A method for treating wastewater containing ammonia nitrogen

Abstract

The application provides a treatment method of ammonia-nitrogen-containing wastewater, and belongs to the technical field of wastewater treatment; a preparation process thereof comprises the following steps: preparation of a wastewater treatment agent; preparation of an immobilized microbial compound; and treatment of ammonia-nitrogen-containing wastewater. The immobilized microbial carrier prepared by the application forms a stable double-network structure and suitable pores through the synergistic effect of polyvinyl alcohol, carboxymethyl chitosan and polyurethane; secondary crosslinking significantly enhances the stability of the carrier, optimizes the internal pores, and is beneficial to the adhesion and proliferation of microorganisms; the specific surface area and functional groups of the corn straw biochar are improved after Ca / Al modification, and the physicochemical adsorption of ammonia-nitrogen is enhanced. Through the combination of the three, the ammonia-nitrogen in wastewater is efficiently removed through the synergistic effect of carrier adsorption and microbial metabolism.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and specifically to a method for treating wastewater containing ammonia nitrogen. Background Technology

[0002] Ammonia nitrogen is a significant contributor to eutrophication and environmental pollution. Its large-scale discharge not only leads to excessive algal blooms, disrupting the aquatic ecosystem and causing environmental problems such as red tides and algal blooms, but also poses a toxic effect on aquatic organisms, inhibiting the growth and reproduction of fish and other aquatic life. Furthermore, under certain conditions, ammonia nitrogen can be converted into nitrites and nitrates, posing a potential threat to human health. For example, nitrites can be converted into carcinogenic nitrosamines after entering the human body.

[0003] Currently, the main methods for treating ammonia nitrogen-containing wastewater include physical, chemical, and biological methods. While physical methods offer high treatment efficiency, they suffer from high energy consumption and the potential for secondary pollution. Chemical methods, although fast, require large dosages of chemicals, resulting in high costs, and some chemicals may introduce new pollutants. Biological methods struggle to maintain long-term operational stability. Therefore, the practical application of these methods is limited. Immobilized microorganism technology can immobilize microorganisms within a porous carrier, protecting them while maintaining their activity, thus contributing to long-term denitrification stability.

[0004] PVA, as the most commonly used embedding material, has become the first choice for many research and practical applications due to its low price, high chemical stability, and good biocompatibility. However, PVA-based carriers have obvious drawbacks: their mechanical strength is poor, making them prone to breakage during actual treatment; adhesion can also occur during use, affecting treatment efficiency and ease of operation. The low mechanical strength and overly dense pore distribution of PVA-based carriers limit further improvement in ammonia nitrogen removal efficiency, making it difficult to meet increasingly stringent environmental protection requirements.

[0005] Therefore, we propose a method for treating ammonia nitrogen-containing wastewater, which can efficiently remove ammonia nitrogen from the wastewater. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for treating ammonia nitrogen-containing wastewater.

[0007] A method for treating ammonia nitrogen-containing wastewater includes the following steps: S1: Preparation of wastewater treatment agents Biochar was prepared from corn stalk powder and modified with calcium / aluminum to prepare a wastewater treatment agent. S2: Preparation of immobilized microbial complexes Using polyvinyl alcohol, carboxymethyl chitosan and waterborne polyurethane as carrier materials, and loading microbial culture, the immobilized microbial complex was prepared by cross-linking with aluminum sulfate octadecahydrate and boric acid, and then cross-linking with anhydrous sodium sulfate. S3: Treatment of ammonia nitrogen-containing wastewater The landfill leachate is pretreated, then nitrification-denitrification is carried out using an immobilized microbial complex to obtain secondary treated wastewater. The secondary treated wastewater is then treated with a wastewater treatment agent, and finally passed through a granular activated carbon column to obtain the final treated wastewater.

[0008] Furthermore, the preparation of the wastewater treatment agent in step S1 specifically includes the following steps: S1.1: Mix calcium chloride and aluminum chloride in a calcium / aluminum molar ratio of 1:1, add the mixture to deionized water, adjust the pH to 2-3, stir and mix for 20-30 min to prepare a mixed solution with a total concentration of 1-2 mol / L. S1.2: Add 10-12 parts by weight of dried corn stalk powder to 100-120 parts by weight of mixed solution, mix and stir at 300-500 rpm for 20-30 min, and then shake at 160-180 rpm in a 25-28℃ air bath constant temperature shaker for 20-24 h to obtain the mixture; S1.3: Centrifuge the mixture at 3000-3500 rpm for 6-8 min, then dry and grind it. Pyrolyze the powder obtained by grinding in a muffle furnace at 550-580℃ for 100-105 min under nitrogen atmosphere at a heating rate of 5-8℃ / min. Then hold at the temperature for 60-70 min, cool down, wash 3-5 times, and dry to obtain the wastewater treatment agent.

[0009] Further, step S2, preparing the immobilized microbial complex, specifically includes the following steps: S2.1: Add 10-12 parts by weight of polyvinyl alcohol to 80-90 parts by weight of deionized water, stir at 90-92℃ and 240-260 rpm for 2-3 hours, then cool to 50-52℃, then add 1-2 parts by weight of carboxymethyl chitosan, stir at 360-400 rpm for 2-3 hours, cool to room temperature, then add 1-2 parts by weight of aqueous polyurethane, stir and mix for 20-30 minutes to obtain a mixed gel solution; S2.2: Add microbial culture to the mixed gel solution, then stir and mix at 360-400 rpm for 1-2 hours to obtain a mixture. Then, use a syringe to drop the mixture into the cross-linking solution at a uniform rate, cross-link for 60-70 minutes, and then wash with deionized water 2-3 times to obtain immobilized microspheres after the first cross-linking treatment. S2.3: The immobilized microspheres that have undergone the first cross-linking treatment are added to a 0.5 mol / L anhydrous sodium sulfate solution and cross-linked for 120-130 min. Then, the microspheres are washed with deionized water 2-3 times to obtain the immobilized microbial complex.

[0010] Furthermore, the treatment of ammonia nitrogen-containing wastewater in step S3 specifically includes the following steps: S3.1: The landfill leachate is pretreated by passing it through a bar screen and an air flotation tank to remove suspended solids and grease, resulting in pretreated wastewater; S3.2: The pH of the pretreated wastewater was adjusted to 7.5-8 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex was added to the fluidized bed reactor and treated under aeration conditions of 30-32℃, DO of 2-4 mg / L, C / N ratio of 3-4 for 40-48 h to obtain the secondary treated wastewater. S3.3: Let the wastewater after secondary treatment stand for 1-2 hours, transfer the supernatant to the deep treatment unit, then add wastewater treatment agent at a rate of 1.5-2 g / L, stir at 20-30 rpm for 1-2 hours, and finally let stand for 1-2 hours, filter, and obtain the wastewater after tertiary treatment. S3.4: Pass the wastewater after three treatments through a granular activated carbon column to obtain the final treated wastewater.

[0011] Further, in step S2.2, the microbial inoculum is a suspension of nitrifying bacteria and denitrifying bacteria mixed in a mass ratio of 1:1.

[0012] Further, the cross-linking mixed solution in step S2.2 is specifically a mixed solution of 7.1-8.2 wt% aluminum sulfate octadeca and 4-5 wt% boric acid.

[0013] Furthermore, in step S3.2, the amount of immobilized microbial complex added is 2-3% (v / v) of the wastewater volume.

[0014] Further, the acclimatization process of the immobilized microbial complex in step S3.2 is as follows: the immobilized microbial complex is added to the fluidized bed reactor, and landfill leachate is added at a dosage ratio of 10-20 mg / L. Under aeration conditions, the mixture is treated for 1-2 days. Then, landfill leachate is added at a dosage ratio of 40-50 mg / L, and the mixture is treated for 2-3 days under aeration conditions. Then, landfill leachate is added at a dosage ratio of 100-120 mg / L, and the mixture is treated for 2-3 days under aeration conditions. Finally, landfill leachate is added at a dosage ratio of 200-300 mg / L, and the mixture is treated for 2-3 days under aeration conditions to obtain the acclimatized immobilized microbial complex.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention prepares a carrier for immobilized microorganisms using polyvinyl alcohol, carboxymethyl chitosan, and waterborne polyurethane as carrier raw materials. Polyvinyl alcohol plays a decisive role in the sphericity and internal pore structure of the immobilized microbial complex. Carboxymethyl chitosan has good biocompatibility, which is conducive to the adhesion and proliferation of microorganisms. It can also increase the viscosity of the gel solution, which is beneficial to the formation of the immobilized microbial complex and improve its mechanical strength. The waterborne polyurethane and polyvinyl alcohol interact with each other, causing the waterborne polyurethane molecular chains and polyvinyl alcohol molecular chains to become entangled, effectively supporting the skeleton structure of the immobilized microbial complex, improving its mechanical strength, and promoting the formation of a macroporous structure on the surface of the immobilized microbial complex. This can effectively improve the pore size of the immobilized microbial complex and give it a stable pore structure. Thus, the prepared immobilized microbial complex can achieve efficient removal of ammonia nitrogen from wastewater through the synergistic effect of the adsorption of the carrier itself and the metabolism of microorganisms.

[0016] 2. This invention effectively improves the performance of the immobilized microbial complex through a two-stage crosslinking process. The aluminum ions released from aluminum sulfate octadechydrate in the crosslinking solution can form irreversible coordination and ionic bonds with polyvinyl alcohol and carboxymethyl chitosan, rapidly constructing a rigid framework. Boric acid, on the other hand, forms reversible borate ester bonds with polyvinyl alcohol, imparting flexibility to the network. The synergistic effect of these two processes causes the polymer chains to aggregate directionally during crosslinking, spontaneously forming a uniform, interconnected pore structure. This abundant pore structure facilitates the attachment of microorganisms within the immobilized microbial complex, thereby enhancing its ammonia nitrogen removal capabilities. The immobilized microbial complex undergoes a secondary crosslinking process in anhydrous sodium sulfate solution. During this secondary crosslinking, the SO42- in the sodium sulfate solution... 2- When the microorganisms enter the interior of the composite, the hydroxyl groups on the polyvinyl alcohol become more active, and more hydrogen bonds are formed between the hydroxyl groups. This increases the degree of cross-linking of the immobilized microbial composite, thereby enhancing its stability and optimizing its pore structure, thus improving the ammonia nitrogen removal rate.

[0017] 3. In this invention, corn stalks are pyrolyzed to form a porous carbon structure with a high specific surface area and abundant pores. This structure can capture ammonia nitrogen in the solution through physical adsorption. Ca / Al modification significantly enhances the functional groups on the surface of the biochar. These functional groups enhance the chemical adsorption of pollutants in wastewater through hydrogen bonding and other interactions. Furthermore, dual metal ion modification can optimize the pore structure and specific surface area of ​​the wastewater treatment agent. The optimization of the pore structure and the increase in specific surface area of ​​the wastewater treatment agent can increase the number of surface active sites, which is beneficial for the adsorption of pollutants in wastewater and achieves the effect of wastewater purification.

[0018] 4. This invention achieves nitrification-denitrification under aeration, with its core advantage lying in the ingenious utilization of the mass transfer characteristics of the immobilized microbial complex. When oxygen diffuses into the immobilized microorganisms, the mass transfer resistance causes a significant oxygen concentration gradient between the inside and outside of the microorganisms. Under the influence of this concentration difference, an anaerobic or hypoxic environment is formed in local areas inside the immobilized microorganisms, providing suitable survival and metabolic conditions for denitrifying bacteria. At the same time, the aerobic area outside the immobilized microorganisms can meet the growth requirements of nitrifying bacteria. Based on this, the immobilized microbial complex can simultaneously support nitrifying and denitrifying bacteria, achieving simultaneous nitrification and denitrification, significantly improving wastewater treatment efficiency and simplifying the treatment process. Attached Figure Description

[0019] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate embodiments of the invention and, together with the specification, further serve to explain the principles of the invention and enable those skilled in the art to practice and use the invention.

[0020] Figure 1 This is a flowchart of a method for treating ammonia nitrogen-containing wastewater used in an embodiment of the present invention; Figure 2 The images show SEM images of the immobilized microbial complexes prepared in Example 1 and Comparative Example 5 of this invention. Figure 3 The images show the Fourier transform infrared spectra of the wastewater treatment agents prepared in Example 1 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0021] The method for treating ammonia-nitrogen-containing wastewater provided by the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0022] Example 1 A method for treating ammonia nitrogen-containing wastewater, such as Figure 1 As shown, it includes the following steps: S1: Preparation of wastewater treatment agents S1.1: Calcium chloride and aluminum chloride are mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH is adjusted to 2, and the mixture is stirred for 20 min to prepare a mixed solution with a total concentration of 1 mol / L. S1.2: Add 10 parts by weight of dried corn stalk powder to 100 parts by weight of mixed solution, mix and stir at 300 rpm for 20 min, and then shake at 160 rpm for 20 h in a 25℃ air bath constant temperature shaker to obtain a mixture; S1.3: The mixture was centrifuged at 3000 rpm for 6 min, then dried and ground. The powder obtained from the grinding was pyrolyzed in a muffle furnace at 550℃ for 100 min under nitrogen atmosphere at a heating rate of 5℃ / min. After holding at the temperature for 60 min, the mixture was cooled, washed 3 times, and dried to obtain the wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: Add 10 parts by weight of polyvinyl alcohol to 80 parts by weight of deionized water, stir at 90°C and 240 rpm for 2 hours, then cool to 50°C, then add 1 part by weight of carboxymethyl chitosan, stir at 360 rpm for 2 hours, cool to room temperature, then add 1 part by weight of aqueous polyurethane, stir and mix for 20 minutes to obtain a mixed gel solution. S2.2: Microbial solution was added to the mixed gel solution. The microbial solution was a suspension of nitrifying bacteria and denitrifying bacteria in a mass ratio of 1:1. The amount of microbial solution added was 4 wt% of the mixed gel solution. The mixture was then stirred at 360 rpm for 1 h to obtain a mixture. The mixture was then dripped into the cross-linking solution at a uniform rate using a syringe. The cross-linking solution was a mixture of 7.1 wt% aluminum sulfate octadeca and 4 wt% boric acid. Cross-linking was carried out for 60 min. The mixture was then washed twice with deionized water to obtain immobilized microspheres after the first cross-linking treatment. S2.3: The immobilized microspheres that have undergone the first cross-linking treatment are added to a 0.5 mol / L anhydrous sodium sulfate solution and cross-linked for 120 min. Then, they are washed twice with deionized water to obtain the immobilized microbial complex. S3: Treatment of ammonia nitrogen-containing wastewater S3.1: The landfill leachate is pretreated by passing it through a bar screen and an air flotation tank to remove suspended solids and grease, resulting in pretreated wastewater; S3.2: The pH of the pretreated wastewater was adjusted to 7.5 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex was added to the fluidized bed reactor at 2% (v / v) of the wastewater volume. The pretreated wastewater was treated for 40 h at 30℃, with DO of 2 mg / L and C / N ratio of 3, to obtain the secondary treated wastewater. S3.3: Let the wastewater after secondary treatment stand for 1 hour, transfer the supernatant to the deep treatment unit, then add wastewater treatment agent at a rate of 1.5 g / L, stir at 20 rpm for 1 hour, and finally let stand for 1 hour, filter, and obtain the wastewater after tertiary treatment. S3.4: Pass the wastewater after three treatments through a granular activated carbon column to obtain the final treated wastewater; The acclimatization process of the immobilized microbial complex is as follows: Immobilized microbial complex is added to a fluidized bed reactor, and landfill leachate is added at a dosage ratio of 10 mg / L. The mixture is treated for 1 day under aeration conditions. Then, landfill leachate is added at a dosage ratio of 40 mg / L, and the mixture is treated for 2 days under aeration conditions. Next, landfill leachate is added at a dosage ratio of 100 mg / L, and the mixture is treated for 2 days under aeration conditions. Finally, landfill leachate is added at a dosage ratio of 200 mg / L, and the mixture is treated for 2 days under aeration conditions to obtain the acclimatized immobilized microbial complex.

[0023] Example 2 A method for treating ammonia nitrogen-containing wastewater, such as Figure 1 As shown, it includes the following steps: S1: Preparation of wastewater treatment agents S1.1: Calcium chloride and aluminum chloride are mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH is adjusted to 3, and the mixture is stirred for 20 min to prepare a mixed solution with a total concentration of 2 mol / L. S1.2: Add 12 parts by weight of dried corn stalk powder to 120 parts by weight of mixed solution, mix and stir at 300 rpm for 20 min, and then shake at 160 rpm for 20 h in a 25℃ air bath constant temperature shaker to obtain a mixture; S1.3: The mixture was centrifuged at 3000 rpm for 6 min, then dried and ground. The powder obtained from the grinding was pyrolyzed in a muffle furnace at 550℃ for 100 min under nitrogen atmosphere at a heating rate of 5℃ / min. After holding at the temperature for 60 min, the mixture was cooled, washed 3 times, and dried to obtain the wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: Add 12 parts by weight of polyvinyl alcohol to 90 parts by weight of deionized water, stir at 90°C and 240 rpm for 2 hours, then cool to 50°C, then add 2 parts by weight of carboxymethyl chitosan, stir at 360 rpm for 2 hours, cool to room temperature, then add 2 parts by weight of aqueous polyurethane, stir and mix for 20 minutes to obtain a mixed gel solution. S2.2: Microbial solution was added to the mixed gel solution. The microbial solution was a suspension of nitrifying bacteria and denitrifying bacteria in a mass ratio of 1:1. The amount of microbial solution added was 5 wt% of the mixed gel solution. The mixture was then stirred at 360 rpm for 1 h to obtain a mixture. The mixture was then dripped into the cross-linking solution at a uniform rate using a syringe. The cross-linking solution was a mixture of 8.2 wt% aluminum sulfate octadeca and 5 wt% boric acid. Cross-linking was carried out for 60 min. The mixture was then washed twice with deionized water to obtain immobilized microspheres after the first cross-linking treatment. S2.3: The immobilized microspheres that have undergone the first cross-linking treatment are added to a 0.5 mol / L anhydrous sodium sulfate solution and cross-linked for 120 min. Then, they are washed twice with deionized water to obtain the immobilized microbial complex. S3: Treatment of ammonia nitrogen-containing wastewater S3.1: The landfill leachate is pretreated by passing it through a bar screen and an air flotation tank to remove suspended solids and grease, resulting in pretreated wastewater; S3.2: The pH of the pretreated wastewater was adjusted to 8 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex was added to the fluidized bed reactor at 3% (v / v) of the wastewater volume. The pretreated wastewater was treated for 40 h at 30℃, with DO of 4 mg / L and C / N ratio of 4, to obtain the secondary treated wastewater. S3.3: Let the wastewater after secondary treatment stand for 1 hour, transfer the supernatant to the deep treatment unit, then add wastewater treatment agent at a rate of 2 g / L, stir at 20 rpm for 1 hour, and finally let stand for 1 hour and filter to obtain wastewater after tertiary treatment. S3.4: Pass the wastewater after three treatments through a granular activated carbon column to obtain the final treated wastewater; The acclimatization process of the immobilized microbial complex was as follows: Immobilized microbial complex was added to a fluidized bed reactor, and landfill leachate was added at a dosage ratio of 20 mg / L. The mixture was treated for 1 day under aeration conditions. Then, landfill leachate was added at a dosage ratio of 50 mg / L, and the mixture was treated for 2 days under aeration conditions. Then, landfill leachate was added at a dosage ratio of 120 mg / L, and the mixture was treated for 2 days under aeration conditions. Finally, landfill leachate was added at a dosage ratio of 300 mg / L, and the mixture was treated for 2 days under aeration conditions to obtain the acclimatized immobilized microbial complex.

[0024] Example 3 A method for treating ammonia nitrogen-containing wastewater, such as Figure 1 As shown, it includes the following steps: S1: Preparation of wastewater treatment agents S1.1: Calcium chloride and aluminum chloride are mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH is adjusted to 2, and the mixture is stirred for 30 min to prepare a mixed solution with a total concentration of 1 mol / L. S1.2: Add 10 parts by weight of dried corn stalk powder to 100 parts by weight of mixed solution, mix and stir at 500 rpm for 30 min, and then shake at 180 rpm for 24 h in a 28℃ air bath constant temperature shaker to obtain a mixture; S1.3: The mixture was centrifuged at 3500 rpm for 8 min, then dried and ground. The powder obtained from the grinding was pyrolyzed in a muffle furnace at 580℃ for 105 min under nitrogen atmosphere at a heating rate of 8℃ / min. After holding at the temperature for 70 min, it was cooled, washed 5 times, and dried to obtain the wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: Add 10 parts by weight of polyvinyl alcohol to 80 parts by weight of deionized water, stir at 92°C and 260 rpm for 3 hours, then cool to 52°C, then add 1 part by weight of carboxymethyl chitosan, stir at 400 rpm for 3 hours, cool to room temperature, then add 1 part by weight of aqueous polyurethane, stir and mix for 30 minutes to obtain a mixed gel solution. S2.2: Microbial culture solution was added to the mixed gel solution. The microbial culture solution was a suspension of nitrifying bacteria and denitrifying bacteria in a mass ratio of 1:1. The amount of microbial culture solution added was 4 wt% of the mixed gel solution. The mixture was then stirred at 400 rpm for 2 h to obtain a mixture. The mixture was then dripped into the cross-linking solution at a uniform rate using a syringe. The cross-linking solution was a mixture of 7.1 wt% aluminum sulfate octadeca and 4 wt% boric acid. Cross-linking was carried out for 70 min. The mixture was then washed three times with deionized water to obtain immobilized microspheres after the first cross-linking treatment. S2.3: The immobilized microspheres that have undergone the first cross-linking treatment are added to a 0.5 mol / L anhydrous sodium sulfate solution and cross-linked for 130 min. Then, they are washed three times with deionized water to obtain the immobilized microbial complex. S3: Treatment of ammonia nitrogen-containing wastewater S3.1: The landfill leachate is pretreated by passing it through a bar screen and an air flotation tank to remove suspended solids and grease, resulting in pretreated wastewater; S3.2: The pH of the pretreated wastewater was adjusted to 7.5 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex was added to the fluidized bed reactor at 2% (v / v) of the wastewater volume. The pretreated wastewater was treated for 48 h at 32℃, with DO of 2 mg / L and C / N ratio of 3, to obtain the secondary treated wastewater. S3.3: After the secondary treatment, the wastewater was allowed to stand for 2 hours. The supernatant was transferred to the deep treatment unit, and then wastewater treatment agent was added at a rate of 1.5 g / L. The mixture was stirred at 30 rpm for 2 hours, and then allowed to stand for 2 hours. After filtration, the wastewater after the third treatment was obtained. S3.4: Pass the wastewater after three treatments through a granular activated carbon column to obtain the final treated wastewater; The acclimatization process of the immobilized microbial complex is as follows: Immobilized microbial complex is added to a fluidized bed reactor, and landfill leachate is added at a dosage ratio of 10 mg / L. The mixture is treated for 2 days under aeration conditions. Then, landfill leachate is added at a dosage ratio of 40 mg / L, and the mixture is treated for 3 days under aeration conditions. Next, landfill leachate is added at a dosage ratio of 100 mg / L, and the mixture is treated for 3 days under aeration conditions. Finally, landfill leachate is added at a dosage ratio of 200 mg / L, and the mixture is treated for 3 days under aeration conditions to obtain the acclimatized immobilized microbial complex.

[0025] Comparative Example 1 Compared with Example 1, Comparative Example 1 differs in that it removes calcium chloride in step S1.1 while the remaining steps remain unchanged to treat ammonia nitrogen-containing wastewater, and is referred to as Comparative Example 1.

[0026] Comparative Example 2 Compared with Example 1, Comparative Example 2 differs in that it removes aluminum chloride in step S1.1 while the remaining steps remain unchanged to treat ammonia nitrogen-containing wastewater, and is referred to as Comparative Example 2.

[0027] Comparative Example 3 Compared with Example 1, Comparative Example 3 differs in that Comparative Example 3 removes aluminum chloride and calcium chloride in step S1.1, while the remaining steps remain unchanged to treat ammonia nitrogen-containing wastewater, and is referred to as Comparative Example 3.

[0028] Comparative Example 4 Compared with Example 1, Comparative Example 4 differs in that it removes carboxymethyl chitosan in step S2.1, while the remaining steps remain unchanged to treat ammonia nitrogen-containing wastewater, and is referred to as Comparative Example 4.

[0029] Comparative Example 5 Compared with Example 1, Comparative Example 5 differs in that Comparative Example 5 removes the waterborne polyurethane in step S2.1, while the remaining steps remain unchanged to treat ammonia nitrogen-containing wastewater, and is referred to as Comparative Example 5.

[0030] Comparative Example 6 Compared with Example 1, Comparative Example 6 differs in that Comparative Example 6 removes step S2.3. The immobilized microspheres in the first cross-linking treatment in step S2.2 are the immobilized microbial complexes. The remaining steps are unchanged for the treatment of ammonia nitrogen-containing wastewater, and it is referred to as Comparative Example 6.

[0031] Comparative Example 7 Compared with Example 1, Comparative Example 7 differs in that Comparative Example 7 removes aluminum sulfate octadecahydrate in step S2.2, while the remaining steps remain unchanged to treat ammonia nitrogen-containing wastewater, and is referred to as Comparative Example 7.

[0032] The specific surface area, pore size and pore volume of the wastewater treatment agents prepared in Examples 1-3 and Comparative Examples 1-3 were measured, and the results are shown in Table 1.

[0033] Table 1. Results of Specific Surface Area, Pore Diameter and Pore Volume Measurement of Wastewater Treatment Agents

[0034] As can be seen from the data in Table 1, the 1:1 calcium / aluminum molar ratio formulation can stably generate mesoporous materials with good structural uniformity. As can be seen from the data in Comparative Example 1, without the skeletal support of Ca²⁺, AlCl₃ alone easily forms a finer microporous structure through pyrolysis. The microporous structure is easily blocked by impurities. As can be seen from the data in Comparative Example 2, the lack of aluminum source leads to a loose pore structure and insufficient specific surface area, resulting in insufficient adsorption capacity. Therefore, the synergistic effect of calcium and aluminum can construct a mesoporous structure, which is conducive to the diffusion and adsorption of ammonia nitrogen molecules. The high specific surface area provides sufficient active sites, which is beneficial to the treatment of wastewater.

[0035] The ammonia nitrogen concentration and total nitrogen concentration in the initial landfill leachate of Examples 1-3 and Comparative Examples 1-7 were measured. After the wastewater treatment was completed, the ammonia nitrogen concentration and total nitrogen concentration in the final treated wastewater were measured again, and the ammonia nitrogen removal rate and total nitrogen removal rate were calculated. The measurement results are shown in Table 2.

[0036] Table 2. Results of ammonia nitrogen removal rate determination in Examples 1-3 and Comparative Examples 1-7

[0037] Table 2 shows that the data from Comparative Examples 1-3 can significantly improve the removal rate of ammonia nitrogen by using Ca / Al modified wastewater treatment agents. Comparative Examples 4-5 show that the immobilized microbial complex prepared by polyvinyl alcohol, carboxymethyl chitosan, and waterborne polyurethane can efficiently remove ammonia nitrogen from wastewater. Comparative Examples 6-7 show that the removal capacity of the immobilized microbial complex for ammonia nitrogen in wastewater can be improved through two cross-linking processes, and the cross-linking after adding aluminum sulfate octadecahydrate can improve the removal rate of ammonia nitrogen by the immobilized microbial complex.

[0038] The apparent properties of the immobilized microbial complexes prepared in Examples 1-3 and Comparative Examples 4-5 were evaluated, and the evaluation results are shown in Table 3.

[0039] Table 3. Evaluation results of the apparent properties of the immobilized microbial complexes of Examples 1-3 and Comparative Examples 4-5

[0040] As can be seen from Comparative Example 4 in Table 3, the addition of carboxymethyl chitosan is beneficial to the formation of immobilized microbial complex and improves the mechanical strength of immobilized microbial complex. As can be seen from Comparative Example 5, the addition of waterborne polyurethane can improve the mechanical strength of immobilized microbial complex.

[0041] from Figure 2 It can be seen that, Figure 2 The image above is a SEM image of the surface of the immobilized microbial complex prepared in Comparative Example 5. Figure 2 The following is a SEM image of the surface of the immobilized microbial complex prepared in Example 1. It can be seen that the immobilized microbial complex prepared after adding waterborne polyurethane forms a macroporous structure on its surface, which enriches the pore structure of the immobilized microbial complex.

[0042] Figure 3 The Fourier transform infrared spectra of the wastewater treatment agents in Example 1 and Comparative Examples 1-3 show that, through comparative analysis, the Ca and Al composite modification significantly enhances the functional groups on the surface of the wastewater treatment agents.

[0043] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for treating ammonia nitrogen-containing wastewater, characterized in that, Includes the following steps: S1: Preparation of wastewater treatment agents S1.1: Mix calcium chloride and aluminum chloride in a calcium / aluminum molar ratio of 1:1, add the mixture to deionized water, adjust the pH to 2-3, stir and mix for 20-30 min to prepare a mixed solution with a total concentration of 1-2 mol / L. S1.2: Add 10-12 parts by weight of dried corn stalk powder to 100-120 parts by weight of mixed solution, mix and stir at 300-500 rpm for 20-30 min, and then shake at 160-180 rpm in a 25-28℃ air bath constant temperature shaker for 20-24 h to obtain the mixture; S1.3: Centrifuge the mixture at 3000-3500 rpm for 6-8 min, then dry and grind it. Pyrolyze the powder obtained by grinding in a muffle furnace at 550-580℃ for 100-105 min under nitrogen atmosphere at a heating rate of 5-8℃ / min. Then hold it at the temperature for 60-70 min, cool it down, wash it 3-5 times, and dry it to obtain the wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: Add 10-12 parts by weight of polyvinyl alcohol to 80-90 parts by weight of deionized water, stir at 90-92℃ and 240-260 rpm for 2-3 hours, then cool to 50-52℃, then add 1-2 parts by weight of carboxymethyl chitosan, stir at 360-400 rpm for 2-3 hours, cool to room temperature, then add 1-2 parts by weight of aqueous polyurethane, stir and mix for 20-30 minutes to obtain a mixed gel solution; S2.2: Add microbial culture to the mixed gel solution, then stir and mix at 360-400 rpm for 1-2 hours to obtain a mixture. Then, use a syringe to drop the mixture into the cross-linking solution at a uniform rate, cross-link for 60-70 minutes, and then wash with deionized water 2-3 times to obtain immobilized microspheres after the first cross-linking treatment. S2.3: The immobilized microspheres that have undergone the first cross-linking treatment are added to a 0.5 mol / L anhydrous sodium sulfate solution and cross-linked for 120-130 min. Then, they are washed with deionized water 2-3 times to obtain the immobilized microbial complex. S3: Treatment of ammonia nitrogen-containing wastewater The landfill leachate is pretreated, then nitrification-denitrification is carried out using an immobilized microbial complex to obtain secondary treated wastewater. The secondary treated wastewater is then treated with a wastewater treatment agent, and finally passed through a granular activated carbon column to obtain the final treated wastewater.

2. The method for treating ammonia-nitrogen-containing wastewater according to claim 1, characterized in that, Step S3, the treatment of ammonia nitrogen-containing wastewater, specifically includes the following steps: S3.1: The landfill leachate is pretreated by passing it through a bar screen and an air flotation tank to remove suspended solids and grease, resulting in pretreated wastewater; S3.2: The pH of the pretreated wastewater was adjusted to 7.5-8 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex was added to the fluidized bed reactor at a concentration of 8-10% (v / v) of the wastewater volume. The pretreated wastewater was treated under aeration conditions of 30-32℃, DO of 2-4 mg / L, C / N ratio of 3-4 for 40-48 hours to obtain the secondary treated wastewater. S3.3: Let the wastewater after secondary treatment stand for 1-2 hours, transfer the supernatant to the deep treatment unit, then add wastewater treatment agent at a rate of 1.5-2 g / L, stir at 20-30 rpm for 1-2 hours, and finally let stand for 1-2 hours, filter, and obtain the wastewater after tertiary treatment. S3.4: Pass the wastewater after three treatments through a granular activated carbon column to obtain the final treated wastewater.

3. The method for treating ammonia-nitrogen-containing wastewater according to claim 1, characterized in that, Step S2.2 The microbial inoculum is a suspension of nitrifying bacteria and denitrifying bacteria mixed in a mass ratio of 1:

1.

4. The method for treating ammonia-nitrogen-containing wastewater according to claim 1, characterized in that, In step S2.2, the amount of microbial inoculum added is 4-5 wt% of the mixed gel solution.

5. The method for treating ammonia-nitrogen-containing wastewater according to claim 1, characterized in that, In step S2.2, the cross-linking mixed solution is specifically a mixed solution of 7.1-8.2 wt% aluminum sulfate octadeca and 4-5 wt% boric acid.

6. The method for treating ammonia-nitrogen-containing wastewater according to claim 2, characterized in that, In step S3.2, the amount of immobilized microbial complex added is 2-3% (v / v) of the wastewater volume.

7. The method for treating ammonia-nitrogen-containing wastewater according to claim 2, characterized in that, The acclimatization process of the immobilized microbial complex in step S3.2 is as follows: the immobilized microbial complex is added to the fluidized bed reactor, and landfill leachate is added at a dosage ratio of 10-20 mg / L. Under aeration conditions, the mixture is treated for 1-2 days. Then, landfill leachate is added at a dosage ratio of 40-50 mg / L, and the mixture is treated for 2-3 days under aeration conditions. Next, landfill leachate is added at a dosage ratio of 100-120 mg / L, and the mixture is treated for 2-3 days under aeration conditions. Finally, landfill leachate is added at a dosage ratio of 200-300 mg / L, and the mixture is treated for 2-3 days under aeration conditions to obtain the acclimatized immobilized microbial complex.

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