Method for enhancing denitrification by anaerobic ammonia oxidation by using iron-loaded polyurethane porous material
By loading Fe(OH)3 colloid and active iron onto polyurethane sponge and modifying the polyurethane material with mixed iron salts, the problems of slow microbial enrichment and low denitrification efficiency in the anaerobic ammonia oxidation process were solved, achieving rapid start-up and high-efficiency denitrification.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN INST OF TECH
- Filing Date
- 2025-08-11
- Publication Date
- 2026-05-26
AI Technical Summary
In existing anaerobic ammonia oxidation processes, the accumulation of functional microorganisms is slow and easily lost, the start-up period is long and the denitrification efficiency is unstable. The hydrophobicity of the polyurethane carrier surface and the lack of active sites limit the directional accumulation of microorganisms. Traditional modification methods result in uneven distribution of active sites and low electron transfer efficiency.
Polyurethane porous materials modified with mixed iron salts were used. Fe(OH)3 colloid and active iron such as α-Fe2O3 and γ-FeOOH were loaded onto polyurethane sponge through hydrothermal synthesis to enhance the adhesion ability of microorganisms. Combined with hydrothermal synthesis, the crystal form and dispersibility of iron oxides were optimized to form more active sites and improve the hydrophilicity and specific surface area of the carrier.
It significantly improved the affinity of anaerobic ammonia-oxidizing bacteria, shortened the system start-up time, increased the removal rates of NH4+-N, NO2--N and total nitrogen, enhanced the electron transfer efficiency, and avoided excessive iron release and damage to the carrier structure.
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Figure CN120774565B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method for enhancing anaerobic ammonia oxidation denitrification using iron-loaded polyurethane porous materials. Background Technology
[0002] Anaerobic ammonia oxidation (AAO) has become the mainstream nitrogen removal technology in wastewater treatment due to its advantages such as requiring no carbon source and producing less sludge. However, in practical applications, it still faces problems such as slow accumulation and easy loss of functional microorganisms, long start-up cycles, and unstable nitrogen removal efficiency.
[0003] The performance of the carrier directly affects the attachment and metabolic activity of microorganisms. Polyurethane is widely used due to its porous structure (porosity >85%) and high mechanical strength, but its surface hydrophobicity and lack of active sites limit the targeted enrichment of functional bacterial communities. In microbial cells, iron has a significant impact on enzyme synthesis, activity, and transcriptional regulation. Existing polyurethane carrier modification methods mostly employ impregnation and chemical precipitation techniques to load active substances (such as activated carbon or iron powder), resulting in uneven distribution of active sites, low electron transfer efficiency, high iron dissolution rate, and unstable denitrification effect. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by proposing a method for enhancing anaerobic ammonia oxidation denitrification using iron-loaded polyurethane porous materials. This effectively solves problems such as poor carrier performance, low denitrification efficiency of anaerobic ammonia oxidation technology, and slow microbial enrichment.
[0005] The purpose of this invention is to provide a method for enhancing anaerobic ammonia oxidation denitrification using iron-loaded polyurethane porous materials. The method involves thoroughly mixing anaerobic ammonia oxidation sludge, iron-loaded polyurethane porous materials, and wastewater containing ammonia nitrogen and nitrite nitrogen in an anaerobic ammonia oxidation reactor, and then reacting the mixture under anaerobic conditions at a temperature of 31-35°C.
[0006] The preparation method of iron-loaded polyurethane porous material is as follows:
[0007] Polyurethane sponge was selected as the carrier. After cutting and cleaning, it was placed in a mixed iron salt solution for impregnation and stirring for a period of time. The pH of the mixed solution was adjusted to alkaline, and a red precipitate was generated. Then, iron-loaded polyurethane porous material was synthesized by hydrothermal synthesis.
[0008] The mixed iron salt solution includes ferric chloride and ferric nitrate.
[0009] Further, cut it into cubes with sides of 1-3cm.
[0010] Furthermore, the mixed iron salt solution comprises FeCl3·6H2O and Fe(NO3)3·9H2O in a molar ratio of 2:1.
[0011] Furthermore, the iron concentration in the mixed iron salt solution is 0.1~1.0 mol / L.
[0012] Furthermore, the impregnation stirring rate is 150~250 r / min, and the stirring time is 1~3 h.
[0013] Further, adjusting the pH of the solution to 9-11, the red precipitate is ferric hydroxide.
[0014] Furthermore, the hydrothermal synthesis in step S1 uses a high-pressure reactor lined with polytetrafluoroethylene, with a reaction temperature of 105~120℃ and a reaction time of 6~12 h.
[0015] Furthermore, the anaerobic ammonia oxidation reactor includes one of an upflow anaerobic reactor or a sequencing batch reactor.
[0016] Furthermore, the volume of the iron-loaded polyurethane porous material added is 25-75% of the volume of the anammox sludge in the reactor.
[0017] Furthermore, NH4 + -N removal rate greater than 95%, NO2 - -N removal rate greater than 95%, total nitrogen removal rate greater than 85%.
[0018] This invention employs a mixture of ferric salts, ferric chloride and ferric nitrate, for modification. Ferric nitrate, as a strong oxidant, promotes the oxidation of the polyurethane surface, forming more active sites and thus enhancing the adhesion ability of microorganisms. The Fe(OH)3 colloid generated by the hydrolysis of ferric chloride carries a positive charge, enhancing the electrostatic attraction between the colloid and the negatively charged anaerobic ammonia-oxidizing bacteria. Furthermore, it binds to the amino and ester groups on the polyurethane surface, increasing the surface roughness, porosity, and hydrophilicity of the carrier, thereby improving the adsorption and colonization capabilities of the bacteria. Therefore, the use of a dual-ferric salt composite, combined with isothermal hydrothermal synthesis conditions, systematically optimizes the crystal form and dispersibility of the iron oxide, uniformly loading iron elements into the pores of the polyurethane, effectively avoiding the damage to the carrier structure caused by traditional processes, and significantly increasing the specific surface area and iron loading. Simultaneously, it enhances the affinity of the anaerobic ammonia-oxidizing functional bacteria, enabling rapid start-up and efficient denitrification of anaerobic ammonia oxidation.
[0019] This invention prepares a biocompatible iron-loaded polyurethane porous material. The polyurethane carrier has increased internal pore size and is loaded with active iron in the form of α-Fe2O3, γ-FeOOH, Fe(OH)3, etc. The surface functional groups are increased, the water absorption and adsorption capacity are enhanced, the specific surface area is larger, and microorganisms are directionally enriched, effectively shortening the biofilm formation time of the anaerobic ammonia oxidation system, providing a suitable growth habitat for organisms and preventing biomass loss.
[0020] The iron-loaded polyurethane porous material prepared by this invention can effectively shorten the start-up time of the process when applied to an anaerobic ammonia oxidation system, promote the enrichment and biofilm formation of anaerobic ammonia oxidizing bacteria, and achieve a total nitrogen removal rate that is superior to that of the original polyurethane carrier, the single iron salt thermally modified carrier, and the carrier prepared by the impregnation method. The effective adhesion of iron salt promotes the transfer of electrons between systems and enhances the reduction of nitrates.
[0021] The method for preparing iron-loaded polyurethane porous materials according to this invention is simple and easy to operate. The entire process does not involve complex chemicals or high-energy-consuming operations, shortens the carrier preparation time, and is green and environmentally friendly. Attached Figure Description
[0022] Figure 1 These are sample images of the hydrothermally synthesized ferric salt modified polyurethane material and the ordinary impregnated polyurethane material described in this invention;
[0023] Figure 2 SEM images of the hydrothermal synthesized iron-modified polyurethane material and the ordinary impregnated polyurethane material of this invention;
[0024] Figure 3 The image shows the EDS energy dispersive spectroscopy (EDS) analysis of the iron-modified polyurethane material prepared in Example 1.
[0025] Figure 4 EDS energy dispersive spectroscopy (EDS) analysis of the iron-modified polyurethane material prepared in Comparative Example 2;
[0026] Figure 5a The changes in ammonia nitrogen concentration and removal rate in the reactors of Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are shown.
[0027] Figure 5b The changes in nitrite nitrogen concentration and removal rate in the reactors of Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 are shown.
[0028] Figure 5c The total nitrogen concentration changes and removal rates in the reactors of Examples 1, 2, 3 and 4 are shown. Detailed Implementation
[0029] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.
[0030] Example 1
[0031] A method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials includes the following steps:
[0032] 1) Pretreatment of unmodified polyurethane (PU)
[0033] Hydrophilic polyurethane sponge filler was selected as the raw material, cut into cubes with a side length of 1cm, washed and dried in an oven at 60℃.
[0034] 2) Preparation of modified polyurethane biomaterials (Fe / PU) by mixing iron salts
[0035] This material was prepared via a hydrothermal synthesis method. 13.525 g of FeCl3·6H2O and 6.725 g of Fe(NO3)3·9H2O were mixed and dissolved in 500 ml of deionized water to prepare a mixed iron salt solution with a molar ratio of 2:1 and an iron content of 0.15 mol / L, with an initial pH of 1.3. 30% (by volume) of PU was immersed in the above iron salt solution and stirred at room temperature for 1 h. A small amount of ammonia was added dropwise to the mixed solution while stirring, and the pH was measured to reach 9, at which point ferric hydroxide precipitate formed. The pH-adjusted PU-Fe solid-liquid mixture was poured into a clean, high-pressure reactor lined with polytetrafluoroethylene, and then placed in a forced-air drying oven at 105℃ for 6 h. After the reaction was complete, the polyurethane material was removed, repeatedly rinsed with deionized water, and then dried in a 60℃ oven to obtain the mixed iron salt modified polyurethane material.
[0036] 3) Preparation of anaerobic ammonia oxidation sludge simulated wastewater culture medium. Specific components are as follows: KH₂PO₄ (27 mg / L), NaHCO₃ (1000 mg / L), KHCO₃ (1000 mg / L), CaCl₂ (136 mg / L), MgSO₄ (20 mg / L); trace element 1 (1 mL / L), trace element 2 (1.25 mL / L). The composition of trace element 1 is as follows: EDTA (5 g / L), FeSO₄·7H₂O (5 g / L). The composition of trace element 2 is as follows: EDTA (5.0 g / L), ZnSO4·7H2O (0.43 g / L), CuSO4·5H2O (0.25 g / L), NiCl2·6H2O (0.19 g / L), MnCl2·4H2O (0.99 g / L), CoCl2·6H2O (0.24 g / L), Na2MoO4·2H2O (0.22 g / L) (the composition of the simulated wastewater culture medium is the same in the following examples and will not be repeated). Anaerobic ammonia oxidation sludge was inoculated into the anaerobic ammonia oxidation reactor, with the sludge amount being 10% of the reactor volume. The reactor temperature was controlled at 33℃, the hydraulic retention time at 22 h, the dissolved oxygen concentration at 0.2~0.5 mg / L, and the initial pH at 8. Initial NH4+ was set. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2- -N concentration, maximum NH4+ in the system + -N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. The NH4+ concentration in the anaerobic system at this point was then measured. + -N average removal rate was 83.08%, NO2 - The average removal rate of -N was 78.59%, and the average removal rate of TN was 70.82%.
[0037] 4) Fe / PU material was added to the stably operating anaerobic ammonia oxidation reactor at a volume of 30% of the sludge volume to increase nitrogen loading by shortening the hydraulic retention time. The initial NH4 in the reactor... + -N concentration is 200 mg / L, NO2 - -N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + -N average removal rate was 97.94%, NO2 - The average removal rate of -N was 95.58%, and the average removal rate of TN was 85.15%.
[0038] Comparative Example 1
[0039] A method for enhancing anaerobic ammonium oxidation denitrification by adding mixed iron salts includes the following steps:
[0040] 1) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium. Inoculate the anaerobic ammonia oxidation reactor with anaerobic ammonia oxidation sludge, the amount of sludge being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 22 h, dissolved oxygen concentration to 0.2~0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system + -N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + The average removal rate of NO2- was 82.73%. -The average removal rate of -N was 80.97%, and the average removal rate of TN was 69.74%.
[0041] 2) A mixed solution of 0.1 mM FeCl3·6H2O and 0.05 mM Fe(NO3)3·9H2O was directly added to a stably operating anaerobic ammonia oxidation reactor to increase the nitrogen loading by shortening the hydraulic retention time. The initial NH4+ in the reactor... + -N concentration is 200 mg / L, NO2 - -N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + -N average removal rate was 86.52%, NO2 - The average removal rate of -N was 86.74%, and the average removal rate of TN was 76.11%.
[0042] Comparative Example 2
[0043] A method for enhancing anaerobic ammonia oxidation denitrification with an iron-loaded polyurethane carrier includes the following steps:
[0044] 1) Preparation of thermally modified polyurethane materials using single iron salt solution
[0045] The iron salt used is FeCl3·6H2O, which is used to modify polyurethane materials via hydrothermal synthesis. 20.29 g of FeCl3·6H2O was dissolved in 500 ml of deionized water to prepare an iron salt solution with an iron content of 0.15 mol / L. 30% (by volume) of PU was immersed in the iron salt solution and stirred at room temperature for 1 h. The PU-Fe solid-liquid mixture was then poured into a clean, high-pressure reactor lined with polytetrafluoroethylene (PTFE), and placed in a forced-air drying oven at 105℃ for 6 h. After the reaction was complete, the polyurethane material was removed, repeatedly rinsed with deionized water, and then dried in a 60℃ oven to obtain the polyurethane material modified with a single iron salt.
[0046] 2) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium, and inoculate anaerobic ammonia oxidation sludge into the anaerobic ammonia oxidation reactor, with the sludge volume being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 22 h, dissolved oxygen concentration to 0.2–0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system +-N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + -N average removal rate was 81.88%, NO2 - The average removal rate of -N was 80.78%, and the average removal rate of TN was 71.50%.
[0047] 3) Add a thermally modified polyurethane material, consisting of iron brine, to a stably operating anaerobic ammonia oxidation reactor. The volume of the added material is 30% of the sludge volume. This increases the nitrogen loading by shortening the hydraulic retention time. The initial NH4 in the reactor... + -N concentration is 200 mg / L, NO2 - -N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + -N average removal rate was 85.97%, NO2 - The average removal rate of -N was 90.17%, and the average removal rate of TN was 78.15%.
[0048] Comparative Example 3
[0049] A method for enhanced anaerobic ammonium oxidation denitrification by adding a single iron salt includes the following steps:
[0050] 1) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium. Inoculate the anaerobic ammonia oxidation reactor with anaerobic ammonia oxidation sludge, the amount of sludge being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 22 h, dissolved oxygen concentration to 0.2~0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system + -N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + -N average removal rate was 80.24%, NO2 - The average removal rate of -N was 82.68%, and the average removal rate of TN was 72.41%.
[0051] 2) Adding 0.05 mM FeCl3·6H2O to a stably operating anaerobic ammonia oxidation reactor increases the nitrogen load by shortening the hydraulic retention time. The initial NH4+ in the reactor... + -N concentration is 200 mg / L, NO2 - -N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + -N average removal rate was 83.67%, NO2 - The average removal rate of -N was 86.54%, and the average removal rate of TN was 75.16%.
[0052] Comparative Example 4
[0053] A method for enhancing anaerobic ammonia oxidation denitrification with an iron-loaded polyurethane carrier includes the following steps:
[0054] 1) Preparation of mixed iron salt modified polyurethane materials by immersion method
[0055] The modified material was prepared by an immersion method. 13.525 g of FeCl3·6H2O and 6.725 g of Fe(NO3)3·9H2O were mixed and dissolved in 500 ml of deionized water to prepare a mixed iron salt solution with a molar ratio of 2:1 and an iron content of 0.15 mol / L, with an initial pH of 1.3. 30% (by volume) of polyurethane (PU) was immersed in the above iron salt solution and stirred at room temperature for 1 h. A small amount of ammonia was added dropwise to the mixed solution while stirring, and the pH was measured until it reached 9. During this process, ferric hydroxide precipitate was formed. Stirring was continued for 12 h, and the mixture was then removed, repeatedly rinsed with deionized water, and dried in a 60℃ oven to obtain the mixed iron salt modified polyurethane material.
[0056] 2) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium. Inoculate the anaerobic ammonia oxidation reactor with anaerobic ammonia oxidation sludge, the amount of sludge being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 12 h, dissolved oxygen concentration to 0.2~0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system + -N concentration not exceeding 200 mg / L, NO2 --N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + -N average removal rate was 83.02%, NO2 - The average removal rate of -N was 80.93%, and the average removal rate of TN was 71.12%.
[0057] 3) Add the mixed iron salt-modified polyurethane material prepared in step 1 to the stably operating anaerobic ammonia oxidation reactor. The volume of the added material is 30% of the sludge volume, thereby increasing the nitrogen load by shortening the hydraulic retention time. The initial NH4 in the reactor... + -N concentration is 200 mg / L, NO2 - The nitrogen concentration was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was reduced from 22 h to 8 h. After a period of denitrification treatment under these conditions, the nitrogen concentration changes were observed. The final nitrogen concentration in the reaction system was measured. + -N average removal rate was 90.18%, NO2 - The average removal rate of -N was 91.52%, and the average removal rate of TN was 80.15%.
[0058] Comparative Example 5
[0059] A method for enhancing anaerobic ammonia oxidation denitrification with a hydrothermally modified polyurethane carrier includes the following steps:
[0060] 1) Preparation of hydrothermally modified polyurethane materials
[0061] Polyurethane materials were directly modified via hydrothermal synthesis. Cut hydrophilic polyurethane sponge filler and water were poured into a clean, high-pressure reactor lined with polytetrafluoroethylene (PTFE), and then placed in a forced-air drying oven at 105°C for 6 hours. After the reaction was complete, the polyurethane material was removed, repeatedly rinsed with deionized water, and then dried in a 60°C oven to obtain the hydrothermally modified polyurethane material.
[0062] 2) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium, and inoculate anaerobic ammonia oxidation sludge into the anaerobic ammonia oxidation reactor, with the sludge volume being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 22 h, dissolved oxygen concentration to 0.2–0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system +-N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + The average removal rate of NO2- was 82.63%. - The average removal rate of -N was 79.82%, and the average removal rate of TN was 71.15%.
[0063] 3) Hydrothermally modified polyurethane material was added to the stably operating anaerobic ammonia oxidation reactor at a volume of 30% of the sludge volume to increase nitrogen loading by shortening the hydraulic retention time. The initial NH4 in the reactor... + -N concentration is 200 mg / L, NO2 - -N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + The average removal rate of NO2- was 85.93%. - The average removal rate of -N was 87.25%, and the average removal rate of TN was 76.62%.
[0064] Comparative Example 6
[0065] A method for enhancing anaerobic ammonia oxidation denitrification by adding an unmodified polyurethane carrier includes the following steps:
[0066] 1) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium. Inoculate the anaerobic ammonia oxidation reactor with anaerobic ammonia oxidation sludge, the amount of sludge being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 22 h, dissolved oxygen concentration to 0.2~0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system + -N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + -N average removal rate was 84.17%, NO2 - The average removal rate of -N was 80.85%, and the average removal rate of TN was 72.13%.
[0067] 2) Cleaned and unmodified hydrophilic polyurethane sponge packing material, cut and washed, is added to the stably operating anaerobic ammonia oxidation reactor. The volume of the added material is 30% of the sludge volume, thereby increasing the nitrogen loading by shortening the hydraulic retention time. The initial NH4 in the reactor... + -N concentration is 200 mg / L, NO2 - -N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + -N average removal rate was 85.15%, NO2 - The average removal rate of -N was 85.70%, and the average removal rate of TN was 76.05%.
[0068] Comparative Example 7
[0069] An anaerobic ammonia oxidation denitrification method without the addition of a polyurethane carrier includes the following steps:
[0070] 1) Prepare a simulated anaerobic ammonia oxidation wastewater culture medium. Inoculate the anaerobic ammonia oxidation reactor with anaerobic ammonia oxidation sludge, the amount of sludge being 10% of the reactor volume. Control the reactor temperature to 33℃, hydraulic retention time to 22 h, dissolved oxygen concentration to 0.2~0.5 mg / L, and initial pH to 8. Set the initial NH4+. + -N concentration is 100 mg / L, NO2 - The -N concentration was initially 130 mg / L, and was subsequently gradually increased as needed for NH4. + -N and NO2 - -N concentration, maximum NH4+ in the system + -N concentration not exceeding 200 mg / L, NO2 - -N concentration not exceeding 260 mg / L. Nitrogen removal efficiency was measured daily, and the influent nitrogen load was adjusted according to the effluent TN concentration until TN removal stabilized. NH4+ levels in the anaerobic system were measured. + -N average removal rate was 82.17%, NO2 - The average removal rate of -N was 79.85%, and the average removal rate of TN was 70.92%.
[0071] 2) No carrier packing is added to the stably operating anaerobic ammonia oxidation reactor; the nitrogen loading is increased by shortening the hydraulic retention time. The initial NH4+ in the reactor... + -N concentration is 200 mg / L, NO2 --N was set at 260 mg / L, while other reaction conditions remained constant. The hydraulic retention time in the reactor was shortened from 22 h to 8 h. After denitrification treatment under these conditions for a period of time, the change in nitrogen concentration was observed. The final nitrogen concentration in the reaction system was measured. + The average removal rate of NO2- was 79.77%. - The average removal rate of -N was 72.59%, and the average removal rate of TN was 68.94%.
[0072] The accompanying drawings of this invention are described in detail below:
[0073] Figure 1 These are modified polyurethane sponge fillers prepared using different methods according to this invention. This invention prepares iron-loaded polyurethane composite materials by introducing loaded iron onto unmodified polyurethane materials; different modification methods exhibit different effects. Figure 1 (a) is a porous polyurethane material with iron loading, which is thermally modified using mixed iron-salt water, compared to the original polyurethane ( Figure 1 (d) The pores are more obvious and the color is reddish-brown, indicating that iron ions have been tightly bound on the surface and inside of the carrier. Figure 1 (b) is a polyurethane filler produced by thermal modification using a single ferric hydrate, compared to Figure 1 (a) The filler modified by this method is coffee-colored and has small pores. Figure 1 (c) is a polyurethane filler impregnated with mixed iron salts. It is light yellow, has a significantly lower iron ion load than the previous two, and has a denser pore structure. Figure 1 (d) is the original unmodified polyurethane filler.
[0074] Figure 2 and Figure 3 The appearance morphology and elemental distribution of polyurethane modified by mixed iron salt and single iron salt water methods are shown under scanning electron microscopy (SEM-Energy Dispersive X-ray Spectroscopy (EDS). Figure 2 (a) and Figure 2 (b) represents the iron-loaded polyurethane porous material after thermal modification with mixed iron-salt water. Figure 2 (c) and Figure 2 (d) indicates a polyurethane filler that has been thermally modified with a single ferric salt solution. For example... Figure 2 (a) and Figure 2 (b) and Figure 2As shown, the polyurethane carrier skeleton modified with mixed iron salts formed a few micropores, and the surface was rough with a small number of nano-spherical particles, which is consistent with the microstructure of nano-iron particles. While single iron salt, under the same conditions, also showed trace amounts of nanoparticles, no additional micropores were observed. Furthermore, EDS energy dispersive spectroscopy analysis of the Fe element distribution on the filler surface showed that the Fe content on the filler surface under the thermal modification condition of mixed iron salt was 25.09% (…). Figure 3 ), compared to the single iron salt modification method in Example 2, 1.24% ( Figure 4 Therefore, using mixed iron-salt water to thermally modify polyurethane can not only provide more attachment sites and growth space for anaerobic ammonium oxidation, but also allow the iron attached to the polyurethane skeleton to be slowly released, participating in electron transfer and microbial film formation during the anaerobic ammonium oxidation process, promoting the growth of anaerobic ammonium sludge and the effective denitrification reaction.
[0075] Figure 5a -c shows the system denitrification efficiency curves after adding different packing materials to the reactor. Figure 5a , Figure 5b and Figure 5c The changes in ammonia nitrogen concentration, nitrite nitrogen concentration, and total nitrogen concentration and removal rate in the reactors of Examples 1, 2, 3, and 4 are respectively presented. It can be seen that, under the same reaction conditions, the reactor using the thermally modified iron-loaded polyurethane porous material with mixed iron-salt water exhibits significantly better performance than other packing materials. NH4 + The nitrogen removal rate reached 97.94%, which is 12.8%, 11.98%, and 6.76% higher than that of ordinary methods, single ferric salt modification, and mixed ferric salt impregnation, respectively. The reason for this phenomenon is explained as follows: Ferric nitrate and ferric chloride have different physicochemical properties. Ferric nitrate, as a strong oxidant, promotes the oxidation of the polyurethane surface under hydrothermal conditions, forming more active sites, increasing the roughness, hydrophilicity, and specific surface area of the filler, and improving the adhesion and mass transfer efficiency of microorganisms. Combined with hydrothermal conditions, this ensures that iron ions adhere tightly to the surface and interior of the polyurethane, preventing excessive iron release and thus providing a suitable amount of usable iron ions for the anaerobic ammonia oxidation system.
[0076] For any points not covered above, existing technologies shall apply.
[0077] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials, characterized in that, Includes the following steps: Anaerobic ammonia oxidation reactor is used to thoroughly mix anaerobic ammonia oxidation sludge, iron-loaded polyurethane porous material and wastewater containing ammonia nitrogen and nitrite nitrogen, and then react under anaerobic conditions at a reaction temperature of 31~35℃. The preparation method of iron-loaded polyurethane porous material is as follows: Polyurethane sponge was selected as the carrier. After cutting and cleaning, it was placed in a mixed iron salt solution for impregnation and stirring for a period of time. The pH of the mixed solution was adjusted to alkaline, and red precipitate iron hydroxide was generated. Then, iron-loaded polyurethane porous material was synthesized by hydrothermal synthesis. The mixed iron salt solution includes ferric chloride and ferric nitrate.
2. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, Cut into cubes with sides of 1-3cm.
3. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, The mixed iron salt solution comprises FeCl3·6H2O and Fe(NO3)3·9H2O in a molar ratio of 2:
1.
4. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, The iron concentration in the mixed iron salt solution is 0.1~1.0 mol / L.
5. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, The impregnation stirring rate is 150~250 r / min, and the stirring time is 1~3 h.
6. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, Adjust the pH of the solution to 9-11.
7. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, The hydrothermal synthesis was carried out in a high-pressure reactor lined with polytetrafluoroethylene, with a reaction temperature of 105~120℃ and a reaction time of 6~12 h.
8. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, Anaerobic ammonia oxidation reactors include either upflow anaerobic reactors or sequencing batch reactors.
9. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, The volume of the iron-loaded polyurethane porous material added is 25-75% of the volume of the anammox sludge in the reactor.
10. The method for enhancing anaerobic ammonium oxidation denitrification using iron-loaded polyurethane porous materials according to claim 1, characterized in that, NH4 + -N removal rate greater than 95%, NO2 - -N removal rate greater than 95%, total nitrogen removal rate greater than 85%.