Process for stabilizing anaerobic fermentation system

Abstract

The invention relates to environment-friendly treatment of poultry manure, in particular to a process for stabilizing an anaerobic fermentation system, which comprises the following steps: fully collecting manure with ts concentration of 6%, performing anaerobic fermentation, improving the variety of antibiotics, promoting the activity of a hydrogen-philic methanogen flora, and improving an electrode material of a microbial electrolysis cell, the obtained anaerobic fermentation system is high in stability and rich in methane yield.

Description

Technical Field

[0001] The invention belongs to the technical field of anaerobic fermentation, and in particular relates to a process for stabilizing an anaerobic fermentation system. Background Art

[0002] Anaerobic fermentation is a decomposition and metabolism process of organic matter by the joint action of a variety of specific microorganisms. In this process, organic matter (such as human and animal feces, straw, weeds, etc.) is decomposed and metabolized by various microorganisms under certain moisture, temperature and anaerobic conditions, and finally forms a combustible mixed gas mainly composed of methane and carbon dioxide (containing a small amount of hydrogen sulfide and ammonia, etc.), and produces a certain amount of biogas slurry and biogas residue.

[0003] The anaerobic fermentation process does not require oxygen, which reduces power consumption and usage costs; the biogas produced after anaerobic fermentation is a clean energy source; after the fermentation of organic solid matter, high-quality organic fertilizers and soil conditioners can be obtained, which has good economic benefits; in the process of converting organic matter into methane, waste reduction is achieved. Anaerobic fermentation technology can effectively achieve the "harmlessness, reduction and resource utilization" of solid waste treatment, so it has broad application prospects.

[0004] As a common antibiotic, sulfonamide antibiotics are often used in livestock and poultry farming, and are discharged into manure in the form of parent compounds and metabolites, affecting the anaerobic fermentation of manure. During the anaerobic fermentation process of microorganisms, due to the reverse conversion of acesulfonamide in the metabolites of sulfonamide antibiotics to a certain extent, negative migration often occurs during the process, resulting in an increase in the content of sulfonamide antibiotics discharged into the environment. When the content of sulfonamide antibiotics increases, it may pose a threat to the growth of microorganisms and affect the structure and function of the microbial community. Therefore, selecting a suitable sulfonamide antibiotic to promote anaerobic fermentation to the greatest extent is the research focus of the present invention.

[0005] Biosurfactants have the advantages of being green, environmentally friendly and highly efficient, and have been widely used in pollutant treatment. Surfactants can effectively reduce the reactive energy of the reaction, thereby accelerating the reaction process, and can effectively enhance the hydrolysis of salt-containing sludge after thermophilic bacteria treatment and promote the release of enzymes to further enhance the metabolism of organic matter. Adding surfactants to promote bacterial activity is the research focus of the present invention.

[0006] The microbial electrolysis cell is driven by electroactive microorganisms. Under the condition of applying a small voltage, it can convert organic waste into valuable products. The basic principle of the microbial electrolysis cell is that the electroactive microorganisms attached to the anode surface of the microbial electrolysis cell oxidize organic matter into electrons, protons and carbon dioxide. The electroactive microorganisms transfer electrons to the anode through the extracellular electron transfer mechanism. Driven by the external electric field, the electrons are transferred from the anode to the cathode through the external circuit and combine with hydrogen ions to produce hydrogen.

[0007] Although the microbial electrolytic cell-anaerobic fermentation can significantly improve the methane production performance compared to the traditional anaerobic fermentation, its conversion efficiency is still low. In order to further improve the performance of the microbial electrolytic cell-anaerobic fermentation, it is necessary to improve the microbial electrolytic cell. There are many factors that affect the performance of the microbial electrolytic cell, such as reactor configuration, input voltage, biological activity, and electrode materials. Among them, the electrode material is not only a carrier of functional microorganisms, but also the electron transfer efficiency determined by it also has a crucial influence on the performance of the microbial electrolytic cell. Therefore, it is necessary to select a material with better electrochemical properties, which is one of the key directions of the present invention. Summary of the invention

[0008] In order to solve the above technical problems, the specific preparation process of the present invention is as follows:

[0009] The livestock and poultry breeding waste with a TS concentration of 6% is fully collected as a fermentation raw material and added to a microbial electrolytic cell for anaerobic fermentation. A DC power supply is used as a power supply to apply a voltage of 40-60V at both ends of the electrolytic cell. The anode of the microbial electrolytic cell is connected to the positive electrode of the power supply, the cathode is connected to the negative electrode, and a 10Ω resistor is connected in series in the circuit; after the connection is completed, 100 portions of livestock and poultry breeding waste are taken, 8-10% of hydrogenophilic methanogens are added, 0.03-0.12% of sulfonamide antibiotics are supplemented, nitrilotriacetic acid is added to adjust the pH to 6-6.5, and 4-8% of a surfactant is added to promote microbial anaerobic fermentation. Nitrogen with a purity of 99% is first filled for 5 minutes. When no gas is produced, the biofilm stage is completed. After electrolysis for 12 hours, intermittent power supply is used and 5 cycles are operated;

[0010] The hydrogenophilic methanogens include a mixture of Methanobacterium buchneri and Methanobacterium boggsii;

[0011] The intermittent power supply is a 12-hour power-on state and a 12-hour power-off state, which is one cycle;

[0012] The sulfonamide antibiotic is sulfamethoxazole.

[0013] The surfactant is dialkylethanolamine ester methyl ammonium methyl sulfate.

[0014] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 h before use and then washed with deionized water; the anode is obtained by brushing modified carbon cloth, specifically:

[0015] Anode modification raw material: 60-70 parts of 25% ferric chloride hexahydrate solution and an equal amount of 10-18% modification liquid and 25 parts of water are mixed and ultrasonicated for 30 minutes. After uniform mixing, the mixture is added into a stainless steel autoclave lined with polytetrafluoroethylene, and reacted at 130°C for 72 hours. After natural cooling, the product is collected by centrifugation, and the obtained product is washed three times with deionized water at 70°C for 2 hours according to a material-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a material-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and then ground to obtain the modified raw material, which is stored in a dry environment for later use;

[0016] Anode modified carbon cloth coating: Mix 0.5-0.8 parts of the modified raw material prepared above with 1 part of ethanol, 0.6-0.8 parts of water, and 0.1 parts of polytetrafluoroethylene and shake until uniform, spread 2cmx4cm carbon cloth and apply the mixture on the carbon cloth, and dry it in a vacuum oven at 60°C for 12h.

[0017] The modified liquid is 5-sulfoanthranilic acid.

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention relates to environmentally friendly treatment of poultry manure, and in particular to a process for stabilizing an anaerobic fermentation system. The present invention fully collects manure with a TS concentration of 6%, and after anaerobic fermentation, improves the types of antibiotics, promotes the activity of hydrogenophilic methanogens, and improves the electrode materials of the microbial electrolytic cell, so that the obtained anaerobic fermentation system has high stability and rich methane production.

[0020] 2. Sulfadiazine can significantly increase the production of short-chain fatty acids during anaerobic fermentation, which helps to improve the conversion efficiency of organic matter during the fermentation process. In addition, there are a variety of microbial strains that can degrade sulfonamides in activated sludge, soil and feces after long-term treatment. They can use sulfadiazine as the only carbon source for growth and reproduction, thereby degrading sulfadiazine. Sulfadiazine is not only degraded during anaerobic fermentation, but the antibacterial activity of its metabolites is significantly reduced, thereby reducing the risk of the spread of resistance genes. While degrading, it also increases the growth of anaerobic bacteria.

[0021] 3. The presence of sulfamethanolide promotes hydrogenophilic methanogens. These bacteria can effectively transform organic matter into methane in an anaerobic environment, thereby improving energy recovery efficiency. The presence of sulfamethanolide promotes hydrogenophilic methanogens. These bacteria can effectively transform organic matter into methane in an anaerobic environment, thereby improving energy recovery efficiency. Sulfamethanolide inhibits the growth of specific bacteria through competition, and can effectively reduce the bacteria of most harmful microorganisms such as Gram-positive and Gram-negative bacteria, thereby facilitating the reproduction and metabolism of beneficial microorganisms in anaerobic fermentation systems.

[0022] 4. The methoxy structure contained in sulfamethoxazole increases the reactivity of compounds connected to the methoxy group through the conjugation effect, allowing microorganisms to more effectively convert sulfonamide antibiotics and their metabolites into other harmless or more easily degradable substances, reducing the occurrence of negative migration and ensuring the stability of the anaerobic fermentation system.

[0023] 5. Dialkylethanolamine esters Ammonium methylsulfate is a cationic surfactant. The ethanolamine ester and ammonium methylsulfate parts in its molecular structure give it good biocompatibility and mild properties, making it perform well in various applications.

[0024] 6. Utilize the hydrophobic and hydrophilic properties of dialkylethanolamine methyl ammonium sulfate to reduce the surface tension of non-aqueous phase organic matter to increase the water solubility of organic matter; utilize its charge to disperse sludge flocs, change the cell structure of microorganisms, and separate other bacterial aggregates attached to the surface of microorganisms, thereby promoting anaerobic fermentation and acid production; inhibit the activity of methanogens in anaerobic systems by destroying their cell membranes, reducing acetic acid consumption and accumulating volatile fatty acids.

[0025] 7. Dialkylethanolamine ester methyl ammonium methyl sulfate changes the surface charge of the substrate to weaken the repulsive force through two different ethanolamine esters and methyl ammonium methyl sulfate, thereby promoting the interaction between the hydrolase and the substrate, significantly improving the solubilization and hydrolysis efficiency, promoting the acidification process, and providing better substrate conditions for subsequent methane fermentation, thereby optimizing the efficiency and stability of the entire anaerobic fermentation process.

[0026] 8. By self-assembling 5-sulfoanthranilic acid and iron ions to form highly ordered porous crystals, the obtained anode electrolytic material not only has a large specific surface area, high porosity, etc., but also exhibits strong redox activity. 5-sulfoanthranilic acid has multiple functional groups that can form coordination bonds with iron ions, promote the binding between molecules, and form a stable complex. Therefore, the modified electrolytic material can not only facilitate the attachment of microorganisms and the fixation of corresponding enzymes, but also increase the electron transfer rate, thereby accelerating the production of hydrogen, promoting the growth of hydrogen-producing methanogens, and thus increasing methane production and system stability.

[0027] 9. The modified electrolytic cell can not only accelerate the decomposition and utilization of volatile acids, reduce the concentration of volatile acids in the whole cycle, thereby reducing acid inhibition and increasing methane production; it produces more ammonia nitrogen at low concentrations, promotes the growth of methanogens, and plays an important role in increasing its methane production. And combined with the intermittent power supply operation mode, high methane production can be achieved with low energy consumption. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the embodiments.

[0029] All raw materials used in the embodiments of the present invention are waste materials from nearby livestock and poultry farms and farmland. The DC stabilized power supply was purchased from Shanghai Xishun Electric Co., Ltd., the carbon cloth was 2cmx4cm, specification was wls1011, purchased from Taiwan Carbon Energy Company, and the remaining raw materials or chemical reagents, unless otherwise specified, were obtained through conventional commercial channels.

[0030] The ts concentration refers to livestock and poultry breeding waste. According to 3.4 of Jiangxi Provincial Local Standard DB36 / T1546-2021, full collection, storage and transportation refers to the collection, temporary storage and transportation of all livestock and poultry breeding waste generated by the farm through corresponding measures. The third-party agency should sign an agreement with the livestock and poultry breeding enterprises (households) to establish a complete livestock and poultry breeding waste collection, storage and transportation system to ensure that the total solids of livestock and poultry manure is not less than 6% and that dead livestock and poultry can be collected.

[0031] Example 1

[0032] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1mol / LH2SO4 for 4h before use and then washed with deionized water; the anode is obtained by brushing modified carbon cloth, specifically:

[0033] Anode modification raw material: 65 parts of 25% ferric chloride hexahydrate solution and an equal amount of 14% 5-sulfoanthranilic acid and 25 parts of water were mixed and ultrasonicated for 30 minutes. After mixing evenly, they were added into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, reacted at 130°C for 72 hours, cooled naturally, and the products were collected by centrifugation. The obtained product was washed three times with deionized water at 70°C for 2 hours according to a material-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a material-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and ground to obtain the modified raw material, which was stored in a dry environment for later use;

[0034] Anode modified carbon cloth coating: Take 0.6 parts of the modified raw material prepared above and mix with 1 part of ethanol, 0.7 parts of water, and 0.1 parts of polytetrafluoroethylene and shake until uniform, spread 2cmx4cm carbon cloth and apply the mixture on the carbon cloth, and dry it in a vacuum oven at 60°C for 12h.

[0035] The livestock and poultry breeding waste with a TS concentration of 6% was fully collected as a fermentation raw material and added into a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used as the power supply to apply a voltage of 50V at both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive pole of the power supply, the cathode was connected to the negative pole, and a 10Ω resistor was connected in series in the circuit. After the connection was completed, 100 portions of livestock and poultry breeding waste were taken, 9% of hydrogenophilic methanogens were added, 0.07% of sulfamethoxazole was supplemented, and nitrilotriacetic acid was added to adjust the pH to 6.2, and then 6% of dialkylethanolamine methyl ammonium sulfate was added to promote microbial anaerobic fermentation. Nitrogen with a purity of 99% was first filled for 5 minutes. When no gas was produced, the biofilm stage was completed. After 12 hours of electrolysis, intermittent power supply was used, with the power on for 12 hours and the power off for 12 hours, and 5 cycles were run.

[0036] Example 2

[0037] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1mol / LH2SO4 for 4h before use and then washed with deionized water; the anode is obtained by brushing modified carbon cloth, specifically:

[0038] Anode modification raw material: 60 parts of 25% by mass ferric chloride hexahydrate solution and an equal amount of 18% by mass 5-sulfoanthranilic acid and 25 parts of water were mixed and ultrasonicated for 30 minutes. After being evenly mixed, they were added into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, reacted at 130°C for 72 hours, cooled naturally, and the products were collected by centrifugation. The obtained product was washed three times with deionized water at 70°C for 2 hours according to a material-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a material-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and ground to obtain the modified raw material, which was stored in a dry environment for later use;

[0039] Anode modified carbon cloth coating: Take 0.8 parts of the modified raw material prepared above and 1 part of ethanol, 0.6 parts of water, and 0.1 parts of polytetrafluoroethylene, mix and shake until uniform, spread 2cmx4cm carbon cloth and apply the mixture on the carbon cloth, and dry it in a vacuum oven at 60°C for 12h.

[0040] The livestock and poultry breeding waste with a TS concentration of 6% was fully collected as a fermentation raw material and added into a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used as the power supply and a voltage of 60V was applied to both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive pole of the power supply, the cathode was connected to the negative pole, and a 10Ω resistor was connected in series in the circuit. After the connection was completed, 100 portions of livestock and poultry breeding waste were taken, 8% of hydrogenophilic methanogens were added, 0.12% of sulfamethoxazole was supplemented, and nitrilotriacetic acid was added to adjust the pH to 6, and then 8% of dialkylethanolamine methyl ammonium sulfate was added to promote microbial anaerobic fermentation. Nitrogen with a purity of 99% was first filled for 5 minutes. When gas was no longer produced, the biofilm stage was completed. After 12 hours of electrolysis, intermittent power supply was used, the power was turned on for 12 hours, and the power was turned off for 12 hours, and 5 cycles were run.

[0041] Example 3

[0042] The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1mol / LH2SO4 for 4h before use and then washed with deionized water; the anode is obtained by brushing modified carbon cloth, specifically:

[0043] Anode modification raw material: 70 parts of ferric chloride hexahydrate solution with a mass fraction of 25% and an equal amount of 5-sulfoanthranilic acid with a mass fraction of 10% and 25 parts of water were mixed and ultrasonicated for 30 minutes. After mixing evenly, they were added into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, reacted at 130°C for 72 hours, cooled naturally, and the products were collected by centrifugation. The obtained product was washed three times with deionized water at 70°C for 2 hours according to a material-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a material-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and ground to obtain the modified raw material, which was stored in a dry environment for later use;

[0044] Anode modified carbon cloth coating: Take 0.5 parts of the modified raw material prepared above and mix with 1 part of ethanol, 0.8 parts of water, and 0.1 parts of polytetrafluoroethylene and shake until uniform, spread 2cmx4cm carbon cloth and apply the mixture on the carbon cloth, and dry it in a vacuum oven at 60°C for 12h.

[0045] The livestock and poultry breeding waste with a TS concentration of 6% is fully collected as a fermentation raw material and added into a microbial electrolysis cell for anaerobic fermentation. A DC power supply is used as a power supply to apply a voltage of 40-60V at both ends of the electrolysis cell. The anode of the microbial electrolysis cell is connected to the positive pole of the power supply, the cathode is connected to the negative pole, and a 10Ω resistor is connected in series in the circuit. After the connection is completed, 100 portions of livestock and poultry breeding waste are taken, 10% of hydrogenophilic methanogens are added, 0.03% of sulfamethoxazole is supplemented, and nitrilotriacetic acid is added to adjust the pH to 6.5, and then 4% of dialkylethanolamine methyl ammonium sulfate is added to promote microbial anaerobic fermentation. Nitrogen with a purity of 99% is first filled for 5 minutes. When no gas is produced, the biofilm formation stage is completed. After 12 hours of electrolysis, intermittent power supply is used, the power is turned on for 12 hours, and the power is turned off for 12 hours, and 5 cycles are run.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that this comparative example does not use an electrolytic cell device, and the specific steps are as follows:

[0048] Fully quantitatively collect livestock and poultry breeding waste with a TS concentration of 6% as fermentation raw materials, take 100 portions of livestock and poultry breeding waste, add 10% of hydrogenophilic methanogens, supplement 0.03% of sulfamethoxazole, add nitrilotriacetic acid to adjust the pH to 6.5, add 4% of dialkylethanolamine methyl ammonium sulfate to promote microbial anaerobic fermentation, first fill with 99% purity nitrogen for 5 minutes, and then continue fermentation for 5.5 days.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 1 is that the anode in the electrolyte is not modified, the anode is a 2cmx4cm carbon cloth, and the cathode is a 316L stainless steel mesh, which is soaked in 1mol / LH2SO4 for 4h before use and then washed with deionized water;

[0051] The livestock and poultry breeding waste with a TS concentration of 6% was fully collected as a fermentation raw material and added into a microbial electrolysis cell for anaerobic fermentation. A DC power supply was used as the power supply to apply a voltage of 50V at both ends of the electrolysis cell. The anode of the microbial electrolysis cell was connected to the positive pole of the power supply, the cathode was connected to the negative pole, and a 10Ω resistor was connected in series in the circuit. After the connection was completed, 100 portions of livestock and poultry breeding waste were taken, 9% of hydrogenophilic methanogens were added, 0.07% of sulfamethoxazole was supplemented, and nitrilotriacetic acid was added to adjust the pH to 6.2, and then 6% of dialkylethanolamine methyl ammonium sulfate was added to promote microbial anaerobic fermentation. Nitrogen with a purity of 99% was first filled for 5 minutes. When no gas was produced, the biofilm stage was completed. After 12 hours of electrolysis, intermittent power supply was used, with the power on for 12 hours and the power off for 12 hours, and 5 cycles were run.

[0052] Comparative Example 3

[0053] The difference between this comparative example and Example 1 is that 5-sulfoanthranilic acid is replaced by benzoic acid in the steps; the rest is the same as Example 1.

[0054] Comparative Example 4

[0055] The difference between this comparative example and Example 1 is that the amount of 5-sulfoanthranilic acid added is different; specific anode modification raw materials: 65 parts of ferric chloride hexahydrate solution with a mass fraction of 25% and an equal amount of 5-sulfoanthranilic acid with a mass fraction of 28% and 25 parts of water are mixed and ultrasonicated for 30 minutes. After mixing evenly, they are added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, reacted at 130°C for 72 hours, and after natural cooling, the products are collected by centrifugation, and the obtained product is washed three times with deionized water at 70°C for 2 hours according to a solid-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a solid-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and ground to obtain the modified raw material, which is stored in a dry environment for use; the rest is the same as Example 1.

[0056] Comparative Example 5

[0057] The difference between this comparative example and Example 1 is that the amount of 5-sulfoanthranilic acid added is different; specific anode modification raw materials: 65 parts of ferric chloride hexahydrate solution with a mass fraction of 25% and an equal amount of 5-sulfoanthranilic acid with a mass fraction of 6% and 25 parts of water are mixed and ultrasonicated for 30 minutes. After mixing evenly, they are added to a stainless steel high-pressure reactor lined with polytetrafluoroethylene, reacted at 130°C for 72 hours, and after natural cooling, the products are collected by centrifugation, and the obtained product is washed 3 times with deionized water at 70°C for 2 hours according to a solid-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a solid-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and ground to obtain the modified raw material, which is stored in a dry environment for use; the rest is the same as Example 1.

[0058] Comparative Example 6

[0059] The difference between this comparative example and Example 1 is that sulfamethoxazole is not added; the rest is the same as Example 1.

[0060] Comparative Example 7

[0061] The difference between this comparative example and Example 1 is that sulfadiazine is sulfadiazine; the rest is the same as Example 1.

[0062] Comparative Example 8

[0063] The difference between this comparative example and Example 1 is that the amount of sulfamethoxazole added in this comparative example is different, specifically: livestock and poultry breeding waste with a TS concentration of 6% is fully collected as a fermentation raw material and added to a microbial electrolytic cell for anaerobic fermentation, a DC power supply is used as the power supply and a voltage of 50V is applied to both ends of the electrolytic cell, the anode of the microbial electrolytic cell is connected to the positive electrode of the power supply, the cathode is connected to the negative electrode, and a 10Ω resistor is connected in series in the circuit; after the connection is completed, 100 portions of livestock and poultry breeding waste are taken, 9% of hydrogenophilic methanogens are added, 0.16% of sulfamethoxazole is supplemented, nitrilotriacetic acid is added to adjust the pH to 6.2, and then 6% of dialkylethanolamine methyl ammonium sulfate is added to promote microbial anaerobic fermentation, first fill with nitrogen with a purity of 99% for 5 minutes, and complete the biofilm stage when no gas is produced, and use intermittent power supply after 12 hours of electrolysis, turn on the power state for 12 hours, turn off the power state for 12 hours, and run 5 cycles; the rest is the same as Example 1.

[0064] Comparative Example 9

[0065] The difference between this comparative example and Example 1 is that the amount of sulfamethoxazole added in this comparative example is different, specifically: livestock and poultry breeding waste with a TS concentration of 6% is fully collected as a fermentation raw material and added to a microbial electrolytic cell for anaerobic fermentation, a DC power supply is used as the power supply and a voltage of 50V is applied to both ends of the electrolytic cell, the anode of the microbial electrolytic cell is connected to the positive electrode of the power supply, the cathode is connected to the negative electrode, and a 10Ω resistor is connected in series in the circuit; after the connection is completed, 100 portions of livestock and poultry breeding waste are taken, 9% of hydrogenophilic methanogens are added, 0.01% of sulfamethoxazole is supplemented, nitrilotriacetic acid is added to adjust the pH to 6.2, and 6% of dialkylethanolamine methyl ammonium sulfate is added to promote microbial anaerobic fermentation, first fill with nitrogen with a purity of 99% for 5 minutes, and complete the biofilm stage when no gas is produced, and intermittent power supply is used after 12 hours of electrolysis, the power is turned on for 12 hours, and the power is turned off for 12 hours, and 5 cycles are run; the rest is the same as Example 1.

[0066] Comparative Example 10

[0067] The difference between this comparative example and Example 1 is that dialkylethanolamine methyl ammonium methyl sulfate is not added in this comparative example; the rest is the same as Example 1.

[0068] Comparative Example 11

[0069] The difference between this comparative example and Example 1 is that the dialkylethanolamine ester methylammonium sulfate in this comparative example is alkylpropylenediamine; the rest is the same as Example 1.

[0070] Comparative Example 12

[0071] The difference between this comparative example and Example 1 is that the amount of dialkylethanolamine ester methyl ammonium sulfate methyl ester is different in this comparative example, specifically: livestock and poultry breeding waste with a TS concentration of 6% is fully collected as a fermentation raw material and added to a microbial electrolytic cell for anaerobic fermentation, a DC power supply is used as a power supply and a voltage of 50V is applied to both ends of the electrolytic cell, the anode of the microbial electrolytic cell is connected to the positive electrode of the power supply, the cathode is connected to the negative electrode, and a 10Ω resistor is connected in series in the circuit; after the connection is completed, 100 portions of livestock and poultry breeding waste are taken, 9% of hydrogenophilic methanogens are added, 0.07% of sulfamethoxazole is supplemented, nitrilotriacetic acid is added to adjust the pH to 6.2, and then 12% of dialkylethanolamine ester methyl ammonium sulfate methyl ester is added to promote microbial anaerobic fermentation, first fill with nitrogen with a purity of 99% for 5 minutes, and complete the biofilm stage when no gas is produced, and intermittent power supply is used after electrolysis for 12 hours, the power is turned on for 12 hours, and the power is turned off for 12 hours, and 5 cycles are run; the rest is the same as Example 1.

[0072] Comparative Example 13

[0073] The difference between this comparative example and Example 1 is that the amount of dialkylethanolamine ester methyl ammonium sulfate methyl ester is different in this comparative example, specifically: livestock and poultry breeding waste with a TS concentration of 6% is fully collected as a fermentation raw material and added to a microbial electrolytic cell for anaerobic fermentation, a DC power supply is used as a power supply and a voltage of 50V is applied to both ends of the electrolytic cell, the anode of the microbial electrolytic cell is connected to the positive electrode of the power supply, the cathode is connected to the negative electrode, and a 10Ω resistor is connected in series in the circuit; after the connection is completed, 100 portions of livestock and poultry breeding waste are taken, 9% of hydrogenophilic methanogens are added, 0.07% of sulfamethoxazole is supplemented, nitrilotriacetic acid is added to adjust the pH to 6.2, and then 2% of dialkylethanolamine ester methyl ammonium sulfate methyl ester is added to promote microbial anaerobic fermentation, first fill with nitrogen with a purity of 99% for 5 minutes, and complete the biofilm stage when no gas is produced, and intermittent power supply is used after electrolysis for 12 hours, the power is turned on for 12 hours, and the power is turned off for 12 hours, and 5 cycles are run; the rest is the same as Example 1.

[0074] Test 1: Determination of volatile fatty acid content

[0075] Volatile fatty acids were determined using an Agilent 7890B gas chromatograph. 5 g of the anaerobic fermentation products of Examples 1-3 and Comparative Examples 1-13 were filtered through a 60-mesh (pore size of about 0.25 mm) filter screen, and the liquid phase was taken as the research object. The results are shown in Table 1.

[0076] Table 1 Volatile fatty acid concentration

[0077] Group Acetic acid content (%) Propionic acid content (%) Isobutyric acid content (%) Example 1 89.75 7.05 1.84 Example 2 88.76 7.21 1.86 Example 3 88.64 7.77 1.87 Comparative Example 1 58.16 15.89 3.80 Comparative Example 2 66.87 13.20 3.24 Comparative Example 3 68.59 11.54 2.57 Comparative Example 4 84.76 9.84 2.10 Comparative Example 5 79.41 10.36 2.39 Comparative Example 6 68.74 14.78 3.69 Comparative Example 7 72.85 14.23 3.31 Comparative Example 8 85.42 9.28 1.98 Comparative Example 9 80.23 11.47 2.18 Comparative Example 10 70.64 13.69 3.54 Comparative Example 11 74.58 11.87 2.83 Comparative Example 12 84.72 8.91 2.07 Comparative Example 13 81.62 9.64 2.26

[0078] Experiment 2: Methane production and stability of the anaerobic fermentation process of the present invention

[0079] The anaerobic fermentation process was carried out according to the methods of Examples 1-3 and Comparative Examples 1-13, the CH4 production per unit material and the CO2 production per unit material of the anaerobic fermentation were tested, and the CH4 / CO2 ratio was calculated. During the fermentation process, CO2 is both an intermediate product in the liquefaction stage and a raw material for the production of acetic acid and CH4 in the acid production stage and the methanogenesis stage. Therefore, the larger the CH4 / CO2 ratio, the stronger the activity of the methanogens and the better the stability of the anaerobic system. The results are shown in Table 2 below.

[0080] Table 2 Methane production and stability

[0081]

[0082]

Claims

1. A process for stabilizing an anaerobic fermentation system, characterized in that: The livestock and poultry breeding waste with a TS concentration of 6% was fully collected as a fermentation raw material and added to a microbial electrolytic cell for anaerobic fermentation. A DC power supply was used as a power supply and a voltage of 40-60V was applied to both ends of the electrolytic cell. The anode of the microbial electrolytic cell was connected to the positive electrode of the power supply, the cathode was connected to the negative electrode, and a 10Ω resistor was connected in series in the circuit. After the connection was completed, 100 portions of livestock and poultry breeding waste were taken, 8-10% of hydrogenophilic methanogens were added, 0.03-0.12% of sulfonamide antibiotics were supplemented, nitrilotriacetic acid was added to adjust the pH to 6-6.5, and 4-8% of a surfactant was added to promote microbial anaerobic fermentation. Nitrogen with a purity of 99% was first filled for 5 minutes. When no gas was produced, the biofilm stage was completed. After 12 hours of electrolysis, intermittent power supply was used and 5 cycles were run. The hydrogenophilic methanogens include a mixture of Methanobacterium buchneri and Methanobacterium boggsii; The intermittent power supply is a 12-hour power-on state and a 12-hour power-off state, which is one cycle; The sulfonamide antibiotic is sulfamethoxazole.

2. A process for a stable anaerobic fermentation system as claimed in claim 1, characterized in that: The surfactant is dialkylethanolamine ester methylammonium methyl sulfate.

3. A process for a stable anaerobic fermentation system as claimed in claim 2, characterized in that: The cathode of the microbial electrolysis cell is a 316L stainless steel mesh, which is soaked in 1 mol / L H2SO4 for 4 h before use and then washed with deionized water; the anode is obtained by brushing modified carbon cloth, specifically: Anode modification raw material: 60-70 parts of 25% by mass ferric chloride hexahydrate solution and an equal amount of 10-18% by mass modification liquid and 25 parts of water were mixed and ultrasonicated for 30 minutes. After being mixed evenly, they were added into a stainless steel high-pressure reactor lined with polytetrafluoroethylene, reacted at 130°C for 72 hours, cooled naturally, and the products were collected by centrifugation. The obtained product was washed three times with deionized water at 70°C for 2 hours according to a material-liquid ratio of 1:350, and then washed once with anhydrous ethanol at 70°C for 12 hours according to a material-liquid ratio of 1:350, and then dried at 150°C under vacuum conditions for 12 hours and then ground to obtain the modified raw material, which was stored in a dry environment for later use; Anode modified carbon cloth coating: Mix 0.5-0.8 parts of the modified raw material prepared above with 1 part of ethanol, 0.6-0.8 parts of water, and 0.1 parts of polytetrafluoroethylene and shake until uniform. Spread 2cmx4cm carbon cloth and apply the mixture on the carbon cloth. Dry it in a vacuum oven at 60℃ for 12h.

4. A process for a stable anaerobic fermentation system as claimed in claim 3, characterized in that: The modified liquid is 5-sulfoanthranilic acid.

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