Method for rapidly converting electrolytic manganese residues in soil by using microbiological method

Abstract

The invention belongs to the technical field of organic waste treatment, and particularly relates to a method for rapidly converting electrolytic manganese residues from soil by using a microbiological method. Comprising the following steps: (1) mixing bagasse pith powder, sugar refinery filter mud and red mud according to a certain proportion, adding the mixture, electrolytic manganese residues and water into a reaction tank, and fully reacting for 6 hours to obtain corresponding mixed waste residues; (2) mixing and stirring the mixed waste residue, a bio-organic fertilizer and a No.1 compound microbial agent, feeding the mixture into a tank-type fermentation tank for aerobic fermentation, performing rapid fermentation for 144 hours, and turning for 2-3 times during the period, so as to obtain active waste residue with low heavy metal ion content; (3) adding sulfur powder and a No.2 compound microbial agent into the active waste residues, carrying out rapid fermentation for 48 hours, and turning for 2-3 times during the period, so as to obtain regenerated soil; the method fundamentally solves the problems that a large amount of electrolytic manganese residues are piled up for a long time, treatment is difficult, and the treatment cost is high, treats waste with waste, and has great significance on green development of the manganese industry.

Description

Technical Field

[0001] The invention belongs to the technical field of organic waste treatment, and specifically is a method for rapidly soilifying electrolytic manganese slag using a microbial method. Background Art

[0002] 1. Electrolytic manganese slag

[0003] Manganese metal is known as a "strategic metal". It is an extremely important industrial raw material and one of the basic raw materials for national pillar industries such as aerospace, machinery, chemical industry, and agriculture. Since the 21st century, with the rapid development of clean energy, lithium-ion batteries with manganese compounds as positive electrode materials have also developed rapidly, making electrolytic manganese metal develop more rapidly. However, the electrolytic manganese industry belongs to the traditional hydrometallurgical industry. While promoting the rapid development of the local economy, it also produces a large amount of "three wastes" - wastewater, waste residue and waste gas, which greatly limits the sustainable development of the electrolytic manganese industry. Among them, the electrolytic manganese industry produces a large amount of waste residue, that is, the filtered acid residue produced in the process of electrolytic manganese, which is commonly referred to as electrolytic manganese residue (Electrolytic manganese residue, referred to as "manganese residue"). At present, the main way for electrolytic manganese enterprises to deal with manganese residue is to send it to a dedicated site for damming and storage. Long-term accumulation will consume a large area of ​​land, resulting in a waste of resources. At the same time, it increases environmental pressure, groundwater will be polluted, and even cause great harm to human health. Therefore, the storage of electrolytic manganese residue is currently the most prominent environmental problem in the entire electrolytic manganese industry.

[0004] Electrolytic manganese slag is a powdery solid waste, which is black fine particles with a high moisture content, with an average moisture content of about 30%. The main phases of electrolytic manganese slag are quartz (SiO2), pyrite (FeS2), calcium sulfate (CaSO4), gypsum (CaSO4·2H2O), aluminum oxide and manganese oxide. The particles of electrolytic manganese slag are fine and distributed in a disorderly manner, with columnar crystal particles interlaced with other substances, and some fluff-like particles are filled in between, and the distribution is dense.

[0005] 2. Red Mud

[0006] As one of the major alumina producers, China produces about 70 million tons of red mud every year. It is estimated that China's current red mud reserves have exceeded 600 million tons, which are mainly discharged in the form of land storage in red mud dumps. Red mud, also known as red mud, is an industrial solid waste discharged after alumina is extracted from bauxite. It generally contains a large amount of iron oxide and looks similar to red soil, hence the name. However, some are brown or even grayish white because they contain less iron oxide. Red mud is an insoluble residue and can be divided into sintered red mud, Bayer red mud and combined red mud. The main components are SiO2, Al2O3, CaO, Fe2O3, etc. The land storage of red mud not only wastes land resources, but is also easily affected by rainwater leaching and wind erosion, thereby polluting the atmosphere, water and soil systems in the surrounding areas, bringing negative impacts on the ecological health of red mud dumps and their surrounding areas that cannot be underestimated.

[0007] The lack of biological activity and strong alkalinity of the soil are the main problems to be solved in the comprehensive utilization of red mud. On the one hand, red mud comes from the waste residue produced after alkaline washing and high-temperature treatment of bauxite. The organic matter, nutrient content and soil biological activity are extremely low, and it is almost "dead mud" and does not have the conditions for biological growth. On the other hand, the existence of alkaline substances in red mud includes free alkali and chemically bound alkali. About 20%-25% of the alkaline substances exist in the form of free alkali, and the rest exist in the form of chemically bound alkali in alkaline minerals. Free alkali mainly exists in the form of NaOH, Na2CO3, NaAl(OH)4, Na2SiO3, etc., which are easily dissolved to form alkaline anions, resulting in an increase in the pH value of red mud. Chemically bound alkali mainly includes sodalite, cancrystal, hydrated garnet, calcite, tricalcium aluminate, etc., which are desiliconization products in the production process of alumina. The dissolution reaction of chemically bound alkali causes the red mud to be alkaline and forms a pH buffer zone. Domestic and foreign scholars have conducted extensive research on the safe disposal and storage of red mud. The ideal measure to solve the problem of red mud storage and reduce the risk of environmental pollution is the resource utilization of red mud, including the recovery of valuable metals such as Al, Fe and rare earth metals, adsorbents for sewage treatment, additives for ceramics and building materials, roadbed materials and soil remediation agents. However, so far, the global red mud reuse rate is less than 2%. According to the "2019-2020 China Bulk Industrial Solid Waste Comprehensive Utilization Industry Development Report", China's red mud comprehensive utilization rate in 2020 is 8%, and the utilization volume is only 8.49 million tons. The large-scale comprehensive utilization of red mud is difficult to achieve. Therefore, the ecological disposal of red mud as a feasible measure for the harmless utilization of bulk waste has attracted widespread attention. By adding regulators to achieve the purpose of reducing the alkalinity of red mud, increasing nutrients and improving the physical structure, thereby accelerating the soilization of red mud and the restoration of vegetation, and ultimately achieving the ecological reconstruction of the red mud dump, it is a very potential and practical way in the process of ecological disposal of red mud.

[0008] 3. Sugar factory sludge (sulfite process)

[0009] Sugar mill filter mud mainly comes from the purification process in the sugar production process. In the sugar production process, after the sugarcane juice is clarified, the residue will be discharged through a filter press or a vacuum filter. These residues are called filter mud. There are two types of filter mud: sulfite filter mud and carbonic acid filter mud. Sulfite filter mud is produced by treating sugarcane juice with lime and sulfur dioxide as clarifiers, while carbonic acid filter mud is produced by treating sugarcane juice with lime and carbon dioxide as clarifiers.

[0010] The main components of the filter mud of the sulfite process sugar mill are: about 69.55% water, about 58.66% organic matter, about 1.19% N, about 1.24% P2O5, about 0.52% K2O, about 5.59% CaO, about 1.07% MgO. Due to the small amount of ash added, the calcium salt content is low, the organic content is high, and it contains nitrogen, phosphorus, potassium and trace elements required by sugarcane. The pH value is about 6.0, which is weakly acidic. Improper stacking of untreated sugar mill filter mud will occupy land resources, and because it contains a variety of organic matter and sugar substances, it is very easy to mold and stink, breed flies, and bring certain environmental problems. Therefore, the comprehensive utilization of filter mud is an important link in the development of circular economy, improvement of economic benefits and realization of sustainable development in the sugar industry.

[0011] 4. Sugarcane pith

[0012] The pith is the inner part of the sugarcane plant. It is the residue left after the juice is squeezed during the sugar production process and is usually removed in the bagasse. The main components of the pith include cellulose, hemicellulose and lignin, which are carbohydrates composed of simple sugars like starch or sucrose. Due to the low calorific value of pith, burning it in boilers may cause operational problems as well as environmental pollution and health hazards, so it needs to be properly handled.

[0013] Sugarcane pith can be used as roughage for ruminants, replacing part of the grass. In order to improve its nutritional value as feed, physical, chemical, microbiological and other methods can be used to improve its digestibility, palatability and nutritional value. For example, its nutritional value can be improved by alkali treatment, acid treatment or physical methods such as grinding, heating, cooking and other pretreatments. Summary of the invention

[0014] The present invention aims to provide a method for rapidly soilifying electrolytic manganese slag using a microbial method, so as to solve the technical problems raised in the background technology.

[0015] The present invention solves the above technical problems with the following technical solutions: a method for quickly soilifying electrolytic manganese slag using a microbial method, a method for quickly soilifying electrolytic manganese slag using a microbial method, comprising the following steps:

[0016] (1) Mixing sugarcane pith powder, sugar mill filter mud and red mud in a certain proportion, adding them together with electrolytic manganese slag and water into a reaction tank, and obtaining the corresponding mixed waste residue after 6 hours of full reaction;

[0017] (2) After the mixed waste residue, biological organic fertilizer and No. 1 compound microbial agent are mixed and stirred, they are sent into a tank fermentation tank for aerobic fermentation. After 144 hours of rapid fermentation, during which the pile is turned over 2 to 3 times, active waste residue with low heavy metal ion content can be obtained;

[0018] (3) Sulfur powder and compound microbial agent No. 2 are added to the active waste residue, and after 48 hours of rapid fermentation, the pile is turned over 2 to 3 times during the fermentation period, and regenerated soil is obtained.

[0019] Furthermore, the sugarcane pith powder is particles of about 2 mm, the sugar factory filter mud has been filter-filtered, and the mass ratio of the sugarcane pith powder, the sugar factory filter mud and the red mud is 0.8-1.5:0.5-1.5:1. When the sugarcane pith powder, the sugar factory filter mud and the strongly alkaline red mud are mixed, the lignin in the sugarcane pith can be dissolved into small molecules under the action of the strong alkali, which promotes the separation of lignin and cellulose and is beneficial to the subsequent rapid fermentation; the organic matter and various inorganic elements such as N, P, K, Ca, etc. rich in the sugar factory filter mud can also promote the subsequent fermentation.

[0020] Further, the mass ratio of the electrolytic manganese slag, red mud, sugar factory filter mud, sugarcane pith mixture and water added to the reaction tank is adjusted according to the actual situation, and the water is added in time during the reaction process, preferably the water submerges the solid, to ensure that the soluble substances in the red mud, sugar factory filter mud and manganese slag are dissolved and fully reacted, the reaction time is 6h, to ensure that the final substrate water content is between 60% and 70%, and the pH value reaches between 6.0 and 7.5. During the reaction, there should be appropriate stirring operation, and the electrolytic manganese slag and red mud undergo acid-base neutralization reaction, and the product of the neutralization reaction can solidify some of the heavy metal elements such as manganese (Mn), arsenic (As), lead (Pb), chromium (Cr) in the waste residue mixture, thereby preliminarily reducing the content of heavy metal ions. Lignin in sugarcane pith can be dissolved to form small molecules under strong alkaline conditions, which promotes the separation of lignin, cellulose and hemicellulose. The three-dimensional network molecular structure of lignin is broken in this process, forming multiple smaller molecules with straight-chain structures, which helps microorganisms to decompose and utilize lignin, cellulose and hemicellulose more efficiently, thereby significantly improving the efficiency of fermentation degradation.

[0021] Furthermore, the mass ratio of the waste residue to the biological organic fertilizer is 4:1-2, the addition amount of No. 1 and No. 2 compound microbial agents is 3-5% of the total mass of the substrate, and the addition amount of sulfur powder is 5-10% of the total mass of the substrate.

[0022] Furthermore, the No. 1 compound microbial agent contains one or more of Bacillus megaterium, Bacillus mucilaginosus, Bacillus subtilis, Bacillus laterosporus, Bacillus acidobacillus, Bacillus thermophilus, Bacillus acidothiophilus, phosphate-solubilizing bacteria, and potassium-solubilizing bacteria. The main function of the No. 1 compound microbial agent is to reduce the heavy metal ion content and salinity in the mixed waste residue, making it more suitable for microbial growth and facilitating subsequent further processing.

[0023] Furthermore, the mesh size of the sulfur powder is required to be between 100 and 200 meshes. The sulfur powder can react chemically with heavy metals in the soil to form insoluble sulfides, thereby reducing the activity of heavy metals in the soil. The sulfur powder can be used as a sulfur source to promote the growth of specific microorganisms and help bioleaching heavy metals from the soil.

[0024] Furthermore, the compound microbial agent No. 2 includes one or more of silicate bacteria, phosphorus bacteria, potassium bacteria, yeast, nitrogen-fixing Rhodospirillum, lactobacillus, Bacillus subtilis, red yeast, oxalicum, Penicillium, and stratosphere Bacillus. The compound microbial agent No. 2 can form chelates with nutrients and microbial metabolites, which can greatly improve the absorption and utilization rate of nutrients by plants; at the same time, the microorganisms and their metabolites can be used to cement fine particles of waste residue and improve the physical structure of the waste residue. Before adding the compound microbial agent No. 2, it is necessary to ensure that the moisture content of the substrate is above 50%.

[0025] Furthermore, the compound microbial agent is a high-performance strain screened out by high-throughput screening technology, and flow cytometry is used to sort cells or particles.

[0026] Specifically, the compound microbial inoculant is firstly inoculated into a test tube slant for activation, the culture temperature is 28-35° C., and the pH is 6.0-7.5; and then the compound microbial inoculant is gradually amplified and cultured in flat bottles, shake bottles and seed tanks to obtain a large number of highly active compound strains.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention invents a low-cost, large-scale, rapid, green and pollution-free soil electrolytic manganese slag process by comprehensively utilizing the action of microorganisms. The process includes three main steps: acid-base neutralization, quality improvement and reclamation. At present, in the electrolytic manganese slag treatment and utilization process, there are many problems such as difficulty in large-scale consumption of electrolytic manganese slag, unclear economic benefits, high energy consumption of the utilization process, and secondary pollution, which makes it still only in the exploration stage in many fields and has not been truly industrialized. The present invention is advanced in technology in this field, and innovatively combines the soil electrolytic manganese slag with red mud, agricultural and aquaculture wastes and microorganisms, which has excellent environmental friendliness while achieving good economic benefits. On the one hand, the method utilizes red mud and electrolytic manganese slag to produce acid-base neutralization reaction, so as to achieve low-cost, rapid, efficient and pollution-free dealkalization of electrolytic manganese slag; on the other hand, the method utilizes microorganisms to quickly and efficiently decompose agricultural waste, which can increase the content of organic matter and nutrients in electrolytic manganese slag and the biological activity of beneficial bacteria at low cost and high efficiency. In summary, the present invention aims at the pain points of the current electrolytic manganese slag treatment, fundamentally solves the problems of long-term large-scale storage, difficulty in treatment and high cost of treatment of electrolytic manganese slag, and treats waste with waste, which is of great significance to the green development of the manganese industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a processing flow chart of a method for rapidly soilifying electrolytic manganese slag using a microbial method according to the present invention;

[0030] Figure 2 This is a flow chart of cultivating the composite formula strain of the present invention; DETAILED DESCRIPTION

[0031] The present invention is further described below with reference to the accompanying drawings and embodiments, but they do not limit the protection scope of the claims of the present invention.

[0032] See also Figure 1The present invention provides a method for rapidly soilifying electrolytic manganese slag using a microbial method, and the process is as follows: first, sugarcane pith powder, red mud and sugar factory filter mud are mixed in a certain proportion, and added into a reaction tank together with electrolytic manganese slag and water, and neutral mixed waste residue is obtained after 6 hours of sufficient reaction; then the mixed waste residue, biological organic fertilizer and No. 1 compound microbial inoculant are mixed and stirred, and then sent into a biological fermentation tank for aerobic fermentation, and after 48 hours of rapid fermentation, during which the pile is turned 2 to 3 times, active waste residue with low heavy metal ion content can be obtained; then sulfur powder and No. 2 compound microbial inoculant are added to the active waste residue, and after 144 hours of rapid fermentation, during which the pile is turned 2 to 3 times, regenerated soil can be obtained, and after all indicators are qualified, economic forest planting can be carried out. By combining water-fertilizer integrated technology (application publication numbers: CN116195418A, CN116283372A patents have been disclosed) and planting plants for joint restoration, soil fertility and biological activity are further improved, and finally a regenerated soil is obtained that is free of heavy metal pollution and rich in organic matter, trace elements and microorganisms beneficial to plant growth.

[0033] In the present invention, the cane pith powder is a particle of about 2 mm, and the mass ratio of cane pith powder, sugar factory filter mud and red mud is 0.8-1.5:0.5-1.5:1. Mixing cane pith powder, sugar factory filter mud and red mud can optimize the carbon-nitrogen ratio, improve the physical structure of the mixture, provide trace elements required for plant growth, and promote the decomposition of organic matter through microbial activity. This mixing also helps to adjust the pH value, making it more suitable for microbial growth, reducing environmental pollution, and converting waste into valuable resources, thereby accelerating the fermentation process and improving fermentation efficiency.

[0034] The mass ratio of the mixture of electrolytic manganese slag, red mud, sugarcane pith and sugar factory filter mud added to the reaction tank to water is adjusted according to the actual situation, and the water is added in time during the reaction process, preferably the water covers the solid, to ensure that the soluble substances in the red mud and manganese slag are dissolved and fully reacted. The reaction time is about 6h, and the final substrate water content is guaranteed to be about 60%, and the pH value reaches about 6.0-7.0, which can be regarded as complete reaction. Appropriate stirring operation should be performed during the reaction. Acidic electrolytic manganese slag and sugar factory filter mud can undergo acid-base neutralization reaction with red mud. The product of the neutralization reaction can solidify some heavy metal elements such as Mn, As, Pb, Cr in the waste residue mixture, and initially reduce the content of heavy metal ions. In addition, under the action of strong alkali, the lignin in the sugarcane pith can be decomposed into small molecules, thereby promoting the separation of lignin, cellulose and hemicellulose. The complex three-dimensional network structure of lignin is broken to form multiple smaller molecules with linear structures, which is conducive to the more efficient decomposition and utilization of lignin, cellulose and hemicellulose by microorganisms, and significantly improves the efficiency of fermentation degradation.

[0035] The mass ratio of the waste residue to the organic biofertilizer is 4:1-2, the addition amount of No. 1 and No. 2 compound microbial agents is 3-5% of the total mass of the substrate, and the addition amount of sulfur powder is 5-10% of the total mass of the substrate.

[0036] The No. 1 compound microbial agent contains one or more of Bacillus megaterium, Bacillus colloidus, Bacillus subtilis, Bacillus laterosporus, Bacillus acidobacillus, Bacillus thermophilus, Bacillus acidothiophilus, phosphate-solubilizing bacteria, and potassium-solubilizing bacteria. The No. 1 compound microbial agent mainly reduces the heavy metal ion content and salinity in the mixed waste residue, making it more suitable for microbial growth and facilitating subsequent further treatment.

[0037] The mesh size of the sulfur powder is required to be between 100 and 200. The main functions of sulfur powder are, on the one hand, chemical reaction with heavy metals in the soil to form insoluble sulfides, thereby further reducing the activity of heavy metals in the soil; on the other hand, sulfur powder can be used as a sulfur source to promote the growth of specific microorganisms and help bioleaching heavy metals from the soil.

[0038] The compound microbial agent No. 2 includes one or more of silicate bacteria, phosphorus bacteria, potassium bacteria, yeast, nitrogen-fixing Rhodospirillum, lactobacillus, Bacillus subtilis, red yeast, Penicillium oxalicum, Penicillium luminosporum, and stratosphere Bacillus. The main functions of the compound microbial agent No. 2 are: on the one hand, it can form chelates with nutrients (such as calcium, iron, etc.) and microbial metabolites (such as humic acid, amino acids, etc.), which can greatly improve the absorption and utilization rate of nutrients by plants; on the other hand, it can cement waste residue fine particles and improve the physical structure of waste residue through microorganisms and their metabolites. Before adding the compound microbial agent No. 2, it is necessary to ensure that the moisture content of the substrate is above 50%.

[0039] The compound microbial agent is a high-performance strain screened out by high-throughput screening technology. During the implementation process, flow cytometry (FCM) is used to sort cells or particles.

[0040] like Figure 2 As shown, the compound microbial agent is first inoculated into the test tube slope for activation, the culture temperature is 28-35°C, and the pH is 7.0; then it is cultured in a flat bottle or a shaking bottle and a seed tank step by step to obtain a large number of highly active composite strains. The purpose of the first-level seed culture is to reproduce a large number of bacteria with strong vitality. The culture medium should contain less sugar and more organic nitrogen, and the culture conditions should be considered to be conducive to bacterial growth. The second-level seed culture is to further expand the number of bacteria to achieve a sufficient number of bacterial strains required for fermentation.

[0041] A method for rapidly soilifying electrolytic manganese slag using waste biomass from sugarcane production, characterized in that the detection indicators for soilification of electrolytic manganese slag include: bulk density, pH, organic matter content, heavy metal ion content and soil respiration intensity. The indicators should meet the following requirements: bulk density ≤ 1.8 g / cm3; pH between 6.5 and 7.5; total organic carbon (TOC) ≥ 10.0 g / kg; heavy metal ion content should not be higher than the pollution risk screening value in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard" (GB 15618-2018); daily average soil respiration intensity ≥ 3.6 g / (m2·d).

[0042] A method for rapidly soilifying electrolytic manganese slag using waste biomass from sugarcane production, characterized in that after the regenerated soil is recultivated, a season of plants, preferably water spinach or edible sweet bamboo shoots, needs to be planted, and combined with water-fertilizer integration technology to further improve the biological activity and fertility of the soil, so that the quality of the cultivated land reaches a level higher than grade 10 in the "Land Use Status Classification" (GB / T 21010-2017) standard or grade 6 in the "Quality Grade of Cultivated Land" (GB / T33469-2016) standard.

[0043] The present invention mixes red mud, electrolytic manganese slag and sugar factory filter mud (collectively referred to as waste residue) to not only achieve acid-base neutralization, but also provide exchangeable Ca2+, promote the formation of aggregates and maintain the stability of the aggregate structure. The Ca2+ dissolved in the manganese slag and sugar factory filter mud can replace the Na+ and Mg2+ in the waste residue, and directly participate in the construction of the cationic bridge between clay and organic matter, promote the clay (C), multivalent cations (P) and organic molecules (OM) to form an organic-inorganic complex (C-P-OM), and these complexes are further combined to form large-particle aggregates, thereby increasing the number and stability of the aggregates. Some heavy metal elements such as As, Pb, and Cr in the red mud are precipitated; some metal ions are initially solidified.

[0044] Using biological methods to soilify electrolytic manganese slag: Microorganisms can promote the formation of soil aggregate structure. After adding organic materials, microorganisms produce biopolymers or organic cementing substances through metabolism or decomposition. The viscosity and cementing properties of these substances promote the formation of large-size aggregates and also reduce the content of small-size aggregates in the soil. Biopolymers are natural polymers produced by organisms. In other words, they are polymerized biological molecules derived from cells or extracellular substances. Biopolymers have covalent bonds and will form monomer units with larger structures. According to the monomer units used and the structure of the biopolymers formed, biopolymers are divided into two major categories: polynucleotides, polypeptides and polysaccharides. As natural polymers produced by biological organisms, biopolymers added to soil show excellent potential in enhancing inter-particle cohesion and reducing soil erodibility. Studies have found that biopolymers added to soil will form surface adhesion, cell self-adhesion biofilms, protective barriers, etc., which can promote water retention and nutrient accumulation around plant roots, and can effectively improve the stability of slope soil and improve the soil's anti-erosion ability.

[0045] Microorganisms can enhance soil nutrient absorption, improve soil fertility, and promote plant growth and development through their own life activities and interactions with the surrounding environment. At the same time, they increase crop yields, prevent and control plant diseases and insect pests through various mechanisms, such as nitrogen fixation, dissolving potassium and phosphorus, excreting plant hormones, producing substances that inhibit plant pathogens, and protecting plants from abiotic and biotic stresses. In addition, microorganisms can adsorb heavy metal ions through charged cell surfaces (especially cell walls), or use their metabolites to combine with heavy metals to produce precipitation. They can also directly absorb heavy metals as necessary nutrients and enrich them in different parts of the cell, reducing the mobility of heavy metals. For example, humic acid produced after fermentation of sugarcane pith can not only promote the aggregation of dispersed waste particles to form stable and larger aggregates, but also act as a chelating agent for trace metal elements. Humic acid can reduce the content of metal ions and trace elements in the soil, reduce mineralization, and thus affect the toxicity and bioavailability of metal ions.

[0046] The growth and development of plants in the soil can improve the soil: on the one hand, the root system of plants, as the part that is in direct contact with the soil, plays a role of interpenetration, improves the permeability of the soil, and improves the physical and chemical properties of the soil; on the other hand, the root, stem, and leaf residues of plants can be decomposed by microorganisms and converted into organic matter in the soil, thereby improving soil fertility. Plants and microorganisms form a symbiotic system in the soil. The growth and metabolism of plants provide nutrients and necessary living conditions for the survival and reproduction of microorganisms, and the reproduction of microorganisms creates more nutrients for plant growth. At the same time, the interaction of this symbiotic system improves the physical and chemical properties of the soil and forms a soil nutrient circulation system, making long-term improvement of soil nutrients possible.

[0047] Soil is the crust of the earth, where geography and biology meet. The land surface provides habitats for plants, animals and microscopic life. Soil is the most suitable environment for microorganisms to live. It has all the conditions required for microorganisms to grow, reproduce and carry out life activities. Soil organic matter can be divided into three categories, namely insoluble, soluble and microbial. Soil organic matter has various sources, such as cellulose, wood and plant remains and polysaccharides (such as pectin).

[0048] Soil biological activity refers to the sum of the life intensity of various organisms in the soil. The activity of soil organisms depends to a large extent on the physical and chemical properties of the soil. It mainly involves factors such as soil temperature, humidity, ventilation conditions, gas composition, pH, content and composition of organic and inorganic substances. Soil respiration intensity and fiber decomposition intensity are important indicators of soil biological activity; they also reflect the speed and intensity of biological activity and decomposition of organic residues in the soil.

[0049] Soil organisms are usually compared to "converters" of soil nutrient cycles, "purifiers" of environmental pollutants, and "regulators" of terrestrial ecosystem stability. It can be said that without soil microorganisms, the soil loses its biological activity and its production capacity. But how to improve the activity of soil microorganisms? When the soil temperature is low and lacks organic matter and microbial populations, the soil biological activity is low. Therefore, red mud should be treated in a targeted manner to restore its soil biological activity. Agricultural technical measures (including tillage, cultivation, fertilization, irrigation, drainage and application of pesticides, etc.) can also affect the activity of soil organisms. Under certain conditions, targeted inoculation measures can also be used to purposefully increase the number and biochemical intensity of certain microorganisms.

[0050] Active organic matter is an important component of soil, mainly including dissolved organic carbon, microbial biomass, and light organic matter. In terms of soil nutrients, soil biological activity, and chemical properties: the dissolved organic carbon and microbial biomass carbon and nitrogen content in the soil are positively correlated with the content of soil organic phosphorus, total nitrogen, and alkaline nitrogen; active organic matter is affected by factors such as soil texture, water content, and humidity, and is also related to soil pH, cation exchange capacity, etc. The soil microbial biomass carbon and the ratio of microbial biomass carbon to organic carbon are positively correlated with the content of soil clay and silt, and negatively correlated with the content of sand.

[0051] The meaning of arable land quality usually refers to the soil fertility and soil environment quality that can meet the needs of crop growth and safe production. It is called arable land quality. Generally, arable land is divided into common arable land and temporary arable land. Common arable land refers to land that is specially used to grow crops, is cultivated regularly, and can be harvested normally; while temporary arable land is land that is temporarily reclaimed outside common arable land and cannot be harvested normally. According to the national standard "Classification of Land Use Status" (GB / T 21010-2017), the classification of arable land grades: 1. There are 15 grades of arable land quality, among which grade 1 is the best, and grade 15 is the worst. 2. Grades 1 to 4 of arable land quality are excellent land, grades 5 to 8 are high-grade land, grades 9 to 12 are medium-grade land, and grades 13 to 15 are low-grade land. The standard "Arable Land Quality Grade" (GB / T 33469-2016) uses a comprehensive index method to evaluate the ability of arable land fertility, soil health status, and field infrastructure to meet the continuous output and quality safety of agricultural products. The quality of cultivated land is divided into 10 levels. The greater the comprehensive index of cultivated land quality, the higher the level of cultivated land quality. The first-grade cultivated land has the highest quality, and the tenth-grade cultivated land has the lowest quality. The detection indicators of electrolytic manganese slag soilification include: bulk density, pH, organic matter content, heavy metal ion content and soil respiration intensity. The indicators should meet the following requirements: bulk density ≤ 1.8g / cm3; pH between 6.5 and 7.5; total organic carbon (TOC) ≥ 10.0g / kg; heavy metal ion content should not be higher than the pollution risk screening value in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard" (GB 15618-2018); daily average soil respiration intensity ≥ 3.6g / (m2·d).

[0052] Microbial breeding and cultivation technology

[0053] Application of high-throughput screening of compound microbial agents (engineered strains). Traditional manual screening methods are inefficient, labor-intensive, and require a lot of manpower and material resources. In this context, high-throughput screening technology came into being. Usually, high-throughput screening should meet two basic conditions:

[0054] 1. Develop a suitable screening model based on the characteristics of the target product (physical and chemical properties, biological properties, etc.), and convert the characteristics of the sample into a variety of signals that can be efficiently sensed and identified by cameras and high-speed computers.

[0055] 2. Execute relevant test processes with an automated operating system controlled by artificial intelligence, including: automatically completing operations such as pipetting, inoculation, and cleaning

[0056] During the implementation process, flow cytometry (FCM) is used to sort cells or particles. FCM is a new type of analysis and screening technology that uses a flow cytometer to make cells or particles flow in a liquid flow, pass a beam of incident light, and use a highly sensitive detector to record the scattered light and different fluorescent signals, so as to quickly measure cells or other particles in the liquid flow.

[0057] FCM mainly includes sample flow technology, cell sorting and counting technology, and data collection and analysis technology, etc. It has the characteristics of fast measurement speed, multiple measurement parameters, large amount of collected data, comprehensive analysis, flexible methods, and accurate sorting of target cells.

[0058] FCM can not only be used to count cells, analyze characteristics, analyze cell cycles, sort chromosomes, etc., but can also be used to measure genome size, perform flow cytometry karyotype analysis, and further locate genes and construct chromosome libraries.

[0059] Excellent composite strains are the foundation and key value of this technology. First of all, there must be industrial production strains with improved performance. The purpose of selecting and breeding composite strains is to improve the characteristics of the strains so that they meet the needs of actual implementation. Strain selection and breeding include two parts: selection and breeding. During the implementation process, the requirements for composite strains are: they have their own self-protection mechanism, fast growth and reaction speed, can grow on culture media made of cheap raw materials, have high yields of target products, are easy to recover, the bacteria themselves are not pathogenic, the strains are not easy to mutate and degenerate, are genetically stable, have mild culture conditions, are easy to control, and have high yields.

[0060] Seed expansion culture is the process of obtaining a certain quantity and quality of composite strains by inoculating the composite strains into the test tube slope for activation, and then gradually amplifying and culturing them through flat bottles, shake bottles and seed tanks. The expansion culture of composite strains is of great significance. The fermentation tanks in the large-scale implementation process produce dozens of cubic meters of strains. In the implementation process, the preparation of composite strains is divided into two stages: laboratory composite strain preparation and production workshop strain preparation stage.

[0061] Preparation of bacterial strains in the production workshop: Liquid bacterial strains prepared in the laboratory are moved into seed tanks for expansion culture. The function of the seed tank is to make the bacterial strains grow rapidly after being inoculated and reach a certain amount of bacterial body volume to facilitate further reaction of the product. Seed age and inoculation amount are two very important process conditions in the process of bacterial strain expansion culture.

[0062] The purpose of primary seed culture is to reproduce a large number of bacteria with strong vitality. The culture medium should contain less sugar and more organic nitrogen, and the culture conditions should be considered to be conducive to bacterial growth. Secondary seed culture is to further expand the number of bacteria to reach a sufficient number of bacterial populations required for fermentation.

[0063] Example: A manganese company in Guangxi

[0064] Manganese slag was collected from the manganese slag yard of the enterprise, and red mud was collected from the red mud yard of an aluminum company in Guangxi. The sample collection method was implemented in accordance with the sampling standards specified in the "Technical Specifications for Soil Environmental Testing (HJ / T166-2004)". Five sub-sampling points were set up using the plum blossom sampling method, and about 1 t of samples from 0 to 20 cm depth on the surface were collected. After mixing, they were transported back to the laboratory. The basic physical and chemical properties and heavy metal content of the collected manganese slag and red mud are shown in the following table.

[0065] Table 1 Basic physical and chemical properties of manganese slag

[0066]

[0067]

[0068] Table 2 Basic physical and chemical properties of red mud

[0069] Test items Test results pH 10.62 Total organic carbon (TOC), g / kg 3.45 Available phosphorus, mg / kg 13.39 Available potassium, mg / kg 16.81 Total nitrogen, mg / kg 2.33 Bulk density, g / cm3 2.75 Daily average soil respiration intensity, g / (m2·d) ≤0.1

[0070] Table 3 Heavy metal ion content of manganese slag and red mud (mg / kg)

[0071] sample Cu Zn As Pb Cr Mn Cd Ni Red Mud 35.04 366.79 37.81 280.83 186.49 76.23 0.91 37.28 Manganese slag - 91.86 - 90.37 33.82 44614 0.40 41.69

[0072] According to the regulations on agricultural soil pollution values ​​in the Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (GB 15618-2018), the Mn content in manganese slag significantly exceeded the standard. In addition, the content of other heavy metals in the sample did not exceed the pollution risk control value, but the content of some heavy metals exceeded the pollution risk screening value. That is, the pollution risk is high and further control is needed before crops can be planted.

[0073] 1 ton of electrolytic manganese slag was treated with soil, mainly through the steps of neutralization, quality improvement and phytoremediation. Neutralization: 1.2 tons of red mud, sugar factory filter mud and cane pith mixture (the mass ratio of red mud, sugar factory filter mud and cane pith is 1:1.2:1.2) and 1 ton of electrolytic manganese slag were neutralized in the reaction tank, and the mixture was produced in a muddy state and filtered. Quality improvement: 200 kg of biological organic fertilizer and 50 kg of compound microbial agent 1 were added to the neutral mixture produced, and fermented for 48 hours to passivate or solidify the heavy metal ions; then 400 kg of biological organic fertilizer, 100 kg of sulfur powder and 50 kg of compound microbial agent 2 were added, and fermented for 144 hours to increase its organic matter content and soil biological activity; finally, the electrolytic manganese slag was initially soilized. After the initial soilization of red mud was completed, a series of experiments and tests were carried out on it, and the results are as follows.

[0074] Table 4 Basic physical and chemical properties of manganese slag after biological soil treatment

[0075] Test items Test results pH 7.11 Total organic carbon (TOC), g / kg 10.94 Available phosphorus, mg / kg 28.89 Available potassium, mg / kg 28.14 Total nitrogen, mg / kg 845.26 Bulk density, g / cm3 1.66 Daily average soil respiration intensity, g / (m2·d) 5.7

[0076] Table 5 Heavy metal ion content of manganese slag after biological soil treatment (mg / kg)

[0077] Cu Zn As Pb Cr Mn Cd Ni 17.87 101.13 5.28 60.77 79.36 773.18 0.09 13.51

[0078] Table 6 Water spinach seed germination rate

[0079] Planting medium Germination rate Untreated manganese slag 0％ Manganese slag after biological treatment 78％

[0080] The above data show that the daily average soil respiration intensity, organic matter and nutrient content of manganese slag after biological soil treatment have been greatly improved, while the bulk density has been greatly reduced, that is, the physical and chemical structure of the soil has been greatly improved; the heavy metal content of manganese slag treated by microbial method is also lower than the pollution risk screening value in the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard" (GB 15618-2018), that is, the risk of heavy metals in the soil to the quality and safety of agricultural products, crop growth or soil ecological environment is low and can be ignored under normal circumstances. Due to the improvement of the extreme physical and chemical properties of manganese slag, the germination rate of water spinach seeds has increased from 0% to 78%, which is very suitable for plant growth. This is conducive to further phytoremediation of manganese slag (planting water spinach) to improve soil fertility and biological activity, and can improve the stability of soil aggregate structure, so that the quality of cultivated land reaches higher than level 10 in the "Land Use Status Classification" (GB / T21010-2017) standard or level 6 in the "Cultivated Land Quality Grade" (GB / T 33469-2016) standard, and finally fully realize the soil biological activity reclamation of manganese slag.

Claims

1. A method for rapidly soilifying electrolytic manganese slag using a microbial method, characterized in that: The following steps are involved: (1) Mixing sugarcane pith powder, sugar mill filter mud and red mud in a certain proportion, adding them together with electrolytic manganese slag and water into a reaction tank, and obtaining the corresponding mixed waste residue after 6 hours of full reaction; (2) After the mixed waste residue, biological organic fertilizer and No. 1 compound microbial agent are mixed and stirred, they are sent into a tank fermentation tank for aerobic fermentation. After 144 hours of rapid fermentation, during which the pile is turned over 2 to 3 times, active waste residue with low heavy metal ion content can be obtained; (3) Sulfur powder and compound microbial agent No. 2 are added to the active waste residue, and after 48 hours of rapid fermentation, the pile is turned over 2 to 3 times during the fermentation period, and regenerated soil is obtained.

2. The method for rapidly soilifying electrolytic manganese slag using microbial method according to claim 1, characterized in that: The sugarcane pith powder is particles of about 2 mm, the sugar factory filter mud has been filter-pressed, and the mass ratio of the sugarcane pith powder, the sugar factory filter mud and the red mud is 0.8-1.5:0.5-1.5:

1. When the sugarcane pith powder, the sugar factory filter mud and the strongly alkaline red mud are mixed, the lignin in the sugarcane pith can be dissolved into small molecules under the action of the strong alkali, which promotes the separation of lignin and cellulose and is beneficial to the subsequent rapid fermentation; the organic matter and various inorganic elements such as N, P, K, Ca, etc. rich in the sugar factory filter mud can also promote the subsequent fermentation.

3. The method for rapidly soilifying electrolytic manganese slag using a microbial method according to claim 2, characterized in that: The mass ratio of the electrolytic manganese slag, red mud, sugar factory filter mud, sugarcane pith mixture and water added to the reaction tank is adjusted according to actual conditions, and water is added in time during the reaction process, preferably the water covers the solid, to ensure that the soluble substances in the red mud, sugar factory filter mud and manganese slag are dissolved and fully reacted. The reaction time is 6 hours, to ensure that the final substrate water content is between 60% and 70%, and the pH value reaches between 6.0 and 7.

5. Appropriate stirring operation should be performed during the reaction. The electrolytic manganese slag and red mud undergo acid-base neutralization reaction. The product of the neutralization reaction can solidify some heavy metal elements such as Mn, As, Pb, Cr in the waste residue mixture, preliminarily reduce the content of heavy metal ions, and the lignin in the sugarcane pith can be dissolved into small molecular substances under the action of strong alkali, thereby promoting the separation of lignin, cellulose and hemicellulose. Lignin is broken from a complex three-dimensional network molecule into multiple smaller molecules with a straight-chain structure, which is conducive to more efficient decomposition and utilization of lignin, cellulose and hemicellulose by microorganisms, greatly improving the fermentation degradation efficiency.

4. The method for rapidly converting electrolytic manganese slag into soil using a microbial method according to claim 3, characterized in that: The mass ratio of the waste residue to the biological organic fertilizer is 4:1-2, the addition amount of No. 1 and No. 2 compound microbial agents is 3-5% of the total mass of the substrate, and the addition amount of sulfur powder is 5-10% of the total mass of the substrate.

5. The method for rapidly soilifying electrolytic manganese slag using microbial method according to claim 4, characterized in that: The No. 1 compound microbial agent contains one or more of Bacillus megaterium, Bacillus mucilaginosus, Bacillus subtilis, Bacillus laterosporus, Bacillus acidobacillus, Bacillus thermophilus, Bacillus acidothiophilus, phosphate-solubilizing bacteria, and potassium-solubilizing bacteria. The main function of the No. 1 compound microbial agent is to reduce the heavy metal ion content and salinity in the mixed waste residue, making it more suitable for microbial growth and facilitating subsequent further treatment.

6. The method for rapidly soilifying electrolytic manganese slag using microbial method according to claim 5, characterized in that: The mesh size of the sulfur powder is required to be between 100 and 200 meshes. The sulfur powder can react chemically with heavy metals in the soil to form insoluble sulfides, thereby reducing the activity of heavy metals in the soil. The sulfur powder can be used as a sulfur source to promote the growth of specific microorganisms and help bioleaching heavy metals from the soil.

7. The method for rapidly soilifying electrolytic manganese slag using microbial method according to claim 6, characterized in that: The No. 2 compound microbial agent includes one or more of silicate bacteria, phosphorus bacteria, potassium bacteria, yeast, nitrogen-fixing Rhodospirillum, lactobacillus, Bacillus subtilis, red yeast, Penicillium oxalicum, Penicillium photosporum, and stratosphere Bacillus. The No. 2 compound microbial agent can form chelates with nutrient elements and microbial metabolites, which can greatly improve the absorption and utilization rate of nutrient elements by plants; at the same time, fine particles of waste residue can be cemented by microorganisms and their metabolites to improve the physical structure of the waste residue. Before adding the No. 2 compound microbial agent, it is necessary to ensure that the moisture content of the substrate is above 50%.

8. The method for rapidly soilifying electrolytic manganese slag using microbial method according to claim 7, characterized in that: The compound microbial agent is a high-performance strain screened out by high-throughput screening technology, and flow cytometry is used to sort cells or particles.

9. The method for rapidly converting electrolytic manganese slag into soil using a microbial method according to claim 8, characterized in that: The compound microbial inoculant is firstly inoculated into a test tube slant for activation, the culture temperature is 28-35°C, and the pH is 6.0-7.5; and then the compound microbial inoculant is gradually amplified and cultured in flat bottles, shaking bottles and seed tanks to obtain a large number of highly active compound strains.

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