Modified MABR membrane material for inhibiting nitrite oxidizing bacteria

Abstract

The invention relates to the technical field of sewage treatment, in particular to a modified MABR membrane material for inhibiting nitrite oxidizing bacteria, the membrane material comprises a hollow fiber membrane matrix and a functional layer loaded on the outer surface of the hollow fiber membrane matrix, the functional layer comprises an iron-based active component and a carrier matrix, the functional layer is combined with the hollow fiber membrane matrix in a chemical bonding or molecular embedding manner. The membrane material disclosed by the invention can selectively inhibit the activity of nitrite oxidizing bacteria at a membrane-biological membrane interface by slowly releasing iron ions (Fe < 2 + > and Fe < 3 + >) in an operation process, stabilize nitrite accumulation and promote an anaerobic ammonia oxidation denitrification process. Compared with the prior art, the MABR-Anammox composite material has the advantages of precise and long-acting inhibition effect, high biological selectivity, firm structure, excellent mass transfer performance and the like, and provides core material support for engineering application of an MABR-Anammox process.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment technology, specifically to a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria. Background Technology

[0002] Anammox, a mainstream wastewater denitrification technology, is considered a revolutionary direction for next-generation wastewater treatment due to its lack of organic carbon sources, low sludge production, and low energy consumption and carbon emissions. The successful implementation of this technology relies on the stable and efficient supply of the reaction substrate—nitrite (NO2). – The membrane aerated biofilm reactor (MABR), with its unique "gas-phase oxygen supply and reverse mass transfer" characteristics, can spontaneously form a dissolved oxygen gradient within a single biofilm. This provides an ideal platform for enriching ammonia-oxidizing bacteria (AOB, responsible for oxidizing ammonia nitrogen to nitrite) and anaerobic ammonia-oxidizing bacteria (AnAOB) under mainstream conditions, and is one of the key technologies for realizing mainstream anaerobic ammonia oxidation.

[0003] However, this technological approach faces a fundamental challenge: competition from nitrite-oxidizing bacteria (NOB). NOB uses nitrite as a substrate, oxidizing it to nitrate, directly consuming the nitrite required for the Anammox reaction, and competing with AOB for oxygen and living space with AnAOB. ​​In mainstream wastewater environments with low temperatures and fluctuating substrate concentrations, NOB has an unpredictable proliferation potential, often leading to instability in short-cut nitrification processes, failure of nitrite accumulation, and ultimately, the collapse of the entire autotrophic denitrification system. Traditional strategies for suppressing NOB, such as controlling dissolved oxygen, sludge age, temperature, pH, or adding chemical inhibitors (such as hydroxylamine and chlorate), generally suffer from problems in practical wastewater treatment applications, including complex control, unstable effects, high operating costs, or ecological risks.

[0004] In recent years, studies have shown that certain forms of iron (such as Fe) 2+ / Fe 3+ It has a selective inhibitory effect on the metabolic activity of NOB. Its mechanism may involve interfering with cytochrome c oxidase or nitrite oxidoreductase (NXR). Existing technology usually adds soluble iron salts to the water in a homogeneous manner. However, this method has significant drawbacks: (1) Iron ions diffuse and dilute rapidly in the reactor, making it difficult to maintain an effective concentration at the critical biofilm-membrane interface; (2) Intermittent addition leads to concentration fluctuations and the inhibitory effect is not sustained; (3) Excessive iron ions may be toxic to other functional bacteria such as AnAOB and lead to increased effluent color and secondary pollution; (4) It increases the consumption of reagents and operating costs.

[0005] To overcome the aforementioned shortcomings, existing technologies attempt to directly load iron-based materials onto membrane modules. For example, one study disclosed a Fe / C-based membrane module where an iron-carbon powder layer is deposited onto the surface of a hydrophobic organic membrane via vacuum filtration to enhance the in-situ dissimilatory reduction of nitrates produced by anaerobic ammonia oxidation. While this technology can alleviate nitrate accumulation to some extent, its core purpose is "end-of-pipe treatment" of nitrates, rather than inhibiting NOB proliferation at the source. Furthermore, the powder layer formed through physical filtration has weak binding force and is prone to detachment under long-term hydraulic shear. Additionally, the additional thick layer may increase oxygen mass transfer resistance, affecting the core oxygen supply efficiency of MABR. Another study disclosed a method for preparing a nanofiber-loaded membrane, where nano-iron is loaded onto a fiber mat via electrospinning for the catalytic reduction removal of pollutants in water. However, the fiber mat prepared by this technology has a non-woven fabric structure, not a hollow fiber membrane, making it unsuitable for the gas reverse mass transfer mode of MABR reactors. Moreover, its mechanism of action is chemical reduction, without involving selective biological inhibition of NOB.

[0006] For a long time, technicians have generally believed that loading functional layers onto the membrane surface increases oxygen mass transfer resistance, and that the thicker the functional layer and the more functional components loaded, the better the suppression effect. Therefore, existing technologies tend to use thicker functional layers, without considering the possibility of maintaining excellent mass transfer performance while ensuring suppression effects with ultrathin functional layers. Therefore, developing a modified membrane material that can suppress NOB in situ, continuously, and selectively, with robust loading, minimal impact on oxygen mass transfer, and specifically designed for MABR systems, has become a key problem that urgently needs to be solved to promote the engineering application of the MABR-Anammox process. Summary of the Invention

[0007] This application provides a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria. The primary purpose is to overcome the shortcomings of existing NOB inhibition methods, such as unstable effects, non-selectivity, potential secondary pollution, and complex operation. The modified MABR membrane material provided in this application achieves in-situ, long-term, and precise inhibition of NOB by directly integrating the inhibition function into the mass transfer core—the surface of the hollow fiber membrane.

[0008] Another objective of this application is to provide a method for preparing the above-mentioned modified MABR membrane material. This method includes two technical routes: in-situ synthesis and blend spinning. The process is controllable, can be mass-produced, and can enable the functional layer to form a strong bond with the membrane substrate through chemical bonding or molecular embedding.

[0009] Another objective of this application is to provide the application of the above-mentioned modified MABR membrane material in wastewater treatment, particularly in membrane aerated biofilm reactors for constructing and stabilizing anaerobic ammonia oxidation denitrification processes based on short-cut nitrification or short-cut denitrification.

[0010] To achieve the above objectives, this application provides a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria and its preparation method. The modified MABR membrane material uses a hollow fiber membrane as the matrix, and a composite functional layer formed by iron-based active components and a carrier matrix is ​​firmly loaded onto the membrane surface through in-situ synthesis or co-spinning. The slow-release effect of the iron-based components is used to achieve long-term selective inhibition of NOB at the membrane-biomembrane interface, thereby stabilizing nitrite accumulation and promoting the anaerobic ammonia oxidation denitrification process. It has the advantages of strong binding, stable inhibition effect, minimal impact on functional bacteria, and ease of engineering application.

[0011] On one hand, this application provides a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria. The membrane material includes a hollow fiber membrane substrate and a functional layer loaded on the outer surface of the hollow fiber membrane substrate. The functional layer includes an iron-based active component and a carrier matrix for selectively inhibiting nitrite-oxidizing bacteria at the membrane-biomembrane interface. The functional layer is bonded to the hollow fiber membrane substrate by chemical bonding or molecular encapsulation. The thickness of the functional layer is 0.1-10 μm, and the functional layer is configured to release a total iron ion concentration of 0.1-10 μM at the membrane-biomembrane interface.

[0012] The iron ion release concentration is determined by the following factors: (1) Functional layer thickness: The thickness affects the total loading of iron-based active components. A thickness range of 0.1-10 μm can achieve a sustained release concentration of 0.1-10 μM; (2) Loading of iron-based active components: It accounts for 5%-60% of the total mass of the functional layer, which is achieved by regulating the iron precursor concentration (0.05-0.5 M) and reaction time; (3) Sustained release characteristics of the carrier matrix: Different carrier matrices (such as polydopamine, silica sol-gel) regulate the release rate of iron ions through their porous structure and chemical bonding ability. Through the synergistic regulation of the above parameters, a stable release of iron ions in the range of 0.1-10 μM can be achieved. Studies have found that when the iron ion concentration is below 0.1 μM, the inhibitory effect on NOB is not significant; when the iron ion concentration is above 10 μM, it may cause toxicity to AOB and AnAOB. Therefore, controlling the iron ion concentration within the range of 0.1-10 μM can effectively inhibit NOB while ensuring the activity of the core functional bacterial community.

[0013] In one optional embodiment, the thickness of the functional layer is 0.5-5 μm. Within this preferred thickness range, sufficient loading of the iron-based active component can be ensured while minimizing oxygen mass transfer resistance, achieving an optimal balance between inhibition effect and mass transfer efficiency.

[0014] In one optional embodiment, the hollow fiber membrane matrix is ​​made of at least one of polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyethersulfone, or polydimethylsiloxane.

[0015] In one optional embodiment, the hollow fiber membrane has an outer diameter of 0.5-3 mm, a wall thickness of 0.2-1 mm, and an average pore size of 0.01-1 μm.

[0016] In one alternative embodiment, the iron-based active component includes at least one of zero-valent iron nanoparticles and iron oxides.

[0017] In one optional embodiment, the iron-based active component has a particle size of 10-200 nm and accounts for 5 wt%-60 wt% of the total mass of the functional layer.

[0018] In one alternative embodiment, the iron oxide nanoparticles are selected from at least one of iron(II,III) oxide, goethite, or ferrohydrite.

[0019] In one alternative embodiment, the carrier matrix is ​​used to immobilize and disperse the iron-based active component and regulate its sustained-release behavior, the carrier matrix comprising at least one of silica sol-gel, polydopamine, chitosan, sodium alginate, polyethyleneimine, polyvinyl alcohol, or polyacrylic acid.

[0020] Secondly, this application provides a method for preparing a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria, wherein a functional layer is loaded onto the outer surface of the hollow fiber membrane using an in-situ synthesis method or a blending spinning method.

[0021] In one optional embodiment, the in-situ synthesis method includes the following steps: S11, performing surface activation pretreatment on the hollow fiber membrane substrate; S12, immersing the pretreated membrane substrate in a mixed solution containing an iron precursor and a carrier matrix precursor; S13, curing and post-treating the membrane loaded with the functional layer.

[0022] In one optional embodiment, in the in-situ synthesis method, the molar ratio of the iron precursor to the carrier matrix precursor is 1:1-5. Preferably, the molar ratio of the iron precursor to the carrier matrix precursor is 1:2.

[0023] In one alternative embodiment, in the in-situ synthesis method, the curing step includes stirring in an inert atmosphere for 1-4 hours. The post-treatment step includes immersing the cured film in anhydrous ethanol for 5-20 minutes and then drying it at a temperature of 30-60 °C for 12-36 hours.

[0024] In one optional embodiment, the surface activation pretreatment method in the in-situ synthesis method includes at least one of chemical coupling, vapor deposition, plasma treatment, and photochemical treatment.

[0025] In one alternative embodiment, the iron precursor comprises at least one of ferrous sulfate or ferric chloride.

[0026] In one optional embodiment, the carrier matrix precursor is tetraethyl orthosilicate, and the in-situ reaction is a hydrolysis-condensation reaction occurring at a pH of 8.0-10.0 to generate a silica sol-gel network and adsorb and immobilize iron ions (Fe). 2+ and Fe 3+ The stirring speed during the hydrolysis-condensation reaction is 300-500 rpm.

[0027] In one optional embodiment, the carrier matrix precursor is dopamine hydrochloride, and the in-situ reaction is an oxidative self-polymerization reaction occurring at a pH of 8.0-9.0 to generate a polydopamine layer and complex and fix iron ions (Fe). 2+ and Fe 3+ ).

[0028] In one optional embodiment, in the in-situ synthesis method, the pretreated membrane substrate is immersed in a mixed solution containing an iron precursor and a carrier matrix precursor for 1-60 hours.

[0029] In one optional embodiment, the blend spinning method includes the following steps: S21, mixing iron-based nanoparticles, membrane matrix polymer, carrier matrix, solvent and pore-forming agent to form a uniform casting solution; S22, using a dry-wet spinning process to extrude the casting solution through a spinneret, and solidifying it into a film through phase inversion, wherein the iron-based nanoparticles are embedded in the membrane wall composed of the membrane matrix polymer and the carrier matrix; S23, performing post-treatment on the formed membrane.

[0030] In one alternative embodiment, the post-treatment step in the blend spinning method includes immersing the membrane sequentially in deionized water and a 40wt%-60wt% ethanol solution for 12-48 hours each, followed by drying.

[0031] In one alternative embodiment, the carrier matrix in the blend spinning method is selected from at least one of chitosan, sodium alginate, polyethyleneimine, polyvinyl alcohol, or polyacrylic acid.

[0032] In one alternative embodiment, in the blend spinning process, the amount of iron-based nanoparticles added is 1%-15% of the polymer mass of the membrane matrix.

[0033] In one alternative embodiment, in the blend spinning process, the amount of the carrier matrix added is 5%-30% of the polymer mass of the membrane matrix.

[0034] In one alternative embodiment, in the blend spinning process, the amount of solvent added is 400%-800% of the molecular weight of the membrane matrix.

[0035] In one alternative embodiment, in the blend spinning process, the amount of the pore-forming agent added is 5%-30% of the polymer mass of the membrane matrix.

[0036] In one optional embodiment, the thickness of the functional layer is controlled by adjusting the amount of iron-based nanoparticles added, wherein the amount of iron-based nanoparticles added is 1%-15% of the polymer mass of the membrane matrix.

[0037] In one alternative embodiment, the membrane matrix polymer includes at least one of polyvinylidene fluoride, polysulfone, or polyethersulfone.

[0038] In one alternative embodiment, the solvent comprises N-methylpyrrolidone.

[0039] In one alternative embodiment, the porogen comprises polyvinylpyrrolidone.

[0040] Thirdly, the modified MABR membrane material provided in this application for inhibiting nitrite-oxidizing bacteria, or the modified MABR membrane material prepared by a method for inhibiting nitrite-oxidizing bacteria, is used in wastewater treatment. The modified MABR membrane material is used in a membrane aeration biofilm reactor to selectively inhibit nitrite-oxidizing bacteria during the treatment of ammonia-containing wastewater, thereby stabilizing nitrite accumulation and promoting the anaerobic ammonia oxidation denitrification process.

[0041] The technical solution of this application has the following advantages: 1. This application provides a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria. The membrane material includes a hollow fiber membrane substrate and a functional layer loaded on the outer surface of the hollow fiber membrane substrate. The functional layer includes an iron-based active component and a carrier matrix. The functional layer is bonded to the hollow fiber membrane substrate by chemical bonding or molecular embedding. The thickness of the functional layer is 0.1-10 μm, and it is configured to release a total iron ion concentration of 0.1-10 μM at the membrane-biomembrane interface. The modified MABR membrane material provided in this application directly immobilizes the inhibitor on the outer surface of the MABR hollow fiber membrane—the mass transfer interface between oxygen and microbial metabolites—achieving "precise inhibition" of the target microbial community (NOB). The functional layer is firmly bonded to the membrane substrate through chemical bonding (in-situ synthesis) or molecular embedding (co-spinning). Its sustained-release characteristics ensure the long-term and stable inhibitory effect, avoiding the concentration fluctuations and detachment failure problems caused by traditional homogeneous addition or physical filtration loading, thus achieving precise and long-lasting inhibition. This application also includes "high-efficiency bubble-free aeration." Innovatively integrating the two major functions of "selective bioinhibition" into the MABR membrane material, the membrane material, while fulfilling its core oxygen supply function, actively shapes a biofilm microenvironment favorable to AOB and AnAOB and unfavorable to NOB. This achieves effective synergy between physical mass transfer regulation and chemobiological regulation, greatly enhancing process robustness and realizing functional integration and synergy. By optimizing the morphology, loading, and compounding mode of iron-based active components, the inhibitory effect can be mainly confined to the micron-scale biofilm on the membrane surface, greatly reducing the total amount of reagents added and the impact on the entire water body. The slow-release, extremely low concentration of iron ions (Fe)... 2+ and Fe 3+ (0.1-10 μM) has minimal impact on core bacterial communities such as AnAOB, and can even be used as a beneficial trace element, exhibiting high bioselectivity and achieving both environmental friendliness and high selectivity; the ultra-thin functional layer (0.1-10 μm) formed by in-situ synthesis or the integrated structure formed by blend spinning has lower oxygen mass transfer resistance compared to the thick powder layer (usually >50 μm) formed by physical filtration. Meanwhile, this application constructs a synergistic mechanism of "DO gradient + iron ion slow release + biomembrane stratification" by loading iron-based active components onto the surface of MABR hollow fiber membranes through chemical bonding or molecular encapsulation. Specifically, the reverse mass transfer characteristics of MABR itself form a stratified structure of an aerobic inner layer (AOB enrichment zone) and an anoxic outer layer (AnAOB enrichment zone) within the biomembrane; the functional layer slowly releases 0.1-10 μM iron ions at the membrane-biomembrane interface, selectively inhibiting NOB activity; the two work synergistically to construct a micro-niche in the inner layer of the biomembrane that is conducive to the growth of AOB and AnAOB but unfavorable to the reproduction of NOB.

[0042] The modified MABR membrane provided in this application is fully compatible with conventional MABR membrane materials in terms of morphology, size, and installation method. It can be directly used for upgrading existing MABR systems or new projects without changing the main structure of the reactor, pipelines, and control system. It is easy to achieve industrialization and promotion and has strong engineering applicability. The modified MABR membrane provided in this application can maintain a high nitrite accumulation rate (NAR>80%) in the MABR system for a long time, providing a reliable substrate for the core autotrophic denitrification process (Anammox), and ultimately achieving efficient removal of total nitrogen (>90%), while significantly reducing the emission risk of greenhouse gas N2O caused by NOB competition.

[0043] 2. This application provides a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria, wherein the thickness of the functional layer is 0.5-5 μm. Experimental results show that within the preferred thickness range of 0.5-5 μm, the oxygen mass transfer coefficient (KLa) attenuation rate is <5%, which can maximize the core oxygen supply efficiency of the MABR while achieving the inhibition function, thus achieving structural stability and high mass transfer efficiency. Furthermore, a functional layer thickness of 0.5-5 μm is more conducive to process control, and the functional layer loaded on the hollow fiber membrane substrate is uniform and firm, making it difficult for stress to cause cracks or peeling.

[0044] 3. This application provides a method for preparing a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria, which uses either in-situ synthesis or blend spinning to load a functional layer onto the outer surface of the hollow fiber membrane. The two preparation methods provided in this application are suitable for different scenarios: the in-situ synthesis method is suitable for surface functionalization upgrades of existing commercial MABR membrane modules, with a simple process and minimal impact on the original membrane's mass transfer performance; the blend spinning method is suitable for the integrated development of novel membrane materials, where functional components are uniformly dispersed within the membrane wall, fundamentally avoiding the risk of functional layer detachment and achieving long-term stability matching the membrane's lifespan.

[0045] 4. The application of a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria and a method for preparing the modified MABR membrane material provided in this application in wastewater treatment. This application uses the modified MABR membrane material in a membrane aeration biofilm reactor to selectively inhibit nitrite-oxidizing bacteria during the treatment of ammonia-containing wastewater, thereby stabilizing nitrite accumulation and promoting the anaerobic ammonia oxidation denitrification process. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a process flow diagram of the in-situ synthesis method for preparing modified MABR membrane materials provided in this application; Figure 2 This is a process flow diagram of the preparation of modified MABR membrane materials by the blend spinning method provided in this application. Detailed Implementation

[0048] The following embodiments are provided to better understand this application. However, the following embodiments do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining the features of this application with other prior art, falls within the scope of protection of this application.

[0049] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0050] The technical solution adopted in this application is as follows: 1. A modified MABR membrane material for inhibiting nitrite-oxidizing bacteria: The modified MABR membrane material includes a hollow fiber membrane matrix and an iron-based nanocomposite functional layer loaded on its outer surface; the functional layer is composed of iron-based active components and a carrier matrix, and is used to selectively inhibit nitrite-oxidizing bacteria at the membrane-biomembrane interface.

[0051] The hollow fiber membrane substrate is a hydrophobic or hydrophilically modified porous polymer membrane, and its material is selected from at least one of polypropylene (PP), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polysulfone (PSF), polyethersulfone (PES), or polydimethylsiloxane (PDMS). The hollow fiber membrane has an outer diameter of 0.5-3.0 mm, a wall thickness of 0.2-1.0 mm, and an average pore size of 0.01-1.0 μm.

[0052] The iron-based active component is a nanoscale iron compound particle with selective NOB inhibition activity, selected from at least one of zero-valent iron nanoparticles (nZVI), magnetite nanoparticles (Fe3O4), goethite nanoparticles (α-FeOOH), and ferrihydrite nanoparticles. Its average particle size is 10-200 nm, accounting for 5%-60% of the total mass of the functional layer.

[0053] The carrier matrix is ​​used to immobilize and disperse the iron-based active component and regulate its sustained-release behavior, and is selected from at least one of silica sol-gel, polydopamine (PDA), chitosan (CS), sodium alginate (SA), polyethyleneimine (PEI), polyvinyl alcohol (PVA), or polyacrylic acid (PAA).

[0054] The functional layer is bonded to the hollow fiber membrane substrate via chemical bonding or molecular embedding, uniformly covering the outer surface of the hollow fiber membrane substrate as a coating with a thickness of 0.1-10 μm. The functional layer is configured to release a total iron ion concentration of 0.1-10 μM (Fe2+) at the membrane-biomembrane interface. 2+ and Fe 3+ Preferably, the thickness of the functional layer is 0.5-5 μm. Within this preferred thickness range, sufficient loading of iron-based active components can be ensured while minimizing oxygen mass transfer resistance, achieving an optimal balance between inhibition effect and mass transfer efficiency. When the thickness is less than 0.5 μm, the loading of iron-based active components is insufficient, and the persistence of the inhibitory effect decreases; when the thickness is greater than 5 μm, the oxygen mass transfer resistance increases significantly, which may affect the oxygen supply efficiency of the AOB inner layer of the biofilm. Preferably, the functional layer has a porous structure to ensure that the effective diffusion of oxygen through the functional layer to the biofilm is not significantly affected.

[0055] 2. Preparation method of the above-mentioned modified MABR membrane material: This application provides two main preparation methods: in-situ synthesis and blend spinning.

[0056] See Figure 1 As shown, this application provides a method for preparing a modified MABR membrane, namely, an in-situ synthesis method. Includes the following steps: a. Surface activation pretreatment of the hollow fiber membrane substrate to introduce active groups (such as -OH, -COOH, -NH2). Treatment methods include, but are not limited to: plasma treatment (oxygen, nitrogen, or air plasma), strong oxidant treatment (such as H2SO4 / H2O2 mixture), alkali treatment (such as NaOH solution), or ultraviolet irradiation grafting.

[0057] b. The pretreated membrane substrate is immersed in a mixed solution containing an iron precursor and a carrier matrix precursor, and a composite functional layer is formed on the membrane surface through in-situ reaction. The carrier matrix precursor is selected from at least one of tetraethyl orthosilicate (TEOS) or dopamine hydrochloride; the iron precursor is selected from at least one of ferrous sulfate or ferric chloride.

[0058] c. Reaction initiation under specific conditions: When the carrier matrix precursor is tetraethyl orthosilicate, a hydrolysis-condensation reaction occurs under alkaline conditions (pH 8.0-10.0), generating a silica sol-gel network and adsorbing and immobilizing iron ions (Fe). 2+ and Fe 3+ When the carrier matrix precursor is dopamine hydrochloride, an oxidative self-polymerization reaction occurs under weakly alkaline conditions (pH 8.0-9.0), generating a polydopamine layer and complexing and fixing iron ions (Fe). 2+ and Fe 3+ ).

[0059] d. The membrane loaded with the functional layer is cured and post-treated, including cleaning, drying and other steps, to obtain the modified MABR membrane material.

[0060] See Figure 2 As shown, this application provides a method for preparing a modified MABR membrane, namely, a blend spinning method. Includes the following steps: A. Iron-based nanoparticles, a membrane matrix polymer, a carrier matrix, a solvent, and a pore-forming agent are mixed to form a uniform casting solution. The amount of iron-based nanoparticles added is 1%-15% of the mass of the membrane matrix polymer; the carrier matrix is ​​selected from at least one of chitosan, sodium alginate, polyethyleneimine, polyvinyl alcohol, or polyacrylic acid; the membrane matrix polymer includes at least one of polyvinylidene fluoride, polysulfone, or polyethersulfone; the solvent includes N-methylpyrrolidone (NMP); and the pore-forming agent includes polyvinylpyrrolidone (PVP).

[0061] B. The casting solution is extruded through a spinneret using a dry-wet spinning process. After passing through an air gap, it enters a coagulation bath, where a phase transformation occurs and the solution solidifies into a film. The iron-based nanoparticles are embedded in the film wall, which is composed of a film matrix polymer and a carrier matrix.

[0062] C. Post-process the formed membrane, including cleaning, drying and other steps, to obtain the modified MABR membrane material.

[0063] 3. Mechanism of action: When the modified MABR membrane material is installed in a MABR reactor to treat ammonia nitrogen-containing wastewater, the iron-based active components in the functional layer continuously act on the inner layer of the biofilm (i.e., the region where NOB and AOB compete most fiercely) closely adhering to the membrane surface through one or more of the following synergistic mechanisms: (1) Slow-release inhibition mechanism: Under the influence of the microenvironment within the biofilm (such as specific pH, organic acids, and microbial secretions), the iron-based nanoparticles in the functional layer undergo slow oxidation, reduction, or complexation dissolution, continuously releasing trace amounts (0.1-10 μM) of Fe. 2+ / Fe 3+ Ions. Among them, Fe 2+ It can penetrate the NOB cell membrane, interfering with electron transport in its respiratory chain, or bind to the active site of nitrite oxidoreductase (NXR); Fe 3+ These ions can competitively adsorb and deprive NOB of the trace elements it needs. The two work synergistically to selectively inhibit NOB metabolic activity. These ions can penetrate the NOB cell membrane, interfering with electron transport in its respiratory chain, or bind to the active site of nitrite oxidoreductase (NXR), thereby selectively inhibiting its metabolic activity.

[0064] (2) Local micro electric field mechanism: When the iron-based active component is nZVI or Fe3O4, these nanoparticles with conductive or semiconductor properties may form micro galvanic cells in the water-containing environment of the biofilm, generating locally changing redox potentials and creating a micro-niche that is unfavorable to NOB growth but relatively unaffected by AOB.

[0065] (3) Competitive adsorption and nutrient deprivation mechanism: Iron oxides (such as α-FeOOH, Ferrihydrite) have a huge specific surface area and abundant surface hydroxyl groups. They have a strong affinity for some trace metal elements (such as Cu, Mo) that are necessary for the growth of NOB. They may deprive NOB of the opportunity to obtain these nutrients through adsorption, thereby limiting its proliferation.

[0066] 4. Applications of the above-mentioned modified MABR membrane materials: The modified MABR membrane material is assembled into membrane bundles or modules using conventional methods and installed in an MABR reactor for treating wastewater containing ammonia nitrogen, particularly municipal sewage or industrial wastewater with a carbon-to-nitrogen ratio (C / N) below 5. During operation, the slow-release inhibition effect of the functional layers achieves long-term selective inhibition of NOB, stabilizes nitrite accumulation, and promotes the anaerobic ammonia oxidation denitrification process.

[0067] Example 1 This embodiment provides a method for preparing a modified membrane material for inhibiting nitrite-oxidizing bacteria. The method involves in-situ synthesis of a polydopamine / zero-valent iron (PDA / nZVI) composite coating modified PVDF-MABR membrane. The specific steps and methods are as follows: 1. Pretreatment: Take a section of commercial PVDF hollow fiber membrane (outer diameter 1.8 mm, wall thickness 0.4 mm, average pore size 0.1 μm) and ultrasonically clean it sequentially with acetone, ethanol, and deionized water for 15 minutes each to remove surface grease and impurities. Immerse the cleaned membrane in 0.5 M NaOH solution and treat it at 60℃ for 1 hour to perform surface hydrolysis activation and introduce more hydroxyl groups. After removal, wash with deionized water until neutral.

[0068] 2. PDA Substrat Modification: Take the membrane material activated in step 1 and immerse it completely in 10 mM Tris-HCl buffer (pH=8.5) containing 2.0 mg / mL dopamine hydrochloride. Incubate at 120 rpm for 24 hours at room temperature. During this process, dopamine undergoes oxidative self-polymerization, forming a strongly adhesive polydopamine (PDA) layer on the membrane surface. Remove the membrane and rinse with deionized water to remove loosely attached particles.

[0069] 3. In-situ loading of nZVI: Prepare 200 mL of 0.1 M FeSO4·7H2O aqueous solution, bubble with high-purity nitrogen for 30 minutes to remove oxygen, immerse the PDA-modified membrane material from step 2 into the FeSO4·7H2O aqueous solution, and slowly add 100 mL of 0.1 M NaBH4 aqueous solution (dropping rate approximately 2 mL / min) under nitrogen protection, while continuously stirring gently. During this process, a reduction reaction occurs in the aqueous solution to generate zero-valent iron. The newly generated zero-valent iron nanoparticles are strongly captured and fixed by the PDA layer on the membrane material. The entire dropping process is carried out in an ice-water bath to control the reaction rate. The reduction reaction in the aqueous solution is shown in equation (I): Equation (I) 4. Curing and Post-treatment: After the addition is complete, continue stirring for 2 hours under nitrogen protection. Remove the membrane and immediately immerse it in anhydrous ethanol for 10 minutes to terminate the reaction and displace the water. Then place the membrane in a vacuum drying oven and dry it at 40°C for 24 hours to obtain the PDA / nZVI modified PVDF-MABR membrane.

[0070] The surface morphology and elemental analysis of the prepared membrane material were observed. The results showed that the membrane surface was uniformly covered with a composite coating, and nano-sized particles (with a particle size of about 30-80 nm) were distributed in the coating, which were identified as zero-valent iron nanoparticles. The coating thickness was about 1-2 μm, and the Fe element was uniformly distributed on the membrane surface.

[0071] Iron ion concentration detection: On days 30, 90, 180, and 360 of operation, the Fe concentration at the membrane-biofilm interface was measured using microelectrode technology. 2+ and Fe 3+ Concentration. Fe 2+ The concentration was determined using the o-phenanthroline spectrophotometric method, Fe 3+ The concentration was determined using the potassium thiocyanate spectrophotometric method, and the total iron ion concentration was the sum of the two. The results showed that the total iron ion concentration remained stable within the range of 0.5-5 μM during operation, fully meeting the design target of 0.1-10 μM. Specific data are shown in Table 7.

[0072] Example 2 This embodiment provides a method for preparing a modified membrane material for inhibiting nitrite-oxidizing bacteria. The method involves in-situ synthesis of a silica sol-gel / goethite (SiO2 / α-FeOOH) composite coating modified PP-MABR membrane. Specific steps and methods are as follows: 1. Pretreatment: Take a polypropylene (PP) hollow fiber membrane (outer diameter 2.0 mm, wall thickness 0.5 mm, average pore size 0.2 μm) and wash it with ethanol and deionized water. Place it in a low-temperature oxygen plasma treatment instrument and treat it for 5 minutes at a power of 100W and an oxygen flow rate of 50 sccm to introduce oxygen-containing polar groups.

[0073] 2. Preparation of coating solution: 0.5 g of commercially available goethite nanorods (α-FeOOH, purity ≥99.5%, moisture content ≤1.0%, length 80-120 nm, diameter 15-25 nm, specific surface area 80-120 m²) 2 / g, bulk density 0.4-0.6 g / cm³ 3 The mixture (purchased from Shanghai Maclean Biochemical Technology Co., Ltd.) was dispersed in 50 mL of anhydrous ethanol and sonicated for 30 minutes to ensure complete dispersion. Then, 4 mL of tetraethyl orthosilicate (TEOS) and 2 mL of 0.1 M hydrochloric acid were added sequentially as catalysts. The mixture was then magnetically stirred at 400 rpm for 30 minutes to form a uniform pale yellow sol.

[0074] 3. Immersion and Lifting Coating: Fix the PP film after plasma treatment in step 1 on the lifting machine, immerse it vertically in the sol in step 2, stay for 60 seconds, and then lift it out of the liquid surface at a constant speed of 3 cm / min.

[0075] 4. Gelization and Heat Treatment: The wet film coated in step 3 was aged for 24 hours at room temperature and 50% relative humidity to allow TEOS to fully hydrolyze and condense, forming a SiO2 gel network in which α-FeOOH nanorods were embedded. Subsequently, the film was transferred to an oven and dried at 80°C for 12 hours to further solidify the gel.

[0076] 5. Post-treatment: After cooling, gently rinse the membrane surface with deionized water and air dry at room temperature.

[0077] The modified membrane prepared in this embodiment has a robust light yellow composite coating on its surface. The coating thickness was measured to be approximately 3-5 μm. Contact angle measurement showed that it has good hydrophilicity, and gas permeation test showed that the coating has a porous structure and does not significantly hinder oxygen mass transfer.

[0078] Example 3 This embodiment provides a method for preparing a modified membrane material for inhibiting nitrite-oxidizing bacteria. A chitosan / zero-valent iron (CS / nZVI) composite modified PVDF-MABR membrane is prepared using a blend spinning method. The specific steps and methods are as follows: 1. Preparation of casting solution: PVDF powder (15 g), chitosan (CS, 3 g), nZVI nanoparticles (1.5 g, particle size about 50 nm), and polyvinylpyrrolidone (PVP, 3 g) were added to N-methylpyrrolidone (NMP, 80 mL). The mixture was mechanically stirred at 400 rpm for 12 hours at 60 °C. Then, it was ultrasonically degassed at 150 W for 45 minutes to form a uniform casting solution. The amount of nZVI added was 10% of the mass of PVDF.

[0079] 2. Spinning and Forming: A dry-wet spinning process is adopted. The casting solution is extruded through a ring spinneret (outer diameter 2.0 mm, inner diameter 1.0 mm), passes through a 10 cm air gap, and then enters a deionized water coagulation bath (25℃). Solvent and non-solvent exchange occurs, polymer phase separation occurs, and solidification forms a hollow fiber membrane.

[0080] 3. Post-treatment: The formed membrane fibers are immersed in deionized water and 50% ethanol solution for 24 hours each to replace the residual solvent. Finally, they are air-dried at room temperature to obtain CS / nZVI blended modified PVDF-MABR membrane.

[0081] Cross-sectional observation and elemental analysis of the prepared membrane material showed that the nZVI nanoparticles were uniformly dispersed within the membrane wall without obvious aggregation. Fe was uniformly distributed from the inside to the outside of the membrane wall cross-section, confirming the uniform embedding of the nanoparticles in the membrane matrix. The functional layer thickness was measured to be approximately 0.5–2 μm, the outer diameter of the membrane was 1.9 mm, the total membrane wall thickness was 0.45 mm, and the average pore size was 0.15 μm.

[0082] Iron ion concentration detection: On days 30, 90, 180, and 360 of operation, the Fe concentration at the membrane-biofilm interface was measured using microelectrode technology. 2+ and Fe 3+Concentration. The results showed that the total iron ion concentration remained stable within the range of 0.3-3 μM during operation, fully meeting the design target of 0.1-10 μM. Specific data are shown in Table 7.

[0083] Example 4 This embodiment provides a method for preparing a modified membrane material for inhibiting nitrite-oxidizing bacteria. A sodium alginate / ferric oxide (SA / Fe3O4) composite modified PSF-MABR membrane is prepared using a blend spinning method. The specific steps and methods are as follows: 1. Preparation of casting solution: Polysulfone (PSF) powder (15 g), sodium alginate (SA, 2.5 g), Fe3O4 nanoparticles (1.2 g, particle size approximately 30 nm), and polyvinylpyrrolidone (PVP, 3 g) were added to N-methylpyrrolidone (NMP, 80 mL). The mixture was mechanically stirred at 400 rpm for 12 hours at 60°C, followed by ultrasonic degassing at 150 W for 45 minutes to form a uniform casting solution. The amount of Fe3O4 added was 8% of the mass of PSF, and the amount of SA added was 16.7% of the mass of PSF.

[0084] 2. Spinning and forming: The dry-wet spinning process is adopted. The casting solution is extruded through an annular spinneret (outer diameter 2.0 mm, inner diameter 1.0 mm), and after passing through a 10 cm air gap, it enters a deionized water coagulation bath (25℃) to solidify into a hollow fiber membrane.

[0085] 3. Post-treatment: The formed membrane fibers are immersed in deionized water and 50% ethanol solution for 24 hours each to replace the residual solvent. Finally, they are air-dried at room temperature to obtain SA / Fe3O4 blended modified PSF-MABR membrane.

[0086] Cross-sectional observation and elemental analysis of the prepared membrane material showed that Fe3O4 nanoparticles were uniformly dispersed within the membrane wall without significant agglomeration; Fe element was uniformly distributed across the membrane wall cross-section. The membrane had an outer diameter of 1.9 mm, a wall thickness of 0.45 mm, and an average pore size of 0.15 μm.

[0087] Example 5 This embodiment provides a method for preparing a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria. The method involves preparing a polyethyleneimine / zero-valent iron (PEI / nZVI) composite modified PVDF-MABR membrane using a blend spinning method. The specific steps and methods are as follows: 1. Preparation of casting solution: PVDF powder (15 g), polyethyleneimine (PEI, molecular weight 10000, 2.5 g), nZVI nanoparticles (1.2 g, particle size approximately 50 nm), and polyvinylpyrrolidone (PVP, 3 g) were added to N-methylpyrrolidone (NMP, 80 mL). The mixture was mechanically stirred at 400 rpm for 12 hours at 60°C, followed by ultrasonic degassing at 150 W for 45 minutes to form a uniform casting solution. The amount of nZVI added was 8% of the mass of PVDF, and the amount of PEI added was 16.7% of the mass of PVDF.

[0088] 2. Spinning and Forming: A dry-wet spinning process is adopted. The casting solution is extruded through a ring spinneret (outer diameter 2.0 mm, inner diameter 1.0 mm), passes through a 10 cm air gap, and then enters a deionized water coagulation bath (25℃). Solvent and non-solvent exchange occurs, polymer phase separation occurs, and solidification forms a hollow fiber membrane.

[0089] 3. Post-treatment: The formed membrane fibers are immersed in deionized water and 50% ethanol solution for 24 hours each to replace the residual solvent. Finally, they are air-dried at room temperature to obtain PEI / nZVI blended modified PVDF-MABR membrane.

[0090] Cross-sectional observation and elemental analysis of the prepared membrane material revealed that nZVI nanoparticles were uniformly dispersed within the membrane wall without significant agglomeration. EDS analysis confirmed the uniform distribution of Fe. The membrane had an outer diameter of 1.9 mm, a wall thickness of 0.45 mm, and an average pore size of 0.15 μm. The functional layer was essentially the surface region of the membrane wall. Due to the hydrophilicity of PEI, some nZVI was enriched on the membrane surface, but the overall structure remained integrated.

[0091] Iron ion concentration detection: On days 30, 90, 180, and 360 of operation, the Fe concentration at the membrane-biofilm interface was measured using microelectrode technology. 2+ and Fe 3+ Concentration. The results showed that the total iron ion concentration remained stable within the range of 0.2-4 μM during operation, fully meeting the design target of 0.1-10 μM. Specific data are shown in Table 7.

[0092] Comparative Example 1 This comparative example provides a method for preparing a MABR membrane material. An iron-carbon supported MABR membrane is prepared using a vacuum filtration method, and the preparation method is based on CN121063709A. The specific steps are as follows: 1. Preparation of iron-carbon materials: Straw was soaked in a 45wt% ferric chloride solution for 2 hours, then dried at 60℃ for 6 hours, and then pyrolyzed at 600℃ for 2 hours in a tube furnace under N2 atmosphere to obtain iron-carbon composite materials.

[0093] 2. Preparation of suspension: The above iron-carbon materials were ultrasonically dispersed in deionized water to obtain a suspension with a concentration of 5 mg / mL.

[0094] 3. Vacuum filtration: Using a commercially available PVDF hollow fiber membrane of the same specifications as in Example 1 as the base membrane, a vacuum filtration device was used to filter and deposit the iron-carbon suspension onto the membrane surface, forming an iron-carbon material layer. The filtration pressure was 0.08 MPa, and the filtration time was 10 minutes.

[0095] 4. Drying: The iron-carbon loaded membrane is dried at room temperature to obtain the iron-carbon loaded MABR membrane prepared by vacuum filtration.

[0096] Measurements showed that the membrane surface was covered with a loose layer composed of iron-carbon particles, with a thickness of approximately 80-120 μm.

[0097] Comparative Example 2 A standard commercial PVDF-MABR membrane was used as a control, with the same brand and specifications as in Example 1 but without any modification, as a raw PVDF hollow fiber membrane.

[0098] Comparative Example 3 This comparative example provides a method for preparing a modified MABR membrane material. The method involves preparing a nano-iron-loaded fiber membrane using electrospinning, and obtaining a polyvinyl alcohol fiber membrane loaded with nano-iron according to the method provided in Example 1 of CN102517799A.

[0099] Application example: Verifying the effect in a MABR reactor simulating mainstream domestic sewage: 1. Construct eight identical laboratory-scale submerged MABR reactors (R1-R8), each with an effective volume of 10L and an effective membrane area of ​​0.5 m². 2 The membrane material. Reactor configuration is shown in Table 1: Table 1 Reactor Configuration

[0100] 2. Inoculation and Influent: Six reactors were inoculated with a mixture of aerobic activated sludge and anaerobic ammonia oxidation granular sludge from a municipal wastewater treatment plant (sludge concentration 3000 mg / L). The influent was artificially prepared simulated mainstream domestic sewage, with the main component being NH4Cl (providing NH4). + -N 60±5 mg / L, CH3COONa provides COD 200±20 mg / L, NaHCO3 acts as a buffer to maintain pH 7.5-8.0, and essential trace elements are provided. Temperature is controlled at 20±1℃.

[0101] Operating conditions: All reactors operate in continuous flow mode with a hydraulic retention time (HRT) of 12 hours. Oil-free compressed air is introduced into the membrane material cavity, and the internal pressure is maintained at a constant 5 kPa via a precision pressure regulating valve to ensure that the oxygen mass transfer flux of each system is essentially consistent in the initial stage. The operating cycle is 360 days.

[0102] 3. Monitoring items: 3.1 Daily monitoring of influent and effluent water quality: NH4 + -N, NO2 - -N, NO3 - -N, COD, TN.

[0103] 3.2 Calculation of nitrite accumulation rate: NAR = NO2 - -N / (NO2 - -N + NO3 - -N) × 100%.

[0104] 3.3 On days 30, 90, 180, and 360, biofilm samples were scraped from the membrane surface, total DNA was extracted, and functional genes were analyzed by quantitative PCR (qPCR).

[0105] The specific detection method is as follows: Total DNA was extracted from biofilms using a soil DNA extraction kit. Using the extracted DNA as a template, the SYBR Green I real-time quantitative PCR method was employed for detection on a real-time PCR instrument. (AOB) amoA The gene primer sequence is amoA-1F (5'-GGGGTTTCTACTGGTGGT-3') and amoA-2R (5'-CCCCTCKGSAAAGCCTTCTTC-3'); NOB ( Nitrospira )of nxrB The gene primer sequence is nxrB-1F (5'-ACGTGGAGACCAAGCCGGG-3') and nxrB- 1R (5'-CCGTGCTGTTGAYGTTGTTAA-3'); AnAOB hzsB The gene primer sequence is hz sB_396F (5'-ATTCCCAGTTTGGGATGG-3') and hz sB_742R (5'-TGTCTACCTGCTTGACCG-3'). Reaction conditions were: 95℃ pre-denaturation for 3 minutes; 95℃ denaturation for 15 seconds, 55℃ annealing for 30 seconds, and 72℃ extension for 30 seconds, for a total of 40 cycles. Copy numbers of each functional gene were calculated using a standard curve. Alternatively, samples can be sent to professional testing institutions such as Shanghai Meiji Biotechnology Co., Ltd. for qPCR analysis.

[0106] 3.4. The N2O emission flux in the reactor headspace is monitored using an online gas analyzer.

[0107] 3.5. Measure the oxygen mass transfer coefficient (KLa) of each membrane material before and after operation to evaluate the effect of modification on mass transfer performance.

[0108] The method for determining KLa is the dynamic deoxygenation-re-aeration method: sodium sulfite (at a stoichiometric ratio of 1.5) and cobalt chloride catalyst are added to the reactor for deoxygenation. After the dissolved oxygen drops to zero, aeration is started and the curve of dissolved oxygen change over time is recorded. The KLa value is calculated using formula (II).

[0109] Formula (II) Where C* is the saturated dissolved oxygen concentration, C0 is the initial dissolved oxygen concentration, and C... t Let t be the dissolved oxygen concentration at time t.

[0110] 3.6 The functional layer stability of the modified MABR membrane materials prepared in Examples 1, 3 and Comparative Example 1 was tested. Specifically, the modified MABR membrane materials were placed in deionized water and continuously rinsed at 200 rpm for 30 days. The change in Fe content before and after rinsing was measured and the Fe retention rate was calculated.

[0111] 3.7 Iron ion concentration determination experiment: Microelectrode technology was used to determine the iron ion concentration at the membrane-biomembrane interface of each embodiment at days 30, 90, 180, and 360 of operation. 2+ and Fe 3+ Concentration. Fe 2+ The concentration was determined using the o-phenanthroline spectrophotometric method, Fe 3+ The concentration was determined using the potassium thiocyanate spectrophotometric method, and the total iron ion concentration was Fe. 2+ and Fe 3+ The sum of concentrations.

[0112] 3.8 Comparison of inhibition effects of different iron-based active components: nZVI, Fe3O4, α-FeOOH and Ferrihydrite were used as iron-based active components, and modified membranes were prepared using the same method as in Example 1. The membranes were run under the same conditions for 360 days, and the abundance of NAR and NOB was compared.

[0113] 3.9 Comparison of sustained-release performance of different carrier matrices: Polydopamine, silica sol-gel, chitosan, sodium alginate, and polyethyleneimine were used as carrier matrices, respectively. Modified membranes were prepared using the same method as in Example 1, and their Fe content in deionized water was measured. 2+ / Fe 3+ Sustained-release curves to compare sustained-release rate and duration.

[0114] 3.10. Iron ion concentration gradient experiment: Prepare solutions containing different concentrations of Fe 2+ / Fe 3+ Mixed solution (Fe) 2+ :Fe 3+ In a 1:1 medium with total iron ion concentrations of 0.05 μM, 0.1 μM, 1 μM, 5 μM, 10 μM, 20 μM, and 50 μM, pure strains of NOB (Nitrospira moscoviensis, ATCC 700422), AOB (Nitrosomonas europaea, ATCC 19718), and AnAOB (Candidatus Brocadia anammoxidans, isolated from enrichment cultures) were cultured. After culturing at 30°C for 14 days, the growth activity of each bacterial group was measured. Using a control group without added iron ions as a baseline (relative activity set at 100%), the relative activity at each concentration was calculated. Relative activity = (experimental group bacterial density / control group bacterial density) × 100%. Bacterial density was measured using OD0.05. 600 Absorbance value determination.

[0115] Experimental results: 1. Long-term stability of nitrite accumulation rate (NAR): Table 2 Nitrite Accumulation Rate

[0116] According to the results in Table 2, Examples 1-5 of this application consistently maintained a NAR above 74% during 360 days of operation, demonstrating excellent long-term stability. Examples 3 (CS / nZVI) and 5 (PEI / nZVI) showed the best performance, with NAR stable at 78%-80%; Example 4 (SA / Fe3O4) was slightly lower but still remained above 75%. Comparative Example 1 (filtration method) initially showed a high NAR, but it began to decline significantly after 30 days, indicating that the iron-carbon powder layer was detaching or its activity was decreasing, leading to gradual NOB proliferation. Comparative Example 2 (conventional membrane) initially showed successful short-cut nitrification, but the NAR continued to decline after 30 days, eventually tending towards full nitrification. Comparative Example 3 (electrospun membrane) had a consistently low NAR due to the fiber felt structure being unsuitable for the MABR mode and poor biofilm adhesion.

[0117] 2. Total nitrogen (TN) removal efficiency (360-day average): Table 3 Total nitrogen (TN) removal efficiency (360-day average)

[0118] As shown in Table 3, the TN removal rates of Examples 1-5 of this application are significantly higher than those of the comparative examples, thanks to the stable nitrite supply ensuring the efficient operation of the Anammox process. Examples 3 and 5 have the highest TN removal rates, reaching 90% and 89%, respectively.

[0119] 3. Microbial community analysis (after 360 days of operation): Table 4. Microbial community analysis (after 360 days of operation)

[0120] Microbial community analysis results obtained by qPCR, as shown in Table 4, indicate that after 360 days of operation, the NOB abundance in Examples 1-5 of this application was 1-2 orders of magnitude lower than that in the control group, while the AOB abundance was comparable to that in the control group, demonstrating that the modified membrane of this application has a significant and specific inhibitory effect on NOB. Among them, Example 3 (CS / nZVI) and Example 1 (PDA / nZVI) showed the best NOB inhibition effect.

[0121] 4. N2O emission monitoring: During the 360-day operation period, the average N2O emission fluxes for R1-R5 were 0.11-0.14 mg / L, for R6 it was 0.29 mg / L, for R7 it was 0.34 mg / L, and for R8 it was 0.38 mg / L. The N2O emissions in this embodiment are approximately 50%-60% lower than the control group, which is related to stable short-cut nitrification and an active Anammox process.

[0122] 5. Comparison of oxygen mass transfer performance: Table 5 Oxygen mass transfer coefficients of various membrane materials

[0123] As shown in Table 5, the modified MABR membranes provided in Examples 1, 3, and 5 of this application have minimal impact on oxygen mass transfer, and the KLa decay rate is less than 8% after long-term operation. The decay rate of Example 4 is slightly higher (9.1%), but it is still significantly better than the comparative examples. In Comparative Example 1 (vacuum filtration method), the initial KLa was already low due to the increased mass transfer resistance caused by the thick powder layer, and the decay was severe after operation. In Comparative Example 3 (electrospun membrane), the mass transfer performance is poor due to the fiber felt structure.

[0124] 6. Functional layer stability testing: The membrane materials of Examples 1, 3, 5 and Comparative Example 1 were placed in deionized water and continuously rinsed at 200 rpm for 30 days. The retention rate of Fe element before and after rinsing was measured.

[0125] Table 6. Iron retention rate of various membrane materials

[0126] According to the results in Table 6, the membrane materials prepared by the in-situ synthesis method and the blending spinning method in this application have a strong functional layer bond and strong resistance to water erosion; while the powder layer physically deposited by the vacuum filtration method detaches in large quantities.

[0127] 7. Experiment for determining iron ion concentration: Table 7 Total iron ion concentration (μM) of membrane materials during operation for each embodiment

[0128] The results showed that the total iron ion concentration at the membrane-biomembrane interface remained stable within the range of 0.1-10 μM during 360 days of operation, verifying the controllable sustained-release performance of the functional layer. The iron ion concentration was slightly higher in Example 1 (PDA / nZVI system) (2.9-4.8 μM), slightly lower in Example 3 (CS / nZVI system) (1.6-2.9 μM), and intermediate in Examples 4 (SA / Fe3O4) and 5 (PEI / nZVI system) (2.0-3.5 μM), all within the design target range.

[0129] 8. Comparative experiment on the inhibitory effects of different iron-based active components: Table 8 Comparison of inhibitory effects of different iron-based active components (180 days)

[0130] The results showed that all four iron-based active components could effectively inhibit NOB, with nZVI showing the best effect, followed by Fe3O4 and α-FeOOH, all of which are within the scope of protection of this application.

[0131] 9. Comparative experiment on the sustained-release performance of different carrier matrices: Table 9 Comparison of sustained-release performance of different carrier matrices

[0132] The results show that different carrier matrices have different sustained-release properties for iron ions, but all of them can control the iron ion concentration within the effective range (0.1-10 μM), which meets the design requirements of this application.

[0133] 10. Iron ion concentration gradient experiment: The effect of iron ions on functional bacterial communities was determined using pure culture experiments. *Nitrospira moscoviensis* (ATCC 700422) was used for NOB, *Nitrosomonas europaea* (ATCC 19718) for AOB, and *Candidatus Brocadia anammoxidans* (isolated and identified from laboratory enrichment cultures) for AnAOB. ​​After culturing at 30°C for 14 days, the growth activity (OD) of each bacterial community was measured. 600 The absorbance values ​​were used as a baseline (with the blank group without added iron ions set as 100%). The relative activities at each concentration were calculated, and the results are shown in Table 10.

[0134] Table 10. Relative activities of functional bacterial communities at different total iron concentrations

[0135] The results showed that iron ion concentrations within the range of 0.1–10 μM effectively inhibited NOB activity (relative activity <85%), while having minimal impact on AOB and AnAOB (relative activity >88%). At concentrations below 0.1 μM, the inhibitory effect on NOB was insufficient; and at concentrations above 10 μM, the toxicity to AOB and AnAOB significantly increased. These results validate the scientific validity and necessity of controlling the iron ion concentration within the 0.1–10 μM range in this application.

[0136] 11. Comparison experiment on functional layer thickness: Modified films with functional layer thicknesses of 0.1 μm, 0.3 μm, 2 μm, 8 μm, 10 μm, and 15 μm were prepared using the same in-situ synthesis method as in Example 1. Different thicknesses were achieved by adjusting the impregnation time. Specific control parameters were as follows: a fixed dopamine hydrochloride concentration of 2.0 mg / mL, and impregnation times of 3 hours (0.1 μm), 6 hours (0.3 μm), 12 hours (0.5 μm), 24 hours (2 μm), 36 hours (5 μm), 48 hours (8 μm), 60 hours (10 μm), and 72 hours (15 μm). The films were run under the same conditions for 180 days, and the changes in NAR and KLa were compared. The results are shown in Table 11.

[0137] Table 11 NAR and KLa with different functional layer thicknesses

[0138] The results in Table 11 show that when the thickness is in the range of 0.5-5 μm, good mass transfer performance (KLa decay rate <6%) can be maintained while ensuring the inhibition effect (NAR>75%). At a thickness of 0.1 μm, although the mass transfer performance is excellent, the inhibition effect decreases significantly (NAR<60%). At a thickness of 10 μm, the mass transfer resistance increases significantly (KLa decay rate>12%), and the inhibition effect also begins to decline. This result verifies that the thickness range of 0.1-10 μm is reasonable, and 0.5-5 μm is the preferred range for further optimization. When the thickness is less than 0.1 μm, the loading of the iron-based active component is extremely low, the slow-release effect is short-lived, and long-term inhibition cannot be achieved. When the thickness is greater than 10 μm, the oxygen mass transfer resistance increases significantly, and excessively thick coatings are prone to cracking or even detachment under membrane bending or hydraulic shear, leading to functional failure. Therefore, a thickness range of 0.1-10 μm ensures both functional achievement and process feasibility.

[0139] As can be seen from the long-term stability test (Table 2), Examples 1-5 can maintain more than 74% NAR during 360 days of operation. Among them, Examples 3 (CS / nZVI) and Examples 5 (PEI / nZVI) have the best performance, with NAR reaching 80% and 78% respectively after 360 days (Table 2), showing excellent long-term stability.

[0140] The functional layer thickness comparison experiment (Table 11) shows that when the functional layer thickness is controlled within the range of 0.5-5 μm, the membrane material can maintain more than 75% NAR during 180 days of operation, and the KLa decay rate is less than 6%, demonstrating a good balance between inhibition effect and mass transfer performance. This proves that a functional layer thickness of 0.5-5 μm is a further optimization choice. The 0.5-5 μm coating can ensure sufficient loading of iron-based active components, and at the same time, through the slow-release regulation of the carrier matrix, the total iron ion concentration (Fe) at the membrane-biomembrane interface can be controlled. 2+ and Fe 3+ The thickness is maintained within a range that effectively suppresses NOB (0.1-10 μM) and is non-toxic to AOB / AnAOB. ​​This thickness range facilitates the formation of a uniform and robust coating through in-situ synthesis or blend spinning, avoiding cracking or peeling caused by internal stress in excessively thick coatings. In contrast, the powder layer thickness formed by the filtration method in Comparative Example 1 reached 80-120 μm, far exceeding the range of this application. Its NAR decreased sharply after 90 days (Table 2), and the KLa decay rate reached 34.2% (Table 5), confirming the negative impact of excessively thick functional layers on system performance.

[0141] Therefore, it can be seen that the modified MABR membrane material provided in this application, by in-situ synthesis or blend spinning, firmly loads the iron-based nanocomposite functional layer onto the surface or interior of the hollow fiber membrane, achieving selective and long-term inhibition of NOB. Compared with existing technologies (vacuum filtration, electrospinning, and ordinary membranes), the membrane material of this application has the following outstanding advantages: (1) Long-lasting and stable inhibition effect: NAR is maintained above 74% during 360 days of operation, and NOB abundance is reduced by 1-2 orders of magnitude; (2) Strong bioselectivity: While significantly inhibiting NOB, it has minimal impact on AOB and AnAOB activity; (3) Robust structure and long lifespan: The functional layer has strong erosion resistance and Fe retention rate >94%, which is much higher than that of the vacuum filtration method; (4) Excellent mass transfer performance: The ultra-thin functional layer or integrated structure has little impact on oxygen mass transfer, and the KLa decay rate is <10% after long-term operation; (5) Significant environmental benefits: N2O emissions are reduced by more than 50%, which meets the requirements of low-carbon operation. Therefore, this application provides a practical core material solution for the engineering application of the MABR-Anammox process.

[0142] This application creatively integrates selective bio-inhibition function with efficient bubble-free aeration and mass transfer function into a single MABR hollow fiber membrane material. Unlike the traditional method of adding chemical agents to water or using physical filtration to form a loose interlayer, this application achieves in-situ, precise and continuous inhibition of NOB at the "source interface" (i.e., membrane-biofilm interface) of pollutant-oxygen mass transfer by constructing a chemically bonded composite functional layer on the membrane surface. This solves the contradiction between low inhibition efficiency and large side effects from both spatial and mechanistic perspectives, realizing functional integration and in-situ regulation. A composite coating with a slow-release carrier matrix (such as polydopamine, silica gel) encapsulating or loading specific iron-based nano-active components (such as zero-valent iron, goethite) was designed and prepared. This design not only ensures the strong bond (chemical bonding or molecular encapsulation) and long-term stability of the iron active components to the membrane substrate, but more importantly, it achieves the controlled and slow release of active iron species to the attached biofilm through the regulation of the carrier matrix, avoiding concentration shocks and achieving long-term, mild inhibition. This represents an innovation from the perspective of composite functional layer materials. It reveals that the modified membrane selectively suppresses NOB through the synergistic effect of multiple mechanisms such as "slow-release inhibition", "local micro-electric field interference" and "competitive adsorption". This mechanism, in synergy with the "aerobic-anoxic" biofilm layered structure formed by the dissolved oxygen gradient within the MABR itself, jointly creates a micro-ecological niche that is conducive to the growth of AOB and AnAOB but unfavorable to the reproduction of NOB. This fundamentally enhances the start-up speed and long-term operational stability of mainstream anaerobic ammonia oxidation processes, achieving an innovative synergy between the inhibition mechanism and the process. Simultaneously, this application provides two distinct technical routes—in-situ synthesis and blend spinning—both of which can achieve a firm bond between functional components and the membrane substrate. The in-situ synthesis method is suitable for upgrading existing membrane modules, imbuing them with inhibitory functions while maintaining the original membrane structure. The blend spinning method enables the integrated molding of functional components and membrane materials, fundamentally avoiding the risk of functional layer detachment, and providing a new approach for developing next-generation high-performance MABR membrane materials.

[0143] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A modified MABR membrane material for inhibiting nitrite-oxidizing bacteria, characterized in that, The membrane material includes a hollow fiber membrane matrix and a functional layer loaded on the outer surface of the hollow fiber membrane matrix. The functional layer includes an iron-based active component and a carrier matrix, which is used to selectively inhibit nitrite-oxidizing bacteria at the membrane-biomembrane interface. The functional layer is combined with the hollow fiber membrane matrix by chemical bonding or molecular encapsulation. The thickness of the functional layer is 0.1-10 μm, and the functional layer is configured to release a total iron ion concentration of 0.1-10 μM at the membrane-biomembrane interface.

2. The modified MABR membrane material according to claim 1, characterized in that, The thickness of the functional layer is 0.5-5 μm; And / or, the iron ions include Fe 2+ or Fe 3+ At least one of them.

3. The modified MABR membrane material according to claim 1, characterized in that, The hollow fiber membrane matrix is ​​made of at least one of polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyethersulfone, or polydimethylsiloxane. And / or, the hollow fiber membrane has an outer diameter of 0.5-3 mm, a wall thickness of 0.2-1 mm, and an average pore size of 0.01-1 μm.

4. The modified MABR membrane material according to claim 1, characterized in that, The iron-based active component includes at least one of zero-valent iron nanoparticles and iron oxides; And / or, the particle size of the iron-based active component is 10-200 nm, and the iron-based active component accounts for 5 wt%-60 wt% of the total mass of the functional layer.

5. The modified MABR membrane material according to claim 4, characterized in that, The iron oxide is selected from at least one of iron oxide, goethite, or ferrophosphate. And / or, the carrier matrix includes at least one of silica sol-gel, polydopamine, chitosan, sodium alginate, polyethyleneimine, polyvinyl alcohol, or polyacrylic acid.

6. A method for preparing a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria as described in any one of claims 1-5, characterized in that, The functional layer is loaded onto the outer surface of the hollow fiber membrane using an in-situ synthesis method or a blend spinning method.

7. The method for preparing the modified MABR membrane material according to claim 6, characterized in that, The in-situ synthesis method includes the following steps: S11. Perform surface activation pretreatment on the hollow fiber membrane substrate; S12. Immerse the pretreated membrane substrate in a mixed solution containing iron precursor and carrier matrix precursor; S13. Curing and post-treatment of the membrane loaded with the functional layer; The blending spinning method includes the following steps: S21. Iron-based nanoparticles, membrane matrix polymer, carrier matrix, solvent and pore-forming agent are mixed to form a uniform casting solution; S22. The casting solution is extruded through a spinneret using a dry-wet spinning process and then solidified into a film through phase inversion. S23. Perform post-treatment on the formed film.

8. The method for preparing the modified MABR membrane material according to claim 7, characterized in that, The surface activation pretreatment method in the in-situ synthesis method includes at least one of the following: chemical coupling method, vapor deposition method, plasma treatment method, and photochemical treatment method. And / or, the iron precursor includes at least one of ferrous sulfate or ferric chloride; And / or, the carrier matrix precursor is tetraethyl orthosilicate, and the in-situ reaction is a hydrolysis-condensation reaction occurring under conditions of pH 8.0-10.0; And / or, the carrier matrix precursor is dopamine hydrochloride, and the in-situ reaction is an oxidative self-polymerization reaction occurring under conditions of pH 8.0-9.0; And / or, in the blend spinning method, the carrier matrix is ​​selected from at least one of chitosan, sodium alginate, polyethyleneimine, polyvinyl alcohol, or polyacrylic acid; And / or, in the in-situ synthesis method, the immersion time of the pretreated membrane substrate in a mixed solution containing iron precursor and carrier matrix precursor is 1-60 h; And / or, in the blending spinning method, the thickness of the functional layer is controlled by adjusting the amount of iron-based nanoparticles added, wherein the amount of iron-based nanoparticles added is 1%-15% of the polymer mass of the membrane matrix.

9. The preparation method of the modified MABR membrane material according to claim 8, characterized in that, The membrane matrix polymer includes at least one of polyvinylidene fluoride, polysulfone, or polyethersulfone. And / or, the solvent includes N-methylpyrrolidone; And / or, the pore-forming agent includes polyvinylpyrrolidone.

10. The application of a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria as described in any one of claims 1-5, or a modified MABR membrane material for inhibiting nitrite-oxidizing bacteria prepared by any one of claims 6-9, in wastewater treatment.

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