Controllable-release composite carbon source-fungicide microsphere and preparation method and application thereof

Abstract

The invention relates to the technical field of sewage treatment, and discloses a controllable release composite carbon source-microbial agent microsphere and a preparation method and application thereof.The microsphere is composed of a composite carbon source, a microbial agent, a slow release matrix, a cross-linking agent, a reinforcing agent and an adversity-resistant auxiliary agent and is of a multi-stage pore structure; the precise gradient release of the carbon source and the efficient long-term attachment of the fungicide can be realized. By preferably selecting a low-temperature-resistant / high-salt denitrifying strain and cooperating with an adversity-resistant auxiliary agent, the microspheres show excellent denitrification performance in a low-temperature (5-15 DEG C) or high-salt (salinity of 1%-5%) environment, and the denitrification efficiency is improved by 20%-50% compared with that of a conventional technology. The microsphere is particularly prominent in denitrification application in sewage treatment, can efficiently treat industrial wastewater, urban sewage, marine pollution and other problems, is efficient and simple in preparation process, and has remarkable industrialization value and environmental benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a composite carbon source-bacteria agent microsphere with controllable release, and a preparation method and application thereof. Background Art

[0002] With the rapid development of industrialization and urbanization, sewage treatment has become an important issue in environmental protection. Nitrogen pollution is one of the main causes of eutrophication of water bodies, and biological denitrification processes are widely used due to their high efficiency and economy. However, there are still many challenges in actual sewage treatment: the dosage of added carbon sources (such as methanol, sodium acetate) is difficult to accurately control, which can easily cause waste or secondary pollution; the activity of microbial agents is easily affected by environmental conditions (such as pH, temperature, dissolved oxygen), and the loss of agents is serious; in low temperature (<15°C) or high salt (salinity>1%) environments, the activity of denitrifying bacteria decreases significantly, resulting in reduced denitrification efficiency or even process failure; the release rate of traditional composite materials is difficult to control, and they lack adaptability to extreme environments.

[0003] In recent years, researchers have attempted to improve denitrification efficiency by immobilizing carbon sources and microbial agents on carriers. However, existing technologies have proven to be inadequate. For example, the carbon source release rate is uncontrollable, the preparation process is complex, and the cost is high. Furthermore, under extreme conditions such as low temperatures or high salinity, microbial activity is difficult to maintain, resulting in poor denitrification results. These bottlenecks have limited the application of composite materials in complex wastewater treatment scenarios.

[0004] Therefore, there is an urgent need to develop a new type of microsphere material that can achieve efficient denitrification, controllable release and environmental adaptability in low temperature or high salt environments, which has become a technical problem that needs to be solved urgently. Summary of the Invention

[0005] The present invention aims to provide a composite carbon source-bacteria agent microsphere with controllable release, and a preparation method and application thereof, so as to solve the bottleneck problem of denitrification in low temperature or high salt environment in the prior art.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a composite carbon source-microbe microsphere with adjustable release, the raw materials, calculated by mass, include 20 to 50 parts of composite carbon source material, 10 to 30 parts of microbial agent, 15 to 40 parts of slow-release matrix material, 5 to 15 parts of cross-linking agent, 0 to 10 parts of enhancer, and 0 to 10 parts of adversity resistance additive, and the microsphere has a multi-level pore structure.

[0007] Preferably, as an improvement, the average particle size of the microspheres is 2 to 3 mm.

[0008] Preferably, as an improvement, the composite carbon source is at least one of glucose, sodium acetate, starch, and polylactic acid.

[0009] Preferably, as an improvement, the microbial agent is a low-temperature-resistant or high-salt-resistant denitrifying bacteria.

[0010] Preferably, as an improvement, the sustained-release matrix material is at least one of sodium alginate, chitosan, and polyvinyl alcohol; the cross-linking agent is at least one of calcium chloride and glutaraldehyde; and the reinforcing agent is at least one of nanocellulose and diatomaceous earth.

[0011] Preferably, as an improvement, the stress-resistant additive is at least one of glycerol, betaine, and trehalose.

[0012] Preferably, as an improvement, a composite carbon source-bacteria agent microsphere with controllable release is used as a low-temperature / high-salt denitrifier for sewage treatment.

[0013] Preferably, as an improvement, the temperature of the low temperature is 5-15° C., and the salinity of the high salt is 1-5%.

[0014] Preferably, as an improvement, a method for preparing composite carbon source-bacteria agent microspheres with controllable release comprises the following steps:

[0015] Step I: adding the composite carbon source, the slow-release matrix material, and the stress-resistant additive into deionized water and stirring until a uniform and transparent gel matrix is ​​formed;

[0016] Step II, slowly adding the microbial agent and the enhancer to the gel matrix, stirring under sterile conditions to obtain a mixed solution;

[0017] Step III, dropping the mixed solution into the stirred crosslinker solution to perform a crosslinking reaction to form microspheres;

[0018] Step IV: Wash the microspheres with sterile deionized water to remove residual cross-linking agent on the surface, and store them for future use.

[0019] Preferably, as an improvement, in step III, the cross-linking time is 10 to 60 minutes, and the carbon source release rate of the microspheres is 0.1 to 0.5 g / L·d.

[0020] The principle and advantages of this solution are: in actual application, in response to the bottleneck problem of denitrification in low temperature or high salt environment in the existing technology, this technical solution comprehensively optimizes the dosage form, formula composition and preparation process of the denitrifier. In terms of dosage form, a sustained-release matrix (sodium alginate) and a cross-linking agent (calcium chloride) are used to work together to construct a multi-level pore structure with a pore size distribution of 50nm to 500μm. Sodium alginate as a sustained-release matrix has good gelation and biocompatibility. After cross-linking with calcium chloride, it forms a stable multi-level pore structure, which significantly improves the mechanical strength and carbon source storage capacity of the microspheres, so that the carbon source storage capacity reaches 0.5 to 1.2g / g microspheres, and the bacterial agent attachment density reaches 10 9CFU / g. In terms of formula composition, by adjusting the ratio of slow-release matrix (15-40%) and cross-linking time (10-60 minutes), the carbon source release rate can be precisely controlled within the range of 0.1-0.5g / L·d to meet different denitrification requirements in wastewater treatment. In addition, this technical solution has outstanding innovative advantages in the optimization of carbon sources, cross-linking agents and other additives:

[0021] In terms of carbon source optimization: glucose and sodium acetate: glucose provides a rapidly available carbon source to support the efficient metabolism of the bacterial agent in the early stage; sodium acetate serves as a slow-release carbon source to extend the carbon source supply cycle. In Example 1, the combination of glucose (25%) and sodium acetate (15%) enables the microspheres to exhibit excellent denitrification performance in urban sewage treatment, and the denitrification efficiency is increased by about 30% compared to a single carbon source. Comparative tests show that the release rate of the glucose + polylactic acid combination fluctuates greatly (±30%), while glucose + sodium acetate can achieve linear release (R 2 >0.95). Starch and polylactic acid: Starch offers excellent biodegradability and cost advantages, while polylactic acid provides long-term, stable carbon source release. This combination performs exceptionally well in high-salt environments, delivering a stable and sustained carbon source release rate, making it suitable for marine pollution control.

[0022] Optimizing the crosslinking agents: Calcium chloride and glutaraldehyde: Calcium chloride rapidly forms the microsphere skeleton through ionic crosslinking, while glutaraldehyde further enhances the chemical crosslinking strength, improving the stability and durability of the microspheres. The dual crosslinking of calcium chloride (ionic crosslinking) and glutaraldehyde (covalent crosslinking) allows the microspheres to maintain structural integrity even under high water flow. Controlling the crosslinking time within 10 to 60 minutes achieves an ideal pore structure, reduces the microsphere swelling rate from 120% to 50%, and extends the sustained-release period to over 30 days.

[0023] In addition, the synergistic effect of low-temperature / high-salt strains (microbial agents) and betaine (adversity-resistant additive) increases the denitrification efficiency of the microspheres by 20% to 50% in an environment of 5 to 15°C or a salinity of 1% to 5%; nanocellulose (enhancer) and sodium alginate (sustained-release matrix) work together, with nanocellulose enhancing the mechanical strength and pore structure stability of the microspheres, and synergizing with sodium alginate to improve the microspheres' resistance to water flow impact and extend their service life.

[0024] During the technology research and development stage, how to maintain the activity of microorganisms in low temperature / high salt environment is one of the research and development difficulties of this technical solution. The activity of traditional denitrifying bacteria decreases significantly in low temperature (5-15°C) or high salt (salinity 1%-5%) environment, resulting in low denitrification efficiency. This patent significantly improves the survival ability and metabolic activity of bacterial agents in extreme environments by screening low temperature / high salt resistant strains (such as Psychrobacter genera and Halomonas genera) and combining them with stress-resistant adjuvants (such as betaine and trehalose). The denitrification efficiency is increased by 20% to 50% compared with conventional technologies. On the basis of ensuring the maintenance of microbial activity, how to make the bacterial agents adhere for a long time to avoid loss is another research and development difficulty of this technical solution. In traditional carrier fixation technology, microbial agents are easily lost with water, and their activity is difficult to maintain for a long time. This solution constructs microspheres with high attachment density (the attachment density of the bacterial agent reaches 109 CFU / g) through the synergistic effect of slow-release matrix and cross-linking agent, which significantly improves the stability of the bacterial agent. In addition, to ensure the long-term release of the composite carbon source-bacteria agent microspheres, this technical solution achieves an adjustable carbon source release rate within the range of 0.1 to 0.5 g / L·d by constructing a multi-level pore structure (pore size 50 nm to 500 μm) and a preferred slow-release matrix (such as sodium alginate), thus solving the technical bottleneck of excessively fast or slow release of the carbon source.

[0025] The composite carbon source-microbes of this technical solution have the following advantages through component optimization and process innovation:

[0026] 1. Adaptability to extreme environments: This solution prefers low-temperature / high-salt tolerant strains (such as Psychrobacter sp.) and supplements them with stress-tolerant additives (such as betaine). The denitrification efficiency is stably maintained at 70-85% at 5°C or 5% salinity, which is 20-50% higher than conventional technologies.

[0027] 2. Mechanical strength and sustainability: Reinforcements (such as nanocellulose) make the compressive strength of the microspheres reach 50-80 kPa, extending the service life to more than 60 days, and the material is biodegradable, meeting green environmental protection requirements.

[0028] 3. The construction of a multi-level pore structure enables the regulation of carbon source release and the attachment and activity maintenance of microbial agents: The multi-level pore structure (pore size distribution 50nm to 500μm) provides ample storage space for the carbon source (storage capacity reaches 0.5-1.2g / g microspheres), and regulates the release rate through pore size and distribution, ensuring precise gradient release of the carbon source to avoid waste or insufficiency. In addition, the multi-level pores provide a high density of attachment sites for microbial agents (109 CFU / g), while the pore structure protects the agents from external water erosion and environmental stress, maintaining long-term activity. The pore structure and stress-resistant additives work synergistically to enhance the stability of the microspheres in low-temperature / high-salt environments, significantly improving denitrification efficiency.

[0029] 4. Wide range of applications for denitrification in sewage treatment: The microspheres have shown excellent denitrification capabilities in sewage treatment. Specific application scenarios include:

[0030] (1) Industrial wastewater treatment: For high COD wastewater (COD>5000mg / L) from chemical, pharmaceutical and other industries, microspheres can stably provide carbon sources and support bacterial denitrification, with a denitrification efficiency of over 80%;

[0031] (2) Urban sewage treatment: Under low temperature conditions in winter (5-10°C), microspheres maintain high denitrification efficiency, reduce carbon source waste, and reduce operating costs by 15-30%;

[0032] (3) Marine pollution control: For marine aquaculture tail water (salinity 3-5%), the denitrification efficiency of microspheres in a high-salt environment reaches 75-85%, effectively reducing nitrogen pollution emissions.

[0033] In summary, the beneficial effects of this technical solution are: the release of the composite carbon source-bacterial agent microsphere carbon source of this technical solution is precise and controllable, which significantly improves the carbon source utilization rate in sewage treatment; the bacterial agent has stable attachment and prolongs the denitrification cycle; the denitrification efficiency is high under extreme environments, which broadens the application scope of sewage treatment; the preparation process is efficient and simple, low-cost, and easy to promote and apply. DETAILED DESCRIPTION

[0034] The following is further described in detail through specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials, reagents, etc. used are all commercially available.

[0035] Program Overview:

[0036] The invention discloses a composite carbon source-microbe agent microsphere with controllable release. The microsphere is composed of the following components by mass percentage: 20% to 50% composite carbon source material, 10% to 30% microbial agent, 15% to 40% slow-release matrix material, 5% to 15% cross-linking agent, 0% to 10% enhancer, and 0% to 10% stress resistance additive.

[0037] Wherein, the composite carbon source is at least one of glucose, sodium acetate, starch and polylactic acid.

[0038] The microbial agent is a low-temperature-resistant or high-salt-resistant denitrifying bacterium, such as a bacterial solution of a strain of the genus Psychrobacter, Halomonas or Paracoccus.

[0039] The sustained-release matrix material is at least one of sodium alginate, chitosan and polyvinyl alcohol.

[0040] The cross-linking agent is at least one of calcium chloride and glutaraldehyde.

[0041] The reinforcing agent is at least one of nanocellulose and diatomaceous earth.

[0042] The stress-resistant additive is at least one of glycerol, betaine, and trehalose; and is used to enhance the activity of the microbial agent in low or high temperature environments.

[0043] A method for preparing composite carbon source-bacteria agent microspheres with controllable release comprises the following steps:

[0044] Step I: adding the composite carbon source, the slow-release matrix material, and the stress-resistant additive into deionized water and stirring until a uniform and transparent gel matrix is ​​formed;

[0045] Step II, slowly adding the microbial agent and the enhancer to the gel matrix, stirring under sterile conditions to obtain a mixed solution;

[0046] Step III, dropping the mixed solution into the stirred crosslinker solution to perform a crosslinking reaction to form microspheres;

[0047] Step IV: Wash the microspheres with sterile deionized water to remove residual cross-linking agent on the surface, and store them for future use.

[0048] The invention relates to the application of a composite carbon source-bacteria agent microsphere with controllable release as a low-temperature / high-salt denitrifier for sewage treatment.

[0049] Example 1: Municipal sewage treatment denitrification test

[0050] A composite carbon source-bacteria agent microsphere with controllable release, the microsphere is composed of the following components by mass percentage:

[0051] Composite carbon source: glucose 25g (25% by mass), sodium acetate 15g (15% by mass);

[0052] Microbial agent: Psychrobacter sp. (bacterial concentration 10 8 CFU / mL) 40mL (20% by mass);

[0053] Sustained-release matrix: sodium alginate 35g (35% by mass);

[0054] Cross-linking agent: 500 mL of calcium chloride solution (concentration 2% w / v);

[0055] Reinforcement agent: nanocellulose 5g (5% by mass);

[0056] Stress resistance additive: betaine 5g (5% by mass).

[0057] A method for preparing composite carbon source-bacteria agent microspheres with controllable release comprises the following steps:

[0058] Step I: Glucose, sodium acetate, sodium alginate, and betaine were added to 100 mL of deionized water and stirred at 200 rpm for 20 minutes at 25° C. until a uniform, transparent gel matrix (viscosity of approximately 1500 mPa·s) was formed;

[0059] Step II: Slowly add the Psychrobacter sp. bacterial solution and nanocellulose into the gel matrix and stir at 150 rpm for 10 minutes under sterile conditions to ensure that the bacterial agent is evenly dispersed and its activity is not destroyed;

[0060] Step III: The mixed solution was added dropwise to a stirred 2% calcium chloride solution (stirring speed 100 rpm) using a titration device (needle inner diameter 0.8 mm, dripping rate 1 mL / s) and the cross-linking reaction was carried out for 30 minutes to form microspheres with an average particle size of about 2-3 mm;

[0061] Step IV: Wash the microspheres three times with sterile deionized water (100 mL each time) to remove residual calcium chloride on the surface, and then seal and store at 4°C for later use.

[0062] Experimental Example 1 Denitrification Application Test

[0063] Application background: In the winter operation of sewage treatment plants in northern cities, the total nitrogen (TN) concentration in the water is high and the temperature is low, and traditional denitrification methods are not efficient enough.

[0064] Experimental conditions: Municipal sewage (initial TN 50 mg / L, COD 200 mg / L, water temperature 5°C, pH 7.0) was tested in a 10-L sequencing batch reactor (SBR). The microspheres prepared in Example 1 were added at a dosage of 20 g / L, the aeration rate was 0.5 L / min, and the operation cycle was 12 hours / time.

[0065] Test method: Samples were taken daily to determine the TN concentration (Water quality - Determination of total nitrogen - Alkaline potassium persulfate digestion - UV spectrophotometry method, HJ 636-2012 standard) and the carbon source release was recorded (determined by TOC analyzer).

[0066] Microsphere compressive strength: measured using a universal material testing machine.

[0067] Analysis of results: The results show that: the denitrification efficiency of Example 1 reached 78% (55% for conventional carbon source-microbial agent system), TN was reduced from 50 mg / L to 11 mg / L; the carbon source release rate was stable at 0.3 g / L·d, and the release was sustained for 45 days, with a cumulative release of about 13.5 g / L of carbon source; the microspheres had a compressive strength of 65 kPa (measured by a universal material testing machine), a service life of 60 days, and no obvious breakage was observed; the operating cost was reduced by 20% (due to the reduction in additional carbon source addition and microbial agent supplementation).

[0068] Example 2 High-salt industrial wastewater denitrification test

[0069] The difference between this embodiment and embodiment 1 is that in this embodiment, the stress-resistant auxiliary agent is changed to 5 g of trehalose (5% by mass), and the other components are the same as those in embodiment 1.

[0070] The preparation method comprises the following steps:

[0071] Step I: Glucose, sodium acetate, sodium alginate, and trehalose were added to 100 mL of deionized water and stirred at 200 rpm for 25 minutes at 30°C to form a uniform gel matrix (viscosity of approximately 1600 mPa·s);

[0072] Step II: Add the Psychrobacter sp. bacterial solution and nanocellulose to the gel matrix and stir at 150 rpm for 12 minutes to ensure the activity of the bacterial agent;

[0073] Step III: The mixed solution was added dropwise to a 2% calcium chloride solution using a titration apparatus (dropping rate 1.2 mL / s), and the crosslinking time was extended to 40 minutes to form microspheres with a particle size of approximately 2.5 mm;

[0074] Step IV: Wash with deionized water three times (100 mL each time) and store at 4°C.

[0075] Experimental Example 2 Denitrification Application Test

[0076] Application background: Chemical enterprises discharge high-salinity wastewater (high salinity, high COD and TN concentrations), and traditional biological denitrification is severely inhibited by salinity.

[0077] Experimental conditions: Chemical wastewater (initial TN 80 mg / L, COD 6000 mg / L, salinity 5%, pH 6.8, water temperature 15°C) was tested in a 5L anaerobic-aerobic (A / O) reactor with a microsphere dosage of 25 g / L, DO controlled at 2-3 mg / L, and an operating cycle of 24 hours / time.

[0078] Test method: TN and COD concentrations were measured daily (TN using HJ 636-2012 standard, COD using the "Determination of Chemical Oxygen Demand in Water - Dichromate Method" HJ 828-2017 standard), and the amount of carbon source released by the microspheres and the activity of the bacterial agent (CFU count) were monitored.

[0079] Result analysis: The results show that the denitrification efficiency of the microspheres in Example 2 reached 82% (58% for the conventional carbon source-microorganism system), TN decreased from 80 mg / L to 14.4 mg / L; the COD removal rate reached 85%, decreased from 6000 mg / L to 900 mg / L; the carbon source release rate was 0.25 g / L·d, and the release lasted for 50 days, with a cumulative release of about 12.5 g / L of carbon source; the compressive strength of the microspheres was 70 kPa, the microorganism activity was maintained above 108 CFU / g, and the service life was 65 days.

[0080] Example 3 Marine aquaculture tail water denitrification test

[0081] The difference between this embodiment and embodiment 1 is that in this embodiment, the microbial agent is changed to 40 mL (20% by mass) of Halomonas sp. (bacterial solution concentration 108 CFU / mL), and the other components are the same as those in embodiment 1.

[0082] The preparation method comprises the following steps:

[0083] Step I: Glucose, sodium acetate, sodium alginate, and betaine were added to 100 mL of deionized water and stirred at 200 rpm for 20 minutes at 25° C. to form a gel matrix (viscosity of approximately 1550 mPa·s);

[0084] Step II: Add the Halomonas sp. bacterial solution and nanocellulose to the gel matrix and stir at 150 rpm for 15 minutes under sterile conditions to ensure uniform distribution of the bacterial agent;

[0085] Step III: The mixed solution was added dropwise to a 2% calcium chloride solution using a titration apparatus (dropping rate 1 mL / s) and cross-linked for 35 minutes to form microspheres with a particle size of approximately 2.2 mm;

[0086] Step IV: Wash with sterile deionized water three times (100 mL each time) and store at 4°C.

[0087] Experimental Example 3 Denitrification Application Test

[0088] Application background: Marine aquaculture tail water has the characteristics of high salinity and low TN concentration, requiring an efficient and low-cost denitrification solution.

[0089] Experimental conditions: Marine aquaculture tail water (initial TN 30 mg / L, COD 150 mg / L, salinity 4%, pH 7.5, water temperature 20°C) was tested in a 5L aerated biological filter (BAF) with a microsphere dosage of 15g / L, an aeration rate of 0.3L / min, and an operation cycle of 12 hours / time.

[0090] Test method: TN concentration (HJ 636-2012 standard) was measured daily, and the carbon source release rate (TOC analysis) and microsphere mechanical properties (compressive strength and deformation rate) were recorded.

[0091] Results showed that the denitrification efficiency of the microspheres in Example 3 reached 85% (60% for conventional methods), and TN was reduced from 30 mg / L to 4.5 mg / L. The carbon source release rate was 0.2 g / L·d, and the release lasted for 55 days, with a cumulative carbon source release of approximately 11 g / L. The microspheres had a compressive strength of 60 kPa, a deformation rate of less than 5%, and a service life of 70 days. The bacterial agent activity was stable at 109 CFU / g, and the TN emissions after tail water treatment met the first-level standard of the Pollutant Discharge Standard for Municipal Wastewater Treatment Plants (GB 18918-2002).

[0092] Example 4 Industrial wastewater denitrification test under low temperature environment

[0093] The difference between this embodiment and embodiment 1 is that in this embodiment, the microspheres include:

[0094] Composite carbon source: glucose 20g (20% by mass), polylactic acid 20g (20% by mass);

[0095] Microbial agent: Psychrobacter sp. (bacterial concentration 108 CFU / mL) 40 mL (20% by mass);

[0096] Sustained-release matrix: sodium alginate 30 g (30% by mass);

[0097] Cross-linking agent: 500 mL of calcium chloride solution (concentration 2% w / v);

[0098] Reinforcement agent: nanocellulose 5g (5% by mass);

[0099] Adversity resistance additive: 5g glycerol (5% by mass).

[0100] The preparation method comprises the following steps:

[0101] Step I: Glucose, polylactic acid, sodium alginate, and glycerol were added to 100 mL of deionized water and stirred at 250 rpm for 25 minutes at 25°C to form a uniform gel matrix (viscosity of approximately 1400 mPa·s);

[0102] Step II: Add the Psychrobacter sp. bacterial solution and nanocellulose to the gel matrix and stir at 150 rpm for 12 minutes under sterile conditions to ensure that the bacterial agent is evenly dispersed and the activity is not affected;

[0103] Step III: The mixed solution was added dropwise to a stirred 2% calcium chloride solution (stirring speed 120 rpm) using a titration apparatus (needle inner diameter 0.8 mm, dripping rate 1 mL / s). The cross-linking reaction was allowed to proceed for 35 minutes to form microspheres with an average particle size of approximately 2.5 mm.

[0104] Step IV: Wash the microspheres three times with sterile deionized water (100 mL per wash) to remove any surface residues, then seal and store at 4°C for later use.

[0105] Experimental Example 4 Denitrification Application Test

[0106] Application background: For industrial wastewater treatment in northern regions during winter, low temperatures lead to a decrease in microbial activity, and traditional denitrification processes are difficult to meet emission requirements.

[0107] Experimental conditions: Industrial wastewater (initial TN 60 mg / L, COD 3000 mg / L, salinity 0.5%, pH 7.2, water temperature 8°C) was tested in a 10L moving bed biofilm reactor (MBBR). The microsphere dosage was 20 g / L, the filler filling rate was 30%, the DO was controlled at 2-3 mg / L, and the operation cycle was 24 hours / time.

[0108] Test method: Samples were taken daily to determine TN and COD concentrations (TN using HJ 636-2012 standard, COD using HJ 828-2017 standard), and the carbon source release rate (determined by TOC analyzer) and bacterial agent activity (CFU count) were recorded.

[0109] Results: The denitrification efficiency of the microspheres prepared in Example 4 reached 80% (compared to 50% for conventional carbon source-microbial agent systems), and the TN dropped from 60 mg / L to 12 mg / L. The COD removal rate reached 82%, dropping from 3000 mg / L to 540 mg / L. The carbon source release rate was stable at 0.28 g / L·d, and the release lasted for 50 days, with a cumulative release of about 14 g / L. The microspheres had a compressive strength of 68 kPa (measured by a universal material testing machine), a deformation rate of less than 4%, and a service life of 65 days.

[0110] The activity of the bacterial agent is maintained above 108 CFU / g, and the TN concentration of the treated wastewater meets the first-level requirements of the "Integrated Sewage Discharge Standard" (GB8978-1996).

[0111] Comparative Example 1 Single carbon source system

[0112] The difference between this comparative example and Example 1 is that this comparative example uses only a single carbon source - sodium acetate.

[0113] Comparative Example 2 Traditional carrier and cross-linking agent

[0114] The difference between this comparative example and Example 1 is that this comparative example uses polyurethane foam as a carrier and single glutaraldehyde as a cross-linking agent.

[0115] Comparative Example 3

[0116] The difference between this comparative example and Example 1 is that no adversity-resistant additive is added in this comparative example.

[0117] Experimental Example 5

[0118] The sewage treatment systems / microspheres of the above comparative examples were subjected to application tests, and the test conditions were the same as those of Experimental Example 1.

[0119] Application background: In the winter operation of sewage treatment plants in northern cities, the total nitrogen (TN) concentration in the water is high and the temperature is low, and traditional denitrification methods are not efficient enough.

[0120] Experimental conditions: Municipal sewage (initial TN 50 mg / L, COD 200 mg / L, water temperature 5°C, pH 7.0) was tested in a 10L sequencing batch reactor (SBR). The dosage of the sewage treatment system in each comparative example was 20 g / L, the aeration volume was 0.5 L / min, and the operation cycle was 12 hours / time.

[0121] Test method: Samples were taken daily to determine the TN concentration (Water quality - Determination of total nitrogen - Alkaline potassium persulfate digestion - UV spectrophotometry method, HJ 636-2012 standard) and the carbon source release was recorded (determined by TOC analyzer).

[0122] Microsphere compressive strength: measured using a universal material testing machine.

[0123] The results show that: Comparative Example 1 uses a single carbon source, sodium acetate, which results in a too fast carbon source release rate (>1g / L·d), resulting in high initial denitrification efficiency but rapid depletion, and the denitrification efficiency drops to below 30% after 7 days. When using single glucose, the carbon source is released within 24 hours, resulting in subsequent denitrification interruption (efficiency drops by 60%). The embodiment of the present invention optimizes the release curve by using a composite carbon source (such as glucose + sodium acetate), achieving 5 days of continuous release and long-term stable carbon source supply, and maintaining a denitrification efficiency of more than 80%.

[0124] Comparative Example 2 used a traditional carrier and cross-linking agent. The results showed that the pore structure was single (pore size > 1 mm), the bacterial agent attachment density was only 106 CFU / g, and it was easily washed away by water flow, resulting in bacterial agent loss. When using a single glutaraldehyde cross-linking agent, the porosity of the microspheres was only 20%, and the bacterial agent loading was <10 7 CFU / g, and the denitrification efficiency is reduced by 50%. The embodiment of the present invention uses a slow-release matrix such as sodium alginate to construct a multi-level pore structure, and the bacterial agent attachment density is increased to 109 CFU / g, which significantly improves the stability.

[0125] Comparative Example 3, which lacks an adversity-resistant additive, results in a rapid decrease in bacterial activity at low temperatures (10°C) or high salinity (3%), resulting in a denitrification efficiency of only 40% to 50%. However, the introduction of betaine and trehalose in the examples of the present invention boosts the denitrification efficiency of the microspheres to 70% to 90% in these extreme environments, demonstrating excellent adaptability.

[0126] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A composite carbon source-bacteria agent microsphere with controllable release, characterized in that: The raw materials, calculated by mass, include 20-50 parts of composite carbon source material, 10-30 parts of microbial agent, 15-40 parts of slow-release matrix material, 5-15 parts of cross-linking agent, 0-10 parts of reinforcing agent, and 0-10 parts of adversity resistance additive. The microspheres have a multi-level pore structure.

2. The controllable release composite carbon source-bacteria agent microsphere according to claim 1, characterized in that: The average particle size of the microspheres is 2 to 3 mm.

3. The controllable release composite carbon source-bacteria agent microsphere according to claim 2, characterized in that: The composite carbon source is at least one of glucose, sodium acetate, starch and polylactic acid.

4. The controllable release composite carbon source-bacteria agent microsphere according to claim 3, characterized in that: The microbial agent is a low-temperature-resistant or high-salt-resistant denitrifying bacterium.

5. The controllable release composite carbon source-bacteria agent microsphere according to claim 4, characterized in that: The sustained-release matrix material is at least one of sodium alginate, chitosan, and polyvinyl alcohol; the cross-linking agent is at least one of calcium chloride and glutaraldehyde; and the reinforcing agent is at least one of nanocellulose and diatomaceous earth.

6. The controllable release composite carbon source-bacteria agent microsphere according to claim 5, characterized in that: The stress-resistant auxiliary agent is at least one of glycerol, betaine and trehalose.

7. Use of the controllable release composite carbon source-bacteria agent microspheres according to any one of claims 1 to 6 as a low-temperature / high-salt denitrifier for sewage treatment.

8. The use of the controllable release composite carbon source-bacteria agent microspheres as a low-temperature / high-salt denitrifier for sewage treatment according to claim 7, characterized in that: The low temperature is 5-15° C., and the salinity of the high salt is 1-5%.

9. The method for preparing a controllable release composite carbon source-bacteria agent microsphere according to any one of claims 1 to 6, characterized in that: The steps include: Step I: adding the composite carbon source, the slow-release matrix material, and the stress-resistant additive into deionized water and stirring until a uniform and transparent gel matrix is ​​formed; Step II, slowly adding the microbial agent and the enhancer to the gel matrix, stirring under sterile conditions to obtain a mixed solution; Step III, dropping the mixed solution into the stirred crosslinker solution to perform a crosslinking reaction to form microspheres; Step IV: Wash the microspheres with sterile deionized water to remove residual cross-linking agent on the surface, and store them for future use.

10. The method for preparing a controllable release composite carbon source-bacteria agent microsphere according to claim 8, characterized in that: In step III, the cross-linking time is 10 to 60 minutes, and the carbon source release rate of the microspheres is 0.1 to 0.5 g / L·d.