected to the main water inlet pipe (21). Each water distribution branch pipe (221) is provided with multiple water distribution holes (222) at intervals.

5. The integrated device for treating low-concentration domestic sewage according to claim 1, characterized in that, The flow field optimization unit (4) is located at the upper part of the reactor cavity and sleeved outside the main water inlet pipe (21). It includes a water passage part (41) and a flow hood (42) connected to the lower end of the water passage part (41). A water passage channel is formed between the water passage part (41) and the main water inlet pipe (21). The flow hood (42) is a frustoconical structure that is narrow at the top and wide at the bottom. Its side wall is a concave streamlined curved surface, which is used to guide the water flow to form a vortex along a preset direction and then discharge it from the water passage above. This enhances the collision and aggregation of sludge particles while avoiding particle breakage caused by local water flow turbulence.

6. The integrated device for treating low-concentration domestic sewage according to claim 1, characterized in that, The sequential batch operation cycle is a staged process that includes effluent, influent, settling, aeration, and settling again. By switching the timing of each stage, sludge particles can be cultivated in a low-concentration wastewater environment.

7. A method for cultivating aerobic granular sludge based on any one of claims 1-6, suitable for treating low-concentration domestic sewage, characterized in that, include: Step 1, parameter presetting: Based on the characteristics of low-concentration wastewater and the sludge granulation target, set the sequential batch operation cycle and supporting strategy of the device, clarify the total number of operation cycles, the time allocation of each stage, and the aeration timing and aeration volume of the bottom aeration unit and the middle aeration unit in the dual-zone aeration unit (3). Step 2, Inoculation and Initial Water Distribution: Inoculate sludge and inject low-concentration wastewater into the reactor cavity at a uniform speed to the preset liquid level through the whole-area water distribution unit (2) to complete the construction of the sludge-water mixing system; Step 3, Periodic Operation and Cultivation: Start the timing control unit and automatically switch between different operating stages according to the preset periodic strategy: In the effluent stage, discharge the liquid treated in the previous cycle; in the influent stage, inject an equal volume of low-concentration sewage simultaneously; in the settling stage, use gravity to promote the settling and stratification of sludge particles; in the aeration stage, construct a dissolved oxygen environment and matching hydraulic shear force through bottom aeration unit and middle aeration unit. Each stage is repeated until the aerobic granular sludge reaches the target requirements.

8. The method for cultivating aerobic granular sludge according to claim 7, characterized in that, In each cycle, the time ratios of the effluent stage, effluent stage, settling stage, aeration stage, and settling stage are 2:9:6:18:

1.

9. The method for cultivating aerobic granular sludge according to claim 8, characterized in that, The sequential batch operation cycle is such that the middle aeration unit and the bottom aeration unit are turned on simultaneously in one cycle every day or every two days, and only the middle aeration unit is turned on in other cycles.

10. The application of the aerobic granular sludge cultivated by the cultivation method of any one of claims 8-9 in wastewater treatment.

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