A biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products.

Abstract

This invention relates to a biochemical treatment method for high-concentration organic wastewater generated during the preparation of soybean products. The specific steps are as follows: Soybean product organic wastewater collected by a grating in a collection well is transported to a coagulation sedimentation tank. Its pH is adjusted, and a compound agent is added for coagulation and sedimentation treatment. After removing sludge, the wastewater enters the next process. The compound agent, by weight, comprises 22-33 parts polyaluminum chloride, 1-3 parts polyacrylamide, 54-70 parts quaternary ammonium cationic demulsifier, 6-12 parts modified straw biochar, and 1-2 parts Streptococcus thermophilus YXX1. The treated wastewater is then subjected to dissolved air flotation to remove scum and transported to a black film anaerobic digester for anaerobic fermentation. The effluent from the black film anaerobic digester is directly used for irrigation or discharged after further treatment. This invention, through the combination of compound agent treatment and anaerobic fermentation in a black film anaerobic digester, achieves high biogas yield and output, with high methane content. When the clean water is discharged, the COD is low. cr The values ​​are all below 150 mg / L, making them environmentally friendly and safe.

Description

Technical Field

[0001] This invention belongs to the field of organic wastewater treatment technology for soybean products, specifically relating to a biochemical treatment method for high-concentration organic wastewater generated during the soybean product preparation process. Background Technology

[0002] Soy product processing is one of my country's traditional and rapidly developing food industries. The high concentration of organic wastewater discharged during its production process has become a bottleneck restricting the industry's green development. This type of wastewater has the typical characteristics of "four highs and one low": COD as high as 20,000–50,000 mg / L, suspended solids (SS) 6,000–12,000 mg / L, ammonia nitrogen 200–800 mg / L, and oil 1,000–3,000 mg / L, while the C / N ratio is low (≈3–5). The wastewater is acidic (pH 4–6), dark in color, and contains a large amount of protein, polysaccharides, saponins, and surfactants. During peak discharge periods, the water temperature can reach above 40℃. Although it has high biodegradability, direct biochemical treatment is prone to system acidification, scum caking, low methanogenesis efficiency, and even "dead tanks" due to the high oil and suspended solids content.

[0003] Currently, the industry generally adopts a combined process of "coagulation-air flotation-black membrane tank anaerobic fermentation-A / O wastewater treatment system-advanced treatment", but the following prominent problems still exist: Low methanogenesis efficiency: When the COD of organic wastewater from soybean products is around 25,000 mg / L, the methanogenesis rate in the black film anaerobic fermentation tank is only 0.25–0.30 Nm³. 3 The COD is approximately 40% / kg, and the methane content is around 40%, resulting in poor resource recovery and utilization. Currently, there is limited research on using agricultural waste to prepare biochar loaded with conventional coagulants to improve biogas yield, output, and methane content. Based on the aforementioned technical issues, this application proposes a biochemical treatment method for high-concentration organic wastewater generated during soybean product preparation. Summary of the Invention

[0004] The purpose of this invention is to provide a biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products in order to solve the above-mentioned problems.

[0005] The present invention achieves the above objectives through the following technical solutions: A biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products, comprising the following specific steps: Step 1: The organic wastewater from soybean products collected by the sump screen is transported to the coagulation sedimentation tank, where the pH is adjusted and compound agents are added for coagulation sedimentation treatment. After removing the sludge, the wastewater enters the next process. The raw materials for preparing the compound agent, by weight, include 22-33 parts of polyaluminum chloride, 1-3 parts of polyacrylamide, 54-70 parts of quaternary ammonium salt cationic demulsifier, 6-12 parts of modified straw biochar, and 1-2 parts of thermophilic streptococcus YXX1. The dosage of the compound agent is 50-100 g / m³. 3 ; Step 2: The wastewater from Step 1 is treated with dissolved air flotation to remove scum, and then transported to a black film anaerobic tank for anaerobic fermentation. Step 3: The effluent from the black membrane anaerobic tank is used directly for irrigation or discharged after further treatment; The advanced treatment includes treating the effluent from the black membrane anaerobic tank using the AO two-stage activated sludge process, followed by sedimentation and coagulation to remove sludge, and finally discharging clean water.

[0006] As a further optimization of the present invention, the method for obtaining the modified straw biochar is as follows: (1) After the dried biomass straw is crushed and sieved, it is added to ZnCl2 solution in proportion and stirred evenly. After sealing, impregnation and activation and drying, it is kept at 500-800℃ for 30-50 minutes under nitrogen atmosphere. The carbonized product is washed with distilled water until neutral, dried, ground and sieved to obtain straw biomass. (2) Add straw biochar to citric acid solution in proportion, shake at room temperature for 5-7 hours, then vacuum filter, wash until neutral, and dry to obtain straw biochar-COOH; (3) Add straw biochar-COOH to FeCl3 solution in a certain proportion, shake at room temperature for 3-5 hours, then filter under vacuum, wash until neutral, and dry to obtain straw biochar-Fe 3 ⁺; (4) The straw biochar-Fe 3 ⁺ Add dimethyl diallyl ammonium chloride aqueous solution in proportion, shake at room temperature for 2-4 hours, then vacuum filter and dry to obtain straw biochar-Fe 3 ⁺-Dimethyldiallylammonium chloride, also known as modified straw biochar.

[0007] As a further optimization of the present invention, the biomass straw is at least one of corn straw, soybean straw, and rice straw.

[0008] As a further optimization of the present invention, in step (1), the dried biomass straw powder after crushing and sieving is dispersed in a 2-7 mol / L ZnCl2 solution at a ratio of 1 g: 1-10 mL; In step (2), the straw biochar is added to a 0.5-2 mol / L citric acid solution at a ratio of 1 g: 10 mL; In step (3), the straw biochar-COOH is added to a 0.3-0.8 mol / L FeCl3 solution at a ratio of 1 g: 30 mL; In step (4), the straw biochar-Fe 3 ⁺ Add to a 2-5 wt% aqueous solution of dimethyl diallyl ammonium chloride at a ratio of 1 g: 50 mL.

[0009] As a further optimization of the present invention, the method for obtaining the composite agent is as follows: modified straw biochar is mixed with polyaluminum chloride solution, the pH is adjusted to 3.5-4.0, and stirred at 200 r / min for 1-2 h; then polyacrylamide solution is added, the pH is adjusted to 6-7, and stirred at 100 r / min for 1-2 h; finally, quaternary ammonium salt cationic demulsifier solution is added, the pH is adjusted to 7-8, and stirred at 200 r / min for 20-40 min; the product obtained after vacuum filtration and drying is mixed with Streptococcus thermophilus YXX1 to obtain the composite agent.

[0010] As a further optimization of the present invention, in step two, the grid gap of the water collection well grid is 1-7mm.

[0011] As a further optimization of the present invention, in step two, the dissolved air flotation process, the air dissolved in the water is precipitated as microbubbles of 20-30 μm.

[0012] As a further optimization of the present invention, in step two, the top of the black membrane anaerobic tank is a 1-2 mm HDPE membrane, and the bottom and its sidewalls are 0.5-1.5 mm HDPE membranes.

[0013] As a further optimization of the present invention, in step two, the fermentation temperature in the black film anaerobic tank is 20℃-30℃, and the fermentation time is 2-3 months.

[0014] The beneficial effects of this invention are as follows: This invention collects organic wastewater from soybean products through a collection well grid, which can separate larger solid particles such as suspended solids, garbage, and floating matter from the organic wastewater. Through coagulation and sedimentation with compound agents, the settleable organic suspended solids and microparticles are separated from the water body. Dissolved air flotation is used to remove scum. The black film anaerobic pond undergoes anaerobic fermentation, has a long sewage retention period, and can also produce biogas with a high methane content, which can be used as a combustion gas source, making full use of resources. The effluent from the black film anaerobic pond can be directly discharged after further deep treatment. This invention involves sequentially loading modified straw biochar with polyaluminum chloride, polyacrylamide, and a quaternary ammonium salt cationic demulsifier before feeding it into organic wastewater from soybean products for coagulation and sedimentation. The treated wastewater undergoes anaerobic fermentation in a black membrane anaerobic tank for two months, resulting in high biogas yield and output, as well as high methane content. The COD level is low upon discharge. cr The values ​​are all below 150 mg / L, making them environmentally friendly and safe.

[0015] This invention, through the synergistic combination of soybean straw and rice straw, can significantly increase biogas production and biogas yield, and also significantly increase the methane content in the biogas, thus affecting the COD of the final clean water discharge. cr The value suggests that there may be a synergistic effect between soybean straw and rice straw, which has a significant advantage in the treatment of organic wastewater from soybean products. The thermophilic streptococcus YXX1 strain of the present invention has specificity and synergistic effect in the compound agent, which can significantly improve biogas production and biogas yield, and has high methane selectivity. It can also reduce the CODcr value of discharged water and has high environmental protection performance. Detailed Implementation

[0016] The present application will now be described in further detail. It should be noted that the following specific embodiments are only used to further illustrate the present application and should not be construed as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application based on the above application content.

[0017] Material The COD of the organic wastewater from soybean products is 25000 mg / L; 2) A 2-7 mol / L ZnCl2 solution, preferably a 5 mol / L ZnCl2 solution; a 0.5-2 mol / L citric acid solution, preferably a 1 mol / L citric acid solution; a 0.3-0.8 mol / L FeCl3 solution, preferably a 0.5 mol / L FeCl3 solution; and a 2-5 wt% aqueous solution of dimethyl diallyl ammonium chloride, preferably a 4 wt% aqueous solution of dimethyl diallyl ammonium chloride. 3) The raw materials for preparing the compound agent, by weight, include 22-33 parts of polyaluminum chloride (purchased from Shanghai Yuanye Biotechnology Co., Ltd., purity 99%), 1-3 parts of polyacrylamide (purchased from Shandong Yonglida New Material Technology Co., Ltd., purity 99%, molecular weight 12 million), 54-70 parts of quaternary ammonium salt cationic demulsifier (dodecyl dimethyl benzyl ammonium chloride, purchased from Hubei Qifei Pharmaceutical Chemical Co., Ltd., purity 99%), 6-12 parts of modified straw biochar, and 1-2 parts of thermophilic streptococcus YXX1 (enzyme activity 7.3×10⁻⁶). 5U / g); wherein, polyaluminum chloride, polyacrylamide, and quaternary ammonium salt cationic demulsifier are dissolved in water to obtain polyaluminum chloride solution (115 g / L), polyacrylamide solution (3 g / L), and quaternary ammonium salt cationic demulsifier solution (20 g / L). 4) Water collection well screen: the screen gap is 1-7mm, preferably 3mm; 5) The top of the black film anaerobic tank is made of 1-2 mm (preferably 1.5 mm) HDPE membrane, and the bottom and its side walls are made of 0.5-1.5 mm (preferably 1.0 mm) HDPE membrane; 6) pH adjusters: sodium hydroxide, sodium carbonate; 7) Streptococcus thermophilus YXX1: The live pure culture of Streptococcus thermophilus YXX1 has been deposited at the China Center for Type Culture Collection on August 24, 2021, with accession number CCTCCNO: M 20211075. 8) Streptococcus thermophilus ATCC 19987: Purchased from Shanghai Xuanke Biotechnology Co., Ltd., catalog number XK-SH-12886, enzyme activity 7.5×10 5 U / g.

[0018] Unless otherwise specified, all methods used in this application are conventional methods known to those skilled in the art, and all reagents and materials used are commercially available products unless otherwise specified.

[0019] method 2.1 Preparation of modified straw biochar 2.1.1 After crushing and sieving the dried biomass straw (80 mesh sieve), disperse it in a 5 mol / L ZnCl2 solution at a mass ratio of 1 g: 8 mL and stir evenly. Seal and impregnate for 48 h. After drying at 80℃, keep it at 500-800℃ for 30-50 min under a nitrogen atmosphere. The resulting carbonized product is washed with distilled water until neutral, dried at 110℃, ground and sieved (200 mesh sieve) to obtain straw biomass. 2.1.2 Add straw biochar at a ratio of 1g:10mL to 1mol / L citric acid solution, shake at room temperature for 6h, vacuum filter, wash with deionized water until neutral, and dry at 80℃ for 12h to obtain straw biochar-COOH (surface carboxylated straw biochar). 2.1.3. Add straw biochar-COOH to a 0.5 mol / L FeCl3 solution at a ratio of 1 g: 30 mL, shake at room temperature for 4 h, vacuum filter, quickly wash 1-2 times with deionized water, and vacuum dry at 60℃ for 12 h to obtain straw biochar-Fe 3 ⁺(Fe 3 ⁺ It is chemically adsorbed / coordinated and anchored on the char surface, forming "straw biochar-Fe". 3 (⁺” complex); 2.1.4. The straw biochar-Fe 3 - Add 4wt% dimethyl diallyl ammonium chloride aqueous solution at a ratio of 1g:50mL, shake at room temperature for 3 hours, filter under vacuum, and dry at 80℃ for 12 hours to obtain straw biochar-Fe 3 ⁺-Dimethyldiallylammonium chloride (the carbon surface has both chelated iron active sites and is covered with cationic quaternary ammonium groups, forming "straw biochar-Fe"). 3 (⁺-DMDAAC” ternary complex), store at -4℃ for later use.

[0020] 2.2 Preparation of Compound Drugs The raw materials for preparing the compound agent, by weight, include 27 parts of polyaluminum chloride, 2 parts of polyacrylamide, 60 parts of quaternary ammonium salt cationic demulsifier, 9 parts of modified straw biochar, and 2 parts of thermophilic streptococcus YXX1.

[0021] Modified straw biochar was mixed with polyaluminum chloride solution, and the pH was adjusted to 3.5-4.0 (preferably pH 3.8). The mixture was stirred at 200 r / min for 1-2 h (preferably 1.5 h). Then, polyacrylamide solution was added, and the pH was adjusted to 6-7 (preferably pH 6.5). The mixture was stirred at 100 r / min for 1-2 h (preferably 1.5 h). Finally, quaternary ammonium salt cationic demulsifier solution was added, and the pH was adjusted to 7-8 (preferably pH 7). The mixture was stirred at 200 r / min for 20-40 min (preferably 30 min). The product obtained after vacuum filtration and drying was then mixed with Streptococcus thermophilus YXX1 to obtain a composite agent.

[0022] 2.3. Method for biochemical treatment of high-concentration organic wastewater generated during the preparation of soy products using compound agents. 2.3.1 The organic wastewater from soybean products collected by the sump screen is transported to a coagulation sedimentation tank, where its pH is adjusted and a compound agent (dosage 65g / m³) is added. 3 After coagulation and sedimentation to remove sludge, the wastewater enters the next process. 2.3.2 The wastewater from step one is treated with dissolved air flotation (in the dissolved air flotation treatment, the air dissolved in the water is released as microbubbles of 20-30μm) to remove scum, and then transported to a black film anaerobic tank for anaerobic fermentation (using Bio-Volume Methanogens). The fermentation temperature is 20℃-30℃, and the fermentation time is 2-3 months (preferably 24℃±2℃ for 2 months). 2.3.3 The effluent from the black membrane anaerobic tank is used directly for irrigation or discharged after advanced treatment. The advanced treatment includes using the AO two-stage activated sludge process (stage A is also known as the anaerobic hydrolysis acidification tank, where anaerobic microorganisms and hydrolytic enzymes decompose complex organic molecules into simpler compounds under anaerobic conditions; biological hydrolysis actually includes two stages: hydrolysis and acidification. Acidification can degrade complex organic matter into simple organic acids; stage O is also known as the aerobic biological oxidation tank, which is a conventional technology and will not be described in detail here) to treat the effluent from the black membrane anaerobic tank (the wastewater enters stage O after stage A, where organic matter is oxidized and decomposed in the aerobic stage, and ammonia nitrogen is converted into nitrate nitrogen through nitrification. The mixed liquor is then returned to stage A for denitrification to remove total nitrogen), followed by sedimentation and coagulation to finally remove sludge before discharging clear water.

[0023] To further investigate the effects of modified straw biochar prepared from different biomass straws on biogas production, biogas yield, methane content, and COD during the anaerobic fermentation stage of a black film anaerobic digester, this study aimed to further investigate the effects of modified straw biochar on biogas production, biogas yield, methane content, and COD during clean water discharge. cr To investigate the effect of the concentration (mg / L), this application also conducted experimental designs for the following groups, as shown in Table 1: Table 1 Experimental design of different biomass straws in modified straw biochar ; Under the same testing conditions, the biogas production, biogas yield, and methane content of groups A1-A7 in the anaerobic fermentation stage of the black film anaerobic pond were tested, and the CODcr value (mg / L) of the treated water was measured. The experimental data are recorded in Table 2. Table 2. Statistical analysis of experimental data on different biomass straws in modified straw biochar. ; Experimental conclusions: Table 1-2 shows that different types of modified straw biochar affect the biogas yield, biogas production rate, methane content, and COD of the treated water during the anaerobic fermentation stage in the black film anaerobic digester. cr All values ​​were affected. Among them, when soybean straw and rice straw were used in combination, biogas production and biogas yield were significantly increased, and the methane content in biogas reached 63.5%, which was significantly higher than that of other groups. This suggests that there may be a synergistic effect between soybean straw and rice straw.

[0024] To further investigate the effects of modified straw biochar prepared at different carbonization temperatures on biogas production, biogas yield, methane content, and COD during the anaerobic fermentation stage of a black film anaerobic digester, this study aimed to further investigate the effects of modified straw biochar prepared at different carbonization temperatures on biogas production, biogas yield, methane content, and COD during clean water discharge. cr To investigate the effect of the concentration (mg / L), this application also conducted experimental designs for the following groups, as shown in Table 3: Table 3 Experimental design for different carbonization temperatures in modified straw biochar ; Under the same testing conditions, the biogas production, biogas yield, and methane content of groups A6, A6-1 to A6-4 in the anaerobic fermentation stage of the black film anaerobic pond were tested. The CODcr value (mg / L) of the treated water was also measured. The experimental data are recorded in Table 4. Table 4. Statistical analysis of experimental data on modified straw biochar at different carbonization temperatures. ; Experimental conclusions: Table 3-4 shows that carbonization temperature is also a key factor in the preparation of modified straw biochar. Modified straw biochar (straw biochar-Fe) prepared at a carbonization temperature of 700-750℃ is the most effective. 3 After loading polyaluminum chloride, polyacrylamide, and quaternary ammonium salt cationic demulsifier onto ⁺-dimethyldiallyl ammonium chloride in sequence, the mixture was added to organic wastewater from soybean products for coagulation and sedimentation. The effect was significantly better than that of other experimental groups.

[0025] To further investigate the effects of modified straw biochar prepared with different carbonization and heat preservation times on biogas production, biogas yield, methane content, and COD during the anaerobic fermentation stage of a black film anaerobic digester, this study aimed to further investigate the effects of modified straw biochar prepared with different carbonization and heat preservation times on biogas production, biogas yield, methane content, and COD during clean water discharge. cr To investigate the effect of the concentration (mg / L), this application also conducted experimental designs for the following groups, as shown in Table 5: Table 5 Experimental design for different carbonization holding times in modified straw biochar ; Based on the above group A6-2-1, a blank control experimental design was also designed: Blank group 1: Unmodified straw biomass (soybean straw and rice straw, carbonization temperature of 700℃, carbonization holding time of 40min, i.e., without modification by citric acid, FeCl3, and dimethyl diallyl ammonium chloride) was used as blank group 1.

[0026] Blank group 2: The composite agent without modified straw biochar (the raw materials for preparing the composite agent, by weight, include 27 parts of polyaluminum chloride, 2 parts of polyacrylamide, and 62 parts of quaternary ammonium salt cationic demulsifier, i.e., the modified straw biochar is omitted) was used as blank group 2.

[0027] Under the same testing conditions, the biogas production, biogas yield, and methane content of groups A6-2, A6-2-1 to A6-2-2, and blank groups 1 to 2 during the anaerobic fermentation stage in the black film anaerobic tank were measured. The CODcr value (mg / L) of the treated water was also measured. The experimental data are recorded in Table 6. Table 6. Different carbonization holding times in modified straw biochar And statistical analysis of experimental data from control groups 1-2 ; Experimental conclusions: Table 5-6 shows that further experiments revealed the optimal carbonization holding time at a carbonization temperature of 700℃ to be 40 min. The resulting modified straw biochar (straw biochar-Fe) was... 3 After sequentially loading polyaluminum chloride, polyacrylamide, and quaternary ammonium salt cationic demulsifiers onto ⁺-dimethyldiallylammonium chloride, the mixture was added to organic wastewater from soybean products for coagulation and sedimentation. After anaerobic fermentation in a black membrane anaerobic tank for two months, the methane content in the biogas significantly increased, reaching 73.8%, indicating a high methane content. The CODcr value of the discharged water was below 120 mg / L, making it environmentally safe.

[0028] Compared with the control group, it can be seen that the modified straw biochar, after being sequentially loaded with polyaluminum chloride, polyacrylamide, and quaternary ammonium salt cationic demulsifiers, and then added to the organic wastewater from soybean products for coagulation and sedimentation, has the advantage of effectively adsorbing dissolved organic matter and pigments in the wastewater, while also providing a good loading platform for polyaluminum chloride, polyacrylamide, and quaternary ammonium salt cationic demulsifiers, enhancing their dispersibility and stability. Furthermore, the modification treatment first introduces "Fe..." 3 The "⁺-dimethyldiallylammonium chloride" functional layer, loaded with polyaluminum chloride, polyacrylamide, and quaternary ammonium salt cationic demulsifiers, integrates "oxidation-demulsification-coagulation-flocculation" onto the same particle, which synergistically enhances the effect.

[0029] Comparative Example 1 In this comparative example, the difference from group A6-2-1 is that, in this embodiment, equal parts by mass of *Streptococcus thermophilus* ATCC 19987 replaced *Streptococcus thermophilus* YXX1, recorded as Comparative Example 1; and equal parts by mass of diatomaceous earth replaced *Streptococcus thermophilus* YXX1 as a blank control group, recorded as Blank Group 3; under the same experimental conditions, the results showed that after 2 months of fermentation, the biogas yield of Comparative Example 1 was 0.65 Nm³. 3 / kgCOD; biogas production 1685.7m³ 3 / d; methane content was 69.8%; CODcr value of clean water discharge was 137.4 mg / L; experimental data of blank group 3 showed a biogas yield of 0.70 Nm³. 3 / kgCOD; biogas production 1800.4m³ 3 / d; methane content is 72.3%; CODcr value of clean water discharge is 115.8 mg / L; This demonstrates that the thermophilic streptococcus YXX1 strain with flocculation effect of the present invention has specificity. This strain has a synergistic effect in the compound agent, which can significantly improve biogas production and biogas yield, and has high methane selectivity. It can also reduce the CODcr value of discharged water, and has high environmental protection performance.

[0030] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products, characterized in that: Includes the following steps: Step 1: The organic wastewater from soybean products collected by the sump screen is transported to the coagulation sedimentation tank, where the pH is adjusted and compound agents are added for coagulation sedimentation treatment. After removing the sludge, the wastewater enters the next process. The composite agent is prepared from the following raw materials by weight: 22-33 parts of polyaluminum chloride, 1-3 parts of polyacrylamide, 54-70 parts of quaternary ammonium salt cationic demulsifier, 6-12 parts of modified straw biomass charcoal, and 1-2 parts of Streptococcus thermophilus YXX1. 3 ; The method for obtaining the modified straw biochar is as follows: (1) After the dried biomass straw is crushed and sieved, it is added to a 2-7 mol / L ZnCl2 solution at a ratio of 1g:1-10mL. After stirring evenly, it is sealed, impregnated and activated, and then dried. Under a nitrogen atmosphere, it is kept at 500-800℃ for 30-50min. The resulting carbonization product is washed with distilled water until neutral, dried, ground and sieved to obtain straw biochar. (2) Add straw biochar to 0.5-2 mol / L citric acid solution at a ratio of 1 g: 10 mL, shake at room temperature for 5-7 h, then vacuum filter, wash until neutral, and dry to obtain straw biochar-COOH; (3) Add straw biochar-COOH to a 0.3-0.8 mol / L FeCl3 solution at a ratio of 1 g: 30 mL, shake at room temperature for 3-5 h, then vacuum filter, wash until neutral, and dry to obtain straw biochar-Fe 3+ ; (4) The straw biochar-Fe 3+ Add the straw biochar-Fe at a ratio of 1g:50mL to a 2-5wt% aqueous solution of dimethyl diallyl ammonium chloride, shake at room temperature for 2-4 hours, then vacuum filter and dry to obtain straw biochar-Fe. 3+ - Dimethyl diallyl ammonium chloride, i.e. modified straw biochar; Step 2: The wastewater from Step 1 is treated with dissolved air flotation to remove scum, and then transported to a black film anaerobic tank for anaerobic fermentation. Step 3: The effluent from the black membrane anaerobic tank is used directly for irrigation or discharged after further treatment; The advanced treatment includes treating the effluent from the black membrane anaerobic tank using the AO two-stage activated sludge process, followed by sedimentation and coagulation to remove sludge, and finally discharging clean water.

2. The biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products according to claim 1, characterized in that: The biomass straw is at least one of corn straw, soybean straw, and rice straw.

3. The biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products according to claim 1, characterized in that: The method for obtaining the composite agent is as follows: the modified straw biochar is mixed with polyaluminum chloride solution, the pH is adjusted to 3.5-4.0, and the mixture is stirred at 200 r / min for 1-2 h. Add polyacrylamide solution, adjust pH to 6-7, and stir at 100 r / min for 1-2 h; finally add quaternary ammonium salt cationic demulsifier solution, adjust pH to 7-8, and stir at 200 r / min for 20-40 min; after vacuum filtration and drying, the product is mixed with thermophilic streptococcus YXX1 to obtain a composite agent.

4. The biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products according to claim 1, characterized in that: In step one, the grid spacing of the water collection well grid is 1-7mm.

5. The biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products according to claim 1, characterized in that: In step two, during the dissolved air flotation process, the air dissolved in the water is released as microbubbles of 20-30 μm.

6. The biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products according to claim 1, characterized in that: In step two, the top of the black membrane anaerobic tank is made of 1-2 mm HDPE membrane, and the bottom and sidewalls are made of 0.5-1.5 mm HDPE membrane.

7. The biochemical treatment method for high-concentration organic wastewater generated during the preparation of soy products according to claim 1, characterized in that: In step two, the fermentation temperature in the black film anaerobic tank is 20℃-30℃, and the fermentation time is 2-3 months.