Biological denitrification composite carbon source for sewage plant and preparation method thereof

Abstract

This invention provides a method for preparing a biological denitrification composite carbon source for wastewater treatment plants, belonging to the field of wastewater treatment. The method includes the following steps: 1. Crushing kitchen waste residue, treating it in boiling water, cooling it, and then fermenting it to obtain a carbon source fermentation broth; 2. Filtering the carbon source fermentation broth, adding an accelerator and straw fragments to the liquid-phase carbon source broth to obtain a liquid-phase carbon source, mixing the liquid-phase carbon source and solid-phase carbon source evenly, and crushing them to obtain a carbon source mixture; 3. Spraying an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, molding it, and drying it to obtain the aforementioned biological denitrification composite carbon source for wastewater treatment plants. The biological denitrification composite carbon source prepared by this invention can simultaneously and slowly release the solid and liquid components in the carbon source fermentation broth, and also promotes the effective utilization of the carbon source by denitrifying bacteria, exhibiting good denitrification utilization.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a biological denitrification composite carbon source for wastewater treatment plants and its preparation method. Background Technology

[0002] As eutrophication of water bodies becomes increasingly severe, wastewater discharge standards are becoming more and more stringent. Wastewater needs to undergo denitrification treatment before entering the environment, and denitrification biological denitrification packages are currently the most commonly used denitrification method in wastewater treatment.

[0003] Biological denitrification primarily relies on the metabolism of denitrifying microorganisms to degrade pollutants. These microorganisms are heterotrophic and require a continuous supply of large amounts of carbon to remove nitrate nitrogen. The most direct and effective method is the addition of a carbon source. However, due to the diversity of denitrifying microbial communities, a single carbon source weakens this diversity, hindering the system's resilience to shock loads. Therefore, the carbon source composition is a key factor limiting the efficiency of total nitrogen removal by denitrifying microorganisms. Current technologies utilize film-forming materials to achieve slow-release of carbon sources and maintain a continuous supply, thus improving denitrification efficiency. However, these film-forming materials are difficult to maintain in wastewater environments, failing to achieve long-term, uniform slow-release. Furthermore, the carbon source is difficult for denitrifying bacteria to effectively absorb and utilize, resulting in excessive carbon input and resource waste.

[0004] In summary, there is an urgent need for a biological carbon source for nitrogen removal that can achieve both long-term, uniform, and slow release of carbon and ensure that the carbon source is effectively absorbed and utilized by denitrifying bacteria. Summary of the Invention

[0005] To address the problems existing in the background technology, the present invention provides a biological denitrification composite carbon source for wastewater treatment plants and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a biological denitrification composite carbon source for wastewater treatment plants includes the following:

[0008] S1. Crush the kitchen waste residue and pass it through an 80-100 mesh sieve to obtain kitchen waste residue fragments. Add the kitchen waste residue fragments to boiling water, where the mass ratio of kitchen waste residue fragments to water is 1:10. Stir evenly and treat in boiling water for 1-2 hours. Cool to obtain a mixed liquid. Add fermentation bacteria to the mixed liquid and let it ferment for 3-5 days to obtain a carbon source fermentation liquid.

[0009] S2. Filter the carbon source fermentation liquid to obtain solid carbon source and liquid carbon source liquid separately. Treat the liquid carbon source liquid separately. First, add the accelerator to the liquid carbon source liquid and stir evenly. Then add 60-70 mesh straw fragments, soak fully, concentrate under reduced pressure, and dry to obtain liquid carbon source. Then mix the liquid carbon source and solid carbon source evenly, crush, and pass through a 16-20 mesh sieve to obtain carbon source mixture. The mass ratio of liquid carbon source, accelerator and straw fragments is 1000:(4-6):(30-50).

[0010] S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain the biological denitrification composite carbon source for wastewater treatment plants.

[0011] The preparation of the accelerator in step S2 includes the following steps: under stirring conditions, add 25-35 parts itaconic acid and 3-5 parts acrylamide to 100 parts water, mix evenly, control the temperature at 70-90℃, and then add 1.5-2 parts hydroxypropyl acrylate and 0.4-0.6 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 2-3 hours, cool, and obtain the accelerator.

[0012] Preferably, the preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0013] (A1) By weight, 1 part of nano-SiO2 and 0.15~0.25 parts of methacrylate are added to 40~60 parts of anhydrous ethanol, sulfuric acid is added to adjust the pH to 3~4, the mixture is heated to 50~60℃, stirred for 4~6h under nitrogen protection, filtered, and dried to obtain modified SiO2.

[0014] (A2) Add 4-6 parts of polyvinyl alcohol and 0.6-1 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 60-70℃, and stir for 2-4 hours to obtain a pretreated polyvinyl alcohol solution;

[0015] (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 15-25 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

[0016] Preferably, the amount of alkenylated polyvinyl alcohol solution added in step S3 is 2 to 2.5% of the mass of the carbon source mixture.

[0017] Preferably, the fermentation strain in step S1 is Bacillus subtilis (solid freeze-dried powder, 5.2 × 10⁻⁶). 8 CFU / g) and Lactobacillus (solid lyophilized powder, 2.1×10⁻⁶) 8 The mixed strain (CFU / g) contains Bacillus subtilis and Lactobacillus in a mass ratio of 1:(1.8~2.2), and is added at a rate of 0.1~0.2% (w / w) of the mass of the mixed liquid.

[0018] Preferably, the straw in step S2 is one or a mixture of at least two of the following: corn straw, sorghum straw, rice straw, wheat straw, and oat straw.

[0019] This application has the following beneficial effects:

[0020] 1. The biological denitrification composite carbon source provided by this invention uses kitchen waste as raw material, realizing waste utilization. After fermentation, the kitchen waste is rich in nutrients and contains trace elements and probiotics that are easily absorbed by microorganisms, which is conducive to enhancing the diversity of the microbial community. After fermentation of kitchen waste, the liquid part of the carbon source fermentation liquid is treated separately and then mixed with solid carbon source. It is coated with alkenylated polyvinyl alcohol, which can simultaneously release the solid and liquid components in the carbon source fermentation liquid and promote the effective utilization of carbon source by denitrifying bacteria, resulting in good denitrification utilization.

[0021] 2. The alkenylation treatment of polyvinyl alcohol can improve its hydrophobic properties and enhance its coating effect on carbon sources in wastewater systems, thereby improving the slow-release effect of carbon sources and the denitrification efficiency of microorganisms. The addition of accelerators can prevent precipitation from accumulating on the surface of carbon sources, avoiding and reducing the impact of precipitation on biological activity and reverse digestion efficiency. At the same time, the alkenylation treatment of polyvinyl alcohol and accelerators can work synergistically to form a coating layer on the outer layer of carbon sources, further improving denitrification efficiency. Detailed Implementation

[0022] The present application will be further described in detail below with reference to the embodiments.

[0023] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available. Example 1

[0024] A method for preparing a biological denitrification composite carbon source for wastewater treatment plants includes the following:

[0025] S1. Crush the kitchen waste residue, pass it through an 80-mesh sieve to obtain kitchen waste residue fragments, add the kitchen waste residue fragments to boiling water, wherein the mass ratio of kitchen waste residue fragments to water is 1:10, stir evenly, treat in boiling water for 1 hour, cool to obtain a mixed liquid, add fermentation bacteria to the mixed liquid, let it stand for 4 days to obtain carbon source fermentation liquid.

[0026] S2. Filter the carbon source fermentation broth to obtain solid carbon source and liquid carbon source liquid separately. The liquid carbon source liquid is processed separately. First, add the accelerator to the liquid carbon source liquid and stir evenly. Then add 60-mesh straw fragments, soak them fully, concentrate under reduced pressure, and dry to obtain liquid carbon source. Then mix the liquid carbon source and solid carbon source evenly, crush them, and pass them through a 16-mesh sieve to obtain carbon source mixture. The straw is a mixture of corn straw and wheat straw in a mass ratio of 1:1. The mass ratio of liquid carbon source liquid, accelerator and straw fragments is 1000:5:40.

[0027] S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain a composite carbon source for biological denitrification in wastewater treatment plants.

[0028] The preparation of the accelerator in step S2 includes the following: under stirring conditions, add 30 parts itaconic acid and 4 parts acrylamide to 100 parts water, mix evenly, control the temperature at 80°C, and then add 1.5 parts hydroxyethyl acrylate and 0.5 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 2 hours, cool, and obtain the accelerator.

[0029] The preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0030] (A1) By weight, 1 part of nano SiO2 and 0.2 parts of methacrylate were added to 50 parts of anhydrous ethanol, sulfuric acid was added to adjust the pH to 3-4, the mixture was heated to 55°C, stirred for 5 hours under nitrogen protection, filtered, and dried to obtain modified SiO2.

[0031] (A2) Add 5 parts of polyvinyl alcohol and 0.8 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 65°C and stir for 3 hours to obtain a pretreated polyvinyl alcohol solution;

[0032] (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 20 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

[0033] In step S3, the amount of alkenylated polyvinyl alcohol solution added is 2.2% of the mass of the carbon source mixture.

[0034] The fermentation strain mentioned in step S1 is Bacillus subtilis (solid freeze-dried powder, 5.2 × 10⁻⁶). 8 CFU / g) and Lactobacillus (solid lyophilized powder, 2.1×10⁻⁶) 8 The mixed strain (CFU / g) contains Bacillus subtilis and Lactobacillus in a mass ratio of 1:2, and the amount of fermentation strain added is 0.15% (w / w) of the mixed liquid. Example 2

[0035] A method for preparing a biological denitrification composite carbon source for wastewater treatment plants includes the following:

[0036] S1. Crush the kitchen waste residue and pass it through an 80-mesh sieve to obtain kitchen waste residue fragments. Add the kitchen waste residue fragments to boiling water, where the mass ratio of kitchen waste residue fragments to water is 1:10. Stir evenly and treat in boiling water for 2 hours. Cool to obtain a mixed liquid. Add fermentation bacteria to the mixed liquid and let it stand for 3 days to obtain a carbon source fermentation liquid.

[0037] S2. Filter the carbon source fermentation broth to obtain solid carbon source and liquid carbon source liquid separately. The liquid carbon source liquid is processed separately. First, add the accelerator to the liquid carbon source liquid and stir evenly. Then add 70-mesh straw fragments, soak fully, concentrate under reduced pressure, and dry to obtain liquid carbon source. Then mix the liquid carbon source and solid carbon source evenly, crush, and pass through a 20-mesh sieve to obtain carbon source mixture. The straw is corn straw, and the mass ratio of liquid carbon source, accelerator and straw fragments is 1000:4:30.

[0038] S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain the biological denitrification composite carbon source for wastewater treatment plants.

[0039] The preparation of the accelerator in step S2 includes the following: under stirring conditions, add 25 parts itaconic acid and 3 parts acrylamide to 100 parts water, mix evenly, control the temperature at 70°C, and then add 1.5 parts hydroxypropyl acrylate and 0.4 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 2 hours, cool, and obtain the accelerator.

[0040] The preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0041] (A1) By weight, 1 part of nano SiO2 and 0.15 parts of methacrylate were added to 40 parts of anhydrous ethanol, sulfuric acid was added to adjust the pH to 3-4, the mixture was heated to 50°C, stirred for 4 hours under nitrogen protection, filtered, and dried to obtain modified SiO2.

[0042] (A2) Add 4 parts of polyvinyl alcohol and 0.6 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 70°C, and stir for 2 hours to obtain a pretreated polyvinyl alcohol solution.

[0043] (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 25 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

[0044] In step S3, the amount of alkenylated polyvinyl alcohol solution added is 2% of the mass of the carbon source mixture.

[0045] The fermentation strain mentioned in step S1 is a mixed strain of Bacillus subtilis (solid freeze-dried powder, 5.2×10⁸ CFU / g) and Lactobacillus (solid freeze-dried powder, 2.1×10⁸ CFU / g), with a mass ratio of Bacillus subtilis to Lactobacillus of 1:1.8, and the amount of fermentation strain added is 0.1% (w / w) of the mixed liquid. Example 3

[0046] A method for preparing a biological denitrification composite carbon source for wastewater treatment plants includes the following:

[0047] S1. Crush the kitchen waste residue and pass it through a 100-mesh sieve to obtain kitchen waste residue fragments. Add the kitchen waste residue fragments to boiling water, where the mass ratio of kitchen waste residue fragments to water is 1:10. Stir evenly and treat in boiling water for 1 hour. Cool to obtain a mixed liquid. Add fermentation bacteria to the mixed liquid and let it stand for 3 days to obtain a carbon source fermentation liquid.

[0048] S2. Filter the carbon source fermentation broth to obtain solid-phase carbon source and liquid-phase carbon source solutions separately. The liquid-phase carbon source solution is treated separately: first, an accelerator is added and stirred evenly; then, 60-mesh straw fragments are added, fully soaked, concentrated under reduced pressure, and dried to obtain the liquid-phase carbon source. The liquid-phase carbon source and solid-phase carbon source are then mixed evenly, pulverized, and passed through a 20-mesh sieve to obtain a carbon source mixture. The straw is oat straw, and the mass ratio of liquid-phase carbon source, accelerator, and straw fragments is 1000:4:50.

[0049] S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain the biological denitrification composite carbon source for wastewater treatment plants.

[0050] The preparation of the accelerator in step S2 includes the following: under stirring conditions, add 35 parts itaconic acid and 3 parts acrylamide to 100 parts water, mix evenly, control the temperature at 90°C, and then add 2 parts hydroxypropyl acrylate and 0.4 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 2 hours, cool, and obtain the accelerator.

[0051] The preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0052] (A1) By weight, 1 part of nano SiO2 and 0.15 parts of methacrylate were added to 60 parts of anhydrous ethanol, sulfuric acid was added to adjust the pH to 3-4, the mixture was heated to 50°C, stirred for 6 hours under nitrogen protection, filtered, and dried to obtain modified SiO2.

[0053] (A2) Add 5 parts of polyvinyl alcohol and 0.6 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 65°C and stir for 3 hours to obtain a pretreated polyvinyl alcohol solution.

[0054] (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 25 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

[0055] In step S3, the amount of alkenylated polyvinyl alcohol solution added is 2.3% of the mass of the carbon source mixture.

[0056] The fermentation strain mentioned in step S1 is a mixed strain of Bacillus subtilis (solid freeze-dried powder, 5.2×10⁸ CFU / g) and Lactobacillus (solid freeze-dried powder, 2.1×10⁸ CFU / g), with a mass ratio of Bacillus subtilis to Lactobacillus of 1:2, and the amount of fermentation strain added is 0.2% (w / w) of the mixed liquid. Example 4

[0057] A method for preparing a biological denitrification composite carbon source for wastewater treatment plants includes the following:

[0058] S1. Crush the kitchen waste residue and pass it through a 100-mesh sieve to obtain kitchen waste residue fragments. Add the kitchen waste residue fragments to boiling water, where the mass ratio of kitchen waste residue fragments to water is 1:10. Stir evenly and treat in boiling water for 2 hours. Cool to obtain a mixed liquid. Add fermentation bacteria to the mixed liquid and let it stand for 5 days to obtain a carbon source fermentation liquid.

[0059] S2. Filter the carbon source fermentation broth to obtain solid carbon source and liquid carbon source liquid separately. The liquid carbon source liquid is processed separately. First, add the accelerator to the liquid carbon source liquid and stir evenly. Then add 70-mesh straw fragments, soak fully, concentrate under reduced pressure, and dry to obtain liquid carbon source. Then mix the liquid carbon source and solid carbon source evenly, crush, and pass through a 20-mesh sieve to obtain carbon source mixture. The straw is wheat straw, and the mass ratio of liquid carbon source, accelerator and straw fragments is 1000:6:50.

[0060] S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain the biological denitrification composite carbon source for wastewater treatment plants.

[0061] The preparation of the accelerator in step S2 includes the following: under stirring conditions, add 35 parts itaconic acid and 5 parts acrylamide to 100 parts water, mix evenly, control the temperature at 90°C, and then add 2 parts hydroxypropyl acrylate and 0.6 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 3 hours, cool, and obtain the accelerator.

[0062] The preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0063] (A1) By weight, 1 part of nano SiO2 and 0.25 parts of methacrylate were added to 60 parts of anhydrous ethanol, sulfuric acid was added to adjust the pH to 3-4, the mixture was heated to 60°C, stirred for 4 hours under nitrogen protection, filtered, and dried to obtain modified SiO2.

[0064] (A2) Add 6 parts of polyvinyl alcohol and 1 part of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 60°C and stir for 4 hours to obtain a pretreated polyvinyl alcohol solution.

[0065] (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 15 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

[0066] In step S3, the amount of alkenylated polyvinyl alcohol solution added is 2% of the mass of the carbon source mixture.

[0067] The fermentation strain mentioned in step S1 is a mixed strain of Bacillus subtilis (solid freeze-dried powder, 5.2×10⁸ CFU / g) and Lactobacillus (solid freeze-dried powder, 2.1×10⁸ CFU / g), with a mass ratio of Bacillus subtilis to Lactobacillus of 1:1.8, and the amount of fermentation strain added is 0.2% (w / w) of the mixed liquid. Example 5

[0068] A method for preparing a biological denitrification composite carbon source for wastewater treatment plants includes the following:

[0069] S1. Crush the kitchen waste residue and pass it through an 80-mesh sieve to obtain kitchen waste residue fragments. Add the kitchen waste residue fragments to boiling water, where the mass ratio of kitchen waste residue fragments to water is 1:10. Stir evenly and treat in boiling water for 2 hours. Cool to obtain a mixed liquid. Add fermentation bacteria to the mixed liquid and let it stand for 4 days to obtain a carbon source fermentation liquid.

[0070] S2. Filter the carbon source fermentation broth to obtain solid carbon source and liquid carbon source liquid separately. The liquid carbon source liquid is processed separately. First, add the accelerator to the liquid carbon source liquid and stir evenly. Then add 60-mesh straw fragments, soak fully, concentrate under reduced pressure, and dry to obtain liquid carbon source. Then mix the liquid carbon source and solid carbon source evenly, crush, and pass through a 16-mesh sieve to obtain carbon source mixture. The straw is rice straw, and the mass ratio of liquid carbon source, accelerator and straw fragments is 1000:5:30.

[0071] S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain the biological denitrification composite carbon source for wastewater treatment plants.

[0072] The preparation of the accelerator in step S2 includes the following: under stirring conditions, add 25 parts itaconic acid and 3 parts acrylamide to 100 parts water, mix evenly, control the temperature at 80°C, and then add 2 parts hydroxypropyl acrylate and 0.4 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 3 hours, cool, and obtain the accelerator.

[0073] The preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0074] (A1) By weight, 1 part of nano SiO2 and 0.25 parts of methacrylate were added to 50 parts of anhydrous ethanol, sulfuric acid was added to adjust the pH to 3-4, the mixture was heated to 55°C, stirred for 4 hours under nitrogen protection, filtered, and dried to obtain modified SiO2.

[0075] (A2) Add 6 parts of polyvinyl alcohol and 0.6 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 70°C, and stir for 2 hours to obtain a pretreated polyvinyl alcohol solution.

[0076] (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 25 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

[0077] In step S3, the amount of alkenylated polyvinyl alcohol solution added is 2.5% of the mass of the carbon source mixture.

[0078] The fermentation strain mentioned in step S1 is a mixed strain of Bacillus subtilis (solid freeze-dried powder, 5.2×10⁸ CFU / g) and Lactobacillus (solid freeze-dried powder, 2.1×10⁸ CFU / g), with a mass ratio of Bacillus subtilis to Lactobacillus of 1:2.2, and the amount of fermentation strain added is 0.2% (w / w) of the mixed liquid. Comparative Example 1

[0079] The only difference between this comparative example and Example 1 is that, in step S2, the liquid carbon source liquid is not separated into solid and liquid phases; instead, the carbon source fermentation broth is processed together. The specific details are as follows:

[0080] S2. Add an accelerator to the carbon source fermentation liquid, then add 60-mesh straw fragments, soak thoroughly, concentrate under reduced pressure, and dry to obtain a carbon source mixture, wherein the mass ratio of carbon source fermentation liquid, accelerator and straw fragments is 1000:5:40. Comparative Example 2

[0081] The only difference between this comparative example and Example 1 is that no accelerator was added in step S2. Comparative Example 3

[0082] The only difference between this comparative example and Example 1 is that, in the preparation of the alkenylated polyvinyl alcohol solution in step S3, the polyvinyl alcohol was not subjected to alkenylation treatment. The specific details are as follows:

[0083] The preparation of the alkenylated polyvinyl alcohol solution in step S3 includes the following:

[0084] (A1) Add 5 parts of polyvinyl alcohol and 0.8 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 65°C, and stir for 3 hours to obtain a pretreated polyvinyl alcohol solution.

[0085] (A2) The pretreated polyvinyl alcohol solution was stirred under ultraviolet light for 20 min to obtain an alkenylated polyvinyl alcohol solution. Comparative Example 4

[0086] The only difference between this comparative example and Example 1 is that no accelerator was added in step S2, and the polyvinyl alcohol was not alkenylated in the preparation of the alkenylated polyvinyl alcohol solution in step S3.

[0087] Proof of effectiveness

[0088] Wastewater samples from a wastewater treatment plant were selected for denitrification experiments. The sludge concentration was 3.7 g / L, and the raw water contained 85 mg / L total nitrogen and 80 mg / L COD. 1000 mL of water sample was placed in a closed reactor, with the temperature controlled at 30 ± 1℃ and the stirring speed at 150 rpm. Nitrogen gas was continuously introduced to maintain dissolved oxygen ≤0.5 mg / L. The initial pH was adjusted to 7.5, and the denitrification composite carbon sources from Examples 1-5 and Comparative Examples 1-4 were added according to a C / N ratio of 6. The experiment was conducted in the dark throughout, with samples taken at 4 h, 8 h, and 24 h. After filtration through a 0.45 μm filter membrane, the nitrogen concentration was determined by ultraviolet spectrophotometry, and the denitrification rate was calculated. Specific results are shown in Table 1.

[0089] Table 1

[0090]

[0091] Results Analysis

[0092] Analysis of Examples 1-5 and Comparative Examples 1-4, and in conjunction with Table 1, shows that the biological nitrogen removal composite carbon source for wastewater treatment plants provided by this invention achieves a nitrogen removal rate of over 98.1%, enabling highly efficient nitrogen removal from wastewater. Specific analysis is as follows:

[0093] Compared with Example 1, in Comparative Example 1, the liquid carbon source liquid was not separated into solid and liquid phases in step 2. Instead, the carbon source fermentation liquid was treated together. The denitrification rate during the denitrification process remained low and the final denitrification rate was significantly reduced. This indicates that separating the carbon source fermentation liquid into solid and liquid phases and treating the liquid carbon source liquid separately has a significant impact on the denitrification effect and can significantly improve the denitrification rate.

[0094] Compared with Example 1, no accelerator was added in step 2 of Comparative Example 2. The denitrification rate decreased at 4h and 8h, and the final denitrification rate decreased significantly, indicating that the accelerator can significantly improve the denitrification efficiency.

[0095] Compared with Example 1, in the preparation of the alkenylated polyvinyl alcohol solution in step 3, the polyvinyl alcohol was not alkenylated. The denitrification rate decreased in the 4th and 8th hours, and the final denitrification rate was significantly reduced. The alkenylation treatment of polyvinyl alcohol can significantly improve the denitrification efficiency.

[0096] Compared with Example 1, no accelerator was added in step 2 of Comparative Example 4, and no alkenylation treatment was performed on polyvinyl alcohol in the preparation of the alkenylated polyvinyl alcohol solution in step 3. The denitrification rate decreased in the 4th and 8th hours, and the final denitrification rate decreased significantly. Combined with Comparative Examples 2-3, this shows that the accelerator and the alkenylation treatment of polyvinyl alcohol can interact to produce a synergistic effect and jointly improve the denitrification efficiency.

[0097] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0098] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a biological denitrification composite carbon source for wastewater treatment plants, characterized in that, The preparation method includes the following: S1. Crush the kitchen waste residue and pass it through an 80-100 mesh sieve to obtain kitchen waste residue fragments. Add the kitchen waste residue fragments to boiling water, where the mass ratio of kitchen waste residue fragments to water is 1:

10. Stir evenly and treat in boiling water for 1-2 hours. Cool to obtain a mixed liquid. Add fermentation bacteria to the mixed liquid and let it ferment for 3-5 days to obtain a carbon source fermentation liquid. S2. Filter the carbon source fermentation liquid to obtain solid carbon source and liquid carbon source liquid separately. Treat the liquid carbon source liquid separately. First, add the accelerator to the liquid carbon source liquid and stir evenly. Then add 60-70 mesh straw fragments, soak fully, concentrate under reduced pressure, and dry to obtain liquid carbon source. Then mix the liquid carbon source and solid carbon source evenly, crush, and pass through a 16-20 mesh sieve to obtain carbon source mixture. The mass ratio of liquid carbon source liquid, accelerator and straw fragments is 1000:(4-6):(30-50). S3. Spray an alkenylated polyvinyl alcohol solution onto the surface of the carbon source mixture, stir evenly, shape, and dry to obtain the biological denitrification composite carbon source for wastewater treatment plants; The preparation of the accelerator in step S2 includes the following: by weight, under stirring conditions, add 25-35 parts itaconic acid and 3-5 parts acrylamide to 100 parts water, mix evenly, control the temperature at 70-90℃, and then add 1.5-2 parts hydroxypropyl acrylate and 0.4-0.6 parts ammonium peroxide dropwise. After the addition is complete, keep warm for 2-3 hours, cool, and obtain the accelerator; The method for preparing the alkenylated polyvinyl alcohol solution in step S3 includes the following: (A1) By weight, 1 part of nano SiO2 and 0.15-0.25 parts of methacrylate are added to 40-60 parts of anhydrous ethanol, sulfuric acid is added to adjust the pH to 3-4, the mixture is heated to 50-60℃, stirred for 4-6 hours under nitrogen protection, filtered, and dried to obtain modified SiO2. (A2) Add 4-6 parts of polyvinyl alcohol and 0.6-1 parts of mercaptoacetic acid to 200 parts of 5% sulfuric acid solution, heat to 60-70℃, and stir for 2-4 hours to obtain a pretreated polyvinyl alcohol solution. (A3) Add modified SiO2 to the pretreated polyvinyl alcohol solution and stir for 15-25 min under ultraviolet light irradiation to obtain an alkenylated polyvinyl alcohol solution.

2. The method for preparing a biological denitrification composite carbon source for wastewater treatment plants according to claim 1, characterized in that, In step S3, the amount of alkenylated polyvinyl alcohol solution added is 2-2.5% of the mass of the carbon source mixture.

3. The method for preparing a biological denitrification composite carbon source for wastewater treatment plants according to claim 1, characterized in that, The fermentation strain mentioned in step S1 is 5.2 × 10⁻⁶. 8 CFU / g Bacillus subtilis solid lyophilized powder and 2.1×10 8 The mixed strain of CFU / g Lactobacillus solid freeze-dried powder has a Bacillus subtilis to Lactobacillus mass ratio of 1:(1.8-2.2) and is added at a rate of 0.1-0.2% (w / w) of the mixed liquid mass.

4. The method for preparing a biological denitrification composite carbon source for wastewater treatment plants according to claim 1, characterized in that, The straw mentioned in step S2 is one or a mixture of at least two of the following: corn straw, sorghum straw, rice straw, wheat straw, and oat straw.

5. A composite carbon source for biological nitrogen removal in wastewater treatment plants, characterized in that, It is prepared by the method described in any one of claims 1-4 for a biological denitrification composite carbon source for wastewater treatment plants.

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