Immobilized exogenous electron shuttle as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of sewage treatment, and discloses an immobilized exogenous electron shuttle and a preparation method and application thereof.The preparation method comprises the following steps that hydrophilic polyurethane sponge is cleaned with ultrapure water and sterilized through a sterilization pot; the preparation method comprises the following steps: dissolving fulvic acid, N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride in ultrapure water; putting the sterilized hydrophilic polyurethane sponge into the prepared solution, and stirring for reaction; and after the reaction is completed, taking out the hydrophilic polyurethane sponge loaded with the electron shuttle, and washing the hydrophilic polyurethane sponge with ultrapure water to prepare the immobilized exogenous electron shuttle. The carrier immobilized exogenous electron shuttle accelerates the transmission rate of electrons from an ammonia nitrogen source to nitrite nitrogen, strengthens the electron transmission capability of anaerobic ammonium oxidation flora, promotes the adhesion growth of the anaerobic ammonium oxidation flora on the carrier, strengthens the anaerobic ammonium oxidation denitrification efficiency and maintains the stability of the anaerobic ammonium oxidation process.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and in particular relates to an immobilized exogenous electron shuttle and a preparation method and application thereof. Background Art

[0002] In the current context of urban modernization, the treatment of nitrogen-containing wastewater has become a pressing environmental issue. With population growth and increased industrial activity, nitrogen emissions have increased significantly, leading to increasingly serious eutrophication of water bodies. This not only threatens water quality and ecosystem balance, but can also lead to a decrease in aquatic biodiversity and water quality safety issues.

[0003] Anaerobic ammonium oxidation (anammox) technology, as an emerging biological denitrification method, has received widespread attention in recent years, especially in the treatment of high ammonia nitrogen wastewater, which has irreplaceable advantages. The process is carried out under anaerobic or anoxic conditions, and anaerobic ammonium oxidizing bacteria as functional bacteria use nitrite nitrogen (NO2 - -N) is an electron acceptor, and ammonia nitrogen (NH4 + -N) is converted into nitrogen gas (N2), thereby achieving efficient removal of ammonia nitrogen in wastewater. Compared with the traditional nitrification / denitrification biological denitrification treatment process, this technology can significantly reduce oxygen energy consumption and carbon source demand. However, since anaerobic ammonium oxidizing bacteria are more sensitive to operating environmental conditions, how to achieve the denitrification efficiency of anaerobic ammonium oxidizing bacteria during operation is more important. It is worth noting that during the anaerobic ammonium oxidation reaction, the transfer of electrons between anaerobic ammonium oxidizing bacteria is crucial: electrons are released from the oxidation of ammonia and then used for the reduction of nitrite. This electron transport chain involves a variety of intracellular enzymes and coenzymes, including nitrite reductase (NIR) and a series of redox proteins. It can be found that the nitrogen removal efficiency of the anaerobic ammonium oxidation process can be improved by improving the anaerobic ammonium oxidation electron transfer rate.

[0004] Exogenous electron shuttles are a class of chemical substances that can transfer electrons during microbial metabolism. Their mechanisms of action include enhancing electron transfer efficiency, accelerating reduction reactions, and increasing microbial activity. By helping to transfer electrons generated during microbial metabolism from intracellular enzyme systems to external electron acceptors (such as NO⁻), exogenous electron shuttles effectively reduce electron transfer losses and improve electron transfer efficiency. Furthermore, exogenous electron shuttles maintain microbial activity by reducing the accumulation of electrons within bacterial cells and avoiding the electron "saturation" effect. Quinone compounds, as electron shuttles, have been identified as effective enhancers of key enzyme activity in anaerobic ammonium oxidation systems, particularly increasing the intracellular activity of hydrazine dehydrogenase, nitrite, and nitrate reductase in anaerobic ammonium-oxidizing bacteria. Notably, because quinone compounds act as electron shuttles in anaerobic ammonium oxidation systems, the question of how to immobilize these electron shuttles and achieve their repeated use remains a pressing issue. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an immobilized exogenous electron shuttle and its preparation method and application, so as to enhance the electron transfer ability of the anaerobic ammonium oxidation bacteria, promote the anaerobic ammonium oxidation denitrification efficiency and maintain the stability of the anaerobic ammonium oxidation process.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for preparing an immobilized exogenous electron shuttle comprises the following steps: (1) Wash the hydrophilic polyurethane sponge with ultrapure water and sterilize it in an autoclave; (2) Dissolve fulvic acid, N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride in ultrapure water; (3) Place the sterilized hydrophilic polyurethane sponge into the prepared solution and stir to react; (4) After the reaction is completed, the hydrophilic polyurethane sponge carrying the electron shuttle is taken out and rinsed with ultrapure water to obtain the immobilized exogenous electron shuttle.

[0007] In the above scheme, in step (1), the temperature of the sterilizer is set to 121°C and the sterilization time is 30 minutes.

[0008] In the above scheme, in step (1), the porosity of the hydrophilic polyurethane sponge is 97%, the pore diameter is 1.5 mm, and the specific surface area exceeds 4500 m² / m³.

[0009] In the above scheme, in step (2), the mass ratio of fulvic acid, N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is 0.3:1:1.

[0010] In the above scheme, in step (3), the reaction temperature is 30°C, the reaction time is 56 hours, and the mixture is stirred every 8 hours.

[0011] An immobilized exogenous electron shuttle prepared by the preparation method described above.

[0012] An application of the immobilized exogenous electron shuttle as described above in an anaerobic ammonium oxidation reaction.

[0013] In a further technical solution, an immobilized exogenous electron shuttle is added to an anaerobic ammonium oxidation reactor, and an anaerobic ammonium oxidation reaction is carried out at a temperature of 33-35° C. and a pH of 7.5.

[0014] In a further technical solution, the anaerobic ammonium oxidation reactor is an upflow anaerobic reactor with an effective volume of 1.5L.

[0015] Through the above technical solution, the present invention provides an immobilized exogenous electron shuttle and its preparation method and application, which have the following beneficial effects: This invention uses a hydrophilic polyurethane sponge (HPBS) with high porosity and large specific surface area to immobilize the electron shuttle (fulvic acid). This allows for the reuse of the electron shuttle, enhances system stability and reaction controllability, and reduces the impact of environmental fluctuations on biological activity, resulting in significant environmental and economic benefits. Furthermore, the addition of the carrier provides sufficient surface area to promote the attachment and growth of anaerobic ammonium-oxidizing bacteria, maintaining the denitrification stability of the anaerobic ammonium-oxidizing system.

[0016] The invention adopts N-hydroxysuccinimide as a catalyst and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride as a stabilizer, which can improve the reaction efficiency and stability of the electron shuttle fulvic acid on the carrier HPBS, and still has good electron transfer ability after repeated use.

[0017] This invention introduces an exogenous electron shuttle into the anaerobic ammonium oxidation system, significantly improving electron transfer efficiency and accelerating the ammonia oxidation reaction, thereby increasing the denitrification rate and overall treatment efficiency. Due to its unique chemical stability and biocompatibility, the immobilized electron shuttle can function long-term in anaerobic environments, significantly enhancing denitrification efficiency and system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0019] Figure 1 The morphology of the carrier HPBS before and after loading with FA; (a) before loading; (b) after loading; Figure 2 Comparison of ammonia nitrogen degradation rates under the conditions of Application Example 1 (HPBS@FA) with the addition of 0.5 mM FA and Application Comparative Example 1 (HPBS) with the addition of 0 mM FA; Figure 3 Comparison of nitrite nitrogen degradation rates under the conditions of Application Example 1 (HPBS@FA) with the addition of 0.5 mM FA and Application Comparative Example 1 (HPBS) with the addition of 0 mM FA; Figure 4 FTIR comparison of the prepared immobilized exogenous electron shuttle (HPBS@FA) before and after use, (a) is HPBS@FA before use, and (b) is HPBS@FA after use. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] Preparation of immobilized exogenous electron shuttle: Preparation Example 1: (1) A hydrophilic polyurethane sponge (HPBS) with a porosity of 97%, a pore size of 1.5 mm, and a specific surface area of ​​more than 4500 m² / m³ was selected and cleaned with ultrapure water and sterilized in an autoclave; the temperature of the autoclave was set at 121°C and the sterilization time was 30 min.

[0022] (2) Fulvic acid (FA), N-hydroxysuccinimide, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride were dissolved in 1 L of ultrapure water at a mass ratio of 0.3:1:1, wherein the concentration of FA was 0.5 mM.

[0023] (3) Add the sterilized hydrophilic polyurethane sponge to the prepared solution at a concentration of 12.5 ± 0.5 g / L and stir at 30°C for 56 hours, stirring every 8 hours to ensure that the electron shuttle fully infiltrates the carrier HPBS.

[0024] (4) After the reaction is completed, the hydrophilic polyurethane sponge loaded with the electron shuttle is removed and rinsed with ultrapure water to remove unreacted chemicals, thereby obtaining the immobilized exogenous electron shuttle (HPBS@FA).

[0025] (5) The prepared immobilized exogenous electron shuttle was immersed in ultrapure water for 24 hours to further ensure the cleanliness of the carrier. Figure 1 The shape of the material before and after loading.

[0026] Preparation Example 2 The concentration of FA was 0.1 mM, and the rest was the same as in Preparation Example 1.

[0027] Preparation Example 3 The concentration of FA was 1 mM, and the rest was the same as in Preparation Example 1.

[0028] Preparation Example 4 The concentration of FA is 10 mM, and the rest is the same as in Preparation Example 1. Preparation Comparative Example 1 During the preparation of HPBS@FA, FA was replaced with anthraquinone-2,6-sodium sulfonate (AQDS), and the rest of the process was the same as in Preparation Example 1 to obtain an immobilized exogenous electron shuttle (HPBS@AQDS).

[0029] application: In the upflow anaerobic reactor (UASB), the influent culture medium contains ammonia nitrogen and nitrite nitrogen at a molar ratio of 1:132; the anaerobic ammonium oxidation activated sludge concentration is 4000-4500 mg / L. In the influent culture medium, trace elements I include: FeSO4·7H2O (5 g / L), EDTA (5 g / L); trace elements II include: EDTA (15 g / L), H3BO3(0.011g / L), MnCl2·4H2O (0.99 g / L); CuSO4·5H2O (0.25 g / L), ZnSO4·7H2O (0.43 g / L),NiCl2·6H2O (0.19 g / L), Na2MoO4·2H2O (0.22 g / L), CoCl2·6H2O (0.24 g / L),NaSeO4·10H2O (0.21 g / L).

[0030] Application Example 1 The immobilized exogenous electron shuttle (HPBS@FA) prepared in Preparation Example 1 was added to UASB, and an anaerobic ammonium oxidation reaction was carried out at a temperature of 33-35° C. and a pH of 7.5.

[0031] Application Example 2 The immobilized exogenous electron shuttle (HPBS@FA) prepared in Preparation Example 2 was added to UASB, and the rest was the same as in Application Example 1.

[0032] Application Example 3 The immobilized exogenous electron shuttle (HPBS@FA) prepared in Preparation Example 3 was added into UASB, and the rest was the same as in Application Example 1.

[0033] Application Example 4 The immobilized exogenous electron shuttle (HPBS@FA) prepared in Preparation Example 4 was added to UASB, and the rest was the same as in Application Example 1.

[0034] Comparative Application Example 1 Original HPBS without electron shuttle loading was added, the concentration of FA was 0 mM, and the rest was the same as in Application Example 1.

[0035] Application Comparative Example 2 The immobilized exogenous electron shuttle (HPBS@AQDS) prepared in Comparative Example 1 was added to UASB, and the rest was the same as in Application Example 1.

[0036] Test results: 1. Fulvic acid (FA) concentration The operation time of the reactor in Application Example 1, Application Example 2, Application Example 3, Application Example 4 and Application Comparative Example 1 was 360 min, and the ammonia nitrogen and nitrite nitrogen in water were measured every 60 min. The degradation rates of the two were compared under different FA concentrations. The results are as follows: Figure 2 As shown, the ammonia nitrogen degradation rate of the reactor of Application Comparative Example 1 in which only HPBS was added was 3.3 mgN / (gVSS·h), and the ammonia nitrogen degradation rate of the reactor of Application Example 1 in which immobilized exogenous electron shuttle (HPBS@FA) was added and the FA concentration was 0.5 mM reached 4.1 mg N / (gVSS·h), which was higher than that of the reactors of Application Example 2 (2.7 mg N / (gVSS·h)) and Application Example 3 (2.4 mg N / (gVSS·h)). In addition, in Application Example 4, under high concentration of FA, the ammonia nitrogen degradation rate was much lower than that of other examples (0.7 mg N / (gVSS·h)).

[0037] like Figure 3 As shown, the nitrite-nitrogen degradation rate of the reactor using Comparative Example 1, which added only HPBS without the electron shuttle, was 4.3 mg N / (gVSS·h). The nitrite-nitrogen degradation rate of the reactor using Example 1, which added an immobilized exogenous electron shuttle (HPBS@FA) at a FA concentration of 0.5 mM, reached 4.7 mg N / (gVSS·h). The nitrite-nitrogen degradation rates of Example 2, Example 3, and Example 4 were 3.9 mg N / (gVSS·h), 3.4 mg N / (gVSS·h), and 1.2 mg N / (gVSS·h), respectively, all lower than those of Example 1. Therefore, the optimal FA concentration was determined to be 0.5 mM.

[0038] 2. HPBS@FA reusability test After running two sludge ages in Application Example 1, the HPBS@FA after use was taken out and compared with the HPBS@FA before use prepared in Preparation Example 1 by Fourier transform infrared spectroscopy (FTIR). Figure 4The results show that the FA characteristic peak OH bond (2651 cm -1 ) The corresponding carboxyl absorption peaks were strong before and after the reaction, indicating that the stability of fulvic acid was reflected.

[0039] 3. Comparison of the degradation rate of ammonia nitrogen in the influent of electron shuttles with different loads After 360 minutes of reactor operation, the influent ammonia nitrogen degradation rates of the anaerobic ammonium oxidation process using Comparative Example 2 were compared with those using Example 1. The results showed that the ammonia nitrogen degradation rate in HPBS@AQDS (0.5 mM) was 3.6 mg N / (gVSS·h), lower than the 4.1 mg N / (gVSS·h) in Example 1.

[0040] 4. Comparison of the degradation rate of nitrite nitrogen in the influent of electron shuttles with different loads After 360 minutes of reactor operation, the degradation rates of nitrite nitrogen in the influent of the anaerobic ammonium oxidation process using Comparative Example 2 were compared with those using Example 1. The results showed that the degradation rate of nitrite nitrogen in HPBS@AQDS (0.5 mM) was 3.1 mg N / (gVSS·h), which was lower than the 4.7 mg N / (gVSS·h) in Example 1.

[0041] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an immobilized exogenous electron shuttle, characterized in that: The steps include: (1) Wash the hydrophilic polyurethane sponge with ultrapure water and sterilize it in an autoclave; (2) Dissolve fulvic acid, N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride in ultrapure water; (3) Place the sterilized hydrophilic polyurethane sponge into the prepared solution and stir to react; (4) After the reaction is completed, the hydrophilic polyurethane sponge carrying the electron shuttle is taken out and rinsed with ultrapure water to obtain the immobilized exogenous electron shuttle.

2. The method for preparing an immobilized exogenous electron shuttle according to claim 1, characterized in that: In step (1), the temperature of the sterilizer is set to 121°C and the sterilization time is 30 minutes.

3. The method for preparing an immobilized exogenous electron shuttle according to claim 1, wherein: In step (1), the porosity of the hydrophilic polyurethane sponge is 97%, the pore size is 1.5 mm, and the specific surface area exceeds 4500 m² / m³.

4. The method for preparing an immobilized exogenous electron shuttle according to claim 1, wherein: In step (2), the mass ratio of fulvic acid, N-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride is 0.3:1:

1.

5. The method for preparing an immobilized exogenous electron shuttle according to claim 1, wherein: In step (3), the reaction temperature was 30°C, the reaction was carried out for 56 hours, and stirring was performed every 8 hours.

6. An immobilized exogenous electron shuttle prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the immobilized exogenous electron shuttle according to claim 6 in an anaerobic ammonium oxidation reaction.

8. The use according to claim 7, characterized in that The immobilized exogenous electron shuttle is added into the anaerobic ammonium oxidation reactor, and the anaerobic ammonium oxidation reaction is carried out at a temperature of 33-35° C. and a pH of 7.

5.

9. The use according to claim 8, characterized in that The anaerobic ammonium oxidation reactor is an upflow anaerobic reactor with an effective volume of 1.5L.

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