Aerobic granular sludge cultivation method and its application based on the reuse of sludge hydrothermal treatment products

Abstract

This invention discloses an aerobic granular sludge cultivation method and its application based on the reuse of hydrothermal treatment products from sludge, belonging to the technical field of wastewater biological treatment and sludge resource utilization. The method includes the following steps: collecting excess sludge discharged from the SBR reactor system, performing preliminary dewatering, and then subjecting it to hydrothermal treatment, followed by solid-liquid separation to obtain solid-phase hydrothermal carbon and liquid-phase process water; reusing the hydrothermal carbon in the sludge system of the SBR reactor system as a nucleus or framework material for microbial attachment and aggregation; mixing the process water with the original influent of the SBR reactor system, and cultivating aerobic granular sludge using an intermittent activated sludge process; each cycle of the intermittent activated sludge process sequentially includes influent, anaerobic stirring, aerobic aeration, sedimentation, and effluent discharge. This method can simultaneously achieve the synergistic coupling of excess sludge reduction and hydrothermal product resource reuse, accelerate the formation of aerobic granular sludge, and improve the system's settling performance, volumetric loading, and treatment capacity.

Description

Technical Field

[0001] This invention relates to the field of wastewater biological treatment and sludge resource utilization technology, specifically to an aerobic granular sludge cultivation method and its application based on the reuse of sludge hydrothermal treatment products. Background Technology

[0002] The sequencing batch reactor (SBR) process has been widely used in municipal wastewater treatment and some industrial wastewater treatment due to its compact process, flexible operation, and strong resistance to shock loads. With the increasing demand for upgrading and expanding wastewater treatment plants, how to increase biomass concentration, improve settling performance, and enhance nitrogen and phosphorus removal efficiency within existing tank volumes to improve system treatment capacity has become an important research direction in this field. Activated sludge removes organic matter, nitrogen, and phosphorus from wastewater through microbial metabolism and flocculation sedimentation. Conventional activated sludge has a loose flocculent structure and mainly separates through flocculation sedimentation, with a limited oxygen mass transfer gradient. Compared with conventional activated sludge, aerobic granular sludge has advantages such as dense structure, good settling performance, high biomass, strong resistance to shock loads, and the ability to remove multiple types of pollutants in a single reactor. It is considered an important direction for upgrading traditional activated sludge to high-efficiency biological treatment.

[0003] However, the cultivation of aerobic granular sludge in existing SBR systems often suffers from problems such as long start-up periods, unstable granule formation, and easy granule disintegration. This is especially true for municipal wastewater treatment plants with low influent concentrations, where the substrate selection pressure on microorganisms is insufficient, hindering the rapid formation and long-term maintenance of granular sludge. Existing technologies typically promote granulation by altering cultivation conditions. For example, Chinese patent document CN116477755A discloses a method for cultivating aerobic granular sludge. This invention utilizes a mixture of activated sludge and oily sludge used for treating aromatic hydrocarbon wastewater to construct an inoculated sludge system. An intermittent activated sludge method is used to cultivate aerobic granular sludge in this inoculated sludge system. Chinese patent document CN120208415A discloses a method for cultivating low-temperature aerobic granular sludge. This method employs high-concentration dissolved oxygen aeration and a long-cycle operation mode to enhance microbial carbon metabolism and extracellular polymer secretion, thereby improving the microorganisms' tolerance to low-temperature environments and their adhesion ability. However, these methods often suffer from high operating costs or insufficient industrial scale-up adaptability.

[0004] On the other hand, wastewater treatment plants continuously generate large amounts of excess sludge during operation. This excess sludge has high water content and poor stability, resulting in high costs for subsequent thickening, dewatering, transportation, and disposal, becoming a significant burden on wastewater treatment plant operations. Hydrothermal treatment technology can achieve sludge pyrolysis, volume reduction, and resource recovery under high temperature and autogenous pressure conditions, typically yielding solid-phase hydrothermal carbon and liquid-phase process water. Existing sludge hydrothermal treatment technologies mostly focus on sludge reduction, improved dewatering performance, or energy recovery, while paying insufficient attention to the synergistic reuse of hydrothermal carbon and process water within the wastewater treatment plant. This results in limited resource recovery and makes it difficult to form an integrated closed-loop process of "sludge reduction - material reuse - treatment enhancement."

[0005] Therefore, there is an urgent need to provide a new synergistic process suitable for SBR wastewater treatment plants, which can achieve a significant reduction in excess sludge while cultivating aerobic granular sludge, accelerate the formation of aerobic granular sludge and improve its stability, and further enhance the treatment efficiency and expansion potential of the wastewater treatment system. Summary of the Invention

[0006] To overcome the problems of slow start-up, insufficient stability, and disconnect between waste sludge reduction and resource utilization in existing SBR systems, this invention provides an aerobic granular sludge cultivation method and its application based on the reuse of sludge hydrothermal treatment products. This method uses hydrothermal carbon obtained from the hydrothermal treatment of waste sludge as granules to form crystal nuclei and reuses them in the SBR system. Process water is also reused in the influent system to increase substrate concentration and selectivity, thereby achieving rapid cultivation, stable maintenance, and synergistic reduction of waste sludge.

[0007] The specific technical solution adopted is as follows: An aerobic granular sludge cultivation method based on the reuse of sludge hydrothermal treatment products includes the following steps: The excess sludge discharged from the SBR reaction system is collected, preliminarily dewatered, and then subjected to hydrothermal treatment at 160-260℃ for 0.5-8 hours. The hydrothermal reaction products are then separated into solid and liquid phases to obtain solid hydrothermal carbon and liquid process water. Hydrothermal carbon is recycled into the sludge system of the SBR reactor, serving as a nucleus or framework material for microbial attachment and aggregation. Simultaneously, process water is mixed with the original influent of the SBR reactor, and aerobic granular sludge is cultivated using an intermittent activated sludge process. Each cycle of the intermittent activated sludge process involves sequential influent, anaerobic mixing, aerobic aeration, sedimentation, and drainage. During aerobic aeration, the dissolved oxygen concentration is controlled at 1-4 mg / L, and during cultivation, the pH of the sludge system is controlled at 6-9, and the temperature at 15-25℃.

[0008] This invention provides a hydrothermal treatment method for excess sludge. On one hand, it enables the resource utilization of excess sludge, allowing its organic components to undergo hydrolysis, pyrolysis, and recombination under specific hydrothermal conditions to obtain solid-phase hydrothermal carbon and liquid-phase process water. On the other hand, the hydrothermal carbon is reused in the sludge system of the SBR reactor, serving as a nucleus or framework material for microbial attachment, growth, and aggregation, promoting the transformation of flocculent sludge into aerobic granular sludge. Furthermore, all or part of the process water obtained from the hydrothermal treatment is reused in the influent system of the SBR reactor, which enhances the substrate selection pressure during SBR cycle operation, promotes the formation of aerobic granular sludge, and improves its stability. Simultaneously, by controlling the process operating conditions of the SBR system, aerobic granular sludge is cultivated and its stability is maintained, achieving the reduction of excess sludge and the on-site resource reuse of hydrothermal carbon and process water within the plant.

[0009] Furthermore, the total solids content of the residual sludge is 20-180 g / L, more preferably 40-120 g / L, and most preferably 60-100 g / L, preferably taken from the residual activated sludge discharged from the SBR reaction system.

[0010] Preferably, the remaining sludge is initially dewatered to a moisture content of 80%-85%.

[0011] Preferably, the temperature of the hydrothermal treatment is 160-240℃, more preferably 180-220℃; and the hydrothermal treatment time is 0.5-6 hours, more preferably 1-2 hours.

[0012] The hydrothermal carbon described herein serves as a crystal nucleus support, a carrier for microbial attachment, and a means of constructing an organic microenvironment. Its rough surface structure and oxygen-containing functional groups facilitate microbial adhesion, biofilm formation, and extracellular polymer accumulation, thereby promoting the generation of aerobic granular sludge and enhancing its resistance to shearing, impact, and disintegration.

[0013] Preferably, the hydrothermal carbon is crushed and sieved before being reused in the sludge system of the SBR reaction system. The particle size of the reused hydrothermal carbon is 1-500 μm, preferably 10-300 μm, and most preferably 50-150 μm.

[0014] Preferably, the hydrothermal carbon is added to the sludge system of the SBR reaction system at a concentration of 10-5000 mg / L mixed liquor. More preferably, it is added at a concentration of 3000-5000 mg / L mixed liquor during the aerobic granular sludge start-up phase and at a concentration of 20-100 mg / L mixed liquor during the normal operation phase. The hydrothermal carbon can be added continuously or intermittently during the aerobic granular sludge start-up phase, or it can be added supplementally during the stable operation phase of the system to enhance the stability of the granular structure.

[0015] Preferably, the process water undergoes one or more of the following treatments before reuse: flash evaporation, cooling, homogenization, and pH adjustment, in order to meet the requirements for stable operation of the SBR system.

[0016] Preferably, the reuse ratio of the process water is 0.05-1% of the original influent volume of the SBR reaction system cycle, more preferably 0.05-0.5%, and most preferably 0.05-0.1%. Reusing all or part of the process water in the wastewater treatment plant's influent system—for mixing with the original wastewater, replacing part of the makeup water, or returning it to the SBR influent section—increases the concentration of organic matter and / or soluble substrate in the influent, intensifies the selective pressure of "eutrophic uptake - oligotrophic metabolism," and thus promotes the formation of aerobic granular sludge. In this way, microorganisms can rapidly uptake high concentrations of substrate during the influent stage, and then undergo endogenous metabolism and structural remodeling during the subsequent aeration stage, which is more conducive to the formation and stability of granular sludge.

[0017] Furthermore, in the raw influent of the SBR reaction system, the COD is 100-1200 mg / L (preferably 150-600 mg / L), the ammonia nitrogen is 20-80 mg / L, the total nitrogen is 30-100 mg / L, and the total phosphorus is 4-10 mg / L.

[0018] The influent to the SBR reaction system is either municipal wastewater or industrial wastewater. Industrial wastewater includes food processing wastewater, brewing wastewater, and aquaculture wastewater. This invention is applicable not only to municipal wastewater treatment plants but also to wastewater treatment systems for food processing, brewing, aquaculture, and other industrial wastewater with good biodegradability. For different types of SBR systems, the hydrothermal carbon addition method and process water reuse ratio can be optimized based on the influent organic load, nitrogen-phosphorus ratio, hydraulic retention time, and target effluent standards to achieve a balance between sludge reduction and system enhancement.

[0019] The parameters for the intermittent activated sludge process include: one operating cycle is set to 3-6 hours, with 4-8 cycles per day; hydraulic retention time is 12-24 hours; influent time is 0.1-1 hour (more preferably 0.5-0.75 hours); anaerobic mixing time is 0.5-2 hours (more preferably 1.0-1.5 hours); aerobic aeration time is 1.5-4.0 hours (more preferably 2-3 hours); settling time is 5-30 minutes (more preferably 5-10 minutes); effluent ratio is 25%-50% (more preferably 30%-35%); sludge age is 10-25 days (more preferably 15-20 days); dissolved oxygen concentration during aerobic aeration is controlled at 1-4 mg / L (more preferably 1-3 mg / L); and surface air velocity is 0.3-2.5 cm / s (preferably 0.5-1.8 cm / s). These operating parameters can be adjusted according to the influent water quality and the granule cultivation stage. For example, in the early stage of granule cultivation, the sedimentation time should be appropriately shortened and a higher aeration shear should be maintained to eliminate flocculent sludge with poor settling performance; after the granules are gradually formed, the sludge age should be appropriately stabilized and the drainage ratio controlled to maintain the dominant position of granular sludge.

[0020] The optimal parameters for the intermittent activated sludge process include: a 6-hour operating cycle, 4 cycles per day, and a hydraulic retention time of 12 hours. Each operating cycle includes a 0.5-hour static influent stage, 2 hours of anaerobic agitation, 3.16 hours of aerobic aeration, a 5-minute sedimentation stage, and the remaining time as an idle stage. By shortening the sedimentation time, controlling the wastewater ratio (30%-35%), and increasing the aeration shear intensity (0.8-1.5 cm / s), aerobic granular sludge with good settling performance can be further screened and enriched.

[0021] By controlling parameters such as influent time, aeration time, sedimentation time, effluent ratio, hydraulic shear strength, dissolved oxygen concentration, and sludge age, the synergistic promoting effect of hydrothermal carbon recycling and process water recycling is regulated. Granular sludge with larger particle size, denser structure, and better settling performance is selected, and finally a stable aerobic granular sludge system is formed.

[0022] This invention also provides the application of the aforementioned aerobic granular sludge cultivation method in SBR wastewater treatment. Furthermore, during the cultivation process of the aerobic granular sludge, the state of the sludge is observed periodically to analyze and judge the degree of granulation and the long-term stability of the aerobic granular sludge. After a mature aerobic granular sludge system is formed and operated stably, the removal effect on pollutants in municipal wastewater is tested. Experimental results show that the corresponding method can enhance the pollutant removal effect of municipal wastewater with low raw water concentration.

[0023] Hydrothermal carbon and process water generated from sludge hydrothermal treatment are reused in situ in the aerobic granular sludge cultivation process, thereby accelerating the formation of aerobic granular sludge, improving granular stability, and further enhancing the treatment efficiency and expansion potential of the wastewater treatment system.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention performs hydrothermal treatment on the residual sludge generated by the sewage treatment plant. The resulting hydrothermal carbon is used as a crystal nucleus and recycled to the SBR system to cultivate aerobic granular sludge. At the same time, the process water generated by the hydrothermal treatment is recycled to the inlet or the reaction system, thereby increasing the organic matter concentration of the raw water and the selective pressure of the system. The synergistic effect of the reuse of hydrothermal carbon and process water is conducive to the rapid enrichment of microorganisms, the formation and stable maintenance of particle structure, and can significantly shorten the cultivation cycle of aerobic granular sludge, improve particle size, density and settling stability, and simultaneously achieve sludge reduction and the improvement of the wastewater treatment capacity of the SBR system.

[0025] (2) The present invention reuses the process water generated by hydrothermal treatment in the feed water system of the SBR reaction system, which increases the concentration of available substrates in the raw water and the system selectivity pressure, which is conducive to the rapid enrichment of microorganisms, the formation of particle structure and the stable maintenance, and is especially suitable for municipal sewage treatment scenarios with low raw water concentration.

[0026] (3) The method of the present invention organically couples sludge reduction, product resource utilization and reaction system enhancement. Without relying on a large amount of external carriers or additional carbon sources, it constructs a closed-loop utilization path within the sewage treatment plant, which can reduce the burden of sludge transportation and disposal and improve resource utilization efficiency.

[0027] (4) The aerobic granular sludge system formed by the method of the present invention has a higher biomass retention capacity and better sedimentation and separation performance, which can improve the volume load and treatment capacity of the SBR wastewater treatment reactor and provide technical support for the upgrading and expansion of existing SBR wastewater treatment plants.

[0028] (5) The process flow of the present invention can be coupled with existing sewage treatment plant facilities, the scope of engineering transformation is relatively controllable, and it has good promotion and application value. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of an aerobic granular sludge cultivation method based on the reuse of sludge hydrothermal treatment products.

[0030] Figure 2 A schematic diagram illustrating the process by which hydrothermal carbon and process water promote the formation of aerobic granular sludge.

[0031] Figure 3The following are comparative graphs showing the formation and settling performance of aerobic granular sludge in the examples and comparative examples, where (a) is a statistical graph of start-up time, (b) is a statistical graph of average particle size, and (c) is a statistical graph of sludge volume index after 30 minutes.

[0032] Figure 4 This is a comparison graph showing the pollutant removal effects in the examples and comparative examples. Detailed Implementation

[0033] To make the objectives, features, and advantages of this invention more apparent and understandable, a detailed description is provided below through specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below. Technical features in various embodiments of the invention can be combined appropriately without mutual conflict.

[0034] Unless otherwise specified, the operating methods in the following examples are generally performed under conventional conditions or as recommended by the manufacturer. Contents not described in detail in this specification are prior art known to those skilled in the art. Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0035] Example 1 like Figure 1 and Figure 2 As shown, a wastewater treatment plant using the SBR process treats municipal wastewater and discharges excess sludge during routine operation. The excess sludge is introduced into a sludge hydrothermal treatment unit, concentrated to 80% moisture content, and then transferred to a hydrothermal reactor for 2 hours at 200°C. This hydrothermal treatment causes the organic components in the sludge to decompose and reconstruct. After treatment, the hydrothermal reaction products are separated into solid and liquid phases to obtain solid-phase hydrothermal carbon and liquid-phase process water. The obtained hydrothermal carbon is pulverized and sieved for later use. The typical quality of the obtained process water is: COD 45000-70000 mg / L, SCOD 35000-60000 mg / L, volatile fatty acids (as COD) 4500-25000 mg / L, and ammonia nitrogen 1000-2000 mg / L. After being reused at the influent end, the overall influent COD increases to approximately 300-900 mg / L. The obtained process water is then cooled and homogenized for later use.

[0036] The aforementioned hydrothermal carbon was reused in the sludge system of the SBR reactor in the wastewater treatment plant. The average particle size of the reused hydrothermal carbon was 100 μm. It was added at a concentration of 4000 mg / L mixed liquor during the aerobic granular sludge start-up phase and at a concentration of 100 mg / L mixed liquor during normal operation. The process water was reused at the influent end of the SBR reactor at a rate of 0.1% of the cycle influent volume to increase the concentration of available organic matter in the raw water and enhance the matrix gradient during cycle operation. The raw influent to the SBR reactor simulated low-concentration municipal wastewater, with the following influent qualities: COD 220±50 mg / L, ammonia nitrogen 32±5 mg / L, total nitrogen 42±5 mg / L, and total phosphorus 4.5±0.4 mg / L. The raw influent to the SBR reactor was taken from the SBR system of a municipal wastewater treatment plant, with the initial MLSS controlled at approximately 3500 mg / L. The effective volume of the SBR reactor was 20. L. Aerobic granular sludge was cultivated using an intermittent activated sludge process at a temperature of 15-25℃. Each cycle of the intermittent activated sludge process consisted of influent, anaerobic mixing, aerobic aeration, sedimentation, and effluent discharge. The parameters for the intermittent activated sludge process included: a 6-hour operating cycle, 4 cycles per day, and a hydraulic retention time of 12 hours. Each operating cycle included a 0.5-hour static influent phase, 2 hours of anaerobic mixing, 3.16 hours of aerobic aeration, a 5-minute sedimentation phase, and the remaining time as a resting phase. The pH of the sludge system was 6-9, the effluent ratio was 25%-50%, the sludge age was 10-25 days, and the dissolved oxygen concentration was controlled at 1-4 mg / L during aerobic aeration. Sludge granulation was considered complete when the average particle size of the aerobic granular sludge reached 0.2 mm or more than 50%-60%. The cultivation period was 18 days.

[0037] Through the above process, the hydrothermal treatment products of sludge are not treated as external waste, but are instead reused in situ within the wastewater treatment plant. Specifically, the hydrothermal carbon provides the physical support and microscopic attachment sites necessary for particle formation, while the process water increases substrate supply and selective pressure. Together, these factors promote the rapid formation of aerobic granular sludge and improve the particles' resistance to shock loads and structural stability. Simultaneously, the volume and subsequent disposal burden of excess sludge are significantly reduced after hydrothermal treatment, achieving the simultaneous goals of sludge reduction and process enhancement.

[0038] Comparative Example 1 The only difference between the process steps and parameters of this invention and Example 1 is that hydrothermal carbon is not added and process water is not reused.

[0039] Comparative Example 2 The only difference between the process steps and parameters of this invention and Example 1 is that only recycled process water is added, and hydrothermal carbon is not added.

[0040] Comparative Example 3 The only difference between the process steps and parameters of this invention and Example 1 is that only hydrothermal carbon is added, and recycled process water is not added.

[0041] Sample Analysis (1) The particle formation and sedimentation properties of Comparative Example 1 and Comparative Examples 1-3 are shown in Table 1 and 2. Figure 3 As shown in (a)-(c).

[0042] Table 1 Particle formation and sedimentation properties

[0043] The results showed that both reusing process water alone and adding hydrothermal carbon alone could promote particle formation, but the synergistic effect of the two was more significant. Example 1 was superior to the comparative examples in terms of start-up time, particle size growth, and sedimentation performance improvement, indicating that the nucleation effect of hydrothermal carbon and the enhancement of substrate selection pressure by process water have a significant synergistic effect.

[0044] (2) The pollutant removal effects of Comparative Example 1 and Comparative Examples 1-3 are shown in Table 2 and 3. Figure 4 As shown.

[0045] Table 2 Pollutant Removal Efficiency

[0046] The results show that the embodiments of the present invention have the best performance in controlling effluent COD, ammonia nitrogen, total nitrogen and total phosphorus, indicating that the resource recycling technology of the present invention can not only promote the formation of granular sludge, but also simultaneously improve the comprehensive treatment performance of the reaction system.

[0047] (3) The sludge reduction and resource utilization effects of Example 1 and conventional sludge disposal mode are compared and the results are shown in Table 3.

[0048] Table 3. Sludge Reduction and Resource Utilization Effects

[0049] The above results demonstrate that this invention significantly reduces the amount of excess sludge transported off-site while achieving closed-loop utilization of sludge hydrothermal treatment products within the wastewater treatment plant. The resource recovery rate within the wastewater treatment plant is calculated as the proportion of the sum of the mass of hydrothermal carbon and process water reused in the SBR system or at the influent end to the total mass of the hydrothermal treatment products.

[0050] Further analysis of Comparative Examples 1-3: Comparative Example 1 did not include a sludge hydrothermal treatment unit, nor did it add any nucleating materials or process water reuse stream. The results showed that although the system could form some granular sludge after a relatively long operating cycle, the particle size was small, the structure was loose, the sludge volume index (SVI) was high, and the stability was poor, making it prone to disintegration after influent impact or load fluctuations. Comparative Example 2 included a process water reuse branch at the front end of the SBR system, reusing 0.1% of the process water obtained after sludge hydrothermal treatment at the influent end, but without adding hydrothermal carbon to the system. This method could promote sludge aggregation by increasing the substrate concentration and instantaneous selective pressure, and the particle formation rate was faster than that of conventional SBR. However, due to the lack of stable nuclei and structural support, the density and long-term stability of the resulting particles were still limited. Comparative Example 3 added 4.0 g / L hydrothermal carbon as a nucleation material to the SBR system, but did not reuse process water. This method significantly improved microbial attachment conditions, promoted the transformation of flocs into granular sludge, and improved settling performance. However, under low-concentration influent conditions, the system substrate gradient and selectivity were insufficient, and the granulation efficiency and pollutant removal enhancement were still lower than the scheme that simultaneously implemented process water reuse. Compared with the above comparative examples, the embodiment, through the dual coupling path of "hydrothermal carbon nucleation reuse + in-situ reuse of process water," showed superior effects in terms of rapid granular sludge formation, long-term stable maintenance, efficient pollutant removal, and excess sludge reduction, demonstrating a significant synergistic effect.

[0051] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for cultivating aerobic granular sludge based on the reuse of sludge hydrothermal treatment products, characterized in that, Includes the following steps: The excess sludge discharged from the SBR reaction system is collected, preliminarily dewatered, and then subjected to hydrothermal treatment at 160-260℃ for 0.5-8 hours. The hydrothermal reaction products are then separated into solid and liquid phases to obtain solid hydrothermal carbon and liquid process water. Hydrothermal carbon is recycled into the sludge system of the SBR reaction system, serving as a nucleus or framework material for microbial attachment and aggregation. At the same time, process water is mixed with the original influent of the SBR reaction system, and aerobic granular sludge is cultivated using the intermittent activated sludge method. In each cycle of the intermittent activated sludge process, the following operations are performed sequentially: influent, anaerobic mixing, aerobic aeration, sedimentation, and drainage. During aerobic aeration, the dissolved oxygen concentration is controlled at 1-4 mg / L. During the cultivation period, the pH of the sludge system is controlled at 6-9, and the temperature is controlled at 15-25℃.

2. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The remaining sludge is initially dewatered to a moisture content of 80%-85%.

3. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The hydrothermal carbon is crushed and sieved before being reused in the sludge system of the SBR reaction system; the particle size of the reused hydrothermal carbon is 1-500 μm.

4. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The hydrothermal carbon is added to the sludge system of the SBR reaction system at a concentration of 10-5000 mg / L mixed liquor.

5. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, Before being mixed with the raw influent of the SBR reaction system, the process water undergoes one or more of the following treatments: flash evaporation, cooling, homogenization, and pH adjustment.

6. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The reuse rate of process water is 0.05-1% of the original influent volume of the SBR reaction system per cycle.

7. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The raw influent to the SBR reaction system contains COD of 100-1200 mg / L, ammonia nitrogen of 20-80 mg / L, total nitrogen of 30-100 mg / L, and total phosphorus of 4-10 mg / L.

8. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The initial influent to the SBR reaction system is municipal wastewater or industrial wastewater.

9. The method for cultivating aerobic granular sludge according to claim 1, characterized in that, The parameters for the intermittent activated sludge process include: one operating cycle is set to 3-6 hours, 4-8 cycles per day, hydraulic retention time is 12-24 hours, influent time is 0.1-1.0 hours, anaerobic mixing time is 0.5-2.0 hours, aerobic aeration time is 1.5-4.0 hours, sedimentation time is 5-30 minutes, effluent ratio is 25%-50%, sludge age is 10-25 days, and dissolved oxygen concentration is controlled at 1-4 mg / L during aerobic aeration.

10. The application of the aerobic granular sludge cultivation method according to any one of claims 1-9 in SBR wastewater treatment.

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