A device and method for disposing of calcified canda particles of sludge based on particle size classification

Abstract

The present application relates to sewage biological denitrification and sludge resource treatment technical field, disclose a kind of based on particle size classification's calcification CANDAN granular sludge disposal device and method, comprising: particle size classification unit, respectively with ultrasonic recovery unit, CANDAN granular sludge reactor and phosphorus recovery component communication, the ultrasonic recovery unit with granule rescreening unit communication, the granule rescreening unit with CANDAN granular sludge reactor communication.Differentiated disposal of calcification CANDAN granular sludge is realized by particle size classification, large particle size granules with recovery potential are recycled after low-intensity ultrasonic treatment, and are used for denitrification with medium particle size granules, to reduce functional sludge loss and improve particle mass transfer conditions;At the same time, small particle size granules and residues that are difficult to recover are acid-dissolved to release phosphorus and precipitate to recover, to realize the activity recovery of calcification granular sludge, effective sludge reuse and phosphorus resource utilization, to reduce the impact of traditional acid washing or overall sludge discharge on system stability.

Description

Technical Field

[0001] This invention relates to the field of wastewater biological denitrification and sludge resource utilization technology, and in particular to a device and method for treating calcified CANDAN granular sludge based on particle size classification. Background Technology

[0002] As the wastewater treatment industry moves towards low-carbon, energy-saving, and resource-based development, autotrophic nitrogen removal technology based on anaerobic ammonia oxidation has attracted widespread attention. Among them, the CANDAN process converts nitrate nitrogen into nitrite nitrogen through short-cut denitrification, and then anaerobic ammonia oxidizing bacteria further utilize nitrite nitrogen and ammonia nitrogen to achieve simultaneous nitrogen removal. This process can achieve synergistic removal of ammonia nitrogen and nitrate nitrogen while reducing the demand for external carbon sources and aeration energy consumption, and has good engineering application potential.

[0003] To improve the retention capacity, settling performance, and system stability of granular sludge related to anammox, current research and engineering practices often promote granular sludge formation and stabilization through calcium phosphate mineral induction, hydroxyapatite enhancement, or other inorganic mineral coupling methods. This type of CANDAN-HAP granular sludge system can improve particle density and shock resistance to a certain extent, and also possesses the potential for phosphorus enrichment or removal. However, during long-term operation, calcium ions and phosphates in the influent, as well as the alkaline microenvironment formed within the system, may promote the continuous deposition of calcium phosphate minerals. When inorganic deposits accumulate excessively on the particle surface or inside the pores, a dense mineralized coating layer easily forms, hindering substrate transfer into the particle interior, reducing the activity of anammox bacteria and related functional microorganisms, ultimately resulting in decreased ammonia nitrogen removal rate, poorer total nitrogen removal efficiency, and calcification and deactivation of the granular sludge.

[0004] Existing treatment methods for calcified granular sludge mainly include acid washing, chemical dissolution, sludge removal and replacement, or re-inoculation. While acid washing or chemical dissolution can remove some inorganic deposits, it easily causes damage to microbial cells, disruption of extracellular polymer structures, and disintegration of granular sludge. Direct sludge removal or replacement leads to the loss of functional sludge, especially for slow-growing anaerobic ammonia-oxidizing bacteria, resulting in long system recovery cycles and poor operational stability. Furthermore, existing treatment methods typically treat calcified granular sludge as a whole, failing to fully consider the differences in calcification degree, structural integrity, activity recovery potential, and resource value among particles of different sizes. This easily leads to the waste of recoverable particles or the accumulation of ineffective particles through recirculation.

[0005] In fact, different particle size components in calcified CANDAN granular sludge have different disposal values. For example, large-sized particles often have a more complete granular skeleton and the potential to retain internal functional bacteria, but the surface mineralization is heavier, making them suitable for reuse after weakening the inorganic coating layer through low-intensity physical action; medium-sized particles usually still have good settling properties and biological activity, and can be directly returned to maintain the effective sludge volume in the reactor; small-sized particles, fragments, and residues are mostly characterized by broken structures, poor settling performance, or a high degree of inorganic mineral enrichment, and continued return may increase the system burden, but the calcium and phosphorus minerals enriched in them have phosphorus resource recovery value.

[0006] In view of this, how to provide a method that can differentiate the treatment of calcified granular sludge according to its particle size and structural state, so as to gently restore the activity of recoverable granules and reuse them, and to recover small particles, fragments and residues that are difficult to restore by acid dissolution of phosphorus and precipitation crystallization, thereby simultaneously realizing the activity restoration of calcified CANDAN granular sludge, effective sludge reuse and phosphorus resource utilization, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a particle size-based CANDAN granular sludge treatment device and method. Addressing the problems of particle calcification, limited mass transfer, decreased sludge activity, and insufficient phosphorus resource recovery caused by calcium and phosphorus mineral deposition during the long-term operation of CANDAN-HAP granular sludge, this invention establishes a synergistic treatment method of "particle size classification—differentiated treatment—activated sludge reuse—calcium and phosphorus resource recovery." This method can reduce functional sludge loss while achieving the classification and restoration of calcified granular sludge and the resource utilization of ineffective mineralized components. It is applicable to the operation, maintenance, and risk control of CANDAN, CANDAN-HAP, and short-cut denitrification / anaerobic ammonia oxidation coupled granular sludge systems in the treatment of calcium-, phosphorus-, and nitrogen-containing wastewater, thus solving the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention provides a calcified CANDAN granular sludge treatment device based on particle size classification, comprising: a particle size classification unit, which is connected to an ultrasonic recovery unit, a CANDAN granular sludge reactor and a phosphorus recovery component, wherein the ultrasonic recovery unit is connected to a particle re-screening unit and the particle re-screening unit is connected to the CANDAN granular sludge reactor. The particle size classification unit and particle re-screening unit are used to screen calcified CANDAN granular sludge according to particle size. The ultrasonic recovery unit is used to restore the activity of calcified CANDAN granular sludge. The CANDAN granular sludge reactor is used to denitrify nitrogen-containing wastewater. The phosphorus recovery component is used to recover phosphorus from calcified CANDAN granular sludge.

[0009] Furthermore, the phosphorus recovery assembly includes: The acid-dissolving phosphorus unit is used to acid-dissolve calcified CANDAN granular sludge to form a mixed liquor containing soluble calcium. 2+ and PO4 3- ; A solid-liquid separation unit, connected to the acid-dissolving phosphorus unit, is used to separate the mixture into a supernatant and residual solids. The precipitation and crystallization unit is connected to the solid-liquid separation unit, so that phosphorus in the supernatant is precipitated in the form of hydroxyapatite, amorphous calcium phosphorus, magnesium ammonium phosphate or other calcium phosphorus precipitates and recovered by the phosphorus product recovery unit.

[0010] This invention also provides a method for treating calcified CANDAN granular sludge based on particle size classification, using a particle size classification-based calcified CANDAN granular sludge treatment device, comprising the following steps: S1: The calcified CANDAN granular sludge is removed from the CANDAN granular sludge reactor and placed into the particle size classification unit, where it is sieved into large, medium, and small particles according to particle size. Large particles are sent to the ultrasonic recovery unit for ultrasonic activity restoration treatment; medium particles are sent to the CANDAN granular sludge reactor for denitrification of nitrogenous wastewater; and small particles are sent to the acid dissolution and phosphorus release unit to form a mixed solution containing soluble calcium carbonate. 2+ and PO4 3- ; S2: The solid-liquid separation unit separates the mixture into supernatant and residual solids, and the precipitation and crystallization unit precipitates phosphorus in the supernatant as phosphorus product and recovers it through the phosphorus product recovery unit.

[0011] Furthermore, it also includes the following steps: After large-diameter particles undergo ultrasonic activity restoration treatment in the ultrasonic restoration unit, they are sieved into return particles and residue in the particle re-sieving unit. The return particles are sent to the CANDAN granular sludge reactor for denitrification, while the residue is sent to the acid-dissolving phosphorus unit.

[0012] Furthermore, the particle size of large-diameter particles is greater than 1.0 mm, the particle size of medium-diameter particles and reflux particles is 0.5-1.0 mm, and the particle size of small-diameter particles and residue is less than 0.5 mm.

[0013] Furthermore, the ultrasonic recovery unit has an ultrasonic frequency of 20-50kHz, a processing time of 5-30min for large-diameter particles, a temperature of 15-35℃ during the processing, and a sludge volume fraction controlled at 5%-40%.

[0014] Furthermore, the acid-dissolving phosphorus unit uses hydrochloric acid, nitric acid, acetic acid, citric acid, or a combination thereof, with a pH of 3.0-5.5, a reaction time of 5-120 min, and a stirring intensity of 50-300 rpm.

[0015] Furthermore, in step S2, when the target product to be recovered is calcium phosphorus, a calcium source is added to the supernatant or the Ca / P molar ratio is adjusted to 1.5-1.8, and the pH is adjusted to 7.5-10.5, so that phosphorus precipitates out in the form of hydroxyapatite, amorphous calcium phosphorus, or other calcium phosphorus precipitates; when the target product to be recovered is magnesium ammonium phosphate, a magnesium source and an ammonium source are added to the supernatant to control the Mg / N / P molar ratio at 1.0-1.5:1.0-1.5:1, and the pH is adjusted to 7.5-9.5, so that phosphorus precipitates out as magnesium ammonium phosphate crystals.

[0016] Furthermore, the CANDAN granular sludge reactor can be a sequencing batch reactor, an upflow sludge bed reactor, a continuous flow granular sludge reactor, or an internal circulation granular sludge reactor.

[0017] Furthermore, when NH4 appears in the CANDAN granular sludge reactor... + When -N increases, TN removal rate decreases, particle color becomes lighter, particle density increases, the proportion of calcified CANDAN granular sludge with a particle size greater than 1.0 mm increases, the proportion of calcified CANDAN granular sludge with a particle size less than 0.5 mm increases, or calcium and phosphorus content accumulates, repeat steps S1-S2.

[0018] The present invention discloses the following technical effects: Differentiated treatment of calcified CANDAN granular sludge is achieved through particle size classification. Large-diameter particles with recovery potential are recycled after low-intensity ultrasonic treatment and used together with medium-diameter particles for denitrification, reducing functional sludge loss and improving particle mass transfer conditions. At the same time, small-diameter particles and residues that are difficult to recover are acid-dissolved for phosphorus and precipitated for crystallization recovery, realizing the activity restoration of calcified granular sludge, effective sludge reuse, and phosphorus resource utilization, reducing the impact of traditional acid washing or overall sludge discharge on system stability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a layout diagram of the calcified CANDAN granular sludge treatment device based on particle size classification according to the present invention. The system includes: 1. Particle size classification unit; 2. Ultrasonic recovery unit; 3. Particle re-screening unit; 4. CANDAN granular sludge reactor; 5. Acid-dissolving phosphorus unit; 6. Solid-liquid separation unit; 7. Precipitation and crystallization unit; and 8. Phosphorus product recovery unit. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Those skilled in the art will understand that the term "comprising" as used in this application means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements present. Furthermore, "connected" or "coupled" as used herein can include wireless connections or wireless coupling. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1 As shown, this embodiment of the invention provides a calcified CANDAN granular sludge treatment device based on particle size classification, including: a particle size classification unit 1, which is connected to an ultrasonic recovery unit 2, a CANDAN granular sludge reactor 4 and a phosphorus recovery component, respectively; the ultrasonic recovery unit 2 is connected to a particle re-screening unit 3; and the particle re-screening unit 3 is connected to the CANDAN granular sludge reactor 4. The particle size classification unit 1 and the particle re-screening unit 3 are used to screen the calcified CANDAN granular sludge according to particle size. The ultrasonic recovery unit 2 is used to restore the activity of the calcified CANDAN granular sludge. The CANDAN granular sludge reactor 4 is used to denitrify nitrogen-containing wastewater. The phosphorus recovery component is used to recover phosphorus from the calcified CANDAN granular sludge.

[0025] In some embodiments, the phosphorus recovery assembly includes: Acid-dissolving phosphorus unit 5 is used to acid-dissolve calcified CANDAN granular sludge to form a mixed liquor containing soluble Ca. 2+and PO4 3- ; Solid-liquid separation unit 6 is connected to acid-dissolving phosphorus unit 5 and is used to separate the mixture into supernatant and residual solids. The precipitation and crystallization unit 7 is connected to the solid-liquid separation unit 6, so that phosphorus in the supernatant is precipitated in the form of hydroxyapatite, amorphous calcium phosphorus, magnesium ammonium phosphate or other calcium phosphorus precipitates and recovered by the phosphorus product recovery unit 8.

[0026] This invention also provides a method for treating calcified CANDAN granular sludge based on particle size classification, using a particle size classification-based calcified CANDAN granular sludge treatment device, comprising the following steps: S1: The calcified CANDAN granular sludge is removed from the CANDAN granular sludge reactor 4 and placed into the particle size classification unit 1. Based on particle size, it is sieved into large, medium, and small particles. Large particles retain a relatively intact particle structure and high functional bacteria retention potential, and are sent to the ultrasonic recovery unit 2 for low-intensity ultrasonic activity recovery treatment. Medium particles still have good settling performance and biological activity and are directly sent to the CANDAN granular sludge reactor 4 for denitrification of nitrogenous wastewater. Small particles (including fragments), due to their broken structure, poor settling performance, or high enrichment of calcium and phosphorus minerals, are sent to the acid dissolution phosphorus unit 5, where acid dissolution forms a mixed liquid containing soluble calcium and phosphorus. 2+ and PO4 3- ; S2: The solid-liquid separation unit 6 separates the mixture into supernatant and residual solid. The precipitation and crystallization unit 7 precipitates phosphorus in the supernatant as a phosphorus product and recovers it through the phosphorus product recovery unit 8.

[0027] For medium-sized particles, if their settling properties, color characteristics, activity indicators, or nitrogen conversion performance meet the reuse requirements, they can be directly recycled to the CANDAN granular sludge reactor 4. If medium-sized particles exhibit mild calcification or surface mineral coating, they can also be sent to the ultrasonic recovery unit 2 for short-term, low-intensity ultrasonic treatment, with a treatment time of 3-15 minutes. Generally, medium-sized particles usually have good biological activity retention capacity and high recycling value, and can serve as the main sludge source for restoring the functional sludge concentration and particle structure stability within the reactor.

[0028] In some embodiments, the following steps are also included: After large-diameter particles undergo ultrasonic activity restoration treatment in ultrasonic restoration unit 2, they are sieved into return particles and residue (including fragments) through particle re-sieving unit 3. The return particles are sent to CANDAN granular sludge reactor 4 for denitrification, and the residue is sent to acid dissolution phosphorus unit 5.

[0029] In some embodiments, the particle size of large-diameter particles is greater than 1.0 mm, the particle size of medium-diameter particles and reflux particles is 0.5-1.0 mm, and the particle size of small-diameter particles and residue is less than 0.5 mm.

[0030] In some embodiments, the ultrasonic frequency of the ultrasonic recovery unit 2 is 20-50 kHz, the treatment time for large-diameter particles is 5-30 min, the temperature during treatment is 15-35℃, and the sludge volume fraction is controlled at 5%-40%. Ultrasonic cavitation and micro-shearing disrupt the dense inorganic coating layer on the particle surface or in the pores, promoting the recovery of mass transfer channels within the particles, while minimizing irreversible damage to anaerobic ammonia-oxidizing bacteria and short-range denitrifying bacteria.

[0031] In some embodiments, the acid-dissolving phosphorus unit 5 uses hydrochloric acid, nitric acid, acetic acid, citric acid, or combinations thereof, with a pH of 3.0-5.5, a reaction time of 5-120 min, and a stirring intensity of 50-300 rpm. The acid-dissolving phosphorus unit 5 can release calcium phosphate minerals, HAP, amorphous calcium phosphate precipitates, and other inorganic sediments from small-diameter particles and residues into soluble calcium phosphate. 2+ PO4 3- .

[0032] In some embodiments, after the solid-liquid separation unit 6 separates the mixture into a supernatant and residual solids, the residual solids can be washed and then disposed of, refluxed, or further stabilized depending on their organic matter content and activity.

[0033] In some embodiments, in step S2, when the target product to be recovered is calcium phosphate, a calcium source is added to the supernatant or the Ca / P molar ratio is adjusted to 1.5-1.8, and the pH is adjusted to 7.5-10.5, so that phosphorus precipitates out as hydroxyapatite, amorphous calcium phosphate, or other calcium phosphate precipitates. When the target product to be recovered is magnesium ammonium phosphate, a magnesium source and an ammonium source are added to the supernatant to control the Mg / N / P molar ratio at 1.0-1.5:1.0-1.5:1, and the pH is adjusted to 7.5-9.5, so that phosphorus crystallizes out as magnesium ammonium phosphate. The crystallized product is then settled, filtered, and dried to obtain a recoverable phosphorus product, which can be used for phosphorus resource utilization or as a raw material for slow-release fertilizers.

[0034] In some embodiments, the CANDAN granular sludge reactor 4 is a sequencing batch reactor, an upflow sludge bed reactor, a continuous flow granular sludge reactor, or an internal circulation granular sludge reactor. The CANDAN granular sludge reactor 4 operates under anoxic or anaerobic stirring conditions, utilizing short-range denitrifying bacteria to reduce nitrate nitrogen to nitrite nitrogen, which is then autotrophically removed by anaerobic ammonia-oxidizing bacteria using both nitrite and ammonia nitrogen. When the effluent ammonia nitrogen and total nitrogen removal performance gradually recovers and the particle settling performance stabilizes, granular reflux operation continues. When effluent ammonia nitrogen levels rise, total nitrogen removal rate decreases, or significant calcification reappears on the particle surface, steps S1 and S2 are repeated.

[0035] In some embodiments, pH and NH4 can be monitored online or offline during the operation of the CANDAN granular sludge reactor 4. + -N, NH3 - -N, NO2 - -N, TN, COD, Ca 2+ PO4 3- The parameters include sludge concentration, SVI, particle size distribution, and effluent turbidity. When the ammonia nitrogen concentration in the effluent of CANDAN granular sludge reactor 4 continues to rise or the total nitrogen removal rate falls below the set value, the ultrasonic treatment ratio of ultrasonic recovery unit 2 is increased or the ultrasonic treatment time is extended; when the particle breakage ratio increases after ultrasonic treatment or the suspended solids in the effluent increase, the ultrasonic treatment time or ultrasonic intensity of ultrasonic recovery unit 2 is reduced; when NH4 appears in CANDAN granular sludge reactor 4... + When -N increases, TN removal rate decreases (10%-30% lower than stable operation), particle color lightens, particle density increases, the proportion of calcified CANDAN granular sludge with a particle size greater than 1.0 mm increases (reaching 20%-50%), the proportion of calcified CANDAN granular sludge with a particle size less than 0.5 mm increases (reaching 10%-30%), or calcium and phosphorus content accumulates, repeat steps S1-S2.

[0036] To further illustrate the technical effects of the present invention, the following examples are provided in conjunction with the graded treatment process of calcified CANDAN-HAP granular sludge. In the examples, before screening, particles larger than 1.0 mm accounted for 56.4% of the calcified granular sludge, particles between 0.5 and 1.0 mm accounted for 29.6%, and particles and fragments smaller than 0.5 mm accounted for 14.0%; the original NH4 in the CANDAN granular sludge reactor... + The nitrogen removal rate was 64.6%, the total nitrogen (TN) removal rate was 74.8%, and the sludge denitrification activity was 42.3 mg N / (g VSS·h). The CANDAN granular sludge reactor was operated at a temperature of 28±2℃ under anoxic or anaerobic conditions with stirring.

[0037] Table 1. Main operating conditions for different embodiments Table 2 Main technical effects of different embodiments As shown in Tables 1 and 2, after particle size classification, large-diameter calcified particles can have their surface mineralization coating weakened and their sludge denitrification activity improved by low-intensity ultrasonic treatment. Medium-diameter particles can maintain the effective sludge quantity in the reactor after direct or short-term treatment followed by recirculation. Small-diameter particles, fragments, and ultrasonic residues can achieve high phosphorus release and recovery rates after acid dissolution of phosphorus and precipitation crystallization treatment. These results indicate that the present invention can simultaneously achieve sludge activity restoration of calcified CANDAN particles, effective sludge reuse, and phosphorus resource recovery.

[0038] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0039] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0040] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A device for treating calcified CANDAN granular sludge based on particle size classification, characterized in that, include: The particle size classification unit (1) is connected to the ultrasonic recovery unit (2), the CANDAN granular sludge reactor (4) and the phosphorus recovery component, respectively. The ultrasonic recovery unit (2) is connected to the particle re-screening unit (3), and the particle re-screening unit (3) is connected to the CANDAN granular sludge reactor (4). The particle size classification unit (1) and particle re-screening unit (3) are used to screen calcified CANDAN granular sludge according to particle size. The ultrasonic recovery unit (2) is used to restore the activity of calcified CANDAN granular sludge. The CANDAN granular sludge reactor (4) is used to denitrify nitrogen-containing wastewater. The phosphorus recovery component is used to recover phosphorus from calcified CANDAN granular sludge.

2. The calcified CANDAN granular sludge treatment device based on particle size classification according to claim 1, characterized in that, The phosphorus recovery assembly includes: The acid-dissolving phosphorus unit (5) is used to acid-dissolve calcified CANDAN granular sludge to form a mixed liquor containing soluble Ca. 2+ and PO4 3- ; The solid-liquid separation unit (6) is connected to the acid-dissolving phosphorus unit (5) and is used to separate the mixture into supernatant and residual solids; The precipitation crystallization unit (7) is connected to the solid-liquid separation unit (6) so that phosphorus in the supernatant is precipitated in the form of hydroxyapatite, amorphous calcium phosphorus, magnesium ammonium phosphate or other calcium phosphorus precipitates and recovered by the phosphorus product recovery unit (8).

3. A method for treating calcified CANDAN granular sludge based on particle size classification, characterized in that, The application of the calcified CANDAN granular sludge treatment device based on particle size classification as described in claim 2 includes the following steps: S1: The calcified CANDAN granular sludge is removed from the CANDAN granular sludge reactor (4) and placed into the particle size classification unit (1), where it is sieved into large-diameter, medium-diameter, and small-diameter particles according to their particle size. Among them, the large-diameter particles are sent to the ultrasonic recovery unit (2) for ultrasonic activity recovery treatment, the medium-diameter particles are sent to the CANDAN granular sludge reactor (4) for denitrification, and the small-diameter particles are sent to the acid dissolution phosphorus release unit (5) to form a mixed liquid containing soluble Ca. 2+ and PO4 3- ; S2: The solid-liquid separation unit (6) separates the mixture into supernatant and residual solid, and the precipitation and crystallization unit (7) precipitates phosphorus in the supernatant as phosphorus product and recovers it through the phosphorus product recovery unit (8).

4. The method for treating calcified CANDAN granular sludge based on particle size classification according to claim 3, characterized in that, It also includes the following steps: After the large-diameter particles are subjected to ultrasonic activity restoration treatment by the ultrasonic restoration unit (2), they are screened into return particles and residue by the particle re-screening unit (3). The return particles are sent to the CANDAN granular sludge reactor (4) for denitrification of nitrogen-containing wastewater, and the residue is sent to the acid dissolution phosphorus unit (5).

5. The method for treating calcified CANDAN granular sludge based on particle size classification according to claim 4, characterized in that, Large-diameter particles have a diameter greater than 1.0 mm, medium-diameter particles and reflux particles have a diameter of 0.5-1.0 mm, and small-diameter particles and residues have a diameter less than 0.5 mm.

6. The method for treating calcified CANDAN granular sludge based on particle size classification according to claim 3, characterized in that, The ultrasonic recovery unit (2) has an ultrasonic frequency of 20-50kHz, a treatment time of 5-30min for large-diameter particles, a temperature of 15-35℃ during the treatment process, and a sludge volume fraction controlled at 5%-40%.

7. The method for treating calcified CANDAN granular sludge based on particle size classification according to claim 3, characterized in that, The acid-dissolving phosphorus unit (5) uses hydrochloric acid, nitric acid, acetic acid, citric acid or a combination thereof, with a pH of 3.0-5.5, a reaction time of 5-120 min, and a stirring intensity of 50-300 rpm.

8. A method for treating calcified CANDAN granular sludge based on particle size classification according to claim 3, characterized in that, In step S2, when the target product to be recovered is calcium phosphorus, a calcium source is added to the supernatant or the Ca / P molar ratio is adjusted to 1.5-1.8, and the pH is adjusted to 7.5-10.5, so that phosphorus precipitates out in the form of hydroxyapatite, amorphous calcium phosphorus, or other calcium phosphorus precipitates; when the target product to be recovered is magnesium ammonium phosphate, a magnesium source and an ammonium source are added to the supernatant to control the Mg / N / P molar ratio at 1.0-1.5:1.0-1.5:1, and the pH is adjusted to 7.5-9.5, so that phosphorus precipitates out as magnesium ammonium phosphate crystals.

9. A method for treating calcified CANDAN granular sludge based on particle size classification according to claim 3, characterized in that, The CANDAN granular sludge reactor (4) is a sequencing batch reactor, an upflow sludge bed reactor, a continuous flow granular sludge reactor, or an internal circulation granular sludge reactor.

10. A method for treating calcified CANDAN granular sludge based on particle size classification according to claim 3, characterized in that, When NH4 appears in the CANDAN granular sludge reactor (4) + When -N increases, TN removal rate decreases, particle color becomes lighter, particle density increases, the proportion of calcified CANDAN granular sludge with a particle size greater than 1.0 mm increases, the proportion of calcified CANDAN granular sludge with a particle size less than 0.5 mm increases, or calcium and phosphorus content accumulates, repeat steps S1-S2.

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