A microbial composite preparation for sludge reduction in municipal sewage sludge treatment and a preparation method thereof

Abstract

This invention relates to the field of wastewater treatment technology, and discloses a microbial composite preparation for sludge reduction in urban wastewater sludge treatment and its preparation method. The preparation comprises a composite functional microbial community, a bio-enhancing carrier, and a stabilizing agent. The composite functional microbial community is a mixture of Bacillus subtilis, Bacillus licheniformis, Pseudomonas, Candida tropicalis, and thermophilic actinomycetes in a specific ratio of viable cells. The bio-enhancing carrier consists of modified corn starch, potassium humate, and carboxymethyl chitosan. The stabilizing agent consists of glycerol, potassium dihydrogen phosphate, and anhydrous lactose. The finished product is obtained through microbial activation, seed culture, propagation fermentation, microbial community compounding, adjuvant compounding, and filling. This preparation can improve the biodegradation and latent growth utilization efficiency of complex sludge organic components, reduce excess sludge production while maintaining wastewater treatment effectiveness, and has good stability during room temperature storage.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a microbial composite preparation for sludge reduction in urban sewage sludge treatment and its preparation method. Background Technology

[0002] Urban wastewater treatment processes generate large amounts of excess activated sludge. This sludge is characterized by high water content, high organic matter content, easy putrefaction, and trace pollutants. Improper disposal can easily cause secondary environmental pollution. Currently, municipal wastewater treatment plants in China commonly use sludge thickening, filtration, landfill, and incineration methods, which suffer from high disposal costs, large land occupation, low resource utilization, and significant risks of secondary pollution. Sludge reduction technology can reduce excess sludge production at the source, lowering the load and cost of subsequent sludge disposal, and is currently the mainstream development direction in the field of sludge treatment.

[0003] Existing sludge reduction technologies mainly include physical, chemical, and biological methods. Physical methods (ultrasound, thermal drying, mechanical crushing) are energy-intensive and require large equipment investments, making them difficult to implement on a large scale. Chemical methods require the addition of large amounts of chemical agents, which can easily cause secondary pollution of water bodies, damage the microbial community structure of the biological system, and affect the wastewater treatment effect. Biological sludge reduction technology, with its advantages of being green and environmentally friendly, low-cost, producing no secondary pollution, and adapting to existing wastewater treatment processes, has become the most promising sludge reduction technology.

[0004] Currently, most sludge reduction microbial agents on the market are single-species or simple mixed-species agents, which have obvious technical defects: First, the adaptability of the strains is poor. Ordinary strains are difficult to adapt to the fluctuations in water quality and quantity of urban sewage and the high-load sludge environment, resulting in low strain activity and easy inactivation. Second, the synergy of the bacterial community is weak. Single-species agents have limited functions and can only decompose specific organic matter. They cannot comprehensively degrade complex components in sludge such as extracellular polymers, microbial residues, and organic colloids, resulting in sludge reduction efficiency generally below 25%. Third, the formulation has poor stability. It is easy for the strains to inactivate and the bacterial community to settle when stored at room temperature, resulting in a short shelf life. Fourth, after addition, it is easy to disrupt the biological system, which can lead to a decrease in the denitrification and phosphorus removal effect of sewage, making it impossible to achieve simultaneous water quality optimization and sludge reduction.

[0005] In view of the many shortcomings of existing technologies, there is an urgent need to develop a special microbial compound preparation and a large-scale preparation process that is adapted to the complex environment of urban sewage sludge, has strong synergistic microbial community, high volume reduction efficiency, good stability, and does not affect the sewage treatment effect. Summary of the Invention

[0006] The purpose of this invention is to provide a microbial composite preparation for sludge reduction in urban sewage sludge treatment and its preparation method. Through the synergistic metabolic effect of composite functional bacteria, the adsorption, attachment and slow release effect of bio-enhancing carrier, and the protective effect of stabilizing agent, the preparation improves the colonization stability of the preparation in urban sewage biochemical system and its ability to degrade and utilize complex organic components of sludge, thereby reducing the production of excess sludge and maintaining the original sewage treatment system's COD, ammonia nitrogen, total nitrogen and total phosphorus removal efficiency.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a microbial composite preparation for sludge reduction in urban sewage sludge treatment, comprising a composite functional microbial community, a bio-enhancing carrier, and a stabilizing agent; the composite functional microbial community is a liquid fermentation live bacteria system with a total live bacteria count of 110. 8 CFU / mL, the ratio of live bacteria for each species is as follows: Bacillus subtilis 20-30 parts, Bacillus licheniformis 15-25 parts, Pseudomonas aeruginosa 18-28 parts, Candida tropicalis 10-18 parts, and Thermophilic Actinomyces 8-15 parts.

[0008] Furthermore, the bio-enhancing carrier is a mixture of modified corn starch, potassium humate, and carboxymethyl chitosan, with a mass ratio of 3:2:1, and the amount added is 3% to 6% of the total mass of the compound functional microbial fermentation broth.

[0009] Furthermore, the stabilizer is a mixture of glycerol, potassium dihydrogen phosphate, and anhydrous lactose in a mass ratio of 2:1:3, and the amount added is 1.5% to 3% of the total mass of the compound functional microbial fermentation broth.

[0010] Furthermore, each bacterial strain is a corresponding strain obtained through gradient acclimation screening of municipal sewage sludge. The gradient acclimation includes at least gradient acclimation of sludge supernatant, gradient acclimation of organic load, and gradient acclimation of salinity.

[0011] Furthermore, the preparation method of the microbial composite agent for sludge reduction in urban sewage sludge treatment includes the following steps: (1) Activation culture of strains: Bacillus subtilis, Bacillus licheniformis, Pseudomonas, Candida tropicalis and thermophilic actinomycetes stored at low temperature were inoculated into the corresponding solid slant culture medium and activated at constant temperature to obtain activated strains; (2) Preparation of primary seed culture: Each activated strain was inoculated into liquid seed culture medium and cultured under constant temperature and shaking to prepare primary seed culture of a single strain. The viable cell concentration of each strain in the seed culture was 1:10. 8 CFU / mL; (3) Secondary propagation and fermentation: Each primary seed liquid is inoculated into the liquid fermentation medium in the fermentation tank, and fermentation is carried out under controlled temperature to obtain the fermentation liquid of each single strain; (4) Mixing of microbial communities: According to the preset ratio of live bacteria, the fermentation liquids of each single strain are aseptically mixed and stirred evenly to obtain the fermentation liquid of the compound microbial community; (5) Additive compound modification: Add bio-enhancing carrier and stabilizer to the compound microbial fermentation broth in sequence, stir at low speed to mix evenly, and mature at room temperature for 2-4 hours; (6) Aseptic filling and storage: After maturation, the aggregates are removed by filtration through an 80-120 mesh sieve under aseptic conditions and then filled to obtain the finished microbial compound preparation, which is stored at room temperature away from light.

[0012] Furthermore, in step (1), the culture temperature of Bacillus subtilis, Bacillus licheniformis and Pseudomonas is 30-35℃ and the culture time is 24-30h; the culture temperature of Candida tropicalis is 28-32℃ and the culture time is 30-36h; the culture temperature of thermophilic actinomycetes is 37-42℃ and the culture time is 48-54h.

[0013] Furthermore, in step (3), the initial pH value of fermentation is 6.8 to 7.5, the aeration rate is 0.8 to 1.2 vvm, the stirring speed is 180 to 220 r / min, and the fermentation time is 48 to 72 h.

[0014] Furthermore, in step (5), the stirring speed is 60-100 r / min, the stirring time is 30-60 min, and the maturation process is carried out under closed and sterile conditions.

[0015] Furthermore, the activated microbial compound preparation is added to the front end of the aerobic or anoxic tank of the urban sewage treatment system, intermittently at a rate of 0.03 to 0.1% of the effective water volume of the sewage treatment system, 1 to 2 times per week.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: (1) Complementary functions of the complex microbial community. Bacillus subtilis and Bacillus licheniformis have strong extracellular enzyme secretion capabilities, which can promote the hydrolysis of macromolecular organic matter such as proteins and polysaccharides; Pseudomonas is beneficial for utilizing the soluble organic matter formed after hydrolysis; Candida tropicalis can participate in the transformation of various organic substrates; thermophilic actinomycetes are beneficial for further decomposing some cell residues and relatively difficult-to-degrade organic components. The synergistic effect of multiple bacteria can improve the graded degradation and reuse of sludge organic matter.

[0017] (2) The bio-enhancing carrier has both adsorption and attachment functions as well as system stabilization functions. The porous structure of modified corn starch, together with potassium humate and carboxymethyl chitosan, constitutes a microscale attachment carrier, which can reduce the loss caused by free suspension of bacteria and help bacteria to contact sludge flocs and dissolved organic matter.

[0018] (3) Stabilizers can mitigate the decline in viable bacterial count during storage of liquid preparations at room temperature. Glycerin provides osmotic protection, potassium dihydrogen phosphate provides buffering and inorganic nutrition, and anhydrous lactose provides a certain degree of protection for the bacterial cells, so that the finished product still maintains a high level of viable bacteria after storage.

[0019] (4) The present invention adopts a process of separately propagating each strain and then compounding it according to the number of live bacteria, which makes it easy to control the proportion of compound bacteria and the dosage is low. It can be directly used for the maintenance enhancement of existing urban sewage biochemical treatment units without the need for major modifications to the main treatment process. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the preparation method of the microbial compound preparation of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] I. Culture medium and general culture conditions Bacterial slant and seed culture media: glucose 10 g / L, peptone 10 g / L, yeast extract 5 g / L, sodium chloride 5 g / L, agar 18 g / L (liquid media without agar), pH 7.0–7.2. Candida tropicalis culture medium: glucose 20 g / L, peptone 20 g / L, yeast extract 10 g / L, agar 18 g / L (liquid media without agar), pH 6.0–6.5. Thermophilic actinomycete culture medium: soluble starch 10 g / L, peptone 5 g / L, yeast extract 5 g / L, K₂HPO₄ 1 g / L, MgSO₄·7H₂O 0.5 g / L, NaCl 2 g / L, agar 18 g / L (liquid media without agar), pH 7.0–7.3. All the above media should be sterilized at 121°C for 20 min before use.

[0023] The fermentation medium per liter consists of: 15g molasses, 10g corn steep liquor dry matter, 5g peptone, 3g yeast extract, 1g / L K₂HPO₄, 0.3g MgSO₄·7H₂O, and the remainder is water. For Candida tropicalis fermentation, the molasses concentration is increased to 20g / L. For thermophilic actinomycetes fermentation, an additional 5g / L of soluble starch is added. The pH is adjusted to 6.8–7.5 before fermentation.

[0024] II. Preparation of Modified Corn Starch 20 kg of corn starch was dispersed in 80 kg of water, the pH was adjusted to 5.8, 60 g of β-amylase was added, and the mixture was stirred at 48 °C for 2 h. The temperature was then raised to 90 °C and maintained for 10 min, cooled to room temperature, filtered, washed twice with water, dried at 58 °C to constant weight, and pulverized through an 80-mesh sieve to obtain modified corn starch. This batch of modified corn starch was used in all the following examples.

[0025] III. Strain Domestication and Screening Bacillus subtilis, Bacillus licheniformis, Pseudomonas, Candida tropicalis, and thermophilic actinomycetes, identified by species identification, were subjected to environmental gradient acclimatization in municipal wastewater sludge. Secondary sedimentation tank return sludge from a municipal wastewater treatment plant was allowed to stand for 30 minutes. The supernatant was collected, pre-filtered through a 0.45 μm filter membrane, and then sterilized at 121°C for 20 minutes to obtain sludge supernatant. Using the corresponding liquid seed culture medium for each species as the basal medium, the sludge supernatant was used to replace 25%, 50%, 75%, and 100% of the prepared water, respectively. Each gradient was passaged twice consecutively, with an inoculum size of 5% (v / v) each time. The viable count reached 110 at the end of the culture. 8 When the concentration of CFU / mL exceeds a certain level, proceed to the next gradient.

[0026] After completing the acclimatization with the sludge supernatant ratio gradient, further acclimatization with organic loading and salinity gradients was conducted in a 100% sludge supernatant system. Glucose and sodium acetate were used to supplement the carbon source, and the initial COD of the culture system was adjusted sequentially to 1500 mg / L, 2500 mg / L, and 3500 mg / L, with each gradient subcultured twice. Subsequently, the NaCl concentration was adjusted sequentially to 0.5%, 1.0%, and 1.5%, with each gradient subcultured twice. The results were measured using plate viable counts and OD... 600 The recovery growth rate after transfer was used as a screening index. Selected cells were those that could stably proliferate under the highest organic load and salinity conditions, with a viable count of no less than 110 for two consecutive generations. 8 The strains with a concentration of CFU / mL were used in subsequent examples. The above acclimatization process only altered the environmental adaptability of the strains and did not change the species attributes of each strain.

[0027] IV. Examples Each embodiment was prepared following the sequence of: primary seed culture for strain activation, secondary propagation of fermentation microorganisms, compounding of adjuvants, aseptic filling, and storage. After fermentation of each single-strain fermentation broth, the viable cell count was determined using the plate count method. The added volume of each fermentation broth was calculated based on the measured viable cell concentration to ensure that the viable cell ratio among the combined strains met the specified ratio. The bio-enhancing carriers were all premixed from modified corn starch, potassium humate, and carboxymethyl chitosan in a mass ratio of 3:2:1; the stabilizers were all premixed from glycerol, potassium dihydrogen phosphate, and anhydrous lactose in a mass ratio of 2:1:3.

[0028] Example 1 (1) Activation culture of strains: Bacillus subtilis, Bacillus licheniformis and Pseudomonas were inoculated into the corresponding solid slant culture medium and cultured at 30℃ for 24h; Candida tropicalis was cultured at 28℃ for 30h; and thermophilic actinomycetes were cultured at 37℃ for 48h to obtain activated strains.

[0029] (2) Preparation of primary seed culture: The above-mentioned activated strains were inoculated into the corresponding liquid seed culture medium at an inoculation rate of 3% (v / v) and cultured with shaking at 150 r / min; Bacillus subtilis, Bacillus licheniformis and Pseudomonas were cultured for 24 h, Candida tropicalis for 30 h, and thermophilic actinomycetes for 48 h, so that the viable concentration of each strain was not less than 110. 8 Primary seed culture at CFU / mL.

[0030] (3) Secondary propagation and fermentation: Each primary seed liquid was inoculated into the corresponding fermentation tank culture medium at an inoculation rate of 5% (v / v), with an initial pH of 6.8, an aeration rate of 0.8vvm, a stirring speed of 180r / min, and fermentation for 48h to obtain the fermentation liquid of each single strain.

[0031] (4) Microbial community compounding and adjuvant compounding: The fermentation broths of each single microbial species were aseptically mixed according to the live count ratio of Bacillus subtilis: Bacillus licheniformis: Pseudomonas: Candida tropicalis: Thermophilic actinomycetes = 20:15:18:10:8 to obtain the compound microbial community fermentation stock solution. Based on the mass of the compound microbial community fermentation stock solution, 3.0% of bio-enhancing carrier and 1.5% of stabilizer were added, stirred at 60 r / min for 30 min, and matured in a sealed container at 25℃ for 2 h; after maturation, the mixture was filtered through a 100-mesh aseptic sieve to remove agglomerates and then bottled to obtain the microbial compound preparation of Example 1.

[0032] Example 2 (1) Activation culture of bacterial strains: Bacillus subtilis, Bacillus licheniformis and Pseudomonas were cultured at 32℃ for 27h; Candida tropicalis was cultured at 30℃ for 33h; and thermophilic actinomycetes were cultured at 40℃ for 51h to obtain activated bacterial strains.

[0033] (2) Preparation of primary seed culture: Each activated strain was inoculated into the corresponding liquid seed culture medium at 3% (v / v) and cultured at 150 r / min until the viable cell concentration of each strain was not less than 110. 8 CFU / mL.

[0034] (3) Secondary propagation and fermentation: Each primary seed liquid was inoculated into the corresponding fermentation tank culture medium at 5% (v / v), and the initial pH was controlled at 7.1, the aeration rate was 1.0vvm, the stirring speed was 200r / min, and the fermentation was carried out for 60h to obtain the fermentation liquid of each single strain.

[0035] (4) Microbial community compounding and adjuvant compounding: Bacillus subtilis: Bacillus licheniformis: Pseudomonas: Candida tropicalis: Thermophilic actinomycetes = 25:20:23:14:12 viable bacteria were compounded; based on the mass of the obtained compound microbial community fermentation broth, 4.5% of bio-enhancing carrier and 2.25% of stabilizing agent were added, stirred at 80 r / min for 45 min, and matured in a sealed container at 25℃ for 3 h. After filtration through a 100-mesh sterile screen, the microbial compound preparation of Example 2 was obtained.

[0036] Example 3 (1) Activation culture of bacterial strains: Bacillus subtilis, Bacillus licheniformis and Pseudomonas were cultured at 35℃ for 30h; Candida tropicalis was cultured at 32℃ for 36h; and thermophilic actinomycetes were cultured at 42℃ for 54h to obtain activated bacterial strains.

[0037] (2) Preparation of primary seed culture: Each activated strain was inoculated into the corresponding liquid seed culture medium at 3% (v / v) and cultured at 150 r / min until the viable cell concentration of each strain was not less than 110. 8 CFU / mL.

[0038] (3) Secondary propagation and fermentation: Each primary seed liquid was inoculated into the corresponding fermentation tank culture medium at 5% (v / v), and the initial pH was controlled at 7.5, the aeration rate was 1.2vvm, the stirring speed was 220r / min, and the fermentation was carried out for 72h to obtain the fermentation liquid of each single strain.

[0039] (4) Microbial community compounding and adjuvant compounding: Bacillus subtilis: Bacillus licheniformis: Pseudomonas: Candida tropicalis: Thermophilic actinomycetes = 30:25:28:18:15 viable bacteria were compounded; based on the mass of the obtained compound microbial community fermentation broth, 6.0% of bio-enhancing carrier and 3.0% of stabilizer were added, stirred at 100 r / min for 60 min, and matured in a sealed container at 25℃ for 4 h. After filtration through a 100-mesh sterile screen, the microbial compound preparation of Example 3 was obtained.

[0040] Comparative Example 1 The difference between this comparative example and Example 3 is that: the compound functional microbial community uses only Bacillus subtilis, and the total number of viable bacteria in the finished product is basically the same as that in Example 3 by adjusting the amount of its fermentation broth added; the bio-enhancing carrier, stabilizing agent and other preparation conditions are the same as those in Example 3.

[0041] Comparative Example 2 The difference between this comparative example and Example 3 is that thermophilic actinomycetes are not added to the composite functional microbial community, and Bacillus subtilis with an equal number of live bacteria is used to supplement it, so that the total number of live bacteria in the finished product is basically the same as that in Example 3; all other conditions are the same as those in Example 3.

[0042] Comparative Example 3 The difference between this comparative example and Example 3 is that: no bio-enhancing carrier composed of modified corn starch, potassium humate and carboxymethyl chitosan is added, and the mixture is made up with an equal mass of chlorine-free water; all other conditions are the same as in Example 3.

[0043] Comparative Example 4 The difference between this comparative example and Example 3 is that the modified corn starch in the bio-enhancing carrier is replaced with an equal mass of ordinary corn starch that has not been enzymatically modified, and the amounts of potassium humate and carboxymethyl chitosan remain unchanged; all other conditions are the same as in Example 3.

[0044] Comparative Example 5 The difference between this comparative example and Example 3 is that: no stabilizing agent consisting of glycerol, potassium dihydrogen phosphate and anhydrous lactose was added, and the mixture was made up with an equal mass of chlorine-free water; all other conditions were the same as in Example 3.

[0045] Comparative Example 6 The difference between this comparative example and Example 3 is that the five strains were not acclimatized with sludge supernatant ratio gradient, organic load gradient and salinity gradient, but were directly activated, propagated and compounded with unacclimatized strains of the same species; the remaining bacterial count ratio, adjuvant composition and preparation conditions are the same as in Example 3.

[0046] Performance testing To evaluate the sludge reduction effect, impact on wastewater treatment performance, and room temperature storage stability of the microbial composite preparations in each example and comparative example, the following tests were conducted. Unless otherwise specified, three parallel samples were set up for each group, and the results were taken as the arithmetic mean.

[0047] (a) Testing methods 1. Total viable count: Determined using a tenfold serial dilution and plate culture counting method. Counts were performed according to the corresponding culture conditions and colony morphology for each bacterial species. The sum of the viable counts of the five functional bacteria was taken as the total viable count of the finished product, and the results were expressed as CFU / mL.

[0048] 2. Stability at room temperature: Each preparation was stored in a sealed container at 252℃ in the dark, and the total viable count was measured at 0d, 90d and 180d. The viable count retention rate at 180d was calculated as the total viable count at 180d / the total viable count at 0d = 100%.

[0049] 3. Sludge reduction experiment: Ten 5L sequencing batch reactors with identical structure and effective volume were used, including Examples 1-3, Comparative Examples 1-6, and a control group. Each reactor was inoculated with return sludge from the secondary sedimentation tank of the same municipal wastewater treatment plant, with an initial MLSS of 3500-100 mg / L. The influent was the same batch of municipal domestic sewage. The temperature was controlled at 252℃, pH at 6.8-7.5, dissolved oxygen at 2.0-3.0 mg / L during the aerobic stage, and hydraulic retention time at 12 hours. The reactors operated for two cycles daily for 30 consecutive days.

[0050] 4. Dosing Method of the Formulation: Before addition, each microbial compound formulation was diluted with effluent from the secondary sedimentation tank at a volume ratio of 1:10, activated by aeration at 25℃ for 1 hour, and added at 0.05% of the effective water volume of the reactor, once every 3 days; the control group was added with an equal volume of effluent from the secondary sedimentation tank. The MLSS of each reactor was maintained at 3000-200 mg / L by discharging excess sludge. All excess sludge was collected within 30 days, dried to constant weight at 105℃, and the cumulative dry mass of the discharged sludge was calculated. The sludge reduction rate was calculated as (cumulative dry mass of discharged sludge in the control group - cumulative dry mass of discharged sludge in the experimental group) / cumulative dry mass of discharged sludge in the control group × 100%.

[0051] 5. Effluent quality: During the 26th to 30th day of stable operation, influent and effluent samples were collected daily to measure COD, ammonia nitrogen, total nitrogen, and total phosphorus. The 5-day average removal rate was calculated to determine whether the addition of the microbial compound preparation affected the pollutant removal capacity of the original sewage treatment system.

[0052] Table 1: Results of sludge reduction tests for each group Group 30-day cumulative dry mass of sludge / g Sludge reduction rate / % Example 1 17.60 31.8 Example 2 17.26 33.1 Example 3 17.42 32.5 Comparative Example 1 20.69 19.8 Comparative Example 2 19.35 25.0 Comparative Example 3 19.22 25.5 Comparative Example 4 18.58 28.0 Comparative Example 5 17.52 32.1 Comparative Example 6 19.71 23.6 Blank group 25.80 0 Table 2: Average Removal Rate of Pollutants in Effluent of Each Group Group COD removal rate / % Ammonia nitrogen removal rate / % TN removal rate / % TP removal rate / % Example 1 93.3 95.0 71.1 85.1 Example 2 93.8 95.6 72.0 85.8 Example 3 93.6 95.3 71.6 85.5 Comparative Example 1 90.8 92.6 67.0 81.9 Comparative Example 2 91.7 93.6 68.5 83.0 Comparative Example 3 92.0 93.8 68.9 83.4 Comparative Example 4 92.5 94.2 69.5 84.0 Comparative Example 5 93.4 95.1 71.3 85.0 Comparative Example 6 91.2 93.0 67.8 82.5 Blank group 90.2 92.0 66.4 81.1 Table 3: Changes in total viable bacteria count during storage at 252℃ in the dark Group 0d / (CFU / mL) 90d / (CFU / mL) 180d / (CFU / mL) 180d retention rate / % Example 1 <![CDATA[1.1810 9 ]]> <![CDATA[1.0610 9 ]]> <![CDATA[9.7910 8 ]]> 83.0 Example 2 <![CDATA[1.2410 9 ]]> <![CDATA[1.1310 9 ]]> <![CDATA[1.0510 9 ]]> 84.7 Example 3 <![CDATA[1.2910 9 ]]> <![CDATA[1.1910 9 ]]> <![CDATA[1.1110 9 ]]> 86.0 Comparative Example 1 <![CDATA[1.2210 9 ]]> <![CDATA[1.1010 9 ]]> <![CDATA[1.0210 9 ]]> 83.6 Comparative Example 2 <![CDATA[1.2310 9 ]]> <![CDATA[1.1110 9 ]]> <![CDATA[1.0310 9 ]]> 83.7 Comparative Example 3 <![CDATA[1.2310 9 ]]> <![CDATA[9.9410 8 ]]> <![CDATA[8.6410 8 ]]> 70.2 Comparative Example 4 <![CDATA[1.2310 9 ]]> <![CDATA[1.0110 9 ]]> <![CDATA[9.2810 8 ]]> 75.4 Comparative Example 5 <![CDATA[1.2210 9 ]]> <![CDATA[7.0810 8 ]]> <![CDATA[4.2110 8 ]]> 34.5 Comparative Example 6 <![CDATA[1.2110 9 ]]> <![CDATA[1.0710 9 ]]> <![CDATA[9.8010 8 ]]> 81.0 As shown in Table 1, the sludge reduction rates of Examples 1-3 ranged from 31.8% to 33.1%, with little difference among the three groups. This indicates that stable sludge reduction effects can be achieved within the ranges of bacterial community ratio, carrier addition amount, and stabilizer addition amount specified in this invention. In Comparative Example 1, the sludge reduction rate decreased to 19.8% when only Bacillus subtilis was used, and in Comparative Example 2, it decreased to 25.0% after removing thermophilic actinomycetes. This demonstrates that functional complementarity and synergistic metabolism among multiple bacterial species are beneficial for improving the graded degradation of complex organic components in sludge.

[0053] Comparative Example 3 showed a sludge reduction rate of 25.5% without the addition of a bio-enhancing carrier, while Comparative Example 4 showed a reduction rate of 28.0% when ordinary corn starch was replaced with modified corn starch. Both were lower than those in Examples 1-3, indicating that the bio-enhancing carrier formed by modified corn starch, potassium humate, and carboxymethyl chitosan can improve the adhesion stability of bacteria and its contact efficiency with sludge flocs. Comparative Example 6 showed a sludge reduction rate of 23.6% when using unacclimated strains, indicating that gradient acclimation based on sludge supernatant, organic load, and salinity is beneficial for improving the adaptability of functional bacteria in urban sewage sludge environments.

[0054] As shown in Table 3, Comparative Example 5 still exhibits a high sludge reduction capacity in its fresh state, but its 180-day viable cell retention rate is only 34.5%, significantly lower than the 83.0%–86.0% of Examples 1–3. This indicates that the stabilizing agent composed of glycerol, potassium dihydrogen phosphate, and anhydrous lactose mainly improves the shelf-life stability of the formulation by slowing down the decline in viable cell count during storage. The viable cell retention rates of Comparative Examples 3 and 4 also decreased, indicating that the bio-enhancing carrier has a certain synergistic effect on the stable dispersion and adhesion protection of bacteria in the liquid system.

[0055] As shown in Table 2, the average removal rates of COD, ammonia nitrogen, total nitrogen, and total phosphorus in Examples 1-3 were not lower than those in the blank group and remained at a high level. This indicates that the microbial compound preparation of the present invention can reduce the production of excess sludge without having a significant adverse impact on the original urban sewage biochemical treatment system, and can balance sludge reduction and effluent quality stability.

[0056] It should be further noted that the portions mentioned in each embodiment are the relative number of live bacteria calculated based on the actual live bacteria concentration of each single strain of fermentation broth, rather than the mass portions of each fermentation broth; when compounding, the volume to be added is first calculated based on the plate count results, and then sterile water is added to the set batch size, so as to ensure that the proportion of live bacteria in the microbial community is consistent between different batches.

[0057] It should be noted that, in this document, the terms include, encompass, or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the inclusion of a defined element by a statement does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0059] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A microbial compound preparation for sludge reduction in urban sewage sludge treatment, characterized in that, It includes a complex functional microbial community, a bio-enhancing carrier, and a stabilizing agent; the complex functional microbial community is a liquid fermentation live microbial system with a total live count of 110. 8 CFU / mL, the ratio of live bacteria for each species is as follows: Bacillus subtilis 20-30 parts, Bacillus licheniformis 15-25 parts, Pseudomonas aeruginosa 18-28 parts, Candida tropicalis 10-18 parts, and Thermophilic Actinomyces 8-15 parts.

2. The microbial composite preparation for sludge reduction in urban sewage sludge treatment according to claim 1, characterized in that, The bio-enhancing carrier is a mixture of modified corn starch, potassium humate, and carboxymethyl chitosan in a mass ratio of 3:2:1, and is added at 3% to 6% of the total mass of the compound functional microbial fermentation broth.

3. The microbial composite preparation for sludge reduction in urban sewage sludge treatment according to claim 1, characterized in that, The stabilizer is a mixture of glycerol, potassium dihydrogen phosphate, and anhydrous lactose in a mass ratio of 2:1:3, and is added at a rate of 1.5% to 3% of the total mass of the compound functional microbial fermentation broth.

4. The microbial compound preparation for sludge reduction in urban sewage sludge treatment according to claim 1, characterized in that, Each strain was obtained through gradient acclimatization screening of municipal sewage sludge. The gradient acclimatization included at least gradient acclimatization of sludge supernatant ratio, organic load, and salinity.

5. A method for preparing a microbial composite agent for sludge reduction in urban sewage sludge treatment as described in any one of claims 1 to 4, characterized in that, Includes the following steps: (1) Activation culture of strains: Bacillus subtilis, Bacillus licheniformis, Pseudomonas, Candida tropicalis and thermophilic actinomycetes stored at low temperature were inoculated into the corresponding solid slant culture medium and activated at constant temperature to obtain activated strains; (2) Preparation of primary seed culture: Each activated strain was inoculated into liquid seed culture medium and cultured under constant temperature and shaking to prepare primary seed culture of a single strain. The viable cell concentration of each strain in the seed culture was 1:

10. 8 CFU / mL; (3) Secondary propagation and fermentation: Each primary seed liquid is inoculated into the liquid fermentation medium in the fermentation tank, and fermentation is carried out under controlled temperature to obtain the fermentation liquid of each single strain; (4) Mixing of microbial communities: According to the preset ratio of live bacteria, the fermentation liquids of each single strain are aseptically mixed and stirred evenly to obtain the fermentation liquid of the compound microbial community; (5) Additive compound modification: Add bio-enhancing carrier and stabilizer to the compound microbial fermentation broth in sequence, stir at low speed to mix evenly, and mature at room temperature for 2-4 hours; (6) Aseptic filling and storage: After maturation, the aggregates are removed by filtration through an 80-120 mesh sieve under aseptic conditions and then filled to obtain the finished microbial compound preparation, which is stored at room temperature away from light.

6. The preparation method according to claim 5, characterized in that, In step (1), the culture temperature of Bacillus subtilis, Bacillus licheniformis and Pseudomonas is 30-35℃ and the culture time is 24-30h; the culture temperature of Candida tropicalis is 28-32℃ and the culture time is 30-36h; the culture temperature of thermophilic actinomycetes is 37-42℃ and the culture time is 48-54h.

7. The preparation method according to claim 5, characterized in that, In step (3), the initial pH value of fermentation is 6.8 to 7.5, the aeration rate is 0.8 to 1.2 vvm, the stirring speed is 180 to 220 r / min, and the fermentation time is 48 to 72 h.

8. The preparation method according to claim 5, characterized in that, In step (5), the stirring speed is 60-100 r / min and the stirring time is 30-60 min. The maturation process is carried out under closed and sterile conditions.

9. A method of applying the microbial compound preparation according to any one of claims 1 to 4, characterized in that, After activation, the microbial compound preparation is added to the front end of the aerobic or anoxic tank of the urban sewage treatment system, intermittently at a concentration of 0.03 to 0.1% of the effective water volume of the sewage treatment system, 1 to 2 times per week.

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