An aerobic granular sludge cultivation system and a method for operating the same

Abstract

This invention belongs to the field of sludge cultivation technology, specifically relating to an aerobic granular sludge cultivation system and its operation method. The system includes an influent system, a sludge treatment system, an aeration system, and multiple independent granular sludge tank cultivation systems. Each granular sludge tank cultivation system includes a granular sludge tank, in which an aeration homogenizer unit, a water distribution homogenizer unit, a sludge promoter unit, and a drainage stabilization unit are arranged in a stacked manner from bottom to top. The sludge promoter unit is connected to the inlet of the sludge treatment system. The output of the sludge treatment system is equipped with multiple branch return pipelines, one of which is used to discharge flocculent sludge, while the remaining branches are connected to the influent system or the granular sludge tank cultivation system. This invention, through overall design and precise control, not only improves the operational efficiency of the aerobic granular sludge treatment system but also solves problems such as uneven oxygen supply, poor sludge quality, and low treatment efficiency found in traditional wastewater treatment systems.

Description

Technical Field

[0001] This invention belongs to the field of sludge cultivation technology, specifically relating to an aerobic granular sludge cultivation system and its operation method. Background Technology

[0002] Currently, in the field of wastewater treatment, especially in traditional processes using activated sludge, there are several key technical challenges that limit the successful cultivation and efficient and stable operation of aerobic granular sludge.

[0003] First, traditional processes cannot effectively promote the rapid formation and long-term stability of aerobic granular sludge due to their influent methods. Typically, wastewater enters the biological treatment tank by gravity flow through corridors or pipes, causing rapid mixing with the existing microbial community. This rapid mixing is detrimental to the optimal growth and granulation process of core microorganisms such as polyphosphate-accumulating organisms (PAOs) in the granular sludge. Once small granular sludge particles are formed, due to the limitations of the influent method, they often struggle to preferentially acquire sufficient organic matter to further increase in size, ultimately affecting the overall system's treatment efficiency and stability.

[0004] Secondly, traditional aeration methods are insufficient in controlling dissolved oxygen concentration and aeration volume, making it difficult to create the ideal stratified structure of granular sludge with anaerobic interior and aerobic exterior. Excessive dissolved oxygen damages the internal structure of granular sludge, causing granules to disintegrate and lose their excellent settling and treatment performance. Simultaneously, traditional aeration systems easily generate large amounts of condensate during operation. Without an effective drainage mechanism, this not only increases energy consumption but also further affects the normal formation and maintenance of granular sludge.

[0005] Finally, the sludge discharge stage in traditional wastewater treatment processes does not adequately consider the effective screening and separation of granular and flocculent sludge. Due to the lack of a dedicated sludge screening system, both immature small granular sludge and well-formed high-quality granular sludge are discharged together during the sludge discharge process, significantly reducing the accumulation and recycling of granular sludge. This not only wastes resources but also hinders the accumulation and stable operation of granular sludge within the system. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides an aerobic granular sludge cultivation system and its operation method. By innovating and optimizing the influent drainage, aeration and sludge discharge processes, the system can achieve efficient cultivation of granular sludge, maintain its stability and improve the overall efficiency of wastewater treatment.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0010] 1. An aerobic granular sludge cultivation system, comprising an influent system, a sludge treatment system, an aeration system, and multiple independent granular sludge tank cultivation systems. The aeration system includes an aeration distribution unit and multiple aeration homogenizer units, each installed within a corresponding granular sludge tank cultivation system. Each granular sludge tank cultivation system includes a granular sludge tank, wherein the granular sludge tank is arranged from bottom to top with aeration homogenizer units, water distribution homogenizer units, sludge promoter units, and drainage stabilization units spaced at intervals. The aeration homogenizer units uniformly distribute the gas from the aeration system. The wastewater is dispersed into the tank to ensure good oxygen supply for the granular sludge; the water distributor unit evenly distributes the pretreated influent into the tank, achieving effective contact between the wastewater and microorganisms; the influent system is connected to the water distributor unit so that the pretreated wastewater can evenly enter the granular sludge cultivation system; the sludge promoter unit is connected to the inlet of the sludge treatment system to effectively collect and transport the sludge generated during the treatment process; the sludge treatment system output is equipped with multiple branch return pipelines, of which at least one branch is used to discharge flocculent sludge, and the remaining branches are connected to the influent system or the granular sludge cultivation system.

[0011] Optionally, the aeration system also includes multiple exhaust units, which are connected to the aeration uniformizer unit.

[0012] Optionally, the sludge treatment system includes a sludge buffer tank and a particle screen unit. The inlet of the sludge buffer tank is connected to the sludge promoter unit, and the outlet of the sludge buffer tank is connected to the particle screen unit. The sludge buffer tank is also equipped with a sludge separation unit and an outlet.

[0013] Optionally, the water inlet system includes an inlet buffer unit and an inlet distribution unit. The outlet of the inlet buffer unit is connected to the inlet of the inlet distribution unit via a pipeline, and the outlet of the inlet distribution unit is connected to the water distribution homogenizer unit.

[0014] Optionally, the granular screener unit is provided with multiple branches for outputting sludge, at least one branch for discharging flocculent sludge, and the remaining branches are connected to the granular sludge tank cultivation system to directly or indirectly return the screened granular sludge to the granular sludge tank.

[0015] Optionally, it also includes a dosing system, which is connected to the granular sludge tank and the influent distribution unit respectively.

[0016] A method for operating an aerobic granular sludge cultivation system, the method comprising:

[0017] S1, Water Inlet and Drainage Stage:

[0018] The wastewater to be treated is distributed by the influent distribution unit and guided by the water distribution homogenizer unit, and injected into each granular sludge tank cultivation system in a plug flow manner. As the wastewater is continuously injected, the liquid level in each granular sludge tank rises. The suspended solids in the wastewater settle under the adsorption and biodegradation of the granular sludge. As the liquid level rises, the supernatant is discharged through the drainage unit when the liquid level exceeds the set threshold.

[0019] Aeration is suspended during this stage to promote anaerobic fermentation and denitrification in the granular sludge tank;

[0020] S2, Sludge Removal Stage:

[0021] After the influent and effluent processes are completed, the sludge promoter unit discharges the flocculent sludge and a small amount of granular sludge from the granular sludge tank into the sludge buffer tank. This process is accompanied by a drop in the liquid level, which exposes the effluent stabilizing unit to the outside.

[0022] S3, Aeration Biochemical Reaction Stage:

[0023] After the sludge is discharged, air enters the aeration uniform unit inside each granular sludge tank cultivation system through the aeration distribution unit to uniformly aerate the granular sludge tank cultivation system. At the same time, the exhaust unit regulates the air during the aeration process.

[0024] During this stage, the undischarged flocculent sludge is transformed into granular sludge under the action of aeration shear force, and the particle size of the granular sludge increases to 0.2 mm and above. In this process, phosphorus adsorption and removal, biodegradation of organic pollutants and nitrification reaction are achieved to achieve the goal of wastewater purification.

[0025] S4. Sludge recycling stage:

[0026] During the aeration reaction stage, the sludge in the sludge buffer tank undergoes sludge-water separation through the sludge separation unit. The supernatant obtained from the separation is combined with the drainage from the granular sludge tank and discharged downstream for further treatment. The remaining sludge after sludge-water separation is discharged into the granular screening unit. After processing by the granular screening unit, the high-quality granular sludge selected is returned to the granular sludge tank or the influent buffer unit to replenish the granular sludge tank. At the same time, the flocculent sludge is discharged to the subsequent sludge treatment process.

[0027] S5, Settlement Stabilization Stage:

[0028] After the aeration phase ends, the granular sludge settles to the bottom of the granular sludge tank in preparation for a new round of wastewater injection.

[0029] Optionally, it also includes a dosing operation, in which sodium acetate is added to the influent distribution unit or granular sludge tank when an imbalance in the influent carbon-nitrogen ratio (C / N ratio less than 5) or a decrease in the total nitrogen removal efficiency in the granular sludge tank is detected (the difference between the total nitrogen in the effluent and the discharge limit is within 1 mg / L).

[0030] When a decrease in phosphorus removal efficiency is detected in the granular sludge tank, polyaluminum chloride (PAC) is added to the granular sludge tank or influent distribution unit via the dosing system. Adding phosphorus removal agents is an emergency measure. During peak wastewater treatment plant periods with a sharp increase in water volume, PAC is added to the granular sludge tank or influent distribution unit via the dosing system to ensure that effluent suspended solids (SS) and total phosphorus levels meet treatment standards, thus reducing pressure on the advanced treatment stages.

[0031] Optionally, the time ratio of the water inlet and drainage stage, the sludge removal stage, the aeration and biochemical reaction stage, and the settling and stabilization stage is 1-1.5:0.01-0.1:1-2.5:0.1-1.

[0032] Optionally, the wastewater discharged after the S4 step of granulated sludge cultivation has a COD of 5-30 mg / L, ammonia nitrogen of less than 1 mg / L, total phosphorus of 0.1-0.5 mg / L, total nitrogen of less than 15 mg / L, and suspended solids of less than 10 mg / L; the particle size of the granulated sludge discharged during the sludge discharge stage is controlled below 0.2 mm, and the particle size of the granulated sludge recovered in the granular screen unit is above 0.1 mm.

[0033] (III) Beneficial Effects

[0034] This invention ensures uniform gas distribution within the granular sludge tank through the aeration distribution unit and aeration homogenizer unit in the aeration system, effectively improving oxygen supply efficiency and the biological activity of the granular sludge.

[0035] The design incorporates a hierarchical structure within the granular sludge tank, such as the sequential arrangement of aeration homogenizer units and water distribution homogenizer units. This ensures good contact between wastewater and microorganisms, which helps improve wastewater treatment efficiency and the formation and settling of granular sludge.

[0036] The sludge treatment system includes a sludge buffer tank and a granular screen unit, which can effectively collect, classify and reuse the generated sludge, reducing sludge discharge while improving the granulation quality and quantity of sludge within the system.

[0037] During the sludge discharge stage, flocculent sludge and some granular sludge are transferred to the sludge buffer tank through the sludge promoter unit, and high-quality granular sludge is recovered through the granular screen unit, thus optimizing the sludge recycling process.

[0038] The inlet system includes an inlet buffer unit and an inlet distribution unit, ensuring that the pretreated wastewater can enter the granular sludge cultivation system stably and evenly, thus avoiding the impact of water quality fluctuations on the treatment effect.

[0039] A dosing system is introduced to add sodium acetate and polyaluminum chloride chemical reagents in a timely manner based on real-time monitored water quality parameters, in order to adjust the carbon-nitrogen ratio, improve total nitrogen removal efficiency, and enhance phosphorus removal.

[0040] The system defines multiple operational stages, including water inlet and outlet, sludge removal, aeration, and sedimentation, and clearly defines the ideal time ratio between each stage, ensuring the scientific and efficient operation of the system.

[0041] The wastewater treated by this system and its operating methods shows significantly better water quality indicators (COD, ammonia nitrogen, total phosphorus, total nitrogen, and suspended solids) than existing treatment methods, meeting high discharge standards and demonstrating remarkable wastewater treatment effectiveness.

[0042] In summary, through overall design and precise control, this invention not only improves the operational efficiency of the aerobic granular sludge treatment system, but also achieves efficient removal of harmful substances from wastewater and maximizes the utilization of sludge resources, solving problems such as uneven oxygen supply, poor sludge quality, and low treatment efficiency in traditional wastewater treatment systems.

[0043] Instruction manual illustrations

[0044] Figure 1 This invention provides a layout scheme for an aerobic granular sludge cultivation system. Detailed Implementation

[0045] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0046] Example 1

[0047] See attached document Figure 1This embodiment provides an aerobic granular sludge cultivation system. The system includes an influent system, a sludge treatment system, an aeration system, and multiple independent granular sludge tank cultivation systems. The aeration system includes an aeration distribution unit and multiple aeration homogenizer units. Each aeration homogenizer unit is installed inside a corresponding granular sludge tank cultivation system. The granular sludge tank cultivation system includes a granular sludge tank. From bottom to top, the granular sludge tank is arranged with aeration homogenizer units, water distribution homogenizer units, sludge promoter units, and drainage stabilization units at intervals. The aeration homogenizer units uniformly distribute the gas from the aeration system. The wastewater is evenly dispersed into the tank to ensure good oxygen supply for the granular sludge. The water distribution homogenizer unit ensures that the pretreated influent is evenly distributed into the tank, achieving effective contact between the wastewater and microorganisms. The influent system is connected to the water distribution homogenizer unit so that the pretreated wastewater can evenly enter the granular sludge cultivation system. The sludge promoter unit is connected to the inlet of the sludge treatment system to effectively collect and transport the sludge generated during the treatment process. The sludge treatment system output is equipped with multiple branch return pipelines, of which at least one branch is used to discharge flocculent sludge, and the remaining branches are connected to the influent system or the granular sludge cultivation system.

[0048] Each independent granular sludge cultivation system operates intermittently, and can be divided into five key stages: influent and effluent discharge, sludge discharge, sludge recycling, aeration and reaction, and sedimentation. In the influent and effluent discharge stage, wastewater enters the tank, and the granular sludge comes into full contact with the wastewater, undergoing adsorption and biodegradation. In the aeration and reaction stage, the aeration system provides sufficient oxygen to the microorganisms, promoting the oxidation and decomposition of organic matter and the stabilization of the granular sludge. In the sedimentation stage, after aeration stops, the granular sludge settles, and the supernatant is discharged for the next treatment stage.

[0049] To ensure continuous influent and effluent operation, the system is typically designed with at least three granular sludge cultivation tanks. This allows two tanks to be in the aeration or sedimentation phase while the third tank is handling influent and effluent. This staggered operation improves the overall system's processing capacity and continuity.

[0050] When a granular sludge cultivation system is about to enter the influent and effluent stages, the influent system responds in real time by starting pumps and adjusting valves to introduce wastewater stored in the influent buffer unit into the designated granular sludge cultivation system. The existence of the influent buffer not only stabilizes the influent flow rate but also alleviates the mismatch between the influent flow rate and the downstream treatment rhythm, ensuring smooth and efficient operation of the entire system.

[0051] During the process of wastewater being pumped from the influent distribution unit to the granular sludge tank, the liquid level in the influent buffer unit gradually decreases as wastewater is pumped out. Simultaneously, the influent buffer unit continuously receives new wastewater to be treated. Precise liquid level control ensures a sufficient supply of water for the subsequent granular sludge cultivation system to treat the wastewater, while preventing overflow due to excessive influent flow. This ensures continuous wastewater treatment while effectively controlling the influent flow rate and liquid level, maintaining stable operation of the entire system.

[0052] The water distribution homogenizer unit is designed to ensure that wastewater enters the granular sludge cultivation system in a plug-flow manner, uniformly and orderly. This flow pattern allows the larger granular sludge particles at the bottom to come into contact with the incoming wastewater first, enabling the microorganisms within these granular sludge particles (such as those capable of storing volatile fatty acids (VFA) and polyhydroxyalkanoates (PHA)) to preferentially utilize the carbon source in the wastewater. This preferential carbon source uptake is crucial for the stability and growth of the granular sludge, as larger granular sludge particles have better settling properties and stronger biodegradation capabilities, which is beneficial for the efficient operation and mature growth of the entire aerobic granular sludge cultivation system.

[0053] Each independent granular sludge cultivation system is equipped with a drainage stabilization unit. This drainage stabilization unit is installed at the top of the granular sludge tank to minimize disturbance to the sludge layer inside the tank when discharging the supernatant, ensuring the stability of the sludge bed, and in particular preventing the formed granular sludge from being broken or floated due to improper drainage operations, which would affect its settling performance and treatment efficiency.

[0054] In the wastewater treatment process, after the wastewater in the granular sludge tank has undergone aerobic biological reaction and is fully treated, the supernatant can be discharged in an orderly manner through this top-mounted drainage stabilization unit when it meets the discharge standards. This ensures a stable drainage flow rate without affecting the structure of the granular sludge and the efficiency of biological treatment within the tank, while the granular sludge containing a large number of microorganisms remains in the tank to continue its purification function. Simultaneously, the stable discharge of the supernatant provides stable and compliant influent conditions for subsequent wastewater treatment processes.

[0055] The drainage stabilization unit is not only a key drainage facility within the granular sludge tank, but it also plays a role in connecting the entire wastewater treatment process. Its drainage is directly connected to the subsequent process stages of the wastewater treatment plant (such as sedimentation tanks, filtration tanks, or disinfection tanks), ensuring the smooth operation of the entire wastewater treatment process and the final discharge of effluent that meets the standards.

[0056] The drainage stabilization unit comprises the following components: a collection tank, a level control device, a flow stabilization device, automatic control valves or pumps, backflow prevention design, an emergency discharge channel, and connections to subsequent treatment facilities. The core of the drainage stabilization unit is the collection tank, located at the top or side of the granular sludge tank, used to collect and control the discharge of supernatant. The design incorporates fluid dynamics principles to ensure a stable drainage process and avoid significant disturbance to the sludge bed. Level sensors and controllers monitor and control the liquid level within the granular sludge tank, ensuring that only clarified supernatant is discharged during the drainage phase, without carrying away excessive activated sludge.

[0057] The flow stabilization device includes a guide plate, a ramp, and an orifice to ensure stable water flow during drainage and to prevent instability of the sludge layer and increased concentration of SS (suspended solids) in the supernatant due to excessively fast water flow.

[0058] Based on the liquid level control signal, the valves or pumps are automatically controlled to open and close, so as to achieve timed and quantitative drainage, maintain the balance of liquid level in the system and the stability of drainage flow.

[0059] When the system stops draining, the drainage stabilization unit has the function of preventing the supernatant from flowing back into the granular sludge tank.

[0060] The drainage stabilization unit is connected to subsequent sedimentation tanks, filtration tanks or other advanced treatment facilities through pipelines to ensure that the discharged supernatant can smoothly enter the next treatment stage.

[0061] The water distribution homogenization unit includes water distribution pipes, which are distributed along multiple inlet pipes at the bottom or side wall of the treatment tank. Through reasonable layout and angle design, the water flow is ensured to uniformly cover the entire tank.

[0062] Water distribution nozzles are installed at the end of the water distribution pipe to disperse the water flow into small and uniform water droplets or streams, so that the wastewater can be evenly distributed throughout the pool.

[0063] Flow regulating device: used to precisely control the flow rate of each or multiple water inlets to ensure that the water inlet rate is consistent at all points and achieve a homogeneous effect.

[0064] A grid structure is installed below the water distributor to further disperse the water flow and prevent excessive local scouring force from damaging the sludge bed.

[0065] The liquid level control equipment, through the liquid level gauge and controller, ensures that the water distributor can maintain uniform water distribution under different liquid level conditions, especially when the liquid level in the treatment tank changes.

[0066] Optionally, the aeration system also includes multiple exhaust units, which are connected to the aeration uniformizer unit.

[0067] The aeration distribution unit is a comprehensive assembly of equipment including blowers, pipes, valves, and flow meters. The blower powers the entire aeration system, delivering compressed air or oxygen evenly to each granular sludge tank cultivation unit via the piping system. Valves control the gas flow rate and its opening / closing, while flow meters precisely measure and monitor the gas flow rate, ensuring each granular sludge tank receives a suitable and constant aeration. The aeration homogenizer unit, connected to the aeration distribution unit, further refines and evenly distributes the gas from the piping system to the bottom area of ​​the granular sludge tank. Aeration homogenizers are typically designed to disperse the gas into microbubbles, allowing for better mixing with the granular sludge, enhancing oxygen transfer efficiency to microorganisms, and promoting aerobic biological reactions.

[0068] The exhaust unit is connected to the aeration homogenizer unit, but it is located outside the granular sludge tank. The main function of the exhaust unit is to discharge excess or saturated gases generated during aeration to maintain the internal pressure balance of the system and to treat the discharged gases to reduce noise and odor pollution. Simultaneously, by regulating the exhaust unit, a suitable dissolved oxygen concentration can be maintained inside the granular sludge tank, preventing granular sludge breakage and system instability caused by over-aeration. These three units constitute the core of the aeration system, and through coordinated operation, ensure that the aerobic biological treatment process in the granular sludge tank can proceed stably and efficiently under ideal oxygen conditions. Optionally, the sludge treatment system includes a sludge buffer tank and a granular screen unit. The inlet of the sludge buffer tank is connected to the sludge promoter unit, and the outlet of the sludge buffer tank is connected to the granular screen unit. The sludge buffer tank is also equipped with a sludge separation unit and an effluent outlet.

[0069] Optionally, the water inlet system includes an inlet buffer unit and an inlet distribution unit. The outlet of the inlet buffer unit is connected to the inlet of the inlet distribution unit via a pipeline, and the outlet of the inlet distribution unit is connected to the water distribution homogenizer unit.

[0070] Optionally, the granular screener unit is provided with multiple branches, at least one of which is used to discharge flocculent sludge, and the remaining branches are connected to the influent buffer unit or the granular sludge tank cultivation system.

[0071] Optionally, the system also includes a dosing system, which is connected to the granular sludge tank and the influent distribution unit.

[0072] The sludge promoter unit is deployed in the upper middle part of each granular sludge tank unit. Its function is to promote sludge activity, help the formation and stabilization of granular sludge, and effectively remove aged or incompletely matured sludge from the granular sludge tank to maintain the appropriate concentration and activity of sludge in the tank.

[0073] The sludge buffer tank unit is connected to the sludge promoter unit and is used to receive excess sludge discharged from each granular sludge tank unit. This unit is a temporary storage container that can temporarily store and regulate the sludge flow rate discharged from the sludge promoter to avoid impacting subsequent treatment processes.

[0074] The sludge separation unit treats the sludge-water mixture received from the sludge buffer tank cultivation system, and its core technology lies in sludge-water separation. Through this unit, the supernatant from the mixture and the supernatant discharged from the granular sludge tank can be discharged together to the subsequent wastewater treatment unit for further treatment. At the same time, the separated excess sludge is transported to the granular screen unit.

[0075] The granular sludge screen unit is connected to the previously mentioned sludge buffer tank unit, and its main task is to perform fine screening of the excess sludge in the buffer tank. Through the screening process, a small amount of high-quality granular sludge can be separated from the excess sludge. Due to their excellent performance and activity, these screened granular sludge particles can be returned to the various granular sludge tank equipment units to participate in a new round of wastewater treatment, thereby achieving efficient utilization of sludge resources.

[0076] The remaining sludge that fails the screening, meaning that most of it does not meet the granular sludge standards, is discharged from the granular screen unit and sent to the sludge thickening tank in the wastewater treatment plant for further treatment. This sludge includes flocculent sludge, incompletely matured granular sludge, and other impurities. Through treatment in the thickening tank, the sludge volume can be reduced and some solid-liquid separation can be achieved, facilitating subsequent dewatering, disposal, or resource utilization.

[0077] Through the coordinated work of these units, the entire aerobic granular sludge cultivation system can effectively manage sludge, promote the formation and stabilization of granular sludge, and enable the reasonable classification, screening and recycling of sludge, while ensuring the continuity and effectiveness of the wastewater treatment process.

[0078] Example 2

[0079] See attached document Figure 1 This embodiment provides an operation method for an aerobic granular sludge cultivation system, characterized in that the method includes:

[0080] S1, Water Inlet and Drainage Stage:

[0081] The wastewater to be treated is distributed by the influent distribution unit and guided by the water distribution homogenizer unit, and injected into each granular sludge tank cultivation system in a plug flow manner. As the wastewater is continuously injected, the liquid level in each granular sludge tank rises. The suspended solids in the wastewater settle under the adsorption and biodegradation of the granular sludge. As the liquid level rises, the supernatant is discharged through the drainage unit when the liquid level exceeds the set threshold.

[0082] Aeration is suspended during this stage to promote anaerobic fermentation and denitrification in the granular sludge tank;

[0083] S2, Sludge Removal Stage:

[0084] After the influent and effluent processes are completed, the sludge promoter unit discharges the flocculent sludge and a small amount of granular sludge from the granular sludge tank into the sludge buffer tank. This process is accompanied by a drop in the liquid level, which exposes the effluent stabilizing unit to the outside.

[0085] S3, Aeration Biochemical Reaction Stage:

[0086] After the sludge is discharged, air enters the aeration uniform unit inside each granular sludge tank cultivation system through the aeration distribution unit to uniformly aerate the granular sludge tank cultivation system. At the same time, the exhaust unit regulates the air during the aeration process.

[0087] During this stage, the undischarged flocculent sludge is transformed into granular sludge under the action of aeration shear force, and the particle size of the granular sludge increases to more than 0.2 mm. In this process, phosphorus adsorption and removal, biodegradation of organic pollutants and nitrification reaction are achieved to achieve the goal of wastewater purification.

[0088] S4. Sludge recycling stage:

[0089] During the aeration reaction stage, the sludge in the sludge buffer tank undergoes sludge-water separation through the sludge separation unit. The supernatant obtained from the separation is combined with the drainage from the granular sludge tank and discharged downstream for further treatment. The remaining sludge after sludge-water separation is discharged into the granular screening unit. After processing by the granular screening unit, the high-quality granular sludge selected is returned to the granular sludge tank or the influent buffer unit to replenish the granular sludge tank. At the same time, the flocculent sludge is discharged to the subsequent sludge treatment process.

[0090] S5, Settlement Stabilization Stage:

[0091] After the aeration phase ends, the granular sludge settles to the bottom of the granular sludge tank in preparation for a new round of wastewater injection.

[0092] During the influent and effluent operation of the granular sludge cultivation system, the water distributor homogenizer unit is responsible for uniformly and stably introducing wastewater into the granular sludge tank. This ensures that the wastewater enters in a plug flow (i.e., a continuous flow of water similar to a piston) rather than a large-scale, rapid diffusion. This prevents the water flow from causing severe disturbance to the already formed granular sludge layer within the tank. By avoiding large-scale agitation of the sludge layer, suspended solids (SS) can be effectively prevented from being carried into the effluent due to water flow impact, thus ensuring that the SS concentration in the effluent remains at a low level.

[0093] The drainage stabilization unit ensures that the supernatant flows out smoothly and in a controlled manner, avoiding water flow fluctuations caused by sudden large-scale drainage. This suppresses the mixing of suspended solids (SS) in the supernatant into the drainage due to disturbance, ultimately ensuring that the SS concentration in the drainage remains within acceptable limits. This portion of the supernatant will then be safely and stably discharged into the advanced treatment system unit for further processing via the drainage stabilization unit.

[0094] In aerobic granular sludge cultivation systems, the sludge removal process is to remove immature or inactive sludge to maintain the activity and efficiency of the granular sludge. Lowering the sludge tank level during the sludge removal stage allows the drainage stabilization unit (collection tank) to be exposed above the drainage surface, eliminating the need for sealing. This is because sludge removal effectively lowers the liquid level within the granular sludge tank, ensuring the drainage stabilization unit is exposed to air during non-influent and non-aeration phases. This prevents water accumulation and pressure buildup, thus preventing wastewater from flowing back into the granular sludge tank during the next fluent influent intake, ensuring water quality and quantity control during influent intake.

[0095] The purpose of the drainage stabilization unit is to ensure that the supernatant can be discharged stably during the influent and effluent stages without carrying too much sludge. The water collection stabilization unit exposed above the liquid surface can freely discharge the supernatant without worrying about the influence of air pressure, and it will not affect the normal operation of the granular sludge tank.

[0096] In the aerobic granular sludge cultivation system of this invention, since a static pressure sludge discharge method is adopted, it is not necessary to rely on active sludge discharge equipment such as flow meters and pumps during the sludge discharge stage. This is because, in the design, the sludge tank is located lower than the downstream sludge discharge point, and the hydrostatic pressure generated by the liquid level difference is used to drive the sludge to be discharged naturally.

[0097] In practice, sludge discharge is easily achieved by controlling the opening and closing of valves at the bottom of the sludge tank. The control of the sludge discharge process is primarily based on changes in the liquid level inside the sludge tank. When the liquid level rises to a certain threshold, the valve is closed to maintain the sludge within the tank for biological treatment. When sludge discharge is required, simply open the valve; utilizing the level difference between the inside and outside of the tank, the sludge will automatically flow out by gravity to a lower sludge buffer tank or other treatment facilities. This makes the entire sludge discharge process more energy-efficient, simpler, and easier to automate.

[0098] In this way, the system can achieve continuous and orderly operation, while effectively controlling sludge discharge and supernatant separation, ensuring wastewater treatment effect and system stability.

[0099] When the granular sludge tank cultivation system is receiving water, the electric valve in the aeration distribution unit will close in real time, cutting off the air supply to the aeration uniformizer unit and thus stopping the aeration process. At this time, the exhaust unit can play its role to ensure that the gas in the pipeline is effectively controlled, avoiding excessive mixing of sewage and gas during the water intake process, which would affect the stability of the influent and the state of the sludge layer.

[0100] After the water intake is complete, the water pumps and electric valves in the influent distribution unit will shut off simultaneously, ceasing water injection into the granular sludge cultivation system. Next, the system will activate the sludge promoter unit to transfer the flocculent sludge that failed to form a good granular structure from the granular sludge tank to the sludge buffer tank unit. As the sludge promoter discharges sludge, the liquid level in the granular sludge tank gradually decreases. This process gradually exposes the drainage stabilization unit, which was previously submerged, preparing it for subsequent settling and drainage stages. This effectively removes substandard flocculent sludge while ensuring the granular sludge tank maintains a good initial condition for the next wastewater treatment cycle.

[0101] After the granular sludge cultivation system completes sludge discharge, the electric valve in the aeration distribution unit will be reopened to aerate the system. Through the aeration uniformizer unit, air can be evenly distributed throughout the tank, effectively preventing sludge accumulation in corners or other areas. Simultaneously, the uniform bubble distribution applies a uniform hydraulic shear force to the sludge, which is crucial for promoting sludge granulation and increasing the granular sludge formation rate.

[0102] Based on the actual influent volume of each granular sludge tank unit, the aeration rate can be precisely controlled to ensure that the aeration of each unit matches the wastewater load, thereby reducing energy consumption caused by frequent start-stop of the blower. Furthermore, the exhaust unit plays a crucial role in the aeration process, effectively regulating the gas generated after aeration and preventing condensation from forming inside the aeration uniformizer unit. This not only reduces aeration energy consumption but also improves the stability and economic efficiency of the entire system. Through these refined control methods, the aerobic granular sludge technology equipment system of this invention achieves the goal of high efficiency and energy saving.

[0103] When the granular sludge cultivation system is aerated, the sludge and water are thoroughly mixed. The phosphate released by the granular sludge during the anaerobic stage is re-adsorbed and ingested by microorganisms, achieving a transfer of phosphorus from the aqueous phase to the biological phase. Simultaneously, biodegradable pollutants in the wastewater are oxidized and decomposed by the microorganisms. During this process, ammonium ions in the wastewater are oxidized to nitrate on the surface of the granular sludge. Further within the granular sludge, microorganisms utilize the organic matter and biopolymers stored during the anaerobic stage to reduce nitrate to nitrogen gas through denitrification, thereby removing nitrogen from the water.

[0104] After the pollutant purification process ends and aeration stops, the exhaust unit ensures that the gas remains within the pipes, preventing granular sludge from being carried into the exhaust system. With the cessation of aeration, the granular sludge, due to its own gravity and large particle size, can rapidly settle to the bottom of the granular sludge tank within a very short time, typically within minutes. This rapid settling capability allows the granular sludge tank to be ready in a timely manner to receive the next batch of wastewater, ensuring the continuity and efficiency of the entire wastewater treatment process.

[0105] When sludge from the granular sludge tank is discharged into the sludge buffer tank, the buffer tank has sufficient capacity to hold the entire batch of sludge discharged from the granular sludge cultivation system. This design facilitates a smooth transition of sludge flow between different process stages, avoiding the impact on subsequent treatment processes caused by excessive instantaneous sludge discharge.

[0106] The sludge separation unit separates the sludge-water mixture from the sludge buffer tank, allowing the supernatant to be combined with the drainage from the granular sludge tank before being discharged into the advanced treatment unit for further purification. The separated excess sludge is then sent to the granular screening unit.

[0107] The granular screening unit performs fine screening of excess sludge, selecting larger, higher-quality granular sludge particles and reintroducing them into the granular sludge cultivation system or the influent buffer unit to maintain a high granulation rate and efficient treatment capacity. Excess sludge that fails screening, with smaller particles or poorer quality, is discharged to the next sludge treatment stage of the wastewater treatment plant for further processing or proper disposal. In this way, the entire system achieves efficient utilization and refined management of sludge resources.

[0108] Optionally, it also includes a dosing operation, in which sodium acetate is added to the granular sludge tank or influent distribution unit by the dosing system when an imbalance in the carbon-nitrogen ratio or a decrease in total nitrogen removal efficiency is detected in the granular sludge tank.

[0109] Adding phosphorus removal agents is an emergency measure. When the sewage treatment plant is in peak supply and discharge period and the water volume increases sharply, polyaluminum chloride is added to the granular sludge tank or influent distribution unit by the dosing system to ensure that the effluent SS and total phosphorus meet the treatment standards and reduce the pressure on the deep treatment section.

[0110] In the aerobic granular sludge cultivation system of the present invention, the dosing unit plays a key role, which precisely controls the dosage of two important chemical agents—sodium acetate and polyaluminum chloride.

[0111] Sodium acetate is mainly added to address the problem of insufficient carbon source encountered during the treatment process, especially when the total nitrogen removal rate is low. As a carbon source that is easily utilized by microorganisms, sodium acetate can supplement the carbon source energy required by microorganisms in the process of degrading nitrogen pollutants, thereby improving the total nitrogen removal efficiency and maintaining the nitrogen balance of the entire system.

[0112] The addition of polyaluminum chloride (PAC) is primarily used to address the risk of excessive total phosphorus levels due to large volumes of wastewater during peak treatment periods. As a commonly used coagulant, PAC combines with phosphates in water through a chemical reaction to form insoluble precipitates, effectively removing phosphorus and ensuring that the total phosphorus content in the effluent remains within specified limits even when treating large volumes of wastewater. Through an intelligent dosing unit, the dosage of sodium acetate and PAC can be dynamically adjusted based on actual operating conditions and water quality changes, ensuring efficient and stable operation of the entire aerobic granular sludge process under various conditions.

[0113] Optionally, the time ratio of the water inlet and drainage stage, the sludge removal stage, the aeration and biochemical reaction stage, and the settling and stabilization stage is 1-1.5:0.01-0.1:1-2.5:0.1-1.

[0114] The time ratios of each key operational stage were flexibly adjusted to optimize the entire treatment process and improve treatment efficiency. Specifically, the time allocation for the influent / drainage stage, sludge removal stage, aeration stage, and settling stage can be adjusted according to the ratio of 1-1.5 hours: 0.01-0.1 hours: 1-2.5 hours: 0.1-1 hours. This time ratio selection aims to ensure that the stages are properly connected and alternated to maximize wastewater purification efficiency and the maturity of granular sludge.

[0115] In aerobic granular sludge cultivation systems, setting the time ratios of the influent / drainage stage, sludge discharge stage, aeration stage, and settling stage too high or too low will negatively impact the system's operational performance and efficiency. If the influent / drainage stage is too long, excessive disturbance to the sludge layer will affect the stability and settling performance of the granular sludge, increase the concentration of suspended solids (SS) in the effluent, and reduce the quality of the effluent. Simultaneously, excessively long influent / drainage times will hinder the subsequent aeration and settling stages, affecting the removal efficiency of organic matter and nitrogen and phosphorus.

[0116] If the sludge removal stage is too short, it will be insufficient to completely remove the flocculent sludge, affecting the purity and maturity of the granular sludge, and also hindering the formation of new granular sludge. Conversely, if the sludge removal time is too long, it will reduce the amount of effective sludge, affecting the overall system's treatment capacity.

[0117] Inappropriate aeration time settings can also affect wastewater treatment efficiency. Insufficient aeration time fails to provide enough oxygen for microorganisms to perform biodegradation, reducing the removal efficiency of organic matter, nitrogen, and phosphorus, and also leading to instability in the internal structure of granular sludge. Excessive aeration time results in excessive oxygen consumption and energy waste, while also disrupting the internal anaerobic / aerobic stratification of the granular sludge, affecting its stability.

[0118] If the settling time is insufficient, the granular sludge cannot settle sufficiently, which will increase the turbidity of the effluent and also hinder the accumulation and maturation of the granular sludge. If the settling time is too long, the system's treatment efficiency will be reduced because the settled granular sludge needs to enter the next cycle treatment stage as soon as possible.

[0119] In conclusion, correctly setting the time ratios of these stages is crucial for maintaining the efficient and stable operation of the system. Excessive or insufficient time allocation leads to decreased treatment efficiency, increased energy consumption, and increased complexity in sludge management. In practice, the time ratios of each stage need to be dynamically adjusted based on specific circumstances and experimental results to achieve optimal wastewater treatment performance.

[0120] Optionally, the wastewater discharged after the S4 step of granulated sludge cultivation has a COD of 5-30 mg / L, ammonia nitrogen of less than 1 mg / L, total phosphorus of 0.1-0.5 mg / L, total nitrogen of less than 15 mg / L, and suspended solids of less than 10 mg / L; the particle size of the granulated sludge discharged during the sludge discharge stage is controlled below 0.2 mm, and the particle size of the granulated sludge recovered in the granular screen unit is above 0.1 mm.

[0121] Controlling the particle size of granulated sludge to above 0.2 mm is beneficial for improving sludge settling performance: the smaller the particle size, the larger the specific surface area of ​​the sludge, which theoretically makes it easier to adsorb organic and inorganic matter in the water. However, excessively small particle size leads to slow settling speed, affecting the efficiency of sludge separation from water. Therefore, controlling the particle size of discharged sludge to below 0.2 mm ensures that it has a certain capacity to adsorb and degrade pollutants, while also ensuring relatively good settling performance in subsequent treatment stages, reducing turbidity in the wastewater.

[0122] The granular sludge screening unit recovers sludge particles larger than 0.1 mm, identifying larger granular sludge particles. In sludge treatment, granular sludge with a particle size greater than 0.1 mm is generally considered high-quality granular sludge seed material with good structural stability, biological activity, and settling properties. Screening and recovering these larger granular sludge particles allows them to be recycled back into the system, maintaining the granulation rate of sludge in the granular sludge tank and improving the overall system's treatment efficiency and stability. Excessively fine sludge will drift away with the water flow or fail to settle effectively, while sludge with a particle size greater than 0.1 mm is more likely to maintain its granular shape, making it suitable for further biological treatment processes.

[0123] The setting of these two particle size thresholds is based on practical experience and technical requirements, aiming to balance the treatment efficiency, settling performance and resource recovery efficiency of sludge, and ensure that the entire wastewater treatment system reaches the optimal operating state.

[0124] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for operating a continuous feeding and draining aerobic granular sludge cultivation system, characterized in that, The method includes: S1, Water Inlet and Drainage Stage: The wastewater to be treated is distributed by the influent distribution unit and guided by the water distribution homogenizer unit, and injected into each granular sludge tank cultivation system in a plug flow manner. As the wastewater is continuously injected, the liquid level in each granular sludge tank rises. The suspended solids in the wastewater settle under the adsorption and biodegradation of the granular sludge. As the liquid level rises, the supernatant is discharged through the drainage unit when the liquid level exceeds the set threshold. Aeration is suspended during this stage to promote anaerobic fermentation and denitrification in the granular sludge tank; S2, Sludge Removal Stage: After the influent and effluent procedures are completed, the sludge promoter unit discharges the flocculent sludge and a small amount of granular sludge from the granular sludge tank into the sludge buffer tank. This process is accompanied by a drop in the liquid level, causing the drain outlet of the effluent stabilization unit to be exposed outside the liquid level. S3, Aeration Biochemical Reaction Stage: After the sludge is discharged, air enters the aeration uniform unit inside each granular sludge tank cultivation system through the aeration distribution unit to uniformly aerate the granular sludge tank cultivation system. At the same time, the exhaust unit regulates the air during the aeration process. During this stage, the undischarged flocculent sludge is transformed into granular sludge under the action of aeration shear force, and the particle size of the granular sludge increases to more than 0.2 mm. In this process, phosphorus adsorption and removal, biodegradation of organic pollutants and nitrification reaction are achieved to achieve the goal of wastewater purification. S4. Sludge recycling stage: During the aeration reaction stage, the sludge in the sludge buffer tank undergoes sludge-water separation through the sludge separation unit. The supernatant obtained from the separation is combined with the drainage from the granular sludge tank and discharged downstream for further treatment. The remaining sludge after sludge-water separation is discharged into the granular screening unit. After processing by the granular screening unit, the high-quality granular sludge selected is returned to the granular sludge tank or the influent buffer unit to replenish the granular sludge tank. At the same time, the flocculent sludge is discharged to the subsequent sludge treatment process. S5, Settlement Stabilization Stage: After the aeration phase ends, the granular sludge settles to the bottom of the granular sludge tank in preparation for a new round of wastewater injection; and While two of the granular sludge tanks are undergoing aeration or settling, at least one other granular sludge tank is undergoing influent and effluent discharge operations. The time ratio of the water inlet and drainage stage, sludge removal stage, aeration and biochemical reaction stage, and settling and stabilization stage is 1-1.5:0.01-0.1:1-2.5:0.1-1.

2. The operation method of the continuous feeding and draining water's aerobic granular sludge cultivation system according to claim 1, characterized in that, It also includes chemical dosing operations. When the total nitrogen removal efficiency in the granular sludge tank is reduced when the influent carbon-nitrogen ratio is less than 5 or the difference between the total nitrogen in the effluent and the discharge limit is within 1 mg / L, sodium acetate is added to the influent distribution unit or granular sludge tank by the chemical dosing system. When a decrease in phosphorus removal efficiency is detected in the granular sludge tank, polyaluminum chloride is added to the granular sludge tank or influent distribution unit by the dosing system.

3. The operation method of the continuous influent and effluent aerobic granular sludge cultivation system according to claim 1, characterized in that, After granulated sludge cultivation, the wastewater discharged in step S4 has a COD of 5-30 mg / L, ammonia nitrogen of less than 1 mg / L, total phosphorus of 0.1-0.5 mg / L, total nitrogen of less than 15 mg / L, and suspended solids of less than 10 mg / L. The particle size of the granulated sludge discharged during the sludge discharge stage is controlled below 0.2 mm, and the particle size of the granulated sludge recovered in the granular screening unit is above 0.1 mm.

4. A continuous influent and effluent aerobic granular sludge cultivation system based on the operating method according to any one of claims 1-3, characterized in that, The system includes an influent system, a sludge treatment system, an aeration system, and at least three independent granular sludge cultivation tanks. The aeration system includes an aeration distribution unit and multiple aeration homogenizer units, each installed within a corresponding granular sludge cultivation tank. Each granular sludge cultivation tank includes a granular sludge tank, in which aeration homogenizer units, water distribution homogenizer units, sludge promoter units, and drainage stabilization units are arranged sequentially from bottom to top. The aeration homogenizer units uniformly distribute the gas from the aeration system into the tank. Ensure good oxygen supply conditions for granular sludge; the water distribution homogenizer unit evenly distributes the pretreated influent into the tank, achieving effective contact between wastewater and microorganisms; the influent system is connected to the water distribution homogenizer unit so that the pretreated wastewater can evenly enter the granular sludge tank cultivation system; the sludge promoter unit is connected to the inlet of the sludge treatment system to effectively collect and transport the sludge generated during the treatment process; the sludge treatment system output is equipped with multiple branch return pipelines, of which at least one branch is used to discharge flocculent sludge, and the remaining branches are connected to the influent system or the granular sludge tank cultivation system; The aeration system includes an aeration distribution unit, which includes a blower, pipes, valves and flow meters to ensure uniform and controllable aeration; The water distribution homogenizer unit includes water distribution pipes, water distribution nozzles, flow regulating devices, screens, and liquid level control equipment to ensure that sewage enters the granular sludge tank cultivation system in a plug flow manner in a uniform and orderly manner. The water inlet system includes an inlet buffer unit and an inlet distribution unit. The outlet of the inlet buffer unit is connected to the inlet of the inlet distribution unit through a pipeline, and the outlet of the inlet distribution unit is connected to the water distribution homogenizer unit. The sludge treatment system includes a sludge buffer tank and a granular screen unit. The inlet of the sludge buffer tank is connected to the sludge promoter unit, and the outlet of the sludge buffer tank is connected to the granular screen unit. The sludge buffer tank is also equipped with a sludge separation unit and an outlet. The sludge separation unit treats the sludge-water mixture received from the granular sludge tank cultivation system for sludge-water separation, and discharges the supernatant in the sludge-water mixture together with the supernatant discharged from the granular sludge tank into the subsequent wastewater treatment unit. The granular screener unit is equipped with multiple branches for outputting sludge. At least one branch is used to discharge flocculent sludge, and the remaining branches are connected to the influent buffer unit or the granular sludge tank cultivation system to directly or indirectly return the screened granular sludge to the granular sludge tank. The drainage stabilization unit includes: a water collection tank, a liquid level control device, a flow stabilization device, an automatic control valve or pump, an anti-backflow design, an emergency discharge channel, and pipes connecting to subsequent treatment facilities. The drainage stabilization unit is installed at the top of the granular sludge tank to stably discharge the supernatant that meets the discharge standards, ensuring the stability of the sludge bed and preventing the formed granular sludge from being broken or floating.

5. The aerobic granular sludge cultivation system with continuous influent and effluent flow according to claim 4, characterized in that, The aeration system also includes multiple exhaust units, which are connected to the aeration uniformizer unit.

6. The aerobic granular sludge cultivation system with continuous influent and effluent flow according to claim 4, characterized in that, It also includes a dosing system, which is connected to the granular sludge tank and the influent distribution unit.

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