Treatment method for degrading low-concentration perchlorate in silage

Abstract

The invention discloses a treatment method for degrading low-concentration perchlorate in silage. The treatment method comprises the following steps: adjusting the pH value of an original bacteria solution, and performing multiple rounds of domestication by taking lactic acid and sodium acetate as a carbon source and an electron donor to obtain perchlorate reducing bacteria; the highly enriched perchlorate reducing bacteria are further obtained through the adsorbent; in the ensiling and airing process, the high-enrichment perchlorate reducing bacteria adsorbent is crushed into powder, and the powder is uniformly sprayed on the filled and compacted ensiling raw material and the crushed ensiling raw material; meanwhile, warm sugar water and lactic acid bacteria are blended for activation, activated lactic acid bacteria liquid is obtained, and the activated lactic acid bacteria liquid is evenly sprayed to the filled and compacted crushed silage raw materials; the harvested and aired silage raw materials need to enter the crushing unit to be cut into small sections, so that the silage raw materials are pressed more compactly during silage. According to the method, the removal effect of the low-concentration perchlorate in the silage can be efficiently and safely improved, meanwhile, the safety and nutritional value of the silage are guaranteed, and the process operability is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental microorganisms, relates to a perchlorate microbial reduction method, and particularly relates to a method for treating low-concentration perchlorate in silage. Background Art

[0002] Perchlorate is a persistent pollutant. The main sources of perchlorate in the environment are artificial production processes, including its use in kinetic boosters, rocket solid fuel, fireworks, electroplating, smelting, and other fields, as well as the production of chlorine-containing disinfectants, lubricants, and fertilizers. Perchlorate is easily soluble in water, highly stable, and difficult to degrade. It can migrate rapidly and over large areas with water bodies, thereby contaminating food and drinking water. The main route of human exposure to perchlorate is through the intake of perchlorate through vegetables and their products, milk and dairy products, drinking water, and fruits and their products. As an endocrine disruptor, perchlorate has an inhibitory effect on thyroid function. The perchlorate anion competitively inhibits the binding of iodine to the sodium-iodide transporter on the basolateral side of the thyroid follicular epithelial cell membrane, thereby inhibiting the uptake and use of iodine by the thyroid follicular epithelial cells.

[0003] With improved living standards, the consumption of milk and dairy products has been increasing year by year. Maintaining the safety of milk and dairy products is crucial to people's health. The U.S. Food and Drug Administration's "Total Diet Study" report found that perchlorate levels in liquid milk range from 0.9 µg / L to 10.3 µg / L. Silage is the most important roughage resource for dairy animals, accounting for 40% to 50% of their daily diet. The quality of silage is not only crucial to the health of dairy animals, but also to the quality of milk. Recent studies examining the sources of perchlorate contamination in liquid milk have revealed elevated levels of perchlorate in some silage raw materials. Due to its water solubility, perchlorate is readily absorbed by dairy animals through their gastrointestinal tract, leading to elevated perchlorate levels in their milk.

[0004] At present, the methods for treating perchlorate are mainly divided into physical and chemical methods and biological methods. The physical and chemical methods mainly include adsorbent adsorption method, ion exchange method, reverse osmosis membrane separation method, chemical reduction and electrochemical reduction method. Silage is an important feeding resource, and its safety and quality have an important impact on the health and production performance of dairy animals. Therefore, it is difficult to use physical and chemical methods to treat low concentrations of perchlorate in silage. In particular, for the problem of low concentrations of perchlorate in silage, the microbial method with the characteristics of low cost, high safety, no energy consumption and significant effect has shown its unique advantages. Because in an anaerobic environment, perchlorate can serve as an electron acceptor for microbial metabolism, and perchlorate-reducing bacteria are used to reduce perchlorate to chloride: ClO4 - —ClO3 - —ClO2- —Cl - +O2.

[0005] Given that the presence of perchlorate in silage poses a potential threat to dairy safety and thus affects human health, it is particularly urgent to develop an economical and efficient treatment technology. Summary of the Invention

[0006] The present invention aims to provide a method for degrading low-concentration perchlorate in silage, thereby resolving one or more of the aforementioned technical problems. The technical solution provided by the present invention can address the difficulty in degrading low-concentration perchlorate in silage, helping to improve silage quality, reduce perchlorate contamination in milk and dairy product production, and promote the sustainable development of animal husbandry.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A method for degrading low-concentration perchlorate in silage according to the present invention comprises the following steps: Step (1) pH adjustment unit, including: adding the original bacterial liquid to the pH adjustment unit to ensure that the microorganisms in the subsequent steps can grow and metabolize in a suitable pH environment; Step (2) a perchlorate-reducing bacteria acclimation unit, comprising: acclimating the pH-adjusted bacterial solution, using lactic acid and sodium acetate as carbon sources and electron donors, and obtaining successfully acclimated perchlorate-reducing bacteria after multiple rounds of acclimation; Step (3) a perchlorate-reducing bacteria enrichment and activation unit, comprising: using lactic acid and sodium acetate as carbon sources and electron donors, taking the perchlorate-reducing bacteria obtained in step (2) as inoculum, using an adsorbent to achieve efficient enrichment and collection of the perchlorate-reducing bacteria, and crushing the adsorbent into powder; (4) during the ensiling process, (5) warm sugar water is mixed with the lactic acid bacteria for activation to obtain an activated lactic acid bacteria liquid, which is evenly sprayed onto the silage raw material crushed after filling and compacting in step (4); (6) the harvested and air-dried silage raw material needs to enter a crushing unit to obtain small pieces of silage raw material crushed; Step (4) silage unit, comprising: evenly sprinkling the highly enriched perchlorate-reducing bacteria adsorbent powder obtained in step (3) onto the silage raw material fragments that have been filled and compacted; Step (5) a lactic acid bacteria activation unit, comprising: mixing warm sugar water with lactic acid bacteria for activation to obtain an activated lactic acid bacteria liquid, and spraying the activated lactic acid bacteria liquid evenly onto the silage raw material fragments that have been loaded and compacted in step (4); Step (6) a crushing unit, comprising: the harvested and air-dried silage raw materials are fed into a crushing unit to obtain small pieces of silage raw materials; Step (7) drying unit, comprising: analogously to step (4), evenly sprinkling the highly enriched perchlorate-reducing bacteria adsorbent powder obtained in step (3) onto the silage raw material to be dried.

[0008] A further improvement of the present invention is that steps (1) (2) (3) (5) specifically include: the temperature should be set at 35~37℃, and the device should be sealed and provided with a stirring device.

[0009] A further improvement of the present invention is that steps (2) and (3) specifically include: using nutrients as a source of trace elements, lactic acid and sodium acetate as carbon sources and electron donors, and regulating the overall pH to about 5.0-6.5.

[0010] A further improvement of the present invention is that step (1) specifically includes: the original bacterial liquid is taken from the laboratory of the solid waste treatment and resource utilization research group of Xi'an Jiaotong University, which can degrade high-concentration ammonium perchlorate wastewater with a pH between 7.0 and 8.5. It needs to be acidified and the pH is adjusted to about 5.5.

[0011] A further improvement of the present invention is that step (2) specifically includes: adding a certain concentration of perchlorate as an electron acceptor, and a certain concentration of lactic acid and sodium acetate as a carbon source and electron donor (the ratio of perchlorate concentration to lactic acid and sodium acetate concentration is 1:3). If the concentration of perchlorate decreases significantly over time, it indicates that the perchlorate-reducing bacteria have been successfully domesticated and effectively degraded perchlorate.

[0012] A further improvement of the present invention is that step (3) specifically includes: adding an adsorbent to enrich the perchlorate-reducing bacteria, and after the adsorption is completed, crushing the perchlorate-reducing bacteria adsorbent into powder and evenly sprinkling it into steps (4) and (7).

[0013] A further improvement of the present invention is that step (4) specifically includes: (4) generally being a silo (silage pit or silage tower), the fermentation temperature is about 35-37°C, the silage raw material crushed materials are filled and compacted at the same time, and the addition of the perchlorate-reducing bacteria adsorbent powder and the lactic acid bacteria liquid in steps (3) and (5) should be done before the compaction step.

[0014] A further improvement of the present invention is that step (5) specifically includes: preparing 2% warm sugar water, adding lactic acid bacteria strains (solid-to-liquid ratio of 1:67), fully mixing, and then leaving at room temperature for 1.5 hours to activate the lactic acid bacteria strains. After the strains are activated, a certain amount of tap water (the mass ratio of tap water to silage raw material is 1:4) is added, and after stirring evenly, the diluted bacterial solution is sprayed onto the silage raw material in (4) to promote the proliferation of lactic acid bacteria and the fermentation of the silage raw material.

[0015] A further improvement of the present invention is that step (6) specifically includes: in order to create an anaerobic environment, the silage raw materials must be chopped into small segments before ensilage, and the length of the small segments is about 1 to 2 cm. This can reduce the gaps between the silage raw materials and make them more compact during ensilage.

[0016] A further improvement of the present invention is that step (7) specifically includes: the moisture content of the air-dried silage raw material is about 65±5%, the harvested silage raw material needs to be piled up during the air-dried process, and the perchlorate-reducing bacteria adsorbent powder should be gradually added during the piled up process. The added amount is ensured to be greater than or equal to 20% of the mass of the silage raw material.

[0017] The present invention provides a method for degrading low-concentration perchlorate in silage, comprising inoculating successfully domesticated perchlorate-reducing bacteria into (3), with the inoculation rate being greater than or equal to 5% of the substrate.

[0018] Compared with the prior art, the present invention has the following beneficial effects: Physical and chemical methods alone are difficult to use to remove low-concentration perchlorates in silage. The present invention provides new ideas and prospects for the practical application of biological methods to remove low-concentration perchlorates in silage. Specifically, lactic acid and sodium acetate are used as carbon sources and electron donors for perchlorate-reducing bacteria, eliminating the need for additional large amounts of electron donors and simplifying the process. It can efficiently and safely remove low-concentration perchlorates in silage, preventing perchlorates from entering the human body through milk and dairy products and causing serious harm. In an embodiment of the present invention, the treatment method can achieve a perchlorate removal rate of over 80% in silage with a concentration of 16 mg / L through biodegradation.

[0019] In the present invention, a perchlorate-reducing bacteria acclimation unit is added with a certain concentration of perchlorate, a nutrient, sodium acetate, and lactic acid. Multiple rounds of acclimation are performed, and acclimation is considered successful when no perchlorate is detected. The nutrient provides trace elements for the microorganisms, while the lactic acid and sodium acetate serve as electron donors and carbon sources.

[0020] In the present invention, after the perchlorate-reducing bacteria are adsorbed in the perchlorate-reducing bacteria enrichment and activation unit, the adsorbent is crushed into a powder and sprinkled into the airing unit and the silage unit to complete perchlorate degradation. When the successfully domesticated perchlorate-reducing bacteria are inoculated into the perchlorate-reducing bacteria enrichment and activation unit, the inoculation rate is greater than or equal to 5% of the substrate.

[0021] In the present invention, the suitable temperature for perchlorate-reducing bacteria is 35-37°C and an anaerobic environment is required. Too high or too low a temperature and oxygen content will affect the activity of microorganisms in the silage unit. The required temperature for silage is around 35°C, and an anaerobic environment is also required. Therefore, the temperature control and oxygen content operation in the silage unit are omitted, thereby reducing operating expenses and lowering costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 The present invention is a schematic flow chart of a method for degrading low-concentration perchlorate in silage. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The best implementation mode of the present invention will be described through preferred embodiments. The specific implementation modes here are intended to illustrate the present invention in detail and should not be understood as limiting the present invention. Various variations and modifications can be made without departing from the spirit and substantial scope of the present invention, and all of these should be included in the scope of protection of the present invention.

[0025] The present invention implements a treatment method for degrading low-concentration perchlorate in silage, comprising: (1) a pH adjustment unit, (2) a perchlorate-reducing bacteria acclimation unit, (3) a perchlorate-reducing bacteria enrichment and activation unit, (4) an silage unit, (5) a lactic acid bacteria activation unit, (6) a crushing unit, and (7) an airing unit.

[0026] After entering the pH adjustment unit, the original bacterial solution is treated with acid to adjust the pH to approximately 5.5. This ensures that the microorganisms in subsequent steps can grow and metabolize in an appropriate pH environment. After pH adjustment, the original bacterial solution enters the perchlorate-reducing bacteria acclimation unit. By adding a certain concentration of perchlorate, nutrients, and lactic acid, the overall pH is adjusted to approximately 5.0-6.5. Multiple rounds of acclimation are performed, and acclimation is considered successful when no perchlorate is detected. Nutrients provide trace elements for the microorganisms, while lactic acid and sodium acetate serve as electron donors and carbon sources.

[0027] The successfully domesticated perchlorate-reducing bacteria were inoculated into the perchlorate-reducing bacteria enrichment and activation unit at an inoculation rate greater than or equal to 5% of the substrate, and a certain concentration of perchlorate, lactic acid, sodium acetate (the ratio of perchlorate concentration to lactic acid and sodium acetate concentration was 1:3) and nutrients were added to activate the perchlorate-reducing bacteria.

[0028] Optionally, a certain amount of adsorbent is added to enrich the perchlorate-reducing bacteria, and the enriched adsorbent is crushed into powder, and the powder is evenly sprinkled into the silage raw materials in the drying unit and the whole silage raw material crushed and compacted in the silage unit at an amount greater than or equal to 20% of the mass of the silage raw materials. The moisture content of the dried silage raw materials is about 65±5%. During the drying process, the harvested silage raw materials need to be piled up, and the perchlorate-reducing bacteria adsorbent powder needs to be added while piling.

[0029] Alternatively, mix 2% warm sugar water with the lactic acid bacteria (solid-to-liquid ratio of 1:67) and leave it at room temperature for 1.5 hours to activate the bacteria. After activation, add a certain amount of tap water (with a mass ratio of tap water to silage material of 1:4), stir thoroughly, and spray the mixture evenly onto the compacted silage material in the silage unit. Mix thoroughly to evenly activate the lactic acid bacteria. Harvested and air-dried silage should be chopped into small pieces approximately 1-2 cm long in the shredder unit to reduce gaps between the silage pieces and ensure a more compact silage.

[0030] Compared with the existing technology, the present invention provides a new idea for biological removal of low-concentration perchlorate in silage. By using lactic acid and sodium acetate as carbon sources and electron donors, it not only achieves efficient and safe perchlorate degradation, but also promotes the growth and metabolic activity of microorganisms, reduces the cost of additional investment, and improves the treatment efficiency. Compared with the physical and chemical methods alone, the biological method has the advantages of simple operation, low cost, and environmental friendliness. By utilizing the metabolic activities of microorganisms, perchlorate can be converted into harmless substances, avoiding the secondary pollution problem that may be caused by chemical agents. Through multiple rounds of acclimation and enrichment, efficient perchlorate-reducing bacteria were successfully cultivated, which can reproduce rapidly under suitable temperature and anaerobic environment, and effectively degrade low-concentration perchlorate in silage.

[0031] Experiments have shown that the method of the present invention can achieve a perchlorate removal rate of more than 80% at a concentration of 16 mg / L in silage, showing good application prospects.

[0032] In summary, the present invention discloses a treatment method for degrading low-concentration perchlorate in silage, which provides an effective biotechnology means to solve the problem of low-concentration perchlorate in silage, helps to improve the quality of silage, reduce perchlorate pollution in milk and dairy product production, and promote the sustainable development of animal husbandry. It is expected to provide reference and reference for further research in related fields and promote the application and promotion of biodegradation technology in animal husbandry production.

[0033] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for degrading low-concentration perchlorate in silage, characterized in that: The following steps are involved: (1) Add the original bacterial solution to the pH adjustment unit to ensure that the microorganisms in the subsequent steps can grow and metabolize in a suitable pH environment; (2) domesticating the pH-adjusted bacterial solution, using lactic acid and sodium acetate as carbon sources and electron donors, and obtaining successfully domesticated perchlorate-reducing bacteria after multiple rounds of domestication; (3) using lactic acid and sodium acetate as carbon sources and electron donors, taking the perchlorate-reducing bacteria obtained in step (2) as inoculum, using an adsorbent to achieve efficient enrichment and collection of the perchlorate-reducing bacteria, and crushing the adsorbent into powder; (4) During the silage process, the highly enriched perchlorate-reducing bacteria adsorbent powder obtained in step (3) is evenly sprinkled onto the silage raw material fragments that have been filled and compacted; (5) warm sugar water and lactic acid bacteria are mixed and activated to obtain activated lactic acid bacteria liquid, which is evenly sprayed onto the silage that has been loaded and compacted in step (4); (6) The harvested and dried silage raw materials need to enter the crushing unit to obtain silage raw material fragments cut into small pieces; (7) Analogously to step (4), the highly enriched perchlorate-reducing bacteria adsorbent powder obtained in step (3) is evenly sprinkled onto the silage material to be air-dried; The temperature of steps (1), (2), (3), and (5) should be set at 35-37°C, and the mixture should be sealed and equipped with a stirring device; In the step (2), a certain concentration of perchlorate is added as an electron acceptor, and a certain concentration of lactic acid and sodium acetate are added as carbon sources and electron donors (the ratio of perchlorate concentration to lactic acid and sodium acetate concentration is 1:3). If the concentration of perchlorate decreases significantly over time, it indicates that the perchlorate-reducing bacteria have been successfully domesticated and effectively degraded perchlorate; In the steps (2) and (3), the nutrient agent is used as a source of trace elements, lactic acid and sodium acetate are used as carbon sources and electron donors, and the overall pH is adjusted to about 5.0-6.5; In the step (3), an adsorbent is added to enrich the perchlorate-reducing bacteria. After the adsorption is completed, the perchlorate-reducing bacteria adsorbent is crushed into powder and evenly sprinkled into the steps (4) and (7); The step (4) is generally a silo (silo or silo tower), the fermentation temperature is about 35-37°C, the silage raw material crushed materials will be filled and compacted at the same time, and the addition of the perchlorate-reducing bacteria adsorbent powder and the lactic acid bacteria liquid in steps (3) and (5) should be before the compaction stage; In step (6), the silage materials must be chopped into small pieces before silage, and the length of the small pieces is about 1 to 2 cm. This can reduce the gaps between the silage materials and make them more compact during silage. The moisture content of the silage raw material after drying in step (7) is about 65±5%. During the drying process, the harvested silage raw material needs to be piled up, and the perchlorate-reducing bacteria adsorbent powder should be gradually added during the stacking process; ensuring that the added amount is greater than or equal to 20% of the mass of the silage raw material.

2. A method for degrading low-concentration perchlorate in silage according to claim 1, characterized in that: Step (1) specifically includes: the original bacterial liquid is taken from the laboratory of the solid waste treatment and resource utilization research group of Xi'an Jiaotong University, which can degrade high-concentration ammonium perchlorate wastewater with a pH between 7.0 and 8.

5. It needs to be acidified and the pH adjusted to about 5.

5.

3. A method for degrading low-concentration perchlorate in silage according to claim 1, characterized in that: Step (5) specifically includes: preparing 2% warm sugar water, adding lactic acid bacteria strains (solid-liquid ratio is 1:67), fully mixing, and then placing at room temperature for 1.5 hours to activate the lactic acid bacteria strains; after the strains are activated, adding a certain amount of tap water (the mass ratio of tap water to silage raw material crushed material is 1:4), stirring evenly, and spraying the diluted bacterial solution onto the silage raw material crushed material in (4) to promote the proliferation of lactic acid bacteria and the fermentation of the silage raw material crushed material.

4. A method for degrading low-concentration perchlorate in silage according to claim 1, characterized in that: The successfully domesticated perchlorate-reducing bacteria are inoculated into step (3) with an inoculation rate greater than or equal to 5% of the substrate.

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