Composite carbon source particle for rapid denitrification, and preparation method therefor and use thereof

Abstract

Provided are a composite carbon source particle for rapid denitrification, and a preparation method therefor and the use thereof. The composite carbon source particle for rapid denitrification is prepared from raw materials including a sustained-release framework, a carbon source and an optional functionalized modification material. The composite carbon source particle for rapid denitrification can ensure the stable supply of a carbon source to microorganisms during the whole denitrification process, prevents a reduction in denitrification efficiency caused by discontinuous or non-uniform supply of a carbon source, has the characteristics of easily forming a biofilm, good fluidizability, stable carbon release, long-lasting carbon supply, relatively high mechanical strength, low cost, a wide application range, low risk of fragmentation, a long service cycle and a large specific surface area, and can be applied as a microbial carrier to a biological sewage treatment system.

Description

Fast denitrification composite carbon source particles, and preparation method and application thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment materials, and further relates to fast denitrification composite carbon source particles, and a preparation method and application thereof. BACKGROUND

[0002] With the rapid economic development and the acceleration of urbanization process, the discharge of domestic sewage and industrial sewage is increasing, which makes the task of sewage treatment heavier year by year. In order to implement the national "14th Five-Year Plan" and continue to improve the environmental quality, the local governments have increased the efforts to treat sewage and put forward more stringent discharge standards for sewage treatment plants, which undoubtedly increases the difficulty of sewage treatment. The biochemical treatment of sewage utilizes microorganisms to take up carbon (C), nitrogen (N) and phosphorus (P) in water to promote their own growth while treating sewage. Generally speaking, when the carbon-nitrogen ratio (C / N) is 20:1-30:1, microorganisms can fully utilize organic matter and nitrogen for growth and metabolism, thereby achieving good sewage treatment effect. However, the excessive use of pesticides and fertilizers has led to a serious imbalance in the C / N of the sewage system in China, with a large increase in N and P content, and microorganisms lacking carbon sources cannot actively obtain organic matter in water for biosynthesis, resulting in that the N content in the tail water after biological sewage treatment still does not meet the standard. Therefore, the addition of carbon source to ensure sufficient carbon source in sewage is the key to realizing sewage treatment.

[0003] Due to the difficulty in controlling the dosage of liquid carbon source, excessive or insufficient dosage will affect the water quality. Solid carbon source has the advantage of controllable dosage, and has attracted attention. Among them, natural carbon source has large carbon release amount and low cost, but its carbon release is unstable and the mechanical strength is relatively low; synthetic polymer carbon source has relatively stable and controllable carbon release and relatively high mechanical strength, but its price is expensive. Therefore, the core creativity of the present application lies in combining the advantages of the two types of solid carbon sources, designing and regulating the formula, proportion and structure to develop new composite carbon source particles with excellent performance and high cost-effectiveness. However, due to the significant differences in chemical composition and physical properties between natural carbon source and synthetic carbon source, how to effectively realize the uniform mixing of the two materials to ensure the consistency and performance stability of the final product, and how to improve the mechanical strength of the composite material while maintaining excellent carbon release performance to ensure the durability and operation reliability of the material in actual application are technical problems to be solved by the present application.

[0004] Bio-fluidized bed is a new type of sewage treatment technology with high efficiency, which combines the advantages of traditional activated sludge process and biofilm process, and introduces chemical fluidization technology. Microorganisms are attached to carrier particles, and the large specific surface area of the carrier particles provides sufficient space for the growth of microorganisms, thereby effectively increasing the concentration of microorganisms in the system, and having the advantages of high reaction efficiency, low sludge yield, high organic load, strong impact resistance, small occupied area, etc.

[0005] However, in the conventional bio-fluidized bed sewage treatment system, the commonly used particles such as volcanic rock, glass beads, zeolite, polyethylene, polypropylene and polystyrene can only be used as a carrier for microbial attachment, and cannot provide carbon source for the growth of microorganisms, so it is impossible to achieve the purpose of adding carbon source. The particles that can provide carbon source are currently mainly used in biological filter or fixed bed denitrification system, which has slow sewage treatment rate, high operation cost and low utilization efficiency of carbon source.

[0006] Therefore, it is also necessary to develop a carrier suitable for bio-fluidized bed.

[0007] SUMMARY

[0008] To solve the problems in the prior art, the present application provides a rapid nitrogen removal composite carbon source particle and a preparation method and application thereof. The present application combines the advantages of two types of solid carbon sources (natural carbon source and artificial synthetic carbon source), and develops a new type of composite carbon source particle with excellent performance and high cost-effectiveness by designing and regulating the formula, proportion and structure. The rapid nitrogen removal composite carbon source particle prepared by the present application can ensure stable carbon source supply for microorganisms during the entire nitrogen removal process, avoiding the decrease of nitrogen removal efficiency caused by discontinuous or uneven carbon source supply. The rapid nitrogen removal composite carbon source particle prepared by the present application also has the characteristics of easy biofilm formation, easy fluidization, stable carbon release, long-lasting carbon supply, high mechanical strength, low cost, wide application range, not easy to break, long service life and large specific surface area. The rapid nitrogen removal composite carbon source particle of the present application can be used as a microbial carrier in a biological sewage treatment system. On the one hand, the large specific surface area of the particle can provide sufficient space for the growth of microorganisms, thereby increasing the concentration of microorganisms. On the other hand, the particle itself and the carbon source released by the degradation of the particle under the action of microorganisms can adjust the C / N of the treated sewage system and enhance the impact resistance of the system.

[0009] One of the purposes of the present application is to provide a rapid nitrogen removal composite carbon source particle, which is prepared from raw materials including a slow-release skeleton, a carbon source and an optional functional modification material;

[0010] The slow-release skeleton is selected from a non-water-soluble high molecular material or a hydrophilic high molecular material which swells into a gel when contacted with water; and the carbon source includes at least one of a natural carbon source or an artificial synthetic polymer carbon source;

[0011] The content of the slow-release skeleton is 40-80% based on the total mass of the slow-release skeleton and the carbon source being 100 wt%.

[0012] In the fast denitrification composite carbon source particles described in the application, preferably,

[0013] The carbon source is selected from natural carbon sources and artificial synthetic polymer carbon sources;

[0014] Preferably, the content of the slow-release skeleton is 40-80% based on the total mass of the slow-release skeleton and the carbon source being 100 wt%.

[0015] The content of the slow-release skeleton is 40-80% based on the total mass of the slow-release skeleton and the carbon source being 100 wt.%; such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, and any parameter range composed of any two of the above parameters.

[0016] The content of the natural carbon source is 10-50%; such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and any parameter range composed of any two of the above parameters.

[0017] The content of the artificial synthetic polymer carbon source is 10-50%; such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and any parameter range composed of any two of the above parameters.

[0018] Through multiple tests, the application explores the best molding and carbon release formula of the slow-release skeleton and the carbon source, and the preparation of fast denitrification composite carbon source particles with different structures by functional modification on the basis of the slow-release skeleton and the carbon source.

[0019] The natural carbon source and the artificial synthetic polymer are mixed to prepare a composite carbon source core. Suitable melt blending or specific coupling agents are used to improve the compatibility of the two types of carbon sources, so as to realize the effective combination and uniform dispersion of the two types of carbon sources.

[0020] At the same time, the application precisely controls the carbon release rate and improves the mechanical strength of the new carbon source particles by fine control of the formula and production process, such as temperature control, ratio adjustment of various materials and additives, structure change and optimization of curing time, and at the same time, the composite carbon source is endowed with hydrophilicity, biocompatibility, roughness, porosity and magnetic characteristics. Through the above method, the application develops a new type of composite carbon source particle, which not only has the advantages of easy biofilm formation, easy fluidization, stable carbon release, strong carbon supply capacity, high mechanical strength and low price, but also realizes the overall optimization of cost and performance, and shows significant creativity and practical value.

[0021] The quick denitrification composite carbon source particles of the present application can selectively add or not add functional modification materials according to the use requirements; the functional modification materials include one or more of hydrophilic agents, biological affinity substances, adsorbents, magnetic substances, microbial rapid growth and reproduction promoters, and pore-forming agents; the functional modification materials endow the quick denitrification composite carbon source particles with hydrophilicity, biological affinity, roughness, porosity, magnetism and other characteristics; the quick denitrification composite carbon source particles of the present application have the characteristics of easy biofilm formation, easy fluidization, stable carbon release, long-lasting carbon supply, high mechanical strength, low cost and wide application range.

[0022] In the quick denitrification composite carbon source particles of the present application, preferably,

[0023] The non-water-soluble high molecular material is selected from at least one of polyethylene (PE), polypropylene (PP), polystyrene (PS) or polyolefin elastomer; and / or,

[0024] The water-swelling gel-forming hydrophilic high molecular material is selected from at least one of natural gum materials, cellulose materials, non-cellulose polysaccharides, ethylene polymers or acrylic resins; and / or,

[0025] The natural carbon source is selected from at least one of corn cob (OS), wheat straw, straw, rice husk, reed, wood chips, reed, sugarcane residue, cattail or peanut shell; and / or,

[0026] The artificial synthetic polymer carbon source is selected from at least one of poly-3-hydroxybutyric acid (PHB), polycaprolactone (PCL), polybutylene succinate (PBS), polylactic acid (PLA), polyhydroxyalkanoate (PHA), poly-β-carboxybutyric acid valerate (PHBV), polyhydroxybutyrate hexanoate (PHBH), poly-3-hydroxybutyric acid-4-hydroxybutyric acid ester (P34HB);

[0027] Preferably,

[0028] The natural gum material is selected from at least one of sodium alginate (SA), gum arabic, agarose; and / or,

[0029] The cellulose material is selected from at least one of hydroxypropyl methyl cellulose (HPMC), methyl cellulose (MC), hydroxyethyl cellulose (HEC); and / or,

[0030] The non-cellulose polysaccharide is selected from at least one of chitosan or galactomannan; and / or,

[0031] The ethylene polymer is selected from polyvinyl alcohol (PVA); and / or,

[0032] The acrylic resin is selected from carbomer.

[0033] In the fast denitrification composite carbon source particles described in the present application, preferably,

[0034] The functional modification material includes at least one of a hydrophilic agent, a biological affinity substance, an adsorbent, a magnetic substance, a microbial rapid growth and reproduction promoter, a pore-forming agent, a dispersion coupling agent or a wetting agent;

[0035] Preferably,

[0036] The hydrophilic agent accounts for 1-10% of the total mass of the slow-release skeleton and carbon source; and / or,

[0037] The biological affinity substance accounts for 1-10% of the total mass of the slow-release skeleton and carbon source; and / or,

[0038] The adsorbent accounts for 1-5% of the total mass of the slow-release skeleton and carbon source; and / or,

[0039] The magnetic substance accounts for 3-15% of the total mass of the slow-release skeleton and carbon source; and / or,

[0040] The microbial rapid growth and reproduction promoter accounts for 0.5-5% of the total mass of the slow-release skeleton and carbon source; and / or,

[0041] The pore-forming agent accounts for 0.5-5% of the total mass of the slow-release skeleton and carbon source; and / or,

[0042] The dispersion coupling agent accounts for 0.1-2% of the total mass of the slow-release skeleton and carbon source; and / or,

[0043] The wetting agent accounts for 0.1-1% of the total mass of the slow-release skeleton and carbon source.

[0044] In the fast denitrification composite carbon source particles described in the present application, preferably,

[0045] The functional modification material includes at least one of a hydrophilic agent, a biological affinity substance, an adsorbent, a magnetic substance, a microbial rapid growth and reproduction promoter, a pore-forming agent, a dispersion coupling agent or a wetting agent;

[0046] Preferably,

[0047] The hydrophilic agent is selected from at least one of polyvinyl alcohol, silicon dioxide, polyacrylamide or stearic acid; and / or,

[0048] The biological affinity substance is selected from at least one of agar, starch or calcium alginate; and / or,

[0049] The adsorbent is selected from at least one of activated carbon, silica gel, aluminum oxide, natural clay or biochar; and / or,

[0050] the magnetic substance is selected from at least one of ferrite (ordinary ferrite), strontium ferrite or barium ferrite; and / or,

[0051] the microbial rapid growth and reproduction promoter is selected from trace element powder; selected from at least one of iron, magnesium, zinc, copper, manganese, molybdenum or selenium; and / or,

[0052] the pore-forming agent is selected from at least one of sodium bicarbonate, ammonium bicarbonate, industrial urea or starch; and / or,

[0053] the dispersing coupling agent is selected from at least one of a silane coupling agent or an acid ester coupling agent; preferably, the silane coupling agent is selected from at least one of γ-aminopropyl triethoxysilane (KH-550) or vinyl triethoxysilane (VTES); the acid ester coupling agent is selected from at least one of titanium tetraacetate, titanium isopropylate, tetrabutyl zirconium or zirconium acrylate; and / or,

[0054] the wetting agent comprises at least one selected from pine oil, liquid paraffin, white mineral oil, stearic acid or water.

[0055] The quick denitrification composite carbon source particle of the present application, the slow-release skeleton (i.e. base skeleton) has good formability, stable chemical properties in water, and good mechanical and thermal properties; the carbon source material can provide carbon source for the growth and metabolism of microorganisms; the hydrophilic agent can improve the hydrophilic property of the particle to improve the mass transfer efficiency of the substrate on the surface thereof in sewage; the biological affinity material can improve the microbial affinity of the particle surface; the adsorbent can effectively enhance the adsorption capacity of the particle surface; the magnetic material can endow the particle with certain magnetism; the microbial rapid growth promoter can accelerate the adhesion and growth of microorganisms and biofilm on the particle surface; the pore-forming agent can increase the porosity and roughness of the particle surface, which is beneficial to the adhesion of microorganisms. The addition of the dispersing coupling agent can well improve the compatibility between the inner core and the functional material during the preparation process; the addition of the wetting agent can prevent the caking between materials during the preparation process. All the materials used in the quick denitrification composite carbon source particle of the present application not only play their own roles, but also exhibit synergistic effects under the combined application and specific proportion, which not only enhances the basic properties of the materials, but also improves the overall efficiency and stability. For example, at high temperature, the base skeleton and the artificial synthetic polymer carbon source material will exhibit a molten state, while the natural fiber material will not melt but decompose at a certain temperature. This difference enables the molten skeleton and the polymer carbon source to surround and fill into the voids generated by the decomposition of the natural carbon source, forming a pore structure. Therefore, their organic combination realizes a particle with good mechanical strength and more pore structures, and the porosity and pore size can be controlled by adjusting the proportion of different components to meet different application requirements. In addition, when the hydrophilic agent improves the hydrophilic property of the particle surface, making the particle more easily contact with the microorganisms in water, the biological affinity material further promotes the stable adhesion and growth of these microorganisms on the particle surface, and the two synergistically improve the efficiency of the microorganisms in treating sewage.

[0056] The mass percentage of the base skeleton, carbon source material and functional modification material of the composite carbon source inner core is a scheme after multiple experiments and improvements, which can meet the smooth processing and molding of the particle; in particular, the ratio of the base skeleton and the carbon source material of the composite carbon source inner core of the present application is specially designed.

[0057] The second object of the present application is to provide a preparation method of the quick denitrification composite carbon source particle of the first object of the present application, which is selected from the following three methods:

[0058] Method one, comprising the following steps: mixing raw materials including slow-release skeleton material, carbon source and optional functional modification material uniformly, melt extruding, granulating to obtain blended structure fast denitrification composite carbon source particles;

[0059] Method two, comprising the following steps:

[0060] Step (1) preparation of carbon source core: mixing slow-release skeleton material and optional carbon source uniformly, melt extruding, granulating to obtain core;

[0061] Optional step (2): mixing core with dispersing coupling agent and / or wetting agent uniformly in a mixing machine;

[0062] Step (3): under heating condition, first adding core prepared in step (1) or core prepared in step (2) into the mixing machine; then adding functional modification material, optional carbon source little by little into the mixing machine, mixing with core prepared in step (1) or core prepared in step (2), and adding dispersing coupling agent and / or wetting agent during the mixing process to obtain core-shell structure fast denitrification composite carbon source particles; wherein, when carbon source is added in core prepared in step (1), carbon source can or can not be added in step (3); when carbon source is not added in core prepared in step (1), carbon source needs to be added in step (3);

[0063] Method three, comprising the following steps:

[0064] Mixing water-swelling gel hydrophilic polymer slow-release skeleton material, carbon source and optional functional modification material uniformly, pouring into a mold, forming by repeated freezing-thawing, obtaining shaped composite particles, placing the shaped composite particles into a crosslinking agent for chemical crosslinking and curing, repeatedly washing the particles after crosslinking and curing, drying to obtain gel structure fast denitrification composite carbon source particles; wherein, when the functional modification material includes pore-forming agent, the particles after crosslinking and curing need to be placed in a foaming agent for reaction until no gas is released.

[0065] In method one of the present application, the specific ratio of slow-release skeleton material and carbon source is explored, and then mixed with functional modification material uniformly, melt extruding, granulating to obtain the blended structure fast denitrification composite carbon source particles. This melt blending method does not change the chemical structure of the material itself and does not occur chemical reaction, but can supplement the defects of any material, obtain new performance characteristics that single polymer cannot achieve, and is simple in operation, low in cost and high in feasibility. The carbon source prepared by this method is also more economical and more suitable for commercial application. More importantly, the particles prepared by this method are close to circular or elliptical in shape, rough in surface, and even have more micropores on the surface after modification, and the density is slightly greater than water, which is easy to fluidize in the fluidized bed to realize fast denitrification.

[0066] In the method one of the present application, the melt extrusion end is immediately connected to the cold water tank cooling forming, with the blowing water fan running continuously to cool down; the screw of the double screw extrusion granulator is the building block type screw structure, the diameter is 21.7 mm, the length-diameter ratio is 40:1, the main screw speed is 200-300 r / min, preferably, the side feeding screw speed is less than 10 r / min; the head temperature of the double screw extrusion granulator is 140-200℃, the middle section temperature is 160-200℃, and the extrusion temperature is 130-170℃; the power of the blowing water fan is 0.37 kw, and the cooling temperature of the cold water tank is 10-35℃; the extrusion die hole diameter of the double screw extrusion granulator is 3.8 mm; and the particle cutting diameter is about 2-6 mm.

[0067] In the method two of the present application, the mixing process of step (3) is carried out in a high-speed mixer while heating and mixing at high speed. In this process, the functional modification material melts and wraps outside the composite carbon source core. In addition, a proper amount of dispersing coupling agent and wetting agent is added to promote the polymerization of the functional modification material shell and the wrapping of the composite carbon source core. After a certain period of insulation, the paste shell completely and uniformly wraps outside the core, and then slowly cools to room temperature to obtain the core-shell structure rapid denitrification composite carbon source particles. In the method two of the present application, the core-shell structure includes the core and the functional shell layer. The core layer can be the core formed by the slow-release skeleton material and the carbon source, or the core layer can be formed by the slow-release skeleton material, and the functional shell layer is formed by the carbon source and other functional materials. The functional modification material and the optional carbon source are combined with the core stirred in the high-speed mixer, adhered to the core to form a functional shell layer, and the particle size gradually increases with rotation to obtain spherical particles.

[0068] In the method two of the present application, the core can be mixed with the dispersing coupling agent and the wetting agent first, and then mixed with the functional modification material. The dispersing coupling agent and the wetting agent are also added during the mixing process of the functional modification material. In this way, the core-shell structure rapid denitrification composite carbon source particles prepared contain the dispersing coupling agent and the wetting agent inside and outside, ensuring the particle forming and forming a stable double-layer structure.

[0069] The functional shell layer of the core-shell structure rapid denitrification composite carbon source particle can contain a pore-forming agent, so that the consumption outer layer of the particle has a large number of microporous structures, significantly increasing the specific surface area of the particle, and better providing an attachment site for microorganisms, making it easier and faster to contact the required carbon source, and improving the denitrification efficiency. The functional shell layer contains carbon source, which can be released quickly at the initial stage of denitrification, meeting the immediate needs of microorganisms in water, helping the rapid growth of denitrifying microorganisms, and accelerating the entire denitrification process. On the one hand, the dense biofilm increases the total amount of microorganisms in the treated water, improving the biological activity of denitrification; on the other hand, the formation of the biofilm also helps to fix and protect the microorganisms, preventing them from being washed away by the water flow, thereby improving the stability and efficiency of the denitrification system.

[0070] In the second method of the present application, carbon source is added to the inner core prepared in step (1), and carbon source is also added in step (3), so that a particle with a double-layer carbon structure can be formed. This structure can serve as a carbon source repository, working with the outer shell layer to achieve slow and continuous release of carbon source. When the inner core is a combination of skeleton and carbon source, as the outer shell layer carbon source is gradually depleted, the carbon source in the inner core is maintained through a slow-release mechanism. In addition, the design of the outer shell layer for rapid release of carbon source also enables the core-shell structure rapid denitrification composite carbon source particle to quickly respond to changes in the environment in the wastewater treatment system. In the case of a sudden increase in carbon source demand, such as an increase in nitrogen load in wastewater, the carbon source in the outer shell layer can quickly supplement the required carbon source, ensuring that the denitrification process is not affected by insufficient carbon source.

[0071] When no carbon source is added to the inner core prepared in step (1), carbon source needs to be added in step (3); when the inner core is only a skeleton, the function of providing carbon source is mainly realized by the outer shell layer. This core-shell structure ensures that microorganisms have a carbon source supply throughout the denitrification process, especially the core-shell structure with carbon source inside and outside, which further enhances the carbon supply capacity and stability, avoiding the decrease in denitrification efficiency caused by discontinuous or uneven carbon supply. However, in the process of biological wastewater treatment, the carbon source for denitrification process and the removal of nitrate theoretically follow a certain ratio, usually 2.86:1, so in practical application, COD cannot be completely used for denitrification reaction, and suitable carbon source needs to be prepared and regulated according to the demand for removal of nitrate nitrogen in the target water body.

[0072] In the method three of the present application, when the mixture is frozen, the movement speed of the hydrogel molecules is greatly reduced in the low-temperature frozen state, the molecular chains themselves or between the molecular chains are tightly cross-linked to form microcrystalline regions through van der Waals forces and hydrogen bonding, and the water not participating in cross-linking forms ice crystals as a pore-forming agent, which forms a pore structure and is retained in the repeated freezing-thawing process, thereby forming a uniform microporous structure in the particles, enhancing the hydrophilicity and biological affinity, and in the freezing-thawing process, the functional modified materials are uniformly distributed in the interior of the particles, obtaining the shaped composite particles with specific functions, the shaped particles are placed in a cross-linking agent for chemical cross-linking and curing, the particles after cross-linking and curing are washed with clean water to remove the surface residues, and finally dried in air or using a drying oven for drying treatment, to obtain the gel structure rapid denitrification composite carbon source particles. When the pore-forming agent is added in the method three of the present application, it needs to be placed in a foaming agent for foaming treatment, otherwise it does not need to be placed in a foaming agent for foaming treatment. The amount of the foaming agent is just enough to completely immerse the shaped particles, and the foaming time lasts for more than 30 minutes to allow sufficient foaming reaction and ensure complete reaction of the pore-forming agent.

[0073] In the method three of the present application, the freezing-thawing method can form a stable structure of hydrogen bonds between and within PVA chain molecules and microcrystalline regions three-dimensional network, and the hydrogel presents a reticular structure surface layer, which can increase the surface area and improve the mass transfer performance, realizes a stable carbon release rate, and improves the biological denitrification efficiency.

[0074] The present application explores the best molding and particle forming ratio of the core of the rapid denitrification particles, which can ensure the maximum carbon source release amount (i.e. increasing the addition amount of natural cellulose materials as much as possible under the condition of meeting the particle molding), so as to ensure rapid denitrification. The density of the rapid denitrification composite carbon source particles of the present application is close to that of water and slightly higher than that of water, which is more easy to realize fluidization and biofilm formation in a fluidized bed bioreactor, saves energy consumption, and improves the reaction efficiency.

[0075] In the preparation method of the rapid denitrification composite carbon source particles of the present application, preferably,

[0076] In the method one,

[0077] The mixing is carried out in a mixing machine at a rotation speed of 150-1500 r / min;

[0078] The temperature for melt extrusion is 140-200℃; melt extrusion is carried out by using a double-screw extrusion granulator; preferably, the head temperature of the double-screw extrusion granulator used is 140-200℃, the middle temperature is 160-200℃, and the extrusion temperature is 130-170℃; and / or,

[0079] In the method two,

[0080] Step (1), the temperature for melt extrusion is 140-200℃; melt extrusion is carried out by using a double-screw extruder; preferably, the temperature of the head of the double-screw extruder used is 140-200℃, the temperature of the middle section is 160-200℃, and the extrusion temperature is 130-170℃; and / or,

[0081] Step (2), the temperature for mixing is room temperature; and / or,

[0082] The diameter of the core prepared in Step (1) is 2-6mm; and / or,

[0083] Step (3), the temperature for processing in the mixing machine is 150-200℃; and / or,

[0084] The time for processing in the mixing machine is 30-60min; and / or,

[0085] The speed for stirring in the mixing machine is 150-300r / min; and / or,

[0086] The mixing machine in the present application is selected from a high-speed mixing machine, and the heating temperature of the high-speed mixing machine is 150-200℃ to ensure that the core is in a micro-melting state.

[0087] In Method Three,

[0088] The number of times for repeated freeze-thaw molding is 3-5 times; preferably, 4 times;

[0089] The crosslinking agent is selected from at least one of a calcium chloride (CaCl2) solution, a saturated boric acid solution, and a saturated boric acid solution containing CaCl2; preferably, the concentration of the CaCl2 solution is 3-5wt%; and the concentration of CaCl2 in the saturated boric acid solution containing CaCl2 is 3-5wt%;

[0090] The crosslinking agent is not directly added into the preparation mixture of the carbon source core particles, but after the particles are molded and subjected to a freezing process, the molded particles are soaked in the above-mentioned crosslinking agent solution prepared in advance for crosslinking and solidification treatment, so that the molded particles are completely immersed.

[0091] The foaming agent is at least one of saturated citric acid or acetic acid at room temperature.

[0092] In the preparation method of the rapid denitrification composite carbon source particles described in the present application, preferably,

[0093] The diameter of the prepared rapid denitrification composite carbon source particles is 3-10mm, preferably 4-6mm; and / or,

[0094] The density of the prepared rapid denitrification composite carbon source particles is 700-2500kg / m 3Preferred weight: 1100-1200 kg / m³ 3 The above characteristics ensure that the particles are smoothly fluidized in the liquid-solid fluidized bed, resulting in lower system energy consumption during fluidized bed operation and promoting stable system operation.

[0095] The rapid denitrification composite carbon source particles of the present invention can be either solid or porous. A porous structure is preferred because it allows for the enrichment of microorganisms within the pores beforehand or during wastewater treatment. These microporous structures create different aerobic environments on the surface of the carrier particles and within the pores, thereby enriching different types of aerobic microorganisms and further promoting the formation of a microenvironment conducive to microbial growth on the surface of the carrier particles or within the microporous structure, or the treatment of organic pollutants in wastewater.

[0096] The rapid denitrification composite carbon source particles of the present invention can be regularly spherical, near-spherical, near-cylindrical, or ellipsoidal, with uniform or non-uniform dimensions and density; the surface of the rapid denitrification composite carbon source particles is rough. Preferably, the rapid denitrification composite carbon source particles have a large specific surface area, a shape similar to a sphere or cylinder, uniform size, a density close to that of a liquid, and a surface suitable for microbial growth.

[0097] A third objective of this invention is to provide an application of the rapid denitrification composite carbon source particles described in one objective of this invention in wastewater treatment.

[0098] In the application described in this invention, preferably,

[0099] The rapid denitrification composite carbon source particles of this invention are used as microbial carriers in biological fluidized bed wastewater treatment systems. These particles can be applied as microbial carriers in biological wastewater treatment systems. On one hand, the large specific surface area of ​​the particles provides sufficient space for microbial growth, increasing microbial concentration. On the other hand, under the action of microorganisms, the particles can be biodegraded and slowly release carbon sources for microbial growth, adjusting the C / N ratio of the treated wastewater system and enhancing the system's shock resistance.

[0100] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of various ranges, the endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0101] Compared with existing technologies, the present invention has the following advantages:

[0102] The carbon release stability, carbon release cycle, mechanical strength, hydrophilicity, biological affinity, porosity and roughness of the quick denitrification composite carbon source particle are improved, and the particle has the advantages of easy fluidization, easy biofilm formation, low cost, not easy to break, and long service life.

[0103] The quick denitrification composite carbon source particle has a large specific surface area, can provide sufficient space for microbial growth, effectively improves the microbial concentration in the system, and has light density and is easy to fluidize, so that the system energy consumption is small when the particle is operated in a fluidized bed, and the stable operation of the system is facilitated.

[0104] The quick denitrification composite carbon source particle can be used as a microbial carrier in a fluidized bed biological wastewater treatment system, on the one hand, the large specific surface area of the particle can provide sufficient space for microbial growth and improve the microbial concentration, on the other hand, the particle can be biodegraded under the action of microorganisms to release carbon source for microbial growth, adjust the C / N of the treated wastewater system, enhance the impact resistance of the system, and realize rapid and efficient wastewater denitrification treatment. BRIEF DESCRIPTION OF DRAWINGS

[0105] Figure 1 is a real picture of the blended structure composite carbon source particle prepared in embodiments 1-3 of the present application, from left to right, the mass ratio of the synthetic material is PE:PHB:OS=4:3:3, 4:1:5, 4:5:1 respectively;

[0106] Figure 2 is a scanning electron microscope (SEM) picture of PE, PHB and OS raw materials alone and the composite carbon source particles prepared in embodiments 1-3 of the present application;

[0107] Figure 3 is a graph of the change of the carbon release amount of PE, PHB and OS raw materials alone and the composite carbon source particles described in embodiments 1-5 of the present application with time;

[0108] Figure 4 is a graph of the analysis results of the carbon release stability and carbon supply durability of the composite carbon source particles prepared in embodiments 1-5 of the present application by fitting equation;

[0109] Figure 5 is a structural schematic diagram of the quick denitrification composite carbon source particle prepared in the embodiments of the present application. DETAILED DESCRIPTION

[0110] The present application will be specifically described below in combination with specific drawings and embodiments, and it is necessary to point out here that the following embodiments are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application, and some non-essential improvements and adjustments of the present application made by those skilled in the art according to the content of the present application still belong to the protection scope of the present application.

[0111] It should be further noted that the various technical features described in the following detailed description can be combined in any suitable manner unless otherwise contradicted by context. To avoid unnecessary repetition, the present application will not recite further descriptions of various possible combinations.

[0112] Furthermore, various different embodiments of the present application can be combined in any suitable manner, as long as it does not violate the spirit of the present application, and the technical solutions thus formed are part of the original disclosure of the present specification and fall within the protection scope of the present application.

[0113] The raw materials used in the examples and comparative examples, if not specifically limited, are disclosed in the prior art, such as can be directly purchased or prepared according to the preparation method disclosed in the prior art.

[0114] Examples 1-5

[0115] The blended structure rapid denitrification composite carbon source particles are prepared according to Method One, including the following steps:

[0116] The base skeleton PE and the carbon sources PHB and OS are mixed in a mass ratio of 4:3:3, 4:1:5, 4:5:1, 4:2:4, and 4:4:2, respectively, and placed in a high-speed mixing machine to mix at a speed of 300 r / min at room temperature for 10 min until uniform, and then the mixture is placed in a twin-screw extrusion granulator to melt extrude, draw, and cut to obtain cylindrical-like blended structure rapid denitrification composite carbon source particles, which can also be used as the core of the core-shell structure composite carbon source particles; the main screw speed of the granulator during operation is 250 r / min, and the middle section temperature of the twin-screw extrusion granulator is set to 170℃, 180℃, 195℃, 195℃, and 195℃, respectively, and the extrusion temperature is set to 150℃.

[0117] The actual pictures of the composite carbon source particles prepared in Examples 1-3 of the present application are shown in Figure 1; the SEM of the raw materials of PE, PHB, and OS alone and the composite carbon source particles prepared in Examples 1-3 of the present application are shown in Figure 2.

[0118] The densities of the composite carbon source particles prepared by the above method are 1.038 g / cm 3 , 0.993 g / cm 3 , 1.088 g / cm 3 , 0.998 g / cm 3 , and 1.068 g / cm 3 , respectively, and the average diameters are 5 mm, 4 mm, 4 mm, 3.5 mm, and 4.5 mm (the mass ratio of the materials corresponding in turn is PE:PHB:OS=4:3:3, 4:1:5, 4:5:1, 4:2:4, and 4:4:2), respectively.

[0119] At high temperature, the base skeleton and the synthetic polymer carbon source material can be melted, while the natural fiber material will not be melted but decomposed at a certain temperature. This difference enables the molten state of the skeleton and the polymer carbon source to surround and fill the voids generated by the decomposition of the natural carbon source, forming a pore structure. Therefore, their organic combination realizes a particle with both good mechanical strength and more pore structure, and the porosity and pore size can be controlled by adjusting the proportion of different components to meet different application requirements. The present application uses SEM to observe the changes in the surface structure of the carbon source raw materials and the composite particles. As can be seen from the structure of Figure 2, the composite carbon source particles prepared by the present application have more pores, which is more conducive to the attachment of microorganisms and easier to form a biofilm than PHB with a smooth surface and OS with a slightly rough surface.

[0120] In addition, when the density of the particles is close to the density of water, the particles can be more easily suspended or fluidized by the water flow. Good fluidization state can make the organic matter in the sewage fully contact with the biofilm on the surface of the particles, thereby improving the treatment efficiency. If the density of the particles is greatly different from that of water or the diameter of the particles is too large, the particles may aggregate together, causing the reactor to be blocked, affecting the treatment efficiency and system stability. The rapid nitrogen removal composite carbon source particles prepared by the present application have a density close to that of water, so they are more easily fluidized than the raw materials (with a larger or smaller density or a large difference from water), which helps to reduce energy consumption; the particle diameter is also very suitable for use in a fluidized bed.

[0121] Examples 6-9

[0122] The blended structure rapid nitrogen removal composite carbon source particles are prepared according to Method 1, including the following steps:

[0123] The base skeleton PE and the carbon source materials PHB and OS are mixed in a mass ratio of 8:1:1, 6:2:2, 6:3:1 and 6:1:3 respectively, placed in a high-speed mixing machine at a speed of 300 r / min at room temperature for 10 min until uniform, and then the mixture is placed in a double-screw extrusion granulator for melt extrusion, drawing and cutting to obtain composite carbon source particles in a cylindrical shape. The main screw speed of the granulator during operation is 250 r / min, and the temperature in the middle section of the double-screw extrusion granulator is set to 170℃, 180℃, 195℃, 195℃ and 195℃ in turn, and the extrusion temperature is set to 150℃.

[0124] Application Example 1

[0125] Performance test:

[0126] 1. Static carbon release experiment in clear water

[0127] The present application provides an evaluation method of the carbon release performance of the granules prepared in the above Examples 1-5 and Comparative Examples 1-3. A static carbon release experiment of clean water is set up in the laboratory, and the specific operation includes the following steps: 5 g of the composite carbon source granules prepared in the above Examples 1-5 and 5 g of PE, PHB and OS alone are weighed as samples, and are put into a ground conical flask containing 150 mL of ultrapure water, the bottle mouth is sealed with a rubber plug, and the materials are uniformly dispersed in the ultrapure water by shaking; since the composite carbon source granules will be applied to a fluidized bed reactor, they will be continuously mixed and contacted with water under the impact of water flow, in order to avoid the deviation of the carbon release data caused by the lack of mixing and stirring in the static experiment, the conical flask is placed in a 25°C constant temperature shaking table, and is shaken at a speed of 120 r / min, and before sampling, it is shaken thoroughly and is left to stand, the supernatant is taken, is passed through a 0.45 μm water filter membrane with a needle tube, and is stored in a 4°C refrigerator for testing. Sampling is performed at 1 h, 4 h, 10 h, 24 h, 48 h…, sampling is continuously performed for 7 days, and then sampling is performed every 48 h, a total of 15 days, the concentration of chemical oxygen demand (COD, mg / L) in the leaching liquid is determined, the water is completely changed after sampling every 24 h; the change trend of COD with time (h) is recorded, and the active carbon release capacity of the raw materials and the blended structure rapid denitrification composite carbon source granules prepared under different preparation conditions is analyzed, and the specific results are shown in FIG. 3.

[0128] As shown in FIG. 3, the carbon release of the above materials can be divided into three categories, PHB with little or almost no carbon release is one category, OS with obviously high carbon release is one category, and the composite carbon source granules (Examples 1-5) with moderate carbon release are one category. Since the degree of polymerization of PHB is very high, the carbon source contained therein is difficult to release. The carbon source release processes of OS and PHB are obviously different, rapid and large carbon release occurs within the first 24 h, and then the carbon source is slowly released and tends to be stable. The soluble carbon source of each material is almost completely released within 15 days, and needs to be further released under the action of microorganisms. Compared with the composite carbon source granules of Examples 1-5, the COD content released by OS is too high, which is easy to cause COD pollution of the effluent, and the carbon leaching amount of PHB is too small to meet the requirement of providing carbon source, and the surface is smooth and not easy to form a biofilm, so neither of them is suitable as an external solid carbon source in the C / N imbalance wastewater treatment process. Among the blended structure rapid denitrification composite carbon source granules of Examples 1-5, the granules of the group with PE:PHB:OS=4:3:3 have moderate and stable carbon release amount, rough surface and porous internal structure, and are more suitable as an external solid carbon source.

[0129] 2. Fitting analysis of stable carbon release and carbon supply durability

[0130] This invention analyzes the carbon release stability and carbon supply persistence of the blended rapid nitrogen removal composite carbon source particles prepared in Examples 1-5 by fitting equations, as shown in Figure 4. By comparing the correlation coefficients of the fitted equations, the carbon release rate and carbon release capacity of different materials are determined. It was found that several carbon source materials fit the first-order kinetic equations well (R0). 2 >0.96), indicating that the carbon release rate of each carbon source is directly proportional to the carbon concentration in the solution, that is, the carbon source is released at a certain proportion per unit time.

[0131] The carbon release rate constants of the blended rapid denitrification composite carbon source particles prepared in Examples 1-5 above, as well as the individual PHB and OS raw materials, are shown in Table 1.

[0132] Table 1

[0133] A larger mass transfer coefficient K indicates a smaller resistance to carbon release and a easier release of organic carbon. Based on the fitting results, the K value of the natural carbon source OS is (625 mg·(h·g·L)). -1 The concentration is much greater than that of the biodegradable polymer PHB (3.2092 mg / (h·g·L)). -1 The K-value of the composite carbon source particles falls between these two extremes. In practical engineering, the K-value should not be too large or too small. If the K-value is too large, the carbon release rate will be too fast, which can easily cause secondary pollution of the water body; if the K-value is too small, the mass transfer will be slow, which is also not conducive to the release of carbon source inside the carrier. Therefore, in comparison, although OS can quickly release carbon to start the denitrification system, it may require frequent replenishment; carbon sources with PHB and high PHB content have too much resistance to release, and it is difficult to meet the carbon source requirements of biological denitrification while ensuring the economic efficiency of the project. The composite carbon source carriers of this invention (especially #3, #4, and #6) have a moderate mass transfer rate and are more suitable as external carbon sources.

[0134] According to the second-order kinetic equation, the time t required for the released COD to reach half of the maximum release amount is... 1 / 2 The smaller the value, the faster the release of organic carbon to equilibrium. (OS's t) 1 / 2 Much smaller than PHB, the composite carbon source particles prepared in the embodiments of the present invention have a t 1 / 2 The value lies between the two, further illustrating that natural cellulose carbon sources release carbon rapidly and are suitable for applications requiring rapid denitrification, while biodegradable polymers release carbon steadily but infrequently, making them suitable for applications where the carbon release rate and total amount are not critical. The composite carbon source material prepared in this embodiment falls between the two, exhibiting suitable carbon release and stability. Specifically, the values ​​for groups #3, 4, 5, and 7 are... 1 / 2 With similar values, #3 exhibits higher saturated carbon release concentration and mass transfer coefficient, demonstrating better carbon release and carbon supply capacity. While #6's mass transfer coefficient and saturated carbon release concentration are close to #3's, its t...1 / 2 The release performance of the #3 is the worst. Therefore, the #3 in the blended structure fast denitrification composite carbon source particle has extremely high advantages in carbon release amount and carbon release period, and is more suitable for being applied to the denitrification of the tail water with C / N imbalance as a solid carbon source.

[0135] 3. Mechanical strength analysis

[0136] The composite carbon source particles prepared in the above example 1 and examples 6-9 are subjected to mechanical strength analysis, and the specific results are shown in table 2.

[0137] Table 2

[0138] It can be seen from the results in table 2 that the mechanical strength of the composite carbon source particle prepared in the present application is between the raw materials PHB and PE, and the mechanical strength is moderate, which meets the strength requirement of the carrier in the fluidized bed sewage treatment system.

[0139] 4. Cost analysis

[0140] The cost of the composite carbon source particle prepared in example 1 of the present application is analyzed, and the specific results are shown in table 3.

[0141] Table 3

[0142] Using a hypothetical calculation (if only considering the operating and maintenance cost accounting for 20% of the raw materials), although the cost of the composite carbon source is higher than that of using OS alone, it is more economical than using PHB alone, because the processing process of PHB is difficult, and the overall cost is also relatively high. In addition, the composite carbon source can provide better product performance and environmental benefits.

[0143] In summary, it can be seen that the composite carbon source particle prepared in the present application has more pores, which is beneficial to the adhesion of microorganisms and is more prone to biofilm formation. The density of the composite carbon source particle prepared in the present application is close to water, so it is more prone to fluidization than the raw materials (with large or small density or with a large difference from water), and is more suitable for use in the fluidized bed. The composite carbon source particle prepared in the present application has moderate and stable carbon release amount, and is a more suitable slow-release carbon source. The composite carbon source particle prepared in the present application has extremely high advantages in carbon release amount and carbon release period, and is more suitable for being applied to the denitrification of the tail water with C / N imbalance as an additional carbon source. The mechanical strength and cost of the composite carbon source particle prepared in the present application are moderate. Therefore, the composite carbon source particle prepared in the present application is very suitable for being used as a carrier particle of the fluidized bed biological reactor, and is used for synergistically treating the tail water with C / N imbalance.

[0144] Example 10

[0145] The core-shell structure fast denitrification composite carbon source particle is prepared according to method two, including the following steps:

[0146] Preparation of carbon source core: the PE:PHB:OS is mixed in a mass ratio of 4:3:3 according to the method of Example 1 to obtain the core; preparation of carbon source shell: under heating conditions, the core prepared above is added into a mixing machine, the heating temperature is 200℃; then 5% of the carbon source (carbon source is OS, the mass of the carbon source is 5% of the mass of the core) except for the dispersing coupling agent (KH-550) and / or wetting agent is added into the mixing machine in small amounts and multiple times, mixed with the prepared core, and then the dispersing coupling agent (KH-550) accounting for 1% of the mass of the core and water accounting for 0.5% of the mass of the core are added in small amounts and multiple times during the mixing process to obtain the core-shell structure rapid denitrification composite carbon source particles.

[0147] The core-shell structure rapid denitrification composite carbon source particles prepared by the above method can have a diameter of 3-8mm, the shell can have a diameter of 4-9mm, and the density of the core-shell structure rapid denitrification composite carbon source particles prepared by the above method can be ensured to be 1050-1200kg / m 3 between.

[0148] Application Example 2

[0149] The application provides an application of the rapid denitrification composite carbon source particles in treating sewage in a fluidized bed bioreactor, which comprises the following steps:

[0150] The fluidized bed bioreactor is made of transparent organic glass tube, the main body part has an inner diameter of 7 cm and a height of 1.5 m, a tapered expansion section and an expansion column are arranged on the top, a liquid overflow device is connected to the right side, and a circulating liquid outlet is arranged at the overflow port to make the liquid circulate; the fluidized bed is added with fast denitrification composite carbon source particles (prepared in Example 10) with a volume loading of 30%, which can provide carbon nutrient source for the growth and metabolism of microorganisms. The fluidized bed bioreactor is used for the process of sewage treatment as follows: after the device and equipment are normally and stably operated under clean water conditions, the reactor is started to operate. The secondary biochemical sludge (after concentration) of a certain sewage treatment plant is inoculated into the fluidized bed bioreactor, and is allowed to be smothered and exposed, and the fluidization speed is adjusted to the minimum liquid speed at this time which can make the particles fluidize, the reactor is kept closed to run and create an anaerobic environment, and the starting of the system is completed; the simulated sewage configured in the laboratory is pumped into the system from the bottom by a pulse pump, and the effluent is discharged through the overflow port. After the liquid passes through the electromagnetic flowmeter, the circulating liquid flow is controlled by adjusting the frequency of the circulating pump and the size of the valve. In the reactor, the fast denitrification composite carbon source particles which are in constant random motion can provide carbon source for the growth and metabolism of microorganisms; the microorganisms attached to the surface of the carrier particles and the free microorganisms are in full contact with the sewage to realize the denitrification process of nitrate, the environmental temperature is kept at 20-29°C, the reactor is kept closed to run and create an anaerobic environment; in order to monitor the changes of COD, NH4 + -N, NO3 - -N, NO2 - -N in the influent and effluent, as well as the concentration of particles and pH value in the system, real-time monitoring instruments are installed at the inlet and outlet of the reactor. A plurality of test ports are arranged at the middle of one side of the reactor, which are used to connect particle concentration measurement probes, dissolved oxygen probes, pH meters and the like, so as to perform real-time detection and timely adjust the parameters in the system to be in the range of better operating parameters.

[0151] For this example, the daily sewage treatment capacity of the fluidized bed bioreactor is 24 L, and during the operation period, the initial NO3 - -N content in the influent is 27.1 mg / L, the average TN in the influent is 35 g / m 3 , the total phosphorus is 5 g / m 3 , after 7 h of operation, the NO3 - -N decreases to 0.4 mg / L, the removal load is 0.059 kg N / (m 3 ·d), and after a hydraulic retention time of 12 h, 95% of TN can be removed.

[0152] Example 11

[0153] The porous gel structure fast denitrification composite carbon source particles are prepared according to Method Three, including the following steps:

[0154] The porous gel framework is prepared by mixing PVA and SA; the mass ratio of PVA to SA is 8:1. The preparation method of the porous gel structure rapid denitrification composite carbon source particle is as follows: first, PVA and SA are mixed in proportion, and ultrapure water is added to form a solution, which is heated in a 95℃ water bath for at least 2h to obtain a PVA-SA hydrogel framework; the gel framework is mixed with 10.5g of PHB and 10.5g of OS carbon source, and then poured into a mold, and repeatedly frozen at a temperature of-20℃ for 18h and then thawed for 8h, repeated 4 times to form a porous gel structure; then the formed particles are placed in a saturated boric acid solution containing 5% CaCl2 for chemical crosslinking and curing, and finally the cured particles are washed with ultrapure water on the surface of the particles for more than 5 times to remove the excess chemical crosslinking agent on the surface, to obtain the porous gel structure rapid denitrification composite carbon source particle, which is sealed and stored in a 4℃ refrigerator for standby and use.

[0155] The freeze-thaw method can make the hydrogen bonds between and within PVA chain molecules and the three-dimensional network of the crystalline region form a stable structure, and the hydrogel presents a reticular structure on the surface layer, which can increase the surface area, improve the mass transfer performance, realize a stable carbon release rate, and improve the biological denitrification efficiency. The porous gel structure rapid denitrification composite carbon source particle prepared by the above method can be successfully fluidized in a liquid-solid fluidized bed in a positive direction, so that the system energy consumption is small when the fluidized bed is running, which is conducive to the stable operation of the system.

[0156] The structure schematic diagram of the rapid denitrification composite carbon source particle prepared in the embodiment of the present application is shown in Figure 5, which can be a composite carbon source core structure formed by only the slow-release skeleton and the carbon source without including the functionalized modified material, or a blending structure, a core-shell structure, a gel structure rapid denitrification composite carbon source particle combined with the functionalized modified material and formed by changes. The above rapid denitrification composite carbon source particle of the present application is in a fluidized state under the joint action of liquid, gas or both liquid and gas. For a liquid-solid two-phase fluidized system, the driving force of the fluidization of the rapid denitrification composite carbon source particle is liquid; for a gas-liquid-solid three-phase fluidized system, the particle can be in a fluidized state under the action of a single gas or the joint action of liquid and gas.

[0157] Comparative Example 1

[0158] Preparation of the composite carbon source material: the base skeleton PE and the carbon source materials PHB and OS are mixed in a mass ratio of 2:4:4, placed in a high-speed mixing machine, mixed at a speed of 300r / min at room temperature for 10min until uniform, and then placed in a double-screw extrusion granulator for melt extrusion, wire drawing and cutting to obtain a composite carbon source core in a cylindrical shape; the main screw rotation speed of the granulator is 250r / min, and the middle section temperature of the double-screw extrusion granulator is set to 170℃, 180℃, 195℃, 195℃ and 195℃ in sequence, and the extrusion temperature is set to 150℃.

[0159] It is found that the composite carbon source material prepared in Comparative Example 1 cannot be shaped.

[0160] Comparative Example 2

[0161] Preparation of the composite carbon source material: the base framework PE and the carbon source materials PHB and OS are mixed in a mass ratio of 8:1:1, and then placed in a high-speed mixing machine to mix at a speed of 300 r / min at room temperature for 10 min until uniform, and then the mixture is placed in a twin-screw extrusion granulator to melt extrude, draw and cut to obtain a composite carbon source core in a cylindrical shape; the main screw speed of the granulator during operation is 250 r / min, and the temperature of the middle section of the twin-screw extrusion granulator is set to 170℃, 180℃, 195℃, 195℃, 195℃ in turn, and the extrusion temperature is set to 150℃.

[0162] It is found that the composite carbon source material prepared in Comparative Example 2 has poor carbon release performance and cannot meet the demand for external carbon source in the rapid denitrification process.

[0163] In summary, the present application provides a rapid denitrification composite carbon source particle and a preparation method thereof. The particle combined with the biological fluidized bed technology can strengthen the sewage treatment effect, has the advantages of easy biofilm formation, easy fluidization, stable carbon release, long-lasting carbon supply, high mechanical strength, low cost, wide application range, etc.

[0164] The present application has been described in detail by combining with the specific embodiments and exemplary examples, but these descriptions cannot be understood as limitations of the present application. Those skilled in the art understand that the technical solutions and embodiments of the present application can be variously replaced, modified or improved without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

[0165] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the definition in this specification prevails.

[0166] When the present specification derives materials, substances, methods, steps, devices or components, etc. with the word head "known to those skilled in the art", "prior art" or similar terms, the objects derived by the word head cover those commonly used in the art at the time of the present application, but also include those which are not commonly used at present, but will be recognized as suitable for similar purposes in the art.

[0167] In the context of the present specification, unless explicitly stated otherwise, any reference to any item or matter not mentioned is to be taken as a direct reference to those known in the art without any need for any change.

Claims

1. A rapid denitrification composite carbon source particle, characterized by, is prepared from raw materials including a slow-release skeleton, a carbon source, and an optional functional modification material; the slow-release skeleton is selected from a non-water-soluble high molecular material or a hydrophilic high molecular material that swells into a gel when in contact with water; the carbon source includes at least one of a natural carbon source or an artificially synthesized polymer carbon source; wherein the content of the slow-release skeleton is 40%-80% based on the total mass of the slow-release skeleton and the carbon source being 100wt%.

2. The fast denitrification composite carbon source particle according to claim 1, wherein: the carbon source is selected from a natural carbon source and an artificially synthesized polymer carbon source; preferably, the content of the slow-release skeleton is 40-80% based on the total mass of the slow-release skeleton and the carbon source being 100wt%. the content of the natural carbon source is 10-50%; and the content of the artificially synthesized polymer carbon source is 10-50%.

3. The fast denitrification composite carbon source particle according to claim 1, wherein: the non-water-soluble high molecular material is selected from at least one of polyethylene, polypropylene, polystyrene, or polyolefin elastomer; and / or, the hydrophilic high molecular material that swells into a gel when in contact with water is selected from at least one of a natural gum material, a cellulose material, a non-cellulose polysaccharide, an ethylene polymer, or an acrylic resin; and / or, the natural carbon source is selected from at least one of corn cob, wheat straw, rice straw, rice husk, reed, wood chips, giant reed, sugar cane residue, cattail, or peanut shell; and / or, the artificially synthesized polymer carbon source is selected from at least one of poly-3-hydroxybutyric acid, polycaprolactone, polybutylene succinate, polylactic acid, polyhydroxyalkanoate, poly-β-carboxybutyric acid valerate, polyhydroxybutyrate caproate, or poly-3-hydroxybutyric acid-4-hydroxybutyric acid ester; preferably, the natural gum material is selected from at least one of sodium alginate, gum arabic, agarose; and / or, the cellulose material is selected from at least one of hypromellose, methyl cellulose, hydroxyethyl cellulose; and / or, the non-cellulose polysaccharide is selected from at least one of chitosan or galactomannan; and / or, the ethylene polymer is selected from polyvinyl alcohol; and / or, the acrylic resin is selected from carbomer.

4. The fast denitrification composite carbon source particle according to claim 1, wherein: the functional modification material includes at least one of a hydrophilic agent, a biological affinity substance, an adsorbent, a magnetic substance, a microbial rapid growth and reproduction promoter, a pore-forming agent, a dispersion coupling agent, or a wetting agent; preferably, the content of the hydrophilic agent is 1-10% based on the total mass of the slow-release skeleton and the carbon source; and / or, the content of the biological affinity substance is 1-10% based on the total mass of the slow-release skeleton and the carbon source; and / or, the content of the adsorbent is 1-5% based on the total mass of the slow-release skeleton and the carbon source; and / or, the content of the magnetic substance is 3-15% based on the total mass of the slow-release skeleton and the carbon source; and / or, the content of the microbial rapid growth and reproduction promoter is 0.5-5% based on the total mass of the slow-release skeleton and the carbon source; and / or, the content of the pore-forming agent is 0.5-5% based on the total mass of the slow-release skeleton and the carbon source; and / or, ​ The dispersing coupling agent accounts for 0.1-2% of the total mass of the slow-release skeleton, carbon source; and / or, The wetting agent accounts for 0.1-1% of the total mass of the slow-release skeleton, carbon source.

5. The fast denitrogenation composite carbon source particle according to claim 4, characterized in that: The hydrophilic agent is selected from at least one of polyvinyl alcohol, silicon dioxide, polyacrylamide or stearic acid; and / or, The biological affinity substance is selected from at least one of agar, starch or calcium alginate; and / or, The adsorbent is selected from at least one of activated carbon, silica gel, aluminum oxide, natural clay or biochar; and / or, The magnetic substance is selected from at least one of ferrite, iron-strontium oxide or barium ferrite; and / or, The microbial fast growth and reproduction promoter is selected from trace element powder; at least one of iron, magnesium, zinc, copper, manganese, molybdenum or selenium; and / or, The pore-forming agent is selected from at least one of sodium bicarbonate, ammonium bicarbonate, industrial urea or starch; and / or, The dispersing coupling agent is selected from at least one of a silane coupling agent or an acid ester coupling agent; preferably, the silane coupling agent is selected from at least one of γ-aminopropyl triethoxysilane or vinyl triethoxysilane; the acid ester coupling agent is selected from at least one of titanium tetraacetate, titanium isopropylate, tetrabutyl zirconium or zirconium acrylate; and / or, The wetting agent includes at least one of turpentine oil, liquid paraffin, white mineral oil, stearic acid or water.

6. The method of claim 1-5, wherein the method is characterized by, Selected from the following three methods: Method one, including the following steps: mixing raw materials including slow-release skeleton material, carbon source and optional functional modification material uniformly, melt extrusion, granulation, to get blended structure fast denitrogenation composite carbon source particle; Method two, including the following steps: Step (1) preparation of carbon source core: mix the slow-release skeleton material with optional carbon source uniformly, melt extrusion, granulation, to get the core; Optional step (2): mix the core with dispersing coupling agent and / or wetting agent uniformly; Optional step (3): under heating condition, first add the core prepared in step (1) or the core prepared in step (2) into a mixing machine; then add the functional modification material, optional carbon source except for the dispersing coupling agent and / or wetting agent into the mixing machine, mix with the core prepared in step (1) or the core prepared in step (2), and then add the dispersing coupling agent and / or wetting agent during the mixing process to mix uniformly, to get the core-shell structure fast denitrogenation composite carbon source particle; when the core prepared in step (1) has added carbon source, it is allowed to add or not to add carbon source in step (3); when the core prepared in step (1) has not added carbon source, it is required to add carbon source in step (3); Method three, including the following steps: Mixing the water-swellable hydrophilic polymer slow-release skeleton material, the carbon source and the optional functional modification material uniformly, pouring into a mold, repeating freeze-thaw molding to obtain the shaped composite particles, chemically crosslinking and curing the shaped composite particles in a crosslinking agent, repeatedly washing the crosslinked and cured particles, drying to obtain the gel structure rapid denitrification composite carbon source particles; when the functional modification material includes a pore-forming agent, the crosslinked and cured particles are placed in a foaming agent to react until no gas is emitted.

7. The preparation method of the rapid denitrification composite carbon source particles according to claim 6, characterized in that: In method one, The temperature of melt extrusion is 140-200℃; melt extrusion is carried out by using a double-screw extrusion granulator; preferably, the head temperature of the double-screw extrusion granulator used is 140-200℃, the middle section temperature is 160-200℃, and the extrusion temperature is 130-170℃; and / or, In method two, In step (1), the temperature of melt extrusion is 140-200℃; melt extrusion is carried out by using a double-screw extrusion granulator; preferably, the head temperature of the double-screw extrusion granulator used is 140-200℃, the middle section temperature is 160-200℃, and the extrusion temperature is 130-170℃; and / or, The diameter of the inner core prepared in step (1) is 2-6mm; and / or, In step (3), the temperature of processing in the mixing machine is 150-200℃; and / or, The time of mixing and processing in the mixing machine is 30-60min; and / or, The stirring speed in the mixing machine is 150-300r / min; and / or, In method three, The number of times of repeating freeze-thaw molding is 3-5 times; and / or, The crosslinking agent is selected from at least one of CaCl2 solution, saturated boric acid solution, and CaCl2-containing saturated boric acid solution; preferably, the concentration of CaCl2 solution is 3-5wt%; the concentration of CaCl2 in the CaCl2-containing saturated boric acid solution is 3-5wt%.

8. The preparation method of the rapid denitrification composite carbon source particles according to claim 6, characterized in that: The diameter of the prepared rapid denitrification composite carbon source particles is 3-10mm, preferably 4-6mm; and / or, The density of the prepared fast denitrification composite carbon source particles is 700-2500 kg / m 3 , preferably 1100-1200 kg / m 3 .

9. The application of the rapid denitrification composite carbon source particles according to any one of claims 1-5 in sewage treatment.

10. The application according to claim 9, characterized in that: The application of the rapid denitrification composite carbon source particles as the microbial carrier in the fluidized bed in a biological fluidized bed sewage treatment system.

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