Activated sludge-loaded composite material, preparation method and application of activated sludge-loaded composite material in agricultural wastewater treatment

Abstract

The invention relates to the technical field of environmental engineering and agricultural non-point source pollution abatement, and discloses an activated sludge loaded composite material, a preparation method and application of the activated sludge loaded composite material in agricultural wastewater treatment.The composite material is prepared from, by weight, 40-65 parts of activated sludge loaded porous biomass charcoal, 10-30 parts of colloid and 3-12 parts of plant fiber, the porous biomass charcoal is prepared by taking agricultural wastes as raw materials and combining a biological template green pore-forming technology, is sequentially modified by acid and sodium lignin sulfonate, is economical and environment-friendly, and is high in stability of loading activated sludge. Through polymorphic design of the composite material, 'customized 'treatment is realized, and various scenes such as non-point source pollution spreading, fixed bed reactor and emergency treatment are covered, so that in-situ remediation of agricultural wastewater is achieved.

Description

Technical Field

[0001] This invention relates to the fields of environmental engineering and agricultural non-point source pollution control, and in particular to a composite material loaded with activated sludge, its preparation method, and its application in agricultural wastewater treatment. Background Technology

[0002] In the process of agricultural modernization, nitrogen, phosphorus, and other pollutants discharged from farmland runoff have become one of the main causes of eutrophication in water bodies, posing a serious threat to the safety of aquatic ecosystems and human health. Biochar, with its unique porous structure and excellent adsorption properties, has shown great application potential in environmental remediation. However, its inherent defects, such as limited surface functional groups and poor loading stability, severely restrict the practical application effect of biochar in pollutant removal.

[0003] Currently, to improve the pollutant removal capacity of biochar, a common strategy is to combine surface modification with the introduction of microorganisms through activated sludge. For example, biochar is first acid-modified to introduce some active groups on its surface, and then activated sludge is loaded through physical adsorption. However, the density of active functional groups formed by acid modification is limited, making it difficult to form a strong and stable bond with activated sludge. The intermolecular forces that physical adsorption relies on are inherently weak, and activated sludge easily detaches from the surface of biochar when faced with hydraulic shocks or fluctuations in environmental conditions. Summary of the Invention

[0004] To address the aforementioned technical problem of weak bonding between biochar and activated sludge, this invention provides a composite material for loading activated sludge, wherein the biochar-based carrier structure can stably load activated sludge.

[0005] The specific technical solution of the present invention is as follows: a composite material loaded with activated sludge, comprising the following components by weight: 40-65 parts of porous biochar loaded with activated sludge, 10-30 parts of colloid, and 3-12 parts of plant fiber, wherein the porous biochar is sequentially modified by acid and sodium lignosulfonate.

[0006] In the aforementioned composite material, acid modification increases the surface active sites on the porous biochar surface, introduces functional groups, and regulates the surface charge distribution, providing abundant binding sites for subsequent grafting and fixation of sodium lignosulfonate. Then, the porous biochar is modified with sodium lignosulfonate. The sulfonic acid groups in the sodium lignosulfonate molecules can bind with the carboxyl and hydroxyl functional groups on the surface of the biochar through various forces such as hydrogen bonds and ionic bonds, forming a network of sulfonic acid functional groups on the surface of the porous biochar. The sulfonic acid groups can adsorb organic and inorganic matter in the activated sludge, thereby improving the loading stability of the biochar carrier on the activated sludge. In addition, the network structure formed by sodium lignosulfonate can also encapsulate and fix the activated sludge particles to a certain extent, forming a stable complex and preventing them from settling or being lost in the water. The porous biochar loaded with activated sludge described above is combined with plant fibers and colloids. The plant fibers have high mechanical strength and flexibility, which can build a stable physical framework structure in the carrier, providing support for the biochar and colloids and enhancing the strength of the carrier. The colloids enhance the structural toughness and anchor the sludge in the carrier pores, enhancing the chemical and physical bonding force, so that the carrier can stably load activated sludge.

[0007] Optionally, by weight, it may also include 1 to 5 parts of nano-titanium oxide and 0.5 to 3 parts of zeolite.

[0008] In the above technical solution, zeolite and porous biochar form a hierarchical pore complementary structure to fill the pores, and nano-titanium oxide strengthens the interfacial bonding, thereby synergistically improving the compressive strength of the composite material. In addition, the organic matter adsorbed by zeolite undergoes photocatalytic degradation on the surface of nano-titanium oxide, forming an "adsorption-catalysis" cycle, which improves the decontamination ability of the composite material.

[0009] Furthermore, the mass ratio of nano-titanium oxide to zeolite is 1 to 3:1.

[0010] Optionally, the porous biochar is treated with a biotemplate solution and a pore-forming agent before modification.

[0011] In the above technical solution, porous biochar is treated with a biological template solution and a pore-forming agent to construct an ordered pore structure, increase porosity and specific surface area, enabling it to load more activated sludge and adsorb more pollutants.

[0012] Furthermore, the biotemplate solution is an aqueous extract of ginkgo leaves and bamboo leaves; or, the pore-forming agent is ammonium bicarbonate.

[0013] In the above technical solution, the natural active ingredients in ginkgo leaves and bamboo leaves are used as pore nucleation sites to guide the formation of micropore-mesopore multi-level channels by the gases (NH3, CO2) generated by the pyrolysis of ammonium bicarbonate. This overcomes the problem of uneven pore distribution caused by traditional single chemical pore-forming methods, increasing the specific surface area to 500-700 m². 2 / g provides ample space for pollutant adsorption and the colonization of activated sludge for nitrogen and phosphorus removal.

[0014] Optionally, the acid modification process specifically involves immersing porous biochar in an acidic solution for reaction, and then removing and washing it until it is neutral.

[0015] Furthermore, the solid-liquid mass ratio of the porous biochar to the acidic solution is 1:3 to 5.

[0016] Furthermore, the mass fraction of the acidic solution is 50-70%.

[0017] Furthermore, the acidic solution is a nitric acid solution.

[0018] In the above technical solution, nitric acid modification increases the surface active sites on the porous biochar surface, introduces functional groups such as carboxyl and hydroxyl groups, regulates the surface charge distribution, and facilitates the subsequent grafting and fixation of sodium lignosulfonate.

[0019] Optionally, the specific operation of the sodium lignosulfonate modification is as follows: first spray the acid-modified porous biochar with sodium lignosulfonate solution, then spray with tea polyphenol aqueous solution, and repeat the cycle multiple times until the total loading of the two is 8-15% of the mass of the porous biochar.

[0020] In the above technical solution, a dynamic spraying technology is used to construct a sodium lignosulfonate-tea polyphenol crosslinking system loaded onto biochar. This method effectively avoids the aggregation of sodium lignosulfonate while minimizing its loss. The synergistic effect of sodium lignosulfonate and tea polyphenols in the crosslinking system significantly enhances the hydrophilicity of the biochar surface, promoting the spreading and adhesion of denitrification and phosphorus removal activated sludge, increasing the contact area between the two. Furthermore, it provides nutrients and electron donors and forms a stable microenvironment. This multi-dimensional synergistic effect significantly improves the loading capacity and stability of the biochar for denitrification and phosphorus removal activated sludge. In the above text, the total loading capacity refers to the portion of the sodium lignosulfonate solution and tea polyphenol aqueous solution loaded onto the porous biochar. The total loading capacity is calculated as the mass difference between the porous biochar after loading and before loading.

[0021] Furthermore, the sodium lignosulfonate solution has a mass fraction of 5-10%, and the tea polyphenol aqueous solution has a mass fraction of 3-5%.

[0022] Optionally, the activated sludge is nitrogen and phosphorus removal activated sludge; or, the colloid is a chitosan-humic acid composite adhesive; or, the plant fiber is coconut shell fiber.

[0023] In the above technical solutions, the chitosan-humic acid composite adhesive not only has high bonding strength, but also the rich functional groups of both synergistically enhance the adsorption performance of pollutants, broadening the range of pollutant treatment. The biocompatibility of chitosan and the pH buffering and nutrient supply capabilities of humic acid create a friendly microenvironment for microorganisms in activated sludge, maintaining their activity and helping to improve the overall removal efficiency of pollutants. Coconut shell fiber has a natural porous network structure, which can form a multi-level pore network with the mesopores of porous biochar. The macropore structure preferentially adsorbs large molecular pollutants, while the micropores adsorb small molecular substances, forming a "hierarchical adsorption" mechanism, which helps to improve the overall removal efficiency of pollutants.

[0024] Furthermore, in the chitosan-humic acid composite adhesive, the mass ratio of chitosan to humic acid is 2 to 4:1.

[0025] Furthermore, when the porous biochar is ≤50 parts, the chitosan-humic acid composite adhesive is ≥15 parts.

[0026] The second specific technical solution of the present invention is: a method for preparing a composite material supported on activated sludge, comprising the following steps: (1) Mix the porous biochar source with the biotemplate solution, separate the solid and mix it with the pore-forming agent, then pyrolyze and carbonize it to obtain porous biochar. (2) The porous biochar was modified by acid modification and sodium lignosulfonate modification to obtain modified porous biochar. (3) The modified porous biochar was immersed in activated sludge liquid, and after dynamic cultivation, N-acyl homoserine lactone was added and statically activated to obtain porous biochar loaded with activated sludge. (4) Plant fibers are mixed with porous biochar loaded with activated sludge to form a preform, and then the preform is immersed in a colloidal aqueous solution to form a composite material with a three-dimensional network structure of fiber-colloid-biochar filled with activated sludge. The surface of the composite material is sprayed with an additive, which is prepared by dispersing nano-titanium oxide and zeolite in ethanol.

[0027] In the above technical solution, agricultural waste, such as straw, can be used as a porous biochar source. After treatment in steps (1) and (2), the porous biochar has a rich and uniform pore structure, and a sulfonic acid functional group network is formed on its surface, which improves the stability and loading of the loaded activated sludge. Using N-acyl homoserine lactone as a self-inducing agent, the activated sludge quorum sensing system is activated, which promotes the secretion of extracellular polymers (EPS) by the bacterial community, forming a dual fixation system of "biofilm-chemical bond". Then, by constructing a three-dimensional network structure of fiber-colloid-biochar, the anchoring of activated sludge is strengthened and the resistance to water flow impact is improved. Its hierarchical pore structure realizes the adsorption-biodegradation coupling of pollutants of different scales. The internal microenvironment promotes the spatial differentiation of functional bacterial communities in activated sludge, realizing the efficient removal of nitrogen, phosphorus and organic pollutants. N-acyl homoserine lactone is a type of signaling molecule secreted by Gram-negative bacteria.

[0028] Optionally, in step (1), the preparation process of the biotemplate solution is as follows: weigh ginkgo leaf powder and bamboo leaf powder at a mass ratio of 1 to 3:1, mix them, add water and boil, and the liquid obtained after separation is the biotemplate solution; or, the pore-forming agent is ammonium bicarbonate.

[0029] Optionally, in step (1), the specific operation of the pyrolysis carbonization is as follows: under the protection of inert gas, the temperature is raised to 500-800°C at a heating rate of 10-15°C / min, and the temperature is held for 1-3 hours to carry out pyrolysis carbonization. After cooling, porous biochar is obtained.

[0030] Further, in step (1), the porous biochar is sieved to obtain nano-sized porous biochar powder.

[0031] Optionally, in step (2), the acid modification is specifically performed by immersing the porous biochar in an acidic solution for reaction, and then washing it until it is neutral; the sodium lignosulfonate modification is specifically performed by spraying sodium lignosulfonate solution onto the acid-modified porous biochar, and then spraying tea polyphenol aqueous solution, repeating the process multiple times until the total loading of the two is 8-15% of the mass of the porous biochar.

[0032] Optionally, in step (3), the preparation process of the activated sludge liquid is as follows: the activated sludge is mixed with a culture medium containing nitrogen and phosphorus elements, and aerobic and anaerobic culture is carried out alternately. The concentrations of nitrogen and phosphorus elements are increased every once in a while to obtain activated sludge liquid with nitrogen and phosphorus removal.

[0033] Furthermore, the initial concentration of nitrogen in the culture medium is 40-60 mg / L, and the initial concentration of phosphate is 4-6 mg / L. The concentrations of nitrate and phosphate are increased by 20-30% every 70-74 hours until the total nitrogen concentration reaches 200-300 mg / L and the total phosphorus concentration reaches 30-40 mg / L.

[0034] Furthermore, the aerobic and anaerobic alternating culture process is as follows: 3-4 hours of aerobic culture and 1-2 hours of anaerobic culture are alternated, with the dissolved oxygen concentration controlled at 2-4 mg / L for aerobic culture and below 0.2 mg / L for anaerobic culture.

[0035] Optionally, in step (3), the N-acyl homoserine lactone is composed of N-octanoyl-L-homoserine lactone and N-dodecanoyl-L-homoserine lactone in a molar ratio of 2 to 5:1.

[0036] In the above technical solution, sodium lignosulfonate-tea polyphenol crosslinking modification forms a network of sulfonic acid functional groups on the surface of biochar. Combined with the self-inducing agent formed by N-octanoyl-L-homoserine lactone and N-dodecanoyl-L-homoserine lactone, it activates the quorum sensing system of denitrification and phosphorus removal activated sludge, prompting the bacteria to secrete extracellular polymers (EPS) to form a biofilm, thus constructing a dual immobilization system of "chemical bond-biofilm".

[0037] Furthermore, the concentration of the N-acylhomoserine lactone is 0.01–0.02 mg / L.

[0038] Optionally, in step (3), the conditions for dynamic cultivation are: water flow impact conditions with a flow velocity of 0.5±0.2m / s and a hydraulic shear force of 10±5Pa.

[0039] Optionally, in step (3), the static activation specifically refers to static activation at 25-30°C under light-protected conditions for 6-8 hours.

[0040] Optionally, in step (4), the solid content of the additive is 4-8%.

[0041] Optionally, in step (4), the composite material is in the form of powder or granules with a particle size distribution of 2–10 nm and a porosity of 55–65%; or, the composite material is in the form of powder or granules with a diameter of 5–15 mm and a specific surface area of ​​400–550 m². 2 The composite material has a spherical structure with a porosity of 55-65% and a unit pore size of 3-8 mm, a wall thickness of 1.0-1.5 mm, and a bulk density of 0.35-0.55 g / cm³. 3 The composite material has a honeycomb structure; or, the composite material has a sheet-like structure with a thickness of 2-3 mm and a porosity of 50-60%.

[0042] In the above technical solutions, the composite materials have multiple forms such as powder, honeycomb, and sheet to meet the diverse application needs in farmland runoff treatment and achieve "customized" treatment. For example, powder and granular forms are suitable for application in agricultural non-point source pollution control areas, spherical structures are suitable for low-flow-rate rivers or pump station outlets, honeycomb structures are suitable for high-flow-rate, low-concentration farmland runoff treatment systems, and sheet structures are suitable for intermittent farmland runoff treatment with medium to high concentrations of COD (chemical oxygen demand).

[0043] The third specific technical solution of the present invention is: the application of a composite material loaded with activated sludge in the treatment of agricultural wastewater, wherein the composite material loaded with activated sludge is the aforementioned composite material, the agricultural wastewater includes agricultural wastewater containing nitrogen and phosphorus pollutants, and the composite material loaded with activated sludge is placed at the location of the agricultural wastewater to perform in-situ remediation of the agricultural wastewater.

[0044] Compared with the prior art, the present invention has at least the following advantages: (1) Good load-bearing capacity of composite materials: Porous biochar has a rich and uniform pore structure, and a network of sulfonic acid functional groups is formed on its surface. It has high load stability and large load capacity. The porous biochar first loads activated sludge, and then combines with plant fibers and colloids, so that the microorganisms in the activated sludge preferentially occupy the pores on the carbon surface with a high specific surface area, avoiding spatial conflicts in the subsequent composite process. By constructing a three-dimensional network structure of fiber-colloid-biochar, a protective layer is formed on the outer layer of biochar, which further enhances the load stability of activated sludge. (2) High decontamination ability of composite materials: This invention increases the specific surface area to 500-700 m² through bio-template synergistic pore-forming technology. 2 / g, combined with acid modification and sodium lignosulfonate modification to introduce abundant sulfonic acid functional groups and synergistic effect with activated sludge metabolism, the total nitrogen and total phosphorus removal rates within 72h are both ≥80%. (3) Composite materials can maintain microbial activity: This invention uses sodium lignosulfonate-tea polyphenol crosslinking modification and self-inducing agent to activate activated sludge to form a biofilm. The diverse microenvironment formed by the three-dimensional network structure provides good conditions for the formation and function of the biofilm, so that the shedding rate of bacteria at a water flow rate of 0.8-1.0 m / s is ≤5%, and the activity retention rate after 10 dry and wet cycles is ≥85%, which solves the problem of easy biofilm inactivation in traditional technology. (4) The cost of composite materials is low: the compressive strength reaches 6-8 MPa, the porosity is ≥60%, and it can withstand the impact of suspended solids and water quality fluctuations in farmland runoff. The biofilm regeneration cycle is extended to more than 30 days, which greatly reduces maintenance costs. (5) "Customized" treatment can be achieved: Through multi-form design (such as honeycomb structure to adapt to high flow rate, sheet structure to deal with high COD), "customized" treatment can be achieved, covering multiple scenarios such as non-point source pollution application, fixed bed reactor and emergency treatment, with high overall operating efficiency; (6) Green and environmentally friendly: Using agricultural waste (straw, coconut shell) as raw materials, combined with biological template green pore-forming technology to produce porous biochar, it is more economical and environmentally friendly than other adsorption materials. At the same time, most of the materials used are recycled waste resources. The dynamic spraying process controls the loss of sodium lignosulfonate to within 5%, saving 30-50% of reagent usage compared with the traditional impregnation method. Attached Figure Description

[0045] Figure 1 These are scanning electron microscope (SEM) images of the biochar prepared in Examples 1, 1, 2, and 3 of this invention. Figure 2 These are the COD, TN, and TP removal rates of the effluent from Examples 1-2 and Comparative Examples 1-5 of the present invention. Detailed Implementation

[0046] The present invention will now be described through specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Variations and advantages that can be conceived by those skilled in the art without departing from the spirit and scope of the inventive concept are included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0047] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Unless otherwise specified, the raw materials and equipment used in this invention are conventional in the art and can be obtained through conventional commercial means; unless otherwise specified, the methods used in this invention are conventional methods in the art.

[0048] In this invention, sodium lignosulfonate was purchased from Jineng Chemical (Shandong) Co., Ltd.; N-octanoyl-L-homoserine lactone, N-dodecanoyl-L-homoserine lactone and tea polyphenols were all purchased from Shanghai Saikerui Biotechnology Co., Ltd.; chitosan-humic acid composite adhesive was prepared according to existing processes, which will not be described in detail in this invention.

[0049] In this invention, the source of activated sludge is not limited and can be obtained from common sources such as eutrophic lake sediment and municipal sludge, depending on actual needs; zeolite can be natural or artificial zeolite. The focus of this invention is on improving the stability of the combination of activated sludge and biochar, and does not involve the screening of microbial species in the activated sludge. In the following embodiments, the activated sludge is obtained from eutrophic lake sediment.

[0050] The composite material of the present invention can be prepared into finished products of different shapes through a variety of molding processes. The following steps are only illustrative examples. In practical applications, those skilled in the art can adjust and optimize the process parameters such as raw material type, ratio, molding pressure, temperature, and time according to product requirements without departing from the core technical concept of the present invention, or use other molding processes not listed in detail for preparation.

[0051] Example 1: This invention provides a composite material for supporting activated sludge, comprising the following components: 50 parts of porous biochar supported on activated sludge, 20 parts of colloid, 10 parts of plant fiber, 3 parts of nano-titanium oxide, and 3 parts of zeolite. The colloid is a chitosan-humic acid composite adhesive, with a chitosan to humic acid mass ratio of 3:1; the zeolite is natural zeolite; the plant fiber is coconut shell fiber; and the porous biochar source is straw.

[0052] The aforementioned porous biochar is a modified porous biochar that has first been treated with a biological template solution and a pore-forming agent, and then successively modified with acid and sodium lignosulfonate.

[0053] This invention also provides a method for preparing a composite material supported on activated sludge, comprising the following steps: (1) Ginkgo leaves and bamboo leaves were mixed at a mass ratio of 3:1, crushed and passed through a 100-mesh sieve to obtain mixed powder; 70g of mixed powder was weighed, added to 600mL of boiling water and boiled for 1.5h, cooled to room temperature and filtered, and the filtrate was collected as a biological template solution. (2) After washing and removing impurities from rice straw, crush it and pass it through a 100-mesh sieve to obtain straw powder. As a porous biochar source, mix 120g of straw powder with 300mL of biotemplate solution, sonicate for 2h, filter and dry at 60℃. Add 7wt% ammonium bicarbonate pore-forming agent to the dried mixture, stir mechanically for 40min, place it in a tube furnace, heat it to 800℃ at 15℃ / min under nitrogen protection, pyrolyze for 2h, cool and pass it through a 200-mesh sieve to obtain nano-sized porous biochar powder. (3) The nano-sized porous biochar powder was immersed in 70% nitric acid solution with a solid-liquid ratio of 1:5 and ultrasonically treated for 2 hours. After washing with deionized water until neutral, it was dried and then spread flat on a spray conveyor belt. A 10% sodium lignosulfonate solution was sprayed at a spray pressure of 0.4 MPa and a distance of 15 cm. Each spray lasted 25 seconds. Immediately afterward, a 5% tea polyphenol solution was sprayed (spray parameters were the same as before). Ten cycles of spraying were completed. The total load was 15% of the dry weight of the acid-modified porous biochar, and the modified porous biochar was obtained. (4) Modified porous biochar was immersed in activated sludge solution, and the mass ratio of sludge solution to biochar was controlled at 5:1. Under simulated water flow impact conditions with a flow velocity of 0.3 m / s and a hydraulic shear force of 5 Pa, the mixture was dynamically cultured for 24 h to promote the formation of a stable load of nitrogen and phosphorus removal activated sludge. Then, N-acylhomoserine lactone self-inducing agent with a concentration of 0.01 mg / L was added to the biochar system loaded with nitrogen and phosphorus removal activated sludge solution. The mixture was then statically activated at 25 °C under light-proof conditions for 6 h to obtain porous biochar loaded with activated sludge. The N-acylhomoserine lactone was composed of N-octanoyl-L-homoserine lactone and N-dodecanoyl-L-homoserine lactone with a molar ratio of 5:1 at a concentration of 0.01 mg / L. The preparation of activated sludge solution was the same as in Example 1. (5) Mix plant fiber with porous biochar loaded with activated sludge, and cold press it in a mold at 2MPa pressure for 5min to form a porous skeleton. Then, prepare a 15% aqueous solution of colloid and impregnate the porous skeleton for 30min. Cure at 25℃ for 12h. Finally, disperse nano-titanium oxide and natural zeolite in a 5% ethanol solution, atomize and spray it onto the surface of the porous skeleton, and dry and cure at 60℃ to obtain a honeycomb composite material.

[0054] Testing revealed that the composite material unit has a pore size of 5 mm, a wall thickness of 1.2 mm, and a density of 0.55 g / cm³. 3 It has a compressive strength of 6.0 MPa and a porosity of approximately 65%.

[0055] The activated sludge mentioned above is activated sludge that has undergone nitrogen and phosphorus removal treatment. The treatment process is as follows: The activated sludge is taken from the bottom sediment of eutrophic lakes and a sequencing batch reactor (SBR) is used as the enrichment device. The reactor is equipped with microporous aeration discs and a stirrer on the top. The activated sludge is added to a culture medium containing an initial total nitrogen concentration of 40 mg / L and an initial total phosphorus concentration of 4 mg / L. The sludge is cultured in alternating aerobic and anaerobic conditions at 30℃ and 120 rpm. The nitrogen and phosphorus concentrations are increased in stages, by 20% every 72 hours, until the total nitrogen concentration reaches 200 mg / L and the total phosphorus concentration reaches 30 mg / L. Activated sludge liquid with a nitrogen and phosphorus removal rate of ≥70% is selected. The anaerobic alternating culture conditions are as follows: aerobic culture lasts for 3 hours, under aerobic conditions with dissolved oxygen concentration controlled at 2 mg / L; anaerobic culture lasts for 1 hour, under anaerobic conditions with dissolved oxygen concentration controlled below 0.2 mg / L.

[0056] The culture medium was prepared with the following proportions: NH4Cl 100 mg / L, NaNO2 120 mg / L, NaHCO3 1000 mg / L, KH2PO4 20 mg / L, CaCl2·2H2O 5 mg / L, MgSO4·7H2O 300 mg / L, and trace element I and trace element II each 1 mL / L.

[0057] In the trace element composition, the mass concentration of EDTA reaches 10 g / L, provided by trace elements I and II; the mass concentration of FeSO4·7H2O reaches 5 g / L, derived from trace element I; trace element II also includes 0.99 g / L of MnCl2·4H2O, 0.25 g / L of CuSO4·5H2O, 0.19 g / L of NiCl2·6H2O, 0.24 g / L of CoCl2·6H2O, 0.22 g / L of NaMoO4·2H2O, 0.43 g / L of ZnSO4·7H2O, 0.014 g / L of H3BO4, and 0.05 g / L of NaWO4·2H2O.

[0058] It should be noted that the activated sludge denitrification and phosphorus removal method of the present invention is not limited to the above-described method, and other existing denitrification and phosphorus removal methods can also be used for treatment.

[0059] Example 2: This invention provides a composite material for supporting activated sludge, comprising the following components: 65 parts of porous biochar supported on activated sludge, 10 parts of colloid, 12 parts of plant fiber, 5 parts of nano-titanium oxide, and 3 parts of zeolite. The colloid is a chitosan-humic acid composite adhesive, with a chitosan to humic acid mass ratio of 2:1; the zeolite is natural zeolite; the plant fiber is coconut shell fiber; and the porous biochar source is straw. The aforementioned porous biochar is a modified porous biochar that has been treated with a biological template solution and a pore-forming agent, followed by acid modification and sodium lignosulfonate modification.

[0060] This invention also provides a method for preparing a composite material supported on activated sludge, comprising the following steps: (1) Ginkgo leaves and bamboo leaves were mixed at a mass ratio of 3:1, crushed and passed through a 100-mesh sieve to obtain mixed powder; 70g of mixed powder was weighed, added to 600mL of boiling water and boiled for 1.5h, cooled to room temperature and filtered, and the filtrate was collected as a biological template solution. (2) After washing and removing impurities from rice straw, crush it and pass it through a 100-mesh sieve to obtain straw powder. As a porous biochar source, mix 120g of straw powder with 300mL of biotemplate solution, sonicate for 2h, filter and dry at 60℃. Add 7wt% ammonium bicarbonate pore-forming agent to the dried mixture, stir mechanically for 40min, place it in a tube furnace, heat it to 800℃ at 15℃ / min under nitrogen protection, pyrolyze for 2h, cool and pass it through a 200-mesh sieve to obtain nano-sized porous biochar powder. (3) The nano-sized porous biochar powder was immersed in 70% nitric acid solution with a solid-liquid ratio of 1:5 and ultrasonically treated for 2 hours. After washing with deionized water until neutral, it was dried and then spread flat on a spray conveyor belt. A 10% sodium lignosulfonate solution was sprayed at a spray pressure of 0.4 MPa and a distance of 15 cm. Each spray lasted 25 seconds. Immediately afterward, a 5% tea polyphenol solution was sprayed (spray parameters were the same as before). Ten cycles of spraying were completed. The total load was 15% of the dry weight of the acid-modified porous biochar, and the modified porous biochar was obtained. (4) Modified porous biochar was immersed in activated sludge solution, and the mass ratio of sludge solution to biochar was controlled at 8:1. Under simulated water flow impact conditions with a flow velocity of 0.7 m / s and a hydraulic shear force of 15 Pa, the mixture was dynamically cultured for 48 h to promote the formation of a stable load of nitrogen and phosphorus removal activated sludge. Then, N-acylhomoserine lactone self-inducing agent with a concentration of 0.02 mg / L was added to the biochar system loaded with nitrogen and phosphorus removal activated sludge solution. The mixture was then statically activated at 30 °C under light-proof conditions for 8 h to obtain porous biochar loaded with activated sludge. The N-acylhomoserine lactone was composed of N-octanoyl-L-homoserine lactone and N-dodecanoyl-L-homoserine lactone, both with a concentration of 0.02 mg / L, in a molar ratio of 2:1. The preparation of activated sludge solution was the same as in Example 2. (5) Mix plant fiber with porous biochar loaded with activated sludge, and cold press it in a mold at 2MPa pressure for 5min to form a porous skeleton. Then, prepare a 15% aqueous solution of colloid and impregnate the porous skeleton for 30min. Cure at 25℃ for 12h. Finally, disperse nano-titanium oxide and natural zeolite in a 5% ethanol solution, atomize and spray it onto the surface of the porous skeleton, and dry and cure at 60℃ to obtain a honeycomb composite material.

[0061] Testing revealed that the composite material unit has a pore size of 8 mm, a wall thickness of 1.5 mm, and a density of 0.35 g / cm³. 3 It has a compressive strength of 8.0 MPa and a porosity of approximately 60%.

[0062] The activated sludge mentioned above is nitrogen and phosphorus removal treated activated sludge. The treatment process is as follows: The activated sludge is taken from the bottom sediment of eutrophic lakes and enriched using a sequencing batch reactor (SBR) equipped with microporous aeration discs and a stirrer on top. The activated sludge is added to a culture medium containing an initial total nitrogen concentration of 60 mg / L and an initial total phosphorus concentration of 6 mg / L. Alternating aerobic and anaerobic culture is carried out at 32°C and 150 rpm, with nitrogen and phosphorus concentrations gradually increased by 20% every 70 hours until the total nitrogen concentration reaches 300 mg / L and the total phosphorus concentration reaches 40 mg / L. Activated sludge solutions with a nitrogen and phosphorus removal rate ≥70% are selected. The anaerobic alternating culture conditions are: aerobic culture for 4 hours, with dissolved oxygen concentration controlled at 4 mg / L under aerobic conditions; and anaerobic culture for 2 hours, with dissolved oxygen concentration controlled below 0.2 mg / L under anaerobic conditions. The composition of the culture medium is the same as in Example 1, with the content of each component adjusted according to actual conditions.

[0063] Example 3: This invention provides a composite material for supporting activated sludge, comprising the following components: 40 parts of porous biochar supported on activated sludge, 30 parts of colloid, 3 parts of plant fiber, 1.5 parts of nano-titanium oxide, and 0.5 parts of zeolite. The colloid is a chitosan-humic acid composite adhesive, with a chitosan to humic acid mass ratio of 4:1; the zeolite is natural zeolite; the plant fiber is coconut shell fiber; and the porous biochar source is straw.

[0064] The aforementioned porous biochar is a modified porous biochar that has first been treated with a biological template solution and a pore-forming agent, and then successively modified with acid and sodium lignosulfonate.

[0065] This invention provides a method for preparing a composite material supported on activated sludge, using the composite material of Example 3, and includes the following steps: (1) Ginkgo leaves and bamboo leaves were mixed at a mass ratio of 3:1, crushed and passed through a 100-mesh sieve to obtain mixed powder; 70g of mixed powder was weighed, added to 600mL of boiling water and boiled for 1.5h, cooled to room temperature and filtered, and the filtrate was collected as a biological template solution. (2) After washing and removing impurities from rice straw, crush it and pass it through a 100-mesh sieve to obtain straw powder. As a porous biochar source, mix 120g of straw powder with 300mL of biotemplate solution, sonicate for 2h, filter and dry at 60℃. Add 7wt% ammonium bicarbonate pore-forming agent to the dried mixture, stir mechanically for 40min, place it in a tube furnace, heat it to 800℃ at 15℃ / min under nitrogen protection, pyrolyze for 2h, cool and pass it through a 200-mesh sieve to obtain nano-sized porous biochar powder. (3) The nano-sized porous biochar powder was immersed in 70% nitric acid solution with a solid-liquid ratio of 1:5 and ultrasonically treated for 2 hours. After washing with deionized water until neutral, it was dried and then spread flat on a spray conveyor belt. A 10% sodium lignosulfonate solution was sprayed at a spray pressure of 0.4 MPa and a distance of 15 cm. Each spray lasted 25 seconds. Immediately afterward, a 5% tea polyphenol solution was sprayed (spray parameters were the same as before). Ten cycles of spraying were completed. The total load was 15% of the dry weight of the acid-modified porous biochar, and the modified porous biochar was obtained. (4) Modified porous biochar was immersed in activated sludge solution, and the mass ratio of sludge solution to biochar was controlled at 6:1. Under simulated water flow impact conditions with a flow velocity of 0.5 m / s and a hydraulic shear force of 12 Pa, the mixture was dynamically cultured for 36 h to promote the formation of a stable load of nitrogen and phosphorus removal activated sludge. Then, N-acylhomoserine lactone self-inducing agent with a concentration of 0.01 mg / L was added to the biochar system loaded with nitrogen and phosphorus removal activated sludge solution. The mixture was then statically activated at 30 °C under light-proof conditions for 7 h to obtain porous biochar loaded with activated sludge. The N-acylhomoserine lactone was composed of N-octanoyl-L-homoserine lactone and N-dodecanoyl-L-homoserine lactone, both with a concentration of 0.01 mg / L, in a molar ratio of 3:1. The preparation of activated sludge solution was the same as in Example 3. (5) First, mix plant fiber with porous biochar loaded with activated sludge, add binder and water, and stir thoroughly to form a plastic material. Place the material into a special sheet mold and cold press it for 5 minutes at 8MPa on a hydraulic press. Control the thickness of the sheet structure to 2mm. After demolding, immerse the sheet blank in a prepared 15% colloidal aqueous solution for 30 minutes. After taking it out, place it on a flat pallet and cure it for 12 hours in an environment of 25℃ and 70% relative humidity. Finally, disperse nano-titanium oxide and natural zeolite in a 5% ethanol solution, atomize and spray it onto the surface of the sheet blank, and dry and cure it at 60℃ to obtain the sheet composite material.

[0066] Tests showed that the composite material has a thickness of 2 mm and a porosity of approximately 60%.

[0067] The activated sludge mentioned above is activated sludge that has undergone nitrogen and phosphorus removal treatment. The treatment process is as follows: The activated sludge is taken from the bottom sediment of eutrophic lakes and a sequencing batch reactor (SBR) is used as the enrichment device. The reactor is equipped with microporous aeration discs and a stirrer on the top. The activated sludge is added to a culture medium with an initial total nitrogen concentration of 50 mg / L and an initial total phosphorus concentration of 5 mg / L. The sludge is then cultured in alternating aerobic and anaerobic conditions at 31°C and 150 rpm. The nitrogen and phosphorus concentrations are gradually increased by 30% every 74 hours until the total nitrogen concentration reaches 250 mg / L and the total phosphorus concentration reaches 35 mg / L. Activated sludge solutions with nitrogen and phosphorus removal rates ≥70% are selected. The alternating anaerobic culture conditions are the same as in Example 1. The composition of the culture medium is the same as in Example 1, but the content of each component is adjusted according to the actual situation.

[0068] Example 4 This invention provides a composite material for loading activated sludge, using the composite material of Example 1.

[0069] This invention provides a method for preparing a composite material using activated sludge-loaded material, differing from Example 1 in that: plant fibers are mixed with porous biochar loaded with activated sludge, placed in a pulverizer, and pulverized at 12,000 rpm for 30 minutes. The mixture is then sieved through a 200-mesh sieve to obtain a uniform powder. This powder is then poured into a prepared 15% colloidal aqueous solution and mechanically stirred for 1 hour to ensure thorough impregnation. Finally, it is dried and cured at 60°C to obtain a composite material in both powder and particle form. Testing shows that the particle size distribution of this composite material is 2–10 nm, and the porosity is approximately 55%.

[0070] Example 5 This invention provides a composite material for loading activated sludge, using the composite material of Example 1.

[0071] This invention provides a method for preparing a composite material supported on activated sludge, differing from Example 1 in that: plant fibers are mixed with porous biochar supported on activated sludge, 10% binder and appropriate amount of water are added, the moisture content is adjusted to 25%, and the mixture is stirred for 5 minutes to form agglomerated material. This agglomerated material is then granulated into 5mm spherical particles using a centrifugal granulator, and cold-pressed at 2MPa for 5 minutes to form a spherical porous framework. The spherical porous framework is then immersed in a prepared 15% colloidal aqueous solution for 60 minutes and cured at 25℃ for 12 hours. Finally, nano-titanium oxide and natural zeolite are dispersed in a 5% ethanol solution and atomized and sprayed onto the surface of the spherical porous framework. The mixture is then dried and cured at 60℃ to obtain the spherical composite material. Testing shows that the composite material has a diameter of 10mm and a specific surface area of ​​500m². 2 / g, porosity approximately 55%.

[0072] Example 6 This invention provides an application of a composite material loaded with activated sludge in the treatment of agricultural wastewater. The composite materials used in Examples 1-5 are employed. The agricultural wastewater includes agricultural wastewater containing nitrogen and phosphorus pollutants. The composite material loaded with activated sludge is placed at the location of the agricultural wastewater for in-situ remediation. The honeycomb composite material obtained in Examples 1 and 2 is suitable for high-flow, low-concentration farmland runoff treatment systems; the sheet-like composite material obtained in Example 3 is suitable for intermittent farmland runoff treatment with medium to high concentrations of COD; the powder and granular composite material obtained in Example 4 is suitable for application in agricultural non-point source pollution control areas; and the spherical composite material obtained in Example 5 is suitable for low-flow-rate rivers or pump station outlets.

[0073] Comparative Example 1: This comparative example provides a composite material with the same formulation and preparation process as Example 1, except that the porous biochar is porous biochar without activated sludge loading, and it has not been treated with biotemplate solution and pore-forming agent, nor has it undergone acid modification and sodium lignosulfonate modification.

[0074] Comparative Example 2: This comparative example provides a composite material with the same formulation and preparation process as Example 1, except that the porous biochar is porous biochar without activated sludge loading, and it has not been treated with a pore-forming agent, nor has it undergone acid modification or sodium lignosulfonate modification.

[0075] Comparative Example 3: This comparative example provides a composite material with the same formulation and preparation process as Example 1, except that the porous biochar is porous biochar without activated sludge loading and it has not been modified with sodium lignosulfonate.

[0076] Example 4: This comparative example provides a composite material with the same formulation and preparation process as in Example 1, except that the porous biochar is porous biochar without activated sludge loading.

[0077] Comparative Example 5: This comparative example provides a composite material with the same formulation and preparation process as in Example 1, except that N-acyl homoserine lactone self-inducing agent was not added during the process of loading activated sludge with porous biochar.

[0078] Scanning electron microscopy was performed on the composite materials of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. The results are as follows: Figure 1As shown in the figure, a is Comparative Example 7, b is Comparative Example 2, c is Comparative Example 3, and d is Example 1. From the figure, it can be seen that: Comparative Example 1 has a disordered morphology of biochar particles, a relatively smooth surface, and sparse and irregular pores. This is because Comparative Example 1 did not undergo pore-forming or modification treatments, retaining the original structure of the raw material. The lack of developed pores results in a small specific surface area, making it difficult to provide sufficient adsorption sites and attachment space for nitrogen and phosphorus removal activated sludge, leading to poor performance in pollutant removal. Compared to Comparative Example 1, Comparative Example 2 shows some pore structures, indicating that pore-forming treatment has a certain effect, but the pore distribution is uneven, with sparse pores in some areas and irregular shapes in others. Comparative Example 3 has a more complex pore structure, exhibiting a honeycomb-like morphology with a certain degree of pore connectivity, providing loading sites for nitrogen and phosphorus removal activated sludge. Example 1 has a highly developed and uniform multi-level pore structure, with interconnected channels forming a good network, providing an ideal habitat for nitrogen and phosphorus removal activated sludge, allowing it to adhere tightly to the surface and pores of the biochar.

[0079] The specific surface area, porosity, and average pore size of Examples 1-2 and Comparative Examples 1-3 were measured. The specific surface area and pore size distribution of biochar were determined using a specific surface area and porosity analyzer. The biochar was degassed at 100°C and tested using the N2 adsorption-desorption method. The specific surface area was calculated using the BET multi-point method, and the porosity was then measured. The average pore size was calculated using the formula relating total pore volume and specific surface area. The results are shown in Table 1.

[0080] Table 1. Test results of specific surface area, porosity, and average pore size. As can be seen from the table, the specific surface area, porosity, and average pore size of Examples 1 and 2 are all superior to those of Comparative Examples 1-3, which proves that the treatment of porous biochar by the present invention can optimize its structure and improve its loading capacity. The average pore size and specific surface area of ​​Examples 1 and 2 are more than 50% higher than those of Comparative Example 2, which uses traditional single chemical pore-forming technology. This indicates that the porous biochar, which uses biological templates and ammonium bicarbonate to synergistically form pores, will form a microporous-mesoporous multi-level structure, overcoming the problem of uneven pore distribution caused by traditional single chemical pore-forming technology.

[0081] The detergency of the composite materials prepared in Examples 1-2 and Comparative Examples 1-5 was tested, and the specific testing methods are as follows: Using drainage ditch water from a rice-growing area as the influent, the COD concentration was 130 mg / L, TN concentration was 45 mg / L, TP concentration was 6.2 mg / L, pH was 7.5, and the flow rate was 0.6 m / s. The composite materials prepared in Examples 1-2 and Comparative Examples 1-5 were filled into the farmland drainage reactor, and the hydraulic retention time was controlled at 15 min. The system was run continuously for 72 h. After the system had been running stably for 30 days, the water quality indicators were monitored for 10 consecutive days. The water sample was filtered through a 0.45 μm filter membrane, digested at high temperature, and the nitrogen and phosphorus concentrations were measured using a UV spectrophotometer. At the same time, the COD concentration was measured according to HJ 828-2017 "Determination of Chemical Oxygen Demand in Water - Potassium Dichromate Method". The average value of each indicator data was finally taken. The biofilm's pollutant removal efficiency dropped to 70-80% of the initial stable value, or there was obvious shedding and a significant decrease in microbial activity, as the criteria for the need for biofilm regeneration.

[0082] The results are as follows Figure 2 As shown: After 30 days of stable operation, Examples 1-2 showed COD and TP removal rates of ≥80%, TN removal rate of over 75%, and biofilm regeneration cycle of over 30 days, all significantly better than Comparative Examples 1-5, demonstrating the high decontamination capacity of the composite material of the present invention; Comparative Example 1 showed a removal rate of approximately 50%, verifying the limitations of single physical adsorption; Comparative Example 2 showed a removal rate of approximately 60%, indicating that although multi-level pores improve adsorption capacity, the lack of metabolic and chemical action of activated sludge for nitrogen and phosphorus removal results in insufficient long-term effectiveness; Comparative Example 3 showed a removal rate of approximately 65%, indicating that the adsorption performance improvement of acid-modified biochar alone is limited; Comparative Example 4 showed a TN / TP removal rate that decreased by approximately 30% compared to Example 1, indicating that synergistic action with activated sludge for nitrogen and phosphorus removal is required to achieve efficient degradation; Comparative Example 5 showed a removal rate lower than the examples, indicating the key role of the self-inducing agent in biofilm formation and microbial activity in activated sludge for nitrogen and phosphorus removal.

[0083] The specific testing methods for the wastewater treatment capacity of Examples 1-2 and Comparative Example 5 are as follows.

[0084] When determining the detachment of activated sludge, bacterial cultures were first separated using a 75μm sieve. 0.1g of wet biochar was soaked in 10mL of culture medium for 5 minutes. This culture medium was the same as that used in Example 1 for culturing activated sludge. The mixture was ultrasonically bathed for 10 minutes and vortexed twice for 3 minutes each time. Cells were extracted, and 0.1mL of bacterial solution was taken from the culture medium, continuously diluted 10 times, and spread on a plate. After incubation at 30℃ for 48 hours, individual colonies on the plate were counted. Finally, the plate count results were displayed as the number of cells per gram of wet biochar. The samples were then placed in a 0.8-1.0 m / s simulated water flow device and run for 24 hours. The cell extraction and counting steps were repeated, and the shedding rate was calculated. When determining the biofilm activity retention rate, the samples were subjected to 10 wet-dry cycles (soaking for 2 hours each time and drying at 30°C to constant weight). The final enzyme activity A1 was then measured, and the activity retention rate was calculated according to the formula. The initial enzyme activity and the final enzyme activity were then detected using a cell acid phosphatase (ACP) activity assay kit and a nitrate reductase (NR) activity assay kit to calculate the enzyme activity enhancement rate. The results are shown in Table 2.

[0085] Table 2. Wastewater Treatment Capacity Test Results Group sludge removal rate Biomembrane activity retention rate nitrate reductase activity enhancement rate phosphatase activity enhancement rate Example 1 ≤5％ ≥85％ 37.68％ 43.25％ Example 2 ≤5％ ≥88％ 38.24％ 44.71％ Comparative Example 5 15-20％ ≤60％ 13.50％ 11.21％ Table 2 shows that in Examples 1-2, the sludge shedding rate was ≤5% at a water flow rate of 0.8–1.0 m / s, and the activity retention rate was ≥85% after 10 wet-dry cycles, significantly better than Comparative Example 5, demonstrating strong resistance to environmental fluctuations. The nitrate reductase and phosphatase activities in Examples 1-2 were increased by 35±5% and 40±5% respectively compared to Comparative Example 5. This is because the sodium lignosulfonate-tea polyphenol cross-linking modification formed a sulfonic acid functional group network on the surface of porous biochar, which, combined with self-inducing agents, promoted biofilm formation, constructing a dual immobilization system of "chemical bonds-biofilm".

[0086] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A composite material supported on activated sludge, characterized in that, By weight, it comprises the following components: 40-65 parts of porous biochar loaded with activated sludge, 10-30 parts of colloid, and 3-12 parts of plant fiber, wherein the porous biochar is successively modified by acid and sodium lignosulfonate.

2. The composite material for supporting activated sludge according to claim 1, characterized in that, Before modification, the porous biochar is treated with a biotemplate solution and a pore-forming agent. The preparation process of the biotemplate solution is as follows: ginkgo leaf powder and bamboo leaf powder are weighed at a mass ratio of 1 to 3:1, mixed, added to water and boiled, and the liquid obtained after separation is the biotemplate solution; the pore-forming agent is ammonium bicarbonate.

3. The composite material for supporting activated sludge according to claim 1, characterized in that, The specific operation of acid modification is as follows: the porous biochar is immersed in an acidic solution for reaction, and then taken out and washed until neutral; or, the specific operation of sodium lignosulfonate modification is as follows: the sodium lignosulfonate solution is sprayed onto the acid-modified porous biochar first, and then the tea polyphenol aqueous solution is sprayed on, and the cycle is repeated multiple times until the total loading of the two is 8 to 15% of the mass of the porous biochar.

4. The composite material for supporting activated sludge according to claim 1, characterized in that, The sludge may also include 1 to 5 parts by weight of nano-titanium oxide and 0.5 to 3 parts by weight of zeolite; or, the activated sludge may be activated sludge for denitrification and phosphorus removal; or, the colloid may be chitosan-humic acid composite adhesive; or, the plant fiber may be coconut shell fiber.

5. A method for preparing a composite material supported on activated sludge, characterized in that, Includes the following steps: (1) Mix the porous biochar source with the biotemplate solution, separate the solid and mix it with the pore-forming agent, then pyrolyze and carbonize it to obtain porous biochar. (2) The porous biochar was modified by acid modification and sodium lignosulfonate modification to obtain modified porous biochar. (3) The modified porous biochar was immersed in activated sludge liquid, and after dynamic cultivation, N-acyl homoserine lactone was added and statically activated to obtain porous biochar loaded with activated sludge. (4) Plant fibers are mixed with porous biochar loaded with activated sludge to form a preform, and then the preform is immersed in a colloidal aqueous solution to form a composite material with a three-dimensional network structure of fiber-colloid-biochar filled with activated sludge. The surface of the composite material is sprayed with an additive, which is prepared by dispersing nano-titanium oxide and zeolite in ethanol.

6. The method for preparing a composite material supported on activated sludge according to claim 5, characterized in that, In step (2), the acid modification is specifically performed by immersing the porous biochar in an acidic solution for reaction, and then washing it until it is neutral. The sodium lignosulfonate modification is specifically performed by spraying sodium lignosulfonate solution onto the acid-modified porous biochar, followed by spraying tea polyphenol aqueous solution, repeating the process multiple times until the total loading of both is 8-15% of the mass of the porous biochar.

7. The method for preparing a composite material supported on activated sludge according to claim 5, characterized in that, In step (3), the preparation process of the activated sludge liquid is as follows: the activated sludge is mixed with a culture medium containing nitrogen and phosphorus elements, and aerobic and anaerobic culture is carried out alternately. The concentrations of nitrogen and phosphorus elements are increased every once in a while to obtain activated sludge liquid with nitrogen and phosphorus removal.

8. The method for preparing a composite material supported on activated sludge according to claim 5, characterized in that, In step (3), the N-acyl homoserine lactone is composed of N-octanoyl-L-homoserine lactone and N-dodecanoyl-L-homoserine lactone in a molar ratio of 2 to 5:

1.

9. A method for preparing a composite material supported on activated sludge according to any one of claims 5 to 8, characterized in that, In step (4), the composite material is in the form of powder and granules with a particle size distribution of 2-10 nm and a porosity of 55-65%; or, the composite material is in the form of powder and granules with a diameter of 5-15 mm and a specific surface area of ​​400-550 m². 2 The composite material has a spherical structure with a porosity of 55-65% and a unit pore size of 3-8 mm, a wall thickness of 1.0-1.5 mm, and a bulk density of 0.35-0.55 g / cm³. 3 The composite material has a honeycomb structure; or, the composite material has a sheet-like structure with a thickness of 2-3 mm and a porosity of 50-60%.

10. The application of a composite material loaded with activated sludge in the treatment of agricultural wastewater, wherein the composite material loaded with activated sludge is the composite material according to any one of claims 1-4, characterized in that, The agricultural wastewater includes agricultural wastewater containing nitrogen and phosphorus pollutants. The composite material loaded with activated sludge is placed at the location of the agricultural wastewater to perform in-situ remediation of the agricultural wastewater.

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