Bottom mud purifying agent for in-situ degradation of sludge at bottoms of rivers and lakes

Abstract

The invention relates to the technical field of environmental protection, and particularly discloses a bottom mud purifying agent for in-situ degradation of sludge at the bottoms of rivers and lakes. The purifying agent comprises an aerobic microbial agent, an anaerobic microbial agent, an enzyme preparation, a nutrition additive, a carrier, a slow-release oxidizing agent and a biological surfactant, and all the components are adaptive to the complex environment of bottom mud and the degradation requirement of composite pollutants. The preparation method sequentially comprises the steps of carrier pretreatment, microorganism mixing and activation, component homogenization, immobilization mixing, segmented gradient fermentation domestication, drying cooling and screening, and process design fitting functional component characteristics. The purifying agent can degrade pollutants such as organic matters, nitrogen and phosphorus in the river and lake bottom mud in situ, and has the advantages of high multi-component synergism, high purifying efficiency and good environmental adaptability; the preparation method is controllable in operation, can effectively guarantee microbial activity and product stability, and is suitable for large-scale production and actual river and lake sediment treatment scenes.

Description

Technical Field

[0001] This application relates to the field of environmental protection technology, and more specifically, it relates to a sediment purification agent for in-situ degradation of silt at the bottom of rivers and lakes. Background Technology

[0002] The sediment at the bottom of rivers and lakes is an important reservoir for water pollutants. The long-term accumulation of pollutants such as organic matter, nitrogen and phosphorus not only causes the sediment to turn black and smelly, but also releases it into the overlying water through interstitial water, causing problems such as eutrophication and reduced dissolved oxygen, which seriously damages the ecological environment of rivers and lakes. Therefore, in-situ purification of sediment is a key step in improving the water quality of rivers and lakes.

[0003] Currently, many sediment purification products on the market suffer from problems such as single component functions and insufficient synergistic effects: some products rely solely on single microbial agents or enzyme preparations, making it difficult to simultaneously and efficiently degrade multiple pollutants in the sediment; some products lack optimized design for the survival environment of microorganisms, failing to stabilize local dissolved oxygen conditions and pH values, resulting in limited microbial activity; and some products do not consider the solubilization problem of hydrophobic organic matter and the need for microbial adhesion protection, ultimately leading to low degradation efficiency of complex pollutants. Summary of the Invention

[0004] To address the issues of low degradation efficiency and poor component synergy of existing sediment purifiers for complex pollutants such as organic matter, nitrogen, and phosphorus, this application provides a sediment purifier for in-situ degradation of silt at the bottom of rivers and lakes.

[0005] In a first aspect, this application provides a sediment purification agent for in-situ degradation of silt at the bottom of rivers and lakes, employing the following technical solution:

[0006] A sediment purification agent for in-situ degradation of silt at the bottom of rivers and lakes, comprising the following components by weight: 10-30 parts aerobic microbial agent, 5-15 parts anaerobic microbial agent, 2-10 parts enzyme preparation, 1-5 parts nutrient additive, 40-60 parts carrier, 5-15 parts slow-release oxidant, and 1-5 parts biosurfactant.

[0007] By employing the above technical solutions, aerobic and anaerobic microbial agents work synergistically to degrade pollutants in both aerobic and anaerobic zones of the sediment, respectively, thus covering the degradation needs of different oxidative environments in the sediment. Enzyme preparations target and decompose proteins, fats, and cellulose organic matter in the sediment, assisting microorganisms in enhancing the decomposition efficiency of organic matter. Nutrient additives provide nitrogen and phosphorus nutrients and metal ions necessary for enzyme activity, ensuring microbial survival and enzyme catalytic activity. Carriers provide attachment sites for microorganisms and enzyme preparations, fixing functional components and extending their activity period in the sediment. Slow-release oxidants gradually release oxygen, regulating the local dissolved oxygen concentration in the sediment and preventing sudden increases in oxygen concentration from inhibiting anaerobic bacterial activity. Biosurfactants reduce the interfacial tension between hydrophobic organic matter and water, solubilizing insoluble pollutants in the sediment and improving the contact efficiency between functional components and pollutants. Thus, a complete sediment purification system is constructed from a component synergistic perspective, achieving systematic treatment of sediment pollutants.

[0008] Preferably, the aerobic microbial agent includes Bacillus subtilis and nitrifying bacteria, and the weight ratio of Bacillus subtilis to nitrifying bacteria is 3:2 to 4:1 based on the total weight of the aerobic microbial agent.

[0009] By adopting the above technical solution, the aerobic microbial agent is specifically composed of Bacillus subtilis and nitrifying bacteria, and the weight ratio of the two is controlled within the range of 3:2 to 4:1. Bacillus subtilis can aerobically decompose macromolecular organic matter in the sediment, such as protein and cellulose degradation intermediates, while nitrifying bacteria can gradually convert ammonia nitrogen in the sediment into nitrite nitrogen and nitrate nitrogen. This ratio allows the small molecule carbon source produced by Bacillus subtilis decomposing organic matter to provide nutrition for nitrifying bacteria. At the same time, the consumption of ammonia nitrogen by nitrifying bacteria can avoid the inhibition of Bacillus subtilis by ammonia nitrogen. This achieves the complementary function of the two agents and synergistically improves the treatment effect of organic matter and ammonia nitrogen in the aerobic zone. The specific composition and ratio design logic of the aerobic microbial agent are further clarified, and the technical details of the internal component matching of the agent are disclosed to ensure the targeting and effectiveness of the aerobic degradation function.

[0010] Preferably, the anaerobic microbial agent includes denitrifying bacteria and methanogens, and the weight ratio of denitrifying bacteria to methanogens is 1:1 to 7:3 based on the total weight of the anaerobic microbial agent.

[0011] By adopting the above technical solution, the anaerobic microbial agent is specifically composed of denitrifying bacteria and methanogens, with their weight ratio controlled within the range of 1:1 to 7:3. Denitrifying bacteria can convert nitrate nitrogen and nitrite nitrogen in the sediment into nitrogen gas under anaerobic conditions, achieving complete nitrogen removal. Methanogens, on the other hand, can decompose complex organic matter in the sediment that is difficult for other microorganisms to utilize and produce methane. This ratio allows the small-molecule metabolites produced by the methanogens from the decomposition of organic matter to provide a carbon source for the denitrifying bacteria. Simultaneously, the consumption of nitrates by the denitrifying bacteria can alleviate their inhibition of methanogens. This results in the two agents complementing each other under anaerobic conditions, synergistically enhancing nitrogen removal and decomposition of recalcitrant organic matter in the anaerobic zone. The specific composition and proportion design logic of the anaerobic microbial agent are further clarified, and the technical details of the internal component combination of the agent are disclosed to ensure the targeted and effective anaerobic degradation function.

[0012] Preferably, the enzyme preparation includes protease, lipase and cellulase, and the weight ratio of protease, lipase and cellulase is 4:2:1 to 6:4:3 based on the total weight of the enzyme preparation.

[0013] By adopting the above technical solution, the enzyme preparation is specifically composed of protease, lipase, and cellulase, and the weight ratio of the three is controlled within the range of 4:2:1 to 6:4:3. Among them, protease can catalyze the hydrolysis of protein substances in sediment into amino acids, lipase can promote the decomposition of fat substances into fatty acids and glycerol, and cellulase can degrade cellulose into small molecule carbohydrates such as glucose. This ratio is designed according to the common content ratio of protein, fat, and cellulose in sediment, allowing the three enzymes to target their respective pollutants. At the same time, the small molecule sugars produced by cellulase degradation can provide a suitable environment for the catalytic reaction of protease and lipase, and the amino acids produced by protease decomposition can also help enhance lipase activity. This plays a role in the complementary function of the three enzymes and synergistically enhancing the decomposition efficiency of various organic substances in sediment. The specific composition and ratio design logic of the enzyme preparation are further clarified, and the technical details of the internal component matching of the enzyme preparation are disclosed to ensure the targeted matching of enzymatic hydrolysis function with sediment pollutant composition.

[0014] Preferably, the nutritional additive includes urea, potassium dihydrogen phosphate, and a mixture of trace elements, with the weight ratio of urea, potassium dihydrogen phosphate, and the mixture of trace elements being 6:3:1 to 16:3:1 based on the total weight of the nutritional additive; the mixture of trace elements includes ferrous sulfate, zinc sulfate, and sodium molybdate, with a weight ratio of 3:2:1 to 2:2:1.

[0015] By adopting the above technical solution, the nutrient additive is specifically composed of urea, potassium dihydrogen phosphate, and a mixture of trace elements, with the weight ratio of the three controlled within the range of 6:3:1 to 16:3:1. The trace element mixture specifically includes ferrous sulfate, zinc sulfate, and sodium molybdate in a weight ratio of 3:2:1 to 2:2:1. Urea provides nitrogen nutrition for microorganisms, and potassium dihydrogen phosphate provides phosphorus nutrition; their ratio is adapted to the nitrogen and phosphorus requirements of microbial growth. Ferrous sulfate participates in the synthesis of microbial cytochromes and enzymes, zinc sulfate is an activator of various enzymes, and sodium molybdate is an essential component of nitrification and denitrification-related enzymes. The ratio of these three components is designed based on the microbial and enzyme requirements for trace elements. This combination and ratio allows nitrogen and phosphorus nutrition to work synergistically with trace elements, meeting the basic nutritional needs of microbial proliferation while providing necessary metal ion assistance for enzyme catalytic activity. This achieves precise nutrient supply and avoids excess or deficiency of any single nutrient. Furthermore, the specific composition and ratio design logic of the nutrient additive are clarified, and the technical details of the internal component combination of the nutrient supply system are disclosed to ensure that nutritional support matches the functional needs of microorganisms and enzymes.

[0016] Preferably, the carrier is modified zeolite or modified activated carbon, and the particle size of the carrier is 0.5-2.0 mm; the slow-release oxidant is a complex of calcium peroxide and sodium carbonate, with a weight ratio of 4:1 to 3:1; and the biosurfactant is rhamnolipid or sophorolipid.

[0017] By adopting the above technical solutions, the carrier is limited to modified zeolite or modified activated carbon with a particle size controlled between 0.5-2.0 mm. The modification treatment enhances the pore structure and adsorption performance of the carrier. The suitable particle size ensures uniform dispersion in the sediment and provides sufficient attachment sites for microorganisms and enzymes, thus stabilizing and immobilizing functional components. The slow-release oxidant is limited to a complex of calcium peroxide and sodium carbonate with a weight ratio of 4:1 to 3:1. Calcium peroxide slowly releases oxygen, while sodium carbonate regulates the oxygen release rate to prevent a sudden increase in local oxygen concentration. The combination of the two continuously regulates the dissolved oxygen environment in the sediment. The biosurfactant is limited to rhamnolipids or sophorolipids. These two bio-derived surfactants reduce the interfacial tension between hydrophobic organic matter and water, have good biocompatibility, and promote the contact between pollutants and functional components, thus solubilizing insoluble pollutants. Further clarify the specific types, forms, and proportions of carriers, slow-release oxidants, and biosurfactants, and supplement the disclosure of technical details of these three components to ensure that their functions are specifically matched to the needs of sediment purification.

[0018] Secondly, this application provides a method for preparing a sediment purification agent for in-situ degradation of river and lake bottom silt, employing the following technical solution:

[0019] A method for preparing a sediment purification agent for in-situ degradation of river and lake bottom silt includes the following steps:

[0020] S1. Carrier pretreatment: Soak the carrier in a 5-10% hydrochloric acid solution for 2-4 hours, then wash it with deionized water until neutral, and dry it at 105-120℃ for later use.

[0021] S2. Microbial mixing and activation: Aerobic and anaerobic microbial agents are mixed under aseptic conditions, with the mixing temperature controlled at 25-35℃ and the mixing time at 10-30 min. During the mixing process, sterile air is introduced at a rate of 0.5-1.5 L / min to obtain a microbial mixture.

[0022] S3. Component homogenization: Add enzyme preparations, nutrient additives and biosurfactants to the microbial mixture, and mix at a stirring speed of 50-100 r / min for 15-45 min to obtain a primary mixture;

[0023] S4. Immobilized mixing: The pretreated carrier and slow-release oxidant are added to the primary mixture and mixed for 30-60 minutes using a three-dimensional mixer at a speed of 20-40 r / min to obtain a homogeneous mixture.

[0024] S5. Segmented gradient fermentation and microbial domestication: The homogeneous mixture is fermented in segments at 30-40℃ for 48-96 hours to obtain the fermentation product.

[0025] S6. Drying, cooling and sieving: The fermentation product is dried at a temperature of 40-60℃ until the moisture content is less than 8%, and then particles with a particle size of 0.2-2.5mm are screened out to obtain the bottom mud purifier.

[0026] By adopting the above technical solution, the S1 carrier pretreatment step involves soaking the carrier in a 5-10% hydrochloric acid solution for 2-4 hours to remove surface impurities and open pores. The carrier is then washed with deionized water until neutral and dried at 105-120℃. This optimizes the carrier's adsorption performance and pore structure, providing a suitable carrier for subsequent functional component immobilization. The S2 microbial mixing and activation step involves mixing aerobic and anaerobic microbial agents at 25-35℃ for 10-30 minutes under aseptic conditions, while simultaneously introducing sterile air at a rate of 0.5-1.5 L / min. This avoids contamination by other microorganisms and provides a suitable initial environment for aerobic bacteria, promoting uniform mixing and initial activation of their activity. The S3 component homogenization step involves adding enzyme preparations, nutrient additives, and biosurfactants to the microbial mixture and mixing at a stirring speed of 50-100 r / min for 15-45 minutes. This process allows the enzymes, nutrients, and surfactants to integrate with the microbial agents. The process involves several steps: First, the pretreated carrier and slow-release oxidant are fully contacted and uniformly dispersed. Second, in step S4 (immobilization and mixing), the pretreated carrier and slow-release oxidant are added to the primary mixture and mixed for 30-60 minutes at 20-40 rpm using a three-dimensional mixer. The multi-angle agitation of the three-dimensional mixer ensures the functional components are uniformly loaded onto the carrier surface and pores. Third, in step S5 (segmented gradient fermentation and microbial acclimatization), the homogeneous mixture is fermented in stages at 30-40℃ for 48-96 hours, with the temperature gradually adjusted to simulate changes in the sediment environment. This process acclimates the microorganisms to the actual sediment environment, promoting their proliferation and functional expression. Fourth, in step S6 (drying, cooling, and sieving), the fermentation product is dried at 40-60℃ until the moisture content is below 8% for storage. After cooling, particles with a diameter of 0.2-2.5 mm are sieved out. This process controls the product's moisture content and ensures particle uniformity for dispersion in the sediment. These steps work synergistically to ensure the prepared sediment purifier has uniform components and stable function.

[0027] Preferably, in step S2, the pH value during mixing is controlled at 6.5-7.5, and a microbial activator, accounting for 0.1-0.3% of the total weight of the microbial agent, is added in three equal portions during the mixing process.

[0028] By adopting the above technical solution, and by controlling the pH value during mixing in step S2 to be between 6.5 and 7.5, this range is suitable for the survival environment of both aerobic and anaerobic microbial agents. This avoids damage to the microbial cell membrane structure and enzyme activity caused by excessively acidic or alkaline conditions, thus maintaining the initial activity of the microorganisms. Simultaneously, by adding a microbial activator in three equal portions (0.1-0.3% of the total weight of the microbial agent) during the mixing process, compared to adding it all at once, this method avoids the inhibitory effect of excessively high local concentrations of the activator on the microorganisms. Furthermore, by continuously replenishing the activation signal, it promotes the rapid awakening of the microorganisms and the initiation of metabolic activities, gradually enhancing the activity of the agent. The combination of these two methods further optimizes the conditions for microbial mixing and activation, and supplements the disclosure of specific technical details for microbial activity regulation, ensuring that the mixed microbial mixture maintains high activity and laying the foundation for subsequent purification functions.

[0029] Preferably, in step S5, the segmented fermentation process is divided into three stages: the first stage ferments at 30-33℃ for 18-24 hours, the second stage ferments at 33-36℃ for 18-24 hours, and the third stage ferments at 36-40℃ for 12-18 hours; the temperature is increased at a rate of 0.5-1℃ / h when each stage is switched.

[0030] By adopting the above technical solution, and defining three specific stages of segmented fermentation in step S5, the first stage ferments at 30-33℃ for 18-24 hours. This temperature range is suitable for the initial adaptation of microorganisms to the mixed system environment, which is conducive to the slow proliferation of the microbial community and the establishment of a basic community structure, thus allowing the microorganisms to initially adapt to the new environment. The second stage ferments at 33-36℃ for 18-24 hours. This temperature is slightly higher than the first stage, which can promote the synthesis and activity expression of microbial metabolic enzymes, accelerate the utilization of nutrients in the system, and enhance the metabolic capacity of microorganisms. The third stage ferments at 36-40℃ for 12-18 hours. This temperature is further optimized and can specifically activate functional genes related to the degradation of sediment pollutants in microorganisms, enhance their ability to degrade specific pollutants, and enhance the purification function of microorganisms. At the same time, the temperature is limited to a rate of 0.5-1℃ / h during the transition between each stage. The slow heating rate can avoid the impact of sudden temperature changes on the established microbial community structure, prevent the inactivation of some sensitive microorganisms, and maintain the stability of the microbial community. The overall design uses gradient temperature control and slow heating to simulate the temperature change trends that may occur in the sediment, thereby gradually acclimating the microorganisms. The specific temperature and time parameters and heating rate details of the staged fermentation are disclosed to ensure that the acclimated microorganisms can better adapt to the actual sediment environment and give full play to their degradation function.

[0031] Preferably, in step S6, the drying air velocity is 1.0-2.0 m / s, the dried material is cooled at 15-25℃ for 20-40 min, and then sieved.

[0032] By adopting the above technical solution, the drying air velocity is limited to 1.0-2.0 m / s in step S6. This air velocity range ensures that hot air penetrates the fermentation products evenly, promotes stable moisture evaporation, and avoids low drying efficiency and material clumping due to prolonged high humidity caused by excessively low air velocity. It also prevents excessively high air velocity from causing sudden local moisture loss and surface crusting of particles, which hinders internal moisture release. Simultaneously, it reduces the impact on the activity of microorganisms in the product, achieving uniform drying and maintaining the integrity and microbial activity of the product particles. Furthermore, the dried material is cooled at 15-25℃ for 20-40 minutes. This ambient temperature cooling condition allows the material, which is at a relatively high temperature after drying, to gradually decrease to a suitable screening temperature. This prevents the material from becoming brittle and sticky during screening due to excessively high temperature, or from accumulating internal heat during subsequent storage, affecting product stability. This stabilizes the physical form of the product and ensures screening accuracy. Further clarification of the specific parameters for drying air velocity and cooling conditions, and supplementary disclosure of the technical details of the drying and cooling process, ensures that the final product's moisture content, particle size, and physical form meet the requirements for uniform dispersion in the sediment and long-term storage, providing a guarantee for subsequent use.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. Because this application adopts a multi-component synergistic formulation containing aerobic and anaerobic microbial agents, compound enzyme preparations, nutrient additives, carriers, slow-release oxidants and biosurfactants, the slow-release oxidants can continuously improve the local dissolved oxygen environment and stabilize the pH value, the biosurfactants can effectively solubilize hydrophobic organic matter, multiple microorganisms and enzyme preparations work together to target different pollutants, and the carrier provides attachment protection for microorganisms, thus achieving a synergistic purification effect that significantly improves the degradation efficiency of compound pollutants such as organic matter, nitrogen and phosphorus in river and lake sediments.

[0035] 2. In this application, a specific weight ratio of Bacillus subtilis and nitrifying bacteria is preferred to form an aerobic bacterial agent, denitrifying bacteria and methanogens are preferred to form an anaerobic bacterial agent, and protease, lipase and cellulase are preferred to form a complex enzyme preparation. The particle size of the carrier and the ratio of the slow-release oxidant are also limited. Because of this preferred combination, the functions of each microorganism and enzyme are more targeted and the ratio is coordinated. The physicochemical properties of the carrier and oxidant are best matched, thereby obtaining a more stable and longer-lasting pollutant degradation kinetic process and a better microbial ecosystem construction effect.

[0036] 3. The method of this application enhances the adsorption and loading capacity of the carrier through acid washing pretreatment, preactivates the microorganisms through air circulation and activator addition during the microbial mixing stage, achieves uniform dispersion of the carrier through three-dimensional mixing, and acclimates the microbial community through segmented gradient fermentation. Due to the synergistic optimization of these key steps, the high activity and high stability of the functional microorganisms in the final product are effectively guaranteed. Therefore, the beneficial effect of significantly improving the in-situ degradation efficiency and extending the action period of the purifier in practical applications is obtained. Attached Figure Description

[0037] Figure 1 This is a flowchart of a method for preparing a sediment purification agent for in-situ degradation of silt at the bottom of rivers and lakes, as provided in this application. Detailed Implementation

[0038] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0039] Technical concept:

[0040] Existing technologies for sediment purification generally suffer from insufficient functional synergy, poor microbial environmental adaptability, and unsatisfactory product stability. The core reason lies in the failure to fully integrate the actual environmental characteristics of alternating aerobic and anaerobic conditions in sediment with the complex properties of pollutants into the design scheme. On the one hand, most technologies use single bacterial agents or enzyme preparations, which are difficult to cover the pollutant degradation needs of different oxidation zones in sediment. Furthermore, the low matching degree between nutrient supply, carrier adsorption, and functional components leads to the isolation of each component's function and the inability to form a synergistic effect. On the other hand, the microbial activation and acclimatization process lacks specificity. For example, the use of constant-temperature fermentation does not simulate the temperature fluctuations of the sediment, which can easily cause a sharp drop in the activity of microorganisms after they enter the sediment due to environmental incompatibility. At the same time, the preparation process parameters such as drying and cooling do not take into account both microbial activity and product physical morphology, often resulting in particle clumping or microbial inactivation, ultimately affecting the purification effect.

[0041] This technical solution employs a combination of aerobic and anaerobic microbial agents, a precise ratio of protease, lipase, and cellulase, and a synergistic nutrient system of urea, potassium dihydrogen phosphate, and trace elements, along with a modified carrier and a slow-release oxidant of calcium peroxide and sodium carbonate, to construct a multi-component synergistic purification system. In terms of the preparation process, the adsorption performance is optimized through carrier acid washing pretreatment; step S2 controls the pH to 6.5-7.5 and adds activators in three stages to enhance microbial activation; step S5 designs a three-stage gradient fermentation and slow heating to simulate sediment temperature changes for microbial acclimatization; and step S6 controls a drying air velocity of 1.0-2.0 m / s and cooling conditions of 15-25℃ to ensure product morphology and microbial activity. Finally, through the synergistic design of components and process adaptation, the purifier is ensured to possess efficient degradation capabilities and environmental adaptability in sediment.

[0042] Preparation Example 1

[0043] The preparation process of modified zeolite is as follows:

[0044] Ordinary clinoptilolite ore was crushed by a jaw crusher and passed through a standard sieve to obtain 1000 grams of zeolite particles with a particle size of 0.5-2.0 mm. The particles were added to 5000 ml of 8% ammonium chloride solution at a solid-liquid ratio of 1:5 and stirred in a constant temperature water bath at 35℃ for 2 hours for ion exchange modification. After standing for 4 hours, the mixture was filtered, and the filter residue was washed with deionized water until the pH of the washing liquid was neutral. The filter residue was then dried in an oven at 105℃ for 4 hours and then calcined in a muffle furnace at 450℃ for 2 hours. After naturally cooling to room temperature, the desired modified zeolite was obtained.

[0045] Preparation Example 2

[0046] The preparation process of modified activated carbon is as follows:

[0047] Take 500g of raw coal-based activated carbon with a particle size of 0.5-2.0mm, add it to 4000ml of 10% nitric acid solution with a solid-liquid ratio of 1:8, and heat it under reflux in an 80℃ constant temperature water bath for 3 hours. After reflux, stop heating, stir and cool to room temperature, filter, and wash the filter residue repeatedly with deionized water until the pH of the washing liquid is 6.5-7.5. Place the filter residue in an oven at 110℃ and dry it for 6 hours, then transfer it to a vacuum drying oven and vacuum dry it at 120℃ for 2 hours. After cooling, the desired modified activated carbon is obtained.

[0048] Preparation Example 3

[0049] The preparation process of calcium peroxide-sodium carbonate slow-release oxidant is as follows:

[0050] Weigh food-grade calcium peroxide powder and anhydrous sodium carbonate powder at a weight ratio of 3.5:1, i.e., take 350 grams of calcium peroxide powder with a purity ≥98% and 100 grams of anhydrous sodium carbonate powder with a purity ≥99.5%, and add them together into a three-dimensional mixer; set the mixer speed to 25 r / min and the mixing time to 30 minutes; after mixing, transfer the mixture to a twin-screw granulator, control the granulation temperature at 40-50℃, and prepare granular composites with a particle size of 0.3-0.8 mm. Then place them in a 50℃ forced-air drying oven to dry for 2 hours, and after cooling, the desired slow-release oxidant is obtained.

[0051] The following are the main raw materials and reagents used in the preparation examples, embodiments, and comparative examples, and their sources and specifications are as follows; unless otherwise specified, all reagents are commercially available analytical grade or higher products:

[0052] 1. Bacillus subtilis was purchased from Shanghai Chunshi Biotechnology Co., Ltd., CAS: 68038-70-0;

[0053] 2. The nitrifying bacteria were purchased from Weifang Ruichen Biotechnology Co., Ltd., product number: nitrifying bacteria | nitrifying bacteria;

[0054] 3. The denitrifying bacteria were purchased from Weifang Ruichen Biotechnology Co., Ltd., product number: denitrifying bacteria;

[0055] 4. Methanogens were purchased from Henan Jingchuan Environmental Protection Technology Co., Ltd., item number: 0236;

[0056] 5. The protease was purchased from Jiangsu Duoyang Biotechnology Co., Ltd., CAS: 9025-49-4;

[0057] 6. Lipase was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S10035;

[0058] 7. Cellulase was purchased from Shaanxi Runfeng Biotechnology Co., Ltd., CAS: 9012-54-8;

[0059] 8. Rhamnose glycolipids were purchased from Shanghai Xuanya Biotechnology Co., Ltd., CAS: 869062-42-0;

[0060] 9. Sophorolipids were purchased from Jiangxi Ruiwei Biotechnology Co., Ltd., CAS: 148409-20-5.

[0061] Example 1

[0062] This application provides a sediment purification agent for in-situ degradation of river and lake bottom silt, which includes the following components by weight: 20 parts aerobic microbial agent, 10 parts anaerobic microbial agent, 6 parts enzyme preparation, 3 parts nutrient additive, 50 parts carrier, 10 parts slow-release oxidant, and 3 parts biosurfactant.

[0063] Among them, the aerobic microbial agent includes Bacillus subtilis and nitrifying bacteria. Based on the total weight of the aerobic microbial agent, the weight ratio of Bacillus subtilis to nitrifying bacteria is 3.5:1.5.

[0064] Among them, the anaerobic microbial inoculant includes denitrifying bacteria and methanogens. Based on the total weight of the anaerobic microbial inoculant, the weight ratio of denitrifying bacteria to methanogens is 6:4.

[0065] The enzyme preparation includes protease, lipase and cellulase. Based on the total weight of the enzyme preparation, the weight ratio of protease, lipase and cellulase is 5:3:2.

[0066] The nutritional additives include urea, potassium dihydrogen phosphate and a mixture of trace elements. Based on the total weight of the nutritional additives, the weight ratio of urea, potassium dihydrogen phosphate and the mixture of trace elements is 11:3:1.

[0067] The trace element mixture includes ferrous sulfate, zinc sulfate and sodium molybdate in a weight ratio of 2.5:2:1.

[0068] The carrier is modified zeolite with a particle size of 1.25 mm.

[0069] The slow-release oxidant is a complex of calcium peroxide and sodium carbonate in a weight ratio of 3.5:1.

[0070] Among them, the biosurfactant is rhamnolipid;

[0071] The preparation method of the above-mentioned sediment purification agent for in-situ degradation of river and lake bottom silt includes the following steps:

[0072] S1. Carrier pretreatment: Soak the carrier in a 7.5% hydrochloric acid solution for 3 hours, then wash it with deionized water until neutral, and dry it at 112.5℃ for later use.

[0073] S2. Microbial mixing and activation: Aerobic and anaerobic microbial agents are mixed under aseptic conditions, with the mixing temperature controlled at 30℃ and the mixing time at 20 min. Simultaneously, sterile air is introduced at a rate of 1.0 L / min during the mixing process to obtain a microbial mixture.

[0074] The pH value during mixing is controlled at 7.0, and a microbial activator, accounting for 0.2% of the total weight of the microbial agent, is added in three equal portions during the mixing process.

[0075] S3. Component homogenization: Add enzyme preparations, nutrient additives and biosurfactants to the microbial mixture, mix for 30 min at a stirring speed of 75 r / min to obtain a primary mixture;

[0076] S4. Immobilized Mixing: The pretreated carrier and slow-release oxidant are added to the primary mixture and mixed for 45 minutes at a speed of 30 r / min using a three-dimensional mixer to obtain a homogeneous mixture.

[0077] S5. Segmented gradient fermentation and microbial domestication: The homogeneous mixture was fermented in segments at 35°C for 72 hours to obtain the fermentation product.

[0078] The segmented fermentation process is divided into three stages: the first stage ferments at 31.5℃ for 21 hours, the second stage ferments at 34.5℃ for 21 hours, and the third stage ferments at 38℃ for 15 hours; the temperature is increased at a rate of 0.75℃ / h when each stage is switched.

[0079] S6. Drying, cooling and sieving: The fermentation product is dried at 50°C until the moisture content is less than 8%, and then particles with a particle size of 1.35 mm are screened out to obtain the bottom mud purifier.

[0080] The drying process involves an air velocity of 1.5 m / s, followed by cooling the dried material at 20°C for 30 minutes before sieving.

[0081] Example 2

[0082] This application provides a sediment purification agent for in-situ degradation of river and lake bottom silt, which includes the following components by weight: 10 parts aerobic microbial agent, 5 parts anaerobic microbial agent, 2 parts enzyme preparation, 1 part nutrient additive, 40 parts carrier, 5 parts slow-release oxidant, and 1 part biosurfactant.

[0083] Among them, the aerobic microbial agent includes Bacillus subtilis and nitrifying bacteria. Based on the total weight of the aerobic microbial agent, the weight ratio of Bacillus subtilis to nitrifying bacteria is 3:2.

[0084] Among them, the anaerobic microbial inoculant includes denitrifying bacteria and methanogens. Based on the total weight of the anaerobic microbial inoculant, the weight ratio of denitrifying bacteria to methanogens is 1:1.

[0085] The enzyme preparation includes protease, lipase and cellulase. Based on the total weight of the enzyme preparation, the weight ratio of protease, lipase and cellulase is 4:2:1.

[0086] The nutritional additives include urea, potassium dihydrogen phosphate and a mixture of trace elements. Based on the total weight of the nutritional additives, the weight ratio of urea, potassium dihydrogen phosphate and the mixture of trace elements is 6:3:1.

[0087] The trace element mixture includes ferrous sulfate, zinc sulfate and sodium molybdate in a weight ratio of 3:2:1.

[0088] The carrier is modified activated carbon with a particle size of 0.5 mm.

[0089] The slow-release oxidant is a complex of calcium peroxide and sodium carbonate in a weight ratio of 4:1.

[0090] The biosurfactant is sophorolipid.

[0091] The preparation method of the above-mentioned sediment purification agent for in-situ degradation of river and lake bottom silt includes the following steps:

[0092] S1. Carrier pretreatment: Soak the carrier in a 5% hydrochloric acid solution for 2 hours, then wash it with deionized water until neutral, and dry it at 105℃ for later use.

[0093] S2. Microbial mixing and activation: Aerobic and anaerobic microbial agents are mixed under aseptic conditions, with the mixing temperature controlled at 25℃ and the mixing time at 10 min. During the mixing process, sterile air is introduced at a rate of 0.5 L / min to obtain a microbial mixture.

[0094] The pH value during mixing was controlled at 6.5, and a microbial activator, accounting for 0.1% of the total weight of the microbial agent, was added in three equal portions during the mixing process.

[0095] S3. Component homogenization: Add enzyme preparations, nutrient additives and biosurfactants to the microbial mixture, mix for 15 min at a stirring speed of 50 r / min to obtain a primary mixture;

[0096] S4. Immobilized Mixing: The pretreated carrier and slow-release oxidant are added to the primary mixture and mixed for 30 minutes at a speed of 20 r / min using a three-dimensional mixer to obtain a homogeneous mixture;

[0097] S5. Segmented gradient fermentation and microbial domestication: The homogeneous mixture was fermented in segments at 30°C for 48 hours to obtain the fermentation product.

[0098] The segmented fermentation process is divided into three stages: the first stage ferments at 30℃ for 18 hours, the second stage ferments at 33℃ for 18 hours, and the third stage ferments at 36℃ for 12 hours; the temperature is increased at a rate of 0.5℃ / h when each stage is switched.

[0099] S6. Drying, cooling and sieving: The fermentation product is dried at 40℃ until the moisture content is less than 8%, and then particles with a particle size of 0.2mm are screened out to obtain the bottom mud purifier.

[0100] The drying process involves an air velocity of 1.0 m / s, followed by cooling the dried material at 15°C for 20 minutes before sieving.

[0101] Example 3

[0102] This application provides a sediment purification agent for in-situ degradation of river and lake bottom silt, which includes the following components by weight: 30 parts aerobic microbial agent, 15 parts anaerobic microbial agent, 10 parts enzyme preparation, 5 parts nutrient additive, 60 parts carrier, 15 parts slow-release oxidant, and 5 parts biosurfactant.

[0103] Among them, the aerobic microbial agent includes Bacillus subtilis and nitrifying bacteria. Based on the total weight of the aerobic microbial agent, the weight ratio of Bacillus subtilis to nitrifying bacteria is 4:1.

[0104] Among them, the anaerobic microbial inoculant includes denitrifying bacteria and methanogens. Based on the total weight of the anaerobic microbial inoculant, the weight ratio of denitrifying bacteria to methanogens is 7:3.

[0105] The enzyme preparation includes protease, lipase and cellulase. Based on the total weight of the enzyme preparation, the weight ratio of protease, lipase and cellulase is 6:4:3.

[0106] The nutritional additives include urea, potassium dihydrogen phosphate and a mixture of trace elements. Based on the total weight of the nutritional additives, the weight ratio of urea, potassium dihydrogen phosphate and the mixture of trace elements is 16:3:1.

[0107] The trace element mixture includes ferrous sulfate, zinc sulfate, and sodium molybdate in a weight ratio of 2:2:1.

[0108] The carrier is modified zeolite with a particle size of 2.0 mm.

[0109] The slow-release oxidant is a complex of calcium peroxide and sodium carbonate in a weight ratio of 3:1.

[0110] Among them, the biosurfactant is rhamnolipid.

[0111] The preparation method of the above-mentioned sediment purification agent for in-situ degradation of river and lake bottom silt includes the following steps:

[0112] S1. Carrier pretreatment: Soak the carrier in a 10% hydrochloric acid solution for 4 hours, then wash it with deionized water until neutral, and dry it at 120°C for later use.

[0113] S2. Microbial mixing and activation: Aerobic and anaerobic microbial agents are mixed under aseptic conditions, with the mixing temperature controlled at 35℃ and the mixing time at 30 min. During the mixing process, sterile air is introduced at a rate of 1.5 L / min to obtain a microbial mixture.

[0114] The pH value during mixing is controlled at 7.5, and a microbial activator, accounting for 0.3% of the total weight of the microbial agent, is added in three equal portions during the mixing process.

[0115] S3. Component homogenization: Add enzyme preparations, nutrient additives and biosurfactants to the microbial mixture, and mix for 45 minutes at a stirring speed of 100 r / min to obtain a primary mixture;

[0116] S4. Immobilized Mixing: The pretreated carrier and slow-release oxidant are added to the primary mixture and mixed for 60 minutes at 40 r / min using a three-dimensional mixer to obtain a homogeneous mixture;

[0117] S5. Segmented gradient fermentation and microbial domestication: The homogeneous mixture was fermented in segments at 40℃ for 96 hours to obtain the fermentation product.

[0118] The segmented fermentation process is divided into three stages: the first stage ferments at 33℃ for 24 hours, the second stage ferments at 36℃ for 24 hours, and the third stage ferments at 40℃ for 18 hours; the temperature is increased at a rate of 1℃ / h when each stage is switched.

[0119] S6. Drying, cooling and sieving: The fermentation product is dried at 60℃ until the moisture content is less than 8%, and then particles with a particle size of 2.5mm are screened out to obtain the bottom mud purifier.

[0120] The drying process involves an air velocity of 2.0 m / s, followed by cooling the dried material at 25°C for 40 minutes before sieving.

[0121] Comparative Example 1

[0122] The only difference between this comparative example and Example 1 is that cellulase is omitted in the enzyme preparation, and only protease and lipase are used, with their weight ratio maintained at 5:3. The remaining components, dosages, and preparation methods are exactly the same as in Example 1.

[0123] Comparative Example 2

[0124] The only difference between this comparative example and Example 1 is that nitrifying bacteria are omitted from the aerobic microbial inoculant, and only Bacillus subtilis is used. The remaining components, dosages, and preparation methods are exactly the same as in Example 1.

[0125] Comparative Example 3

[0126] The only difference between this comparative example and Example 1 is that the biosurfactant rhamnolipid is replaced with an equal amount of the conventional chemical surfactant sodium dodecylbenzenesulfonate. All other components, amounts, and preparation methods are exactly the same as in Example 1.

[0127] Comparative Example 4

[0128] The only difference between this comparative example and Example 1 is that the carrier is replaced with ordinary zeolite, while the other components, dosages, and preparation methods are exactly the same as in Example 1.

[0129] Comparative Example 5

[0130] The only difference between this comparative example and Example 1 is that step S1, the carrier pretreatment, is omitted, and the original zeolite carrier that has not undergone acid washing is used directly. The remaining components, amounts, and preparation methods are exactly the same as in Example 1.

[0131] Comparative Example 6

[0132] The only difference between this comparative example and Example 1 is that the segmented gradient fermentation in step S5 is changed to constant temperature fermentation, that is, fermentation is carried out at 35°C for 72 hours. The other components, dosages, and preparation methods are exactly the same as in Example 1.

[0133] I. Test Item 1: Determination of Organic Matter Degradation Rate and Volatile Solids Removal Rate in Sediment

[0134] The experimental contents are as follows: In the preparation stage of experimental materials, fresh bottom sediment from 0-20cm at the bottom of the target river or lake needs to be collected. After removing impurities such as stones and branches, it is homogenized by passing it through a 2mm sieve. Then, the initial chemical oxygen demand and volatile solids content of the bottom sediment are measured. The bottom sediment purifiers of Examples 1-3, Comparative Examples 1-6, and the blank control group are selected respectively. No purifier is added to the blank control group. Each group is set up with 3 parallel experiments to ensure the reliability of the data.

[0135] During the experiment, 500g of homogenized sediment and 300mL of deionized water were added to a 1L serum bottle to simulate the in-situ water environment of the sediment. The experimental group was given the corresponding purification agent at a dosage of 5% of the dry weight of the sediment, while the blank control group was given no purification agent. After sealing the serum bottle, it was placed in a 25℃ light-proof incubator for static culture for 14 days. During the culture period, the serum bottle was gently shaken once every 2 days to simulate a slight disturbance in the water body.

[0136] Three 10g sediment samples were collected from each group on days 7 and 14 of cultivation. The COD content of the sediment was determined using the potassium dichromate method, and the VS content was determined using the ignition method at 550℃ for 2 hours. The organic matter degradation rate and VS removal rate were calculated, with the organic matter degradation rate expressed as the COD removal rate. The calculation formula is as follows:

[0137] ;

[0138] The formula for calculating VS removal rate is:

[0139] .

[0140] II. Test Item 2: Determination of Nitrogen and Phosphorus Content Changes in Bottom Sediment and Overlying Water

[0141] The experiment was conducted in the same reaction system as Test 1, without the need for additional experimental groups, enabling sample reuse and data correlation. Experimental materials and culture conditions were consistent with Test 1. Three 20mL samples of overlying water were taken from each group on day 0 (initial state), day 7, and day 14 of culture. The total nitrogen content of the overlying water was determined using alkaline potassium persulfate digestion and ultraviolet spectrophotometry, and the total phosphorus content was determined using molybdenum-antimony anti-spectrophotometry. Simultaneously, three 10g samples of bottom sediment were taken. For bottom sediment TN determination, Kjeldahl digestion was required first; for bottom sediment TP determination, sulfuric acid-perchloric acid digestion was required first. Then, the bottom sediment TN content was determined using Kjeldahl digestion and the bottom sediment TP content was determined using molybdenum-antimony anti-spectrophotometry, respectively. The bottom sediment TN removal rate, bottom sediment TP removal rate, and overlying water TN reduction rate and overlying water TP reduction rate were calculated. The calculation formulas for bottom sediment TN removal rate and TP removal rate were consistent with those for COD removal rate. The calculation formula for overlying water TN reduction rate was:

[0142] ;

[0143] The formula for calculating the TP reduction rate of overlying water is consistent with that for the TN reduction rate of overlying water.

[0144] III. Determination of viable counts and enzyme activities of functional microorganisms in sediment

[0145] This project reflects the effectiveness of the product's mechanism of action and is the core driving factor related to the first two performance indicators. The experiment was still conducted in the reaction system of test item 1, and the experimental materials and culture conditions were the same as those of test item 1. On day 14 of cultivation, three 10g sediment samples were taken from each group. The viable count of functional microorganisms was determined using the serial dilution plate counting method. Bacillus subtilis and nitrifying bacteria among aerobic bacteria were cultured on LB medium at 28°C for 48 hours under aerobic conditions. Denitrifying bacteria and methanogens among anaerobic bacteria were cultured on TSB medium at 30°C for 72 hours under anaerobic conditions. The viable count per gram of dry sediment was then calculated in CFU / g. Simultaneously, three 5g sediment samples were taken, homogenized with pH 7.0 phosphate buffer, and centrifuged at 8000 rpm for 15 minutes at 4°C. The supernatant was used as enzyme extract, and enzyme activity was determined using the corresponding enzyme activity assay kits. Protease was determined using the Folin-Ciocalteu method, lipase using the titration method, and cellulase using the DNS method. Enzyme activity was expressed in U / g, defined as the amount of enzyme required per gram of sediment per hour to catalyze the production of 1 μmol of product from the substrate.

[0146] The results of the determination of the degradation rate of organic matter and the removal rate of volatile solids in the sediment are shown in Table 1.

[0147] Table 1:

[0148] Group COD removal rate on day 7 (%) COD removal rate (%) on day 14 Day 7 VS Removal Rate (%) Day 14 VS Removal Rate (%) Blank control group 5.2±0.8 8.5±1.1 4.1±0.6 7.0±0.9 Example 1 45.3±2.1 68.9±1.8 38.7±1.5 60.2±1.4 Example 2 42.1±1.9 65.5±2.0 36.2±1.7 57.8±1.6 Example 3 43.8±2.3 66.7±1.7 37.9±1.8 58.9±1.5 Comparative Example 1 38.5±1.5 55.4±1.9 32.4±1.3 48.1±1.7 Comparative Example 2 35.2±1.7 58.7±1.6 30.1±1.4 50.3±1.5 Comparative Example 3 32.8±1.4 51.6±2.1 28.7±1.6 45.9±1.8 Comparative Example 4 29.6±1.8 47.2±1.7 25.3±1.2 42.5±1.3 Comparative Example 5 28.1±1.3 45.8±1.9 24.8±1.5 41.0±1.6 Comparative Example 6 31.4±1.6 50.1±1.8 27.2±1.4 44.7±1.7

[0149] The results of the nitrogen and phosphorus content changes in the bottom sediment and overlying water (day 14) are shown in Table 2.

[0150] Table 2:

[0151] Group TN removal rate in sediment (%) TP removal rate in sediment (%) TN reduction rate (%) of overlying water TP reduction rate (%) of overlying water Blank control group 4.3±0.7 3.8±0.5 -15.2±2.1 -22.5±3.0 Example 1 55.7±1.9 48.6±1.7 45.3±2.3 51.8±2.5 Example 2 52.4±2.1 46.2±1.9 42.1±2.0 48.9±2.1 Example 3 53.9±1.8 47.5±1.6 43.8±2.2 50.5±2.4 Comparative Example 1 50.1±1.7 45.8±1.8 40.5±1.9 47.2±2.0 Comparative Example 2 38.9±1.5 44.1±1.4 25.7±1.8 46.5±1.9 Comparative Example 3 47.5±1.6 42.3±1.7 38.2±2.1 44.1±2.2 Comparative Example 4 41.2±1.9 38.7±1.5 32.9±1.7 40.8±1.8 Comparative Example 5 39.8±1.4 37.5±1.6 31.4±1.5 39.6±1.7 Comparative Example 6 45.6±1.8 40.2±1.3 35.8±1.6 42.7±1.9

[0152] The results of the determination of the number of viable functional microorganisms and enzyme activity in the sediment (day 14) are shown in Table 3.

[0153] Table 3:

[0154] Group <![CDATA[Bacillus subtilis (×10 8 CFU / g)]]> <![CDATA[Nitrifying bacteria (×10 7 CFU / g)]]> <![CDATA[Denitrifying bacteria (×10 7 CFU / g)]]> Protease (U / g) Lipase (U / g) Cellulase (U / g) Blank control group 0.5±0.1 0.3±0.1 0.8±0.2 12.5±1.2 8.3±0.9 5.1±0.7 Example 1 8.9±0.5 5.6±0.4 7.8±0.5 125.6±5.8 98.7±4.2 65.4±3.5 Example 2 7.5±0.6 4.8±0.3 6.9±0.4 115.2±4.9 90.1±3.8 58.9±3.1 Example 3 8.2±0.4 5.1±0.5 7.2±0.6 120.8±5.5 95.3±4.5 62.1±3.8 Comparative Example 1 8.5±0.5 5.4±0.4 7.5±0.5 118.9±5.1 96.1±4.0 25.3±2.1 Comparative Example 2 8.7±0.6 0.9±0.2 7.6±0.4 122.4±5.3 97.5±4.1 63.8±3.4 Comparative Example 3 6.1±0.4 3.2±0.3 5.4±0.3 95.7±4.2 75.8±3.5 52.1±2.9 Comparative Example 4 4.3±0.3 2.5±0.2 3.9±0.3 85.4±3.8 65.2±3.1 45.8±2.5 Comparative Example 5 3.8±0.4 2.1±0.3 3.5±0.4 80.1±3.6 60.9±2.8 42.3±2.3 Comparative Example 6 5.5±0.5 3.8±0.3 4.8±0.4 90.2±4.0 70.5±3.3 48.7±2.7

[0155] As can be seen from Examples 1-3 and Comparative Example 1, along with Tables 1, 2, and 3, cellulase plays a crucial role in sediment purification. Together with proteases and lipases, it constitutes a degradation system targeting different types of organic matter in the sediment. Proteases decompose proteinaceous organic matter, lipases decompose fatty organic matter, and cellulases decompose cellulose organic matter; the synergistic effect of these three is necessary to achieve comprehensive and efficient degradation of sediment organic matter. A lack of cellulase leads to insufficient decomposition of cellulose organic matter in the sediment, directly reducing the overall organic matter degradation efficiency. Furthermore, insufficient carbon source supply from cellulose decomposition indirectly affects the nutrient acquisition of microorganisms, thus restricting microbial activity, enzyme system synergy, and nitrogen-phosphorus conversion processes. Ultimately, this results in purification performance lower than that of the products in the examples.

[0156] Combining Examples 1-3 and Comparative Example 2 with Tables 1, 2, and 3, it can be seen that nitrifying bacteria in aerobic microbial agents and denitrifying bacteria in anaerobic microbial agents have a crucial synergistic effect. Together, they constitute a nitrification-denitrification nitrogen cycle system. Nitrifying bacteria are responsible for converting ammonia nitrogen in the sediment into nitrate nitrogen, while denitrifying bacteria use nitrate nitrogen as a substrate to convert it into nitrogen gas for removal under anaerobic conditions. The lack of nitrifying bacteria leads to the ineffective conversion of ammonia nitrogen into nitrate nitrogen, and denitrifying bacteria, lacking the necessary substrate, cannot fully exert their function, thus significantly reducing the TN removal rate of the sediment and the TN reduction rate of the overlying water. Phosphorus removal mainly relies on microbial absorption and fixation and carrier adsorption, which is not directly related to nitrifying bacteria. Therefore, it has a relatively small impact on the TP removal rate of the sediment and the TP reduction rate of the overlying water. This result also clarifies the irreplaceable role of nitrifying bacteria in efficient nitrogen removal and their synergistic dependence with denitrifying bacteria.

[0157] Combining Examples 1-3 and Comparative Example 3 with Tables 1, 2, and 3, it can be seen that the difference in the impact of biosurfactants and conventional chemical surfactants on sediment purification performance lies primarily in the protection of microbial activity and compatibility with the system. Rhamnose lipolipids, as biosurfactants, not only effectively reduce the interfacial tension between sediment and water and promote the dissolution and release of organic matter, but also possess good biocompatibility, not inhibiting microorganisms but rather providing a certain growth environment. While sodium dodecylbenzenesulfonate can act as a surfactant, it exhibits certain toxic inhibitory effects on microorganisms, leading to a reduction in the number of viable functional microorganisms and decreased enzyme activity, thereby affecting the degradation of organic matter and the efficiency of nitrogen and phosphorus conversion. Consequently, its purification performance is lower than that of the products in the examples using biosurfactants.

[0158] As can be seen from Examples 1-3 and Comparative Example 4, and Tables 1, 2, and 3, the modification of the carrier is crucial to its functionality. Modified zeolite exhibits superior performance compared to ordinary zeolite. The modification process expands the pore structure of the zeolite, increases its specific surface area, and enhances its surface adsorption activity. This allows the modified zeolite to not only more effectively adsorb pollutants in the sediment but also provide more sufficient immobilization sites for microorganisms and enzymes, prolonging their residence time in the sediment and maintaining their activity. Ordinary zeolite, due to its smaller pore size, weaker adsorption capacity, and poor immobilization effect, leads to the easy loss of microorganisms and enzymes with the water or a rapid decline in activity, thereby reducing the overall purification efficiency. This demonstrates the key supporting role of the modified carrier in improving the performance of sediment purifiers.

[0159] As can be seen from Examples 1-3 and Comparative Example 5, and in conjunction with Tables 1, 2, and 3, carrier pretreatment is a crucial step in ensuring carrier performance. Hydrochloric acid washing effectively removes impurities adhering to the zeolite surface, preventing clogging of the zeolite pores. Simultaneously, moderate etching further expands the pore size and increases surface active sites, thereby enhancing the carrier's adsorption capacity and microbial immobilization effect. The original zeolite, without pretreatment, suffers from unremoved surface impurities and an unoptimized pore structure, resulting in a significant decrease in both adsorption and immobilization performance. This prevents microorganisms and enzymes from effectively attaching and functioning, and pollutants are difficult to adsorb and fix by the carrier. Ultimately, the sediment purifier's performance in organic matter degradation, nitrogen and phosphorus removal, and other aspects is lower than that of the pretreated product.

[0160] Combining Examples 1-3 and Comparative Example 6 with Tables 1, 2, and 3, it can be seen that the segmented gradient fermentation process has a significant effect on the domestication and activity enhancement of microorganisms. Segmented gradient fermentation, by gradually increasing the temperature, allows microorganisms to gradually adapt to temperature changes, completing proliferation, metabolic optimization, and activity enhancement at different temperature stages, ultimately forming a highly active and adaptable microbial community. In contrast, isothermal fermentation cannot achieve gradual domestication of microorganisms; microorganisms cannot fully activate their metabolic functions at a single temperature, and their adaptability to the subsequent sediment environment is poor, leading to a reduction in the number of viable functional microorganisms and decreased enzyme activity, thereby affecting the degradation of organic matter and the efficiency of nitrogen and phosphorus conversion. This demonstrates the importance of the segmented gradient fermentation process in improving the quality of the microbial community and the overall performance of the sediment purifier.

[0161] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A sediment purification agent for in-situ degradation of silt at the bottom of rivers and lakes, characterized in that: By weight, it includes the following components: 10-30 parts aerobic microbial agent, 5-15 parts anaerobic microbial agent, 2-10 parts enzyme preparation, 1-5 parts nutrient additive, 40-60 parts carrier, 5-15 parts slow-release oxidant, and 1-5 parts biosurfactant.

2. The sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 1, characterized in that: The aerobic microbial agent includes Bacillus subtilis and nitrifying bacteria, with the weight ratio of Bacillus subtilis to nitrifying bacteria being 3:2 to 4:1 based on the total weight of the aerobic microbial agent.

3. The sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 1, characterized in that: The anaerobic microbial agent includes denitrifying bacteria and methanogens, and the weight ratio of denitrifying bacteria to methanogens is 1:1 to 7:3 based on the total weight of the anaerobic microbial agent.

4. A sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 1, characterized in that: The enzyme preparation includes protease, lipase and cellulase, and the weight ratio of protease, lipase and cellulase is 4:2:1 to 6:4:3 based on the total weight of the enzyme preparation.

5. A sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 1, characterized in that: The nutritional additives include urea, potassium dihydrogen phosphate, and a mixture of trace elements. Based on the total weight of the nutritional additives, the weight ratio of urea, potassium dihydrogen phosphate, and the mixture of trace elements is 6:3:1 to 16:3:

1. The mixture of trace elements includes ferrous sulfate, zinc sulfate, and sodium molybdate, with a weight ratio of 3:2:1 to 2:2:

1.

6. A sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 1, characterized in that: The carrier is modified zeolite or modified activated carbon, and the particle size of the carrier is 0.5-2.0 mm; the slow-release oxidant is a complex of calcium peroxide and sodium carbonate, with a weight ratio of 4:1 to 3:1; the biosurfactant is rhamnolipid or sophorolipid.

7. A method for preparing a sediment purification agent for in-situ degradation of river and lake bottom silt, characterized in that, A sediment purification agent for in-situ degradation of river and lake bottom silt as described in any one of claims 1-6 comprises the following steps: S1. Carrier pretreatment: Soak the carrier in a 5-10% hydrochloric acid solution for 2-4 hours, then wash it with deionized water until neutral, and dry it at 105-120℃ for later use. S2. Microbial mixing and activation: Aerobic and anaerobic microbial agents are mixed under aseptic conditions, with the mixing temperature controlled at 25-35℃ and the mixing time at 10-30 min. During the mixing process, sterile air is introduced at a rate of 0.5-1.5 L / min to obtain a microbial mixture. S3. Component homogenization: Add enzyme preparations, nutrient additives and biosurfactants to the microbial mixture, and mix at a stirring speed of 50-100 r / min for 15-45 min to obtain a primary mixture; S4. Immobilized mixing: The pretreated carrier and slow-release oxidant are added to the primary mixture and mixed for 30-60 minutes using a three-dimensional mixer at a speed of 20-40 r / min to obtain a homogeneous mixture. S5. Segmented gradient fermentation and microbial domestication: The homogeneous mixture is fermented in segments at 30-40℃ for 48-96 hours to obtain the fermentation product. S6. Drying, cooling and sieving: The fermentation product is dried at a temperature of 40-60℃ until the moisture content is less than 8%, and then particles with a particle size of 0.2-2.5mm are screened out to obtain the bottom mud purifier.

8. The method for preparing a sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 7, characterized in that: In step S2, the pH value during mixing is controlled at 6.5-7.5, and microbial activator is added in three equal portions, accounting for 0.1-0.3% of the total weight of the microbial agent, during the mixing process.

9. The method for preparing a sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 7, characterized in that: In step S5, the segmented fermentation process is divided into three stages: the first stage ferments at 30-33℃ for 18-24 hours, the second stage ferments at 33-36℃ for 18-24 hours, and the third stage ferments at 36-40℃ for 12-18 hours; the temperature is increased at a rate of 0.5-1℃ / h when each stage is switched.

10. A method for preparing a sediment purification agent for in-situ degradation of river and lake bottom silt according to claim 7, characterized in that: In step S6, the drying air velocity is 1.0-2.0 m / s, the dried material is cooled at 15-25℃ for 20-40 minutes, and then sieved.

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