Sulfur autotrophic denitrification biofilter composite filler and preparation method thereof

Abstract

The application relates to the field of sewage treatment, and discloses a sulfur autotrophic denitrification biofilter composite filler and a preparation method thereof. The method comprises the following steps: carrying out a silane hydrolysis reaction on a silane coupling agent containing a mercaptan group to prepare a hydrolysis solution, and then adding hydroxylated polystyrene microspheres into the hydrolysis solution to carry out a grafting reaction and prepare the sulfur autotrophic denitrification biofilter composite filler. The method grafts mercaptan groups to the surface of the polystyrene microspheres by using the silane coupling agent containing the mercaptan group. The mercaptan groups can specifically combine with sulfur transport proteins on the cell membrane of sulfur autotrophic denitrification microorganisms, so that the sulfur autotrophic denitrification microorganisms can selectively colonize on the surface of the polystyrene microspheres, competition between other microorganisms and the sulfur autotrophic microorganisms can be avoided, the colonization stability of the sulfur autotrophic microorganisms is improved, and the biofilm formation efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, and in particular to a sulfur-autotrophic denitrification biological filter composite packing and its preparation method. Background Technology

[0002] Denitrifying biological filters are important devices for wastewater treatment. These devices use the denitrification action of denitrifying microorganisms to convert nitrate nitrogen and nitrite nitrogen in wastewater into nitrogen gas. Denitrifying biological filters are favored by those skilled in the art due to their advantages such as simple operation, low operating cost, and stable effluent quality.

[0003] Packing material is a crucial component of denitrifying biological filters. Denitrifying microorganisms can only perform denitrification biological treatment of wastewater after completing biofilm formation on the packing material. Therefore, improving the biofilm formation efficiency of denitrifying microorganisms on the packing material is of great significance for improving treatment efficiency. Traditional biofilm formation processes mainly rely on natural biofilm formation, but this process has a long cycle and is unstable. Existing technologies shorten the biofilm formation cycle and improve point-value stability through artificial inoculation. Both of these methods primarily shorten the biofilm formation cycle and improve microbial colonization efficiency by regulating the microorganisms. Existing technology CN118108346A discloses a composite packing material for a sulfur autotrophic denitrifying biological filter, its manufacturing method, and its application, which improves the biofilm colonization rate of denitrifying microorganisms by optimizing the packing material. This technical solution involves loading ferrous sulfide and elemental sulfur nanoparticles into the pores of triethylamine polystyrene microspheres. The triethylamine groups enhance hydrophilicity and generate electrostatic attraction with negatively charged microorganisms, enabling denitrifying microorganisms to attach more stably and rapidly to the composite packing surface, thereby increasing the colonization rate and biofilm formation efficiency of denitrifying microorganisms. However, during practical application, it was found that the types of microorganisms involved in biofilm formation need to be strictly controlled. If other microorganisms capable of electrostatic attraction to the packing material are present, these microorganisms will compete with the denitrifying microorganisms, leading to a decrease in their colonization rate. Therefore, a highly selective denitrifying filter packing material is needed to prevent the denitrifying microorganisms from being affected by other microorganisms, thus improving the colonization stability of denitrifying microorganisms. Summary of the Invention

[0004] The objective of this invention is to provide a composite packing material for denitrifying biological filters that specifically incorporates sulfur-autotrophic denitrifying microorganisms.

[0005] This invention modifies polystyrene microspheres by grafting thiol groups onto the surface of the polystyrene microspheres. The thiol groups can specifically bind to sulfur transport proteins on the cell membranes of sulfur autotrophic denitrifying bacteria, enabling the sulfur autotrophic denitrifying bacteria to specifically bind to the packing material without being affected by other microorganisms. This improves the colonization stability and colonization efficiency of denitrifying microorganisms.

[0006] The specific technical solution of this invention is as follows: A sulfur-autotrophic denitrification biofilter composite packing material comprises, by mass ratio: hydroxylated polystyrene microspheres and a mercaptan-containing silane coupling agent, wherein the mass ratio of the mercaptan-containing silane coupling agent to the hydroxylated polystyrene microspheres is 0.8~1:1.

[0007] Preferably, the thiol-containing silane coupling agent includes one or more of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and mercaptopropylmethyldimethoxysilane.

[0008] Preferably, hydroxylated polystyrene microspheres are loaded with elemental sulfur and ferrous sulfide.

[0009] A method for preparing the above-mentioned sulfur autotrophic denitrification biofilter composite packing includes the following steps: (1) Prepare a hydrolysate by hydrolyzing a thiol-containing silane coupling agent; (2) Hydroxylated polystyrene microspheres were added to the hydrolysate to carry out a grafting reaction to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0010] Preferably, the conditions for the silane hydrolysis reaction include: an aqueous solution of ethanol as the solvent, a pH of 3-4, and a reaction temperature of 30-60 °C.

[0011] Preferably, the ethanol-water solution is anhydrous ethanol and deionized water, with a volume ratio of anhydrous ethanol to deionized water of 8~10:1.

[0012] Preferably, hydroxylated polystyrene microspheres are prepared by plasma modification.

[0013] Preferably, the grafting reaction conditions include: a protective atmosphere, a reaction temperature of 50~60 ℃, and a reaction time of 4~8 h.

[0014] Preferably, the protective atmosphere is nitrogen.

[0015] Preferably, the grafting reaction is completed by filtration and washing of the filter media with anhydrous ethanol, followed by drying.

[0016] As a preferred option, the imidization treatment conditions include: temperature 80~300 ℃, time 2~6 h.

[0017] This invention provides a composite packing material for a sulfur autotrophic denitrification biofilter. This packing material grafts thiol groups onto the surface of polystyrene microspheres using a thiol-based silane coupling agent. The thiol groups can specifically bind to sulfur transport proteins on the cell membranes of sulfur autotrophic denitrifying microorganisms, enabling these microorganisms to quickly and firmly attach to the polystyrene microspheres. This avoids competition from other microorganisms and improves the biofilm stability and efficiency of the sulfur autotrophic microorganisms.

[0018] This invention also provides a method for preparing the above-mentioned sulfur autotrophic denitrifying microbial composite packing material. The method first involves hydrolyzing a thiol-containing silane coupling agent to convert the silane into silicic acid. Then, hydroxyl-modified polystyrene microspheres are added to the hydrolysate to allow the hydroxyl and silicic acid groups to condense, thereby grafting the thiol-containing silane coupling agent onto the surface of the polystyrene microspheres and grafting thiol groups onto the surface of the polystyrene microspheres. This preparation method is simple and easy to operate.

[0019] Compared with the prior art, this application has the following technical effects: This invention uses a thiol-containing silane coupling agent to graft thiol groups onto the surface of polystyrene microspheres. The thiol groups can specifically bind to sulfur transport proteins on the cell membranes of sulfur autotrophic denitrifying microorganisms, enabling sulfur autotrophic denitrifying microorganisms to selectively colonize the surface of polystyrene microspheres. This avoids competition between other microorganisms and sulfur autotrophic microorganisms, improves the colonization stability of sulfur autotrophic microorganisms, and increases biofilm formation efficiency. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments.

[0021] To better understand the content of this invention, further explanation is provided below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of this invention.

[0022] Example 1: A method for preparing a composite packing material for a sulfur-autotrophic denitrification biological filter includes the following steps: (1) Dissolve the thiol-containing silane coupling agent (γ-mercaptopropyltrimethoxysilane) in an aqueous ethanol solution (anhydrous ethanol and deionized water in a volume ratio of 9:1), and then add acetic acid (concentration of 0.1 mol / L) to adjust the pH to 4 to 5 and stir at room temperature for 30 to 60 minutes to prepare a hydrolysate; (2) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (3) Place the polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce an argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to prepare hydroxylated polystyrene microspheres. (4) The hydroxylated polystyrene microspheres were dispersed in the hydrolysate. The mass ratio of γ-mercaptopropyltrimethoxysilane to the hydroxylated polystyrene microspheres was 1:1. The mixture was stirred for 4 h under a nitrogen atmosphere at 60 °C to form a condensation reaction and a slurry. The precipitate was separated by centrifugation, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 50 °C for 12 h to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0023] Example 2: A method for preparing a composite packing material for a sulfur-autotrophic denitrification biological filter includes the following steps: (1) Dissolve the thiol-containing silane coupling agent (γ-mercaptopropyltriethoxysilane) in an aqueous ethanol solution (anhydrous ethanol and deionized water in a volume ratio of 9:1), and then add acetic acid (concentration of 0.1 mol / L) to adjust the pH to 4 to 5 and stir at room temperature for 30 to 60 minutes to prepare a hydrolysate; (2) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (3) Place the polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce an argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to prepare hydroxylated polystyrene microspheres. (4) The hydroxylated polystyrene microspheres were dispersed in the hydrolysate. The mass ratio of γ-mercaptopropyltriethoxysilane to the hydroxylated polystyrene microspheres was 0.9:1. The mixture was stirred for 8 h under a nitrogen atmosphere at 50 °C to form a condensation reaction and a slurry. The precipitate was separated by centrifugation, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 50 °C for 12 h to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0024] Example 3: A method for preparing a composite packing material for a sulfur-autotrophic denitrification biological filter includes the following steps: (1) Dissolve the thiol-containing silane coupling agent (mercaptopropylmethyldimethoxysilane) in an aqueous ethanol solution (anhydrous ethanol and deionized water in a volume ratio of 9:1), then add acetic acid (concentration of 0.1 mol / L) to adjust the pH to 4 to 5 and stir at room temperature for 30 to 60 min to prepare a hydrolysate; (2) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (3) Place the polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce an argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to prepare hydroxylated polystyrene microspheres. (4) The hydroxylated polystyrene microspheres were dispersed in the hydrolysate. The mass ratio of mercaptopropylmethyldimethoxysilane to the hydroxylated polystyrene microspheres was 0.8:1. The mixture was stirred for 6 h under a nitrogen atmosphere at 55 °C to form a condensation reaction to prepare a slurry. The precipitate was separated by centrifugation, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 50 °C for 12 h to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0025] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not use a thiol-based silane coupling agent to modify the microspheres, and the modification included the following steps: (1) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (2) Place polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to make sulfur autotrophic denitrification biofilter composite packing.

[0026] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses a common silane coupling agent to modify the microspheres, including the following steps: (1) Dissolve the thiol-containing silane coupling agent (vinyltriethoxysilane) in an aqueous ethanol solution (anhydrous ethanol and deionized water in a volume ratio of 9:1), then add acetic acid (concentration of 0.1 mol / L) to adjust the pH to 4 to 5 and stir at room temperature for 30 to 60 minutes to prepare a hydrolysate; (2) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (3) Place the polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce an argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to prepare hydroxylated polystyrene microspheres. (4) The hydroxylated polystyrene microspheres were dispersed in the hydrolysate. The mass ratio of vinyltriethoxysilane to hydroxylated polystyrene microspheres was 1:1. The mixture was stirred for 4 h under a nitrogen atmosphere at 60 °C to form a condensation reaction and a slurry. The precipitate was separated by centrifugation, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 50 °C for 12 h to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0027] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the amount of the thiol-containing silane coupling agent used is too small, including the following steps: (1) Dissolve the thiol-containing silane coupling agent (γ-mercaptopropyltrimethoxysilane) in an aqueous ethanol solution (anhydrous ethanol and deionized water in a volume ratio of 9:1), and then add acetic acid (concentration of 0.1 mol / L) to adjust the pH to 4 to 5 and stir at room temperature for 30 to 60 minutes to prepare a hydrolysate; (2) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (3) Place the polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce an argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to prepare hydroxylated polystyrene microspheres. (4) The hydroxylated polystyrene microspheres were dispersed in the hydrolysate. The mass ratio of γ-mercaptopropyltrimethoxysilane to the hydroxylated polystyrene microspheres was 0.5:1. The mixture was stirred for 4 h under a nitrogen atmosphere at 60 °C to form a condensation reaction and a slurry. The precipitate was separated by centrifugation, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 50 °C for 12 h to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0028] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that the amount of the thiol-containing silane coupling agent used is excessive, including the following steps: (1) Dissolve the thiol-containing silane coupling agent (γ-mercaptopropyltrimethoxysilane) in an aqueous ethanol solution (anhydrous ethanol and deionized water in a volume ratio of 9:1), and then add acetic acid (concentration of 0.1 mol / L) to adjust the pH to 4 to 5 and stir at room temperature for 30 to 60 minutes to prepare a hydrolysate; (2) Iron-containing acid solution (iron chloride mass fraction of 10 wt%) is prepared by fully dissolving ferric chloride in a mixture of hydrogen chloride and sodium chloride (mass fraction of hydrogen chloride is 5 wt%) and sodium chloride is 5 wt%). A sulfur-containing alkaline solution is prepared by dissolving sodium hydroxide solution (mass fraction of sodium hydroxide is 7.5 wt%) and sodium sulfide solution (mass fraction of sodium sulfide is %). Polystyrene microspheres are added to the iron-containing acid solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated to prepare iron-loaded polystyrene microspheres. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The iron-loaded polystyrene microspheres are then added to the sulfur-containing alkaline solution at a dosage of 0.15 g / mL and stirred at 20 °C for 12 h. The microspheres are then separated. The iron-loaded polystyrene microspheres are rinsed with sodium chloride solution until neutral. The microspheres are then placed in deionized water at 30 °C for 12 h. The microspheres are then separated and dried to prepare sulfur / ferrous sulfide-loaded polystyrene microspheres. (3) Place the polystyrene microspheres loaded with sulfur / ferrous sulfide in a plasma reaction chamber, introduce an argon / oxygen mixture (argon to oxygen volume ratio 4:1), and process with 100 W power for 5 min to prepare hydroxylated polystyrene microspheres. (4) The hydroxylated polystyrene microspheres were dispersed in the hydrolysate. The mass ratio of γ-mercaptopropyltrimethoxysilane to the hydroxylated polystyrene microspheres was 1.5:1. The mixture was stirred for 4 h under a nitrogen atmosphere at 60 °C to form a condensation reaction and a slurry. The precipitate was separated by centrifugation, washed three times with anhydrous ethanol, and dried in a vacuum drying oven at 50 °C for 12 h to prepare a sulfur autotrophic denitrification biological filter composite packing.

[0029] Example of detection: The thiol grafting density of the sulfur autotrophic denitrification biological filter composite packing prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The thiol group content was quantitatively determined using Ellman's reagent disclosed in CN107325192A. The sulfur-autotrophic denitrifying biological filter composite packing materials prepared in Test Examples 1-3 and Comparative Examples 1-4 were used for wastewater treatment. The treatment steps included: (1) The composite packing is filled into a filter column with a diameter of 150 mm and an effective height of 1000 mm. The filling height of the composite packing is 500 mm, and the support layer is gravel with a diameter of 30 mm and an effective height of 180 mm. (2) The sludge was inoculated from the secondary sedimentation tank of a municipal wastewater treatment plant. The concentration of suspended solids in the sludge was 8000 mg / L. The filter was operated in an upflow mode. The total nitrogen concentration in the influent was 23 mg / L, the nitrate concentration was 21 mg / L, and the total phosphorus concentration was 1.5 mg / L. The influent flow rate was controlled to allow the empty bed contact time to be 60 min. The water temperature was controlled to be 28~33 ℃, and the pH was controlled to be 7~8. The acclimatization and biofilm formation time for total nitrogen concentration <1.5 mg / L and total phosphorus concentration <0.2 mg / L in the water was calculated. The test results are shown in Table 1. Table 1 Test Results As shown in Table 1, the acclimatization and biofilm formation time of the sulfur autotrophic denitrification biofilter composite packing material prepared by the present invention is 56-63 h. Compared with the composite packing material without grafted thiol groups in Comparative Example 1, the acclimatization and biofilm formation time is shortened by 6 times, the microbial acclimatization and biofilm formation time is significantly shortened, and the biofilm formation efficiency of denitrifying microorganisms is significantly increased.

[0030] The results from Example 1 and Comparative Examples 1 and 2 show that the biofilm formation time of the composite packing without silane coupling modification reached 650 h, while the biofilm formation time of the composite packing modified with ordinary silane coupling agent reached 820 h. Both techniques showed significantly shorter biofilm formation times than Example 1. Analysis revealed that grafting thiol groups onto the packing surface allows for selective binding with sulfur-autotrophic denitrifying microorganisms, making it easier for these microorganisms to colonize the packing surface and thus accelerating biofilm formation. Furthermore, the type of the other end group of the silane coupling agent significantly affects the hydrophilicity of the packing after modification with ordinary silane coupling agent. Low hydrophilicity reduces the binding ability between microorganisms and the packing, leading to a significant increase in biofilm formation time.

[0031] The results of Examples 1, 2, and 3, and Comparative Examples 3 and 4, show that when using silane coupling agents containing thiol groups to modify the packing material, the amount of silane coupling agent has a significant impact on the acclimatization and biofilm formation time of denitrifying microorganisms. Different silane coupling agents containing thiol groups also have a significant impact on the acclimatization and biofilm formation time of denitrifying microorganisms. Further analysis revealed that the amount and type of silane coupling agent containing thiol groups affect the grafting density of thiols on the packing material surface. As the thiol density increases, the acclimatization and biofilm formation time first increases and then decreases, indicating that within this range of thiol grafting density, the acclimatization and biofilm formation time is significantly reduced. Conversely, when the thiol grafting density is too low or too high, the acclimatization and biofilm formation time increases significantly. The investigation revealed that the hydrophilicity of the packing material decreased after modification with a silane coupling agent. Therefore, the higher the grafting content of thiol groups, the lower the hydrophilicity of the packing material, resulting in a longer biofilm formation time for microorganisms. Conversely, a lower grafting content of thiol groups weakens the selectivity of the packing material for sulfur-autotrophic denitrifying microorganisms, further increasing the biofilm formation time of these microorganisms on the packing material. Furthermore, this invention also found that excessive use of silane coupling agent can lead to self-polymerization, causing over-coverage of the packing material and reducing the release of sulfur and ferrous sulfide from the packing. Therefore, it is necessary to select an appropriate grafting content of thiol groups.

[0032] 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 packing material for a sulfur-autotrophic denitrification biological filter, characterized in that the raw material... include: Hydroxylated polystyrene microspheres and a thiol-containing silane coupling agent, wherein the mass ratio of the thiol-containing silane coupling agent to the hydroxylated polystyrene microspheres is 0.8~1:

1.

2. The composite packing material for the sulfur-autotrophic denitrification biological filter according to claim 1, characterized in that, Thiol-containing silane coupling agents include one or more of γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and mercaptopropylmethyldimethoxysilane.

3. The composite packing material for a sulfur-autotrophic denitrification biological filter according to claim 1, characterized in that, Hydroxylated polystyrene microspheres are loaded with elemental sulfur and ferrous sulfide.

4. A method for preparing the composite packing material for a sulfur-autotrophic denitrification biological filter according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Prepare a hydrolysate by hydrolyzing a thiol-containing silane coupling agent; (2) Hydroxylated polystyrene microspheres were added to the hydrolysate to carry out a grafting reaction to prepare a sulfur autotrophic denitrification biological filter composite packing.

5. The preparation method according to claim 4, characterized in that, The conditions for the silane hydrolysis reaction include: the solvent is an aqueous ethanol solution, the pH is 3-4, and the reaction temperature is 30-60 ℃.

6. The preparation method according to claim 5, characterized in that, The aqueous ethanol solution is composed of anhydrous ethanol and deionized water, with a volume ratio of anhydrous ethanol to deionized water of 8~10:

1.

7. The preparation method according to claim 4, characterized in that, Hydroxylated polystyrene microspheres were prepared using plasma modification.

8. The preparation method according to claim 4, characterized in that, The conditions for the grafting reaction include: a protective atmosphere, a reaction temperature of 50-60 °C, and a reaction time of 4-8 h.

9. The preparation method according to claim 8, characterized in that, The protective atmosphere is nitrogen.

10. The preparation method according to claim 4, characterized in that, After the grafting reaction was completed, the filter was filtered and the filter media was washed with anhydrous ethanol and then dried.

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