Biological carrier aerobic granular sludge culture system under multi-stage selective pressure

Abstract

The invention discloses a biological carrier aerobic granular sludge culture system and method under multistage selective pressure, the system comprises a cyclone impurity removal unit, a carrier loading and photo-biological reaction unit and a cyclone grading reflux unit which are connected in sequence along a treatment flow, and sludge rich in phosphorus accumulating bacteria is screened through the cyclone impurity removal unit; the sludge enters a carrier loading area from the bottom, is fully mixed with a carrier injected through a carrier adding structure and is matched with a water impeller, then enters a light regulation and control area through a micro-flocculation grid and is subjected to intensified treatment, and heavy sludge which is compact in structure and excellent in settling performance quickly settles downwards under the action of gravity after climbing over a V-shaped weir plate and returns to the bottom of a reaction area. Finally, the sludge enters the rotational flow grading reflux unit for precise separation, and heavy sludge and light sludge are regulated and controlled to flow back according to different reflux ratios; aged sludge flocs with poor settling performance and low activity and generated scum continue to float upwards under the driving of upward flow and finally gather at the topmost end of the reactor to be discharged.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment, specifically a multi-stage selective pressure biological carrier aerobic granular sludge cultivation system. Background Technology

[0002] Aerobic granular sludge technology has attracted much attention due to its advantages such as high treatment efficiency, good settling performance, and small footprint. However, its widespread application, especially in existing continuous flow processes, faces challenges such as long start-up cycles, unstable granulation, and susceptibility to interference. Traditional cultivation methods often rely on hydraulic shear or settling time as the selective pressure, resulting in a passive and extensive process that makes it difficult to directionally regulate the microbial community and particle structure.

[0003] While existing technologies have attempted to improve sludge performance by adding carriers or introducing algae, they often lack a systematic approach: adding inert carriers alone mainly improves the physical structure but is insufficient for inducing microbial ecology; simply introducing algae faces problems such as poor aggregate strength and easy loss. At the same time, the control of the particle "growth-elimination" process is not precise enough, aging sludge cannot be effectively separated, and there is a lack of precise means to control particle size.

[0004] Therefore, there is an urgent need for a new approach that can overcome the bottlenecks of continuous flow processes. Summary of the Invention

[0005] This invention breaks down the granular sludge cultivation process into two stages: "high-quality seed sludge preparation" and "mainstream acclimatization." The core key lies in developing a dedicated system capable of rapidly and stably producing seed sludge with high settling properties and strong aggregation potential. This system must actively optimize the microbial environment, inducing them to transform into target traits, and accurately screen out qualified sludge for enhanced recycling, thus laying a solid foundation for the successful acclimatization of aerobic granular sludge in the main process.

[0006] To solve the above-mentioned technical problems, the inventors, through practice and summarization, derived the technical solution of this invention, which adopts the following technical solution:

[0007] A multi-stage selective pressure biological carrier aerobic granular sludge cultivation system includes, along the treatment process, a cyclone impurity removal unit, a carrier loading and photobiological reaction unit, and a cyclone staged reflux unit connected in sequence.

[0008] The carrier loading and photobioreactor unit includes a box, with a mud inlet pipe at the bottom of the box, which is connected to the overflow port at the top of the cyclone cleaning unit;

[0009] The box is equipped with a carrier loading zone, a light control zone, a granular sludge return pipe and a light sludge return pipe. The sludge inlet pipe enters the carrier loading zone, which is equipped with a carrier feeding structure and a flow promoter. The flow promoter mixes the sludge and the carrier. The light control zone is located at the top of the carrier loading zone. The outlets of the granular sludge return pipe and the light sludge return pipe extend into the carrier loading zone.

[0010] The feed inlet of the cyclone classifying and reflux unit is connected to the bottom outlet of the box. The bottom outlet of the cyclone classifying and reflux unit is connected to the granular sludge return pipe and the external discharge pipe via a three-way valve. The overflow outlet of the cyclone classifying and reflux unit is connected to the light sludge return pipe and the external discharge pipe via a three-way valve.

[0011] In a preferred embodiment, the carrier dosing structure is a ring-shaped dosing tube, which uniformly dispenses the carrier along the circumference;

[0012] The amount of carrier added is 5-10% of the concentration of suspended solids in the mixture within the carrier loading zone.

[0013] In a preferred embodiment, the carrier is a "charcoal-algae microsphere", which is formed by co-immobilizing Scenedesmus obliquus cells and biochar powder in a diatomaceous earth suspension, wherein the dry weight percentage of Scenedesmus obliquus cells is 5-8%.

[0014] Scenedesmus cells and biochar powder were compounded in a ratio of 1:(4-7) by dry weight.

[0015] In a preferred embodiment, the light-dark cycle of the light-regulating zone is 8-16 hours, and the illumination period is 8-16 hours. The light-regulating zone is equipped with a tubular illumination system with independent zone control. The tubular illumination system includes at least one high-intensity illumination section and one low-intensity maintenance illumination section for light regulation of the symbiotic system.

[0016] In a preferred embodiment, the illuminance of the high-intensity illumination section is 80-120 μmol / (m²). 2 •s), used to maximize the photosynthesis and proliferation of Scenedesmus obliquee;

[0017] The light intensity in the low-intensity maintenance illumination segment is 40-60 μmol / (m²). 2 ·s), used to maintain algal cell activity and promote the exchange of substances between bacteria and algae.

[0018] In a preferred embodiment, a V-shaped weir plate is provided at the top of the tubular lighting system, and a transparent anti-sticking layer is provided on both the V-shaped weir plate and the surface of the tubular lighting system.

[0019] In a preferred embodiment, the carrier loading area is a cylindrical structure located in the middle of the box, with the bottom of the cylindrical structure being closed and the top being provided with a micro-flocculation grid.

[0020] In a preferred embodiment, the top of the box is provided with an aging sludge overflow weir and a side collection trough, and an external discharge pipe is provided on the side collection trough;

[0021] Both the underflow port and the overflow port of the swirl stage reflux unit are equipped with flow regulation devices;

[0022] The system also includes a dissolved oxygen monitor and a pH online monitor, and is linked with a tubular lighting system;

[0023] When dissolved oxygen levels fall below a set threshold, the tubular lighting system automatically increases the light intensity.

[0024] When the pH value rises to the set upper limit due to excessive algae, the tubular lighting system automatically switches to a low-intensity maintenance lighting segment.

[0025] The preferred solution comprises the following steps:

[0026] Step 1: Preprocessing

[0027] Wastewater enters the cyclone removal unit, which uses a hydrocyclone without built-in rotating parts. It is driven by the system inlet water pressure to form a high-speed cyclone. Under the action of centrifugal force, the heavier impurities are thrown to the wall and sink and discharged, while the activated sludge overflows from the top and enters the carrier loading area through the sludge discharge pipe.

[0028] The shear force and hydraulic conditions generated by the hydrocyclone help to screen out highly adaptable polyphosphate-accumulating bacteria, which significantly increase their proportion in sludge.

[0029] Step 2: Carrier loading and mixing

[0030] After the pretreated sludge enters the carrier loading zone, the carrier feeding structure evenly adds the prefabricated carrier along the circumference. The flow booster set at the bottom of the carrier loading zone is activated to generate an upward flow, which pushes the sludge and carrier upward and mixes them thoroughly with the carrier. At the same time, it ensures the uniform distribution of dissolved oxygen and matrix, so that the carrier and sludge can be mixed quickly and evenly.

[0031] Step 3: Central water distribution and reaction enhancement

[0032] The mixed mud-carrier two-phase flow is injected into the light control zone through a micro-flocculation grid via a central water distribution method.

[0033] The light control zone provides specific light to activate the photosynthesis of Scenedesmus obliquus, forming a symbiotic system with microorganisms attached to biochar and sludge. This system efficiently degrades pollutants and stimulates microorganisms to secrete EPS, thereby enhancing sludge aggregation.

[0034] Step 4: Internal grading and removal of aged sludge

[0035] Under the action of the flow booster, the mixture continues to rise, and when it reaches the upper part of the reaction zone, it will overturn the V-shaped weir plate;

[0036] Heavy sludge recirculation: After passing over the V-shaped weir, the dense and well-settling heavy sludge settles rapidly downwards due to gravity and returns to the bottom of the reaction zone to participate in the next cycle of growth, forming the first stage of settling selection inside the reactor.

[0037] Aging sludge stripping: At the same time, the aging sludge flocs with poor settling performance and low activity, as well as the generated scum, continue to float upward under the influence of the upflow, and finally accumulate at the top of the reactor. The aging sludge is then continuously or intermittently discharged from the system through the aging sludge overflow weir, side collection tank and external discharge pipe.

[0038] Step 5: Secondary Cyclone Precision Sorting and Circulation

[0039] The well-formed mixed sludge that settles to the bottom of the reactor is pumped to the secondary cyclone system (cyclone staged reflux unit).

[0040] Inside the hydrocyclone, the sludge is subjected to centrifugal force and is precisely separated according to density and particle size;

[0041] Underflow: The heaviest and densest high-quality granular sludge separated is directly transported back to the system's carrier addition structure and micro-flocculation grid or the inlet of the main biochemical reactor through the underflow port, serving as "nuclei" to enter the next growth cycle and continuously enhance its growth.

[0042] Overflow: The lighter and finer flocculent sludge separated is discharged through the overflow port. A portion of the sludge is returned to the sludge cultivation area in the system to further regulate the overall sludge shape, while the remainder is discharged from the system as excess sludge.

[0043] A multi-stage selective pressure biological carrier aerobic granular sludge cultivation system, as an independent seed sludge preparation module, is applied in a continuous flow wastewater treatment process. The seed sludge preparation module is operated to continuously produce modified sludge flocs or aerobic granular sludge with high settling performance, and this is used as high-quality seed sludge to be added to the continuous flow mainstream bioreactor to accelerate and stabilize the aerobic granular sludge formation process in the mainstream reactor.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] 1. This invention innovatively adds a functional carrier composed of pre-cultured Scenedesmus obliquus and porous biochar, and sets up a photobioreactor zone in the reactor. By precisely controlling the light intensity and light-dark cycle, it actively induces and enhances the mutually beneficial symbiosis between aerobic granular sludge and Scenedesmus obliquus. This system not only utilizes algae to enhance nitrogen and phosphorus removal and organic matter degradation, but also removes heavy metals through algal biosorption and significantly stimulates microbial secretion of extracellular polymers (EPS), fundamentally improving the sludge aggregation performance and system treatment efficiency.

[0046] 2. This invention creatively combines three types of selective pressure to form a progressive screening and enrichment process: First, physical selective pressure is applied through a primary non-powered cyclone impurity removal stage to remove inorganic impurities; second, in the carrier loading and reaction unit, biological-ecological selective pressure is applied through uniform supply of composite carrier and precise light control to directionally enrich functional microorganisms and construct a symbiotic core of bacteria and algae, and to achieve separation of light and heavy sludge through sedimentation and sieving; finally, hydraulic selective pressure is applied through a secondary cyclone unit to achieve precise separation of light and heavy sludge, and growth (return of heavy sludge) and elimination (discharge of light flocs) pressures are applied respectively to achieve multi-dimensional and refined control of the entire process of granular sludge formation.

[0047] 3. This invention utilizes a bottom-mounted flow promoter to create an upward circulation within the tank, combined with a special top weir structure, to achieve automatic hydraulic separation: well-formed heavy sludge overturns the weir and settles back, while aged sludge and scum are carried by the upward flow to the upper discharge outlet for automatic discharge. This design achieves in-situ, continuous separation of aged sludge and active renewal of the system's microbial community, effectively preventing activity decay and ensuring the long-term operational stability of the system.

[0048] 4. By precisely coordinating the operating pressure (inlet pressure) and product splitting ratio (underflow to overflow return ratio) of the secondary cyclone classifier, the "cutting point" or selective pressure of the hydraulic separation can be dynamically changed. This allows the system to flexibly and directionally control the particle size range of the retained and circulated sludge according to requirements, achieving active regulation of the target growth particle size of aerobic granular sludge and ensuring the uniformity and controllability of product properties.

[0049] 5. The system incorporates multiple optimized designs: It employs a primary cyclone separator with no internal rotating parts, driven by residual system pressure, resulting in low energy consumption and easy maintenance; it combines a carrier-loaded cylindrical structure with central water inlet and annular dosing to ensure rapid and uniform mixing and distribution of the carrier and sludge, requiring less floor space compared to traditional processes; traditional activated sludge screening systems primarily focus on screening and discharge, lacking a cultivation process, which easily leads to the disintegration of initial aerobic granular sludge. This patented secondary cyclone unit is designed with "circulatory cultivation" as its core objective, rather than simple discharge, achieving continuous screening and enrichment of high-quality sludge for reflux. These structures collectively constitute a highly efficient, energy-saving, and easy-to-maintain modular circulating cultivation equipment. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the aerobic granular sludge cultivation system of the present invention.

[0051] Figure 2 This is a schematic diagram of the internal structure of the carrier loading and photobioreaction unit of the present invention.

[0052] Figure 3 This is a schematic diagram of the tubular lighting system of the present invention.

[0053] Figure 4 This is a schematic diagram of the structure of the aging sludge overflow weir and side collection tank of the present invention. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0055] like Figures 1 to 4 As shown, a multi-stage selective pressure biological carrier aerobic granular sludge cultivation system includes, along the treatment process, a cyclone impurity removal unit 10, a carrier loading and photobiological reaction unit 20, and a cyclone staged reflux unit 30 connected in sequence.

[0056] The hydrocyclone removal unit 10 employs a hydrocyclone without built-in rotating parts, relying solely on the system's inlet water pressure to create a high-speed vortex. Under centrifugal force, heavier inorganic gravel and other impurities are thrown against the wall and sink to be discharged, while activated sludge overflows from the top into the carrier loading zone. Simultaneously, the rising overflow sludge environment of the hydrocyclone promotes the accumulation of polyphosphate-accumulating bacteria (PACs) in the Bacteroidetes phylum. Extensive experiments have shown that the shear force and hydraulic conditions generated by the hydrocyclone help screen for highly adaptable PACs, significantly increasing their proportion in the sludge. These PACs remove and accumulate phosphorus by absorbing organic matter and phosphates from the wastewater, thus improving the system's biological phosphorus removal efficiency.

[0057] The carrier loading and photobioreactor unit 20 includes a box 21. A mud inlet pipe 22 is provided at the bottom of the box 21. The mud inlet pipe 22 is connected to the upper overflow port of the cyclone cleaning unit 10. The mud inlet pipe 22 is located in the central area and is injected into the carrier loading area 27 from the bottom upward.

[0058] The housing 21 is equipped with a carrier loading area 27, a light control area 28, a granular sludge return pipe 23 and a light sludge return pipe 24. The sludge inlet pipe 22 enters the carrier loading area 27, and the carrier loading area 27 is equipped with a carrier feeding structure 25 and a flow booster 26.

[0059] The carrier addition structure 25 is a ring-shaped dosing pipe, uniformly adding the carrier along its circumference. The carrier addition amount is 5-10% of the suspended solids concentration of the mixed liquid in the carrier loading zone 27. The carrier is a "charcoal-algae microsphere," formed by the co-immobilization of *Scenedesmus obliquus* cells and biochar powder in a diatomaceous earth suspension, with *Scenedesmus obliquus* cells accounting for 5-8% of the dry weight; the *Scenedesmus obliquus* cells and biochar powder are compounded in a dry weight ratio of 1:4-7. Since the sludge is injected from the bottom center, the carrier addition structure 25 is arranged in the sludge flow direction to achieve convection, realizing a two-phase flow of sludge-water and carrier, ensuring that the microorganisms in the reaction zone can obtain nutrients evenly, avoiding local nutrient excess or deficiency. In actual operation, the influent water quality of the mainstream process fluctuates greatly, and the initially formed single-substrate aerobic granular sludge is prone to disintegration, appearing as fine oily sludge. Therefore, *Scenedesmus obliquus* is added to improve the effect.

[0060] The flow booster 26 consists of multiple aeration discs arranged circumferentially below the sludge inlet pipe 22. These discs generate an upward flow, propelling the sludge and carrier upwards and ensuring thorough mixing with the carbon source, while simultaneously guaranteeing uniform distribution of dissolved oxygen and substrate. During this process, a light-controlled zone provides specific illumination, activating the photosynthesis of *Scenedesmus obliquus*, which forms a symbiotic system with the microorganisms attached to the biochar and sludge. This system efficiently degrades pollutants and stimulates the secretion of EPS by the microorganisms, enhancing sludge aggregation performance.

[0061] The light-regulating region 28 is located at the top of the carrier loading region 27. The light-dark cycle of the light-regulating region 28 is 8-16 hours, and the illumination / 8-16 hours cycle is also present. The light-regulating region 28 is equipped with a zone-independently controlled tubular illumination system 29. The tubular illumination system 29 includes at least one high-intensity illumination section and one low-intensity maintenance illumination section, used for light regulation of the symbiotic system. The illumination intensity of the high-intensity illumination section is 80-120 μmol / (m²). 2 •s), used to maximize the photosynthesis and proliferation of Scenedesmus obliquus; the light intensity of the low-intensity maintenance phase is 40-60 μmol / (m 2•s), used to maintain algal cell activity and promote the exchange of substances between bacteria and algae. A V-shaped weir plate 210 is provided on the top of the tubular lighting system 29. Both the V-shaped weir plate 210 and the surface of the tubular lighting system 29 are provided with a transparent anti-sticking layer to prevent sludge from sticking.

[0062] The outlets of the granular sludge return pipe 23 and the light sludge return pipe 24 extend into the carrier loading area 27;

[0063] The carrier loading area 27 is a cylindrical structure located in the middle of the box 21, with the bottom of the cylindrical structure being closed and the top being equipped with a micro-flocculation grid 211.

[0064] The top of the box 21 is provided with an aging sludge overflow weir 212 and a side collection trough 213, and an external discharge pipe 214 is provided on the side collection trough 213;

[0065] The inlet of the cyclone classifying and reflux unit 30 is connected to the underflow port of the housing 21. The underflow port of the cyclone classifying and reflux unit 30 is connected to the granular sludge return pipe 23 and the first discharge pipe 31 via a three-way valve. The overflow port of the cyclone classifying and reflux unit 30 is connected to the light sludge return pipe 24 and the second discharge pipe 32 via a three-way valve. Both the underflow port and the overflow port of the cyclone classifying and reflux unit 30 are equipped with flow regulating devices 33. By precisely coordinating the operating pressure (inlet water pressure) and product splitting ratio (underflow to overflow reflux ratio) of the cyclone classifying and reflux unit 20, the "cutting point" or selective pressure of hydraulic separation can be dynamically changed. This allows the system to flexibly and directionally control the particle size range of the retained and circulated sludge according to requirements, achieving active control of the target growth particle size of aerobic granular sludge and ensuring the uniformity and controllability of product properties.

[0066] The system also includes a dissolved oxygen monitor 40 and a pH online monitor 50, and is linked with a tubular lighting system 29;

[0067] When dissolved oxygen is below a set threshold, the tubular lighting system 29 automatically increases the light intensity;

[0068] When the pH value rises to the set upper limit due to excessive algae, the tubular lighting system 29 automatically switches to a low-intensity maintenance lighting segment.

[0069] A cultivation method for a multi-stage selective pressure biological carrier aerobic granular sludge cultivation system, comprising the following steps:

[0070] Step 1: Preprocessing

[0071] Wastewater enters the cyclone removal unit 10, which uses a hydrocyclone without built-in rotating parts. It is driven by the system inlet water pressure to form a high-speed cyclone. Under the action of centrifugal force, the heavier impurities are thrown to the wall and sink and discharged, while the activated sludge overflows from the top and enters the carrier loading area 27 through the sludge discharge pipe.

[0072] The shear force and hydraulic conditions generated by the hydrocyclone help to screen out highly adaptable polyphosphate-accumulating bacteria, which significantly increase their proportion in sludge.

[0073] This step consumes very little energy, has a simple structure, is easy to maintain, and simultaneously removes impurities and interferences that could interfere with subsequent cyclic culture processes.

[0074] Step 2: Carrier loading and mixing

[0075] After the pretreated sludge enters the carrier loading zone 27, the carrier feeding structure 25 uniformly feeds the prefabricated carrier along the circumference. The pusher 26 set at the bottom of the carrier loading zone 27 is activated to generate an upward flow, which pushes the sludge and carrier upward and mixes them thoroughly with the carrier. At the same time, it ensures the uniform distribution of dissolved oxygen and matrix, so that the carrier and sludge can be mixed quickly and evenly.

[0076] Step 3: Central water distribution and reaction enhancement

[0077] The mixed mud-carrier two-phase flow is injected into the light control zone 28 through the micro-flocculation grid 211 via a central water distribution method.

[0078] The light control zone 28 provides specific light to activate the photosynthesis of Scenedesmus obliquus, forming a symbiotic system with microorganisms attached to biochar and sludge, which efficiently degrades pollutants and stimulates microorganisms to secrete EPS, thereby enhancing sludge aggregation.

[0079] Step 4: Internal grading and removal of aged sludge

[0080] Under the action of the flow booster 26, the mixture continues to rise, and when it reaches the upper part of the reaction zone, it will overturn the V-shaped weir plate;

[0081] Heavy sludge recirculation: After passing over the V-shaped weir, the dense and well-settling heavy sludge settles rapidly downwards due to gravity and returns to the bottom of the reaction zone to participate in the next cycle of growth, forming the first stage of settling selection inside the reactor.

[0082] Sludge stripping: At the same time, sludge flocs with poor settling performance and low activity, as well as the generated scum, continue to float upward under the influence of the upflow and eventually accumulate at the top of the reactor. The sludge is then continuously or intermittently discharged from the system through the sludge overflow weir 212, the side collection tank 213, and the external discharge pipe 214. This design enables the active renewal of the microbial community and maintains the overall activity of the system.

[0083] Step 5: Secondary Cyclone Precision Sorting and Circulation

[0084] The well-formed mixed sludge that settles to the bottom of the reactor is pumped to the cyclone classification and reflux unit 30; the core purpose of this unit is not simply discharge, but to achieve precise screening and circulating cultivation.

[0085] Inside the hydrocyclone, the sludge is subjected to centrifugal force and is precisely separated according to density and particle size;

[0086] Bottom flow (high-quality seed sludge return): The heaviest and densest high-quality granular sludge separated is directly transported back to the system between the carrier addition structure 25 and the micro-flocculation grid 211 or at the inlet of the main biochemical reactor through the bottom flow port, and enters the next growth cycle as "crystal nuclei" to continuously enhance the growth.

[0087] Overflow (Light Floc Disposal): The separated lighter, finer flocculent sludge is discharged through the overflow outlet. A portion of the sludge is returned to the sludge cultivation zone in the system to further regulate the overall sludge shape, while the remainder is discharged from the system as excess sludge. This creates an adjustable hydraulic growth selective pressure outside the system.

[0088] The above process forms a complete closed-loop cycle of "influent → impurity removal → mixing / carrier loading → reaction / internal sorting → external classification / recirculation". By monitoring sludge properties (particle size, SVI) and treatment efficiency online, the amount of carrier in the annular dosing, the stirring intensity of the impeller, the feed pressure of the secondary cyclone, and the underflow / overflow ratio can be dynamically adjusted. This allows for precise control of the biological induction intensity and hydraulic screening particle size, ensuring the system operates stably at its optimal state and continuously producing high-quality aerobic granular sludge.

[0089] The system's workflow is a lean, closed-loop cultivation process centered on "impurity removal-induction-sorting-recirculation". Through the precise synergy of physical, biological, and hydraulic selective pressures, it transforms the traditional passive and extensive granulation process into an active, directional, and efficient "acclimatization-screening" production line, thereby achieving rapid cultivation and property control of aerobic granular sludge.

[0090] A multi-stage selective pressure biological carrier aerobic granular sludge cultivation system, as an independent seed sludge preparation module, is applied in a continuous flow wastewater treatment process. The seed sludge preparation module is operated to continuously produce modified sludge flocs or aerobic granular sludge with high settling performance, and this is used as high-quality seed sludge to be added to the continuous flow mainstream bioreactor to accelerate and stabilize the aerobic granular sludge formation process in the mainstream reactor.

[0091] This invention creates a two-stage solution of "side-line / pre-treatment seed sludge preparation + mainstream tank acclimatization". This system is dedicated to the efficient preparation of high-quality seed sludge, solving the fundamental problem of low efficiency in directly cultivating granular sludge in a large and complex continuous flow system, and providing a practical and feasible path for the upgrading and transformation of aerobic granular sludge technology in existing wastewater treatment plants.

[0092] Abandoning the traditional approach of passively waiting for granulation, this method achieves active induced modification through "composite carrier addition" and "precise light control," optimizing the aggregation behavior of microorganisms from an ecological and physiological perspective. "Multi-stage cyclone separation" enables precise sieving, efficiently enriching sludge with target properties. The synergy of these two methods achieves systematic and targeted modification of sludge performance, resulting in rapid cultivation and strong targeting.

[0093] The produced modified sludge flocs combine the advantages of bacterial-algae symbiosis with the characteristics of carrier enhancement. They are characterized by dense structure, extremely fast settling speed (SVI5 is significantly lower than that of ordinary activated sludge), high microbial activity, and rich EPS, making them an excellent "precursor" and "seed" for the subsequent formation of aerobic granular sludge.

[0094] The system adopts a compact, cyclic culture mode and a modular design, resulting in a small footprint. The core sorting equipment is a hydrocyclone without moving parts, which has low energy consumption and is easy to maintain. As a side-stream system, it has minimal interference with the mainstream process, and its modification and operating costs are far lower than the costs incurred by completely modifying the mainstream pool or operating it inefficiently for a long period of time.

[0095] By adjusting the induction conditions (light, carrier addition) and screening parameters (cyclone pressure, reflux ratio), the properties of the produced seed mud (such as particle size distribution and density) can be flexibly controlled to adapt to the influent characteristics and operating requirements of different mainstream processes, and it has a wide range of applications.

[0096] Example 1: Rapid cultivation and operation of independent aerobic granular sludge

[0097] System construction: The cyclone purification unit is a Φ50mm hydrocyclone; the carrier loading, mixing, and photobioreactor unit is a 100L cylindrical reactor equipped with an LED light panel (light intensity 100 μmol / (m²)). 2 •s), 12h: 12h light and dark cycle), with a propeller at the bottom, a slag discharge port at the top, and a carrier addition tank on the side; the cyclone grading and reflux unit is a Φ25mm hydrocyclone.

[0098] Operation: Ordinary activated sludge is introduced, followed by continuous addition of *Scenedesmus obliquus*-biochar composite carrier (dry weight ratio 1:5, dosage 10% MLSS). The mixed liquor is pumped into a cyclone staged reflux unit, with the inlet pressure controlled at approximately 0.1 MPa, and the underflow reflux ratio adjusted to approximately 30% and the overflow reflux ratio to 20%.

[0099] After 40 days of operation, mature aerobic granular sludge with an average particle size >500μm and SVI5 <50 mL / g is formed in the system.

[0100] Example 2: Application of a side-flow seed mud preparation module in a continuous flow AAO process

[0101] The system was installed as a side-flow module next to the AAO process at a municipal wastewater treatment plant. The system operates continuously, adding granular sludge / flocs with an average particle size of about 300 μm and excellent settling performance (30≤SVI5≤50 mL / g) to the head end of the AAO aerobic tank daily at a ratio of about 0.5% of the sludge volume in the main aerobic section.

[0102] Results: After 60 days of addition, the proportion of visibly granular sludge in the aerobic section of the AAO system significantly increased, with the percentage of particles larger than 200μm in the sludge increasing from <2% to approximately 10%, and the overall SVI (Sludge Viscosity Index) improving. 30 The suspended solids (SS) in the secondary sedimentation tank effluent decreased from approximately 120 mL / g to approximately 70 mL / g, while the removal efficiencies for total nitrogen and total phosphorus increased by approximately 12% and 18%, respectively. This demonstrates that this system, as a seed sludge preparation module, can effectively promote and stabilize the aerobic granular sludge production process in the mainstream continuous flow process.

[0103] 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. The substitutions may be replacements of some structures, devices, or method steps, or they may be complete technical solutions. Equivalent substitutions or modifications made to the technical solutions and inventive concepts of the present invention should all be covered within the scope of protection of the present invention.

Claims

1. A multi-stage selective pressure biological carrier aerobic granular sludge cultivation system, characterized in that, The process flow includes a cyclone impurity removal unit (10), a carrier loading and photobiological reaction unit (20), and a cyclone grading and reflux unit (30) connected in sequence. The carrier loading and photobioreactor unit (20) includes a box (21), and a mud inlet pipe (22) is provided at the bottom of the box (21). The mud inlet pipe (22) is connected to the upper overflow port of the cyclone cleaning unit (10). The housing (21) is equipped with a carrier loading area (27), a light control area (28), a granular sludge return pipe (23), and a light sludge return pipe (24). The sludge inlet pipe (22) enters the carrier loading area (27). The carrier loading area (27) is equipped with a carrier feeding structure (25) and a flow booster (26). The flow booster (26) mixes sludge and carrier. The light control area (28) is located at the top of the carrier loading area (27). The outlets of the granular sludge return pipe (23) and the light sludge return pipe (24) extend into the carrier loading area (27). The feed inlet of the cyclone grading reflux unit (30) is connected to the bottom outlet of the box (21). The bottom outlet of the cyclone grading reflux unit (30) is connected to the granular sludge reflux pipe (23) and the first external discharge pipe (31) via a three-way valve. The overflow outlet of the cyclone grading reflux unit (30) is connected to the light sludge reflux pipe (24) and the second external discharge pipe (32) via a three-way valve.

2. The aerobic granular sludge cultivation system with multi-stage selective pressure as described in claim 1, characterized in that, The carrier dosing structure (25) is an annular dosing tube that uniformly dispenses the carrier along the circumference; The amount of carrier added is 5-10% of the concentration of suspended solids in the mixed liquid in the carrier loading zone (27).

3. The aerobic granular sludge cultivation system with multi-stage selective pressure as described in claim 2, characterized in that, The carrier is "charcoal-algae microspheres", which are formed by co-immobilizing Scenedesmus obliquus cells and biochar powder in diatomaceous earth suspension, wherein the dry weight percentage of Scenedesmus obliquus cells is 5-8%; Scenedesmus cells and biochar powder were compounded in a ratio of 1:(4-7) by dry weight.

4. The aerobic granular sludge cultivation system for a biological carrier under multi-stage selective pressure according to claim 2, characterized in that, The light-dark cycle of the light control zone (28) is 8-16 hours and the illumination / 8-16 hours. The light control zone (28) is equipped with a tubular illumination system (29) with independent zone control. The tubular illumination system (29) includes at least one high-intensity illumination section and one low-intensity maintenance illumination section for light control of the symbiotic system.

5. The aerobic granular sludge cultivation system for a biological carrier under multi-stage selective pressure according to claim 4, characterized in that, The light intensity of the high-intensity illumination section is 80-120 μmol / (m²). 2 •s), used to maximize the photosynthesis and proliferation of Scenedesmus obliquee; The light intensity in the low-intensity maintenance illumination segment is 40-60 μmol / (m²). 2 ·s), used to maintain algal cell activity and promote the exchange of substances between bacteria and algae.

6. The aerobic granular sludge cultivation system for a biological carrier under multi-stage selective pressure according to claim 4, characterized in that, The top of the tubular lighting system (29) is provided with a V-shaped weir plate (210), and both the V-shaped weir plate (210) and the surface of the tubular lighting system (29) are provided with a transparent anti-stick layer.

7. The aerobic granular sludge cultivation system for a biological carrier under multi-stage selective pressure according to claim 1, characterized in that, The carrier loading area (27) is a cylindrical structure located in the middle of the box (21), with the bottom of the cylindrical structure being closed and the top being provided with a micro-flocculation grid (211).

8. The aerobic granular sludge cultivation system for a biological carrier under multi-stage selective pressure according to claim 1, characterized in that, The top of the box (21) is provided with an aging sludge overflow weir (212) and a side collection trough (213), and an external discharge pipe (214) is provided on the side collection trough (213). Both the underflow port and the overflow port of the swirl stage reflux unit (30) are equipped with flow regulating devices (33). The system also includes a dissolved oxygen monitor (40) and a pH online monitor (50), and is linked with a tubular lighting system (29); When dissolved oxygen is below a set threshold, the tubular lighting system (29) automatically increases the light intensity; When the pH value rises to the set upper limit due to excessive algae, the tubular lighting system (29) automatically switches to the low-intensity maintenance lighting segment.

9. A method for cultivating aerobic granular sludge using a biological carrier under multi-stage selective pressure, characterized in that, The aerobic granular sludge cultivation system using a biological carrier under multi-stage selective pressure as described in any one of claims 1 to 8 comprises the following steps: Step 1: Preprocessing Wastewater enters the cyclone removal unit (10), which uses a hydrocyclone without built-in rotating parts. It is driven by the system inlet water pressure to form a high-speed cyclone. Under the action of centrifugal force, the heavier impurities are thrown to the wall and sink and discharged. The activated sludge overflows from the top and enters the carrier loading area (27) through the sludge discharge pipe. The shear force and hydraulic conditions generated by the hydrocyclone help to screen out highly adaptable polyphosphate-accumulating bacteria, which significantly increase their proportion in sludge. Step 2: Carrier loading and mixing After the pretreated sludge enters the carrier loading zone (27), the carrier feeding structure (25) uniformly feeds the prefabricated carrier along the circumference. The pusher (26) set at the bottom of the carrier loading zone (27) is activated to generate an upward flow, which pushes the sludge and carrier upward and mixes them thoroughly with the carrier. At the same time, it ensures the uniform distribution of dissolved oxygen and matrix, so that the carrier and sludge can be mixed quickly and evenly. Step 3: Central water distribution and reaction enhancement The mixed mud-carrier two-phase flow is injected into the light control zone (28) through the micro-flocculation grid (211) via the central water distribution method. The light control zone (28) provides specific light to activate the photosynthesis of Scenedesmus obliquus, forming a symbiotic system of bacteria and algae with microorganisms attached to biochar and sludge, which efficiently degrades pollutants and stimulates microorganisms to secrete EPS, thereby strengthening sludge aggregation. Step 4: Internal grading and removal of aged sludge Under the action of the flow booster (26), the mixture continues to rise and when it reaches the upper part of the reaction zone, it will overturn the V-shaped weir plate; Heavy sludge recirculation: After passing over the V-shaped weir, the dense and well-settling heavy sludge settles rapidly downwards due to gravity and returns to the bottom of the reaction zone to participate in the next cycle of growth, forming the first stage of settling selection inside the reactor. Sludge stripping: At the same time, the sludge flocs with poor settling performance and low activity, as well as the scum produced, continue to float upward under the influence of the rising flow, and eventually gather at the top of the box (21). The sludge is then discharged from the system continuously or intermittently through the sludge overflow weir (212), the side collection tank (213), and the external discharge pipe (214). Step 5: Secondary Cyclone Precision Sorting and Circulation The well-formed mixed sludge that settles to the bottom of the reactor is pumped to the cyclone staged reflux unit (30). Inside the hydrocyclone, the sludge is subjected to centrifugal force and is precisely separated according to density and particle size; Bottom flow: The heaviest and densest high-quality granular sludge separated is directly transported back to the system between the carrier addition structure (25) and the micro-flocculation grid (211) or the inlet of the main biochemical reactor through the bottom flow port, and enters the next growth cycle as "crystal nuclei" to continuously enhance the growth. Overflow: The lighter and finer flocculent sludge separated is discharged through the overflow port. A portion of the sludge is returned to the sludge cultivation area in the system to further regulate the overall sludge shape, while the remainder is discharged from the system as excess sludge.

10. An aerobic granular sludge cultivation system for biological carriers under multi-stage selective pressure according to any one of claims 1 to 8, used as an independent seed sludge preparation module in a continuous flow wastewater treatment process, characterized in that, The seed sludge preparation module is operated to continuously produce modified sludge flocs or aerobic granular sludge with high settling performance, and this is used as high-quality seed sludge to be added to the continuous flow mainstream bioreactor to accelerate and stabilize the aerobic granular sludge formation process in the mainstream reactor.

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