Method for converting livestock and poultry manure and urine into composite microbial liquid fertilizer

Abstract

This invention discloses a three-stage method for efficiently converting livestock and poultry manure into compound microbial liquid fertilizer. The method first inactivates and pre-treats the raw materials through physical high-temperature treatment, effectively killing harmful microorganisms such as E. coli and insect eggs, and initially degrading COD, BOD, ammonia nitrogen, and total phosphorus. Then, a pulsed electric field, ultrasound, and micro-nano bubble composite field energy are used to synergistically stimulate the substrate and functional microbial communities, putting them in a highly active metabolic state. Finally, aerobic, anaerobic, and facultative anaerobic microbial communities are introduced for symbiotic fermentation. Through coupled processes of nitrification-denitrification, nitrogen fixation, phosphorus dissolution, and organic matter conversion, deep removal of pollutants and efficient nutrient conversion are achieved. After a short period of activation and maturation, the product is bottled. The product processed by this process has a viable bacteria count ≥2×10⁸ CFU / mL, and the removal rates of COD, ammonia nitrogen, and total phosphorus reach over 85%, 85%, and 70%, respectively, which is conducive to achieving near-zero pollution emission targets. The resulting liquid fertilizer can significantly improve soil structure, enhance crop stress resistance, and effectively reduce the amount of chemical fertilizer applied.

Description

Technical Field

[0001] This invention relates to the technology of resource utilization of livestock and poultry breeding waste, bio-fermentation and organic fertilizer preparation, specifically a method for converting livestock and poultry manure and urine into compound microbial liquid fertilizer through a three-stage process. Background Technology

[0002] While the livestock and poultry farming industry is developing rapidly, the discharged manure and urine (hereinafter referred to as "raw urine liquid") generally has problems such as high concentrations of organic matter (COD, BOD), high levels of ammonia nitrogen and phosphorus, coliform bacteria and parasite eggs in feces, and possible contamination with antibiotics and disinfection byproducts. To address these issues, domestic and international methods mainly employ physical methods (heating, pasteurization, solid-liquid separation, membrane separation, etc.), chemical methods (lime disinfection, coagulation sedimentation, oxidant treatment, etc.), and biological methods (aerobic / anaerobic fermentation, nitrification-denitrification, etc.) and their combined processes for volume reduction and compliance treatment. However, traditional chemical or enhanced oxidation pathways may have problems such as high energy consumption and the generation of secondary salts and sludge requiring further treatment; single-path biological methods are easily affected by fluctuations in the raw liquid and inhibitors (such as high free ammonia and antibiotic residues), resulting in slow start-up, poor shock resistance, and insufficient effluent stability. Meanwhile, many existing treatment routes aim for "end-of-pipe emission compliance" and lack a systematic technical framework and replicable parameter window for "safety-resource-high-value" transformation of urine concentrate into agricultural compound microbial liquid fertilizer. This makes it difficult to balance hygiene and safety, synergistic reduction of pollutants, and agronomic benefits of the product.

[0003] Furthermore, from the perspective of "waste-to-fertilizer conversion," directly converting urine stock solution into highly active, stable, and transportable compound microbial liquid fertilizer still faces multiple engineering and microbial ecological challenges: First, the stock solution exhibits large fluctuations in composition, high salt and ammonia nitrogen concentrations, and strong odor and foaming tendency, which inhibit the colonization and metabolism of probiotics; Second, in the single-stage fermentation process, the demands of aerobic and anaerobic (and facultative anaerobic) bacterial communities for dissolved oxygen and oxidation-reduction potential (ORP) are contradictory, easily leading to an imbalance in bacterial community competition and metabolic "disruptions," resulting in incomplete removal of organic matter, insufficient nitrogen conversion, and difficulty in the stable enrichment of live bacteria and active enzyme systems; Third, many existing technologies lack synergistic design for "inactivation of pathogenic microorganisms / insect eggs, inhibition of antibiotic risks, improvement of biodegradability, and efficiency of probiotic activation," making it difficult to simultaneously meet safety and functionality requirements. Therefore, the industry urgently needs a complete set of methods for resource-based products: to effectively inactivate pathogenic factors and weaken inhibitors in the pretreatment stage, and to stably build dominant bacterial communities and multi-enzyme systems in the subsequent biological stage through staged control and clear process windows such as DO / ORP, temperature, and pH, so as to obtain compound microbial liquid fertilizer that has hygiene and safety, emission reduction effect and agronomic efficiency, and can be scaled up and promoted. Summary of the Invention

[0004] This invention provides a method for converting livestock and poultry manure into compound microbial liquid fertilizer, applicable to the production and preparation of liquid organic fertilizer. The method employs a three-stage treatment process: physical high-temperature inactivation, field energy-based compound activation of microbial communities, and synergistic fermentation of three types of microbial communities. It further incorporates target activation and final preparation stages. The method introduces compound field energy activation methods (pulsed electric field + ultrasound + bubbles) to promote the biochemical transformation of the substrate. Simultaneously, it sets a programmed three-stage fermentation control (aerobic – anaerobic – facultative anaerobic), coupled with a real-time parameter adjustment system (DO, ORP, temperature, pH, etc.), balancing hygiene and safety, pollutant reduction, and the high activity and stability of the final product. This constructs a standardized technical path that can be modularly deployed and scaled up. Compared with existing technologies, this invention has significant differences and technological advancements in process structure and functional implementation. For example, the existing patent with publication number CN110123456B uses anaerobic fermentation to treat livestock and poultry urine, but it lacks pretreatment steps and a microbial activation mechanism. The fermentation process lacks precise control over key parameters such as dissolved oxygen (DO), oxidation-reduction potential (ORP), and temperature, leading to microbial imbalance, unstable metabolic efficiency, and significant fluctuations in product performance. In contrast, this invention not only achieves rigid inactivation of pathogenic factors and a significant improvement in substrate availability at the front end, but also precisely drives aerobic, anaerobic, and facultative anaerobic bacteria to perform their functions sequentially through an online, controllable, multi-stage fermentation strategy, synergistically completing organic matter degradation, nitrogen and phosphorus conversion, and functional product enrichment. The product obtained by this method has a high viable bacterial count, strong total enzyme activity, and better stability than traditional processes. The overall technical solution possesses outstanding inventiveness, practicality, and scalability. The specific technical solution of this method includes the following:

[0005] S1 first involves coarse filtration of the stock solution to remove large suspended solids. The pH is then adjusted to a suitable buffer zone (acidic window pH 5.5–6.5 or alkaline window pH 8.5–9.5) to effectively inhibit ammonia nitrogen volatilization and excessive protein denaturation, maintaining the biodegradability of the substrate. Next, the conditioned stock solution is pasteurized at 80°C for 30–45 minutes to significantly inactivate pathogenic factors such as fecal coliforms and parasite eggs, while maintaining the system's bioavailability. Optionally, a certain concentration of magnesium salt (in Mg²⁺) can be added in parallel during this step. + The concentration is calculated to be 20–100 mg / L, which promotes the formation of struvite (MgNH4PO4·6H2O) microcrystalline precipitate of nitrogen and phosphorus, thereby achieving some nitrogen and phosphorus co-precipitation and transfer, and reducing the load of subsequent biological treatment.

[0006] S2 Field Energy Composite Activation of Microbial Community: In this step, three types of physical energy—pulsed electric field (PEF), ultrasound, and micro / nanobubbles—are synergistically applied to the pretreated stock solution matrix. This composite field energy effectively enhances the metabolic initiation rate and substrate availability of the inoculated microbial community by increasing cell membrane permeability, disrupting microaggregate structure, and promoting the release of soluble carbon sources, thus providing a more efficient reaction environment for subsequent co-fermentation.

[0007] S3 Three-Type Microbial Co-fermentation: 1) Microbial Community Composition: Aerobic microorganisms, such as Bacillus subtilis and nitrifying bacteria, have the functions of ammonia oxidation and primary carbon source decomposition. Anaerobic microorganisms, mainly including denitrifying bacteria and degrading bacteria with extracellular enzyme secretion capabilities, are used for deep organic matter cleavage and nitrogen reduction conversion. Facultative anaerobic microorganisms, such as lactic acid bacteria and yeast, have multifunctional metabolic characteristics and can continue to play a role under changes in oxygen environment. In addition, functional photosynthetic bacteria and salt-tolerant bacteria with the functions of regulating microecology and enhancing metabolic activity are introduced to improve the overall microbial community's stress resistance and ecological stability; 2) Three-stage programmed control process: The fermentation process is set sequentially as aerobic stage—anaerobic stage—facultative anaerobic stage. Under the condition that key parameters such as dissolved oxygen (DO), oxidation-reduction potential (ORP), and temperature are controllable, different microbial communities are driven to dominate the fermentation reaction in sequence. The specific functions are as follows: Aerobic stage - mainly ammonia oxidation and primary carbon source oxidation to improve the biodegradability of substrate. Anaerobic stage - promotes denitrification and deep cleavage of organic macromolecules, significantly reducing COD and nitrogen load. Facultative anaerobic stage - guides the synthesis and enrichment of metabolites such as organic acids, polysaccharides, and extracellular enzymes, enhancing the functionality of the final product; 3) Online control window and synergistic mechanism regulation: The entire process of this invention is equipped with real-time online monitoring points, covering parameters such as DO, ORP, pH, temperature, and stirring power density, constructing a controllable microenvironment regulation system. By precisely regulating the microecological conditions, the competition and antagonism between bacterial communities are suppressed and transformed into efficient synergistic effects, ensuring high stability and high efficiency of multi-strain symbiotic metabolism.

[0008] S4 Target Activation and Maturation (2h): In this stage, by setting an appropriate shear rate and intermittent aeration strategy, the metabolic potential of microorganisms is further stimulated while ensuring the integrity of the cell structure and the maintenance of activity. This promotes the enrichment and secretion of extracellular enzyme systems and metabolic polysaccharides, thereby significantly improving the functionality and storage stability of liquid fertilizer products and bringing them to their optimal state in terms of enzyme activity and biological effects.

[0009] S5 terminal preparation and filling: After 80–100μm fine filtration to remove residual suspended solids, food-grade activated carbon can be optionally added for adsorption treatment to remove odors and further remove any possible residual antibiotic substances, ultimately obtaining a stable product that meets the quality standards of microbial liquid fertilizer.

[0010] This invention solves the efficiency and stability problems in liquid organic fertilizer production through a three-stage process: physical high-temperature inactivation, field energy-based combined activation of microbial communities, and synergistic fermentation of three types of microbial communities. Its beneficial effects are as follows:

[0011] Safety: 1) Significant reduction in pathogenic factors: The S1 pasteurization zone (80℃×30–45min) rigidly inactivates fecal coliforms and Salmonella, while the S2 "field energy complex activated bacteria" gently breaks down membranes and solubilizes without damaging the nutrient substrate, allowing subsequent dominant bacteria to quickly occupy the substrate. The finished product has fecal coliforms ≤100MPN / mL and insect eggs ≤1 / L, meeting the safety standards for agricultural organic fertilizer. 2) Synergistic removal of antibiotics and odors: Magnesium salt-induced partial nitrogen and phosphorus co-precipitation + activated carbon contact (1–3g / L, 10–20min) can significantly reduce residual antibiotics and volatile amines, reducing the risk of drug resistance and odors during storage and transportation; compared with similar chemical disinfection routes, there are no secondary toxic byproducts. 3) Process traceability: The entire process of DO / ORP / temperature / pH / PEF voltage-frequency / ultrasonic power / gas content is recorded online. Any deviation from the limit triggers an interlock, ensuring the safety consistency of each batch. 4) Soil and crop friendliness: It does not introduce quaternary ammonium salts or strong oxidant residues; the process avoids high alkali / strong acid shocks, does not cause salt stress after use, and is conducive to the restoration of crop rhizosphere microecology.

[0012] High-efficiency emission reduction: 1) Rapid reduction of organic load: Three-stage programmed fermentation achieves a synergistic pathway of "first aerobic improvement of biodegradability - then anaerobic deep pyrolysis - finally facultative anaerobic integration", reducing COD by ≥85%; ammonia oxidation + denitrification coupling reduces ammonia nitrogen by ≥85%; Mg² + 1) Induction + bio-phosphorus synergy, total phosphorus is reduced by ≥70%; 2) Near-zero emission support: the effluent is stably within the window of COD≤2500mg / L, NH3-N≤200mg / L, and TP≤50mg / L, creating conditions for subsequent reuse / recycling and reducing the impact load on existing sewage treatment plants; 3) Controllable energy and chemical consumption: PEF + ultrasound + micro-nano bubbles adopt a short-range, low-energy-density combination to avoid the increase in energy and chemical consumption and secondary treatment pressure caused by traditional long-term aeration and high-dose flocculation.

[0013] High activity: 1) Viable cell count and stability: Programmed symbiotic fermentation of three types of microorganisms and S4 "2h target activation" result in a viable cell count of ≥2×10⁻⁶ in the finished product. 81) CFU / mL, shelf life ≥6 months under light-protected conditions at 4–25℃ (based on viable cell retention ≥70%), meeting the requirements for ambient temperature logistics; 2) Multi-enzyme enrichment: total enzyme activity ≥150U / mL including protease, cellulase, lipase, nitrate reductase, etc.; the presence of metabolic polysaccharides improves the adhesion and slow-release performance of liquid fertilizer and improves the rhizosphere microenvironment. 3) Clear functional bacterial composition: complementary functions of photosynthetic bacteria, Bacillus subtilis, Bacillus licheniformis, lactic acid bacteria, yeast, and nitrifying / denitrifying bacteria, taking into account organic matter decomposition, nitrogen cycling, and antagonism of harmful bacteria, reducing batch-to-batch fluctuations. 4) Low-risk auxiliary material system: buffer system and adsorbents are all made of food / agricultural grade raw materials to avoid introducing potentially harmful chemicals into arable land.

[0014] Agronomic Benefits: 1) Improved Soil Structure: High levels of active bacteria and polysaccharides enhance the formation and stability of soil micro-aggregates, reducing bulk density, increasing porosity and permeability, effectively mitigating compaction, and improving root aeration and water and fertilizer retention. 2) Enhanced Photosynthesis and Nutrient Absorption: Rhizosphere microorganisms and active enzymes promote the conversion of soluble nitrogen, phosphorus, potassium, and micronutrients, significantly increasing SPAD value and net photosynthetic rate, resulting in thicker, greener, and brighter leaves, and shortening the window period for tender young leaves. 3) Enhanced Stress Resistance and Health: Symbiotic bacteria and their metabolites have antagonistic and enzymatic decomposition effects on harmful rhizosphere bacteria and insect eggs, resulting in: reduced lesion incidence, more developed root systems, and enhanced drought resistance and water retention. 4) Potential for Reduced Fertilizer / Pesticide Use: Due to improved fertilizer efficiency and reduced pest and disease control, fertilizer application can be reduced by 20-30% (based on nitrogen), and pesticide use can be reduced accordingly, leading to simultaneous improvement in crop yield and quality (soluble solids, flavor), increasing production and income.

[0015] Scalable for large-scale application: 1) Clear parameter windows: Each step (S1–S5) provides executable process ranges (temperature / time, PEF field strength and frequency, ultrasonic frequency and power density, bubble size and gas holdup, DO / ORP window, stirring power density, etc.), facilitating direct application to equipment of different scales. 2) Modular combination: Field energy modules (PEF / ultrasound / micro / nano bubbles) support combination; reactors support series / parallel connection and cycle-type operation, easily connecting and expanding with existing farms or organic fertilizer workshops. 3) Compatibility of strains and stock solutions: Provides salt-tolerant / ammonia-tolerant formulation windows, adaptable to urine from different sources such as chicken, pig, and cattle; online DO / ORP closed-loop automatic switching of three stages ensures stable operation even with complex stock solutions.

[0016] Figure 1 This is a schematic diagram of the method for converting livestock and poultry manure and urine into a suitable microbial liquid fertilizer according to the present invention. Detailed Implementation

[0017] Example 1 (Standard operating conditions, 1m³ class)

[0018] Stock solution: Mixed urine from the same broiler farm was first coarsely filtered through a 0.8mm drum sieve, and the following values ​​were measured: COD 18500 mg / L, ammonia nitrogen 1520 mg / L, total phosphorus 160 mg / L, and fecal coliforms 1.2 × 10⁻⁶. 6 MPN / mL, 15 eggs / L.

[0019] Processing steps:

[0020] S1: Adjust the pH of the filtered stock solution to 6.0 using a citric acid-sodium bicarbonate buffer, and add MgCl2 to make Mg²⁺... + 60 mg / L, incubate at 80℃ for 35 min;

[0021] S2: Transfer to the coupling reactor (electrode gap 3mm, ultrasonic transducer at the bottom, effective radiation area 0.025m² / L), pulse electric field 15kV / cm, pulse width 5μs, frequency 300Hz, simultaneously turn on 30kHz ultrasound (power density 0.5W / mL), micro-nano bubble (air) gas content 1.5%, total processing time 6min, material temperature ≤42℃ throughout the process;

[0022] S3: Press 1×10 8 CFU / mL of a complex bacterial culture (10% photosynthetic bacteria, 35% Bacillus subtilis, 20% Bacillus licheniformis, 10% lactic acid bacteria, 10% yeast, 10% nitrifying / denitrifying bacteria, and 5% halophilic bacteria) was introduced. The culture was first aerobic for 4 hours (DO 3.0 mg / L, ORP +120 mV, 32℃), then anaerobic for 12 hours (ORP –250 mV, 34℃), and finally facultative anaerobic for 6 hours (DO 1.0 mg / L, ORP 0 mV, 32℃).

[0023] S4: The target activation section adopts a 10min aeration / 5min aeration stop cycle, with the DO probe closed-loop maintained at 0.8–1.2 mg / L, and the DO decrease rate during the aeration stop phase is 0.12 mg / (L·min), lasting for 2 hours;

[0024] S5: 80μm mesh fine filtration, with 2g / L of food-grade activated carbon added for 15min, and filled under normal pressure.

[0025] Test results: Effluent COD 2300 mg / L, ammonia nitrogen 180 mg / L, total phosphorus 42 mg / L, removal rates 87.6%, 88.2%, and 73.8%, respectively; viable bacteria count 2.8 × 10⁻⁶. 8 CFU / mL; Total enzyme activity 185 U / mL; Fecal coliforms <100 MPN / mL; Eggs ≤1 / L; Viable bacteria retention rate 75% after 6 months of storage at 4–25℃ in the dark.

[0026] Technical effect: This embodiment achieves rigid inactivation of pathogenic bacteria, deep reduction of organic load, and rapid enrichment of functional bacteria-enzyme system simultaneously through "ternary field energy coupling + three-stage DO / ORP programmed switching".

[0027] Example 2 (High-salt conditions, 0.5m³ level)

[0028] Original solution: Urine from pig farm, conductivity 18.7 mS / cm, other indicators are the same as in Example 1.

[0029] Processing steps:

[0030] The only differences from Example 1 are: ① S1 pH adjusted to 8.8, 80℃×40min; ② S2 ultrasound is omitted, only 2% PEF 20kV / cm + micro-nano bubbles (oxygen-rich); ③ S3 the proportion of salt-tolerant Halomonassp. and photosynthetic bacteria is increased to 20%.

[0031] Test results: COD 2650 mg / L, ammonia nitrogen 210 mg / L, total phosphorus 48 mg / L; viable bacteria count 2.4 × 10⁻⁶. 8 CFU / mL; total enzyme activity 171 U / mL; other safety indicators are the same as in Example 1. This demonstrates that under high salt inhibition conditions, the removal rate and viable bacteria level can still be obtained with the same efficiency as in Example 1 through "salt-tolerant bacteria-photosynthetic bacteria synergy + binary field energy".

[0032] Comparative Example 1 (Activation without field energy)

[0033] Processing steps: S2 is omitted, the rest is exactly the same as in Example 1.

[0034] Test results: COD 4900 mg / L, ammonia nitrogen 420 mg / L, total phosphorus 86 mg / L; removal rates only 73.5%, 72.4%, and 46.3%; viable bacteria count 8.5 × 10⁻⁶. 7 CFU / mL; total enzyme activity 102 U / mL. This indicates that in the absence of field coupling, substrate availability is insufficient, and subsequent bacterial community metabolic efficiency is significantly reduced.

[0035] Comparative Example 2 (Continuous aerobic only, without three stages)

[0036] Treatment steps: S3 was changed to continuous aerobic 12h (DO 3.0mg / L), and the rest was the same as in Example 1.

[0037] Test results: COD 6200 mg / L, ammonia nitrogen 610 mg / L, total phosphorus 103 mg / L; removal rates 66.5%, 59.9%, and 35.6%, respectively; viable bacteria count 6.1 × 10⁻⁶. 7CFU / mL; total enzyme activity 88 U / mL. This confirms that aerobic metabolism alone cannot complete the full metabolic chain of denitrification-degradable organic matter cleavage-polysaccharide integration, leading to a simultaneous decrease in pollutant reduction and enzyme activity.

[0038] Results and Data

[0039] Test methods: 1) COD, ammonia nitrogen, and total phosphorus were determined according to HJ828-2017, HJ535-2009, and GB11893-89; 2) Viable bacteria count was determined by plate spread method (NY / T2321-2013); 3) Total enzyme activity was the sum of protease, cellulase, lipase, and nitrate reductase, and was uniformly converted to U / mL; 4) Fecal coliforms were determined by MPN three-step method (GB / T19524.1-2004); 5) Eggs were counted directly under a microscope (NY / T3442-2019).

[0040] Agronomic validation (sweet pepper / leafy vegetable field, 30 days)

[0041] Example 1: Compared with conventional fertilizer control, the application area showed an 8-12% increase in SPAD, a 10-15% increase in net photosynthetic rate, and a 9-13% increase in aboveground fresh weight. Compared with conventional fertilization, the leaf infection area index (Disease Index) was reduced, with a highly significant difference (P < 0.01), and fertilizer application was reduced by 20-30% (based on nitrogen).

[0042] Quality Standard Testing

[0043] Finished liquid fertilizer: viable bacteria count ≥2×10⁸ CFU / mL; pH 6.0–7.5; total nitrogen ≥0.20% (w / w); fecal coliforms ≤100 MPN / mL; insect eggs ≤1 / L; heavy metals meet the relevant limits for agricultural microbial fertilizers.

[0044] Online process recording: DO, ORP, temperature, pH, PEF voltage / frequency, ultrasonic power, and micro / nano bubble gas content closed-loop recording.

[0045] In summary, this invention provides a method for converting livestock manure into compound microbial liquid fertilizer, constructing a continuous three-stage process path of "physical high-temperature inactivation—field energy composite activation—synergistic fermentation of three types of microbial communities—target activation—terminal preparation." This method uses raw urine as a substrate, achieving effective inactivation of pathogenic microorganisms and insect eggs through Pasteurized temperature control and pH buffering. Subsequently, a gentle treatment using a composite "field energy" of at least two of pulsed electric fields, ultrasound, and micro / nano bubbles is employed to improve substrate availability and metabolic initiation efficiency for subsequent inoculation. Then, a programmed fermentation strategy of aerobic-anaerobic-facultative fermentation synergistically achieves deep conversion of organic matter, nitrogen bioconversion, and phosphorus bioaccumulation / migration. The active enzymes and metabolic polysaccharides reach their peak during the 2-hour target activation stage, and terminal preparation is achieved through 50–100 μm fine filtration and optional activated carbon removal. This method features a clear parameter window, online monitoring and traceability of the process, and produces products with high live bacteria content and rich functional enzyme systems. It has comprehensive advantages such as hygiene and safety, synergistic reduction of pollutants, significant improvement of soil and crop efficiency, and expected reduction of chemical fertilizers and pesticides. It is suitable for modular deployment and large-scale promotion in farms, either on-site or near-site, and has good industrial applicability and comprehensive environmental and economic benefits.

[0046] The above embodiments are used to illustrate the present invention, but do not limit the scope of the invention. Those skilled in the art, based on the teachings disclosed in this invention, can make various modifications or equivalent substitutions, all of which should fall within the protection scope of the claims of this invention.

Claims

1. A method for converting livestock and poultry manure and urine into compound microbial liquid fertilizer, characterized in that, The method includes the following steps: A) Physical high-temperature inactivation and pretreatment: The urine stock solution is coarsely filtered, the pH is adjusted to the buffer range, and heat-treated at 80℃ for 30–45 minutes to inactivate pathogenic microorganisms and insect eggs, and to initially degrade pollutants; B) Field energy composite activation of microbial communities: The liquid obtained in step A is treated for 3–10 minutes under the combined action of pulsed electric field, ultrasound and micro-nano bubbles to improve substrate bioavailability and the metabolic initiation rate of microbial communities; C) Co-fermentation of three types of microbial communities: The substrate obtained in step B is inoculated with a mixed microbial community containing aerobic, anaerobic and facultative anaerobic bacteria, and undergoes a programmed fermentation process in sequence through aerobic, anaerobic and facultative anaerobic stages to achieve deep transformation of organic matter, nitrogen and phosphorus biomigration and accumulation of functional substances; D) Target activation and maturation: The fermentation broth is subjected to intermittent aeration and mild shearing treatment to promote the enrichment and stabilization of active enzymes and metabolites; E) Solid-liquid separation and filling: Suspended solids are removed by fine filtration, and activated carbon can be added for adsorption and deodorization before filling to obtain a compound microbial liquid fertilizer product.

2. The method according to claim 1, wherein the pH adjustment range in step A is 5.5–6.5 or 8.5–9.5, the buffer system used is a citric acid-sodium bicarbonate system, and Mg²⁺ is added in parallel. + Magnesium salts at concentrations of 20–100 mg / L were used to promote nitrogen-phosphorus co-precipitation.

3. The method according to claim 1, wherein in step B the pulse electric field strength is 10–25 kV / cm, the ultrasonic frequency is 20–40 kHz, the micro-nano bubble gas content is 1–3%, and the liquid temperature is controlled below 45°C when the three work synergistically.

4. According to the method of claim 1, the three types of microbial groups include at least two or more of the following species: photosynthetic bacteria, Bacillus subtilis, Bacillus licheniformis, lactic acid bacteria, yeast, nitrifying bacteria, denitrifying bacteria, and salt-tolerant bacteria.

5. The method according to claim 1, wherein the three-stage control parameters of step C are as follows: A) Aerobic stage: DO 2.0–4.0 mg / L, ORP +50 to +200 mV, temperature 30–34°C, duration 2–6 hours. B) Anaerobic stage: DO <0.2 mg / L, ORP −150 to −350 mV, temperature 32–36°C, duration 6–18 hours. C) Facultative anaerobic stage: DO 0.5–1.5 mg / L, ORP −50 to +50 mV, temperature 30–34°C, duration 4–12 hours.

6. The method according to claim 1, wherein the target activation stage in step D employs intermittent micro / nano bubble aeration, with the shear rate controlled between 10 and 40 s. - ¹, pH was maintained at 6.2–7.2 for 2 hours.

7. The method according to claim 1, wherein in step E, 1–3 g / L of food-grade activated charcoal is added and the mixture is contacted for 10–20 minutes to remove residual antibiotics and odors.

8. The compound microbial liquid fertilizer product obtained according to claim 1 meets the following indicators: viable count ≥ 2 × 10⁻⁶. 8 CFU / mL, pH value between 6.0 and 7.5, ammonia nitrogen ≤80mg / L, fecal coliform count ≤100MPN / mL, and parasite egg count ≤1 / L.

9. A compound microbial liquid fertilizer prepared by the method according to any one of claims 1-8, characterized in that, The liquid fertilizer contains a variety of active enzymes, including protease, cellulase, lipase and nitrate reductase, with a total enzyme activity ≥150U / mL, and also contains metabolic polysaccharides.

Images