Carbon core driven method for rapid expansion of anaerobic ammonia oxidation granular sludge

Abstract

The application discloses a kind of carbon core driven anaerobic ammonia oxidation granular sludge rapid expansion methods, comprising the following steps;Step 1: select agricultural waste sawdust as raw material, prepare biochar;Biochar is directly added to EGSB reactor, as the nucleation carrier of granular sludge;Step 2: set the operating conditions of EGSB reactor;Step 3: add flocculent anaerobic ammonia oxidation sludge to EGSB reactor, by biochar induction and hydraulic shear force synergistic effect, promote sludge from flocculent to granular transformation;Step 4: sludge enrichment and system load regulation, finally form carbon core Anammox granules.The present application realizes the rapid formation of carbon core Anammox granular sludge, greatly improves the settling performance of sludge and system denitrification efficiency.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei. Background Technology

[0002] Anaerobic ammonium oxidation (Anammox) is a novel and highly efficient biological nitrogen removal technology with significant advantages such as no need for external carbon sources, low energy consumption, high nitrogen removal efficiency, and low sludge production. It has been widely applied in the treatment of high-ammonia nitrogen wastewater and has good potential for energy conservation and sustainable development. However, Anammox technology still faces several key technical bottlenecks in engineering practice, especially the extremely slow growth rate of its core functional bacteria—anaerobic ammonium oxidizing bacteria (AnAOB) (doubling time approximately 21 days). This results in a long enrichment period and slow system start-up, becoming a major obstacle to its rapid promotion and stable operation.

[0003] In the Anammox system, the efficient and stable construction of granular sludge is crucial for achieving high-density enrichment of functional bacteria and improving system performance. Ideal Anammox granular sludge should possess a dense and regular structure, high AnAOB enrichment capacity, good settling properties, and resistance to shock loads. However, the formation process of existing granular sludge mainly relies on the natural aggregation of microorganisms and the flocculation process dominated by extracellular polymeric substances (EPS), lacking effective nucleation centers and structural support. This results in slow particle nucleation, loose structure, poor settling performance, easy particle disintegration and loss, and poor system operational stability.

[0004] Currently, commonly used sludge carrier materials are mostly inert materials such as polymer particles and ceramsite, which have the following shortcomings: First, the material cost is high, which is not conducive to large-scale engineering applications; second, the surface affinity with AnAOB is poor, which is not conducive to bacterial attachment and stable biofilm growth; third, the granular core lacks skeletal support, and the formed granules are easily broken and unstable. In addition, in EGSB (expanded granular sludge bed) systems, the effect of hydraulic parameters (such as reflux ratio, upflow velocity, etc.) on granulation has not yet formed an effective control strategy, which often leads to severe granule disturbance, blurred stratification, low granule formation efficiency, and difficulty in ensuring system settling performance and treatment stability.

[0005] Therefore, existing technologies still have the following significant shortcomings in promoting the rapid expansion and granulation of anammox sludge: ① The expansion rate of anammox sludge is low, and the system start-up cycle is long; ② The granular sludge has a loose structure and poor settling performance, and the particles are easy to disintegrate, affecting the stability of the system; ③ The carrier material is expensive and has poor biocompatibility, which is not conducive to cell colonization and stable particle formation; ④ The EGSB system lacks a synergistic hydraulic control strategy and fails to effectively drive the granulation process.

[0006] Therefore, there is an urgent need to develop a new carrier material with low cost and high biocompatibility to construct a stable granular skeleton structure. At the same time, by combining precise and efficient hydraulic control methods, the nucleation and granulation process of anammox sludge can be accelerated, significantly improving the granular settling performance and the system's denitrification capacity, thereby achieving rapid start-up and long-term stable operation of the Anammox system. Summary of the Invention

[0007] To overcome the above technical problems, the present invention aims to provide a method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei. By introducing natural porous sawdust biochar as a nucleation carrier and combining it with the high reflux ratio and upward flow velocity control of the EGSB system, the rapid formation of anammox carbon nuclei is achieved, which greatly improves the sludge settling performance and the system's denitrification efficiency.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei includes the following steps;

[0010] Step 1: Use agricultural waste wood chips as raw material to prepare biochar; add the biochar directly into the EGSB reactor as a nucleation carrier for granular sludge;

[0011] Step 2: Set the operating conditions for the EGSB reactor;

[0012] Step 3: Add flocculent anaerobic ammonia oxidation sludge to the EGSB reactor. Through the synergistic effect of biochar induction and hydraulic shear force, the sludge is transformed from flocculent to granular.

[0013] Step 4: Sludge enrichment and system load regulation are carried out to ultimately form anaerobic ammonia oxidation granular sludge with biochar as the core.

[0014] In step 1, biochar with a porous structure is prepared by pyrolysis at 300±20℃, and the biochar particle size is controlled to be about 2mm. The obtained biochar with a porous structure is directly added to the EGSB reactor as a nucleation carrier for granular sludge, and the addition amount is 10g / L.

[0015] The biochar prepared at this temperature possesses abundant functional groups (such as carboxyl and hydroxyl groups) and a significant porous structure, with micropores and mesopores dominating the pore size distribution, which is conducive to the attachment and growth of microorganisms. Furthermore, the biochar surface carries a certain negative charge, which can adsorb EPS and other microorganisms through electrostatic interactions, thus optimizing the microenvironment of granular sludge.

[0016] In step 1, the raw material for biochar is agricultural waste, such as sawdust, rice husks, or corn stalks.

[0017] Step 2 specifically involves:

[0018] The operating parameters of the EGSB reactor are controlled as follows: hydraulic upflow velocity range of 3.5–5.5 m / h, preferably 4.5 ± 0.5 m / h; reflux ratio controlled between 1.5 and 3, preferably 2; hydraulic retention time (HRT) controlled between 2 and 4 hours, preferably 3 hours; influent total nitrogen concentration of 300 mg / L, NH4+... + / NO2 - The molar ratio was 1:1; the reaction temperature was 35℃; and the pH was controlled within the range of 7.5–8.2.

[0019] The above operating parameters are set to provide an optimal growth and metabolic environment for anammox functional bacteria. Specifically, a suitable hydraulic upflow velocity prevents granular sludge loss and maintains a good sludge bed structure; a reasonable reflux ratio helps improve nitrogen transfer efficiency and the reactor's denitrification capacity; and the HRT setting ensures sufficient reaction while avoiding product accumulation and inhibition due to excessive residence time.

[0020] NH4 in water + / NO2 - Adding the bacteria at a 1:1 ratio conforms to the theoretical stoichiometric ratio for the Anammox reaction, which is conducive to the complete reaction. The mesophilic conditions of 35°C and the slightly alkaline pH help maintain the optimal enzyme activity of Anammox bacteria, thereby enhancing system stability and nitrogen removal efficiency.

[0021] Step 3 specifically involves:

[0022] In the initial stage of the reaction, a hydraulic upflow velocity of 3 m / h was used to promote the attachment and initial biofilm formation of anaerobic ammonia-oxidizing bacteria on the biochar surface; when NH4 + -N and NO2 - -N removal rate remained above 85% for a week, and NO3 production - When the -N ratio is close to the theoretical value (0.26), the system effluent fluctuation is less than ±10%, and the initial formation of particle structure is confirmed by microscopic observation, the reactor is considered to have entered the stable operation stage. The upward flow velocity can be gradually increased to 4.5 m / h to enhance particle collision and compaction and promote the formation of Anammox carbon core particles.

[0023] In step 3, during the granulation induction stage, 100 mL of anaerobic ammonia oxidation flocculent sludge with a particle size <1 mm is used for inoculation. Small-particle-size flocculent sludge has a higher specific surface area and better biological activity, enabling it to adapt to the new environment more quickly and initiate the Anammox reaction. Simultaneously, smaller-particle-size flocs are more likely to rapidly aggregate, settle, and granulate under the guidance of hydraulic shear force and the carrier surface, which is beneficial for forming dense granular sludge with good mass transfer performance. Through the synergistic effect of biochar induction and hydraulic shear force, the sludge is transformed from flocculent to granular, significantly shortening the enrichment time of granular sludge and laying the foundation for subsequent system load increases and stable operation.

[0024] In step 4, during system operation, the influent flow rate is gradually increased every 5-7 days, while maintaining NH4 levels. + -N / NO2 - The molar ratio of -N is 1:1;

[0025] During the cultivation process, indicators such as sludge particle size distribution, sludge volume index (SVI), denitrification efficiency, and volatile solids concentration (VSS) are continuously monitored to evaluate the granulation process and system performance.

[0026] The Anammox granules with a biochar core have a particle size of 2.5–3.2 mm and a biofilm thickness of 0.325–0.678 mm. The core layer consists of approximately 2 mm thick biochar as the core framework, with high porosity, providing physical space for microbial colonization and exhibiting good structural stability and pressure resistance, which helps the granular sludge maintain its integrity and good settling performance under shear force. The biochar surface initially adsorbs active anaerobic ammonia-oxidizing bacteria and flocculent particles, forming a primary biofilm. The porous structure and surface functional groups promote strong microbial attachment and induce EPS secretion. As the system operates and hydraulic conditions improve, the EPS generated between the microbial communities gradually aggregates and coats the entire particle, forming a dense and continuous shell with good mass transfer and structural integrity. Anaerobic ammonia-oxidizing bacteria account for approximately 50% of the biofilm.

[0027] The synergistic effect of hydraulic shear and biochar induction effectively promotes the rapid transformation of anaerobic ammonia oxidation sludge from flocculent to granular form. Biochar, acting as a nucleation carrier, utilizes its porous structure, surface functional groups, and negative charge to provide a template for microbial attachment and induce EPS secretion, constructing the core structure for particle formation. Simultaneously, the moderate hydraulic shear force in the EGSB reactor enhances collision and aggregation among microorganisms, driving the biofilm to evolve into three-dimensional particles, thereby improving particle density and structural stability. This synergistic effect significantly accelerates the formation and enrichment of granular sludge, stabilizing the average particle size in the system at 1–3 mm, and increasing the proportion of particles larger than 2 mm to no less than 21.4%, laying a solid foundation for subsequent system load increases and efficient nitrogen removal operation.

[0028] The obtained Anammox granules with biochar cores exhibit excellent settling performance and structural stability, with a settling velocity ≥35 m / h, a sludge volume index (SVI) below 15 mL / g, and a mechanical strength exceeding 98%, demonstrating significant resistance to hydraulic erosion. The granules possess a dense internal structure, with biochar serving as the core framework to enhance overall strength and stability. The EPS-rich outer shell forms a synergistic adsorption interface with the biochar surface, effectively capturing and buffering intermediate metabolites (such as NO2). - NO3 - (etc.), which slows down the inhibitory effect on functional bacteria, thereby improving the stability of system operation. At the same time, the dense particle structure is conducive to increasing the specific activity of microorganisms per unit volume and particle density, accelerating particle settling rate, and enhancing the reactor's ability to withstand high load operation.

[0029] The beneficial effects of this invention are:

[0030] (1) It significantly accelerates the growth rate of sludge, with the growth rate of anammox sludge reaching 0.161 gVSS / (L·d), which is more than 3 times that of the control group (0.054 gVSS / (L·d)).

[0031] (2) By optimizing hydraulic conditions (such as upflow velocity and reflux ratio) to achieve precise control, the rapid formation of granular sludge can be effectively promoted, significantly shortening the system start-up cycle from the traditional approximately 30 days to less than 20 days. The mechanism is as follows: Appropriate hydraulic shear force helps suspended flocs continuously collide, aggregate, and compact during flow, promoting their evolution into more stable three-dimensional particles; on the other hand, it accelerates the removal of weakly bound microorganisms and excess EPS from the particle surface, selectively retaining structurally stable and dense particles, thereby improving the overall particle quality. Furthermore, hydraulic disturbance enhances mass transfer efficiency, which is beneficial for anaerobic ammonia oxidizing bacteria and substrates (NH4+). + With NO2 -The full contact and reaction between the microorganisms accelerates the recovery of microbial activity and the enrichment of dominant bacterial groups, thereby synergistically improving the system's particle formation efficiency and denitrification performance.

[0032] (3) The obtained Anammox charcoal core particles have a dense structure and excellent performance, with a particle size of 2.5–3.2 mm and a biofilm thickness of 0.325–0.678 mm. The core layer is composed of porous wood-based biochar with high porosity. As a stable skeletal structure, it not only provides abundant space for microbial colonization but also possesses good pressure resistance and structural integrity, helping to maintain the particle's intact shape and excellent settling performance under hydraulic shear forces. The biochar surface preferentially adsorbs active anaerobic ammonia-oxidizing bacteria and flocculent micro-clusters, forming a primary bacterial film. Its rich pore structure and surface functional groups promote the firm attachment of microorganisms and induce EPS secretion. With prolonged operation and enhanced hydraulic conditions, the bacterial community continuously secretes EPS and gradually accumulates on the particle surface, forming a dense and continuous "bacterial floc shell" layer, further improving the particle's structural stability and mass transfer performance. The Anammox carbon core particles have a settling velocity of up to 35 m / h, an SVI of less than 15 mL / g, and a mechanical strength of over 98%. The abundance of anaerobic ammonia-oxidizing bacteria in the biofilm is about 50%, providing a solid microbial foundation for the system to achieve efficient and stable denitrification.

[0033] (4) The system has good resistance to shock loads, and the denitrification efficiency deviation is less than 5% under the condition of fluctuating influent ammonia nitrogen concentration;

[0034] (5) The present invention uses natural porous biochar as a carrier, which significantly reduces material costs and has good prospects for practical application and promotion. Attached Figure Description

[0035] Figure 1 This is a schematic diagram showing the changes in sludge concentration.

[0036] Figure 2 This is a schematic diagram of the specific growth rate of sludge.

[0037] Figure 3 This diagram illustrates the variation in sludge particle size distribution. a represents sludge <2mm, b represents sludge 0.25-1mm, c represents sludge 1-2mm, and d represents sludge >2mm.

[0038] Figure 4 This study examines the evolution process and microstructural characteristics of Anammox particles in carbon nuclei.

[0039] Figure 5 This is a schematic diagram of the three-dimensional structure of Anammox particles with carbon nuclei, obtained using micro-CT technology. a is a frontal three-dimensional view, b is a side three-dimensional view, c is a frontal view, and d is a side view.

[0040] Figure 6 This is a quantitative analysis chart showing the volume percentage of granular sludge and its biofilm. Detailed Implementation

[0041] The present invention will now be described in further detail with reference to the accompanying drawings.

[0042] This embodiment provides a rapid expansion method for anaerobic ammonia oxidation granular sludge driven by carbon cores. The experiment was carried out in an EGSB (expanded granular sludge bed) reactor with an effective volume of 1L.

[0043] (1) Preparation and addition of biochar carrier

[0044] Wood chips were used as raw material and pyrolyzed in a pyrolysis furnace at 300℃ for 2 hours under nitrogen protection. The resulting biochar was sieved, and particles with a diameter of approximately 2 mm were selected for the experiment. The specific surface area of ​​this biochar was 8.12 m². 2 / g, pore volume 0.49cm 3 / g, possessing good microbial adhesion properties. 10g / L biochar was added to the reactor as a nucleation carrier for granular sludge.

[0045] (2) Setting operating conditions for the EGSB reactor

[0046] The reactor's operating parameters are set as follows:

[0047] The initial hydraulic upflow velocity was set at 3.0 m / h to promote biofilm formation by anaerobic ammonia-oxidizing bacteria on the biochar surface. After stable operation, the velocity was gradually increased to 4.5 m / h to enhance the collision frequency between sludge and biochar and improve particle compaction. The reflux ratio was set to 2; the hydraulic retention time (HRT) was 3 hours; and the total nitrogen concentration in the influent was 300 mg / L, with NH4+ concentrations of 300 mg / L and 4+, 50 mg / L ... + -N and NO2 - The molar ratio of -N is 1:1; the temperature is kept constant at 35℃, and the pH value is controlled between 7.5 and 8.0.

[0048] (3) Granular sludge induction start-up

[0049] Inoculate the reactor with 100 mL of flocculent anammox sludge (particle size <1 mm) from a stably operating Anammox system. In the initial stage of the system, maintain a low upflow velocity (3.0 m / h) and a low influent load to facilitate the initial attachment of the microorganisms to the biochar surface.

[0050] (4) Sludge enrichment and system load regulation

[0051] Starting from day 7, gradually increase the influent flow rate every 5–7 days to increase the system load, while maintaining NH4 levels. + -N / NO2 -The -N molar ratio was 1:1. Samples were collected every 3 days throughout the entire cultivation period for the following analysis: average sludge particle size; particle size distribution percentage; SVI (sludge volume index); settling velocity; particle mechanical strength; denitrification efficiency; and VSS concentration.

[0052] (5) Operation results and particle properties

[0053] After 90 days of operation, a large number of Anammox particles with biochar cores and anaerobic ammonia-oxidizing bacteria layers as outer shells were formed in the reactor, with particles larger than 2 mm accounting for 21.4%. The sludge growth rate reached 0.161 gVSS / (L·d), more than three times that of the group without biochar. The settling velocity reached 35.6 m / h, the SVI value decreased to 13.7 mL / g, and the mechanical strength of the granular sludge was measured to be 98.4% by compression test. The total nitrogen removal efficiency of the system was stably maintained above 91.5%, and the system showed good shock resistance during operation, with nitrogen removal efficiency fluctuations of less than 4% when the influent ammonia nitrogen fluctuated by ±50 mg / L.

[0054] (6) Anammox particle formation cycle

[0055] Through biochar-induced nucleation, optimized hydraulic conditions, and load control, the rapid transformation of sludge from flocculent to granular form was achieved, reaching a stable operating state within a short period. The formation cycle of Anammox granules is approximately 90 days, significantly shortening the traditional cultivation time. Biochar, with its porous structure, surface charge, and excellent adsorption properties, promotes microbial attachment and EPS secretion, accelerating biofilm formation and granular structure construction. The resulting granules, with biochar as the core framework and a dense microbial community and EPS coating, exhibit good structural stability, excellent settling performance, and efficient mass transfer capacity, providing a solid foundation for stable system operation and large-scale application.

[0056] (7) Application prospects and uses

[0057] The anammox particles with carbon cores prepared by this method possess advantages such as structural stability, excellent settling performance, high mass transfer efficiency, and strong reactivity, demonstrating broad application potential. This granular sludge is expected to be used for the efficient treatment of high-nitrogen wastewater, such as landfill leachate, aquaculture wastewater, and dewatered sludge supernatant; it is also suitable as the main reactive sludge in short-process anammox denitrification processes, replacing traditional nitrification-denitrification systems to achieve energy conservation and emission reduction; simultaneously, it can be used as highly active seed sludge in one-stage and two-stage anammox reactors, enabling rapid system start-up and improved stability. Furthermore, this granular sludge has significant scientific research value and application prospects in the study of anammox mechanisms and pilot-scale scale-up, and can be further expanded to innovative applications in related biological denitrification and sludge engineering fields in the future.

[0058] The main features of the Anammox carbon core particles of this invention include:

[0059] (1) Addition of biochar: Biochar serves as a nucleation carrier. Its porous structure and functional groups provide an ideal template for microbial attachment. At the same time, its negative charge is conducive to the adsorption of extracellular polymers (EPS), providing a material basis for the formation of biofilm.

[0060] (2) Hydraulic regulation and shearing: During the particle induction stage, the hydraulic upward flow velocity is gradually increased to enhance the collision and compaction between particles, and promote the aggregation of bacterial flocs on the surface of biochar to form a dense shell.

[0061] (3) Addition of small-particle-size floc seed mud: Small-particle-size flocs with high activity and large surface area can be quickly adsorbed on the surface of biochar, serving as the basis for the outer layer of bacterial flocs and further improving the structure of Anammox particles in the carbon core.

[0062] Functional advantages: Improves the structural stability and water erosion resistance of granular sludge; the EPS and biochar in the shell synergistically adsorb intermediate metabolites, improving system stability; helps to increase specific activity and particle density, accelerates settling rate and system load capacity.

[0063] From the appendix Figure 1 , Figure 2 It can be seen that the addition of biochar significantly increased both MLSS and MLVSS in the system, indicating that biochar significantly promoted the rapid expansion of anaerobic ammonia oxidation granular sludge. From day 30 to day 90 after the reaction, the sludge concentration in the biochar group was consistently higher than that in the control group, and the difference gradually increased over time. Especially on day 90, the sludge concentration in the biochar group reached approximately 5.3 times its initial value and 2.36 times that of the control group, indicating that biochar had a significant promoting effect during system startup and granular sludge enrichment. The growth rate curves of the microorganisms in the control and biochar groups over time show that the overall growth rate of the microorganisms in the biochar group was higher than that in the control group, and the peak occurred earlier, indicating that the introduction of biochar accelerated the reproduction of the dominant bacterial community and the system startup process.

[0064] From the appendix Figure 3As the operating time progressed, the proportion of sludge particles smaller than 1 mm gradually decreased, and the rate of decrease in the biochar group was significantly faster than that in the control group, indicating that biochar accelerated the transformation of sludge from flocs to granules. Particularly in the 1–2 mm and larger particle size range, the proportion of granules in the biochar group continuously increased, significantly higher than the control group, reflecting the significant promoting effect of biochar on the formation of medium and large particles. This is mainly attributed to the induction of Anammox particles with char nuclei. Biochar, as a stable nucleation core, facilitates EPS secretion and bacterial aggregation, thereby promoting particle growth and structural maturation. In contrast, under conditions without external loading (control group), the spontaneous granulation ability of sludge was limited, and the proportion of medium and large-sized particles changed slowly. Therefore, biochar not only optimized the sludge particle size distribution and improved the homogeneity and stability of the particle structure, but also provided crucial support for the rapid acquisition of granular sludge.

[0065] From the appendix Figure 4 It can be seen that Anammox granular sludge with biochar cores exhibits distinct stages of evolution during rapid cultivation. Biochar, as a stable nucleation core, provides support for microbial attachment and initial biofilm growth, promoting the gradual formation and maturation of the granular structure. In the initial stage, microorganisms first aggregate and colonize on the biochar surface, followed by the gradual expansion of the biofilm, forming a covering shell, and finally developing into mature granules with a dense structure and stable morphology.

[0066] The left side of the image shows a schematic diagram of the reactor structure and a real-world image of the granulation and rapid expansion process. The middle section shows the appearance changes of the granular sludge during the colonization, growth, and maturity stages, revealing that the granules gradually become rounded, with the black biochar core gradually enveloped by an orange-red bacterial film. The right side shows the microstructure characterization results; scanning electron microscopy images show a continuous biofilm formed on the biochar surface, with a thickness of approximately 0.561 mm. Further fluorescence in situ hybridization (FISH) analysis reveals a high bacterial abundance in the biofilm, with anaerobic ammonia-oxidizing bacteria (AnAOB) showing a highly enriched distribution at the biochar boundary. This indicates that biochar not only promotes biofilm formation but also achieves the targeted enrichment of functional bacteria, playing a crucial role in granular structure construction and reaction function.

[0067] From the appendix Figure 5The granules are generally spherical or ellipsoidal in shape, with a dense internal structure and strong encapsulation. Analysis of the grayscale differences in the images reveals that the biofilm thickness of the granular sludge ranges from approximately 0.277 mm to 0.687 mm, exhibiting a distinct concentric ring structure of "core-shell," further verifying the structural characteristics of biochar as the nucleation core and the outer shell composed of microbial extracellular matrix and cell bodies. A certain number of small pores exist within the granules, providing favorable conditions for mass transfer and reaction in the system. This CT image reveals the internal spatial organization of the biochar-induced Anammox granular sludge at the microscopic scale, providing important evidence for evaluating the granule formation quality and stability.

[0068] Appendix Figure 6 Further quantitative analysis of the grayscale information in the CT images revealed that the total particle volume was 20.93 mm. 3 The biofilm volume was 10.43 mm. 3 This represents 48.95% of the total particle volume. This result verifies the abundant distribution of biofilm within the particles at the volume level, indicating the formation of a stable and continuous biofilm structure induced by biochar. This provides crucial data support for subsequent evaluation of granular sludge quality and improvement of system performance.

Claims

1. A method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei, characterized in that, Includes the following steps; Step 1: Use agricultural waste wood chips as raw material to prepare biochar; add the biochar directly into the EGSB reactor as a nucleation carrier for granular sludge; Step 2: Set the operating conditions for the EGSB reactor; Step 3: Add flocculent anaerobic ammonia oxidation sludge to the EGSB reactor; The synergistic effect of biochar induction and hydraulic shear force promotes the transformation of sludge from flocculent to granular. Step 4: Sludge enrichment and system load regulation are carried out to ultimately form anaerobic ammonia oxidation granular sludge with biochar core; The anaerobic ammonia oxidation granular sludge uses biochar as its core, with a particle size of 2.5–3.2 mm and a biofilm thickness of 0.325–0.678 mm. The core layer consists of 2 mm diameter biochar as its core framework. The biochar surface first adsorbs active anaerobic ammonia oxidizing bacteria and flocculent particles to form a primary bacterial film. The porous structure and surface functional groups promote the firm attachment of microorganisms and induce EPS secretion. As the system operates and hydraulic conditions improve, the EPS generated between the microbial communities gradually aggregates and coats the entire particle, forming a dense and continuous shell. The proportion of anaerobic ammonia oxidizing bacteria in the biofilm is 50%. The average particle size of the anaerobic ammonia oxidation granular sludge with biochar core in the system is stable at 2.5–3.2 mm, and the proportion of particles with a diameter greater than 2 mm is increased to no less than 21.4%. Step 2 specifically involves: The operating parameters of the EGSB reactor are controlled as follows: hydraulic upflow velocity range of 3.5–5.5 m / h, reflux ratio controlled between 1.5 and 3, hydraulic retention time controlled between 2 and 4 hours, influent total nitrogen concentration of 300 mg / L, and NH4+ concentration of 300 mg / L. + / NO2 - The molar ratio was 1:1; the reaction temperature was 35℃, and the pH was controlled at 7.5–8.

2. Step 3 specifically involves: In the initial stage of the reaction, a hydraulic upflow velocity of 3 m / h was used to promote the attachment and initial biofilm formation of anaerobic ammonia-oxidizing bacteria on the biochar surface; when NH4 + -N and NO2 - -N removal rate remained above 85% for a week, and NO3 production - When the -N ratio is close to the theoretical value, the fluctuation of the system effluent is less than ±10%, and the initial formation of the particle structure is confirmed by microscopic observation, the reactor is considered to have entered the stable operation stage, and the upward flow velocity is gradually increased to 4.5 m / h.

2. The method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei according to claim 1, characterized in that, In step 1, biochar with a porous structure is prepared by pyrolysis at 300±20℃, and the biochar particle size is controlled to be 2mm; the dosage is 10g / L, which is used as a nucleation carrier for the formation of granular sludge.

3. The method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei according to claim 1, characterized in that, In step 1, the raw material for biochar is agricultural waste, which is one of sawdust, rice husks or corn stalks. The surface of biochar carries a certain negative charge and adsorbs EPS through electrostatic action.

4. The method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei according to claim 1, characterized in that, In step 3, during the granulation induction stage, anaerobic ammonia oxidation flocculent seed mud with a particle size of <1mm is used for inoculation.

5. The method for rapid expansion and cultivation of anaerobic ammonia oxidation granular sludge driven by carbon nuclei according to claim 1, characterized in that, In step 4, during system operation, the influent flow rate is gradually increased every 5-7 days, while maintaining NH4 levels. + -N / NO2 - The molar ratio of -N is 1:1.

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