A microbial preparation, a preparation method and application thereof

Abstract

This invention relates to the field of wastewater treatment technology, specifically to a microbial preparation, its preparation method, and its application, comprising: a composite microbial agent; and a calcium alginate / polyvinyl alcohol interpenetrating network aerogel carrier loaded with the composite microbial agent; the aerogel carrier contains uniformly dispersed modified nano-attapulgite clay. The microbial preparation of this invention exhibits good wastewater treatment performance and long-lasting effect.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a microbial preparation, its preparation method, and its application. Background Technology

[0002] With the acceleration of urbanization, the amount of municipal solid waste generated is increasing year by year, and landfill has become the main disposal method. Landfill leachate is a high-concentration organic wastewater produced during the landfilling or storage process due to compaction, fermentation, and leaching by rainfall. Its water composition is extremely complex, typically containing high concentrations of chemical oxygen demand (COD), ammonia nitrogen, heavy metals, salts, and persistent organic pollutants such as humic substances and polycyclic aromatic hydrocarbons that are difficult to biodegrade. In addition, the quality and quantity of landfill leachate fluctuate drastically with the age of the landfill and seasonal changes, making its treatment extremely difficult.

[0003] Existing landfill leachate treatment technologies mainly include physicochemical and biological methods. Physicochemical methods, such as membrane separation, advanced oxidation, and coagulation sedimentation, offer relatively stable treatment results, but generally suffer from high investment and operating costs, membrane fouling, and secondary pollution problems such as the generation of large amounts of concentrate or chemical sludge. Traditional biological treatment processes, represented by activated sludge and biofilm processes, are the core of landfill leachate treatment due to their relatively low operating costs and lack of secondary pollution. However, high concentrations of ammonia nitrogen in landfill leachate inhibit nitrifying bacteria activity, and high salinity and complex toxic substances lead to the loss and decreased activity of functional microorganisms, resulting in poor operational stability of traditional biological processes.

[0004] Microbial immobilization technology is a technique that uses physical or chemical means to confine free functional bacteria within a specific carrier region, thereby maintaining their high density and bioactivity and enhancing their tolerance. This technology can effectively solve problems such as easy loss of bacteria and vulnerability to toxic substances in traditional biological methods. The carrier material used for microbial immobilization is crucial in determining the performance of the microbial agent. Currently, sodium alginate, polyvinyl alcohol, agar, and polyacrylamide are commonly used immobilization carrier matrices. Among them, calcium alginate gel has the advantages of easy molding and being friendly to microbial activity, but it has drawbacks such as poor mechanical strength and easy disintegration due to ion replacement in wastewater containing phosphates or high concentrations of cations. Polyvinyl alcohol gel can form physical cross-links through freeze-thaw cycles, resulting in relatively good mechanical strength and water resistance, but its network structure is relatively dense, leading to high mass transfer resistance, and its excessive hydrophilicity causes severe swelling and deformation. Using a single polymer often makes it difficult to balance mechanical strength, mass transfer performance, and biocompatibility. Summary of the Invention

[0005] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a microbial preparation, its preparation method, and its application.

[0006] The technical solution adopted is as follows: A microbial preparation comprising: Compound microbial inoculants; And a calcium alginate / polyvinyl alcohol interpenetrating network aerogel carrier loaded with the composite microbial agent; The aerogel carrier contains uniformly dispersed modified nano-attapulgite clay.

[0007] Furthermore, the modified nano-attapulgite soil comprises, from the inside out, a polydopamine anchoring layer, a struvite coating layer, and a polycaprolactone-polyethylene glycol block copolymer layer.

[0008] Attapulgite is a natural one-dimensional nanofiber silicate mineral with an extremely high aspect ratio. When uniformly dispersed, it forms strong physical entanglement and hydrogen bonds with the molecular chains of calcium alginate and polyvinyl alcohol, significantly improving the rigidity and compressive strength of the aerogel carrier. Furthermore, through physical cross-linking points, it limits the excessive extension of polymer molecular chains in water, preventing excessive swelling, rupture, or dissolution of the carrier under long-term immersion and aeration, thus ensuring long-term immobilization of microorganisms. It also promotes the formation of a more stable and abundant interconnected porous structure in the aerogel carrier. This structure facilitates the efficient diffusion of oxygen and nutrients (such as carbon and nitrogen sources) into the internal microorganisms while simultaneously allowing metabolic waste products to be discharged, providing a breathable and unobstructed living environment for the microorganisms.

[0009] After modification, the multi-level structure formed by nano-attapulgite fully leverages its synergistic effect: The innermost polydopamine layer is firmly anchored to the attapulgite surface through strong hydrogen bonds and coordination between its catechol groups and the silanol groups on the surface. Simultaneously, its surface active groups provide numerous nucleation sites for the in-situ growth of struvite grains. The middle struvite layer, acting as a nutrient reservoir, can slowly dissolve and release Mg. 2+ NH4 + and PO4 3- It provides a continuous and stable supply of nutrients (phosphorus, magnesium and nitrogen) for the embedded microorganisms. It also has a certain pH buffering function, which helps to maintain a suitable growth environment for microorganisms and improve their stress resistance and survival rate. The outermost polycaprolactone-polyethylene glycol block copolymer layer plays a blocking role in regulating the dissolution rate of struvite, while improving the interfacial compatibility between nanoparticles and organic gel matrix, promoting uniform dispersion and enhancing interfacial bonding.

[0010] Furthermore, the preparation method of the modified nano-attapulgite is as follows: Nano-attapulgite clay was dispersed in Tris-HCl buffer solution, and dopamine hydrochloride was added to react and form a polydopamine anchoring layer. Then disperse it in a Mg-containing 2+ NH4 + PO43- In the solution, the pH of the solution is controlled to allow magnesium ammonium phosphate nanocrystals to grow in situ, forming a struvite coating layer; Finally, the copolymer was dispersed in a dichloromethane solution of polycaprolactone-polyethylene glycol block copolymer, stirred to evaporate the solvent, and then vacuum dried.

[0011] Furthermore, the pH of the solution is controlled to be 8-9.

[0012] Furthermore, the compound microbial agent is composed of Bacillus subtilis, Bacillus licheniformis, Pseudomonas schrenckii and Paracoccus denitrificans, and the ratio of the four to the number of live bacteria is (2-3):(1-2):(3-5):(1-2).

[0013] These four bacterial strains exhibit synergistic symbiotic effects: Bacillus subtilis and Bacillus licheniformis are facultative anaerobic spore-producing bacteria that secrete various extracellular enzymes such as proteases, amylases, and lipases, which can initially hydrolyze recalcitrant large organic molecules in leachate into smaller molecules, improving the biodegradability of wastewater and providing a usable carbon source for denitrifying bacteria; Pseudomonas schlegelii is a highly efficient aerobic denitrifying bacterium that can reduce nitrite and nitrate to gaseous nitrogen under aerobic conditions, while also possessing strong salt tolerance and adaptability to a wide pH range; and Paracoccus denitrifyingis is a typical heterotrophic nitrifying-aerobic denitrifying bacterium capable of simultaneously performing nitrification and denitrification, efficiently removing ammonia nitrogen and total nitrogen. When these four bacteria are combined in a specific ratio, a stable microecological system can be constructed that integrates organic matter hydrolysis and acidification, nitrification, denitrification, and phosphorus removal functions.

[0014] Furthermore, in the calcium alginate / polyvinyl alcohol interpenetrating network aerogel carrier, the mass ratio of sodium alginate to polyvinyl alcohol is (1-3):(1-3).

[0015] When the ratio of the two is within this range, the interpenetration between the ionic cross-linking network and the freeze-thaw physical cross-linking network is the highest, and the resulting aerogel has the most ideal mechanical and mass transfer properties. If there is too much sodium alginate, the carrier becomes too soft and the anti-swelling ability decreases; if there is too much polyvinyl alcohol, the network becomes too dense, the mass transfer resistance increases, and the microbial activity is limited.

[0016] This invention also provides a method for preparing a microbial preparation, comprising: Prepare sodium alginate solution and polyvinyl alcohol solution; mix sodium alginate solution and polyvinyl alcohol solution, add modified nano-attapulgite clay and disperse evenly, vacuum degassing treatment to obtain mixed sol; drop the mixed sol into calcium chloride aqueous solution to solidify into spheres, freeze-thaw after freeze-thaw cycle treatment to obtain interpenetrating network aerogel carrier; immerse the interpenetrating network aerogel carrier in composite microbial agent suspension, vacuum impregnate until adsorption saturation, remove and dry.

[0017] Furthermore, the amount of modified nano-attapulgite added is 5%-15% of the total mass of sodium alginate and polyvinyl alcohol.

[0018] If the amount added is too low, the enhancement effect and nutrient slow-release ability will not be significant; if the amount added is too high, the sol viscosity will be too high, making it difficult to form spheres, and the excessive aggregation of nanoparticles will degrade the carrier performance.

[0019] Furthermore, the freeze-thaw cycle treatment involves freezing at -20°C for 10-20 hours, then thawing at room temperature for 10-20 hours, and repeating this process 1-5 times.

[0020] This invention also provides the application of the above-mentioned microbial preparations in wastewater treatment.

[0021] Specifically, the microbial preparation is suitable for the bio-enhanced treatment of recalcitrant wastewater with high ammonia nitrogen, high organic matter concentration, and toxic substances, such as landfill leachate, livestock and poultry breeding wastewater, coking wastewater, pharmaceutical wastewater, and food processing wastewater.

[0022] In practical applications, the microbial preparations can be directly added to aerobic tanks, anoxic tanks, or membrane bioreactors in a suspended state, depending on the treatment process and water quality characteristics. They can also be used as biological carriers in fixed beds, fluidized beds, or aerated biological filters. The dosage is generally 0.1-10 g / L based on wastewater volume, and can be adjusted according to the influent chemical oxygen demand (COD) and ammonia nitrogen load.

[0023] The microbial preparation exhibits excellent reusability. After a single treatment cycle, the carrier can be recovered through simple sieving or sedimentation, rinsed with clean water, and then reused in the next batch. After multiple consecutive cycles, if the treatment efficiency decreases due to the depletion of the struvite nutrient layer or the loss of some microorganisms, the recovered carrier can be regenerated, achieving multiple recycling of the carrier. Furthermore, this microbial preparation can also be used as a substrate for constructed wetlands or as a biological rotating disc packing material to construct a highly efficient wastewater treatment system with simultaneous nitrogen and phosphorus removal functions.

[0024] The technical solution provided by this invention has the following significant beneficial effects: This invention constructs a modified nano-attapulgite with multi-level coating of polydopamine / struvite / polycaprolactone-polyethylene glycol block copolymer. The polydopamine layer is firmly anchored to the attapulgite surface through strong hydrogen bonds and coordination between its catechol groups and the silanol groups on the surface. Simultaneously, its surface active groups provide numerous nucleation sites for the in-situ growth of struvite grains. The intermediate struvite layer acts as a nutrient reservoir, slowly dissolving and releasing Mg. 2+ NH4 + and PO4 3-It provides a continuous and stable supply of nutrients (phosphorus, magnesium, and nitrogen) for the embedded microorganisms. It also has a certain pH buffering function, which helps maintain a suitable growth environment for microorganisms, improves their resistance and survival rate, and can maintain high biological activity and cell density of bacteria during long-term operation, thus improving the denitrification and phosphorus removal effect and operational stability. The outermost polycaprolactone-polyethylene glycol block copolymer layer plays a blocking role in regulating the dissolution rate of struvite, while improving the interfacial compatibility between nanoparticles and organic gel matrix, promoting uniform dispersion and enhancing interfacial bonding.

[0025] Freeze-drying technology removes moisture from gel microspheres while maintaining their three-dimensional network structure, forming an aerogel carrier with numerous micron- and nano-sized interconnected pores. This hierarchical porous structure significantly reduces mass transfer resistance, facilitating the diffusion of dissolved oxygen and organic substrates into the carrier and the outward expulsion of metabolic products, allowing the embedded microorganisms to fully exert their degradation activity. Simultaneously, the introduction of nano-attapulgite and struvite nanocrystals increases the surface roughness and hydrophilic microregions of the carrier, promoting early microbial attachment and biofilm formation.

[0026] The four selected functional strains complement each other in terms of systematic classification, physiological function, and ecological niche: Bacillus-like bacteria produce enzymes for hydrolysis, while Paracoccus denitrifying and Pseudomonas schrenckii cooperate to achieve simultaneous nitrification and denitrification. The entire micro-ecosystem demonstrates significantly higher removal efficiencies for COD, ammonia nitrogen, total nitrogen, and total phosphorus in landfill leachate compared to single strains or conventional inoculants, and exhibits significantly enhanced resistance to toxicity and shock loads. The preparation method of this invention employs mild process conditions, and most of the raw materials used are biodegradable or environmentally friendly, preventing secondary pollution to the treatment system and facilitating industrial scale-up. Detailed Implementation

[0027] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0028] Example 1:

[0029] A method for preparing a microbial preparation: S1: 2.0 g of nano-attapulgite was added to 200 mL of Tris-HCl buffer (10 mmol / L, pH 8.5) and ultrasonically dispersed for 30 min to obtain a suspension. 0.4 g of dopamine hydrochloride was added with stirring, and the reaction was continued for 12 h under light-protected conditions. After the reaction was complete, the mixture was centrifuged and washed three times with deionized water to obtain nano-attapulgite coated with a polydopamine anchoring layer. The product was redispersed in 150 mL of deionized water, and 2.03 g of MgCl2·6H2O, 0.53 g of NH4Cl and 1.36 g of KH2PO4 were added sequentially. The mixture was stirred until completely dissolved, and the pH of the system was adjusted to 8.5 with 0.1 mol / L NaOH solution. The reaction was continued at 55 °C in the dark with stirring for 6 h. After returning to room temperature, the product was centrifuged, collected, washed and dried. It was then transferred to 100 mL of dichloromethane solution containing 1 g of polycaprolactone-polyethylene glycol block copolymer (Yusi Pharmaceutical, YS-P2PCL23). The mixture was stirred at room temperature for 2 h, and then the dichloromethane was removed by rotary evaporation. The product was then dried in a vacuum drying oven to obtain modified nano-attapulgite.

[0030] S2: Weigh 2g of sodium alginate and dissolve it in 98mL of deionized water to prepare a sodium alginate solution; weigh 2g of polyvinyl alcohol and add it to 98mL of deionized water, then heat appropriately to prepare a polyvinyl alcohol solution. Mix the sodium alginate solution and polyvinyl alcohol solution evenly, and slowly add modified nano-attapulgite (the amount of modified nano-attapulgite is 10% of the total mass of sodium alginate and polyvinyl alcohol) while stirring. Sonicate for 30min to obtain a dispersion. Degas the mixture under vacuum at -0.08MPa for 10min, then dropwise add it to a continuously stirred 2wt% calcium chloride solution. The droplets crosslink upon contact with calcium ions to form microspheres. Soak and solidify for 4h, filter out the microspheres, wash with deionized water, freeze at -25℃ for 15h, then thaw at room temperature for 15h. Repeat this freeze-thaw cycle 3 times, and finally freeze-dry at -50℃ for 24h to obtain an interpenetrating network aerogel carrier.

[0031] S3: Bacillus subtilis, Bacillus licheniformis, Pseudomonas schlegelii, and Paracoccus denitrificans were activated by slant culture and then cultured in liquid seed culture. They were then inoculated into sterile expansion medium and cultured at 30°C and 150 rpm in a shaker until the stationary phase. The bacterial cells were collected by centrifugation and washed twice with sterile physiological saline. Based on the plate count results of each strain, they were resuspended in sterile phosphate buffer (pH 7.0) and mixed according to the viable cell ratio. The bacterial suspensions used in the embodiments of this invention were prepared according to the following ratio: Bacillus subtilis: Bacillus licheniformis: Pseudomonas schlegelii: Paracoccus denitrificans viable cell ratio was 2.5:1.5:4:1.5, and the final total viable cell concentration of the suspension was approximately 5 × 10⁻⁶. 9 CFU / mL.

[0032] S4: Take 1.0 g of interpenetrating network aerogel carrier, immerse it in 50 mL of the above-mentioned composite bacterial agent suspension, place it in a vacuum filtration flask, maintain -0.08 MPa for 30 min, restore normal pressure and continue to soak for 30 min to allow the bacteria to be deeply adsorbed, take out the interpenetrating network aerogel carrier, use sterile filter paper to absorb the excess liquid on the surface, and place it in a 30℃ sterile airflow drying oven for gentle drying.

[0033] Example 2:

[0034] This embodiment is basically the same as embodiment 1, except that the S2 part is different.

[0035] S2: Weigh 3g of sodium alginate and dissolve it in 97mL of deionized water to prepare a sodium alginate solution; weigh 1g of polyvinyl alcohol and add it to 99mL of deionized water, then heat appropriately to prepare a polyvinyl alcohol solution. Mix the sodium alginate solution and the polyvinyl alcohol solution evenly, and slowly add modified nano-attapulgite (the amount of modified nano-attapulgite is 10% of the total mass of sodium alginate and polyvinyl alcohol) while stirring. Sonicate for 30min to obtain a dispersion. Degas the mixture under vacuum at -0.08MPa for 10min, then dropwise add it to a continuously stirred 2wt% calcium chloride solution. The droplets crosslink upon contact with calcium ions to form microspheres. Soak and solidify for 4h, filter out the microspheres, wash with deionized water, freeze at -25℃ for 15h, then thaw at room temperature for 15h. Repeat this freeze-thaw cycle 3 times, and finally freeze-dry at -50℃ for 24h to obtain an interpenetrating network aerogel carrier.

[0036] Example 3:

[0037] This embodiment is basically the same as embodiment 1, except that the S2 part is different.

[0038] S2: Weigh 1g of sodium alginate and dissolve it in 99mL of deionized water to prepare a sodium alginate solution; weigh 3g of polyvinyl alcohol and add it to 97mL of deionized water, then heat appropriately to prepare a polyvinyl alcohol solution. Mix the sodium alginate solution and the polyvinyl alcohol solution evenly, and slowly add modified nano-attapulgite (the amount of modified nano-attapulgite is 10% of the total mass of sodium alginate and polyvinyl alcohol) while stirring. Sonicate for 30min to obtain a dispersion. Degas the mixture under vacuum at -0.08MPa for 10min, then dropwise add it to a continuously stirred 2wt% calcium chloride solution. The droplets crosslink upon contact with calcium ions to form microspheres. Soak and solidify for 4h, filter out the microspheres, wash with deionized water, freeze at -25℃ for 15h, then thaw at room temperature for 15h. Repeat this freeze-thaw cycle 3 times, and finally freeze-dry at -50℃ for 24h to obtain an interpenetrating network aerogel carrier.

[0039] Example 4:

[0040] This embodiment is basically the same as embodiment 1, except that: the amount of modified nano-attapulgite clay used in S2 is 5% of the total mass of sodium alginate and polyvinyl alcohol.

[0041] Example 5:

[0042] This embodiment is basically the same as embodiment 1, except that: the amount of modified nano-attapulgite clay used in S2 is 15% of the total mass of sodium alginate and polyvinyl alcohol.

[0043] Comparative Example 1: This comparative example is basically the same as Example 1, except that no modified nano-attapulgite clay is added in S2.

[0044] Comparative Example 2: This comparative example is basically the same as Example 1, except that: in S1, only polydopamine coating is performed, that is, after washing and drying the nano-attapulgite clay coated with polydopamine anchoring layer, struvite and block copolymer coating are not performed, and it is used directly as a modified component.

[0045] Comparative Example 3: This comparative example is basically the same as Example 1, except that: after the struvite coating is completed in S1, the polycaprolactone-polyethylene glycol block copolymer layer coating is not performed, and the nano-attapulgite double-layer coated with polydopamine-struvite is washed, dried and used directly as the modified component.

[0046] Comparative Example 4: This comparative example is basically the same as Example 1, except that: in S2, an equal mass of unmodified nano-attapulgite (without any surface treatment) is added instead of modified nano-attapulgite.

[0047] Performance testing: ① To verify the performance of the microbial preparation of the present invention, the samples prepared in the above embodiments and comparative examples were subjected to the following tests. The landfill leachate used in the tests was taken from the equalization pond of a municipal solid waste sanitary landfill. After natural sedimentation to remove large particulate suspended solids, its water quality characteristics were as follows: COD 3850±250 mg / L, ammonia nitrogen 1380±120 mg / L, total nitrogen (TN) 1520±150 mg / L, total phosphorus (TP) 18±5 mg / L, pH 7.2±0.3, and conductivity 28.5 mS / cm.

[0048] Take 300 mL of the above-mentioned landfill leachate and place it in a 500 mL Erlenmeyer flask. Add microbial preparation at a dosage of 1 g / L. Seal the flask with a breathable sealing film and place it in a constant temperature shaker at 30℃ and 150 rpm for incubation. After 24 h of treatment, filter the water sample and determine COD using the dichromate method (HJ 828-2017), ammonia nitrogen using Nessler's reagent spectrophotometry (HJ 535-2009), total nitrogen using alkaline potassium persulfate digestion-ultraviolet spectrophotometry (HJ 636-2012), and total phosphorus using ammonium molybdate spectrophotometry (GB 11893-89). Use landfill leachate without any carrier and shaken under the same conditions as a blank control to calculate the removal rate of each pollutant.

[0049] The microbial preparation that has completed one 24-hour treatment cycle is removed with sterile tweezers, the surface is gently rinsed with sterile deionized water, and then put back into another 300 mL of fresh leachate from the same batch. This process is repeated for four more batches. The COD removal rate of the last batch after 24 hours of treatment is measured. The COD removal rate of the last batch is calculated as a baseline using the COD removal rate of the first batch. This is used to evaluate the reusability and structural stability of the microbial preparation.

[0050] ② Accurately weigh 0.10g of the microbial preparation and transfer it to a glass homogenizer containing 10mL of sterile physiological saline. Homogenize thoroughly under ice bath conditions. Serially dilute the homogenate with sterile physiological saline, and spread the appropriate dilution onto LB agar plates. Incubate at 30℃ for 48h, then count the colonies. The bacterial load is expressed as colony forming units (CFU / g) of viable bacteria per gram of carrier. Separately, add 0.10g of the microbial preparation to 100mL of sterilized landfill leachate (water quality characteristics as above), stir well, and place in a 30℃ constant temperature incubator at 85% relative humidity for 96h. Then, determine the viable bacteria count using the homogenization, dilution, and plating methods described above.

[0051] Survival rate is calculated using the formula: Survival rate (%) = (Number of viable bacteria after 96 hours of storage / Initial number of viable bacteria) × 100%.

[0052] The test results are shown in Table 1 below.

[0053] Table 1: As shown in Table 1 above, the microbial preparations in this invention exhibit good leachate treatment performance and long-lasting effects.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A microbial preparation, characterized in that, include: Compound microbial inoculants; And a calcium alginate / polyvinyl alcohol interpenetrating network aerogel carrier loaded with the composite microbial agent; The aerogel carrier contains uniformly dispersed modified nano-attapulgite clay.

2. The microbial preparation according to claim 1, characterized in that, The modified nano-attapulgite soil comprises, from the inside out, a polydopamine anchoring layer, a struvite coating layer, and a polycaprolactone-polyethylene glycol block copolymer layer.

3. The microbial preparation according to claim 2, characterized in that, The modified nano-attapulgite clay is prepared as follows: Nano-attapulgite clay was dispersed in Tris-HCl buffer solution, and dopamine hydrochloride was added to react and form a polydopamine anchoring layer. Then disperse it in a Mg-containing 2+ NH4 + PO4 3- In the solution, the pH of the solution is controlled to allow magnesium ammonium phosphate nanocrystals to grow in situ, forming a struvite coating layer; Finally, the copolymer was dispersed in a dichloromethane solution of polycaprolactone-polyethylene glycol block copolymer, stirred to evaporate the solvent, and then vacuum dried.

4. The microbial preparation according to claim 3, characterized in that, Control the pH of the solution to 8-9.

5. The microbial preparation according to claim 1, characterized in that, The compound microbial agent is composed of Bacillus subtilis, Bacillus licheniformis, Pseudomonas schrenckii and Paracoccus denitrificans, and the ratio of the four to the number of live bacteria is (2-3):(1-2):(3-5):(1-2).

6. The microbial preparation according to claim 1, characterized in that, In the calcium alginate / polyvinyl alcohol interpenetrating network aerogel carrier, the mass ratio of sodium alginate to polyvinyl alcohol is (1-3):(1-3).

7. A method for preparing a microbial preparation as described in any one of claims 1-6, characterized in that, include: Prepare sodium alginate solution and polyvinyl alcohol solution; Sodium alginate solution and polyvinyl alcohol solution were mixed, modified nano-attapulgite clay was added and dispersed evenly, and vacuum degassing was performed to obtain a mixed sol. The mixed sol was dropped into calcium chloride aqueous solution to solidify into spheres, and after freeze-thaw cycle treatment, it was freeze-dried to obtain an interpenetrating network aerogel carrier. The interpenetrating network aerogel carrier was immersed in a composite microbial agent suspension, vacuum impregnated until adsorption saturation, and then removed and dried.

8. The method for preparing the microbial preparation according to claim 7, characterized in that, The amount of modified nano-attapulgite added is 5%-15% of the total mass of sodium alginate and polyvinyl alcohol.

9. The method for preparing the microbial preparation as described in claim 7, characterized in that, The freeze-thaw cycle involves freezing at -20°C for 10-20 hours, then thawing at room temperature for 10-20 hours, and repeating this process 1-5 times.

10. The use of the microbial preparation as described in any one of claims 1-6 in wastewater treatment.

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