A method for reducing heavy metal content in livestock and poultry manure using a treatment agent

Abstract

The present invention relates to environmentally friendly treatment of poultry manure, and in particular to a treatment method for reducing the heavy metal content in livestock and poultry manure. The present invention collects manure with a TS concentration of 6% in full quantity, first performs anaerobic fermentation, and adds a substance suitable for regulating the community environment during the anaerobic fermentation process to improve fermentation efficiency and enhance the adsorption of heavy metals by microorganisms. In addition, an acidified metal treatment agent is added to reduce the heavy metal content. The treatment agent is safe and environmentally friendly, and can also influence the reduction of the effective state of heavy metals among microbial communities, enhance fermentation, and increase biogas production. Finally, the mixed biogas slurry is subjected to solid-liquid separation and adsorption using a highly anti-fouling separation membrane to obtain biogas slurry with a low COD concentration.

Description

Technical Field

[0001] The present invention belongs to the field of heavy metal pollution, relates to the environmentally friendly treatment of heavy metals in livestock and poultry manure, and particularly refers to a treatment method for reducing the heavy metal content in livestock and poultry manure using a treatment agent. Background Art

[0002] To improve livestock and poultry production performance and feed efficiency, trace amounts of heavy metals such as copper, iron, manganese, and zinc are often added to feed. However, only about 30% of the heavy metals added to feed are absorbed and utilized by animals, with the vast majority excreted in feces. Harmless treatment of livestock and poultry manure and its subsequent return to the fields as organic fertilizer is the most economical and effective way to recycle livestock and poultry manure. Anaerobic digestion is a widely used method for treating livestock and poultry waste in my country. While anaerobic digestion can reduce the amount of livestock and poultry waste, it struggles to remove heavy metals, particularly the large doses of Cu and Zn used to promote pig growth and prevent disease, which pose potential risks to soil, groundwater, and the ecological environment.

[0003] Commonly used additives for reducing heavy metals include passivators, chelating agents, chemical leaching agents, physical adsorbents, or the introduction of electrolysis equipment. Because the effect of a single heavy metal remover is not outstanding, composite passivators are usually used to significantly improve heavy metal passivation, or passivators are combined with other metal removal methods. For example, chemical leaching and passivation are combined to treat heavy metals in manure and sewage, and electrolysis equipment is used as an auxiliary. This has achieved good results in the adsorption and removal of heavy metals in manure and sewage. However, in the industrial production process, the introduction of new electrolysis equipment also involves a certain amount of capital investment, and the parameters of the electrolysis equipment also require a certain amount of time to debug and adapt. Therefore, the most efficient way in industrial production is to improve from the aspect of composite agents.

[0004] In order to reduce the risk of heavy metal pollution, the most effective method is to passivate the heavy metal elements in livestock and poultry manure, that is, to use physical, chemical or biological methods to change the valence structure of heavy metal elements, so that the easily released ionic state is converted into an organic state that is difficult to release or slowly released, thereby reducing the harm of heavy metal elements to the environment; this study screened suitable substances for anaerobic microbial fermentation, and allowed the microorganisms to first produce a certain adsorption of heavy metals, and then used safe and environmentally friendly heavy metal treatment agents. Through the combination of microorganisms and treatment agents, the heavy metals are synergistically adsorbed and passivated, thereby slowing down the pollution of heavy metal elements to the environment.

[0005] The present invention also focuses on how to maximize the utilization and improve the quality of the biogas residue and biogas liquid obtained after anaerobic fermentation. Summary of the Invention

[0006] In order to solve the above technical problems, the specific preparation process of the present invention is as follows:

[0007] (1) Anaerobic fermentation: Fully collect manure with a TS concentration of 6%, add it to a fermentation tank for anaerobic fermentation, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 50-80 parts of an additive that promotes electroactivity to 2000-2500 parts of manure in the fermentation tank, stir for 10 minutes, and then introduce nitrogen until the air is completely exhausted. After 5 days of fermentation, add 1%-4% of a metal treatment agent. During the whole process, the pH is between 5.5-7 and the temperature is 32-38°C. Ferment for a total of 20 days to obtain a biogas mixture with a concentration of 4%, and collect the generated biogas;

[0008] The additive that promotes electroactivity is N-isopropyl octopamine;

[0009] The metal treatment agent is specifically prepared by dissolving 30-40 parts of S-2',6'-dimethyltyrosine hydrochloride in an acidic solution consisting of 11-23 parts of malonic acid, 12-26 parts of sulfuric acid, 8-13 parts of calcium bicarbonate, 12-16 parts of sodium acetate, and 100 parts of water. The solution is heated to 40°C and stirred for 25-40 minutes to acidify the solution. 40-50 parts of water is then added, and sodium hydroxide is added to adjust the pH to 4-6.

[0010] (2) performing solid-liquid separation on the biogas-liquid mixture at a rotation speed of 3000 r / min for 30-45 min to obtain biogas residue and biogas liquid;

[0011] (3) The biogas residue is processed for resource utilization through secondary fermentation, and the biogas liquid is further adsorbed and separated by a polysilicone separation membrane.

[0012] The resource-based treatment of biogas residue includes: first, exposing it to sunlight and air-drying it, controlling the moisture content of the biogas residue to about 30%, adding 0.1% of Bacillus subtilis, 0.1% of Trichoderma, and 0.1% of Bacillus subtilis, stirring it for 15-30 minutes, controlling the fermentation temperature to 50-65°C, turning it over 1-2 times a day for 7-10 days, and composting it after the temperature drops below 45°C and maintains it for 10-15 days;

[0013] The preparation of the polysilicone separation membrane comprises: mixing 20-60 parts of polysilicone, 20-30 parts of toluene, 10-20 parts of glycerin, and 4-8 parts of an additive, heating the mixture to 80°C while stirring at a speed of 200-300 rpm, and stirring for 10-15 minutes to obtain a precursor solution; subjecting the separation membrane precursor solution to swelling treatment, then reacting the mixture in a water bath controlled at 60°C, and continuing stirring for 1-2 hours to obtain the separation membrane; casting the separation membrane solution onto a clean glass plate to form a membrane, and drying the membrane in an oven at 70°C for 4 hours to obtain the separation membrane;

[0014] The precursor solution of the separation membrane is subjected to swelling treatment: 5-10 parts of ethylene glycol, 0.5-2 parts of a polar swelling agent with a negatively charged group, and 2-5 parts of a pore-forming agent are added to the mixed precursor, stirred for 5-10 minutes, maintained at a water bath temperature of 35-38°C, and allowed to swell for 30 minutes;

[0015] The polar swelling agent having a negatively charged group is 3,4,5-tricarboxylic acid aniline.

[0016] The beneficial effects of the present invention are:

[0017] 1. The present invention relates to the environmentally friendly treatment of poultry manure. The collected manure is first subjected to anaerobic fermentation. During the anaerobic fermentation process, substances suitable for regulating the community environment are added to improve the fermentation efficiency and enhance the adsorption of heavy metals by microorganisms. In addition, a metal treatment agent after acidification is added to reduce the heavy metal content. The treatment agent is safe and environmentally friendly, and can also affect the microbial community to reduce the effective state of heavy metals, enhance the fermentation effect, and increase the production of biogas. Finally, the mixed biogas liquid is separated and adsorbed by a highly anti-fouling separation membrane to obtain a biogas liquid with a low COD concentration. The process is simple and efficient, and can maximize the efficiency of treating the heavy metal content in manure.

[0018] 2. N-isopropyloctopamine can regulate the pH value of the fermentation system, maintaining an appropriate acid-base balance and enabling microbial growth within a suitable pH range. N-isopropyloctopamine can undergo certain redox reactions with humic acid substances, producing an effect similar to that of an electron shuttle. N-isopropyloctopamine modifies the specific structure of humic acid, regulating the spacing and interaction strength between its molecules, thereby improving the electron transport properties in the complex. By providing electrons, it participates in the fermentation process of anaerobic microorganisms, participates in energy metabolism and produces ATP. The presence of microbial electroactivity can enhance the efficiency of the electron transport chain and increase the product yield and rate during the fermentation process.

[0019] 3. In an environment where N-isopropyloctopamine provides microbial electroactivity, microorganisms can enhance their adsorption capacity for metals by regulating the cell surface charge and changing the cell wall permeability, and simultaneously adsorb heavy metals during the fermentation process. In addition, microbial electroactivity can also promote the reduction or oxidation reaction of metal ions, thereby changing the chemical state of the metal. Other forms of copper in manure will be converted into exchangeable copper. The synthesis of electron shuttles can increase the available active sites on the electrode surface, thereby improving the microbial adsorption capacity, improving the clarity of the biogas slurry, and the opportunity and efficiency of metal adsorption.

[0020] 4. First, after the metal treatment agent is acidified, the sensitivity of the treatment agent in complexing metals can be improved, and the reaction rate can be accelerated. Secondly, the stability of the reaction product is improved after acidification, and the macromolecular organic matter in the organic waste is decomposed into small molecular organic matter during the reaction process, thereby reducing the COD concentration to a certain extent, which is beneficial to the subsequent separation and treatment. The oxygen-rich surface functional groups (hydroxyl, carboxyl and phenol groups) in S-2', 6'-dimethyltyrosine hydrochloride will adsorb heavy metals in the contaminated water environment. Heavy metals can be surrounded by multiple coordination molecules in S-2', 6'-dimethyltyrosine hydrochloride to form inner-sphere complexes to form stable compounds, or with free hydroxyl groups in the functional groups on the surface of S-2', 6'-dimethyltyrosine hydrochloride for surface inner-sphere complexation. This complex adsorption has a strong attraction for transition metals containing partially filled d orbitals, thereby reducing the mobility and bioavailability of heavy metals, and playing a synergistic role with microbial adsorption to jointly remove heavy metals.

[0021] 5. S-2',6'-dimethyltyrosine hydrochloride is added as a treatment agent to the anaerobic fermentation pond to inhibit the growth of ammonia-oxidizing bacteria, thereby reducing the ammonia oxidation reaction, delaying the gas production peak during the fermentation process, extending the fermentation cycle, and increasing biogas production. It can also promote the growth of certain nitrite-reducing bacteria and methane-producing bacteria, thereby improving the structure of the bacterial community and enhancing the correlation between bacteria and heavy metal components. Therefore, the prepared treatment agent can not only directly chelate heavy metals, but also indirectly reduce the effective state of heavy metals by affecting the microbial community in the pile, and enhance the fermentation effect and increase biogas production.

[0022] 6. Adding metal treatment agents during the second fermentation treatment of biogas residue can neutralize and reduce the odor of the biogas residue, interact with the molecules or ions in the biogas residue through hydrogen bonds, ion complexation, etc., break the mutual attraction or chemical bonds between them, thereby promoting the dissolution and penetration of the biogas residue, and promoting the quality of organic fertilizer formed by subsequent composting and other treatments of the biogas residue.

[0023] 7. After using the composite electron shuttle and metal treatment agent in the above-mentioned heavy metal adsorption process, if the amount involved is not removed and remains in the biogas residue, it will affect the subsequent biogas residue preparation fertilizer, causing agglomeration and other adverse effects. Therefore, the mixed biogas slurry after heavy metal treatment is subjected to separation membrane adsorption. In addition, membrane separation is easily affected by deposited organic matter and particulate matter during use, which may cause degradation or inactivation, requiring regular maintenance or replacement. Therefore, 3,4,5-tricarboxylic acid aniline is introduced into the surface of the separation membrane through swelling treatment to improve the contact angle of the separation membrane surface and reduce the contact angle. 3,4,5-tricarboxylic acid aniline is highly water-soluble and the polycarboxylic acid structure therein has both hydrophilic and polar group effects, first increasing the hydrophilicity of the membrane. The better the hydrophilicity, the better the anti-fouling performance of the membrane, the less susceptible the membrane is to contamination, improving its susceptibility to contamination and increasing renewability, improving recovery rate, and saving costs. The presence of phenyl groups in 3,4,5-tricarboxylic acid aniline can also improve thermal stability, avoiding the destruction of thermodynamic stability caused by temperature increase.

[0024] After 8.3,4,5-tricarboxylic acid amine is introduced into the separation membrane, its charge is opposite to that of phenyl N-isopropyloctopamine, enabling targeted removal. Furthermore, the membrane surface exhibits a charge that repels like-charged negative ions, creating a porous membrane with a one-dimensional array of vertically connected channels. This significantly increases the retention rate of organic matter, suspended solids, and microorganisms, thereby purifying the biogas slurry and effectively removing organic matter and inorganic salts from it. This improves the water quality of the biogas slurry, significantly reduces the COD content, and minimizes the impact of subsequent use on the environment and crops. The adsorbed organic components can be recycled and reused through subsequent treatment. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the embodiments.

[0026] All raw materials used in the embodiments of the present invention are waste materials from nearby livestock and poultry farms and farmlands. The remaining raw materials or chemical reagents, unless otherwise specified, are obtained through conventional commercial channels.

[0027] Among them, the subsequent resource treatment of the sludge after anaerobic fermentation includes: first exposing it to light, air drying it, controlling the moisture content of the sludge to 30%, adding 0.1% of Bacillus subtilis, 0.1% of Trichoderma, and 0.1% of Bacillus subtilis, stirring it for 15-30 minutes, controlling the fermentation temperature to 55°C, plowing it 1-2 times a day, maintaining it for 7-10 days, and waiting for the temperature to drop below 45°C and maintain it for 10-15 days before the composting is completed.

[0028] Example 1

[0029] 1) The metal treatment agent is specifically: 35 parts of S-2',6'-dimethyltyrosine hydrochloride is dissolved in an acidic solution consisting of 16 parts of malonic acid, 20 parts of sulfuric acid, 10 parts of calcium bicarbonate, 14 parts of sodium acetate, and 100 parts of water, heated to 40°C and stirred for 32 minutes to acidify, then 45 parts of water is added thereto, and sodium hydroxide is added to adjust the pH to 5, to obtain the product;

[0030] 2) Anaerobic fermentation: Fully collect manure with a TS concentration of 6% and add it to a fermentation tank for anaerobic fermentation. To 2200 parts of manure in the fermentation tank, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 65 parts of N-isopropyloctopamine. After stirring for 10 minutes, nitrogen is introduced until the air is completely exhausted. After 5 days of fermentation, 2.5% of a metal treatment agent is added. The pH is maintained at around 6.2 and the temperature is maintained at 35°C. Fermentation is carried out for a total of 20 days to obtain a biogas mixture with a concentration of 4%. The generated biogas is collected.

[0031] 3) performing solid-liquid separation on the biogas slurry mixture at a rotation speed of 3000 r / min for 36 min to obtain biogas residue and biogas slurry;

[0032] 4) Preparation of polysilicone separation membrane: 40 parts of polysilicone, 25 parts of toluene, 15 parts of glycerin, and 6 parts of an additive were mixed, heated to 80°C with stirring at 250 rpm, and stirred for 12 minutes to obtain a precursor solution; 8 parts of ethylene glycol, 1.2 parts of 3,4,5-tricarboxylic acid aniline, and 3 parts of a pore-forming agent were added to the mixed precursor, stirred for 8 minutes, and the water bath temperature was maintained at 36°C, and static swelling was performed for 30 minutes; the reaction was then controlled in a water bath at 60°C and stirred for 1.5 hours to obtain the separation membrane solution. The separation membrane solution was cast onto a clean glass plate to form a membrane, and dried in an oven at 70°C for 4 hours to obtain the membrane;

[0033] 5) The biogas residue is subjected to secondary fermentation for resource recovery, and the biogas liquid is further adsorbed and separated by a polysilicone separation membrane.

[0034] Example 2

[0035] 1) The metal treatment agent is specifically: 35 parts of S-2',6'-dimethyltyrosine hydrochloride is dissolved in an acidic solution consisting of 16 parts of malonic acid, 20 parts of sulfuric acid, 10 parts of calcium bicarbonate, 14 parts of sodium acetate, and 100 parts of water, heated to 40°C and stirred for 32 minutes to acidify, then 45 parts of water is added thereto, and sodium hydroxide is added to adjust the pH to 5, to obtain the product;

[0036] 2) Anaerobic fermentation: Fully collect manure with a TS concentration of 6% and add it to a fermentation tank for anaerobic fermentation. To 2000 parts of manure in the fermentation tank, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 80 parts of N-isopropyloctopamine. After stirring for 10 minutes, nitrogen is introduced until the air is completely exhausted. After 5 days of fermentation, 1% of a metal treatment agent is added. The pH is maintained at around 7 and the temperature is maintained at 38°C throughout the fermentation process. The fermentation lasts for 20 days to obtain a biogas mixture with a concentration of 4%, and the generated biogas is collected.

[0037] 3) performing solid-liquid separation on the biogas slurry mixture at a rotation speed of 3000 r / min for 30 min to obtain biogas residue and biogas slurry;

[0038] 4) Preparation of polysilicone separation membrane: 60 parts of polysilicone, 30 parts of toluene, 10 parts of glycerin, and 4 parts of an additive were mixed, heated to 80°C with stirring at 300 rpm, and stirred for 10 minutes to obtain a precursor solution; 10 parts of ethylene glycol, 0.5 parts of 3,4,5-tricarboxylic acid aniline, and 2 parts of a pore-forming agent were added to the mixed precursor, stirred for 10 minutes, and the water bath temperature was maintained at 38°C, and static swelling was performed for 30 minutes; the reaction was then controlled in a water bath at 60°C and stirred for 1 hour to obtain the separation membrane solution. The separation membrane solution was cast onto a clean glass plate to form a membrane, and dried in an oven at 70°C for 4 hours to obtain the membrane;

[0039] 5) The biogas residue is subjected to secondary fermentation for resource recovery, and the biogas liquid is further adsorbed and separated by a polysilicone separation membrane.

[0040] Example 3

[0041] 1) The metal treatment agent is specifically: 35 parts of S-2',6'-dimethyltyrosine hydrochloride is dissolved in an acidic solution consisting of 16 parts of malonic acid, 20 parts of sulfuric acid, 10 parts of calcium bicarbonate, 14 parts of sodium acetate, and 100 parts of water, heated to 40°C and stirred for 32 minutes to acidify, then 45 parts of water is added thereto, and sodium hydroxide is added to adjust the pH to 5, to obtain the product;

[0042] 2) Anaerobic fermentation: Fully collect manure with a TS concentration of 6% and add it to a fermentation tank for anaerobic fermentation. To 2500 parts of manure in the fermentation tank, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 50 parts of N-isopropyloctopamine. After stirring for 10 minutes, nitrogen is introduced until the air is completely exhausted. After 5 days of fermentation, 4% of metal treatment agent is added. The pH is around 5.5 and the temperature is 32°C. Fermentation is carried out for a total of 20 days to obtain a biogas mixture with a concentration of 4%. The generated biogas is collected.

[0043] 3) performing solid-liquid separation on the biogas slurry mixture at a rotation speed of 3000 r / min for 40 min to obtain biogas residue and biogas slurry;

[0044] 4) Preparation of polysilicone separation membrane: 20 parts of polysilicone, 20 parts of toluene, 20 parts of glycerin, and 8 parts of an additive were mixed, heated to 80°C with stirring at a speed of 200-300 rpm, and stirred for 15 minutes to obtain a precursor solution; 5 parts of ethylene glycol, 2 parts of 3,4,5-tricarboxylic acid aniline, and 5 parts of a pore-forming agent were added to the mixed precursor, stirred for 5-10 minutes, and the water bath temperature was maintained at 38°C, and the mixture was allowed to swell statically for 30 minutes; the reaction was then controlled in a water bath at 60°C and stirred for 1-2 hours to obtain the separation membrane solution. The separation membrane solution was cast onto a clean glass plate to form a membrane, and dried in an oven at 70°C for 4 hours to obtain the membrane;

[0045] 5) The biogas residue is subjected to secondary fermentation for resource recovery, and the biogas liquid is further adsorbed and separated by a polysilicone separation membrane.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that N-isopropyloctopamine, which promotes electroactivity, is not added in step (2), and the rest is the same as Example 1.

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 1 is that in step (2), N-isopropyloctopamine is ammonium chloride, and the rest is the same as Example 1.

[0050] Comparative Example 3

[0051] The difference between this comparative example and Example 1 is that the amount of N-isopropyloctopamine added to promote electroactivity in step (2) is different. Specifically, the anaerobic fermentation process in step (2) is as follows: fully collect feces with a TS concentration of 6%, add it to a fermentation tank for anaerobic fermentation, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 97 parts of N-isopropyloctopamine to 2500 parts of feces in the fermentation tank, stir for 10 minutes, and then introduce nitrogen until the air is completely exhausted. After 5 days of fermentation, 4% of a metal treatment agent is added. The pH is maintained at about 5.5 and the temperature is 32°C throughout the fermentation process. The fermentation is carried out for a total of 20 days to obtain a biogas slurry mixture with a concentration of 4%, and the generated biogas is collected. The rest is the same as in Example 1.

[0052] Comparative Example 4

[0053] The difference between this comparative example and Example 1 is that the amount of N-isopropyloctopamine added to promote electroactivity in step (2) is different. Specifically, the anaerobic fermentation process in step (2) is as follows: fully collect feces with a TS concentration of 6%, add it to a fermentation tank for anaerobic fermentation, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 32 parts of N-isopropyloctopamine to 2500 parts of feces in the fermentation tank, stir for 10 minutes, and then introduce nitrogen until the air is completely exhausted. After fermentation for 5 days, 4% of a metal treatment agent is added. The pH is maintained at about 5.5 and the temperature is 32°C throughout the fermentation process. The fermentation lasts for 20 days to obtain a biogas slurry mixture with a concentration of 4%, and the generated biogas is collected. The rest is the same as in Example 1.

[0054] Comparative Example 5

[0055] The difference between this comparative example and Example 1 is that metal passivation is performed by physical adsorption of zeolite powder. Specifically, the anaerobic fermentation process in step (2) is as follows: fully collect feces with a TS concentration of 6%, add them to a fermentation tank for anaerobic fermentation, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 97 parts of N-isopropyloctopamine to 2200 parts of feces in the fermentation tank, stir for 10 minutes, and then introduce nitrogen until the air is completely exhausted. After 5 days of fermentation, 2.5% zeolite powder is added. The pH of the whole process is about 6.2, the temperature is 35°C, and the concentration of the biogas mixture is obtained to be 4%, and the generated biogas is collected; the rest is the same as in Example 1.

[0056] Comparative Example 6

[0057] The difference between this comparative example and Example 1 is that in step (1), S-2',6'-dimethyltyrosine hydrochloride is trisodium phosphate, and the rest is the same as Example 1.

[0058] Comparative Example 7

[0059] The difference between this comparative example and Example 1 is that the metal treatment agent in step (1) is not acidified. Specifically, the metal treatment agent in step (1) is prepared as follows: 35 parts of S-2',6'-dimethyltyrosine hydrochloride, 100 parts of water, and sodium hydroxide is added to adjust the pH to 5; the rest is the same as in Example 1.

[0060] Comparative Example 8

[0061] The difference between this comparative example and Example 1 lies in the different amount of S-2',6'-dimethyltyrosine hydrochloride added in step (1). Specifically, the metal treatment agent is prepared as follows: 15 parts of S-2',6'-dimethyltyrosine hydrochloride is added to an acidic solution consisting of 16 parts of malonic acid, 20 parts of sulfuric acid, 10 parts of calcium bicarbonate, 14 parts of sodium acetate, and 100 parts of water. After heating to 40°C and stirring for 32 minutes to acidify, 45 parts of water is added thereto, and sodium hydroxide is added to adjust the pH to 5. The preparation method is the same as that of Example 1.

[0062] Comparative Example 9

[0063] The difference between this comparative example and Example 1 lies in the different amount of S-2',6'-dimethyltyrosine hydrochloride added in step (1). Specifically, the metal treatment agent is prepared as follows: 55 parts of S-2',6'-dimethyltyrosine hydrochloride is added to an acidic solution consisting of 16 parts of malonic acid, 20 parts of sulfuric acid, 10 parts of calcium bicarbonate, 14 parts of sodium acetate, and 100 parts of water. After heating to 40°C and stirring for 32 minutes to acidify, 45 parts of water is added thereto, and sodium hydroxide is added to adjust the pH to 5. The preparation method is the same as that of Example 1.

[0064] Comparative Example 10

[0065] The difference between this comparative example and Example 1 is that the biogas slurry is not subjected to adsorption separation using a polysilicone separation membrane. The specific process is as follows:

[0066] 1) The metal treatment agent is specifically: 35 parts of S-2',6'-dimethyltyrosine hydrochloride is dissolved in an acidic solution consisting of 16 parts of malonic acid, 20 parts of sulfuric acid, 10 parts of calcium bicarbonate, 14 parts of sodium acetate, and 100 parts of water, heated to 40°C and stirred for 32 minutes to acidify, then 45 parts of water is added thereto, and sodium hydroxide is added to adjust the pH to 5, to obtain the product;

[0067] 2) Anaerobic fermentation: Fully collect manure with a TS concentration of 6% and add it to a fermentation tank for anaerobic fermentation. To 2200 parts of manure in the fermentation tank, add 3 parts of anaerobic methanogens and 3 parts of anaerobic Lactobacillus acidophilus, and 65 parts of N-isopropyloctopamine. After stirring for 10 minutes, nitrogen is introduced until the air is completely exhausted. After 5 days of fermentation, 2.5% of a metal treatment agent is added. The pH is maintained at around 6.2 and the temperature is maintained at 35°C. Fermentation is carried out for a total of 20 days to obtain a biogas mixture with a concentration of 4%. The generated biogas is collected.

[0068] 3) performing solid-liquid separation on the biogas slurry mixture at a rotation speed of 3000 r / min for 36 min to obtain biogas residue and biogas slurry;

[0069] 4) Resource-based treatment of biogas residue through secondary fermentation.

[0070] Comparative Example 11

[0071] The difference between this comparative example and Example 1 is that the 3,4,5-tricarboxylic acid aniline in step (4) is EDTA, and the rest is the same as Example 1.

[0072] Comparative Example 12

[0073] The difference between this comparative example and Example 1 is that the amount of 3,4,5-tricarboxylic acid aniline added in step (4) is different. The specific separation membrane is prepared as follows: 40 parts of polysilicone, 25 parts of toluene, 15 parts of glycerin, and 6 parts of an auxiliary agent are mixed, heated to 80°C while stirring at a speed of 250 rpm, and stirred for 12 minutes to obtain a precursor solution; 8 parts of ethylene glycol, 2.5 parts of 3,4,5-tricarboxylic acid aniline, and 3 parts of a pore-forming agent are added to the mixed precursor, stirred for 8 minutes, and the water bath temperature is maintained at 36°C, and static swelling is performed for 30 minutes; then the water bath is controlled to react at 60°C, and stirring is continued for 1.5 hours to obtain the separation membrane. The above separation membrane liquid is cast into a film on a clean glass plate, and dried in an oven at 70°C for 4 hours to obtain the obtained film; the rest is the same as in Example 1.

[0074] Comparative Example 13

[0075] The difference between this comparative example and Example 1 is that the amount of 3,4,5-tricarboxylic acid aniline added in step (4) is different. The specific separation membrane is prepared as follows: 40 parts of polysilicone, 25 parts of toluene, 15 parts of glycerin, and 6 parts of an auxiliary agent are mixed, heated to 80°C while stirring at a speed of 250 rpm, and stirred for 12 minutes to obtain a precursor solution; 8 parts of ethylene glycol, 0.5 parts of 3,4,5-tricarboxylic acid aniline, and 3 parts of a pore-forming agent are added to the mixed precursor, stirred for 8 minutes, and the water bath temperature is maintained at 36°C, and static swelling is performed for 30 minutes; then the water bath is controlled to react at 60°C, and stirring is continued for 1.5 hours to obtain the separation membrane. The above separation membrane liquid is cast into a film on a clean glass plate, and dried in an oven at 70°C for 4 hours to obtain the obtained film; the rest is the same as Example 1.

[0076] 1. Determination of passivation rate of heavy metal elements:

[0077] (1) 1 ml of each sample from Examples 1-3 and Comparative Examples 1-13 was weighed, and 40 mL of 0.1 mol / L acetic acid was added. The mixture was shaken at 22±5°C for 16 h and centrifuged at 3000 rpm for 20 min. The heavy metal content in the supernatant was determined using a flame atomic absorption spectrometer (Shenyang Huaguang 9601).

[0078] (2) Heavy metal element passivation rate = (heavy metal element content in the supernatant before fermentation - total amount of heavy metal elements in the supernatant after fermentation) / total amount of heavy metal elements in the supernatant before fermentation ╳ 100%

[0079] (3) The control group was: fully collected feces with a TS concentration of 6%, added to the fermentation tank for anaerobic fermentation, 3 parts of composite anaerobic microbial flora and 65 parts of N-isopropyloctopamine were added to 2200 parts of feces in the fermentation tank, and nitrogen was introduced until the air was completely exhausted and the pH was around 6.2. The temperature was 35°C, and the first fermentation was carried out for 18 days, and the generated biogas was collected; the results are shown in Table 1.

[0080] 2. COD determination of biogas slurry samples: Using the potassium dichromate-microwave method, 5 ml of 0.25 mol·L-1 potassium dichromate digestion solution and 10 ml of sulfuric acid-silver sulfate catalyst were added to 10 ml of water sample, shaken well, and the biogas slurry sample was sealed and heated for digestion using a microwave COD digestion device; the excess potassium dichromate in the digested liquid was titrated with ammonium ferrous sulfate using ferrochlore as an indicator, and the COD value of the biogas slurry sample was calculated according to the following formula: The calculation formula is: COD (mg / L) = [(V0-V1)×C×8×1000] / V2; wherein, V0: the amount of ammonium ferrous sulfate consumed by the blank, V1: the amount of ammonium ferrous sulfate consumed by the biogas slurry sample, V2: the volume of the biogas slurry sample, C: the concentration of the ammonium ferrous sulfate solution, and 8: the molar mass of oxygen (1 / 2O); the measurement results of Examples 1-3 and Comparative Examples 10-13 are shown in Table 2.

[0081] Table 1 Passivation rate of different heavy metal elements (%)

[0082] Group Cu Fe Zn Mn control group 28.18 18.26 2.31 0.39 Example 1 100.57 65.94 42.48 21.73 Example 2 98.74 63.42 38.35 18.87 Example 3 99.95 61.25 40.32 20.47 Comparative Example 1 68.43 42.56 29.58 11.36 Comparative Example 2 72.56 38.97 32.45 13.84 Comparative Example 3 76.28 46.81 24.96 16.92 Comparative Example 4 80.49 44.53 27.13 15.83 Comparative Example 5 87.60 45.22 30.82 15.02 Comparative Example 6 70.28 43.56 25.87 13.84 Comparative Example 7 74.93 50.26 30.59 14.87 Comparative Example 8 78.63 52.74 32.87 15.66 Comparative Example 9 80.94 53.44 33.68 15.83

[0083] Table 2 COD concentration measurement results

[0084] Group COD content (mg / L) Example 1 16.71 Example 2 18.54 Example 3 17.43 Comparative Example 10 68.02 Comparative Example 11 47.61 Comparative Example 12 26.36 Comparative Example 13 29.72

Claims

1. A method for reducing the heavy metal content in livestock and poultry manure by using a treatment agent, characterized in that: (1) Anaerobic fermentation: Fully collect manure with a TS concentration of 6% and add it to the fermentation tank for anaerobic fermentation. Add 3 parts of anaerobic methanogens and 3 parts of anaerobic lactobacillus acidophilus and 50-80 parts of additives that promote electroactivity to 2000-2500 parts of manure in the fermentation tank. After stirring for 10 minutes, nitrogen is introduced until the air is completely exhausted. After 5 days of fermentation, 1%-4% of metal treatment agent is added. The pH value of the whole process is between 5.5-7 and the temperature is 32-38℃. The fermentation is carried out for 20 days to obtain a biogas mixture with a concentration of 4%. The generated biogas is collected. (2) The biogas slurry mixture is subjected to solid-liquid separation at a rotation speed of 3000 r / min for 30-45 min to obtain biogas residue and biogas slurry; (3) The biogas residue is treated as a resource by secondary fermentation, and the biogas liquid is further adsorbed and separated by a polysilicone separation membrane; The additive that promotes electroactivity is N-isopropyl octopamine.

2. The method for reducing the heavy metal content in livestock and poultry manure according to claim 1, characterized in that: The metal treatment agent is specifically 30-40 parts of S-2',6'-dimethyltyrosine hydrochloride in an acidic solution consisting of 11-23 parts of malonic acid, 12-26 parts of sulfuric acid, 8-13 parts of calcium bicarbonate, 12-16 parts of sodium acetate, and 100 parts of water. After heating to 40°C and stirring for 25-40 minutes to acidify, 40-50 parts of water are added thereto, and sodium hydroxide is added to adjust the pH to 4-6 to obtain the metal treatment agent.

3. The method for reducing the heavy metal content in livestock and poultry manure according to claim 1, wherein: The preparation of the polysilicone separation membrane includes: mixing 20-60 parts of polysilicone, 20-30 parts of toluene, 10-20 parts of glycerin, and 4-8 parts of an additive, heating them to 80°C while stirring, at a rotation speed of 200-300 rpm, and stirring for 10-15 minutes to obtain a precursor solution; swelling the precursor solution, then controlling the reaction in a water bath at 60°C, and continuing to stir for 1-2 hours to obtain a separation membrane liquid, casting the above-mentioned separation membrane liquid into a film on a clean glass plate, and drying it in an oven at 70°C for 4 hours.

4. The method for reducing the heavy metal content in livestock and poultry manure according to claim 3, characterized in that: The swelling treatment of the precursor solution of the separation membrane includes: adding 5-10 parts of ethylene glycol, 0.5-2 parts of a polar swelling agent with a negatively charged group, and 2-5 parts of a pore-forming agent to the mixed precursor, stirring for 5-10 minutes, maintaining a water bath temperature of 35-38°C, and static swelling for 30 minutes.

5. The method for reducing the heavy metal content in livestock and poultry manure according to claim 4, characterized in that: in, The polar swelling agent having a negatively charged group is 3,4,5-tricarboxylic acid aniline.

6. The method for reducing heavy metal content in livestock and poultry manure according to claim 1, wherein: The resource utilization treatment of the biogas residue in step (3) includes: first exposing it to light, air-drying it, controlling the moisture content of the biogas residue to 30%, adding 0.1% of Bacillus subtilis, 0.1% of Trichoderma, and 0.1% of Bacillus subtilis, stirring it for 15-30 minutes, controlling the fermentation temperature to 50℃-65℃, plowing it 1-2 times a day, maintaining it for 7-10 days, and waiting for the temperature to drop below 45℃ and maintain it for 10-15 days before the composting is completed.