Composite slow-release carbon materials coupled with heterotrophic nitrification and aerobic denitrification bacteria and their application in water treatment

Abstract

The present invention relates to a composite slow-release carbon material coupled with aerobic denitrifying bacteria, comprising a slow-release carbon carrier and immobilized heterotrophic nitrification-aerobic denitrifying bacteria, wherein the slow-release carbon carrier is formed by mixing naked algae particles with polybutylene adipate and then attaching and fixing the mixed material to an elastic filler, and the immobilized heterotrophic nitrification-aerobic denitrifying bacteria are formed by attaching and fixing Pseudomonas stutzeri and / or Microbacterium oxidans to an elastic filler. The present invention is conducive to coordinating the carbon release rate with the denitrification and denitrification process, strengthening aerobic denitrifying bacteria that can adapt to a wide temperature range, and the two bacteria used at the same time have advantages in utilizing polybutylene adipate and naked algae paramylon, avoiding excessive utilization of carbon sources by other aerobic bacteria; in the process of treating aquaculture tail water with a low carbon-nitrogen ratio, a longer service life and better denitrification effect can be obtained, and the problem of excessive COD in the effluent is less likely to occur, which helps to meet the discharge standards of the tail water.

Description

Technical Field

[0001] The present invention relates to a method for deep denitrification of low carbon-nitrogen ratio sewage by denitrification, and specifically proposes the application of a euglena-based slow-release carbon material coupled with heterotrophic nitrification-aerobic denitrifying bacteria in water treatment, belonging to the technical field of water treatment. Background Art

[0002] With the rapid development of aquaculture in my country, the residual feed and the excrement of aquaculture organisms rich in nitrogen, phosphorus and organic matter contained in the aquaculture tailwater will aggravate the eutrophication of the waters adjacent to the aquaculture, resulting in increasingly prominent problems such as environmental pollution caused by the discharge of aquaculture tailwater in my country.

[0003] At present, the treatment methods for aquaculture tailwater are mainly divided into three types: physical, chemical and biological remediation. Among them, biological remediation is considered to be the most economical, reasonable and environmentally friendly method. Bioremediation is mainly divided into two methods: phytoremediation and microbial remediation. However, for phytoremediation, its purification effect is significantly affected by seasonal factors. Its purification capacity is weaker in autumn and winter. If it is not harvested in time during the withering season, it will cause secondary pollution to the water body. Although microbial remediation can minimize the concentration of pollutants such as nitrogen and phosphorus, it needs to solve the problem of low denitrification efficiency caused by insufficient carbon source in aquaculture tailwater, as well as overcome the cumbersome steps of traditional aerobic nitrification-anoxic denitrification.

[0004] Therefore, to ensure smooth and efficient denitrification, an external carbon source is required. Currently, most denitrification carbon sources use traditional nitrogen sources such as alcohols, acetic acid, and glucose, which are subject to high dosage, high operating costs, and easy loss in water. To overcome the drawbacks of adding traditional liquid carbon sources like methanol, acetic acid, and glucose, slow-release carbon materials have emerged, combining natural polymers (such as plant cellulose and starch) with synthetic biodegradable polymers (such as polylactic acid, polycaprolactone, and polyvinyl alcohol). While these composite slow-release carbon materials offer some control over carbon source release compared to traditional liquid carbon sources or natural polymers alone, they do so because a high proportion of the natural polymers used are readily soluble or dispersible in water. For example, 24.68% of the organic carbon in plant straw is highly soluble in water, releasing all of it into the water within two days of immersion. Consequently, these composite slow-release carbon materials still pose secondary pollution issues, such as high effluent color and excessive COD levels. In addition, materials like plant straw that have been soaked in water for a long time will have obvious disadvantages such as becoming soft, collapsing or breaking.

[0005] Furthermore, traditional denitrification requires the separation of aerobic nitrification and anoxic / anaerobic denitrification units, each performed by different bacteria. This is exemplified by the A2O process (anaerobic-anoxic-aerobic) commonly used in sewage treatment plants. However, in situ remediation of natural water bodies lacks the stringent control required in sewage treatment plants, significantly impacting denitrification efficiency. Furthermore, the bacterial communities are naturally domesticated, lacking the ability to enhance denitrification with enhanced bacteria that can adapt to a wider temperature range.

[0006] A search revealed that Chinese patent publication number CN114349281A discloses a denitrification and phosphorus removal device and method for treating low-carbon-nitrogen ratio contaminated water. This device separates traditional aerobic nitrification from anaerobic denitrification, implementing them separately using different bacterial species. This is because aerobic nitrifiers are autotrophic and require a reduced carbon source to create an alkaline environment, while anaerobic denitrifiers are heterotrophic and require an increased carbon source to create a weakly alkaline environment. The device's ecological treatment chamber houses plants to absorb some nitrogen and phosphorus, while aeration creates an aerobic environment and promotes nitrification by aerobic nitrifiers. The enhanced denitrification chamber utilizes physical adsorption using zeolite and shell powder, while the anaerobic denitrification chamber creates a weakly alkaline environment to promote anaerobic denitrification at optimal pH conditions. Furthermore, the anaerobic denitrification chamber uses lightweight biochar cross-linked with dense diatomaceous earth, which has excellent adsorption and oxidizing properties. Glucose or starch is loaded onto the biochar as a usable carbon source. This patent focuses more on denitrification and phosphorus removal, but does not mind the COD content of the effluent water quality. Its effluent COD is higher than the discharge standard of aquaculture tail water, and is not suitable for application in aquaculture tail water purification. In order to improve denitrification and phosphorus removal, this patent uses glucose and starch as loaded carbon sources, the release of which is difficult to control and easily forms a short-term carbon source excess. Therefore, the nitrogen and phosphorus content of the raw water treated by this patent is extremely high, and it is not suitable for the treatment of aquaculture tail water with low effluent COD, which is a polluted water body with low nitrogen and phosphorus content. At the same time, since glucose and starch can be used by most bacterial communities in nature and are quickly utilized carbon sources, not only anaerobic denitrifying bacteria can use them, the anaerobic denitrifying bacteria and other anaerobic bacteria have a greater competitive pressure on carbon sources.

[0007] The Chinese patent with publication number CN114506919A discloses a high-efficiency purification composite biological filler and its preparation method. This method also separates traditional aerobic nitrification from anaerobic denitrification, and realizes them separately by different bacterial species. The patent mixes diatomaceous earth pellets with naturally domesticated aerobic biological activated sludge until the microorganisms fully form biofilms to form diatomaceous earth biological pellets, forming an aerobic nitrifying bacterial community located in the upper layer of the device; a composite biological filler containing quartz sand, zero-valent iron, activated carbon, composite microbial agents and porous slow-release biomass carbon source is added to the deep purification layer. The composite microbial agent adopts an artificially added facultative anaerobic denitrification and denitrification composite bacterial preparation, and the bacterial species include Pseudomonas, Bacillus and Alcaligenes. The porous slow-release biomass carbon source of this patent is a porous biomass solid carbon source produced by hot alkali processing of natural carbon sources such as corn cobs, rice husks, sawdust or corn stalks. About a quarter of the organic carbon in plant straw is highly soluble in water, and treatment with a hot alkaline aqueous solution further disperses about half of the non-degradable lignin in the alkaline water. If this high-chroma, high-organic alkaline wastewater is not properly treated, it will also cause significant environmental pollution. Furthermore, plant straw treated with this alkaline method is soaked in water for a long time and, after being acted upon by microorganisms, becomes significantly softer and more easily broken. Furthermore, residual non-degradable substances may still remain, which can easily cause blockage of water pores. The bacterial agent used does not employ some immobilization measures, and is easily lost with the water flow. Furthermore, this type of straw processed with the hot alkaline method mainly contains cellulose, hemicellulose, and residual lignin. Bacteria that can use cellulose and hemicellulose as carbon sources are also very common in nature, so the added anaerobic denitrifying bacteria face a high competition for carbon sources with other anaerobic bacteria. At the same time, this patent only measures the ammonia nitrogen content in water bodies. Ammonia nitrogen is a form of nitrogen in water bodies and is also the form of nitrogen that is easiest to remove in biological denitrification. However, part of it may be directly utilized by organisms, while the other part is converted into other forms of nitrogen and still exists in the water body. Summary of the Invention

[0008] The technical problem to be solved by the present invention is: in view of the problems existing in the prior art, a composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria is proposed for use in water treatment.

[0009] To achieve the above object, the technical solution of the present invention is as follows:

[0010] A euglena-based slow-release carbon material coupled with heterotrophic nitrification-aerobic denitrification bacteria comprises a slow-release carbon carrier and immobilized heterotrophic nitrification-aerobic denitrification bacteria. The slow-release carbon carrier is formed by mixing euglena particles with polybutylene adipate and then attaching and fixing the mixed particles to an elastic filler. The immobilized heterotrophic nitrification-aerobic denitrification bacteria are composed of Pseudomonas stutzeri and / or Microbacterium oxidans.

[0011] In the above technical solution, Euglena is a single-cell algae, and the main component of Euglena is blood red Euglena ( Euglena sanguinea ), its cells are rich in a type of paramylon, which can account for over 56% of the dry matter content, and as high as 85%. Paramylon is a linear β-1,3 glucan, distinct from the linear α-1,4 glycosidic chains or branched α-1,6 glycosidic chains found in common starches. Paramylon has a dense triple helix structure, making it insoluble in water. It can serve as a carbon source for denitrifying bacteria that produce β-1,3 glucanases, thereby reducing carbon consumption by other aerobic bacteria.

[0012] Polybutylene adipate (PBA) offers excellent molding and processing properties, unlike materials like polylactic acid and polyvinyl alcohol, which can become noticeably soft or break after prolonged immersion in water. PBA not only serves as a carrier for microbial attachment but also provides a carbon source for specific denitrifying bacteria, reducing carbon source consumption by other aerobic bacteria. Furthermore, the range of bacteria capable of degrading PBA is further reduced, significantly reducing carbon source competition from other bacteria.

[0013] Compared with polybutylene adipate, paramylon is more easily decomposed and utilized by bacteria. The present invention coordinates carbon release, carbon utilization and aerobic denitrification processes by combining PBA with Euglena to obtain a longer service life of the slow-release carbon carrier and better effluent water quality.

[0014] Pseudomonas stutzeri ( Pseudomonas stutzeri ), deposited on October 19, 2020, at the General Microbiology Center of the China General Culture Collection (CGMCC), located at No. 3, Yard 1, Beichen 4th Road, Chaoyang District, Beijing, under the accession number CGMCC No. 20910. Pseudomonas stutzeri can use inorganic nitrogen such as ammonia, nitrite, or nitrate in water as its sole nitrogen source. It also has a wide range of carbon sources, including the ability to decompose and utilize complex macromolecules such as starch, paramyxoline, cellulose, and polybutylene adipate. It can also simultaneously carry out heterotrophic nitrification and aerobic denitrification in situ at temperatures between 6 and 35°C.

[0015] Microbacterium oxydans ( Microbacterium oxydans), deposited on June 21, 2021, at the General Microbiology Center of the China General Culture Collection (CGMCC), located at No. 3, Yard 1, Beichen 4th Road, Chaoyang District, Beijing, under the accession number CGMCC No. 22738. Microbacterium oxidans can absorb more than three times the phosphorus of ordinary bacteria and can use inorganic nitrogen such as ammonia and nitrate in water as its sole nitrogen source. It also utilizes a wide range of carbon sources, breaking down and utilizing complex macromolecules such as starch, paramyxocarp, cellulose, polybutylene adipate, and phenol. It can also simultaneously carry out heterotrophic nitrification and aerobic denitrification in situ at temperatures between 6 and 35°C.

[0016] In summary, the present invention utilizes low-temperature-resistant heterotrophic nitrifying and aerobic denitrifying bacteria, enabling nitrification and denitrification to occur simultaneously under heterotrophic and aerobic conditions, and to be completed by the same bacteria. The slow-release carbon carrier employed is composed of Euglena particles and polybutylene adipate. Euglena is rich in paramylon, which has a dense triple-helix structure, making it insoluble in water. Furthermore, paramylon has a β-1,3 glycosidic chain, which differs from the linear α-1,4 or branched α-1,6 glycosidic chains of common starch. This structure can serve as a carbon source for denitrifying bacteria with β-1,3 glucanases, thereby reducing carbon source consumption by other aerobic bacteria lacking β-1,3 glucanases. Furthermore, polybutylene adipate, as the main component of the slow-release carbon carrier, does not become noticeably soft or breakable after prolonged immersion in water, and the range of bacteria capable of degrading it is further reduced, significantly reducing carbon source competition from other bacteria.

[0017] The technical solution further optimized by the present invention is as follows:

[0018] Furthermore, the naked algae particles and polybutylene adipate are mixed uniformly at a mass ratio of 1:20-400 and then attached and fixed to a brush-shaped elastic filler; the Pseudomonas stutzeri and Microbacterium oxidans are mixed uniformly at a concentration ratio of 1-3:1-2 and then attached and fixed to a brush-shaped elastic filler.

[0019] Furthermore, the Pseudomonas stutzeri is Pseudomonas stutzeri ( Pseudomonas stutzeri )ZJ4, which has a deposit number of CGMCC NO.20910; the oxidans Microbacterium is oxidans Microbacterium ( Microbacterium oxydans )XJ, its deposit number is CGMCC NO.22738.

[0020] The present invention provides a method for preparing a euglena-based slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria, comprising the following steps:

[0021] The first step is to prepare a slow-release carbon carrier. Euglena particles are prepared by combining Euglena powder with a binder through a bridging effect. The Euglena particles are mixed with polybutylene adipate to obtain a mixed solution. A brush-shaped elastic filler is then immersed in the mixed solution for attachment to obtain an elastic filler loaded with a slow-release carbon material.

[0022] Step 2: Preparation of immobilized heterotrophic nitrifying-aerobic denitrifying bacteria: Pseudomonas stutzeri and / or Microbacterium oxidans are added to a polyvinyl alcohol solution to obtain a bacterial solution. A brush-shaped elastic filler is then immersed in the bacterial solution, and a saturated boric acid solution is added dropwise to the bacterial solution to allow the Pseudomonas stutzeri and / or Microbacterium oxidans to adhere to the elastic filler, thereby obtaining an elastic filler loaded with immobilized heterotrophic nitrifying-aerobic denitrifying bacteria.

[0023] The third step is to mix and match the elastic filler loaded with slow-release carbon material and the elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria to obtain a euglena-based slow-release carbon material coupled with heterotrophic nitrification-aerobic denitrification bacteria.

[0024] In the first step, euglena or pure cultured sanguineous euglena are collected, dried, ground, and sieved through a 200-mesh sieve for later use; 4-6% polyvinyl alcohol (PVA) is prepared as a binder; 1 kg of euglena powder is added to a mixing granulator, and the binder is evenly sprayed in a mist form through a high-pressure nozzle to form euglena particles with a particle size of 0.3-2 mm. After drying, the particles are sieved through a 20-mesh sieve for later use; polybutylene adipate (PBA) is melted at 75° C., and the polybutylene adipate and euglena particles are mixed in a mass ratio of 20:1 to 400:1 to obtain a mixed liquid; a brush-shaped elastic filler is immersed in the mixed liquid for attachment, removed from the liquid surface after 20±5 seconds, and cooled at room temperature to fix the filler into shape.

[0025] In the second step, polyvinyl alcohol (PVA) is heated and dissolved in water to a final concentration greater than 6%, and then cooled to below 40°C to obtain a polyvinyl alcohol solution; Pseudomonas stutzeri and / or Microbacterium oxydans are added to the polyvinyl alcohol solution to a final bacterial concentration of 1×10 6 CFU / mL~2×10 7 CFU / mL, immerse the brush-shaped elastic filler in the bacterial solution, stir slowly, and add saturated boric acid solution according to 4% to 10% of the volume of the bacterial solution during the stirring process. Continue stirring for 1 minute to make the sticky substances attached to the elastic filler significantly aggregate. Gently take out the elastic filler, and then slowly immerse it in saturated boric acid solution for 1 to 12 hours, and then soak it in water for 4 to 6 hours to obtain the elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria.

[0026] In the above technical solution, the concentration ratio of Pseudomonas stutzeri to Microbacterium oxydans is preferably 1-3:1-2.

[0027] Furthermore, the Pseudomonas stutzeri is Pseudomonas stutzeri ( Pseudomonas stutzeri )ZJ4, which has a deposit number of CGMCC NO.20910; the oxidans Microbacterium is oxidans Microbacterium ( Microbacterium oxydans )ZJ, its deposit number is CGMCC NO.22738.

[0028] The present invention also provides an application of a euglena-based slow-release carbon material coupled with heterotrophic nitrification-aerobic denitrification bacteria in water treatment.

[0029] The application of the above-mentioned naked algae-based slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria in purifying aquaculture tail water.

[0030] Furthermore, the elastic filler loaded with slow-release carbon material and the elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria were mixed in a ratio of 10:1, hung below the floating bed support on the water surface, and immersed in the aquaculture tail water.

[0031] The present invention uses a brush-shaped elastic filler loaded with fixed heterotrophic nitrification-aerobic denitrification bacteria as a bacterial reservoir for continuously strengthening aerobic denitrification bacteria, so that the bacteria to be strengthened will not be gradually lost due to water impact, and the two bacteria used in the present invention have good low-temperature resistance.

[0032] In the present invention, “%” unless otherwise specified refers to weight percentage.

[0033] The present invention is conducive to coordinating the carbon release rate and the denitrification and denitrification process, strengthens aerobic denitrifying bacteria that adapt to a wide temperature range, and the two bacteria used at the same time have advantages in utilizing polybutylene adipate and paramylon, avoiding excessive utilization of carbon sources by other aerobic bacteria; in the process of treating aquaculture tail water with a low carbon-nitrogen ratio, a longer service life and better denitrification effect can be obtained, and the problem of excessive COD in the effluent is less likely to occur, which helps to meet the discharge standards of the tail water. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] Figure 1 Schematic diagram of the degradation effect of PBA under the treatment conditions of Pseudomonas stutzeri, Microbacterium oxidans and Pseudomonas stutzeri + Microbacterium oxidans in the present invention.

[0036] Figure 2 Schematic diagram of the effect of the amount of Euglena added on the TN removal effect in the present invention.

[0037] Figure 3 Schematic diagram of the structure of the reactor in the present invention.

[0038] Figure 4This is a schematic diagram of the COD treatment effect of aquaculture tail water in Example 1 of the present invention.

[0039] Figure 5 This is a schematic diagram of the TN water treatment effect of aquaculture tail in Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be described in further detail below with reference to the following examples, but the present invention is not limited to the examples given.

[0041] The present invention provides an application of a euglena-based slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria in purifying aquaculture tail water, specifically comprising:

[0042] Preparation of slow-release carbon carrier: Collect naked algae or pure cultured blood-red naked algae, dry them, grind them, and pass them through a 200-mesh sieve for later use; prepare 4-6% polyvinyl alcohol (PVA) as a binder; add 1 kg of naked algae powder into a mixing granulator, and spray the binder evenly in a mist form through a high-pressure nozzle to form naked algae particles with a particle size of 0.3-2 mm. After drying, pass them through a 20-mesh sieve for later use; melt polybutylene adipate (PBA) at 75°C, and mix them at a mass ratio of polybutylene adipate to naked algae particles of 20:1 to 400:1 to obtain a mixed liquid; immerse a brush-shaped elastic filler made of PP material (purchased from Yixing Lianyi Environmental Protection Co., Ltd.) in the mixed liquid for attachment, remove it from the liquid surface after 20±5s, and cool it at room temperature to fix it into shape.

[0043] Preparation of immobilized heterotrophic nitrification-aerobic denitrification bacteria: Polyvinyl alcohol (PVA) was heated and dissolved in water to a final concentration greater than 6%, and then cooled to below 40°C to obtain a polyvinyl alcohol solution; Pseudomonas stutzeri and Microbacterium oxidans were added to the polyvinyl alcohol solution to a final bacterial concentration of 1×10 6 CFU / mL~2×10 7 CFU / mL, the concentration ratio of Pseudomonas stutzeri to Microbacterium oxidans is preferably 1-3: 1-2, a brush-shaped elastic filler made of PP material (purchased from Yixing Lianyi Environmental Protection Co., Ltd.) is immersed in the bacterial solution and slowly stirred. During the stirring process, a saturated boric acid solution is added dropwise at a rate of 4% to 10% of the volume of the bacterial solution. Stirring is continued for 1 minute to allow the sticky substance attached to the elastic filler to significantly aggregate. The elastic filler is gently removed and slowly immersed in a saturated boric acid solution for 1 to 12 hours, followed by soaking in water for 4 to 6 hours to obtain an elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria.

[0044] The brush-shaped elastic filler attached with slow-release carbon carrier and the brush-shaped elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria are matched in a ratio of 10:1, hung under various types of floating bed supports on the water surface, and immersed in the aquaculture tail water.

[0045] The chemical reagents and materials used in the present invention are all commercially available.

[0046] Pseudomonas stutzeri ( Pseudomonas stutzeri ), deposited on October 19, 2020, at the General Microbiology Center of China Culture Collection Administration (CGMCC), address: No. 3, Yard 1, Beichen 4th Road, Chaoyang District, Beijing, with the deposit number CGMCC No. 20910.

[0047] Microbacterium oxydans ( Microbacterium oxydans ), deposited on June 21, 2021 at the General Microbiology Center of China Culture Collection Administration (CGMCC), address: No. 3, Yard 1, Beichen 4th Road, Chaoyang District, Beijing, with the deposit number CGMCC No. 22738.

[0048] In the present invention, the synergistic effect of Pseudomonas stutzeri and Microbacterium oxidans is beneficial to improving the degradation rate of PBA. The specific verification method is as follows: using a triangular flask as a container and adopting intermittent shaking flask culture, 1.5g PBA is added as the sole carbon source to 200mL of denitrification culture medium (including NaCl 2.5g / L, MgSO4·7H2O 0.1 g / L, FeSO4·7H2O 0.02 g / L, MnSO40.016 g / L, CaCl20.02 g / L, NaCO30.02 g / L, KH2PO40.213 g / L, KNO30.722 g / L, and trace elements are the same as Hoagland medium), and the ambient temperature is 25°C. The strain is aseptically cultured in LB medium, collected by centrifugation, washed with sterile water and set aside. Three treatments were set up, namely, adding Pseudomonas stutzeri alone (1.24×10 7 / mL), Microbacterium oxidans (1.35×10 7 / mL), combined with Pseudomonas stutzeri (8.1×10 6 / mL) + Microbacterium oxidans (4.6×10 6 The results showed that the combined treatment of Pseudomonas stutzeri and Microbacterium oxidans significantly improved the degradation rate of PBA, which was 43.84% higher than that of adding Microbacterium oxidans alone and 520.31% higher than that of adding Pseudomonas stutzeri alone (see Figure 1 ).

[0049] In this study, using Euglena and PBA as carbon sources can help accelerate TN (total nitrogen) removal to a certain extent. The specific verification method is as follows: 1.0 g of PBA was added to 200 mL of 10% Hoagland broth in a shake flask using a triangular flask as the container. The strain was sterilely cultured in LB medium, collected by centrifugation, washed with sterile water, and then added to a final concentration of Pseudomonas stutzeri (1.8 × 10 6 / mL) + Microbacterium oxidans (2.5×10 6 Five treatments were set up, with 0 g, 0.005 g, 0.010 g, 0.025 g, and 0.075 g of Euglena dry powder added, respectively. The culture was carried out at an ambient temperature of 25°C for 14 days. The results showed that the addition of an appropriate amount of Euglena rich in paramylon can significantly improve the efficiency of denitrification. When 0.0100 g of Euglena was added, the TN removal rate increased significantly by 22.90% (see Figure 2 ). Example 1

[0050] The aquaculture tail water is transported to the reactor for purification. Figure 3 As shown, the main body of the reactor is a rectangular block made of plastic with an effective volume of 12L. A brush-shaped elastic filler with an attached slow-release carbon carrier and a brush-shaped elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria are set in the main body of the reactor. The total filling volume of the two is about 30% of the effective volume of the reactor. The bottom of the reactor body is equipped with an aeration head to maintain DO greater than 3 mg / L and an ambient temperature of 25°C. The daily water exchange rate is 50%. The results showed that after a 20-day startup period, when the system operated stably, the influent COD concentration was 82.53±1.98 mg / L, and the effluent COD concentration was 8.80±2.11 mg / L; the influent TN concentration was 8.19±0.13 mg / L, and the effluent TN concentration was 1.56±0.17 mg / L (see Figure 4 and Figure 5 The effluent COD and TN levels meet the Class I standards for freshwater aquaculture tailwater discharge (COD ≤ 15mg / L, TN ≤ 3mg / L). Carbon source supplementation lasts for more than 60 days. Example 2

[0051] The aquaculture tail water is transported to the reactor for purification. Figure 3As shown, the reactor body is a rectangular plastic block with an effective volume of 12 L. The reactor body is equipped with brush-shaped elastic packing containing slow-release carbon carriers and immobilized heterotrophic nitrifying-aerobic denitrifying bacteria. The total volume of these two packings accounts for approximately 30% of the reactor's effective volume. Aeration heads are installed at the bottom of the reactor body to maintain a DO (dosage reduction) greater than 3 mg / L. The ambient temperature is 16°C. The daily water exchange rate is 40%. Results showed that after a 20-day startup period, when the system stabilized, the inlet COD concentration was 84.34 ± 1.94 mg / L and the effluent COD concentration was 9.32 ± 2.20 mg / L. The inlet TN concentration was 8.01 ± 0.15 mg / L and the effluent TN concentration was 1.87 ± 0.12 mg / L. The effluent COD and TN concentrations met the Class I standards for freshwater aquaculture effluent discharge (COD ≤ 15 mg / L, TN ≤ 3 mg / L). Example 3

[0052] The aquaculture tail water in the reactor is purified. Figure 3 As shown, the reactor body is a rectangular plastic block with an effective volume of 12 L. The reactor body is equipped with brush-shaped elastic packing containing slow-release carbon carriers and immobilized heterotrophic nitrifying-aerobic denitrifying bacteria. The total volume of these two packings accounts for approximately 30% of the reactor's effective volume. Aeration heads are installed at the bottom of the reactor body to maintain a DO greater than 3 mg / L. The ambient temperature is 8°C. The daily water exchange rate is 15%. Results showed that after a 25-day startup period, when the system stabilized, the inlet COD concentration was 83.72 ± 2.18 mg / L and the effluent COD concentration was 17.41 ± 1.25 mg / L. The inlet TN concentration was 8.23 ± 0.15 mg / L and the effluent TN concentration was 1.79 ± 0.11 mg / L. The effluent COD concentration met the secondary discharge standard for freshwater aquaculture effluent (COD ≤ 25 mg / L), and the effluent TN concentration met the primary discharge standard for freshwater aquaculture effluent (TN ≤ 3 mg / L).

[0053] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria, characterized in that: The invention comprises a slow-release carbon carrier and immobilized heterotrophic nitrification-aerobic denitrifying bacteria, wherein the slow-release carbon carrier is formed by mixing algae particles and polybutylene adipate and then adhering and fixing them to an elastic filler, and the immobilized heterotrophic nitrification-aerobic denitrifying bacteria are composed of Pseudomonas stutzeri and / or Microbacterium oxidans; the Pseudomonas stutzeri is Pseudomonas stutzeri ( Pseudomonas stutzeri )ZJ4, which has a deposit number of CGMCC NO.20910; the oxidans Microbacterium is oxidans Microbacterium ( Microbacterium oxydans )XJ, its deposit number is CGMCC NO.22738.

2. The composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria according to claim 1, characterized in that: The Euglena particles and polybutylene adipate are mixed evenly at a mass ratio of 1:20-400 and then attached and fixed to a brush-shaped elastic filler; the Pseudomonas stutzeri and Microbacterium oxidans are mixed evenly at a concentration ratio of 1-3:1-2 and then attached and fixed to a brush-shaped elastic filler.

3. The method for preparing a composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria according to claim 1 or 2, characterized in that: The following steps are involved: The first step is to prepare a slow-release carbon carrier. Euglena particles are prepared by combining Euglena powder with a binder through a bridging effect. The Euglena particles are mixed with polybutylene adipate to obtain a mixed solution. A brush-shaped elastic filler is then immersed in the mixed solution for attachment to obtain an elastic filler loaded with a slow-release carbon material. Step 2: Preparation of immobilized heterotrophic nitrifying-aerobic denitrifying bacteria: Pseudomonas stutzeri and / or Microbacterium oxidans are added to a polyvinyl alcohol solution to obtain a bacterial solution. A brush-shaped elastic filler is then immersed in the bacterial solution, and a saturated boric acid solution is added dropwise to the bacterial solution to allow the Pseudomonas stutzeri and / or Microbacterium oxidans to adhere to the elastic filler, thereby obtaining an elastic filler loaded with immobilized heterotrophic nitrifying-aerobic denitrifying bacteria. The third step is to mix the elastic filler loaded with the slow-release carbon material with the elastic filler loaded with the immobilized heterotrophic nitrification-aerobic denitrification bacteria to obtain the euglena-based slow-release carbon material coupled with heterotrophic nitrification-aerobic denitrification bacteria.

4. The method for preparing a composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria according to claim 3, characterized in that: In the first step, euglena or pure cultured sanguineous euglena are collected, dried, ground, and sieved through a 200-mesh sieve for later use; 4-6% polyvinyl alcohol is prepared as a binder; 1 kg of euglena powder is added to a mixing granulator, and the binder is evenly sprayed in a mist form through a high-pressure nozzle to form euglena particles with a particle size of 0.3-2 mm. After drying, the particles are sieved through a 20-mesh sieve for later use; polybutylene adipate is melted at 75° C., and the polybutylene adipate and euglena particles are mixed in a mass ratio of 20:1 to 400:1 to obtain a mixed solution; a brush-shaped elastic filler is immersed in the mixed solution for attachment, removed after 20±5 seconds, and cooled at room temperature to fix the filler into shape.

5. The method for preparing a composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria according to claim 4, characterized in that: In the second step, polyvinyl alcohol is heated and dissolved in water to a final concentration greater than 6%, and then cooled to below 40°C to obtain a polyvinyl alcohol solution; Pseudomonas stutzeri and / or Microbacterium oxidans are added to the polyvinyl alcohol solution to a final bacterial concentration of 1×10 6 CFU / mL~2×10 7 CFU / mL, immerse the brush-shaped elastic filler in the bacterial solution, stir slowly, and add saturated boric acid solution according to 4% to 10% of the volume of the bacterial solution during the stirring process to make the sticky substances attached to the elastic filler significantly aggregate. Take out the elastic filler, and then slowly immerse it in saturated boric acid solution for 1 to 12 hours, and then soak it in water for 4 to 6 hours to obtain the elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria.

6. The method for preparing a composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria according to claim 5, characterized in that: The Pseudomonas stutzeri is Pseudomonas stutzeri ( Pseudomonas stutzeri )ZJ4, which has a deposit number of CGMCC NO.20910; the oxidans Microbacterium is oxidans Microbacterium ( Microbacterium oxydans )XJ, its deposit number is CGMCC NO.22738.

7. Use of the composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria as claimed in any one of claims 1 to 2 in water treatment.

8. The use of the composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria in water treatment according to claim 7, characterized in that: Used to purify aquaculture tail water.

9. The use of the composite slow-release carbon material coupled with heterotrophic nitrification and aerobic denitrification bacteria in water treatment according to claim 8, characterized in that: The elastic filler loaded with slow-release carbon material and the elastic filler loaded with immobilized heterotrophic nitrification-aerobic denitrification bacteria are mixed in a ratio of 10:1, hung below the floating bed support on the water surface, and immersed in the aquaculture tail water.

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