Method for producing denitrification carbon source for sewage treatment by using organic waste residue of food industry

Abstract

This invention provides a method for producing denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, relating to the field of solid waste resource utilization. The method includes: pretreating organic waste residue from the food industry to obtain an organic slurry; subjecting the organic slurry to reverse osmosis concentration to obtain a concentrated liquid; adding anaerobic sludge to an anaerobic fermentation reactor, injecting the concentrated liquid into the reactor, and inoculating with acetose-producing fermenting bacteria for anaerobic fermentation; centrifuging the anaerobic fermentation products and collecting the supernatant, which is the denitrifying carbon source for wastewater treatment. The addition of acetose-producing fermenting bacteria during anaerobic fermentation significantly increases the COD of the denitrifying carbon source and improves hydrolysis acidification efficiency. The carbon source produced by this bacteria can significantly increase the denitrification rate and denitrification potential in denitrification applications, resulting in higher carbon source utilization and better denitrification capacity. This invention has the advantages of simple process, low cost, and convenient operation.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, specifically to a method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry. Background Technology

[0002] Nitrogen is an essential nutrient for plant growth, but large amounts of nitrogen discharged into water bodies can easily lead to eutrophication, harm aquatic animals, and cause serious environmental problems. Therefore, improving the nitrogen removal efficiency of wastewater treatment plants and reducing the nitrogen content in effluent has always been a focus of research. Nitrogen compounds in wastewater can be removed through physicochemical methods or transformed through biological processes, but biological nitrogen removal technology is the most economical and is therefore widely used. The mechanism of biological nitrogen removal is that under anaerobic or anoxic conditions, denitrifying bacteria utilize organic matter as a carbon source and energy source to reduce nitrates or nitrites to gaseous nitrogen. The carbon source is crucial to the nitrogen removal process and directly affects the efficiency of denitrification. Adding external carbon sources to enhance the denitrification process and improve nitrogen removal efficiency has been extensively studied.

[0003] External carbon sources for enhanced denitrification generally include traditional chemical carbon sources, high-concentration organic wastewater, granular carbon sources, and anaerobic fermentation products. Traditional chemical carbon sources, such as methanol, acetic acid, and glucose, are easily absorbed and metabolized by microorganisms, rapidly providing energy for the denitrification process. However, studies have shown that improper dosage of these carbon sources can easily lead to effluent quality deterioration, and their high cost makes large-scale use in actual wastewater treatment difficult. High-concentration organic wastewater is rich in various organic compounds and has a high concentration, but its complex composition requires consideration of its potential adverse effects on microorganisms, the introduction of new pollutants, and the potential deterioration of effluent quality. Granular carbon sources include natural plant materials (wheat straw, bark, cotton, and reeds, etc.) and biodegradable polymers, but these are slow-release carbon sources with limited improvement in denitrification efficiency. Anaerobic fermentation transforms complex organic matter in the substrate into smaller organic molecules, such as organic acids and alcohols. These substances can be rapidly degraded and utilized by microorganisms, providing energy for metabolic activities and exhibiting a faster denitrification rate. Wastewater treatment plant sludge, with its high organic content, is an ideal substrate for anaerobic fermentation to produce carbon sources for denitrification and is beneficial for reducing sludge production, thus attracting widespread attention from researchers. However, the sludge hydrolysis process is slow, severely affecting the efficiency of subsequent acidification.

[0004] Organic waste from the food industry refers to waste generated by food processing enterprises during the processing of target products using animal and plant materials. It is characterized by containing large amounts of organic matter such as protein, carbohydrates, and fats, as well as a large amount of suspended solids, and relatively low toxicity. As organic solid waste, improper disposal of food industry organic waste can have environmental impacts. Proper disposal of food industry organic waste is essential and should adhere to the principles of harmlessness, reduction, and resource recovery. Currently, the main technologies for treating food industry organic waste include landfill, incineration, composting, feed production, and anaerobic fermentation. However, the amount of organic waste from the food industry is increasing daily, and most of it is only treated through landfill, incineration, or composting, without effective recycling and utilization, resulting in serious resource waste and environmental hygiene and safety hazards.

[0005] In recent years, domestic and international research institutions have conducted some research on the preparation of carbon sources from organic waste. However, existing technologies only involve simple physical crushing and pretreatment of organic waste followed by simple hydrolysis and acidification. The resulting carbon source products have low effective COD equivalents and are classified as low-concentration carbon source products. In practical engineering applications, the amount of such carbon source products required is larger than that of traditional carbon source products, and they are subject to greater limitations in transportation radius and higher transportation costs. How to improve the hydrolysis and acidification efficiency and the COD equivalent of the obtained carbon source products from organic waste residue in the food industry has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defects of low hydrolysis acidification efficiency and low COD equivalent when using organic waste residue from the food industry to produce denitrification carbon source for wastewater treatment in the prior art, thereby providing a method for producing denitrification carbon source for wastewater treatment using organic waste residue from the food industry that can improve the utilization rate of organic matter, obtain a carbon source with high COD concentration, and achieve efficient recovery of carbon source.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] In a first aspect, the present invention provides a method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, comprising the following steps:

[0009] (1) Organic slurry is prepared by pretreating organic waste residue from the food industry;

[0010] (2) The organic slurry is subjected to reverse osmosis concentration treatment to obtain a concentrated solution;

[0011] (3) Add anaerobic sludge to the anaerobic fermentation reactor, inject the concentrated liquid into the anaerobic fermentation reactor, and inoculate with acetic acid sugar-producing fermenting bacteria to carry out anaerobic fermentation;

[0012] (4) Centrifuge the anaerobic fermentation product and take the supernatant to obtain the denitrification carbon source for wastewater treatment.

[0013] Further, in step (3), the acetic acid fermenting bacteria is specifically selected as Saccharofermentans acetigenes CGMCC 1.5064.

[0014] Further, in step (3), 20% to 30% of the volume of the concentrated liquid is added to the bacterial solution of the acetic acid-producing fermenting bacteria, wherein the viable count of the bacterial solution of the acetic acid-producing fermenting bacteria is 1.2 × 10⁻⁶. 8 ~1.3×10 8 cfu / L.

[0015] Further, in step (3), the amount of anaerobic sludge used is 15%~25% of the volume of the concentrated liquid; the VSS / TSS of the anaerobic sludge is greater than 0.7, and the sludge concentration is 5000±100mg / L.

[0016] Further, in step (3), the conditions for anaerobic fermentation are: pH value 8.0~8.5, temperature 35~45℃, and time 36~48h (fermentation is stopped when the components in the reactor are basically stable).

[0017] Further, in step (1), the pretreatment includes: crushing the organic waste residue from the food industry, adding hot water and mixing evenly, filtering, and obtaining the organic slurry, wherein the pressure during crushing is controlled at 0.13~0.15Mpa; the mass of the hot water added is 2~5 times the mass of the organic waste residue, and the hot water temperature is 80~90℃; the filtration is performed by filtering 1~3 times using a sieve with a mesh size of 10~50 mesh.

[0018] Furthermore, in step (2), the reverse osmosis concentration treatment uses a disc tube reverse osmosis membrane; the organic slurry is concentrated 3 to 5 times through the reverse osmosis concentration treatment.

[0019] Furthermore, in step (4), the centrifugation conditions are: 4000~6000 rpm, and the time is 8~12 minutes.

[0020] Secondly, the present invention provides a denitrifying carbon source for wastewater treatment prepared by the method described herein.

[0021] Thirdly, the present invention provides a wastewater treatment method, including denitrification treatment of wastewater, wherein the carbon source used in the denitrification treatment process is obtained by the method provided by the present invention.

[0022] The technical solution of this invention has the following advantages:

[0023] The present invention provides a method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, comprising the steps of pretreatment, reverse osmosis concentration treatment, anaerobic fermentation, and centrifugation.

[0024] This invention enriches and retains high-protein substances in organic waste residue into filter residue through pretreatment, which can reduce the release of nitrogen sources from the organic waste residue itself during hydrolysis. This avoids adding these nitrogen sources to the wastewater in the form of carbon sources, increasing the nitrogen load of the wastewater treatment plant, and affecting the denitrification effect of the products when used for wastewater treatment. Most of the organic slurry collected after pretreatment is starchy carbohydrates, which are easily degraded by microorganisms, thus improving the utilization rate of organic matter.

[0025] This invention reduces the amount of concentrated water by highly concentrating the slurry after pretreatment of organic waste residue from the food industry, maximizing the degradation of organic matter in the organic waste residue, improving the utilization rate of organic matter, producing carbon source products with higher COD equivalent, and achieving efficient carbon source recovery.

[0026] This invention, by inoculating anaerobic sludge and acetic acid-producing fermenting bacteria during anaerobic fermentation, facilitates the control of the fermentation process at the hydrolysis, acidification, and acetic acid production stages. This process hydrolyzes and converts large organic molecules into easily biodegradable small organic molecules, producing volatile fatty acids (VFAs) with high denitrification rates, thus obtaining a relatively stable liquid denitrification carbon source. Experimental comparisons have verified that the addition of acetic acid-producing fermenting bacteria significantly increases the COD of the denitrification carbon source and improves hydrolysis and acidification efficiency. The carbon source produced by this bacteria significantly enhances the denitrification rate and denitrification potential in denitrification applications, resulting in higher carbon source utilization and better denitrification capacity.

[0027] The process of this invention is simple, economical, and easy to operate, enabling the resource utilization of organic waste residue in the food industry, and has good prospects for promotion and application. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a process flow diagram of producing denitrifying carbon source for wastewater treatment using organic waste residue from the food industry in Embodiment 1 of the present invention. Detailed Implementation

[0030] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0031] The acetic acid-producing fermenting bacteria used in the embodiments and experimental examples of this invention are specifically acetic acid-producing fermenting bacteria (Saccharofermentans acetigenes) CGMCC 1.5064, purchased from the China General Microbiological Culture Collection Center, located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCCNo.1.5064.

[0032] The anaerobic sludge used in the embodiments and experimental examples of this invention is anaerobic activated sludge taken from a sewage treatment plant, with a VSS / TSS (the proportion of anaerobic bacteria in the sludge) greater than 0.7 and a sludge concentration of 5000±100mg / L.

[0033] DTRO System: LT-S 20000, Kunshan Weishengda Environmental Protection Equipment Co., Ltd.

[0034] Anaerobic fermentation reactor: BL-BJGD, B. Braun Bioengineering Equipment (Jiangsu) Co., Ltd.

[0035] Where specific experimental steps or conditions are not specified in the embodiments, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. All raw materials or instruments used are commercially available conventional products, including but not limited to those used in the embodiments of this application.

[0036] Example 1

[0037] This embodiment provides a method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry. The process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0038] (1) Pretreatment: The organic waste residue from the food industry is crushed under the extrusion of 0.15 MPa, and hot water (85℃) with a mass of 3 times the organic waste residue is added and mixed evenly. The mixture is filtered through 10-mesh and 20-mesh screens to control the particle size of the organic slurry to below 0.25 mm. The filter residue retains about 46% of the protein in the organic waste residue.

[0039] (2) Reverse osmosis concentration: The organic slurry is conveyed to the DTRO system by a high-pressure pump and conveyor belt for concentration to obtain a 4-fold concentrate;

[0040] (3) Anaerobic fermentation: Anaerobic sludge is added to the anaerobic fermentation reactor, and the concentrated liquid is injected into the anaerobic fermentation reactor. The volume of anaerobic sludge is 15% of the volume of concentrated liquid. Acetic acid sugar producing fermentation bacteria (live bacteria count of 1.2 × 10⁻⁶) are added at 20% of the volume of concentrated liquid. 8 The pH value in the anaerobic fermentation reactor was adjusted to 8.0 (cfu / L), the fermentation temperature was 40℃, and the anaerobic fermentation was carried out in a sealed environment for 40 hours.

[0041] (4) Centrifugation: After centrifuging the anaerobic fermentation product at 5000 rpm for 10 minutes, the supernatant is taken to obtain a high concentration of small molecule carbon source, which can be directly used as a liquid carbon source for denitrification.

[0042] The COD concentration of the high-concentration small molecule carbon source was found to reach 500,000 mg / L.

[0043] Example 2

[0044] This embodiment provides a method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry. The process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0045] (1) Pretreatment: The organic waste residue from the food industry is crushed under the extrusion of 0.16 MPa, and hot water (83℃) of 4 times the mass of the organic waste residue is added and mixed evenly. The mixture is filtered through 10-mesh and 20-mesh screens to control the particle size of the organic slurry to below 0.25 mm. The filter residue retains about 46% of the protein in the organic waste residue.

[0046] (2) Reverse osmosis concentration: The organic slurry is conveyed to the DTRO system by a high-pressure pump and conveyor belt for concentration to obtain a 5-fold concentrate;

[0047] (3) Anaerobic fermentation: Anaerobic sludge is added to the anaerobic fermentation reactor, and the concentrated liquid is injected into the anaerobic fermentation reactor. The volume of anaerobic sludge is 20% of the volume of concentrated liquid. Acetic sugar-producing fermentation bacteria (live count of 1.2 × 10⁻⁶) are added at 25% of the volume of concentrated liquid. 8 The pH value in the anaerobic fermentation reactor was adjusted to 8.2 (cfu / L), the fermentation temperature was 43℃, and the anaerobic fermentation was carried out in a sealed environment for 42 hours.

[0048] (4) Centrifugation: After centrifuging the anaerobic fermentation product at 6000 rpm for 8 minutes, the supernatant was taken to obtain a high concentration of small molecule carbon source, which can be used directly as a liquid carbon source for denitrification.

[0049] The COD concentration of the high-concentration small molecule carbon source was found to be 530,000 mg / L.

[0050] Example 3

[0051] This embodiment provides a method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry. The process flow is as follows: Figure 1 As shown, the specific operation steps are as follows:

[0052] (1) Pretreatment: The organic waste residue from the food industry is crushed under the extrusion of 0.14 MPa, and hot water (88℃) with a mass of 3 times the organic waste residue is added and mixed evenly. The mixture is filtered through 10-mesh and 20-mesh screens to control the particle size of the organic slurry to below 0.25 mm. The filter residue retains about 46% of the protein in the organic waste residue.

[0053] (2) Reverse osmosis concentration: The organic slurry is conveyed to the DTRO system by a high-pressure pump and conveyor belt for concentration to obtain a 5-fold concentrate;

[0054] (3) Anaerobic fermentation: Anaerobic sludge is added to the anaerobic fermentation reactor, and the concentrated liquid is injected into the anaerobic fermentation reactor. The volume of anaerobic sludge is 25% of the volume of concentrated liquid. Acetic acid sugar producing fermentation bacteria (live bacteria count of 1.2 × 10⁻⁶) are added at 30% of the volume of concentrated liquid. 8 The pH value in the anaerobic fermentation reactor was adjusted to 8.5 (cfu / L), the fermentation temperature was 38℃, and the anaerobic fermentation was carried out in a sealed environment for 48 hours.

[0055] (4) Centrifugation: After the anaerobic fermentation product is centrifuged at 6000 rpm for 12 minutes, the supernatant is taken to obtain a high concentration of small molecule carbon source, which can be used directly as a liquid carbon source for denitrification.

[0056] The COD concentration of the high-concentration small molecule carbon source was found to be 590,000 mg / L.

[0057] Experiment Example 1: Anaerobic Fermentation Comparative Experiment

[0058] To investigate the effect of adding acetic acid-producing fermenting bacteria on the anaerobic fermentation effect, the concentrated liquid obtained in step (2) of Example 1 was used as the anaerobic fermentation substrate, and two identical batch reactors were set up for comparative experiments. The effective volume of the reactor was 2L, the pH value was set to 8, and the reactor was kept homogeneous and constant in temperature during the fermentation process by using a stirrer and a 40℃ water bath. 200mL of anaerobic sludge with a concentration of 5000mg / L and 1L of concentrated liquid were added to the reactor, along with the bacterial solution of acetic acid-producing fermenting bacteria (with a viable count of 1.2×10⁻⁶). 8 The concentration of cfu / L was added to the reactor at 20% of the volume of the concentrated liquid, and a reactor without the addition of acetic acid sugar-producing fermenting bacteria was used as a control group.

[0059] Samples (50 mL each time) were taken from the reactor every 12 hours for analysis. Fermentation was stopped when the components in the system remained relatively stable. COD, ammonia nitrogen, and total carbohydrates were analyzed immediately after each sampling. The fermentation broth was centrifuged at 50,000 rpm for 10 minutes, and the supernatant was filtered through a 0.45 μm filter membrane. The filtrate was analyzed to determine soluble COD, carbohydrates, and VFAs.

[0060] COD was determined using the standard method of GB 11914-89 "Determination of Chemical Oxygen Demand in Water - Dichromate Method".

[0061] Ammonia nitrogen was determined using the standard method of HJ 535-2009 "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometric Method".

[0062] Carbohydrates were determined using the anthrone reagent method, and VFAs were analyzed by gas chromatography.

[0063] The acidification rate of anaerobic fermentation is calculated using the following formula:

[0064]

[0065] In the formula:

[0066] SCOD—Dissolved COD in the reactor after fermentation, in g / L;

[0067] COD VFAs —COD equivalent of VFAs in the reactor after fermentation, g / L.

[0068] From COD VFAs In terms of concentration, when anaerobic fermentation is carried out with the addition of acetic sugar-producing bacteria, the COD in the reactor after fermentation is [data missing]. VFAs The concentration was 508,300 g / L, which was 2.6 times that of the control group. Calculations showed that the acidification rate of the reactor with added acetic acid-producing fermenting bacteria was 2.4 times that of the control group. This demonstrates that the acetic acid-producing fermenting bacteria significantly improved the hydrolysis and acidification efficiency of the substrate.

[0069] Experiment Example 2: Denitrification Comparison Experiment

[0070] To investigate the effect of adding anaerobic fermentation broth containing acetose-producing bacteria as a carbon source on denitrification performance, a denitrification experiment was conducted using the fermentation broth from Experiment 1 after it had stabilized. For comparison, three sealed bottles were prepared, with carbon sources for the blank, fermentation broth 1 (fermentation broth obtained with acetose-producing bacteria), and fermentation broth 2 (fermentation broth obtained without acetose-producing bacteria). Before the denitrification experiment, to ensure comparable sludge activity, the anaerobic sludge taken from the wastewater treatment plant was acclimated using the aforementioned carbon source until its nitrogen removal rate stabilized above 90%. The acclimated anaerobic sludge was then washed with ultrapure water and placed in a sealed bottle. The volume was adjusted to 1.5 L with ultrapure water, and N2 was introduced to remove dissolved oxygen. NaNO3 and the carbon source (blank, fermentation broth 1, and fermentation broth 2) were then added to increase the NO3- content. - The final mass concentrations of NO3- and COD were (35±5) mg / L and (250±20) mg / L, respectively, and the sludge mass concentration was (2000±100) mg / L. The pH of the reaction system was maintained between 7.0 and 8.0. During the experiment, a stirrer was used for continuous mixing, and NO3- samples were taken for analysis at regular intervals. - -N, NO2 - -N and COD.

[0071] Denitrification rate (Vf) of fermentation broth as a carbon source DN The calculation formula for ) is as follows:

[0072] V DN = d(NO) x - N)

[0073]

[0074] In the formula:

[0075] V DN —Denitrification rate, mg / (g·h);

[0076] X — Sludge mass concentration (MLSS), g / L;

[0077] t — Denitrification time, h;

[0078] NO x，in —NO at the beginning of the reaction x Concentration, mg / L;

[0079] NO x，end（t） ——NO at time t x Concentration, mg / L.

[0080] The denitrification capacity of fermentation broth as a carbon source (P DN The calculation formula for ) is as follows:

[0081]

[0082] COD in —Added carbon source COD concentration, mg / L;

[0083] COD end —COD concentration at the end of denitrification, mg / L;

[0084] NO x，end NO when the carbon source is exhausted by microorganisms x Concentration, mg / L.

[0085] The experimental data are shown in Table 1.

[0086] Table 1 Results of the comparative experiment on denitrification

[0087]

[0088] As shown in Table 1, the denitrification capacity (P0) of fermentation broth 1 cultured with acetic acid-producing fermenting bacteria is as follows: DN ) and denitrification rate (V DN The P content in fermentation broth 1 was significantly higher than that in the control group. DN Compared to fermentation broth 2 without added acetic acid-producing bacteria, V's yield was more than 20% higher. DN The difference of more than 30% indicates that the denitrification rate and denitrification potential of the anaerobic fermentation broth with added acetic sugar-producing fermenting bacteria are significantly improved, the carbon source utilization rate is higher, and the denitrification capacity is better.

[0089] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, characterized in that, Includes the following steps: (1) Organic slurry is prepared by pretreating organic waste residue from the food industry; (2) The organic slurry is subjected to reverse osmosis concentration treatment to obtain a concentrated solution; (3) Add anaerobic sludge to the anaerobic fermentation reactor, inject the concentrated liquid into the anaerobic fermentation reactor, and inoculate with acetic acid sugar-producing fermenting bacteria to carry out anaerobic fermentation; (4) Centrifuge the anaerobic fermentation product and take the supernatant to obtain the denitrification carbon source for wastewater treatment. In step (3), 20% to 30% of the volume of the concentrated liquid is added to the bacterial solution of the acetic acid-producing fermenting bacteria, wherein the viable count of the bacterial solution of the acetic acid-producing fermenting bacteria is 1.2 × 10⁻⁶. 8 ~1.3×10 8 The concentration of anaerobic sludge is 15% to 25% of the volume of the concentrated liquid; the proportion of anaerobic bacteria in the anaerobic sludge is greater than 0.7, the sludge concentration is 5000±100mg / L, and the anaerobic fermentation conditions are: pH 8.0 to 8.5, temperature 35 to 45℃, and time 36 to 48h.

2. The method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, as described in claim 1, is characterized in that... In step (1), the pretreatment includes: crushing the organic waste residue from the food industry, adding hot water and mixing evenly, filtering, and obtaining the organic slurry, wherein the pressure during crushing is controlled at 0.13~0.15 MPa; the mass of the hot water added is 2~5 times the mass of the organic waste residue, and the hot water temperature is 80~90℃; the filtration is performed by filtering 1~3 times using a sieve with a mesh size of 10~50 mesh.

3. The method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, as described in claim 1, is characterized in that... In step (2), the reverse osmosis concentration process uses a disc tube reverse osmosis membrane; the organic slurry is concentrated 3 to 5 times through the reverse osmosis concentration process.

4. The method for producing a denitrifying carbon source for wastewater treatment using organic waste residue from the food industry, as described in claim 1, is characterized in that... In step (4), the centrifugation conditions are: 4000~6000 rpm, and the time is 8~12 minutes.

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