Anaerobic ammonia oxidation gel particles and methods of preparing and enhancing nitrogen removal performance of anaerobic ammonia oxidation processes under high total nitrogen loading conditions

Abstract

The present application belongs to the field of wastewater biological denitrification treatment, and discloses an anaerobic ammonia oxidation gel particle and a method for preparing and strengthening the denitrification performance of an anaerobic ammonia oxidation process under a high total nitrogen load condition. The preparation method of the anaerobic ammonia oxidation gel particle comprises the following steps: preparation of chitosan modified diatomite, preparation of a gelling agent, and preparation of the anaerobic ammonia oxidation gel particle. By mixing and adding the ANAMMOX gel particle and the ANAMMOX particle sludge with a low total nitrogen load into an anaerobic ammonia oxidation process reactor with a high total nitrogen load, the problem that the denitrification efficiency of the ANAMMOX process in the prior art is significantly reduced and the operation is unstable under a high total nitrogen load condition is solved.

Description

Technical Field

[0001] This invention belongs to the field of biological denitrification treatment of wastewater, and more specifically, relates to anaerobic ammonia oxidation gel particles and methods for preparing and enhancing the denitrification performance of anaerobic ammonia oxidation processes under high total nitrogen load conditions. Background Technology

[0002] Anaerobic ammonia oxidation (ANAMMOX) is a novel biological nitrogen removal technology. Compared to traditional biological nitrogen removal technologies, it offers significant advantages, including eliminating the need for aeration, requiring no additional carbon source, and boasting a high reaction rate. Reports indicate that ANAMMOX technology, when treating nitrogen-containing wastewater, eliminates the need for carbon sources, aeration systems, and related electrical equipment compared to traditional nitrification-denitrification processes, thus significantly reducing operating and maintenance costs. Simultaneously, it significantly reduces excess sludge production, eliminating the need for a sludge treatment unit and consequently reducing the footprint of process structures. Furthermore, since the gas produced by the ANAMMOX reaction is primarily nitrogen, it significantly reduces greenhouse gas emissions. Therefore, the ANAMMOX process is considered an economical, energy-efficient, highly effective, and low-carbon novel biological nitrogen removal technology with significant potential for widespread application.

[0003] However, the ANAMMOX process, currently widely adopted, still faces some significant challenges. For example, ANAMMOX bacteria grow slowly and require relatively high temperatures. Furthermore, when the influent total nitrogen load is high, the ANAMMOX denitrification process often suffers from sludge floating and loss, difficulty in biomass retention, and consequently, a significant reduction in the reactor's denitrification capacity and a marked deterioration in treatment efficiency. Improving the operational stability and denitrification efficiency of the ANAMMOX process under high total nitrogen loads remains a challenging issue. Achieving good operational stability and high denitrification efficiency under high total nitrogen loads will greatly promote the practical application of ANAMMOX technology.

[0004] Currently, researchers are constantly trying and exploring ways to improve the treatment performance of the ANAMMOX process under high total nitrogen load. These efforts mainly include improving the structure of the reaction device, controlling appropriate hydraulic conditions, collecting and breaking up floating sludge aggregates before adding them back into the reactor, and using externally sourced quorum sensing signals to regulate sludge settling performance.

[0005] However, the methods mentioned above are still subject to many limitations in practical applications. For example, improving the structure of the reaction device is cumbersome and costly to implement; controlling appropriate hydraulic conditions is only applicable to specific conditions where the influent flow rate is slow; and adding external quorum sensing signals also faces issues such as signal cost.

[0006] Therefore, there is an urgent need to propose an anaerobic ammonia oxidation gel particle and its preparation method, and to apply it to enhance the denitrification performance of anaerobic ammonia oxidation process under high total nitrogen load conditions. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing anammox gel particles and methods for their preparation and enhancement of the nitrogen removal performance of anammox processes under high total nitrogen load conditions. This invention solves the problems of significantly reduced nitrogen removal efficiency and unstable operation in existing anammox processes under high total nitrogen load conditions by mixing ANAMMOX gel particles with ANAMMOX granular sludge with low total nitrogen load and adding the mixture to the reactor of an anammox process with a high total nitrogen load.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing anaerobic ammonia oxidation gel particles, the method comprising the following steps:

[0009] S1: Preparation of chitosan-modified diatomaceous earth

[0010] Chitosan is mixed with water to obtain a chitosan aqueous solution; the chitosan aqueous solution is mixed with diatomaceous earth and then subjected to stirring, vacuum filtration, calcination and grinding in sequence to obtain the chitosan-modified diatomaceous earth;

[0011] S2: Preparation of gelling agent

[0012] Polyvinyl alcohol, sodium alginate, and high-temperature distilled water are mixed and stirred to obtain a gel-like mixture; the gel-like mixture is then mixed and stirred evenly with chitosan-modified diatomaceous earth, and cooled to obtain the gel agent;

[0013] S3: Preparation of anaerobic ammonia oxidation gel particles

[0014] The anammox sludge is uniformly mixed with the gelling agent and nano-zero ferric iron to obtain a mixed solution; the mixed solution is mixed with calcium chloride aqueous solution and subjected to a first crosslinking to obtain anammox primary gel microspheres; the anammox primary gel microspheres are mixed with potassium dihydrogen phosphate aqueous solution and subjected to a second crosslinking to obtain the anammox gel particles.

[0015] According to the present invention, preferably, in step S1:

[0016] The equipment for the stirring process includes a temperature-controlled magnetic stirrer; the temperature for the stirring process is 30-35℃, the time is 3-5h, and the stirring rate is 120-130r / min.

[0017] The equipment for the roasting process includes a muffle furnace; the roasting temperature is 450-550℃ and the time is 3-4 hours.

[0018] The chitosan-modified diatomaceous earth, sieved through a 120-150 mesh screen, had a particle size range of 100-125 μm and a specific surface area of ​​90-100 m². 2 / g, with a pore size of 19-136nm.

[0019] According to the present invention, preferably, in step S2:

[0020] The high-temperature distilled water is distilled water with a temperature ≥90℃;

[0021] Based on the total weight of the gel-like mixture, the content of polyvinyl alcohol is 11-15 wt%, and the content of sodium alginate is 1-2 wt%.

[0022] The concentration of chitosan-modified diatomaceous earth in the gelling agent is 2-6 g / L;

[0023] The cooling process involves cooling the gel to 45-55°C.

[0024] In this invention, as a preferred embodiment, in step S2, polyvinyl alcohol, sodium alginate and high-temperature distilled water are mixed and stirred continuously to obtain a uniform gel-like mixture; within 5-15 minutes after the start of the aforementioned stirring, the gel-like mixture is mixed and stirred with the chitosan-modified diatomaceous earth, and the stirring intensity is increased to ensure uniform stirring, and then cooled to obtain the gel agent.

[0025] According to the present invention, preferably, in step S3:

[0026] The calcium chloride aqueous solution has a mass fraction of 7-9 wt%.

[0027] The first crosslinking time is 12-24 hours, and the temperature is 30-35℃;

[0028] The molar concentration of the potassium dihydrogen phosphate aqueous solution is 0.7-1.0 mol / L;

[0029] The second crosslinking time is 1-5 hours, and the temperature is 30-35℃;

[0030] The anaerobic ammonia oxidation sludge has a total nitrogen load of less than 0.4 kg-TN / (m³). 3 Anaerobic ammonia oxidation sludge under d);

[0031] The volume ratio of the gelling agent to the anaerobic ammonia oxidation sludge is (10-5):(3-4);

[0032] The concentration of nano-zero valent iron in the mixture is 1.1-2.3 g / L, and the particle size of nano-zero valent iron is 100-150 nm.

[0033] In this invention, in step S3, the mixture of anaerobic ammonia oxidation sludge, the gelling agent, and nano-zero-valent iron needs to be slowly stirred to prevent the nano-zero-valent iron from being oxidized. Preferably, the mixture is added dropwise to a 7-9 wt% CaCl2 aqueous solution using a peristaltic pump, and crosslinked at room temperature for 12-24 hours to complete the first crosslinking process, forming anaerobic ammonia oxidation primary gel spheres. Then, these anaerobic ammonia oxidation primary gel spheres are added to a 0.7-1.0 mol / L KH2PO4 aqueous solution and crosslinked at room temperature for 1-5 hours to complete the second crosslinking process. At this point, structurally stable and highly active anaerobic ammonia oxidation gel particles are obtained. These particles are then rinsed with deionized water and stored at 4°C for later use.

[0034] According to the present invention, preferably, the preparation method of the nano-zero valent iron is a liquid-phase reduction method, comprising: mixing an aqueous solution of high valent iron with citric acid and an aqueous solution of a strong reducing agent, mixing and stirring evenly under a nitrogen atmosphere, and then vacuum filtering, rinsing and vacuum drying to obtain the nano-zero valent iron.

[0035] According to the present invention, preferably, the molar concentration of the high-valent iron aqueous solution is 1.1-1.3 mol / L; the high-valent iron aqueous solution is Fe 3+ Aqueous solutions and / or Fe 2+ Aqueous solution.

[0036] According to the present invention, preferably, the molar concentration of the aqueous solution of the strong reducing agent is 0.8-1.2 mol / L; the strong reducing agent is sodium borohydride and / or potassium borohydride.

[0037] According to the present invention, preferably, the vacuum drying temperature is 55-65°C and the time is 15-25 hours.

[0038] In this invention, the preparation method of the nano-zero-valent iron includes: weighing 12.5-14.2 g of FeCl3·6H2O and preparing a 1.1-1.3 mol / L FeCl3·6H2O solution; uniformly stirring using a precision quantitative electric stirrer, with nitrogen gas introduced during stirring to remove oxygen. Then, preparing 105-115 mL of 0.2 mol / L sodium borohydride (NaBH4) aqueous solution, and adding the NaBH4 aqueous solution dropwise to the FeCl3·6H2O solution using a peristaltic pump under electric stirring conditions. As the solution gradually turns black and the NaBH4 addition is complete, the reaction continues under stirring for approximately 30 minutes. The black mixture is then vacuum filtered to obtain stable black nano-iron particles, which are first rinsed with a 20%-30% ethanol aqueous solution, and then rinsed again with anhydrous ethanol. Finally, the rinsed black nanoparticles were dried in a vacuum drying oven at 60℃ for 20 hours to obtain nano-zero valent iron (nZVI, 100-150 nm), which was then stored in a vacuum desiccator. The reaction equation for the preparation of nZVI is shown below:

[0039] 4Fe 3+ +3BH4 - +9H₂O→4Fe 0 ↓+3H2BO3 - +12H + +6H2↑;

[0040] The principle of preparing nano-zero-valent iron using the liquid-phase reduction method is based on the high-valent iron solution, such as Fe... 3+ and / or Fe 2+ Adding a strong reducing agent (such as sodium borohydride and / or potassium borohydride) to the solution allows for the formation of stable black nano-sized zero-valent iron particles under the dispersion and stabilization effects of the strong reducing agent. This method is simple, low-cost, and yields highly reactive nano-sized zero-valent iron.

[0041] According to the present invention, preferably, the particle size of the anaerobic ammonia oxidation gel particles is 3-8 mm.

[0042] The second aspect of the present invention provides anaerobic ammonia oxidation gel particles prepared by the method described above.

[0043] A third aspect of the present invention provides a method for enhancing the denitrification performance of an anammox process under high total nitrogen load conditions, the method comprising inoculating an anammox granular sludge and the anammox gel particles into an anammox reactor.

[0044] According to the present invention, preferably, the high total nitrogen loading conditions include a total nitrogen loading of 26.3-35.5 kg-TN / (m³). 3·d), the pH of the reactor influent is 7.0-8.0, the dissolved oxygen concentration of the reactor influent is below 0.4 mg / L, and the reactor operating temperature is 33-38℃.

[0045] According to the present invention, preferably, the reactor is an upflow sludge bed reactor (UASB). As a preferred embodiment, the height of the upflow sludge bed reactor is 80-100 cm and the inner diameter is 8-12 cm.

[0046] According to the present invention, preferably, the anaerobic ammonia oxidation granular sludge is taken from a plant that has been operating for more than 2 years with a total nitrogen load of less than 0.4 kg-TN / (m³). 3 ·d) The reactor, wherein the particle size of the anaerobic ammonia oxidation granular sludge is 0.8-2.5 mm.

[0047] According to the present invention, preferably, the volume ratio of the anaerobic ammonia oxidation gel particles to the anaerobic ammonia oxidation granular sludge is (1-2):(2-1).

[0048] According to the present invention, preferably, the ratio of the total volume of the anaerobic ammonia oxidation gel particles and the anaerobic ammonia oxidation granular sludge to the effective volume of the reactor is 1:(5-20).

[0049] The working principle of this invention:

[0050] Under high total nitrogen load conditions, the denitrification performance and operational stability of the ANAMMOX process severely deteriorate. This is mainly because high total nitrogen load leads to abnormal secretion of extracellular polymers in ANAMMOX granular sludge, further resulting in a loose granular structure, reduced density, and subsequent granule floating and loss. This invention addresses this by encapsulating and immobilizing ANAMMOX sludge to form ANAMMOX gel particles. Compared to ANAMMOX granular sludge, ANAMMOX gel particles exhibit significantly improved particle stability and mechanical strength. Therefore, under high total nitrogen load conditions, the use of ANAMMOX gel particles can effectively increase the retention of microorganisms within the reactor. Furthermore, ANAMMOX gel particles demonstrate strong resistance to variations in influent nitrogen concentration, temperature, toxic substance concentration, and organic matter load. This invention develops an economical, readily biodegradable, and activity-maintaining encapsulation material with excellent mass transfer performance and high mechanical strength, successfully applying encapsulation and immobilization technology to enhance the denitrification performance and operational stability of the ANAMMOX process under high total nitrogen load conditions.

[0051] In this invention, polyvinyl alcohol (PVA) is selected as the encapsulating agent. It is inexpensive, has a regular polyol structure, and exhibits good stability. However, PVA has limited mass transfer performance; therefore, improving its mass transfer performance and specific surface area is one of the core technologies of this invention. Diatomaceous earth is a biogenic siliceous rock composed of the siliceous remains of diatoms and other microorganisms. It has a large specific surface area, strong surface adsorption performance, and is widely available and easily obtained. Furthermore, diatomaceous earth can adsorb cations such as ammonia nitrogen under neutral or weakly alkaline conditions. Therefore, this invention modifies diatomaceous earth using chitosan, disrupting its original porous structure and forming a novel three-dimensional porous structure. The specific surface area and adsorption performance of chitosan-modified diatomaceous earth are further improved compared to unmodified diatomaceous earth. Thus, this invention significantly improves the mass transfer performance and specific surface area of ​​the encapsulating agent PVA by adding chitosan to modified diatomaceous earth. This is a key reason why the ANAMMOX gel particles prepared in this invention exhibit excellent mass transfer and adsorption performance. The addition of nano-zero valent iron (nZVI) effectively stimulated the activity of ANAMMOX bacteria in ANAMMOX gel particles.

[0052] However, the ANAMMOX activity of ANAMMOX gel particles with added nZVI and chitosan-modified diatomaceous earth was still not as high as that of ANAMMOX granular sludge during its structurally stable phase. To ensure sufficient biomass retention in the reactor and maintain high ANAMMOX activity, thereby achieving optimal overall nitrogen removal performance of the anammox process under high total nitrogen loads, both ANAMMOX gel particles and ANAMMOX granular sludge were simultaneously added to the reactor.

[0053] The beneficial effects of the technical solution of the present invention are as follows:

[0054] (1) The main materials used in the preparation of anaerobic ammonia oxidation gel particles are inexpensive and widely available, and the process of preparing anaerobic ammonia oxidation gel particles is relatively simple. Therefore, the implementation cost of the invention is low.

[0055] (2) In this invention, the addition of chitosan-modified diatomite significantly improves the adsorption and mass transfer performance of the prepared anammox gel particles compared with ordinary gel particles. In addition, the addition of nano-zero valent iron (nZVI) also effectively stimulates the activity of ANAMMOX bacteria. Therefore, the technology of this invention can effectively increase the biomass retention of ANAMMOX bacteria in the reactor and help maintain the activity of ANAMMOX bacteria, which can enable the high total nitrogen load anammox process reactor to maintain high denitrification efficiency and operational stability.

[0056] (3) The technology of this invention is applicable to different types of reaction devices and different influent flow rates, and has strong resistance to toxic substances or other water quality changes in the influent, and has a wide range of applications;

[0057] (4) The PVA (polyvinyl alcohol), chitosan and diatomaceous earth used in this invention are all environmentally friendly materials, so this invention will not cause secondary environmental pollution.

[0058] (5) This invention addresses the problem of significantly reduced denitrification efficiency and unstable operation of the ANAMMOX process under high total nitrogen load conditions by encapsulating and immobilizing ANAMMOX sludge to form ANAMMOX gel particles, and by mixing ANAMMOX gel particles with ANAMMOX granular sludge with low total nitrogen load and adding them to the anaerobic ammonia oxidation process reactor with high total nitrogen load.

[0059] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0060] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0061] Figure 1 The diagram illustrates the effect of different volume ratios of gel particles and granular sludge on the total nitrogen removal rate under high total nitrogen load, as provided in Examples 2-4 of this invention, on the method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation under high total nitrogen load.

[0062] Figure 2 The diagram illustrates the effect of different inoculants on the total nitrogen removal rate under high total nitrogen load in the anaerobic ammonia oxidation process provided in Example 2 and Comparative Examples 1-2 of the present invention. Detailed Implementation

[0063] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0064] Example 1

[0065] This embodiment proposes a method for preparing anaerobic ammonia oxidation gel particles, the preparation method comprising the following steps:

[0066] S1: Preparation of chitosan-modified diatomaceous earth

[0067] First, take chitosan and place it in an Erlenmeyer flask. Add an appropriate amount of distilled water to prepare a chitosan aqueous solution. Then, weigh diatomaceous earth and add it to the chitosan aqueous solution. Stir using a temperature-controlled magnetic stirrer for 3-5 hours (room temperature, 120-130 r / min). Filter the solution using a vacuum filtration device. Place the filtered material in a muffle furnace and calcine for 3-4 hours (500℃). After calcination, grind the material and sieve it through 120-mesh and 150-mesh screens to obtain a particle size of 100-125 μm and a specific surface area of ​​96 m². 2 / g, chitosan-modified diatomaceous earth with a pore size of 19-136nm.

[0068] S2: Preparation of gelling agent

[0069] Polyvinyl alcohol (degree of polymerization 1830±20, saponification degree approximately 99%, analytical grade), sodium alginate (viscosity of sodium alginate (SA) approximately 162 mPa·s) were mixed with distilled water at a temperature above 90°C and stirred continuously to obtain a uniform gel-like mixture (the content of polyvinyl alcohol was 11 wt% and the content of sodium alginate was 1.5 wt% based on the total weight of the gel-like mixture). Within 5-15 minutes of the start of the stirring, the gel-like mixture was mixed and stirred with the chitosan-modified diatomaceous earth (the concentration of chitosan-modified diatomaceous earth in the gelling agent was 2 g / L), and the stirring intensity was increased to ensure uniform stirring. The mixture was then cooled to 50°C to obtain the gelling agent.

[0070] S3: Preparation of anaerobic ammonia oxidation gel particles

[0071] Anaerobic ammonia oxidation sludge (total nitrogen load less than 0.4 kg-TN / (m³)) 3 The anammox sludge under d) is uniformly mixed with the gelling agent and nano-zero ferric iron to obtain a mixed solution (the volume ratio of the gelling agent to the anammox sludge is 10:9; the concentration of nano-zero ferric iron in the mixed solution is 1.1 g / L, and the particle size of nano-zero ferric iron is 100-150 nm).

[0072] The above mixture was added dropwise to a 7wt% CaCl2 aqueous solution using a peristaltic pump, and crosslinked at room temperature for 20 hours to complete the first crosslinking process, which forms anaerobic ammonia oxidation primary gel microspheres. Then, the anaerobic ammonia oxidation primary gel microspheres were added to a 0.7mol / L KH2PO4 aqueous solution and crosslinked at room temperature for 3 hours to complete the second crosslinking process. At this time, anaerobic ammonia oxidation gel particles with stable structure and high activity (the particle size of the anaerobic ammonia oxidation gel particles is 3-8mm) can be obtained. After rinsing the anaerobic ammonia oxidation gel particles with deionized water, they were stored at 4℃ for later use.

[0073] The preparation method of the nano-zero valent iron is a liquid-phase reduction method, including: weighing 12.5g FeCl3·6H2O and preparing a 1.1mol / L FeCl3·6H2O solution, and uniformly stirring using a precision quantitative electric stirrer, with nitrogen gas introduced during stirring to remove oxygen. Then, prepare 105mL of 0.2mol / L sodium borohydride (NaBH4) aqueous solution. Under electric stirring, add the NaBH4 aqueous solution dropwise to the above FeCl3·6H2O solution using a peristaltic pump. As the solution gradually turns black and the NaBH4 addition is complete, continue the reaction under stirring for 30 minutes. Then, vacuum filter the above black mixture to obtain stable black nano-iron particles. Wash the black nano-particles first with a 30% ethanol aqueous solution, and then wash them again with anhydrous ethanol. Finally, dry the washed black nano-particles in a vacuum drying oven at 60℃ for 20h to obtain nano-zero valent iron (nZVI, 100-150nm), which is then stored in a vacuum desiccator.

[0074] Example 2

[0075] This embodiment provides a method for enhancing the nitrogen removal performance of anammox process under high total nitrogen load conditions. The method includes inoculating anammox granular sludge and anammox gel particles (Group A (Group V2)) into the anammox process reactor.

[0076] The high total nitrogen load conditions were manually adjusted.

[0077] During operation phase I (days 1-10), the influent ammonia nitrogen concentration was 350 mg / L, the influent nitrite nitrogen concentration was 462 mg / L, and the hydraulic retention time (HRT) was controlled at 8 h (total nitrogen load was approximately 1.50 kg-TN / (m³)). 3 ·d)); The reactor influent also contains KH2PO4 (78 mg / L), KHCO3 (347 mg / L), MgSO4·7H2O (370 mg / L), CaCl2·2H2O (70 mg / L), NH4Cl and NaNO2 at 400 mg / L and 687 mg / L respectively, with 1 mL / L of trace element solutions I and II added. Trace element solution I consists of 5.00 g / L EDTA and 5.00 g / L FeSO4; trace element solution II consists of 15.00 g / L EDTA, 0.43 g / L ZnSO4·4H2O, 0.99 g / L MnCl2·4H2O, 0.014 g / L H3BO4, 0.25 g / L CuSO4·5H2O, 0.22 g / L Na2MoO4·2H2O, 0.21 g / L Na2SeO4·10H2O, and 0.19 g / L NiCl2·6H2O.

[0078] During operation phase II (11-40 days), the influent ammonia nitrogen concentration was maintained at 284 mg / L and nitrite nitrogen concentration at 369 mg / L, and the HRT was reduced to 4 h (total nitrogen load was approximately 3.92 kg-TN / (m³)). 3 ·d));

[0079] During Phase III of operation (days 41-75), the influent ammonia nitrogen concentration was further increased to 400 mg / L and nitrite nitrogen concentration to 520 mg / L. The HRT was adjusted to 3.5 h (total nitrogen load was approximately 6.45 kg-TN / (m³)). 3 ·d));

[0080] During operation phase IV (76-110 days), the influent ammonia nitrogen concentration was further increased to 450 mg / L and nitrite nitrogen concentration to 585 mg / L, and the HRT was adjusted to 3.0 h (total nitrogen load was approximately 8.40 kg-TN / (m³)). 3 ·d)).

[0081] Throughout the operation, the pH of the reactor influent was 7.2-8.0, the dissolved oxygen concentration of the reactor influent was below 0.1 mg / L, and the reactor operating temperature was 33-35℃.

[0082] The reactor is an upflow sludge blanket reactor (UASB), with a height of 95cm, an inner diameter of 9.5cm, and made of acrylic. The outermost layer is a water bath layer, and the effluent internal recirculation ratio is set to 2.5.

[0083] The anaerobic ammonia oxidation granular sludge was taken from a plant that had been operating stably for more than 2 years with a total nitrogen load of less than 0.4 kg-TN / (m³). 3 ·d) The reactor, wherein the particle size of the anaerobic ammonia oxidation granular sludge is 0.8-2.5 mm.

[0084] The volume ratio of the anaerobic ammonia oxidation gel particles to the anaerobic ammonia oxidation granular sludge is 1:1.

[0085] The ratio of the total volume of the anammox gel particles and anammox granular sludge to the effective volume of the reactor is 1:5.

[0086] Example 3

[0087] This embodiment provides a method for enhancing the denitrification performance of anammox process under high total nitrogen load conditions. The only difference between this embodiment and Embodiment 2 is that the volume ratio of the anammox gel particles and the anammox granular sludge is 1:0.5 (Group V1).

[0088] Example 4

[0089] This embodiment provides a method for enhancing the denitrification performance of anammox process under high total nitrogen load conditions. The only difference between this embodiment and Embodiment 2 is that the volume ratio of the anammox gel particles and the anammox granular sludge is 1:2 (Group V3).

[0090] like Figure 1 As shown, during the entire operation, the total nitrogen removal rate of group V2 was the highest, with total nitrogen removal rates of 91%, 85%, 90%, and 82% in operation stages I to IV, respectively; the total nitrogen removal rates of group V1 were 89%, 77%, 69%, and 56%, respectively; while the total nitrogen removal rate of group V3 was the lowest, with total nitrogen removal rates of 92%, 69%, 61%, and 48% in stages I to IV, respectively.

[0091] Comparative Example 1

[0092] This comparative example provides an anaerobic ammonia oxidation process under high total nitrogen loading conditions. The only difference between this process and Example 1 is that only the same anaerobic ammonia oxidation gel particles (Group B) as Group A (Example 2) are inoculated in the anaerobic ammonia oxidation process reactor.

[0093] The ratio of the volume of the anaerobic ammonia oxidation gel particles to the effective volume of the reactor is 1:5.

[0094] Comparative Example 2

[0095] This comparative example provides an anaerobic ammonia oxidation process under high total nitrogen loading conditions. The only difference between this process and Example 1 is that only the same anaerobic ammonia oxidation granular sludge (Group C) as Group A (Example 2) is inoculated into the anaerobic ammonia oxidation process reactor.

[0096] The ratio of the volume of the anaerobic ammonia oxidation granular sludge to the effective volume of the reactor is 1:5.

[0097] like Figure 2 As shown:

[0098] During operation phase I, with a total nitrogen load of approximately 1.50 kg-TN / (m3·d), the total nitrogen removal rates of reactors A, B, and C remained at a high level on day 5, at 91%, 90%, and 93%, respectively.

[0099] During operation phase II, the total nitrogen load was increased to 4.92 kg-TN / (m3·d). By the 25th day of operation, the total nitrogen removal rates of reactors A, B and C had decreased to 87%, 75% and 68%, respectively. However, the total nitrogen removal rate of group A was significantly higher than that of groups B and C.

[0100] During operation phase III, the total nitrogen load continued to increase to 6.51 kg-TN / (m3·d). When the reactors were running for 55 days, the total nitrogen removal rates of reactors in groups B and C decreased significantly to 67% and 57%, respectively, while the total nitrogen removal rate of reactor group A increased to 94%.

[0101] During operation phase IV, the total nitrogen load had increased to 18.43 kg-TN / (m3·d). After 105 days of operation, the nitrogen removal performance of reactor group C deteriorated significantly, with its total nitrogen removal rate dropping sharply to 34%. The total nitrogen removal rate of reactor group B was higher than that of group C (60%). However, the total nitrogen removal rate of reactor group A under this high total nitrogen load was significantly higher than that of groups B and C, reaching as high as 84%.

[0102] Meanwhile, monitoring revealed that a considerable number of anaerobic ammonia oxidizing bacteria from disintegrated anaerobic ammonia oxidizing granular sludge were adsorbed on the surface of the anaerobic ammonia oxidizing gel particles in reactor A. This meant that the biomass retention in reactor A was not significantly lower than that in reactor B, but the denitrification rate in reactor A was significantly higher.

[0103] As can be seen from Examples 2-4 and Comparative Examples 1-2, inoculating anammox granular sludge and the anammox gel particles of the present invention into the anammox reactor can effectively improve the denitrification performance and operational stability of the ANAMMOX system under high total nitrogen load conditions. The optimal mixing ratio of gel particles and granular sludge is 1:1. The technology of the present invention has great application potential.

[0104] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for enhancing the nitrogen removal performance of an anaerobic ammonia oxidation process under high total nitrogen loading conditions, characterized in that, The method includes inoculating an anammox granular sludge and an anammox gel particle into an anammox process reactor. The preparation method of the anaerobic ammonia oxidation gel particles includes the following steps: S1: Preparation of chitosan-modified diatomaceous earth Chitosan is mixed with water to obtain a chitosan aqueous solution; the chitosan aqueous solution is mixed with diatomaceous earth and then subjected to stirring, vacuum filtration, calcination and grinding in sequence to obtain the chitosan-modified diatomaceous earth; The roasting equipment includes a muffle furnace; the roasting temperature is 450-550℃, and the time is 3-4 hours. S2: Preparation of gelling agent Polyvinyl alcohol, sodium alginate, and high-temperature distilled water are mixed and stirred to obtain a gel-like mixture; the gel-like mixture is then mixed and stirred evenly with chitosan-modified diatomaceous earth, and cooled to obtain the gel agent; S3: Preparation of anaerobic ammonia oxidation gel particles Anaerobic ammonia oxidation sludge is uniformly mixed with the gelling agent and nano-zero valent iron to obtain a mixed solution; the mixed solution is mixed with calcium chloride aqueous solution and subjected to a first cross-linking to obtain anaerobic ammonia oxidation primary gel microspheres; the anaerobic ammonia oxidation primary gel microspheres are mixed with potassium dihydrogen phosphate aqueous solution and subjected to a second cross-linking to obtain anaerobic ammonia oxidation gel particles. The high total nitrogen loading conditions include total nitrogen loading of 26.3-35.5 kg-TN / (m³). 3 (d) The pH of the reactor influent is 7.0-8.0, the dissolved oxygen concentration of the reactor influent is below 0.4 mg / L, and the reactor operating temperature is 33-38℃.

2. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 1, wherein, In step S1: The stirring equipment includes a temperature-controlled magnetic stirrer; the stirring temperature is 30-35℃, the stirring time is 3-5 hours, and the stirring speed is 120-130 r / min. The chitosan-modified diatomaceous earth has a particle size range of 100-125µm and a specific surface area of ​​90-100m². 2 / g, with a pore size of 19-136nm.

3. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 1, wherein, In step S2: The high-temperature distilled water is distilled water with a temperature ≥90℃; Based on the total weight of the gel-like mixture, the content of polyvinyl alcohol is 11-15 wt%, and the content of sodium alginate is 1-2 wt%. The concentration of chitosan-modified diatomaceous earth in the gelling agent is 2-6 g / L; The cooling process involves cooling the gel to 45-55°C.

4. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 1, wherein, In step S3: The calcium chloride aqueous solution has a mass fraction of 7-9 wt%. The first crosslinking time is 12-24 hours, and the temperature is 30-35℃; The molar concentration of the potassium dihydrogen phosphate aqueous solution is 0.7-1.0 mol / L; The second crosslinking time is 1-5 hours, and the temperature is 30-35℃; The anaerobic ammonia oxidation sludge has a total nitrogen load of less than 0.4 kg-TN / (m³). 3 Anaerobic ammonia oxidation sludge under d) The volume ratio of the gelling agent to the anammox sludge is (10-5):(3-4). The concentration of nano-zero valent iron in the mixture is 1.1-2.3 g / L, and the particle size of the nano-zero valent iron is 100-150 nm.

5. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 1 or 4, wherein, The preparation method of the nano-zero valent iron includes: mixing an aqueous solution of high valent iron with an aqueous solution of citric acid and a strong reducing agent, stirring the mixture evenly under a nitrogen atmosphere, and then vacuum filtering, rinsing and vacuum drying to obtain the nano-zero valent iron.

6. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 5, wherein, The molar concentration of the high-valent iron aqueous solution is 1.1-1.3 mol / L; the high-valent iron aqueous solution is Fe 3+ Aqueous solutions and / or Fe 2+ Aqueous solution; The molar concentration of the aqueous solution of the strong reducing agent is 0.8-1.2 mol / L; the strong reducing agent is sodium borohydride and / or potassium borohydride; The vacuum drying temperature is 55-65℃, and the time is 15-25h.

7. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 1, wherein, The particle size of the anaerobic ammonia oxidation gel particles is 3-8 mm.

8. The method for enhancing the nitrogen removal performance of anaerobic ammonia oxidation process under high total nitrogen loading conditions according to claim 1, wherein, The reactor is an upflow sludge bed reactor; The anaerobic ammonia oxidation granular sludge was taken from a facility that had been operating for more than 2 years with a total nitrogen load of less than 0.4 kg-TN / (m³). 3 ·d) The reactor, wherein the particle size of the anammox granular sludge is 0.8-2.5 mm; The volume ratio of the anaerobic ammonia oxidation gel particles to the anaerobic ammonia oxidation granular sludge is (1-2):(2-1). The ratio of the total volume of the anaerobic ammonia oxidation gel particles and anaerobic ammonia oxidation granular sludge to the effective volume of the reactor is 1:(5-20).

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