Composite biological filler, preparation method, sewage treatment method and system

Abstract

The application discloses a kind of composite biological fillers, comprising: core, the structure of the core includes by polyurethane sponge synchronous loading Fe3O4 With PEI, wherein Fe3O4 loading capacity is 6-8 wt% of the mass of core, and PEI grafting density is 1.5-2.0 mg / cm 2 ;Outer layer: the structure of the outer layer includes the pure PEI modified polyurethane sponge layer of core, and PEI grafting density is 2.0-3.0 mg / cm 2 ;Binding layer: between the core and the outer layer, material is sodium alginate and CaCl2 gel.The application also discloses a kind of preparation method of composite biological fillers, further discloses a kind of sewage treatment method, further discloses a kind of sewage treatment system.Compared with prior art, the application can realize the efficient treatment efficiency of sewage.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a composite biological packing material, its preparation method, a wastewater treatment method, and a system. Background Technology

[0002] In the current wastewater treatment field, with the continuous improvement of water purification efficiency and advanced treatment requirements, aerobic granular sludge (AGS) technology has become a core research hotspot in the industry due to its significant advantages. This technology not only has excellent settling performance, which can effectively solve the problems of poor sludge settling and easy sludge bulking in the traditional activated sludge process, but also has multiple microbial functions, less residual sludge, strong tolerance to biotoxins and organic load fluctuations, and can also achieve simultaneous nitrogen and phosphorus removal without the need to build additional complex process units, which greatly simplifies the wastewater treatment process and reduces operating costs. However, despite the promising potential of AGS technology in theoretical and laboratory research, its transformation into practical engineering applications still faces three major bottlenecks: First, the start-up period is too long, typically requiring more than 60 days to form stable aerobic granular sludge. This not only prolongs the construction and commissioning cycle of the wastewater treatment system but also increases the initial operating costs and management difficulties. Second, it has weak resistance to shock loads. When the influent water quality (such as COD and ammonia nitrogen concentration) or flow rate fluctuates, AGS is prone to structural loosening, making it difficult to maintain stable treatment efficiency, and in severe cases, it may even lead to substandard effluent quality. Third, the particles are prone to disintegration. During long-term operation, the aerobic granular sludge that has been formed is prone to breakage and disintegration due to factors such as hydraulic conditions, changes in pollutant concentration, or imbalance of the microbial community, resulting in sludge loss and thus reducing the overall treatment efficiency of the system. In the field of wastewater treatment, traditional biological suspended media (such as polyurethane sponges, volcanic rock media, and MBBR media) are often used in conventional activated sludge processes and biofilm processes. By increasing the amount of biological carrier, the total number of microorganisms in the system is enhanced, thereby improving pollutant degradation efficiency or sludge settling properties. Traditional polyurethane sponge media, as one of the commonly used biological carriers in wastewater treatment, has a special structure that allows for nitrification on the outer surface of a single biological carrier in the aeration tank and denitrification of nitrite internally. This involves not only simple physical adsorption but also the attraction of positive and negative charges, giving the carrier surface certain cationic active groups and hydrophilic groups such as hydroxyl groups. These groups can form bonds and valences with negatively charged microorganisms in the wastewater, thus firmly fixing the microorganisms and enzymes to the carrier. This prevents the survival of microorganisms from being lost under the shearing action of water and air, resulting in a large microbial loading capacity and high volumetric loading, thereby simultaneously reducing ammonia nitrogen and total nitrogen in the wastewater. It also has advantages such as strong bubble-cutting ability, high space utilization, and no dead zones. The common defects of traditional polyurethane foam fillers are as follows: First, they have poor hydrophilicity, a typical characteristic of traditional polyurethane foam fillers. Their contact angle is usually greater than 100°, which significantly increases the difficulty for microorganisms to attach to the surface of the filler and requires a longer time to form a stable biofilm, with the biofilm formation period generally lasting 14-21 days. Second, they have high mass transfer resistance, a simple pore structure, and a lack of reasonable pore size gradient and connectivity, which are inherent structural defects of traditional polyurethane foam fillers. When wastewater flows inside the filler, it is easy to form stagnant areas, which hinder the efficient transfer of key substances such as oxygen, organic pollutants, and nitrogen and phosphorus compounds between the aqueous phase (wastewater) and the biological phase (microorganisms). This not only directly reduces the degradation efficiency of pollutants by microorganisms, but may also form anaerobic dead zones due to poor local material exchange, breeding harmful microorganisms such as sulfur-reducing bacteria and disrupting the balance of the microbial community in the system. Finally, they have limited functionality and cannot create differentiated microenvironments.

[0003] AGS technology, with its "core-shell" layered structure, enriches denitrifying bacteria and polyphosphate-accumulating bacteria in the core anoxic zone and nitrifying bacteria in the outer aerobic zone, achieving simultaneous nitrogen and phosphorus removal and enabling the colonization of microorganisms in designated zones.

[0004] In view of this, based on the commonalities and advantages and disadvantages of polyurethane sponge filler and AGS technology, and imitating the structural characteristics and performance features of aerobic granular sludge (AGS), a composite biological filler, preparation method, wastewater treatment method and system are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a composite biological packing material, a preparation method, a wastewater treatment method, and a system to achieve high-efficiency wastewater treatment.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A composite biological packing material, comprising: The core, the structure of which comprises Fe3O4 nanoparticles and PEI simultaneously loaded on polyurethane sponge, wherein the Fe3O4 loading is 6-8 wt% of the core mass and the PEI grafting density is 1.5-2.0 mg / cm². Outer layer: The structure of the outer layer includes a pure PEI-modified polyurethane sponge layer that encapsulates the core, with a PEI grafting density of 2.0-3.0 mg / cm²; Adhesive layer: located between the core and the outer layer, the material is sodium alginate and CaCl2 gel; The composite biological packing material described herein uses polyurethane sponge as the core material, simultaneously loading 6-8 wt% of Fe3O4 nanoparticles and PEI with a grafting density of 1.5-2.0 mg / cm². This structural design effectively promotes microbial proliferation by slowly releasing iron to supplement essential trace elements for microbial growth. The PEI density optimizes the biocompatibility of the core surface, aiding microbial attachment and colonization, and together with the loaded Fe3O4, creates a microenvironment suitable for anaerobic microorganisms, providing the necessary conditions for the anaerobic metabolic processes within the core. The outer layer is a pure PEI-modified polyurethane sponge layer encasing the core, with a PEI grafting density increased to 2.0-3.0 mg / cm². This high-density PEI forms a strongly positively charged interface on the outer layer of the packing material, efficiently capturing microorganisms (especially aerobic microorganisms) in wastewater through charge adsorption, significantly shortening the time for microbial enrichment and biofilm formation. This improves upon the problems of poor hydrophilicity and long biofilm formation cycles in traditional packing materials. Simultaneously, the outer sponge structure provides a stable attachment carrier and metabolic space for aerobic microorganisms, ensuring the efficient functioning of aerobic metabolism. The bonding layer located between the core and outer layer, made of sodium alginate and CaCl2 gel, not only achieves a tight connection between the core and outer layer, ensuring the overall structural stability of the packing and meeting the strength requirements of actual wastewater treatment processes, but also utilizes the properties of the gel to form microporous channels at the interface. These channels promote the smooth transfer of wastewater, oxygen, and various pollutants between the inner and outer layers, avoiding problems such as high mass transfer resistance and wastewater retention caused by the simple pore structure of traditional packings. At the same time, it helps to define the spatial boundary between the anaerobic zone of the core and the aerobic zone of the outer layer, providing structural support for simulating the "core-shell" stratified metabolic mechanism of aerobic granular sludge. Ultimately, through the synergistic effect of anaerobic metabolism in the core and aerobic metabolism in the outer layer, the simultaneous nitrogen and phosphorus removal efficiency of the packing is improved, enhancing the wastewater treatment system's resistance to shock loads.

[0007] In a preferred embodiment, the pore size of the outer polyurethane sponge layer is smaller than that of the inner polyurethane sponge layer. The pore size design of the outer polyurethane sponge layer being smaller than that of the inner polyurethane sponge layer creates a gradient pore size structure that precisely matches the layered function of the packing material: from the perspective of microbial colonization, the larger pores in the inner core provide more ample living space for anaerobic microorganisms, facilitating the aggregation and reproduction of anaerobic functional microorganisms such as denitrifying bacteria. Simultaneously, the larger pores also facilitate wastewater flow within the core, creating a suitable environment for anaerobic metabolism in conjunction with the Fe3O4 magnetic core and the low-density PEI. Meanwhile, the smaller pores in the outer layer increase the specific surface area of ​​the sponge, allowing the positively charged capture interface constructed by the high-density PEI to more fully contact the wastewater, enhancing the adsorption and fixation effect on aerobic microorganisms. Furthermore, the smaller pores slow down the wastewater flow rate, prolonging the contact time between aerobic microorganisms and pollutants, and strengthening the degradation effect of aerobic metabolism on pollutants. From the perspective of mass transfer efficiency, this pore size gradient can also optimize the transport path of wastewater and matter: wastewater first undergoes preliminary filtration and microbial action through the smaller pores of the outer layer, and then enters the larger pores of the inner core for deep anaerobic treatment. This avoids the wastewater retention problem that is prone to occur in traditional single-pore packing materials, and at the same time reduces the diffusion of oxygen from the outer aerobic zone to the inner anaerobic zone, further consolidating the spatial separation between the anaerobic environment of the inner core and the aerobic environment of the outer layer, and ensuring the stable operation of the "core-shell" stratified metabolic mechanism. In a preferred embodiment, the Fe3O4 nanoparticles are carboxylated, with a particle size of 30-50 nm, and their surface is treated with 0.3 M HCl. Carboxylation introduces hydrophilic groups, which, combined with the small particle size, reduces particle aggregation. The 0.3 M HCl treatment removes surface impurities. These three factors synergistically improve the dispersibility of the particles in the PEI mixture, ensuring uniform distribution of the magnetic core and preventing localized accumulation of microorganisms. The carboxyl groups form strong interactions with the sponge and PEI, while the HCl treatment activates the surface, enhancing particle loading stability, reducing shedding under water flow impact, and ensuring the long-term effectiveness of the magnetic core function. The 30-50 nm particle size is suitable for the magnetic response requirements of microorganisms. The modified and treated surface is mild and non-toxic, and it can also provide energy to microorganisms through slow iron release, promoting stable proliferation of microorganisms in the anaerobic zone of the core and supporting the efficient operation of the "core-shell" metabolic mechanism.

[0008] A composite biological packing material, the preparation method of which includes: Core preparation: Alkali-activated polyurethane sponge was immersed in a mixture containing Fe3O4 and PEI, wherein Fe3O4 was 6-8 wt%, PEI was 1.5-2.0 wt%, pH was 9.5, and the mixture was vacuum impregnated at 60℃ for 4 hours, followed by washing with water. Outer layer preparation: Immerse the alkali-activated polyurethane sponge in a 2.0-3.0 wt% PEI solution at pH 10.0 for 4 hours at 60℃, then wash with water; Double-layer combination: After the core surface is coated with sodium alginate and CaCl2 gel, wherein sodium alginate is 2 wt% and CaCl2 is 1 wt%, the outer sponge is wrapped and rolled to shape.

[0009] This preparation method achieves precise construction of composite biofillers through step-by-step processing: The core layer is prepared by alkali-activated polyurethane sponge, which is impregnated in a mixture containing 6-8 wt% Fe3O4 and 1.5-2.0 wt% PEI (pH 9.5) at 60°C under vacuum for 4 hours. The vacuum environment promotes the full penetration of the mixture into the sponge pores, ensuring uniform loading of Fe3O4 and PEI. Alkali activation pretreatment enhances the surface activity of the sponge and improves loading stability. Washing removes unbound components. The outer layer is prepared by immersing the alkali-activated sponge in a 2.0-3.0 wt% PEI solution (pH 10.0) at 60°C for 4 hours. The alkaline conditions and temperature synergistically promote efficient PEI grafting, forming a high-density positively charged interface. Washing ensures the purity of the outer layer. The double-layer combination is achieved by coating with 2 wt% PEI... Sodium alginate and 1wt% CaCl2 gel are used to roll and shape the core and outer layer tightly. The gel ensures both adhesion strength and forms microporous channels. The overall process steps are clear and the parameters are controllable, which can stably prepare composite biological packing with layered structure and function to meet the needs of sewage treatment.

[0010] In a preferred embodiment, the Fe3O4 nanoparticles are carboxylated, with a particle size of 30-50 nm, and their surface is treated with 0.3 M HCl. The carboxylation modification, controlled 30-50 nm particle size, and 0.3 M HCl surface treatment of the Fe3O4 nanoparticles optimize core performance in multiple dimensions: carboxylation introduces hydrophilic carboxyl groups, which, combined with the small 30-50 nm particle size, significantly reduces the tendency for particle aggregation, while the 0.3 M HCl treatment removes impurities and hydroxyl contaminants from the particle surface; simultaneously, carboxylation modification and HCl treatment activate the particle surface, enhancing its bonding with polyurethane foam and PEI, reducing shedding under water flow impact, and ensuring long-term stability of the magnetic core function; the 30-50 nm particle size is suitable for the magnetic response requirements of microorganisms, the modified and treated surface is mild and non-toxic, and it can also provide energy for microorganisms through slow iron release, helping the stable proliferation of microorganisms in the anaerobic zone of the core and supporting the efficient operation of the "core-shell" metabolic mechanism.

[0011] A wastewater treatment method, using the aforementioned composite biological packing material, or using the aforementioned method for preparing the composite biological packing material.

[0012] A wastewater treatment system that uses the aforementioned composite biological packing material, or the method for preparing the aforementioned composite biological packing material, or the aforementioned wastewater treatment method.

[0013] Compared with existing technologies, in the composite biological packing material of this invention, Fe3O4 nanoparticles can form a magnetic core, which can achieve the slow release of iron, providing the necessary trace elements for microbial growth and driving efficient microbial proliferation. Meanwhile, the grafted density of PEI optimizes the surface properties of the core, further assisting microbial attachment, and synergistically creates a microenvironment suitable for anaerobic microbial colonization with Fe3O4, laying the foundation for subsequent anaerobic metabolic processes. The outer layer is a polyurethane sponge layer modified with pure PEI and a grafting density increased to 2.0-3.0 mg / cm². The high-density PEI can construct a strong positive charge capture interface on the outer layer of the packing material, efficiently capturing microorganisms (especially aerobic microorganisms) in wastewater through charge adsorption, significantly accelerating the enrichment rate of microorganisms on the packing surface, solving the problem of long biofilm formation cycles caused by poor hydrophilicity in traditional packing materials. Simultaneously, the outer sponge structure can also provide a stable attachment and metabolic space for aerobic microorganisms, realizing aerobic metabolic functions. The gel bonding layer, composed of sodium alginate and CaCl2, located between the core and outer layer, not only ensures a tight bond between the core and outer layer, guaranteeing the overall structural stability of the packing (the bonding strength meets practical application requirements), but also utilizes the gel's own properties to form microporous channels at the interface. These channels facilitate the transfer of wastewater, oxygen, and pollutants between the inner and outer layers, avoiding the problems of high mass transfer resistance and wastewater retention caused by the single pore size of traditional packing. They also help to achieve spatial separation between the anaerobic zone of the core and the aerobic zone of the outer layer, providing structural support for the "core-shell" stratified metabolic mechanism of aerobic granular sludge. Ultimately, through the synergy of anaerobic metabolism in the core and aerobic metabolism in the outer layer, the efficiency of simultaneous nitrogen and phosphorus removal by the packing is improved, while enhancing the system's resistance to shock loads and alleviating the bottlenecks of long start-up cycles and easy particle disintegration in aerobic granular sludge technology. Attached Figure Description

[0014] Figure 1 This invention relates to a hierarchical structure diagram of a composite biological packing material.

[0015] Kernel 1; Outer layer 2; Adhesive layer 3. Detailed Implementation

[0016] The present invention will be further described in detail below with reference to the accompanying drawings.

[0017] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention. Example 1

[0018] like Figure 1 As shown, a composite biological packing material includes: The core, the structure of which comprises Fe3O4 nanoparticles and PEI simultaneously loaded on polyurethane sponge, wherein the Fe3O4 loading is 6-8 wt% of the core mass, the PEI grafting density is 1.5-2.0 mg / cm², the Fe3O4 nanoparticles are carboxylated modified, the particle size is 30-50 nm, and the surface is treated with 0.3 M HCl; Outer layer: The structure of the outer layer includes a pure PEI modified polyurethane sponge layer that wraps the core, with a PEI grafting density of 2.0-3.0 mg / cm², and the pore size of the polyurethane sponge layer in the outer layer is smaller than that in the polyurethane sponge layer of the core. Adhesive layer: Located between the core and the outer layer, the material is sodium alginate and CaCl2 gel.

[0019] This embodiment presents a composite biological filler based on a "magnetic core-biological interface" bilayer biomimetic structure and its preparation method. Through the layered combination of the core (Fe3O4 / PEI-sponge) and the outer layer (pure PEI modified sponge), the following is achieved: the core—iron slow-release drives microbial proliferation; the outer layer—high-density positive charge interface captures microorganisms.

[0020] kernel <![CDATA[Polyurethane sponge + co-loaded Fe3O4 / PEI]]> Microbial proliferation <![CDATA[The loading amount of Fe3O4 is 6 - 8 wt%, and the density of PEI is 1.5 - 2.0 mg / cm²]]> outer layer Polyurethane foam + pure PEI modification Highly efficient microbial capture PEI density 2.0-3.0 mg / cm² Example 2

[0021] A method for preparing a composite biological packing material, comprising: Core preparation: Immerse the alkali-activated polyurethane sponge in a mixture containing PEI (6-8 wt%, PEI 1.5-2.0 wt%, pH 9.5), vacuum impregnate at 60℃ for 4 hours, and then wash with water. Outer layer preparation: Immerse the alkali-activated polyurethane sponge in a 2.0-3.0 wt% PEI solution at pH 10.0 for 4 hours at 60℃, then wash with water; Double-layer combination: After the core surface is coated with sodium alginate and CaCl2 gel, wherein sodium alginate is 2 wt% and CaCl2 is 1 wt%, the outer sponge is wrapped and rolled to shape.

[0022] Furthermore, the nanoparticles are carboxylated, have a particle size of 30-50 nm, and their surface is treated with 0.3 M HCl.

[0023] Furthermore, the double-layer assembly step specifically includes: coating the core surface with sodium alginate and CaCl2 gel, wherein sodium alginate is 2 wt% and CaCl2 is 1 wt%, wrapping the outer sponge, and then rolling to shape it. The following is an example: 1. Kernel preparation: Take sponge balls, activate them with 5% NaOH, immerse them in a mixed solution (1.5% PEI + 8% activated Fe3O4, pH 9.5), react at 60℃ for 4 h, and then wash with water.

[0024] 2. Outer layer preparation: Immerse the sponge sheet in 2.5% PEI (pH 10.0) → react at 60℃ for 4 h → wash with water.

[0025] 3. Combination: The core surface is coated with sodium alginate and CaCl2 gel → wrapped with an outer sponge sheet → rolled into shape.

[0026] The advantages of the composite biological filler prepared by the method for preparing composite biological materials according to this embodiment are explained below: I. Shape Advantages Spherical core-shell structure: The core is a spherical sponge to optimize fluid contact efficiency; the outer layer is a uniform coating layer to ensure the integrity of the microbial capture interface.

[0027] Compared to traditional packing materials: cubic / cylindrical packings have hydraulic dead zones, while the spherical design reduces short-circuiting (improving flow velocity uniformity by 40%). Gradient pore size distribution: large pores in the core promote the enrichment of denitrifying bacteria; small pores in the outer layer enhance the attachment of nitrifying bacteria.

[0028] Gel bonding interface: Sodium alginate and CaCl2 gel layer form microporous channels to promote the exchange of substances between the inner and outer layers; The technical advantages of this embodiment are explained below: 1. The microbial regulation advantage core attracts anaerobic bacteria through a Fe3O4 magnetic core (6-8 wt%) and low PEI method; the outer layer enriches aerobic bacteria through high-density PEI (2.0-3.0 mg / cm²). This achieves spatial separation of anaerobic and aerobic bacteria, enabling targeted enrichment and metabolic synergy of microorganisms.

[0029] 2. Process compatibility: Compatible with mainstream SBR / MBBR / IFAS / CASS processes. Example 3

[0030] A wastewater treatment method that uses the composite biological packing material described in Example 1, or the preparation method of the composite biological packing material described in Example 2. Example 4

[0031] A wastewater treatment system, characterized in that it uses the composite biological packing material described in Example 1, or the preparation method of the composite biological packing material described in Example 2, or the wastewater treatment method described in Example 3.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element. Additionally, in this document, "greater than," "less than," "exceeding," etc., are understood to exclude the stated number; "above," "below," "within," etc., are understood to include the stated number.

[0033] The above description of the embodiments is provided to facilitate understanding and use of the present invention by those skilled in the art. It is obvious to those skilled in the art that various modifications can be easily made to the embodiments, and the general principles described herein can be applied to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A composite biological packing material, characterized in that, include: The core, the structure of which comprises Fe3O4 nanoparticles and PEI simultaneously loaded on polyurethane sponge, wherein the Fe3O4 loading is 6-8 wt% of the core mass and the PEI grafting density is 1.5-2.0 mg / cm². Outer layer: The structure of the outer layer includes a pure PEI-modified polyurethane sponge layer that wraps around the core, with a PEI grafting density of 2.0-3.0 mg / cm²; Adhesive layer: located between the core and the outer layer, the material is sodium alginate and CaCl2 gel; The pore size of the outer polyurethane foam layer is smaller than that of the polyurethane foam layer of the core.

2. The composite biological packing material according to claim 1, characterized in that, The Fe3O4 nanoparticles are carboxylated, with a particle size of 30-50 nm, and their surface is treated with 0.3 M HCl.

3. The composite biological packing material according to claim 1, characterized in that, Its preparation methods include: Core preparation: Alkali-activated polyurethane sponge was immersed in a mixture containing Fe3O4 and PEI, wherein Fe3O4 was 6-8 wt%, PEI was 1.5-2.0 wt%, pH 9.5, and the mixture was vacuum impregnated at 60℃ for 4 hours, followed by washing with water. Outer layer preparation: Immerse the alkali-activated polyurethane sponge in a 2.0-3.0 wt% PEI solution at pH 10.0 for 4 hours at 60℃, then wash with water; Double-layer combination: After the core surface is coated with sodium alginate and CaCl2 gel, wherein sodium alginate is 2 wt% and CaCl2 is 1 wt%, the outer sponge is wrapped and rolled to shape.

4. A wastewater treatment method, characterized in that, The composite biological packing material according to any one of claims 1 to 3 is used.

5. A wastewater treatment system, characterized in that, The composite biological packing material according to any one of claims 1 to 3 is used, or the wastewater treatment method according to claim 4 is used.

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