Closed-loop treatment system and method for antibiotics in livestock and poultry manure

Abstract

The invention discloses a closed-loop treatment system and method for antibiotics in livestock and poultry manure. The system comprises a pretreatment system, a saturated biochar regeneration system, an anaerobic fermentation system and a biochar modification system, the method comprises the following steps: introducing an acidified material generated by a hydrolytic acidification system in an anaerobic fermentation system into a pretreatment tank, adjusting the pH value of a solution in combination with hydrochloric acid, quickly releasing antibiotics in livestock and poultry manure, quickly separating in a solid-liquid separation device, and adsorbing the antibiotics in the solution by adopting modified biochar in a biochar adsorption device. Secondary adhesion and deposition of the released antibiotics are avoided, and saturated biochar adsorbing the antibiotics is separated out by using a biochar separation device; the saturated biochar after adsorption of the antibiotics is subjected to closed-loop high-temperature gasification in a saturated biochar regeneration system to realize complete decomposition of the antibiotics, and is mixed with biogas residues for further stabilization to prepare a carbon-based organic matrix, so that the value and application safety of an anaerobic fermentation product are improved.

Description

Technical Field

[0001] This invention relates to the resource utilization of biomass organic solid waste and anaerobic fermentation technology, specifically to a closed-loop treatment system and method for antibiotics in livestock and poultry manure. Background Technology

[0002] In recent years, with the increasing application of antibiotics in various industries such as pharmaceuticals, animal husbandry, and aquaculture, the problem of antibiotic abuse has become increasingly serious. Very little antibiotic is absorbed in the intestines; only a small amount is absorbed by the body and undergoes processes such as hydroxylation, cleavage, and glucuronidation to produce non-toxic and harmless substances. Approximately 60% to 90% is excreted unchanged in feces and urine. Currently, the main methods of utilizing manure resources are fertilizer production or biogas production, and antibiotics are often applied to the soil along with this fertilizer. When antibiotics accumulate to a certain level in the soil, they not only affect the community structure of microorganisms but also induce the production of antibiotic resistance genes. Antibiotic resistance genes are genes that enable bacteria to resist antibiotics. They can persist, spread, and diffuse in various environmental media such as soil, water, and air, and enter the human body through the food chain, posing a threat to human health.

[0003] Chinese invention patent application CN 116081755A discloses a method for rapidly and efficiently reducing antibiotics in livestock and poultry manure. This method releases antibiotics from organic manure by adding ethylenediaminetetraacetic acid (EDTA), followed by the addition of biochar to adsorb the released antibiotics, significantly reducing the antibiotic content in the manure. However, the EDTA added in this patent persists in the environment and can easily enter the soil through biogas residue. Furthermore, its strong chelating properties may lead to the activation and migration of heavy metals in soil or water, causing secondary pollution. Additionally, it may inhibit the activity of anaerobic microorganisms in anaerobic fermentation systems, reducing methane yield.

[0004] Chinese invention patent application CN 115286443A discloses a method for enhancing antibiotic degradation and heavy metal passivation in composting through high-temperature pretreatment combined with biochar. This method involves pretreating livestock and poultry manure and composting additives at high temperature, followed by the addition of biochar for co-composting, which promotes the degradation of antibiotics and the passivation of heavy metals in the compost material. This method can achieve rapid maturation of livestock and poultry manure and has a significant effect on pollutant removal. However, the biochar, after adsorbing antibiotics and heavy metals, does not separate from the compost product, and there is still a risk of release after the composting period.

[0005] In summary, during conventional anaerobic fermentation, the degradation capacity of microorganisms is limited, and some antibiotics (such as sulfonamides and tetracyclines) are difficult to completely degrade, potentially promoting the accumulation of drug-resistant bacteria and resulting in the residue of antibiotic resistance genes (ARGs) in the fermentation products. Biochar's porous structure and abundant surface functional groups can increase the surface area for microbial attachment, and it can accumulate specific degrading bacteria with a certain adsorption capacity for antibiotics. However, biochar itself has limited adsorption capacity, and loading it with other acids, alkalis, or metals can cause secondary pollution. Furthermore, there is a lack of economically feasible post-treatment solutions for saturated biochar, which may lead to a greater environmental burden. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a closed-loop treatment system and method for antibiotics in livestock and poultry manure. This solution removes antibiotics from livestock and poultry manure in an economical and efficient manner, avoiding secondary pollution caused by the biogas residue and biogas slurry obtained from the anaerobic fermentation of livestock and poultry manure during subsequent resource utilization.

[0007] Technical Solution: This invention provides a closed-loop treatment system for antibiotics in livestock and poultry manure, comprising a pretreatment system, a saturated biochar regeneration system, an anaerobic fermentation system, and a biochar modification system; wherein, the anaerobic fermentation system includes a hydrolysis acidification system, a methanogenic system, and a sludge-liquid separation device; the inlet of the pretreatment system is used to introduce livestock and poultry manure, and the pretreatment system is used to remove antibiotics from the livestock and poultry manure; the outlet of the pretreatment system is connected to the inlet of the saturated biochar regeneration system and the inlet of the hydrolysis acidification system, respectively, for introducing the saturated biochar produced by the pretreatment system into the saturated biochar regeneration system, and for introducing the solid material produced by the pretreatment system into the hydrolysis acidification system; the outlet of the saturated biochar regeneration system is connected to the inlet of the biochar modification system, for introducing... The biochar produced by the saturated biochar regeneration system is fed into the biochar modification system. The outlet of the hydrolysis acidification system is connected to the inlet of the methanogenic system and the inlet of the pretreatment system, respectively, to feed the acidified products produced by the hydrolysis acidification system into the methanogenic system and the pretreatment system. The outlet of the methanogenic system is connected to the inlet of the sludge-liquid separation device, which separates the biogas sludge and biogas slurry produced by the methanogenic system. The outlet of the sludge-liquid separation device is connected to the inlet of the biochar modification system, to feed the biogas slurry separated by the sludge-liquid separation device into the biochar modification system. The outlet of the biochar modification system is connected to the inlet of the pretreatment system and the inlet of the methanogenic system, respectively, to feed the modified biochar produced by the biochar modification system into the pretreatment system and the methanogenic system.

[0008] Furthermore, the pretreatment system includes a pretreatment tank, a solid-liquid separation device, a biochar adsorption device, and a biochar separation device connected in sequence.

[0009] Furthermore, the pretreatment tank has a livestock and poultry manure inlet, a first acidified substance inlet, and a circulating diluent inlet at the top, and a mixed raw material outlet at the bottom; the livestock and poultry manure inlet is used to introduce livestock and poultry manure; the first acidified substance inlet is connected to the acidified substance outlet on the hydrolysis acidification system; the circulating diluent inlet is connected to the filtrate outlet on the biochar separation device; and the mixed raw material outlet is connected to the mixed raw material inlet on the solid-liquid separation device.

[0010] Furthermore, the solid-liquid separation device has a bottom liquid outlet and a top liquid outlet; the bottom liquid outlet is connected to the fermentation raw material inlet of the hydrolysis acidification system, and is used to pass the solid material obtained after solid-liquid separation into the hydrolysis acidification system; the top liquid outlet is connected to the top liquid inlet of the biochar adsorption device, and is used to pass the solution obtained after solid-liquid separation into the biochar adsorption device.

[0011] Furthermore, the biochar adsorption device has a first modified biochar inlet and a mixed liquid outlet. The first modified biochar inlet is connected to the biochar outlet on the biochar modification system, and the mixed liquid outlet is connected to the mixed liquid inlet on the biochar separation device.

[0012] Furthermore, the biochar separation device has a saturated biochar outlet, which is connected to the saturated biochar inlet on the saturated biochar regeneration system.

[0013] Furthermore, the saturated biochar regeneration system includes a vertical segmented furnace and a low-oxygen combustion hot blast stove. The vertical segmented furnace has a high-temperature furnace gas outlet. The low-oxygen combustion hot blast stove is configured with two layers: an inner cylindrical combustion chamber and an outer rectangular flue gas mixing zone. The cylindrical combustion chamber has a high-temperature furnace gas inlet connected to a high-temperature furnace gas outlet. A biogas burner is installed inside the cylindrical combustion chamber, which provides a stable continuous flame for the low-oxygen combustion hot blast stove.

[0014] Furthermore, the biochar modification system has a biogas slurry inlet, a biochar inlet, and a biochar outlet; the biogas slurry inlet is connected to the biogas slurry outlet on the sludge-liquid separation device, the biochar inlet is connected to the biochar outlet on the saturated biochar regeneration system, and the biochar outlet is connected to the second modified biochar inlet on the methanogenic system.

[0015] Based on the same inventive concept, the present invention provides a closed-loop treatment method for antibiotics in livestock and poultry manure, applied to the aforementioned closed-loop treatment system for antibiotics in livestock and poultry manure, comprising:

[0016] Pretreatment and Antibiotic Separation: Adjust the solid-liquid mass ratio of livestock and poultry manure, introduce acidified material from the hydrolysis acidification system outlet into the pretreatment tank in proportion, and mix thoroughly; add hydrochloric acid solution as needed to adjust the pH value of the solution, so that the antibiotics adhering to the livestock and poultry manure are released into the solution; after the antibiotics are released, immediately separate the mixture through a solid-liquid separation device to obtain antibiotic-free solid material and a solution with high antibiotic content; the solution with high antibiotic content enters the biochar adsorption device; the biochar in the biochar adsorption device adsorbs antibiotics, and after adsorption saturation, the biochar is separated in the biochar separation device, and the resulting solution is introduced into the pretreatment tank for recycling; the saturated biochar obtained after adsorbing antibiotics enters the saturated biochar regeneration system.

[0017] Saturated biochar regeneration: Saturated biochar that has adsorbed antibiotics enters the saturated biochar regeneration system and is co-gasified with biomass to obtain harmless biochar and high-temperature furnace gas; part of the obtained harmless biochar enters the biochar modification system, and the other part is used to prepare carbon-based organic matrix.

[0018] Anaerobic fermentation of processed raw materials: The antibiotic-free solid material obtained from the pretreatment and antibiotic separation step is fed into the hydrolysis acidification system and methanogenic system of the anaerobic fermentation system after the pH value and solid-liquid ratio are adjusted by biogas slurry and clean water. The final product is biogas, biogas residue and biogas slurry. Among them, the biogas residue and biogas slurry are introduced into the residue-liquid separation device. The separated biogas residue is mixed with harmless biochar provided by the saturated biochar regeneration system to prepare carbon-based organic matrix. The separated biogas slurry is fed into the biochar modification system.

[0019] Biochar modification: The biogas slurry separated by the sludge-liquid separation device is mixed with harmless biochar provided by the saturated biochar regeneration system and stirred evenly, so that the organic functional groups in the biogas slurry are combined with the surface of the harmless biochar to obtain modified biochar. Modified biochar has both the high surface area and porosity of high-temperature biochar and the high functional group content of low-temperature biochar.

[0020] Furthermore, the pH value of the solution in the pretreatment tank is 2.5-4.0, the biochar addition ratio in the biochar adsorption device is 0.5-5 g / L, and the adsorption time is 30-90 min.

[0021] This invention introduces the acidified material from the outlet of the hydrolysis acidification tank into a pretreatment tank, and uses hydrochloric acid to adjust the pH of the solution, thereby achieving rapid release of antibiotics from livestock and poultry manure. The antibiotics are then rapidly separated in a solid-liquid separation device and adsorbed in a biochar adsorption device using modified biochar, preventing secondary adhesion and deposition of the antibiotics after release. The saturated biochar after antibiotic adsorption is separated using a biochar separation device. The saturated biochar after antibiotic adsorption is then completely decomposed by closed-loop high-temperature gasification in a saturated biochar regeneration system. It is then mixed with the biogas residue separated by the sludge-liquid separation device for further stabilization to prepare a carbon-based organic matrix, thus improving the value and application safety of the anaerobic fermentation products.

[0022] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows: (1) By setting up a pretreatment system and a saturated biochar regeneration system, the antibiotic removal rate is significantly improved through the synergistic effect of multiple links such as "acidified pretreatment release + rapid separation and anti-re-adsorption + biochar adsorption modified by biogas slurry + pyrolysis and gasification for complete decomposition", avoiding secondary pollution from the source to the end and improving the safety and added value of the product; (2) The acidified substances produced by the hydrolysis acidification system are introduced into the pretreatment system, which can produce the following technical effects: The acidified substances (VFA) produced by the hydrolysis acidification tank, as a natural acidic medium, work synergistically with the acidic environment regulated by hydrochloric acid: on the one hand, by regulating the pH value through H⁺, the charge properties and chemical binding state of antibiotics and solid particles are changed; on the other hand, through the penetration, competitive adsorption and auxiliary structural destruction of VFA, the antibiotics are efficiently transferred from the solid phase of feces to the liquid phase through the dual pathways of "interfacial desorption" and "internal release", which is conducive to the subsequent "rapid" (3) Saturated biochar is first pyrolyzed and gasified at high temperature in the regeneration gasifier in the saturated biochar regeneration system to achieve the desorption of antibiotics and obtain biochar with high surface area and porosity. Then, the biochar is modified by anaerobic fermentation by-product biogas slurry in the biochar modification system to obtain modified biochar. During the modification process, the carboxyl and amino groups on the surface of biochar are increased, or elements such as phosphorus and nitrogen are introduced to enhance the chemical adsorption of antibiotics by modified biochar. The system resources are used to form an efficient cycle of preparation-adsorption-regeneration-reuse. (4) An independent biogas burner is used to provide a stable flame for the hot air furnace to achieve efficient and stable combustion of the high temperature furnace gas generated by the vertical gasifier, and to generate high temperature flue gas rich in water vapor and CO2. This flue gas is used as the heat source of the gasifier and the gasification agent for biochar modification to achieve the internal circulation of energy and matter in the gasification process and improve the energy efficiency of the system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a closed-loop treatment system for antibiotics in livestock and poultry manure disclosed in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the hot blast stove in this invention;

[0025] Figure 3 This is a schematic flowchart of a closed-loop treatment method for antibiotics in livestock and poultry manure disclosed in an embodiment of the present invention. Detailed Implementation

[0026] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0027] Example 1

[0028] like Figure 1 As shown, the present invention discloses a closed-loop treatment system for antibiotics in livestock and poultry manure, comprising a pretreatment system, a saturated biochar regeneration system, an anaerobic fermentation system, and a biochar modification system; wherein the anaerobic fermentation system includes a hydrolysis acidification system, a methanogenesis system, and a solid-liquid separation device. The inlet of the pretreatment system is used to introduce livestock and poultry manure, and the pretreatment system is used to remove antibiotics from the livestock and poultry manure. The outlet of the pretreatment system is connected to the inlet of the saturated biochar regeneration system and the inlet of the hydrolysis acidification system, respectively, for introducing the saturated biochar produced by the pretreatment system into the saturated biochar regeneration system, and for introducing the solid material produced by the pretreatment system into the hydrolysis acidification system. The outlet of the saturated biochar regeneration system is connected to the inlet of the biochar modification system, for introducing the biochar produced by the saturated biochar regeneration system into the biochar modification system. The outlet of the hydrolysis acidification system is connected to the inlet of the methanogenesis system and the inlet of the pretreatment system, respectively, for introducing the acidified material produced by the hydrolysis acidification system into the methanogenesis system and the pretreatment system. The outlet of the methanogenic system is connected to the inlet of the sludge-liquid separation unit, which separates the biogas sludge and biogas slurry produced by the methanogenic system. The outlet of the sludge-liquid separation unit is connected to the inlet of the biochar modification system, allowing the biogas slurry separated by the sludge-liquid separation unit to be fed into the biochar modification system. The outlet of the biochar modification system is connected to the inlet of the pretreatment system and the inlet of the methanogenic system, respectively, allowing the modified biochar produced by the biochar modification system to be fed into the pretreatment system and the methanogenic system.

[0029] The pretreatment system includes a pretreatment tank, a solid-liquid separation device, a biochar adsorption device, and a biochar separation device connected in sequence. The pretreatment tank has a livestock manure inlet 111, a first acidified substance inlet 112, and a circulating diluent inlet 113 at the top, and a mixed raw material outlet 114 at the bottom. The livestock manure inlet 111 is used to introduce livestock manure. The first acidified substance inlet 112 is connected to the acidified substance outlet 312 on the hydrolysis acidification system. The circulating diluent inlet 113 is connected to the filtrate outlet 143 on the biochar separation device. The mixed raw material outlet 114 is connected to the mixed raw material inlet 121 on the solid-liquid separation device.

[0030] The solid-liquid separation device is a hydrocyclone, having a mixed raw material inlet 121, a bottom liquid outlet 122, and a top liquid outlet 123. The bottom liquid outlet 122 is connected to the fermentation raw material inlet 311 in the hydrolysis-acidification system, and is used to pass the solid material obtained after solid-liquid separation into the hydrolysis-acidification system. The top liquid outlet 123 is connected to the top liquid inlet 131 on the biochar adsorption device, and is used to pass the solution obtained after solid-liquid separation into the biochar adsorption device.

[0031] The biochar adsorption device is a corrosion-resistant stirred reactor with a top flow inlet 131, a first modified biochar inlet 132, and a mixed liquid outlet 133. The first modified biochar inlet 132 is connected to the biochar outlet 413 on the biochar modification system, and the mixed liquid outlet 133 is connected to the mixed liquid inlet 141 on the biochar separation device.

[0032] The biochar separation device is a plate and frame filter press, which has a mixed liquor inlet 141, a saturated biochar outlet 142 and a filtrate outlet 143. The saturated biochar outlet 142 is connected to the saturated biochar inlet 211 on the saturated biochar regeneration system.

[0033] The main equipment of the saturated biochar regeneration system consists of a vertical segmented furnace and a low-oxygen combustion hot blast stove. The vertical segmented furnace is equipped with a saturated biochar inlet 211, a biomass inlet 212, a high-temperature furnace gas outlet 213, a high-temperature flue gas inlet for the heating jacket 214, a medium-temperature flue gas outlet for the heating jacket 215, a medium-temperature flue gas inlet for the furnace chamber 216, and a biochar outlet 217. The vertical segmented furnace is internally equipped with a rotating segmented material plate for the gradual descent of material, and the descent speed is controlled according to the rotation speed to ensure sufficient contact between the biochar and the medium-temperature flue gas gasifying agent.

[0034] like Figure 2 As shown, the low-oxygen combustion hot blast stove is a double-layered structure. The inner layer is a cylindrical combustion chamber A, and the outer layer is a rectangular flue gas mixing zone B, with an air preheating jacket C at the bottom. The cylindrical combustion chamber A has a high-temperature furnace gas inlet 221, a biogas burner 222, and a primary air inlet 223. The high-temperature furnace gas inlet 221 is connected to the high-temperature furnace gas outlet 213. The biogas burner 222 is installed inside the cylindrical combustion chamber A, providing a stable continuous flame for the low-oxygen combustion hot blast stove. The rectangular flue gas mixing zone B has a high-temperature flue gas outlet 224, and the air preheating jacket C has an air inlet 225 and a hot air outlet 226. A flue gas composition detector 227 is installed on the pipe of the high-temperature flue gas outlet 224 of the low-oxygen combustion hot blast stove to detect the oxygen content in real time and adjust the amount of primary air accordingly.

[0035] In the anaerobic fermentation system, the hydrolysis acidification system uses a hydrolysis acidification tank, the methanogenesis system uses a methanogenesis tank, and the residue-liquid separation device uses a screw extruder. The hydrolysis acidification tank has a fermentation feed inlet 311 and an acidified product outlet 312 at its bottom. The methanogenesis tank has a second acidified product inlet 321, a second modified biochar inlet 322, a biogas outlet 323, and a biogas residue and biogas slurry outlet 324. The fermentation feed inlet 311 of the hydrolysis acidification tank is connected to the underflow outlet 122 of the solid-liquid separation device in the pretreatment system. The acidified product outlet 312 is connected via pipes to the first tank acidified product inlet 112 and the second acidified product inlet 321, respectively. The biogas outlet 323 of the methanogenesis tank is connected via pipes to the biogas burner 222 and the biogas purification and separation system (not described in this patent). The residue-liquid separation device has a biogas residue and biogas slurry inlet 331, a biogas slurry outlet 332, and a biogas residue outlet 333. The biogas residue and biogas slurry inlet 331 is connected to the biogas residue and biogas slurry outlet 324 of the methanogenic tank, and the biogas residue outlet 333 is used to discharge biogas residue.

[0036] The hydrolysis acidification tank and methanogenic tank are also equipped with stirring devices, temperature control devices, detection devices, and heat preservation devices, which are all standard features and will not be described in detail.

[0037] The core equipment of the biochar modification system is the biochar modification tank (i.e., a corrosion-resistant reactor), which has a biogas slurry inlet 411, a biochar inlet 412, and a biochar outlet 413. The biogas slurry inlet 411 is connected to the biogas slurry outlet 332 on the sludge-liquid separation device, the biochar inlet 412 is connected to the biochar outlet 217 on the saturated biochar regeneration system, and the biochar outlet 413 is connected to the first modified biochar inlet 132 and the second modified biochar inlet 322. The biochar outlet 413 is connected to the first modified biochar inlet 132 via a drying system.

[0038] Example 2

[0039] like Figure 2 As shown, the closed-loop treatment method for antibiotics in livestock and poultry manure of the present invention is applied to the closed-loop treatment system for antibiotics in livestock and poultry manure described in Example 1, and includes the following steps:

[0040] S1. Pretreatment and Antibiotic Separation: Adjust the solid-liquid mass ratio of livestock and poultry manure, introduce acidified substances from the hydrolysis acidification system outlet into the pretreatment tank in proportion, and mix thoroughly; add hydrochloric acid solution as needed to adjust the pH value of the solution, so that the antibiotics adhering to the livestock and poultry manure are released into the solution; after the antibiotics are released, immediately separate the mixture through a solid-liquid separation device to obtain solid material without antibiotics and a solution with high antibiotic content; the solution with high antibiotic content enters the biochar adsorption device; the biochar in the biochar adsorption device adsorbs antibiotics, and after adsorption saturation, the biochar is separated in the biochar separation device, and the resulting solution is introduced into the pretreatment tank for recycling; the saturated biochar obtained after adsorbing antibiotics enters the saturated biochar regeneration system for harmless treatment.

[0041] The livestock and poultry manure includes one or more of chicken, pig, and cow manure; the antibiotics are commonly used in livestock and poultry farming, such as quinolones, macrolides, tetracyclines, and sulfonamides; the solid content of the livestock and poultry manure in the pretreatment tank is 5-10 wt%; the pH of the solution in the pretreatment tank is adjusted to 2.5-4.0 using a 0.5 mol / L hydrochloric acid solution; the temperature in the pretreatment tank is 45-55℃; the pretreatment time is 20-60 min; the biochar addition ratio in the biochar adsorption device is 0.5-5 g / L, and the adsorption time is 30-90 min. The solids obtained from solid-liquid separation are adjusted in concentration and pH using biogas slurry, with a biogas slurry reuse rate of 10-25%.

[0042] S2. Saturated Biochar Regeneration: The saturated biochar that has adsorbed antibiotics is sent to the saturated biochar regeneration system via a screw conveyor, where it is co-gasified with biomass to obtain harmless biochar and high-temperature furnace gas. The high-temperature furnace gas is directly sent to a specially designed hot blast stove for complete combustion, producing high-temperature flue gas, which is then used as an indirect heating source for the gasifier and as a gasifying agent for biochar gasification, successively entering the heating jacket and furnace of the gasifier. The remaining portion is purified and discharged in compliance with standards. Part of the obtained harmless biochar is sent to the biochar modification system to produce adsorbents for antibiotics, and the other part is used to prepare carbon-based organic matrices.

[0043] The biomass consists of one or more agricultural, forestry, and livestock wastes, such as corn stalks, sawdust, or livestock manure. The biomass entering the regeneration gasifier has a moisture content ≤20% and a length ≤5cm. The temperatures at the bottom and top of the regeneration gasifier are 750-850℃ and 350-400℃, respectively. The temperatures of the high-temperature flue gas entering and exiting the heating jacket of the regeneration gasifier are 850-900℃ and 450-500℃, respectively. The residence time of the biochar in the furnace is 60-120 minutes. The flow rate of the flue gas entering the gasifier furnace as a gasifying agent after combustion is 1200-3000 m³ / h. 3 / h.

[0044] S3. Anaerobic fermentation of treated raw materials: The antibiotic-free solid material obtained from the pretreatment and antibiotic separation step is fed into the hydrolysis acidification system and methanogenic system of the anaerobic fermentation system after the pH value and solid-liquid ratio are adjusted by biogas slurry and clean water. The resulting biogas, biogas residue and biogas slurry are produced. The biogas residue and biogas slurry are introduced into the residue-liquid separation device. The separated biogas residue is mixed with harmless biochar provided by the saturated biochar regeneration system to prepare carbon-based organic matrix. The separated biogas slurry is fed into the biochar modification system.

[0045] In this step, the temperature in the hydrolysis acidification system is 20-35℃, the pH value is 5.5-6.5, and the residence time is 3-6 days. The amount of material discharged from the hydrolysis acidification tank and recycled to the pretreatment system is 5-20% of the livestock and poultry manure treated. The temperature in the methanogenesis system is 30-35℃, the pH value is 6.8-7.8, and the residence time is 10-25 days. The amount of modified biochar added to the methanogenesis system is 2-5% of the solids. A portion of the biogas is fed into the biogas burner of the hot air furnace as fuel, and the remaining portion is purified and sold. The biogas residue and residual biogas slurry are mixed with and stabilized with the residual biochar from the saturated biochar regeneration system to prepare a carbon-based organic matrix.

[0046] S4. Biochar Modification: The biogas slurry separated by the sludge-liquid separation device is mixed with harmless biochar provided by the saturated biochar regeneration system and stirred evenly. This process binds organic functional groups such as humic acid, amino acids, carboxyl groups, and hydroxyl groups in the biogas slurry to the surface of the harmless biochar, resulting in modified biochar. This modified biochar possesses both the high surface area and porosity of high-temperature biochar and the high functional group content of low-temperature biochar, thereby improving its adsorption capacity for harmful substances such as antibiotics.

[0047] The mixing ratio of biochar to biogas slurry is 1:10-15. The mixing and stirring time of biochar and biogas slurry is 12-36 hours. The remaining biogas slurry can be sprayed on the surface of biogas residue and biochar materials for aerobic fermentation to prepare carbon-based organic matrix.

[0048] This invention integrates pretreatment, anaerobic fermentation, biochar regeneration, and biochar modification units to transform in-system acidified substances, biogas slurry, biochar, and high-temperature furnace gas into pretreatment agents, modifiers, adsorbents, and gasification agents. This achieves a closed-loop cycle of "waste-resource-product," reduces pollutant emissions and dependence on external resources, completely decomposes antibiotics, reduces the addition of chemical reagents, minimizes negative impacts on the ecological environment, and achieves the dual goals of harmless treatment of pollutants and efficient utilization of resources.

[0049] This invention proposes an economical and efficient biochar modification method to improve the adsorption performance of biochar, and to effectively decompose and regenerate the biochar after it has been saturated with adsorption. This method is of great significance for the resource utilization of anaerobic fermentation products of livestock and poultry manure.

[0050] The method of the present invention will be verified through a specific embodiment below.

[0051] S1. Livestock and poultry manure is added to a pretreatment tank, and diluted solution from the biochar separation unit is added while continuously stirring to reduce the solid content of the livestock and poultry manure raw material to 8%. While continuing stirring, 10 wt% of the undiluted livestock and poultry manure treatment volume of acidifier is added. Then, 1 mol / L hydrochloric acid solution is added to the pretreatment tube to adjust the pH of the solution to 3.5. The system temperature is maintained at 40℃, and stirring is continued for 60 minutes. Solid-liquid separation is then performed to obtain pretreated livestock and poultry manure raw material and a solution with high antibiotic content. Testing showed that the removal rates of tetracyclines, sulfonamides, fluoroquinolones, and macrolides in the treated livestock and poultry manure were 93.5%, 85.6%, 94.9%, and 70.4%, respectively. The solution with high antibiotic content is transferred to a stirred reactor (No. 1), and modified biochar is added at a ratio of 1.2 g / L. After stirring for 60 minutes, a plate and frame filter press is used for separation to obtain saturated biochar and filtrate (used to dilute the livestock and poultry manure raw material).

[0052] S2. The saturated biochar, after antibiotic adsorption, is conveyed via a screw conveyor into a regeneration gasification furnace and co-gasified for 90 minutes with pretreated corn stalks (length ≤5cm, moisture content ≤20%) to obtain harmless biochar and high-temperature furnace gas. The upper part of the furnace reaches 400℃, and the bottom reaches 800℃ (the inlet and outlet temperatures of the heating jacket are 900℃ and 450℃, respectively). The resulting high-temperature furnace gas is directly fed into a hot blast stove for combustion, generating high-temperature flue gas, which then enters the heating jacket of the regeneration gasification furnace to provide heat. The flue gas exiting the heating jacket is discharged at a rate of 1500m³ / min. 3 A flow rate of / h enters the furnace of the regeneration gasifier as a gasifying agent, and the remaining part is purified and discharged in compliance with standards; antibiotics are undetectable in the regenerated biochar (below the minimum detection limit).

[0053] In step S2, the pretreated corn stalks (length ≤ 5cm, moisture content ≤ 20%) are conveyed to the vertical gasifier by a screw conveyor. After pyrolysis, they are fully contacted with the gasifying agent (exiting the heating jacket flue gas) fed into the bottom of the furnace to obtain biochar (the inlet and outlet temperatures of the annular flue gas are 900℃ and 450℃, respectively).

[0054] S3. After pretreatment, the livestock and poultry manure is adjusted to pH 6 and solid content 12% by biogas slurry and clean water and then put into a hydrolysis fermentation tank. It is fermented at 20-35℃ for 3 days to obtain acidified products. The acidified products are recycled back to the pretreatment tank according to the required proportion. The remaining part is added with 2% modified biochar and then put into a methanogenic tank. It is fermented at 30℃ for 15 days to obtain biogas slurry, biogas residue and biogas.

[0055] S4. The obtained biochar portion is added to the No. 2 stirred reactor, and biogas slurry is added at a ratio of 1:15. After stirring evenly for 24 hours, it is separated and dried. The organic functional groups such as humic acid, amino acids, carboxyl groups, and hydroxyl groups in the biogas slurry are combined to the surface of the biochar to obtain modified biochar. The remaining biochar is further stabilized by aerobic fermentation with the biogas residue and biogas slurry produced by the anaerobic fermentation system to prepare a carbon-based organic matrix.

[0056] In this step, the biochar is transported to a storage facility via a water-cooled screw conveyor. Part of it is mixed with the biogas residue produced by the anaerobic fermentation system and further subjected to aerobic fermentation to achieve stabilization, ultimately producing a carbon-based organic matrix. Part of it is added to the biogas slurry modification reactor, mixed with the biogas slurry at a ratio of 1:15, and stirred thoroughly for 24 hours. After soaking, it is dried using the system's residual heat to obtain modified biochar.

[0057] The main indicators of biochar and modified biochar are as follows:

[0058] Table 1. Comparison of parameters between biochar and modified biochar

[0059]

[0060] As the chart shows, through physical loading and sedimentation, biogas slurry successfully loaded nutrients such as nitrogen and phosphorus, as well as organic matter and salts, onto biochar. Although this resulted in a decrease in specific surface area, microporosity, and fixed carbon content, it significantly increased surface functional groups (enhancing chemical activity), lowered pH (improving alkalinity), and introduced ash (mainly sediment precipitation from biogas slurry). These changes combined transform modified biochar from a high-specific-surface-area alkaline adsorbent into an environmentally functional material rich in surface functional groups, with higher nutrient content and a milder pH, potentially making it more suitable for applications such as soil improvement, slow nutrient release, or targeted adsorption of specific pollutants.

Claims

1. A closed-loop treatment system for antibiotics in livestock and poultry manure, characterized in that: It includes a pretreatment system, a saturated biochar regeneration system, an anaerobic fermentation system, and a biochar modification system; wherein, the anaerobic fermentation system includes a hydrolysis acidification system, a methanogenic system, and a residue-liquid separation device; The inlet of the pretreatment system is used to introduce livestock and poultry manure, and the pretreatment system is used to remove antibiotics from the livestock and poultry manure; the outlet of the pretreatment system is connected to the inlet of the saturated biochar regeneration system and the inlet of the hydrolysis acidification system, respectively, and is used to introduce the saturated biochar produced by the pretreatment system into the saturated biochar regeneration system, and to introduce the solid material produced by the pretreatment system into the hydrolysis acidification system. The outlet of the saturated biochar regeneration system is connected to the inlet of the biochar modification system, and is used to introduce the biochar produced by the saturated biochar regeneration system into the biochar modification system. The outlet of the hydrolysis acidification system is connected to the inlet of the methanogenic system and the inlet of the pretreatment system, respectively, for passing the acidified products generated by the hydrolysis acidification system into the methanogenic system and the pretreatment system. The outlet of the methanogenic system is connected to the inlet of the sludge-liquid separation device, which is used to separate the biogas sludge and biogas slurry produced by the methanogenic system. The outlet of the sludge-liquid separation device is connected to the inlet of the biochar modification system, which is used to pass the biogas slurry separated by the sludge-liquid separation device into the biochar modification system. The outlet of the biochar modification system is connected to the inlet of the pretreatment system and the inlet of the methanogenic system, respectively, for introducing the modified biochar produced by the biochar modification system into the pretreatment system and the methanogenic system.

2. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 1, characterized in that: The pretreatment system includes a pretreatment tank, a solid-liquid separation device, a biochar adsorption device, and a biochar separation device connected in sequence.

3. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 2, characterized in that: The pretreatment tank has a livestock and poultry manure inlet (111), a first acidified inlet (112), and a circulating diluent inlet (113) at the top, and a mixed raw material outlet (114) at the bottom. The livestock and poultry manure inlet (111) is used to introduce livestock and poultry manure; the first acidification inlet (112) is connected to the acidification outlet (312) on the hydrolysis acidification system; The circulating diluent inlet (113) is connected to the filtrate outlet (143) on the biochar separation device; The mixed raw material outlet (114) is connected to the mixed raw material inlet (121) on the solid-liquid separation device.

4. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 2, characterized in that: The solid-liquid separation device has a bottom liquid outlet (122) and a top liquid outlet (123). The underflow outlet (122) is connected to the fermentation raw material inlet (311) in the hydrolysis acidification system, and is used to pass the solid material obtained after solid-liquid separation into the hydrolysis acidification system; The topflow outlet (123) is connected to the topflow inlet (131) on the biochar adsorption device, and is used to pass the solution obtained after solid-liquid separation into the biochar adsorption device.

5. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 2, characterized in that: The biochar adsorption device has a first modified biochar inlet (132) and a mixed liquid outlet (133). The first modified biochar inlet (132) is connected to the biochar outlet (413) on the biochar modification system, and the mixed liquid outlet (133) is connected to the mixed liquid inlet (141) on the biochar separation device.

6. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 2, characterized in that: The biochar separation device has a saturated biochar outlet (142), which is connected to a saturated biochar inlet (211) on a saturated biochar regeneration system.

7. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 1, characterized in that: The saturated biochar regeneration system includes a vertical segmented furnace and a low-oxygen combustion hot blast stove, with the vertical segmented furnace having a high-temperature furnace gas outlet (213). The low-oxygen combustion hot air furnace is configured in two layers. The inner layer is a cylindrical combustion chamber and the outer layer is a rectangular flue gas mixing zone. The cylindrical combustion chamber has a high-temperature furnace gas inlet (221) and is connected to the high-temperature furnace gas outlet (213). The cylindrical combustion chamber is equipped with a biogas burner (222), which is used to provide a stable continuous flame for the low-oxygen combustion hot air furnace.

8. The closed-loop treatment system for antibiotics in livestock and poultry manure according to claim 1, characterized in that: The biochar modification system has a biogas slurry inlet (411), a biochar inlet (412), and a biochar outlet (413). The biogas slurry inlet (411) is connected to the biogas slurry outlet (332) on the sludge-liquid separation device, the biochar inlet (412) is connected to the biochar outlet (217) on the saturated biochar regeneration system, and the biochar outlet (413) is connected to the second modified biochar inlet (322) on the methanogenic system.

9. A closed-loop treatment method for antibiotics in livestock and poultry manure, characterized in that, This method is applied to the closed-loop treatment system for antibiotics in livestock and poultry manure as described in claim 2, comprising: Pretreatment and Antibiotic Separation: Adjust the solid-liquid mass ratio of livestock and poultry manure, introduce acidified material from the hydrolysis acidification system outlet into the pretreatment tank in proportion, and mix thoroughly; add hydrochloric acid solution as needed to adjust the pH value of the solution, so that the antibiotics adhering to the livestock and poultry manure are released into the solution; after the antibiotics are released, immediately separate the mixture through a solid-liquid separation device to obtain antibiotic-free solid material and a solution with high antibiotic content; the solution with high antibiotic content enters the biochar adsorption device; the biochar in the biochar adsorption device adsorbs antibiotics, and after adsorption saturation, the biochar is separated in the biochar separation device, and the resulting solution is introduced into the pretreatment tank for recycling; the saturated biochar obtained after adsorbing antibiotics enters the saturated biochar regeneration system. Saturated biochar regeneration: Saturated biochar that has adsorbed antibiotics enters the saturated biochar regeneration system and is co-gasified with biomass to obtain harmless biochar and high-temperature furnace gas; part of the obtained harmless biochar enters the biochar modification system, and the other part is used to prepare carbon-based organic matrix. Anaerobic fermentation of processed raw materials: The antibiotic-free solid material obtained from the pretreatment and antibiotic separation step is fed into the hydrolysis acidification system and methanogenic system of the anaerobic fermentation system after the pH value and solid-liquid ratio are adjusted by biogas slurry and clean water. The final product is biogas, biogas residue and biogas slurry. Among them, the biogas residue and biogas slurry are introduced into the residue-liquid separation device. The separated biogas residue is mixed with harmless biochar provided by the saturated biochar regeneration system to prepare carbon-based organic matrix. The separated biogas slurry is fed into the biochar modification system. Biochar modification: The biogas slurry separated by the sludge-liquid separation device is mixed with harmless biochar provided by the saturated biochar regeneration system and stirred evenly, so that the organic functional groups in the biogas slurry are combined with the surface of the harmless biochar to obtain modified biochar. Modified biochar has both the high surface area and porosity of high-temperature biochar and the high functional group content of low-temperature biochar.

10. The closed-loop treatment method for antibiotics in livestock and poultry manure according to claim 9, characterized in that: The pH value of the solution in the pretreatment tank is 2.5-4.0, the biochar addition ratio in the biochar adsorption device is 0.5-5 g / L, and the adsorption time is 30-90 min.

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