Simultaneous nitrogen and phosphorus removal biological ferrous iron filler and preparation method thereof

Abstract

The present application relates to sewage treatment technical field, specifically disclose the biological sulfur iron filler of simultaneous nitrogen and phosphorus removal and its preparation method, including biological sulfur is 38-45%, the reduced iron powder is 24-39%, low alkali cement (P.O42.5) is 20-25%, sodium silicate is 3-6%. The specific preparation method is as follows: step one: according to the proportion of raw materials: reduced iron powder, biological sulfur is screened through 200 mesh, the reduced iron powder, biological sulfur, low alkali cement is uniformly mixed into ash material according to proportion;Step two: the sodium silicate is dissolved in deionized water, to obtain the adhesive solution;Step three: 50% of the ash material and the adhesive are uniformly mixed to obtain the modifier;Step four: start the granulator, add the modifier, evenly sprinkle the adhesive solution when the machine is running to make the surface of the modifier wet, and gradually add the remaining ash material, until the surface is evenly attached, forming 7-9mm spherical filler;Step five: place it in 85℃ constant temperature drying oven for 4h, then take it out, and naturally cure it at 25℃ for 7 days to obtain the biological sulfur iron filler.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a biological sulfur-iron packing material for simultaneous nitrogen and phosphorus removal and its preparation method. Background Technology

[0002] With the acceleration of global industrialization, nitrogen and phosphorus pollution has become a key factor restricting water quality and ecosystem health. Nitrogen and phosphorus are among the main causes of eutrophication. Excessive nitrogen and phosphorus entering water bodies can lead to the proliferation of algae, disrupting the ecological balance of aquatic bodies and causing a series of environmental problems such as water quality deterioration and algal blooms.

[0003] Currently, the traditional method for nitrogen removal is mainly microbial denitrification. Microbial denitrification requires sufficient electron donors, usually carbon sources in wastewater. However, the lack of carbon sources in low C / N ratio wastewater limits its denitrification efficiency. Autotrophic denitrification technology using inorganic carbon sources as substrates offers a new approach to treating low C / N ratio wastewater. Research has found that using inorganic ions such as sulfur and iron as electron donors, and inorganic carbon compounds (bicarbonate, carbon dioxide) as carbon sources for sulfur autotrophic denitrification, iron autotrophic denitrification, and iron-mediated anaerobic ammonium oxidation can significantly improve the denitrification efficiency of wetlands for low C / N ratio wastewater. While using sulfur or iron alone as electron donors can improve the denitrification efficiency of low C / N ratio wastewater, it also leads to the accumulation of byproducts (sulfur autotrophic denitrification produces sulfate SO4). 2- Material failure (iron surfaces easily form oxide films, passivation hinders electron transfer), complex pH control (sulfur autotrophic denitrification reaction produces acid H+). + This leads to core bottlenecks such as a decrease in system pH. The synergistic effect of iron-sulfur multi-electron donors can overcome the limitations of traditional autotrophic denitrification, which relies on a single electron donor.

[0004] Traditionally, phosphorus removal methods include biological, chemical, and ecological methods. Biological methods rely on polyphosphate-accumulating bacteria to release phosphorus under anaerobic conditions and accumulate it under aerobic conditions. However, their phosphorus removal efficiency is relatively low, highly dependent on water quality conditions (such as temperature, pH, and dissolved oxygen), has a long treatment time, and is unstable, making it difficult to achieve complete compliance with discharge standards. Ecological methods require a large area, and their phosphorus removal efficiency is affected by factors such as season and water temperature, resulting in limited removal effects. In contrast, chemical phosphorus removal utilizes the large specific surface area and high porosity of adsorbents, offering advantages such as high efficiency, speed, stability, and ease of operation. It can also respond quickly to changes in water quality and is suitable for various water quality conditions. Furthermore, chemical phosphorus removal removes phosphorus by forming insoluble precipitates, avoiding secondary pollution. The phosphorus removal effect can be precisely controlled by adjusting the dosage of chemical reagents, which is particularly important for situations requiring rapid compliance with discharge standards.

[0005] While sulfur minerals possess some potential for phosphorus removal as adsorbents, they suffer from drawbacks such as low adsorption capacity, difficulty in treating high-concentration phosphorus pollution, easy oxidation leading to a reduction in adsorption sites and efficiency, and potential secondary pollution; easy surface coverage by impurities further weakening adsorption capacity; poor regenerability and difficulty in reuse, increasing costs and wasting resources. They also exhibit poor affinity for microorganisms.

[0006] Therefore, developing a high-efficiency, low-cost, and environmentally friendly nitrogen and phosphorus removal material that provides an iron-sulfur multi-electron donor for nitrogen removal and an adsorbent for phosphorus removal is of significant practical importance and has broad application prospects. This invention aims to provide a bio-sulfur-iron packing material for simultaneous nitrogen and phosphorus removal and its preparation method, to solve the problems existing in the prior art, improve the removal efficiency of nitrogen and phosphorus, reduce treatment costs, and provide a new technical means for water environment management. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a bio-sulfur iron packing material for simultaneous nitrogen and phosphorus removal and its preparation method, thereby solving the problems mentioned in the background art.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a bio-sulfur iron filler for simultaneous denitrification and phosphorus removal, comprising 38-45% bio-sulfur, 24-39% reduced iron powder, 20-25% low-alkali cement (strength grade 42.5), and 3-6% sodium silicate.

[0009] As a preferred embodiment of the present invention, the method for preparing the bio-sulfur is as follows:

[0010] Step 1: Take activated sludge from the sewage treatment plant, screen it and let it stand for 24 hours to make SS < 30g / L;

[0011] Step 2: Place it in an AFB reactor for sulfide acclimatization, initially adding 50 mg S. 2- / L, increase by 50mg / L every 7 days until the target concentration of 200mg / L is reached, during which sodium acetate (C source) is added to maintain C / S = 2:1; control pH 7.0-7.5 and temperature 25-30℃;

[0012] Step 3: Add nitrate NO3 - =100 mg / L enrichment of denitrifying sulfur bacteria, utilizing their metabolic characteristics of coupled sulfur oxidation and denitrification; simultaneously adding 50 mg / L of Ca 2+ 30 mg / L Mg 2+ This neutralizes the negative charge on the surface of microorganisms, ultimately forming biological desulfurization sludge;

[0013] Step 4: After natural settling, the bottom layer of biological desulfurization sludge is centrifuged for 10 minutes at a speed of 3000 r / min. After centrifugation, the sludge is evenly spread in an evaporating dish and placed in an oven to dry. To prevent sulfur sublimation, it is vacuum dried at 50℃ for 6 hours. The dried desulfurization sludge is then ground in a mortar and filtered through an 80-mesh sieve to ensure that the sludge particles are all below 0.2 mm, thereby obtaining biological sulfur.

[0014] A method for preparing a bio-sulfur-iron packing material for simultaneous nitrogen and phosphorus removal as described above, comprising the following specific steps:

[0015] Step 1: Prepare raw materials according to the proportions: pass reduced iron powder and biological sulfur through a 200-mesh sieve, and mix the reduced iron powder, biological sulfur, and low-alkali cement evenly in the proportions to form ash.

[0016] Step 2: Dissolve sodium silicate in deionized water to obtain an adhesive solution;

[0017] Step 3: Mix 50% of the ash and adhesive evenly to obtain the finished product;

[0018] Step 4: Start the granulator, add the modifier, and while the machine is running, evenly spray the binder solution to wet the surface of the modifier. Gradually add the remaining ash material until it adheres evenly to the surface and forms 7-9mm spherical fillers.

[0019] Step 5: Place it in an 85℃ constant temperature drying oven for 4 hours, then remove it and allow it to cure naturally at 25℃ for 7 days to obtain the bio-sulfur iron filler.

[0020] As a preferred technical solution of the present invention: in step two, the ratio of sodium silicate to water is 1:1.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. Cost-effectiveness and resource availability: The preparation of bio-sulfur iron filler uses low-cost raw materials such as bio-sulfur and iron, which significantly reduces production costs compared to materials such as clay and limestone used in the preparation of traditional fillers. These raw materials are easy to obtain, further simplifying the supply chain and improving production efficiency.

[0023] 2. Environmental friendliness: The preparation of this filler makes full use of bio-sulfur, reducing waste accumulation and environmental pollution. This process realizes resource recycling and reuse, which is in line with the concept of sustainable development and green chemistry, and is of great significance to promoting the development of environmentally friendly materials.

[0024] 3. Simplified process and low energy consumption: The preparation process is simple, without the need for complex production lines and high equipment investment. More importantly, the preparation process of this filler does not require high-temperature firing, which greatly reduces energy consumption and carbon emissions, demonstrating significant environmental friendliness and economy.

[0025] 4. Structural and performance advantages: The bio-sulfur iron packing has a porous structure, which provides abundant adsorption sites, enabling it to exhibit excellent adsorption performance in wastewater treatment and other fields.

[0026] 5. Innovative Design: This packing material cleverly combines the properties of bio-sulfur and iron. In this packing, bio-sulfur acts as an electron donor for denitrification, while iron achieves deep purification through phosphorus removal via precipitation and by promoting sulfur cycling. The two work synergistically to form a sulfur-iron electron chain, achieving simultaneous nitrogen and phosphorus removal from low-carbon wastewater. Through a unique formula and process, a new material that is both economical and environmentally friendly has been created. This innovative design provides a new direction for the development of packing materials and has broad application prospects. Attached Figure Description

[0027] Figure 1 This is a BET adsorption-desorption curve of the bio-sulfur iron packing material of the present invention;

[0028] Figure 2 This is a comparison image of the bio-sulfur iron packing material of the present invention before and after phosphate adsorption using scanning electron microscopy (SEM).

[0029] In the figure, (a) and (c) show the results before phosphate adsorption, and (b) and (d) show the results after phosphate adsorption.

[0030] Figure 3 This is a comparison of XRD patterns before and after phosphate adsorption in this invention.

[0031] Figure 4 This is a comparison of XRD patterns after phosphate adsorption according to the present invention;

[0032] Figure 5 These are FTIR images of the bio-sulfur iron packing material of the present invention before and after phosphate adsorption;

[0033] Figure 6 The isothermal adsorption curve of the bio-sulfur iron packing material of the present invention is shown.

[0034] Figure 7 This is an adsorption kinetic curve of the bio-sulfur iron packing material of the present invention. Detailed Implementation

[0035] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0036] Example: The present invention provides a technical solution: a bio-sulfur iron packing material for simultaneous nitrogen and phosphorus removal, specifically comprising: 38-45% bio-sulfur, 24-39% reduced iron powder, 20-25% low-alkali cement (strength grade 42.5), and 3-6% sodium silicate.

[0037] Methods for preparing bio-sulfur:

[0038] Step 1: Take activated sludge from the sewage treatment plant, screen it and let it stand for 24 hours to make SS < 30g / L;

[0039] Step 2: Place it in an AFB reactor for sulfide acclimatization, initially adding 50 mg S. 2- / L, increase by 50mg / L every 7 days until the target concentration of 200mg / L is reached, during which sodium acetate (C source) is added to maintain C / S = 2:1; control pH 7.0-7.5 and temperature 25-30℃;

[0040] Step 3: Add nitrate NO3 - =100 mg / L enrichment of denitrifying sulfur bacteria, utilizing their metabolic characteristics of coupled sulfur oxidation and denitrification; simultaneously adding 50 mg / L of Ca 2+ 30 mg / L Mg 2+ This neutralizes the negative charge on the surface of microorganisms, ultimately forming biological desulfurization sludge;

[0041] Step 4: After natural settling, the bottom layer of biological desulfurization sludge is centrifuged for 10 minutes at a speed of 3000 r / min. After centrifugation, the sludge is evenly spread in an evaporating dish and placed in an oven to dry. To prevent sulfur sublimation, it is vacuum dried at 50℃ for 6 hours. The dried desulfurization sludge is then ground in a mortar and filtered through an 80-mesh sieve to ensure that the sludge particles are all below 0.2 mm, thereby obtaining biological sulfur.

[0042] Biological sulfur verification experiment:

[0043] 0.01 g of recovered elemental sulfur was weighed and dissolved in 100 mL of tetrachloroethylene. The solution was then filtered through a 0.22 μm organic membrane. Chromatographic conditions were as follows: Agilent SB-C18 column (4.6 mm × 250 mm); mobile phase: methanol:water = 95:5; flow rate: 1 mL / min; injection volume: 10 μL; UV detector; detection wavelength: 263 nm; column temperature: 35 °C. Qualitative analysis was performed using peak retention time, and quantitative analysis was performed using peak area using the external standard method. The results showed that the peak at 10 min was elemental sulfur. The purity of elemental sulfur was calculated to be 98%.

[0044] Biological sulfur affinity experiment:

[0045] The specific procedure involves culturing denitrifying bacteria in a laboratory using ordinary culture medium. Biological sulfur and industrial sulfur are placed in conical flasks, and 100 mL of bacterial solution is added. Another 100 mL of bacterial solution is taken as a control group. The conical flasks are then placed in a constant temperature incubator at 30°C and shaken at 150 rpm for 24 hours. After removing the flasks and allowing the bacterial solution to return to room temperature, the bacterial concentration is measured at 660 nm using a spectrophotometer with the blank bacterial solution as a reference.

[0046] By comparing the absorbance values ​​before and after the addition of bio-sulfur, it was found that the absorbance of the bacterial solution with bio-sulfur was 1.103, the absorbance of the bacterial solution with industrial sulfur was 1.336, and the absorbance of the bacterial solution without bio-sulfur was 1.421. The concentration of the bacterial solution with industrial sulfur was higher than that with bio-sulfur. This indicates that more microorganisms adhered to the surface of bio-sulfur, suggesting that bio-sulfur has better affinity.

[0047] A method for preparing a bio-sulfur-iron packing material for simultaneous nitrogen and phosphorus removal as described above, comprising the following specific steps:

[0048] Step 1: Prepare raw materials according to the proportions: pass reduced iron powder and biological sulfur through a 200-mesh sieve, and mix the reduced iron powder, biological sulfur, and low-alkali cement evenly in the proportions to form ash.

[0049] Step 2: Dissolve sodium silicate in deionized water to obtain an adhesive solution, with a sodium silicate:water ratio of 1:1;

[0050] Step 3: Mix 50% of the ash and adhesive evenly to obtain the finished product;

[0051] Step 4: Start the granulator, add the modifier, and while the machine is running, evenly spray the binder solution to wet the surface of the modifier. Gradually add the remaining ash material until it adheres evenly to the surface and forms 7-9mm spherical fillers.

[0052] Step 5: Place it in an 85℃ constant temperature drying oven for 4 hours, then remove it and allow it to cure naturally at 25℃ for 7 days to obtain the bio-sulfur iron filler.

[0053] Validation of the optimal formulation:

[0054] Fifteen groups of samples were prepared according to the specified formulation. 1.0 g of each sample was weighed and placed in 100 mL of a 1.0 g / L phosphate solution, adjusting the pH to approximately 7.0. The samples were then placed in a constant-temperature shaker and shaken at 25°C and 120 rpm for 24 hours. The phosphorus removal efficiency of each group was calculated by measuring the phosphorus concentration in the supernatant, and the results are shown in Table 1.

[0055] Table 1: Raw Material Ratio and its Phosphorus Removal Effect

[0056] 1 38 39 20 3 88.3 2 42 30 23 5 98.1 3 45 24 25 6 90.2 4 50 15 25 10 33.6 5 30 50 15 5 51.8 6 40 35 21 4 92.4 7 38 24 30 8 62.0 8 43 28 24 5 94.1 9 47 22 18 13 28.4 10 35 45 18 2 67.9 11 48 20 27 5 33.1 12 42 40 18 0 41.5 13 42 18 35 5 45.9 14 38 20 30 12 58.6 15 36 42 17 5 69.9

[0057] The experimental results show that when the bio-sulfur content is >45%, the phosphorus removal rate is reduced by as much as 63.8%; when the reduced iron powder content is <24%, the phosphorus removal rate is reduced by as much as 51.3%; and when the low-alkali cement content is >25%, the phosphorus removal rate is reduced by 34.7%. Therefore, it can be concluded that the best phosphorus removal effect is achieved when the bio-sulfur content is 38-45%, the reduced iron powder content is 24-39%, the low-alkali cement content (P.O42.5) is 20-25%, and the sodium silicate content is 3-6%.

[0058] The following examples demonstrate its phosphorus removal effect:

[0059] Example 1: Structural Characterization

[0060] Raw material preparation: 20g bio-sulfur, 15g reduced iron powder, 12g low-alkali cement, 2.5g sodium silicate;

[0061] The above raw materials were made into ash and binder solution and put into a granulator. The particles larger than 5 mm were picked out by a sieve and cured at room temperature for 7 days to finally obtain sample 1.

[0062] like Figure 1 As shown, Figure 1 The BET adsorption-desorption curve of the bio-sulfur iron filler is shown. The specific surface area of ​​the material, obtained using a specific surface area analyzer, is 4.0064 m². 2 / g, Langmuir surface area is 48.32m² 2 The material has an average pore size of 26.50 nm, with a surface area of ​​ / g. This indicates that the material surface is predominantly mesoporous with uneven adsorption sites, which facilitates rapid mass transfer and makes it suitable for treating high-concentration phosphate wastewater. The adsorption-desorption curves do not overlap, forming an H3-type hysteresis loop (with a steeply closed desorption branch), suggesting that the pore structure may be a narrow slit pore formed by the accumulation of plate-like particles, where phosphate ions may be adsorbed through physical interception or weak chemical bonding. The steep decrease in the desorption curve within the P / P0 range of 0.45-0.5 suggests the presence of narrow ink bottle-shaped pores.

[0063] like Figure 2 As shown, Figure 2 Comparison of scanning electron microscopy (SEM) images of the bio-sulfur iron packing material before and after phosphate adsorption. Figure 2 In the diagram, (a) and (c) represent the state before phosphate adsorption. Figure 2 (b) and (d) in the figure represent the adsorption of phosphate.

[0064] Before adsorption: The surface exhibits "island-like" protrusions and bottle-shaped pores. This open pore structure is conducive to the diffusion of the adsorbate (phosphate). The surface particles are irregularly stacked in sheets, with weak interparticle bonding and obvious grain boundary gaps. This is consistent with the "mesoporous structure and ink bottle pores" result obtained by the specific surface area analyzer.

[0065] After adsorption: A large number of submicron-sized particles (100-500 nm) were deposited on the surface, partially covering the original pore structure. The particle packing density was significantly increased, forming a dense "coral reef"-like composite structure. This indicates that phosphate is adsorbed through physical retention and chemical bonding, which is consistent with the above results obtained by using a surface area analyzer. The "H3-type hysteresis ring (steeply closed desorption branch)" indicates that the pore structure may be a narrow pore formed by the accumulation of plate-like particles, and phosphate ions may be adsorbed through physical retention or weak chemical bonding.

[0066] pass Figure 3 , Figure 4 Comparative analysis revealed that Kidwellite and Brushite were formed after adsorption. This indicates that the material achieves phosphate adsorption through chemical precipitation and ion exchange. 3+ and Ca 2+ Sodium silicate reacts with phosphate to form sodium hydroxyapatite and calcium phosphate, respectively, thus fixing the phosphate by forming insoluble minerals; sodium silicate provides Na + with Fe 3+ / Ca 2+ Exchange promotes phosphate release and participation in the precipitation reaction. This is consistent with the results obtained from the above characterization analysis. After adsorption, the surface pores are covered, and submicron-sized particles are deposited, corresponding to the formation of sodium hydroxyapatite and calcium phosphate microcrystals (chemical precipitation products).

[0067] like Figure 5 As shown, by comparing the adsorption of phosphate before and after, it can be concluded that phosphate adsorption is achieved through ion exchange (PO4). 3- Replace SiO4 4- Chemical precipitation (Ca-P formation) disrupted the silicate network, resulting in a 1108.4 cm⁻¹. -1 The peak disappeared; the original height was 610.5 cm. -1 Ca disappears in low-alkali cement 2+ The formation of calcium phosphate with phosphate leads to a shift in the Ca-O peak, adding 456.7 cm⁻¹. -1 The characteristic peaks of the Fe-PO bond confirm the formation of sodium hydroxyphosphorus iron.

[0068] Example 2:

[0069] Weigh out 40g of bio-sulfur, 30g of reduced iron powder, 20g of low-alkali cement, and 5g of sodium silicate. Prepare the above raw materials into a granulator and binder solution, then place them into a granulator. Use a sieve to remove particles larger than 5mm, and cure at room temperature for 7 days to obtain sample 2.

[0070] Isothermal adsorption experiments were conducted on sample 2. A series of 100 ml phosphate solutions with concentrations of 50, 100, 150, 200, 400, 800, 1200, 2000, 4000, 5000, and 8000 mg / L were prepared. 2 g of sample 2 was added to each of the above solutions. The pH of the solutions was adjusted to approximately 7. The solutions were then placed in a constant temperature shaker (25℃, 120 rpm) and shaken for 24 h. Samples were then taken, and the phosphorus concentration in the supernatant was measured.

[0071] from Figure 6 As shown, the Sips model obtained after data processing has the highest fitting accuracy (R²). 2 =0.97333), indicating that the adsorption behavior of phosphate in sample 2 is neither pure monolayer adsorption nor pure multilayer adsorption. In the low concentration region (Ce < 1000 mg / L), the adsorption behavior is close to the Langmuir model (monolayer adsorption is dominant), with homogeneous sites on the surface being rapidly occupied. In the high concentration region (Ce > 1000 mg / L), the adsorption behavior approaches the Freundlich model (multilayer adsorption or heterogeneous surface interaction), possibly due to enhanced intermolecular interactions of the adsorbate or pore-filling effects at high concentrations. This indicates the existence of heterogeneous adsorption sites on the material surface (e.g., Fe). 3+ Ca 2+ Si-O - The coexistence of [elements] still demonstrates high adsorption potential in the treatment of high-concentration phosphate wastewater. This is consistent with the results obtained above from high Langmuir surface area.

[0072] Example 3: Weigh out 10.525g of bio-sulfur, 7.5g of reduced iron powder, 5.725g of low-alkali cement, and 1.25g of sodium silicate. Prepare the above raw materials into ash and binder solution, place them in a granulator, use a sieve to remove particles larger than 5mm, and cure at room temperature for 7 days to obtain sample 3.

[0073] Adsorption kinetics experiments were conducted on sample 3. Several 100 ml solutions of 5 g / L phosphate were prepared, and 2 g of sample 3 was added to each solution. The solution was adjusted to pH 7 and placed in a constant temperature shaker (25℃, 120 rpm) for 5 min, 15 min, 30 min, 1 h, 2 h, 4 h, 8 h and 24 h. Samples were then taken and the phosphorus concentration in the supernatant was measured.

[0074] like Figure 7 As shown, after data processing, it was found that the adsorption process involves both physical and chemical adsorption processes, and the pseudo-second-order kinetic model has a better fit (R0). 2 =0.98793), and the theoretical maximum adsorption capacity is 71.33017 mg / g. Within the initial 2 hours, the adsorption capacity (Qe) can rapidly increase to 80% of the total adsorption capacity; its high performance originates from Ca. 2+ Precipitation and Fe3+ The complexation synergistic mechanism is suitable for the rapid treatment of medium- to high-concentration phosphate wastewater.

[0075] Example 4: Actual Wastewater Treatment Experiment

[0076] The reactor was filled with packing material and inoculated with desulfurizing bacteria for 10 days. Then, the treated wastewater from mandarin fish farming was introduced. Under a hydraulic retention time of 24 hours, the total nitrogen concentration in the wastewater decreased from 34.92 mg / L to 2.91 mg / L (removal rate 91.7%), and the total phosphorus concentration decreased from 2.72 mg / L to 0.11 mg / L (removal rate 95.59%). The effluent quality met the Class I standard of the "Jiangsu Province Pond Aquaculture Wastewater Discharge Standard" (DB 32 / 4043-2021).

[0077] The above embodiments merely illustrate implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A bio-sulfur iron packing material for simultaneous nitrogen and phosphorus removal, characterized in that: It includes 38-45% bio-sulfur, 24-39% reduced iron powder, 20-25% low-alkali cement, and 3-6% sodium silicate, with the low-alkali cement having a strength grade of 42.

5.

2. The bio-sulfur iron packing material for simultaneous nitrogen and phosphorus removal according to claim 1, characterized in that: The method for preparing the bio-sulfur: Step 1: Take activated sludge from the sewage treatment plant, screen it and let it stand for 24 hours to make SS < 30g / L; Step 2: Place it in an AFB reactor for sulfide acclimatization, with an initial addition of 50 mg S. 2- / L, increase by 50mg / L every 7 days until the target concentration of 200 mg / L is reached, during which sodium acetate is added to maintain C / S=2:1; control pH 7.0-7.5 and temperature 25-30℃; Step 3: Add nitrate NO3 - =100 mg / L enriched denitrifying sulfur bacteria, utilizing their metabolic characteristics of coupled sulfur oxidation and denitrification; simultaneously added 50 mg / L Ca 2+ 30 mg / L Mg 2+ This neutralizes the negative charge on the surface of microorganisms, ultimately forming biological desulfurization sludge; Step 4: After natural settling, the bottom layer of biological desulfurization sludge is centrifuged for 10 minutes at a speed of 3000 r / min. After centrifugation, the sludge is evenly spread in an evaporating dish and placed in an oven to dry the moisture. To prevent sulfur sublimation, it is vacuum dried at 50℃ for 6 hours. The dried desulfurization sludge is then ground in a mortar and then filtered through an 80-mesh sieve to ensure that the sludge particles are all below 0.2 mm, thereby obtaining biological sulfur.

3. A method for preparing a bio-sulfur-iron packing material for simultaneous nitrogen and phosphorus removal as described in any one of claims 1-2, characterized in that: The specific steps are as follows: Step 1: Prepare raw materials according to the proportions: pass reduced iron powder and biological sulfur through a 200-mesh sieve, and mix the reduced iron powder, biological sulfur, and low-alkali cement evenly in the proportions to form ash. Step 2: Dissolve sodium silicate in deionized water to obtain an adhesive solution; Step 3: Mix 50% of the ash and adhesive evenly to obtain the finished product; Step 4: Start the granulator, add the modifier, and while the machine is running, evenly spray the binder solution to wet the surface of the modifier. Gradually add the remaining ash material until it adheres evenly to the surface and forms 7-9mm spherical fillers. Step 5: Place it in an 85℃ constant temperature drying oven for 4 hours, then remove it and allow it to cure naturally at 25℃ for 7 days to obtain the bio-sulfur iron filler.

4. The preparation method of the bio-sulfur-iron packing material for simultaneous nitrogen and phosphorus removal according to claim 3, characterized in that: In step two, the ratio of sodium silicate to water is 1:1.

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