Compound microbial agent and application thereof in urban sludge drying

Abstract

The application discloses a kind of composite microbial inoculant and its application in city sludge drying, belong to the field of biotechnology.The application mixes city sludge and corn straw and adjusts moisture content to 60%~70%;Then add composite microbial inoculant (include bacillus subtilis, bacillus licheniformis, ordinary high-temperature actinomyces, bacillus ureafermmentans and kuraishia sp.);After the material containing composite microbial inoculant is uniformly mixed, it is implanted into fermentation tank.By fermentation tank system, maintain certain ventilation, the heap >90 DEG C can be maintained for more than 10 days in fermentation process, fermentation 10~13 days end fermentation, its moisture content significantly decreases, realizes the rapid and efficient dewatering of city sludge.This technology can realize the rapid decomposition of city sludge material, moisture content decreases greatly, significantly shortens drying period, and operation process is simple, it is a kind of rapid realization city sludge dewatering and drying microbial composite flora and process.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology applications, specifically relating to a compound microbial agent and its application in urban sludge drying. Background Technology

[0002] With the expansion of my country's urban population and the improvement of people's living standards, the consumption of domestic and industrial water has been rising continuously, leading to a year-on-year increase in the amount of wastewater treated by urban sewage treatment plants. Simultaneously, the production of dewatered sludge after filter press treatment has also increased annually, creating a pressing issue for sludge treatment and disposal. According to statistics from the Ministry of Housing and Urban-Rural Development, by the end of 2020, my country's annual municipal sludge production had exceeded 60 million tons, and it is projected to exceed 100 million tons by 2025. In contrast to the rapid development of wastewater treatment, the development of sludge treatment and disposal technologies has been very slow. Currently, the dewatered sludge produced by urban wastewater treatment plants suffers from high water content and unstable biochemical properties. To reduce its environmental impact and lower disposal costs, drying treatment is essential, which is currently the key to solving the sludge disposal problem. Current sludge biological drying technology, as a green and energy-saving new drying technology, uses the heat generated by natural microbial fermentation and external air blowing to reduce the moisture content of the dewatered sludge.

[0003] Sludge drying technology is a crucial step in wastewater treatment, primarily aimed at reducing the moisture content of sludge for subsequent processing or utilization. There are various sludge drying and dewatering technologies, which can be categorized as follows: thermal drying, mechanical filter press drying, microwave drying, and biological drying. Biological sludge drying technology, due to its unique advantages, has attracted considerable attention from researchers. Chinese patent CN102381822A describes a high-temperature rapid digestion process for sludge using a multi-strain composite microbial system, which can rapidly reduce sludge volume to approximately one-fifth of its original volume. Chinese patent CN102851246A addresses the problem that traditional composting, which typically utilizes indigenous microorganisms in the compost material, often suffers from long fermentation times, severe odor pollution, and low maturity. Inoculating the composting process with microbial agents at the initial stage can improve composting efficiency and product quality. The mechanisms by which inoculating microorganisms promote composting include: 1) increasing the microbial population in the early stages of composting and enhancing their degradation activity; 2) shortening the time to reach the high-temperature phase; and 3) inoculating microorganisms with strong organic matter decomposition capabilities. Some thermophilic bacteria, mesophilic bacteria, actinomycetes, and fungi isolated from compost are often used as compost inoculants to accelerate cell wall and lignin / cellulose hydrolysis, promoting the humification process. Chinese patent CN111979156A indicates that a microbial composition formed by adding thermophilic bacteria, when applied to the resource utilization of urban sludge, can raise the fermentation temperature by 30-40°C compared to traditional sludge composting, significantly shortening the fermentation cycle, simplifying the process, and enhancing the harmless treatment effect. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a compound microbial agent and its application in the drying of urban sludge. The present invention provides a microbial energy conversion ultra-high temperature fermentation method. Using this method to treat urban sludge results in a short fermentation cycle, thorough harmlessness and good deodorization, while also achieving better resource utilization of urban sludge.

[0005] To address the aforementioned technical problems, this invention discloses a composite microbial agent and its application in urban sludge drying. The specific technical solution is as follows:

[0006] A compound microbial agent comprising a combination of Bacillus licheniformis, Bacillus belye, Bacillus urealyticum, Bacillus subtilis, common thermophilic actinomycetes, and Saccharomyces cerevisiae.

[0007] The Bacillus licheniformis mentioned above is classified as Bacillus licheniformis, strain number JAAS-21, accession number GDMCC No:63662, and accession date is July 18, 2023.

[0008] The aforementioned Bacillus velezensis is classified as Bacillus velezensis, strain number JAAS-22, accession number GDMCC No:63724, and accession date is August 10, 2023.

[0009] The aforementioned *Ureibacillus suwonensis* is classified as *Ureibacillus suwonensis*, strain number JAAS-41, accession number GDMCC No:65934, and accession date February 20, 2025.

[0010] The Bacillus subtilis mentioned above is classified as Bacillus subtilis and has the accession number CICC10028.

[0011] The common thermophilic actinomycete is classified as Thermoactinomyces vulgaris and has the accession number CICC 10650.

[0012] The aforementioned *Saccharomycopsis fibuligera* yeast is classified as *Saccharomycopsis fibuligera*, with accession number CICC 1717. The concentration of *Bacillus subtilis* in the compound microbial agent is 1–7 × 10⁻⁶. 8 CFU / mL, the concentration of Bacillus licheniformis is 1–5 × 10⁻⁶. 8The concentration of Bacillus belycetamol is 2–7 × 10⁻⁶ CFU / mL. 8 CFU / mL, the concentration of common thermophilic actinomycetes is 1–5 × 10⁻⁶. 7 CFU / mL, the concentration of Bacillus urealyticum is 1–5 × 10⁻⁶ CFU / mL. 7 The concentration of *CFU / mL* of *Streptomyces cuspidatum* was 1–5 × 10⁻⁶ CFU / mL. 8 CFU / mL. Preferably, the content of Bacillus subtilis is 1–2 × 10⁻⁶ CFU / mL. 8 CFU / mL, Bacillus licheniformis content is 3-5 × 10⁻⁶. 8 CFU / mL, the content of Bacillus belyssus is 3-4 × 10⁻⁶. 8 CFU / mL, the content of common thermophilic actinomycetes is 2-4 × 10⁻⁶. 7 CFU / mL, the content of Bacillus urealyticum is 2-3 × 10⁻⁶ CFU / mL. 7 The CFU / mL content of *Streptomyces cladosporium* was 1–2 × 10⁻⁶ CFU / mL. 8 CFU / mL.

[0013] In a second aspect, the present invention provides a method for preparing the composite microbial agent described in the first aspect, comprising the following steps: fermenting and culturing Bacillus licheniformis, Bacillus belye, Bacillus urealyticum, Bacillus subtilis, common thermophilic actinomycetes, and Bacillus thuringiensis to obtain Bacillus licheniformis fermentation broth, Bacillus belye fermentation broth, Bacillus urealyticum fermentation broth, Bacillus subtilis fermentation broth, common thermophilic actinomycetes fermentation broth, and Bacillus thuringiensis fermentation broth, and mixing them to obtain the composite microbial agent.

[0014] The fermentation temperature of *Bacillus licheniformis* is 35–38℃, and the fermentation time is 48–50 h, preferably 37℃ for 48 h. The fermentation temperature of *Bacillus belyssus* is 35–38℃, and the fermentation time is 48–50 h, preferably 37℃ for 48 h. The fermentation temperature of *Bacillus subtilis* is 35–38℃, and the fermentation time is 48–50 h, preferably 37℃ for 48 h. The fermentation temperature of *Common thermophilic actinomycetes* is 50–60℃, and the fermentation time is 50–55 h, preferably 55℃ for 52 h. The fermentation temperature of *Bacillus urealyticum* is 50–60℃, and the fermentation time is 50–55 h, preferably 55℃ for 52 h. The fermentation temperature of *Bacillus urealyticum* is 28–32℃, and the fermentation time is 48–50 h, preferably 30℃ for 48 h.

[0015] More preferably, the fermentation medium used in the fermentation process of Bacillus licheniformis, Bacillus belye, Bacillus urealyticum, Bacillus subtilis, common thermophilic actinomycetes, and Saccharomyces cerevisiae includes: 5 g / L corn steep liquor powder, 5 g / L yeast powder, 5 g / L sodium chloride, 10 g / L glucose, 2 g / L tryptone, and 10 g / L molasses.

[0016] The mixing volume ratio of Bacillus licheniformis fermentation broth, Bacillus belye fermentation broth, Bacillus urealyticum fermentation broth, Bacillus subtilis fermentation broth, common thermophilic actinomycete fermentation broth, and Saccharomyces cerevisiae fermentation broth is 0.5–1.5:0.5–1.5:0.5–1.5:0.5–1.5:0.5–1.5, preferably 1:1:1:1:1:1.

[0017] Preferably, the fermentation broth is obtained by large-scale production in fermenters.

[0018] Thirdly, the present invention provides the application of the composite microbial agent described in the first aspect in the drying of urban sewage sludge.

[0019] The compound microbial agent is inoculated into a mixture of urban sludge and corn stalks for aerobic fermentation, thereby drying the urban sludge.

[0020] In the mixture of urban sludge and corn stalks, the mixing mass ratio of urban sludge and corn stalks is 0.5 to 2:1, preferably 1:1; the inoculation amount of the compound microbial agent is 1 to 5‰ v / v, preferably 3‰ v / v.

[0021] The aerobic fermentation process involves a fermentation cycle of 10-13 days. This aerobic fermentation is high-temperature aerobic fermentation, where the pile temperature can rise to 90℃ within 24 hours. After 12 days of high-temperature composting, the moisture content decreases from 60-65% to 30-35%, and the high temperature can be maintained for more than 10 days, resulting in a 30% reduction in pile volume.

[0022] Beneficial effects:

[0023] This invention discloses a composite microbial agent comprising a combination of Bacillus licheniformis, Bacillus belye, Bacillus urealyticum, Bacillus subtilis, common thermophilic actinomycetes, and *Cytomyces hymenopsicae*. Using this composite microbial agent to treat municipal sludge enables rapid composting of the sludge, significantly reduces its moisture content, and substantially shortens the drying cycle. The process is simple and represents a composite microbial agent and process for the rapid dewatering and drying of municipal sludge. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0025] Figure 1 These are clear zone plates for hydrolysis of strains with high protease activity. A consists of *Bacillus urealyticum* cultured at 55°C, B consists of *Bacillus belysinus* cultured at 37°C, and C consists of *Diplostomum clavatum* cultured at 30°C.

[0026] Figure 2 These are clear zone plates for hydrolysis of strains with high amylase activity. A represents Bacillus subtilis cultured at 37°C, B represents Bacillus belyssus cultured at 37°C, and C represents *Diplostomum tumefaciens* cultured at 30°C.

[0027] Figure 3 These are clear zone plates for hydrolysis of strains with high lipase activity. A represents common thermophilic actinomycetes cultured at 55°C, B represents Bacillus subtilis cultured at 37°C, and C represents Bacillus licheniformis cultured at 37°C.

[0028] Figure 4 These are clear zone plates for hydrolysis of strains with high cellulase activity. A represents common thermophilic actinomycetes cultured at 55°C, B represents Bacillus subtilis cultured at 37°C, and C represents Bacillus licheniformis cultured at 37°C.

[0029] Figure 5 The diagram shows the material properties of compost pile 1 at different treatment stages. Among them, A is a physical picture of compost pile 1 in the initial stage of mixing, B is the compost pile properties of compost pile 1 after the end of composting, C is the high temperature of 97℃ that compost pile 1 can reach during fermentation, D is a physical picture of compost pile 1 during fermentation, and E is the trend of compost temperature and moisture content of compost pile 1 with the treatment time. Figure 6 The diagram shows the material properties of compost pile 2 at different treatment stages. Among them, A is a physical picture of compost pile 2 in the initial stage of mixing, B is the compost pile properties of compost pile 2 after the end of composting, C is the high temperature of 98℃ that compost pile 2 can reach during fermentation, D is a physical picture of compost pile 2 during fermentation, and E is the trend of composting temperature and moisture content of compost pile 2 with treatment time. Detailed Implementation

[0030] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0031] Example 1: Screening of microbial strains with high enzyme activity

[0032] The screening plates for protease, amylase, lipase, and cellulase are prepared according to the following methods:

[0033] Protease screening plates: 20 g / L agar, 2% (g / mL) skim milk; sterilized at 121℃ for 15 min.

[0034] Amylase screening plates: soluble starch 2.5 g / L, peptone 5 g / L, ammonium sulfate 2.5 g / L, potassium dihydrogen phosphate 3 g / L, calcium chloride hexahydrate 0.25 g / L, agar 20 g / L; sterilized at 121℃ for 15 min, and after incubation, 1 mL of Lugol's iodine solution was added to show hydrolysis zones.

[0035] Lipase screening plate: yeast extract 2.5 g / L, tryptone 2.5 g / L, agar 12 g / L, adjust pH to 7±0.1, add bromocresol purple, sterilize at 121℃ for 15 min, cool to 50-55℃, add 20 mL / L tributyrate; (plate color is purple).

[0036] Cellulase screening plate: Sodium nitrate 1 g / L, disodium hydrogen phosphate 1.2 g / L, potassium dihydrogen phosphate 0.9 g / L, magnesium sulfate 0.5 g / L, potassium chloride 0.5 g / L, yeast extract 0.5 g / L, acid-hydrolyzed casein 0.5 g / L, Congo red 0.2 g / L, cellulose powder 5 g / L, agar 15 g / L, pH ± 0.1. After culturing, add 1 mol / L sodium chloride solution and soak for 15 minutes, then discard the sodium chloride solution and observe the hydrolysis zone.

[0037] Screening method for high enzyme activity microbial strains: After liquid activation culture, 5 μL of bacterial solution was taken from the sludge drying and manure composting related strains preserved in our laboratory and dropped onto screening plates for protease, amylase, lipase and cellulase. The plates were incubated at 30℃, 37℃ and 55℃ for 24 hours respectively. The size of the transparent zone was used as an indicator to screen for target strains with high enzyme activity.

[0038] 1. Screening of strains with high protease activity:

[0039] Two strains with high protease activity were screened out under 55℃ culture conditions: Bacillus urealyticum and common thermophilic actinomycetes.

[0040] Three strains with high protease activity were screened out under 37℃ culture conditions: Bacillus subtilis, Bacillus licheniformis, and Bacillus belye.

[0041] A strain with high protease activity was obtained by screening at 30℃, which is *Diplostomum tumefaciens*.

[0042] The hydrolysis clear zones of the high protease activity strains screened under three different temperature incubation conditions are as follows: Figure 1 As shown.

[0043] 2. Screening of strains with high amylase activity:

[0044] No strains exhibited amylase activity when cultured at 55°C.

[0045] Two strains with high amylase activity were screened out under 37℃ culture conditions: Bacillus subtilis and Bacillus belye.

[0046] A strain with high amylase activity was obtained by screening at 30℃, which is *Diplostomum tumefaciens*.

[0047] The hydrolytic clear zone of the high amylase activity strains obtained through screening, such as Figure 2 As shown.

[0048] 3. Screening of strains with high lipase activity:

[0049] A strain with high lipase activity was obtained by screening at 55℃, which is a common thermophilic actinomycete.

[0050] Two strains with high lipase activity were screened at 37℃: Bacillus subtilis and Bacillus licheniformis. No strains with high lipase activity were screened from the target bacterial library at 30℃.

[0051] The hydrolysis clear zone of the high lipase activity strains obtained through screening, such as Figure 3 As shown.

[0052] 4. Screening of cellulase-highly active strains:

[0053] Two strains with high cellulase activity were screened out under 55℃ culture conditions: Bacillus urealyticum and common thermophilic actinomycetes.

[0054] Three strains with high cellulase activity were screened out under 37℃ culture conditions: Bacillus subtilis, Bacillus licheniformis, and Bacillus belesii.

[0055] A strain with high cellulase activity was obtained by screening at 30℃, which is *Diplostomum tumefaciens*.

[0056] The hydrolysis clear zone of the high cellulase activity strains obtained through screening, such as Figure 4 As shown.

[0057] The relevant data on the hydrolysis zone diameter of each strain are shown in Table 1.

[0058] Table 1. Enzyme activity of the target strain and the maximum diameter of the hydrolytic clear zone.

[0059]

[0060] Based on the enzyme activity of the above strains, the six high-enzyme-activity target strains screened in this invention were sent to the company for 16S rDNA sequencing and species confirmation. The sequencing sequences of *Bacillus licheniformis* are shown in SEQ ID No. 1, *Bacillus belyssus* in SEQ ID No. 2, and *Bacillus urealyticum* in SEQ ID No. 3. Preservation information for each strain is as follows:

[0061] The Bacillus licheniformis strain, classified as Bacillus licheniformis, strain number JAAS-21, has the accession number GDMCC No: 63662 and was deposited on July 18, 2023, at the Guangdong Provincial Microbial Culture Collection Center (GDMCC), located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou.

[0062] The aforementioned Bacillus velezensis, classified as Bacillus velezensis, strain number JAAS-22, accession number GDMCC No: 63724, accession date August 10, 2023, is deposited at the Guangdong Provincial Microbial Culture Collection Center (GDMCC), located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou.

[0063] The aforementioned *Ureibacillus suwonensis*, with strain number JAAS-41 and accession number GDMCC No: 65934, was deposited on February 20, 2025, at the Guangdong Provincial Microbial Culture Collection Center (GDMCC), located at the Institute of Microbiology, Guangdong Academy of Sciences, 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou.

[0064] The other three strains are: Thermoactinomyces vulgaris CICC 10650; Bacillus subtilis CICC 10028; and Saccharomycopsis fibuligera CICC 1717.

[0065] This invention utilizes the above-mentioned 6 strains with high enzyme activity to prepare a compound microbial agent, which is applied to the drying treatment of urban sewage sludge.

[0066] Example 2: Fermentation Cultivation and Preparation of Compound Microbial Agent

[0067] 1. Seed culture

[0068] Bacillus subtilis CICC 10028, Bacillus licheniformis JAAS-21, and Bacillus bereaves JAAS-22 were streaked onto LB agar plates and incubated at 37°C for 18-24 h (20 h in this example). Mature single colonies were picked and transferred to 150 mL of LB liquid medium. The incubation conditions were: stirring speed 100-200 rpm (150 rpm in this example), incubation temperature 37°C, and incubation time 18-24 h (20 h in this example), which was the primary shake flask culture. The seed culture from the primary shake flask was inoculated into 300 mL of LB liquid medium at an inoculation rate of 5% v / v, which was the secondary shake flask culture. The incubation conditions were the same as the primary shake flask culture. Secondary shake flask seed cultures of Bacillus subtilis, Bacillus licheniformis, and Bacillus bereaves were obtained.

[0069] Common thermophilic actinomycete CICC 10650 and Bacillus urealyticum JAAS-41 were streaked onto LB agar plates and incubated at 55°C for 18-24 h (20 h in this example). Mature single colonies were picked and transferred to 150 mL of LB liquid medium. The incubation conditions were: stirring speed 100-200 rpm (150 rpm in this example), incubation temperature 55°C, and incubation time 18-24 h (20 h in this example), which was the first-stage shake flask culture. The seed culture from the first-stage shake flask was inoculated into 300 mL of LB liquid medium at an inoculation rate of 5% v / v, which was the second-stage shake flask culture. The incubation conditions were the same as the first-stage shake flask culture. Secondary shake flask seed cultures of common thermophilic actinomycete and Bacillus urealyticum were obtained.

[0070] CICC 1717 of *Cytomyces cladosporium* was streaked onto PDA agar plates and incubated at 30°C for 18-24 hours (20 hours in this example). Mature single colonies were picked and transferred to 150 mL of PDA liquid medium. The culture conditions were: stirring speed 100-200 rpm (150 rpm in this example), culture temperature 30°C, and culture time 18-24 hours (20 hours in this example), which was the first-stage shake flask culture. The seed culture from the first-stage shake flask was inoculated into 300 mL of PDA liquid medium at an inoculation rate of 5% v / v, which was the second-stage shake flask culture. The culture conditions were the same as the first-stage shake flask culture, resulting in the second-stage shake flask seed culture of *Cytomyces cladosporium*.

[0071] 2. Fermentation and Preparation

[0072] Fermentation tank culture medium: corn steep liquor powder 5g / L, yeast powder 5g / L, sodium chloride 5g / L, glucose 10g / L, tryptone 2g / L, molasses 10g / L.

[0073] (1) Primary seed fermentation tank culture:

[0074] Prepare 30L fermentation medium into a 50L seed fermentation tank, autoclave at 121℃ for 20 minutes, and inoculate with 10% v / v of the Bacillus subtilis secondary shake flask seed culture prepared above. Incubate at 37℃, with a stirring speed of 200 rpm and an aeration rate of 0.7 m³ / min. 3 The culture time is 48-50 hours, and the first-stage seed tank fermentation broth is obtained. The culture process for Bacillus licheniformis and Bacillus bereaves is the same as above.

[0075] Prepare 30L fermenter culture medium into a 50L seed fermenter, autoclave at 121℃ for 20 minutes, and inoculate with 10% v / v of the commonly prepared secondary shake-flask seed culture of common thermophilic actinomycetes. Incubate at 55℃, with a stirring speed of 200 rpm and an aeration rate of 0.7 m³ / min. 3 The culture time is 50-55 hours, and the first-stage seed tank fermentation broth is obtained. The culture procedure for Bacillus urealyticum JAAS-41 is the same as above, with a culture temperature of 55℃.

[0076] Prepare 30L fermentation culture medium into a 50L seed fermentation tank, autoclave at 121℃ for 20 minutes, and inoculate with 10% v / v of the prepared *Diplostomum tumefaciens* secondary shake flask seed culture. Incubate at 30℃, with a stirring speed of 200 rpm and an aeration rate of 0.7 m³ / min. 3 / h, the culture time is 48-50h, and the first-stage seed tank fermentation broth is obtained.

[0077] (2) Secondary seed fermentation tank culture:

[0078] Prepare 300L of fermentation culture medium into a 500L secondary seed fermentation tank, autoclave at 121℃ for 20 minutes, inoculate with 30L of Bacillus subtilis from the primary seed tank, and incubate at 37℃ with a stirring speed of 100-150rpm (130rpm in this example) and an aeration rate of 7m³ / h. 3 The culture time is 48-50 hours, and the secondary seed tank fermentation broth is obtained. The culture process for Bacillus licheniformis and Bacillus bereaves is the same as above.

[0079] Prepare 300L of fermentation medium for a 500L secondary seed fermenter, autoclave at 121℃ for 20 minutes, inoculate with 30L of common thermophilic actinomycetes from the primary seed tank, and incubate at 55℃ with a stirring speed of 100-150 rpm (130 rpm in this example) and an aeration rate of 7 m³ / min. 3 The culture time is 50-55 hours, and the secondary seed tank fermentation broth is obtained. The culture procedure for Bacillus urealyticum JAAS-41 is the same as above, and the culture temperature is 55℃.

[0080] Prepare 300L fermenter culture medium into a 500L secondary seed fermenter, autoclave at 121℃ for 20 minutes, and inoculate with 30L of *Diplostomum spp.* from the primary seed tank. Maintain the culture temperature at 30℃, stirring speed at 100-150 rpm (130 rpm in this example), and aeration rate of 7 m³ / h. 3 / h, the culture time is 48-50h, and the secondary seed tank fermentation broth is obtained.

[0081] (3) Large-scale cultivation and preparation in ton-scale fermenters:

[0082] Prepare 3000L fermenter culture medium into a 5000L fermenter, autoclave at 121℃ for 20 minutes, inoculate with 300L of Bacillus subtilis from the secondary seed tank, and incubate at 37℃ with a stirring speed of 60-120rpm (100rpm in this example) and an aeration rate of 70-75m³ / h. 3 The fermentation broth of Bacillus subtilis is obtained by incubating at a rate of 1 / h for 48-50 hours. The culture process for Bacillus licheniformis and Bacillus bereaves is the same as above.

[0083] Prepare 3000L fermenter culture medium for a 5000L fermenter, autoclave at 121℃ for 20 minutes, inoculate with 300L of common thermophilic actinomycetes from the secondary seed tank, and incubate at 55℃ with a stirring speed of 60-120rpm (100rpm in this example) and an aeration rate of 70-75m³ / h. 3 The fermentation broth of common thermophilic actinomycetes is obtained by incubating at a rate of 50-55 h. The culture procedure for Bacillus urealyticum JAAS-41 is the same as above, with a culture temperature of 55℃.

[0084] Prepare 3000L fermenter culture medium for a 5000L fermenter, autoclave at 121℃ for 20 minutes, then inoculate with 300L of *Saccharomyces cerevisiae* from the secondary seed tank. Incubate at 30℃, with a stirring speed of 60-120 rpm (100 rpm in this example) and an aeration rate of 70-75 m³ / h. 3 / h, culture time is 48-50h, to obtain the fermentation broth of *Saccharomyces cerevisiae*.

[0085] The fermentation broths of the above-mentioned cultured strains were directly mixed in equal volume ratios of 1:1:1:1:1:1 to obtain a compound microbial agent. The number of viable bacteria in the compound microbial agent was detected, as shown in Table 2.

[0086] Table 2 Results of viable bacteria count in compound microbial agents

[0087] strain name viable bacteria count (CFU / mL) Bacillus subtilis <![CDATA[1.3×10 8 ]]> Bacillus licheniformis <![CDATA[4.1×10 8 ]]> Bacillus belesiensis <![CDATA[3.5×10 8 ]]> Common high-temperature actinomycetes <![CDATA[3.5×10 7 ]]> Bacillus urealyticum <![CDATA[2.4×10 7 ]]> Yeast sacchariformis <![CDATA[1.6×10 8 ]]>

[0088] Example 3: Optimization of the formulation of compound microbial inoculants

[0089] Test materials and supplies: urban sludge (sludge produced by sewage treatment plants, with a moisture content of 70%-80% after pressure filtration), corn stalks, and compound microbial agents.

[0090] Urban sludge and corn stalks were mixed evenly at a mass ratio of 1:1. The moisture content of the urban sludge was 77%, and the moisture content of the corn stalks was 40%. The inoculation volume of the compound microbial agent was 3‰ of the pile volume. After mixing, the moisture content was 66%. The following six combinations of compound microbial agents were used for inoculation. The preparation method of the compound microbial agents was the same as in Example 2. The combinations of compound microbial agents are as follows:

[0091] Formula combination 1: Bacillus licheniformis: Bacillus belye: Bacillus urealyticum: Saccharomyces hygroscopicus, and their fermentation broth is mixed in a volume ratio of 1:1:1:1;

[0092] Formula combination 2: Bacillus subtilis: Bacillus belye: common thermophilic actinomycetes: Bacillus urealyticum, the fermentation broth is mixed in a volume ratio of 1:1:1:1;

[0093] Formula combination 3: Bacillus subtilis: Bacillus licheniformis: common thermophilic actinomycetes: Bacillus urealyticum: Saccharomyces cerevisiae, and their fermentation broth is mixed in a volume ratio of 1:1:1:1:1;

[0094] Formula combination 4: Bacillus subtilis: Bacillus belye: common thermophilic actinomycetes: Bacillus urealyticum: Saccharomyces hygroscopicus, and their fermentation broth is mixed in a volume ratio of 1:1:1:1:1;

[0095] Formula combination 5: Bacillus licheniformis: Bacillus belye: common thermophilic actinomycetes: Bacillus urealyticum: Saccharomyces hygroscopicus, and their fermentation broth is mixed in a volume ratio of 1:1:1:1:1;

[0096] Formula combination 6: Bacillus subtilis: Bacillus licheniformis: Bacillus belye: common thermophilic actinomycetes: Bacillus urealyticum: Saccharomyces hygroscopicus, and their fermentation broth is mixed in a volume ratio of 1:1:1:1:1:1;

[0097] Based on the above proportions, the mixture is divided into 6 groups, each with a pile volume of 10 cubic meters. An air supply pipe is installed at the bottom of the fermentation tank, and air is supplied to the pile via a blower to ensure the oxygen required for the high-temperature aerobic fermentation process. The ventilation rate is controlled at 0.03-0.09 m³ / h. 3 / min; the pile was turned over every 48-72 hours to enter the next fermentation stage. After 18-21 days, fermentation was completed. Detailed results are shown in Table 3. It can be seen that the ratio combination 6 has the best drying effect on the material, with a maximum temperature of 80℃, a fermentation cycle of 18 days, and a final moisture content of 38%. Therefore, the ratio combination 6 (Bacillus subtilis: Bacillus licheniformis: Bacillus belye: common thermophilic actinomycetes: Bacillus urealyticum: Saccharomyces cerevisiae, mixed in equal volume ratios of 1:1:1:1:1:1) was selected as the optimal combination for large-scale testing.

[0098] Table 3. Formulation and Small-Scale Test Results of Compound Microbial Agents

[0099] Mixing ratio Maximum temperature (℃) Period (d) Final moisture content (%) Combination 1 68 21 44 Combination 2 73 21 43 Combination 3 75 18 40 Combination 4 74 18 42 Combination 5 72 21 41 Combination 6 80 18 38

[0100] Example 4: Large-scale test of efficient drying and dewatering of urban sludge

[0101] Test materials and materials: urban sludge (sludge produced by sewage treatment plants, with a moisture content of 70%-80% after pressure filtration), corn stalks, and the composite microbial agent prepared in Example 2.

[0102] 1. Test stack 1 for efficient drying and dewatering of urban sludge:

[0103] Urban sewage sludge and corn stalks were mixed evenly at a mass ratio of 1:1. The moisture content of the urban sewage sludge was 76.9%, and the moisture content of the corn stalks was 40%. The composite microbial agent prepared in Example 2 was inoculated, with an inoculation volume of 3‰ of the pile volume. After mixing, the moisture content was 65%, and the total volume was 200 cubic meters. The pile was stacked to the top of the fermentation tank. An air supply pipe was installed at the bottom of the fermentation tank, and air was supplied to the pile through a blower to ensure the oxygen required for the high-temperature aerobic fermentation process. The ventilation rate was controlled at 0.03-0.09 m³ / h. 3 / min; the fermentation pile is turned over every 48 hours to proceed to the next stage of fermentation. After 10-13 days of fermentation, fermentation is stopped when the moisture content of the fermentation product is below 40%, thus completing the entire fermentation process. Figure 5 As shown, after 12 days of high-temperature composting, the moisture content decreased from 65-70% to 30-36%, and the high temperature of 90℃ could be maintained for more than 10 days, resulting in a reduction of more than 30% in the compost volume.

[0104] 2. Test stack 2 for efficient drying and dewatering of urban sludge:

[0105] Urban sewage sludge and corn stalks were mixed evenly at a mass ratio of 1:1. The moisture content of the urban sewage sludge was 73.5%, and the moisture content of the corn stalks was 40%. The composite microbial agent prepared in Example 2 was inoculated, with an inoculation volume of 3‰ of the pile volume. After mixing, the moisture content was 63%, and the total volume was 200 cubic meters. The pile was stacked to the top of the fermentation tank. An air supply pipe was installed at the bottom of the fermentation tank, and air was supplied to the pile through a blower to ensure the oxygen required for the high-temperature aerobic fermentation process. The ventilation volume was controlled at 0.5 m³ / h. 3 / min; the fermentation pile is turned over every 48 hours to proceed to the next stage of fermentation. After 10-13 days of fermentation, fermentation is stopped when the moisture content of the fermentation product is below 40%, thus completing the entire fermentation process. Figure 6 As shown, after 12 days of high-temperature composting, the moisture content decreased from 60-65% to 30-35%, and the high temperature of 90℃ could be maintained for more than 10 days, resulting in a reduction of more than 30% in the compost volume.

[0106] Due to the high fermentation temperature, the two piles fermented at temperatures above 90°C for more than 10 days during the entire 13-day fermentation cycle. The microbial community proliferated actively under the high-temperature and aerobic conditions above 90°C, resulting in rapid water evaporation, low moisture content in the fermentation products, and significant volume reduction.

[0107] This invention provides a composite microbial agent and its application in urban sludge drying, along with a method and approach. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A compound microbial agent, characterized in that, It includes a combination of Bacillus licheniformis, Bacillus belye, Bacillus urealyticum, Bacillus subtilis, common thermophilic actinomycetes, and Saccharomyces cerevisiae; The aforementioned Bacillus licheniformis is classified as follows: Bacillus licheniformis The strain number is JAAS-21, the accession number is GDMCC No: 63662, and the accession date is July 18, 2023; The aforementioned Bacillus belye is classified as follows: Bacillus velezensis The strain number is JAAS-22, the accession number is GDMCC No: 63724, and the accession date is August 10, 2023; The aforementioned Bacillus urealyticum is classified as follows: Ureibacillus suwonensis The strain number is JAAS-41, the accession number is GDMCC No: 65934, and the accession date is February 20, 2025; The aforementioned Bacillus subtilis is classified as follows: Bacillus subtilis The accession number is CICC 10028; The common thermophilic actinomycetes are classified and named as follows: Thermoactinomyces vulgaris The accession number is CICC10650; The classification and nomenclature of the *Cyclocarya paliurus*. Saccharomycopsis fibuligera The accession number is CICC1717.

2. The compound microbial agent according to claim 1, characterized in that, The concentration of Bacillus subtilis in the aforementioned compound microbial agent is 1~7×10⁻⁶. 8 CFU / mL, the concentration of Bacillus licheniformis is 1~5×10 8 CFU / mL, the concentration of Bacillus belyceae is 2~7×10 8 CFU / mL, the concentration of common thermophilic actinomycetes is 1~5×10⁻⁶. 7 CFU / mL, the concentration of Bacillus urealyticum is 1~5×10⁻⁶. 7 The concentration of *CFU / mL* of *Streptomyces cuspidatum* is 1–5 × 10⁻⁶ CFU / mL. 8 CFU / mL.

3. The method for preparing the composite microbial agent according to any one of claims 1 to 2, characterized in that, The process includes the following steps: fermenting and culturing Bacillus licheniformis, Bacillus belye, Bacillus urealyticum, Bacillus subtilis, common thermophilic actinomycetes, and Bacillus thuringiensis yeast separately to obtain Bacillus licheniformis fermentation broth, Bacillus belye fermentation broth, Bacillus urealyticum fermentation broth, Bacillus subtilis fermentation broth, common thermophilic actinomycetes fermentation broth, and Bacillus thuringiensis yeast fermentation broth, then mixing them to obtain the aforementioned compound microbial agent.

4. The preparation method according to claim 3, characterized in that, The fermentation temperature of the Bacillus licheniformis is 35~38 ℃, and the fermentation time is 48~50 h; The fermentation temperature of the aforementioned Bacillus belye is 35~38 ℃, and the fermentation time is 48~50 h; The fermentation temperature of the Bacillus subtilis is 35~38 ℃, and the fermentation time is 48~50 h; The fermentation temperature of the common high-temperature actinomycetes is 50~60 ℃, and the fermentation time is 50~55 h; The fermentation temperature of the aforementioned Bacillus urealyticum is 50~60 ℃, and the fermentation time is 50~55 h; The fermentation temperature of the aforementioned *Cyclocarya paliurus* is 28-32 °C, and the fermentation time is 48-50 h.

5. The preparation method according to claim 3, characterized in that, The mixing volume ratio of the Bacillus licheniformis fermentation broth, Bacillus belye fermentation broth, Bacillus urealyticum fermentation broth, Bacillus subtilis fermentation broth, common thermophilic actinomycete fermentation broth, and Saccharomyces cerevisiae fermentation broth is 0.5~1.5: 0.5~1.5: 0.5~1.5: 0.5~1.5: 0.5~1.5: 0.5~1.

5.

6. The application of the composite microbial agent according to any one of claims 1 to 2 in the drying of urban sewage sludge.

7. The application according to claim 6, characterized in that, The aforementioned compound microbial agent is inoculated into a mixture of urban sludge and corn stalks for aerobic fermentation, thereby drying the urban sludge.

8. The application according to claim 7, characterized in that, In the mixture of urban sludge and corn stalks, the mixing mass ratio of urban sludge to corn stalks is 0.5~2:1; The inoculation amount of the compound microbial agent is 1-5‰ v / v.

9. The application according to claim 7, characterized in that, The aforementioned aerobic fermentation has a fermentation cycle of 10 to 13 days.

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