Method for preparing organic fertilizer through cooperation of pre-activated coal gangue and municipal sludge reinforced aerobic composting as well as product and application thereof

Abstract

The invention provides a method for preparing an organic fertilizer through cooperation of pre-activated coal gangue and municipal sludge reinforced aerobic composting as well as a product and application of the organic fertilizer. The method comprises the following steps: firstly, crushing coal gangue to obtain coal gangue powder; activating the surface structure of the coal gangue and partially decomposing macromolecular organic matters by using an advanced oxidation system solution; the coal gangue powder subjected to advanced oxidation activation is subjected to low-temperature activation in an alkaline urea solution, so that interlayer silicon-aluminum structures are dissociated, and dissolution of organic matter is promoted; finally, mixing the activated coal gangue with municipal sludge according to a certain proportion, and inoculating the compounded thermophilic microbial flora in stages for aerobic composting fermentation; and fermenting for 28-35 days to obtain an organic fertilizer product which is rich in nutrient, safe and reliable. The coal gangue organic fertilizer prepared through the method has high fertilizer efficiency, and meanwhile heavy metal passivation and effective degradation of benzo [a] pyrene are achieved.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue resource utilization technology, specifically relating to a method for preparing organic fertilizer by pre-activated coal gangue in conjunction with municipal sludge for enhanced aerobic composting, as well as its products and applications. Background Technology

[0002] my country is the world's largest coal producer, generating and accumulating massive amounts of coal gangue, which has become one of the largest sources of industrial solid waste in my country in terms of both emissions and accumulation. Long-term open-air stockpiling of coal gangue not only occupies vast amounts of land resources but also easily leads to problems such as heavy metal leaching, dust dispersion, and spontaneous combustion of gangue piles, posing a serious threat to the surrounding ecological environment. Although the comprehensive utilization rate of coal gangue has been increasing year by year under the impetus of relevant policies, compared with its enormous production and stockpile, my country's overall coal gangue processing capacity remains significantly insufficient. This is especially true in the central and western regions, where the vast land area, sparse population, weak economic foundation, limited local disposal capacity, and high transportation costs present even more severe challenges to coal gangue disposal. Therefore, there is an urgent need to develop a new approach to the resource utilization of coal gangue that is highly efficient, environmentally friendly, and economically feasible.

[0003] my country's central and western regions are rich in coal resources but have fragile ecosystems. Arid and semi-arid climates exacerbate the ecological damage caused by coal mining. Simultaneously, the region suffers from widespread soil desertification, salinization, and nutrient depletion, severely hindering local ecological restoration and agricultural development. Notably, there is a high degree of spatial overlap between my country's major coal gangue producing areas and the distribution of degraded and sandy soils. Some coal gangue itself has a high organic matter content (approximately 20-40%) and is rich in inorganic nutrients such as silicon, aluminum, and iron. Its elemental composition, chemical properties, and mineral structure are highly similar to those of soil. With appropriate activation treatment, this type of coal gangue has the potential to serve as an organic fertilizer substrate, thereby improving soil structure and enhancing soil fertility. Therefore, if coal gangue can be processed into high-quality organic fertilizer for the restoration of my country's vast potential usable land resources, it will not only effectively alleviate the pressure of land resource scarcity but also provide a low-cost, high-efficiency outlet for the large stockpiles of coal gangue.

[0004] In existing technologies, coal gangue land application technologies are mainly divided into two types. One type involves mechanically crushing coal gangue into powder and applying it directly to the land. Although this method is simple and low-cost, the internal structure of coal gangue is dense, and organic matter and silica-alumina minerals are highly combined. Coal gangue that has not undergone activation treatment has a strong inert surface, making it difficult to release the organic matter and nutrients required by plants. In addition, coal gangue particles have poor water and fertilizer retention capacity in the soil. Furthermore, the coal gangue itself lacks essential plant nutrients such as nitrogen, phosphorus, and potassium, resulting in a serious lack of nutrient availability after application and a limited actual promoting effect on soil improvement. Another approach involves directly mixing crushed coal gangue with organic solid waste, or applying it after natural aerobic composting. While this method can partially degrade organic matter and mix the materials, thus mitigating the lack of nutrient variety when coal gangue is used alone, the stable mineral phase structure of the crushed coal gangue results in poor interfacial reactivity between minerals and organic matter, leading to weak organic carbon release. This ultimately results in low composting efficiency and insufficient fertilizer maturity, failing to meet the needs of soil remediation and crop growth. Furthermore, neither of these existing technologies effectively treats pollutants in coal gangue. It not only suffers from high activity of various heavy metals but also from high concentrations of polycyclic aromatic hydrocarbons (such as benzo[a]pyrene), thiophene, and pyridine. These pollutants are prone to migration and accumulation after application to the land, posing potential risks to the surrounding ecological environment and human health, severely limiting the safe application of coal gangue in land use.

[0005] In summary, existing coal gangue land utilization technologies generally suffer from core problems such as insufficient activation of organic matter and mineral nutrients, low humification efficiency, and incomplete pollutant treatment. To address these shortcomings, this invention, considering the material composition and structural characteristics of coal gangue, proposes a resource utilization technology based on coal gangue activation and co-composting of organic solid waste. Through innovative processing, it achieves efficient activation of the fertilizer components in coal gangue, deep passivation of pollutants, and significant enhancement of the humification process. In particular, it effectively controls recalcitrant organic pollutants such as benzo[a]pyrene, providing a novel and feasible approach for the resource utilization of coal gangue. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sludge, as well as its products and applications. Specifically, it employs a multi-step activation and composite thermophilic microbial community-enhanced synergistic composting strategy to jointly prepare organic fertilizer from coal gangue and municipal sludge. This achieves efficient activation, enhanced humification, and pollutant reduction of coal gangue during the composting process, resulting in high-quality organic fertilizer with stable fertilizer efficacy and strictly controllable heavy metal and benzo[a]pyrene content. This effectively solves the problems of insufficient organic matter degradation, inefficient activation of minerals and organic matter, limited humification, and insufficient pollutant control in existing technologies during coal gangue composting.

[0007] To achieve the above objectives, this invention provides a method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sludge, comprising the following steps: Coal gangue pretreatment: The coal gangue is crushed to a particle size of less than 50 mesh to obtain a specific surface area of ​​300-400 m². 2 / kg of coal gangue powder; Activation of advanced oxidation system: Coal gangue powder is stirred and reacted in an advanced oxidation system solution at 30-50℃ for initial activation treatment. After solid-liquid separation, the solid material is collected, which is the initially activated coal gangue powder. Low-temperature alkaline urea solution activation: The primary activated coal gangue powder is mixed with alkaline urea solution in a low-temperature environment, stirred and reacted, and the precipitate is obtained after solid-liquid separation, which is the secondary activated coal gangue powder. Preparation of compound thermophilic microbial culture: thermophilic fungi, thermophilic actinomycetes, thermophilic Bacillus and thermophilic potassium-solubilizing bacteria are fermented and cultured, and the resulting active fermentation broths are compounded to obtain compound thermophilic microbial culture. Enhanced synergistic aerobic composting: After mixing secondary activated coal gangue powder with municipal sludge in a certain proportion, aerobic composting is carried out. At the end of the composting heating period and the middle of the thermophilic period, the prepared compound thermophilic microbial liquid is inoculated in batches. After 28-35 days of aerobic composting, coal gangue organic fertilizer can be obtained.

[0008] Preferably, in the coal gangue pretreatment step, the coal gangue has an organic matter content of 20-40% and a chemical composition including: SiO2 40-60%, Al2O3 5.0-20%, K2O 1.0-5.0%, Fe2O3 2.0-14%, SO3 0.8-6.1%, CaO 0.42-2.32%, MgO 0.18-2.41%, TiO2 0.90-4%, and P2O5 0.07-0.24%.

[0009] Preferably, in the activation step of the advanced oxidation system method, the advanced oxidation system solution includes one or more of the following: Fenton system, persulfate activation system, and alkaline activated hydrogen peroxide system; In this invention, through activation treatment with an advanced oxidation system, high oxidation potential oxidizing factors can be generated in situ on the surface of coal gangue powder, achieving chain breaking, hydroxylation and ring opening of macromolecular inert organic matter, thereby improving surface hydrophilicity and chemical activity; at the same time, the active sites of the silicon-aluminum framework are exposed, which helps subsequent microbial adhesion and mineral phase interlayer dissociation. In the Fenton system, hydrogen peroxide (H₂O₂) is used as the oxidant, and ferrous ions (Fe) are used as the active ingredient. 2+Ferrous sulfate (usually derived from ferrous sulfate, ferrous chloride, etc.) acts as a catalyst, and the two react under acidic to neutral conditions to produce hydroxyl radicals (·OH). The persulfate system uses persulfates (including permonosulfates, such as potassium permonosulfate; or perdisulfates, such as sodium persulfate, ammonium persulfate) as oxidants, which are activated by ferrous sulfate to produce sulfate radicals (SO4·). - The alkaline-activated hydrogen peroxide system is developed under alkaline conditions (pH=10-12) by adding alkaline substances (such as sodium hydroxide or potassium hydroxide) to decompose hydrogen peroxide (H2O2) and generate hydrogen peroxide anions (HOO). - Active substances such as ) More preferably, in the Fenton system, the mass ratio of hydrogen peroxide solution to ferrous sulfate is (5-8):1; most preferably, the mass concentration of the hydrogen peroxide solution is 30%. More preferably, in the persulfate system, the mass ratio of persulfate to ferrous sulfate is (1-5):1; More preferably, in the alkaline-activated hydrogen peroxide system, the mass ratio of hydrogen peroxide solution to alkaline substance is (1-2):1, ensuring that the pH of the reaction system is maintained in the range of 10-12; most preferably, the mass concentration of the hydrogen peroxide solution is 30%.

[0010] Preferably, in the activation step of the advanced oxidation system method, the solid-liquid mass ratio of the coal gangue powder to the advanced oxidation system solution is 1:(8-12).

[0011] Preferably, in the activation step of the advanced oxidation system method, the reaction temperature is 30-50℃, the stirring speed is 100-300 rpm, and the reaction time is 2-4 h.

[0012] Preferably, in the low-temperature alkaline urea solution activation step, the alkaline urea solution has a pH of 10-12 and is composed of alkaline substances, urea, and water. Based on the total mass of the alkaline urea solution, the content of alkaline substances is 2-5 wt%, the content of urea is 8-12 wt%, and the balance is water. More preferably, the alkaline substances include one or more of sodium hydroxide, potassium hydroxide, wood ash, alkali residue, and lime.

[0013] Preferably, in the low-temperature alkaline urea solution activation step, the solid-liquid mass ratio of the initially activated coal gangue powder to the alkaline urea solution is 1:(2-10).

[0014] Preferably, in the low-temperature alkaline urea solution activation step, the low-temperature environment is -15 to -5°C.

[0015] Preferably, in the low-temperature alkaline urea solution activation step, the stirring speed is 100-300 rpm and the stirring time is 2-4 hours.

[0016] This invention limits the reaction temperature to below zero degrees Celsius, so that the alkaline environment provided by the alkaline urea solution can, to a certain extent, disrupt the bonding of aluminosilicates and break the intramolecular and intermolecular hydrogen bonds of organic matter. At the same time, the stable hydrogen bond network formed by urea undergoes hydrogen bond substitution and interlayer expansion with the layered silicates of coal gangue, making the particle structure more porous and thus improving the soluble organic carbon content.

[0017] Preferably, in the step of preparing the compound thermophilic microbial inoculum, the thermophilic fungi include: *Thermophilus hygrophilus* and / or *Thermophilus hygrophilus*; wherein, *Thermophilus hygrophilus* ( Thermomyces lanuginosus Purchased from the China Center for Type Culture Collection, catalog number CCTCC AF 200043; *Thermophilus pyriformis* ( Myceliophthora thermophila Purchased from the China Center for Type Culture Collection, catalog number CCTCC AF 2012002.

[0018] Preferably, in the step of preparing the compound thermophilic microbial culture, the thermophilic actinomycetes include: *Saccharomyces viride* and / or *Saccharomyces cerevisiae*; wherein, *Saccharomyces viride* (… Saccharomonospora viridis Purchased from the China General Microbiological Culture Collection Center, catalog number CGMCC 4.1324; *Schizospora brownii* (… Thermobifida fusca Purchased from Beina Biotechnology Co., Ltd., item number BNCC 353960.

[0019] Preferably, in the step of preparing the compound thermophilic microbial culture, the thermophilic Bacillus includes: *Bacillus thermodenitrifyingus* (…). Geobacillus thermodenitrificans ) and / or Bacillus licheniformis ( Bacillus licheniformis In the step of preparing the compound thermophilic microbial culture, *Bacillus thermodenitrificationis* (…) Geobacillus thermodenitrificans Purchased from the China General Microbiological Culture Collection Center, catalog number CGMCC 1.8654; Bacillus licheniformis ( Bacillus licheniformis Purchased from the China Center for Type Culture Collection, catalog number CCTCC AB 91061.

[0020] Preferably, in the step of preparing the compound thermophilic microbial bacterial solution, the thermophilic potassium-solubilizing bacteria include: Bacillus mucilaginosus and / or Bacillus spp.; wherein, Bacillus mucilaginosus ( Bacillus mucilaginosus Purchased from the China Industrial Microbial Culture Collection Center, number CICC 21700; *Bacillus sphaeroides* ( Bacillus edaphicus Purchased from the China Center for Type Culture Collection, catalog number CCTCC M 200040.

[0021] Preferably, in the step of preparing the compound thermophilic microbial inoculum, the method for preparing the active fermentation broth of the thermophilic fungi is as follows: Preparation of thermophilic fungal suspension: Mix thermophilic fungi with deionized water at a concentration of 1 g / L, shake well, and prepare thermophilic fungal suspension; Preparation of liquid culture medium: Mix 20 g / L soluble starch, 4 g / L yeast extract, 3 g / L peptone, 1 g / L KH2PO4, 0.5 g / L MgSO4·7H2O, and 1 g / L CaCO3 with deionized water to prepare a liquid culture medium with a pH of 6.5-7.0. Autoclave at 121℃ for 20 min and then cool for later use. Fermentation culture: The prepared thermophilic fungal suspension is inoculated into the prepared liquid culture medium at an inoculum rate of 2-8% (v / v), and cultured at 55-60℃ with shaking at 150-200 r / min for 48 hours to obtain a cell concentration of 10. 8 -10 9 Fermentation broth containing thermophilic fungi at CFU / mL.

[0022] Preferably, in the step of preparing the compound thermophilic microbial inoculum, the method for preparing the active fermentation broth of the thermophilic bacteria is as follows: Preparation of thermophilic bacterial suspension: The thermophilic bacteria (thermophilic Bacillus, thermophilic Actinomycetes, and thermophilic potassium-solubilizing bacteria) are mixed with deionized water at a concentration of 1 g / L, shaken evenly, and prepared into thermophilic bacterial suspension. Preparation of liquid culture medium: Mix 10 g / L glucose, 5 g / L peptone, 3 g / L yeast extract, 1 g / L KH2PO4, 0.5 g / L MgSO4·7H2O, and 0.1 g / L CaCl2 with deionized water to prepare a liquid culture medium with a pH of 7.0-7.2. Autoclave at 121℃ for 20 min and then cool for later use. Fermentation culture: The prepared thermophilic bacterial suspension was inoculated into the prepared liquid culture medium at an inoculation rate of 2-8% (v / v), and cultured at 55-60℃ with shaking at 150-200 r / min for 48 hours to obtain a bacterial cell concentration of 10. 8 -10 9 Thermophilic bacterial fermentation broth with CFU / mL.

[0023] Preferably, in the step of preparing the compound thermophilic microbial culture, every 100 parts by weight of the compound thermophilic microbial culture comprises: 20-30 parts of thermophilic fungal active fermentation broth, 20-30 parts of thermophilic actinomycete active fermentation broth, 20-30 parts of thermophilic Bacillus active fermentation broth, and 20-30 parts of thermophilic potassium-solubilizing bacteria active fermentation broth; the cell concentration in each active fermentation broth is 10. 8 -109 CFU / mL.

[0024] The organic matter in coal gangue mainly consists of stable organic carbon components such as condensed aromatic and aliphatic polymers and humic precursors, which are difficult to degrade by conventional mesophilic microorganisms. Furthermore, the thermophilic period of composting is the main period for organic matter degradation, humic precursor formation, and pollutant reduction during composting. Therefore, enhancing the activity of microorganisms during the thermophilic period of composting is key to improving the quality of compost products. In this invention, the thermophilic fungi and thermophilic actinomycetes used can secrete various cellulases, laccases, catalases, and polyphenol oxidases under high-temperature conditions, which can effectively destroy the aromatic rings in the organic matter of coal gangue, thereby further accelerating the formation of humification precursors; thermophilic Bacillus secretes various organic acids, amylases, and proteases, which rapidly decompose easily degradable organic matter (such as amino acids and polysaccharides), maintaining continuous metabolic heat generation in the compost pile; thermophilic potassium-solubilizing bacteria can release structural potassium in coal gangue through organic acid erosion, complexation, chelation, and other mechanisms under thermophilic conditions, converting mineral potassium into a soluble form and increasing the nutrient content in compost products; by combining the active fermentation liquid of the above-mentioned microbial agents, a highly efficient enzyme system can be generated to promote the degradation of organic matter in coal gangue, control the content of heavy metals and organic matter such as benzo[a]pyrene, and at the same time, the organic acids and polysaccharides produced by microbial metabolism can promote the synthesis of humus, improving the fertilizer efficiency and stability of organic fertilizer.

[0025] Preferably, in the enhanced synergistic aerobic composting step, the municipal sludge is collected from a domestic sewage treatment plant and has a moisture content of 75-85%.

[0026] Preferably, in the enhanced synergistic aerobic composting step, the mass ratio of the secondary activated coal gangue powder to municipal sludge is (1.5-2):1.

[0027] Preferably, in the enhanced synergistic aerobic composting step, the aerobic composting cycle is 28-35 days, the thermophilic period is maintained at 55-65℃, and the thermophilic period lasts for 7-12 days.

[0028] Preferably, in the enhanced synergistic aerobic composting step, the total inoculation amount of the composite thermophilic microbial liquid is 1-3% of the total mass of the secondary activated coal gangue powder and municipal sludge, wherein the mass ratio of the inoculation amount at the end of the heating period to the inoculation amount in the middle of the thermophilic period is (2:8)-(4:6); more preferably, the mass ratio of the inoculation amount at the end of the heating period to the inoculation amount in the middle of the thermophilic period is 3:7, that is, the inoculation amount at the end of the heating period accounts for 30% of the total inoculation amount, and the inoculation amount in the middle of the thermophilic period accounts for 70% of the total inoculation amount; the end of the heating period is: when the pile body starts heating and reaches 45-50℃ for the first time; the middle of the thermophilic period is: the 4th-6th day after the pile body temperature reaches 50℃.

[0029] In this invention, when aerobic composting secondary activated coal gangue powder with municipal sludge, a complex thermophilic microbial community is inoculated in batches at the end of the heating period and the middle of the thermophilic period. At the end of the heating period, the temperature is close to the thermophilic period, allowing the inoculation of the complex thermophilic microbial community to rapidly colonize and occupy the ecological niche, initiating the degradation reaction in the thermophilic stage. In the middle of the thermophilic period, inoculation maintains enzyme activity and heat production, prolonging the duration of the thermophilic period. This invention, through its batch inoculation strategy, significantly improves the colonization performance and metabolic efficiency of exogenous microorganisms, enhances the humification and pollutant removal capabilities of the composting system, and strengthens the degradation of organic matter.

[0030] The present invention also provides coal gangue organic fertilizer prepared by any of the above methods. Through the above environmentally friendly, low-consumption and high-value preparation methods, coal gangue organic fertilizer with both rich nutrients and low pollutant content can be obtained. The resulting product has excellent performance and broad application prospects.

[0031] The organic fertilizer tested showed that the organic matter content was ≥48.2%, the moisture content was ≤25.7%, the humic content was ≥200.3 g / kg, and the total nutrients were ≥8.7%. The heavy metals arsenic, mercury, lead, cadmium, and chromium in the coal gangue organic fertilizer were converted into residual form, and the benzo[a]pyrene content was ≤0.31 mg / kg. The product quality met the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

[0032] The present invention also provides the application of coal gangue organic fertilizer prepared by any of the above methods in soil improvement, agricultural planting, urban greening, and solid waste resource utilization.

[0033] Compared with the prior art, the technical solution of the present invention has the following advantages: 1. In terms of processing technology, existing coal gangue activation methods mostly employ mechanical crushing or single chemical modification, resulting in incomplete structural destruction, unstable aluminosilicate lattices, and difficulty in releasing nutrients. This invention employs a two-step activation technology combining advanced oxidation and low-temperature alkaline urea solution. Under mild conditions, this technology can break the inert bonds of organic matter in coal gangue, significantly increasing surface-active functional groups and specific surface area, thereby promoting the dissolution of organic matter and transforming the inert organic matter in coal gangue into organic matter that is easily utilized by microorganisms.

[0034] 2. Regarding the quality of the finished compost, although traditional methods of directly applying crushed coal gangue to the land or mixing it with organic solid waste are low-cost and convenient, crushed coal gangue suffers from problems such as unstable organic matter binding, poor water and fertilizer retention, low microbial activity, and insufficient nutrient activation. This invention achieves multi-enzyme synergistic degradation by mixing activated coal gangue with municipal sludge in a specific ratio and inoculating with a composite thermophilic bacterial community in batches during the heating and thermophilic phases. Activated coal gangue provides a porous carrier for the proliferation of composting microorganisms, while municipal sludge replenishes the nitrogen, phosphorus, potassium, and other plant elements lacking in the coal gangue. The fertilizer efficiency of the finished compost is significantly improved compared to directly applying crushed coal gangue. The resulting organic fertilizer has an organic matter content ≥48.2% and total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) ≥8.7%, with stable nutrient release and long-term improvement of soil physicochemical properties. Experiments on desertified and barren soils have verified that this fertilizer can significantly improve soil aggregate structure and water retention capacity, promote crop root development, and is suitable for applications in various fields such as desertified land improvement, mining area reclamation, and ecological agricultural restoration.

[0035] 3. Regarding the safety of the finished compost, this invention effectively reduces pollutants by co-compiling activated coal gangue and municipal sludge in a specific ratio, and by inoculating specific complex thermophilic microbial communities in batches during the composting heating and thermophilic periods. The resulting organic fertilizer contains heavy metals mainly in the residual state, with a significant reduction in benzo[a]pyrene content, meeting the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers".

[0036] 4. In terms of industrial production, compared with the high-energy-consuming activation processes such as high-temperature calcination, hydrothermal reaction or strong acid and alkali leaching used in traditional coal gangue processing, the activation process temperature of this invention is below 50℃, and the temperature during the composting stage is maintained between 55-65℃. No external high-temperature and high-pressure equipment is required, and energy consumption is significantly reduced. The by-products can be recycled, which has good environmental friendliness and economic benefits, and is especially suitable for large-scale industrial production. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 X-ray powder diffraction phase analysis of the raw coal gangue used in Example 1 of this invention; Figure 3The X-ray photoelectron spectra of the (1) O 1s orbital and (2) C 1s orbital of the raw coal gangue used in Example 1 of this invention are shown. Figure 4 This is a scanning electron microscope image of the raw coal gangue used in Example 1 of the present invention; Figure 5 Solid-state nuclear magnetic resonance (NMR) of the raw coal gangue used in Example 1 of this invention. 13 C-map; Figure 6 Three-dimensional fluorescence spectra of soluble organic matter used in Example 1 of this invention: (1) raw coal gangue and (2) secondary activated coal gangue powder; Figure 7 The organic matter content of (1) the original coal gangue raw material and (2) the secondary activated coal gangue powder used in Example 1 of the present invention; Figure 8 The diagram shows the phytotoxicity test results of (1) raw coal gangue and (2) coal gangue organic fertilizer used in Example 1 of this invention, as well as the seed germination index (GI). Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] This invention provides a method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sludge, addressing the problems of insufficient activation of organic matter and plant nutrients in coal gangue, and the inability to simultaneously achieve nutrient activation and pollutant removal in existing technologies. The coal gangue-based organic fertilizer prepared by the method provided by this invention exhibits excellent fertility, is green and sustainable, and can effectively treat nutrient-poor and sandy soils. The overall design concept of this invention aligns with the national principles of zero-waste city construction and sustainable development, and has broad application prospects.

[0041] The technical solution of this application will be described in detail below through specific embodiments: In this invention, the weight parts can be weight units known in the art such as µg, mg, g, kg, or multiples thereof, such as 1 / 10, 1 / 100, 10 times, 100 times, etc.

[0042] Unless otherwise specified, the technical means used in this invention are conventional means well known to those skilled in the art. All raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared using existing methods. Unless otherwise specified, all reagents used in this invention are of analytical grade.

[0043] The municipal sludge used in this invention is dewatered sludge from a domestic sewage treatment plant, with a moisture content of 75-85%. The coal gangue raw material used in this invention is sourced from Ordos City, Inner Mongolia. Its chemical composition is shown in Table 1, and its industrial analysis is shown in Table 2. Table 1. Organic matter content and chemical composition (%) of coal gangue raw materials

[0044] Table 2 Industrial Analysis of Coal Gangue Raw Material (%)

[0045] Example 1 A method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sewage sludge includes the following steps: (1) Coal gangue crushing treatment: 100 kg of coal gangue is crushed to a particle size of less than 50 mesh to obtain a specific surface area of ​​320 m². 2 / kg of coal gangue powder; (2) Activation of advanced oxidation system (Fenton system): In a stirred reactor, 100 kg of coal gangue powder, 994 kg of water, 5 kg of 30% hydrogen peroxide and 1 kg of ferrous sulfate were stirred and mixed, and the reaction was carried out at 40°C for 3 hours under stirring conditions of 200 rpm. (3) Initial solid-liquid separation: The product after the advanced oxidation reaction is separated by centrifugation to obtain 100 kg of initially activated coal gangue powder and 1000 kg of mixed solution (hydrogen peroxide-ferrous sulfate). The recovered mixed solution can be recycled for the advanced oxidation process of coal gangue powder. (4) Low-temperature alkaline urea solution activation: 12 kg sodium hydroxide, 30 kg urea and 258 kg water are mixed to form an alkaline urea solution, pre-cooled to -10℃ and then mixed with 100 kg of initially activated coal gangue powder. The mixture is then reacted in a stirred reactor at 200 rpm for 3 hours. (5) Secondary solid-liquid separation: The product activated by low-temperature alkaline urea solution is separated by centrifugation to obtain 100 kg of secondary activated coal gangue powder and 300 kg of mixed solution (sodium hydroxide-urea). The recovered mixed solution can be recycled for the low-temperature alkaline urea solution activation process of the primary activated coal gangue powder. (6) Preparation of compound thermophilic microbial culture: For thermophilic Bacillus, thermophilic Actinomycetes, and thermophilic potassium-solubilizing bacteria, prepare thermophilic bacterial liquid culture medium (10 g / L glucose, 5 g / L peptone, 3 g / L yeast extract, 1 g / L KH2PO4, 0.5 g / L MgSO4·7H2O, 0.1 g / L CaCl2, pH 7.0, autoclaved at 121℃ for 20 min and cooled for later use); For thermophilic fungi, prepare thermophilic fungal liquid culture medium (20 g / L soluble starch, 4 g / L yeast extract, 3 g / L peptone, 1 g / L KH2PO4, 0.5 g / L MgSO4·7H2O, 1 g / L CaCO3, pH 7.0, autoclaved at 121℃ for 20 min and cooled for later use). Thermophilic fungi ( ) were added at a concentration of 1 g / L. Myceliophthora thermophila ), thermophilic actinomycetes ( Thermobifida fusca ), thermophilic bacillus ( Bacillus licheniformis ), thermophilic potassium-solubilizing bacteria ( Bacillus edaphicus Mix each of the above ingredients with deionized water, shake well, and prepare bacterial suspensions. Inoculate the resulting bacterial suspensions into the corresponding liquid culture media at an inoculum rate of 6% (v / v), and incubate at 57°C with shaking for 48 hours to achieve a bacterial concentration of 10⁻⁶. 8 -10 9 CFU / mL, which is the active fermentation broth of each strain; Collect the active fermentation broth of each strain separately, and calculate by mass percentage. Myceliophthora thermophila 20% Thermobifida fusca 30% Bacillus licheniformis 30% and Bacillus edaphicus 20% is added and mixed thoroughly to obtain a mixed bacterial solution; (7) Enhanced aerobic co-composting: 100 kg of secondary activated coal gangue powder was mixed with 50 kg of municipal sludge (moisture content 80.5%) for aerobic composting. When the pile temperature first reached 45℃ and on the 5th day after the pile temperature reached ≥50℃, 0.9 kg and 2.1 kg of mixed bacterial solution were sprayed respectively. After a 30-day composting cycle, 92 kg of coal gangue organic fertilizer was obtained, of which the thermophilic period at 55-65℃ was 10 days, which met the requirements for harmless composting.

[0046] The prepared coal gangue organic fertilizer was found to have an organic matter content of 53.5%, a moisture content of 25.3%, a total nutrient content (nitrogen + phosphorus pentoxide + potassium oxide) of 9.2%, a humic content of 205.5 g / kg, a seed germination index of 85.6%, and a pH of 7.8. In the finished compost, cadmium, lead, and arsenic were converted from active to residual states, and the benzo[a]pyrene content was 0.20 mg / kg. The product quality met the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

[0047] Example 2 A method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sewage sludge includes the following steps: (1) Coal gangue crushing treatment: 100 kg of coal gangue was crushed to a particle size of less than 50 mesh to obtain a specific surface area of ​​365 m². 2 / kg of coal gangue powder; (2) Activation of advanced oxidation system (persulfate system): In a stirred reactor, 100 kg of coal gangue powder, 797 kg of water, 2.0 kg of potassium persulfate and 1.0 kg of ferrous sulfate were stirred and mixed, and the advanced oxidation reaction was carried out at 45°C for 1.5 hours under stirring conditions of 200 rpm. (3) Initial solid-liquid separation: The product after the advanced oxidation reaction is separated by centrifugation to obtain 100 kg of initially activated coal gangue powder and 800 kg of mixed solution (potassium hydrogen sulfate-ferrous sulfate). The recovered mixed solution can be recycled for the advanced oxidation process of coal gangue powder. (4) Low-temperature alkaline urea solution activation: Mix 10 kg potassium hydroxide, 25 kg urea and 265 kg water to form an alkaline urea solution, pre-cool to -5℃, mix with 100 kg of initially activated coal gangue powder, and react for 30 minutes in a stirred reactor at 150 rpm. (5) Secondary solid-liquid separation: The product activated by low-temperature alkaline urea solution is separated by centrifugation to obtain 100 kg of secondary activated coal gangue powder and 300 kg of mixed solution (potassium hydroxide-urea). The recovered mixed solution can be recycled for the low-temperature alkaline urea solution activation process of the primary activated coal gangue powder. (6) Preparation of compound thermophilic microbial culture: For thermophilic Bacillus, thermophilic Actinomycetes, and thermophilic potassium-solubilizing bacteria, prepare thermophilic bacterial liquid culture medium (10 g / L glucose, 5 g / L peptone, 3 g / L yeast extract, 1 g / L KH2PO4, 0.5 g / L MgSO4·7H2O, 0.1 g / L CaCl2, pH 7.0, autoclaved at 121℃ for 20 min and cooled for later use); For thermophilic fungi, prepare thermophilic fungal liquid culture medium (20 g / L soluble starch, 4 g / L yeast extract, 3 g / L peptone, 1 g / L KH2PO4, 0.5 g / L MgSO4·7H2O, 1 g / L CaCO3, pH 7.0, autoclaved at 121℃ for 20 min and cooled for later use). Thermophilic fungi ( ) were added at a concentration of 1 g / L. Thermomyces lanuginosus ), thermophilic actinomycetes ( Saccharomonospora viridis ), thermophilic bacillus ( Geobacillus thermodenitrificans ), thermophilic potassium-solubilizing bacteria ( Bacillus mucilaginosus Mix each of the above ingredients with deionized water, shake well, and prepare bacterial suspensions. Inoculate the resulting bacterial suspensions into the corresponding liquid culture media at a 5% (v / v) inoculation rate, and incubate at 60°C with shaking for 48 hours to achieve a bacterial concentration of 10⁻⁶. 8 -10 9 CFU / mL, which is the active fermentation broth of each strain; Collect the active fermentation broth of each strain separately, and calculate by mass percentage. Thermomyces lanuginosus 25%, Saccharomonospora viridis 25%, Geobacillus thermodenitrificans 30%, and Bacillus mucilaginosus 20% is added and mixed thoroughly to obtain a mixed bacterial solution; (7) Enhanced aerobic co-composting: 100 kg of secondary activated coal gangue powder was mixed with 60 kg of municipal sludge (moisture content 81.2%) for aerobic composting. When the pile temperature first reached 46℃ and on the 5th day after the pile temperature reached ≥50℃, 0.6 kg and 1.4 kg of mixed bacterial solution were sprayed respectively. After a 30-day composting cycle, 90 kg of coal gangue organic fertilizer was obtained, of which the thermophilic period of 55-65℃ lasted for 9 days, which met the requirements for harmless composting.

[0048] The prepared coal gangue organic fertilizer was found to have an organic matter content of 48.2%, a moisture content of 25.7%, a total nutrient content (nitrogen + phosphorus pentoxide + potassium oxide) of 8.7%, a humic content of 200.3 g / kg, a seed germination index of 87.6%, and a pH of 7.6. In the finished compost, cadmium, lead, and arsenic were converted from active to residual states, and the benzo[a]pyrene content was 0.31 mg / kg. The product quality met the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

[0049] Example 3 A method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sewage sludge includes the following steps: (1) Coal gangue crushing treatment: 100 kg of coal gangue is crushed to a particle size of less than 50 mesh to obtain coal gangue powder with a specific surface area of ​​380 m² / kg; (2) Activation of the advanced oxidation system (alkali-activated hydrogen peroxide system): In a stirred reactor, add 100 kg of coal gangue powder and 800 kg of water, followed by 5 kg of sodium hydroxide. After stirring and dissolving, the pH of the system is approximately 11. Under stirring conditions of 200 rpm, slowly add 8 kg of 30% hydrogen peroxide to the slurry and react at 45°C for 3 hours; (3) Initial solid-liquid separation: The product after reaction is separated by centrifugation to obtain 100 kg of initially activated coal gangue powder and 813 kg of mixed solution. The recovered mixed solution can be recycled for the advanced oxidation process of coal gangue powder. (4) Low-temperature alkaline urea solution activation: 9 kg sodium hydroxide, 28 kg urea and 263 kg water are mixed to form an alkaline urea solution, pre-cooled to -8℃ and then mixed with 100 kg of initially activated coal gangue powder. The mixture is then reacted in a stirred reactor at 180 rpm for 2.5 hours. (5) Secondary solid-liquid separation: The product activated by low-temperature alkaline urea solution is separated by centrifugation to obtain 100 kg of secondary activated coal gangue powder and 300 kg of mixed solution (sodium hydroxide-urea). The recovered mixed solution can be recycled for the low-temperature alkaline urea solution activation process of the primary activated coal gangue powder. (6) Preparation of compound thermophilic microbial culture: thermophilic bacteria liquid culture medium: glucose 10 g / L, peptone 5 g / L, yeast extract 3 g / L, KH2PO4 1 g / L, MgSO4·7H2O 0.5 g / L, CaCl2 0.1 g / L, pH 7.0, autoclaved at 121℃ for 20 min and cooled for later use; thermophilic fungi liquid culture medium: soluble starch 20 g / L, yeast extract 4 g / L, peptone 3 g / L, KH2PO4 1 g / L, MgSO4·7H2O 0.5 g / L, CaCO3 1 g / L, pH 7.0, autoclaved at 121℃ for 20 min and cooled for later use; Thermophilic fungi ( ) were added at a concentration of 1 g / L. Thermomyces lanuginosus ), thermophilic actinomycetes ( Saccharomonospora viridis ), thermophilic bacillus ( Geobacillus thermodenitrificans ), thermophilic potassium-solubilizing bacteria ( Bacillus mucilaginosus Mix each of the above ingredients with deionized water, shake well, and prepare bacterial suspensions. Inoculate the resulting bacterial suspensions into the corresponding liquid culture media at an inoculation rate of 4% (v / v), and incubate at 60°C with shaking for 48 hours to achieve a bacterial concentration of 10⁻⁶. 8 -10 9 CFU / mL was used to obtain the active fermentation broth for each strain; Blended by weight percentage: Thermomyces lanuginosus 25%, Saccharomonospora viridis 25%, Geobacillus thermodenitrificans 25%, Bacillus mucilaginosus 25%, mix thoroughly and evenly to obtain a composite thermophilic microbial bacterial solution; (7) Enhanced aerobic co-composting: 100 kg of secondary activated coal gangue powder was mixed with 55 kg of municipal sludge (moisture content 80.2%) for aerobic composting. When the temperature of the compost pile first reached 46℃ and on the 6th day after the temperature of the compost pile reached ≥50℃, 0.5 kg and 1.5 kg of compound thermophilic microbial liquid were sprayed respectively. After a 30-day composting cycle, 93 kg of coal gangue organic fertilizer was obtained, of which the thermophilic period of 55–65℃ lasted for 8 days, which met the requirements for harmless composting.

[0050] Testing revealed that the prepared coal gangue organic fertilizer contained 49.5% organic matter, 25.5% moisture, 8.8% total nutrients (nitrogen + phosphorus pentoxide + potassium oxide), 201.8 g / kg humic matter, 86.1% seed germination index, and 7.6 pH. In the finished compost, cadmium, lead, and arsenic were converted from active to residual states, and the benzo[a]pyrene content was 0.28 mg / kg. The product quality meets the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

[0051] Comparative Example 1 The difference between this comparative example and Example 1 is that steps (2)-(6) are omitted, no advanced oxidation system and low-temperature alkaline urea solution are used for activation during composting, and no compound thermophilic microbial community is inoculated. Other methods and steps are the same as in Example 1 and will not be repeated.

[0052] The composition of the product was tested, and the results showed that its organic matter content was 50.2%, moisture content was 28.7%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 3.5%, humic matter content was 150.2 g / kg, seed germination index was 65.3%, and pH was 7.6. In the compost product, only a portion of cadmium, lead, and arsenic were converted into residual state, while the majority remained in active state. The benzo[a]pyrene content was 0.62 mg / kg. The product quality did not meet the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

[0053] Because the coal gangue was not pre-activated and no thermophilic microorganisms were inoculated during the composting process, the organic matter in the coal gangue could not be effectively utilized by the native microorganisms of composting. This resulted in a significant delay in its heating and humification processes, with the thermophilic period lasting only 4 days. This failed to meet the requirements for harmless composting, and the nutrient content and maturity of the compost were insufficient.

[0054] Comparative Example 2 The difference between this comparative example and Example 1 is that step (6) is omitted, and the compound thermophilic microbial community is not inoculated during the composting process in step (7). Other methods and steps are the same as in Example 1 and will not be repeated.

[0055] The composition of the product was tested, and the results showed that its organic matter content was 50.4%, moisture content was 27.2%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 3.8%, humic matter content was 191.2 g / kg, seed germination index was 72.3%, and pH was 7.1. In the compost product, only a portion of cadmium, lead, and arsenic were converted into residues, while the majority remained in active form. The benzo[a]pyrene content was 0.72 mg / kg. The product quality did not meet the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

[0056] The thermophilic period in this comparative example was shortened to 6 days compared to the example. Furthermore, despite the two-step treatment of advanced oxidation activation and low-temperature alkaline urea solution activation, the lack of inoculation with a complex thermophilic microbial community during composting prevented efficient degradation of organic matter in the compost raw materials, resulting in a delayed humification process.

[0057] Comparative Example 3 The difference between this comparative example and Example 1 is that steps (2) to (5) are omitted before composting the coal gangue and municipal sludge. The crushed coal gangue is not activated by advanced oxidation and low-temperature alkaline urea solution. Other methods and steps are the same as in Example 1 and will not be repeated.

[0058] The composition of the obtained product was tested, and the results showed that its organic matter content was 53.2%, moisture content was 28.2%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 4.3%, humic matter content was 180.2 g / kg, seed germination index was 60.3%, and pH was 7.1. In the finished compost, only a portion of cadmium, lead, and arsenic were converted to residual states, with the majority remaining in active states. The benzo[a]pyrene content was 0.60 mg / kg. The product quality did not meet the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers". The thermophilic period of this comparative example was only 3 days, which could not meet the requirements for harmless composting.

[0059] Because the coal gangue powder was not pre-activated, the large molecular organic matter bound to the minerals in the coal gangue could not be effectively released. Although a compound thermophilic microbial community was inoculated at the end of the heating period and in the middle of the thermophilic period of composting, the improved compost microbial community still could not effectively utilize the unactivated organic matter in the coal gangue. This resulted in weakened microbial degradation capacity, insufficient heat of reaction, and difficulty in maintaining the thermophilic period, leading to a lag in the composting humification process and insufficient maturity of the compost.

[0060] Comparative Example 4 The difference between this comparative example and Example 1 is that steps (2) and (3) are omitted before composting coal gangue and municipal sludge. The pulverized coal gangue is not activated by an advanced oxidation system, but only activated by a low-temperature alkaline urea solution. Other methods and steps are the same as in Example 1 and will not be repeated.

[0061] The composition of the obtained product was tested, and the results showed that its organic matter content was 52.8%, moisture content was 28.5%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 4.1%, humic matter content was 175.8 g / kg, seed germination index was 62.1%, and pH was 7.3. In the finished compost, only a portion of cadmium, lead, and arsenic were converted to residual states, with the majority remaining in active states. The benzo[a]pyrene content was 0.58 mg / kg. The product quality does not meet the requirements of GB 38400-2019 and NY / T 525-2021.

[0062] In this comparative example, because the coal gangue was not activated by an advanced oxidation system, the large-molecule inert organic matter could not be effectively destroyed. This meant that the organic matter released by the subsequent low-temperature alkaline urea solution activation was still mainly inert large-molecule organic matter, weakening the degradation and humification of organic matter in the coal gangue during the aerobic composting process.

[0063] Comparative Example 5 The difference between this comparative example and Example 1 is that: before composting coal gangue and municipal sludge, the crushed coal gangue is only activated by an advanced oxidation system, omitting steps (4) and (5), and is not activated by low-temperature alkaline urea solution. Other methods and steps are the same as in Example 1, and will not be repeated.

[0064] The composition of the product was tested, and the results showed that the organic matter content was 51.5%, the moisture content was 26.9%, the total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 5.2%, the humic content was 185.4 g / kg, the seed germination index was 70.5%, and the pH was 7.9. The proportion of active heavy metals in the compost product was relatively high, and the benzo[a]pyrene content was 0.48 mg / kg.

[0065] In this comparative example, the lack of an alkaline urea activation step resulted in insufficient dissociation of the layered structure of the coal gangue, which affected the further release of nutrients and the humification process.

[0066] Comparative Example 6 The difference between this comparative example and Example 1 is that the low-temperature environment (-10℃) in step (4) is changed to room temperature (25℃) for alkaline urea solution activation. Other methods and steps are the same as in Example 1. They will not be repeated here.

[0067] The composition of the obtained product was tested, and the results showed that its organic matter content was 50.9%, moisture content was 26.3%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 6.0%, humic matter content was 190.1 g / kg, seed germination index was 75.8%, and pH was 7.7; the benzo[a]pyrene content in the compost product was 0.41 mg / kg. Although many indicators of the product were better than those of Comparative Example 5, the total nutrient and humic matter content were still significantly lower than those of Example 1, and the degradation of benzo[a]pyrene was incomplete.

[0068] This comparative example demonstrates that, compared to normal temperature conditions, specific low-temperature conditions can effectively promote the dissociation of the urea hydrogen bond network from the interlayer structure of coal gangue minerals and the release of nutrients.

[0069] Comparative Example 7 The difference between this comparative example and Example 1 is that: in step (6) when preparing the compound thermophilic microbial liquid, no thermophilic fungal active fermentation liquid is added, and the other three active fermentation liquids are increased to 100% in proportion to their mass percentage in Example 1, so that the cell concentration in each fermentation liquid is consistent with that in Example 1, and the total amount of compound thermophilic microbial liquid added is consistent with that in Example 1.

[0070] The other methods and steps are the same as in Example 1. They will not be repeated here.

[0071] The composition of the product was tested, and the results showed that the organic matter content was 49.8%, the moisture content was 25.8%, the total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 7.5%, the humic content was 150.6 g / kg, the seed germination index was 78.2%, and the pH was 7.8; the benzo[a]pyrene content in the compost product was 0.38 mg / kg.

[0072] The significantly reduced humus content in the product obtained in this comparative example indicates that thermophilic fungi play a key role in degrading stubborn organic structures such as lignin and promoting humus formation.

[0073] Comparative Example 8 The difference between this comparative example and Example 1 is that: in step (6) when preparing the compound thermophilic microbial culture, no thermophilic actinomycete active fermentation broth is added, and the other three active fermentation broths are increased to 100% in proportion to their mass percentage in Example 1, so that the cell concentration in each fermentation broth is consistent with that in Example 1, and the total amount of compound thermophilic microbial culture added is consistent with that in Example 1.

[0074] The other methods and steps are the same as in Example 1. They will not be repeated here.

[0075] The composition of the product was tested, and the results showed that the organic matter content was 50.2%, the moisture content was 25.9%, the total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 7.8%, the humic content was 188.3 g / kg, the seed germination index was 76.5%, and the pH was 7.8. The composting thermophilic period lasted only 6 days, and the benzo[a]pyrene content was 0.35 mg / kg.

[0076] The reduced duration of the thermophilic phase in this comparative example indicates that thermophilic actinomycetes are crucial for maintaining the thermophilic phase and degrading complex organic matter.

[0077] Comparative Example 9 The difference between this comparative example and Example 1 is that: in step (6) when preparing the compound thermophilic microbial culture, no active fermentation liquid of Bacillus thermophilus is added, and the other three active fermentation liquids are increased to 100% in proportion to their mass percentage in Example 1, so that the cell concentration in each fermentation liquid is consistent with that in Example 1, and the total amount of compound thermophilic microbial culture is consistent with that in Example 1.

[0078] The other methods and steps are the same as in Example 1. They will not be repeated here.

[0079] The composition of the obtained product was tested, and the results showed that: the organic matter content was 51.0%, the moisture content was 28.1%, the total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 5.2%, the humus content was 160.0 g / kg, the seed germination index was 60.8%, and the pH was 7.7; the composting temperature rise rate was slowed down and the thermophilic period of composting was only maintained for 3 days, and the benzo[a]pyrene content was 0.66 mg / kg.

[0080] This comparative example demonstrates that Bacillus thermophilus plays an irreplaceable role in rapidly initiating composting and maintaining high temperatures.

[0081] Comparative Example 10 The difference between this comparative example and Example 1 is that: in step (6) when preparing the compound thermophilic microbial culture, no thermophilic potassium-solubilizing bacteria active fermentation liquid is added, and the other three active fermentation liquids are increased to 100% in proportion to their mass percentage in Example 1, so that the bacterial concentration in each fermentation liquid is consistent with that in Example 1, and the total amount of compound thermophilic microbial culture is consistent with that in Example 1.

[0082] The other methods and steps are the same as in Example 1. They will not be repeated here.

[0083] The composition of the obtained product was tested, and the results showed that its organic matter content was 52.1%, moisture content was 25.5%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 6.9%, humic matter content was 199.5 g / kg, seed germination index was 82.1%, pH was 7.8, and benzo[a]pyrene content was 0.25 mg / kg.

[0084] The total nutrient content of the product obtained in this comparative example was significantly lower, especially the potassium content, which demonstrates the core value of thermophilic potassium-solubilizing bacteria in activating structural potassium in coal gangue.

[0085] Comparative Example 11 The difference between this comparative example and Example 1 is that in step (7), the compound thermophilic microbial inoculum is added all at once at the beginning of composting, instead of being inoculated in batches at the end of the heating period and the middle of the thermophilic period. Other methods and steps are the same as in Example 1. They will not be repeated here.

[0086] The composition of the obtained product was tested, and the results showed that its organic matter content was 50.8%, moisture content was 26.4%, total nutrients (nitrogen + phosphorus pentoxide + potassium oxide) was 7.8%, humic matter content was 195.0 g / kg, seed germination index was 80.5%, pH was 7.8, and benzo[a]pyrene content was 0.33 mg / kg.

[0087] While the quality of this comparative product is superior to most comparative examples, it is still inferior to Example 1. This demonstrates that a batch inoculation strategy is more in line with the laws of microbial ecological succession and can more effectively exert the efficacy of the microbial agent.

[0088] Detailed test data of the products obtained in Examples 1-3 and Comparative Examples 1-11 are shown in Table 3. Table 3. Comparison of compost product quality between the examples and the comparative examples.

[0089] * Standard references: "Limits of Toxic and Hazardous Substances in Fertilizers" (GB 38400), "Organic Fertilizers" (NY / T525) As shown in Table 3, the technical solution of this invention can simultaneously activate nutrients and control heavy metals and benzo[a]pyrene in coal gangue through pre-activation of coal gangue and inoculation with a composite thermophilic microbial community to enhance the composting process in a simple, efficient, and low-energy-consumption manner. The resulting coal gangue organic fertilizer is rich in organic matter and plant nutrients, which are easily absorbed and utilized directly by plants and microorganisms. The coal gangue organic fertilizer prepared by this method is nutritionally complete, safe and reliable, and has an active microbial community, making it suitable for use as an organic fertilizer or soil conditioner.

[0090] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing organic fertilizer through enhanced aerobic composting of pre-activated coal gangue and municipal sewage sludge, characterized in that, Includes the following steps: Coal gangue pretreatment: The coal gangue is crushed to a particle size of less than 50 mesh to obtain a specific surface area of ​​300-400 m². 2 / kg of coal gangue powder; Activation of advanced oxidation system: Coal gangue powder is stirred and reacted in an advanced oxidation system solution at 30-50℃ for initial activation treatment. After solid-liquid separation, the solid material is collected, which is the initially activated coal gangue powder. Low-temperature alkaline urea solution activation: The primary activated coal gangue powder is mixed with alkaline urea solution in a low-temperature environment, stirred and reacted, and the precipitate is obtained after solid-liquid separation, which is the secondary activated coal gangue powder. Preparation of compound thermophilic microbial culture: thermophilic fungi, thermophilic actinomycetes, thermophilic Bacillus and thermophilic potassium-solubilizing bacteria are fermented and cultured, and the resulting active fermentation broths are compounded to obtain compound thermophilic microbial culture. Enhanced synergistic aerobic composting: After mixing secondary activated coal gangue powder with municipal sludge in a certain proportion, aerobic composting is carried out. At the end of the composting heating period and the middle of the thermophilic period, the prepared compound thermophilic microbial liquid is inoculated in batches. After 28-35 days of aerobic composting, coal gangue organic fertilizer can be obtained.

2. The method for preparing organic fertilizer by pre-activated coal gangue and municipal sludge enhanced aerobic composting as described in claim 1, characterized in that, In the coal gangue pretreatment step, the coal gangue contains 20-40% organic matter and has the following chemical composition: SiO2 40-60%, Al2O3 5.0-20%, K2O 1.0-5.0%, Fe2O3 2.0-14%, SO3 0.8-6.1%, CaO 0.42-2.32%, MgO 0.18-2.41%, TiO2 0.90-4%, and P2O5 0.07-0.24%.

3. The method for preparing organic fertilizer by pre-activated coal gangue and municipal sludge enhanced aerobic composting as described in claim 1, characterized in that, In the advanced oxidation system activation step, the advanced oxidation system solution includes one or more of the following: Fenton system, persulfate activation system, and alkaline activated hydrogen peroxide system; The solid-liquid mass ratio of the coal gangue powder to the advanced oxidation system solution is 1:(8-12). The stirring speed is 100-300 rpm, and the stirring time is 2-4 hours.

4. The method for preparing organic fertilizer by pre-activated coal gangue and municipal sludge enhanced aerobic composting as described in claim 1, characterized in that, In the low-temperature alkaline urea solution activation step, The alkaline urea solution has a pH of 10-12 and is composed of alkaline substances, urea and water. Based on the total mass of the alkaline urea solution, the content of alkaline substances is 2-5 wt%, the content of urea is 8-12 wt%, and the balance is water. The alkaline substances include one or more of sodium hydroxide, potassium hydroxide, wood ash, alkali residue, and lime; The solid-liquid mass ratio of the initially activated coal gangue powder to the alkaline urea solution is 1:(2-10). The low-temperature environment is -15℃ to -5℃; The stirring speed is 100-300 rpm, and the stirring time is 2-4 hours.

5. The method for preparing organic fertilizer by pre-activated coal gangue and municipal sludge enhanced aerobic composting as described in claim 1, characterized in that, In the step of preparing the compound thermophilic microbial culture, every 100 parts by weight of the compound thermophilic microbial culture includes: 20-30 parts of active fermentation broth of thermophilic fungi, 20-30 parts of active fermentation broth of thermophilic actinomycetes, 20-30 parts of active fermentation broth of thermophilic Bacillus, and 20-30 parts of active fermentation broth of thermophilic potassium-solubilizing bacteria. The bacterial cell concentration in each of the active fermentation broths is 10. 8 -10 9 CFU / mL.

6. The method for preparing organic fertilizer by pre-activated coal gangue and municipal sludge enhanced aerobic composting as described in claim 1, characterized in that, In the enhanced synergistic aerobic composting step, the mass ratio of the secondary activated coal gangue powder to municipal sludge is (1.5-2):1; The thermophilic period of the aerobic composting is maintained at 55-65℃ and lasts for 7-12 days. The total inoculation amount of the composite thermophilic microbial liquid is 1-3% of the total mass of the secondary activated coal gangue powder and municipal sludge, wherein the mass ratio of the inoculation amount at the end of the heating period to the inoculation amount in the middle of the thermophilic period is (2:8)-(4:6).

7. Coal gangue organic fertilizer prepared by the method according to any one of claims 1-6.

8. The coal gangue organic fertilizer prepared according to claim 7, characterized in that, The coal gangue organic fertilizer has an organic matter content of ≥48.2%, a moisture content of ≤25.7%, a humic content of ≥200.3 g / kg, and a total nutrient content of ≥8.7%. The heavy metal elements arsenic, mercury, lead, cadmium, and chromium in the coal gangue organic fertilizer are all converted into residual state, and the benzo[a]pyrene content is ≤0.31 mg / kg. The product quality meets the requirements of GB 38400-2019 "Limits of Toxic and Hazardous Substances in Fertilizers" and NY / T 525-2021 "Organic Fertilizers".

9. The application of coal gangue organic fertilizer prepared by the method according to any one of claims 1-6 in soil improvement, agricultural planting, and urban greening solid waste resource utilization.

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