Method for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes using nitrogen-doped nanofibers anchored with nickel nanoparticles

Abstract

A method for enhancing anaerobic methane production and reducing sludge resistance genes in high-solid sludge using nitrogen-doped nanofiber-anchored nickel nanoparticles relates to a method for treating high-solid excess sludge. The method aims to address the technical issues of poor treatment efficiency and low methane production in existing anaerobic digestion systems using conductive materials. This method involves: 1. preparing a nickel nanoparticle precursor using a sol-gel method; 2. preparing nanofibers containing the nickel precursor by electrospinning; 3. preparing nitrogen-doped nanofiber-anchored nickel nanoparticles by high-temperature sintering; 4. adding high-solid sludge, inoculated anaerobic sludge, and nitrogen-doped nanofiber-anchored nickel nanoparticles to an anaerobic digestion reactor for anaerobic digestion. Compared to a blank control, the cumulative methane production and maximum production rate increased by 25.66% and 28.21%, respectively; the average COD degradation rate increased by 34.22%; and the resistance gene content decreased by 8.18% to 19.10%. This method can be used in the treatment of high-solid sludge.

Description

Technical Field

[0001] The invention relates to a method for treating high-solid-content excess sludge, and belongs to the field of solid waste treatment. Background Art

[0002] Since sludge contains a large amount of toxic, harmful and perishable pollutants, it will cause great damage to the environment and human health if not properly handled.

[0003] Anaerobic digestion has many advantages because it can treat sludge harmlessly while recycling resources, including reducing the amount of sludge, killing pathogenic microorganisms and recovering bioenergy in the form of methane. Therefore, it has become a popular sludge treatment technology. Usually, the total solid content of 15% (mass ratio) is used as the boundary to distinguish between high-solid anaerobic digestion systems (total solid content greater than 15%) and low-solid anaerobic digestion systems (total solid content less than 15%). Compared with the low-solid sludge anaerobic digestion system, the high-solid sludge anaerobic digestion system is considered to be a more feasible method due to its smaller reactor volume, low heating energy consumption, low sewage production, and high unit volume of biogas production.

[0004] In recent years, a growing number of studies have proposed adding conductive materials to anaerobic digestion systems to promote direct electron transfer between microbial species, thereby accelerating methane production and increasing cumulative methane production. Direct interspecies electron transfer involves direct contact transfer of electrons from electron donors, such as acidogenic bacteria, to electron acceptors, such as methanogens, via conductive cilia or extracellular conductive substances. Direct interspecies electron transfer has been shown to be more efficient than interspecies hydrogen transfer in terms of electron transfer rates and overcomes the thermodynamic barrier to acid production. However, traditional conductive materials struggle to function in high-solids systems. Due to the system's solids content, the addition of conductive materials hinders rapid establishment of efficient electron transfer between microorganisms, hindering energy transfer. Furthermore, most existing conductive materials are difficult to recover from fermented biogas slurry and digestate. Their methanogenesis-boosting mechanisms are relatively limited, resulting in limited methane production gains, making them difficult to achieve sustained, stable, and efficient improvements in methane production. Summary of the Invention

[0005] The present invention aims to solve the technical problems of poor treatment effect and low methane production in existing anaerobic digestion systems using conductive materials, and provides a method for using nitrogen-doped nanofibers to anchor nickel nanoparticles to enhance anaerobic methane production in high-solid sludge and reduce sludge resistance genes.

[0006] The method of the present invention for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles is carried out in the following steps:

[0007] 1. Preparation of nickel nanoparticle precursors by sol-gel method: nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was dissolved in a mixed solution of ethanol and water, and ammonia was added to adjust the pH value to 9-11. The mixture was stirred at 100-120 rpm for 0.5-1 hour to undergo hydrolysis reaction to generate uniformly dispersed sol particles. The sol was then allowed to stand for 4-6 hours to undergo spontaneous gelation to obtain nano-nickel precursors.

[0008] 2. Dispersing the nano-nickel precursor uniformly in a polyacrylonitrile solution having a mass percentage concentration of 10% to 16% in N,N-dimethylformamide (DMF) as a solvent to obtain an electrospinning solution; adding the electrospinning solution to an electrospinning machine for electrospinning to obtain nascent nanofibers; and vacuum drying the nascent nanofibers to obtain nanofibers containing the nickel precursor;

[0009] 3. Place the nanofibers containing nickel precursor in a high temperature tube furnace at 10-15℃ min -1 The heating rate is raised to 400-420℃ and kept at this temperature for 1-1.5h, then the temperature is raised at 10-15℃ min -1 The heating rate is continued to increase to 900-950°C and kept at this temperature for 2-2.5 hours, and finally cooled to room temperature to obtain nitrogen-doped nanofiber-anchored nickel nanoparticles;

[0010] 4. Add the high-solid sludge into an anaerobic digestion reactor, inoculate the anaerobic sludge, and then add nitrogen-doped nanofiber-anchored nickel nanoparticles; the headspace volume of the reactor is 20% to 25% of the effective volume of the reactor, and the amount of nitrogen-doped nanofiber-anchored nickel nanoparticles added is 5% to 12% of the dry weight of the high-solid sludge; continuously introduce nitrogen into the anaerobic digestion reactor to remove mixed oxygen in the system, and then operate the anaerobic digestion reactor at a temperature of 35 to 38°C. The hydraulic retention time of the high-solid sludge in the anaerobic digestion reactor is 30 to 35 days, thereby completing the anaerobic methanogenesis of the high-solid sludge and the reduction of sludge resistance genes.

[0011] Furthermore, in the electrospinning described in step 2, the voltage of the electrospinning machine is 20 kV and the solution injection speed is 1.5 mL·h -1 , humidity is 25% to 30%, and the distance between the rollers is 20cm.

[0012] Furthermore, the vacuum drying in step 2 is carried out under vacuum conditions at a temperature of 70 to 80° C. for 10 to 12 hours to remove the residual organic solvent;

[0013] Furthermore, the high-solid sludge in step 4 has a solid content of 16% to 20% by mass;

[0014] Furthermore, the main microorganisms in the anaerobic sludge in step 4 are Methanothrix, Methanobacterium and Methanolinea.

[0015] Furthermore, in the anaerobic sludge described in step 4, the abundance of Methanothrix by mass percentage is 40% to 45%, the abundance of Methanobacterium by mass percentage is 18% to 20%, and the abundance of Methanolinea by mass percentage is 15% to 17%.

[0016] The present invention prepares a method for promoting methanogenesis by anaerobic digestion of high-solid sludge using a nitrogen-doped carbon nanofiber-anchored nickel nanoparticle. The method has the following main features:

[0017] (1) Material preparation method and structural characteristics: The material was prepared by sol-gel method, electrospinning and pyrolysis carbonization technology. It has a fiber spiral winding structure and a large surface area, which is conducive to the attachment and growth of microorganisms. The surface contains multiple functional groups, which promote the extracellular electron transfer of bacteria. Combined X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM / TEM) analysis confirmed the uniform distribution and stable loading of nitrogen functional groups and nickel nanoparticles. Oxidative stress detection showed that the level of reactive oxygen species (ROS) increased by 28.1-65.9% under the action of nickel nanoparticles.

[0018] (2) Adsorption and inactivation of bacteriophages: The conductive material of the present invention has the ability to adsorb and inactivate bacteriophages. The surface of the material contains nickel nanoparticles with an average particle size of 10 to 50 nm, which can interact with the surface proteins of the bacteriophage, physically capture and inactivate the bacteriophage. In addition, the nickel nanoparticles can produce reactive oxygen species (ROS) with a concentration of 5 to 20 μM through oxidative stress, further destroying the shell and genome structure of the bacteriophage, reducing the activity of the bacteriophage, thereby effectively inhibiting the horizontal transfer of resistance genes and reducing the risk of resistance gene spread. In the reactor to which the nitrogen-doped carbon nanofiber-anchored nickel nanoparticles of the present invention were added, the total content of multiple resistance genes such as sul2, tetW, tetA, and macB decreased by 8.18% to 19.10% compared with the blank control group. Horizontal gene transfer experiments and qPCR detection further showed that the abundance of resistance genes of phages decreased by 27.8 to 47.2% after treatment with the modified material, and the gene horizontal transfer rate was significantly reduced.

[0019] (3) Changes in extracellular polymers in sludge: After 35 days of anaerobic digestion of sludge, the conductive material of the present invention was added and the extracellular polymers in the sludge were extracted by thermal extraction and analyzed by Fourier transform infrared spectroscopy at 1600-1700 cm -1Testing revealed that the α-helical content of sludge proteins in the reactor decreased by 17.3% to -29.1% compared to the blank control group without the addition of conductive materials, indicating that the addition of nitrogen-doped nanofibers anchored with nickel nanoparticles can loosen the protein secondary structure. Furthermore, the COD content in the liquid phase increased significantly, indicating that the conductive material further promoted the lysis and hydrolysis of the sludge, thereby facilitating the hydrolysis process. Three-dimensional fluorescence spectroscopy analysis revealed that the fluorescence area integral values ​​of Region IV and Region V, representing humic acid substances, decreased by 12.85% to 21.31% compared to the blank control group without the addition of conductive materials. The content of humic acid substances in the sludge extracellular polymers was significantly reduced, indicating that the addition of conductive materials can promote the decomposition and transformation of difficult-to-degrade substances in the sludge and improve the biodegradability of the fermentation broth.

[0020] (4) Promote methane production and organic matter degradation: After the conductive material of the present invention is added to the high-solid sludge anaerobic digestion reactor, the average COD degradation rate of the reactor with nanoparticles added is increased by 34.22% compared with the reactor without nanoparticles, and the cumulative methane production and maximum production rate are increased by 25.66% and 28.21% respectively. The addition of the material significantly improves the sludge hydrolysis rate, the organic matter degradation rate and the methane production rate in the anaerobic digestion reactor. At the same time, after the sludge is anaerobic treated, the nitrogen-doped nanofiber-anchored nickel nanoparticles therein can be recovered after magnetic adsorption and ultrapure water washing. The saturation magnetization intensity of the recovered conductive material is as high as 117.21A·m 2 / kg, reusable. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the nitrogen-doped nanofibers anchored with nickel nanoparticles prepared in step 3 of Example 1;

[0022] Figure 2 This is a graph showing the cumulative methane production and maximum methane production rate of the conductive material-added group and the blank control group in Example 1;

[0023] Figure 3 This is a graph showing the functional enzyme activity of the conductive material-added group and the blank control group after treatment with high-solid sludge in Example 1;

[0024] Figure 4 1. It is a graph showing the types and contents of sludge resistance genes in the conductive material-added group and the blank control group after treatment with high-solid sludge in Example 1;

[0025] Figure 5 This is a graph showing the change in the number of bacteriophages in sludge after treatment with high-solid sludge in the conductive material-added group and the blank control group in Example 1;

[0026] Figure 6This is a graph showing the changes in the number of cytochrome-related genes encoded in the sludge after the high-solid sludge treatment of the conductive material-added group and the blank control group in Example 1. DETAILED DESCRIPTION

[0027] The beneficial effects of the present invention are demonstrated with the following examples.

[0028] Example 1: The method of this example using nitrogen-doped nanofibers anchored with nickel nanoparticles to enhance anaerobic methanogenesis in high-solid sludge and reduce sludge resistance genes is carried out in the following steps:

[0029] 1. Preparation of nickel nanoparticle precursors by sol-gel method: 25 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was dissolved in a mixed solution of 50 mL of ethanol and 150 mL of water, and ammonia was added to adjust the pH value to 10. The mixture was stirred for 1 hour for hydrolysis reaction to generate uniformly dispersed sol particles. The sol was then allowed to stand for 5 hours for spontaneous gelation to obtain nano-nickel precursors.

[0030] 2. Prepare a 15% polyacrylonitrile solution using 10 mL of N,N-dimethylformamide (DMF) as solvent, and evenly disperse the nano-nickel precursor prepared in step 1 in the polyacrylonitrile solution to obtain an electrospinning solution. Add the electrospinning solution to an electrospinning machine, set the voltage of the electrospinning machine to 20 kV, and the solution injection rate to 1.5 mL·h. -1 , humidity of 30%, and an axis-roller distance of 20 cm for electrospinning to obtain nascent nanofibers; then, the nascent nanofibers were peeled off from the aluminum foil, placed in a vacuum drying oven at a temperature of 80° C. and vacuum dried for 12 hours to remove residual organic solvent, and vacuum dried to obtain nanofibers containing a nickel precursor;

[0031] 3. Place the nanofibers containing nickel precursor in a high temperature tube furnace at 15℃ min -1 The heating rate was raised to 400℃ and kept at that temperature for 1h, and then the temperature was raised at 10℃ min -1 The heating rate was continued to increase to 900 °C and kept for 2 h, and finally cooled to room temperature to obtain nitrogen-doped nanofiber-anchored nickel nanoparticles;

[0032] 4. The excess sludge was taken from the return sludge of the secondary sedimentation tank of a municipal sewage treatment plant in Harbin. The excess sludge was centrifuged and stored in a refrigerator at 4°C. Before use, it was allowed to stand and the supernatant was discharged for concentration treatment to make the solid content of the excess sludge 20% by mass, which was used as high-solid sludge. The inoculum anaerobic sludge was taken from a continuously operated semi-continuous reactor for anaerobic digestion of sludge in the laboratory. The operating temperature of the reactor was 37°C and the hydraulic retention time was 30 days. The main microorganisms in the inoculum anaerobic sludge were identified as Methanothrix, Methanobacterium and Methanolinea, among which the abundance of Methanothrix by mass was 41.27%, the abundance of Methanobacterium by mass was 18.82%, and the abundance of Methanolinea by mass was 16.48%.

[0033] Two groups of reactors were set up, and 650 mL of high-solid sludge was added to two identical anaerobic bottles with an effective volume of 1000 mL, and then 150 mL of inoculated anaerobic sludge was added to each group; one group was added with 120 mg of nitrogen-doped nanofiber-anchored nickel nanoparticles as the experimental group, and the other group was not added with nanoparticles as the blank control group. The other designs were exactly the same; the headspace volume of the anaerobic bottle was 200 mL; nitrogen with a purity of >99% was continuously introduced into the anaerobic bottle to remove mixed oxygen in the system, and then the anaerobic bottle was sealed with a rubber stopper, and then placed in a constant temperature shaker at 37°C and rotated at 150 rpm. A 200 mL air bag was connected to the outside of the anaerobic bottle to collect the generated biogas. The high-solid sludge was treated for 30 days, and various tests were performed during the treatment process.

[0034] The scanning electron microscope (SEM) photograph of the nitrogen-doped nanofibers anchored with nickel nanoparticles prepared in step 3 of this embodiment is shown in FIG. Figure 1 As shown, from Figure 1 As can be seen, the nickel nanoparticles formed by the sol-gel method are anchored to the fibers, exhibiting a helically wound structure and a large surface area, which is conducive to the attachment and growth of microorganisms. The uniform distribution of the nickel nanoparticles, ranging in size from 10 to 100 nm, not only improves the conductivity and activity of the conductive material but also enhances electron transfer between it and the microorganisms during anaerobic digestion, thereby increasing the rate of methane production during anaerobic digestion. The surface of the nitrogen-doped nanofiber-anchored nickel nanoparticles contains various functional groups that promote extracellular electron transfer in bacteria.

[0035] After 30 days of treatment with high-solid sludge in the anaerobic bottle, the conductivity of the anaerobic sludge in the two groups of reactors was tested. The results showed that after adding nitrogen-doped carbon nanofiber-anchored nickel nanoparticles, the conductivity of the anaerobic sludge increased by 31.58% compared with the blank control group without nanoparticles. It also promoted the secretion of extracellular polymeric substances (EPS), and the EPS content increased by 29.23%. The increase in EPS content can improve the flocculation strength of anaerobic granular sludge and the electron transfer ability between anaerobic microorganisms.

[0036] After 30 days of treatment with high-solid sludge in the anaerobic bottles, the abundance of mycelium in the anaerobic sludge from the two reactors was tested. The results showed that the addition of nitrogen-doped carbon nanofiber-anchored nickel nanoparticles promoted an increase in the abundance of hydrogen- and acetogenic bacteria, Methanothrix, in the anaerobic reactors, by 12.52% compared to the control anaerobic reactor without nanoparticles, while the abundance of Methanothrix decreased by 6.37%. This result indicates that the addition of nitrogen-doped carbon nanofiber-anchored nickel nanoparticles promoted the growth and metabolism of acetogenic methanogens and microorganisms capable of direct electron transfer, thereby indirectly improving the efficiency of interspecies electron transfer among microorganisms and promoting the increase in methane yield in anaerobic sludge digestion.

[0037] The volume of the biogas in the gas bag of Example 1 was measured every 3 days, and the gas composition was determined by gas chromatography (GC-7890A). The cumulative methane production and the maximum methane production rate of the blank control group and Example 1 were as follows: Figure 2 As shown, Figure 2 The results showed that the cumulative methane production of the blank control group was 178.87 mL / gVS, and the maximum methane production rate was 10.81 mL / d / gVS. The cumulative methane production of the reactor with nitrogen-doped nanofiber-anchored nickel nanoparticles was 224.77 mL / gVS, and the maximum methane production rate was 13.86 mL / d / gVS. The cumulative methane production of the reactor with nitrogen-doped nanofiber-anchored nickel nanoparticles increased by 25.66% compared with the blank control group, the maximum methane production rate increased by 28.21%, and the average COD degradation rate increased by 34.22%.

[0038] After 30 days of high solid sludge treatment in the anaerobic bottle, 10 mL of sludge was sampled from the bottom, middle and top of the reactor, and mixed evenly as the sludge samples for functional enzyme activity detection. The functional enzyme activity of the blank control group and Example 1 was as follows: Figure 3 As shown, Figure 3The results showed that compared with the blank control group, the activities of functional enzymes such as protease, α-glycosidase, acetate kinase, methanogenic coenzyme F420, and F430 were significantly improved in the reactor with nitrogen-doped nanofibers anchored nickel nanoparticles. Compared with the blank control group, the activities of protease, α-glycosidase, acetate kinase, methanogenic coenzyme F420, and coenzyme F430 in the conductive material group of Example 1 increased by 15.25%, 12.46%, 17.91%, 22.32%, and 26.47%, respectively. After adding nitrogen-doped carbon nanofibers anchored nickel nanoparticles, Ni was detected in the fermentation broth. + Ni is an essential element for microbial synthesis of coenzyme F420 and coenzyme F430. + The increase in content indicates that the conductive material can release Ni + Promote the synthesis of related functional enzymes, thereby improving the conversion efficiency of organic matter.

[0039] After 30 days of anaerobic treatment of high-solids sludge in anaerobic flasks, samples of the anaerobic digestion sludge were collected and analyzed using three-dimensional fluorescence spectroscopy, fluorescence area integration, and parallel factor analysis. The results showed that the fluorescence area integration values ​​of Region IV and Region V, representing humic acid substances, were significantly lower in the reactor containing nitrogen-doped nanofiber-anchored nickel nanoparticles compared to the blank control group. The fermentation broth was dried and analyzed using Fourier transform infrared spectroscopy and circular dichroism spectroscopy. The results showed that the α-helix was significantly reduced in the reactor containing the conductive material, indicating that the addition of nitrogen-doped nanofiber-anchored nickel nanoparticles can loosen the protein structure.

[0040] After 30 days of treatment of high-solid sludge in the anaerobic bottle, the sludge after anaerobic digestion was centrifuged at 12000rpm for 10 minutes, and DNA was extracted from the centrifuged sludge. The types and contents of sludge resistance genes in the sludge were analyzed using metagenomic sequencing technology. The types and contents of sludge resistance genes after high-solid sludge treatment in the conductive material group and the blank control group are shown in the figure. Figure 4 As shown, from Figure 4 It can be seen that in the reactor with nitrogen-doped carbon nanofibers anchored with nickel nanoparticles, the total content of multiple resistance genes such as sul2, tetW, tetA, and macB decreased by 8.18% to 19.10% compared with the blank control group.

[0041] The changes in the number of bacteriophages in the high-solid sludge treated with the conductive material addition group and the blank control group in Example 1 were detected by qPCR. The obtained changes in the number of bacteriophages are shown in the figure below: Figure 5As shown, the number of phage resistance genes in the conductive material-treated group in Example 1 decreased by 31.2%, and the horizontal gene transfer rate was significantly reduced. Nucleic acid leakage and protein denaturation analysis showed that the conductive material effectively destroyed the phage shell and genome structure.

[0042] Figure 6 This is a graph showing the changes in the number of cytochrome-related genes encoded by the sludge after the high-solid sludge treatment in the conductive material addition group and the blank control group in Example 1. Figure 6 It can be seen that the cytochrome-related genes (cyt, c-type, b-type, d-type) encoded in the sludge with the addition of nitrogen-doped nanofiber-anchored nickel nanoparticles of this embodiment increased by 15.2%, 12.9%, 23.8%, and 42.1% respectively compared with the group without addition, indicating that nitrogen-doped nanofiber-anchored nickel nanoparticles can enhance the electron transfer ability between microorganisms.

[0043] High-gradient magnetic separation technology was used to separate the conductive material from the treated sludge and then immersed in a 60% by mass ethanol solution to remove organic matter and inorganic salts attached to the surface. The material was then washed three times with ultrapure water and then vacuum-dried at 40°C for 24 hours to remove any remaining water from the washed, nitrogen-doped carbon nanofiber-anchored nickel nanoparticles. Tests showed that the saturation magnetization of the conductive material, nitrogen-doped carbon nanofiber-anchored nickel nanoparticles, was 117.21 A·m. 2 / kg.

[0044] The recovered and cleaned nitrogen-doped carbon nanofiber-anchored nickel nanoparticles were reused and added back into the residual sludge anaerobic digestion reactor. After 30 days of medium-temperature fermentation, the cumulative methane production increased by 12.78% and the maximum methane production rate increased by 8.21% compared with the control group without adding conductive materials, showing good separation, recovery and reuse performance.

[0045] Example 1 demonstrates that nitrogen-doped and nickel nanoparticle surface-modified materials can significantly inhibit the activity of bacteriophages and the risk of resistance gene spread through multiple mechanisms, including capture, inactivation, induction of oxidative stress, and genome destruction.

Claims

1. A method for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles, characterized in that The method proceeds as follows:

1. Preparation of nickel nanoparticle precursors using a sol-gel method: nickel nitrate hexahydrate is dissolved in a mixed solution of ethanol and water, ammonia is added to adjust the pH to 9-11, and the mixture is stirred at 100-120 rpm for 0.5-1 hour to undergo a hydrolysis reaction to generate uniformly dispersed sol particles. The sol is then allowed to stand for 4-6 hours to undergo spontaneous gelation to obtain a nano-nickel precursor; 2. Evenly dispersing the nano-nickel precursor in a polyacrylonitrile solution having a mass percentage concentration of 10% to 16% using N,N-dimethylformamide as a solvent to obtain an electrospinning solution; adding the electrospinning solution to an electrospinning machine for electrospinning to obtain nascent nanofibers; and then vacuum drying the nascent nanofibers to obtain nanofibers containing the nickel precursor; 3. Place the nanofibers containing nickel precursor in a high temperature tube furnace at 10-15℃ min -1 The heating rate is raised to 400-420℃ and kept at this temperature for 1-1.5h, then the temperature is raised at 10-15℃ min -1 The heating rate is continued to increase to 900-950°C and kept at this temperature for 2-2.5 hours, and finally cooled to room temperature to obtain nitrogen-doped nanofiber-anchored nickel nanoparticles; 4. Add the high-solid sludge into an anaerobic digestion reactor, then inoculate the anaerobic sludge, and then add nitrogen-doped nanofiber-anchored nickel nanoparticles; the headspace volume of the reactor is 20% to 25% of the effective volume of the reactor, and the amount of nitrogen-doped nanofiber-anchored nickel nanoparticles added is 5% to 12% of the dry weight of the high-solid sludge; continuously introduce nitrogen into the anaerobic digestion reactor to remove mixed oxygen in the system, and then operate the anaerobic digestion reactor at a temperature of 35 to 38°C. The hydraulic retention time of the high-solid sludge in the anaerobic digestion reactor is 30 to 35 days, thereby completing the anaerobic methanogenesis of the high-solid sludge and the reduction of sludge resistance genes.

2. The method of using nitrogen-doped nanofibers anchored with nickel nanoparticles to enhance anaerobic methanogenesis in high-solid sludge and reduce sludge resistance genes according to claim 1, characterized in that: For the electrospinning described in step 2, the voltage of the electrospinning machine was 20 kV and the solution injection speed was 1.5 mL·h -1 , humidity is 25% to 30%, and the distance between the rollers is 20cm.

3. The method for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1 or 2, characterized in that: The vacuum drying in step 2 is carried out under vacuum conditions at a temperature of 70 to 80° C. for 10 to 12 hours.

4. The method for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1 or 2, characterized in that: The high-solid sludge in step 4 has a solid content of 16% to 20% by mass.

5. The method for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1 or 2, characterized in that: The main microorganisms in the anaerobic sludge described in step 4 are Methanothrix, Methanobacterium and Methanolinea.

6. The method of enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1 or 2, characterized in that: The size of the nitrogen-doped nanofiber-anchored nickel nanoparticles prepared in step 3 is 10 to 100 nm.

7. The method for enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1 or 2, characterized in that: The amount of doped nanofiber-anchored nickel nanoparticles added in step four is 10% to 12% of the dry weight of the high-solid sludge; under such conditions, the fluorescence area integral values ​​of Region IV and Region V representing humic acid substances in the reactor are reduced by 12.85% to 21.31% compared with the blank control group without addition, indicating that the material can improve the biodegradability of the fermentation broth.

8. The method of enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1 or 2, characterized in that: The amount of the doped nanofiber-anchored nickel nanoparticles added in step 4 is 8% to 10% of the dry weight of the high-solid sludge; under such conditions, after 35 days of anaerobic digestion of the sludge, the extracellular polymers of the sludge are extracted by thermal extraction, and the 1600-1700 cm -1 Tests showed that the α-helix of the sludge protein in the reactor was reduced by 17.3%-29.1% compared with the α-helix of the sludge protein in the blank control group without addition, indicating that the addition of nitrogen-doped nanofibers anchored nickel nanoparticles can loosen the protein structure, thereby promoting the hydrolysis process of the sludge.

9. The method of enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1, characterized in that: The amount of the doped nanofiber-anchored nickel nanoparticles added in step 4 is 10% to 12% of the dry weight of the high-solid sludge; after the anaerobic digestion of the sludge is completed, the doped nanofiber-anchored nickel nanoparticles are recovered by magnetic adsorption and water washing, and the saturation magnetization intensity of the obtained liquid nitrogen-doped carbon nanofiber-anchored nickel nanoparticles is 117.21A·m 2 / kg.

10. The method of enhancing anaerobic methanogenesis in high-solid sludge and reducing sludge resistance genes by using nitrogen-doped nanofibers anchored with nickel nanoparticles according to claim 1, characterized in that: After the anaerobic digestion treatment of the sludge described in step 4 is completed, the conductivity of the sludge is increased by 18.1% to 33.9% compared with the blank control group without addition. At the same time, the abundance of cytochrome-related genes cyt, c-type, b-type, and d-type in the sludge increases by 12.9% to 42.1%, indicating that nitrogen-doped nanofibers anchored nickel nanoparticles enhance the electron transfer ability between microorganisms.

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