A composite biofilm carrier and preparation and application thereof

Abstract

The application belongs to the technical field of water pollution control, and discloses a composite biofilm carrier and preparation and application thereof, and particularly relates to preparation of the composite biofilm carrier based on a sulfur-iron circulation mechanism and a simultaneous nitrogen and phosphorus removal method thereof. In the composite biofilm carrier: one is paraffin-sulfur-acetate starch which provides a multi-electron donor for denitrification, and the other is paraffin-sulfur-FeCl3 which controls iron release to realize stable phosphorus removal while ensuring that the total iron concentration of effluent keeps at a low level. The two composite biofilm carriers with porous core-shell structures take paraffin and sulfur powder as the outer "shell", take paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 as the inner "core" respectively, are prepared through multi-step melting-cooling circulation and core-shell-porous coordination design, and are coupled for simultaneous nitrogen and phosphorus removal of low carbon / nitrogen ratio wastewater. Coupling application of the two composite biofilm carriers drives continuous sulfur-iron circulation, and excellent long-term simultaneous nitrogen and phosphorus removal performance is exhibited.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water pollution control, and relates to a composite biofilm carrier and preparation and application thereof, in particular to preparation of a composite biofilm carrier based on a sulfur-iron cycle mechanism and a simultaneous nitrogen and phosphorus removal method. TECHNICAL BACKGROUND

[0002] Nitrogen and phosphorus are the main nutrients leading to eutrophication of aquatic environments, and the deep removal of these nutrients in wastewater treatment has become a global challenge. Especially for the secondary wastewater with low carbon / nitrogen ratio, the lack of carbon source greatly limits the effective removal of nitrogen and phosphorus. In recent years, autotrophic denitrification process has attracted much attention due to its advantages such as no need for external carbon source, low sludge production, environmental friendliness, and low operation cost. Both sulfur and iron can be used as electron donors to promote autotrophic denitrification. In addition, iron ions can also effectively remove phosphate. Therefore, natural iron ore including pyrite and greigite has been used as a biofilm carrier in a biological filter system for simultaneous removal of autotrophic denitrification and phosphorus. However, compared with sulfur autotrophic denitrification processes driven by sulfide, elemental sulfur and thiosulfate as electron donors, the nitrogen removal rate is relatively slow and unstable when these natural iron ores are used as biofilm carriers. In order to improve the nitrogen removal rate, solid sulfur and natural iron ore are used together in the nitrogen and phosphorus removal system. However, the poor solubility of solid sulfur and natural iron ore limits the mass transfer between the substances, resulting in that the nitrogen and phosphorus removal reactions mainly occur at the solid-solid or solid-liquid interface, which greatly reduces the heterogeneous reaction rate. In addition, due to the differences in size, shape and density between solid sulfur and natural iron ore, the biofilm carrier distribution and stratification phenomenon may occur after backwashing of these biological reactors, which affects the effluent water quality. Moreover, the impurities contained in the natural iron ore may leach into water, which may cause the risk of secondary pollution, which is also a problem that needs to be concerned.

[0003] At the same time, the presence of appropriate amount of organic carbon in the sulfur-iron simultaneous nitrogen and phosphorus removal system is considered to not only accelerate the start-up of the sulfur autotrophic denitrification system and reduce the production of sulfate, but also promote the sulfur and iron cycle. Organic carbon can be used as an electron donor for the biological reduction of iron and sulfate. Therefore, some studies have added liquid or solid organic carbon source to enhance the performance of the sulfur autotrophic denitrification system, but this increases the complexity of operation and the potential risk of secondary pollution. Slow-release technology is considered as a green technology that can achieve long-term, continuous and controllable release of substances. However, when sulfur is used as a binder of slow-release materials, its dense structure will hinder the release of active components.

[0004] Therefore, it is urgent to develop a more efficient and practical composite biofilm carrier based on sulfur-iron cycle mechanism and a method for simultaneous removal of nitrogen and phosphorus, so as to solve the problems of high production of sulfate, uncontrollable release of iron, introduction of natural iron ore impurities and stratification caused by the difference in characteristics of the biofilm carrier in the current sulfur-iron denitrification and phosphorus removal system, thereby realizing efficient and simultaneous removal of nitrogen and phosphorus in low carbon / nitrogen ratio water. SUMMARY

[0005] To overcome the above technical problems, the present application provides a preparation of a composite biofilm carrier based on a sulfur-iron cycle mechanism and a method for simultaneous removal of nitrogen and phosphorus, thereby realizing water purification. Paraffin and sulfur are used as the outer "shell", paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 are used as the inner "core", and a porous core-shell structure of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 composite biofilm carriers are prepared by using multi-step melting-cooling cycles and core-shell-porous collaborative design. The two kinds of composite biofilm carriers prepared by multi-step melting-cooling cycles and core-shell-porous collaborative design improve the dispersibility and interfacial combination of the active components of paraffin, sulfur, acetate starch and FeCl3, improve the stability of the carrier, realize the controllable release of the active components, and at the same time increase the specific surface area of the carrier, which shows high efficiency, stability and potential for long-term use in simultaneous removal of nitrogen and phosphorus. Paraffin-sulfur-acetate starch can provide multi-electron donors including sulfur, paraffin and acetate starch for mixed nutrient denitrification. Paraffin-sulfur-FeCl3 can realize the controllable release of iron to realize the stable removal of phosphorus while ensuring a low iron concentration in the water body. The coupling of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 can drive continuous sulfur-iron cycle to realize efficient and long-term simultaneous removal of nitrogen and phosphorus in low carbon / nitrogen ratio water.

[0006] An application of the composite biofilm carrier in simultaneous removal of nitrogen and phosphorus in water, wherein the composite biofilm carrier is added to the water to be treated to simultaneously remove nitrogen and phosphorus in the water.

[0007] The composite biofilm carrier is paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3.

[0008] In some preferred embodiments, the composite biofilm carrier is paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3; preferably, the volume ratio of paraffin-sulfur-acetate starch to paraffin-sulfur-FeCl3 is 0.5-2.

[0009] In some preferred embodiments, paraffin-sulfur-acetate starch and paraffin-sulfur-FeC13 are added to the reactor, and the reactor filling ratio is 10%-80%; for example, 10%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 40%, 50%, 60%, 70%, 80%.

[0010] In some preferred embodiments, the nitrogen is present in the form selected from any one or a combination of at least two of: NO3 - -N, NO2 - -N, NH4 + -N;

[0011] The phosphorus is present in the form of PO4 3- -P.

[0012] In some preferred embodiments, the paraffin-degrading bacteria, heterotrophic denitrifying bacteria and sulfur autotrophic denitrifying bacteria need to be inoculated into the reaction system.

[0013] In a second aspect, the present application provides a composite biofilm carrier as described above, wherein the composite biofilm carrier is a core-shell structure, and the core-shell structure is composed of a core structure and a shell structure.

[0014] The material of the shell structure is selected from paraffin and sulfur.

[0015] The material of the core structure is selected from paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3.

[0016] In some preferred embodiments, the core of the core-shell structure is a porous structure with a pore size of 400-800 μm.

[0017] Preferably, the particle size of the core-shell structure is 15-20 mm, and the thickness of the shell structure is 2-5 mm.

[0018] In some preferred embodiments, the composite biofilm carrier is a porous core-shell structure paraffin-sulfur-acetate starch composite biofilm carrier and a paraffin-sulfur-FeCl3 composite biofilm carrier.

[0019] Preferably, in the paraffin-sulfur-acetate starch composite biofilm carrier, the material of the shell structure is paraffin and sulfur, and the material of the core structure is paraffin-sulfur-acetate starch.

[0020] Preferably, in the paraffin-sulfur-FeCl3 composite biofilm carrier, the material of the shell structure is paraffin and sulfur, and the material of the core structure is paraffin-sulfur-FeCl3.

[0021] In some preferred embodiments, the paraffin-sulfur-acetate starch provides a multi-electron donor to achieve mixed nutrient denitrification, and the paraffin-sulfur-FeCl3 controls the release of iron in the process of phosphorus removal, ensuring a low concentration of iron in the water body while achieving phosphorus removal.

[0022] In some preferred embodiments, the paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 coupling drives the redox cycle of sulfur species and iron species by biological and non-biological factors, achieving efficient simultaneous removal of nitrogen and phosphorus in low carbon / nitrogen ratio water bodies.

[0023] In a third aspect, the present application provides a preparation method of the composite biofilm carrier, comprising the following steps:

[0024] 1) mixing paraffin and sulfur, heating and melting to obtain a mixed melt of paraffin and sulfur, adding acetate starch or FeCl3 to the melt of paraffin and sulfur, stirring uniformly, and cooling to obtain a core structure of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3;

[0025] 2) heating and melting the core structure obtained in step 1) once to obtain a melt of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3, adding activated carbon powder to the melt, stirring uniformly, and cooling to obtain a core structure of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 again;

[0026] 3) heating and melting the core structure of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 obtained in step 2) twice, adding a volatile solvent during the cooling process of the two melts, and stirring while maintaining the molten state;

[0027] 4) stirring and slowly volatilizing the volatile solvent during the cooling process to form a porous structure in the core material paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3;

[0028] 5) quickly injecting the molten core structure material into a pre-cooled mold to obtain a porous core structure of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3;

[0029] 6) placing the porous core structure material obtained in step 5) into an oven for low-temperature drying to completely remove residual volatile solvent;

[0030] 7) mixing and heating the shell layer material paraffin and sulfur, and stirring to obtain a melt of the shell layer material;

[0031] 8) quickly dipping the porous core structure material obtained in step 6) into the melt of the shell layer material obtained in step 7) to take out a layer of the melt of the shell layer material, and cooling to obtain a composite biofilm carrier with a core-shell porous structure.

[0032] In some preferred embodiments, the volatile solvent is selected from ethanol, preferably 5-10 wt% ethanol; more preferably, 5-10 wt% ethanol is added when the melt is cooled to 70-80°C, and the mixture is stirred at a speed of 200-600 rpm to ensure uniform dispersion, and the melt is quickly injected into a mold for molding when it is cooled to 60-70°C.

[0033] Preferably, the heating and melting temperature in steps 1), 2), 3), and 7) is 80–150°C;

[0034] Preferably, in step 3), a volatile solvent is added when the molten core structure material is cooled to 70-80°C, and the material is rapidly molded when cooled to 60-70°C.

[0035] Preferably, the temperature of the molten core structure material in step 5) is controlled at 60–70°C;

[0036] Preferably, in step 5), the mold is pre-cooled to 0-10°C;

[0037] Preferably, the temperature of the oven for low-temperature drying in step 6) is 30–40°C;

[0038] Preferably, steps 1), 2), and 8) involve cooling to 20–30°C;

[0039] Preferably, the mold in step 5) is spherical; more preferably, the diameter of the sphere is 15-20 mm.

[0040] Preferably, in steps 1) and 2), the materials of the core structure are mixed and stirred at a speed of 600-1000 rpm for 10-30 minutes to achieve uniform dispersion;

[0041] Preferably, in steps 3) and 4), the stirring after adding the volatile solvent is carried out at a speed of 200-600 rpm to ensure uniform dispersion.

[0042] Preferably, in step 7), the shell structure material is mixed and stirred at 600-1000 rpm for 10-30 minutes to achieve uniform dispersion;

[0043] In some more preferred embodiments, the preparation method of the composite biofilm carrier includes the following steps: preparation of porous core-shell structured paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 composite biofilm carriers: paraffin and sulfur powder are mixed at a mass ratio of 0.3 to 3 and heated to 80 to 150°C, stirred at 600 to 1000 rpm for 10 to 30 minutes to ensure uniform mixing of paraffin and sulfur powder; acetate starch or FeCl3 is added to the uniformly mixed molten mixture of paraffin and sulfur, and stirring is continued at 600 to 1000 rpm for 10 to 30 minutes to ensure uniform mixing of paraffin and sulfur powder. Powder, acetate starch, paraffin, sulfur powder, and FeCl3 are mixed evenly and cooled to 20–30°C to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures. The obtained paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures are then heated again to 80–150°C to obtain two molten mixtures. Activated carbon powder is added to each molten mixture, and the mixture is stirred at 600–1000 rpm for 10–30 minutes to ensure uniform mixing. The mixtures are then cooled to 20–30°C again to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures. Cl3 core structure; the obtained paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 core structures were heated to 80-150℃ and cooled to 70-80℃ respectively. Then, 5-10 wt% ethanol (volatile solvent) was added to each of the two molten mixtures while stirring at 200-600 rpm to ensure uniform dispersion of the ethanol. While adding ethanol (volatile solvent) and stirring, the two molten mixtures were cooled to 60-70℃. The two molten mixtures were then rapidly poured into a mold pre-cooled to 0-10℃ to obtain porous core structures of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3. l3; The obtained porous core structure material was placed in an oven and dried at a low temperature of 30-40℃ to completely remove residual volatile solvents; the shell structure material paraffin and sulfur were mixed at a mass ratio of 0.3-3 and heated, and stirred at a speed of 600-1000 rpm for 10-30 min to obtain a uniformly mixed shell material melt; the core structure paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3, which had been completely de-ethanolified, were quickly dipped into a layer of the shell material melt and taken out, and cooled to 20-30℃ to obtain a core-shell porous composite biofilm carrier paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3.

[0044] In some preferred embodiments, the method for simultaneous nitrogen and phosphorus removal using a composite biofilm carrier comprises the following steps:

[0045] I) Water body to be treated:

[0046] The water body to be treated is either an actual polluted water body with a low carbon / nitrogen ratio or a laboratory-simulated wastewater, with the simulated wastewater containing NO3. --N, NH4 +- N and PO4 3- It is configured with -P, etc., without adding or adding a small amount of carbon source.

[0047] II) Inoculating the reaction system with microorganisms:

[0048] II-I) Enrichment of heterotrophic and sulfur-autotrophic denitrifying bacteria: heterotrophic and sulfur-autotrophic denitrifying bacteria were enriched using anaerobic sludge in heterotrophic and sulfur-autotrophic denitrifying bacteria enrichment cultures.

[0049] II-II) Biofilm attachment on the surface of the biofilm carrier: The paraffin-sulfur-acetic acid starch composite biofilm carrier was placed in a container, and paraffin-degrading bacteria solution, enriched heterotrophic denitrifying bacteria, sulfur autotrophic denitrifying bacteria and experimental water were added. The anaerobic environment was maintained by nitrogen blowing and sealing. The biofilm attachment system was then placed in a constant temperature shaking incubator for cultivation.

[0050] The paraffin-degrading bacteria play two roles in the system: first, they decompose paraffin in the shell structure, with biological action synergistically regulating the release of active components; second, the small-molecule organic matter produced from paraffin decomposition serves as an organic carbon source (electron donor) to support the heterotrophic denitrification process. The heterotrophic denitrifying bacteria utilize the small-molecule organic matter produced from the decomposition of acetate starch and paraffin as a carbon source for heterotrophic denitrification. The sulfur-autotrophic denitrifying bacteria utilize the sulfur released from the composite biofilm carrier as an electron donor for sulfur-autotrophic denitrification. Furthermore, the acetate starch and the small-molecule organic matter produced from paraffin decomposition can promote the redox cycle of sulfur and iron in the system, thereby promoting heterotrophic-autotrophic mixed nutrient denitrification.

[0051] The experimental water was prepared by adding carbon, nitrogen and phosphorus sources to deionized water. After several days of cultivation, the addition of carbon sources to the experimental water was stopped to simulate a low carbon / nitrogen ratio environment.

[0052] III) Coupled simultaneous nitrogen and phosphorus removal using composite biofilm carriers: Paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 biofilm carriers with a volume ratio of 0.5-2 were added to the reactor, with a filling ratio of 5-15%. Simulated water was added, and nitrogen blowing was used to maintain an anaerobic environment. Samples were taken at regular intervals, filtered through the membrane, and NO3 was measured. - -N, NO2 - -N, NH4 + -N,PO4 3- Water quality indicators such as -P and Fe concentrations are high, when NO3... - When NO3- is completely removed, replace the simulated water. The simulated water should have no external carbon source added or only a small amount added, and should be supplied with NO3-. - -N, NH4 +-N and PO4 3- It is configured with -P, etc.

[0053] In the above-mentioned denitrification and phosphorus removal process, ① a porous core-shell structured paraffin-sulfur-acetic acid starch composite biofilm carrier can provide multiple electron donors for the denitrification process, achieving nitrogen removal through mixed nutrient denitrification. ② A porous core-shell structured paraffin-sulfur-FeCl3 composite biofilm carrier can regulate iron release, ensuring a low iron concentration in the water while achieving phosphorus removal. ③ A porous core-shell structured paraffin-sulfur-acetic acid starch coupled with paraffin-sulfur-FeCl3 is used for simultaneous denitrification and phosphorus removal: paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 are added to the reactor in different volume ratios. This coupled application in the reactor can drive a continuous sulfur-iron cycle, achieving simultaneous denitrification and phosphorus removal in water with a low carbon / nitrogen ratio.

[0054] The beneficial effects of this invention are at least as follows:

[0055] (1) Two composite biofilm carriers prepared through multi-step melt-cooling cycles and core-shell-porous synergistic design improved the dispersibility and interfacial bonding of active components such as paraffin, sulfur, acetate starch, and FeCl3, enhanced the stability of the carriers, and enabled the controlled release of active components. Simultaneously, the specific surface area of ​​the carriers was increased by 20-50%. These carriers demonstrated high efficiency, stability, and long-term application potential in the simultaneous denitrification and phosphorus removal process in low C / N ratio water bodies without the addition of any external substances. The coupled application of the two composite biofilm carriers was effective for 90-180 days, and the combined application of the two composite biofilm carriers could remove 95-99% of NO3. - -N, TN and PO4 3- -P, the effluent Fe concentration remains stable in a low range of 0-0.5 mg / L. Furthermore, with a low composite biofilm carrier loading ratio (e.g., 5-15%), and influent total nitrogen and total phosphorus loadings of 20-25 mg / L and 1-2 mg / L respectively, nitrogen and phosphorus removal rates can reach 20-30 mg·L⁻¹. -1 ·d -1 and 3.5-4 mg·L -1 ·d -1 .

[0056] (2) Paraffin and sulfur, as the outer "shell" of the composite biofilm carrier, can not only effectively regulate the release of active components such as acetate starch and FeCl3 through non-biological means, but also, in the process of decomposing paraffin, paraffin-degrading bacteria can further regulate the release of these substances through their biological action.

[0057] (3) The paraffin-sulfur-acetic acid starch composite biofilm carrier can simultaneously provide paraffin, sulfur and acetate starch as multiple electron donors, which can efficiently support the denitrification process of mixed nutrients in water bodies with low carbon / nitrogen ratio.

[0058] The paraffin-sulfur-FeCl3 composite biofilm carrier can control iron release, thus achieving stable phosphorus removal while maintaining iron concentration in the effluent at a low level (0-0.5 mg / L). Meanwhile, mixed-nutrient denitrification overcomes to some extent the problems of slow start-up and high sulfate production in pure sulfur autotrophic denitrification, as well as the disadvantages of pure heterotrophic denitrification requiring continuous external carbon source replenishment and high sludge production. Furthermore, the water treatment process described in this application has a fast start-up time, does not require additional carbon source addition, and produces low SO4 levels in the effluent. 2- By controlling the concentration within the lower range of 50-80 mg / L, sludge production was reduced by 50-70%.

[0059] (4) The coupled use of two biofilm carriers, paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3, drives a continuous sulfur-iron cycle. Under the action of sulfur-autotrophic denitrifying microorganisms, reduced sulfur is oxidized to SO4. 2- Organic carbon, acting as an electron donor, bioreduces SO4. 2- and Fe 3+ Generate S 2- and Fe 2+ The generated S 2- and Fe 2+ It can act as an electron donor to further drive denitrification. Furthermore, Fe... 3+ and S 2- Fe is generated through non-biological reactions. 2+ and S 0 The processes facilitate mutual redox cycles, which promote the transformation of sulfur and iron species, thereby enhancing the sulfur and iron cycle. The active sulfur and iron cycle formed after the coupling of the two biofilm carriers promotes S… 0 / S 2- / S n 2- Driven by sulfur autotrophic denitrification, Fe 2+ Iron-driven autotrophic denitrification, heterotrophic denitrification driven by small-molecule organic matter from the degradation of acetate starch and paraffin, and Fe 2+ / Fe 3+ The driven iron-ammonia oxidation process together achieves nitrogen removal. PO4 3- -P is mainly released via Fe from a paraffin-sulfur-FeCl3 composite biofilm carrier. 3+The combined structure forms a precipitate for removal. Furthermore, when these two composite biofilm carriers of the same shape and size are coupled and applied to a packed bed bioreactor, stratification of the biofilm carrier after backwashing can be effectively avoided, ensuring the stability of nitrogen and phosphorus removal efficiency. Attached image description:

[0060] Figure 1 This is a photograph of the biofilm carrier prepared in the examples;

[0061] Figure 2 It is NO3 during the 15-day sequential batch experiment in Example 4. - -N and NO2 - -N concentration variation graph;

[0062] Figure 3 In the 15-day batch experiment of Example 4, NH4 + -N concentration variation graph;

[0063] Figure 4 It is NO3 during the 15-day sequential batch experiment in Example 4. - -N and TN removal rate variation graph;

[0064] Figure 5 This refers to PO4 during the 15-day batch experiment in Example 4. 3- -P concentration and PO4 3- -P removal rate variation graph;

[0065] Figure 6 This is a graph showing the change in Fe concentration during the 15-day sequencing batch experiment in Example 4;

[0066] Figure 7 It is NO3 during the 15-day sequential batch experiment in Example 4. - -N removal rate variation graph;

[0067] Figure 8 This refers to PO4 during the 15-day batch experiment in Example 4. 3- -P removal rate variation graph;

[0068] Figure 9 This diagram illustrates the process by which two composite biomembrane carriers couple to promote the sulfur and iron cycle. Detailed implementation method:

[0069] A method for preparing a composite biofilm carrier includes a method for preparing a porous core-shell structured paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3: paraffin and sulfur powder in different mass ratios are added as the outer "shell" of the composite biofilm carrier, and paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 are respectively used as the inner "core" of the composite biofilm carrier. The two carriers, paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3, are prepared through a multi-step melt-cooling cycle and a core-shell-porous synergistic design.

[0070] (1) Mix paraffin wax and sulfur powder at a mass ratio of 0.3 to 3 and heat to 80 to 150°C. Stir at 600 to 1000 rpm for 10 to 30 minutes to ensure that the paraffin wax and sulfur powder are mixed evenly.

[0071] (2) Add acetate starch or FeCl3 to the molten mixture of paraffin and sulfur, and continue stirring at 600-1000 rpm for 10-30 min to ensure that the paraffin, sulfur powder, acetate starch and paraffin, sulfur powder and FeCl3 are mixed evenly. Cool to 20-30℃ to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures.

[0072] (3) The obtained paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures were heated to 80-150℃ to obtain two molten mixtures. Activated carbon powder was added to the two molten mixtures respectively, and the mixtures were stirred at 600-1000 rpm for 10-30 min to ensure that the two molten mixtures and activated carbon powder were mixed evenly. The mixtures were cooled to 20-30℃ to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures again.

[0073] (4) The obtained paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures were heated to 80-150°C and cooled to 70-80°C. Then, 5-10 wt% ethanol (volatile solvent) was added to the two molten mixtures and stirred at 200-600 rpm to ensure uniform dispersion of ethanol.

[0074] (5) While adding ethanol (volatile solvent), stir until the two molten mixtures are cooled to 60-70°C. Then, quickly pour the two molten mixtures into a mold that has been pre-cooled to 0-10°C to obtain porous core structure paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3.

[0075] (6) The obtained porous core structure material is placed in an oven and dried at a low temperature of 30-40°C to completely remove residual volatile solvents;

[0076] (7) Mix the shell structure material paraffin and sulfur at a mass ratio of 0.3 to 3 and heat them. Stir at a speed of 600 to 1000 rpm for 10 to 30 minutes to obtain a uniformly mixed shell material molten liquid.

[0077] (8) The core structure paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3, which have been completely de-ethanolified, are quickly dipped into a layer of shell material molten liquid and taken out, and cooled to 20-30℃ to obtain the core-shell porous composite biofilm carrier paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3.

[0078] The method for simultaneous nitrogen and phosphorus removal using a composite biofilm carrier involves the following steps: adding the composite biofilm carrier to the water body to be treated to simultaneously remove nitrogen and phosphorus.

[0079] In some specific implementation schemes, the method of simultaneous nitrogen and phosphorus removal using composite biofilm carriers involves the following steps:

[0080] I) Water body to be treated:

[0081] The water to be treated is either an actual polluted water body with a low carbon / nitrogen ratio or a laboratory simulated water sample, for example, a carbon / nitrogen ratio of 0 to 4; the simulated water sample does not have any external carbon source added or has only a small amount added, and is produced by NO3. - -N, NH4 + -N and PO4 3- It is configured with -P, etc.

[0082] For example, the simulated water solution is prepared from KNO3, NH4Cl, KH2PO4, etc., with the specific composition being: NO3 - -N = 20 mg / L, NH4 + -N=5mg / L,PO4 3- -P=2mg / L, COD=0~100mg / L.

[0083] The term "carbon / nitrogen ratio" refers to the ratio of the total carbon content to the total nitrogen content in organic matter.

[0084] II) Inoculating the reaction system with microorganisms:

[0085] II-I) Enrichment of heterotrophic and sulfur-autotrophic denitrifying bacteria: heterotrophic and sulfur-autotrophic denitrifying bacteria were enriched using anaerobic sludge in heterotrophic and sulfur-autotrophic denitrifying bacteria enrichment cultures.

[0086] II-II) Biofilm attachment on the surface of the biofilm carrier: The paraffin-sulfur-acetic acid starch composite biofilm carrier was placed in a container, and paraffin-degrading bacteria solution, enriched heterotrophic denitrifying bacteria, sulfur autotrophic denitrifying bacteria and experimental water were added. The anaerobic environment was maintained by nitrogen blowing and sealing. The biofilm attachment system was then placed in a constant temperature shaking incubator for cultivation.

[0087] The experimental water was prepared by adding carbon, nitrogen, and phosphorus sources to deionized water. After several days of cultivation, the addition of external carbon sources was stopped to maintain a low carbon / nitrogen ratio environment. For example, the experimental water was obtained by adding CH3COONa, KNO3, and KH2PO4 to deionized water, with a specific composition of: COD = 300 mg / L, NO3... - -N=50mg / L,PO4 3- -P = 10 mg / L. No more sodium acetate (COD = 0 mg / L) was added to the experimental water after day 10.

[0088] The term "biofilm carrier surface attachment" refers to the inoculation of microorganisms into a reactor. Water treatment processes utilize microorganisms for nitrogen and phosphorus removal, requiring the inoculation of reactors with microorganisms capable of removing nitrogen and phosphorus. During the biofilm attachment process, a biofilm loaded with microorganisms grows on a biofilm carrier. The biofilm carrier is then added to the reaction system or reactor to carry out the reaction in the water to be treated. Subsequent separate inoculation of microorganisms into the reactor is unnecessary.

[0089] III) Coupled simultaneous nitrogen and phosphorus removal using composite biofilm carriers: Paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 biofilm carriers with a volume ratio of 0.5-2 were placed in a reactor. Simulated water was added, and nitrogen blowing was used to maintain an anaerobic environment. Samples were taken at regular intervals, filtered through the membrane, and NO3 was measured. - -N, NO2 - -N, NH4 + -N,PO4 3- Water quality indicators such as -P and Fe concentrations are high, when NO3... - When -N is completely removed, replace the simulated water supply.

[0090] The term "anaerobic environment" refers to an environment where there is almost no or only a very small amount of free oxygen. For example, the oxygen content in water is less than or equal to 5.0 mg, 4.5 mg, 3.0 mg, 2.5 mg, 1.0 mg, 0.7 mg, 0.5 mg, 0.3 mg, 0.2 mg, 0.1 mg, or 0 mg per liter.

[0091] The composite biofilm carrier is paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3, preferably paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3, more preferably, the volume ratio of paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 is 0.5-2;

[0092] like Figure 9 As shown, in the microscopic process of the coupling of the two packing materials, the slowly released acetate starch from paraffin-sulfur-acetic acid starch can promote the redox cycle of sulfur and iron species, that is, promote the production of SO4 during sulfur autotrophic denitrification. 2- Restore to S 2- S 2- It can act as an electron donor for sulfur autotrophic denitrification, thereby driving the redox cycle of sulfur species. The slowly released acetate starch from paraffin-sulfur-acetate starch can also promote the slow release of some Fe from paraffin-sulfur-FeCl3. 3+ Reduced to Fe 2+ Fe 2+ It drives ferroautotrophic denitrification, thereby driving the redox cycle of iron species. Besides the biologically driven sulfur and iron species cycle, starch acetate promotes SO42-. 2- S produced by reduction 2- It can also be with Fe 3+ Abiotic reactions occur, thereby driving the cycling of sulfur and iron species. The redox cycle of sulfur and iron species can better achieve simultaneous nitrogen and phosphorus removal.

[0093] The present invention will be further described below with reference to specific embodiments. However, the scope of protection claimed by the present invention is not limited to the scope described in the embodiments. Anyone can derive other various forms of products under the guidance of the present invention. However, regardless of any changes made in their shape or composition ratio, any technical solution that is the same as or similar to that of the present application falls within the protection scope of the present invention.

[0094] Example 1

[0095] I. Preparation of composite biofilm carrier: paraffin-sulfur-acetic acid starch:

[0096] 1) Mix paraffin wax and sulfur powder at a mass ratio of 1:3, heat to 150℃, and stir at 800 rpm for 10 minutes to ensure that the paraffin wax and sulfur powder are mixed evenly;

[0097] 2) Add acetate starch to the molten mixture of paraffin and sulfur, and continue stirring at 800 rpm for 10 min to ensure that the paraffin, sulfur powder and acetate starch are mixed evenly. Cool to 25°C to obtain the paraffin-sulfur-acetate starch core structure.

[0098] 3) The obtained paraffin-sulfur-acetate starch core structure was heated to 150°C to obtain a molten mixture. Activated carbon powder was added to the molten mixture and stirred at 800 rpm for 10 min to ensure that the molten mixture and activated carbon powder were mixed evenly. The mixture was then cooled to 25°C to obtain the paraffin-sulfur-acetate starch core structure again.

[0099] 4) The obtained paraffin-sulfur-acetate starch core structure was heated to 150°C and cooled to 75°C. Then, 8 wt% ethanol (volatile solvent) was added to the molten mixture and stirred at 400 rpm to ensure uniform dispersion of ethanol.

[0100] 5) While adding ethanol (volatile solvent), stir until the molten mixture is cooled to 65°C, then quickly pour the molten mixture into a mold that has been pre-cooled to 5°C to obtain a porous core structure paraffin-sulfur-acetic acid starch.

[0101] 6) Place the obtained porous core structure material in an oven and dry it at a low temperature of 40°C to completely remove residual volatile solvents;

[0102] 7) Mix the shell structure material paraffin and sulfur powder at a mass ratio of 1:3 and heat them. Stir at 800 rpm for 10 minutes to obtain a uniformly mixed molten shell material.

[0103] 8) Quickly dip a layer of shell material molten liquid into the core structure paraffin-sulfur-acetic acid starch that has been completely deethanol removed, cool it to 25°C, and obtain the core-shell porous composite biofilm carrier paraffin-sulfur-acetic acid starch.

[0104] II. Preparation of composite biofilm carrier: paraffin-sulfur-FeCl3:

[0105] By replacing "acetic acid starch" with "FeCl3" in the above section "Preparation of composite biofilm carrier: paraffin-sulfur-acetic acid starch", we obtain the composite biofilm carrier: paraffin-sulfur-FeCl3.

[0106] Appendix Figure 1 The images show actual photos of the composite biofilm carriers paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3, respectively.

[0107] III. Simultaneous removal of nitrogen and phosphorus from water using the composite biofilm carrier prepared above.

[0108] I) Water body to be treated:

[0109] The simulated water mixture is prepared from KNO3, NH4Cl, KH2PO4, etc., with the specific composition being: NO3 - -N = 20 mg / L, NH4 + -N=5mg / L,PO43- -P = 2 mg / L, COD = 0.

[0110] II) Inoculating the reaction system with microorganisms:

[0111] II-I) Enrichment of heterotrophic and sulfur-autotrophic denitrifying bacteria: Using anaerobic sludge, heterotrophic and sulfur-autotrophic denitrifying bacteria are enriched in heterotrophic and sulfur-autotrophic denitrifying bacteria enrichment cultures.

[0112] II-II) Biofilm formation on the biofilm carrier surface: A certain amount of paraffin-sulfur-acetic acid starch composite biofilm carrier was placed in a 500mL container. Logarithmic-phase paraffin-degrading bacteria solution, enriched heterotrophic denitrifying bacteria, sulfur-autotrophic denitrifying bacteria, and 450mL of experimental water were added. Nitrogen gas was purged for 15 minutes to remove oxygen. The bottle mouth was quickly sealed with a butyl rubber stopper, and the cap was tightened to maintain an anaerobic environment. A 50mL syringe was inserted into the stopper to maintain the air pressure inside and outside the bottle. The headspace bottle was placed in a constant temperature shaking incubator at 25±1℃ and 70rpm. The experimental water was changed every 2 days for a total of 40 days for biofilm formation.

[0113] II-III) Preparation of Experimental Water: The experimental water was obtained by adding CH3COONa, KNO3, KH2PO4, etc. to deionized water. The specific composition was: COD = 300 mg / L, NO3... - -N=50mg / L,PO4 3- -P = 10 mg / L. No more sodium acetate (COD = 0 mg / L) was added to the experimental water after day 10.

[0114] III) Coupled Simultaneous Nitrogen and Phosphorus Removal with Composite Biofilm Carrier: Paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 biofilm carriers with a volume ratio of 2:1 (filling ratio 10%) were added to the reactor. The biofilm carrier addition amount was 200 g / L. Simulated water was added, and nitrogen was purged for 15 min to ensure an anaerobic environment. The filtration flask was placed in a constant temperature shaking incubator at 25±1℃ and 70 rpm. Samples were taken at regular intervals, filtered through a 0.22 μm filter membrane, and the NO3 content in the water sample was measured. - -N, NO2 - -N, NH4 + -N,PO4 3- -P and Fe concentrations, when NO3 - When -N is completely removed, replace the simulated water supply.

[0115] IV. Experimental Results

[0116] During the 15-day sequencing batch experiment, NO3 --N achieved a maximum removal rate of 90.89%, TN achieved a maximum removal rate of 89.63%, and NO3... - The maximum removal rate of -N was 16.22 ± 0.28 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 80.28%, PO4 3- The maximum removal rate of -P was 1.88 ± 0.47 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent remained stable at 0.48±0.33 mg / L.

[0117] Example 2

[0118] Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the first and second parts of the composite biofilm carrier was changed to 3:1; all other contents remained the same.

[0119] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 96.65%, TN achieved a maximum removal rate of 93.37%, and NO3... - The maximum removal rate of -N was 16.66 ± 0.14 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 76.46%, PO4 removal rate 3- The maximum removal rate of -P was 2.89 ± 0.88 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent remained stable at 0.53±0.42 mg / L.

[0120] Example 3

[0121] Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the first and second parts of the composite biofilm carrier was changed to 1:1; all other contents remained the same.

[0122] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 89.78%, TN achieved a maximum removal rate of 86.57%, and NO3... - The maximum removal rate of -N was 10.98 ± 0.42 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 78.21%, PO4 3- The maximum removal rate of -P was 2.27 ± 0.45 mg·L⁻¹. -1 ·d -1The Fe concentration in the effluent remained stable at 0.38±0.24 mg / L.

[0123] Example 4

[0124] Based on Example 1, the third part, which utilizes the composite biofilm carrier prepared above to remove nitrogen and phosphorus from water, is changed to "the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 is changed to 1:1"; all other contents remain the same.

[0125] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 99.99%, TN achieved a maximum removal rate of 98.67%, and NO3... - The maximum removal rate of -N reached 19.06 ± 0.74 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 98.53%, PO4 removal rate 3- The maximum removal rate of -P reached 3.62 ± 0.22 mg·L⁻¹ -1 ·d -1 The Fe concentration in the effluent remained stable at 0.29 ± 0.41 mg / L. (Attached) Figure 2 This is Example NO3 - -N and NO2 - -N concentration variation graph, NO3 in almost every cycle during operation - -N decreased from approximately 20 mg / L to 0 mg / L, and the slope of the trend line in the graph shows that as the reactor operated, NO3... - The removal rate of NO2- is continuously increasing. Furthermore, during operation... - -N exhibits a trend of first increasing and then decreasing in each cycle. These results demonstrate that the coupling of the two composite packing materials can efficiently and stably achieve NO3- reduction. - -N is removed without accumulating the toxic and harmful intermediate NO2. - -N. (Attached) Figure 3 For this embodiment, NH4 + -N concentration variation graph, during reactor operation, influent NH4+ + -N is around 5 mg / L, and NH4 is present at the end of each cycle. + -N decreased to 0 mg / L, and NH4 was also observed during this process. + The -N concentration increased and then decreased, which may be attributed to the dissimilatory reduction of nitrate to ammonium by microorganisms. Overall, the coupled application of the two composite biofilm carriers can efficiently and stably remove low concentrations of NH4 in water with low C / N ratios. + -N. (Attached) Figure 4 This is Example NO3 --N and TN removal rate variation graph. NO3 removal rate for each cycle throughout the entire operation. - The removal rates of NO3- and TN remained almost stable at 100%, indicating that the coupled application of the two composite biofilm carriers can achieve efficient and stable NO3 removal. - Removal of -N and TN. (Appendix) Figure 5 This is PO4 of the embodiment. 3- -P concentration and PO4 3- -P removal rate variation graph. PO4 levels in each cycle throughout the entire operation. 3- The PO4 concentration decreased from 2 mg / L to 0 mg / L, indicating almost 100% removal. This demonstrates that the coupled application of the two composite biofilm carriers can also achieve efficient and stable PO4 removal. 3- -P synchronization removal. (See attached) Figure 6 This is a graph showing the Fe concentration variation in this embodiment. At the end of each cycle during operation, the average Fe concentration in the effluent did not exceed 0.5 mg / L, indicating that the coupled application of the two composite biofilm carriers can ensure low concentrations of metal ions leaching into the water. (See attached image) Figure 7 NO3 - -N removal rate variation graph, as the reactor operates NO3 - -N removal rate gradually increases, reaching a maximum of 19.06 ± 0.74 mg·L⁻¹. -1 ·d -1 Appendix Figure 8 PO4 3- -P removal rate variation graph, the coupled application of two composite biofilm carriers can achieve PO4 removal 3- Stable removal of -P, average PO4 3- -P removal rate was 3.62 ± 0.22 mg·L⁻¹ -1 ·d -1 Appendix Figure 9 The process by which two composite biomembrane carriers are coupled to promote sulfur and iron cycling was analyzed.

[0126] Example 5

[0127] Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the first and second part composite biofilm carriers was changed to 3:1;

[0128] The third part, which utilizes the composite biofilm carrier prepared above to remove nitrogen and phosphorus from water, is modified by changing the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 to 1:1; all other contents remain the same.

[0129] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 94.87%, TN achieved a maximum removal rate of 92.36%, and NO3... -The maximum removal rate of -N was 14.68 ± 0.28 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 91.22%, PO4 3- The maximum removal rate of -P was 2.02 ± 0.21 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent remained stable at 0.36±0.24 mg / L.

[0130] Example 6

[0131] Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the first and second part composite biofilm carriers was changed to 1:1;

[0132] The third part, which utilizes the composite biofilm carrier prepared above to remove nitrogen and phosphorus from water, is modified by changing the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 to 1:1; all other contents remain the same.

[0133] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 95.21%, TN achieved a maximum removal rate of 92.18%, and NO3... - The maximum removal rate of -N was 16.22 ± 0.72 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 90.89%, PO4 3- The maximum removal rate of -P was 2.48 ± 0.12 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent remained stable at 0.45±0.21 mg / L.

[0134] Example 7

[0135] Based on Example 1, the third part, which utilizes the composite biofilm carrier prepared above to remove nitrogen and phosphorus from water, is modified by changing the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 to 1:2; all other contents remain the same.

[0136] Experimental results: During the 15-day sequential batch experiment, NO3... - The maximum removal rate of -N reached 88.78%, and the maximum removal rate of TN reached 85.43%, NO3... - The maximum removal rate of -N was 9.98 ± 0.58 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 85.66%, PO4 3-The maximum removal rate of -P was 2.56 ± 0.18 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent remained stable at 0.66±0.38 mg / L.

[0137] Example 8

[0138] Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the first and second part composite biofilm carriers was changed to 3:1;

[0139] The third part, which utilizes the composite biofilm carrier prepared above to remove nitrogen and phosphorus from water, is modified by changing the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 to 1:2; all other contents remain the same.

[0140] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 90.87%, TN achieved a maximum removal rate of 86.41%, and NO3... - The maximum removal rate of -N was 8.89 ± 0.66 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 91.22%, PO4 3- The maximum removal rate of -P was 2.22 ± 0.21 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent remained stable at 0.71±0.23 mg / L.

[0141] Example 9

[0142] Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the first and second part composite biofilm carriers was changed to 1:1;

[0143] The third part, which utilizes the composite biofilm carrier prepared above to remove nitrogen and phosphorus from water, is modified by changing the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 to 1:2; all other contents remain the same.

[0144] During the 15-day sequencing batch experiment, NO3 - -N achieved a maximum removal rate of 86.78%, TN achieved a maximum removal rate of 84.75%, and NO3... - The maximum removal rate of -N was 9.86 ± 0.28 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate reached 93.54%, PO4 removal rate 3- The maximum removal rate of -P was 2.78 ± 0.34 mg·L⁻¹. -1 ·d-1 The Fe concentration in the effluent remained stable at 0.58±0.27 mg / L.

[0145] Comparative Example 1: Using only one type of biofilm carrier

[0146] Comparative Example 1-1: Based on Example 1, the application of the composite biofilm carrier in Part 3, "paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 volume ratio 2:1" was changed to "only paraffin-sulfur-acetic acid starch was added"; all other contents remained the same.

[0147] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 80.13%, TN achieved a maximum removal rate of 74.22%, and NO3... - The maximum removal rate of -N was 12.65 ± 0.77 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate and removal speed are both 0.

[0148] Comparative Examples 1-2: Based on Example 1, the application of the composite biofilm carrier in Part 3 was changed from "paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 volume ratio 2:1" to "only paraffin-sulfur-FeCl3 was added"; all other contents remained the same.

[0149] Experimental results: During the 15-day sequential batch experiment, NO3... - The maximum removal rate of -N reached 72.68%, and the maximum removal rate of TN reached 69.45%, NO3 - The maximum removal rate of -N was 8.77 ± 0.23 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate was 70.33%, PO4 3- The maximum removal rate of -P was 2.24 ± 0.16 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent was 3.11 ± 0.27 mg / L.

[0150] In Comparative Example 1 above, based on Example 1, water treatment was carried out using a single type of biofilm carrier. The results showed that compared to the treatment with the composite biofilm carrier in Example 1, the NO3 content was significantly reduced. - Both NO3- and TN removal rates decreased significantly by approximately 10-20%. Furthermore, NO3- - -N and PO4 3- The maximum removal rates of P and P also showed a significant decreasing trend. In particular, in Comparative Example 1-1, the removal of P from the water could not be achieved by using paraffin-sulfur-acetic acid starch alone.

[0151] Comparative Example 2: Using only one type of biofilm carrier

[0152] Comparative Example 2-1: Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the composite biofilm carrier in Part 1 was changed to 3:1; the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 in Part 3 was changed from 2:1 to "only paraffin-sulfur-acetic acid starch was added"; all other contents remained the same.

[0153] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 68.89%, TN achieved a maximum removal rate of 66.57%, and NO3... - The maximum removal rate of -N was 6.68 ± 0.11 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate and removal speed are both 0.

[0154] Comparative Example 2-2: Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the composite biofilm carrier in Part 1 was changed to 3:1; the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 in Part 3 was changed from 2:1 to "only paraffin-sulfur-FeCl3 was added"; all other contents remained the same.

[0155] Experimental results: During the 15-day sequential batch experiment, NO3... - The maximum removal rate of -N reached 58.73%, and the maximum removal rate of TN reached 56.68%, NO3... - The maximum removal rate of -N was 6.95 ± 0.12 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate was 68.45%, PO4 removal rate was 68.45%. 3- The maximum removal rate of -P was 1.96 ± 0.27 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent was 3.65 ± 0.11 mg / L.

[0156] Comparative Example 3: Using only one type of biofilm carrier

[0157] Comparative Example 3-1: Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the composite biofilm carrier in Part 1 was changed to 1:1; the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 in Part 3 was changed from 2:1 to "only paraffin-sulfur-acetic acid starch was added"; all other contents remained the same.

[0158] Experimental results: During the 15-day sequential batch experiment, NO3... - -N achieved a maximum removal rate of 77.91%, TN achieved a maximum removal rate of 73.56%, and NO3... - The maximum removal rate of -N was 8.45 ± 0.18 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate and removal speed are both 0.

[0159] Comparative Example 3-2: Based on Example 1, the mass ratio of paraffin to sulfur in the preparation of the composite biofilm carrier in Part 1 was changed to 1:1; the volume ratio of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 in Part 3 was changed from 2:1 to "only paraffin-sulfur-FeCl3 was added"; all other contents remained the same.

[0160] Experimental results: During the 15-day sequential batch experiment, NO3... - The maximum removal rate of -N reached 66.28%, the maximum removal rate of TN reached 63.48%, and NO3... - The maximum removal rate of -N was 8.56 ± 0.24 mg·L⁻¹. -1 ·d -1 PO4 3- -P removal rate was 70.53%, PO4 3- The maximum removal rate of -P was 2.06 ± 0.46 mg·L⁻¹. -1 ·d -1 The Fe concentration in the effluent was 2.98 ± 0.21 mg / L.

[0161] In Comparative Examples 2 and 3 above, based on Example 1, different mass ratios of paraffin to sulfur were used, and only a single biofilm carrier was used for water treatment. The results were consistent with Comparative Example 1. Compared with Example 1, the removal effect and removal rate were significantly reduced, or the simultaneous removal effects of N and P could not be achieved.

[0162] Comparative Example 4

[0163] Natural pyrite is crushed using a crusher, and particles of 1-4 mm are sieved out. It is then added to a 10% (v / v) HCl solution for 2 hours to remove oxides from the surface of the pyrite. Afterward, it is repeatedly washed with deionized water until the pH is neutral, vacuum dried, and then sealed for later use. This pretreated natural pyrite is then packed into a reactor (45-50% packing ratio) for denitrification. Influent NO3 - -N concentration 30.43±1.70 mg / L, NO3 - -N removal rate ranged from -2.9 to 17.5 mg·L⁻¹ -1 ·d-1 .

[0164] Comparative Example 5

[0165] Natural pyrrhotite is crushed using a crusher, and particles of 2.36-5.12 mm are sieved out. These particles are then added to a 10% (v / v) HCl solution for 2 hours to remove oxides from the surface of the pyrrhotite. Afterward, it is repeatedly washed with deionized water until the pH is neutral, vacuum dried, and then sealed for later use. This pretreated natural pyrrhotite is then packed into a reactor (45-50% packing ratio) for denitrification. Influent NO3 - -N concentration and PO4 3- –P concentrations were 28 mg / L and 6 mg / L, respectively, NO3 - -N and PO4 3- –P removal rates were 26.87 mg·L⁻¹ -1 ·d -1 and 5.72 mg·L -1 ·d -1 .

Claims

1. A method for preparing a composite biomembrane carrier, comprising the following steps: 1) Mix paraffin and sulfur, heat to melt to obtain a paraffin and sulfur molten liquid, add acetate starch or FeCl3 to the molten mixture of paraffin and sulfur, stir evenly, cool to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures; 2) The core structure obtained in step 1) is heated and melted once to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 melt. Activated carbon powder is added to the melt, stirred evenly, and cooled to obtain paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structures again. 3) The paraffin-sulfur-acetate starch and paraffin-sulfur-FeCl3 core structure obtained in step 2) are heated and melted again. A volatile solvent is added during the cooling of the two melts, while stirring to maintain the molten state. 4) During stirring and cooling, the volatile solvent slowly evaporates, forming a porous structure in the core materials paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3; 5) The molten core structure material is rapidly injected into the pre-cooled mold to obtain porous core structure paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3; 6) Place the porous core structure material obtained in step 5) into an oven and dry it at low temperature to completely remove residual volatile solvents; 7) Mix paraffin wax and sulfur, the materials for the shell structure, heat and stir to obtain a molten liquid of the shell material; 8) The porous core structure material obtained in step 6) is quickly dipped into the molten shell material obtained in step 7) to obtain a layer of molten shell material. After cooling, a composite biofilm carrier with a porous core-shell structure is obtained.

2. The method for preparing the composite biomembrane carrier according to claim 1, wherein, The volatile solvent is selected from ethanol; And / or, the heating and melting temperature in steps 1), 2), 3), and 7) is 80~150℃; And / or, in step 3), when the molten core structure material is cooled to 70~80°C, a volatile solvent is added, and when it is cooled to 60~70°C, it is quickly molded. And / or, in step 5), the temperature of the molten core structure material is controlled at 60~70°C; And / or, in step 5), the mold is pre-cooled to 0-10°C; And / or, the temperature of the oven for low-temperature drying in step 6) is 30~40℃; And / or, steps 1), 2), and 8) are cooled to 20-30°C; And / or, in step 5), the mold is spherical; And / or, in steps 1) and 2), the materials of the core structure are mixed separately and stirred at 600-1000 rpm for 10-30 minutes to disperse them evenly; And / or, in steps 3) and 4), after adding the volatile solvent, the stirring is carried out at a speed of 200-600 rpm to disperse the solvent evenly. And / or, in step 7), the shell structure material is mixed and stirred at 600~1000 rpm for 10-30 minutes to disperse it evenly.

3. The method for preparing the composite biomembrane carrier according to claim 2, wherein, The ethanol is 5-10 wt% ethanol; And / or, in step 5), the diameter of the sphere is 15~20 mm.

4. A composite biofilm carrier obtained by the preparation method according to any one of claims 1 to 3, wherein, The composite biofilm carrier has a core-shell structure, with a shell structure covering a core structure; The shell structure is made of paraffin wax and sulfur powder; The materials of the core structure are paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3.

5. A composite biofilm carrier according to claim 4, wherein, In the core-shell structure, the core body paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 have a porous structure with a pore size of 400~800μm.

6. A composite biofilm carrier according to claim 5, wherein, The core-shell structure has a grain size of 15-20 mm; the shell structure has a thickness of 2-5 mm.

7. A composite biofilm carrier according to claim 4, wherein, The composite biofilm carrier is a porous core-shell structured paraffin-sulfur-acetic acid starch composite biofilm carrier and a paraffin-sulfur-FeCl3 composite biofilm carrier.

8. A composite biofilm carrier according to claim 7, wherein, In the paraffin-sulfur-acetic acid starch composite biofilm carrier, the shell structure is made of paraffin and sulfur, and the core structure is made of paraffin-sulfur-acetic acid starch. In the paraffin-sulfur-FeCl3 composite biofilm carrier, the shell structure is made of paraffin and sulfur, and the core structure is made of paraffin-sulfur-FeCl3.

9. The composite biofilm carrier according to any one of claims 4 to 8, wherein, The paraffin-sulfur-acetic acid starch provides a multi-electron donor to achieve mixed nutrient denitrification, while the paraffin-sulfur-FeCl3 controls the release of iron during the phosphorus removal process, thus ensuring a low iron concentration in the water while achieving phosphorus removal.

10. The composite biomembrane carrier according to claim 9, wherein, The coupling of paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3 drives the redox cycle of sulfur and iron species through biological and abiotic factors, achieving efficient and simultaneous removal of nitrogen and phosphorus in water with low carbon / nitrogen ratio.

11. An application of the composite biofilm carrier according to any one of claims 4 to 10 for the simultaneous removal of nitrogen and phosphorus from water, wherein, The composite biofilm carrier is added to the water body to be treated to simultaneously remove nitrogen and phosphorus from the water body; The composite biofilm carrier is paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3.

12. The application according to claim 11, wherein, The composite biofilm carrier is paraffin-sulfur-acetic acid starch and paraffin-sulfur-FeCl3.

13. The application according to claim 12, wherein, The volume ratio of the paraffin-sulfur-acetic acid starch to the paraffin-sulfur-FeCl3 is 0.5~2.

14. The application according to claim 11, wherein, The nitrogen is present in any of the following forms or at least a combination of two: NO3 - -N, NO2 - -N, NH4 + -N; The phosphorus exists in the form of PO4. 3- -P.

15. The application according to any one of claims 11 to 14, wherein, At the beginning of operation, paraffin-degrading bacteria, heterotrophic denitrifying bacteria, and sulfur autotrophic denitrifying bacteria need to be inoculated into the reaction system.

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