Preparation method and application of bentonite-based iron-carbon immobilized microbial particles

Abstract

The invention belongs to the technical field of water treatment, and relates to a preparation method and application of bentonite-based iron-carbon immobilized microbial particles. The preparation method of the bentonite-based iron-carbon immobilized microbial particles comprises the following steps: S1, mixing bentonite, plant powder and zero-valent iron, granulating, and pyrolyzing to obtain bentonite-based iron-carbon particles; s2, mixing and wrapping the bentonite-based iron carbon particles, an adhesive and microorganisms in sequence to obtain bentonite iron carbon-microorganism particles; s3, mixing and wrapping the bentonite iron carbon-microorganism particles with an adhesive and a flocculating agent in sequence to obtain bentonite iron carbon microorganism-adhesive flocculation structure particles; and S4, mixing the bentonite iron-carbon microbe-bonded flocculation structure particles with efficient degradation bacteria, and drying to obtain the bentonite-based iron-carbon immobilized microbe particles. The preparation method is easy to operate and low in cost, iron-carbon micro-electrolysis is increased to promote the microbial effect, the activity of microorganisms is improved, and the method is suitable for the field of in-situ remediation of micro-polluted water.

Description

Technical Field

[0001] The present invention belongs to the field of water treatment technology, more specifically to the field of water treatment technology for micro-polluted water treatment and in-situ restoration of polluted water, and relates to a preparation method and application of bentonite-based iron-carbon immobilized microbial particles. Background Art

[0002] Untreated industrial and agricultural wastewater and domestic sewage discharged directly or indirectly into natural waters will lead to excessive levels of organic matter, nitrogen, phosphorus, heavy metals and pesticides in the water, and the pollution load far exceeds the self-purification capacity of the water. Eutrophication problems are prominent, and even serious black and smelly phenomena occur, which have a bad impact on the lives and health of surrounding residents. Therefore, the treatment of micro-polluted water bodies and in-situ remediation of polluted water bodies are imminent.

[0003] In-situ remediation technology is a common method in sewage treatment. It refers to the treatment of polluted water bodies on site by directly adding microorganisms, fillers, chemicals, etc. without changing the original riverbed. It has the characteristics of simple operation, economical and excellent results, and is widely used in practical applications. Commonly used in-situ remediation methods at home and abroad are divided into three types: physical, chemical and biological methods. Among them, biological methods mostly use microorganisms to reduce, eliminate, absorb and transform pollutants in polluted environmental media (such as sediments) to partially or completely restore polluted water bodies to their original state. Bioremediation technology has little impact on the environment and can minimize the concentration of pollutants. However, due to the fast flow of the river itself and the unfavorable environmental conditions around it, the bacteria lack carriers in the river, are easy to lose, and the density of bacteria is reduced, which limits the purification effect of microorganisms.

[0004] In the entire immobilized microorganism system, the biological carrier is the technical core, among which the immobilized microorganism method is divided into four types: adsorption method, embedding method, cross-linking method and covalent bonding. The adsorption method is that the microorganism adheres to the surface of the carrier through physical or ionic adsorption force. The adsorption method has a mild reaction, simple operation, low cost and no secondary pollution. Therefore, it is widely used in the immobilization of microorganisms on carrier materials. In the prior art, it is mentioned that the immobilized microorganism particles are prepared by the adsorption method, such as first granulating with ore powder, binder, flocculant and water and then calcining as the core, and then wrapping microorganisms and high-efficiency degradation bacteria in turn to obtain microbial immobilized particles. Although this method can effectively improve the mechanical strength of the immobilized particles to a certain extent, in practical applications, the number of microorganisms loaded by such particles is limited and the activity is low, resulting in poor microbial treatment effect. Therefore, it is still necessary to seek a new method for preparing immobilized microbial particles and their application to solve the existing technical defects, improve the activity and quantity of microorganisms, and make the pollutant removal effect better. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of bentonite-based iron-carbon immobilized microbial particles to solve the problems existing in the above-mentioned prior art. The preparation method of the present invention is simple to operate, low in cost, increases iron-carbon micro-electrolysis to promote the action of microorganisms, improves the activity of microorganisms, and is suitable for the field of in-situ remediation of micro-polluted water bodies.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing bentonite-based iron-carbon immobilized microbial particles, the steps comprising:

[0008] S1, mixing bentonite, plant powder and zero-valent iron, granulating, and pyrolyzing to obtain bentonite-based iron-carbon particles;

[0009] S2, mixing and encapsulating the bentonite-based iron-carbon particles with a binder and a microorganism in sequence to obtain bentonite-iron-carbon-microorganism particles;

[0010] S3, mixing and encapsulating the bentonite iron-carbon-microorganism particles with a binder and a flocculant in sequence to obtain bentonite iron-carbon microorganism-adhesive flocculation structure particles;

[0011] S4, mixing the bentonite iron-carbon microorganism-bonding flocculation structure particles with high-efficiency degradation bacteria and drying them to obtain bentonite-based iron-carbon immobilized microorganism particles.

[0012] Bentonite can be used as a carrier of microbial agents. It has excellent adsorption capacity and affinity, helps to fix and protect microorganisms, and also adsorbs nutrients such as nitrogen and phosphorus in water. Plant powder and zero-valent iron are pyrolyzed at high temperature to form an iron-carbon composite material. The high specific surface area and adsorption capacity of biochar, as well as the iron-carbon micro-electrolysis performance, are used to improve the adsorption and degradation effect of the material on pollutants. The adhesive can attach a variety of microorganisms and also flocculate and reduce the bottom mud. Microorganisms can not only degrade organic pollutants in water, but also improve the light transmittance and odor of water. Flocculants can effectively remove pollutants and treat bottom mud through various mechanisms such as coagulation, precipitation and adsorption. High-efficiency degradation bacteria can effectively degrade pollutants such as nitrogen and phosphorus in water by evenly attaching to the surface of particles and self-propagating according to water quality conditions, while achieving a balance of bacterial species, making the sewage treatment process simpler and more efficient.

[0013] The bentonite-based iron-carbon particles provided by the present invention can not only protect the microorganisms inside the mineral particles, but also have the ability to fix external efficient degradation bacteria. The bentonite-based iron-carbon structure, the adhesive flocculation material and the microorganisms interact with each other, give full play to their own advantages, and are optimally prepared according to different polluted water bodies, which can effectively improve the water purification capacity and achieve the goals of energy conservation, emission reduction and resource utilization.

[0014] In steps S1 to S3 of the present invention, some water needs to be added or sprayed for granulation or mixed packaging. The amount of water is not particularly limited here and can be added according to the conventional experience of granulation and mixed packaging mastered by those skilled in the art.

[0015] Furthermore, the bentonite and plant powder are sieved through a 100-200 mesh sieve, preferably 200 mesh.

[0016] Bentonite and plant powders with smaller particle sizes will have a larger specific surface area, increase their contact area with liquids or other substances, and improve adsorption capacity.

[0017] Furthermore, the mass ratio of the bentonite to the plant powder is 2:1 to 6:1.

[0018] Furthermore, the amount of zero-valent iron used is 10% to 30% of the mass of bentonite.

[0019] There is no particular limitation on the granulation process in the present invention, and conventional extrusion granulation or roller granulation can be used. The particle size of the extrusion granulation is preferably 1 to 2 mm, and the shape is preferably spherical.

[0020] The bentonite used in the present invention is one of the clay minerals that are relatively abundant on the surface. It has the advantages of wide sources, low cost, easy availability, environmental protection and non-toxicity, large surface area, large cation exchange capacity, high porosity, and active sites on the surface. It is considered to be a low-cost adsorption material. As an immobilized microbial carrier, its large specific surface area and porous structure not only provide adsorption sites for microorganisms, but also have a high efficiency in adsorption of pollutants such as nitrogen and phosphorus.

[0021] The present invention uses plant powder (agricultural and forestry waste and / or wetland plants) as raw materials, pyrolyzes and prepares biochar, which largely realizes the resource utilization of waste and reduces environmental pollution. At the same time, the production cost of biochar is relatively low, and it has a high specific surface area and porous structure, as well as abundant surface functional groups, so that it has good adsorption performance and can effectively adsorb pollutants in water bodies. Through the excellent performance of biochar, it provides sufficient attachment sites for microorganisms, making it easier for microorganisms to be fixed on the surface, thereby increasing the microbial load.

[0022] The source of zero-valent iron in the present invention is not particularly limited, and the purchasing method does not affect the realization of the technical effect.

[0023] The plant powder in the present invention is powder of agricultural and forestry waste or wetland plants, preferably wetland plant powder, more preferably canna powder.

[0024] Furthermore, the pyrolysis temperature is 500-600°C, the heating rate is 5-10°C / min, and the pyrolysis time is 1-2h.

[0025] Furthermore, the mass ratio of the bentonite-based iron-carbon particles, the binder and the microorganisms is 90-110:0.1-0.5:0.8-1.5.

[0026] Furthermore, the microorganism includes at least one of Bacillus subtilis, methanogens and alkaligenes.

[0027] The microorganisms used in the present invention are all commercially available products, and the total viable count is not less than 2×10 11 cfu / g.

[0028] Furthermore, the mass ratio of the bentonite iron-carbon-microorganism particles, the adhesive and the flocculant is 90-110:1-2:3-5.

[0029] Furthermore, in step S2 and step S3, the adhesive is selected from at least one of chitosan, carboxymethyl chitosan, sodium alginate and polyvinyl alcohol.

[0030] Furthermore, the flocculant includes at least one of aluminum sulfate, polyaluminum chloride (PAC), polyaluminum sulfate (PAS), polyferric chloride (PFS), starch, cellulose and polyacrylamide (PAM).

[0031] Furthermore, the mass ratio of the bentonite iron-carbon microorganism-bonding flocculation structure particles and the high-efficiency degradation bacteria is 90-110:0.8-1.5.

[0032] Furthermore, the efficient degradation bacteria include at least one of nitrifying bacteria, denitrifying bacteria and phosphorus removal bacteria.

[0033] The high-efficiency degradation bacteria used in the present invention are all commercially available products, and the total number of viable bacteria is not less than 2×10 10 cfu / g.

[0034] Furthermore, the drying temperature is 30-40° C. and the drying time is 6-8 hours.

[0035] The second technical solution of the present invention is to provide bentonite-based iron-carbon immobilized microbial particles prepared by the above preparation method.

[0036] The bentonite-based iron-carbon immobilized microbial particles prepared by the present invention fix the microorganisms on the surface and inside of the carrier material, reduce the toxicity of external pollutants and the competition of harmful microorganisms, make the bacteria continuously proliferate in the carrier and diffuse outward, and avoid the loss of the original bacteria.

[0037] The third technical solution of the present invention is to provide an application of the above-mentioned bentonite-based iron-carbon immobilized microbial particles in the treatment of slightly polluted wastewater.

[0038] The present invention discloses the following technical effects:

[0039] The present invention synthesizes iron-carbon micro-electrolysis materials through high-temperature pyrolysis of zero-valent iron and biomass materials such as plant powder (agricultural and forestry waste and / or wetland plants), which not only provides electron donors for the denitrification process of the microbial community, but also promotes the increase of the abundance of functional microbial communities and related functional enzymes, thereby achieving synergistic removal of pollutants and realizing efficient purification of micro-polluted water bodies in a relatively short time. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0041] Figure 1 The finished products of bentonite-based iron-carbon immobilized microbial particles prepared in Example 1 and Comparative Example 1, wherein (a) is Example 1 and (b) is Comparative Example 1;

[0042] Figure 2 The removal effect of the immobilized microbial particles prepared in Example 1 and Comparative Example 1 on COD in the experimental water body;

[0043] Figure 3 The removal effect of the immobilized microbial particles prepared in Example 1 and Comparative Example 1 on TP in the experimental water body;

[0044] Figure 4 The immobilized microbial particles prepared in Example 1 and Comparative Example 1 reacted with NH4 + -N removal effect;

[0045] Figure 5 The figure shows the removal effect of TN in the experimental water by the immobilized microbial particles prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0046] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0047] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0048] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0049] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0050] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0051] The raw materials and reagents used in the specific implementation of the present invention are all commercially available products, among which bentonite is provided by Sichuan Lanxin Runda Mining Co., Ltd.; zero-valent iron is provided by Chengdu Jinshan Chemical Reagent Co., Ltd.; plant powder raw materials are selected from Canna indica, a common plant in wetlands; microorganisms are provided by Wuhan Guize Biotechnology Co., Ltd., and the total viable count is 2×10 11 cfu / g, mainly composed of Bacillus subtilis; the efficient degradation bacteria were provided by Beihai Yeshengwang Biotechnology Co., Ltd., with a total viable count of 2×10 10 cfu / g, mainly composed of nitrifying bacteria and denitrifying bacteria.

[0052] Example 1

[0053] The preparation steps of bentonite-based iron-carbon immobilized microbial particles are as follows:

[0054] S1. Use canna, a common plant in wetlands, as raw material. After harvesting, rinse it three times with ultrapure water, wash it, cut it into 3-6 cm small pieces with a guillotine, put it in an oven, heat it to 105°C, bake it to constant weight, take it out, crush it, and pass it through a 200-mesh sieve for later use;

[0055] Grind the bentonite and pass it through a 200-mesh sieve for later use;

[0056] S2, weighing 100g of sieved bentonite powder, 20g of plant powder (canna powder), 10g of zero-valent iron and 40mL of water, mixing them evenly and granulating them in a granulator, screening particles with a particle size of 1-2mm after granulation, placing them in a nitrogen atmosphere tubular furnace for pyrolysis, and the pyrolysis parameters are: heating rate 5°C / min, heating to 500°C for pyrolysis for 1h, and naturally cooling to room temperature to obtain spherical bentonite-based iron-carbon particles with a particle size of 1-2mm;

[0057] S3, weighing 20g of bentonite-based iron-carbon particles, and mixing with 0.04g of a binder (chitosan) and 0.1g of a microorganism (Bacillus subtilis powder) in sequence for coating, spraying water to assist the coating process, to obtain bentonite-iron-carbon-microorganism particles;

[0058] S4, weighing 20g of bentonite iron-carbon-microorganism particles, and sequentially encapsulating them with 0.4g of adhesive (chitosan) and 1g of flocculant (PAC), spraying water to assist the encapsulation process, to obtain bentonite iron-carbon microorganism-adhesive flocculent particles;

[0059] S5. Weigh 20g of bentonite iron-carbon microorganism-bonded flocculation particles and 0.2g of high-efficiency degradation bacteria (denitrifying bacteria powder and nitrifying bacteria powder in a mass ratio of 1:1) and wrap them in sequence. The obtained particles are placed in a drying oven at 35°C and dried for 8h to obtain bentonite-based iron-carbon immobilized microbial particles. The actual picture is as follows Figure 1 As shown in (a) in .

[0060] Comparative Example 1

[0061] The preparation steps of immobilized microbial particles are as follows:

[0062] S1, grind the bentonite and pass it through a 200 mesh sieve for later use;

[0063] S2, weighing 100g of sieved bentonite powder and 35mL of water, mixing them evenly, granulating them in a granulator, screening particles with a particle size of 1 to 2mm after granulation, placing them in a muffle furnace and calcining them at 500°C for 1h, cooling them naturally to room temperature, and obtaining spherical bentonite calcined particles with a particle size of 1 to 2mm;

[0064] S3, weighing 20 g of bentonite calcined particles, and sequentially encapsulating them with 0.04 g of a binder (chitosan) and 0.1 g of a microorganism (Bacillus subtilis powder), spraying water to assist the encapsulation during the encapsulation process, to obtain bentonite calcined-microorganism particles;

[0065] S4, weighing 20 g of bentonite calcined-microorganism particles, and sequentially encapsulating them with 0.4 g of a binder (chitosan) and 1 g of a flocculant (PAC), during which water can be sprayed to assist the encapsulation, to obtain bentonite calcined microorganism-adhesive flocculent particles;

[0066] S5. Weigh 20 g of bentonite calcined microorganism-bonded flocculation particles and 0.2 g of high-efficiency degradation bacteria (denitrifying bacteria powder and nitrifying bacteria powder in a mass ratio of 1:1) and wrap them in sequence. The obtained particles are placed in a drying oven at 35°C and dried for 8 hours to obtain immobilized microbial particles. The actual picture is as follows: Figure 1 As shown in (b) in .

[0067] Test example

[0068] The immobilized microbial particles prepared in Example 1 and Comparative Example 1 were mixed with experimental water at a solid-liquid ratio of 1:100 to perform a small-scale experiment to simulate in-situ remediation of micro-pollution. The specific operation was to take 1g of immobilized microbial particles and add them to a conical flask containing 100mL of experimental water, and then place them in a constant temperature shaker at 25°C and shake slowly (90rpm). Water samples were taken at regular intervals to measure COD and NH4 + -N, TP, TN values, and analyze the concentration trend of each pollutant. The water quality indicators of the experimental water body are shown in Table 1.

[0069] The experimental water body was adjusted by adding glucose, ammonium chloride and potassium dihydrogen phosphate to the actual water sample to adjust the COD and NH4 + -N, TP and other values ​​are within the concentration range of the indicators shown in Table 1. The nitrogen and phosphorus concentrations are increased to better observe the restoration process of simulated water bodies contaminated by nitrogen and phosphorus using immobilized microorganisms. The restoration standard is the requirement for Class V surface water.

[0070] Table 1 Water quality indicators of experimental water bodies

[0071]

[0072] The results of the COD adsorption amount of the immobilized microbial particles prepared in Example 1 and the COD removal rate of the experimental water body over time are statistically analyzed. The calculation formula of the removal rate is as follows:

[0073]

[0074] Where η is the removal rate; C0 is the initial concentration; C e is the concentration after purification.

[0075]

[0076] Results Figure 2 .

[0077] Figure 2 The results of the adsorption of COD by the immobilized microbial particles obtained in Example 1 and Comparative Example 1 and the removal effect of COD in the experimental water body over time are shown in FIG. Figure 2It can be seen that the removal of COD in the experimental water body first increases and then tends to stabilize over time. At 56h of the experiment, the adsorption of COD by bentonite-based iron-carbon immobilized microbial particles reached 2.13mg / g, and the COD removal rate of the water body could reach up to 63.88%. Compared with the immobilized microbial particles prepared in Comparative Example 1, the bentonite-based iron-carbon immobilized particles have a better COD removal effect. The removal of COD in the water body is due to the adsorption of particles and the degradation of microorganisms.

[0078] Figure 3 The removal effect of the immobilized microbial particles prepared in Example 1 and Comparative Example 1 on TP in the experimental water body. It can be seen from the figure that the total phosphorus in the experimental water body is removed in large quantities in a very short time. When the bentonite-based iron-carbon immobilized particles treat the water body for 24 hours, the total phosphorus content reaches the lowest, close to 0, and then increases slightly and stabilizes at about 0.03 mg / L, reaching the surface water environmental quality Class II water standard. In the later stage of the experiment, the adsorption of total phosphorus by the bentonite-based iron-carbon immobilized particles is significantly higher than that of the immobilized microbial particles prepared in the comparative example. It can be seen that the particles have a better adsorption effect on total phosphorus, and the adsorption amount can reach up to 0.19 mg / g. In the later stage of the experiment, the removal rate of total phosphorus is also stabilized at 98%, which is about 10% higher than the removal rate of the immobilized particles in the comparative example. The rapid removal of total phosphorus is the adsorption effect of the bentonite-based iron-carbon particles.

[0079] Figure 4 The immobilized microbial particles prepared in Example 1 and Comparative Example 1 reacted with NH4 + -N removal effect. As can be seen from the figure, the removal of ammonia nitrogen in the experimental water body shows an overall trend of first increasing and then stabilizing over time. At 32 hours of the experiment, the adsorption of ammonia nitrogen by bentonite-based iron-carbon fixed particles reached 0.48 mg / g, and the removal rate was 37.15%. At 108 hours in the later stage of the experiment, the adsorption of particles reached a maximum of 0.53 mg / g, and the removal rate was 41.78%. Compared with Comparative Example 1, the bentonite-based iron-carbon fixed particles had a significant effect on the removal of NH4 + -N removal was relatively stable, and the overall fluctuation was not as obvious as that of the control group. During the experiment, the removal of ammonia nitrogen may be due to the adsorption of bentonite-based iron-carbon particles and the degradation of microorganisms.

[0080] Figure 5The removal effect of TN in the experimental water body by the immobilized microbial particles prepared in Example 1 and Comparative Example 1 is shown in the figure. As can be seen from the figure, the total nitrogen removal in the experimental water body shows an overall trend of first increasing and then stabilizing over time. The immobilized particles adsorbed 0.65 mg / g of total nitrogen at 24 hours of the experiment, and then at 108 hours, the adsorption reached 1.10 mg / g, which was higher than the adsorption of total nitrogen by the immobilized microbial particles prepared in Comparative Example 1, and the removal rate reached a maximum of 28.36%. In the later stage of the experiment, the total nitrogen content showed a downward trend, which was due to the role played by denitrifying bacteria in the later stage. During the experiment, the removal of total nitrogen was mainly due to the adsorption of bentonite-based iron-carbon particles and the denitrification of microorganisms.

[0081] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0082] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing bentonite-based iron-carbon immobilized microbial particles, characterized in that the steps include: S1, mixing bentonite, plant powder and zero-valent iron, granulating, and pyrolyzing to obtain bentonite-based iron-carbon particles; S2, mixing and encapsulating the bentonite-based iron-carbon particles with a binder and a microorganism in sequence to obtain bentonite-iron-carbon-microorganism particles; S3, mixing and encapsulating the bentonite iron-carbon-microorganism particles with a binder and a flocculant in sequence to obtain bentonite iron-carbon microorganism-adhesive flocculation structure particles; S4, mixing the bentonite iron-carbon microorganism-adhesive flocculation structure particles with high-efficiency degradation bacteria and drying them to obtain the bentonite-based iron-carbon immobilized microorganism particles.

2. The preparation method according to claim 1, characterized in that The bentonite and plant powder are sieved through 100-200 mesh sieves; the mass ratio of the bentonite to the plant powder is 2:1-6:1; and the amount of the zero-valent iron is 10%-30% of the mass of the bentonite.

3. The preparation method according to claim 1, characterized in that: The plant powder is powder of agricultural and forestry waste or wetland plants; the particle size of the bentonite-based iron-carbon particles is 1 to 2 mm.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the bentonite iron-carbon-microorganism particles, adhesive and flocculant is 90-110:1-2:3-5; the mass ratio of the bentonite iron-carbon microorganism-adhesive flocculation structure particles and high-efficiency degradation bacteria is 90-110:0.8-1.

5.

5. The preparation method according to claim 1, characterized in that: The microorganisms include at least one of Bacillus subtilis, methanogens and alkali-producing bacteria; the high-efficiency degradation bacteria include at least one of nitrifying bacteria, denitrifying bacteria and phosphorus-removing bacteria.

6. The preparation method according to claim 1, characterized in that: In step S2 and step S3, the adhesive is selected from at least one of chitosan, carboxymethyl chitosan, sodium alginate and polyvinyl alcohol.

7. The preparation method according to claim 1, characterized in that: The flocculant includes at least one of aluminum sulfate, polyaluminum chloride, polyaluminum sulfate, polyferric chloride, starch, cellulose and polyacrylamide.

8. The preparation method according to claim 1, characterized in that: The pyrolysis temperature is 500-600° C., the heating rate is 5-10° C. / min, and the pyrolysis time is 1-2 hours; the drying temperature is 30-40° C., and the drying time is 6-8 hours.

9. Bentonite-based iron-carbon immobilized microbial particles prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the bentonite-based iron-carbon immobilized microbial granules as claimed in claim 9 in treating slightly polluted wastewater.

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