Treatment method of ammonia-nitrogen-containing wastewater

Abstract

The invention provides a treatment method of ammonia-nitrogen-containing wastewater, and belongs to the technical field of wastewater treatment. The preparation process comprises the following steps: preparing the wastewater treatment agent; preparing an immobilized microbial compound; and treating the ammonia-nitrogen-containing wastewater. According to the immobilized microbial carrier prepared by the invention, a stable dual-network structure and proper pore channels are formed through the synergistic effect of the polyvinyl alcohol, the carboxymethyl chitosan and the polyurethane; secondary cross-linking significantly enhances the stability of the carrier, optimizes internal pore channels, and is beneficial to attachment and proliferation of microorganisms; after the corn straw biochar is modified by Ca / Al, the specific surface area and functional groups are increased, and the physicochemical adsorption of ammonia nitrogen is enhanced. The three are combined, and ammonia nitrogen in wastewater is efficiently removed through synergism of carrier adsorption and microbial metabolism.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and in particular to a method for treating wastewater containing ammonia nitrogen. Background Art

[0002] Ammonia nitrogen is a major contributor to water eutrophication and environmental pollution. Its large-scale release not only leads to excessive algae growth in water bodies, disrupting aquatic ecological balance and triggering environmental problems such as red tides and algal blooms, but also the free ammonia in it is toxic to aquatic organisms, inhibiting the growth and reproduction of fish and other aquatic organisms. 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 upon entering the human body.

[0003] Currently, treatment methods for ammonia-nitrogen wastewater mainly include physical, chemical, and biological methods. While physical methods for treating ammonia-nitrogen wastewater have the characteristics of high treatment efficiency, they also have problems such as high energy consumption and the susceptibility to secondary pollution. While chemical methods have fast reaction speeds, they require large amounts of reagents, resulting in high treatment costs, and some chemical reagents may introduce new pollutants. Biological methods are difficult to maintain long-term operational stability, thus limiting the practical application of these methods. Immobilized microbial technology can fix microorganisms within porous carriers, protecting them while ensuring their activity, which is beneficial for long-term denitrification stability.

[0004] As the most commonly used embedding material, PVA is the preferred choice in numerous research and practical applications due to its low price, high chemical stability, and good biocompatibility. However, PVA-based carriers have significant drawbacks: their poor mechanical strength makes them susceptible to breakage during actual handling; they also experience adhesion during use, impacting treatment efficiency and ease of operation. Furthermore, the low mechanical strength and dense pore distribution of PVA-based carriers limit further improvements in ammonia nitrogen removal, making it difficult to meet increasingly stringent environmental protection requirements.

[0005] Therefore, we proposed a treatment method for 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 prior art, the present invention aims to provide a method for treating ammonia-nitrogen-containing wastewater.

[0007] A method for treating ammonia-nitrogen-containing wastewater comprises the following steps: S1: Preparation of wastewater treatment agents Corn straw powder is used to prepare biochar, which is then modified with calcium / aluminum to prepare a wastewater treatment agent. S2: Preparation of immobilized microbial complexes Polyvinyl alcohol, carboxymethyl chitosan and aqueous polyurethane were used as carrier materials and loaded with microbial culture liquid, followed by cross-linking with aluminum sulfate 18hydrate and boric acid, and then with anhydrous sodium sulfate to prepare an immobilized microbial complex. S3: Treatment of ammonia-nitrogen wastewater The landfill leachate is pretreated and then subjected to nitrification-denitrification treatment 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 final treated wastewater.

[0008] Furthermore, the preparation of the wastewater treatment agent in step S1 specifically includes the following steps: S1.1: Calcium chloride and aluminum chloride were mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH was adjusted to 2-3 and the mixture was stirred for 20-30 minutes 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 straw powder to 100-120 parts by weight of the mixed solution, stir at 300-500 rpm for 20-30 minutes, and then oscillate at 160-180 rpm in an air bath constant temperature oscillator at 25-28°C for 20-24 hours to obtain a mixture; S1.3: Centrifuge the mixture at 3000-3500 rpm for 6-8 minutes, then dry and grind. Pyrolyze the ground powder in a muffle furnace at 550-580°C under a nitrogen atmosphere for 100-105 minutes at a heating rate of 5-8°C / min. Then keep the mixture warm for 60-70 minutes. After cooling, wash it 3-5 times and dry it to obtain a wastewater treatment agent.

[0009] Furthermore, step S2 is to prepare the immobilized microbial complex, which 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°C and 240-260 rpm for 2-3 hours, then cool to 50-52°C, add 1-2 parts by weight of carboxymethyl chitosan, stir at 360-400 rpm for 2-3 hours, cool to room temperature, add 1-2 parts by weight of aqueous polyurethane, and stir for 20-30 minutes to obtain a mixed gel solution; S2.2: Add the microbial culture solution to the mixed gel solution, then stir at 360-400 rpm for 1-2 hours to obtain a mixture. Then, use a syringe to uniformly add the mixture to the crosslinking mixed solution. Crosslink for 60-70 minutes, then wash with deionized water 2-3 times to obtain the immobilized microspheres after the first crosslinking treatment. S2.3: Add the immobilized microspheres after the first cross-linking treatment into a 0.5 mol / L anhydrous sodium sulfate solution, cross-link for 120-130 minutes, and then wash with deionized water 2-3 times to obtain an immobilized microbial complex.

[0010] Furthermore, step S3 of treating the ammonia nitrogen-containing wastewater specifically comprises the following steps: S3.1: Pre-treat the landfill leachate through a screen filter and flotation tank to remove suspended solids and grease to obtain pre-treated wastewater; S3.2: The pH of the pretreated wastewater is adjusted to 7.5-8 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex is added to a fluidized bed reactor and treated at 30-32°C, a DO of 2-4 mg / L, a C / N ratio of 3-4, and aeration conditions for 40-48 hours to obtain secondary treated wastewater. S3.3: The secondary treated wastewater is allowed to stand for 1-2 hours. The supernatant is transferred to the advanced treatment unit. A wastewater treatment agent is then added at a rate of 1.5-2 g / L. The mixture is stirred at 20-30 rpm for 1-2 hours. The mixture is allowed to stand for 1-2 hours and filtered to obtain the tertiary treated wastewater. S3.4: The wastewater after the tertiary treatment is passed through a granular activated carbon column to obtain the final treated wastewater.

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

[0012] Furthermore, the cross-linking mixed solution in step S2.2 is specifically a mixed solution of 7.1-8.2 wt % of aluminum sulfate 18hydrate and 4-5 wt % of boric acid.

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

[0014] Furthermore, the acclimation process of the immobilized microbial complex after acclimation in step S3.2 is as follows: adding the immobilized microbial complex to the fluidized bed reactor, and adding leachate at a dosage ratio of 10-20 mg / L, treating for 1-2 days under aeration conditions, then adding leachate at a dosage ratio of 40-50 mg / L, treating for 2-3 days under aeration conditions, then adding leachate at a dosage ratio of 100-120 mg / L, treating for 2-3 days under aeration conditions, and finally adding leachate at a dosage ratio of 200-300 mg / L, treating for 2-3 days under aeration conditions to obtain the acclimated immobilized microbial complex.

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

[0016] 2. The present invention can effectively improve the performance of the immobilized microbial complex through two cross-linking effects. The aluminum ions released by aluminum sulfate 18hydrate in the cross-linked mixed solution can form irreversible coordination bonds and ionic bonds with polyvinyl alcohol and carboxymethyl chitosan to quickly build a rigid skeleton; boric acid forms reversible borate ester bonds with polyvinyl alcohol, giving the network flexibility. The synergistic effect of the two causes the polymer chains to aggregate in a directional manner during cross-linking, spontaneously forming a pore structure with uniform size and interconnectedness. These rich pore structures are conducive to the attachment of microorganisms inside the immobilized microbial complex, thereby facilitating the removal of ammonia nitrogen by the immobilized microbial complex. The immobilized microbial complex is placed in anhydrous sodium sulfate solution for secondary cross-linking. During the secondary cross-linking, SO4 in the sodium sulfate solution 2- When entering the interior of the complex, the hydroxyl groups on the polyvinyl alcohol become active and more hydrogen bonds are formed between the hydroxyl groups, thereby increasing the cross-linking degree of the immobilized microbial complex, thereby enhancing the stability of the immobilized microbial complex, and at the same time optimizing the pore structure of the immobilized microbial complex, thereby improving the removal rate of ammonia nitrogen.

[0017] 3. In the present invention, corn straw forms a porous carbon structure after pyrolysis, which has a high specific surface area and abundant pores, and can capture ammonia nitrogen in the solution through physical adsorption. After Ca / Al modification, the functional groups on the surface of biochar are significantly enhanced. These functional groups enhance the chemical adsorption of pollutants in wastewater through hydrogen bonding, etc., and the double 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 the specific surface area of ​​the wastewater treatment agent can increase the number of surface active sites, which is beneficial to the adsorption of pollutants in the wastewater and achieve the effect of wastewater purification.

[0018] 4. The present invention realizes the nitrification-denitrification process under an aerated environment, and its core advantage lies in the clever use of the mass transfer characteristics of the immobilized microbial complex. When oxygen diffuses into the interior of the immobilized microorganism, the mass transfer resistance causes a significant oxygen concentration gradient to be generated inside and outside the immobilized microorganism. Under the influence of this concentration difference, an anaerobic or anoxic environment will be formed in the local area inside the immobilized microorganism, providing suitable living and metabolic conditions for denitrifying bacteria. At the same time, the aerobic area outside the immobilized microorganism can meet the growth requirements of nitrifying bacteria. Based on this, the immobilized microbial complex can simultaneously load nitrifying bacteria and denitrifying bacteria, realize the simultaneous progress of nitrification and denitrification, significantly improve the sewage treatment efficiency, and simplify the treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 1 A flow chart of a method for treating ammonia-nitrogen-containing wastewater adopted in an embodiment of the present invention; Figure 2 Surface SEM images of the immobilized microbial complexes prepared in Example 1 of the present invention and Comparative Example 5; Figure 3 The following are Fourier transform infrared spectra of the wastewater treatment agents prepared in Example 1 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION

[0021] The following describes in detail a method for treating ammonia-nitrogen wastewater provided by the present invention, in conjunction with the accompanying drawings and specific examples. It is also noted that, to provide a more detailed description, the following examples are optimal and preferred embodiments, and those skilled in the art may employ alternative methods for implementing certain known technologies. Furthermore, the accompanying drawings are intended only to provide a more detailed description of the embodiments and are not intended to limit the present invention.

[0022] Example 1 A method for treating wastewater containing ammonia nitrogen, such as Figure 1 As shown, the following steps are included: S1: Preparation of wastewater treatment agents S1.1: Calcium chloride and aluminum chloride were mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH was adjusted to 2 and the mixture was stirred for 20 minutes to prepare a mixed solution with a total concentration of 1 mol / L. S1.2: Add 10 parts by weight of dried corn straw powder to 100 parts by weight of the mixed solution, stir at 300 rpm for 20 minutes, and then oscillate at 160 rpm in a constant temperature oscillator at 25°C for 20 hours to obtain a mixture; S1.3: The mixture was centrifuged at 3000 rpm for 6 min, then dried and ground. The ground powder was pyrolyzed in a muffle furnace at 550°C for 100 min under a nitrogen atmosphere at a heating rate of 5°C / min. The mixture was then kept at this temperature for 60 min, cooled, washed three times, and dried to obtain a wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: 10 parts by weight of polyvinyl alcohol was added to 80 parts by weight of deionized water, and the mixture was stirred at 90°C and 240 rpm for 2 h. The mixture was then cooled to 50°C, followed by the addition of 1 part by weight of carboxymethyl chitosan and stirring at 360 rpm for 2 h. After cooling to room temperature, 1 part by weight of aqueous polyurethane was added and the mixture was stirred for 20 min to obtain a mixed gel solution. S2.2: Add a microbial suspension to the mixed gel solution, wherein the microbial suspension is a suspension of nitrifying bacteria and denitrifying bacteria in a mass ratio of 1:1, and the amount of microbial suspension added is 4 wt % of the mixed gel solution. Then, the mixture is stirred at 360 rpm for 1 hour to obtain a mixture. Then, the mixture is dripped into the cross-linked mixed solution at a uniform rate using a syringe. Specifically, the cross-linked mixed solution is a mixed solution of 7.1 wt % aluminum sulfate 18hydrate and 4 wt % boric acid. The cross-linking is carried out for 60 minutes, and then the microspheres are washed twice with deionized water to obtain the immobilized microspheres subjected to the first cross-linking treatment. S2.3: Add the immobilized microspheres obtained from the first cross-linking treatment to a 0.5 mol / L anhydrous sodium sulfate solution, cross-link for 120 min, and then wash twice with deionized water to obtain an immobilized microbial composite. S3: Treatment of ammonia-nitrogen wastewater S3.1: Pre-treat the landfill leachate through a screen filter and flotation tank to remove suspended solids and grease to obtain pre-treated 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 a fluidized bed reactor at a concentration of 2% (v / v) of the wastewater volume. The pretreated wastewater was treated at 30°C, a DO of 2 mg / L, a C / N ratio of 3, and aeration conditions for 40 h to obtain secondary treated wastewater. S3.3: The secondary treated wastewater was allowed to stand for 1 hour, and the supernatant was transferred to the advanced treatment unit. A wastewater treatment agent was then added at a rate of 1.5 g / L. The mixture was stirred at 20 rpm for 1 hour, and finally allowed to stand for 1 hour. The mixture was filtered to obtain the tertiary treated wastewater. S3.4: Pass the tertiary treated wastewater through a granular activated carbon column to obtain final treated wastewater; The acclimation process of the immobilized microbial complex 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 mg / L, and treated for 1 day under aeration conditions. Then, landfill leachate is added at a dosage ratio of 40 mg / L, and treated for 2 days under aeration conditions. Then, landfill leachate is added at a dosage ratio of 100 mg / L, and treated for 2 days under aeration conditions. Finally, landfill leachate is added at a dosage ratio of 200 mg / L, and treated for 2 days under aeration conditions to obtain the acclimated immobilized microbial complex.

[0023] Example 2 A method for treating wastewater containing ammonia nitrogen, such as Figure 1 As shown, the following steps are included: S1: Preparation of wastewater treatment agents S1.1: Calcium chloride and aluminum chloride were mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH was adjusted to 3 and stirred for 20 minutes to prepare a mixed solution with a total concentration of 2 mol / L. S1.2: Add 12 parts by weight of dried corn straw powder to 120 parts by weight of the mixed solution, stir at 300 rpm for 20 min, and then oscillate at 160 rpm in a 25°C air bath constant temperature oscillator for 20 h to obtain a mixture; S1.3: The mixture was centrifuged at 3000 rpm for 6 min, then dried and ground. The ground powder was pyrolyzed in a muffle furnace at 550°C for 100 min under a nitrogen atmosphere at a heating rate of 5°C / min. The mixture was then kept at this temperature for 60 min, cooled, washed three times, and dried to obtain a wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: 12 parts by weight of polyvinyl alcohol was added to 90 parts by weight of deionized water, and the mixture was stirred at 90°C and 240 rpm for 2 h. The mixture was then cooled to 50°C, followed by the addition of 2 parts by weight of carboxymethyl chitosan and stirring at 360 rpm for 2 h. After cooling to room temperature, 2 parts by weight of aqueous polyurethane was added and the mixture was stirred for 20 min to obtain a mixed gel solution. S2.2: Add a microbial suspension to the mixed gel solution, wherein the microbial suspension is a suspension of nitrifying bacteria and denitrifying bacteria in a mass ratio of 1:1, and the amount of microbial suspension added is 5 wt % of the mixed gel solution. Then, the mixture is stirred at 360 rpm for 1 hour to obtain a mixture. Then, the mixture is dripped into the cross-linked mixed solution at a uniform rate using a syringe. Specifically, the cross-linked mixed solution is a mixed solution of 8.2 wt % aluminum sulfate 18hydrate and 5 wt % boric acid. The cross-linking is carried out for 60 minutes, and then the microspheres are washed twice with deionized water to obtain the immobilized microspheres subjected to the first cross-linking treatment. S2.3: Add the immobilized microspheres obtained from the first cross-linking treatment to a 0.5 mol / L anhydrous sodium sulfate solution, cross-link for 120 min, and then wash twice with deionized water to obtain an immobilized microbial composite. S3: Treatment of ammonia-nitrogen wastewater S3.1: Pre-treat the landfill leachate through a screen filter and flotation tank to remove suspended solids and grease to obtain pre-treated 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 a fluidized bed reactor at a concentration of 3% (v / v) of the wastewater volume. The pretreated wastewater was treated at 30°C, a DO of 4 mg / L, a C / N ratio of 4, and aeration conditions for 40 h to obtain secondary treated wastewater. S3.3: The secondary treated wastewater was allowed to stand for 1 hour, and the supernatant was transferred to the advanced treatment unit. A wastewater treatment agent was then added at a rate of 2 g / L. The mixture was stirred at 20 rpm for 1 hour, allowed to stand for 1 hour, and filtered to obtain the tertiary treated wastewater. S3.4: Pass the tertiary treated wastewater through a granular activated carbon column to obtain final treated wastewater; The acclimation process of the immobilized microbial complex is as follows: the immobilized microbial complex is added to the fluidized bed reactor, and landfill leachate is added at a dosage ratio of 20 mg / L, and treated for 1 day under aeration conditions. Then, landfill leachate is added at a dosage ratio of 50 mg / L, and treated for 2 days under aeration conditions. Then, landfill leachate is added at a dosage ratio of 120 mg / L, and treated for 2 days under aeration conditions. Finally, landfill leachate is added at a dosage ratio of 300 mg / L, and treated for 2 days under aeration conditions to obtain the acclimated immobilized microbial complex.

[0024] Example 3 A method for treating wastewater containing ammonia nitrogen, such as Figure 1 As shown, the following steps are included: S1: Preparation of wastewater treatment agents S1.1: Calcium chloride and aluminum chloride were mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH was adjusted to 2 and the mixture was stirred for 30 minutes to prepare a mixed solution with a total concentration of 1 mol / L. S1.2: Add 10 parts by weight of dried corn straw powder to 100 parts by weight of the mixed solution, stir at 500 rpm for 30 minutes, and then oscillate at 180 rpm in a constant temperature oscillator at 28°C for 24 hours to obtain a mixture; S1.3: The mixture was centrifuged at 3500 rpm for 8 minutes, then dried and ground. The ground powder was pyrolyzed in a muffle furnace at 580°C for 105 minutes under a nitrogen atmosphere at a heating rate of 8°C / min. The mixture was then kept at this temperature for 70 minutes, cooled, washed five times, and dried to obtain a wastewater treatment agent. S2: Preparation of immobilized microbial complexes S2.1: 10 parts by weight of polyvinyl alcohol was added to 80 parts by weight of deionized water, and the mixture was stirred at 92°C and 260 rpm for 3 h. The mixture was then cooled to 52°C. Then, 1 part by weight of carboxymethyl chitosan was added, and the mixture was stirred at 400 rpm for 3 h. After cooling to room temperature, 1 part by weight of aqueous polyurethane was added, and the mixture was stirred for 30 min to obtain a mixed gel solution. S2.2: Add a microbial solution to the mixed gel solution, wherein the microbial solution is a suspension of nitrifying bacteria and denitrifying bacteria in a mass ratio of 1:1, and the amount of the microbial solution added is 4 wt % of the mixed gel solution. Then, the mixture is stirred at 400 rpm for 2 hours to obtain a mixture. Then, the mixture is dripped into the cross-linked mixed solution at a uniform rate using a syringe. Specifically, the cross-linked mixed solution is a mixed solution of 7.1 wt % aluminum sulfate 18hydrate and 4 wt % boric acid. The cross-linking is carried out for 70 minutes, and then the microspheres are washed with deionized water three times to obtain the immobilized microspheres subjected to the first cross-linking treatment. S2.3: Add the immobilized microspheres obtained from the first cross-linking treatment to a 0.5 mol / L anhydrous sodium sulfate solution and cross-link for 130 min. Then, wash with deionized water three times to obtain an immobilized microbial composite. S3: Treatment of ammonia-nitrogen wastewater S3.1: Pre-treat the landfill leachate through a screen filter and flotation tank to remove suspended solids and grease to obtain pre-treated 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 a fluidized bed reactor at a concentration of 2% (v / v) of the wastewater volume. The pretreated wastewater was treated at 32°C, a DO of 2 mg / L, a C / N ratio of 3, and aeration conditions for 48 h to obtain secondary treated wastewater. S3.3: The secondary treated wastewater was allowed to stand for 2 hours, and the supernatant was transferred to the advanced treatment unit. A wastewater treatment agent was then added at a rate of 1.5 g / L. The mixture was stirred at 30 rpm for 2 hours, allowed to stand for 2 hours, and filtered to obtain the tertiary treated wastewater. S3.4: Pass the tertiary treated wastewater through a granular activated carbon column to obtain final treated wastewater; The acclimation process of the immobilized microbial complex is as follows: the immobilized microbial complex is added to the fluidized bed reactor, and leachate is added at a dosage ratio of 10 mg / L, and treated for 2 days under aeration conditions. Then, 40 mg / L of leachate is added, and the treatment is carried out for 3 days under aeration conditions. Then, 100 mg / L of leachate is added, and the treatment is carried out for 3 days under aeration conditions. Finally, 200 mg / L of leachate is added, and the treatment is carried out for 3 days under aeration conditions to obtain the acclimated immobilized microbial complex.

[0025] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that, in Comparative Example 1, calcium chloride in step S1.1 is removed, and the remaining steps remain unchanged to treat the ammonia nitrogen-containing wastewater, which is recorded as Comparative Example 1.

[0026] Comparative Example 2 Compared with Example 1, the difference of Comparative Example 2 is that the aluminum chloride in step S1.1 is removed in Comparative Example 2, and the other steps remain unchanged to treat the ammonia nitrogen-containing wastewater, which is recorded as Comparative Example 2.

[0027] Comparative Example 3 Compared with Example 1, the difference of Comparative Example 3 is that the aluminum chloride and calcium chloride in step S1.1 are removed in Comparative Example 3, and the other steps remain unchanged to treat the ammonia nitrogen-containing wastewater, which is recorded as Comparative Example 3.

[0028] Comparative Example 4 Compared with Example 1, Comparative Example 4 is different in that the carboxymethyl chitosan in step S2.1 is removed in Comparative Example 4, and the remaining steps remain unchanged to treat the ammonia nitrogen-containing wastewater, which is recorded as Comparative Example 4.

[0029] Comparative Example 5 Compared with Example 1, the difference of Comparative Example 5 is that, in Comparative Example 5, the aqueous polyurethane in step S2.1 is removed, and the other steps remain unchanged to treat the ammonia nitrogen-containing wastewater, which is recorded as Comparative Example 5.

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

[0031] Comparative Example 7 Compared with Example 1, the difference of Comparative Example 7 is that the aluminum sulfate 18hydrate in step S2.2 is removed in Comparative Example 7, and the other steps remain unchanged to treat the ammonia nitrogen-containing wastewater, which is recorded as Comparative Example 7.

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

[0033] Table 1. Specific surface area, pore size and pore volume of wastewater treatment agents

[0034] As can be seen from the data in Table 1, a formula with a calcium / aluminum molar ratio of 1:1 can stably generate mesoporous materials with good structural uniformity. As can be seen from the data in Comparative Example 1, due to the lack of the skeleton support of Ca²⁺, AlCl3 alone is easily pyrolyzed to form a finer microporous structure, which is easily blocked by impurities. As can be seen from the data in Comparative Example 2, the lack of an aluminum source leads to a loose pore structure and insufficient specific surface area, which in turn leads to 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. Ammonia nitrogen removal rate measurement results of Examples 1-3 and Comparative Examples 1-7

[0037] From the data of Comparative Examples 1-3 in Table 2, it can be seen that the use of Ca / Al-modified wastewater treatment agents can significantly improve the removal rate of ammonia nitrogen. From Comparative Examples 4-5, it can be seen that the immobilized microbial complex prepared by polyvinyl alcohol, carboxymethyl chitosan and aqueous polyurethane can efficiently remove ammonia nitrogen from wastewater. From the data of Comparative Examples 6-7, it can be seen that the ability of the immobilized microbial complex to remove ammonia nitrogen from wastewater can be improved by double cross-linking, and the addition of aluminum sulfate 18hydrate followed by cross-linking can improve the removal rate of ammonia nitrogen by the immobilized microbial complex.

[0038] The apparent performance of the immobilized microbial composites prepared in Examples 1-3 and Comparative Examples 4-5 was evaluated. 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] From Comparative Example 4 in Table 3, it can be seen that the addition of carboxymethyl chitosan is beneficial to the formation of the immobilized microbial complex and improves the mechanical strength of the immobilized microbial complex. From Comparative Example 5, it can be seen that the addition of waterborne polyurethane can improve the mechanical strength of the immobilized microbial complex.

[0041] from Figure 2 It can be seen that Figure 2 The above is a surface SEM image 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 a macroporous structure is formed on the surface of the immobilized microbial complex prepared after adding water-based polyurethane, which enriches the pore structure of the immobilized microbial complex.

[0042] Figure 3 The Fourier transform infrared spectra of the wastewater treatment agents of Example 1 and Comparative Examples 1-3 show that, through comparative analysis, the composite modification of Ca and Al 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 present invention. Anyone skilled in the art may 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 one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for treating ammonia nitrogen-containing wastewater, characterized in that: The steps include: S1: Preparation of wastewater treatment agents Corn straw powder is used to prepare biochar, which is then modified with calcium / aluminum to prepare a wastewater treatment agent. S2: Preparation of immobilized microbial complexes Polyvinyl alcohol, carboxymethyl chitosan and aqueous polyurethane were used as carrier materials and loaded with microbial culture liquid, followed by cross-linking with aluminum sulfate 18hydrate and boric acid, and then with anhydrous sodium sulfate to prepare an immobilized microbial complex. S3: Treatment of ammonia-nitrogen wastewater The landfill leachate is pretreated and then subjected to nitrification-denitrification treatment 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 final treated wastewater.

2. The method for treating ammonia-nitrogen-containing wastewater according to claim 1, wherein: Step S1: Preparation of wastewater treatment agent, specifically comprising the following steps: S1.1: Calcium chloride and aluminum chloride were mixed in a calcium / aluminum molar ratio of 1:1 and added to deionized water. The pH was adjusted to 2-3 and the mixture was stirred for 20-30 minutes 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 straw powder to 100-120 parts by weight of the mixed solution, stir at 300-500 rpm for 20-30 minutes, and then oscillate at 160-180 rpm in an air bath constant temperature oscillator at 25-28°C for 20-24 hours to obtain a mixture; S1.3: Centrifuge the mixture at 3000-3500 rpm for 6-8 minutes, then dry and grind. Pyrolyze the ground powder in a muffle furnace at 550-580°C under a nitrogen atmosphere for 100-105 minutes at a heating rate of 5-8°C / min. Then keep the mixture warm for 60-70 minutes. After cooling, wash it 3-5 times and dry it to obtain a wastewater treatment agent.

3. The method for treating ammonia-nitrogen-containing wastewater according to claim 2, wherein: Step S2 is to prepare the immobilized microbial complex, which 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°C and 240-260 rpm for 2-3 hours, then cool to 50-52°C, add 1-2 parts by weight of carboxymethyl chitosan, stir at 360-400 rpm for 2-3 hours, cool to room temperature, add 1-2 parts by weight of aqueous polyurethane, and stir for 20-30 minutes to obtain a mixed gel solution; S2.2: Add the microbial culture solution to the mixed gel solution, then stir at 360-400 rpm for 1-2 hours to obtain a mixture. Then, use a syringe to uniformly add the mixture to the crosslinking mixed solution. Crosslink for 60-70 minutes, then wash with deionized water 2-3 times to obtain the immobilized microspheres after the first crosslinking treatment. S2.3: Add the immobilized microspheres after the first cross-linking treatment into a 0.5 mol / L anhydrous sodium sulfate solution, cross-link for 120-130 minutes, and then wash with deionized water 2-3 times to obtain an immobilized microbial complex.

4. The method for treating ammonia-nitrogen-containing wastewater according to claim 3, wherein: Step S3: Treatment of ammonia nitrogen-containing wastewater, specifically comprising the following steps: S3.1: Pre-treat the landfill leachate through a screen filter and flotation tank to remove suspended solids and grease to obtain pre-treated wastewater; S3.2: The pH of the pretreated wastewater is adjusted to 7.5-8 using 1 mol / L NaHCO3 solution and 1 mol / L HCl solution. The acclimated immobilized microbial complex is added to a fluidized bed reactor at a concentration of 8-10% (v / v) of the wastewater volume. The pretreated wastewater is treated under aeration conditions at 30-32°C, a DO of 2-4 mg / L, a C / N ratio of 3-4 for 40-48 hours to obtain secondary treated wastewater. S3.3: The secondary treated wastewater is allowed to stand for 1-2 hours. The supernatant is transferred to the advanced treatment unit. A wastewater treatment agent is then added at a rate of 1.5-2 g / L. The mixture is stirred at 20-30 rpm for 1-2 hours. The mixture is allowed to stand for 1-2 hours and filtered to obtain the tertiary treated wastewater. S3.4: The wastewater after the tertiary treatment is passed through a granular activated carbon column to obtain the final treated wastewater.

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

1.

6. The method for treating ammonia-nitrogen-containing wastewater according to claim 3, wherein: In step S2.2, the amount of microbial culture solution added is 4-5 wt% of the mixed gel solution.

7. The method for treating ammonia-nitrogen-containing wastewater according to claim 3, wherein: The cross-linking mixed solution in step S2.2 is specifically a mixed solution of 7.1-8.2 wt % of aluminum sulfate 18hydrate and 4-5 wt % of boric acid.

8. The method for treating ammonia-nitrogen-containing wastewater according to claim 4, wherein: The amount of immobilized microbial complex added in step S3.2 is 2-3% (v / v) of the wastewater volume.

9. The method for treating ammonia-nitrogen-containing wastewater according to claim 4, wherein: The acclimation process of the immobilized microbial complex after acclimation in step S3.2 is as follows: add the immobilized microbial complex to the fluidized bed reactor, and add the landfill leachate at a dosage ratio of 10-20 mg / L, treat it for 1-2 days under aeration conditions, then add the landfill leachate at a dosage ratio of 40-50 mg / L, treat it for 2-3 days under aeration conditions, then add the landfill leachate at a dosage ratio of 100-120 mg / L, treat it for 2-3 days under aeration conditions, and finally add the landfill leachate at a dosage ratio of 200-300 mg / L, treat it for 2-3 days under aeration conditions to obtain the acclimated immobilized microbial complex.

Images