A method for enhancing denitrification by anaerobic ammonia oxidation

Abstract

The application relates to the technical field of environmental engineering, and particularly discloses a method for strengthening denitrification by anaerobic ammonia oxidation. The method comprises the following steps: adding a zeolite-Fe3O4 composite material to an anaerobic ammonia oxidation reactor, wherein the zeolite-Fe3O4 composite material is prepared by a coprecipitation method; inoculating nitrite-type anaerobic ammonia oxidation granular sludge in the anaerobic ammonia oxidation reactor, and taking wastewater containing NH4 + -N and NO2 ‑ -N as influent water; and operating under the conditions of a temperature of 25-30 DEG C, dissolved oxygen <0.2 mg / L, pH 7.5-8.5, and a hydraulic retention time of 3-30 h. The method provided by the application can make the ammonia nitrogen removal rate reach more than 95%, the SAA activity is high, the stability of sludge particles is significantly strengthened, the average particle size of functional bacteria is significantly increased, the abundance of core functional bacteria is greatly improved, and the problems of sludge loss and insufficient bacterial activity are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of environmental engineering technology, and specifically to a method for enhancing anaerobic ammonia oxidation denitrification. Background Technology

[0002] With the acceleration of urbanization and industrial development in my country, wastewater discharge continues to increase, among which ammonia nitrogen (NH4+) is a significant component. + -N) and nitrite nitrogen (NO2) - Nitrogen pollutants such as nitrogen (N-N) are key factors causing eutrophication and damaging aquatic ecosystems. Traditional biological nitrogen removal processes (such as nitrification-denitrification) require the addition of organic carbon sources, resulting in high operating costs, large sludge production, and high greenhouse gas emissions.

[0003] Anammox is a novel autotrophic biological nitrogen removal technology that uses NO2 as a nitrogen source. - -N is the electron acceptor, directly converting NH4+ + -N is oxidized to N2 without the need for an external organic carbon source, offering advantages such as low operating costs, low sludge production, and low carbon emissions, making it a promising candidate for application in low C / N ratio wastewater treatment. However, the Anammox process still faces key technical bottlenecks in its engineering applications: slow growth of anaerobic ammonia-oxidizing bacteria (generation cycle of approximately 10-15 days), resulting in a long reactor start-up period; low substrate mass transfer efficiency, leading to easy sludge loss; and insufficient activity and community stability of functional bacteria, which restrict further improvement in the system's nitrogen removal efficiency.

[0004] To enhance the nitrogen removal efficiency of Anammox reactors, researchers attempted to add functional materials to the reactor. Zeolite, a porous aluminosilicate mineral, possesses a large specific surface area and excellent ion exchange performance, enabling it to adsorb NH4 from wastewater. + -N creates an ammonia-rich microenvironment for Anammox bacteria and can also serve as a carrier for microbial attachment, reducing sludge loss. However, adding zeolite alone can only achieve physical enrichment of the substrate and cannot enhance the metabolic activity of microorganisms and the extracellular electron transfer process, resulting in limited improvement in denitrification efficiency.

[0005] On the other hand, iron(III) oxide (Fe3O4) possesses excellent electrical conductivity and redox activity, which can mediate extracellular electron transfer in microorganisms and enhance the activity of functional enzymes. Simultaneously, Fe... 3+ Fe3O4 can act as an additional electron acceptor in the Feammox process to enhance total nitrogen removal. However, when Fe3O4 is added alone, the particles are easily lost with the water flow, making it difficult to remain stably in the reactor. Furthermore, it lacks the ability to actively enrich the substrate, raising concerns about the long-term stability and recycling of the material.

[0006] Currently, there is no systematic technical solution in the existing technology for preparing composite materials by loading Fe3O4 onto the surface of zeolite and using them to enhance the Anammox process. Simply mixing zeolite and Fe3O4 cannot achieve synergistic effects, and Fe3O4 is prone to loss, resulting in a discontinuous conductive network.

[0007] Therefore, there is an urgent need to develop an Anammox denitrification enhancement method that can simultaneously leverage the adsorption and enrichment effects of zeolite and the electron transfer enhancement effect of Fe3O4, while also possessing good material stability and recyclability, in order to solve the technical problems of low denitrification efficiency, easy sludge loss, and long start-up period in existing processes. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems of low denitrification efficiency, insufficient activity of functional bacteria, easy sludge loss, and lack of stable materials that combine substrate enrichment and electron transfer enhancement in existing anaerobic ammonia oxidation processes.

[0009] To achieve the above objectives, the present invention provides a method for enhanced anaerobic ammonia oxidation denitrification, comprising the following steps: Zeolite-Fe3O4 composite material was added to an anaerobic ammonia oxidation reactor. The zeolite-Fe3O4 composite material was prepared by a co-precipitation method, comprising: adding natural zeolite to Fe... 3+ and Fe 2+ In a mixed solution, the pH was adjusted to alkaline to allow Fe3O4 nanoparticles to be generated in situ and loaded onto the surface of natural zeolite. Nitrite-type anaerobic ammonia oxidation granular sludge was inoculated into the anaerobic ammonia oxidation reactor to contain NH4+. + -N and NO2 - -N wastewater is used as influent, and the system operates under the following conditions: temperature 25-30℃, dissolved oxygen <0.2 mg / L, pH 7.5-8.5, and hydraulic retention time 3-30h.

[0010] Compared with the prior art, the present invention has at least the following advantages: (1) The denitrification efficiency of the present invention is significantly improved. After adding zeolite-Fe3O4 composite material, the NH4 in the reactor is reduced. + -N removal rate remained stable at over 95%, reaching a maximum of 97.27%, which was significantly higher than the blank control group (74.70%), the zeolite-only group (78.07%), and the Fe3O4-only group (95.47%).

[0011] (2) The functional bacteria of the present invention have significantly improved activity, reaching 3.13 mg N / (gVSS·h) compared with anaerobic ammonia oxidation (SAA), which is 24.12% higher than that of the inoculated sludge and more than 22.60% higher than that of the blank control group.

[0012] (3) The sludge particles of the present invention have enhanced stability, significantly increased EPS secretion of granular sludge, PN / PS ratio of more than 2.59, average particle size increased by 107.62% (to 352.44nm) compared with inoculated sludge, significantly improved mechanical strength and shock resistance of sludge, and reduced sludge loss.

[0013] (4) The microbial community optimization of the present invention has a relative abundance of 49.66% of the Planctomycetota phylum, with the core functional genus Candidatus Brocadia becoming the dominant genus, and filamentous bacteria and functional bacteria forming a stable symbiotic system.

[0014] (5) The material of the present invention has good stability and can be recycled. The microstructure of the composite material is intact after 90 days of operation, and the change rate of the core element is <±5%. It can be recycled by magnetic separation and reused after simple activation, thereby reducing operating costs.

[0015] (6) The process of the present invention is simple and highly applicable. It does not require an external organic carbon source, has clear operating parameters, and can adjust the dosage according to different influent concentrations. It is suitable for the treatment of municipal sewage and industrial wastewater with low carbon-to-nitrogen ratio. Attached Figure Description

[0016] Figure 1 This is an XRD pattern and magnetic separation characteristic diagram of a zeolite-Fe3O4 composite material in a preferred embodiment of the present invention; Figure 2 This refers to the specific anaerobic ammonium oxidation activity of the sludge in the reactor at the initial stage of operation in Test Example 1 of the present invention; Figure 3 This is the specific anaerobic ammonium oxidation activity of the sludge in the reactor after 90 days of operation in Test Example 1 of the present invention; Figure 4 This is the nitrogen conversion performance change curve of the reactor during operation in Test Example 1 of the present invention; Figure 5 This is the ammonia nitrogen removal rate (ARE) change curve during reactor operation in Test Example 1 of the present invention; Figure 6 This is a diagram showing the EPS composition of the sludge in the reactor after 90 days of operation in Test Example 2 of the present invention; Figure 7 This is a diagram showing the microstructure and average particle size of the sludge in the reactor after 90 days of operation in Test Example 3 of this invention. Figure 8 The images show the microstructure and EDS elemental analysis of the zeolite-Fe3O4 composite material in the reactor during test example 4 of this invention, after running for 0 days and 90 days. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] As mentioned above, the first aspect of the present invention provides a method for enhanced anaerobic ammonia oxidation denitrification, comprising the following steps: Zeolite-Fe3O4 composite material was added to an anaerobic ammonia oxidation reactor. The zeolite-Fe3O4 composite material was prepared by a co-precipitation method, comprising: adding natural zeolite to Fe... 3+ and Fe 2+ In a mixed solution, the pH was adjusted to alkaline to allow Fe3O4 nanoparticles to be generated in situ and loaded onto the surface of natural zeolite. Nitrite-type anaerobic ammonia oxidation granular sludge was inoculated into the anaerobic ammonia oxidation reactor to contain NH4+. + -N and NO2 - -N wastewater is used as influent, and the system operates under the following conditions: temperature 25-30℃, dissolved oxygen <0.2mg / L, pH 7.5-8.5, and hydraulic retention time 3-30h.

[0019] Preferably, the method of the present invention further includes that the anaerobic ammonia oxidation reactor has no fixed sludge discharge.

[0020] Preferably, the method of the present invention further includes adjusting the pH of the influent by adding NaHCO3.

[0021] It should be noted that, in this invention, the nitrite-type anaerobic ammonia oxidation granular sludge refers to a granular bioaggregate formed by the self-aggregation of anaerobic ammonia oxidation bacteria that can carry out anaerobic ammonia oxidation reactions using nitrite as an electron acceptor and ammonia nitrogen as an electron donor.

[0022] According to a preferred embodiment, the zeolite is natural clinoptilolite with a silica-alumina ratio of 4.2-5.5 and an average pore size of 0.40-0.65 nm.

[0023] In a preferred embodiment, the Fe3O4 loading in the zeolite-Fe3O4 composite material is 16.6-22.8 wt% of the mass of the natural zeolite.

[0024] In a preferred embodiment, when the NH4 in the influent... + -N concentration is 50 mg / L, NO2 - When the -N concentration is 65 mg / L, the dosage of the zeolite-Fe3O4 composite material is 4.5-5.5 g / L.

[0025] It should be noted that, in this invention, the dosage of the zeolite-Fe3O4 composite material is the weight (g) of the zeolite-Fe3O4 composite material per L of influent in the anaerobic ammonia oxidation reactor.

[0026] More preferably, when the NH4 in the influent... + -N concentration is 50 mg / L, NO2 - When the -N concentration is 65 mg / L, the dosage of the zeolite-Fe3O4 composite material is 5.0 g / L.

[0027] More preferably, when the NH4 in the influent... + When the -N concentration increases, the dosage of the zeolite-Fe3O4 composite material is increased proportionally.

[0028] Preferably, when the influent contains NH4 + When the -N concentration increases, the method for proportionally increasing the dosage of the zeolite-Fe3O4 composite material includes: under initial conditions (influent NH4) + -NN is 50 mg / L, dosage is 5.0 g / L) as the baseline, the dosage is compared with the influent NH4 + -N concentration shows a linear proportional relationship, i.e., dosage (g / L) = 0.1 × influent NH4. + -N concentration (mg / L). For example, when the influent NH4... + When the -N concentration is increased to 100 mg / L, the dosage of zeolite-Fe3O4 composite material is correspondingly increased to 10.0 g / L.

[0029] According to a preferred embodiment, the effective volume of the anaerobic ammonia oxidation reactor is 1.5-2 L, the inoculum amount of the nitrite-type anaerobic ammonia oxidation granular sludge is 3.5 g·VSS / L, and the influent flow rate is 0.25 L / h.

[0030] In a preferred embodiment, after the zeolite-Fe3O4 composite material has been continuously operated in the anaerobic ammonia oxidation reactor for 90 days, the content change rate of its core elements Si, Al and Fe is within ±5wt%, based on the element content at day 0.

[0031] Preferably, after the zeolite-Fe3O4 composite material has been continuously operated in the anaerobic ammonia oxidation reactor for 90 days, the microstructure of the zeolite-Fe3O4 composite material shows no cracking or collapse.

[0032] It should be noted that in this invention, the content change rate is based on the element content at day 0 of operation, and the calculation formula is: (content after 90 days of operation - initial content) / initial content × 100%.

[0033] In a preferred embodiment, the method of the present invention further includes a step of magnetic separation and recovery of zeolite-Fe3O4 composite material in the effluent of the anaerobic ammonia oxidation reactor: separation is performed using a magnet with a magnetic field strength of 8000-12000 GS, and the collected material is rinsed with deionized water, dried and activated at 65-100℃, and then reused.

[0034] In a preferred embodiment, the nitrite-type anammox granular sludge is washed with PBS buffer until the supernatant contains NH4. + -N and NO2 - Use only after the -N concentration is below 0.5 mg / L.

[0035] It should be noted that, in this invention, the NH4 + The NO2- concentration was detected using Nessler's reagent spectrophotometry. - -N concentration was determined using diazo coupling spectrophotometry.

[0036] Preferably, the natural zeolite is clinoptilolite, and the co-precipitation method includes: reacting the natural zeolite with Fe... 3+ and Fe 2+ After stirring the mixture in a mixed solution at 70°C for 0.5 h, add 2 mol / L NaOH solution to adjust the pH to 10, continue the reaction at 70°C for 1 h, and then wash, dry and grind with deionized water to obtain the final product.

[0037] Preferably, in the Fe 3+ and Fe 2+ In the mixed solution, the Fe 3+ The concentration of Fe is 0.2 mol / L. 2+ The concentration is 0.1 mol / L.

[0038] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used are all commercially available products.

[0039] Natural zeolite: It is natural clinoptilolite with a silica-alumina ratio of 4.85 and an average pore size of 0.525 nm. It was purchased from Henan Borun New Materials Co., Ltd. Nitrite-type anaerobic ammonia oxidation granular sludge: purchased from Jia Yi Environmental Protection Co., Ltd.

[0040] Anaerobic ammonia oxidation reactor: effective volume is 1.5 L.

[0041] NH4+ -N concentration: determined by Nessler's reagent spectrophotometry; NO2 - -N concentration: Detected using diazo coupling spectrophotometry.

[0042] Preparation Example 1 Preparation of zeolite-Fe3O4 composite materials: Weigh out FeCl3·6H2O to prepare 250 mL of FeCl3·6H2O solution with a concentration of 0.2 mol / L. 3+ To prepare a solution, weigh out FeSO4·7H2O and prepare 250 mL of a 0.1 mol / L Fe solution. 2+ Solution, and the prepared Fe 3+ Solution and Fe 2+ The solution was added to the conical flask to obtain Fe. 3+ and Fe 2+ Mixed solution. Using a co-precipitation method, accurately weigh 5g of natural zeolite and add it to the above Fe... 3+ and Fe 2+ The mixture was then placed in a 70°C constant temperature water bath shaker and stirred for 0.5 h. Then, 2 mol / L NaOH solution was added dropwise until the pH reached 10, and the mixture was placed in a 70°C constant temperature water bath shaker to continue the reaction for 1 h. Finally, the mixture was washed with deionized water, dried, and ground to obtain a zeolite-Fe3O4 composite material with a Fe3O4 loading of 22.4 wt% of the natural zeolite mass, named P1.

[0043] Figure 1 The images show the XRD patterns and magnetic separation characteristics of the composite material obtained by X-ray diffraction (XRD). Figure 1 (a) shows the XRD pattern of the zeolite-Fe3O4 composite material. It can be seen that the composite material exhibits the characteristic peaks of natural zeolite at 2θ=9.87°, 20.9°, 22.3°, 25.6°, 26.7° and 27.7°, and at the same time, five characteristic peaks of Fe3O4 (2θ=30.1°, 35.6°, 43.3°, 57.2° and 62.7°) appear, confirming the successful synthesis of the zeolite-Fe3O4 composite material.

[0044] Figure 1 (b) shows the magnetic separation test results of the zeolite-Fe3O4 composite material. It can be seen that under the action of an external magnetic field (neodymium iron boron button magnet, magnetic field strength 8000-12000 GS), the originally uniformly dispersed composite material powder rapidly moves towards the magnet and accumulates, showing good magnetic response characteristics.

[0045] Example 1

[0046] This embodiment illustrates that the anaerobic ammonia oxidation denitrification enhancement method of the present invention is carried out according to the following steps: Zeolite-Fe3O4 composite material was added to the anaerobic ammonia oxidation reactor at a dosage of 5.0 g / L. Nitrite-type anaerobic ammonia oxidation granular sludge was washed with PBS buffer until NH4 was added to the supernatant. + -N and NO2 - After the -N concentration was below 0.5 mg / L, it was inoculated into the anaerobic ammonia oxidation reactor (inoculation amount was 3.5 g·VSS / L) to contain 50 mg / L NH4. + -N and 65 mg / L NO2 - The wastewater from the -N reactor was used as the influent (flow rate of 0.25 L / h). The reactor operated for 90 days under the following conditions: temperature 25℃, dissolved oxygen <0.2 mg / L, pH adjusted to 8.0±0.2 using NaHCO3, and hydraulic retention time of 6 h. During this period, the anaerobic ammonia oxidation reactor did not discharge any fixed sludge.

[0047] The zeolite-Fe3O4 composite material in the effluent of the anaerobic ammonia oxidation reactor was magnetically separated and recovered: a magnet with a magnetic field strength of 10000 GS was used for separation, and the collected material was rinsed with deionized water, dried and activated at 80℃ and then reused.

[0048] Examples 2-6

[0049] The same method as in Example 1 was used, except that the dosage of the zeolite-Fe3O4 composite material was different: 1.0 g / L in Example 2, 2.0 g / L in Example 3, 3.0 g / L in Example 4, 4.0 g / L in Example 5, and 6.0 g / L in Example 6.

[0050] Comparative Example 1 The same method as in Example 1 was used, except that the dosage of the zeolite-Fe3O4 composite material was 0 g / L.

[0051] Comparative Example 2 The procedure was carried out using a method similar to that in Example 1, except that an equal mass of natural zeolite was used instead of the zeolite-Fe3O4 composite material.

[0052] Comparative Example 3 The procedure was carried out using a method similar to that in Example 1, except that an equal mass of Fe3O4 was used instead of the zeolite-Fe3O4 composite material.

[0053] Test Example 1 The specific anaerobic ammonium oxidation (SAA) activity of the sludge in the reactors during the initial operation of the above examples was measured. The results are shown in [link to results]. Figure 2 , Figure 2As can be seen, the SAA activity first increases and then decreases with the increase of the dosage of zeolite-Fe3O4 composite material. Among them, 5.0 g / L is the optimal dosage, at which the SAA activity reaches the maximum value of 3.49 mgN / (g VSS·h), which is 62.3% higher than that of the blank group. When the dosage is increased to 6 g / L, the SAA activity drops to 3.43 mg N / (g VSS·h), indicating that excessive addition will have an inhibitory effect.

[0054] The specific anammox activity (SAA activity) of the sludge in the reactors of the above examples was measured after 90 days of operation to evaluate the microbial activity of anammox. The results are shown in [link to results]. Figure 3 In this context, nitrite-type anaerobic ammonia oxidation granular sludge is referred to as inoculation sludge, Example 1 is referred to as A2, Comparative Example 1 is referred to as A1, Comparative Example 2 is referred to as A3, and Comparative Example 3 is referred to as A4. Figure 3 It can be seen that the SAA activity of A2 is 3.20 mg N / (g VSS·h), which is significantly higher than that of reactor A1 (2.55 mg N / (g VSS·h), A3 (2.77 mg N / (g VSS·h), and A4 (2.94 mg N / (g VSS·h).

[0055] The nitrogen conversion performance curves for each reactor in the above examples were measured during operation. The results are shown in [link to results]. Figure 4 In this context, Example 1 is denoted as A2, Comparative Example 1 as A1, Comparative Example 2 as A3, and Comparative Example 3 as A4; The ammonia nitrogen removal rate (ARE) variation curves were measured during reactor operation in the above examples. The results are shown in [link to results]. Figure 5 In the figure, Example 1 is referred to as A2, Comparative Example 1 is referred to as A1, Comparative Example 2 is referred to as A3, and Comparative Example 3 is referred to as A4. As can be seen from the figure, during the 90-day operation of the reactor, the ammonia nitrogen removal rate of reactor A2 was stable at over 95%, reaching a maximum of 97.27%, while the ammonia nitrogen removal rates of reactors A1, A3, and A4 were 74.70%, 78.07%, and 95.47%, respectively.

[0056] Test Example 2 The EPS (extracellular polymeric substances) composition of the sludge in the reactors of the above examples was determined after 90 days of operation. The results are shown in [link to results]. Figure 6 In this context, Example 1 is denoted as A2, Comparative Example 1 as A1, Comparative Example 2 as A3, Comparative Example 3 as A4, Tightly bonded EPS as T-EPS, Loosely bonded EPS as L-EPS, and Soluble EPS as S-EPS.

[0057] Figure 6As can be seen from (a) and (b), the protein concentration in A1, A2, A3, and A4 is significantly higher than that in carbohydrates. Among them, A2 has the highest protein concentration.

[0058] In addition, a higher PN / PS ratio is beneficial for Anammox granular sludge granulation and increases granule strength, and can be used as a key indicator for granule formation. Figure 6 In (c), the PN / PS ratio of the inoculated sludge was 1.53. After 90 days of operation, the PN / PS ratios of A1, A2, A3, and A4 increased to 1.79, 2.59, 2.07, and 2.81, respectively. A2 had the highest PN / PS ratio, presumably due to the adsorption of substrate by zeolite and the presence of Fe3O4. 3+ The metabolic characteristics of AnAOB promote PN secretion and maintain the stability of Anammox granular sludge. This is consistent with the finding that A2 has a high ARE (Acid-Residue-Retaining Capacity) during reactor operation, and also explains the mechanism by which the zeolite-Fe3O4 composite material enhances granular stability by increasing PN / PS. Furthermore, PN content is positively correlated with sludge settling performance; the higher the PN concentration, the better the settling performance of the granular sludge. Microorganisms in A2 promote EPS secretion, reduce AnAOB loss, enhance biomass retention, and improve the denitrification efficiency of Anammox.

[0059] Test Example 3 The microstructure and average particle size of the sludge in the reactors of the above examples after 90 days of operation were determined by scanning electron microscopy. See the results below. Figure 7 In this context, Example 1 is denoted as A2, Comparative Example 1 as A1, Comparative Example 2 as A3, and Comparative Example 3 as A4.

[0060] Figure 7 As can be seen, the anaerobic ammonia-oxidizing bacteria in each group of sludge particles are mainly oval and spherical, consisting of short bacilli and cocci, consistent with the typical morphological characteristics of anaerobic ammonia-oxidizing bacteria. The average particle size of anaerobic ammonia-oxidizing bacteria in the inoculated sludge was 169.75 nm. After 90 days of operation, the particle size of bacteria in each group showed an increasing trend. In group A1, without the assistance of exogenous materials, relying solely on the metabolism and proliferation of the bacteria themselves, the particle size was 186.49 nm, an increase of 9.86% compared to the inoculated sludge. In group A3, the addition of natural zeolite resulted in a microbial particle size of 208.04 nm, an increase of 22.56%. In group A4, the addition of Fe3O4 resulted in an average microbial particle size of 286.16 nm, an increase of 68.58% compared to the inoculated sludge. In group A2, the addition of zeolite-Fe3O4 composite material resulted in a functional bacterial particle size of 352.44 nm, an increase of 107.62% compared to the inoculated sludge, the highest increase among all groups.

[0061] Further analysis at the phylum and genus levels revealed that the dominant phyla in the inoculated sludge were Planctomycetota, Pseudomonadota, and Bacteroidota, with relative abundances of 31.93%, 22.62%, and 16.20% of all phyla, respectively. In A1, the relative abundances of these three phyla were 34.86%, 22.54%, and 11.19% of all phyla, respectively, for a total relative abundance of 68.60%. In A2, the relative abundances of these three phyla were 49.66% (with Candidatus Brocadia being the most dominant genus at 5.68 wt%), 19.77%, and 7.01% of all phyla, respectively, for a total relative abundance of 76.44%. In A3, the relative abundances of these three phyla were 32.47%, 26.07%, and 11.57% of all phyla. The total relative abundance of the top three dominant bacteria was 70.12%. The relative abundance of the three A4 phyla was 32.56%, 27.06%, and 10.5% of all phyla.

[0062] It is evident that the relative abundance of Planctomycetota in the inoculated sludge was the lowest among all samples. However, after 90 days of reactor operation, the relative abundance of Planctomycetota in groups A1, A2, A3, and A4 all increased, with increases of 9.18%, 14.8%, 1.7%, and 0.63%, respectively. It can be seen that the A2 reactor, which incorporated the zeolite-Fe3O4 composite material, showed the most significant increase in the relative abundance of Planctomycetota in the sludge particles.

[0063] Test Example 4 Microstructure and EDS elemental analysis were performed on the zeolite-Fe3O4 composite material in the reactor during 0 and 90 days of operation in Example 1. The results are shown in [link to results]. Figure 8 .

[0064] As shown in the figure, the initial zeolite-Fe3O4 composite material exhibits a loose, porous, three-dimensional network structure with clear and regular morphological features. After 90 days, the composite material became slightly denser, with some pores being covered by EPS, but there was no cracking or collapse, and the skeletal structure remained intact.

[0065] The initial weight contents of Si, Al, and Fe in the zeolite-Fe3O4 composite material were 53.01%, 10.56%, and 28.83%, respectively. After 90 days, these contents were 53.69%, 10.77%, and 28.37%, respectively. The change rate of the core element content was within ±5wt%, with no significant loss. Only the C element increased slightly by 0.03%, which was due to EPS adhering to the surface and did not affect the chemical properties of the material.

[0066] The results show that the method provided by this invention, through the addition of zeolite-Fe3O4 composite material, achieves a stable ammonia nitrogen removal rate of over 95% (maximum 97.27%) in the anaerobic ammonia oxidation reactor, and increases SAA activity to 3.13 mg N / (g VSS·h), which is more than 22.60% higher than the blank control. It significantly enhances the stability of sludge particles, significantly increases the average particle size of functional bacteria, and greatly improves the abundance of core functional bacteria, effectively solving the problems of sludge loss and insufficient bacterial activity. After 90 days of continuous operation, the composite material maintains a complete microstructure with a core element change rate of less than ±5%, and can be recycled through magnetic separation, achieving long-term stable operation and low-cost recycling.

[0067] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for enhanced anaerobic ammonium oxidation denitrification, characterized in that, Includes the following steps: Zeolite-Fe3O4 composite material was added to an anaerobic ammonia oxidation reactor. The zeolite-Fe3O4 composite material was prepared by a co-precipitation method, comprising: adding natural zeolite to Fe... 3+ and Fe 2+ In a mixed solution, the pH was adjusted to alkaline to allow Fe3O4 nanoparticles to be generated in situ and loaded onto the surface of natural zeolite. Nitrite-type anaerobic ammonia oxidation granular sludge was inoculated into the anaerobic ammonia oxidation reactor to contain NH4+. + -N and NO2 - -N wastewater is used as influent, and the system operates under the following conditions: temperature 25-30℃, dissolved oxygen <0.2mg / L, pH 7.5-8.5, and hydraulic retention time 3-30 h.

2. The method according to claim 1, characterized in that, The zeolite is natural clinoptilolite with a silica-alumina ratio of 4.2-5.5 and an average pore size of 0.40-0.65 nm.

3. The method according to claim 1 or 2, characterized in that, The loading of Fe3O4 in the zeolite-Fe3O4 composite material is 16.6-22.8 wt% of the mass of the natural zeolite.

4. The method according to claim 1 or 2, characterized in that, When the influent contains NH4 + -N concentration is 50 mg / L, NO2 - When the -N concentration is 65 mg / L, the dosage of the zeolite-Fe3O4 composite material is 4.5-5.5 g / L.

5. The method according to claim 1 or 2, characterized in that, When the influent contains NH4 + -N concentration is 50 mg / L, NO2 - When the -N concentration is 65 mg / L, the dosage of the zeolite-Fe3O4 composite material is 5.0 g / L.

6. The method according to claim 1 or 2, characterized in that, The effective volume of the anaerobic ammonia oxidation reactor is 1.5-2 L, the inoculum amount of the nitrite-type anaerobic ammonia oxidation granular sludge is 3.5 g·VSS / L, and the influent flow rate is 0.25 L / h.

7. The method according to claim 1 or 2, characterized in that, After the zeolite-Fe3O4 composite material was continuously operated in the anaerobic ammonia oxidation reactor for 90 days, the content change rate of its core elements Si, Al and Fe was within ±5wt%, based on the element content at day 0.

8. The method according to claim 1 or 2, characterized in that, The method also includes a step of magnetic separation and recovery of zeolite-Fe3O4 composite material in the effluent of the anaerobic ammonia oxidation reactor: separation is performed using a magnet with a magnetic field strength of 8000-12000 GS, and the collected material is rinsed with deionized water, dried and activated at 65-100℃ and then reused.

9. The method according to claim 1 or 2, characterized in that, The nitrite-type anammox granular sludge was washed with PBS buffer until NH4 was added to the supernatant. + -N and NO2 - Use only after the -N concentration is below 0.5 mg / L.

10. The method according to claim 1 or 2, characterized in that, The coprecipitation method includes: reacting the natural zeolite in Fe... 3+ and Fe 2+ After stirring the mixture in a solution at 70°C for 0.5 h, add 2 mol / L NaOH solution to adjust the pH to 10, continue the reaction at 70°C for 1 h, and then wash, dry and grind to obtain the final product.

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