Micro-polluted water odor targeting composite biological filter material and its preparation and application

Abstract

The application discloses micro-polluted water smell targeting composite biological filter material and preparation and application thereof, the filter material is a spherical particle, and sequentially comprises a high-density manganese sand core accounting for 75% of the diameter, an amino-chitosan biological affinity layer accounting for 15%-20%, and a COF-graphene hybrid adsorption layer accounting for 5%-10%; the three-layer structure cooperatively realizes selective adsorption, electrochemical activation and biological mineralization of geosmin, 2-MIB and other odor-causing substances; the outer layer is rich in easily degradable nutrients for metabolism of the middle-layer indigenous bacteria, the inner layer delta-MnO2 and graphene construct an electron transfer channel, and oxidation degradation is strengthened; the filter material has excellent sedimentation, mechanical strength and self-sustaining ecological functions, and significantly improves long-term, stability and impact resistance of smell removal, and is suitable for deep treatment of drinking water.

Description

Technical Field

[0001] This application relates to the field of water treatment materials and deep water purification technology, specifically to the field of odor-targeted composite biological filter media for micro-polluted water and its preparation and application technology. Background Technology

[0002] In the deep treatment of tap water, slightly polluted water sources (such as reservoir water and river water) often contain low concentrations of highly perceptible odor-causing substances such as geosmin and 2-methylisoborneol (2-MIB), which can easily lead to user complaints.

[0003] Currently, the mainstream process is biological activated carbon (BAC) filtration, but it has also revealed some problems in practical applications. First, activated carbon has a broad-spectrum adsorption capacity, but its pores are easily clogged by natural organic matter. Its adsorption capacity for geosmin / 2-MIB decays rapidly, resulting in a short lifespan (typically penetrating within 3–6 months). Also, because activated carbon relies solely on an unstable biofilm attached to its surface, it lacks electron transfer enhancement and microenvironment regulation, making it difficult to achieve complete mineralization of odor-causing substances. Another reason for its short lifespan is the low density (≈0.4–0.5 g / cm³) and weak strength of activated carbon. It is easily lost in upward flow and easily caking in downward flow, resulting in poor backwashing effect and high losses.

[0004] Although some studies have attempted to replace them with gel balls, metal oxide filter media, etc., they are generally difficult to apply in engineering due to reasons such as not being able to settle on their own, easy inactivation of bacteria, or the shell not being water-resistant and incompatible with microorganisms.

[0005] Therefore, there is an urgent need to develop a new type of composite filter material that combines good settling performance, engineerable backwashing, high selective adsorption capacity, and stable biological load to replace or enhance existing activated carbon processes and improve the long-term effectiveness and reliability of odor control in micro-polluted water. Summary of the Invention

[0006] This application proposes a targeted composite biological filter material for odor and taste control in slightly polluted water, as well as its preparation and application, to solve the technical bottlenecks of traditional activated carbon processes in controlling odor and taste in slightly polluted water, such as poor adsorption selectivity, weak biological activity, short service life, and difficulty in stable backwashing.

[0007] To achieve the above objectives, the present application adopts the following technical solution: Firstly, this application proposes a micro-polluted water odor-targeting composite biological filter media, wherein the filter media is spherical particles, comprising, from the inside out: The inner manganese sand core accounts for 75% of the overall sphere diameter, with a true density of 3.2–3.6 g / cm³, of which δ-MnO2 mass content is 40%–50%. The middle bio-affinity functionalized layer, which accounts for 15%–20% of the overall sphere diameter and has a true density of 1.0–1.2 g / cm³, is composed of amino-grafted chitosan. The outer COF-graphene hybrid adsorption layer, with a thickness of 5%–10% of the overall sphere diameter and a true density of 0.3–0.8 g / cm³, is a three-dimensional hierarchical porous conductive network formed by in-situ co-assembly of covalent organic framework (COF) and graphene.

[0008] This invention constructs a three-in-one spherical composite structure consisting of a "high-density manganese sand core, an amino-chitosan bio-affinity functional layer, and a COF-graphene hybrid adsorption layer," which synergistically achieves long-term, efficient, and stable removal of odor-causing substances such as geosmodium and 2-MIB from slightly polluted water, and endows the filter media with self-sustaining and self-enhancing ecological functions.

[0009] Specifically, the outer COF-graphene hybrid layer has the dual function of selectively adsorbing odor-causing substances (such as geosmin and 2-MIB) and enriching easily degradable small molecule nutrients, providing a directional carbon source for the functional bacteria anchored by the middle layer of aminated chitosan, promoting their activity and stability; the inner high-density manganese sand core (containing 40%–50% δ-MnO2) ensures the settling properties and mechanical strength of the filter media, and works synergistically with the outer graphene layer to construct an electron transport pathway, driving the oxidative degradation of adsorbed odor-causing substances. The products are immediately mineralized by the middle layer of bacteria, thereby achieving self-maintenance and long-term stability of odor removal efficiency.

[0010] In some possible implementations, the internal porosity of the filter media is 45%–55%.

[0011] In some possible implementations, the micropore size of the COF-graphene hybrid adsorption layer is 1–2 nm, and the mesopore / macropore size is 20–100 nm.

[0012] Secondly, this application also proposes a method for preparing the micro-polluted water odor-targeting composite biological filter material as described above, comprising the following steps: Step S1: Spray granulation combined with high-temperature sintering at 800–1000℃ is used to prepare spherical manganese sand cores that account for 75% of the overall sphere diameter and have a δ-MnO2 content of 40%–50%. Step S2: Immerse the manganese sand core in an aminated grafted chitosan solution, form a uniform coating by fluidized bed coating, and obtain manganese sand-chitosan composite spheres after drying and curing. Step S3: On the surface of the manganese sand-chitosan composite spheres, a covalent organic framework-graphene hybrid network shell is constructed in situ using microfluidic technology or multiple emulsion interfacial polymerization. Step S4: Place the obtained composite sphere in After pre-freezing at 80°C for 4 hours, under a vacuum degree <10Pa and shelf temperature Freeze-dry at 20°C for 24 hours to set the shape.

[0013] In some possible implementations, the method further includes a step of contacting the manganese sand-chitosan composite balls with a bacterial solution derived from the local water treatment environment prior to step S3 to enrich indigenous microorganisms.

[0014] In some possible implementations, the local water treatment environment is a water source to be treated, a biological activated carbon filter in a water plant, or an activated sludge system.

[0015] In some possible implementations, the contact operation of the indigenous microbial enrichment solution is carried out at 25–35°C and pH 6.5–8.0.

[0016] In some possible implementations, step S3 is carried out under mild conditions in an aqueous phase at room temperature using microfluidic technology or multiple emulsion interfacial polymerization.

[0017] Thirdly, this application also proposes the application of the micro-polluted water odor-targeting composite biological filter media as described above in the deep treatment of tap water plants. The micro-polluted water odor-targeting composite biological filter media is periodically supplemented or partially replaced with the original filter media at a ratio of no more than 20% of the total volume of the biological activated carbon filter media in a single addition. It is either layered alone or mixed with activated carbon and filled in the biological activated carbon filter.

[0018] In some possible implementations, the spherical particles have a diameter of 4.5–5.5 mm, and when the micro-polluted water odor-targeting composite biological filter media is filled in a biological activated carbon filter, the packing porosity of the formed filter bed is 36%–40%. Attached Figure Description

[0019] Figure 1 This is a flowchart of the preparation method in this application. Detailed Implementation

[0020] The following examples further illustrate the features of this application and other related features in detail, so as to facilitate understanding by those skilled in the art: It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions in the attached diagrams, while the terms “bottom surface,” “top surface,” “inner,” and “outer” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0021] Furthermore, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this case based on the specific circumstances.

[0022] Unless otherwise specified, all materials, reagents, and instruments used in the embodiments of this invention can be obtained through commercial channels. The main raw materials include: high-grade manganese ore powder (MnO2 content >45%, particle size <100 mesh), chitosan (degree of deacetylation ≥85%, viscosity-average molecular weight 100,000–200,000), epichlorohydrin or glutaraldehyde (for amylation grafting modification), covalent organic framework monomers (such as trimesaldehyde, p-phenylenediamine, etc.), and graphene oxide dispersion (concentration 2 mg / mL).

[0023] The main instruments and equipment include: spray drying tower (controllable inlet air temperature), high-temperature muffle furnace (maximum temperature 1200℃), fluidized bed coating machine, vacuum freeze dryer (ultimate vacuum degree <5Pa), constant temperature shaking incubator, scanning electron microscope (SEM), specific surface area and pore size analyzer, and ultraviolet-visible spectrophotometer.

[0024] The testing methods are as follows: true density was determined using the gas specific gravity bottle method; porosity was calculated using a mercury porosimeter combined with the water absorption saturation method; microbial activity was determined using the ATP bioluminescence method and dehydrogenase activity determination; adsorption performance was tested using standard water samples containing geosmin (100 ng / L) and 2-MIB (100 ng / L), and the breakthrough curve was determined through a dynamic column experiment; mechanical strength was tested using an abrasion rate meter to simulate abrasion under backwashing conditions.

[0025] Firstly, in practical applications, such as in the advanced treatment of tap water, the odor-targeting composite biological filter media described in this application should be periodically replenished or partially replaced with the original filter media, with a single addition amount not exceeding 20% ​​of the total volume of the biological activated carbon filter media. This media can be added separately in layers or mixed with activated carbon and filled into the biological activated carbon filter. To achieve backwashing capability, stable settling is required, the technical principles and calculation basis of which are as follows.

[0026] The composite biological filter material is designed as spherical particles with an overall diameter of 5.0 mm. From the inside out, it includes an inner manganese sand core, a middle bio-affinity functionalized layer, and an outer COF-graphene hybrid adsorption layer. The structural parameters and true densities of each layer are as follows: Inner layer: manganese sand core; accounting for 75% of the overall sphere diameter, i.e., a diameter of 3.75 mm; true density of 3.2–3.6 g / cm³, with a typical value of 3.4 g / cm³, of which δ-MnO2 mass content is 40%–50%; Middle layer: bio-affinity functionalized layer; thickness accounting for 15%–20% of the overall sphere diameter, i.e., a thickness of 0.8–1.0 mm; true density of 1.0–1.2 g / cm³, with a typical value of 1.1 g / cm³, which can enrich indigenous microorganisms; Outer layer: COF-graphene hybrid adsorption layer; thickness accounting for 5%–10% of the overall sphere diameter, i.e., a thickness of 0.25–0.45 mm; true density of 0.3–0.8 g / cm³, with a typical value of 0.5 g / cm³, which is a three-dimensional hierarchical porous conductive network formed by in-situ co-assembly of covalent organic framework (COF) and graphene. The micropores of the COF-graphene hybrid adsorption layer have a diameter of 1–2 nm, and the mesopores / macropores have a diameter of 20–100 nm.

[0027] Based on the above geometric structure, the volume proportion of each layer is calculated as follows: The inner layer's volume percentage is approximately 42.19% (3.75 / 5.0)³. The outer layer is a thin-shell structure, and its volume percentage can be calculated using the formula for the volume of a spherical shell, approximately 12.81%. The middle layer's volume percentage is 100%. 42.19% 12.81% ≈ 45.00%.

[0028] Therefore, the weighted average method is used to calculate the overall true density (ρ_overall) of the filter media: ρ_total = (3.4 g / cm³ × 42.19%) + (1.1 g / cm³ × 45.00%) + (0.5 g / cm³ × 12.81%) = 1.434 + 0.495 + 0.064 ≈ 1.993 g / cm³.

[0029] Considering the 45%–55% porosity within the filter media (including the pores in the manganese sand-chitosan and porous framework), the apparent density of a single filter media particle (i.e., the density actually manifested in water) can be further estimated as follows: ρapparent = ρtotal × (1 Porosity) ∈ [1.993×(1 0.55), 1.993×(1 [0.45)]≈1.35–1.45g / cm³.

[0030] Since the apparent density is significantly greater than that of water (1.0 g / cm³), the composite biological filter media described in this application can achieve rapid and stable settling in water without floating or being lost with the water flow.

[0031] Furthermore, in engineering applications, when this filter media is filled into a biological activated carbon filter bed with a particle size of 4.5–5.5 mm, the resulting filter bed has a porosity of 36%–40% and a corresponding wet bulk density of 0.85–0.95 t / m³, which fully meets the requirements of conventional waterworks filters for filter media settling properties, backwashing stability, and hydraulic characteristics.

[0032] The preparation method of the micro-polluted water odor-targeted composite biological filter material described above will be explained below. First, the preferred embodiment with the optimal preparation parameters will be adopted.

[0033] Step S1: Preparation of spherical manganese sand cores. High-grade manganese ore powder is crushed to a particle size of less than 100 mesh and mixed with a 5% PVA solution at a solid-liquid ratio of 3:1 to form a slurry. The slurry is then granulated using a spray drying tower, with the inlet air temperature controlled at 180℃, yielding green balls with a particle size of approximately 3.75 mm. The green balls are then placed in a muffle furnace and sintered at 900℃ for 2 hours, with a heating rate controlled at 5℃ / min. After cooling, spherical manganese sand cores with a true density of 3.4 g / cm³ and a δ-MnO₂ content of 45% are obtained, with a diameter accounting for 75% of the final finished sphere diameter (5 mm diameter). It should be noted that the sintering temperature can be selected within the range of 800℃–1000℃, which mainly affects mechanical strength. Adjustments can be made within an appropriate range according to the requirements of the application environment; however, no further examples are provided in this application to illustrate this.

[0034] Step S2: Immerse the manganese sand core in an aminated grafted chitosan solution, coat it with a fluidized bed to form a uniform coating, and then dry and cure it to obtain manganese sand-chitosan composite spheres.

[0035] Chitosan with a degree of deacetylation ≥85% and a viscosity-average molecular weight of 100,000–200,000 was dissolved in a 1% (v / v) aqueous acetic acid solution to prepare a 2–3 wt% chitosan solution. Under nitrogen protection and stirring, epichlorohydrin (10%–20% of the chitosan mass) or glutaraldehyde (25% aqueous solution, 5%–15% of the chitosan mass) was slowly added, and the reaction was carried out at 50–60°C for 4–6 h. Subsequently, an aqueous solution of ethylenediamine (or diethylenetriamine) (1.5–2 times the molar amount of epichlorohydrin) was added dropwise, and the reaction was continued for 2–4 h to introduce additional amino groups. After the reaction was completed, the pH was adjusted to 9–10 with NaOH solution, the product was precipitated, filtered, repeatedly washed with deionized water until neutral, and then freeze-dried to obtain aminated grafted chitosan solid. Before use, it was dissolved in dilute acetic acid solution to prepare a functional layer coating solution of the required concentration.

[0036] The spherical manganese sand cores (approximately 3.75 mm in diameter) obtained in step S1 were placed in a fluidized bed coating machine. Aminated grafted chitosan solids, synthesized and freeze-dried using the aforementioned method, were dissolved in a 0.5%–1.0% (v / v) acetic acid aqueous solution to prepare a 4%–6% (w / v) functional coating solution. This solution was then filtered through a 0.45 μm filter membrane and used as the coating liquid. The coating process was carried out at an inlet air temperature of 50–60°C, a material temperature of 35–45°C, and an atomization pressure of 1.5–2.5 bar. Under the conditions of spraying rate of 3–6 mL / min and suitable fluidization air velocity, the coating liquid is uniformly sprayed onto the surface of the fluidized manganese sand core by top spraying. The coating amount is controlled so that the coating thickness accounts for about 15%–20% of the final sphere diameter (i.e., thickened to about 5.0 mm). After coating, it is dried at 50–60℃ for 1–2 h until the coating is completely cured. After cooling, manganese sand-aminated chitosan composite spheres with strong biocompatibility and rich amino functional groups on the surface are obtained.

[0037] In some other embodiments, to enhance biocompatibility, the following drying method can be used: After coating with a chitosan layer, the mixture is heat-treated at 60–80°C for 1 hour under a nitrogen atmosphere. Through controlled pyrolysis of the chitosan molecular chains, active aldehyde groups are generated in situ on the surface, followed by cooling to room temperature.

[0038] In practical applications, this odor-targeting composite biological filter media for slightly polluted water can be directly put into operation. Relying on its strong biocompatibility, it naturally adsorbs and enriches indigenous microorganisms from the raw water, gradually forming a stable biofilm. To accelerate the start-up process, before addition, the manganese sand-chitosan composite spheres can be contacted with bacterial solutions from the local water treatment environment to enrich indigenous microorganisms. The local water treatment environment can be the water source to be treated, a biological activated carbon filter in a water plant, or an activated sludge system. In specific operations, short-term (e.g., 12-24 hours) static or dynamic biofilm formation can be performed to inoculate indigenous functional bacteria that have been acclimatized to the local environment and have a high capacity for degrading geosmin and / or 2-MIB. A constant-temperature shaking incubator can also be used as an auxiliary method.

[0039] Step S3: Constructing the COF-graphene hybrid adsorption layer. This can be achieved using microfluidic technology or a multiple emulsion interfacial polymerization method to in-situ construct the COF-graphene hybrid shell on the surface of manganese sand-aminated chitosan composite spheres. Both methods are carried out in an aqueous phase at room temperature, providing mild conditions that effectively protect the activity of the internal indigenous microorganisms. Simultaneously, they allow for controllable construction of the shell thickness and pore structure, ensuring a strong bond between the shell and the inner layer. In this embodiment, a multiple emulsion interfacial polymerization method is used. The aforementioned manganese sand-aminated chitosan composite spheres are dispersed in an aqueous phase containing a graphene oxide dispersion, and COF monomers (trimethylbenzenealdehyde and p-phenylenediamine in a molar ratio of 2:3) are added. The reaction is carried out at 25°C in an aqueous phase for 12 hours. During this process, COF polymerizes in-situ at the oil-water interface (i.e., the surface of the composite spheres) and self-assembles with graphene to form a hybrid shell with a thickness of approximately 0.35 mm (accounting for 7% of the overall diameter).

[0040] In some embodiments, to improve microbial adhesion performance, when constructing the shell using a multiple emulsion interfacial polymerization method, a discontinuous "island-like" microstructure array composed of COF-graphene hybrid materials is constructed in situ on the surface of the manganese sand-aminochitosan composite spheres by controlling the oil / water phase interfacial tension and reaction kinetics, rather than forming a dense, continuous film. The size of this "island-like" structure is 1–5 μm, with interconnected micron-level trenches and pores between the islands. This provides abundant attachment anchors for microorganisms; furthermore, the three-dimensional interconnected network formed between the islands constitutes an efficient channel for microbial growth and material transport, greatly promoting the diffusion of dissolved oxygen and nutrients into the biofilm and the timely removal of metabolic products.

[0041] Step S4: Freeze-drying and shaping. The obtained composite spheres were pre-frozen in an ultra-low temperature freezer at -80℃ for 4 hours, and then transferred to a vacuum freeze dryer for sublimation drying at a vacuum degree <10Pa and shelf temperature of -20℃ for 24 hours to obtain the final micro-polluted water odor-targeting composite biological filter material.

[0042] The prepared filter media was found to be regularly spherical with an overall diameter of 5.0 ± 0.2 mm. Test results showed that the overall true density of the filter media was approximately 1.98 g / cm³, with an internal porosity of 50%. The micropores in the COF-graphene layer had a diameter of approximately 1.5 nm, while the mesopores had a diameter of approximately 40 nm. Indigenous microbial activity testing showed that the bacterial survival rate remained at approximately 50% after the above preparation process. Therefore, this embodiment successfully prepared a composite biological filter media with a three-layer hierarchical structure. The thickness ratio, density, and pore structure of each layer met the design requirements, and the biological activity of the indigenous microorganisms was effectively maintained, demonstrating the feasibility of the technical solution of this invention.

[0043] In this application, the δ-MnO2 content in the manganese sand core has a major impact on the overall settling performance and catalytic effect. Data on the lower and upper limits of the δ-MnO2 content were prepared accordingly. With other preparation conditions identical to the preferred embodiment, only the raw material ratio and sintering process in step S1 were adjusted to ensure that the δ-MnO2 mass content in the obtained spherical manganese sand core was 40% (lower limit). The remaining conditions remained unchanged, and the product was obtained. The test results show that the overall true density of the product is 1.95 g / cm³, and its mechanical strength is slightly lower than that of the preferred embodiment, but still meets the requirements for filter operation. In the dynamic experiment for removing geosmin, its removal efficiency is slightly lower than that of the preferred embodiment (approximately 5%), but still significantly better than that of traditional activated carbon filter media.

[0044] Conversely, with other preparation conditions the same as in the preferred embodiment, only the raw material ratio and sintering process in step S1 are adjusted so that the δ-MnO2 mass content in the obtained spherical manganese sand core is 50% (upper limit value), and the other conditions remain unchanged, and the product is obtained.

[0045] The test results showed that the overall true density of the product was 2.02 g / cm³, and the electron transfer efficiency test showed that its conductivity was improved by about 8% compared with the preferred embodiment. However, in the wear rate test, it was found that its brittleness increased slightly, and the wear rate increased by about 3% compared with the preferred embodiment, but it was still within an acceptable range. Therefore, it can be seen that the technical solution of the present invention still has good feasibility and stability under both the lower and upper limits of δ-MnO2 content.

[0046] It should be noted that all dynamic removal performance tests were conducted under simulated water plant operating conditions: filter media were packed into an 800 mm filter bed in an plexiglass column with an inner diameter of 50 mm and a height of 1000 mm. The feed water contained 20–50 ng / L of geosmin and 15–40 ng / L of 2-MIB. The system was operated continuously at an empty bed contact time (EBCT) of 15 min and a water temperature of 20–25 °C.

[0047] To eliminate the impact of the start-up period, performance data were collected after the system reached biological stability—that is, the concentration of odor-causing substances in the effluent fluctuated by less than ±5% for three consecutive days and the ATP biomass tended to stabilize. In the preferred embodiment, stability was typically achieved on days 10–12, while samples with 40% and 50% δ-MnO2 content reached stability on days 12–14 and 11–13, respectively. All removal efficiency data were uniformly taken as the average of 72 consecutive hours starting from the 15th day to ensure comparability.

[0048] Furthermore, the thickness ratio of the middle bio-affinity functionalized layer also affects the overall sedimentation, and the resulting change in the indigenous microbial load affects the overall deodorization effect. With other preparation conditions the same as in the preferred embodiment, only the thickness of the bio-affinity functionalized layer in step S2 was adjusted to 15% of the overall sphere diameter (corresponding to a thickness of approximately 0.75 mm), while keeping other conditions unchanged, to obtain the product. Test results show that the bioload of this product is reduced by approximately 10% compared to the preferred embodiment, but in high-flow-rate (10 m / h) filtration tests, its pressure drop increases slowly, indicating excellent hydraulic performance. The efficiency in removing 2-MIB is comparable to the preferred embodiment in the initial stage of operation, but after long-term operation (30 days), the removal rate decreases slightly faster than in the preferred embodiment. Therefore, this product can still achieve the technical effects of the present invention.

[0049] Conversely, with other preparation conditions the same as in the preferred embodiment, only the thickness of the bio-affinity functionalized layer in step S2 was adjusted to be 20% of the overall sphere diameter (corresponding to a thickness of about 1.0 mm), while the other conditions remained unchanged, and the product was obtained.

[0050] The test results show that the bioburden of this product is increased by approximately 12% compared to the preferred embodiment, and it achieves better removal depth for low-concentration odorants. However, due to the increased thickness of the bioaffinity functionalized layer, the overall true density slightly decreases to 1.92 g / cm³, and the settling velocity slows down slightly, but it still settles stably. Therefore, this product can still achieve the technical effects of the present invention, demonstrating that within the parameter range of a 20% bioaffinity functionalized layer thickness, the technical solution of the present invention has good feasibility and is suitable for scenarios with extremely high requirements for effluent water quality.

[0051] Corresponding to the thickness of the bio-affinity functionalized layer, the varying proportion of the outer COF-graphene hybrid adsorption layer thickness affects the shock load resistance and permeability. Test results show that when the COF-graphene hybrid adsorption layer thickness accounts for 5% of the overall sphere diameter, the buffering capacity against high-concentration shock loads is slightly weaker, but its permeability is significantly improved. When the COF-graphene hybrid adsorption layer thickness accounts for 10% of the overall sphere diameter, the shock load resistance is strongest, but the flow resistance increases, resulting in an initial pressure drop in the filter that is approximately 15% higher than in the preferred embodiment. Therefore, the thickness setting of the outer COF-graphene hybrid adsorption layer satisfies the implementation conditions of this invention.

[0052] Finally, a comparative example is used to illustrate the effect of the micro-polluted water odor-targeting composite biological filter material of this application compared with the prior art.

[0053] The comparative example was commercially available coal-based granular activated carbon (GAC) with a particle size of 4-6 mm, a true density of 0.5 g / cm³, and a porosity of 55%.

[0054] The test items include: (1) Settling performance: the settling velocity of a single particle in water and the backwash loss rate; (2) Adsorption selectivity: under the background interference of humic acid (10 mg / L), the adsorption capacity and breakthrough time of geosmin (100 ng / L) and 2-MIB (100 ng / L) are determined; (3) Biodegradation efficiency: the total removal rate of odor-causing substances and the accumulation of intermediate products are determined after 60 days of dynamic column experiment; (4) Mechanical strength: the wear rate after 100 backwashes is simulated.

[0055] sample Settlement velocity (mm / s) Backwash loss rate (%) Geosmin adsorption capacity (ng / g) Total removal rate (%) over 60 days Wear rate (%) Preferred embodiment 45.2 0.5 1250 96.5 1.2 Comparative Example 12.5 18.5 800 65.0 8.5 Table 1 As shown in Table 1, in terms of settling performance, the preferred embodiment of the present invention exhibits a settling velocity as high as 45.2 mm / s and a backwash loss rate of only 0.5%, significantly superior to the comparative embodiment's 12.5 mm / s and 18.5% loss rate. This indicates that the present invention effectively solves the engineering pain point of easy activated carbon loss through its high-density manganese sand core design.

[0056] Regarding the synergistic effect of adsorption selectivity and biodegradation, the preferred embodiment of the present invention achieves an adsorption capacity of 1250 ng / g for geosmin, and the total removal rate after 60 days of operation is as high as 96.5%, far exceeding the 65.0% of the comparative example. Although the comparative example has a certain adsorption capacity in the early stage, its performance deteriorates rapidly due to a lack of selectivity and the pores being easily blocked by humic acid.

[0057] In terms of mechanical strength and lifespan, the wear rate of the preferred embodiment of the present invention is only 1.2%, which is far superior to the comparative example. This is due to the dual protection of the high-temperature sintered manganese sand core and the robust COF-graphene shell.

[0058] Thus, the odor-targeting composite biological filter media for micro-polluted water in this application achieves long-term, efficient, and stable removal of odor-causing substances such as geosmodium and 2-MIB from micro-polluted water through an integrated design of "high-density manganese sand core - aminated chitosan bioaffinity layer - COF / graphene hybrid adsorption layer", and has the ability to self-maintain and gradually enhance its performance during operation.

[0059] Specifically, the outer COF-graphene hybrid structure constructs a high specific surface area, three-dimensional conductive porous network. Its pore size and surface functional groups are directionally regulated, which can selectively adsorb target odorants and effectively suppress competitive interference from natural organic matter (NOM). At the same time, this layer can also enrich readily biodegradable components in NOM (such as low molecular weight organic acids, amino acids, monosaccharides, etc.), forming a local nutrient microenvironment on the surface of the filter material, providing a continuous carbon source and energy for the middle layer degrading bacteria, and driving a positive cycle of "adsorption energy supply - biodegradation".

[0060] Subsequently, the middle-layer aminated chitosan becomes positively charged (–NH3) at the pH of conventional water treatment. +It can efficiently capture local native functional bacteria in water plants using electrostatics, and combined with the nutrient supply provided by the outer layer, it can quickly build a highly active and highly attached biological interface to achieve in-situ mineralization of adsorbed odorants.

[0061] Finally, the inner high-density manganese sand core ensures that the filter media has good settling properties and mechanical strength, meeting the backwashing requirements of the filter bed; its δ-MnO2 acts as a highly efficient electron acceptor, working synergistically with the outer graphene to form a cross-scale electron transfer channel, promoting the electrochemical activation and oxidation of odorants, and further improving degradation efficiency.

[0062] In summary, the odor-targeting composite biological filter media for micro-polluted water in this application, compared with traditional activated carbon filter media, not only avoids the problem of sudden performance drop after adsorption saturation, but also dynamically optimizes its own micro-ecosystem through active ecological regulation of the material structure, significantly improving the system's adaptability to water quality fluctuations and long-term operational stability, and is suitable for the engineering needs of odor control in the deep treatment of drinking water.

[0063] As stated above, this case protects the odor-targeting composite biological filter material for micro-polluted water and its preparation and application. All technical solutions that are the same as or similar to this case should be considered to fall within the scope of protection of this case.

Claims

1. A micro-polluted water odor-targeting composite biological filter media, characterized in that, The filter media consists of spherical particles, comprising, from the inside out: The inner manganese sand core accounts for 75% of the overall sphere diameter, with a true density of 3.2–3.6 g / cm³, of which δ-MnO2 mass content is 40%–50%. The middle bio-affinity functionalized layer, which accounts for 15%–20% of the overall sphere diameter and has a true density of 1.0–1.2 g / cm³, is composed of amino-grafted chitosan. The outer COF-graphene hybrid adsorption layer, with a thickness of 5%–10% of the overall sphere diameter and a true density of 0.3–0.8 g / cm³, is a three-dimensional hierarchical porous conductive network formed by in-situ co-assembly of covalent organic framework (COF) and graphene.

2. The odor-targeted composite biological filter media for micro-polluted water as described in claim 1, characterized in that, The internal porosity of the filter media is 45%–55%.

3. The odor-targeted composite biological filter media for micro-polluted water as described in claim 1, characterized in that, The micropores of the COF-graphene hybrid adsorption layer have a diameter of 1–2 nm, and the mesopores / macropores have a diameter of 20–100 nm.

4. A method for preparing a micro-polluted water odor-targeting composite biological filter media, used to prepare the micro-polluted water odor-targeting composite biological filter media as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Step S1: Spray granulation combined with high-temperature sintering at 800–1000℃ is used to prepare spherical manganese sand cores that account for 75% of the overall sphere diameter and have a δ-MnO2 content of 40%–50%. Step S2: Immerse the manganese sand core in an aminated grafted chitosan solution, form a uniform coating by fluidized bed coating, and obtain manganese sand-chitosan composite spheres after drying and curing. Step S3: On the surface of the manganese sand-chitosan composite spheres, a covalent organic framework-graphene hybrid network shell is constructed in situ using microfluidic technology or multiple emulsion interfacial polymerization. Step S4: Place the obtained composite sphere in After pre-freezing at 80°C for 4 hours, under a vacuum degree <10Pa and shelf temperature Freeze-dry at 20°C for 24 hours to set the shape.

5. The preparation method of the micro-polluted water odor-targeting composite biological filter material as described in claim 4, characterized in that, It also includes a step of contacting the manganese sand-chitosan composite balls with a bacterial solution derived from the local water treatment environment before step S3 to enrich indigenous microorganisms.

6. The preparation method of the micro-polluted water odor-targeted composite biological filter material as described in claim 5, characterized in that, The local water treatment environment refers to the water source to be treated, the biological activated carbon filter of the water plant, or the activated sludge system.

7. The preparation method of the micro-polluted water odor-targeting composite biological filter material as described in claim 5, characterized in that, The contact operation of the bacterial solution enriched with the indigenous microorganisms was carried out at 25–35°C and pH 6.5–8.

0.

8. The preparation method of the micro-polluted water odor-targeting composite biological filter material as described in claim 5, characterized in that, In step S3, microfluidic technology or multiple emulsion interfacial polymerization is used under mild conditions in an aqueous phase at room temperature.

9. The application of micro-polluted water odor-targeted composite biological filter media in the advanced treatment of tap water plants, characterized in that... The micro-polluted water odor-targeting composite biological filter media as described in any one of claims 1 to 3 is periodically replenished or partially replaced with the original filter media at a single addition rate not exceeding 20% ​​of the total volume of the biological activated carbon filter media, either in layers alone or mixed with activated carbon in the biological activated carbon filter.

10. The application of the micro-polluted water odor-targeting composite biological filter media as described in claim 9 in the advanced treatment of tap water plants, characterized in that, The spherical particles have a diameter of 4.5–5.5 mm. When the micro-polluted water odor-targeting composite biological filter media is filled into a biological activated carbon filter, the packing porosity of the filter media bed is 36%–40%.

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