A sulfur autotrophic denitrification process
By preparing a porous ceramic carrier combined with inorganic energy materials and denitrifying bacteria, the problems of high production cost and poor hydrophilicity of sulfur autotrophic denitrification packing were solved, achieving efficient denitrification and a stable pH environment, and shortening the system commissioning time.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG ZONE KING ENVIRONMENTAL SCI&TECH CO LTD
- Filing Date
- 2026-05-25
- Publication Date
- 2026-06-30
AI Technical Summary
Existing sulfur-autotrophic denitrification packing materials have high production costs, difficulty in adjusting water quality changes, and poor hydrophilicity and biological affinity, resulting in low nitrogen removal efficiency and long system commissioning cycles.
Hydroxyapatite powder was synthesized using calcium nitrate tetrahydrate and ammonium dihydrogen phosphate under alkaline conditions. A porous ceramic carrier was prepared by combining it with a foaming agent, foam stabilizer, and adhesive. Inorganic energy substances and denitrifying bacteria were added to form a biofilm, which buffered the pH value and improved hydrophilicity.
It enables in-situ generation of denitrifying bacteria, improves nitrogen removal efficiency, maintains pH stability, enhances biofilm adhesion, and shortens the system commissioning cycle.
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This application relates to the field of wastewater treatment, and in particular to a sulfur autotrophic denitrification process. Background Technology
[0002] Sulfur autotrophic denitrification is an emerging biological denitrification technology with advantages such as low operating cost, high denitrification performance, strong resistance to shock loads, and wide applicability. Due to its unique advantages, it has received widespread attention and application in the field of wastewater treatment.
[0003] The key to sulfur autotrophic denitrification technology is the sulfur autotrophic denitrification packing material. Its function is mainly achieved through two aspects: microbial attachment and electron donor supply. On the one hand, the packing material provides a living carrier for sulfur autotrophic denitrifying bacteria, enabling them to form a biofilm. On the other hand, the sulfur source in the packing material acts as an electron donor, promoting the denitrifying bacteria to reduce nitrate nitrogen in the water to nitrogen gas.
[0004] The manufacturing process of conventional sulfur autotrophic denitrification packing has the following drawbacks: First, the production process is relatively complex, inevitably requiring steps such as heating and granulation, resulting in high production costs. Second, after the packing is formed, the ratio between the sulfur source and alkalinity regulator in the packing is fixed. When the influent water quality fluctuates, it is difficult to make flexible and effective adjustments, often resulting in pH levels that are too low or too high, affecting the activity of denitrifying bacteria and nitrogen removal efficiency. Third, in practical applications, conventional inorganic packing has poor hydrophilicity and biocompatibility, and the inoculated sulfur autotrophic denitrifying bacteria often require a long time to form a stable biofilm on the packing surface, leading to a long system commissioning cycle. Summary of the Invention
[0005] In order to improve the shortcomings of existing sulfur autotrophic denitrification processes, this application provides a sulfur autotrophic denitrification process.
[0006] This application provides a sulfur autotrophic denitrification process for nitrogen removal, which adopts the following technical solution: A sulfur autotrophic denitrification process includes the following specific steps: S1: After adjusting the pH of calcium nitrate tetrahydrate solution and ammonium dihydrogen phosphate solution to alkaline, triethanolamine is added dropwise to the calcium nitrate solution, followed by the addition of ammonium dihydrogen phosphate solution to form a reaction solution. The pH of the reaction solution is maintained at alkaline, and the reaction is heated. After filtration, washing, and drying, hydroxyapatite powder is obtained. The hydroxyapatite powder is mixed with a foaming agent, foam stabilizer, and adhesive, pressed into shape, and sintered to obtain a porous ceramic carrier. S2: Add porous ceramic carrier, ground inorganic energy material, and denitrifying bacteria to the wastewater to be treated, mix them, and then perform a simmering and aeration treatment. Regularly replenish the inorganic energy material to complete the sulfur autotrophic denitrification process.
[0007] By adopting the above technical solution, after a period of use, only inorganic energy materials need to be added; there is no need to add denitrifying bacteria. The denitrifying bacteria in the system will quickly attach to the surface of the porous ceramic carrier and proliferate. The inorganic energy materials, acting as electron donors, directly convert nitrate nitrogen in the wastewater into harmless nitrogen gas, completing denitrification. The pores of the porous ceramic carrier can trap denitrifying bacteria, forming a biofilm to prevent bacterial loss. Simultaneously, it can adsorb nitrate nitrogen and phosphate in the wastewater, first adsorbing and then biodegrading them. This neutralizes the acid produced by sulfur oxidation during sulfur autotrophic denitrification, preventing the system pH from becoming too low and inhibiting bacterial enzyme activity, thus maintaining the activity of denitrifying bacteria and denitrification efficiency.
[0008] Hydroxyapatite is synthesized from calcium nitrate tetrahydrate solution and ammonium dihydrogen phosphate solution under alkaline conditions. The surface contains hydroxyl and phosphate groups, which can promote the high hydrophilicity of the prepared porous ceramic carrier, which is beneficial to improve the attachment and adsorption of denitrifying bacteria. At the same time, it can also buffer the acidity generated in the sulfur autotrophic denitrification process, maintain the pH stability of the system, and avoid acidification that inhibits bacterial activity.
[0009] By combining foaming agents, foam stabilizers, and adhesives with hydroxyapatite powder, the foaming agent decomposes upon heating during subsequent sintering to generate gas, forming interconnected pores within the ceramic and increasing the specific surface area and adsorption capacity. The foam stabilizer fixes the pore structure, preventing pore collapse and merging during sintering, thus avoiding closed-cell and dead-pore phenomena in the prepared porous ceramic carrier. The adhesive binds the hydroxyapatite powder particles, assisting in the solid-phase sintering of the particles during sintering and improving the overall compressive strength and mechanical strength of the ceramic carrier.
[0010] Preferably, the inorganic energy material includes sulfur powder, calcium carbonate and pyrite, and the volume ratio of sulfur powder, calcium carbonate and pyrite in the inorganic energy material is (5-8):1:(5-10).
[0011] By employing the above technical solution, calcium carbonate can slowly dissolve and release alkalinity, stabilizing the pH of the reaction system within the suitable weakly alkaline range for microorganisms. Simultaneously, calcium carbonate can dissolve calcium ions, which can precipitate phosphates in wastewater, aiding in phosphorus removal. Furthermore, calcium ions can enhance microbial flocculation and facilitate biofilm adhesion on the ceramic carrier. Pyrite and sulfur powder can serve as sulfur sources, participating in sulfur autotrophic denitrification, supplementing electron donors, and improving total nitrogen removal capacity and efficiency.
[0012] Preferably, the aeration time is 5-7 days, and the denitrifying bacteria are Thiobacillus.
[0013] Preferably, the heating reaction temperature in step S1 is 70-80℃, and the calcination temperature is 600-800℃.
[0014] Preferably, the mass ratio of calcium nitrate tetrahydrate, ammonium dihydrogen phosphate, and triethanolamine in the hydroxyapatite powder raw material is (3-5):1:(0.1-0.3).
[0015] Preferably, the porous ceramic carrier comprises the following raw materials in parts by weight: 5-8% foaming agent, 10-15% foam stabilizer, 8-12% adhesive, and the balance being hydroxyapatite powder.
[0016] Preferably, the foaming agent is one of potassium lauryl sulfate and sodium dodecyl sulfate, the foam stabilizer is one of carboxymethyl cellulose and xanthan gum, and the adhesive is water-soluble silica gel.
[0017] By adopting the above technical solution, the foaming agent is responsible for creating small and uniform bubbles, the foam stabilizer is responsible for stabilizing the bubbles to prevent them from collapsing and maintaining their shape, and the water-soluble silica gel is responsible for bonding and molding at room temperature and sintering at high temperature to strengthen the structure. The three work together to make the prepared porous ceramic carrier have the advantages of high porosity, uniform pore connectivity, and high strength.
[0018] Preferably, the porous ceramic carrier surface is coated with a polydopamine coating, which includes the following specific steps: immersing the porous ceramic carrier in a polydopamine solution, shaking and mixing to react, ultrasonically washing, and then drying.
[0019] By adopting the above technical solution, polydopamine contains catechol groups, which enhances the hydrophilicity of the ceramic carrier surface and the adhesion between particles, enhances the adsorption capacity of the ceramic carrier for nitrate nitrogen, phosphate and organic matter, improves the adhesion of bacteria on the ceramic carrier, provides active functional group anchoring points for subsequent microbial fixation, and promotes the formation of biofilm with strong adhesion and is not easy to fall off.
[0020] Preferably, the mass concentration of the polydopamine solution is (2-5) g / L.
[0021] Preferably, the polydopamine coating has a thickness of 50-100 nm.
[0022] In summary, this application has the following beneficial effects: 1. Since the sulfur autotrophic denitrification process used in this application does not require the additional addition of denitrifying bacteria, the denitrifying bacteria in the reaction system can be generated in situ, requiring only the addition of inorganic energy substances. The porous ceramic carrier prepared by combining foaming agents, foam stabilizers, adhesives, and hydroxyapatite powder has good hydrophilicity, which is conducive to the attachment and adsorption of denitrifying bacteria. It can also buffer the acidity generated in the sulfur autotrophic denitrification process, maintain the pH stability of the system, and avoid acidification that inhibits bacterial activity.
[0023] 2. In this application, potassium laurate and sodium dodecyl sulfate are used as foaming agents, carboxymethyl cellulose and xanthan gum are used as foam stabilizers, and water-soluble silica gel is used as an adhesive. Their synergistic effect results in a porous ceramic carrier with high porosity, uniform pore connectivity, and high strength. The surface of the porous ceramic carrier is coated with polydopamine, which enhances the hydrophilicity of the ceramic carrier surface and the adhesion between particles, thereby strengthening the adhesion of subsequent microorganisms to the ceramic carrier surface and resulting in a biofilm with strong adhesion and resistance to detachment. Detailed Implementation
[0024] The present application will be further described in detail below with reference to the embodiments.
[0025] All raw materials used in the examples are commercially available. Example Example 1
[0026] This embodiment provides a sulfur autotrophic denitrification process. The porous ceramic carrier includes the following raw materials in parts by weight: 7% foaming agent, 13% foam stabilizer, 10% adhesive, and the balance being hydroxyapatite powder; wherein the foaming agent is potassium laurate, the foam stabilizer is carboxymethyl cellulose, and the adhesive is water-soluble silica gel.
[0027] A sulfur autotrophic denitrification process includes the following specific steps: S1: The pH of a 0.5 mol / L calcium nitrate tetrahydrate solution and a 0.3 mol / L ammonium dihydrogen phosphate solution was adjusted to 10 using ammonia. Triethanolamine was added dropwise to the calcium nitrate solution, followed by the addition of ammonium dihydrogen phosphate solution. The mass ratio of calcium nitrate tetrahydrate, ammonium dihydrogen phosphate, and triethanolamine was 4:1:0.2 to form a reaction solution. The pH of the reaction solution was maintained at 11 using ammonia. The solution was heated to 75°C and reacted for 5 hours. After standing for 24 hours, the solution was filtered, washed, and dried to obtain hydroxyapatite powder. The hydroxyapatite powder was mixed with a foaming agent, a foam stabilizer, and an adhesive, pressed into shape, and sintered at 700°C to obtain a porous ceramic carrier with an average pore size of 50 nm.
[0028] S2: Mix and grind sulfur powder, calcium carbonate and pyrite in a volume ratio of 7:1:8 to form an average particle size of 300 mesh. Add porous ceramic carrier, ground inorganic energy material and denitrifying bacteria to the wastewater to be treated. The initial concentration of inorganic energy material in the wastewater is 20 g / L. The denitrifying bacteria are Thiobacillus. Aerate for 6 days and replenish inorganic energy material regularly to complete the sulfur autotrophic denitrification process.
[0029] Example 2
[0030] The difference between Example 2 and Example 1 is that the volume ratio of sulfur powder, calcium carbonate and pyrite in the inorganic energy material is 5:1:10.
[0031] Example 3 The difference between Example 3 and Example 1 is that the volume ratio of sulfur powder, calcium carbonate and pyrite in the inorganic energy material is 8:1:5.
[0032] Example 4 The difference between Example 4 and Example 1 is that the mass ratio of calcium nitrate tetrahydrate, ammonium dihydrogen phosphate, and triethanolamine in the hydroxyapatite powder raw material is 3:1:0.3.
[0033] Example 5 The difference between Example 5 and Example 1 is that the mass ratio of calcium nitrate tetrahydrate, ammonium dihydrogen phosphate, and triethanolamine in the hydroxyapatite powder raw material is 5:1:0.1.
[0034] Example 6 The difference between Example 6 and Example 1 is that the porous ceramic carrier includes the following raw materials in parts by weight: 5% foaming agent, 10% foam stabilizer, 12% adhesive, and the balance being hydroxyapatite powder.
[0035] Example 7 The difference between Example 7 and Example 1 is that the porous ceramic carrier includes the following raw materials in parts by weight: 8% foaming agent, 15% foam stabilizer, 8% adhesive, and the balance being hydroxyapatite powder.
[0036] Example 8 The difference between Example 8 and Example 1 is that the porous ceramic carrier surface is coated with polydopamine.
[0037] A sulfur autotrophic denitrification process includes the following specific steps: S1: The pH of a 0.5 mol / L calcium nitrate tetrahydrate solution and a 0.3 mol / L ammonium dihydrogen phosphate solution was adjusted to 10 using ammonia. Triethanolamine was added dropwise to the calcium nitrate solution, followed by the addition of ammonium dihydrogen phosphate solution. The mass ratio of calcium nitrate tetrahydrate, ammonium dihydrogen phosphate, and triethanolamine was 4:1:0.2 to form a reaction solution. The pH of the reaction solution was maintained at 11 using ammonia. The solution was heated to 75°C and reacted for 5 hours. After standing for 24 hours, the solution was filtered, washed, and dried to obtain hydroxyapatite powder. The hydroxyapatite powder was mixed with a foaming agent, a foam stabilizer, and an adhesive, pressed into shape, and sintered at 700°C to obtain a porous ceramic carrier with an average pore size of 50 nm.
[0038] S2: The porous ceramic carrier is immersed in a polydopamine-tris(hydroxymethyl)aminomethane solution. The CAS number of polydopamine is 51-61-6. The polydopamine solution just submerges the porous ceramic carrier. The mass concentration of the polydopamine solution is 3 g / L. The mixture is shaken and reacted for 24 hours. After ultrasonic washing and drying, a polydopamine coating with an average thickness of 80 nm is formed on the surface of the porous ceramic carrier.
[0039] S3: Mix and grind sulfur powder, calcium carbonate and pyrite in a volume ratio of 7:1:8 to form an average particle size of 300 mesh. Add a porous ceramic carrier with a composite polydopamine coating, the ground inorganic energy material and denitrifying bacteria to the wastewater to be treated. The initial concentration of the inorganic energy material in the wastewater is 20 g / L. The denitrifying bacteria are Thiobacillus. Aerate for 6 days and replenish the inorganic energy material regularly to complete the sulfur autotrophic denitrification process.
[0040] Example 9 The difference between Example 9 and Example 8 is that the mass concentration of the polydopamine solution in the composite polydopamine coating process on the porous ceramic carrier surface is 2 g / L.
[0041] Example 10 The difference between Example 10 and Example 8 is that the mass concentration of the polydopamine solution in the composite polydopamine coating process on the porous ceramic carrier surface is 5 g / L.
[0042] Comparative Example Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the sulfur autotrophic denitrification process includes the following specific steps: Sulfur powder, calcium carbonate, and pyrite are mixed and ground in a volume ratio of 7:1:8 to form an inorganic energy material with an average particle size of 300 mesh. Porous ceramics, the ground inorganic energy material, and denitrifying bacteria are then added to the wastewater to be treated. The porous ceramics are ordinary commercially available alumina ceramics with an average pore size of 50 nm. The initial concentration of the inorganic energy material in the wastewater is 20 g / L. The denitrifying bacteria are Thiobacillus. The mixture is aerated for 6 days, and the inorganic energy material is replenished periodically to complete the sulfur autotrophic denitrification process.
[0043] Performance testing Based on the sulfur autotrophic denitrification process provided in Examples 1-10 and Comparative Example 1 of this application, the following performance tests were conducted, and the specific test results are shown in Table 1.
[0044] Detection methods I. Denitrification rate The wastewater from a rural area was treated for denitrification. The average total nitrogen content of the raw wastewater was 14.5 mg / L, and the average total phosphorus content was 20 mg / L. The sulfur autotrophic denitrification process provided in this application was used, with continuous influent and the effluent flow rate adjusted to the target treatment volume of 15,000 m³ / L. 3 / d, the total nitrogen and total phosphorus concentrations in the water were detected, and the total nitrogen concentration in the effluent after 30 days of continuous treatment was calculated to determine the total nitrogen removal rate.
[0045] Table 1: Performance Test Results Data Table
[0046] The performance test results show that the sulfur autotrophic denitrification process used in this application can achieve a total nitrogen removal rate of over 90% and a total phosphorus removal rate of over 80%, indicating that the sulfur autotrophic denitrification process used in this application has a good removal effect and can achieve the TN treatment target. It also has a removal effect on COD, suspended solids, and TP. A comparison between Comparative Example 1 and Example 1 shows that Comparative Example 1 uses conventional commercially available alumina ceramics, and the performance test results show that the dechlorination effect decreases, and the denitrification efficiency drops significantly after a certain period of operation. This further demonstrates that the porous ceramic carrier prepared by combining the components in this application can adsorb nitrate nitrogen and phosphate in wastewater, neutralize the acid produced by sulfur oxidation during sulfur autotrophic denitrification, avoid excessively low pH inhibiting bacterial enzyme activity, retain denitrifying bacteria, form a biofilm, prevent bacterial loss, and prolong the denitrification effect.
[0047] As can be seen from Examples 8-10, the composite polydopamine coating on the surface of the porous ceramic carrier further enhances the denitrification effect in wastewater treatment, as shown by the performance test results. This further illustrates that the hydrophilicity of the polydopamine-coated ceramic carrier surface and the adhesion between particles promote the formation of a biofilm with strong adhesion and resistance to detachment.
[0048] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A sulfur autotrophic denitrification process for nitrogen removal, characterized in that, The specific steps include the following: S1: After adjusting the pH of calcium nitrate tetrahydrate solution and ammonium dihydrogen phosphate solution to alkaline, triethanolamine is added dropwise to the calcium nitrate solution, followed by the addition of ammonium dihydrogen phosphate solution to form a reaction solution. The pH of the reaction solution is maintained at alkaline, and the reaction is heated. After filtration, washing, and drying, hydroxyapatite powder is obtained. The hydroxyapatite powder is mixed with a foaming agent, foam stabilizer, and adhesive, pressed into shape, and sintered to obtain a porous ceramic carrier. S2: Add porous ceramic carrier, ground inorganic energy material, and denitrifying bacteria to the wastewater to be treated, mix them, and then perform a simmering and aeration treatment. Regularly replenish the inorganic energy material to complete the sulfur autotrophic denitrification process.
2. The sulfur autotrophic denitrification process according to claim 1, characterized in that, The inorganic energy material includes sulfur powder, calcium carbonate and pyrite, and the volume ratio of sulfur powder, calcium carbonate and pyrite in the inorganic energy material is (5-8):1:(5-10).
3. The sulfur autotrophic denitrification process according to claim 1, characterized in that, The aeration time is 5-7 days, and the denitrifying bacteria are Thiobacillus.
4. The sulfur autotrophic denitrification process according to claim 1, characterized in that, In step S1, the heating reaction temperature is 70-80℃, and the calcination temperature is 600-800℃.
5. The sulfur autotrophic denitrification process according to claim 1, characterized in that, The mass ratio of calcium nitrate tetrahydrate, ammonium dihydrogen phosphate, and triethanolamine in the hydroxyapatite powder raw material is (3-5):1:(0.1-0.3).
6. The sulfur autotrophic denitrification process according to claim 5, characterized in that, The porous ceramic carrier comprises the following raw materials in parts by weight: 5-8% foaming agent, 10-15% foam stabilizer, 8-12% adhesive, and the balance being hydroxyapatite powder.
7. The sulfur autotrophic denitrification process according to claim 6, characterized in that, The foaming agent is one of potassium lauryl sulfate and sodium dodecyl sulfate, the foam stabilizer is one of carboxymethyl cellulose and xanthan gum, and the adhesive is water-soluble silica gel.
8. The sulfur autotrophic denitrification process according to claim 6, characterized in that, The porous ceramic carrier surface is coated with a polydopamine coating, which includes the following specific steps: immersing the porous ceramic carrier in a polydopamine solution, shaking and mixing to react, ultrasonically washing, and then drying.
9. The sulfur autotrophic denitrification process according to claim 8, characterized in that, The mass concentration of the polydopamine solution is (2-5) g / L.
10. The sulfur autotrophic denitrification process according to claim 8, characterized in that, The thickness of the polydopamine coating is 50-100 nm.