Method for preparing organic fertilizer from municipal sludge

Abstract

The invention discloses a method for preparing an organic fertilizer from municipal sludge, and belongs to the technical field of municipal sludge treatment and resource utilization. Municipal sludge is rich in nutrients, but is easy to cause the problems of uneven fermentation, poor stability of finished products and the like when being directly used for fertilizer preparation. According to the technical scheme, the method is characterized by comprising the following steps: airing municipal sludge with the moisture content of 80%-85% until the moisture content is 60%-65%, crushing, adding 11%-15% of modified coal ash powder, 12%-16% of banana cauloid residues and 3%-6% of bagasse powder into the pretreated sludge, and stirring; then inoculating 1%-2% of a compound microbial agent, wherein the microbial agent is composed of thermophilic sporotrichum and bacillus subtilis in a viable count ratio of 1: (1-2); and finally, stacking the inoculated material for aerobic fermentation, and cooling and screening after fermentation to obtain the organic fertilizer. Harmless treatment of the municipal sludge is realized, the product can be used as an organic fertilizer for agricultural production, and resource utilization of the sludge is realized.

Description

Technical Field

[0001] This invention relates to the field of municipal solid waste treatment and resource utilization technology. More specifically, this invention relates to a method for preparing organic fertilizer using municipal sewage sludge. Background Technology

[0002] With the acceleration of urbanization, the scale of municipal sewage treatment is constantly expanding, and the output of municipal sludge is also increasing dramatically. Municipal sludge contains a certain amount of organic matter, nitrogen, phosphorus, potassium, and other nutrients, possessing the potential to be converted into organic fertilizer. Therefore, using it for organic fertilizer preparation has become an important direction for sludge resource utilization. However, when municipal sludge is directly used for fertilizer preparation, it often faces many problems that urgently need to be solved. Among these, uneven fermentation and poor product stability are particularly prominent, seriously restricting the efficiency and safety of its resource utilization. When municipal sludge is first discharged, its moisture content is generally as high as 80%-85%. If such high-moisture sludge is directly fermented, the material is highly viscous and has extremely poor permeability, easily forming an anaerobic environment inside the pile, leading to uneven microbial activity. Some areas can ferment and heat up normally due to sufficient oxygen, while other areas are in a hypoxic state, resulting not only in low fermentation efficiency but also the potential production of malodorous gases such as hydrogen sulfide. Even with simple sun-drying, without scientific moisture control methods, it is difficult to stabilize the moisture content within a suitable range for fermentation. Furthermore, the fine sludge particles are prone to clumping after sun-drying, further exacerbating the uneven distribution of materials during the fermentation process. Summary of the Invention

[0003] Another objective of this invention is to provide a method for preparing organic fertilizer using municipal sewage sludge.

[0004] To achieve these objectives and other advantages according to the present invention, a method for preparing organic fertilizer using municipal sewage sludge is provided, comprising the following steps: Step 1: Spread municipal sludge with a moisture content of 80%-85% into a 15cm-20cm thick layer and let it air dry naturally until the moisture content of the municipal sludge drops to 60%-65%. During the drying period, turn the pile over every 6 hours. After drying, crush the sludge into particles with a diameter of 5mm-10mm to obtain pretreated sludge. Step 2: Add 11%-15% of modified fly ash powder, 12%-16% of banana pseudostem residue, and 3%-6% of sugarcane bagasse powder to the pretreated sludge by total mass. Stir at 110 r / min-130 r / min for 25 min-45 min to obtain a mixture. The modified fly ash powder is prepared by mixing fly ash powder with a particle size of 25μm-45μm with a calcium hydroxide solution with a mass concentration of 5%-10% at a mass ratio of 1:0.8-1.2. Stir at 60 r / min-100 r / min at 40℃-60℃ for 120 min-180 min, and then let stand for 12 h-24 h to obtain a mixed slurry. Separate the solid and liquid components of the mixed slurry and dry it at 105℃-125℃ to constant weight to obtain modified fly ash powder. Step 3: Inoculate the mixture with a compound microbial agent. The inoculation amount of the compound microbial agent is 1%-2% of the total mass of the mixture. Stir to obtain the inoculated material. The compound microbial agent is composed of thermophilic laterosporium and Bacillus subtilis. The ratio of viable bacteria of thermophilic laterosporium to Bacillus subtilis is 1:1-2. Step 4: Pile the inoculated material into a fermentation pile for aerobic fermentation. After fermentation, spread the fermentation pile to a thickness of 5cm-8cm and leave it for 24 hours. Then, sieve it using a sieve with a mesh size of 3mm-6mm to obtain organic fertilizer.

[0005] Preferably, the compound microbial agent is added to the mixture and stirred at a speed of 60-80 r / min for 10-15 min. Then, 0.5%-1% of calcium carbonate powder (total mass of the mixture and the compound microbial agent) of the total mass of the system is added to the system and the stirring speed is increased to 120-150 r / min and maintained for 20-30 min to obtain the inoculated material.

[0006] Preferably, the calcium carbonate powder is pretreated before being added, specifically by adding 10%-15% of its mass of sodium humate solution to the calcium carbonate powder and mixing and soaking for 5-15 minutes, and then drying at 20℃-40℃ until the moisture content is less than 5% to obtain pretreated calcium carbonate powder, wherein the mass concentration of sodium humate solution is 3%-5%.

[0007] Preferably, the sodium humate solution is prepared by dissolving sodium humate in water to prepare a first solution with a mass concentration of 3%-5%, then adding sodium alginate equivalent to 20%-30% of the mass of sodium humate to the first solution, stirring, and finally adding a saturated calcium citrate solution equivalent to 1%-2% of the total volume of the first solution, stirring, and thus obtaining the sodium humate solution.

[0008] Preferably, in step four, the height of the fermentation pile is 1.0m-1.8m, and the aerobic fermentation method is as follows: The first stage begins after the stockpile is stacked. When the temperature at the center of the stockpile exceeds 65°C, the stockpile is turned over and dumped. The first stage is completed when the temperature at the center of the stockpile continues to drop and stabilizes below 50°C within 36 hours after the turning operation. In the second stage, after the first stage is completed, the pile is turned over and re-piled, and the height of the pile is reduced to 1 / 2 to 2 / 3 of the original height. It is then covered with a semi-permeable membrane and fermented until the overall color of the pile is dark brown and there is no ammonia odor. Every day, 0.8% of the pile mass of a compound biological enzyme preparation is sprayed onto the surface of the pile using a high-pressure sprayer. The compound biological enzyme preparation is composed of xylanase, cellulase and laccase in an enzyme activity unit ratio of 1:1.5:0.5. In the third stage, the semi-permeable membrane is removed, and the pile is spread to a thickness of 10-15cm. It is then aged in a ventilated environment at room temperature, and turned over every two days until the temperature difference between the pile and the ambient temperature stabilizes within ±5℃, thus obtaining the matured compost.

[0009] Preferably, during the first stage, the oxygen concentration at the center of the pile is monitored by an oxygen probe buried in the pile body. When the volume fraction of oxygen at the center of the pile body is less than 10%, the pile body is aerated by blowing air until the volume fraction of oxygen rises to more than 15%.

[0010] Preferably, the compound biological enzyme preparation is microencapsulated. The microencapsulation method is as follows: the enzyme solution of the compound biological enzyme preparation is used as the core material, and sodium alginate and chitosan are used as the wall material. The total mass of the wall material to the volume of the core material is 1:1-3 g / mL. The microencapsulation is carried out by sharp-pore coagulation bath method to prepare microcapsule particles with a particle size of 100-500μm. The mass ratio of sodium alginate to chitosan in the wall material is 1:1-1.5. Before use, the compound biological enzyme preparation is dispersed in an aqueous solution containing 0.1%-0.3% surfactant at a mass ratio of 1:10-20 to form a suspension before spraying.

[0011] Preferably, the surfactant is an environmentally friendly nonionic surfactant or a biosurfactant, wherein the environmentally friendly nonionic surfactant is an alkyl polysaccharide glycoside, and the biosurfactant is a sophorolipid.

[0012] Preferably, the semi-permeable membrane comprises a main membrane and a humidity regulating layer disposed inside the main membrane. The main membrane is a polypropylene microporous breathable membrane with a moisture permeability of not less than 2000 g / (m²). 2 • 24h), with an average pore size of 0.1-10 μm, and a humidity regulating layer with a basis weight of 40-80 g / m³. 2The non-woven fabric is soaked in a buffer solution with a pH of 6.5-7.5 until the moisture content is 150%-200% before covering. First, the wetted humidity conditioning layer is brought into contact with the surface of the stack, and then the main coating is placed on top of it.

[0013] Preferably, the buffer solution is a disodium hydrogen phosphate-sodium dihydrogen phosphate buffer or a sodium carbonate-sodium bicarbonate buffer.

[0014] The present invention has at least the following beneficial effects: First, the preparation method of this invention effectively solves the problems of anaerobic environment and uneven fermentation caused by direct fermentation of high-moisture sludge, transforming municipal solid waste into usable organic fertilizer, significantly improving the efficiency of sludge resource utilization, and reducing the environmental pressure caused by solid waste disposal. Secondly, the present invention significantly enhances the functional efficiency of coal ash in the composting system by modifying it with calcium hydroxide. Calcium hydroxide reacts chemically with inorganic components such as aluminosilicates on the surface of coal ash, introducing a large number of active functional groups such as hydroxyl groups. The modification process optimizes the pore structure of the coal ash, increases its specific surface area, and improves its surface hydrophilicity and hydrophobicity, enabling it to form a more uniform mixing system with sludge and other organic additives. This effectively improves the overall air permeability and looseness of the material, avoids the formation of local anaerobic environments in the compost pile, and creates favorable physical conditions for the uniform distribution and efficient metabolism of functional microorganisms. This, in turn, accelerates the decomposition and transformation of organic substrates, promoting the quality and efficiency of the fermentation process.

[0015] Third, in this invention, calcium carbonate plays a crucial role in enhancing the transformation and stabilization of organic nutrients in the composting system. Sodium humate modification utilizes its high dispersibility and adsorption properties to break up the aggregation of calcium carbonate particles, ensuring uniform dispersion in the mixture and significantly improving the contact efficiency between calcium carbonate and microorganisms and organic substrates. Sodium alginate added to the sodium humate solution forms a three-dimensional gel network structure, encapsulating the sodium humate-modified calcium carbonate and enabling the slow release of active ingredients. Calcium citrate forms a coordination complex system with sodium alginate and sodium humate, further enhancing the stability of the encapsulation structure and slowing the release rate of calcium and the active ingredients in sodium humate. This synergistic system of "calcium carbonate - sodium humate - sodium alginate + calcium citrate" ensures that the mineral supply function of calcium carbonate is continuous and efficient, avoiding premature decay of the peak effect, while promoting the transformation of organic nutrients into a stable humic form, significantly improving the nutrient retention capacity and composting quality of organic fertilizer.

[0016] Fourth, the present invention utilizes a phased fermentation process to dynamically adjust conditions according to the core needs of composting at different stages. The first stage uses a high-temperature environment to kill harmful microorganisms and initially decompose easily degradable organic matter. The second stage creates a mild and stable degradation environment. The third stage uses ventilation and aging to stabilize the quality of the finished product, providing an optimal environment for the action of functional microorganisms and enzymes. The humidity regulating layer of the double-layer semi-permeable membrane can maintain a suitable moisture content in the compost pile through buffer wetting. The main membrane ensures gas exchange while isolating external environmental interference, effectively avoiding drastic fluctuations in temperature and humidity in the compost pile, and providing a stable physicochemical environment for enzyme activity and microbial metabolism. After microencapsulation, the sodium alginate-chitosan wall material of the composite bio-enzyme can isolate the enzyme activity from adverse factors such as high temperature and acid / alkali, achieving slow release and continuous action of the enzyme. Through the synergistic effect of these three factors, the staged fermentation provides a precisely matched environmental window for the release rhythm of microencapsulated enzymes, the semi-permeable membrane provides a stable environmental foundation for the efficient action of enzymes, and microencapsulation extends the action cycle of enzymes, enabling biological enzymes to continuously and efficiently decompose recalcitrant organic matter in a suitable environment. At the same time, the staged turning and aeration control further accelerate the transformation and accumulation of organic matter, significantly shorten the fermentation cycle, improve the organic matter content and stability of organic fertilizer, and ensure the safety of the product for plant growth.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0019] It should be understood that the following embodiments are only used to further illustrate and demonstrate the present invention, and are not intended to limit the scope of protection of the present invention. Appropriate modifications and implementations can be made within the scope defined by the claims of the present invention.

[0020] <Example 1> A method for preparing organic fertilizer using municipal sewage sludge includes the following steps: Step 1: Spread municipal sludge with a moisture content of 82%-85% into a 16cm-18cm thick layer and allow it to air dry naturally until the moisture content of the municipal sludge drops to 62%-64%. During the drying period, turn the pile over every 6 hours (a tracked turner can be used to turn the pile over every 6 hours during the drying period). After drying, crush the sludge to a particle size of 7mm-10mm to obtain pretreated sludge. Step 2: Add 11% modified fly ash powder, 12% banana pseudostem residue, and 3% sugarcane bagasse powder (by total mass of the pretreated sludge) to the pretreated sludge, and stir at 110 r / min for 25 min to obtain a mixture. The modified fly ash powder is prepared by mixing fly ash powder with a particle size of 30μm-35μm with a 5% calcium hydroxide solution at a mass ratio of 1:0.8, stirring at 60 r / min for 120 min at 40℃, and then letting it stand for 12 h to obtain a mixed slurry. Separate the solid and liquid components of the mixed slurry and dry it at 105℃ to constant weight to obtain modified fly ash powder. Step 3: Inoculate the mixture with a compound microbial agent. The inoculation amount of the compound microbial agent is 1% of the total mass of the mixture. Stir to obtain the inoculated material. The compound microbial agent is composed of thermophilic laterosporium and Bacillus subtilis. The ratio of viable bacteria of thermophilic laterosporium to Bacillus subtilis is 1:1. Step 4: Pile the inoculated material into a fermentation pile for aerobic fermentation. After fermentation, spread the fermentation pile to a thickness of 6cm-8cm and leave it for 24 hours. Then, sieve it using a 5mm mesh screen to obtain organic fertilizer.

[0021] Add the compound microbial agent to the mixture and mix at a stirring speed of 60 for 10 minutes. Then add 0.5% calcium carbonate powder of the total mass of the system and increase the stirring speed to 120 r / min and maintain it for 20 minutes to obtain the inoculated material.

[0022] Before adding calcium carbonate powder, it is pretreated by adding 10% sodium humate solution of its mass to calcium carbonate powder and mixing and soaking for 5 minutes. Then, it is dried at 20°C until the moisture content is less than 5% to obtain pretreated calcium carbonate powder. The mass concentration of sodium humate solution is 3%.

[0023] The preparation method of sodium humate solution is as follows: First, dissolve sodium humate in water to prepare a first solution with a mass concentration of 3%. Then, add sodium alginate equivalent to 20% of the mass of sodium humate to the first solution and stir. Finally, add calcium citrate saturated solution equivalent to 1% of the total volume of the first solution and stir to obtain sodium humate solution.

[0024] In step four, the height of the fermentation pile is 1.0m-1.3m, and the aerobic fermentation method is as follows: The first stage begins after the stockpile is stacked. When the temperature at the center of the stockpile exceeds 65°C, the stockpile is turned over and dumped. The first stage is completed when the temperature at the center of the stockpile continues to drop and stabilizes below 50°C within 36 hours after the turning operation. In the second stage, after the first stage is completed, the pile is turned over and re-piled, and the height of the pile is reduced to 1 / 2 to 2 / 3 of the original height. It is then covered with a semi-permeable membrane and fermented until the overall color of the pile is dark brown and there is no ammonia odor. Every day, 0.8% of the pile mass of a compound biological enzyme preparation is sprayed onto the surface of the pile using a high-pressure sprayer. The compound biological enzyme preparation is composed of xylanase, cellulase and laccase in an enzyme activity unit ratio of 1:1.5:0.5. In the third stage, the semi-permeable membrane is removed, and the pile is spread to a thickness of 10-15cm. It is then aged in a ventilated environment at room temperature, and turned over every two days until the temperature difference between the pile and the ambient temperature stabilizes within ±5℃, thus obtaining the matured compost. Spread the decomposed material to a thickness of 6cm-8cm and let it sit for 24 hours. Then, sieve it using a 5mm mesh screen to obtain organic fertilizer.

[0025] During the first stage, the oxygen concentration at the center of the pile is monitored by oxygen probes buried in the pile body. When the volume fraction of oxygen at the center of the pile body is less than 10%, the pile body is aerated by blowing air until the volume fraction of oxygen rises to more than 15%.

[0026] The compound biological enzyme preparation was microencapsulated using the following method: the enzyme solution of the compound biological enzyme preparation was used as the core material, and sodium alginate and chitosan were used as the wall material. The total mass of the wall material to the volume of the core material was 1:1 g / mL. The microencapsulation was carried out using the sharp-pore-coagulation bath method to prepare microcapsule particles with a particle size of 100-150 μm. The mass ratio of sodium alginate to chitosan in the wall material was 1:1. Before use, the compound biological enzyme preparation is dispersed in an aqueous solution containing 0.1% surfactant at a mass ratio of 1:10 to form a suspension before spraying.

[0027] The surfactant is an environmentally friendly nonionic surfactant, and the environmentally friendly nonionic surfactant is an alkyl polysaccharide.

[0028] The semi-permeable membrane comprises a main membrane and a humidity regulating layer disposed inside the main membrane. The main membrane is a polypropylene microporous breathable membrane with a moisture permeability of not less than 2000 g / (m²). 2 • 24h), with an average pore size of 0.1 μm, and a humidity regulating layer with a basis weight of 40 g / m³. 2 The nonwoven fabric was soaked in a buffer solution with a pH of 6.5 until the moisture content reached 150% before covering. First, the wetted humidity conditioning layer is brought into contact with the surface of the stack, and then the main coating is placed on top of it.

[0029] The buffer solution is a disodium hydrogen phosphate-sodium dihydrogen phosphate buffer.

[0030] <Example 2> A method for preparing organic fertilizer using municipal sewage sludge includes the following steps: Step 1: Spread municipal sludge with a moisture content of 82%-85% into a 16cm-18cm thick layer and allow it to air dry naturally until the moisture content of the municipal sludge drops to 62%-64%. During the drying period, turn the pile over every 6 hours (a tracked turner can be used to turn the pile over every 6 hours during the drying period). After drying, crush the sludge to a particle size of 7mm-10mm to obtain pretreated sludge. Step 2: Add 13% modified fly ash powder, 14% banana pseudostem residue, and 5% sugarcane bagasse powder (by total mass of the pretreated sludge) to the pretreated sludge, and stir at 120 r / min for 30 min to obtain a mixture. The modified fly ash powder is prepared by mixing fly ash powder with a particle size of 30μm-35μm with a 7% calcium hydroxide solution at a mass ratio of 1:1, stirring at 80 r / min for 150 min at 50℃, and then letting it stand for 18 h to obtain a mixed slurry. Separate the solid and liquid components of the mixed slurry and dry it at 115℃ to constant weight to obtain modified fly ash powder. Step 3: Inoculate the mixture with a compound microbial agent. The inoculation amount of the compound microbial agent is 1.5% of the total mass of the mixture. Stir to obtain the inoculated material. The compound microbial agent is composed of thermophilic laterosporium and Bacillus subtilis. The ratio of viable bacteria of thermophilic laterosporium to Bacillus subtilis is 1:1-2. Step 4: Pile the inoculated material into a fermentation pile for aerobic fermentation. After fermentation, spread the fermentation pile to a thickness of 6cm-8cm and leave it for 24 hours. Then, sieve it using a 5mm mesh screen to obtain organic fertilizer.

[0031] The compound microbial agent was added to the mixture and stirred at 70 r / min for 12 min. Then, 0.7% calcium carbonate powder of the total mass of the system was added to the system and the stirring speed was increased to 135 r / min and maintained for 25 min to obtain the inoculated material.

[0032] Before adding calcium carbonate powder, it is pretreated by adding 13% sodium humate solution by mass to the calcium carbonate powder and mixing and soaking for 10 minutes. Then, it is dried at 30°C until the moisture content is less than 5% to obtain pretreated calcium carbonate powder. The mass concentration of sodium humate solution is 4%.

[0033] The preparation method of sodium humate solution is as follows: First, dissolve sodium humate in water to prepare a first solution with a mass concentration of 4%. Then, add sodium alginate equivalent to 25% of the mass of sodium humate to the first solution and stir. Finally, add calcium citrate saturated solution equivalent to 1.5% of the total volume of the first solution and stir to obtain sodium humate solution.

[0034] In step four, the height of the fermentation pile is 1.3m-1.5m, and the aerobic fermentation method is as follows: The first stage begins after the stockpile is stacked. When the temperature at the center of the stockpile exceeds 65°C, the stockpile is turned over and dumped. The first stage is completed when the temperature at the center of the stockpile continues to drop and stabilizes below 50°C within 36 hours after the turning operation. In the second stage, after the first stage is completed, the pile is turned over and re-piled, and the height of the pile is reduced to 1 / 2 to 2 / 3 of the original height. It is then covered with a semi-permeable membrane and fermented until the overall color of the pile is dark brown and there is no ammonia odor. Every day, 0.8% of the pile mass of a compound biological enzyme preparation is sprayed onto the surface of the pile using a high-pressure sprayer. The compound biological enzyme preparation is composed of xylanase, cellulase and laccase in an enzyme activity unit ratio of 1:1.5:0.5. In the third stage, the semi-permeable membrane is removed, and the pile is spread to a thickness of 10-15cm. It is then aged in a ventilated environment at room temperature, and turned over every two days until the temperature difference between the pile and the ambient temperature stabilizes within ±5℃, thus obtaining the matured compost. Spread the decomposed material to a thickness of 6cm-8cm and let it sit for 24 hours. Then, sieve it using a 5mm mesh screen to obtain organic fertilizer.

[0035] During the first stage, the oxygen concentration at the center of the pile is monitored by oxygen probes buried in the pile body. When the volume fraction of oxygen at the center of the pile body is less than 10%, the pile body is aerated by blowing air until the volume fraction of oxygen rises to more than 15%.

[0036] The compound biological enzyme preparation was microencapsulated using the following method: the enzyme solution of the compound biological enzyme preparation was used as the core material, and sodium alginate and chitosan were used as the wall material. The total mass of the wall material to the volume of the core material was 1:2 g / mL. The microencapsulation was carried out using the sharp-pore-coagulation bath method to prepare microcapsule particles with a particle size of 230-280 μm. The mass ratio of sodium alginate to chitosan in the wall material was 1:1.2. Before use, the compound biological enzyme preparation is dispersed in an aqueous solution containing 0.2% surfactant at a mass ratio of 1:15 to form a suspension before spraying.

[0037] The surfactant is a biosurfactant, and the biosurfactant is sophorolipid.

[0038] The semi-permeable membrane comprises a main membrane and a humidity regulating layer disposed inside the main membrane. The main membrane is a polypropylene microporous breathable membrane with a moisture permeability of not less than 2000 g / (m²). 2 • 24h), with an average pore size of 5 μm, and a humidity regulating layer with a basis weight of 60 g / m 2The nonwoven fabric was soaked in a buffer solution with a pH of 6.5 until the moisture content reached 180% before covering. First, the wetted humidity conditioning layer is brought into contact with the surface of the stack, and then the main coating is placed on top of it.

[0039] The buffer solution is a sodium carbonate-sodium bicarbonate buffer solution.

[0040] <Example 3> A method for preparing organic fertilizer using municipal sewage sludge includes the following steps: Step 1: Spread municipal sludge with a moisture content of 82%-85% into a 16cm-18cm thick layer and allow it to air dry naturally until the moisture content of the municipal sludge drops to 62%-64%. During the drying period, turn the pile over every 6 hours (a tracked turner can be used to turn the pile over every 6 hours during the drying period). After drying, crush the sludge to a particle size of 7mm-10mm to obtain pretreated sludge. Step 2: Add 15% modified fly ash powder, 16% banana pseudostem residue, and 6% sugarcane bagasse powder (by total mass of the pretreated sludge) to the pretreated sludge, and stir at 130 r / min for 45 min to obtain a mixture. The modified fly ash powder is prepared by mixing 30μm-35μm fly ash powder with a 10% calcium hydroxide solution at a mass ratio of 1:1.2, stirring at 100 r / min for 180 min at 60℃, and then letting it stand for 24 h to obtain a mixed slurry. Separate the solid and liquid components of the mixed slurry and dry it at 125℃ to constant weight to obtain modified fly ash powder. Step 3: Inoculate the mixture with a compound microbial agent. The inoculation amount of the compound microbial agent is 2% of the total mass of the mixture. Stir to obtain the inoculated material. The compound microbial agent is composed of thermophilic laterosporium and Bacillus subtilis. The ratio of viable bacteria of thermophilic laterosporium to Bacillus subtilis is 1:2. Step 4: Pile the inoculated material into a fermentation pile for aerobic fermentation. After fermentation, spread the fermentation pile to a thickness of 6cm-8cm and leave it for 24 hours. Then, sieve it using a 5mm mesh screen to obtain organic fertilizer.

[0041] The compound microbial agent was added to the mixture and stirred at 80 r / min for 15 min. Then, 1% calcium carbonate powder of the total mass of the system was added to the system and the stirring speed was increased to 150 r / min and maintained for 30 min to obtain the inoculated material.

[0042] Before adding calcium carbonate powder, it is pretreated by adding 15% sodium humate solution of its mass to calcium carbonate powder and mixing and soaking for 15 minutes. Then, it is dried at 40°C until the moisture content is less than 5% to obtain pretreated calcium carbonate powder. The mass concentration of sodium humate solution is 5%.

[0043] The preparation method of sodium humate solution is as follows: First, dissolve sodium humate in water to prepare a first solution with a mass concentration of 5%. Then, add sodium alginate equivalent to 30% of the mass of sodium humate to the first solution and stir. Finally, add calcium citrate saturated solution equivalent to 2% of the total volume of the first solution and stir to obtain sodium humate solution.

[0044] In step four, the height of the fermentation pile is 1.7m-1.8m, and the aerobic fermentation method is as follows: The first stage begins after the stockpile is stacked. When the temperature at the center of the stockpile exceeds 65°C, the stockpile is turned over and dumped. The first stage is completed when the temperature at the center of the stockpile continues to drop and stabilizes below 50°C within 36 hours after the turning operation. In the second stage, after the first stage is completed, the pile is turned over and re-piled, and the height of the pile is reduced to 1 / 2 to 2 / 3 of the original height. It is then covered with a semi-permeable membrane and fermented until the overall color of the pile is dark brown and there is no ammonia odor. Every day, 0.8% of the pile mass of a compound biological enzyme preparation is sprayed onto the surface of the pile using a high-pressure sprayer. The compound biological enzyme preparation is composed of xylanase, cellulase and laccase in an enzyme activity unit ratio of 1:1.5:0.5. In the third stage, the semi-permeable membrane is removed, and the pile is spread to a thickness of 10-15cm. It is then aged in a ventilated environment at room temperature, and turned over every two days until the temperature difference between the pile and the ambient temperature stabilizes within ±5℃, thus obtaining the matured compost. Spread the decomposed material to a thickness of 6cm-8cm and let it sit for 24 hours. Then, sieve it using a 5mm mesh screen to obtain organic fertilizer.

[0045] During the first stage, the oxygen concentration at the center of the pile is monitored by oxygen probes buried in the pile body. When the volume fraction of oxygen at the center of the pile body is less than 10%, the pile body is aerated by blowing air until the volume fraction of oxygen rises to more than 15%.

[0046] The compound biological enzyme preparation was microencapsulated using the following method: the enzyme solution of the compound biological enzyme preparation was used as the core material, and sodium alginate and chitosan were used as the wall material. The total mass of the wall material to the volume of the core material was 1:3 g / mL. The microencapsulation was carried out using the sharp-pore-coagulation bath method to prepare microcapsule particles with a particle size of 450-500 μm. The mass ratio of sodium alginate to chitosan in the wall material was 1:1.5. Before use, the compound biological enzyme preparation is dispersed in an aqueous solution containing 0.3% surfactant at a mass ratio of 1:20 to form a suspension before spraying.

[0047] The surfactant is a biosurfactant, and the biosurfactant is sophorolipid.

[0048] The semi-permeable membrane comprises a main membrane and a humidity regulating layer disposed inside the main membrane. The main membrane is a polypropylene microporous breathable membrane with a moisture permeability of not less than 2000 g / (m²). 2 • 24h), with an average pore size of 10 μm, and a humidity regulating layer with a basis weight of 80 g / m 2 The nonwoven fabric was soaked in a buffer solution with a pH of 7.5 until the moisture content reached 200% before covering. First, the wetted humidity conditioning layer is brought into contact with the surface of the stack, and then the main coating is placed on top of it.

[0049] The buffer solution is either disodium hydrogen phosphate-sodium dihydrogen phosphate buffer or sodium carbonate-sodium bicarbonate buffer.

[0050] <Example 4> A method for preparing organic fertilizer using municipal sewage sludge includes the following steps: Step 1: Spread municipal sludge with a moisture content of 82%-85% into a 16cm-18cm thick layer and allow it to air dry naturally until the moisture content of the municipal sludge drops to 62%-64%. During the drying period, turn the pile over every 6 hours (a tracked turner can be used to turn the pile over every 6 hours during the drying period). After drying, crush the sludge to a particle size of 7mm-10mm to obtain pretreated sludge. Step 2: Add 13% modified fly ash powder, 14% banana pseudostem residue, and 5% sugarcane bagasse powder (by total mass of the pretreated sludge) to the pretreated sludge, and stir at 120 r / min for 30 min to obtain a mixture. The modified fly ash powder is prepared by mixing fly ash powder with a particle size of 30μm-35μm with a 7% calcium hydroxide solution at a mass ratio of 1:1, stirring at 80 r / min for 150 min at 50℃, and then letting it stand for 18 h to obtain a mixed slurry. Separate the solid and liquid components of the mixed slurry and dry it at 115℃ to constant weight to obtain modified fly ash powder. Step 3: Inoculate the mixture with a compound microbial agent. The inoculation amount of the compound microbial agent is 1.5% of the total mass of the mixture. Stir to obtain the inoculated material. The compound microbial agent is composed of thermophilic laterosporium and Bacillus subtilis. The ratio of viable bacteria of thermophilic laterosporium to Bacillus subtilis is 1:1-2. Step 4: Pile the inoculum material into a fermentation pile. Starting from the completion of the pile, turn it over every 5 days until the temperature at the center of the pile stabilizes within ±5℃ of the ambient temperature for 3 consecutive days to obtain the decomposed material. Pile the inoculum material into a fermentation pile for aerobic fermentation. After fermentation, spread the fermentation pile to a thickness of 5cm-8cm and let it stand for 24 hours. Then, sieve it using a sieve with a mesh size of 3mm-6mm to obtain organic fertilizer.

[0051] <Example 5> Organic fertilizer was prepared using the method described in Example 2, with the following difference: In step four, the inoculum material was piled into a fermentation pile. Starting from the completion of the pile, it was turned over every 5 days until the center temperature of the pile remained stable within ±5°C of the ambient temperature for 3 consecutive days, resulting in a mature compost. The inoculum material was then piled into a fermentation pile for aerobic fermentation. After fermentation, the fermentation pile was spread to a thickness of 5-8 cm and left to stand for 24 hours. Then, it was sieved using a sieve with a mesh size of 3-6 mm to obtain the organic fertilizer. This method did not involve staged processing, microencapsulation, or the use of a two-layer semi-permeable membrane.

[0052] <Example 6> Organic fertilizer was prepared using the method of Example 2, except that the semi-permeable membrane in the second stage was a single-layer polypropylene microporous breathable membrane, and the composite biological enzyme preparation was a direct mixture of xylanase, cellulase and laccase.

[0053] <Example 7> Organic fertilizer was prepared using the method of Example 2, involving multi-stage fermentation, and the semi-permeable membrane used was the same as in Example 2. The difference was that the compound biological enzyme preparation was a direct mixture of xylanase, cellulase and laccase.

[0054] <Example 8> Organic fertilizer was prepared using the method in Example 2, involving multi-stage fermentation and microencapsulation of the compound biological enzyme preparation. The difference was that the semi-permeable membrane in the second stage was a single-layer polypropylene microporous breathable membrane.

[0055] <Example 9> Organic fertilizer was prepared using the method of Example 2, except that no calcium carbonate powder was added and the calcium carbonate powder was not treated.

[0056] <Example 10> Organic fertilizer was prepared using the method in Example 2, with the addition of calcium carbonate powder, except that the calcium carbonate powder was not pretreated.

[0057] <Comparative Example 1> This comparative example aims to use a conventional sludge composting process, wherein the difference is step two, and the remaining steps are the same as in Example 4. Step two is: adding 13% of the total mass of the pretreated sludge with unmodified fly ash powder to the pretreated sludge and stirring at 120 r / min for 30 min to obtain a mixture.

[0058] <Experimental Characterization> 1. Organic matter and fermentation time The total fermentation cycle of Examples 2, 4-10 and Comparative Example 1 was statistically analyzed, from the start of composting to the time to obtain the mature compost. The organic matter content in each group of organic fertilizer products was determined by potassium dichromate oxidation method (external heating method); The total fermentation time and organic matter content are shown in Table 1. Table 1 shows the organic matter content and total fermentation time. Total fermentation time (days) Organic matter content (%) Example 2 21 48.7 Example 4 50 41.3 Example 5 39 44.2 Example 6 35 44.5 Example 7 32 46.2 Example 8 28 47.3 Example 9 45 42.7 Example 10 43 43.5 Comparative Example 1 61 38.5 Example 2 had the shortest total fermentation time (21 days) and the highest organic matter content (48.7%); Comparative Example 1 had the longest total fermentation time (61 days) and the lowest organic matter content (38.5%). Overall, the experimental group using optimized processes such as staged fermentation, microencapsulation of compound bio-enzymes, and double-layer semi-permeable membranes had a shorter fermentation cycle and higher organic matter content. Although the data from Examples 9 and 10 were similar, the pretreatment provided a more sustained slow-release and synergistic effect, which may be more important for the long-term stability of the finished product.

[0059] 2. Seed germination rate This study simulates the real-world environment after organic fertilizer is applied to the soil. By measuring the germination and growth of cucumber seeds in soil mixed with this product and comparing it with pure soil, the study directly reflects the safety of this product for plant growth. The higher the index, the more thoroughly the product is decomposed and the safer it is for the seeds. Samples to be tested: Organic fertilizer products prepared in Examples 2, 4, 1, 5, and 9; Test seeds: Plump, uniform cucumber seeds Each experimental group was prepared according to the following experimental method: organic fertilizer product: soil = 1:9 by volume. The soil moisture content was adjusted to 60-70% of the maximum water holding capacity. Cucumber seeds were then planted in the soil of each group. The culture temperature was 27±1℃. After 4 days of culture, the average germination rate and average root length of each experimental group were counted. The results are shown in Table 2. Table 2 shows the average germination rate and average root length of cucumber seeds. experimental group Average germination rate (%) Average root length (mm) Example 2 95.3 65.2 Example 4 85.0 44.7 Example 5 89.7 51.8 Example 9 86.5 47.6 Comparative Example 1 77.3 19.5 The cucumber seeds in Example 2 exhibited the highest average germination rate (95.3%) and average root length (65.2 mm), while those in Comparative Example 1 showed the lowest germination rate (77.3%) and root length (19.5 mm). The organic fertilizer prepared using the optimized process demonstrates superior safety for plant growth and exhibits better seed germination and overall growth.

[0060] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preparing organic fertilizer using municipal sewage sludge, characterized in that, Includes the following steps: Step 1: Spread municipal sludge with a moisture content of 80%-85% into a 15cm-20cm thick layer and let it air dry naturally until the moisture content of the municipal sludge drops to 60%-65%. During the drying period, turn the pile over every 6 hours. After drying, crush the sludge to a particle size of 5mm-10mm to obtain pretreated sludge. Step 2: Add 11%-15% of modified fly ash powder, 12%-16% of banana pseudostem residue, and 3%-6% of sugarcane bagasse powder to the pretreated sludge by total mass. Stir at 110 r / min-130 r / min for 25 min-45 min to obtain a mixture. The modified fly ash powder is prepared by mixing fly ash powder with a particle size of 25μm-45μm with a calcium hydroxide solution with a mass concentration of 5%-10% at a mass ratio of 1:0.8-1.

2. Stir at 60 r / min-100 r / min at 40℃-60℃ for 120 min-180 min, and then let stand for 12 h-24 h to obtain a mixed slurry. Separate the solid and liquid components of the mixed slurry and dry it at 105℃-125℃ to constant weight to obtain modified fly ash powder. Step 3: Inoculate the mixture with a compound microbial agent. The inoculation amount of the compound microbial agent is 1%-2% of the total mass of the mixture. Stir to obtain the inoculated material. The compound microbial agent is composed of thermophilic laterosporium and Bacillus subtilis. The ratio of viable bacteria of thermophilic laterosporium to Bacillus subtilis is 1:1-2. Step 4: Pile the inoculated material into a fermentation pile for aerobic fermentation. After fermentation, spread the fermentation pile to a thickness of 5cm-8cm and leave it for 24 hours. Then, sieve it using a sieve with a mesh size of 3mm-6mm to obtain organic fertilizer.

2. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 1, characterized in that, Add the compound microbial agent to the mixture and stir at 60-80 r / min for 10-15 min. Then add 0.5%-1% calcium carbonate powder of the total mass of the system and increase the stirring speed to 120-150 r / min and maintain it for 20-30 min to obtain the inoculated material.

3. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 2, characterized in that, Before adding calcium carbonate powder, it is pretreated by adding 10%-15% sodium humate solution to the calcium carbonate powder and mixing and soaking for 5-15 minutes. Then, it is dried at 20℃-40℃ until the moisture content is less than 5% to obtain pretreated calcium carbonate powder. The mass concentration of sodium humate solution is 3%-5%.

4. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 3, characterized in that, The preparation method of sodium humate solution is as follows: First, dissolve sodium humate in water to prepare a first solution with a mass concentration of 3%-5%. Then, add sodium alginate equivalent to 20%-30% of the mass of sodium humate to the first solution and stir. Finally, add calcium citrate saturated solution equivalent to 1%-2% of the total volume of the first solution and stir to obtain sodium humate solution.

5. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 1, characterized in that, In step four, the height of the fermentation pile is 1.0m-1.8m, and the aerobic fermentation method is as follows: The first stage begins after the stockpile is stacked. When the temperature at the center of the stockpile exceeds 65°C, the stockpile is turned over and dumped. The first stage is completed when the temperature at the center of the stockpile continues to drop and stabilizes below 50°C within 36 hours after the turning operation. In the second stage, after the first stage is completed, the pile is turned over and re-piled, and the height of the pile is reduced to 1 / 2 to 2 / 3 of the original height. It is then covered with a semi-permeable membrane and fermented until the overall color of the pile is dark brown and there is no ammonia odor. Every day, 0.8% of the pile mass of a compound biological enzyme preparation is sprayed onto the surface of the pile using a high-pressure sprayer. The compound biological enzyme preparation is composed of xylanase, cellulase and laccase in an enzyme activity unit ratio of 1:1.5:0.

5. In the third stage, the semi-permeable membrane is removed, and the pile is spread to a thickness of 10-15cm. It is then aged in a ventilated environment at room temperature, and turned over every two days until the temperature difference between the pile and the ambient temperature stabilizes within ±5℃, thus obtaining the matured compost.

6. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 5, characterized in that, During the first stage, the oxygen concentration at the center of the pile is monitored by oxygen probes buried in the pile body. When the volume fraction of oxygen at the center of the pile body is less than 10%, the pile body is aerated by blowing air until the volume fraction of oxygen rises to more than 15%.

7. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 5, characterized in that, The compound biological enzyme preparation was microencapsulated using the following method: the enzyme solution of the compound biological enzyme preparation was used as the core material, and sodium alginate and chitosan were used as the wall material. The total mass of the wall material to the volume of the core material was 1:1-3 g / mL. The microencapsulation was carried out using the sharp-pore-coagulation bath method to prepare microcapsule particles with a particle size of 100-500 μm. The mass ratio of sodium alginate to chitosan in the wall material was 1:1-1.

5. Before use, the compound biological enzyme preparation is dispersed in an aqueous solution containing 0.1%-0.3% surfactant at a mass ratio of 1:10-20 to form a suspension before spraying.

8. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 7, characterized in that, The surfactant is an environmentally friendly nonionic surfactant or a biosurfactant. The environmentally friendly nonionic surfactant is an alkyl polysaccharide glycoside, and the biosurfactant is a sophorolipid.

9. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 5, characterized in that, The semi-permeable membrane comprises a main membrane and a humidity regulating layer disposed inside the main membrane. The main membrane is a polypropylene microporous breathable membrane with a moisture permeability of not less than 2000 g / (m²). 2 • 24h), with an average pore size of 0.1-10 μm, and a humidity regulating layer with a basis weight of 40-80 g / m³. 2 The non-woven fabric is soaked in a buffer solution with a pH of 6.5-7.5 until the moisture content is 150%-200% before covering. First, the wetted humidity conditioning layer is brought into contact with the surface of the stack, and then the main coating is placed on top of it.

10. The method for preparing organic fertilizer from municipal sewage sludge as described in claim 9, characterized in that, The buffer solution is either disodium hydrogen phosphate-sodium dihydrogen phosphate buffer or sodium carbonate-sodium bicarbonate buffer.