Sludge waste thermophilic fermentation process and application thereof

Abstract

The application discloses a sludge waste variable-temperature fermentation process and application, precise regulation and control of industrial sludge waste metabolism is realized through collocation of bacterial agents, through high-temperature acid production, mesophilic free fatty acid (FFAs) / glycerol production and low-temperature humification process, carbon closed loop is formed through carbon dioxide absorption and solidification, and maximum utilization of resources is ensured, the application forms a three-stage relay through thermophilic bacteria, fat-degrading bacteria and humus-synthesizing bacteria, efficient biological conversion of industrial sludge waste is realized through synergistic effect of the bacterial flora, and there is no cross inhibition between different bacterial flora, and the process is ensured to be smoothly carried out. Through energyization of isopropyl alcohol and soil improvement of humus, high-value conversion of products is realized, economic value of the products is improved, resource recycling is realized, and the application has good market prospect and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, specifically to a variable-temperature fermentation process for sludge waste and its application. Background Technology

[0002] Industrial sludge, a typical hazardous waste (HW08 category) from the petrochemical, machinery manufacturing, and oil refining industries, has an annual output exceeding 100 million tons, and continues to grow at a rate of 8%-10%. Its composition is complex, containing pollutants such as petroleum hydrocarbons (15%-40%), mineral oil (10%-30%), and polycyclic aromatic hydrocarbons. It exhibits strong hydrophobicity, is difficult to degrade, and is ecotoxic. Improper disposal can lead to environmental risks such as groundwater pollution and soil degradation. However, the high organic matter content of this type of sludge also holds enormous resource potential—petroleum hydrocarbons and mineral oils are essentially hydrocarbons, which can theoretically be biotransformed into high-value products such as fatty acids, used to cultivate beneficial soil bacteria, thus promoting the dual goals of "pollution control" and "resource regeneration."

[0003] Currently, industrial sludge treatment faces a dual dilemma: difficulty in degradation and difficulty in value-added processing. Traditional physicochemical methods, such as pyrolysis and solvent extraction, while capable of partially removing pollutants, often come at the cost of high energy consumption or secondary pollution (such as solvent residues), and neglect the resource value of hydrocarbon components. Conventional biological methods, such as composting and anaerobic digestion, while in line with green and low-carbon principles, suffer from low degradation rates of long-chain hydrocarbons, significant mineral oil encapsulation effects, and low added value of the final products, resulting in insufficient utilization of carbon resources, thus requiring improvement. Summary of the Invention

[0004] To address at least one of the aforementioned technical deficiencies, the present invention provides the following technical solution:

[0005] This invention discloses a temperature-switched fermentation process for sludge waste, comprising the following steps:

[0006] Step 1: Pre-treatment of sludge waste

[0007] Sludge waste is subjected to ultrasonic activation treatment, and acid and / or alkali are added to make the pH of the sludge waste after ultrasonic activation treatment reach 6-8.

[0008] Step 2: Temperature-controlled fermentation

[0009] High-temperature fermentation treatment: Add 0.1-0.5% of functional bacterial group A by mass to the pretreated sludge mixture, raise the temperature to 60-65℃, and ferment in a microaerobic environment for 48-72 hours; wherein, functional bacterial group A is obtained by mixing Bacillus stearothermophilus BNCC338119, Pseudomonas aeruginosa BNCC360090 and Streptococcus thermophilus BNCC363554 in a volume ratio of 4-7:1-2:3-5.

[0010] Mesophilic fermentation treatment: The temperature of the sludge mixture after high-temperature fermentation is reduced to 35-40℃, and 0.1-0.5% of functional bacterial group B is added to the sludge mixture for aerobic fermentation for 96-120 hours. Functional bacterial group B is obtained by mixing Saccharomyces cerevisiae BNCC186741 and Propionibacterium jinseniense BNCC194214 at a volume ratio of 6-8:1-3, and adding 10-20% of mesophilic lipase to the total bacterial solution after mixing.

[0011] Low-temperature fermentation treatment: The sludge mixture after mesophilic fermentation is cooled to 25-30℃ and mixed with sawdust at a volume ratio of 1.5-4:1. Functional bacterial agent C, accounting for 1-2% of the mass of the sludge mixture, is added for fermentation for 120-168 hours to obtain sludge fermentation products. Among them, functional bacterial group C is obtained by mixing Pseudomonas putidae BNCC338119, Bacillus subtilis with accession number CGMCC NO.26196, and Trichoderma longiflorum with accession number CGMCC.NO.40444 at a volume ratio of 1-4:2-6:4-9, and adding 20-30% of the total bacterial solution mass of the mixture with low-temperature lipase.

[0012] The principle is as follows: the cavitation effect of ultrasonic treatment can fully activate sludge waste, and at the same time, it can also partially remove pathogens in sludge. Acids and alkalis can adjust the pH in the reaction and also partially remove pathogens, thus providing a guarantee for subsequent inoculation and fermentation.

[0013] like Figure 1 As shown, the core task of the high-temperature stage is the microbial degradation of long-chain petroleum hydrocarbons (C10-C40) and small-molecule alcohols (such as isopropanol). This stage primarily relies on the action of bacteria such as *Bacillus stearothermophilus* and *Pseudomonas aeruginosa*. *Bacillus stearothermophilus* can tolerate high temperatures and secretes alkane monooxygenase (AlkB), which decomposes long-chain petroleum hydrocarbons (C10-C40) and fatty acids through oxidation. *Pseudomonas aeruginosa*, on the other hand, can dissolve petroleum hydrocarbons through emulsification and assist in further degradation. Ester compounds in mineral oil are also decomposed into fatty acids and isopropanol by *Streptococcus thermophilus* BNCC363554 in this stage. Isopropanol can be extracted and recovered as a gas with a purity of over 85% for subsequent energy conversion. The temperature is controlled between 60°C and 65°C, and a stepped heating method ensures that the microorganisms are active within a suitable temperature range, promoting degradation efficiency. A microaerobic environment can maintain the growth and enzyme activity of microorganisms. The products of this stage are mainly medium- and short-chain fatty acids (such as acetic acid and propionic acid), which are used in the mesophilic fermentation stage.

[0014] The main task of the mesophilic fermentation stage is to process the medium- and short-chain fatty acids (such as C2-C18 free fatty acids) produced in the high-temperature stage. *Acidipropionibacterium jensenii* oxidizes short-chain fatty acids (C2-C6) into carbon dioxide, preventing excessive acidity from inhibiting microbial growth and metabolism. Triglycerides are degraded and utilized by the combined action of mesophilic lipase LipA and *Saccharomyces cerevisiae* BNCC186741. The resulting glycerol is completely retained as a carbon source for the low-temperature stage, maintaining microbial metabolic activity and promoting subsequent reactions. The operating temperature of the mesophilic stage is controlled between 35°C and 40°C to ensure optimal enzyme activity.

[0015] The core task of the low-temperature stage is to utilize glycerol to drive the degradation of FFAs (C16-C18) and recalcitrant polycyclic aromatic hydrocarbons (PAHs, such as phenanthrene and pyrene), and to promote humic synthesis through sawdust. During this stage, low-temperature lipases (LipP) are primarily responsible for decomposing free fatty acids, while *Pseudomonas putida* degrades recalcitrant PAHs through dioxygenases, using glycerol as a co-metabolic carbon source to enhance degradation efficiency. Simultaneously, sawdust provides lignin-like substances. *Bacillus subtilis* and *Trichoderma harzianum* secrete lignin peroxidase (LiP) and laccase to cleave sawdust into phenolic compounds. These phenols react with FFA derivatives to ultimately synthesize humic acid, significantly improving soil structure and fertility.

[0016] Furthermore, *Bacillus stearothermophilus* BNCC338119, *Pseudomonas aeruginosa* BNCC360090, and *Streptococcus thermophilus* BNCC363554 were cultured to a concentration of 3-9 × 10⁻⁹. 10 The bacterial culture was prepared by mixing the bacterial culture at a concentration of cfu / ml according to the volume ratio to obtain functional bacterial group A.

[0017] First, brewer's yeast BNCC186741 and propionibacterium tumefaciens BNCC194214 were cultured to a concentration of 2-8 × 10⁻⁸. 10 The bacterial culture was prepared at a concentration of CFU / ml, and the mesophilic lipase concentration was 2-4 × 10⁻⁴. 4 The concentration of U / ml was then mixed according to the volume ratio to obtain functional bacterial group B.

[0018] First, *Pseudomonas putida* BNCC338119, *Bacillus subtilis* CGMCC.NO.26196, and *Trichoderma longiflora* (CGMCC.NO.40444) were cultured to a concentration of 1-6 × 10⁻⁶. 9The bacterial culture was prepared at CFU / ml, and the low-temperature lipase concentration was 2-8 × 10⁻⁸. 5 The concentration of U / ml was then mixed according to the volume ratio to obtain functional bacterial group C.

[0019] Furthermore, the moisture content of the sludge waste is adjusted to 60-80% before ultrasonic activation treatment;

[0020] The ultrasonic activation treatment uses an ultrasonic frequency of 20-25kHz, an ultrasonic power of 300-500W, a time of 10-20min, and a treatment temperature of 25-30℃, which can better and more comprehensively activate sludge waste.

[0021] Furthermore, in step one, the acid and alkali are boric acid and potassium hydroxide, respectively. The amount of boric acid added is 1-3% of the sludge waste material, and the amount of potassium hydroxide added is 0.5-2% of the sludge waste material. The reaction temperature is 25-30℃, the stirring speed is 100-150 r / min, and the reaction time is 50-70 min. The ratio and temperature are controlled to ensure that the reaction is gentle and complete, while ensuring that the pH value is within the predetermined range.

[0022] Furthermore, in the temperature-controlled fermentation process, the oxygen concentration is 0.5-1%, the stirring speed is 80-100 r / min, and the heating rate is 0.3-0.6℃ / min.

[0023] Furthermore, both high-temperature and mesophilic fermentation are carried out in fermenters, while low-temperature fermentation is carried out separately from the fermenter and in a pile. The fermentation temperature can be easily controlled through the fermenter.

[0024] Furthermore, the waste gas generated during the low-temperature fermentation process is absorbed by the waste gas collection device and solidified by calcium hydroxide in the waste gas collection device. The important product of this stage is carbon dioxide. After being absorbed and solidified by Ca(OH)2, the conversion rate reaches more than 90%, which further realizes carbon sequestration and pollutant degradation. Through the comprehensive effect of this stage, an effective carbon closed loop is formed, completing the degradation and resource utilization of organic pollutants, while improving economic and environmental benefits.

[0025] Hydrogen sulfide waste gas generated during low-temperature fermentation can be removed by alkaline absorption towers and ozone hydrogenation UV photocatalytic reactors.

[0026] The present invention also discloses the application of sludge fermentation products obtained by the above fermentation process in soil conditioners.

[0027] If the moisture content of the fermentation product obtained by the above fermentation process is reduced to 10-30%, and then crushed into granules, the granules can be used to improve the soil. The reduction in moisture content helps the granules to be stored stably for a long time and reduces the risk of mold.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. This invention achieves precise regulation of industrial sludge waste metabolism through the combination of microbial agents. The process of high-temperature acid production, medium-temperature free fatty acid (FFAs) / glycerol production, and low-temperature humification, combined with carbon dioxide absorption and solidification, forms an effective carbon closed loop, ensuring the maximum utilization of resources.

[0030] 2. This invention utilizes a three-tiered relay system of thermophilic bacteria, lipid-degrading bacteria, and humic substance-synergizing bacteria to achieve highly efficient biotransformation of industrial sludge waste through the synergistic effect of the bacterial communities. Furthermore, there is no cross-inhibition between different bacterial communities, ensuring the smooth progress of the process. The high-value transformation of the products is achieved through the energy conversion of isopropanol and soil improvement using humic substances, enhancing the economic value of the products, realizing resource recycling, and demonstrating good market prospects and environmental benefits. Attached Figure Description

[0031] Figure 1 This is a diagram of the fermentation mechanism. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments.

[0033] Bacillus subtilis ( Bacillus subtilis On December 14, 2022, it was deposited at the China General Microbiological Culture Collection Center (CGMCC), accession number: CGMCC.NO.26196, at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0034] Trichoderma longiflora ( Bacillus subtilis On December 14, 2022, it was deposited at the China General Microbiological Culture Collection Center (CGMCC), accession number: CGMCC.NO.40444, at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

[0035] The thermophilic Bacillus stearothermophilus BNCC338119, Pseudomonas aeruginosa BNCC360090, Streptococcus thermophilus BNCC363554, Saccharomyces cerevisiae BNCC186741, Propionibacterium jinsenium BNCC194214, and Pseudomonas putida BNCC338119 were all purchased from Beina Biotechnology. The mesophilic lipase was lipase A, lysosomal acidic form, gene ID 3988, and the pyrogallol lipase was LIP98.

[0036] Among them, *Bacillus stearothermophilus* BNCC338119, *Pseudomonas aeruginosa* BNCC360090, and *Streptococcus thermophilus* BNCC363554 were cultured in specific medium A: peptone 10.0 g / L, beef meal 3.0 g / L, sodium chloride 5.0 g / L, agar 15.0 g / L, pH 7.3±0.1, temperature 46℃, to a concentration of 4.48 × 10⁻⁶. 10 cfu / ml, 6.11×10 10 cfu / ml, 4.21×10 10 CFU / ml bacterial suspension.

[0037] Saccharomyces cerevisiae BNCC186741 and Propionibacterium jinseniense BNCC194214 were cultured in specific medium B: yeast extract 3.0 g / L, malt extract 3.0 g / L, glucose 10.0 g / L, casein peptone 5.0 g / L, agar 20.0 g / L, pH 6.2±0.2, temperature 30℃, to a concentration of 4.55×10⁻⁶. 10 cfu / ml, 5.53×10 10 CFU / ml bacterial suspension.

[0038] *Pseudomonas putida* BNCC338119 was cultured in specific medium C: peptone: 10.0 g / L, beef meal: 3.0 g / L, sodium chloride: 5.0 g / L, agar: 15.0 g / L, pH: 7.3 ± 0.1, temperature: 25℃, until a concentration of 5.48 × 10⁻⁶ was reached. 9 CFU / ml bacterial suspension.

[0039] Bacillus subtilis CGMCC.NO.26196 was cultured on a dedicated fermentation medium D: sodium carboxymethyl cellulose 20 g / L, ammonium sulfate 2 g / L, dipotassium hydrogen phosphate 1 g / L, magnesium sulfate 0.5 g / L, calcium chloride 1 g / L, manganese sulfate 0.05 g / L, ferrous sulfate 0.05 g / L, pH 7.0, temperature 25℃, until a concentration of 2.36 × 10⁻⁶ was reached. 9 CFU / ml bacterial suspension.

[0040] Trichoderma longipes CGMCC.NO.40444 was cultured on a dedicated fermentation medium E: potato extract 200 g / L, dipotassium hydrogen phosphate 2 g / L, sodium carboxymethyl cellulose 20 g / L, guaiacol 0.1 g / L, pH 6.0, at 25℃, until a concentration of 3.41 × 10⁻⁶ was achieved. 9 CFU / ml bacterial suspension.

[0041] The concentration of mesophilic lipase is 3 × 10⁻⁶. 4 cfu / ml, cryolipase is 6×10 5 cfu / ml.

[0042] The composition of the industrial sludge waste to be treated is as follows, by mass: 35% petroleum hydrocarbons, 26% mineral oil substances, 10% polycyclic aromatic hydrocarbons, and the remainder is water.

[0043] Example 1

[0044] A variable-temperature fermentation process for sludge waste includes the following steps:

[0045] Step 1: Pre-treatment of sludge waste

[0046] The moisture content of the above-mentioned industrial sludge waste was adjusted to 70%, and the adjusted sludge waste was subjected to ultrasonic activation treatment using a probe-type ultrasonic transmitter with an ultrasonic frequency of 22kHz, an ultrasonic power of 400W, and an ultrasonic time of 15min.

[0047] Boric acid was added to the ultrasonically activated sludge waste, accounting for 1.5% of the adjusted sludge waste mass. The corresponding amount of potassium hydroxide was also added to ensure that the pH value of the sludge waste was 7.0, the reaction temperature was 25℃, the reaction time was 60 min, and the rotation speed was 120 r / min.

[0048] Step 2: Temperature-controlled fermentation

[0049] The mixture of pretreated industrial sludge waste is added to the fermentation tank.

[0050] High-temperature fermentation treatment: 0.2% of functional bacterial group A was added to the pretreated sludge mixture, and the temperature was increased to 65℃ at a rate of 0.5℃ / min. Under a micro-aerobic environment (oxygen concentration of 0.6%), the stirring speed was 90r / min for 50h. During this process, the concentration of isopropanol was detected by online gas chromatography. When the concentration was ≥5g / L, isopropanol was recovered by gas stripping system and secondary condensation, with a purity ≥85%.

[0051] The above-cultured thermophilic Bacillus stearothermophilus BNCC338119, Pseudomonas aeruginosa BNCC360090, and Streptococcus thermophilus BNCC363554 were mixed in a volume (liquid) ratio of 5:1:4 to obtain functional bacterial group A.

[0052] Mesophilic fermentation treatment: The temperature of the sludge after high-temperature fermentation treatment was reduced to 36℃, and functional bacteria group B, accounting for 0.1% of the sludge mass, was added for aerobic fermentation (oxygen concentration of 4%) for 100 hours with a stirring speed of 75 r / min.

[0053] The above-cultured Saccharomyces cerevisiae BNCC186741 and Propionibacterium genus BNCC194214 were mixed at a volume (liquid) ratio of 7:2, and mesophilic lipase was added at 12% of the total bacterial culture mass of Saccharomyces cerevisiae BNCC186741 and Propionibacterium genus BNCC194214 to obtain functional bacterial group B.

[0054] Low-temperature fermentation treatment: The sludge mixture after medium-temperature fermentation is removed from the fermentation tank. The removed sludge waste is mixed with sawdust (straw pellets) at a volume ratio of 2:1, and functional microbial agent C is added to the mixture at 1.5% of its mass. The total mixture is piled up to a height of 1.5m and fermented at 25℃ for 5 days, with manual turning once a day. Most of the waste gas generated during the low-temperature fermentation process is carbon dioxide. The carbon dioxide is absorbed and solidified by calcium hydroxide in the waste gas recovery device. The hydrogen sulfide in the waste gas first passes through an alkaline absorption tower (NaOH solution, concentration 7%), where H2S reacts with NaOH to generate Na2S (removal rate ≥80%), and then enters an ozone-enhanced UV photocatalytic reactor (ozone dosage 15g / m³). 3 (254 nm UV-excited TiO2 / activated carbon catalyst) to simultaneously oxidize residual H2S and benzene compounds to SO4. 2- The total removal rate of CO2 and H2S is ≥99%, and the emission concentration is ≤0.06 mg / m³. 3 .

[0055] The above-cultured *Pseudomonas putida* BNCC338119, *Bacillus subtilis* with accession number CGMCC NO.26196, and *Trichoderma longiflora* with accession number CGMCC.NO.40444 were mixed in a volume (liquid) ratio of 2:3:5, and 25% of the total bacterial culture mass of low-temperature lipase was added to obtain functional bacterial group C.

[0056] To more clearly demonstrate the effectiveness of this microbial agent combination, a control case has been added as follows:

[0057] Treatment 1: The difference from Example 1 is that no microbial agents or excipients were added in this example.

[0058] Process 2: Same as Example 1.

[0059] Treatment 3: The difference from Example 1 is that no functional bacterial group A is added during the high-temperature fermentation stage.

[0060] Treatment 4: The difference from Example 1 is that no functional bacterial group B is added during the mesophilic fermentation stage.

[0061] Treatment 5: The difference from Example 1 is that no functional bacterial group C is added during the low-temperature fermentation stage.

[0062] Treatment 6: The difference from Example 1 is that, in the low-temperature fermentation stage, Bacillus stearothermophilus BNCC.338119 is not added to functional bacterial group A, but commercially available Bacillus stearothermophilus is used as a substitute.

[0063] Treatment 7: The difference from Example 1 is that, in the low-temperature fermentation stage, Trichoderma longipes preservation number CGMCC.NO.40444 is not added to the functional bacterial group C, and commercially available Trichoderma longipes is used as a substitute.

[0064] Treatment 8: The difference from Example 1 is that, in the low-temperature fermentation stage, functional bacterial group C is not added, but straw composting agent sold by Shandong Sapphire Company is added.

[0065] In the three stages of fermentation, the target treatment material and product were measured respectively. After the third stage, the concentrations of isopropanol and hydrogen sulfide in the exhaust gas were counted. The experimental results are shown in Table 1.

[0066] Table 1

[0067]

[0068] The treatment at each stage showed significant differences with the addition of microbial agents. Treatment 2 achieved optimal or one of the optimal effects at each stage.

[0069] During the high-temperature stage, with the addition of functional microbial group A, the remaining amounts of petroleum hydrocarbons (C10-C40), mineral oil, and medium- and short-chain fatty acids in treatments 2, 4, 5, 7, and 8 did not differ significantly, but were significantly better than treatments 1, 3, and 6. This is because the high-temperature stage is the first stage of fermentation, and treatments 2, 4, 5, 7, and 8 can be considered as a single treatment. The addition of functional microbial group A significantly enhanced the degradation of petroleum hydrocarbons (C10-C40) and mineral oil, and promoted the generation of medium- and short-chain fatty acids. Regarding the remaining amounts of petroleum hydrocarbons (C10-C40) and mineral oil, the order of significance was: treatments 1, 3, and 6. This not only demonstrates the overall indispensability of functional microbial group A, but also indicates that the replacement of *Bacillus stearothermophilus* (BNCC.338119) reduced the degradation of petroleum hydrocarbons (C10-C40). Compared with treatment 2, the replacement of *Bacillus stearothermophilus* (BNCC.338119) in treatments 1, 3, and 6 had a greater impact on the remaining amount of petroleum hydrocarbons (C10-C40) and a smaller impact on the remaining amount of mineral oil and the content of medium- and short-chain fatty acids. This is because *Streptococcus thermophilus* (BNCC363554), which is used for the degradation of esters in mineral oil, was not modified, reflecting the specific functionality of each component in functional group A. In the mesophilic stage, with the addition of functional group B, the remaining amounts of medium- and short-chain fatty acids, remaining amounts of triglycerides, and free fatty acid content in treatments 2, 5, 7, and 8 did not differ significantly, but were significantly better than treatments 1, 3, and 4. This is because the mesophilic stage is the second stage of fermentation, and treatments 2, 5, 7, and 8 can be considered as a single treatment. The remaining amount of medium- and short-chain fatty acids in treatment 6 was significantly lower than in treatment 2 but significantly higher than in treatment 1, which was affected by the delayed decomposition process in the high-temperature stage. Meanwhile, even though treatment 3 lacked the promoting effect of functional bacteria group A during the high-temperature stage, the remaining amounts of medium- and short-chain fatty acids and triglycerides in treatment 3 were significantly lower than those in treatments 1 and 4. This demonstrates that the addition of functional bacteria group B has a significant stage-specific function in the mesophilic stage B. In the low-temperature stage, with the addition of functional bacteria group C, the remaining amounts of recalcitrant mineral oil (polycyclic aromatic hydrocarbons) in treatments 2, 6, and 8 did not differ significantly, but were significantly better than other treatment groups. As the final stage of fermentation, the low-temperature stage resulted in significant differences in the remaining amounts of recalcitrant mineral oil (polycyclic aromatic hydrocarbons) and free fatty acids in treatments 3, 4, and 5 due to the lack of corresponding functional bacteria groups at each stage. However, treatment 5 had significantly higher levels of recalcitrant mineral oil (polycyclic aromatic hydrocarbons) and free fatty acids than treatments 3 and 4, while its humic acid content was significantly lower. This demonstrates that the addition of functional bacteria group C has a significant stage-specific function in the degradation of recalcitrant mineral oil (polycyclic aromatic hydrocarbons) and free fatty acids and the production of humic substances during the low-temperature stage.The amount of free fatty acids remaining in treatment 7 was significantly lower than that in treatments 1 and 5, but significantly higher than that in treatment 2. The humic content in treatment 7 was significantly higher than that in treatment 1, and not significantly different from that in treatment 5, but significantly lower than that in treatment 2. This indicates that the replacement of *Trichoderma longiflorum* (CGMCC.NO.40444) reduced the conversion efficiency of the remaining free fatty acids into humic matter. Meanwhile, the humic content in treatment 8 was lower than that in treatment 2. All of these demonstrate that the replacement of either *Trichoderma longiflorum* (CGMCC.NO.40444) or the replacement of functional bacteria group C hinders the metabolite conversion process. This highlights the high efficiency and irreplaceable role of *Bacillus subtilis* (CGMCC NO.26196) and *Trichoderma longiflorum* (CGMCC.NO.40444) in humic matter production.

[0070] Regarding waste gas recovery, the recovery amounts and rates of isopropanol in treatments 2, 4, 5, 7, and 8 showed no significant differences and were significantly better than those in treatments 1, 3, and 6, further confirming that isopropanol production occurs at high temperatures and is related to the effects of functional bacterial group A. The recovery amounts of H2S in treatments 2, 5, 7, and 8 showed no significant differences and were significantly better than those in treatments 1, 3, 4, and 6, demonstrating that H2S production occurs at high and medium temperatures and is directly influenced by functional bacterial groups A and B.

[0071] The sludge fermentation products from the above treatment groups were dried to reduce their moisture content to 20%, and the fermentation products were crushed into granules, i.e., soil conditioners. Planting tests were conducted on Chinese cabbage. The soil conditioner was mixed with conventional soil at a 1:1 ratio. The germination rate of Chinese cabbage seeds, the nutritional properties of the soil conditioner, and the biosafety are shown in Table 2.

[0072] Table 2

[0073]

[0074] The seed germination rate was 7-day germination rate. As shown in Table 2, Treatment 2 was significantly superior to other products in terms of nutrient content, humic acid content, and pH, indicating nutrient supply capacity. From a plant effect perspective, the germination rate of Treatment 7 was not significantly different from that of Treatment 2, but the residual polycyclic aromatic hydrocarbons were higher, which may inhibit root growth. Treatment 8 showed poor degradation effect on petroleum hydrocarbons (200-250 mg / kg).

[0075] The fermentation products of the above treatment groups were dried to reduce their moisture content to 20%, and then crushed into granules, which became soil conditioners. Rice was used as the subject for planting tests. The soil conditioner was mixed with soil from low-yield fields in Huangni, Jinhua City, Zhejiang Province at a ratio of 1:1, and an additional background group was set up. No soil conditioner was added to the background group, and its relevant indicators were measured as background values. After 30 days of planting, soil samples and rice seedlings were taken to measure the indicators, as shown in Table 3.

[0076] Table 3

[0077]

[0078] As shown in Table 3, the soil treated with treatment 2 was significantly superior to other products in terms of physical properties, nutrient content, organic matter content, pH, and plant growth. Treatment 2 effectively improved soil physical properties, increased nutrient supply, and consequently boosted rice yield. Regarding plant effects, the germination rate of treatment 7 was not significantly different from treatment 2, but it had higher levels of petroleum hydrocarbons and polycyclic aromatic hydrocarbons, leading to root growth inhibition. Treatment 8 showed no significant improvement in physical properties, provided moderate nutrient supply, and had a moderate effect on promoting crop growth. Therefore, the sludge fermentation products obtained using the fermentation process of this invention can be used as soil conditioners.

[0079] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A temperature-switched fermentation process for sludge waste, characterized in that, Includes the following steps: Step 1: Pre-treatment of sludge waste Sludge waste is subjected to ultrasonic activation treatment, and acid and / or alkali are added to react so that the pH of the sludge waste after ultrasonic activation treatment is 6-8. Step 2: Temperature-controlled fermentation High-temperature fermentation treatment: Add 0.1-0.5 wt% of functional bacterial group A to the sludge mixture from step one, raise the temperature to 60-65℃, and ferment under a microaerobic environment for 48-72 hours; among which, Functional bacterial group A was obtained by mixing Bacillus stearothermophilus BNCC338119, Pseudomonas aeruginosa BNCC360090 and Streptococcus thermophilus BNCC363554 in a volume ratio of 4-7:1-2:3-5. Mesophilic fermentation treatment: The temperature of the sludge after high-temperature fermentation is reduced to 35-40℃, and 0.1-0.5 wt% of functional bacterial group B is added to the sludge mixture for aerobic fermentation for 96-120 hours. Functional bacterial group B is obtained by mixing Saccharomyces cerevisiae BNCC186741 and Propionibacterium ragmitesii BNCC194214 at a volume ratio of 6-8:1-3, and adding 10-20 wt% of mesophilic lipase to the total bacterial solution. Low-temperature fermentation treatment: The sludge mixture after mesophilic fermentation is cooled to 25-30℃ and mixed with sawdust at a volume ratio of 1.5-4:

1. 1-2 wt% of functional bacterial agent C is added to the sludge mixture for fermentation for 120-168 hours to obtain sludge fermentation products. Among them, functional bacterial group C is obtained by mixing Pseudomonas putidae BNCC338119, Bacillus subtilis with accession number CGMCC NO.26196, and Trichoderma longiflorum with accession number CGMCC.NO.40444 at a volume ratio of 1-4:2-6:4-9, and adding 20-30 wt% of low-temperature lipase to the total bacterial solution after mixing.

2. The variable-temperature fermentation process for sludge waste as described in claim 1, characterized in that: First, Bacillus stearothermophilus BNCC338119, Pseudomonas aeruginosa BNCC360090, and Streptococcus thermophilus BNCC363554 were cultured to a concentration of 3-9 × 10⁻⁹. 10 The bacterial suspension of CFU / ml was then mixed to obtain functional bacterial group A; First, brewer's yeast BNCC186741 and propionibacterium genisteine ​​BNCC194214 were cultured to a concentration of 2-8 × 10⁻⁸. 10 The bacterial culture with cfu / ml has a mesophilic lipase concentration of 2-4 × 10⁻⁴. 4 U / ml, then mixed to obtain functional bacterial group B; First, *Pseudomonas putida* BNCC338119, *Bacillus subtilis* CGMCC.NO.26196, and *Trichoderma longiflora* (CGMCC.NO.40444) were cultured to a concentration of 1-6 × 10⁻⁶. 9 The bacterial culture had a cfu / ml concentration of lipase at low temperature of 2-8 × 10⁻⁸. 5 U / ml, then mixed to obtain functional bacterial group C.

3. The variable-temperature fermentation process for sludge waste as described in claim 1, characterized in that: The moisture content of the sludge waste should be adjusted to 60-80% before ultrasonic activation treatment; The ultrasonic activation treatment uses an ultrasonic frequency of 20-25kHz, an ultrasonic power of 300-500W, a time of 10-20min, and a treatment temperature of 25-30℃.

4. The variable-temperature fermentation process for sludge waste as described in claim 1, characterized in that: In step one, the acid and alkali are boric acid and potassium hydroxide, respectively. The amount of boric acid added is 1-3% of the sludge waste material, and the amount of potassium hydroxide added is 0.5-2% of the sludge waste material. The reaction temperature is 25-30℃, the stirring speed is 100-150r / min, and the reaction time is 50-70min.

5. The variable-temperature fermentation process for sludge waste as described in claim 1, characterized in that: In the temperature-controlled fermentation process, the oxygen concentration is 0.5-1%, the stirring speed is 80-100 r / min, and the heating rate is 0.3-0.6℃ / min.

6. The variable-temperature fermentation process for sludge waste as described in claim 1, characterized in that: In step two, both high-temperature fermentation and mesophilic fermentation are carried out in fermentation tanks, while low-temperature fermentation is carried out separately from the fermentation tanks and in a pile for fermentation.

7. The variable-temperature fermentation process for sludge waste as described in claim 1, characterized in that: The waste gas generated during the low-temperature fermentation process in step two is absorbed by the waste gas collection device and solidified by calcium hydroxide in the waste gas collection device.

8. The application of sludge fermentation products obtained by the fermentation process according to any one of claims 1-7 in soil conditioners.

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